JP3737983B2 - Electrophotographic organic photoreceptor - Google Patents

Description

（式中のＲ₁〜Ｒ₈は水素またはメチル基を示し、ｎは０または１〜２０の整数である。）
【００２７】
＜チオエポキシ基含有重合性単量体＞
【化２】

（式中のＲ₉〜Ｒ_{1 ２}は水素またはメチル基を示し、ｎは０または１〜２０の整数である。）
【００２８】
＜アジリジン基含有重合性単量体＞
【化３】

【化４】

（式中のＲ_{1 ３}〜Ｒ₃₉は水素またはメチル基を示し、ｎは０または１〜２０の整数である。）
【００２９】
＜オキサゾリン基含有重合性単量体＞
２−ビニル−２−オキサゾリン、２−ビニル−４−メチル−２−オキサゾリン、２−ビニル−５−メチル−２−オキサゾリン、２−ビニル−４−エチル−２−オキサゾリン、２−ビニル−５−エチル−２−オキサゾリン、２−イソプロペニル−２−オキサゾリン、２−イソプロペニル−４−メチル−２−オキサゾリン、２−イソプロペニル−５−メチル−２−オキサゾリン、２−イソプロペニル−４−エチル−２−オキサゾリン、２−イソプロペニル−５−エチル−２−オキサゾリン、２−イソプロペニル−４，５−ジメチル−２−オキサゾリン
【００３０】
＜Ｎ−ヒドロキシアルキルアミド基含有重合性単量体＞
Ｎ−ヒドロキシメチルアクリルアミド、Ｎ−ヒドロキシエチルアクリルアミド、Ｎ−ヒドロキシブチルアクリルアミド、Ｎ−ヒドロキシイソブチルアクリルアミド、Ｎ−ヒドロキシ−２−エチルヘキシルアクリルアミド、Ｎ−ヒドロキシシクロヘキシルアクリルアミド、Ｎ−ヒドロキシメチルメタクリルアミド、Ｎ−ヒドロキシエチルメタクリルアミド、Ｎ−ヒドロキシブチルメタクリルアミド、Ｎ−ヒドロキシイソブチルメタクリルアミド、Ｎ−ヒドロキシ−２−エチルヘキシルメタクリルアミド、Ｎ−ヒドロキシシクロヘキシルメタクリルアミド
【００３１】
〔２〕セグメント（Ａ）の骨格を形成する重合性単量体（ｃ）：
セグメント（Ａ）を所望の骨格となすために、必要により使用できる重合性単量体（ｃ）としては、前記単量体（ａ）及び後述するようなセグメント（Ｂ）を形成する成分としてのラジカル重合性高分子量体（ｂ）と共重合し得るものであれば特に限定されず、得ようとするセグメント（Ａ）の分子構造に応じて、例えばスチレン、ｏ−メチルスチレン、ｍ−メチルスチレン、ｐ−メチルスチレン、α−メチルスチレン、ｐ−メトキシスチレン、ｐ−ｔｅｒｔ−ブチルスチレン、ｐ−フェニルスチレン、ｏ−クロルスチレン、ｍ−クロルスチレン、ｐ−クロルスチレン等のスチレン系モノマー；アクリル酸、アクリル酸メチル、アクリル酸エチル、アクリル酸プロピル、アクリル酸ｎ−ブチル、アクリル酸イソブチル、アクリル酸ドデシル、アクリル酸ステアリル、アクリル酸２−エチルヘキシル、メタクリル酸、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸プロピル、メタクリル酸ｎ−ブチル、メタクリル酸イソブチル、メタクリル酸ｎ−オクチル、メタクリル酸ドデシル、メタクリル酸２−エチルヘキシル、メタクリル酸ステアリル等のアクリル酸あるいはメタクリル酸系モノマー；エチレン、プロピレン、ブチレン、塩化ビニル、酢酸ビニル、アクリルニトリル、アクリルアミド、メタクリルアミド、Ｎ−ビニルピロリドン等の単量体を１種または２種以上適宜用いることができる。
【００３２】
〔３〕セグメント（Ｂ）の主鎖を形成する成分としてのラジカル重合性高分子量体（ｂ）：
ラジカル重合性高分子量体（ｂ）（マクロモノマー）は、例えば、有機溶剤中で片末端カルボキシル基を有する重合体とグリシジル基を有するラジカル重合性単量体を反応させることにより得られる。セグメント（Ｂ）成分の主鎖しては、一例として、ポリシロキサン系構造、ポリ（メタ）アクリル系構造、ポリアルキレングリコールなどのポリエーテル系構造、ポリエステル系構造、ポリアルキレン系構造、ポリアミド構造、ポリイミド構造、ポリウレタン構造、フッ素樹脂構造、等が挙げられ、これらの重合鎖の片末端に反応性基を有するものである。
【００３３】
具体的には、ポリシロキサン系構造を有するラジカル重合性高分子量体（ｂ）としては、例えば（メタ）アクリロイル基含有ポリジメチルシロキサン、スチリル基含有ポリジメチルシロキサン（メタ）アクリロイル基含有部分オクチル置換ポリジメチルシロキサン、スチリル基含有部分オクチル置換ポリジメチルシロキササン、スチリル基含有部分フェニル置換ポリジメチルシロキサン、トリス（トリメチルシロキシ）シリルプロピル（メタ）アクリレート等の重合性ポリシロキサン類が挙げられ、これらの中から１種または２種以上を用いることができ、例えば、以下の構造のものがあげられる。
【００３４】
【化５】

（式中、Ｂは−ＣＯＯ−またはフェニレン基を示し、Ｒ¹は水素原子またはメチル基を、Ｒ²は炭素数１〜６のアルキレン基を、Ｒ³〜Ｒ¹³は同一または異なってアリール基、炭素数１〜６のアルキル基または炭素数１〜１０のアルコキシル基をそれぞれ示し、ａおよびｂは同一または異なって０〜１０の整数を、ｎは０〜２００の整数をそれぞれ示す。）
【００３５】
セグメント（Ｂ）がポリメタ（アクリル）系構造を有する場合、ラジカル重合性高分子量体（ｂ）としては、例えば、以下に示されるような化合物が使用される。
【化６】

（式中、Ｒ¹、Ｒ²は同一または異なって水素原子またはメチル基を示し、Ｒ³は炭素数１〜２５のアルキル基を示し、Ｘは任意の連結鎖であり、Ｙは開始剤末端またはＨ原子、ｎは０〜５００の整数を示す。）
【００３６】
【化７】

（式中、Ｒ¹、Ｒ²、Ｒ⁴は同一または異なって水素原子またはメチル基を示し、Ｒ³、Ｒ⁵は同一または異なって炭素数１〜２５のアルキル基を示し、Ｘは任意の連結鎖であり、Ｙは開始剤末端またはＨ原子、ｍ、ｎはそれぞれ同一または異なって０〜５００の整数を示す。）
【００３７】
【化８】

（式中、Ｒ¹、Ｒ²は同一または異なって水素原子またはメチル基を示し、Ｒ³は炭素数１〜２５のアルキレン基を示し、Ｒ⁴は炭素数１〜２５のアルキル基を示し、Ｘは任意の連結鎖であり、Ｙは開始剤末端またはＨ原子、ｎおよびｍは同一または異なって０〜５００の整数を示す。）
【００３８】
セグメント（Ｂ）がポリアルキレングリコール系構造を有する場合、ラジカル重合性高分子量体（ｂ）としては、例えば、以下に示されるような化合物が使用される。
【化９】

（式中、Ｒ¹、Ｒ²、Ｒ³は同一または異なって水素原子またはメチル基を示し、ｎは０〜５００の整数を示す。）
【００３９】
【化１０】

（式中、Ｒ¹、Ｒ²、Ｒ³、Ｒ⁴は同一または異なって水素原子またはメチル基を示し、ｎおよびｍは同一または異なって０〜５００の整数を示す。）
【００４０】
セグメント（Ｂ）がポリスチレン系構造を有する場合、ラジカル重合性高分子量体（ｂ）としては、例えば、以下に示されるような化合物が使用される。
【化１１】

