JP2004212562A - Electrophotographic photoreceptor, process cartridge, and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high chargeability, high sensitivity, low residual potential and small photomemory after long-term use because it is excellent in wear and scuffing resistances. <P>SOLUTION: The electrophotographic photoreceptor has an uppermost layer containing a thermoplastic resin and inorganic fine particles having a volume average particle diameter of 0.01-2.0 μm, wherein a Universal hardness (Hu) of the uppermost layer obtained by a hardness test of surface coating is 220 N/mm<SP>2</SP>≤Hu≤400 N/mm<SP>2</SP>in an environment at 25°C and 50% humidity, and a plastic deformation ratio of the uppermost layer under an indentor used in the hardness test satisfies the following expression: 50%≤ä(energy required for plastic deformation)×100}÷ä(energy required for plastic deformation)+(energy required for elastic deformation)}≤70%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２２】
また、本発明は、上記子写真感光体を有するプロセスカートリッジ及び電子写真装置である。
【００２３】
【発明の実施の形態】
一般に、有機高分子膜の外部応力に対する膜の変形には、塑性変形と弾性変形があり、全変形量に対するそれぞれの変形の割合により、その膜の物性が性格付けられるといわれている。例えば、炭素繊維のような剛直さがあるものは、全体に占める塑性変形率が１００％に近く、エラストマーのようなゴム状のものは、弾性変形率の割合が大きいといった具合である。
【００２４】
ところで、表面皮膜硬度試験から得られるユニバーサル硬さ値（Ｈｕ）とは、ビッカースダイヤモンド圧子による試験荷重下での押し込み深さを測定することにより下記式（２）によって規定される。
【００２５】
【数３】

【００２６】
また、圧子の荷重を減少させることにより、膜の塑性エネルギー（弾性エネルギー）を解析することもできる。塑性変形率（弾性変形率）は圧子が膜に対して行った仕事量（エネルギー）、即ち圧子の膜に対する荷重の増減によるエネルギーの変化より求めたものであり、式（１）からその値は求まる。
【００２７】
このような測定方法により得られた値を用いて最上層の高耐久化を図ろうとしている。しかし、これを実現するためには、膜の性状として剛直及び柔軟性の両者が必要であり、脆かったり延性があり過ぎたりしても製造上の難点がある。
【００２８】
我々は鋭意検討の結果、電子写真感光体の最上層が少なくとも熱可塑性樹脂と体積平均粒径０．０１〜２．０μｍの無機微粒子を含有し、かつユニバーサル硬さ値（Ｈｕ）と塑性変形率がある特定の範囲内であれば、耐磨耗性は勿論、耐傷性が大きく向上し、また分散助剤を使用しないのでフォトメモリーが良好であることを見出した。
【００２９】
即ち、Ｈｕが２２０Ｎ／ｍｍ^２未満の場合、現状の電子写真プロセスにおいては機械的強度の点で耐磨耗性も耐傷性も不充分であり、また４００Ｎ／ｍｍ^２を超える場合は、電子写真感光体の製造工程におけるハンドリングが著しく悪くなるため、実用上困難であり、２２０Ｎ／ｍｍ^２≦Ｈｕ≦４００Ｎ／ｍｍ^２の範囲で、初めて耐磨耗性、耐傷性と製造上の制約をクリアーできるものである。
【００３０】
また、塑性変形率についても７０％を超える最上層については微粒子との相互作用が弱く、膜から微粒子が脱離し傷が入り易くなる。また、クリーニングブレードや紙粉またはトナーに対しての膜の弾性力が不足しており、それらが感光体表面に圧着し融着の原因になったり傷をつけてしまう。一方、５０％未満であると膜の脆性が大きくなり過ぎ、クラックや、瞬間的な外的衝撃により致命的な傷を生じる。
【００３１】
表面皮膜硬度試験の測定条件に関しては圧子として、ビッカース四角錘ダイヤモンド圧子、ヌープ圧子、ベルコビッチ圧子及びボール圧子等があり、使用する圧子をビッカース四角鍾ダイヤモンド圧子とした場合、この圧子にかける荷重の最大値は５〜３００ｍＮの範囲である。これは電子写真感光体表面に対して、５ｍＮ未満であると膜表面の凹凸等の影響を受けて、測定の精度が低下するためであり、３００ｍＮを超える場合、表面層の膜厚にもよるが、圧子が基板の影響を受け易くなるためである。
【００３２】
このような測定条件のもとで得られたユニバーサル硬さ値（Ｈｕ）、塑性変形率が条件範囲内の値を有する最上層は、無機微粒子の膜補強効果を効果的に引き出すことができ、かつフォトメモリーが良好である。
【００３３】
以下に本発明に用いる樹脂の構成単位の具体例を表１に示すが、これらに限定されるものではない。また、以下の構成単位を２種以上共重合させてもよく、また２種以上混合して使用してもよい。
【００３４】
【表１】

