JP2004061560A - Image forming apparatus and processing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a processing unit performing cleaning to such an extent that influence is not exerted on image formation even in the case of a toner having an average circularity of 0.98 or 0.99, and stably maintaining a high-quality image free from unevenness, excellent in image density and having stability. <P>SOLUTION: In the image forming apparatus using an indirect electrophotographic method where an electrophotographic photoreceptor, an electrifying device, an image exposure device, a developing device, a transfer device, a cleaning device and a fixing device are arranged at suitable positions so as to perform image formation, the electrophotographic photoreceptor is constituted by laminating an undercoating layer, a charge generating layer and a charge transporting layer on a conductive supporting body, and the charge transporting layer is at least an organic photosensitive layer. The apparatus is equipped with an elastic cleaning blade whose edge part served for toner removal while abutting on the electrophotographic photoreceptor has V shape or acute shape like a knife edge and which is arranged to counter abut on the electrophotographic photoreceptor. <P>COPYRIGHT: (C)2004,JPO

Description

ポリビニルブチラール　　　　　　　　　　　　　　　　　　　２部
２−ブタノン　　　　　　　　　　　　　　　　　　　　　２００部
シクロヘキサノン　　　　　　　　　　　　　　　　　　　４００部
〔フィラー非分散電荷輸送層用塗工液〕
ビスフェノールＺ型ポリカーボネート　　　　　　　　　　　１０部
（帝人化成社製：Ｚポリカ　Ｍｖ５万）
下記構造の低分子電荷輸送物質　　　　　　　　　　　　　　　８部
【００９７】
【化２】

テトラヒドラフラン　　　　　　　　　　　　　　　　　２００部
【００９８】
２）フィラー分散電荷輸送層を有する感光体の作製
フィラー非分散電荷輸送層を塗布した有機感光体を加熱乾燥した後冷却し、引き続き、スプレー塗工法でフィラー分散電荷輸送層を２〜１０μｍの間で塗工した。
なお、冷却後引き続きフィラー分散電荷輸送層を塗工したのは、溶媒により界面が解け合い、明確な界面を形成させないためであるが、一晩程度の放置では殆ど問題はない。しかし、数週間放置すると酸化により、局部的にバリアができ、画像品質に悪影響が出やすい。
フィラー非分散電荷輸送層上に、下記記載のバインダー樹脂（ビスフェノールＺ型ポリカーボネート樹脂）と低分子電荷輸送物質（ドナー）、一次粒径が０．２、０．３、０．５、０．７および１μｍの５種類の無機フィラー（α−アルミナ）を用意し、夫々の無機フィラーと分散助剤及び溶剤を硝子ポットに入れ、ボールミルで２４時間分散させて塗工液を作り、スプレー法を用いて１〜５回往復させ、フィラー分散電荷輸送層を塗工した。触指乾燥の後、１５０℃２０分間加熱乾燥させて、フィラー分散電荷輸送層を有する評価用電子写真感光体を作製した。
【００９９】
［フィラー分散電荷輸送層塗工液］（フィラー添加量２５重量％の場合を例示する）
ビスフェノールＺ型ポリカーボネート　　　　　　　　　　１０部
（帝人化成社製：Ｚポリカ　Ｍｖ５万）
下記構造式の電荷輸送物質　　　　　　　　　　　　　　　　　７部
【０１００】
【化３】

アルミナフィラー　　　　　　　　　　　　５．７部（２５重量％の場合）
（住友化学工業製ＡＡ−０２〜ＡＡ−１０、
平均一次粒径：０．２〜１．０μｍ、比抵抗≒２．５×１０^１２Ω・ｃｍ）
テトラヒドロフラン　　　　　　　　　　　　　　　　　４００部
シクロヘキサノン　　　　　　　　　　　　　　　　　　２００部
分散助剤　　　　　　　　　　　　　　　　　　　　　０．０８部
（ＢＹＫ−Ｐ１０４　ビックケミージャパン製）
作製した感光体の特性一覧を表１に示す。
【０１０１】
【表１】

