JP3763190B2 - Electrophotographic photosensitive member and electrophotographic apparatus - Google Patents

Description

【００４９】
（式中、Ａｒ₁ 及びＡｒ₂ はそれぞれ独立に置換もしくは未置換のアリール基を示し、Ｘ₁ は芳香族環構造を有する２価の炭化水素基またはヘテロ原子含有炭化水素基を示し、Ｘ₂ 及びＸ₃ はそれぞれ独立に置換もしくは未置換のアリーレン基を示し、Ｌ₁ は枝分れもしくは環構造を含んでもよい２価の炭化水素基またはヘテロ原子含有炭化水素基を示し、ｍ及びｎは、それぞれ０または１から選ばれる整数を意味する。）
【００５０】
【化５】

【００５１】
（式中、Ａｒ₃ 及びＡｒ₄ はそれぞれ独立に置換もしくは未置換のアリール基を示し、Ｌ₂ は芳香族環構造を有する３価の炭化水素基またはヘテロ原子含有炭化水素基を示す。）
前記一般式（１）中、Ａｒ₁ 及びＡｒ₂ はそれぞれ独立に置換もしくは未置換のアリール基から選ばれ、該アリール基の具体例としては、フェニル基、ビフェニル基、ナフチル基、ピレニル基等が挙げられる。また、置換基としては、メチル基、エチル基、メトキシ基、ハロゲン原子等が挙げられる。
Ｘ₁ は芳香族環構造を有する２価の炭化水素基またはヘテロ原子含有炭化水素基から選ばれる。具体例としては、フェニレン基、ビフェニレン基、ターフェニレン基、ナフチレン基、メチレンジフェニル基、シクロヘキシリデンジフェニル基、オキシジフェニル基、チオジフェニル基等、およびこれらのメチル置換体、エチル置換体、メトキシ置換体、またはハロゲン置換体等が挙げられ、この中でも特に置換もしくは未置換のビフェニレン基が電荷輸送性の点で、特に好ましい。
【００５２】
Ｘ₂ 及びＸ₃ はそれぞれ独立に置換もしくは未置換のアリーレン基から選ばれ、具体的には、フェニレン基、ビフェニレン基、ターフェニレン基、ナフチレン基等、およびこれらのメチル置換体、エチル置換体、メトキシ置換体、またはハロゲン置換体等が挙げられる。
【００５３】
Ｌ₁は枝分れもしくは環構造を含んでもよい２価の炭化水素基またはヘテロ原子含有炭化水素基から選ばれ、上記の好ましい特性の少なくとも１つを発揮するかぎり任意であるが、エーテル結合、エステル結合、カーボネート結合、シロキサン結合等から選ばれる結合基を含み、且つ炭素数が２０以下であるものが好ましい。その具体例としては、以下のものが挙げられる。
【００５４】
【化６】

【００５５】
また、上記一般式（２）中、Ａｒ₃及びＡｒ₄はそれぞれ独立に置換もしくは未置換のアリール基から選ばれ、該アリール基の具体例としては、フェニル基、ビフェニル基、ナフチル基、ピレニル基等が挙げられる。また、置換基としては、炭素数１〜１２個のアルキル基またはアルコキシ基、ジアリールアミノ基、ハロゲン原子等が挙げられる。
【００５６】
Ｌ₂は芳香族環構造を有する３価の炭化水素基またはヘテロ原子含有炭化水素基から選ばれ、上記の好ましい特性の少なくとも１つを発揮するかぎり任意であるが、炭素数が２０以下のものが好ましい。その具体例としては、以下のものが挙げられる。
【００５７】
【化７】

【００５８】
本発明の共重合体を形成する絶縁性ブロックとしては如何なるものでも構わない。絶縁性ブロックの具体例としては、ポリビニルアセタール、ポリアルキルメタクリレート、ポリアルキルアクリレート、ポリ塩化ビニル、ポリスチレン、ポリ酢酸ビニル、ポリアルキルビニルエーテル、ポリカーボネート、ポリエステル、ポリシロキサン等、およびこれらのブロック、グラフト、ランダムまたは交互共重合体等が挙げられる。しかし、機械的強度、可撓性、可視光および赤外光透過性、化学的安定性、絶縁性等の点で、ビニル系モノマーの重合物からなるものが好ましく、特に下記一般式（３）で示されるビニルモノマーの少なくとも１種を重合し得られるものが好ましい。
【００５９】
【化８】

【００６０】
上記一般式（３）中、Ｒ ¹ 〜Ｒ ³ それぞれ独立に水素原子、ハロゲン原子、または置換もしくは未置換のアルキル基またはアリール基から選ばれる。置換もしくは未置換のアルキル基またはアリール基の具体的としては、メチル基、エチル基、メトキシ基、クロロメチル基、フェニル基、トリル基等が挙げられる。
【００６１】
Ｒ ⁴ は置換もしくは未置換のアルキル基、アリール基、アルコキシ基、アシル基、アシルオキシ基、またはアルコキシカルボニル基から選ばれる。アルキル基、アルコキシ基、アシル基、アシルオキシ基、およびアルコキシカルボニル基の炭素数は１〜１８個が好ましく、またアリール基としてはフェニル基、ナフチル基、ピレニル等が挙げられる。置換基としては、ハロゲン原子、フェニル基、ヒドロキシ基、アミノ基、イソシアネート基、エポキシ基、アルコキシシリル基等が挙げられる。
【００６２】
本発明の共重合体において、電荷輸送性ブロック中の繰り返し単位として含有する、上記一般式（１）で表される構造式の具体例を下記表１〜２に示し、上記一般式（２）で表される構造式の具体例を下記表３に示し、また、絶縁性ブロック中の繰り返し単位として含有する、上記一般式（３）で表される構造式の具体例を下記表４に示すが、本発明はこれらに限られるものではない。
【００６３】
【表１】