【００３５】
合成例１（構成単位例１を有するポリアリレート樹脂の合成）
本発明において用いられる構成単位を有する重合体は、ビスフェノールのＣ型をテレフタル酸塩化物／イソフタル酸塩化物の混合物とアルカリの存在下で溶媒／水系中で混合し、界面重合を行うことにより作成される。テレフタル酸塩化物とイソフタル酸塩化物の比率は、その重合体の溶解性を考慮して決定されるもので定説はない。但し、いずれかの塩化物が３０ｍｏｌ％以下になると、合成した重合体の溶解性が極端に低下するので注意が必要である。通常は１／１の比率で合成するのが好ましい。
【００３６】
合成例２（構成単位例６を有するポリフェニレン樹脂の合成）
テトラヒドロフラン１０ｍｌ中に亜鉛粉末２．６ｇ（０．０４ｍｏｌ）を含む溶液に、テトラヒドロフラン３０ｍｌ中に２，５−ジクロロベンゾフェノン２．５ｇ（０．０１ｍｏｌ）と１，４−ジクロロベンゼン１．５ｇ（０．０１ｍｏｌ）を含む溶液をアルゴン下で加えた。
【００３７】
混合物を１時間攪拌後、この溶液にＮｉＣｌ_２ビピリジン０．１０ｇ（０．３６ｍｍｏｌ）を加え、２４時間還流した。放冷後、３００ｍｌのエタノールに反応液を注ぎ、沈殿物（合成したポリマー）を濾取した。乾燥後の収量は２．２ｇ（収率８５．９％）であった。
【００３８】
本発明で用いられる無機微粒子とは、シリカ、アルミナ、酸化亜鉛及び酸化ジルコニウム等の酸化物、窒化炭素、窒化アルミ及び窒化珪素などの窒化物、炭化珪素などの炭化物、またチタン酸ストロンチウム及びチタン酸バリウム等のチタン酸化合物が挙げられ、好ましくはシリカが挙げられる。シリカ粒子としては、天然の珪石または水晶の微粉砕化または球状処理化によるものや、合成シリカ等が挙げられる。また、これらの微粒子は、体積平均粒径が０．０１〜２．０μｍであることが必要である。この粒子径が２．０μｍより大きい場合には、最上層（微粒子含有層）自体に脆さが認められ、目的とする耐久性の向上が充分には発揮されない。しかも、大きな微粒子の存在によりクリーニング機構に損傷が起きる恐れがある。逆に、粒子径が０．０１μｍより小さい場合には、耐久性の向上は望めるが、表面積が増大することから気泡が発生し易く、表面層製造上におけるハンドリングが著しく悪くなるため実用上困難である。
【００３９】
無機微粒子が吸湿性である場合、高湿環境で感光体表面の電気抵抗が低下し、画像ニジミ等の画像不良を生じることがあるため、疎水性であることが好ましい。親水性の無機微粒子の場合は周知の方法で疎水化処理をしておくことが好ましい。微粒子に求められる電気抵抗値は、最上層に必要な電気抵抗値により様々であるが、１０^８Ω・ｃｍ以上であることが望ましい。これより小さいと、感光体の電荷保持性や画像品質などに問題を生じる傾向がある。
【００４０】
電子真感光体製造工程において、使用する溶剤としてはクロロベンゼン、テトラヒドロフラン、１，４−ジオキサン、トルエン及びキシレン等が挙げられ、単独で用いても複数の溶剤を用いてもよい。
【００４１】
本発明の感光体においては、最上層が少なくとも熱可塑性樹脂と無機微粒子を含有し、最上層のユニバーサル硬さ値（Ｈｕ）、塑性変形率の両者が特定の範囲内であることにより、機械的強度、特に耐傷性が向上する。
【００４２】
これは、無機微粒子と熱可塑性樹脂との相互作用が強いということに起因するもので、物性値としては分散粒径に反映され、塗膜状態でも１次粒径に近い微粒子が安定に存在することが挙げられる。
【００４３】
具体的にはある範囲の表面硬度、即ちユニバーサル硬さ値が２２０Ｎ／ｍｍ^２≦Ｈｕ≦４００Ｎ／ｍｍ^２の範囲でかつ塑性変形率が５０％≦塑性変形率≦７０％の範囲の最上層であれば、ユニバーサル硬さ値から膜密度、あるいは高分子鎖の絡み合い密度が高い状態でかつ最適な塑性変形率を有することから、体積平均粒径０．０１〜２．０μｍの無機微粒子との絡み合いも高く、安定して保持することができ、かつ樹脂と微粒子表面との適度な流動（塑性変形）により外的応力を微小スケールで散逸させることができるのではないかと考えている。
【００４４】
以下、本発明に用いる電子写真感光体の構成について説明する。
【００４５】
本発明における電子写真感光体は、感光層が電荷輸送材料と電荷発生材料を同一の層に含有する単層型であっても、電荷輸送層と電荷発生層に分離した積層型でもよいが電子写真特性的には積層型が好ましい。また、最上層として保護層を設けてもよい。
【００４６】
本発明で用いる支持体としては、導電性を有するものであればいずれのものでもよく、例えば、アルミニウム、銅、クロム、ニッケル、亜鉛及びステンレスなどの金属をドラムまたはシート状に成型したもの、アルミニウムや銅などの金属箔をプラスチックフィルムにラミネートしたもの、アルミニウム、酸化インジウム及び酸化スズなどをプラスチックフィルムに蒸着したものなどが挙げられる。
【００４７】
ＬＢＰなど画像入力がレーザー光の場合は散乱による干渉縞防止、または支持体の傷を被覆することを目的とした導電層を設けてもよい。これはカーボンブラックや金属粒子などの導電性粉体をバインダー樹脂に分散させて形成することができる。導電層の膜厚は５〜４０μｍであることが好ましく、１０〜３０μｍであることがより好ましい。
【００４８】
その上に接着機能を有する中間層を設ける。中間層の材料としてはポリアミド、ポリビニルアルコール、ポリエチレンオキシド、エチルセルロース、カゼイン、ポリウレタン及びポリエーテルウレタンなどが挙げられる。これらは適当な溶剤に溶解して塗布される。中間層の膜厚は０．０５〜５μｍであることが好ましく、０．３〜１μｍであることがより好ましい。
【００４９】
中間層の上には電荷発生層が形成される。本発明に用いられる電荷発生物質としてはセレンーテルル、ピリリウム、チアピリリウム系染料、フタロシアニン、アントアントロン、ジベンズピレンキノン、トリスアゾ、シアニン、ジスアゾ、モノアゾ、インジゴ、キナクリドン及び非対称キノシアニン系の各顔料が挙げられる。機能分離型の場合、電荷発生層は電荷発生物質を質量基準で０．３〜４倍量のバインダー樹脂及び溶剤とともにホモジナイザー、超音波分散、ボールミル、振動ボールミル、サンドミル、アトライター、ロールミル及び液衝突型高速分散機などの方法で良く分散し、分散液を塗布し、乾燥させて形成される。電荷発生層の膜厚は５μｍ以下であることが好ましく、０．１〜２μｍであることがより好ましい。
【００５０】
電荷輸送層が最上層の場合、熱可塑性樹脂と無機微粒子とを溶剤中に溶解させ、超音波分散、ボールミル、振動ボールミル、サンドミル、アトライター、ロールミル及び液衝突型高速分散機などの分散方法を用いて分散する。好ましくは液衝突型高速分散機である。更に、分散した液と電荷輸送材料とを溶剤中に溶解させた塗料を塗工し、乾燥して電荷輸送層を形成する。電荷輸送材料は質量基準で０．５〜２倍量のバインダー樹脂と組み合わされ、また電荷輸送層の膜厚は５〜４０μｍであることが好ましく、１５〜３０μｍであることがより好ましい。
【００５１】
次に、感光層を保護する層であるが、熱可塑性樹脂と無機微粒子を用い、更に電荷輸送材料あるいは電気抵抗を制御する導電性金属酸化物などとも併用することができる。このようにして長寿命で品質の高い画像を安定して形成することのできる電子写真用感光体を提供できる。
【００５２】
図１に本発明の電子写真感光体を有するプロセスカートリッジを有する電子写真装置の概略構成を示す。
【００５３】
図１において、１はドラム状の本発明の電子写真感光体であり、軸２を中心に矢印方向に所定の周速度で回転駆動される。感光体１は、回転過程において、一次帯電手段３によりその周面に正または負の所定電位の均一帯電を受け、次いで、スリット露光やレーザービーム走査露光などの像露光手段（不図示）からの画像露光光４を受ける。こうして感光体１の周面に静電潜像が順次形成されていく。
【００５４】
形成された静電潜像は、次いで現像手段５によりトナー現像され、現像されたトナー現像像は、不図示の給紙部から感光体１と転写手段６との間に感光体１の回転と同期取りされて給送された転写材７に、転写手段６により順次転写されていく。
【００５５】
像転写を受けた転写材７は、感光体面から分離されて像定着手段８へ導入されて像定着を受けることにより複写物（コピー）として装置外へプリントアウトされる。
【００５６】
像転写後の感光体１の表面は、クリーニング手段９によって転写残りトナーの除去を受けて清浄面化され、更に前露光手段（不図示）からの前露光光１０により除電処理された後、繰り返し画像形成に使用される。なお、一次帯電手段３が帯電ローラーなどを用いた接触帯電手段である場合は、前露光は必ずしも必要ではない。
【００５７】
本発明においては、上述の電子写真感光体１、一次帯電手段３、現像手段５及びクリーニング手段９などの構成要素のうち、複数のものをプロセスカートリッジとして一体に結合して構成し、このプロセスカートリッジを複写機やレーザービームプリンターなどの電子写真装置本体に対して着脱自在に構成してもよい。例えば、一次帯電手段３、現像手段５及びクリーニング手段９の少なくとも１つを感光体１と共に一体に支持してカートリッジ化し、装置本体のレール１２などの案内手段を用いて装置本体に着脱自在なプロセスカートリッジ１１とすることができる。
【００５８】
また、画像露光光４は、電子写真装置が複写機やプリンターである場合には、原稿からの反射光や透過光、あるいは、センサーで原稿を読取り、信号化し、この信号に従って行われるレーザービームの走査、ＬＥＤアレイの駆動及び液晶シャッターアレイの駆動などにより照射される光である。
【００５９】
本発明の電子写真感光体は電子写真複写機に利用するのみならず、レーザービームプリンター、ＣＲＴプリンター、ＬＥＤプリンター、液晶プリンター及びレーザー製版等電子写真応用分野にも広く用いることができる。
【００６０】
【実施例】
以下、実施例に従って本発明をより詳細に説明する。なお、実施例中「部」は質量部を示す。
【００６１】
本発明で使用する最上層の表面硬度の評価については、表面皮膜硬度測定により行い、ユニバーサル硬さ（Ｈｕ）、塑性変形率を求めた。具体的にはフィッシャーインストルメンツ製、フィッシャースコープＨ−１００Ｖを用い、圧子としては対面角度が１３６°に規定されている四角錐のダイヤモンド圧子を使用し、２５℃、湿度５０％環境下で最大深さを１μｍとし、ユニバーサル硬さ値（Ｈｕ）、塑性変形率を求めた。
【００６２】
〔実施例１〕
３０φ、３５７ｍｍのアルミニウムシリンダーを支持体とし、それに、以下の材料より構成される塗料を支持体上に浸漬コーティング法で塗布し、１４０℃で３０分熱硬化して、膜厚が１５μｍの導電層を形成した。
【００６３】
導電性顔料：ＳｎＯ_２コート処理硫酸バリウム １０部
抵抗調節用顔料：酸化チタン ２部
バインダー樹脂：フェノール樹脂 ６部
レベリング材：シリコーンオイル ０．００１部
溶剤：メタノール、メトキシプロパノール０．２／０．８ ２０部
【００６４】
次に、この上にＮ−メトキシメチル化ポリアミド３部及び共重合ポリアミド３部をメタノール６５部及びｎ−ブタノール３０部の混合溶媒に溶解した溶液を浸漬コーティング法で塗布し、１００℃で１０分乾燥して、膜厚が０．５μｍの中間層を形成した。
【００６５】
次に、ＣｕＫα特性Ｘ線回折におけるブラッグ角２θ±０．２°の９．０°、１４．２°、２３．９°及び２７．１°に強いピークを有するオキシチタニウムフタロシアニン（ＴｉＯＰｃ）４部とポリビニルブチラール（商品名：エスレックＢＭ２、積水化学工業製）２部とシクロヘキサノン６０部とをφ１ｍｍガラスビーズを用いたサンドミル装置で４時間分散した後、エチルアセテート１００部を加えて電荷発生層用分散液を調製した。これを浸漬コーティング法で塗布し、１００℃で１０分乾燥して、膜厚が０．２μｍの電荷発生層を形成した。
【００６６】
次に、電荷輸送層で使用する分散液を調製した。
【００６７】
構成単位例１で示されるポリアリレート樹脂１０部と疎水化シリカパウダー（商品名：ＫＭＰＸ−１００、平均粒径０．１μｍ、信越化学工業製）１０部とをモノクロロベンゼン１００部に混合し、撹拌した後、液衝突型高速分散機で分散処理を施した。疎水化シリカパウダーの分散平均粒径と粒度分布をＬｅｅｄｓ ａｎｄ Ｎｏｒｔｈｒｕｐ製（商品名：マイクロトラックＵＰＡ粒度分析計）で測定したところ、平均粒径０．１２μｍであった。
【００６８】
この疎水化シリカパウダー分散液１２０部にモノクロロベンゼン１０部とジクロロメタン６０部を加え、更に下記構造式（１）で示されるトリアリールアミン化合物１５部
【００６９】
【化１】

