JP3814556B2 - Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus - Google Patents

Description

【００５８】
【表２】

【００５９】
【表３】

【００６０】
【表４】

【００６１】
【表５】

【００６２】
【表６】

【００６３】
【表７】

【００６４】
【表８】

【００６５】
【表９】

【００６６】
【表１０】

【００６７】
【表１１】

【００６８】
【表１２】

電荷輸送層中に含有させた複数種の電荷輸送材料の酸化電位自体は、単に全電荷輸送材料の酸化電位の平均した値をもって吟味するだけでは不十分であり、含有させた割合に応じた重み付けが必要である。即ち、電荷輸送層中のｎ番目の電荷輸送材料の割合をＣｎ、ｎ番目の電荷輸送材料の酸化電位をＥｎとした場合、電化輸送材料の酸化電位の平均値は
Ｅ_ave＝Σ（Ｃｎ・Ｅｎ）［Ｖ］
で算出され、下記式（４）を満足するごく限られた範囲の電荷輸送材料を選択することが好ましい。
【００６９】
０．７３≦Ｅ_ave＜０．８３ （４）
ここで、Ｃｎは電荷輸送層中の全電荷輸送材料における各電荷輸送材料の質量比を表す数値であって、全てのｎにおいて０より大きく１未満の数値を表し、ΣＣｎ＝１となる。酸化電位の平均値：Ｅ_aveが０．７３Ｖ未満であると、電子写真プロセスを連続して繰り返す耐久試験において電位の立下がりが大きくなる傾向があり、また０．８３Ｖを越えると、耐久試験による電位変動は小さくなるものの、電荷輸送層―表面保護層界面や電荷発生層―電荷輸送層界面での電荷滞留による残留電位が高くなる傾向がある。
【００７０】
また、混合する複数種の電荷輸送材料の比率は、各電荷輸送材料の酸化電位を鑑みて決めることが好ましい。│ΔＥｏｘ│が約０．０８７Ｖ以下である場合は、含有比率はそれほど大きな問題にはならず酸化電位の高い電荷輸送材料の含有比率のほうが高くてもかまわないが、０．０８７Ｖよりも大きくなるにつれ、酸化電位の最も高い電荷輸送材料は、その含有量を大幅に減らすことが好ましく、特に下記式（５）で規定されるような範囲で含有させることにより、正孔移動度と電荷輸送層―表面保護層間の電荷授受効率を適正に維持できる。
０．０５≦Ｃ_h≦０．９５×ｅｘｐ｛−４６０×（│ΔＥｏｘ│−０．０５）×（│ΔＥｏｘ│−０．０５）｝ （５）
ここで電荷輸送層中の電荷輸送材料のうち、酸化電位が最も高い電荷輸送材料の質量比がＣ_hであり、│ΔＥｏｘ│は、酸化電位が最も低い電荷輸送材料の酸化電位と、酸化電位が最も高い電荷輸送材料の酸化電位との差を表す。また、│ΔＥｏｘ│が（１）式で規定されるいかなる範囲にある場合でも、酸化電位が最も高い電荷輸送材料の含有比率は５％以上でなければ、複数種の電荷輸送材料を混合させることで得られる本発明の効果が、実質的に得られないことになる可能性が高い。
【００７１】
ここで、（１）式、（４）式、（５）式による電荷輸送材料に関する規定は、電荷輸送材料が電荷輸送層に析出することなく完全に分子分散されていることを前提に定められたものである。それゆえ、各電荷輸送材料の分子量は溶解性の観点から分子量：Ｍｗが１２００以下、特には３００〜８００の範囲であることが好ましい。
【００７２】
電荷輸送層は一般的には前記の電荷輸送物質と結着剤樹脂を溶剤に溶解し、塗布して形成する。電荷輸送物質と結着剤樹脂との混合割合は質量比で２：１〜１：２程度である。溶剤としてはアセトン、メチルエチルケトンなどのケトン類、酢酸メチル、酢酸エチルなどのエステル類、トルエン、キシレンなどの芳香族炭化水素類、クロロベンゼン、クロロホルム、四塩化炭素などの塩素系炭化水素類などが用いられる。この溶液を塗布する際には、例えば浸漬コーティング法、スプレーコーティング法、スピンナーコーティング法などのコーティング法を用いることができ、乾燥は１０℃〜２００℃、好ましくは２０℃〜１５０℃の範囲の温度で、５分〜５時間、好ましくは１０分〜２時間の時間で送風乾燥または静止乾燥下で行うことができる。
【００７３】
電荷輸送層を形成するのに用いられる結着剤樹脂としては、アクリル樹脂、スチレン系樹脂、ポリエステル、ポリカーボネート樹脂、ポリアリレート、ポリサルホン、ポリフェニレンオキシド、エポキシ樹脂、ポリウレタン樹脂、アルキド樹脂、及び不飽和樹脂などの公知の材料材料から選ばれる。特に好ましい樹脂としては、ポリメチルメタクリレート、ポリスチレン、スチレン−アクリロニトリル共重合体、ポリカーボネート樹脂またはジアリルフタレート樹脂が挙げられる。電荷輸送層の膜厚は、５〜２５μｍ、好ましくは７．０以上、１６μｍ未満である。電荷輸送層の膜厚が薄すぎる場合には静電容量が大きすぎて帯電能力が追いつかない場合があり、所望の表面電位に帯電させるのが困難であったり、また帯電できたとしても所望の明電位まで下げるのに必要な電荷数が多くなり電荷発生層から発生する電荷では不足したりする場合がある。逆に厚くなりすぎると、感光層にかかる電界強度が弱く、各感光層界面での電荷滞留が大きくなる。本発明のように、表面に半導電性の表面保護層を有したり、注入帯電装置により帯電したりする場合には、特に電荷輸送層―表面保護層間の電荷の授受効率を上げるために、電界強度をある程度上げる必要があり、従って１６．０μｍ未満の膜厚が好ましい。電荷輸送層の膜厚の測定は、以下の様にして測定した。先ず、感光層を剥離し紫外線硬化タイプのアクリル樹脂で包埋して、次いでウルトラミクロトームを用いて超薄膜切片を作製した。この切片を日立Ｈ−７５００：加速電圧１００ｋＶ型の透過電子顕微鏡を用いて観測し、電荷輸送層の膜厚を割り出した。
【００７４】
また、電荷発生層あるいは電荷輸送層には、酸化防止剤、紫外線吸収剤などの種々の添加剤を含有させることができる。
【００７５】
本発明に使用する表面保護層は、バインダ成分として絶縁性樹脂中に導電性粒子を分散させ、抵抗を調整した膜が用いられる。この絶縁性樹脂としては電気絶縁性の透明樹脂であって、湿度あるいは温度等の変化により電気抵抗が変化しにくく、かつある程度の機械的強度を有する硬化性樹脂を使用する。この条件を満たす樹脂としては、アクリル樹脂、フェノール樹脂、エポキシ樹脂、メラミン樹脂、ウレタン樹脂、シロキサン樹脂など公知の硬化性樹脂材料が挙げられる。これらの樹脂は一般に硬化反応前は、溶剤に対する溶解性を有するが、硬化反応後では、樹脂分子間に３次元架橋鎖が形成されるため、硬化反応前に溶解していた溶剤に対しても殆ど、若しくは全く溶解しなくなる。
【００７６】
これらの硬化性樹脂を硬化させるためには既に公知の硬化剤、開始剤、触媒を添加することが可能である。しかし、これらの硬化剤等の中には僅かでも残留していると感光体としての電子写真特性を阻害する可能性がある。本発明者らは、硬化剤や開始剤等に関しても検討を行った結果、特定の原子を含有する化合物で硬化反応を進めた表面保護層を有する電子写真感光体の特性が劣る点に着目した。即ち、硫黄若しくは燐原子を含有した化合物を添加して硬化を行った場合に、これらの原子の残留量が式（６）で規定される範囲に制御されることで、電子写真特性に及ぼす影響を許容範囲に抑えられる。硫黄原子、燐原子の残留量は、表面保護層表面のＸＰＳ測定により求められ、Ａ_SP［ａｔｏｍｉｃ％］で表される。
【００７７】
Ａ_S＋Ａ_P＜０．２ （６）
また、感光体表面層には酸化防止剤や紫外線吸収剤を添加することも可能であるが、これらの添加剤の中には燐原子や硫黄原子を含む化合物が市販されており、その構造及び添加量に関しても上記式（７）の範囲で、硫黄原子、燐原子の残留量が制御されることが好ましい。
【００７８】
更に、抵抗調整剤である導電性粒子としては、電気抵抗が低く粒径は、像露光に用いられる光の通過を実質上妨げない様、像露光に用いる光の波長（０．４２〜０．８μｍ）以下、好ましくはその１／２以下の粒径、即ち０．３μｍ以下好ましくは０．１μｍ以下の粒子を用いることができる。表面保護層の電気抵抗としては、１０⁹ 〜１０¹⁴Ω・ｃｍとなる様に上記導電性粒子を含有させる必要がある。電気抵抗が１０¹⁴Ω・ｃｍ以上となると、注入帯電による電荷の注入効率が低下して帯電不良を招いたり、更に残留電位が上昇しカブリの多い画像となったりしてしまい、逆に１０⁹ Ω・ｃｍ以下になると画像のボケ、解像力の低下が生じてしまう。電荷輸送層―表面保護層間での電荷授受効率を維持するためには、単に保護層膜としての電気抵抗の調整のみならず、電荷輸送層の正孔が移動するエネルギレベルに適した特定の材料の含有が必要となる。先ず、導電性成分としてインジウムとスズの割合の和：Ａｃ［ａｔｏｍｉｃ ％］（電子写真感光体表面のＸＰＳ（Ｘ線光電子分光）による分析値）が重要であり、本発明においてはこのＡｃ［ａｔｏｍｉｃ ％］が下記式（２）を満足するように導電性粒子を含有させることが必要である。
【００７９】
１．５＜Ａｃ＜１２．０ （２）
電子写真感光体の表面保護層に含有させる導電性粒子としては、ＺｎＯ、ＴｉＯｘ、Ｖ₂Ｏ₅、ＭｏＯ₃、ＮｉＯ、ＣｕＯ等の金属酸化物粉末、或いはＣｕなどの金属微粉体、カーボンブラック、フッ化カーボン等の有機系微粒子が報告されているが、本発明においては、特に複数種の電荷輸送材料を含有し特定の幅のあるエネルギでホッピング伝導を行う電荷輸送層と表面保護層との間の電荷授受を滞りなく行わせるためには、少なくともインジウム若しくはスズが所定の量で含有されていることが必須となるため、ＩＴＯと呼ばれるＳｎＯ₂含有Ｉｎ₂Ｏ₃、Ｉｎ₂Ｏ₃、酸素欠損型ＳｎＯ₂等を単独若しくはブレンドすることにより上記式（２）を満たす表面保護層に調整することが必要であるが、より好ましくはインジウムを含有するほうが好ましく、式（７）を満たす範囲でインジウムが含まれるほうがよい。
【００８０】
３．５＜Ａ_In／Ａ_Sn＜２５ （７）
Ａ_In及びＡ_Snはそれぞれ、表面保護層表面のＸＰＳによる分析値でインジウムの割合：Ａ_In［ａｔｏｍｉｃ％］とスズの割合：Ａ_Sn［ａｔｏｍｉｃ％］を表す。
【００８１】
また、本発明で用いる導電性粒子を表面保護層に含有させるに当っては、帯電部材、現像部材、転写部材、クリーニング部材等の電子写真プロセス中に感光体表面との摺擦負荷による一方的な導電性粒子の摩滅を防止するために、シランカップリング剤、シロキサン系化合物、フッ素原子含有化合物等で上記導電性粒子に表面処理を施すことも可能である。
【００８２】
更に導電性粒子をシランカップリング剤、シロキサン系化合物、フッ素原子含有化合物等で表面処理するだけでは、一方的な導電性粒子の摩滅を防止するのは困難であるため、珪素またはフッ素成分の補充として、これらの原子を含有する樹脂微粒子やオイル、オリゴマ成分を含有させることが必要である。結果として、電子写真感光体表面のＸＰＳ（Ｘ線光電子分光）による分析値でフッ素と珪素の割合の和：Ａ_L［ａｔｏｍｉｃ％］が下記式（３）を満足することが必要である。
【００８３】
５．０＜Ａ_L＜２５．０ （３）
フッ素と珪素の割合の和：Ａ_Lが８．０ａｔｏｍｉｃ％以下である場合には、一方的な導電性粒子の摩滅を防止することが困難であり、逆に２５．０ａｔｏｍｉｃ％を越えると摺擦による傷の発生や表面保護層内での像露光散乱の増加による画質の低下といった弊害が生じる。
【００８４】
電子写真感光体表面のＸＰＳ測定は、ＸＰＳ測定装置として、アルバックファイ社製，Ｑｕａｎｔｕｍ−２０００、Ｘ線光電子分光装置を用いて行った。
【００８５】