【００６４】
【表２】

【００６５】
【表３】

【００６６】
【表４】

【００６７】
本発明の共重合体中の絶縁性ブロックの抵抗値としては、１０¹³Ωｃｍ以上が好ましく、特に、１０¹⁴Ωｃｍが好ましい。上記体積抵抗率がこの範囲より低い絶縁性ブロックを用いた場合、そのブロックによって形成される電気的不活性の相の電気的絶縁性が損なわれＳ字性が失われる傾向にある。尚、共重合体中の電気抵抗率を、直接測定することは困難であり、絶縁性ブロックと同一構造の高分子の電気抵抗率で代用することができる。
【００６８】
本発明の共重合体はブロック共重合体またはグラフト共重合体であれば、その構成ブロックの連結形式は如何なるものでも構わない。すなわち、電荷輸送性ブロックをＡ、絶縁性ブロックをＢと表した時、ＡＢ型、ＡＢＡ型、ＢＡＢ型、（ＡＢ）_n 型、（ＡＢ）_n Ａ型、およびＢ（ＡＢ）_n 型のブロック共重合体、電荷輸送性ブロックを主鎖、絶縁性ブロックを側鎖とするグラフト共重合体、絶縁性ブロックを主鎖、電荷輸送性ブロックを側鎖とするグラフト共重合体、もしくはＡＢＡ型等のブロック共重合体の側鎖にＡおよび／またはＢをグラフト化したブロック−グラフト共重合体等が挙げられる。
電荷輸送性ブロック、絶縁性ブロックともに、２種類以上の構造単位を含むことも可能である。また、共重合体と電荷輸送性高分子化合物、または、且つ、絶縁性高分子化合物を共に用いることができる。この場合、共重合体の構造単位を含む高分子化合物が好ましい。
【００６９】
これらの電荷輸送性ブロックと絶縁性ブロックとを有する共重合体によって、不均一電荷輸送層として好適な変調構造をつくるには、均一相から、二相へ分離させることが必要である。この二相へ分離させる方法としては、両ブロックが加熱により均一相から二相へ分離する特性を有する混合物の場合は、均一相の膜を加熱後、冷却することにより変調構造を作る方法をとることが可能である。また、両者を共通の溶剤に溶解して均一相とし、溶剤が蒸発し高濃度化する過程で、二相へ分離させる方法、両者を混合溶剤に溶解して均一相とし、溶剤が蒸発して溶剤組成が変化する過程で、二相へ分離させる方法等によっても変調構造を作ることができる。
【００７０】
電荷輸送性ブロックと絶縁性ブロックとの体積比は９／１〜１／９の範囲で任意に設定されるが、８／２〜２／８の範囲が好ましい。より好ましくは、７／３〜３／７の範囲である。電荷輸送性ブロックの体積比率が上記範囲より多くても、少なくても変調構造をとることが困難となる。ただし、各々の材料構成、成膜条件などにより変調構造を作りやすい体積比は決定される。
【００７１】
電荷輸送性部分の相のピッチ（図３中、例えば、幅ａで示す）は０．００１〜１μｍが好ましく、より好ましくは０．００５〜０．５μｍ、特に好ましくは０．０１〜０．２μｍの範囲である。電荷輸送性の相のピッチが上記範囲より大きいと、好ましい膜厚の範囲内でのＳ字化に必要な空間的トラップの形成が確率的に低くなり、Ｓ字性が失われることになる。他方、電荷輸送性の相のピッチが上記範囲より小さい場合には、空間的トラップが浅くなりすぎ、Ｓ字性が失われる傾向にある。
【００７２】
共重合体では各ブロックの分子量によって、相のピッチを制御することができる。ブロックの分子量が大きくなれば、相のピッチも大きくなり、ブロックの分子量が小さくなれば相のピッチも小さくなる。各ブロックの分子量は２０００から１００００００の範囲が適当である。各ブロックの分子量が２０００未満では相のピッチが小さくなりすぎ、１００００００以上では相のピッチが大きくなりすぎる。なおここで言う分子量とは体積平均分子量を指す。
【００７３】
また、溶剤の選択、混合溶剤の利用、溶剤の蒸発速度の調整、冷却速度などを適宜調整することによっても相のピッチの調整は可能である。
【００７４】
ここで電荷輸送性ブロックと絶縁性ブロックを構成する物質の好ましい組み合わせとしては、各ブロックと同じ構成の電荷輸送性高分子化合物と絶縁性高分子化合物の溶解度パラメーターを測定したとき、相分離を行わせるための共通溶剤が存在する範囲において、離れている方が好ましい。
【００７５】
本発明で用いる不均一電荷輸送層の膜厚は、均一電荷輸送層と組み合わせず、電荷輸送層を不均一電荷輸送層のみで形成する場合５〜１００μｍが適当であり、好ましくは１０〜５０μｍの範囲に設定される。また、この不均一電荷輸送層を均一電荷輸送層と組み合せて電荷輸送層を形成する場合、０．１〜５０μｍが適当であり、好ましくは０．２〜２０μｍ、さらに好ましくは０．５〜１０μｍの範囲に設定される。上記範囲より薄いとＳ字性が失わる傾向にある。膜厚の上限に関しては、用いるＳ字型電荷輸送層の電荷輸送能により制限され、応答速度、残留電位等が許容される範囲内で設定される。
【００７６】
また、不均一電荷輸送層中に、主たる輸送電荷と逆極性の電荷のみを輸送し得る化合物を添加することにより、残留電位の低下、繰り返し安定性の向上等の効果を得ることもでき、絶縁性高分子化合物よりなる相中に含まれていることが好ましい。
【００７７】
不均一電荷輸送層の塗布方法としては、ブレードコーティング法、ワイヤーバーコーティング法、スプレーコティング法、浸漬コーティング法、ビードコーティング法、エアーナイフコーティング法、カーテンコーティング法等の通常の方法を用いることができる。
【００７８】
均一電荷輸送層、すなわち電荷輸送性マトリックスを含む層としては、従来のＪ字型積層感光体に電荷輸送層として用いられている公知のものを使用することができる。例えば、ベンジジン系化合物、アミン系化合物、ヒドラゾン系化合物、スチルベン系化合物、カルバゾール系化合物等のホール輸送性低分子化合物またはフルオレノン系化合物、マロノニトリル系化合物、ジフェノキノン系化合物等の電子輸送性低分子化合物を、単独でまたは２種以上を混合して、ポリカーボネート、ポリアリレート、ポリエステル、ポリスルホン、ポリメチルメタクリレート等の絶縁性樹脂中に均一分子分散した固溶膜、あるいは、それ自身電荷輸送能を有する高分子化合物等を用いることができる。また、セレン、アモルファスシリコン、アモルファスシリコンカーバイト等の電荷輸送能を有する無機物質を用いることもできる。電荷輸送性高分子化合物としては、ポリビニカルバゾール等の電荷輸送能を有する基を側鎖に含む高分子化合物、特開平５−２３２７２７号公報等に開示されているような電荷輸送能を有する基を主鎖に含む高分子化合物、およびポリシラン等をあげることができる。
【００７９】
本発明における均一電荷輸送層としては、特に製造上、電荷輸送性高分子化合物を用いることが好ましい。すなわち、不均一電荷輸送層と均一電荷輸送層を積層製膜する場合、均一電荷輸送層に電荷輸送性低分子化合物を用いると、電荷輸送性低分子化合物が不均一電荷輸送層に混入してしまい、不均一電荷輸送層の電気的不活性相の主たる電荷に対する絶縁性が低下することによりＳ字性が損なわれたり、あるいは混入分子が電荷トラップとなり残留電位の増大、輸送能の低下及び光感度の低下等の障害が発生する。この問題は特に、湿式塗布法により、各層を成膜する場合に顕著になる。もちろん、これらの問題は、上層の塗布溶剤として下層を溶解および膨潤し難いものを選択するか、または、絶縁性ブロックとして電荷輸送性低分子化合物と相溶性の無いものを選択する等により、回避することが可能ではあるが、高分子同士は相溶することは稀であり相分離を起こすことが一般的であることが知られており、均一電荷輸送層として電荷輸送性高分子化合物を用いた場合、不均一電荷輸送層の電気的不活性相と相溶することなく相分離するため、上記のような混入の問題は殆ど発生せず、材料および製造法の選択に当たっての制約が解消されるという利点を有する。
【００８０】
また、上記理由により、電荷輸送性高分子よりなる均一電荷輸送層を用いる場合には、層中に分子量１０００以下の電荷輸送性化合物が５％以上含まれないことが望ましい。
【００８１】
さらに均一電荷輸送層の電荷輸送性高分子化合物として、前記一般式（１）または（２）で表される構造の少なくとも１種以上を繰り返し単位として含有する電荷輸送性樹脂の場合は、高い電荷輸送能を有し、機械的特性にも優れているので特に好ましい。
【００８２】
この均一電荷輸送層中には、電荷輸送性マトリックスに周囲を囲まれるような状態であれば、電気的不活性な領域が存在してもよい。例えば、表面摩擦の低減、磨耗の低減、または表面付着物の低減等を目的に、電荷輸送性マトリックス層中に絶縁性粒子等を含有させることができる。また、均一電荷輸送層は輸送能の向上などのため、電荷輸送性微粒子等を含むことができる。
【００８３】
均一電荷輸送層の塗布方法としては、ブレードコーティング法、ワイヤーバーコーティング法、スプレーコティング法、浸漬コーティング法、ビードコーティング法、エアーナイフコーティング法、カーテンコーティング法等の通常の方法を用いることができる。また、気相成膜可能なものは、真空蒸着法等により直接成膜することもできる。
【００８４】
本発明で用いる均一電荷輸送層の膜厚は１〜１００μｍ、好ましくは５〜５０μｍに設定される。
【００８５】
本発明において、電荷輸送層全体の合計厚みは一般的には、５〜１００μｍが適当であり、好ましくは１０〜５０μｍの範囲に設定される。
【００８６】
電荷輸送層が電荷発生層と露光光源の間に存在する場合、実効の光感度の低下を防ぐ上で、電荷輸送層は露光波長の光に対し事実上透明であることが望ましい。好ましくは、電荷輸送層における露光に用いる光の透過率は５０％以上である。より好ましくは７０％以上であり、さらに好ましくは９０％以上である。しかしながら、低感度での使用が望まれる場合には、露光波長の光に対し事実上吸収のある電荷輸送層を用い、実効的な光感度を調整することもできる。
電荷発生層と電荷輸送層よりなる光導電層の上には、さらに必要に応じて保護層を設けてもよい。この保護層は、帯電部材から発生するオゾンや酸化性ガス等、および紫外光等の化学的ストレス、あるいは、現像剤、紙、クリーニング部材等との接触に起因する機械的ストレスから光導電層を保護し、光導電層の実質の寿命を改善するために有効である。特に、薄層の電荷発生層を上層に用いる層構成において、効果が顕著である。
【００８７】
保護層は、導電性材料を適当な結着樹脂中に含有させて形成される。導電性材料としては、ジメチルフェロセン等のメタロセン化合物、酸化アンチモン、酸化スズ、酸化チタン、酸化インジウム、ＩＴＯ等の金属酸化物等の材料を用いることができるが、これらに限定されるものではない。結着樹脂としては、ポリアミド、ポリウレタン、ポリエステル、ポリカーボネート、ポリスチレン、ポリアクリルアミド、シリコーン樹脂、メラミン樹脂、フェノール樹脂、エポキシ樹脂等の公知の樹脂を用いることができる。また、アモルファスカーボン等の導電性無機膜も保護層として用いることができる。
【００８８】
保護層の電気抵抗は１０⁹ 〜１０¹⁴Ω・ｃｍの範囲が好ましい。電気抵抗がこの範囲以上になると残留電位が増加し、他方、この範囲以下になると沿面方向での電荷漏洩が無視できなくなり、解像力の低下が生じてしまう。
【００８９】
保護層の膜厚は０．５〜２０μｍが適当であり、好ましくは１〜１０μｍの範囲に設定される。 また、保護層を設けた場合、必要に応じて、感光層と保護層との間に、保護層から感光層への電荷の漏洩を阻止するブロッキング層を設けることができる。このブロッキング層としては、保護層の場合と同様に公知のものを用いることができる。
【００９０】
本発明の電子写真感光体においては、電子写真装置中で発生するオゾンや酸化性ガス、あるいは、光、熱による感光体の劣化を防止する目的で、各層または最上層中に酸化防止剤、光安定剤、熱安定剤等を添加することができる。
【００９１】
酸化防止剤としては、公知のものを用いることができ、例えば、ヒンダードフェノール、ヒンダードアミン、パラフェニレンジアミン、ハイドロキノン、スピロクロマン、スピロインダノンおよびそれらの誘導体、有機硫黄化合物、有機燐化合物等があげられる。
【００９２】
光安定剤としては、公知のものを用いることができ、例えば、ベンゾフェノン、ベンゾトリアゾール、ジチオカルバメート、テトラメチルピペリジン等の誘導体、および、光励起状態をエネルギー移動あるいは電荷移動により失活し得る電子吸引性化合物または電子供与性化合物等があげられる。
【００９３】
さらに、表面磨耗の低減、転写性の向上、クリーニング性の向上等を目的として、最表面層にフッ素樹脂等の絶縁性粒子を分散させてもよい。
【００９４】
本発明の電子写真感光体を搭載する電子写真装置としては、電子写真法を用いるものであれば如何なるものでも構わないが、特にデジタル処理された画像信号に基づき露光を行う電子写真装置が好ましい。デジタル処理された画像信号に基づき露光を行う電子写真装置とは、レーザーまたはＬＥＤ等の光源を用い、２値またはパルス幅変調や強度変調を行い多値化された光により露光する電子写真装置であり、例としてＬＥＤプリンター、レーザープリンター、レーザー露光式デジタル複写機などを挙げることができる。Ｓ字型感光体のＥ_50% ／Ｅ_10% 値は５以下の値である。好ましいデジタル特性を発揮するには、Ｅ_50% ／Ｅ_10% 値が３未満の値であることが好ましい。より好ましくは２未満の値である。
【００９５】
また、現像後の感光体の初期化あるいは電子写真特性の安定化等の目的で、画像形成用の露光光源とは別に、露光用の光源を併用することができ、その光源の発光域としては、不均一電荷輸送層に吸収されるものであっても吸収されないものであっても構わないが、少なくとも電荷発生層まで光が届く方が好ましい。
【００９６】
【実施例】
以下、本発明を実施例によって具体的に説明する。しかしながら、本発明は以下の実施例に限定されるものではなく、当業者は電子写真技術の公知の知見から、以下の実施例に変更を加えることが可能である。
【００９７】
〔合成例１：反応性重合開始剤 ４，４’−アゾビス（４−シアノ吉草酸クロリド）の合成〕
塩化チオニル１４０ｍｌを氷冷し、４，４’−アゾビス（４−シアノ吉草酸）４８ｇを徐々に加えた。３０°Ｃで６時間加熱し、過剰の塩化チオニルを減圧下で留去した。残留物をクロロホルムより再結晶して２２ｇの４，４’−アゾビス（４−シアノ吉草酸クロリド）結晶を得た。
【００９８】
〔合成例２：両末端にアゾ型重合開始剤を有する電荷輸送性重合体の合成〕
３，３’−ジメチル−Ｎ，Ｎ’−ビス（ｐ，ｍ−ジメチルフェニル）−Ｎ，Ｎ’−ビス［４−（２−メトキシカルボニルエチル）フェニル］−［１，１’−ビフェニル］−４，４’−ジアミン １００ｇ、エチレングリコール ２００ｇおよびテトラブトキシチタン ５ｇを、窒素気流下で３時間加熱還流した。３，３’−ジメチル−Ｎ，Ｎ’−ビス（ｐ，ｍ−ジメチルフェニル）−Ｎ，Ｎ’−ビス［４−（２−メトキシカルボニルエチル）フェニル］−［１，１’−ビフェニル］−４，４’−ジアミンが消費されたことを確認したのち、０．５ｍｍＨｇに減圧しエチレングリコールを留去しながら２３０°Ｃに加熱し、さらに７時間反応を続けた。その後、室温まで冷却し、塩化メチレンを加え不溶分を溶解させ、アセトンから再沈殿することにより、下記の構造式（１）で表される両末端にヒドロキシ基を有する電荷輸送性重合体９０ｇを得た。得られた重合体の重量平均分子量は７．２×１０⁴ であった。
【００９９】
【化９】

【０１００】
この両末端にヒドロキシ基を有する電荷輸送性重合体４３ｇとトリエチルアミン０．５ｇをジクロロメタン１２０ｍｌに溶解し、０°Ｃに冷却した。ここに、上記合成例１で得られた４，４’−アゾビス（４−シアノ吉草酸クロリド）５．６ｇをジクロロメタン２０ｍｌに溶解した溶液を滴下した。室温で１時間反応させた後に３０°Ｃに加温し、さらに４時間反応させた。ここから溶媒を留去し、テトラヒドロフランを加えて溶解させ、メタノールに滴下し、１時間撹拌した後に濾別した。この再沈殿操作をさらに２回繰り返した。残さを乾燥して両末端にアゾ型重合開始剤を有する電荷輸送性重合体４１ｇを得た。
【０１０１】
〔合成例３：下記構造式（２）で表されるブロック共重合体の合成〕
合成例２で得られた末端にアゾ型重合開始剤を有する電荷輸送性重合体６ｇとｎ−ドデシルメタクリレート６ｇをトルエン１２０ｍｌに溶解し、窒素置換した後に６０°Ｃで６５時間加熱した。ここから溶媒を除去し、テトラヒドロフランを加えて、この溶液をメタノールに滴下し、１時間撹拌した後に濾別した。得られた固体は、目的とするブロック共重合体とポリ（ｎ−ドデシルメタクリレート）単独重合体の混合物であり、溶解度差を利用した以下の精製法により、ポリ（ｎ−ドデシルメタクリレート）単独重合体を除去し、目的のブロック共重合体を得た。すなわち、合成例２の電荷輸送性重合体は不溶であり、且つポリ（ｎ−ドデシルメタクリレート）が易溶である溶剤ｎ−ヘキサンにより、上記混合物を十分に洗浄することで、目的とするブロック共重合体６ｇを得た。得られたブロック共重合体の１Ｈ−ＮＭＲスペクトルの両ブロック固有のプロトンに対応するピークの積分比から、電荷輸送性ブロックとポリ（ｎ−ドデシルメタクリレート）からなる絶縁性ブロックの体積組成比はおよそ５５：４５と計算される。また、合成例のブロック共重合体の絶縁性ブロックと同一構造を持つポリ（ｎ−ドデシルメタクリレート）の体積抵抗率は１０¹⁴Ω・ｃｍ以上であった。
【０１０２】
【化１０】

【０１０３】
〔合成例４：下記構造式（２’）で表されるブロック共重合体の合成〕
合成例２で得られた両末端にアゾ型重合開始基を有する電荷輸送性高分子２０ｇとｔｅｒｔ−ブチルメタクリレート３５ｇをトルエン４００ｍｌに溶解し、窒素置換した後に６５°Ｃで１００時間加熱した。これをヘキサンに滴下し、１時間撹拌した後に濾別した。ここから溶媒を除去し、テトラヒドロフランを加え、この溶液をメタノールに滴下し、１時間撹拌した後に濾別した。さらにトルエン／ヘキサンによる再沈殿操作を２回繰り返した。残査を減圧乾燥して、下記構造式（２’）で示されるブロック共重合体３０ｇを得た。
【０１０４】
【化１１】

【０１０５】
得られた共重合体の１Ｈ−ＮＭＲスペクトルの各ブロックに帰属されるプロトンの積分強度比から、電荷輸送性ブロックと絶縁性ブロックの体積組成比はおよそ５２／４８と計算された。なお、本実施例のブロック共重合体の絶縁性ブロックと同一構造を持つポリ（ｔｅｒｔ−ブチルメタクリレート）の体積抵抗率は１０¹⁴Ω・ｃｍ以上であった。
【０１０６】
〔合成例５：下記構造式（３）で表されるトリブロック共重合体の合成〕
Ｎ，Ｎ’−ビス（ｐ，ｍ−ジメチルフェニル）−Ｎ，Ｎ’−ビス［ｐ−（２−メトキシカルボニルエチル）フェニル］−［３，３’−ジメチル−１，１’−ビフェニル］−４，４’−ジアミンをＮ，Ｎ−ジフェニル−Ｎ−［（３，５−ビスメトキシカルボニルエチル）フェニル］アミンに変えた以外は合成例２と同様にして、両末端にアゾ型重合開始剤を有する電荷輸送性重合体を合成した。さらに、この両末端にアゾ型重合開始剤を有する電荷輸送性重合体を用いたこと以外は合成例３と同様にして、下記構造式（３）で示されるトリブロック共重合体を合成した。
【０１０７】
トリアリールアミン構造を含む電荷輸送性プレポリマーの重量平均分子量は５．２×１０³ であった。得られた共重合体の１Ｈ−ＮＭＲスペクトルの各ブロックに帰属されるプロトンの積分強度比から、電荷輸送性ブロックと絶縁性ブロックの体積組成比はおよそ５９／４１と計算された。
【０１０８】
【化１２】

