JP4136622B2 - Image forming apparatus and process cartridge - Google Patents

Description

【００２０】
但し、上記一般式(I)中、A及びBは、下記一般式(II)〜(VIII)で表されるカプラー残基を示す。
【００２１】
【化２】

【００２２】
但し、上記一般式(II)中、X1、Y1及びZはそれぞれ以下のものを表す。X1：−ＯＨ、−ＮＨＣＯＣＨ₃、又は−ＮＨＳＯ₂ＣＨ₃。Y1：−ＣＯＮ（Ｒ２）（Ｒ３）、−ＣＯＮＨＮ＝Ｃ(R6)(R7)、−ＣＯＮＨＮ(R8)(R9)、−ＣＯＮＨＣＯＮＨ(R12)、水素原子、−ＣＯＯＨ、−ＣＯＯＣＨ₃、−ＣＯＯＣ₆Ｈ₅、又はベンズイミダゾリル基。（R2、R3は水素原子、置換若しくは無置換のアルキル基、置換若しくは無置換のアリール基、置換若しくは無置換のヘテロ環基を示し、R2、R3はそれらに結合する窒素原子と共に環を形成しても良い。R6、R7は水素原子、置換若しくは無置換のアルキル基、置換若しくは無置換のアラルキル基、置換若しくは無置換のアリール基、置換若しくは無置換のスチリル基、置換若しくは無置換のヘテロ環基を示し、R6、R7はそれらに結合する炭素原子と共に環を形成しても良い。R8、R9は水素原子、置換若しくは無置換のアルキル基、置換若しくは無置換のアラルキル基、置換若しくは無置換のアリール基、置換若しくは無置換のスチリル基、置換若しくは無置換のヘテロ環基を示し、R8、R9は5員環あるいは6員環を形成してもよく、この場合5員環あるいは6員環は、縮合芳香族環を有しても良い。R12は置換若しくは無置換のアルキル基、置換若しくは無置換のアリール基、置換若しくは無置換のヘテロ環基を示す。）Z：ベンゼン環と結合してナフタレン環、アントラセン環、カルバゾール環、ベンゾカルバゾール環、ジベンゾカルバゾール環、ジベンゾフラン環、ベンゾナフトフラン環、及びジベンゾチオフェン環から選ばれる多環芳香族環又はヘテロ環を形成するのに必要な残基。これらの環には置換基が有ってもよい。
【００２３】
【化３】

【００２４】
但し、上記一般式(III)中、R4は水素原子、置換若しくは無置換のアルキル基、又は置換若しくは無置換のアリール基を示す。
【００２５】
【化４】

【００２６】
但し、上記一般式(IV)中、R5は水素原子、置換若しくは無置換のアルキル基、又は置換若しくは無置換のアリール基を示す。
【００２７】
【化５】

【００２８】
但し、上記一般式(V)中、Yは芳香族炭化水素の2価の基、又は窒素原子を環内に含むヘテロ環の2価の基を示す。
【００２９】
【化６】

【００３０】
但し、上記一般式(VI)中、Yは芳香族炭化水素の２価の基、又は窒素原子を環内に含むヘテロ環の２価の基を示す。
【００３１】
【化７】

【００３２】
但し、上記一般式(VII)中、R10は水素原子、炭素数１乃至８の低級アルキル基、カルボキシル基、又はそのエステルを示し、Ar1は置換若しくは無置換の芳香族炭化水素環基を示す。
【００３３】
【化８】

【００３４】
但し、上記一般式(VIII)中、R11は水素原子、炭素数１乃至８の低級アルキル基、カルボキシル基、又はそのエステルを示し、Ar2は置換若しくは無置換の芳香族炭化水素環基を示す。
【００３５】
本例の電荷発生層に必要に応じて用いられるバインダー樹脂としては、ポリアミド、ポリウレタン、エポキシ樹脂、ポリケトン、ポリカーボネート、シリコーン樹脂、アクリル樹脂、ポリビニルブチラール、ポリビニルホルマール、ポリビニルケトン、ポリスチレン、ポリ−Ｎ−ビニルカルバゾール、ポリアクリルアミドなどが用いられる。これらのバインダー樹脂は、単独または２種以上の混合物として用いることが出来る。更に必要に応じて後述する電荷輸送物質を添加してもよい。
電荷発生層を形成する方法として、大きくは真空薄膜作製法か溶液分散系からのキャスティング法を採用する。前者の方法には、真空蒸着法、グロー放電分解法、イオンプレーティング法、スパッタリング法、反応性スパッタリング法、ＣＶＤ法等が含まれ、この方法により上述した無機系材料、有機系材料が良好に形成できる。また、後述のキャスティング法により上述した無機系もしくは有機系電荷発生物質を必要ならばバインダー樹脂と共にテトラヒドロフラン、シクロヘキサノン、ジオキサン、ジクロロエタン、ブタノン等の溶媒を用いてボールミル、アトライター、サンドミル等により分散し、分散液を適度に希釈して塗布することにより、形成できる。塗布は、浸漬塗工法やスプレーコート、ビードコート法などを採用することができる。
以上のようにして設けられる電荷発生層の膜厚は、0.01〜5μm程度が適当であり、好ましくは0.05〜2μmである。
【００３６】
また、本例の電荷輸送層は、電荷輸送材とバインダー樹脂とともにテトラヒドロフラン、シクロヘキサノン、ジオキサン、ジクロロエタン、ブタノン等の溶媒を用いてこれらを溶解、塗工し成膜することにより形成される。塗工方法としては浸漬塗工法やスプレーコート、ビードコート法などを採用することができる。電荷輸送層とし使用できるバインダー樹脂としてはフィルム性の良いポリカーボネート（ビスフェノールAタイプ、ビスフェノールZタイプ、ビスフェノールCタイプ、あるいはこれら共重合体）、ポリアリレート、ポリスルフォン、ポリエステル、メタクリル樹脂、ポリスチレン、酢酸ビニル、エポキシ樹脂、フェノキシ樹脂などが用いられる。これらのバインダーは、単独または2種以上の混合物として用いることが出来る。
電荷輸送層に使用される電荷輸送物質は、オキサゾール誘導体、オキサジアゾール誘導体（特開昭52-139065、52-139066号公報に記載）イミダゾール誘導体、トリフェニルアミン誘導体（特願平1-77839号に記載）、ベンジジン誘導体（特公昭58-32372号公報に記載）、α−フェニルスチルベン誘導体（特開昭57-73075号に記載）、ヒドラゾン誘導体（特開昭55-154955、55-156954、55-52063、56-81850などの公報に記載）、トリフェニルメタン誘導体（特公昭51-10983号公報に記載）、アントラセン誘導体（特開昭51-94829号公報に記載）、スチリル誘導体（特開昭56-29245、58-198043号の各公報に記載）、カルバゾール誘導体（特開昭58-58552号公報に記載）、ピレン誘導体（特願平2-94812号に記載）などを使用することができる。
これら多くの電荷輸送物質のなかでも下記一般式（IX）で表される構造を有するものを用いた場合、特に光感度の面で優れた特性を示し高感度な感光体を得ることが出来る。
【００３７】
【化９】

