JP3595702B2 - Magnetic particles for charging, electrophotographic apparatus and process cartridge - Google Patents

Description

【００６０】
本発明の帯電用磁性粒子は、カップリング剤を表面に存在させる場合、その存在量が０．５重量％以下、好ましくは０．２重量％以下であるから、抵抗値的には、表面に存在させない磁性粒子とほぼ同等の抵抗値が得られるため、導電性粒子分散樹脂を用いる場合などに比べて製造上の安定性や品質の安定性が高い。
【００６１】
更に、該カップリング剤の反応率が８０％以上であることが好ましく、更に好ましくは８５％以上である。本発明においては、比較的長鎖のアルキル基を有するカップリング剤を用いるため、未反応物の割合が多いと、流動性の悪化につながるからである。また、使用する感光体表面が、実質的に非架橋樹脂である場合、未反応の処理剤が、感光体表面に浸透し、曇りや割れを生じる場合がある。この理由により、磁性粒子表面と反応できるカップリング剤を用いるのが好ましい。
【００６２】
また、該カップリング剤の反応率の測定方法としては、使用するカップリング剤を溶解可能な溶媒を選択し、洗浄前後の存在率を測定すればよい。
【００６３】
例えば、処理された磁性粒子の１００倍量の溶媒に浸し、溶媒中のカップリング剤成分を、クロマトグラフィーで定量する方法、また、洗浄後の磁性粒子表面に残るカップリング剤成分を、ＸＰＳ、元素分析及び熱重量分析（ＴＧＡ）などで定量し、洗浄前後の存在量を定量する方法などが可能である。
【００６４】
また、本発明に用いられる帯電用磁性粒子は、その体積抵抗値が１×１０^４ 〜１×１０^９ Ωｃｍであることが好ましい。１×１０^４ Ωｃｍより低いと、ピンホールリークを起こす傾向にあり、１×１０^９ Ωｃｍを超えると、感光体の帯電が不十分となり易い。
【００６５】
磁性粒子の体積抵抗値は、図２に示すセルＡに磁性粒子を充填し、該磁性粒子に接するよう電極２１及び２２を配し、該電極間に電圧を印加し、その時流れる電流を測定することにより得た。測定条件は、温度２３℃、相対湿度６５％の環境で充填磁性粒子と電極との接触面積が２ｃｍ^２ 、厚み（ｄ）が１ｍｍ、上部電極の荷重が１０ｋｇ、印加電圧が１００Ｖである。なお、図２中、２３はガイドリング、２４は電流計、２５は電圧計、２６は定電圧装置、２７は測定サンプル、２８は絶縁物である。
【００６６】
本発明のクリーナレス画像形成方法の原理について、図１を用いて説明する。
【００６７】
磁性粒子１５をコーティングした磁石内包非磁性導電性スリーブ１６により構成される磁気ブラシ帯電装置１１によって帯電された感光体１２は、露光手段からの露光光１３により静電潜像を形成する。潜像は、例えば現像剤１０と磁石を内包した導電性非磁性スリーブ１７などからなる現像装置１８により反転現像されて、感光体１２上の露光された部分にトナーにより可視化された画像を形成する。１９は攪拌スクリュウである。可視化された像は、転写手段１４により転写材に転写され、感光体上には転写残りのトナーが存在する。この転写残りのトナーは、転写の影響を受け、帯電極性としてはマイナスからプラスまで様々に分布する。このような転写残りトナーを回転摺擦する磁気ブラシ帯電装置１１にて掻き取りながら、感光体を帯電しつつ、磁気ブラシを構成する磁性粒子トナーの摩擦帯電において転写残りのトナーを所望の極性に揃えることが可能である。なお、図中のプラス、マイナスは、トナーの極性を表す。
【００６８】
従って、所謂放電現象を利用した磁気ブラシ帯電装置においても、放電または磁気ブラシを構成する磁性粒子とトナーとの摩擦帯電を利用し、独立のクリーニング手段がなくとも鮮明な画像形成が可能となる。
【００６９】
更には、放電現象を利用しない接触注入帯電方法を用いたときにも、磁性粒子と転写残りのトナーの摩擦帯電を利用し、所望の極性に制御することにより、独立のクリーニング手段がなくとも鮮明な画像形成が可能となる。
【００７０】
磁性粒子の平均粒径はレーザー回折式粒度分布測定装置ＨＥＲＯＳ（日本電子製）を用いて、０．５〜２００μｍの範囲を３２対数分割して測定し、体積５０％メジアン径をもって平均粒径とした。
【００７１】
本発明では、平均粒径５〜１００μｍの範囲が好ましく用いられる、５μｍよりも小さいと磁性粒子がもれ易く、１００μｍを超えると帯電一様性が悪化する傾向がある。更に好ましくは１５〜８０μｍである。注入帯電法を用いる場合は、その接触性をかんがみ、１５〜４０μｍが好適に用いられる。
【００７２】
本発明においては、導電性支持体より最も離れた層、即ち表面層として電荷注入層を有する感光体を用いることにより、放電させることなく、印加電圧の直流成分の絶対値に対して８０％以上、更には９０％以上の帯電電位を得ることができる。従って、パッシェンの法則により解釈される帯電方法に比較して、印加電圧を低く抑えることができ、また、更なるオゾンレス帯電方式を実現することができる。
【００７３】
電荷注入層は、十分な帯電性と画像流れを起こさない条件を満足するために、体積抵抗値が１×１０^８ 〜１×１０^１５Ωｃｍの範囲であることが好ましい。より好ましくは、画像流れなどの点から１×１０^１０〜１×１０^１５Ωｃｍ、更に環境変動なども考慮すると１×１０^１２〜１×１０^１５Ωｃｍであることが好ましい。１×１０^８ Ωｃｍより小さい体積抵抗値では静電潜像を保持できにくく、特に高温高湿下において画像流れを発生し易い。一方、１×１０^１５Ωｃｍより大きい体積抵抗値であると帯電部材からの電荷を十分に受け取ることができず、帯電不良を生じる傾向にある。
【００７４】
電荷注入層としては、絶縁性の結着樹脂に光透過性でかつ導電性の粒子を適量分散させて中抵抗とした材料で構成することが可能であり、上記抵抗を有する無機層を形成することも有効な手段である。このような機能層表面を設けることによって、帯電部材より注入された電荷を保持する役割を果し、更に、露光時にはこの電荷を感光体支持体に逃す役割を果し残留電位を低減させる。
【００７５】
ここで、感光体の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）上に表面層と同様の層（厚さ３ｍｍ）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４１４０Ｂ ｐＡＭＡＴＥＲ）にて温度２３℃、相対湿度６５％の環境で１００Ｖの電圧を印加し測定した。
【００７６】
導電性粒子の粒径は、透光性の観点から０．３μｍ以下が好ましく、最適には、０．１μｍ以下である。結着樹脂１００重量部に対して２〜２５０重量部、好ましくは２〜１９０重量部である。２重量部よりも少ないと好ましい体積抵抗値が得られにくく、２５０重量部を超えると膜強度が低下する傾向があり、電荷注入層が削れ易くなる傾向にある。電荷注入層の膜厚は、好ましくは０．１〜１０μｍ、最適には１〜７μｍである。
【００７７】
また、好ましくは、前記電荷注入層に滑材粉末が含有される。期待される効果としては、帯電時に感光体と帯電部材の摩擦が低減され帯電に関与するニップが拡大され帯電特性が向上することが挙げられる。また、感光体表面の離型性が向上するため、磁性粒子が付着しにくくなる。特に滑材粉末としては、臨界表面張力の低い、フッ素樹脂、シリコーン樹脂またはポレオレフィン樹脂を用いるのが好ましい。特に好ましくは、４フッ化ポリエチレン樹脂が用いられる。この場合、滑材粉末の添加量は、好ましくは結着樹脂１００重量部に対して２〜５０重量部である。より好ましくは５〜４０重量部である。２重量部より少ないと、滑材粉末の量が十分でないため、感光体帯電性の向上効果が十分でなく、クリーナレス装置という観点からは転写残トナーが増える傾向にある。また、５０重量部を超えると、画像の分解能及び感光体の感度が低下する傾向にある。
【００７８】
また、表面層に無機層を被覆する際は、その下層の光導電層は、アモルファスシリコンであることが好ましく、グロー放電などによってシリンダー上に阻止層、光導電層及び電荷注入層を順次形成することが好ましい。
【００７９】
感光層としては、従来公知のものが使用できる。例えば、有機材料であれば、フタロシアニン顔料及びアゾ顔料などが挙げられる。
【００８０】
更に、電荷注入層と感光層の間に中間層を設けることもできる。このような中間層は、電荷注入層と感光層の接着性を高め、あるいは電荷のバリアー層として機能させることを目的とする。中間層としては、例えば、エポキシ樹脂、ポリエステル樹脂、ポリアミド樹脂、ポリスチレン樹脂、アクリル樹脂及びシリコーン樹脂などの市販の樹脂材料が使用可能である。
【００８１】
前記、感光体用の導電性支持体としては、アルミニウム、ニッケル、ステンレス及びスチールなどの金属や、導電性膜を有するプラスチックあるいは硝子、また導電化した紙などを用いることができる。
【００８２】
更に、使用されるトナーと帯電部材の磁性粒子間の摩擦帯電性においても好ましい範囲があり、帯電部材磁性粒子１００に対して、使用されるトナー７の割合にて、測定されるトナーのトリボ値が、感光体の帯電極性と同じであり、その絶対値が好ましくは１〜９０ｍＣ／ｋｇ、より好ましくは５〜８０ｍＣ／ｋｇ、更に好ましくは１０〜４０ｍＣ／ｋｇであると、トナーの取り込みや掃き出し、感光体の帯電特性に対し特に良好な特性を付与し得る。
【００８３】
トナーの摩擦帯電量の測定法を以下に示す。測定装置概略を図３に示す。
【００８４】
２３℃、相対湿度６０％環境下、測定する磁性粒子０．０４０ｋｇにトナー０．００２８ｋｇを加えた混合物を５０〜１００ｍｌ容量のポリエチレン製の瓶に入れ、１５０回手で震蘯する。次いで、底に５００メッシュのスクリーン３３のある金属製の測定容器３２に前記混合物０．０００５ｋｇを入れ、金属製のフタ３４をする。３０は測定サンプルである。この時の測定容器３２全体の重量を秤りＷ１ｇとする。次に、吸引機（測定容器３２と接する部分は少なくとも絶縁体）において、吸引口３７から吸引し風量調節弁３６を調節して真空計３５の圧力を２５０ｍｍＡｑとする。この状態で吸引機３１により３分間吸引を行い現像剤を吸引除去する。この時の電位計３９の電位をＶ（ボルト）とする。ここで３８はコンデンサーであり容量をＣ（ｍＦ）とする。また吸引後の測定機全体の重量を秤りＷ２（ｋｇ）とする。この現像剤のトリボ値（ｍＣ／ｋｇ）は、通常下式の如く計算される。
【００８５】
摩擦帯電量（ｍＣ／ｋｇ）＝ＣＶ／（Ｗ１−Ｗ２）
【００８６】
但し、本発明に用いられる磁性粒子は、粒径が細かいので、５００メッシュのスクリーンでも相当量メッシュを抜けてしまうため、メッシュを抜けた磁性粒子については、トナーの摩擦帯電量とキャンセルすると考え、補正を含んだ以下の式の如く計算される。
【００８７】
あらかじめ秤量された磁性粒子の質量をＭ１、トナーをＭ２とし、この混合物のうちＭ３を５００メッシュのスクリーン３３のある金属製の測定容量３２に入れたとき
摩擦帯電量（ｍＣ／ｋｇ）＝ＣＶ／｛Ｍ３×Ｍ２／（Ｍ１＋Ｍ２）｝
である。
【００８８】
本発明の電子写真装置においては、感光体に接触する帯電部材として磁性粒子により形成された磁気ブラシを用いるが、帯電手段の構成としては、帯電用磁性粒子保持部材として、マグネットロール、または、内部にマグネットロールを持つ導電性スリーブを用い、その表面に帯電用磁性粒子を均一にコーティングしたものが好適に用いられる。
【００８９】
帯電用磁性粒子保持部材と感光体の最近接ギャップは、０．３〜２．０ｍｍが好ましく用いられる。０．３ｍｍより近くなると印加電圧によっては、帯電用磁性粒子保持部材の導電性部分と感光体間にリークを生じ、感光体にダメージを与えることがある。
【００９０】
帯電用磁気ブラシの移動方向は、感光体の移動方向に対して、その接触部分において順、逆を問わないが、転写残りのトナーの取り込み性及び帯電の均一性の観点からは逆方向に移動するのが好ましい。
【００９１】
帯電用磁性粒子保持部材に保持される帯電用磁性粒子の量は、好ましくは５０〜５００ｍｇ／ｃｍ^２ 、更に好ましくは１００〜３００ｍｇ／ｃｍ^２ である。この範囲であると、特に安定した帯電性を得ることができる。
【００９２】
帯電部材に印加する帯電バイアスは、注入帯電法を用いる場合、直流成分のみでもさしつかえないが、若干の交流成分を印加すると画質の向上が見られるので好ましい。直流成分は得ようとする感光体の表面電位と同等の電圧でよいが、絶対値が若干大きい電圧であることが好ましい。交流成分としては、装置のプロセススピードにもよるが、１００Ｈｚ〜１０ｋＨｚ程度の周波数で、印加交流成分のピークピーク間電圧は１０００Ｖ程度以下が好ましい。１０００Ｖを超えると印加電圧に応じた感光体上に電位が生じるので、潜像面が電位的に波打ち、かぶりや濃度薄を生じることがある。
【００９３】
放電を用いる方法においては、印加する帯電バイアスは、帯電均一性の点から、直流成分に交流成分を重畳した電圧であることが好ましい。直流成分のみの場合、放電開始電圧に得ようとする感光体の表面電位を加えた電圧の絶対値より大きい電圧が必要である。交流成分としては、装置のプロセススピードにもよるが、１００Ｈｚ〜１０ｋＨｚ程度の周波数で、印加交流成分のピーク間電圧は、１０００Ｖ程度以上で、放電開始電圧の２倍以上が好ましい。磁気ブラシと感光体表面において十分な均し効果を得るためである。印加する交流成分の波形は、サイン波、矩形波及び鋸波などが使用できる。放電開始電圧の２倍以上のピーク間電圧を有する交流成分を印加した場合、直流成分は、得ようとする感光体の表面電位と同等の電圧でよい。