（式中、Ｒ¹は水素原子またはメチル基を示し、Ｘは任意の連結鎖であり、Ｙは開始剤末端またはＨ原子、Ｚは水素原子、ハロゲン置換基または炭素数１〜８のアルキル基、ｎは０〜５００の整数を示す。）
【００４１】
なお、上記式群において示す連結鎖Ｘについては、例えば、「マクロモノマーの化学と工業」（山下雄也監修、（株）アイピーシー発行、平成元年９月２０日）に詳しく示されており、いずれも使用することができる。
【００４２】
ラジカル触媒としては、通常、ビニル単量体の重合に用いられているものであればいずれも使用できる。代表的なものとしては、２，２´−アゾビスイソブチロニトリル、２，２´−アゾビス（２，４−ジメチルバレロニトリル）等のアゾ系化合物；ベンゾリルパーオキシド、ジ−ｔｅｒｔ−ブチルパーオキシド、ｔｅｒｔ−ブチルパーオクトエート、ｔｅｒｔ−ブチルパーオキシ−２−エチルヘキサノエート等の過酸化物系化合物等が挙げられ、これらは通常単量体１００重量部当たり０．２〜１０重量部、好ましくは０．５〜５重量部の範囲内で使用される。また溶剤としては、用いられる単量体、ラジカル重合性高分子量体の種類に応じて適宜選択される。
【００４３】
上記のようにして得られるグラフトないしはブロック型重合体の分子量については特に制限されないが、顔料粒子に対するグラフト化の効果や、顔料粒子との反応時の作業性を考慮すると平均分子量は１，０００〜１，０００，０００の範囲とすることが好ましく、より好ましくは５，０００〜１００，０００の範囲である。
【００４４】
また、グラフトないしはブロック型重合体におけるセグメント（Ａ）およびセグメント（Ｂ）の分子量としても特に制限されるものではなく、これらのセグメントを構成する重合鎖の種類等によっても左右されるが、顔料粒子に対するグラフト効率の面からするとセグメント（Ａ）は平均分子量３００〜１００，０００の範囲、より好ましくは５，０００〜５０，０００の範囲とすることが好ましく、また顔料粒子に付与しようとする分散性改質効果の面からするとセグメント（Ｂ）は平均分子量５００〜１００，０００の範囲、より好ましくは１，０００〜５０，０００の範囲とすることが好ましい。さらに、グラフトないしはブロック型重合体のセグメント（Ａ）が有する反応性基の数としても特に限定されるものではないが、重合体１分子当り平均して１〜５０、更には１〜２０程度が好ましい。
【００４５】
ポリマーをグラフト化した顔料粒子に関して、顔料粒子に対するグラフト重合体の割合が、１００重量部に対し１〜２００重量部、特に５〜１００重量部であることが好ましい。グラフト重合体が１重量部未満の場合、得られた顔料粒子同士が凝集してしまう。またグラフト重合体が２００重量部を越える場合は、必要以上に重合体がグラフト化されていることになり、このポリマーをグラフト化した顔料粒子を使用して作製される中間層形成用塗布液の塗布性能、形成した中間層の物性や、その中間層を含有して形成された電子写真感光体の電気特性を悪化させる。
【００４６】
中間層形成用塗布液は、ポリマーをグラフト化した顔料粒子とバインダー樹脂と溶剤から構成されるが、中間層のバインダー樹脂の平均分子量は1，０００〜１，０００，０００の範囲とすることが好ましく、更には５，０００〜２００，０００の範囲がより好ましい。またポリマーをグラフト化した顔料粒子とバインダー樹脂の量比は、グラフト化顔料粒子１００重量部に対し、バインダー樹脂５〜５００重量部、特に２０〜２００重量部であることが好ましい。バインダー樹脂が５重量部未満の場合、形成した中間層が十分な成膜性を有さず、バインダー樹脂が５００重量部以上の場合、中間層としての十分な電気特性を有さない。
【００４７】
本発明の電子写真有機感光体の中間層に用いられるバインダー樹脂としては、従来公知の感光層に使用されている種々の樹脂を使用することができる。特に、ポリアミド樹脂、ポリビニルアセタール樹脂、フェノール樹脂、メラミン樹脂、ポリエステル樹脂、シリコン樹脂、アクリル樹脂が好ましい。また、前記バインダー樹脂は、単独または２種以上をブレンドして使用することができる。
【００４８】
本発明の電子写真感光体の中間層に、ポリマーによりグラフト化されている顔料粒子に加えて、金属酸化物やペリレンテトラカルボン酸ジイミド誘導体等のある程度の導電性を有した有機顔料を別途添加してもよい。この場合、ポリマーによりグラフト化されている顔料粒子は、別途添加した顔料の分散助剤としても働き、別途添加した顔料の分散性も向上するので有効である。
【００４９】
また、ポリマーグラフト化された顔料粒子に関して、セグメント（Ｂ）に、不飽和二重結合基、水酸基、カルボキシル基およびアルコキシシリル基よりなる群から選ばれる少なくとも１種または２種以上を有していてもよい。バインダー樹脂として硬化性樹脂を使用した場合の中間層に関しては、この反応性基を有したポリマーでグラフト化された顔料粒子を使用することで、硬化の過程で中間層組成物の硬化に寄与することができ、その結果、高強度皮膜を形成し、より成膜性に優れ、かつ電気特性等の諸物性にも優れた中間層を得ることができる。
【００５０】
本発明の電子写真有機感光体の中間層は、上記バインダー樹脂中にポリマーによりグラフト化された顔料粒子の他に、従来公知の電子輸送剤、ホール輸送剤、顔料、添加剤等と併用して含有させても良い。また、これらの化合物は単独または２種以上をブレンドして使用しても良い。前記添加剤としては、フタル酸エステル等の可塑剤、ヒンダードアミンやヒンダードフェノール系等の酸化防止剤、ラジカル補足剤、紫外線吸収剤、増粘剤等が挙げられる。
【００５１】
中間層を形成する場合には、まず上記例示のバインダー樹脂、及びポリマーによりグラフト化された顔料粒子等の構成材料を適当な分散媒とともに、公知の方法、例えばロールミル、ボールミル、アトライタ、ペイントシェーカー、超音波分散機等を用いて分散混合して塗布液を調整する。次いで、この塗布液を公知の手段、例えばブレード法、浸漬法、スプレー法により塗布して乾燥／硬化させれば良い。
【００５２】
塗布液を作るための分散媒としては、従来公知の有機溶媒が挙げられる。例えばメタノール、エタノール、イソプロパノール、ブタノール等のアルコール類；ｎ−ヘキサン、オクタン、シクロヘキサン等の脂肪族系炭化水素；ベンゼン、トルエン、キシレン等の芳香族系炭化水素、ジクロロメタン、ジクロロエタン、クロロホルム、四塩化炭素、クロロベンゼン等のハロゲン化炭化水素；ジメチルエーテル、ジエチルエーテル、テトラヒドロフラン、エチレングリコールジメチルエーテル、ジエチレングリコールジメチルエーテル等のエーテル類；アセトン、メチルエチルケトン、シクロヘキサノン等のケトン類；酢酸エチル、酢酸メチル等のエステル類；ジメチルホルムアルデヒド、ジメチルホルムアミド、ジメチルスルホキシド等があげられる。さらに、界面活性剤、レベリング剤等を使用しても良い。
