JP4065508B2 - Image forming method - Google Patents

Description

（式中、Ｌ_０は、粒子像と同じ投影面積をもつ円の周囲長を示し、Ｌは、粒子の投影像の周囲長を示す。）
前記現像剤担持体の基体上に形成された樹脂被覆層中には、少なくとも被覆層用結着樹脂及び導電性物質を含有することが好ましい。
【００５３】
前記現像剤担持体の基体上に形成された樹脂被覆層中には、少なくとも被覆層用結着樹脂及び潤滑性物質を有することが好ましい。
【００５６】
また、イミダゾール化合物が、下記式（１）又は（２）で示される化合物であることが好ましい。
【００５７】
【化４】

〔式中、Ｒ_１及びＲ_２は、水素原子、又は、アルキル基、アラルキル基及びアリール基からなる群より選ばれる置換基を表わし、Ｒ_１及びＲ_２は同一であっても異なっていても良く、Ｒ_３及びＲ_４は、炭素数が３〜３０の直鎖状アルキル基を表わし、Ｒ_３及びＲ_４は同一であっても異なっていても良い。〕
【００５８】
【化５】

〔式中、Ｒ_５及びＲ_６は、水素原子、又は、アルキル基、アラルキル基及びアリール基からなる群より選ばれる置換基を表わし、Ｒ_５及びＲ_６は同一であっても良く、Ｒ_７は、炭素数が３〜３０の直鎖状アルキル基を表わす。〕
該樹脂被覆層が、導電性物質及び含窒素複素環化合物に加えて更に、個数平均粒径０．３〜３０μｍの球状粒子を有することが好ましい。
【００５９】
球状粒子が、樹脂粒子であることが好ましい。
【００６０】
球状粒子が、真密度３ｇ／ｃｍ^３以下の導電性球状粒子であることが好ましい。
【００６２】
該含窒素ビニルモノマーはビニル重合性モノマーを有することが好ましい。
【００６３】
該共重合体は、３，０００〜５０，０００の重量平均分子量（Ｍｗ）を有していることが好ましい。
【００６４】
該共重合体は、重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）との比（Ｍｗ／Ｍｎ）３．５以下を有していることが好ましい。
【００６５】
該含窒素ビニルモノマーは、窒素含有基を有する（メタ）アクリル酸誘導体及び含窒素複素環式Ｎ−ビニル化合物からなるグループから選択される１種以上のモノマーを有することが好ましい。
【００６６】
該含窒素ビニルモノマーとしては、下記一般式（３）
【００６７】
【化６】

〔式中、Ｒ_７，Ｒ_８，Ｒ_９及びＲ_１０は、水素原子あるいは炭素数１〜４の飽和炭化水素基を示し、ｎは１〜４の整数を示す。〕
で示されるものが好ましい。
【００６８】
また上記の現像装置において、前記現像剤担持体の基体上に形成された該樹脂被覆層中には、正帯電性物質として、結着樹脂及びビニル重合性単量体とスルホン酸基含有アクリルアミド単量体との共重合体を含有していることが好ましい。また、同時に被覆層用結着樹脂はその一部又は全てが、その分子構造中に少なくとも−ＮＨ_２基、＝ＮＨ基、もしくは−ＮＨ−結合のいずれかを有することが好ましい。
【００６９】
前記ビニル重合性単量体とスルホン酸基含有アクリルアミド系単量体の共重合比（質量％）が、９８：２〜８０：２０であり、重量平均分子量（Ｍｗ）が２，０００〜５０，０００の共重合体であることが好ましい。
【００７０】
前記共重合体が、ビニル重合性単量体と２−アクリルアミド−２−メチルプロパンスルホン酸との共重合体であることが好ましい。
【００７１】
前記結着樹脂中に、少なくともフェノール樹脂が含有されることが好ましい。
【００７２】
前記フェノール樹脂が、含窒素化合物を触媒として用いて製造されたフェノール樹脂であり、その構造中に−ＮＨ_２基、＝ＮＨ基、もしくは−ＮＨ−結合のいずれかを有するが好ましい。
【００７３】
前記結着樹脂中に、少なくともポリアミド樹脂が含有されることが好ましい。
【００７４】
前記結着樹脂中に、少なくともポリウレタン樹脂が含有されることが好ましい。
【００７５】
前記樹脂層中に被覆層表面に凹凸を形成するために、球状粒子が含有されていることが好ましく、該球状粒子の個数平均粒径が０．３〜３０μｍであることがより好ましい。
【００７６】
被覆層表面に凹凸を形成するための粒子が球状であり、且つ真密度が３ｇ／ｃｍ^３以下であることが好ましい。
【００７７】
被覆層表面に凹凸を形成するための粒子が導電性の球状粒子であることが好ましい。
【００７８】
さらに上記の本発明の現像装置の有する前記現像剤層厚規制部材が、磁性ブレード或いは弾性ブレードであることが好ましい。
【００７９】
前記現像剤が、磁性トナー粒子を有する磁性現像剤であることが好ましい。
【００８０】
前記現像剤の重量平均粒径（Ｄ４）が、４〜１０μｍであることが好ましい。
【００８１】
前記現像剤が粒径０．６０〜１５９．２１μｍの粒子に関する個数基準の粒度分布において、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を１５〜６０個数％含有し、且つ３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子を１５〜７０個数％含有することが好ましい。
【００８２】
前記現像剤は、体積平均粒径が０．１〜１０μｍである導電性微粒子を有していることが好ましい。
【００８３】
前記現像剤は、体積抵抗値が１０^０〜１０^９Ω・ｃｍ、より好ましくは１０^１〜１０^６Ω・ｃｍである導電性微粒子を有していることが好ましい。
【００８４】
前記導電性微粒子が非磁性であることが好ましい。
【００８５】
前記導電性微粒子が、酸化亜鉛、酸化スズ、酸化チタンから選択される少なくとも一種の酸化物を含有することが好ましい。
【００９７】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
【００９８】
＜現像剤＞
本発明に用いられる現像剤としては、トナー粒子及び導電性微粉末を少なくとも有する一成分系現像剤が好ましい。
【００９９】
本発明に用いられる現像剤は、結着樹脂および着色剤を少なくとも含有するトナー粒子と導電性微粉末とを少なくとも有し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を１５〜６０個数％含有し、且つ３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子を１５〜７０個数％含有することが好ましい。更には、外添剤として、平均一次粒径が４〜８０ｎｍである無機微粉末を含有していることが好ましい。
【０１００】
このような現像剤を用いることにより、良好な帯電性を安定して現像剤に付与することができ、現像剤の長期にわたる繰り返し使用においても帯電不良が生じずに良好な画像が得られ、且つ廃トナー量を大幅に減らすことが可能な、低コストで小型化に有利な現像兼クリーニング工程を有する画像形成方法が可能となる。
【０１０１】
また、このような現像剤を用いることにより、オゾンなどの放電生成物が実質的に無く、低い印加電圧で均一な帯電が得られる直接注入帯電機構を用いた帯電を簡易な構成で良好に行うことができ、現像剤の長期にわたる繰り返し使用においても帯電不良を生じない良好な画像が得られる画像形成方法が可能となる。また、このような現像剤を用いることによって、多量の現像剤成分が接触帯電部材に付着または混入しても、一様帯電性の低下を抑制することができ、像担持体の帯電不良による画像不良を抑制することができる、接触帯電による画像形成方法が可能となる。
【０１０２】
また、このような現像剤を用いた現像兼クリーニング画像形成方法において、良好な摩擦帯電特性を安定して示す現像剤が得られ、現像剤の長期にわたる繰り返し使用においても、転写残トナー粒子の回収不良や、一様帯電または潜像形成の阻害による画像不良を生ずることなく良好な画像が得られ、且つ廃トナー量を大幅に減らすことが可能な、低コストで小型化に有利な現像兼クリーニング画像形成方法が可能となる。
【０１０３】
現像剤が有する導電性微粉末は、像担持体に形成された静電潜像が現像される際に、トナー粒子とともに適当量が現像剤担持体から潜像担持体に移行する。静電潜像が現像されることにより潜像担持体上に形成されたトナー画像は、転写工程において紙などの転写材に転移する。このとき、潜像担持体上の導電性微粉末も一部は転写材に付着するが、残りは潜像担持体上に付着保持されて残留する。トナー粒子の帯電極性と逆極性の転写バイアスを印加して転写を行う場合には、トナーは転写材側に引かれて積極的に転移するが、潜像担持体上の導電性微粉末は導電性であるため転写材側に転移し難い。このため、導電性微粉末の一部は転写材に付着するものの残りは潜像担持体上に付着保持されて残留する。
【０１０４】
クリーニング工程のように、潜像担持体上に付着保持されて残留した導電性微粉末を潜像担持体上から取り除く工程を持たない画像形成方法では、転写工程後の潜像担持体表面に残存したトナー粒子（以下、これを「転写残トナー粒子」という）および導電性微粉末は、潜像担持体において像を担持する面（以下、これを「像担持面」という）の移動に伴って帯電部に運ばれる。すなわち、帯電工程に接触帯電部材を用いる場合は、導電性微粉末は潜像担持体と接触帯電部材とが接触して形成される接触部に運ばれ、接触帯電部材に付着・混入する。従って、潜像担持体と接触帯電部材との接触部に導電性微粉末が介在した状態で潜像担持体の接触帯電が行われる。
【０１０５】
本発明においては、導電性微粉末を帯電部に積極的に運ぶことにより、転写残トナー粒子の付着・混入により接触帯電部材が汚染されるにも拘わらず、接触帯電部材の接触抵抗を維持できるため、接触帯電部材による潜像担持体の帯電を良好に行うことができる。
【０１０６】
しかし、接触帯電部材の帯電部に十分な量の導電性微粉末が介在しない場合には、転写残トナー粒子の接触帯電部材への付着・混入による像担持体の帯電の低下が容易に起こり、画像汚れを生ずる。
【０１０７】
更に、導電性微粉末を潜像担持体と接触帯電部材とが接触して形成する接触部に積極的に持ち運ぶことにより、接触帯電部材の潜像担持体への緻密な接触性と接触抵抗を維持できるため、接触帯電部材による潜像担持体の直接注入帯電を良好に行わせることができる。
【０１０８】
また、接触帯電部材に付着・混入した転写残トナー粒子は、接触帯電部材から徐々に潜像担持体上に吐き出され、像担持面の移動に伴って現像部に至り、現像工程において現像兼クリーニング、すなわち転写残トナー粒子の回収が行われる。接触帯電部材に付着・混入した導電性微粉末も同様に接触帯電部材から徐々に像担持体上に吐き出され、像担持面の移動に伴って現像部に至る。すなわち、転写残トナー粒子とともに導電性微粉末が潜像担持体上に存在し、現像工程において転写残トナー粒子の回収が行われる。現像工程における転写残トナー粒子の回収が現像バイアス電界を利用するものである場合には、転写残トナー粒子が現像バイアス電界によって回収されるのに対して、潜像担持体上の導電性微粉末は導電性であるため回収され難い。このため、導電性微粉末の一部は回収されるものの、残りは潜像担持体上に付着保持されて残留する。本発明者らの検討によれば、このように現像工程で回収され難い導電性微粉末が像担持体上に存在することで、潜像担持体上の転写残トナー粒子の回収性を向上させる効果を有することが判明した。すなわち、像担持体上の導電性微粉末が潜像担持体上の転写残トナー粒子の回収助剤として働き、現像工程における転写残トナー粒子の回収をより確実なものとし、転写残トナー粒子の回収不良によるポジゴーストやカブリ等の画像欠陥を有効に防止することができる。
【０１０９】
従来、現像剤に導電性微粉末を外部添加する目的の多くが、トナー粒子表面に導電性微粉末を付着させることによってトナーの摩擦帯電性を制御することであり、トナー粒子から遊離或いは脱離する導電性微粉末は、現像剤特性の変化或いは劣化を招く弊害として扱われてきた。これに対し、本発明の現像剤は、導電性微粉末をトナー粒子表面から積極的に遊離させる点で、従来多く検討されてきた現像剤への導電性微粉末の外部添加とは異なる。導電性微粉末を、転写後の潜像担持体上を経由させて像担持体と接触帯電部材とが接触して形成する接触部である帯電部に持ち運び、介在させることによって潜像担持体の帯電性を積極的に向上させることにより、安定して均一な一様帯電を可能とし、潜像担持体の帯電低下による画像不良の発生を防止する。また、現像工程において導電性微粉末が潜像担持体上に存在することで、導電性微粉末が潜像担持体上の転写残トナー粒子の回収助剤として働き、現像工程における転写残トナー粒子の回収をより確実なものとし、転写残トナー粒子の回収不良によるポジゴーストやカブリ等の画像欠陥を有効に防止することができる。
【０１１０】
本発明の現像剤においては、トナー粒子表面に付着してトナー粒子と共に挙動する導電性微粉末は、本発明の現像剤が効果として発現する潜像担持体の帯電性の促進及び現像兼クリーニング性能の向上に対しての寄与が少なく、トナー粒子の現像性の低下、現像兼クリーニング工程での転写残トナー粒子回収性の低下、及び転写性の低下によって転写残トナー粒子量が増加することにより、一様帯電を阻害する等の弊害を生む場合がある。
【０１１１】
本発明の現像剤に含有される導電性微粉末は、画像形成が繰り返されることにより、帯電工程および現像工程を経て像担持面に移行し、さらに像担持面の移動に伴い転写工程を経て再び帯電部に持ち運ばれることにより、帯電部に導電性微粉末が逐次供給され続ける。従って、帯電部において導電性微粉末が脱落するなどして減少したり、導電性微粉末の一様帯電性促進能力が劣化した場合でも、帯電部に導電性微粉末が供給され続けるため、装置の長期にわたる繰り返し使用においても像担持体の帯電性の低下を防止し、良好な一様帯電が安定して維持される。
【０１１２】
現像剤に添加する導電性微粉末の粒径の、潜像担持体の帯電性促進効果及び現像兼クリーニング性に対する影響についての本発明者らの検討によれば、導電性微粉末のうち粒子径が非常に小さいもの（例えば０．１μｍ程度以下のもの）は、トナー粒子表面に強固に付着し易く、現像工程で潜像担持体上の非画像部に導電性微粉末を十分に供給することができず、転写工程においてもトナー粒子表面から導電性微粉末が遊離しない。このため、転写後の潜像担持体上に導電性微粉末を積極的に残留させ、帯電部に導電性微粉末を積極的に供給することができない。従って、潜像担持体の帯電性を向上させる効果が得られず、接触帯電部材に転写残トナー粒子が付着混入した場合には潜像担持体の帯電性低下による画像不良を生ずる。
【０１１３】
また、現像兼クリーニング工程においても、潜像担持体上に導電性微粉末を供給することができないため、また、潜像担持体上に供給されたとしても導電性微粉末の粒子径が小さすぎるために、転写残トナー粒子の回収性を向上させる効果が得られず、転写残トナー粒子の回収不良によるポジゴーストやカブリ等の画像欠陥を有効に防止することができない。
【０１１４】
また、導電性微粉末のうち粒子径が大きすぎるもの（例えば４μｍ程度以上のもの）は、帯電部に供給されても粒径が大きいために、導電性微粉末が帯電部材から脱落しやすくなり、安定して十分な粒子数の導電性微粉末を帯電部に介在させ続けることが困難となり、均一な潜像担持体の帯電性を促進することができない。更に、単位重量当たりの導電性微粉末の粒子数が減少するため、潜像担持体の均一帯電促進効果を十分に得られるだけの粒子数の導電性微粉末を帯電部に介在させる（帯電部における潜像担持体と導電性微粉末との接触点数を多くすることによって、潜像担持体の一様帯電性を促進する効果が高まるため、帯電部に介在する導電性微粉末の粒子数が多いことが求められる。）には、導電性微粉末の現像剤に対する添加量を大きくせざるを得なくなる。しかし、導電性微粉末の添加量を多くしすぎると、現像剤全体としての摩擦帯電能や現像性を低下させ、画像濃度低下やトナー飛散を生ずる。また、導電性微粉末の粒径が大きいために、現像工程における転写残トナー粒子の回収助剤としての効果が十分には得られない。転写残トナー粒子の回収を高めるために、導電性微粉末の像担持体上での存在量を大きくしすぎると、粒径が大きいために潜像形成工程への悪影響、例えば画像露光を遮ることによる画像欠陥を生じる場合がある。
【０１１５】
本発明者らは、導電性微粉末の粒径の検討から、さらに実際の現像剤の挙動に直接関与する、外部添加剤を含む現像剤の粒度分布の検討へ進め、鋭意検討の末、本発明に至った。
【０１１６】
すなわち、現像剤を、結着樹脂および着色剤を少なくとも含有するトナー粒子と、一次粒子の個数平均粒径が４〜８０ｎｍである無機微粉末と、導電性微粉末とを少なくとも有し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を１５〜６０個数％含有し、且つ３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子を１５〜７０個数％含有する構成とすることで、接触帯電による潜像担持体の帯電不良を有効に防止することができ、直接注入帯電機構での潜像担持体の一様帯電性を向上させることができる。また、現像兼クリーニングでの転写残トナー粒子の回収を高め、転写残トナー粒子の回収不良によるポジゴーストやカブリ等の画像欠陥を有効に防止することができる。
【０１１７】
より詳細に説明すると、本発明の現像剤が有する一次粒子の個数平均粒径が４〜８０ｎｍである無機微粉末は、トナー粒子表面に付着してトナー粒子とともに挙動することで、現像剤の流動性を改良し、トナー粒子の摩擦帯電特性を均一化させる。このため、トナー粒子の転写性を向上させ、接触帯電部材への転写残トナー粒子の混入量を低減し、潜像担持体の帯電性低下を防止し、現像工程における転写残トナー粒子の回収での負荷を低減できる。
【０１１８】
この無機微粉末は、トナー粒子表面に付着してトナー粒子とともに挙動すること、および一次粒子の個数平均粒径が４〜８０ｎｍと小さく、トナーに付着している状態での粒径も一次粒径から凝集体でも０．１μｍ以下のものであり、現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲における個数基準の粒度分布に実質的に影響を与えない。
【０１１９】
これに対し、本発明の現像剤が有する導電性微粉末は、現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数墓準の粒度分布において、粒径が１．００μｍ以上２．００μｍ未満の粒子を１５〜６０個数％含有させることに寄与する。より具体的には、本発明の現像剤が有する導電性微粉末を、少なくとも１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を有するものとし、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が上記範囲となるように、この導電性微粉末を現像剤中に含有させることにより、上記本発明の効果を得ることができる。本発明者らの検討によれば、１．００μｍ以上２．００μｍ未満の粒径範囲の導電性微粉末が現像剤中に存在することにより、接触帯電における接触帯電部材への転写残トナー粒子の付着・混入による像担持体の帯電不良を防止し、直接注入帯電における潜像担持体の一様帯電性を向上させ、現像兼クリーニングを用いた画像形成方法における帯電不良および転写残トナー粒子の回収不良を有効に防止する効果が大きいことが判明した。また、導電性微粉末の現像工程における転写残トナー粒子の回収助剤としての効果には、導電性微粉末の粒径が大きく関与し、転写残トナー粒子の回収助剤として最適な導電性微粉末の粒径範囲が存在し、特に１．００μｍ以上２．００μｍ未満の粒径範囲の粒径を有する導電性微粉末の含有量（個数％）が転写残トナー粒子の回収助剤として効果に深く関与することが判明した。
【０１２０】
１．００μｍ以上２．００μｍ未満の粒径範囲の導電性微粉末の粒子は、トナー粒子表面に強固に付着しにくく、現像工程において像担持体上の非画像部にまで十分に供給され、転写工程においてトナー粒子表面から積極的に遊離し、転写後の潜像担持面を経て効率良く帯電部に供給される。また、上記導電性微粉末は、帯電部において均一に分散して介在できることにより潜像担持体の帯電促進効果が高く、帯電部に安定して保持されるため、画像形成装置の長期にわたる繰り返し使用においても潜像担持体の帯電性の低下を防止し、良好な一様帯電が安定して維持される。また、帯電工程に接触帯電部材を用いた現像兼クリーニング画像形成法のように、転写残トナー粒子による帯電部材の汚染が避けられない場合でも、潜像担持体の帯電性の低下を防止することができる。さらに、導電性微粉末の粒子が転写後の潜像担持面へ効率良く供給され、転写残トナー粒子の回収助剤として特に優れた効果を発揮することで、現像兼クリーニング工程での転写残トナー粒子の回収性を高めることができる。
【０１２１】
上述したように、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布における１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量が１５〜６０個数％であることを特徴とする。上記粒径測定範囲における１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量を上記範囲とすることにより、帯電工程における像担持体の一様帯電性の向上を図ることができる。また、適度な量の導電性微粉末を帯電部に安定して存在させることができるため、後の露光工程において、導電性微粉末が像担持体上に過剰に存在することによる露光不良を防止することができる。現像剤中の１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量が上記範囲よりも少なすぎる場合には、接触帯電による像担持体の一様帯電性を充分に向上させることができず、現像兼クリーニングでの転写残トナー粒子の回収不良を有効に防止する効果が十分ではない。また、現像剤中の１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量が上記範囲よりも多すぎる場合には、過剰の導電性微粉末が帯電部に供給されるため、帯電部に保持しきれない導電性微粉末が露光光を遮る程度までに像担持体上に排出され、露光不良による画像欠陥を生じる、或いは飛散して機内を汚染する等の弊害を著しく生じ易くなる。
【０１２２】
本発明の現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布における粒子径が１．００以上２．００μｍ未満の粒子の含有量は、２０〜５０個数％であることがより好ましく、２０〜４５個数％であることがさらに好ましい。上記粒子の含有量をこの範囲とすることで、接触帯電による潜像担持体の一様帯電性をより向上させ、且つ現像兼クリーニングを用いた画像形成方法における転写残トナー粒子の回収不良を有効に防止する効果がより高まる。更に、過剰の導電性微粉末が帯電部に供給されることを防止し、帯電部に保持しきれない導電性微粉末が多量に潜像担持体上に排出されることによる露光不良による画像欠陥の発生をより確実に抑制できる。
【０１２３】
上述したように、本発明の現像剤に、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を１５〜６０個数％含有させるには、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が上記範囲となるように、この導電性微粉末を現像剤中に含有させればよい。しかしながら、現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子は上記導電性微粉末のみに限られるものではなく、トナー粒子や現像剤に添加される他の粒子が含まれていてもよい。
【０１２４】
本発明の現像剤に含有される少なくとも結着樹脂および着色剤を含有するトナー粒子は、公知の製法によって得ることが可能であり、トナー製法及び製造条件（例えば、トナーの平均粒径や粉砕法によって作製される場合の粉砕条件）によって生じる１．００μｍ以上２．００μｍ未満の粒径範囲のトナー粒子の量は変化する。しかし、現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、トナー粒子に起因する１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量が１０個数％を超えると、１．００μｍ以上２．００μｍ未満の粒径範囲のトナー粒子が有する摩擦帯電性が、平均粒径付近の粒径のトナー粒子が有する摩擦帯電性と大きく異なるため、トリボ分布がブロードになり、現像性が低下する傾向にある。
【０１２５】
すなわち、現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、導電性微粉末に起因する１．００μｍ以上２．００μｍ未満の粒子を５〜６０個数％含有することが好ましい。
【０１２６】
また、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子を１５〜７０個数％含有することを特徴とする。
【０１２７】
本発明の現像剤において、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子は、潜像担持体上に形成された静電潜像を現像してトナー画像を形成し、このトナー画像を転写材に転写することにより転写材上にトナー画像を形成するために、所定量が必要である。また、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子には、潜像担持体上に形成された静電潜像に静電的に付着し、静電潜像を忠実にトナー画像として現像するのに適した摩擦帯電特性を持たせることができる。
【０１２８】
３．００μｍ未満の粒径の粒子は、過剰な帯電を保持するまたは過度に摩擦帯電電荷を減衰させる等、安定した摩擦帯電特性を持たせることが困難となる。そのため、潜像担持体上の静電潜像のない部分（画像の白地部）への付着量が多くなり易く、忠実に静電潜像をトナー画像として現像することが困難である。また、３．００μｍ未満の粒径の粒子は、表面に凹凸を有する転写材（例えば、表面に繊維による凹凸を有する紙）に対しては良好な転写性を維持することが困難となるため、転写残トナー粒子が増大する。このため、転写残トナー粒子が潜像担持体に多量に付着した状態で帯電工程に供され、更には接触帯電部材に多量の転写残トナー粒子が付着・混入するため、潜像担持体の帯電が阻害され、導電性微粉末を介して接触帯電部材が潜像担持体と緻密な接触性を有することで潜像担持体の帯電性を高める本発明の効果を阻害する傾向がある。また、転写残トナー粒子の粒径が小さくなると、現像工程において転写残トナー粒子に働く機械的、静電的、さらに磁性トナーの場合には磁気的な回収力が小さくなるため、相対的に転写残トナー粒子と潜像担持体との付着カが大きくなり、現像工程での転写残トナー粒子の回収性が低下し、転写残トナー粒子の回収不良によるポジゴーストやカブリ等の画像欠陥を生じやすくする傾向がある。
【０１２９】
また、８．９６μｍ以上の粒径の粒子は、静電潜像を忠実にトナー画像として現像するのに十分に高い摩擦帯電特性を持たせることが困難である。一般に、現像剤の粒径が大きいほど得られるトナー画像の解像性が低いものになるが、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が所定の範囲となるように導電性微粉末を含有させた本発明の現像剤では、現像剤中に多くの導電性微粉末の粒子を含有するため、特に粒子径の大きいトナー粒子の摩擦帯電量がより低下し易くなり、８．９６μｍ以上の粒径の粒子には、静電潜像を忠実にトナー画像として現像するのに十分に高い摩擦帯電特性を持たせることが困難となり、良好な解像性を有するトナー画像を得ることがより困難となる。
【０１３０】
従って、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量を上記範囲とすることにより、静電潜像を忠実にトナー画像として現像するのに適した摩擦帯電特性を持たせるトナー粒子を確保し、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が所定の範囲となるように導電性微粉末を含有させた本発明の現像剤を用いて、高画像濃度で解像性に優れた画像を得ることが可能となる。
【０１３１】
本発明において、現像剤中の３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量が上記範囲よりも少なすぎる場合には、静電潜像を忠実にトナー画像として現像するのに適した摩擦帯電特性を持つトナー粒子を確保することが困難となる。このため、得られる画像がカブリが多い、画像濃度が低いまたは解像性の低いものとなる。
【０１３２】
また、現像剤中の３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量が上記範囲よりも多すぎる場合は、前述した１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量を本発明において規定する範囲内とすることが困難となる。また、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が本発明において規定する範囲内にあったとしても、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量に対して、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子が相対的に不足する。このため、接触帯電による像担持体の一様帯電性を十分に向上させることができず、現像兼クリーニングでの転写残トナー粒子の回収不良を有効に防止する効果が十分には得られない。
【０１３３】
本発明の現像剤の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布における粒径が３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量は、２０〜６５個数％であることがより好ましく、２５〜６０個数％であることがさらに好ましい。上記粒子の含有量をこの範囲とすることで、接触帯電による像担持体の一様帯電性をより向上させ、現像兼クリーニングを用いた画像形成方法における転写残トナー粒子の回収不良を有効に防止する効果をより高めることができ、かつ高画像濃度でカブリが少なく解像性に優れた画像を得ることができる。
【０１３４】
上述したように、静電潜像を忠実にトナー画像として現像するのに適した摩擦帯電特性を持たせる粒子を確保し、高画像濃度でカブリが少なく解像性に優れた画像を得るために、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子を、１５〜７０個数％含有する。従って、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の現像剤中の含有量が、トナー粒子に起因することが望ましい。しかしながら、現像剤中の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子はトナー粒子のみに限られるものではなく、導電性微粉末や現像剤に添加される他の粒子が含まれていてもよい。
【０１３５】
本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、８．９６μｍ以上の粒径の粒子を０〜２０個数％含有することが好ましい。
【０１３６】
前述したように、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の現像剤中の含有量が本発明において規定する範囲となるように導電性微粉末を含有させた本発明の現像剤では、現像剤中に多くの導電性微粉末の粒子を含有するため、８．９６μｍ以上の粒径の粒子に静電潜像を忠実にトナー画像として現像するのに十分に高い摩擦帯電特性を持たせることが困難となる。このような上記粒径測定範囲における８．９６μｍ以上の粒子の現像剤中の含有量が、上記範囲よりも多すぎる場合は、現像剤全体として静電潜像を忠実にトナー画像として現像するのに十分に高い摩擦帯電特性を持たせることが困難となり、得られる画像の解像性が低いものになりやすい。
【０１３７】
また、粒子径が８．９６μｍ以上のトナー粒子では、トナー粒子表面において局所的に高い摩擦帯電電荷を保持しやすく、このような部位に導電性微粉末が付着すると、導電性微粉末がトナー粒子から遊離せずにトナー粒子とともに挙動するようになり、転写後の潜像担持体上に供給される導電性微粉末が減少しやすくなる。
【０１３８】
このため、帯電部に導電性微粉末が介在することによる潜像担持体の帯電促進効果が十分には得られない場合がある。また、転写後の潜像担持体上に供給される導電性微粉末が減少しやすいことで、転写残トナーの回収性を向上させる効果が得られない場合がある。
【０１３９】
更に、粒径の大きなトナー粒子が、転写残トナー粒子として帯電部に持ち運ばれると、接触帯電部材の潜像担持体への接触性を損ない、潜像担持体の帯電不良を引き起こし易くなる。すなわち、導電性微粉末を介して接触帯電部材が潜像担持体と緻密な接触性を有することで潜像担持体の一様帯電性を高める本発明の効果が得られない場合がある。また、粒径の大きな転写残トナー粒子を現像工程で回収しようとする場合にも、粒径の大きな転写残トナー粒子が回収されずに画像欠陥を生じてしまう、あるいは潜像形成工程での露光を遮ることで画像欠陥となってしまう場合がある。
【０１４０】
従って、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、８．９６μｍ以上の粒子径の粒子が現像剤中で０〜１０個数％であることがより好ましく、０〜７個数％であることがさらに好ましい。上記粒子の含有量をこの範囲とすることで、より高画像濃度でカブリが少なく解像性に優れた画像を得ることができる。また、導電性微粉末を介して接触帯電部材が潜像担持体と緻密な接触性を有することで潜像担持体の一様帯電性を高める上でより優位であり、現像での転写残トナーの回収不良及び潜像形成工程での露光の遮光による画像欠陥の発生を抑制する上でより優位となる。
【０１４１】
また、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量をＡ個数％、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量をＢ個数％としたときに、Ａ＞Ｂの関係を満足することが好ましく、Ａ＞２Ｂの関係を満足することがより好ましい。
【０１４２】
すなわち、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量Ｂ個数％は、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量Ａ個数％よりも少ないことが好ましい。本発明の現像剤の０．６０μｍ以上１５９．２１μｍ未満の測定粒径範囲における個数基準の粒度分布が上記関係を満足する場合、帯電部において導電性微粉末が均一に分散して介在することができ、良好な一様帯電性が得られる。
【０１４３】
上記ＡおよびＢがＡ＞Ｂの関係を満足しない場合には、帯電部に介在する導電性微粉末の均一分散性が低下し、あるいは接触帯電部材での導電性微粉末の保持性が劣り、潜像担持体の帯電均一化効果が低下し易くなる。また、帯電部への導電性微粉末の供給性が劣り、長期にわたる繰り返し使用によって、潜像担持体の帯電の促進効果が低下して潜像担持体の帯電が不安定となりやすい。また、上記Ａ＞Ｂの関係が成立しない場合には、転写性が比較的低い２．００μｍ以上３．００μｍ未満の粒径範囲のトナー粒子がより多く帯電部に供給され保持されるために、導電性微粉末の帯電部での保持性を相対的に低下させ、画像形成装置の長期にわたる繰り返し使用によっては潜像担持体の一様帯電を阻害しやすく、転写残トナー粒子中のトナー粒子の微粒子が増加することで、転写残トナー粒子の回収性が低下し、ポジゴーストやカブリを生じ易くなる。
【０１４４】
つまり、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子のうちの導電性微粉末粒子は、１．００μｍ以上２．００μｍ未満の粒径範囲の粒径を有する導電性微粉末よりも帯電部に導電性微粉末が介在することによって得られる帯電促進効果が大幅に劣り、転写残トナー粒子の現像での回収性向上効果にも劣る。２．００μｍ以上３．００μｍ未満の粒径範囲の粒子のうちのトナー粒子は、摩擦帯電性が不安定であるためにカブリを生じやすく、転写性も低い。このため、より多くの転写残トナー粒子が帯電部に供給されることとなり、潜像担持体の一様帯電を阻害しやすい。また、転写残トナー粒子が増加すること、及び転写残トナーの摩擦帯電性が不安定であることにより、現像での転写残トナー粒子の回収性が低下しやすい。よって、２．００μｍ以上３．００μｍ未満の粒径範囲の粒径を有する粒子の含有量が少ないことが好ましい。すなわち、現像剤の粒度分布全体における、２．００μｍ以上３．００μｍ未満の粒径範囲の粒径を有する粒子の含有比率が少ない方が好ましい。
【０１４５】
これらの観点より、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量Ａ個数％が、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量Ｂ個数％よりも多いことが好ましく、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量Ａ個数％が、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量Ｂ個数％の２倍よりも大きいことがより好ましい。
【０１４６】
また、３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量をＣ個数％とするとき、このＣ個数％が２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量Ｂ個数％の２倍よりも大きいことが好ましく、３倍よりも大きいことがより好ましい。
【０１４７】
０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、２．００μｍ以上３．００μｍ未満の粒径範囲の粒子の含有量Ｂ個数％は、２０個数％以下であることが好ましく、より好ましくは１０％以下であり、特に好ましくは５％以下である。
【０１４８】
また、本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布において、３．００μｍ以上１５．０４μｍ未満の粒径範囲での次式で示される個数分布の変動係数Ｋ_ｎが、５〜４０であることが好ましい。
【０１４９】
個数基準の粒度分布の変動係数Ｋ_ｎ＝（Ｓ_ｎ／Ｄ_１）×１００
〔式中、Ｓ_ｎは３．００μｍ以上１５．０４μｍ未満の粒径範囲における個数分布の標準偏差を表し、Ｄ_１は３．００μｍ以上１５．０４μｍ未満の粒径範囲における個数基準の平均円相当径（μｍ）を表す。〕
上記変動係数Ｋ_ｎを５〜４０とすることにより、トナー粒子と導電性微粉末との均一な混合性が得られ、導電性微粉末が潜像担持体上へより均一に供給されることにより、潜像担持体の帯電均一化効果をより高めることができる。また、トナー粒子の帯電量分布がシャープ化され、カブリとなるトナー粒子及び転写残トナー粒子が減少し、潜像担持体の帯電阻害をより安定して抑制できる。また、現像工程での転写残トナー粒子の回収をより安定して行うことができるため、回収不良に起因する画像欠陥をより確実に抑制できる。トナー粒子の帯電量分布をさらにシャープ化させるためには、上記変動係数Ｋ_ｎが５〜３０であることがより好ましい。
【０１５０】
また本発明の現像剤は、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる現像剤の重量平均粒径（Ｄ_４）が４〜１０μｍであることが好ましく、３．００μｍ以上１５．０４μｍ未満の粒径範囲において下記式で示される体積基準の粒度分布の変動係数Ｋ_ｖが１０〜３０であることが好ましい。
【０１５１】
体積基準の粒度分布の変動係数Ｋ_ｖ＝（Ｓ_ｖ／Ｄ_４）×１００
〔式中、Ｓ_ｖは３．００μｍ以上１５．０４μｍ未満の粒径範囲における体積分布の標準偏差を表し、Ｄ_４は３．００μｍ以上１５．０４μｍ未満の粒径範囲における体積基準の体積平均粒径（μｍ）を表す。〕
上記体積基準の粒度分布の変動係数Ｋ_ｖが１０〜３０であることで、現像剤の３．００μｍ以上１５．０４μｍ未満の粒径範囲での粒子の帯電量分布がシャープ化され、カブリとなるトナー粒子及び転写残トナー粒子が減少し、より安定して像担持体の帯電阻害を抑制できる。また、現像兼クリーニング工程での転写残トナー粒子の回収性を高めることができるため、回収不良による画像欠陥を有効に防止できる。したがって、上記変動係数Ｋ_ｖは１０〜２５であることがより好ましい。
【０１５２】
上記変動係数Ｋ_ｎまたはＫ_ｖが上記範囲よりも小さすぎる場合には、トナー粒子の製造が困難となリ、上記変動係数Ｋ_ｎまたはＫ_ｖが上記範囲よりも大きすぎる場合には、トナー粒子と無機微粉末及び導電性微粉末との均一な混合性が得られにくく、像担持体の安定した帯電促進効果が得られにくい。また、現像剤全体としての帯電量分布がブロードとなり、画像濃度の低下、カブリの増大などによる画質低下を生じる。更には、転写残トナー粒子量が増大し、帯電性を阻害し、現像兼クリーニング工程での転写残トナー粒子の回収率が低下する。
【０１５３】
上記変動係数Ｋ_ｖを１５〜３０とすることにより、現像剤の３．００μｍ以上１５．０４μｍ未満の粒径範囲における粒子の帯電量分布がシャープ化され、カブリとなるトナー粒子及び転写残トナー粒子が減少し、像担持体の帯電阻害をより安定して抑制できる。また、現像兼クリーニング工程での転写残トナー粒子の回収性を高めることができるため、トナー粒子の回収不良による画像欠陥を有効に防止できる。なお、上記変動係数Ｋ_ｖは１５〜２５であることがより好ましい。
【０１５４】
更に、本発明の現像剤は、下記式より求められるトナーの平均円形度が０．９７０未満が好ましい。平均円形度が０．９７０以上である場合には、トナー表面上に外添剤が保持されにくくなり、結果として帯電が不均一となりカブリが発生しやすくなる。また、耐久使用中の現像剤撹拌や昇温などによる外添剤の埋め込まれ等が起こり、トナー表面の劣化が著しいものとなり耐久性等に問題を生じる様になる。
【０１５５】
円形度ａ＝Ｌ_０／Ｌ
〔式中、Ｌ_０は粒子の投影像と同じ面積をもつ円の周囲長を示し、Ｌは粒子の投影像の周囲長を表す。〕
本発明の現像剤は、３．００μｍ以上１５．０４μｍ未満の粒径範囲において、下記式より求められる円形度分布の標準偏差ＳＤが０．０４５以下であることが好ましい。
標準偏差ＳＤ＝｛Σ（ａ_ｉ−ａ_ｍ）^２／ｎ｝^１／２
〔式中、ａ_ｉは３．００μｍ以上１５．０４μｍ未満の粒径範囲における各粒子の円形度を表し、ａ_ｍは３．００μｍ以上１５．０４μｍ未満の粒子の平均円形度を表し、ｎは粒径が３．００μｍ以上１５．０４μｍ未満の全粒子数を示す。〕
現像剤の上記円形度分布の標準偏差ＳＤが０．０４５以下であることで、トナー粒子からの導電性微粉末の遊離性が安定し、像担持体上への導電性微粉末の供給がより安定するため、より安定して像担持体の帯電阻害を抑制でき、現像とクリーニングを行う工程（すなわち、現像兼クリーニング工程）でのトナー粒子の回収性がより安定する。
【０１５６】
本発明において、現像剤の粒径、粒度分布及び円形度分布は、フロー式粒子像分析装置ＦＰＩＡ−１０００（東亜医用電子社製）によって測定される円相当径を「粒径」と定義し、粒径０．６０μｍ以上１５９．２１μｍ未満の個数基準の粒度分布及び円形度分布を用いて求められる値である。
【０１５７】
フロー式粒子像分析装置による測定は以下の方法によって行われる。フィルターを通して微細なごみを取り除き、その結果として１０^３ｃｍ^３中に測定範囲（例えば、円相当径０．６０μｍ以上１５９．２１μｍ未満）の粒子数が２０個以下とした水１０ｍｌ中に希釈した界面活性剤（好ましくはアルキルベンゼンスルフォン酸塩を微細なごみを取り除いた水で１０倍程度に薄めたもの）を数滴加える。これに測定試料を適当量（例えば、０．５〜２０ｍｇ）加え、超音波ホモジナイザー（出力５０Ｗ、６ｍｍ径ステップ型チップ）で３分間分散処理を行い、測定試料の粒子濃度を７０００〜１００００個／１０^−３ｃｍ^３（測定円相当径範囲の粒子を対象として）に調整した試料分散液を用いて、０．６０μｍ以上１５９．２１μｍ未満の円相当径を有する粒子の粒度分布及び円形度分布を測定する。
【０１５８】
測定の概略は、東亜医用電子社（株）発行のＦＰＩＡ−１０００のカタログ（１９９５年６月版）、測定装置の操作マニュアル及び特開平８−１３６４３９号公報に記載されているが、以下の通りである。
【０１５９】
試料分散液は、フラットで扁平な透明フローセル（厚み約２００μｍ）の流路（流れ方向に沿って広がっている）を通過させる。フローセルの厚みに対して交差して通過する光路を形成するように、ストロボとＣＣＤカメラが、フローセルに対して、相互に反対側に位置するように装着される。試料分散液が流れている間に、ストロボ光がフローセルを流れている粒子の画像を得るために１／３０秒間隔で照射される。その結果、それぞれの粒子は、フローセルに平行な一定範囲を有する２次元画像として撮影される。それぞれの粒子の２次元画像の面積から、この２次元画像の面積と同一の面積を有する円の直径を円相当径として算出する。
【０１６０】
また、それぞれの粒子の２次元画像から各粒子の周長が求められ、この２次元画像の面積と同一の面積を有する円の周長との比を算出することにより円形度分布が求められる。
【０１６１】
測定結果（粒度分布及び円形度分布の頻度％及び累積％）は、下記の表１に示す通り、０．０６〜４００μｍの範囲を２２６チャンネル（１オクターブに対し３０チャンネルに分割）に分割して得ることができる。実際の測定では、円相当径が０．６０μｍ以上１５９．２１μｍ未満の範囲で粒子の測定を行う。
【０１６２】
【表１】

【０１６３】
なお、本発明で用いている測定装置である「ＦＰＩＡ−１０００」は、各粒子の円形度を算出後、平均円形度の算出に当たって、粒子を得られた円形度によって、円形度０．４０〜１．００を６１分割したクラスに分け、分割点の中心値と頻度を用いて平均円形度の算出を行う算出法を用いている。しかしながら、この算出法で算出される平均円形度の値と、各粒子の円形度の相加平均によって算出される平均円形度との誤差は、非常に少なく、実質的には無視できる程度のものであり、本発明においては、算出時間の短縮化や算出演算式の簡略化等のデータの取り扱い上の理由で、このような算出法を用いてもよい。
【０１６４】
また、本発明の現像剤は、粒径が０．１〜１０μｍの導電性微粉末の粒子をトナー粒子１００個あたり５〜５００個有することが好ましい。粒径が０．１〜１０μｍの導電性微粉末の粒子は、トナー粒子から遊離して挙動し易く、帯電部材に均一に付着し且つ安定して保持される。このため、現像剤中に粒径が０．１〜１０μｍの導電性微粉末の粒子をトナー粒子１００個あたり５〜５００個有することで、現像工程及び転写工程において像担持体上への導電性微粉末の供給がより促進され、像担持体の帯電性をより安定して均一化できる。また、現像剤中に粒径が０．１〜１０μｍの導電性微粉末の粒子をトナー粒子１００個あたり５〜５００個有することで、現像兼クリーニング工程における転写残トナー粒子の回収性がより安定する。
【０１６５】
本発明の現像剤において、粒径が０．１〜１０μｍの導電性微粉末の粒子がトナー粒子１００個あたり５個未満の場合には、導電性微粉末に起因する１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を５〜６０個数％含有させることが困難であり、上述した１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を１５〜６０個数％含有することによる像担持体の帯電促進効果および現像兼クリーニングにおける転写残トナー粒子の回収性向上効果等の本発明の効果が著しく減少する場合もある。また、本発明の現像剤において、粒径が０．１〜１０μｍの導電性微粉末の粒子がトナー粒子１００個あたり５００個よりも大幅に多いと、トナー粒子に対する導電性微粉末の粒子の比率が高すぎるために、トナー粒子の摩擦帯電を阻害し、現像剤としての現像性および転写性を低下させ、画像濃度の低下、カブリの増加、転写残トナー粒子の増加による一様帯電性の低下および現像兼クリーニングでの転写残トナー粒子の回収不良の発生を生じ易くなる。このような観点から、現像剤中に０．１〜１０μｍの導電性微粉末の粒子をトナー粒子１００個あたり５〜３００個有することがより好ましく、１０〜２００個有することが更に好ましい。
【０１６６】
本発明の現像剤中でのトナー粒子１００個あたりの０．１〜１０μｍの導電性微粉末の個数は、以下のように測定することにより得られる値である。すなわち、走査型電子顕微鏡により拡大撮影した現像剤の写真と、更に走査型電子顕微鏡に付属させたＸＭＡ等の元素分析手段によって導電性微粉末の含有する元素でマッピングされた現像剤の写真を対照し、トナー粒子１００個に対して、トナー粒子表面に付着或いは遊離して存在している導電性微粉末を特定し、特定された導電性微粉末のうち画像処理装置（例えば、日立製作所製ＦＥ−ＳＥＭＳ−８００から、３０００〜１００００倍に拡大した画像情報をインターフェースを介して、例えばニレコ社製画像解析装置ＬｕｚｅｘＩＩＩに導入し解析する）によって求められる円相当径０．１〜１０μｍの導電性微粉末の粒子数をカウントして得られる値である。
【０１６７】
また、本発明の現像剤は、導電性微粉末の含有量が現像剤全体の０．１〜１０質量％であることが好ましい。導電性微粉末の含有量を上記範囲とすることにより、像担持体の帯電を促進するための適度な量の導電性微粉末を帯電部に供給することができ、現像兼クリーニングにおいて転写残トナー粒子の回収性を高めるために必要な量の導電性微粉末を像担持体上に供給することができる。現像剤の導電性微粉末の含有量が上記範囲よりも小さすぎる場合には、帯電部に供給される導電性微粉末量が不足し易く、像担持体の安定した帯電促進効果が得られにくい。この場合、現像兼クリーニングを用いる画像形成においても、現像時に転写残トナー粒子とともに像担持体上に介在する導電性微粉末量が不足し易く、転写残トナー粒子の回収性が十分には向上しない場合がある。また、現像剤の導電性微粉末の含有量が上記範囲よりも大きすぎる場合には、過剰の導電性微粉末が帯電部に供給され易く、帯電部に保持しきれない導電性微粉末が多量に像担持体上に排出されることによる露光不良を生じ易くなる。また、トナー粒子の摩擦帯電特性を低下させる、或いは乱し、画像濃度低下やカブリの増加の原因となる場合がある。
【０１６８】
このような観点から、現像剤の導電性微粉末の含有量は、０．１〜１０質量％であることがより好ましく、０．２〜５質量％であることがさらに好ましい。
【０１６９】
また、導電性微粉末の抵抗は、潜像担持体の帯電促進効果および転写残トナー粒子回収性の向上効果を現像剤に付与するために、１０^９Ω・ｃｍ以下であることが好ましい。導電性微粉末の抵抗が上記範囲よりも大きすぎると、導電性微粉末を帯電部材と潜像担持体との接触部或いはその近傍の帯電領域に介在させ、導電性微粉末を介しての接触帯電部材の潜像担持体への緻密な接触性を維持させても、潜像担持体の良好な一様帯電性を得るための帯電促進効果が小さくなる。現像兼クリーニングにおいても、導電性微粉末が転写残トナー粒子と同極性の電荷を帯び易くなり、導電性微粉末の電荷が転写残トナー粒子と同極性で大きくなると、転写残トナー粒子回収性の向上効果が大幅に低下する。
【０１７０】
導電性微粉末による潜像担持体の帯電促進効果を十分に引き出し、潜像担持体の良好な一様帯電性を安定して得るためには、導電性微粉末の抵抗が接触帯電部材の表面部或いは潜像担持体との接触部の抵抗よりも小さいことが好ましく、この接触帯電部材の抵抗の１／１００以下であることがさらに好ましい。
【０１７１】
更に、導電性微粉末の抵抗が１０^６Ω・ｃｍ以下であることが、絶縁性の転写残トナー粒子の接触帯電部材への付着・混入による帯電阻害に打ち勝って像担持体の一様帯電をより良好に行わせる上で、また、現像兼クリーニングにおいて転写残トナー粒子の回収性の向上効果をより安定して得る上で好ましい。この導電性微粉末の抵抗は１０^０〜１０^５Ω・ｃｍであることがさらに好ましい。
【０１７２】
本発明において、導電性微粉末の抵抗測定は錠剤法により測定し正規化して求めることができる。即ち、底面積２．２６ｃｍ^２の円筒内に約０．５ｇの粉体試料を入れ、粉体試料の上下に配置された上下電極間に１４７Ｎ（１５ｋｇ）の加圧を行うと同時に１００Ｖの電圧を印加して抵抗値を計測し、その後正規化して比抵抗を算出する。
【０１７３】
また、導電性微粉末は、透明、白色または淡色の導電性微粉末であることが、転写材上に転写される導電性微粉末がカブリとして目立たないため好ましい。潜像形成工程における露光光の妨げになることを防ぐ点からも、導電性微粉末は透明、白色或いは淡色の導電性微粉末であることが好ましい。さらに、導電性微粉末はこの静電潜像を形成する像露光光に対する透過率が３０％以上であることが好ましい。この透過率は３５％以上であることがさらに好ましい。
【０１７４】
以下、本発明における導電性微粉末の光透過性の測定方法の一例を示す。片面に接着層を有する透明なフィルムの接着層上に導電性微粉末を一層分固定した状態で透過率を測定する。光はシートの鉛直方向から照射し、フィルム背面まで透過した光を集光してその光量を測定する。フィルムのみの場合と導電性微粉末を付着したときの光量の差に基づいて、正味の光量としての光透過率を算出した。実際にはＸ−Ｒｉｔｅ社製３１０Ｔ透過型濃度計を用いて測定することができる。
【０１７５】
また、導電性微粉末は非磁性であることが好ましい。導電性微粉末が非磁性であることで、透明、白色または淡色の導電性微粉末が得られやすい。反対に、磁性を有する導電性材料は、透明、白色または淡色とすることが困難である。また、現像剤担持のために磁気力による現像剤の搬送及び保持を行う画像形成法においては、磁性を有する導電性微粉末は現像されにくいため、像担持体上への導電性微粉末の供給が不足したり、現像剤担持体表面に導電性微粉末が蓄積することにより、トナー粒子の現像を妨げる等の弊害を起こし易い。更に、磁性トナー粒子に磁性を有する導電性微粉末を添加すると、磁気的凝集力によりトナー粒子から導電性微粉末が遊離しにくくなる傾向があり、導電性微粉末の像担持体上への供給性が低下し易い。
【０１７６】
本発明における導電性微粉末としては、例えばカーボンブラック、グラファイトの如き炭素微粉末；銅、金、銀、アルミニウム、ニッケルの如き金属微粉末；酸化亜鉛、酸化チタン、酸化錫、酸化アルミニウム、酸化インジウム、酸化珪素、酸化マグネシウム、酸化バリウム、酸化モリブデン、酸化鉄、酸化タングステンの如き金属酸化物；硫化モリブデン、硫化カドミウム、チタン酸カリの如き金属化合物、あるいはこれらの複合酸化物が必要に応じて粒度及び粒度分布を調整することで使用できる。
【０１７７】
導電性微粉末は、これらの中でも酸化亜鉛、酸化スズ、酸化チタンから選ばれる少なくとも一種の酸化物を含有していることが好ましい。更には、酸化亜鉛、酸化スズ、酸化チタンの如き無機酸化物を少なくとも表面に有する微粒子が特に好ましい。これらの酸化物は、導電性微粉末としての抵抗を低く設定することが可能であり、非磁性であり、白色或いは淡色であり、転写材上に転写される導電性微粉末がカブリとして目立たないため好ましい。
【０１７８】
また、導電性微粉末が導電性無機酸化物からなる場合或いは導電性無機酸化物を含む場合には、抵抗値を制御する等の目的で、該導電性無機酸化物の主金属元素と異なるアンチモン、アルミニウムの如き元素を含有させた金属酸化物や、導電性材料を用いることもできる。例えば、アルミニウムを含有する酸化亜鉛、アンチモンを含有する酸化第二スズ微粒子、あるいは酸化チタン、硫酸バリウム或いはホウ酸アルミニウムの表面をアンチモンを含有する酸化スズで処理して得られる微粒子である。導電性無機酸化物にアンチモン、アルミニウムなどの元素を含有させる量としては、０．０５〜２０質量％とすることが好ましく、より好ましくは０．０５〜１０質量％、特に好ましくは０．１〜５質量％である。
【０１７９】
また、該無機酸化物を酸素欠損型とした導電性無機酸化物も好ましく用いられる。
【０１８０】
市販の酸化スズ・アンチモン処理された導電性酸化チタン微粒子としては、例えばＥＣ−３００（チタン工業株式会社）、ＥＴ−３００、ＨＪ−１、ＨＩ−２（以上、石原産業株式会社）、Ｗ−Ｐ（三菱マテリアル株式会社）などが挙げられる。
【０１８１】
市販のアンチモンドープの導電性酸化スズとしては、例えばＴ−１（三菱マテリアル株式会社）やＳＮ−１００Ｐ（石原産業株式会社）などが、また市販の酸化第二スズとしては、ＳＨ−Ｓ（日本化学産業株式会社）などが挙げられる。
【０１８２】
特に好ましいものとしては、高い白色度或いは透光性が得られる点で、アルミニウムを含有する酸化亜鉛等の金属酸化物、酸素欠損型の酸化亜鉛、酸化スズ、酸化チタン等の金属酸化物、及びこれらを少なくとも表面に有する微粒子が挙げられる。
【０１８３】
また、粒径は０．１〜１０μｍであることが好ましい。導電性微粉末の体積平均粒径が上記範囲よりも小さすぎると、現像性の低下を防ぐために、導電性微粉末の現像剤に対する含有量を小さく設定しなければならない。導電性微粉末の添加量を少なく設定しすぎると、導電性微粉末の有効量を確保できず、帯電工程において、絶縁性の転写残トナー粒子の付着・混入による接触帯電部材への帯電阻害に打ち勝って潜像担持体の帯電を良好に行わせるのに十分な量の導電性微粉末を、帯電部材と潜像担持体との接触部或いはその近傍の帯電領域に介在させることができず、帯電不良を生じ易くなる。この観点から、導電性微粉末の体積平均粒径は０．１μｍ以上、好ましくは０．１５μｍ以上、更に好ましくは０．２μｍ以上が良い。
【０１８４】
また、導電性微粉末の体積平均粒径が上記範囲よりも大きすぎると、帯電部材から脱落した導電性微粉末が、静電潜像を形成する露光光を遮光或いは拡散するため、静電潜像の欠陥を生じて画像品位を低下させる場合があり好ましくない。更に、導電性微粉末の体積平均粒径が上記範囲よりも大きすぎると、単位重量当たりの導電性微粉末の粒子数が減少するため、転写残トナー粒子の回収性向上が十分には得られなくなる。また、導電性微粉末の粒子数が減少するため、帯電部材からの導電性微粉末の脱落等による帯電部材及びその近傍に介在する導電性微粉末の減少、劣化を考慮すると、導電性微粉末を帯電部材と像担持体との接触部或いはその近傍の帯電領域に逐次供給し続け介在させるために、また、接触帯電部材が導電性微粉末を介して像担持体への緻密な接触性を維持し良好な一様帯電性を安定して得るためには、導電性微粉末の現像剤に対する含有量を大きくせざるを得なくなる。しかし、導電性微粉末の含有量を大きくしすぎると、特に高湿環境下での現像剤全体としての帯電能、現像性を低下させ、画像濃度低下やトナー飛散を生ずる。このような観点から、導電性微粉末の体積平均粒径は１０μｍ以下であることがより好ましく、最適には５μｍ以下であることが良い。
【０１８５】
上記導電性微粉末の体積平均粒径及び粒度分布の測定法を例示する。コールター社製、ＬＳ−２３０型レーザー回折式粒度分布測定装置にリキッドモジュールを取り付けて０．０４〜２０００μｍの粒径を測定範囲とし、得られる体積基準の粒度分布より導電性微粉末の体積平均粒径を算出する。測定手順としては、純水１０ｃｃに微量の界面活性剤を添加し、これに導電性微粉末の試料１０ｍｇを加え、超音波分散機（超音波ホモジナイザー）にて１０分間分散した後、測定時間９０秒、測定回数１回で測定する。
【０１８６】
トナーからの測定においては、純水１００ｇに対して、微量の界面活性剤を添加してトナーを２〜１０ｇを加え、超音波分散機（超音波ホモジナイザー）にて１０分間分散した後、遠心分離機等により、トナー粒子と上記導電性微粉末を分離する。磁性トナーの場合は磁石を利用することもできる。分離した分散液を測定時間９０秒、測定回数１回で測定する。
【０１８７】
本発明において、導電性微粉末の粒径及び粒度分布の調整方法としては、導電性微粉末の一次粒子が製造時において所望の粒径及び粒度分布が得られるように製造法、製造条件を設定する方法以外にも、一次粒子の小さな粒子を凝集させる方法、一次粒子の大きな粒子を粉砕する方法或いは分級による方法等が可能であり、更には、所望の粒径及び粒度分布の基材粒子の表面の一部もしくは全部に導電性粒子を付着或いは固定化する方法、所望の粒度及び粒度分布の粒子に導電性成分が分散された形態を有する導電性微粒子を用いる方法等も可能であり、これらの方法を組み合わせて導電性微粉末の粒径及び粒度分布を調整することも可能である。
【０１８８】
導電性微粉末の粒子が凝集体として構成されている場合の粒径は、その凝集体としての平均粒径として定義される。導電性微粉末は、一次粒子の状態で存在するばかりでなく二次粒子の凝集した状態で存在することも間題はない。どのような凝集状態であれ、凝集体として帯電部材と像担持体との接触部或いはその近傍の帯電領域に介在し、帯電補助或いは促進の機能が実現できればその形態は問わない。
【０１８９】
本発明の現像剤は、一次粒子の個数平均粒径が４〜８０ｎｍの無機微粉末をさらに有する。無機微粉末の一次粒子の個数平均粒径が上記範囲よりも大きすぎる場合、または上記範囲の無機微粉末が添加されていない場合には、転写残トナー粒子が帯電部材へ付着した際に帯電部材に固着し易くなり、潜像担持体の良好な一様帯電性を安定して得ることが困難となる。また、導電性微粉末を現像剤中でトナー粒子に対して均一に分散させることが困難となり、導電性微粉末の潜像担持体上への供給むらを生じやすく、接触帯電部材への供給むらを生じた場合には導電性微粒子の供給が不足した部分に対応した潜像担持体の帯電不良を生じ、画像欠陥となりやすい。また、現像兼クリーニング時において潜像担持体上の導電性微粉末の介在量のむらが生ずる場合には、転写残トナー粒子の回収性が一時的或いは部分的に低下することによる回収不良を生じる。更に、現像剤の良好な流動性が得られず、トナー粒子への摩擦帯電付与が不均一になり易いため、カブリの増大、画像濃度の低下、トナー飛散等の問題が生じやすい。無機微粉末の一次粒子の個数平均粒径が４ｎｍよりも小さい場合には、無機微粉末の凝集性が強まり、一次粒子ではなく解砕処理によっても解れ難い強固な凝集性を持つ粒度分布の広い凝集体として挙動し易くなるため、無機微粉末の凝集体の現像による画像抜け、像担持体、現像剤担持体或いは接触帯電部材等を傷つけるなどによる画像欠陥を生じ易くなる。これらの観点から、無機微粉末の一次粒子の個数平均粒径は６〜５０ｎｍであることがより好ましく、８〜３５ｎｍであることが更に好ましい。
【０１９０】
すなわち本発明において、上記一次粒子の平均径を有する無機微粉末は、トナー粒子の表面に付着させることで現像剤の流動性を改良し、トナー粒子の摩擦帯電を均一化するために添加されるのみでなく、導電性微粉末を現像剤中でトナー粒子に対して均一に分散させ、潜像担持体上に均一に導電性微粉末を供給せしめる効果も併せ持つ。
【０１９１】
本発明において、無機微粉末の一次粒子の個数平均粒径は以下の方法により測定することにより得られる値である。すなわち、走査型電子顕微鏡により拡大撮影した現像剤の写真と、更に走査型電子顕微鏡に付属させたＸＭＡ等の元素分析手段によって無機微粉末の含有する元素でマッピングされた現像剤の写真を対照し、トナー表面に付着或いは遊離して存在している無機微粉末の一次粒子を１００個以上測定し、個数平均粒径を求めることが出来る。
【０１９２】
また、本発明において無機微粉末は、一次粒子の個数平均粒径４〜８０ｎｍのシリカ、チタニア、アルミナから選ばれる少なくとも１種を含有することが好ましい。例えば、シリカ微粉体としてはケイ素ハロゲン化物の蒸気相酸化により生成されたいわゆる乾式法又はヒュームドシリカと称される乾式シリカ、及び水ガラス等から製造されるいわゆる湿式シリカの両者が使用可能であるが、表面及びシリカ微粉体の内部にあるシラノール基が少なく、またＮａ_２Ｏ、ＳＯ^３−等の製造残滓の少ない乾式シリカの方が好ましい。また乾式シリカにおいては、製造工程において例えば、塩化アルミニウム、塩化チタンの如き金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによって、シリカと他の金属酸化物の複合微粉体を得ることも可能でありそれらも包含する。
【０１９３】
また、本発明において無機微粉末は、疎水化処理されていることが好ましい。無機微粉末を疎水化処理することによって、無機微粉末の高湿環境における帯電性の低下を防止し、無機微粉末が表面に付着したトナー粒子の摩擦帯電量の環境安定性を向上させることで、現像剤としての画像濃度、カブリ等の現像特性の環境安定性をより高めることができる。無機微粉末の帯電性、及び無機微粉末が表面に付着したトナー粒子の摩擦帯電量の環境による変動を抑制することで、導電性微粉末のトナー粒子からの遊離し易さが変動することを防止でき、導電性微粉末の像担持体上への供給量を安定化し、像担持体の帯電性及び転写残トナー粒子回収性の環境安定性を高めることができる。
【０１９４】
疎水化処理の処理剤としては、シリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シラン化合物、シランカッブリング剤、その他有機硅素化合物、有機チタン化合物の如き処理剤を単独で或いは併用して処理しても良い。その中でも、無機微粉末は少なくともシリコーンオイルで処理されていることが特に好ましい。
【０１９５】
上記シリコーンオイルは、２５℃における粘度が１０〜２００，０００ｍｍ^２／ｓのものが、さらには３，０００〜８０，０００ｍｍ^２／ｓのものが好ましい。シリコーンオイルの粘度が上記範囲よりも小さすぎる場合には、無機微粉末の処理に安定性が無く、処理したシリコーンオイルが熱および機械的な応力により脱離、転移或いは劣化して画質が劣化する傾向がある。また、粘度が上記範囲よりも大きすぎる場合には、無機微粉末の均一な処理が困難になる傾向がある。
【０１９６】
使用されるシリコーンオイルとしては、例えばジメチルシリコーンオイル、メチルフェニルシリコーンオイル、α−メチルスチレン変性シリコーンオイル、クロルフェニルシリコーンオイル、フッ素変性シリコーンオイルが特に好ましい。
【０１９７】
シリコーンオイルの処理の方法としては、例えばシラン化合物で処理された無機微粉末とシリコーンオイルとをヘンシェルミキサー等の混合機を用いて直接混合してもよいし、無機微粉末にシリコーンオイルを噴霧する方法を用いてもよい。あるいは適当な溶剤にシリコーンオイルを溶解あるいは分散せしめた後、シリカ微粉体を加え混合し溶剤を除去する方法でもよい。無機微粉末の凝集体の生成が比較的少ない点から、噴霧機を用いる方法がより好ましい。
【０１９８】
シリコーンオイルの処理量は無機微粉末１００質量部に対し１〜２３質量部、好ましくは５〜２０質量部が良い。シリコーンオイルの量が上記範囲よりも少なすぎると良好な疎水性が得られず、多すぎるとカブリ発生等の不具合が生ずることがある。
【０１９９】
また、本発明において無機微粉末は、少なくともシラン化合物で処理すると同時に、またはその後にシリコーンオイルで処理されていることが好ましい。無機微粉末の処理にシラン化合物を用いることが、シリコーンオイルの無機微粉末への付着性を高めて、無機微粉末の疎水性及び帯電性を均一化する上で特に好ましい。
【０２００】
無機微粉末の処理条件としては、例えば第一段反応としてシリル化反応を行いシラノール基を化学結合により消失させた後、第二段反応としてシリコーンオイルにより表面に疎水性の薄膜を形成することができる。
【０２０１】
また、本発明の現像剤は、無機微粉末の含有量が現像剤全体の０．１〜３．０質量％であることが好ましい。無機微粉末の含有量が上記範囲より少なすぎる場合には、無機微粉末を添加することの効果が十分に得られず、また上記範囲より多すぎる場合には、トナー粒子に対して過剰な無機微粉末が導電性微粉末を被覆してしまい、導電性微粉末が抵抗が高い場合と同様な挙動を示すようになり、像担持体上への導電性微粉末の供給性の低下、帯電促進効果の低下、転写残トナー粒子の回収性の低下等の本発明の効果を損なうようになる。無機微粉末の含有量は、現像剤全体の０．３〜２．０質量％であることがより好ましく、さらに好ましくは０．５〜１．５質量％である。
【０２０２】
本発明で用いられる一次粒子の個数平均径が４〜８０ｎｍの無機微粉末は、ＢＥＴ法で測定した窒素吸着による比表面積が２０〜２５０ｍ^２／ｇのものが好ましく、４０〜２００ｍ^２／ｇのものがより好ましい。比表面積は、ＢＥＴ法に従い、比表面積測定装置オートソーブ１（湯浅アイオニクス社製）を用いて試料表面に窒素ガスを吸着させ、ＢＥＴ多点法を用いて算出することができる。
【０２０３】
本発明において、トナー粒子は結着樹脂及び着色剤を少なくとも含有する着色樹脂粒子である。トナー粒子の抵抗は１０^１０Ω・ｃｍ以上であることが好ましく、１０^１２Ω・ｃｍ以上であることがより好ましい。トナー粒子が実質的に絶縁性を示さなければ、現像性と転写性とを両立することが困難である。また、トナー粒子への現像電界による電荷の注入を生じ易く、現像剤の帯電を乱しカブリを生ずる。
【０２０４】
本発明に使用されるトナー粒子が含有する結着樹脂の種類としては、例えば、スチレン系樹脂、スチレン系共重合樹脂、ポリエステル樹脂、ポリ塩化ビニル樹脂、フェノール樹脂、天然変性フェノール樹脂、天然樹脂変性マレイン酸樹脂、アクリル樹脂、メタクリル樹脂、ポリ酢酸ビニール、シリコーン樹脂、ポリウレタン樹脂、ポリアミド樹脂、フラン樹脂、エポキシ樹脂、キシレン樹脂、ポリビニルブチラール、テルペン樹脂、クマロンインデン樹脂、石油系樹脂等が使用できる。
【０２０５】
スチレン系共重合体のスチレンモノマーに対するコモノマーとしては、例えば、ビニルトルエンの如きスチレン誘導体；例えば、アクリル酸又はアクリル酸メチル、アクリル酸エチル、アクリル酸ブチル、アクリル酸ドデシル、アクリル酸オクチル、アクリル酸−２−エチルヘキシル、アクリル酸フェニルの如きアクリル酸エステル類；例えば、メタクリル酸又はメタクリル酸メチル、メタクリル酸エチル、メタクリル酸ブチル、メタクリル酸オクチルの如きメタクリル酸エステル類；例えば、マレイン酸又はマレイン酸ブチル、マレイン酸メチル、マレイン酸ジメチルの如き二重結合を有するジカルボン酸エステル類；例えば、アクリルアミド、アクリロニトリル、メタクリロニトリル、ブタジエン又は塩化ビニル、酢酸ビニル、安息香酸ビニルの如きビニルエステル類；例えば、エチレン、プロピレン、ブチレンの如きエチレン系オレフィン類；例えば、ビニルメチルケトン、ビニルヘキシルケトンの如きビニルケトン類；例えば、ビニルメチルエーテル、ビニルエチルエーテル、ビニルイソブチルエーテルの如きビニルエーテル類；といったビニル系単量体が単独もしくは２つ以上用いられる。
【０２０６】
ここで、架橋剤としては、主として２個以上の重合可能な二重結合を有する化合物が用いられ、例えば、ジビニルベンゼン、ジビニルナフタレンの如き芳香族ジビニル化合物；例えばエチレングリコールジアクリレート、エチレングリコールジメタクリレート、１，３−ブタンジオールジメタクリレートの如き二重結合を２個有するカルボン酸エステル；ジビニルアニリン、ジビニルエーテル、ジビニルスルフィド、ジビニルスルホンの如きジビニル化合物；及び３個以上のビニル基を有する化合物；が単独もしくは混合物として用いられる。
【０２０７】
結着樹脂のガラス転移点温度（Ｔｇ）は、５０〜７０℃であることが好ましい。ガラス転移点温度が上記範囲よりも低すぎると場合には現像剤の保存性が低下し、高すぎる場合には定着性に劣る。
【０２０８】
本発明に係る現像剤は、示差熱分析測定装置（ＤＳＣ）によるＤＳＣチャートの吸熱曲線において、最大吸熱ピークが７０℃以上１２０℃未満の温度領域にあることが好ましい。このような温度領域に最大吸熱ピークを有するためには、トナー粒子中にワックス成分を含有させることが好ましい。
【０２０９】
本発明に用いられるトナー粒子に含有されるワックスとしては、低分子量ポリエチレン、低分子量ポリプロピレン、ポリオレフィン、ポリオレフィン共重合体、マイクロクリスタリンワックス、パラフィンワックス、フィッシャートロプシュワックスの如き脂肪族炭化水素系ワックス；酸化ポリエチレンワックスの如き脂肪族炭化水素系ワックスの酸化物；または、それらのブロック共重合物；カルナバワックス、モンタン酸エステルワックスなどの脂肪酸エステルを主成分とするワックス類；脱酸カルナバワックスの如き脂肪酸エステル類を一部または全部を脱酸化したものなどが挙げられる。さらに、パルミチン酸、ステアリン酸、モンタン酸、あるいは更に長鎖のアルキル基を有する長鎖アルキルカルボン酸類の如き飽和直鎖脂肪酸類；ブラシジン酸、エレオステアリン酸、バリナリン酸の如き不飽和脂肪酸類；ステアリルアルコール、アラルキルアルコール、ベヘニルアルコール、カルナウビルアルコール、セチルアルコール、メリシルアルコール、あるいは更に長鎖のアルキル基を有する長鎖アルキルアルコール類の如き飽和アルコール類；ソルビトールの如き多価アルコール類；リノール酸アミド、オレイン酸アミド、ラウリン酸アミドの如き脂肪酸アミド類；メチレンビスステアリン酸アミド、エチレンビスカブリン酸アミド、エチレンビスラウリン酸アミド、ヘキサメチレンビスステアリン酸アミドの如き飽和脂肪酸ビスアミド類、エチレンビスオレイン酸アミド、ヘキサメチレンビスオレイン酸アミド、Ｎ，Ｎ’−ジオレイルアジピン酸アミド、Ｎ，Ｎ’−ジオレイルセバシン酸アミドの如き不飽和脂肪酸アミド類；ｍ−キシレンビスステアリン酸アミド、Ｎ，Ｎ’−ジステアリルイソフタル酸アミドの如き芳香族系ビスアミド類；ステアリン酸カルシウム、ラウリン酸カルシウム、ステアリン酸亜鉛、ステアリン酸マグネシウムの如き脂肪酸金属塩（一般に金属石けんといわれているもの）；脂肪族炭化水素系ワックスにスチレンやアクリル酸などのビニル系モノマーを用いてグラフト化させたワックス類；ベヘニン酸モノグリセリドの如き脂肪酸と多価アルコールの部分エステル化物；植物性油脂の水素添加などによって得られるヒドロキシル基を有するメチルエステル化合物などが挙げられる。
【０２１０】
本発明においては、該ワックスを結着樹脂１００質量部に対して好ましくは０．５〜２０質量部、より好ましくは０．５〜１５質量部の範囲で用いられる。
【０２１１】
本発明に使用されるトナー粒子が含有する着色剤としては、カーボンブラック、ランプブラック、鉄黒、群青、ニグロシン染料、アニリンブルー、フタロシアニンブルー、フタロシアニングリーン、ハンザイエローＧ、ローダミン６Ｇ、カルコオイルブルー、クロムイエロー、キナクリドン、ベンジジンイエロー、ローズベンガル、トリアリールメタン系染料、モノァゾ系、ジスアゾ系染顔料といった従来公知の染顔料を単独或いは混合して使用し得る。
【０２１２】
本発明の現像剤は、磁場７９．６ｋＡ／ｍにおける磁化の強さが１０〜４０Ａｍ^２／ｋｇである磁性現像剤であることが好ましい。現像剤の磁化の強さは２０〜３５Ａｍ^２／ｋｇであることがより好ましい。
【０２１３】
本発明において磁場７９．６ｋＡ／ｍにおける磁化の強さを規定する理由は以下の通りである。通常、磁性体の磁気特性を表す量としては磁気飽和における磁化の強さ（飽和磁化）が用いられるが、本発明においては画像形成装置内で実際に磁性現像剤に作用する磁場における磁性現像剤の磁化の強さが重要であるためである。画像形成装置に磁性現像剤が適用される場合、磁性現像剤に作用する磁場は、画像形成装置外への磁場の漏洩を大きくしないため或いは磁場発生源のコストを低く抑えるために、市販されている多くの画像形成装置において数十から百数十ｋＡ／ｍであり、画像形成装置内で実際に磁性現像剤に作用する磁場の代表的な値として磁場７９．６ｋＡ／ｍ（１０００エルステッド）を選択し、磁場７９．６ｋＡ／ｍにおける磁化の強さを規定した。
【０２１４】
現像剤の磁場７９．６ｋＡ／ｍにおける磁化の強さが上記範囲よりも小さすぎる場合には、磁気力により現像剤搬送を行うことが困難となり、現像剤担持体上に均一に現像剤を担持させることができなくなる。また、磁気力により現像剤搬送を行う場合には、一成分系磁性現像剤の穂立ちを均一に形成できないために、導電性微粉末の潜像担持体への供給性が低下し、転写残トナー粒子の回収性も低下する。磁場７９．６ｋＡ／ｍにおける磁化の強さが上記範囲よりも大きすぎる場合には、トナー粒子の磁気凝集性が高まり、導電性微粉末の現像剤中での均一な分散及び潜像担持体への供給が困難となり、本発明の効果である像担持体の帯電促進効果又はトナー回収性促進効果が損なわれる。
【０２１５】
このような磁性現像剤を得る手段としては、トナー粒子に磁性体を含有させる。本発明において現像剤を磁性現像剤とするためトナー粒子に含有させる磁性体としては、マグネタイト、マグヘマイト、フェライトの如き磁性酸化鉄、鉄；コバルト、ニッケルの如き金属或いはこれらの金属とアルミニウム、コバルト、銅、鉛、マグネシウム、錫、亜鉛、アンチモン、ベリリウム、ビスマス、カドミウム、カルシウム、マンガン、セレン、チタン、タングステン、バナジウムの如き金属の合金及びその混合物が挙げられる。
【０２１６】
これらの磁性体の磁気特性としては、磁場７９５．８ｋＡ／ｍ下で飽和磁化が１０〜２００Ａｍ^２／ｋｇ、残留磁化が１〜１００Ａｍ^２／ｋｇ、抗磁力が１〜３０ｋＡ／ｍであるものが好ましく用いられる。これらの磁性体は結着樹脂１００質量部に対し、２０〜２００質量部で用いられる。このような磁性体の中でもマグネタイトを主とするものが特に好ましい。
【０２１７】
本発明において磁性現像剤の磁化の強さは、振動型磁カ計ＶＳＭＰ−１−１０（東英工業社製）を用いて、２５℃の室温にて外部磁場７９．６ｋＡ／ｍで測定することができる。また、磁性体の磁気特性は、２５℃の室温にて外部磁場７９６ｋＡ／ｍで測定することができる。
【０２１８】
また、本発明において現像剤は、目開き１４９μｍの篩を通過し、目開き７４μｍの篩を通過できない（目開き１４９μｍパス−目開き７４μｍオン）粒径の球形鉄粉に対する摩擦帯電量が、絶対値で２０〜１００ｍＣ／ｋｇであることが好ましい。現像剤の摩擦帯電量が絶対値で上記範囲よりも小さすぎる場合には、トナー粒子の転写性が低下することで転写残トナー粒子が増大するため、潜像担持体の帯電性が低下し易くなり、転写残トナー粒子の回収の負荷が大きくなり回収不良を生じ易くなる。現像剤の摩擦帯電量が絶対値で上記範囲よりも大きすぎる場合には、現像剤の静電的凝集性が高まり、導電性微粉末の現像剤中での均一な分散及び像担持体への供給が困難となり、本発明の効果である像担持体の帯電促進効果又はトナー回収性促進効果が損なわれる。特に磁性現像剤の場合には、現像剤が磁気凝集性を併せ持つために静電的凝集性をより抑制することが必要であり、磁性現像剤の目開き１４９μｍパス−目開き７４μｍオンの球形鉄粉に対する摩擦帯電量は絶対値で２５〜５０ｍＣ／ｋｇであることが好ましい。
【０２１９】
本発明における現像剤の摩擦帯電量の測定法を図面を用いて詳述する。図４は現像剤の摩擦帯電量を測定する装置の説明図である。２３℃，相対湿度６０％の環境下、先ず摩擦帯電量を測定しようとする現像剤と目開き１４９μｍパス−目開き７４μｍオンの粒径の球形の鉄粉キャリア（例えば、同和鉄粉社製球形鉄粉ＤＳＰ１３８を使用することが可能である）の質量比５：９５（例えば、現像剤０．５ｇに鉄粉キャリア９．５ｇ）の混合物を５０〜１００ｍｌの容量のポリエチレン製の瓶に入れ１００回振とうする。次いで、底に目開き３１μｍのスクリーン２３を備える金属製の測定容器２２に前記混合物約０．５ｇを入れ、金属製のフタ２４をする。この時の測定容器２２全体の重量を秤り、これをＷ１（ｇ）とする。次に、吸引機２１（少なくとも測定容器２２と接する部分は絶縁体）において、吸引口２７から吸引し、風量調節弁２６を調整することにより真空計２５の圧力を２４５０Ｐａとする。この状態で充分（約１分間）吸引を行いトナーを吸引除去する。この時の電位計２９の電位をＶ（ボルト）とする。ここで２８はコンデンサーであり容量をＣ（μＦ）とする。また、吸引後の測定容器全体の重量を秤りＷ２（ｇ）とする。この現像剤の摩擦帯電量は下式の如く計算される。
【０２２０】
現像剤の摩擦帯電量（ｍＣ／ｋｇ）＝Ｃ×Ｖ／（Ｗ１−Ｗ２）
本発明において現像剤は、荷電制御剤を含有することが好ましい。荷電制御剤のうち、現像剤を正荷電性に制御するものとして、例えば下記の物質がある。
【０２２１】
ニグロシン及び脂肪酸金属塩等による変性物；トリブチルベンジルアンモニウム−１−ヒドロキシ−４−ナフトスルフォン酸塩、テトラブチルアンモニウムテトラフルオロボレートの如き四級アンモニウム塩、及びこれらの類似体であるホスホニウム塩等のオニウム塩及びこれらのレーキ顔料、トリフェニルメタン染料及びこれらのレーキ顔料（レーキ化剤としては、りんタングステン酸、りんモリブデン酸、りんタングステンモリブデン酸、タンニン酸、ラウリン酸、没食子酸、フェリシアン化物、フェロシアン化物など）、高級脂肪酸の金属塩；ジブチルスズオキサイド、ジオクチルスズオキサイド、ジシクロヘキシルスズオキサイドの如きジオルガノスズオキサイド；ジブチルスズボレート、ジオクチルスズボレート、ジシクロヘキシルスズボレートの如きジオルガノスズボレート類；グアニジン化合物、イミダゾール化合物。これらを単独で或いは２種類以上組み合わせて用いることができる。これらの中でも、トリフェニルメタン化合物、カウンターイオンがハロゲンでない四級アンモニウム塩が好ましく用いられる。また一般式（４）で表されるモノマーの単重合体：前述したスチレン、アクリル酸エステル、メタクリル酸エステルの如き重合性モノマーとの共重合体を正荷電性制御剤として用いることができる。この場合これらの荷電制御剤は、結着樹脂（の全部または一部）としての作用をも有する。
【０２２２】
【化７】

