JP3639718B2 - Image forming method - Google Patents

Description

〔式中、Ｘ_１およびＸ_２は水素原子、低級アルキル基、低級アルコキシ基、ニトロ基及びハロゲン原子からなるグループから選択されるメンバーを示し、Ｘ_１とＸ_２は同じ又は異なっており、ｍおよびｍ′は１〜３の整数を示し、Ｒ_１およびＲ_３は水素原子、Ｃ_１〜Ｃ_１８のアルキル基、Ｃ_２〜Ｃ_１８のアルケニル基、スルホンアミド基、メシル基、スルホン酸基、カルボキシエステル基、ヒドロキシ基、Ｃ_１〜Ｃ_１８のアルコキシ基、アセチルアミノ基、ベンゾイルアミノ基及びハロゲン原子からなるグループから選択されるメンバーを示し、Ｒ_１とＲ_３は同じ又は異なっており、ｎおよびｎ′は１〜３の整数を示し、Ｒ_２およびＲ_４は水素原子またはニトロ基を示し、Ａ^＋は、アンモニウムイオン、水素イオン、ナトリウムイオン、カリウムイオン及びそれらの混合イオンからなるグループから選択されるカチオンイオンを示す。〕で示される化合物を有し、該トナー粒子は、重合性単量体、該カーボンブラック及び該アゾ系鉄化合物を少なくとも含有する重合性単量体組成物を水系媒体中で重合することにより製造されたものであり、該重合性単量体組成物は、該カーボンブラック及び該アゾ系鉄化合物を第１の重合性単量体に分散させた分散液を少なくとも第２の重合性単量体と混合して調製されたものであることを特徴とする画像形成方法に関する。
【００４２】
本発明によれば、トナー組成物としての特定のアゾ系鉄化合物及び特定の物性を有するカーボンブラックを用いたトナーは、トナー帯電の迅速な立ち上がりが可能となり、高品位な画像が得られ、よって転写残トナーを像担持体表面から除去するためのクリーニング工程が、現像部で現像工程と同時に行なわれる現像同時クリーニング方式を用いた画像形成方法に適用した場合に、トナーの転写効率が向上し、転写残トナーによる像担持体の帯電阻害を十分に抑制し、さらに、転写残トナーを現像時に円滑に回収し、安定した現像性能を得ることが可能となる。
【００４３】
【発明の実施の形態】
本発明の画像形成方法に用いられる現像装置としては、（ｉ）トナー及びキャリアを有する二成分系現像剤を担持するための現像剤担持体として、磁石を内包した現像スリーブを用い、この現像スリーブ表面に二成分系現像剤を担持させ、この二成分系現像剤によって形成される磁気ブラシを像担持体としての感光体表面と接触させて現像を行なう二成分接触現像法、又は（ｉｉ）一成分系現像剤であるトナーを担持するためのトナー担持体として、弾性ローラーを用い、この弾性ローラー表面にトナーをコーティングしてトナー層を形成し、このトナー層を像担持体としての感光体表面と接触させて現像を行なう一成分接触現像法を用いることができる。
【００４４】
一成分接触現像法においては、トナーは、磁性又は非磁性のいずれでも良く、トナー層と感光体表面が接触していることが重要となる。トナー担持体は実質的に感光体表面と接触していることが好ましいが、これは、トナー担持体からトナー層を除いたときに該トナー担持体が感光体表面と接触しているということを意味する。このとき、トナーを介して、感光体と感光体表面に対向する弾性ローラー間に働く電界によってエッジ効果のない画像を得るためには、弾性ローラ表面あるいは表面近傍が電位をもち、感光体表面とトナー担持体表面間で電界が形成される必要がある。このため、弾性ローラーの低抵抗の芯材の表面に弾性ゴムによって形成される弾性層が中抵抗領域に抵抗制御されて感光体表面との導通を防ぎつつ電界を保つこと、または低抵抗の導電性ローラーの表面層に薄層の誘電層を設けることも利用できる。さらには、導電性ローラー上に感光体表面に対向する表面側を絶縁性物質により被覆した構成、あるいは、絶縁性スリーブで感光体に対向しない内面側に導電層を設けた構成も可能である。
【００４５】
一成分接触現像法を用いた場合、トナーを担持するためのトナー担持体としての現像ローラー表面と感光体表面とは、同方向に回転していてもよいし、逆方向に回転していてもよい。その回転方向が同方向である場合には、現像ローラー表面の周速は、感光体の周速に対して、周速比で１００％よりも大きいことが好ましい。１００％以下であると、ラインの切れが悪いなどの画像品質に問題を残す。周速比が高まれば高まるほど、現像部位に供給されるトナーの量は多く、潜像に対しトナーの脱着頻度が多くなり、不要な部分は掻き落とされ必要な部分には付与されるという繰り返しにより、潜像に忠実な画像が得られる。
【００４６】
本発明においては、転写工程で転写されずに像担持体の表面に存在している転写残トナーを除去するためのクリーニング工程を現像時に現像工程と同時に行なう現像同時クリーニング方式を用いる。
【００４７】
現像同時クリーニング方式においては、転写部と帯電部との間及び帯電部と現像部との間に、像担持体の表面に当接して像担持体の表面に存在する転写残トナーを除去するためのクリーニング部材を有していない。
【００４８】
転写残トナーの帯電は、転写バイアス条件、転写材の抵抗によっても大きく変化する。転写バイアスは一般にトナーの帯電極性とは逆極性の電圧が印加されるが、現像が正現像（トナー帯電極性と感光体帯電極性が逆）である場合、転写材が厚紙、ＯＨＴフィルムのように高抵抗なものであると、高い帯電を持つたトナー粒子が感光体との強い付着力によって転写されることなく、そのままの帯電極性でクリーニング工程へと進むことから、クリーニングしきれなくなり易い。
【００４９】
したがって、トナーとしては、感光体上の現像されたトナーの帯電量が適正に制御され、元々高い帯電量のトナーが感光体に現像されていないことが好ましい。
【００５０】
高い帯電量のトナーが感光体に現像されないようにするためには、トナーへの帯電付与或いはトナーの帯電性を押さえる必要があるが、トナーの帯電が十分でないとカブリ、トナー飛散、転写性の低下の如き弊害が生じ易くなる。
【００５１】
本発明の特定のカーボンブラックと、特定のアゾ系鉄化合物とを併用したトナーを用いることで、過剰な高帯電トナー粒子の生成を抑制し、適正な帯電量をトナーに持たせることが可能となった。これにより現像工程においても耐久性に優れた安定した性能を示す。これは、本発明の特定のカーボンブラックと特定のアゾ系鉄化合物を併用したトナーが有するカーボンブラックの良好な分散による荷電制御効果と、アゾ系鉄化合物自体の過剰な帯電を抑制する荷電制御効果の相乗効果と考えられる。
【００５２】
現像が反転現像（トナー帯電極性と感光体帯電極性が同極性）の場合、転写材が薄紙のように電界を通し易いものであると、転写バイアスによって逆極性に強く帯電されるトナー粒子ができ、この逆極性に強く帯電したトナー粒子は、やはり感光体との強い付着力をもちクリーニングしきれなくなり易い。
【００５３】
これに対し、本発明の特定のカーボンブラックと特定のアゾ系鉄化合物を併用したトナーを用いることで、過剰に逆極性に帯電したトナー粒子の生成を抑制することが可能となった。
【００５４】
転写バイアスによるトナー帯電の制御も、本発明の特定のカーボンブラックと特定のアゾ系鉄化合物を併用したことによるカーボンブラックの良好な分散による荷電制御効果と、アゾ系鉄化合物自体の過剰な帯電を抑制する荷電制御効果の相乗効果によってもたらされると考えられる。
【００５５】
これらの理由については必ずしも明らかではないが、本発明者らの知見によれば、本発明に用いられる特定のアゾ系鉄化合物が、トナーが過剰に高帯電量となること（いわゆるチャージアップ現象）を防止する効果で、転写工程でトナー極性と逆電界を印加されても、過剰な逆電荷をトナー粒子が保持しにくくしていることに加えて、アゾ系鉄化合物が分散剤としても機能し、カーボンブラックの分散性が向上した結果、各トナー粒子の摩擦帯電量が均一となることによるものと考えられる。
【００５６】
現像同時クリーニング方式の原理は、電子写真各工程における感光体上のトナーの帯電極性及び帯電量を制御することと反転現像方法を用いることにある。
【００５７】
例を挙げて説明すると、マイナス帯電性の感光体及びマイナス帯電性のトナーを用いた場合、その転写工程において、プラス極性の転写部材によって可視化された像を転写材に転写することになるが、転写材の種類（厚み、抵抗、誘電率の違い）と画像面積の関係により、転写残余のトナーの帯電極性がプラスからマイナスまで変動する。しかし、マイナス帯電性の感光体を帯電する際のマイナス極性の帯電部材により、感光体表面と共に転写残余のトナーまでもが、転写工程においてプラス極性に振れていたとしても、一様にマイナス側へ帯電極性を揃えることが出来る。これゆえ、現像時に一様にマイナス極性に帯電したトナー粒子が感光体表面に存在していても、現像方法として反転現像を用いた場合、マイナスに帯電された転写残余のトナーは、トナーの現像されるべき明部電位部には残り、トナーの現像されるべきでない暗部電位には、現像電界の関係上トナー担持体の方に引き寄せられ、残留しない。
【００５８】
しかしながら、現像同時クリーニング方式を用いて、より高速なプロセススピードの画像形成を行おうとする場合には、感光体単位表面積あたりの帯電時間の減少に相関して、帯電部材により感光体表面を帯電すると共に、転写残余のトナーの帯電極性を一様に揃えることが困難となる。これゆえ、現像方法として反転現像を用いた場合、トナーの現像されるべきでない暗部電位上の転写残トナーが、現像電界によってトナー担持体の方に引き寄せられ回収することをも困難となる。さらに、トナー担持体に摺擦の如き機械的力によって回収されたとしても、転写残トナーの帯電が均一に揃えられていないと、トナー担持体上のトナーの帯電性に悪影響を及ぼし、現像特性を低下させる。
【００５９】
感光体の帯電と同時に転写残余のトナーの帯電極性を制御することにより、現像同時クリーニング方式を用いた画像形成方法が成立する。しかし、このように、より高速なプロセススピードの画像形成において、現像同時クリーニング方式を用いた画像形成方法を適用する場合には、転写残トナーの帯電極性制御が困難になり現像での回収不良を起こし易くなり、現像自体も高速化されるため現像工程で回収される転写残トナーの帯電が現像特性により大きく影響し、現像性能の低下を招き易くなるという問題点がある。
【００６０】
さらに、高速なプロセススピードの画像形成において、現像同時クリーニング方式を用いた場合には、帯電部材の汚染による帯電不良も起こしやすくなる。
【００６１】
本発明者らの検討より、現像ローラーのプロセススピードが１２０ｍｍ／ｓｅｃ以上、更には１５０ｍｍ／ｓｅｃ以上のより高速なプロセススピードの画像形成において、現像同時クリーニング方式を用いた画像形成方法においては、現像時の転写残トナーの回収性向上には、帯電極性制御がより迅速に行われなばならず、現像性能の保持には、帯電部材を通過する際、転写残トナーがより確実に且つ均一に帯電極性制御されねばならないことが判明した。
【００６２】
特に、帯電部材と感光体を当接させ帯電を行う、いわゆる接触帯電法においては、その帯電機構としては、所謂パッションの法則にしたがう放電を利用すると、帯電部材が感光体に接触している事および放電エネルギーによるトナー劣化に起因する帯電部材への付着性の悪化も生ずる。
【００６３】
従来行なわれていた現像前クリーニング方式においては、ブレード又は、ファーブラシの如きクリーニング部材により、転写残余のトナーが感光体上からクリーニングされており、感光体上に存在するトナーの帯電、現像装置での回収性及びこのトナーが現像装置内に回収され再利用される際の現像性能への影響を考慮に入れた検討は、従来行われていなかった。
【００６４】
本発明者らは、様々なトナーについて鋭意検討を行い、現像同時クリーニング方式を用いた画像形成方法においては、トナーの帯電部材通過時の帯電制御特性が、これら耐久特性、画像品質特性に密接につながりのあることを見い出し、特にカーボンブラックを含有するトナーにおいては、特定のカーボンブラック及び特定のアゾ系鉄化合物を併用することで、トナーの帯電部材通過時の帯電制御特性が改善されることを見い出し本発明に至った。
【００６５】
本発明の画像形成方法における特徴の一つは、粒径が２５〜８０ｎｍであるカーボンブラックと、特定のアゾ系鉄化合物を併用したトナーを用いることである。
【００６６】
本発明者らは、現像同時クリーニング、クリーナレス画像形成方法に特定のカーボンブラック及び特定のアゾ系鉄化合物を含有するトナーを用いることにより、感光体上の転写残トナーの帯電部材による帯電極性制御及び帯電量制御がより確実に且つ均一になされ、現像工程での転写残トナーのより安定した回収性（クリーニング性）及び現像特性を得ることができることを見出した。
【００６７】
この理由については必ずしも明らかではないが、本発明者らの知見によれば、本発明に用いられる特定のアゾ系鉄化合物が、トナーが異常に高帯電量となる（いわゆるチャージアップ現象）ことを防止する効果で、転写工程でトナー極性と逆電界を印加されても、過剰な逆電界をトナーが保持しにくくしていること、及びアゾ系鉄錯体化合物が分散剤としても機能し、カーボンブラックの分散性が向上した効果で、各トナー粒子ごとの帯電均一性が向上することの組合わせによるものと考えられる。
【００６８】
カーボンブラックの平均一次粒径が２５ｎｍよりも小さいと、本発明で用いるアゾ系鉄化合物と併用した場合、一次粒径が微細なため、十分な分散が得られにくく、本発明の効果を得られない。更に、懸濁重合法にてトナー粒子を製造する場合には、トナー粒度が粗粒化する傾向があり、使いこなすのが困難である。
【００６９】
カーボンブラックの平均一次粒径が、８０ｎｍよりも大きい場合には、良好に分散してもトナーとしての着色力の不足から、低濃度の画像しか得られない、或いはトナー消費量が増大するという不都合が生ずる。
【００７０】
本発明においては、カーボンブラックの平均一次粒径は、２５〜５５ｎｍであることが好ましく、より好ましくは３５〜５５ｎｍであることが良い。本発明の特定のアゾ系鉄化合物と併用した場合、カーボンブラックの粒径がこの範囲にあると、転写残トナーの帯電部材による帯電極性及び帯電量を制御がより確実に且つ均一になされ、トナーの帯電量の安定性及びトナー着色力の面でもより有利である。
【００７１】
本発明におけるトナー中のカーボンブラックの平均一次粒径は、透過型電子顕微鏡で拡大した写真を撮影して測定することができる。
【００７２】
本発明に用いられるカーボンブラックは、ＤＢＰ吸油量が好ましくは４０〜１５０ｍｌ／１００ｇ、より好ましくは５０〜１４０ｍｌ／１００ｇであることが良い。
【００７３】
ＤＢＰ吸油量が４０ｍｌ／１００ｇ未満のストラクチャーの短いカーボンブラックを用いた場合には、トナーの帯電量が低くなりすぎる傾向にあり、ＤＢＰ吸油量が１５０ｍｌ／１００ｇを超えると強固な長ストラクチャーのためカーボンブラックの微細な分散が得られにくい。
【００７４】
カーボンブラックのＤＢＰ吸油量の測定は、「ＡＳＴＭ法Ｄ２４１４−７９」に準拠して行う。
【００７５】
本発明に用いられるカーボンブラックは、窒素吸着による比表面積が１００ｍ²／ｇ以下、好ましくは３０〜９０ｍ²／ｇ、より好ましくは４０〜９０ｍ²／ｇであることが良くさらに、揮発分が２％以下、好ましくは０．１〜１．８％、より好ましくは０．１〜１．７％であることが良い。この本発明に係わるカーボンブラックは、通常トナーに多く用いられているカーボンブラックよりも比表面積が小さく、揮発分も少ない。
【００７６】
比表面積が小さく、かつ揮発分の少ないカーボンブラックは、重合阻害性の官能基が少ないことから、重合阻害性が低い利点があり、トナー中でのカーボンブラックの均一な分散にも有利である。
【００７７】
カーボンブラックの窒素吸着による比表面積が、１００ｍ²／ｇよりも大きくなると重合阻害性を生じ易くなる。カーボンブラックの揮発分が２％を超えると、表面に重合阻害性の官能基が多数存在するため好ましくない。
【００７８】
カーボンブラックの窒素吸着による比表面積の測定は、「ＡＳＴＭ法Ｄ３０３７−７８」に準拠して行う。
【００７９】
カーボンブラックの揮発分の測定は、「ＪＩＳ Ｋ ６２２１−１９８２」に準拠して行う。具体的には、まず測定サンプルとするカーボンブラックを白金るつぼ又はそれと同形、同容量の落としふた付き磁気るつぼに、ふた下２ｍｍを超えない程度まで打振して詰め、その質量を量る。これにふたをして電気炉に入れ、９５０±２５℃で正確に７分間加熱した後取り出し、デシケーター中で室温になるまで放冷して加熱後の質量を量り、次の式によって揮発分を求める。
【００８０】
【外３】

Ｖ：揮発分（％）
Ｗ_D：加熱前の乾燥試料の質量（ｇ）
Ｗ_R：加熱後の乾燥試料の質量（ｇ）
【００８１】
トナーを重合法で製造する場合、本発明に係わるカーボンブラックと前記アゾ系鉄錯体化合物を重合性単量体中に前分散するマスターバッチ工程を行うことが、より高濃度でカーボンブラックを分散できるためせん断力がかかり易くなり、分散性向上の効果が大きくなるため好ましい。
【００８２】
図８は本発明に係わるカーボンブラック及びアゾ系鉄化合物をスチレン単量体中で分散したときの分散液の粘度変化を示す。図からも明らかなように、アゾ系鉄化合物を添加することにより分散液の粘度が飛躍的に増大し、高せん断力でカーボンブラックが安定して分散されることを示している。
【００８３】
図９において、粒径２５〜８０ｎｍのカーボンブラックにおいて、一定量のアゾ系鉄化合物を添加しスチレン単量体中で分散したときのカーボンブラックの吸油量と分散液の粘度の関係を示す。この図から、４０ｍｌ／１００ｇ以上の高吸油量のカーボンブラックの方が分散系の粘度が高く、分散性が良いことが示されている。しかしながら、カーボンブラックの吸油量が１５０ｍｌ／１００ｇを超えると分散液の粘度が高くなりすぎ、重合時の造粒性を損ない易くなる。
【００８４】
本発明者らの検討によると、トナー粒子の重量に対して、前記カーボンブラックの含有量Ａ〔ｗｔ％〕と、前記アゾ系鉄錯体化合物Ｂ〔ｗｔ％〕が、好ましくは下記条件
２≦Ａ／Ｂ≦３５
を満たすことが良く、より好ましくは下記条件
３≦Ａ／Ｂ≦３５
を満たすことが良い。
【００８５】
カーボンブラックの含有量に対してアゾ系鉄化合物の含有量が少なすぎると、図７からも明らかなように粘度が上がらず、カーボンブラックが安定して分散しない。この場合、時間の経過とともにカーボンブラックが沈殿し、この分散液を用いてトナーを製造すると着色力が上がらない。
【００８６】
カーボンブラックの含有量に対してアゾ系鉄化合物の含有量が多すぎると、アゾ系鉄化合物が二次凝集を起こし、分散性が低下するとともに、この二次凝集物が重合阻害を起こし、トナー粒子を良好に製造することが困難となる。
【００８７】
本発明において、トナー粒子のカーボンブラックの含有量は、好ましくは０．１〜３０重量％、より好ましくは１〜２０重量％、さらに好ましくは３〜１５重量％であることが良い。
【００８８】
本発明において、トナー粒子のアゾ系鉄化合物の含有量は、好ましくは０．０１〜２０重量％、より好ましくは０．１〜１０重量％、さらに好ましくは０．１〜３．０重量％であることが良い。
【００８９】
トナー粒子のカーボンブラックの含有量が０．１重量％未満の場合には、トナーとしての着色力が低く、高画像濃度が得られ難い為、他の着色剤を併用する必要性を生じる為、好ましくない。又、３０重量％を超える場合には、本発明で用いるアゾ系鉄化合物を使用しても、カーボンブラックの分散性が充分に均一にならず、カブリやトナー飛散が生じ易くなる。トナー粒子のアゾ系鉄化合物の含有量が０．０１重量％未満の場合には、分散液粘度が高がり易く、カーボンブラックの分散性向上効果が充分に発揮されず、２０重量％を超える場合には、逆に分散液粘度が低下してしまい、カーボンブラックの分散性向上効果が低下してしまう。
【００９０】
上述したように、本発明者らは、特定の吸油量範囲で適正なストラクチャーを有し、比表面積が小さく、揮発分も少ないカーボンブラックを特定のアゾ系鉄錯体化合物と併用することで、転写トナーの帯電部材通過時の帯電制御特性が、より改善されるトナーを得ることを見い出した。
【００９１】
このようにして得られたトナーを適用することで、より高速なプロセススピードの現像同時クリーニング方式においては、感光体帯電部材を通過する際、トナーがより確実に且つ均一に帯電極性制御されることで、現像での安定した回収性を示し、転写残トナーとして現像で回収された後現像にその一部が再利用される際にも、現像特性に悪影響を及ぼすことなく、高品質な画像を安定して実現することができる。
【００９２】
本発明で使用するアゾ系鉄化合物は、下記式（１）で示す構造を有している。
【００９３】
【外４】

〔式中、Ｘ₁ およびＸ₂ は水素原子、低級アルキル基、低級アルコキシ基、ニトロ基及びハロゲン原子からなるグループから選択されるメンバーを示し、Ｘ₁ とＸ₂ は同じ又は異なっており、ｍおよびｍ′は１〜３の整数を示し、Ｒ₁ およびＲ₃ は水素原子、Ｃ₁ 〜Ｃ₁₈のアルキル基、Ｃ₂ 〜Ｃ₁₈のアルケニル基、スルホンアミド基、メシル基、スルホン酸基、カルボキシエステル基、ヒドロキシ基、Ｃ₁ 〜Ｃ₁₈のアルコキシ基、アセチルアミノ基、ベンゾイルアミノ基及びハロゲン原子からなるグループから選択されるメンバーを示し、Ｒ₁ とＲ₃ は同じ又は異なっており、ｎおよびｎ′は１〜３の整数を示し、Ｒ₂ およびＲ₄ は水素原子またはニロト基を示し、Ａ⁺ は、アンモニウムイオン、水素イオン、ナトリウムイオン、カリウムイオン及びそれらの混合イオンからなるグループから選択されるカチオンイオンを示す。〕
【００９４】
尚、本発明において、「低級」とは、炭素数１〜６を意味する。
【００９５】
前記一般式のアゾ系鉄錯体化合物の代表的な具体例としては、次のような化合物が挙げられる。
【００９６】
【外５】

【００９７】
【外６】

【００９８】
上記アゾ系鉄錯体化合物は負荷電制御剤としても用いられる。該化合物は公知の方法により合成できる。
【００９９】
本発明において、トナーの形状は、多数枚の画出しにおけるトナー担持体上のトナー融着や帯電部材表面の汚染を改善する観点から、球形に近い形状であることが好ましい。トナーの形状を示す形状係数ＳＦ−１及びＳＦ−２は好ましくはＳＦ−１の値が１００＜ＳＦ−１≦１６０であり、かつＳＦ−２の値が１００＜ＳＦ−２≦１４０が良く、さらに好ましくはＳＦ−１の値が１００＜ＳＦ−１≦１４０であり、かつＳＦ−２の値が１００＜ＳＦ−２≦１２０であることが、現像性を維持しながら転写性を向上させるために好ましい。
【０１００】
本発明において、形状係数を示すＳＦ−１及びＳＦ−２は、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、その画像情報は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（Ｌｕｚｅｘ ＩＩＩ）に導入し解析を行い下式より算出し得られた値を形状係数ＳＦ−１、ＳＦ−２と定義する。
【０１０１】
【外７】