及び下記構造式（２）で示されるスチルベン化合物２部
【００７０】
【化２】

と構成単位例１で示されるポリアリレート樹脂１２部とを加え溶解させ電荷輸送層用塗料とし、前記電荷発生層上に浸漬コーティング法で塗布後、１２０℃で１時間乾燥して、膜厚が２７μｍの電荷輸送層を設け電子写真感光体とした。
【００７１】
次に、評価について説明する。
【００７２】
作製した電子写真感光体をＡＣ電圧を重畳したローラー接触帯電手段（ＡＣ／ＤＣローラー接触帯電手段）を有する複写機でプロセススピード２１０ｍｍ／ｓｅｃを有する「ＧＰ−４０」（キヤノン製）に取り付け、温度２３℃、湿度５０％ＲＨの常温常湿環境（Ｎ／Ｎ）下で暗部電位Ｖｄ、感度ＥΔ５００及び残留電位Ｖｒを測定した。ＧＰ−４０には、感光体の電子写真特性を測定するための改造を施した。
【００７３】
暗部電位Ｖｄは絶対値が大きい程帯電能が良いことを示し、感度ＥΔ５００は−７００Ｖから−２００Ｖに電位を減衰させるのに必要な光量で、値が小さい程感度が良いことを示す。
【００７４】
更に、常温常湿下で５０，０００枚の通紙耐久試験を行い、５０，０００枚後の暗部電位Ｖｄ、感度ＥΔ５００及び残留電位Ｖｒを測定した。また、５０，０００枚後の磨耗量も測定した。磨耗量の測定にはフィッシャー製渦電流式膜厚測定機（パーマスコープ タイプＥ１１１）を用いた。
【００７５】
画像はＡ４で、印字率４％の格子パターンとした。また、シーケンスはプリント１枚毎に１回停止する間欠モードとした。トナーがなくなったならば補給した。
【００７６】
更に、電子写真感光体の一部に３０００ｌｕｘ、２０分間の白色蛍光灯の光を当て４分間放置後明部電位を測定し、光を当てる前から明部電位がどれだけ下がったかを測定し、フォトメモリー値とした。０から５０Ｖの変化量は○、５１から１００Ｖの変化量は△、１０１Ｖ以上では×とした。結果を表３に示す。
【００７７】
また、５０，０００枚の通紙耐久試験後の目視で、傷の発生を確認した。傷が発生していないか、または発生しているが画像欠陥が認められない程度である・・・○、多少画像欠陥が認められる程度の傷が発生する・・・△、明らかに画像欠陥が認められる程度の傷が発生する・・・×とした。結果を表３に示す。
【００７８】
〔実施例２〜１０〕
実施例１の電子写真感光体において電荷輸送層中の熱可塑性樹脂及び無機微粒子を疎水化シリカパウダー（商品名：Ｘ−１２０、平均粒径０．０２μｍ、信越化学工業製）、シリカドール（商品名：３０Ｇ−１００、平均粒径０．１μｍ、日本化学工業製）、アルミナ（商品名：ＬＳ−２３５、平均粒径０．１μｍ、日本軽金属製）、酸化亜鉛（商品名：ＦＩＮＥＸ−２５ＬＰ、平均粒径０．１μｍ、堺化学工業製）等に代え、表２に示すユニバーサル硬さ値（Ｈｕ）及び塑性変形率を有する電荷輸送層に代えた以外は実施例１と同様に電子写真感光体を作成し評価した。その結果を表３に示す。
【００７９】
〔実施例１１〕
実施例１の電子写真感光体において電荷輸送層を代え、更に保護層を設けた。即ち、電荷輸送層としてポリカーボネート樹脂（商品名：ユーピロンＺ４００、三菱瓦斯化学製）３０部と実施例１で示用いた電荷輸送材料（１）２３部と電荷輸送材料（２）３部とをモノクロロベンゼン１３０部とジクロロメタン６０部に加え、溶解させ、電荷輸送層用塗料とし、浸漬コーティング法で塗布後、１２０℃で６０分間乾燥して、膜厚が１８μｍの電荷輸送層を設けた。
【００８０】
次に、保護層の分散液としては構成単位例１で示されるポリアリレート樹脂１０部と疎水化シリカパウダー（商品名：ＫＭＰＸ−１００、平均粒径０．１μｍ、信越化学工業製）１０部とをモノクロロベンゼン１００部に混合し、撹拌した後、実施例１と同様に分散を行った（分散平均粒径０．１２μｍ）。この疎水化シリカパウダー分散液２５部と電荷輸送層で用いた電荷輸送材料（１）３部と構成単位例１のポリアリレート樹脂３部とをモノクロロベンゼン２０部とジクロルメタン２０部に混合し、溶解して表面保護層用塗料とした。この塗料を上記電荷輸送層上に霧化塗布し、１２０℃で６０分間乾燥して、膜厚が５．０μｍの保護層を形成し、電子写真感光体を作成、評価した。その結果を表３に示す。
【００８１】
〔比較例１〕
実施例１の電荷輸送層において、無機微粒子を除いた以外は実施例１と同様とした。具体的には構成単位例１で示されるポリアリレート樹脂３０部にモノクロロベンゼン１３０部とジクロロメタン５０部を加え、更に電荷輸送材料（１）２０部と電荷輸送材料（２）２部とを加え電荷輸送層用塗料とした。
【００８２】
〔比較例２〜６〕
実施例６、７、８、９、１０の電荷輸送層において、無機微粒子を除いた以外は比較例１と同じとした。
【００８３】
〔比較例７〕
実施例１の電荷輸送層中のバインダーをポリカーボネート樹脂（商品名：ユーピロンＺ２００、三菱瓦斯化学製）に代えた以外は実施例１と同様に電子写真感光体を作成し評価した（分散平均粒径０．１５μｍ）。その結果を表３に示す。
【００８４】
〔比較例８〕
実施例１の電荷輸送層中のバインダーの構成単位を下記構造式（３）で示される熱可塑性樹脂（重量平均分子量：４６０００）に代えた以外は実施例１と同様に電子写真感光体を作成し評価した（分散平均粒径０．１６μｍ）。その結果を表３に示す。
【００８５】
【化３】

