JP2004302033A - Electrophotographic photoreceptor, process cartridge, image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which prevents lowering of sharpness liable to occur in high-speed copying or in a low temperature and low humidity environment, when an electrophotographic image is formed, therefore prevents lowering of image density due to a potential variation of a solid black image portion and deterioration of sharpness due to letter thinning, in reversal development, and stably obtains a high density and high resolution clear electrophotographic image, and to provide a process cartridge using the electrophotographic photoreceptor, an image forming method and an image forming apparatus. <P>SOLUTION: The electrophotographic photoreceptor contains two or more compounds having an average molecular weight of ≤2,500 and different from each other in the value (n) in formula (1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３９】
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【化３３】

【００６４】
以上の化合物例は、前記一般式（１）中の複数のＢ、Ｒ_１、Ｒ_２、Ｒ_３が同一の化合物例であるが、本発明では、これら複数のＢ、Ｒ_１、Ｒ_２、Ｒ_３が同一でないものも含まれる。例えば、下記のような一般式（８）の化合物も本発明の一般式（１）の化合物として挙げられる。
【００６５】
【化３４】

【００６６】
一般式（８）中、Ａｒ_１は２価の置換、無置換の芳香族基、フラン基又はチオフェン基を示し、Ｒ_１〜Ｒ_３、Ｒ_１′〜Ｒ_３′は水素原子、置換、無置換のアルキル基、１価の置換、無置換の芳香族基を示し、Ａはトリアリールアミン基を含有する２価の基又は前記一般式（３）の基を示し、Ｂ、Ｂ′は１価の置換又は無置換の芳香族基を示す。ｍは各々０又は１、ｎは０〜３０の自然数を表す。
【００６７】
前記一般式（８）の代表的な化合物の化学構造を下記に挙げる。本発明は各々の化合構造で、ｎが異なる化合物の混合物を電荷輸送物質として用いることである。
【００６８】
【化３５】

【００６９】
【化３６】

【００７０】
【化３７】

【００７１】
本発明の前記一般式（１）のｎが異なる２種以上の化合物（混合物）の平均分子量は２５００以下である。該平均分子量はポリスチレン換算の重量平均分子量で表し、平均分子量が２５００を超えると溶媒溶解性が低下し、電荷輸送層のバインダー樹脂との相溶性が劣化し、その結果電荷輸送物質の分散性が低下し、感度や均一帯電性等の電子写真特性が著しく低下する。前記平均分子量は７００〜２５００が好ましく、８００〜２３００がより好ましい。
【００７２】
以下に、本発明の化合物（混合物）の合成例を記載する。
以下の合成例では、原材料等を化合物合成の機構（スキーム）中に付した番号を用いて説明する。
【００７３】
合成例（１）；化合物（例示化学構造１４（ｍ＝０））の合成
【００７４】
【化３８】

【００７５】
１００ｍｌの４頭フラスコに窒素導入管、冷却管、温度計、撹拌機を装着し、４（カリウム−ｔｅｒｔ−ブトキシド）：１．９６ｇ（０．０７５ｍｏｌ）及びテトラヒドロフラン（以下ＴＨＦ）２０ｍｌを入れ、窒素を導入しながら撹拌した。
【００７６】
１の化合物：１．０ｇ（０．００３ｍｏｌ）、２の化合物：２．４６ｇ（０．００７ｍｏｌ）及び３の化合物：２．４１ｇ（０．００８ｍｏｌ）をＴＨＦ２０ｍｌに溶解して前記４（カリウム−ｔｅｒｔ−ブトキシ）／ＴＨＦ混合液に内温４５℃以下に保ちながらゆっくり滴下した。滴下終了後、内温４５〜５０℃を保ちながら５時間反応した。
【００７７】
別に、２００ｍｌビーカーに撹拌機を装着し、メタノール２０ｍｌを入れ撹拌した。これに前記５時間反応した反応液を注いだ後、水２０ｍｌを更に注いで、約３０分撹拌しろ過を行った。メタノール／水＝１／１約４０ｍｌにて洗浄し、５０〜６０℃にて一晩乾燥し、粗結晶を得た。
【００７８】
この粗結晶をトルエン３０ｍｌに溶解し、ワコーゲルＢ−０（和光純薬）３ｇを加えて、約３０分撹拌しろ過を行った。トルエン３０ｍｌにてワコーゲルＢ−０を洗浄し、ロ液及び洗液を濃縮乾固した。これに酢酸エチル１０ｍｌを加え溶解し、メタノール６０ｍｌに滴下して再沈精製を行い、濾別乾燥して例示化学構造１４（ｍ＝０）の化合物を３．２０ｇ得た。
【００７９】
高速液体クロマトグラフィー及び質量分析の結果、得られた化合物はｎ＝０〜５の混合物であり、組成比（高速液体クロマトグラフィーの面積比）はｎ＝０／１／２／３／４＝２４．３／４４．４／２１．５／７．２／２．３／０．３であった。
【００８０】
尚、高速液体クロマトグラフィーの測定条件は下記で行なった。
測定器：島津ＬＣ６Ａ（島津製作所製）
カラム：ＣＬＣ−ＯＤＳ（島津製作所製）
検出波長：２９０ｎｍ
移動相：メタノール／テトラヒドロフラン＝３／１の混合溶媒
移動相の流速：約１ｍｌ／ｍｉｎ
合成例（２）；化合物（例示化学構造２６（ｍ＝０））の合成
【００８１】
【化３９】