【０１０２】
＜帯電部材＞
１）接触帯電用の帯電部材
本発明の実施例に記載の帯電部材は、６ｍｍの真鍮製ロット棒にカーボンを均一分散し、電気抵抗を６×１０^５Ω・ｃｍ（１００ＶＤＣ印加時）に調整したエピクロルヒドリンゴムを３ｍｍの厚さになるように塗布して研磨し、その層上にエピクロルヒドリンゴムにカーボン、シリカ、フッ素樹脂を分散し電気抵抗が（３〜５）×１０^８Ω・ｃｍ（１００ＶＤＣ印加時）になる様に調合したエピクロルヒドリンゴムを厚さ１ｍｍに均一塗布して、φ１４ｍｍ×３１４ｍｍ（有効帯電幅：３１２ｍｍ）の寸法形状にしたものである。（電子写真複写機　イマジオＭＦ２２００に使用）
【０１０３】
２）非接触帯電用の帯電部材
８ｍｍの真鍮製ロット棒に電気抵抗が（４〜６）×１０^５Ω・ｃｍ（１００ＶＤＣ印加時）となるカーボン、シリカ、フッ素樹脂を分散したエピクロルヒドリンゴムを、φ６ｍｍの真鍮製ロット棒に厚さが１ｍｍとなる様に塗布したφ１０ｍｍ×３２７ｍｍ（有効帯電幅：３０８ｍｍ）の帯電部材を作製した。この帯電部材の両端部から１．５ｍｍ内側に、厚さ４９μｍ、幅８ｍｍ、長さ３１ｍｍの菱形にカットしたＰＥＴ（ポリエチレンテレフタレート）を張り付けスペーサーとした非接触帯電部材を作製した。感光体と帯電部材間の距離は平均で５３μｍであった。（カラーレーザービームプリンタ　イプシオカラー８０００に使用）
【０１０４】
＜制振部材＞
制振材の材料に損失正接ｔａｎδが０．８のブチルゴムを用い、金型成型により作製した。
形成後の弾性体Ａの寸法は、肉厚部がφ２４．７ｍｍ、肉薄部がφ１２．７ｍｍ、肉厚部の中央部にフランジの電極用の凹み（φ２２ｍｍ、深さ６ｍｍ）を形成した円柱状の制振部材、弾性体Ｂは肉薄部が２ｍｍｔ、肉厚部が８ｍｍｔで、外形が２８．２ｍｍの円筒状制振部材であった。長さは弾性体Ａ、Ｂとも３１２ｍｍであった。なお、感光体の内径は２８．５ｍｍである。
感光体に挿入する前に弾性体Ａの外側、および弾性体Ｂの外側にフッ素系潤滑剤（ＰＴＦＥ粉末　商品名ルブロンＬ−５　ダイキン工業製）を不織布につけてほぼ均一に塗り、あらかじめ片側にフランジをセットしておいた感光体の中に弾性体Ｂを挿入し、次に、弾性体Ａを挿入し、弾性体Ａを軽くたたきながら完全に挿入した後、反対側のフランジをセットした。感光体へのセット状態は図２５の通りである。
【０１０５】
＜感光体表層の摩擦係数低減化方法＞
本発明では、トナー中にステアリン酸亜鉛を０．０２重量％添加することによって、現像剤を介して感光体表層に潤滑剤を付与する方法で行なった。
【０１０６】
＜現像剤＝キャリア＋トナー＞
キャリアには、重量平均粒径５８μｍの磁性キャリア（ＦＰＣ−３００ＬＣ）を使用した。
乳化重合法で作製された重量平均粒径が約４．６μｍで、平均円形度０．９８１〜０．９８７の球形トナー（イエロー、マゼンタ、シアン、ブラック）をトナー［１］とする
粉砕法で作製された重量平均粒径６．３μｍ、平均円形度０．９１４のトナーをトナー［２］とする。
これらのトナーはキャリアに対して５重量％の割合で添加して現像剤とした。
これらのトナーには感光体表層の摩擦係数を低減化させる手段として、ステアリン酸亜鉛が０．０２重量％含有される。
【０１０７】
＜クリーニングブレード＞
クリーニングブレード［１］
ＪＩＳ−Ａ硬度７４度、８１度、８７度、９２度の４種のポリウレタンゴム製クリーニングブレードを金型成形によって作製した。形成後の寸法は板厚が２．８ｍｍ、高さ１５ｍｍ、長さ３２０ｍｍ、斜めカット部の長さが４ｍｍの台形状（形状は図２１の通り）である。感光体との当接部のバリをカットし、カット部の幅は約０．３ｍｍとなった。ＪＩＳ−Ａ硬度の測定はＪＩＳ　Ｋ　６３０１に準じて作製された（株）テクロックＧＳ−７０１Ｎを使用した。
前記ブレードを板厚０．８ｍｍで８度の角度に曲げた長さ３６３ｍｍの鉄板に、斜めカット部を感光体の回転方向の上流向き（転写装置側）にして、エポキシ系の２液性接着剤（アラルダイト８　２５４−０１　バンティコ社）を使用して、自由長が５ｍｍになるように接着しクリーニング部材を完成した。（電子写真複写機　イマジオＭＦ２２００に使用）
【０１０８】
クリーニングブレード［２］
ＪＩＳ−Ａ硬度が８７度のポリウレタンゴム製クリーニングブレードを、型によって作製した。形成後の寸法は板厚が２．８ｍｍ、高さ１０ｍｍ、長さ３２５ｍｍ、斜めカット部の長さが３ｍｍの台形状である。感光体との当接部のエッジはバリをカットし、カット部の幅は約０．２ｍｍとなった。形状は図２１の通りである。ＪＩＳ−Ａ硬度の測定はＪＩＳ　Ｋ　６３０１に準じて作製された（株）テクロックＧＳ−７０１Ｎを使用した。
そのブレードを板厚０．８ｍｍで直角に曲げた３２５ｍｍの鉄板に、エポキシ系の２液性接着剤（アラルダイト８　２５４−０１　バンティコ社）を使用して、斜めカット部を感光体の回転方向の上流向き（転写装置側）にして、自由長が４．５ｍｍになるように接着して、クリーニング部材を完成した。（カラーレーザービームプリンタ　イプシオカラー８０００に使用）
【０１０９】
＜評価方法＞