【００３８】
但し式(IX)中、R1、R2、R3およびR4は水素元素、置換もしくは無置換の炭素数１乃至８の低級アルキル基、置換もしくは無置換のアリール基を表し、Ar1は置換又は無置換のアリール基を表し、Ar2置換又は無置換のアリーレン基を表し、Ar1とR1は共同で環を形成してもよく、またｎは０又は１の整数である。
以上のようにして設けられる電荷輸送層の膜厚は5〜100μm程度が適当であり、好ましくは10〜30μm程度である。
【００３９】
次に、単層型の感光層について述べる。
キャスティング法等で単層の感光層を設ける場合、上記した電荷発生物質ならびに電荷輸送物質、バインダー樹脂等の材料を用いて単層構成とすればよい。このようにして構成する感光層には、必要により可塑剤やレベリング剤を添加することもできる。単層の感光層の膜厚は、5〜100μm程度が適当であり、好ましくは、10〜30μm程度が適当である。
上記のように、いずれの型式の感光層でも、感光体の電荷発生材料として特定の構造を有するジスアゾ顔料もしくはY型オキシチタニルフタロシアニンを用い、電荷輸送層に特定の構造を有する電荷輸送物質を用いることによりさらに高速なプロセスに対応可能とする。
【００４０】
次に、保護層について説明する。
本発明の感光体における保護層は、少なくとも無機フィラーとバインダー樹脂からなる。
無機フィラーとしては酸化チタン、シリカ、酸化錫、アルミナ、酸化ジルコニウム、酸化インジウム、窒化ケイ素、酸化カルシウム、酸化亜鉛、硫酸バリウム等を採用することができる。
これら無機フィラーは分散性向上などの理由から無機物、有機物で表面処理されてもよい。その中には、一般に行われているように、撥水性処理としてシランカップリング剤で処理、あるいはフッ素系シランカップリング剤処理、高級脂肪酸処理が含まれる。無機物処理としてはアルミナ、ジルコニア、酸化スズ、シリカによるフィラー表面処理が含まれる。
無機フィラーとしては中でも、酸化チタン、シリカ、アルミナを用いた場合、特に良好な耐摩耗性と静電特性を発現し、本発明の画像形成装置への適用に好適となる。特に、電子写真感光体の高耐久化を図る意味では、α−アルミナが特に優れた特性を示す。これはα−アルミナがダイアモンドに次いで優れた硬度（モース硬度）を示すことと、透光性を有することに起因する。前者の特性は感光体の耐摩耗性の向上に対して極めて有利に作用し後者は優れた静電特性維持に有利であり、結果として感光体の総合的な特性の向上に結びつけることができる。
とりわけ、以下の特徴を有するα−アルミナは、膜中のフィラー充填性に優れるため、フィラーの含有量を高くしても表面平滑な膜形成が可能となる。
すなわち、フィラーとして用いるα−アルミナは、実質的に破砕面を有さず、且つ、多面体粒子であり、且つ、α−アルミナの六方格子面に平行な最大粒子径をＤ、六方稠密格子面に垂直な粒子径をＨとした場合に、Ｄ／Ｈ比が0.5以上5.0以下であるα−アルミナ粒子からなるものが望ましい。
保護層のバインダー樹脂としては、低分子電荷輸送物質、及び高分子電荷輸送物質と粉砕、分散し、塗工される。バインダー樹脂としてはアクリル樹脂、ポリエステル、ポリカーボネート（ビスフェノールAタイプ、ビスフェノールZタイプ、ビスフェノールCタイプ、あるいはこれら共重合体）、ポリアリレート、ポリアミド、ポリウレタン、ポリスチレン、エポキシ樹脂等が挙げられ、保護層中の無機フィラー含有量は3〜50重量％で、好ましくは5〜30重量％であり、3重量％以下であると耐摩耗性はあるものの十分でない、40重量％以上であると感光層の透明性が損なわれる。
【００４１】
また、無機フィラーの平均粒子径dは、上記(1)式、即ち
0.1＜3.75×10^-3L/λ＜d/λ＜0.5
を満たしていれば良く、0.2〜0.4μmであることが、上記したとおり耐摩耗性と画像品質を両立させる点から好ましい。
これは、平均粒子径dが大きくなり過ぎると感光体上に形成される潜像が乱れやすくなり、画像品質が低下し、逆に無機フィラーの平均粒子径dが小さくなりすぎると、保護層中のバインダー樹脂との結びつきが弱くなり、摩耗が進行した場合に保護層より脱離しやすくなり耐刷性が低下してしまうといった耐摩耗性の面で悪影響が生じるからである。また、平均粒子径を著しく小さくした場合、成膜時に非常に密に配置されるため電荷移動の際のトラップとなり露光後の光減衰特性が悪化したり残留電位の上昇が生じてしまう。さらに、平均粒子径が小さすぎると塗工液として凝集しやすく保護層として成膜した場合、均一な膜質が得られないといった理由からである。
また、保護層における無機フィラーの存在確率を一定に保つことが耐摩耗性、画像特性の向上に対する重要な課題である。つまり、保護層を設けたことにより感光層の感度、静電的安定性を損なわず、かつ露光の精細性を損なうことなく、耐摩耗性にもとづく薄膜化によりさらに高精細化と高速応答化を図ることを可能とするために必要な条件になるからである。この要求を満足するためには、保護層の任意断面における無機フィラーの含有量がその平面内での面積占有率として2乃至6％であることが望ましい。面積占有率で2％未満であると、耐摩耗性が不足し、6％より大きいと残留電位の上昇、感度低下、解像度低下、フィルミングに起因する異常画像発生が生ずる。
【００４２】
保護層における上記面積占有率の制御は、使用する材料の粒径とその分布、塗工液処方、塗工装置により可能である。
上記のフィラーはバインダー樹脂とともにテトラヒドロフラン、シクロヘキサノン、ジオキサン、ジクロロメタン、ジクロロエタン、ブタノン等の溶媒分散されて、浸漬塗工法やスプレーコート、ビードコート法などを用いて形成されるが、特に好ましいバインダー樹脂としてはポリカーボネート樹脂、ポリアリレート樹脂が採用可能である。
上記のように、保護層中に用いられるバインダー樹脂をポリカーボネート樹脂もしくはポリアリレート樹脂のいずれか、あるいはそれらを混合して用いることによって、より高い耐久性を与えることが可能となる。
さらに、保護層に含有される電荷輸送物質のイオン化ポテンシャル（Ip）の値が、前記感光層に含有される電荷輸送物質のIpの値以下となるような関係が成り立つような電荷輸送物質を含有することでいっそうの高速対応が可能となる。
【００４３】
なお、本例の感光体には、導電性支持基体と感光層との間に適宜中間層を設けるようにしても良い。ここに使用可能な中間層であるが、中間層は一般に樹脂を主成分とするもの用いられたりするが、これらの樹脂はその上に感光層を、溶剤を用いて塗布することを考えると、一般の有機溶剤に対して耐溶解性の高い樹脂であることが望ましい。このような樹脂としては、ポリビニルアルコール、カゼイン、ポリアクリル酸ナトリウム等の水溶性樹脂、共重合ナイロン、メトキシメチル化ナイロン、等のアルコール可溶性樹脂、ポリウレタン、メラミン樹脂、アルキッド樹脂、メラミン樹脂、エポキシ樹脂等、三次元網目構造を形成する硬化型樹脂などが挙げられる。
また、酸化チタン、シリカ、アルミナ、酸化ジルコニウム、酸化スズ、酸化インジウム等で例示できる金属酸化物、あるいは金属硫化物、金属窒化物などの微粉末を中間層中のフィラーとして加えることにより、さらに安定した帯電性を保持することが出来る。これらの中間層は、適当な溶媒、塗工法を用いて形成することが可能で、膜厚としては0.1〜20、好ましくは0.5〜10μｍが適当である。
【００４４】
ここで、上記感光体を用いて電子写真プロセスによる画像形成を行う本発明の画像形成装置について説明する。
図１は本発明の画像形成装置に係わる画像形成部の一例を概略図にて示す。
図１を参照し、例示する画像形成部の構成及び、その画像形成プロセスを説明する。図示の画像形成部では、通常の電子写真方式に従った画像形成プロセスである帯電，露光，現像，転写により記録紙上に画像が形成される。
ここでは、レーザービーム（図１中Ｌとして示す）で画像が書き込まれる感光体１は、ドラム状の形状をなす。なお、感光体１はドラム状以外の、シート状、エンドレスベルト状のものであっても良い。
ドラム状の感光体１に対し電子写真プロセスに従った操作を行うための手段として、図１に示すように、帯電，露光，現像，転写のプロセス順に除電ランプ２、帯電チャージャ３、イレーサ４、画像露光部５、現像ユニット６、転写前チャージャ７、転写チャージャ１０、分離チャージャ１１、分離爪１２、クリーニング前チャージャ１３、ファーブラシ１４、クリーニングブラシ１５を感光体ドラムの周囲に備える。帯電チャージャ３、転写前チャージャ７、転写チャージャ１０、分離チャージャ１１、クリーニング前チャージャ１３には、コロトロン、スコロトロン、固体帯電器（ソリッド・ステート・チャージャー）、帯電ローラを始めとする公知の手段が用いられる。なお、転写手段には、図に示されるように転写チャージャー１０と分離チャージャー１１を併用したものが効果的であるが、転写チャージャのみの一般な手段としても良い。
【００４５】
ここで、図１に簡略化して示した画像露光部５について説明を加える。
図１において、ドラム状の感光体１は同図中の矢示Ａ方向に回転（副走査）され、又その感光面が図面に垂直（主走査）方向にライン走査するレーザービームＬによりスポット露光され、そこに潜像を生成する。こうした画像露光部５の動作はレーザービーム書き込み装置により行われる。
図２は本例の画像形成装置に用いるレーザービーム書き込み装置の一例を示す。 図２を参照すると、レーザービーム書き込み装置は、画像形成装置全体を制御するプリンタ制御部２２の制御下に、画像書き込み制御部２１、ポリゴンモータ制御部２５及びステッピングモータ制御部２３を備える。
プリンタ制御部２２の制御動作に従い、画像書き込み制御部２１は、取り込んだ画像データによってＬＤ２６の点灯を制御する。ＬＤ２６から発する光ビームは、結像光学系（図示せず）を経て、ポリゴンモータ制御部５により等速回転（図２、矢示C）するポリゴンミラー４で偏向され、その後、ｆθレンズ２８によって感光体ドラム１上に一定小径の光スポットとして結像され、感光面を等速で主走査し（図２、矢示B）、光ビーム書き込みを行う。
このとき、主ライン走査方向の書き込みは、定位置に設けた同期検知センサ２７によりビームを検出することにより発生する同期信号に基づいて生成するタイミング信号LGATEに従い書き込みを開始する。一方、副走査方向（図２、矢示A）の書き込みは、ステッピングモータ制御部２３により回転が制御される感光体ドラム１上のドラム回転方向の基準位置に基づいて定めた書き込みタイミング信号に従い、その開始が制御される。
【００４６】
画像書き込み制御部２１では、書き込み画像のソースとなる画像データを生成する画像入力装置（例えば、スキャナ、外部で生成された印刷データをＩ／Ｆを介して受け取るプリンタコントローラ等）から送信されてくる画像データに基づいてＬＤ２６の発光を制御するための変調信号を生成し、ＬＤドライバがこの変調信号によりＬＤ２６を駆動することにより画像を担ったビームを発生させる。ここでは、ＬＤ２６からのレーザービームによりスポット露光をして、画素ドットにより画像を表現する方式を採用しているので、この方式に応じた変調信号を生成し、ＬＤ２６の発光を制御する。画素ドットにより画像を表現する方式においては、濃度調整や階調表現をする場合に、画素ドットを一定の大きさ（径）にして記録密度を変更したり、或いは画素ドットの大きさを変更したりするやり方を用いるので、こうしたやり方に従って光出力の変調を行う。画素ドットの大きさを変更する方式の場合、光出力を点灯時間にて変調（パルス幅：PWM変調）する方式や強度変調方式等が採用される。
ところで、画像形成装置の書き込みに利用するレーザービームＬを発生する光源としては、発生波長の異なる種々の半導体レーザー（ＬＤ）等を用いることができる。書き込み用の光源としては、画質を向上させるためにはビームスポット径を小さくすることが望ましく、現状では短波長側に移行しつつある。
こうした種々の波長のＬＤを画像形成装置の書き込みに利用する場合に、感光面に作られる露光スポット径の大きさL（＝露光スポットの短軸長）を上記した条件式(1)、即ち、
0.1＜3.75×10^-3L/λ＜d/λ＜0.5
に従って定めるようにする。
この条件式を満足する設定を行うためには、第１に画像書き込み制御部２１によりＬＤの発光を調整・制御するという方式を採用する。即ち、ＬＤを点灯時間変調（PWM変調）又は強度変調するときの設定を変更することにより、露光スポットの短軸長を調整する。第２に、走査光学系を構成する要素の配置を微調整して結像条件を変更することにより、露光スポットの短軸長を調整する、という方式を採用しても良い。
【００４７】
本発明の画像形成装置に係わる実施形態として図１を例示したが、感光体１への画像形成プロセスには、図１に示される工程の他に光照射を併用した転写工程、除電工程、クリーニング工程、あるいは前露光などの工程を設けることにより種々の光が照射されるような装置構成をとる場合があり得、こうした形態で実施しても良い。また、現像ユニット６により感光体１上に現像されたトナーは、レジストローラ８を通して送り込まれる転写紙９に転写されるが、全部が転写されるわけではなく、感光体１上に残存するトナーも生ずる。このようなトナーは、ファーブラシ１４およびブレード１５により、感光体より除去される。クリーニングは、クリーニングブラシだけで行なわれることもあり、クリーニングブラシにはファーブラシ、マグファーブラシを始めとする公知のものが用いられる。
また、電子写真方式による感光体に正(負)帯電を施し、画像露光を行なうと、感光体表面上には正(負)の静電潜像が形成される。これを負(正)極性のトナー（検電微粒子）で現像すれば、ポジ画像が得られるし、また正(負)極性のトナーで現像すれば、ネガ画像が得られる。かかる現像手段には、公知の方法が適用されるし、また、除電手段にも公知の方法が用いられる。
上記で実施形態として図１に示した画像形成部は、複写装置、ファクシミリ、プリンタ内に固定して組み込まれていてもよいが、その一部を着脱可能なプロセスカートリッジの形で交換部品として装置内に組み込む方式により構成するようにしてもよい。
図３はプロセスカートリッジとして実施する形態の１例を示す。図３に示すように、プロセスカートリッジには、感光体１６を内蔵する他に、帯電チャージャ１７、画像露光部１９、現像ローラ２０を含む現像部、転写部、クリーニングブラシ１８を含むクリーニング部、除電部（図示せず）を要素として備え、１つの装置（部品）を構成する。図３に示す実施形態では、感光体以外に、帯電手段（帯電チャージャ１７）、現像手段、クリーニング手段を一体化して保有するカートリッジを例示したが、帯電手段、現像手段、クリーニング手段の少なくとも一手段を感光体と一体化する形式でカートリッジを構成するようにしても良い。
【００４８】
次に、実施例及び参考例によって本発明を更に詳細に説明する。なお、これらの例中使用する部は、すべて重量部を表わす。
「参考例１〜３」
まず、下記要領にて参考例１〜３に用いる電子写真感光体を得た。
導電性支持基体としてφ30mmのアルミニウムドラムに、下記成分を混合しボールミル粉砕をおこない、浸漬法で塗工、加熱乾燥することにより、3.5μmの中間層を形成した。
〔中間層用塗工液〕
・アルキッド樹脂（ベッコゾール 1307-60-EL，大日本インキ化学工業製） 6部
・メラミン樹脂（スーパーベッカミン G-821-60，大日本インキ化学工業製）4部
・酸化チタン（CR-EL，石原産業社製） 40部
・メチルエチルケトン 200部
次に、上記工程で形成した中間層上に下記の電荷発生層用塗工液を浸漬法で塗工、加熱乾燥することにより膜厚0.2μmの電荷発生層を形成した。
〔電荷発生層用塗工液〕
下記成分を混合しボールミルで分散した。
・下記式（X）に示す構造のジスアゾ化合物 5部
・ポリビニルブチラール（エスレックBL-S，積水化学製） 1.5部
・シクロヘキサノン 120部
・メチルエチルケトン 120部
【００４９】
【化１０】

【００５０】
次に、上記工程で形成した電荷発生層上に下記電荷輸送層用塗工液を浸漬法で塗工し、加熱乾燥することにより膜厚19μmの電荷輸送層を形成した。
〔電荷輸送層用塗工液〕
下記成分を混合溶解せしめ、電荷輸送層用塗工液とした。
・下記式(XI)に示す構造構造の電荷輸送物質（イオン化ポテンシャル：5．50eV） 7部
・ポリカーボネート（Zポリカ，帝人化成社製 Mv5万） 10部
・塩化メチレン 100部
・1％シリコーンオイル（KF50，信越シリコーン社製）塩化メチレン溶液 1部
【００５１】
【化１１】

【００５２】
次に、上記工程で形成した電荷輸送層上に、下記成分を直径9cmの硬質ガラスポットに投入し直径2mmジルコニアビーズを用いてボールミル分散を96時間おこない保護層用塗工液として、スプレー法で塗工して2.5μmの保護層を設け本参考例の電子写真感光体を得た。
・ポリカーボネート樹脂（Ｚポリカ，帝人化成社製 Ｍｖ5万） 5部
・アルミナ（住友化学工業製） 2部
・下記式（XII）に示す構造の電荷輸送物質（イオン化ポテンシャル：5.39eV） 3部
・シクロヘキサノン 200部
【００５３】
【化１２】