【００５３】
中間層の厚さは０．１〜５０μｍ、好ましくは１〜３０μｍである。中間層と感光層との間に、塗布性改善、（電荷発生剤用の塗布液の）浸みこみ防止、乾燥性改善、電子写真特性（画像かぶり・画像ムラ・繰り返し特性など）の向上などのために、電荷の輸送制御を阻害しない範囲で樹脂層を設けてもよい。
【００５４】
＜支持基体＞
本発明で用いられる支持基体としては、導電性を有する種々の材料を使用することができ、例えば鉄、アルミニウム、銅、スズ、白金、銀、バナジウム、モリブデン、クロム、カドミウム、チタン、ニッケル、パラジウム、インジウム、ステンレス鋼、真鍮等の金属単体や、前記金属が蒸着またはラミネートされたプラスチック材料、ヨウ化アルミニウム、酸化スズ、酸化インジウム等で被覆されたガラス、カーボンブラック等が分散された樹脂基体等があげられる。
【００５５】
支持基体の形状は、使用する画像形成装置の構造に合わせて、シート状、ドラム状等のいずれであっても良く、基体自体が導電性を有するか、あるいは基体の表面が導電性を有していれば良い。また、支持基体は、使用に際して十分な機械的強度を有するものが好ましい。
【００５６】
支持基体の表面には、必要に応じて粗面化処理、酸化処理、エッチング加工などの表面処理が施されていても良い。
【００５７】
＜感光層＞
本発明の電子写真有機感光体における感光層は、その構成により単層型と積層型に分けられる。単層型感光体は、支持基体上に、少なくともバインダー樹脂と電荷輸送剤と電荷発生剤とを含有する単一の感光層を設けたものである。積層型感光体は、導電性基体上にバインダー樹脂と電荷発生剤とを含有する電荷発生層、及びバインダー樹脂と電荷輸送剤を含有する電荷輸送層とをこの順で、あるいは逆の順で積層したものである。
【００５８】
感光層に含有させる電荷発生剤、電荷輸送剤（ホール輸送剤、電子輸送剤）バインダー樹脂としては、従来公知の化合物を１種あるいは２種以上を組み合わせて用いることができる。
【００５９】
単層型感光層においては、バインダー樹脂１００重量部に対して、電荷発生剤を０．１〜５０重量部、特に０．５〜３０重量部の割合で、またホール輸送剤を５〜５００重量部、特に２５〜２００重量部の割合で、それぞれ含有させるのが好ましい。また、電子輸送剤を含有させる場合は、バインダー樹脂１００重量部に対して５〜１００重量部、特に１０〜８０重量部の割合で含有させるのが好ましい。ホール輸送剤と電子輸送剤を併用する場合は、その総量は、バインダー樹脂１００重量部に対して２０〜５００重量部、特に３０〜２００重量部が好ましい。単層型感光層の厚みは５〜１００μｍ、特に１０〜５０μｍ程度が好ましい。
【００６０】
積層型感光層においては、バインダー樹脂１００重量部に対して、電荷発生剤を５〜１０００重量部、特に３０〜５００重量部の割合で含有させるのが好ましい。また電荷輸送層においては、バインダー樹脂１００重量部に対して、電子輸送剤を含有させる場合は、当該電子輸送剤を０．１〜２５０重量部、特に０．５〜１５０重量部の割合で、ホール輸送剤を含有させる場合は、当該ホール輸送剤を１０〜５００重量部、特に２５〜２００重量部の割合でそれぞれ含有させるのが好ましい。積層型感光層の厚みは、電荷発生層が０．０１〜５μｍ、特に０．１〜３μｍ程度、電荷輸送層が２〜１００μｍ、特に５〜５０μｍ程度が好ましい。
【００６１】
感光層には、上記各成分の他に、例えばフルオレン系化合物、紫外線吸収剤、可塑剤、界面活性剤、レベリング剤などの種々の添加剤を添加することもできる。また感光体の感度を向上させるために、例えばターフェニル、ハロナフトキノン類、アセナフチレンなどの増感剤を添加してもよい。本発明の電子写真有機感光体の表面には、保護層が形成されていても良い。
【００６２】
【実施例】
以下、本発明を実施例及び比較例に基づいて説明する。なお、以下の実施形態は本発明を具体化した一例であって、本発明の技術的範囲を限定するものではない。
【００６３】
＜中間層用塗布液の作製＞
＜製造実施例１＞攪拌機、不活性ガス導入管、還流冷却管、及び温度計を備えたセパラブルフラスコに、ポリアミドマクロモノマー（セグメント（Ｂ）の主鎖を形成する成分としてのラジカル重合性高分子量体（ｂ）に相当）４０重量部、スチレンモノマー（セグメント（Ａ）の骨格を形成する重合性単量体（ｃ）に相当）７．５重量部、２−（１−アジリジニル）エチルメタクリレート（顔料粒子表面の官能基と反応可能な反応性基を分子内に有する重合性単量体（ａ）に相当）５重量部、開始剤としてアゾイソブチロニトリル５重量部を、エタノール（グラフト化の反応溶媒）７５重量部に溶解させた。窒素気流下で９０℃、４時間の重合反応を行い、更に１１０℃、２時間重合させた後、冷却して不揮発分４０％の重合体溶液Ａを得た。
【００６４】
更に、攪拌機、還流冷却管を備えたセパラブルフラスコに、表面処理を施していないカーボンブラック（三菱化成製ＭＡ−６００）１６重量部、上記重合体溶液Ａ１０重量部、エタノール（グラフト化の反応溶媒）７４重量部、ジルコニアビーズ７５０重量部を仕込んだ。回転数８００ｒｐｍで攪拌しながら１００℃、１．５時間でグラフト化反応を行い、ジルコニアビーズを分離した後、１００ｒｐｍで攪拌しながら混練しながら冷却し、粉砕してポリマーグラフト化されたカーボンブラックの分散液を得た（カーボンブラック／グラフトポリマー／エタノール＝１６／４／８０）。
【００６５】
上記のポリマーグラフト化されたカーボンブラックの分散液１００重量部、中間層用バインダー樹脂としての溶剤可溶性ポリアミド（帝國化学産業製トレジンＭＦ−３０）１２重量部、メタノール１０８重量部を溶解、分散し、中間層用塗布液を作製した。
【００６６】
＜製造実施例２〜５＞製造実施例１において、セグメント（Ｂ）の主鎖を形成する成分としてのラジカル重合性高分子量体（ｂ）、セグメント（Ａ）の骨格を形成する重合性単量体（ｃ）、顔料粒子表面の官能基と反応可能な反応性基を分子内に有する重合性単量体（ａ）、顔料粒子、グラフト化の反応溶媒、中間層用バインダー樹脂を表１に示す材料に置き換えて中間層用塗布液を作製した。
【００６７】
【表１】