【００８２】
１００ｍｌの４頭フラスコに窒素導入管、冷却管、温度計、撹拌機を装着し、４（カリウム−ｔｅｒｔ−ブトキシド）：１．９６ｇ（０．０７５ｍｏｌ）及びＴＨＦ２０ｍｌを入れ、窒素を導入しながら撹拌した。
【００８３】
１の化合物：１．０ｇ（０．００３ｍｏｌ）、２の化合物：２．４６ｇ（０．００７ｍｏｌ）及び３の化合物：２．４１ｇ（０．００８ｍｏｌ）をＴＨＦ２０ｍｌに溶解して４（カリウム−ｔｅｒｔ−ブトキシド）／ＴＨＦ混合液に内温４５℃以下に保ちながらゆっくり滴下した。滴下終了後、内温４５〜５０℃を保ちながら５時間反応した。
【００８４】
別に、２００ｍｌビーカーに撹拌機を装着し、メタノール２０ｍｌを入れ撹拌した。これに反応液を注いだ後、水２０ｍｌを更に注いで、約３０分撹拌しろ過を行った。メタノール／水＝１／１約４０ｍｌにて洗浄し、５０〜６０℃にて一晩乾燥しし、粗結晶を得た。
【００８５】
この粗結晶をトルエン３０ｍｌに溶解し、ワコーゲルＢ−０（和光純薬）３ｇを加えて、約３０分撹拌しろ過した。トルエン３０ｍｌにてワコーゲルＢ−０を洗浄し、ロ液及び洗液を濃縮乾固した。これに酢酸エチル１０ｍｌを加え溶解し、メタノール６０ｍｌに滴下して再沈精製を行い、濾別乾燥して例示化学構造２６（ｍ＝０）の化合物を３．３５ｇ得た。
【００８６】
前記と同様の高速液体クロマトグラフィー及び質量分析の結果、得られた化合物はｎ＝０〜４の混合物であり、組成比（高速液体クロマトグラフィーの面積比）はｎ＝０／１／２／３／４＝３２．５／４５．０／１６．５／６．２／１．６であった。
【００８７】
次に、上記のような本発明の化合物を電荷輸送物質として用いた電子写真感光体、特に有機感光体の層構成について記載する。
【００８８】
本発明の有機感光体とは電子写真感光体の構成に必要不可欠な電荷発生機能及び電荷輸送機能の少なくとも一方の機能を有機化合物に持たせて構成された電子写真感光体を意味し、公知の有機電荷発生物質又は有機電荷輸送物質から構成された感光体、電荷発生機能と電荷輸送機能を高分子錯体で構成した感光体等公知の有機電子写真感光体を全て含有する。
【００８９】
以下に本発明に用いられる有機感光体の構成について記載する。
導電性支持体
感光体に用いられる導電性支持体としてはシート状、円筒状のどちらを用いても良いが、画像形成装置をコンパクトに設計するためには円筒状導電性支持体の方が好ましい。
【００９０】
円筒状導電性支持体とは回転することによりエンドレスに画像を形成できるに必要な円筒状の支持体を意味し、真直度で０．１ｍｍ以下、振れ０．１ｍｍ以下の範囲にある導電性の支持体が好ましい。この真直度及び振れの範囲を超えると、良好な画像形成が困難になる。
【００９１】
導電性の材料としてはアルミニウム、ニッケルなどの金属ドラム、又はアルミニウム、酸化錫、酸化インジュウムなどを蒸着したプラスチックドラム、又は導電性物質を塗布した紙・プラスチックドラムを使用することができる。導電性支持体としては常温で比抵抗１０^３Ωｃｍ以下が好ましい。
【００９２】
本発明で用いられる導電性支持体は、その表面に封孔処理されたアルマイト膜が形成されたものを用いても良い。アルマイト処理は、通常例えばクロム酸、硫酸、シュウ酸、リン酸、硼酸、スルファミン酸等の酸性浴中で行われるが、硫酸中での陽極酸化処理が最も好ましい結果を与える。硫酸中での陽極酸化処理の場合、硫酸濃度は１００〜２００ｇ／Ｌ、アルミニウムイオン濃度は１〜１０ｇ／Ｌ、液温は２０℃前後、印加電圧は約２０Ｖで行うのが好ましいが、これに限定されるものではない。又、陽極酸化被膜の平均膜厚は、通常２０μｍ以下、特に１０μｍ以下が好ましい。
【００９３】
中間層
本発明においては導電性支持体と感光層の間に、バリヤー機能を備えた中間層を設けることもできる。
【００９４】
本発明においては導電性支持体と前記感光層のとの接着性改良、或いは該支持体からの電荷注入を防止するために、該支持体と前記感光層の間に中間層（下引層も含む）を設けることもできる。該中間層の材料としては、ポリアミド樹脂、塩化ビニル樹脂、酢酸ビニル樹脂並びに、これらの樹脂の繰り返し単位のうちの２つ以上を含む共重合体樹脂が挙げられる。これら下引き樹脂の中で繰り返し使用に伴う残留電位増加を小さくできる樹脂としてはポリアミド樹脂が好ましい。又、これら樹脂を用いた中間層の膜厚は０．０１〜０．５μｍが好ましい。
【００９５】
又、本発明に好ましく用いられる中間層はシランカップリング剤、チタンカップリング剤等の有機金属化合物を熱硬化させた硬化性金属樹脂を用いた中間層が挙げられる。硬化性金属樹脂を用いた中間層の膜厚は、０．１〜２μｍが好ましい。
【００９６】
又、本発明に好ましく用いられる中間層は無機粒子をバインダー樹脂中に分散した中間層が挙げられる。無機粒子の平均粒径は０．０１〜１μｍが好ましい。特に、表面処理をしたＮ型半導性微粒子をバインダー中に分散した中間層が好ましい。例えばシリカ・アルミナ処理及びシラン化合物で表面処理した平均粒径が０．０１〜１μｍの酸化チタンをポリアミド樹脂中に分散した中間層が挙げられる。このような中間層の膜厚は、１〜２０μｍが好ましい。
【００９７】
Ｎ型半導性微粒子とは、導電性キャリアを電子とする性質をもつ微粒子を示す。すなわち、導電性キャリアを電子とする性質とは、該Ｎ型半導性微粒子を絶縁性バインダーに含有させることにより、基体からのホール注入を効率的にブロックし、また、感光層からの電子に対してはブロッキング性を示さない性質を有するものをいう。
【００９８】
ここで、Ｎ型半導性粒子の判別方法について説明する。
導電性支持体上に膜厚５μｍの中間層（中間層を構成するバインダー樹脂中に粒子を５０質量％分散させた分散液を用いて中間層を形成する）を形成する。該中間層に負極性に帯電させて、光減衰特性を評価する。又、正極性に帯電させて同様に光減衰特性を評価する。
【００９９】
Ｎ型半導性粒子とは、上記評価で、負極性に帯電させた時の光減衰が正極性に帯電させた時の光減衰よりも大きい場合に、中間層に分散された粒子をＮ型半導性粒子という。
【０１００】
前記Ｎ型半導性微粒子は、具体的には酸化チタン（ＴｉＯ_２）、酸化亜鉛（ＺｎＯ）、酸化スズ（ＳｎＯ_２）等の微粒子が挙げられるが、本発明では、特に酸化チタンが好ましく用いられる。
【０１０１】
本発明に用いられるＮ型半導性微粒子の平均粒径は、数平均一次粒径において１０ｎｍ以上５００ｎｍ以下の範囲のものが好ましく、より好ましくは１０ｎｍ〜２００ｎｍ、特に好ましくは、１５ｎｍ〜５０ｎｍである。
【０１０２】
数平均一次粒径の値が前記範囲内にあるＮ型半導性微粒子を用いた中間層は層内での分散を緻密なものとすることができ、十分な電位安定性、及び黒ポチ発生防止機能を有する。
【０１０３】
前記Ｎ型半導性微粒子の数平均一次粒径は、例えば酸化チタンの場合、透過型電子顕微鏡観察によって１００００倍に拡大し、ランダムに１００個の粒子を一次粒子として観察し、画像解析によりフェレ径の数平均径として測定される。
【０１０４】
本発明に用いられるＮ型半導性微粒子の形状は、樹枝状、針状および粒状等の形状があり、このような形状のＮ型半導性微粒子は、例えば酸化チタン粒子では、結晶型としては、アナターゼ型、ルチル型及びアモルファス型等があるが、いずれの結晶型のものを用いてもよく、また２種以上の結晶型を混合して用いてもよい。その中でもルチル型のものが最も良い。
【０１０５】
Ｎ型半導性微粒子に行われる疎水化表面処理の１つは、複数回の表面処理を行い、かつ該複数回の表面処理の中で、最後の表面処理が反応性有機ケイ素化合物による表面処理を行うものである。また、該複数回の表面処理の中で、少なくとも１回の表面処理がアルミナ、シリカ、及びジルコニアから選ばれる少なくとも１種類以上の表面処理であり、最後に反応性有機ケイ素化合物の表面処理を行うことが好ましい。
【０１０６】
尚、アルミナ処理、シリカ処理、ジルコニア処理とはＮ型半導性微粒子表面にアルミナ、シリカ、或いはジルコニアを析出させる処理を云い、これらの表面に析出したアルミナ、シリカ、ジルコニアにはアルミナ、シリカ、ジルコニアの水和物も含まれる。又、反応性有機ケイ素化合物の表面処理とは、処理液に反応性有機ケイ素化合物を用いることを意味する。
【０１０７】
この様に、酸化チタン粒子の様なＮ型半導性微粒子の表面処理を少なくとも２回以上行うことにより、Ｎ型半導性微粒子表面が均一に表面被覆（処理）され、該表面処理されたＮ型半導性微粒子を中間層に用いると、中間層内における酸化チタン粒子等のＮ型半導性微粒子の分散性が良好で、かつ黒ポチ等の画像欠陥を発生させない良好な感光体を得ることができるのである。
【０１０８】
感光層
本発明の感光体の感光層構成は前記中間層上に電荷発生機能と電荷輸送機能を１つの層に持たせた単層構造の感光層構成でも良いが、より好ましくは感光層の機能を電荷発生層（ＣＧＬ）と電荷輸送層（ＣＴＬ）に分離した構成をとるのがよい。機能を分離した構成を取ることにより繰り返し使用に伴う残留電位増加を小さく制御でき、その他の電子写真特性を目的に合わせて制御しやすい。負帯電用の感光体では中間層の上に電荷発生層（ＣＧＬ）、その上に電荷輸送層（ＣＴＬ）の構成を取ることが好ましい。正帯電用の感光体では前記層構成の順が負帯電用感光体の場合の逆となる。本発明の最も好ましい感光層構成は前記機能分離構造を有する負帯電感光体構成である。
【０１０９】
以下に機能分離負帯電感光体の感光層構成について説明する。
電荷発生層
電荷発生層には電荷発生物質（ＣＧＭ）を含有する。その他の物質としては必要によりバインダー樹脂、その他添加剤を含有しても良い。
【０１１０】
電荷発生物質（ＣＧＭ）としては公知の電荷発生物質（ＣＧＭ）を用いることができる。例えばフタロシアニン顔料、アゾ顔料、ペリレン顔料、アズレニウム顔料などを用いることができる。これらの中で繰り返し使用に伴う残留電位増加を最も小さくできるＣＧＭは複数の分子間で安定な凝集構造をとりうる結晶構造を有するものであり、具体的には特定の結晶構造を有するフタロシアニン顔料、ペリレン顔料のＣＧＭが挙げられる。例えばＣｕ−Ｋα線に対するブラッグ角２θが２７．２°に最大ピークを有するチタニルフタロシアニン、同２θが１２．４に最大ピークを有するベンズイミダゾールペリレン等のＣＧＭは繰り返し使用に伴う劣化がほとんどなく、残留電位増加小さくすることができる。
【０１１１】
電荷発生層にＣＧＭの分散媒としてバインダーを用いる場合、バインダーとしては公知の樹脂を用いることができるが、最も好ましい樹脂としてはホルマール樹脂、ブチラール樹脂、シリコーン樹脂、シリコーン変性ブチラール樹脂、フェノキシ樹脂等が挙げられる。バインダー樹脂と電荷発生物質との割合は、バインダー樹脂１００質量部に対し２０〜６００質量部が好ましい。これらの樹脂を用いることにより、繰り返し使用に伴う残留電位増加を最も小さくできる。電荷発生層の膜厚は０．０１μｍ〜２μｍが好ましい。
【０１１２】
電荷輸送層
電荷輸送層には電荷輸送物質（ＣＴＭ）及びＣＴＭを分散し製膜するバインダー樹脂を含有する。その他の物質としては必要により酸化防止剤等の添加剤を含有しても良い。
【０１１３】
電荷輸送物質（ＣＴＭ）としては、前記した平均分子量が２５００以下で且つ前記一般式（１）のｎが異なる２種以上の化合物の混合物を用いる。又、前記一般式（１）のｎが異なる化合物の２種以上の混合物と共に、例えばトリフェニルアミン誘導体、ヒドラゾン化合物、スチリル化合物、ベンジジン化合物、ブタジエン化合物などを併用して用いることができる。これら電荷輸送物質は通常、適当なバインダー樹脂中に溶解して層形成が行われる。
【０１１４】
電荷輸送層（ＣＴＬ）に用いられる樹脂としては、例えばポリスチレン、アクリル樹脂、メタクリル樹脂、塩化ビニル樹脂、酢酸ビニル樹脂、ポリビニルブチラール樹脂、エポキシ樹脂、ポリウレタン樹脂、フェノール樹脂、ポリエステル樹脂、アルキッド樹脂、ポリカーボネート樹脂、シリコーン樹脂、メラミン樹脂並びに、これらの樹脂の繰り返し単位構造のうちの２つ以上を含む共重合体樹脂。又これらの絶縁性樹脂の他、ポリ−Ｎ−ビニルカルバゾール等の高分子有機半導体が挙げられる。
【０１１５】
これらＣＴＬのバインダーとして最も好ましいものはポリカーボネート樹脂である。ポリカーボネート樹脂はＣＴＭの分散性、電子写真特性を良好にすることにおいて、最も好ましい。バインダー樹脂と電荷輸送物質との割合は、バインダー樹脂１００質量部に対し１０〜２００質量部が好ましい。
【０１１６】
又、電荷輸送層には酸化防止剤を含有させることが好ましい。該酸化防止剤とは、その代表的なものは電子写真感光体中ないしは電子写真感光体表面に存在する自動酸化性物質に対して、光、熱、放電等の条件下で酸素の作用を防止ないし、抑制する性質を有する物質である。代表的には下記の化合物群が挙げられる。
【０１１７】
【化４０】

