JP2004045517A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electrophotographic photoreceptor which is excellent in both of mechanical strength such as abrasion resistance and electrical properties such as sensitivity. <P>SOLUTION: A polyarylate resin is used as binder resin for a charge transfer layer.The ratio of charge transfer material in the charge transfer layer exceeds 50wt%. Since the polyarylate resin has high compatibility with the charge transfer material, the strength of the charge transfer layer is hardly reduced even in the case of increasing the ratio of the charge transfer material, on the other hand, the property such as the sensitivity is improved by increasing the ratio of the charge transfer material. Then, the photoreceptor having excellent strength and properties is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

【０００７】
ポリアリレート樹脂は、電子写真感光体で広く用いられているポリカーボネート樹脂と同様に、帯電、露光、現像、転写、クリーニングといった電気的、機械的な力が直接的または間接的に繰り返し加えられる電子写真プロセスにおける表面層の使用において優れており、適した材料のひとつと言える。
【０００８】
そこで、本発明では課題として示したできるだけ複雑にならない感光体の層構成において優れた電荷輸送機能と、優れた機械的強度をもつ感光体の達成するために、電荷輸送材とバインダー樹脂からなる電荷輸送層中の電荷輸送材料比率を高めることに着目した。また電荷輸送材料の比率を高めることにより表面層としての特性の低下、たとえばクリーニングブレードでの摩耗、クリーニングブレードや帯電部材との接触や加圧によって生じる表面層の変形や該層中からの電荷輸送材料の偏析や析出などの変性を生じさせない系であることをめざした。そこで、本発明では特定構造を持つポリアリレート樹脂を用いることにより、電荷輸送材料の比率が５０％を越えても上述した諸問題の発生を抑えることが可能であり、さらに電荷輸送材料比率の増加による電気的特性の向上が達成され、さらに良好な機械的強度の向上も達成できた。また特定の電荷輸送材料を用いるとその効果の発現はより大きく得られた。この効果のメカニズムの詳細は明確にはなっていないが、電荷輸送層を構成する層内において比較的芳香環を多く持つポリアリレートと芳香環をもつ電荷輸送材料との重なりがしやすいことにより両者の親和性が高まっていたり、さらにポリマー鎖の芳香環に置換基を持たせることにより立体構造的に適度な空間と適度な制限さらには適度なポリマー鎖間の重なりが得られていることなどが推測される。すなわち、電荷輸送層中における電荷輸送材料の比率が５０％を越えて用いる場合において、広く用いられているポリカーボネートでは、電荷輸送材料とバインダー樹脂を溶媒中に溶解させた溶液中や該溶液を塗布乾燥させて形成した電荷輸送層において電荷輸送材料の析出や該層の強度低下によるクラックなどを誘発する。そのためポリカーボネートなどの系では電荷輸送材料の比率を５０％以下とした使用が強いられており、さらに選択する材料によっては４０％以下でならない場合も生じるが、本発明の系では、電荷輸送材料の比率を高めることが可能であり、電気的特性、機械的特性の向上がはかれ、良好な感光体が得られる。
【０００９】
【発明の実施の形態】
式（１）で示されるポリアリレート樹脂は、一般的にビスフェノールＣ型と呼ばれる構造を持ち、そのビスフェノールＣ型モノマーとフタル酸から構成されるホモポリマーをはじめ、他構造を持つビスフェノールモノマーと共重合させたコポリマー、さらには他種のポリマーを混合したブレンド系においても用いることができる。本発明において使用できるポリマーは、その構造中に少なくとも式（１）に示したビスフェノールＣ型を持つことが効果の発現に必要でありホモポリマーのほかとして、コポリマーとして用いられるポリアリレートの構造の一例を次に示す。
【外７】

【００１０】
【外８】

【００１１】
これらにおいてコポリマーとする場合の式（１）で示される構造と他構造の比率は式（１）が１０％以上必要であり、それ以下では本発明の効果の発現が著しく小さくなる。また、共重合する構造としては（５−１）、（５−１２）が特に好ましい。さらに、これらのポリアリレート樹脂の合成方法に限定はなく、モノマーとして各種ビスフェノールとフタル酸からの重縮合の常法（例えば、界面重縮合法）により得られる。フタル酸は置換基の位置により生成されたポリアリレート樹脂の特性（例えば、強度や溶解性）に影響を与えるが、本発明では特に限定はされないが、好ましくはテレフタル酸／イソフタル酸を用い、その比率を７／３から３／７の間とした系である。
【００１２】
本発明に用いるポリアリレート樹脂の重量平均分子量は１０，０００〜２００，０００であることが好ましく、特には２０，０００〜１５０，０００であることが好ましい。分子量はゲルパーミエーションクロマトグラフィーを用い、標準試料としてポリスチレンを用いて測定した値で示した。電荷輸送材料の詳細は次に述べるが、本発明では電荷輸送層の総重量のうち電荷輸送材料の比率が５０％を越えていることであるが７５％までが特に好ましい。
【００１３】
本発明において用いられる構造式（４）及び（５）の化合物について詳しく説明する。
【００１４】
式（４）において、Ａｒ１およびＡｒ２はフェニル、ナフチル及びアンスリルなどの芳香環基を示す。
【００１５】
Ａｒ３はベンゼン、ナフタレン及びアントラセンなどの芳香環またはチオフェン及びフランなどの複素環より２個の水素原子をとった２価の芳香環基または２価の複素環基を示す。Ｒ３はメチル、エチル、プロピル、及びブチルなどのアルキル基またはフェニル基及びナフチル基などの芳香環基を示す。Ｒ４はメチル、エチル、プロピル、及びブチルなどアルキル基；フェニル及びナフチルなどの芳香環基または水素原子を示す。また、ｎ１は１または２を示す。
【００１６】
Ａｒ１，Ａｒ２，Ａｒ３，Ｒ３及びＲ４はいずれも置換基を有してもよく、有してもよい置換基としては、メチル、エチル、プロピル及びブチルなどのアルキル基；メトキシ、エトキシ及びプロポキシなどのアルコキシ基；フェノキシ、及びナフトキシなどのアリールオキシ基；フッ素、塩素及び臭素等のハロゲン原子；またはジメチルアミノ、ジエチルアミノ及びジフェニルアミノ等のジ置換アミノ基などが挙げられる。また、Ｒ１とＲ２は直接、または炭素原子、硫黄原子及び酸素原子などを介して結合することにより環を形成してもよい。
【００１７】
式（５）において、Ａｒ４，Ａｒ５及びＡｒ６はフェニル、ナフチル、アンスリル、ピレニル、フルオレニル、フェナンスリル、９−１０−ジヒドロフェナンスリル、キノリル、ジベンゾチェニル、ジベンゾフリル、ｎ−メチルカルバゾル、ｎ−エチルカルバゾル及びｎ−トリルカルバゾル等の複素環基を示す。
【００１８】
Ａｒ４，Ａｒ５及びＡｒ６はいずれも置換基を有してもよく、有してもよい置換基をしては、メチル、エチル、プロピル及びブチルなどのアルキル基；ベンジル、フェネチル及びナフチルメチル等のアラルキル基；メトキシ、エトキシ及びプロポキシ等のアルコキシ基；フェノキシ、及びナフトキシ等のアリールオキシ基；フッ素、塩素及び臭素等のハロゲン原子；フェニル及びビフェニル等の芳香環基；ジフェニルアミノ及びジトリルアミノ等のジアリールアミノ基；ジメチルアミノ及びジエチルアミノなどのジアルキルアミノ基；ジベンジルアミノ及びジフェネチルアミノ等のジアラルキルアミノ基；べンジルメチルアミノ及びベンジルエチルアミノ等のアルキルアラルキルアミノ基；ニトロ基及びヒドロキシ基などが挙げられる。
【００１９】
また、以下に電荷輸送材料の具体例を示すが、これらに限定されるものではない。
【外９】

