JP2004118161A - Electrophotographic photoreceptor and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which covers defects on a conductive substrate without impairing superior electrophotographic properties and is excellent in repetition stability and environmental characteristics. <P>SOLUTION: In the electrophotographic photoreceptor obtained by forming a photosensitive layer on a conductive support by way of an undercoat layer, the undercoat layer contains a polyimide resin represented by formula (1) (where X is a divalent polycyclic aromatic group in which aromatic rings may be linked by a hetero atom and n is an integer which represents a polymerization degree) and the thickness of the undercoat layer is 1.0-50 μm. Thus, an electrophotographic photoreceptor which has superior electrophotographic properties, cleanability and oil resistance and simplifies maintenance is provided. <P>COPYRIGHT: (C)2004,JPO

Description

〔式中、Ｘは芳香環が異種原子で連結されてもよい２価の多環芳香族基であり、ｎは重合度を表す整数である。〕で表されるポリイミド樹脂を含有し、該下引層の膜厚が１．０μｍ〜５０μｍであることを特徴とする電子写真感光体に関するものである。該下引層により成膜性が向上し、薄膜においても導電性支持体のピンホール等の欠陥が被覆され、感光層のバリアー機能、接着機能が従来のポリアミド樹脂の場合よりも格段に優れたものとなり、かつ画像の状態がポリアミド樹脂の場合よりも格段に優れたものとなる。また、本発明の下引層には、ポリイミド化する前の中間体が含まれていてもよく、ポリイミド前駆体とポリイミド樹脂との混合割合は、該ポリイミド樹脂を該ポリイミド樹脂と該ポリイミド前駆体との合計重量の２０〜７０％含有させるのがよく、好ましくは３０〜５０％の範囲がよい。２０％未満だと下引層が有機溶剤に溶解してしまい、７０％超だとイミド化に近い状態となり、繰り返し使用後の残留電位が蓄積され画像不良となる。
【００１２】
ポリイミド樹脂の分子量は、１，０００〜１００，０００、特に１０，０００〜３０，０００の範囲のものが好ましい。Ｘの具体例は、下記のとおりである。
【化３】

【化４】

【化５】

（Ｙは、水素原子、ハロゲン原子、炭素数１〜６のアルキル基若しくはアルコキシ基、又は置換していてもよいアリール基を表す。）
【００１３】
また、前記下引層に酸化チタンを含有させることによって、下引層の誘電率を高くすることができ、分散性も向上する。さらにポリイミド樹脂と酸化チタンとの重量比が２：１〜１：４の範囲であることが好ましい。
【００１４】
また、前記下引層を形成する際の乾燥温度が１１０℃〜１７０℃の範囲であることが好ましい。１１０℃以下では下引層が溶剤で溶解してしまう為、感光体に塗布できない。なお、１１０℃以上で乾燥すると有機溶剤に溶解しない。１７０℃超だと繰り返し使用後の残留電位が上昇し、画像にチリカブリが発生してしまう問題が生ずる。
【００１５】
また、該下引層が一般式（１）で表されるポリイミド樹脂と酸化チタンとを含有することによって、下引層の誘電率を高くすることができ、厚膜にすることが可能になり、分散性も向上する。
【００１６】
さらに、該下引層が一般式（１）で表されるポリイミド樹脂を含有する層とその上に熱硬化性樹脂又は熱可塑性樹脂からなる層の２層構造を設けることによって、下引層が厚膜化しても残留電位の蓄積を抑えられ、帯電性を安定させられることから画像品質が向上する。
【００１７】
さらに、請求項１の電子写真感光体において、導電性支持体が無切削管を用いることにより、本発明の目的を達成することができる。
さらに、請求項１の電子写真感光体において、帯電手段として接触帯電手段を有することを特徴とする電子写真装置によって、本発明の目的を達成することができる。さらに、請求項２において、半導体レーザーによる露光手段を適用することによって画像の干渉縞を解消することができる。
【００１８】
【発明の実施の形態】
以下、本発明に係る電子写真感光体の好ましい実施の形態を詳細に説明する。本発明は、例えば、導電性支持体の上に少なくとも電荷発生剤が含有される電荷発生層が形成され、その上に少なくとも電荷移動剤が含有される電荷移動層が形成される機能分離型電子写真感光体に適用されるものである。この場合、電荷発生層と電荷移動層とにより感光層が形成される。
【００１９】
また、本発明は、電荷発生剤と電荷移動剤が同一の層に含有される単層型電子写真感光体や、電荷移動層、電荷発生層の順に積層された逆積層型電子写真感光体等に対しても適用することができる。
【００２０】
本発明に用いることができる導電性支持体としては、アルミニウム、真鍮、ステンレス鋼、ニッケル、クロム、チタン、金、銀、銅、錫、白金、モリブデン、インジウム等の金属単体やその合金の加工体や、上記金属や炭素等の導電性物質を蒸着、メッキ等の方法で処理し、導電性を持たせたプラスチック板及びフィルム、さらに酸化錫、酸化インジウム、ヨウ化アルミニウムで被覆した導電性ガラス等、種類や形状に制限されることなく、導電性を有する種々の材料を使用して導電性支持体を構成することができる。また、導電性支持体の形状については、ドラム状、棒状、板状、シート状、ベルト状のものを使用することができる。
この中でも、ＪＩＳ３０００系、ＪＩＳ５０００系、ＪＩＳ６０００系等のアルミニウム合金が用いられ、ＥＩ法、ＥＤ法、ＤＩ法、ＩＩ法等一般的な方法により成形を行なったものであり、ダイヤモンドバイト等による表面切削加工や研磨、陽極酸化処理等の表面処理を行なわない無切削管が好ましい。
【００２１】
本発明に用いることができる電荷発生剤としては、ジスアゾ顔料やオキシチタニウムフタロシアニンが感度の相性が良い点で望ましいが、それに限定されるものではない。その他、例えば、セレン、セレン−テルル、セレン−砒素、アモルファスシリコン、無金属フタロシアニン、他の金属フタロシアニン顔料、モノアゾ顔料、トリスアゾ顔料、ポリアゾ顔料、インジゴ顔料、スレン顔料、トルイジン顔料、ピラゾリン顔料、ペリレン顔料、キナクリドン顔料、多環キノン顔料、ピリリウム塩等を用いることができる。特にオキシチタニウムフタロシアニンには、いくつもの結晶型が紹介されているが、その中でもＣｕＫαを線源とするＸ線回折スペクトルにおいてブラック角（２θ±０．２°）２７．３°に最大回折ピークを示す結晶型（図２に示す）、７．６°及び２８．３°に主たる回折ピークを示す結晶型及び７．５°に最大ピークを有し、かつ他の回折ピーク強度が７．５°の回折ピーク強度に対して２０％以下の強度である結晶型（図１に示す）のものが本発明の電子写真感光体用に特に好ましい。膜厚は、０．０１〜５．０μｍ、好ましくは０．１〜１．０μｍの範囲がよい。
【００２２】
上記電荷発生剤は単体で用いてもよいし、適切な光感度波長や増感作用を得るために２種類以上を混合して用いてもよい。
【００２３】
本発明の電子写真感光体は、下引層を介して感光層を形成した電子写真感光体において、該下引層が一般式（１）で表されるポリイミド樹脂を含有することにより、成膜性が向上し、薄膜においても導電性支持体のピンホール等の欠陥が被覆され、感光層のバリアー機能，接着機能が優れている。膜厚は１．０〜５０μｍ、好ましくは２０〜４０μｍで使用される。
【００２４】
また、該下引層を形成する際の乾燥温度が１１０℃〜１７０℃の範囲が適当であり、好ましくは１３０℃〜１５０℃が良い。１１０℃未満では下引層が溶剤で溶解してしまう為、感光体に塗布できない。なお、１１０℃以上で乾燥すると有機溶剤に溶解しない。１７０℃超だと繰り返し使用後の残留電位が上昇し、画像濃度変化が発生してしまうという若干の問題が生ずる。
【００２５】
さらに下引層が一般式（１）で表されるポリイミド樹脂を含有する層とその上に熱硬化性樹脂又は熱可塑性樹脂からなる層の２層構造を設けることによって、下引層が厚膜化しても残留電位の蓄積を抑えられ、かつ画像品質が向上する。
【００２６】
感光層を形成するために用いることができる結着樹脂としては、ポリカーボネート樹脂、スチレン樹脂、アクリル樹脂、スチレン−アクリル樹脂、エチレン−酢酸ビニル樹脂、ポリプロピレン樹脂、塩化ビニル樹脂、塩素化ポリエーテル、塩化ビニル−酢酸ビニル樹脂、ポリエステル樹脂、フラン樹脂、ニトリル樹脂、アルキッド樹脂、ポリアセタール樹脂、ポリメチルペンテン樹脂、ポリアミド樹脂、ポリウレタン樹脂、エポキシ樹脂、ポリアリレート樹脂、ジアリレート樹脂、ポリスルホン樹脂、ポリエーテルスルホン樹脂、ポリアリルスルホン樹脂、シリコーン樹脂、ケトン樹脂、ポリビニルブチラール樹脂、ポリエーテル樹脂、フェノール樹脂、ＥＶＡ（エチレン・酢酸ビニル・共重合体）樹脂、ＡＣＳ（アクリロニトリル・塩素化ポリエチレン・スチレン）樹脂、ＡＢＳ（アクリロニトリル・ブタジエン・スチレン）樹脂、エポキシアリレート等の光硬化樹脂等がある。これらは、１種でも２種以上混合して使用することも可能である。また、分子量の異なった樹脂を混合して用いれば、硬度や耐摩耗性を改善できるのでより好ましい。
【００２７】
本発明の電子写真感光体は、下引層に酸化チタンを含有させてもよい。本発明で用いる酸化チタンは、体積抵抗値を低下させない限り、酸化チタン粒子表面に種々の処理を施してもよい。例えば、アルミニウム，ケイ素ニッケル等を処理剤として、その粒子表面に酸化膜の被覆を行うことができる。その他、必要に応じてカップリング材等の撥水性を付与することも可能である。また、酸化チタンの平均粒径１μｍ以下のものが好ましく、０．０１〜０．５μｍのものがさらに好ましい。酸化チタンの含有量はポリイミド１に対して０．５〜４倍の範囲が好ましい。
【００２８】
さらに、下引層として、ポリイミド樹脂からなる層とその上に熱硬化性樹脂又は熱可塑性樹脂からなる層の２層構造を設けてもよい。熱硬化性樹脂としては、エポキシ樹脂、ポリウレタン、フェノール、メラミン・アルキド樹脂、不飽和ポリエステル樹脂等が挙げられる。熱可塑性樹脂としては、スチレン系エラストマー、オレフィン系エラストマー、ウレタン系エラストマー、ポリ塩化ビニル系エラストマー等が挙げられる。ポリイミド樹脂層の上に設ける樹脂層の膜厚は０．１〜１０．０μｍ、好ましくは０．８〜５．０μｍの範囲で使用できる。
【００２９】
また、上記２層からなる層の両方又は片方の層中に、半導体レーザー露光時の光干渉を抑制する目的で白色顔料を含有させてもよい。例えば、酸化チタン，酸化亜鉛，シリカ等が挙げられる。
【００３０】
本発明に用いることができる電荷移動材料としては、一般式（２）及び／又は一般式（３）で表される化合物が好ましい。
【００３１】
【化６】