【０１１８】
【化４１】

【０１１９】
【化４２】

【０１２０】
【化４３】

【０１２１】
電荷輸送層は２層以上の層構成にしてもよい。この場合は表面の電荷輸送層が本発明の構成を満たせばよい。又、電荷輸送層の膜厚は１０〜４０μｍが好ましい。
【０１２２】
上記では本発明の最も好ましい感光体の層構成を例示したが、本発明では上記以外の感光体層構成でも良い。
【０１２３】
感光層、中間層、表面層等の層形成に用いられる溶媒又は分散媒としては、ｎ−ブチルアミン、ジエチルアミン、エチレンジアミン、イソプロパノールアミン、トリエタノールアミン、トリエチレンジアミン、Ｎ，Ｎ−ジメチルホルムアミド、アセトン、メチルエチルケトン、メチルイソプロピルケトン、シクロヘキサノン、ベンゼン、トルエン、キシレン、クロロホルム、ジクロロメタン、１，２−ジクロロエタン、１，２−ジクロロプロパン、１，１，２−トリクロロエタン、１，１，１−トリクロロエタン、トリクロロエチレン、テトラクロロエタン、テトラヒドロフラン、ジオキソラン、ジオキサン、メタノール、エタノール、ブタノール、イソプロパノール、酢酸エチル、酢酸ブチル、ジメチルスルホキシド、メチルセロソルブ等が挙げられる。本発明はこれらに限定されるものではないが、ジクロロメタン、１，２−ジクロロエタン、メチルエチルケトン等が好ましく用いられる。また、これらの溶媒は単独或いは２種以上の混合溶媒として用いることもできる。
【０１２４】
又、これらの各層の塗布溶液は塗布工程に入る前に、塗布溶液中の異物や凝集物を除去するために、金属フィルター、メンブランフィルター等で濾過することが好ましい。例えば、日本ポール社製のプリーツタイプ（ＨＤＣ）、デプスタイプ（プロファイル）、セミデプスタイプ（プロファイルスター）等を塗布液の特性に応じて選択し、濾過をすることが好ましい。
【０１２５】
次に有機電子写真感光体を製造するための塗布加工方法としては、浸漬塗布、スプレー塗布、円形量規制型塗布等の塗布加工法が用いられるが、感光層の上層側の塗布加工は下層の膜を極力溶解させないため、又、均一塗布加工を達成するためスプレー塗布又は円形量規制型（円形スライドホッパ型がその代表例）塗布等の塗布加工方法を用いるのが好ましい。なお保護層は前記円形量規制型塗布加工方法を用いるのが最も好ましい。前記円形量規制型塗布については例えば特開昭５８−１８９０６１号公報に詳細に記載されている。
【０１２６】
次に、本発明の電子写真感光体を用いた画像形成方法及び画像形成装置の説明をする。
【０１２７】
図１は本発明の画像形成方法の１例としての画像形成装置の断面構成図である。
【０１２８】
図１に於いて５０は像担持体である感光体ドラム（感光体）で、有機感光層をドラム上に塗布した感光体で、接地されて時計方向に駆動回転される。５２はスコロトロンの帯電器（帯電手段）で、感光体ドラム５０周面に対し一様な帯電をコロナ放電によって与えられる。この帯電器５２による帯電に先だって、前画像形成での感光体の履歴をなくすために発光ダイオード等を用いた帯電前露光部５１による露光を行って感光体周面の除電をしてもよい。
【０１２９】
感光体への一様帯電の後、像露光手段としての像露光器５３により画像信号に基づいた像露光が行われる。この図の像露光器５３は図示しないレーザダイオードを露光光源とする。回転するポリゴンミラー５３１、ｆθレンズ等を経て反射ミラー５３２により光路を曲げられた光により感光体ドラム上の走査がなされ、静電潜像が形成される。
【０１３０】
ここで反転現像プロセスとは帯電器５２により、感光体表面を一様に帯電し、像露光が行われた領域、即ち感光体の露光部電位（露光部領域）を現像工程（手段）により、顕像化する画像形成方法である。一方未露光部電位は現像スリーブ５４１に印加される現像バイアス電位により現像されない。
【０１３１】
その静電潜像は次いで現像手段としての現像器５４で現像される。感光体ドラム５０周縁にはトナーとキャリアとから成る現像剤を内蔵した現像器５４が設けられていて、マグネットを内蔵し現像剤を保持して回転する現像スリーブ５４１によって現像が行われる。現像器５４内部は現像剤攪拌搬送部材５４４、５４３、搬送量規制部材５４２等から構成されており、現像剤は攪拌、搬送されて現像スリーブに供給されるが、その供給量は該搬送量規制部材５４２により制御される。該現像剤の搬送量は適用される電子写真感光体の線速及び現像剤比重によっても異なるが、一般的には２０〜２００ｍｇ／ｃｍ^２の範囲である。
【０１３２】
現像剤は、例えば前述のフェライトをコアとしてそのまわりに絶縁性樹脂をコーティングしたキャリアと、前述のスチレンアクリル系樹脂を主材料としてカーボンブラック等の着色剤と荷電制御剤と低分子量ポリオレフィンからなる着色粒子に、シリカ、酸化チタン等を外添したトナーとからなるもので、現像剤は搬送量規制部材によって層厚を規制されて現像域へと搬送され、現像が行われる。この時通常は感光体ドラム５０と現像スリーブ５４１の間に直流バイアス、必要に応じて交流バイアス電圧をかけて現像が行われる。また、現像剤は感光体に対して接触あるいは非接触の状態で現像される。感光体の電位測定は電位センサー５４７を図１のように現像位置上部に設けて行う。
【０１３３】
記録紙Ｐは画像形成後、転写のタイミングの整った時点で給紙ローラー５７の回転作動により転写域へと給紙される。
【０１３４】
転写域においては転写のタイミングに同期して感光体ドラム５０の周面に転写電極（転写手段：転写器）５８が作動し、給紙された記録紙Ｐにトナーと反対極性の帯電を与えてトナーを転写する。
【０１３５】
次いで記録紙Ｐは分離電極（分離器）５９によって除電がなされ、感光体ドラム５０の周面により分離して定着装置６０に搬送され、熱ローラー６０１と圧着ローラー６０２の加熱、加圧によってトナーを溶着したのち排紙ローラー６１を介して装置外部に排出される。なお前記の転写電極５８及び分離電極５９は記録紙Ｐの通過後、一次作動を中止し、次なるトナー像の形成に備える。図１では転写電極５８にコロトロンの転写帯電極を用いている。転写電極の設定条件としては、感光体のプロセススピード（周速）等により異なり一概に規定することはできないが、例えば、転写電流としては＋１００〜＋４００μＡ、転写電圧としては＋５００〜＋２０００Ｖを設定値とすることができる。
【０１３６】
一方記録紙Ｐを分離した後の感光体ドラム５０は、クリーニング器（クリーニング手段）６２のブレード６２１の圧接により残留トナーを除去・清掃し、再び帯電前露光部５１による除電と帯電器５２による帯電を受けて次なる画像形成のプロセスに入る。
【０１３７】
尚、７０は感光体、帯電器、転写器、分離器及びクリーニング器が一体化されている着脱可能なプロセスカートリッジである。
【０１３８】
本発明の電子写真感光体は電子写真複写機、レーザプリンター、ＬＥＤプリンター及び液晶シャッター式プリンター等の電子写真装置一般に適応するが、更に、電子写真技術を応用したディスプレー、記録、軽印刷、製版及びファクシミリ等の装置にも幅広く適用することができる。
【０１３９】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されない。但し、下記文中の「部」は「質量部」を示す。
【０１４０】
下記のごとくして、感光体を作製した。
感光体１の作製

上記成分を混合溶解して中間層塗布液を調製した。この塗布液をの円筒状アルミニウム基体上に浸漬塗布法で塗布し、乾燥後、膜厚１．０μｍの中間層を形成した。

上記成分を混合し、サンドミルを用いて１０時間分散し、電荷発生層塗布液を調製した。この塗布液を前記中間層の上に浸漬塗布法で塗布し、乾燥後、膜厚０．３μｍの電荷発生層を形成した。

上記成分を混合溶解して電荷輸送層塗布液を調製した。この塗布液を前記電荷発生層の上に浸漬塗布法で塗布し、１００℃４０分間乾燥して、膜厚２２μｍの電荷輸送層を形成し感光体１を作製した。
【０１４１】
感光体２〜１４の作製
感光体１において、電荷発生物質、電荷輸送物質の化合物、化合物の量、電荷輸送層の膜厚を表１〜表４のように変更した以外は同様にして感光体２〜１４を作製した。
【０１４２】
感光体１５の作製
感光体１において、電荷輸送物質を合成例（２）の化合物を液体クロマトグラフィーで各成分を分離し、化合物２６（ｍ＝０）のｎ＝０のみの成分を電荷輸送物質として用いた他は同様にして感光体１５を作製した。
【０１４３】
感光体１６の作製
感光体１において、電荷輸送物質を合成例（１）の化合物を液体クロマトグラフィーで各成分を分離し、化合物２６（ｍ＝０）のｎ＝３のみの成分を電荷輸送物質として用いた他は同様にして感光体１６を作製したが、電荷輸送物質がバインダー樹脂と相溶せず析出して、評価できる感光体が得られなかった。
【０１４４】
【表１】