酸化チタン：堺化学製ルチル型酸化チタンＳＴＲ−６０Ｎ
【００６８】
〔単層型感光体の作製〕
＜単層型感光体実施例１〜５＞上記製造実施例１〜５で得られた中間層用塗布液を、φ３０のアルミニウム素管（支持基体）上にディップコート法により塗布し、１５０℃で３０分間乾燥させて、平均膜厚が１０μｍの中間層を形成した。
【００６９】
そして、電荷発生剤（Ｘ型無金属フタロシアニン）３．５重量部、電子輸送剤（ＥＴＭ−１）３５重量部、ホール輸送剤（ＨＴＭ−１）５５重量部、重量平均分子量１００，０００のビスフェノールＺ型ポリカーボネート樹脂１００重量部を、テトラヒドロフラン８００重量部と共に、ボールミル中で２４時間分散あるいは溶解させ、単層型感光層用塗布液を調合した。この塗布液を、上記中間層上にディップコート法により塗布し、平均膜厚が３５μｍの単層型感光体を作製した。
【００７０】
＜単層型感光体比較例１＞顔料粒子として未処理のカーボンブラックを使用した以外は製造実施例１と同様にして中間層用塗布液を作製し、単層型感光体実施例１〜５と同様にして、単層型感光体を作製した。
【００７１】
＜単層型感光体比較例２＞顔料粒子として未処理の酸化チタンを使用した以外は製造実施例３と同様にして中間層用塗布液を作製し、単層型感光体実施例１〜５と同様にして、単層型感光体を作製した。
【００７２】
〔積層型感光体の作製〕
＜積層型感光体比較例１〜５＞前記製造実施例１〜５で得られた中間層上に、更に、溶剤可溶性ポリアミド（帝國化学産業製トレジンＭＦ−３０）２重量部をメタノール９８重量部に溶解させた溶液をディップコート法により塗布し、１５０℃で３０分間乾燥させて、膜厚０．１μｍのバリア層を形成した。
【００７３】
そして、電荷発生剤（Ｙ型チタニルフタロシアニン）１００重量部を、分散媒としてのエチルセロソルブ３９００重量部に添加し、超音波分散機を用いて１次分散させた。この分散液にさらに、バインダー樹脂としてのポリビニルブチラール（積水化学工業株式会社製ＢＭ−１）１００重量部を、９００重量部のエチルセロソルブに溶解させた液を添加して、再び超音波分散機を用いて２次分散させて、電荷発生層用の塗布液を作製した。次にこの塗布液を、上記で作製したバリア層上にディップコート法により塗布し、１１０℃で５分間乾燥させて、膜厚０．４μｍの電荷発生層を形成した。
【００７４】
次いで、電子輸送剤（ＥＴＭ−２）６重量部と、ホール輸送剤（ＨＴＭ−１）９０重量部と、バインダー樹脂であるビスフェノールＺ型ポリカーボネート１００重量部とを、８００重量部のテトラヒドロフランと共に混合、分散させて、電荷輸送層用の塗布液を得た。そしてこの塗布液を、上記電荷発生層上に浸漬塗布し、１１０℃で３０分間乾燥させて、膜厚３３μｍの電荷輸送層を形成した。
【００７５】
＜積層型感光体比較例１＞顔料粒子として未処理のカーボンブラックを使用した以外は製造実施例１と同様にして中間層用塗布液を作製し、積層型感光体実施例１〜５と同様にして、積層型感光体を作製した。
【００７６】
＜積層型感光体比較例２＞顔料粒子として未処理の酸化チタンを使用した以外は製造実施例３と同様にして中間層用塗布液を作製し、積層型感光体実施例１〜５と同様にして、積層型感光体を作製した。
【００７７】
＜ＨＴＭ−１＞
【化１２】