【００５４】
なお保護層成膜後のアルミナの平均粒径を断面のＴＥＭ写真から測定したところ0.30μmであった。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した装置、を用いて120000枚までの通紙試験を行った。
この参考例では、感光体面上の露光スポット径の短軸長Ｌをそれぞれ変化させ、参考例１では70μm、参考例２では50μm、参考例３では20μmとした。
参考例１〜３それぞれについて、通紙試験120000枚後に以下の項目について評価をおこなった。
・感光体膜厚減少量‥‥通紙試験後の膜厚減少量を渦電流式膜厚計フィシャー社製フィシャーコープMMSで測定した。
・機内電位（露光部電位）‥‥帯電電位-600Vとしたときの露光部電位の推移について評価した。
・画像品質‥‥出力画像のベタ濃度、黒ポチなどの局所欠陥、地肌汚れ、異常画像等を総合的に評価して“良好“、”僅かに低品質“、”品質不良“の三段階に分類した。
・解像度‥‥1200dpiで独立１ドットの画像形成をおこない、画像上のドットの再現性について顕微鏡観察して評価し“良好”、“僅かに再現性低下”、“再現性不良”の三段階に分類した。
・細線再現性‥‥細線書込みをおこない画像上での再現性を評価し“良好”、“僅かに再現性低下”、“再現性不良”の三段階に分類した。
これらの評価結果を下記表１に示す。
【００５５】
【表１】

【００５６】
「参考例４，５」
これらの参考例は保護層に添加する無機フィラーを参考例１と異なる物質に変更したものである。
参考例４で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられるアルミナ（住友化学工業製）を酸化チタン（石原産業製）に代えて保護層用塗工液の分散条件を、直径2mmのジルコニアビーズから直径5mmのＰＳＺボールに変更し、ボールミル分散時間を96時間から120時間に変更した以外は、参考例１で用いた感光体と全く同様にして参考例４で用いる感光体を作製した。
なお、この保護層成膜後の酸化チタンの平均粒径を断面のＴＥＭ写真から測定したところ0.25μmであった。
また、参考例５で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられるアルミナ（住友化学工業製）をシリカ（日本アエロジル製）に代えて保護層用塗工液の分散条件を、直径2mmのジルコニアビーズから直径1cmのアルミナボールに変更し、ボールミル分散時間を96時間から144時間に変更した以外は、参考例１で用いた感光体と全く同様にして参考例５で用いる感光体を作製した。
なお、この保護層成膜後のシリカの平均粒径を断面のＴＥＭ写真から測定したところ0.20μmであった。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットに改造を施した装置、を用いて120000枚までの通紙試験を行った。
参考例４，５では感光体面上の露光スポット径の短軸長Lをいずれも50μmとした。
参考例４，５それぞれについて、通紙試験後、参考例１と同様の評価をおこなった。
これらの評価結果を下記表２に示す。
【００５７】
【表２】

【００５８】
「参考例６〜８」
参考例６〜８は電荷発生層を形成するための〔電荷発生層用塗工液〕を参考例１と異なる成分に変更したものである。
参考例６〜８で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体における〔電荷発生層用塗工液〕を以下のように変更した。
・Y型オキシチタニルフタロシアニン 8部
・ポリビニルブチラール 5部
・2−ブタノン 400部
この電荷発生層用塗工液を浸漬法で塗工、加熱乾燥することにより膜厚0.2μmの電荷発生層を形成した以外は、参考例１で用いた感光体と全く同様にして参考例６〜８それぞれで用いる感光体を作製した。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が780nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットに改造を施した装置、を用いて120000枚までの通紙試験を行った。
この参考例では、感光体面上の露光スポット径の短軸長Lをそれぞれ変化させ、参考例６では75μm、参考例７では60μm、参考例８では20μmとした。
参考例６〜８それぞれについて、通紙試験後、参考例１と同様の評価をおこなった。
これらの評価結果を下記表３に示す。
【００５９】
【表３】

【００６０】
「参考例９，１０」
これらの参考例は保護層に添加する無機フィラーを参考例６と異なる物質に変更したものである。
参考例９で用いる電子写真感光体を下記要領にて得た。
参考例６で用いた感光体を作製する際に、保護層に用いられるアルミナ（住友化学工業製）を酸化チタン（石原産業製）に代えて保護層用塗工液の分散条件を、直径2mmのジルコニアビーズから直径5mmのＰＳＺボールに変更し、ボールミル分散時間を96時間から120時間に変更した以外は、参考例６で用いた感光体と全く同様にして参考例９で用いる感光体を作製した。
なお、この保護層成膜後の酸化チタンの平均粒径を断面のＴＥＭ写真から測定したところ0.25μmであった。
また、参考例１０で用いる電子写真感光体を下記要領にて得た。
参考例６で用いた感光体を作製する際に、保護層に用いられるアルミナ（住友化学工業製）をシリカ（日本アエロジル製）に代えて保護層用塗工液の分散条件を、直径2mmのジルコニアビーズから直径1cmのアルミナボールに変更し、ボールミル分散時間を96時間から144時間に変更した以外は、参考例６で用いた感光体と全く同様にして参考例１０で用いる感光体を作製した。
なお、この保護層成膜後のシリカの平均粒径を断面のＴＥＭ写真から測定したところ0.20μmであった。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が780nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットに改造を施した装置、を用いて120000枚までの通紙試験を行った。
参考例９，１０では感光体面上の露光スポット径の短軸長Lをいずれも50μmとした。
参考例９，１０それぞれについて、通紙試験後、参考例１と同様の評価をおこなった。
これらの評価結果を下記表４に示す。
【００６１】
【表４】

【００６２】
「参考例１１〜１６」
参考例１１〜１６は感光体を構成する感光層或いは保護層を参考例１と異なる成分に変更したものである。
参考例１１で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられる電荷輸送物質を加えなかった以外は、参考例１で用いた感光体と全く同様にして参考例１１で用いる感光体を作製した。
また、参考例１２で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、電荷発生層、電荷輸送層を設ける代わりに下記成分の感光層用塗工液を用いて膜厚25μmの単層構成の感光層を形成した以外は、参考例１で用いた感光体と全く同様にして参考例１２で用いる感光体を作製した。
〔感光層用塗工液〕
下記成分を混合しボールミルで分散した。
・上記式（X）に示す構造のジスアゾ化合物 5部
・上記式（XII）に示す構造の電荷輸送物質 50部
・Z型ポリカーボネート（分子量6万） 97部
・テトラヒドロフラン 328部
また、参考例１３で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、電荷輸送層に用いられる電荷輸送物質を下記のものに代えた以外は、参考例１で用いた感光体と全く同様にして参考例１３で用いる感光体を作製した。
・上記式（XII）に示す構造の電荷輸送物質 7部
また、参考例１４で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられる電荷輸送物質を下記のものに代えた以外は、参考例１で用いた感光体と全く同様にして参考例１４で用いる感光体を作製した。
・下記式（XIII）に示す構造の電荷輸送物質（イオン化ポテンシャル：5.3eV） 3部
【００６３】
【化１３】

【００６４】
また、参考例１５で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられる電荷輸送物質を下記のものに代えた以外は参考例１で用いた感光体と全く同様にして参考例１５で用いる感光体を作製した。
・上記式（XI）に示す構造の電荷輸送物質 3部
また、参考例１６で用いる電子写真感光体を下記要領にて得た。
参考例１で用いた感光体を作製する際に、保護層に用いられるバインダー樹脂をポリアリレート（U100，ユニチカ製）に代えた以外は参考例１で用いた感光体と全く同様にして参考例１６で用いる感光体を作製した。
上記工程で作製した各電子写真感光体を電子写真複写機：イマジオMF2200(（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットに改造を施した装置、を用いて120000枚までの通紙試験を行った。
参考例１１〜１６では感光体面上の露光スポット径の短軸長Lをいずれも50μmとした。
参考例１１〜１６それぞれについて、通紙試験後、参考例１と同様の評価をおこなった。
これらの評価結果を下記表５に示す。
【００６５】
【表５】

「実施例１」
実施例１は、感光体の感光層、保護層の構成成分及び感光体面上の露光に用いるレーザー光の波長を変更したものである。
実施例１で用いる電子写真感光体を下記要領にて得た。
参考例１と同様に形成した中間層上に下記の電荷発生層用塗工液を浸漬法で塗工、加熱乾燥することにより膜厚0.2μmの電荷発生層を形成した。
〔電荷発生層用塗工液〕
下記成分を混合しボールミルで分散し、この分散液を電荷発生層用塗工液とした。
・Y型オキソチタニウムフタロシアニン 1.5部
・ポリビニルブチラール（エスレックBL-S：積水化学製） 1部
・シクロヘキサノン 220部
・メチルエチルケトン 220部
この電荷発生層上に下記電荷輸送層用塗工液を浸漬法で塗工し、加熱乾燥することにより膜厚19μmの電荷輸送層を形成した。
〔電荷輸送層用塗工液〕
下記成分を混合溶解せしめ電荷輸送層用塗工液とした。
・下記（XIV）に示す構造の電荷輸送物質 7部
・ポリカーボネート（Zポリカ、：帝人化成社製 Mv5万） 10部
・塩化メチレン 100部
・１％シリコーンオイル（KF5０信越シリコーン社製）塩化メチレン溶液 1部
【化１４】

次に、上記工程で形成した電荷輸送層上に、下記成分を直径9cmの硬質ガラスポットに投入し直径1cmのアルミナボールを用いてボールミル分散を４８時間おこない保護層用塗工液とした。
この液をスプレー法で塗工して2.6μmの保護層を設け本例の電子写真感光体を得た。
・ポリカーボネート樹脂（Zポリカ、：帝人化成社製 Mv5万） 5部
・アルミナ（住友化学工業製） 2部
・上記（XIV）に示す構造の電荷輸送物質 3部
・シクロヘキサノン 200部
なお、この保護層成膜後のアルミナの平均粒径を断面のＴＥＭ写真から測定したところ0.20μmであった。
上記工程で作製した電子写真感光体を電子写真複写機イマジオMF2200［（株）リコ−製］をベースとした像露光のための書込みレーザービームの波長が405nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した画像形成装置を用いて120000枚までの通紙試験を行った。
実施例１では感光体面上の露光スポット径の短軸長Lをいずれも15μmとした。通紙試験後、参考例１と同様の評価をおこなった。
この評価結果を下記表６に示す。
【表６】

【００６６】
次に、本発明の上記式(1)を満たさない設定条件による比較例を示し、その評価結果により本発明の参考例の効果を確認する。なお、比較例中に使用する部は、すべて重量部を表わす。
「比較例１」
下記要領にて比較例１で用いる電子写真感光体を得た。
参考例１〜３で用いた感光体を作製する際に、保護層中に用いられるアルミナ（住友化学工業製）を加えなかった以外は、参考例１〜３で用いた感光体と全く同様にして比較例１で用いる感光体を作製した。
このようにして作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットに改造を施した装置、を用いて120000枚までの通紙試験を行った。
なお、比較例１では、参考例２と同様に感光体面上の露光スポット径の短軸長Lを50μmとした。
比較例１について、通紙試験後、参考例１と同様の評価を行った。
この評価結果を下記表７に示す。
【００６７】
【表７】

【００６８】
この評価結果を参考例２と対比すると、膜厚減少量、露光部電位の数値に違いが示されるとともに、画像品質、細線再現性の不良が現れており、保護層中に添加されたアルミナの効果が確認できる。
【００６９】
「比較例２」
下記要領にて比較例２で用いる電子写真感光体を得た。
参考例１〜３で用いた感光体を作製する際に、保護層塗工液の分散条件を、直径2mmのジルコニアビーズから直径2mmのＰＳＺボールに変更し、ボールミル分散時間を96時間から24時間に変更した以外は、参考例１〜３で用いた感光体と全く同様にして比較例２で用いる感光体を作製した。
なお、この保護層成膜後のアルミナの平均粒径を断面のＴＥＭ写真から測定したところ、0.50μm（参考例１〜３では0.30μm）であった。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した装置、を用いて120000枚までの通紙試験を行った。
なお、比較例２では、参考例２と同様に感光体面上の露光スポット径の短軸長Ｌを50μmとした。
比較例２について、通紙試験後、参考例１と同様の評価を行った。
この評価結果を下記表８に示す。
【００７０】
【表８】

【００７１】
この評価結果を参考例２と対比すると、露光部電位の数値に著しい違いが示されるとともに、比較例２ではd/λ=0.76で0.5を大きく越えており、画像品質、細線再現性の不良が現れており、保護層中に添加されたアルミナの平均粒径と使用波長の関係d/λ<0.5を満たす設定条件による効果が確認できる。
【００７２】
「比較例３」
参考例１〜３で用いた感光体を作製する際と同様にして比較例３で用いる電子写真感光体を得た。
このようにして作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した装置、を用いて120000枚までの通紙試験を行った。
なお、比較例３では、感光体面上の露光スポット径の短軸長Ｌを85μmとした（参考例１のL=70μmよりも大きくした）。
比較例３について、通紙試験後、参考例１と同様の評価を行った。
この評価結果を下記表９に示す。
【００７３】
【表９】