【００９４】
また、帯電器内に余分の帯電用磁性粒子を保持し、循環をさせてもよい。
【００９５】
本発明における露光手段としては、レーザー及びＬＥＤなどの公知の手段を用いる。
【００９６】
現像手段としては、特に選ばないが、クリーニング手段を有しない画像形成装置の場合、反転現像が好ましく、また、現像剤と感光体が接触するような構成が好ましい。例えば、接触２成分現像法及び接触１成分法などが好適な方法として挙げられる。現像剤と転写残りトナーが感光体上にて接触している場合、静電気的力に摺擦力が加わり、効果的に転写残りのトナーを現像手段にて回収できる傾向にあるからである。現像に印加されるバイアスについては、その直流成分は、黒字部（反転現像の場合、露光部分）と白地部の電位の間に来ることが好ましい。
【００９７】
転写手段としては、コロナ、ローラー及びベルトなど公知の方法が用いられる。
【００９８】
本発明においては、電子写真感光体と帯電手段、更に必要に応じて現像手段やクリーニング手段を一体に支持し、電子写真装置本体に着脱自在のプロセスカートリッジ（図１の２０）とすることができる。また、現像手段を電子写真感光体を有するカートリッジと別体のカートリッジにすることもできる。
【００９９】
本発明においては、転写残りトナーを一時的に回収した帯電器から、感光体表面を利用して、現像部分に搬送し回収再利用するために、感光体の帯電バイアスを変更する必要はない。但し、ジャムが生じた場合、あるいは画像比率の高い画像を連続して得る場合は、帯電器に混入する転写残りトナーが非常に多くなることがある。
【０１００】
この場合は、電子写真装置の動作中、感光体上に画像を形成しない時を利用して、帯電部から現像器へとトナーを移動させてもよい。この非画像形成時とは、前回転時、後回転時及び転写材間などである。その場合、トナーが帯電手段より感光体に移り易いような帯電バイアスに変更することも好ましい。帯電手段から放出し易くする方法としては、交流成分のピーク間電圧を小さめにする、直流成分のみとする、あるいは、ピーク間電圧は変えずに、波形を変更して交流実効値を下げるなどが挙げられる。
【０１０１】
本発明に用いるトナーとしては、特に制限はないが、トナー飛散の観点から、その転写効率において好ましい形態が存在する。つまり、磁気ブラシに突入する転写残りのトナーが少なければ、飛散する可能性のあるトナーの絶対量が少ないため、本発明の電子写真装置との組み合わせ効果が大きい。トナーのその形状係数において、ＳＦ−１が１００〜１４０、ＳＦ−２が１００〜１２０の範囲のものは、転写性が良好になる傾向にある。特に、重合法により形成され、形状係数が上記範囲にあるものが特に転写効率がよく好ましい。
【０１０２】
ここで、ＳＦ−１、ＳＦ−２について、以下のように計測される。
【０１０３】
例えば、日立製作所製ＦＥ−ＳＥＭ（Ｓ−８００）を用い、１０００倍に拡大した２μｍ以上のトナー像を１００個無作為にサンプリングし、その画像情報をインターフェースを介して、例えばニコレ社製画像解析装置（ＬｕｚｅｘＩＩＩ）に導入し解析を行い、下式より得られた値と定義する。
【０１０４】
【外２】

【０１０５】
ここで、式中のＭＸＬＮＧは粒子の絶対最大長、ＰＥＲＩＭＥは粒子の周囲長、ＡＲＥＡは粒子の投影面積を示す。ＳＦ−１は粒子の丸さの度合いを示し、ＳＦ−２は粒子の凹凸を示し、両者が１００に近ければ近い程、真球に近いことを示す。
【０１０６】
更に、本発明におけるプロセスカートリッジは、その帯電器部分の寿命、及びマグネット内包非磁性スリーブを用いることを考慮すると、そのコスト面の要請により、トナーを更に追加できるような構成が好ましい。その場合、帯電用磁性粒子としても、必要最低限の量よりも多量に帯電部分に存在させ、循環させることにより耐久性を更に伸ばす構成が好ましい（図８及び９）。
【０１０７】
図８中、８０１は帯電器、８０２は撹拌部材、８０３はカットブレード、８０４はトナー補給口、８０５は現像器、８０６は現像容器、８０７は現像剤の撹拌及び送りスクリュウ、８０８は現像剤、８０９はマグネット内包導電性スリーブ、８１０は感光体、８１１は帯電用磁性粒子、８１２はマグネット内包導電性スリーブ、８１３は帯電用磁性粒子容器を示す。また、図９中、９０１は帯電器、９０２は撹拌部材、９０３はカットブレード、９０４はトナー補給口、９０５は現像器、９０６は現像容器、９０７はトナー撹拌子、９０８はトナー塗布ローラー、９０９はトナー、９１０は現像用弾性ローラ、９１１は感光体、９１２は帯電用磁性粒子、９１３はマグネット内包導電性スリーブ、９１４は帯電用磁性粒子容器を示す。
【０１０８】
循環させる手段としては、機械的に撹拌するか、あるいは、磁性粒子を循環できるような磁極構成あるいは、磁性粒子を格納する容器内で、磁性粒子を移動させるような部材を設けることが好ましい。例えば、磁気ブラシ背後に、撹拌するスクリュウ部材（図５）、または、反発極を設け磁性粒子を剥しながら再コートするような構成（図７）、磁性粒子の流れを阻害するような邪魔部材などを設けることが挙げられる。
【０１０９】
図５及び７中、５１及び７１は帯電器、５２及び７２はカットブレード、５３及び７３は帯電用磁性粒子容器、５４及び７４はマグネット、５５及び７５は非磁性導電性スリーブ、５６及び７６は撹拌部材、５７及び７７は帯電用磁性粒子、５８及び７８は感光体を示す。
【０１１０】
以下、本発明を実施例によって説明するが、これによって本発明が限定されるものではない。
【０１１１】
まず、本発明に使用される部材の構成、材質及び製造方法などを例示する。
【０１１２】
〔帯電用磁性粒子製造例１〕
Ｆｅ_２ Ｏ_３ ５４モル％
ＭｎＯ ３５モル％
ＭｇＯ １１モル％
【０１１３】
以上の金属酸化物計１００重量部に、リンを０．０５重量部添加し、ボールミルにて粉砕、混合し、分散剤及び結着剤と水を加えスラリーとした後、スプレードライヤーにより造粒操作を行った。適宜分級した後に、必要に応じ、酸素濃度を調整した雰囲気中、１２００℃にて焼成を行った。
【０１１４】
得られたフェライトを解砕処理の後分級を行い、平均粒径２７．６μｍのフェライト粒子を得た。
【０１１５】
フェイト粒子の体積抵抗値は４×１０^７ Ωｃｍ、８×１０^４ Ａ／ｍ（１ｋＯｅ）での磁化が５７Ａｍ^２ ｋｇ（５７ｅｍｕ／ｇ）であった。特性の詳細は、表１に挙げたごとくである。
【０１１６】
また、この粒子表面のリンの存在比率は、全粒子のリンの比率の３０倍であった。
【０１１７】
特性を表１にまとめる。
【０１１８】
〔帯電用磁性粒子製造例２〕
帯電用磁性粒子製造例１と同様に製造を行い、平均粒径３７．０μｍの粒子を得た。
【０１１９】
特性を表１に挙げる。
【０１２０】
〔帯電用磁性粒子製造例３〕
リンを０．５重量部添加した以外は、帯電用磁性粒子製造例１と同様に製造を行い、平均粒径２８．０μｍの粒子を得た。
【０１２１】
特性を表１に挙げる。
【０１２２】
〔帯電用磁性粒子製造例４〕
リンを１．０重量部添加した以外は、帯電用磁性粒子製造例１と同様に製造を行い、平均粒径２７．５μｍの粒子を得た。
【０１２３】
特性を表１に挙げる。
【０１２４】
〔帯電用磁性粒子製造例５〕
Ｆｅ_２ Ｏ_３ ５０モル％
ＭｎＯ ３０モル％
ＭｇＯ ２０モル％
とし、リンを１．０重量部添加した以外は、帯電用磁性粒子製造例１と同様に製造を行い、平均粒径２７．０μｍの粒子を得た。
【０１２５】
特性を表１に挙げる。
【０１２６】
〔帯電用磁性粒子製造例６〕
リンを添加しないことを除いて、帯電用磁性粒子製造例１と同様に製造を行った。
【０１２７】
特性を表１にまとめて挙げる。
【０１２８】
〔帯電用磁性粒子製造例７〕
リンを添加しないことを除いて、帯電用磁性粒子製造例５と同様に製造を行った。
【０１２９】
特性を表１にまとめて挙げる。
【０１３０】
〔帯電用磁性粒子製造例８〕
シランカップリング剤であるドデシルトリメトキシシラン０．０５重量部をメチルエチルケトン２０重量部に溶解した溶液に帯電用磁性粒子製造例１にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、１５０℃のオーブンに入れ、キュアリングを行った。
【０１３１】
特性は表２に挙げる。
【０１３２】
〔帯電用磁性粒子製造例９〕
シランカップリング剤であるオクチルトリメトキシシラン０．０５重量部をメチルエチルケトン２０重量部に溶解した溶液に帯電用磁性粒子製造例１にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、１００℃のオーブンに入れ、キュアリングを行った。
【０１３３】
特性は表２に挙げる。
【０１３４】
〔帯電用磁性粒子製造例１０〕
チタンカップリング剤であるイソプロポキシトリイソステアロイルチタネート０．０５重量部をメチルエチルケトン２０重量部に溶解した溶液に帯電用磁性粒子製造例１にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、２００℃のオーブンに入れ、キュアリングを行った。
【０１３５】
特性は表２に挙げる。
【０１３６】
〔帯電用磁性粒子製造例１１〕
チタンカップリング剤であるイソプロポキシトリイソステアロイルチタネート０．０５重量部をメチルエチルケトン３０重量部に溶解した溶液に帯電用磁性粒子製造例２にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、２００℃のオーブンに入れ、キュアリングを行った。
【０１３７】
特性は表２に挙げる。
【０１３８】
〔帯電用磁性粒子製造例１２〕
チタンカップリング剤であるイソプロポキシトリイソステアロイルチタネート０．１５重量部をメチルエチルケトン３０重量部に溶解した溶液に帯電用磁性粒子製造例３にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、２００℃のオーブンに入れ、キュアリングを行った。
【０１３９】
特性は表２に挙げる。
【０１４０】
〔帯電用磁性粒子製造例１３〕
チタンカップリング剤であるイソプロポキシトリイソステアロイルチタネート０．１０重量部をメチルエチルケトン３０重量部に溶解した溶液に帯電用磁性粒子製造例４にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、２００℃のオーブンに入れ、キュアリングを行った。
【０１４１】
特性は表２に挙げる。
【０１４２】
〔帯電用磁性粒子製造例１４〕
チタンカップリング剤であるイソプロポキシトリイソステアロイルチタネート０．１０重量部をメチルエチルケトン３０重量部に溶解した溶液に帯電用磁性粒子製造例５にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、２００℃のオーブンに入れ、キュアリングを行った。
【０１４３】
特性は表２に挙げる。
【０１４４】
〔帯電用磁性粒子製造例１５〕
シランカップリング剤であるγ−グリシドキシプロピルトリメトキシシラン０．１０重量部をメチルエチルケトン２０重量部に溶解した溶液に帯電用磁性粒子製造例６にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、１００℃のオーブンに入れ、キュアリングを行った。
【０１４５】
特性は表２に挙げる。
【０１４６】
〔帯電用磁性粒子製造例１６〕
カップリング剤であるγ−メタクリロキシプロピルトリメトキシシラン０．０５重量部をメチルエチルケトン２０重量部に溶解した溶液に帯電用磁性粒子製造例６にて製造した磁性粒子１００重量部を加え、撹拌しながら７０℃に保ち、溶媒を蒸発した後に、１００℃のオーブンに入れ、キュアリングを行った。
【０１４７】
特性については表２に挙げる。
【０１４８】
〔帯電用磁性粒子製造例１７〕
Ｆｅ_２ Ｏ_３ ５３モル％
ＣｕＯ ２７モル％
ＺｎＯ ２０モル％
【０１４９】
以上の金属酸化物、計１００重量部にリンを０．２重量部を添加し、ボールミルにて粉砕混合し、分散剤及び結着樹脂と水を加え、スラリーとした後、スプレードライヤーにより造粒操作を行った。適宜分級した後に、１０００℃にて燒結を行った。
【０１５０】
得られたフェライトを解砕処理の後分級を行い、平均粒径２８．１μｍのフェライト粒子を得た。特性を表１に挙げる。
【０１５１】
〔帯電用磁性粒子製造例１８〕
Ｆｅ_２ Ｏ_３ ５０モル％
ＭｎＯ ２５モル％
ＺｎＯ ２５モル％
【０１５２】
以上の金属酸化物、計１００重量部にリンを１．０重量部を添加し、ボールミルにて粉砕混合し、分散剤及び結着樹脂と水を加え、スラリーとした後、スプレードライヤーにより造粒操作を行った。適宜分級した後に、適宜酸素濃度を調節し、１０００℃にて燒結をおこなった。
【０１５３】
得られたフェライトを解砕処理の後分級を行い、平均粒径２７．９μｍのフェライト粒子を得た。特性を表１に挙げる。
【０１５４】
〔帯電用磁性粒子製造例１９〕
Ｆｅ_２ Ｏ_３ ５３モル％
ＭｇＯ ２５モル％
ＺｎＯ １７モル％
ＭｎＯ ５モル％
【０１５５】
以上の金属酸化物、計１００重量部にリンを０．７重量部を添加し、ボールミルにて粉砕混合し、分散剤及び結着樹脂と水を加え、スラリーとした後、スプレードライヤーにより造粒操作を行った。適宜分級した後に、適宜酸素濃度を調節し、１１００℃にて燒結をおこなった。
【０１５６】
得られたフェライトを解砕処理の後分級を行い、平均粒径２８．３μｍのフェライト粒子を得た。特性を表１に挙げる。
【０１５７】
【表１】

【０１５８】
【表２】

【０１５９】
〔感光体製造例１〕
φ３０ｍｍのアルミニウムシリンダー上に機能層を５層設ける。