測定条件としては、Ｘ線源ＡｌＫα（単色化）、１０１．２Ｗ、９０度、１８７．８５ｅＶ、分析領域２×３ｍｍとした。
【００８６】
珪素またはフッ素原子を含む樹脂微粒子か分子量の高いオイル成分が好ましい。珪素若しくはフッ素原子を含む低分子化合物は界面／表面移行性が強く、分子量の特に低いオリゴマ性の化合物では、先に述べたとおり表面／界面での電荷の注入性や授受を阻害する作用が強くなりすぎるためである。
【００８７】
また、本発明における表面保護層の膜厚は１０μｍ以下が好ましく、更には透過率、強度の点から１〜５μｍがより好ましい。
【００８８】
次に、放電による感光体のダメージを減らした本発明にかかる帯電方式についての全体的な概略構成について述べる。
【００８９】
図３は本発明にかかる帯電装置を用いた概略構成図である。本実施例の画像記録装置は、転写式電子写真プロセス利用、直接注入帯電方式、トナーリサイクルプロセス（クリーナレスシステム）のレーザプリンタ（記録装置）である。
【００９０】
（電子写真装置の全体的概略構成）
１は電子写真感光体であり、本構成においてはφ３０ｍｍの回転ドラム型の負極性電子写真感光体（ネガ感光体、以下、感光ドラムと記す）である。この感光ドラム１は矢印の時計方向に周速度９４ｍｍ／ｓｅｃ（＝プロセススピードＰＳ、印字速度）の一定速度をもって回転駆動される。
【００９１】
帯電ローラ２は、帯電導電粒子Ｍ（帯電粒子としての導電性粒子）と、粒子担持体としての中抵抗層２ｂ及び芯金２ａにより構成される。帯電ローラ２は感光ドラム１に所定の侵入量をもって当接し、帯電接触部ｎを形成する。
【００９２】
帯電ローラ２はこの帯電接触部ｎにおいて感光ドラム１の回転方向と逆方向（カウンタ）で回転駆動され、感光ドラム１面に対して速度差を持って接触する。またプリンタの画像記録時には該帯電ローラ２に帯電バイアス印加電源Ｓ１から所定の帯電バイアスが印加される。これにより感光ドラム１の周面が直接注入帯電方式で所定の極性・電位に一様に接触帯電処理される。本実施例ではＳ１の印加電源による印加バイアスをＤＣ電圧−７００Ｖが印加された。
【００９３】
帯電導電粒子は現像剤に添加して蓄積されトナーの現像とともに感光ドラムを介して帯電ローラに供給される。
【００９４】
６０は現像装置である。回転感光ドラム１面の静電潜像はこの現像装置６０により現像部位ａにてトナー画像として現像される。現像装置６０内には現像剤ｔに帯電導電粒子Ｍを添加した混合剤ｔｍが備えられている。
【００９５】
本構成のプリンタはトナーリサイクルプロセスであり、画像転写後の感光ドラム１面上に残留した転写残トナーは専用のクリーナ（クリーニング装置）で除去されることなく感光ドラム１の回転にともないカウンタ回転する帯電ローラに一時的に回収されローラ外周を周回するにつれて、反転したトナー電荷が正規化され順次感光ドラムに吐き出されて現像部位ａに至り、現像器６０において現像同時クリーニングにて回収・再利用される。
【００９６】
４はレーザダイオード・ポリゴンミラー等を含むレーザビームスキャナ（露光装置）である。このレーザビームスキャナ４は目的の画像情報の時系列ディジタル画像信号に対応して強度変調されたレーザ光を出力し、該レーザ光で上記回転感光ドラム１の一様帯電面を走査露光Ｌする。
【００９７】
この走査露光Ｌにより回転感光ドラム１の面に目的の画像情報に対応した静電潜像が形成される。
【００９８】
７は熱定着方式等の定着装置である。転写ニップ部ｂに給紙されて感光ドラムｌ側のトナー画像の転写を受けた転写材Ｐは回転感光ドラム１の面から分離されてこの定着装置７に導入され、トナー画像の定着を受けて画像形成物（プリントコピー）として装置外へ排出される。
【００９９】
次に、本帯電器の主たる構成部材について述べる。
【０１００】
［帯電ローラ］
帯電ローラ２は芯金２ａ上にゴムあるいは発泡体の中抵抗層２ｂを形成することにより作製される。中抵抗層２ｂは樹脂（例えばウレタン）、導電性粒子（例えばカーボンブラック）、硫化剤、発泡剤等により処方され、芯金２ａの上にローラ状に形成するものである。本帯電ローラの特徴としては、弾性を持たせ十分な接触状態を得ると同時に、移動する電子写真感光体を充電するに十分低い抵抗を有する必要がある。一方では電子写真感光体にピンホールなどの欠陥部位が存在した場合に電圧のリークを防止する必要がある。電子写真感光体として電子写真用感光体を用いた場合、十分な帯電性と耐リーク性を得るには１０⁴〜１０⁷Ωの抵抗が好ましい。
【０１０１】
帯電ローラの硬度は、硬度が低すぎると形状安定しないために接触性が悪くなり、高すぎると帯電ニップを確保できないだけでなく、感光体表面へのミクロな接触性が悪くなるので、アスカーＣ硬度で２５度から５０度が好ましい範囲である。
【０１０２】
帯電ローラの材質としては、弾性発泡体に限定するものでは無く、弾性体の材料として、ＥＰＤＭ、ウレタン、ＮＢＲ、シリコーンゴムや、ＩＲ等に抵抗調整のためにカーボンブラックや金属酸化物等の導電性物質を分散したゴム剤や、またこれらを発泡させたものがあげられる。また、特に導電性物質を分散せずに、イオン導電性の材料を用いて抵抗調整をすることも可能である。
【０１０３】
帯電部材は、帯電ローラに限定されるものではなく、パイル１本１本が弾性を持つファーブラシ等の弾性体も使用可能である。ここでファーブラシローラーは、抵抗調整された繊維（ユニチカ性−Ｒｅｃ等）を植え密度１５５本／ｍｍ²、繊維長３ｍｍパイル上に形成し、その後そのパイルをφ６ｍｍ芯金に巻き固定し、ローラ状に成形したものも使用可能である。特に電子写真感光体の帯電能力は感光体表面との接触効率に大きく依存するが、特に、帯電部材は電子写真感光体と接触する部分においてカウンタ方向に回転（従って、電子写真感光体と帯電ローラの回転方向自体は同じである）させることが重要である。
【０１０４】
［帯電促進粒子］
粒子の材料としては、他の金属酸化物などの導電性無機粒子や有機物との混合物など各種導電粒子が使用可能である。ここで、粒子抵抗は粒子を介した電荷の授受を行うため比抵抗としては１０¹⁰Ω・ｃｍ以下が好ましい。ここで抵抗測定は、錠剤法により測定し正規化して求めた。低面積２．２６ｃｍ² の円筒内に凡そ０．５ｇの粉体試料を入れ上下電極に１．５７ＭＰａ（１５ｋｇｆ／ｃｍ² ）の加圧を行うと同時に１００Ｖの電圧を印加し、抵抗値を計測、その後正規化して比抵抗を算出した。また、粒径は良好な帯電均一性を得るために１０μｍ以下が好ましい。粒径の下限値は、粒子が安定して得られるものとして１０ｎｍが限界である。本発明において、粒子が凝集体として構成されている場合の粒径は、その凝集体としての平均粒径として定義した。粒径の測定には、光学あるいは電子顕微鏡による観察から、１００個以上抽出し、水平方向の最大弦長をもって体積粒度分布を算出しその５０％平均粒径をもって決定することができる。
【０１０５】
［帯電促進粒子塗布手段］
帯電促進粒子をローラと感光体の接触ニップに均一に供給するために、帯電促進粒子塗布手段を設けることができる。供給手段としては規制ブレードを感光体に当接し、感光体と規制ブレード間に帯電促進粒子を保持する構成をとる。そして、感光体の回転にともない一定量の帯電促進粒子がローラに塗布される。より簡易な構成としては、現像器の中に、現像剤と共にこの帯電促進粒子を均一に添加しておき、現像時に現像剤と共に電子写真感体上に供給させ、転写プロセス時に殆ど転写させない状態にすることで帯電ローラに供給することが可能であるし、或いは帯電促進粒子を含ませた発泡体あるいはファーブラシを電子写真感光体に当接する方法などがあるが、本構成に限定するものでない。
【０１０６】
［帯電器の動作］
本発明における帯電器の動作の一例について説明する。電子写真感光体は表面に上述した特定の表面保護層が設けてあって、ドラム状であり、周速が３０〜１００ｍｍ／ｓｅｃ程度の一定速度で回転する。この表面を一様に帯電する帯電器とし本発明にかかる帯電器を使用した。ただし、この場合の周速度は、所望のプロセススピードにより決定されるのであって、本発明はこの周速度に限定されるわけではない。
【０１０７】
まず、感光体表面に帯電促進粒子が現像プロセスにより現像器より電子写真感光体表面に付着する。その後、転写プロセスを通り抜け、帯電ローラ部に到達する。帯電ローラはそのローラ表面が感光体と互いに逆方向に等速度で移動するよう凡そ５０〜１５０ｒｐｍで駆動し、その帯電ローラの芯金に−５００〜−８００Ｖの直流電圧を印加した。ただし、この帯電ローラの周速度も、所望のプロセススピードや電子写真感光体に周速度により決定されるのであって、本発明はこの周速度に限定されるわけではない。
【０１０８】
このプロセスにより、感光体表面は印加電圧と等しい電位に帯電される。本実施例において帯電は、帯電ローラと電子写真感光体の接触ニップに存在する帯電促進粒子が電子写真感光体表面を隙間無く摺擦することで直接、電荷が電子感光体表面に設けた表面保護層中の導電性粒子へ注入して帯電が行われるのである。この注入帯電プロセスにおいて、表面保護層中の導電性粒子の存在が重要であり、この導電性粒子の比率が帯電ローラとの摺擦作用によっても変わらないことが、帯電性、電子写真特性を維持するために必要である。
【０１０９】
【実施例】
以下、本発明を実施例により説明する。
【０１１０】
（感光層例１）
φ３０ｍｍ×２６０．５ｍｍのアルミニウムシリンダーを支持体として、この上にポリアミド樹脂（商品名：アミランＣＭ８０００、東レ製）の５質量％メタノール溶液を浸漬法で塗布し、０．５μｍの下引き層を設けた。
【０１１１】
次に、ＣｕＫαのＸ線回折スペクトルにおける回折角２θ±０．２゜の、９．０、１４．２、２３．９、２７．１゜に強いピークを有するオキシチタニウムフタロシアニン顔料４部（質量部、以下同様）、ポリビニルブチラール樹脂ＢＸ−１（積水化学（株）製）２部、及び、シクロヘキサノン８０部を、φ１ｍｍガラスビーズ入りサンドミル装置で、４時間ほど分散した。この溶液を、前記下引き層上に塗布し、１０５℃、１０分熱風乾燥して、０．２２μｍの電荷発生層を形成した。
【０１１２】
次いで、電荷輸送材料として例示化合物ＣＴＭ−４３を１部（酸化電位：０．８１Ｖ）、及び、ＣＴＭ‐６（酸化電位：０．７６Ｖ）を９部、ビスフェノールＺ型ポリカーボネート（商品名：Ｚ−４００、三菱ガス化学（株）製）１３質量部を、モノクロロベンゼン７５質量部及びジメトキメタン２５質量部に溶解した。この溶液を、前記電荷発生層上に浸漬塗布し、１２０℃、３０分間をかけて熱風乾燥して、１５μｍの電荷輸送層を形成した。従って、酸化電位の差：│ΔＥｏｘ│＝０．０５Ｖであり、平均酸化電位：Ｅａｖｅ＝０．７６５Ｖである。
【０１１３】
（感光層例２）
感光体層１において電荷発生層を以下のようして設けた以外は、同様にして感光層を作製した。
【０１１４】
ＣｕＫαのＸ線回折における回折角２θ±０．２の２８．１°に最も強いピークを有するヒドロキシガリウムフタロシアニンの結晶３質量部とポリビニルブチラール２質量部をシクロヘキサノン１００質量部に添加し、１ｍｍφガラスビーズ入りサンドミルで１時間分散し、これにメチルエチルケトン１００質量部を加えて希釈して電荷発生層用塗料を調製し、上記下引き層上に、この電荷発生層用塗料を浸漬塗布し、９０℃で１０分間乾燥して、膜厚０．１５μｍの電荷発生層を形成した。
【０１１５】
（感光層例３〜３０）
感光層例２において、電荷輸送層中の各電荷輸送材料を表１３〜１４に示した構造及び割合に変えた以外は同様にして感光体を作製した。
【０１１６】
【表１３】