（式中、ＭＸＬＮＧは粒子の絶対最大長、ＰＥＲＩは粒子の周囲長、ＡＲＥＡは粒子の投影面積を示す。）
形状係数ＳＦ−１はトナー粒子の丸さの度合いを示し、形状係数ＳＦ−２はトナー粒子の凹凸の度合いを示している。
【０１０２】
トナーの形状係数ＳＦ−１が１６０を超えると、球形から離れて不定形に近づき、現像器内でトナーが破砕され易く、粒度分布が変動したり、帯電量分布がブロードになりやすく地カブリや反転カブリが生じやすい。トナー形状係数ＳＦ−２が１４０を超えると、感光体から転写材への転写時におけるトナー像の転写効率の低下、及び文字やライン画像の転写中抜けを招き好ましくない。
【０１０３】
更に高画質化のため微小な潜像ドットを忠実に現像するために、トナー粒子は、重量平均径が３μｍ〜９μｍ、好ましくは、４μｍ〜８μｍであり、個数分布における変動係数が３５％以下、好ましくは２５％以下であることが良い。重量平均径が３μｍ未満のトナー粒子においては、転写効率の低下から感光体や中間転写体上に転写残のトナー粒子が多く、さらに、カブリ、転写不良に基づく画像の不均一ムラの原因となりやすい。トナー粒子の重量平均径が９μｍを超える場合には、感光体表面、中間転写材等の部材への融着が起きやすい。トナー粒子の個数分布における変動係数が３５％を超えると更にその傾向が強まる。
【０１０４】
トナー粒子の個数分布における変動係数Ａは下記式から算出される。
【０１０５】
変動係数＝〔Ｓ／Ｄ₁ 〕×１００
〔式中、Ｓは、トナー粒子の個数分布における標準偏差値を示し、Ｄ₁ は、トナー粒子の個数平均粒径（μｍ）を示す。〕
【０１０６】
トナー粒子の平均粒径及び粒度分布はコールターカウンターＴＡ−ＩＩ型あるいはコールターマルチサイザー（コールター社製）等を用い、個数分布、体積分布を出力するインターフェイス（日科機製）及びＰＣ９８０１パーソナルコンピュータ（ＮＥＣ製）を接続し、電解液は１級塩化ナトリウムを用いて１％ＮａＣｌ水溶液を調製する。たとえば、ＩＳＯＴＯＮ Ｒ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。測定法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として界面活性剤（好ましくはアルキルベンゼンスルフォン酸塩）を０．１〜５ｍｌ加え、更に測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は超音波分散器で約１〜３分間分散処理を行ない前記コールターカウンターＴＡ−ＩＩ型によりアパーチャーとして１００μｍアパーチャーを用いて、２μｍ以上のトナーの体積、個数を測定して体積分布と個数分布とを算出した。それから、本発明に係わる体積分布から求めた体積基準の重量平均粒径（Ｄ４）、個数分布から求めた個数基準の個数平均粒径（Ｄ１）を求めた。
【０１０７】
本発明において、トナーの定着性及び耐オフセット性を向上させるために、離型剤をトナー粒子に添加することが好ましい。
【０１０８】
本発明に用いられる離型剤としては、ＡＳＴＭ Ｄ３４１８−８に準拠し測定されたＤＳＣ曲線における主体吸熱極大ピーク（融点）が、３０〜１２０℃、より好ましくは４０〜９０℃の範囲にある化合物が好ましい。ワックスの極大ピーク値（融点）が３０℃未満であると離型剤の自己凝集力が弱くなり、結果として耐高温オフセット性が弱くなり好ましくない。ワックスの極大ピーク値（融点）が１２０℃を超えると定着温度が高くなり、定着画像表面を適度に平滑化させることが困難となり混色性低下の点から好ましくない。
【０１０９】
更に重合方法によりトナー粒子を得る場合においては、水系媒体中で造粒・重合を行うため、吸熱極大ピーク値（融点）が高いと主に造粒中に離型剤が析出してくるので好ましくない。
【０１１０】
離型剤の極大ピーク値の温度（融点）の測定には、例えばパーキンエルマー社製ＤＳＣ−７を用いる。装置検出部の温度補正はインジウムと亜鉛の融点を用い、熱量の補正についてはインジウムの融解熱を用いる。サンプルはアルミニウム製パンを用い対照用に空パンをセットし、温度２０℃から１８０℃まで昇温速度１０℃／ｍｉｎで測定を行う。
【０１１１】
離型剤としては、パラフィンワックス，ポリオレフィンワックス，フィッシャートロピッシュワックスの如きポリメチレンワックス，アミドワックス，高級脂肪酸，高級脂肪酸金属塩、長鎖アルキルアルコール，エステルワックス及びこれらの誘導体（例えばこれらのグラフト化合物又はブロック化合物）が挙げられる。特に、エステルワックスは、トナー画像の加熱定着時にスチレン−アクリル共重合体の如きトナーの結着樹脂の可塑剤として作用することから、定着性を高めることができる点でより好ましい。
【０１１２】
本発明においては、トナーにコア／シェル構造をもたせ、シェル部分を重合により合成された重合体によって形成され、コア部分を離型剤としてのワックスで構成するようなトナーを本発明の画像形成方法に用いることにより、トナー粒子の劣化や画像形成装置への汚染を防止することが出来るので良好な帯電性が維持され、ドット潜像の再現に優れたトナー画像を長期にわたって形成し得ることが可能となる。また、加熱加圧定着時にはワックスが効率良く作用する為、低温定着性と耐高温オフセット性とを向上させることができるから好ましい。
【０１１３】
本発明において、コア／シェル構造を有するトナーとは、離型剤としてのワックスによるコア部の表面を重合性単量体の重合によって合成された重合体によって形成されるシェル部が被覆している形態のトナーを意味する。
【０１１４】
本発明において、トナーのコア／シェル構造は、トナー粒子の断層面観察により確認することが出来る。
【０１１５】
トナー粒子の断層面を観察する具体的方法としては、常温硬化性のエポキシ樹脂中にトナー粒子を十分分散させた後、４０℃の雰囲気中で２日間硬化させ、得られた硬化物を四三酸化ルテニウム、必要により四三酸化オスミウムを併用し染色を施した後、ダイヤモンド歯を備えたミクロトームを用い薄片状のサンプルを切り出し、透過電子顕微鏡（ＴＥＭ）を用いトナー粒子の断層形態を観察する。ワックスと外殻を構成する樹脂との若干の結晶化度の違いを利用して材料間のコントラストを付けるため四三酸化ルテニウム染色法を用いることが好ましい。代表的な一例を図１０に示す。
【０１１６】
本発明において、離型剤のトナー粒子における含有量は、好ましくは、２〜３０重量％、より好ましくは、２〜２５重量％であることが好ましい。離型剤の含有量が２重量％未満では定着性の改善が不十分であり、３０重量％を超える場合は、重合法による製造においても造粒時にトナー粒子同士の合一が起きやすく、粒度分布の広いものが生成しやすく、本発明には不適当であった。
【０１１７】
本発明においては、コア／シェル構造を有するトナーを製造する場合、シェル部が離型剤としてのワックスによるコア部を内包化せしめたるためシェル部を構成する更に極性樹脂を添加せしめることが特に好ましい。
【０１１８】
本発明に用いられる極性樹脂としては、スチレンと（メタ）アクリル酸の共重合体，マレイン酸共重合体，飽和ポリエステル樹脂，エポキシ樹脂が好ましく用いられる。
【０１１９】
トナー粒子中極性樹脂の含有量は、好ましくは、１〜２０重量％、より好ましくは２〜１６重量％（トナー粒子の重量基準）であることが良い。
【０１２０】
極性樹脂の含有量が１重量％未満の場合は、添加効果が十分に発現されず、又、２０重量％を超える場合には、トナーの帯電特性に影響を及ぼすことが多く、特に高温高湿環境下でのトナーの帯電性の低下を招き易く、好ましくない。
【０１２１】
本発明においては、トナーの表面にさらに最外殻樹脂層を設けても良い。
【０１２２】
該最外殻樹脂層のガラス転移温度は、耐ブロッキング性のさらなる向上のため外殻樹脂層のガラス転移温度以上に設計されること、さらに定着性を損なわない程度に架橋されていることが好ましい。この最外殻樹脂層には帯電性向上のため極性樹脂や荷電制御剤が含有されていることが好ましい。
【０１２３】
該最外殻層を設ける方法としては、特に限定されるものではないが例えば以下のような方法が挙げられる。
【０１２４】
１．重合反応後半、または終了後、反応系中に必要に応じて、極性樹脂、荷電制御剤、架橋剤を溶解、分散したモノマーを添加し重合粒子に吸着させ、重合開始剤を添加し重合を行う方法。
【０１２５】
２．必要に応じて、極性樹脂、荷電制御剤、架橋剤を含有したモノマーからなる乳化重合粒子またはソープフリー重合粒子を反応系中に添加し、重合粒子表面に凝集、必要に応じて熱により固着させる方法。
【０１２６】
３．必要に応じて、極性樹脂、荷電制御剤、架橋剤を含有したモノマーからなる乳化重合粒子またはソープフリー重合粒子を乾式で機械的にトナー粒子表面に固着させる方法。
【０１２７】
本発明において、着色剤及び重合性単量体と共に離型剤としてのワックス及び極性樹脂を含有する単量体組成物を水系媒体中で重合することによりトナー粒子を製造する重合法によって、ワックス及び極性樹脂を含有するトナー粒子を製造する場合には、製造されたトナー粒子はワックスによるコア部と、重合性単量体の重合により合成された重合体及び極性樹脂によって構成されるシェル部とを有するコア／シェル構造を有し、さらにシェル部の最外殻樹脂層に極性樹脂が位置する形態となる。したがって、このような形態のトナー粒子の場合には、着色剤として用いるカーボンブラックの表面には、極性基が存在しているため、カーボンブラックは、非極性のワックス中には入り込まず、シェル部に位置することになり、トナー粒子中に均一にカーボンブラックが分散している形態のトナー粒子に比べて着色力が低下し易い傾向にあり、また、シェル部の最外殻層には極性樹脂が位置するため、トナー粒子の表面部に位置するカーボンブラックの割合が少なくなることから、樹脂樹脂を含有しないトナー粒子に比べて、トナーの摩擦帯電性が低い傾向にある。
【０１２８】
しかしながら、本発明においては、トナー粒子は、上述の如く、カーボンブラック及び特定のアゾ系鉄化合物を含有していることから、アゾ系鉄化合物によるカーボンブラックの分散性向上効果によりトナーの着色力の低下を抑制し、かつカーボンブラックの分散性向上効果とアゾ系鉄化合物の高い荷電制御効果によりトナーの摩擦帯電性の低下を抑制することが可能である。
【０１２９】
本発明において、一成分接触現像方式の画像形成方法においては、現像時にトナー担持体上のトナーが像担持体の表面に接触することから、トナーの耐久性やトナー担持体の表面及び像担持体の表面に対するトナーの耐融着性を有していることが好ましい。
【０１３０】
従って、一成分非接触現像方式やトナー及びキャリアを有する二成分現像方式に用いるトナーに比べて、一成分接触現像方式に用いるトナーは、より高い機械的特性を有することが要求される。
【０１３１】
本発明に用いられるトナー粒子の樹脂成分は、ＴＨＦ（テトラヒドロフラン）と不溶なＣ成分及びＴＨＦに可溶な成分を有しており、ＴＨＦに可溶な成分は、ゲルパーミエーションクロマトグラム（ＧＰＣ）で測定される分子量分布において、分子量１００万未満のＡ成分及び分子量１００万以上のＢ成分を有しており、これらＡ成分、Ｂ成分及びＣ成分が下記条件を満たしていることが好ましい。
【０１３２】
本発明に係るトナー粒子の樹脂成分のＴＨＦに可溶な成分（上記Ａ成分とＢ成分に相当）は、ＧＰＣの分子量分布において数平均分子量（Ｍｎ）が好ましくは９０００〜１００００００、より好ましくは、１００００〜５０００００であり、重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）の比（Ｍｗ／Ｍｎ）が好ましくは５〜５００、より好ましくは７〜４００であることがトナーに求められる諸特性をバランス良く達成する事が出来る。
【０１３３】
これらトナー粒子の樹脂成分は、樹脂成分の重量基準で（１）Ａ成分の含有量（Ｗ_A）が好ましくは３０〜９５重量％、より好ましくは５０〜９０重量％であり、（２）Ｂ成分の含有量（Ｗ_B）が好ましくは０〜２０重量％、より好ましくは、１〜２０重量％であり、（３）、Ｃ成分の含有量（Ｗ_C）が好ましくは０〜７０重量％、より好ましくは１〜７０重量％であり、（４）Ｂ成分とＣ成分の総含有量（Ｗ_B＋Ｗ_C）が好ましくは、５〜７０重量％、より好ましくは１０〜５０重量％であることが本発明の画像形成方法に好ましく用いることが出来る。
【０１３４】
本発明に用いられるトナー粒子の樹脂成分は、ＴＨＦに可溶な成分のＧＰＣの分子量分布において、前述のＡ成分（分子量１００万未満のＴＨＦ可溶分）が分子量３０００〜５万、より好ましくは分子量５０００〜２２０００の領域にメインピークを有することにより画像形成装置とのマッチングが良好なものとなり好適である。メインピークが分子量３０００未満の場合、トナーの帯電特性の悪化や画像形成装置との接触部分に融着を生じたり、耐高温オフセット性や耐ブロッキング性の低下を招き易い。メインピークが分子量５万を越える場合、画像形成装置との接触部分に傷を生じたり、低温定着性の著しい低下を招き易い。
【０１３５】
Ａ成分の含有量（Ｗ_A）が３０重量％未満の場合には、低温定着性が低下する傾向にあり、９５重量％を超える場合には、画像形成装置とのマッチング性が悪化し、トナー融着や画質の劣化が生じ易い。
【０１３６】
Ｂ成分の含有量（Ｗ_B）が２０重量％を越えると耐高温オフセット性は向上するものの、低温定着性が低下するので好ましくない。
【０１３７】
Ｃ成分の含有量（Ｗ_C）が７０重量％より多いと、画像形成装置とのマッチングに障害を生じたり、低温定着が困難となり好ましくない。尚、Ｃ成分が全く無くてもＢ成分が好ましくは５〜２０重量％、より好ましくは１０〜２０重量％含有していれば現像性や定着性を維持することが可能である。逆に、Ｂ成分が全く無くてもＣ成分が好ましくは、５〜７０重量％、より好ましくは１０〜７０重量％含有していれば、現像性や定着性を維持することが可能である。
【０１３８】
更に、Ｂ成分と、Ｃ成分との総含有量（Ｗ_B＋Ｗ_C）が好ましくは、５〜７０重量％、より好ましくは１０〜５０重量％であることが良い。Ｂ成分と、Ｃ成分との総含有量（Ｗ_B＋Ｗ_C）が５重量％未満の場合、トナーの帯電特性や耐高温オフセット性、更には画像形成装置とのマッチングが悪化し、トナーの融着や画質の劣化を招き易く、７０重量％を越える場合には、低温定着性が低下する為、好ましくない。
【０１３９】
尚、本発明においてトナー粒子中の各樹脂成分（Ａ〜Ｃ成分）の分子量や含有量（Ｗ_A、Ｗ_B及びＷ_C）は以下の方法により測定、算出される。
【０１４０】
本発明においてＴＨＦに不溶なＣ成分とは、トナー粒子中の樹脂成分のＴＨＦ（テトラヒドロフラン）に対して不溶性となった樹脂成分を示し、その含有量は架橋成分を含む樹脂組成物の架橋の程度を示す目安となるが、ＴＨＦ不溶分が０重量％であっても必ずしも架橋していないという訳ではない。ＴＨＦに不溶なＣ成分の含有量とは、以下のように測定された値をもって定義する。
【０１４１】
まず、予め公知の方法で顔料等のトナー粒子中の添加剤の含有率などを測定しておく。次に、現像剤０．５〜１．０ｇの一定量を秤量し（Ｗ₁ ｇ）、円筒濾紙（東洋濾紙製Ｎｏ．８６Ｒ）に入れてソックスレー抽出器にかけ、溶媒としてＴＨＦ１００〜２００ｍｌを用いて２０時間抽出し、溶媒によって抽出された可溶成分をエバポレートした後、１００℃数時間真空乾燥し、ＴＨＦ可溶樹脂成分量を秤量する（Ｗ₂ ｇ）。そして、該現像剤一定量中に含まれている顔料等の添加剤のうち、ＴＨＦに可溶な成分の重量をＷ₃ ｇ、ＴＨＦに不溶な成分の重量をＷ₄ ｇすると、以下の式に従って樹脂成分中のＴＨＦ不溶分（前記Ｃ成分）が算出される。
【０１４２】
【外８】