【００２０】
【外１０】

【００２１】
【外１１】

【００２２】
以下、本発明の電子写真感光体の構成について説明する。
【００２３】
本発明の電子写真感光体は、感光層が電荷輸送層と電荷発生層に分離した積層型であり、使用する導電性基体は、導電性を有するものであればよく、アルミニウム、ステンレスなどの金属、あるいは導電層を設けた金属、紙、プラスチックなどが挙げられ、形状はシート上、円筒状などが挙げられる。
【００２４】
レーザービームプリンターに代表される潜像形成にレーザー光を用いる系においては、基体におけるレーザー光での散乱による干渉縞防止、及び基体の傷を被覆することを目的とした導電層を設けてもよい。これはカーボンブラック、金属粒子、金属酸化物などをバインダー樹脂に分散させて形成することができる。導電層の膜厚は５〜４０μｍ、好ましくは１０〜３０μｍが適当である。
【００２５】
その上に接着機能を有する中間層を設ける。中間層の材料としてはポリアミド、ポリビニルアルコール、ポリエチレンオキシド、エチルセルロース、カゼイン、ポリウレタン、ポリエーテルウレタン、などが挙げられる。これらは適当な溶剤に溶解して塗布される。中間層の膜厚は０．０５〜５μｍ、好ましくは０．３〜１μｍが適当である。
【００２６】
中間層の上には電荷発生層が形成される。本発明における電荷発生材としては、通常知られているものが使用可能であり、たとえばセレン−テルル、ピリリウム、金属フタロシアニン、無金属フタロシアニン、アントアントロン、ジべンズピレンキノン、トリスアゾ、シアニン、ジスアゾ、モノアゾ、インジゴ、キナクドリンなどの各顔料が挙げられる。これらの顔料は０．３〜４倍の重量のバインダー樹脂および溶剤ともにホモジナイザー、超音波分散、ボールミル、振動ミル、サンドミルアトライター、ロールミル、液衝突型高速分散機等を使用して、良く分散した分散液とする。積層型感光体の場合、この液を塗布し、乾燥することによって電荷発生層が得られる。膜厚は５μｍ以下であることが好ましく、特には０．１〜２μｍであることが好ましい。
【００２７】
電荷輸送材は、通常用いられるものが使用できるが、前記した化学式（４）、（５）に示される化合物が好ましい。これらの化合物は前記したバインダー樹脂とともに溶剤に溶解し溶液とする。積層型感光体を得るために、この液を塗布し、乾燥することによって電荷輸送層が得られる。膜厚は５〜４０μｍであることが好ましく、特には１５〜３０μｍであることが好ましい。
【００２８】
これらの感光体の塗布方法としての限定はなく、浸漬塗布法、スプレー塗布法、バーコート法など通常知られている手段で使用できるが、生産性などを考慮すると浸漬塗布法が好ましい。
【００２９】
以下実施形態に従って、本発明をより詳細に説明する。実施形態中「部」は重量部を表す。
【００３０】
（第１の実施形態）
３０φ×３５７ｍｍのアルミシリンダー上に、以下の材料より構成される塗料を浸漬塗布法にて塗布し、１４０℃で３０分熱硬化することにより、膜厚が１５μｍの導電層を形成した。
【００３１】
導電性顔料：ＳｎＯ_２コート処理硫酸バリウム　　　１０部
抵抗調整用顔料：酸化チタン　　　　　　　　　　　　２部
バインダー樹脂：フェノール樹脂　　　　　　　　　　６部
レベリング材：シリコーンオイル　　　　　　０．００１部
溶剤：メタノール／メトキシプロパノール＝２／８　２０部
次に、この導電層上に、Ｎ−メトキシメチル化ナイロン３部及び共重合ナイロン３部をメタノール６５部及びｎ−ブタノール３０部の混合溶剤に溶解した溶液を浸漬塗布法で塗布し、乾燥することによって、膜厚が０．５μｍの中間層を形成した。
【００３２】
次にＣｕＫα特性Ｘ繰回折におけるブラック角２θ±０．２°の９．０°、１４．２°、２３．９°、２７．１°に強いピークを有するオキシチタニウムフタロシアニン４部、ポリビニルブチラール（商品名：エスレックＢＭ２、積水化学製）２部及びシクロヘキサノン６０部を１ｍｍφガラスビーズを用いたサンドミル装置で４時間分散した後、酢酸エチル１００部を加えて電荷発生層用分散液を調整した。この分散液を中間層上に浸漬塗布法で塗布し、乾燥することによって、膜厚が０．１μｍの電荷発生層を形成した。
【００３３】
次に、例示化合物（４−８）のアミン化合物　２部
例示化合物（５−５）のアミン化合物　１０部
バインダー樹脂として式（１）で示すポリアリレート樹脂（Ｍｗ＝１００，０００）１０部を溶媒としてモノクロロベンゼン５５部、ジクロロメタン３５部に溶解し電荷輸送層用の塗布液を得た。該塗布液を浸漬塗布法で塗布し、１２０℃、１時間乾燥し、膜厚２７μｍの電荷輸送層を形成した（電荷輸送材比率５４．５％）。
【００３４】