【０１０９】
（実施例１）
アルミニウム基板上に、ジルコニウムアルコキシド化合物（商品名：オルガチックスＺＣ５４０、マツモト製薬社製）１０重量部およびシラン化合物（商品名：Ａ１１１０、日本ユニカー社製）１重量部とイソプロパノール４０重量部およびブタノール２０重量部からなる溶液を浸漬コーティング法で塗布し、１５０℃において１０分間加熱乾燥し、膜厚０．１μｍの下引き層を形成した。
【０１１０】
次に、ＣｕＫαを線源とするＸ線回折スペクトルのブラッグ角度（２θ±０．２°）が、少なくとも７．４°、１６．６°、２５．５°、および２８．３°に強い回折ピークを有するクロロガリウムフタロシアニン微結晶４重量部を、塩化ビニル−酢酸ビニル共重合体（商品名：ＵＣＡＲソリューションビニル樹脂ＶＭＣＨ、ユニオンカーバイド社製）２重量部、キシレン６７重量部、および酢酸ブチル３３重量部と混合し、ガラスビーズとともにペイントシェーク法で２時間処理して分散した後、得られた塗布液を浸漬コーティング法で上記下引き層上に塗布し、１００℃において１０分間加熱乾燥し、膜厚０．５μｍの電荷発生層を形成した。
【０１１１】
次に、合成例３で示した電荷輸送ブロックと絶縁性ブロックを有するブロック共重合体２０重量部をトルエン８０重量部に溶解した塗布液を、上記電荷発生層上に浸漬コーティング法で塗布し、１１５℃において３０分間加熱乾燥させて、膜厚２０μｍの不均一電荷輸送層を形成し、図６に示す如き層構成の電子写真用感光体を作製した。
【０１１２】
このようにして得られた電子写真用感光体に対し、一部改造を加えた静電複写紙試験装置（エレクトロスタティックアナライザーＥＰＡ−８１００、川口電機製作所社製）を用いて、常温常湿（２０℃、４０％ＲＨ）の環境下、電子写真特性の評価を行った。コロナ放電電圧を調整し、感光体表面を−７５０Ｖに帯電させた後、干渉フィルターを通し７５０ｎｍに単色化したハロゲンランプ光を感光体表面上で１ｍＷ／ｍ² の光強度になるように調整し、７秒間照射したところ、図１２に示すＳ字型の光誘起電位減衰を示した。また、光照射後の電位を残量電位とした。この光誘起電位減衰曲線からＥ_50% 値が３．５ｍＪ／ｍ² 、Ｅ_50% ／Ｅ_10% 値は１．６と算出された。また、残留電位は−８０Ｖであった。
【０１１３】
この感光体の断面をルテニウム酸で染色し、透過型電子顕微鏡により観察したところ、濃い部分と薄い部分とからなる複雑に入り組んだ変調構造と思われる構造が見られた。これは、電荷輸送性の相と、電気的不活性の相が相分離しており、片方の相がルテニューム酸で染色されたものと推定される。相のピッチはおおよそ０．０８μｍであった。
【０１１４】
（比較例１）
合成例３におけるｎ−ドデシルメタクリレートの添加量を変えて、ブロック共重合体中の絶縁性ブロックであるポリ（ｎ−ドデシルメタクリレート）の含有比率を下記表５のようにした共重合体を使用し、また、不均一電荷輸送層を形成した以外は、実施例１と同様に電子写真用感光体を作製した。
【０１１５】
この感光体の断面をルテニウム酸で染色し、透過型電子顕微鏡により観察したところ、濃い部分が電荷輸送性の相、薄い部分が電気的不活性の相である海島構造と思われる構造が見られた。
【０１１６】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表５に示す。
【０１１７】
（比較例２）
合成例３におけるｎ−ドデシルメタクリレートの添加量を変えて、ブロック共重合体中の絶縁性ブロックであるポリ（ｎ−ドデシルメタクリレート）の含有比率を下記表５のようにした共重合体を使用し、また、不均一電荷輸送層を形成した以外は、実施例１と同様に電子写真用感光体を作製した。
【０１１８】
この感光体の断面を実施例１と同様にして観察したところ、比較例１とは濃淡が逆になった海島構造と思われる構造が見られた。
【０１１９】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表５に示す。
【０１２０】
（比較例３）
合成例３における絶縁ブロックであるｎ−ドデシルメタクリレートの添加量を０とした以外は、実施例１と同様に電子写真用感光体を作製した。
【０１２１】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表５に示す。
【０１２２】
【表５】

【０１２３】
表５より明らかなように、本発明の変調構造の不均一電荷輸送層を有する実施例１の感光体はＳ字特性に優れ、残留電位も好適であった。一方、海島構造の不均一電荷輸送層を有する比較例１、２の感光体はＳ字特性又は残留電位のいずれかが劣っていた。また、絶縁ブロックを含まない比較例３の感光体はＪ字型の光誘起電位減衰特性であった。
【０１２４】
（実施例２）
不均一電荷輸送層の膜厚を５μｍとした以外は実施例１と同様にして下引き層を設けた基板上に電荷活性層と不均一電荷輸送層とを積層した。
【０１２５】
さらに、高分子電荷輸送材料である分子量８万の下記構造式（４）で示される繰り返し単位よりなる化合物２０重量部をトルエン８０重量部に溶解した塗布液をアプリケータにて塗布し、１１５℃において１時間加熱乾燥させて、膜厚１５μｍの均一電荷輸送層を形成し、図７に示す如き層構成を有する電子写真用感光体を作製した。
【０１２６】
【化１３】

【０１２７】
このようにして得られた電子写真用感光体を、実施例１と同様にして評価したところ、その光誘起電位減衰特性はＥ_50% 値が３．３ｍＪ／ｍ² 、Ｅ_50% ／Ｅ_10% 値は１．５のＳ字型であった。また、残留電位は−４０Ｖであった。
【０１２８】
この感光体の断面を実施例１と同様に観察したところ、濃い部分と薄い部分とからなる複雑に入り組んだ変調構造と思われる構造が見られた。相のピッチはおおよそ０．０８μｍであった。
【０１２９】
（実施例３）
合成例３の共重合体の代わりに合成例４の共重合体を用いて不均一電荷輸送層を形成した以外は実施例１と同様に電子写真感光体を作製した。
【０１３０】
このようにして得られた電子写真用感光体を、実施例１と同様にして評価したところ、その光誘起電位減衰特性はＥ_50% 値が３．９ｍＪ／ｍ² 、Ｅ_50% ／Ｅ_10% 値が１．８のＳ字型であった。また、残留電位は−５０Ｖであった。評価結果を下記表２に示す。
【０１３１】
この感光体の断面を実施例１と同様に観察したところ、濃い部分と薄い部分とからなる複雑に入り組んだ変調構造と思われる構造が見られた。相のピッチはおおよそ０．０８μｍであった。
【０１３２】
（比較例４）
合成例４のｔｅｒｔ−ブチルメタクリレートの添加量を変えて、ブロック共重合体中の絶縁性ブロックであるポリ（ｔｅｒｔ−ブチルメタクリレート）の含有比率を表６のようにした共重合体を使用し、また、不均一電荷輸送層を形成した以外は、実施例３と同様に電子写真用感光体を作製した。
【０１３３】
この感光体の断面を実施例１と同様にして観察したところ、濃い部分が電荷輸送性の相、薄い部分が電気的不活性の相である海島構造と思われる構造が見られた。
【０１３４】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表６に示す。
【０１３５】
（比較例５）
合成例４におけるｔｅｒｔ−ブチルメタクリレートの添加量を変えて、ブロック共重合体中の絶縁性ブロックであるポリ（ｔｅｒｔ−ブチルメタクリレート）の含有比率を下記表５のようにした共重合体を使用し、また、不均一電荷輸送層を形成した以外は、実施例１と同様に電子写真用感光体を作製した。
【０１３６】
この感光体の断面を実施例１と同様にして観察したところ、比較例３とは濃淡が逆になった海島構造と思われる構造が見られた。
【０１３７】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表６に示す。
【０１３８】
（比較例６）
合成例４における絶縁ブロックであるｔｅｒｔ−ブチルメタクリレートの添加量を０とした以外は、実施例１と同様に電子写真用感光体を作製した。
【０１３９】
このようにして得られた電子写真用感光体の電子写真特性と不均一電荷輸送層断面を実施例１と同様に評価した結果を表６に示す。
【０１４０】
【表６】