【０１４３】
一方、ＴＨＦに可溶な成分のＧＰＣの分子量分布における分子量１００万未満のＡ成分のメインピーク位置と含有量（Ｗ_A）及び１００万以上のＢ成分の含有量（Ｗ_B）（樹脂成分の重量基準）は、前述のソックスレー抽出の際に得られたＴＨＦ可溶樹脂成分をＧＰＣの測定サンプルとして用い、得られた分子量分布から求める。
【０１４４】
尚、分子量１００万未満の領域（Ａ成分）及び分子量１００万以上の領域（Ｂ成分）の面積％は重量％と等しいと仮定した上で、樹脂成分の重量基準に換算し、Ａ成分及びＢ成分の重量％（Ｗ_A及びＷ_B）を求める。
【０１４５】
尚、本発明において、樹脂成分には、結着樹脂に加え、ワックス成分を含むものである。
【０１４６】
本発明において、トナー粒子中の樹脂成分の分子量分布はＧＰＣ（ゲルパミエーションクロマトグラフィ）により次の条件で測定される。尚、試料は予め溶媒に分散／溶解させた後、耐溶剤性メンブランフィルター（ポア径：０．３μｍ）で濾過したものを用いる。
【０１４７】
装置：ＧＰＣ−１５０Ｃ（ウォーターズ社製）
カラム：ＫＦ８０１〜７（ショウデックス社製）の７連
温度：４０℃
溶媒：ＴＨＦ
流速：１．０ｍｌ／ｍｉｎ
試料：濃度０．０５〜０．６重量％の試料を０．１ｍｌ注入
【０１４８】
以上の条件で測定し、試料の分子量算出にあたっては単分散ポリスチレン標準試料により作成した分子量校正曲線を使用する。
【０１４９】
本発明に用いられるトナーの結着樹脂としては、一般的に用いられているスチレン−（メタ）アクリル共重合体，ポリエステル樹脂，エポキシ樹脂，スチレン−ブタジエン共重合体を利用することが出来る。重合法によってトナー粒子を得る方法においては、それらの単量体が好ましく用いられる。具体的には、スチレン，ｏ−（ｍ−、ｐ−）−メチルスチレン，ｍ−（ｐ−）−エチルスチレンの如きスチレン系単量体；（メタ）アクリル酸メチル，（メタ）アクリル酸エチル，（メタ）アクリル酸プロピル，（メタ）アクリル酸ブチル，（メタ）アクリル酸オクチル，（メタ）アクリル酸ドデシル，（メタ）アクリル酸ステアリル，（メタ）アクリル酸ベヘニル，（メタ）アクリル酸２−エチルヘキシル，（メタ）アクリル酸ジメチルアミノエチル，（メタ）アクリル酸ジエチルアミノエチルの如き（メタ）アクリル酸エステル系単量体；ブタジエン，イソプレン，シクロヘキセン，（メタ）アクリロニトリル，アクリル酸アミドの如きエン系単量体が好ましく用いられる。これらの単量体は、ポリマーハンドブック第２版−Ｐ１３９〜１９２（ＪｏｈｎＷｉｌｅｙ＆Ｓｏｎｓ社製）に記載の理論ガラス転移温度（Ｔｇ）が、４０〜７５℃を示すように単量体を単独で又は適宜混合し用いられる。理論ガラス転移温度が４０℃未満の場合には、トナーの保存安定性や現像剤の耐久安定性の面から問題が生じ、７５℃を超える場合は定着点の上昇をもたらす。
【０１５０】
さらに、本発明においては、上記のＴＨＦ不溶分を生成させるために及び／又は分子量１００００００以上の成分を生成させるために結着樹脂の合成時に架橋剤を用いることが好ましい。
【０１５１】
本発明のトナーに用いられる架橋剤としては、２官能の架橋剤として、ジビニルベンゼン、ビス（４−アクリロキシポリエトキシフェニル）プロパン、エチレングリコールジアクリレート、１，３−ブチレングリコールジアクリレート、１，４−ブタンジオールジアクリレート、１，５−ペンタンジオールジアクリレート、１，６−ヘキサンジオールジアクリレート、ネオペンチルグリコールジアクリレート、ジエチレングリコールジアクリレート、トリエチレングリコールジアクリレート、テトラエチレングリコールジアクリレート、ポリエチレングリコール＃２００、＃４００、＃６００の各ジアクリレート、ジプロピレングリコールジアクリレート、ポリプピレングリコールジアクリレート、ポリエステル型ジアクリレート（ＭＡＮＤＡ日本化薬）及び上記のジアクリレートをメタクリレートにかえたものが挙げられる。
【０１５２】
多官能の架橋剤としてペンタエリスリトールトリアクリレート、トリメチロールエタントリアクリレート、トリメチロールプロパントリアクリレート、テトラメチロールメタンテトラアクリレート、オリゴエステルアクリレート及びそのメタクリレート、２，２−ビス（４−メタクリロキシ、ポリエトキシフェニル）プロパン、ジアリルフタレート、トリアリルシアヌレート、トリアリルイソシアヌレート及びトリアリルトリメリテートが挙げられる。
【０１５３】
これらの架橋剤は、他のビニル系単量体１００重量部に対して、好ましくは０．０５〜１０重量部、より好ましくは０．１〜５重量部であることが良い。
【０１５４】
架橋剤の使用量が０．０５重量部未満の場合には、結着樹脂の架橋反応が充分に行なわれず、１０重量部を超える場合には、結着樹脂の架橋反応が進行しすぎてしまい、いずれもトナー粒子のＴＨＦ不溶分の含有量を５〜７０重量％の範囲内にコントロールすることが困難となる。
【０１５５】
本発明に用いられるアゾ系鉄錯体化合物は、荷電制御剤としての機能も有しているが、更に別の荷電制御剤を併用してもよい。別の荷電制御剤としては、公知のものが利用できるが、帯電スピードが速く且つ一定の帯電量を安定して維持できる荷電制御剤が好ましい。更に本発明において重合方法でトナー粒子を製造する場合には、重合阻害性が無く水系への可溶化物の無い荷電制御剤が特に好ましい。
【０１５６】
別の荷電制御剤の具体的化合物としては、ネガ系としてサリチル酸、ナフトエ酸、ダイカルボン酸またはその誘導体の金属化合物、アゾ顔料またはその誘導体の金属化合物、スルホン酸、カルボン酸を側鎖に持つ高分子型化合物、ホウ素化合物、尿素化合物、ケイ素化合物、カリークスアレーンが利用できる。ポジ系としてニグロシン、トリフェニルメタン系化合物、四級アンモニウム塩、該四級アンモニウム塩を側鎖に有する高分子型化合物、グアニジン化合物、イミダゾール化合物が好ましく用いられる。
【０１５７】
別の荷電制御剤は結着樹脂１００重量部に対し好ましくは０．２〜１０重量部、より好ましくは０．５〜５重量部トナー粒子中に含有することが良い。しかしながら、本発明において別の荷電制御剤の添加は必須ではなく、非磁性一成分ブレードコーティング現像方法を用いた場合においてもブレード部材やスリーブ部材との摩擦帯電を積極的に利用することでトナー中に必ずしも別の荷電制御剤を含む必要はない。
【０１５８】
本発明で重合方法でトナー粒子を製造する場合には、重合開始剤として、例えば、２，２′−アゾビス−（２，４−ジメチルバレロニトリル）、２，２′−アゾビスイソブチロニトリル、１，１′−アゾビス（シクロヘキサン−１−カルボニトリル）、２，２′−アゾビス−４−メトキシ−２，４−ジメチルバレロニトリル、アゾビスイソブチロニトリルの如きアゾ系重合開始剤；ベンゾイルペルオキシド、メチルエチルケトンペルオキシド、ジイソプロピルペルオキシカーボネート、クメンヒドロペルオキシド、２，４−ジクロロベンゾイルペルオキシド、ラウロイルペルオキシドの如き過酸化物系重合開始剤が用いられる。
【０１５９】
該重合開始剤の添加量は、目的とする重合度により変化するが一般的には単量体に対し０．５〜２０重量％添加され用いられる。開始剤の種類は、重合方法により若干異なるが、十時間半減期温度を参考に、単独又は混合し利用される。
【０１６０】
重合度を制御するための公知の架橋剤・連鎖移動剤・重合禁止剤を更に添加し用いることも可能である。
【０１６１】
本発明に係るトナー製造方法として懸濁重合を利用する場合には、用いる分散剤として例えば無機系酸化物として、リン酸三カルシウム，リン酸マグネシウム，リン酸アルミニウム，リン酸亜鉛，炭酸カルシウム，炭酸マグネシウム，水酸化カルシウム，水酸化マグネシウム，水酸化アルミニウム，メタケイ酸カルシウム，硫酸カルシウム，硫酸バリウム，ベントナイト，シリカ，アルミナ，磁性体，フェライトが挙げられる。有機系化合物としては例えばポリビニルアルコール，ゼラチン，メチルセルロース，メチルヒドロキシプロピルセルロース，エチルセルロース，カルボキシメチルセルロースのナトリウム塩，デンプンが水相に分散させて使用される。これら分散剤は、重合性単量体１００重量部に対して０．２〜１０．０重量部使用することが好ましい。
【０１６２】
これらの分散剤は、市販のものをそのまま用いても良いが、細かい均一な粒度を有す分散粒子を得るために、分散媒中にて高速撹拌下にて該無機化合物を生成させて用いることも出来る。例えば、リン酸三カルシウムの場合、高速撹拌下において、リン酸ナトリウム水溶液と塩化カルシウム水溶液を混合することで懸濁重合方法に好ましい分散剤を得ることが出来る。これら分散剤の微細化のため０．００１〜０．１重量部の界面活性剤を併用しても良い。具体的には市販のノニオン，アニオン，カチオン型の界面活性剤が利用でき、例えばドデシル硫酸ナトリウム，テトラデシル硫酸ナトリウム，ペンタデシル硫酸ナトリウム，オクチル硫酸ナトリウム，オレイン酸ナトリウム，ラウリル酸ナトリウム，ステアリン酸カリウム，オレイン酸カルシウムが好ましく用いられる。
【０１６３】
本発明に係るトナー製造方法に重合方法を用いる場合におていは、以下の如き製造方法によって具体的にトナーを製造することが可能である。
【０１６４】
重合性単量体中にカーボンブラック及びアゾ系鉄化合物、さらに必要に応じて荷電制御剤，重合開始剤，その他の添加剤を加え、ホモジナイザー又は超音波分散機の如き混合装置によって均一に溶解又は分散せしめて重合性単量体組成物を調製する。この調製された重合性単量体組成物を、分散安定剤を含有する水相中に通常の撹拌機またはホモミキサー又はホモジナイザーの如き混合装置により分散せしめる。好ましくは重合性単量体組成物からなる液滴が所望のトナー粒子のサイズを有するように撹拌速度・時間を調製し、造粒する。その後は分散安定剤の作用により、粒子状態が維持され、且つ粒子の沈降が防止される程度の撹拌を行えば良い。重合温度は４０℃以上、一般的には５０〜９０℃の温度に設定して重合を行う。重合反応後半に昇温しても良く、更に、本発明のトナーを用いた画像形成方法における耐久性向上の目的で、未反応の重合性単量体，副生成物を除去するために重合反応後半、又は、重合反応終了後に一部水系媒体を留去しても良い。重合反応終了後、生成したトナー粒子を洗浄し、ろ過により回収し、乾燥する。懸濁重合法においては、通常単量体系１００重量部に対して水３００〜３０００重量部を分散媒として使用するのが好ましい。
【０１６５】
本発明においては、前述した通り、トナー粒子中でのカーボンブラックの分散性を向上させるために、マスターバッチ工程を経て重合性単量体組成物を調製する。
【０１６６】
具体的には、第１の重合性単量体１００重量部に対して、好ましくは４〜４０重量部、より好ましくは５〜２５重量部のカーボンブラック及び好ましくは０．２〜５重量部、より好ましくは０．５〜３重量部のアゾ系鉄化合物を混合して分散させることにより、重合性単量体に対してカーボンブラックを非常に高濃度にして混合できるため、分散液の粘度が高まり、混合時のシェアが充分にかかることから、アゾ系鉄化合物による分散効果との組合わせで、カーボンブラックの分散性を飛躍的に向上させることができる。
【０１６７】
カーボンブラックの混合量が４重量部未満の場合には、アゾ系鉄化合物を使用したとしても分散液の粘度が小さく、十分な分散は達成しにくい。一方、４０重量部を超える場合には、分散液の粘度をコントロールしずらくなり、結果として分散が不均一になりやすい。
【０１６８】
アゾ系鉄化合物の混合量が０．２重量部未満の場合には、分散液の粘度を高める効果が不十分であり、一方、５重量部を超える場合には、逆にまた粘度が低下してしまい分散が不均一になりやすい。
【０１６９】
この第１の重合性単量体、カーボンブラック及びアゾ系鉄化合物、必要に応じてワックス成分及び／又は荷電制御剤を含有する（マスターバッチ）分散液の粘度は、好ましくは１００〜２０００センチポイズ、より好ましくは１５０〜１６００センチポイズであることが良い。
【０１７０】
この分散液の粘度が１００センチポイズ未満の場合には、粘度が低すぎ分散のシェアがかからず、カーボンブラックの均一分散が難しくなる。一方、２０００センチポイズを超える場合には、粘度が高すぎ、均一な分散状態が維持しにくくなると同時に、製造装置からの排出性が悪化し、生産性の低下を招く。
【０１７１】
この分散液を第２の重合性単量体及びさらに必要に応じてワックス成分、極性官能基を含む高分子重合体、荷電制御剤、重合開始剤及びその他の添加剤と混合して重合性単量体組成物を調製する。
【０１７２】
この分散液１００重量部に対する第２の重合性単量体の混合量は、好ましくは２０〜１００重量部、より好ましくは３０〜７０重量部であることが、マスターバッチ成分の第２の重合性単量体への均一分散性の点で良い。
【０１７３】
この第２の重合性単量体の混合量が２０重量部未満の場合には、均一に分散するまでに時間を要し、１００重量部を超える場合には、カーボンブラックの再凝集等が生じやすくなり、やはり均一分散に時間がかかってしまう。
【０１７４】
この重合性単量体組成物中での重合性単量体組成物の重量に対するカーボンブラックの含有割合は、好ましくは１〜２０重量％、より好ましくは３〜１５重量％であることがトナーの着色力及びトナーの帯電安定化の点で良い。
【０１７５】
重合性単量体組成物中でのカーボンブラックの含有割合が、１重量％未満の場合には、高画像濃度を達成するのが難しくなり、２０重量％を超える場合には、特に高湿下でのトナーの帯電が低くなりやすい。
【０１７６】
この重合性単量体組成物中での重合性単量体組成物の重量に対するアゾ系鉄化合物の含有割合は、好ましくは０．１〜３．０重量％、より好ましくは０．２〜２．０重量％であることが分散液粘度を適正状態に維持して、カーボンブラックの均一分散性を向上させる点で良い。
【０１７７】
重合性単量体組成物中でのアゾ系鉄化合物の含有割合が０．１重量％未満の場合には、分散液粘度が上がらずに、カーボンブラックの分散性向上効果が発揮されず、３．０重量％を超える場合には、逆に分散液粘度が低下してしまい、やはりカーボンブラックの分散性向上効果が消失してしまう。
【０１７８】
本発明においては、トナー粒子表面を外添剤により被覆することにより、トナー粒子に適度な流動性と帯電性を付与すると共に、クリーニング性の向上や感光体帯電部材等の接触部材からのストレスを緩和出来る構成をとることが望ましく、トナー表面の外添剤被覆率が、好ましくは５〜９９％、さらに好ましくは１０〜９９％であることが良い。さらにトナー粒子表面に外添剤として無機微粉体を有することで、転写効率の向上及び文字やライン画像の転写中抜けが改善される。
【０１７９】
トナー粒子表面の外添剤被覆率は、日立製作所製ＦＥ−ＳＥＭ（Ｓ−８００）を用いトナー像を１００個無作為にサンプリングし、その画像情報はインターフェースを介してニコレ社製画像解析装置（Ｌｕｚｅｘ３）に導入し解析を行い算出した。
【０１８０】
本発明に使用される外添剤としては、トナーに添加した時の耐久性の点から、トナー粒子の重量平均径の１／１０以下の平均粒径であることが好ましい。この添加剤の平均粒径とは、電子顕微鏡におけるトナー粒子の表面観察により求めたその平均粒径を意味する。
【０１８１】
外添剤としては、たとえば、金属酸化物（酸化アルミニウム，酸化チタン，チタン酸ストロンチウム，酸化セリウム，酸化マグネシウム，酸化クロム，酸化錫及び酸化亜鉛）、窒化物（窒化ケイ素）、炭化物（炭化ケイ素）、金属塩（硫酸カルシウム，硫酸バリウム及び炭酸カルシウム）、脂肪酸金属塩（ステアリン酸亜鉛及びステアリン酸カルシウム）、カーボンブラック及びシリカが挙げられる。
【０１８２】
これら外添剤は、トナー粒子１００重量部に対し、好ましくは０．０１〜１０重量部用いられ、より好ましくは０．０５〜５重量部用いられる。これら外添剤は、単独で用いても、また、複数併用しても良い。疎水化処理を行ったものが、より好ましい。
【０１８３】
本発明に用いられる無機微粉体としては、特に帯電安定性、現像性、流動性、保存性向上の為、少なくとも１種はシリカ、アルミナ、チタニア、あるいはその複酸化物の中から選ばれる微粒子であることが好ましい。さらに、シリカであることがより好ましい。例えば、かかるシリカは硅素ハロゲン化物やアルコキシドの蒸気相酸化により生成されたいわゆる乾式法又はヒュームドシリカと称される乾式シリカ、及びアルコキシド水ガラスから製造されるいわゆる湿式シリカの両者が使用可能である。表面及びシリカ微粉体の内部にあるシラノール基が少なく、またＮａ₂Ｏ、ＳＯ₃ ^2-の如き製造残滓の少ない乾式シリカの方がより好ましい。乾式シリカにおいては、製造工程において例えば、塩化アルミニウム、塩化チタンの如き他の金属ハロゲン化合物を硅素ハロゲン化合物と共に用いることによって、シリカと他の金属酸化物の複合微粉体を得ることも可能でありそれらも包合する。
【０１８４】
本発明に用いられる無機微粉体は、ＢＥＴ法で測定した窒素吸着による比表面積が３０ｍ²／ｇ以上、特に５０〜４００ｍ²／ｇの範囲のものが良好な結果を与える。無機微粉体は、トナー粒子１００重量部に対して好ましくは０．１〜８重量部、より好ましくは０．５〜５重量部、さらに好ましくは１．０重量部を超えて３．０重量部まで使用するのが良い。本発明に用いられる無機微粉体は、必要に応じ、疎水化、帯電性制御等の目的でシリコーンワニス、各種変性シリコーンワニス、シリコーンオイル、各種変性シリコーンオイル、シランカップリング剤、官能基を有するシランカップリング剤、その他有機硅素化合物、有機チタン化合物の如き処理剤を単独であるいは、併用して処理されていることも可能である。
【０１８５】
高い帯電量を維持し、低消費量及び高転写率を達成するためには、無機微粉体は少なくともシリコンオイルで処理されていることがさらに好ましい。
【０１８６】
転写および／またはクリーニング性向上のために一次粒径５０ｎｍ以上（好ましくは比表面積が３０ｍ²／ｇ未満）の無機又は有機の球状に近い微粒子をさらに添加することも好ましい形態のひとつである。この球状に近い微粒子としては、例えば球状シリカ粒子、球状ポリメチルシルセスキオキサン粒子、球状樹脂粒子が好ましく用いられる。
【０１８７】
本発明に用いられるトナーには、実質的な悪影響を与えない範囲内で更に他の添加剤、例えば、テフロン粉末、ステアリン酸亜鉛粉末、ポリフッ化ビニリデン粉末の如き滑剤粉末；酸化セリウム粉末、炭化硅素粉末、チタン酸ストロンチウム粉末の如き研磨剤；例えば酸化チタン粉末、酸化アルミニウム粉末の如き流動性付与剤；ケーキング防止剤；例えばカーボンブラック粉末、酸化亜鉛粉末、酸化スズ粉末の如き導電性付与剤；逆極性の有機微粒子；及び無機微粒子；を現像性向上剤として少量用いることもできる。
【０１８８】
本発明に用いられるトナー粒子を作製するには、上述した重合法の他には、例えば、結着樹脂、アゾ系鉄錯体化合物、カーボンブラック、離型剤を加圧ニーダーやエクストルーダー又はメディア分散機を用い均一に分散せしめた後、機械的又はジェット気流下でターゲットに衝突させ、所望のトナー粒径に微粉砕化せしめた後、更に分級工程を経て粒度分布をシャープ化せしめトナー化する所謂粉砕方法によるトナーの製造方法；特公昭５６−１３９４５号公報に記載のディスク又は多流体ノズルを用い溶融混合物を空気中に霧化し球状トナーを得る方法；重合性単量体には可溶で得られる重合体が不溶な有機溶剤を用い重合性単量体の重合によって直接トナーを生成する分散重合方法；又は水溶性極性重合開始剤存在下で直接重合しトナーを生成するソープフリー重合方法に代表される乳化重合方法；が挙げられる。
【０１８９】
また、本発明は、感光体表面に離型性を付与することが好ましく、感光体表面の水に対する接触角は８５度以上であることが好ましい。より好ましくは感光体表面の水に対する接触角は９０度以上である。
【０１９０】
感光体表面が高い接触角を有することは、感光体表面が高い離型性有することを示し、この効果により、転写残余のトナー量を著しく減少させることができ、クリーニング工程での負荷を大幅に低減し、クリーニング不良の発生をより確実に防止することができる。
【０１９１】
さらに、感光体表面が高い離型性を有することにより、転写残余のトナー量を著しく減少させることができ、転写残トナーによる遮光がほとんどなくネガゴースト画像を本質的に防止できると共に現像時に転写残トナーの現像域での回収効率も向上し、ポジゴースト画像を防止する。
【０１９２】
ここで、ゴースト画像の発生メカニズムを説明する。
【０１９３】
転写残トナーによる遮光が特に問題となるのは、一枚の転写材に対し感光体表面が繰り返し使用される場合、つまり感光体一周分の長さが転写材の進行方向長さよりも短い場合、転写残トナーが感光体上に存在する状態で帯電、露光及び現像をしなければならないため、転写残トナーの存在する感光体表面部での電位が充分落ちきらず現像コントラストが不十分になるため反転現像については周囲よりも濃度が低い、ネガゴーストとして画像上に現れる。
【０１９４】
一方、現像時に転写残トナーのクリーニング効果が不十分であれば、転写残トナーの存在する感光体表面上に、トナーが現像されるため周囲よりも濃度が高く、ポジゴーストが発生する。
【０１９５】
本発明の構成にて、上記説明のゴースト画像を本質的に防止できる。
【０１９６】
本発明の画像形成方法において、感光体表面が高分子結着剤を主体として構成される場合に有効である。例えば、（ｉ）セレン、アモルファスシリコンの如き無機感光体の上に、樹脂を主体とした保護膜を設ける場合；（ｉｉ）機能分離型有機感光体の電荷輸送層として、電荷輸送材と樹脂を有する表面層をもつ場合；（ｉｉｉ）さらにその上に上記のような保護層を設ける場合がある。このような表面層に離型性を付与する手段としては、
▲１▼膜を構成する樹脂自体に表面エネルギーの低いものを用いる、
▲２▼撥水、親油性を付与するような添加剤を加える、
▲３▼高い離型性を有する材料を粉体状にして分散する、
が挙げられる。▲１▼としては、樹脂の構造中にフッ素含有基、シリコーン含有基を導入することにより達成する。▲２▼としては、界面活性剤を添加剤として添加すればよい。▲３▼としては、ポリ４フツ化エチレン、ポリフッ化ビニリデン及びフッ化カーボンの如きフッ素原子を含む化合物を用いることが挙げられる。
【０１９７】
これらの手段によって感光体表面の水に対する接触角を８５度以上とすることができる。感光体表面の水に対する接触角が８５度未満では耐久によるトナーおよびトナー担持体の劣化が生じやすい。
【０１９８】
この中でも特にポリ４フッ化エチレンやポリフッ化ビニリデンの如き含フッ素樹脂が好適である。本発明においては、▲３▼の粉体として含フッ素樹脂を離型性粉体として用いた場合には、最表面層への分散が好適である。
【０１９９】
これらの粉体を表面に含有させるためには、バインダー樹脂中に該粉体を分散させた層を感光体最表面に設けるか、あるいは、元々樹脂を主体として構成されている有機感光体であれば、新たに表面層を設けなくても、最表面層に該粉体を分散させれば良い。
【０２００】
該粉体の表面層への添加量は、表面層総重量に対して、１〜６０重量％、さらには２〜５０重量％が好ましい。１重量％より少ないと転写残余のトナーが充分に減少せず、転写残トナーのクリーニング効率も充分でなく、ゴースト防止効果が不十分であり、６０重量％を超えると膜の強度が低下したり、感光体への入射光量が著しく低下したりするため、好ましくない。該粉体の粒径については、画質の面から、１μｍ以下、好ましくは０．５μｍ以下が望ましい。１μｍより大きいと入射光の散乱によりラインの切れが悪くなり実用に耐えない。
【０２０１】
本発明は、帯電手段が帯電部材を感光体に当接させる接触帯電法の場合に特に効果的である。すなわち、クリーニングの後の残トナーが多いと、それが後工程である直接帯電部材に付着してしまい、帯電不良を引き起こす。従って、帯電手段が感光体に接することのないコロナ放電に比べて、残トナーの量はより少なく、付着し難くする必要がある。
【０２０２】
本発明に用いられる感光体の好ましい様態のひとつを以下に説明する。
【０２０３】
導電性基体としては、アルミニウム又はステンレスの如き金属；アルミニウム合金又は酸化インジウム−酸化錫合金による被膜層を有するプラスチック；導電性粒子を含侵させた紙又はプラスチック；導電性ポリマーを有するプラスチック；の円筒状シリンダー及びフィルムが用いられる。
【０２０４】
これら導電性基体上には、感光層の接着性向上、塗工性改良、基体の保護、基体上に欠陥の被覆、基体からの電荷注入性改良及び感光層の電気的破壊に対する保護を目的として下引き層を設けても良い。
【０２０５】
下引き層は、ポリビニルアルコール、ポリ−Ｎ−ビニルイミダゾール、ポリエチレンオキシド、エチルセルロース、メチルセルロース、ニトロセルロース、エチレン−アクリル酸コポリマー、ポリビニルブチラール、フェノール樹脂、カゼイン、ポリアミド、共重合ナイロン、ニカワ、ゼラチン、ポリウレタン又は酸化アルミニウムの材料によって形成される。下引き層の膜厚は通常０．１〜１０μｍ、好ましくは０．１〜３μｍが良い。
【０２０６】
電荷発生層は、アゾ系顔料、フタロシアニン系顔料、インジゴ系顔料、ペリレン系顔料、多環キノン系顔料、スクワリリウム色素、ピリリウム塩類、チオピリリウム塩類、トリフェニルメタン系色素又はセレンや非晶質シリコンの如き無機物質の電荷発生物質を適当な結着剤に分散し塗工する、あるいは蒸着により形成する。なかでもフタロシアニン系顔料が感光体感度を本発明に適合する感度に調整するうえで好ましい。結着剤としては、広範囲な結着性樹脂から選択でき、例えば、ポリカーボネート樹脂、ポリエステル樹脂、ポリビニルブチラール樹脂、ポリスチレン樹脂、アクリル樹脂、メタクリル樹脂、フェノール樹脂、シリコーン樹脂、エポキシ樹脂、酢酸ビニル樹脂が挙げられる。電荷発生層中に含有される結着剤の量は８０重量％以下、好ましくは０〜４０重量％であることが良い。電荷発生層の膜厚は５μｍ以下、特には０．０５〜２μｍが好ましい。
【０２０７】
電荷輸送層は、電界の存在下で電荷発生層から電荷キャリアを受け取り、これを輸送する機能を有している。電荷輸送層は電荷輸送物質を必要に応じて結着樹脂と共に溶剤中に溶解し、塗工することによって形成され、その膜厚は一般的には５〜４０μｍである。電荷輸送物質としては、主鎖または側鎖にビフェニレン、アントラセン、ピレン及びフェナントレンの如き多環芳香族化合物；インドール、カルバゾール、オキサジアゾール及びピラゾリンの如き含窒素環式化合物；ヒドラゾン化合物；スチリル化合物；セレン；セレン−テルル；非晶質シリコン；硫化カドニウムが挙げられる。
【０２０８】
これら電荷輸送物質を分散させる結着樹脂としては、ポリカーボネート樹脂、ポリエステル樹脂、ポリメタクリル酸エステル、ポリスチレン樹脂、アクリル樹脂及びポリアミド樹脂の如き樹脂；ポリ−Ｎ−ビニルカルバゾール及びポリビニルアントラセンの如き有機光導電性ポリマーが挙げられる。
【０２０９】
表面層として、保護層を設けてもよい。保護層の樹脂としては、ポリエステル、ポリカーボネート、アクリル樹脂、エポキシ樹脂、フェノール樹脂、あるいはこれらの樹脂の硬化剤が単独あるいは２種以上組み合わされて用いられる。
【０２１０】
保護層の樹脂中に導電性微粒子を分散してもよい。導電性微粒子の例としては、金属又は金属酸化物が挙げられる。好ましくは、酸化亜鉛、酸化チタン、酸化スズ、酸化アンチモン、酸化インジウム、酸化ビスマス、酸化スズ被膜酸化チタン、スズ被膜酸化インジウム、アンチモン被膜酸化スズ又は酸化ジルコニウムの超微粒子がある。これらは単独で用いても２種以上を混合して用いても良い。一般的に保護層に粒子を分散させる場合、分散粒子による入射光の散乱を防ぐために入射光の波長よりも粒子の粒径の方が小さいことが必要であり、保護層に分散される導電性、絶縁性粒子の粒径としては０．５μｍ以下であることが好ましい。保護層中での含有量は、保護層総重量に対して２〜９０重量％が好ましく、５〜８０重量％がより好ましい。保護層の膜厚は、０．１〜１０μｍが好ましく、１〜７μｍがより好ましい。
【０２１１】
表面層の塗工は、樹脂分散液をスプレーコーティング、ビームコーティングあるいは浸透（ディッピング）コーティングすることによって行うことができる。
【０２１２】
本発明に用いられる好ましい現像工程の条件としては、現像剤と感光体表面が接触しているということと、反転現像方法を用いるということである。二成分磁気ブラシ現像方法を用いる場合は、そのキャリアとして、フェライト、マグネタイト、鉄粉あるいは、それらをアクリル樹脂、シリコーン樹脂、フッ素樹脂等でコーティングしたものが用いられる。このとき、現像時あるいは現像前後の空白時には、直流あるいは交流成分のバイアスを印加し、現像と感光体上の残余のトナーを回収出来るような電位に制御される。このとき直流成分は、明部電位と暗部電位の間に位置する。
【０２１３】
一成分現像剤の場合、トナー担持体して弾性ローラーを用い、弾性ローラー表面にトナーをコーティングして形成したトナー層を感光体表面と接触させる方法も用いられる。このとき、トナーは磁性又は非磁性のいずれであっても良く、トナー層と感光体表面が接触していることが重要となる。トナー担持体は実質的に感光体表面と接触しているが、これは、トナー担持体からトナー層を除いたときに該トナー担持体が感光体表面と接触しているということを意味する。このとき、トナー層を介して、感光体表面と感光体表面に対向する弾性ローラーとの間に働く電界によってエッジ効果のない画像を得るためには、弾性ローラー表面あるいは、表面近傍が電位をもち、感光体表面とトナー担持表面との間で電界を有する必要性がある。このため、弾性ローラーの弾性ゴムが中抵抗領域に抵抗制御されて感光体表面との導通を防ぎつつ電界を保つか、または導電性ローラーの表面層に薄層の絶縁層を設ける方法も利用できる。さらには、導電性ローラーの感光体表面に対向する外面側を絶縁性物質により被覆した導電性樹脂スリーブ、あるいは、絶縁性スリーブの感光体表面に対向しない内面側に導電層を設けた構成も可能である。トナー担持体として剛体ローラーを用い、感光体をベルトのごときフレキシブルなものとした構成も可能である。トナー担持体として現像ローラーの電気抵抗としては１０²〜１０⁹Ωの範囲が好ましい。
【０２１４】
現像ローラーの電気抵抗は、以下の方法で測定する。すなわち、図１１に示すように直径１６ｍｍのアルミローラー１０２と現像ローラー１０１を当接荷重４．９Ｎ（５００ｇ）で当接させ、該アルミローラー１０２を２ｒｐｓで回転させる。次に現像ローラー１０１にＶ₁＝４００Ｖの直流電圧を印加する。アース側に可変抵抗Ｒを配置し、現像ローラー１０１に応じて該可変抵抗Ｒの抵抗値を調整しながらその両端の電圧Ｖ₂を測定し、電流値を算出することにより現像ローラー１０１の電気抵抗を算出する。
【０２１５】
一成分接触現像法を用いた場合そのトナーを担持する現像ローラー表面は、感光体表面の移動方向と同方向に回転していてもよいし、逆方向に回転していてもよい。その回転が同方向である場合感光体の周速に対して、周速比で１００％よりも速いことが望ましい。１００％以下であると、画像品質が悪い。周速比が高まれば高まるほど、現像部位に供給されるトナーの量は多く、潜像に対しトナーの脱着頻度が多くなり、不要な部分は掻き落とされ必要な部分には付与されるという繰り返しにより、潜像に忠実な画像が得られる。具体的には、トナー担持体表面の移動速度が感光体表面の移動速度に対し、１．０５〜３．０倍の速度であることが好ましい。
【０２１６】
以下、本発明の画像形成方法に適用可能な転写工程について具体的に説明する。
【０２１７】
転写工程においては、感光体表面に転写材を介して転写手段を当接させながらトナー画像を転写材に静電転写する接触転写方式を用いることが好ましい。転写手段の感光体表面に対する当接圧力としては、好ましくは線圧２．９Ｎ／ｍ（３ｇ／ｃｍ）以上であることが良く、より好ましくは９．８〜４９０Ｎ／ｍ（１０〜５００ｇ／ｃｍ）であることが良い。当接圧力としての線圧が２．９Ｎ／ｍ（３ｇ／ｃｍ）未満であると、転写材の搬送ずれや転写不良の発生が起こりやすくなるため好ましくない。当接圧力が高すぎる場合には、感光体表面の劣化やトナーの付着を招き、結果として、感光体表面へのトナー融着を生じるようになる。
【０２１８】
接触転写工程における転写手段としては、転写ローラーあるいは転写ベルトを有する装置が使用される。転写ローラーは少なくとも芯金と芯金を被覆する導電性弾性層を有し、導電性弾性層はカーボンの如き導電性微粒子を分散させたウレタンやＥＰＤＭの如き体積抵抗１０⁶〜１０¹⁰Ωｃｍ程度の弾性体で作られている。
【０２１９】
本発明は、感光体の表面が有機化合物である様な画像形成装置において特に有効に用いられる。即ち、有機化合物が感光体の表面層を形成している場合には、無機材料を用いた他の感光体よりもトナー粒子に含まれる結着樹脂との接着性が高いことから転写性がより低下する傾向にあるという技術課題を有している。従って、本発明で用いるトナーによる高い転写性による効果は、より顕著となる。
【０２２０】
本発明に係わる感光体の表面物質としては、たとえばシリコーン樹脂、塩化ビニリデン、エチレン−塩化ビニル、スチレン−アクリロニトリル、スチレン−メチルメタクリレート、スチレン、ポリエチレンテレフタレートおよびポリカーボネート等が挙げられるが、これらに限定されることはなく他のモノマーあるいは前述の結着樹脂間での共重合体およびブレンド体等も使用することができる。
【０２２１】
本発明においては、直径が５０ｍｍ以下の小径のドラム状の感光体を有する画像形成装置に対し特に有効に用いられる。即ち、小径の感光体ドラムの場合には、同一の線圧での接触部材の当接部における圧力の集中が起こりやすいためである。ベルト感光体でも同一の現像があると考えられるが、本発明は、当接部での曲率半径が２５ｍｍ以下の感光体ベルトを用いた画像形成装置に対しても有効である。
【０２２２】
さらに本発明においては、トナーに高い帯電付与を行なうため現像に際して、トナーの総帯電量をコントロールすることが望ましい。そのため、本発明に係わるトナー担持体の表面は導電性微粒子及び／又は滑剤を分散した樹脂層で被覆されていることが好ましい。
【０２２３】
帯電方法としては、コロトロンあるいはスコロトロンと呼ばれる公知のコロナ帯電方法が用いられるほか、ピン電極を用いた方法も使用できる。巧に感光体表面に帯電部材を当接させて帯電を行なう接触帯電法も同様に使用できる。
【０２２４】
本発明においては、帯電手段が帯電部材を感光体表面に当接させる接触帯電法の場合に特に効果的である。すなわち、帯電手段が感光体表面に接することのない非接触コロナ放電に比べて、接触帯電法は感光体表面の劣化を生じ易く、耐久性の観点から転写性の低下による転写残トナーの増加がクリーニング性に厳しい方向にあるという技術課題を有している。従って、本発明で用いる高い転写性による効果は、より顕著となる。
【０２２５】
接触帯電部材として帯電ローラーを用いたときの好ましいプロセス条件としては、帯電ローラーの当接圧が４．９〜４９０Ｎ／ｍ（５〜５００ｇ／ｃｍ）、より好ましくは、９．８〜３９２Ｎ／ｍ（１０〜４００ｇ／ｃｍ）であり、さらに、転写残トナーの極性を感光体帯電極性と同じ極性に揃え、現像時での回収を容易にするため、直流電圧の印加がよいが、直流電圧に交流電圧を重畳したものを用いたときには、２×Ｖｔｈ（Ｖ）〔Ｖｔｈ；直流印加における放電開始電圧（Ｖ）〕未満のピーク間電圧を有する交流電圧を直流電圧に重畳することが好ましい。
【０２２６】
この他の接触帯電部材としては、帯電ブレードを用いる方法や、導電性ブラシを用いる方法がある。これらの接触帯電手段は、高電圧が不要になったり、オゾンの発生が低減するといった効果がある。
【０２２７】
接触帯電部材としては、ローラーまたはブレードの場合は、導電性基体として、鉄、銅、ステンレスの如き導電性金属；カーボン分散樹脂；金属あるいは金属酸化物分散樹脂が用いられる。プレードの場合には、その形状としては棒状、板状が使用できる。弾性ローラの構成としては、導電性基体上に弾性層、導電層及び抵抗層を設けたものが用いられる。
【０２２８】
弾性層としては、クロロプレンゴム、イソプレンゴム、ＥＰＤＭゴム、ポリウレタンゴム、エポキシゴム及びプチルゴムの如きゴム又はゴムの発泡体であるスポンジ、スチレン−ブタジエンサーモプラスチックエラストマー、ポリウレタン系サーモプラスチックエラストマー、ポリエステル系サーモプラスチックエラストマー、エチレン−酢ビサーモプラスチックエラストマーの如きサーモプラスチックエラストマーで形成することができる。
【０２２９】
導電層は、体積抵抗率が好ましくは、１０⁷Ω・ｃｍ以下、より好ましくは１０¹〜１０⁶Ω・ｃｍであることが良い。導電層としては、例えば、金属蒸着膜、導電性粒子分散樹脂、導電性樹脂等が用いられる。具体例としては、アルミニウム、インジウム、ニッケル、銅、及び鉄の如き導電性金属の蒸着膜；カーボン、アルミニウム、ニッケル及び酸化チタンの如き導電性粒子をウレタン、ポリエステル、酢酸ビニル−塩化ビニル共重合体及びポリメタクリル酸メチル如き樹脂中に分散した導電性粒子分散樹脂；４級アンモニウム塩含有ポリメタクリル酸メチル、ポリビニルアニリン、ポリビニルピロ−ル、ポリジアセチレン及びポリエチレンイミンの如き導電性樹脂が挙げられる。
【０２３０】
抵抗層は、体積抵抗率が１０⁶〜１０¹²Ω・ｃｍの層であることが良い。抵抗層としては、半導性樹脂又は導電性粒子分散絶縁樹脂を用いることができる。半導性樹脂としては、例えば、エチルセルロース、ニトロセルロース、メトキシメチル化ナイロン、エトキシメチル化ナイロン、共重合ナイロン、ポリビニルヒドリン又はカゼインが用いられる。導電性粒子分散樹脂としては、例えば、カーボン、アルミニウム、酸化インジウム、酸化チタンの如きの導電性粒子をウレタン、ポリエステル、酢酸ビニル−塩化ビニル共重合体、ポリメタクリル酸メチルの如き絶縁性樹脂中に少量分散したものが挙げられる。
【０２３１】
接触帯電部材としての導電性ブラシは、一般に用いられている繊維に導電材を分散させて抵抗調整されたものが用いられる。繊維としては、一般に知られている繊維が使用可能であり、例えばナイロン、アクリル、レーヨン、ポリカーボネ−ト又はポリエステルが挙げられる。導電材としては、一般に知られている導電材が使用可能であり、例えば、銅、ニッケル、鉄、アルミニウム、金及び銀の如き導電性金属；酸化鉄、酸化亜鉛、酸化スズ、酸化アンチモン、酸化チタンの如き導電性金属の酸化物；又はカーボンブラックの如き導電粉が挙げられる。なおこれら導電材は必要に応じ疎水化、抵抗調整の目的で表面処理が施されていてもよい。使用に際しては、繊維との分散性や生産性を考慮して選択して用いる。
【０２３２】
導電性ブラシの形状としては、繊維の太さが１〜２０デニール（繊維径１０〜５００μｍ程度）、ブラシの繊維の長さは１〜１５ｍｍ、ブラシ密度は１平方インチ当たり１万〜３０万本（１平方メートル当り１．５×１０⁷〜４．５×１０⁸本程度）のものが好ましく用いられる。
【０２３３】
本発明の画像形成方法を添付図面を参照しながら説明する。
【０２３４】
図１は、本発明の画像形成方法の実施例の一例として、クリーニングブレードの如きクリーニング部材を有するクリーニングユニットを除去したプロセスカートリッジを有する画像形成装置を模式的に示した図である。
【０２３５】
接触帯電手段である帯電ローラ３１により感光体３６を帯電し、レーザー光４０で画像部分を露光して静電潜像を形成する。現像器３２に収納されているトナー３０をトナー塗布ローラ３５及び塗布ブレード３３によりトナー担持体３４上に塗布し、トナー担持体３４上のトナー層を感光体３６の表面に接触させて感光体３６上の静電潜像を反転現像法により現像し、トナー画像を感光体３６上に形成する。トナー担持体３４にはバイアス印加手段４１により少なくとも直流バイアスが印加される。感光体３６上のトナー画像は搬送されてくる転写材としての記録材３８上へ、バイアス印加手段４２によりバイアスが印加されている転写手段である転写ローラー３７により転写され、記録材上に転写されたトナー画像は、加熱ローラと加圧ローラーとを有する加熱加圧定着手段４３により定着される。
【０２３６】
転写工程後の感光体３６上の転写残トナーは、ブレードクリーニング手段の如きクリーニング部材によるクリーニング工程を経由することなく、帯電ローラー３１の所まで搬送される。転写残トナーを有する感光体３６は、再度、帯電ローラー３１で帯電され、帯電後にレーザー光４０の露光により静電潜像が形成される。転写残トナーを有する感光体３６は、トナー担持体３４上のトナーによる静電潜像の現像とともに、転写残トナーのトナー担持体３４への回収がおこなわれる。現像同時クリーニング工程後の感光体３６上のトナー画像は、搬送されてくる記録材３８上に転写ローラー３７により転写される。転写工程後の感光体３６は、帯電ローラー３１により再度帯電され、以後同様な工程が繰り返し実施される。
【０２３７】
反転現像方法において、現像同時クリーニングを実施するための好ましい現像条件としては、感光体表面の暗部電位（Ｖ_d）と明部電位（Ｖ₁）とトナー担持体に印加される直流バイアス（Ｖ_DC）とが、｜Ｖ_d−Ｖ_DC｜＞｜Ｖ₁−Ｖ_DC｜の関係を満足するように設定するのが良い。より好ましくは、｜Ｖ_d−Ｖ_DC｜の値が｜Ｖ₁−Ｖ_DC｜の値よりも１０Ｖ以上大きい方が良い。
【０２３８】
図２は、トナー担持体としての現像スリーブに対するトナーの供給に加えて、現像スリーブからの現像に寄与したトナーのはぎ取りをより円滑に行うことのできる画像形成装置の他の例を示す。
【０２３９】
図２において、１は感光ドラムで、その周囲に接触帯電手段である一次帯電ローラー２、現像手段である現像器８、接触転写手段である転写帯電ローラー２１、レジスタローラー１９が設けられている。そして感光ドラム１は一次帯電ローラー２によって例えば−７００Ｖに帯電される。バイアス印加手段５による印加電圧は直流電圧が例えば−１３５０Ｖである。そして、レーザー発生装置６によりレーザー光７を感光ドラム１に照射することによって露光され、デジタルな静電潜像が形成される。感光ドラム１上の静電潜像は現像器８によって非磁性一成分トナー１５で現像され、転写材としての記録材２０を介して感光ドラム１に当接されたバイアス印加手段２４でバイアス電圧が印加されている転写ローラー２１により記録材２０上へ転写される。トナー画像２６をのせた記録材２０は搬送ベルト２５により加熱ローラー２８及び加圧ローラー２９を有する加熱加圧定着器２７へ運ばれ記録材２０上に定着される。
【０２４０】
帯電ローラー２は、中心の芯金４とその外周を形成した導電性弾性層３とを基本構成とするものである。
【０２４１】
現像器８は図３及び図４に示すように感光ドラム１にトナー担持体としての現像スリーブ９上のトナー層が接触し、バイアス印加手段１８でバイアスが印加されている芯金１０及び弾性層１１を有する弾性ローラー９からなるトナー担持体としての現像スリーブが配設される。現像器８内にはバイアス印加手段１７でバイアスが印加されている芯金１３と弾性層１４を有するトナー塗布ローラー１３が配設されている。現像スリーブ９に付着して搬送されるトナー量を規制する部材として、トナー規制ブレード１６が配設されトナー規制ブレード１６の現像スリーブ９に対する当接圧により現像領域に搬送されるトナー量（トナー層厚）が制御される。現像領域では、現像スリーブ９に少なくとも直流の現像バイアスが印加され、現像スリーブ上トナー層は、感光ドラム１表面に接触し、静電潜像に応じて感光ドラム１上に転移してトナー画像を形成する。
【０２４２】
現像同時クリーニングを実施するためには、感光ドラム１の明部電位が０〜２５０Ｖであり、暗部電位が３００〜１０００Ｖである場合に、バイアス印加手段１７により印加される供給バイアス電圧が１００〜９００Ｖであり、バイアス印加手段１８により印加される現像バイアス電圧が１００〜９００Ｖであることが好ましい。さらに、バイアス印加手段１７により印加される供給バイアス電圧は、バイアス印加手段１８により印加される現像バイアス電圧よりも絶対値で１０〜４００Ｖ大きい方が、非磁性トナー１５の現像スリーブ９への供給及び非磁性トナーの現像スリーブ９からのはぎ取りが円滑におこなわれるので好ましい。
【０２４３】
現像スリーブ９の回転方向に対して、トナー塗布ローラー１２は、矢印で示す通りお互いの表面がカウンター方向に移動する（回転方向は同方向）ことが、非磁性トナーの供給及びはぎ取りの点で好ましい。
【０２４４】
上記の図１及び２で示す画像形成装置においては、中間転写体を用いず像担持体上に形成されたトナー画像を直接記録材に転写するタイプの画像形成方法を採用するものである。
【０２４５】
次に、像担持体上に形成されたトナー画像を転写材としての中間転写体に第１の転写を行ない、中間転写体上に転写されたトナー画像を記録材に第２の転写を行なう画像形成方法について、図４に示す画像形成装置を用いて説明する。
【０２４６】
図４において、像担持体としての感光体ドラム５１に対抗し接触回転する帯電ローラー５２により感光体ドラム５１上に表面電位を持たせ露光手段５３により静電潜像を形成する。静電潜像は一成分接触現像方式の現像器５４，５５，５６，５７によりマゼンタトナー、シアントナー、イエロートナー及びブラックトナーの４色のトナーによって、現像されフルカラーのトナー画像が形成される。現像時には、各現像器５４，５５，５６及び５７のいずれか１つが移動することにより、感光体ドラム５１の表面に現像器のトナー担持体が当接して現像が行なわれ、現像後に再度元の位置に現像器が移動することにより、感光体ドラム５１の表面からトナー担持体が離間する。この動作が各現像器ごとに４回くり返される。該トナー画像は一色毎に中間転写材５８上に転写され、複数回繰り返されることにより、多重トナー像が形成される。
【０２４７】
中間転写体５８はドラム状のものが用いられ、外周面に保持部材を張設したもの、基材上に導電付与部材、例えばカーボンブラック，酸化亜鉛，酸化錫，炭化珪素又は酸化チタン等を十分分散させた弾性層（例えばニトリルブタジェンラバー）を有するものが用いられる。ベルト状の中間転写体を用いても良い。
【０２４８】
中間転写体５８は、支持部材５９の表面に形成した硬度が１０〜５０度（ＪＩＳ Ｋ−６３０１）の弾性層６０を有するドラム状のものや、転写ベルトの場合では転写材（記録材）への転写部でこの硬度を有する弾性層６０を持つ支持部材で構成されていることが好ましい。
【０２４９】
感光体ドラム５１から中間転写体５８への転写は、電源６６より中間転写体５８の支持部材としての芯金５９上にバイアスを付与することで転写電流が得られトナー画像の転写が行なわれる。保持部材又はベルトの背面からのコロナ放電やローラー帯電を利用しても良い。
【０２５０】
中間転写体５８上の多重トナー画像は、転写手段６１により記録材Ｓ上に一括転写される。転写手段はコロナ帯電器や転写ローラー、転写ベルトを用いた接触静電転写手段が用いられる。
【０２５１】
トナー画像を有する記録材Ｓは、加熱体６７を内部に有する定着部材としての定着ローラー６８とこの定着ローラー６８と圧接する加圧ローラー６９とを有する加熱定着装置７０の定着ローラー６８と加圧ローラー６９との当接ニップ部を、記録材Ｓが通過することにより、記録材Ｓにトナー画像の定着が行なわれる。
【０２５２】
本発明で用いられるカーボンブラックを含有しているトナーは、ブラックトナーとして上記の画像形成装置の現像器５４、５５、５６及び５７から選択される１つの現像器に用いられ、残りの３つの現像器には、３色の有彩色のカラートナーが用いられるものである。そして本発明で用いるブラックトナーは、有彩色のカラートナーとを組み合わせてカラー画像又はフルカラー画像の形成に或いはブラックトナーのみによりモノクロ画像の形成に用いられるものである。
【０２５３】
図４における画像形成装置においては、現像器５４が現像可能な位置まで移動して現像が行なわれ、現像されたトナー画像が中間転写体５８に転写され、この第１の転写後に感光体ドラム５１の表面上に残存するトナーは、現像器５４で回収クリーニングされる。感光ドラム５１の表面上に残存するトナーが現像器５４で回収されると、現像器５４が移動して元の位置にもどり、次に現像器５５が現像可能な位置まで移動して以降現像器５４と同様に作動し、現像器５５及び５６についても順次同様に作用するものである。６５は、第２の転写後に中間転写体５８の表面上に残存するトナーを除去するためのクリーニング部材６４を有するクリーナー（第２のクリーニング手段）である。
【０２５４】
二成分接触現像法を用いた画像形成方法について、図５及び６を用いて説明する。
【０２５５】
図５は、後述する実施例で用いた、本発明の画像形成方法の実施例の一例として用いた、磁気ブラシ現像用二成分系現像剤を使用する現像器を用いた画像形成装置を模式的に示した図で説明する。
【０２５６】
図５において、感光体７２の帯電手段である帯電ブラシローラー７５（ナイロン繊維にカーボンブラックを分散させて抵抗調整された、繊維の太さが６デニール、ブラシの繊維の長さは３ｍｍ、ブラシ密度は１平方インチ当たり１０万本、感光体回転と逆方向に周速１２０％で回転）を感光体７２と接触させてバイアス印加して帯電し、レーザー光による露光７６（６００ｄｐｉ、２値）により、感光体７２に静電荷潜像を形成する。現像器８５の現像剤担持体７１上のトナーと磁性キャリアとを有する二成分系現像剤で形成された磁気ブラシを感光体７２と接触させて、反転現像法により感光体７２の静電荷潜像を現像してトナー画像を形成する。
【０２５７】
現像剤担持体７１には、バイアス印加手段により少なくとも直流バイアスが印加される（直流成分として現像コントラストが５００Ｖとなるように設定、交流成分としては１．８ｋＶを印加）。
【０２５８】
感光体７２上のトナー画像は、搬送されてくる転写材としての記録材７４へ、転写手段である転写コロナ帯電器７３（感光体７２とは非接触）により転写され、記録材７４上のトナー画像は、ヒータ７８を内包する加熱ローラ７７と加圧ローラ７９とを有する加熱加圧定着手段により記録材７４に定着される。感光体７２としては、感光体表面の水に対する接触角が８５度以上である感光体製造例７１の感光体を使用した。転写工程後の感光体７２上の転写残トナーは、クリーニング工程を経由することはない。イレース露光８１により除電された感光体７２は、再度帯電ブラシローラー７５で帯電され、露光７６により静電荷潜像を形成する。転写残トナーを有する感光体７２は、現像剤担持体７１上の磁気ブラシによる静電荷潜像の現像とともに、転写残トナーの現像剤担持体７１への回収がおこなわれる。現像同時クリーニング工程後の感光体７２上のトナー画像は、搬送されてくる記録材７４上へ転写コロナ帯電器７３により転写され、転写工程後の感光体７２は、イレース露光８１で除電され、帯電ブラシローラー７５で再度帯電され、以後同様な工程が繰り返し実施される。
【０２５９】
図６に、図５の現像部の拡大図を示す。図６において、感光体７２と、現像剤担持体７１上の二成分系現像剤９０で形成されている磁気ブラシと接触している。
【０２６０】
現像剤担持体７１は、例えばアルミニウム、ＳＵＳ３１６の如き非磁性材料で構成されている。現像剤担持体７１は現像器８５の左下方壁に容器長手方向に形成した横長開口に右略半周面を現像器８５内へ突入させ、左略半周面を容器外へ露出させて回転自在に軸受けさせて横設してあり、矢印方向に回転駆動される。
【０２６１】
現像剤担持体７１内に挿入し図示の位置姿勢に位置決め保持した固定磁界発生手段としての固定の永久磁石（マグネット）であり、現像剤担持体７１が回転駆動されてもこの磁石９４は図示の位置・姿勢にそのまま固定保持される。この磁石９４はＮ極の磁極９２，９５及び９６を有し、Ｓ極の磁極９１及び９３の５磁極を有する。磁石９４は永久磁石に代えて電磁石を配設してもよい。
【０２６２】
８３は現像剤担持体７１を配設した現像剤供給器開口の上縁側に、基部を容器側壁に固定した現像剤規制部材としての非磁性ブレードであり、例えばＳＵＳ３１６を横断面路図の如くＬ字形に曲げ加工したものである。
【０２６３】
８４は非磁性ブレード（現像剤規制部材）８３の下面側に上面を接触させ前端面を現像剤案内面とした磁性キャリア限定部材である。非磁性ブレード８３及び磁性キャリア返し部材８４などによって構成される部分が規制部である。
【０２６４】
９０はトナー及び磁性キャリアを有する現像剤層である。８６は非磁性トナーである。
【０２６５】
９７はトナー濃度検出センサー（不図示）によって得られる出力に応じて作動するトナー補給ローラーである。センサーとしては、現像剤の体積検知方式、圧電素子、インダクタンス変化検知素子、交番バイアスを利用したアンテナ方式、光学濃度を検知する方式を利用することができる。該ローラーの回転または停止によって非磁性トナー８６の補給を行う。トナー８６が補給されたフレッシュな現像剤は現像剤搬送ローラ８７によって搬送されながら混合及び撹拌される。従ってこの搬送中において補給されたトナーにトリボ付与が行われる。８８はしきり板で現像器の長手方向両端部において切り欠かれており、この部分でスクリュー８７によって搬送されたフレッシュな現像剤がスクリュー８９へ受け渡される。
【０２６６】
Ｎ磁極９６は搬送極である。現像後の回収現像剤を容器内に回収し、さらに容器内の現像剤を規制部まで搬送する。
【０２６７】
Ｎ磁極９６付近では、現像剤担持体７１に近接して設けたスクリュー８９によって搬送されてきたフレッシュな現像剤と現像後の回収現像剤とを交換する。
【０２６８】
非磁性ブレード８３の端部と現像剤担持体１面との距離ｄは４００μｍとした。好ましいｄの設定範囲は１００〜９００μｍである。この距離が１００μｍより小さいとキャリア粒子がこの間に詰まり現像剤層にムラを生じやすいと共に良好な現像を行うのに必要な現像剤を塗布することが出来ず濃度の薄いムラの多い現像画像しか得られない場合がある。一方、この距離が９００μｍより大きいと現像剤担持体７１上へ塗布される現像剤量が増加し所定の現像剤層厚の規制が行えず、潜像担持体への磁性粒子付着が多くなると共に現像剤の循環、現像剤限定部材８４による現像規制が弱まりトナーのトリボが不足しカブリやすくなる傾向がある。
【０２６９】
現像剤担持体７１上の現像剤層の厚さを、現像剤担持体７１と感光体７２との対向空隙距離よりも若干大きくすることが好ましい。この距離は、４００μｍに設定した。好ましくは、５０〜８００μｍに設定するのが良い。
【０２７０】
【実施例】
以下、トナーおよび感光体ドラムの具体的な製造方法、実施例、比較例をもって本発明をさらに詳細に説明する。
【０２７１】
表１に示すカーボンブラックを用意した。
【０２７２】
【表１】