感光体およびクリーニングブレード用の評価機として、光源の発振波長を６５５ｎｍとするＬＤ素子を用いた接触帯電方式で、感光体と現像装置、クリーニングブレードが一体構成となったプロセスユニットを内蔵する、乾式電子写真複写機（イマジオＭＦ２２００、リコー製）、および非接触帯電方式、感光体とクリーニングブレードを一体構成とするプロセスユニットを内蔵する４連タンデム方式のカラーレーザービームプリンタ［ＣＬＢＰ］（イプシオカラー８０００、リコー製）を用意した。
評価用に用意した電子写真複写機（イマジオＭＦ２２００、リコー製）は帯電装置への高圧電源供給が直流電圧であるため、交流電圧が重畳可能な高圧電源（長野愛知電気製　タイプＨＶ−２５５）を別途用意し、標準設定の直流電源と切り替えながらの評価を実施した。
帯電部材に交流重畳直流電圧を印加するする場合には、交流電圧を１５００Ｖ／１３５０Ｈｚに固定し、直流電圧を調整して、現像装置位置での暗部電位を設定した。
カラーレーザービームプリンタは標準設定（デフォルト）の状態で使用し評価を行なった。
評価枚数はＡ４サイズ各５万枚（Ａ４サイズ）とし、初期の感光層膜厚と５万枚後の膜厚を渦電流式膜厚計（フィッシャー社製　タイプＭＭＳ）を使って測定し、感光層の摩耗量を評価した。
鉛筆硬度はＪＩＳ　Ｋ　５４０１に基づいて作製された鉛筆引っ掻き試験器（表面性測定器　新東科学社製　ＨＥＩＤＯＮ−１４型）とＪＩＳ規格標準鉛筆（三菱鉛筆“ユニ”）とを使用し、加重に１００ｇの分銅を用いて、測定用に作製した感光体を５０×８０（ｍｍ）の大きさに切断して測定した。
真円度、真直度は表面粗さ輪郭形状統合測定器（東京精密社製　サーフコム１４００Ｄ）を用いて、感光体長手方向１３カ所、周方向９０度毎に４カ所測定した。
摩擦係数の測定は、測定に供する感光体を台座に固定して、幅３０ｍｍ×長さ２９０ｍｍ×厚み８５μｍの上質紙（リコー社製、タイプ６２００ペーパー、縦目使用）をベルトとし、前記上質紙を感光体の周方向に乗せ、ベルト端部の一方に１００ｇｒのおもりを取り付け、もう一方の片端に重量測定用のデジタル・フォース・ゲージを取り付け、デジタル・フォース・ゲージをゆっくり引き、ベルトの移動開始時の重量を読みとり、オイラーの方式より導き出された下式より（静止）摩擦係数μｓを算出した。
μｓ＝２／π×ｌｎ（Ｆ／Ｗ）
ただし、μｓ：静止摩擦係数、Ｆ：読みとり荷重、Ｗ：分銅の重さ、π：円周率
画像品質評価は、電子写真複写機で評価する場合は、画像品質評価は、ＪＩＳＺ　６００８にしたがって作成された試験票板（コダック社製）を使用して解像度を評価し、別途用意したリコー製テストチャートでドットパターンの再現性及び地肌汚れの評価を実施した。
一方、カラーレーザービームプリンタで評価する場合は、別途用意したパソコンに入力した各種パターンを使用して、解像度、１ドットパターンの再現性、ノイズ、色むら等についての評価を行なった。
評価時以外の通紙ランニング中の原稿は両評価機とも画像面積６％の画像パターンを使用し、２２〜２４（℃）／５８〜６５（％ＲＨ）環境にて通紙ランニングを行なった。
評価は初期、１００枚後（摩擦係数測定のみ）、５万枚後に行なった。
【０１１０】
実施例１〜４
評価用の感光体として、表１に記載のＮｏ．４（実施例１）、Ｎｏ．５（実施例２）、Ｎｏ．６（実施例３）、Ｎｏ．７（実施例４）のサンプルを使用した。評価用に用意した電子写真複写機に搭載したこれらの感光体は、いずれも図２３の様な制振性の高い損失正接ｔａｎδが０．８の制振部材を密着内蔵したもので、真円度、真直度は夫々０〜２０μｍ、±２０μｍを満足したものである。
感光体に印加する現像装置位置での電界強度は、Ｎｏ．４のサンプルでは４．５×１０^５Ｖ／ｃｍ、Ｎｏ．５のサンプルでは３．０４×１０^５Ｖ／ｃｍ、Ｎｏ．６のサンプルでは２．３３×１０^５Ｖ／ｃｍ、Ｎｏ．７のサンプルでは２×１０^５Ｖ／ｃｍとして、５万枚の通紙ランニングを行なった。
感光体サンプルは、電荷発生層上に２〜２８（μｍ）の間で、４種類の膜厚を変えて塗布したフィラー非分散電荷輸送層上に、一次平均粒径が０．３μｍのα−アルミナをフィラー分散電荷輸送層の２５重量％になる様に添加して、２〜８μｍの膜厚に積層した。
フィラー分散電荷輸送層の電荷輸送層に対する膜厚の比率は８０％〜６．７％である。また、感光体の１０点平均粗度は０．４８μｍ台であり、鉛筆硬度はＨＢ〜Ｈであった。
【０１１１】
これらの感光体を硬度８１度に調整して作製されたクリーニングブレードを搭載し、感光体に対する当接圧が２４．０ｇ／ｃｍになる様に、評価用の電子写真複写機の感光体ユニットにセットした。
トナーは平均円形度０．９８１〜０．９８７のブラックトナーを使用し、キャリアに対して５重量％を混合した。なお、トナーへの潤滑剤（ステアリン酸亜鉛）は未添加である。
これらの評価結果を表２に示す。
【０１１２】
実施例に使用したフィラー分散電荷輸送層の膜厚の割合が６．７％〜８０％のサンプルのいずれにおいても、画像品質は良好で、表には記載していないが、７．１〜９．０本／ｍｍの高解像度を示し、ハーフトーン再現性も良好であった。一方、平均円形度の高いトナーを使用した場合は、帯電部材が若干汚れる程度の漏れは確認されたが、画像には影響は認められず、実用上の問題は発生しなかった。また、高硬度のブレードを使用した影響はクリーニング性が高いため、ブレードの下を通過するトナーが遮断されることもあって、感光体には画像には出ない程度のブレードによる軽い摺擦傷は生じるものの、深いスクラッチの発生は認められなかった。
【０１１３】
【表２】