【０１６０】
第１層は導電層であり、アルミニウムシリンダーの欠陥などをならすため、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である。
【０１６１】
第２層は正電荷注入防止層であり、アルミニウムシリンダー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、アミラン樹脂とメトキシメチル化ナイロンによって１０^６ Ωｃｍ程度に抵抗調整された厚さ約１μｍの中抵抗層である。
【０１６２】
第３層は電荷発生層であり、オキシチタニウムフタロシアニン系の顔料を樹脂に分散した厚さ約０．３μｍの層であり、露光を受けることによって正負の電荷対を発生する。
【０１６３】
第４層は電荷輸送層であり、ポリカーボネート樹脂にヒドラゾンを分散したものであり、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。厚さ１５μｍとした。
【０１６４】
電荷輸送層の体積抵抗値は、３×１０^１５Ωｃｍであった。
【０１６５】
第５層として電荷注入層を形成する。該電荷注入層は、光硬化性のアクリル樹脂にＳｎＯ_２ 超微粒子を分散した厚さ３μｍの層である。具体的には、アンチモンをドーピングして低抵抗化した粒径約０．０３μｍのＳｎＯ_２ 粒子を樹脂１００重量部に対して１５０重量部、更に、粒径約０．２５μｍの４フッ化エチレン樹脂粒子を２０重量部、分散剤を１．２重量部分散したものである。
【０１６６】
感光体の表面層の体積抵抗値は、２×１０^１３Ωｃｍである。
【０１６７】
〔感光体製造例２〕
φ３０ｍｍのアルミニウムシリンダー上に機能層を５層設ける。
【０１６８】
第１層、第２層、第３層及び第４層は、感光体製造例１と同様に作成し、第５層に電荷注入層を形成する。該電荷注入層は、光硬化性のアクリル樹脂にＳｎＯ_２ 超微粒子を分散した厚さ３μｍの層である。具体的には、アンチモンをドーピングし、低抵抗化した粒径約０．０３μｍのＳｎＯ_２ 粒子を樹脂１００重量部に対して１７０重量部、更に、４フッ化エチレン樹脂粒子を２０重量部、分散剤を１．２重量部分散したものである。
【０１６９】
感光体の表面層の体積抵抗値は、４×１０^１２Ωｃｍである。
【０１７０】
〔トナー製造例１〕
ポリエステル樹脂 １００重量部
含金属アゾ染料 ２重量部
低分子量ポリプロピレン ３重量部
カーボンブラック ５重量部
【０１７１】
上記材料を乾式混合した後に、１５０℃に設定した２軸混練押出機にて混練した。得られた混練物を冷却し、気流式粉砕機により微粉砕した後に風力分級して粒度分布の調整されたトナー組成物を得た。このトナー組成物に、疎水処理された酸化チタン１．７重量％を外添して、重量平均粒径６．３μｍのトナーを作成した。
【０１７２】
〔トナー製造例２〕
スチレン８８重量部、ｎ−ブチルアクリレート１２重量部、低分子量ポリプロピレン３重量部、カーボンブラック４重量部、含金属アゾ染料１．２重量部及びアゾ系開始剤３重量部を分散混合し、上記溶液を燐酸カルシウム４重量部を分散した純水５００重量部に加え、ホモミキサーにより分散し、７０℃で、８時間重合し得られた重合体をろ過し、洗浄を行った後に、乾燥分級し、トナー組成物を得た。
【０１７３】
上記トナー組成物に、疎水化処理された酸化チタン１．７重量％を外添し、重量平均粒径６．３μｍのトナーを作成した。
【０１７４】
形状係数はＳＦ−１は１２５、ＳＦ−２は１１５であった。
【０１７５】
〔現像剤製造例１〕
平均粒径６０μｍのニッケル亜鉛フェライトに、シリコーン樹脂をコートしたもの１００重量部に対し、トナーの製造例１のトナー６重量部を混合し現像剤とした。
【０１７６】
〔現像剤製造例２〕
平均粒径６０μｍのニッケル亜鉛フェライトに、アクリル変性シリコーン樹脂をコートしたもの１００重量部に対し、トナーの製造例２のトナー６重量部を混合し現像剤とした。
【０１７７】
次いで、本発明の実施例及び比較例において使用される評価用機械及び方法、及び実施例及び比較例を用い本発明を説明する。
【０１７８】
〔デジタル複写機１〕
電子写真装置としてレーザービームを用いたデジタル複写機（キヤノン製：ＧＰ５５）を用意した。該装置の概略は、感光体の帯電手段としてコロナ帯電器を備え、現像手段として１成分ジャンピング現像方法を採用した１成分現像器を備え、転写手段としてコロナ帯電器、ブレードクリーニング手段、帯電前露光手段を備える。また、感光体用帯電器、クリーニング手段及び感光体は一体型のユニット（プロセスカートリッジ）となっている。プロセススピード１５０ｍｍ／ｓである。該デジタル複写機に以下のように改造を施した。
【０１７９】
まず、プロセススピードを２００ｍｍ／ｓとした。
【０１８０】
現像部分を１成分ジャンピング現像から、２成分現像剤を使用可能に改造を施した。更に、帯電部分にマグネットローラーを内包した１６φ導電性非磁性スリーブを配し、帯電用磁気ブラシを形成する。帯電用の導電性スリーブと感光体との最小ギャップは、０．５ｍｍに設定した。また、現像バイアスは、−５００Ｖの直流成分にピーク間電圧（Ｖｐｐ）１０００Ｖ、周波数３ｋＨｚの矩形波を重畳する。更に、コロナ帯電器を用いた転写手段をローラー転写方式に変更し、帯電前露光手段を取り除いた。
【０１８１】
更に、クリーニングブレードを取り去り、クリーナレス複写装置とした。図４に概略図を示す。図中、４０１は定着器、４０２は帯電器、４０３は帯電用磁性粒子、４０４は磁石を内包する導電性スリーブ、４０５は感光体、４０６は露光光、４０７は現像スリーブ、４０８は現像器、４０９及び４１０は撹拌スクリュウ、４１１は現像剤、４１２は紙搬送ガイド、４１３は転写紙、４１４は転写ローラ、４１５は紙搬送ベルトを示す。
【０１８２】
〔評価方法〕
実際の耐久評価としては、デジタル複写機１を用い、磁性粒子のコーティング密度が１８０ｍｇ／ｃｍ^２ となるように帯電器に装着し、感光体を装着する。帯電方法は、本発明中に記載のある注入帯電方法を用いる。なお、１８０ｍｇ／ｃｍ^２ となるように装着するためには、最低限３０ｇの量を必要とする。
【０１８３】
まず３％文字原稿にてＡ４横送りで５００枚通紙を連続に行う。この際、帯電部材に印加するバイアスは、印加電圧−７００Ｖの直流電圧に１ｋＨｚ、７００Ｖｐｐの矩形波交流電圧を重畳した電圧であり、２５℃／相対湿度６０％の条件下耐久試験を行う。
【０１８４】
更に、連続通紙時、最初の一枚目の画像が形成され得る以前の帯電時（前回転時）、画像形成間（紙間）及び５００枚目の画像形成終了の後の感光体帯電時（後回転時）については、帯電部材に−７００Ｖに直流電圧に１ｋＨｚ、３００Ｖｐｐの矩形波交流電圧を重畳した電圧を印加し、感光体を帯電させつつ、帯電磁気ブラシ中に混入するトナーを感光体上に移動させ、現像部分にて回収する。
【０１８５】
感光体帯電時と異なる帯電バイアスを印加するタイミングとして、本実施例では、前回転時、後回転時及び紙間を選択したが、これに限らず、画像形成せずに感光体が移動するタイミングを見図ればよい。
【０１８６】
この際、図１に示すごとく、転写残りのトナーは、磁気ブラシに回収され、その摩擦帯電極性を感光体帯電極性と同じにし、感光体上を経て現像または回収される。
【０１８７】
上記５００枚の連続通紙を繰り返し行い、耐久枚数２００００枚（４０回反復）毎に、帯電部材に印加電圧−７００Ｖの直流電圧に１ｋＨｚ、７００Ｖｐｐの矩形波交流電圧を重畳した電圧を印加し、感光体の表面電位が０Ｖから印加電圧の直流成分である−７００Ｖの何％に到達するかを測定し、電位収束率とした。
【０１８８】
収束率は、９０％以上であれば良好、９５％以上であれば優良な帯電性である。
【０１８９】
〔実施例１〜実施例１３〕
表３に示すような組み合わせで、装填量５０ｇにて、前述の評価方法により評価を行った。各実施例において、初期より帯電電位収束率が安定であった。
【０１９０】
但し、カップリング剤による表面処理を行っていない磁性粒子を用いた場合は、感光体削れがやや多く、カブリを生じた時点で感光体交換を行った。
【０１９１】
〔実施例１４〕
帯電用磁性粒子の装填量を２倍の１００ｇにし、図６の如く撹拌部材を投入した以外は実施例７と同様にして耐久試験を行ったところ、１３００００枚でも帯電性の劣化がなかった。１３００００枚において、感光体削れによるカブリを生じたのでここでストップした。
【０１９２】
図６中、６１は帯電器、６２はカットブレード、６３は撹拌部材、６４は帯電用磁性粒子容器、６５はマグネット、６６は非磁性導電性スリーブ、６７は帯電用磁性粒子、６８は感光体を示す。
【０１９３】
〔比較例１〕
帯電用磁性粒子製造例６で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０１９４】
その結果、６００００枚程度までは良好であったものの、８００００枚では帯電性が低下した。
【０１９５】
〔比較例２〕
帯電用磁性粒子製造例７で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０１９６】
初期の帯電特性は問題なく、耐久性についても、６００００枚程度までは問題がないものの、８００００枚程度から劣化による著しい帯電性の低下が見られた。
【０１９７】
〔比較例３〕
帯電用磁性粒子製造例１５で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０１９８】
初期の帯電特性は問題なく、耐久性についても、６００００枚程度までは問題がないものの、８００００枚程度から劣化による著しい帯電性の低下が見られた。しかも、カップリング剤で処理してあるものの、感光体寿命が処理していないものとほぼ同じである。これは、磁性粒子の組成が本発明とは異っていることに加え、カップリング剤の構造が、長鎖のアルキル成分を含んでいないため潤滑性に乏しいためと考えられる。
【０１９９】
〔比較例４〕
感光体製造例２で得られた感光体及び帯電用磁性粒子製造例１６で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０２００】
初期の帯電特性は問題なく、耐久性についても、６００００枚程度までは問題がないものの、８００００枚程度から劣化による著しい帯電性の低下が見られた。しかも、カップリング剤で処理してあるものの、感光体寿命が処理していないものとほぼ同じである。これは磁性粒子の組成が本発明とは異なっていることに加え、カップリング剤の構造が、長鎖のアルキル成分を含んでいないため潤滑性に乏しいためと考えられる。
【０２０１】
〔比較例５〕
帯電用磁性粒子製造例１７で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０２０２】
その結果、６００００枚までは帯電性は良好であったが、８００００枚では帯電性が低下しはじめ、また感光体削れに起因するカブリが生じたため、感光体を変換して更に耐久試験を続けたが、１０００００枚では帯電性が明らかに低下した。
【０２０３】
〔比較例６〕
帯電用磁性粒子製造例１８で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０２０４】
その結果、８００００枚では帯電性が劣化した。
【０２０５】
〔比較例７〕
帯電用磁性粒子製造例１９で得られた磁性粒子を用いた以外は実施例１と同様にして耐久試験を行った。
【０２０６】
その結果、６００００枚で帯電性が劣化しはじめ、８００００枚では明らかに劣化した。
【０２０７】
【表３】

【０２０８】
【発明の効果】
以上のように、本発明によれば、耐久性に優れ、クリーナレスシステムにも好ましく用いられる帯電用磁性粒子、該帯電用磁性粒子を用いた電子写真装置及びプロセスカートリッジを提供することができた。
【図面の簡単な説明】
【図１】クリーナレスシステムの原理を示す概略図である。
【図２】磁性粒子の体積抵抗値の測定装置の概略断面図である。
【図３】トナーの摩擦帯電量の測定装置の概略図である。
【図４】電子写真方式のデジタル複写機の構成例の概略図である。
【図５】撹拌機構を備えた帯電部分の概略図である。
【図６】撹拌機構を備えた帯電部分の概略図である。
【図７】撹拌機構を備えた帯電部分の概略図である。
【図８】２成分現像器を備えたプロセスカートリッジの構成例の概略図である。
【図９】１成分現像器を備えたプロセスカートリッジの構成例の概略図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic apparatus having a charging member using magnetic particles and a process cartridge. More specifically, the present invention relates to an electrophotographic apparatus and a process cartridge such as a copying machine, a printer and a facsimile having a charging member using magnetic particles having a specific composition, and particularly to an electrophotographic apparatus and a process cartridge suitably used for a cleanerless image forming method. .