【０２７３】
〔マスターバッチ分散液１〜１９の調製〕
下記表２に示す通り、スチレン単量体２０００ｇに対して、表１に示すカーボンブラックａ〜ｌ及び分散剤をそれぞれ表２に示す種類及び添加量で組み合わせたものをアトライター１Ｓ（三井鉱山社製）に添加し、２ｍｍのジルコニアビーズを用いて、２００ｒｐｍにて温度２５℃で１８０分間攪拌を行い、スチレン単量体にカーボンブラック及び分散剤が分散されたマスターバッチ分散液１〜１９を作製した。得られたマスターバッチ分散液１〜１９の粘度を表２に示す。
【０２７４】
【表２】

【０２７５】
【外９】

【０２７６】
〔重合トナーの製造例Ａ〕
２リットル用四つ口フラスコ中のイオン交換水７００ｇに、０．１Ｍ−Ｎａ₃ ＰＯ₄ 水溶液５００ｇを投入し、６０℃に加温した後、高速攪拌装置ＴＫ式ホモミキサー（特殊機化工業製）を用いて、１２０００ｒｐｍにて攪拌した。これに１．０Ｍ−ＣａＣｌ₂ 水溶液７６ｇを徐々に添加し、微小な難水溶性分散安定剤を含む水系媒体を得た。
【０２７７】
（前分散液）マスターバッチ分散液２０ １１２ｇ
（モノマー）スチレン ６６ｇ
ｎ−ブチルアクリレート（ｎ−ＢＡ） ３４ｇ
（極性レジン）飽和ポリエステル（プロポキシ化ビスフェノールとテレフタル酸との縮合物、酸価１４、ピーク分子量７０００） ８ｇ
（離型剤）エステルワックス（融点 ５８℃） ３０ｇ
【０２７８】
上記処方を６０℃に加温、均一に溶解し、分散した。これに、重合開始剤２，２′−アゾビス（２，４−ジメチルバレロニトリル）１０ｇを溶解し、重合性単量体組成物を調製した。
【０２７９】
前記水系媒体中に上記重合性単量体組成物を投入し、６０℃，Ｎ₂ 雰囲気下において、ＴＫ式ホモミキサーにて１２０００ｒｐｍで１０分間攪拌し、重合性単量体組成物を造粒した。その後、パドル攪拌翼で攪拌しつつ（５０ｒｐｍ）、同温度で５時間反応させた後、８０℃に昇温し、さらに５時間反応させた。重合反応終了後、減圧下で残存モノマーを留去し、冷却後、塩酸を加えリン酸カルシウムを溶解させた後、ろ過、水洗、乾燥して、重量平均径約６．７μｍのシャープな黒色重合粒子（ブラックトナー粒子）を得た。
【０２８０】
得られたブラックトナー粒子１００重量部に対して、ＢＥＴ法による比表面積が１４０ｍ² ／ｇである疎水性シリカを１．８重量部外添し、重合トナーＡを得た。得られたトナーの物性を表４に示した。
【０２８１】
〔重合トナーの製造例Ｂ〜Ｆ〕
アゾ系鉄錯体化合物（１）の添加量を表２に示すように変更したマスターバッチ分散液２〜６を用いることを除いては〔重合トナーの製造例Ａ〕と同様にして重合トナーＢ〜Ｆを作製した。得られたトナーの物性を表４に示した。
【０２８２】
〔重合トナーの製造例Ｇ〕
カーボンブラックａのかわりに表１に示すカーボンブラックｂを用いたマスターバッチ分散液７を用いることを除いては、〔重合トナーの製造例Ａ〕と同様にして重合トナーＧを作製した。得られたトナーの物性を表４に示した。
【０２８３】
〔重合トナーの製造例Ｈ，Ｉ〕
０．１Ｍ−Ｎａ₃ ＰＯ₄ 水溶液と１．０Ｍ−ＣａＣｌ₂ 水溶液の量を調整することで粒度の異なるトナーを〔重合トナーの製造例Ｇ〕と同様にして重合トナーＨ，Ｉを作製した。得られたトナーの物性を表４に示した。
【０２８４】
〔重合トナーの製造例Ｊ〜Ｒ〕
カーボンブラックａのかわりに表１に示すカーボンブラックｃ〜ｌを用いたマスターバッチ分散液８〜１７を用いることを除いては、〔重合トナーの製造例Ａ〕と同様にして重合トナーＪ〜Ｒを作製した。尚、マスターバッチ分散液１６は、粘度が高すぎてしまい取り出すことができず、トナーを得ることはできなかった。得られたトナーの物性を表４に示した。
【０２８５】
〔重合トナーの製造例Ｓ，Ｔ〕
アゾ系鉄化合物（１）のかわりにアゾ系クロム化合物及びジターシャリーブチルサリチル酸の亜鉛化合物をそれぞれ用いたマスターバッチ分散液１８及び１９を用いることを除いては、〔重合トナーの製造例Ａ〕と同様にして重合トナーＳ，Ｔを作製した。得られたトナーの物性を表４に示した。
【０２８６】
〔重合トナーの製造例Ｕ，Ｖ〕
重合性単量体組成物の処方を表３に示す通り、変更することを除いては、〔重合トナーの製造例Ｂ〕と同様にして重合トナーＵ，Ｖを作製した。得られたトナーの物性を表４に示した。
【０２８７】
〔重合トナーの製造例Ｗ〜Ｚ〕
重合性単量体組成物に含まれるスチレン単量体の一部分をジビニルベンゼンとジエチレングリコールジメタクリレートの混合物に変更することを除いては、〔重合トナーの製造例Ｂ〕と同様にして重合トナーＷ〜Ｚを作製した。得られたトナーの物性を表４に示す。
【０２８８】
〔重合トナーの製造例ＡＡ，ＢＢ〕
重合開始剤の添加量と重合反応時の温度条件を変更することを除いては、〔重合トナーの製造例Ｂ〕と同様にして重合トナーＡＡ，ＢＢを作製した。得られたトナーの物性を表４に示した。
【０２８９】
上記の重合トナーＡ〜Ｚ，ＡＡ，ＢＢの処方を表３に示す。
【０２９０】
〔粉砕トナーの製造例ＣＣ〕
（結着樹脂）スチレン−ブチルアクリレート共重合体 １００重量部
（重量平均分子量約３０万、Ｔｇ６０℃）
（着色剤）カーボンブラックｅ ７重量部
（荷電制御剤）アゾ系鉄化合物（１） ２重量部
（離型剤）エステルワックス ３重量部
【０２９１】
上記材料をあらかじめ混合し、二軸押し出し機にて１３０℃で溶融混練を行った。この溶融混練物をハンマーミルにて粗砕し、１ｍｍメッシュパスのトナー粗砕物を得た。さらにこの粗砕物をジェット気流を利用した衝突式粉砕機で微粉砕した後、風力分級し、重量平均径約６．７μｍのブラックトナー粒子を得た。得られたブラックトナー粒子１００重量部に対して、ＢＥＴ法による比表面積が１４０ｍ² ／ｇである疎水性シリカを１．５重量部外添し、粉砕トナーＣＣを得た。得られたトナーの物性を表４に示した。
【０２９２】
〔粉砕トナーの製造例ＤＤ〕
カーボンブラックｅのかわりに表１に示すカーボンブラックｊを用いる以外は〔粉砕トナーの製造例ＣＣ〕と同様にして粉砕トナーＤＤを得た。得られたトナーの物性を表４に示した。
【０２９３】
【表３】

【０２９４】
【表４】

【０２９５】
（感光体製造例１）
直径３０ｍｍ、長さ２５４ｍｍのアルミニウムシリンダーを基体とした。この基体に、次に示す構成の層を順次浸漬塗布により積層して、感光体１を作製した。
【０２９６】
（１）導電性被覆層：酸化錫及び酸化チタンの粉末をフェノール樹脂に分散したものを主体とする。膜厚１５μｍ。
【０２９７】
（２）下引き層：変性ナイロン及び共重合ナイロンを主体とする。膜厚０．６μｍ。
【０２９８】
（３）電荷発生層：長波長域に吸収を持つアゾ顔料をブチラール樹脂に分散したものを主体とする。膜厚０．６μｍ。
【０２９９】
（４）電荷輸送層：ホール搬送性トリフェニルアミン化合物をポリカーボネート樹脂（オストワル粘度法による分子量２万）に８：１０の重量比で溶解したものを主体とし、さらにポリ４フッ化エチレン粉体（粒径０．２μｍ）を総固形分に対して１０重量％添加し、均一に分散した。膜厚２５μｍ。
【０３００】
得られた感光体１の表面の水に対する接触角は９５度であった。
【０３０１】
接触角の測定は、純水を用い、装置は、協和界面科学（株）、接触角計ＣＡ−ＤＳ型を用いた。
【０３０２】
（感光体製造例２）
電荷輸送層にポリ４フッ化エチレン粉体（粒径０．２μｍ）を添加しなかったことを除いては感光体製造例１と同様に膜厚２５μｍの電荷輸送層を形成し、感光体２を作製した。
【０３０３】
得られた感光体２の表面の水に対する接触角は７９度であった。
【０３０４】
〈実施例１〉
図１に示す画像形成装置として６００ｄｐｉレーザービームプリンタ（キヤノン製：ＬＢＰ−８６０）を用意し、プロセススピードは、９４ｍｍ／ｓに改造した。
【０３０５】
プロセスカートリッジにおけるクリーニングゴムブレードを取りはずし、装置の帯電方式をゴムローラーを当接する接触帯電とし、印加電圧を直流成分（−１４００Ｖ）とした。プロセススピードを速めている分、感光体の均一な帯電には厳しい条件となっている。
【０３０６】
感光体としては、感光体製造例１で製造した感光体１を用いた。
【０３０７】
次に、プロセスカートリッジにおける現像部分を改造した。トナー担持体であるステンレススリーブの代わりに発泡ウレタンからなる中抵抗ゴムローラー（１６φ、硬度ＡＳＫＥＲ Ｃ４５度、抵抗１０⁵ Ω・ｃｍ）を用いて、感光体に当接させた。該トナー担持体の表面の移動方向は、感光体表面の移動方向と同方向であり、該感光体回転周速に対し１３０％となるように駆動する。
【０３０８】
トナー担持体にトナーを塗布する手段として、現像部分に塗布ローラーを該トナー担持体に当接させて設けた。さらに、該トナー担持体上にトナーのコート層制御のために樹脂をコートしたステンレス製ブレードを取付けた。現像時のトナー担持体に対して印加する現像バイアス電圧をＤＣ成分（−４５０Ｖ）のみとした。
【０３０９】
これらのプロセスカートリッジの改造に適合するよう画像形成装置の改造及びプロセス条件設定を行った。
【０３１０】
感光体帯電電位は、暗部電位を−８００Ｖとし、明部電位を−１５０Ｖとした。転写材としては７５ｇ／ｍ² の紙を用いた。
【０３１１】
重合トナーＡを用い、この画像形成装置で耐久枚数２０００枚の画出しを行ったところ、高濃度で画像汚れのない高品質の画像が得られた。定着性にもまったく問題がなかった。
【０３１２】
画像評価は、初期より印字面積比率４％の文字画像を１００枚連続プリントした後、及び２０００枚連続プリントした後の画像濃度及び画像汚れについて行った。
【０３１３】
（１）画像濃度
一辺が５ｍｍの正方形のベタ黒画像を形成し、Ｍａｃｂｅｔｈ社製画像濃度測定機ＲＤ９１８を用いて、ベタ黒画像の画像濃度を測定した。
【０３１４】
（２）画像汚れ
画像汚れの評価は、定着後の画像を目視で観察し、以下の評価基準に基づいて評価を行なった。
【０３１５】
Ａ：未発生
Ｂ：かすかに発生
Ｃ：ある程度発生
Ｄ：発生が著しく悪い
【０３１６】
さらに、初期より印字面積比率４％の文字画像を１００枚連続プリントした後の転写性、カブリ、解像度及び帯電ローラ汚れについて評価を行なった。
【０３１７】
（３）転写性
転写性はベタ黒画像形成時の感光体上の転写残トナーを、マイラーテープによりテーピングしてはぎ取り、はぎ取ったマイラーテープを紙上に貼ったもののマクベス濃度から、マイラーテープのみを紙上に貼ったもののマクベス濃度を差し引いた数値で評価した。したがって、数値の小さいほど転写性が良好である。
【０３１８】
（４）カブリ
カブリはベタ白画像形成時の感光体上の転写残トナーを、マイラーテープによりテーピングしてはぎ取り、はぎ取ったマイラーテープを紙上に貼ったもののマクベス濃度から、マイラーテープのみを紙上に貼ったもののマクベス濃度を差し引いた数値で評価した。したがって、数値の小さいほどカブリ抑制が良好である。
【０３１９】
（５）解像度
解像力は潜像電界によって電界が閉じやすく、再現しにくい図６に示す様な６００ｄｐｉの５０μｍ小径孤立ドットの再現性によって評価した。
【０３２０】
Ａ：１００個中の欠損が５個以下
Ｂ：１００個中の欠損が６〜１０個
Ｃ：１００個中の欠損が１１〜２０個
Ｄ：１００個中の欠損が２０個以上
【０３２１】
（６）帯電ローラの汚染量
帯電ローラーの汚れは、帯電ローラー上の単位面積当たりのトナー重量（ｍｇ／ｃｍ² ）を測定した。
【０３２２】
さらに２０００枚連続プリントした後の現像ローラー、感光体ドラム及び定着装置のそれぞれに対するマッチングについては、以下の通り評価を行った。
【０３２３】
（７）現像ローラーとのマッチング
プリントアウト試験終了後、現像ローラー表面への残留トナーの固着の様子とプリントアウト画像への影響を目視で評価した。
【０３２４】
Ａ：非常に良好（未発生）
Ｂ：良好（ほとんど発生せず）
Ｃ：普通（固着があるが、画像への影響が少ない）
Ｄ：悪い（固着が多く、画像ムラを生じる）
【０３２５】
（８）感光体ドラムとのマッチング
プリントアウト試験終了後、感光体ドラム表面の傷や残留トナーの固着の発生状況とプリントアウト画像への影響を目視で評価した。
【０３２６】
Ａ：非常に良好（未発生）
Ｂ：良好（わずかに傷の発生が見られるが、画像への影響はない）
Ｃ：普通（固着や傷があるが、画像への影響が少ない）
Ｄ：悪い（固着が多く、縦スジ状の画像欠陥を生じる）
【０３２７】
（９）定着装置とのマッチング
プリントアウト試験終了後、定着ローラー表面の傷や残留トナーの固着状況を目視で評価した。
【０３２８】
Ａ：非常に良好（未発生）
Ｂ：良好（わずかに固着が見られるものの、画像への影響はない）
Ｃ：普通（固着や傷があるが、画像への影響が少ない）
Ｄ：悪い（固着が多く、画像欠陥を生じる）
【０３２９】
〈実施例２〉
プロセススピードを、１２０ｍｍ／ｓにアップにすることを除いては実施例１と同様にして評価した。結果は表５に示すように、プロセススピードのアップにより、より厳しい条件となるため実施例１と比較するとやや劣るものの、概ね良好な結果であった。
【０３３０】
〈実施例３〜１４〉
トナーとして、重合トナーＢ〜Ｅ，Ｇ，Ｊ〜Ｐを使用することを除いては実施例１と同様にして評価した。結果を表５に示す。
【０３３１】
〈比較例１〉
トナーとして、重合トナーＦを使用することを除いては実施例１と同様にして評価した。結果を表５に示すように、初期から著しい画像汚れが発生し、２０００枚の連続プリントが困難であった為、やむなく途中で評価を中止した。
【０３３２】
〈比較例２及び３〉
トナーとして、重合トナーＱ及びＲを使用することを除いては実施例１と同様にして評価した。結果を表５に示すように、本発明中の特定のアゾ系鉄化合物を用いなかったり、トナーに用いたカーボンブラックが本発明中の特定のカーボンブラックではないため、良好な結果が得られなかった。
【０３３３】
〈比較例４及び５〉
トナーとして、重合トナーＳ，Ｔを使用することを除いては、実施例１と同様にして評価を行なった。結果は表５に示すように、トナーに用いた分散剤が本発明中の特定のアゾ系鉄化合物ではないため、良好な結果が得られなかった。重合トナーＳは、初期から画像濃度低下等を招いた。又、重合トナーＴは、初期こそ良好な画像濃度を示したが、２０００枚時には画像濃度の低下のみならずカブリや画像汚れが著しく悪化した。又、画像形成装置とのマッチングも十分ではなかった。
【０３３４】
〈実施例１５〜２２〉
トナーとして、重合トナーＵ〜Ｚ，ＡＡ，ＢＢを使用することを除いては、実施例１と同様にして評価を行なった。結果を表５に示す。
【０３３５】
〈参考例１〉
トナーとして、粉砕トナーＣＣを使用することを除いては実施例１と同様にして評価した。結果は表５に示すように、概ね良好な結果を得た。
【０３３６】
〈比較例６〉
トナーとして、粉砕トナーＤＤを使用することを除いては実施例１と同様にして評価した。結果は表５に示すように、初期から著しい画像汚れが発生し、２０００枚の連続プリントが困難であった為、やむなく途中で評価を中止した。
【０３３７】
【表５】

【０３３８】
〈実施例２４〜３２〉
トナーとして、重合トナーＧ〜Ｉを使用し、それぞれの外添剤（ＢＥＴ法による比表面積が１４０ｍ² ／ｇである疎水性シリカ）添加量を０．５％、１．８％、３．０％変化させたことを除いては、実施例１と同様にして評価した。結果は表６に示すように、外添剤添加量を０．５％では、カブリの増加に伴う帯電ローラー汚れがやや多く、３．０％では現像同時クリーニングは達成されるものの、定着性がやや劣るが、概ね良好な結果を得た。
【０３３９】
【表６】

【０３４０】
〈実施例３３〉
実施例１で用いた画像形成装置において、現像容器３２中のトナー塗布ローラ３５として、単層構造のスポンジローラーを用い、このトナー塗布ローラ３５に図示されていないバイアス印加手段からバイアス電圧を印加するように変更することを除いては、実施例１と同様にして画像形成を行ない評価を行なった。
【０３４１】
この現像時の現像ローラ３４に印加する現像バイアス電圧として、直流成分のみを−３００Ｖ印加し、トナー塗布ローラ３５には、塗布バイアス電圧として直流成分のみを−４８０Ｖ印加した。
【０３４２】
評価結果は、実施例１に比べて、画像濃度やカブリ抑制ともに安定して良好であり、現像同時クリーニングも達成され、優れた画像品質を得た。
【０３４３】
画像形成装置とのマッチングも良好であった。
【０３４４】
〈実施例３４〉
重合トナー製造例Ｂで製造された重合トナーＢを図４に示す画像形成装置の現像器５７に用いて画像形成を行なった。
【０３４５】
画像形成装置には、図４に示す通り、転写工程後感光体ドラム表面に存在するトナーをクリーニング除去するための第１のクリーニング部材を有するクリーナーは、転写部と現像部との間に設けられておらず、第２の転写工程後、中間転写体表面に残存するトナーを除去するためのクリーニング手段として、中間転写体表面に当接するクリーニング部材を有するクリーナーが、第２の転写部より下流側であり、第１の転写部よりも上流側に設けられている。
【０３４６】
現像器５７としては、図２及び図３に示す現像器８の構成のものを用いた。第１の転写後感光体ドラム表面に残存するトナーは、帯電部で帯電バイアスの印加により、トナーの帯電極性を負極性にそろえた後、現像時に現像部で非画像領域に存在するトナーのみ現像器中に回収させる構成にした。
【０３４７】
現像器８において、カーボンブラックを分散して抵抗を調整したシリコーンゴムからなる中抵抗ゴムローラ（１６φ）をトナー担持体９とし、感光体に当接した。トナー担持体９の表面の移動方向及び回転周速は、感光体表面との接触部分において同方向であり、該感光体回転周速に対し１５０％となるように駆動する。つまり、トナー担持体の周速は１２０ｍｍ／ｓであり、感光体表面に対する相対速度は８０ｍｍ／ｓである。
【０３４８】
トナー担持体にトナーを塗布する手段として、単層構成のスポンジローラは塗布ローラー１２として設け、該トナー担持体に当接させた。接触部において、塗布ローラー１２の表面の移動方向が、トナー担持体の移動方向と反対方向に移動するように回転させることによりトナーをトナー担持体上に塗布した。さらに、該トナー担持体上トナーのコート層制御のために、樹脂をコートしたステンレス製ブレード１６を取付けた。
【０３４９】
感光体としては（感光体製造例１）で製造した感光体１を用い、トナーはトナーＢを用い、以下の現像条件及び転写条件を満足するよう画像形成条件を設定した。
【０３５０】
感光体暗部電位：−７００Ｖ
感光体明部電位：−１５０Ｖ
現像ローラーに印加する現像バイアス：−４５０Ｖ（直流成分のみ）
トナー塗布ローラー印加するバイアス：−３００Ｖ（直流成分のみ）
第１の転写工程で中間転写体に印加する転写バイアス：３５０Ｖ（直流成分のみ）
第２の転写工程で転写ローラーに印加する転写バイアス：１１００Ｖ（直流成分のみ）
【０３５１】
上記の画像形成条件によって、記録材上に転写されたトナー画像は、以下の加熱定着装置によって、記録材に加熱定着した。
【０３５２】
加熱定着装置７０にはオイル塗布機能のない熱ロール方式の定着装置を用いた。この時上部ローラー６８、下部ローラー６９共にフッ素系樹脂の表面層を有するものを使用し、ローラーの直径は６０ｍｍであった。また、定着温度は１５０℃、ニップ幅を７ｍｍに設定した。
【０３５３】
上記の構成の画像形成装置を用いて、２０００枚の連続画出し試験を行なったところ、高濃度で画像汚れのない高品位の画像が得られた。
【０３５４】
又、帯電ローラー上のトナー付着重量は０．４１ｍｇ／ｃｍ² と軽微であり、その他の画像形成装置とのマッチングも良好であった。
【０３５５】
（実施例３５）
重合トナーＡにキャリアを混合して二成分系現像剤を調製し、図５及び図６に示す画像形成装置に、この二成分系現像剤を用いてプロセススピード１８０ｍｍ／ｓｅｃで画像形成を行なったところ高濃度で画像汚れのない高品質の画像が得られた。また定着性にもまったく問題がなかった。
【０３５６】
画像評価は、初期より印字面積比率４％の文字を１００枚連続プリントした後、１００枚めの画像濃度及び画像の帯電不良による画像汚れを評価し、さらに帯電ローラー単位表面積〔ｃｍ² 〕あたりのトナー付着量〔ｍｇ〕（帯電ローラー汚染量）を測定した。印字比率４％文字を２０００枚プリントした後にも、画像濃度及び画像汚れを評価した。
【０３５７】
さらに、初期より印字面積比率４％の文字を１００枚連続プリントした後の転写性、カブリ、及び解像度について評価した。
【０３５８】
上記の画像濃度、画像汚れ、帯電ローラー汚染量、転写性、カブリ及び解像度についての評価は、実施例１と同様にして評価を行なった。
【０３５９】
上記の二成分系現像剤のキャリアとしては平均粒径６０μｍの表層をシリコーン系樹脂でコートしたフェライトキャリアを用い、トナー濃度は７％に設定した。
【０３６０】
評価結果を表７に示す。
【０３６１】
〈実施例３６〉
感光体として、感光体製造例２の感光体を使用する以外は実施例３５と同様にして評価した。結果は表７に示すように、実施例３５と比較するとやや劣るものの、概ね良好な結果を得た。
【０３６２】
〈実施例３７〜４０〉
トナーとして、重合トナーＢ〜Ｅを使用する以外は実施例３５と同様にして評価した。結果は表７に示すように、概ね良好な結果を得た。
【０３６３】
〈比較例７〉
トナーとして、重合トナーＦを使用する以外は実施例３５と同様にして評価した。結果は表７に示すように、本発明中の特定のアゾ系鉄錯体化合物を含有しないため、帯電部材をトナーが著しく汚染し、帯電不良による著しい画像不良となった。
【０３６４】
【表７】