【０１４１】
（実施例４）
合成例１の共重合体の代わりに合成例５の共重合体を用いて不均一電荷輸送層を形成した以外は実施例２と同様に電子写真感光体を作製した。
【０１４２】
このようにして得られた電子写真用感光体を、実施例１と同様にして評価したところ、その光誘起電位減衰特性はＥ_50% 値が４．２ｍＪ／ｍ² 、Ｅ_50% ／Ｅ_10% 値が２．２のＳ字型であった。また、残留電位は−７０Ｖであった。
【０１４３】
この感光体の断面を実施例１と同様に観察したところ、濃い部分と薄い部分とからなる複雑に入り組んだ変調構造と思われる構造が見られた。相のピッチはおおよそ０．０５μｍであった。
【０１４４】
（実施例５）
アルミニウム基板の代わりにアルミニウムドラムを使用した以外は、実施例２と同様にして電子写真用感光体を作製し、レーザープリンター（Ｌａｓｅｒ Ｐｒｅｓｓ ４１０５、富士ゼロックス社製）に搭載し、印字試験を行った。この際、最適な露光量を得るため、レーザー光の光路にＮＤフィルターを入れた。このレーザプリンターの概略構成図を図１３に示す。
【０１４５】
感光体ドラム１１の周りに前露光用光源（赤色ＬＥＤ）１２、帯電用スコロトロン１３、露光用レーザー光学系１４、現像器１５、転写用コロトロン１６およびクリーニングブレード１７がプロセスの順序に順次配置されている。露光用レーザー光学系１４は、発信波長７８０ｎｍの露光用レーザーダイオードを備えており、デジタル処理された画像信号に基づき発光する。発光したレーザー光１４ａはポリゴンミラーと複数のレンズ、ミラーによりスキャンされながら感光体上を露光するように構成されている。なお、１８は用紙を示す。
【０１４６】
（比較例７）
アルミニウム基板の代わりにアルミニムドラムを使用した以外は、比較例３と同様にして電子写真用感光体を作製し、実施例５と同様に印字試験を行った。
【０１４７】
実施例５と比較例７で得られた印字の品質を目視にて比べたところ、実施例５の方が細線の再現性等の点で、印字品質が優れていた。
【０１４８】
【発明の効果】
本発明の電子写真感光体は、Ｓ字型光誘起電位減衰特性を示す感光体であって、電荷輸送層中に電荷輸送性の相と電気的不活性の相よりなる変調構造をとる相分離状態にある電荷輸送性ブロックと絶縁性ブロックよりなるブロック共重合体またはグラフト共重合体を含むことによって、残留電位の増加、光感度の低下、電荷輸送速度の低下などの電荷輸送路が分断されることに起因する障害がなく、良好なＳ字性を有する電子写真感光体を提供できるという卓越した効果を奏する。
【０１４９】
また、本発明のＳ字型電子写真用感光体を使用した電子写真装置は、デジタル処理された画像信号に基づき露光を行うことにより、印字品質、および画質の優れた印字画像を得ることができる。
【図面の簡単な説明】
【図１】 Ｊ字型電子写真感光体における露光量と表面電位の関係を示すグラフである。
【図２】 Ｓ字型電子写真感光体における露光量と表面電位の関係を示すグラフである。
【図３】 電荷輸送性の相と電気的不活性の相よりなる変調構造を示す２次元的な模式図である。
【図４】 支持体上に電荷発生層、不均一電荷輸送層を順次設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図５】 支持体上に電荷発生層、不均一電荷輸送層と均一電荷輸送層とからなる電荷輸送層を順次設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図６】 支持体と電荷発生層との間に下引き層を設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図７】 支持体上に電荷発生層、下引き層、不均一電荷輸送層と均一電荷輸送層とからなる電荷輸送層を順次設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図８】 支持体上に不均一電荷輸送層、電荷発生層を順次設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図９】 支持体上に不均一電荷輸送層と均一電荷輸送層とからなる電荷輸送層、電荷発生層を順次設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図１０】 支持体と不均一電荷輸送層との間に下引き層を設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図１１】 支持体と不均一電荷輸送層と均一電荷輸送層とからなる電荷輸送層の間に下引き層を設けた本発明の電子写真用感光体の例を示す模式的断面図である。
【図１２】 実施例１の光誘起電位減衰特性を示すグラフである。
【図１３】 実施例に用いたデジタル処理された画像信号に基づき露光を行う本発明の電子写真装置の概略の構成図である。
【符号の説明】
１…導電性支持体
２…電荷発生層
３…不均一電荷輸送層
４…均一電荷輸送層
５…電荷輸送層
６…下引き層
１１…感光体ドラム
１２…前露光用光源
１３…帯電用スコロトロン
１４…露光用レーザー光学系
１５…現像器
１６…転写用コロトロン
１７…クリーニングブレード
１８…用紙[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an electrophotographic photoreceptor including a conductive substrate, a charge generation layer, and a charge transport layer, and more particularly to an electrophotographic photoreceptor suitable for digital electrophotography. The present invention also relates to a digital electrophotographic apparatus using these electrophotographic photosensitive members.
[0002]
[Prior art]
  In recent years, the electrophotographic technology plays an important role in the fields of copiers, printers, facsimiles and the like because it has advantages such as high speed and high print quality.
[0003]
  As electrophotographic photoreceptors used in electrophotographic technology, those using inorganic photoconductive materials such as selenium, selenium-tellurium alloy, selenium-arsenic alloy have been widely known. On the other hand, research on electrophotographic photoconductors using organic photoconductive materials, which have advantages in terms of cost, manufacturability, disposal, etc., compared to these inorganic photoconductors, has become active, and now inorganic photoconductors are active. It has surpassed the body.
[0004]
In particular, the development of a function-separated stack structure that separates photocharge generation and charge transport, which are the elementary processes of photoelectric conduction, into separate layers increases the freedom of material selection and significantly improves performance. At present, this functionally separated organic photoreceptor is the mainstream of electrophotographic photoreceptors. As a charge generation layer for a functionally separated laminated organic photoreceptor, a quinone pigment, a perylene pigment, an azo pigment, a phthalocyanine pigment, a pigment having a charge generation ability such as selenium is directly formed by vapor deposition or the like. Alternatively, those dispersed in a binder resin at a high concentration are in practical use. On the other hand, as the charge transport layer, a low molecular weight compound having charge transport ability such as a hydrazone compound, a benzidine compound, an amine compound, or a stilbene compound is molecularly dispersed in an insulating resin.
[0005]
  Conventionally, as a photoconductor used in an analog electrophotographic copying machine that optically forms an image on a photoconductor and exposes it, in order to improve the reproducibility of halftone by density gradation, A photosensitive member having photoinduced potential attenuation characteristics as shown in FIG. 1, that is, a photosensitive member (hereinafter referred to as “J-shaped photosensitive member”) that causes a potential attenuation in proportion to the exposure amount is required. The above inorganic photoreceptors and function-separated stacked organic photoreceptors all exhibit photoinduced potential decay characteristics that fall within this category. However, in the digital electrophotographic apparatus that has been actively researched and developed in response to the recent demands for higher image quality, higher added value, and networking, in general, the area scale that produces gradation at the area ratio of dots, etc. The so-called S-shaped photo-induced potential attenuation characteristic in which the potential is not attenuated until a certain exposure amount is reached, but a steep potential attenuation occurs when the exposure amount is exceeded, as shown in FIG. It is desirable to use a photoconductor having the following (hereinafter referred to as “S-shaped photoconductor”) from the viewpoint of increasing the sharpness of the pixel.
[0006]
  The S-shaped photoinduced potential decay characteristic is a well-known phenomenon in a single-layer photoreceptor in which an inorganic pigment such as ZnO or an organic pigment such as phthalocyanine is dispersed in a resin [for example, R.R. M.M. Schaffert: “Electrophotography”, Focal Press, p. 344 (1975), J. MoI. W. Weigl, J .; Mamino, G.M. L. Whitaker, R.A. W. Radler, J .; F. Byrne: “Current Problems in Electrophotography”, Walter de Gruter, p. 287 (1972)]. In particular, many single-layer photoreceptors for laser exposure have been proposed in which a phthalocyanine pigment having photosensitivity in the near-infrared region, which is the transmission wavelength of semiconductor lasers that are widely used at present, is dispersed in a resin [for example, Nguyen Chan・ Ke, Aizawa; Journal of the Chemical Society of Japan, p. 393 (1986), JP-A-1-169454, 2-207258, 3-31847, 5-313387]. However, although these single layer type photoreceptors need to have both charge generation and charge transport functions with a single material, there are rare materials that have excellent performance in both functions, and those that can withstand practical use are still not available. Not obtained. In particular, pigment particles generally have a large number of trap levels, and thus have disadvantages such as low charge transport ability and residual charge, and are not suitable for carrying charge transport. The only exceptional practical example is a ZnO resin-dispersed single-layer photoconductor, which is used as a master plate for offset printing that utilizes the hydrophilicity of ZnO and forms a plate with an area gradation method based on the presence or absence of hydrophobic toner. [For example, Kawamura “Basics and Applications of Electrophotographic Technology”, edited by the Electrophotographic Society, Corona, p. 424 (1988)]. However, this is also a successful example because it was used as a master plate with low demands on high speed and printing durability, and as a photoconductor used in a copying machine, printer, etc., which is a field of application of the present invention, it is at a level that can withstand practical use. Absent. From these viewpoints, it is desired to introduce a function-separated layer structure in the S-shaped photoconductor in order to increase the degree of freedom of material selection and thus improve the overall photoconductor characteristics.
[0007]
  D. M.M. Pai and the like include at least two charge transport regions and one electrically inactive region as a charge transport layer in a laminated type photoreceptor composed of a charge generation layer and a charge transport layer, and the charge transport regions are in contact with each other and rotated. It has been reported that S-shaped photoinduced potential decay characteristics can be realized in combination with an arbitrary charge generation layer by using a non-uniform charge transport layer formed in the shape of a charge transport path [JP-A-6-83077]. Publication (U.S. Pat. No. 5,306,586)].
[0008]
  In this report, as a method for producing a heterogeneous charge transport layer in which charge transport regions are in contact with each other to form a spiral charge transport path, inorganic or organic particles or microcrystals capable of transporting charges are insulated. A method for producing a heterogeneous charge transport layer immersed in a coalescence, or by producing a charge transport layer from a solid solution of charge transport molecules in a polymer binder and crystallizing one of the phases, for example. A method and a method for producing a charge transport block from a block copolymer surrounded by a non-transport block have been proposed.
[0009]
  However, since inorganic or organic particles or microcrystals capable of charge transport generally have many trap levels, the heterogeneous particles or microcrystals capable of charge transport are immersed in an insulating polymer. Such a method for producing a charge transporting layer has drawbacks such as low charge transporting ability and charge remaining. In addition, in a method for producing a charge transport layer from a solid solution of charge transport molecules in a polymer binder and, for example, by crystallizing one of the phases, a compound that satisfies the above conditions is rare, so that it can withstand practical use. This is a major obstacle in designing a photoconductor that can be used. Furthermore, although the method for producing the charge transport block from the block copolymer surrounded by the non-transport block does not have the above-described problems, the charge transport speed is improved by securing the charge transport path, the residual potential is decreased, It is difficult to ensure S-characteristics such as repetitive stability, and if the charge transport block is increased and the charge transport path is secured, the S-characteristics deteriorates, the charge transport block is reduced and the S-characteristic is improved. Attempts to divide the charge transport path result in a decrease in charge transport speed, an increase in residual potential, a deterioration in repeated stability, and the like, and it has been difficult to obtain a good photoconductor having the above characteristics compatible.
[0010]
  In response to such a problem, the present inventors previously proposed a photoconductor including, in a charge transport layer, a polymer compound in a phase separated state composed of an electrically inactive phase having a modulation structure and a charge transport phase. (Japanese Patent Application No. 8-158520). In the heterogeneous charge transport layer in the phase separation state composed of the electrically inactive phase having the modulation structure and the charge transporting phase, the size of the phase in the phase separation state is hardly affected by the manufacturing conditions. And so on, for further optimization.
[0011]
[Problems to be solved by the invention]
  The present invention has been made in view of the above-described circumstances in the prior art, and an object of the present invention is to provide a novel S-shaped photoconductor structure that can overcome the above-described problems. is there.
[0012]
  That is, an object of the present invention is to provide a high-performance S-shaped photoreceptor excellent in electrophotographic characteristics in an electrophotographic photoreceptor including at least a conductive substrate, a charge generation layer, and a charge transport layer. Another object of the present invention is to provide a digital electrophotographic apparatus using a high-performance S-shaped photoreceptor.
[0013]
[Means for Solving the Problems]
  In the electrophotographic photosensitive member in which a charge generation layer and a charge transport layer are provided on a conductive substrate, the above problem is a phase having a modulation structure composed of a charge transporting phase and an electrically inactive phase in the charge transporting layer. In a separated state, including a block copolymer or graft copolymer comprising a charge transporting block and an insulating block, and the exposure amount required for 50% potential attenuation is less than 5 times the exposure amount required for 10% potential attenuation This is solved by an electrophotographic photosensitive member.
[0014]
  The modulation structure is a structure that is generated by separating a homogeneous phase into two phases by spinodal decomposition. However, in the present invention, one of the two phases in the phase-separated state is isolated like a sea-island structure. It refers to the state that exists in a complicated way. FIG. 3 shows a two-dimensional schematic diagram of the modulation structure.
[0015]
When the charge transporting phase and the electrically inactive phase have a sea-island structure in which the charge transporting portion is an island and the electrically inactive portion is the sea, the charge transporting portion is an island and exists independently. Transport is hindered, which tends to cause an increase in residual potential, a decrease in photosensitivity, a decrease in charge transport speed, and the like, making control difficult. On the other hand, when the electrically inactive portion becomes an island and the charge transport portion becomes the sea, a charge transport path is secured, but it becomes difficult to form a spatial trap for temporarily stopping the charge, and the S-shape is deteriorated.
[0016]
  A spatial trap is a portion where the charge transporting portion is convex with respect to the direction in which the charge is to be transported, and acts as a trap only when an electric field is applied. The presence of many spatial traps is the key to creating an S-shaped PIDC. In the case of a modulation structure consisting of a charge transporting part and an electrically inactive part, the charge transporting part is a continuous phase without being isolated, so that charge transport can be carried out without breaking the charge transporting path. In addition, since the charge transporting portion and the electrically inactive portion are mixed in a complicated shape, there are many portions that are convex with respect to the direction in which the charge should be transported that can act as a spatial trap. .
[0017]
Thus, in the case of a modulation structure consisting of a charge transporting portion and an electrically inactive portion, the securing of the charge transporting path and the securing of the spatial trap are compatible, resulting in an increase in residual potential, a decrease in photosensitivity, charge An electrophotographic photosensitive member having good sigmoidal properties is obtained without any obstruction caused by the charge transport path being divided, such as a decrease in transport speed.
[0018]
  According to the present invention, the charge transport layer is in a phase-separated state consisting of a charge transporting phase and an electrically inactive phase, and has a modulation structure. This phase separation state is preferably formed by a block copolymer or a graft copolymer comprising a charge transporting block and an insulating block.
[0019]
  Here, it is known that the scale of phase separation in the block copolymer and graft copolymer is generally the same dimension as the average length of each block and is approximately proportional to the molecular weight. Therefore, not only can the phase size be controlled by adjusting the molecular weight, but the size of this phase does not vary greatly depending on the manufacturing conditions, and a photoreceptor having stable characteristics can be provided.
[0020]
  The electrical inactivity referred to here means that the transport energy level is far away from the transport energy level of the main transport charge, and the transport charge is not substantially injected at a normal electric field strength. It means that the electric charge is in a substantially electrically insulated state.
[0021]