（式中、Ｒ_１及びＲ_２は、各々独立に置換基を有してもよい炭素数１〜６のアルキル基を表し、Ｒ_３は、水素原子又は少なくとも一つのアルキル基が炭素数２以上のジアルキルアミノ基のいずれかを表す。）
【００３２】
【化７】

（式中、Ｒ_４〜Ｒ_７は、各々同一であっても異なっていてもよく、各々独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基若しくはアルコキシ基、又は置換基を有してもよいアリール基のいずれかを表し、Ｒ_８は水素原子、ハロゲン原子、炭素数１〜６のアルキル基若しくはアルコキシ基、置換基を有してもよいアリール基、又は置換基を有してもよいアルケニル基若しくはアルカジエニル基、若しくは一般式（４）のいずれかを表し、ｍは０又は１の整数を表す。）
【００３３】
【化８】

（式中、Ｒ_９、Ｒ_１０は、各々同一であっても異なっていてもよく、各々独立に水素原子、ハロゲン原子、炭素数１〜６のアルキル基若しくはアルコキシ基、又は置換基を有してもよいアリール基のいずれかを表し、ｎは０又は１の整数を表す。）
上記電荷移動材料は、オキシチタニウムフタロシアニンとの相性がよく、本発明の電子写真感光体は、高感度かつ低残留電位という優れた電気特性を示すものである。
一般式（１）に示す化合物において、特に式（５）及び式（６）に示す化合物がオキシチタニウムフタロシアニンとの相性がよく好ましい。
【００３４】
【化９】

【００３５】
【化１０】

また、一般式（３）に示す化合物において、特に式（７）、式（８）、式（９）、式（１０）に示す化合物がオキシチタニウムフタロシアニンとの相性がよく好ましい。
【００３６】
【化１１】