［但し、Ｒ_１、Ｒ_２、Ｒ_３は水素原子あるいは炭素数１〜４の飽和炭化水素基を示す。］
本発明の構成においては、正荷電制御剤としては、特に下記一般式（５）で表される化合物が好ましい。
【０２２３】
【化８】

〔式中、Ｒ^１，Ｒ^２，Ｒ^３，Ｒ^４，Ｒ^５，Ｒ^６は、各々互いに同一でも異なっていてもよく、水素原子、置換もしくは未置換のアルキル基または、置換もしくは未置換のアリール基を表す。Ｒ^７，Ｒ^８，Ｒ^９は、各々互いに同一でも異なっていてもよく、水素原子、ハロゲン原子、アルキル基、アルコキシ基を表す。Ａ⁻は、硫酸イオン、硝酸イオン、ほう酸イオン、りん酸イオン、水酸イオン、有機硫酸イオン、有機スルホン酸イオン、有機りん酸イオン、カルボン酸イオン、有機ほう酸イオン、テトラフルオロボレートの如き陰イオンを示す。〕
また、現像剤を負荷電性に制御するものとして次の物質が挙げられる。例えば、有機金属錯体、キレート化合物が有効であり、モノアゾ金属錯体、アセチルアセトン金属錯体、芳香族ハイドロキシカルボン酸、芳香族ダイカルボン酸系の金属錯体がある。他には、芳香族ハイドロキシカルボン酸、芳香族モノ及びポリカルボン酸及びその金属塩、無水物、エステル類、ビスフェノール等のフェノール誘導体類がある。
【０２２４】
また、次に示した一般式（６）で表されるアゾ系金属錯体が好ましい。
【０２２５】
【化９】

〔式中、Ｍは配位中心金属を表わし、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅが挙げられる。Ａｒはアリール基であり、フェニル基、ナフチル基が挙げられ、置換基を有していてもよい。この場合の置換基としては、ニトロ基ハロゲン基、カルポキシル基、アニリド基および炭素数１〜１８のアルキル基、アルコキシ基が挙げられる。Ｘ、Ｘ′、Ｙ、Ｙ′は−Ｏ−、−ＣＯ−、−ＮＨ−又は−ＮＲ−（Ｒは炭素数１〜４のアルキル基）である。Ｋは水素、ナトリウム、カリウム、アンモニウム、脂肪族アンモニウムを示す。〕
特に中心金属としてはＦｅ、Ｃｒが好ましく、置換基としてはハロゲン、アルキル基、アニリド基が好ましく、カウンターイオンとしては水素、アンモニウム、脂肪族アンモニウムが好ましい。
【０２２６】
あるいは、次の一般式（７）に示した塩基性有機酸金属錯体も負帯電性を与えるものであり、本発明に使用できる。
【０２２７】
【化１０】

【０２２８】
一般式（７）において、特に中心金属としてはＦｅ、Ａｌ、Ｚｎ、Ｚｒ、Ｃｒが好ましく、置換基としてはハロゲン、アルキル基、アニリド基が好ましく、カウンターイオンとしては水素、アルカリ金属、アンモニウム、脂肪族アンモニウムが好ましい。またカウンターイオンの異なる錯塩の混合物も好ましく用いられる。
【０２２９】
荷電制御剤を現像剤に含有させる方法としては、トナー粒子内部に添加する方法と外添する方法とがある。これらの荷電制御剤の使用量としては、結着樹脂の種類、他の添加剤の有無、分散方法を含めたトナー製造方法によって決定されるもので、一義的に限定されるものではないが、好ましくは結着樹脂１００質量部に対して０．１〜１０質量部、より好ましくは０．１〜５質量部の範囲で用いられる。
【０２３０】
本発明に係るトナー粒子を製造するにあたっては、上述したような構成材料をボールミルその他の混合機により十分混合した後、加熱ロール、ニーダー、エクストルーダー等の熱混練機を用いて良く混練し、冷却固化後、粉砕、分級、必要に応じてトナー形状調整等の表面処理を行ってトナー粒子を得る方法がい。
【０２３１】
トナー粒子の形状調整のための処理としては、粉砕法により得られたトナー粒子を水中或いは有機溶液中に分散させ加熱或いは膨潤させる方法、熱気流中を通過させる熱処理法、機械的エネルギーを付与して処理する機械的衝撃法などが挙げられる。機械的衝撃力を加える手段としては、例えばホソカワミクロン社製のメカノフージョンシステムや奈良機械製作所製のハイブリダイゼーションシステム等の装置のように、高速回転する羽根によりトナー粒子をケーシングの内側に遠心力により押しつけ、圧縮力又は／及び摩擦力等の力によりトナー粒子に機械的衝撃力を加える方法が挙げられる。
【０２３２】
本発明においては、機械的衝撃を加える処理を行う場合には、処理時の雰囲気温度をトナー粒子のガラス転移点Ｔｇ付近の温度（Ｔｇ±３０℃）とすることが、凝集防止、生産性の観点から好ましい。さらに好ましくは、処理時の雰囲気温度がトナーのガラス転移点Ｔｇ±２０℃の範囲の温度で、熱機械的衝撃によるトナー粒子の球形化処理を行うことが、導電性微粉末を有効に働かせるのに特に有効である。
【０２３３】
熱機械的衝撃力を繰り返し与えることによりトナー粒子の球形化処理を行う方法の一例を図６及び図７を参照しながら具体的に説明する。
【０２３４】
図６は後述のトナー粒子の製造例２〜４で用いたトナー粒子球形化処理装置の構造を示す模式的概略構成図であり、図７は、図６の処理部１の構造を示す模式的部分的断面図である。
【０２３５】
このトナー粒子球形化処理装置は、高速回転する羽根によりトナー粒子をケーシングの内側に遠心力により押しつけ、少なくとも圧縮力及び摩擦力による熱機械的衝撃力を繰り返し与えることによりトナー粒子を球形化処理するものである。図７に示すように、処理部Ｉには鉛直方向に４枚の回転ロータ７２ａ、７２ｂ、７２ｃおよび７２ｄが設置されている。これら回転ロータ７２ａ〜７２ｄは、最外縁部の周速が例えば１００ｍ／秒となるように、電動モータ８４により回転駆動軸７３を回転させることによって回転される。この時の回転ロータ７２ａ〜７２ｄの回転数は、例えば、１３０ｓ^−１である。さらに、吸引ブロア８５（図６参照）を稼働させて、各回転ロータ７２ａ〜７２ｄと一体に設けられたブレード７９ａ〜７９ｄの回転によって発生する気流量と同等、またはそれよりも多い風量を吸引する。フィーダ８６からトナー粒子が空気とともにホッパー８２に吸引導入され、導入されたトナー粒子は、粉体供給管８１及び粉体供給口８０を通って第１の円筒状処理室８９ａの中央部に導入される。このトナー粒子は、第１の円筒状処理室８９ａでブレード７９ａと側壁７７により球形化処理を受け、次いで、球形化処理を受けたトナー粒子はガイド板７８ａの中央部に設けられた第１の粉体排出口９０ａを通って、第２の円筒状処理室８９ｂの中央部に導入され、さらにブレード７９ｂと側壁７７により球形化処理を受ける。
【０２３６】
第２の円筒状処理室８９ｂで球形化処理されたトナー粒子は、ガイド板７８ｂの中央部に設けられた第２の粉体排出口９０ｂを通って第３の円筒状処理室８９ｃの中央部に導入され、さらにブレード７９ｃと側壁７７により球形化処理を受け、さらに、ガイド板７８ｃの中央部に設けられた第３の粉体排出口９０ｃを通って第４の円筒状処理室８９ｄの中央部にトナー粒子は導入され、ブレード７９ｄと側壁７７により球形化処理を受け、さらに、ガイド板７８ｄの中央部に設けられた第３の粉体排出口９０ｄを通って、搬出管９３より搬出される。トナー粒子を搬送している空気は、第１〜第４の円筒状処理室８９ａ〜８９ｄを経由し、搬出管９３、サイクロン９１、バグフィルター９２、及び吸引ブロア８５を通って装置システムの系外に排出される。
【０２３７】
各円筒状処理室８９ａ〜８９ｄ内に導入されたトナー粒子は、各ブレード７９ａ〜７９ｄによって瞬聞的に機械的打撃作用を受け、さらに、側壁７７に衝突して機械的衝撃力を受ける。回転ロータ７２ａ〜７２ｄにそれぞれ設置されている所定の大きさのブレード７９ａ〜７９ｄの回転により、回転ロータ面の上方空間に、中央部から外周へ、外周から中央部へ循環する対流が発生する。トナー粒子は円筒状処理室８９ａ〜８９ｄ内に滞留し、球形化処理を受ける。この機械的衝撃力により発生する熱により、トナー粒子表面がトナー粒子を構成する結着樹脂のガラス転移温度付近にまで温度上昇する場合には、熱機械的衝撃力によるトナー粒子の球形化がなされる。各円筒状処理室８９ａ〜８９ｄを経由することにより、連続的に効率良くトナー粒子は球形化される。
【０２３８】
トナー粒子の球形化の度合いは、トナー粒子の球形化処理部での滞留時間及び温度等によって調整することが可能であり、具体的には、回転ロータの回転速度、回転数、ブレードの高さ、幅及び枚数、ブレード外周と側壁とのクリアランス、吸引ブロアの吸引風量、また、球形化処理部に導入される際のトナー粒子温度及びトナー粒子を搬送する空気温度等によって調整される。
【０２３９】
また、バッチ式の装置として、奈良機械（株）製として商品化されているハイブリタイゼーションシステムを用いるのも好ましい例の一つである。
【０２４０】
粉砕法により得られるトナー粒子の形状を制御するには、結着樹脂等のトナー粒子構成材料の選択及び粉砕時の条件を適宜設定することで可能であるが、気流式粉砕機でトナー粒子の円形度を高めようとすると生産性が低下し易く、機械式粉砕機を用いてトナー粒子の円形度を高める条件を設定することが好ましい。
【０２４１】
本発明においては、トナー粒子の粒度分布の変動係数を低く抑えるためには、分級工程において多分割分級機を用いることが生産性の点で好ましい。また、１．００μｍ以上２．００μｍ未満の粒径範囲のトナー粒子の超微粒子を少なくするためには、粉砕工程において機械式粉砕機を用いることが好ましい。
【０２４２】
上記のようにして得られたトナー粒子に外部添加剤を加え混合機により混合し、さらに必要に応じ篩を通過させることで、本発明に係る現像剤を製造することができる。
【０２４３】
粉砕法によってトナー粒子を製造する場合に用いられる製造装置としては、例えば混合機としては、ヘンシェルミキサー（三井鉱山社製）；スーパーミキサー（カワタ社製）；リボコーン（大川原製作所社製）；ナウターミキサー、タービュライザー、サイクロミックス（ホソカワミクロン社製）；スパイラルピンミキサー（太平洋機工社製）；レーディゲミキサー（マツボー社製）が挙げられ、混練機としては、ＫＲＣニーダー（栗本鉄工所社製）；ブス・コ・ニーダー（Ｂｕｓｓ社製）；ＴＥＭ型押し出し機（東芝機械社製）；ＴＥＸ二軸混練機（日本製鋼所社製）；ＰＣＭ混練機（池貝鉄工所社製）；三本ロールミル、ミキシングロールミル、ニーダー（井上製作所社製）；ニーデックス（三井鉱山社製）；ＭＳ式加圧ニーダー、ニダールーダー（森山製作所社製）；バンバリーミキサー（神戸製鋼所社製）が挙げられ、粉砕機としては、カウンタージェットミル、ミクロンジェット、イノマイザ（ホソカワミクロン社製）；ｌＤＳ型ミル、ＰＪＭジェット粉砕機（日本ニューマチック工業社製）；クロスジェットミル（栗本鉄工所社製）；ウルマックス（８曹エンジニアリング社製）；ＳＫジェット・オー・ミル（セイシン企業社製）；クリプトロン（川崎重工業社製）；ターボミル（ターボ工業社製）が挙げられ、この中でもクリプトロン、ターボミル等の機械式粉砕機を用いることがより好ましい。分級機としては、クラッシール、マイクロンクラッシファイアー、スペディッククラシファイアー（セイシン企業社製）；ターボクラッシファイアー（日清エンジニアリング社製）；ミクロンセパレータ、ターボプレックス（ＡＴＰ）、ＴＳＰセパレータ（ホソカワミクロン社製）；エルボージェット（日鉄鉱業社製）、ディスパージョンセパレータ（日本ニューマチック工業社製）；ＹＭマイクロカット（安川商事社製）が挙げられ、この中でもエルボージェット等の多分割分級機を用いることがより好ましい。粗粒などをふるい分けるために用いられる篩い装置としては、ウルトラソニック（晃栄産業社製）；レゾナシーブ、ジャイロシフター（徳寿工作所社）；バイブラソニックシステム（ダルトン社製）；ソニクリーン（新東工業社製）；ターボスクリーナー（ターボ工業社製）；ミクロシフター（槙野産業社製）；円形振動篩い等が挙げられる。
【０２４４】
本発明で用いられる各種特性付与を目的とした現像剤への添加剤としては、例えば、以下のようなものが用いられる。
【０２４５】
（１）研磨剤としては、チタン酸ストロンチウム、酸化セリウム、酸化アルミニウム、酸化マグネシウム、酸化クロムの如き金属酸化物；窒化ケイ素の如き窒化物；炭化ケイ素の如き炭化物；硫酸カルシウム、硫酸バリウム、炭酸カルシウムの如き金属塩が挙げられる。
【０２４６】
（２）滑剤としては、ポリフッ化ビニリデン、ポリテトラフルオロエチレンの如きフッ素系樹脂粉末；シリコーン系樹脂粉末；ステアリン酸亜鉛、ステアリン酸カルシウムの如き脂肪酸金属塩が挙げられる。
【０２４７】
これら添加剤は、トナー粒子１００質量部に対し、０．０５〜１０質量部が用いられ、好ましくは０．１〜５質量部が用いられる。これら添加剤は、単独で用いても、また、複数併用しても良い。
【０２４８】
＜現像装置、プロセスカートリッジ及び画像形成方法＞
次に、本発明の現像剤を好適に用いることができる本発明の現像装置及び画像形成方法について説明する。また、本発明のプロセスカートリッジについても説明する。
【０２４９】
本発明の現像装置は、（Ｉ）現像剤を収容するための現像容器、（ＩＩ）該現像容器に収容されている該現像剤を担持し、現像領域に搬送するための現像剤担持体、及び（ＩＩＩ）現像剤担持体上に担持される現像剤の層厚を規制するための現像剤層厚規制部材を少なくとも有するものである。
【０２５０】
本発明の画像形成方法は、（Ｉ）潜像担持体を帯電する帯電工程、（ＩＩ）帯電工程において帯電された潜像担持体の帯電面に静電潜像として画像情報を書き込む潜像形成工程、（ＩＩＩ）前記静電潜像を、現像剤を担持しながら前記潜像担持体と対向する現像領域に現像剤を搬送する現像剤担持体を備えた現像装置を用いて現像し、現像剤像として可視化する現像工程、（ＩＶ）現像工程において形成された現像剤画像を転写材に転写する転写工程、及び（Ｖ）前記転写材上に転写された現像剤像を定着手段により定着する定着工程を有し、これら各工程を繰り返して画像形成を行う方法である。
【０２５１】
そして、本発明の画像形成方法の第１態様は、上記帯電工程が、潜像担持体に帯電手段を接触させて帯電を行う工程であり、帯電手段と潜像担持体との当接部に、上記現像剤が有する導電性粒子が介在した状態で電圧を印加することにより像担持体を帯電する、接触帯電方法を用いたものである。
【０２５２】
また、本発明の画像形成方法の第２の態様は、上記現像工程が、前記静電潜像を可視化するとともに、前記現像剤像が前記転写材に転写された後に、前記潜像担持体上に残留した現像剤を回収する工程である。
【０２５３】
すなわち、この第２態様の画像形成方法は、現像工程がトナー画像を転写材に転写した後に像担持体上に残留した現像剤を回収する工程を兼ねる、いわゆる現像兼クリーニング法を用いたものである。
【０２５４】
本発明のプロセスカートリッジは、静電潜像を担持するための潜像担持体と、前記潜像担持体を帯電するための帯電手段と、前記像担持体に形成された静電潜像を、本発明の現像剤を用いて現像することにより現像剤像を形成する現像手段とを少なくとも有し、前記現像装置及び前記潜像担持体は一体化され、画像形成装置本体に対して着脱可能に装着される構成を有する。
【０２５５】
本発明のプロセスカートリッジの第１の態様は、前記帯電手段が、潜像担持体に接触しており、当接部において、上記現像剤が有する導電性微粒子が介在した状態で電圧を印加することにより潜像担持体を帯電する、接触帯電方法を用いたものである。
【０２５６】
本発明のプロセスカートリッジの第２の態様は、前記現像装置が、前記潜像担持体に形成された静電潜像を、現像剤を用いて現像を行うことにより現像剤像として可視化するとともに、該現像剤像が転写材に転写された後に前記潜像担持体上に残留した現像剤の回収を行う。
【０２５７】
本発明の前記現像手段は、前記潜像担持体に対向して配置される現像剤担持体とこの現像剤担持体上に薄層の現像剤層を形成する現像剤層規制部材とを少なくとも有し、前記現像剤担持体上の現像剤層から前記潜像担持体へ前記現像剤を転移させることにより前記トナー画像を形成する手段であることが好ましい。
【０２５８】
前記現像手段は、前記潜像担持体に対向して配置される現像剤担持体とこの現像剤担持体上に薄層の現像剤層を形成する現像剤層規制部材とを少なくとも有することが好ましい。
【０２５９】
以下、本発明の現像装置、プロセスカートリッジ及び画像形成方法について詳細に説明する。
【０２６０】
まず、本発明の画像形成方法における帯電工程は、帯電手段としてのコロナ帯電器等の非接触型の帯電装置、または被帯電体である像担持体に、ローラ型（帯電ローラ）、ファーブラシ型、磁気ブラシ型、ブレード型等の導電性の帯電部材（接触帯電部材・接触帯電器）を接触させ、この帯電部材（以下「接触帯電部材」と表記する）に所定の帯電バイアスを印加して、被帯電体面を所定の極性および電位に帯電させる接触帯電装置によって行われる。本発明においては、コロナ帯電器等の非接触型の帯電装置と比較して低オゾン、低電カ等の利点がある接触帯電装置を用いることが好ましい。
【０２６１】
また、潜像担持体上の転写残トナー粒子は、形成する画像のパターンに対応するものと、画像の形成されていない部分のいわゆるカブリトナーに起因するものが考えられる。形成する画像のパターンに対応する転写残トナー粒子は、現像兼クリーニングでの完全な回収が困難であり、回収が不十分であると回収不良のトナー粒子がそのまま次に形成される画像に現れてパターンゴーストを生ずる。このような画像のパターンに対応する転写残トナー粒子は、転写残トナー粒子のパターンを均すことによって現像兼クリーニングでの回収性を大幅に向上させることができる。例えば、現像工程が接触現像プロセスであれば、現像剤を担持する現像剤担持体の移動速度と、現像剤担持体に接触している潜像担持体の移動速度に相対的速度差を持たせることで、転写残トナー粒子のパターンを均すと同時に転写残トナー粒子を効率良く回収することができる。しかしながら、画像形成中の電源の瞬断または紙詰まり時のように多量の転写残トナー粒子が像担持体上に残る場合には、転写残トナー粒子が像担持体上に残ったパターンで画像露光等の潜像形成を阻害するためのパターンゴーストを生ずる。これに対し、接触帯電装置を用いた場合は、接触帯電部材によって転写残トナー粒子のパターンを均すことで、現像工程が非接触現像プロセスであっても転写残トナー粒子を効率良く回収することができ、回収不良によるパターンゴーストの発生を防止することができる。また、多量の転写残トナー粒子が潜像担持体上に残る場合にも、接触帯電部材が一旦転写残トナー粒子を堰き止め、転写残トナー粒子のパターンを均して徐々に転写残トナー粒子を像担持体上に吐き出すことにより、潜像形成阻害によるパターンゴーストを防止することができる。多量の転写残トナー粒子が接触帯電部材に堰き止められる場合の接触帯電部材の汚染による潜像担持体の帯電性の低下に関しては、本発明の特定の現像剤を用いることで潜像担持体の一様帯電性の低下を実用上問題ない範囲にまで低減することができる。この点からも、本発明においては接触帯電装置を用いることが好ましい。
【０２６２】
本発明においては、帯電部材の表面における移動速度と潜像担持体の表面における移動速度との間に、相対的速度差を設けることが好ましい。帯電部材の表面における移動速度と像担持体の表面における移動速度との間に相対的速度差を設けると、接触帯電部材と潜像担持体との間での大幅なトルクの増大、接触帯電部材及び潜像担持体表面の顕著な削れ等を生じるが、接触帯電部材と潜像担持体との接触部に現像剤が有する成分を介在させることにより、潤滑効果（摩擦低減効果）が得られ、大幅なトルクの増大や顕著な削れを伴うことなく速度差を設けることが可能となる。
【０２６３】
また、潜像担持体と潜像担持体に接触する帯電部材との接触部に介在する現像剤の有する成分が、少なくとも上述の導電性微粉末を含有することが好ましい。更には、この接触部に介在する現像剤成分全体に対する導電性微粉末の含有比率が、上記本発明の現像剤に含有される導電性微粉末（本発明の画像形成に供される前の現像剤中の導電性微粉末）の含有比率よりも高いことがより好ましい。上記接触部に介在する現像剤の有する成分が、少なくとも導電性微粉末を含有することで、潜像担持体と接触帯電部材との間の導通路が確保され、接触帯電部材への転写残トナー粒子の付着或いは混入による潜像担持体の一様帯電性の低下を抑制することができる。また、上記接触部に介在する現像剤成分全体に対する導電性微粉末の含有比率が、上記本発明の現像剤に含有される導電性微粉末の含有比率よりも高いことにより、接触帯電部材への転写残トナー粒子の付着或いは混入による潜像担持体の一様帯電性の低下をより安定して抑制することができる。更に、本発明の現像剤を用いることで、帯電部において接触帯電部材と潜像担持体との相対移動速度を比較的大きく持たせた場合でも、優れた潤滑性を発揮する１．００μｍ以上２．００μｍ未満の粒径範囲の粒子を多く含む導電性微粉末が帯電部に供給されることで、接触帯電部材及び潜像担持体の削れ・傷を抑制することができる。
【０２６４】
接触帯電部材に対する印加帯電バイアスは、直流電圧のみであっても潜像担持体の良好な帯電性を得ることが可能であるが、直流電圧に交番電圧（交流電圧）を重畳したものであってもよい。このような交番電圧の波形としては、正弦波、矩形波、三角波等適宜使用可能である。また、交番電圧は、直流電源を周期的にオン／オフすることによって形成されたパルス波の電圧であっても良い。このように、交番電圧としては、周期的にその電圧値が変化するような波形を有するバイアスが使用できる。
【０２６５】
本発明において、接触帯電部材に対する印加帯電バイアスは、放電生成物を生じない範囲で印加することが好ましい。すなわち、接触帯電部材と被帯電体（潜像担持体）との間の放電開始電圧よりも低いことが好ましい。また、直接注入帯電機構が支配的である帯電方法であることが好ましい。
【０２６６】
現像兼クリーニング方法では、潜像担持体上に残余する絶縁性の転写残トナー粒子が接触帯電部材に接触し、付着或いは混入することで潜像担持体の帯電性が低下するが、放電帯電機構が支配的である帯電方法の場合には、接触帯電部材表面に付着したトナー層が放電電圧を阻害する抵抗となるあたりから、潜像担持体の帯電性の低下が急激に起こる。これに対し、直接注入帯電機構が支配的である帯電方法の場合には、接触帯電部材に付着或いは混入した転写残トナー粒子が接触帯電部材表面と被帯電体との接触確率を低下させることにより被帯電体（潜像担持体）の一様帯電性が低下し、これが静電潜像のコントラスト及び均一性の低下となり、画像濃度を低下させる或いはカブリを増大させる。放電帯電機構および直接注入帯電機構の帯電性低下のメカニズムに基づくと、少なくとも潜像担持体と像担持体に接触する帯電部材との接触部に導電性微粉末を介在させることによる潜像担持体の帯電性低下の防止効果及び帯電促進効果は、直接注入帯電機構においてより顕著であり、直接注入帯電機構に本発明の現像剤を適用することが好ましい。すなわち、放電帯電機構において潜像担持体と潜像担持体に接触する帯電部材との接触部に少なくとも導電性微粉末を介在させることによって、転写残トナー粒子が接触帯電部材に付着或いは混入して形成するトナー層が帯電部材から潜像担持体への放電電圧を阻害する抵抗とならないようにするためには、潜像担持体と潜像担持体に接触する帯電部材との接触部およびその近傍の帯電領域に介在する現像剤成分全体に対する導電性微粉末の含有比率をより大きくしなければならない。従って、多量の転写残トナー粒子が接触帯電部材に付着或いは混入する場合には、接触帯電部材に付着或いは混入したトナー層が放電電圧を阻害する抵抗とならないように付着或いは混入する転写残トナー粒子量を制限するために、潜像担持体上により多くの転写残トナー粒子を吐き出さねばならず、潜像形成を阻害し易くなるのである。これに対し、直接注入帯電機構においては、少なくとも潜像担持体と潜像担持体に接触する帯電部材との接触部に導電性微粉末を介在させることによって、容易に導電性微粉末を介して接触帯電部材と被帯電体との接触点を確保でき、接触帯電部材に付着或いは混入した転写残トナー粒子が接触帯電部材と被帯電体との接触確率を低下させることを防止し、潜像担持体の帯電性の低下を抑制することができる。
【０２６７】
特に、接触帯電部材の表面における移動速度と潜像担持体の表面における移動速度との間に相対的速度差を設ける場合、潜像担持体と接触帯電部材との接触部に介在する現像剤成分全体の量が接触帯電部材と潜像担持体との摺擦によって制限されることで潜像担持体の帯電阻害をより確実に抑制し、かつ接触帯電部材と潜像担持体の接触部において導電性微粉末が潜像担持体に接触する機会を格段に増加することで、接触帯電部材と潜像担持体のより高い接触性を得ることができ、導電性微粉末を介しての潜像担持体への直接注入帯電をより促進することができる。これに対して、放電帯電は潜像担持体と接触帯電部材との接触部ではなく、潜像担持体と接触帯電部材とが非接触で微小間隙を有する領域で放電が行われるため、接触部に介在する現像剤成分全体の量が制限されることによる帯電阻害を抑制する効果が期待できない。
【０２６８】
この観点からも、本発明においては直接注入帯電機構が支配的である帯電方法を用いることが好ましく、放電帯電機構に頼らない直接注入帯電機構が支配的である。
【０２６９】
帯電方法を実現するために、接触帯電部材に対する印加帯電バイアスは、接触帯電部材と被帯電体（潜像担持体）との間の放電開始電圧よりも低いことが好ましい。
【０２７０】
接触帯電部材の表面における移動速度と潜像担持体の表面における移動速度との間に相対的速度差を設ける構成としては、接触帯電部材を回転駆動することによって速度差を設けることが好ましい。
【０２７１】
また、帯電部材の表面における移動方向と潜像担持体の表面における移動方向とは、互いに逆方向であることが好ましい。すなわち、帯電部材と潜像担持体は互いに逆方向に移動することが好ましい。接触帯電部材に持ち運ばれる潜像担持体上の転写残トナー粒子を接触帯電部材に一時的に回収し均す効果を高めるために、接触帯電部材と潜像担持体は互いに逆方向に移動させることが好ましい。例えば、接触帯電部材を回転駆動し、さらに、その回転方向は潜像担持体表面の移動方向とは逆方向に回転するように構成することが望ましい。すなわち、逆方向回転で像担持体上の転写残トナー粒子を一旦、潜像担持体から引き離し帯電を行うことにより、優位に直接注入帯電を行うこと、及び潜像形成の阻害を抑制することが可能である。更には、転写残トナー粒子のパターンを均す効果を高めることで、転写残トナー粒子の回収性を高め、回収不良によるパターンゴーストの発生をより確実に防止することが可能となる。
【０２７２】
帯電部材を潜像担持体表面の移動方向と同じ方向に移動させて相対的速度差をもたせることも可能である。しかし、直接注入帯電の帯電性は潜像担持体の移動速度と潜像担持体の移動遠度に対する帯電部材の相対移動速度との比に依存するため、逆方向と同じ相対移動速度比を得るには、順方向では帯電部材の移動速度が逆方向の時に比べて大きくなるので、帯電部材を逆方向に移動させる方が移動速度の点で有利である。また、転写残トナー粒子のパターンを均す効果においても、帯電部材を潜像担持体表面の移動方向と逆方向に移動させる方が有利である。
【０２７３】
本発明においては、潜像担持体の移動速度と帯電部材の移動速度の比（相対移動速度比）は、１０〜５００％であることが好ましく、２０〜４００％であることがより好ましい。相対移動速度比が、上記範囲よりも小さすぎる場合には、接触帯電部材と潜像担持体との接触確率を増加させることが十分にはできず、直接注入帯電による潜像担持体の帯電性を維持することが難しい場合がある。更に、上述の潜像担持体と接触帯電部材との接触部に介在する導電性微粉末の量を接触帯電部材と潜像担持体との摺擦によって制限することにより潜像担持体の帯電阻害を抑制する効果、及び転写残トナー粒子のパターンを均し現像兼クリーニングでの現像剤の回収性を高める効果が十分には得られない場合もある。相対移動速度比が、上記範囲よりも大きすぎる場合には、帯電部材の移動速度を高めることとなるために、潜像担持体と接触帯電部材との接触部に持ち連ばれた現像剤成分が飛散することによる装置内の汚染を生じ易く、潜像担持体及び接触帯電部材が摩耗し易くなるあるいは傷の発生を生じ易くなり短寿命化する傾向がある。
【０２７４】
また、帯電部材の移動速度が０である場合（帯電部材が静止している状態）は、帯電部材の潜像担持体との接触点が定点となるため、帯電部材の像担持体への接触部の摩耗または劣化を生じ易く、像担持体の帯電阻害を抑制する効果及び転写残トナー粒子のパターンを均し現像兼クリーニングでの現像剤の回収性を高める効果が低下しやすく好ましくない。
【０２７５】
ここで記述した相対的速度差を示す相対移動速度比は次式で表すことができる。なお、ここで帯電部材の移動速度をＶｃ、像担持体の移動速度をＶｐとし、帯電部材の移動速度は接触部において帯電部材表面が潜像担持体表面と同じ方向に移動するときを潜像担持体の移動速度と同符号の値としている。
【０２７６】
相対移動速度比（％）＝｜［（Ｖｃ−Ｖｐ）／Ｖｐ］×１００｜
本発明においては、潜像担持体上の転写残トナー粒子を一時的に帯電部材に回収するとともに、導電性微粉末を帯電部材に担持し、潜像担持体と帯電部材との接触部を設けて直接注入帯電を優位に実行するために、接触帯電部材が弾性を有することが好ましい。また、接触帯電部材によって転写残トナー粒子のパターンを均すことで転写残トナー粒子の回収性を高める上でも、接触帯電部材が弾性を有することが好ましい。
【０２７７】
また、本発明においては、帯電部材に電圧を印加することにより潜像担持体を帯電するために、帯電部材は導電性であることが好ましい。従って、帯電部材は弾性導電ローラ、磁性粒子を磁気拘束させた磁気ブラシ部を有し該磁気ブラシ部を被帯電体に接触させた磁気ブラシ接触帯電部材、または導電性繊維からなるブラシであることが好ましい。帯電部材の構成が簡易化できる点で、帯電部材は弾性導電ローラ或いは導電性を有するブラシローラであることがより好ましく、帯電部材に付着或いは混入する現像剤成分（例えば、転写残トナー粒子や導電性微粉末）を飛散することなく安定して保持しやすい点で、帯電部材は弾性導電ローラであることが特に好ましい。
【０２７８】
ローラ部材としての弾性導電ローラの硬度は、硬度が低すぎると形状が安定しないために被帯電体との接触性が悪くなり、更に、帯電部材と潜像担持体との接触部に介在する導電性微粉末が弾性導電ローラ表層を削る或いは傷つけてしまうため、潜像担持体の安定した帯電性が得られない。また、硬度が高すぎると被帯電体との間に帯電接触部を確保できないだけでなく、被帯電体（潜像担持体）表面へのミクロな接触性が悪くなるので、潜像担持体の安定した帯電性が得られない。更には、転写残トナー粒子のパターンを均す効果が低下して転写残トナー粒子の回収性を高めることができなくなる。そこで、帯電接触部及び均し効果が十分得られるように、潜像担持体への弾性導電口ーラの接触圧を高めると、接触帯電部材或いは潜像担持体の削れ、傷等が発生し易くなる。これらの観点よりローラ部材としての弾性導電ローラのアスカーＣ硬度は２０〜５０の範囲であることが好ましく、２５〜５０の範囲であることがより好ましく、２５〜４０の範囲であることがさらに好ましい。ここで、アスカーＣ硬度は、ＪｌＳＫ６３０１で規定されるスプリング式硬度計アスカーＣ（高分子計器株式会社製）を用いて測定される硬度である。本発明においては、荷重を９．８Ｎとし、ローラの形態において測定を行う。
【０２７９】
本発明においては、接触帯電部材としてのローラ部材表面は、導電性微粒子を安定して保持させるために微少なセルまたは凹凸を有していることが好ましい。
【０２８０】
また、導電性弾性ローラは弾性を持たせて潜像担持体との十分な接触状態を得ると同時に、移動する潜像担持体を帯電するのに十分低い抵抗を有する電極として機能することが重要である。一方では、潜像担持体にピンホールなどの欠陥部位が存在した場合に、電圧のリークを防止する必要がある。被帯電体として電子写真用感光体等の潜像担持体を用いた場合、十分な帯電性と耐リークを得るには、導電性弾性ローラの抵抗は、１０^３〜１０^８Ω・ｃｍであることが好ましく、１０^４〜１０^７Ω・ｃｍであることがより好ましい。導電性弾性ローラの抵抗は、ローラに４９Ｎ／ｍの当接圧があかるよう直径３０ｍｍの円筒状アルミドラムにローラを圧着した状態で、芯金とアルミドラムとの間に１００Ｖを印加し、計測することができる。
【０２８１】
例えば、導電性弾性ローラは芯金上に可撓性部材としてのゴムあるいは発泡体の中抵抗層を形成することにより作製される。中抵抗層は樹脂（例えばウレタン）、導電性粒子（例えばカーボンブラック）、硫化剤、発泡剤等により処方され、芯金の上にローラ状に形成され、その後必要に応じて切削、表面を研磨して形状を整え導電性弾性ローラを作製することができる。
【０２８２】
導電性弾性ローラの材質としては、弾性発泡体に限定するものでは無く、弾性体の材料として、エチレン−プロピレン−ジエンポリエチレン（ＥＰＤＭ）、ウレタン、ブタジエンアクリロニトリルゴム（ＮＢＲ）、シリコーンゴムやイソプレンゴムの如きゴム材が挙げられ、抵抗調整のためにカーボンブラックや金属酸化物等の導電性物質を分散させることもでき、また、これらを発泡させたものが挙げられる。また、導電性物質を分散せずに、或いは導電性物質と併用してイオン導電性の材料を用いて抵抗調整をすることも可能である。
【０２８３】
導電性弾性ローラは被帯電体である潜像担持体に対して、弾性に抗して所定の押圧力で圧接させて配設され、導電性弾性ローラと潜像担持体との接触部である帯電接触部が形成される。この帯電接触部の幅は特に制限されるものではないが、導電性弾性ローラと潜像担持体とが安定して密な密着性を得るために１ｍｍ以上、より好ましくは２ｍｍ以上であることが好ましい。
【０２８４】
また、本発明の帯電工程に用いられる帯電部材は、導電性繊維からなるブラシ（ブラシ部材）に電圧を印加することにより像担持体を帯電するものであっても良い。このような接触帯電部材としての帯電ブラシは、一般に用いられている繊維に導電材を分散させて抵抗調整されたものを用いることができる。繊維としては、一般に知られている繊維が使用可能であり、例えばナイロン、アクリル、レーヨン、ポリカーボネート、ポリエステルが挙げられる。導電材としては、一般に知られているものが使用可能であり、例えば、ニッケル、鉄、アルミニウム、金、銀の如き導電性金属、或いは酸化鉄、酸化亜鉛、酸化スズ、酸化アンチモン、酸化チタンの如き導電性の金属酸化物、更にはカーボンブラックの如き導電粉が挙げられる。なおこれら導電材は必要に応じ疎水化、抵抗調整の目的で表面処理が施されていてもよい。なお、使用に際しては、繊維との分散性や生産性を考慮して上記導電材を適宜選択して用いる。
【０２８５】
接触帯電部材としての帯電ブラシには、固定型と回動可能なロール状のものがある。ロール状の帯電ブラシとしては、例えば導電性繊維をパイル地にしたテープを金属製の芯金にスパイラル状に巻き付けてロールブラシとしたものがある。導電性繊維は、繊維の太さが１〜２０デニール（繊維径１０〜５００μｍ程度）、ブラシの繊維の長さは１〜１５ｍｍ、ブラシ密度は１平方インチ当たり１万〜３０万本（１平方メートル当たり１．５×１０^７〜４．５×１０^８本）のものが好ましく用いられる。
【０２８６】
帯電ブラシは、極力ブラシ密度の高い物を使用することが好ましく、１本の繊維を数本〜数百本の微細な繊維から作ることも好ましい。例えば、３００デニール／５０フィラメントのように３００デニールの微細な繊維を５０本束ねて１本の繊維として植毛することも可能である。しかしながら、本発明においては、直接注入帯電の帯電ポイントを決定しているのは、主には帯電部材と潜像担持体との帯電接触部及びその近傍の導電性微粉末の介在密度に依存しているため、帯電部材の選択の範囲は広められている。
【０２８７】
帯電ブラシの抵抗値は、弾性導電性ローラの場合と同様に、像担持体の十分な帯電性と耐リークを得るためには１０^３〜１０^８Ω・ｃｍであることが好ましく、より好ましくは１０^４〜１０^７Ω・ｃｍである。
【０２８８】
帯電ブラシの材質としては、ユニチカ（株）製の導電性レーヨン繊維ＲＥＣ−Ｂ、ＲＥＣ−Ｃ、ＲＥＣ−Ｍ１、ＲＥＣ−Ｍ１０、さらに東レ（株）製のＳＡ−７、日本蚕毛（株）製のサンダーロン、カネボウ製のベルトロン、クラレ（株）製のクラカーボ、レーヨンにカーボンを分散したもの、三菱レーヨン（株）製のローバル等があるが、環境安定性の点でＲＥＣ−Ｂ、ＲＥＣ−Ｃ、ＲＥＣ−Ｍ１、ＲＥＣ−Ｍ１０を用いることが特に好ましい。
【０２８９】
また、接触帯電部材が可撓性を有していることが、接触帯電部材と潜像担持体の接触部において導電性微粉末が潜像担持体に接触する機会を増加させ、高い接触性を得ることができ、直接注入帯電性を向上させる点で好ましい。つまり、接触帯電部材が導電性微粉末を介して密に潜像担持体に接触して、接触帯電部材と潜像担持体の接触部に存在する導電性微粉末が潜像担持体表面を隙間なく摺擦することで、接触帯電部材による潜像担持体の帯電は、放電現象を用いない、導電性微粉末を介した安定かつ安全な直接注入帯電が支配的となる。従って、導電性微粉末を介しての直接注入帯電を適用することにより、従来の放電帯電によるローラ帯電等では得られなかった高い帯電効率が得られ、接触帯電部材に印加した電圧とほぼ同等の電位を潜像担持体に与えることができる。更に、接触帯電部材が可撓性を有していることで、多量の転写残トナー粒子が接触帯電部材に供給された場合に、一時的に転写残トナー粒子を堰き止める効果及び転写残トナー粒子のパターンを均す効果が高まることで、潜像形成阻害及び転写残トナー粒子の回収不良による画像不良の発生をより確実に防止することができる。
【０２９０】
潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量は、少なすぎると導電性微粉末による潤滑効果が十分に得られず、潜像担持体と接触帯電部材との摩擦が大きくなるため、接触帯電部材を潜像担持体に対して速度差を持って回転駆動させることが困難となる。つまり、導電性微粉末の介在量が少ないと駆動トルクが過大となり、無理に回転させると接触帯電部材や潜像担持体の表面が削れやすくなる。更に導電性微粉末による接触機会増加の効果が十分には得られないこともあり、潜像担持体の良好な帯電性能が得られない場合がある。一方、上記接触部における導電性微粉末の介在量が多すぎると、導電性微粉末の接触帯電部材からの脱落が著しく増加し、画像露光の遮光等の潜像形成阻害を起こして作像上に悪影響が出やすい。
【０２９１】
本発明者らの検討によると、潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量は、１０^３個／ｍｍ^２以上であることが好ましく、１０^４個／ｍｍ^２以上であることがより好ましい。この導電性微粉末の介在量が１０^３個／ｍｍ^２以上であることで、駆動トルクが過大となることがなく、導電性微粉末による潤滑効果が十分に得られる。介在量が１０^３個／ｍｍ^２より大幅に低いと十分な所望の接触機会増加の効果が得られず、像担持体の帯電性の低下が生じる傾向がある。
【０２９２】
また、直接注入帯電方式を現像兼クリーニング画像形成における潜像担持体の一様帯電として適用する場合には、転写残トナー粒子の帯電部材への付着或いは混入による潜像担持体の帯電性の低下が懸念される。転写残トナー粒子の帯電部材への付着及び混入を抑制し、または転写残トナー粒子の帯電部材への付着或いは混入による潜像担持体の帯電阻害に打ち勝って、良好な直接注入帯電を行うには、像担持体と接触帯電部材との接触部における導電性微粉末の介在量が１０^４個／ｍｍ^２以上であることが好ましい。介在量が１０^４個／ｍｍ^２より大幅に低いと、転写残トナー粒子が多い場合に潜像担持体の帯電性が低下しやすい。
【０２９３】
帯電工程における潜像担持体上での導電性微粉末の存在量の適正範囲は、導電性微粉末をどれぐらいの密度で潜像担持体上に塗布することで、潜像担持体の均一帯電性の効果が得られるかによっても決定される。
【０２９４】
潜像担持体の帯電時は、少なくとも記録解像度よりは均一な接触帯電が必要なことは言うまでもない。しかしながら、図３の人間の目の視覚特性を示すグラフのように、空間周波数が１０ｃｙｃｌｅｓ／ｍｍ以上では、画像上の識別諧調数が限りなく１に近づいていく、すなわち濃度ムラを識別できなくなる。この特性を積極的に利用すると、潜像担持体上に導電性微粉末を付着させた場合、少なくとも像担持体上で１０ｃｙｃｌｅｓ／ｍｍ以上の密度で導電性微粉末を存在させ、直接注入帯電を行えば良いことになる。たとえ導電性微粉末の存在しないところに潜像担持体上でミクロな帯電不良が発生したとしても、その帯電不良によって発生する画像上の濃度ムラは、人間の視覚特性を越えた空間周波数領域に発生するため、画像上では問題は無いことになる。
【０２９５】
導電性微粉末の潜像担持体上への塗布密度が変化したときに、画像上に濃度ムラとしての帯電不良が認知されるかどうかについては、導電性微粉末がわずかにでも塗布されれば（例えば１０個／ｍｍ^２）、帯電ムラ発生の抑制に効果が認められるが、画像上の濃度ムラが人間にとって許容可能かどうかと言う点においてはまだ不十分である。ところがその塗布量を１０^２個／ｍｍ^２以上にすると、画像の客観評価において急激に好ましい結果が得られるようになる。更に、塗布量を１０^３個／ｍｍ^２以上増加させていくことにより、帯電不良に起因する画像上の問題点は皆無となる。
【０２９６】
直接注入帯電方式による帯電では、放電帯電方式とは根本的に異なり、帯電部材が被帯電体に確実に接触する事で帯電が行われているが、たとえ導電性微粉末を像担持体上に過剰に塗布したとしても、接触できない部分は必ず存在する。ところが本発明の人間の視覚特性を積極的に利用した導電性微粉末の塗布を行うことで、実用上この問題点を解決する。
【０２９７】
また、導電性微粉末の潜像担持体上での存在量の上限値は、導電性微粉末が潜像担持体上に１層が均一に塗布されるまでであり、それ以上塗布されても効果が向上するわけではなく、逆に帯電工程後に過剰の導電性微粉末が吐き出されることで露光光源を遮ったり、散乱させたりという弊害が生じる。
【０２９８】
塗布密度上限値は、導電性微粉末の粒径や接触帯電部材の導電性微粉末の保持性等によっても変わってくるために、一概にはいえないが、強いて記述するならば導電性微粉末が像担持体上に１層が均一に塗布される量が上限とすることができる。
【０２９９】
導電性微粉末の潜像担持体上での存在量は、導電性微粉末の粒径等にもよるが、５×１０^５個／ｍｍ^２を超えると、導電性微粉末の潜像担持体からの脱落が著しく増加する傾向にあり、画像形成装置内を汚染するとともに、導電性微粉末自体の光透過性を問わず潜像担持体への露光量不足が生じる場合がある。この存在量が５×１０^５個／ｍｍ^２以下であれば、脱落する粒子量も低く抑えられ、導電性微粉末の飛散による装置内の汚染を低減するとともに、露光の阻害を改善できる。
【０３００】
更に、現像兼クリーニング工程において、潜像担持体上での導電性微粉末の存在量による転写残トナー粒子の回収性の向上効果についても実験を行ったところ、帯電後現像前の潜像担持体上での導電性微粉末の存在量が１０^２個／ｍｍ^２を超えると、潜像担持体上に導電性微粉末が存在しない場合と比較して明らかに転写残トナー粒子の回収性が向上し、潜像担持体上に導電性微粉末が１層均一に塗布される程度まで画像欠陥のない現像兼クリーニングによる画像が得られた。転写後帯電前の潜像担持体上での導電性微粉末の存在量の場合と同様に、導電性微粉末の存在量が５×１０^５個／ｍｍ^２を超えるあたりから、徐々に導電性微粉末の潜像担持体からの脱落が顕著となり、潜像形成に影響を与えカブリが増加する傾向が見られた。
【０３０１】
すなわち、潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量を１０^３個／ｍｍ^２以上に設定し、且つ潜像担持体上の導電性微粉末の存在量を１０^２個／ｍｍ^２以上とし５×１０^５個／ｍｍ^２を大きく超えないように設定することが、潜像担持体の帯電性が良好であり、転写残トナー粒子の回収性が良好であり、装置内汚染や露光阻害による画像欠陥のない画像を形成するためには好ましい。潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量は１０^４個／ｍｍ^２以上に設定することがより好ましい。
【０３０２】
潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量と潜像形成工程での潜像担持体上の導電性微粉末の存在量との関係は、▲１▼潜像担持体と接触帯電部材との接触部への導電性微粉末の供給量、▲２▼潜像担持体及び接触帯電部材への導電性微粉末の付着性、▲３▼接触帯電部材の導電性微粉末に対する保持性、▲４▼潜像担持体の導電性微粉末に対する保持性等の要因があるため、一概には決定されない。実験的には、潜像担持体と接触帯電部材との接触部における導電性微粉末の介在量が１０^３〜１０^６個／ｍｍ^２の範囲において、潜像担持体上に脱落した粒子の存在量（潜像形成工程での潜像担持体上の導電性微粉末の存在量）を測ると１０^２〜１０^５個／ｍｍ^２であった。
【０３０３】
帯電接触部での導電性微粉末の介在量及び潜像形成工程での潜像担持体上の導電性微粉末の存在量の測定方法について述べる。帯電部での導電性微粉末の介在量は接触帯電部材と潜像担持体の接触面部における値を直接測ることが好ましいが、接触部を形成する接触帯電部材の表面の移動方向が潜像担持体の表面の移動方向とは逆方向である場合、接触帯電部材に接触する前に潜像担持体上に存在した粒子の多くは逆方向に移動しながら接触する帯電部材に剥ぎ取られることから、本発明では接触面部に到達する直前の接触帯電部材表面の粒子量をもって介在量としている。具体的には、帯電バイアスを印加しない状態で像担持体及び弾性導電性ローラの回転を停止し、潜像担持体及び弾性導電性ローラの表面をビデオマイクロスコープ（ＯＬＹＭＰＵＳ製ＯＶＭ１０００Ｎ）及びデジタルスチルレコーダ（ＤＥＬＴＩＳ製ＳＲ−３１００）で撮影する。弾性導電性ローラについては、弾性導電性ローラを像担持体に当接するのと同じ条件でスライドガラスに当接し、スライドガラスの背面からビデオマイクロスコープにて接触面を１０００倍の対物レンズで１０箇所以上撮影した。得られたデジタル画像から個々の粒子を領域分離するため、ある閾値を持って２値化処理し、粒子の存在する領域の数を所望の画像処理ソフトを用いて計測する。また、潜像担持体上の存在量についても像担持体上を同様のビデオマイクロスコープにて撮影し同様の処理を行い計測する。
【０３０４】
潜像担持体上の導電性微粉末の存在量は、上記と同様の手段で転写後帯電前及び帯電後現像前の潜像担持体上を撮影して画像処理ソフトを用いて計測する。
【０３０５】
本発明において、潜像担持体の最表面層の体積抵抗が１×１０^９〜１×１０^１４Ω・ｃｍ、より好ましくは１×１０^１０〜１×１０^１４Ω・ｃｍであることにより、より良好な潜像担持体の帯電性を与えることができ好ましい。電荷の直接注入による帯電方式においては、被帯電体側の抵抗を下げることでより効率良く電荷の授受が行えるようになる。このためには、最表面層の体積抵抗値としては１×１０^１４Ω・ｃｍ以下であることが好ましい。一方、潜像担持体として静電潜像を一定時間保持するためには、最表面層の体積抵抗値としては１×１０^９Ω・ｃｍ以上であることが好ましい。高湿環境下においても微小な潜像まで乱されることなく静電潜像を保持するためには抵抗値として１×１０^１０Ω・ｃｍ以上であることが好ましい。
【０３０６】
更に、潜像担持体が電子写真感光体であり、該電子写真感光体の最表面層の体積抵抗が１×１０^９〜１×１０^１４Ω・ｃｍであることにより、プロセススピードの速い装置においても、像担持体に十分な帯電性を与えることができより好ましい。
【０３０７】
また、潜像担持体はアモルファスセレン、ＣｄＳ、ＺｎＯ_２、アモルファスシリコン又は有機系感光物質の様な光導電絶縁物質層を持つ感光ドラムもしくは感光ベルトであることが好ましく、アモルファスシリコン感光層、又は有機感光層を有する感光体が特に好ましく用いられる。
【０３０８】
有機感光層としては、感光層が電荷発生物質及び電荷輸送性能を有する物質を同一層に含有する単一層型でもよく、又は電荷輸送層と電荷発生層を有する機能分離型感光層であっても良い。導電性基体上に電荷発生層、次いで電荷輸送層の順で積層されている構造の積層型感光層は好ましい例の一つである。
【０３０９】
潜像担持体の表面抵抗を調整することで、更に安定して潜像担持体の均一な帯電を行うことができる。
【０３１０】
潜像担持体の表面抵抗を調整することによって電荷注入をより効率化或いは促進する目的で、電子写真感光体の表面に電荷注入層を設けることも好ましい。電荷注入層は、樹脂中に導電性微粒子を分散させた形態が好ましい。
【０３１１】
電荷注入層を設ける形態としては、例えば、
（ｉ）セレン、アモルファスシリコンの如き無機感光体もしくは単一層型有機感光体の上に、電荷注入層を設ける
（ｉｉ）機能分離型有機感光体の電荷輸送層として、電荷輸送剤と樹脂を有する表面層を持つものに電荷注入層としての機能を兼ねさせる（例えば、電荷輸送層として樹脂中に電荷輸送剤と導電性粒子を分散させる、あるいは電荷輸送剤自体もしくはその存在状態によって、電荷輸送層に電荷注入層としての機能を持たせる）
（ｉｉｉ）機能分離型有機感光体上に最表面層として電荷注入層を設ける等があるが、最表面層の体積抵抗が好ましい範囲にあることが重要である。
【０３１２】
電荷注入層としては、例えば、金属蒸着膜等の無機材料の層、あるいは導電性微粒子を結着樹脂中に分散させた導電粉分散樹脂層等によって構成され、蒸着膜は蒸着、導電粉分散樹脂層はディッピング塗工法、スプレー塗工法、ロールコート塗工法及びビーム塗工法等の適当な塗工法にて塗工することによって形成される。
【０３１３】
また、絶縁性のバインダーに光透過性の高いイオン導電性を持つ樹脂を混合もしくは共重合させて構成するもの、または中抵抗で光導電性のある樹脂単体で構成するものでもよい。
【０３１４】
この中でも、潜像担持体の最表面層が、少なくとも金属酸化物からなる導電性微粒子（以下、「酸化物導電微粒子」と表記する）が分散された樹脂層であることが好ましい。すなわち、像担持体の最表面層をこのような構成にすることにより、電子写真感光体の表面の抵抗を下げてより効率良く電荷の授受を行うことができ、かつ表面の抵抗を下げたことで像担持体が静電潜像を保持している間に潜像電荷が拡散することによる潜像のボケもしくは流れを抑制できるため好ましい。
【０３１５】
上記酸化物導電微粒子が分散された樹脂層の場合、分散された粒子による入射光の散乱を防ぐために、入射光の波長よりも酸化物導電微粒子の粒径の方が小さいことが好ましい。従って、分散される酸化物導電微粒子の粒径としては０．５μｍ以下であることが好ましい。酸化物導電微粒子の含有量は、最外層の総質量に対して２〜９０質量％が好ましく、５〜７０質量％がより好ましい。酸化物導電微粒子の含有量が上記範囲よりも少なすぎる場合には、所望の体積抵抗値を得にくくなる。また、含有量が上記範囲よりも多すぎる場合には、膜強度が低下してしまうため、電荷注入層が削り取られやすくなり、感光体の寿命が短くなる傾向があり、また抵抗が低くなりすぎてしまうことによって潜像電位が流れることによる画像不良を生じやすくなる。
【０３１６】
また、電荷注入層の層厚は、０．１〜１０μｍが好ましく、潜像の輪郭のシャープさを得る上では５μｍ以下であることがより好ましく、電荷注入層の耐久性の点からは１μｍ以上であることがより好ましい。
【０３１７】
電荷注入層のバインダーは下層のバインダーと同じとすることも可能であるが、この場合には電荷注入層の塗工時に下層（例えば電荷輸送層）の塗工面を乱してしまう可能性があるため、形成方法を特に選択する必要がある。
【０３１８】
なお、本発明における潜像担持体の最表面層の体積抵抗値の測定方法は、表面に金を蒸着させたポリエチレンテレフタレート（ＰＥＴ）フィルム上に像担持体の最表面層と同様の組成からなる層を作成し、これを体積抵抗測定装置（ヒューレットパッカード社製４１４０ＢｐＡＭＡＴＥＲ）にて、温度２３℃，湿度６５％の環境で１００Ｖの電圧を印加して測定するというものである。
【０３１９】
また、本発明においては、潜像担持体表面に離型性を付与することが好ましく、潜像担持体表面の水に対する接触角は８５度以上であることが好ましい。より好ましくは潜像担持体表面の水に対する接触角は９０度以上である。
【０３２０】
潜像担持体表面が高い接触角を有することは、潜像担持体表面がトナー粒子に対して高い離型性を有することを示す。この効果により、現像兼クリーニング工程においては現像剤の回収効率が向上する。また、転写残トナー粒子量を著しく減少させることができるため、転写残トナー粒子による潜像担持体の帯電性低下を抑制することもできる。
【０３２１】
潜像担持体表面に離型性を付与する手段としては、例えば、
▲１▼膜を構成する樹脂自体に表面エネルギーの低いものを用いる。
▲２▼撥水、親油性を付与するような添加剤を加える。
▲３▼高い離型性を有する材料を粉体状にして分散する。
が挙げられる。
【０３２２】
▲１▼としては、樹脂の構造中にフッ素含有基、シリコーン含有基を導入することにより達成する。▲２▼としては、界面活性剤を添加剤として添加すればよい。▲３▼としては、ポリ４フッ化エチレン、ポリフッ化ビニリデン及びフッ化カーボンの如きフッ素原子を含む化合物、シリコーン系樹脂又はポリオレフィン系樹脂を用いることが挙げられる。
【０３２３】
これらの手段によって潜像担持体表面の水に対する接触角を８５度以上とすることが可能である。
【０３２４】
この中でも潜像担持体の最表面層が、少なくともフッ素系樹脂、シリコーン系樹脂又はポリオレフィン系樹脂から選ばれる少なくとも１種以上の材料からなる滑剤微粒子が分散された層であることが好ましい。特に、ポリ４フッ化エチレンやポリフッ化ビニリデンの如き含フッ素樹脂を用いることが好適である。本発明においては、▲３▼の粉体として含フッ素樹脂を離型性粉体として用いた場合には、最表面層への分散が好適である。
【０３２５】
これらの粉体を表面に含有させるためには、バインダー樹脂中に該粉体を分散させた層を感光体最表面に設けるか、あるいは、元々樹脂を主体として構成されている有機感光体であれば、新たに表面層を設けなくても、最表面層に該粉体を分散させれば良い。
【０３２６】
上記の離型性を有する粉体の潜像担持体の表面層への添加量は、表面層総質量に対して、１〜６０質量％であることが好ましく、２〜５０質量％であることがより好ましい。添加量が上記範囲よりも少なすぎると転写残トナー粒子が充分に減少せず、現像兼クリーニング装置での現像剤の回収効率が充分でない。添加量が上記範囲よりも大きすぎると膜の強度が低下したり、感光体への入射光量が著しく低下して像担持体の帯電性を損ねたりするため好ましくない。該粉体の粒径については、画質の面から１μｍ以下であることが好ましく、０．５μｍ以下であることがより好まし粒径が上記範囲よりも大きすぎると入射光の散乱によりラインの切れが悪くなりやすく、解像性を損ねやすい。
【０３２７】
本発明において、接触角の測定は純水を用い、装置は協和界面科学（株）製接触角計ＣＡ−ＤＳ型を用いた。
【０３２８】
本発明に用いられる潜像担持体としての感光体の好ましい様態のひとつを以下に説明する。導電性基体としては、アルミニウム又はステンレスの如き金属；アルミニウム合金又は酸化インジウム−酸化錫合金による被膜層を有するプラスチック；導電性粒子を含浸させた紙又はプラスチック；導電性ポリマーを有するプラスチック；の円筒状シリンダー及びフィルムが用いられる。
【０３２９】
これら導電性基体上には、感光層の接着性向上、塗工性改良、基体の保護、基体上に欠陥の被覆、基体からの電荷注入性改良または感光層の電気的破壊に対する保護を目的として下引き層を設けても良い。
【０３３０】
下引き層は、ポリビニルアルコール、ポリ−Ｎ−ビニルイミダゾール、ポリエチレンオキシド、エチルセルロース、メチルセルロース、二トロセルロース、エチレン−アクリル酸コポリマー、ポリビニルブチラール、フェノール樹脂、カゼイン、ポリアミド、共重合ナイロン、ニカワ、ゼラチン、ポリウレタン又は酸化アルミニウムの如き材料によって形成される。下引き層の膜厚は通常０．１〜１０μｍ、好ましくは０．１〜３μｍが良い。
【０３３１】
電荷発生層は、アゾ系顔料、フタロシアニン系顔料、インジゴ系顔料、ペリレン系顔料、多環キノン系顔料、スクワリリウム色素、ピリリウム塩類、チオピリリウム塩類、トリフェニルメタン系色素又はセレンや非晶質シリコンの如き無機物質等の電荷発生物質を適当な結着剤に分散し塗工する、あるいは蒸着により形成する。なかでもフタロシアニン系顔料が感光体感度を本発明に適合する感度に調整するうえで好ましい。結着剤としては、例えば、ポリカーボネート樹脂、ポリエステル樹脂、ポリビニルブチラール樹脂、ポリスチレン樹脂、アクリル樹脂、メタクリル樹脂、フェノール樹脂、シリコーン樹脂、エポキシ樹脂、酢酸ビニル樹脂が挙げられる。電荷発生層中に含有される結着剤の量は８０質量％以下、好ましくは０〜４０質量％であることが良い。電荷発生層の膜厚は５μｍ以下、特には０．０５〜２μｍが好ましい。
【０３３２】
電荷輸送層は、電界の存在下で電荷発生層から電荷キャリアを受け取り、これを輸送する機能を有している。電荷輸送層は電荷輸送物質を必要に応じて結着樹脂と共に溶剤中に溶解し、塗工することによって形成され、その膜厚は一般的には５〜４０μｍである。電荷輸送物質としては、主鎖または側鎖にビフェニレン、アントラセン、ピレン及びフェナントレンの如き多環芳香族化合物；インドール、カルバゾール、オキサジアゾール及びピラゾリンの如き含窒素環式化合物；ヒドラゾン化合物；スチリル化合物；セレン；セレン−テルル；非晶質シリコン；硫化カドニウムが挙げられる。
【０３３３】
これら電荷輸送物質を分散させる結着樹脂としては、ポリカーボネート樹脂、ポリエステル樹脂、ポリメタクリル酸エステル、ポリスチレン樹脂、アクリル樹脂及びポリアミド樹脂の如き樹脂；ポリ−Ｎ−ビニルカルバゾール及びポリビニルアントラセンの如き有機光導電性ポリマーが挙げられる。
【０３３４】
表面層として、電荷注入をより効率化或いは促進するために樹脂中に導電性微粒子を分散させた層を設けてもよい。表面層の樹脂としては、ポリエステル、ポリカーボネート、アクリル樹脂、エポキシ樹脂、フェノール樹脂、あるいはこれらの樹脂の硬化剤が単独あるいは２種以上組み合わされて用いられる。導電性微粒子の例としては、金属又は金属酸化物が挙げられる。好ましくは、酸化亜鉛、酸化チタン、酸化スズ、酸化アンチモン、酸化インジウム、酸化ビスマス、酸化スズ被膜酸化チタン、スズ被膜酸化インジウム、アンチモン被膜酸化スズ又は酸化ジルコニウムの超微粒子がある。これらは単独で用いても２種以上を混合して用いても良い。
【０３３５】
図５は、表面層として電荷注入層を設けた潜像担持体（感光体）の層構成模型図である。即ち感光体は、導電性基体（アルミニウムドラム基体）１１上に導電層１２、正電荷注入防止層１３、電荷発生層１４、電荷輸送層１５の順に重ねて塗工された一般的な有機感光体ドラムに電荷注入層１６を塗布することにより、電荷注入による帯電性能を向上させたものである。
【０３３６】
潜像担持体の最表層に形成される電荷注入層１６として重要な点は、表層の体積抵抗値が１×１０^９〜１×１０^１４Ω・ｃｍの範囲にあることである。本構成のように電荷注入層１６を設けない場合でも、例えば潜像担持体の最表層となる電荷輸送層１５が上記抵抗範囲にある場合は同等の効果が得られる。例えば、表層の体積抵抗が約１０^１３Ω・ｃｍであるアモルファスシリコン感光体等を用いても同様に電荷注入による良好な帯電性が得られる。
【０３３７】
本発明においては、潜像担持体の帯電面に静電潜像を形成する潜像形成工程及び潜像形成手段が、潜像担持体表面に静電潜像としての画像情報を像露光により書き込む工程及び像露光手段であることが好ましい。静電潜像形成のための画像露光手段としては、デジタル的な潜像を形成するレーザー走査露光手段に限定されるものではなく、通常のアナログ的な画像露光やＬＥＤなどの他の発光素子でも構わないし、蛍光燈等の発光素子と液晶シャッター等の組み合わせによるものなど、画像情報に対応した静電潜像を形成できるものであるなら構わない。
【０３３８】
潜像担持体は静電記録誘電体であっても良い。この場合は、像担持体面としての誘電体面を所定の極性、電位に一様に一次帯電した後、除電針ヘッド、電子銃等の除電手段で選択的に除電して目的の静電潜像を書き込み形成する。
【０３３９】
前述したように本発明の現像剤は、トナー劣化防止のためのトナー表面上の外添剤の保持といった観点から、トナーの平均円形度が０．９７０未満が好ましい。しかしトナーの円形度が低いと帯電量が不十分となり、転写効率の低下を生じやすい。また更に、たとえトナー粒子に添加する導電性微粒子の粒径を巧く調整したとしても、やはりトナー粒子の摩擦帯電特性の低下は、完全には防ぐことが出来ない場合が多い。そのためこのような平均円形度が０．９７０未満で、且つ導電性微粒子が外添されたトナーを用いる場合、現像剤担持体による帯電付与性を高める必要がある。
【０３４０】
そこで本発明において、該現像剤担持体として、基体と該基体上に形成された樹脂被覆層とを有しており、該樹脂被覆層に正帯電性の物質を含有させたものを用いている。更に現像剤の過剰帯電を防止し帯電量を適正化するため、該樹脂被覆層中には、少なくとも導電性物質を含有し、該樹脂被覆層は導電性樹脂被覆層となっていることが好ましい。
【０３４１】
本発明で使用する現像剤担持体の被覆層用結着樹脂としては、一般に公知の樹脂がいずれも使用可能である。例えば、スチレン系樹脂、ビニル系樹脂、スチレン−ジエン系樹脂、ポリエーテルスルホン樹脂、ポリカーボネート樹脂、ポリフェニレンオキサイド樹脂、ポリアミド樹脂、フッ素樹脂、繊維素系樹脂、アクリル系樹脂等の熱可塑性樹脂、エポキシ樹脂、ポリエステル樹脂、アルキッド樹脂、フェノール樹脂、メラミン樹脂、ポリウレタン樹脂、尿素樹脂、シリコーン樹脂、ポリイミド樹脂等の熱硬化性或いは光硬化性の樹脂等を使用することができる。これらの中でも、シリコーン樹脂、フッ素樹脂のような離型性に優れるもの、或いは、ポリエーテルスルホン樹脂、ポリカーボネート樹脂、ポリフェニレンオキサイド樹脂、ポリアミド樹脂、フェノール樹脂、ポリエステル樹脂、ポリウレタン樹脂、スチレン系樹脂、アクリル系樹脂のような機械的性質に優れたものを使用することがより好ましい。
【０３４２】
これら公知の結着樹脂に正帯電性物質を添加して用いることも好ましい。
【０３４３】
正帯電性物質とは、単独で鉄粉と混合して摩擦帯電させた場合に正極性に帯電するものであれば良い。また、分散される被覆層用結着樹脂中において正帯電を示すのであれば、そのような樹脂と組み合わせて用いる場合には、必ずしも単独で鉄粉と混合して摩擦帯電させた場合において正極性に帯電するものとは限らない。
【０３４４】
そのような正帯電性物質としては、ニグロシン系染料，トリフェニルメタン系染料，四級アンモニウム塩，グアニジン誘導体，イミダゾール誘導体，アミン系及びポリアミン系化合物の如き一般に正電荷制御剤として用いられるもの；合成シリカ、石英粉、アルミナ、ハイドロタルサイト類化合物の如き無機粉体；スルホン酸基含有アクリルアミドを構成モノマーとして有する共重合体がある。またこれら無機微粉体にアミノシランカップリング剤を処理して用いる方法もある。
【０３４５】
これらの中でも、次に挙げる化合物が、現像剤を良好に帯電させるために、好ましく用いられる。
【０３４６】
▲１▼正帯電性物質として、被覆層中に含窒素複素環化合物を含有することが好ましい。
【０３４７】
この際に使用する含窒素複素環化合物としては、個数平均粒径が、好ましくは２０μｍ以下、より好ましくは０．１〜１５μｍのものを使用する。即ち、含窒素複素環化合物の個数平均粒径が２０μｍを超える場合には、現像スリーブを構成する導電性樹脂被覆層中における含窒素複素環化合物の分散不良が生じ、帯電性能の向上効果が充分に得られ難くなり、好ましくない。
【０３４８】
本発明で使用し得る含窒素複素環化合物としては、イミダゾール、イミダリン、イミダゾロン、ピラゾリン、ピラゾール、ピラゾロン、オキサゾリン、オキサゾール、オキサゾロン、チアゾリン、チアゾール、チアゾロン、セレナゾリン、セレナゾール、セレナゾロン、オキサジアゾール、チアジアゾール、テトラゾール、ベンゾイミダゾール、ベンゾトリアゾール、ベンゾオキサゾール、ベンゾチアゾール、ベンゾセレナゾール、ピラジン、ピリミジン、ピリダジン、トリアジン、オキサジン、チアジン、テトラジン、ポリアザイン、ピリダジン、ピリミジン、ピラジン、インドール、イソインドール、インダゾール、カルバゾール、キノリン、ピリジン、イソキノリン、シンノリン、キナゾリン、キナキサリン、フタラジン、プリン、ピロール、トリアゾール、フェナジンの如き化合物が挙げられる。本発明においては、特にイミダゾール化合物が、本発明に用いる現像剤担持体とトナーとの相互作用による効果を促進するため好ましい。
【０３４９】
本発明においては、イミダゾール化合物の中でも、特に、下記一般式（１）又は（２）で示されるイミダゾール化合物を、現像剤担持体の導電性樹脂被覆層に用いれば、トナーに対する迅速且つ均一な帯電付与能を与えることができ、更に、導電性樹脂被覆層の強度を高めることができるのでより好ましい。
【０３５０】
【化１１】