【００７４】
この評価結果を参考例１と対比すると、露光部電位の数値に違いが示されるとともに、比較例３では3.75×10^-3L/λ=0.49でd/λ=0.46を越えており、解像度における再現性の不良、細線再現性の僅かな低下が現れており、3.75×10^-3L/λ（露光スポット径の短軸長に対する使用波長に関係する数値）<d/λ（保護層中に添加されたアルミナの平均粒径に対する使用波長に関係する数値）を満たす設定条件による効果が確認できる。
【００７５】
「比較例４」
下記要領にて比較例４で用いる電子写真感光体を得た。
参考例１〜３で用いた感光体を作製する際に、保護層塗工液の分散条件を、直径2mmのジルコニアビーズから直径1cmのステンレスボールに変更し、ボールミル分散時間を96時間から179時間に変更した以外は、参考例１〜３で用いた感光体と全く同様にして比較例４で用いる感光体を作製した。
なお、この保護層成膜後のアルミナの平均粒径を断面のＴＥＭ写真から測定したところ、0.10μm（参考例１〜３では0.30μm）であった。
上記工程で作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した装置、を用いて120000枚までの通紙試験を行った。
なお、比較例４では、参考例２と同様に感光体面上の露光スポット径の短軸長Ｌを50μmとした。
比較例４について、通紙試験後、参考例１と同様の評価を行った。
この評価結果を下記表１０に示す。
【００７６】
【表１０】

【００７７】
この評価結果を参考例２と対比すると、膜厚減少量の数値に違いが示され耐久性の低下が示されるとともに、比較例４ではd/λ=0.15となってこの値が、3.75×10^-3L/λ=0.29よりもさらに小さくなっており、画像品質の不良、細線再現性の僅かな低下が現れており、3.75×10^-3L/λ（露光スポット径の短軸長に対する使用波長に関係する数値）<d/λ（保護層中に添加されたアルミナの平均粒径に対する使用波長に関係する数値）を満たす設定条件による効果が確認できる。
【００７８】
「比較例５」
参考例１〜３で用いた感光体を作製する際と同様にして比較例５で用いる電子写真感光体を得た。
このようにして作製した電子写真感光体を電子写真複写機：イマジオMF2200（（株）リコ−製）をベースとした画像形成装置、即ち像露光のための書込みレーザービームの波長が655nmであり、かつ感光体面上の露光スポット径を可変出来るように光学ユニットの改造を施した装置、を用いて120000枚までの通紙試験を行った。
なお、比較例５では、感光体面上の露光スポット径の短軸長Lを10μmとした（参考例３のL=20μmよりもさらに小さくした）。
比較例５について、通紙試験後、参考例１と同様の評価を行った。
この評価結果を下記表１１に示す。
【００７９】
【表１１】

【００８０】
この評価結果を参考例３と対比すると、比較例３では3.75×10^-3L/λ=0.06で0.1よりも小さくなっており、細線再現性の不良が現れており、0.1<3.75×10^-3L/λ（露光スポット径の短軸長に対する使用波長に関係する数値）を満たす設定条件による効果が確認できる。
【００８１】
【発明の効果】
（１） 請求項１の発明に対する効果
露光スポットの短軸長Ｌと露光に用いる光ビームの波長λの関係を示す値、(3.75×10^-3L/λ)を0.1以下とならないようにすると、潜像形成の際に感光体表面上の粗さによる乱反射の影響を受け難くなり細線再現性等で問題が生じることが無く、又この値（3.75×10^-3L/λ）を保護層に含まれる無機フィラーの平均粒子径ｄと露光に用いる光ビームの波長λの関係を示すd/λより大きくならないようにすると、解像度の低下が起きることが無く、さらに感光体の耐摩耗性、耐久性が低下せず、又d/λ値を0.5以上にならないようにすると、感光体露光後の残留電位の上昇が大きくなり、画像形成時における露光部電位の上昇が生じることなく、耐摩耗性にも問題がない条件を定めることができ、高画質、長寿命、高信頼性を高いレベルで達成することが可能になる。又 400 〜 450nm の波長を有する半導体レーザーを用いることにより、高解像度化、装置のコンパクト化の実現が可能になる。
（２） 請求項２の発明に対する効果
感光体面上の露光スポットの短軸長 L が 10 〜 40 μ m となる条件を用いることにより、乱反射の影響（ L が小さい場合）を受けることなく、耐摩耗性と画像品質を両立させ、上記（１）の効果を高レベルで達成することが可能になる。
（３） 請求項３の発明に対する効果
上記（１）、（２）の効果をプロセスカートリッジを有する画像形成装置において具現化することが可能になる。
【図面の簡単な説明】
【図１】本発明の画像形成装置に係わる画像形成部の一例を概略図にて示す。
【図２】本発明の画像形成装置に係わるレーザービーム書き込み装置の一例を概略図にて示す。
【図３】プロセスカートリッジとして実施する形態の１例を示す。
【符号の説明】
１…感光体、 ５…画像露光部、
２６…ＬＤ（レーザーダイオード）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic process (for example, a copying machine, a printer, a facsimile machine, a plotter, a printing machine, etc.), and more particularly, to form an optimal image on a photosensitive member spot-exposed by a light beam. The present invention relates to the image forming apparatus having conditions for performing the above and a process cartridge used in the image forming apparatus.
[0002]
[Prior art]
In the case of an “electrophotographic process”, generally, a photoconductive photoreceptor is first charged in a dark place by, for example, corona discharge, and then exposed to an image to selectively dissipate the charge of only the exposed portion, thereby forming an electrostatic latent image. One of the image forming methods in which the latent image portion is developed and visualized with electrophotographic fine particles (toner) comprising a colorant such as a dye or pigment and a binder such as a polymer substance to form an image. Point to.
As basic characteristics required for a photoreceptor used in such an electrophotographic process,
(1) It can be charged to an appropriate potential in a dark place.
(2) Less charge dissipation in the dark.
(3) A charge can be quickly dissipated by light irradiation.
Etc.
Among these methods, the so-called digital electrophotographic process, in which image exposure is performed with a laser beam, has become the mainstream, and has been put into practical use in laser printers and digital copying machines. In this method, the optical output of a semiconductor laser (hereinafter referred to as “LD (laser diode)”) is modulated and controlled by digital image data, and the photoconductor is raster-scanned by a light beam emitted from the LD (when a photoconductor drum is used, The photosensitive drum is rotated in the sub-scanning direction orthogonal to the main scanning line of the beam to perform raster scanning), and the photosensitive surface is exposed with spot light.
[0003]
In recent years, in the image forming apparatus using the above-described method using an electrophotographic process, high image quality is required, and high durability of a photoconductor used with high speed and miniaturization is required. The life of an image forming apparatus is often determined by the photoconductor, which is a deterioration of the photoconductor that is subjected to mechanical and chemical effects during the repeated charging, exposure, development, transfer, and cleaning processes in the electrophotographic process. Due to remarkable things. Mechanical deterioration appears as photoconductor wear and scratches, and chemical deterioration appears as binder resin, oxidative deterioration of the charge transfer material, and deposits due to the generated ozone, all of which degrade image quality. In addition, as the speed and size of the photoconductor drum are reduced, the diameter of the photoconductor drum becomes smaller, and the conditions for use in the electrophotographic process become severe. In particular, a rubber blade is used in the cleaning section, and the rubber hardness increases and the contact pressure increases in order to perform sufficient cleaning. Is forced to rise. For this reason, wear of the photoconductor is promoted, and potential fluctuations and sensitivity fluctuations occur, resulting in problems such as a color balance of an abnormal image and a color image being lost and a problem in color reproducibility.
[0004]
For this reason, attempts have been made to increase the film thickness of the photosensitive layer in order to increase the margin for wear, but in the case of a photoconductor having a laminated structure comprising a charge generation layer and a charge transport layer, which are currently mainstream, As a result, the thickness of the charge transporting layer responsible for charge transport is increased, and this causes problems such as the dissipation of charges during charge transfer and disturbance of the latent image, resulting in a decrease in resolution. .
Therefore, as another method for solving this problem and improving the wear resistance, a proposal has been made that employs a method of providing a protective layer or adding an inorganic filler to the photosensitive layer (for example, the following patent document). 1-5).
However, although the wear resistance is improved by these, the bright portion potential is increased by long-term continuous repetition, and image deterioration such as image density reduction occurs. In order to solve this problem, a proposal has been made to further improve the protective layer in which metal oxide fine particles are dispersed (see Patent Document 6 below).
[Patent Document 1]
Japanese Unexamined Patent Publication No. 1-205171
[Patent Document 2]
JP 7-333881 A
[Patent Document 3]
Japanese Patent Laid-Open No. 8-15887
[Patent Document 4]
Japanese Patent Laid-Open No. 8-123053
[Patent Document 5]
Japanese Patent Laid-Open No. 8-14641
[Patent Document 6]
Japanese Unexamined Patent Publication No. 8-179542
[0005]
[Problems to be solved by the invention]
However, although the photoconductor having a protective layer proposed in this conventional example has high mechanical strength and improved wear resistance, the image resolving power is reduced due to scattering of light during exposure by the protective layer. In the developed image, thick characters are observed, and sufficient resolution cannot be obtained.
Moreover, in laser printers and digital copying machines that perform spot exposure with laser beams such as LDs that are currently in use, fine powders such as inorganic fillers contained in the surface layer in order to suppress the scattering of laser light that passes through the surface layer It has been known that it is effective to make the particle size of the body shorter than the laser wavelength (there is also a description of particles dispersed in the protective layer in the conventional example). However, if the particle size is simply made too small, it may be advantageous in terms of latent image formation, but it may not be possible to satisfy wear resistance, or it may be affected by irregular reflection due to roughness on the surface of the photoreceptor. It is easy to deteriorate the fine line reproducibility. There is no technical solution to these problems yet.
The present invention has been made in view of the above-described problems of the prior art, and its purpose is to provide a photosensitive layer containing a charge generating material and a charge transport material on a conductive substrate, an inorganic filler, and a binder resin. In an image forming apparatus provided with an exposure means for spot-exposing a photosensitive member having a protective layer made of a light source from a light source whose light output is modulated to generate an electrostatic latent image on a photosensitive surface. Reduced image resolving power due to scattering generated in the protective layer in which metal oxide fine particles are dispersed, and reduction in fine line reproducibility caused by excessively reducing the particle size of the particles dispersed in the protective layer. Another object of the present invention is to provide an image forming apparatus capable of achieving a long life and high reliability at a high level, and a process cartridge used in the image forming apparatus.
[0006]
[Means for Solving the Problems]
  According to a first aspect of the present invention, there is provided an image including a photosensitive member and an exposure unit that spot-exposes the photosensitive member by scanning a light beam from a light source whose light output is modulated by image data and generates an electrostatic latent image on the photosensitive surface. A forming apparatus, wherein the photoconductor includes a charge generation material and a charge transport material on a conductive substrate;Inorganic fillerAnd a protective layer comprising a binder resin,Inorganic fillerAverage particle diameter: d, wavelength of light beam: λ, minor axis length of exposure spot on photosensitive surface: L is represented by the following formula, 0.1 <3.75 × 10^-3Determined to have a value that satisfies the relationship of L / λ <d / λ <0.5As a light source of the light beam, the wavelength is 400 ~ 450nm A semiconductor laser having a wavelength ofAn image forming apparatus.
[0007]
  A second aspect of the present invention is the image forming apparatus according to the first aspect, whereinShort axis length of exposure spot: L But Ten ~ 40 μ mIt is characterized by being.
[0008]
  The invention of claim 3 is the image forming apparatus according to claim 1 or 2.Has a process cartridge integrally supporting at least one of the photosensitive member and the charging means, the developing means, and the cleaning means.It is characterized by this.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an image forming apparatus having a photoreceptor and a means for spot exposing the photoreceptor by scanning with a light beam, and achieves high image quality development on the photoreceptor, long life of the photoreceptor, and high reliability at a high level. Therefore, the object is to optimize the structural requirements and exposure conditions in the photoconductor, and this purpose is such that the photoconductor includes a charge generation material and a charge transport material on a conductive substrate, A protective layer is provided on the surface, and the protective layer is directed to a structure in which an inorganic filler is added to a binder resin in order to improve wear resistance.
In the present invention, the average particle diameter of the inorganic filler added to the protective layer, the wavelength of the laser beam for image exposure to the photoreceptor, and the value of the exposure spot diameter by the laser beam (usually the exposure spot diameter is circular or elliptical). This means the value of the minor axis length, and when changing the exposure spot diameter such as power modulation, the maximum diameter means the full dot diameter. It is possible to obtain a high-quality developed image without causing a decrease in resolution due to the dissipation of charges generated during charge transfer during the formation of an electrostatic latent image, and to improve the wear resistance of the photoreceptor.
The exposure spot diameter of the laser beam in the present invention is 1 / e of the light intensity distribution of the laser beam spot expressed by a Gaussian function.²This means the width of the beam diameter when it is doubled (e represents the base of the natural logarithm). The minor axis length of the exposure spot is 1 / e.²When the beam diameter (width) is different between the main scanning direction and the sub-scanning direction of the double diameter, the shorter beam diameter is meant.
[0013]
The above specific relationship is expressed by the following formula when the average particle diameter of the inorganic filler added to the protective layer: d, the wavelength of the light beam: λ, and the short axis length of the exposure spot on the photoreceptor surface by the light beam: L This is based on a new discovery that the photosensitive member is configured and exposed to satisfy the relationship shown in (1).
0.1 <3.75 × 10^-3L / λ <d / λ <0.5 (1)
This conditional expression is based on the following knowledge. That is, first, a value indicating the relationship between the short axis length L of the exposure spot and the wavelength λ of the light beam used for exposure, 3.75 × 10^-3When L / λ is 0.1 or less, it is easily affected by irregular reflection due to the roughness on the surface of the photosensitive member, and the influence at the time of forming a latent image appears, causing a problem in fine line reproducibility. Second, a value indicating the relationship between the short axis length L and the wavelength λ, 3.75 × 10^-3When L / λ is larger than d / λ, which indicates the relationship between the average particle diameter d of the inorganic filler contained in the protective layer and the wavelength λ of the light beam used for exposure, the resolution becomes conspicuous. The amount of wear on the body also increases and the durability decreases. Third, a value indicating the relationship between the average particle diameter d and the wavelength λ described above, and d / λ of 0.5 or more is excellent in abrasion resistance, but the increase in the residual potential after exposure to the photoreceptor is increased, and image formation is performed. There arises a problem that the potential of the exposed portion increases at the time.
Therefore, a reliable image forming apparatus that can achieve both high image quality and high durability can be obtained only by configuring the image forming apparatus so as to satisfy the condition represented by the expression (1).
[0014]
The average particle diameter d of the inorganic filler is particularly preferably 0.2 to 0.4 μm from the viewpoint of achieving both wear resistance and image quality. If the average particle diameter d is too large, the latent image formed on the photoreceptor is likely to be disturbed, and it becomes a trap during charge transfer, resulting in deterioration of light attenuation characteristics after exposure and an increase in residual potential. On the other hand, if the average particle diameter d is too small, there is an adverse effect in terms of wear resistance. That is, if the average particle diameter d is too small, the bond with the binder resin in the protective layer is weakened, and it is easy to be detached from the protective layer, so that wear is accelerated and printing durability is lowered. On the other hand, if the average particle diameter d is too small, it is easy to agglomerate as a coating solution, and a uniform film quality cannot be obtained when a protective layer is formed. This is the reason why the particularly preferable average particle diameter d is 0.2 to 0.4 μm.
[0015]
The short axis length L of the exposure spot on the photoreceptor surface is preferably 10 to 80 μm. The exposure spot diameter is a factor that has an important influence on image quality. Due to the characteristics of the laser beam used for exposure, the shorter the wavelength, the smaller the diffractive power, the easier it is to narrow the beam waist, and the exposure spot can be reduced. Therefore, considering the average particle diameter d of the inorganic filler preferable for a short wavelength light source, the upper limit of the short axis length L is suitably 80 μm. The smaller the exposure spot, the more accurately the latent image can be formed. Therefore, the exposure spot is more preferably 60 μm or less, and even more preferably 40 μm or less. In this range, the gradation of the highlight portion is greatly improved.
However, asking the meaning of making the exposure spot diameter as small as possible, there is actually a limit to the developer particle diameter, and even if the resolution that can be realized with this developer particle is exceeded, there is almost no improvement in image quality. Further, if the exposure spot diameter becomes too small, there arises a problem that it is easily affected by irregular reflection due to the roughness of the surface of the photoreceptor. As a result of taking such constraints into consideration, the lower limit of the short axis length of the exposure spot on the photoreceptor surface is determined, and this is the reason for setting it to 10 μm. Accordingly, the range of the short axis length L of the preferred exposure spot as described above is 10 to 80 μm, more preferably 10 to 60 μm, and further preferably 10 to 40 μm.
As described above, the shorter the wavelength of the laser beam used for exposure, the smaller the diffractive power, the easier it is to narrow the beam waist, and the exposure spot can be reduced. Specifically, exposure spot diameter: L is a relationship of L∝ (π / 4) (λf / d) (where λ is the wavelength of the laser beam, f is the focal length of the fθ lens, and D is the lens diameter). As shown, the smaller the λ and f and the larger D, the smaller the spot diameter can be theoretically.
However, in order to reduce L to 10 μm to 15 μm level or to reduce f or increase D, ultra-high precision optical components or large optical members are required. Furthermore, in order to use such an ultra-high-precision optical component or a large optical member, it is difficult to put it to practical use due to the problem of the installation space of the optical member when it is actually incorporated into an image forming apparatus. . Accordingly, it is very effective to reduce the value of λ, that is, the wavelength, in order to narrow L to a smaller value. From these points, it is preferable to set the wavelength to 400 to 450 nm, which is the oscillation wavelength region of the short wavelength semiconductor laser in the blue region, in order to reduce the exposure spot and increase the resolution, and to reduce the cost and space.
[0016]
Furthermore, in the present invention, the protective layer in the above-described invention is made to contain a charge transport material, and the charge transport is promoted to increase the sensitivity.
In addition, the photosensitive layer in the above-described invention is functionally separated as a layer structure composed of a charge generation layer and a charge transport layer, thereby achieving high sensitivity.
In addition, it is possible to obtain excellent wear resistance by using one or a mixture selected from titanium oxide, silica, and alumina as the inorganic filler added to the protective layer in the above-described invention.
[0017]
  In the following, the image forming apparatus according to the above-described invention will be described with reference to the accompanying drawings.,ExampleAnd reference examplesBased on
  First, an embodiment relating to a photoreceptor used in the image forming apparatus of the present invention will be described. The photoreceptor is formed by laminating a photosensitive layer containing a charge generating material and a charge transport material, a protective layer made of an inorganic filler and a binder resin on a conductive substrate.
  The conductive substrate used in the present embodiment is obtained by conducting a conductive treatment on the conductor itself or an insulator. As the conductor, for example, a metal such as Al, Fe, Cu, Au, or an alloy thereof, polyester, polycarbonate Insulating substrates such as polyimide and glass, metals such as Al, Ag and Au, or In₂O_Three, SnO₂For example, a thin film made of a conductive material such as paper or paper subjected to a conductive treatment can be used. The shape of the conductive support is not particularly limited, and any of a plate shape, a drum shape, and a belt shape can be used.
[0018]
Next, the photosensitive layer will be described.
Since the photosensitive layer to which the present invention is applied is not basically limited, it may be implemented in either a single layer type or a laminated type.
First, a stacked type functionally separated into a charge generation layer and a charge transport layer will be described.
The charge generation layer is a layer mainly composed of a charge generation material, and a binder resin may be used as necessary. As the charge generation material, inorganic materials and organic materials can be used.
Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compound, and amorphous silicon. In amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms, phosphorus atoms, or the like are preferably used.
On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzo An azo pigment having a thiophene skeleton, an azo pigment having a fluorenone skeleton, an azo pigment having an oxadiazol skeleton, an azo pigment having a bisstilbene skeleton, an azo pigment having a distyryl oxadiazol skeleton, and a distyrylcarbazole skeleton Azo pigments, perylene pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Jigoido pigments, bisbenzimidazo - such as Le based pigments. These charge generation materials can be used alone or as a mixture of two or more.
In particular, when a disazo pigment represented by the following general formula (I) is used, it is possible to obtain a highly sensitive photoreceptor exhibiting particularly excellent characteristics in terms of photosensitivity.
[0019]
[Chemical 1]