【００３７】
【化１２】

【００３８】
【化１３】

【００３９】
【化１４】

【００４０】
また、一般式（２）から選ばれる化合物と一般式（３）から選ばれる化合物を同時に電荷移動材料として用いても、よい特性が得られて好ましい。
【００４１】
上記電荷移動材料以外の他の電荷移動材料を用いることもできる。他の電荷移動材料としては、ポリビニルカルバゾール、ハロゲン化ポリビニルカルバゾールさらに、本発明の電子写真感光体の感光層中には、他の電荷移動剤を添加することもできる。その場合には、感光層の感度を高めたり、残留電位を低下させることができるので、本発明の電子写真感光体の特性を改良することができる。
【００４２】
そのような特性改良のために添加できる電荷移動剤としては、ポリビニルカルバゾール、ハロゲン化ポリビニルカルバゾール、ポリビニルピレン、ポリビニルインドロキノキサリン、ポリビニルベンゾチオフェン、ポリビニルアントラセン、ポリビニルアクリジン、ポリビニルピラゾリン、ポリアセチレン、ポリチオフェン、ポリピロール、ポリフェニレン、ポリフェニレンビニレン、ポリイソチアナフテン、ポリアニリン、ポリジアセチレン、ポリヘプタジイエン、ポリピリジンジイル、ポリキノリン、ポリフェニレンスルフィド、ポリフェロセニレン、ポリペリナフチレン、ポリフタロシアニン等の導電性高分子化合物を用いることができる。
【００４３】
また、低分子化合物として、トリニトロフルオレノン、テトラシアノエチレン、テトラシアノキノジメタン、キノン、ジフェノキノン、ナフトキノン、アントラキノン及びこれらの誘導体等、アントラセン、ピレン、フェナントレン等の多環芳香族化合物、インドール、カルバゾール、イミダゾール等の含窒素複素環化合物、フルオレノン、フルオレン、オキサジアゾール、オキサゾール、ピラゾリン、トリフェニルメタン、トリフェニルアミン、エナミン、スチルベン、前記以外のブタジエン、前記以外のヒドラゾン化合物等を電荷移動剤として添加することができる。
【００４４】
また、同様の目的の電荷移動剤として、ポリエチレンオキシド、ポリプロピレンオキシド、ポリアクリロニトリル、ポリメタクリル酸等の高分子化合物にＬｉ（リチウム）イオン等の金属イオンをドープした高分子固体電解質等を添加することもできる。
【００４５】
さらに、同様の目的の電荷移動剤として、テトラチアフルバレン−テトラシアノキノジメタンで代表される電子供与性物質と電子受容性物質で形成された有機電荷移動錯体等も用いることができる。
【００４６】
なお、前記電荷移動剤は、１種だけ添加しても、２種以上の化合物を混合して添加しても所望の感光体特性を得ることができる。電荷移動層の膜厚は、５．０〜５０μｍ、好ましくは１０〜３０μｍがよい。
また、本発明の電子写真感光体の場合、感光層全体の膜厚は、１０〜５０μｍ、好ましくは１５〜２５μｍの範囲がよい。例えば下引層を２５μｍ程度に厚く設けた場合は、電荷移動層は１５μｍ程度に薄く設ければよい。逆に下引層を１μｍ程度に薄く設けた場合は、電荷移動層を２５μｍ程度に厚く設ければよい。この理由として、帯電手段として、接触帯電手段を有する電子写真プロセスにおいて、感光体の耐圧性が要求されている。一般に、耐圧性が低い感光体は、リーク電流により感光体内から表面において欠陥が生じ、これが画像欠陥として現われる。即ち、感光体の耐圧性は感光体の総膜厚により決定されるので、下引層の膜厚を厚くすることで、耐圧性が向上するため電荷移動層を薄膜にできる。
【００４７】
本発明の電子写真感光体は、光導電材料や結着樹脂の酸化劣化による特性変化、クラックの防止、機械的強度の向上の目的で、その感光層中に酸化防止剤や紫外線吸収剤を含有することが好ましい。
【００４８】
本発明に用いることができる酸化防止剤としては、２，６−ジ−ｔｅｒｔ−ブチルフェノール、２，６−ジ−ｔｅｒｔ−４−メトキシフェノール、２−ｔｅｒｔ−ブチル−４−メトキシフェノール、２，４−ジメチル−６−ｔｅｒｔ−ブチルフェノール、２，６−ジ−ｔｅｒｔ−ブチル−４−メチルフェノール、ブチル化ヒドロキシアニソール、プロピオン酸ステアリル−β−（３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシフェニル）、α−トコフェロール、β−トコフェロール、ｎ−オクタデシル−３−（３′−５′−ジ−ｔｅｒｔ−ブチル−４′−ヒドロキシフェニル）プロピオネート等のモノフェノール系、２，２′−メチレンビス（６−ｔｅｒｔ−ブチル−４−メチルフェノール）、４，４′−ブチリデン−ビス−（３−メチル−６−ｔｅｒｔ−ブチルフェノール）、４，４′−チオビス（６−ｔｅｒｔ−ブチル−３−メチルフェノール）、１，１，３−トリス（２−メチル−４−ヒドロキシ−５−ｔｅｒｔ−ブチルフェニル）ブタン、１，３，５−トリメチル−２，４，６−トリス（３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシベンジル）ベンゼン、テトラキス〔メチレン−３（３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシフェニル）プロピオネート〕メタン等のポリフェノール系等が好ましく、これらを１種若しくは２種以上を同時に感光層中に含有することができる。
【００４９】
また、紫外線吸収剤としては、２−（５−メチル−２−ヒドロキシフェニル）ベンゾトリアゾール、２−〔２−ヒドロキシ−３，５−ビス（α，α−ジメチルベンジル）フェニル〕−２Ｈ−ベンゾトリアゾール、２−（３，５−ジ−ｔｅｒｔ−ブチル−２−ヒドロキシフェニル）ベンゾトリアゾール、２−（３−ｔｅｒｔ−ブチル−５−メチル−２−ヒドロキシフェニル）−５−クロロベンゾトリアゾール、２−（３，５−ジ−ｔｅｒｔ−ブチル−２−ヒドロキシフェニル）−５−クロロベンゾトリアゾール、２−（３，５−ジ−ｔｅｒｔ−アミル−２−ヒドロキシフェニル）ベンゾトリアゾール、２−（２′−ヒドロキシ−５′−ｔｅｒｔ−オクチルフェニル）ベンゾトリアゾール等のベンゾトリアゾール系、サリチル酸フェニル、サリチル酸−ｐ−ｔｅｒｔ−ブチルフェニル、サリチル酸−ｐ−オクチルフェニル等のサリチル酸系が好ましく、これらを１種若しくは２種以上を同時に感光層に含有することができる。
【００５０】
また、酸化防止剤と紫外線吸収剤を同時に添加することもできる。これらの添加は感光層中であれば何れの層でもよいが、最表面の層特に電荷移動層に添加することが好ましい。
【００５１】
なお、酸化防止剤は、結着樹脂に対して３〜２０重量％とすることが好ましく、紫外線吸収剤の添加量は、結着樹脂に対して３〜３０重量％とすることが好ましい。さらに、酸化防止剤と紫外線吸収剤との両者を添加する場合には、両成分の添加量は、結着樹脂に対して５〜４０重量％とすることが好ましい。
【００５２】
前記酸化防止剤、紫外線吸収剤以外にも、ヒンダードアミン、ヒンダードフェノール化合物等の光安定剤、ジフェニルアミン化合物等の老化防止剤、界面活性剤等を感光層に添加することもできる。
【００５３】
感光層の形成方法としては、所定の感光材料と結着樹脂と共に溶媒に分散あるいは溶解して塗工液を作成し、所定の下地上に塗工する方法が一般的である。
【００５４】
塗工方法としては、浸漬塗工、カーテンフロー、バーコート、ロールコート、リングコート、スピンコート、スプレーコート等、下地の形状や塗工液の状態に合わせて行うことができる。
また、電荷発生層は真空蒸着法により形成させることもできる。
【００５５】
塗工液に使用する溶剤には、メタノール、エタノール、ｎ−プロパノール、ｉ−プロパノール、ブタノール、メチルセルソルブ、エチルセルソルブ等のアルコール類、ペンタン、ヘキサン、ヘプタン、オクタン、シクロヘキサン、シクロヘプタン等の飽和脂肪族炭化水素、トルエン、キシレン等の芳香族炭化水素、ジクロロメタン、ジクロロエタン、クロロホルム、クロロベンゼン等の塩素系炭化水素、ジメチルエーテル、ジエチルエーテル、テトラヒドロフラン（ＴＨＦ）等のエーテル類、アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン類、ギ酸エチル、ギ酸プロピル、酢酸メチル、酢酸エチル、酢酸プロピル、酢酸ブチル、プロピオン酸メチル等のエステル類、Ｎ，Ｎ−ジメチルホルムアミド、ジメチルスルホキシド、Ｎ−メチル−２−ピロリドン等のアミド類等がある。これらは単独で用いても、２種類以上の溶剤を混合して用いてもよい。
【００５６】
また、本発明の下引層には、樹脂中に金属化合物、金属酸化物、カーボン、シリカ、樹脂粉体等を分散させた中間層を用いることもできる。さらに、特性改善のために各種顔料、電子受容性物質や電子供与性物質等を含有させることもできる。
【００５７】
加えて、感光層の表面に、ポリビニルホルマール樹脂、ポリカーボネート樹脂、フッ素樹脂、ポリウレタン樹脂、シリコーン樹脂等の有機薄膜や、シランカップリング剤の加水分解物で形成されるシロキサン構造体から成る薄膜を成膜して表面保護層を設けてもよく、その場合には、感光体の耐久性が向上するので好ましい。この表面保護層は、耐久性向上以外の他の機能を向上させるために設けてもよい。
【００５８】
次に、本発明の電子写真プロセス、電子写真装置について説明する。本発明の電子写真プロセスには、帯電手段、露光手段、現像手段、転写手段、定着手段、クリーニング手段等公知の手段を使用することができる。帯電手段においては、コロナ帯電方式等の非接触帯電方式、帯電ローラー、帯電ブラシ等の接触帯電方式を用いることができる。像露光手段の光源は、ハロゲン光、蛍光灯及びレーザー光等を用いることができる。半導体レーザーの波長は、７８０ｎｍ以下、好ましくは７８０〜５００ｎｍであり、レーザービーム径を絞る等の方式でもよい。現像方式は、乾式現像法、湿式現像法、２成分、１成分、磁性／非磁性いずれでもよい。転写方式もローラー、ベルトいずれでもよい。
【００５９】
【実施例】
以下、本発明に係る電子写真感光体の実施例を比較例とともに詳細に説明する。
【００６０】
実施例１
直径３０ｍｍの無切削アルミニウムからなる円筒ドラム上に、アルミナ被覆された酸化チタン粒子と一般式（１）のＸが［Ｘ−１］のポリイミド樹脂を重量比で１：１の割合で混合した溶液を塗布し、１４０℃で３０分乾燥し、膜厚２０．０μｍの第１の下引層を形成した。次いで、前記下引層上に、熱硬化性樹脂としてのメラミン・アルキド樹脂と酸化チタンとを１：３の割合とし、メチルエチルケトンに溶解して塗布液として、前記下引層上に第２の下引層を１．０μｍの膜厚で積層した。
【００６１】
次いで、結着樹脂としてポリビニルブチラールを用い、図１に示すオキシチタニウムフタロシアニンの分散液を浸漬塗工により０．１μｍ塗布し、電荷発生層を形成した。
【００６２】
次いで、結着樹脂としてポリカーボネート共重合体と、電荷移動剤として式６のブタジエン化合物と、酸化防止剤として２，６−ジ−ｔｅｒｔ−ブチル−４−メチルフェノールとを、ポリカーボネート共重合体＝１．０／０．８／０．１８の重量比でクロロホルムに溶解して塗工液を調製した。
【００６３】
そして、浸漬塗工によりこの塗工液を塗布した後、１００℃の温度下で１時間乾燥し、２０μｍの膜厚の電荷移動層を形成し、電子写真感光体を作製した。
【００６４】
実施例２
実施例１の第１下引層のポリイミド樹脂と酸化チタンの重量比を２：１に代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００６５】
実施例３
実施例１の無切削アルミニウムを切削アルミニウムに代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００６６】
実施例４
実施例１の第１下引層のポリイミド樹脂と酸化チタンの重量比を１：４に代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００６７】
実施例５
実施例１の第１下引層の膜厚を５．０μｍに代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００６８】
実施例６
実施例１の第１下引層の膜厚を３０．０μｍに代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００６９】
実施例７
実施例１の第２下引層のメラミン・アルキド樹脂をナイロン樹脂に代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００７０】
実施例８
実施例１の第２下引層を削除した以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００７１】
実施例９
実施例１の式６の電荷移動剤を式７の電荷移動剤に代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００７２】
実施例１０
実施例１の式６の電荷移動剤と、式７の電荷移動剤を混合した以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００７３】
実施例１１
実施例１の図１の電荷発生剤を、図２の電荷発生剤に代えた以外は、実施例１と同様の方法で電子写真感光体を作製した。
【００７４】
実施例１２
実施例１の第１下引層の酸化チタン及び第２下引層を無くした以外は、実施例１と同様の方法により電子写真感光体を作製した。
【００７５】
実施例１３
実施例１の第１下引層の酸化チタンを無くした以外は、実施例１と同様の方法により電子写真感光体を作製した。
【００７６】
比較例１
実施例１の第１下引層の膜厚を０．５μｍにした以外は、実施例１と同様の方法により電子写真感光体を作製した。
【００７７】
比較例２
実施例１の第１下引層をなくした以外は、実施例１と同様の方法により電子写真感光体を作製した。
【００７８】
比較例３
実施例１の第１及び第２下引層をなくした以外は、実施例１と同様の方法により電子写真感光体を作製した。
【００７９】
評価方法１
〔静電特性の測定、繰り返しサイクル試験、画像試験〕
常温常湿（２４℃、４０％ＲＨ）の環境下にて、直接帯電方式の沖データ社製Ｍｉｃｒｏｌｉｎｅ１４プリンターを用い、実施例１〜９及び比較例１〜３によって作製された円筒状電子写真感光体を帯電後の感光体表面電位が−８００Ｖになるよう帯電させ、ＬＥＤ露光後の感光体の表面電位が−５０Ｖになるようにして初期設定し、次いでＡ４用紙２０，０００枚印字後の表面電位Ｖ０（−Ｖ）、残留電位ＶＲ（−Ｖ）を測定した。画像試験は、２０，０００枚連続印字後の画像を評価した。以上の結果を表１に示す。判定は、「○」は良好なもの、「×」は画像不良等があり実用上問題があるものとした。
【００８０】
【表１】