  Further, the charge transport layer is in a phase separation state having a modulation structure composed of a charge transporting phase and an electrically inactive phase, and more than a block copolymer or graft copolymer composed of a charge transporting block and an insulating block. By providing a charge transport layer having different characteristics of this non-uniform charge transport layer and a uniform charge transport layer including a charge transport matrix, charge transport can be made smooth and charge transport speed can be increased, Effects such as potential reduction can also be achieved.
[0022]
  In addition, charge transport and a layer made of a block copolymer or graft copolymer made of a charge transporting block and an insulating block in a phase-separated state having a modulation structure consisting of a charge transporting phase and an electrically inactive phase. Since the layer made of the chargeable matrix is laminated in this order, the layer made of the charge transportable matrix becomes the outermost layer, so that the wear resistance, ozone resistance, NO resistance_XAn electrophotographic photoreceptor excellent in properties and the like can be provided.
[0023]
  Furthermore, by using the electrophotographic photosensitive member, it is possible to provide an electrophotographic apparatus having an exposure unit that performs exposure based on a digitally processed image signal with good image quality and stability.
[0024]
  The S-shaped scale of the photoinduced potential decay curve includes, for example, the exposure amount E required to attenuate the charging potential by 50%._50%Exposure amount E required to attenuate 10%_Ten%Ratio E_50%/ E_Ten%Can be used. When the potential decay is proportional to the exposure amount in an ideal J-shaped photoconductor, E_50%/ E_Ten%The value is 5. In a general J-shaped photoconductor, the charge generation efficiency and / or the charge transport ability decreases as the electric field strength decreases._50%/ E_Ten%Indicates a value exceeding 5. On the other hand, in the S-shaped ultimate, a step-like photo-induced potential decay curve in which the potential is not attenuated at all up to a certain exposure amount, and the potential is attenuated at once to the residual potential level._50%/ E_Ten%The value is 1. Therefore, S-shaped is E_50%/ E_Ten%Values are defined as being in the range of 1-5.
[0025]
  In addition, a layer containing a block copolymer or a graft copolymer having a charge transporting block and an insulating block in a phase separation state having a modulation structure consisting of a charge transporting phase and an electrically inactive phase. Is abbreviated as “non-uniform charge transport layer”, and a layer containing a charge transport matrix is abbreviated as “uniform charge transport layer”.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, each layer constituting the electrophotographic photosensitive member of the present invention will be described in more detail.
[0027]
  4 and 5 are schematic views showing a cross section of the electrophotographic photoreceptor of the present invention. In FIG. 4, a charge generation layer 2 responsible for photocharge generation is provided on a conductive support 1, and a non-uniform charge transport layer 3 is provided thereon. In FIG. 5, a charge generation layer 2 responsible for photocharge generation is provided on a conductive support 1, a non-uniform charge transport layer 3 for S-shape is provided thereon, and a smooth surface is further provided thereon. A uniform charge transport layer 4 for charge transport is provided, and the charge transport layer 5 is formed by the non-uniform charge transport layer 3 and the uniform charge transport layer 4. In FIGS. 6 and 7, an undercoat layer 6 is further provided between the conductive support 3 and the charge generation layer 1.
[0028]
  8 to 11 are schematic views showing a cross section of an electrophotographic photoreceptor according to another embodiment of the present invention. In FIG. 8, the non-uniform charge transport layer 3 is provided on the conductive support 1, and the charge generation layer 2 is provided thereon. In FIG. 9, a uniform charge transport layer 4 is provided on a conductive support 1, a non-uniform charge transport layer 3 is provided thereon, and a charge transport layer 5 is formed by both 4, 3, A charge generation layer 2 is provided thereon. In FIGS. 10 and 11, an undercoat layer 6 is further provided between the conductive support 1 and the uniform charge transport layer 4.
[0029]
  These electrophotographic photoreceptors may further include a protective layer and / or a diffuse reflection layer, if desired.
[0030]
  As described above, if the moving distance until the charge generated in the charge generation layer temporarily stops in the non-uniform charge transport layer is sufficiently small with respect to the total film thickness of the photosensitive layer, the potential attenuation during that period can be ignored. Thus, a more ideal S-shaped photoconductor is obtained. That is, the S-shaped property is better when the charge generation layer and the non-uniform charge transport layer for S-shape are close to each other. However, an intermediate layer may be provided between the charge generation layer and the non-uniform charge transport layer for the purpose of charge injection and assisting the generation of charge. It is also possible to insert a uniform charge transport layer between the charge generation layer and the non-uniform charge transport layer in order to obtain the desired incomplete S-shape.
[0031]
  In addition to the photoelectric function, the surface layer has charge retention during charging, ozone generated from charging members, etc., NO_XAnd the like, and resistance to abrasion caused by paper, a cleaning member, and the like are required at the same time. The stacked type of only the charge generation layer and the charge transport layer having a non-uniform structure as shown in FIG. 4 has the simplest configuration, but the non-uniform charge transport layer has the above-mentioned durability function, charge transport property and S A characterizing function is required, and it is difficult to satisfy all these functions at the same time, and the range of selection of materials is narrowed. In the case of the electrophotographic photosensitive member having the structure as shown in FIGS. 5 to 6, since the uniform charge transport layer is on the surface side, the S-shape is applied to the non-uniform charge transport layer inside the photosensitive layer. The above functions required for the layer can be designed separately from charge generation and S-shape, and the degree of design freedom is further increased.
[0032]
  These electrophotographic photoreceptors may further include a protective layer and / or a diffuse reflection layer, if desired.
[0033]
  The conductive support may be opaque or substantially transparent, and the materials are metals such as aluminum, nickel, chromium, stainless steel, and aluminum, titanium, nickel, chromium, stainless steel, gold, Examples thereof include a plastic film provided with a thin film such as vanadium, tin oxide, indium oxide and ITO, glass or the like, paper coated with or impregnated with a conductivity imparting agent, a plastic film and glass. These conductive supports are used in an appropriate shape such as a drum shape, a sheet shape, and a plate shape, but are not limited thereto. Furthermore, if necessary, various treatments can be performed on the surface of the conductive support within a range that does not affect the image quality. For example, surface oxidation treatment, chemical treatment, coloring treatment, or irregular reflection treatment such as graining can be performed.
[0034]
  One or more undercoat layers may be provided between the conductive support and the photoconductive layer. This undercoat layer functions as an adhesive layer that prevents the injection of charges from the conductive support to the photosensitive layer when the photosensitive layer is charged, and also holds the photosensitive layer integrally bonded to the conductive support. In some cases, it exhibits an antireflection effect of light from the conductive support.
[0035]
  As the undercoat layer, known materials can be used. For example, polyethylene resin, acrylic resin, methacrylic resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polycarbonate resin, polyurethane resin, polyimide resin, Vinylidene chloride resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol resin, water-soluble polyester resin, alcohol-soluble nylon resin, nitrocellulose, casein, gelatin, polyglutamic acid, starch, starch acetate, amino starch, poly Resins such as acrylic acid and polyacrylamide and their copolymers, or curable metal organic compounds such as zirconium alkoxide compounds, titanium alkoxide compounds, and silane coupling agents can be used alone. It can be used in combination of two or more. A material that can transport only a charge having the same polarity as the charged polarity can also be used.
[0036]
  Moreover, 0.01-10 micrometers is suitable for the film thickness of an undercoat layer, Preferably it is the range of 0.05-5 micrometers. As a coating method, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method can be used.
[0037]
  As the charge generation material in the charge generation layer of the electrophotographic photoreceptor of the present invention, a known material used as a charge generation layer in a conventional J-shaped laminated photoreceptor can be used. For example, amorphous selenium, selenium-tellurium alloy, selenium-arsenic alloy, other selenium compounds and selenium alloys, inorganic photoconductive materials such as zinc oxide, titanium oxide, α-Si, α-SiC, phthalocyanine-based, squalium Organic pigments and dyes such as, anthanthrone, perylene, azo, anthraquinone, pyrene, pyrylium salts and thiapyrylium salts can be used, but are not limited thereto. These organic pigments and dyes can be used alone or in combination of two or more.
[0038]
  Phthalocyanine compounds have excellent photosensitivity at 600 to 850 nm, which is the emission wavelength of LEDs and laser diodes that are currently preferred and used as light sources in digital electrophotographic devices. Particularly preferred. Specifically, there are metal-free phthalocyanines, metal phthalocyanines, and dimers thereof, and the central metals of metal phthalocyanines include Cu, Ni, Zn, Co, Fe, V, Si, Al, Sn, Ge, Ti, In Ga, Mg, Pb and the like, and oxides, hydroxides, halides, alkylates, alkoxylates and the like of these central metals can also be used. Specific examples include metal-free phthalocyanine, titanyl phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, 1,2-di (oxogallium phthalocyaninyl) ethane, vanadyl phthalocyanine, chloroindium phthalocyanine, dichlorotin phthalocyanine, and copper phthalocyanine. be able to. Moreover, what contains arbitrary substituents in these phthalocyanine rings can also be used. Furthermore, those in which any carbon atom in these phthalocyanine rings is substituted with a nitrogen atom are also effective. As the form of these phthalocyanine compounds, amorphous or all known crystalline polymorphs can be used. These phthalocyanine compounds can be used alone or as a mixture of two or more thereof.
[0039]
  Among these phthalocyanine compounds, titanyl phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, 1,2-di (oxogallium phthalocyaninyl) ethane, metal-free phthalocyanine, vanadyl phthalocyanine, and dichlorotin phthalocyanine are particularly excellent light. It has sensitivity and is particularly preferable as a charge generation material. Among these, particularly preferred crystal systems are X-type for metal-free phthalocyanine and α-type for vanadyl phthalocyanine. In the titanyl phthalocyanine crystal, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using CuKα as a radiation source is at least 9.2 °, 13.1 °, 20.7 °, 26.2 °, And having strong diffraction peaks at 27.1 °, those having strong diffraction peaks at least 7.6 °, 12.3 °, 16.3 °, 25.3 ° and 28.7 °, and at least 9 Examples thereof include hydrates having strong diffraction peaks at .5 °, 11.7 °, 15.0 °, 23.5 °, and 27.3 °. In a chlorogallium phthalocyanine crystal, a Bragg angle (2θ ± 0.2 °) of an X-ray diffraction spectrum using CuKα as a radiation source has a strong diffraction peak at least 13.4 ° and 27.0 °, and And those having strong diffraction peaks at least at 7.4 °, 16.6 °, 25.5 ° and 28.3 °. In the hydroxygallium phthalocyanine crystal, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using CuKα as a radiation source is at least 7.5 °, 9.9 °, 12.5 °, 16.3 °. , 18.6 °, 25.1 ° and 28.3 ° having strong diffraction peaks. In the 1,2-di (oxogallium phthalocyaninyl) ethane crystal, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using CuKα as the radiation source is at least 6.9 °, 13.0 °. , 15.9 °, 25.6 °, and 26.1 °, which have strong diffraction peaks. In the dichlorotin phthalocyanine crystal, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using CuKα as a radiation source has strong diffraction peaks at least 8.3 °, 13.7 ° and 28.3 °. Have strong diffraction peaks at least 8.5 °, 11.2 °, 14.5 ° and 27.2 °, and at least 9.2 °, 12.2 °, 13.4 °, 14 Those having strong diffraction peaks at .6 °, 17.0 ° and 25.3 ° can be mentioned.
[0040]
  In addition, most phthalocyanine compounds have the property of a p-type semiconductor having holes as the main transport charge, whereas dichlorotin phthalocyanine has the property of being an n-type semiconductor having electrons as the main transport charge. ing. Therefore, an S-shaped photoreceptor comprising dichlorotin phthalocyanine as a charge generation material and sequentially laminating a charge generation layer and a charge transport layer on a conductive substrate is highly sensitive when used with a negative charge. Injecting positive charges from the conductive substrate is suppressed, and the electrophotographic characteristics are excellent with low dark decay and high chargeability.
[0041]
  The charge generation layer is formed by layering the charge generation material on a conductive support by a vacuum vapor deposition method, or by dispersing or dissolving the charge generation material in a binder resin and coating the conductive support on the conductive support. It can be produced by drying.
[0042]
  Here, as the binder resin used for the charge generation layer, polyvinyl butyral resin, polyvinyl formal resin, partially modified polyvinyl acetal resin, polycarbonate resin, polyester resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, chloride A vinyl-vinyl acetate copolymer, a silicone resin, a phenol resin, a poly-N-vinylcarbazole resin, and the like can be mentioned, but the invention is not limited to these. These binder resins can be block, random or alternating copolymers. These binder resins can be used alone or in combination of two or more.
[0043]
  The blending ratio (volume ratio) between the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10. More preferably, it is set in the range of 3: 1 to 1: 3. When the blending ratio of the charge generating material to the binder resin is larger than the above range, dark decay is increased and mechanical properties are deteriorated. On the other hand, when the amount is less than the above range, problems such as a decrease in photosensitivity and an increase in residual potential occur. In general, the thickness of the charge generation layer used in the present invention is suitably 0.05 to 5 μm, and preferably set in the range of 0.1 to 2.0 μm. As a coating method, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method can be used.
[0044]
  The heterogeneous charge transport layer is in a phase-separated state having a modulation structure composed of a charge transport phase and an electrically inactive phase, and is a block copolymer or graft copolymer composed of a charge transport block and an insulating block The charge transporting phase is formed by a charge transporting block, and the electrically inactive phase is formed by an insulating block.
[0045]
  As a block copolymer or graft copolymer comprising a charge transporting block and an insulating block as a material for forming a heterogeneous charge transporting layer having a modulation structure, a block comprising a known charge transporting block and an insulating block Copolymers or graft copolymers can be used.
[0046]
Examples of usable block or graft copolymers include multiblock copolymers prepared by copolymerization of vinyl carbazole and dodecyl methacrylate described in US Pat. No. 3,994,994. Others described in U.S. Pat. Nos. 4,618,551, 4,806,443, 4,818,650, 4,935,487, and 4,956,440 Also, low molecular weight polysiloxanes, aliphatic and aromatic polyesters, block copolymers containing polyurethane units and produced by condensation can be used.
[0047]
Further, when the charge transporting block is a copolymer containing a triarylamine structure as a repeating unit, it is preferable because it has a high charge transporting ability, and the triarylamine structure is preferably represented by the following general formula (1). Or the case where at least 1 sort (s) or more of the structure represented by (2) is contained as a repeating unit is especially preferable.
[0048]
[Formula 4]