【０１４５】
【表２】

【０１４６】
【表３】

【０１４７】
【表４】

【０１４８】
表中、Ｙはチタニルフタロシアニン顔料（Ｃｕ−Ｋα特性Ｘ線回折スペクトルで、ブラッグ角２θの最大ピークが２７．３°の顔料）
Ｚはベンズイミダゾールペリレン顔料（Ｃｕ−Ｋα特性Ｘ線回折スペクトルで、ブラッグ角２θの最大ピークが１２．４°の顔料）を示す。
【０１４９】
又、平均分子量Ｍｗはゲル浸透クロマトグラフィー（ＧＰＣ）より求めた重量平均分子量（ポリスチレン換算）を示す。
【０１５０】
評価
以上のようにして得た感光体１〜１６を各々コニカ（株）製の反転現像方式デジタル複写機「Ｋｏｎｉｃａ７０８５」（スコロトロン帯電器、半導体レーザ像露光器（波長６８０ｎｍ）、反転現像手段を有するＡ４紙８５枚／分機）に搭載し、下記評価項目について評価した。評価は、評価項目毎に、環境条件（温湿度条件）を変えて行なった。評価は、基本的に画素率が７％の文字画像、ハーフトーン画像、ベタ白画像、ベタ黒画像がそれぞれ１／４等分にあるオリジナル画像をＡ４で１枚間欠モードにて１万枚の複写を行い、評価した。評価結果を表５に示す。
【０１５１】
評価条件
ラインスピード；４２０ｍｍ／秒
像露光から現像位置までの到達時間；０．１０８秒
帯電条件
帯電器；スコロトロン帯電器（負帯電）
帯電電位；−７００Ｖ〜−７５０Ｖ
露光条件
べた黒画像電位を−１００Ｖにする露光量に設定。
【０１５２】
露光ビーム；レーザは６８０ｎｍの半導体レーザを使用
現像条件
現像剤は、フェライトをコアとして絶縁性樹脂をコーティングしたキャリアとスチレンアクリル系樹脂を主材料としてカーボンブラックの着色剤と荷電制御剤と低分子量ポリオレフィンからなる重合法で作製した体積平均粒径５．３μｍの着色粒子に、シリカ、酸化チタンを外添したトナーの現像剤を使用した。
【０１５３】
転写条件
転写極；コロナ帯電方式（正帯電）
分離条件
分離爪ユニットの分離手段を用いた
クリーニング条件
クリーニング部に硬度７０°、反発弾性６５％、厚さ２（ｍｍ）、自由長９ｍｍのクリーニングブレードをカウンター方向に線圧１８（ｇ／ｃｍ）となるように重り荷重方式で当接した。
【０１５４】
評価項目及び評価方法
低温低湿（１０℃２０％ＲＨ）環境下での高速応答性（べた黒画像の電位変化）
低温低湿（１０℃２０％ＲＨ）環境下で、画素率が７％の文字画像、ハーフトーン画像、ベタ白画像、ベタ黒画像がそれぞれ１／４等分にあるオリジナル画像をＡ４で１枚間欠モードにて１万枚の複写を行い、初期と１万枚後の現像位置でのべた黒画像の電位変化（｜ΔＶ｜）を評価した。｜ΔＶ｜が小さい方が低温低湿（１０℃２０％ＲＨ）環境下での高速応答性が優れている。
【０１５５】
◎；べた黒画像の電位変化｜ΔＶ｜が５０Ｖ未満（良好）
○；べた黒画像の電位変化｜ΔＶ｜が５０Ｖ〜１５０Ｖ（実用上問題なし）
×；べた黒画像の電位変化｜ΔＶ｜が１５０Ｖより大きい（実用上問題有り）
文字細り（低温低湿（１０℃２０％ＲＨ）の環境下）
０．１ｍｍ、０．２ｍｍ幅の線画像が印刷されたオリジナル画像を複写し、評価した。
【０１５６】
◎；複写画像の線幅がオリジナル画像の線幅の７５％以上で再現されている（良好）
○；複写画像の線幅がオリジナル画像の線幅の４０％〜７４％で再現されている（実用上問題ないレベル）
×；複写画像の線幅がオリジナル画像の線幅の３９％以下、又は線幅が切断されている（実用上問題となるレベル）
ブラックスポット（高温高湿（３０℃８０％ＲＨ））
ハーフトーン画像上のブラックスポット（苺状のスポット画像）の発生状況を下記の基準で判定した。
【０１５７】
◎；感光体上にブラックスポットの発生核がみられず、ハーフトーン画像にもブラックスポットの発生なし（良好）
○；感光体上にブラックスポットの発生核がみられるが、ハーフトーン画像にはブラックスポットの発生なし（実用上問題なし）
×；感光体上にブラックスポットの発生核がみられ、ハーフトーン画像にもブラックスポットが発生している（実用上問題有り）
周期性の画像欠陥（高温高湿（３０℃８０％ＲＨ）
周期性が感光体の周期と一致し、目視できる白ヌケ、黒ポチ、筋状の画像欠陥が、Ａ４サイズ当たり何個あるかで判定した。
【０１５８】
◎；０．４ｍｍ以上の画像欠陥の頻度：全ての複写画像が５個／Ａ４以下（良好）
○；０．４ｍｍ以上の画像欠陥の頻度：６個／Ａ４以上、１０個／Ａ４以下が１枚以上発生（実用上問題なし）
×；０．４ｍｍ以上の画像欠陥の頻度：１１個／Ａ４以上が１枚以上発生（実用上問題有り）
クラック
上記デジタル複写機Ｋｏｎｉｃａ７０８５を３０℃、８０％ＲＨの環境下で、感光体を搭載したまま、電源をｏｆｆにし、２日間放置した。感光体周辺の部材はこの間動作を停止しているだけの状態、即ち、クリーニングブレード、現像剤搬送体等の部材は、感光体に当接したままにした。その後、感光体の表面を観察し、クラックの発生の有無を観察した。又、画像評価も行い、クラック発生に伴う筋状の画像欠陥の発生の有無も評価した。
【０１５９】
◎；１００本の感光体を評価し、クラックの発生も、筋状の画像欠陥の発生もなし（良好））
◯；１００本の感光体を評価し、微細なクラックの発生はあるが、筋状の画像欠陥の発生はない（実用上問題ないレベル）
×；１００本の感光体を評価し、クラックの発生と筋状の画像欠陥の発生が見られる（実用上問題となるレベル）
画像濃度（低温低湿（１０℃２０％ＲＨ））
べた黒部の画像濃度はマクベス社製ＲＤ−９１８を使用し反射濃度で測定した。相対濃度（複写していないＡ４紙の濃度を０．００とする）で評価した。
【０１６０】
◎；１．２以上（良好）
○；１．２未満〜０．８（実用上問題ないレベル）
×；０．８未満（実用上問題となるレベル）
鮮鋭性
画像の鮮鋭性は、低温低湿（１０℃２０％ＲＨ）、高温高湿（３０℃８０％ＲＨ）の両環境において画像を出し、文字潰れで評価した。３ポイント、５ポイントの文字画像を形成し、下記の判断基準で評価した。
【０１６１】
◎；３ポイント、５ポイントとも明瞭であり、容易に判読可能
○；３ポイントは一部判読不能、５ポイントは明瞭であり、容易に判読可能
×；３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能
【０１６２】
【表５】