【００８１】
表１から明らかなように、実施例１〜１１の電子写真感光体は２０，０００枚繰り返し後の帯電性、光疲労特性において良好であり、画像においてもカブリ等の画像欠陥が全く発生しなかった。
【００８２】
加えて、ポリイミド樹脂に酸化チタンを混合した場合やポリイミド樹脂層の上に熱硬化性樹脂、熱可塑性樹脂を積層した場合でも良好な結果が得られた。
つまり実施例１〜１１の場合、結果が特に良好であった。
【００８３】
実施例１２及び１３の電子写真感光体は、第１下引層中の酸化チタンを除いた場合、濃度低下が生じたが、他の点は概ね良好であった。
これに対し、比較例１の第１下引層が１．０μｍ未満の薄膜ではリークが発生し、画像に黒点となって表れた。比較例２及び３はいずれもポリイミド樹脂層がない場合は、転写メモリーによる黒点が発生した。
【００８４】
【発明の効果】
本発明の電子写真感光体は、表面電位や露光後電位等の静電特性は、繰り返し後でも大きな劣化がなく、画像欠陥が全く発生せず、繰り返し安定性に強い。
よって、本発明によれば、優れた電子写真特性、クリーニング性、耐油性を有し、かつ、メンテナンスの簡略化が図れる電子写真感光体を提供できる。
【図面の簡単な説明】
【図１】本発明に使用するオキシフタロシアニンのうち、実施例に用いたもののＸ線回折図を示す。
【図２】本発明に使用するオキシフタロシアニンのうち、他の実施例に用いたもののＸ線回折図を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic photoreceptor used for an electrophotographic apparatus such as a copying machine, an LED, and an LD printer, and more particularly, to an electrophotographic photoreceptor using an organic photoconductive material having an undercoat layer formed thereon and a photoreceptor using the same. The present invention relates to a mounted electrophotographic apparatus.
[0002]
[Prior art]
Generally, an electrophotographic process using a photoreceptor is performed as follows. That is, in a dark place, for example, charged by a charging roller as a contact charging method, and then, using an LED or LD as an image exposure unit, an electric charge of only an exposed portion is selectively eliminated to form an electrostatic latent image, and further, Visualize with a developer to form an image.
The basic characteristics required of such an electrophotographic photoreceptor include (i) being able to be charged to an appropriate potential in a dark place, and (ii) being provided with a function capable of eliminating surface charges by light irradiation.
The electrophotographic photoreceptor currently in practical use has a basic configuration in which a photosensitive layer is formed on a conductive support, but the photosensitive layer is formed due to unnecessary charge injection from the conductive support to the photosensitive layer. The conductive support is used to prevent the occurrence of image defects such as dust and fog due to the disappearance or reduction of the surface charge, to remove the defects on the conductive support surface by coating, to improve the chargeability, and to improve the adhesiveness of the photosensitive layer. An undercoat layer is provided between the photosensitive layer and the photosensitive layer.
[0003]
It is known that a resin material such as polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, silicone resin, and polyamide resin is used for the undercoat layer. Among these resins, a polyamide resin is particularly preferred.
However, in an electrophotographic photoreceptor using a polyamide resin or the like for the undercoat layer, the volume resistivity of the electrophotographic photoreceptor is 10%. ¹² -10 ^Fifteen Since the thickness is about Ω · cm, unless the thickness of the undercoat layer is reduced to 1 μm or less, a residual potential is accumulated on the photoconductor, and fogging occurs in an image. On the other hand, when the film is thinned, not only is it impossible to cover the defects on the conductive support, but also the injection of holes from the substrate during repeated use is accelerated, the charging potential is significantly reduced, and the photosensitivity is also reduced, so that the image is fogged. As a result, there is a problem that image quality is impaired.
[0004]
Japanese Unexamined Patent Publication No. Hei 8-30007 describes an undercoat layer using a polyimide resin soluble in an organic solvent. In the examples, the undercoat layer has a thickness of 0.5 μm. (For example, refer to Patent Document 1).
[0005]
[Patent Document 1]
JP-A-8-30007 (page 3-11, Example 1)
[0006]
However, when an undercoat layer containing a polyimide resin is formed as a thin film having a thickness of 1 μm or less as described in Patent Document 1, the residual potential after repeated use of the photoconductor is reduced. As a result, there is a problem that dust rises in the image.
In addition, when the photoconductor is used in an electrophotographic apparatus including a charging device having a contact member to which a charging voltage is applied in contact with the photoconductor, a high voltage is directly applied to the electrophotographic photoconductor so that dust fog is generated. There was a problem that was likely to occur.
[0007]
[Problems to be solved by the invention]
Furthermore, besides the occurrence of dust fog, when cutting a cutting aluminum tube, which is a photoconductor support, with a diamond tool, cutting oil and cutting powder remain on the support, and the photosensitive layer is applied on it. There is also a problem that a defect appears at the time of image formation, or when a high voltage is applied to the surface of the photoreceptor, current flows from a defective portion such as a cutting burr of the support and a short circuit occurs partially.
[0008]
An object of the present invention is to provide an electrophotographic photoreceptor which covers defects on a conductive substrate without impairing excellent electrophotographic characteristics and has excellent repetition stability and environmental characteristics.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, in an electrophotographic photosensitive member having a photosensitive layer formed on a conductive support via an undercoat layer, the undercoat layer is a specific polyimide An electrophotographic photoreceptor containing a resin and having an undercoat layer having a thickness of 1.0 μm to 50 μm and containing a thickened polyimide resin is free from the problems of the above-mentioned conventional technology, and is used for a long time. The inventors have found that excellent electrostatic characteristics are maintained, and have completed the present invention.
[0010]
As a result of intensive studies, the present inventors have found that a commonly used undercoat layer of a thin film of less than 1.0 μm cannot not only cover defects on the conductive support, but also the chargeability of the photoconductor is not stable, and After use, it was confirmed that hole injection from the photoreceptor substrate was accelerated and dust fog was generated in the image. As a condition for solving these problems, it has been found that controlling the film thickness of the undercoat layer improves the image quality.
[0011]
That is, the present invention relates to an electrophotographic photosensitive member having a photosensitive layer formed on a conductive support via an undercoat layer, wherein the undercoat layer has the general formula (1)
Embedded image