［式中、Ｒ_１及びＲ_２は、水素原子、又は、アルキル基、アラルキル基及びアリール基からなる群より選ばれる置換基を表し、Ｒ_１及びＲ_２は、同一であっても異なっていてもよい。Ｒ_３及びＲ_４は、炭素数が３〜３０の直鎖状アルキル基を表し、Ｒ_３及びＲ_４は、同一であっても異なっていてもよい。］
【０３５１】
【化１２】

［式中、Ｒ_５及びＲ_６は、水素原子、又は、アルキル基、アラルキル基及びアリール基からなる群より選ばれる置換基を表し、Ｒ_５及びＲ_６は、同一であっても異なっていてもよい。Ｒ_７は炭素数が３〜３０の直鎖状アルキル基を表す。］
上記した構造を有するイミダゾール化合物を用いることが好ましい理由としては、上記一般式（１）又は（２）で示される構造を有するイミダゾール化合物は、置換基として炭素数３〜３０の直鎖状アルキル基を有するため、被覆層用結着樹脂に対する分散性が良好であるので、現像スリーブの導電性樹脂被覆層の他の構成材料と共に良好に分散され、特に優れた分散状態の導電性樹脂被覆層表面の形成が可能となる結果、現像スリーブのトナーに対する摩擦帯電特性がより良好になるものと考えている。
【０３５２】
本発明において好適に使用し得る上記一般式（１）又は（２）で示される構造を有するイミダゾール化合物の如き含窒素複素環化合物は、これを構成する含窒素複素環基が、単環であってもよいし、他の基と縮環していてもよく、また、置換されていてもよい。更に、本発明で好適に使用し得る含窒素複素環化合物の含複素環基が置換されている場合には、その置換基として、例えば、アルキル基、アラルキル基、アルケニル基、アルキニル基、アルコキシ基、アリール基、置換アミノ基、ウレイド基、ウレタン基、アリールオキシ基、スルファモイル基、カルバモイル基、アルキル又はアリールチオ基、アルキル又はアリールスルホニル基、アルキル又はアリールスルフィニル基、ヒドロキシ基、ハロゲン原子、シアノ基、スルホ基、アリールオキシカルボニル基、アシル基、アルコキシカルボニル基、アシルオキシ基、カルボンアミド基、スルホンアミド基、カルボシル基、リン酸アミド基、ジアシルアミノ基、イミド基等を有するものを用いることができる。これらの置換基は、さらに置換基を有していてもよい。その際の置換基の例としては、含窒素複素環の置換基として上記で挙げた置換基を用いることができる。
【０３５３】
次に導電性樹脂被覆層の含窒素複素環化合物及び導電性微粒子の含有量について説明する。しかし、これは本発明において特に好ましい範囲であって、本発明はこれに限定されるものではない。先ず、導電性樹脂被覆層中に分散させる含窒素複素環化合物の含有量としては、被覆層用結着樹脂１００質量部に対して、好ましくは０．５〜６０質量部、より好ましくは１〜５０質量部の範囲とした場合に、特に好ましい結果を与える。即ち、含窒素複素環化合物の含有量が０．５質量部未満の場合には含窒素複素環化合物の添加効果が小さく、６０質量部を超える場合には、導電性樹脂被覆層の体積抵抗を低く制御することが難しくなり、チャージアップ現象が発生し易くなる。
【０３５４】
導電性樹脂被覆層中に含窒素複素環化合物と併用して分散含有させる導電性微粒子の含有量としては、被覆層用結着樹脂１００質量部に対して、好ましくは４０質量部以下、より好ましくは２〜３５質量部の範囲で使用すると特に好ましい結果が得られる。即ち、導電性微粒子の含有量が４０質量部を超える場合には、導電性樹脂被覆層の被膜強度の低下、及びトナーの帯電量の低下が認められるため、好ましくない。
【０３５５】
▲２▼本発明の現像剤担持体においては、正帯電性の物質として被覆層中に含窒素化合物を含有することも好ましい。そのような材料としては、例えば含窒素ビニルモノマーに由来するユニットが含まれる共重合体が挙げられる。共重合体を形成するポリマーとしては、ビニル重合性モノマーが好ましい。樹脂被覆層が含有するバインダー樹脂が、機械的強度が高いビニル重合性モノマーと、現像剤に対して高い負摩擦帯電特性を有する含窒素ビニルモノマーの共重合体を有していることにより、現像剤担持体は、樹脂被覆層の耐摩耗性、耐トナー付着・融着性が高く、多数枚耐久後まで良好な摩擦帯電付与特性を有する。
【０３５６】
また、この共重合体は、含窒素ビニルモノマーを有していることから、カーボンブラック及びグラファイトの如き導電性微粉末の樹脂被覆層中での分散性が向上する。よって、樹脂被覆層の電気的抵抗が良好に低下し、且つ樹脂被覆層表面での摩擦帯電付与特性の均一性が向上し、より現像剤に対する摩擦帯電付与特性が高く、且つ現像剤の帯電量分布がシャープになり、さらに、樹脂被覆層自体の被膜強度も向上するため、より多数枚耐久性に優れるものである。共重合体がこの含窒素ビニルモノマーを有していることで、カーボンブラック及びグラファイトの如き導電性微粉末の樹脂被覆層中での分散性が向上する理由は、明確には分からないが、含窒素ビニルモノマーにおける窒素原子に基づく極性基を含むことにより、溶媒、特に極性を有する溶媒への溶解性が良好となるため、樹脂が溶解している溶解液の導電性微粒子に対する濡れ性が向上し、溶解液中での導電性微粒子を塗工して樹脂被覆層を形成した場合に、樹脂被覆層中での導電性微粒子の分散性が向上するためと考えられる。特に、導電性微粒子が、カーボンブラックの如き極性基を表面に有する物質の場合には、窒素原子に基づく極性基により親和性がより高まるため、より効果的である。
【０３５７】
本発明において、ビニル重合性モノマー（Ｍ）及び含窒素ビニルモノマー（Ｎ）を有する共重合体の共重合ｍｏｌ比率は、Ｍ：Ｎ＝４：１〜９９９：１を満たすことが好ましい。Ｍの割合が９９９：１を超える場合には、含窒素ビニルモノマーの添加効果がほとんどない、すなわち摩擦帯電付与性を向上させる効果が極めて少なく、共重合させる効果がほとんどみられなくなってしまう。Ｍの割合が４：１未満の場合には、例えばＴｇが下がることにより樹脂層が安定せず、電子写真装置本体の昇温により樹脂層の帯電付与、耐摩耗性の特性が損なわれたり、トナーが固着しやすくなったりする可能性がある。また、これ以上含窒素ビニルモノマーの比率を上げても帯電付与効果は飽和されるため特に必要とされない。
【０３５８】
本発明において、上記共重合体の主成分と為りうるビニル重合性モノマーとしては、例えば、スチレン、α−メチルスチレン、アクリル酸、アクリル酸メチル、アクリル酸エチル、アクリル酸プロピル、アクリル酸ｎ−ブチル、アクリル酸ｉｓｏ−ブチル、アクリル酸ドデシル、アクリル酸オクチル、アクリル酸−２−エチルヘキシル、アクリル酸フェニル、アクリル酸シクロヘキシル、ヒドロキシエチルアクリレート、ジメチル（アミノ）エチルアクリレート、ジエチル（アミノ）エチルアクリレート、メタクリル酸、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸プロピル、メタクリル酸ｎ−ブチル、メタクリル酸ｉｓｏ−ブチル、メタクリル酸オクチル、メタクリル酸シクロヘキシル、ヒドロキシエチルメタクリレート、ジメチル（アミノ）エチルメタクリレート、ジエチル（アミノ）エチルメタクリレート、アクリロニトリル、メタクリロニトリル、アクリルアミドの如き二重結合を有するモノカルボン酸、若しくはそのエステル化合物；例えば、マレイン酸、マレイン酸ブチル、マレイン酸メチル、マレイン酸ジメチルの如き二重結合を有するジカルボン酸、及びそのエステル化合物；が挙げられ、これらは単独で、もしくは２種以上の混合で使用することができる。特に、ビニル基を有する酸モノマー或いは酸エステルモノマーを含有させると、現像剤担持体上での現像剤の帯電安定性に効果がある。その場合、摩擦帯電量の安定効果としては、酸エステルモノマーよりも酸モノマーを用いた方がやや良好である。
【０３５９】
本発明ではビニル重合性モノマーとしてメチルメタクリレートを用いることが好ましい。メチルメタクリレートはポリマーとして用いられた場合、機械的強度に優れている。またスリーブ表面層の結着樹脂に含有させて用いた場合には、良好な現像剤に対する摩擦帯電付与性が得られる。しかしながら、ホモポリマーとして用いた場合には摩擦帯電付与性が不十分であることが多く、カーボンブラック、グラファイトなどの顔料の分散性もそれほど良くはない。本発明のように含窒素ビニルモノマーを含む共重合体として用いることによって、摩擦帯電付与性を向上させることができる。また本発明においては、好ましくはメチルメタクリレート成分が８０％以上の比率で含有されることから、メチルメタクリレートのホモポリマーと比較しても機械的強度、例えば耐磨耗性を損なうことはない。さらに含窒素ビニルモノマー成分が含有されていることから、樹脂層中に導電性微粉末などの顔料成分を分散した場合においては、分散性が向上し、この点においても耐磨耗性等にとっては好ましい。
【０３６０】
含窒素ビニルモノマーに由来するユニットが含まれる共重合体の分子量としては、重量平均分子量Ｍｗで、３０００〜５００００の範囲にあることが好ましい。分子量Ｍｗが３０００未満の場合には低分子量成分が多すぎるため、トナーがスリーブに付着または固着しやすくなったり、樹脂の帯電付与性が低下したりする。またＭｗが５００００を超える場合には、分子量が高すぎ、また溶媒中の樹脂粘度が高いため、塗工不良や顔料類を添加した場合には分散不良の原因となり、樹脂層の組成が不均一になりトナー帯電が安定しない、表面粗さが安定しない、耐磨耗性が減少するなどの原因となる。
【０３６１】
また含窒素ビニルモノマーに由来するユニットが含まれる共重合体の重量平均分子量と数平均分子量の比を表すＭｗ／Ｍｎは３．５以下であることが好ましい。Ｍｗ／Ｍｎが３．５を超えた場合、低分子量成分が増加するために、トナーの付着性の増加や融着が増加したり、トナーへの摩擦帯電付与性の低下が生じたりしやすい。
【０３６２】
本発明において、含窒素ビニルモノマーに由来するユニットが含まれる共重合体のＧＰＣによるクロマトグラムの分子量分布は次のように測定される。すなわち、４０℃のヒートチャンバー中でカラムを安定化させ、この温度におけるカラムに、溶媒としてＴＨＦを毎分１ｍｌの流速で流し、ＴＨＦ試料溶液を約１００μｌ注入して測定する。試料の分子量測定にあたっては、試料の有する分子量分布を、数種類の単分散ポリスチレン標準試料により作成された検量性の対数値とカウント数との関係から算出した。検量線作成用の標準ポリスチレン試料としては、例えば、東ソー社製あるいは、昭和電工製の分子量が１０^２〜１０^７程度のものを用い、少なくとも１０点程度の標準ポリスチレン試料を用いるのが適当である。また、検出器にはＲＩ（屈折率）検出器を用いる。なおカラムとしては、市販のポリスチレンジェルカラムを複数本組み合わせるのが良く、例えば昭和電工社製のＳｈｏｄｅｘＧＰＣＫＦ−８０１，８０２，８０３，８０４，８０５，８０６，８０７，８００Ｐの組み合わせや、東ソー社製のＴＳＫｇｅｌＧ１０００Ｈ（Ｈ_ＸＬ），Ｇ２０００Ｈ（Ｈ_ＸＬ），Ｇ３０００Ｈ（Ｈ_ＸＬ），Ｇ４０００Ｈ（Ｈ_ＸＬ），Ｇ５０００Ｈ（Ｈ_ＸＬ），Ｇ６０００Ｈ（Ｈ_ＸＬ），Ｇ７０００Ｈ（Ｈ_ＸＬ），ＴＳＫｇｕａｒｄｃｏｌｕｍｎの組み合わせを挙げることができる。
【０３６３】
含窒素ビニルモノマーの代表例としては、例えば、ｐ−ジメチルアミノスチレン、ジメチルアミノメチルアクリレート、ジメチルアミノエチルアクリレート、ジメチルアミノプロピルアクリレート、ジエチルアミノメチルアクリレート、ジエチルアミノエチルアクリレート、ジメチルアミノメチルメタクリレート、ジエチルアミノメチルメタクリレート、ジメチルアミノプロピルメタクリレート、ジエチルアミノメチルメタクリレート、ジエチルアミノエチルメタクリレートが挙げられ、さらに、Ｎ−ビニルイミダゾール、Ｎ−ビニルベンズイミダゾール、Ｎ−ビニルカルバゾール、Ｎ−ビニルピロール、Ｎ−ビニルピペリジン、Ｎ−ビニルモルフォリン、Ｎ−ビニルインドールの如き含窒素複素環式Ｎ−ビニル化合物が挙げられる。
【０３６４】
特には、ジメチルアミノメチルアクリレート、ジメチルアミノエチルアクリレート、ジメチルアミノプロピルアクリレート、ジエチルアミノメチルアクリレート、ジエチルアミノエチルアクリレート、ジメチルアミノメチルメタクリレート、ジエチルアミノメチルメタクリレート、ジメチルアミノプロピルメタクリレート、ジエチルアミノメチルメタクリレート、ジエチルアミノエチルメタクリレートの如き下記一般式（３）
【０３６５】
【化１３】

〔式中、Ｒ_７，Ｒ_８，Ｒ_９及びＲ_１０は、水素原子あるいは炭素数１〜４の飽和炭化水素基を示し、ｎは１〜４の整数を示す。〕
で表される含窒素ビニルモノマーを用いることが好ましい。
【０３６６】
特には、ジメチルアミノエチルメタクリレート、ジエチルアミノエチルアクリレートの如き下記一般式（８）
【０３６７】
【化１４】

［但し、Ｒ_１、Ｒ_２、Ｒ_３は水素原子あるいは炭素数１〜４の飽和炭化水素基を示す。］
に示される含窒素ビニルモノマーを用いることが好ましい。
【０３６８】
また、本発明に用いられる含窒素ビニルモノマーとしては、４級アンモニウム基含有ビニルモノマーを用いることもできる。４級アンモニウム基含有ビニルモノマーとしては、下記一般式（９）に示されるものが挙げられる。
【０３６９】
【化１５】

〔式中、Ｒ₅は水素原子又はメチル基を示し、Ｒ₆は、炭素数１〜４のアルキレン基を示し、Ｒ₇〜Ｒ₉は、メチル基、エチル基又はプロピル基を示し、Ｘ₁は、−ＣＯＯ−又は−ＣＯＮＨ−を示し、Ａ^-はＣｌ^-，（１／２）ＳＯ₄ ^2-の如きアニオンを示す。〕
本発明において、含窒素ビニルモノマーを含む共重合体は、それ単独で被覆層用結着樹脂として用いても、他の結着樹脂に添加して使用しても良い。他の結着樹脂に添加して使用する場合、上述したような一般に公知の樹脂が使用可能である。現像剤担持体に要求される機械的強度を考慮すると熱硬化性の樹脂がより好ましいが、十分な機械的強度を有するものであれば、熱可塑性樹脂も適用可能である。
【０３７０】
また、この様な樹脂を荷電制御剤的にこれより更に強度の高い熱硬化性樹脂等にブレンドして用いても良い。そのような場合にも、該含窒素ビニルモノマーに起因する効果によってスリーブの正帯電性は良好なものとなる。
【０３７１】
▲３▼更に本発明の現像剤担持体においては、正帯電性物質として、現像担持体表面の被覆層中に、少なくともビニル重合性モノマーとスルホン酸基含有アクリルアミドモノマーとの共重合体を含有させ、且つ同時に、被覆層用結着樹脂として、その分子構造中に少なくとも−ＮＨ_２基、＝ＮＨ基、もしくは−ＮＨ−結合のいずれかを含有する樹脂を用いることも好ましい。
【０３７２】
本発明において、正帯電性を示すという明確な理由は定かではないが、ビニル重合性モノマーとスルホン酸基含有アクリルアミドモノマーとの共重合体を、分子構造中に少なくとも−ＮＨ_２基、＝ＮＨ基、もしくは−ＮＨ−結合のいずれかを有する被覆層用結着樹脂に分散させて用いると、均一に分散し、前記共重合体と結着樹脂との構造的な相互作用により、樹脂組成物全体の帯電性が均一且つ十分な正帯電性を有するようになるためではないかと考えられる。
【０３７３】
本発明における上記重合体は、ビニル重合性モノマーとスルホン酸基含有アクリルアミドモノマーとの質量に基づく共重合比が９８：２〜８０：２０であり、重量平均分子量が２０００〜５００００の重合体であることが好ましい。スルホン酸基含有アクリルアミドモノマーの割合が２質量％より少なくなると、トナーに対し正電荷を誘起させる能力に劣る。２０質量％超になると、耐湿性などの環境安定性の低下、被覆膜特性の低下が生じ好ましくない。また重量平均分子量が２０００未満になると低分子量成分が多すぎるため、トナーがスリーブに付着または固着しやすくなったり、樹脂の帯電付与性が低下したりする。重量平均分子量が５００００超になると、樹脂との相溶性が低下し、環境変動や経時により安定した帯電性が得られなくなり、また、溶媒中の樹脂粘度が高いため、塗工不良や顔料類を添加した場合には分散不良の原因となり、樹脂被覆層の組成が不均一になりトナー帯電が安定せず、さらに樹脂被覆層の表面粗さが安定せず、耐摩耗性が減少するなどの原因となる。
【０３７４】
上記に示したような本発明で使用するスルホン酸基含有アクリルアミドモノマーの添加量は、結着樹脂１００質量部に対して１〜１００質量部とすることが好ましい。１質量部未満では添加による帯電付与性の向上が見られず、１００質量部を超えると結着樹脂中への分散不良となり被膜強度の低下を招きやすい。
【０３７５】
本発明における上記共重合体を製造するのに用いることのできるビニル重合性モノマーとしては、スチレン、α−メチルスチレン、メチル（メタ）アクリレート、エチル（メタ）アクリレート、プロピル（メタ）アクリレート、ｎ−ブチル（メタ）アクリレート、ｉｓｏ−ブチル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、ジメチル（アミノ）エチル（メタ）アクリレート、ジエチル（アミノ）エチル（メタ）アクリレート、ヒドロキシエチル（メタ）アクリレート、（メタ）アクリル酸、酢酸ビニル、プロピオン酸ビニルが挙げられ、これらは単独で、もしくは２種以上の混合で使用することができる。好ましくはスチレンとアクリル酸エステルまたはメタクリル酸エステルとの組み合わせが挙げられる。なお、一般にトナー用結着剤樹脂のガラス転移点は、７０℃以下ないし６０℃以下である場合が多いので、上記ビニル重合性モノマーを使用するに際しては、被覆膜表面へのトナーの付着を避ける上で６５℃以上、好ましくは７０℃以上、さらに好ましくは９０℃以上のガラス転移点を有する被覆膜が形成されるように適宜選択して被覆層用結着樹脂とするのが好ましい。
【０３７６】
またスルホン酸基含有アクリルアミドモノマーとしては、２−アクリルアミドプロパンスルホン酸、２−アクリルアミド−ｎ−ブタンスルホン酸、２−アクリルアミド−ｎ−ヘキサンスルホン酸、２−アクリルアミド−ｎ−オクタンスルホン酸、２−アクリルアミド−ｎ−ドデカンスルホン酸、２−アクリルアミド−ｎ−テトラデカンスルホン酸、２−アクリルアミド−２−メチルプロパンスルホン酸、２−アクリルアミド−２−フェニルプロパンスルホン酸、２−アクリルアミドー２，２，４−トリメチルペンタンスルホン酸、２−アクリルアミド−２−メチルフェニルエタンスルホン酸、２−アクリルアミド−２−（４−クロロフェニル）プロパンスルホン酸、２−アクリルアミド−２−カルボキシメチルプロパンスルホン酸、２−アクリルアミド−２−（２−ピリジル）プロパンスルホン酸、２−アクリルアミド−１−メチルプロパンスルホン酸、３−アクリルアミド−３−メチルブタンスルホン酸、２−メタクリルアミド−ｎ−デカンスルホン酸、２−メタクリルアミド−ｎ−テトラデカンスルホン酸を挙げることができる。好ましくは２−アクリルアミド−２−メチルプロパンスルホン酸が挙げられる。
【０３７７】
前記ビニル重合性モノマーと、スルホン酸基含有アクリルアミドモノマーを共重合させるに際して用いることのできる重合開始剤としては、過酸化物開始剤またはアゾ系開始剤等であるが、その分解物がカルボキシル基を有し、負帯電性に効果のある過酸化物開始剤が良く、その開始剤をモノマー混合物に対し、０．５〜５質量％の範囲で用いるのが好ましい。また、その重合法としては、溶液重合、懸濁重合、塊状重合などいずれの方法を用いることも可能であり、特に限定するものではないが、メタノール、イソプロパノール、ブタノール等の低級アルコールを含む有機溶剤中で、上記モノマー混合物を共重合させる溶液重合法を採用するのが特に好ましい。
【０３７８】
この場合の現像剤担持体における被覆層の結着樹脂としては、前記ビニル重合性モノマーとスルホン酸基含有アクリルアミドモノマーとの共重合体、及び、その一部又は全てに、その分子構造中に少なくとも−ＮＨ_２基、＝ＮＨ基、もしくは−ＮＨ−結合のいずれかを有する結着樹脂を使用する。
【０３７９】
−ＮＨ_２基を有する物質としては、Ｒ−ＮＨ_２で表される第１アミンもしくはそれらを有するポリアミン、ＲＣＯ−ＮＨ_２で表される第１アミドもしくはそれらを有するポリアミド等、＝ＮＨ基を有する物質としては、Ｒ＝ＮＨで表される第２アミンもしくはそれらを有するポリアミン、（ＲＣＯ）_２＝ＮＨで表される第２アミドもしくはそれらを有するポリアミド等、−ＮＨ−結合を有する物質としては、前述したポリアミン、ポリアミドの他に−ＮＨＣＯ−結合を有するポリウレタン等が挙げられ、以上の物質を１種又は２種以上、あるいは共重合体として含有し、工業的に合成された樹脂が好適に用いられる。それらのうちアンモニアを触媒としたフェノール樹脂、ポリアミド樹脂、及びウレタン樹脂が好ましい。本発明において使用する結着樹脂を構成するフェノール樹脂としては、本発明者らが鋭意検討を重ねた結果、その製造工程において含窒素化合物を触媒として使用したフェノール樹脂を用いることで、加熱硬化時に前記共重合体との構造的な相互作用が起こりやすく、樹脂組成物全体の帯電性が均一且つ十分な正帯電性を有するようになることがわかった。
【０３８０】
そのためこのようなフェノール樹脂を本発明における現像剤担持体上の被覆層を構成する材料の１つとして用いることで、良好なネガ付与性が得られる。本発明に使用するフェノール樹脂の製造工程において触媒として用いられる含窒素化合物としては、例えば酸性触媒としては、硫酸アンモニウム、燐酸アンモニウム、スルファミド酸アンモニウム、炭酸アンモニウム、酢酸アンモニウム、マレイン酸アンモニウムといった、酸のアンモニウムまたはアミノ塩類、また、塩基性触媒としては、アンモニア、或はジメチルアミン、ジエチルアミン、ジイソプロピルアミン、ジイソブチルアミン、ジアミルアミン、トリメチルアミン、トリエチルアミン、トリｎ−ブチルアミン、トリアミルアミン、ジメチルベンジルアミン、ジエチルベンジルアミン、ジメチルアニリン、ジエチルアニリン、ｎ，ｎ−ジｎ−ブチルアニリン、ｎ，ｎ−ジアミルアニリン、ｎ，ｎ−ジｔ−アミルアニリン、ｎ−メチルエタノールアミン、ｎ−エチルエタノールアミン、ジエタノールアミン、トリエタノールアミン、ジメチルエタノールアミン、ジエチルエタノールアミン、エチルジエタノールアミン、ｎ−ブチルジエタノールアミン、ジｎ−ブチルエタノールアミン、トリイソプロパノールアミン、エチレンジアミン、ヘキサメチレンテトラアミンの如きアミノ化合物、ピリジン、αピコリン、βピコリン、γピコリン、２，４−ルチジン、２，６−ルチジンの如きピリジン及びその誘導体、キノリン化合物、イミダゾール、２−メチルイミダゾール、２，４−ジメチルイミダゾール、２−エチル−４−メチルイミダゾール、２−フェニルイミダゾール、２−フェニル−４−メチルイミダゾール、２−ヘプタデシルイミダゾールの如き含窒素複素環式化合物がある。
【０３８１】
また、本発明において使用する結着樹脂を構成するポリアミド樹脂としては、例えば、ナイロン６、６６、６１０、１１、１２、９、１３、Ｑ２ナイロン、或いはこれらを主成分とするナイロンの共重合体、或いはＮ−アルキル変性ナイロン、Ｎ−アルコキシルアルキル変性ナイロン、いずれも好適に用いることができる。更にはポリアミド変性フェノール樹脂等のようにポリアミドにて変性された各種樹脂、或いは、硬化剤としてポリアミド樹脂を用いたエポキシ樹脂、といったように、ポリアミド樹脂分を含有している樹脂であれば、いずれも好適に用いることができる。
【０３８２】
また、本発明において使用する結着樹脂を構成するウレタン樹脂としてはウレタン結合を含んだ樹脂で有れば、いずれも好適に用いることができる。このウレタン結合はポリイソシアネートとポリオールとの重合付加反応によって得られる。
【０３８３】
このポリウレタン樹脂の主原料となるポリイソシアネートとしては、ジフェニレンメタン−４，４’−ジイソシアネート（ＭＤＩ）、イソホロンジイソシアネート（ＩＰＤＩ）、ポリメチレンポリフェニルポリイソシアネート、トリレンジイソシアネート、ヘキサメチレンジイソシアネート、１，５−ナフタリンジイソシアネート、４，４’−ジシクロヘキシルメタンジイソシアネート、カルボジイミド変性ジフェニルメタン−４，４’−ジイソシアネート、トリメチルヘキサャ｀レンジイソシアネート、オルトトルイジンジイソシアネート、ナフチレンジイソシアネート、キシレンジイソシアネート、パラフェニレンジイソシアネート、リジンジイソシアネートメチルエステル、ジメチルジイソシアネートが使用可能である。
【０３８４】
またポリウレタン樹脂の主原料となるポリオールとしては、ポリエチレンアジペートエステル、ポリブチレンアジペートエステル、ポリジエチレングリコールアジペートエステル、ポリヘキセンアジペートエステル、ポリカプロラクトンエステルの如きポリエステルポリオール、ポリテトラメチレングリコール、ポリプロピレングリコールの如きポリエーテルポリオールが使用可能である。
【０３８５】
本発明においては、上記のような材料で現像剤担持体表面に形成する樹脂被覆層の体積抵抗を１０^３Ω・ｃｍ以下、更には、１０^３〜１０^−２Ω・ｃｍに調整することが好ましい。即ち、樹脂被覆層の体積抵抗が１０^３Ω・ｃｍを超える場合には、チャージアップが発生し易くなり、ゴーストの悪化や濃度低下を引き起こし易い。そこで、本発明の現像装置では、現像剤担持体表面の樹脂被覆層の体積抵抗を上記のような好ましい範囲に調整するために、樹脂被覆層の被膜形成材料である結着樹脂中に導電性物質を分散含有させる。この際に使用する導電性物質としては、その粒径が、個数平均粒径で２０μｍ以下のものであることが好ましく、１０μｍ以下のものを用いることがより好ましい。更に、樹脂被覆層表面に形成される凹凸を避けるためには、１μｍ以下のものを用いることが好ましい。
【０３８６】
この際に使用し得る導電性物質としては、例えば、ファーネスブラック、ランプブラック、サーマルブラック、アセチレンブラック、チャンネルブラックの如きカーボンブラック；酸化チタン、酸化スズ、酸化亜鉛、酸化モリブデン、チタン酸カリ、酸化アンチモン及び酸化インジウムの如き金属酸化物；アルミニウム、銅、銀、ニッケルの如き金属、グラファイト、金属繊維、炭素繊維の如き無機系充填剤が挙げられる。樹脂被覆層中におけるこれらの導電性物質の添加量としては、結着樹脂１００質量部に対して１００質量部以下の範囲で使用することが好ましい。添加量が１００質量部を超えると被膜強度の低下が起こり易く、また、多量の導電性物質の添加は、トナーの帯電量の低下を引き起こす傾向がある。
【０３８７】
更に、本発明の現像装置においては、使用する現像剤担持体の表面に設ける樹脂被覆層の構成として、上記した正帯電性物質や導電性物質に加えて、更に、粒径が０．３〜３０μｍ程度の球状粒子を被覆樹脂層中に分散させた構成とすることが好ましい。このような構成とすれば、現像剤担持体の表面粗さを安定化させることができ、現像剤担持体上のトナーコート量を最適化することが可能となる。また、球状粒子を樹脂被覆層中に含有させることは、現像剤担持体表面に均一な表面粗度を保持させると同時に、現像剤担持体表面に設けた樹脂被覆層が摩耗した場合でも該被覆層の表面粗度の変化を少なくできるので、現像剤担持体へのトナー汚染やトナー融着を発生しにくくする効果が得られる。更に、上記のような球状粒子を含有させると、樹脂被覆層中に含有している含窒素複素環化合物との相互作用により、含窒素複素環化合物の有する荷電制御の効果がより高まり、トナーに対する迅速且つ均一な帯電付与特性をより向上させることができ、更に、帯電付与性能を安定化させる効果もある。
【０３８８】
本発明において使用する球状粒子としては、個数平均粒径が０．３〜３０μｍ、更には、２〜２０μｍのものが好ましい。即ち、樹脂被覆層中に含有させる球状粒子の個数平均粒径が０．３μｍ未満であると、現像剤担持体の表面に均一な粗さを付与する効果と、帯電付与性能を高める効果が少なく、現像剤への迅速且つ均一な帯電が不充分となると共に、樹脂被覆層の磨耗によってトナーのチャージアップや、トナー汚染及びトナー融着が発生する傾向があり、ゴーストの悪化、画像濃度低下を生じ易くなるため好ましくない。一方、個数平均粒径が３０μｍを超える球状粒子を加えた場合には、樹脂被覆層表面の粗さが大きくなり過ぎる傾向があり、トナーの帯電が充分に行なわれにくくなってしまうと共に、樹脂被覆層の機械的強度が低下してしまうため、好ましくない。
【０３８９】
更に、本発明で使用する球状粒子としては、その真密度が、３ｇ／ｃｍ^３以下、好ましくは２．７ｇ／ｃｍ^３以下、より好ましくは０．９〜２．３ｇ／ｃｍ^３のものを使用するとよい。即ち、球状粒子の真密度が３ｇ／ｃｍ^３を超える場合には、樹脂被覆層中における球状粒子の分散性が不充分となり、被覆層表面に均一な粗さを付与しにくくなると共に、含窒素複素環化合物の分散も均一に行われなくなり、トナーへの迅速且つ均一な帯電付与能、及び被覆層の強度が不充分となるので好ましくない。一方、球状粒子の真密度が０．９ｇ／ｃｍ^３より小さい場合にも、被覆層中での球状粒子の分散性が不充分となり易いため、好ましくない。
【０３９０】
本発明で言う球状粒子における球状とは、粒子の長径／短径の比が１．０〜１．５程度のものを意味しているが、更に好ましくは、長径／短径の比が１．０〜１．２の真球状により近い球状粒子を使用することがよい。即ち、球状粒子の長径／短径の比が１．５を超える場合には、導電性樹脂被覆層中での球状粒子の分散性が低下すると共に、該被覆層中への正帯電性物質の分散性の低下、及び被覆層表面の粗さの不均一化が発生し、トナーに対する迅速且つ均一な帯電付与性、及び、形成される樹脂被覆層の被膜強度の点からも好ましくない。
【０３９１】
本発明に用いられる球状粒子としては、公知の球状粒子が使用可能である。例えば、球状の樹脂粒子、球状の金属酸化物粒子、球状の炭素化物粒子等が挙げられる。また、球状の樹脂粒子としては、例えば、懸濁重合、分散重合法等によって直接得られる所望の粒径を有する球状の樹脂粒子が挙げられる。本発明においては、これらの中でも特に球状の樹脂粒子が、より少ない添加量で好適な表面粗さが得られ、更に均一な表面形状が得られ易いので好適である。この様な球状の樹脂粒子としては、ポリアクリレート、ポリメタクリレートの如きアクリル系樹脂粒子、ナイロンの如きポリアミド系樹脂粒子、ポリエチレン、ポリプロピレンの如きポリオレフィン系樹脂粒子、シリコーン系樹脂粒子、フェノール系樹脂粒子、ポリウレタン系樹脂粒子、スチレン系樹脂粒子、ベンゾグアナミン粒子が挙げられる。これらの樹脂粒子は、先に述べた重合法によって得られるものに限定されず、粉砕法により得られた樹脂粒子を、熱的に或いは物理的な球形化処理を行ったものを用いてもよい。
【０３９２】
更に、本発明においては、上記した球状粒子の表面に、無機微粉末を付着或いは固着させて用いてもよい。この際に用いる無機微粉体としては、例えば、ＳｉＯ_２、ＳｒＴｉＯ_３、ＣｅＯ_２、ＣｒＯ、Ａｌ_２Ｏ_３、ＺｎＯ、ＭｇＯの如き酸化物、Ｓｉ_３Ｎ_４の如き窒化物、ＳｉＣの如き炭化物、ＣａＳＯ_４、ＢａＳＯ_４、ＣａＣＯ_３の如き硫酸塩や炭酸塩が挙げられる。このような無機微粉末は、カップリング剤により処理したものを用いてもよい。
【０３９３】
特に、結着樹脂との密着性を向上させる目的で、或いは球状粒子に疎水性を与える等々の目的で、無機微粉末をカップリング剤で処理すしたものを使用することが好ましい。この際に用いるカップリング剤としては、例えば、シランカップリング剤、チタンカップリング剤、ジルコアルミネートカップリング剤がある。より具体的には、例えば、シランカップリング剤としては、ヘキサメチルジシラザン、トリメチルシラン、トリメチルクロルシラン、トリメチルエトキシシラン、ジメチルジクロルシラン、メチルトリクロルシラン、アリルジメチルクロルシラン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ブロムメチルジメチルクロルシラン、α−クロルエチルトリクロルシラン、β−クロルエチルトリクロルシラン、クロルメチルジメチルクロルシラン、トリオルガノシリルメルカプタン、トリメチルシリルメルカプタン、トリオルガノシリルアクリレート、ビニルジメチルアセトキシシラン、ジメチルジエトキシシラン、ジャ｀ルジメトキシシラン、ジフェニルジエトキシシラン、ヘキサメチルジシロキサン、１，３−ジビニルテトラメチルジシロキサン、１，３−ジフェニルテトラメチルジシロキサン、及び、１分子当たり２〜１２個のシロキサン単位を有し、末端に位置する単位に夫々１個あての硅素原子に結合した水酸基を含有したジメチルポリシロキサンが挙げられる。
【０３９４】
以上のようにして、好ましくはカップリング剤で処理された無機微粒子を球状粒子表面に付着或いは固着して処理することによって、導電性樹脂被覆層中への球状粒子の分散性、該被覆層表面の均一性や耐汚染性、トナーへの帯電付与性、導電性樹脂被覆層の耐磨耗性等を向上させることができる。
【０３９５】
更に、本発明においては、上記の球状粒子として導電性のものを使用することが好ましい。即ち、球状粒子に導電性を持たせることによって、その導電性のゆえに球状粒子表面にチャージが蓄積しにくくなるので、現像剤担持体へのトナー付着の軽減や、トナーに対する帯電付与能を向上させることができる。その際に使用する球状粒子としては、体積抵抗値が１０^６Ω・ｃｍ以下、より好ましくは１０^−３〜１０^６Ω・ｃｍの導電性を有するものが好ましい。即ち、本発明において使用する球状粒子の体積抵抗が１０^６Ω・ｃｍを超えると、摩耗によって被覆層表面に露出した球状粒子を核としてトナーの汚染や融着が発生し易くなると共に、迅速且つ均一なトナーの帯電が行われにくくなるため、好ましくない。
【０３９６】
このような体積抵抗を有する導電性球状粒子を得る方法としては、以下のような方法を用いること好ましいが、必ずしもこれらの方法に限定されるものではない。即ち、本発明に好適に使用できる導電性球状粒子を得る方法としては、例えば、樹脂系球状粒子やメソカーボンマイクロビーズを焼成して、炭素化及び／又は黒鉛化して低密度且つ良導電性の球状炭素粒子を得る方法が挙げられる。そして、この際に用いる樹脂系球状粒子としては、例えば、フェノール樹脂、ナフタレン樹脂、フラン樹脂、キシレン樹脂、ジビニルベンゼン重合体、スチレン−ジビニルベンゼン共重合体、ポリアクリロニトリルの如き樹脂が挙げられる。また、メソカーボンマイクロビーズは、通常、中ピッチを加熱焼成していく過程で生成する球状結晶を、多量のタール、中油、キノリンの如き溶剤で洗浄することによって製造することができる。
【０３９７】
本発明で使用できるより好ましい導電性球状粒子を得る方法としては、フェノール樹脂、ナフタレン樹脂、フラン樹脂、キシレン樹脂、ジビニルベンゼン重合体、スチレン−ジビニルベンゼン共重合体、ポリアクリロニトリルの如き球状樹脂粒子表面に、メカノケミカル法によってバルクメソフェーズピッチを被覆し、被覆された粒子を酸化性雰囲気化で熱処理した後に、不活性雰囲気下又は真空下で焼成して炭素化及び／又は黒鉛化し、導電性球状炭素粒子を得る方法が挙げられる。この方法で得られる球状炭素粒子は、黒鉛化されることによって球状炭素粒子の被覆部の結晶化が進み、導電性が向上したものとなるので、本発明において使用する球状粒子としてはより好ましい。
【０３９８】
上記した方法で得られる導電性の球状炭素粒子は、いずれの方法で製造する場合においても、焼成条件を変化させることによって得られる球状炭素粒子の導電性をある程度制御することが可能であるので、本発明において好ましく使用できる球状炭素粒子が容易に得られる。又、上記の方法で得られる球状炭素粒子は、場合によっては更に導電性を高めるために、導電性球状粒子の真密度が３ｇ／ｃｍ^３を超えない程度の範囲で、その表面に、導電性の金属及び／又は金属酸化物のメッキを施してもよい。
【０３９９】
本発明で好適に使用できる導電性球状粒子を得る他の方法としては、球状樹脂粒子からなる芯粒子に対して、芯粒子の粒径より小さい導電性微粒子を適当な配合比で機械的に混合することによって、ファンデルワールス力及び静電気力の作用により、芯粒子の周囲に均一に導電性微粒子を付着させた後、例えば、機械的衝撃力を付与することによって生ずる局部的温度上昇により芯粒子表面を軟化させ、芯粒子表面に導電性微粒子を固着させて該粒子で芯粒子表面を被覆し、導電化処理した球状樹脂粒子を得る方法が挙げられる。上記の芯粒子には、有機化合物からなる真密度の小さい球形の樹脂粒子を使用することが好ましく、樹脂としては、例えば、ＰＭＭＡ、アクリル樹脂、ポリブタジエン樹脂、ポリスチレン樹脂、ポリエチレン、ポリプロピレン、ポリブタジエン、又はこれらの共重合体、ベンゾグアナミン樹脂、フェノール樹脂、ポリアミド樹脂、ナイロン、フッ素系樹脂、シリコーン樹脂、エポキシ系樹脂、ポリエステル樹脂が挙げられる。これらの材料からなる芯粒子（母粒子）の表面に被覆させる導電性微粒子（小粒子）としては、導電性微粒子からなる被膜が芯粒子表面に均一に設けられるようにするために、小粒子として、その粒径が母粒子の粒径に対して１／８以下であるものを使用することが好ましい。
【０４００】
更に、本発明に好適に使用できる導電性球状粒子を得る他の方法としては、球状樹脂粒子中に導電性微粒子を均一に分散させることにより、導電性微粒子が分散された導電性球状粒子を得る方法が挙げられる。球状樹脂粒子中に導電性微粒子を均一に分散させる方法としては、例えば、結着樹脂と導電性微粒子とを混練して導電性微粒子を分散させた後、冷却固化し、所定の粒径に粉砕し、機械的処理及び熱的処理により球形化して導電性球状粒子を得る方法；又は、重合性単量体中に重合開始剤、導電性微粒子及びその他の添加剤を加え、分散機によって均一に分散せしめた重合性単量体組成物を、分散安定剤を含有する水相中に撹拌機等によって所定の粒子径になるように懸濁させて重合を行い、導電性微粒子が分散された球状粒子を得る方法等が挙げられる。
【０４０１】
これらの方法で得られる結着樹脂中に導電性微粒子が分散された導電性球状樹脂粒子の場合においても、これを芯粒子とし、前記したと同様に、該芯粒子よりも小さい粒径の導電性微粒子を適当な配合比で機械的に混合して、ファンデルワールス力及び静電気力の作用により、導電性球状粒子の周囲に均一に導電性微粒子を付着させた後、例えば、機械的衝撃力を付与することにより生ずる局部的温度上昇により導電性球状粒子の表面を軟化させ、芯粒子表面に導電性微粒子を固着させて導電性微粒子で芯粒子表面を被覆して、更に導電性を高めて使用してもよい。
【０４０２】
更に、上記導電性樹脂被覆層中に分散させる球状粒子の含有量としては、被覆層用結着樹脂１００質量部に対して、好ましくは２〜１２０質量部、より好ましくは２〜８０質量部の範囲とした場合に、特に好ましい結果が得られる。即ち、球状粒子の含有量が２質量部未満の場合には球状粒子の添加効果が小さく、１２０質量部を超える場合にはトナーの帯電性が低くなり過ぎてしまう場合がある。
【０４０３】
更に、本発明の現像装置においては、現像担持体として、その表面に設けられている樹脂被覆層中に、上記構成に加えて更に潤滑性物質が分散されていると、より本発明の効果が促進されるので好ましい。この際に使用できる潤滑性物質としては、例えば、グラファイト、二硫化モリブデン、窒化硼素、雲母、フッ化グラファイト、銀−セレン化ニオブ、塩化カルシウム−グラファイト、滑石、ステアリン酸亜鉛の如き脂肪酸金属塩が挙げられる。これらのなかでも特にグラファイトは、導電性樹脂被覆層の導電性を損なわないので好ましく用いられる。また、これらの潤滑性物質としては、個数平均粒径が、好ましくは０．２〜２０μｍ程度、より好ましくは、０．３〜１５μｍのものを使用するとよい。
【０４０４】
更に、上記潤滑性物質の添加量としては、被覆層用結着樹脂１００質量部に対して好ましくは５〜１２０質量部、より好ましくは１０〜１００質量部の範囲とした場合に特に好ましい結果を与える。即ち、潤滑性粒子の含有量が１２０質量部を超える場合には、被膜強度の低下及びトナーの帯電量の低下が認められ、５質量部未満では、７μｍ以下の小粒径トナーを用いて、長期間に渡って現像装置を使用した場合等において、樹脂被覆層表面にトナー汚染が発生し易くなる傾向がみられる。
【０４０５】
本発明で使用する現像剤担持体は、少なくとも、基体及びその上に形成した上記で説明した材料からなる導電性樹脂被覆層から構成される。基体としては、金属円筒管が使用されるが、金属円筒管としては、例えば、ステンレススチール及びアルミニウム製の円筒管が好適に用いられる。
【０４０６】
本発明においては、上記のような構成材料によって樹脂被覆層を形成する場合に、その表面粗度を中心線平均粗さ（以下、「Ｒａ」と称す）で表した場合に、Ｒａの値が好ましくは０．３〜３．５μｍ、より好ましくは０．５〜３．０μｍとなるように調整することが好ましい。即ち、導電性樹脂被覆層表面のＲａが０．３μｍ未満の場合には、トナーの搬送性が低下してしまい充分な画像濃度が得られなくなる場合があり、一方、導電性樹脂被覆層表面のＲａが３．５μｍを超える場合には、トナーの搬送量が多くなり過ぎてトナーが充分に帯電できなくなることが生じる場合がある。
【０４０７】
更に、上記したような構成の樹脂被覆層は、その層厚を、好ましくは２５μｍ以下、より好ましくは２０μｍ以下、更に好ましくは４〜２０μｍとすると均一な膜厚が得られるのでる好ましい。しかし、特にこの層厚に限定されるものではない。このような層厚の樹脂被覆層は、該樹脂被覆層の形成材料にもよるが、付着重量として、４，０００〜２０，０００ｍｇ／ｍ^２程度にすれば良い。
【０４０８】
以下に本発明に関わる物性の測定方法について述べる。
【０４０９】
（１）樹脂被覆層の帯電極性の測定
＜サンプル板の作製方法＞：帯電極性を測定したい樹脂被覆層（カーボン及びグラファイト等の導電性物質を除いたもの）の形成用の樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを乾燥・加熱等によって成膜させ（乾燥・加熱温度及び時間は、熱可塑性樹脂の場合は溶液が完全に蒸発するまで、熱硬化性樹脂の場合は樹脂の架橋が完全に行われるまで）、サンプル板を作製する。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置する。
【０４１０】
＜粒子の調整方法＞：鉄粉（粒径約１００μｍ）を接地した状態で、２３℃，相対湿度６０％環境下にて一晩以上放置する。
【０４１１】
＜測定方法＞：測定は２３℃、相対湿度６０％環境下で行う。先ず、上記で作製したサンプル板を図８に示す表面帯電量測定装置ＴＳ−１００ＡＳ（東芝ケミカル（株）製）にセットし、電位計５５を接地して値を０にする。上記で調湿した鉄粉５１を滴下器５２に入れ、ＳＴＡＲＴスイッチを押して２０秒間鉄粉５１をサンプル板５３上に滴下し、予め接地を施した受容器５４で受ける。この時の電位計５５の示す極性を読み取って、鉄粉に対する樹脂被覆層（樹脂分のみ）の帯電極性とする。尚、５６はコンデンサーである。
【０４１２】
（２）中心線平均粗さ（Ｒａ）の測定
ＪＩＳＢ０６０１の表面粗さの測定方法に基づき、小坂研究所製サーフコーダーＳＥ−３３００にて、軸方向３点×周方向２点＝６点について各々測定し、その平均値をとった。
【０４１３】
（３）粒子の体積抵抗の測定
粒状試料を直径４０ｍｍのアルミリングに入れ、２５００Ｎで加圧成型し、抵抗率計ロレスタＡＰ、又はハイレスタＩＰ（共に、三菱油化製）にて４端子プローブを用いて体積抵抗値を測定した。尚、測定環境は、２０〜２５℃，５０〜６０％ＲＨとした。
【０４１４】
（４）樹脂被覆層の体積抵抗の測定
厚さ１００μｍのＰＥＴシート上に、７〜２０μｍの厚さの被覆層を形成して測定用サンプルを作製し、該サンプルについてＡＳＴＭ規格（Ｄ−９９１−８２）及び、日本ゴム協会標準規格ＳＲＩＳ（２３０１−１９６９）に準拠した、導電性ゴム及びプラスチックの体積抵抗測定用の４端子構造の電極を設けた電圧降下式デジタルオーム計（川口電機製作所製）を使用して測定した。尚、測定環境は２０〜２５℃，５０〜６０ＲＨ％とした。
【０４１５】
（５）球状粒子の真密度の測定
本発明で使用する球状粒子の真密度は、乾式密度計アキュピック１３３０（島津製作所製）を用いて測定した。
【０４１６】
（６）球状粒子の粒径測定
レーザー回折型粒度分布計のコールターＬＳ−１３０型粒度分布計（コールター社製）を用いて下記のようにして測定した。測定方法としては、水系モジュールを用い、測定溶媒としては純水を使用する。先ず、純水にて粒度分布計の測定系内を約５分間洗浄し、消泡剤として測定系内に亜硫酸ナトリウムを１０〜２５ｍｇ加えてバックグラウンドファンクションを実行する。次に、純水１０ｍｌ中に界面活性剤３〜４滴を加え、更に測定試料を５〜２５ｍｇ加える。この試料を懸濁した水溶液を超音波分散機で約１〜３分間分散処理を行い測定用の試料液を得て、前記測定装置の測定系内に試料液を徐々に加えて測定を行う。その際、装置の画面上のＰＩＤＳが４５〜５５％になるように測定系内の試料濃度を調整して測定を行い、個数分布から算術して個数平均粒径を求める。
【０４１７】
（７）現像剤に含有される導電性微粒子の粒径測定
導電性微粒子の粒径は、電子顕微鏡を用いて測定した。撮影倍率は６万倍とするが、難しい場合は、低倍率で撮影した後に６万倍となるように写真を拡大プリントする。写真上で一次粒子の粒径を測る。この際、長軸と短軸を測り、平均した値を粒径とする。これを、１００サンプルについて測定し、５０％値をもって平均粒径とする。
【０４１８】
次に、本発明において好適な現像条件に関して説明する。
【０４１９】
本発明において、現像剤担持体上に３〜３０ｇ／ｍ^２の現像剤層を形成することが好ましい。現像剤担持体上に３〜３０ｇ／ｍ^２の現像剤層を形成することで、均一な現像剤層を形成し易く、導電性微粉末が像担持体上に均一に供給されることで、像担持体の均一な帯電が得られ易い。現像剤担持体上の現像剤量が上記範囲よりも少なすぎる場合には、十分な画像濃度が得られにくく、現像剤担持体上の現像剤層の微小なむらが、画像濃度むら及び導電性微粉末の供給むらによる像担持体の帯電むらとして現れ易くなる。現像剤担持体上の現像剤量が上記範囲よりも多すぎる場合には、トナー粒子への摩擦帯電の付与が不十分となり易く、トナー飛散を生じ易くなり、カブリの増大、転写性の低下により像担持体の帯電を阻害し易くなる。
【０４２０】
また、現像剤担持体上に５〜２５ｇ／ｍ^２の現像剤層を形成することがより好ましい。現像剤担持体上に５〜２５ｇ／ｍ^２の現像剤層を形成することで、現像剤担持体上の現像剤への摩擦帯電付与がより均一に行われ易く、回収した転写残トナー粒子が現像剤担持体近傍のトナー粒子の摩擦帯電に与える影響を軽減し、より安定した現像兼クリーニング性が得られる。現像剤担持体上の現像剤量が上記範囲よりも少なすぎる場合には、回収した転写残トナー粒子が現像担持体近傍のトナー粒子の摩擦帯電に影響を与え易く、一部のトナー粒子の摩擦帯電が過剰になることによる現像剤層のムラを生じ、転写残トナー粒子の回収性が不均一となることがある。現像剤担持体上の現像剤量が上記範囲よりも多すぎる場合には、回収した転写残トナー粒子が再度の摩擦帯電を十分には付与されることなく再び現像部に搬送され、現像に供されることでカブリをより生じ易くなる。
【０４２１】
また、本発明においては、現像剤を担持する現像剤担持体表面は、像担持体表面の移動方向と同方向に移動していてもよいし、逆方向に移動していてもよい。その移動方向が同方向である場合、像担持体の移動速度に対して比で１００％以上であることが望ましい。１００％未満であると画像品質が悪くなる場合がある。
【０４２２】
現像剤担持体表面の移動速度の像担持体表面の移動速度に対する移動速度比が１００％以上（現像剤担持体表面の移動速度が、像担持体表面の移動逮度よりも大きいまたは同じ）であれば、現像剤担持体側から像担持体側へのトナー粒子の供給が十分に行われるため、十分な画像濃度を得易く、導電性微粉末の供給も十分に行われるため、像担持体の良好な帯電性を得ることができる。
【０４２３】
更に、現像剤担持体表面の移動速度が像担持体表面の移動速度に対し、１．０５〜３．０倍の速度であることがより好ましい。移動速度比が高まるほど現像部位に供給されるトナーの量は多く、潜像に対しトナーの脱着頻度が多くなり、不要な部分は掻き落とされ必要な部分には付与されるという繰り返しにより、転写残トナー粒子の回収性が向上し、回収不良によるパターンゴーストの発生をより確実に抑制することができる。更には、潜像に忠実な画像が得られる。また、接触現像プロセスにおいては、移動速度比が高まるほど像担持体と現像剤担持体との摺擦により転写残トナー粒子の回収性がより向上する。しかし、移動速度比が上記範囲を大きく超えると、現像剤担持体上からの現像剤の飛散によるカブリ、画像汚れを生じ易くなり、接触現像プロセスでは像担持体あるいは現像剤担持体が摺擦による摩耗や削れのために短寿命化し易くなる。現像剤担持体上の現像剤量を規制する現像剤層厚規制部材が現像剤を介して現像剤担持体に当接されている場合には、現像剤層厚規制部材または現像剤担持体が摺擦による摩耗や削れのために短寿命化し易い。上記観点から、現像剤担持体表面の移動速度が像担持体表面の移動速度に対し、１．１〜２．５倍の遠度であることがさらに好ましい。
【０４２４】
本発明において、非接触型現像方法を適用するために、現像剤担持体の像担持体に対する所定の離間距離よりも、現像剤担持体上の現像剤層を薄く形成することが好ましい。本発明によって、従来は困難であった非接触型現像方法を用いた現像兼クリーニング画像形成を高い画像品位で実現することが可能となった。現像工程において、像担持体に対して現像剤層を非接触とし、像担持体の静電潜像をトナー画像として可視化する非接触型現像方法を適用することで、電気抵抗値が低い導電性微粉末を現像剤中に多量に添加しても、現像バイアスが像担持体へ注入することによる現像かぶりが発生しない。そのため、良好な画像を得ることができる。
【０４２５】
また、現像剤担持体は像担持体に対して１００〜１０００μｍの離間距離を有して対向して設置されることが好ましい。現像剤担持体の像担持体に対する離間距離が上記範囲よりも小さすぎると、離間距離の振れに対する現像剤の現像特性の変化が大きくなるため、安定した画像性を満足する画像形成装置を量産することが困難となる。現像剤担持体の像担持体に対する離間距離が上記範囲よりも大きすぎると、像担持体上の潜像に対するトナー粒子の追従性が低下するために、解像性の低下、画像濃度の低下等の画質低下を招きやすい。また、像担持体上への導電性微粉末の供給性が低下し易く、像担持体の帯電性が低下し易くなる。より好ましくは現像剤担持体は像担持体に対して１００〜６００μｍの離間距離を有して対向して設置されることである。現像剤担持体の像担持体に対する離間距離が１００〜６００μｍであることで、現像兼クリーニング工程における転写残トナー粒子の回収性がより優位に行える。離間距離が上記範囲よりも大きすぎると、現像装置への転写残トナー粒子の回収性が低下し、回収不良によるカブリを生じ易くなる。
【０４２６】
本発明では、現像剤担持体と像担持体との間に交番電界（交流電界）を形成して現像を行う現像工程で現像されることが好ましい。交番電界は現像剤担持体と像担持体との間に交番電圧を印加することにより形成することができる。印加する現像バイアスは直流電圧に交番電圧（交流電圧）を重畳したものであってもよい。
【０４２７】
交番電圧の波形としては、正弦波、矩形波、三角波等適宜使用可能である。また、直流電源を周期的にオン／オフすることによって形成されたパルス波であっても良い。このように交番電圧の波形としては周期的にその電圧値が変化するようなバイアスが使用できる。
【０４２８】
現像剤を担持をする現像剤担持体と像担持体との間に、少なくともピークトゥーピークの電界強度で３×１０^６〜１０×１０^６Ｖ／ｍ、周波数１００〜５０００Ｈｚの交流電界（交番電界）を、現像バイアスを印加することによって形成することが好ましい。現像バイアスを印加することにより上記範囲の交流電界を形成することで、現像剤中に添加された導電性微粉末が均等に像担持体側に移行されやすく、帯電部において導電性微粉末を介しての接触帯電部材と像担持体との均一かつ緻密な接触を得ることで、像担持体の一様帯電（特に直接注入帯電）を顕著に促進することができる。また、交流電界を現像バイアスにより形成することで、現像剤担持体と像担持体間に高電位差がある場合でも、現像部における像担持体への電荷注入が生じないため、導電性微粉末を現像剤中に多量に添加しても、現像バイアスが像担持体へ電荷注入することによる現像かぶりが発生せず、良好な画像を得ることができる。現像剤担持体と像担持体との間に現像バイアスを印加することで形成される交流電界の強度が上記範囲よりも小さすぎると、像担持体に供給される導電性微粉末の量が不足しやすく、像担持体の一様帯電性が低下し易い。また、現像力が小さいために画像濃度の低い画像となり易い。一方、交流電界の強度が上記範囲よりも大きすぎると、現像力が大き過ぎるために細線の潰れによる解像性の低下、カブリの増大による画質低下及び像担持体の帯電性の低下を生じ易く、現像バイアスの像担持体へのリークによる画像欠陥を生じ易くなる。また、現像剤担持体と像担持体との間に現像バイアスを印加することで形成される交流電界の周波数が上記範囲よりも小さすぎると、像担持体に均一に導電性微粉末が供給されにくく、像担持体の一様帯電のむらを生じ易くなる。交流電界の周波数が上記範囲よりも大きすぎると、像担持体に供給される導電性微粉末の量が不足しやすく、像担持体の一様帯電性が低下し易い。
【０４２９】
さらに、現像剤を担持する現像剤担持体と潜像担持体との間に、少なくともピークトゥーピークの電界強度で４×１０^６〜１０×１０^６Ｖ／ｍ、周波数５００〜４０００Ｈｚの交流電界（交番電界）を、現像バイアスを印加することによって形成することがより好ましい。上記範囲の交流電界を現像バイアスにより形成することで、現像剤中に添加された導電性微粉末が均等に潜像担持体側に移行されやすく、転写後の潜像担持体に均一に導電性微粉末を塗布することができ、非接触型現像方法を適用した場合においても高い転写残トナー粒子の回収性が維持できる。
【０４３０】
現像剤担持体と潜像担持体との間に現像バイアスを印加することで形成される交流電界の強度が上記範囲よりも小さすぎると、現像装置への転写残トナー粒子の回収性が低下し、回収不良によるカブリを生じ易くなる。また、現像剤担持体と潜像担持体との間に現像バイアスを印加することで形成される交流電界の周波数が上記範囲よりも小さすぎると、潜像に対するトナーの脱着頻度が少なくなり、現像装置への転写残トナー粒子の回収性が低下しやすく、画像品質も低下し易い。交流電界の周波数が上記範囲よりも大きすぎると、電界の変化に追従できるトナー粒子が少なくなるために、転写残トナー粒子の回収性が低下し、転写残トナー粒子の回収不良によるポジゴーストを生じ易くなる。
【０４３１】
本発明において、転写工程は現像工程によって形成されたトナー画像を中間転写体に転写した後に、紙等の記録媒体に再転写する工程であっても良い。すなわち、潜像担持体からトナー画像の転写を受ける転写材は転写ドラム等の中間転写体であってもよい。転写材を中間転写体とする場合、中間転写体から紙などの記録媒体に再度転写することでトナー画像が得られる。中間転写体を適用することで厚紙等の種々の記録媒体に寄らず潜像担持体上の転写残トナー粒子量を低減できる。
【０４３２】
また、本発明において、転写時に転写部材が転写材（配録媒体）を介して潜像担持体に当接していることが好ましく良い。
【０４３３】
潜像担持体と転写材を介して転写手段を当接しながら潜像担持体上のトナー画像を転写材に転写する接触転写工程では、転写手段の当接圧力としては線圧２．９４〜９８０Ｎ／ｍであることが好ましく、より好ましくは１９．６〜４９０Ｎ／ｍである。転写手段の当接圧力が上記範囲よりも小さすぎると、転写材の搬送ずれや転写不良の発生が起こりやすくなるため好ましくない。当接圧力が上記範囲よりも大きすぎる場合には、潜像担持体表面の劣化やトナー粒子の付着を招き、結果として潜像担持体表面へのトナー融着を生じる場合がある。
【０４３４】
また、接触転写工程における転写手段としては、転写ローラあるいは転写ベルトを有する装置が好ましく使用される。転写ローラは少なくとも芯金と芯金を被覆する導電性弾性層とを有し、導電性弾性層はポリウレタンゴム、エチレン−プロピレン−ジエンポリエチレン（ＥＰＤＭ）の如き弾性材料に、カーボンブラック、酸化亜鉛、酸化スズ、炭化硅素のごとき導電性付与剤を配合分散して電気抵抗値（体積抵抗率）を１０^６〜１０^１０Ω・ｃｍの中抵抗に調整した、ソリッドあるいは発泡肉質の層等による弾性体であることが好ましい。
【０４３５】
転写ローラでの好ましい転写プロセス条件としては、転写ローラの当接圧が２．９４〜４９０Ｎ／ｍであり、より好ましくは１９．６〜２９４Ｎ／ｍである。当接圧力としての線圧が上記範囲よりも小さすぎる場合には、転写残トナー粒子が増加し潜像担持体の帯電性を阻害し易くなる。転写手段の当接圧力が上記範囲よりも大きすぎると、押圧力により導電性微粉末が転写材に転写され易くなり、導電性微粉末の潜像担持体または接触帯電部材への供給量が減少することで、潜像担持体の帯電促進効果が低下し、現像兼クリーニングでの転写残トナー粒子の回収性が低下する。また、画像上でのトナーの飛び散りが増加する。
【０４３６】
転写材を介して潜像担持体に転写手段を当接させながらトナー画像を転写材に静電転写する接触転写工程では、印加される直流電圧は±０．２〜±１０ｋＶであることが好ましい。
【０４３７】
また、本発明の現像装置は、潜像担持体として直径が３０ｍｍ以下の小径の感光体を有する画像形成装置に対し特に有効に用いられる。即ち、転写工程後かつ帯電工程前に独立したクリーニング工程を有さないことで、帯電、露光、現像、転写各工程の配置の自由度が高まり、直径が３０ｍｍ以下の小径の感光体と組み合わせて、画像形成装置の小型化、省スペース化を達成できる。ベルト状感光体でも同様に各工程の配置の自由度が高まることで、画像形成装置の小型化、省スペース化を達成する上で、当接部での曲率半径が２５ｍｍ以下の感光体ベルトを用いた画像形成装置に対しても有効である。
【０４３８】
また、本発明の画像形成装置は、上記したような潜像担持体と現像手段とを少なくとも有するプロセスカートリッジを画像形成装置本体に着脱可能に装着するものであっても良い。なお、このプロセスカートリッジは、上記帯電手段をさらに有するものであってもよい。
【０４３９】
【実施例】
以下に、実施例を挙げて本発明をより具体的に説明するが、本発明はこれらの実施例にのみ限定されるものではない。
【０４４０】
まず、本発明の実施例に用いる潜像担持体としての感光体の製造例について述べる。
【０４４１】
＜感光体製造例＞
負帯電用の有機光導電性物質を用いた感光体（以下「ＯＰＣ感光体」と表記する）を製造した。感光体の基体には、直径２４ｍｍのアルミニウム製のシリンダーを用いた。このシリンダー上に下記の各層を浸漬塗布することにより順次積層して、図５に示すような構成の感光体を作製した。
【０４４２】
第１層は導電層１２であり、アルミニウム基体１１の欠陥等をならすため、またレーザー露光の反射によるモアレの発生を防止するために設けられている厚さ約２０μｍの導電性粒子分散樹脂層（酸化錫及び酸化チタンの粉末をフェノール樹脂に分散したものを主体とする）である。
【０４４３】
第２層は正電荷注入防止層１３であり、アルミニウム基体１１から注入された正電荷が感光体表面に帯電された負電荷を打ち消すのを防止する役割を果たし、メトキシメチル化ナイロンによって１０^６Ω・ｃｍ程度に抵抗調整された厚さ約１μｍの中抵抗層である。
【０４４４】
第３層は電荷発生層１４であり、ジスアゾ系の顔料をプチラール樹脂に分散した厚さ約０．３μｍの層であり、レーザー露光を受けることによって正負の電荷対を発生する。
【０４４５】
第４層は電荷輸送層１５であり、ポリカーボネート樹脂にヒドラゾン化合物を分散した厚さ約２５μｍの層であり、Ｐ型半導体である。従って、感光体表面に帯電された負電荷はこの層を移動することはできず、電荷発生層で発生した正電荷のみを感光体表面に輸送することができる。
【０４４６】
第５層は電荷注入層１６であり、光硬化性のアクリル樹脂に導電性酸化スズ超微粒子及び粒径約０．２５μｍの四フッ化エチレン樹脂粒子を分散したものである。具体的には、樹脂に対して、アンチモンをドーピングし低抵抗化した粒径約０．０３μｍの酸化スズ粒子を１００質量％、更に四フッ化エチレン樹脂粒子を２０質量％、分散剤を１．２質量％を分散したものである。このようにして調製した塗工液をスプレー塗工法にて厚さ約２．５μｍに塗工して電荷注入層１６とした。
【０４４７】
このようにして得られた感光体の最表面層における体積抵抗は、５×１０^１２Ω・ｃｍ、感光体表面の水に対する接触角は、１０２度であった。
【０４４８】
次に、本発明の実施例で用いられる帯電部材の製造例について述べる。
【０４４９】
＜帯電部材の製造例＞
直径６ｍｍ，長さ２６４ｍｍのＳＵＳローラを芯金とし、芯金上にウレタン樹脂、導電性粒子としてのカーボンブラック、硫化剤、発泡剤等を処方した中抵抗の発泡ウレタン層をローラ状に形成し、さらに切削研磨し形状及び表面性を整えた。このようにして、直径１２ｍｍ，長さ２３４ｍｍの可撓性を有する発泡ウレタンローラを有する帯電ローラを作製した。
【０４５０】
得られた帯電ローラは、発泡ウレタンローラの抵抗が１０^５Ω・ｃｍであり、硬度は、アスカーＣ硬度で３０度であった。
【０４５１】
＜トナー粒子の製造例Ｔｓ−１＞
・スチレン−アクリル酸ブチル−マレイン酸ブチルハーフエステル共重合体（Ｔｇ６３℃、分子量：Ｍｐ１２０００、Ｍｎ６５００、Ｍｗ２３００００） １００質量部
・磁性酸化鉄（平均粒子径０．２２μｍ、７９５．５ｋＡ／ｍ磁場での抗磁力（Ｈｃ）５．２ｋＡ／ｍ、飽和磁化（σｓ）８５Ａｍ^２／ｋｇ、残留磁化（σｒ）５．０Ａｍ^２／ｋｇ） ９０質量部
・モノアゾ鉄錯体（負帯電性制御剤） ２質量部
・低分子量エチレン−プロピレン共重合体 ４質量部
上記材料をブレンダーにて混合し、混合物を１３０℃に加熱したエクストルーダーにより溶融混練し、得られた混練物を冷却後、粗粉砕し、ジェット気流を用いた微粉砕機を用いて微粉砕した。さらに得られた微粉砕品をコアンダ効果を利用した多分割分級装置で厳密に分級して、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径７．９μｍのトナー粒子Ｔｓ−１を得た。トナー粒子Ｔｓ−１の抵抗は、１０^１４Ω・ｃｍ以上であった。
【０４５２】
円形度分布は、発明の実施の形態で述べようにフロー式粒子像分析装置ＦＰＩＡ−１０００（東亜医用電子社製）を用いた方法で測定した。より詳細に記述すると、内径３０ｍｍ、高さ６５ｍｍの硬質ガラス製ネジ口瓶（例えば、日電理化硝子株式会社製３０ｍｌ用ネジ口瓶ＳＶ−３０）に、フィルターを通して微細なごみを取り除いた水（円相当径０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の粒子数が１０^３ｃｍ^３中に測定２０個以下とすることが好ましい）１０ｍｌと、希釈した界面活性剤（好ましくはアルキルベンゼンスルフォン酸塩を微細なごみを取り除いた水で１０倍程度に薄めたもの）を数滴加えた。これに測定試料を測定円相当径範囲の粒子を対象として測定試料の粒子濃度が７０００〜１００００個／１０^３ｃｍ^３となるように適当量（例えば、０．５〜２０ｍｇ）加え、超音波ホモジナイザーで３分間分散処理（出カ５０Ｗ、周波数２０ｋＨｚの株式会社エスエムテー社製ＵＬＴＲＡＳＯＮＩＣＨＯＭＯＧＥＮＩＺＥＲＵＨ−５０に６ｍｍ径ステップ型チップを適用し、パワーコントロールボリュームの目盛りを７に設定して、すなわち同チップを用いた場合の最大出カの半分程度の分散力で処理）を行った試料分散液を用いて、０．６０μｍ以上１５９．２１μｍ未満の円相当径を有する粒子の粒度分布及び円形度分布を測定した。
【０４５３】
得られた粒度分布から、１．００μｍ以上２．００μｍ未満の粒径範囲の粒子の含有量（個数％）、円形度を求めた。トナー粒子Ｔｓ−１の上記各物性値を表２に示す。
【０４５４】
＜トナー粒子の製造例Ｔｓ−２＞
トナー粒子の製造例Ｔｓ−１で得られた粗粉砕物を機械式粉砕機により微粉砕した。得られた微粉砕品を多分割分級装置で分級し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径６．８μｍのトナー粒子Ｔｓ−２を得た。トナー粒子の抵抗は、１０^１４Ω・ｃｍ以上であった。
【０４５５】
＜トナー粒子の製造例Ｔｓ−３＞
トナー粒子の製造例Ｔｓ−２で得られた分級品を、図６および図７に示すトナー粒子球形化処理装置を用いて熱機械的衝撃力を粒子に繰り返し与えることにより球形化処理し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径６．５μｍのトナー粒子Ｔｓ−３を得た。
【０４５６】
＜トナー粒子の製造例Ｔｓ−４＞
トナー粒子の製造例Ｔｓ−３で得られた分級品を、３００℃熱風中を瞬間的に通過させる球形化処理を行い、重量平均粒径６．９μｍの磁性のトナー粒子Ｔｓ−４を得た。磁性のトナー粒子Ｔｓ−４の抵抗は１０^１４Ω・ｃｍであった。
【０４５７】
＜トナー粒子の製造例Ｔｐ−１＞
・ポリエステル樹脂（Ｔｇ６０℃、酸価２０ｍｇＫＯＨ／ｇ、水酸基価３０ｍｇＫＯＨ／ｇ、分子量：Ｍｐ７０００、Ｍｎ３０００、Ｍｗ５５０００） １００質量部
・磁性酸化鉄（平均粒子径０．２０μｍ、７９５．５ｋＡ／ｍ磁場でのＨｃ９．２ｋＡ／ｍ、σｓ８２Ａｍ^２／ｋｇ、σｒ１１．５Ａｍ^２／ｋｇ） ９０質量部
・モノアゾ鉄錯体（負帯電性制御剤） ２質量部
・低分子量エチレン−プロピレン共重合体 ４質量部
上記材料をトナー粒子の製造例Ｔｓ−１と同様の方法で溶融混練・粗粉砕・ジェット気流を用いた微粉砕機を用いて微粉砕し、分級して、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径８．１μｍのトナー粒子Ｔｐ−１を得た。トナー粒子Ｔｐ−１の抵抗は、１０^１４Ω・ｃｍ以上であった。
【０４５８】
＜トナー粒子の製造例Ｔｐ−２＞
トナー粒子の製造例Ｔｐ−１で得られた粗粉砕物を機械式粉砕機により微粉砕した。得られた微粉砕品を多分割分級装置で分級し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径７．０μｍのトナー粒子Ｔｐ−２を得た。トナー粒子の抵抗は、１０^１４Ω・ｃｍ以上であった。
【０４５９】
＜トナー粒子の製造例Ｔｐ−３＞
トナー粒子の製造例Ｔｐ−２で得られた分級品を、図６および図７に示すトナー粒子球形化処理装置を用いて熱機械的衝撃力を粒子に繰り返し与えることにより球形化処理し、０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の体積基準の粒度分布から求められる重量平均粒径６．７μｍのトナー粒子Ｔｐ−３を得た。
【０４６０】
＜トナー粒子の製造例Ｔｐ−４＞
トナー粒子の製造例Ｔｐ−３で得られた分級品を、３００℃熱風中を瞬間的に通過させる球形化処理を行い、重量平均粒径７．２μｍの磁性のトナー粒子Ｔｐ−４を得た。磁性のトナー粒子Ｔｐ−４の抵抗は１０^１４Ω・ｃｍであった。
【０４６１】
上記各トナー粒子Ｔｓ−１〜４及びＴｐ−１〜４の代表的物性値を表２に示す。
【０４６２】
【表２】