※表中μは摩擦係数を表わし、添え字の０は初期、０．１Ｋは１００枚、５０Ｋは５万枚を示す。摩耗量は初期の感光層の膜厚から５万枚後の膜厚を引いた値で、１３ポイントの平均値である（以下の実施例も同様）。判定の○は良好を示す（以下の実施例も同様）。
【０１１４】
実施例５〜６
感光体サンプルＮｏ．５（実施例５）およびＮｏ．６（実施例６）のサンプルを用い、平均円形度０．９１の粉砕トナーを使用し、実施例１〜４に同じ内容で評価を行なった。感光体に印加する電界強度をＮｏ．５で３．０４×１０^５Ｖ／ｃｍ、Ｎｏ．６では２．３３×１０^５Ｖ／ｃｍとした。結果を表３に示す。
【０１１５】
円形度の低い粉砕トナーを使用した場合は、トナーのブレード抜けはほぼ皆無であり、極めて良好なクリーニング性を示した。また、解像度も６．３〜８本／ｍｍと良好であり、濃度ムラも皆無であった。感光層の摩耗は重合トナーを使用した場合に比べて、少し多めとなったが、８μｍのフィラー分散電荷輸送層にすることにより、高画質で高耐久化が可能となった。
【０１１６】
【表３】

判定の◎は優秀を示す（以下の実施例も同様）。
【０１１７】
実施例７〜９
乳化重合方法で製造した平均円形度が０．９８１〜０．９８７のブラックトナーに、潤滑剤として平均粒径０．３μｍのステアリン酸亜鉛を０．０３重量％添加したトナーと、キャリア（ＦＰＣ−３００ＬＣ）とを５重量％になるよう混合した現像剤を使用した。一方、感光体として、制振部材を内蔵しないＮｏ．５（実施例７）、Ｎｏ．６（実施例８）、Ｎｏ．７（実施例９）を使用して、実施例１〜４の同様の内容で感光体評価を行なった。結果を表４に示す。これらの感光体はいずれも真円度が０〜２０μｍ、真直度が±２０μｍを満足する感光体である。
【０１１８】
トナー中に潤滑剤を極微量添加することによって、感光体の摩擦係数が低減化する効果がもたらされた。その結果、トナーの感光体への付着力が弱められ、画像品質の向上、特には転写効率のアップが生じ、感光体上の残留トナーが少なくなり、クリーニング性に好結果が得られ、クリーニング性は実施例２〜４の結果よりも更に改善効果を高めることができた。解像度は実施例２〜４同様な結果であったが、よりシャープになった。感光層の摩耗は摩擦係数が低下したため、改善が見られ、更に、低摩耗となった。
【０１１９】
【表４】

【０１２０】
比較例１〜５
表１に記載のＮｏ．１（比較例１）およびＮｏ．２（比較例２）のフィラー非分散電荷輸送層の感光体、Ｎｏ．３（比較例３）、Ｎｏ．６（比較例４）およびＮｏ．７（比較例５）のサンプルを使用して、クリーニングブレードをＪＩＳ−Ａ硬度７７度の評価用電子写真複写機に標準設置されている短冊状のポリウレタンブレード（幅２ｍｍ×１３ｍｍ×３２０ｍｍ、自由長８．５ｍｍ）に戻して５万枚の通紙ランニングを行なった。
感光体に対する現像装置位置での電界強度を、Ｎｏ．１では３．１８×１０^５Ｖ／ｃｍ、Ｎｏ．２では２．８６×１０^５Ｖ／ｃｍ、Ｎｏ．３では５．８×１０^５Ｖ／ｃｍ、Ｎｏ．６では２．３３×１０^５Ｖ／ｃｍ、Ｎｏ．７では２×１０^５Ｖ／ｃｍに夫々設定した。現像剤に使用したトナーは平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーであり、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を使用した。
その他の条件は実施例１〜４に記載の方法で行なった。結果を表５に示す。
【０１２１】
Ｎｏ．３の感光体のように、フィラー分散電荷輸送層の膜厚比が０．８３と大きい場合は、フィラー分散電荷輸送層の膜厚が最大でも８μｍ程度に抑えないと、解像性や残留電位に影響が生じるため、フィラー非分散電荷輸送層の膜厚は薄くせざるを得ない。この様な状況では、静電容量が大きくなってしまうために、電界強度が大きくなってしまい、画像形成に必要な表面電位が低くなってしまい、画像濃度が低く、クリーニング性も不充分であったためにプアーな画像品質となった。
Ｎｏ．３以外の感光体においても、フィラー平均球形度が高い乳化重合法で製造した球形トナーは短冊状のクリーニングブレードではクリーニングが不充分であり、特にフィラー非分散電荷輸送層のみの感光体（Ｎｏ．１およびＮｏ．２）では、更にクリーニング不良が悪化する傾向が見られた。クリーニング不良が起きたことによって、帯電部材に著しい汚れが帯状に生じ、ハーフトーン画像では僅かに筋の発生が確認された。
フィラー非分散電荷輸送層のみの感光体では感光層の硬度が低い（鉛筆硬度でＢ）ためと、摩擦係数が高い（０．６以上）ための現象と考えられるが、フィラー分散電荷輸送層を有する感光体でもクリーニング不良が生じたのは、前記したようにブレードのエッジの歪みによるものと解される。
また、フィラー非分散電荷輸送層のみのＮｏ．１およびＮｏ．２の感光体は、摩耗が大きくなり、耐久性が不充分である以外に、現像剤中のトナーの流動剤として添加しているシリカや酸化チタンの、感光層への潜り込み（刺さり）が生じ、ハーフトーン画像にムラを生じる要因となった。
【０１２２】
【表５】

表中、×はクリーニング不良、画像品質悪化のため、実用性を持たないことを意味する。
【０１２３】
実施例１０〜１３
フィラー分散電荷輸送層中のフィラー分散量を変えて評価用感光体を作製した。使用した感光体サンプルは表１中のＮｏ．８〜Ｎｏ．１３で、フィラー分散電荷輸送層中のフィラー分散量は、夫々、Ｎｏ．８では１０重量％（ＨＢ）（実施例１０）、Ｎｏ．９では２０重量％（ＨＢ）（実施例１１）、Ｎｏ．１０では３０重量％（Ｈ）（実施例１２）、Ｎｏ．１１では４０重量％（Ｈ）（実施例１３）とした。括弧内は鉛筆硬度。これらの感光体には損失正接ｔａｎδが０．８のブチルゴムからなる制振部材を内蔵し、真円度、真直度はいずれも２０μｍ、±２０μｍの範囲内である。
鉛筆硬度向上のためのフィラーには平均粒径０．５μｍのα−アルミナを使用し、電荷輸送層の膜厚を２７μｍ、フィラー分散電荷輸送層の膜厚を５μｍとした。このときの現像装置位置での電界強度は２．２×１０^５Ｖ／ｃｍとした。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。クリーニングブレードは、ＪＩＳ−Ａ硬度８１度の鋭角にシャープカットされた図２０の形式のブレードを当接圧（線圧）２４ｇ／ｃｍに設定して、電子写真複写機による５万枚の通紙ランニング評価を実施した。
サンプルの表面粗度は表１に示すように１０点平均表面粗度で０．４〜０．８を満足している。結果を表６に示す。
クリーニング性はフィラー分散量が１０重量％程度ではやや不良気味であるが、２０重量％になると、殆ど問題ない程度にクリーニング性が維持される。画像品質は２０、３０重量％が良好で、フィラー分散量が少ないと、クリーニング性の低下による帯電ローラの汚染で、フィラーが４０重量％になると、摩耗が抑制されるためにコロナ生成物の除去が充分でないために、局部的に解像性低下（４．０〜４．５本／ｍｍ）が生じた。
すなわち、フィラー添加量の好適な範囲は１０重量％、４０重量％を除いた範囲が良好と判断される。
【０１２４】
【表６】