[0002]
[Prior art]
Conventionally, many methods are known as electrophotography, but generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the latent image is formed with toner. After developing, a visible image is formed, and if necessary, a toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat or pressure to obtain a copy. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.
[0003]
As a charging means in such an electrophotographic method, a means using corona discharge called so-called corotron and scorotron has been used, but a large amount of ozone is generated at the time of corona discharge, particularly when generating negative or positive corona. Therefore, it is necessary to provide a filter for capturing ozone in the electrophotographic apparatus, and there have been problems such as an increase in the size of the apparatus and an increase in running cost.
[0004]
As a technique for solving such a problem, a charging member such as a roller and a blade is brought into contact with the surface of the photoreceptor to form a narrow space in the vicinity of the contacting portion, which can be interpreted by the so-called Paschen's law. For example, Japanese Patent Application Laid-Open Nos. Sho 57-178257, 56-104351, 58-40566, and 58-58566 disclose a charging method in which ozone generation is minimized by forming a discharge. No. 139156 and JP-A-58-150975.
[0005]
However, in a method of charging by bringing a charging member such as a blade and a roller into contact with the photoconductor, a problem such as fusion of toner on the photoconductor tends to occur.
[0006]
For this reason, a method has been studied in which the charging member is kept close to the photoreceptor and used without direct contact. Examples of the member for charging the photoconductor include the above-described roller, blade, brush, and an elongated conductive plate member having a resistance layer.
[0007]
However, this method has a problem that it is difficult to control the distance between the charging member and the photosensitive member, and has a problem in practical use.
[0008]
Therefore, a technique of using a so-called magnetic brush as a charging member, which is formed by holding magnetic particles with a magnet and having a relatively small load due to contact with the photoconductor, is being studied.
[0009]
For example, Japanese Patent Application Laid-Open No. Sho 59-133569 discloses a method in which particles coated with iron powder are held on a magnet roll and charged by applying a voltage. Japanese Patent Application Laid-Open No. 7-72667 discloses a method for improving environmental dependency. Therefore, it is disclosed that magnetic particles coated with a styrene acrylic resin or the like are used.
[0010]
However, these techniques have a problem that it is difficult to obtain a stable charging property during continuous use. For example, as disclosed in Japanese Patent Application Laid-Open No. 6-301265, there is a problem that these techniques exist in a magnetic brush. There has been proposed a configuration in which toner is supplied so as to keep the amount of toner to be constant, thereby stabilizing the resistance.
[0011]
Further, as a new attempt, there is a method in which a voltage is applied to a contact conductive member such as a charging roller, a charging brush, and a charging magnetic brush, and charge is injected into a trap level on the surface of the photoreceptor to perform contact injection charging.
[0012]
JP-A-8-106200 proposes a charging device that satisfies charging properties and pinhole leakage resistance by using an image carrier having a charge injection layer and a magnetic brush having a specific resistance. Injection charging has been proposed, and as a feature thereof, there is no discharge start point due to a discharge phenomenon, and a configuration capable of obtaining a charging potential substantially linearly with applied voltage has been proposed.
[0013]
Further, for the purpose of improving the durability of the contact injection charging method using magnetic particles, JP-A-8-6355 discloses a method of mixing magnetic particles having a smooth surface and magnetic particles having an uneven surface. JP-A-69156 discloses a method of forming a resin layer on the surface of magnetic particles for charging, and JP-A-8-69149 discloses a method in which the particle size distribution of magnetic particles for charging has a plurality of peaks. Has been proposed.
[0014]
In the injection charging, since the discharge does not dominate the charging as described above, the surface of the photoreceptor is damaged by a product generated by the discharge, and the problem that deterioration or image flow under high temperature and high humidity is easily caused does not easily occur. It is preferable in that respect.
[0015]
On the other hand, magnetic particles used in electrophotography are mainly used as a developer, and are widely used for a method of supporting a toner and developing an electrostatic latent image. At present, studies on preferable characteristics have not been sufficiently conducted. Further, from the standpoint of practical application, as far as the present inventor can know, there is no example of using a magnetic brush as a photosensitive member charging member in an electrophotographic apparatus such as a copying machine on the market.
[0016]
JP-A-51-151545 discloses a charging method using a magnetic powder, and JP-A-61-57958 discloses a charging method using a semiconductive protective film and conductive particles. The conductive particles include metals such as copper, nickel, iron, aluminum, gold and silver, and conductive powders such as iron oxide, ferrite, zinc oxide, tin oxide, antimony oxide, titanium oxide and carbon black as a binder resin. The use of dispersed fine powder is described.
[0017]
JP-A-63-187267 discloses that an amorphous selenium drum is charged by using magnetic particles.
[0018]
Japanese Patent Application Laid-Open No. 4-116674 discloses metals such as iron, chromium, nickel and cobalt, and ferric oxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite and manganese-copper alloy. ing.
[0019]
JP-A-7-98530 and JP-A-7-92764 disclose that, as magnetic particles for charging, ferrite particles containing 3d, 4d and 5d metals have an activity of decomposing ozone generated during charging. It has been proposed from the viewpoint of.
[0020]
However, regarding magnetic particles as a photoreceptor charging member, it is insufficient to consider what the preferable composition and its effects are from the viewpoint of the composition, and the preferable configuration of the magnetic particles used for charging applications is insufficient. Development is desired.
[0021]
The cleaning process in electrophotography has conventionally used blade cleaning, fur brush cleaning, roller cleaning, and the like. In either method, the toner remaining after transfer is mechanically scraped off or dammed and collected in a waste toner container. Therefore, there has been a problem caused by such a member being pressed against the surface of the photoreceptor. For example, it has been mentioned that a photosensitive member is worn out by strongly pressing a member to shorten the life of the photosensitive member. From the standpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which has been a bottleneck when aiming for a more compact apparatus.
[0022]
In addition, from the viewpoint of ecology, an image forming system that does not generate waste toner has been desired in order to effectively use toner.
[0023]
These are technologies called simultaneous cleaning or cleanerless development, in which the developing means is a substantial cleaning means, i.e., on the photoreceptor after transfer between the transfer position and the charging position and between the charging position and the developing position. This is a system in which cleaning is performed by a developing unit without a cleaning unit that collects and stores the remaining toner. For example, JP-A-59-133573, JP-A-62-203182, JP-A-63-133179, JP-A-64-20587, JP-A-2-51168, and JP-A-2-302772 JP-A-5-2287, JP-A-5-2289, JP-A-5-53482 and JP-A-5-61383. However, these known techniques use a corona, a fur brush or a roller as a charging means, and have not yet achieved all of the contamination of the photoreceptor surface due to discharge products and the uniformity of charging.
[0024]
For this reason, a cleaner-less technique using a so-called magnetic brush holding a magnetic particle with a magnet body, which has a relatively small contact load to the photoconductor, as a charging member is being studied.
[0025]
For example, Japanese Patent Application Laid-Open No. Hei 4-21873 proposes an image forming apparatus which does not require a cleaning device using a magnetic brush to which an AC voltage having a peak value exceeding a discharge limit value is applied. Further, Japanese Patent Application Laid-Open No. Hei 6-118855 proposes an image forming apparatus equipped with a magnetic brush charging cleaning device without an independent cleaning device. Examples of magnetic particles used include iron, chromium, and nickel. And metals such as cobalt or alloys or compounds thereof, ferric oxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite and manganese-copper alloys, and styrene-based resins, vinyl-based resins, ethylene There are disclosures of particles obtained by coating with a base resin, a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin and a polyester resin, or a resin containing magnetic fine particles dispersed therein. Japanese Patent Application Laid-Open No. 4-21873 discloses iron powder, iron oxide powder and various ferrite powders. However, the preferred composition of the magnetic powder for charging is not disclosed, and there is a problem to be further studied from the viewpoint of magnetic particles suitable for a cleanerless method.
[0026]
JP-A-8-22150 discloses MnO, MgO and Fe as development carriers.₂  O₃  And a configuration in which a part of the composition is replaced by SrO is disclosed.
[0027]
Further, Japanese Patent Application Laid-Open No. 8-69155 discloses Li₂  Ferrite particles composed of O, MnO, MgO, etc. are used as magnetic particles for charging the photoreceptor.₂  O, K₂  O, CaO, SrO, Al₂  O₃  , SiO₂  And Bi₂  O₃  Proposals have been made to form a solid solution of the component (1).
[0028]
JP-A-60-227265 discloses that MgO-ZnO-Fe is used as a carrier for development.₂  O₃  A technique for preventing crystal exfoliation and breakage by introducing at least one of P, As, Sb, Bi, and V among group V elements in a system ferrite is introduced.
[0029]
Further, in Japanese Patent Application Laid-Open No. H06-110253, CuO-ZnO-Fe is used as a magnetic particle of a developing carrier which is dry-coated with resin.₂  O₃  Describes that a composition obtained by adding an element such as P or As to the composition described above is used, and the configuration prevents damage to the photoconductor caused during cleaning due to damaged particles. Japanese Patent Application Laid-Open No. 7-20658 describes a method of manufacturing a developing carrier for controlling static resistance by adding phosphorus to ferrite, and Cu, Zn, Fe, Co, Although there are disclosures of general compositions of Ni, Mn, Cd, and Mg, there is no mention of charging of a photoreceptor.
[0030]
[Problems to be solved by the invention]
Thus, charging magnetic particles suitable as a charging member have been desired. That is, there has been a demand for magnetic particles that have a stable charging property during continuous use and can form a magnetic brush charging member with little environmental dependency.
[0031]
Also in a cleanerless system, there has been a demand for a charging member having a stable charging property and capable of suitably processing the toner remaining after transfer.
[0032]
An object of the present invention is to provide magnetic particles for charging having excellent durability.
[0033]
Another object of the present invention is to provide an electrophotographic apparatus and a process cartridge using the charging magnetic particles.
[0034]
Another object of the present invention is to provide an electrophotographic apparatus which is equipped with a cleaner-less system using a charging member and can obtain a stable image for a long period of time.