【０１１７】
【表１４】

（感光層例３１）
感光層例２において、電荷輸送層を以下のようにして設けた以外は同様にして感光体を作製した。
【０１１８】
電荷輸送材料として例示化合物ＣＴＭ−２０を８質量部（酸化電位：０．７４Ｖ）、及び、ＣＴＭ−２７（酸化電位：０．８４Ｖ）を２質量部、ビスフェノールＡ型ポリカーボネート（重量平均分子量：２７０００）１５質量部を、モノクロロベンゼン３０質量部及びジクロロメタン７０質量部に溶解した。この溶液を、前記電荷発生層上に浸漬塗布し、１２０℃、３０分間をかけて熱風乾燥して、１６μｍの電荷輸送層を形成した。従って、酸化電位の差：│ΔＥｏｘ│＝０．１０Ｖであり、平均酸化電位：Ｅａｖｅ＝０．７６０Ｖである。
【０１１９】
（感光層例３２〜４１）
感光層３１において、電荷輸送層中の各電荷輸送材料を表１５に示した構造及び割合に変えた以外は同様にして感光体を作製した。
【０１２０】
【表１５】

（保護層例１）
導電性粒子として含フッ素シランカップリング剤：Ｃ₅Ｆ₁₁ＣＨ₂ＣＨ₂ＣＨ₂Ｓｉ（ＯＣ₂Ｈ₅）₃で表面処理（処理量６．５％）した平均粒径が０．０３μｍの酸素欠損型ＳｎＯ₂粒子を５０質量部、アセトン１５０質量部をサンドミルにて７２時間かけて分散を行い、更にポリクロロトリフルオロエチレン粒子（ＰＣＴＦＥ、平均粒径：０．２７μｍ）１０質量部を加えて分散を行った後、アミノ樹脂であるサイメルＣ−２０４（三井サイテック（株）製）を１５質量部溶解して、保護層溶液を作製した。この溶液中に前記感光層を浸漬塗布し、１６０℃で５０分の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。このようにして設けた保護層表をＸＰＳにて解析し、
スズ＋インジウムの割合：Ａｃ＝５．５ａｔｏｍｉｃ％
インジウムとスズの比率：Ａ_In／Ａ_Sn＝０
フッ素＋珪素の割合：Ａ_L＝１５．６ａｔｏｍｉｃ％
硫黄＋燐の割合：Ａｓｐは０．０１ａｔｏｍｉｃ％以下
の測定結果を得た。
【０１２１】
（保護層例２〜６）
保護層例１において、含フッ素シランカップリング剤による処理量、ＰＣＴＦＥ粒子の分散量及びアミノ樹脂であるサイメルＣ−２０４（三井サイテック（株）製）の溶解量を調整し、浸漬塗布し、１６０℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層形成後のＸＰＳ分析値が表７になるように保護層塗料を調製し、感光層上に浸漬塗布し、１６０℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。
【０１２２】
（保護層例７）
保護層例１において、導電性粒子を平均粒径０．０２μｍの酸化Ｓｎ含有酸化インジウム粒子（ＩＴＯ粒子）３５質量部に変え、アミノ樹脂の変わりにレゾール型フェノール樹脂：ＸＰＬ−８２６４Ｂ（群栄化学工業（株）製）を用い、かつ、その量を調整した以外は同様にして保護層塗料を作製し、保護層を設けた。
【０１２３】
（保護層例８〜１３）
保護層例７において、含フッ素シランカップリング剤による処理量、ＰＣＴＦＥ粒子の分散量及びレゾール型フェノール樹脂の変かわりにアミノ樹脂であるサイメルＣ−２０４（三井サイテック（株）製）を用い、かつその溶解量を調整し、浸漬塗布し、１６０℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層形成後のＸＰＳ分析値が表７になるように保護層塗料を調整し、感光層上に浸漬塗布し、１６０℃で５０分の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。
【０１２４】
（保護層例１４）
導電性粒子として含フッ素シランカップリング剤：Ｃ₅Ｆ₁₁ＣＨ₂ＣＨ₂ＣＨ₂Ｓｉ（ＯＣ₂Ｈ₅）₃で表面処理（処理量６．５％）した平均粒径が０．０３μｍのアンチモンドープＳｎＯ₂粒子を１０質量部、含フッ素シランカップリング剤：Ｃ₄Ｆ₉ＣＨ₂ＣＨ₂ＣＨ₂Ｓｉ（ＯＣＨ₃）₃で表面処理（処理量８．５％）した平均粒径が０．０２μｍの酸化インジウム粒子３８部、アセトン１５０質量部をサンドミルにて７２時間かけて分散を行い、更にＰＣＴＦＥ粒子（平均粒径：０．２７μｍ）１０質量部を加えて分散を行った後、レゾール型フェノー樹脂：ＸＰＬ−８２６４Ｂを２９質量部溶解して、保護層溶液を作製した。この溶液中に前記感光層を浸漬塗布し、１６０℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。
【０１２５】
（保護層例１５）
導電性粒子として含フッ素シランカップリング剤：Ｃ₅Ｆ₁₁ＣＨ₂ＣＨ₂ＣＨ₂Ｓｉ（ＯＣ₂Ｈ₅）₃で表面処理（処理量６．５％）した平均粒径が０．０３μｍのＩＴＯ粒子を３０質量部、メチルハイドロジェンシリコンオイルで処理した平均粒径が０．０３μｍの酸素欠損型ＳｎＯ₂粒子（処理量１２％）、アセトン１５０質量部をサンドミルにて７２時間かけて分散を行い、更にテトラフルオロエチレン−ヘキサフルオロプロピレン共重合体粒子（ＥＴＦＥ、平均粒径：０．３０μｍ）１０質量部を加えて分散を行った後、レゾール型フェノー樹脂：ＸＰＬ−８２６４Ｂを３５質量部溶解して、保護層溶液を作製した。この溶液中に前記感光層を浸漬塗布し、１６０℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。
【０１２６】
（保護層例１６）
保護層例７において、レゾール型フェノール樹脂の変わりにアミノ樹脂（サイメル Ｃ２０１、三井サイテック（株）製）を用いた以外は同様にして保護層を作製した。
【０１２７】
（保護層例１７）
保護層例７において、レゾール型フェノール樹脂の変わりに、クレゾールノボラック型エポキシ樹脂１１質量部及び硬化剤として下記構造式で示されるチオエーテル化合物５質量部に変えた以外は同様にして感光体を作製した。
【０１２８】
【化１】

（保護層例１８）
下記構造式で示されるアクリル系モノマ６０質量部、分散前の平均粒子系が０．０４μｍの酸化スズ超微粒子３０質量部、光開始剤として含硫黄原子化合物の２−メチルチオキサントン２質量部、メチルセルソルブ３００質量部をサンドミルにて９６時間分散を行って保護層塗料とし、前記感光層上にビームコーティング法により膜を形成した後に、高圧水銀灯にて８ｍＷ／ｃｍ²の光強度で３０秒間光硬化を行い３μｍの保護層を設けた。
【０１２９】
【化２】

（保護層例１９）
保護層例１８において、酸化スズ超微粒子を、含フッ素シランカップリング剤：Ｃ₅Ｆ₁₁ＣＨ₂ＣＨ₂ＣＨ₂Ｓｉ（ＯＣ₂Ｈ₅）₃で表面処理（処理量６．５％）した。該粒子を平均粒径が０．０２μｍのＩＴＯ粒子に変え、更に平均粒径が０．３０μｍのＥＴＦＥ粒子１２質量部を分散した以外は同様にして保護層を設けた。
【０１３０】
（保護層例２０）
保護層例１９において、光開始剤を下記構造式の燐原子含有化合物６質量部に変えた以外は同様にして感光体を作製した。
【０１３１】
【化３】

（保護層例２１）
ポリクロロトリフルオロエチレン粒子（ＰＣＴＦＥ、平均粒径：０．２７μｍ）１２質量部を加えて分散を行った後、アミノ樹脂（サイメルＣ２０１、三井サイテック（株）１５質量部溶解して、保護層溶液を作製した。この溶液中に前記感光層を浸漬塗布し、１５７℃で５０分間の加熱硬化反応をおこない、電荷輸送層上に３μｍの保護層を設けた。
【０１３２】
保護層例１〜２１の保護層に関し、保護層形成後にそれぞれの保護層塗料で使用していた溶剤であるアセトン或いはメチルセルソルブを含浸させた脱脂綿にて表面を払き、保護層の耐溶剤性を確認したが、何れも殆ど溶解することはなく、加熱若しくは紫外線照射により保護層膜内に３次元架橋鎖が形成され、硬化反応が進んだものと予想された。
【０１３３】
【表１６】

（電子写真感光体の作製）
上記感光層例１〜４１の上に保護層例１〜２１で示した保護層を設けることにより、実施例及び比較例の各電子写真感光体を作製した。
【０１３４】
これらの電子写真感光体の保護層を強制的に研磨して除いた後に電荷輸送層を溶媒にて溶解し、更にシリカゲルカラムクロマトグラフィーにより、各電荷輸送材料を単離して再度上述のサイクリックボルタメトリ法により酸化電位を測定したが、各電荷輸送材料とも酸化電位自体の変化は無いことが確認された。
（評価試験１）
これらの電子写真感光体をキヤノン製レーザプリンタ：ＬＢＰ−ＮＸ（ローラ帯電、直流／交流重畳、ウレタンゴム製クリーニングブレードによる残トナーのクリーニング）を用い、気温５℃／湿度１０ＲＨ％、及び気温３２．５℃／湿度８５ＲＨ％の各環境にて７，０００枚の耐久試験を行った。耐久試験最後における画像品位をまとめた結果を表８、表９に示す。帯電条件として、帯電ローラにＤＣ成分：−７００Ｖに、ＡＣ成分：２，０００Ｖｐｐを重畳したＡＣ／ＤＣ帯電方式により各電子写真感光体表面を帯電した。レーザ光量は、現像器位置で各電子写真感光体の明部電位が−２００Ｖとなるように強度を調整した。
【０１３５】
また、転写プロセス時や感光体表面と接触する部材との摩擦帯電等により感光体表面がプラスに帯電された状態が続くことにより、その部分の暗減衰が大きくなったり、光感度が高くなったりするプラスメモリという現象に対する指標として、これらの感光体表面の一部を＋７００Ｖに帯電し、２時間後にレーザプリンタ：ＬＢＰ−ＮＸに装着して、ハーフトーン画像を印字し、プラス帯電履歴部分の濃度が非帯電部分とどの程度差があるかを判断した。
【０１３６】
【表１７】

【０１３７】
【表１８】

【０１３８】
【表１９】

保護層７の表面分析値：
Ａｃ＝４．２ ａｔｏｍｉｃ ％、
Ａ_L＝１３．７ ａｔｏｍｉｃ ％、
Ａ_In／Ａ_Sn＝５．５６ ａｔｏｍｉｃ％、
Ａｓ＋Ａｐ＜０．０１ ａｔｏｍｉｃ ％
以上の実施例、比較例の対比より、限られた特定の範囲のＡｃ値並びにＡ_L値を有する保護層を設けた電子写真感光体において、同時にその電荷輸送層中に、限られた特定の範囲の│ΔＥ│を有する電荷輸送材料を複数種含有させることで、電子写真特性を維持し、高品位な画像を得ることができる。その中でも特に平均の酸化電位：Ｅａｖｅが０．７３〜０．８３Ｖという範囲にあり、かつトリアリールアミン系やスチリル系といった非ヒドラゾン型の電荷輸送材料を選択することで、特に優れた耐久特性を得られる。
【０１３９】
【表２０】

【０１４０】
【表２１】

以上の実施例、比較例の対比より、電荷輸送層中に限られた特定の範囲の│ΔＥ│を有する電荷輸送材料を複数種含有させ、同時に限られた特定の範囲のＡｃ値並びにＡ_L値を有する保護層を設けることで、電子写真特性を維持し、高品位な画像を得ることができる。更に保護層中のインジウムとスズの比率を特定の範囲に制御し、燐原子、硫黄原子の量を０．２ａｔｏｍｉｃ ％以下に抑えることで、より高い次元で耐久安定性を有する電子写真感光体を提供可能である。
【０１４１】
（評価試験２）
実施例で作製した電子写真感光体の評価は、ヒューレットパッカード（株）製レーザージェット４０００を図３に記載した構成に改造を施した実機を用いた。この時の一次帯電用導電粒子の体積抵抗は、１（Ω・ｃｍ）であり、弾性帯電部材への導電粒子の耐久初期の担持量を帯電粒子担持体の表面粗さＲａ［μｍ］で除した値は０．１ｍｇ／ｃｍ²／μｍであった。一次帯電部材に印加する電圧は、ＤＣ成分のみで−７００Ｖであった。レーザ光量は、現像器位置で各電子写真感光体の明部電位が−２００Ｖとなるように強度を調整した。更に、温度３２．５℃、湿度９０％の高温／高湿環境下で、上記の電子写真感光体の１０，０００枚出力の耐久試験を行った。評価結果を、表２２にまとめて示す。
【０１４２】
【表２２】