【０１６３】
表５より、本発明の平均分子量が２５００以下で且つ前記一般式（１）のｎが異なる２種以上の化合物を電荷輸送物質として用いた感光体１〜１３は、低温低湿（１０℃２０％ＲＨ）環境下での高速応答性（べた黒画像の電位変化）が優れ、このため低温低湿下の文字細りもなく、しかも、ブッラクスポット、周期性画像欠陥、クラック等の発生もなく、画像濃度、鮮鋭性に優れた特性を示している。一方、平均分子量が２５００より大きい化合物を電荷輸送物質として用いた感光体１４は電荷輸送層中への分散性が低下し、低温低湿（１０℃２０％ＲＨ）環境下での高速応答性（べた黒画像の電位変化）が劣化し、このため文字細り、鮮鋭性が劣化している。又、ｎ＝０の低分子量の化合物のみを用いた感光体１５は低温低湿（１０℃２０％ＲＨ）環境下での高速応答性が劣り、文字細りを発生している他に、電荷輸送層の膜質が柔らかく、ブッラクスポット、周期性画像欠陥も発生し、画像濃度、鮮鋭性が低下している。又、ｎ＝３の高分子量の化合物のみを用いた感光体１６の場合は、バインダー樹脂との溶解不良で、感度等もほとんどなく、評価に値しなかった。
【０１６４】
【発明の効果】
本発明の電子写真感光体、プロセスカートリッジ、画像形成装置及び画像形成方法を用いることにより、低温低湿環境で発生しやすい高速適応性等の感度不良に伴う画像不良と高温高湿で発生しやすい画像欠陥を防止し、画像濃度、鮮鋭性が良好な電子写真画像を提供することができる。
【図面の簡単な説明】
【図１】本発明の画像形成方法の１例としての画像形成装置の断面構成図である。
【符号の説明】
５０ 感光体ドラム（感光体）
５１ 帯電前露光部
５２ 帯電器
５３ 像露光器
５４ 現像器
５４１ 現像スリーブ
５４３、５４４ 現像剤攪拌搬送部材
５４７ 電位センサー
５７ 給紙ローラー
５８ 転写電極
５９ 分離電極（分離器）
６０ 定着装置
６１ 排紙ローラー
６２ クリーニング器
７０ プロセスカートリッジ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member, a process cartridge, an image forming apparatus, and an image forming method used for forming an electrophotographic image, and more particularly, to an electrophotographic image forming apparatus used in a copier or a printer. The present invention relates to an electrophotographic photosensitive member, a process cartridge, an image forming apparatus, and an image forming method.
[0002]
[Prior art]
Electrophotographic photoreceptors have significant advantages over inorganic photoreceptors such as selenium-based photoreceptors and amorphous silicon photoreceptors in that they have a wider range of material choices, are more environmentally friendly, and have lower production costs. In recent years, organic photoconductors have become the mainstream in place of inorganic photoconductors.
[0003]
On the other hand, in recent years, electrophotographic image forming methods have been used as hard copy printers for personal computers, and even with ordinary copying machines, because of the ease of image processing and the ease of application to multifunction machines, image exposure using LEDs or lasers is performed. The digital image forming method used as a light source has rapidly spread. Further, a technique for producing a high-quality electrophotographic image by promoting the resolution of a digital image has been developed. For example, image exposure is performed with a laser beam having a small spot area to increase the density of a dot latent image to form a high-definition latent image, and the latent image is developed with a small particle size toner to obtain a high-quality electrophotographic image. The technology for producing is disclosed. (Patent Document 1)
In forming such a high-quality digital image, an organic photoreceptor having high sensitivity and stable characteristics against changes in the greenhouse environment is required.
[0004]
Conventionally, in order to satisfy the requirements of the organic photoreceptor as described above, the organic photoreceptor has a photosensitive layer having a layer structure in which a charge generation layer and a charge transport layer are functionally separated, and the charge transport layer has a low molecular weight of about 500. The configuration was such that a large amount of a charge transport material having a molecular weight was contained. However, in the charge transport layer having such a configuration, the film quality is deteriorated, and the charge transport layer on the surface layer is easily contaminated with foreign matter. That is, the surface of the photoconductor is easily contaminated with paper dust or the toner composition by the developing unit, the transfer unit, the cleaning unit, and the like arranged around the photoconductor, and as a result, the black spot (strawberry-like spot image) and the transfer Periodic image defects such as dropping are likely to occur. In addition, sufficient sensitivity cannot be obtained in a high-speed copier or a low-temperature, low-humidity environment where the time between the exposure process and the development process is short, and as a result, the dot image is not faithfully reproduced, and the image in which the fine line is cut is not obtained. It is easy to occur.
[0005]
As a method for solving such a problem, use of a charge transport material having a large molecular weight has been reported. For example, an organic photoreceptor containing a charge transport substance having a chemical structure of bisstyryl and a molecular weight of 1,000 or more has been reported (Patent Document 2). However, when these charge transporting substances are contained in the charge transporting layer, the compatibility of the charge transporting layer with the binder resin tends to be insufficient, the charge transporting substance is not uniformly dispersed, and the sensitivity is not sufficient, and Breakage scratches such as cracks are likely to occur in the transport layer. Also, photoreceptors using a charge transport material of a compound having a molecular weight of 3,000 to 5,000 have been reported (Patent Documents 3 and 4). However, since the end group of this compound is not blocked, the residual charge tends to increase. Further, the compatibility with the binder resin has not been sufficiently solved.
[0006]
Further, in order to prevent contamination of the photoreceptor surface, an organic photoreceptor having a surface layer containing fluorine resin particles has been proposed (Patent Document 5). However, an organic photoreceptor containing fluorine-based resin particles tends to cause image blur. In addition, the mechanical strength of the surface layer is easily reduced, and the surface of the photoreceptor is liable to be worn out due to friction with the cleaning means or the like, so that a satisfactory electrophotographic image cannot always be provided.
[0007]
[Patent Document 1]
JP 2001-255885 A
[Patent Document 2]
JP-A-3-149560
[Patent Document 3]
JP-A-10-310635
[Patent Document 4]
JP-A-5-25102
[Patent Document 5]
JP-A-63-65449
[Problems to be solved by the invention]
The present invention has been proposed in order to solve the above-described problems, and an object of the present invention is to form an electrophotographic image, which is likely to occur in high-speed copying or in a low-temperature and low-humidity environment. The cause of the decrease, namely, in reversal development, is to prevent a decrease in image density due to potential fluctuation of a solid black image portion or a decrease in sharpness due to occurrence of thinning of characters, and also, due to surface contamination of the electrophotographic photosensitive member. Prevents periodic image defects such as black spots and transfer defects that are likely to occur, and does not cause breaks such as cracks, and provides stable high-density, high-resolution clear electrophotographic images. An object of the present invention is to provide an electrophotographic photosensitive member obtained by the above, a process cartridge using the electrophotographic photosensitive member, an image forming method, and an image forming apparatus.
[0013]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have conducted detailed studies on the binder resin and the charge transport material constituting the charge transport layer of the electrophotographic photoreceptor in order to solve the above problems of the present invention. By using a mixture of compounds having different chemical weights and having different molecular weights as the charge transporting material, even if a large molecular weight charge transporting material is used, the compatibility with the binder resin is good, and a high-speed process can be performed. The response of sensitivity under low temperature and low humidity environment is improved, and the surface layer is less likely to be contaminated, black spots, prevent periodic image defects such as transfer defects, and do not cause breakage such as cracks and the like, The present inventors have found that a clear image with high density and high resolution can be stably obtained, and completed the present invention.
[0014]
The object of the present invention is achieved by adopting one of the following constitutions.
1. An electrophotographic photosensitive member comprising two or more compounds having an average molecular weight of 2500 or less and different n in the general formula (1).
[0015]
2. A charge generation layer and a charge transport layer are provided on a conductive support, and the charge transport layer contains two or more compounds having an average molecular weight of 2500 or less and different n in the general formula (1). Electrophotographic photoreceptor.
[0016]
3. 3. The electrophotographic photoreceptor according to the above item 1 or 2, wherein the divalent group containing a triarylamine group of A is a group represented by the general formula (4).
[0017]
4. 4. The electrophotographic photosensitive member according to the item 3, wherein Ar ₂ is a group represented by the general formula (5).
[0018]
5. 3. The electrophotographic photoreceptor according to the above item 1 or 2, wherein the divalent group containing a triarylamine group of A is a group represented by the general formula (6).
[0019]
6. 6. The electrophotographic photosensitive member according to any one of the above items 1 to 5, wherein B is a group represented by the general formula (7).
[0020]
7. An electrophotographic photosensitive member containing two or more compounds having an average molecular weight of 2500 or less and different n of the general formula (1), a charging means for uniformly charging the electrophotographic photosensitive member, and a charged electrophotographic device Latent image forming means for forming an electrostatic latent image on the photoreceptor, developing means for visualizing the electrostatic latent image on the electrophotographic photoreceptor, and transfer of the visualized toner image onto the electrophotographic photoreceptor At least one of a transfer unit for transferring onto the material, a charge removing unit for removing charges on the electrophotographic photosensitive member after transfer, and a cleaning unit for removing residual toner on the electrophotographic photosensitive member after transfer is provided. A process cartridge which is integrally supported and is detachably mountable to an image forming apparatus main body.
[0021]
8. An image forming apparatus comprising the process cartridge according to the above item 7.
[0022]
9. An image forming method, wherein an electrophotographic image is formed using the image forming apparatus according to the above item 8.
[0023]
Hereinafter, the present invention will be described in detail.
Configuration of Electrophotographic Photoreceptor The electrophotographic photoreceptor used in the present invention is characterized by containing two or more compounds having an average molecular weight of 2500 or less and different n in the following general formula (1).
[0024]
Further, the electrophotographic photoreceptor used in the present invention has a charge generation layer and a charge transport layer on a conductive support, and the charge transport layer has an average molecular weight of 2500 or less and n of the general formula (1). Are characterized by containing two or more different compounds.
[0025]
The electrophotographic photoreceptor of the present invention, having the above-described configuration, can easily prevent a decrease in sharpness such as thinning of characters due to a decrease in sensitivity, which is likely to occur in high-speed copying or in a low-temperature and low-humidity environment. In addition, a clear electrophotographic image having a high density and a high resolution can be produced without generating periodic image defects such as transfer defects, generating breakage such as cracks, and the like.
[0026]
In the present invention, “comprising two or more compounds having different n in the general formula (1)” means a substance (mixture) in which two or more compounds of the general formula (1) and having different numbers of chain structures are mixed. When the mixture is used as a charge transporting substance, the charge transporting property is remarkably improved, high-speed response, low sensitivity under low temperature and low humidity can be overcome, and the average molecular weight of the mixture is 2500. By using the following, the compatibility with the solvent and the binder resin is remarkably improved, and there is no occurrence of periodic image defects such as the above-mentioned black spots and transfer defects, and generation of breakage scratches such as cracks. The electrophotographic photoreceptor for producing a clear electrophotographic image with high density and high resolution can be produced without causing any problem.
[0027]
Hereinafter, an electrophotographic photoreceptor using a mixture of two or more compounds having different n in the general formula (1) as a charge transport material will be described.
[0028]
In the general formula (1), the divalent group containing a triarylamine group refers to a structure in which a trivalent bonding group of a nitrogen atom is bonded to an aromatic ring, and the group as a whole is divalent. Means a group having a linking group of
[0029]
Further, the monovalent group containing a triarylamine group is a group having a structure in which a trivalent bonding group of a nitrogen atom is bonded to an aromatic ring, and having a monovalent linking group as a whole group. Means
[0030]
As the divalent substituted or unsubstituted aromatic group of Ar _{1 in} the general formula (1), a phenylene group, a naphthylene group, a biphenylene group and the like are preferable, and as the substituent, an alkyl group is preferable. Further, a divalent furan group and a divalent thiophene group are also preferable.
[0031]
R _{1 to} R _{3 each} represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group, a monovalent substituted or unsubstituted aromatic group, but a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, Preferred are an alkoxy group, an unsubstituted phenyl group, a halogen or a phenyl group having an alkyl group having 1 to 4 carbon atoms.
[0032]
As the divalent group of A, in addition to the group of the general formula (3), the group of the general formula (4) or the general formula (6) is preferable as the divalent group containing a triarylamine group.
[0033]
R ₆ in the general formula (3) represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, and preferably an alkyl group having 1 to 4 carbon atoms, a phenyl group and the like.
[0034]
Ar ₂ in the general formula (4) is a substituted or unsubstituted monovalent aromatic group, preferably an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group. Is mentioned.
[0035]
Ar ₃ and Ar ₄ in the general formula (6) each represent a substituted or unsubstituted monovalent aromatic group, and are preferably substituted with an unsubstituted phenyl group, an alkyl group having 1 to 4 carbon atoms or an alkoxy group. Phenyl group.
[0036]
As the monovalent substituted or unsubstituted aromatic group for B, a substituted or unsubstituted triphenylamine group and a substituted or unsubstituted phenyl group are preferable. As the substituent, an alkyl group having 1 to 4 carbon atoms, a dialkylamino group and an alkylarylamino group are preferable, and a methyl group is particularly preferable. n is a natural number of 0 to 30, preferably 0 to 20.
[0037]
In the following, structural formulas of typical compounds of the general formula (1) are shown below. In the present invention, a mixture of compounds having different chemical structures and different n's is used as a charge transport material. Further, even if the following chemical structures are the same, they are different compounds if m in the general formula (1) is different. For example, the following chemical structure No. Even if m is 0 or 1, m is another compound. The mixture of compounds having different n used in the present invention may have an average molecular weight of 2500 or less even if the mixing ratio is different.
[0038]
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[0039]
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[0040]
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[0041]
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[0042]
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[0043]
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[0044]
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[0045]
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[0046]
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[0047]
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[0048]
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[0049]
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[0050]
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[0051]
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[0052]
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[0053]
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[0054]
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[0055]
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[0056]
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[0057]
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[0058]
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[0059]
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[0060]
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[0061]
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[0062]
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[0063]
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[0064]
The above compound examples are compound examples in which a plurality of B, R ₁ , R ₂ , and R _{3 in the} general formula (1) are the same, but in the present invention, these plurality of B, R ₁ , R ₂ , Also included are those in which R ₃ is not identical. For example, the compound of the following general formula (8) is also exemplified as the compound of the general formula (1) of the present invention.
[0065]
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[0066]
In the general formula (8), Ar ₁ represents a divalent substituted or unsubstituted aromatic group, a furan group or a thiophene group, and R _{1 to} R ₃ and R ₁ ′ to R ₃ ′ represent a hydrogen atom, a substituted or unsubstituted group. A represents a substituted alkyl group, a monovalent substituted or unsubstituted aromatic group, A represents a divalent group containing a triarylamine group or a group represented by the general formula (3), and B and B ′ represent 1 It represents a substituted or unsubstituted aromatic group. m represents 0 or 1, and n represents a natural number of 0 to 30.
[0067]
The chemical structures of representative compounds of the general formula (8) are shown below. The present invention uses a mixture of compounds having different n in each compound structure as a charge transporting substance.
[0068]
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[0069]
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[0070]
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[0071]
The average molecular weight of two or more compounds (mixtures) of the general formula (1) in which n differs from each other is 2500 or less. The average molecular weight is represented by a weight average molecular weight in terms of polystyrene. If the average molecular weight exceeds 2500, the solubility of the solvent decreases, the compatibility with the binder resin of the charge transport layer deteriorates, and as a result, the dispersibility of the charge transport material decreases. And the electrophotographic properties such as sensitivity and uniform chargeability are significantly reduced. The average molecular weight is preferably from 700 to 2500, more preferably from 800 to 2300.
[0072]
Hereinafter, synthesis examples of the compound (mixture) of the present invention will be described.
In the following synthesis examples, raw materials and the like will be described using numbers given to the mechanism (scheme) of compound synthesis.
[0073]
Synthesis Example (1): Synthesis of Compound (Exemplary Chemical Structure 14 (m = 0))
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[0075]
A 100 ml four-necked flask was equipped with a nitrogen inlet tube, a cooling tube, a thermometer, and a stirrer. 4 (potassium-tert-butoxide): 1.96 g (0.075 mol) and 20 ml of tetrahydrofuran (hereinafter, THF) were charged. While stirring.
[0076]
Compound (1): 1.0 g (0.003 mol), compound (2): 2.46 g (0.007 mol), and compound (3): 2.41 g (0.008 mol) were dissolved in THF (20 ml) and the solution of 4 (potassium-tert) was dissolved. −Butoxy) / THF mixture was slowly added dropwise while maintaining the internal temperature at 45 ° C. or lower. After completion of the dropwise addition, the reaction was carried out for 5 hours while maintaining the internal temperature at 45 to 50 ° C.
[0077]
Separately, a stirrer was attached to a 200 ml beaker, and 20 ml of methanol was added and stirred. After pouring the reaction solution reacted for 5 hours, 20 ml of water was further poured, and the mixture was stirred for about 30 minutes and filtered. The resultant was washed with about 40 ml of methanol / water = 1/1, and dried at 50 to 60 ° C. overnight to obtain crude crystals.
[0078]
The crude crystals were dissolved in 30 ml of toluene, 3 g of Wakogel B-0 (Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred for about 30 minutes and filtered. Wakogel B-0 was washed with 30 ml of toluene, and the filtrate and the washing solution were concentrated to dryness. Ethyl acetate (10 ml) was added and dissolved, and the mixture was added dropwise to methanol (60 ml) for reprecipitation purification, followed by filtration and drying to obtain 3.20 g of a compound having Exemplified Chemical Structure 14 (m = 0).
[0079]
As a result of high performance liquid chromatography and mass spectrometry, the compound obtained was a mixture of n = 0 to 5, and the composition ratio (area ratio of high performance liquid chromatography) was n = 0/1/2/3/4 = 24. 0.3 / 44.4 / 21.5 / 7.2 / 2.3 / 0.3.
[0080]
In addition, the measurement conditions of the high performance liquid chromatography were performed as follows.
Measuring instrument: Shimadzu LC6A (manufactured by Shimadzu Corporation)
Column: CLC-ODS (manufactured by Shimadzu Corporation)
Detection wavelength: 290 nm
Mobile phase: mixed solvent of methanol / tetrahydrofuran = 3/1 Flow rate of mobile phase: about 1 ml / min
Synthesis Example (2); Synthesis of Compound (Exemplary Chemical Structure 26 (m = 0))
Embedded image