[In the formula, X is a divalent polycyclic aromatic group in which aromatic rings may be linked by different atoms, and n is an integer representing the degree of polymerization. And an undercoat layer having a thickness of 1.0 μm to 50 μm. The undercoat layer improves film formability, and covers defects such as pinholes in the conductive support even in a thin film, and the barrier function and adhesive function of the photosensitive layer are much better than those of conventional polyamide resins. And the state of the image is much better than that of the polyamide resin. Further, the undercoat layer of the present invention may contain an intermediate before polyimide conversion, the mixing ratio of the polyimide precursor and the polyimide resin, the polyimide resin and the polyimide resin and the polyimide precursor 20 to 70% of the total weight of the above, and preferably in the range of 30 to 50%. If it is less than 20%, the undercoat layer will be dissolved in the organic solvent, and if it exceeds 70%, it will be in a state close to imidization, and the residual potential after repeated use will accumulate, resulting in image failure.
[0012]
The molecular weight of the polyimide resin is preferably in the range of 1,000 to 100,000, particularly 10,000 to 30,000. Specific examples of X are as follows.
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(Y represents a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an optionally substituted aryl group.)
[0013]
Further, when the undercoat layer contains titanium oxide, the dielectric constant of the undercoat layer can be increased, and the dispersibility can be improved. Further, the weight ratio between the polyimide resin and the titanium oxide is preferably in the range of 2: 1 to 1: 4.
[0014]
Further, it is preferable that the drying temperature at the time of forming the undercoat layer is in the range of 110 ° C to 170 ° C. If the temperature is lower than 110 ° C., the undercoat layer is dissolved by the solvent, so that it cannot be applied to the photoreceptor. When dried at 110 ° C. or higher, it does not dissolve in the organic solvent. If the temperature exceeds 170 ° C., the residual potential after repeated use rises, which causes a problem that dust fog is generated on an image.
[0015]
Further, when the undercoat layer contains the polyimide resin represented by the general formula (1) and titanium oxide, the dielectric constant of the undercoat layer can be increased, and a thick film can be formed. Also, the dispersibility is improved.
[0016]
Further, by providing the undercoat layer with a two-layer structure of a layer containing a polyimide resin represented by the general formula (1) and a layer made of a thermosetting resin or a thermoplastic resin thereon, Even if the film is thickened, the accumulation of the residual potential can be suppressed and the chargeability can be stabilized, so that the image quality can be improved.
[0017]
Further, in the electrophotographic photoreceptor of the first aspect, the object of the present invention can be achieved by using a non-cutting tube as the conductive support.
Further, the object of the present invention can be achieved by an electrophotographic apparatus characterized in that the electrophotographic photoreceptor of the present invention has a contact charging means as a charging means. Further, the interference fringes of the image can be eliminated by applying an exposure unit using a semiconductor laser.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the electrophotographic photosensitive member according to the present invention will be described in detail. The present invention provides, for example, a function-separated electron in which a charge generation layer containing at least a charge generation agent is formed on a conductive support, and a charge transfer layer containing at least a charge transfer agent is formed thereon. It is applied to photographic photoreceptors. In this case, a photosensitive layer is formed by the charge generation layer and the charge transfer layer.
[0019]
Further, the present invention provides a single-layer type electrophotographic photoreceptor in which a charge generating agent and a charge transfer agent are contained in the same layer, and an inversely laminated type electrophotographic photoreceptor in which a charge transfer layer and a charge generating layer are laminated in this order. It can also be applied to
[0020]
Examples of the conductive support that can be used in the present invention include aluminum, brass, stainless steel, nickel, chromium, titanium, gold, silver, copper, tin, platinum, molybdenum, indium and the like, and a processed product of an alloy thereof. Or a conductive plastic plate or film obtained by treating a conductive substance such as the above-mentioned metal or carbon by vapor deposition, plating or the like, and further providing a conductive glass coated with tin oxide, indium oxide, or aluminum iodide. The conductive support can be constituted by using various materials having conductivity without being limited by the type or shape. The conductive support may be in the form of a drum, a rod, a plate, a sheet, or a belt.
Among these, aluminum alloys such as JIS 3000 series, JIS 5000 series, and JIS 6000 series are used, and are formed by a general method such as the EI method, the ED method, the DI method, and the II method. A non-cutting tube which is not subjected to processing, polishing, or surface treatment such as anodizing treatment is preferable.
[0021]
As the charge generating agent that can be used in the present invention, disazo pigments and oxytitanium phthalocyanine are preferable in terms of good sensitivity compatibility, but are not limited thereto. Others, for example, selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, metal-free phthalocyanine, other metal phthalocyanine pigments, monoazo pigments, trisazo pigments, polyazo pigments, indigo pigments, selenium pigments, toluidine pigments, pyrazoline pigments, perylene pigments And quinacridone pigments, polycyclic quinone pigments, pyrylium salts, and the like. In particular, various crystal forms of oxytitanium phthalocyanine are introduced. Among them, the X-ray diffraction spectrum using CuKα as a source has a maximum diffraction peak at a black angle (2θ ± 0.2 °) of 27.3 °. The crystal form shown (shown in FIG. 2), the crystal form showing the main diffraction peaks at 7.6 ° and 28.3 ° and the maximum peak at 7.5 °, and the other diffraction peak intensity is 7.5 ° The crystal type (shown in FIG. 1) having an intensity of not more than 20% with respect to the diffraction peak intensity is particularly preferable for the electrophotographic photosensitive member of the present invention. The film thickness is in the range of 0.01 to 5.0 μm, preferably 0.1 to 1.0 μm.
[0022]
The above-mentioned charge generators may be used alone, or two or more kinds may be used in combination in order to obtain an appropriate photosensitivity wavelength and sensitizing effect.
[0023]
In the electrophotographic photoreceptor of the present invention, the electrophotographic photoreceptor having a photosensitive layer formed with an undercoat layer interposed therebetween contains the polyimide resin represented by the general formula (1) to form a film. In addition, the thin film is covered with defects such as pinholes of the conductive support, and the photosensitive layer has excellent barrier function and adhesive function. The film is used at a thickness of 1.0 to 50 μm, preferably 20 to 40 μm.
[0024]
The drying temperature for forming the undercoat layer is suitably in the range of 110 ° C to 170 ° C, preferably 130 ° C to 150 ° C. If the temperature is lower than 110 ° C., the undercoat layer is dissolved by the solvent, and thus cannot be applied to the photoreceptor. When dried at 110 ° C. or higher, it does not dissolve in the organic solvent. If the temperature exceeds 170 ° C., the residual potential after repeated use rises, causing a slight problem that the image density changes.
[0025]
Further, the undercoat layer has a two-layer structure of a layer containing a polyimide resin represented by the general formula (1) and a layer made of a thermosetting resin or a thermoplastic resin, so that the undercoat layer has a thick film. Therefore, the accumulation of the residual potential can be suppressed, and the image quality can be improved.
[0026]
Examples of the binder resin that can be used to form the photosensitive layer include polycarbonate resin, styrene resin, acrylic resin, styrene-acryl resin, ethylene-vinyl acetate resin, polypropylene resin, vinyl chloride resin, chlorinated polyether, and chloride resin. Vinyl-vinyl acetate resin, polyester resin, furan resin, nitrile resin, alkyd resin, polyacetal resin, polymethylpentene resin, polyamide resin, polyurethane resin, epoxy resin, polyarylate resin, diallylate resin, polysulfone resin, polyether sulfone resin, Polyallyl sulfone resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, EVA (ethylene / vinyl acetate / copolymer) resin, ACS (acrylonitrile / chlorination) Riechiren styrene) resin, ABS (acrylonitrile butadiene styrene) resins, photocurable resins such as epoxy arylate. These can be used alone or in combination of two or more. It is more preferable to use a mixture of resins having different molecular weights because the hardness and abrasion resistance can be improved.
[0027]
In the electrophotographic photoreceptor of the present invention, the undercoat layer may contain titanium oxide. The titanium oxide used in the present invention may be subjected to various treatments on the surface of the titanium oxide particles as long as the volume resistance is not reduced. For example, the surface of the particles can be coated with an oxide film using aluminum, silicon nickel or the like as a treating agent. In addition, it is also possible to impart water repellency such as a coupling material as needed. The average particle diameter of titanium oxide is preferably 1 μm or less, more preferably 0.01 to 0.5 μm. The content of titanium oxide is preferably in the range of 0.5 to 4 times that of polyimide 1.
[0028]
Further, as the undercoat layer, a two-layer structure of a layer made of a polyimide resin and a layer made of a thermosetting resin or a thermoplastic resin may be provided thereon. Examples of the thermosetting resin include an epoxy resin, a polyurethane, a phenol, a melamine alkyd resin, an unsaturated polyester resin, and the like. Examples of the thermoplastic resin include a styrene-based elastomer, an olefin-based elastomer, a urethane-based elastomer, and a polyvinyl chloride-based elastomer. The thickness of the resin layer provided on the polyimide resin layer can be used in the range of 0.1 to 10.0 μm, preferably 0.8 to 5.0 μm.
[0029]
Further, a white pigment may be contained in both or one of the two layers for the purpose of suppressing light interference during semiconductor laser exposure. For example, titanium oxide, zinc oxide, silica and the like can be mentioned.
[0030]
As the charge transfer material that can be used in the present invention, a compound represented by the general formula (2) and / or the general formula (3) is preferable.
[0031]
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(Where R ₁ And R ₂ Represents an alkyl group having 1 to 6 carbon atoms which may have a substituent, ₃ Represents a hydrogen atom or a dialkylamino group in which at least one alkyl group has 2 or more carbon atoms. )
[0032]
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(Where R ₄ ~ R ₇ May be the same or different, and each independently represents a hydrogen atom, a halogen atom, an alkyl or alkoxy group having 1 to 6 carbon atoms, or an aryl group which may have a substituent. Represents, R ₈ Is a hydrogen atom, a halogen atom, an alkyl or alkoxy group having 1 to 6 carbon atoms, an aryl group which may have a substituent, an alkenyl group or an alkadienyl group which may have a substituent, or a compound represented by the general formula (4 ), And m represents an integer of 0 or 1. )
[0033]
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(Where R ₉ , R ₁₀ May be the same or different, and each independently represents a hydrogen atom, a halogen atom, an alkyl or alkoxy group having 1 to 6 carbon atoms, or an aryl group which may have a substituent. And n represents an integer of 0 or 1. )
The charge transfer material has good compatibility with oxytitanium phthalocyanine, and the electrophotographic photoreceptor of the present invention exhibits excellent electrical characteristics such as high sensitivity and low residual potential.
Among the compounds represented by the general formula (1), the compounds represented by the formulas (5) and (6) are particularly preferred because they have good compatibility with oxytitanium phthalocyanine.
[0034]
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[0035]
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Further, among the compounds represented by the general formula (3), the compounds represented by the formulas (7), (8), (9) and (10) are particularly preferred because they have good compatibility with oxytitanium phthalocyanine.
[0036]
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[0037]
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[0038]
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[0039]
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[0040]
In addition, it is preferable to use a compound selected from the general formula (2) and a compound selected from the general formula (3) at the same time as a charge transfer material because good characteristics are obtained.
[0041]
Charge transfer materials other than the above charge transfer materials can also be used. As other charge transfer materials, polyvinyl carbazole, halogenated polyvinyl carbazole, and other charge transfer agents can be added to the photosensitive layer of the electrophotographic photoreceptor of the present invention. In that case, the sensitivity of the photosensitive layer can be increased or the residual potential can be reduced, so that the characteristics of the electrophotographic photosensitive member of the present invention can be improved.