上記の実施例より、本発明の帯電システムにおいても、保護層表面のＡｃ及びＡ_Lを適正な範囲に制御した電子写真感光体においては、注入帯電性及び感光体表面の摩滅が常に安定しており、ＡＣ帯電系で認められた若干の画像ボケも発生することも無く、極めて良好な画像の出力が可能であり、同時に感光体帯電時に感光体にかかる電界強度が高くない本帯電システムにおいても、電荷輸送層中に限られた特定の範囲の│ΔＥ│を有する電荷輸送材料を複数種含有させることで、電子写真特性を維持し、高品位な画像を得ることができる。
【０１４３】
その中でも特に電荷輸送層中の電荷輸送材料に関しては、平均の酸化電位：Ｅａｖｅが０．７３〜０．８３Ｖという範囲であり、かつトリアリールアミン系やスチリル系といった非ヒドラゾン型の電荷輸送材料を選択し、保護層中のインジウムとスズの比率を特定の範囲に制御し、燐原子、硫黄原子の量を０．２ａｔｏｍｉｃ％以下に抑えることで、より高い次元で耐久安定性を有する電子写真感光体を提供可能である。
【０１４４】
【発明の効果】
以上説明したように、本発明によれば、電荷輸送層中に少なくとも２種類以上の電荷輸送材料を含有し、該電荷輸送材料のうち最も低い酸化電位及び最も高い酸化電位の差：｜ΔＥｏｘ｜、電子写真感光体表面のＸＰＳ（Ｘ線光電子分光）による分析値で表面保護層に含まれるインジウムとスズの割合の和：Ａｃ［ａｔｏｍｉｃ％］と表面保護層に含まれるフッ素と珪素の割合の和：Ａ_L［ａｔｏｍｉｃ％］を特別な範囲に制御することで、表面保護層−電荷輸送層間での電荷の授受を滞りなく行うことが可能となり、優れた画像品位の電子写真感光体を提供することが可能となる。また、電荷輸送材料に関しては、特定の範囲の平均の酸化電位を持った非ヒドラゾン型の電荷輸送材料を選択し、表面保護層中のインジウムとスズの比率を特定の範囲に制御し、燐原子、硫黄原子の量を０．２ａｔｏｍｉｃ ％以下に抑えることで、長時間にわたる耐久試験においても良好な特性を示す。更に、平均粒径が１０μｍ〜１０ｎｍ、抵抗が１０¹²から１０^-1Ω・ｃｍである導電性無機粒子を主成分とする帯電粒子と、導電性と弾性を有した表面を備えた帯電粒子担持体であって、かつ該帯電粒子の担持量を該帯電粒子担持体の表面粗さＲａ［μｍ］で除した値が０．００５から１ｍｇ／ｃｍ²／μｍである帯電粒子担持体により構成された帯電用部材が電子写真感光体との接触面においてカウンタ方向に回転し、該電子写真感光体を接触注入帯電する帯電装置においても、高い次元で耐久安定性を有する電子写真感光体を提供可能である。
【図面の簡単な説明】
【図１】本発明の帯電ローラにＤＣ電圧のみを印加したときの放電帯電と注入帯電の違いを示す図である。
【図２】本発明の帯電ローラにＤＣ電圧にＡＣ電圧を重畳し、電圧を印加したときの放電帯電と注入帯電の違いを示す図である。
【図３】本発明の電子写真システムの概略を示す図である。
【符号の説明】
１ａ 注入層付き感光ドラム
１ｂ 感光ドラム
２ 帯電ローラ
２ａ 芯金
２ｂ 導電弾性ローラ
Ｍ 帯電導電粒子（帯電粒子）
３Ａ 帯電導電粒子供給器
３７Ａ 攪拌羽根
３９Ａ ファーブラシ
４ レーザ露光装置
５Ａ ２成分現像装置
５２ マグネットロール
５１ 現像スリーブ
６０ １成分磁性現像器
６ 転写帯電器
７ 定着装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic photoreceptor having a surface protective layer in this order, which contains at least a charge generation layer, a charge transport layer, and conductive particles on a conductive support, and is formed using a curable resin. Is. The present invention also provides an electrophotographic photosensitive member characterized by using a charging method in which charging is predominantly performed by injecting charge directly from the charging member in contact with the electrophotographic photosensitive member to the surface of the electrophotographic photosensitive member, The present invention relates to a process cartridge and an electrophotographic apparatus using an electrophotographic photosensitive member.
[0002]
[Prior art]
In the electrophotographic method, basic processes such as charging, exposure, development, transfer, and fixing are performed on an electrophotographic photosensitive member such as amorphous silicon or an organic photoconductor. Therefore, when obtaining an image, the charging process has been conventionally performed by applying a high voltage (5 to 8 kV DC) to a metal wire and charging with a generated corona. However, with this method, when corona occurs, the surface of the electrophotographic photosensitive member is altered by corona products such as ozone and NOx to cause image blurring and deterioration, and wire contamination affects image quality. And other problems such as black streaks.
[0003]
In particular, an electrophotographic photoreceptor whose photosensitive layer is mainly composed of an organic photoconductor is less chemically stable than other amorphous silicon photoreceptors, and when exposed to a corona product, a chemical reaction (mainly Oxidation reaction) occurs and tends to deteriorate. Therefore, when it is repeatedly used under corona charging, image blur due to the above-described deterioration, sensitivity reduction, copy density thinning due to increase in residual potential, and print resistance (copy resistance) life tend to be shortened.
[0004]
Further, in the case of corona charging, the electric current toward the photoconductor is only 5 to 30% in terms of power, and most of the current flows to the shield plate, and the charging means is inefficient. Furthermore, repeating the electrophotographic process by corona charging increases the concentration of ozone, NOx, etc., which is a serious problem in providing a comfortable use environment.
[0005]
Therefore, in order to make up for such problems, for example, JP-A-57-178267, JP-A-56-104351, JP-A-58-40566, JP-A-58-139156, As proposed in Japanese Patent Laid-Open No. 58-150975 and the like, a method for contacting and charging without using a corona discharger has been studied. Specifically, the surface of the photoconductor is charged to a predetermined potential by bringing a charging member such as a conductive elastic roller to which a DC voltage of about 1 to 2 kV is applied from the outside into contact with the surface of the photoconductor. It is a method to make it.
[0006]
However, this direct charging method is disadvantageous in comparison with the corona charging method in terms of non-uniform charging and occurrence of dielectric breakdown of the photosensitive member due to discharge when a voltage is directly applied. Here, due to the non-uniformity of charging, streaky charging unevenness occurs in a direction perpendicular to the moving direction of the surface to be charged and having a length of 2 to 200 mm and a width of 0.5 mm or less. Thus, image defects such as white streaks (a phenomenon in which white streaks appear in solid black or halftone images) that occur in the case of the normal development method and black streaks that occur in the case of the reversal development method occur.
[0007]
In order to solve such problems and improve the uniformity of charging, a method has been proposed in which an AC voltage is superimposed on a DC voltage and applied to the charging member. (See JP-A 63-149668). In this charging method, a pulsating voltage is obtained by superimposing an AC voltage (Vac) of a DC voltage (Vdc), and this is applied to perform uniform charging.
[0008]
In this case, in order to maintain the uniformity of charging and prevent image defects such as white spots in the normal development method, black spots in the reverse development method, and fogging, the superimposed alternating voltage is the discharge start voltage Vth according to Paschen's law. It is necessary to have a peak-to-peak potential difference (Vpp) of 2 times or more.
[0009]
However, if the superimposed alternating voltage is increased in order to prevent image defects, dielectric breakdown occurs due to discharge in a slight defect portion inside the photosensitive member due to the maximum applied voltage of the pulsating voltage. In particular, when the photoconductor is an organic photoconductor having a low withstand voltage, this dielectric breakdown is significant. In this case, in the normal development method, the image is whitened along the longitudinal direction of the contact portion (the width direction of the recording material), and in the reversal development method, black stripes are generated. Further, since the discharge is in a minute gap, there is a problem that damage to the photoconductor is large, the photoconductor is greatly scraped, and its durability is inferior.
[0010]
As described above, the strength of the electrophotographic photosensitive member surface is always regarded as a big problem, and in order to solve this problem, a proposal has been made to provide a surface protective layer with a material having high mechanical strength on the photosensitive member surface. . However, simply providing a surface protective layer with high mechanical strength does not transfer charges to and from the photosensitive layer, causing a problem that the residual potential increases during the electrophotographic process. There have been many proposals of semi-conductive type surface protective layers containing conductive particles such as metals having low electric resistance and adjusting the resistance. However, the charge transfer method in the photosensitive layer, particularly the charge transport layer, is generally called hopping conduction in which holes travel while hopping through the highest occupied orbit (HOMO) of each charge transport material molecule. The charge transfer method in the semiconductive material with controlled electric resistance is the conduction of electrons in the controlled electric resistance with free electrons in the conductive particles such as metal, which is completely different from the former. It is a method. Therefore, at the interface between the charge transport layer that is hopping conduction and the surface protective layer interface that contains conductive particles that are electron conduction, the charges must be recombined by different charge transfer methods. The actual situation is that stagnation was inevitable. The problem of charge retention at the charge transport layer-surface protective layer interface is a specific technical problem that occurs in an electrophotographic photoreceptor having a surface protective layer containing conductive particles on a hopping conductive charge transport layer. It can be said that there is.
[0011]
In the electrophotographic photoreceptor provided with such a surface protective layer having semiconductivity, the fact that the number put on the market is remarkably small compared with the number of proposals is the charge transport layer-surface protective layer interface. It can be said that the technical problem of how difficult it is to control transfer is exposed. Practical problems caused by poor charge transfer at the charge transport layer-surface protective layer interface are negative ghosts, positive ghosts, etc., where the printed part of the previous electrophotographic process appears in the next process. This is a plus memory in which the density of a positively charged portion on the surface of the photoreceptor is changed. In general, in order to reduce the charge retention at the interface between the charge transport layer and the surface protective layer, the oxidation potential of the charge transport material contained in the charge transport layer is lowered or the amount of conductive particles in the surface protective layer is reduced. The direction to increase is good. However, when this oxidation potential is lowered, the potential fluctuation due to the repeated electrophotographic process tends to increase, and if the amount of conductive particles in the surface protective layer is too large, the charge that is an electrostatic latent image As a result, the image blurring occurs and the photoconductor that completely solves the charge retention at the interface between the charge transport layer and the surface protective layer has not yet been realized.
[0012]
Furthermore, the electrophotographic photosensitive member is subjected to a rubbing load in individual electrophotographic processes such as charging, development, transfer, and cleaning of residual developer. Therefore, today, proposals for a curable surface protective layer having high mechanical strength are increasing. At this time, the surface protective layer containing conductive particles and controlling the electric resistance is not suitable in a micro area. It is a homogeneous system, and therefore it is difficult to make the strength of the surface protective layer uniform even in the micro range. Therefore, it is difficult to uniformly control the wear of the surface protective layer surface in the rubbing load of the electrophotographic process, and when the conductive particles are more actively worn away, the charging characteristics are deteriorated. If the strength of the binder component of the protective layer is weak, only the binder component in the surface protective layer is worn away, the absolute amount of conductive particles increases, and it becomes difficult to hold the charge on the surface of the photoreceptor, and image blurring occurs. A new problem arises.
[0013]
In addition, many proposals using a curable resin to obtain a surface protective layer with high hardness are seen, but generally a curable resin is rarely capable of undergoing a curing reaction alone, and requires the addition of a curing agent or a curing catalyst. To do. However, many of these curing agents and curing catalysts themselves deteriorate the electrophotographic properties, in particular, the charge transfer due to the charge trapping action. In addition, even if the curing agent or curing catalyst does not have a significant adverse effect, the substance produced by decomposition of these during the curing reaction may have a trapping action, and the strength of the surface protective layer and the electrophotographic characteristics of the photoconductor It was difficult to achieve both.
[0014]
There have been proposals to reduce the damage caused by discharge products by adding additives such as antioxidants and stabilizers to the photoreceptor surface layer, but these additives also have electrophotographic properties depending on their structure. Some of them were observed to interfere with this.
[0015]
In order to solve the problem related to the discharge in the process of charging the surface of the photoreceptor, the present inventors have studied a process of charging by directly injecting the charge onto the photoreceptor. Furthermore, it has also been found that, in the process of direct charge injection, charging is further stabilized by superimposing an AC voltage as compared with the case of applying only a DC voltage.
[0016]
There is a big difference between the case where the charge that directly injects this charge onto the photoreceptor is dominant and the case where the discharge is dominant. That is, as shown in FIG. 1, in the case of discharge, this difference is different from that when the applied voltage to the charging member is equal to or higher than the discharge start voltage, the discharge is started for the first time, and then the applied voltage exceeds the discharge start voltage. Charged on the body. That is, in the case of discharge charging with only a DC voltage, the relationship between the applied voltage Vdc and the photoreceptor surface potential Vd is as shown in Expression (8).
[0017]
| Vd | ≈ | Vdc | − | Vth | (8)
However, Vth (discharge start voltage) = (7737.7 × D)^1/2+ 312 + 6.2 × D
D = L (photosensitive film thickness μm) / K (photosensitive layer relative dielectric constant)
On the other hand, in charging in which injection charging is dominant, as shown in FIG. 1, the applied voltage of the charging member and the photoreceptor surface potential are almost the same, and there is no threshold like the discharge start voltage in the case of discharge. Is also a feature. Although it is difficult to define the charge itself that the injection charge is dominant, it is possible that the injection charge is occurring at least when the formula (9) is satisfied.
[0018]
| Vdc | − | Vd | <| Vth | (9)
However, under this condition, there is a possibility that Expression (9) may be satisfied even if injection charging does not occur, such as when the photoreceptor surface potential Vd becomes higher due to frictional charging or when the resistance of the charging member becomes abnormally high. . Further, if the equation (8) is a discharge charge, injection charge may occur where the value of (Vdc−Vd) in the equation (9) is close to Vth. Would be more appropriate. Therefore, the charging with dominant discharge is expressed by the equation (10).
| Vth / 2 | <| Vdc | − | Vd | <Vth (10)
Then, the electrification in which the injection electrification is dominant is the formula (11).
| Vdc | − | Vd | ≦ | Vth / 2 | (11)
It is easy to understand if the charge is defined as
[0019]
A case where an alternating voltage Vac (V) is simultaneously applied from the primary charging member to the photoconductor in addition to the DC voltage Vdc will be considered with reference to FIG. This charging is generally referred to as an AC / DC superposition system. When the peak-to-peak voltage of the alternating voltage Vac is Vpp (V), in the case of discharge charging, in order to stabilize charging, if Vpp is set so as to satisfy the equation (12), the photoreceptor surface potential Vd is expressed by equation (13).
[0020]
| Vpp | ≧ 2 × | Vth | (12)
| Vd | ≈ | Vdc | (13)
That is, at the time of AC / DC discharge charging, the voltage applied to the primary charging member is set so as to satisfy the condition of Expression (12) in order to stabilize the chargeability.
[0021]
However, when the Vpp is in the condition as in the equation (14), the photoreceptor surface potential Vd has a value as in the equation (15).
[0022]
| Vpp | <2 × | Vth | (14)
| Vd | ≈ | Vpp / 2 | + | Vdc |-| Vth | (15)
That is, assuming that the DC component Vdc (V) of the applied voltage and the discharge start voltage Vth (V) are constant, when the peak-to-peak voltage Vpp (V) of the alternating voltage is gradually lowered, the photoreceptor surface potential Vd ( V) decreases accordingly, and when Vpp becomes 0, it becomes the same as DC charging, and is the same as equation (8). In addition, the formula (15) may be more accurately written as the formula (16) in consideration of the dark decay of the photosensitive member.
[0023]
| Vd | ≦ | Vpp / 2 | + | Vdc | − | Vth | (16)
On the other hand, in the AC / DC superposition system in the charging in which the injection charging is dominant, the AC component has a strong auxiliary meaning, and usually does not make Vpp very strong. That is, Vpp is given to the extent that Expression (14) holds. Here, the injection charge is greatly different from the discharge system in that the charge on which the injection charge is dominant is that the surface potential Vd of the photosensitive member is almost the same as the DC component of the charging member. That is, in the charging in which the injection charging is dominant, the expression (11) is established. Further, not Expression (16) but Expression (17) is established.
[0024]
| Vd |> | Vpp / 2 | + | Vdc |-| Vth | (17)
As described above, it can be understood that charging and discharging charging in which injection charging is dominant are completely different charging methods both in the case of applying only DC from the charging member and in the AC / DC superimposing system. In electrification in which injection charge is dominant, since charge is directly injected onto the photoconductor, it is not accompanied by discharge or little with discharge, so there is little deterioration due to NOx and ozone accompanying discharge, Further, the damage given to the photoreceptor is negligible, and it can be said that the charge is better than ever.
[0025]
On the other hand, in the case of contact charging with conventional discharge, the voltage applied to the charging roller in contact is high, and the electric field strength inside the photosensitive member at that portion is the electric field strength due to the charging potential of the target surface. Higher than. In the case of corona charging, since the distance between the charger and the electrophotographic photosensitive member is large even when the applied voltage is high, the electric field applied to the electrophotographic photosensitive member during charging is not significantly different from that during injection charging. The width of the charger itself is considerably wider than the nip width of the charging member in injection charging. As a result, the number of surplus charges accumulated in the photoreceptor is small. However, in the case of injection charging, the electric field applied to the photoconductor during charging does not greatly exceed the electric field strength due to the charging potential of the photoconductor, and the width of the charging member (particularly in contact with the electrophotographic photoconductor). The width is also relatively narrow. Therefore, a phenomenon that excessive charges in the photosensitive layer tend to stay easily occurs. Furthermore, in the case of a photoconductor having a semiconductive surface protective layer on the charge transport layer, the charge transport layer-surface protection which is a problem of the photoconductor having the semiconductive surface protective layer described above. A negative synergistic effect is observed in which charge retention between the layer interfaces is further increased.
[0026]