[0082]
A 100 ml four-necked flask was equipped with a nitrogen inlet tube, a cooling tube, a thermometer, and a stirrer, and charged with 4 (potassium-tert-butoxide): 1.96 g (0.075 mol) and THF (20 ml), and stirred while introducing nitrogen. did.
[0083]
Compound (1): 1.0 g (0.003 mol), compound (2): 2.46 g (0.007 mol), and compound (3): 2.41 g (0.008 mol) were dissolved in THF (20 ml) to obtain 4 (potassium-tert-). The mixture was slowly added dropwise to the butoxide) / THF mixture while maintaining the internal temperature at 45 ° C. or lower. After completion of the dropwise addition, the reaction was carried out for 5 hours while maintaining the internal temperature at 45 to 50 ° C.
[0084]
Separately, a stirrer was attached to a 200 ml beaker, and 20 ml of methanol was added and stirred. After pouring the reaction solution, 20 ml of water was further poured, and the mixture was stirred for about 30 minutes and filtered. The resultant was washed with about 40 ml of methanol / water = 1/1 and dried at 50 to 60 ° C. overnight to obtain crude crystals.
[0085]
The crude crystals were dissolved in 30 ml of toluene, 3 g of Wakogel B-0 (Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred for about 30 minutes and filtered. Wakogel B-0 was washed with 30 ml of toluene, and the filtrate and the washing solution were concentrated to dryness. Ethyl acetate (10 ml) was added and dissolved, and the mixture was added dropwise to methanol (60 ml) for reprecipitation purification, followed by filtration and drying to obtain 3.35 g of a compound having the exemplified chemical structure 26 (m = 0).
[0086]
As a result of the same high performance liquid chromatography and mass spectrometry as described above, the obtained compound was a mixture of n = 0 to 4, and the composition ratio (area ratio of the high performance liquid chromatography) was n = 0/1/2/3. /4=32.5/45.0/16.5/6.2/1.6.
[0087]
Next, the layer structure of an electrophotographic photoreceptor, particularly an organic photoreceptor, using the above-described compound of the present invention as a charge transport material will be described.
[0088]
The organic photoreceptor of the present invention means an electrophotographic photoreceptor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function, which are indispensable for the configuration of the electrophotographic photoreceptor, and is known. All known organic electrophotographic photoreceptors such as a photoreceptor composed of an organic charge generating substance or an organic charge transporting substance, and a photoreceptor having a charge generating function and a charge transporting function composed of a polymer complex are included.
[0089]
Hereinafter, the constitution of the organic photoreceptor used in the present invention will be described.
Conductive Support The conductive support used for the photoreceptor may be in the form of a sheet or a cylinder, but a cylindrical conductive support is preferred for designing a compact image forming apparatus. .
[0090]
The cylindrical conductive support means a cylindrical support necessary for forming an image endlessly by rotating, and a conductive material having a straightness of 0.1 mm or less and a runout of 0.1 mm or less. Supports are preferred. Exceeding the ranges of straightness and runout makes it difficult to form a good image.
[0091]
As the conductive material, a metal drum of aluminum, nickel, or the like, a plastic drum on which aluminum, tin oxide, indium oxide, or the like is deposited, or a paper or plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.
[0092]
The conductive support used in the present invention may have a surface on which a sealed alumite film is formed. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, and sulfamic acid. Anodizing treatment in sulfuric acid gives the most preferable result. In the case of the anodic oxidation treatment in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / L, the aluminum ion concentration is 1 to 10 g / L, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average thickness of the anodic oxide coating is usually 20 μm or less, particularly preferably 10 μm or less.
[0093]
Intermediate layer In the present invention, an intermediate layer having a barrier function may be provided between the conductive support and the photosensitive layer.
[0094]
In the present invention, in order to improve the adhesion between the conductive support and the photosensitive layer, or to prevent charge injection from the support, an intermediate layer (an undercoat layer is also provided) between the support and the photosensitive layer. ) Can be provided. Examples of the material for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of the repeating units of these resins. Among these undercoating resins, a polyamide resin is preferable as a resin capable of reducing an increase in residual potential due to repeated use. The thickness of the intermediate layer using these resins is preferably 0.01 to 0.5 μm.
[0095]
The intermediate layer preferably used in the present invention includes an intermediate layer using a curable metal resin obtained by thermally curing an organic metal compound such as a silane coupling agent and a titanium coupling agent. The thickness of the intermediate layer using the curable metal resin is preferably 0.1 to 2 μm.
[0096]
The intermediate layer preferably used in the present invention includes an intermediate layer in which inorganic particles are dispersed in a binder resin. The average particle size of the inorganic particles is preferably from 0.01 to 1 μm. Particularly, an intermediate layer in which surface-treated N-type semiconductor fine particles are dispersed in a binder is preferable. For example, an intermediate layer in which titanium oxide having an average particle diameter of 0.01 to 1 μm, which is surface-treated with a silica / alumina treatment and a silane compound, is dispersed in a polyamide resin may be used. The thickness of such an intermediate layer is preferably from 1 to 20 μm.
[0097]
The N-type semiconductive fine particles are fine particles having a property of using a conductive carrier as an electron. That is, the property of making the conductive carrier an electron means that by including the N-type semiconductor fine particles in an insulating binder, hole injection from the substrate can be efficiently blocked, and electrons from the photosensitive layer can be prevented. On the other hand, it has a property of not exhibiting a blocking property.
[0098]
Here, a method for determining N-type semiconductor particles will be described.
An intermediate layer having a thickness of 5 μm (an intermediate layer is formed using a dispersion liquid in which particles are dispersed in a binder resin constituting the intermediate layer by 50% by mass) is formed on the conductive support. The intermediate layer is negatively charged, and the light attenuation characteristics are evaluated. In addition, the light-attenuating characteristics are similarly evaluated by charging to a positive polarity.
[0099]
N-type semiconductive particles are particles that are dispersed in the intermediate layer when the light attenuation when charged negatively is greater than the light attenuation when charged positively in the above evaluation. It is called semiconductive particles.
[0100]
Specific examples of the N-type semiconductor fine particles include fine particles such as titanium oxide (TiO ₂ ), zinc oxide (ZnO), and tin oxide (SnO ₂ ). In the present invention, titanium oxide is particularly preferably used. Can be
[0101]
The average particle diameter of the N-type semiconductor fine particles used in the present invention is preferably in the range of 10 nm or more and 500 nm or less in number average primary particle diameter, more preferably 10 nm to 200 nm, and particularly preferably 15 nm to 50 nm. .
[0102]
The intermediate layer using the N-type semiconductive particles having a number average primary particle diameter within the above range can make the dispersion in the layer dense, provide sufficient potential stability, and generate black spots. Has a prevention function.
[0103]
For example, in the case of titanium oxide, the number-average primary particle diameter of the N-type semiconductive fine particles is magnified 10,000 times by transmission electron microscope observation, 100 particles are randomly observed as primary particles, and the ferrite particles are analyzed by image analysis. It is measured as the number average diameter of the diameter.
[0104]
The shape of the N-type semiconductive fine particles used in the present invention includes dendritic, needle-like and granular shapes, and the N-type semiconductive fine particles having such a shape are, for example, titanium oxide particles having a crystal type. There are anatase type, rutile type, amorphous type and the like, and any crystal type may be used, or two or more crystal types may be mixed and used. Among them, the rutile type is best.
[0105]
One of the hydrophobizing surface treatments performed on the N-type semiconductive particles is to perform a plurality of surface treatments, and the last one of the plurality of surface treatments is a surface treatment with a reactive organosilicon compound. Is what you do. Further, among the plurality of surface treatments, at least one surface treatment is at least one or more surface treatments selected from alumina, silica, and zirconia, and finally, the surface treatment of the reactive organosilicon compound is performed. Is preferred.
[0106]
The alumina treatment, the silica treatment, and the zirconia treatment refer to a treatment for depositing alumina, silica, or zirconia on the surface of the N-type semiconductor fine particles. Also included are hydrates of zirconia. Further, the surface treatment of the reactive organosilicon compound means to use the reactive organosilicon compound in the treatment solution.
[0107]
As described above, the surface treatment of the N-type semiconductor fine particles such as titanium oxide particles is performed at least twice, so that the surface of the N-type semiconductor fine particles is uniformly coated (treated), and the surface treatment is performed. When the N-type semiconductive fine particles are used in the intermediate layer, a good photoreceptor that has good dispersibility of the N-type semiconductive fine particles such as titanium oxide particles in the intermediate layer and does not generate image defects such as black spots can be obtained. You can get it.
[0108]
Photosensitive Layer The photosensitive layer of the photoreceptor of the present invention may have a single-layer structure in which a charge generation function and a charge transport function are provided in one layer on the intermediate layer, but more preferably the function of the photosensitive layer Is preferably separated into a charge generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which functions are separated, an increase in residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoreceptor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the case of a positively charged photoreceptor, the order of the layer configuration is opposite to that of the negatively charged photoreceptor. The most preferable constitution of the photosensitive layer of the present invention is a constitution of a negatively charged photoreceptor having the function separation structure.
[0109]
The configuration of the photosensitive layer of the function-separated negatively charged photoconductor will be described below.
Charge Generation Layer The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.
[0110]
As the charge generation material (CGM), a known charge generation material (CGM) can be used. For example, phthalocyanine pigments, azo pigments, perylene pigments, azurenium pigments and the like can be used. Among these, CGM that can minimize the increase in residual potential due to repeated use has a crystal structure that can take a stable aggregated structure among a plurality of molecules, and specifically, a phthalocyanine pigment having a specific crystal structure, And CGM of perylene pigment. For example, CGMs such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu-Kα radiation, and benzimidazole perylene having a maximum peak at a 2θ of 12.4 have almost no deterioration due to repeated use, and remain as such. The potential increase can be reduced.
[0111]
In the case where a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder. No. The ratio between the binder resin and the charge generating substance is preferably from 20 to 600 parts by mass per 100 parts by mass of the binder resin. By using these resins, an increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.
[0112]
Charge transport layer The charge transport layer contains a charge transport material (CTM) and a binder resin for dispersing the CTM to form a film. As other substances, additives such as antioxidants may be contained as necessary.
[0113]
As the charge transport material (CTM), a mixture of two or more compounds having an average molecular weight of 2500 or less and different n in the general formula (1) is used. In addition, for example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used in combination with a mixture of two or more compounds having different n's in the general formula (1). These charge transporting substances are usually dissolved in a suitable binder resin to form a layer.
[0114]
Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resins, silicone resins, melamine resins, and copolymer resins containing two or more of the repeating unit structures of these resins. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinyl carbazole may be used.
[0115]
The most preferred binder for these CTLs is a polycarbonate resin. Polycarbonate resins are most preferred in improving the dispersibility and electrophotographic properties of CTM. The ratio of the binder resin to the charge transporting material is preferably from 10 to 200 parts by mass per 100 parts by mass of the binder resin.
[0116]
Further, it is preferable that the charge transport layer contains an antioxidant. The antioxidant typically prevents the effect of oxygen on the autoxidizing substance present in or on the electrophotographic photoreceptor under conditions of light, heat, discharge, etc. In addition, it is a substance having the property of suppressing. Typically, the following compound groups are mentioned.
[0117]
Embedded image