【００７８】
＜ＥＴＭ−１＞
【化１３】

【００７９】
＜ＥＴＭ−２＞
【化１４】

【００８０】
〔画像評価〕
上記単層型感光体実施例・比較例で得られた中間層を有する単層型感光体を、ブラザー工業（株）社製レーザプリンタＨＬ−１６７０改造機に搭載して、温度５０℃、湿度９０％の環境下において、黒白帯状の画像を１６０枚連続印写した。そして１６０枚目の画像カブリを目視にて判断した。
【００８１】
一方、上記積層型感光体実施例・比較例で得られた中間層を有する積層型感光体を、キャノン（株）社製レーザプリンタＬＢＰ−４５０に搭載して、単層型感光体の場合と同様にして画像カブリを評価した。
【００８２】
表２に画像評価結果を示した。
【表２】

【００８３】
画像評価の判定基準は以下の通りとした。
○：画像カブリが目視では確認できない。
△：画像カブリが確認される。
×：画像カブリが発生していることが一目でわかり、その程度がひどい。
【００８４】
以上の評価結果より、本発明の、ポリマーによりグラフト化された顔料粒子を含有する中間層を有する電子写真有機感光体を使用することにより、中間層の導電性のムラが著しく軽減され、カブリのない良好な画像を得ることができる。また、中間層の導電性のムラが軽減される理由としては、中間層に使用されるバインダー樹脂または樹脂溶液中での、ポリマーによりグラフト化した顔料粒子の分散性が良好であるためと考えられる。
【００８５】
【発明の効果】
以上記述したように、本発明の電子写真有機感光体を使用することにより、中間層の導電性のムラが著しく軽減され、カブリのない良好な画像を得ることができる。
【００８６】
【図面の簡単な説明】
【図１】ポリマーによりグラフト化された顔料粒子を示す概略図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic organic photoreceptor used in an image forming apparatus such as a laser printer, an electrostatic copying machine, a plain paper facsimile apparatus, and a composite apparatus having these functions.
[0002]
[Prior art]
In the above image forming apparatus, a so-called organic photoreceptor comprising a charge generating agent that generates charges by light irradiation, a charge transporting agent that transports the generated charges, and a binder resin that constitutes a layer in which these substances are dispersed. Is widely used. Organic photoconductors can be broadly classified as those having a single-layer type photosensitive layer containing a charge generating agent and a charge transporting agent in the same layer, a charge generating layer containing the charge generating agent, and a charge transporting agent. A photoreceptor having a laminated photosensitive layer in which a charge transport layer containing an agent is laminated is generally used.
[0003]
However, the above photoreceptor has the following problems.
1. In the charging process at the time of image output, either positive or negative charge is added to the surface of the photoconductor, and at this time, a charge having a polarity opposite to that of the photoconductor surface is generated on the support substrate side. In the absence of the intermediate layer, the charge on the support substrate side is injected into the photosensitive layer, causing a reduction in charge on the surface of the photoreceptor and causing image fogging.
2. When the photosensitive layer is directly coated on the supporting substrate, the photosensitive layer may not be sufficiently bonded to the supporting substrate depending on the type of binder resin and coating conditions.
3. If there are defects such as scratches on the surface of the support substrate, black spots are generated on the image.
[0004]
In order to solve the above problems, there is a method in which an intermediate layer containing a binder resin is provided on a support substrate and a photosensitive layer is provided thereon. That is, by providing an intermediate layer, it is possible to prevent the charge on the support substrate side from being easily injected into the photosensitive layer, and to firmly bond the photosensitive layer on the support substrate to cover defects on the surface of the support substrate. Can be smoothed.
[0005]
However, when the intermediate layer is composed only of the binder resin, since the electrical conductivity is low, there is a problem that image fog occurs unless the film thickness of the intermediate layer is set to the submicron level. This is because in the exposure process during image output, positive and negative charges are generated in the exposed area by the charge generator, but the charge to be transported to the support substrate side (charge having the same polarity as the surface of the photoreceptor) is intermediate. This is because it is blocked by the layer and remains in the photosensitive layer. Furthermore, the charge on the surface of the photoconductor cannot be removed in the charge removal step after the transfer step, and the increase in the residual potential also contributes to image fogging. On the other hand, if the intermediate layer is made thin, it becomes difficult to cover defects on the surface of the support substrate.
[0006]
Accordingly, it is conceivable to increase the conductivity of the intermediate layer to ensure the film thickness. For example, Japanese Patent Laid-Open No. 59-93453 describes that a titanium oxide powder whose surface is treated with tin oxide or alumina is contained, and Japanese Patent Laid-Open No. 6-202366 describes that non-conductive titanium oxide particles are contained in the intermediate layer. Has been.
[0007]
However, during the formation of the intermediate layer by coating, drying and solidifying the coating liquid in which metal oxide particles such as titanium oxide are dispersed on the support substrate, the metal oxide aggregates to generate aggregated particles. . For this reason, the conductivity of the entire intermediate layer increases, but the conductivity becomes uneven, and charges are trapped in a portion with low conductivity. As a result, the residual potential is increased and the same problem as described above is caused.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above technical problem, to significantly reduce the non-uniformity of the conductivity of the intermediate layer as compared with the prior art, and to provide an electrophotographic organic photoreceptor free from image fog.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted intensive research, and in an electrophotographic organic photoreceptor in which an organic photosensitive layer is formed on a conductive substrate via an intermediate layer, the intermediate layer has at least An electrophotographic organic material formed by dispersing pigment particles in a binder resin, wherein the pigment particles are grafted with a polymer having at least a reactive group capable of reacting with a functional group on the surface of the pigment particles. It has been found that the photoreceptor has remarkably little unevenness in the conductivity of the intermediate layer and no image fog. In particular, the reactive group of the polymer is preferably at least one group selected from an epoxy group, a thioepoxy group, an aziridine group, an oxazoline group, an isocyanate group, and an N-hydroxyalkylamide group.
[0010]
[Operation of the present invention]
The “pigment particles grafted with a polymer” described in the present specification refers to pigment particles in which a polymer portion (polymer chain) is grafted on the pigment particles. A polymer is grafted to primary particles or several aggregates of pigment particles. Furthermore, “grafting” as defined in this specification is defined by Jean-Baptiste Donnet et al. In his book “Carbon Black” (Kodansha 1978). It is an irreversible addition. By performing an irreversible addition reaction, the polymer portion can be chemically bonded to the pigment particle surface portion.
[0011]
Specifically, “a pigment particle grafted with a polymer” means a pigment particle and a polymer having a reactive group having reactivity with a functional group such as a hydroxyl group or a carboxyl group on the surface of the pigment particle. It has been reacted.
[0012]
The pigment particles added to the intermediate layer function as a resistance adjuster for the intermediate layer as described in the above-described prior art, but generally have poor dispersibility in the binder resin solution. Aggregation is likely to occur, and unevenness in the conductivity of the intermediate layer is likely to occur.
[0013]
Therefore, the present inventors use a functional group on the surface of the pigment particle to graft a polymer having a reactive group capable of chemically reacting with the functional group onto the surface of the pigment particle, so that the polymer becomes the surface of the pigment particle. It has been found that this polymer exhibits an action as a dispersant, the affinity between the pigment particles and the binder resin is improved, and the dispersibility in the binder resin is remarkably improved.
[0014]
FIG. 1 shows an outline of pigment particles grafted with a polymer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the electrophotographic organic photoreceptor of the present invention, an organic photosensitive layer may be formed on an electrically conductive substrate through an intermediate layer containing pigment particles grafted with a binder resin and a polymer. A single layer type containing a binder resin, a charge generating agent and a charge transporting agent, a charge generating layer containing a binder resin and a charge generating agent, and a charge transporting layer containing a binder resin and a charge transporting agent Either of the stacked types may be used.
[0016]
The constitution or constituent material of the electrophotographic organic photoreceptor of the present invention will be described in detail below.
[0017]
<Intermediate layer>
As the pigment particles used in the intermediate layer of the electrophotographic organic photoreceptor of the present invention, conventionally known organic pigments or inorganic pigments can be used, but the average particle size is 1.0 μm or less, more preferably the average Inorganic pigments or metal oxides such as carbon black having a particle size of 300 nm or less, titanium oxide, aluminum oxide, silicon carbide, zirconia oxide, zinc oxide and tin oxide are preferably used. When the average particle diameter exceeds 1.0 μm, the pigment particles grafted with the obtained polymer may not be able to impart sufficient dispersibility.
[0018]
Among the pigment particles, acidic carbon black has many functional groups such as carboxyl groups on the surface and is easily grafted. In addition, the electrical properties as intermediate layer pigment particles are excellent. Even neutral carbon black can be easily converted to acidic carbon black by oxidation treatment. As the carbon black, any type such as furnace black, channel black, acetylene black, lamp black and the like can be used, but furnace black is preferable.
[0019]
When a metal oxide is used as the pigment particles, the electrical characteristics as an intermediate layer are excellent. Among metal oxides, titanium oxide particles are particularly excellent. The titanium oxide particles may be either crystalline or amorphous. The crystalline form of crystalline titanium oxide is most commonly rutile, but may be anatase, brookite, or the like. The metal oxide pigment particles are preferably not subjected to organic surface treatment with polysiloxane or the like. When the treatment rate of the organic surface treatment is high, the grafting rate of the polymer is lowered and sufficient dispersibility cannot be imparted. However, for example, there is no particular problem with an inorganic surface treatment in which the titanium oxide surface is coated with an inorganic material such as alumina, silica, zirconia, or the like.
[0020]
All the pigment particles exemplified above can be used alone or in combination of two or more.
[0021]
The polymer to be reacted with the pigment particles includes a segment (B) having a high affinity for the target medium (dispersion medium and binder resin for forming an intermediate layer added later) and a segment having a lower affinity for the target medium than the segment (B). (A), and the molecular design is such that only the segment (A) has a reactive group that reacts with the surface functional group of the pigment particle to be grafted, and the target medium or properties close to this. Grafting is preferably carried out in a dispersion medium composed of a medium having (polarity).
[0022]
The polymer produced by the above method and reacted with the pigment particles is composed of the segment (A) having a reactive group and the segment (B) having affinity for the target medium as described above. Oriented toward the dispersion medium liquid, the segment (A) surrounds the surface of the pigment particles, and the pigment particles can be grafted.
[0023]
In general, as a method for obtaining a graft-type polymer, for example, a polymerization initiator and a polymerizable monomer are subjected to solution polymerization, emulsion polymerization, bulk polymerization, or suspension polymerization in the presence of a high molecular weight polymer that becomes a graft chain. Thus, a method for polymerizing a polymer as a main chain is known. However, if the high molecular weight material does not have a radical polymerizable functional group, the resulting graft copolymer contains a large amount of ungrafted polymer, and has the disadvantage that the graft efficiency is low. Yes. Therefore, it is preferable to use a radical polymerizable high molecular weight as the high molecular weight. Such a radical polymerizable high molecular weight substance is generally referred to as a “macromonomer” and is a high molecular weight substance having a radical polymerizable group at one end, for example, a (meth) acryloyl group, a styryl group, etc. It is obtained by reacting a polymer having a carboxyl group at one end with a radical polymerizable monomer having a glycidyl group in an organic solvent. Japanese Patent Publication No. 43-11224 discloses a reaction of a prepolymer obtained by radical polymerization of a radical polymerizable monomer in an organic solvent in the presence of mercaptoacetic acid with glycidyl methacrylate in the presence of a dimethyllaurylamine catalyst. The method obtained is disclosed.
[0024]
That is, polymerization having in the molecule a reactive group capable of reacting with a functional group on the surface of the pigment particle in the presence of the radical polymerizable high molecular weight substance (b) as a component forming the main chain of the segment (B) It is obtained by adding a radical polymerization catalyst and polymerizing the polymerizable monomer (a) and the polymerizable monomer (c) forming the skeleton of the segment (A) blended as necessary (see FIG. 1). ).
[0025]
[1] Polymerizable monomer (a) having in its molecule a reactive group capable of reacting with a functional group on the pigment particle surface:
In order to make the grafting more reliable and stable, it is desirable to bind irreversibly to the pigment particle via a covalent bond. Examples of the bond include an ester bond, a thioester bond, an amide bond, and an amino bond. , Ether bond, thioether bond, carbonyl bond, thiocarbonyl bond and sulfonyl bond. The reactive group is preferably at least one or more selected from the group consisting of an epoxy group, a thioepoxy group, an aziridine group, an N-hydroxyacrylamide group, and an oxazoline group. However, the reactive groups for the pigment particles are not necessarily limited to these. Specific examples of the polymerizable monomer (a) are shown below.
[0026]
<Epoxy group-containing polymerizable monomer>
[Chemical 1]

(R in the formula₁~ R₈Represents hydrogen or a methyl group, and n is 0 or an integer of 1 to 20. )
[0027]
<Thioepoxy group-containing polymerizable monomer>
[Chemical formula 2]

(R in the formula₉~ R_{1 2}Represents hydrogen or a methyl group, and n is 0 or an integer of 1 to 20. )
[0028]
<Aziridine group-containing polymerizable monomer>
[Chemical Formula 3]

[Formula 4]