次に評価について説明する。装置はキヤノン（株）製複写機ＧＰ２１５（直流に交流を重畳した電圧を印可した接触帯電部材により帯電する系）を用いた。２３℃、５５％ＲＨの環境下において、暗部電位を−７００Ｖに設定し、明部電位を測定し感度とした。
【００３５】
また、Ａ４サイズの普通紙を１００００枚の繰り返し複写を行った。また、感光体膜厚を繰り返し複写の前後に測定し、摩耗量を求めた。
【００３６】
その後、感光体をクリーニングブレードと接触帯電部材に当接したまま１ケ月間、３２℃、８５％ＲＨの環境に放置した後、各当接部での電荷輸送材料の析出などの表面層の変化を観察した。
【００３７】
（第２の実施形態）
電荷輸送層用の塗布液の調製において、電荷輸送材料として式（５−５）を１３部に増した以外は第１の実施形態と同様に行い感光体を作製した（電荷輸送材比率６０．０％）。
【００３８】
（第３の実施形態）
電荷輸送層用の塗布液の調製において、電荷輸送材料として式（５−５）を１５部とし、式（４−８）を５部に増した以外は第１の実施形態と同様に行い感光体を作製した（電荷輸送材比率６６．７％）。
【００３９】
（第４の実施形態）
電荷輸送層用の塗布液の調製において、電荷輸送材料として式（５−５）を１８部とし、式（４−８）を６部に増した以外は第１の実施形態と同様に行い感光体を作製した（電荷輸送材比率７０．６％）。
【００４０】
（第５の実施形態）
電荷輸送層用の塗布液の調製において、バインダー樹脂を式（１）／（５−１）の共重合体（比率＝５／５、Ｍｗ＝８０，０００）とした以外は、第２の実施形態と同様に感光体を行い作製した。
【００４１】
（第６の実施形態）
電荷輸送層用の塗布液の調製において、バインダー樹脂を式（１）／（５−３）の共重合体（比率＝５／５、Ｍｗ＝８０，０００）とした以外は、実施形態２と同様に行い感光体を作製した。
【００４２】
（第７の実施形態）
電荷輸送層用の塗布液の調製において、バインダー樹脂を式（１）／（５−１２）の共重合体（比率＝５／５、Ｍｗ＝８０，０００）とした以外は、第２の実施形態と同様に行い感光体を作製した。
【００４３】
（第８の実施形態）
電荷輸送層用の塗布液の調製において、電荷輸送材料として式（４−２）を１５部のみとした以外は第１の実施形態と同様に行い感光体を作製した。
【００４４】
（第９の実施形態）
電荷輸送層用の塗布液の調製において、電荷輸送材料として（５−１）を１５部のみとした以外は第１の実施形態と同様に行い感光体を作製した。
【００４５】
（比較例１）
電荷輸送層用の塗布液の調製において、バインダー樹脂としてＺ型ポリカーボネート樹脂（三菱瓦斯化学製ユーピロンＺ４００）とした以外は第２の実施形態と同様に感光体を作製した（樹脂Ｍｗ＝約１００，０００：電荷輸送比率６０．０％）。
【００４６】
（比較例２）
電荷輸送層用の塗布液の調製において、バインダー樹脂としてＡ型ポリアリレート樹脂（ユニチカ製Ｕ１００）とした以外は第２の実施形態と同様に感光体を作製した（樹脂Ｍｗ＝約７０，０００：電荷輸送材比率６０．０％）。
【００４７】
（比較例３）
電荷輸送層用の塗布液の調製において、バインダー樹脂をポリエステル樹脂（バイロン、東洋紡（株））に変えた以外は第２の実施形態と同様に作製した（樹脂Ｍｗ＝約７０，０００：電荷輸送材比率６０．０％）。
【００４８】
（比較例４）
電荷輸送層用の塗布液の調製において、バインダー樹脂としてＺ型ポリカーボネート樹脂（三菱瓦斯化学製ユーピロンＺ４００）７部とした以外は第１の実施形態と同様に行い感光体を作製した（電荷輸送材比率４５．０％）。
【００４９】
（比較例５）
電荷輸送層用の塗布液の調製において、バインダー樹脂としてＺ型ポリカーボネート樹脂（三菱瓦斯化学製ユーピロンＺ４００）とした以外は第２の実施形態と同様に電荷輸送層を塗工し膜厚７μｍ（第一電荷輸送層）とした（電荷輸送材比率６０．０％）。
【００５０】
次いで第二電荷輸送層用としての塗布液の調製において、バインダー樹脂としてＺ型ポリカーボネート樹脂（三菱瓦斯化学製ユーピロンＺ４００）１０部とし、式４−８を１部、式５−５を４部としクロロベンゼン１００部、ジクロロメタン５０部に溶解した。この塗布液を第一電荷輸送層上にスプレー塗布して２０μｍの第二電荷輸送層を形成し感光体を作製した（電荷輸送材比率３３．３％）。
【００５１】
【表１】

【００５２】
（第１０の実施形態）
第１の実施形態で示した手法によりアルミシリンダー上に導電層、中間層を塗工した。
【００５３】
次いで下記構造式（６）で示されるアゾ顔料を４部、ポリビニルブチラール（商品名：エスレックＢＭ２、積水化学製）２部及びシクロヘキサノン６０部を１ｍｍφガラスビーズを用いたサンドミル装置で４時間分散した後、ＴＨＦ１００部を加えて電荷発生層用分散液を調整した。この分散液を中間層上に浸漬塗布法で塗布し、乾燥することによって、膜厚が０．１μｍの電荷発生層を形成した。
【外１２】