[0118]
Embedded image

[0119]
Embedded image

[0120]
Embedded image

[0121]
The charge transport layer may have two or more layers. In this case, the charge transport layer on the surface may satisfy the structure of the present invention. The thickness of the charge transport layer is preferably from 10 to 40 μm.
[0122]
Although the most preferred layer configuration of the photoreceptor of the present invention has been described above, other layer configurations of the photoreceptor may be used in the present invention.
[0123]
Solvents or dispersion media used for forming layers such as a photosensitive layer, an intermediate layer, and a surface layer include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, and methyl ethyl ketone. , Methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane , Tetrahydrofuran, dioxolan, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, etc. And the like. Although the present invention is not limited to these, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone and the like are preferably used. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.
[0124]
Further, it is preferable that the coating solution for each of these layers is filtered with a metal filter, a membrane filter, or the like in order to remove foreign substances and aggregates in the coating solution before entering the coating process. For example, it is preferable to select a pleated type (HDC), a depth type (profile), a semi-depth type (profile star), etc., manufactured by Nippon Pall Co., Ltd. in accordance with the characteristics of the coating solution, and then perform filtration.
[0125]
Next, as a coating processing method for manufacturing an organic electrophotographic photoreceptor, coating processing methods such as dip coating, spray coating, and circular amount control type coating are used. In order to prevent the film from being dissolved as much as possible and to achieve a uniform coating process, it is preferable to use a coating process method such as spray coating or coating with a circular amount control type (a typical example is a circular slide hopper type). It is most preferable that the protective layer be formed by the above-mentioned circular amount-regulating coating method. The circular amount control type coating is described in detail in, for example, JP-A-58-189061.
[0126]
Next, an image forming method and an image forming apparatus using the electrophotographic photosensitive member of the present invention will be described.
[0127]
FIG. 1 is a sectional view of an image forming apparatus as an example of the image forming method of the present invention.
[0128]
In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) serving as an image bearing member, which is a photosensitive member having an organic photosensitive layer applied on the drum, and which is grounded and driven to rotate clockwise. Reference numeral 52 denotes a scorotron charger (charging means) for uniformly charging the peripheral surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, in order to eliminate the history of the photoconductor in the previous image formation, exposure by the pre-charging exposure unit 51 using a light emitting diode or the like may be performed to remove the charge on the peripheral surface of the photoconductor.
[0129]
After the photosensitive member is uniformly charged, an image exposure based on an image signal is performed by an image exposure device 53 as an image exposure unit. The image exposure device 53 in this figure uses a laser diode (not shown) as an exposure light source. The light on the photosensitive drum is scanned by the light whose optical path is bent by the reflection mirror 532 via the rotating polygon mirror 531, the fθ lens, and the like, and an electrostatic latent image is formed.
[0130]
Here, the reversal development process is to uniformly charge the surface of the photoreceptor by the charger 52, and to carry out the region where the image exposure has been performed, that is, the exposed portion potential (exposed portion region) of the photoreceptor by the developing step (means). This is an image forming method for visualizing the image. On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.
[0131]
The electrostatic latent image is then developed by a developing device 54 as a developing unit. A developing device 54 containing a developer including a toner and a carrier is provided on the peripheral edge of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer. The inside of the developing device 54 is composed of developer stirring / conveying members 544 and 543, a conveyance amount regulating member 542, and the like. The developer is agitated and conveyed and supplied to the developing sleeve. Controlled by member 542. The transport amount of the developer varies depending on the linear velocity of the electrophotographic photosensitive member to be applied and the specific gravity of the developer, but is generally in the range of ^{20 to} 200 mg / cm ² .
[0132]
The developer is, for example, a carrier formed by coating the above-described ferrite core with an insulating resin around the core, a coloring agent such as carbon black, a charge control agent, and a low molecular weight polyolefin using the above-described styrene acrylic resin as a main material. The toner is composed of a toner in which silica, titanium oxide, or the like is externally added to the particles. The developer is transported to the developing area with the layer thickness regulated by the transport amount regulating member, where the developer is developed. At this time, development is usually performed by applying a DC bias voltage between the photosensitive drum 50 and the developing sleeve 541 and, if necessary, an AC bias voltage. Further, the developer is developed in a state of contact or non-contact with the photoconductor. The potential measurement of the photoconductor is performed by providing a potential sensor 547 above the developing position as shown in FIG.
[0133]
After the image is formed, the recording paper P is fed to the transfer area by the rotation of the paper feed roller 57 at the time when the transfer timing is adjusted.
[0134]
In the transfer area, a transfer electrode (transfer means: transfer unit) 58 operates on the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and applies a charge of the opposite polarity to the toner to the fed recording paper P. Transfer the toner.
[0135]
Next, the recording paper P is discharged by a separation electrode (separator) 59, separated by the peripheral surface of the photosensitive drum 50, conveyed to the fixing device 60, and heated and pressed by the heat roller 601 and the pressure roller 602 to remove the toner. After welding, the sheet is discharged to the outside of the apparatus via a sheet discharge roller 61. After the transfer electrode 58 and the separation electrode 59 have passed through the recording paper P, the primary operation is stopped, and preparation is made for the formation of the next toner image. In FIG. 1, the transfer electrode 58 is a corotron transfer band electrode. The setting conditions of the transfer electrode vary depending on the process speed (peripheral speed) of the photoconductor and cannot be specified unconditionally. For example, the transfer current is set to +100 to +400 μA and the transfer voltage is set to +500 to +2000 V. can do.
[0136]
On the other hand, after the recording paper P is separated, the photosensitive drum 50 removes and cleans the residual toner by pressing the blade 621 of the cleaning device (cleaning means) 62, and removes electricity by the pre-charging exposure unit 51 again and charges by the charger 52. Then, the process of the next image formation is started.
[0137]
Reference numeral 70 denotes a detachable process cartridge in which a photosensitive member, a charger, a transfer device, a separator, and a cleaning device are integrated.
[0138]
The electrophotographic photoreceptor of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, and furthermore, displays, recording, light printing, plate making, and plate making using electrophotographic technology. It can be widely applied to devices such as facsimile machines.
[0139]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples, but embodiments of the present invention are not limited thereto. However, “parts” in the following text indicates “parts by mass”.
[0140]
A photoreceptor was prepared as described below.
Production of photoconductor 1

The above components were mixed and dissolved to prepare an intermediate layer coating solution. The coating solution was applied on a cylindrical aluminum substrate by a dip coating method, and dried to form an intermediate layer having a thickness of 1.0 μm.

The above components were mixed and dispersed for 10 hours using a sand mill to prepare a charge generating layer coating solution. This coating solution was applied on the intermediate layer by a dip coating method, and after drying, a charge generation layer having a thickness of 0.3 μm was formed.

The above components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied on the charge generation layer by a dip coating method, and dried at 100 ° C. for 40 minutes to form a charge transport layer having a thickness of 22 μm.
[0141]
Preparation of Photoreceptors 2 to 14 Photoreceptor 1 was prepared in the same manner as photoreceptor 1 except that the charge generating substance, the compound of the charge transporting substance, the amount of the compound, and the thickness of the charge transporting layer were changed as shown in Tables 1 to 4. 2 to 14 were produced.
[0142]
Preparation of Photoconductor 15 In Photoconductor 1, each component of the compound of Synthesis Example (2) was separated by liquid chromatography, and the component of compound 26 (m = 0) in which only n = 0 was used as the charge transport material. A photoreceptor 15 was produced in the same manner except that the photoconductor 15 was used.
[0143]
Preparation of Photoreceptor 16 In Photoreceptor 1, the charge transporting material was prepared by separating each component of the compound of Synthesis Example (1) by liquid chromatography, and the compound of compound 26 (m = 0) having only n = 3 was converted to a charge transporting material. The photoreceptor 16 was prepared in the same manner except that the photoreceptor was used, but the charge transporting substance was not compatible with the binder resin and was deposited, and a photoreceptor that could be evaluated was not obtained.
[0144]
[Table 1]

[0145]
[Table 2]

[0146]
[Table 3]

[0147]
[Table 4]