【０３６５】
【発明の効果】
本発明においては、特定のカーボンブラックと特定のアゾ系鉄錯体化合物を併用したことによるカーボンブラックの良好な分散による荷電制御効果と、アゾ系鉄錯体化合物自体の過剰な帯電を抑制する荷電制御効果の相乗効果によって、過剰な帯電が抑制されたトナー担持体上でのトナーの良好な帯電制御性により、優れた現像特性が得られる。
【０３６６】
さらに、現像同時クリーニング方式を用いる場合に、感光体上の転写残トナーの帯電部材による帯電極性制御及び帯電量制御がより確実に且つ均一になされ、現像工程での転写残トナーのより安定した回収性と現像性を得ることができる。
【０３６７】
さらに、プロセススピードの速い画像形成方法に対しても、現像同時クリーニングプロセスを補助部材を付加することなく低コストで適用できる。
【図面の簡単な説明】
【図１】本発明の画像形成方法の一例として用いた、接触一成分現像装置を用い、かつ現像同時クリーニング方式を採用した画像形成装置を模式図に示した図である。
【図２】本発明の画像形成方法のさらに他の例として用いた、接触一成分現像装置を用いた画像形成方法を模式図に示した図である。
【図３】図２に示す画像形成装置の現像器の拡大図である。
【図４】中間転写体を用いた画像形成装置を模式的に示した図である。
【図５】本発明の画像形成方法の一例として用いた、磁気ブラシ現像用二成分系現像剤を使用する接触二成分現像装置を用い、かつ現像同時クリーニング方式を採用した画像形成装置を模式的に示した図である。
【図６】図５の現像部の拡大図である。
【図７】現像度を評価するための孤立ドットパターンの説明図である。
【図８】本発明に係わるカーボンブラック及びアゾ系鉄錯体化合物をスチレン中で分散したときの粘度変化を示す図である。
【図９】本発明に係わるカーボンブラックにおいて、一定量のアゾ系鉄錯体化合物を添加しスチレン中で分散したときのカーボンブラックの吸油量と粘度の関係を示す図である。
【図１０】ワックス成分を内包しているトナー粒子の断面の一例を示す模式図である。
【図１１】現像ローラーの電気抵抗値を測定する為の測定装置の概略的説明図である。
【符号の説明】
１ 現像剤担持体
２ 感光体（像担持体）
４ 転写材
５ 帯電ブラシローラー
１３ 非磁性ブレード
１５ 現像器
２０ 二成分系現像剤
２４ 磁石
３０ トナー
３１ 帯電ロラー
３２ 現像容器
３３ トナー規制ブレード
３４ トナー担持体（弾性ローラー）
３５ トナー塗布ローラー
３６ 感光体（像担持体）
３７ 転写ローラー
３８ 転写材
４０ レーザー光（露光）
４１，４２ バイアス印加手段
４３ 定着器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method using an electrophotographic method, an electrostatic recording method, or a magnetic recording method. More specifically, the present invention relates to an image forming method used in an image forming apparatus such as a copying machine, a printer, or a fax machine that forms a toner image on a photosensitive member and then transfers the toner image onto a transfer material to form an image.
[0002]
[Prior art]
Conventionally, a number of methods are known as electrophotographic methods. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the electric latent image is converted into a toner. The image is developed with a visible image, and if necessary, the 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 fixed image. is there. At this time, the toner remaining on the photoreceptor without being transferred to the transfer material after the transfer is cleaned by various methods.
[0003]
As a method for visualizing an electric latent image, a cascade development method, a magnetic brush development method, a nonmagnetic one-component development method, and a pressure development method are known. Furthermore, a magnetic one-component developing method is also used in which a magnetic toner is used and a rotating sleeve having a magnetic pole at the center is used to fly between the photosensitive member and the sleeve by an electric field.
[0004]
LED and LBP printers have become the mainstream in the recent market, and the direction of technology is higher resolution, that is, what is conventionally 240 dpi or 300 dpi has become 400 dpi, 600 dpi, or 1200 dpi. Accordingly, the development method is also required to have higher definition. Copiers are also becoming more sophisticated, and are therefore moving toward digitalization. In the digital system, since a method of forming an electrostatic charge image with a laser is mainly used, the resolution is still high, and therefore, a high resolution and high definition development system is required like a printer.
[0005]
For this reason, the toner particle size has been reduced, and Japanese Patent Application Laid-Open Nos. 1-112253, 1-1191156, 2-214156, 2-284158, and 3-181955. No. 4-162048 proposes a toner having a specific particle size distribution and a small particle size.
[0006]
Conventionally, the toner image formed on the photoconductor in the development process is transferred to a transfer material in the transfer process, but the transfer residual toner remaining on the photoconductor is cleaned in the cleaning process, and the toner is stored in the waste toner container. . For this cleaning process, conventionally, cleaning methods such as blade cleaning, fur brush cleaning, and roller cleaning have been used. In any of the cleaning methods, a cleaning member is brought into contact with the surface of the photosensitive member to mechanically scrape off or remove the residual toner after transfer, and collect it in a waste toner container. Therefore, all of these cleaning methods have problems caused by the pressing of the cleaning member against the surface of the photosensitive member, for example, the pressing of the cleaning member strongly causes the photosensitive member to wear and shorten the life of the photosensitive member. It was. From the standpoint of the apparatus, since the apparatus is inevitably enlarged in order to have such a cleaning apparatus, it has become a bottleneck when aiming to make the apparatus compact.
[0007]
Furthermore, from the viewpoint of ecology, a system that does not use waste toner in the sense of effective use of toner, and a system that has excellent fixing properties and offset resistance from the viewpoint of energy saving have been desired.
[0008]
The disclosure of a technique called conventional simultaneous cleaning or cleanerless has focused on positive memory and negative memory due to the influence of residual toner on the image as disclosed in Japanese Patent Laid-Open No. 5-2287. . However, as the use of electrophotography progresses, it is necessary to transfer toner images to various transfer materials. In this sense, the transfer images are not satisfactory.
[0009]
Prior arts that disclose technologies related to cleanerless are disclosed in JP 59-133573, JP 62-203182, JP 63-133179, JP 64-20587. No. 2, JP-A-2-302277, JP-A-5-2289, JP-A-5-53482, and JP-A-5-61383, all of these prior arts are desirable for image formation. It does not describe the method, nor does it mention the toner composition.
[0010]
Further, in the development simultaneous cleaning that essentially does not have a cleaning device, it is essential to have a structure in which the surface of the photoreceptor is rubbed with toner and a toner carrier, and for this reason, toner deterioration due to long-term use, toner carrier surface deterioration, Since the surface of the photoreceptor is deteriorated or worn, and the durability is easily deteriorated, the prior art cannot sufficiently solve the problem, and it has been desired to achieve both the fixing property and the durability. At the same time, where speeding up of image formation is desired at the same time, in the simultaneous development cleaning of a device with a faster process speed, charge control of the residual toner before recovery for improving the recoverability of the residual toner during development, and control of the recovered toner In terms of maintaining the stability of development during reuse, the prior art does not provide a sufficient solution.
[0011]
Japanese Patent Laid-Open No. 3-259161 provides a non-magnetic one-component developer in which a shape factor, a specific surface area, and a particle size are defined. However, the developer defined in this prior art has insufficient durability. Met.
[0012]
Japanese Patent Application Laid-Open No. 61-279864 proposes a toner that defines shape factors SF-1 and SF-2. However, this prior art has no description about the transfer, and as a result of reexamining the examples, the transfer efficiency is low and further improvement is required.
[0013]
Japanese Patent Application Laid-Open No. 63-235953 proposes a magnetic toner that is spheroidized by a mechanical impact force. However, in this prior art, the transfer efficiency is still insufficient and further improvement is required.
[0014]
In recent years, from the viewpoint of environmental protection, in a conventional primary charging process and transfer process using corona discharge, a contact charging method in which charging is performed by bringing a charging member into contact with the surface of the photoreceptor, and transfer to the surface of the photoreceptor A contact transfer method in which transfer is performed by bringing a transfer member into contact with each other through a material is becoming mainstream.
[0015]
Such a contact charging method and a contact transfer method are proposed in, for example, Japanese Patent Laid-Open Nos. 63-149669 and 2-123385. In these methods, a conductive elastic roller is brought into contact with the photosensitive member, and the photosensitive member is uniformly charged while a voltage is applied to the conductive roller. A transfer material is passed while pressing another conductive roller to which a voltage is applied, and a toner image on the photoreceptor is transferred to the transfer material, and then a copy image is obtained through a fixing step.
[0016]
However, in such a contact transfer method, the transfer member is brought into contact with the photoconductor via the transfer material at the time of transfer, so that the toner image is formed when the toner image formed on the photoconductor is transferred to the transfer material. There arises a problem of partial transfer failure, which is referred to as a so-called “transfer dropout”.
[0017]
Furthermore, as the diameter of the toner decreases, the adhesion force (such as mirror image force and van der Waals force) of the toner particles to the photosensitive member becomes larger than the clonal force applied to the toner particles during transfer, resulting in a residual transfer. There was a tendency for toner to increase.
[0018]
Therefore, the toner and the photoreceptor used in such an image forming method are required to have excellent releasability.
[0019]
In order to improve the releasability of the toner from the photoconductor and improve the transferability of the toner, it is possible to use a nearly spherical toner manufactured by suspension polymerization. No. 5,659,857). Toners produced by the suspension polymerization method have been proposed for a long time (for example, Japanese Patent Publication No. 36-10231). In this suspension polymerization method, a monomer composition is prepared by uniformly dissolving or dispersing a polymerizable monomer and a colorant (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives). After the monomer composition is prepared, the monomer composition is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer by using a suitable stirrer, and a polymerization reaction is performed to obtain a toner having a desired particle size. Particles are obtained.
[0020]
In this suspension polymerization method, droplets of the monomer composition are generated in a dispersion medium having a large polarity such as water. Therefore, the component having a polar group contained in the monomer composition is an interface with the aqueous phase. Thus, it is possible to produce a spherical toner having a so-called core / shell structure or sea-island structure in which a non-polar component does not exist in the surface layer portion.
[0021]
The toner by the polymerization method has been able to satisfy both the low-temperature fixing property and the anti-blocking property and the high-temperature offset-resistant property by embedding the wax component as a release agent.
[0022]
When such a toner is used, it is difficult to expose the colorant to the surface, and there is an advantage that the toner has uniform triboelectric chargeability. Furthermore, since the classification process can be omitted, the manufacturing cost reduction effect such as energy saving, time reduction, and process yield improvement is great.
[0023]
However, since the shape of the toner obtained by this polymerization method is substantially spherical, a simultaneous development cleaning system in which the cleaning process for removing the transfer residual toner from the surface of the photoreceptor is performed simultaneously with the development process at the time of development is used. When this spherical polymerized toner is applied to a conventional image forming method, the external additive tends to be buried in the toner surface when used for a long time, and the chargeability of the toner is lowered. In many cases, image quality was degraded. In particular, this development becomes more remarkable as the process speed of the developing roller becomes higher.
[0024]
It is also widely known that carbon black is contained as a black colorant in a toner. Carbon black is known to have a significant influence on its dispersibility due to its physical properties such as primary particle size, specific surface area, structure structure, and surface properties (functional groups on the surface, etc.). It is also known that the selection greatly affects the toner characteristics.
[0025]
For example, carbon black is very difficult to disperse because it has a small primary particle size, a large specific surface area, and a structure structure compared to other pigments. If the dispersibility of the carbon black in the toner particles is insufficient, the chargeability of the toner is impaired, and fogging occurs at the time of development. In addition, an image for reducing the coloring power of the toner particles Other adverse effects such as low density or increased toner consumption also occur.
[0026]
When the toner is prepared using carbon black as a pigment in the polymerization method, a further problem occurs.
[0027]
First, carbon black has a functional group that inhibits the polymerizability of the monomer, such as a quinone group, on the surface. Therefore, when a toner is produced by a polymerization method, the polymerization rate becomes slow and the degree of polymerization does not increase. Particles become unstable at the time of granulation, causing aggregation and coalescence, making it difficult to take out as particles.
[0028]
Secondly, a monomer composition is prepared by uniformly dissolving or dispersing a polymerizable monomer and carbon black (further, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives). At this time, carbon black is difficult to disperse in the monomer composition, and when the toner composition is produced by suspending and dispersing the monomer composition in a hydrogen medium, the carbon black is unevenly distributed in the toner particles, Toner particles not containing carbon black are easily generated.
[0029]
Third, since carbon black is conductive, the charge on the surface of the toner is likely to leak, greatly affecting the chargeability of the toner. Variation in the carbon black content, dispersibility, and presence / absence of aggregation for each toner particle results in variation in the chargeability of the toner particles, which causes a decrease in development efficiency and an increase in fog.
[0030]
Such carbon black content between each toner particle, dispersion of dispersion and aggregation, uneven distribution within the particle, toner particles having a much higher charge amount and toner particles having a lower charge amount than the desired charge amount. As a result, toner chargeability becomes unstable.
[0031]
It is also known to contain an azo-based iron complex compound as a charge control agent in the toner.
[0032]
Japanese Patent Laid-Open No. 7-281485 proposes a suspension polymerization toner in which a specific azo-based iron complex compound is contained in a toner and the chargeability is improved by a nonmagnetic one-component development method. However, carbon black that greatly affects the polymerizability and chargeability of the toner has not been studied.
[0033]
Furthermore, in the image development method of the simultaneous development cleaning system, there has not yet been found a prior art that sufficiently solves the problems in using the toner containing carbon black.
[0034]
[Problems to be solved by the invention]
A further object of the present invention is to provide an image forming method which essentially does not have a cleaning device.
[0035]
The object of the present invention is to provide an image forming method using the simultaneous development cleaning structure, and has extremely good transferability to various transfer materials such as plain paper, cardboard and transparent film for overhead projectors. An object of the present invention is to provide an image forming method capable of designing a system with a wide latitude in a transfer process.
[0036]
An object of the present invention is to provide an image forming method which is excellent in transferability, has little transfer residual toner, and does not cause transfer loss even in a contact transfer method, or in which development thereof is suppressed.
[0037]
An object of the present invention is to provide an image having durability capable of smoothly recovering untransferred toner during development even when applied to a higher-speed image forming process and stably realizing a high-quality image over a long period of time by stable development performance. It is to provide a forming method.
[0038]
An object of the present invention is to provide an image forming method capable of obtaining a stable image over a long period of time without causing defective charging even in a contact charging method using a contact charging member.
[0039]
[Means for Solving the Problems]
The above object is achieved by the following configurations of the present invention.
[0040]
The present invention relates to a charging step for charging an image carrier for carrying an electrostatic latent image; an exposure step for forming an electrostatic latent image on the charged image carrier by image exposure; And developing the toner image to form a toner image; and transferring the toner image formed on the surface of the image carrier to a transfer material; and after the transfer step, the surface of the image carrier In the image forming method using the simultaneous development cleaning method in which the developing device also serves to collect the remaining toner in the developing step, the toner contains at least a binder resin, carbon black, and an azo-based iron compound. It has toner particles and inorganic fine powder, the carbon black has an average primary particle size of 25 to 80 nm, and the azo-based iron compound has the following general formula (1)
[0041]
[Outside 2]

[Where X₁And X₂Represents a member selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group and a halogen atom,₁And X₂Are the same or different, m and m ′ represent an integer of 1 to 3, and R₁And R₃Is a hydrogen atom, C₁~ C₁₈Alkyl group of₂~ C₁₈Alkenyl group, sulfonamide group, mesyl group, sulfonic acid group, carboxyester group, hydroxy group, C₁~ C₁₈A member selected from the group consisting of an alkoxy group, an acetylamino group, a benzoylamino group and a halogen atom,₁And R₃Are the same or different, n and n ′ represent an integer of 1 to 3, and R₂And R₄Represents a hydrogen atom or a nitro group, and A⁺Represents a cation ion selected from the group consisting of ammonium ion, hydrogen ion, sodium ion, potassium ion and mixed ions thereof. Having a compound represented byThe toner particles are produced by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer, the carbon black, and the azo-based iron compound in an aqueous medium. The polymerizable monomer composition was prepared by mixing a dispersion obtained by dispersing the carbon black and the azo-based iron compound in the first polymerizable monomer with at least the second polymerizable monomer. IsThe present invention relates to an image forming method.
[0042]
According to the present invention, a toner using a specific azo-based iron compound as a toner composition and carbon black having a specific physical property can quickly start up toner charging, and a high-quality image can be obtained. When the cleaning process for removing the transfer residual toner from the surface of the image carrier is applied to an image forming method using a simultaneous development cleaning method performed simultaneously with the development process in the developing unit, the toner transfer efficiency is improved, Inhibition of charging of the image carrier due to the transfer residual toner can be sufficiently suppressed, and the transfer residual toner can be smoothly collected during development to obtain stable development performance.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
As the developing device used in the image forming method of the present invention, (i) as a developer carrying member for carrying a two-component developer having toner and carrier, a developing sleeve containing a magnet is used, and this developing sleeve is used. A two-component contact development method in which a two-component developer is carried on the surface, and development is performed by bringing a magnetic brush formed by the two-component developer into contact with the surface of the photoreceptor as an image carrier, or (ii) one An elastic roller is used as a toner carrier for carrying toner as a component developer, and a toner layer is formed by coating the surface of the elastic roller with a toner, and this toner layer is used as an image carrier. A one-component contact development method in which development is performed in contact with the substrate can be used.
[0044]
In the one-component contact development method, the toner may be either magnetic or non-magnetic, and it is important that the toner layer is in contact with the photoreceptor surface. It is preferable that the toner carrier is substantially in contact with the surface of the photosensitive member, which means that the toner carrier is in contact with the surface of the photosensitive member when the toner layer is removed from the toner carrier. means. At this time, in order to obtain an image having no edge effect by an electric field acting between the photosensitive member and the elastic roller facing the surface of the photosensitive member via the toner, the elastic roller surface or the vicinity of the surface has a potential, An electric field needs to be formed between the surfaces of the toner carrier. For this reason, the elastic layer formed of elastic rubber on the surface of the low resistance core material of the elastic roller is controlled in resistance to the middle resistance region to prevent electric conduction with the surface of the photoconductor, or the low resistance conductive It is also possible to use a thin dielectric layer on the surface layer of the conductive roller. Furthermore, a configuration in which the surface side facing the surface of the photoreceptor is coated with an insulating material on a conductive roller, or a configuration in which a conductive layer is provided on the inner surface side not facing the photoreceptor with an insulating sleeve is also possible.
[0045]
When the one-component contact development method is used, the surface of the developing roller as the toner carrying member for carrying the toner and the surface of the photosensitive member may be rotated in the same direction or in the opposite direction. Good. When the rotation direction is the same direction, the peripheral speed on the surface of the developing roller is preferably larger than 100% in terms of the peripheral speed ratio with respect to the peripheral speed of the photosensitive member. If it is 100% or less, there is a problem in image quality such as poor line cut. The higher the peripheral speed ratio, the more toner is supplied to the development site, the more frequently the toner is desorbed from the latent image, and the unnecessary parts are scraped off and applied to the necessary parts. Thus, an image faithful to the latent image can be obtained.
[0046]
In the present invention, a simultaneous development cleaning system is used in which a cleaning process for removing transfer residual toner that is not transferred in the transfer process and exists on the surface of the image carrier is performed simultaneously with the development process during development.
[0047]
In the simultaneous development cleaning system, in order to remove the transfer residual toner existing on the surface of the image carrier by contacting the surface of the image carrier between the transfer unit and the charging unit and between the charging unit and the development unit. The cleaning member is not provided.
[0048]
The charge of the untransferred toner varies greatly depending on the transfer bias condition and the resistance of the transfer material. In general, a voltage having a polarity opposite to the charging polarity of the toner is applied to the transfer bias. However, when the development is normal development (the toner charging polarity and the photosensitive member charging polarity are reversed), the transfer material is a thick paper, an OHT film, or the like. If the toner has a high resistance, the toner particles having a high charge are not transferred due to strong adhesion to the photosensitive member, and proceed to the cleaning step with the same charging polarity, so that the cleaning cannot easily be completed.
[0049]
Therefore, as the toner, it is preferable that the charge amount of the developed toner on the photoconductor is appropriately controlled, and the toner having the originally high charge amount is not developed on the photoconductor.
[0050]
In order to prevent a high charge amount toner from being developed on the photosensitive member, it is necessary to prevent the toner from being charged or to prevent the toner from being charged. Detrimental effects such as reduction are likely to occur.
[0051]
By using a toner in which the specific carbon black of the present invention and a specific azo-based iron compound are used in combination, it is possible to suppress the generation of excessively charged toner particles and to give the toner an appropriate charge amount. became. As a result, stable performance excellent in durability is exhibited even in the development process. This is because the charge control effect due to the good dispersion of the carbon black of the toner in which the specific carbon black of the present invention and the specific azo iron compound are used, and the charge control effect that suppresses excessive charging of the azo iron compound itself. This is considered to be a synergistic effect.
[0052]
When the development is reversal development (the toner charging polarity and the photosensitive member charging polarity are the same polarity), if the transfer material is easy to pass an electric field like thin paper, toner particles that are strongly charged to the reverse polarity by the transfer bias can be formed. The toner particles that are strongly charged with the opposite polarity still have a strong adhesion to the photoconductor and cannot be easily cleaned.
[0053]
On the other hand, it is possible to suppress the generation of toner particles that are excessively charged with a reverse polarity by using the toner in which the specific carbon black of the present invention and the specific azo-based iron compound are used in combination.
[0054]
The toner charging control by the transfer bias also includes the charge control effect by the good dispersion of the carbon black due to the combination of the specific carbon black of the present invention and the specific azo iron compound, and the excessive charging of the azo iron compound itself. It is thought to be brought about by the synergistic effect of the charge control effect to suppress.
[0055]
Although these reasons are not necessarily clear, according to the knowledge of the present inventors, the specific azo-based iron compound used in the present invention causes the toner to have an excessively high charge amount (so-called charge-up phenomenon). In addition to making it difficult for the toner particles to retain excessive reverse charge even when a toner polarity and a reverse electric field are applied in the transfer process, the azo-based iron compound also functions as a dispersant. As a result of the improved dispersibility of carbon black, it is considered that the triboelectric charge amount of each toner particle becomes uniform.
[0056]
The principle of the simultaneous development cleaning system is to control the charge polarity and charge amount of the toner on the photoreceptor in each electrophotographic process and to use a reversal development method.
[0057]
For example, when a negatively charged photoconductor and a negatively charged toner are used, in the transfer process, an image visualized by a positive polarity transfer member is transferred to a transfer material. Depending on the relationship between the type of transfer material (difference in thickness, resistance, and dielectric constant) and the image area, the charge polarity of the residual toner varies from positive to negative. However, the negatively charged charging member for charging the negatively chargeable photoconductor causes the surface of the photoconductor and even the residual toner to be transferred to the negative side even if the toner remains in the positive polarity in the transfer process. Charge polarity can be made uniform. Therefore, even if toner particles that are uniformly negatively charged at the time of development are present on the surface of the photosensitive member, if reversal development is used as the development method, the negatively charged transfer residual toner is not developed in the toner. The dark portion potential that should remain in the bright portion potential that should not be developed is attracted toward the toner carrier due to the development electric field and does not remain.
[0058]
However, when image development at a higher process speed is performed using the simultaneous development cleaning method, the surface of the photoconductor is charged by the charging member in correlation with a decrease in the charging time per unit surface area of the photoconductor. At the same time, it is difficult to make the charging polarity of the toner remaining after transfer uniform. Therefore, when reversal development is used as a developing method, it becomes difficult for the transfer residual toner on the dark portion potential that should not be developed by the toner to be attracted toward the toner carrier by the developing electric field and collected. Furthermore, even if the toner carrier is recovered by mechanical force such as rubbing, if the charge of the transfer residual toner is not uniform, the chargeability of the toner on the toner carrier will be adversely affected, and the development characteristics Reduce.
[0059]
By controlling the charging polarity of the residual toner at the same time as the charging of the photoconductor, an image forming method using the simultaneous development cleaning method is established. However, when an image forming method using the simultaneous development cleaning method is applied to image formation at a higher process speed as described above, it becomes difficult to control the charge polarity of the residual toner after transfer, which causes poor recovery during development. This is likely to occur, and the speed of development itself is also increased. Therefore, there is a problem in that charging of transfer residual toner collected in the development process greatly affects the development characteristics, and the development performance is likely to deteriorate.
[0060]
Furthermore, in the image formation at a high process speed, when the simultaneous development cleaning method is used, charging failure due to contamination of the charging member is likely to occur.
[0061]
According to the study by the present inventors, in the image forming method using the simultaneous development cleaning method in the image formation at a higher process speed of 120 mm / sec or more, more preferably 150 mm / sec or more, the development speed is 120 mm / sec or more. In order to improve the recoverability of the transfer residual toner at the time, the charge polarity control must be performed more rapidly, and in order to maintain the development performance, the transfer residual toner is more surely and uniformly when passing through the charging member. It has been found that the charge polarity must be controlled.
[0062]
In particular, in the so-called contact charging method in which charging is performed by bringing a charging member into contact with the photosensitive member, the charging member is in contact with the photosensitive member by using discharge according to the so-called passion law as the charging mechanism. In addition, adhesion to the charging member is also deteriorated due to toner deterioration due to discharge energy.
[0063]
In the conventional pre-development cleaning method, the toner remaining on the transfer is cleaned from the photosensitive member by a cleaning member such as a blade or a fur brush, and the toner existing on the photosensitive member is charged by a developing device. In the past, no consideration has been made in consideration of the recovery performance of the toner and the influence on the development performance when the toner is collected and reused in the developing device.
[0064]
The present inventors have diligently studied various toners, and in the image forming method using the simultaneous development cleaning method, the charge control characteristics when the toner passes through the charging member are closely related to the durability characteristics and the image quality characteristics. Finding that there is a connection, especially in toners containing carbon black, by using a specific carbon black and a specific azo-based iron compound together, the charge control characteristics when the toner passes through the charging member is improved. The present invention has been found.
[0065]
One of the features of the image forming method of the present invention is that a toner using a combination of carbon black having a particle size of 25 to 80 nm and a specific azo-based iron compound is used.
[0066]
The present inventors use a toner containing a specific carbon black and a specific azo-based iron compound for simultaneous development cleaning and a cleanerless image forming method, thereby controlling the charge polarity of the transfer residual toner on the photosensitive member by a charging member. In addition, the inventors have found that the charge amount control can be performed more reliably and uniformly, and more stable recoverability (cleanability) and development characteristics of the transfer residual toner in the development process can be obtained.
[0067]
The reason for this is not necessarily clear, but according to the knowledge of the present inventors, the specific azo-based iron compound used in the present invention has an abnormally high charge amount (so-called charge-up phenomenon). Due to the effect of preventing the toner polarity even if a reverse electric field is applied to the polarity of the toner in the transfer process, it is difficult for the toner to retain an excessive reverse electric field, and the azo-based iron complex compound also functions as a dispersant. The effect of improving the dispersibility of the toner is considered to be due to a combination of improving the charging uniformity for each toner particle.
[0068]
When the average primary particle size of carbon black is smaller than 25 nm, when used in combination with the azo-based iron compound used in the present invention, the primary particle size is fine, so that it is difficult to obtain sufficient dispersion and the effects of the present invention can be obtained. Absent. Furthermore, when toner particles are produced by a suspension polymerization method, the toner particle size tends to become coarser and difficult to use.
[0069]
If the average primary particle size of the carbon black is larger than 80 nm, there is a disadvantage that only a low density image can be obtained or the toner consumption is increased due to insufficient coloring power as a toner even when dispersed well. Will occur.
[0070]
In the present invention, the average primary particle size of carbon black is preferably 25 to 55 nm, and more preferably 35 to 55 nm. When used in combination with the specific azo iron compound of the present invention, if the particle size of the carbon black is within this range, the charge polarity and charge amount of the transfer residual toner by the charging member can be controlled more reliably and uniformly. It is more advantageous in terms of the stability of the charge amount and the toner coloring power.
[0071]
The average primary particle size of carbon black in the toner in the present invention can be measured by taking a photograph enlarged with a transmission electron microscope.
[0072]
The carbon black used in the present invention preferably has a DBP oil absorption of 40 to 150 ml / 100 g, more preferably 50 to 140 ml / 100 g.
[0073]
When a short carbon black structure with a DBP oil absorption of less than 40 ml / 100 g is used, the charge amount of the toner tends to be too low, and when the DBP oil absorption exceeds 150 ml / 100 g, the carbon has a strong long structure. It is difficult to obtain a fine dispersion of black.
[0074]
The DBP oil absorption of carbon black is measured according to “ASTM method D2414-79”.
[0075]
The carbon black used in the present invention has a specific surface area of 100 m by nitrogen adsorption.²/ G or less, preferably 30 to 90 m²/ G, more preferably 40 to 90 m²The volatile content is 2% or less, preferably 0.1 to 1.8%, and more preferably 0.1 to 1.7%. The carbon black according to the present invention has a smaller specific surface area and a smaller volatile content than the carbon black commonly used in toners.
[0076]
Carbon black having a small specific surface area and a small amount of volatile matter has the advantage of low polymerization inhibition because it has few functional groups having polymerization inhibition, and is also advantageous for uniform dispersion of carbon black in the toner.
[0077]
Specific surface area of carbon black by nitrogen adsorption is 100m²When it exceeds / g, polymerization inhibition tends to occur. If the volatile content of carbon black exceeds 2%, a large number of polymerization-inhibiting functional groups are present on the surface, which is not preferable.
[0078]
The measurement of the specific surface area by nitrogen adsorption of carbon black is performed according to “ASTM method D3037-78”.
[0079]
The volatile content of carbon black is measured in accordance with “JIS K 6221-1982”. Specifically, first, carbon black as a measurement sample is struck into a platinum crucible or a magnetic crucible having the same shape and capacity as a drop lid, and packed to the extent that it does not exceed 2 mm below the lid, and its mass is measured. Cover it, put it in an electric furnace, heat it at 950 ± 25 ° C for exactly 7 minutes, take it out, let it cool to room temperature in a desiccator, measure the mass after heating, and calculate the volatile content by the following formula. Ask.
[0080]
[Outside 3]

V: Volatile content (%)
W_D: Weight of dried sample before heating (g)
W_R: Mass of dried sample after heating (g)
[0081]
When the toner is produced by a polymerization method, it is possible to disperse the carbon black at a higher concentration by performing a master batch process of pre-dispersing the carbon black according to the present invention and the azo-based iron complex compound in the polymerizable monomer. Therefore, it is preferable because shearing force is easily applied and the effect of improving dispersibility is increased.
[0082]
FIG. 8 shows the viscosity change of the dispersion when the carbon black and the azo iron compound according to the present invention are dispersed in a styrene monomer. As is clear from the figure, the addition of the azo-based iron compound dramatically increases the viscosity of the dispersion, indicating that the carbon black is stably dispersed with a high shear force.
[0083]
FIG. 9 shows the relationship between the oil absorption of carbon black and the viscosity of the dispersion when a certain amount of azo-based iron compound is added and dispersed in styrene monomer in carbon black having a particle size of 25 to 80 nm. From this figure, it is shown that carbon oil having a high oil absorption of 40 ml / 100 g or higher has a higher dispersion viscosity and better dispersibility. However, when the oil absorption of carbon black exceeds 150 ml / 100 g, the viscosity of the dispersion becomes too high, and the granulation property during polymerization tends to be impaired.
[0084]
According to the study by the present inventors, the content A [wt%] of the carbon black and the azo-based iron complex compound B [wt%] with respect to the weight of the toner particles are preferably as follows.
2 ≦ A / B ≦ 35
It is good to satisfy, more preferably the following conditions
3 ≦ A / B ≦ 35
Good to meet.
[0085]
If the content of the azo-based iron compound is too small with respect to the content of carbon black, the viscosity does not increase as is apparent from FIG. 7, and the carbon black is not stably dispersed. In this case, carbon black precipitates with the passage of time, and when a toner is produced using this dispersion, the coloring power does not increase.
[0086]
If the content of the azo-based iron compound is too large with respect to the carbon black content, the azo-based iron compound causes secondary aggregation, dispersibility decreases, and this secondary aggregate causes polymerization inhibition, resulting in toner. It becomes difficult to produce the particles well.
[0087]
In the present invention, the carbon black content of the toner particles is preferably 0.1 to 30% by weight, more preferably 1 to 20% by weight, and still more preferably 3 to 15% by weight.
[0088]
In the present invention, the content of the azo iron compound in the toner particles is preferably 0.01 to 20% by weight, more preferably 0.1 to 10% by weight, still more preferably 0.1 to 3.0% by weight. It is good to be.
[0089]
When the content of carbon black in the toner particles is less than 0.1% by weight, the coloring power as a toner is low, and it is difficult to obtain a high image density. It is not preferable. On the other hand, if it exceeds 30% by weight, even if the azo-based iron compound used in the present invention is used, the dispersibility of the carbon black is not sufficiently uniform, and fog and toner scattering tend to occur. When the content of the azo-based iron compound in the toner particles is less than 0.01% by weight, the dispersion viscosity is likely to increase, and the effect of improving the dispersibility of the carbon black is not sufficiently exhibited. On the contrary, the viscosity of the dispersion liquid is lowered, and the effect of improving the dispersibility of carbon black is lowered.
[0090]
As described above, the present inventors have used carbon black having a proper structure in a specific oil absorption range, a small specific surface area, and a small volatile content in combination with a specific azo-based iron complex compound, thereby transferring It has been found that the toner can be improved in charge control characteristics when the toner passes through the charging member.
[0091]
By applying the toner thus obtained, in the simultaneous development cleaning method with a higher process speed, the toner can be more reliably and uniformly charged with polarity control when passing through the photosensitive member charging member. Therefore, even if a part of the toner is recovered as a residual transfer toner after being recovered by development and reused for development, a high-quality image can be obtained without adversely affecting the development characteristics. It can be realized stably.
[0092]
The azo-based iron compound used in the present invention has a structure represented by the following formula (1).
[0093]
[Outside 4]

[Where X₁ And X₂ Represents a member selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group and a halogen atom,₁ And X₂ Are the same or different, m and m ′ represent an integer of 1 to 3, and R₁ And R_Three Is a hydrogen atom, C₁ ~ C₁₈Alkyl group of₂ ~ C₁₈Alkenyl group, sulfonamide group, mesyl group, sulfonic acid group, carboxyester group, hydroxy group, C₁ ~ C₁₈A member selected from the group consisting of an alkoxy group, an acetylamino group, a benzoylamino group and a halogen atom,₁ And R_Three Are the same or different, n and n ′ represent an integer of 1 to 3, and R₂ And R_Four Represents a hydrogen atom or a Nirot group, and A⁺ Represents a cation ion selected from the group consisting of ammonium ion, hydrogen ion, sodium ion, potassium ion and mixed ions thereof. ]
[0094]
In the present invention, “lower” means 1 to 6 carbon atoms.
[0095]
Typical examples of the azo-type iron complex compound of the above general formula include the following compounds.
[0096]
[Outside 5]

[0097]
[Outside 6]

[0098]
The azo-based iron complex compound is also used as a negative charge control agent. The compound can be synthesized by a known method.
[0099]
In the present invention, the shape of the toner is preferably a shape close to a sphere from the viewpoint of improving toner fusion on the toner carrier and contamination of the surface of the charging member when a large number of images are printed. The shape factors SF-1 and SF-2 indicating the shape of the toner are preferably such that the value of SF-1 is 100 <SF-1 ≦ 160 and the value of SF-2 is 100 <SF-2 ≦ 140. More preferably, the value of SF-1 is 100 <SF-1 ≦ 140 and the value of SF-2 is 100 <SF-2 ≦ 120 in order to improve transferability while maintaining developability. Is preferable.
[0100]
In the present invention, SF-1 and SF-2 indicating shape factors are randomly sampled 100 toner images of 2 μm or more magnified 1000 times using, for example, FE-SEM (S-800) manufactured by Hitachi, The image information is introduced into, for example, an image analysis apparatus (Luzex III) manufactured by Nicole via an interface, analyzed, and values obtained from the following equations are defined as shape factors SF-1 and SF-2.
[0101]
[Outside 7]