表中、△は枚数が５万枚の評価時点で、僅かにクリーニング性や画像品質に問題があることを意味する。（以下の実施例も同様）
【０１２５】
実施例１４〜１７
フィラー分散電荷輸送層に分散する一次平均粒径が０．２〜０．７μｍの評価用感光体を作製した。使用した感光体サンプルは表１中のＮｏ．１２〜Ｎｏ．１５で、フィラー分散電荷輸送層中のα−アルミナフィラーの一次粒径は、夫々、Ｎｏ．１２では０．２μｍ（ＨＢ）（実施例１４）、Ｎｏ．１３では０．３μｍ（Ｈ）（実施例１５）、Ｎｏ．１４では０．５μｍ（ＨＢ）（実施例１６）、Ｎｏ．１５では０．７μｍ（Ｈ）（実施例１７）とした。括弧内は鉛筆硬度。これらの感光体には損失正接ｔａｎδが０．８のブチルゴムからなる制振部材を内蔵し、真円度、真直度はいずれも０〜２０μｍ、±２０μｍの範囲内である。
フィラーの添加量は２５重量％で電荷輸送層の膜厚を２７μｍ、フィラー分散電荷輸送層の膜厚を５μｍとした。このときの現像装置位置での電界強度は２．２×１０^５Ｖ／ｃｍとした。表面粗度はいずれも１０点平均粗さは０．４μｍ〜０．８μｍ内であり、最大粗さも１．０μｍ以下である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。クリーニングブレードは、ＪＩＳ−Ａ硬度８１度の鋭角にシャープカットされた図２２の形式のブレードを当接圧（線圧）２４ｇ／ｃｍに設定して、電子写真複写機による５万枚の通紙ランニング評価を実施した。評価結果を表７に示す。
フィラー分散電荷輸送層中の一次平均粒径を変えることによって、表面粗度が変化するが、上記表面粗度の範囲内のサンプルはいずれも、クリーニング性、画像品質とも良好であった。
【０１２６】
【表７】

【０１２７】
比較例６〜８
フィラー分散電荷輸送層に分散する一次平均粒径１．０μｍの分散量を２０、３０、４０重量％と変えた評価用感光体を作製した。使用した感光体サンプルは表１中のＮｏ．１６〜Ｎｏ．１８で、フィラー分散電荷輸送層中のα−アルミナフィラーの分散量は、夫々、Ｎｏ．１６で２０重量％（Ｈ）（比較例６）、Ｎｏ．１７では３０重量％（２Ｈ）（比較例７）、Ｎｏ．１８では４０重量％（２Ｈ）（比較例８）とした。括弧内は鉛筆硬度。これらの感光体には損失正接ｔａｎδが０．８のブチルゴムからなる制振部材を内蔵し、真円度、真直度はいずれも２０μｍ、±２０μｍの範囲内である。
フィラーの添加量は２５重量％で電荷輸送層の膜厚を２７μｍ、フィラー分散電荷輸送層の膜厚を５μｍとした。このときの現像装置位置での電界強度は２．２×１０^５Ｖ／ｃｍとした。表面粗度はいずれも１０点平均粗さは０．８μｍ以上であり、最大粗さも１．０μｍ以上である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。クリーニングブレードは、ＪＩＳ−Ａ硬度８１度の鋭角にシャープカットされた図２３の形式のブレードを当接圧（線圧）２４ｇ／ｃｍに設定して、電子写真複写機による５万枚の通紙ランニング評価を実施した。評価結果を表８に示す。
フィラーの一次平均粒径が１．０μｍであっても、分散量を少なくすることによって、表面粗度が低く抑えられる傾向はあるが、感光層上にフィラーの凸部があるために、クリーニング性、画像品質共に影響が出る傾向があり、トナー抜けによる、帯電部材の汚れや、地汚れが微かに発生した。また分散量が多くなるにつれ、表面粗度が大きくなり、クリーニング性、画像品質とも悪化が見られた。
【０１２８】
【表８】

【０１２９】
実施例１８〜１９
表１に記載のＮｏ．１５と同等の感光体を２本用意し、ＪＩＳ硬度が８１度（実施例１８）、８７度（実施例１９）、のポリウレタンゴムブレードを感光体ユニットにセットし、当接圧（線圧）を２４ｇ／ｃｍに設定して電子写真複写機による５万枚の通紙ランニング評価を実施した。
フィラー分散電荷輸送層中のフィラーは平均粒径が０．７μｍα−アルミナとし、添加量は２５重量％で、電荷輸送層の膜厚は２７μｍ、フィラー分散電荷輸送層の膜厚は５μｍである。この感光体に印加される現像装置位置での電界強度は、２．２×１０^５Ｖ／ｃｍとした。表面粗度はいずれも１０点平均粗さは０．８μｍ以上であり、最大粗さも１．０μｍ以上である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。評価結果を表９に示す。
ＪＩＳ−Ａ硬度が８１度、８７度のブレードとも殆どトナー抜けは確認されず、画像への影響もなく、良好な画像品質であった。
【０１３０】
【表９】