[0042]
Examples of charge transfer agents that can be added for such property improvement include polyvinyl carbazole, halogenated polyvinyl carbazole, polyvinyl pyrene, polyvinyl indoloquinoxaline, polyvinyl benzothiophene, polyvinyl anthracene, polyvinyl acridine, polyvinyl pyrazoline, polyacetylene, polythiophene, Conductive polymer compounds such as polypyrrole, polyphenylene, polyphenylenevinylene, polyisothianaphthene, polyaniline, polydiacetylene, polyheptadiene, polypyridinediyl, polyquinoline, polyphenylene sulfide, polyferrosenylene, polyperinaphthylene, and polyphthalocyanine Can be used.
[0043]
Further, as low molecular compounds, trinitrofluorenone, tetracyanoethylene, tetracyanoquinodimethane, quinone, diphenoquinone, naphthoquinone, anthraquinone and derivatives thereof, anthracene, pyrene, polycyclic aromatic compounds such as phenanthrene, indole, carbazole As a charge transfer agent, nitrogen-containing heterocyclic compounds such as imidazole, fluorenone, fluorene, oxadiazole, oxazole, pyrazoline, triphenylmethane, triphenylamine, enamine, stilbene, butadiene other than the above, and hydrazone compounds other than the above. Can be added.
[0044]
In addition, as a charge transfer agent for the same purpose, a polymer solid electrolyte in which a metal ion such as Li (lithium) ion is doped into a polymer compound such as polyethylene oxide, polypropylene oxide, polyacrylonitrile, and polymethacrylic acid is added. You can also.
[0045]
Further, as a charge transfer agent for the same purpose, an organic charge transfer complex formed of an electron-donating substance represented by tetrathiafulvalene-tetracyanoquinodimethane and an electron-accepting substance or the like can be used.
[0046]
The desired photoreceptor characteristics can be obtained by adding only one kind of the charge transfer agent or mixing and adding two or more kinds of compounds. The thickness of the charge transfer layer is 5.0 to 50 μm, preferably 10 to 30 μm.
In the case of the electrophotographic photoreceptor of the present invention, the thickness of the entire photosensitive layer is in the range of 10 to 50 μm, preferably 15 to 25 μm. For example, when the undercoat layer is provided as thick as about 25 μm, the charge transfer layer may be provided as thin as about 15 μm. Conversely, when the undercoat layer is provided as thin as about 1 μm, the charge transfer layer may be provided as thick as about 25 μm. For this reason, the pressure resistance of the photoreceptor is required in an electrophotographic process having a contact charging means as the charging means. Generally, in a photoreceptor having low pressure resistance, a defect occurs on the surface from the photoreceptor due to a leak current, and this appears as an image defect. That is, since the pressure resistance of the photoreceptor is determined by the total thickness of the photoreceptor, by increasing the thickness of the undercoat layer, the pressure resistance is improved and the charge transfer layer can be made thin.
[0047]
The electrophotographic photoreceptor of the present invention contains an antioxidant or an ultraviolet absorber in its photosensitive layer for the purpose of preventing the occurrence of cracks and improving mechanical strength due to oxidative deterioration of the photoconductive material and the binder resin. Is preferred.
[0048]
Antioxidants that can be used in the present invention include 2,6-di-tert-butylphenol, 2,6-di-tert-4-methoxyphenol, 2-tert-butyl-4-methoxyphenol, 2,4 -Dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxyanisole, stearyl-β- (3,5-di-tert-butyl-4-hydroxyphenyl propionate) ), Α-tocopherol, β-tocopherol, monophenols such as n-octadecyl-3- (3′-5′-di-tert-butyl-4′-hydroxyphenyl) propionate, and 2,2′-methylenebis (6 -Tert-butyl-4-methylphenol), 4,4'-butylidene-bis- (3-methyl- -Tert-butylphenol), 4,4'-thiobis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis [methylene-3 (3,5-di-tert-butyl-4) -Hydroxyphenyl) propionate], and polyphenols such as methane, and the like, and one or more of these may be simultaneously contained in the photosensitive layer.
[0049]
Examples of the ultraviolet absorber include 2- (5-methyl-2-hydroxyphenyl) benzotriazole and 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole. 2- (3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- ( 3,5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-tert-amyl-2-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy Benzotriazoles such as -5'-tert-octylphenyl) benzotriazole, phenyl salicylate, salicyl Salicylic acids such as acid-p-tert-butylphenyl and salicylic acid-p-octylphenyl are preferred, and one or more of these can be simultaneously contained in the photosensitive layer.
[0050]
Further, an antioxidant and an ultraviolet absorber can be added simultaneously. These additives may be added to any layer in the photosensitive layer, but are preferably added to the outermost layer, particularly to the charge transfer layer.
[0051]
In addition, it is preferable that an antioxidant is 3-20 weight% with respect to a binder resin, and it is preferable that the addition amount of an ultraviolet absorber is 3-30 weight% with respect to a binder resin. Further, when both the antioxidant and the ultraviolet absorber are added, the addition amount of both components is preferably 5 to 40% by weight based on the binder resin.
[0052]
In addition to the antioxidant and the ultraviolet absorber, a light stabilizer such as a hindered amine and a hindered phenol compound, an antioxidant such as a diphenylamine compound, a surfactant and the like can be added to the photosensitive layer.
[0053]
As a method for forming the photosensitive layer, a method is generally used in which a coating solution is prepared by dispersing or dissolving a predetermined photosensitive material and a binder resin in a solvent, and then applied to a predetermined underlayer.
[0054]
As a coating method, dip coating, curtain flow, bar coating, roll coating, ring coating, spin coating, spray coating and the like can be performed according to the shape of the base and the state of the coating liquid.
Further, the charge generation layer can be formed by a vacuum evaporation method.
[0055]
Solvents used in the coating solution include alcohols such as methanol, ethanol, n-propanol, i-propanol, butanol, methylcellosolve, ethylcellosolve, pentane, hexane, heptane, octane, cyclohexane, cycloheptane, etc. Saturated aliphatic hydrocarbons, aromatic hydrocarbons such as toluene and xylene, chlorinated hydrocarbons such as dichloromethane, dichloroethane, chloroform and chlorobenzene, ethers such as dimethyl ether, diethyl ether and tetrahydrofuran (THF), acetone, methyl ethyl ketone and methyl isobutyl Ketones, ketones such as cyclohexanone, esters such as ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, N, N-dimethylformamide; Methyl sulfoxide, there are amides such as N- methyl-2-pyrrolidone. These may be used alone or as a mixture of two or more solvents.
[0056]
Further, as the undercoat layer of the present invention, an intermediate layer in which a metal compound, metal oxide, carbon, silica, resin powder and the like are dispersed in a resin can be used. Further, various pigments, an electron accepting substance, an electron donating substance, and the like can be contained for improving properties.
[0057]
In addition, an organic thin film such as a polyvinyl formal resin, a polycarbonate resin, a fluorine resin, a polyurethane resin, or a silicone resin, or a thin film composed of a siloxane structure formed by a hydrolyzate of a silane coupling agent is formed on the surface of the photosensitive layer. A film may be provided with a surface protective layer. In this case, the durability of the photoconductor is improved, which is preferable. This surface protective layer may be provided to improve functions other than the improvement of durability.
[0058]
Next, the electrophotographic process and the electrophotographic apparatus of the present invention will be described. In the electrophotographic process of the present invention, known means such as charging means, exposure means, developing means, transfer means, fixing means, and cleaning means can be used. As the charging unit, a non-contact charging system such as a corona charging system and a contact charging system such as a charging roller and a charging brush can be used. As a light source of the image exposure means, a halogen light, a fluorescent lamp, a laser light, or the like can be used. The wavelength of the semiconductor laser is 780 nm or less, preferably 780 to 500 nm, and a method such as narrowing the laser beam diameter may be used. The developing method may be any of dry developing method, wet developing method, two-component, one-component, and magnetic / non-magnetic. The transfer system may be either a roller or a belt.
[0059]
【Example】
Hereinafter, examples of the electrophotographic photosensitive member according to the present invention will be described in detail along with comparative examples.
[0060]
Example 1
A solution in which alumina-coated titanium oxide particles and a polyimide resin of the formula (1) where X is [X-1] are mixed at a weight ratio of 1: 1 on a cylindrical drum made of non-cut aluminum having a diameter of 30 mm. And dried at 140 ° C. for 30 minutes to form a first undercoat layer having a thickness of 20.0 μm. Next, a melamine alkyd resin as a thermosetting resin and titanium oxide are mixed in a ratio of 1: 3 on the undercoat layer, and dissolved in methyl ethyl ketone to form a coating solution, and a second undercoat layer is formed on the undercoat layer. A subbing layer was laminated with a thickness of 1.0 μm.
[0061]
Next, using a polyvinyl butyral as a binder resin, a dispersion of oxytitanium phthalocyanine shown in FIG. 1 was applied by dip coating to a thickness of 0.1 μm to form a charge generation layer.
[0062]
Next, a polycarbonate copolymer as a binder resin, a butadiene compound of the formula 6 as a charge transfer agent, and 2,6-di-tert-butyl-4-methylphenol as an antioxidant, the polycarbonate copolymer = 1 It was dissolved in chloroform at a weight ratio of 0.0 / 0.8 / 0.18 to prepare a coating solution.
[0063]
Then, after applying this coating liquid by dip coating, the coating liquid was dried at a temperature of 100 ° C. for 1 hour to form a charge transfer layer having a thickness of 20 μm, thereby producing an electrophotographic photosensitive member.
[0064]
Example 2
An electrophotographic photosensitive member was produced in the same manner as in Example 1, except that the weight ratio of the polyimide resin and titanium oxide of the first undercoat layer in Example 1 was changed to 2: 1.
[0065]
Example 3
An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the non-cut aluminum in Example 1 was replaced with cut aluminum.
[0066]
Example 4
An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the weight ratio of the polyimide resin to titanium oxide in the first undercoat layer in Example 1 was changed to 1: 4.
[0067]
Example 5
An electrophotographic photosensitive member was produced in the same manner as in Example 1, except that the thickness of the first undercoat layer in Example 1 was changed to 5.0 μm.
[0068]
Example 6
An electrophotographic photosensitive member was manufactured in the same manner as in Example 1, except that the thickness of the first undercoat layer in Example 1 was changed to 30.0 μm.
[0069]
Example 7
An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the melamine / alkyd resin of the second undercoat layer in Example 1 was changed to a nylon resin.
[0070]
Example 8
An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the second undercoat layer in Example 1 was omitted.
[0071]
Example 9
An electrophotographic photosensitive member was produced in the same manner as in Example 1, except that the charge transfer agent of Formula 6 in Example 1 was replaced with the charge transfer agent of Formula 7.
[0072]
Example 10
An electrophotographic photosensitive member was prepared in the same manner as in Example 1, except that the charge transfer agent of Formula 6 in Example 1 and the charge transfer agent of Formula 7 were mixed.
[0073]
Example 11
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the charge generating agent of FIG. 1 in Example 1 was replaced with the charge generating agent of FIG.
[0074]
Example 12
An electrophotographic photoreceptor was manufactured in the same manner as in Example 1 except that the titanium oxide and the second undercoat layer of the first undercoat layer in Example 1 were omitted.
[0075]
Example 13
An electrophotographic photosensitive member was manufactured in the same manner as in Example 1 except that the titanium oxide in the first undercoat layer in Example 1 was eliminated.
[0076]
Comparative Example 1
An electrophotographic photosensitive member was manufactured in the same manner as in Example 1, except that the thickness of the first undercoat layer in Example 1 was changed to 0.5 μm.
[0077]
Comparative Example 2
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the first undercoat layer in Example 1 was omitted.
[0078]
Comparative Example 3
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the first and second undercoat layers of Example 1 were omitted.
[0079]
Evaluation method 1
[Measurement of electrostatic characteristics, repeated cycle test, image test]
Cylindrical electrophotographic photosensitive members produced in Examples 1 to 9 and Comparative Examples 1 to 3 using a direct charging type Okidata Microline 14 printer in an environment of normal temperature and normal humidity (24 ° C., 40% RH). The body is charged so that the surface potential of the photoreceptor after charging becomes -800 V, and the surface potential of the photoreceptor after LED exposure is initialized to be -50 V, and then the surface after printing 20,000 sheets of A4 paper. The potential V0 (−V) and the residual potential VR (−V) were measured. The image test evaluated the image after continuous printing of 20,000 sheets. Table 1 shows the above results. In the judgment, “○” was good, and “×” was image failure or the like, which had a problem in practice.
[0080]
[Table 1]