【００５４】
電荷輸送層用の塗布液は、第１の実施形態に示した物を用い、電荷発生層上に浸漬漬塗布し、１８μｍの電荷輸送層を得た（電荷輸送材比率５４．５％）。
【００５５】
次に評価について説明する。装置はキヤノン（株）製複写機ＮＰ６０３５（直流電圧を印可した接触帯電部材により帯電する系）を用いた。２３℃、５５％ＲＨの環境下において、暗部電位を−７００Ｖに設定し、明部電位を測定し感度とした。また、Ａ４サイズの普通紙を１００００枚の繰り返し複写を行った。感光体膜厚を繰り返し複写の前後に測定し、摩耗量を求めた。
【００５６】
（第１１の実施形態）
第１０の実施形態と同様に電荷発生層を塗工した。その上に第２の実施形態に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した（電荷輸送材比率６０．０％）。
【００５７】
（第１２の実施形態）
第１０の実施形態と同様に電荷発生層を塗工した。その上に第３の実施形態に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した（電荷輸送材比率６６．７％）。
【００５８】
（第１３の実施形態）
第１０の実施形態と同様に電荷発生層を塗工した。その上に第４の実施形態に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した（電荷輸送材比率７０．６％）。
【００５９】
（比較例６）
第１０の実施形態と同様に電荷発生層を塗工した。その上に比較例１に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した。
【００６０】
（比較例７）
第１０の実施形態と同様に電荷発生層を塗工した。その上に比較例２に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した。
【００６１】
（比較例８）
第１０の実施形態と同様に電荷発生層を塗工した。その上に比較例４に示した電荷輸送層用の塗布液を塗工して１８μｍの電荷輸送層を形成した。
【００６２】
【表２】

【００６３】
表１および表２に示したように、本発明で示す電荷輸送層を形成する主たるバインダー樹脂として少なくとも式（１）で示される構造を含むポリアリレートを用いることにより、電荷輸送材料の仕率を高めて用いることが可能となり、すなわち感度で示される電気的特性を良好とすることができ、かつ繰り返し使用時の摩耗量を低く抑えることができた。すなわち感度向上などを狙って、従来において広く用いられているポリカーボネート樹脂などを用いて電荷輸送材料の仕率を高めた系では、耐摩耗性の低下が生じたり、クリーニングブレードなどを当接させた部位において電荷輸送材の析出などの問題が生じるため達成できなかった。また、ポリカーボネートにおいてはブレード部での電荷輸送材の析出を抑えるためには電荷輸送材料の比率を５０％以下にする必要があり、それにともない明部電位で示される感度の低下が生じてしまった。また、比較例５に示すように電荷輸送層を２層構成とし電荷輸送層の比率の差を設けたものでは、ある程度の特性は得られたが、その特性は十分ではなく、その理由としては積層した界面の形成状態に影響されていると推測される。また、今回の比較例では第二電荷輸送層をスプレー塗布により形成したが、浸漬塗布法では第二電荷輸送層を塗布する際に第二電荷輸送層用の塗料に浸漬した際に第一電荷輸送層が溶解してしまい不均一な塗膜しかけいせいできなかった。このように電荷輸送材料比率を変えた電荷輸送層を積層する系や比較的薄膜である保護層を表面に設ける手段での対応は容易ではなく、本発明の例では上述した問題がないため、簡単な層構成によって良好な電気特性、摩耗性、安定性の備わった感光体が得られた。
【００６４】
【発明の効果】
本発明によれば、感度などの電気的特性と耐摩耗性などの機械的特性の両者の特性を向上させた電子写真感光体の提供ができた。
【００６５】
本発明で示す電荷輸送層を形成する主たるバインダー樹脂として少なくとも式（１）で示される構造を含むポリアリレート樹脂を用いることにより、電荷輸送材料の比率を高めて用いることが可能となり、すなわち感度で示される電気的特性を良好とすることができ、かつ繰り返し使用時の摩耗量を低く抑えることができ良好な画像を繰り返し提供することが可能となった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor in which a ratio of a specific binder resin for forming a photosensitive layer to a charge transport material is specified.
[0002]
[Prior art]
The electrophotographic method comprises a support coated with an insulating material in the dark where the electrical resistance varies according to the dose received during image exposure, as shown in U.S. Pat. No. 2,298,691. A photoconductive material is used. The basic characteristics required of an electrophotographic photoreceptor using this photoconductive material include (1) being able to be charged to an appropriate potential in a dark place, (2) having little potential dissipation in a dark place, And (3) Quickly dissipating the charge by light irradiation. Electrophotographic photoreceptors include inorganic materials typified by selenium, cadmium sulfide, and zinc oxide. In recent years, however, organic materials have been used in view of their low pollution, high productivity, ease of material design, and future potential. Is being actively developed. Of course, these electrophotographic photoreceptors are required to have various characteristics such as electrical, mechanical, and optical characteristics according to the applied electrophotographic process. In particular, in the case of a photoreceptor that is repeatedly used, since electrical and mechanical forces such as charging, exposure, development, transfer, and cleaning are repeatedly applied directly or indirectly, durability against these is required.
[0003]
In particular, as described above, the charge transport layer in the laminated photoreceptor often serves also as a surface layer, and electrical and mechanical properties are required. In order to relatively satisfy those properties, a charge transport material is used. A system using a mixture of a polycarbonate having a skeleton of bisphenol and a binder resin for forming the layer has been used in many fields. Although there is a characteristic of the material used as a factor affecting various characteristics of the charge transport layer, there is a ratio of the charge transport material to the binder resin. That is, the ratio of the charge transport material has been increased when giving priority to electrical characteristics such as sensitivity, and the ratio of the binder resin has been increased when giving priority to mechanical strength such as abrasion resistance. In addition, the compatibility of the charge transport material and the binder resin is also involved in the various properties, and even if the charge transport material ratio is increased to a certain ratio or more to give priority to the electrical characteristics, the strength of the coating film decreases. In the case where the charge transporting material or the binder resin is dissolved in a solvent or in a coating film after application and drying, the charge transporting material is precipitated, and the ratio is limited. That is, in the charge transport layer of the photoreceptor described so far, the practical ratio of the charge transport material in the charge transport layer is from 30% to 45%. If the content is not satisfied and exceeds 50%, problems such as insufficient mechanical strength, deposition of the charge transporting material, and cracks induced by them are not used as a surface layer of the photoreceptor. Further, a method of improving the abrasion resistance by providing a protective layer having excellent strength and a relatively thin thickness on the surface layer of the charge transport layer, or forming substantially two charge transport layers as shown in Japanese Patent No. 2541283. By changing the charge transport material and the resin ratio of each layer as a stacked type, that is, in the layer in contact with the charge generation layer, the charge transport material ratio is increased and the characteristics such as sensitivity are superior, while on the surface layer, the resin ratio is improved. In some systems, the layer structure is complicated by any means, and in systems where a protective layer is provided, the charge transport layer and the protective layer are in close contact with each other. There are problems such as compatibility and the compatibility of the binder resin type, and in a system in which substantially two charge transport layers are laminated, particularly in a system in which the same type of binder resin is laminated, when performing dip coating with excellent productivity. Since the solubility in the solvent is similar, when the second charge transport layer is applied, the elution of one charge transport layer occurs, so that there are problems such as selection of the solvent and improvement of the coating method. Therefore, it is necessary to consider this point in mass production, and the whole system such as a layer configuration and a production method becomes complicated. Thus, it has not been easy to achieve a photoreceptor excellent in both electrical characteristics such as sensitivity and mechanical strength characteristics such as abrasion resistance with a relatively simple layer structure.
[0004]
[Problems to be solved by the invention]
As described above, the characteristics of the charge transport layer are affected by the ratio of the charge transport material and the binder resin used in the charge transport layer, but as the characteristics of the electrophotographic photoreceptor, without lowering the electrical characteristics such as sensitivity, There is a need for contradictory properties of improving mechanical strength such as abrasion resistance.
[0005]
In the present invention, in order to satisfy the above-described various properties, and to achieve a layer configuration of the photoreceptor that is not as complicated as possible, instead of means such as stacking a plurality of layers having different charge transporting material ratios, a single layer is used. An object of the present invention is to achieve a photoreceptor having an excellent charge transport function and an excellent mechanical strength in a charge transport layer.
[0006]
[Means for Solving the Problems]
The present inventors have earnestly studied to improve the above-mentioned problems, and as a result, have reached the present invention. That is, in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer is formed by sequentially laminating a charge generation layer on the support side and a charge transport layer on the surface layer side. The charge transport layer comprises at least a main binder resin forming a layer and a charge transport material, and the binder resin is at least a polyarylate polymer or a copolymer having a structure shown in the following (1): An electrophotographic photoreceptor characterized in that the charge transport material accounts for more than 50% of the total weight of the charge transport material forming the charge transport layer and the binder resin.
[Outside 6]