In addition, the charging efficiency in the injection charging is greatly affected by the contact efficiency between the charging member and the surface of the photosensitive member as the member to be charged. Therefore, in order to increase the injection charging efficiency, a charging particle comprising a charged particle mainly composed of conductive inorganic particles and a surface having conductivity and elasticity and carrying the charged particle is supported. The contact member may be rotated in the counter direction on the contact surface with the photoreceptor to increase the contact efficiency in the micro area. However, by interposing inorganic particles between the photosensitive member and the charging member and rotating the charging member in the counter direction on the contact surface with the photosensitive member, the contact efficiency is increased, but the rubbing load on the surface of the photosensitive member is increased. Becomes stronger at the same time. At this time, the surface protective layer containing the conductive particles and controlling the electrical resistance is a non-uniform system in the micro area, so it is difficult to make the strength of the surface protective layer uniform in the micro area. is there. Therefore, in the charging system as described above, it is difficult to uniformly control the wear of the surface protective layer surface, and when the conductive particles are more actively worn, the injection charging characteristics deteriorate, and conversely If the strength of the binder component of the protective layer is weak, only the binder component in the surface protective layer is worn away, the absolute amount of conductive particles increases, and it becomes difficult to hold the charge on the surface of the photoreceptor, and image blurring occurs. The problem due to the rubbing load is further increased and becomes a problem.
[0027]
[Problems to be solved by the invention]
An object of the present invention is to suppress image potential defects such as ghosts and memories due to charge retention between the charge transport layer and the surface protection layer and fluctuations in the potential of the photoreceptor due to a durability test in a photoreceptor having a surface protection layer on a charge transport layer. It is.
[0028]
  The present inventionTakeThe charging method does not involve any discharge or is slight even with discharge, so there is little deterioration due to NOx and ozone accompanying the discharge, and there is very little damage to the photoconductor, and the amount of abrasion of the photoconductor Although there are few and excellent charging as ever, the electric field applied to the photoconductor does not become stronger than the electric field at the time of charging in the conventional contact charging process, and the surface charge injection layer or the photosensitive layer and the surface charge A problem peculiar to the present charging process that the charge retention and ghost at the interface with the injection layer worsen occurred. Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member, an electrophotographic process cartridge, and an electrophotographic apparatus capable of outputting a high-quality image without generating a ghost even in the above-described novel charging system. .
[0029]
  In addition, the present inventionTakeIn the charging method, a charging member constituted by a charged particle carrier that carries charged particles mainly composed of conductive inorganic particles rotates in the counter direction on the contact surface with the photoreceptor to perform contact injection charging. An electrophotographic photoreceptor that can maintain a uniform rubbing load on the surface of the photoreceptor, which is a problem unique to this charging system, and suppress variations in charging efficiency and surface resistance due to endurance tests, and can output high-quality images. A photographic process cartridge and an electrophotographic apparatus are provided.
[0030]
[Means for Solving the Problems]
  That is, the present invention provides at least a charge generation layer and a charge transport layer on a conductive support.,And conductive particlesContainsCurable resinFormed usingIn the electrophotographic photoreceptor having the surface protective layer in this order,
The charge transport layerButContains at least two types of charge transport materials,
TheIn the charge transport layerOf charge transport materialsThe oxidation potential isLowestCharge transport materialOxidation potentialAnd oxidation potentialhighestCharge transport materialOxidation potentialWhenDifference: | ΔEox | [V],followingFormula (1)
      0.02 <| ΔEox | <0.13      (1)
Satisfied,
TheAnalyzed by XPS (X-ray photoelectron spectroscopy) on the surface of an electrophotographic photoreceptorTheSum of ratio of indium and tin contained in surface protective layer: A_c[Atomic%] andTheSum of proportions of fluorine and silicon contained in surface protective layer: A_L[Atomic%]WhenBut,followingEquations (2) and (3)
      1.5 <A _c <12.0      (2)
      5.0 <A _L <25.0      (3)
Is an electrophotographic photosensitive member characterized by satisfying the above.
[0031]
  MaIn addition, the present invention is a process cartridge and an electrophotographic apparatus provided with the above electrophotographic photosensitive member.
[0032]
As a result of intensive studies on the above problems, the present inventors have included two or more kinds having a specific oxidation potential difference with respect to the charge transport material in the charge transport layer, and at the same time the electron conductivity in the surface protective layer. As shown in the formula (2) as a specific component related to the above, by controlling the amount of indium and tin, the charge transfer at the interface between the charge transport layer and the surface protective layer is smoothly performed, and further expressed by the formula (3). In this way, it was found that the chargeability and the charge retention ability can be stabilized over a long period of time by controlling the amounts of fluorine and silicon.
[0033]
  Formula (1) is the charge transport materialThe oxidation potential isLowestCharge transport materialOxidation potentialAnd oxidation potentialhighestCharge transport materialOxidation potentialWhenDifference | ΔEox | [V] represents the optimum value, and the expressions (2) and (3) are the analytical values obtained by XPS (X-ray photoelectron spectroscopy) on the surface of the electrophotographic photosensitive member. Sum of proportions of indium and tin contained: Ac [atomic%] and sum of proportions of fluorine and silicon contained in the surface protective layer: A_LIt is a formula showing the optimal value of [atomic%].
[0034]
0.02 <| ΔEox | <0.13 (1)
1.5 <Ac <12.0 (2)
5.0 <A_L<25.0 (3)
This is because the holes hop and move at an energy level having a specific width corresponding to the difference in oxidation potential of the plurality of types of charge transport materials as defined by the formula (1), and the surface protective layer further Only when the surface protective layer contains a certain amount of indium or tin that contributes to the electron conduction defined by the formula (2), charge can be transferred even at the interface with the protective layer having a completely different charge transfer mode. This is presumed to be due to the fact that it was carried out efficiently and no charge retention occurred.
[0035]
Furthermore, the surface protective layer contains fluorine and silicon atoms in the range defined by the formula (3), so that it can be rubbed with a member in contact with a series of electrophotographic processes such as charging, development, transfer, and cleaning. However, since indium and tin, which are conductive components, and the binder component can be uniformly worn, it is expected that the amounts of indium and tin on the outermost surface of the surface protective layer are always kept within a certain range. In addition, substances containing fluorine or silicon atoms generally have a strong surface / interface transition, and A_LIs contained more than specified by the formula (3), the charge injection property at the surface / interface and the effect of inhibiting the transfer are too strong. For example, the conductivity of the charge transport material or the surface protective layer Even if the characteristics of the components are in the range defined by the formulas (1) and (2), there is a problem that the electrophotographic characteristics are deteriorated. Accordingly, the characteristic effects of the present invention can be brought out only when fluorine and silicon atoms are controlled within a range satisfying the expression (3).
[0036]
Furthermore, the present inventors also paid attention to the oxidation potential of the entire charge transport layer as a factor other than the difference in oxidation potential with respect to the charge transport material, and average oxidation potential represented by the following formula (4): E_aveIt has been found that by controlling to a very limited specific range, even in an endurance test in which the electrophotographic process is continuously repeated, fluctuations in the potential of the photoreceptor can be suppressed and the performance as the photoreceptor can be improved.
[0037]
0.73 ≦ E_ave<0.83 (4)
Average oxidation potential: E_aveTherefore, it is necessary to consider not only the average value of the oxidation potential of the charge transport material contained but the proportion contained in the charge transport layer. When the ratio of the charge transport material is Cn and the oxidation potential of the nth charge transport material is En, E_ave= Σ (Cn · En) [V]. Here, Cn is a numerical value representing the mass ratio of each charge transport material in all the charge transport materials in the charge transport layer, and represents a numerical value greater than 0 and less than 1 for all n, and ΣCn = 1. Average oxidation potential: E_aveIs lower than the prescribed range of the formula (4), the potential fluctuation when the electrophotographic process is continuously repeated becomes large, and conversely, when it is high, the charge transport layer—the surface protective layer or the charge transport layer—the charge. There is a tendency for the charge retention between the generation layers to increase.
[0038]
  Further, in the present invention, the charge transport layer is characterized by containing two or more kinds of charge transport materials, but the ratio of each charge transport material is expressed by the following formula (5). It was found that charge transfer and transfer can be performed more efficiently by mixing in consideration of the oxidation potential of the charge transport material.
0.05 ≦ C_h≦ 0.95 × exp {−460 × (| ΔEox | −0.05) × (| ΔEox | −0.05)} (5)
  Here, of all the charge transport materials in the charge transport layer,Oxidation potentialMostHighNoCharge transport materialMass ratio of C_h│ΔEox│ isThe oxidation potential isLowestCharge transport materialOxidation potentialAnd the oxidation potential ishighestCharge transport materialOxidation potentialWhenRepresents the difference between
[0039]
Furthermore, among compounds added for the purpose of advancing the curing reaction during the formation of the surface protective layer and compounds added for the purpose of preventing the surface protective layer from being deteriorated by oxidation or light, it contains specific elements such as sulfur and phosphorus. Since the compound to be used may inhibit the electrophotographic characteristics, the content thereof is preferably controlled within the range defined by the following formula (6).
[0040]
As + Ap <0.2 (6)
Here, As + Ap is an analysis value by XPS of the surface protective layer, which is the sum of the ratios of sulfur atoms and phosphorus atoms contained in the surface protective layer, and is expressed in atomic%.
[0041]
Furthermore, regarding the electron conduction component in the surface protective layer, it is possible to more efficiently perform charge transfer with the hopping conduction layer as represented by the expression (1) by satisfying the following expression (7). It was found that charge retention at the interface between the charge transport layer and the surface protective layer can be suppressed.
[0042]
3.5 <A_In/ A_Sn<25 (7)
Here, the ratio of indium and tin, which are electron conducting components, is determined by analysis by XPS (X-ray photoelectron spectroscopy), and the ratio of indium contained in the surface protective layer is A._In[Atomic%], the ratio of tin contained in the surface protective layer is A_SnIt is expressed in [atomic%].
[0043]
In particular, it is preferable to keep the amount of indium and tin within the range of the formula (7) by containing indium-tin oxide, so-called ITO, in the surface protective layer, which is a plurality of charges whose oxidation potential has a specific difference. It is presumed that charge transfer between the charge transport layer containing the transport material and the ITO in the surface protective layer is performed specifically and efficiently.
[0044]
In the present invention, the average particle size is 10 μm to 10 nm, and the resistance is 10¹²To 10^-1Conductive inorganic particle carrier having a conductive inorganic particle having Ω · cm for promoting injection charging (hereinafter referred to as “charged particle”), and a conductive and elastic surface carrying the conductive inorganic particle. And the value obtained by dividing the supported amount of the conductive inorganic particles by the surface roughness Ra [μm] of the conductive inorganic particle support is 0.005 to 1 mg / cm²In the charging device for charging the photosensitive member by contact injection charging by rotating the charging member having a thickness of / μm in the counter direction on the contact surface with the electrophotographic photosensitive member, the conventional electrophotographic photosensitive member of the present invention is used. In addition to not causing damage to the photoreceptor due to electric discharge, the ratio of the conductive component on the surface of the photoreceptor can be controlled within a desired range and applied by a strong rubbing load with the charging member interposing inorganic particles. Since the electric field is almost equal to the charging potential and no strong electric field is applied to the photosensitive layer, and the charging width is narrow, even in this charging system with a small capacity for discharging the accumulated charges, it is possible to suppress the accumulation of charges as long as possible. It has become possible to provide high-quality images over a wide range.
[0045]
  The present invention also provides an electrophotographic apparatus using the electrophotographic photosensitive member of the present invention, andThe electrophotographic photosensitive member of the present invention and a charging device for contact injection charging to the electrophotographic photosensitive member are integrated, and the process cartridge is detachable from the main body of the electrophotographic device.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
[Electrophotographic photoreceptor]
The electrophotographic photoreceptor used in the present invention has a laminated photoreceptor structure having at least a charge generation layer, a charge transport layer, and a surface protective layer in this order on a conductive support. Further, an undercoat layer such as an injection blocking layer, an interference fringe preventing layer, or a binding layer may be provided between the conductive support and the charge generation layer.
[0047]
As the conductive support, the support itself can be conductive, for example, aluminum, aluminum alloy, stainless steel, etc. In addition, aluminum, aluminum alloy, indium oxide-tin oxide alloy, etc. are vacuum deposited. Conductive support, plastic, and conductive fine particles (for example, carbon black, tin oxide, titanium oxide, silver particles, etc.) having a layer formed by coating with a suitable binder and plastic or paper impregnated with conductive binder, conductive A plastic having a functional binder can be used.
[0048]
Undercoat layer between conductive support and photosensitive layer is improved adhesion of photosensitive layer, improved coatability, protection of support, coating of defects in support, improvement of charge injection from support, photosensitive layer It is formed for the purpose of protecting against electrical breakdown. The undercoat layer can be formed of casein, polyvinyl alcohol, ethyl cellulose, ethylene-acrylic acid copolymer, polyamide, modified polyamide, polyurethane, gelatin, aluminum oxide, or the like. The thickness of the binding layer is preferably 5 μm or less, and more preferably 0.2 to 3 μm.
[0049]
Examples of the charge generating material used in the present invention include phthalocyanine pigments, azo pigments, indigo pigments, polycyclic quinone pigments, perylene pigments, quinacridone pigments, azulenium salt pigments, pyrylium dyes, thiopyrylium dyes, squarylium dyes, cyanine dyes, xanthene dyes, Examples include quinoneimine dyes, triphenylmethane dyes, styryl dyes, selenium, selenium-tellurium, amorphous silicon, cadmium sulfide, and zinc oxide.
[0050]
The solvent used in the charge generation layer coating is selected from the solubility and dispersion stability of the resin and charge generation material used, and the organic solvents include alcohols, sulfoxides, ketones, ethers, esters, fats. Group halogenated hydrocarbons or aromatic compounds can be used.
[0051]
The charge generation layer is well dispersed by a method such as a homogenizer, ultrasonic wave, ball mill, sand mill, attritor, roll mill, etc. together with the above-mentioned charge generation material, 0.3 to 4 times the amount of binder resin and solvent. , Dried and formed. The thickness is preferably 5 μm or less, particularly preferably in the range of 0.01 to 1 μm.
[0052]
As the charge transport material, known materials such as triarylamine compounds, styryl compounds, butadiene compounds, carbazole compounds, and hydrazone compounds can be used. However, chemical stability during the formation of the curable protective layer can be used. Therefore, a charge transport material having no hydrazone skeleton is preferable.
[0053]
The characteristic of the charge transport material in the present invention is that two or more kinds of charge transport materials having a specific difference in oxidation potential are contained. The oxidation potential is measured by using the following materials and a three-electrode cyclic It was done by voltammetry.
Electrode: Working electrode-glassy carbon electrode, counter electrode-platinum electrode
Reference electrode-saturated calomel electrode (0.1 mol / l KCl aqueous solution)
Measurement solution Electrolyte: 0.1 mol of t-butylammonium perchlorate
Measurement substance: 0.001 mol of charge transport material
Solvent: 1 liter of acetonitrile
The above was prepared to prepare a measurement solution.
[0054]
The peak top of the first oxidation potential of the measurement result was the oxidation potential of the charge transport material.
[0055]
Here, if the difference between the highest oxidation potential and the lowest oxidation potential among the charge transport materials in the charge transport layer: | ΔEox | is 0.02 V or less, the spread of the energy level at which the charge is hopped is too narrow, If charge transfer with the surface protective layer is not performed efficiently and conversely | ΔEox | is 0.13 V or more, hole hopping is not performed by the charge transport material having a high oxidation potential, and the charge transport material is There is a problem that the meaning of mixing a plurality of species is lost, or the hole mobility in the charge transport layer is lowered due to the trapping action of charges.
[0056]
Examples of structures and oxidation potentials of various charge transport materials measured by the above method are summarized in Tables 1 to 12. However, the present invention is not limited only to the following charge transport material.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
[Table 3]