【０４６３】
＜無機微粉末の製造例Ｉ−１＞
ヘキサメチルジシラザンで処理した後にジメチルシリコーンオイルで処理された疎水性乾式シリカ微粉体を無機微粉末Ｉ−１とした。この無機微粉末Ｉ−１の一次粒子の個数平均径は１２ｎｍ、ＢＥＴ比表面積は１２０ｍ^２／ｇであった。
【０４６４】
＜無機微粉末の例Ｉ−２＞
ヘキサメチルジシラザンで処理した乾式シリカ微粉体を無機微粉末Ｉ−２とした。この無機微粉末Ｉ−２の一次粒子の個数平均径は１６ｎｍ、ＢＥＴ比表面積は１７０ｍ^２／ｇであった。
【０４６５】
上記各無機微粉末Ｉ−１〜Ｉ−２の代表的物性値を表３に示す。
【０４６６】
【表３】

【０４６７】
＜導電性微粒子の例Ｃ−１〜３＞
体積平均粒径０．０７μｍ、１．５２μｍ、２．０３μｍの酸化亜鉛を導電性微粒子Ｃ−１、Ｃ−２、Ｃ−３とした。発明の実施の形態において述べた錠剤法によって測定された導電性微粒子の抵抗はそれぞれ１．２×１０^３Ω・ｃｍ、８．９×１０^３Ω・ｃｍ、２．７×１０^４Ω・ｃｍであった。
【０４６８】
＜導電性微粒子の例Ｃ−４〜６＞
体積平均粒径０．５０μｍ、１．１５μｍ、５．２２μｍの酸化スズを導電性微粒子Ｃ−４、Ｃ−５、Ｃ−６とした。発明の実施の形態において述べた錠剤法によって測定された導電性微粒子の抵抗はそれぞれ７．３×１０^４Ω・ｃｍ、１．２×１０^５Ω・ｃｍ、１．８×１０^７Ω・ｃｍであった。
【０４６９】
＜導電性微粒子の例Ｃ−７＞
粒径約０．１μｍの酸化チタン粉体に質量比で５０％の酸化スズを付着させた導電性微粒子を導電性微粒子Ｃ−７とした。発明の実施の形態において述べた錠剤法によって測定された導電性微粒子の抵抗は３．１×１０^２Ω・ｃｍであった。
【０４７０】
上記各導電性微粒子Ｃ−１〜Ｃ−７の代表的物性値を表４に示す。
【０４７１】
【表４】

【０４７２】
＜現像剤の製造例Ｒｓ−０＞
トナー粒子の製造例Ｔｓ−１で得られた磁性トナー粒子Ｔｓ−１を１００質量部に対し、無機微粉末Ｉ−１を１．２３質量部添加し、ミキサーで均一に混合して現像剤Ｒｓ−０を得た。
【０４７３】
得られた磁性現像剤Ｒｓ−０の０．６０μｍ以上１５９．２１μｍ未満の粒径範囲の個数基準の粒度分布は、前記トナー粒子製造例で述べようにフロー式粒子像分析装置ＦＰＩＡ−１０００（東亜医用電子社製）を用いた方法で測定した。現像剤Ｒｓ−０の上記各物性値を表５に示す。
【０４７４】
＜現像剤の製造例Ｒｓ−１＞
トナー粒子の製造例Ｔｓ−１で得られた磁性トナー粒子Ｔｓ−１を１００質量部に対し、無機微粉末Ｉ−１を１．２３質量部及び導電性微粒子Ｃ−４を１．０３質量部添加し、ミキサーで均一に混合して現像剤Ｒｓ−１を得た。
【０４７５】
＜現像剤の製造例Ｒｓ−２〜７＞
現像剤の製造例Ｒｓ−１において、導電性微粒子Ｃ−４をそれぞれＣ−５、Ｃ−２、Ｃ−３、Ｃ−７、Ｃ−６、Ｃ−１とした以外は、現像剤の製造例ＲＳ−１と同様にして現像剤Ｒｓ−２、Ｒｓ−３、Ｒｓ−４、Ｒｓ−５、Ｒｓ−６、Ｒｓ−７を得た。
【０４７６】
＜現像剤の製造例Ｒｓ−８〜１０＞
現像剤の製造例Ｒｓ−１において、トナー粒子Ｔｓ−１の代わりにトナー粒子Ｔｓ−２、Ｔｓ−３、Ｔｓ−４をそれぞれ用いた以外は、現像剤の製造例Ｒｓ−１と同様にして現像剤Ｒｓ−８、Ｒｓ−９、Ｒｓ−１０を得た。
【０４７７】
＜現像剤の製造例Ｒｐ−０＞
トナー粒子の製造例Ｔｐ−１で得られた磁性トナー粒子Ｔｐ−１を１００質量部に対し、無機微粉末Ｉ−２を１．２３質量部添加し、ミキサーで均一に混合して現像剤Ｒｐ−０を得た。
【０４７８】
＜現像剤の製造例Ｒｐ−１＞
トナー粒子の製造例Ｔｐ−１で得られた磁性トナー粒子Ｔｐ−１を１００質量部に対し、無機微粉末Ｉ−２を１．２３質量部及び導電性微粒子Ｃ−４を１．０３質量部添加し、ミキサーで均一に混合して現像剤Ｒｐ−１を得た。
【０４７９】
＜現像剤の製造例Ｒｐ−２〜７＞
現像剤の製造例Ｒｐ−１において、導電性微粉末Ｃ−４をそれぞれＣ−５、Ｃ−２、Ｃ−３、Ｃ−７、Ｃ−６、Ｃ−１とした以外は、現像剤の製造例Ｒｐ−１と同様にして現像剤Ｒｐ−２、Ｒｐ−３、Ｒｐ−４、Ｒｐ−５、Ｒｐ−６、Ｒｐ−７を得た。
【０４８０】
＜現像剤の製造例Ｒｐ−８〜１０＞
現像剤の製造例Ｒｐ−１において、トナー粒子Ｔｐ−１の代わりにトナー粒子Ｔｐ−２、Ｔｐ−３、Ｔｐ−４をそれぞれ用いた以外は、現像剤の製造例Ｒｐ−１と同様にして現像剤Ｒｐ−８、Ｒｐ−９、Ｒｐ−１０を得た。
【０４８１】
上記各現像剤Ｒｓ−０〜１０及びＲｐ−０〜１０の重量平均粒径、１．００μｍ以上２．００μｍ未満および３．００μｍ以上８．９６μｍ未満の粒径範囲の粒子の含有量（個数％）を表５にそれぞれ示す。
【０４８２】
【表５】

【０４８３】
＜現像剤担持体製造例Ｄｐ−ｌ−１＞
正帯電性物質である含窒素複素環化合物としては、一般式Ｂ−１で示される個数平均粒径３μｍのイミダゾール化合物粒子を用いた。
【０４８４】
【化１６】

【０４８５】
・レゾール型フェノール樹脂溶液（メタノール５０％含有） ４００質量部
・含窒素複素環化合物Ｂ−１（イミダゾール化合物） １５質量部
・イソプロピルアルコール ３３５質量部
上記材料を直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製した。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置し、これを前述したようにして鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
【０４８６】
導電性球状粒子として、個数平均粒径７．８μｍの球状フェノール樹脂粒子１００質量部にライカイ機（自動乳鉢、石川工業製）を用いて個数平均粒径２μｍ以下の石炭系バルクメソフェーズピッチ粉末１４質量部を均一に被覆し、空気中下２８０℃で熱安定化処理した後に窒素雰囲気下２０００℃で焼成することにより黒鉛化し、更に分級して得られた個数平均粒径７．２μｍの球状導電性炭素粒子を用いた。
・導電性カーボンブラック２０質量部
・個数平均粒径３．４μｍのグラファイト８０質量部
・レゾール型フェノール樹脂溶液（メタノール５０％含有）４００質量部
・含窒素複素環化合物Ｂ−１（イミダゾール化合物）１５質量部
・球状炭素粒子（個数平均粒径７．２μｍ）１０質量部
・イソプロピルアルコール１２５質量部
上記材料を直径２ｍｍのジルコニア粒子にて３時間サンドミル分散を行い、その後ジルコニア粒子を篩いで分離し、イソプロピルアルコールで固形分を４０％に調整し塗工液（ｃ（カーボン）／ＧＦ（グラファイト）／Ｂ（フェノール樹脂）／ＣＡ（含窒素複素環化合物Ｂ−１）／Ｒ（球状粒子）＝０．２／０．８／２．０／０．１５／０．１）を得た。この塗工液を絶縁シート上にバーコーターにてコート・乾燥させ、これを定形にカットし、低抵抗率計ロレスター（三菱化学社製）にて測定したところ、体積抵抗率は３．５２Ω・ｃｍであった。
【０４８７】
この塗料をスプレー法にて直径１６ｍｍのＡｌ円筒体上に１５μｍの被膜を形成させ、次いで熱風乾燥器により１５０℃／３０分間加熱・硬化させ現像剤担持体Ｄｐ−ｌ−１を作製した。この現像剤担持体上の導電性被覆層表面のＲａをサーフコーダーＳＥ−３３００（小坂研究所製）にて、評価長さ４ｍｍ、６点測定しその平均値を算出したところ、Ｒａ＝１．２１μｍであった。
【０４８８】
＜現像剤担持体製造例Ｄｐ−ｌ−２〜４＞
含窒素複素環化合物としては、一般式Ｂ−２〜４で示される個数平均粒径３μｍのイミダゾール化合物粒子を用いた。
【０４８９】
【化１７】

【０４９０】
これを現像剤担持体製造例Ｄｐ−ｌ−１と同様にして鉄粉との摩擦帯電極性を測定したところ、いずれも正帯電性を示した。
【０４９１】
これを現像剤担持体製造例Ｄｐ−ｌ−１と同様の操作で分散・塗工し、現像剤担持体Ｄｐ−ｌ−２〜４を作製し、同様の評価を行った。
【０４９２】
＜現像剤担持体製造例Ｄｐ−ｎ−１＞
・レゾール型フェノール樹脂溶液（メタノール５０％含有） ６００質量部
・含窒素複素環化合物Ｂ−１（イミダゾール化合物） ２０質量部
・イソプロピルアルコール ４４７質量部
上記材料を、直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製する。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置する。これを発明の実施の形態で述べたように、鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
・導電性カーボンブラック ２０質量部
・個数平均粒径３．４μｍのグラファイト ８０質量部
・レゾール型フェノール樹脂溶液（メタノール５０％含有） ６００質量部
・含窒素複素環化合物Ｂ−１（イミダゾール化合物） ２０質量部
・球状炭素粒子（個数平均粒径３．７μｍ） １０質量部
・イソプロピルアルコール ７００質量部
上記材料に直径２ｍｍのジルコニアビーズをメディア粒子として加え、サンドミルにて２時間分散し、フルイを用いてビーズを分離し、イソプロピルアルコールで固形分を４０％に調整し塗工液（ｃ（カーボン）／ＧＦ（グラファイト）／Ｂ（結着樹脂）／ＣＡ（含窒素複素環化合物Ｂ−１）／Ｒ（球状粒子）＝０．２／０．８／３．０／０．２／０．１）を得た。
【０４９３】
これを現像剤担持体製造例Ｄｐ−ｌ−１と同様の操作で分散・塗工し、現像剤担持体Ｄｐ−ｎ−１を作製し、同様の評価を行った。
【０４９４】
＜現像剤担持体製造例Ｄｐ−ｎ−２〜４＞
現像剤担持体製造例Ｄｐ−ｎ−１において、含窒素複素環化合物をＢ−２〜４に代えたこと以外は現像剤担持体製造例Ｄｐ−ｎ−１と同様にして現像剤担持体Ｄｐ−ｎ−２〜４を作製し、同様の評価を行った。
【０４９５】
【表６】

【０４９６】
＜現像剤担持体製造例Ｄｍ−ｌ−１＞
・レゾール型フェノール樹脂（固形分５０％） ３２０質量部
・メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−１（固形分５０％）（モル比９０：１０、Ｍｗ＝１０，２００、Ｍｎ＝４，５００、Ｍｗ／Ｍｎ＝２．３） ８０質量部
・ＭＥＫ ４００質量部
上記材料を直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製する。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置する。これを発明の実施の形態で述べたように、鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
【０４９７】
球状粒子として、個数平均粒径７．８μｍの球状フェノール樹脂粒子１００部にライカイ機（自動乳鉢、石川工場製）を用いて個数平均粒径２μｍ以下の石炭系バルクメソフェーズピッチ粉末１４部を均一に被覆し、空気中下２８０℃で熱安定化処理した後に窒素雰囲気下２０００℃で焼成することにより黒鉛化し、更に分級して得られた個数平均径１１．７μｍの球状導電性炭素粒子を用いた。
・カーボンブラック ２０質量部
・個数平均粒径４．８μｍの結晶性グラファイト ８０質量部
・レゾール型フェノール樹脂（固形分５０％） ３２０質量部
・メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−１（固形分５０％）（モル比９０：１０、Ｍｗ＝１０，２００、Ｍｎ＝４，５００、Ｍｗ／Ｍｎ＝２．３） ８０質量部
・球状炭素粒子（個数平均粒径１１．７μｍ） ３０質量部
・ＭＥＫ １３０質量部
上記材料をφ２ｍｍのジルコニア粒子にて３時間サンドミル分散を行い、その後ジルコニア粒子を篩いで分離し、ＭＥＫで固形分を４０％に調整し、塗工液（ｃ（カーボン）／ＧＦ（グラファイト）／Ｂ（フェノール樹脂）／Ｄ（共重合体Ｐ−１）／Ｒ（球状粒子）＝０．２／０．８／１．６／０．４／０．３）を得た。この塗工液を絶縁シート上にバーコーターにてコート・乾燥させ、これを定形にカットし、低抵抗率計ロレスター（三菱化学社製）にて測定したところ、体積抵抗率は５．０３Ω・ｃｍであった。
【０４９８】
この塗料をスプレー法にて直径１６ｍｍのＡｌ円筒体上に１５μｍの被膜を形成させ、次いで熱風乾燥器により１５０℃／３０分間加熱・硬化させ現像剤担持体Ｄ−１を作製した。この現像剤担持体上の導電性被覆層表面のＲａをサーフコーダーＳＥ−３３００（小坂研究所製）にて、評価長さ４ｍｍ、６点測定しその平均値を算出したところ、Ｒａ＝１．２７μｍであった。
【０４９９】
＜現像剤担持体製造例Ｄｍ−ｌ−２〜４＞
現像剤担持体製造例Ｄｍ−ｌ−１で用いた共重合体Ｐ−１に替えて、共重合体の分子量及びメチルメタクリレートとジメチルアミノエチルメタクリレートのモル比を変化させた共重合体Ｐ−２〜４を用いて、現像剤担持体製造例Ｄｍ−ｌ−１と同様にして現像剤担持体Ｄｍ−ｌ−２〜４を作製し、現像剤担持体製造例Ｄｍ−ｌ−１と同様の評価を行った。
【０５００】
現像剤担持体Ｄｍ−ｌ−２に使用した共重合体
メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−２（固形分４０％）（モル比９０：１０、Ｍｗ＝４０，０００、Ｍｎ＝１９，０００、Ｍｗ／Ｍｎ＝２．１）
現像剤担持体Ｄｍ−ｌ−３に使用した共重合体
メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−３（固形分４０％）（モル比９０：１０、Ｍｗ＝３，７００、Ｍｎ＝２，３００、Ｍｗ／Ｍｎ＝１．６）
現像剤担持体Ｄｍ−ｌ−４に使用した共重合体
メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−４（固形分４０％）（モル比７０：３０、Ｍｗ＝８，５００、Ｍｎ＝２，９００、Ｍｗ／Ｍｎ＝２．９）
＜現像剤担持体製造例Ｄｍ−ｎ−１＞
・レゾール型フェノール樹脂（固形分５０％） ４６０質量部
・メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−１（固形分５０％） １４０質量部
・ＭＥＫ ４００質量部
上記材料を上記材料を直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製する。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置する。これを発明の実施の形態で述べたように、鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
・カーボンブラック ２０質量部
・個数平均粒径４．８μｍの結晶性グラファイト ８０質量部
・レゾール型フェノール樹脂（固形分５０％） ４６０質量部
・メチルメタクリレート−ジメチルアミノエチルメタクリレート共重合体Ｐ−１（固形分５０％） １４０質量部
・球状炭素粒子（個数平均粒径７．２μｍ） ３０質量部
・ＭＥＫ １３０質量部
上記材料に直径２ｍｍのジルコニアビーズをメディア粒子として加え、サンドミルにて２時間分散し、フルイを用いてビーズを分離し、ＭＥＫで固形分を４０％に調整し塗工液（ｃ（カーボン）／ＧＦ（グラファイト）／Ｂ（結着樹脂）／Ｄ（共重合体Ｐ−１）／Ｒ（球状粒子）＝０．２／０．８／２．３／０．７／０．３）を得た。
【０５０１】
これを現像剤担持体製造例Ｄｍ−ｌ−１と同様の操作で分散・塗工し、現像剤担持体Ｄｍ−ｎ−１を作製し、同様の評価を行った。
【０５０２】
＜現像剤担持体製造例Ｄｍ−ｎ−２〜４＞
現像剤担持体製造例Ｄｍ−ｎ−１において、共重合体をＰ−２〜４に代えたこと以外は現像剤担持体製造例Ｄｍ−ｎ−１と同様にして現像剤担持体Ｄｍ−ｎ−２〜４を作製し、同様の評価を行った。
【０５０３】
【表７】

【０５０４】
＜現像剤担持体製造例Ｄｆ−ｌ−１＞
＜電荷制御樹脂の製造＞
・メタノール： ３００質量部
・トルエン： １００質量部
・スチレン： ４６８質量部
・２−エチルヘキシルアクリレート： ９０質量部
・２−アクリルアミド−２−メチルプロパンスルホン酸： ４２質量部
・ラウロイルパーオキサイド： ６質量部
上記原料をフラスコに仕込み、撹拌装置、温度測定装置、窒素導入装置を装着して、窒素雰囲気下６５℃で溶液重合させ、１０時間保持して重合反応を終了させた。得られた重合物を減圧乾燥、粉砕して、重量平均分子量１０，０００の電荷制御樹脂Ｆ−１を得た。
【０５０５】
以下、組成比を表８に示すように変更することにより、電荷制御樹脂Ｆ−２、Ｆ−３を得た。
【０５０６】
電荷制御樹脂Ｆ−１ ５０質量部をメチルエチルケトン５０質量部に溶解させることにより、電荷制御樹脂溶液Ｆ−１を作製した。
・フェノール樹脂（メタノール５０％含有） ３４０質量部
・電荷制御樹脂溶液Ｆ−１（ＭＥＫ５０％含有） ６０質量部
・イソプロピルアルコール ２６７質量部
上記材料を直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製する。このサンプル板を接地した状態で、２３℃，相対湿度６０％環境下にて一晩放置する。これを発明の実施の形態で述べたように、鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
・カーボンブラック ２０質量部
・個数平均粒径５．５μｍの結晶性グラファイト ８０質量部
・アンモニアを触媒として製造されたフェノール樹脂（メタノール５０％含有）
３４０質量部
・電荷制御樹脂溶液Ｆ−１（ＭＥＫ５０％含有） ６０質量部
・球状炭素粒子（個数平均粒径１１．７μｍ） ２０質量部
・イソプロピルアルコール １２０質量部
【０５０７】
この塗料をスプレー法にて直径１６ｍｍのＡｌ円筒体上に１５μｍの被膜を形成させ、次いで熱風乾燥器により１５０℃／３０分間加熱・硬化させ現像剤担持体Ｄｆ−ｌ−１を作製した。この現像剤担持体上の導電性被覆層表面のＲａをサーフコーダーＳＥ−３３００（小坂研究所製）にて、評価長さ４ｍｍ、６点測定しその平均値を算出したところ、Ｒａ＝１．０７μｍであった。
【０５０８】
＜現像剤担持体製造例Ｄｆ−ｌ−２＞
現像剤担持体製造例Ｄｆ−ｌ−１において、アンモニアを触媒として製造されたフェノール樹脂を、ヘキサメチレンテトラミンを触媒として製造されたフェノール樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｌ−１と同様にして現像剤担持体Ｄｆ−ｌ−２を作製し、現像剤担持体製造例Ｄｆ−ｌ−１と同様の評価を行った。
【０５０９】
＜現像剤担持体製造例Ｄｆ−ｌ−３＞
現像剤担持体製造例Ｄｆ−ｌ−１で用いた電荷制御樹脂Ｆ−１に代えて、組成比を表８に示すように変更することにより得られた電荷制御樹脂Ｆ−２を用い、アンモニアを触媒として製造されたフェノール樹脂をポリアミド樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｌ−１と同様にして現像剤担持体Ｄｆ−ｌ−３を作製し、現像剤担持体製造例Ｄｆ−ｌ−１と同様の評価を行った。
【０５１０】
＜現像剤担持体製造例Ｄｆ−ｌ−４＞
現像剤担持体製造例Ｄｆ−ｌ−１で用いた電荷制御樹脂Ｆ−１に代えて、組成比を表８に示すように変更することにより得られた電荷制御樹脂Ｆ−３を用い、アンモニアを触媒として製造されたフェノール樹脂をポリウレタン樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｌ−１と同様にして現像剤担持体Ｄｆ−ｌ−４を作製し、現像剤担持体製造例Ｄｆ−ｌ−１と同様の評価を行った。
【０５１１】
＜現像剤担持体製造例Ｄｆ−ｎ−１＞
・フェノール樹脂（メタノール５０％含有） ５００質量部
・電荷制御樹脂溶液Ｆ−１（ＭＥＫ５０％含有） １００質量部
・イソプロピルアルコール ４００質量部
上記材料を直径２ｍｍのガラス粒子にて１時間サンドミル分散を行い、その後ガラス粒子を篩いで分離し、この樹脂溶液を、ＳＵＳ板上にバーコーター（＃６０）にて塗布し、これを１５０℃／３０分で加熱・硬化させ、サンプル板を作製する。このサンプル板を接地した状態で、２３℃、相対湿度６０％環境下にて一晩放置する。これを発明の実施の形態で述べたように、鉄粉との摩擦帯電極性を測定したところ、正帯電性を示した。
・カーボンブラック ２０質量部
・個数平均粒径５．５μｍの結晶性グラファイト ８０質量部
・アンモニアを触媒として製造されたフェノール樹脂（メタノール５０％含有）
５００質量部
・電荷制御樹脂溶液Ｆ−１（ＭＥＫ５０％含有） １００質量部
・球状炭素粒子（個数平均粒径７．２μｍ） ２０質量部
・イソプロピルアルコール １２０質量部
上記材料に直径２ｍｍのジルコニアビーズをメディア粒子として加え、サンドミルにて２時間分散し、フルイを用いてビーズを分離し、イソプロピルアルコールで固形分を４０％に調整し塗工液（ｃ（カーボン）／ＧＦ（グラファイト）／Ｂ（結着樹脂）／ＣＡ（電荷制御樹脂Ｆ−１）／Ｒ（球状粒子）＝０．２／０．８／２．５／０．５／０．２）を得た。
【０５１２】
これを現像剤担持体製造例Ｄｆ−ｌ−１と同様の操作で塗工し現像剤担持体Ｄｆ−ｎ−１を作製し、現像剤担持体製造例Ｄｆ−ｌ−１と同様の評価を行った。
【０５１３】
＜現像剤担持体製造例Ｄｆ−ｎ−２＞
現像剤担持体製造例Ｄｆ−ｎ−１において、アンモニアを触媒として製造されたフェノール樹脂を、ヘキサメチレンテトラミンを触媒として製造されたフェノール樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｎ−１と同様にして現像剤担持体Ｄｆ−ｎ−２を作製し、現像剤担持体製造例Ｄｆ−ｎ−１と同様の評価を行った。
【０５１４】
＜現像剤担持体製造例Ｄｆ−ｎ−３＞
現像剤担持体製造例Ｄｆ−ｎ−１で用いた電荷制御樹脂Ｆ−１に代えて、組成比を表８に示すように変更することにより得られた電荷制御樹脂Ｆ−２を用い、アンモニアを触媒として製造されたフェノール樹脂をポリアミド樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｎ−１と同様にして現像剤担持体Ｄｆ−ｎ−３を作製し、現像剤担持体製造例Ｄｆ−ｎ−１と同様の評価を行った。
【０５１５】
＜現像剤担持体製造例Ｄｆ−ｎ−４＞
現像剤担持体製造例Ｄｆ−ｎ−１で用いた電荷制御樹脂Ｆ−１に代えて、組成比を表８に示すように変更することにより得られた電荷制御樹脂Ｆ−３を用い、アンモニアを触媒として製造されたフェノール樹脂をポリウレタン樹脂に代えたこと以外は現像剤担持体製造例Ｄｆ−ｎ−１と同様にして現像剤担持体Ｄｆ−ｎ−４を作製し、現像剤担持体製造例Ｄｆ−ｎ−１と同様の評価を行った。
【０５１６】
【表８】

【０５１７】
＜画像形成装置例の説明＞
図１は、本発明の画像形成装置の構成の一例を示す図である。この画像形成装置は、転写式電子写真プロセスを利用した現像兼クリーニングプロセス（クリーナレスシステム）のレーザープリンター（記録装置）である。クリーニングブレードなどのクリーニング部材を有するクリーニングユニットを除去したプロセスカートリッジを有し、現像剤としては磁性１成分系現像剤（すなわち、外添剤と磁性トナー粒子を有する磁性トナー）を使用し、現像剤担持体上の現像剤層と像担持体とが非接触となるように配置された非接触現像の画像形成装置の一例である。
【０５１８】
（１）画像形成装置の構成
１は潜像担持体としての、感光体製造例１の回転ドラム式のＯＰＣ感光体であり、時計方向（矢印の方向）に１００ｍｍ／ｓｅｃの周速度（プロセススピード）をもって回転駆動される。
【０５１９】
２は接触帯電部材としての帯電部材製造例の帯電ローラであり、芯金２ａと弾性層２ｂとよりなる。帯電ローラ２は感光体１に対して弾性に抗して所定の押圧力で圧接させて配設してある。ｎは感光体１と帯電ローラ２との接触部である帯電部である。本実施例では、帯電ローラ２は感光体１との接触部である帯電部ｎにおいてカウンター方向（感光体表面の移動方向と逆方向）に１４１ｍｍ／ｓｅｃ（相対移動速度比２５０％）の周速度で回転駆動されている。また、帯電ローラ２の表面には、塗布量がおよそ一層で均一になるように、トナー粒子ｔに外添された導電性微粉末ｍと同一の導電性微粉末ｍをあらかじめ塗付した。
【０５２０】
また帯電ローラ２の芯金２ａには、帯電バイアス印加電源Ｓ１から−７００Ｖの直流電圧を帯電バイアスとして印加した。本実施例では、感光体１の表面は帯電ローラ２に対する印加電圧とほぼ等しい電位（−６８０Ｖ）に直接注入帯電方式によって一様に帯電処理される。これについては後述する。
【０５２１】
３はレーザダイオード、ポリゴンミラー等を含むレーザビームスキャナ（露光器）である。このレーザビームスキャナは、目的の画像情報の時系列電気デジタル画素信号に対応して強度変調されたレーザー光（波長７４０ｎｍ）を出力し、該レーザ光で感光体１の一様帯電面を走査露光する。この走査露光により感光体１に目的の画像情報に対応した静電潜像が形成される。
【０５２２】
４は現像装置である。感光体１表面の静電潜像がこの現像装置によりトナー画像として現像される。本実施例の現像装置４は、現像剤として負帯電性１成分絶縁現像剤である現像剤１を用いた、非接触型の反転現像装置である。現像剤４ｄはトナー粒子ｔおよび導電性微粉末ｍを有する。
【０５２３】
４ａは現像剤担持搬送部材としての、マグネットロール４ｂを内包させた直径１６ｍｍの非磁性現像スリーブである。この現像スリーブ４ａは、感光体１に対して３００μｍの離間距離をあけて対向配設され、感光体１との対向部である現像部（現像領域部）ａにて感光体１の回転方向と順方向に感光体１の周速の１２０％の周速（周速度１２０ｍｍ／ｓｅｃ）で回転される。
【０５２４】
この現像スリーブ４ａ上に、現像剤４ｄが弾性ブレード４ｃによって薄層にコートされる。現像剤４ｄは、弾性ブレード４ｃによって現像スリーブ４上での層厚が規制されるとともに電荷が付与される。
【０５２５】
現像スリーブ４ａにコートされた現像剤４ｄは、スリーブ４ａが回転することによって、感光体１と当該スリーブ４ａとの対向部である現像部ａに搬送される。また、スリーブ４ａには、現像バイアス印加電源Ｓ２により現像バイアス電圧が印加される。現像バイアス電圧は−４２０Ｖの直流電圧と、周波数１６００Ｈｚ、ピーク間電圧１５００Ｖ（電界強度５×１０^６Ｖ／ｍ）の矩形の交流電圧とを重畳したものを用いて、現像スリーブ４ａと感光体１との間で１成分のジャンピング現像を行った。
【０５２６】
５は接触転写手段としての中抵抗の転写ローラであり、感光体１に９８Ｎ／ｍの線圧で圧接させて転写当接部ｂを形成している。この転写当接部ｂに図示せぬ給紙部から所定のタイミングで記録媒体としての転写材Ｐが給紙され、かつ転写ローラ５に転写バイアス印加電源Ｓ３から所定の転写バイアス電圧が印加されることで、感光体１側のトナー像が転写当接部ｂに給紙された転写材Ｐの面に順次に転写されていく。
【０５２７】
本実施例では、転写ローラ５は抵抗が５×１０^８Ωｃｍのものを用い、＋３０００Ｖの直流電圧を印加して転写を行った。即ち、転写当接部ｂに導入された転写材Ｐはこの転写当接部ｂを挟持搬送されて、その表面側に感光体１の表面に形成担持されているトナー画像が順次に静電気力と押圧力にて転写されていく。
【０５２８】
６は熱定着方式等の定着装置である。転写二ップ部ｂに給紙され感光体１側のトナー像の転写を受けた転写材Ｐは、感光体１の表面から分離されてこの定着装置６に導入され、トナー像の定着を受けて画像形成物（プリント、コピー）として装置外へ排出される。
【０５２９】
本例の画像形成装置はクリーニングユニットを除去しており、転写材Ｐに対するトナー像転写後の感光体１の表面に残留した転写残りの現像剤（転写残トナー粒子）はクリーニング手段で除去されることなく、感光体１の回転に伴い帯電部ｎを経由して現像部ａに至り、現像装置４において現像兼クリーニング（回収）される。
【０５３０】
本例の画像形成装置は、感光体１、帯電ローラ２、現像装置４の３つのプロセス機器を一括して画像形成装置本体に対して着脱自在のプロセスカートリッジ７として構成してある。本発明においてはプロセスカートリッジ化するプロセス機器の組み合わせ等は上記に限られるものではなく任意である。なお、８はプロセスカートリッジ着脱案内・保持部材である。
【０５３１】
（２）導電性微粉末の挙動
現像装置４の現像剤４ｄに含有される導電性微粉末ｍは、感光体１側の静電潜像の現像装置４によるトナー現像時に、トナー粒子ｔとともに適当量が感光体１側に移行する。
【０５３２】
感光体１上のトナー画像（すなわちトナー粒子）は、転写部ｂにおいて転写バイアスの影響で記録媒体である転写材Ｐ側に引かれて積極的に転移する。しかし、感光体１上の導電性微粉末ｍは導電性であるため転写材Ｐ側には積極的には転移せず、感光体１上に実質的に付着保持されて残留する。
【０５３３】
本実施例においては、画像形成装置はクリーニング工程を有さないため、転写後の感光体１の表面に残存した転写残トナー粒子および導電性微粉末は、感光体１の回転に伴って、感光体１と接触帯電部材である帯電ローラ２の接触部である帯電部ｎに運ばれて、帯電ローラ２に付着する。従って、感光体１と帯電ローラ２との接触部ｎにこの導電性微紛末ｍが存在した状態で感光体１の直接注入帯電が行われる。
【０５３４】
この導電性微粉末ｍの存在により、帯電ローラ２に転写残トナー粒子が付着した場合でも、帯電ローラ２の感光体１への綴密な接触性と接触抵抗を維持できるため、該帯電ローラ２による感光体１の直接注入帯電を行わせることができる。
【０５３５】
つまり、帯電ローラ２が導電性微粉末ｍを介して密に感光体１に接触し、この導電性微粉末ｍが感光体１表面を隙間なく摺擦する。これにより、帯電ローラ２による感光体１の帯電を、放電現象を用いない、安定かつ安全な直線注入帯電が支配的とすることが可能になり、従来のローラ帯電等では得られなかった高い帯電効率が得られる。従って、帯電ローラ２に印加した電圧とほぼ同等の電位を感光体１に与えることができる。
【０５３６】
また帯電ローラ２に付着或いは混入した転写残トナー粒子は、帯電ローラ２から徐々に感光体１上に吐き出され、感光体１表面の移動に伴って現像部ａに至り、現像装置４において現像兼クリーニング（回収）される。
【０５３７】
現像兼クリーニングは、転写後に感光体１上に残留したトナー粒子を、画像形成工程の次回以降の現像時（現像後、再度帯電工程、露光工程を介した後の潜像の現像時）において、現像装置のかぶり取りバイアス（現像装置に印加する直流電圧と感光体の表面電位間の電位差であるかぶり取り電位差Ｖｂａｃｋ）によって回収するものである。本実施例における画像形成装置のように、反転現像の場合、この現像兼クリーニングは、現像バイアスによる感光体の暗部電位から現像スリーブにトナー粒子を回収する電界と、現像スリーブから感光体の明部電位ヘトナー粒子を付着させる（現像する）電界の作用でなされる。
【０５３８】
また、画像形成装置が稼働されることで、現像装置４の現像剤に含有された導電性微粉末ｍが、現像部ａで感光体１表面に移行し、感光体１表面の移動に伴って転写部ｂを経て帯電部ｎに持ち運ばれることによって、帯電部ｎに新しい導電性微粉末ｍが逐次供給され続けるため、帯電部ｎにおいて導電性微粉末ｍが脱落等で減少したり、帯電部ｎの導電性微粉末ｍが劣化したりしても、帯電性の低下が生じることが防止されて感光体１の良好な帯電性が安定して維持される。
【０５３９】
かくして、接触帯電方式、転写方式、トナーリサイクルプロセスの画像形成装置において、接触帯電部材として簡易な帯電ローラ２を用いて、像担持体としての感光体１に均一な帯電性を低印加電圧で与えることができる。しかも、帯電部にまで転写残トナー粒子が到着したような場合であっても、オゾンレスの直接注入帯電を長期に渡り安定に維持させることができ、均一な帯電性を与えることができる。よって、オゾン生成物による障害、帯電不良による障害等のない、簡易な構成、低コストな画像形成装置を得ることができる。
【０５４０】
前述のように、導電性微粉末は帯電性を損なわないために、抵抗値が１×１０^９Ω・ｃｍ以下である必要がある。導電性微粉末の抵抗値が１×１０^９Ω・ｃｍよりも大きいと、帯電ローラ２が導電性微粉末を介して密に感光体１に接触し、導電性微粉末が感光体１表面を摺擦しても、感光体１への電荷注入が十分には行われず、感光体１を所望の電位に帯電させることが困難となる。また、現像剤が直接感光体１に接触する接触現像装置を用いた場合には、現像部ａにおいて現像剤中の導電性微粉末を通じて、現像バイアスにより感光体１に電荷注入され、画像かぶりあるいは画像の欠け、濃度薄が発生してしまう。
【０５４１】
本実施例では現像装置は非接触型現像装置であるので、現像バイアスが感光体１に注入されることがなく、良好な画像を得ることができる。また、現像部ａにおいて感光体１への電荷注入が生じないため、交流バイアスなど現像スリーブ４ａと感光体１との間に高電位差を持たせることが可能となる。これにより導電性微粉末ｍが均等に現像されやすくなるため、均一に導電性微粉末ｍを感光体１表面に塗布し、帯電部で均一な接触を行い、良好な帯電性を得ることができ、良好な面像を得ることが可能となる。
【０５４２】
帯電ローラ２と感光体１との接触面に介在された導電性微粉末の潤滑効果（摩擦低減効果）により、帯電ローラ２と感光体１との間に容易に効果的に速度差を設けることが可能となる。この潤滑効果により、帯電ローラ２と感光体１との摩擦を低減し、駆動トルクを低減し、帯電ローラ２や感光体１の表面の削れあるいは傷を防止できる。また、この速度差を設けることにより、帯電ローラ２と感光体１の相互接触部（帯電部）ｎにおいて導電性微粉末が感光体１に接触する機会を格段に増加させ、高い接触性を得ることができる。よって、良好な直接注入帯電を可能としている。
【０５４３】
本実施例では、帯電ローラ２を回転駆動し、その回転方向は感光体１表面の移動方向とは逆方向に回転するように構成することで、帯電部ｎに持ち運ばれる感光体１上の転写残トナー粒子を帯電ローラ２に一時的に回収し、帯電部ｎに介在する転写残トナー粒子の存在量を均す効果を得ている。このため、転写残トナー粒子の帯電部ｎでの偏在による帯電不良の発生が防止され、より安定した帯電性が得られる。
【０５４４】
さらに、帯電ローラ２を逆方向に回転することによって、感光体１上の転写残トナー粒子を感光体１から一旦引き離して帯電を行うことにより、優位に直接注入帯電を行うことが可能である。また、導電性微粉末の帯電ローラ２からの過度の脱落による帯電性の低下を起こさない。
【０５４５】
＜実施例Ｌ−１＞
現像剤Ｒｓ−１、現像剤担持体Ｄｐ−ｌ−１の組合せを用いた。トナーカートリッジ内に１２０ｇの現像剤Ｒｓ−１を充填して、評価環境２３℃／６０％で、５％カバレッジの画像の３５００枚の連続プリントにより、トナーカートリッジ内で現像剤量が少なくなるまで使用した。転写材としては９０ｇ／ｍ^２のＡ４コピー紙を用いた。その結果、初期および３５００枚の連続プリント後においても画像濃度が十分に高く、カブリが少なく、また現像性の低下は見られなかった。
【０５４６】
また、３５００枚の連続プリント後、帯電ローラ上で感光体との接触部ｎに対応する部分を観察したところ、微量の転写残トナー粒子が確認されるものの、ほぼ導電性微粒子Ｃ−４で覆われていた。
【０５４７】
また、感光体と帯電ローラとの接触部ｎに導電性微粒子Ｃ−４が存在した状態で、かつ導電性微粒子Ｃ−４の抵抗が十分に低いために、初期より３５００枚の連続プリント後まで帯電不良に起因する画像欠陥を生じず、良好な直接注入帯電性が得られた。
【０５４８】
また、潜像担持体として感光体の最表面層の体積抵抗が５×１０^１２Ω・ｃｍの感光体を用いたことにより、静電潜像を維持することができ、シャープな輸郭の文字画像が得られ、３５００枚の連続プリント後も十分な帯電性が得られる直接注入帯電を実現できた。３５００枚の連続プリント後の直接注入帯電後、感光体電位は、印加帯電バイアス−７００Ｖに対して−６９０Ｖであり、初期からの帯電性の低下は見られず、帯電性の低下による画像品質の低下は認められなかった。
【０５４９】
更に、潜像担持体の表面の水に対する接触角が１０２度である感光体を用いたこととあいまって、転写効率は初期及び３５００枚の連続プリント後も非常に優れていた。転写後の感光体上に転写残トナー粒子量が少ないことを勘案しても、３５００枚の連続プリント後の帯電ローラ上での転写残トナー粒子が微量であったことと非画像部のカブリが少ないことより、現像での転写残トナー粒子の回収性が良好であったことが解る。
【０５５０】
以下、プリント画像の評価法について述べる。
【０５５１】
（ａ）画像濃度
初期、及び３５００枚の連続プリントアウトを終了した後、２日放置して再び電源を入れた１枚目の画像濃度により評価した。尚、画像濃度は「マクベス反射濃度計」（マクベス社製）を用いて、原稿濃度が０．００の白地部分のプリントアウト画像に対する相対濃度を測定した。評価結果を表１１に示す。なお、表１１中の各記号は、それぞれ以下の評価を意味する。
Ａ：非常に良好で、グラフィックな画像まで高品位に表現するために十分な画像濃度（１．４０以上）。
Ｂ：良好で、ノングラフィックで高品位な画質を得るために十分な画像濃度（１．３５以上１．４０未満）。
Ｃ：普通で、文字を認識する上では十分として許容される画像濃度（１．２０以上１．３５未満）。
Ｄ：悪い。非常に薄い画像濃度（１．２０未満）。
【０５５２】
（ｂ）画像カブリ
初期、および３５００枚の連続プリントアウトを終了した後に、プリントアウト画像をサンプリングし、プリントアウト画像の白地部分の白色度と転写紙の白色度の差から、カブリ濃度（％）を算出し、画像カブリを評価した。白色度は「リフレクトメーター」（東京電色社製）により測定した。評価結果を表１１に示す。なお、表１１中の各記号は、それぞれ以下の評価を意味する。
Ａ：非常に良好で、肉限では一般に認識されないカブリ（１．５％未満）。
Ｂ：良好で、注意して見ないと認識できないカブリ（１．５％以上乃至２．５％未満）。
Ｃ：普通。カブリを認識することは容易であるが、許容されるカブリ（２．５％以上乃至４．０％未満）。
Ｄ：悪い。画像汚れとして認識されるカブリ（４．０％以上）。
【０５５３】
（ｃ）ゴースト
ベタ白部とベタ黒部が隣り合う画像を現像した後、ハーフトーン画像を現像し、ハーフトーン画像上に現れるベタ白部とベタ黒部の境界に起因する濃淡差を目視で観察し、下記の基準で評価した。
Ａ：濃淡差が全く見られない。
Ｂ：軽微な濃淡差が見られる。
Ｃ：濃淡差がやや見られるが実用可。
Ｄ：濃淡差が顕著に見られる。
【０５５４】
（ｄ）転写性
初期および３５００枚プリントアウト終了後に、転写性の評価を行った。転写性は、ベタ黒画像形成時の感光体上の転写残トナー粒子を、マイラーテープによりテーピングしてはぎ取り、はぎ取ったマイラーテープを紙上に貼ったもののマクベス濃度から、マイラーテープのみを紙上に貼ったもののマクベス濃度を差し引いた数値で評価した。評価結果を表１１に示す。なお、表１１中の各記号は、それぞれ以下の評価を意味する。
Ａ：非常に良好（０．０５未満）
Ｂ：良好（０．０５以上乃至０．１０未満）
Ｃ：普通（０．１０以上乃至０．２０未満）
Ｄ：悪い（０．２０以上）
（ｅ）像担持体の帯電性
約４０〜５０枚プリントアウトした後、及び３５００枚の連続プリントアウトを終了した後、通常通り感光体を帯電し、その際の感光体表面電位を現像器位置にセンサを配置して測定し、両時点における電位の差分により像担持体の帯電性を評価した。評価結果を表１１に示す。差分がマイナスに大きくなるほど潜像担持体の帯電性の低下が大きいことを示す。
【０５５５】
（ｆ）パターン回収不良
縦線の同一パターン（２ドット９８スペースの縦線繰り返し）を連続プリントアウトした後、ハーフトーン画像（２ドット３スペースの横線繰り返し）のプリントアウト試験を行い、ハーフトーン画像上に縦線のパターンに対応した濃淡が生じるかどうかを目視で評価した。評価結果を表１１に示す。なお、表１１中の各記号は、それぞれ以下の評価を意味する。
Ａ：非常に良好（未発生）
Ｂ：良好（わずかに濃淡の発生が見られる）
Ｃ：普通（濃淡むらを生じるが、実用上許容レベルの範囲である）
Ｄ：悪い（濃淡むらが顕著に発生する）
（ｇ）画像汚れ
画像汚れの評価は、定着後の画像を目視で観察し、以下の評価基準に基づいて評価を行った。評価結果を表１１に示す。
Ａ：未発生。
Ｂ：かすかに発生。画像への影響は極めて軽微である。
Ｃ：ある程度発生。実用上許容できるレベルである。
Ｄ：画像汚れが著しい。
【０５５６】
上記結果を実施例Ｌ−１の評価として表１１に示す。
【０５５７】
＜実施例Ｌ−２〜６０、８５〜１０８＞
表９と１０に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１１〜１３、１４〜１５に示す。
【０５５８】
＜実施例Ｌ−６１〜７２＞
表１０に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１３に示す。初期からカブリがやや多く、パターン回収不良がやや悪かった。３５００枚の連続プリント終了後の像担持体の帯電性の低下もやや大きいが、実用上は許容できる範囲内であった。
【０５５９】
＜実施例Ｌ−７３〜８４＞
表１０に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１４に示す。初期からやや画像濃度が低く、パターン回収不良の発生も見られたが、実用上は許容できる範囲内であった。
【０５６０】
＜比較例Ｌ−０＞
導電性微粉末の外添されていない現像剤製造例Ｒｓ−０、現像剤担持体Ｄｐ−ｌ−１の組合せで評価を行ったところ、像担持体の帯電性の低下が大きく、カブリが悪化した。
【０５６１】
＜比較例Ｌ−１〜９、２２＞
直径１６ｍｍのＡｌ円筒体を＃８０の不定形アルミナ粒子でブラストし、Ｒａ＝０．３２の現像剤担持体を用いた。現像剤は表９と１０の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１１〜１５に示す。画像濃度が低かった。
【０５６２】
＜比較例Ｌ−１０〜２１＞
表１０に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１５に示す。トナー粒子表面の導電性微粉末が欠落しやすくなり、そのため像担持体の帯電性低下が大きく、カブリ及び画像汚れも目立った。
【０５６３】
【表９】

【０５６４】
【表１０】

【０５６５】
【表１１】

【０５６６】
【表１２】

【０５６７】
【表１３】

【０５６８】
【表１４】

【０５６９】
【表１５】

【０５７０】
＜実施例Ｎ−１〜６０、８５〜１０８＞
表１６と１７に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１８〜２１に示す。
【０５７１】
＜実施例Ｎ−６１〜７２＞
表１７に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表２０に示す。初期からカブリがやや多く、パターン回収不良がやや悪かった。３５００枚の連続プリント終了後の像担持体の帯電性の低下もやや大きいが、実用上は許容できる範囲内であった。
【０５７２】
＜実施例Ｎ−７３〜８４＞
表１７に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表２１に示す。初期からやや画像濃度が低く、パターン回収不良の発生も見られたが、実用上は許容できる範囲内であった。
【０５７３】
＜比較例Ｎ−０＞
導電性微粉末の外添されていない現像剤製造例Ｒｐ−０・現像剤担持体Ｄｐ−ｎ−１の組合せで評価を行ったところ、像担持体の帯電性の低下が大きく、カブリが悪化した。
【０５７４】
＜比較例Ｎ−１〜９、２２＞
比較例Ｌ−１〜９、２２のＡｌブラスト現像剤担持体を用い、現像剤は表１６と１７の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表１８〜２２に示す。画像濃度が低かった。
【０５７５】
＜比較例Ｎ−１０〜２１＞
表１７に示すような現像剤及び現像剤担持体の組合せにて、実施例Ｌ−１と同様に評価を行った。結果を表２２に示す。トナー粒子表面の導電性微粉末が欠落しやすくなり、そのため像担持体の帯電性低下が大きく、カブリ及び画像汚れも目立った。
【０５７６】
【表１６】