[0020]
However, in the above general formula (I), A and B represent coupler residues represented by the following general formulas (II) to (VIII).
[0021]
[Chemical 2]

[0022]
However, in the above general formula (II), X1, Y1 and Z each represent the following. X1: —OH, —NHCOCH_ThreeOr -NHSO₂CH_Three. Y1: -CON (R2) (R3), -CONHN = C (R6) (R7), -CONHN (R8) (R9), -CONHCONH (R12), hydrogen atom, -COOH, -COOCH_Three, -COOC₆H_FiveOr a benzimidazolyl group. (R2 and R3 represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, and R2 and R3 form a ring together with the nitrogen atom bonded thereto. R6 and R7 are each a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted styryl group, a substituted or unsubstituted heterocycle R6 and R7 may form a ring together with carbon atoms bonded to them, R8 and R9 are hydrogen atoms, substituted or unsubstituted alkyl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted An aryl group, a substituted or unsubstituted styryl group, a substituted or unsubstituted heterocyclic group, and R8 and R9 may form a 5-membered ring or a 6-membered ring. The member ring may have a condensed aromatic ring, and R12 represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group.) Z: a benzene ring Necessary for bonding to form a polycyclic aromatic ring or heterocycle selected from naphthalene ring, anthracene ring, carbazole ring, benzocarbazole ring, dibenzocarbazole ring, dibenzofuran ring, benzonaphthofuran ring, and dibenzothiophene ring residue. These rings may have a substituent.
[0023]
[Chemical 3]

[0024]
In the general formula (III), R4 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
[0025]
[Formula 4]

[0026]
In the general formula (IV), R5 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
[0027]
[Chemical formula 5]

[0028]
In the general formula (V), Y represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocyclic ring containing a nitrogen atom in the ring.
[0029]
[Chemical 6]

[0030]
However, in the general formula (VI), Y represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocyclic ring containing a nitrogen atom in the ring.
[0031]
[Chemical 7]

[0032]
In the general formula (VII), R10 represents a hydrogen atom, a lower alkyl group having 1 to 8 carbon atoms, a carboxyl group, or an ester thereof, and Ar1 represents a substituted or unsubstituted aromatic hydrocarbon ring group.
[0033]
[Chemical 8]

[0034]
In the general formula (VIII), R11 represents a hydrogen atom, a lower alkyl group having 1 to 8 carbon atoms, a carboxyl group, or an ester thereof, and Ar2 represents a substituted or unsubstituted aromatic hydrocarbon ring group.
[0035]
The binder resin used as necessary for the charge generation layer of this example is polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-. Vinyl carbazole, polyacrylamide, etc. are used. These binder resins can be used alone or as a mixture of two or more. Furthermore, you may add the electric charge transport material mentioned later as needed.
As a method for forming the charge generation layer, a vacuum thin film manufacturing method or a casting method from a solution dispersion system is generally employed. The former method includes a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, etc., and the inorganic material and the organic material described above are favorably improved by this method. Can be formed. In addition, if necessary, the inorganic or organic charge generating material described above is dispersed by a ball mill, an attritor, a sand mill or the like using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone together with a binder resin by a casting method described later, The dispersion can be formed by appropriately diluting and applying. For the application, dip coating, spray coating, bead coating, or the like can be employed.
The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, and preferably 0.05 to 2 μm.
[0036]
The charge transport layer of this example is formed by dissolving, coating, and forming a film using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, and butanone together with a charge transport material and a binder resin. As the coating method, a dip coating method, a spray coating method, a bead coating method, or the like can be employed. Binder resin that can be used as a charge transport layer is polycarbonate with good film properties (bisphenol A type, bisphenol Z type, bisphenol C type, or copolymers thereof), polyarylate, polysulfone, polyester, methacrylic resin, polystyrene, vinyl acetate. Epoxy resin, phenoxy resin and the like are used. These binders can be used alone or as a mixture of two or more.
Charge transport materials used in the charge transport layer include oxazole derivatives, oxadiazole derivatives (described in JP-A-52-139065 and 52-139066), imidazole derivatives, and triphenylamine derivatives (Japanese Patent Application No. 1-77839). ), Benzidine derivatives (described in JP-B-58-32372), α-phenylstilbene derivatives (described in JP-A-57-73075), hydrazone derivatives (JP-A-55-154955, 55-156954, 55). -52063, 56-81850, etc.), triphenylmethane derivatives (described in Japanese Patent Publication No. 51-10983), anthracene derivatives (described in Japanese Patent Publication No. 51-94829), styryl derivatives (Japanese Unexamined Patent Publication No. 56-29245, 58-198043), carbazole derivatives (described in JP-A-58-58552), pyrene derivatives (described in Japanese Patent Application No. 2-94812), etc. can be used. .
Among these many charge transport materials, when a material having a structure represented by the following general formula (IX) is used, a highly sensitive photoreceptor can be obtained which exhibits particularly excellent characteristics in terms of photosensitivity.
[0037]
[Chemical 9]