[0049]
  (Wherein Ar₁And Ar₂Each independently represents a substituted or unsubstituted aryl group, and X₁Represents a divalent hydrocarbon group or heteroatom-containing hydrocarbon group having an aromatic ring structure, and X₂And X_ThreeEach independently represents a substituted or unsubstituted arylene group;₁Represents a divalent hydrocarbon group or heteroatom-containing hydrocarbon group which may contain a branched or ring structure, and m and n each represents an integer selected from 0 or 1. )
[0050]
[Chemical formula 5]

[0051]
  (Wherein Ar_ThreeAnd Ar_FourEach independently represents a substituted or unsubstituted aryl group, and L₂Represents a trivalent hydrocarbon group or heteroatom-containing hydrocarbon group having an aromatic ring structure. )
  In the general formula (1), Ar₁And Ar₂Are independently selected from a substituted or unsubstituted aryl group, and specific examples of the aryl group include a phenyl group, a biphenyl group, a naphthyl group, and a pyrenyl group. Examples of the substituent include a methyl group, an ethyl group, a methoxy group, and a halogen atom.
  X₁Is selected from a divalent hydrocarbon group having an aromatic ring structure or a heteroatom-containing hydrocarbon group. Specific examples include a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, a methylene diphenyl group, a cyclohexylidene diphenyl group, an oxydiphenyl group, a thiodiphenyl group, and the like, and methyl-substituted, ethyl-substituted, methoxy-substituted thereof. And substituted or unsubstituted biphenylene groups are particularly preferred from the viewpoint of charge transportability.
[0052]
  X₂And X_ThreeAre each independently selected from a substituted or unsubstituted arylene group, specifically, a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, etc., and their methyl-substituted, ethyl-substituted, methoxy-substituted, or And halogen-substituted products.
[0053]
  L₁Is selected from a divalent hydrocarbon group or a heteroatom-containing hydrocarbon group which may contain a branched or ring structure, and may be any one as long as it exhibits at least one of the above-mentioned preferable characteristics. And those having a linking group selected from a carbonate bond, a siloxane bond and the like and having 20 or less carbon atoms. Specific examples thereof include the following.
[0054]
[Chemical 6]

[0055]
  In the general formula (2), Ar_ThreeAnd Ar_FourAre independently selected from a substituted or unsubstituted aryl group, and specific examples of the aryl group include a phenyl group, a biphenyl group, a naphthyl group, and a pyrenyl group. Moreover, as a substituent, a C1-C12 alkyl group or an alkoxy group, a diarylamino group, a halogen atom, etc. are mentioned.
[0056]
  L₂Is selected from a trivalent hydrocarbon group having an aromatic ring structure or a heteroatom-containing hydrocarbon group, and may be any as long as it exhibits at least one of the above-mentioned preferred characteristics, but preferably has 20 or less carbon atoms. . Specific examples thereof include the following.
[0057]
[Chemical 7]

[0058]
  Any insulating block may be used to form the copolymer of the present invention. Specific examples of the insulating block include polyvinyl acetal, polyalkyl methacrylate, polyalkyl acrylate, polyvinyl chloride, polystyrene, polyvinyl acetate, polyalkyl vinyl ether, polycarbonate, polyester, polysiloxane, and the like, graft, random Or an alternating copolymer etc. are mentioned. However, in terms of mechanical strength, flexibility, visible and infrared light transparency, chemical stability, insulation, etc., those made of a vinyl monomer polymer are preferred, and in particular, the following general formula (3) Those obtained by polymerizing at least one vinyl monomer represented by the formula (1) are preferred.
[0059]
[Chemical 8]

[0060]
  In the general formula (3),R ¹ ~ R ^Three Each is independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group or aryl group. Specific examples of the substituted or unsubstituted alkyl group or aryl group include a methyl group, an ethyl group, a methoxy group, a chloromethyl group, a phenyl group, and a tolyl group.
[0061]
  R ^Four Is selected from a substituted or unsubstituted alkyl group, aryl group, alkoxy group, acyl group, acyloxy group, or alkoxycarbonyl group. The alkyl group, alkoxy group, acyl group, acyloxy group, and alkoxycarbonyl group preferably have 1 to 18 carbon atoms, and examples of the aryl group include a phenyl group, a naphthyl group, and a pyrenyl group. Examples of the substituent include a halogen atom, a phenyl group, a hydroxy group, an amino group, an isocyanate group, an epoxy group, and an alkoxysilyl group.
[0062]
  Specific examples of structural formulas represented by the above general formula (1), which are contained as repeating units in the charge transport block in the copolymer of the present invention, are shown in the following Tables 1 and 2, and the above general formula (2). Specific examples of the structural formula represented by formula (3) are shown in Table 3 below, and specific examples of the structural formula represented by the general formula (3) contained as a repeating unit in the insulating block are shown in Table 4 below. However, the present invention is not limited to these.
[0063]
[Table 1]

[0064]
[Table 2]

[0065]
[Table 3]

[0066]
[Table 4]

[0067]
  The resistance value of the insulating block in the copolymer of the present invention is 10¹³Ωcm or more is preferable, especially 10¹⁴Ωcm is preferred. When an insulating block having a volume resistivity lower than this range is used, the electrical insulation of the electrically inactive phase formed by the block tends to be lost and the S-shape tends to be lost. Note that it is difficult to directly measure the electrical resistivity in the copolymer, and the electrical resistivity of a polymer having the same structure as that of the insulating block can be substituted.
[0068]
  As long as the copolymer of the present invention is a block copolymer or a graft copolymer, the connecting form of the constituent blocks may be any. That is, when the charge transporting block is represented by A and the insulating block is represented by B, AB type, ABA type, BAB type, (AB)_nMold, (AB)_nType A and B (AB)_nType block copolymer, graft copolymer having charge transporting block as main chain and insulating block as side chain, graft copolymer having insulating block as main chain and charge transporting block as side chain, or Examples thereof include a block-graft copolymer obtained by grafting A and / or B to the side chain of a block copolymer such as ABA type.
  Both the charge transporting block and the insulating block can include two or more kinds of structural units. In addition, a copolymer and a charge transporting polymer compound or an insulating polymer compound can be used together. In this case, a polymer compound containing a structural unit of a copolymer is preferable.
[0069]
  In order to produce a modulation structure suitable as a heterogeneous charge transport layer using a copolymer having these charge transport blocks and insulating blocks, it is necessary to separate the homogeneous phase into two phases. As a method of separating into two phases, in the case of a mixture in which both blocks are separated from a uniform phase into two phases by heating, a method of forming a modulation structure by heating and cooling the uniform phase film is used. It is possible. In addition, both are dissolved in a common solvent to form a homogeneous phase, and in the process where the solvent evaporates and increases in concentration, a method of separating into two phases, both are dissolved in a mixed solvent to form a uniform phase, and the solvent evaporates. In the process of changing the solvent composition, the modulation structure can also be made by a method of separating into two phases.
[0070]
  The volume ratio of the charge transporting block and the insulating block is arbitrarily set in the range of 9/1 to 1/9, but the range of 8/2 to 2/8 is preferable. More preferably, it is the range of 7/3 to 3/7. Even if the volume ratio of the charge transport block is larger or smaller than the above range, it is difficult to take a modulation structure. However, the volume ratio at which a modulation structure can be easily formed is determined depending on each material configuration, film forming conditions, and the like.
[0071]
  The phase pitch of the charge transporting portion (in FIG. 3, for example, indicated by the width a) is preferably 0.001 to 1 μm, more preferably 0.005 to 0.5 μm, and particularly preferably 0.01 to 0.2 μm. Range. When the pitch of the charge transporting phase is larger than the above range, the formation of a spatial trap necessary for S-shape within the preferable film thickness range is stochastically lowered, and the S-shape is lost. On the other hand, when the pitch of the charge transporting phase is smaller than the above range, the spatial trap becomes too shallow and the S-shape tends to be lost.
[0072]
  In the copolymer, the phase pitch can be controlled by the molecular weight of each block. As the molecular weight of the block increases, the phase pitch also increases, and as the block molecular weight decreases, the phase pitch also decreases. The molecular weight of each block is suitably in the range of 2,000 to 1,000,000. When the molecular weight of each block is less than 2000, the phase pitch is too small, and when it is 1000000 or more, the phase pitch is too large. The molecular weight here refers to the volume average molecular weight.
[0073]
  The phase pitch can also be adjusted by appropriately selecting the solvent, using the mixed solvent, adjusting the evaporation rate of the solvent, and the cooling rate.
[0074]
  Here, as a preferable combination of substances constituting the charge transporting block and the insulating block, phase separation is performed when the solubility parameter of the charge transporting polymer compound and the insulating polymer compound having the same configuration as each block is measured. It is preferable that they are separated as long as there is a common solvent for mixing.
[0075]
  The film thickness of the non-uniform charge transport layer used in the present invention is suitably 5 to 100 μm, preferably 10 to 50 μm, when the charge transport layer is formed only by the non-uniform charge transport layer without being combined with the uniform charge transport layer. Set to range. In addition, when the charge transport layer is formed by combining this non-uniform charge transport layer with the uniform charge transport layer, 0.1 to 50 μm is appropriate, preferably 0.2 to 20 μm, more preferably 0.5 to 10 μm. Is set in the range. If it is thinner than the above range, the S-shape tends to be lost. The upper limit of the film thickness is limited by the charge transport ability of the S-shaped charge transport layer to be used, and is set within the allowable range of response speed, residual potential, and the like.
[0076]
  In addition, by adding a compound capable of transporting only the charge of the opposite polarity to the main transport charge in the heterogeneous charge transport layer, it is possible to obtain effects such as reduction of residual potential and improvement of repeated stability. It is preferable that it is contained in the phase which consists of a conductive polymer compound.
[0077]
  As a method for applying the non-uniform charge transport layer, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method may be used. it can.
[0078]
  As the uniform charge transporting layer, that is, a layer containing a charge transporting matrix, a known layer used as a charge transporting layer in a conventional J-shaped laminated photoreceptor can be used. For example, hole transporting low molecular compounds such as benzidine compounds, amine compounds, hydrazone compounds, stilbene compounds, carbazole compounds or electron transporting low molecular compounds such as fluorenone compounds, malononitrile compounds, diphenoquinone compounds, etc. A solid solution film in which molecules are uniformly dispersed in an insulating resin such as polycarbonate, polyarylate, polyester, polysulfone, polymethyl methacrylate, or a polymer having its own charge transporting ability A compound or the like can be used. In addition, an inorganic substance having a charge transporting ability such as selenium, amorphous silicon, and amorphous silicon carbide can also be used. Examples of the charge transporting polymer compound include a polymer compound having a charge transporting group such as polyvinylcarbazole in a side chain, and a group having a charge transporting ability as disclosed in JP-A-5-232727. And the like, and polysilanes and the like, which contain a main chain in the main chain.
[0079]
  As the uniform charge transport layer in the present invention, it is preferable to use a charge transporting polymer compound particularly in production. That is, when a non-uniform charge transport layer and a uniform charge transport layer are laminated and formed, if a charge transporting low molecular weight compound is used for the uniform charge transport layer, the charge transporting low molecular weight compound is mixed into the heterogeneous charge transport layer. As a result, the sigmoid property is impaired due to a decrease in insulation against the main charge of the electrically inactive phase of the inhomogeneous charge transport layer, or mixed molecules become charge traps, resulting in an increase in residual potential, a decrease in transport capability, and light. Problems such as a decrease in sensitivity occur. This problem is particularly noticeable when each layer is formed by a wet coating method. Of course, these problems can be avoided by selecting an upper layer coating solvent that does not dissolve and swell the lower layer, or selecting an insulating block that is incompatible with the charge transporting low molecular weight compound. However, it is known that polymers are rarely compatible with each other and generally cause phase separation, and a charge transporting polymer compound is used as a uniform charge transporting layer. In such a case, phase separation without incompatibility with the electrically inactive phase of the heterogeneous charge transport layer hardly occurs, so the above problem of mixing hardly occurs, and restrictions on selection of materials and manufacturing methods are eliminated. Has the advantage of.
[0080]
  For the above reasons, when a uniform charge transport layer made of a charge transport polymer is used, it is desirable that the layer does not contain 5% or more of a charge transport compound having a molecular weight of 1000 or less.
[0081]
  Furthermore, in the case of a charge transporting resin containing at least one of the structures represented by the general formula (1) or (2) as a repeating unit as the charge transporting polymer compound of the uniform charge transporting layer, a high charge It is particularly preferable because it has transportability and is excellent in mechanical properties.
[0082]
  In the uniform charge transport layer, an electrically inactive region may exist as long as it is surrounded by the charge transport matrix. For example, in order to reduce surface friction, wear, or surface deposits, insulating particles or the like can be included in the charge transporting matrix layer. In addition, the uniform charge transport layer can include charge transporting fine particles for the purpose of improving transport ability.
[0083]
  As a method for applying the uniform charge transport layer, a normal method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method can be used. . Moreover, what can be vapor-phase-deposited can also be directly formed by a vacuum deposition method or the like.
[0084]
  The film thickness of the uniform charge transport layer used in the present invention is set to 1 to 100 μm, preferably 5 to 50 μm.
[0085]
  In the present invention, the total thickness of the entire charge transport layer is generally 5 to 100 μm, preferably 10 to 50 μm.
[0086]
  When the charge transport layer is present between the charge generation layer and the exposure light source, it is desirable that the charge transport layer is substantially transparent to light having an exposure wavelength in order to prevent a decrease in effective photosensitivity. Preferably, the transmittance of light used for exposure in the charge transport layer is 50% or more. More preferably, it is 70% or more, More preferably, it is 90% or more. However, when use with low sensitivity is desired, the effective light sensitivity can be adjusted by using a charge transport layer that substantially absorbs light of the exposure wavelength.
  A protective layer may be further provided on the photoconductive layer composed of the charge generation layer and the charge transport layer, if necessary. This protective layer protects the photoconductive layer from chemical stress such as ozone and oxidizing gas generated from the charging member and ultraviolet light, or mechanical stress caused by contact with the developer, paper, cleaning member, etc. It is effective to protect and improve the real life of the photoconductive layer. In particular, the effect is remarkable in a layer configuration in which a thin charge generation layer is used as an upper layer.
[0087]
  The protective layer is formed by containing a conductive material in a suitable binder resin. Examples of the conductive material include metallocene compounds such as dimethylferrocene, metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and ITO, but are not limited thereto. As the binder resin, known resins such as polyamide, polyurethane, polyester, polycarbonate, polystyrene, polyacrylamide, silicone resin, melamine resin, phenol resin, and epoxy resin can be used. A conductive inorganic film such as amorphous carbon can also be used as the protective layer.
[0088]
  The electrical resistance of the protective layer is 10⁹-10¹⁴A range of Ω · cm is preferred. When the electric resistance exceeds this range, the residual potential increases. On the other hand, when the electric resistance falls below this range, charge leakage in the creeping direction cannot be ignored, resulting in a decrease in resolution.
[0089]
  The thickness of the protective layer is suitably from 0.5 to 20 μm, preferably set in the range of 1 to 10 μm. When a protective layer is provided, a blocking layer that prevents leakage of charges from the protective layer to the photosensitive layer can be provided between the photosensitive layer and the protective layer as necessary. As this blocking layer, a known layer can be used as in the case of the protective layer.
[0090]
  In the electrophotographic photosensitive member of the present invention, for the purpose of preventing deterioration of the photosensitive member due to ozone or oxidizing gas generated in the electrophotographic apparatus, light, or heat, an antioxidant or light is contained in each layer or the uppermost layer. Stabilizers, heat stabilizers and the like can be added.
[0091]
  As the antioxidant, known ones can be used, and examples thereof include hindered phenol, hindered amine, paraphenylenediamine, hydroquinone, spirochroman, spiroidanone and their derivatives, organic sulfur compounds, and organic phosphorus compounds. .
[0092]
  As the light stabilizer, known ones can be used, for example, derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine, and an electron withdrawing property that can deactivate the photoexcited state by energy transfer or charge transfer. Examples thereof include compounds and electron donating compounds.
[0093]
  Furthermore, for the purpose of reducing surface wear, improving transferability, improving cleaning properties, etc., insulating particles such as fluororesin may be dispersed in the outermost surface layer.
[0094]
  The electrophotographic apparatus equipped with the electrophotographic photosensitive member of the present invention may be any apparatus as long as it uses an electrophotographic method, but an electrophotographic apparatus that performs exposure based on a digitally processed image signal is particularly preferable. An electrophotographic apparatus that performs exposure based on a digitally processed image signal is an electrophotographic apparatus that uses a light source such as a laser or an LED and performs exposure with multilevel light by performing binary or pulse width modulation or intensity modulation. Examples include LED printers, laser printers, laser exposure digital copiers, and the like. E of S-shaped photoreceptor_50%/ E_Ten%The value is 5 or less. To achieve favorable digital characteristics, E_50%/ E_Ten%The value is preferably less than 3. More preferably, the value is less than 2.
[0095]
  In addition to the exposure light source for image formation, an exposure light source can be used together for the purpose of initializing the photoreceptor after development or stabilizing the electrophotographic characteristics. Although it may be absorbed or not absorbed by the non-uniform charge transport layer, it is preferable that light reaches at least the charge generation layer.
[0096]
【Example】
  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the following examples, and those skilled in the art can add modifications to the following examples based on known knowledge of electrophotographic technology.
[0097]
[Synthesis Example 1: Synthesis of Reactive Polymerization Initiator 4,4'-Azobis (4-cyanovaleric Acid Chloride)]
  140 ml of thionyl chloride was ice-cooled, and 48 g of 4,4′-azobis (4-cyanovaleric acid) was gradually added. The mixture was heated at 30 ° C. for 6 hours, and excess thionyl chloride was distilled off under reduced pressure. The residue was recrystallized from chloroform to obtain 22 g of 4,4'-azobis (4-cyanovaleric chloride) crystals.
[0098]
[Synthesis Example 2: Synthesis of charge transporting polymer having azo type polymerization initiator at both ends]
  3,3′-dimethyl-N, N′-bis (p, m-dimethylphenyl) -N, N′-bis [4- (2-methoxycarbonylethyl) phenyl]-[1,1′-biphenyl]- 100 g of 4,4′-diamine, 200 g of ethylene glycol and 5 g of tetrabutoxy titanium were heated to reflux for 3 hours under a nitrogen stream. 3,3′-dimethyl-N, N′-bis (p, m-dimethylphenyl) -N, N′-bis [4- (2-methoxycarbonylethyl) phenyl]-[1,1′-biphenyl]- After confirming that 4,4′-diamine was consumed, the pressure was reduced to 0.5 mmHg, and the mixture was heated to 230 ° C. while distilling off ethylene glycol, and the reaction was continued for another 7 hours. Thereafter, the mixture is cooled to room temperature, methylene chloride is added to dissolve insoluble components, and reprecipitation from acetone is performed to obtain 90 g of a charge transporting polymer having hydroxy groups at both ends represented by the following structural formula (1). Obtained. The weight average molecular weight of the obtained polymer was 7.2 × 10^FourMet.
[0099]
[Chemical 9]