[0007]
Polyarylate resin, like polycarbonate resin widely used in electrophotographic photoreceptors, is electrophotographic in which electrical and mechanical forces such as charging, exposure, development, transfer, and cleaning are repeatedly applied directly or indirectly. It is excellent in the use of the surface layer in the process, and is one of the suitable materials.
[0008]
Therefore, in the present invention, in order to achieve a photoconductor having excellent charge transport function and excellent mechanical strength in the layer configuration of the photoconductor which is not as complicated as shown as a problem, a charge comprising a charge transport material and a binder resin is required. We focused on increasing the charge transport material ratio in the transport layer. Also, by increasing the ratio of the charge transporting material, the characteristics of the surface layer are reduced, for example, abrasion with the cleaning blade, deformation of the surface layer caused by contact with the cleaning blade or the charging member or pressurization, and charge transport from the layer. The aim was to be a system that does not cause denaturation such as segregation or precipitation of the material. Therefore, in the present invention, by using a polyarylate resin having a specific structure, even if the ratio of the charge transport material exceeds 50%, it is possible to suppress the occurrence of the above-described problems, and further increase the charge transport material ratio. The improvement of the electrical characteristics by this was achieved, and also the improvement of the mechanical strength was able to be achieved. When a specific charge transporting material was used, the effect was more significantly obtained. Although the details of the mechanism of this effect have not been clarified, since the polyarylate having a relatively large number of aromatic rings and the charge transporting material having an aromatic ring easily overlap in the layer constituting the charge transporting layer, both of them are likely to overlap. And the addition of a substituent to the aromatic ring of the polymer chain provides an appropriate three-dimensional space and moderate restriction, as well as an appropriate overlap between polymer chains. Guessed. That is, when the ratio of the charge transport material in the charge transport layer exceeds 50%, in a widely used polycarbonate, a solution in which the charge transport material and the binder resin are dissolved in a solvent or the solution is applied. In the charge transport layer formed by drying, precipitation of the charge transport material and cracks due to a decrease in the strength of the layer are induced. Therefore, in a system such as polycarbonate, the ratio of the charge transporting material is required to be 50% or less, and depending on the material to be selected, the ratio may not be 40% or less. However, in the system of the present invention, the charge transporting material is not used. The ratio can be increased, and the electrical characteristics and mechanical characteristics can be improved, and a good photoreceptor can be obtained.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The polyarylate resin represented by the formula (1) has a structure generally called bisphenol C type, and is copolymerized with a bisphenol monomer having another structure including a homopolymer composed of the bisphenol C type monomer and phthalic acid. The copolymer may be used in a blended system in which other types of polymers are mixed. It is necessary for the polymer that can be used in the present invention to have at least the bisphenol C type represented by the formula (1) in its structure in order to exhibit the effect, and in addition to the homopolymer, an example of the structure of polyarylate used as a copolymer Is shown below.
[Outside 7]

[0010]
[Outside 8]