[0038]
In the formula (IX), R1, R2, R3 and R4 represent a hydrogen element, a substituted or unsubstituted lower alkyl group having 1 to 8 carbon atoms, a substituted or unsubstituted aryl group, and Ar1 represents a substituted or unsubstituted group. Represents an aryl group, represents an Ar2 substituted or unsubstituted arylene group, Ar1 and R1 may form a ring together, and n is an integer of 0 or 1;
The thickness of the charge transport layer provided as described above is suitably about 5 to 100 μm, preferably about 10 to 30 μm.
[0039]
Next, a single layer type photosensitive layer will be described.
When a single photosensitive layer is provided by a casting method or the like, a single layer structure may be formed using the above-described materials such as a charge generation material, a charge transport material, and a binder resin. If necessary, a plasticizer and a leveling agent can be added to the photosensitive layer thus constituted. The thickness of the single photosensitive layer is suitably about 5 to 100 μm, and preferably about 10 to 30 μm.
As described above, in any type of photosensitive layer, a disazo pigment or Y-type oxytitanyl phthalocyanine having a specific structure is used as a charge generation material of a photoreceptor, and a charge transport material having a specific structure is used in the charge transport layer. This makes it possible to handle even faster processes.
[0040]
Next, the protective layer will be described.
The protective layer in the photoreceptor of the present invention comprises at least an inorganic filler and a binder resin.
Examples of the inorganic filler that can be used include titanium oxide, silica, tin oxide, alumina, zirconium oxide, indium oxide, silicon nitride, calcium oxide, zinc oxide, and barium sulfate.
These inorganic fillers may be surface-treated with an inorganic material or an organic material for reasons such as improving dispersibility. Among them, as is generally done, water repellency treatment includes treatment with a silane coupling agent, treatment with a fluorinated silane coupling agent, and higher fatty acid treatment. Inorganic treatment includes filler surface treatment with alumina, zirconia, tin oxide, and silica.
In particular, when titanium oxide, silica, or alumina is used as the inorganic filler, particularly excellent wear resistance and electrostatic characteristics are exhibited, and it is suitable for application to the image forming apparatus of the present invention. In particular, α-alumina exhibits particularly excellent characteristics in terms of increasing the durability of the electrophotographic photosensitive member. This is because α-alumina exhibits excellent hardness (Mohs' hardness) next to diamond and has translucency. The former characteristic is extremely advantageous for improving the wear resistance of the photoreceptor, and the latter is advantageous for maintaining excellent electrostatic characteristics. As a result, the overall characteristics of the photoreceptor can be improved.
In particular, α-alumina having the following characteristics is excellent in filler filling property in the film, so that even when the filler content is high, a film having a smooth surface can be formed.
In other words, α-alumina used as a filler has substantially no crushed surface, is a polyhedral particle, and has a maximum particle diameter D parallel to the hexagonal lattice surface of α-alumina and a hexagonal close-packed lattice surface. When the vertical particle diameter is H, those composed of α-alumina particles having a D / H ratio of 0.5 to 5.0 are desirable.
As the binder resin of the protective layer, a low molecular charge transport material and a polymer charge transport material are pulverized, dispersed, and applied. Examples of the binder resin include acrylic resin, polyester, polycarbonate (bisphenol A type, bisphenol Z type, bisphenol C type, or copolymers thereof), polyarylate, polyamide, polyurethane, polystyrene, epoxy resin, and the like. The content of the inorganic filler is 3 to 50% by weight, preferably 5 to 30% by weight. If it is 3% by weight or less, the wear resistance is not sufficient, but if it is 40% by weight or more, the transparency of the photosensitive layer is sufficient. Is damaged.
[0041]
The average particle diameter d of the inorganic filler is the above formula (1), that is,
0.1 <3.75 × 10^-3L / λ <d / λ <0.5
And is preferably 0.2 to 0.4 μm from the viewpoint of achieving both wear resistance and image quality as described above.
This is because if the average particle diameter d is too large, the latent image formed on the photoreceptor is likely to be disturbed, and the image quality is deteriorated. Conversely, if the average particle diameter d of the inorganic filler is too small, This is because the bond with the binder resin is weakened, and when wear progresses, it tends to be detached from the protective layer, resulting in an adverse effect in terms of wear resistance such that printing durability is reduced. Further, when the average particle diameter is remarkably reduced, it is arranged very densely during the film formation, so that it becomes a trap at the time of charge transfer and the light attenuation characteristic after exposure is deteriorated or the residual potential is increased. Furthermore, if the average particle diameter is too small, the coating liquid is likely to aggregate and a uniform film quality cannot be obtained when a protective layer is formed.
In addition, keeping the existence probability of the inorganic filler in the protective layer constant is an important issue for improving wear resistance and image characteristics. In other words, by providing a protective layer, the sensitivity and electrostatic stability of the photosensitive layer are not impaired, and the fineness of exposure is not impaired. This is because it becomes a necessary condition to make it possible to plan. In order to satisfy this requirement, it is desirable that the content of the inorganic filler in an arbitrary cross section of the protective layer is 2 to 6% as an area occupation ratio in the plane. When the area occupancy is less than 2%, the wear resistance is insufficient, and when it is more than 6%, the residual potential increases, the sensitivity decreases, the resolution decreases, and abnormal images are generated due to filming.
[0042]
The area occupancy in the protective layer can be controlled by the particle size and distribution of the material used, the coating liquid formulation, and the coating apparatus.
The filler is formed by using a dip coating method, a spray coating, a bead coating method, etc., with a binder resin and a solvent dispersion of tetrahydrofuran, cyclohexanone, dioxane, dichloromethane, dichloroethane, butanone, etc. Polycarbonate resin and polyarylate resin can be used.
As described above, the binder resin used in the protective layer can be given higher durability by using either a polycarbonate resin or a polyarylate resin, or a mixture thereof.
Furthermore, it contains a charge transport material that satisfies the relationship that the ionization potential (Ip) value of the charge transport material contained in the protective layer is less than or equal to the Ip value of the charge transport material contained in the photosensitive layer. By doing so, it becomes possible to cope with higher speed.
[0043]
In the photoreceptor of this example, an intermediate layer may be appropriately provided between the conductive support substrate and the photosensitive layer. Although it is an intermediate layer that can be used here, the intermediate layer is generally used as a main component of a resin, but considering that these resins are coated with a photosensitive layer using a solvent, It is desirable that the resin is highly resistant to dissolution in general organic solvents. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, alkyd resin, melamine resin, and epoxy resin. And a curable resin that forms a three-dimensional network structure.
In addition, metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, etc., or fine powders such as metal sulfides and metal nitrides are added as fillers in the intermediate layer for further stability. The charged property can be maintained. These intermediate layers can be formed using an appropriate solvent and coating method, and the film thickness is 0.1 to 20, preferably 0.5 to 10 μm.
[0044]
Here, the image forming apparatus of the present invention that forms an image by an electrophotographic process using the above-described photoreceptor will be described.
FIG. 1 is a schematic view showing an example of an image forming unit according to the image forming apparatus of the present invention.
With reference to FIG. 1, the configuration of the exemplified image forming unit and the image forming process will be described. In the illustrated image forming unit, an image is formed on the recording paper by charging, exposure, development, and transfer, which are image forming processes according to a normal electrophotographic system.
Here, the photosensitive member 1 on which an image is written with a laser beam (indicated as L in FIG. 1) has a drum shape. The photoreceptor 1 may be a sheet or endless belt other than the drum.
As means for performing an operation in accordance with the electrophotographic process on the drum-shaped photosensitive member 1, as shown in FIG. 1, a charge eliminating lamp 2, a charging charger 3, an eraser 4, An image exposure unit 5, a developing unit 6, a pre-transfer charger 7, a transfer charger 10, a separation charger 11, a separation claw 12, a pre-cleaning charger 13, a fur brush 14, and a cleaning brush 15 are provided around the photosensitive drum. For the charging charger 3, the pre-transfer charger 7, the transfer charger 10, the separation charger 11, and the pre-cleaning charger 13, known means such as a corotron, a scorotron, a solid state charger, and a charging roller are used. It is done. As shown in the figure, the transfer means using the transfer charger 10 and the separation charger 11 in combination is effective, but a general means having only the transfer charger may be used.
[0045]
Here, the image exposure unit 5 shown in a simplified manner in FIG. 1 will be described.
In FIG. 1, a drum-shaped photosensitive member 1 is spot-exposed by a laser beam L that is rotated (sub-scanned) in the direction indicated by an arrow A in FIG. And generate a latent image there. The operation of the image exposure unit 5 is performed by a laser beam writing device.
FIG. 2 shows an example of a laser beam writing apparatus used in the image forming apparatus of this example. Referring to FIG. 2, the laser beam writing apparatus includes an image writing control unit 21, a polygon motor control unit 25, and a stepping motor control unit 23 under the control of a printer control unit 22 that controls the entire image forming apparatus.
According to the control operation of the printer control unit 22, the image writing control unit 21 controls the lighting of the LD 26 according to the captured image data. The light beam emitted from the LD 26 is deflected by the polygon mirror 4 that rotates at a constant speed (FIG. 2, arrow C) by the polygon motor control unit 5 through an imaging optical system (not shown), and then by the fθ lens 28. An image is formed as a light spot having a constant small diameter on the photosensitive drum 1, and the photosensitive surface is subjected to main scanning at a constant speed (arrow B in FIG. 2) to write light beams.
At this time, writing in the main line scanning direction starts in accordance with a timing signal LGATE generated based on a synchronization signal generated by detecting a beam by the synchronization detection sensor 27 provided at a fixed position. On the other hand, writing in the sub-scanning direction (FIG. 2, arrow A) is performed according to a writing timing signal determined based on a reference position in the drum rotation direction on the photosensitive drum 1 whose rotation is controlled by the stepping motor control unit 23. Its start is controlled.
[0046]
The image writing control unit 21 is transmitted from an image input device (for example, a scanner or a printer controller that receives externally generated print data via an I / F) that generates image data serving as a source of a written image. A modulation signal for controlling the light emission of the LD 26 is generated based on the image data, and an LD driver drives the LD 26 with the modulation signal to generate a beam carrying an image. Here, since a method is used in which spot exposure is performed by a laser beam from the LD 26 and an image is expressed by pixel dots, a modulation signal corresponding to this method is generated, and light emission of the LD 26 is controlled. In the method of expressing an image with pixel dots, when density adjustment or gradation expression is used, the recording density is changed by changing the pixel dots to a certain size (diameter), or the size of the pixel dots is changed. Therefore, the optical output is modulated according to such a method. In the case of a method of changing the size of pixel dots, a method of modulating the light output with the lighting time (pulse width: PWM modulation), an intensity modulation method, or the like is employed.
By the way, as a light source for generating the laser beam L used for writing in the image forming apparatus, various semiconductor lasers (LD) having different generation wavelengths can be used. As a light source for writing, it is desirable to reduce the beam spot diameter in order to improve the image quality, and at present, the light source is shifting to the short wavelength side.
When these various wavelength LDs are used for writing in the image forming apparatus, the size L of the exposure spot diameter formed on the photosensitive surface (= the minor axis length of the exposure spot) is expressed by the above conditional expression (1), that is,
0.1 <3.75 × 10^-3L / λ <d / λ <0.5
To be determined according to
In order to make a setting that satisfies this conditional expression, first, a method of adjusting and controlling the light emission of the LD by the image writing control unit 21 is adopted. That is, the minor axis length of the exposure spot is adjusted by changing the setting when the LD is subjected to lighting time modulation (PWM modulation) or intensity modulation. Second, a method of adjusting the short axis length of the exposure spot by finely adjusting the arrangement of elements constituting the scanning optical system and changing the imaging condition may be employed.
[0047]
Although FIG. 1 is illustrated as an embodiment relating to the image forming apparatus of the present invention, the image forming process on the photosensitive member 1 includes a transfer step, a static elimination step, and a cleaning using light irradiation in addition to the steps shown in FIG. There may be a case where an apparatus configuration in which various kinds of light are irradiated by providing a process or a process such as pre-exposure may be employed, and such an embodiment may be implemented. Further, the toner developed on the photosensitive member 1 by the developing unit 6 is transferred to the transfer paper 9 fed through the registration roller 8, but not all is transferred, and the toner remaining on the photosensitive member 1 is also not transferred. Arise. Such toner is removed from the photoreceptor by the fur brush 14 and the blade 15. Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.
Further, when a positive (negative) charge is applied to an electrophotographic photoreceptor and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photoreceptor. When this is developed with negative (positive) polarity toner (electrodetection fine particles), a positive image can be obtained, and when developed with positive (negative) polarity toner, a negative image can be obtained. A known method is applied to the developing unit, and a known method is also used for the charge eliminating unit.
The image forming unit shown in FIG. 1 as an embodiment described above may be fixedly incorporated in a copying machine, a facsimile, or a printer, but a part of the image forming unit may be used as a replacement part in the form of a removable process cartridge. You may make it comprise by the system built in.
FIG. 3 shows an example of an embodiment implemented as a process cartridge. As shown in FIG. 3, the process cartridge includes a photosensitive member 16, a charging charger 17, an image exposing unit 19, a developing unit including a developing roller 20, a transfer unit, a cleaning unit including a cleaning brush 18, a static eliminating unit. A unit (not shown) is provided as an element to constitute one device (part). In the embodiment shown in FIG. 3, in addition to the photosensitive member, the cartridge that integrally holds the charging unit (charging charger 17), the developing unit, and the cleaning unit is illustrated, but at least one unit of the charging unit, the developing unit, and the cleaning unit is illustrated. The cartridge may be configured in such a manner as to be integrated with the photosensitive member.
[0048]
  Next, the exampleAnd reference examplesThe present invention will be described in more detail. In addition,theseAll parts used in the examples represent parts by weight.
  "referenceExamples 1-3 "
  First, follow the instructions belowreferenceThe electrophotographic photosensitive member used in Examples 1 to 3 was obtained.
  The following components were mixed in a φ30 mm aluminum drum as a conductive support substrate, ball milled, applied by an immersion method, and dried by heating to form a 3.5 μm intermediate layer.
  [Coating liquid for intermediate layer]
・ Alkyd resin (Beccosol 1307-60-EL, manufactured by Dainippon Ink and Chemicals) 6 parts
・ Melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals) 4 parts
・ Titanium oxide (CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) 40 parts
・ Methyl ethyl ketone 200 parts
  Next, a charge generation layer having a thickness of 0.2 μm was formed by applying the following charge generation layer coating solution on the intermediate layer formed in the above step by a dipping method and heating and drying.
  [Coating liquid for charge generation layer]
  The following components were mixed and dispersed with a ball mill.
-Disazo compound having the structure shown in the following formula (X) 5 parts
・ Polyvinyl butyral (S-REC BL-S, manufactured by Sekisui Chemical Co., Ltd.) 1.5 parts
・ Cyclohexanone 120 parts
・ Methyl ethyl ketone 120 parts
[0049]
[Chemical Formula 10]