【００８６】
〔比較例９〕
実施例１の電荷輸送層中のバインダーの構成単位を下記構造式（４）で示される熱可塑性樹脂（重量平均分子量：５９０００）に代えた以外は実施例１と同様に電子写真感光体を作成し評価した（分散平均粒径０．１５μｍ）。その結果を表３に示す。
【００８７】
【化４】

【００８８】
〔比較例１０〕
実施例１の電荷輸送層中のバインダーの構成単位を下記構造式（５）で示される熱可塑性樹脂（重量平均分子量：１２０００）に代えた以外は実施例１と同様に電子写真感光体を作成し評価した（分散平均粒径０．１７μｍ）。その結果を表３に示す。
【００８９】
【化５】

【００９０】
〔比較例１１〕
実施例１の電荷輸送層中の無機微粒子をアルミナ（商品名：ＡＯ８０９、１０μｍアドマテックス（株））に代えた以外は実施例１と同様に電子写真感光体を作成し評価した。その結果を表３に示す。
【００９１】
〔比較例１２〕
実施例１の電荷輸送層中の無機微粒子を有機微粒子であるポリテトラフルオロエチレン微粒子（商品名：ルブロンＬ−２、ダイキン工業製、粒径０．５μｍ）に代え、分散液を調製するに際し、分散助剤であるクシ型フッ素系グラフトポリマ−（商品名アロンＧＦ−３００、東亜合成化学工業製）１部を加えた以外は実施例１と同様に電子写真感光体を作成し評価した。その結果を表３に示す。
【００９２】
【表２】

【００９３】
【表３】

【００９４】
以上の結果から、本発明で得られる最上層を用いた電子写真感光体は機械的強度が良好で、特に耐傷性が良好であり、かつ電気的感度が良好で、繰り返し特性などにも優れているということが示された。
【００９５】
以上本発明の実施例について説明したが、本発明の好適な実施の態様を以下のとおり列挙する。
【００９６】
［実施態様１］
導電性支持体上に感光層を有する電子写真感光体において、該電子写真感光体の最上層が少なくとも熱可塑性樹脂と体積平均粒径０．０１〜２．０μｍの無機微粒子を含有し、かつ該最上層の表面皮膜硬度試験から求められるユニバーサル硬さ（Ｈｕ）が２５℃で湿度５０％の環境下で２２０Ｎ／ｍｍ^２≦Ｈｕ≦４００Ｎ／ｍｍ^２であり、更に表面皮膜硬度試験に用いた圧子による該最上層の塑性変形率が下記式（１）を満足することを特徴とする電子写真感光体。
【００９７】
【数４】