[0011]
In these cases, when the copolymer is used as a copolymer, the ratio of the structure represented by the formula (1) to the other structure needs to be 10% or more in the formula (1), and below this, the effect of the present invention is significantly reduced. Further, as the structure to be copolymerized, (5-1) and (5-12) are particularly preferable. Further, the method for synthesizing these polyarylate resins is not limited, and can be obtained by a conventional method of polycondensation of various bisphenols and phthalic acid as monomers (for example, interfacial polycondensation method). Phthalic acid affects the properties (eg, strength and solubility) of the resulting polyarylate resin depending on the position of the substituent, but is not particularly limited in the present invention. Preferably, terephthalic acid / isophthalic acid is used. This is a system in which the ratio is between 7/3 and 3/7.
[0012]
The weight average molecular weight of the polyarylate resin used in the present invention is preferably from 10,000 to 200,000, and particularly preferably from 20,000 to 150,000. The molecular weight was shown by a value measured using gel permeation chromatography and using polystyrene as a standard sample. The details of the charge transport material will be described below. In the present invention, the ratio of the charge transport material to the total weight of the charge transport layer is more than 50%, but is particularly preferably up to 75%.
[0013]
The compounds of the structural formulas (4) and (5) used in the present invention will be described in detail.
[0014]
In the formula (4), Ar1 and Ar2 represent aromatic ring groups such as phenyl, naphthyl and anthryl.
[0015]
Ar3 represents a divalent aromatic ring group or a divalent heterocyclic group obtained by taking two hydrogen atoms from an aromatic ring such as benzene, naphthalene and anthracene or a heterocyclic ring such as thiophene and furan. R3 represents an alkyl group such as methyl, ethyl, propyl, and butyl, or an aromatic ring group such as a phenyl group and a naphthyl group. R4 represents an alkyl group such as methyl, ethyl, propyl and butyl; an aromatic ring group such as phenyl and naphthyl or a hydrogen atom. N1 represents 1 or 2.
[0016]
Ar 1, Ar 2, Ar 3, R 3 and R 4 may each have a substituent. Examples of the substituent which may be present include alkyl groups such as methyl, ethyl, propyl and butyl; methoxy, ethoxy and propoxy. Aryloxy groups such as phenoxy and naphthoxy; halogen atoms such as fluorine, chlorine and bromine; and disubstituted amino groups such as dimethylamino, diethylamino and diphenylamino. Further, R1 and R2 may form a ring directly or by bonding via a carbon atom, a sulfur atom, an oxygen atom or the like.
[0017]
In the formula (5), Ar4, Ar5 and Ar6 are phenyl, naphthyl, anthryl, pyrenyl, fluorenyl, phenanthryl, 9-10-dihydrophenanthryl, quinolyl, dibenzothenyl, dibenzofuryl, n-methylcarbazole, n- And a heterocyclic group such as ethyl carbazole and n-tolyl carbazole.
[0018]
Ar4, Ar5 and Ar6 each may have a substituent, and the substituent which may be present is an alkyl group such as methyl, ethyl, propyl and butyl; an aralkyl such as benzyl, phenethyl and naphthylmethyl. Groups; alkoxy groups such as methoxy, ethoxy and propoxy; aryloxy groups such as phenoxy and naphthoxy; halogen atoms such as fluorine, chlorine and bromine; aromatic ring groups such as phenyl and biphenyl; diarylamino groups such as diphenylamino and ditolylamino. Dialkylamino groups such as dimethylamino and diethylamino; diaralkylamino groups such as dibenzylamino and diphenethylamino; alkylaralkylamino groups such as benzylmethylamino and benzylethylamino; nitro groups and hydroxy groups. .
[0019]
Further, specific examples of the charge transport material are shown below, but the invention is not limited thereto.
[Outside 9]

[0020]
[Outside 10]

[0021]
[Outside 11]