[0081]
As is evident from Table 1, the electrophotographic photoreceptors of Examples 1 to 11 are excellent in chargeability and light fatigue characteristics after 20,000 sheets are repeated, and no image defects such as fog occur in the images. Was.
[0082]
In addition, good results were obtained when titanium oxide was mixed with the polyimide resin or when a thermosetting resin or a thermoplastic resin was laminated on the polyimide resin layer.
That is, in the case of Examples 1 to 11, the results were particularly good.
[0083]
In the electrophotographic photoreceptors of Examples 12 and 13, when the titanium oxide in the first undercoat layer was removed, the density decreased, but the other points were generally good.
In contrast, when the first undercoat layer of Comparative Example 1 had a thickness of less than 1.0 μm, a leak occurred and the image appeared as a black dot. In Comparative Examples 2 and 3, when there was no polyimide resin layer, black spots occurred due to the transfer memory.
[0084]
【The invention's effect】
The electrophotographic photoreceptor of the present invention does not have significant deterioration in electrostatic properties such as surface potential and post-exposure potential even after repetition, has no image defects, and has high repetition stability.
Therefore, according to the present invention, it is possible to provide an electrophotographic photoreceptor having excellent electrophotographic properties, cleaning properties, and oil resistance and capable of simplifying maintenance.
[Brief description of the drawings]
FIG. 1 shows an X-ray diffraction diagram of oxyphthalocyanine used in the present invention among those used in the present invention.
FIG. 2 shows an X-ray diffraction diagram of oxyphthalocyanine used in another example among oxyphthalocyanines used in the present invention.