【００９８】
［実施態様２］
前記最上層が電荷輸送層である実施態様１に記載の電子写真感光体。
【００９９】
［実施態様３］
前記熱可塑性樹脂がポリアリレート樹脂である実施態様１または２に記載の電子写真感光体。
【０１００】
［実施態様４］
前記無機微粒子がシリカ微粒子である実施態様１至３のいずれかに記載の電子写真感光体。
【０１０１】
［実施態様５］
前記シリカ微粒子が疎水化されたシリカ微粒子である実施態様４に記載の電子写真感光体。
【０１０２】
［実施態様６］
触帯電方式に使用される実施態様１至５のいずれかに記載の電子写真感光体。
【０１０３】
【発明の効果】
本発明による最上層を形成してなる電子写真感光体は優れた機械的強度、特に傷に関する強度が良好で、かつ優れた電子写真特性を示す。表面皮膜硬度試験から求められるユニバーサル硬さ（Ｈｕ）、塑性変形率の両者が特定の範囲内の値を有する最上層は、無機微粒子と樹脂との相互作用が良好で、微粒子の膜補強効果を効果的に引き出すことができ、かつ分散助剤がないことから、フォトメモリーが良好である。
【０１０４】
更に、本発明による電子写真感光体は接触帯電手段を用いた電子写真プロセスで使用することができ、帯電特性、感度、残留電位及びこれらの繰り返し特性等の電子写真特性に優れた電子写真感光体、該電子写真感光体を有するプロセスカートリッジ及び電子写真装置を提供することが可能となった。
【図面の簡単な説明】
【図１】本発明のプロセスカートリッジを有する電子写真装置の一例の概略構成図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member, a process cartridge having the electrophotographic photosensitive member, and an electrophotographic apparatus.
[0002]
[Prior art]
Electrophotographic methods use a photoconductive material whose electrical resistance varies according to the amount of radiation received during image exposure and which consists of a support coated with an insulating substance in the dark. The basic characteristics required of an electrophotographic photoreceptor using this photoconductive material include (1) being able to be charged to an appropriate potential in a dark place, (2) having little potential dissipation in a dark place, (3) Quickly dissipating the charge by light irradiation (for example, see Patent Document 1).
[0003]
Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly containing an inorganic photoconductive compound such as selenium, zinc oxide or cadmium sulfide has been widely used. However, they satisfy the above conditions (1) to (3), but are not always satisfactory in heat stability, moisture resistance, durability and productivity.
[0004]
In recent years, electrophotographic photoreceptors containing various organic photoconductive compounds as main components have been actively developed in order to overcome the disadvantages of inorganic photoreceptors. For example, a photoreceptor having a charge transport layer containing triallyl pyrazoline (for example, see Patent Document 2), a charge generation layer composed of a perylene pigment derivative and a charge transport layer composed of a condensate of 3-propylene and formaldehyde And the like (for example, see Patent Document 3).
[0005]
Further, the organic photoconductive compound can freely select the photosensitive wavelength range of the electrophotographic photoreceptor depending on the compound, and azo pigments exhibiting high sensitivity in the visible region are disclosed (for example, Patent Literatures 4 and 5) and compounds having sensitivity up to the infrared region are disclosed (for example, see Patent Literatures 6 and 7).
[0006]
Among these materials, those having sensitivity in the infrared region are used in laser beam printers (hereinafter abbreviated as LBPs) and LED printers, which have been making remarkable progress in recent years, and the demand frequency thereof is increasing.
[0007]
Electrophotographic photoreceptors using these organic photoconductive compounds are used as function-separated type photoreceptors in which a charge transport layer and a charge generation layer are laminated in order to satisfy both electrical and mechanical properties. Often. On the other hand, it is needless to say that the electrophotographic photoreceptor is required to have sensitivity, electrical characteristics, and optical characteristics according to the electrophotographic process to be applied.
[0008]
Particularly, in an electrophotographic photoreceptor that is used repeatedly, the surface of the electrophotographic photoreceptor is directly subjected to electrical and mechanical external forces such as corona or direct charging, image exposure, toner development, transfer process and surface cleaning. In addition, durability and slipperiness for them are also required.
[0009]
Specifically, discharge during charging, electrical deterioration due to ozone and nitrogen oxides, and durability against mechanical deterioration in which the surface is worn or scratches are generated by rubbing of the cleaning member are required. The occurrence of scratches is fatal in maintaining the photoreceptor, and requires immediate improvement. However, unlike an inorganic photoreceptor, an organic photoreceptor having many soft materials is inferior in durability, is easily worn, and is apt to be damaged at the same time.
[0010]
In addition to the above, electrical degradation as an electrophotographic characteristic includes a phenomenon in which carriers stay in a portion irradiated with light and a potential difference occurs with a portion not irradiated with light. It is a big problem.
[0011]
As a resin that is often used for the surface layer and has good durability, a polycarbonate resin, a polyarylate resin commercially available under the trade name of “U-polymer” (for example, see Patent Document 8), and the like have attracted attention. In fact, the use of these materials slightly reduces the occurrence of wear and scratches, but is still insufficient and requires further higher durability. Therefore, these resins cannot solve all of the above-mentioned problems, and need to impart further wear resistance and scratch resistance.
[0012]
Specifically, fluorine-containing resin fine particles (for example, see Patent Literatures 9 to 12) and inorganic fine particles (for example, see Patent Literatures 13 and 14) as agents for reducing the friction coefficient of the photoreceptor surface, reducing surface energy, and reducing wear. ) Etc. have been proposed. However, if the fluorine-containing resin particles agglomerate or settle in the surface layer paint, they become non-uniform in the surface layer of the photoreceptor. Differences, etc., which cause image defects. As a countermeasure, it is possible to add a surfactant or the like as a dispersing aid to improve the dispersion stability of the fluorine-containing resin fine particles. It degrades the body's potential characteristics.
[0013]
On the other hand, as for the inorganic fine particles, no dispersing aid is required for the hydrophobic fine silica particles, alumina fine particles, zinc oxide and the like. Further, by adding inorganic fine particles to the uppermost layer, the surface hardness (universal hardness) is increased, and the abrasion resistance is improved. However, as an adverse effect, an external impact surrounding the photoreceptor easily damages the photoreceptor and causes image defects. That is, even if the abrasion resistance is improved, the scratch resistance is reduced, and even if inorganic fine particles are added, the effect may be reduced in terms of the total durability. That is, even if the addition of the inorganic fine particles can provide a film reinforcing effect of 50% if no scratch is generated, if a scratch is generated, only about 10% of the film reinforcing effect can be obtained as a whole durability. . Scratches are actually a major problem, but if the most suitable resin is selected, the interaction with the fine particles is strong, and the film reinforcing effect as a so-called filler (inorganic fine particles) related to high durability can be effectively obtained. there is a possibility. However, to date, the proposal has been limited to the improvement of the wear resistance only, and there is little mention of the effective use of the inorganic fine particles to enhance the film reinforcing effect, that is, the total durability of the wear resistance and the scratch resistance. Not been.
[0014]
By the way, hardness is one measure of the strength of a material against mechanical deterioration. This definition is regarded as the stress from the material on the indentation of the indenter. Therefore, an attempt has been made to quantitatively quantify the mechanical strength by using this hardness as a physical parameter for knowing the surface film strength. As examples thereof, a scratch hardness test, a pencil hardness test, a Vickers hardness test, and the like, which have been widely used, are widely known.