(R in the formula_{1 3}~ R₃₉Represents hydrogen or a methyl group, and n is 0 or an integer of 1 to 20. )
[0029]
<Oxazoline group-containing polymerizable monomer>
2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-5 Ethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-4-ethyl- 2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4,5-dimethyl-2-oxazoline
[0030]
<N-hydroxyalkylamide group-containing polymerizable monomer>
N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-hydroxybutylacrylamide, N-hydroxyisobutylacrylamide, N-hydroxy-2-ethylhexylacrylamide, N-hydroxycyclohexylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethyl Methacrylamide, N-hydroxybutyl methacrylamide, N-hydroxyisobutyl methacrylamide, N-hydroxy-2-ethylhexyl methacrylamide, N-hydroxycyclohexyl methacrylamide
[0031]
[2] Polymerizable monomer (c) forming the skeleton of segment (A):
As the polymerizable monomer (c) that can be used as necessary in order to make the segment (A) into a desired skeleton, the monomer (a) and a component that forms the segment (B) as described later are used. It is not particularly limited as long as it can be copolymerized with the radically polymerizable high molecular weight substance (b). For example, styrene, o-methylstyrene, m-methylstyrene depending on the molecular structure of the segment (A) to be obtained. , Styrene monomers such as p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene; acrylic acid , Methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, Stearyl crylate, 2-ethylhexyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate , Acrylic acid or methacrylic acid monomers such as stearyl methacrylate; one or more monomers such as ethylene, propylene, butylene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, N-vinylpyrrolidone It can be used as appropriate.
[0032]
[3] Radical polymerizable high molecular weight substance (b) as a component forming the main chain of segment (B):
The radical polymerizable high molecular weight substance (b) (macromonomer) can be obtained, for example, by reacting a polymer having a terminal carboxyl group with a radical polymerizable monomer having a glycidyl group in an organic solvent. As the main chain of the segment (B) component, for example, polysiloxane structure, poly (meth) acrylic structure, polyether structure such as polyalkylene glycol, polyester structure, polyalkylene structure, polyamide structure, Examples thereof include a polyimide structure, a polyurethane structure, a fluororesin structure, and the like, which have a reactive group at one end of these polymer chains.
[0033]
Specifically, as the radical polymerizable high molecular weight body (b) having a polysiloxane structure, for example, (meth) acryloyl group-containing polydimethylsiloxane, styryl group-containing polydimethylsiloxane (meth) acryloyl group-containing partially octyl-substituted poly Polymerizable polysiloxanes such as dimethylsiloxane, styryl group-containing partially octyl-substituted polydimethylsiloxasan, styryl group-containing partially phenyl-substituted polydimethylsiloxane, tris (trimethylsiloxy) silylpropyl (meth) acrylate, and the like are listed. 1 type (s) or 2 or more types can be used, For example, the thing of the following structures is mention | raise | lifted.
[0034]
[Chemical formula 5]

(In the formula, B represents —COO— or a phenylene group, R¹Represents a hydrogen atom or a methyl group, R²Represents an alkylene group having 1 to 6 carbon atoms, R^Three~ R¹³Are the same or different and each represents an aryl group, an alkyl group having 1 to 6 carbon atoms or an alkoxyl group having 1 to 10 carbon atoms, a and b are the same or different and each represents an integer of 0 to 10; Each integer is shown. )
[0035]
In the case where the segment (B) has a polymeth (acrylic) structure, for example, a compound as shown below is used as the radical polymerizable high molecular weight body (b).
[Chemical 6]

(Wherein R¹, R²Are the same or different and each represents a hydrogen atom or a methyl group;^ThreeRepresents an alkyl group having 1 to 25 carbon atoms, X represents an arbitrary connecting chain, Y represents an initiator terminal or an H atom, and n represents an integer of 0 to 500. )
[0036]
[Chemical 7]

(Wherein R¹, R², R^FourAre the same or different and each represents a hydrogen atom or a methyl group;^Three, R^FiveAre the same or different and each represents an alkyl group having 1 to 25 carbon atoms, X is an arbitrary connecting chain, Y is an initiator terminal or H atom, and m and n are the same or different and each represents an integer of 0 to 500 . )
[0037]
[Chemical 8]

(Wherein R¹, R²Are the same or different and each represents a hydrogen atom or a methyl group;^ThreeRepresents an alkylene group having 1 to 25 carbon atoms, R^FourRepresents an alkyl group having 1 to 25 carbon atoms, X represents an arbitrary connecting chain, Y represents an initiator terminal or an H atom, and n and m are the same or different and represent an integer of 0 to 500. )
[0038]
In the case where the segment (B) has a polyalkylene glycol structure, as the radical polymerizable high molecular weight body (b), for example, compounds as shown below are used.
[Chemical 9]

(Wherein R¹, R², R^ThreeAre the same or different and each represents a hydrogen atom or a methyl group, and n represents an integer of 0 to 500. )
[0039]
Embedded image

(Wherein R¹, R², R^Three, R^FourAre the same or different and each represents a hydrogen atom or a methyl group, and n and m are the same or different and each represents an integer of 0 to 500. )
[0040]
In the case where the segment (B) has a polystyrene-based structure, as the radical polymerizable high molecular weight body (b), for example, the following compounds are used.
Embedded image