[0060]
[Table 4]

[0061]
[Table 5]

[0062]
[Table 6]

[0063]
[Table 7]

[0064]
[Table 8]

[0065]
[Table 9]

[0066]
[Table 10]

[0067]
[Table 11]

[0068]
[Table 12]

The oxidation potential itself of the multiple types of charge transport materials contained in the charge transport layer is not sufficient to simply examine the average value of the oxidation potentials of all the charge transport materials, and weighting according to the proportions contained. is required. That is, when the ratio of the nth charge transport material in the charge transport layer is Cn, and the oxidation potential of the nth charge transport material is En, the average value of the oxidation potential of the charge transport material is
E_ave= Σ (Cn · En) [V]
It is preferable to select a charge transporting material within a very limited range that satisfies the following formula (4).
[0069]
0.73 ≦ E_ave<0.83 (4)
Here, Cn is a numerical value representing the mass ratio of each charge transport material in all the charge transport materials in the charge transport layer, and represents a numerical value greater than 0 and less than 1 for all n, and ΣCn = 1. Average oxidation potential: E_aveIs less than 0.73V, the potential fall tends to increase in the endurance test in which the electrophotographic process is continuously repeated. On the other hand, if it exceeds 0.83V, the potential fluctuation due to the endurance test is reduced. Residual potentials due to charge retention at the transport layer-surface protective layer interface and charge generation layer-charge transport layer interface tend to increase.
[0070]
  Further, the ratio of the plurality of types of charge transport materials to be mixed is preferably determined in view of the oxidation potential of each charge transport material. When │ΔEox│ is about 0.087V or less, the content ratio is not a big problem and the content ratio of the charge transport material having a high oxidation potential may be higher, but it is larger than 0.087V. Accordingly, it is preferable that the content of the charge transporting material having the highest oxidation potential is greatly reduced. In particular, by containing the charge transporting material within the range defined by the following formula (5), the hole mobility and the charge transporting layer are increased. -The charge transfer efficiency between the surface protective layers can be properly maintained.
0.05 ≦ C_h≦ 0.95 × exp {−460 × (| ΔEox | −0.05) × (| ΔEox | −0.05)} (5)
  Of the charge transport materials in the charge transport layer,Oxidation potentialMostHighNoCharge transport materialMass ratio of C_h│ΔEox│ isThe oxidation potential isLowestCharge transport materialOxidation potentialAnd the oxidation potential ishighestCharge transport materialOxidation potentialWhenRepresents the difference between In addition, even if │ΔEox│ is in any range defined by Equation (1),Highest oxidation potentialIf the content ratio of the charge transport material is not 5% or more, it is highly likely that the effect of the present invention obtained by mixing a plurality of types of charge transport materials will not be substantially obtained.
[0071]
Here, the regulations relating to the charge transport material according to the formulas (1), (4), and (5) are determined on the assumption that the charge transport material is completely molecularly dispersed without being deposited on the charge transport layer. It is a thing. Therefore, the molecular weight of each charge transport material is preferably in the range of molecular weight: Mw of 1200 or less, particularly 300 to 800 from the viewpoint of solubility.
[0072]
The charge transport layer is generally formed by dissolving the charge transport material and the binder resin in a solvent and applying them. The mixing ratio of the charge transport material and the binder resin is about 2: 1 to 1: 2 by mass ratio. Solvents include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and chlorinated hydrocarbons such as chlorobenzene, chloroform and carbon tetrachloride. . When this solution is applied, for example, a coating method such as a dip coating method, a spray coating method, or a spinner coating method can be used, and drying is performed at a temperature in the range of 10 ° C to 200 ° C, preferably 20 ° C to 150 ° C. And for 5 minutes to 5 hours, preferably 10 minutes to 2 hours, can be carried out under blast drying or static drying.
[0073]
Binder resins used for forming the charge transport layer include acrylic resins, styrene resins, polyesters, polycarbonate resins, polyarylate, polysulfone, polyphenylene oxide, epoxy resins, polyurethane resins, alkyd resins, and unsaturated resins. It selects from well-known material materials, such as. Particularly preferred resins include polymethyl methacrylate, polystyrene, styrene-acrylonitrile copolymer, polycarbonate resin or diallyl phthalate resin. The film thickness of the charge transport layer is 5 to 25 μm, preferably 7.0 or more and less than 16 μm. If the thickness of the charge transport layer is too thin, the electrostatic capacity may be too large to catch up with the charging capability, and it may be difficult to charge to the desired surface potential, In some cases, the number of charges required to lower the light potential increases, and the charge generated from the charge generation layer may be insufficient. On the other hand, if the thickness is too thick, the electric field strength applied to the photosensitive layer is weak, and charge retention at each photosensitive layer interface increases. As in the present invention, in the case where the surface has a semiconductive surface protective layer or is charged by an injection charging device, particularly in order to increase the charge transfer efficiency between the charge transport layer and the surface protective layer, The electric field strength needs to be increased to some extent, and therefore a film thickness of less than 16.0 μm is preferred. The thickness of the charge transport layer was measured as follows. First, the photosensitive layer was peeled off and embedded with an ultraviolet curable acrylic resin, and then an ultrathin film slice was prepared using an ultramicrotome. This slice was observed using a transmission electron microscope of Hitachi H-7500: acceleration voltage 100 kV type, and the thickness of the charge transport layer was determined.
[0074]
The charge generation layer or the charge transport layer may contain various additives such as an antioxidant and an ultraviolet absorber.
[0075]
As the surface protective layer used in the present invention, a film in which conductive particles are dispersed in an insulating resin as a binder component and the resistance is adjusted is used. As this insulating resin, an electrically insulating transparent resin, which is a curable resin that hardly changes its electric resistance due to changes in humidity or temperature and has a certain mechanical strength, is used. Examples of the resin that satisfies this condition include known curable resin materials such as acrylic resin, phenol resin, epoxy resin, melamine resin, urethane resin, and siloxane resin. These resins generally have solubility in a solvent before the curing reaction. However, after the curing reaction, a three-dimensional crosslinked chain is formed between the resin molecules. Little or no dissolution.
[0076]
In order to cure these curable resins, it is possible to add already known curing agents, initiators and catalysts. However, if even a small amount remains in these curing agents, etc., there is a possibility that the electrophotographic characteristics of the photoreceptor will be hindered. As a result of examining the curing agent, the initiator, and the like, the present inventors have focused on the inferior characteristics of the electrophotographic photosensitive member having a surface protective layer that has advanced the curing reaction with a compound containing a specific atom. . That is, when curing is performed by adding a compound containing sulfur or phosphorus atoms, the residual amount of these atoms is controlled within the range defined by the formula (6), thereby affecting the electrophotographic characteristics. Can be kept within an allowable range. The residual amount of sulfur atoms and phosphorus atoms is determined by XPS measurement of the surface protective layer surface._SPIt is expressed in [atomic%].
[0077]
A_S+ A_P<0.2 (6)
In addition, it is possible to add an antioxidant or an ultraviolet absorber to the surface layer of the photoreceptor, but among these additives, compounds containing phosphorus atoms and sulfur atoms are commercially available, and their structures and Regarding the addition amount, it is preferable that the residual amounts of sulfur atoms and phosphorus atoms are controlled within the range of the above formula (7).
[0078]
Further, as the conductive particles as the resistance adjusting agent, the wavelength of light used for the image exposure (0.42 to .0 .0 so that the electrical resistance is low and the particle diameter does not substantially prevent the passage of the light used for the image exposure. 8 μm) or less, preferably ½ or less, that is, 0.3 μm or less, preferably 0.1 μm or less. The electrical resistance of the surface protective layer is 10⁹-10¹⁴It is necessary to contain the conductive particles so as to be Ω · cm. Electric resistance is 10¹⁴If it is Ω · cm or more, the charge injection efficiency due to injection charging is reduced, leading to poor charging, and the residual potential is further increased, resulting in an image with much fogging.⁹If it is less than Ω · cm, the image blurs and the resolution decreases. In order to maintain the charge transfer efficiency between the charge transport layer and the surface protective layer, not only adjustment of the electrical resistance as the protective layer film, but also a specific material suitable for the energy level at which the holes of the charge transport layer move Is required. First, the sum of the ratios of indium and tin: Ac [atomic%] (analyzed value by XPS (X-ray photoelectron spectroscopy) on the surface of the electrophotographic photosensitive member) is important as the conductive component. In the present invention, this Ac [atomic %] Needs to contain conductive particles so that the following formula (2) is satisfied.
[0079]
1.5 <Ac <12.0 (2)
As the conductive particles to be included in the surface protective layer of the electrophotographic photosensitive member, ZnO, TiOx, V₂O_Five, MoO_ThreeMetal oxide powders such as NiO and CuO, metal fine powders such as Cu, and organic fine particles such as carbon black and carbon fluoride have been reported. In the present invention, a plurality of types of charge transport materials are used. In order to allow the charge transfer between the charge transport layer and the surface protective layer that contain hopping conduction with a specific width of energy and to perform the transfer without delay, at least indium or tin must be contained in a predetermined amount. SnO called ITO because it becomes essential₂Containing In₂O_Three, In₂O_Three, Oxygen deficient SnO₂It is necessary to adjust to a surface protective layer satisfying the above formula (2) by singly or blending, etc., but it is more preferable to contain indium, and indium is contained within a range satisfying formula (7). Better.
[0080]
3.5 <A_In/ A_Sn<25 (7)
A_InAnd A_SnIs the analysis value by XPS of the surface protective layer surface, the ratio of indium: A_In[Atomic%] and tin ratio: A_Sn[Atomic%] is represented.
[0081]
Further, when the surface protective layer contains the conductive particles used in the present invention, it is unilaterally caused by a frictional load with the surface of the photoreceptor during the electrophotographic process such as a charging member, a developing member, a transfer member, or a cleaning member. In order to prevent wear of the conductive particles, the conductive particles can be surface-treated with a silane coupling agent, a siloxane compound, a fluorine atom-containing compound, or the like.
[0082]
Furthermore, it is difficult to prevent wear of the one-sided conductive particles only by surface treatment of the conductive particles with a silane coupling agent, a siloxane compound, a fluorine atom-containing compound, etc. Therefore, it is necessary to contain resin fine particles, oil, and oligomer components containing these atoms. As a result, the sum of the ratios of fluorine and silicon as analyzed by XPS (X-ray photoelectron spectroscopy) on the surface of the electrophotographic photosensitive member: A_L[Atomic%] needs to satisfy the following formula (3).
[0083]
5.0 <A_L<25.0 (3)
Sum of proportions of fluorine and silicon: A_LIs less than 8.0 atomic%, it is difficult to prevent wear of one-sided conductive particles. Conversely, if it exceeds 25.0 atomic%, scratches caused by rubbing or in the surface protective layer There is a problem that image quality deteriorates due to an increase in image exposure scattering.
[0084]
The XPS measurement on the surface of the electrophotographic photoreceptor was performed using an Quantum-2000, X-ray photoelectron spectrometer manufactured by ULVAC-PHI as an XPS measurement apparatus.
[0085]
The measurement conditions were an X-ray source AlKα (monochromatic), 101.2 W, 90 degrees, 187.85 eV, and an analysis area of 2 × 3 mm.
[0086]
Resin fine particles containing silicon or fluorine atoms or oil components having a high molecular weight are preferred. Low molecular weight compounds containing silicon or fluorine atoms have a strong interface / surface migration property, and oligomeric compounds with a particularly low molecular weight have a strong effect of inhibiting the charge injection and transfer at the surface / interface as described above. This is because it becomes too much.
[0087]
Moreover, the film thickness of the surface protective layer in the present invention is preferably 10 μm or less, and more preferably 1 to 5 μm from the viewpoint of transmittance and strength.
[0088]
  Next, the present invention reduces the damage of the photoreceptor due to the discharge.TakeThe overall schematic configuration of the charging method will be described.
[0089]
  FIG. 3 shows the present invention.TakeIt is a schematic block diagram using a charging device. The image recording apparatus of the present embodiment is a laser printer (recording apparatus) using a transfer type electrophotographic process, a direct injection charging system, and a toner recycling process (cleanerless system).
[0090]
(Overall schematic configuration of electrophotographic apparatus)
Reference numeral 1 denotes an electrophotographic photosensitive member, which is a rotating drum type negative electrophotographic photosensitive member (negative photosensitive member, hereinafter referred to as a photosensitive drum) having a diameter of 30 mm in this configuration. The photosensitive drum 1 is driven to rotate at a constant speed of 94 mm / sec (= process speed PS, printing speed) in the clockwise direction of the arrow.
[0091]
The charging roller 2 includes charged conductive particles M (conductive particles as charged particles), a medium resistance layer 2b and a cored bar 2a as particle carriers. The charging roller 2 contacts the photosensitive drum 1 with a predetermined amount of penetration to form a charging contact portion n.
[0092]
The charging roller 2 is driven to rotate in a direction (counter) opposite to the rotation direction of the photosensitive drum 1 at the charging contact portion n, and contacts the surface of the photosensitive drum 1 with a speed difference. A predetermined charging bias is applied to the charging roller 2 from the charging bias application power source S1 during image recording by the printer. As a result, the peripheral surface of the photosensitive drum 1 is uniformly contact-charged to a predetermined polarity and potential by the direct injection charging method. In this embodiment, a DC voltage of −700 V was applied as an applied bias by the applied power source of S1.
[0093]
The charged conductive particles are added to the developer and accumulated, and are supplied to the charging roller via the photosensitive drum together with the development of the toner.
[0094]
Reference numeral 60 denotes a developing device. The electrostatic latent image on the surface of the rotary photosensitive drum 1 is developed as a toner image by the developing device 60 at the development site a. In the developing device 60, a mixed agent tm obtained by adding charged conductive particles M to the developer t is provided.
[0095]
The printer of this configuration is a toner recycling process, and the transfer residual toner remaining on the surface of the photosensitive drum 1 after the image transfer is not removed by a dedicated cleaner (cleaning device), but rotates counter by the rotation of the photosensitive drum 1. As the toner is temporarily collected by the charging roller and circulates around the outer periphery of the roller, the reversed toner charge is normalized and sequentially discharged to the photosensitive drum to reach the development site a. The
[0096]
Reference numeral 4 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like. The laser beam scanner 4 outputs a laser beam whose intensity is modulated in accordance with a time-series digital image signal of target image information, and scans and exposes the uniformly charged surface of the rotating photosensitive drum 1 with the laser beam.
[0097]
By this scanning exposure L, an electrostatic latent image corresponding to target image information is formed on the surface of the rotary photosensitive drum 1.
[0098]
Reference numeral 7 denotes a fixing device such as a heat fixing method. The transfer material P that has been fed to the transfer nip portion b and has received the transfer of the toner image on the photosensitive drum l side is separated from the surface of the rotating photosensitive drum 1 and is introduced into the fixing device 7 to receive the toner image fixing. It is discharged out of the apparatus as an image formed product (print copy).
[0099]
Next, main components of the charger will be described.
[0100]
[Charging roller]
The charging roller 2 is manufactured by forming a middle resistance layer 2b of rubber or foam on the core metal 2a. The middle resistance layer 2b is formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfurizing agent, a foaming agent, and the like, and is formed in a roller shape on the core metal 2a. As a feature of the present charging roller, it is necessary to have a sufficiently low resistance to charge a moving electrophotographic photosensitive member while providing elasticity and obtaining a sufficient contact state. On the other hand, it is necessary to prevent voltage leakage when a defective portion such as a pinhole is present in the electrophotographic photosensitive member. When an electrophotographic photosensitive member is used as the electrophotographic photosensitive member, 10 is required to obtain sufficient charging property and leakage resistance.^Four-10⁷A resistance of Ω is preferred.
[0101]
If the hardness of the charging roller is too low, the shape will not be stable and contact will be poor. If it is too high, not only will the charging nip be secured, but the micro-contact to the surface of the photoreceptor will deteriorate. The preferred range is 25 to 50 degrees in hardness.
[0102]
The material of the charging roller is not limited to the elastic foam, but as the material of the elastic body, conductive materials such as EPDM, urethane, NBR, silicone rubber, and carbon black or metal oxide for adjusting resistance to IR, etc. Examples thereof include a rubber agent in which an active substance is dispersed and a foamed product of these. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance.
[0103]
The charging member is not limited to the charging roller, and an elastic body such as a fur brush in which each pile has elasticity can be used. Here, the fur brush roller is planted with 155 fibers / mm in which resistance-adjusted fibers (Unitika-Rec etc.) are planted.²It is also possible to use a fiber that is formed on a pile having a fiber length of 3 mm, and then wound and fixed on a φ6 mm metal core and formed into a roller shape. In particular, the charging ability of the electrophotographic photosensitive member depends greatly on the contact efficiency with the surface of the photosensitive member. In particular, the charging member rotates in the counter direction at the portion in contact with the electrophotographic photosensitive member. It is important that the rotation direction itself is the same).
[0104]
[Charge promoting particles]
As the material of the particles, various conductive particles such as conductive inorganic particles such as other metal oxides and mixtures with organic substances can be used. Here, the particle resistance is 10 as the specific resistance because the charge is transferred through the particles.^TenΩ · cm or less is preferable. Here, the resistance was measured by the tablet method and normalized. Low area 2.26cm²A powder sample of about 0.5 g is put in a cylinder of 1.57 MPa (15 kgf / cm) on the upper and lower electrodes.²At the same time, a voltage of 100 V was applied, the resistance value was measured, and then normalized to calculate the specific resistance. The particle size is preferably 10 μm or less in order to obtain good charging uniformity. The lower limit of the particle size is 10 nm, as long as particles can be stably obtained. In the present invention, the particle size when the particles are constituted as an aggregate is defined as an average particle size as the aggregate. For the measurement of the particle size, 100 or more samples are extracted from observation with an optical or electron microscope, and the volume particle size distribution is calculated with the maximum chord length in the horizontal direction and can be determined with the 50% average particle size.
[0105]
[Charging accelerating particle coating means]
In order to uniformly supply the charge promoting particles to the contact nip between the roller and the photoreceptor, a charge promoting particle applying means can be provided. As the supply means, a regulating blade is brought into contact with the photosensitive member, and the charge promoting particles are held between the photosensitive member and the regulating blade. Then, a certain amount of charge promoting particles is applied to the roller as the photosensitive member rotates. As a simpler configuration, the charge accelerating particles are uniformly added together with the developer in the developing device, and are supplied onto the electrophotographic photosensitive member together with the developer at the time of development, so that the image is hardly transferred during the transfer process. Thus, it is possible to supply to the charging roller, or there is a method in which a foam or a fur brush containing the charge accelerating particles is brought into contact with the electrophotographic photosensitive member, but it is not limited to this configuration.
[0106]
  [Charger operation]
  An example of the operation of the charger in the present invention will be described. The electrophotographic photosensitive member is provided with the above-mentioned specific surface protective layer on the surface, is in a drum shape, and rotates at a constant speed of about 30 to 100 mm / sec. The present invention is a charger that uniformly charges this surface.TakeA charger was used. However, the peripheral speed in this case is determined by a desired process speed, and the present invention is not limited to this peripheral speed.
[0107]
First, the charge accelerating particles adhere to the surface of the electrophotographic photosensitive member from the developing device by the developing process on the surface of the photosensitive member. Thereafter, the toner passes through the transfer process and reaches the charging roller portion. The charging roller was driven at about 50 to 150 rpm so that the roller surface moved at a constant speed in the opposite direction to the photoreceptor, and a DC voltage of −500 to −800 V was applied to the core of the charging roller. However, the peripheral speed of the charging roller is also determined by the desired process speed and the peripheral speed of the electrophotographic photosensitive member, and the present invention is not limited to this peripheral speed.
[0108]
By this process, the surface of the photoreceptor is charged to a potential equal to the applied voltage. In this embodiment, charging is performed by surface protection in which the charge is directly provided on the surface of the electrophotographic photosensitive member because the charge accelerating particles existing in the contact nip between the charging roller and the electrophotographic photosensitive member rub the surface of the electrophotographic photosensitive member without gaps. Charging is performed by injecting into the conductive particles in the layer. In this injection charging process, the presence of conductive particles in the surface protective layer is important, and the ratio of the conductive particles is not changed by the rubbing action with the charging roller. Is necessary to do.
[0109]
【Example】
Hereinafter, the present invention will be described with reference to examples.
[0110]
(Photosensitive layer example 1)
Using an aluminum cylinder of φ30mm × 260.5mm as a support, a 5% methanol solution of polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) is applied thereon by a dipping method to provide an undercoat layer of 0.5 μm. It was.
[0111]
Next, 4 parts (mass parts) of an oxytitanium phthalocyanine pigment having strong peaks at 9.0, 14.2, 23.9, and 27.1 degrees at diffraction angles 2θ ± 0.2 degrees in the X-ray diffraction spectrum of CuKα. The same applies hereinafter), 2 parts of polyvinyl butyral resin BX-1 (manufactured by Sekisui Chemical Co., Ltd.) and 80 parts of cyclohexanone were dispersed by a sand mill apparatus with φ1 mm glass beads for about 4 hours. This solution was applied onto the undercoat layer and dried with hot air at 105 ° C. for 10 minutes to form a 0.22 μm charge generation layer.
[0112]
Next, 1 part of exemplary compound CTM-43 (oxidation potential: 0.81 V) and 9 parts of CTM-6 (oxidation potential: 0.76 V) as a charge transport material, bisphenol Z-type polycarbonate (trade name: Z- 400, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was dissolved in 75 parts by mass of monochlorobenzene and 25 parts by mass of dimethoxymethane. This solution was dip coated on the charge generation layer and dried with hot air at 120 ° C. for 30 minutes to form a 15 μm charge transport layer. Therefore, the difference in oxidation potential: | ΔEox | = 0.05V, and the average oxidation potential: Eave = 0.765V.
[0113]
(Photosensitive layer example 2)
A photosensitive layer was prepared in the same manner except that the charge generation layer was provided in the photoreceptor layer 1 as follows.
[0114]
3 parts by mass of hydroxygallium phthalocyanine crystal and 2 parts by mass of polyvinyl butyral having the strongest peak at 28.1 ° of diffraction angle 2θ ± 0.2 in X-ray diffraction of CuKα are added to 100 parts by mass of cyclohexanone, and 1 mmφ glass beads Disperse with a sand mill for 1 hour, add 100 parts by weight of methyl ethyl ketone and dilute to prepare a coating for a charge generation layer, dip coat the coating for a charge generation layer on the undercoat layer, and The film was dried for 10 minutes to form a charge generation layer having a thickness of 0.15 μm.
[0115]
(Photosensitive layer examples 3 to 30)
A photoconductor was prepared in the same manner as in Photosensitive Layer Example 2 except that the charge transport materials in the charge transport layer were changed to the structures and ratios shown in Tables 13-14.
[0116]
[Table 13]