[0015]
However, in any of the measuring means, there are advantages and disadvantages when measuring the strength of an elastic film such as an organic substance.For example, Vickers hardness measurement measures the length of an indentation on the film to determine the hardness. It is not suitable for an elastically deformable material such as Therefore, it is desirable that the hardness of the organic substance with respect to the film can be evaluated by a value obtained by adding the plastic deformation and the elastic deformation of the film by the indenter. Recently, a universal hardness value (Hu) suitable for measurement of an organic polymer film has been used. This is not a method in which the indenter is pushed into the sample surface as in the conventional micro Vickers method, and the residual dent after unloading is measured with a microscope to determine the hardness. This is a measuring method in which the depth is read directly and the hardness is continuously obtained.
[0016]
Further, the work load (energy) performed on the film can be determined by increasing or decreasing the test load applied to the indenter, and the plastic deformation rate (elastic deformation rate) can be obtained.
[0017]
The universal hardness value (Hu), the plastic deformation rate, and the like are each an index of wearability and susceptibility to damage, and attempts have been made to know the strength of the surface layer.
[0018]
[Patent Document 1]
U.S. Pat. No. 2,297,691
[Patent Document 2]
US Patent No. 3837851
[Patent Document 3]
U.S. Pat. No. 3,871,880
[Patent Document 4]
JP-A-61-272754
[Patent Document 5]
JP-A-56-167759
[Patent Document 6]
JP-A-57-19567
[Patent Document 7]
JP-A-61-228453
[Patent Document 8]
JP-A-56-135844
[Patent Document 9]
Japanese Patent Application Laid-Open No. 50-23231
[Patent Document 10]
JP-A-61-116362
[Patent Document 11]
JP-A-61-204633
[Patent Document 12]
JP-A-61-270768
[Patent Document 13]
JP-A-56-117245
[Patent Document 14]
JP-A-59-223443
[0019]
[Problems to be solved by the invention]
The object of the present invention is to improve the abrasion resistance and scratch resistance for the purpose of improving the durability and electrical properties, and furthermore, to improve the photo memory, at least a thermoplastic resin and inorganic fine particles are contained in the uppermost layer. Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member capable of effectively bringing out a film reinforcing effect of inorganic fine particles, and a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member. That is, an electrophotographic photoreceptor having high chargeability and sensitivity due to excellent abrasion resistance and scratch resistance, a low residual potential, and excellent in the repetition characteristics thereof, and having a small photo memory, and the electrophotographic photoreceptor. To provide a process cartridge and an electrophotographic apparatus having the same.
[0020]
[Means for Solving the Problems]
That is, in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the uppermost layer of the electrophotographic photosensitive member contains at least a thermoplastic resin and inorganic fine particles having a volume average particle size of 0.01 to 2.0 μm, And a universal hardness (Hu) determined from a surface film hardness test of the uppermost layer is 220 N / mm in an environment of 25 ° C. and 50% humidity. ² ≦ Hu ≦ 400N / mm ² And a plastic deformation rate of the uppermost layer by an indenter used for a surface film hardness test satisfies the following expression (1).
[0021]
(Equation 2)

[0022]
Further, the present invention is a process cartridge and an electrophotographic apparatus having the above-mentioned photoreceptor.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Generally, there are plastic deformation and elastic deformation in the deformation of an organic polymer film due to external stress, and it is said that the physical properties of the film are characterized by the ratio of each deformation to the total amount of deformation. For example, a material having rigidity such as carbon fiber has a plastic deformation rate close to 100% of the whole, and a rubber-like material such as elastomer has a large elastic deformation ratio.
[0024]
By the way, the universal hardness value (Hu) obtained from the surface film hardness test is defined by the following formula (2) by measuring the indentation depth under a test load by a Vickers diamond indenter.
[0025]
[Equation 3]

[0026]
Also, by reducing the load of the indenter, the plastic energy (elastic energy) of the film can be analyzed. The plastic deformation rate (elastic deformation rate) is obtained from the work (energy) performed by the indenter on the film, that is, the change in energy due to the increase and decrease of the load on the film of the indenter. I get it.
[0027]
Attempts are made to increase the durability of the uppermost layer using the values obtained by such a measurement method. However, in order to realize this, both rigidity and flexibility are required as properties of the film, and there is a problem in manufacturing even if the film is brittle or too ductile.
[0028]
As a result of intensive studies, we have found that the uppermost layer of the electrophotographic photosensitive member contains at least a thermoplastic resin and inorganic fine particles having a volume average particle size of 0.01 to 2.0 μm, and has a universal hardness value (Hu) and a plastic deformation rate. Within a certain range, it was found that not only the abrasion resistance but also the scratch resistance were greatly improved, and that the photo memory was good because no dispersing aid was used.
[0029]
That is, Hu is 220 N / mm ² If it is less than 3, the abrasion resistance and the scratch resistance are insufficient in terms of mechanical strength in the current electrophotographic process, and 400 N / mm. ² If it exceeds, the handling in the manufacturing process of the electrophotographic photoreceptor is significantly deteriorated, so that it is practically difficult and 220 N / mm ² ≦ Hu ≦ 400N / mm ² For the first time, abrasion resistance, scratch resistance and manufacturing restrictions can be cleared.
[0030]
Further, the uppermost layer having a plastic deformation rate of more than 70% has a weak interaction with the fine particles, so that the fine particles are detached from the film and are easily damaged. In addition, the elasticity of the film against the cleaning blade, the paper powder, or the toner is insufficient, and they are pressed against the surface of the photoreceptor to cause fusion or damage. On the other hand, if it is less than 50%, the brittleness of the film becomes too large, causing cracks and fatal scratches due to momentary external impact.
[0031]
Regarding the measurement conditions of the surface film hardness test, there are Vickers square pyramid diamond indenter, Knoop indenter, Berkovich indenter and ball indenter as the indenter. Values range from 5 to 300 mN. This is because if it is less than 5 mN with respect to the surface of the electrophotographic photoreceptor, the accuracy of measurement is reduced due to the influence of unevenness on the film surface, and if it exceeds 300 mN, it depends on the thickness of the surface layer. However, this is because the indenter is easily affected by the substrate.
[0032]
The uppermost layer having a universal hardness value (Hu) and a plastic deformation rate within the condition range obtained under such measurement conditions can effectively bring out the film reinforcing effect of the inorganic fine particles, And the photo memory is good.
[0033]
Hereinafter, specific examples of the structural unit of the resin used in the present invention are shown in Table 1, but are not limited thereto. Further, two or more of the following structural units may be copolymerized, or two or more of them may be used in combination.
[0034]
[Table 1]