(Wherein R¹Represents a hydrogen atom or a methyl group, X is an arbitrary connecting chain, Y is an initiator terminal or H atom, Z is a hydrogen atom, a halogen substituent or an alkyl group having 1 to 8 carbon atoms, and n is 0 to 500 Indicates an integer. )
[0041]
The linking chain X shown in the above formula group is described in detail in, for example, “Macromonomer Chemistry and Industry” (supervised by Yuya Yamashita, published by IPC Corporation, September 20, 1989), Either can be used.
[0042]
Any radical catalyst can be used as long as it is usually used for the polymerization of vinyl monomers. Typical examples include azo compounds such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, di-tert-butyl. And peroxide compounds such as peroxide, tert-butyl peroctoate, and tert-butyl peroxy-2-ethylhexanoate. These are usually 0.2 to 10 weights per 100 weight parts of monomer. Parts, preferably in the range of 0.5 to 5 parts by weight. The solvent is appropriately selected according to the type of monomer and radical polymerizable high molecular weight used.
[0043]
The molecular weight of the graft or block polymer obtained as described above is not particularly limited, but in view of the effect of grafting on the pigment particles and workability at the time of reaction with the pigment particles, the average molecular weight is 1,000 to It is preferable to set it as the range of 1,000,000, More preferably, it is the range of 5,000-100,000.
[0044]
In addition, the molecular weight of the segment (A) and the segment (B) in the graft or block polymer is not particularly limited, and may vary depending on the type of polymer chain constituting these segments. From the viewpoint of graft efficiency with respect to the polymer, the segment (A) is preferably in the range of an average molecular weight of 300 to 100,000, more preferably in the range of 5,000 to 50,000, and the dispersibility to be imparted to the pigment particles. From the viewpoint of the modification effect, the segment (B) is preferably in the range of an average molecular weight of 500 to 100,000, more preferably in the range of 1,000 to 50,000. Further, the number of reactive groups contained in the segment (A) of the graft or block polymer is not particularly limited, but it is 1 to 50 on average per polymer molecule, more preferably about 1 to 20 preferable.
[0045]
With respect to the pigment particles grafted with the polymer, the ratio of the graft polymer to the pigment particles is preferably 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, based on 100 parts by weight. When the graft polymer is less than 1 part by weight, the obtained pigment particles are aggregated. Further, when the graft polymer exceeds 200 parts by weight, the polymer is grafted more than necessary, and the coating liquid for forming an intermediate layer prepared using the pigment particles grafted with this polymer is used. The coating performance, the physical properties of the formed intermediate layer, and the electrical characteristics of the electrophotographic photoreceptor formed containing the intermediate layer are deteriorated.
[0046]
The coating solution for forming an intermediate layer is composed of pigment particles grafted with a polymer, a binder resin, and a solvent. The average molecular weight of the binder resin in the intermediate layer may be in the range of 1,000 to 1,000,000. The range of 5,000 to 200,000 is more preferable. In addition, the amount ratio of the pigment particles to which the polymer is grafted and the binder resin is preferably 5 to 500 parts by weight, particularly 20 to 200 parts by weight, based on 100 parts by weight of the grafted pigment particles. When the binder resin is less than 5 parts by weight, the formed intermediate layer does not have sufficient film formability, and when the binder resin is 500 parts by weight or more, the intermediate layer does not have sufficient electrical characteristics.
[0047]
As the binder resin used in the intermediate layer of the electrophotographic organic photoreceptor of the present invention, various resins used in conventionally known photosensitive layers can be used. In particular, polyamide resin, polyvinyl acetal resin, phenol resin, melamine resin, polyester resin, silicon resin, and acrylic resin are preferable. Moreover, the said binder resin can be used individually or in mixture of 2 or more types.
[0048]
In addition to pigment particles grafted with a polymer, an organic pigment having a certain degree of conductivity such as a metal oxide or a perylenetetracarboxylic acid diimide derivative is separately added to the intermediate layer of the electrophotographic photoreceptor of the present invention. May be. In this case, the pigment particles grafted with the polymer act as a dispersion aid for the separately added pigment, and are effective in improving the dispersibility of the separately added pigment.
[0049]
Further, regarding the polymer-grafted pigment particles, the segment (B) has at least one or more selected from the group consisting of an unsaturated double bond group, a hydroxyl group, a carboxyl group, and an alkoxysilyl group. Also good. Regarding the intermediate layer when a curable resin is used as the binder resin, the use of pigment particles grafted with the polymer having the reactive group contributes to the curing of the intermediate layer composition during the curing process. As a result, a high-strength film can be formed, and an intermediate layer having excellent film forming properties and various physical properties such as electrical properties can be obtained.
[0050]
The intermediate layer of the electrophotographic organic photoreceptor of the present invention is used in combination with conventionally known electron transport agents, hole transport agents, pigments, additives, etc. in addition to the pigment particles grafted with the polymer in the binder resin. It may be included. These compounds may be used alone or in combination of two or more. Examples of the additive include plasticizers such as phthalate esters, antioxidants such as hindered amines and hindered phenols, radical scavengers, ultraviolet absorbers, and thickeners.
[0051]
In the case of forming the intermediate layer, first, the binder resin exemplified above and a constituent material such as pigment particles grafted with a polymer together with an appropriate dispersion medium, a known method such as a roll mill, a ball mill, an attritor, a paint shaker, A coating solution is prepared by dispersing and mixing using an ultrasonic disperser or the like. Next, this coating solution may be applied and dried / cured by a known means such as a blade method, a dipping method, or a spray method.
[0052]
Examples of the dispersion medium for preparing the coating liquid include conventionally known organic solvents. For example, alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane, dichloroethane, chloroform and carbon tetrachloride Halogenated hydrocarbons such as chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and methyl acetate; Examples thereof include dimethylformamide and dimethyl sulfoxide. Furthermore, you may use surfactant, a leveling agent, etc.
[0053]
The intermediate layer has a thickness of 0.1 to 50 μm, preferably 1 to 30 μm. Between the intermediate layer and the photosensitive layer, improvement of coating properties, prevention of soaking (of the coating solution for charge generating agent), improvement of drying properties, improvement of electrophotographic characteristics (image fogging, image unevenness, repeat characteristics, etc.) Therefore, a resin layer may be provided in a range that does not hinder charge transport control.
[0054]
<Support substrate>
As the support substrate used in the present invention, various materials having conductivity can be used. For example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium , Indium, stainless steel, brass and other simple metals, plastic materials on which the metal is vapor-deposited or laminated, glass coated with aluminum iodide, tin oxide, indium oxide, etc., resin substrate in which carbon black, etc. are dispersed, etc. Can be given.
[0055]
The shape of the support substrate may be either a sheet shape or a drum shape according to the structure of the image forming apparatus to be used. The substrate itself has conductivity, or the surface of the substrate has conductivity. It should be. Further, it is preferable that the support substrate has sufficient mechanical strength when used.
[0056]
The surface of the support substrate may be subjected to a surface treatment such as a roughening treatment, an oxidation treatment, or an etching process as necessary.
[0057]
<Photosensitive layer>
The photosensitive layer in the electrophotographic organic photoreceptor of the present invention is classified into a single layer type and a multilayer type depending on the constitution. The single-layer type photoreceptor is obtained by providing a single photosensitive layer containing at least a binder resin, a charge transport agent, and a charge generator on a support substrate. In the multilayer type photoreceptor, a charge generating layer containing a binder resin and a charge generating agent and a charge transporting layer containing a binder resin and a charge transporting agent are laminated on a conductive substrate in this order or in the reverse order. It is a thing.
[0058]
As the charge generating agent and charge transporting agent (hole transporting agent, electron transporting agent) binder resin to be contained in the photosensitive layer, conventionally known compounds can be used alone or in combination of two or more.
[0059]
In the single-layer type photosensitive layer, the charge generating agent is 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, and the hole transporting agent is 5 to 500 parts by weight with respect to 100 parts by weight of the binder resin. Part, particularly 25 to 200 parts by weight. Moreover, when it contains an electron transport agent, it is preferable to make it contain in the ratio of 5-100 weight part with respect to 100 weight part of binder resin, especially 10-80 weight part. When the hole transport agent and the electron transport agent are used in combination, the total amount is preferably 20 to 500 parts by weight, particularly 30 to 200 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the single-layer type photosensitive layer is preferably 5 to 100 μm, particularly preferably about 10 to 50 μm.
[0060]
In the multilayer photosensitive layer, the charge generator is preferably contained in an amount of 5 to 1000 parts by weight, particularly 30 to 500 parts by weight with respect to 100 parts by weight of the binder resin. Further, in the charge transport layer, when the electron transport agent is contained with respect to 100 parts by weight of the binder resin, the electron transport agent is 0.1 to 250 parts by weight, particularly 0.5 to 150 parts by weight. When the hole transport agent is contained, the hole transport agent is preferably contained in an amount of 10 to 500 parts by weight, particularly 25 to 200 parts by weight. The thickness of the laminated photosensitive layer is preferably 0.01 to 5 μm, particularly about 0.1 to 3 μm for the charge generation layer, and 2 to 100 μm, particularly about 5 to 50 μm for the charge transport layer.
[0061]
In addition to the components described above, various additives such as a fluorene compound, an ultraviolet absorber, a plasticizer, a surfactant, and a leveling agent can be added to the photosensitive layer. In order to improve the sensitivity of the photoreceptor, a sensitizer such as terphenyl, halonaphthoquinones, and acenaphthylene may be added. A protective layer may be formed on the surface of the electrophotographic organic photoreceptor of the present invention.
[0062]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0063]
<Preparation of coating solution for intermediate layer>
<Manufacturing Example 1> In a separable flask equipped with a stirrer, an inert gas introduction tube, a reflux condenser, and a thermometer, a polyamide macromonomer (highly radically polymerizable as a component forming the main chain of the segment (B)) 40 parts by weight of the molecular weight body (b)), 7.5 parts by weight of a styrene monomer (corresponding to the polymerizable monomer (c) forming the skeleton of the segment (A)), 2- (1-aziridinyl) ethyl methacrylate 5 parts by weight (corresponding to a polymerizable monomer (a) having a reactive group capable of reacting with a functional group on the pigment particle surface in the molecule), 5 parts by weight of azoisobutyronitrile as an initiator, ethanol (graft The reaction solvent was dissolved in 75 parts by weight. The polymerization reaction was performed at 90 ° C. for 4 hours under a nitrogen stream, and further polymerized at 110 ° C. for 2 hours, and then cooled to obtain a polymer solution A having a nonvolatile content of 40%.
[0064]
Furthermore, in a separable flask equipped with a stirrer and a reflux condenser, 16 parts by weight of carbon black (Mitsubishi Kasei MA-600) without surface treatment, 10 parts by weight of the above polymer solution A, ethanol (grafting reaction solvent) ) 74 parts by weight and 750 parts by weight of zirconia beads were charged. The grafting reaction was carried out at 100 ° C. for 1.5 hours while stirring at a rotational speed of 800 rpm, and after separating the zirconia beads, the mixture was cooled while being kneaded while stirring at 100 rpm, and pulverized to polymer-grafted carbon black. A dispersion was obtained (carbon black / graft polymer / ethanol = 16/4/80).
[0065]
Dissolve and disperse 100 parts by weight of the polymer-grafted carbon black dispersion, 12 parts by weight of a solvent-soluble polyamide (Teijin Chemical Industries Toraysin MF-30) as an intermediate layer binder resin, and 108 parts by weight of methanol. An intermediate layer coating solution was prepared.
[0066]
<Production Examples 2 to 5> In Production Example 1, the radically polymerizable high molecular weight body (b) as a component forming the main chain of the segment (B), the polymerizable single monomer forming the skeleton of the segment (A) Table 1 shows the body (c), the polymerizable monomer (a) having a reactive group capable of reacting with the functional group on the pigment particle surface, pigment particles, the grafting reaction solvent, and the binder resin for the intermediate layer. An intermediate layer coating solution was prepared in place of the indicated materials.
[0067]
[Table 1]