[0035]
[Means for Solving the Problems]
That is, the present invention provides a charging magnetic particle that is arranged in contact with an electrophotographic photosensitive member and forms a charging member that charges the electrophotographic photosensitive member when a voltage is applied, wherein the magnetic particles are:
General formula (MnO) x (MgO) y (Fe₂  O₃  ) Z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having the composition described above, wherein the phosphorus content ratio on the surface of the magnetic particles is larger than the phosphorus ratio of the entire magnetic particles. The magnetic particles for charging are characterized in that:
[0036]
Further, the present invention includes an electrophotographic photosensitive member, a charging member formed of magnetic particles, and disposed in contact with the electrophotographic photosensitive member, and charges the electrophotographic photosensitive member by applying a voltage to the charging member. In an electrophotographic apparatus having a charging unit, an exposing unit, a developing unit and a transferring unit, the magnetic particles are
General formula (MnO) x (MgO) y (Fe₂  O₃  ) Z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having the composition described above, wherein the phosphorus content ratio on the surface of the magnetic particles is larger than the phosphorus ratio of the entire magnetic particles. An electrophotographic apparatus characterized in that:
[0037]
Further, the present invention includes an electrophotographic photosensitive member, a charging member formed of magnetic particles, and disposed in contact with the electrophotographic photosensitive member, and charges the electrophotographic photosensitive member by applying a voltage to the charging member. In a process cartridge which integrally supports the charging means to be detachable from the electrophotographic apparatus main body, the magnetic particles
General formula (MnO) × (MgO) y (Fe₂  O₃  ) Z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having the composition described above, wherein the phosphorus content ratio on the surface of the magnetic particles is larger than the phosphorus ratio of the entire magnetic particles. A process cartridge.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
A major feature of the present invention is that the durability of the charging member is dramatically improved by using the magnetic particles having the above-mentioned extremely limited composition for the charging member.
[0039]
In the case of magnetic particles for charging, the deterioration of the charging characteristics
1. Degradation of energization due to continuous flow of charging current to photoconductor
2. Photoreceptor is scraped by rubbing against photoreceptor, and contamination due to the shavings adhering
3. Contamination due to toner adhering to the cleaning device
4. In the case of cleanerless, contamination by transfer residual toner
5. Particle surface abrasion caused by friction between particles peculiar to charging applications caused by the very small amount of toner existing between magnetic particles compared to development
And other factors.
[0040]
The mechanism of action of the present invention is currently under study, and the melting point of phosphorus is relatively low, and it is difficult to form a solid solution with ferrite. I guess, but I don't know the details. However, as is clear from the examples described later, it is certain that extremely excellent durability can be obtained as compared with the case where magnetic particles other than the composition of the present invention are used.
[0041]
In the present invention, the ratio of phosphorus present on the surface of the magnetic particles is preferably at least 5 times, more preferably at least 10 times the ratio of phosphorus in the entire magnetic particles.
[0042]
The proportion of phosphorus present on the surface of the magnetic particles can be determined by X-ray photoelectron spectroscopy (XPS). In the present invention, the measurement was performed according to the following procedure.
[0043]
The sample is adhered on cellophane tape and fixed on a carbon sheet. The apparatus used was a 1600S X-ray photoelectron spectrometer (manufactured by ULVAC-PHI, Inc.), Mg Kα rays (400 W) was used as the X-ray source, and the analysis area was 800 μmφ. From the measured peak intensities of the respective element ratios, the surface atomic concentration (atomic%) was estimated using a relative sensitivity factor provided by the company. The ratio of the atomic% of phosphorus to the sum of the atomic% of the ferrite constituent metals except phosphorus is defined as the phosphorus existing ratio on the surface of the magnetic particles. The measurement area near the surface by this method is several tens nm deep from the surface.
[0044]
The composition of the whole particles and the composition ratio of phosphorus were measured by an ICP-AES method using a sample dissolved with alkali melting, hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, or the like. The apparatus used was ICAP-575, manufactured by Jarrele Ash Japan Ltd. The obtained composition ratio is converted into mol%, and the ratio of mol% of phosphorus to the sum of mol% of metal elements excluding phosphorus constituting ferrite is defined as the phosphorus ratio of the entire magnetic particles.
[0045]
Further, in the magnetic particles used in the present invention, in the surface shape, the engraving of the gap between the crystals is deepened, and in particular, in a cleaner-less state, the contaminants due to the transfer residual toner enter the gap. In addition, it has a characteristic that contamination of a surface portion contributing to charging hardly progresses.
[0046]
If the amount of phosphorus present in the ferrite is less than 0.01 part by weight, the effect of the present invention is insufficient, and if it exceeds 3 parts by weight, the magnetic properties of the ferrite deteriorate and the production becomes difficult.
[0047]
In order to further enhance the effects of the present invention, the magnetic particles of the present invention are preferably treated with a coupling agent having a configuration in which 6 or more carbon atoms are linearly connected.
[0048]
Since the magnetic particles for charging and the photoreceptor are strongly rubbed, the organic photoreceptor is easily shaved especially. In the present invention, the lubricating property is imparted by the long-chain alkyl group, which is effective in improving the damage of the photoreceptor and preventing contamination of the surface of the charging magnetic particles. In particular, when the photoconductor surface layer is composed of an organic compound, it has a remarkable effect.
[0049]
In this respect, the alkyl group preferably has 6 or more carbon atoms, more preferably 8 or more carbon atoms, and preferably 30 or less carbon atoms. When the number of carbon atoms is less than 6, it is difficult to obtain the above-mentioned effect, and when the number of carbon atoms exceeds 30, it tends to be insoluble in a solvent, and it is difficult to uniformly treat the surface of the magnetic particles. In addition, the flowability of the charged magnetic particles is extremely deteriorated, and the chargeability tends to be non-uniform.
[0050]
The amount of the coupling agent is preferably 0.0001 to 0.5% by weight based on the charging magnetic particles including the coupling agent. The effect of using a coupling agent less than 0.0001% by weight is insufficient, and if it exceeds 0.5% by weight, the flowability of the magnetic particles for charging tends to deteriorate. In this sense, the content is more preferably 0.001 to 0.2% by weight.
[0051]
The abundance can be evaluated by heating loss. The weight loss on heating is preferably 0.5% by weight or less, more preferably 0.2% by weight or less.
[0052]
Here, the heating loss refers to a weight loss from 150 ° C. to 800 ° C. in a nitrogen atmosphere in an analysis using a thermobalance.
[0053]
In the present invention, it is basically preferable that the surface of the magnetic particles for charging is composed only of a coupling agent, but it is also possible to coat a small amount of a resin component. In this case, the amount is preferably equal to or less than the amount of the coupling agent.
[0054]
Further, it can be used in combination with resin-coated magnetic particles for charging. In this case, the mixing ratio of the resin-coated magnetic particles is preferably 50% by weight or less based on the total weight of the magnetic particles in the charger. If the content exceeds 50% by weight, the effect of the magnetic particles for charging of the present invention is weakened.
[0055]
The above-mentioned coupling agent refers to a compound having a hydrolyzable group and a hydrophobic group in the same molecule and bonded to a central element such as silicon, aluminum, titanium, and zirconium. This hydrophobic group has a long-chain alkyl group.
[0056]
As the hydrolyzable group, for example, an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, which is relatively hydrophilic, is used. In addition, an acryloxy group, a methacryloxy group, a halogen and a modified product thereof are also used.
[0057]
Further, as the hydrophobic group, any structure may be used as long as it has a structure in which six or more carbon atoms are linearly connected in its structure. In the form of bonding with the central element, carboxylate, alkoxy, sulfonate and They may be bonded via a phosphate ester or directly. Further, the structure of the hydrophobic group may include a functional group such as an ether bond, an epoxy group, and an amino group.
[0058]
Some specific examples of the compounds that can be used in the present invention include:
(CH₃  O)₃  -Si-C₁₂H₂₅
(CH₃  O)₃  -Si-C₁₈H₃₇
(CH₃  O)₃  -Si-C₈  H₁₇
(CH₃  O)₂  -Si- (C₁₂H₂₅)₂
[0059]
[Outside 1]

[0060]
When the coupling agent is present on the surface of the charging magnetic particles of the present invention, the amount thereof is 0.5% by weight or less, preferably 0.2% by weight or less. Since a resistance value substantially equal to that of the magnetic particles not to be present can be obtained, the stability in production and the stability in quality are higher than in the case where a conductive particle-dispersed resin is used.
[0061]
Further, the reaction rate of the coupling agent is preferably 80% or more, more preferably 85% or more. This is because, in the present invention, since a coupling agent having a relatively long-chain alkyl group is used, a large proportion of unreacted substances leads to deterioration in fluidity. When the surface of the photoreceptor to be used is substantially a non-crosslinked resin, the unreacted processing agent may permeate the surface of the photoreceptor and cause clouding or cracking. For this reason, it is preferable to use a coupling agent that can react with the magnetic particle surface.
[0062]
As a method for measuring the reaction rate of the coupling agent, a solvent capable of dissolving the coupling agent to be used may be selected, and the abundance before and after washing may be measured.
[0063]
For example, a method of immersing in a solvent 100 times the amount of the treated magnetic particles and quantifying the coupling agent component in the solvent by chromatography, or coupling the coupling agent component remaining on the magnetic particle surface after washing with XPS, A method of quantifying by elemental analysis and thermogravimetric analysis (TGA) and quantifying the abundance before and after washing is possible.
[0064]
Further, the magnetic particles for charging used in the present invention have a volume resistance of 1 × 10⁴  ~ 1 × 10⁹  It is preferably Ωcm. 1 × 10⁴  If it is lower than Ωcm, pinhole leak tends to occur, and 1 × 10⁹  If it exceeds Ωcm, the charging of the photoconductor tends to be insufficient.
[0065]
The volume resistance of the magnetic particles is determined by filling the cell A shown in FIG. 2 with magnetic particles, arranging the electrodes 21 and 22 so as to be in contact with the magnetic particles, applying a voltage between the electrodes, and measuring the current flowing at that time. It was obtained by doing. The measurement conditions were as follows: the contact area between the filled magnetic particles and the electrode was 2 cm in an environment of a temperature of 23 ° C. and a relative humidity of 65%.²  The thickness (d) is 1 mm, the load on the upper electrode is 10 kg, and the applied voltage is 100 V. In FIG. 2, 23 is a guide ring, 24 is an ammeter, 25 is a voltmeter, 26 is a constant voltage device, 27 is a measurement sample, and 28 is an insulator.
[0066]
The principle of the cleanerless image forming method of the present invention will be described with reference to FIG.
[0067]
The photoreceptor 12 charged by the magnetic brush charging device 11 constituted by the magnet-containing nonmagnetic conductive sleeve 16 coated with the magnetic particles 15 forms an electrostatic latent image by exposure light 13 from the exposure means. The latent image is reversely developed by a developing device 18 including, for example, a conductive non-magnetic sleeve 17 containing a developer 10 and a magnet, and forms an image visualized by toner on an exposed portion of the photoconductor 12. . 19 is a stirring screw. The visualized image is transferred to a transfer material by the transfer means 14, and the untransferred toner exists on the photoreceptor. The toner remaining after the transfer is affected by the transfer, and the charge polarity is variously distributed from minus to plus. While the photoreceptor is being charged while scraping off such transfer residual toner with a magnetic brush charging device 11 that rotates and rubs, the transfer residual toner is brought into a desired polarity by frictional charging of the magnetic particle toner constituting the magnetic brush. It is possible to align. Note that plus and minus in the figure represent the polarity of the toner.
[0068]
Therefore, even in a magnetic brush charging device utilizing a so-called discharge phenomenon, a clear image can be formed without using an independent cleaning means by utilizing the frictional charging between the toner or the magnetic particles constituting the discharge or the magnetic brush.
[0069]
Furthermore, even when a contact injection charging method that does not use a discharge phenomenon is used, the toner particles are transferred to a desired polarity by utilizing the frictional charging of the magnetic particles and the toner remaining after transfer, so that a clear image can be obtained without an independent cleaning unit. Image formation becomes possible.
[0070]
The average particle size of the magnetic particles is measured using a laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.) by dividing the range of 0.5 to 200 μm into 32 logarithms. did.
[0071]
In the present invention, the average particle size is preferably in the range of 5 to 100 μm. When the average particle size is smaller than 5 μm, the magnetic particles tend to leak, and when the average particle size exceeds 100 μm, the charging uniformity tends to deteriorate. More preferably, it is 15 to 80 μm. When the injection charging method is used, 15 to 40 μm is preferably used in consideration of the contact property.
[0072]
In the present invention, by using a layer farthest from the conductive support, that is, a photoconductor having a charge injection layer as a surface layer, 80% or more with respect to the absolute value of the DC component of the applied voltage without discharging. Further, a charged potential of 90% or more can be obtained. Therefore, compared to the charging method interpreted by Paschen's law, the applied voltage can be kept low, and a further ozoneless charging method can be realized.
[0073]
The charge injection layer has a volume resistivity of 1 × 10 4 in order to satisfy the conditions of sufficient chargeability and image deletion.⁸  ~ 1 × 10^FifteenIt is preferably in the range of Ωcm. More preferably, 1 × 10¹⁰~ 1 × 10^FifteenΩcm, 1 × 10¹²~ 1 × 10^FifteenIt is preferably Ωcm. 1 × 10⁸  If the volume resistance value is smaller than Ωcm, it is difficult to hold the electrostatic latent image, and the image flow is likely to occur particularly under high temperature and high humidity. On the other hand, 1 × 10^FifteenIf the volume resistance value is larger than Ωcm, the charge from the charging member cannot be sufficiently received, and the charging tends to be poor.
[0074]
The charge injection layer can be made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin, and forms an inorganic layer having the above resistance. This is also an effective means. By providing such a functional layer surface, it plays a role of retaining the charge injected from the charging member, and also plays a role of releasing this charge to the photosensitive member support during exposure, thereby reducing the residual potential.