[0148]
In the table, Y is a titanyl phthalocyanine pigment (a pigment having a maximum peak of 27.3 ° at a Bragg angle 2θ in a Cu-Kα characteristic X-ray diffraction spectrum)
Z represents a benzimidazole perylene pigment (a pigment having a maximum peak of 12.4 ° at a Bragg angle 2θ in a Cu-Kα characteristic X-ray diffraction spectrum).
[0149]
The average molecular weight Mw indicates a weight average molecular weight (in terms of polystyrene) determined by gel permeation chromatography (GPC).
[0150]
The photoreceptors 1 to 16 obtained as described above were each provided with a reversal developing system digital copying machine “Konica 7085” (a scorotron charger, a semiconductor laser image exposing device (wavelength: 680 nm), reversal developing means) manufactured by Konica Corporation. (A4 paper 85 sheets / min), and the following evaluation items were evaluated. The evaluation was performed by changing environmental conditions (temperature and humidity conditions) for each evaluation item. Basically, the original image having a pixel rate of 7% for a character image, a halftone image, a solid white image, and a solid black image, each of which is equal to 1/4, was converted to A4 by 10,000 sheets in an intermittent mode. Duplicates were made and evaluated. Table 5 shows the evaluation results.
[0151]
Evaluation conditions Line speed: 420 mm / sec. Time required from image exposure to development position; 0.108 sec. Charging condition Charger: Scorotron charger (negative charge)
Charging potential: -700V to -750V
Exposure conditions Set the exposure amount to make the solid black image potential -100V.
[0152]
Exposure beam; 680 nm semiconductor laser used. Development conditions: Developer: Carrier coated with insulating resin with ferrite as core, styrene acrylic resin as main material, carbon black colorant, charge control agent, and low molecular weight polyolefin. A toner developer obtained by externally adding silica and titanium oxide to colored particles having a volume average particle diameter of 5.3 μm produced by a polymerization method comprising:
[0153]
Transfer condition Transfer pole; Corona charging method (positive charging)
Separation Condition Cleaning Condition Using Separation Means of Separation Claw Unit A cleaning blade having a hardness of 70 °, a rebound resilience of 65%, a thickness of 2 (mm) and a free length of 9 mm was applied to the cleaning portion in a counter direction at a linear pressure of 18 (g / cm). And contacted by the weight load method.
[0154]
Evaluation items and evaluation method High-speed response under low-temperature, low-humidity (10 ° C, 20% RH) environment (potential change of solid black image)
In a low-temperature, low-humidity (10 ° C, 20% RH) environment, an original image with a pixel rate of 7%, a halftone image, a solid white image, and a solid black image each divided into 1/4 equal parts is intermittent in A4 Copying of 10,000 sheets was performed in the mode, and the potential change (| ΔV |) of the solid black image at the initial and the developing positions after 10,000 sheets was evaluated. The smaller | ΔV |, the better the high-speed response under a low temperature and low humidity (10 ° C., 20% RH) environment.
[0155]
A: Potential change | ΔV | of solid black image is less than 50 V (good)
；: Potential change | ΔV | of solid black image is 50 V to 150 V (no problem in practical use)
×: The potential change | ΔV | of the solid black image is larger than 150 V (there is a problem in practice)
Character thinning (under low temperature and low humidity (10 ° C 20% RH) environment)
The original image on which the line images of 0.1 mm and 0.2 mm width were printed was copied and evaluated.
[0156]
A: The line width of the copied image is reproduced at 75% or more of the line width of the original image (good)
；: The line width of the copied image is reproduced at 40% to 74% of the line width of the original image (a level at which there is no practical problem)
×: The line width of the copied image is 39% or less of the line width of the original image, or the line width is cut off (a level that poses a practical problem).
Black spot (high temperature and high humidity (30 ° C 80% RH))
The occurrence of black spots (strawberry spot images) on the halftone image was determined based on the following criteria.
[0157]
A: No nuclei of black spots were found on the photoreceptor, and no black spots were found on halftone images (good)
；: Black spot generation nuclei are observed on the photoreceptor, but no black spot is generated in the halftone image (no problem in practical use)
X: Black spot generation nuclei were observed on the photoreceptor, and black spots were also generated on the halftone image (a problem in practical use)
Periodic image defects (high temperature and high humidity (30 ° C, 80% RH)
The periodicity coincided with the period of the photoreceptor, and the number of visible white spots, black spots, and streak-like image defects that were visible per A4 size was determined.
[0158]
頻 度: Frequency of image defects of 0.4 mm or more: All copied images are 5 / A4 or less (good)
；: Frequency of image defects of 0.4 mm or more: 1 or more of 6 / A4 or more and 10 or less of A4 (no problem in practical use)
×: Frequency of image defects of 0.4 mm or more: 11 / A4 or more of one or more defects (practical problem)
Crack The power of the digital copying machine Konica 7085 was turned off in a 30 ° C., 80% RH environment with the photosensitive member mounted, and the digital copying machine was allowed to stand for 2 days. The members around the photoreceptor only stopped operating during this time, that is, the members such as the cleaning blade and the developer conveying member were kept in contact with the photoreceptor. Thereafter, the surface of the photoreceptor was observed, and the occurrence of cracks was observed. In addition, image evaluation was also performed, and the presence or absence of streak-like image defects due to the occurrence of cracks was also evaluated.
[0159]
A: Evaluation of 100 photoconductors, no occurrence of cracks and no streak-like image defects (good)
◯: 100 photosensitive members were evaluated, and fine cracks were generated, but no streak-like image defects were generated (a level that is not problematic in practical use)
×: Evaluation of 100 photoconductors shows occurrence of cracks and generation of streak-like image defects (a level that poses a problem in practical use)
Image density (low temperature and low humidity (10 ° C 20% RH))
The image density of the solid black portion was measured by reflection density using RD-918 manufactured by Macbeth. The evaluation was made based on the relative density (the density of A4 paper not copied was set to 0.00).
[0160]
◎: 1.2 or more (good)
；: Less than 1.2 to 0.8 (a level that does not cause a problem in practical use)
×: less than 0.8 (a level that poses a problem in practical use)
Sharpness The sharpness of an image was evaluated in both low-temperature and low-humidity (10 ° C., 20% RH) and high-temperature, high-humidity (30 ° C., 80% RH) environments, and evaluated by character collapse. Three-point and five-point character images were formed and evaluated according to the following criteria.
[0161]
◎; 3 points and 5 points are clear and easily readable ○; 3 points are partially illegible, 5 points are clear and easily readable ×; 3 points are almost unreadable and 5 points and 1 point Part or all are illegible [0162]
[Table 5]

[0163]
As shown in Table 5, the photoconductors 1 to 13 of the present invention in which two or more compounds having an average molecular weight of 2500 or less and having different n of the general formula (1) were used as the charge transporting material were low temperature and low humidity (10 ° C. 20% RH) Excellent high-speed response (potential change of solid black image) under the environment, therefore, there is no thinning of characters under low temperature and low humidity, and there is no occurrence of black spots, periodic image defects, cracks, etc., and image density , Exhibiting excellent sharpness. On the other hand, the photoreceptor 14 using a compound having an average molecular weight of more than 2500 as a charge transporting substance has reduced dispersibility in the charge transporting layer, and has a high speed response (solid) in a low temperature and low humidity (10 ° C., 20% RH) environment. The potential change of the black image) is deteriorated, and thus the character thinning and sharpness are deteriorated. Also, the photoreceptor 15 using only a low molecular weight compound of n = 0 is inferior in high-speed response in a low-temperature and low-humidity (10 ° C., 20% RH) environment. Has a soft film quality, black spots and periodic image defects also occur, and image density and sharpness are reduced. In the case of the photoreceptor 16 using only a high molecular weight compound of n = 3, poor solubility with the binder resin, little sensitivity, etc., did not deserve evaluation.
[0164]
【The invention's effect】
By using the electrophotographic photoreceptor, the process cartridge, the image forming apparatus and the image forming method of the present invention, an image defect due to poor sensitivity such as high-speed adaptability which is likely to occur in a low-temperature and low-humidity environment and an image likely to occur in a high-temperature and high-humidity environment Defects can be prevented, and an electrophotographic image with good image density and sharpness can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus as an example of an image forming method of the present invention.
[Explanation of symbols]
50 Photoconductor drum (photoconductor)
Reference Signs List 51 Exposure unit before charging 52 Charger 53 Image exposure unit 54 Developing unit 541 Developing sleeve 543, 544 Developer stirring and conveying member 547 Potential sensor 57 Feed roller 58 Transfer electrode 59 Separation electrode (separator)
Reference Signs List 60 fixing device 61 discharge roller 62 cleaning device 70 process cartridge

Claims (9)

An electrophotographic photoreceptor comprising an average molecular weight of 2500 or less and two or more compounds of the following general formula (1) wherein n is different.

In the general formula (1), Ar ₁ represents a divalent substituted or unsubstituted aromatic group, a divalent furan group or a thiophene group, or the following general formula (2), wherein R _{1 to} R ₃ are a hydrogen atom, A represents a substituted or unsubstituted alkyl group, a monovalent substituted or unsubstituted aromatic group, A represents a divalent group containing a triarylamine group or a group represented by the following general formula (3), and B represents 1 It represents a substituted or unsubstituted aromatic group. However, a plurality of B, R ₁ , R ₂ , and R ₃ may be different from each other. m represents 0 or 1, and n represents a natural number of 0 to 30.

In the general formula (2), Y is a single bond, an oxygen atom, a sulfur atom, —CH ＝ CH—, or —C (R ₄ ) (R ₅ ) —, and R ₄ and R ₅ are bonded to each other. Is also good.

In the general formula (3), X ₁ represents a single bond, an alkylene group, an oxygen atom or a sulfur atom, and R ₆ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group. A charge generation layer and a charge transport layer are provided on a conductive support, and the charge transport layer contains two or more compounds having an average molecular weight of 2500 or less and different n in the general formula (1). Electrophotographic photoreceptor. 3. The electrophotographic photoreceptor according to claim 1, wherein the divalent group containing a triarylamine group of A is a group represented by the following general formula (4).

In the general formula (4), Ar ₂ represents a substituted or unsubstituted monovalent aromatic group. The electrophotographic photosensitive member according to claim 3, wherein Ar ₂ is a group represented by the following general formula (5).

In Formula (5), R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , and R _{25 each} represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. However, at least one of R ₂₁ and R ₂₅ is an alkyl group having 1 to 4 carbon atoms. 3. The electrophotographic photoreceptor according to claim 1, wherein the divalent group containing a triarylamine group of A is a group represented by the following general formula (6).

In the general formula (6), X ₂ is a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted divalent aromatic group, and Ar ₃ and Ar ₄ are a substituted or unsubstituted monovalent aromatic group. Is shown. The electrophotographic photosensitive member according to any one of claims 1 to 5, wherein B is a group represented by the following general formula (7).

In the general formula (7), R ₄₁ , R ₄₂ , R ₄₃ , R ₄₄ , R ₄₅ , R ₅₁ , R ₅₂ , R ₅₃ , R ₅₄ and R ₅₅ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. . However, at least one of R ₄₁ , R ₄₅ , R ₅₁ , and R ₅₅ is an alkyl group having 1 to 4 carbon atoms. An electrophotographic photosensitive member containing two or more compounds having an average molecular weight of 2500 or less and different n of the general formula (1), a charging means for uniformly charging the electrophotographic photosensitive member, and a charged electrophotographic device Latent image forming means for forming an electrostatic latent image on the photoreceptor, developing means for visualizing the electrostatic latent image on the electrophotographic photoreceptor, and transfer of the visualized toner image onto the electrophotographic photoreceptor At least one of a transfer unit for transferring onto the material, a charge removing unit for removing charges on the electrophotographic photosensitive member after transfer, and a cleaning unit for removing residual toner on the electrophotographic photosensitive member after transfer is provided. A process cartridge which is integrally supported and is detachably mountable to an image forming apparatus main body. An image forming apparatus comprising the process cartridge according to claim 7. An image forming method for forming an electrophotographic image using the image forming apparatus according to claim 8.

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