[0035]
Synthesis Example 1 (Synthesis of polyarylate resin having structural unit example 1)
The polymer having the constitutional unit used in the present invention is prepared by mixing the C-form of bisphenol with a mixture of terephthalic acid chloride / isophthalic acid chloride in a solvent / water system in the presence of an alkali and performing interfacial polymerization. Is done. The ratio between terephthalic acid chloride and isophthalic acid chloride is determined in consideration of the solubility of the polymer and is not defined. However, care must be taken when the content of any of the chlorides is 30 mol% or less, since the solubility of the synthesized polymer is extremely reduced. Usually, it is preferable to synthesize at a ratio of 1/1.
[0036]
Synthesis Example 2 (Synthesis of polyphenylene resin having structural unit example 6)
In a solution containing 2.6 g (0.04 mol) of zinc powder in 10 ml of tetrahydrofuran, 2.5 g (0.01 mol) of 2,5-dichlorobenzophenone and 1.5 g of 1,4-dichlorobenzene (0.0 g in 30 ml of tetrahydrofuran). 01 mol) was added under argon.
[0037]
After stirring the mixture for 1 hour, NiCl was added to the solution. ₂ 0.10 g (0.36 mmol) of bipyridine was added, and the mixture was refluxed for 24 hours. After cooling, the reaction solution was poured into 300 ml of ethanol, and the precipitate (synthesized polymer) was collected by filtration. The yield after drying was 2.2 g (85.9% yield).
[0038]
The inorganic fine particles used in the present invention include oxides such as silica, alumina, zinc oxide and zirconium oxide, nitrides such as carbon nitride, aluminum nitride and silicon nitride, carbides such as silicon carbide, and strontium titanate and titanate. Examples include titanate compounds such as barium, and preferably include silica. Examples of the silica particles include particles obtained by pulverizing or spheroidizing natural silica or quartz, and synthetic silica. In addition, these fine particles need to have a volume average particle size of 0.01 to 2.0 μm. If the particle diameter is larger than 2.0 μm, the uppermost layer (fine particle-containing layer) itself is fragile, and the intended improvement in durability cannot be sufficiently exhibited. In addition, the cleaning mechanism may be damaged by the presence of large particles. On the other hand, when the particle diameter is smaller than 0.01 μm, improvement in durability can be expected, but bubbles are easily generated due to an increase in surface area, and handling in the production of the surface layer is extremely poor, so that it is practically difficult. is there.
[0039]
When the inorganic fine particles are hygroscopic, the electrical resistance of the surface of the photoreceptor decreases in a high humidity environment, which may cause image defects such as image bleeding. Therefore, the inorganic fine particles are preferably hydrophobic. In the case of hydrophilic inorganic fine particles, it is preferable to perform a hydrophobic treatment by a known method. The electric resistance required for the fine particles varies depending on the electric resistance required for the uppermost layer. ⁸ It is preferable that the resistance is Ω · cm or more. If it is smaller than this, problems tend to occur in the charge retention of the photoconductor, image quality, and the like.
[0040]
In the manufacturing process of the electrophotographic photosensitive member, examples of the solvent used include chlorobenzene, tetrahydrofuran, 1,4-dioxane, toluene, and xylene. A single solvent or a plurality of solvents may be used.
[0041]
In the photoreceptor of the present invention, the uppermost layer contains at least a thermoplastic resin and inorganic fine particles, and both the universal hardness value (Hu) and the plastic deformation rate of the uppermost layer are within specific ranges. Strength, especially scratch resistance, is improved.
[0042]
This is due to the strong interaction between the inorganic fine particles and the thermoplastic resin, and the physical property value is reflected in the dispersed particle size, and fine particles close to the primary particle size are stably present even in the state of the coating film. It is mentioned.
[0043]
Specifically, a certain range of surface hardness, that is, a universal hardness value of 220 N / mm ² ≦ Hu ≦ 400N / mm ² If the plastic deformation rate is in the range of 50% ≦ plastic deformation rate ≦ 70% and the uppermost layer is in the range of from the universal hardness value, the film density or the entanglement density of the polymer chains is high and the optimum plastic deformation is performed. Entanglement with the inorganic fine particles having a volume average particle diameter of 0.01 to 2.0 μm is high, can be stably held, and is caused by appropriate flow (plastic deformation) between the resin and the fine particle surface. We believe that external stress can be dissipated on a small scale.
[0044]
Hereinafter, the configuration of the electrophotographic photosensitive member used in the present invention will be described.
[0045]
The electrophotographic photoreceptor in the present invention may be a single layer type in which the photosensitive layer contains a charge transport material and a charge generation material in the same layer, or a laminated type in which a charge transport layer and a charge generation layer are separated. From the standpoint of photographic characteristics, a laminated type is preferred. Further, a protective layer may be provided as the uppermost layer.
[0046]
The support used in the present invention may be any conductive material, for example, aluminum, copper, chromium, nickel, zinc and a metal such as stainless steel molded into a drum or sheet, aluminum Examples thereof include those obtained by laminating a metal foil such as copper or copper on a plastic film, and those obtained by depositing aluminum, indium oxide, tin oxide, or the like on a plastic film.
[0047]
When the image input is a laser beam such as LBP, a conductive layer may be provided for the purpose of preventing interference fringes due to scattering or covering a scratch on the support. This can be formed by dispersing a conductive powder such as carbon black or metal particles in a binder resin. The thickness of the conductive layer is preferably from 5 to 40 μm, more preferably from 10 to 30 μm.
[0048]
An intermediate layer having an adhesive function is provided thereon. Examples of the material of the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are applied by dissolving in an appropriate solvent. The thickness of the intermediate layer is preferably from 0.05 to 5 μm, more preferably from 0.3 to 1 μm.
[0049]
A charge generation layer is formed on the intermediate layer. Examples of the charge generating substance used in the present invention include selenium-tellurium, pyrylium, thiapyrylium dyes, phthalocyanine, anthantrone, dibenzapyrene quinone, trisazo, cyanine, disazo, monoazo, indigo, quinacridone, and asymmetric quinocyanine pigments. In the case of the function separation type, the charge generation layer contains a charge generation material in a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, and a liquid collision together with a binder resin and a solvent in an amount of 0.3 to 4 times by mass. It is formed by dispersing well by a method such as a mold high-speed disperser, applying a dispersion, and drying. The thickness of the charge generation layer is preferably 5 μm or less, more preferably 0.1 to 2 μm.
[0050]
When the charge transport layer is the uppermost layer, a thermoplastic resin and inorganic fine particles are dissolved in a solvent, and a dispersion method such as ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, and a liquid collision type high-speed disperser is used. Disperse using Preferably, it is a liquid collision type high-speed disperser. Further, a paint in which the dispersed liquid and the charge transport material are dissolved in a solvent is applied and dried to form a charge transport layer. The charge transporting material is combined with a binder resin in an amount of 0.5 to 2 times the mass on a mass basis, and the thickness of the charge transporting layer is preferably 5 to 40 μm, more preferably 15 to 30 μm.
[0051]
Next, as a layer for protecting the photosensitive layer, a thermoplastic resin and inorganic fine particles can be used, and further a charge transport material or a conductive metal oxide for controlling electric resistance can be used in combination. Thus, it is possible to provide an electrophotographic photoreceptor capable of stably forming a long-life, high-quality image.
[0052]
FIG. 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.
[0053]
In FIG. 1, reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is driven to rotate around an axis 2 at a predetermined peripheral speed in a direction indicated by an arrow. The photoreceptor 1 receives a uniform charge of a predetermined positive or negative potential on its peripheral surface by the primary charging means 3 during the rotation process, and then receives a charge from an image exposure means (not shown) such as slit exposure or laser beam scanning exposure. It receives image exposure light 4. Thus, an electrostatic latent image is sequentially formed on the peripheral surface of the photoconductor 1.
[0054]
The formed electrostatic latent image is then subjected to toner development by the developing unit 5, and the developed toner developed image is transferred between the photoconductor 1 and the transfer unit 6 by a rotation of the photoconductor 1 from a feeding unit (not shown). The transfer unit 6 sequentially transfers the transfer material 7 that has been synchronized and fed.
[0055]
The transfer material 7 having undergone the image transfer is separated from the surface of the photoreceptor, introduced into the image fixing means 8 and subjected to image fixing to be printed out of the apparatus as a copy.
[0056]
The surface of the photoreceptor 1 after the image transfer is cleaned and cleaned by removing the untransferred toner by a cleaning unit 9, and further subjected to a charge removal process by a pre-exposure light 10 from a pre-exposure unit (not shown). Used for image formation. When the primary charging unit 3 is a contact charging unit using a charging roller or the like, the pre-exposure is not necessarily required.
[0057]
In the present invention, among the above-mentioned components such as the electrophotographic photosensitive member 1, the primary charging unit 3, the developing unit 5, and the cleaning unit 9, a plurality of components are integrally connected as a process cartridge. May be detachably attached to the main body of an electrophotographic apparatus such as a copying machine or a laser beam printer. For example, a process in which at least one of the primary charging unit 3, the developing unit 5, and the cleaning unit 9 is integrally supported together with the photoreceptor 1 to form a cartridge, and is detachably attached to the apparatus main body using a guide unit such as a rail 12 of the apparatus main body. The cartridge 11 can be used.
[0058]
When the electrophotographic apparatus is a copier or a printer, the image exposure light 4 is reflected light or transmitted light from the original, or the original is read by a sensor and converted into a signal, and a laser beam is emitted according to the signal. Light emitted by scanning, driving of an LED array, driving of a liquid crystal shutter array, and the like.
[0059]
The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.
[0060]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, "parts" indicates parts by mass.
[0061]
The surface hardness of the uppermost layer used in the present invention was evaluated by measuring the surface film hardness, and the universal hardness (Hu) and the plastic deformation rate were determined. Specifically, a Fischer Scope H-100V manufactured by Fisher Instruments was used, and a diamond indenter of a quadrangular pyramid having a facing angle of 136 ° was used as an indenter. The universal hardness value (Hu) and the plastic deformation rate were determined by setting the height to 1 μm.
[0062]
[Example 1]
A 30φ, 357mm aluminum cylinder is used as a support, and a coating composed of the following materials is applied on the support by a dip coating method, and is thermoset at 140 ° C for 30 minutes to form a conductive layer having a thickness of 15µm. Was formed.
[0063]
Conductive pigment: SnO ₂ Coated barium sulfate 10 parts
Pigment for resistance adjustment: 2 parts of titanium oxide
Binder resin: 6 parts of phenolic resin
Leveling material: 0.001 part of silicone oil
Solvent: methanol, methoxypropanol 0.2 / 0.8 20 parts
[0064]
Next, a solution obtained by dissolving 3 parts of N-methoxymethylated polyamide and 3 parts of copolymerized polyamide in a mixed solvent of 65 parts of methanol and 30 parts of n-butanol was applied thereon by a dip coating method, and was then applied at 100 ° C. for 10 minutes. After drying, an intermediate layer having a thickness of 0.5 μm was formed.
[0065]
Next, 4 parts of oxytitanium phthalocyanine (TiOPc) having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° at Bragg angles 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction. And 2 parts of polyvinyl butyral (trade name: Esrec BM2, manufactured by Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone were dispersed in a sand mill using φ1 mm glass beads for 4 hours, and then 100 parts of ethyl acetate was added to disperse the charge generating layer. A liquid was prepared. This was applied by a dip coating method and dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.2 μm.
[0066]
Next, a dispersion used for the charge transport layer was prepared.
[0067]
10 parts of the polyarylate resin shown in Structural Unit Example 1 and 10 parts of hydrophobized silica powder (trade name: KMPX-100, average particle size: 0.1 μm, manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed with 100 parts of monochlorobenzene, and stirred. After that, dispersion treatment was performed by a liquid collision type high-speed dispersion machine. The dispersion average particle size and the particle size distribution of the hydrophobized silica powder were measured by Leeds and Northrup (trade name: Microtrac UPA particle size analyzer) to find that the average particle size was 0.12 μm.
[0068]
To 120 parts of the hydrophobized silica powder dispersion, 10 parts of monochlorobenzene and 60 parts of dichloromethane are added, and further 15 parts of a triarylamine compound represented by the following structural formula (1) is added.
[0069]
Embedded image