[0075]
Here, the method of measuring the volume resistance value of the surface layer of the photoreceptor is as follows. A layer (thickness: 3 mm) similar to the surface layer is formed on polyethylene terephthalate (PET) having gold deposited on the surface, and the volume resistance is measured. The measurement was performed by applying a voltage of 100 V in an environment of a temperature of 23 ° C. and a relative humidity of 65% using a measuring device (4140B pAMATOR manufactured by Hewlett-Packard Company).
[0076]
The particle size of the conductive particles is preferably 0.3 μm or less from the viewpoint of translucency, and most preferably 0.1 μm or less. It is 2 to 250 parts by weight, preferably 2 to 190 parts by weight, based on 100 parts by weight of the binder resin. If the amount is less than 2 parts by weight, it is difficult to obtain a preferable volume resistance value, and if it exceeds 250 parts by weight, the film strength tends to decrease, and the charge injection layer tends to be scraped. The thickness of the charge injection layer is preferably 0.1 to 10 μm, and most preferably 1 to 7 μm.
[0077]
Preferably, the charge injection layer contains a lubricant powder. The expected effect is that the friction between the photosensitive member and the charging member during charging is reduced, the nip involved in charging is enlarged, and charging characteristics are improved. In addition, since the releasability of the photoreceptor surface is improved, magnetic particles are less likely to adhere. In particular, as the lubricant powder, it is preferable to use a fluororesin, a silicone resin or a polyolefin resin having a low critical surface tension. Particularly preferably, a tetrafluoroethylene resin is used. In this case, the amount of the lubricant powder is preferably 2 to 50 parts by weight based on 100 parts by weight of the binder resin. More preferably, it is 5 to 40 parts by weight. If the amount is less than 2 parts by weight, the amount of the lubricant powder is not sufficient, so that the effect of improving the chargeability of the photoreceptor is not sufficient, and the transfer residual toner tends to increase from the viewpoint of a cleanerless device. If it exceeds 50 parts by weight, the resolution of the image and the sensitivity of the photoreceptor tend to decrease.
[0078]
When the surface layer is coated with the inorganic layer, the underlying photoconductive layer is preferably amorphous silicon, and a blocking layer, a photoconductive layer, and a charge injection layer are sequentially formed on a cylinder by glow discharge or the like. Is preferred.
[0079]
As the photosensitive layer, conventionally known ones can be used. For example, if it is an organic material, a phthalocyanine pigment, an azo pigment and the like can be mentioned.
[0080]
Further, an intermediate layer can be provided between the charge injection layer and the photosensitive layer. The purpose of such an intermediate layer is to enhance the adhesion between the charge injection layer and the photosensitive layer or to function as a charge barrier layer. As the intermediate layer, for example, commercially available resin materials such as epoxy resin, polyester resin, polyamide resin, polystyrene resin, acrylic resin, and silicone resin can be used.
[0081]
As the conductive support for the photoreceptor, a metal such as aluminum, nickel, stainless steel, and steel, plastic or glass having a conductive film, or conductive paper can be used.
[0082]
Further, there is a preferable range also in the triboelectric charging property between the toner used and the magnetic particles of the charging member, and the tribo value of the toner measured by the ratio of the toner 7 used to the magnetic particles 100 of the charging member is measured. Is the same as the charging polarity of the photoreceptor, and its absolute value is preferably 1 to 90 mC / kg, more preferably 5 to 80 mC / kg, and still more preferably 10 to 40 mC / kg. In particular, it can impart particularly good characteristics to the charging characteristics of the photoreceptor.
[0083]
The method for measuring the triboelectric charge of the toner is described below. FIG. 3 shows an outline of the measuring apparatus.
[0084]
A mixture of 0.040 kg of magnetic particles to be measured and 0.0028 kg of toner is placed in a polyethylene bottle having a capacity of 50 to 100 ml under an environment of 23 ° C. and a relative humidity of 60%, and shaken by hand 150 times. Next, 0.0005 kg of the mixture is put into a metal measuring container 32 having a 500-mesh screen 33 at the bottom, and a metal lid 34 is closed. Reference numeral 30 denotes a measurement sample. At this time, the weight of the entire measurement container 32 is weighed and is defined as W1 g. Next, in the suction device (at least the portion in contact with the measuring container 32 is an insulator), the pressure of the vacuum gauge 35 is adjusted to 250 mmAq by adjusting the air volume control valve 36 by suctioning from the suction port 37. In this state, suction is performed by the suction device 31 for three minutes to remove the developer. The potential of the electrometer 39 at this time is set to V (volt). Here, a capacitor 38 has a capacity of C (mF). Further, the weight of the entire measuring machine after suction is weighed and is defined as W2 (kg). The tribo value (mC / kg) of this developer is usually calculated as in the following equation.
[0085]
Triboelectric charge (mC / kg) = CV / (W1-W2)
[0086]
However, since the magnetic particles used in the present invention have a small particle size, a considerable amount of the particles pass through the mesh even with a 500-mesh screen. It is calculated as the following equation including the correction.
[0087]
When the mass of the magnetic particles weighed in advance is M1, the toner is M2, and M3 of this mixture is placed in a metal measuring volume 32 having a screen 33 of 500 mesh.
Triboelectric charge (mC / kg) = CV / {M3 × M2 / (M1 + M2)}
It is.
[0088]
In the electrophotographic apparatus of the present invention, a magnetic brush formed of magnetic particles is used as a charging member that comes into contact with the photoreceptor. Preferably, a conductive sleeve having a magnet roll is used, and the surface thereof is uniformly coated with magnetic particles for charging.
[0089]
The closest gap between the charging magnetic particle holding member and the photoconductor is preferably 0.3 to 2.0 mm. If the distance is less than 0.3 mm, depending on the applied voltage, a leak may occur between the conductive portion of the magnetic particle holding member for charging and the photoconductor, and the photoconductor may be damaged.
[0090]
The direction of movement of the magnetic brush for charging may be the same as the direction of movement of the photoreceptor at the contact portion, but may move in the opposite direction from the viewpoint of the incorporation of the transfer residual toner and the uniformity of charging. Is preferred.
[0091]
The amount of the magnetic particles for charging held by the magnetic particle holding member for charging is preferably 50 to 500 mg / cm.²  , More preferably 100-300 mg / cm²  It is. Within this range, particularly stable charging properties can be obtained.
[0092]
As for the charging bias applied to the charging member, when an injection charging method is used, only a DC component can be used. However, it is preferable to apply a slight AC component because image quality can be improved. The DC component may be a voltage equivalent to the surface potential of the photosensitive member to be obtained, but is preferably a voltage having a slightly larger absolute value. The AC component is preferably at a frequency of about 100 Hz to 10 kHz and the peak-to-peak voltage of the applied AC component is preferably about 1000 V or less, depending on the process speed of the apparatus. If the voltage exceeds 1000 V, a potential is generated on the photoconductor in accordance with the applied voltage, and thus the latent image surface may be waved in potential, causing fogging and low density.
[0093]
In the method using discharge, the charging bias to be applied is preferably a voltage in which an AC component is superimposed on a DC component from the viewpoint of charging uniformity. In the case of only the DC component, a voltage larger than the absolute value of the voltage obtained by adding the surface potential of the photosensitive member to be obtained to the discharge starting voltage is required. The AC component has a frequency of about 100 Hz to 10 kHz, the peak-to-peak voltage of the applied AC component is about 1000 V or more, and preferably twice or more the discharge starting voltage, although it depends on the process speed of the apparatus. This is to obtain a sufficient leveling effect on the magnetic brush and the surface of the photoconductor. As the waveform of the applied AC component, a sine wave, a square wave, a sawtooth wave, or the like can be used. When an AC component having a peak-to-peak voltage that is twice or more the discharge starting voltage is applied, the DC component may be a voltage equivalent to the surface potential of the photoconductor to be obtained.
[0094]
Further, extra charging magnetic particles may be held in the charger and circulated.
[0095]
As the exposure unit in the present invention, a known unit such as a laser and an LED is used.
[0096]
The developing unit is not particularly limited, but in the case of an image forming apparatus having no cleaning unit, reversal development is preferable, and a configuration in which the developer and the photoreceptor are in contact is preferable. For example, a contact two-component development method, a contact one-component method, and the like are mentioned as suitable methods. This is because, when the developer and the transfer residual toner are in contact with each other on the photoreceptor, a rubbing force is applied to the electrostatic force, and the transfer residual toner tends to be effectively collected by the developing unit. Regarding the bias applied to the development, it is preferable that the DC component comes between the black portion (the exposed portion in the case of reversal development) and the potential of the white background portion.
[0097]
As a transfer unit, a known method such as a corona, a roller, and a belt is used.
[0098]
In the present invention, a process cartridge (20 in FIG. 1) detachably mountable on the main body of the electrophotographic apparatus can be provided by integrally supporting the electrophotographic photosensitive member and the charging means, and further, if necessary, the developing means and the cleaning means. . Further, the developing means may be a cartridge separate from the cartridge having the electrophotographic photosensitive member.
[0099]
In the present invention, there is no need to change the charging bias of the photoreceptor in order to transport the toner remaining from the charging device from which the transfer residual toner has been temporarily recovered to the developing portion by using the surface of the photoreceptor and collect and reuse the toner. However, when a jam occurs or when images with a high image ratio are continuously obtained, the amount of transfer residual toner mixed into the charger may be extremely large.
[0100]
In this case, during the operation of the electrophotographic apparatus, the toner may be moved from the charging unit to the developing device by utilizing the time when an image is not formed on the photoconductor. The non-image forming time includes the time of pre-rotation, the time of post-rotation, and between transfer materials. In this case, it is preferable to change the charging bias so that the toner is more easily transferred to the photoconductor than the charging unit. Methods of facilitating release from the charging means include reducing the peak-to-peak voltage of the AC component, using only the DC component, or changing the waveform without changing the peak-to-peak voltage to lower the AC effective value. No.
[0101]
The toner used in the present invention is not particularly limited. However, from the viewpoint of toner scattering, there is a preferable mode in terms of transfer efficiency. In other words, if the amount of the transfer residual toner that enters the magnetic brush is small, the absolute amount of the toner that may be scattered is small. When the shape factor of the toner is in the range of 100 to 140 for SF-1 and 100 to 120 for SF-2, the transferability tends to be good. In particular, those formed by a polymerization method and having a shape coefficient in the above range are particularly preferred because of their high transfer efficiency.
[0102]
Here, SF-1 and SF-2 are measured as follows.
[0103]
For example, using an FE-SEM (S-800) manufactured by Hitachi, Ltd., 100 toner images of 2 μm or more that are enlarged 1000 times are randomly sampled, and the image information is analyzed via an interface, for example, by an image analyzer manufactured by Nicole. It is introduced into an apparatus (Luzex III), analyzed, and defined as a value obtained from the following equation.
[0104]
[Outside 2]

[0105]
Here, MXLNG in the formula is the absolute maximum length of the particle, PERIME is the peripheral length of the particle, and AREA is the projected area of the particle. SF-1 indicates the degree of roundness of the particles, and SF-2 indicates the unevenness of the particles. The closer they are to 100, the closer to a true sphere.
[0106]
Further, the process cartridge of the present invention preferably has a configuration in which toner can be further added due to cost requirements, in consideration of the life of the charger portion and the use of a magnet-containing non-magnetic sleeve. In this case, it is preferable that the magnetic particles for charging also be present in the charged portion in a larger amount than the minimum required amount and circulated to further extend the durability (FIGS. 8 and 9).
[0107]
8, 801 denotes a charger, 802 denotes a stirring member, 803 denotes a cutting blade, 804 denotes a toner supply port, 805 denotes a developing device, 805 denotes a developing container, 806 denotes a developer stirring and feed screw, 807 denotes a developer, and 808 denotes a developer. 809 denotes a magnet-containing conductive sleeve, 810 denotes a photoreceptor, 811 denotes a charging magnetic particle, 812 denotes a magnet-containing conductive sleeve, and 813 denotes a charging magnetic particle container. 9, 901 denotes a charger, 902 denotes a stirring member, 903 denotes a cut blade, 904 denotes a toner supply port, 904 denotes a developing device, 905 denotes a developing container, 906 denotes a toner stirrer, 907 denotes a toner application roller, and 908 denotes a toner application roller. Denotes a toner, 910 denotes an elastic roller for development, 911 denotes a photoconductor, 912 denotes magnetic particles for charging, 913 denotes a conductive sleeve containing a magnet, and 914 denotes a magnetic particle container for charging.
[0108]
As means for circulating, it is preferable to stir mechanically, or to provide a magnetic pole configuration capable of circulating magnetic particles, or to provide a member for moving magnetic particles in a container for storing magnetic particles. For example, a screw member that stirs behind the magnetic brush (FIG. 5), a configuration in which a repulsion pole is provided and the magnetic particles are peeled off and re-coated (FIG. 7), an obstruction member that obstructs the flow of the magnetic particles, and the like Is provided.