【０１３１】
比較例８〜９
表１に記載のＮｏ．１５と同等の感光体を２本用意し、ＪＩＳ硬度が７４度（比較例８）、９２度（比較例９）、のポリウレタンゴムブレードを感光体ユニットにセットし、当接圧（線圧）を２４ｇ／ｃｍに設定して電子写真複写機による５万枚の通紙ランニング評価を実施した。
フィラー分散電荷輸送層中のフィラーは平均粒径が０．７μｍのα−アルミナとし、添加量は２５重量％で、電荷輸送層の膜厚は２７μｍ、フィラー分散電荷輸送層の膜厚は５μｍである。この感光体に印加される現像装置位置での電界強度は、２．２×１０^５Ｖ／ｃｍとした。表面粗度はいずれも１０点平均粗さは０．８μｍ以上であり、最大粗さも１．０μｍ以上である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。評価結果を表１０に示す。
評価した結果、ＪＩＳ−Ａ硬度が７４度および９２度のブレードとも良い結果では無かった。硬度が低い場合には、従来の短冊状のクリーニングブレードより良好ではあったが、トナー抜け現象は生じ、帯電ローラにトナー付着が生じ、ハーフトーン画像に僅かに筋模様が生じた。
一方、硬度が９２度と大きい場合には、７４度の硬度のブレードよりは更にトナー抜けは良くなったが、感光体上に僅かにトナーの付着が見られ、帯電部材に薄くトナー付着が見られたが、５万枚時点では画像への影響はハーフトーン画像に僅かに濃淡差が見られる程度の微少な影響であった。
【０１３２】
【表１０】

【０１３３】
実施例２０
評価用の感光体として表１のＮｏ．６の感光体を４本（マゼンタ（Ｍ）、イエロー（Ｙ）、シアン（Ｃ）、ブラック（Ｂｋ）用）用意した。クリーニングブレードにはＪＩＳ−Ａ硬度８７の図２０に図示するシャープカットされた形態のブレードを当接圧（線圧）２１．５ｇ／ｃｍになる様に感光体ユニットに取り付けた。
平均円形度０．９８１〜０．９８７の乳化重合法で製造したＭ、Ｙ、Ｃ、およびＢｋトナーに、平均粒径０．３μｍのステアリン酸亜鉛を０．０３重量％添加したトナー、キャリアには重量平均粒径５８μｍの磁性紛（ＦＰＣ−３００ＬＣ）を使用し、５重量％濃度の現像剤を現像ユニットに投入した。
感光体ユニットおよび現像装置を、評価用に用意したカラーレーザービームプリンタに搭載し、現像位置での感光体に印加される電界強度は２．５×１０^５Ｖ／ｃｍとして、５万枚のランニング評価を実施した。結果を表１１に示す。表中上よりマゼンタ（Ｍ）、イエロー（Ｙ）、シアン（Ｃ）、ブラック（Ｂｋ）の結果を示す。
トナー中にはいずれも潤滑剤が入っているため、トナーのクリーニング性は良好で、トナーフィルミングの兆候は見られなかった。１ドット再現性も良好で、ドット間のにじみはなく、良好なカラー再現性を示した。
【０１３４】
【表１１】

【０１３５】
比較例１０〜１２
評価用感光体サンプルとして、表１に記載のＮｏ．１９（比較例１０）、Ｎｏ．２０（比較例１１）、Ｎｏ．２１（比較例１２）の感光体を用意した。Ｎｏ．１９の感光体についての真直度および真円度の測定結果を図２６および図２７に示す。真円度は０〜２０（μｍ）を満足しているが、真直度は＋２０μｍを大きく外れ、＋３５μｍを示している。Ｎｏ．２０、Ｎｏ．２１の感光体は図示しないが、真円度は２２〜２４μｍ、真直度は＋３０〜４５μｍと＋２０μｍを大きく外れている。
クリニングブレードには、ＪＩＳ硬度が８７度の図２２に示す形状のポリウレタンゴムブレード（先端部エッジの幅０．２ｍｍ）を感光体ユニットにセットし、当接圧（線圧）を３０ｇ／ｃｍに設定して電子写真複写機による５万枚の通紙ランニング評価を実施した。
フィラー分散電荷輸送層中のフィラーは平均粒径が０．３μｍ（Ｎｏ．１９、２０）および０．５μｍ（Ｎｏ．２１）のα−アルミナとし、添加量は２５重量％で、電荷輸送層の膜厚は２０μｍ（Ｎｏ．１９）、２７μｍ（Ｎｏ．２０、２１）、フィラー分散電荷輸送層の膜厚は５μｍとした。この感光体に印加される現像装置位置での電界強度を、Ｎｏ．１９のサンプルが３×１０^５Ｖ／ｃｍ、Ｎｏ．２０、２１のサンプルが２．２×１０^５Ｖ／ｃｍとした。表面粗度はいずれも１０点平均粗さで０．５μｍ前後であり、最大粗さは０．７μｍ前後である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤非分散ブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。評価結果を表１２に示す。
感光体の真円度、真直度が大きい場合は、感光体が歪んでいることを意味するが、感光体と帯電部材間および感光体とクリーニング部材間の距離が不均一になるため、帯電ムラおよび、クリーニング不良（トナー抜け）の要因となる。比較例１０のサンプルでは真円度は０〜２０μｍの中に入っているが、真直度の暴れが大きいため、トナー抜けが局部的に起こり、筋状にフィルミング、擦り傷が発生した。また、帯電ローラに汚れが起こり、また画像ムラも若干生じた。一方、比較例１１および１２では真円度、真直度とも大きいため、クリーニング性不良、コピー画像上に薄い濃度ムラが生じ、局所的に解像度が５．６本／と低い領域があった。さらに、微かに地肌汚れが認められた。
【０１３６】
【表１２】