(In the formula, MXLNG represents the absolute maximum length of the particle, PERI represents the perimeter of the particle, and AREA represents the projected area of the particle.)
The shape factor SF-1 indicates the degree of roundness of the toner particles, and the shape factor SF-2 indicates the degree of unevenness of the toner particles.
[0102]
When the toner shape factor SF-1 exceeds 160, the toner moves away from the spherical shape and approaches an indeterminate shape, so that the toner is easily crushed in the developing device, the particle size distribution is fluctuated, and the charge amount distribution is likely to be broad. Inverted fog is likely to occur. When the toner shape factor SF-2 exceeds 140, the transfer efficiency of the toner image during transfer from the photosensitive member to the transfer material and the loss of transfer of characters and line images are undesirably caused.
[0103]
Furthermore, in order to faithfully develop minute latent image dots for higher image quality, the toner particles have a weight average diameter of 3 μm to 9 μm, preferably 4 μm to 8 μm, and a coefficient of variation in number distribution of 35% or less. Preferably it is 25% or less. In toner particles having a weight average diameter of less than 3 μm, there are many toner particles remaining on the photosensitive member or intermediate transfer member due to a decrease in transfer efficiency, and this tends to cause uneven image unevenness due to fogging or transfer defects. . When the weight average diameter of the toner particles exceeds 9 μm, fusion to a member such as the surface of the photoreceptor or an intermediate transfer material tends to occur. This tendency is further enhanced when the coefficient of variation in the number distribution of toner particles exceeds 35%.
[0104]
The variation coefficient A in the toner particle number distribution is calculated from the following equation.
[0105]
Coefficient of variation = [S / D₁ ] × 100
[In the formula, S represents a standard deviation value in the number distribution of toner particles, and D₁ Indicates the number average particle diameter (μm) of the toner particles. ]
[0106]
For the average particle size and particle size distribution of the toner particles, a Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter) is used, an interface (manufactured by Nikkiki Co., Ltd.) for outputting the number distribution and volume distribution and a PC9801 personal computer (manufactured by NEC). ) And 1% NaCl aqueous solution is prepared using 1st grade sodium chloride as the electrolyte. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of toners of 2 μm or more were measured using the Coulter counter TA-II with a 100 μm aperture as an aperture. Volume distribution and number distribution were calculated. Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention and the number-based number average particle diameter (D1) obtained from the number distribution were obtained.
[0107]
In the present invention, it is preferable to add a release agent to the toner particles in order to improve the fixing property and offset resistance of the toner.
[0108]
The release agent used in the present invention is a compound having a main endothermic maximum peak (melting point) in a DSC curve measured in accordance with ASTM D3418-8 in the range of 30 to 120 ° C, more preferably 40 to 90 ° C. Is preferred. When the maximum peak value (melting point) of the wax is less than 30 ° C., the self-cohesive force of the release agent becomes weak, and as a result, the high temperature offset resistance becomes weak, which is not preferable. When the maximum peak value (melting point) of the wax exceeds 120 ° C., the fixing temperature becomes high, and it becomes difficult to appropriately smooth the surface of the fixed image, which is not preferable from the viewpoint of lowering the color mixing property.
[0109]
Further, when toner particles are obtained by a polymerization method, since granulation and polymerization are performed in an aqueous medium, a high endothermic maximum peak value (melting point) is preferable because a release agent is mainly precipitated during granulation. Absent.
[0110]
For example, DSC-7 manufactured by Perkin Elmer is used to measure the temperature (melting point) of the maximum peak value of the release agent. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. For the sample, an aluminum pan is used, and an empty pan is set as a control.
[0111]
Release agents include polymethylene waxes such as paraffin wax, polyolefin wax, Fischer tropish wax, amide wax, higher fatty acid, higher fatty acid metal salt, long chain alkyl alcohol, ester wax and derivatives thereof (for example, grafts thereof). Compound or block compound). In particular, ester wax is more preferable in that it can improve fixability because it acts as a plasticizer for a binder resin of a toner such as a styrene-acrylic copolymer when the toner image is heat-fixed.
[0112]
In the present invention, a toner having a core / shell structure in the toner, the shell portion being formed by a polymer synthesized by polymerization, and the core portion being composed of wax as a release agent is used for the image forming method of the present invention. By using the toner, it is possible to prevent deterioration of toner particles and contamination of the image forming apparatus, so that good chargeability is maintained and a toner image excellent in reproducing a latent dot image can be formed over a long period of time. It becomes. Further, since the wax acts efficiently at the time of heat and pressure fixing, the low temperature fixing property and the high temperature offset resistance can be improved.
[0113]
In the present invention, the toner having a core / shell structure is such that the surface of the core portion made of wax as a releasing agent is covered with a shell portion formed by a polymer synthesized by polymerization of a polymerizable monomer. Means toner in the form.
[0114]
In the present invention, the core / shell structure of the toner can be confirmed by observing the tomographic plane of the toner particles.
[0115]
As a specific method for observing the tomographic plane of the toner particles, the toner particles are sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at 40 ° C. for 2 days. After staining with ruthenium oxide and, if necessary, osmium tetroxide, a flaky sample is cut out using a microtome equipped with diamond teeth, and the tomographic morphology of toner particles is observed using a transmission electron microscope (TEM). It is preferable to use a ruthenium tetroxide dyeing method in order to provide contrast between materials by utilizing a slight difference in crystallinity between the wax and the resin constituting the outer shell. A typical example is shown in FIG.
[0116]
In the present invention, the content of the release agent in the toner particles is preferably 2 to 30% by weight, and more preferably 2 to 25% by weight. When the content of the release agent is less than 2% by weight, the fixing property is insufficiently improved. When the content exceeds 30% by weight, the toner particles are likely to coalesce during granulation even in the production by the polymerization method. Those having a wide distribution are likely to be generated and are not suitable for the present invention.
[0117]
In the present invention, when a toner having a core / shell structure is produced, it is particularly preferable to add a polar resin that constitutes the shell portion because the shell portion encapsulates the core portion made of wax as a release agent. .
[0118]
As the polar resin used in the present invention, a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, a saturated polyester resin, and an epoxy resin are preferably used.
[0119]
The content of the polar resin in the toner particles is preferably 1 to 20% by weight, more preferably 2 to 16% by weight (based on the weight of the toner particles).
[0120]
When the content of the polar resin is less than 1% by weight, the effect of addition is not sufficiently exhibited. When the content exceeds 20% by weight, the charging characteristics of the toner are often affected. This is not preferable because it tends to cause a decrease in chargeability of the toner in the environment.
[0121]
In the present invention, an outermost shell resin layer may be further provided on the toner surface.
[0122]
The glass transition temperature of the outermost shell resin layer is preferably designed to be higher than the glass transition temperature of the outer shell resin layer in order to further improve the blocking resistance, and is preferably crosslinked to such an extent that the fixing property is not impaired. . The outermost shell resin layer preferably contains a polar resin or a charge control agent in order to improve chargeability.
[0123]
The method for providing the outermost shell layer is not particularly limited, and examples thereof include the following methods.
[0124]
1. In the latter half of the polymerization reaction or after completion, if necessary, a polar resin, a charge control agent, and a crosslinking agent are dissolved and dispersed in the reaction system, added to the polymerized particles, adsorbed onto the polymerized particles, and then added with a polymerization initiator for polymerization Method.
[0125]
2. If necessary, emulsion polymer particles or soap-free polymer particles composed of monomers containing a polar resin, a charge control agent, and a cross-linking agent are added to the reaction system and aggregated on the surface of the polymer particles, and if necessary, fixed by heat. Method.
[0126]
3. A method in which emulsion-polymerized particles or soap-free polymerized particles comprising a monomer containing a polar resin, a charge control agent, and a cross-linking agent are mechanically fixed to the toner particle surface in a dry manner, if necessary.
[0127]
In the present invention, by a polymerization method for producing toner particles by polymerizing a monomer composition containing a wax and a polar resin as a release agent together with a colorant and a polymerizable monomer in an aqueous medium, the wax and In the case of producing toner particles containing a polar resin, the produced toner particles have a core part made of wax and a shell part made of a polymer synthesized by polymerization of a polymerizable monomer and a polar resin. It has a core / shell structure, and a polar resin is located in the outermost shell resin layer of the shell portion. Therefore, in the case of toner particles having such a form, since a polar group exists on the surface of carbon black used as a colorant, carbon black does not enter non-polar wax, and the shell portion The coloring power tends to be lower than that of toner particles in which carbon black is uniformly dispersed in the toner particles, and the outermost shell layer of the shell portion has a polar resin. Therefore, since the ratio of carbon black located on the surface portion of the toner particle is reduced, the triboelectric chargeability of the toner tends to be lower than that of the toner particle not containing the resin resin.
[0128]
However, in the present invention, since the toner particles contain carbon black and a specific azo iron compound as described above, the coloring power of the toner is improved by the effect of improving the dispersibility of carbon black by the azo iron compound. It is possible to suppress the decrease in the triboelectric chargeability of the toner by suppressing the decrease, and by the effect of improving the dispersibility of carbon black and the high charge control effect of the azo-based iron compound.
[0129]
In the present invention, in the one-component contact development type image forming method, since the toner on the toner carrier contacts the surface of the image carrier during development, the durability of the toner, the surface of the toner carrier and the image carrier It is preferable that the toner has anti-fusing resistance to the surface.
[0130]
Therefore, the toner used in the one-component contact development method is required to have higher mechanical characteristics than the toner used in the one-component non-contact development method and the two-component development method having a toner and a carrier.
[0131]
The resin component of the toner particles used in the present invention has a C component insoluble in THF (tetrahydrofuran) and a component soluble in THF. The component soluble in THF is a gel permeation chromatogram (GPC). In the molecular weight distribution measured in (1), it has an A component having a molecular weight of less than 1 million and a B component having a molecular weight of 1 million or more, and these A component, B component and C component preferably satisfy the following conditions.
[0132]
The component (corresponding to the A component and B component) soluble in THF of the resin component of the toner particles according to the present invention preferably has a number average molecular weight (Mn) of 9000 to 1000000 in the molecular weight distribution of GPC, more preferably The properties required of the toner are 10,000 to 500,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) is preferably 5 to 500, more preferably 7 to 400. Can be achieved in a balanced manner.
[0133]
The resin component of these toner particles is based on the weight of the resin component (1) A component content (W_A) Is preferably 30 to 95% by weight, more preferably 50 to 90% by weight. (2) Content of component B (W_B) Is preferably 0 to 20% by weight, more preferably 1 to 20% by weight. (3) Content of component C (W_C) Is preferably 0 to 70% by weight, more preferably 1 to 70% by weight. (4) Total content of component B and component C (W_B+ W_C) Is preferably 5 to 70% by weight, more preferably 10 to 50% by weight, in the image forming method of the present invention.
[0134]
The resin component of the toner particles used in the present invention has a molecular weight of 3000 to 50,000, more preferably, the above-mentioned A component (THF soluble component having a molecular weight of less than 1 million) in the molecular weight distribution of GPC, a component soluble in THF. Having a main peak in the molecular weight range of 5000 to 22000 is preferable because it matches well with the image forming apparatus. When the main peak has a molecular weight of less than 3000, it tends to cause deterioration of the charging characteristics of the toner, fusion at the contact portion with the image forming apparatus, and deterioration of high temperature offset resistance and blocking resistance. When the main peak exceeds the molecular weight of 50,000, the contact portion with the image forming apparatus is likely to be damaged or the low-temperature fixability is likely to be significantly reduced.
[0135]
Content of component A (W_A) Is less than 30% by weight, the low-temperature fixability tends to be reduced. If it exceeds 95% by weight, matching with the image forming apparatus is deteriorated, and toner fusion and image quality are deteriorated. easy.
[0136]
Content of B component (W_B) Exceeding 20% by weight is not preferable because the high-temperature offset resistance is improved but the low-temperature fixability is lowered.
[0137]
C component content (W_C) Is more than 70% by weight, it is not preferable because it causes troubles in matching with the image forming apparatus and makes low-temperature fixing difficult. Even if there is no C component, it is possible to maintain developability and fixability if the B component is preferably contained in an amount of 5 to 20% by weight, more preferably 10 to 20% by weight. On the other hand, even if there is no B component, the C component is preferably contained in an amount of 5 to 70% by weight, more preferably 10 to 70% by weight, so that developability and fixability can be maintained.
[0138]
Further, the total content of component B and component C (W_B+ W_C) Is preferably 5 to 70% by weight, more preferably 10 to 50% by weight. Total content of component B and component C (W_B+ W_C) Is less than 5% by weight, the charging characteristics of the toner, the high-temperature offset resistance, and the matching with the image forming apparatus are deteriorated. Is not preferred because the low-temperature fixability is lowered.
[0139]
In the present invention, the molecular weight and content (W) of each resin component (AC components) in the toner particles._A, W_BAnd W_C) Is measured and calculated by the following method.
[0140]
In the present invention, the C component insoluble in THF refers to a resin component insoluble in THF (tetrahydrofuran) as a resin component in the toner particles, and the content thereof is the degree of crosslinking of the resin composition containing a crosslinking component. However, even if the THF-insoluble content is 0% by weight, it does not necessarily mean that it is not crosslinked. The content of component C insoluble in THF is defined by the values measured as follows.
[0141]
First, the content of additives in toner particles such as pigment is measured in advance by a known method. Next, a certain amount of developer 0.5 to 1.0 g is weighed (W₁ g), put in a cylindrical filter paper (Toyo Filter Paper No. 86R), put on a Soxhlet extractor, extract for 20 hours using 100 to 200 ml of THF as a solvent, evaporate soluble components extracted with the solvent, Vacuum dry for a time and weigh the amount of THF soluble resin component (W₂ g). Of the additives such as pigments contained in a fixed amount of the developer, the weight of the component soluble in THF is expressed as W._Three g, Weight of components insoluble in THF_Four g, the THF-insoluble matter (the C component) in the resin component is calculated according to the following formula.
[0142]
[Outside 8]