【０５７７】
【表１７】

【０５７８】
【表１８】

【０５７９】
【表１９】

【０５８０】
【表２０】

【０５８１】
【表２１】

【０５８２】
【表２２】

【０５８３】
【発明の効果】
以上説明したように、本発明によれば、転写残トナー粒子の回収性に優れた現像兼クリーニング画像形成方法を達成することが可能となり、特に、従来は困難であった非接触型現像法を適用した場合にも画像品位に優れた現像兼クリーニング画像形成方法を可能とする現像剤が得られた。
【０５８４】
また、接触帯電方式、転写方式、トナーリサイクルプロセスの画像形成装置において、潜像形成への阻害が抑制され、転写残トナー粒子の回収性に優れ、パターンゴーストが十分に抑制された現像兼クリーニング画像形成装置が可能となった。
【０５８５】
また、接触帯電部材への導電性微粉末の供給性を制御し、転写残トナー粒子の付着・混入による帯電阻害に打ち勝って像担持体の帯電を良好に行わせることができる現像剤が得られた。さらに、良好な現像兼クリーニング性を示し、廃トナー量を大幅に減らすことができ、低コストで小型化の点でも優位なプロセスカートリッジを得ることができた。
【０５８６】
また、接触帯電部材として簡易な部材を用いることができ、接触帯電部材の転写残トナー粒子による汚染にかかわらず、低印加電圧でオゾンレスの直接注入帯電を長期に渡り安定に維持させることができ、しかも像担持体の均一な帯電性を与えることができる。従って、オゾン生成物による障害、帯電不良による障害等のない、簡易な構成、低コストなプロセスカートリッジを得ることができる。
【０５８７】
更に、導電性微粉末を帯電部材と像担持体との接触部に介在させることによる長期に渡って繰り返し使用された場合での、像担持体上の傷を大幅に減少でき、画像上の画像欠陥を抑制することができる。
【０５８８】
本発明によれば、従来用いられていた現像剤担持体よりも均一且つ迅速なトナーへの帯電付与能が向上するとともに、更に耐久性が向上するため、良好な画像を長い間提供することができる状態を保持することが可能となる。
【０５８９】
従って、本発明によれば、繰り返し複写又は耐久による現像剤担持体表面の被覆層の磨耗及びトナー汚染のごとき劣化が生じない高耐久且つ帯電付与能の良好な現像剤担持体によって、異なる環境下においても画像濃度低下やスリーブゴースト、カブリの悪化が発生せず、文字ラインのシャープ性が良好で、画像濃度が高い高品位な画像を長期に渡り提供することができる。
【０５９０】
また本発明によれば、異なる環境条件下においても長期に渡ってトナーに対する負帯電付与性を安定化させ、更にトナーコートを均一化させ、繰り返し複写又は耐久による現像剤担持体表面の導電性被覆層の摩耗及びトナーによるスリーブ汚染及びスリーブ融着等が生じない高耐久な現像剤担持体によって、画像濃度低下やゴーストの発生、カブリの悪化のない高品位な画像を長期に渡り提供することができる。
【図面の簡単な説明】
【図１】本発明の実施例における画像形成装置の概略を示す構成図である。
【図２】各帯電部材の帯電特性を示すグラフである。
【図３】空間周波数による人の視覚特性を示すグラフである。
【図４】本発明において用いた現像剤の帯電量測定装置の概略を示す模式図である。
【図５】本発明の像担持体としての感光体の層構成を示す模型図である。
【図６】本発明の実施例において用いたトナー粒子球形化装置の概略を示す構成図である。
【図７】本発明の実施例において用いたトナー粒子球形化装置の処理部の模式図である。
【図８】樹脂被覆層の帯電極性を測定するための表面帯電量測定装置の説明図である。[0001]
BACKGROUND OF THE INVENTION
  The present invention is used for an electrophotographic apparatus, an electrostatic recording apparatus, a magnetic recording apparatus, and the like.PaintingImage formationTo the lawRelated.
[0002]
[Prior art]
The present invention also relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a plotter that forms an image by previously forming a toner image on an image carrier and then transferring the toner image onto a recording medium such as a transfer material. The present invention relates to a process cartridge that can be attached to and detached from the image forming apparatus.
[0003]
In recent years, in electrophotographic image forming methods, many contact charging devices have been proposed as charging devices for charged objects such as latent image carriers because they have advantages such as low ozone and low power compared to corona chargers. Has been put to practical use.
[0004]
The contact charging device contacts a charged object such as an image carrier with a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Then, a predetermined voltage bias is applied to the contact charging member to charge the charged body surface to a predetermined polarity and potential.
[0005]
The charging roller is manufactured using a conductive or medium-resistance rubber material or foam, and some of these rubber materials and foam are laminated to obtain desired characteristics.
[0006]
The charging roller has elasticity in order to obtain a certain contact state with the member to be charged, but has a large frictional resistance, and is often driven by the member to be charged or with a slight speed difference. Therefore, even if direct injection charging is attempted, a decrease in absolute charging ability, lack of contactability, contact unevenness due to the roller shape, and charging unevenness due to deposits on the object to be charged cannot be avoided.
[0007]
FIG. 2 is a graph showing an example of the charging efficiency of contact charging in electrophotography. The horizontal axis represents the bias applied to the contact charging member, and the vertical axis represents the charging potential of the member to be charged (hereinafter referred to as the photosensitive member) obtained at that time.
[0008]
The charging characteristic in the case of roller charging is represented by A. That is, the surface potential of the photoconductor starts to rise after the applied voltage exceeds the discharge threshold of about −500 V, and thereafter, the photoconductor surface potential increases linearly with a slope of approximately 1 with respect to the applied voltage. This threshold voltage is set to the charging start voltage V_thIt is defined as Therefore, when charging to -500 V, apply a DC voltage of -1000 V, or in addition to the charging voltage of -500 V DC, for example, an AC with a peak-to-peak voltage of 1200 V so as to always have a potential difference greater than the discharge threshold. A method of applying a voltage to converge the photoreceptor potential to a charged potential is common.
[0009]
In other words, the photoreceptor surface potential V required for electrophotography._dTo get the V_d+ V_thIt is necessary to apply a DC voltage exceeding that required to the charging roller. A method of charging by applying only the DC voltage to the contact charging member in this way is referred to as a “DC charging method”.
[0010]
However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations, etc., and if the film thickness changes as the photoconductor is scraped, V_thSince it fluctuates, it is difficult to set the potential of the photoreceptor to a desired value.
[0011]
In addition, when AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging sound) between the contact charging member and the photosensitive member due to the electric field of the AC voltage, and photosensitive member due to discharge The deterioration of the surface and the like became prominent and became a new problem.
[0012]
Fur brush charging uses a member (fur brush charger) having a conductive fiber brush portion as a contact charging member, and the conductive fiber brush portion is brought into contact with a photosensitive member as a member to be charged to thereby form conductive fibers. A predetermined charging bias is applied to the brush portion to charge the surface of the photosensitive member to a predetermined polarity and potential.
[0013]
Fur brush chargers are available in fixed and roll types. A fixed type is a medium-resistance fiber folded into a base fabric and bonded to an electrode. The roll type is formed by winding a pile around a metal core. The fiber density is 100 / mm²However, the contactability is still insufficient for sufficiently uniform charging by direct injection charging. In order to perform sufficiently uniform charging by direct injection charging, it is necessary for the fur brush charger to have a speed difference that is difficult as a mechanical configuration with respect to the photoreceptor, which is not practical.
[0014]
Charging characteristics of the fur brush charged when a DC voltage is applied are shown in FIG. Therefore, even in the case of fur brush charging, both the fixed type and the roll type are charged using a discharge phenomenon by applying a high charging bias.
[0015]
On the other hand, the magnetic brush charging uses a member (magnetic brush charger) having a magnetic brush portion formed in a brush shape by magnetically restraining conductive magnetic particles with a magnet roll or the like as a contact charging member. Is contacted with a photosensitive member as a member to be charged, and a predetermined charging bias is applied to charge the surface of the photosensitive member to a predetermined polarity and potential. In the case of this magnetic brush charging, the direct injection charging mechanism is dominant as the charging mechanism.
[0016]
By using conductive magnetic particles constituting the magnetic brush portion having a particle diameter of 5 to 50 μm and providing a sufficient speed difference from the photoreceptor, direct injection charging that is nearly uniform is possible.
[0017]
Charging characteristics at the time of direct current application of magnetic brush charging are represented by C in FIG. As shown in FIG. 2, it is possible to obtain a charging potential substantially proportional to the applied bias.
[0018]
However, the magnetic brush charging has other disadvantages such as a complicated device configuration and conductive magnetic particles constituting the magnetic brush portion dropping off and adhering to the photoreceptor. Thus, there is a demand for a simple and stable uniform charging device that uses a direct injection charging mechanism that substantially does not generate discharge products such as ozone and that can achieve uniform charging with a low applied voltage.
[0019]
On the other hand, an image forming method that does not generate waste toner is desired in terms of saving resources, reducing waste, and effectively using toner. For example, the latent image is developed with toner to form a visible image, and after the toner image is transferred to a recording medium such as paper, the toner remaining on the latent image carrier without being transferred to the recording medium is cleaned by various methods. So-called toner reuse, in which this toner is circulated in the developing device and reused, has been put into practical use. However, there is a problem that the latent image carrier is worn and shortened due to the cleaning member being pressed against the surface of the latent image carrier. Further, from the standpoint of the apparatus, the image forming apparatus is inevitably increased in size to include such a toner reuse device and a cleaning device, and this has become a bottleneck when aiming for a compact device.
[0020]
On the other hand, as a system without waste toner, a technique called development / cleaning or cleanerless has been proposed. Conventional techniques relating to development and cleaning or cleanerless are mainly focused on positive memory, negative memory, etc. due to the influence of transfer residual toner on the image, as disclosed in Japanese Patent Laid-Open No. 5-2287. It was. However, with the progress of the use of electrophotography, there is a need to transfer toner images to various recording media. In this sense, it has not been satisfactory for various recording media.
[0021]
There are JP-A-2-302277, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, and the like that disclose technologies related to cleanerless. A desirable image forming method was not described, and a toner configuration was not mentioned.
[0022]
As a developing method that essentially has no cleaning device and is preferably applied to development / cleaning or cleanerless, a structure in which the surface of the latent image carrier is rubbed with toner and a toner carrier has been essential. Many contact development methods in which the developer contacts the latent image carrier have been studied. This is because a configuration in which the toner or the developer contacts and rubs the latent image carrier in order to collect the transfer residual toner particles in the developing unit is considered to be advantageous. However, the development / cleaning or cleanerless process using the contact development method causes toner deterioration, toner carrier surface deterioration, photoconductor surface deterioration or wear, etc., due to long-term use, and is a sufficient solution to durability characteristics. Not done. Therefore, a development and cleaning method using a non-contact development method has been desired.
[0023]
In this developing and cleaning method and cleanerless image forming method, the charge polarity and charge amount of the transfer residual toner particles on the photosensitive member are controlled, and the transfer residual toner particles are stably recovered in the development process. The point is not to make it worse. For this reason, the charging polarity and the charge amount of the transfer residual toner particles are controlled by the charging member. This will be specifically described using a general laser printer as an example.
[0024]
In the case of reversal development using a charging member to which a negative polarity voltage is applied, a negatively charged photosensitive member, and a negatively charged toner, an image visualized by the transfer member to which a positive polarity voltage is applied in the transfer process However, depending on the relationship between the type of recording medium (thickness, resistance, dielectric constant, etc.) and the image area, the charge polarity of the residual toner will fluctuate and have a positive charge. To those with negative charges. However, even if the transfer residual toner is shifted to a positive polarity in the transfer process, when the photosensitive member is charged by the negative polarity charging member, the charging polarity of the residual transfer toner is uniformly negative with the surface of the photosensitive member. Can be aligned. Therefore, when reversal development is used as the developing method, the toner of the transfer portion that is negatively charged remains in the bright portion potential portion where the toner is to be developed, while the toner is present in the dark portion potential where the toner is not to be developed. The toner to be attracted to the toner carrier due to the development electric field is collected without remaining transfer toner particles on the photosensitive member having the dark portion potential. That is, by controlling the charging polarity of the toner remaining on the transfer simultaneously with the charging of the photosensitive member by the charging member, the developing / cleaning and cleanerless image forming method is established.
[0025]
However, if the transfer residual toner particles exceed the toner charge polarity control capability of the contact charging member and adhere to or mix with the contact charging member, the transfer polarity of the transfer residual toner particles cannot be uniformly uniform. It becomes difficult to collect the toner. Further, even if the transfer residual toner particles are collected on the toner carrier by a mechanical force such as rubbing, if the transfer residual toner particles are not uniformly charged, the triboelectric chargeability of the toner on the toner carrier Adversely affect the development characteristics. That is, in the development / cleaning and cleanerless image forming method, the charge control characteristics of the transfer residual toner particles when passing through the charging member and the adhesion / mixing characteristics to the charging member are closely related to the durability characteristics and the image quality characteristics. .
[0026]
In the development and cleaning image forming method, Japanese Patent Application Laid-Open No. 11-15206 discloses a technique for improving the development and cleaning performance by improving the charge control characteristics when the transfer residual toner particles pass through the charging member. An image forming method using a toner having toner particles containing a specific azo-based iron compound and inorganic fine powder has been proposed. Further, in the development and cleaning image forming method, it has also been proposed to improve the development and cleaning performance by reducing the amount of residual toner particles with a toner having excellent transfer efficiency that defines the shape factor of the toner. However, the contact charging used here is also due to the discharge charging mechanism, not the direct injection charging mechanism, and thus has the above-mentioned problems due to discharge charging. Furthermore, even though these proposals have the effect of suppressing the chargeability deterioration due to the transfer residual toner particles of the contact charging member, the effect of positively increasing the chargeability cannot be expected.
[0027]
Furthermore, some commercially available electrophotographic printers use a roller member that contacts the photoreceptor during the transfer process and the charging process, and assists or controls the recovery of the residual toner particles in the development process. There is also a device. Such an image forming apparatus exhibits good developing and cleaning properties and can greatly reduce the amount of waste toner, but the cost is increased and the advantages of developing and cleaning are impaired in terms of miniaturization.
[0028]
Japanese Patent Publication No. 7-99442 also discloses a configuration in which powder is applied to a contact surface of a contact charging member with a surface to be charged in order to prevent uneven charging and perform stable uniform charging. However, the contact charging member (charging roller) is configured to be driven and rotated (without speed difference driving) by the body to be charged (photosensitive body), and the generation of ozone products is remarkably reduced as compared with a corona charger such as Scorotron. However, as in the case of the roller charging described above, the charging principle still mainly uses the discharge charging mechanism. In particular, in order to obtain more stable charging uniformity, a voltage obtained by superimposing an AC voltage on a DC voltage is applied, and therefore, more ozone products are generated due to discharge. Therefore, when the apparatus is used for a long time, adverse effects such as image flow due to ozone products tend to appear. Further, when the above configuration is applied to a cleanerless image forming apparatus, it becomes difficult for the applied powder to uniformly adhere to the charging member due to mixing of transfer residual toner particles, and the effect of uniform charging is obtained. It will fade.
[0029]
Japanese Patent Laid-Open No. 5-150539 discloses that in an image forming method using contact charging, toner particles and silica fine particles that could not be blade-cleaned after repeated image formation for a long time adhere to and accumulate on the surface of the charging means. In order to prevent charging inhibition due to the above, it is disclosed that the developer contains at least visible particles and conductive particles having an average particle size smaller than the visible particles. However, the contact charging or proximity charging used here is based on the discharge charging mechanism and not the direct injection charging mechanism, and thus has the above-described problems due to discharge charging. Further, when this configuration is applied to a cleanerless image forming apparatus, compared to the case where the cleaning mechanism is provided, a large amount of conductive fine particles and transfer residual toner particles are prevented from being charged. No consideration is given to the influence, the recoverability of the large amount of conductive fine particles and transfer residual toner particles in the development process, and the influence of the collected conductive fine particles and transfer residual toner particles on the development characteristics of the developer. Further, when the direct injection charging mechanism is applied to the contact charging, a necessary amount of the conductive fine particles is not supplied to the contact charging member, resulting in a charging failure due to the influence of the residual toner particles.
[0030]
Further, in proximity charging, it is difficult to uniformly charge the photosensitive member with a large amount of conductive fine particles and transfer residual toner particles, and an effect of leveling the pattern of transfer residual toner particles cannot be obtained. A pattern ghost is generated by shielding the pattern image exposure. Further, when the power supply is interrupted or a paper jam occurs during image formation, the contamination in the apparatus by the developer becomes significant.
[0031]
On the other hand, in Japanese Patent Application Laid-Open No. 10-307456, a developer containing a toner particle and a conductive charge-accelerating particle having a particle size equal to or smaller than ½ of the toner particle size is developed using a direct injection charging mechanism. An image forming apparatus applied to a cleaning image forming method is disclosed. According to this proposal, it is possible to obtain a developing and cleaning image forming apparatus which can greatly reduce the amount of waste toner without generating a discharge product and is advantageous for downsizing at low cost. Alternatively, a good image that does not cause diffusion can be obtained. However, further improvements are desired.
[0032]
Japanese Patent Laid-Open No. 10-307421 discloses a developing and cleaning image forming method using a direct injection charging mechanism with a developer containing conductive particles having a particle size of 1/50 to 1/2 of the toner particle size. An image forming apparatus is disclosed in which the conductive particles are applied to have a transfer promoting effect.
[0033]
Furthermore, in Japanese Patent Application Laid-Open No. 10-307455, the particle size of the conductive fine powder is set so that the particle size of the conductive fine powder is equal to or smaller than the size of one constituent pixel, and in order to obtain better charging uniformity. It is described that the thickness is 10 nm to 50 μm.
[0034]
In Japanese Patent Application Laid-Open No. 10-307457, in order to make it difficult to visually recognize the influence of a poorly charged portion on an image in consideration of human visual characteristics, the conductive particles are about 5 μm or less, preferably 20 nm to 5 μm. It is described that.
[0035]
Further, according to Japanese Patent Laid-Open No. 10-307458, by setting the particle size of the conductive fine powder to be equal to or less than the toner particle size, the development of the toner is inhibited during development, and the development bias is passed through the conductive fine powder. It is described that leakage can be prevented and image defects can be eliminated. At the same time, by setting the particle size of the conductive fine powder to be larger than 0.1 μm, the conductive fine powder is embedded in the image bearing member, which directly solves the adverse effect of shielding the exposure light and realizes excellent image recording. A developing and cleaning image forming method using an injection charging mechanism is described. However, further improvements are desired.
[0036]
According to Japanese Patent Laid-Open No. 10-307456, a conductive fine powder is externally added to the toner, and the conductive fine powder contained in the toner is at least at the contact portion between the flexible contact charging member and the image carrier. Development that adheres to the image carrier in the development process, remains on the image carrier after the transfer process, and is carried and intervened so that a good image can be obtained without causing poor charging and shading of image exposure. A cum-cleaning image forming apparatus is disclosed. However, these proposals also have room for further improvement in performance when toner particles having a smaller particle diameter are used in order to enhance stable performance and resolution in repeated use over a long period of time.
[0037]
In addition, proposals have been made to externally add conductive particles having an average particle size. For example, in Japanese Patent Application Laid-Open No. 9-146293, fine powder A having an average particle diameter of 5 to 50 nm and fine powder B having an average particle diameter of 0.1 to 3 μm are used as external additives, and the toner base particles are 4 to 12 μm. A toner that has adhered more strongly than the above has been proposed, but the object is to reduce the proportion of the fine powder B that is free and the toner that is detached from the toner base particles. Japanese Patent Application Laid-Open No. 11-95479 proposes a toner containing conductive silica particles having a prescribed particle size and a hydrophobic inorganic oxide. It is only intended for the leaking action to the outside by the conductive silica particles.
[0038]
Further, Japanese Patent Application Laid-Open No. 11-194530 proposes a toner having external additive fine particles A and inorganic fine powders B of 0.6 to 4 μm and having a prescribed particle size distribution. The purpose is to prevent toner deterioration by embedding the inorganic fine powder B in the toner base particles due to the presence of A, and no consideration is given to the adhesion / release of the external additive fine particles A to the toner base particles. Japanese Laid-Open Patent Publication No. 10-83096 proposes a toner in which conductive fine particles and silica fine particles are added to the surface of spherical resin fine particles encapsulating a colorant. The purpose of this is to speed up the movement and exchange of charges between toner particles, and to improve the uniformity of toner tribocharging.
[0039]
As described above, the developer for use in the image forming method having the injection charging step, the image forming method having the developing and cleaning step, or the cleanerless image forming method has not been sufficiently studied for the external additive. In addition, there is no proposal of a developer including an external additive that has been sufficiently studied to be applied to an image forming method having an injection charging process, a developing and cleaning image forming method, or a cleanerless image forming method. .
[0040]
Incidentally, image forming apparatuses are increasingly required to be faster and less expensive. For example, with laser printers using the popular electrophotographic method, the printing speed of the introductory model for individuals called the low end was 6 to 8 sheets per minute, but it was as fast as 10 to 15 sheets per minute. The price has been reduced. When the printing speed is converted to the moving speed (process speed) of the image carrier, the speed is increased from about 50 mm / sec to near 100 mm / sec, and it is considered that the speed will be further increased in the future.
[0041]
When the process speed is increased, generally, the recoverability of transfer residual toner particles in development and cleaning tends to be reduced. Due to the high process speed, it is difficult to sufficiently control the charge of the residual toner particles in the primary charge, and the charge of the residual toner particles discharged from the primary charge and proceeding to recovery in development is likely to be uneven. The reason is that it is difficult to suppress the influence on the triboelectric charging property of the developer due to the mixing of the transfer residual toner particles collected by the development. This tendency is particularly remarkable in the non-contact development method. This is because in the recovery of residual toner particles in the contact development method, electrostatic force works more effectively due to contact between the developer carrier and the image carrier, and physical force due to rubbing acts. It is presumed that it is easy to compensate for the decrease in the recovery of the transfer residual toner particles due to the increase in speed.
[0042]
Also, the chargeability of direct injection charging tends to decrease as the process speed increases. This is presumably because the contact probability between the image carrier and the contact charging member via the conductive fine powder is reduced, or the charging time for charging the image carrier by injecting charges is shortened. Furthermore, in order to maintain the contact probability, when the ratio of the moving speed of the charging member to the moving speed of the image carrier is maintained or increased together with the increase of the process speed, a large increase in torque becomes a cost increase factor. Problems such as scratches on the image bearing member and the charging member, and contamination inside the apparatus due to scattering of transfer residual toner particles adhering to or mixing in the charging member are likely to occur. Therefore, the moving speed of the charging member can be suppressed at a higher process speed, the pattern collection failure and image smear do not occur, and the decrease in charging property of the image carrier after repeated use can be sufficiently reduced. A developer and an image forming method are required.
[0043]
[Problems to be solved by the invention]
  The object of the present invention has been made in view of the above problems, and enables toner image formation by a good development and cleaning process.PaintingAn object is to provide an image forming method.
[0044]
  Another object of the present invention is to enable simple and stable uniform charging by a direct injection charging mechanism that substantially does not generate discharge products such as ozone and that can achieve uniform charging at a low applied voltage.PaintingAn object is to provide an image forming method.
[0045]
  Another object of the present invention is to enable a developing and cleaning process that can greatly reduce the amount of waste toner and that is advantageous for downsizing at low cost.PaintingAn object is to provide an image forming method.
[0046]
  Furthermore, an object of the present invention is to provide an image forming method having a developing and cleaning process capable of stably obtaining a good image even when toner particles having a smaller particle diameter are used in order to improve resolution.The lawIt is to provide.
[0047]
  Another object of the present invention is to prevent deterioration of the conductive coating layer on the surface of the developer carrying member due to repeated copying or durability, and provide high durability and stable image quality.PaintingAn image forming method is provided.
[0048]
  The object of the present invention is that high-quality images with high character density, high sharpness of character lines, no problems such as density reduction, sleeve ghosting and fogging do not occur for a long time even under different environmental conditions. Can get stablePaintingAn image forming method is provided.
[0049]
  The object of the present invention is to control the uneven charging of the toner on the surface of the developer carrier, which appears when a toner having a small particle diameter is used, and to carry the developer quickly and appropriately. BodyUseAn image forming method is provided.
[0050]
[Means for Solving the Problems]
The above object is achieved by the following configurations of the present invention.
[0051]
  That is, the present inventionThe image forming method includes a charging step of charging the latent image carrier, a latent image forming step of writing image information as an electrostatic latent image on the charging surface of the latent image carrier charged in the charging step, and the electrostatic A developing step of developing the latent image using a developing device including a developer carrying member that conveys the developer to a developing region facing the latent image carrying member while carrying the developer, and visualizing the developer image; And a transfer step of transferring the developer image onto a transfer material, and a fixing step of fixing the developer image transferred onto the transfer material by a fixing means, and forming each image by repeating these steps. In the image forming method, the developer includes toner particles containing at least a binder resin and a colorant and conductive fine particles, and the toner particles have a circularity a obtained by the following formula of less than 0.970. , The conductive fine particles The volume average particle diameter is 0.1 to 10 μm, and the charging step is a step of charging the latent image carrier with a charging means, and a contact portion between the charging means and the latent image carrier. In addition, the latent image carrier is charged by applying a voltage in a state where the conductive fine particles of the developer are interposed, and the developing device is a developing container for containing the developer. , A developer carrying member for carrying the developer contained in the developing container and transporting it to the developing region, and development for regulating the layer thickness of the developer carried on the developer carrying member There is at least a developer layer thickness regulating member, and there is no cleaning process between the transfer process and the charging process. In the developing process, the electrostatic latent image is visualized and the developer image After the image is transferred to the transfer material The developer remaining on the carrier is collected, and the developer carrier has at least a substrate and a resin coating layer formed on the substrate, and the resin coating layer includes at least a coating layer for the coating layer. A copolymer containing a resin and a positively chargeable substance, wherein the positively chargeable substance includes a unit derived from an imidazole compound or a nitrogen-containing vinyl monomer.It is characterized by that.
[0052]
[Expression 4]

(Where L₀Indicates the perimeter of a circle having the same projected area as the particle image, and L indicates the perimeter of the projected image of the particle. )
The resin coating layer formed on the developer-carrying substrate preferably contains at least a binder resin for the coating layer and a conductive substance.
[0053]
It is preferable that the resin coating layer formed on the base of the developer carrier has at least a binder resin for the coating layer and a lubricating substance.
[0056]
Moreover, it is preferable that an imidazole compound is a compound shown by following formula (1) or (2).
[0057]
[Formula 4]

[In the formula, R₁And R₂Represents a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group;₁And R₂May be the same or different and R₃And R₄Represents a linear alkyl group having 3 to 30 carbon atoms, and R₃And R₄May be the same or different. ]
[0058]
[Chemical formula 5]

[In the formula, R₅And R₆Represents a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group;₅And R₆May be the same, R₇Represents a linear alkyl group having 3 to 30 carbon atoms. ]
It is preferable that the resin coating layer further includes spherical particles having a number average particle size of 0.3 to 30 μm in addition to the conductive substance and the nitrogen-containing heterocyclic compound.
[0059]
The spherical particles are preferably resin particles.
[0060]
Spherical particles have a true density of 3 g / cm³The following conductive spherical particles are preferable.
[0062]
The nitrogen-containing vinyl monomer preferably has a vinyl polymerizable monomer.
[0063]
The copolymer preferably has a weight average molecular weight (Mw) of 3,000 to 50,000.
[0064]
The copolymer preferably has a ratio (Mw / Mn) of 3.5 or less of the weight average molecular weight (Mw) and the number average molecular weight (Mn).
[0065]
The nitrogen-containing vinyl monomer preferably has at least one monomer selected from the group consisting of a (meth) acrylic acid derivative having a nitrogen-containing group and a nitrogen-containing heterocyclic N-vinyl compound.
[0066]
As the nitrogen-containing vinyl monomer, the following general formula (3)
[0067]
[Chemical 6]

[In the formula, R₇, R₈, R₉And R₁₀Represents a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms, and n represents an integer of 1 to 4. ]
Is preferred.
[0068]
In the developing device, the resin coating layer formed on the substrate of the developer carrying member includes a binder resin, a vinyl polymerizable monomer, and a sulfonic acid group-containing acrylamide unit as positively charged substances. It preferably contains a copolymer with a monomer. At the same time, a part or all of the coating layer binder resin has at least —NH in its molecular structure.₂It preferably has either a group, a = NH group, or a -NH- bond.
[0069]
The copolymerization ratio (% by mass) of the vinyl polymerizable monomer and the sulfonic acid group-containing acrylamide monomer is 98: 2 to 80:20, and the weight average molecular weight (Mw) is 2,000 to 50, 000 copolymer is preferred.
[0070]
It is preferable that the copolymer is a copolymer of a vinyl polymerizable monomer and 2-acrylamido-2-methylpropanesulfonic acid.
[0071]
It is preferable that at least a phenol resin is contained in the binder resin.
[0072]
The phenol resin is a phenol resin manufactured using a nitrogen-containing compound as a catalyst, and —NH₂It preferably has either a group, a ═NH group or a —NH— bond.
[0073]
It is preferable that at least a polyamide resin is contained in the binder resin.
[0074]
It is preferable that at least a polyurethane resin is contained in the binder resin.
[0075]
In order to form irregularities on the surface of the coating layer in the resin layer, it is preferable that spherical particles are contained, and the number average particle diameter of the spherical particles is more preferably 0.3 to 30 μm.
[0076]
The particles for forming irregularities on the surface of the coating layer are spherical and the true density is 3 g / cm.³The following is preferable.
[0077]
It is preferable that the particles for forming irregularities on the surface of the coating layer are conductive spherical particles.
[0078]
Furthermore, it is preferable that the developer layer thickness regulating member of the developing device of the present invention is a magnetic blade or an elastic blade.
[0079]
The developer is preferably a magnetic developer having magnetic toner particles.
[0080]
The developer preferably has a weight average particle diameter (D4) of 4 to 10 μm.
[0081]
The developer contains 15-60% by number of particles having a particle size range of 1.00 μm or more and less than 2.00 μm in a particle size distribution based on the number of particles having a particle size of 0.60 to 159.21 μm, and 3.00 μm. It is preferable to contain 15 to 70% by number of particles having a particle size range of less than 8.96 μm.
[0082]
The developer preferably has conductive fine particles having a volume average particle diameter of 0.1 to 10 μm.
[0083]
The developer has a volume resistance of 10⁰-10⁹Ω · cm, more preferably 10¹-10⁶It is preferable to have conductive fine particles of Ω · cm.
[0084]
It is preferable that the conductive fine particles are nonmagnetic.
[0085]
It is preferable that the conductive fine particles contain at least one oxide selected from zinc oxide, tin oxide, and titanium oxide.
[0097]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0098]
<Developer>
The developer used in the present invention is preferably a one-component developer having at least toner particles and conductive fine powder.
[0099]
The developer used in the present invention has at least toner particles containing a binder resin and a colorant and conductive fine powder, and has a particle size distribution based on the number within a particle size range of 0.60 μm or more and less than 159.21 μm. 15 to 60% by number of particles having a particle size range of 1.00 μm or more and less than 2.00 μm and 15 to 70% by number of particles having a particle size range of 3.00 μm or more and less than 8.96 μm. preferable. Furthermore, it is preferable to contain an inorganic fine powder having an average primary particle size of 4 to 80 nm as an external additive.
[0100]
By using such a developer, good chargeability can be stably imparted to the developer, and a good image can be obtained without causing charging failure even in repeated use of the developer over a long period of time, and An image forming method that can greatly reduce the amount of waste toner and has a development and cleaning process that is advantageous for downsizing at low cost is possible.
[0101]
In addition, by using such a developer, charging using a direct injection charging mechanism, which is substantially free of discharge products such as ozone and obtains uniform charging with a low applied voltage, is performed well with a simple configuration. Therefore, an image forming method can be obtained in which a good image can be obtained without causing charging failure even when the developer is repeatedly used over a long period of time. Further, by using such a developer, even if a large amount of developer component adheres to or mixes with the contact charging member, it is possible to suppress a decrease in uniform chargeability, and an image due to poor charging of the image carrier. An image forming method by contact charging that can suppress defects can be realized.
[0102]
In addition, in the developing and cleaning image forming method using such a developer, a developer that stably exhibits good triboelectric charging characteristics can be obtained, and even when the developer is repeatedly used over a long period of time, the transfer residual toner particles can be recovered. Development and cleaning that is advantageous for downsizing at low cost, which can obtain a good image without causing defects or image defects due to uniform charging or inhibition of latent image formation, and can greatly reduce the amount of waste toner. An image forming method is possible.
[0103]
When the electrostatic latent image formed on the image bearing member is developed, an appropriate amount of the conductive fine powder contained in the developer is transferred from the developer bearing member to the latent image bearing member. The toner image formed on the latent image carrier by developing the electrostatic latent image is transferred to a transfer material such as paper in the transfer process. At this time, a part of the conductive fine powder on the latent image carrier also adheres to the transfer material, but the rest remains attached and held on the latent image carrier. When transfer is performed by applying a transfer bias having a polarity opposite to the charged polarity of the toner particles, the toner is attracted to the transfer material and actively transferred, but the conductive fine powder on the latent image carrier is electrically conductive. Therefore, it is difficult to transfer to the transfer material side. For this reason, a part of the conductive fine powder adheres to the transfer material, and the rest remains attached to the latent image carrier.
[0104]
In an image forming method that does not have a step of removing the conductive fine powder adhered and held on the latent image carrier from the latent image carrier as in the cleaning step, the image remains on the surface of the latent image carrier after the transfer step. The toner particles (hereinafter referred to as “transfer residual toner particles”) and the conductive fine powder are moved along with the movement of the surface carrying the image (hereinafter referred to as “image carrying surface”) in the latent image carrier. It is carried to the charging part. That is, when a contact charging member is used in the charging process, the conductive fine powder is carried to a contact portion formed by contact between the latent image carrier and the contact charging member, and adheres to and mixes with the contact charging member. Accordingly, contact charging of the latent image carrier is performed in a state where the conductive fine powder is interposed in the contact portion between the latent image carrier and the contact charging member.
[0105]
In the present invention, the contact resistance of the contact charging member can be maintained even if the contact charging member is contaminated by the adhesion / mixing of the transfer residual toner particles by positively carrying the conductive fine powder to the charging unit. Therefore, the latent image carrier can be favorably charged by the contact charging member.
[0106]
However, when a sufficient amount of conductive fine powder is not present in the charged portion of the contact charging member, the charge of the image carrier easily decreases due to adhesion / mixing of the transfer residual toner particles to the contact charging member, Causes image smearing.
[0107]
Furthermore, the conductive fine powder is actively carried to the contact portion formed by the contact between the latent image carrier and the contact charging member, thereby reducing the contact property of the contact charging member to the latent image carrier and the contact resistance. Therefore, direct injection charging of the latent image carrier by the contact charging member can be performed satisfactorily.
[0108]
In addition, the transfer residual toner particles adhering to and mixed in the contact charging member are gradually discharged from the contact charging member onto the latent image carrier and reach the developing unit along with the movement of the image carrying surface. That is, the transfer residual toner particles are collected. Similarly, the conductive fine powder adhering to and mixed in the contact charging member is gradually discharged from the contact charging member onto the image bearing member, and reaches the developing portion as the image bearing surface moves. That is, the conductive fine powder is present on the latent image carrier together with the transfer residual toner particles, and the transfer residual toner particles are collected in the development process. In the case where recovery of the transfer residual toner particles in the development process utilizes a development bias electric field, the transfer residual toner particles are recovered by the development bias electric field, whereas the conductive fine powder on the latent image carrier Is difficult to recover because it is conductive. For this reason, although a part of the conductive fine powder is recovered, the rest remains attached and held on the latent image carrier. According to the study by the present inventors, the presence of the conductive fine powder that is difficult to be recovered in the development step on the image carrier improves the recoverability of the transfer residual toner particles on the latent image carrier. It was found to have an effect. That is, the conductive fine powder on the image carrier serves as a recovery aid for the transfer residual toner particles on the latent image carrier, and the transfer residual toner particles are more reliably recovered in the development process. Image defects such as positive ghost and fog due to poor collection can be effectively prevented.
[0109]
Conventionally, most of the purpose of externally adding conductive fine powder to the developer is to control the triboelectric chargeability of the toner by attaching the conductive fine powder to the surface of the toner particles. The conductive fine powder that has been treated has been treated as a detrimental effect that causes a change or deterioration in developer characteristics. On the other hand, the developer of the present invention is different from the external addition of the conductive fine powder to the developer that has been conventionally studied in that the conductive fine powder is actively released from the surface of the toner particles. The conductive fine powder is carried over the latent image carrier after the transfer to the charging unit, which is a contact portion formed by the contact between the image carrier and the contact charging member, thereby interposing the latent image carrier. By positively improving the chargeability, it is possible to stably and uniformly charge, and to prevent image defects due to a decrease in charge of the latent image carrier. Further, since the conductive fine powder is present on the latent image carrier in the development process, the conductive fine powder acts as a recovery aid for the transfer residual toner particles on the latent image carrier, and the transfer residual toner particles in the development process. Therefore, image defects such as positive ghosts and fogging due to poor collection of transfer residual toner particles can be effectively prevented.
[0110]
In the developer of the present invention, the conductive fine powder that adheres to the surface of the toner particles and behaves together with the toner particles promotes the chargeability of the latent image carrier and the development and cleaning performance that the developer of the present invention is effective. The amount of residual toner particles increases due to a decrease in the developability of toner particles, a decrease in transfer residual toner particle recoverability in the development and cleaning process, and a decrease in transferability. There is a case where a negative effect such as obstructing uniform charging is caused.
[0111]
The conductive fine powder contained in the developer of the present invention is transferred to the image carrying surface through the charging process and the developing process by repeating the image formation, and again through the transfer process along with the movement of the image carrying surface. By being carried to the charging unit, the conductive fine powder continues to be sequentially supplied to the charging unit. Therefore, the conductive fine powder continues to be supplied to the charging unit even if the conductive fine powder is reduced by dropping off in the charging unit or the uniform charge promoting ability of the conductive fine powder is deteriorated. Even in the repeated use over a long period of time, the chargeability of the image carrier is prevented from being lowered, and good uniform charging is stably maintained.
[0112]
According to the inventors' investigation on the effect of the particle size of the conductive fine powder added to the developer on the effect of promoting the chargeability of the latent image carrier and the development and cleaning properties, the particle size of the conductive fine powder is Is very small (for example, about 0.1 μm or less) and easily adheres firmly to the surface of the toner particles, and sufficiently supplies the conductive fine powder to the non-image area on the latent image carrier in the development process. In the transfer step, the conductive fine powder is not released from the surface of the toner particles. For this reason, the conductive fine powder cannot be positively left on the latent image carrier after the transfer, and the conductive fine powder cannot be positively supplied to the charging portion. Accordingly, the effect of improving the chargeability of the latent image carrier cannot be obtained, and when the transfer residual toner particles adhere to and mix with the contact charging member, an image defect occurs due to the decrease in the chargeability of the latent image carrier.
[0113]
Also, in the developing and cleaning process, the conductive fine powder cannot be supplied onto the latent image carrier, and the particle diameter of the conductive fine powder is too small even if supplied onto the latent image carrier. Therefore, the effect of improving the recoverability of the transfer residual toner particles cannot be obtained, and image defects such as positive ghost and fog due to poor transfer residual toner particle recovery cannot be effectively prevented.
[0114]
Further, among conductive fine powders, those having a particle size that is too large (for example, about 4 μm or more) have a large particle size even when supplied to the charging unit, so that the conductive fine powder easily falls off the charging member. Thus, it becomes difficult to keep the conductive fine powder having a sufficient number of particles stably in the charging portion, and it is impossible to promote the charging property of the uniform latent image carrier. Further, since the number of particles of the conductive fine powder per unit weight is reduced, the conductive fine powder having the number of particles sufficient to obtain a uniform charging promoting effect of the latent image carrier is interposed in the charging portion (charging portion). By increasing the number of contact points between the latent image carrier and the conductive fine powder, the effect of promoting the uniform chargeability of the latent image carrier is enhanced. Therefore, the number of particles of the conductive fine powder intervening in the charging portion is reduced. However, the amount of conductive fine powder added to the developer must be increased. However, if the amount of conductive fine powder added is too large, the triboelectric charging ability and developability of the developer as a whole are lowered, resulting in a decrease in image density and toner scattering. Further, since the conductive fine powder has a large particle size, the effect as a recovery aid for the residual toner particles in the development process cannot be sufficiently obtained. If the amount of the conductive fine powder on the image carrier is increased too much in order to enhance the recovery of the transfer residual toner particles, the particle size is too large to block adverse effects on the latent image forming process, for example, image exposure. May cause image defects.
[0115]
The present inventors proceeded from the study of the particle size of the conductive fine powder to the study of the particle size distribution of the developer containing external additives, which is directly related to the actual developer behavior. Invented.
[0116]
That is, the developer has at least toner particles containing at least a binder resin and a colorant, inorganic fine powder having a primary particle number average particle size of 4 to 80 nm, and conductive fine powder. In the particle size distribution on the basis of the particle size range of 60 μm or more and less than 159.21 μm, 15 to 60% by number of particles having a particle size range of 1.00 μm or more and less than 2.00 μm are contained, and 3.00 μm or more and less than 8.96 μm In the structure containing 15 to 70% by number of particles having a particle size range of 1, it is possible to effectively prevent charging failure of the latent image carrier due to contact charging, and the latent image carrier in the direct injection charging mechanism can be effectively prevented. Uniform charging property can be improved. Further, it is possible to enhance the recovery of transfer residual toner particles during development and cleaning, and to effectively prevent image defects such as positive ghosts and fogging due to poor recovery of transfer residual toner particles.
[0117]
More specifically, the inorganic fine powder having a primary particle number average particle size of 4 to 80 nm of the developer of the present invention adheres to the surface of the toner particle and behaves together with the toner particle, thereby causing the developer to flow. To improve the properties and make the triboelectric charging characteristics of the toner particles uniform. For this reason, the transferability of toner particles is improved, the amount of transfer residual toner particles mixed into the contact charging member is reduced, the chargeability of the latent image carrier is prevented from being lowered, and the transfer residual toner particles are recovered in the development process. Can be reduced.
[0118]
This inorganic fine powder adheres to the toner particle surface and behaves together with the toner particles, and the number average particle size of the primary particles is as small as 4 to 80 nm, and the particle size in the state of adhering to the toner is also the primary particle size. To agglomerates are not more than 0.1 μm and do not substantially affect the number-based particle size distribution of the developer in the particle size range of 0.60 μm or more and less than 159.21 μm.
[0119]
On the other hand, the conductive fine powder possessed by the developer of the present invention has a particle size distribution of 1.00 μm or more and 2. in the particle size distribution of the particle size range of the developer ranging from 0.60 μm to less than 159.21 μm. This contributes to containing 15 to 60% by number of particles less than 00 μm. More specifically, the conductive fine powder of the developer of the present invention has particles having a particle size range of at least 1.00 μm and less than 2.00 μm, and a particle size of 1.00 μm and less than 2.00 μm. The effect of the present invention can be obtained by incorporating the conductive fine powder in the developer so that the content of the particles in the range is in the above range. According to the study by the present inventors, the presence of conductive fine powder having a particle size in the range of 1.00 μm or more and less than 2.00 μm in the developer causes the transfer residual toner particles on the contact charging member in contact charging. Prevention of charging failure of image carrier due to adhesion / mixing, improvement of uniform chargeability of latent image carrier in direct injection charging, recovery of charging failure and transfer residual toner particles in image forming method using development and cleaning It has been found that the effect of effectively preventing defects is great. Further, the particle size of the conductive fine powder greatly contributes to the effect as the transfer residual toner particle recovery aid in the development process of the conductive fine powder. There is a particle size range of the powder, and the content (number%) of the conductive fine powder having a particle size range of 1.00 μm or more and less than 2.00 μm is effective as a recovery aid for the residual toner particles. It turned out to be deeply involved.
[0120]
Conductive fine powder particles having a particle size in the range of 1.00 μm or more and less than 2.00 μm are unlikely to adhere firmly to the surface of the toner particles, and are sufficiently supplied to the non-image area on the image carrier in the development process. In the process, the toner particles are positively released from the surface of the toner particles, and are efficiently supplied to the charging unit through the latent image carrying surface after transfer. In addition, the conductive fine powder can be uniformly dispersed and interposed in the charging part, so that the latent image carrier has a high charge promoting effect and is stably held in the charging part. In this case, the charging property of the latent image carrier is prevented from being lowered, and good uniform charging is stably maintained. Further, even when the charging member is inevitably contaminated by residual toner particles as in the developing and cleaning image forming method using the contact charging member in the charging process, the charging property of the latent image carrier is prevented from being lowered. Can do. Further, the conductive fine powder particles are efficiently supplied to the latent image carrying surface after the transfer, and exhibit a particularly excellent effect as a recovery aid for the residual toner particles. The recoverability of particles can be improved.
[0121]
As described above, the developer of the present invention has a content of particles in the particle size range of 1.00 μm or more and less than 2.00 μm in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm. ˜60% by number. By setting the content of particles in the particle size range of 1.00 μm or more and less than 2.00 μm in the particle size measurement range to the above range, it is possible to improve the uniform chargeability of the image carrier in the charging step. In addition, since a moderate amount of conductive fine powder can be stably present in the charged portion, exposure failure due to excessive presence of the conductive fine powder on the image carrier in the subsequent exposure process is prevented. can do. When the content of particles in the particle size range of 1.00 μm or more and less than 2.00 μm in the developer is too small than the above range, the uniform chargeability of the image carrier by contact charging can be sufficiently improved. The effect of effectively preventing the collection failure of the transfer residual toner particles in the development and cleaning is not sufficient. In addition, when the content of particles having a particle size range of 1.00 μm or more and less than 2.00 μm in the developer is excessively larger than the above range, an excessive amount of conductive fine powder is supplied to the charging unit. The conductive fine powder that cannot be held in the part is discharged onto the image carrier to the extent that the exposure light is blocked, and image defects due to poor exposure, or scattering and contamination of the inside of the machine are remarkably likely to occur. .
[0122]
The content of particles having a particle size of 1.00 to less than 2.00 μm in the number-based particle size distribution in the particle size range of 0.60 μm to less than 159.21 μm is 20 to 50% by number. More preferred is 20 to 45% by number. By setting the content of the particles in this range, the uniform chargeability of the latent image carrier by contact charging is further improved, and the collection failure of transfer residual toner particles in the image forming method using development and cleaning is effective. The effect of preventing is further increased. Furthermore, image defects due to poor exposure due to excessive discharge of conductive fine powder that cannot be held in the charged portion and discharged onto the latent image carrier in a large amount are prevented from being supplied to the charged portion. Can be more reliably suppressed.
[0123]
As described above, the developer of the present invention has 15 to 60 particles having a particle size range of 1.00 μm or more and less than 2.00 μm in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm. In order to make it contained in the developer, the conductive fine powder may be contained in the developer so that the content of the particles having a particle size range of 1.00 μm or more and less than 2.00 μm is in the above range. . However, in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm of the developer, particles having a particle size range of 1.00 μm or more and less than 2.00 μm are limited to the above conductive fine powder only. Instead, toner particles and other particles added to the developer may be included.
[0124]
The toner particles containing at least the binder resin and the colorant contained in the developer of the present invention can be obtained by a known production method, and the toner production method and production conditions (for example, the average particle diameter of the toner and the pulverization method). The amount of toner particles having a particle size range of 1.00 μm or more and less than 2.00 μm generated by the pulverization conditions in the case of (1) is changed. However, in the number-based particle size distribution of the developer in the particle size range of 0.60 μm or more and less than 159.21 μm, the number of particles having a particle size range of 1.00 μm or more and less than 2.00 μm attributable to the toner particles is 10 %, The tribodistribution of toner particles having a particle size range of 1.00 μm or more and less than 2.00 μm is significantly different from the triboelectric charge properties of toner particles having a particle size near the average particle size. It tends to be broad and developability tends to decrease.
[0125]
That is, in the number-based particle size distribution in the particle size range of 0.60 μm or more and less than 159.21 μm of the developer, 5 to 60% by number of particles of 1.00 μm or more and less than 2.00 μm resulting from the conductive fine powder are contained. It is preferable.
[0126]
The developer of the present invention contains 15 to 70% by number of particles having a particle size range of 3.00 μm or more and less than 8.96 μm in a number-based particle size distribution of a particle size range of 0.60 μm or more and less than 159.21 μm. It is characterized by doing.
[0127]
In the developer of the present invention, particles having a particle size range of 3.00 μm or more and less than 8.96 μm develop the electrostatic latent image formed on the latent image carrier to form a toner image. In order to form a toner image on the transfer material by transferring to the transfer material, a predetermined amount is required. Further, particles having a particle size range of 3.00 μm or more and less than 8.96 μm are electrostatically attached to the electrostatic latent image formed on the latent image carrier, and the electrostatic latent image is faithfully used as a toner image. Tribological charging characteristics suitable for development can be provided.
[0128]
It is difficult for particles having a particle size of less than 3.00 μm to have stable triboelectric charging characteristics such as maintaining excessive charge or excessively triboelectric charge attenuation. Therefore, the amount of adhesion to a portion where there is no electrostatic latent image on the latent image carrier (a white background portion of the image) tends to increase, and it is difficult to faithfully develop the electrostatic latent image as a toner image. In addition, particles having a particle size of less than 3.00 μm are difficult to maintain good transferability with respect to a transfer material having irregularities on the surface (for example, paper having irregularities due to fibers on the surface). Transfer residual toner particles increase. For this reason, the transfer residual toner particles are used in the charging process in a state where a large amount of the transfer residual toner particles adhere to the latent image carrier, and furthermore, a large amount of the transfer residual toner particles adhere to and mix with the contact charging member. And the contact charging member has a close contact with the latent image carrier through the conductive fine powder, so that the effect of the present invention for improving the chargeability of the latent image carrier tends to be inhibited. Further, when the particle size of the residual toner particles becomes smaller, the mechanical, electrostatic, and magnetic recovery force that acts on the residual toner particles in the development process becomes smaller, and in the case of magnetic toner, the magnetic recovery force becomes smaller. The adhesion between the residual toner particles and the latent image carrier increases, the transferability of the transfer residual toner particles in the development process decreases, and image defects such as positive ghosts and fogging due to poor recovery of the transfer residual toner particles are likely to occur. Tend to.
[0129]
Further, it is difficult for particles having a particle diameter of 8.96 μm or more to have a sufficiently high triboelectric charging characteristic for developing an electrostatic latent image as a toner image faithfully. Generally, the larger the developer particle size, the lower the resolution of the obtained toner image. However, the content of particles in the particle size range of 1.00 μm or more and less than 2.00 μm is within a predetermined range. In the developer of the present invention containing the conductive fine powder so as to be, since the developer contains many particles of the conductive fine powder, the triboelectric charge amount of toner particles having a large particle diameter is further reduced. It becomes difficult to give particles having a particle size of 8.96 μm or more with a sufficiently high triboelectric charge characteristic to faithfully develop an electrostatic latent image as a toner image. It becomes more difficult to obtain a toner image.
[0130]
Therefore, in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm, by setting the content of particles in the particle size range of 3.00 μm or more and less than 8.96 μm to the above range, electrostatic latent A toner particle having a triboelectric charge characteristic suitable for developing an image faithfully as a toner image is ensured, and the content of particles having a particle size range of 1.00 μm or more and less than 2.00 μm in the developer is within a predetermined range. By using the developer of the present invention containing conductive fine powder so as to obtain an image, it is possible to obtain an image with high image density and excellent resolution.
[0131]
In the present invention, when the content of particles in the particle size range of 3.00 μm or more and less than 8.96 μm in the developer is too small than the above range, the electrostatic latent image can be faithfully developed as a toner image. It becomes difficult to secure toner particles having suitable frictional charging characteristics. For this reason, the obtained image has a lot of fog, the image density is low, or the resolution is low.
[0132]
Further, when the content of particles in the particle size range of 3.00 μm or more and less than 8.96 μm in the developer is excessively larger than the above range, the particle size range of 1.00 μm or more and less than 2.00 μm described above It becomes difficult to keep the content in the developer within the range specified in the present invention. Further, even if the content in the developer of particles having a particle size range of 1.00 μm or more and less than 2.00 μm is within the range defined in the present invention, the particle size range of 3.00 μm or more and less than 8.96 μm There is a relative shortage of particles having a particle size range of 1.00 μm or more and less than 2.00 μm with respect to the content of the particles. For this reason, the uniform chargeability of the image carrier due to contact charging cannot be sufficiently improved, and the effect of effectively preventing the collection failure of transfer residual toner particles during development and cleaning cannot be sufficiently obtained.
[0133]
In the developer of the present invention, the content of particles having a particle size range of 3.00 μm or more and less than 8.96 μm in the number-based particle size distribution of a particle size range of 0.60 μm or more and less than 159.21 μm is 20 to 65. More preferably, it is number%, and more preferably 25-60%. By setting the content of the above particles within this range, the uniform chargeability of the image carrier by contact charging is further improved, and defective collection of residual toner particles in the image forming method using development and cleaning is effectively prevented. The effect can be further enhanced, and an image with high image density and less fogging and excellent resolution can be obtained.
[0134]
As described above, in order to secure particles having triboelectric charging characteristics suitable for developing an electrostatic latent image faithfully as a toner image, to obtain an image with high image density, low fog and excellent resolution. The developer of the present invention contains 15 to 70% by number of particles having a particle size range of 3.00 μm or more and less than 8.96 μm in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm. . Therefore, it is desirable that the content of the particles having a particle size range of 3.00 μm or more and less than 8.96 μm in the developer is attributed to the toner particles. However, in the number-based particle size distribution in the particle size range of 0.60 μm or more and less than 159.21 μm in the developer, particles having a particle size range of 3.00 μm or more and less than 8.96 μm are not limited to toner particles. The conductive fine powder or other particles added to the developer may be contained.
[0135]
The developer of the present invention preferably contains 0 to 20% by number of particles having a particle size of 8.96 μm or more in a number-based particle size distribution in a particle size range of 0.60 μm or more and less than 159.21 μm.
[0136]
As described above, the developer of the present invention in which the conductive fine powder is contained so that the content in the developer of particles having a particle size range of 1.00 μm or more and less than 2.00 μm is in the range specified in the present invention. Then, since the developer contains many particles of conductive fine powder, it has a sufficiently high triboelectric charging characteristic to faithfully develop an electrostatic latent image as a toner image on particles having a particle size of 8.96 μm or more. It becomes difficult to have. When the content of particles having a particle size of 8.96 μm or more in the above particle size measurement range is excessively larger than the above range, the electrostatic latent image is faithfully developed as a toner image as the whole developer. It is difficult to provide a sufficiently high frictional charging characteristic, and the resolution of the obtained image tends to be low.
[0137]
In addition, toner particles having a particle size of 8.96 μm or more are likely to retain a high triboelectric charge locally on the toner particle surface, and when the conductive fine powder adheres to such a portion, the conductive fine powder becomes a toner particle. Therefore, the conductive fine powder supplied on the latent image carrier after transfer is easily reduced.
[0138]
For this reason, there are cases where the effect of promoting the charging of the latent image carrier due to the presence of the conductive fine powder in the charging portion cannot be sufficiently obtained. In addition, since the conductive fine powder supplied onto the latent image carrier after the transfer tends to decrease, the effect of improving the recovery of the transfer residual toner may not be obtained.
[0139]
Further, when toner particles having a large particle diameter are carried to the charging portion as untransferred toner particles, the contact property of the contact charging member to the latent image carrier is impaired, and the latent image carrier tends to be poorly charged. That is, the contact charging member may have a close contact property with the latent image carrier through the conductive fine powder, so that the effect of the present invention for improving the uniform chargeability of the latent image carrier may not be obtained. In addition, when attempting to collect transfer residual toner particles having a large particle diameter in the development process, the transfer residual toner particles having a large particle diameter are not recovered and image defects are caused, or exposure in the latent image forming process is performed. Occasional image defects may occur.
[0140]
Therefore, the developer of the present invention has 0 to 10% by number of particles having a particle size of 8.96 μm or more in the developer in the number-based particle size distribution in the particle size range of 0.60 μm or more and less than 159.21 μm. More preferably, it is more preferably 0 to 7% by number. By setting the content of the particles in this range, it is possible to obtain an image with higher image density and less fog and excellent resolution. In addition, the contact charging member having a close contact with the latent image carrier through the conductive fine powder is more advantageous in improving the uniform chargeability of the latent image carrier, and the transfer residual toner in development. This is more advantageous in suppressing the occurrence of image defects due to the poor collection and the light shielding of the exposure in the latent image forming process.
[0141]
In the developer of the present invention, the content of particles having a particle size range of 1.00 μm or more and less than 2.00 μm in the number-based particle size distribution of the particle size range of 0.60 μm or more and less than 159.21 μm is A number%. When the content of particles in a particle size range of 2.00 μm or more and less than 3.00 μm is defined as B number%, it is preferable to satisfy the relationship of A> B, and more preferably to satisfy the relationship of A> 2B. preferable.
[0142]
That is, the content B number% of particles in the particle size range of 2.00 μm or more and less than 3.00 μm is preferably smaller than the content A number% of particles in the particle diameter range of 1.00 μm or more and less than 2.00 μm. . When the number-based particle size distribution in the measured particle size range of 0.60 μm or more and less than 159.21 μm of the developer of the present invention satisfies the above relationship, the conductive fine powder may be uniformly dispersed in the charging portion. And uniform chargeability can be obtained.
[0143]
When A and B do not satisfy the relationship of A> B, the uniform dispersibility of the conductive fine powder intervening in the charging portion is reduced, or the holding property of the conductive fine powder on the contact charging member is inferior, The effect of uniformizing the charge of the latent image carrier tends to be reduced. In addition, the supply property of the conductive fine powder to the charging unit is poor, and the effect of promoting the charging of the latent image carrier is reduced by repeated use over a long period of time, and the latent image carrier tends to become unstable. Further, when the relationship of A> B is not satisfied, more toner particles having a particle size range of 2.00 μm or more and less than 3.00 μm with relatively low transferability are supplied and held in the charging unit. Relatively lowering the retention of the conductive fine powder at the charged portion, and depending on the repeated use of the image forming apparatus over a long period of time, it tends to hinder uniform charging of the latent image carrier, and the toner particles in the transfer residual toner particles As the fine particles increase, the recoverability of transfer residual toner particles decreases, and positive ghosts and fogging are likely to occur.
[0144]
That is, the conductive fine powder particles in the particle size range of 2.00 μm or more and less than 3.00 μm are charged more than the conductive fine powder particles having a particle size range of 1.00 μm or more and less than 2.00 μm. The effect of facilitating charging obtained by the presence of conductive fine powder in the part is greatly inferior, and the effect of improving the recovery of the transfer residual toner particles during development is also inferior. Of the particles having a particle size range of 2.00 μm or more and less than 3.00 μm, the toner particles are unstable in triboelectric chargeability, so that they are liable to cause fogging and have low transferability. For this reason, more transfer residual toner particles are supplied to the charging unit, and it is easy to inhibit uniform charging of the latent image carrier. In addition, since the residual toner particles increase and the triboelectric chargeability of the residual toner is unstable, the recoverability of the residual toner particles during development tends to be lowered. Therefore, it is preferable that the content of particles having a particle size in the particle size range of 2.00 μm or more and less than 3.00 μm is small. That is, it is preferable that the content ratio of particles having a particle size in the particle size range of 2.00 μm or more and less than 3.00 μm in the entire particle size distribution of the developer is small.
[0145]
From these viewpoints, the content A number% of particles having a particle size range of 1.00 μm or more and less than 2.00 μm is larger than the content B number% of particles having a particle size range of 2.00 μm or more and less than 3.00 μm. Preferably, the content A number% of particles in a particle size range of 1.00 μm or more and less than 2.00 μm is twice the content B number% of particles in a particle size range of 2.00 μm or more and less than 3.00 μm. Is preferably larger.
[0146]
Further, when the content of particles having a particle size range of 3.00 μm or more and less than 8.96 μm is defined as C number%, the content B of particles having a particle size range of 2.00 μm or more and less than 3.00 μm. It is preferably larger than 2 times the number%, more preferably larger than 3 times.
[0147]
In the number-based particle size distribution in the particle size range of 0.60 μm or more and less than 159.21 μm, the content B number% of particles in the particle size range of 2.00 μm or more and less than 3.00 μm is 20 number% or less. More preferably, it is 10% or less, and particularly preferably 5% or less.
[0148]
The developer of the present invention has a number distribution represented by the following formula in a particle size range of 3.00 μm or more and less than 15.04 μm in a particle size distribution of a particle size range of 0.60 μm or more and less than 159.21 μm. Coefficient of variation K_nIs preferably 5 to 40.
[0149]
Variation coefficient K of particle size distribution based on number_n= (S_n/ D₁) × 100
[Where S_nRepresents the standard deviation of the number distribution in the particle size range of 3.00 μm or more and less than 15.04 μm, D₁Represents a number-based average equivalent circle diameter (μm) in a particle size range of 3.00 μm or more and less than 15.04 μm. ]
Coefficient of variation K_n5 to 40, a uniform mixing property between the toner particles and the conductive fine powder is obtained, and the conductive fine powder is more uniformly supplied onto the latent image carrier, whereby the latent image carrier is obtained. The charge uniformizing effect can be further enhanced. In addition, the charge amount distribution of the toner particles is sharpened, the fogging toner particles and the transfer residual toner particles are reduced, and charging inhibition of the latent image carrier can be more stably suppressed. In addition, since the transfer residual toner particles can be more stably collected in the development process, image defects due to poor collection can be more reliably suppressed. In order to further sharpen the charge amount distribution of the toner particles, the variation coefficient K_nIs more preferably 5-30.
[0150]
The developer of the present invention has a weight average particle diameter (D) determined from a volume-based particle size distribution in a particle size range of 0.60 μm or more and less than 159.21 μm.₄) Is preferably 4 to 10 μm, and in the particle size range of 3.00 μm or more and less than 15.04 μm, the variation coefficient K of the volume-based particle size distribution represented by the following formula:_vIs preferably 10-30.
[0151]
Coefficient of variation of volume-based particle size distribution K_v= (S_v/ D₄) × 100
[Where S_vRepresents a standard deviation of volume distribution in a particle size range of 3.00 μm or more and less than 15.04 μm, and D₄Represents a volume-based volume average particle diameter (μm) in a particle diameter range of 3.00 μm or more and less than 15.04 μm. ]
Variation coefficient K of the above volume-based particle size distribution_vIs from 10 to 30, the charge amount distribution of the developer in the particle size range of 3.00 μm or more and less than 15.04 μm is sharpened, and fogged toner particles and transfer residual toner particles are reduced. The charging inhibition of the image carrier can be suppressed more stably. In addition, since it is possible to improve the recoverability of the transfer residual toner particles in the development and cleaning process, it is possible to effectively prevent image defects due to poor recovery. Therefore, the coefficient of variation K_vIs more preferably 10-25.
[0152]
The coefficient of variation K_nOr K_vIs too smaller than the above range, it becomes difficult to produce toner particles._nOr K_vWhen the value is larger than the above range, it is difficult to obtain a uniform mixing property between the toner particles, the inorganic fine powder, and the conductive fine powder, and it is difficult to obtain a stable charge promoting effect of the image carrier. Further, the charge amount distribution as a whole developer becomes broad, and the image quality is lowered due to a decrease in image density and an increase in fog. Furthermore, the amount of toner particles remaining after transfer increases, the chargeability is hindered, and the recovery rate of toner particles remaining after transfer in the development and cleaning process decreases.
[0153]
The coefficient of variation K_vIs set to 15-30, the charge amount distribution of the developer in the particle size range of 3.00 μm or more and less than 15.04 μm is sharpened, the toner particles that become fog and the residual toner particles are reduced, and the image Charge inhibition of the carrier can be more stably suppressed. In addition, since it is possible to improve the recoverability of the transfer residual toner particles in the development and cleaning process, it is possible to effectively prevent image defects due to poor recovery of the toner particles. The coefficient of variation K_vIs more preferably 15-25.
[0154]
Further, in the developer of the present invention, the average circularity of the toner obtained from the following formula is preferably less than 0.970. When the average circularity is 0.970 or more, the external additive is hardly held on the toner surface, and as a result, the charge becomes non-uniform and fog is likely to occur. In addition, external additives are embedded due to stirring of the developer or temperature rise during durable use, and the toner surface is markedly deteriorated, resulting in problems with durability.
[0155]
Circularity a = L₀/ L
[Where L₀Indicates the perimeter of a circle having the same area as the projected image of the particle, and L indicates the perimeter of the projected image of the particle. ]
In the developer of the present invention, the standard deviation SD of the circularity distribution obtained from the following formula is preferably 0.045 or less in a particle size range of 3.00 μm or more and less than 15.04 μm.
Standard deviation SD = {Σ (a_i-A_m)²/ N}^1/2
[Where a_iRepresents the circularity of each particle in a particle size range of 3.00 μm or more and less than 15.04 μm, and a_mRepresents the average circularity of particles of 3.00 μm or more and less than 15.04 μm, and n represents the total number of particles having a particle size of 3.00 μm or more and less than 15.04 μm. ]
Since the standard deviation SD of the circularity distribution of the developer is 0.045 or less, the liberation of the conductive fine powder from the toner particles is stabilized, and the supply of the conductive fine powder onto the image carrier is further improved. Therefore, the charging inhibition of the image bearing member can be suppressed more stably, and the recoverability of the toner particles in the process of developing and cleaning (that is, the developing and cleaning process) is more stable.
[0156]
In the present invention, the particle size, the particle size distribution, and the circularity distribution of the developer are defined as the “equivalent particle diameter” as a circle equivalent diameter measured by a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.) This is a value obtained using a number-based particle size distribution and circularity distribution having a particle size of 0.60 μm or more and less than 159.21 μm.
[0157]
The measurement by the flow type particle image analyzer is performed by the following method. Fine dust is removed through the filter, resulting in 10³cm³A surfactant (preferably alkylbenzene sulfonate was removed from fine particles from 10 ml of water in which the number of particles in the measurement range (for example, equivalent circle diameter of 0.60 μm or more and less than 159.21 μm) was 20 or less. Add a few drops of water diluted 10 times. An appropriate amount (for example, 0.5 to 20 mg) of a measurement sample is added to this, and dispersion treatment is performed for 3 minutes with an ultrasonic homogenizer (output 50 W, 6 mm diameter step type chip). 10^-3cm³Using the sample dispersion adjusted to (measurement circle equivalent diameter range target), the particle size distribution and the circularity distribution of particles having an equivalent circle diameter of 0.60 μm or more and less than 159.21 μm are measured.
[0158]
The outline of the measurement is described in the catalog (June 1995 edition) of FPIA-1000 issued by Toa Medical Electronics Co., Ltd., the operation manual of the measuring apparatus, and JP-A-8-136439. It is.
[0159]
The sample dispersion is passed through a flat and flat transparent flow cell (thickness: about 200 μm) flow path (spread along the flow direction). The strobe and the CCD camera are mounted on the flow cell so as to be opposite to each other so as to form an optical path that passes through the thickness of the flow cell. While the sample dispersion is flowing, strobe light is irradiated at 1/30 second intervals to obtain an image of the particles flowing through the flow cell. As a result, each particle is photographed as a two-dimensional image having a certain range parallel to the flow cell. From the area of the two-dimensional image of each particle, the diameter of a circle having the same area as that of the two-dimensional image is calculated as the equivalent circle diameter.
[0160]
Further, the circumference of each particle is obtained from the two-dimensional image of each particle, and the circularity distribution is obtained by calculating the ratio of the area of this two-dimensional image to the circumference of a circle having the same area.
[0161]
The measurement results (frequency% and cumulative% of particle size distribution and circularity distribution) are divided into a range of 0.06 to 400 μm into 226 channels (divided into 30 channels per octave) as shown in Table 1 below. Obtainable. In actual measurement, particles are measured in the range where the equivalent circle diameter is 0.60 μm or more and less than 159.21 μm.
[0162]
[Table 1]