Titanium oxide: Sakai Chemical's rutile titanium oxide STR-60N
[0068]
[Production of single layer type photoreceptor]
<Single Layer Type Photoconductor Examples 1 to 5> The intermediate layer coating solution obtained in the above Production Examples 1 to 5 was applied on a φ30 aluminum base tube (support base) by dip coating, and 150 ° C. And dried for 30 minutes to form an intermediate layer having an average film thickness of 10 μm.
[0069]
A charge generating agent (X-type metal-free phthalocyanine) 3.5 parts by weight, an electron transporting agent (ETM-1) 35 parts by weight, a hole transporting agent (HTM-1) 55 parts by weight, and a bisphenol having a weight average molecular weight of 100,000. A single layer type photosensitive layer coating solution was prepared by dispersing or dissolving 100 parts by weight of Z-type polycarbonate resin together with 800 parts by weight of tetrahydrofuran in a ball mill for 24 hours. This coating solution was applied onto the intermediate layer by a dip coating method to produce a single layer type photoreceptor having an average film thickness of 35 μm.
[0070]
<Single Layer Type Photoconductor Comparative Example 1> A coating solution for an intermediate layer was prepared in the same manner as in Production Example 1 except that untreated carbon black was used as pigment particles, and single layer type photoconductor examples 1 to 5 were prepared. In the same manner as described above, a single-layer type photoreceptor was produced.
[0071]
<Single Layer Photoreceptor Comparative Example 2> An intermediate layer coating solution was prepared in the same manner as in Production Example 3 except that untreated titanium oxide was used as the pigment particles, and single layer photoreceptor Examples 1 to 5 were prepared. In the same manner as described above, a single-layer type photoreceptor was produced.
[0072]
[Preparation of multilayer photoconductor]
<Multilayer Photoreceptor Comparative Examples 1 to 5> Further, 2 parts by weight of solvent-soluble polyamide (Toresin MF-30 manufactured by Teikoku Chemical Industry Co., Ltd.) is added to 98 parts by weight of methanol on the intermediate layer obtained in Production Examples 1 to 5. The solution dissolved in was applied by dip coating and dried at 150 ° C. for 30 minutes to form a barrier layer having a thickness of 0.1 μm.
[0073]
Then, 100 parts by weight of a charge generator (Y-type titanyl phthalocyanine) was added to 3900 parts by weight of ethyl cellosolve as a dispersion medium, and primary dispersion was performed using an ultrasonic disperser. Furthermore, a liquid prepared by dissolving 100 parts by weight of polyvinyl butyral (BM-1 manufactured by Sekisui Chemical Co., Ltd.) as a binder resin in 900 parts by weight of ethyl cellosolve was added to this dispersion, and the ultrasonic disperser was used again. Then, it was secondarily dispersed to prepare a coating solution for the charge generation layer. Next, this coating solution was applied on the barrier layer prepared above by a dip coating method and dried at 110 ° C. for 5 minutes to form a charge generation layer having a thickness of 0.4 μm.
[0074]
Next, 6 parts by weight of an electron transporting agent (ETM-2), 90 parts by weight of a hole transporting agent (HTM-1), and 100 parts by weight of a bisphenol Z-type polycarbonate as a binder resin are mixed with 800 parts by weight of tetrahydrofuran, Dispersion was performed to obtain a coating solution for the charge transport layer. This coating solution was dip-coated on the charge generation layer and dried at 110 ° C. for 30 minutes to form a charge transport layer having a thickness of 33 μm.
[0075]
<Laminated Photoconductor Comparative Example 1> An intermediate layer coating solution was prepared in the same manner as in Production Example 1 except that untreated carbon black was used as the pigment particles, and the same as in Laminated Photoconductor Examples 1-5. Thus, a laminated photoreceptor was produced.
[0076]
<Laminated Photoconductor Comparative Example 2> An intermediate layer coating solution was prepared in the same manner as in Production Example 3 except that untreated titanium oxide was used as the pigment particles, and the same as in Laminated Photoconductor Examples 1 to 5. Thus, a laminated photoreceptor was produced.
[0077]
<HTM-1>
Embedded image

[0078]
<ETM-1>
Embedded image

[0079]
<ETM-2>
Embedded image

[0080]
[Image evaluation]
The single layer type photoreceptor having the intermediate layer obtained in the above-mentioned single layer type photoreceptor examples and comparative examples is mounted on a laser printer HL-1670 modified machine manufactured by Brother Industries, Ltd., and the temperature is 50 ° C. and the humidity is 50 ° C. Under a 90% environment, 160 black-and-white belt-like images were continuously printed. The 160th image fog was determined visually.
[0081]
On the other hand, the multilayer photoconductor having the intermediate layer obtained in the above-mentioned multilayer photoconductor examples and comparative examples is mounted on a laser printer LBP-450 manufactured by Canon Inc. Similarly, image fog was evaluated.
[0082]
Table 2 shows the image evaluation results.
[Table 2]

[0083]
The criteria for image evaluation were as follows.
○: Image fog cannot be visually confirmed.
Δ: Image fogging is confirmed.
X: It can be seen at a glance that image fogging has occurred, and its level is severe.
[0084]
From the above evaluation results, by using the electrophotographic organic photoreceptor having the intermediate layer containing the pigment particles grafted with the polymer of the present invention, the unevenness of the conductivity of the intermediate layer is remarkably reduced, and the fogging is prevented. No good image can be obtained. In addition, the reason why the uneven conductivity of the intermediate layer is reduced is considered to be because the dispersibility of the pigment particles grafted with the polymer in the binder resin or resin solution used in the intermediate layer is good. .
[0085]
【The invention's effect】
As described above, by using the electrophotographic organic photoreceptor of the present invention, the unevenness of the conductivity of the intermediate layer is remarkably reduced, and a good image free from fogging can be obtained.
[0086]
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing pigment particles grafted with a polymer.

Claims (4)

In the electrophotographic organic photoreceptor in which the organic photosensitive layer is formed on the conductive substrate via the intermediate layer, the intermediate layer is formed by dispersing at least pigment particles in a binder resin, and the pigment particles are An electrophotographic organic photoreceptor, which is grafted with a polymer having at least a reactive group capable of reacting with a functional group on the surface of pigment particles. The reactive group of the polymer is at least one group selected from an epoxy group, a thioepoxy group, an aziridine group, an oxazoline group, an isocyanate group, and an N-hydroxyalkylamide group. Item 2. The electrophotographic organic photoreceptor according to Item 1. The polymer is a block-type or graft-type copolymer comprising a segment (A) having a reactive group capable of reacting with a functional group on the pigment particle surface and a segment (B) having a structure different from the segment. 3. The electrophotographic organic photoreceptor according to claim 1, wherein the electrophotographic organic photoreceptor is present. The segment (B) is at least a polysiloxane structure, poly (meth) acrylic acid structure, polyether structure, poly (meth) acrylonitrile structure, polyester structure, polyalkylene structure, polyamide structure, polyimide system 4. The electrophotographic organic photoreceptor according to claim 3, which has a structure selected from a structure, a polyurethane structure, and a fluororesin structure.

Images