[0143]
On the other hand, in the molecular weight distribution of GPC, which is a component soluble in THF, the main peak position and content (W_A) And more than 1 million B component content (W_B) (Weight basis of resin component) is obtained from the molecular weight distribution obtained using the THF-soluble resin component obtained in the above-described Soxhlet extraction as a GPC measurement sample.
[0144]
It is assumed that the area% of the region having a molecular weight of less than 1,000,000 (A component) and the region having a molecular weight of 1,000,000 or more (B component) are equal to the weight%, and converted to the weight basis of the resin component. % By weight of ingredients (W_AAnd W_B)
[0145]
In the present invention, the resin component includes a wax component in addition to the binder resin.
[0146]
In the present invention, the molecular weight distribution of the resin component in the toner particles is measured under the following conditions by GPC (gel permeation chromatography). The sample used is a sample that has been previously dispersed / dissolved in a solvent and then filtered through a solvent-resistant membrane filter (pore diameter: 0.3 μm).
[0147]
Apparatus: GPC-150C (manufactured by Waters)
Column: 7 columns of KF801-7 (manufactured by Shodex)
Temperature: 40 ° C
Solvent: THF
Flow rate: 1.0 ml / min
Sample: 0.1 ml of a sample having a concentration of 0.05 to 0.6% by weight is injected.
[0148]
Measurement is performed under the above conditions, and a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample is used in calculating the molecular weight of the sample.
[0149]
As the binder resin for the toner used in the present invention, generally used styrene- (meth) acrylic copolymers, polyester resins, epoxy resins, and styrene-butadiene copolymers can be used. In the method of obtaining toner particles by a polymerization method, those monomers are preferably used. Specifically, styrene monomers such as styrene, o- (m-, p-)-methylstyrene, m- (p-)-ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate , Propyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2- (meth) acrylate 2- (Meth) acrylic acid ester monomers such as ethylhexyl, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile, acrylamide A monomer is preferably used. These monomers are used singly or appropriately mixed so that the theoretical glass transition temperature (Tg) described in Polymer Handbook 2nd edition-P139-192 (John Wiley & Sons) is 40-75 ° C. Used. When the theoretical glass transition temperature is less than 40 ° C., a problem arises in terms of storage stability of the toner and durability of the developer, and when it exceeds 75 ° C., the fixing point is increased.
[0150]
Furthermore, in the present invention, it is preferable to use a crosslinking agent during the synthesis of the binder resin in order to generate the above THF-insoluble component and / or to generate a component having a molecular weight of 1,000,000 or more.
[0151]
Examples of the crosslinking agent used in the toner of the present invention include divinylbenzene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1, bifunctional crosslinking agent. 4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200, # 400, # 600 diacrylate, dipropylene glycol diacrylate, polypropylene glycol diacrylate, polyester type diacrylate (MAND Nippon Kayaku) and those changed to methacrylates of the above diacrylate.
[0152]
Pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate and its methacrylate, 2,2-bis (4-methacryloxy, polyethoxyphenyl) Examples include propane, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate and triallyl trimellitate.
[0153]
These crosslinking agents are preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of other vinyl monomers.
[0154]
When the amount of the crosslinking agent used is less than 0.05 parts by weight, the crosslinking reaction of the binder resin is not sufficiently performed, and when it exceeds 10 parts by weight, the crosslinking reaction of the binder resin proceeds excessively. In either case, it becomes difficult to control the content of the THF-insoluble matter in the toner particles within the range of 5 to 70% by weight.
[0155]
The azo-based iron complex compound used in the present invention also has a function as a charge control agent, but another charge control agent may be used in combination. As another charge control agent, a known one can be used, but a charge control agent that has a high charging speed and can stably maintain a constant charge amount is preferable. Further, in the case of producing toner particles by the polymerization method in the present invention, a charge control agent having no polymerization inhibition and no solubilized product in an aqueous system is particularly preferable.
[0156]
Specific examples of other charge control agents include negative-type salicylic acid, naphthoic acid, dicarboxylic acid or its derivative metal compound, azo pigment or its derivative metal compound, sulfonic acid, and carboxylic acid in the side chain. Molecular type compounds, boron compounds, urea compounds, silicon compounds, and calixarenes can be used. As the positive system, nigrosine, triphenylmethane compound, quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, and an imidazole compound are preferably used.
[0157]
Another charge control agent is preferably contained in the toner particles in an amount of preferably 0.2 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin. However, in the present invention, it is not essential to add another charge control agent, and even in the case of using a non-magnetic one-component blade coating development method, the triboelectric charge with the blade member or sleeve member is positively used in the toner. It is not always necessary to include another charge control agent.
[0158]
When the toner particles are produced by the polymerization method in the present invention, examples of the polymerization initiator include 2,2'-azobis- (2,4-dimethylvaleronitrile) and 2,2'-azobisisobutyronitrile. Benzoic initiators such as 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; Peroxide-based polymerization initiators such as peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide are used.
[0159]
The addition amount of the polymerization initiator varies depending on the desired degree of polymerization, but generally 0.5 to 20% by weight is added to the monomer. The kind of the initiator is slightly different depending on the polymerization method, but can be used alone or mixed with reference to the 10-hour half-life temperature.
[0160]
A known crosslinking agent, chain transfer agent, and polymerization inhibitor for controlling the degree of polymerization can be further added and used.
[0161]
When suspension polymerization is used as the toner production method according to the present invention, examples of the dispersant used include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, and carbonate as inorganic oxides. Examples thereof include magnesium, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina, magnetic substance, and ferrite. As the organic compound, for example, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, and starch are used dispersed in an aqueous phase. These dispersants are preferably used in an amount of 0.2 to 10.0 parts by weight with respect to 100 parts by weight of the polymerizable monomer.
[0162]
Although these commercially available dispersants may be used as they are, in order to obtain dispersed particles having a fine and uniform particle size, the inorganic compounds are generated and used in a dispersion medium under high-speed stirring. You can also. For example, in the case of tricalcium phosphate, a preferred dispersant for the suspension polymerization method can be obtained by mixing an aqueous sodium phosphate solution and an aqueous calcium chloride solution under high-speed stirring. You may use together 0.001-0.1 weight part surfactant for refinement | miniaturization of these dispersing agents. Specifically, commercially available nonionic, anionic and cationic surfactants can be used, such as sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, olein. Calcium acid is preferably used.
[0163]
When the polymerization method is used in the toner manufacturing method according to the present invention, the toner can be specifically manufactured by the following manufacturing method.
[0164]
Add carbon black and azo-based iron compound to the polymerizable monomer and, if necessary, charge control agent, polymerization initiator and other additives, and dissolve or mix uniformly with a mixing device such as a homogenizer or ultrasonic disperser. A polymerizable monomer composition is prepared by dispersing. The prepared polymerizable monomer composition is dispersed in an aqueous phase containing a dispersion stabilizer by a mixing device such as an ordinary stirrer, homomixer or homogenizer. Preferably, the agitation speed and time are adjusted so that droplets of the polymerizable monomer composition have a desired toner particle size, and granulated. Thereafter, stirring may be performed to such an extent that the particle state is maintained and the sedimentation of the particles is prevented by the action of the dispersion stabilizer. Polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. The temperature may be raised in the latter half of the polymerization reaction, and for the purpose of improving durability in the image forming method using the toner of the present invention, the polymerization reaction is performed to remove unreacted polymerizable monomers and by-products. A part of the aqueous medium may be distilled off in the latter half or after completion of the polymerization reaction. After completion of the polymerization reaction, the produced toner particles are washed, recovered by filtration, and dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight of the monomer system.
[0165]
In the present invention, as described above, a polymerizable monomer composition is prepared through a master batch process in order to improve the dispersibility of carbon black in the toner particles.
[0166]
Specifically, with respect to 100 parts by weight of the first polymerizable monomer, preferably 4 to 40 parts by weight, more preferably 5 to 25 parts by weight of carbon black and preferably 0.2 to 5 parts by weight, More preferably, by mixing and dispersing 0.5 to 3 parts by weight of an azo-based iron compound, carbon black can be mixed at a very high concentration with respect to the polymerizable monomer. Since the share at the time of mixing is sufficiently increased, the dispersibility of carbon black can be drastically improved in combination with the dispersion effect of the azo-based iron compound.
[0167]
When the amount of carbon black mixed is less than 4 parts by weight, even if an azo-based iron compound is used, the viscosity of the dispersion is small and sufficient dispersion is difficult to achieve. On the other hand, when it exceeds 40 parts by weight, it is difficult to control the viscosity of the dispersion, and as a result, dispersion tends to be non-uniform.
[0168]
When the amount of the azo-based iron compound is less than 0.2 parts by weight, the effect of increasing the viscosity of the dispersion is insufficient. On the other hand, when the amount exceeds 5 parts by weight, the viscosity is decreased again. The dispersion tends to be uneven.
[0169]
The viscosity of this first polymerizable monomer, carbon black and azo-based iron compound, and optionally a wax component and / or a charge control agent (masterbatch) dispersion is preferably 100 to 2000 centipoise, More preferably, it is 150-1600 centipoise.
[0170]
When the viscosity of this dispersion is less than 100 centipoise, the viscosity is too low to take a share of dispersion, and it becomes difficult to uniformly disperse carbon black. On the other hand, when it exceeds 2000 centipoise, the viscosity is too high and it becomes difficult to maintain a uniform dispersed state, and at the same time, the discharge from the manufacturing apparatus deteriorates, leading to a decrease in productivity.
[0171]
This dispersion is mixed with the second polymerizable monomer and, if necessary, a wax component, a polymer containing a polar functional group, a charge control agent, a polymerization initiator and other additives to obtain a polymerizable monomer. A meter composition is prepared.
[0172]
The mixing amount of the second polymerizable monomer with respect to 100 parts by weight of the dispersion is preferably 20 to 100 parts by weight, more preferably 30 to 70 parts by weight. From the viewpoint of uniform dispersibility in the monomer.
[0173]
When the mixing amount of the second polymerizable monomer is less than 20 parts by weight, it takes time to uniformly disperse, and when it exceeds 100 parts by weight, re-aggregation of carbon black occurs. It becomes easy, and it takes time for uniform dispersion.
[0174]
The carbon black content in the polymerizable monomer composition is preferably 1 to 20% by weight, more preferably 3 to 15% by weight based on the weight of the polymerizable monomer composition. This is good in terms of coloring power and toner charge stabilization.
[0175]
When the content ratio of carbon black in the polymerizable monomer composition is less than 1% by weight, it is difficult to achieve a high image density. The toner charge in the toner tends to be low.
[0176]
The content ratio of the azo-based iron compound with respect to the weight of the polymerizable monomer composition in the polymerizable monomer composition is preferably 0.1 to 3.0% by weight, more preferably 0.2 to 2%. It is good that the dispersion viscosity is maintained in an appropriate state and the uniform dispersibility of carbon black is improved.
[0177]
When the content ratio of the azo-based iron compound in the polymerizable monomer composition is less than 0.1% by weight, the dispersion viscosity does not increase, and the effect of improving the dispersibility of carbon black is not exhibited. If it exceeds 0.0% by weight, the viscosity of the dispersion is lowered, and the effect of improving the dispersibility of carbon black is lost.
[0178]
In the present invention, the surface of the toner particles is coated with an external additive to impart appropriate fluidity and chargeability to the toner particles, as well as improving cleaning properties and stress from a contact member such as a photosensitive member charging member. It is desirable to take a structure that can be relaxed, and the external additive coverage on the toner surface is preferably 5 to 99%, more preferably 10 to 99%. Further, by having inorganic fine powder as an external additive on the surface of the toner particles, the transfer efficiency is improved and the omission of transfer of characters and line images is improved.
[0179]
As for the external additive coverage on the surface of the toner particles, 100 toner images were randomly sampled using FE-SEM (S-800) manufactured by Hitachi, Ltd. It was introduced into Luzex 3) and analyzed and calculated.
[0180]
The external additive used in the present invention preferably has an average particle diameter of 1/10 or less of the weight average diameter of the toner particles from the viewpoint of durability when added to the toner. The average particle diameter of the additive means the average particle diameter obtained by observing the surface of the toner particles with an electron microscope.
[0181]
Examples of the external additive include metal oxides (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide and zinc oxide), nitride (silicon nitride), and carbide (silicon carbide). Metal salts (calcium sulfate, barium sulfate and calcium carbonate), fatty acid metal salts (zinc stearate and calcium stearate), carbon black and silica.
[0182]
These external additives are preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. What performed the hydrophobization process is more preferable.
[0183]
As the inorganic fine powder used in the present invention, at least one kind is fine particles selected from silica, alumina, titania, or a double oxide thereof in order to improve charging stability, developability, fluidity, and storage stability. Preferably there is. Further, silica is more preferable. For example, as the silica, both a so-called dry method produced by vapor phase oxidation of silicon halide or alkoxide or dry silica called fumed silica, and so-called wet silica produced from alkoxide water glass can be used. . There are few silanol groups on the surface and inside of the silica fine powder, and Na₂O, SO_Three  ^2-Dry silica with less production residue is more preferred. In dry silica, it is possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. Also include.
[0184]
The inorganic fine powder used in the present invention has a specific surface area of 30 m by nitrogen adsorption measured by the BET method.²/ G or more, especially 50-400m²Those in the / g range give good results. The inorganic fine powder is preferably 0.1 to 8 parts by weight, more preferably 0.5 to 5 parts by weight, and still more preferably more than 1.0 part by weight to 3.0 parts by weight with respect to 100 parts by weight of the toner particles. It is good to use until. The inorganic fine powder used in the present invention is optionally made of silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane having a functional group for the purpose of hydrophobization and charge control. Treatments such as coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or in combination.
[0185]
In order to maintain a high charge amount and achieve a low consumption and a high transfer rate, the inorganic fine powder is more preferably treated with at least silicon oil.
[0186]
Primary particle size of 50 nm or more (preferably a specific surface area of 30 m for improving transfer and / or cleaning properties²It is also one of preferable modes to add inorganic or organic fine particles close to spherical shape (less than / g). As the spherical fine particles, for example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.
[0187]
The toner used in the present invention may further contain other additives, for example, a lubricant powder such as Teflon powder, zinc stearate powder, polyvinylidene fluoride powder; cerium oxide powder, silicon carbide, and the like within a range that does not substantially adversely affect the toner. Abrasives such as powder, strontium titanate powder; fluidity imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; conductivity imparting agents such as carbon black powder, zinc oxide powder and tin oxide powder; Polar organic fine particles; and inorganic fine particles; can also be used in small amounts as developability improvers.
[0188]
In order to prepare the toner particles used in the present invention, in addition to the above-described polymerization method, for example, a binder resin, an azo-based iron complex compound, carbon black, a release agent, a pressure kneader, an extruder, or a media dispersion After being uniformly dispersed using a machine, it is collided with a target under a mechanical or jet stream, finely pulverized to a desired toner particle size, and further subjected to a classification process to sharpen the particle size distribution and make a toner. Toner production method by pulverization method; a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945; A dispersion polymerization method in which a toner is directly produced by polymerization of a polymerizable monomer using an organic solvent in which the polymer is insoluble; or a toner obtained by direct polymerization in the presence of a water-soluble polar polymerization initiator Emulsion polymerization method as typified by generate soap-free polymerization process; and the like.
[0189]
In the present invention, it is preferable to impart releasability to the surface of the photoconductor, and the contact angle of water on the surface of the photoconductor is preferably 85 degrees or more. More preferably, the contact angle of the photoreceptor surface with water is 90 degrees or more.
[0190]
A high contact angle on the surface of the photoconductor indicates that the surface of the photoconductor has a high releasability. This effect can significantly reduce the amount of toner remaining on the transfer, greatly increasing the load on the cleaning process. This can reduce the occurrence of defective cleaning more reliably.
[0191]
Further, since the surface of the photoconductor has a high releasability, the amount of residual toner can be significantly reduced, there is almost no light shielding by the residual toner, and a negative ghost image can be essentially prevented and the residual transfer can be prevented during development. The recovery efficiency of the toner in the development area is also improved, and positive ghost images are prevented.
[0192]
Here, the generation mechanism of the ghost image will be described.
[0193]
The problem of light shielding by the transfer residual toner is particularly problematic when the surface of the photoreceptor is repeatedly used for one transfer material, that is, when the length of the entire circumference of the photoreceptor is shorter than the length of the transfer material in the traveling direction, Since the transfer residual toner must be charged, exposed and developed in the state where the residual toner is present on the photosensitive member, the potential on the surface of the photosensitive member where the residual toner is present does not drop sufficiently and the development contrast becomes insufficient. As for development, it appears on the image as a negative ghost having a lower density than the surroundings.
[0194]
On the other hand, if the cleaning effect of the transfer residual toner is insufficient at the time of development, the toner is developed on the surface of the photoreceptor where the transfer residual toner is present, so that the density is higher than the surroundings and positive ghost is generated.
[0195]
With the configuration of the present invention, the ghost image described above can be essentially prevented.
[0196]
The image forming method of the present invention is effective when the surface of the photoreceptor is mainly composed of a polymer binder. For example, (i) when a protective film mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon; (ii) a charge transport material and a resin are used as a charge transport layer of the function-separated organic photoreceptor. (Iii) In some cases, a protective layer as described above may be provided thereon. As a means for imparting releasability to such a surface layer,
(1) Use a resin having a low surface energy as the resin itself constituting the film.
(2) Add additives that impart water repellency and lipophilicity.
(3) Disperse the material having high releasability in powder form.
Is mentioned. (1) is achieved by introducing a fluorine-containing group or a silicone-containing group into the resin structure. As (2), a surfactant may be added as an additive. (3) includes the use of a compound containing a fluorine atom such as polytetrafluoroethylene, polyvinylidene fluoride and carbon fluoride.
[0197]
By these means, the contact angle with respect to water on the surface of the photoreceptor can be set to 85 degrees or more. When the contact angle of water on the surface of the photoreceptor is less than 85 degrees, the toner and the toner carrier are likely to deteriorate due to durability.
[0198]
Of these, fluorine-containing resins such as polytetrafluoroethylene and polyvinylidene fluoride are particularly suitable. In the present invention, when the fluorine-containing resin is used as the releasable powder as the powder (3), the dispersion to the outermost surface layer is preferable.
[0199]
In order to contain these powders on the surface, a layer in which the powder is dispersed in a binder resin is provided on the outermost surface of the photoreceptor, or an organic photoreceptor that is originally composed mainly of a resin. For example, the powder may be dispersed in the outermost surface layer without providing a new surface layer.
[0200]
The amount of the powder added to the surface layer is preferably 1 to 60% by weight, more preferably 2 to 50% by weight, based on the total weight of the surface layer. If the amount is less than 1% by weight, the residual toner is not sufficiently reduced, the cleaning efficiency of the residual toner is not sufficient, and the ghost prevention effect is insufficient. If the amount exceeds 60% by weight, the strength of the film decreases. This is not preferable because the amount of light incident on the photosensitive member is significantly reduced. The particle size of the powder is 1 μm or less, preferably 0.5 μm or less from the viewpoint of image quality. When it is larger than 1 μm, the line breakage is deteriorated due to scattering of incident light, and it is not practical.
[0201]
The present invention is particularly effective in the case of the contact charging method in which the charging means makes the charging member contact the photoconductor. That is, if there is a large amount of residual toner after cleaning, it adheres to the direct charging member, which is a subsequent process, and causes charging failure. Therefore, compared to corona discharge in which the charging means does not contact the photoconductor, the amount of residual toner is smaller and it is necessary to make it difficult to adhere.
[0202]
One preferred embodiment of the photoreceptor used in the present invention will be described below.
[0203]
As a conductive substrate, a cylinder of a metal such as aluminum or stainless steel; a plastic having a coating layer of an aluminum alloy or an indium oxide-tin oxide alloy; paper or plastic impregnated with conductive particles; a plastic having a conductive polymer; Cylinder and film are used.
[0204]
On these conductive substrates, for the purpose of improving the adhesion of the photosensitive layer, improving the coating property, protecting the substrate, coating defects on the substrate, improving the charge injection from the substrate, and protecting the photosensitive layer from electrical breakdown. An undercoat layer may be provided.
[0205]
Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, polyurethane Alternatively, it is formed of an aluminum oxide material. The thickness of the undercoat layer is usually 0.1 to 10 μm, preferably 0.1 to 3 μm.
[0206]
The charge generation layer is composed of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes or selenium or amorphous silicon. An inorganic charge generating material is dispersed in a suitable binder and coated, or formed by vapor deposition. Of these, phthalocyanine pigments are preferred for adjusting the sensitivity of the photoreceptor to a sensitivity suitable for the present invention. The binder can be selected from a wide range of binder resins such as polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicone resin, epoxy resin, vinyl acetate resin. Can be mentioned. The amount of the binder contained in the charge generation layer is 80% by weight or less, preferably 0 to 40% by weight. The thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.
[0207]
The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin as required, and coating, and the film thickness is generally 5 to 40 μm. Examples of the charge transporting substance include polycyclic aromatic compounds such as biphenylene, anthracene, pyrene and phenanthrene in the main chain or side chain; nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole and pyrazoline; hydrazone compound; styryl compound; Selenium; selenium-tellurium; amorphous silicon; cadmium sulfide.
[0208]
Examples of binder resins for dispersing these charge transport materials include polycarbonate resins, polyester resins, polymethacrylic acid esters, polystyrene resins, acrylic resins and polyamide resins; organic photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene. A functional polymer.
[0209]
A protective layer may be provided as the surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or curing agents for these resins are used alone or in combination of two or more.
[0210]
Conductive fine particles may be dispersed in the resin of the protective layer. Examples of the conductive fine particles include metals and metal oxides. Preferably, there are ultrafine particles of zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide-coated titanium oxide, tin-coated indium oxide, antimony-coated tin oxide or zirconium oxide. These may be used alone or in combination of two or more. In general, when particles are dispersed in a protective layer, it is necessary that the particle size of the particles is smaller than the wavelength of the incident light in order to prevent scattering of incident light by the dispersed particles. The particle diameter of the insulating particles is preferably 0.5 μm or less. The content in the protective layer is preferably 2 to 90% by weight, more preferably 5 to 80% by weight, based on the total weight of the protective layer. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.
[0211]
The surface layer can be applied by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.
[0212]
The preferable development process conditions used in the present invention are that the developer and the surface of the photoreceptor are in contact with each other and that a reversal development method is used. When the two-component magnetic brush developing method is used, as the carrier, ferrite, magnetite, iron powder, or those coated with acrylic resin, silicone resin, fluorine resin or the like are used. At this time, at the time of development or blank time before and after development, a bias of a direct current or alternating current component is applied to control the potential so that the development and the remaining toner on the photoreceptor can be collected. At this time, the direct current component is located between the light portion potential and the dark portion potential.
[0213]
In the case of a one-component developer, a method in which an elastic roller is used as a toner carrier and a toner layer formed by coating toner on the surface of the elastic roller is brought into contact with the surface of the photoreceptor. At this time, the toner may be either magnetic or non-magnetic, and it is important that the toner layer is in contact with the surface of the photoreceptor. The toner carrier is substantially in contact with the surface of the photoreceptor, which means that the toner carrier is in contact with the surface of the photoreceptor when the toner layer is removed from the toner carrier. At this time, the surface of the elastic roller or the vicinity of the surface has a potential in order to obtain an image having no edge effect by the electric field acting between the surface of the photoconductor and the elastic roller facing the surface of the photoconductor through the toner layer. There is a need to have an electric field between the photoreceptor surface and the toner carrying surface. Therefore, it is possible to use a method in which the elastic rubber of the elastic roller is resistance-controlled in the middle resistance region to keep the electric field while preventing conduction with the surface of the photoreceptor, or a method of providing a thin insulating layer on the surface layer of the conductive roller. . Furthermore, a conductive resin sleeve in which the outer surface facing the photosensitive member surface of the conductive roller is covered with an insulating material, or a conductive layer is provided on the inner surface side of the insulating sleeve not facing the photosensitive member surface is also possible. It is. A configuration in which a rigid roller is used as the toner carrying member and the photosensitive member is flexible like a belt is also possible. The electric resistance of the developing roller as the toner carrier is 10²-10⁹A range of Ω is preferred.
[0214]
The electric resistance of the developing roller is measured by the following method. That is, as shown in FIG. 11, the aluminum roller 102 having a diameter of 16 mm and the developing roller 101 are brought into contact with a contact load of 4.9 N (500 g), and the aluminum roller 102 is rotated at 2 rps. Next, the developing roller 101 has V₁Apply a DC voltage of 400V. A variable resistor R is arranged on the ground side, and the voltage V at both ends thereof is adjusted while adjusting the resistance value of the variable resistor R according to the developing roller 101.₂And the electric resistance of the developing roller 101 is calculated by calculating the current value.
[0215]
When the one-component contact development method is used, the surface of the developing roller carrying the toner may be rotated in the same direction as the movement direction of the photosensitive member surface, or may be rotated in the opposite direction. When the rotation is in the same direction, it is desirable that the peripheral speed ratio is faster than 100% with respect to the peripheral speed of the photoreceptor. If it is 100% or less, the image quality is poor. The higher the peripheral speed ratio, the more toner is supplied to the development site, the more frequently the toner is desorbed from the latent image, and the unnecessary parts are scraped off and applied to the necessary parts. Thus, an image faithful to the latent image can be obtained. Specifically, it is preferable that the moving speed of the toner carrying member surface is 1.05 to 3.0 times the moving speed of the photosensitive member surface.
[0216]
Hereinafter, the transfer process applicable to the image forming method of the present invention will be specifically described.
[0217]
In the transfer step, it is preferable to use a contact transfer system in which the toner image is electrostatically transferred to the transfer material while the transfer means is brought into contact with the surface of the photoreceptor via the transfer material. The contact pressure of the transfer unit with respect to the photosensitive member surface is preferably 2.9 N / m (3 g / cm) or more, more preferably 9.8 to 490 N / m (10 to 500 g / cm). ) Is good. If the linear pressure as the contact pressure is less than 2.9 N / m (3 g / cm), it is not preferable because transfer of the transfer material and transfer failure are likely to occur. When the contact pressure is too high, the surface of the photoconductor is deteriorated and the toner adheres, and as a result, the toner is fused to the surface of the photoconductor.
[0218]
As the transfer means in the contact transfer process, an apparatus having a transfer roller or a transfer belt is used. The transfer roller has at least a metal core and a conductive elastic layer covering the metal core. The conductive elastic layer has a volume resistance of 10 such as urethane or EPDM in which conductive fine particles such as carbon are dispersed.⁶-10^TenIt is made of an elastic body of about Ωcm.
[0219]
The present invention is particularly effectively used in an image forming apparatus in which the surface of the photoreceptor is an organic compound. That is, when the organic compound forms the surface layer of the photoreceptor, transferability is higher because the adhesion to the binder resin contained in the toner particles is higher than other photoreceptors using inorganic materials. It has a technical problem that it tends to decrease. Therefore, the effect of high transferability by the toner used in the present invention becomes more remarkable.
[0220]
Examples of the surface material of the photoreceptor according to the present invention include, but are not limited to, silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl methacrylate, styrene, polyethylene terephthalate, and polycarbonate. However, other monomers or copolymers and blends between the aforementioned binder resins can also be used.
[0221]
In the present invention, the present invention is particularly effective for an image forming apparatus having a small drum-shaped photosensitive member having a diameter of 50 mm or less. That is, in the case of a small-diameter photosensitive drum, pressure concentration tends to occur at the contact portion of the contact member with the same linear pressure. Although it is considered that there is the same development on the belt photoreceptor, the present invention is also effective for an image forming apparatus using a photoreceptor belt having a radius of curvature of 25 mm or less at the contact portion.
[0222]
Further, in the present invention, it is desirable to control the total charge amount of the toner during development in order to impart high charge to the toner. Therefore, the surface of the toner carrier according to the present invention is preferably coated with a resin layer in which conductive fine particles and / or a lubricant are dispersed.
[0223]
As a charging method, a known corona charging method called corotron or scorotron is used, and a method using a pin electrode can also be used. A contact charging method in which charging is performed by skillfully bringing a charging member into contact with the surface of the photoreceptor can also be used.
[0224]
In the present invention, the charging means is particularly effective in the case of the contact charging method in which the charging member is brought into contact with the surface of the photoreceptor. That is, compared to non-contact corona discharge in which the charging means does not contact the surface of the photoreceptor, the contact charging method is liable to cause deterioration of the surface of the photoreceptor, and from the viewpoint of durability, the transfer residual toner increases due to a decrease in transferability. It has a technical problem that it is in a strict direction for cleaning performance. Therefore, the effect of the high transferability used in the present invention becomes more remarkable.
[0225]
As a preferable process condition when a charging roller is used as the contact charging member, the contact pressure of the charging roller is 4.9 to 490 N / m (5 to 500 g / cm), more preferably 9.8 to 392 N / m. Furthermore, in order to make the polarity of the transfer residual toner the same as that of the photosensitive member charging polarity and to facilitate recovery during development, it is preferable to apply a DC voltage. When an AC voltage is superimposed, it is preferable to superimpose an AC voltage having a peak-to-peak voltage less than 2 × Vth (V) [Vth; discharge start voltage (V) in DC application] on the DC voltage.
[0226]
Other contact charging members include a method using a charging blade and a method using a conductive brush. These contact charging means are effective in that a high voltage is not required and generation of ozone is reduced.
[0227]
As the contact charging member, in the case of a roller or a blade, a conductive metal such as iron, copper or stainless steel; a carbon dispersion resin; a metal or a metal oxide dispersion resin is used as a conductive substrate. In the case of a blade, a rod shape or a plate shape can be used. As the structure of the elastic roller, a structure in which an elastic layer, a conductive layer, and a resistance layer are provided on a conductive substrate is used.
[0228]
Examples of the elastic layer include chloroprene rubber, isoprene rubber, EPDM rubber, polyurethane rubber, sponge such as epoxy rubber and butyl rubber, or a foam of rubber, styrene-butadiene thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic. It can be formed of an elastomer, a thermoplastic elastomer such as an ethylene-vinegar thermoplastic elastomer.
[0229]
The conductive layer preferably has a volume resistivity of 10⁷Ω · cm or less, more preferably 10¹-10⁶It should be Ω · cm. As the conductive layer, for example, a metal vapor deposition film, a conductive particle dispersed resin, a conductive resin, or the like is used. Specific examples include vapor deposited films of conductive metals such as aluminum, indium, nickel, copper, and iron; conductive particles such as carbon, aluminum, nickel, and titanium oxide, urethane, polyester, vinyl acetate-vinyl chloride copolymer. And conductive particle-dispersed resins dispersed in a resin such as polymethyl methacrylate; and conductive resins such as quaternary ammonium salt-containing polymethyl methacrylate, polyvinyl aniline, polyvinyl pyrrole, polydiacetylene, and polyethyleneimine.
[0230]
The resistive layer has a volume resistivity of 10⁶-10¹²A layer of Ω · cm is preferable. As the resistance layer, a semiconductive resin or a conductive particle-dispersed insulating resin can be used. As the semiconductive resin, for example, ethyl cellulose, nitrocellulose, methoxymethylated nylon, ethoxymethylated nylon, copolymer nylon, polyvinyl hydrin, or casein is used. Examples of the conductive particle dispersion resin include conductive particles such as carbon, aluminum, indium oxide, and titanium oxide in an insulating resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer, and polymethyl methacrylate. A small amount dispersed is mentioned.
[0231]
As the conductive brush as the contact charging member, a conductive brush whose resistance is adjusted by dispersing a conductive material in commonly used fibers is used. As the fiber, a generally known fiber can be used, and examples thereof include nylon, acrylic, rayon, polycarbonate, and polyester. As the conductive material, generally known conductive materials can be used. For example, conductive metals such as copper, nickel, iron, aluminum, gold and silver; iron oxide, zinc oxide, tin oxide, antimony oxide, oxidation Examples thereof include oxides of conductive metals such as titanium; or conductive powders such as carbon black. These conductive materials may be subjected to surface treatment for the purpose of hydrophobization and resistance adjustment as necessary. In use, it is selected in consideration of dispersibility with fibers and productivity.
[0232]
As for the shape of the conductive brush, the fiber thickness is 1 to 20 denier (fiber diameter of about 10 to 500 μm), the length of the brush fiber is 1 to 15 mm, and the brush density is 10,000 to 300,000 per square inch. (1.5 x 10 per square meter⁷~ 4.5 × 10⁸About this) is preferably used.
[0233]
The image forming method of the present invention will be described with reference to the accompanying drawings.
[0234]
FIG. 1 is a view schematically showing an image forming apparatus having a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed as an example of an image forming method according to the present invention.
[0235]
The photosensitive member 36 is charged by a charging roller 31 as a contact charging unit, and an image portion is exposed with a laser beam 40 to form an electrostatic latent image. The toner 30 accommodated in the developing device 32 is applied onto the toner carrier 34 by the toner application roller 35 and the application blade 33, and the toner layer on the toner carrier 34 is brought into contact with the surface of the photoconductor 36 so as to contact the photoconductor 36. The upper electrostatic latent image is developed by a reversal developing method to form a toner image on the photoreceptor 36. At least a DC bias is applied to the toner carrier 34 by the bias applying means 41. The toner image on the photosensitive member 36 is transferred onto a recording material 38 as a transfer material being conveyed by a transfer roller 37 which is a transfer means to which a bias is applied by a bias applying means 42 and transferred onto the recording material. The toner image is fixed by a heat and pressure fixing means 43 having a heat roller and a pressure roller.
[0236]
The untransferred toner on the photoreceptor 36 after the transfer process is conveyed to the charging roller 31 without going through a cleaning process by a cleaning member such as a blade cleaning unit. The photosensitive member 36 having the transfer residual toner is charged again by the charging roller 31, and an electrostatic latent image is formed by exposure with laser light 40 after charging. The photosensitive member 36 having the transfer residual toner is subjected to the development of the electrostatic latent image by the toner on the toner carrier 34 and the recovery of the transfer residual toner to the toner carrier 34. The toner image on the photoconductor 36 after the simultaneous development cleaning process is transferred onto the recording material 38 being conveyed by the transfer roller 37. After the transfer process, the photoconductor 36 is charged again by the charging roller 31, and thereafter the same process is repeatedly performed.
[0237]
In the reversal development method, as a preferable development condition for carrying out the simultaneous development cleaning, the dark portion potential (V_d) And light potential (V₁) And a DC bias (V) applied to the toner carrier._DC)_d-V_DC｜ ＞ ｜ V₁-V_DCIt is better to set so that the relationship | More preferably, | V_d-V_DCThe value of | is | V₁-V_DCIt is better to be at least 10V larger than the value of |.
[0238]
FIG. 2 shows another example of an image forming apparatus that can more smoothly remove toner contributed to development from the developing sleeve in addition to supplying toner to the developing sleeve as a toner carrier.
[0239]
In FIG. 2, reference numeral 1 denotes a photosensitive drum, around which a primary charging roller 2 as a contact charging unit, a developing device 8 as a developing unit, a transfer charging roller 21 as a contact transfer unit, and a register roller 19 are provided. The photosensitive drum 1 is charged to, for example, −700 V by the primary charging roller 2. The voltage applied by the bias applying means 5 is, for example, −1350V DC voltage. And it exposes by irradiating the photosensitive drum 1 with the laser beam 7 by the laser generator 6, and a digital electrostatic latent image is formed. The electrostatic latent image on the photosensitive drum 1 is developed with a non-magnetic one-component toner 15 by the developing unit 8, and a bias voltage is applied by a bias applying unit 24 that is in contact with the photosensitive drum 1 via a recording material 20 as a transfer material. The image is transferred onto the recording material 20 by the applied transfer roller 21. The recording material 20 on which the toner image 26 is placed is conveyed to the heating and pressure fixing device 27 having the heating roller 28 and the pressure roller 29 by the conveying belt 25 and fixed on the recording material 20.
[0240]
The charging roller 2 is basically composed of a central cored bar 4 and a conductive elastic layer 3 formed on the outer periphery thereof.
[0241]
As shown in FIGS. 3 and 4, the developing unit 8 is configured such that the toner layer on the developing sleeve 9 as a toner carrying member is in contact with the photosensitive drum 1 and the bias is applied by the bias applying unit 18 and the elastic layer 10. A developing sleeve serving as a toner carrier comprising an elastic roller 9 having 11 is disposed. A toner application roller 13 having a metal core 13 and an elastic layer 14 to which a bias is applied by a bias applying means 17 is disposed in the developing device 8. A toner regulating blade 16 is provided as a member for regulating the amount of toner that adheres to the developing sleeve 9 and is conveyed, and the amount of toner (toner layer) conveyed to the developing region by the contact pressure of the toner regulating blade 16 against the developing sleeve 9 Thickness) is controlled. In the development area, at least a DC development bias is applied to the development sleeve 9, and the toner layer on the development sleeve comes into contact with the surface of the photosensitive drum 1 and is transferred onto the photosensitive drum 1 in accordance with the electrostatic latent image to form a toner image. Form.
[0242]
In order to perform the simultaneous development cleaning, when the light portion potential of the photosensitive drum 1 is 0 to 250 V and the dark portion potential is 300 to 1000 V, the supply bias voltage applied by the bias applying unit 17 is 100 to 900 V. The developing bias voltage applied by the bias applying means 18 is preferably 100 to 900V. Further, the supply bias voltage applied by the bias applying unit 17 is larger by 10 to 400 V in absolute value than the developing bias voltage applied by the bias applying unit 18, and the supply of the nonmagnetic toner 15 to the developing sleeve 9 and The nonmagnetic toner is preferably peeled off from the developing sleeve 9 smoothly.
[0243]
It is preferable in terms of supplying and stripping non-magnetic toner that the surfaces of the toner application roller 12 move in the counter direction as indicated by the arrows with respect to the rotation direction of the developing sleeve 9 (the rotation direction is the same). .
[0244]
The image forming apparatus shown in FIGS. 1 and 2 employs an image forming method in which a toner image formed on an image carrier is directly transferred to a recording material without using an intermediate transfer member.
[0245]
Next, the toner image formed on the image carrier is subjected to a first transfer to an intermediate transfer member as a transfer material, and the toner image transferred onto the intermediate transfer member is subjected to a second transfer to a recording material. A forming method will be described using the image forming apparatus shown in FIG.
[0246]
In FIG. 4, an electrostatic latent image is formed by the exposure means 53 by applying a surface potential on the photosensitive drum 51 by a charging roller 52 that rotates in contact with the photosensitive drum 51 as an image carrier. The electrostatic latent image is developed by the four-component toners magenta toner, cyan toner, yellow toner, and black toner by the one-component contact developing type developing devices 54, 55, 56, and 57 to form a full-color toner image. At the time of development, any one of the developing devices 54, 55, 56, and 57 is moved so that the toner carrier of the developing device comes into contact with the surface of the photosensitive drum 51 and development is performed. When the developing device moves to the position, the toner carrier is separated from the surface of the photosensitive drum 51. This operation is repeated four times for each developing device. The toner image is transferred onto the intermediate transfer material 58 for each color, and is repeated a plurality of times to form a multiple toner image.
[0247]
The intermediate transfer member 58 is in the form of a drum, and has a holding member stretched on the outer peripheral surface, and a conductive member such as carbon black, zinc oxide, tin oxide, silicon carbide, or titanium oxide is sufficient on the substrate. A material having a dispersed elastic layer (for example, nitrile butadiene rubber) is used. A belt-like intermediate transfer member may be used.
[0248]
The intermediate transfer member 58 is a drum-shaped member having an elastic layer 60 having a hardness of 10 to 50 degrees (JIS K-6301) formed on the surface of the support member 59, or a transfer material (recording material) in the case of a transfer belt. The transfer portion is preferably composed of a support member having an elastic layer 60 having this hardness.
[0249]
In the transfer from the photosensitive drum 51 to the intermediate transfer member 58, a bias current is applied to the metal core 59 as a support member of the intermediate transfer member 58 from the power source 66, whereby a transfer current is obtained and the toner image is transferred. Corona discharge or roller charging from the back of the holding member or belt may be used.
[0250]
The multiple toner images on the intermediate transfer body 58 are collectively transferred onto the recording material S by the transfer means 61. As the transfer means, a contact electrostatic transfer means using a corona charger, a transfer roller, or a transfer belt is used.
[0251]
The recording material S having a toner image includes a fixing roller 68 as a fixing member having a heating body 67 therein, and a pressure roller 69 of a heat fixing device 70 having a pressure roller 69 in pressure contact with the fixing roller 68. As the recording material S passes through the abutting nip portion with respect to 69, the toner image is fixed on the recording material S.
[0252]
The toner containing carbon black used in the present invention is used as a black toner in one developing device selected from the developing devices 54, 55, 56 and 57 of the image forming apparatus described above, and the remaining three developments. The container uses three chromatic color toners. The black toner used in the present invention is used for forming a color image or a full-color image in combination with a chromatic color toner, or for forming a monochrome image using only the black toner.
[0253]
In the image forming apparatus in FIG. 4, development is performed by moving the developing device 54 to a position where development is possible, and the developed toner image is transferred to the intermediate transfer body 58. After this first transfer, the photosensitive drum 51. The toner remaining on the surface of the toner is collected and cleaned by the developing device 54. When the toner remaining on the surface of the photosensitive drum 51 is collected by the developing unit 54, the developing unit 54 is moved back to the original position, and then the developing unit 55 is moved to a position where development is possible. 54, and the developing devices 55 and 56 operate in sequence in the same manner. Reference numeral 65 denotes a cleaner (second cleaning means) having a cleaning member 64 for removing toner remaining on the surface of the intermediate transfer body 58 after the second transfer.
[0254]
An image forming method using the two-component contact development method will be described with reference to FIGS.
[0255]
FIG. 5 is a schematic diagram of an image forming apparatus using a developing device using a two-component developer for magnetic brush development, used as an example of an embodiment of the image forming method of the present invention, used in an embodiment described later. This will be described with reference to FIG.
[0256]
In FIG. 5, a charging brush roller 75 as a charging means for the photosensitive member 72 (resistance is adjusted by dispersing carbon black in nylon fiber, the fiber thickness is 6 denier, the length of the brush fiber is 3 mm, and the brush density. Is 100,000 per square inch, rotating at a peripheral speed of 120% in the opposite direction to the rotation of the photosensitive member) and contacting the photosensitive member 72 to apply a bias to charge, and exposure by laser light 76 (600 dpi, binary) Then, an electrostatic charge latent image is formed on the photoreceptor 72. A magnetic brush formed of a two-component developer having toner and a magnetic carrier on the developer carrier 71 of the developing device 85 is brought into contact with the photosensitive member 72, and the electrostatic charge latent image of the photosensitive member 72 is subjected to reversal development. Is developed to form a toner image.
[0257]
At least a direct current bias is applied to the developer carrier 71 by a bias applying means (a development contrast is set to 500 V as a direct current component, and 1.8 kV is applied as an alternating current component).
[0258]
The toner image on the photoconductor 72 is transferred to a recording material 74 as a transfer material being conveyed by a transfer corona charger 73 (not in contact with the photoconductor 72) as a transfer means, and the toner on the recording material 74 is transferred. The image is fixed on the recording material 74 by a heat and pressure fixing unit having a heating roller 77 including a heater 78 and a pressure roller 79. As the photoconductor 72, the photoconductor of photoconductor production example 71 having a contact angle of 85 ° or more with water on the surface of the photoconductor was used. The transfer residual toner on the photoreceptor 72 after the transfer process does not go through the cleaning process. The photoreceptor 72 that has been neutralized by the erase exposure 81 is charged again by the charging brush roller 75, and an electrostatic charge latent image is formed by the exposure 76. The photosensitive member 72 having the transfer residual toner is subjected to the development of the electrostatic charge latent image by the magnetic brush on the developer carrier 71 and the recovery of the transfer residual toner to the developer carrier 71. The toner image on the photoconductor 72 after the simultaneous development cleaning process is transferred onto the recording material 74 being conveyed by the transfer corona charger 73, and the photoconductor 72 after the transfer process is charged by the erase exposure 81 and charged. The brush roller 75 is charged again, and the same process is repeated thereafter.
[0259]
FIG. 6 is an enlarged view of the developing unit in FIG. In FIG. 6, the photosensitive member 72 is in contact with the magnetic brush formed of the two-component developer 90 on the developer carrier 71.
[0260]
The developer carrier 71 is made of a nonmagnetic material such as aluminum or SUS316. The developer carrier 71 has a substantially right half circumferential surface protruding into the developing device 85 in a laterally long opening formed in the container longitudinal direction on the left lower wall of the developing device 85, and the left substantially half circumferential surface is exposed outside the container so as to be rotatable. The bearing is installed horizontally and is driven to rotate in the direction of the arrow.
[0261]
It is a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is inserted into the developer carrier 71 and positioned and held in the position and orientation shown in the figure. Even when the developer carrier 71 is rotationally driven, this magnet 94 is shown in the figure. Fixed and held in position and orientation. The magnet 94 has N-pole magnetic poles 92, 95, and 96, and has five S-pole magnetic poles 91 and 93. The magnet 94 may be an electromagnet instead of a permanent magnet.
[0262]
Reference numeral 83 denotes a non-magnetic blade as a developer regulating member having a base fixed to the side wall of the container on the upper edge side of the developer supply opening in which the developer carrier 71 is disposed. It is bent into a letter shape.
[0263]
Reference numeral 84 denotes a magnetic carrier limiting member having an upper surface in contact with the lower surface side of a non-magnetic blade (developer regulating member) 83 and having a front end surface as a developer guide surface. A portion constituted by the nonmagnetic blade 83 and the magnetic carrier return member 84 is a restricting portion.
[0264]
Reference numeral 90 denotes a developer layer having toner and a magnetic carrier. Reference numeral 86 denotes a non-magnetic toner.
[0265]
Reference numeral 97 denotes a toner supply roller that operates according to an output obtained by a toner density detection sensor (not shown). As the sensor, a developer volume detection method, a piezoelectric element, an inductance change detection element, an antenna method using an alternating bias, and a method for detecting optical density can be used. The nonmagnetic toner 86 is supplied by rotating or stopping the roller. The fresh developer replenished with the toner 86 is mixed and stirred while being conveyed by the developer conveying roller 87. Therefore, tribo is applied to the toner replenished during the conveyance. Reference numeral 88 denotes a threshold plate, which is notched at both ends in the longitudinal direction of the developing device. Fresh developer conveyed by the screw 87 is transferred to the screw 89 at this portion.
[0266]
The N magnetic pole 96 is a transport pole. The collected developer after development is collected in a container, and the developer in the container is further transported to a regulating portion.
[0267]
In the vicinity of the N magnetic pole 96, the fresh developer conveyed by the screw 89 provided in the vicinity of the developer carrier 71 and the recovered developer after development are exchanged.
[0268]
The distance d between the end of the nonmagnetic blade 83 and the surface of the developer carrying member 1 was 400 μm. A preferable setting range of d is 100 to 900 μm. If this distance is smaller than 100 μm, the carrier particles are clogged in the meantime, and the developer layer is likely to be uneven, and the developer necessary for good development cannot be applied, and only a developed image with a small density and unevenness can be obtained. It may not be possible. On the other hand, if the distance is greater than 900 μm, the amount of developer applied onto the developer carrier 71 increases, and the predetermined developer layer thickness cannot be regulated, and magnetic particle adhesion to the latent image carrier increases. There is a tendency that the circulation of the developer and the development restriction by the developer limiting member 84 are weakened, and the toner tribo is insufficient and fogging easily occurs.
[0269]
It is preferable that the thickness of the developer layer on the developer carrier 71 is slightly larger than the facing gap distance between the developer carrier 71 and the photoconductor 72. This distance was set to 400 μm. Preferably, it is good to set to 50-800 micrometers.
[0270]
【Example】
Hereinafter, the present invention will be described in more detail with specific methods for manufacturing toners and photosensitive drums, examples, and comparative examples.
[0271]
Carbon black shown in Table 1 was prepared.
[0272]
[Table 1]

[0273]
[Preparation of Masterbatch Dispersions 1-19]
As shown in Table 2 below, attritor 1S (Mitsui Mining Co., Ltd.) combines 2,000 g of styrene monomer with carbon blacks a to 1 and dispersant shown in Table 1 in the types and addition amounts shown in Table 2, respectively. 2) Zirconia beads are used and stirred at 200 rpm for 180 minutes at a temperature of 25 ° C. to produce master batch dispersions 1 to 19 in which carbon black and a dispersant are dispersed in a styrene monomer. did. Table 2 shows the viscosities of the obtained master batch dispersions 1 to 19.
[0274]
[Table 2]

[0275]
[Outside 9]

[0276]
[Production Example A of Polymerized Toner]
To 700 g of ion-exchanged water in a 4-liter flask for 2 liters, 0.1 M Na was added._Three PO_Four 500 g of the aqueous solution was added and heated to 60 ° C., and then stirred at 12000 rpm using a high-speed stirring device TK type homomixer (manufactured by Tokushu Kika Kogyo). To this, 1.0M-CaCl₂ 76 g of an aqueous solution was gradually added to obtain an aqueous medium containing a minute hardly water-soluble dispersion stabilizer.
[0277]
(Pre-dispersion) Master batch dispersion 20 112g
(Monomer) Styrene 66g
34 g of n-butyl acrylate (n-BA)
(Polar resin) saturated polyester (condensation product of propoxylated bisphenol and terephthalic acid, acid value 14, peak molecular weight 7000) 8 g
(Release agent) Ester wax (melting point: 58 ° C) 30g
[0278]
The above formulation was heated to 60 ° C., uniformly dissolved and dispersed. Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.
[0279]
The polymerizable monomer composition is charged into the aqueous medium, 60 ° C., N₂ Under an atmosphere, the mixture was stirred at 12000 rpm for 10 minutes with a TK homomixer to granulate the polymerizable monomer composition. Thereafter, while stirring with a paddle stirring blade (50 rpm), the mixture was reacted at the same temperature for 5 hours, then heated to 80 ° C. and further reacted for 5 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water, and drying to obtain sharp black polymer particles having a weight average diameter of about 6.7 μm ( Black toner particles) were obtained.
[0280]
The specific surface area by the BET method is 140 m with respect to 100 parts by weight of the obtained black toner particles.² Polymeric toner A was obtained by externally adding 1.8 parts by weight of hydrophobic silica having a / g concentration. Table 4 shows the physical properties of the obtained toner.
[0281]
[Production Examples B to F of Polymerized Toner]
Polymerized toners B to B were prepared in the same manner as in [Polymerized toner production example A] except that master batch dispersions 2 to 6 were used in which the addition amount of the azo-based iron complex compound (1) was changed as shown in Table 2. F was produced. Table 4 shows the physical properties of the obtained toner.
[0282]
[Production Example G of Polymerized Toner]
A polymerized toner G was produced in the same manner as in [Polymerized toner production example A] except that the master batch dispersion 7 using carbon black b shown in Table 1 was used instead of carbon black a. Table 4 shows the physical properties of the obtained toner.
[0283]
[Production Examples H and I of Polymerized Toner]
0.1M-Na_Three PO_Four Aqueous solution and 1.0M-CaCl₂ Polymerized toners H and I were prepared in the same manner as in [Polymerized toner production example G] by adjusting the amount of the aqueous solution. Table 4 shows the physical properties of the obtained toner.
[0284]
[Production Examples J to R of Polymerized Toner]
Polymerized toners J to R were produced in the same manner as in [Polymerized toner production example A] except that master batch dispersions 8 to 17 using carbon blacks c to l shown in Table 1 were used instead of carbon black a. Was made. The master batch dispersion 16 was too viscous to be taken out, and toner could not be obtained. Table 4 shows the physical properties of the obtained toner.
[0285]
[Production Examples S and T of Polymerized Toner]
Except for using master batch dispersions 18 and 19 using an azo chromium compound and a zinc compound of ditertiary butylsalicylic acid in place of the azo iron compound (1), [Preparation Example A for Polymerized Toner] and Similarly, polymerization toners S and T were produced. Table 4 shows the physical properties of the obtained toner.
[0286]
[Production Examples U and V for Polymerized Toner]
Polymerized toners U and V were produced in the same manner as in [Polymerized toner production example B] except that the prescription of the polymerizable monomer composition was changed as shown in Table 3. Table 4 shows the physical properties of the obtained toner.
[0287]
[Production Examples of Polymerized Toner WZ]
Polymerized toners W to C were prepared in the same manner as in [Polymerized toner production example B] except that a part of the styrene monomer contained in the polymerizable monomer composition was changed to a mixture of divinylbenzene and diethylene glycol dimethacrylate. Z was produced. Table 4 shows the physical properties of the toner thus obtained.
[0288]
[Production Examples AA and BB of Polymerized Toner]
Polymerized toners AA and BB were produced in the same manner as in [Polymerized toner production example B] except that the addition amount of the polymerization initiator and the temperature conditions during the polymerization reaction were changed. Table 4 shows the physical properties of the obtained toner.
[0289]
Table 3 shows the formulations of the above polymerized toners A to Z, AA, and BB.
[0290]
[Production example CC of pulverized toner]
(Binder resin) 100 parts by weight of styrene-butyl acrylate copolymer
(Weight average molecular weight about 300,000, Tg 60 ° C.)
(Coloring agent) Carbon black e 7 parts by weight
(Charge control agent) Azo-based iron compound (1) 2 parts by weight
(Release agent) Ester wax 3 parts by weight
[0291]
The above materials were mixed in advance and melt kneaded at 130 ° C. with a twin screw extruder. This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass toner crushed product. Further, the coarsely pulverized product was finely pulverized by a collision type pulverizer using a jet stream, and then classified by wind to obtain black toner particles having a weight average diameter of about 6.7 μm. The specific surface area by the BET method is 140 m with respect to 100 parts by weight of the obtained black toner particles.² Externally added 1.5 parts by weight of hydrophobic silica of / g to obtain ground toner CC. Table 4 shows the physical properties of the obtained toner.
[0292]
[Production example DD of pulverized toner]
A ground toner DD was obtained in the same manner as in [Crushed toner production example CC] except that carbon black j shown in Table 1 was used instead of carbon black e. Table 4 shows the physical properties of the obtained toner.
[0293]
[Table 3]