【０１３７】
実施例２１〜２２
表１に記載のＮｏ．１の感光体（実施例２１−フィラー添加なし、膜厚２２μｍ）、Ｎｏ．２の感光体（実施例２２−フィラー添加なし）を使用した。鉛筆硬度はいずれもＢであった。これらの感光体には制振部材は内蔵していない。真円度、真直度はいずれも２０μｍ、±２０μｍの範囲内である。
感光体に印加する現像装置位置での電界強度はＮｏ．１のサンプルで２．７×１０^５Ｖ／ｃｍ、Ｎｏ．２のサンプルで２．１４×１０^５Ｖ／ｃｍとした。感光体の表面電位−６００Ｖに相当する電界強度である。
トナーには平均円形度０．９８１〜０．９８７の乳化重合法で製造した潤滑剤を０．０３％分散したブラックトナーを使用し、キャリア（ＦＰＣ−３００ＬＣ）に対し５重量％添加した現像剤を現像ユニットに投入した。クリーニングブレードは、ＪＩＳ−Ａ硬度８７度の鋭角にシャープカットされた図２０の形式のブレードを当接圧（線圧）２２ｇ／ｃｍに設定して、電子写真複写機による５万枚の通紙ランニング評価を実施した。
サンプルの表面粗度は表１に示すように１０点平均表面粗度で０．０９〜０．１であった。結果を表１３に示す。
電荷輸送層を、フィラーを添加しないフィラー非分散電荷輸送層にした場合には、感光層表面が柔らかいという状況にあるため、フィラーを分散した感光層に比べ、若干劣る傾向にはあったが、従来の短冊状のクリーニングブレードに比較して、明らかに良好な状態であった。
【０１３８】
【表１３】