Claims (7)

In an electrophotographic photoreceptor in which a photosensitive layer is formed on a conductive support via an undercoat layer, the undercoat layer has a general formula (1)

[In the formula, X is a divalent polycyclic aromatic group in which aromatic rings may be linked by different atoms, and n is an integer representing the degree of polymerization. An electrophotographic photoreceptor comprising a polyimide resin represented by the formula (1), wherein the thickness of the undercoat layer is from 1.0 μm to 50 μm. 2. The electrophotographic photosensitive member according to claim 1, wherein the undercoat layer contains titanium oxide, and a weight ratio of the polyimide resin to the titanium oxide is in a range of 2: 1 to 1: 4. body. 2. The electrophotographic photoconductor according to claim 1, wherein a drying temperature for forming the undercoat layer is in a range of 110 to 170C. 2. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has a two-layer structure of a layer containing a polyimide resin and a layer made of a thermosetting resin or a thermoplastic resin thereon. Photoconductor. 2. The electrophotographic photoconductor according to claim 1, wherein the conductive support is a non-cutting tube. An electrophotographic apparatus, wherein a contact charging unit is applied to the electrophotographic photosensitive member according to claim 1. An electrophotographic apparatus, wherein an exposure unit using a semiconductor laser is applied to the electrophotographic photosensitive member according to claim 1.

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