And 2 parts of a stilbene compound represented by the following structural formula (2)
[0070]
Embedded image

And 12 parts of the polyarylate resin shown in Structural Unit Example 1 were added and dissolved to form a coating for a charge transport layer. The coating was applied on the charge generation layer by a dip coating method, and then dried at 120 ° C. for 1 hour. An electrophotographic photosensitive member was provided with a charge transport layer of 27 μm.
[0071]
Next, evaluation will be described.
[0072]
The produced electrophotographic photoreceptor was mounted on a "GP-40" (manufactured by Canon) having a process speed of 210 mm / sec by a copying machine having a roller contact charging means (AC / DC roller contact charging means) on which an AC voltage was superimposed. The dark part potential Vd, sensitivity EΔ500, and residual potential Vr were measured in a normal temperature and normal humidity environment (N / N) at 23 ° C. and a humidity of 50% RH. GP-40 was modified to measure the electrophotographic properties of the photoreceptor.
[0073]
The dark part potential Vd indicates that the larger the absolute value is, the better the charging ability is. The sensitivity EΔ500 is the amount of light required to attenuate the potential from −700 V to −200 V, and the smaller the value, the better the sensitivity.
[0074]
Further, a paper passing durability test was performed on 50,000 sheets under normal temperature and normal humidity, and after 50,000 sheets, the dark portion potential Vd, the sensitivity EΔ500, and the residual potential Vr were measured. Also, the amount of wear after 50,000 sheets was measured. An eddy current type film thickness measuring device (Permascope type E111) manufactured by Fischer was used to measure the amount of wear.
[0075]
The image was an A4 grid pattern with a printing rate of 4%. The sequence was an intermittent mode in which the printing was stopped once for each print. When the toner ran out, it was replenished.
[0076]
Further, a portion of the electrophotographic photoreceptor was exposed to light of a white fluorescent lamp for 3000 minutes at 20 minutes and left for 4 minutes to measure the light portion potential. Then, the light portion potential before the light was applied was measured to determine how much the light portion potential decreased. Photo memory values were used. The amount of change from 0 to 50 V was rated as ○, the amount of change from 51 to 100 V was rated as Δ, and 101 or more V was rated as x. Table 3 shows the results.
[0077]
In addition, the occurrence of scratches was confirmed visually after the 50,000 sheet passing durability test. Scratch is not generated, or it is generated but image defect is not recognized ... ○, scratches are generated to the extent that image defects are slightly recognized ... △, image defects are clearly observed A marked scratch was generated. Table 3 shows the results.
[0078]
[Examples 2 to 10]
In the electrophotographic photoreceptor of Example 1, the thermoplastic resin and the inorganic fine particles in the charge transport layer were hydrophobized silica powder (trade name: X-120, average particle size 0.02 μm, manufactured by Shin-Etsu Chemical Co., Ltd.), silica doll (trade name) Name: 30G-100, average particle size 0.1 μm, manufactured by Nippon Chemical Industry, alumina (trade name: LS-235, average particle size 0.1 μm, manufactured by Nippon Light Metal), zinc oxide (trade name: FINEX-25LP) Electrophotographic sensitization was performed in the same manner as in Example 1 except that the charge transport layer having the universal hardness value (Hu) and the plastic deformation rate shown in Table 2 was used instead of the average particle size of 0.1 μm, manufactured by Sakai Chemical Industry. The body was created and evaluated. Table 3 shows the results.
[0079]
[Example 11]
In the electrophotographic photoreceptor of Example 1, the charge transport layer was replaced, and a protective layer was further provided. That is, as a charge transport layer, 30 parts of a polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Gas Chemical Co., Ltd.), 23 parts of the charge transport material (1) used in Example 1 and 3 parts of the charge transport material (2) were used. 130 parts of chlorobenzene and 60 parts of dichloromethane were added and dissolved to obtain a paint for a charge transporting layer, applied by a dip coating method, and dried at 120 ° C. for 60 minutes to provide a charge transporting layer having a thickness of 18 μm.
[0080]
Next, as the dispersion of the protective layer, 10 parts of the polyarylate resin shown in Structural Unit Example 1 and 10 parts of hydrophobized silica powder (trade name: KMPX-100, average particle size 0.1 μm, manufactured by Shin-Etsu Chemical Co., Ltd.) Was mixed with 100 parts of monochlorobenzene, and the mixture was stirred and then dispersed in the same manner as in Example 1 (dispersion average particle size: 0.12 μm). 25 parts of this hydrophobized silica powder dispersion, 3 parts of the charge transport material (1) used in the charge transport layer and 3 parts of the polyarylate resin of the structural unit example 1 were mixed with 20 parts of monochlorobenzene and 20 parts of dichloromethane, and dissolved. Thus, a paint for a surface protective layer was obtained. This paint was applied on the charge transport layer by atomization and dried at 120 ° C. for 60 minutes to form a protective layer having a thickness of 5.0 μm, and an electrophotographic photoreceptor was prepared and evaluated. Table 3 shows the results.
[0081]
[Comparative Example 1]
The charge transport layer of Example 1 was the same as Example 1 except that the inorganic fine particles were removed. Specifically, 130 parts of monochlorobenzene and 50 parts of dichloromethane are added to 30 parts of the polyarylate resin shown in Structural Unit Example 1, and further 20 parts of the charge transport material (1) and 2 parts of the charge transport material (2) are added. This was used as a transport layer paint.
[0082]
[Comparative Examples 2 to 6]
The charge transport layers of Examples 6, 7, 8, 9, and 10 were the same as Comparative Example 1 except that the inorganic fine particles were omitted.
[0083]
[Comparative Example 7]
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that the binder in the charge transport layer of Example 1 was changed to a polycarbonate resin (trade name: Iupilon Z200, manufactured by Mitsubishi Gas Chemical). 0.15 μm). Table 3 shows the results.
[0084]
[Comparative Example 8]
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the structural unit of the binder in the charge transport layer of Example 1 was changed to a thermoplastic resin (weight average molecular weight: 46000) represented by the following structural formula (3). (Dispersion average particle size 0.16 μm). Table 3 shows the results.
[0085]
Embedded image

[0086]
[Comparative Example 9]
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the structural unit of the binder in the charge transport layer of Example 1 was changed to a thermoplastic resin (weight average molecular weight: 59000) represented by the following structural formula (4). (Dispersion average particle size: 0.15 μm). Table 3 shows the results.
[0087]
Embedded image

[0088]
[Comparative Example 10]
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the structural unit of the binder in the charge transport layer of Example 1 was changed to a thermoplastic resin (weight average molecular weight: 12,000) represented by the following structural formula (5). (Dispersion average particle size 0.17 μm). Table 3 shows the results.
[0089]
Embedded image

[0090]
[Comparative Example 11]
An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that the inorganic fine particles in the charge transport layer of Example 1 were changed to alumina (trade name: AO809, 10 μm Admatex Co., Ltd.). Table 3 shows the results.
[0091]
[Comparative Example 12]
In preparing the dispersion, the inorganic fine particles in the charge transport layer of Example 1 were replaced with polytetrafluoroethylene fine particles (trade name: Lubron L-2, manufactured by Daikin Industries, particle size: 0.5 μm) as organic fine particles. An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that 1 part of a comb-type fluorine-based graft polymer (trade name: Aron GF-300, manufactured by Toa Gosei Chemical Industry Co., Ltd.) as a dispersing aid was added. Table 3 shows the results.
[0092]
[Table 2]

[0093]
[Table 3]

[0094]
From the above results, the electrophotographic photoreceptor using the uppermost layer obtained in the present invention has good mechanical strength, particularly good scratch resistance, good electrical sensitivity, and excellent repetition characteristics. It was shown that there is.
[0095]
The embodiments of the present invention have been described above. Preferred embodiments of the present invention are listed below.
[0096]
[Embodiment 1]
In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the uppermost layer of the electrophotographic photosensitive member contains at least a thermoplastic resin and inorganic fine particles having a volume average particle diameter of 0.01 to 2.0 μm, and The universal hardness (Hu) determined from the surface film hardness test of the uppermost layer is 220 N / mm in an environment of 25 ° C. and 50% humidity. ² ≦ Hu ≦ 400N / mm ² And a plastic deformation rate of the uppermost layer by an indenter used in a surface film hardness test satisfies the following expression (1).
[0097]
(Equation 4)

[0098]
[Embodiment 2]
The electrophotographic photosensitive member according to embodiment 1, wherein the uppermost layer is a charge transport layer.
[0099]
[Embodiment 3]
3. The electrophotographic photosensitive member according to claim 1, wherein the thermoplastic resin is a polyarylate resin.
[0100]
[Embodiment 4]
The electrophotographic photoreceptor according to any one of embodiments 1 to 3, wherein the inorganic fine particles are silica fine particles.
[0101]
[Embodiment 5]
The electrophotographic photoreceptor according to embodiment 4, wherein the silica fine particles are hydrophobized silica fine particles.
[0102]
[Embodiment 6]
6. The electrophotographic photosensitive member according to any one of Embodiments 1 to 5, which is used in a contact charging system.
[0103]
【The invention's effect】
The electrophotographic photoreceptor formed with the uppermost layer according to the present invention has excellent mechanical strength, particularly good scratch resistance, and exhibits excellent electrophotographic properties. The uppermost layer, in which both the universal hardness (Hu) and the plastic deformation rate obtained from the surface film hardness test have values within a specific range, has a good interaction between the inorganic fine particles and the resin, and has an effect of reinforcing the film of the fine particles. Since it can be effectively extracted and has no dispersing aid, the photo memory is good.
[0104]
Further, the electrophotographic photoreceptor according to the present invention can be used in an electrophotographic process using a contact charging means, and is excellent in electrophotographic characteristics such as charging characteristics, sensitivity, residual potential and repetition characteristics thereof. Thus, a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus having a process cartridge of the present invention.

Claims (3)

In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the uppermost layer of the electrophotographic photosensitive member contains at least a thermoplastic resin and inorganic fine particles having a volume average particle diameter of 0.01 to 2.0 μm, and The universal hardness (Hu) determined from the surface film hardness test of the uppermost layer is 220 N / mm ² ≦ Hu ≦ 400 N / mm ² in an environment of 25 ° C. and 50% humidity, and the indenter used in the surface film hardness test Wherein the plastic deformation rate of the uppermost layer satisfies the following expression (1).

The electrophotographic photosensitive member according to claim 1, and at least one unit selected from the group consisting of a charging unit, a developing unit and a cleaning unit are integrally supported, and are detachably attached to an electrophotographic apparatus main body. Process cartridge. An electrophotographic apparatus comprising the electrophotographic photosensitive member according to claim 1, a charging unit, an exposing unit, a developing unit, and a transferring unit.

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