[0294]
[Table 4]

[0295]
(Photoreceptor Production Example 1)
An aluminum cylinder having a diameter of 30 mm and a length of 254 mm was used as a substrate. On this substrate, layers having the following constitutions were sequentially laminated by dip coating to produce a photoreceptor 1.
[0296]
(1) Conductive coating layer: Mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenolic resin. Film thickness 15 μm.
[0297]
(2) Undercoat layer: Mainly composed of modified nylon and copolymer nylon. Film thickness 0.6 μm.
[0298]
(3) Charge generation layer: Mainly composed of an azo pigment having absorption in a long wavelength region dispersed in a butyral resin. Film thickness 0.6 μm.
[0299]
(4) Charge transport layer: Mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight of 20,000 by the Ostwald viscosity method) at a weight ratio of 8:10, and polytetrafluoroethylene powder ( 10% by weight with respect to the total solid content was added and dispersed uniformly. Film thickness 25 μm.
[0300]
The contact angle of water on the surface of the obtained photoreceptor 1 with respect to water was 95 degrees.
[0301]
The contact angle was measured using pure water, and the device used was Kyowa Interface Science Co., Ltd., contact angle meter CA-DS type.
[0302]
(Photoreceptor Production Example 2)
A charge transport layer having a film thickness of 25 μm was formed in the same manner as in Photoconductor Production Example 1 except that no polytetrafluoroethylene powder (particle size 0.2 μm) was added to the charge transport layer. Was made.
[0303]
The contact angle of water on the surface of the obtained photoreceptor 2 with respect to water was 79 degrees.
[0304]
<Example 1>
A 600 dpi laser beam printer (manufactured by Canon: LBP-860) was prepared as the image forming apparatus shown in FIG. 1, and the process speed was modified to 94 mm / s.
[0305]
The cleaning rubber blade in the process cartridge was removed, and the charging method of the apparatus was contact charging in contact with the rubber roller, and the applied voltage was DC component (-1400V). As the process speed is increased, uniform charging of the photoreceptor is a severe condition.
[0306]
As the photoconductor, the photoconductor 1 manufactured in Photoconductor Production Example 1 was used.
[0307]
Next, the development part in the process cartridge was modified. Medium resistance rubber roller (16φ, hardness ASKER C45 degree, resistance 10) made of urethane foam instead of stainless steel sleeve as toner carrier^Five (Ω · cm) was used to contact the photoreceptor. The moving direction of the surface of the toner carrying member is the same as the moving direction of the surface of the photosensitive member, and is driven to be 130% with respect to the circumferential speed of the photosensitive member.
[0308]
As a means for applying the toner to the toner carrier, an application roller was provided in contact with the toner carrier at the development portion. Further, a stainless steel blade coated with a resin for controlling the toner coating layer was mounted on the toner carrier. The developing bias voltage applied to the toner carrying member during development was only the DC component (−450 V).
[0309]
The image forming apparatus was remodeled and the process conditions were set to suit these process cartridge modifications.
[0310]
The photosensitive member charging potential was -800V for the dark portion potential and -150V for the bright portion potential. 75g / m as transfer material² Paper was used.
[0311]
Using the polymerized toner A, 2000 images of durable sheets were printed with this image forming apparatus, and a high-quality image with high density and no image contamination was obtained. There was no problem in fixing property.
[0312]
The image evaluation was performed on the image density and image smear after 100 character images having a printing area ratio of 4% were printed from the beginning and 2000 images were continuously printed.
[0313]
(1) Image density
A solid black image having a square of 5 mm on each side was formed, and the image density of the solid black image was measured using an image density measuring machine RD918 manufactured by Macbeth.
[0314]
(2) Image contamination
The image stain was evaluated by visually observing the fixed image and evaluating it based on the following evaluation criteria.
[0315]
A: Not generated
B: Slightly generated
C: Occurrence to some extent
D: The occurrence is extremely bad
[0316]
Furthermore, the transferability, fog, resolution, and charging roller contamination after 100 character images having a printing area ratio of 4% were printed continuously from the beginning were evaluated.
[0317]
(3) Transferability
The transfer property is determined by removing the transfer residual toner on the photoconductor by tape with Mylar tape, and then removing the Mylar tape on the paper. From the Macbeth density on the paper, Macbeth with only Mylar tape on the paper. Evaluation was made by subtracting the concentration. Therefore, the smaller the numerical value, the better the transferability.
[0318]
(4) fog
Fogging removes the transfer residual toner on the photoconductor when solid white image is formed by taping with Mylar tape, and the Macbeth density of only Mylar tape on the paper from the Macbeth density of the peeled Mylar tape on the paper Evaluation was made by subtracting. Therefore, the smaller the value, the better the fog suppression.
[0319]
(5) Resolution
The resolving power was evaluated based on the reproducibility of a 600 dpi 50 μm small-diameter isolated dot as shown in FIG.
[0320]
A: Less than 5 defects in 100
B: 6-10 defects in 100
C: 11-20 defects in 100
D: 20 or more defects in 100
[0321]
(6) Contamination amount of charging roller
The contamination of the charging roller is caused by the toner weight per unit area on the charging roller (mg / cm² ) Was measured.
[0322]
Furthermore, the matching with respect to each of the developing roller, the photosensitive drum and the fixing device after continuous printing of 2000 sheets was evaluated as follows.
[0323]
(7) Matching with developing roller
After the printout test was completed, the appearance of the residual toner on the developing roller surface and the effect on the printout image were visually evaluated.
[0324]
A: Very good (not generated)
B: Good (almost no occurrence)
C: Normal (there is sticking, but there is little influence on the image)
D: Poor (much sticking and causes image unevenness)
[0325]
(8) Matching with photosensitive drum
After completion of the printout test, the occurrence of scratches on the surface of the photosensitive drum and the sticking of the residual toner and the influence on the printout image were visually evaluated.
[0326]
A: Very good (not generated)
B: Good (slight scratches are seen but there is no effect on the image)
C: Normal (there is sticking or scratching, but there is little effect on the image)
D: Poor (there is much sticking and causes vertical stripe-like image defects)
[0327]
(9) Matching with fixing device
After completion of the printout test, scratches on the surface of the fixing roller and the adhesion state of the residual toner were visually evaluated.
[0328]
A: Very good (not generated)
B: Good (although slight fixation is observed, there is no influence on the image)
C: Normal (there is sticking or scratching, but there is little effect on the image)
D: Poor (much sticking and causes image defects)
[0329]
<Example 2>
Evaluation was made in the same manner as in Example 1 except that the process speed was increased to 120 mm / s. As shown in Table 5, since the conditions became more severe due to an increase in process speed, the results were generally good although they were slightly inferior to those of Example 1.
[0330]
<Examples 3 to 14>
Evaluation was performed in the same manner as in Example 1 except that polymerized toners B to E, G, and J to P were used as toners. The results are shown in Table 5.
[0331]
<Comparative example 1>
Evaluation was performed in the same manner as in Example 1 except that the polymerized toner F was used as the toner. As shown in Table 5, since significant image staining occurred from the initial stage and it was difficult to continuously print 2000 sheets, the evaluation was inevitably stopped midway.
[0332]
<Comparative Examples 2 and 3>
Evaluation was performed in the same manner as in Example 1 except that polymerized toners Q and R were used as toners. As shown in Table 5, the specific azo-based iron compound in the present invention is not used, or the carbon black used in the toner is not the specific carbon black in the present invention, so a good result cannot be obtained. It was.
[0333]
<Comparative Examples 4 and 5>
Evaluation was carried out in the same manner as in Example 1 except that polymerized toners S and T were used as toners. As shown in Table 5, since the dispersant used in the toner is not the specific azo-based iron compound in the present invention, good results were not obtained. The polymerization toner S caused a decrease in image density from the beginning. The polymer toner T showed a good image density at the initial stage, but not only the image density decreased but also the fog and the image stain were remarkably deteriorated at 2000 sheets. Also, matching with the image forming apparatus was not sufficient.
[0334]
<Examples 15 to 22>
Evaluation was performed in the same manner as in Example 1 except that polymerized toners U to Z, AA, and BB were used as toners. The results are shown in Table 5.
[0335]
  <Reference example 1>
  Evaluation was performed in the same manner as in Example 1 except that the pulverized toner CC was used as the toner. As shown in Table 5, the results were generally good.
[0336]
<Comparative Example 6>
Evaluation was performed in the same manner as in Example 1 except that pulverized toner DD was used as the toner. As a result, as shown in Table 5, since remarkable image staining occurred from the initial stage and it was difficult to continuously print 2000 sheets, the evaluation was unavoidably stopped midway.
[0337]
[Table 5]

[0338]
<Examples 24-32>
Polymerized toners G to I are used as toners, and each external additive (specific surface area by BET method is 140 m).² Evaluation was performed in the same manner as in Example 1 except that the amount added was 0.5%, 1.8%, and 3.0%. As shown in Table 6, when the amount of the external additive added is 0.5%, there is a little amount of contamination on the charging roller due to the increase in fog. When 3.0%, the simultaneous development cleaning is achieved, but the fixability is high. Although somewhat inferior, generally good results were obtained.
[0339]
[Table 6]

[0340]
<Example 33>
In the image forming apparatus used in the first exemplary embodiment, a single-layer sponge roller is used as the toner applying roller 35 in the developing container 32, and a bias voltage is applied to the toner applying roller 35 from a bias applying unit (not shown). Except for such changes, image formation was performed and evaluated in the same manner as in Example 1.
[0341]
As a developing bias voltage to be applied to the developing roller 34 at the time of development, only a DC component was applied at −300 V, and to the toner application roller 35, only a DC component was applied at −480 V as an application bias voltage.
[0342]
As a result of the evaluation, both the image density and the fog suppression were stable and good as compared with Example 1, the simultaneous development cleaning was also achieved, and an excellent image quality was obtained.
[0343]
Matching with the image forming apparatus was also good.
[0344]
<Example 34>
An image was formed using the polymerized toner B produced in polymerized toner production example B in the developing device 57 of the image forming apparatus shown in FIG.
[0345]
In the image forming apparatus, as shown in FIG. 4, a cleaner having a first cleaning member for cleaning and removing toner existing on the surface of the photosensitive drum after the transfer process is provided between the transfer portion and the developing portion. In addition, after the second transfer step, as a cleaning means for removing the toner remaining on the surface of the intermediate transfer member, a cleaner having a cleaning member that contacts the surface of the intermediate transfer member is located downstream of the second transfer unit. And provided upstream of the first transfer portion.
[0346]
As the developing device 57, the one having the configuration of the developing device 8 shown in FIGS. 2 and 3 was used. The toner remaining on the surface of the photosensitive drum after the first transfer is developed only for the toner existing in the non-image area at the developing portion after development after the charging polarity is made negative by applying a charging bias at the charging portion. It was configured to be collected in the vessel.
[0347]
In the developing device 8, a medium resistance rubber roller (16φ) made of silicone rubber in which carbon black is dispersed to adjust the resistance is used as a toner carrier 9, and is in contact with the photoconductor. The moving direction and the rotational peripheral speed of the surface of the toner carrying member 9 are the same in the contact portion with the surface of the photosensitive member, and are driven so as to be 150% of the photosensitive member rotational peripheral speed. That is, the peripheral speed of the toner carrier is 120 mm / s, and the relative speed with respect to the surface of the photoreceptor is 80 mm / s.
[0348]
As a means for applying toner to the toner carrier, a single layer sponge roller was provided as the application roller 12 and brought into contact with the toner carrier. At the contact portion, the toner was applied onto the toner carrier by rotating so that the moving direction of the surface of the application roller 12 was moved in the direction opposite to the moving direction of the toner carrier. Further, a stainless steel blade 16 coated with resin was attached to control the coat layer of the toner on the toner carrier.
[0349]
As the photoreceptor, the photoreceptor 1 produced in (Photoreceptor Production Example 1) was used, and toner B was used as the toner. Image forming conditions were set so as to satisfy the following development conditions and transfer conditions.
[0350]
Photoconductor dark part potential: -700V
Photoreceptor bright part potential: -150V
Development bias applied to the development roller: -450V (DC component only)
Bias applied to toner application roller: -300V (DC component only)
Transfer bias applied to the intermediate transfer member in the first transfer process: 350 V (only DC component)
Transfer bias applied to the transfer roller in the second transfer step: 1100 V (DC component only)
[0351]
The toner image transferred onto the recording material under the above image forming conditions was heat-fixed on the recording material by the following heat fixing device.
[0352]
As the heat fixing device 70, a heat roll type fixing device having no oil application function was used. At this time, both the upper roller 68 and the lower roller 69 had a fluororesin surface layer, and the diameter of the roller was 60 mm. The fixing temperature was set to 150 ° C., and the nip width was set to 7 mm.
[0353]
Using the image forming apparatus having the above-described configuration, a continuous image output test of 2000 sheets was performed. As a result, a high-quality image with high density and no image contamination was obtained.
[0354]
The toner adhesion weight on the charging roller is 0.41 mg / cm.² The matching with other image forming apparatuses was also good.
[0355]
(Example 35)
A carrier was mixed with the polymerized toner A to prepare a two-component developer, and an image was formed on the image forming apparatus shown in FIGS. 5 and 6 using the two-component developer at a process speed of 180 mm / sec. However, a high-quality image with high density and no image contamination was obtained. Also, there was no problem in fixing property.
[0356]
In the image evaluation, after 100 characters having a printing area ratio of 4% were printed continuously from the beginning, the image density on the 100th sheet and image contamination due to poor charging of the image were evaluated.² The toner adhesion amount [mg] (contamination amount of the charging roller) was measured. The image density and image smear were also evaluated after printing 2000 sheets of characters with a printing ratio of 4%.
[0357]
Furthermore, the transferability, fogging, and resolution after 100 characters having a printing area ratio of 4% were continuously printed from the beginning were evaluated.
[0358]
The image density, image stain, charging roller contamination amount, transferability, fog and resolution were evaluated in the same manner as in Example 1.
[0359]
As the carrier of the above two-component developer, a ferrite carrier in which a surface layer having an average particle diameter of 60 μm was coated with a silicone resin was used, and the toner concentration was set to 7%.
[0360]
Table 7 shows the evaluation results.
[0361]
<Example 36>
Evaluation was conducted in the same manner as in Example 35 except that the photoconductor of Photoconductor Production Example 2 was used. As shown in Table 7, although the results were slightly inferior to those of Example 35, generally good results were obtained.
[0362]
<Examples 37 to 40>
Evaluation was conducted in the same manner as in Example 35 except that polymerized toners B to E were used as toners. As shown in Table 7, the results were generally good.
[0363]
<Comparative Example 7>
Evaluation was conducted in the same manner as in Example 35 except that the polymerized toner F was used as the toner. As a result, as shown in Table 7, since the specific azo-based iron complex compound in the present invention was not contained, the toner was remarkably contaminated with the charging member, resulting in a remarkable image defect due to poor charging.
[0364]
[Table 7]

[0365]
【The invention's effect】
In the present invention, the charge control effect due to the good dispersion of the carbon black due to the combination of the specific carbon black and the specific azo-based iron complex compound, and the charge control effect that suppresses excessive charging of the azo-based iron complex compound itself Due to this synergistic effect, excellent development characteristics can be obtained due to good charge controllability of the toner on the toner carrying member in which excessive charging is suppressed.
[0366]
Furthermore, when using the simultaneous development cleaning method, the charge polarity control and charge amount control of the transfer residual toner on the photosensitive member by the charging member can be performed more reliably and uniformly, and the transfer residual toner in the development process can be recovered more stably. And developability can be obtained.
[0367]
Furthermore, the simultaneous development cleaning process can be applied to an image forming method having a high process speed at a low cost without adding an auxiliary member.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an image forming apparatus that uses a contact one-component developing device and employs a simultaneous development cleaning method, which is used as an example of an image forming method of the present invention.
FIG. 2 is a schematic diagram illustrating an image forming method using a contact one-component developing device, which is used as still another example of the image forming method of the present invention.
3 is an enlarged view of a developing device of the image forming apparatus shown in FIG.
FIG. 4 is a diagram schematically illustrating an image forming apparatus using an intermediate transfer member.
FIG. 5 is a schematic view of an image forming apparatus using a contact two-component developing device using a two-component developer for magnetic brush development, which is used as an example of the image forming method of the present invention, and adopting a simultaneous development cleaning method. It is the figure shown in.
6 is an enlarged view of the developing unit in FIG. 5;
FIG. 7 is an explanatory diagram of an isolated dot pattern for evaluating the degree of development.
FIG. 8 is a graph showing changes in viscosity when carbon black and an azo-based iron complex compound according to the present invention are dispersed in styrene.
FIG. 9 is a graph showing the relationship between the amount of oil absorption and viscosity of carbon black when a certain amount of an azo-based iron complex compound is added and dispersed in styrene in the carbon black according to the present invention.
FIG. 10 is a schematic diagram showing an example of a cross section of toner particles containing a wax component.
FIG. 11 is a schematic explanatory diagram of a measuring device for measuring the electrical resistance value of the developing roller.
[Explanation of symbols]
1 Developer carrier
2 Photoconductor (image carrier)
4 Transfer material
5 Charging brush roller
13 Non-magnetic blade
15 Developer
20 Two-component developer
24 Magnet
30 Toner
31 Charging roller
32 Developer container
33 Toner Regulation Blade
34 Toner carrier (elastic roller)
35 Toner application roller
36 photoconductor (image carrier)
37 Transfer roller
38 Transfer material
40 Laser light (exposure)
41, 42 Bias applying means
43 Fixing device

Claims (47)

A charging step of charging an image carrier for carrying an electrostatic latent image;
An exposure step of forming an electrostatic latent image on the charged image carrier by image exposure;
A developing step of developing the electrostatic latent image with toner included in a developing device to form a toner image; and a transferring step of transferring the toner image formed on the surface of the image carrier to a transfer material;
And an image forming method using a simultaneous development cleaning method in which the developing device also serves to collect the toner remaining on the surface of the image carrier after the transfer step.
The toner has toner particles containing at least a binder resin, carbon black, and an azo-based iron compound, and an inorganic fine powder,
The carbon black has an average primary particle size of 25-80 nm,
The azo-based iron compound has the following general formula (1)
[Outside 1]

[Wherein, X ₁ and X ₂ represent a member selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group and a halogen atom, and X ₁ and X ₂ are the same or different, m And m ′ represents an integer of 1 to 3, R ₁ and R ₃ are a hydrogen atom, a C _{1 to} C ₁₈ alkyl group, a C _{2 to} C ₁₈ alkenyl group, a sulfonamide group, a mesyl group, a sulfonic acid group, carboxy ester group, hydroxy group, an alkoxy group of C ₁ -C _18, shows a member selected acetylamino group, from the group consisting of benzoylamino group and a halogen atom, R ₁ and R ₃ are the same or different, n and n 'is an integer of 1 to 3, _{R 2} and _{R 4} represents a hydrogen atom or a nitro group, ^{a +} is an ammonium ion, hydrogen ion, sodium Ion, showing a cation ion selected from the group consisting of potassium ions and their mixtures ions. ]
Has a compound represented by in,
The toner particles are produced by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer, the carbon black and the azo iron compound in an aqueous medium,
The polymerizable monomer composition is prepared by mixing a dispersion in which the carbon black and the azo-based iron compound are dispersed in a first polymerizable monomer with at least a second polymerizable monomer. image forming method, characterized in that the.   The image forming method according to claim 1, wherein the carbon black has an average primary particle size of 25 to 55 nm.   The image forming method according to claim 1, wherein the carbon black has a DBP oil absorption of 40 to 150 ml / 100 g. 4. The image forming method according to claim 1, wherein the carbon black has a specific surface area due to nitrogen adsorption of 100 m ² / g or less and a volatile content of 2% or less. The toner particles have a carbon black content A weight% and an azo iron compound content B weight% under the following conditions: 2 ≦ A / B ≦ 35
The image forming method according to claim 1, wherein: In the toner, the shape factors SF-1 and SF-2 have the following relationship: 100 <SF-1 ≦ 160
100 <SF-2 ≦ 140
The image forming method according to claim 1, wherein: In the toner, the shape factors SF-1 and SF-2 have the following relationship: 100 <SF-1 ≦ 140
100 <SF-2 ≦ 120
The image forming method according to claim 1, wherein:   The toner particles are produced by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer, the carbon black, the azo-based iron compound, a release agent, and a polar resin in an aqueous medium. The image forming method according to claim 1, wherein the image forming method is one. The polymerizable monomer composition comprises at least a second polymerizable monomer, a release agent, and a dispersion obtained by dispersing the carbon black and the azo-based iron compound in a first polymerizable monomer. The image forming method according to claim 8 , wherein the image forming method is prepared by mixing with the polar resin.   The toner particles contain a wax as a release agent in addition to the binder resin, the carbon black, and the azo-based iron compound, and the toner particles include the core portion of the release agent and the core portion. The image forming method according to claim 1, wherein the image forming method has a core / shell structure having a shell portion having a binder resin for covering the surface thereof.   The toner particles contain a wax and a polar resin as a release agent in addition to the binder resin, the carbon black, and the azo-based iron compound, and the toner particles include a core portion of the release agent and It has a core / shell structure having a shell portion having a binder resin covering the surface of the core portion, and an outer shell resin layer having the polar resin is formed on the surface portion of the shell portion. The image forming method according to claim 1, wherein:   In addition to the binder resin, the carbon black and the azo-based iron compound, the toner particles contain 2 to 30% by weight of a wax as a release agent based on the weight of the toner particles. The image forming method according to claim 1.   In addition to the binder resin, the carbon black, and the azo-based iron compound, the toner particles contain 2 to 25% by weight of a wax as a release agent based on the weight of the toner particles. The image forming method according to claim 1.   In addition to the binder resin, the carbon black, and the azo-based iron compound, the toner particles include 2 to 30% by weight of a wax as a release agent and 1 to 20% by weight of a polar resin, respectively. The image forming method according to claim 1, wherein the image forming method contains the particles on a weight basis.   In addition to the binder resin, the carbon black and the azo-based iron compound, the toner particles have a wax having a maximum endothermic peak in a temperature range of 40 ° C. to 90 ° C. in an endothermic curve by DSC measurement as a release agent. The image forming method according to claim 1, wherein the image forming method is an image forming method. The resin component of the toner particles has a C component insoluble in THF (tetrahydrofuran) and a component soluble in THF, and the component soluble in THF is measured by gel permeation chromatogram (GPC). The molecular weight distribution has an A component having a molecular weight of less than 1,000,000 and a B component having a molecular weight of 1,000,000 or more, and the content of the A component based on the weight of the resin component of the toner particles (W _A ), the content of the B component (W _B ) and the content of the C component (W _C ) are as follows: 30 ≦ W _A ≦ 95
0 ≦ W _B ≦ 20
0 ≦ W _C ≦ 70
5 ≦ W _B + W _C ≦ 70
The image forming method according to any one of claims 1 to 15, characterized in that meets. The resin component of the toner particles has a C component insoluble in THF (tetrahydrofuran) and a component soluble in THF, and the component soluble in THF is measured by gel permeation chromatogram (GPC). The molecular weight distribution has an A component with a molecular weight of less than 1,000,000 and a B component with a molecular weight of 1,000,000 or more, and the content of the A component based on the weight of the resin component of the toner particles (W _A ), the content of the B component (W _B ), and the content of the C component (W _C ) are as follows: 50 ≦ W _A ≦ 90
1 ≦ W _B ≦ 20
1 ≦ W _C ≦ 70
10 ≦ W _B + W _C ≦ 50
The image forming method according to any one of claims 1 to 15, characterized in that meets. The resin component of the toner particles has a component soluble in THF, and the component soluble in THF has a molecular weight distribution measured by gel permeation chromatogram (GPC) of 9000 to 1,000. The number average molecular weight (Mn) of 1,000, and the weight average molecular weight (Mw) of 5 to 500 and the ratio (Mw / Mn) of the number average molecular weight (Mn) of claim 1 to 17 The image forming method according to any one of the above. The resin component of the toner particles has a component soluble in THF, and the component soluble in THF has a molecular weight distribution measured by gel permeation chromatogram (GPC) of 10,000 to 500,000. any number average molecular weight (Mn) and weight average molecular weight of seven to four hundred (Mw) and number average molecular weight (Mn) and the ratio of claims 1 to 17, characterized in that it has a (Mw / Mn) of An image forming method according to claim 1. The toner is in any one of claims 1 to 19, characterized in that it meets with a 5-99% external additive coating ratio be coated by an external additive having an inorganic fine powder to the toner particle surface The image forming method described. 21. The image forming method according to claim 20 , wherein the external additive includes fine particles selected from the group consisting of metal oxides, nitrides, carbides, metal salts, fatty acid metal salts, carbon black, and silica. . The image forming method according to any one of claims 1 to 21 , wherein the inorganic fine powder includes fine particles selected from the group consisting of silica, alumina, titania, and double oxides thereof. The image forming method according to any one of claims 1 to 22 , wherein the inorganic fine powder has a specific surface area of 30 m ² / g by BET method. Inorganic fine powder The image forming method according to any one of claims 1 to 22, characterized in that it has a specific surface area of 50 to 400 m ² / g by BET method. The toner image forming method according to any one of claims 1 to 24, characterized in that the inorganic fine powder contains 0.1 to 8 parts by weight per part by weight of the toner particles 100. The image forming method according to any one of claims 1 to 25 , wherein the inorganic fine powder is treated with at least silicone oil. The image bearing member is made of an electrophotographic photoreceptor, the photoreceptor surface, the image according to any one of claims 1 to 26, characterized in that it has a contact angle to 85 degrees or more water Forming method. 28. The image forming method according to claim 27 , wherein a surface layer in which a compound powder containing fluorine atoms is dispersed in a resin is formed on the surface of the photoreceptor. 29. The image forming method according to claim 28 , wherein the compound powder containing fluorine atoms comprises a fluororesin powder. The developing device has a developing device for holding the toner and a toner carrier for carrying and transporting the toner held in the developing device, and is carried on the surface of the toner carrier. by the toner layer formed by the toner comes into contact with the surface of the image bearing member, an image forming method according to any one of claims 1 to 29, characterized in that the development of the electrostatic latent image is achieved. In the developing step, a toner layer with a regulated toner layer thickness is formed on the surface of the toner carrier by bringing a toner layer thickness regulating member into contact with the toner carried on the toner carrier. The image forming method according to claim 30 . In the development step, the moving direction of the surface of the toner carrying member in the developing area, an image according to any one of claims 30 or 31, characterized in that it is set in the same direction as the moving direction of the surface of the image bearing member Forming method. 3. The developing step, wherein the moving speed of the surface of the toner carrying member in the developing area is set to 1.05 to 3.0 times the moving speed of the surface of the image carrying member. 33. The image forming method according to 32 . The toner is held in the developing instrument, according to any one of claims 30 to 33 by the toner supplying member for supplying the toner to the toner carrying member, characterized in that it is supplied to the toner carrying member Image forming method. The toner supply member is a toner application roller that abuts on the surface of the toner carrier, and the movement direction of the surface of the toner application roller is set to be opposite to the method of movement of the surface of the toner carrier. The image forming method according to claim 34 , wherein A developing bias voltage is applied to the toner carrier when developing the electrostatic latent image, and a coating bias voltage is applied to the toner application roller when supplying toner to the toner carrier. 36. The image forming method according to claim 35 , wherein: The application bias voltage applied to the toner application roller is set to be larger in absolute value than the development bias voltage applied to the toner carrier, and the toner application roller supplies toner to the surface of the toner carrier. 37. The image forming method according to claim 36 , wherein the toner remaining on the surface of the toner carrying member after development is stripped off. The bright part potential of the electrostatic latent image on the image carrier has an absolute value of 0 to 250 V, the dark part potential has an absolute value of 300 to 1000 V, and the application bias voltage applied to the toner application roller is absolute The developing bias voltage applied to the toner carrier has an absolute value of 100 to 900 V, and the coating bias voltage is set to be 10 to 400 V larger in absolute value than the developing bias voltage. 37. The image forming apparatus according to claim 36 , wherein the toner application roller supplies toner to the surface of the toner carrier and strips off toner remaining on the surface of the toner carrier after development. Method. The developing device includes a developing device for holding a two-component developer having the toner and a carrier, and a developer carrying member for carrying and transporting the two-component developer held in the developing device. A magnetic brush of a two-component developer carried on the surface of the developer carrying member is brought into contact with the surface of the image carrier, so that the toner of the two-component developer uses the electrostatic latent image. The image forming method according to any one of claims 1 to 31 , wherein the development is achieved. 40. The image forming method according to claim 39 , wherein a developing bias voltage is applied to the developer carrying member when the electrostatic latent image is developed. In the transfer step, the toner image formed on the image carrier is transferred to the transfer material by bringing a transfer member to which an external voltage is applied into contact with the image carrier via the transfer material. the image forming method according to any one of claims 1 to 40, characterized in that. In the transfer step, a recording material is used as the transfer material, the toner image formed on the surface of the image carrier is transferred to the recording material, and the toner image transferred to the recording material is transferred to the recording material. the image forming method according to any one of claims 1 to 41, characterized in that it is fixed to. In the transfer step, an intermediate transfer member is used as the transfer material, and a first transfer for transferring the toner image formed on the image carrier to the intermediate transfer member is performed and transferred to the intermediate transfer member. second transfer is performed onto a recording medium the toner image, the toner image transferred to the recording material, any one of claims 1 to 41, characterized in that it is fixed on the recording material The image forming method described in 1. In the charging step, by abutting a charging member a voltage is externally applied to the image bearing member, according to any one of claims 1 to 43, characterized in that the charging of the image bearing member is performed Image forming method. 45. The image forming method according to claim 44 , wherein in the charging step, a DC voltage is applied to the charging member from the outside. 45. The image forming method according to claim 44 , wherein in the charging step, a DC voltage and an AC voltage less than twice the discharge start voltage in the DC voltage application are externally applied to the charging member. The transfer portion in the transfer step, the charging portion in the charging step, and the developing portion in the developing step are arranged in the order of the transfer portion, the charging portion, and the developing portion along the moving direction of the image carrier. The toner remaining between the transfer unit and the charging unit and between the charging unit and the development unit is in contact with the surface of the image carrier and collects the toner remaining on the surface of the image carrier. The image forming method according to any one of claims 1 to 46 , wherein the image forming method does not include a cleaning member.

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