[0117]
[Table 14]

(Photosensitive layer example 31)
A photoconductor was prepared in the same manner as in Photosensitive Layer Example 2, except that the charge transport layer was provided as follows.
[0118]
As a charge transport material, 8 parts by mass of exemplary compound CTM-20 (oxidation potential: 0.74 V) and 2 parts by mass of CTM-27 (oxidation potential: 0.84 V), bisphenol A type polycarbonate (weight average molecular weight: 27000) ) 15 parts by mass was dissolved in 30 parts by mass of monochlorobenzene and 70 parts by mass of dichloromethane. This solution was dip coated on the charge generation layer and dried with hot air at 120 ° C. for 30 minutes to form a 16 μm charge transport layer. Therefore, the difference in oxidation potential: | ΔEox | = 0.10V, and the average oxidation potential: Eave = 0.760V.
[0119]
(Photosensitive layer examples 32-41)
A photoconductor was prepared in the same manner as in the photoconductive layer 31, except that each charge transport material in the charge transport layer was changed to the structure and ratio shown in Table 15.
[0120]
[Table 15]

(Protective layer example 1)
Fluorine-containing silane coupling agent as conductive particles: C_FiveF₁₁CH₂CH₂CH₂Si (OC₂H_Five)_ThreeOxygen-deficient SnO having an average particle size of 0.03 μm subjected to surface treatment (treatment amount: 6.5%)₂50 parts by mass of particles and 150 parts by mass of acetone were dispersed in a sand mill for 72 hours, and further 10 parts by mass of polychlorotrifluoroethylene particles (PCTFE, average particle size: 0.27 μm) were added for dispersion. Then, 15 parts by mass of amino resin Cymel C-204 (Mitsui Cytec Co., Ltd.) was dissolved to prepare a protective layer solution. The photosensitive layer was dip coated in this solution, and a heat curing reaction was performed at 160 ° C. for 50 minutes, and a protective layer of 3 μm was provided on the charge transport layer. The protective layer surface thus provided is analyzed by XPS,
Ratio of tin + indium: Ac = 5.5 atomic%
Ratio of indium to tin: A_In/ A_Sn= 0
Ratio of fluorine + silicon: A_L= 15.6 atomic%
Sulfur + phosphorus ratio: Asp is 0.01 atomic% or less
The measurement result was obtained.
[0121]
(Protective layer examples 2 to 6)
In protective layer example 1, the treatment amount with the fluorine-containing silane coupling agent, the dispersion amount of PCTFE particles, and the dissolution amount of Cymel C-204 (Mitsui Cytec Co., Ltd.), which is an amino resin, were adjusted, dip coated, and 160 A heat curing reaction is performed at 50 ° C. for 50 minutes, and a protective layer coating material is prepared so that the XPS analysis value after forming the protective layer of 3 μm on the charge transport layer is as shown in Table 7, dip coated on the photosensitive layer, 160 ° C. Then, a heat curing reaction was performed for 50 minutes, and a protective layer of 3 μm was provided on the charge transport layer.
[0122]
(Protective layer example 7)
In protective layer example 1, the conductive particles were changed to 35 parts by mass of Sn-containing indium oxide particles (ITO particles) having an average particle size of 0.02 μm, and instead of amino resin, resol type phenol resin: XPL-8264B (Gunei Chemical) Kogyo Co., Ltd.) was used, and a protective layer paint was prepared in the same manner except that the amount was adjusted, and a protective layer was provided.
[0123]
(Protective layer examples 8 to 13)
In the protective layer example 7, instead of the treatment amount with the fluorine-containing silane coupling agent, the dispersion amount of the PCTFE particles, and the resol type phenol resin, Cymel C-204 (manufactured by Mitsui Cytec Co., Ltd.) which is an amino resin was used, and Adjust the dissolution amount, dip coat, heat cure reaction at 160 ° C for 50 minutes, and adjust the protective layer paint so that the XPS analysis value after forming the protective layer of 3μm on the charge transport layer becomes Table 7 Then, dip coating was performed on the photosensitive layer, a heat curing reaction was performed at 160 ° C. for 50 minutes, and a protective layer of 3 μm was provided on the charge transport layer.
[0124]
(Protective layer example 14)
Fluorine-containing silane coupling agent as conductive particles: C_FiveF₁₁CH₂CH₂CH₂Si (OC₂H_Five)_ThreeAnd antimony-doped SnO having an average particle size of 0.03 μm, which was surface-treated (treatment amount: 6.5%)₂10 parts by mass of particles, fluorine-containing silane coupling agent: C_FourF₉CH₂CH₂CH₂Si (OCH_Three)_ThreeThen, 38 parts of indium oxide particles having an average particle diameter of 0.02 μm and surface treated with a surface treatment of 8.5% and 150 parts by mass of acetone are dispersed in a sand mill for 72 hours, and further PCTFE particles (average particle diameter: 0.27 μm) After adding 10 parts by mass, dispersion was performed, and 29 parts by mass of resol-type phenol resin: XPL-8264B was dissolved to prepare a protective layer solution. The photosensitive layer was dip-coated in this solution and a heat curing reaction was performed at 160 ° C. for 50 minutes, and a protective layer of 3 μm was provided on the charge transport layer.
[0125]
(Protective layer example 15)
Fluorine-containing silane coupling agent as conductive particles: C_FiveF₁₁CH₂CH₂CH₂Si (OC₂H_Five)_Three30% by mass of ITO particles having an average particle size of 0.03 μm, which was surface-treated with 6.5%, and oxygen-deficient SnO having an average particle size of 0.03 μm treated with methyl hydrogen silicone oil₂Particles (treatment amount: 12%), 150 parts by mass of acetone are dispersed in a sand mill for 72 hours, and further 10 parts by mass of tetrafluoroethylene-hexafluoropropylene copolymer particles (ETFE, average particle size: 0.30 μm) Then, 35 parts by mass of resol type phenol resin: XPL-8264B was dissolved to prepare a protective layer solution. The photosensitive layer was dip coated in this solution and a heat curing reaction was performed at 160 ° C. for 50 minutes, and a protective layer of 3 μm was provided on the charge transport layer.
[0126]
(Protective layer example 16)
In Example 7 of the protective layer, a protective layer was produced in the same manner except that an amino resin (Cymel C201, manufactured by Mitsui Cytec Co., Ltd.) was used instead of the resol type phenol resin.
[0127]
(Protective layer example 17)
In Example 7 of the protective layer, a photoconductor was prepared in the same manner except that instead of the resol type phenol resin, 11 parts by mass of a cresol novolac type epoxy resin and 5 parts by mass of a thioether compound represented by the following structural formula were used as a curing agent. .
[0128]
[Chemical 1]