[0163]
In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle, and then calculates the average circularity. A calculation method is used in which 1.00 is divided into 61 classes and the average circularity is calculated using the center value and frequency of the dividing points. However, there is very little error between the average circularity value calculated by this calculation method and the average circularity calculated by the arithmetic average of the circularity of each particle, and it is practically negligible. In the present invention, such a calculation method may be used for reasons of handling data such as shortening the calculation time or simplifying the calculation formula.
[0164]
In addition, the developer of the present invention preferably has 5 to 500 conductive fine powder particles having a particle diameter of 0.1 to 10 μm per 100 toner particles. The conductive fine powder particles having a particle size of 0.1 to 10 μm are easily separated from the toner particles and behave easily, and are uniformly attached to the charging member and stably held. For this reason, the developer has 5 to 500 particles of conductive fine powder having a particle diameter of 0.1 to 10 μm per 100 toner particles, so that the conductivity on the image carrier in the development process and the transfer process is increased. The supply of fine powder is further promoted, and the chargeability of the image carrier can be made more stable and uniform. In addition, by having 5 to 500 conductive fine powder particles with a particle size of 0.1 to 10 μm per 100 toner particles in the developer, the recovery of transfer residual toner particles in the development and cleaning process is more stable. To do.
[0165]
In the developer of the present invention, when the number of conductive fine powder particles having a particle size of 0.1 to 10 μm is less than 5 per 100 toner particles, 1.00 μm or more and 2.00 μm resulting from the conductive fine powder. It is difficult to contain 5 to 60% by number of particles having a particle size range of less than 1.00 μm and less than 2.00 μm. In some cases, the effects of the present invention such as the effect of promoting charging and the effect of improving the recoverability of transfer residual toner particles in development and cleaning can be significantly reduced. In the developer of the present invention, when the number of conductive fine powder particles having a particle size of 0.1 to 10 μm is significantly larger than 500 particles per 100 toner particles, the ratio of the conductive fine powder particles to the toner particles Is too high to inhibit triboelectric charging of toner particles, lowering the developing property and transferability as a developer, lowering the image density, increasing fog, and lowering the uniform charging property due to the increase in residual toner particles. In addition, it becomes easy to cause a collection failure of transfer residual toner particles in development and cleaning. From such a viewpoint, it is more preferable that the developer has 5 to 300 conductive fine powder particles of 0.1 to 10 μm per 100 toner particles, and more preferably 10 to 200 particles.
[0166]
The number of conductive fine powders of 0.1 to 10 μm per 100 toner particles in the developer of the present invention is a value obtained by measuring as follows. That is, a photograph of the developer magnified with a scanning electron microscope is compared with a photograph of the developer mapped with the elements contained in the conductive fine powder by elemental analysis means such as XMA attached to the scanning electron microscope. Then, for 100 toner particles, the conductive fine powder that is attached to or separated from the toner particle surface is specified, and an image processing apparatus (for example, FE manufactured by Hitachi, Ltd.) is identified among the specified conductive fine powder. -SEMS-800, image information enlarged 3000 to 10000 times is introduced into an image analysis apparatus Luzex III manufactured by Nireco Corporation, for example, via an interface and analyzed). It is a value obtained by counting the number of particles of powder.
[0167]
Moreover, it is preferable that content of electroconductive fine powder is 0.1-10 mass% of the whole developer in the developer of this invention. By setting the content of the conductive fine powder within the above range, an appropriate amount of the conductive fine powder for accelerating the charging of the image carrier can be supplied to the charging unit. An amount of conductive fine powder necessary for enhancing the recoverability of particles can be supplied onto the image carrier. When the content of the conductive fine powder in the developer is too smaller than the above range, the amount of the conductive fine powder supplied to the charging portion is likely to be insufficient, and it is difficult to obtain a stable charge promoting effect of the image carrier. . In this case, even in image formation using development and cleaning, the amount of conductive fine powder interposed on the image carrier together with the transfer residual toner particles during development tends to be insufficient, and the recoverability of transfer residual toner particles is not sufficiently improved. There is a case. In addition, when the content of the conductive fine powder in the developer is too larger than the above range, excessive conductive fine powder is easily supplied to the charging portion, and a large amount of conductive fine powder cannot be held in the charging portion. In addition, exposure failure due to being discharged onto the image carrier is likely to occur. In addition, the frictional charging characteristics of the toner particles may be reduced or disturbed, which may cause a decrease in image density or an increase in fog.
[0168]
From such a viewpoint, the content of the conductive fine powder of the developer is more preferably 0.1 to 10% by mass, and further preferably 0.2 to 5% by mass.
[0169]
Further, the resistance of the conductive fine powder is 10 to provide the developer with the effect of promoting the charging of the latent image carrier and the effect of improving the recoverability of the transfer residual toner particles.⁹It is preferable that it is below Ω · cm. If the resistance of the conductive fine powder is too larger than the above range, the conductive fine powder is interposed in the contact portion between the charging member and the latent image carrier or in the vicinity of the charged region, and the contact through the conductive fine powder. Even if the contact property of the charging member to the latent image carrier is maintained, the charging promotion effect for obtaining a good uniform charging property of the latent image carrier is reduced. Also in the development and cleaning, the conductive fine powder tends to be charged with the same polarity as the transfer residual toner particles, and if the charge of the conductive fine powder becomes the same polarity as the transfer residual toner particles, The improvement effect is greatly reduced.
[0170]
In order to sufficiently obtain the effect of promoting the charging of the latent image carrier by the conductive fine powder and to stably obtain a good uniform charging property of the latent image carrier, the resistance of the conductive fine powder is the surface of the contact charging member. Is preferably smaller than the resistance of the contact portion of the contact charging member or the latent image carrier, and more preferably 1/100 or less of the resistance of the contact charging member.
[0171]
Furthermore, the resistance of the conductive fine powder is 10⁶It is less than Ω · cm to overcome the charging inhibition caused by the adhesion / mixing of insulating transfer residual toner particles to the contact charging member, and to uniformly charge the image carrier, and to develop It is also preferable for more stably obtaining the effect of improving the recoverability of transfer residual toner particles in the cleaning. The resistance of this conductive fine powder is 10⁰-10⁵More preferably, it is Ω · cm.
[0172]
In the present invention, the resistance of the conductive fine powder can be determined by measuring and normalizing by the tablet method. That is, the bottom area 2.26cm²Approximately 0.5 g of powder sample is placed in the cylinder, and 147 N (15 kg) is pressed between the upper and lower electrodes arranged above and below the powder sample, and at the same time a voltage of 100 V is applied to measure the resistance value. Then, the resistivity is calculated by normalization.
[0173]
The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder because the conductive fine powder transferred onto the transfer material is not noticeable as fog. From the viewpoint of preventing exposure light in the latent image forming step, the conductive fine powder is preferably a transparent, white or light-colored conductive fine powder. Further, the conductive fine powder preferably has a transmittance of 30% or more for image exposure light forming this electrostatic latent image. The transmittance is more preferably 35% or more.
[0174]
Hereinafter, an example of a method for measuring the light transmittance of the conductive fine powder in the present invention will be described. The transmittance is measured in a state where the conductive fine powder is fixed on the adhesive layer of a transparent film having an adhesive layer on one side. Light is irradiated from the vertical direction of the sheet, and the light transmitted to the back of the film is collected and the amount of light is measured. The light transmittance as the net light amount was calculated based on the difference in the light amount when the film alone and the conductive fine powder were attached. Actually, it can be measured using a 310T transmission densitometer manufactured by X-Rite.
[0175]
The conductive fine powder is preferably nonmagnetic. Since the conductive fine powder is non-magnetic, it is easy to obtain a transparent, white or light-colored conductive fine powder. On the other hand, it is difficult to make a conductive material having magnetism transparent, white or light color. Further, in the image forming method in which the developer is transported and held by magnetic force for supporting the developer, the conductive fine powder having magnetism is difficult to be developed, so that the conductive fine powder is supplied onto the image carrier. Or the accumulation of conductive fine powder on the surface of the developer carrier tends to cause problems such as hindering the development of toner particles. Further, when magnetic conductive fine powder is added to the magnetic toner particles, the conductive fine powder tends to be difficult to be separated from the toner particles due to the magnetic cohesive force, and the supply of the conductive fine powder onto the image carrier. It is easy to deteriorate.
[0176]
Examples of the conductive fine powder in the present invention include carbon fine powder such as carbon black and graphite; metal fine powder such as copper, gold, silver, aluminum and nickel; zinc oxide, titanium oxide, tin oxide, aluminum oxide and indium oxide. Metal oxides such as silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, iron oxide, and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, and potassium titanate, or composite oxides of these may be used as required. And by adjusting the particle size distribution.
[0177]
Among these, the conductive fine powder preferably contains at least one oxide selected from zinc oxide, tin oxide, and titanium oxide. Furthermore, fine particles having an inorganic oxide such as zinc oxide, tin oxide or titanium oxide at least on the surface are particularly preferable. These oxides can set the resistance as a conductive fine powder low, are non-magnetic, are white or light color, and the conductive fine powder transferred onto the transfer material is not noticeable as fog. Therefore, it is preferable.
[0178]
Further, when the conductive fine powder is composed of a conductive inorganic oxide or contains a conductive inorganic oxide, antimony different from the main metal element of the conductive inorganic oxide for the purpose of controlling the resistance value or the like. Further, a metal oxide containing an element such as aluminum or a conductive material can be used. For example, zinc oxide containing aluminum, stannic oxide fine particles containing antimony, or fine particles obtained by treating the surface of titanium oxide, barium sulfate or aluminum borate with tin oxide containing antimony. The amount of the conductive inorganic oxide to contain an element such as antimony or aluminum is preferably 0.05 to 20% by mass, more preferably 0.05 to 10% by mass, particularly preferably 0.1 to 0.1% by mass. 5% by mass.
[0179]
In addition, a conductive inorganic oxide in which the inorganic oxide is an oxygen deficient type is also preferably used.
[0180]
Commercially available tin oxide / antimony-treated conductive titanium oxide fine particles include, for example, EC-300 (Titanium Industry Co., Ltd.), ET-300, HJ-1, HI-2 (above, Ishihara Sangyo Co., Ltd.), W- P (Mitsubishi Materials Corporation).
[0181]
Examples of commercially available antimony-doped conductive tin oxide include T-1 (Mitsubishi Materials Corporation) and SN-100P (Ishihara Sangyo Co., Ltd.), and examples of commercially available stannic oxide include SH-S (Japan). Chemical Industry Co., Ltd.).
[0182]
Particularly preferred are metal oxides such as zinc oxide containing aluminum, metal oxides such as oxygen deficient zinc oxide, tin oxide, and titanium oxide in that high whiteness or translucency can be obtained, and Examples thereof include fine particles having at least the surface thereof.
[0183]
Moreover, it is preferable that a particle size is 0.1-10 micrometers. If the volume average particle size of the conductive fine powder is too smaller than the above range, the content of the conductive fine powder with respect to the developer must be set small in order to prevent a decrease in developability. If the amount of conductive fine powder added is set too low, an effective amount of the conductive fine powder cannot be secured, and in the charging process, the charging of the contact charging member due to the adhesion / mixing of insulating transfer residual toner particles may be hindered. A sufficient amount of conductive fine powder to overcome the charging of the latent image carrier by overcoming it cannot be interposed in the contact area between the charging member and the latent image carrier or the charged region in the vicinity thereof, It becomes easy to cause charging failure. From this viewpoint, the volume average particle size of the conductive fine powder is 0.1 μm or more, preferably 0.15 μm or more, and more preferably 0.2 μm or more.
[0184]
If the volume average particle size of the conductive fine powder is too larger than the above range, the conductive fine powder that has fallen from the charging member shields or diffuses the exposure light that forms the electrostatic latent image. An image defect may be caused to deteriorate the image quality, which is not preferable. Furthermore, if the volume average particle diameter of the conductive fine powder is too larger than the above range, the number of particles of the conductive fine powder per unit weight is decreased, and thus the recovery of the transfer residual toner particles can be sufficiently improved. Disappear. In addition, since the number of particles of the conductive fine powder is reduced, the conductive fine powder is taken into consideration when the reduction and deterioration of the conductive fine powder intervening in the vicinity of the charging member due to the dropping of the conductive fine powder from the charging member is considered. Is continuously supplied to the contact portion between the charging member and the image carrier or the charged region in the vicinity thereof, and the contact charging member has a fine contact property to the image carrier through the conductive fine powder. In order to maintain and stably obtain good uniform chargeability, the content of the conductive fine powder with respect to the developer must be increased. However, if the content of the conductive fine powder is excessively increased, the chargeability and developability of the developer as a whole in a high humidity environment are deteriorated, resulting in a decrease in image density and toner scattering. From such a viewpoint, the volume average particle size of the conductive fine powder is more preferably 10 μm or less, and most preferably 5 μm or less.
[0185]
The measurement method of the volume average particle diameter and particle size distribution of the said electroconductive fine powder is illustrated. A liquid module is attached to a LS-230 type laser diffraction particle size distribution measuring device manufactured by Coulter, Inc., and a particle size of 0.04 to 2000 μm is set as a measurement range. Calculate the diameter. As a measurement procedure, a trace amount of a surfactant is added to 10 cc of pure water, 10 mg of a conductive fine powder sample is added thereto, and the mixture is dispersed for 10 minutes with an ultrasonic disperser (ultrasonic homogenizer), and then measured for 90 hours. Measured once per second and number of measurements.
[0186]
In measurement from toner, a small amount of surfactant is added to 100 g of pure water, 2 to 10 g of toner is added, and the mixture is dispersed for 10 minutes with an ultrasonic disperser (ultrasonic homogenizer), and then centrifuged. The toner particles and the conductive fine powder are separated by a machine or the like. In the case of magnetic toner, a magnet can be used. The separated dispersion is measured with a measurement time of 90 seconds and a single measurement.
[0187]
In the present invention, as a method for adjusting the particle size and particle size distribution of the conductive fine powder, the production method and the production conditions are set so that the primary particle of the conductive fine powder has a desired particle size and particle size distribution at the time of production. In addition to the above method, a method of agglomerating small particles of primary particles, a method of pulverizing particles of large primary particles or a method by classification, etc. are possible. A method of attaching or fixing conductive particles to a part or all of the surface, a method of using conductive fine particles having a form in which a conductive component is dispersed in particles having a desired particle size and particle size distribution are also possible. It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining these methods.
[0188]
The particle diameter in the case where the conductive fine powder particles are formed as an aggregate is defined as an average particle diameter of the aggregate. There is no problem that the conductive fine powder exists not only in the state of primary particles but also in the state of aggregation of secondary particles. In any aggregated state, any form can be used as long as the aggregate is interposed in the contact portion between the charging member and the image carrier or in the vicinity of the charged region and can realize a charge assisting or promoting function.
[0189]
The developer of the present invention further has an inorganic fine powder having a primary particle number average particle diameter of 4 to 80 nm. When the number average particle size of the primary particles of the inorganic fine powder is too larger than the above range, or when the inorganic fine powder in the above range is not added, the charging member is formed when the transfer residual toner particles adhere to the charging member. It becomes difficult to stably obtain good uniform chargeability of the latent image carrier. Further, it becomes difficult to uniformly disperse the conductive fine powder with respect to the toner particles in the developer, and uneven supply of the conductive fine powder onto the latent image carrier is likely to occur, and uneven supply to the contact charging member. In such a case, the latent image carrier corresponding to a portion where the supply of the conductive fine particles is insufficient causes a charging failure, which is likely to cause an image defect. In addition, when unevenness of the amount of conductive fine powder on the latent image carrier occurs during development and cleaning, a recovery failure occurs due to a temporary or partial decrease in recoverability of transfer residual toner particles. Further, since the developer does not have good fluidity and the triboelectric charge is easily applied to the toner particles, problems such as an increase in fog, a decrease in image density, and toner scattering are likely to occur. When the number average particle size of the primary particles of the inorganic fine powder is smaller than 4 nm, the fineness of the inorganic fine powder is increased, and the particle size distribution is wide and has strong cohesiveness that is difficult to be broken by the crushing treatment instead of the primary particles. Since it tends to behave as an aggregate, image defects due to development of the aggregate of the inorganic fine powder, image defects due to damage to the image carrier, developer carrier, contact charging member, and the like are likely to occur. From these viewpoints, the number average particle diameter of the primary particles of the inorganic fine powder is more preferably 6 to 50 nm, and still more preferably 8 to 35 nm.
[0190]
That is, in the present invention, the inorganic fine powder having the average diameter of the primary particles is added to improve the fluidity of the developer by adhering to the surface of the toner particles and to make the frictional charge of the toner particles uniform. In addition, the conductive fine powder is uniformly dispersed with respect to the toner particles in the developer, so that the conductive fine powder is uniformly supplied onto the latent image carrier.
[0191]
In the present invention, the number average particle size of the primary particles of the inorganic fine powder is a value obtained by measurement by the following method. That is, the photograph of the developer magnified with a scanning electron microscope is compared with the photograph of the developer mapped with the elements contained in the inorganic fine powder by elemental analysis means such as XMA attached to the scanning electron microscope. The number average particle diameter can be determined by measuring 100 or more primary particles of the inorganic fine powder that are attached to or separated from the toner surface.
[0192]
In the present invention, the inorganic fine powder preferably contains at least one selected from silica, titania and alumina having a primary particle number average particle size of 4 to 80 nm. For example, as the silica fine powder, both a so-called dry method produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass or the like can be used. However, there are few silanol groups on the surface and inside the silica fine powder, and Na₂O, SO^3-For example, dry silica with less production residue is preferred. In dry silica, it is also possible to obtain a composite fine powder of silica and other metal oxides by using a metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound in the production process. Includes.
[0193]
In the present invention, the inorganic fine powder is preferably hydrophobized. By hydrophobizing the inorganic fine powder, the chargeability of the inorganic fine powder in the high-humidity environment is prevented from decreasing, and the environmental stability of the triboelectric charge amount of the toner particles adhered to the surface is improved. Further, the environmental stability of development characteristics such as image density and fog as a developer can be further enhanced. Controlling the fluctuation of the chargeability of the inorganic fine powder and the triboelectric charge amount of the toner particles adhering to the surface due to the environment can change the ease of release of the conductive fine powder from the toner particles. The amount of conductive fine powder supplied onto the image carrier can be stabilized, and the environmental stability of the chargeability of the image carrier and the recoverability of transfer residual toner particles can be improved.
[0194]
As treatment agents for hydrophobization treatment, treatment agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or in combination. And may be processed. Among them, the inorganic fine powder is particularly preferably treated with at least silicone oil.
[0195]
The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm.²/ S, even 3,000-80,000mm²/ S is preferred. When the viscosity of the silicone oil is too smaller than the above range, the processing of the inorganic fine powder is not stable, and the processed silicone oil is detached, transferred or deteriorated by heat and mechanical stress, and the image quality is deteriorated. Tend. Moreover, when a viscosity is larger than the said range, there exists a tendency for the uniform process of an inorganic fine powder to become difficult.
[0196]
As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil are particularly preferable.
[0197]
As a method for treating the silicone oil, for example, the inorganic fine powder treated with the silane compound and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, or the silicone oil is sprayed onto the inorganic fine powder. A method may be used. Alternatively, after dissolving or dispersing silicone oil in a suitable solvent, silica fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable because the production of inorganic fine powder aggregates is relatively small.
[0198]
The treatment amount of silicone oil is 1 to 23 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of the silicone oil is too smaller than the above range, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging may occur.
[0199]
In the present invention, the inorganic fine powder is preferably treated with silicone oil at the same time or after treatment with at least the silane compound. It is particularly preferable to use a silane compound for the treatment of the inorganic fine powder in order to increase the adhesion of the silicone oil to the inorganic fine powder and to make the hydrophobicity and chargeability of the inorganic fine powder uniform.
[0200]
As the treatment conditions for the inorganic fine powder, for example, a silylation reaction is performed as a first-stage reaction and silanol groups are eliminated by chemical bonds, and then a hydrophobic thin film is formed on the surface with silicone oil as a second-stage reaction. it can.
[0201]
Moreover, it is preferable that content of an inorganic fine powder is 0.1-3.0 mass% of the whole developer in the developer of this invention. If the content of the inorganic fine powder is less than the above range, the effect of adding the inorganic fine powder cannot be sufficiently obtained, and if it is more than the above range, the inorganic fine powder is excessively inorganic with respect to the toner particles. The fine powder covers the conductive fine powder, and the behavior becomes the same as when the conductive fine powder has high resistance. The effects of the present invention, such as a reduction in the effect and a reduction in the recoverability of transfer residual toner particles, are impaired. The content of the inorganic fine powder is more preferably 0.3 to 2.0% by mass, and further preferably 0.5 to 1.5% by mass with respect to the whole developer.
[0202]
The inorganic fine powder having a primary particle number average diameter of 4 to 80 nm used in the present invention has a specific surface area of 20 to 250 m by nitrogen adsorption measured by the BET method.²/ G is preferable, 40 to 200 m²/ G is more preferable. The specific surface area can be calculated using the BET multipoint method by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics Co., Ltd.) according to the BET method.
[0203]
In the present invention, the toner particles are colored resin particles containing at least a binder resin and a colorant. The toner particle resistance is 10¹⁰Preferably it is Ω · cm or more.¹²More preferably Ω · cm or more. If the toner particles do not substantially exhibit insulation, it is difficult to achieve both developability and transferability. In addition, charge is easily injected into the toner particles due to the developing electric field, and the charging of the developer is disturbed to cause fogging.
[0204]
Examples of the binder resin contained in the toner particles used in the present invention include, for example, a styrene resin, a styrene copolymer resin, a polyester resin, a polyvinyl chloride resin, a phenol resin, a naturally modified phenol resin, and a modified natural resin. Maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyurethane resin, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, etc. can be used .
[0205]
As a comonomer for the styrene monomer of the styrene copolymer, for example, a styrene derivative such as vinyltoluene; for example, acrylic acid or methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, acrylic acid- Acrylic acid esters such as 2-ethylhexyl and phenyl acrylate; for example, methacrylic acid or methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid esters such as octyl methacrylate; for example, maleic acid or butyl maleate, Dicarboxylic acid esters having a double bond such as methyl maleate and dimethyl maleate; for example, acrylamide, acrylonitrile, methacrylonitrile, butadiene or vinyl chloride, vinyl acetate, benzoic acid Vinyl esters such as Nyl; for example, ethylene-based olefins such as ethylene, propylene and butylene; for example, vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; for example, vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether Vinyl monomers such as vinyl ethers may be used alone or in combination of two or more.
[0206]
Here, as the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol dimethacrylate. A carboxylic acid ester having two double bonds such as 1,3-butanediol dimethacrylate; a divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and a compound having three or more vinyl groups. Used alone or as a mixture.
[0207]
The glass transition temperature (Tg) of the binder resin is preferably 50 to 70 ° C. When the glass transition temperature is too lower than the above range, the storage stability of the developer is lowered, and when it is too high, the fixability is poor.
[0208]
The developer according to the present invention preferably has a maximum endothermic peak in a temperature range of 70 ° C. or more and less than 120 ° C. in an endothermic curve of a DSC chart by a differential thermal analyzer (DSC). In order to have the maximum endothermic peak in such a temperature range, it is preferable to include a wax component in the toner particles.
[0209]
Examples of the wax contained in the toner particles used in the present invention include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin, polyolefin copolymer, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; Oxides of aliphatic hydrocarbon waxes such as polyethylene wax; or block copolymers thereof; waxes based on fatty acid esters such as carnauba wax and montanic acid ester wax; fatty acid esters such as deoxidized carnauba wax And the like which have been partially or wholly deoxidized. In addition, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinal acid; Saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvir alcohol, cetyl alcohol, melyl alcohol, or long chain alkyl alcohols having a long chain alkyl group; polyhydric alcohols such as sorbitol; linoleic acid Fatty acid amides such as amides, oleic acid amides, lauric acid amides; saturated fatty acid vinyls such as methylene bis stearic acid amides, ethylene bis lauric acid amides, ethylene bis lauric acid amides, hexamethylene bis stearic acid amides. Amides, unsaturated fatty acid amides such as ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; Aromatic bisamides such as acid amides and N, N′-distearylisophthalamide; fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (commonly referred to as metal soap); Waxes grafted onto aliphatic hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid; Partially esterified products of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; obtained by hydrogenation of vegetable oils and fats Has a hydroxyl group And methyl ester compounds.
[0210]
In the present invention, the wax is used in an amount of preferably 0.5 to 20 parts by mass, more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the binder resin.
[0211]
Examples of the colorant contained in the toner particles used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6G, calco oil blue, Conventionally known dyes such as chrome yellow, quinacridone, benzidine yellow, rose bengal, triarylmethane dyes, monoazo dyes and disazo dyes can be used alone or in combination.
[0212]
The developer of the present invention has a magnetization strength of 10 to 40 Am at a magnetic field of 79.6 kA / m.²The magnetic developer is preferably / kg. Magnetization strength of developer is 20-35Am²/ Kg is more preferable.
[0213]
The reason why the intensity of magnetization at a magnetic field of 79.6 kA / m is defined in the present invention is as follows. Usually, the magnetic strength of the magnetic saturation (saturation magnetization) is used as the quantity representing the magnetic characteristics of the magnetic material. In the present invention, however, the magnetic developer in a magnetic field that actually acts on the magnetic developer in the image forming apparatus. This is because the strength of magnetization is important. When a magnetic developer is applied to an image forming apparatus, the magnetic field acting on the magnetic developer is commercially available in order not to increase leakage of the magnetic field outside the image forming apparatus or to keep the cost of the magnetic field generation source low. In many image forming apparatuses, a magnetic field of 79.6 kA / m (1000 oersted) is used as a representative value of the magnetic field actually acting on the magnetic developer in the image forming apparatus. Selected to define the strength of magnetization at a magnetic field of 79.6 kA / m.
[0214]
When the magnetic strength of the developer at a magnetic field of 79.6 kA / m is too small than the above range, it becomes difficult to transport the developer by the magnetic force, and the developer is uniformly supported on the developer carrier. Can not be made. In addition, when the developer is transported by magnetic force, the monocomponent magnetic developer cannot be uniformly formed, so that the supply of the conductive fine powder to the latent image carrier is reduced, and the transfer residue is reduced. The toner particle recoverability also decreases. When the intensity of magnetization in the magnetic field of 79.6 kA / m is too larger than the above range, the magnetic cohesiveness of the toner particles is increased, and uniform dispersion of the conductive fine powder in the developer and the latent image carrier are achieved. Supply becomes difficult, and the effect of promoting charging of the image carrier or the effect of promoting toner recovery, which is an effect of the present invention, is impaired.
[0215]
As a means for obtaining such a magnetic developer, toner particles contain a magnetic substance. In the present invention, the magnetic substance contained in the toner particles in order to use the developer as a magnetic developer includes magnetic iron oxide such as magnetite, maghemite and ferrite, iron; metal such as cobalt and nickel, and these metals and aluminum, cobalt, Examples include alloys of metals such as copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof.
[0216]
As magnetic characteristics of these magnetic materials, the saturation magnetization is 10 to 200 Am under a magnetic field of 795.8 kA / m.²/ Kg, residual magnetization 1-100Am²/ Kg and a coercive force of 1 to 30 kA / m are preferably used. These magnetic materials are used in an amount of 20 to 200 parts by mass with respect to 100 parts by mass of the binder resin. Among such magnetic materials, those mainly composed of magnetite are particularly preferable.
[0217]
In the present invention, the strength of magnetization of the magnetic developer is measured by using an oscillating magnetometer VSMP-1-10 (manufactured by Toei Kogyo Co., Ltd.) at a room temperature of 25 ° C. and an external magnetic field of 79.6 kA / m. be able to. The magnetic properties of the magnetic material can be measured at an ambient magnetic field of 796 kA / m at a room temperature of 25 ° C.
[0218]
Further, in the present invention, the developer passes through a sieve having a mesh size of 149 μm and cannot pass through a sieve having a mesh size of 74 μm (mesh size of 149 μm pass−mesh size of 74 μm on). The value is preferably 20 to 100 mC / kg. When the triboelectric charge amount of the developer is too small in absolute value, the transferability of the toner particles decreases, resulting in an increase in residual toner particles, and thus the chargeability of the latent image carrier is likely to decrease. As a result, the recovery load of the transfer residual toner particles is increased and the recovery failure tends to occur. When the developer triboelectric charge amount is excessively larger than the above range, the electrostatic cohesiveness of the developer is increased, the conductive fine powder is uniformly dispersed in the developer, and the image carrier is dispersed. The supply becomes difficult, and the effect of promoting charging of the image carrier or the effect of promoting toner recovery, which is an effect of the present invention, is impaired. In particular, in the case of a magnetic developer, it is necessary to further suppress electrostatic agglomeration because the developer has both magnetic agglomeration properties, and a spherical iron having an aperture of 149 μm pass-74 μm on the magnetic developer. The frictional charge amount with respect to the powder is preferably 25 to 50 mC / kg in absolute value.
[0219]
The method for measuring the triboelectric charge amount of the developer in the present invention will be described in detail with reference to the drawings. FIG. 4 is an explanatory diagram of an apparatus for measuring the triboelectric charge amount of the developer. In an environment of 23 ° C. and a relative humidity of 60%, first, a developer for measuring the triboelectric charge amount and a spherical iron powder carrier having a particle size of 149 μm pass-74 μm mesh (for example, a spherical shape manufactured by Dowa Iron Powder Co., Ltd.) A mixture of iron powder DSP138 can be used at a mass ratio of 5:95 (for example, 0.5 g of developer and 9.5 g of iron powder carrier) is placed in a polyethylene bottle having a capacity of 50 to 100 ml. Rotate. Next, about 0.5 g of the mixture is put in a metal measuring container 22 having a screen 23 having an opening of 31 μm at the bottom, and a metal lid 24 is placed. The total weight of the measurement container 22 at this time is weighed, and this is defined as W1 (g). Next, in the suction machine 21 (at least the part in contact with the measurement container 22 is an insulator), the pressure of the vacuum gauge 25 is set to 2450 Pa by suction from the suction port 27 and adjusting the air volume control valve 26. In this state, suction is sufficiently performed (about 1 minute) to remove the toner by suction. The potential of the electrometer 29 at this time is set to V (volt). Here, 28 is a capacitor, and the capacity is C (μF). Moreover, the weight of the whole measurement container after suction is weighed and is defined as W2 (g). The triboelectric charge amount of the developer is calculated as follows:
[0220]
Triboelectric charge amount of developer (mC / kg) = C × V / (W1-W2)
In the present invention, the developer preferably contains a charge control agent. Among the charge control agents, there are the following substances, for example, which control the developer to be positively charged.
[0221]
Modified products by nigrosine and fatty acid metal salts; oniums such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, quaternary ammonium salts such as tetrabutylammonium tetrafluoroborate, and phosphonium salts which are analogs thereof Salts and their lake pigments, triphenylmethane dyes and their lake pigments (as rake agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, Russian salts), metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, dicyclohexyl Such diorgano tin borate such Suzuboreto; guanidine compounds, imidazole compounds. These can be used alone or in combination of two or more. Among these, triphenylmethane compounds and quaternary ammonium salts whose counter ions are not halogen are preferably used. Further, a monomer homopolymer represented by the general formula (4): a copolymer with a polymerizable monomer such as styrene, acrylic acid ester or methacrylic acid ester described above can be used as a positive charge control agent. In this case, these charge control agents also have an action as a binder resin (all or a part thereof).
[0222]
[Chemical 7]

[However, R₁, R₂, R₃Represents a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms. ]
In the constitution of the present invention, the positive charge control agent is particularly preferably a compound represented by the following general formula (5).
[0223]
[Chemical 8]

[In the formula, R¹, R², R³, R⁴, R⁵, R⁶Each may be the same as or different from each other and each represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R⁷, R⁸, R⁹Each may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group. A⁻Indicates anions such as sulfate ion, nitrate ion, borate ion, phosphate ion, hydroxide ion, organic sulfate ion, organic sulfonate ion, organic phosphate ion, carboxylate ion, organic borate ion, tetrafluoroborate . ]
Moreover, the following substances can be cited as examples of controlling the developer to be negatively charged. For example, organometallic complexes and chelate compounds are effective, and there are monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Others include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, phenol derivatives such as bisphenol.
[0224]
Moreover, the azo metal complex represented by the following general formula (6) is preferable.
[0225]
[Chemical 9]

[In the formula, M represents a coordination center metal, and examples thereof include Sc, Ti, V, Cr, Co, Ni, Mn, and Fe. Ar is an aryl group, and examples thereof include a phenyl group and a naphthyl group, which may have a substituent. Examples of the substituent in this case include a nitro group halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, and an alkoxy group. X, X ′, Y and Y ′ are —O—, —CO—, —NH— or —NR— (R is an alkyl group having 1 to 4 carbon atoms). K represents hydrogen, sodium, potassium, ammonium, or aliphatic ammonium. ]
In particular, Fe and Cr are preferable as the central metal, halogen, alkyl group, and anilide group are preferable as the substituent, and hydrogen, ammonium, and aliphatic ammonium are preferable as the counter ion.
[0226]
Alternatively, a basic organic acid metal complex represented by the following general formula (7) also gives negative chargeability and can be used in the present invention.
[0227]
Embedded image

[0228]
In the general formula (7), Fe, Al, Zn, Zr, and Cr are particularly preferable as the central metal, halogen, alkyl group, and anilide group are preferable as the substituent, and hydrogen, alkali metal, ammonium, and aliphatic are preferable as the counter ion. Group ammonium is preferred. A mixture of complex salts having different counter ions is also preferably used.
[0229]
As a method for adding the charge control agent to the developer, there are a method of adding the toner inside the toner particles and a method of adding it externally. The amount of these charge control agents used is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.
[0230]
In producing the toner particles according to the present invention, the constituent materials as described above are sufficiently mixed by a ball mill or other mixer, and then kneaded well using a heat kneader such as a heating roll, a kneader or an extruder, and cooled. There is a method for obtaining toner particles by solidifying and then performing surface treatment such as pulverization, classification, and toner shape adjustment as necessary.
[0231]
The processing for adjusting the shape of the toner particles includes a method in which the toner particles obtained by the pulverization method are dispersed in water or an organic solution and heated or swollen, a heat treatment method in which the toner particles pass through a hot air stream, and mechanical energy is applied. The mechanical impact method etc. which process is mentioned. As a means for applying a mechanical impact force, for example, a device such as a mechano-fusion system manufactured by Hosokawa Micron Co., Ltd. or a hybridization system manufactured by Nara Machinery Co., Ltd., the toner particles are pressed against the inside of the casing by centrifugal force with a high-speed rotating blade. And a method of applying a mechanical impact force to the toner particles by a force such as a compressive force or / and a frictional force.
[0232]
In the present invention, when performing a process of applying mechanical impact, the atmosphere temperature during the process is set to a temperature near the glass transition point Tg (Tg ± 30 ° C.) of the toner particles to prevent aggregation and improve productivity. It is preferable from the viewpoint. More preferably, the toner particles are spheroidized by thermomechanical impact at a temperature in the range of the glass transition point Tg ± 20 ° C. of the toner at the time of processing, so that the conductive fine powder works effectively. Is particularly effective.
[0233]
An example of a method for spheroidizing toner particles by repeatedly applying a thermomechanical impact force will be specifically described with reference to FIGS.
[0234]
6 is a schematic schematic configuration diagram showing the structure of a toner particle spheroidizing apparatus used in toner particle production examples 2 to 4 described later, and FIG. 7 is a schematic diagram showing the structure of the processing unit 1 in FIG. FIG.
[0235]
This toner particle spheroidizing apparatus spheroidizes toner particles by pressing the toner particles against the inside of the casing by centrifugal force with high-speed rotating blades, and repeatedly applying a thermomechanical impact force due to at least a compression force and a friction force. Is. As shown in FIG. 7, the processing unit I is provided with four rotating rotors 72a, 72b, 72c and 72d in the vertical direction. The rotary rotors 72a to 72d are rotated by rotating the rotary drive shaft 73 by the electric motor 84 so that the peripheral speed of the outermost edge portion is, for example, 100 m / sec. The number of rotations of the rotating rotors 72a to 72d at this time is, for example, 130 s.^-1It is. Further, the suction blower 85 (see FIG. 6) is operated to suck an air volume equal to or larger than the air flow rate generated by the rotation of the blades 79a to 79d provided integrally with the rotary rotors 72a to 72d. . Toner particles are sucked into the hopper 82 together with air from the feeder 86, and the introduced toner particles are introduced into the central portion of the first cylindrical processing chamber 89a through the powder supply pipe 81 and the powder supply port 80. The The toner particles are spheroidized by the blade 79a and the side wall 77 in the first cylindrical processing chamber 89a, and then the toner particles subjected to the spheroidizing process are a first portion provided in the central portion of the guide plate 78a. It passes through the powder discharge port 90 a and is introduced into the central portion of the second cylindrical processing chamber 89 b, and is further subjected to spheronization processing by the blade 79 b and the side wall 77.
[0236]
The toner particles spheroidized in the second cylindrical processing chamber 89b pass through the second powder discharge port 90b provided in the central portion of the guide plate 78b, and the central portion of the third cylindrical processing chamber 89c. And is subjected to a spheronization process by the blade 79c and the side wall 77, and further passes through a third powder discharge port 90c provided at the center part of the guide plate 78c to the center of the fourth cylindrical processing chamber 89d. The toner particles are introduced into the part, subjected to spheronization treatment by the blade 79d and the side wall 77, and further carried out from the carry-out pipe 93 through the third powder discharge port 90d provided in the central part of the guide plate 78d. The The air carrying the toner particles passes through the first to fourth cylindrical processing chambers 89 a to 89 d, passes through the carry-out pipe 93, the cyclone 91, the bag filter 92, and the suction blower 85. To be discharged.
[0237]
The toner particles introduced into the cylindrical processing chambers 89a to 89d are instantaneously subjected to a mechanical impact action by the blades 79a to 79d, and further collide with the side wall 77 to receive a mechanical impact force. Due to the rotation of the blades 79a to 79d having predetermined sizes respectively installed in the rotary rotors 72a to 72d, convection circulating from the central part to the outer periphery and from the outer periphery to the central part is generated in the space above the rotary rotor surface. The toner particles stay in the cylindrical processing chambers 89a to 89d and are subjected to a spheronization process. When the temperature of the toner particles rises to near the glass transition temperature of the binder resin constituting the toner particles due to the heat generated by the mechanical impact force, the toner particles are spheroidized by the thermomechanical impact force. The By passing through each of the cylindrical processing chambers 89a to 89d, the toner particles are continuously and efficiently spheroidized.
[0238]
The degree of toner particle spheroidization can be adjusted by the residence time and temperature of the toner particle spheroidizing unit, and specifically, the rotational speed, rotational speed, and blade height of the rotating rotor. The width and the number of sheets, the clearance between the outer periphery of the blade and the side wall, the suction air volume of the suction blower, the temperature of the toner particles when introduced into the spheroidizing unit, the temperature of the air that transports the toner particles, and the like.
[0239]
In addition, as a batch-type apparatus, it is one of preferable examples to use a hybridization system that is commercialized by Nara Machinery Co., Ltd.
[0240]
To control the shape of the toner particles obtained by the pulverization method, it is possible to select the toner particle constituent material such as a binder resin and appropriately set the conditions at the time of pulverization. If the degree of circularity is to be increased, the productivity tends to decrease, and it is preferable to set conditions for increasing the degree of circularity of the toner particles using a mechanical pulverizer.
[0241]
In the present invention, in order to keep the coefficient of variation of the particle size distribution of the toner particles low, it is preferable from the viewpoint of productivity to use a multi-division classifier in the classification process. In order to reduce the ultrafine particles of toner particles having a particle size range of 1.00 μm or more and less than 2.00 μm, it is preferable to use a mechanical pulverizer in the pulverization step.
[0242]
The developer according to the present invention can be produced by adding an external additive to the toner particles obtained as described above, mixing the mixture with a mixer, and passing the mixture through a sieve as necessary.
[0243]
As a production apparatus used when producing toner particles by a pulverization method, for example, as a mixer, Henschel mixer (manufactured by Mitsui Mining); Super mixer (manufactured by Kawata); Ribocorn (manufactured by Okawara Seisakusho); Mixers, turbulizers, cyclomixes (manufactured by Hosokawa Micron Corp.); spiral pin mixers (manufactured by Taiheiyo Kiko Co., Ltd.); ); Bus co-kneader (Buss); TEM type extruder (Toshiba Machine); TEX twin-screw kneader (Nihon Steel Works); PCM kneader (Ikegai Iron Works); Roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho); kneedex (manufactured by Mitsui Mining Co., Ltd.); MS pressure kneader, Nida Luder (manufactured by Moriyama Seisakusho); Banbury mixer (manufactured by Kobe Steel Co., Ltd.). Examples of pulverizers include counter jet mill, micron jet, inomizer (manufactured by Hosokawa Micron); Cross jet mill (manufactured by Kurimoto Iron Works Co., Ltd.); Urmax (manufactured by Hakko Engineering Co., Ltd.); SK Jet O Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Examples thereof include a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and among these, it is more preferable to use a mechanical pulverizer such as a kryptron or a turbo mill. Classifiers include: Classy, Micron Classifier, Spedic Classifier (manufactured by Seishin Enterprise); Turbo Classifier (manufactured by Nissin Engineering); Micron Separator, Turboplex (ATP), TSP Separator (manufactured by Hosokawa Micron) ; Elbow Jet (manufactured by Nippon Steel & Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Industry Co., Ltd.); YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.), etc. More preferred. As a sieving device used for sieving coarse particles, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Resonator Sheave, Gyroshifter (Tokuju Kosakusha Co., Ltd.); Vibrasonic System (Dalton Co., Ltd.); Soniclean (Shinto) (Industry company); Turbo screener (Turbo industry company); Micro shifter (Ogino industry company); Circular vibration sieve, etc.
[0244]
Examples of the additive used in the present invention for developing various properties are as follows.
[0245]
(1) As an abrasive, metal oxides such as strontium titanate, cerium oxide, aluminum oxide, magnesium oxide and chromium oxide; nitrides such as silicon nitride; carbides such as silicon carbide; calcium sulfate, barium sulfate and calcium carbonate And metal salts such as
[0246]
(2) Examples of the lubricant include fluorine resin powders such as polyvinylidene fluoride and polytetrafluoroethylene; silicone resin powders; fatty acid metal salts such as zinc stearate and calcium stearate.
[0247]
These additives are used in an amount of 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner particles. These additives may be used alone or in combination.
[0248]
<Developing device, process cartridge and image forming method>
Next, the developing device and the image forming method of the present invention that can suitably use the developer of the present invention will be described. The process cartridge of the present invention will also be described.
[0249]
The developing device of the present invention includes (I) a developer container for containing a developer, (II) a developer carrier for carrying the developer contained in the developer container and transporting the developer to a development area, And (III) at least a developer layer thickness regulating member for regulating the layer thickness of the developer carried on the developer carrying body.
[0250]
The image forming method of the present invention includes (I) a charging step for charging a latent image carrier, and (II) latent image formation for writing image information as an electrostatic latent image on a charging surface of the latent image carrier charged in the charging step. And (III) developing the electrostatic latent image using a developing device including a developer carrying member that carries the developer to a developing region facing the latent image carrying member while carrying the developer. A developing step for visualizing the developer image, (IV) a transferring step for transferring the developer image formed in the developing step to a transfer material, and (V) fixing the developer image transferred on the transfer material by a fixing means. This method includes a fixing step and repeats each of these steps to form an image.
[0251]
In the first aspect of the image forming method of the present invention, the charging step is a step of charging the latent image carrier with a charging unit, and charging is performed at a contact portion between the charging unit and the latent image carrier. The contact charging method is used in which the image carrier is charged by applying a voltage in the state where the conductive particles of the developer are present.
[0252]
According to a second aspect of the image forming method of the present invention, the developing step visualizes the electrostatic latent image, and after the developer image is transferred to the transfer material, the latent image on the latent image carrier. This is a step of collecting the developer remaining on the surface.
[0253]
That is, the image forming method according to the second aspect uses a so-called developing and cleaning method in which the developing step also serves as a step of collecting the developer remaining on the image carrier after the toner image is transferred to the transfer material. is there.
[0254]
The process cartridge of the present invention comprises a latent image carrier for carrying an electrostatic latent image, a charging means for charging the latent image carrier, and an electrostatic latent image formed on the image carrier. Development means for forming a developer image by developing using the developer of the present invention, and the developing device and the latent image carrier are integrated and detachable from the image forming apparatus main body. It has a configuration to be mounted.
[0255]
In a first aspect of the process cartridge of the present invention, the charging means is in contact with the latent image carrier, and a voltage is applied in a state where the conductive fine particles of the developer are interposed at the contact portion. The latent image carrier is charged by the contact charging method.
[0256]
According to a second aspect of the process cartridge of the present invention, the developing device visualizes the electrostatic latent image formed on the latent image carrier as a developer image by performing development using a developer. After the developer image is transferred to the transfer material, the developer remaining on the latent image carrier is collected.
[0257]
The developing means of the present invention includes at least a developer carrying member disposed to face the latent image carrying member and a developer layer regulating member for forming a thin developer layer on the developer carrying member. Preferably, the toner image is formed by transferring the developer from the developer layer on the developer carrier to the latent image carrier.
[0258]
Preferably, the developing unit includes at least a developer carrying member disposed to face the latent image carrying member and a developer layer regulating member that forms a thin developer layer on the developer carrying member. .
[0259]
Hereinafter, the developing device, the process cartridge, and the image forming method of the present invention will be described in detail.
[0260]
First, the charging step in the image forming method of the present invention is carried out by using a non-contact type charging device such as a corona charger as a charging means, or an image carrier that is a charged body. A conductive charging member (contact charging member / contact charger) such as a magnetic brush type or a blade type is brought into contact, and a predetermined charging bias is applied to the charging member (hereinafter referred to as “contact charging member”). The contact charging device charges the surface of the object to be charged to a predetermined polarity and potential. In the present invention, it is preferable to use a contact charging device having advantages such as low ozone and low power compared with a non-contact type charging device such as a corona charger.
[0261]
Further, the transfer residual toner particles on the latent image carrier may be those corresponding to the pattern of the image to be formed and those due to the so-called fog toner in a portion where no image is formed. Transfer residual toner particles corresponding to the pattern of the image to be formed are difficult to be completely recovered by development and cleaning. If the recovery is insufficient, poorly recovered toner particles appear as they are in the next formed image. A pattern ghost is generated. The transfer residual toner particles corresponding to such an image pattern can greatly improve the recoverability in developing and cleaning by leveling the pattern of the transfer residual toner particles. For example, if the development process is a contact development process, there is a relative speed difference between the movement speed of the developer carrier that carries the developer and the movement speed of the latent image carrier that is in contact with the developer carrier. As a result, the pattern of the residual toner particles can be leveled and the residual toner particles can be efficiently recovered. However, when a large amount of untransferred toner particles remain on the image carrier, such as when the power supply is interrupted or a paper jam occurs during image formation, image exposure is performed with a pattern in which the untransferred toner particles remain on the image carrier. Pattern ghosts for inhibiting latent image formation such as On the other hand, when a contact charging device is used, the transfer residual toner particles can be efficiently collected even if the development process is a non-contact development process by leveling the pattern of the transfer residual toner particles by the contact charging member. And generation of pattern ghosts due to poor collection can be prevented. In addition, even when a large amount of transfer residual toner particles remain on the latent image carrier, the contact charging member temporarily blocks the transfer residual toner particles, smoothes the pattern of the transfer residual toner particles, and gradually removes the transfer residual toner particles. By discharging onto the image carrier, pattern ghosting due to inhibition of latent image formation can be prevented. Regarding a decrease in chargeability of the latent image carrier due to contamination of the contact charging member when a large amount of transfer residual toner particles are blocked by the contact charging member, the use of the specific developer of the present invention allows the latent image carrier to It is possible to reduce the decrease in uniform chargeability to the extent that there is no practical problem. Also from this point, it is preferable to use a contact charging device in the present invention.
[0262]
In the present invention, it is preferable to provide a relative speed difference between the moving speed on the surface of the charging member and the moving speed on the surface of the latent image carrier. If a relative speed difference is provided between the moving speed on the surface of the charging member and the moving speed on the surface of the image carrier, a significant increase in torque between the contact charging member and the latent image carrier is obtained. In addition, although the surface of the latent image carrier is significantly scraped, the lubricating effect (friction reduction effect) is obtained by interposing a component of the developer in the contact portion between the contact charging member and the latent image carrier. It is possible to provide a speed difference without a significant increase in torque or significant wear.
[0263]
Moreover, it is preferable that the component of the developer interposed in the contact portion between the latent image carrier and the charging member that contacts the latent image carrier contains at least the above-described conductive fine powder. Furthermore, the content ratio of the conductive fine powder to the entire developer component intervening in the contact portion is equal to the conductive fine powder contained in the developer of the present invention (development before being used for image formation of the present invention). It is more preferable that the content ratio of the conductive fine powder) in the agent is higher. The component of the developer intervening in the contact portion contains at least conductive fine powder, so that a conduction path between the latent image carrier and the contact charging member is secured, and the transfer residual toner to the contact charging member. It is possible to suppress a decrease in uniform chargeability of the latent image carrier due to adhesion or mixing of particles. Further, since the content ratio of the conductive fine powder to the whole developer component interposed in the contact portion is higher than the content ratio of the conductive fine powder contained in the developer of the present invention, It is possible to more stably suppress a decrease in uniform chargeability of the latent image carrier due to adhesion or mixing of transfer residual toner particles. Further, by using the developer of the present invention, even when the relative charging speed of the contact charging member and the latent image carrier is relatively large in the charging portion, it exhibits excellent lubricity of 1.00 μm or more 2 By supplying the conductive fine powder containing a large amount of particles having a particle size range of less than 0.000 μm to the charging portion, it is possible to prevent the contact charging member and the latent image carrier from being scraped or scratched.
[0264]
The charging electrification bias applied to the contact charging member can obtain good chargeability of the latent image carrier even when only the DC voltage is applied. However, an alternating voltage (AC voltage) is superimposed on the DC voltage. Also good. As a waveform of such an alternating voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. The alternating voltage may be a pulse wave voltage formed by periodically turning on / off a DC power supply. Thus, a bias having a waveform whose voltage value periodically changes can be used as the alternating voltage.
[0265]
In the present invention, the charging bias applied to the contact charging member is preferably applied within a range that does not generate a discharge product. That is, it is preferably lower than the discharge start voltage between the contact charging member and the member to be charged (latent image carrier). Further, a charging method in which the direct injection charging mechanism is dominant is preferable.
[0266]
In the developing and cleaning method, the chargeability of the latent image carrier is reduced by the insulating transfer residual toner particles remaining on the latent image carrier contacting the contact charging member and adhering or mixing. In the charging method in which the toner image is dominant, since the toner layer adhering to the surface of the contact charging member becomes a resistance that inhibits the discharge voltage, the chargeability of the latent image carrier rapidly decreases. On the other hand, in the charging method in which the direct injection charging mechanism is dominant, the transfer residual toner particles adhering to or mixed in the contact charging member reduces the contact probability between the surface of the contact charging member and the object to be charged. The uniform charging property of the member to be charged (latent image carrier) is lowered, and this lowers the contrast and uniformity of the electrostatic latent image, thereby reducing the image density or increasing the fog. Based on the charge-reduction mechanism of the discharge charging mechanism and direct injection charging mechanism, the latent image carrier is formed by interposing a conductive fine powder at least at the contact portion between the latent image carrier and the charging member that contacts the image carrier. The effect of preventing the decrease in chargeability and the effect of promoting charging are more remarkable in the direct injection charging mechanism, and it is preferable to apply the developer of the present invention to the direct injection charging mechanism. That is, at least the conductive fine powder is interposed in the contact portion between the latent image carrier and the charging member that contacts the latent image carrier in the discharge charging mechanism, so that the transfer residual toner particles adhere to or mix with the contact charging member. In order to prevent the toner layer to be formed from becoming a resistance that inhibits the discharge voltage from the charging member to the latent image carrier, the contact portion between the latent image carrier and the charging member that contacts the latent image carrier and the vicinity thereof Therefore, the content ratio of the conductive fine powder to the entire developer component interposed in the charged region must be increased. Therefore, when a large amount of untransferred toner particles adhere to or mix with the contact charging member, the transfer remaining toner particles adhere or mix so that the toner layer attached to or mixed with the contact charging member does not become a resistance that inhibits the discharge voltage. In order to limit the amount, more transfer residual toner particles must be ejected onto the latent image carrier, which tends to hinder the formation of the latent image. On the other hand, in the direct injection charging mechanism, the conductive fine powder is easily interposed via the conductive fine powder by interposing at least the contact portion between the latent image carrier and the charging member in contact with the latent image carrier. The contact point between the contact charging member and the object to be charged can be secured, and the transfer residual toner particles adhering to or mixed in the contact charging member can be prevented from decreasing the contact probability between the contact charging member and the object to be charged, and the latent image is carried. A decrease in chargeability of the body can be suppressed.
[0267]
In particular, when a relative speed difference is provided between the moving speed on the surface of the contact charging member and the moving speed on the surface of the latent image carrier, the developer component interposed in the contact portion between the latent image carrier and the contact charging member The total amount is limited by the rubbing between the contact charging member and the latent image carrier, so that the charging inhibition of the latent image carrier is more reliably suppressed, and the contact portion between the contact charging member and the latent image carrier is conductive. By significantly increasing the chance of the conductive fine powder contacting the latent image carrier, it is possible to obtain a higher contact between the contact charging member and the latent image carrier, and the latent image carrying via the conductive fine powder. Direct injection to the body can be further promoted. On the other hand, the discharge charging is not performed at the contact portion between the latent image carrier and the contact charging member, but is performed in a region where the latent image carrier and the contact charging member are not in contact and have a minute gap. The effect of suppressing charging inhibition due to the restriction of the total amount of the developer component intervening in the toner cannot be expected.
[0268]
Also from this viewpoint, it is preferable to use a charging method in which the direct injection charging mechanism is dominant in the present invention, and the direct injection charging mechanism that does not depend on the discharge charging mechanism is dominant.
[0269]
In order to realize the charging method, the applied charging bias for the contact charging member is preferably lower than the discharge start voltage between the contact charging member and the member to be charged (latent image carrier).
[0270]
As a configuration for providing a relative speed difference between the moving speed on the surface of the contact charging member and the moving speed on the surface of the latent image carrier, it is preferable to provide a speed difference by rotationally driving the contact charging member.
[0271]
The moving direction on the surface of the charging member and the moving direction on the surface of the latent image carrier are preferably opposite to each other. That is, it is preferable that the charging member and the latent image carrier move in opposite directions. The contact charging member and the latent image carrier are moved in opposite directions to increase the effect of temporarily collecting and leveling the transfer residual toner particles on the latent image carrier carried by the contact charging member to the contact charging member. It is preferable. For example, it is desirable that the contact charging member is driven to rotate, and the rotation direction of the contact charging member rotates in the direction opposite to the moving direction of the surface of the latent image carrier. In other words, the transfer residual toner particles on the image carrier are once separated from the latent image carrier by reverse rotation and charged, so that direct injection charging can be performed preferentially and inhibition of latent image formation can be suppressed. Is possible. Furthermore, by increasing the effect of leveling the pattern of residual toner particles, it is possible to improve the recoverability of residual toner particles and more reliably prevent the occurrence of pattern ghosts due to poor recovery.
[0272]
It is also possible to cause the relative speed difference by moving the charging member in the same direction as the moving direction of the surface of the latent image carrier. However, since the chargeability of direct injection charging depends on the ratio of the moving speed of the latent image carrier and the relative moving speed of the charging member to the moving distance of the latent image carrier, the same relative moving speed ratio in the reverse direction is obtained. In the forward direction, since the moving speed of the charging member is higher than that in the reverse direction, it is advantageous in terms of moving speed to move the charging member in the reverse direction. In addition, it is advantageous to move the charging member in the direction opposite to the moving direction of the surface of the latent image carrier also in the effect of leveling the pattern of the residual toner particles.
[0273]
In the present invention, the ratio of the moving speed of the latent image carrier to the moving speed of the charging member (relative moving speed ratio) is preferably 10 to 500%, more preferably 20 to 400%. If the relative movement speed ratio is too smaller than the above range, the contact probability between the contact charging member and the latent image carrier cannot be increased sufficiently, and the chargeability of the latent image carrier by direct injection charging is not sufficient. It may be difficult to maintain. Further, charging of the latent image carrier is inhibited by limiting the amount of the conductive fine powder interposed in the contact portion between the latent image carrier and the contact charging member by rubbing between the contact charging member and the latent image carrier. In some cases, it is not possible to sufficiently obtain the effect of suppressing the toner and the effect of improving the recoverability of the developer in the development and cleaning by leveling the pattern of the residual toner particles. When the relative moving speed ratio is too larger than the above range, the moving speed of the charging member is increased. Therefore, the developer component held in the contact portion between the latent image carrier and the contact charging member is Contamination in the apparatus due to scattering tends to occur, and the latent image carrier and the contact charging member tend to wear or tend to cause scratches, resulting in a short life.
[0274]
When the moving speed of the charging member is 0 (the charging member is stationary), the contact point of the charging member with the latent image carrier becomes a fixed point, so that the charging member contacts the image carrier. This is not preferable because the effect of suppressing charging inhibition of the image carrier and the effect of leveling the pattern of residual toner particles and improving the recoverability of the developer during development and cleaning are likely to decrease.
[0275]
The relative movement speed ratio indicating the relative speed difference described here can be expressed by the following equation. Here, the moving speed of the charging member is Vc, the moving speed of the image carrier is Vp, and the moving speed of the charging member is the latent image when the surface of the charging member moves in the same direction as the surface of the latent image carrier at the contact portion. The value has the same sign as the moving speed of the carrier.
[0276]
Relative moving speed ratio (%) = | [(Vc−Vp) / Vp] × 100 |
In the present invention, the residual toner particles on the latent image carrier are temporarily collected on the charging member, the conductive fine powder is carried on the charging member, and a contact portion between the latent image carrier and the charging member is provided. In order to perform direct injection charging preferentially, it is preferable that the contact charging member has elasticity. The contact charging member preferably has elasticity in order to improve the recoverability of the transfer residual toner particles by leveling the pattern of the transfer residual toner particles with the contact charging member.
[0277]
In the present invention, the charging member is preferably conductive in order to charge the latent image carrier by applying a voltage to the charging member. Accordingly, the charging member is an elastic conductive roller, a magnetic brush contact charging member having a magnetic brush portion in which magnetic particles are magnetically constrained and contacting the magnetic brush portion with a member to be charged, or a brush made of conductive fibers. Is preferred. The charging member is preferably an elastic conductive roller or a conductive brush roller in that the configuration of the charging member can be simplified, and a developer component (for example, transfer residual toner particles or conductive material that adheres to or mixes with the charging member). In particular, the charging member is preferably an elastic conductive roller in that it can be stably held without scattering.
[0278]
If the hardness of the elastic conductive roller as the roller member is too low, the shape is not stable, so that the contact property with the charged body is deteriorated. Since the conductive fine powder scrapes or damages the surface layer of the elastic conductive roller, stable chargeability of the latent image carrier cannot be obtained. In addition, if the hardness is too high, not only a charged contact portion cannot be secured between the charged body but also the micro contact property to the surface of the charged body (latent image carrier) is deteriorated. Stable chargeability cannot be obtained. Furthermore, the effect of leveling the pattern of the residual toner particles is reduced, and the recoverability of the residual toner particles cannot be improved. Therefore, if the contact pressure of the elastic conductive roller to the latent image carrier is increased so that the charging contact portion and leveling effect can be sufficiently obtained, the contact charging member or the latent image carrier may be scraped or scratched. It becomes easy. From these viewpoints, the Asker C hardness of the elastic conductive roller as the roller member is preferably in the range of 20 to 50, more preferably in the range of 25 to 50, and still more preferably in the range of 25 to 40. . Here, Asker C hardness is a hardness measured using a spring type hardness meter Asker C (manufactured by Kobunshi Keiki Co., Ltd.) defined by JlSK6301. In the present invention, the load is 9.8 N and the measurement is performed in the form of a roller.
[0279]
In the present invention, the surface of the roller member as the contact charging member preferably has minute cells or irregularities in order to stably hold the conductive fine particles.
[0280]
In addition, it is important that the conductive elastic roller functions as an electrode having a sufficiently low resistance to charge the moving latent image carrier while at the same time providing elasticity to obtain sufficient contact with the latent image carrier. It is. On the other hand, when a latent part such as a pinhole exists in the latent image carrier, it is necessary to prevent voltage leakage. When a latent image carrier such as an electrophotographic photosensitive member is used as the member to be charged, the resistance of the conductive elastic roller is 10 to obtain sufficient chargeability and leakage resistance.³-10⁸Preferably, Ω · cm is 10⁴-10⁷More preferably, it is Ω · cm. The resistance of the conductive elastic roller is measured by applying 100V between the metal core and the aluminum drum in a state where the roller is pressed against a cylindrical aluminum drum with a diameter of 30 mm so that a contact pressure of 49 N / m is applied to the roller. can do.
[0281]
For example, the conductive elastic roller is manufactured by forming a middle resistance layer of rubber or foam as a flexible member on a cored bar. The medium resistance layer is formulated with resin (eg urethane), conductive particles (eg carbon black), sulfiding agent, foaming agent, etc., and is formed into a roller shape on the core metal, then cut as necessary and polished the surface Thus, the shape of the conductive elastic roller can be adjusted.
[0282]
The material of the conductive elastic roller is not limited to the elastic foam. The elastic material is ethylene-propylene-diene polyethylene (EPDM), urethane, butadiene acrylonitrile rubber (NBR), silicone rubber or isoprene rubber. For example, a conductive material such as carbon black or a metal oxide can be dispersed for resistance adjustment, and those obtained by foaming these materials can be used. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance or in combination with the conductive substance.
[0283]
The conductive elastic roller is disposed in contact with the latent image carrier, which is a member to be charged, with a predetermined pressing force against elasticity, and is a contact portion between the conductive elastic roller and the latent image carrier. A charging contact is formed. The width of the charging contact portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain a stable and close adhesion between the conductive elastic roller and the latent image carrier. preferable.
[0284]
The charging member used in the charging step of the present invention may be one that charges the image carrier by applying a voltage to a brush (brush member) made of conductive fibers. As such a charging brush as a contact charging member, a conductive brush dispersed in a conductive material can be used. As the fiber, generally known fibers can be used, and examples thereof include nylon, acrylic, rayon, polycarbonate, and polyester. As the conductive material, generally known materials can be used. For example, a conductive metal such as nickel, iron, aluminum, gold, silver, or iron oxide, zinc oxide, tin oxide, antimony oxide, titanium oxide. Examples thereof include conductive metal oxides such as these, and conductive powders such as carbon black. These conductive materials may be subjected to surface treatment for the purpose of hydrophobization and resistance adjustment as necessary. In use, the conductive material is appropriately selected and used in consideration of dispersibility with fibers and productivity.
[0285]
The charging brush as the contact charging member includes a fixed type and a rotatable roll type. As a roll-shaped charging brush, for example, there is a roll brush in which a tape made of conductive fibers in a pile is wound around a metal core in a spiral shape. The conductive fiber has a fiber thickness of 1 to 20 denier (fiber diameter of about 10 to 500 μm), a brush fiber length of 1 to 15 mm, and a brush density of 10,000 to 300,000 per square inch (1 square meter) 1.5 × 10 per⁷~ 4.5 × 10⁸The book) is preferably used.
[0286]
It is preferable to use a charging brush having as high a brush density as possible, and it is also preferable to make one fiber from several to several hundreds of fine fibers. For example, it is possible to bundle 50 fine fibers of 300 denier, such as 300 denier / 50 filament, and plant the fibers as one fiber. However, in the present invention, the charging point for direct injection charging is mainly determined by the charged contact portion between the charging member and the latent image carrier and the density of the conductive fine powder in the vicinity thereof. Therefore, the range of selection of the charging member is widened.
[0287]
The resistance value of the charging brush is 10 in order to obtain sufficient chargeability and leakage resistance of the image bearing member, as in the case of the elastic conductive roller.³-10⁸It is preferably Ω · cm, more preferably 10⁴-10⁷Ω · cm.
[0288]
As materials for the charging brush, conductive rayon fibers REC-B, REC-C, REC-M1, and REC-M10 manufactured by Unitika Co., Ltd., SA-7 manufactured by Toray Industries, Inc., Nippon Kashige Co., Ltd. There are Sanderlon made by Kanebo, Beltron made by Kanebo, Kuraray made by Kuraray Co., Ltd., carbon dispersed in rayon, and Roval made by Mitsubishi Rayon Co., Ltd. REC-B, REC in terms of environmental stability. It is particularly preferable to use -C, REC-M1, or REC-M10.
[0289]
In addition, the flexibility of the contact charging member increases the chance that the conductive fine powder contacts the latent image carrier at the contact portion between the contact charging member and the latent image carrier, thereby increasing the contactability. It is preferable in that it can be obtained and the direct injection chargeability is improved. That is, the contact charging member is in close contact with the latent image carrier via the conductive fine powder, and the conductive fine powder existing at the contact portion between the contact charging member and the latent image carrier is spaced from the surface of the latent image carrier. By sliding and rubbing, the latent image carrier is charged by the contact charging member, and stable and safe direct injection charging via conductive fine powder that does not use a discharge phenomenon is dominant. Therefore, by applying direct injection charging through conductive fine powder, high charging efficiency that cannot be obtained by roller charging by conventional discharge charging or the like can be obtained, which is almost equal to the voltage applied to the contact charging member. An electric potential can be applied to the latent image carrier. Further, since the contact charging member has flexibility, when a large amount of transfer residual toner particles are supplied to the contact charging member, the effect of temporarily blocking the transfer residual toner particles and the transfer residual toner particles By increasing the effect of leveling the pattern, it is possible to more reliably prevent the occurrence of image defects due to the latent image formation inhibition and transfer residual toner particle collection failure.
[0290]
If the amount of the conductive fine powder intervened at the contact portion between the latent image carrier and the contact charging member is too small, the lubricating effect of the conductive fine powder cannot be sufficiently obtained, and the friction between the latent image carrier and the contact charging member will not be obtained. Therefore, it becomes difficult to rotationally drive the contact charging member with a speed difference with respect to the latent image carrier. That is, if the amount of the conductive fine powder is small, the driving torque becomes excessive, and if it is forcibly rotated, the surfaces of the contact charging member and the latent image carrier are easily scraped. Further, the effect of increasing the contact opportunity due to the conductive fine powder may not be sufficiently obtained, and the good charging performance of the latent image carrier may not be obtained. On the other hand, if the amount of the conductive fine powder intervened in the contact portion is too large, the drop of the conductive fine powder from the contact charging member increases remarkably, causing latent image formation inhibition such as shading of image exposure and image formation. It is easy to be adversely affected.
[0291]
According to the study by the present inventors, the amount of conductive fine powder interposed at the contact portion between the latent image carrier and the contact charging member is 10³Piece / mm²Preferably, it is 10 or more.⁴Piece / mm²More preferably. The amount of inclusion of this conductive fine powder is 10³Piece / mm²As described above, the driving torque does not become excessive, and the lubricating effect by the conductive fine powder can be sufficiently obtained. Intervening amount is 10³Piece / mm²If it is much lower, sufficient desired contact opportunity increase effect cannot be obtained, and the chargeability of the image carrier tends to be lowered.
[0292]
In addition, when the direct injection charging method is applied as uniform charging of the latent image carrier in development and cleaning image formation, the chargeability of the latent image carrier is reduced due to adhesion or mixing of transfer residual toner particles to the charging member. Is concerned. To suppress the adhesion and mixing of the transfer residual toner particles to the charging member, or to overcome the charging inhibition of the latent image carrier due to the adhesion or mixing of the transfer residual toner particles to the charging member and perform good direct injection charging The amount of conductive fine powder intervened at the contact portion between the image carrier and the contact charging member is 10⁴Piece / mm²The above is preferable. Intervening amount is 10⁴Piece / mm²If it is much lower, the chargeability of the latent image carrier tends to be lowered when there are many untransferred toner particles.
[0293]
The appropriate range of the amount of conductive fine powder present on the latent image carrier in the charging process is to apply the conductive fine powder to the latent image carrier at a certain density so that the latent image carrier is uniformly charged. It is also determined by whether sexual effects can be obtained.
[0294]
Needless to say, at the time of charging the latent image carrier, contact charging more uniform than at least the recording resolution is required. However, as shown in the graph showing the visual characteristics of the human eye in FIG. 3, when the spatial frequency is 10 cycles / mm or more, the number of identification gradations on the image approaches 1 without limit, that is, density unevenness cannot be identified. If this characteristic is utilized positively, when conductive fine powder is deposited on the latent image carrier, the conductive fine powder is present at least at a density of 10 cycles / mm or more on the image carrier, and direct injection charging is performed. You can do it. Even if a micro charge failure occurs on the latent image carrier in the absence of the conductive fine powder, the density unevenness on the image caused by the charge failure is in a spatial frequency region that exceeds human visual characteristics. Since this occurs, there is no problem on the image.
[0295]
When the coating density of the conductive fine powder on the latent image carrier is changed, whether or not the charging failure as density unevenness is recognized on the image is as long as the conductive fine powder is applied even slightly. (For example, 10 pieces / mm²), Which is effective in suppressing the occurrence of charging unevenness, but is still insufficient in terms of whether density unevenness on the image is acceptable to humans. However, the coating amount is 10²Piece / mm²In this way, a favorable result can be obtained rapidly in the objective evaluation of the image. Furthermore, the coating amount is 10³Piece / mm²By increasing the above, there is no problem on the image due to the charging failure.
[0296]
Charging by the direct injection charging method is fundamentally different from the discharge charging method, and charging is performed by reliably contacting the charging member to the object to be charged, but even if the conductive fine powder is placed on the image carrier. Even if it is applied excessively, there is always a part that cannot be contacted. However, this problem is practically solved by applying the conductive fine powder that positively utilizes the human visual characteristics of the present invention.
[0297]
The upper limit of the amount of the conductive fine powder existing on the latent image carrier is until the conductive fine powder is uniformly coated on the latent image carrier, and even if more than that is applied. The effect is not improved, and conversely, excessive conductive fine powder is discharged after the charging step, thereby causing an adverse effect such as blocking or scattering the exposure light source.
[0298]
The upper limit of the coating density varies depending on the particle size of the conductive fine powder and the holding property of the conductive fine powder of the contact charging member. However, the upper limit can be the amount by which one layer is uniformly coated on the image carrier.
[0299]
The abundance of the conductive fine powder on the latent image carrier depends on the particle size of the conductive fine powder, but is 5 × 10.⁵Piece / mm²In the case of exceeding the above, the drop of the conductive fine powder from the latent image carrier tends to increase remarkably, contaminating the inside of the image forming apparatus, and to the latent image carrier regardless of the light transmittance of the conductive fine powder itself. Insufficient exposure may occur. This abundance is 5 × 10⁵Piece / mm²If it is below, the amount of dropped particles can be kept low, reducing contamination in the apparatus due to scattering of conductive fine powder and improving exposure inhibition.
[0300]
Furthermore, in the development and cleaning process, an experiment was conducted on the effect of improving the recoverability of transfer residual toner particles due to the amount of conductive fine powder present on the latent image carrier. The amount of conductive fine powder present above is 10²Piece / mm²Exceeds the case where the conductive fine powder does not exist on the latent image carrier, the recovery of the transfer residual toner particles is clearly improved, and the conductive fine powder is uniformly deposited on the latent image carrier. An image obtained by developing and cleaning free from image defects to the extent of application was obtained. As in the case of the abundance of the conductive fine powder on the latent image carrier after the charge after the transfer, the abundance of the conductive fine powder is 5 × 10 5.⁵Piece / mm²From around this point, the detachment of the conductive fine powder from the latent image bearing member gradually became remarkable, and the tendency to affect the latent image formation and increase the fog was observed.
[0301]
That is, the amount of conductive fine powder intervened at the contact portion between the latent image carrier and the contact charging member is 10.³Piece / mm²The amount of conductive fine powder present on the latent image carrier is set to 10²Piece / mm²5 × 10⁵Piece / mm²Is set so as not to greatly exceed the image quality, the chargeability of the latent image carrier is good, the recoverability of transfer residual toner particles is good, and an image free from image defects due to contamination in the apparatus or exposure inhibition is formed. It is preferable for this purpose. The amount of conductive fine powder intervening at the contact portion between the latent image carrier and the contact charging member is 10⁴Piece / mm²It is more preferable to set the above.
[0302]
The relationship between the amount of conductive fine powder interposed at the contact portion between the latent image carrier and the contact charging member and the amount of conductive fine powder present on the latent image carrier in the latent image forming step is as follows: (1) Latent image Supply amount of conductive fine powder to contact portion between carrier and contact charging member, (2) Adhesion of conductive fine powder to latent image carrier and contact charging member, (3) Conductivity of contact charging member Since there are factors such as retention of fine powder and (4) retention of the latent image carrier with respect to conductive fine powder, it is not generally determined. Experimentally, the amount of conductive fine powder interposed at the contact portion between the latent image carrier and the contact charging member is 10³-10⁶Piece / mm²In this range, the amount of particles dropped on the latent image carrier (the amount of conductive fine powder on the latent image carrier in the latent image forming step) is 10²-10⁵Piece / mm²Met.
[0303]
A method for measuring the amount of conductive fine powder present at the charging contact portion and the amount of conductive fine powder present on the latent image carrier in the latent image forming step will be described. It is preferable to directly measure the amount of conductive fine powder intervening in the charging part at the contact surface part of the contact charging member and the latent image carrier, but the moving direction of the surface of the contact charging member forming the contact part is the latent image carrier. When the moving direction of the body surface is opposite, most of the particles existing on the latent image carrier before contacting the contact charging member are peeled off by the contacting charging member while moving in the opposite direction. In the present invention, the amount of particles on the surface of the contact charging member immediately before reaching the contact surface portion is used as the intervening amount. Specifically, the rotation of the image carrier and the elastic conductive roller is stopped in a state where no charging bias is applied, and the surface of the latent image carrier and the elastic conductive roller is displayed on the video microscope (OVM1000N manufactured by OLYMPUS) and the digital still recorder. Take a picture with (DELTA 3 SR-3100). With respect to the elastic conductive roller, the elastic conductive roller is brought into contact with the slide glass under the same conditions as in contact with the image carrier. I have taken the above. In order to separate individual particles from the obtained digital image, binarization processing is performed with a certain threshold value, and the number of regions where particles are present is measured using desired image processing software. Further, the abundance on the latent image carrier is also measured by photographing the image carrier with the same video microscope and performing the same processing.
[0304]
The abundance of the conductive fine powder on the latent image carrier is measured using image processing software by photographing the latent image carrier before transfer and before charging and after development using the same means as described above.
[0305]
In the present invention, the volume resistance of the outermost surface layer of the latent image carrier is 1 × 10.⁹~ 1x10¹⁴Ω · cm, more preferably 1 × 10¹⁰~ 1x10¹⁴It is preferable that the resistance is Ω · cm because it can provide better chargeability of the latent image carrier. In the charging method using direct injection of charges, charges can be exchanged more efficiently by reducing the resistance on the charged object side. For this purpose, the volume resistance of the outermost layer is 1 × 10¹⁴It is preferable that it is below Ω · cm. On the other hand, in order to hold an electrostatic latent image as a latent image carrier for a certain period of time, the volume resistance value of the outermost surface layer is 1 × 10.⁹It is preferable that it is Ω · cm or more. In order to hold an electrostatic latent image without being disturbed by a minute latent image even in a high humidity environment, the resistance value is 1 × 10.¹⁰It is preferable that it is Ω · cm or more.
[0306]
Further, the latent image carrier is an electrophotographic photosensitive member, and the volume resistance of the outermost surface layer of the electrophotographic photosensitive member is 1 × 10.⁹~ 1x10¹⁴By being Ω · cm, it is more preferable because sufficient chargeability can be imparted to the image carrier even in an apparatus having a high process speed.
[0307]
The latent image carrier is amorphous selenium, CdS, ZnO.₂A photosensitive drum or a photosensitive belt having a photoconductive insulating material layer such as amorphous silicon or an organic photosensitive material is preferable, and an amorphous silicon photosensitive layer or a photosensitive member having an organic photosensitive layer is particularly preferably used.
[0308]
The organic photosensitive layer may be a single layer type in which the photosensitive layer contains a charge generation material and a material having charge transport performance in the same layer, or may be a function-separated type photosensitive layer having a charge transport layer and a charge generation layer. good. A laminated photosensitive layer having a structure in which a charge generation layer and then a charge transport layer are laminated in this order on a conductive substrate is one preferred example.
[0309]
By adjusting the surface resistance of the latent image carrier, the latent image carrier can be more stably and uniformly charged.
[0310]
For the purpose of making charge injection more efficient or accelerating by adjusting the surface resistance of the latent image carrier, it is also preferable to provide a charge injection layer on the surface of the electrophotographic photosensitive member. The charge injection layer preferably has a form in which conductive fine particles are dispersed in a resin.
[0311]
As a form of providing the charge injection layer, for example,
(I) A charge injection layer is provided on an inorganic photoreceptor such as selenium or amorphous silicon or a single layer organic photoreceptor.
(Ii) As a charge transport layer of a function-separated organic photoreceptor, a layer having a surface layer having a charge transport agent and a resin also serves as a charge injection layer (for example, a charge transport agent in a resin as a charge transport layer) And the conductive particles are dispersed, or the charge transport layer has a function as a charge injection layer depending on the charge transport agent itself or its presence state)
(Iii) A charge injection layer is provided as the outermost surface layer on the function-separated organic photoconductor, but it is important that the volume resistance of the outermost surface layer is in a preferable range.
[0312]
The charge injection layer is composed of, for example, an inorganic material layer such as a metal vapor deposition film, or a conductive powder dispersed resin layer in which conductive fine particles are dispersed in a binder resin. The layer is formed by coating by an appropriate coating method such as a dipping coating method, a spray coating method, a roll coating method, or a beam coating method.
[0313]
Further, it may be constituted by mixing or copolymerizing a resin having high light-transmitting ionic conductivity with an insulating binder, or may be constituted by a single resin having medium resistance and photoconductivity.
[0314]
Among these, it is preferable that the outermost surface layer of the latent image carrier is a resin layer in which conductive fine particles made of at least a metal oxide (hereinafter referred to as “oxide conductive fine particles”) are dispersed. In other words, by configuring the outermost surface layer of the image bearing member in this way, the surface resistance of the electrophotographic photosensitive member can be reduced to transfer charges more efficiently, and the surface resistance can be reduced. Thus, it is preferable because blurring or flow of the latent image due to diffusion of the latent image charge can be suppressed while the image carrier holds the electrostatic latent image.
[0315]
In the case of the resin layer in which the oxide conductive fine particles are dispersed, it is preferable that the particle diameter of the oxide conductive fine particles is smaller than the wavelength of the incident light in order to prevent scattering of incident light by the dispersed particles. Accordingly, the particle diameter of the oxide conductive fine particles to be dispersed is preferably 0.5 μm or less. The content of the oxide conductive fine particles is preferably 2 to 90% by mass, and more preferably 5 to 70% by mass with respect to the total mass of the outermost layer. When the content of the oxide conductive fine particles is too smaller than the above range, it is difficult to obtain a desired volume resistance value. Also, if the content is too much above the above range, the film strength will decrease, so the charge injection layer will be easily scraped off, the life of the photoreceptor tends to be shortened, and the resistance will be too low. As a result, an image defect is likely to occur due to the flow of the latent image potential.
[0316]
The layer thickness of the charge injection layer is preferably 0.1 to 10 μm, more preferably 5 μm or less for obtaining the sharpness of the latent image, and 1 μm or more from the viewpoint of durability of the charge injection layer. It is more preferable that
[0317]
The binder of the charge injection layer can be the same as the binder of the lower layer, but in this case, the coating surface of the lower layer (for example, the charge transport layer) may be disturbed when the charge injection layer is applied. Therefore, it is necessary to select a formation method in particular.
[0318]
The method for measuring the volume resistance value of the outermost surface layer of the latent image carrier in the present invention comprises the same composition as that of the outermost surface layer of the image carrier on a polyethylene terephthalate (PET) film having gold deposited on the surface. A layer is prepared, and this is measured by applying a voltage of 100 V in an environment of a temperature of 23 ° C. and a humidity of 65% with a volume resistance measuring device (4140BpAMATOR manufactured by Hewlett-Packard Company).
[0319]
In the present invention, it is preferable to impart releasability to the surface of the latent image carrier, and the contact angle of water on the surface of the latent image carrier is preferably 85 degrees or more. More preferably, the contact angle of the latent image carrier surface with respect to water is 90 degrees or more.
[0320]
The fact that the surface of the latent image carrier has a high contact angle indicates that the surface of the latent image carrier has a high releasability with respect to the toner particles. This effect improves the developer recovery efficiency in the development and cleaning process. In addition, since the amount of residual toner particles can be significantly reduced, it is possible to suppress a decrease in chargeability of the latent image carrier due to residual toner particles.
[0321]
As a means for imparting releasability to the surface of the latent image carrier, for example,
(1) A resin having a low surface energy is used for the resin itself constituting the film.
(2) Add additives that impart water repellency and lipophilicity.
(3) A material having high releasability is dispersed in powder form.
Is mentioned.
[0322]
(1) is achieved by introducing a fluorine-containing group or a silicone-containing group into the resin structure. As (2), a surfactant may be added as an additive. Examples of (3) include the use of a compound containing a fluorine atom such as polytetrafluoroethylene, polyvinylidene fluoride and carbon fluoride, a silicone resin or a polyolefin resin.
[0323]
By these means, the contact angle of the surface of the latent image carrier with water can be 85 degrees or more.
[0324]
Among these, it is preferable that the outermost surface layer of the latent image carrier is a layer in which lubricant fine particles made of at least one material selected from at least a fluorine resin, a silicone resin, or a polyolefin resin are dispersed. In particular, it is preferable to use a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride. In the present invention, when the fluorine-containing resin is used as the releasable powder as the powder (3), the dispersion to the outermost surface layer is preferable.
[0325]
In order to contain these powders on the surface, a layer in which the powder is dispersed in a binder resin is provided on the outermost surface of the photoreceptor, or an organic photoreceptor that is originally composed mainly of a resin. For example, the powder may be dispersed in the outermost surface layer without providing a new surface layer.
[0326]
The addition amount of the powder having releasability to the surface layer of the latent image carrier is preferably 1 to 60% by mass, and 2 to 50% by mass with respect to the total mass of the surface layer. Is more preferable. If the addition amount is too smaller than the above range, the transfer residual toner particles are not sufficiently reduced, and the developer recovery efficiency in the developing and cleaning device is not sufficient. If the addition amount is too larger than the above range, the strength of the film is lowered, or the amount of incident light on the photosensitive member is remarkably lowered to impair the chargeability of the image carrier. The particle size of the powder is preferably 1 μm or less from the viewpoint of image quality, more preferably 0.5 μm or less, and if the particle size is too large, the line breaks due to scattering of incident light. Tends to deteriorate and resolution tends to be impaired.
[0327]
In the present invention, pure water was used for the measurement of the contact angle, and the device used was a contact angle meter CA-DS manufactured by Kyowa Interface Science Co., Ltd.
[0328]
One preferred embodiment of the photoreceptor as a latent image carrier used in the present invention will be described below. As the conductive substrate, a cylindrical shape of a metal such as aluminum or stainless steel; a plastic having a coating layer of aluminum alloy or indium oxide-tin oxide alloy; paper or plastic impregnated with conductive particles; plastic having a conductive polymer; Cylinders and films are used.
[0329]
On these conductive substrates, for the purpose of improving the adhesion of the photosensitive layer, improving the coating property, protecting the substrate, coating defects on the substrate, improving the charge injection from the substrate, or protecting the photosensitive layer from electrical breakdown. An undercoat layer may be provided.
[0330]
Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, Formed by a material such as polyurethane or aluminum oxide. The thickness of the undercoat layer is usually 0.1 to 10 μm, preferably 0.1 to 3 μm.
[0331]
The charge generation layer is composed of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes or selenium or amorphous silicon. A charge generating material such as an inorganic material is dispersed in an appropriate binder and applied, or formed by vapor deposition. Of these, phthalocyanine pigments are preferred for adjusting the sensitivity of the photoreceptor to a sensitivity suitable for the present invention. Examples of the binder include polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicone resin, epoxy resin, and vinyl acetate resin. The amount of the binder contained in the charge generation layer is 80% by mass or less, preferably 0 to 40% by mass. The thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.
[0332]
The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin as required, and coating, and the film thickness is generally 5 to 40 μm. Examples of the charge transport material include polycyclic aromatic compounds such as biphenylene, anthracene, pyrene and phenanthrene in the main chain or side chain; nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole and pyrazoline; hydrazone compound; styryl compound; Selenium; selenium-tellurium; amorphous silicon; cadmium sulfide.
[0333]
Examples of binder resins for dispersing these charge transport materials include polycarbonate resins, polyester resins, polymethacrylic acid esters, polystyrene resins, acrylic resins and polyamide resins; organic photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene. A functional polymer.
[0334]
As the surface layer, a layer in which conductive fine particles are dispersed in a resin may be provided in order to make charge injection more efficient or promote. As the resin for the surface layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or curing agents for these resins may be used alone or in combination of two or more. Examples of the conductive fine particles include metals and metal oxides. Preferably, there are ultrafine particles of zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide-coated titanium oxide, tin-coated indium oxide, antimony-coated tin oxide or zirconium oxide. These may be used alone or in combination of two or more.
[0335]
FIG. 5 is a model diagram of the layer structure of a latent image carrier (photoconductor) provided with a charge injection layer as a surface layer. In other words, the photoreceptor is a general organic photoreceptor in which a conductive layer 12, a positive charge injection preventing layer 13, a charge generation layer 14, and a charge transport layer 15 are coated on a conductive substrate (aluminum drum substrate) 11 in this order. By applying the charge injection layer 16 to the drum, the charging performance by charge injection is improved.
[0336]
The important point as the charge injection layer 16 formed on the outermost surface layer of the latent image carrier is that the volume resistance value of the surface layer is 1 × 10 5.⁹~ 1x10¹⁴It is in the range of Ω · cm. Even when the charge injection layer 16 is not provided as in the present configuration, for example, when the charge transport layer 15 which is the outermost layer of the latent image carrier is in the above resistance range, the same effect can be obtained. For example, the volume resistance of the surface layer is about 10¹³Even when an amorphous silicon photoconductor of Ω · cm or the like is used, good chargeability by charge injection can be obtained similarly.
[0337]
In the present invention, the latent image forming step and the latent image forming means for forming an electrostatic latent image on the charging surface of the latent image carrier write image information as an electrostatic latent image on the surface of the latent image carrier by image exposure. Processes and image exposure means are preferred. The image exposure means for forming the electrostatic latent image is not limited to the laser scanning exposure means for forming a digital latent image, and other light emitting elements such as normal analog image exposure and LEDs may be used. It does not matter as long as it can form an electrostatic latent image corresponding to image information, such as a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter.
[0338]
The latent image carrier may be an electrostatic recording dielectric. In this case, the dielectric surface as the surface of the image carrier is first charged uniformly to a predetermined polarity and potential, and then selectively neutralized by a neutralizing means such as a static elimination needle head or an electron gun to obtain a target electrostatic latent image. Write form.
[0339]
As described above, the developer of the present invention preferably has an average circularity of less than 0.970 from the viewpoint of retaining external additives on the toner surface for preventing toner deterioration. However, when the circularity of the toner is low, the charge amount becomes insufficient, and the transfer efficiency tends to be lowered. Furthermore, even if the particle size of the conductive fine particles added to the toner particles is skillfully adjusted, it is often impossible to completely prevent the reduction in the frictional charging characteristics of the toner particles. Therefore, when using a toner having such an average circularity of less than 0.970 and externally added conductive fine particles, it is necessary to improve the charge imparting property by the developer carrier.
[0340]
Therefore, in the present invention, the developer carrying member includes a substrate and a resin coating layer formed on the substrate, and a resin coating layer containing a positively charged substance is used. . Further, in order to prevent overcharging of the developer and optimize the charge amount, it is preferable that the resin coating layer contains at least a conductive substance, and the resin coating layer is a conductive resin coating layer. .
[0341]
As the binder resin for the coating layer of the developer carrying member used in the present invention, generally known resins can be used. For example, thermoplastic resins such as styrene resins, vinyl resins, styrene-diene resins, polyethersulfone resins, polycarbonate resins, polyphenylene oxide resins, polyamide resins, fluororesins, fiber resins, acrylic resins, and epoxy resins A thermosetting or photocurable resin such as a polyester resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin, or a polyimide resin can be used. Among these, those having excellent releasability such as silicone resin and fluorine resin, or polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, phenol resin, polyester resin, polyurethane resin, styrene resin, acrylic It is more preferable to use a resin having excellent mechanical properties such as a resin.
[0342]
It is also preferable to add a positively chargeable substance to these known binder resins.
[0343]
The positively chargeable substance may be any substance that is positively charged when mixed with iron powder and triboelectrically charged. In addition, if positive charge is exhibited in the binder resin for the coating layer to be dispersed, when used in combination with such a resin, it is not always positive when mixed with iron powder alone and triboelectrically charged. It is not always charged.
[0344]
Examples of such positively chargeable substances include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, guanidine derivatives, imidazole derivatives, amine-based and polyamine-based compounds that are generally used as positive charge control agents; synthesis Inorganic powders such as silica, quartz powder, alumina, hydrotalcite compounds; copolymers having sulfonic acid group-containing acrylamide as a constituent monomer. There is also a method in which an aminosilane coupling agent is treated with these inorganic fine powders.
[0345]
Among these, the following compounds are preferably used in order to satisfactorily charge the developer.
[0346]
(1) As the positively chargeable substance, the coating layer preferably contains a nitrogen-containing heterocyclic compound.
[0347]
As the nitrogen-containing heterocyclic compound used in this case, one having a number average particle diameter of preferably 20 μm or less, more preferably 0.1 to 15 μm is used. That is, when the number average particle diameter of the nitrogen-containing heterocyclic compound exceeds 20 μm, poor dispersion of the nitrogen-containing heterocyclic compound in the conductive resin coating layer constituting the developing sleeve occurs, and the effect of improving the charging performance is sufficient. It is difficult to obtain it.
[0348]
Examples of nitrogen-containing heterocyclic compounds that can be used in the present invention include imidazole, imidazoline, imidazolone, pyrazoline, pyrazole, pyrazolone, oxazoline, oxazole, oxazolone, thiazoline, thiazole, thiazolone, selenazoline, selenazole, selenazolone, oxadiazole, thiadiazole, Tetrazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, benzoselenazole, pyrazine, pyrimidine, pyridazine, triazine, oxazine, thiazine, tetrazine, polyazaine, pyridazine, pyrimidine, pyrazine, indole, isoindole, indazole, carbazole, quinoline , Pyridine, isoquinoline, cinnoline, quinazoline, quinoxaline, phthalazine, purine, Lumpur, triazole, include compounds such as phenazine. In the present invention, an imidazole compound is particularly preferable because it promotes the effect of the interaction between the developer carrying member used in the present invention and the toner.
[0349]
In the present invention, among imidazole compounds, in particular, if an imidazole compound represented by the following general formula (1) or (2) is used for the conductive resin coating layer of the developer carrier, rapid and uniform charging of the toner is performed. The imparting ability can be given, and furthermore, the strength of the conductive resin coating layer can be increased, which is more preferable.
[0350]
Embedded image