[0109]
5 and 7, 51 and 71 are chargers, 52 and 72 are cut blades, 53 and 73 are magnetic particle containers for charging, 54 and 74 are magnets, 55 and 75 are non-magnetic conductive sleeves, and 56 and 76 are A stirring member, 57 and 77 are magnetic particles for charging, and 58 and 78 are photosensitive members.
[0110]
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0111]
First, the configuration, material, manufacturing method, and the like of a member used in the present invention will be exemplified.
[0112]
[Production example 1 of magnetic particles for charging]
Fe₂  O₃              54 mol%
MnO 35 mol%
MgO 11 mol%
[0113]
Phosphorus is added to 100 parts by weight of the above total metal oxide in an amount of 0.05 part by weight, pulverized and mixed by a ball mill, and a dispersant, a binder and water are added to form a slurry, and then a granulation operation is performed by a spray drier. Was done. After classification as appropriate, firing was performed at 1200 ° C. in an atmosphere where the oxygen concentration was adjusted, if necessary.
[0114]
The obtained ferrite was subjected to a classification after the crushing treatment to obtain ferrite particles having an average particle size of 27.6 μm.
[0115]
The volume resistivity of the fate particles is 4 × 10⁷  Ωcm, 8 × 10⁴  The magnetization at A / m (1 kOe) is 57 Am²  kg (57 emu / g). Details of the characteristics are as shown in Table 1.
[0116]
The phosphorus content on the surface of the particles was 30 times the phosphorus content of all the particles.
[0117]
The properties are summarized in Table 1.
[0118]
[Production example 2 of magnetic particles for charging]
Production was conducted in the same manner as in Production Example 1 of magnetic particles for charging, and particles having an average particle size of 37.0 μm were obtained.
[0119]
The properties are listed in Table 1.
[0120]
[Example 3 of manufacturing magnetic particles for charging]
Except that 0.5 parts by weight of phosphorus was added, the production was performed in the same manner as in Production Example 1 of the magnetic particles for charging to obtain particles having an average particle size of 28.0 μm.
[0121]
The properties are listed in Table 1.
[0122]
[Production example 4 of magnetic particles for charging]
Except that 1.0 part by weight of phosphorus was added, the production was carried out in the same manner as in Production Example 1 of the magnetic particles for charging to obtain particles having an average particle size of 27.5 μm.
[0123]
The properties are listed in Table 1.
[0124]
[Example 5 of manufacturing magnetic particles for charging]
Fe₂  O₃              50 mol%
MnO 30 mol%
MgO 20 mol%
Except that 1.0 part by weight of phosphorus was added, the production was performed in the same manner as in Production Example 1 of the magnetic particles for charging to obtain particles having an average particle size of 27.0 μm.
[0125]
The properties are listed in Table 1.
[0126]
[Production example 6 of magnetic particles for charging]
Except that phosphorus was not added, the production was performed in the same manner as in Production Example 1 of magnetic particles for charging.
[0127]
The properties are summarized in Table 1.
[0128]
[Production example 7 of magnetic particles for charging]
Except that phosphorus was not added, production was performed in the same manner as in Production Example 5 of magnetic particles for charging.
[0129]
The properties are summarized in Table 1.
[0130]
[Production Example 8 of Magnetic Particles for Charging]
To a solution of 0.05 parts by weight of dodecyltrimethoxysilane, which is a silane coupling agent, in 20 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles prepared in Preparation Example 1 for charging magnetic particles was added, and the mixture was heated to 70 ° C. while stirring. After keeping the solvent and evaporating the solvent, it was placed in an oven at 150 ° C. and cured.
[0131]
The properties are listed in Table 2.
[0132]
[Example 9 of producing magnetic particles for charging]
To a solution of 0.05 parts by weight of octyltrimethoxysilane, which is a silane coupling agent, in 20 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles produced in Preparation Example 1 for magnetic particles for charging was added, and the mixture was heated to 70 ° C. while stirring. After keeping the solvent and evaporating the solvent, it was placed in an oven at 100 ° C. and cured.
[0133]
The properties are listed in Table 2.
[0134]
[Production Example 10 of Magnetic Particles for Charging]
To a solution prepared by dissolving 0.05 parts by weight of isopropoxytriisostearoyl titanate as a titanium coupling agent in 20 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles prepared in Preparation Example 1 for magnetic particles for charging was added. After the solvent was evaporated at a temperature of 200 ° C., the solution was placed in an oven at 200 ° C. and cured.
[0135]
The properties are listed in Table 2.
[0136]
[Production Example 11 of Magnetic Particles for Charging]
To a solution of 0.05 parts by weight of isopropoxytriisostearoyl titanate, which is a titanium coupling agent, in 30 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles prepared in Preparation Example 2 for magnetic particles for charging was added. After the solvent was evaporated at a temperature of 200 ° C., the solution was placed in an oven at 200 ° C. for curing.
[0137]
The properties are listed in Table 2.
[0138]
[Production Example 12 of Magnetic Particles for Charging]
To a solution of 0.15 parts by weight of isopropoxytriisostearoyl titanate, which is a titanium coupling agent, in 30 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles produced in Preparation Example 3 for magnetic particles for charging was added. After the solvent was evaporated at a temperature of 200 ° C., the solution was placed in an oven at 200 ° C. for curing.
[0139]
The properties are listed in Table 2.
[0140]
[Charge Magnetic Particle Production Example 13]
To a solution of 0.10 parts by weight of isopropoxytriisostearoyl titanate as a titanium coupling agent in 30 parts by weight of methyl ethyl ketone was added 100 parts by weight of the magnetic particles produced in Preparation Example 4 for magnetic particles for charging, and stirred. After the solvent was evaporated at a temperature of 200 ° C., the solution was placed in an oven at 200 ° C. and cured.
[0141]
The properties are listed in Table 2.
[0142]
[Charging Magnetic Particle Production Example 14]
To a solution of 0.10 parts by weight of isopropoxytriisostearoyl titanate, a titanium coupling agent, in 30 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles prepared in Preparation Example 5 for magnetic particles for charging was added, and stirred. After the solvent was evaporated at a temperature of 200 ° C., the solution was placed in an oven at 200 ° C. for curing.
[0143]
The properties are listed in Table 2.
[0144]
[Production Example 15 of Magnetic Particles for Charging]
To a solution of 0.10 parts by weight of γ-glycidoxypropyltrimethoxysilane, which is a silane coupling agent, in 20 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles produced in Production Example 6 for magnetic particles for charging was added, and the mixture was stirred. While keeping the temperature at 70 ° C. while evaporating the solvent, the solution was placed in an oven at 100 ° C. and cured.
[0145]
The properties are listed in Table 2.
[0146]
[Charge Magnetic Particle Production Example 16]
To a solution of 0.05 part by weight of γ-methacryloxypropyltrimethoxysilane as a coupling agent dissolved in 20 parts by weight of methyl ethyl ketone, 100 parts by weight of the magnetic particles produced in Magnetic Particle Production Example 6 for charging were added, and the mixture was stirred. After maintaining the temperature at 70 ° C. and evaporating the solvent, it was placed in an oven at 100 ° C. and cured.
[0147]
The characteristics are listed in Table 2.
[0148]
[Example 17 of manufacturing magnetic particles for charging]
Fe₂  O₃              53 mol%
CuO 27 mol%
20 mol% ZnO
[0149]
Add 0.2 parts by weight of phosphorus to 100 parts by weight of the above metal oxide, pulverize and mix in a ball mill, add a dispersant, a binder resin and water to form a slurry, and granulate with a spray dryer. The operation was performed. After being appropriately classified, sintering was performed at 1000 ° C.
[0150]
The obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having an average particle size of 28.1 μm. The properties are listed in Table 1.
[0151]
[Production Example 18 of Magnetic Particles for Charging]
Fe₂  O₃              50 mol%
MnO 25 mol%
25 mol% ZnO
[0152]
Add 1.0 part by weight of phosphorus to a total of 100 parts by weight of the above metal oxide, pulverize and mix in a ball mill, add a dispersant, a binder resin and water to form a slurry, and granulate with a spray dryer. The operation was performed. After classification as appropriate, the oxygen concentration was adjusted appropriately and sintering was performed at 1000 ° C.
[0153]
After the obtained ferrite was subjected to a crushing treatment, classification was performed to obtain ferrite particles having an average particle size of 27.9 μm. The properties are listed in Table 1.
[0154]
[Production Example 19 of Charging Magnetic Particles]
Fe₂  O₃              53 mol%
MgO 25 mol%
17 mol% ZnO
MnO 5 mol%
[0155]
0.7 parts by weight of phosphorus is added to a total of 100 parts by weight of the above metal oxide, pulverized and mixed by a ball mill, and a dispersant, a binder resin and water are added to form a slurry, and then granulated by a spray drier. The operation was performed. After classification as appropriate, the oxygen concentration was adjusted appropriately and sintering was performed at 1100 ° C.
[0156]
The obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having an average particle size of 28.3 μm. The properties are listed in Table 1.
[0157]
[Table 1]

[0158]
[Table 2]

[0159]
[Photoconductor production example 1]
Five functional layers are provided on an aluminum cylinder having a diameter of 30 mm.
[0160]
The first layer is a conductive particle-dispersed resin layer having a thickness of about 20 μm, which is provided to smooth defects of the aluminum cylinder and to prevent the occurrence of moire due to the reflection of laser exposure.
[0161]
The second layer is a positive charge injection preventing layer, which serves to prevent the positive charge injected from the aluminum cylinder from canceling the negative charge charged on the surface of the photoreceptor.⁶  This is a medium resistance layer having a thickness of about 1 μm and a resistance adjusted to about Ωcm.
[0162]
The third layer is a charge generation layer, and is a layer having a thickness of about 0.3 μm in which an oxytitanium phthalocyanine-based pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.
[0163]
The fourth layer is a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoconductor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoconductor surface. The thickness was 15 μm.
[0164]
The volume resistance value of the charge transport layer is 3 × 10^FifteenΩcm.
[0165]
A charge injection layer is formed as a fifth layer. The charge injection layer is made of a photocurable acrylic resin formed of SnO.₂  This is a layer having a thickness of 3 μm in which ultrafine particles are dispersed. Specifically, antimony-doped SnO particles having a particle diameter of about 0.03 μm₂  The particles are obtained by dispersing 150 parts by weight with respect to 100 parts by weight of the resin, 20 parts by weight of tetrafluoroethylene resin particles having a particle size of about 0.25 μm, and 1.2 parts by weight of a dispersant.
[0166]
The volume resistance of the surface layer of the photoreceptor is 2 × 10^ThirteenΩcm.
[0167]
[Photoconductor production example 2]
Five functional layers are provided on an aluminum cylinder having a diameter of 30 mm.
[0168]
The first layer, the second layer, the third layer, and the fourth layer are formed in the same manner as in the photoconductor production example 1, and the charge injection layer is formed on the fifth layer. The charge injection layer is made of a photocurable acrylic resin formed of SnO.₂  This is a layer having a thickness of 3 μm in which ultrafine particles are dispersed. Specifically, SnO doped with antimony and reduced in resistance has a particle diameter of about 0.03 μm.₂  170 parts by weight of the particles are dispersed with respect to 100 parts by weight of the resin, 20 parts by weight of the tetrafluoroethylene resin particles and 1.2 parts by weight of the dispersant are dispersed.
[0169]
The volume resistance of the surface layer of the photoreceptor is 4 × 10¹²Ωcm.
[0170]
[Toner Production Example 1]
100 parts by weight of polyester resin
2 parts by weight of metal-containing azo dye
3 parts by weight of low molecular weight polypropylene
5 parts by weight carbon black
[0171]
After the above materials were dry-mixed, they were kneaded with a twin-screw kneading extruder set at 150 ° C. The obtained kneaded material was cooled, finely pulverized by an air-flow type pulverizer, and then subjected to air classification to obtain a toner composition having an adjusted particle size distribution. 1.7% by weight of hydrophobically treated titanium oxide was externally added to this toner composition to prepare a toner having a weight average particle diameter of 6.3 μm.
[0172]
[Toner Production Example 2]
88 parts by weight of styrene, 12 parts by weight of n-butyl acrylate, 3 parts by weight of low molecular weight polypropylene, 4 parts by weight of carbon black, 1.2 parts by weight of a metal-containing azo dye and 3 parts by weight of an azo initiator are dispersed and mixed. Was added to 500 parts by weight of pure water in which 4 parts by weight of calcium phosphate was dispersed, dispersed by a homomixer, polymerized at 70 ° C. for 8 hours, filtered, washed, dried, and classified, A toner composition was obtained.
[0173]
1.7 wt% of hydrophobically treated titanium oxide was externally added to the toner composition to prepare a toner having a weight average particle diameter of 6.3 μm.
[0174]
The shape factors were 125 for SF-1 and 115 for SF-2.
[0175]
[Developer Production Example 1]
A developer was prepared by mixing 6 parts by weight of the toner of Production Example 1 with 100 parts by weight of a nickel zinc ferrite having an average particle size of 60 μm coated with a silicone resin.