(Protective layer example 18)
60 parts by mass of an acrylic monomer represented by the following structural formula, 30 parts by mass of ultrafine tin oxide particles having an average particle system of 0.04 μm before dispersion, 2 parts by mass of 2-methylthioxanthone of a sulfur-containing atomic compound as a photoinitiator, methyl 300 parts by weight of Cellsolve was dispersed in a sand mill for 96 hours to form a protective layer paint. After forming a film on the photosensitive layer by a beam coating method, 8 mW / cm using a high-pressure mercury lamp.²Was cured for 30 seconds at a light intensity of 3 μm to provide a protective layer of 3 μm.
[0129]
[Chemical 2]

(Protective layer example 19)
In Protective Layer Example 18, tin oxide ultrafine particles were added to a fluorine-containing silane coupling agent: C_FiveF₁₁CH₂CH₂CH₂Si (OC₂H_Five)_ThreeThe surface treatment was carried out (treatment amount 6.5%). A protective layer was provided in the same manner except that the particles were changed to ITO particles having an average particle diameter of 0.02 μm and 12 parts by mass of ETFE particles having an average particle diameter of 0.30 μm were dispersed.
[0130]
(Protective layer example 20)
A photoconductor was prepared in the same manner except that in Example 19 of the protective layer, the photoinitiator was changed to 6 parts by mass of the phosphorus atom-containing compound having the following structural formula.
[0131]
[Chemical Formula 3]

(Protective layer example 21)
After dispersion by adding 12 parts by mass of polychlorotrifluoroethylene particles (PCTFE, average particle size: 0.27 μm), 15 parts by mass of amino resin (Cymel C201, Mitsui Cytec Co., Ltd.) is dissolved to obtain a protective layer solution The photosensitive layer was dip coated in this solution, and a heat curing reaction was performed at 157 ° C. for 50 minutes, and a 3 μm protective layer was provided on the charge transport layer.
[0132]
Regarding the protective layers of protective layers 1 to 21, the surface was wiped with absorbent cotton impregnated with acetone or methyl cellosolve, which was used in each protective layer paint after the protective layer was formed, and the solvent resistance of the protective layer Although the properties were confirmed, almost none of them were dissolved, and it was predicted that a three-dimensional cross-linked chain was formed in the protective layer film by heating or ultraviolet irradiation, and the curing reaction proceeded.
[0133]
[Table 16]

(Preparation of electrophotographic photoreceptor)
By providing the protective layers shown in the protective layer examples 1 to 21 on the photosensitive layer examples 1 to 41, the electrophotographic photoreceptors of Examples and Comparative Examples were produced.
[0134]
After forcibly removing the protective layer of these electrophotographic photosensitive members, the charge transport layer is dissolved in a solvent, and further, each charge transport material is isolated by silica gel column chromatography, and the above cyclic volta Although the oxidation potential was measured by the measurement method, it was confirmed that there was no change in the oxidation potential itself for each charge transport material.
(Evaluation Test 1)
These electrophotographic photosensitive members were used with a Canon laser printer: LBP-NX (roller charging, DC / AC superposition, residual toner cleaning with urethane rubber cleaning blade), temperature 5 ° C./humidity 10 RH%, and temperature 32. A durability test of 7,000 sheets was performed in each environment of 5 ° C./humidity 85RH%. Tables 8 and 9 show the summary of image quality at the end of the durability test. As charging conditions, the surface of each electrophotographic photosensitive member was charged by an AC / DC charging method in which a DC component: −700 V and an AC component: 2,000 Vpp were superimposed on a charging roller. The intensity of the laser light amount was adjusted so that the light portion potential of each electrophotographic photosensitive member was −200 V at the position of the developing device.
[0135]
In addition, when the surface of the photoconductor is positively charged during the transfer process or due to frictional charging with a member in contact with the surface of the photoconductor, the dark attenuation of the portion increases or the photosensitivity increases. As an index for the phenomenon of positive memory, a part of the surface of these photoconductors is charged to +700 V, and after 2 hours, mounted on a laser printer: LBP-NX, a halftone image is printed, and the density of the positive charge history portion It was judged how much difference is from the non-charged part.
[0136]
[Table 17]

[0137]
[Table 18]

[0138]
[Table 19]

Surface analysis value of protective layer 7:
Ac = 4.2 atomic%,
A_L= 13.7 atomic%,
A_In/ A_Sn= 5.56 atomic%,
As + Ap <0.01 atomic%
From the comparison of the above examples and comparative examples, the Ac value in a limited specific range and A_LIn an electrophotographic photosensitive member provided with a protective layer having a value, the electrophotographic characteristics are maintained by simultaneously including a plurality of charge transport materials having a limited specific range of | ΔE | in the charge transport layer. In addition, a high-quality image can be obtained. Among them, the average oxidation potential: Eave is in the range of 0.73 to 0.83 V, and by selecting a non-hydrazone type charge transport material such as triarylamine type or styryl type, particularly excellent durability characteristics can be obtained. can get.
[0139]
[Table 20]

[0140]
[Table 21]

By comparing the above Examples and Comparative Examples, the charge transport layer contains a plurality of types of charge transport materials having a specific range | ΔE | limited, and at the same time, the Ac value and A of a specific range limited._LBy providing a protective layer having a value, it is possible to maintain the electrophotographic characteristics and obtain a high-quality image. Further, the ratio of indium and tin in the protective layer is controlled within a specific range, and the amount of phosphorus atoms and sulfur atoms is suppressed to 0.2 atomic% or less, whereby an electrophotographic photoreceptor having durability stability at a higher level can be obtained. Can be provided.
[0141]
(Evaluation test 2)
For the evaluation of the electrophotographic photosensitive member produced in the example, an actual machine in which the laser jet 4000 manufactured by Hewlett-Packard Co., Ltd. was modified to the configuration described in FIG. 3 was used. The volume resistance of the conductive particles for primary charging at this time is 1 (Ω · cm), and the initial supported amount of conductive particles on the elastic charging member is divided by the surface roughness Ra [μm] of the charged particle carrier. The value obtained is 0.1 mg / cm²/ Μm. The voltage applied to the primary charging member was −700 V with only the DC component. The intensity of the laser light amount was adjusted so that the light portion potential of each electrophotographic photosensitive member was −200 V at the position of the developing device. Further, a durability test of 10,000 sheets of the electrophotographic photosensitive member was performed in a high temperature / high humidity environment at a temperature of 32.5 ° C. and a humidity of 90%. The evaluation results are summarized in Table 22.
[0142]
[Table 22]

From the above embodiment, in the charging system of the present invention, Ac and A on the surface of the protective layer are also shown._LIn an electrophotographic photosensitive member in which is controlled to an appropriate range, injection charging property and abrasion of the surface of the photosensitive member are always stable, and there is no occurrence of slight image blur recognized in an AC charging system, which is extremely good. A charge transport material having a specific range of | ΔE | limited in the charge transport layer, even in the present charging system in which the electric field strength applied to the photoreceptor is not high when the photoreceptor is charged. By including a plurality of types, the electrophotographic characteristics can be maintained and a high-quality image can be obtained.
[0143]
Among them, particularly for the charge transport material in the charge transport layer, an average oxidation potential: Eave is in the range of 0.73 to 0.83 V, and a non-hydrazone type charge transport material such as triarylamine or styryl is used. By selecting and controlling the ratio of indium and tin in the protective layer to a specific range and suppressing the amount of phosphorus atoms and sulfur atoms to 0.2 atomic% or less, electrophotographic photosensitive having higher stability at higher dimensions The body can be provided.
[0144]
【The invention's effect】
As described above, according to the present invention, the charge transport layer contains at least two kinds of charge transport materials, and the difference between the lowest oxidation potential and the highest oxidation potential among the charge transport materials: | ΔEox | The sum of the ratios of indium and tin contained in the surface protective layer based on the analysis value by XPS (X-ray photoelectron spectroscopy) on the surface of the electrophotographic photosensitive member: Ac [atomic%] and the ratio of fluorine and silicon contained in the surface protective layer Sum: A_LBy controlling [atomic%] to a special range, it is possible to transfer charges between the surface protective layer and the charge transport layer without delay, and it is possible to provide an electrophotographic photosensitive member with excellent image quality. It becomes. As for the charge transport material, a non-hydrazone type charge transport material having an average oxidation potential in a specific range is selected, the ratio of indium and tin in the surface protective layer is controlled to a specific range, By suppressing the amount of sulfur atoms to 0.2 atomic% or less, good characteristics are exhibited even in a durability test over a long period of time. Furthermore, the average particle size is 10 μm to 10 nm, and the resistance is 10¹²To 10^-1A charged particle carrier having a charged particle mainly composed of conductive inorganic particles of Ω · cm, and a surface having conductivity and elasticity, and the amount of the charged particle supported by the charged particle carrier The value divided by the surface roughness Ra [μm] of 0.005 to 1 mg / cm²Even in a charging device in which a charging member composed of a charged particle carrier having a thickness of .mu.m is rotated in the counter direction on the contact surface with the electrophotographic photosensitive member, and the electrophotographic photosensitive member is contact injection charged, it is durable at a high level. An electrophotographic photosensitive member having stability can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a difference between discharge charging and injection charging when only a DC voltage is applied to a charging roller of the present invention.
FIG. 2 is a diagram showing a difference between discharge charging and injection charging when an AC voltage is superimposed on a DC voltage and a voltage is applied to the charging roller of the present invention.
FIG. 3 is a diagram showing an outline of an electrophotographic system of the present invention.
[Explanation of symbols]
1a Photosensitive drum with injection layer
1b Photosensitive drum
2 Charging roller
2a Core
2b Conductive elastic roller
M charged conductive particles (charged particles)
3A Charged conductive particle feeder
37A stirring blade
39A Fur Brush
4 Laser exposure equipment
5A 2-component developing device
52 Magnet Roll
51 Development sleeve
60 One-component magnetic developer
6 Transfer charger
7 Fixing device

Claims (7)

In the electrophotographic photosensitive member having, in this order, at least a charge generation layer, a charge transport layer , and a surface protective layer containing conductive particles and formed using a curable resin on a conductive support.
Charge transporting layer contains at least two kinds of charge transport materials,
Among charge transporting material of the charge transport layer, the difference between the oxidation potential of the highest charge-transporting material is oxidation potential and the oxidation potential of the lowest charge transport material oxidation potential: | ΔEox | [V] is a compound represented by the following formula ( 1)
0.02 <| ΔEox | <0.13 (1)
Satisfied ,
In analysis by XPS (X-ray photoelectron spectroscopy) of the electrophotographic photosensitive member surface, the sum of the proportion of indium and tin contained in the surface protective layer: and A _c [atomic%], the fluorine contained in the surface protective layer the sum of the proportions of silicon: a _L [atomic%] and has the following formula (2) and (3)
1 . 5 <A _c <12.0 (2)
5.0 <A _L <25.0 (3)
An electrophotographic photoreceptor characterized by satisfying When the ratio of the nth charge transport material in the charge transport layer is Cn and the oxidation potential of the nth charge transport material is En, the average oxidation potential of the charge transport material in the charge transport layer: E _ave = Σ (Cn · En) [V] is the following formula (4)
0.73 ≦ E _ave <0.83 (4)
(Here, Cn is a numerical value representing the mass ratio of each charge transport material in all charge transport materials in the charge transport layer, and represents a numerical value greater than 0 and less than 1 for all n, and ΣCn = 1)
The electrophotographic photosensitive member according to 請 Motomeko 1 satisfied. Wherein among the charge transport material in the charge transport layer, the ratio C _h of the charge transport material oxidation potential most have high is represented by the following formula (5)
0.05 ≦ C _h ≦ 0.95 × exp {−460 × (| ΔEox | −0.05) × (| ΔEox | −0.05)} (5)
(Here , | ΔEox | represents the difference between the oxidation potential of the charge transport material having the lowest oxidation potential and the oxidation potential of the charge transport material having the highest oxidation potential among the charge transport materials in the charge transport layer. satisfies the above formula (1). in addition, C _h is relative to the total charge transporting material of the charge transport layer, the oxidation potential represents the mass ratio of the charge transporting material most have high.)
Electronic photograph photoreceptor according to 請 Motomeko 1 or 2 satisfied. In analysis by XPS of the surface protective layer, the ratio As [atomic%] of the sulfur atoms contained in the surface protective layer, the sum of the ratio Ap of the phosphorus atoms contained in the surface protective layer [atomic%], Following formula (6)
As + Ap <0.2 (6)
The electrophotographic photosensitive member according to any one of 請 Motomeko 1-3 you satisfied. The charge plurality of charge transport material transporting layer is, electrophotographic photosensitive member according to any one of I請 Motomeko 1-4 such have a hydrazone skeleton. At least an electrophotographic photosensitive member according to claim 1, having integrally a band electrical location in contact injection charging into the electrophotographic photosensitive member, a process cartridge is detachably attached to an electrophotographic apparatus main body There ,
The charging member used in the charging device is:
(A) charged particles mainly composed of conductive inorganic particles having an average particle diameter of 10 μm to 10 nm and a resistance of 10 ¹² to 10 ⁻¹ Ω · cm;
(B) A charged particle carrier having a surface having conductivity and elasticity, and a value obtained by dividing the amount of the charged particles carried by the surface roughness Ra [μm] of the charged particle carrier. A process cartridge comprising a charged particle carrier of 005 to 1 mg / cm ² / μm and rotating in a counter direction on a contact surface with the electrophotographic photosensitive member. Electrophotographic equipment having a process cartridge according to claim 6.

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