[Wherein R₁And R₂Represents a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group;₁And R₂May be the same or different. R₃And R₄Represents a linear alkyl group having 3 to 30 carbon atoms, and R₃And R₄May be the same or different. ]
[0351]
Embedded image

[Wherein R₅And R₆Represents a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group;₅And R₆May be the same or different. R₇Represents a linear alkyl group having 3 to 30 carbon atoms. ]
The reason why it is preferable to use the imidazole compound having the above structure is that the imidazole compound having the structure represented by the general formula (1) or (2) is a linear alkyl group having 3 to 30 carbon atoms as a substituent. Therefore, the dispersibility to the binder resin for the coating layer is good, so that it is well dispersed with other constituent materials of the conductive resin coating layer of the developing sleeve, and the conductive resin coating layer surface in a particularly excellent dispersion state As a result, it is considered that the triboelectric charging characteristic of the developing sleeve with respect to the toner becomes better.
[0352]
The nitrogen-containing heterocyclic compound such as an imidazole compound having the structure represented by the general formula (1) or (2) that can be preferably used in the present invention has a monocyclic ring. It may be condensed with other groups or may be substituted. Furthermore, when the heterocyclic group that is preferably used in the present invention is substituted, the substituent includes, for example, an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an alkoxy group. , Aryl group, substituted amino group, ureido group, urethane group, aryloxy group, sulfamoyl group, carbamoyl group, alkyl or arylthio group, alkyl or arylsulfonyl group, alkyl or arylsulfinyl group, hydroxy group, halogen atom, cyano group, Those having a sulfo group, an aryloxycarbonyl group, an acyl group, an alkoxycarbonyl group, an acyloxy group, a carbonamido group, a sulfonamido group, a carbosil group, a phosphoric acid amide group, a diacylamino group, an imide group, and the like can be used. These substituents may further have a substituent. As an example of the substituent in that case, the substituent mentioned above as a substituent of a nitrogen-containing heterocyclic ring can be used.
[0353]
Next, the contents of the nitrogen-containing heterocyclic compound and the conductive fine particles in the conductive resin coating layer will be described. However, this is a particularly preferable range in the present invention, and the present invention is not limited to this. First, the content of the nitrogen-containing heterocyclic compound dispersed in the conductive resin coating layer is preferably 0.5 to 60 parts by mass, more preferably 1 to 100 parts by mass with respect to 100 parts by mass of the binder resin for the coating layer. Particularly preferable results are obtained when the range is 50 parts by mass. That is, when the content of the nitrogen-containing heterocyclic compound is less than 0.5 parts by mass, the addition effect of the nitrogen-containing heterocyclic compound is small, and when it exceeds 60 parts by mass, the volume resistance of the conductive resin coating layer is reduced. Low control becomes difficult, and charge-up phenomenon easily occurs.
[0354]
The content of the conductive fine particles dispersed and contained in combination with the nitrogen-containing heterocyclic compound in the conductive resin coating layer is preferably 40 parts by mass or less, more preferably 100 parts by mass or less with respect to 100 parts by mass of the binder resin for the coating layer. Particularly preferable results can be obtained when it is used in the range of 2 to 35 parts by mass. That is, when the content of the conductive fine particles exceeds 40 parts by mass, a decrease in the film strength of the conductive resin coating layer and a decrease in the charge amount of the toner are observed, which is not preferable.
[0355]
(2) In the developer carrying member of the present invention, it is also preferable that the coating layer contains a nitrogen-containing compound as a positively chargeable substance. Examples of such a material include a copolymer containing a unit derived from a nitrogen-containing vinyl monomer. As the polymer forming the copolymer, a vinyl polymerizable monomer is preferable. The binder resin contained in the resin coating layer contains a copolymer of a vinyl polymerizable monomer having a high mechanical strength and a nitrogen-containing vinyl monomer having a high negative frictional charging property with respect to the developer. The agent carrier has high abrasion resistance and toner adhesion / fusion resistance of the resin coating layer, and has good triboelectric charge imparting characteristics until after a large number of sheets have been used.
[0356]
Moreover, since this copolymer has a nitrogen-containing vinyl monomer, the dispersibility of the conductive fine powder such as carbon black and graphite in the resin coating layer is improved. Therefore, the electrical resistance of the resin coating layer is satisfactorily reduced, the uniformity of the triboelectric charging property on the surface of the resin coating layer is improved, the triboelectric charging property to the developer is higher, and the charge amount of the developer Since the distribution becomes sharp and the coating strength of the resin coating layer itself is improved, the durability of a large number of sheets is further improved. The reason why the copolymer has this nitrogen-containing vinyl monomer improves the dispersibility of the conductive fine powder such as carbon black and graphite in the resin coating layer is not clearly understood. By including a polar group based on a nitrogen atom in the nitrogen vinyl monomer, the solubility in a solvent, particularly a solvent having a polarity, is improved, so that the wettability of the solution in which the resin is dissolved to the conductive fine particles is improved. It is considered that the dispersibility of the conductive fine particles in the resin coating layer is improved when the resin coating layer is formed by coating the conductive fine particles in the solution. In particular, when the conductive fine particles are a substance having a polar group on the surface such as carbon black, the affinity is further enhanced by the polar group based on the nitrogen atom, which is more effective.
[0357]
In the present invention, the copolymerization molar ratio of the copolymer having the vinyl polymerizable monomer (M) and the nitrogen-containing vinyl monomer (N) preferably satisfies M: N = 4: 1 to 999: 1. When the ratio of M exceeds 999: 1, there is almost no effect of adding the nitrogen-containing vinyl monomer, that is, the effect of improving the triboelectric charge imparting property is extremely small, and the effect of copolymerization is hardly seen. When the ratio of M is less than 4: 1, for example, the resin layer is not stabilized due to a decrease in Tg, and charging of the resin layer and wear resistance characteristics are impaired due to the temperature rise of the electrophotographic apparatus body. The toner may be easily fixed. Further, even if the ratio of the nitrogen-containing vinyl monomer is further increased, the charge imparting effect is saturated, so that it is not particularly necessary.
[0358]
In the present invention, examples of the vinyl polymerizable monomer that can be the main component of the copolymer include styrene, α-methylstyrene, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, and n-acrylate. Butyl, iso-butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, cyclohexyl acrylate, hydroxyethyl acrylate, dimethyl (amino) ethyl acrylate, diethyl (amino) ethyl acrylate, methacryl Acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, octyl methacrylate, cyclohexyl methacrylate, hydroxyethyl methacrylate, di Monocarboxylic acids having double bonds such as til (amino) ethyl methacrylate, diethyl (amino) ethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, or ester compounds thereof; for example, maleic acid, butyl maleate, methyl maleate, A dicarboxylic acid having a double bond such as dimethyl maleate, and an ester compound thereof. These may be used alone or in combination of two or more. In particular, when an acid monomer or an acid ester monomer having a vinyl group is contained, the charging stability of the developer on the developer carrying member is effective. In that case, as an effect of stabilizing the triboelectric charge amount, it is somewhat better to use the acid monomer than the acid ester monomer.
[0359]
In the present invention, it is preferable to use methyl methacrylate as the vinyl polymerizable monomer. Methyl methacrylate is excellent in mechanical strength when used as a polymer. Further, when it is used in the binder resin of the sleeve surface layer, good triboelectric chargeability to the developer can be obtained. However, when used as a homopolymer, the triboelectric chargeability is often insufficient, and the dispersibility of pigments such as carbon black and graphite is not so good. By using it as a copolymer containing a nitrogen-containing vinyl monomer as in the present invention, the triboelectric charge imparting property can be improved. In the present invention, since the methyl methacrylate component is preferably contained at a ratio of 80% or more, the mechanical strength such as wear resistance is not impaired even when compared with a homopolymer of methyl methacrylate. Furthermore, since a nitrogen-containing vinyl monomer component is contained, when a pigment component such as conductive fine powder is dispersed in the resin layer, the dispersibility is improved. preferable.
[0360]
The molecular weight of the copolymer containing the unit derived from the nitrogen-containing vinyl monomer is preferably in the range of 3000 to 50000 in terms of the weight average molecular weight Mw. When the molecular weight Mw is less than 3000, there are too many low molecular weight components, so that the toner easily adheres to or adheres to the sleeve, or the charge imparting property of the resin decreases. When Mw exceeds 50000, the molecular weight is too high, and the resin viscosity in the solvent is high, so when coating or pigments are added, it causes a dispersion failure and the composition of the resin layer is not uniform. As a result, toner charging becomes unstable, surface roughness becomes unstable, and wear resistance decreases.
[0361]
Moreover, it is preferable that Mw / Mn showing the ratio of the weight average molecular weight of the copolymer containing the unit derived from a nitrogen-containing vinyl monomer and a number average molecular weight is 3.5 or less. When Mw / Mn exceeds 3.5, the low molecular weight component increases, so that the adhesion and adhesion of the toner increase and the triboelectric chargeability of the toner tends to decrease.
[0362]
In this invention, the molecular weight distribution of the chromatogram by GPC of the copolymer containing the unit derived from a nitrogen-containing vinyl monomer is measured as follows. That is, the column is stabilized in a heat chamber at 40 ° C., THF as a solvent is allowed to flow through the column at this temperature at a flow rate of 1 ml / min, and about 100 μl of the THF sample solution is injected and measured. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of calibration and the number of counts prepared from several types of monodisperse polystyrene standard samples. As a standard polystyrene sample for preparing a calibration curve, for example, a molecular weight of 10 manufactured by Tosoh Corporation or Showa Denko is 10²-10⁷It is appropriate to use a standard polystyrene sample of about 10 points. An RI (refractive index) detector is used as the detector. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. (H_XL), G2000H (H_XL), G3000H (H_XL), G4000H (H_XL), G5000H (H_XL), G6000H (H_XL), G7000H (H_XL), A combination of TSK guard column.
[0363]
Representative examples of nitrogen-containing vinyl monomers include, for example, p-dimethylaminostyrene, dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminomethyl acrylate, diethylaminoethyl acrylate, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, Dimethylaminopropyl methacrylate, diethylaminomethyl methacrylate, diethylaminoethyl methacrylate, N-vinylimidazole, N-vinylbenzimidazole, N-vinylcarbazole, N-vinylpyrrole, N-vinylpiperidine, N-vinylmorpholine, Examples thereof include nitrogen-containing heterocyclic N-vinyl compounds such as N-vinylindole.
[0364]
In particular, dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, dimethylaminopropyl acrylate, diethylaminomethyl acrylate, diethylaminoethyl acrylate, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminopropyl methacrylate, diethylaminomethyl methacrylate, diethylaminoethyl methacrylate General formula (3)
[0365]
Embedded image

[In the formula, R₇, R₈, R₉And R₁₀Represents a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms, and n represents an integer of 1 to 4. ]
It is preferable to use the nitrogen-containing vinyl monomer represented by these.
[0366]
In particular, the following general formula (8) such as dimethylaminoethyl methacrylate and diethylaminoethyl acrylate
[0367]
Embedded image

[However, R₁, R₂, R₃Represents a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms. ]
It is preferable to use the nitrogen-containing vinyl monomer shown in the above.
[0368]
Moreover, as a nitrogen-containing vinyl monomer used for this invention, a quaternary ammonium group containing vinyl monomer can also be used. Examples of the quaternary ammonium group-containing vinyl monomer include those represented by the following general formula (9).
[0369]
Embedded image

[In the formula, R_FiveRepresents a hydrogen atom or a methyl group, R₆Represents an alkylene group having 1 to 4 carbon atoms, and R₇~ R₉Represents a methyl group, an ethyl group or a propyl group, and X₁Represents —COO— or —CONH—, and A^-Is Cl^-, (1/2) SO_Four ^2-An anion such as ]
In the present invention, the copolymer containing a nitrogen-containing vinyl monomer may be used alone as a binder resin for a coating layer or may be used by adding to another binder resin. When used by adding to other binder resins, generally known resins as described above can be used. Considering the mechanical strength required for the developer carrying member, a thermosetting resin is more preferable, but a thermoplastic resin can also be applied as long as it has sufficient mechanical strength.
[0370]
Further, such a resin may be blended with a thermosetting resin or the like having a higher strength as a charge control agent. Even in such a case, the positive chargeability of the sleeve is good due to the effect due to the nitrogen-containing vinyl monomer.
[0371]
(3) Further, in the developer carrier of the present invention, as a positively chargeable substance, at least a copolymer of a vinyl polymerizable monomer and a sulfonic acid group-containing acrylamide monomer is contained in the coating layer on the surface of the developer carrier. And at the same time, at least —NH in the molecular structure as a binder resin for the coating layer₂It is also preferable to use a resin containing either a group, a ═NH group or a —NH— bond.
[0372]
In the present invention, the clear reason for exhibiting positive chargeability is not clear, but a copolymer of a vinyl polymerizable monomer and a sulfonic acid group-containing acrylamide monomer is at least —NH in the molecular structure.₂When dispersed in a binder resin for a coating layer having a group, ═NH group, or —NH— bond, it is uniformly dispersed and due to the structural interaction between the copolymer and the binder resin. The chargeability of the entire resin composition is considered to be uniform and sufficient positive chargeability.
[0373]
The polymer in the present invention is a polymer having a copolymerization ratio based on the mass of the vinyl polymerizable monomer and the sulfonic acid group-containing acrylamide monomer of 98: 2 to 80:20 and a weight average molecular weight of 2000 to 50000. It is preferable. When the ratio of the sulfonic acid group-containing acrylamide monomer is less than 2% by mass, the ability to induce a positive charge on the toner is poor. If it exceeds 20% by mass, environmental stability such as moisture resistance and coating film characteristics are deteriorated, which is not preferable. On the other hand, when the weight average molecular weight is less than 2,000, there are too many low molecular weight components, so that the toner easily adheres to or adheres to the sleeve, or the charge imparting property of the resin decreases. When the weight average molecular weight exceeds 50,000, the compatibility with the resin is lowered, and stable chargeability cannot be obtained due to environmental fluctuations and aging. Also, the resin viscosity in the solvent is high, so that coating defects and pigments are reduced. When added, it causes poor dispersion, the composition of the resin coating layer becomes non-uniform, the toner charge is not stable, the surface roughness of the resin coating layer is not stable, and the wear resistance is reduced. It becomes.
[0374]
The addition amount of the sulfonic acid group-containing acrylamide monomer used in the present invention as described above is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the binder resin. If the amount is less than 1 part by mass, the charge imparting property is not improved by addition. If the amount exceeds 100 parts by mass, the dispersion in the binder resin becomes poor and the film strength tends to be lowered.
[0375]
Examples of the vinyl polymerizable monomer that can be used for producing the copolymer in the present invention include styrene, α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n- Butyl (meth) acrylate, iso-butyl (meth) acrylate, cyclohexyl (meth) acrylate, dimethyl (amino) ethyl (meth) acrylate, diethyl (amino) ethyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) Examples thereof include acrylic acid, vinyl acetate, and vinyl propionate, and these can be used alone or in a mixture of two or more. A combination of styrene and an acrylic ester or methacrylic ester is preferable. In general, since the glass transition point of the binder resin for toner is often 70 ° C. or lower to 60 ° C. or lower, when the vinyl polymerizable monomer is used, the toner adheres to the surface of the coating film. In order to avoid this, it is preferable to appropriately select a binder resin for a coating layer so that a coating film having a glass transition point of 65 ° C. or higher, preferably 70 ° C. or higher, more preferably 90 ° C. or higher is formed.
[0376]
Examples of the sulfonic acid group-containing acrylamide monomer include 2-acrylamidopropanesulfonic acid, 2-acrylamide-n-butanesulfonic acid, 2-acrylamide-n-hexanesulfonic acid, 2-acrylamide-n-octanesulfonic acid, and 2-acrylamide. -N-dodecanesulfonic acid, 2-acrylamide-n-tetradecanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, 2-acrylamido-2,2,4-trimethyl Pentanesulfonic acid, 2-acrylamido-2-methylphenylethanesulfonic acid, 2-acrylamido-2- (4-chlorophenyl) propanesulfonic acid, 2-acrylamido-2-carboxymethylpropanesulfonic acid, 2-acrylic acid Luamido-2- (2-pyridyl) propanesulfonic acid, 2-acrylamido-1-methylpropanesulfonic acid, 3-acrylamido-3-methylbutanesulfonic acid, 2-methacrylamide-n-decanesulfonic acid, 2-methacrylamide -N-tetradecanesulfonic acid can be mentioned. Preferably, 2-acrylamido-2-methylpropanesulfonic acid is used.
[0377]
The polymerization initiator that can be used for copolymerizing the vinyl polymerizable monomer and the sulfonic acid group-containing acrylamide monomer is a peroxide initiator or an azo-based initiator. It is preferable to use a peroxide initiator having an effect on the negative chargeability, and the initiator is preferably used in the range of 0.5 to 5% by mass with respect to the monomer mixture. As the polymerization method, any method such as solution polymerization, suspension polymerization, bulk polymerization and the like can be used, and it is not particularly limited, but an organic solvent containing a lower alcohol such as methanol, isopropanol, or butanol. Among them, it is particularly preferable to employ a solution polymerization method in which the monomer mixture is copolymerized.
[0378]
In this case, as the binder resin of the coating layer in the developer carrying member, the copolymer of the vinyl polymerizable monomer and the sulfonic acid group-containing acrylamide monomer, and part or all thereof, at least in the molecular structure thereof -NH₂A binder resin having either a group, ═NH group, or —NH— bond is used.
[0379]
-NH₂As the substance having a group, R-NH₂Or a polyamine having them, RCO-NH₂As the substance having ═NH group, such as a primary amide represented by the formula (I) or a polyamide having them, a secondary amine represented by R═NH or a polyamine having them,₂Examples of the substance having —NH— bond such as secondary amide represented by ═NH or polyamide having them include polyurethane having —NHCO— bond in addition to the above-described polyamine and polyamide. Resins that are contained in one or more types or as a copolymer and are industrially synthesized are preferably used. Of these, phenol resins, polyamide resins, and urethane resins using ammonia as a catalyst are preferable. As a phenol resin constituting the binder resin used in the present invention, as a result of repeated studies by the present inventors, by using a phenol resin using a nitrogen-containing compound as a catalyst in the production process, at the time of heat curing It was found that structural interaction with the copolymer is likely to occur, and the chargeability of the entire resin composition is uniform and has sufficient positive chargeability.
[0380]
Therefore, by using such a phenol resin as one of the materials constituting the coating layer on the developer carrying member in the present invention, good negative imparting properties can be obtained. Examples of the nitrogen-containing compound used as a catalyst in the production process of the phenol resin used in the present invention include acid ammonium such as ammonium sulfate, ammonium phosphate, ammonium sulfamate, ammonium carbonate, ammonium acetate, and ammonium maleate. Or amino salts, and basic catalysts include ammonia or dimethylamine, diethylamine, diisopropylamine, diisobutylamine, diamylamine, trimethylamine, triethylamine, tri-n-butylamine, triamylamine, dimethylbenzylamine, diethylbenzylamine, Dimethylaniline, diethylaniline, n, n-di-n-butylaniline, n, n-diamilaniline, n, n-di-t-amylaniline, n-methyl Such as ethanolamine, n-ethylethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, ethylenediamine, hexamethylenetetraamine Amino compounds, pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine, pyridine and its derivatives such as 2,6-lutidine, quinoline compounds, imidazole, 2-methylimidazole, 2,4-dimethylimidazole, 2 -Nitrogen-containing heterocyclic compounds such as ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole A.
[0381]
The polyamide resin constituting the binder resin used in the present invention is, for example, nylon 6, 66, 610, 11, 12, 9, 13, Q2 nylon, or a nylon copolymer containing these as a main component. Alternatively, N-alkyl-modified nylon and N-alkoxylalkyl-modified nylon can be preferably used. Furthermore, any resin containing a polyamide resin, such as various resins modified with polyamide such as polyamide-modified phenolic resin, or epoxy resin using polyamide resin as a curing agent, Can also be suitably used.
[0382]
Moreover, as a urethane resin which comprises the binder resin used in this invention, if it is resin containing a urethane bond, all can be used suitably. This urethane bond is obtained by polymerization addition reaction of polyisocyanate and polyol.
[0383]
The polyisocyanate used as the main raw material of this polyurethane resin includes diphenylenemethane-4,4′-diisocyanate (MDI), isophorone diisocyanate (IPDI), polymethylene polyphenyl polyisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, 1, 5-naphthalene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, carbodiimide-modified diphenylmethane-4,4′-diisocyanate, trimethylhexadiylene diisocyanate, orthotoluidine diisocyanate, naphthylene diisocyanate, xylene diisocyanate, paraphenylene diisocyanate, lysine diisocyanate methyl Esters and dimethyl diisocyanate can be used.
[0384]
Polyols such as polyethylene adipate ester, polybutylene adipate ester, polydiethylene glycol adipate ester, polyhexene adipate ester, polycaprolactone ester, and polyether such as polytetramethylene glycol and polypropylene glycol Polyols can be used.
[0385]
In the present invention, the volume resistance of the resin coating layer formed on the surface of the developer carrying member with the material as described above is 10.³Ω · cm or less, and 10³-10^-2It is preferable to adjust to Ω · cm. That is, the volume resistance of the resin coating layer is 10³When it exceeds Ω · cm, charge-up is likely to occur, and ghost deterioration and concentration reduction are likely to occur. Therefore, in the developing device of the present invention, in order to adjust the volume resistance of the resin coating layer on the surface of the developer carrying member to a preferable range as described above, the conductive resin is contained in the binder resin that is a film forming material of the resin coating layer. Disperse the substance. In this case, the conductive substance used preferably has a number average particle diameter of 20 μm or less, more preferably 10 μm or less. Furthermore, in order to avoid unevenness formed on the surface of the resin coating layer, it is preferable to use one having a thickness of 1 μm or less.
[0386]
Examples of conductive materials that can be used in this case include carbon black such as furnace black, lamp black, thermal black, acetylene black, and channel black; titanium oxide, tin oxide, zinc oxide, molybdenum oxide, potassium titanate, and oxidation. Examples thereof include metal oxides such as antimony and indium oxide; metals such as aluminum, copper, silver and nickel; inorganic fillers such as graphite, metal fibers and carbon fibers. The addition amount of these conductive substances in the resin coating layer is preferably used within a range of 100 parts by mass or less with respect to 100 parts by mass of the binder resin. When the addition amount exceeds 100 parts by mass, the coating strength is liable to decrease, and the addition of a large amount of a conductive substance tends to cause a decrease in the charge amount of the toner.
[0387]
Furthermore, in the developing device of the present invention, as a constitution of the resin coating layer provided on the surface of the developer carrying member to be used, in addition to the positively charged substance and the conductive substance described above, the particle size is 0.3 to A configuration in which spherical particles of about 30 μm are dispersed in the coating resin layer is preferable. With such a configuration, the surface roughness of the developer carrier can be stabilized, and the toner coat amount on the developer carrier can be optimized. Further, the inclusion of spherical particles in the resin coating layer maintains a uniform surface roughness on the surface of the developer carrier, and at the same time, even when the resin coating layer provided on the surface of the developer carrier is worn. Since the change in the surface roughness of the layer can be reduced, the effect of making it difficult to cause toner contamination and toner fusion to the developer carrying member can be obtained. Further, when spherical particles such as those described above are contained, the effect of controlling the charge of the nitrogen-containing heterocyclic compound is further enhanced by the interaction with the nitrogen-containing heterocyclic compound contained in the resin coating layer. The quick and uniform charge imparting characteristics can be further improved, and the charge imparting performance can be stabilized.
[0388]
The spherical particles used in the present invention preferably have a number average particle size of 0.3 to 30 μm, and more preferably 2 to 20 μm. That is, when the number average particle diameter of the spherical particles contained in the resin coating layer is less than 0.3 μm, the effect of imparting uniform roughness to the surface of the developer carrying member and the effect of enhancing the charge imparting performance are small. In addition, rapid and uniform charging to the developer is insufficient, and the toner coating tends to cause charge up, toner contamination, and toner fusion due to wear of the resin coating layer, resulting in ghost deterioration and image density reduction. Since it becomes easy to occur, it is not preferable. On the other hand, when spherical particles having a number average particle size exceeding 30 μm are added, the surface roughness of the resin coating layer tends to be too large, and the toner is not sufficiently charged. Since the mechanical strength of a layer will fall, it is not preferable.
[0389]
Furthermore, the spherical particles used in the present invention have a true density of 3 g / cm.³Or less, preferably 2.7 g / cm³Or less, more preferably 0.9 to 2.3 g / cm³It is better to use one. That is, the true density of the spherical particles is 3 g / cm.³In the case of exceeding, the dispersibility of the spherical particles in the resin coating layer becomes insufficient, it becomes difficult to impart a uniform roughness to the surface of the coating layer, and the dispersion of the nitrogen-containing heterocyclic compound is not uniformly performed, This is not preferable because the ability to impart quick and uniform charge to the toner and the strength of the coating layer are insufficient. On the other hand, the true density of the spherical particles is 0.9 g / cm.³Even if it is smaller, the dispersibility of the spherical particles in the coating layer tends to be insufficient, such being undesirable.
[0390]
The spherical shape in the spherical particles referred to in the present invention means a particle having a major axis / minor axis ratio of about 1.0 to 1.5. More preferably, the major axis / minor axis ratio is 1. It is better to use spherical particles closer to 0-1.2 true spheres. That is, when the ratio of the major axis / minor axis of the spherical particles exceeds 1.5, the dispersibility of the spherical particles in the conductive resin coating layer decreases, and the positively charged substance in the coating layer decreases. Decreasing dispersibility and non-uniformity of the surface roughness of the coating layer occur, which is not preferable from the viewpoint of quick and uniform charge imparting property to the toner and the coating strength of the formed resin coating layer.
[0390]
Known spherical particles can be used as the spherical particles used in the present invention. Examples include spherical resin particles, spherical metal oxide particles, and spherical carbonized particles. Examples of the spherical resin particles include spherical resin particles having a desired particle diameter directly obtained by suspension polymerization, dispersion polymerization, or the like. In the present invention, among these, spherical resin particles are particularly preferable because a suitable surface roughness can be obtained with a smaller addition amount and a uniform surface shape can be easily obtained. Examples of such spherical resin particles include acrylic resin particles such as polyacrylate and polymethacrylate, polyamide resin particles such as nylon, polyolefin resin particles such as polyethylene and polypropylene, silicone resin particles, phenolic resin particles, Examples include polyurethane resin particles, styrene resin particles, and benzoguanamine particles. These resin particles are not limited to those obtained by the polymerization method described above, and those obtained by thermally or physically spheroidizing resin particles obtained by a pulverization method may be used. .
[0392]
Furthermore, in the present invention, an inorganic fine powder may be adhered or fixed to the surface of the above-described spherical particles. As the inorganic fine powder used in this case, for example, SiO₂, SrTiO₃, CeO₂, CrO, Al₂O₃, Oxides such as ZnO and MgO, Si₃N₄Nitrides such as SiC, carbides such as SiC, CaSO₄, BaSO₄, CaCO₃And sulfates and carbonates such as Such inorganic fine powder may be treated with a coupling agent.
[0393]
In particular, it is preferable to use a material obtained by treating an inorganic fine powder with a coupling agent for the purpose of improving the adhesion to the binder resin or imparting hydrophobicity to the spherical particles. Examples of the coupling agent used at this time include a silane coupling agent, a titanium coupling agent, and a zircoaluminate coupling agent. More specifically, for example, as a silane coupling agent, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane Benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, Dimethyldiethoxysilane, jardimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinylte Tramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2-12 siloxane units per molecule, each containing a hydroxyl group bonded to one silicon atom in the terminal unit Dimethylpolysiloxane.
[0394]
As described above, the dispersibility of the spherical particles in the conductive resin coating layer is preferably achieved by attaching or fixing the inorganic fine particles treated with the coupling agent to the spherical particle surface. Uniformity, stain resistance, charge imparting property to the toner, wear resistance of the conductive resin coating layer, and the like can be improved.
[0395]
Furthermore, in the present invention, it is preferable to use conductive particles as the spherical particles. That is, by imparting electrical conductivity to the spherical particles, it becomes difficult for charges to accumulate on the surface of the spherical particles because of the electrical conductivity, thereby reducing toner adhesion to the developer carrying member and improving the ability to impart charge to the toner. be able to. The spherical particles used at that time have a volume resistance of 10⁶Ω · cm or less, more preferably 10^-3-10⁶Those having conductivity of Ω · cm are preferable. That is, the volume resistance of the spherical particles used in the present invention is 10⁶If it exceeds Ω · cm, the toner is likely to be contaminated and fused with spherical particles exposed on the surface of the coating layer due to abrasion, and it becomes difficult to charge the toner quickly and uniformly.
[0396]
As a method for obtaining conductive spherical particles having such a volume resistance, the following method is preferably used, but is not necessarily limited to these methods. That is, as a method for obtaining conductive spherical particles that can be suitably used in the present invention, for example, resin-based spherical particles or mesocarbon microbeads are baked to be carbonized and / or graphitized to have a low density and good conductivity. The method of obtaining spherical carbon particles is mentioned. Examples of the resin-based spherical particles used at this time include resins such as phenol resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, and polyacrylonitrile. In addition, mesocarbon microbeads can be usually produced by washing spherical crystals produced in the course of heating and firing the medium pitch with a large amount of a solvent such as tar, medium oil, and quinoline.
[0397]
More preferable conductive spherical particles that can be used in the present invention include spherical resin particle surfaces such as phenol resin, naphthalene resin, furan resin, xylene resin, divinylbenzene polymer, styrene-divinylbenzene copolymer, and polyacrylonitrile. In addition, bulk mesophase pitch is coated by a mechanochemical method, and the coated particles are heat-treated in an oxidizing atmosphere, and then calcined and / or graphitized by firing in an inert atmosphere or in a vacuum to form conductive spherical carbon. The method of obtaining particle | grains is mentioned. The spherical carbon particles obtained by this method are more preferable as the spherical particles used in the present invention because they are graphitized to promote the crystallization of the coating portion of the spherical carbon particles and improve the conductivity.
[0398]
The conductive spherical carbon particles obtained by the above method can be controlled to some extent the conductivity of the spherical carbon particles obtained by changing the firing conditions in any of the methods. Spherical carbon particles that can be preferably used in the present invention are easily obtained. In addition, the spherical carbon particles obtained by the above method have a true density of the conductive spherical particles of 3 g / cm in order to further increase the conductivity in some cases.³The surface may be plated with a conductive metal and / or metal oxide within a range not exceeding.
[0399]
As another method for obtaining conductive spherical particles that can be suitably used in the present invention, conductive fine particles smaller than the particle diameter of the core particles are mechanically mixed with the core particles made of spherical resin particles at an appropriate blending ratio. After the conductive fine particles are uniformly attached around the core particles by the action of van der Waals force and electrostatic force, for example, the core particles are caused by a local temperature rise caused by applying a mechanical impact force. There is a method in which the surface is softened, conductive fine particles are fixed on the surface of the core particles, the core particle surface is covered with the particles, and conductive resin-treated spherical resin particles are obtained. For the core particles, spherical resin particles having a small true density made of an organic compound are preferably used. Examples of the resin include PMMA, acrylic resin, polybutadiene resin, polystyrene resin, polyethylene, polypropylene, polybutadiene, or These copolymers, benzoguanamine resin, phenol resin, polyamide resin, nylon, fluorine resin, silicone resin, epoxy resin, and polyester resin can be mentioned. The conductive fine particles (small particles) to be coated on the surface of the core particles (mother particles) made of these materials are small particles so that the coating made of the conductive fine particles is uniformly provided on the surface of the core particles. It is preferable to use one having a particle size of 1/8 or less of the particle size of the mother particle.
[0400]
Furthermore, as another method for obtaining conductive spherical particles that can be suitably used in the present invention, conductive spherical particles in which conductive fine particles are dispersed are obtained by uniformly dispersing conductive fine particles in spherical resin particles. A method is mentioned. As a method for uniformly dispersing the conductive fine particles in the spherical resin particles, for example, the binder resin and the conductive fine particles are kneaded to disperse the conductive fine particles, then cooled and solidified, and pulverized to a predetermined particle size. A method of obtaining spherical conductive particles by mechanical treatment and thermal treatment; or adding a polymerization initiator, conductive fine particles and other additives to the polymerizable monomer, and uniformly using a dispersing machine. The dispersed polymerizable monomer composition is suspended in an aqueous phase containing a dispersion stabilizer so as to have a predetermined particle size by a stirrer or the like, and polymerized to form a spherical shape in which conductive fine particles are dispersed. Examples thereof include a method for obtaining particles.
[0401]
Also in the case of conductive spherical resin particles in which conductive fine particles are dispersed in the binder resin obtained by these methods, this is used as the core particle, and as described above, the conductive particle having a smaller particle diameter than the core particle. After the conductive fine particles are mechanically mixed at an appropriate blending ratio, the conductive fine particles are uniformly adhered around the conductive spherical particles by the action of van der Waals force and electrostatic force, for example, mechanical impact force The surface of the conductive spherical particles is softened by the local temperature rise caused by the application of the slag, the conductive fine particles are fixed on the core particle surface, and the core particle surface is coated with the conductive fine particles, thereby further increasing the conductivity. May be used.
[0402]
Furthermore, as content of the spherical particle disperse | distributed in the said conductive resin coating layer, Preferably it is 2-120 mass parts with respect to 100 mass parts of binder resin for coating layers, More preferably, it is 2-80 mass parts. When it is within the range, particularly preferable results are obtained. That is, when the content of spherical particles is less than 2 parts by mass, the effect of adding spherical particles is small, and when the content exceeds 120 parts by mass, the chargeability of the toner may be too low.
[0403]
Further, in the developing device of the present invention, if a lubricating substance is further dispersed in the resin coating layer provided on the surface of the developing carrier, the effect of the present invention is further improved. It is preferable because it is promoted. Examples of lubricating substances that can be used in this case include graphite, molybdenum disulfide, boron nitride, mica, graphite fluoride, silver-niobium selenide, calcium chloride-graphite, talc, and fatty acid metal salts such as zinc stearate. Can be mentioned. Among these, graphite is preferably used because it does not impair the conductivity of the conductive resin coating layer. Further, as these lubricating substances, those having a number average particle diameter of preferably about 0.2 to 20 μm, more preferably 0.3 to 15 μm may be used.
[0404]
Further, the amount of the lubricating substance added is preferably 5 to 120 parts by weight, more preferably 10 to 100 parts by weight, with respect to 100 parts by weight of the binder resin for the coating layer. give. That is, when the content of the lubricating particles exceeds 120 parts by mass, a decrease in the coating strength and a decrease in the charge amount of the toner are recognized, and when the content is less than 5 parts by mass, a small particle size toner of 7 μm or less is used. When the developing device is used for a long period of time, there is a tendency that toner contamination is likely to occur on the surface of the resin coating layer.
[0405]
The developer carrier used in the present invention comprises at least a substrate and a conductive resin coating layer formed thereon and made of the material described above. As the substrate, a metal cylindrical tube is used. As the metal cylindrical tube, for example, a cylindrical tube made of stainless steel and aluminum is preferably used.
[0406]
In the present invention, when the resin coating layer is formed from the constituent materials as described above, when the surface roughness is expressed by center line average roughness (hereinafter referred to as “Ra”), the value of Ra is It is preferable to adjust so that it may become 0.3-3.5 micrometers more preferably 0.5-3.0 micrometers. That is, when Ra on the surface of the conductive resin coating layer is less than 0.3 μm, the toner transportability may be reduced, and a sufficient image density may not be obtained. If Ra exceeds 3.5 μm, the amount of toner transported may increase so that the toner cannot be sufficiently charged.
[0407]
Furthermore, it is preferable that the resin coating layer having the above-described structure has a uniform thickness when the layer thickness is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 4 to 20 μm. However, it is not particularly limited to this layer thickness. Although the resin coating layer having such a layer thickness depends on the material for forming the resin coating layer, the adhesion weight is 4,000 to 20,000 mg / m.²It should be about.
[0408]
The physical property measurement method according to the present invention will be described below.
[0409]
(1) Measurement of charge polarity of resin coating layer
<Production method of sample plate>: A resin solution for forming a resin coating layer (excluding conductive materials such as carbon and graphite) whose charge polarity is to be measured is placed on a SUS plate with a bar coater (# 60). Apply it and form a film by drying, heating, etc. (Drying / heating temperature and time are until the solution is completely evaporated in the case of thermoplastic resin, and the resin is completely crosslinked in the case of thermosetting resin. Make a sample plate. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%.
[0410]
<Particle adjusting method>: With iron powder (particle size of about 100 μm) in contact with the ground, the particles are left overnight at 23 ° C. and a relative humidity of 60%.
[0411]
<Measurement method>: Measurement is performed in an environment of 23 ° C. and a relative humidity of 60%. First, the sample plate produced above is set in a surface charge measuring device TS-100AS (manufactured by Toshiba Chemical Co., Ltd.) shown in FIG. 8, and the electrometer 55 is grounded to make the value zero. The iron powder 51 conditioned in the above is put in the dropping device 52, the START switch is pressed, and the iron powder 51 is dropped on the sample plate 53 for 20 seconds, and is received by the receiver 54 which has been grounded in advance. At this time, the polarity indicated by the electrometer 55 is read to obtain the charging polarity of the resin coating layer (only the resin component) with respect to the iron powder. Reference numeral 56 denotes a condenser.
[0412]
(2) Measurement of centerline average roughness (Ra)
Based on the surface roughness measurement method of JISB0601, each of 3 points in the axial direction × 2 points in the circumferential direction = 6 points was measured with a surf coder SE-3300 manufactured by Kosaka Laboratory, and the average value was taken.
[0413]
(3) Measurement of volume resistivity of particles
The granular sample was put in an aluminum ring having a diameter of 40 mm, and pressure-molded at 2500 N, and the volume resistance value was measured with a resistivity meter Loresta AP or Hiresta IP (both manufactured by Mitsubishi Yuka) using a 4-terminal probe. The measurement environment was 20 to 25 ° C. and 50 to 60% RH.
[0414]
(4) Measurement of volume resistance of resin coating layer
A measurement sample was prepared by forming a coating layer having a thickness of 7 to 20 μm on a PET sheet having a thickness of 100 μm, and the ASTM standard (D-991-82) and the Japan Rubber Association standard SRIS ( 2301-1969), and a voltage drop type digital ohmmeter (manufactured by Kawaguchi Electric Mfg. Co., Ltd.) provided with an electrode having a 4-terminal structure for measuring volume resistance of conductive rubber and plastic. The measurement environment was 20 to 25 ° C. and 50 to 60 RH%.
[0415]
(5) Measurement of true density of spherical particles
The true density of the spherical particles used in the present invention was measured using a dry density meter Accupic 1330 (manufactured by Shimadzu Corporation).
[0416]
(6) Measurement of spherical particle size
Measurement was performed as follows using a Coulter LS-130 type particle size distribution meter (manufactured by Coulter, Inc.) of a laser diffraction type particle size distribution meter. As a measuring method, an aqueous module is used, and pure water is used as a measuring solvent. First, the measurement system of the particle size distribution meter is washed with pure water for about 5 minutes, and 10 to 25 mg of sodium sulfite is added to the measurement system as an antifoaming agent to execute a background function. Next, 3 to 4 drops of a surfactant is added to 10 ml of pure water, and 5 to 25 mg of a measurement sample is further added. The aqueous solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser to obtain a sample solution for measurement, and the sample solution is gradually added to the measurement system of the measurement apparatus to perform measurement. At that time, measurement is performed by adjusting the sample concentration in the measurement system so that the PIDS on the screen of the apparatus is 45 to 55%, and the number average particle diameter is obtained by arithmetic operation from the number distribution.
[0417]
(7) Measurement of particle size of conductive fine particles contained in developer
The particle diameter of the conductive fine particles was measured using an electron microscope. The shooting magnification is 60,000 times, but if it is difficult, the photograph is enlarged and printed so as to be 60,000 times after shooting at a low magnification. Measure the primary particle size on the photo. At this time, the major axis and the minor axis are measured, and the average value is defined as the particle size. This is measured for 100 samples, and the 50% value is taken as the average particle size.
[0418]
Next, development conditions suitable for the present invention will be described.
[0419]
In the present invention, 3 to 30 g / m on the developer carrier.²It is preferable to form a developer layer. 3-30 g / m on developer carrier²By forming the developer layer, it is easy to form a uniform developer layer, and the conductive fine powder is uniformly supplied onto the image carrier, whereby uniform charge of the image carrier is easily obtained. If the amount of developer on the developer carrier is too smaller than the above range, it is difficult to obtain a sufficient image density, and minute unevenness of the developer layer on the developer carrier may cause uneven image density and conductivity. It tends to appear as uneven charging of the image carrier due to uneven supply of fine powder. If the amount of developer on the developer carrying member is too larger than the above range, the application of triboelectric charge to the toner particles tends to be insufficient, toner scattering tends to occur, fogging increases, and transferability decreases. It becomes easy to inhibit charging of the image carrier.
[0420]
Further, 5 to 25 g / m on the developer carrier.²It is more preferable to form a developer layer. 5-25 g / m on developer carrier²By forming the developer layer, it is easy to apply the triboelectric charge to the developer on the developer carrying member more uniformly, and the collected residual toner particles are used for the tribocharging of the toner particles in the vicinity of the developer carrying member. This reduces the effect on the surface and provides more stable development and cleaning properties. If the amount of developer on the developer carrier is too smaller than the above range, the collected residual toner particles are liable to affect the frictional charging of the toner particles near the developer carrier, and the friction of some toner particles Unevenness of the developer layer due to excessive charging may occur, and the recoverability of transfer residual toner particles may become non-uniform. If the amount of developer on the developer carrying member is too larger than the above range, the collected transfer residual toner particles are transported to the developing unit again without being given sufficient frictional charge again and used for development. As a result, fog is more likely to occur.
[0421]
In the present invention, the surface of the developer carrying member carrying the developer may be moved in the same direction as the moving direction of the image carrying member surface, or may be moved in the opposite direction. When the moving direction is the same direction, it is desirable that the ratio is 100% or more with respect to the moving speed of the image carrier. If it is less than 100%, the image quality may deteriorate.
[0422]
The movement speed ratio of the movement speed of the developer carrier surface to the movement speed of the image carrier surface is 100% or more (the movement speed of the developer carrier surface is greater than or equal to the degree of movement arrest of the image carrier surface). If so, the toner carrier is sufficiently supplied from the developer carrier side to the image carrier side, so that a sufficient image density is easily obtained and the conductive fine powder is sufficiently supplied. Can be obtained.
[0423]
Further, the moving speed of the developer carrying member surface is more preferably 1.05 to 3.0 times the moving speed of the image carrying member surface. As the moving speed ratio increases, the amount of toner supplied to the development site increases, the frequency of toner desorption with respect to the latent image increases, and unnecessary portions are scraped off and transferred to the necessary portions. The recoverability of residual toner particles is improved, and the generation of pattern ghosts due to poor recovery can be more reliably suppressed. Furthermore, an image faithful to the latent image can be obtained. In the contact development process, as the moving speed ratio increases, the recoverability of the transfer residual toner particles is further improved by the rubbing between the image carrier and the developer carrier. However, if the moving speed ratio greatly exceeds the above range, fog and image stains are likely to occur due to scattering of the developer from the developer carrier, and the image carrier or developer carrier is rubbed in the contact development process. It becomes easy to shorten the life due to wear and abrasion. When the developer layer thickness regulating member that regulates the amount of developer on the developer carrier is in contact with the developer carrier via the developer, the developer layer thickness regulating member or the developer carrier is It is easy to shorten the life due to wear and abrasion due to rubbing. From the above viewpoint, it is more preferable that the moving speed of the developer carrying member surface is 1.1 to 2.5 times as far as the moving speed of the image carrying member surface.
[0424]
In the present invention, in order to apply the non-contact developing method, it is preferable to form the developer layer on the developer carrier thinner than the predetermined separation distance of the developer carrier from the image carrier. According to the present invention, it has become possible to realize development and cleaning image formation using a non-contact development method, which has been difficult in the past, with high image quality. In the development process, by applying a non-contact type development method in which the developer layer is made non-contact with the image carrier and the electrostatic latent image on the image carrier is visualized as a toner image, the conductivity is low. Even if a fine powder is added in a large amount to the developer, development fog due to the development bias being injected into the image carrier does not occur. Therefore, a good image can be obtained.
[0425]
Further, it is preferable that the developer carrying member is disposed facing the image carrying member with a separation distance of 100 to 1000 μm. If the distance between the developer carrier and the image carrier is too small than the above range, the change in the development characteristics of the developer with respect to fluctuations in the separation distance will increase, so that mass production of image forming apparatuses satisfying stable image quality will be achieved. It becomes difficult. If the distance between the developer carrier and the image carrier is too larger than the above range, the followability of the toner particles with respect to the latent image on the image carrier is lowered, so the resolution is lowered, the image density is lowered, etc. The image quality is likely to be degraded. Further, the supply property of the conductive fine powder onto the image carrier is likely to be lowered, and the chargeability of the image carrier is likely to be lowered. More preferably, the developer carrying member is disposed facing the image carrying member with a separation distance of 100 to 600 μm. When the developer carrier is separated from the image carrier by 100 to 600 μm, the transfer residual toner particles can be collected more advantageously in the development and cleaning process. If the separation distance is too larger than the above range, the recoverability of the transfer residual toner particles to the developing device is lowered, and fogging due to poor recovery tends to occur.
[0426]
In the present invention, it is preferable that development is performed in a development step in which development is performed by forming an alternating electric field (alternating electric field) between the developer carrier and the image carrier. The alternating electric field can be formed by applying an alternating voltage between the developer carrier and the image carrier. The developing bias to be applied may be one in which an alternating voltage (AC voltage) is superimposed on a DC voltage.
[0427]
As the waveform of the alternating voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Further, it may be a pulse wave formed by periodically turning on / off a DC power source. In this way, a bias that changes the voltage value periodically can be used as the waveform of the alternating voltage.
[0428]
At least a peak-to-peak electric field strength of 3 × 10 3 is provided between the developer carrying body carrying the developer and the image carrying body.⁶-10x10⁶It is preferable to form an alternating electric field (alternating electric field) having a V / m frequency of 100 to 5000 Hz by applying a developing bias. By forming an alternating electric field in the above range by applying a developing bias, the conductive fine powder added in the developer is easily transferred to the image carrier side, and the conductive portion is charged with the conductive fine powder in the charging portion. By obtaining a uniform and dense contact between the contact charging member and the image carrier, uniform charging (particularly direct injection charging) of the image carrier can be significantly promoted. In addition, by forming an alternating electric field with a developing bias, even when there is a high potential difference between the developer carrying body and the image carrying body, charge injection into the image carrying body in the developing section does not occur. Even if it is added in a large amount in the developer, a developing fog due to the charge injection of the developing bias into the image carrier does not occur, and a good image can be obtained. If the intensity of the alternating electric field formed by applying a developing bias between the developer carrier and the image carrier is too small than the above range, the amount of conductive fine powder supplied to the image carrier is insufficient. And the uniform chargeability of the image carrier is likely to decrease. Further, since the developing power is small, an image having a low image density tends to be obtained. On the other hand, if the intensity of the AC electric field is excessively larger than the above range, the developing power is too large, so that the resolution is deteriorated due to the crushing of the thin lines, the image quality is deteriorated due to the fogging, and the chargeability of the image carrier is easily lowered. Image defects due to leakage of the developing bias to the image carrier are likely to occur. Also, if the frequency of the alternating electric field formed by applying a developing bias between the developer carrier and the image carrier is too smaller than the above range, the conductive fine powder is uniformly supplied to the image carrier. It is difficult to cause uneven charging of the image carrier. When the frequency of the AC electric field is too larger than the above range, the amount of the conductive fine powder supplied to the image carrier is likely to be insufficient, and the uniform chargeability of the image carrier tends to be lowered.
[0429]
Further, at least a peak-to-peak electric field strength of 4 × 10 4 is provided between the developer carrying body carrying the developer and the latent image carrying body.⁶-10x10⁶It is more preferable to form an alternating electric field (alternating electric field) having a V / m frequency of 500 to 4000 Hz by applying a developing bias. By forming an alternating electric field in the above range with a developing bias, the conductive fine powder added to the developer is easily transferred to the latent image carrier side, and the conductive fine powder is uniformly applied to the latent image carrier after transfer. Powder can be applied, and high recoverability of transfer residual toner particles can be maintained even when a non-contact development method is applied.
[0430]
If the strength of the AC electric field formed by applying a developing bias between the developer carrying member and the latent image carrying member is too small than the above range, the recoverability of the transfer residual toner particles to the developing device is lowered. Fog due to poor collection is likely to occur. Further, if the frequency of the alternating electric field formed by applying a developing bias between the developer carrying member and the latent image carrying member is too smaller than the above range, the frequency of toner desorption from the latent image is reduced, and the development is performed. The recoverability of transfer residual toner particles to the apparatus is likely to be lowered, and the image quality is also liable to be lowered. If the frequency of the AC electric field is too larger than the above range, the toner particles that can follow the change in the electric field are reduced, so that the recoverability of the transfer residual toner particles is lowered and a positive ghost is generated due to poor recovery of the transfer residual toner particles. It becomes easy.
[0431]
In the present invention, the transfer step may be a step of transferring the toner image formed in the developing step to an intermediate transfer member and then transferring it again to a recording medium such as paper. That is, the transfer material that receives the transfer of the toner image from the latent image carrier may be an intermediate transfer member such as a transfer drum. When the transfer material is an intermediate transfer member, a toner image can be obtained by transferring again from the intermediate transfer member to a recording medium such as paper. By applying the intermediate transfer member, the amount of residual toner particles on the latent image carrier can be reduced without depending on various recording media such as cardboard.
[0432]
In the present invention, it is preferable that the transfer member is in contact with the latent image carrier via a transfer material (registration medium) during transfer.
[0433]
In the contact transfer process in which the toner image on the latent image carrier is transferred to the transfer material while contacting the transfer means via the latent image carrier and the transfer material, the contact pressure of the transfer means is a linear pressure of 2.94 to 980 N. / M, more preferably 19.6 to 490 N / m. If the contact pressure of the transfer means is too smaller than the above range, it is not preferable because transfer of the transfer material and transfer failure are likely to occur. When the abutting pressure is too larger than the above range, the latent image carrier surface may be deteriorated and toner particles may be adhered, resulting in toner fusion to the latent image carrier surface.
[0434]
Further, as the transfer means in the contact transfer process, an apparatus having a transfer roller or a transfer belt is preferably used. The transfer roller has at least a core metal and a conductive elastic layer covering the core metal. The conductive elastic layer is made of an elastic material such as polyurethane rubber, ethylene-propylene-diene polyethylene (EPDM), carbon black, zinc oxide, Mixing and dispersing a conductivity-imparting agent such as tin oxide or silicon carbide to give an electric resistance value (volume resistivity) of 10⁶-10¹⁰It is preferably an elastic body made of a solid or foamed layer adjusted to a medium resistance of Ω · cm.
[0435]
As a preferable transfer process condition with the transfer roller, the contact pressure of the transfer roller is 2.94 to 490 N / m, and more preferably 19.6 to 294 N / m. When the linear pressure as the contact pressure is too smaller than the above range, the residual toner particles increase and the chargeability of the latent image carrier tends to be hindered. If the contact pressure of the transfer means is larger than the above range, the conductive fine powder is easily transferred to the transfer material by the pressing force, and the supply amount of the conductive fine powder to the latent image carrier or the contact charging member is reduced. As a result, the effect of promoting the charging of the latent image carrier is reduced, and the recovery of the transfer residual toner particles during development and cleaning is reduced. In addition, toner scattering on the image increases.
[0436]
In the contact transfer process in which the toner image is electrostatically transferred to the transfer material while the transfer means is brought into contact with the latent image carrier through the transfer material, the applied DC voltage is preferably ± 0.2 to ± 10 kV. .
[0437]
Further, the developing device of the present invention is particularly effective for an image forming apparatus having a small diameter photosensitive member having a diameter of 30 mm or less as a latent image carrier. That is, since there is no independent cleaning process after the transfer process and before the charging process, the degree of freedom of arrangement of the charging, exposure, development, and transfer processes is increased, and combined with a small-diameter photoreceptor having a diameter of 30 mm or less. Therefore, it is possible to reduce the size and space of the image forming apparatus. Similarly, in the belt-shaped photoconductor, the degree of freedom of arrangement of each process is increased, so that the image forming apparatus can be downsized and space-saving. This is also effective for the used image forming apparatus.
[0438]
The image forming apparatus according to the present invention may be such that a process cartridge having at least the latent image carrier and the developing unit as described above is detachably mounted on the image forming apparatus main body. The process cartridge may further include the charging unit.
[0439]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to these examples.
[0440]
First, an example of producing a photoconductor as a latent image carrier used in the embodiments of the present invention will be described.
[0441]
<Example of photoconductor production>
A photoconductor using an organic photoconductive material for negative charging (hereinafter referred to as “OPC photoconductor”) was produced. An aluminum cylinder having a diameter of 24 mm was used as the substrate of the photoreceptor. On the cylinder, the following layers were sequentially laminated by dip coating to prepare a photoconductor having a structure as shown in FIG.
[0442]
The first layer is a conductive layer 12, which is a conductive particle-dispersed resin layer having a thickness of about 20 μm (in order to smooth out defects of the aluminum substrate 11 and to prevent the occurrence of moire due to reflection of laser exposure). Mainly composed of powders of tin oxide and titanium oxide dispersed in a phenolic resin).
[0443]
The second layer is a positive charge injection preventing layer 13 that serves to prevent the positive charge injected from the aluminum substrate 11 from canceling the negative charge charged on the surface of the photoreceptor.⁶This is a medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about Ω · cm.
[0444]
The third layer is a charge generation layer 14, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a petital resin, and generates positive and negative charge pairs upon receiving laser exposure.
[0445]
The fourth layer is a charge transport layer 15, which is a layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin, and is a P-type semiconductor. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.
[0446]
The fifth layer is a charge injection layer 16 in which conductive tin oxide ultrafine particles and ethylene tetrafluoride resin particles having a particle size of about 0.25 μm are dispersed in a photocurable acrylic resin. Specifically, 100 mass% of tin oxide particles having a particle size of about 0.03 μm, doped with antimony and reduced in resistance to the resin, 20 mass% of tetrafluoroethylene resin particles, and 1. 2% by mass is dispersed. The coating solution thus prepared was applied to a thickness of about 2.5 μm by a spray coating method to form a charge injection layer 16.
[0447]
The volume resistance of the outermost surface layer of the photoreceptor thus obtained is 5 × 10¹²The contact angle with respect to water on the surface of the photoreceptor was 102 degrees.
[0448]
Next, a manufacturing example of the charging member used in the embodiment of the present invention will be described.
[0449]
<Production example of charging member>
A SUS roller having a diameter of 6 mm and a length of 264 mm is used as a core, and a medium-resistance urethane foam layer is formed on the core as a roller, in which urethane resin, carbon black as a conductive particle, sulfurizing agent, foaming agent, etc. are prescribed. Further, the shape and surface properties were adjusted by cutting and polishing. In this way, a charging roller having a flexible urethane foam roller having a diameter of 12 mm and a length of 234 mm was produced.
[0450]
The resulting charging roller has a resistance of urethane foam roller of 10⁵The hardness was 30 degrees in terms of Asker C hardness.
[0451]
<Toner Particle Production Example Ts-1>
Styrene-butyl acrylate-maleic acid butyl half ester copolymer (Tg 63 ° C., molecular weight: Mp 12000, Mn 6500, Mw 230000) 100 parts by mass
Magnetic iron oxide (average particle size 0.22 μm, 795.5 kA / m magnetic field coercive force (Hc) 5.2 kA / m, saturation magnetization (σs) 85 Am²/ Kg, remanent magnetization (σr) 5.0 Am²/ Kg) 90 parts by mass
・ Monoazo iron complex (negative charge control agent) 2 parts by mass
・ Low molecular weight ethylene-propylene copolymer 4 parts by mass
The above materials were mixed in a blender, the mixture was melt-kneaded with an extruder heated to 130 ° C., and the obtained kneaded product was cooled, coarsely pulverized, and finely pulverized using a fine pulverizer using a jet stream. . Further, the obtained finely pulverized product is strictly classified by a multi-division classifier using the Coanda effect, and a weight average particle size of 7 determined from a volume-based particle size distribution in a particle size range of 0.60 μm or more and less than 159.21 μm. 9 μm toner particles Ts-1 were obtained. The resistance of the toner particle Ts-1 is 10¹⁴It was Ω · cm or more.
[0452]
The circularity distribution was measured by a method using a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.) as described in the embodiment of the invention. To describe in more detail, water (with an equivalent to a circle) is obtained by removing fine dust through a filter into a hard glass screw mouth bottle (for example, 30 ml screw mouth bottle SV-30 manufactured by Nidec Rika Glass Co., Ltd.) having an inner diameter of 30 mm and a height of 65 mm. The number of particles in the particle size range of 0.60 μm or more and less than 159.21 μm³cm³A few drops of diluted surfactant (preferably an alkylbenzene sulfonate salt diluted about 10 times with water from which fine dust has been removed) were added. The measurement sample is a particle having a measurement circle equivalent diameter range, and the measurement sample has a particle concentration of 7000 to 10,000 particles / 10.³cm³Appropriate amount (for example, 0.5-20 mg) is added, and a 6 mm diameter step type chip is applied to ULTRASONICHOMOGENIZERH-50 manufactured by SMT Co., Ltd. for 3 minutes with an ultrasonic homogenizer (output 50 W, frequency 20 kHz). Using a sample dispersion liquid in which the scale of the power control volume is set to 7, that is, processing with a dispersion force about half of the maximum output when the chip is used) is 0.60 μm or more and 159.21 μm The particle size distribution and circularity distribution of particles having an equivalent circle diameter of less than were measured.
[0453]
From the obtained particle size distribution, the content (number%) of particles having a particle size range of 1.00 μm or more and less than 2.00 μm and the circularity were determined. The physical property values of the toner particles Ts-1 are shown in Table 2.
[0454]
<Toner Particle Production Example Ts-2>
The coarsely pulverized product obtained in Production Example Ts-1 of toner particles was finely pulverized by a mechanical pulverizer. The obtained finely pulverized product is classified by a multi-division classifier, and toner particles Ts-2 having a weight average particle size of 6.8 μm obtained from a volume-based particle size distribution in a particle size range of 0.60 μm or more and less than 159.21 μm are obtained. Obtained. The resistance of the toner particles is 10¹⁴It was Ω · cm or more.
[0455]
<Toner Particle Production Example Ts-3>
The classified product obtained in the toner particle production example Ts-2 is spheroidized by repeatedly applying a thermomechanical impact force to the particles using the toner particle spheroidizing apparatus shown in FIGS. Toner particles Ts-3 having a weight average particle diameter of 6.5 μm determined from a volume-based particle size distribution in a particle diameter range of .60 μm or more and less than 159.21 μm were obtained.
[0456]
<Toner Particle Production Example Ts-4>
The classified product obtained in Production Example Ts-3 of Toner Particles was subjected to a spheronization treatment that instantaneously passed through hot air at 300 ° C. to obtain magnetic toner particles Ts-4 having a weight average particle size of 6.9 μm. . The resistance of the magnetic toner particle Ts-4 is 10¹⁴It was Ω · cm.
[0457]
<Toner Particle Production Example Tp-1>
Polyester resin (Tg 60 ° C., acid value 20 mgKOH / g, hydroxyl value 30 mgKOH / g, molecular weight: Mp7000, Mn3000, Mw55000) 100 parts by mass
Magnetic iron oxide (average particle size 0.20 μm, Hc 9.2 kA / m in a magnetic field of 795.5 kA / m, σs 82 Am²/ Kg, σr11.5Am²/ Kg) 90 parts by mass
・ Monoazo iron complex (negative charge control agent) 2 parts by mass
・ Low molecular weight ethylene-propylene copolymer 4 parts by mass
The above materials are finely pulverized and classified using a fine pulverizer using melt kneading, coarse pulverization, and jet airflow in the same manner as in the toner particle production example Ts-1, and are classified to 0.60 μm or more and less than 159.21 μm. Toner particles Tp-1 having a weight average particle size of 8.1 μm determined from the volume-based particle size distribution in the particle size range were obtained. The resistance of the toner particle Tp-1 is 10¹⁴It was Ω · cm or more.
[0458]
<Toner particle production example Tp-2>
The coarsely pulverized product obtained in the toner particle production example Tp-1 was finely pulverized by a mechanical pulverizer. The obtained finely pulverized product is classified by a multi-division classifier, and toner particles Tp-2 having a weight average particle size of 7.0 μm obtained from a volume-based particle size distribution in a particle size range of 0.60 μm or more and less than 159.21 μm are obtained. Obtained. The resistance of the toner particles is 10¹⁴It was Ω · cm or more.
[0459]
<Toner Particle Production Example Tp-3>
The classified product obtained in the toner particle production example Tp-2 is spheroidized by repeatedly applying a thermomechanical impact force to the particles using the toner particle spheroidizing apparatus shown in FIGS. Thus, toner particles Tp-3 having a weight average particle diameter of 6.7 μm determined from a volume-based particle size distribution in a particle diameter range of 60 μm or more and less than 159.21 μm were obtained.
[0460]
<Toner Particle Production Example Tp-4>
Toner Particle Production Example Tp-3 was subjected to spheronization treatment that instantaneously passed through hot air at 300 ° C. to obtain magnetic toner particles Tp-4 having a weight average particle diameter of 7.2 μm. . The resistance of the magnetic toner particle Tp-4 is 10¹⁴It was Ω · cm.
[0461]
Table 2 shows typical physical property values of the toner particles Ts-1 to T4 and Tp-1 to Tp-4.
[0462]
[Table 2]