[0176]
[Developer Production Example 2]
A developer was prepared by mixing 6 parts by weight of the toner of Production Example 2 with 100 parts by weight of a nickel-zinc ferrite having an average particle size of 60 μm coated with an acryl-modified silicone resin.
[0177]
Next, the present invention will be described using evaluation machines and methods used in Examples and Comparative Examples of the present invention, and Examples and Comparative Examples.
[0178]
[Digital copier 1]
A digital copier (GP55, manufactured by Canon Inc.) using a laser beam was prepared as an electrophotographic apparatus. An outline of the apparatus is provided with a corona charger as a charging unit for the photoreceptor, a one-component developing unit employing a one-component jumping developing method as a developing unit, a corona charger as a transfer unit, a blade cleaning unit, and a pre-charge exposure. Means. The charger for the photoreceptor, the cleaning means and the photoreceptor are an integrated unit (process cartridge). The process speed is 150 mm / s. The digital copier was modified as follows.
[0179]
First, the process speed was set to 200 mm / s.
[0180]
The developed portion was modified from one-component jumping development to use of a two-component developer. Further, a 16φ conductive non-magnetic sleeve containing a magnet roller is disposed on the charged portion to form a charging magnetic brush. The minimum gap between the conductive sleeve for charging and the photoconductor was set to 0.5 mm. As the developing bias, a rectangular wave having a peak-to-peak voltage (Vpp) of 1000 V and a frequency of 3 kHz is superimposed on a DC component of -500 V. Further, the transfer means using the corona charger was changed to a roller transfer method, and the pre-charge exposure means was removed.
[0181]
Further, the cleaning blade was removed to obtain a cleanerless copying machine. FIG. 4 shows a schematic diagram. In the figure, reference numeral 401 denotes a fixing device, 402 denotes a charging device, 403 denotes a charging magnetic particle, 404 denotes a conductive sleeve containing a magnet, 405 denotes a photoconductor, 406 denotes exposure light, 407 denotes a developing sleeve, and 408 denotes a developing device. 409 and 410 are stirring screws, 411 is a developer, 412 is a paper transport guide, 413 is a transfer paper, 414 is a transfer roller, and 415 is a paper transport belt.
[0182]
〔Evaluation method〕
For actual durability evaluation, the digital copying machine 1 was used, and the coating density of the magnetic particles was 180 mg / cm.²  And a photoreceptor is mounted. As the charging method, an injection charging method described in the present invention is used. In addition, 180 mg / cm²  In order to be mounted in such a manner, a minimum amount of 30 g is required.
[0183]
First, 500 sheets of 3% character originals are continuously fed in A4 landscape mode. At this time, a bias applied to the charging member is a voltage obtained by superimposing a rectangular wave AC voltage of 1 kHz and 700 Vpp on a DC voltage of an applied voltage of -700 V, and a durability test is performed under the conditions of 25 ° C./60% relative humidity.
[0184]
Further, at the time of continuous paper feeding, at the time of charging before the first first image can be formed (at the time of pre-rotation), at the time of image formation (between sheets), and at the time of charging of the photoconductor after the end of the 500th image formation Regarding (at the time of post-rotation), a voltage obtained by superimposing a DC voltage of 1 kHz and a rectangular wave AC voltage of 300 Vpp on a charging member is applied to the charging member to charge the photosensitive member while exposing the toner mixed in the charged magnetic brush to the photosensitive member. Move on the body and collect at the developing part.
[0185]
In the present embodiment, the timing of applying the charging bias different from the charging of the photoconductor is selected in the pre-rotation, the post-rotation, and the sheet interval. However, the timing is not limited to this, and the timing in which the photoconductor moves without forming an image is Just look at it.
[0186]
At this time, as shown in FIG. 1, the toner remaining after transfer is collected by a magnetic brush, its frictional charging polarity is made the same as the charging polarity of the photoreceptor, and the toner is developed or collected via the photoreceptor.
[0187]
The above-described continuous feeding of 500 sheets is repeated, and a voltage obtained by superimposing a rectangular wave AC voltage of 1 kHz and 700 Vpp on a DC voltage of applied voltage of -700 V is applied to the charging member every 20,000 sheets (repeated 40 times), The percentage of the surface potential of the photoreceptor from 0 V to -700 V, which is the DC component of the applied voltage, was measured and defined as a potential convergence rate.
[0188]
The convergence rate is good if it is 90% or more, and it is excellent if it is 95% or more.
[0189]
[Examples 1 to 13]
The combinations shown in Table 3 were evaluated by the above-described evaluation method at a loading of 50 g. In each example, the charging potential convergence rate was stable from the beginning.
[0190]
However, when the magnetic particles not subjected to the surface treatment with the coupling agent were used, the photoreceptor was slightly scraped off and the photoreceptor was replaced when fogging occurred.
[0191]
[Example 14]
A durability test was performed in the same manner as in Example 7 except that the charging amount of the magnetic particles for charging was doubled to 100 g, and a stirring member was introduced as shown in FIG. The fogging caused by the scraping of the photoreceptor occurred on 130,000 sheets.
[0192]
6, 61 is a charger, 62 is a cut blade, 63 is a stirring member, 64 is a magnetic particle container for charging, 65 is a magnet, 66 is a non-magnetic conductive sleeve, 67 is magnetic particles for charging, and 68 is a photoconductor. Is shown.
[0193]
[Comparative Example 1]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 6 of magnetic particles for charging were used.
[0194]
As a result, the charging performance was good up to about 60,000 sheets, but the charging property was reduced at 80,000 sheets.
[0195]
[Comparative Example 2]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 7 of magnetic particles for charging were used.
[0196]
There was no problem in the initial charging characteristics, and there was no problem in durability up to about 60,000 sheets, but a remarkable decrease in charging properties due to deterioration was observed from about 80,000 sheets.
[0197]
[Comparative Example 3]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 15 for charging magnetic particles were used.
[0198]
There was no problem in the initial charging characteristics, and there was no problem in durability up to about 60,000 sheets, but a remarkable decrease in charging properties due to deterioration was observed from about 80,000 sheets. In addition, the life of the photosensitive member is almost the same as that of the untreated one, though it is treated with the coupling agent. This is considered to be due to the fact that the composition of the magnetic particles is different from that of the present invention, and that the structure of the coupling agent does not contain a long-chain alkyl component, so that it has poor lubricity.
[0199]
[Comparative Example 4]
A durability test was performed in the same manner as in Example 1 except that the photoconductor obtained in Photoconductor Production Example 2 and the magnetic particles obtained in Production Example 16 of magnetic particles for charging were used.
[0200]
There was no problem in the initial charging characteristics, and there was no problem in durability up to about 60,000 sheets, but a remarkable decrease in charging properties due to deterioration was observed from about 80,000 sheets. In addition, the life of the photosensitive member is almost the same as that of the untreated one, though it is treated with the coupling agent. This is considered to be due to the fact that the composition of the magnetic particles is different from that of the present invention, and the structure of the coupling agent is poor in lubricity because it does not contain a long-chain alkyl component.
[0201]
[Comparative Example 5]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 17 of magnetic particles for charging were used.
[0202]
As a result, the chargeability was good up to 60,000 sheets, but the chargeability began to decrease at 80,000 sheets, and fog caused by scraping of the photoconductor occurred. Therefore, the photoconductor was converted and the durability test was further continued. However, at 100,000 sheets, the chargeability was clearly reduced.
[0203]
[Comparative Example 6]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 18 of magnetic particles for charging were used.
[0204]
As a result, the chargeability was degraded on 80000 sheets.
[0205]
[Comparative Example 7]
A durability test was performed in the same manner as in Example 1 except that the magnetic particles obtained in Production Example 19 of magnetic particles for charging were used.
[0206]
As a result, the chargeability began to deteriorate on 60,000 sheets, and clearly deteriorated on 80,000 sheets.
[0207]
[Table 3]

[0208]
【The invention's effect】
As described above, according to the present invention, it was possible to provide magnetic particles for charging, which is excellent in durability and is preferably used for a cleanerless system, and an electrophotographic apparatus and a process cartridge using the magnetic particles for charging. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the principle of a cleanerless system.
FIG. 2 is a schematic sectional view of an apparatus for measuring the volume resistance of magnetic particles.
FIG. 3 is a schematic diagram of an apparatus for measuring a triboelectric charge amount of toner.
FIG. 4 is a schematic diagram of a configuration example of an electrophotographic digital copying machine.
FIG. 5 is a schematic view of a charging portion provided with a stirring mechanism.
FIG. 6 is a schematic view of a charging portion provided with a stirring mechanism.
FIG. 7 is a schematic view of a charging portion provided with a stirring mechanism.
FIG. 8 is a schematic diagram illustrating a configuration example of a process cartridge including a two-component developing device.
FIG. 9 is a schematic view of a configuration example of a process cartridge provided with a one-component developing device.

Claims (20)

In the charging magnetic particles forming a charging member that is arranged in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member when a voltage is applied,
The magnetic particles,
General formula (MnO) x (MgO) y (Fe ₂ O ₃ ) z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having a composition of
The magnetic particles for charging, wherein the phosphorus content on the surface of the magnetic particles is larger than the phosphorus content of the whole magnetic particles. 2. The magnetic particles for charging according to claim 1, wherein the phosphorus content ratio on the surface of the magnetic particles is at least 5 times the phosphorus ratio of the whole magnetic particles. The magnetic particles for charging according to claim 2, wherein the phosphorus content ratio on the surface of the magnetic particles is at least 10 times the phosphorus ratio of the whole magnetic particles. The charging magnetic particle according to claim 1, wherein the magnetic particle has a volume resistivity of 1 × 10 ⁴ to 1 × 10 ⁹ Ωcm. The charging magnetic particle according to claim 1, wherein the magnetic particle has an average particle size of 5 to 100 μm. The magnetic particle for charging according to any one of claims 1 to 5, wherein the magnetic particle has a coupling agent having a linear alkyl group having 6 or more carbon atoms on its surface. An electrophotographic photosensitive member, a charging unit formed of magnetic particles and having a charging member disposed in contact with the electrophotographic photosensitive member, and a charging unit and an exposure unit for charging the electrophotographic photosensitive member by applying a voltage to the charging member An electrophotographic apparatus having a developing unit and a transfer unit,
The magnetic particles,
General formula (MnO) × (MgO) y (Fe ₂ O ₃ ) z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having a composition of
An electrophotographic apparatus, wherein the phosphorus content on the surface of the magnetic particles is higher than the phosphorus content of the whole magnetic particles. The electrophotographic apparatus according to claim 7, wherein the phosphorus content ratio on the surface of the magnetic particles is at least 5 times the phosphorus ratio of the whole magnetic particles. 9. The electrophotographic apparatus according to claim 8, wherein the phosphorus content on the surface of the magnetic particles is at least 10 times the phosphorus content of the whole magnetic particles. The electrophotographic apparatus according to claim 7, wherein the magnetic particles have a volume resistivity of 1 × 10 ⁴ to 1 × 10 ⁹ Ωcm. The electrophotographic apparatus according to claim 7, wherein the magnetic particles have an average particle size of 5 to 100 μm. 12. The electrophotographic apparatus according to claim 7, wherein the magnetic particles have a coupling agent having a linear alkyl group having 6 or more carbon atoms on the surface thereof. 13. The electrophotographic apparatus according to claim 7, wherein the developing means collects the toner remaining on the electrophotographic photosensitive member after the transfer. 14. The electrophotographic apparatus according to claim 13, wherein there is no cleaning means for collecting and storing the toner remaining on the electrophotographic photosensitive member after the transfer between the transfer means and the charging means and between the charging means and the developing means. . An electrophotographic photoreceptor, having a charging member formed of magnetic particles and arranged in contact with the electrophotographic photoreceptor, and integrally integrating a charging unit for charging the electrophotographic photoreceptor by applying a voltage to the charging member; In the process cartridge which is supported and is detachable from the electrophotographic apparatus main body,
The magnetic particles,
General formula (MnO) × (MgO) y (Fe ₂ O ₃ ) z
(In the formula, x + y + z ≦ 1, and 0.2 <x <0.5, 0.05 <y <0.25, and 0.4 <z <0.6.)
Ferrite particles containing 0.01 to 3 parts by weight of phosphorus with respect to 100 parts by weight of ferrite having a composition of
A process cartridge, wherein the phosphorus content ratio on the surface of the magnetic particles is larger than the phosphorus content of the whole magnetic particles. 16. The process cartridge according to claim 15, wherein the phosphorus content ratio on the surface of the magnetic particles is at least 5 times the phosphorus content of the whole magnetic particles. 17. The process cartridge according to claim 16, wherein the phosphorus content on the surface of the magnetic particles is at least 10 times the phosphorus content of the whole magnetic particles. The process cartridge according to claim 15, wherein the magnetic particles have a volume resistance of 1 × 10 ⁴ to 1 × 10 ⁹ Ωcm. 19. The process cartridge according to claim 15, wherein the magnetic particles have an average particle size of 5 to 100 [mu] m. 20. The process cartridge according to claim 15, wherein the magnetic particles have a coupling agent having a linear alkyl group having 6 or more carbon atoms on the surface thereof.

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