[0100]
  43 g of the charge transporting polymer having hydroxy groups at both ends and 0.5 g of triethylamine were dissolved in 120 ml of dichloromethane and cooled to 0 ° C. A solution prepared by dissolving 5.6 g of 4,4′-azobis (4-cyanovaleric chloride) obtained in Synthesis Example 1 above in 20 ml of dichloromethane was added dropwise thereto. After reacting for 1 hour at room temperature, the mixture was heated to 30 ° C., and further reacted for 4 hours. The solvent was distilled off from this, tetrahydrofuran was added and dissolved, it was added dropwise to methanol, stirred for 1 hour, and then filtered off. This reprecipitation operation was further repeated twice. The residue was dried to obtain 41 g of a charge transporting polymer having an azo polymerization initiator at both ends.
[0101]
[Synthesis Example 3: Synthesis of Block Copolymer Represented by Structural Formula (2) below]
  6 g of a charge transporting polymer having an azo polymerization initiator at the terminal obtained in Synthesis Example 2 and 6 g of n-dodecyl methacrylate were dissolved in 120 ml of toluene, purged with nitrogen, and heated at 60 ° C. for 65 hours. The solvent was removed from this, tetrahydrofuran was added, this solution was added dropwise to methanol, and the mixture was stirred for 1 hour and then filtered off. The obtained solid is a mixture of the target block copolymer and poly (n-dodecyl methacrylate) homopolymer, and the poly (n-dodecyl methacrylate) homopolymer is obtained by the following purification method using the difference in solubility. Then, the desired block copolymer was obtained. That is, the charge transporting polymer of Synthesis Example 2 is insoluble, and the mixture is sufficiently washed with a solvent n-hexane in which poly (n-dodecyl methacrylate) is easily soluble, so that the target block copolymer can be obtained. 6 g of polymer was obtained. From the integral ratio of peaks corresponding to protons specific to both blocks in the 1H-NMR spectrum of the obtained block copolymer, the volume composition ratio of the insulating block consisting of the charge transporting block and poly (n-dodecyl methacrylate) is approximately 55:45. The volume resistivity of poly (n-dodecyl methacrylate) having the same structure as the insulating block of the block copolymer of the synthesis example is 10¹⁴It was Ω · cm or more.
[0102]
Embedded image

[0103]
[Synthesis Example 4: Structural formula below(2 ')Synthesis of block copolymer represented by
  20 g of the charge transporting polymer having an azo-type polymerization initiating group at both ends obtained in Synthesis Example 2 and 35 g of tert-butyl methacrylate were dissolved in 400 ml of toluene, purged with nitrogen, and heated at 65 ° C. for 100 hours. This was added dropwise to hexane, stirred for 1 hour and then filtered off. The solvent was removed from this, tetrahydrofuran was added, this solution was added dropwise to methanol, and the mixture was stirred for 1 hour and then filtered off. Further, the reprecipitation operation with toluene / hexane was repeated twice. The residue is dried under reduced pressure, and the following structural formula(2 ')30 g of a block copolymer represented by
[0104]
Embedded image

[0105]
  From the integral intensity ratio of protons belonging to each block of the 1H-NMR spectrum of the obtained copolymer, the volume composition ratio of the charge transporting block and the insulating block was calculated to be about 52/48. The volume resistivity of poly (tert-butyl methacrylate) having the same structure as the insulating block of the block copolymer of this example is 10¹⁴It was Ω · cm or more.
[0106]
[Synthesis Example 5: Synthesis of triblock copolymer represented by Structural Formula (3) below]
  N, N′-bis (p, m-dimethylphenyl) -N, N′-bis [p- (2-methoxycarbonylethyl) phenyl]-[3,3′-dimethyl-1,1′-biphenyl]- 4,4'-diamine as N, N-Diphenyl-N- [(3,5A charge transporting polymer having an azo polymerization initiator at both ends was synthesized in the same manner as in Synthesis Example 2 except that the compound was changed to -bismethoxycarbonylethyl) phenyl] amine. Further, a triblock copolymer represented by the following structural formula (3) was synthesized in the same manner as in Synthesis Example 3 except that a charge transporting polymer having an azo type polymerization initiator at both ends was used.
[0107]
  The charge transporting prepolymer containing a triarylamine structure has a weight average molecular weight of 5.2 × 10^ThreeMet. From the integral intensity ratio of protons belonging to each block of the 1H-NMR spectrum of the obtained copolymer, the volume composition ratio of the charge transporting block and the insulating block was calculated to be about 59/41.
[0108]
Embedded image

[0109]
(Example 1)
  On an aluminum substrate, a zirconium alkoxide compound (trade name: Orgatics ZC540, manufactured by Matsumoto Pharmaceutical Co., Ltd.) 10 parts by weight and a silane compound (trade name: A1110, manufactured by Nihon Unicar Co., Ltd.) 1 part by weight, isopropanol 40 parts by weight and butanol 20 parts by weight A solution consisting of parts was applied by a dip coating method and dried by heating at 150 ° C. for 10 minutes to form an undercoat layer having a thickness of 0.1 μm.
[0110]
  Next, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using CuKα as a radiation source is a strong diffraction at least at 7.4 °, 16.6 °, 25.5 °, and 28.3 °. 4 parts by weight of chlorogallium phthalocyanine microcrystals having a peak, 2 parts by weight of vinyl chloride-vinyl acetate copolymer (trade name: UCAR solution vinyl resin VMCH, manufactured by Union Carbide), 67 parts by weight of xylene, and 33 parts by weight of butyl acetate After mixing with glass beads and treating with glass beads for 2 hours by a paint shake method, the obtained coating solution is applied onto the undercoat layer by a dip coating method and dried by heating at 100 ° C. for 10 minutes to form a film. A charge generation layer having a thickness of 0.5 μm was formed.
[0111]
  Next, a coating solution prepared by dissolving 20 parts by weight of the block copolymer having the charge transport block and the insulating block shown in Synthesis Example 3 in 80 parts by weight of toluene is applied onto the charge generation layer by a dip coating method. Heat-dried at 115 ° C. for 30 minutes to form a non-uniform charge transport layer having a thickness of 20 μm, and an electrophotographic photoreceptor having a layer structure as shown in FIG. 6 was produced.
[0112]
  The electrophotographic photosensitive member thus obtained was subjected to a partially modified electrostatic copying paper test apparatus (electrostatic analyzer EPA-8100, manufactured by Kawaguchi Denki Seisakusho Co., Ltd.) at room temperature and normal humidity (20 The electrophotographic characteristics were evaluated under the environment of 40 ° C. and 40% RH. After adjusting the corona discharge voltage and charging the surface of the photoreceptor to -750 V, a halogen lamp light monochromatized to 750 nm through an interference filter is 1 mW / m on the surface of the photoreceptor.²When the light intensity was adjusted so that the light intensity was reduced and irradiated for 7 seconds, the S-shaped photoinduced potential decay shown in FIG. 12 was shown. Further, the potential after light irradiation was defined as the remaining potential. From this photoinduced potential decay curve, E_50%The value is 3.5mJ / m², E_50%/ E_Ten%The value was calculated as 1.6. Further, the residual potential was −80V.
[0113]
  When the cross section of this photoconductor was dyed with ruthenic acid and observed with a transmission electron microscope, a structure considered to be a complex modulation structure consisting of a dark portion and a thin portion was observed. This is presumed that the charge transporting phase and the electrically inactive phase are phase-separated, and one of the phases is stained with ruthenium acid. The phase pitch was approximately 0.08 μm.
[0114]
(Comparative Example 1)
  By changing the addition amount of n-dodecyl methacrylate in Synthesis Example 3, a copolymer having a content ratio of poly (n-dodecyl methacrylate) as an insulating block in the block copolymer as shown in Table 5 below was used. Also, an electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the non-uniform charge transport layer was formed.
[0115]
  When the cross-section of this photoconductor is stained with ruthenic acid and observed with a transmission electron microscope, a structure that appears to be a sea-island structure where the dark part is a charge transporting phase and the thin part is an electrically inactive phase is seen. It was.
[0116]
  Table 5 shows the results of evaluating the electrophotographic characteristics and the cross section of the non-uniform charge transport layer of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0117]
(Comparative Example 2)
  By changing the addition amount of n-dodecyl methacrylate in Synthesis Example 3, a copolymer having a content ratio of poly (n-dodecyl methacrylate) as an insulating block in the block copolymer as shown in Table 5 below was used. Also, an electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the non-uniform charge transport layer was formed.
[0118]
  When the cross-section of this photoconductor was observed in the same manner as in Example 1, a structure that appeared to be a sea-island structure in which the shades were opposite to those in Comparative Example 1 was observed.
[0119]
  Table 5 shows the results of evaluating the electrophotographic characteristics and the cross section of the non-uniform charge transport layer of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0120]
(Comparative Example 3)
  An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the amount of n-dodecyl methacrylate, which was an insulating block in Synthesis Example 3, was changed to 0.
[0121]
  Table 5 shows the results of evaluating the electrophotographic characteristics and the cross section of the non-uniform charge transport layer of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0122]
[Table 5]