[0463]
<Production Example I-1 of inorganic fine powder>
Hydrophobic dry silica fine powder treated with hexamethyldisilazane and then treated with dimethyl silicone oil was designated as inorganic fine powder I-1. The number average diameter of the primary particles of this inorganic fine powder I-1 is 12 nm, and the BET specific surface area is 120 m.²/ G.
[0464]
<Example I-2 of inorganic fine powder>
The dry silica fine powder treated with hexamethyldisilazane was designated as inorganic fine powder I-2. The number average diameter of the primary particles of this inorganic fine powder I-2 is 16 nm, and the BET specific surface area is 170 m.²/ G.
[0465]
Table 3 shows typical physical property values of the inorganic fine powders I-1 to I-2.
[0466]
[Table 3]

[0467]
<Examples of conductive fine particles C-1 to C-3>
Zinc oxide having a volume average particle size of 0.07 μm, 1.52 μm, and 2.03 μm was used as conductive fine particles C-1, C-2, and C-3. The resistance of the conductive fine particles measured by the tablet method described in the embodiment of the invention is 1.2 × 10 respectively.³Ω · cm, 8.9 × 10³Ω · cm, 2.7 × 10⁴It was Ω · cm.
[0468]
<Examples C-4 to 6 of conductive fine particles>
Tin oxide having a volume average particle size of 0.50 μm, 1.15 μm, and 5.22 μm was used as conductive fine particles C-4, C-5, and C-6. The resistance of the conductive fine particles measured by the tablet method described in the embodiment of the invention is 7.3 × 10 respectively.⁴Ω · cm, 1.2 × 10⁵Ω · cm, 1.8 × 10⁷It was Ω · cm.
[0469]
<Example C-7 of conductive fine particles>
Conductive fine particles obtained by attaching 50% tin oxide by mass to titanium oxide powder having a particle size of about 0.1 μm were designated as conductive fine particles C-7. The resistance of the conductive fine particles measured by the tablet method described in the embodiment of the invention is 3.1 × 10²It was Ω · cm.
[0470]
Table 4 shows typical physical property values of the conductive fine particles C-1 to C-7.
[0471]
[Table 4]

[0472]
<Developer Production Example Rs-0>
Toner Particle Production Example Ts-1 Magnetic toner particle Ts-1 obtained in 100 parts by mass is added to 1.23 parts by mass of inorganic fine powder I-1, and mixed uniformly with a mixer to produce developer Rs. -0 was obtained.
[0473]
The number-based particle size distribution of the obtained magnetic developer Rs-0 in the particle size range of 0.60 μm or more and less than 159.21 μm is determined by the flow particle image analyzer FPIA-1000 (Toa as described in the toner particle production example). It was measured by a method using a medical electronics company. Table 5 shows the physical property values of the developer Rs-0.
[0474]
<Developer Production Example Rs-1>
Toner Particle Production Example Ts-1 magnetic toner particle Ts-1 obtained in 100 parts by mass, inorganic fine powder I-1 1.23 parts by mass and conductive fine particles C-4 1.03 parts by mass And a developer Rs-1 was obtained by uniformly mixing with a mixer.
[0475]
<Examples of developer production Rs-2 to 7>
Developer Production Example Rs-1 except that the conductive fine particles C-4 were changed to C-5, C-2, C-3, C-7, C-6, and C-1, respectively. Developers Rs-2, Rs-3, Rs-4, Rs-5, Rs-6, and Rs-7 were obtained in the same manner as in Example RS-1.
[0476]
<Production Examples of Developer Rs-8 to 10>
In developer production example Rs-1, in the same manner as in developer production example Rs-1, except that toner particles Ts-2, Ts-3, and Ts-4 were used instead of toner particles Ts-1. Developers Rs-8, Rs-9, and Rs-10 were obtained.
[0477]
<Developer Production Example Rp-0>
Toner Particle Production Example Tp-1 Magnetic toner particle Tp-1 obtained in 100 parts by mass is added with 1.23 parts by mass of inorganic fine powder I-2, and mixed uniformly with a mixer to obtain developer Rp. -0 was obtained.
[0478]
<Developer Production Example Rp-1>
Toner Particle Production Example Tp-1 magnetic toner particle Tp-1 obtained in 100 parts by mass, inorganic fine powder I-2 1.23 parts by mass and conductive fine particles C-4 1.03 parts by mass And a developer Rp-1 was obtained by uniformly mixing with a mixer.
[0479]
<Examples of developer production Rp-2 to 7>
Developer Production Example Rp-1 except that the conductive fine powder C-4 was changed to C-5, C-2, C-3, C-7, C-6, C-1, respectively. Developers Rp-2, Rp-3, Rp-4, Rp-5, Rp-6, and Rp-7 were obtained in the same manner as in Production Example Rp-1.
[0480]
<Production Examples of Developer Rp-8 to 10>
In developer production example Rp-1, in the same manner as in developer production example Rp-1, except that toner particles Tp-2, Tp-3, and Tp-4 were used instead of toner particles Tp-1. Developers Rp-8, Rp-9, and Rp-10 were obtained.
[0481]
Content of particles having a weight average particle size of each of the developers Rs-0 to 10 and Rp-0 to 10, and particle sizes in the range of 1.00 μm to less than 2.00 μm and 3.00 μm to less than 8.96 μm (number%) ) Are shown in Table 5, respectively.
[0482]
[Table 5]

[0483]
<Developer carrier production example Dp-1-1>
As the nitrogen-containing heterocyclic compound which is a positively chargeable substance, imidazole compound particles having a number average particle diameter of 3 μm represented by the general formula B-1 were used.
[0484]
Embedded image

[0485]
・ 400 parts by mass of resol type phenolic resin solution (containing 50% methanol)
・ 15 parts by mass of nitrogen-containing heterocyclic compound B-1 (imidazole compound)
・ Isopropyl alcohol 335 parts by mass
The above-mentioned material is subjected to sand mill dispersion with glass particles having a diameter of 2 mm for 1 hour, and then the glass particles are separated by sieving. The sample plate was prepared by heating and curing at / 30 minutes. When this sample plate was grounded, it was left overnight in an environment of 23 ° C. and a relative humidity of 60%, and when this was measured for the triboelectric charge polarity with the iron powder as described above, it showed positive chargeability. .
[0486]
As conductive spherical particles, 100 parts by mass of spherical phenol resin particles having a number average particle size of 7.8 μm and 14 parts by mass of coal-based bulk mesophase pitch powder having a number average particle size of 2 μm or less using a Reika machine (automatic mortar, manufactured by Ishikawa Kogyo). Spherical conductivity with a number average particle size of 7.2 μm obtained by uniform coating, graphitizing by heat-stabilizing at 280 ° C. in air and then baking at 2000 ° C. in a nitrogen atmosphere, followed by classification Carbon particles were used.
・ 20 parts by mass of conductive carbon black
・ 80 parts by mass of graphite having a number average particle size of 3.4 μm
・ 400 parts by mass of resol type phenol resin solution (containing 50% methanol)
・ 15 parts by mass of nitrogen-containing heterocyclic compound B-1 (imidazole compound)
・ 10 parts by mass of spherical carbon particles (number average particle size 7.2 μm)
・ 125 parts by mass of isopropyl alcohol
The above material is subjected to sand mill dispersion with zirconia particles having a diameter of 2 mm for 3 hours, and then the zirconia particles are separated by sieving, and the solid content is adjusted to 40% with isopropyl alcohol, and coating liquid (c (carbon) / GF (graphite)) / B (phenol resin) / CA (nitrogen-containing heterocyclic compound B-1) / R (spherical particles) = 0.2 / 0.8 / 2.0 / 0.15 / 0.1). This coating solution was coated and dried on an insulating sheet with a bar coater, cut into a regular shape, and measured with a low resistivity meter Lorester (Mitsubishi Chemical Corporation). The volume resistivity was 3.52Ω · cm.
[0487]
This paint was sprayed to form a 15 μm film on an Al cylinder having a diameter of 16 mm, and then heated and cured by a hot air dryer at 150 ° C. for 30 minutes to prepare a developer carrying member Dp-1-1. When Ra of the surface of the conductive coating layer on the developer carrying member was measured with a Surfcoder SE-3300 (manufactured by Kosaka Laboratory) at an evaluation length of 4 mm and 6 points, the average value was calculated. It was 21 μm.
[0488]
<Developer carrying body production example Dp-1-2-4>
As the nitrogen-containing heterocyclic compound, imidazole compound particles having a number average particle diameter of 3 μm represented by general formulas B-2 to B-4 were used.
[0489]
Embedded image

[0490]
When the triboelectric charge polarity with the iron powder was measured in the same manner as in Developer Carrier Production Example Dp-1-1, all showed positive chargeability.
[0491]
This was dispersed and coated in the same manner as in Developer Carrier Production Example Dp-1-1 to produce Developer Carriers Dp-1-2 to 4, and the same evaluation was performed.
[0492]
<Developer carrier production example Dp-n-1>
・ 600 parts by mass of resol type phenolic resin solution (containing 50% methanol)
Nitrogen-containing heterocyclic compound B-1 (imidazole compound) 20 parts by mass
・ 447 parts by mass of isopropyl alcohol
The above material is subjected to sand mill dispersion with glass particles having a diameter of 2 mm for 1 hour, and then the glass particles are separated by sieving, and this resin solution is applied on a SUS plate with a bar coater (# 60). Heat and cure at a temperature of 30 ° C./30 minutes to prepare a sample plate. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%. As described in the embodiment of the present invention, when the triboelectric charge polarity with the iron powder was measured, it showed positive chargeability.
・ 20 parts by mass of conductive carbon black
・ 80 parts by mass of graphite with a number average particle size of 3.4 μm
・ 600 parts by mass of resol type phenolic resin solution (containing 50% methanol)
Nitrogen-containing heterocyclic compound B-1 (imidazole compound) 20 parts by mass
・ Spherical carbon particles (number average particle diameter 3.7 μm) 10 parts by mass
・ 700 parts by mass of isopropyl alcohol
Add zirconia beads with a diameter of 2 mm to the above materials as media particles, disperse in a sand mill for 2 hours, separate the beads with a sieve, adjust the solid content to 40% with isopropyl alcohol, and apply the coating liquid (c (carbon) / GF (graphite) / B (binder resin) / CA (nitrogen-containing heterocyclic compound B-1) / R (spherical particles) = 0.2 / 0.8 / 3.0 / 0.2 / 0.1 )
[0493]
This was dispersed and applied in the same manner as in Developer Carrier Production Example Dp-1-1 to produce Developer Carrier Dp-n-1, and the same evaluation was performed.
[0494]
<Developer carrier production example Dp-n-2 to 4>
Developer support Dp-n-1 is the same as Developer support Dp-n-1, except that the nitrogen-containing heterocyclic compound is replaced with B-2 to B-4. -N-2 to 4 were prepared and evaluated in the same manner.
[0495]
[Table 6]

[0496]
<Developer carrier production example Dm-1-1>
・ 320 parts by mass of resol type phenolic resin (solid content 50%)
Methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-1 (solid content 50%) (molar ratio 90:10, Mw = 10,200, Mn = 4,500, Mw / Mn = 2.3) 80 parts by mass
・ 400 parts by mass of MEK
The above-mentioned material is subjected to sand mill dispersion with glass particles having a diameter of 2 mm for 1 hour, and then the glass particles are separated by sieving. / A sample is prepared by heating and curing in 30 minutes. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%. As described in the embodiment of the present invention, when the triboelectric charge polarity with the iron powder was measured, it showed positive chargeability.
[0497]
As spherical particles, 14 parts of a coal-based bulk mesophase pitch powder having a number average particle diameter of 2 μm or less is uniformly applied to 100 parts of spherical phenol resin particles having a number average particle diameter of 7.8 μm using a laika machine (automatic mortar, manufactured by Ishikawa Factory). Spherical conductive carbon particles having a number average diameter of 11.7 μm obtained by coating, heat-stabilizing at 280 ° C. in air, graphitizing by firing at 2000 ° C. in a nitrogen atmosphere, and further classification were used. .
・ Carbon black 20 parts by mass
・ 80 parts by mass of crystalline graphite having a number average particle diameter of 4.8 μm
・ 320 parts by mass of resol type phenolic resin (solid content 50%)
Methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-1 (solid content 50%) (molar ratio 90:10, Mw = 10,200, Mn = 4,500, Mw / Mn = 2.3) 80 parts by mass
・ Spherical carbon particles (number average particle diameter 11.7 μm) 30 parts by mass
・ 130 parts by mass of MEK
The above material is subjected to sand mill dispersion with zirconia particles having a diameter of 2 mm for 3 hours, after which the zirconia particles are separated by sieving, the solid content is adjusted to 40% with MEK, and the coating liquid (c (carbon) / GF (graphite) / B (phenol resin) / D (copolymer P-1) / R (spherical particles) = 0.2 / 0.8 / 1.6 / 0.4 / 0.3). This coating solution was coated and dried on an insulating sheet with a bar coater, cut into a regular shape, and measured with a low resistivity meter Lorester (Mitsubishi Chemical Corporation). The volume resistivity was 5.03Ω. cm.
[0498]
This paint was sprayed to form a 15 μm film on an Al cylinder having a diameter of 16 mm, and then heated and cured at 150 ° C./30 minutes with a hot air drier to produce developer carrier D-1. When Ra of the surface of the conductive coating layer on the developer carrying member was measured with a Surfcoder SE-3300 (manufactured by Kosaka Laboratory) at an evaluation length of 4 mm and 6 points, the average value was calculated. It was 27 μm.
[0499]
<Developer carrier production example Dm-1-2-4>
Copolymer P-2 in which the molecular weight of the copolymer and the molar ratio of methyl methacrylate to dimethylaminoethyl methacrylate were changed in place of the copolymer P-1 used in Developer Carrier Production Example Dm-1-1 To 4, developer carrier Dm-1-2 to 4 are produced in the same manner as developer carrier production example Dm-1-1, and the same as developer carrier production example Dm-1-1. Evaluation was performed.
[0500]
Copolymer used for developer carrier Dm-1-2
Methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-2 (solid content 40%) (molar ratio 90:10, Mw = 40,000, Mn = 19000, Mw / Mn = 2.1)
Copolymer used for developer carrier Dm-l-3
Methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-3 (solid content 40%) (molar ratio 90:10, Mw = 3,700, Mn = 2,300, Mw / Mn = 1.6)
Copolymer used for developer carrier Dm-1-4
Methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-4 (solid content 40%) (molar ratio 70:30, Mw = 8,500, Mn = 2,900, Mw / Mn = 2.9)
<Developer carrier production example Dm-n-1>
-460 parts by mass of resol type phenolic resin (solid content 50%)
・ 140 parts by mass of methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-1 (solid content 50%)
・ 400 parts by mass of MEK
The above material is subjected to sand mill dispersion for 1 hour with glass particles having a diameter of 2 mm, and then the glass particles are separated by sieving, and this resin solution is applied onto a SUS plate with a bar coater (# 60). Is heated and cured at 150 ° C./30 minutes to prepare a sample plate. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%. As described in the embodiment of the present invention, when the triboelectric charge polarity with the iron powder was measured, it showed positive chargeability.
・ Carbon black 20 parts by mass
・ 80 parts by mass of crystalline graphite having a number average particle diameter of 4.8 μm
-460 parts by mass of resol type phenolic resin (solid content 50%)
・ 140 parts by mass of methyl methacrylate-dimethylaminoethyl methacrylate copolymer P-1 (solid content 50%)
・ Spherical carbon particles (number average particle size 7.2 μm) 30 parts by mass
・ 130 parts by mass of MEK
Add zirconia beads with a diameter of 2 mm to the above materials as media particles, disperse in a sand mill for 2 hours, separate the beads using a sieve, adjust the solid content to 40% with MEK, and apply coating solution (c (carbon) / GF (graphite) / B (binder resin) / D (copolymer P-1) / R (spherical particles) = 0.2 / 0.8 / 2.3 / 0.7 / 0.3) It was.
[0501]
This was dispersed and applied in the same manner as in Developer Carrier Production Example Dm-1-1 to produce Developer Carrier Dm-n-1, and the same evaluation was performed.
[0502]
<Developer carrier production example Dm-n-2 to 4>
Developer carrier Dm-n in the same manner as Developer carrier production example Dm-n-1, except that the copolymer was changed to P-2 to P-4 in Developer carrier production example Dm-n-1. −2 to 4 were prepared and evaluated in the same manner.
[0503]
[Table 7]

[0504]
<Developer carrier production example Df-1-1>
<Manufacture of charge control resin>
・ Methanol: 300 parts by mass
・ Toluene: 100 parts by mass
・ Styrene: 468 parts by mass
・ 2-ethylhexyl acrylate: 90 parts by mass
2-acrylamide-2-methylpropanesulfonic acid: 42 parts by mass
・ Lauroyl peroxide: 6 parts by mass
The above raw materials were charged into a flask, equipped with a stirrer, a temperature measuring device, and a nitrogen introducing device, and solution polymerized at 65 ° C. in a nitrogen atmosphere, and held for 10 hours to complete the polymerization reaction. The obtained polymer was dried under reduced pressure and pulverized to obtain a charge control resin F-1 having a weight average molecular weight of 10,000.
[0505]
Hereinafter, the charge control resins F-2 and F-3 were obtained by changing the composition ratio as shown in Table 8.
[0506]
Charge control resin solution F-1 was prepared by dissolving 50 parts by mass of charge control resin F-1 in 50 parts by mass of methyl ethyl ketone.
・ Phenolic resin (containing 50% methanol) 340 parts by mass
Charge control resin solution F-1 (containing 50% MEK) 60 parts by mass
・ 267 parts by mass of isopropyl alcohol
The above-mentioned material is subjected to sand mill dispersion with glass particles having a diameter of 2 mm for 1 hour, and then the glass particles are separated by sieving. / A sample is prepared by heating and curing in 30 minutes. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%. As described in the embodiment of the present invention, when the triboelectric charge polarity with the iron powder was measured, it showed positive chargeability.
・ Carbon black 20 parts by mass
・ 80 parts by mass of crystalline graphite having a number average particle size of 5.5 μm
・ Phenolic resin produced using ammonia as a catalyst (containing 50% methanol)
340 parts by mass
Charge control resin solution F-1 (containing 50% MEK) 60 parts by mass
・ 20 parts by mass of spherical carbon particles (number average particle diameter 11.7 μm)
・ Isopropyl alcohol 120 parts by mass
[0507]
This paint was sprayed to form a 15 μm film on an Al cylinder having a diameter of 16 mm, and then heated and cured by a hot air dryer at 150 ° C. for 30 minutes to prepare a developer carrying member Df-1-1. When Ra of the surface of the conductive coating layer on the developer carrying member was measured with a Surfcoder SE-3300 (manufactured by Kosaka Laboratory) at an evaluation length of 4 mm and 6 points, the average value was calculated. It was 07 μm.
[0508]
<Developer carrier production example Df-1-2>
Developer carrier production example Df-l except that the phenol resin produced using ammonia as a catalyst in the developer carrier production example Df-1-1 was replaced with a phenol resin produced using hexamethylenetetramine as a catalyst. The developer carrying member Df-1-2 was produced in the same manner as in Example 1, and the same evaluation as in the developer carrying member production example Df-1-1 was performed.
[0509]
<Developer carrier production example Df-l-3>
Instead of the charge control resin F-1 used in developer carrier production example Df-1-1, the charge control resin F-2 obtained by changing the composition ratio as shown in Table 8 was used, and ammonia was used. A developer carrier Df-l-3 was produced in the same manner as in the developer carrier production example Df-l-1, except that the phenol resin produced using the catalyst was replaced with a polyamide resin. Evaluation similar to Example Df-1-1 was performed.
[0510]
<Developer carrier production example Dfl-4>
Instead of the charge control resin F-1 used in Developer Carrier Production Example Df-l-1, charge control resin F-3 obtained by changing the composition ratio as shown in Table 8 was used, and ammonia was used. A developer carrier Df-1-4 was produced in the same manner as in the developer carrier production example Df-l-1, except that the phenol resin produced using the catalyst as a catalyst was replaced with a polyurethane resin. Evaluation similar to Example Df-1-1 was performed.
[0511]
<Developer carrier production example Df-n-1>
・ Phenolic resin (containing 50% methanol) 500 parts by mass
-Charge control resin solution F-1 (containing 50% MEK) 100 parts by mass
・ Isopropyl alcohol 400 parts by mass
The above-mentioned material is subjected to sand mill dispersion with glass particles having a diameter of 2 mm for 1 hour, and then the glass particles are separated by sieving. / A sample is prepared by heating and curing in 30 minutes. With this sample plate grounded, it is left overnight in an environment of 23 ° C. and a relative humidity of 60%. As described in the embodiment of the present invention, when the triboelectric charge polarity with the iron powder was measured, it showed positive chargeability.
・ Carbon black 20 parts by mass
・ 80 parts by mass of crystalline graphite having a number average particle size of 5.5 μm
・ Phenolic resin produced using ammonia as a catalyst (containing 50% methanol)
500 parts by weight
-Charge control resin solution F-1 (containing 50% MEK) 100 parts by mass
・ 20 parts by mass of spherical carbon particles (number average particle size 7.2 μm)
・ Isopropyl alcohol 120 parts by mass
Add zirconia beads with a diameter of 2 mm to the above materials as media particles, disperse in a sand mill for 2 hours, separate the beads with a sieve, adjust the solid content to 40% with isopropyl alcohol, and apply the coating liquid (c (carbon) / GF (graphite) / B (binder resin) / CA (charge control resin F-1) / R (spherical particles) = 0.2 / 0.8 / 2.5 / 0.5 / 0.2) Obtained.
[0512]
This was coated in the same manner as in Developer Carrier Production Example Df-1-1 to produce Developer Carrier Df-n-1, and evaluated in the same manner as Developer Carrier Production Example Df-1-1. went.
[0513]
<Developer carrier production example Df-n-2>
Developer carrier production example Df-n, except that the phenol resin produced using ammonia as a catalyst in the developer carrier production example Df-n-1 was replaced with a phenol resin produced using hexamethylenetetramine as a catalyst. The developer carrying member Df-n-2 was prepared in the same manner as in Example 1, and the same evaluation as in the developer carrying member production example Df-n-1 was performed.
[0514]
<Developer carrier production example Df-n-3>
Instead of the charge control resin F-1 used in Developer Carrier Production Example Df-n-1, a charge control resin F-2 obtained by changing the composition ratio as shown in Table 8 was used, and ammonia was used. A developer carrier Df-n-3 was produced in the same manner as in the developer carrier production example Df-n-1, except that the phenol resin produced using the catalyst was replaced with a polyamide resin. Evaluation similar to Example Df-n-1 was performed.
[0515]
<Developer carrier production example Df-n-4>
Instead of the charge control resin F-1 used in Developer Carrier Production Example Df-n-1, a charge control resin F-3 obtained by changing the composition ratio as shown in Table 8 was used, and ammonia was used. A developer carrier Df-n-4 was produced in the same manner as in the developer carrier production example Df-n-1, except that the phenol resin produced using the catalyst was replaced with a polyurethane resin. Evaluation similar to Example Df-n-1 was performed.
[0516]
[Table 8]

[0517]
<Description of Image Forming Apparatus>
FIG. 1 is a diagram illustrating an example of the configuration of an image forming apparatus according to the present invention. This image forming apparatus is a laser printer (recording apparatus) of a development and cleaning process (cleanerless system) using a transfer type electrophotographic process. A process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed is used, and a magnetic one-component developer (that is, a magnetic toner having an external additive and magnetic toner particles) is used as a developer. 1 is an example of an image forming apparatus for non-contact development in which a developer layer on an image bearing member and an image bearing member are arranged in non-contact with each other.
[0518]
(1) Configuration of image forming apparatus
Reference numeral 1 denotes a rotating drum type OPC photoconductor of the photoconductor production example 1 as a latent image carrier, which is driven to rotate at a peripheral speed (process speed) of 100 mm / sec in the clockwise direction (the direction of the arrow).
[0519]
Reference numeral 2 denotes a charging roller of a manufacturing example of a charging member as a contact charging member, and includes a cored bar 2a and an elastic layer 2b. The charging roller 2 is disposed in pressure contact with the photoreceptor 1 with a predetermined pressing force against elasticity. n is a charging portion that is a contact portion between the photosensitive member 1 and the charging roller 2. In this embodiment, the charging roller 2 has a peripheral speed of 141 mm / sec (relative moving speed ratio 250%) in the counter direction (the direction opposite to the moving direction of the surface of the photoconductor) at the charging unit n which is a contact portion with the photoconductor 1. It is driven by rotation. In addition, the same conductive fine powder m as the conductive fine powder m externally added to the toner particles t was applied in advance to the surface of the charging roller 2 so that the coating amount was uniform in one layer.
[0520]
A DC voltage of -700 V was applied as a charging bias to the cored bar 2a of the charging roller 2 from the charging bias application power source S1. In this embodiment, the surface of the photoreceptor 1 is uniformly charged by a direct injection charging method to a potential (−680 V) substantially equal to the voltage applied to the charging roller 2. This will be described later.
[0521]
A laser beam scanner (exposure device) 3 includes a laser diode, a polygon mirror, and the like. This laser beam scanner outputs intensity-modulated laser light (wavelength 740 nm) corresponding to time-series electric digital pixel signals of target image information, and scans and exposes the uniformly charged surface of the photoreceptor 1 with the laser light. To do. By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the photoreceptor 1.
[0522]
Reference numeral 4 denotes a developing device. The electrostatic latent image on the surface of the photoreceptor 1 is developed as a toner image by the developing device. The developing device 4 of this embodiment is a non-contact type reversal developing device using the developer 1 which is a negatively chargeable one-component insulating developer as a developer. Developer 4d has toner particles t and conductive fine powder m.
[0523]
Reference numeral 4a denotes a non-magnetic developing sleeve having a diameter of 16 mm that includes a magnet roll 4b as a developer carrying member. The developing sleeve 4 a is disposed to face the photosensitive member 1 with a separation distance of 300 μm, and the developing portion (developing region portion) a which is a portion facing the photosensitive member 1 is arranged in the rotational direction of the photosensitive member 1. It is rotated in the forward direction at a peripheral speed 120% of the peripheral speed of the photosensitive member 1 (peripheral speed 120 mm / sec).
[0524]
On the developing sleeve 4a, the developer 4d is coated in a thin layer by the elastic blade 4c. The developer 4d is given a charge while the layer thickness on the developing sleeve 4 is regulated by the elastic blade 4c.
[0525]
The developer 4d coated on the developing sleeve 4a is transported to the developing portion a which is a facing portion between the photoreceptor 1 and the sleeve 4a as the sleeve 4a rotates. A developing bias voltage is applied to the sleeve 4a by a developing bias applying power source S2. The developing bias voltage is a DC voltage of −420 V, a frequency of 1600 Hz, a peak-to-peak voltage of 1500 V (electric field strength of 5 × 10⁶A one-component jumping development was performed between the developing sleeve 4a and the photoreceptor 1 using a superposed voltage of a rectangular alternating voltage of V / m).
[0526]
Reference numeral 5 denotes a medium resistance transfer roller as a contact transfer means, which is brought into pressure contact with the photosensitive member 1 with a linear pressure of 98 N / m to form a transfer contact portion b. A transfer material P as a recording medium is fed to the transfer contact portion b from a paper feed portion (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 5 from a transfer bias application power source S3. Thus, the toner image on the photosensitive member 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer contact portion b.
[0527]
In this embodiment, the transfer roller 5 has a resistance of 5 × 10.⁸Transferring was performed by applying a DC voltage of +3000 V using an Ωcm one. That is, the transfer material P introduced into the transfer contact portion b is nipped and conveyed by the transfer contact portion b, and the toner images formed and supported on the surface of the photosensitive member 1 on the surface side are successively subjected to electrostatic force. It is transferred by pressing force.
[0528]
Reference numeral 6 denotes a fixing device such as a heat fixing method. The transfer material P that has been fed to the transfer nip b and has received the transfer of the toner image on the photosensitive member 1 side is separated from the surface of the photosensitive member 1 and introduced into the fixing device 6 to receive the fixing of the toner image. Then, it is discharged out of the apparatus as an image formed product (print, copy).
[0529]
In the image forming apparatus of this example, the cleaning unit is removed, and residual developer (transfer residual toner particles) remaining on the surface of the photoreceptor 1 after the transfer of the toner image onto the transfer material P is removed by the cleaning unit. Instead, as the photosensitive member 1 rotates, it reaches the developing portion a via the charging portion n and is developed and cleaned (collected) in the developing device 4.
[0530]
In the image forming apparatus of this example, the three process devices of the photosensitive member 1, the charging roller 2, and the developing device 4 are collectively configured as a process cartridge 7 that is detachable from the image forming apparatus main body. In the present invention, the combination of process devices to be process cartridges is not limited to the above, and is arbitrary. Reference numeral 8 denotes a process cartridge attachment / detachment guide / holding member.
[0531]
(2) Conductive fine powder behavior
An appropriate amount of the conductive fine powder m contained in the developer 4d of the developing device 4 is transferred to the photoconductor 1 side together with the toner particles t during toner development by the developing device 4 of the electrostatic latent image on the photoconductor 1 side. .
[0532]
The toner image (that is, toner particles) on the photoreceptor 1 is attracted to the transfer material P, which is a recording medium, under the influence of the transfer bias at the transfer portion b and actively transferred. However, since the conductive fine powder m on the photoconductor 1 is conductive, it does not actively transfer to the transfer material P side, and remains substantially adhered and held on the photoconductor 1.
[0533]
In this embodiment, since the image forming apparatus does not have a cleaning process, the transfer residual toner particles and the conductive fine powder remaining on the surface of the photoreceptor 1 after the transfer are exposed to the photosensitive member 1 as the photoreceptor 1 rotates. It is carried to the charging part n which is a contact part between the body 1 and the charging roller 2 which is a contact charging member, and adheres to the charging roller 2. Therefore, direct injection charging of the photosensitive member 1 is performed in a state where the conductive fine powder m exists in the contact portion n between the photosensitive member 1 and the charging roller 2.
[0534]
Due to the presence of the conductive fine powder m, even when transfer residual toner particles adhere to the charging roller 2, it is possible to maintain the close contact and contact resistance of the charging roller 2 to the photosensitive member 1. It is possible to perform direct injection charging of the photoreceptor 1 by the above.
[0535]
That is, the charging roller 2 is in close contact with the photosensitive member 1 through the conductive fine powder m, and the conductive fine powder m rubs the surface of the photosensitive member 1 without a gap. As a result, the charging of the photosensitive member 1 by the charging roller 2 can be dominated by stable and safe linear injection charging without using a discharge phenomenon, and high charging that cannot be obtained by conventional roller charging or the like. Efficiency is obtained. Accordingly, a potential substantially equal to the voltage applied to the charging roller 2 can be applied to the photoreceptor 1.
[0536]
Further, the transfer residual toner particles adhering to or mixed in the charging roller 2 are gradually discharged from the charging roller 2 onto the photosensitive member 1 and reach the developing unit a along with the movement of the surface of the photosensitive member 1. It is cleaned (collected).
[0537]
In the development and cleaning, the toner particles remaining on the photoreceptor 1 after the transfer are developed at the next and subsequent developments in the image forming process (after development, the latent image is developed again through the charging process and the exposure process). It is recovered by a fog removing bias (fogging potential difference Vback which is a potential difference between the DC voltage applied to the developing device and the surface potential of the photoreceptor) of the developing device. In the case of reversal development, as in the image forming apparatus in this embodiment, this development and cleaning includes an electric field that collects toner particles from the dark portion potential of the photosensitive member due to the developing bias to the developing sleeve, and a bright portion of the photosensitive member from the developing sleeve. This is done by the action of an electric field that attaches (develops) toner particles to the potential.
[0538]
Further, when the image forming apparatus is operated, the conductive fine powder m contained in the developer of the developing device 4 moves to the surface of the photosensitive member 1 at the developing portion a, and moves along with the movement of the surface of the photosensitive member 1. Since the conductive fine powder m continues to be sequentially supplied to the charging portion n by being carried to the charging portion n through the transfer portion b, the conductive fine powder m is reduced in the charging portion n due to dropping or the like. Even if the conductive fine powder m of the part n is deteriorated, the chargeability is prevented from being lowered, and the good chargeability of the photoreceptor 1 is stably maintained.
[0539]
Thus, in an image forming apparatus using a contact charging method, a transfer method, or a toner recycling process, a simple charging roller 2 is used as a contact charging member, and uniform chargeability is imparted to the photoreceptor 1 as an image carrier at a low applied voltage. be able to. In addition, even when the transfer residual toner particles arrive at the charging portion, the ozone-less direct injection charging can be stably maintained over a long period of time, and uniform chargeability can be provided. Therefore, it is possible to obtain an image forming apparatus with a simple configuration and low cost, which is free from troubles caused by ozone products, troubles caused by defective charging, and the like.
[0540]
As described above, the conductive fine powder has a resistance value of 1 × 10 in order not to impair the chargeability.⁹Must be Ω · cm or less. Resistance value of conductive fine powder is 1 × 10⁹If it is greater than Ω · cm, the charging roller 2 is in close contact with the photosensitive member 1 through the conductive fine powder, and even if the conductive fine powder rubs the surface of the photosensitive member 1, the charge on the photosensitive member 1 is increased. The injection is not performed sufficiently, and it becomes difficult to charge the photoreceptor 1 to a desired potential. When a contact developing device in which the developer directly contacts the photoreceptor 1 is used, charge is injected into the photoreceptor 1 by the developing bias through the conductive fine powder in the developer in the developing section a, and image fogging or Image chipping and thin density occur.
[0541]
In this embodiment, since the developing device is a non-contact type developing device, a developing bias is not injected into the photoreceptor 1 and a good image can be obtained. In addition, since no charge is injected into the photosensitive member 1 in the developing portion a, it is possible to give a high potential difference between the developing sleeve 4a and the photosensitive member 1 such as an AC bias. As a result, the conductive fine powder m can be easily developed uniformly, so that the conductive fine powder m can be uniformly applied to the surface of the photosensitive member 1 and uniform contact can be made at the charging portion to obtain good chargeability. It is possible to obtain a good surface image.
[0542]
A speed difference is easily and effectively provided between the charging roller 2 and the photosensitive member 1 by the lubricating effect (friction reducing effect) of the conductive fine powder interposed on the contact surface between the charging roller 2 and the photosensitive member 1. Is possible. By this lubrication effect, friction between the charging roller 2 and the photosensitive member 1 can be reduced, driving torque can be reduced, and the surface of the charging roller 2 and the photosensitive member 1 can be prevented from being scraped or scratched. Also, by providing this speed difference, the chance of the conductive fine powder contacting the photoconductor 1 at the mutual contact portion (charging portion) n between the charging roller 2 and the photoconductor 1 is remarkably increased, and high contactability is obtained. be able to. Therefore, good direct injection charging is possible.
[0543]
In this embodiment, the charging roller 2 is driven to rotate, and the rotation direction of the charging roller 2 rotates in the direction opposite to the moving direction of the surface of the photosensitive member 1, so that the charging roller n is carried on the photosensitive member 1. The transfer residual toner particles are temporarily collected on the charging roller 2 to obtain an effect of leveling the amount of the transfer residual toner particles present in the charging portion n. For this reason, the occurrence of charging failure due to uneven distribution of the transfer residual toner particles at the charging portion n is prevented, and more stable charging property can be obtained.
[0544]
Further, by rotating the charging roller 2 in the reverse direction, the transfer residual toner particles on the photoconductor 1 are once separated from the photoconductor 1 to perform charging, whereby direct injection charging can be advantageously performed. Further, the charging property is not deteriorated due to excessive dropping of the conductive fine powder from the charging roller 2.
[0545]
<Example L-1>
A combination of developer Rs-1 and developer carrier Dp-1-1 was used. 120 g of developer Rs-1 is filled in the toner cartridge, and it is used until the developer amount is reduced in the toner cartridge by continuous printing of 3500 images of 5% coverage in the evaluation environment of 23 ° C./60%. did. 90g / m as transfer material²A4 copy paper was used. As a result, the image density was sufficiently high, fog was small, and no deterioration in developability was observed after the initial printing and after 3500 continuous printings.
[0546]
Further, after continuous printing of 3500 sheets, a portion corresponding to the contact portion n with the photosensitive member was observed on the charging roller, and although a small amount of residual toner particles were confirmed, it was almost covered with conductive fine particles C-4. It was broken.
[0547]
In addition, since the conductive fine particles C-4 are present in the contact portion n between the photosensitive member and the charging roller and the resistance of the conductive fine particles C-4 is sufficiently low, the initial printing is performed after 3500 continuous printings. Good direct injection chargeability was obtained without causing image defects due to poor charging.
[0548]
Further, the volume resistance of the outermost surface layer of the photosensitive member as a latent image carrier is 5 × 10 5.¹²Direct injection that can maintain an electrostatic latent image by using a photoconductor of Ω · cm, obtains a sharp outline character image, and provides sufficient chargeability even after continuous printing of 3500 sheets I was able to realize electrification. After direct injection charging after continuous printing of 3500 sheets, the photoreceptor potential is -690 V with respect to the applied charging bias of -700 V, and no deterioration in charging property is seen from the initial stage. There was no decline.
[0549]
Furthermore, combined with the use of a photoreceptor having a contact angle of 102 degrees with respect to the surface of the latent image carrier, the transfer efficiency was very good at the initial stage and after continuous printing of 3500 sheets. Even considering that the amount of residual toner particles on the photoreceptor after transfer is small, the amount of residual toner particles on the charging roller after 3500 continuous prints was small, and fogging of the non-image area was observed. From the fact that the amount is small, it can be seen that the recoverability of the transfer residual toner particles in the development was good.
[0550]
The print image evaluation method will be described below.
[0551]
(A) Image density
After the initial and 3500 continuous printouts were completed, the evaluation was performed based on the image density of the first sheet that was left for 2 days and turned on again. The image density was measured by using a “Macbeth reflection densitometer” (manufactured by Macbeth Co., Ltd.) to measure a relative density with respect to a printout image of a white background portion having a document density of 0.00. The evaluation results are shown in Table 11. In addition, each symbol in Table 11 means the following evaluation, respectively.
A: Image density (1.40 or more) that is very good and sufficient to express a graphic image with high quality.
B: Image density (1.35 or more and less than 1.40) sufficient to obtain a good, non-graphic and high-quality image.
C: Image density that is normal and acceptable as sufficient for character recognition (between 1.20 and less than 1.35).
D: Bad. Very light image density (less than 1.20).
[0552]
(B) Image fog
The printout image is sampled at the initial stage and after 3500 continuous printouts are finished, and the fog density (%) is calculated from the difference between the whiteness of the white background portion of the printout image and the whiteness of the transfer paper, and the image The fog was evaluated. The whiteness was measured with a “reflectometer” (manufactured by Tokyo Denshoku). The evaluation results are shown in Table 11. In addition, each symbol in Table 11 means the following evaluation, respectively.
A: Fog that is very good and not generally recognized at the meat limit (less than 1.5%).
B: Fog that is good and cannot be recognized without careful attention (1.5% to less than 2.5%).
C: Normal. It is easy to recognize fog, but acceptable fog (2.5% to less than 4.0%).
D: Bad. Fog recognized as image dirt (4.0% or more).
[0553]
(C) Ghost
After developing an image in which the solid white portion and the solid black portion are adjacent, the halftone image is developed, and the density difference caused by the boundary between the solid white portion and the solid black portion appearing on the halftone image is visually observed, and the following criteria are used. It was evaluated with.
A: No difference in shading is observed.
B: A slight shading difference is observed.
C: Practical use is possible although there is a slight difference in shading.
D: A difference in shading is noticeable.
[0554]
(D) Transferability
Evaluation of transferability was performed at the initial stage and after completion of 3500 printouts. For transferability, the residual toner particles on the photoconductor during solid black image formation were removed by taping with Mylar tape. The value was calculated by subtracting the Macbeth concentration. The evaluation results are shown in Table 11. In addition, each symbol in Table 11 means the following evaluation, respectively.
A: Very good (less than 0.05)
B: Good (0.05 to less than 0.10)
C: Normal (from 0.10 to less than 0.20)
D: Bad (over 0.20)
(E) Chargeability of image carrier
After printing out about 40 to 50 sheets and after finishing 3500 continuous printouts, the photoconductor is charged as usual, and the surface potential of the photoconductor at that time is measured by placing a sensor at the position of the developer, The chargeability of the image carrier was evaluated by the difference in potential at both time points. The evaluation results are shown in Table 11. It indicates that the lower the difference is, the greater the decrease in charging property of the latent image carrier.
[0555]
(F) Pattern collection failure
After the same pattern of vertical lines (repetition of vertical lines of 2 dots and 98 spaces) is continuously printed out, a halftone image (repetition of horizontal lines of 2 dots and 3 spaces) is printed, and the pattern of vertical lines is displayed on the halftone image. It was visually evaluated whether the shading corresponding to 1 occurred. The evaluation results are shown in Table 11. In addition, each symbol in Table 11 means the following evaluation, respectively.
A: Very good (not generated)
B: Good (slight shading is observed)
C: Normal (thickness unevenness occurs, but is in a practically acceptable level)
D: Poor (lightness unevenness occurs remarkably)
(G) Image dirt
The image stain was evaluated by visually observing the fixed image and evaluating it based on the following evaluation criteria. The evaluation results are shown in Table 11.
A: Not generated.
B: Slightly generated. The effect on the image is very slight.
C: It occurs to some extent. This is a practically acceptable level.
D: Image contamination is remarkable.
[0556]
The above results are shown in Table 11 as evaluation of Example L-1.
[0557]
<Examples L-2 to 60, 85 to 108>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Tables 9 and 10. The results are shown in Tables 11-13 and 14-15.
[0558]
<Examples L-61 to 72>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 10. The results are shown in Table 13. There was a little fog from the beginning, and the pattern collection failure was a little bad. The decrease in chargeability of the image carrier after the completion of continuous printing on 3,500 sheets was somewhat large, but was within an acceptable range for practical use.
[0559]
<Examples L-73 to 84>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 10. The results are shown in Table 14. Although the image density was slightly low from the beginning and pattern recovery failure was observed, it was within an acceptable range for practical use.
[0560]
<Comparative Example L-0>
When evaluation was performed with a combination of developer production example Rs-0 in which conductive fine powder was not externally added and developer carrier Dp-1-1, the chargeability of the image carrier was greatly reduced, and fogging deteriorated. did.
[0561]
<Comparative Examples L-1 to 9, 22>
An Al cylinder having a diameter of 16 mm was blasted with # 80 amorphous alumina particles, and a developer carrier having Ra = 0.32 was used. The developer was evaluated in the same manner as in Example L-1 with combinations of Tables 9 and 10. The results are shown in Tables 11-15. The image density was low.
[0562]
<Comparative Examples L-10 to 21>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 10. The results are shown in Table 15. The conductive fine powder on the surface of the toner particles tends to be lost, so that the chargeability of the image carrier is greatly reduced, and fogging and image staining are conspicuous.
[0563]
[Table 9]

[0564]
[Table 10]

[0565]
[Table 11]

[0566]
[Table 12]

[0567]
[Table 13]

[0568]
[Table 14]

[0569]
[Table 15]

[0570]
<Examples N-1 to 60, 85 to 108>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Tables 16 and 17. The results are shown in Tables 18-21.
[0571]
<Examples N-61 to 72>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 17. The results are shown in Table 20. There was a little fog from the beginning, and the pattern collection failure was a little bad. The decrease in chargeability of the image carrier after the completion of continuous printing on 3,500 sheets was somewhat large, but was within an acceptable range for practical use.
[0572]
<Examples N-73 to 84>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 17. The results are shown in Table 21. Although the image density was slightly low from the beginning and pattern recovery failure was observed, it was within an acceptable range for practical use.
[0573]
<Comparative Example N-0>
Evaluation of the developer production example Rp-0 and developer carrier Dp-n-1 to which no conductive fine powder was externally added revealed that the chargeability of the image carrier was greatly reduced and fogging deteriorated. did.
[0574]
<Comparative Examples N-1 to 9, 22>
The Al blast developer carriers of Comparative Examples L-1 to 9 and 22 were used, and the developers were evaluated in the same manner as in Example L-1 with combinations of Tables 16 and 17. The results are shown in Tables 18-22. The image density was low.
[0575]
<Comparative Examples N-10 to 21>
Evaluations were made in the same manner as in Example L-1 with combinations of developers and developer carriers as shown in Table 17. The results are shown in Table 22. The conductive fine powder on the surface of the toner particles tends to be lost, so that the chargeability of the image carrier is greatly reduced, and fogging and image staining are conspicuous.
[0576]
[Table 16]

[0577]
[Table 17]

[0578]
[Table 18]

[0579]
[Table 19]

[0580]
[Table 20]

[0581]
[Table 21]

[0582]
[Table 22]

[0583]
【The invention's effect】
As described above, according to the present invention, it is possible to achieve a developing and cleaning image forming method excellent in recoverability of transfer residual toner particles. In particular, a non-contact type developing method, which has been difficult in the past, can be achieved. When applied, a developer capable of developing and cleaning image forming method with excellent image quality was obtained.
[0584]
In addition, in the image forming apparatus of the contact charging method, the transfer method, and the toner recycling process, development and cleaning images in which inhibition of latent image formation is suppressed, transfer residual toner particles are excellently collected, and pattern ghosting is sufficiently suppressed. A forming device became possible.
[0585]
Further, a developer capable of controlling the supply of the conductive fine powder to the contact charging member and overcoming the charging inhibition due to the adhesion / mixing of the transfer residual toner particles and charging the image bearing member satisfactorily can be obtained. It was. Furthermore, it was possible to obtain a process cartridge that showed good developing and cleaning properties, greatly reduced the amount of waste toner, and was advantageous in terms of size reduction at low cost.
[0586]
In addition, a simple member can be used as a contact charging member, and ozone-less direct injection charging can be stably maintained over a long period of time at a low applied voltage regardless of contamination of the contact charging member due to residual toner particles. In addition, uniform chargeability of the image carrier can be provided. Accordingly, it is possible to obtain a process cartridge with a simple configuration and low cost which is free from troubles caused by ozone products and troubles caused by defective charging.
[0587]
Further, the scratches on the image carrier can be greatly reduced when the conductive fine powder is repeatedly used over a long period of time by interposing it in the contact portion between the charging member and the image carrier. Defects can be suppressed.
[0588]
According to the present invention, it is possible to provide a good image for a long time because the charging ability to the toner is more uniform and quicker than that of a conventionally used developer carrier, and the durability is further improved. It is possible to maintain a state that can be performed.
[0589]
Therefore, according to the present invention, the developer carrier having high durability and good charge imparting ability that does not cause deterioration such as abrasion of the coating layer on the surface of the developer carrier and toner contamination due to repeated copying or durability is used in different environments. However, image quality is not lowered, sleeve ghost and fog are not deteriorated, and a high quality image with high image density and high image density can be provided over a long period of time.
[0590]
Further, according to the present invention, the negative charge imparting property to the toner is stabilized over a long period of time even under different environmental conditions, the toner coat is made uniform, and the conductive coating on the surface of the developer carrying member by repeated copying or durability is provided. It is possible to provide a high-quality image for a long period of time without image density reduction, ghosting, and fog deterioration by a highly durable developer carrier that does not cause layer abrasion, toner contamination, sleeve fusing, etc. it can.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing charging characteristics of each charging member.
FIG. 3 is a graph showing human visual characteristics according to spatial frequency.
FIG. 4 is a schematic diagram showing an outline of a developer charge amount measuring apparatus used in the present invention.
FIG. 5 is a model diagram showing a layer structure of a photoconductor as an image carrier of the present invention.
FIG. 6 is a configuration diagram showing an outline of a toner particle spheroidizing apparatus used in an example of the present invention.
FIG. 7 is a schematic diagram of a processing unit of the toner particle spheroidizing apparatus used in the example of the present invention.
FIG. 8 is an explanatory diagram of a surface charge amount measuring device for measuring the charging polarity of a resin coating layer.

Claims (20)

A charging step for charging the latent image carrier, a latent image forming step for writing image information as an electrostatic latent image on the charging surface of the latent image carrier charged in the charging step, and developing the electrostatic latent image. Developing using a developing device provided with a developer carrying member that conveys the developer to a developing region facing the latent image carrying member while carrying the developer, and visualizing the developer image, and the developer image An image forming method in which at least a transfer step of transferring the toner image onto a transfer material, and a fixing step of fixing the developer image transferred onto the transfer material by a fixing unit, and repeating these steps to form an image,
The developer includes toner particles containing at least a binder resin and a colorant and conductive fine particles,
The toner particles have a circularity a obtained from the following formula of less than 0.970, and the conductive fine particles have a volume average particle size of 0.1 to 10 μm.
The charging step is a step of charging by bringing a charging unit into contact with the latent image carrier, and the conductive fine particles of the developer are interposed in a contact portion between the charging unit and the latent image carrier. Charging the latent image carrier by applying a voltage in a state,
The developing device includes a developer container for containing a developer, a developer carrier for carrying the developer contained in the developer container and transporting the developer to a development region, and a developer carrier on the developer carrier. Having at least a developer layer thickness regulating member for regulating the layer thickness of the developer to be carried;
There is no cleaning process after the transfer process until the charging process. In the developing process, the electrostatic latent image is visualized, and after the developer image is transferred to the transfer material, the latent image is transferred. Collect the developer remaining on the image carrier,
The developer carrier has at least a substrate and a resin coating layer formed on the substrate.
The resin coating layer contains at least a binder resin for the coating layer and a positively chargeable substance ,
An image forming method, wherein the positively chargeable substance is a copolymer containing a unit derived from an imidazole compound or a nitrogen-containing vinyl monomer .

(In the formula, L ₀ represents the perimeter of a circle having the same projected area as the particle image, and L represents the perimeter of the projected image of the particle.) The image forming method according to claim 1, wherein the resin coating layer contains a conductive substance. The image forming method according to claim 1, wherein the resin coating layer contains a lubricating substance. The image forming method according to claim 1, wherein the resin coating layer contains a conductive substance and a lubricating substance. The positively chargeable material is an imidazole compound, an image forming method according to any one of claims 1 to 4, characterized in that a compound represented by the following formula (1) or (2).

[Wherein, R ₁ and R ₂ represent a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group, and R ₁ and R ₂ may be the same or different. R ₃ and R ₄ may represent a linear alkyl group having 3 to 30 carbon atoms, and R ₃ and R ₄ may be the same or different. ]

[Wherein R ₅ and R ₆ represent a hydrogen atom or a substituent selected from the group consisting of an alkyl group, an aralkyl group and an aryl group, and R ₅ and R ₆ may be the same, and R ₇ Represents a linear alkyl group having 3 to 30 carbon atoms. ] The positively chargeable substance is a copolymer containing a unit derived from a nitrogen-containing vinyl monomer, and the copolymer has a weight average molecular weight (Mw) of 3,000 to 50,000. The image forming method according to claim 1 . The image forming method according to claim 6 , wherein the copolymer has a ratio (Mw / Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 3.5 or less. The nitrogen-containing vinyl monomers, claim 6, characterized in that it comprises one or more monomers selected from the group consisting having a nitrogen-containing group (meth) acrylic acid derivative and a nitrogen-containing heterocyclic N- vinyl compounds Or the image forming method according to 7 ; The image forming method according to claim 6 or 7 , wherein the nitrogen-containing vinyl monomer is represented by the following general formula (3).

_{Wherein, R 7, R 8, R} 9 and _{R 10} represents a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms, n is an integer of 1-4. ] Wherein a copolymer which positively chargeable material includes units derived from nitrogen-containing vinyl monomers, nitrogen-containing vinyl monomer is a sulfonic acid group-containing acrylamide monomer over, and the coating layer for the binder resin, the At least -NH ₂ group, = NH group image forming method according to claim 1 to 4 Neu Zureka or -NH- have either bond and wherein, in the molecular structure. The copolymer has a copolymerization ratio (% by mass) of a vinyl polymerizable monomer and a sulfonic acid group-containing acrylamide monomer of 98: 2 to 80:20, and a weight average molecular weight (Mw) of 2,000 to 50, The image forming method according to claim 10 , wherein the image forming method is 000. The image forming method according to claim 10 , wherein the copolymer is a copolymer of a vinyl polymerizable monomer and 2-acrylamido-2-methylpropanesulfonic acid. The coating layer binder resin, the image forming method according to any one of claims 10 to 12, characterized in that it contains at least a phenolic resin. The phenol resin is a phenol resin produced using a nitrogen-containing compound as a catalyst, and is a phenol resin having any of —NH ₂ group, ═NH group, and —NH— bond in its structure. 14. The image forming method according to 13 . Wherein the binder resin for the coating layer, the image forming method according to any one of claims 10 to 14, characterized in that at least the polyamide resin is contained. Wherein the binder resin for the coating layer, the image forming method according to any one of claims 10 to 14, wherein at least a polyurethane resin is contained. 2. The developer contains 15-60% by number of particles having a particle size range of 1.00 μm or more and less than 2.00 μm in a number-based particle size distribution for particles having a particle size of 0.60 μm to 159.21 μm; the image forming method according to any one of claims 1 to 16, characterized in that the particles having a particle size range of less than 8.96μm than 00μm containing 15 to 70% by number. The conductive fine particles, an image forming method according to any one of claims 1 to 17, wherein the volume resistivity is 10 ⁰ ~10 ⁹ Ω · cm. The image forming method according to any one of claims 1 to 18, wherein said conductive fine particles are non-magnetic. The conductive fine particles, zinc oxide, tin oxide, an image forming method according to any one of claims 1 to 19, characterized in that it contains at least one oxide selected from titanium oxide.

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