[0050]
Next, the following charge transport layer coating solution was applied on the charge generation layer formed in the above step by a dipping method and dried by heating to form a charge transport layer having a thickness of 19 μm.
[Coating liquid for charge transport layer]
The following components were mixed and dissolved to obtain a charge transport layer coating solution.
-7 parts of charge transport material (ionization potential: 5.50 eV) having the structure shown in the following formula (XI)
・ Polycarbonate (Z Polyca, Mv50,000 manufactured by Teijin Chemicals Ltd.) 10 parts
・ 100 parts of methylene chloride
・ 1% silicone oil (KF50, Shin-Etsu Silicone) methylene chloride solution 1 part
[0051]
Embedded image

[0052]
  Next, on the charge transport layer formed in the above step, the following components are put into a hard glass pot with a diameter of 9 cm, and ball mill dispersion is performed for 96 hours using a zirconia bead with a diameter of 2 mm. Coated and provided with a 2.5μm protective layerreferenceAn example electrophotographic photoreceptor was obtained.
・ Polycarbonate resin (Z Polyca, Tv Kasei Mv50,000) 5 parts
・ Alumina (manufactured by Sumitomo Chemical) 2 parts
・ Charge transport material with the structure shown in the following formula (XII) (ionization potential: 5.39 eV) 3 parts
・ Cyclohexanone 200 parts
[0053]
Embedded image

[0054]
  The average particle diameter of alumina after forming the protective layer was measured from a cross-sectional TEM photograph and found to be 0.30 μm.
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, and A paper passing test of up to 120,000 sheets was conducted using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  thisreferenceIn the example, the minor axis length L of the exposure spot diameter on the photoreceptor surface is changed,referenceIn Example 1, 70 μm,referenceIn Example 2, 50 μm,referenceIn Example 3, the thickness was 20 μm.
  referenceFor each of Examples 1 to 3, the following items were evaluated after 120,000 sheets were passed.
  -Photoreceptor film thickness reduction amount ... The film thickness reduction amount after the paper passing test was measured with a Fischer Corp. MMS manufactured by Fischer Corporation.
  ・ In-machine potential (exposure part potential) ... The transition of the exposure part potential when the charging potential was -600V was evaluated.
  ・ Image quality: Comprehensive evaluation of output image solid density, local defects such as black spots, background stains, abnormal images, etc., in three stages: “Good”, “Slightly low quality”, “Poor quality” Classified.
  ・ Resolution ………… Creates an independent 1-dot image at 1200 dpi, and evaluates the reproducibility of the dots on the image under a microscope. There are three stages: “good”, “slightly reproducible”, and “poor reproducibility”. Classified.
  -Fine line reproducibility ... Fine line writing was performed, and the reproducibility on the image was evaluated and classified into three stages: "good", "slightly reproducible decrease", and "poor reproducibility".
  The evaluation results are shown in Table 1 below.
[0055]
[Table 1]

[0056]
  "referenceExample 4, 5 "
  thesereferenceAn example is inorganic filler added to the protective layer.referenceThis is a different material from Example 1.
  referenceThe electrophotographic photoreceptor used in Example 4 was obtained as follows.
  referenceWhen preparing the photoconductor used in Example 1, the alumina (used by Sumitomo Chemical Co., Ltd.) used for the protective layer is replaced with titanium oxide (made by Ishihara Sangyo), and the dispersion condition of the protective layer coating solution is 2 mm in diameter. Except for changing from zirconia beads to PSZ balls with a diameter of 5 mm and changing the ball mill dispersion time from 96 hours to 120 hours,referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 4 was produced.
  The average particle diameter of the titanium oxide after the formation of the protective layer was measured from a cross-sectional TEM photograph and found to be 0.25 μm.
  Also,referenceThe electrophotographic photoreceptor used in Example 5 was obtained as follows.
  referenceWhen preparing the photoreceptor used in Example 1, the dispersion condition of the protective layer coating solution was changed to zirconia having a diameter of 2 mm by replacing the alumina used in the protective layer (manufactured by Sumitomo Chemical) with silica (manufactured by Nippon Aerosil). Except for changing from beads to 1cm diameter alumina balls and changing the ball mill dispersion time from 96 hours to 144 hours,referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 5 was produced.
  The average particle diameter of the silica after the formation of the protective layer was measured from a cross-sectional TEM photograph and found to be 0.20 μm.
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, and A paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  referenceIn Examples 4 and 5, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  referenceFor each of Examples 4 and 5, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in Table 2 below.
[0057]
[Table 2]

[0058]
  "referenceExamples 6-8 "
  referenceExamples 6 to 8 show [charge generation layer coating solution] for forming the charge generation layer.referenceThe components are different from those in Example 1.
  referenceThe electrophotographic photoreceptor used in Examples 6 to 8 was obtained as follows.
  reference[Coating solution for charge generation layer] in the photoreceptor used in Example 1 was changed as follows.
・ Y-type oxytitanyl phthalocyanine 8 parts
・ Polyvinyl butyral 5 parts
・ 2-butanone 400 parts
  Except for forming a charge generation layer having a thickness of 0.2 μm by applying this charge generation layer coating solution by a dipping method and heating and drying,referenceExactly the same as the photoreceptor used in Example 1.referencePhotoconductors used in Examples 6 to 8 were prepared.
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 780 nm, and A paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  thisreferenceIn the example, the minor axis length L of the exposure spot diameter on the photoreceptor surface is changed,referenceIn Example 6, 75 μm,referenceIn Example 7, 60 μm,referenceIn Example 8, it was 20 μm.
  referenceFor each of Examples 6 to 8, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in Table 3 below.
[0059]
[Table 3]

[0060]
  "referenceExample 9, 10 "
  thesereferenceAn example is inorganic filler added to the protective layer.referenceThe material was changed to a different material from Example 6.
  referenceThe electrophotographic photoreceptor used in Example 9 was obtained as follows.
  referenceWhen producing the photoconductor used in Example 6, the dispersion condition of the protective layer coating solution was changed to 2 mm in diameter by replacing the alumina used in the protective layer (manufactured by Sumitomo Chemical) with titanium oxide (manufactured by Ishihara Sangyo). Except for changing from zirconia beads to PSZ balls with a diameter of 5 mm and changing the ball mill dispersion time from 96 hours to 120 hours,referenceExactly the same as the photoreceptor used in Example 6.referenceThe photoreceptor used in Example 9 was produced.
  The average particle diameter of the titanium oxide after the formation of the protective layer was measured from a cross-sectional TEM photograph and found to be 0.25 μm.
  Also,referenceThe electrophotographic photoreceptor used in Example 10 was obtained as follows.
  referenceWhen preparing the photoreceptor used in Example 6, the dispersion condition of the coating solution for the protective layer was changed to zirconia having a diameter of 2 mm by replacing alumina (manufactured by Sumitomo Chemical) used in the protective layer with silica (manufactured by Nippon Aerosil). Except for changing from beads to 1cm diameter alumina balls and changing the ball mill dispersion time from 96 hours to 144 hours,referenceExactly the same as the photoreceptor used in Example 6.referenceThe photoreceptor used in Example 10 was produced.
  The average particle diameter of the silica after the formation of the protective layer was measured from a cross-sectional TEM photograph and found to be 0.20 μm.
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 780 nm, and A paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  referenceIn Examples 9 and 10, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  referenceFor each of Examples 9 and 10, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  These evaluation results are shown in Table 4 below.
[0061]
[Table 4]

[0062]
  "referenceExamples 11-16 "
  referenceExamples 11 to 16 are examples of a photosensitive layer or a protective layer constituting the photosensitive member.referenceThe components are different from those in Example 1.
  referenceThe electrophotographic photoreceptor used in Example 11 was obtained as follows.
  referenceExcept that the charge transport material used in the protective layer was not added when producing the photoreceptor used in Example 1,referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 11 was produced.
  Also,referenceThe electrophotographic photoreceptor used in Example 12 was obtained as follows.
  referenceWhen producing the photoreceptor used in Example 1, instead of providing a charge generation layer and a charge transport layer, a photosensitive layer having a single-layer structure having a thickness of 25 μm was formed using a photosensitive layer coating solution having the following components: IsreferenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 12 was produced.
  [Coating solution for photosensitive layer]
  The following components were mixed and dispersed with a ball mill.
・ 5 parts of a disazo compound having the structure shown in the above formula (X)
-50 parts of charge transport material having the structure shown in the above formula (XII)
・ Z-type polycarbonate (molecular weight 60,000) 97 parts
・ Tetrahydrofuran 328 parts
  Also,referenceThe electrophotographic photoreceptor used in Example 13 was obtained as follows.
  referenceWhen producing the photoreceptor used in Example 1, except that the charge transport material used in the charge transport layer was changed to the following:referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 13 was produced.
・ 7 parts of charge transport material with the structure shown in the above formula (XII)
  Also,referenceThe electrophotographic photoreceptor used in Example 14 was obtained as follows.
  referenceExcept that the charge transport material used in the protective layer was changed to the following when producing the photoreceptor used in Example 1,referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 14 was produced.
・ Charge transport material with the structure shown in the following formula (XIII) (ionization potential: 5.3eV) 3 parts
[0063]
Embedded image