[0123]
As can be seen from Table 5, the photoreceptor of Example 1 having the non-uniform charge transport layer of the modulation structure of the present invention was excellent in S-characteristics and suitable for the residual potential. On the other hand, the photoreceptors of Comparative Examples 1 and 2 having a non-uniform charge transport layer with a sea-island structure were inferior in either S-characteristics or residual potential. The photoreceptor of Comparative Example 3 that did not include an insulating block had a J-shaped photoinduced potential decay characteristic.
[0124]
  (Example 2)
  A charge active layer and a heterogeneous charge transport layer were laminated on a substrate provided with an undercoat layer in the same manner as in Example 1 except that the thickness of the heterogeneous charge transport layer was 5 μm.
[0125]
Furthermore, a coating solution in which 20 parts by weight of a compound composed of a repeating unit represented by the following structural formula (4) having a molecular weight of 80,000, which is a polymer charge transport material, was dissolved in 80 parts by weight of toluene was applied with an applicator, and 115 ° C. And dried for 1 hour to form a uniform charge transport layer having a film thickness of 15 μm, and an electrophotographic photoreceptor having a layer structure as shown in FIG. 7 was produced.
[0126]
Embedded image

[0127]
  When the electrophotographic photoreceptor thus obtained was evaluated in the same manner as in Example 1, the photoinduced potential decay characteristic was E_50%The value is 3.3 mJ / m², E_50%/ E_Ten%The value was 1.5 S-shaped. Further, the residual potential was −40V.
[0128]
  When the cross section of the photoconductor was observed in the same manner as in Example 1, a structure that was considered to be a complex modulation structure composed of a dark portion and a thin portion was observed. The phase pitch was approximately 0.08 μm.
[0129]
(Example 3)
  An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the heterogeneous charge transport layer was formed using the copolymer of Synthesis Example 4 instead of the copolymer of Synthesis Example 3.
[0130]
  When the electrophotographic photoreceptor thus obtained was evaluated in the same manner as in Example 1, the photoinduced potential decay characteristic was E_50%The value is 3.9 mJ / m², E_50%/ E_Ten%The value was S-shaped with a value of 1.8. The residual potential was −50V. The evaluation results are shown in Table 2 below.
[0131]
  When the cross section of the photoconductor was observed in the same manner as in Example 1, a structure that was considered to be a complex modulation structure composed of a dark portion and a thin portion was observed. The phase pitch was approximately 0.08 μm.
[0132]
  (Comparative Example 4)
  Using the copolymer in which the content ratio of poly (tert-butyl methacrylate), which is an insulating block in the block copolymer, was changed as shown in Table 6 by changing the addition amount of tert-butyl methacrylate in Synthesis Example 4. Further, an electrophotographic photoreceptor was produced in the same manner as in Example 3 except that the non-uniform charge transport layer was formed.
[0133]
  When the cross section of the photoconductor was observed in the same manner as in Example 1, a structure that appeared to be a sea-island structure in which the dark portion was the charge transporting phase and the thin portion was the electrically inactive phase was found.
[0134]
  Table 6 shows the results of evaluating the electrophotographic characteristics and the non-uniform charge transport layer cross section of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0135]
(Comparative Example 5)
  By changing the amount of tert-butyl methacrylate added in Synthesis Example 4, a copolymer having a content ratio of poly (tert-butyl methacrylate) as an insulating block in the block copolymer as shown in Table 5 below was used. Also, an electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the non-uniform charge transport layer was formed.
[0136]
  When the cross section of this photoconductor was observed in the same manner as in Example 1, a structure that appeared to be a sea-island structure in which the shades were opposite to those in Comparative Example 3 was observed.
[0137]
  Table 6 shows the results of evaluating the electrophotographic characteristics and the non-uniform charge transport layer cross section of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0138]
(Comparative Example 6)
  An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the addition amount of tert-butyl methacrylate, which was an insulating block in Synthesis Example 4, was changed to zero.
[0139]
  Table 6 shows the results of evaluating the electrophotographic characteristics and the non-uniform charge transport layer cross section of the electrophotographic photoreceptor thus obtained in the same manner as in Example 1.
[0140]
[Table 6]

[0141]
(Example 4)
  An electrophotographic photoreceptor was produced in the same manner as in Example 2 except that the heterogeneous charge transport layer was formed using the copolymer of Synthesis Example 5 instead of the copolymer of Synthesis Example 1.
[0142]
  When the electrophotographic photoreceptor thus obtained was evaluated in the same manner as in Example 1, the photoinduced potential decay characteristic was E_50%The value is 4.2 mJ / m², E_50%/ E_Ten%The value was S-shaped with 2.2. The residual potential was -70V.
[0143]
  When the cross section of the photoconductor was observed in the same manner as in Example 1, a structure that was considered to be a complex modulation structure composed of a dark portion and a thin portion was observed. The phase pitch was approximately 0.05 μm.
[0144]
  (Example 5)
  A photoconductor for electrophotography was prepared in the same manner as in Example 2 except that an aluminum drum was used instead of the aluminum substrate, mounted on a laser printer (Laser Press 4105, manufactured by Fuji Xerox Co., Ltd.), and a printing test was performed. . At this time, in order to obtain an optimum exposure amount, an ND filter was inserted in the optical path of the laser beam. A schematic configuration diagram of this laser printer is shown in FIG.
[0145]
  Around the photosensitive drum 11, a pre-exposure light source (red LED) 12, a charging scorotron 13, an exposure laser optical system 14, a developing device 15, a transfer corotron 16 and a cleaning blade 17 are sequentially arranged in the order of processes. Yes. The exposure laser optical system 14 includes an exposure laser diode having a transmission wavelength of 780 nm, and emits light based on a digitally processed image signal. The emitted laser beam 14a is configured to expose the photosensitive member while being scanned by a polygon mirror, a plurality of lenses, and a mirror. Reference numeral 18 denotes a sheet.
[0146]
(Comparative Example 7)
  An electrophotographic photoreceptor was prepared in the same manner as in Comparative Example 3 except that an aluminum drum was used instead of the aluminum substrate, and a printing test was conducted in the same manner as in Example 5.
[0147]
  When the print quality obtained in Example 5 and Comparative Example 7 were compared visually, Example 5 was superior in print quality in terms of reproducibility of fine lines.
[0148]
【The invention's effect】
  The electrophotographic photosensitive member of the present invention is a photosensitive member exhibiting S-shaped photoinduced potential decay characteristics, and has a phase separation having a modulation structure comprising a charge transporting phase and an electrically inactive phase in a charge transport layer. By including a block copolymer or graft copolymer consisting of a charge transporting block and an insulating block in a state, the charge transport path such as an increase in residual potential, a decrease in photosensitivity, and a decrease in charge transport speed is disrupted. Therefore, it is possible to provide an electrophotographic photosensitive member having a good sigmoid property without any obstacles.
[0149]
  In addition, an electrophotographic apparatus using the S-shaped electrophotographic photoreceptor of the present invention can obtain a printed image with excellent print quality and image quality by performing exposure based on a digitally processed image signal. .
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between an exposure amount and a surface potential in a J-shaped electrophotographic photosensitive member.
FIG. 2 is a graph showing a relationship between an exposure amount and a surface potential in an S-shaped electrophotographic photosensitive member.
FIG. 3 is a two-dimensional schematic diagram showing a modulation structure comprising a charge transporting phase and an electrically inactive phase.
FIG. 4 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which a charge generation layer and a non-uniform charge transport layer are sequentially provided on a support.
FIG. 5 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which a charge generation layer, a charge transport layer comprising a non-uniform charge transport layer and a uniform charge transport layer are sequentially provided on a support. .
FIG. 6 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which an undercoat layer is provided between a support and a charge generation layer.
FIG. 7 is a schematic view showing an example of the electrophotographic photoreceptor of the present invention in which a charge generation layer, an undercoat layer, a charge transport layer comprising a non-uniform charge transport layer and a uniform charge transport layer are sequentially provided on a support. It is sectional drawing.
FIG. 8 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which a non-uniform charge transport layer and a charge generation layer are sequentially provided on a support.
FIG. 9 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which a charge transport layer composed of a non-uniform charge transport layer and a uniform charge transport layer and a charge generation layer are sequentially provided on a support. .
FIG. 10 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which an undercoat layer is provided between a support and a non-uniform charge transport layer.
FIG. 11 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention in which an undercoat layer is provided between a charge transport layer comprising a support, a non-uniform charge transport layer, and a uniform charge transport layer. .
12 is a graph showing the photoinduced potential decay characteristics of Example 1. FIG.
FIG. 13 is a schematic configuration diagram of an electrophotographic apparatus of the present invention that performs exposure based on a digitally processed image signal used in an embodiment.
[Explanation of symbols]
    1 ... Conductive support
    2. Charge generation layer
    3 ... Non-uniform charge transport layer
    4 ... Uniform charge transport layer
    5 ... Charge transport layer
    6 ... Undercoat layer
  11 ... photosensitive drum
  12 ... Light source for pre-exposure
  13 ... Scorotron for charging
  14 ... Laser optical system for exposure
  15 ... Developer
  16 ... Corotron for transfer
  17 ... Cleaning blade
  18 ... paper

Claims (12)

In an electrophotographic photosensitive member provided with at least a charge generation layer and a charge transport layer on a conductive substrate,
A block copolymer or graft copolymer comprising a charge transporting block and an insulating block in a phase-separated state having a modulation structure comprising a charge transporting phase and an electrically inactive phase in the charge transporting layer Comprising a non-uniform charge transport layer comprising
The electrophotographic photosensitive member is characterized in that the exposure amount required for 50% potential attenuation of the electrophotographic photosensitive member is less than 5 times the exposure amount required for 10% potential attenuation.   2. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer comprises the non-uniform charge transport layer and a uniform charge transport layer including a charge transport matrix.   3. The electrophotographic photoreceptor according to claim 2, wherein a charge generation layer, a non-uniform charge transport layer, and a uniform charge transport layer are sequentially laminated on the conductive substrate.   The charge transporting block in the block copolymer or graft copolymer comprising the charge transporting block and the insulating block contains a triarylamine structure as a repeating unit. An electrophotographic photoreceptor according to any one of the above. The block transporting block or graft copolymer comprising the charge transporting block and the insulating block has at least one of the structures represented by the following general formula (1) or (2) as a repeating unit. The electrophotographic photosensitive member according to claim 4, which is contained.

(In the formula, Ar ₁ and Ar ₂ each independently represent a substituted or unsubstituted aryl group, X ₁ represents a divalent hydrocarbon group or heteroatom-containing hydrocarbon group having an aromatic ring structure, and X ₂ And X ₃ each independently represents a substituted or unsubstituted arylene group, L ₁ represents a divalent hydrocarbon group or a heteroatom-containing hydrocarbon group which may contain a branched or ring structure, and m and n are Each represents an integer selected from 0 or 1.

(In the formula, Ar ₃ and Ar ₄ each independently represent a substituted or unsubstituted aryl group, and L ₂ represents a trivalent hydrocarbon group or heteroatom-containing hydrocarbon group having an aromatic ring structure.)   The insulating block in the block copolymer or graft copolymer comprising the charge transporting block and the insulating block is made of a polymer of a vinyl monomer. Electrophotographic photoreceptor. The electrophotographic photosensitive member according to claim 6, wherein the vinyl monomer contains at least one compound represented by the following general formula (3).

(In the formula, R ^{1 to} R ³ each independently represent a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group or aryl group, and R ⁴ represents a halogen atom, or a substituted or unsubstituted alkyl group or aryl group. Represents an alkoxy group, an acyl group, an acyloxy group, or an alkoxycarbonyl group.)   The electrophotographic photosensitive member according to claim 2, wherein the uniform charge transport layer contains a charge transporting polymer compound.   The charge transporting polymer compound constituting the uniform charge transporting layer contains at least one of the structures represented by the general formula (1) or (2) as a repeating unit. Electrophotographic photoreceptor.   The electrophotographic photosensitive member according to claim 1, wherein the charge generation layer contains a phthalocyanine compound as a charge generation material.   11. The electrophotographic photosensitive member according to claim 1, wherein an exposure amount required for 50% potential attenuation is 3 times or less of an exposure amount required for 10% potential attenuation.   12. An electrophotographic apparatus comprising: the electrophotographic photosensitive member according to claim 1; and an exposure unit that performs exposure based on a digitally processed image signal.

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