[0022]
Hereinafter, the configuration of the electrophotographic photosensitive member of the present invention will be described.
[0023]
The electrophotographic photoreceptor of the present invention is a laminated type in which a photosensitive layer is separated into a charge transport layer and a charge generation layer, and the conductive substrate used may be any one having conductivity, such as a metal such as aluminum or stainless steel. Alternatively, metal, paper, plastic or the like provided with a conductive layer may be mentioned, and the shape may be a sheet-like or cylindrical shape.
[0024]
In a system using laser light for forming a latent image represented by a laser beam printer, a conductive layer may be provided for the purpose of preventing interference fringes caused by scattering of laser light on a substrate and covering a scratch on the substrate. . This can be formed by dispersing carbon black, metal particles, metal oxide, and the like in a binder resin. The thickness of the conductive layer is suitably 5 to 40 μm, preferably 10 to 30 μm.
[0025]
An intermediate layer having an adhesive function is provided thereon. Examples of the material of the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are applied by dissolving in an appropriate solvent. The intermediate layer has a thickness of 0.05 to 5 μm, preferably 0.3 to 1 μm.
[0026]
A charge generation layer is formed on the intermediate layer. As the charge generation material in the present invention, generally known materials can be used, for example, selenium-tellurium, pyrylium, metal phthalocyanine, metal-free phthalocyanine, anthantrone, dibenzpyrenequinone, trisazo, cyanine, disazo, monoazo, Each pigment such as indigo and quinacudrine is exemplified. These pigments were dispersed well using a homogenizer, an ultrasonic disperser, a ball mill, a vibration mill, a sand mill attritor, a roll mill, a liquid collision type high-speed disperser and the like with a binder resin and a solvent 0.3 to 4 times in weight. Make it a dispersion. In the case of a laminated photoreceptor, a charge generation layer is obtained by applying and drying this liquid. The thickness is preferably 5 μm or less, particularly preferably 0.1 to 2 μm.
[0027]
As the charge transporting material, those commonly used can be used, but the compounds represented by the above-mentioned chemical formulas (4) and (5) are preferable. These compounds are dissolved in a solvent together with the binder resin described above to form a solution. In order to obtain a laminated photoreceptor, this liquid is applied and dried to obtain a charge transport layer. The film thickness is preferably from 5 to 40 μm, and particularly preferably from 15 to 30 μm.
[0028]
There is no particular limitation on the method of coating the photoreceptor, and any known method such as a dip coating method, a spray coating method, and a bar coating method can be used, but the dip coating method is preferable in consideration of productivity and the like.
[0029]
Hereinafter, the present invention will be described in more detail according to embodiments. In the embodiments, "parts" represents parts by weight.
[0030]
(1st Embodiment)
A coating composed of the following materials was applied on an aluminum cylinder of 30φ × 357 mm by a dip coating method, and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm.
[0031]
Conductive pigment: SnO ₂ coated barium sulfate 10 parts Resistance adjusting pigment: Titanium oxide 2 parts Binder resin: Phenol resin 6 parts Leveling material: Silicone oil 0.001 parts Solvent: methanol / methoxypropanol = 2/8 20 parts Next A solution obtained by dissolving 3 parts of N-methoxymethylated nylon and 3 parts of copolymer nylon in a mixed solvent of 65 parts of methanol and 30 parts of n-butanol is applied on the conductive layer by dip coating, and dried. Thus, an intermediate layer having a thickness of 0.5 μm was formed.
[0032]
Next, 4 parts of oxytitanium phthalocyanine having strong peaks at 9.0 °, 14.2 °, 23.9 °, and 27.1 ° of the black angle 2θ ± 0.2 ° in the CuKα characteristic X-ray diffraction, 4 parts of polyvinyl butyral ( After 2 parts of a trade name (ESLEC BM2, manufactured by Sekisui Chemical) and 60 parts of cyclohexanone were dispersed in a sand mill using 1 mmφ glass beads for 4 hours, 100 parts of ethyl acetate was added to prepare a dispersion for a charge generation layer. This dispersion was applied onto the intermediate layer by a dip coating method, and dried to form a charge generation layer having a thickness of 0.1 μm.
[0033]
Next, 2 parts of the amine compound of the exemplified compound (4-8) 10 parts of the amine compound of the exemplified compound (5-5) 10 parts of a polyarylate resin (Mw = 100,000) represented by the formula (1) as a binder resin is used as a solvent. Was dissolved in 55 parts of monochlorobenzene and 35 parts of dichloromethane to obtain a coating solution for a charge transport layer. The coating solution was applied by a dip coating method, and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 27 μm (charge transport material ratio: 54.5%).
[0034]
Next, evaluation will be described. As the apparatus, a copying machine GP215 (manufactured by Canon Inc.) which is charged by a contact charging member to which a voltage obtained by superimposing an alternating current on a direct current was applied was used. Under an environment of 23 ° C. and 55% RH, the dark part potential was set to −700 V, and the light part potential was measured to determine the sensitivity.
[0035]
Further, 10,000 sheets of A4 size plain paper were repeatedly copied. Further, the photoreceptor film thickness was repeatedly measured before and after copying, and the abrasion amount was obtained.
[0036]
Thereafter, the photosensitive member is left in contact with the cleaning blade and the contact charging member for one month in an environment of 32 ° C. and 85% RH for one month, and changes in the surface layer such as deposition of the charge transport material at each contact portion. Was observed.
[0037]
(Second embodiment)
In preparing the coating solution for the charge transport layer, a photoconductor was prepared in the same manner as in the first embodiment, except that the formula (5-5) was increased to 13 parts as a charge transport material (charge transport material ratio: 60%). 0%).
[0038]
(Third embodiment)
The preparation of the coating solution for the charge transport layer was carried out in the same manner as in the first embodiment except that the formula (5-5) was changed to 15 parts and the formula (4-8) was increased to 5 parts as the charge transport material. A body was prepared (charge transport material ratio: 66.7%).
[0039]
(Fourth embodiment)
In the preparation of the coating solution for the charge transport layer, the photosensitization was performed in the same manner as in the first embodiment, except that the formula (5-5) was changed to 18 parts as the charge transport material and the formula (4-8) was increased to 6 parts. A body was prepared (charge transport material ratio: 70.6%).
[0040]
(Fifth embodiment)
In the preparation of the coating solution for the charge transport layer, a second example was carried out except that the binder resin was a copolymer of the formula (1) / (5-1) (ratio = 5/5, Mw = 80,000). A photosensitive member was produced in the same manner as in the embodiment.
[0041]
(Sixth embodiment)
Embodiment 2 was the same as Embodiment 2 except that the binder resin was a copolymer of the formula (1) / (5-3) (ratio = 5/5, Mw = 80,000) in the preparation of the coating solution for the charge transport layer. The same procedure was performed to produce a photoreceptor.
[0042]
(Seventh embodiment)
In the preparation of the coating solution for the charge transport layer, a second example was carried out except that the binder resin was a copolymer of the formula (1) / (5-12) (ratio = 5/5, Mw = 80,000). A photoreceptor was produced in the same manner as in the embodiment.
[0043]
(Eighth embodiment)
The preparation of the coating solution for the charge transport layer was carried out in the same manner as in the first embodiment, except that only 15 parts of the formula (4-2) were used as the charge transport material, to produce a photoreceptor.
[0044]
(Ninth embodiment)
The preparation of the coating solution for the charge transport layer was carried out in the same manner as in the first embodiment, except that only 15 parts of (5-1) were used as the charge transport material, thereby producing a photoconductor.
[0045]
(Comparative Example 1)
In the preparation of the coating solution for the charge transport layer, a photoconductor was prepared in the same manner as in the second embodiment except that a Z-type polycarbonate resin (Iupilon Z400 manufactured by Mitsubishi Gas Chemical Company) was used as the binder resin (resin Mw = about 100, 000: charge transport ratio 60.0%).
[0046]
(Comparative Example 2)
In the preparation of the coating solution for the charge transport layer, a photoconductor was prepared in the same manner as in the second embodiment except that an A-type polyarylate resin (U100 manufactured by Unitika) was used as a binder resin (resin Mw = about 70,000: (Charge transport material ratio: 60.0%).
[0047]
(Comparative Example 3)
The preparation of the coating solution for the charge transport layer was performed in the same manner as in the second embodiment except that the binder resin was changed to a polyester resin (Byron, Toyobo Co., Ltd.) (resin Mw = about 70,000: charge transport). Material ratio 60.0%).
[0048]
(Comparative Example 4)
A photosensitive member was prepared in the same manner as in the first embodiment except that 7 parts of a Z-type polycarbonate resin (Iupilon Z400 manufactured by Mitsubishi Gas Chemical Company) was used as a binder resin in preparing a coating solution for the charge transport layer (charge transport material). Ratio 45.0%).
[0049]
(Comparative Example 5)
In preparing the coating solution for the charge transport layer, the charge transport layer was coated in the same manner as in the second embodiment except that a Z-type polycarbonate resin (Iupilon Z400 manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used as a binder resin to form a film having a thickness of 7 μm. (One charge transport layer) (charge transport material ratio: 60.0%).
[0050]
Next, in preparing a coating solution for the second charge transport layer, 10 parts of a Z-type polycarbonate resin (Iupilon Z400 manufactured by Mitsubishi Gas Chemical) was used as a binder resin, 1 part of Formula 4-8 and 4 parts of Formula 5-5. It was dissolved in 100 parts of chlorobenzene and 50 parts of dichloromethane. This coating solution was spray-coated on the first charge transport layer to form a 20 μm second charge transport layer to prepare a photoreceptor (charge transport material ratio: 33.3%).
[0051]
[Table 1]