[0064]
  Also,referenceThe electrophotographic photoreceptor used in Example 15 was obtained as follows.
  referenceExcept that the charge transport material used in the protective layer was changed to the following when producing the photoreceptor used in Example 1.referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 15 was produced.
・ Part 3 of the charge transport material with the structure shown in the above formula (XI)
  Also,referenceThe electrophotographic photoreceptor used in Example 16 was obtained as follows.
  referenceExcept that the binder resin used in the protective layer was replaced with polyarylate (U100, manufactured by Unitika) when producing the photoreceptor used in Example 1.referenceExactly the same as the photoreceptor used in Example 1.referenceThe photoreceptor used in Example 16 was produced.
  Each electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: Imageo MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, In addition, a paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photosensitive member could be varied.
  referenceIn Examples 11 to 16, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  referenceFor each of Examples 11 to 16, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in Table 5 below.
[0065]
[Table 5]

"Example1"
  Example1Are those in which the photosensitive layer of the photoconductor, the constituent components of the protective layer, and the wavelength of the laser beam used for exposure on the photoconductor surface are changed.
  Example1The electrophotographic photoreceptor used in 1 was obtained as follows.
  referenceA charge generation layer having a thickness of 0.2 μm was formed on the intermediate layer formed in the same manner as in Example 1 by applying the following coating solution for charge generation layer by a dipping method and heating and drying.
  [Coating liquid for charge generation layer]
  The following components were mixed and dispersed by a ball mill, and this dispersion was used as a charge generation layer coating solution.
・ Y-type oxotitanium phthalocyanine 1.5 parts
・ Polyvinyl butyral (S-REC BL-S: Sekisui Chemical Co., Ltd.) 1 part
・ 220 parts of cyclohexanone
・ Methyl ethyl ketone 220 parts
  On the charge generation layer, the following charge transport layer coating solution was applied by a dipping method and dried by heating to form a charge transport layer having a thickness of 19 μm.
  [Coating liquid for charge transport layer]
  The following components were mixed and dissolved to form a charge transport layer coating solution.
・ 7 parts of charge transport material with the structure shown below (XIV)
・ Polycarbonate (Z Polyca, Mv50,000 manufactured by Teijin Chemicals Ltd.) 10 parts
・ 100 parts of methylene chloride
・ 1% silicone oil (KF50 Shin-Etsu Silicone) methylene chloride solution 1 part
Embedded image

  Next, on the charge transport layer formed in the above step, the following components were put into a hard glass pot having a diameter of 9 cm, and ball mill dispersion was performed for 48 hours using an alumina ball having a diameter of 1 cm to obtain a coating solution for a protective layer.
  This solution was applied by spraying to provide a 2.6 μm protective layer to obtain an electrophotographic photoreceptor of this example.
・ Polycarbonate resin (Z Polyca, Mv50,000 manufactured by Teijin Chemicals Ltd.) 5 parts
・ Alumina (manufactured by Sumitomo Chemical) 2 parts
・ Part 3 of the charge transport material with the structure shown in (XIV) above
・ Cyclohexanone 200 parts
  The average particle diameter of alumina after the formation of the protective layer was measured from a cross-sectional TEM photograph and found to be 0.20 μm.
  The wavelength of the writing laser beam for image exposure based on the electrophotographic photoconductor Imagio MF2200 [manufactured by Rico Co., Ltd.] based on the electrophotographic photoconductor produced in the above process is 405 nm, and the exposure spot on the photoconductor surface A paper passing test was conducted up to 120,000 sheets using an image forming apparatus in which the optical unit was modified so that the diameter could be changed.
  Example1In this case, the minor axis length L of the exposure spot diameter on the surface of the photoconductor is 15 μm. After the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in Table 6 below.
[Table 6]

[0066]
  Next, a comparative example based on a setting condition that does not satisfy the above formula (1) of the present invention will be shown.referenceCheck the effect of the example. In addition, all the parts used in a comparative example represent a weight part.
  "Comparative Example 1"
  The electrophotographic photosensitive member used in Comparative Example 1 was obtained in the following manner.
  referenceExcept that the alumina used in the protective layer (manufactured by Sumitomo Chemical Co., Ltd.) was not added when producing the photoreceptor used in Examples 1 to 3.referenceA photoconductor used in Comparative Example 1 was prepared in exactly the same manner as the photoconductor used in Examples 1-3.
  The electrophotographic photosensitive member thus produced is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, In addition, a paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photosensitive member could be varied.
  In Comparative Example 1,referenceAs in Example 2, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  For Comparative Example 1, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in the table below.7Shown in
[0067]
[Table 7]

[0068]
  This evaluation resultreferenceCompared with Example 2, the numerical values of the film thickness reduction amount and the exposed portion potential are different, and the image quality and fine line reproducibility are poor, and the effect of alumina added in the protective layer can be confirmed.
[0069]
  “Comparative Example 2”
  An electrophotographic photoreceptor used in Comparative Example 2 was obtained in the following manner.
  referenceWhen preparing the photoreceptor used in Examples 1 to 3, the dispersion condition of the protective layer coating solution was changed from 2 mm diameter zirconia beads to 2 mm diameter PSZ balls, and the ball mill dispersion time was changed from 96 hours to 24 hours. Except for changes,referenceA photoconductor used in Comparative Example 2 was produced in the same manner as the photoconductor used in Examples 1 to 3.
  When the average particle diameter of the alumina after the formation of the protective layer was measured from a TEM photograph of the cross section, 0.50 μm (referenceIn Examples 1 to 3, it was 0.30 μm).
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, and A paper passing test of up to 120,000 sheets was conducted using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  In Comparative Example 2,referenceAs in Example 2, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  For Comparative Example 2, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in the table below.8Shown in
[0070]
[Table 8]

[0071]
  This evaluation resultreferenceCompared with Example 2, the value of the exposure part potential is markedly different. In Comparative Example 2, d / λ = 0.76, which greatly exceeds 0.5, and the image quality and fine line reproducibility are poor. The effect of the setting conditions satisfying the relationship d / λ <0.5 between the average particle diameter of alumina added to the layer and the wavelength used can be confirmed.
[0072]
  “Comparative Example 3”
  referenceThe electrophotographic photosensitive member used in Comparative Example 3 was obtained in the same manner as in the production of the photosensitive member used in Examples 1-3.
  The electrophotographic photosensitive member thus produced is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, In addition, a paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photosensitive member could be varied.
  In Comparative Example 3, the minor axis length L of the exposure spot diameter on the photosensitive member surface was 85 μm (referenceIt was larger than L = 70 μm in Example 1).
  For Comparative Example 3, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in the table below.9Shown in
[0073]
[Table 9]

[0074]
  This evaluation resultreferenceIn contrast to Example 1, the difference in the numerical value of the exposure part potential is shown, and in Comparative Example 3, 3.75 × 10^-3At L / λ = 0.49, it exceeded d / λ = 0.46, which showed poor reproducibility in resolution and slight decrease in fine line reproducibility, 3.75 × 10^-3Effect by setting conditions satisfying L / λ (numerical value related to wavelength used for short axis length of exposure spot diameter) <d / λ (numerical value related to wavelength used for average particle diameter of alumina added in protective layer) Can be confirmed.
[0075]
  “Comparative Example 4”
  The electrophotographic photoreceptor used in Comparative Example 4 was obtained in the following manner.
  referenceWhen preparing the photoreceptor used in Examples 1 to 3, the dispersion condition of the protective layer coating solution was changed from zirconia beads having a diameter of 2 mm to stainless balls having a diameter of 1 cm, and the ball mill dispersion time was changed from 96 hours to 179 hours. Except for changes,referenceA photoconductor used in Comparative Example 4 was produced in the same manner as the photoconductor used in Examples 1-3.
  In addition, when the average particle diameter of the alumina after forming this protective layer was measured from the TEM photograph of the cross section, it was 0.10 μm (referenceIn Examples 1 to 3, it was 0.30 μm).
  The electrophotographic photosensitive member produced in the above process is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, and A paper passing test of up to 120,000 sheets was conducted using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photoreceptor could be varied.
  In Comparative Example 4,referenceAs in Example 2, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 50 μm.
  For Comparative Example 4, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in the table below.10Shown in
[0076]
[Table 10]

[0077]
  This evaluation resultreferenceIn contrast to Example 2, the numerical value of the film thickness reduction amount shows a difference and a decrease in durability is shown. In Comparative Example 4, d / λ = 0.15, which is 3.75 × 10^-3It is even smaller than L / λ = 0.29, showing poor image quality and a slight decrease in fine line reproducibility, 3.75 × 10^-3Effect by setting conditions satisfying L / λ (numerical value related to wavelength used for short axis length of exposure spot diameter) <d / λ (numerical value related to wavelength used for average particle diameter of alumina added in protective layer) Can be confirmed.
[0078]
  "Comparative Example 5"
  referenceThe electrophotographic photosensitive member used in Comparative Example 5 was obtained in the same manner as in the production of the photosensitive member used in Examples 1-3.
  The electrophotographic photosensitive member thus produced is an image forming apparatus based on an electrophotographic copying machine: IMAGIO MF2200 (manufactured by Rico Co., Ltd.), that is, the wavelength of a writing laser beam for image exposure is 655 nm, In addition, a paper passing test of up to 120,000 sheets was performed using an apparatus in which the optical unit was modified so that the exposure spot diameter on the surface of the photosensitive member could be varied.
  In Comparative Example 5, the minor axis length L of the exposure spot diameter on the photoreceptor surface was 10 μm (referenceIt was further smaller than L = 20 μm in Example 3).
  For Comparative Example 5, after the paper passing test,referenceEvaluation similar to Example 1 was performed.
  The evaluation results are shown in Table 1 below.1Shown in
[0079]
[Table 11]

[0080]
  This evaluation resultreferenceIn contrast to Example 3, Comparative Example 3 has 3.75 × 10^-3L / λ = 0.06, which is smaller than 0.1, and poor thin line reproducibility appears, 0.1 <3.75 × 10^-3The effect of the setting condition satisfying L / λ (a numerical value related to the wavelength used with respect to the short axis length of the exposure spot diameter) can be confirmed.
[0081]
【The invention's effect】
  (1) Effect on the invention of claim 1
  A value indicating the relationship between the short axis length L of the exposure spot and the wavelength λ of the light beam used for exposure, (3.75 × 10^-3If L / λ) is not less than 0.1, it becomes difficult to be affected by irregular reflection due to the roughness on the surface of the photoreceptor when forming a latent image, and there is no problem with fine line reproducibility. 3.75 × 10^-3If L / λ) is not larger than d / λ indicating the relationship between the average particle diameter d of the inorganic filler contained in the protective layer and the wavelength λ of the light beam used for exposure, the resolution will not be reduced. If the wear resistance and durability of the photoconductor do not deteriorate and the d / λ value is not set to 0.5 or more, the increase in the residual potential after exposure to the photoconductor will increase, and the potential of the exposed area during image formation will increase. Therefore, it is possible to determine the condition that there is no problem in wear resistance, and it is possible to achieve high image quality, long life, and high reliability at a high level.or 400 ~ 450nm By using a semiconductor laser having a wavelength of 1, it is possible to achieve high resolution and compact equipment.
  (2) Effect on the invention of claim 2
  Short axis length of the exposure spot on the photoreceptor surface L But Ten ~ 40 μ m The effect of diffuse reflection ( L Without receiving)Thus, it is possible to achieve both the wear resistance and the image quality and achieve the effect (1) at a high level.
  (3) Effect on invention of claim 3
UpEffect of (1) and (2)Embodied in an image forming apparatus having a process cartridgeIt becomes possible to do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of an image forming unit according to an image forming apparatus of the present invention.
FIG. 2 is a schematic view showing an example of a laser beam writing apparatus according to the image forming apparatus of the present invention.
FIG. 3 shows an example of an embodiment implemented as a process cartridge.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 5 ... Image exposure part,
26: LD (laser diode).

Claims (3)

An image forming apparatus comprising: a photosensitive member; and an exposure unit that spot-exposes the photosensitive member by scanning a light beam from a light source whose light output is modulated by image data and generates an electrostatic latent image on the photosensitive surface. The photoreceptor has a photosensitive layer containing a charge generation material and a charge transport material on a conductive substrate, and a protective layer composed of an inorganic filler and a binder resin. The average particle diameter of the inorganic filler is d, the light beam Wavelength: λ, short axis length of exposure spot on photosensitive surface: L
0.1 <3.75 × 10 ^-3 L / λ <d / λ <0.5
Determined to have a value that satisfies the relationship, the image forming apparatus according to claim Rukoto using a semiconductor laser having a wavelength of said light beam having a wavelength of 400 ~ 450 nm as a light source. 2. The image forming apparatus according to claim 1, wherein a short axis length L of the exposure spot is 10 to 40 [ mu] m . 3. The image forming apparatus according to claim 1 , further comprising a process cartridge that integrally supports the photosensitive member and at least one of a charging unit, a developing unit, and a cleaning unit. Image forming apparatus.

Images