[0052]
(Tenth embodiment)
A conductive layer and an intermediate layer were applied on an aluminum cylinder by the method described in the first embodiment.
[0053]
Next, 4 parts of an azo pigment represented by the following structural formula (6), 2 parts of polyvinyl butyral (trade name: Eslec BM2, manufactured by Sekisui Chemical) and 60 parts of cyclohexanone were dispersed in a sand mill using 1 mmφ glass beads for 4 hours. And 100 parts of THF was added to prepare a dispersion for a charge generation layer. This dispersion was applied onto the intermediate layer by a dip coating method, and dried to form a charge generation layer having a thickness of 0.1 μm.
[Outside 12]

[0054]
The coating liquid for the charge transport layer was the same as that described in the first embodiment, and was immersed and applied on the charge generation layer to obtain a charge transport layer of 18 μm (charge transport material ratio: 54.5%).
[0055]
Next, evaluation will be described. The apparatus used was a copying machine NP6035 (a system charged by a contact charging member to which a DC voltage was applied) manufactured by Canon Inc. Under an environment of 23 ° C. and 55% RH, the dark part potential was set to −700 V, and the light part potential was measured to determine the sensitivity. Further, 10,000 sheets of A4 size plain paper were repeatedly copied. The photoreceptor film thickness was repeatedly measured before and after copying to determine the amount of wear.
[0056]
(Eleventh embodiment)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer described in the second embodiment was applied thereon to form a charge transport layer of 18 μm (charge transport material ratio: 60.0%).
[0057]
(Twelfth embodiment)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer described in the third embodiment was applied thereon to form a 18 μm charge transport layer (charge transport material ratio: 66.7%).
[0058]
(Thirteenth embodiment)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer described in the fourth embodiment was applied thereon to form a charge transport layer of 18 μm (charge transport material ratio: 70.6%).
[0059]
(Comparative Example 6)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer shown in Comparative Example 1 was applied thereon to form an 18 μm charge transport layer.
[0060]
(Comparative Example 7)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer shown in Comparative Example 2 was applied thereon to form an 18 μm charge transport layer.
[0061]
(Comparative Example 8)
The charge generation layer was applied in the same manner as in the tenth embodiment. The coating liquid for a charge transport layer shown in Comparative Example 4 was applied thereon to form an 18 μm charge transport layer.
[0062]
[Table 2]

[0063]
As shown in Tables 1 and 2, by using a polyarylate having at least the structure represented by the formula (1) as a main binder resin for forming the charge transport layer shown in the present invention, the charge transport material yield can be reduced. It was possible to increase the use, that is, it was possible to improve the electrical characteristics indicated by the sensitivity, and it was possible to reduce the amount of wear when repeatedly used. In other words, in a system in which the charge transport material has a high yield using a polycarbonate resin or the like that has been widely used in the past with the aim of improving sensitivity or the like, a decrease in abrasion resistance occurs or a cleaning blade or the like is brought into contact. This could not be achieved due to problems such as deposition of the charge transport material at the site. Further, in the case of polycarbonate, the ratio of the charge transporting material must be 50% or less in order to suppress the deposition of the charge transporting material at the blade portion, and the sensitivity indicated by the light portion potential is reduced accordingly. . In addition, as shown in Comparative Example 5, when the charge transport layer was formed into a two-layer structure and the difference in the ratio of the charge transport layer was provided, some characteristics were obtained, but the characteristics were not sufficient. It is presumed that it is influenced by the formation state of the laminated interface. In this comparative example, the second charge transport layer was formed by spray coating. However, in the dip coating method, when the second charge transport layer was applied, the first charge transport layer was immersed in the paint for the second charge transport layer. The transport layer was dissolved and a non-uniform coating film could not be formed. As described above, it is not easy to cope with a system in which a charge transport layer having a changed charge transport material ratio is laminated or a means for providing a relatively thin protective layer on the surface, and the example of the present invention does not have the above-described problems. A photoreceptor with good electrical properties, abrasion, and stability was obtained with a simple layer configuration.
[0064]
【The invention's effect】
According to the present invention, it is possible to provide an electrophotographic photoreceptor in which both the electrical characteristics such as sensitivity and the mechanical characteristics such as abrasion resistance are improved.
[0065]
By using a polyarylate resin having at least the structure represented by the formula (1) as a main binder resin for forming the charge transport layer shown in the present invention, it is possible to use the charge transport material at a higher ratio, that is, to improve sensitivity. The electrical characteristics shown can be improved, and the amount of wear at the time of repeated use can be suppressed to a low level, whereby a good image can be repeatedly provided.

Claims (5)

An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer is formed by sequentially laminating a charge generation layer on the support side and a charge transport layer on the surface layer side. Wherein the charge transport layer comprises at least a main binder resin forming a layer and a charge transport material, and the binder resin is at least a polyarylate polymer or copolymer having a structure shown in the following (1); An electrophotographic photoreceptor, wherein the charge transport material accounts for more than 50% of the total weight of the charge transport material forming the transport layer and the binder resin.
[Outside 1]

2. The electrophotographic photosensitive member according to claim 1, wherein the binder resin forming the photosensitive layer is at least a polyarylate copolymer shown in the following (2).
[Outside 2]

2. The electrophotographic photosensitive member according to claim 1, wherein the binder resin forming the photosensitive layer is at least a polyarylate copolymer shown in the following (3).
[Outside 3]

2. The electrophotographic photosensitive member according to claim 1, wherein the charge transporting material is represented by the following structural formula (4).
[Outside 4]

(Wherein, Ar1 and Ar2 represent an optionally substituted aromatic ring group, Ar3 represents an optionally substituted divalent aromatic ring group or a divalent heterocyclic group, and R3 represents an optionally substituted alkyl group. A group or an aromatic ring group, and R4 represents a hydrogen atom, an alkyl group or an aromatic ring group which may be substituted. N1 is 1 or 2, and R3 and R4 may combine to form a ring.) 2. The electrophotographic photosensitive member according to claim 1, wherein the charge transporting material is represented by the following structural formula (5).
[Outside 5]

(In the formula, Ar4, Ar5 and Ar6 each represent an optionally substituted aromatic or heterocyclic group)