【０１３９】
【発明の効果】
以上、詳細且つ具体的な説明より明らかなように、本発明の請求項１乃至３に記載の構成によって、フィラーを分散していないフィラー非分散電荷輸送層とフィラーを分散したフィラー分散電荷輸送層とを合わせた感光層の膜厚に対する、フィラー分散電荷輸送層との膜厚の割合が６．７％〜８０％の感光体と、クリーニングに供されるクリーニング部材が鋭角にシャープカットされた先端部をもつ弾性体とを組み合わせることによって、従来の短冊状の形態で問題があった面接触によって、トナーを帯電部材の方に送り出すことや、局部的な歪みも無視できるため、クリーニング不良を実用上問題ないレベルまで、改善することができる。また、請求項４の構成によって、フィラー分散電荷輸送層中のフィラー濃度をフィラー分散電荷輸送層全重量の１０重量％以上、４０重量％以下にすることによって、適度に摩耗させながら使用できるため、感光体に付着した汚染物質も適度に削られ、異常に付着することが抑制される。その結果、フィラー分散電荷輸送層のない、従来の感光体に比して、高耐久化（感光層の耐摩耗性、スクラッチの発生しにくさ）が図れると共に、安定した、濃度ムラのない画像品質を長く提供できる。また、感光層の硬度アップによって、クリーニングブレードのエッジ部の食い込みが緩和される他、硬度の高いクリーニングブレードが使用されるため、エッジの歪みが少ないこととも相まって、平均円形度が大きいトナーであっても、トナー抜けが起こりにくくなるというメリットが生じる。また、請求項５の構成によって、一次粒径が０．２〜０．７μｍのアルミナフィラーをフィラー分散電荷輸送層に分散したとき、感光層の１０点平均粗さが０．４〜０．８μｍ、最大粗さが１．０μｍ以内にすることによって、ブレードエッジの感光層への食い込みが抑制されるために、エッジ部の局部的な歪みが生じにくい。また、感光層表層が平坦であるために、ブレードと感光層間に隙間が生じ難いために、平均円形度の高い重合法によって作製された球形トナーであっても、良好にクリーニングができる。クリーニングエッジの痛みが少ないために、クリーニングブレードの耐久性も良好になる。また、請求項６の構成によって、感光層表層の摩擦係数を下げることによって、トナーの感光層への付着力が低減するために、トナーのクリーニング性が向上するとともに、トナー像の転写効率がアップするため、局部的な画像抜けがなくなる。またクリーニングブレードの負担が少なくなるために、クリーニングブレードの耐久性を延ばすことが可能である。更に、クリーニングブレードと感光体間の摩擦抵抗が下がるために、振動音が軽減され、騒音が解消する。また、請求項７の構成によって、フィラー分散電荷輸送層の硬度を鉛筆硬度ＨｐでＨＢ≦Ｈｐ＜２Ｈとすることによって、適度な耐摩耗性が図られる。このことによって、感光体の耐久性は向上するが、感光層の摩耗が少しあるために、コロナ生成物のような低抵抗物質が付着しても、適度に摩耗するため、フィルミングの発生に伴う、あるいはコロナ生成物の付着に伴って起こる、画像劣化を最小限にくい止めることができる。また、請求項８、９の構成によって、画像形成時における真円度を０〜２０（μｍ）、真直度を±２０μｍにすることによって、接触帯電部材、非接触帯電部材を使用した場合でも、安定した帯電を行なうことができ、均一性に飛んだ画像が提供可能である。また、請求項１０の構成によって感光層の総膜厚を１０μｍ以上、３０μｍ以下に設定し、電界強度を１．３×１０^５〜４．０×１０^５（Ｖ／ｃｍ）にすることにより、シャープ性、解像性良好な、地肌汚れのないコピー画像が得られる。また、放電破壊し難いため、画像品質が安定している。また、請求項１１の構成によって、クリーニングブレードの硬度をＪＩＳ−Ａ硬度で８０〜９０度の通常より高めに設定することにより、ブレードに歪みや、振動を起こしにくくなるため、感光体との密着性が図られる。その結果、トナーのブレード下を抜ける頻度が大幅に減少し、クリーニング性の向上と、安定性、画像品質の良好な維持を図ることができる。また、請求項１２の構成によって、クリーニングブレードの当接圧（線圧）を２０〜２５（ｇ／ｃｍ）に設定することによって、硬度の高いクリーニングブレードを使用しても、感光体に深い傷をつけることなく良好なクリーニング性能を維持することができる。また、傷つけることが無いため、ブレードエッジの摩耗も少なく、高耐久を維持することができる。また、請求項１３の構成によって、クリーニングブレードの感光層に当接する先端部のエッジを０〜０．５ｍｍにすることにより、感光体との均一な密着性を図ることができるので、良好なクリーニング性を発揮することができる。また、請求項１４の構成によって、クリーニング部材を硬い金属製の支持体に固定することにより、安定した、感光体への当接を保証できるため、安定した画像品質を得ることができる。また、請求項１５の構成によって、上記した感光体および、クリーニングブレードは４連タンデム方式のカラー方式の画像形成装置にも問題なく使用できる。また、請求項１６、１７の構成によって、本発明における感光体、クリーニングブレードは感光体とクリーニングブレードとを一体構成したプロセスユニット、感光体、クリーニングブレード、および現像装置とを一体構成したプロセスユニットとして画像形成装置に組み込むことができるため、組立などの作業効率が向上し、部品交換や清掃などのメンテナンスおよび再生において有利である。
【図面の簡単な説明】
【図１】本発明に使用される複写プロセスを説明する画像形成装置の概略図である。
【図２】本発明に使用される複写プロセスを説明する画像形成装置の他の概略図である。
【図３】本発明の４連タンデム方式のカラーレーザービームプリンタの概略図である。
【図４】本発明のプロセスユニットの一例を示す。
【図５】本発明に使用する電子写真感光体の構成を説明する概略図である。
【図６】電荷輸送層を構成するフィラー分散電荷輸送層の好適な膜厚割合を示すグラフである。
【図７】フィラー分散電荷輸送層の表面粗度の無機フィラー（αアルミナ）平均一次粒径依存性を示すグラフ例である。
【図８】フィラー分散電荷輸送層中へのフィラー添加量による感光層摩耗量および画像品質ランクの関係を示すグラフである。
【図９】制振部材を内蔵した感光体の真直度測定例である。
【図１０】制振部材を内蔵した感光体の真円度測定例である。
【図１１】制振部材を内蔵した感光体の他の真直度測定例である。
【図１２】制振部材を内蔵した感光体の他の真円度測定例である。
【図１３】従来のクリーニングブレードによるトナー抜けを説明する模式図である。
【図１４】クリーニングブレードの側面から見た断面図である。
【図１５】クリーニングブレードの側面から見た他の断面図である。
【図１６】クリーニングブレードを支持基体に固定した状態を説明する概略図である。
【図１７】クリーニングブレードを支持基体に固定した状態を説明する他の概略図である。
【図１８】クリーニングブレードを支持基体に固定した状態を説明する他の概略図である。
【図１９】クリーニングブレードを支持基体に固定した状態を説明する他の概略図である。
【図２０】クリーニングブレードを支持基体に固定した状態を説明する他の概略図である。
【図２１】金型成形で製造したクリーニングブレードの感光体との当接面のバリをカットする状況を説明する概略図である。
【図２２】クリーニングブレードの感光体に当接させた状態、および支持基体からブレードの先端までの自由長を説明する概略図である。
【図２３】クリーニングブレードの感光体に当接させた状態、および支持基体からブレードの先端までの自由長を説明する他の概略図である。
【図２４】本発明のクリーニングブレードによるトナークリーニングの状態を説明する模式図である。
【図２５】感光体内に制振部材を内蔵した状態を示す模式図である。
【図２６】比較例１０に使用した制振部材を内蔵した感光体の真直度測定結果である。
【図２７】比較例１０に使用した制振部材を内蔵した感光体の真円度測定結果である。
【符号の説明】
１：電子写真用感光体（感光体）
２：帯電装置
３：画像露光装置
４：現像装置
５：転写装置
６：分離装置
７：クリーニング装置
７−１：クリーニングブレード
８：定着装置
９：コピー用紙
１０：制振部材
２００：潤滑剤付与装置
２０１：潤滑剤
２０２：潤滑剤塗布ブラシ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is equipped with a blade cleaning device that can perform good cleaning even with a spherical toner having a large circularity, and an electrophotographic photosensitive member in which an inorganic filler is dispersed in a photosensitive layer, and forms an image by indirect electrophotography. The present invention relates to an image forming apparatus for performing.
[0002]
[Prior art]
In image forming apparatuses using indirect electrophotography, such as facsimile, laser beam printer, and electrophotographic copying machine, as technologies related to durability of photoconductors, photoconductors, charging devices, image exposure devices, developing devices, transfer devices, separation devices A device, a cleaning device, a charge removing device, and a fixing device are provided, and an image is formed.
Photoreceptors used for image formation include zinc oxide (ZnO), cadmium sulfide (CdS), cadmium selenide (CdSe), amorphous selenium (a-Se, a-Se-Te, a-As). ₂ Se ₃ Etc.), amorphous silicon (a-Si: H), etc., but in recent years, organic photoreceptors having many advantages such as easy production, high sensitivity design, low cost, and no pollution are mainly used. You.
The organic photoreceptor includes a single-layer type in which a photosensitive layer is integrally formed with functions of a charge generating material and a charge transporting material, and a function-separated type in which a photosensitive layer has a two-layer structure of a charge generating layer and a charge transporting layer. The body is mainly used.
[0003]
In the present invention, a function-separated type photoconductor in which a charge transport layer is formed on the outermost layer of the photoconductor will be described as a typical example.
A general function-separated type organic photoreceptor has a configuration in which a charge generation layer is formed directly on a conductive support or through an undercoat layer (or an intermediate layer), and then a resin layer containing a charge transport material (charge transport layer). Layer) is formed. In the present invention, any of an inorganic material and an organic material can be used for the charge generation layer without any limitation.
On the other hand, as the binder resin material constituting the charge transport layer, a polycarbonate resin material (including A type, C type, and Z type) having high resistance, high transparency, and little polarity dependency is preferably used. Is done. The photosensitive layer using a polycarbonate resin has a Vickers hardness of 10 to 30 kg / mm. ² The pencil hardness is as small as about 2B to F, and the tensile strength is small. Further, corona products such as ozone and nitrogen oxides (NOx) generated at the time of charging tend to adhere, and the free surface energy (or coefficient of friction) decreases. Therefore, the frictional resistance with the cleaning blade is increased, and the photosensitive layer is easily scratched and easily worn. In addition, the sliding friction of the cleaning blade may generate a high-frequency sound (vibration sound) such as a key. Under such circumstances, the number of durable organic photoconductors is about 50,000 to 100,000.
Due to the low number of durable sheets, a user who has a large number of copies frequently exchanges the photoconductor and members related thereto, which is a problem.
The term "durable number" refers to the number of copies until the photosensitive layer is worn and the charge level is lowered, or the unevenness of the wear causes image defects such as background contamination and density unevenness, and the image becomes unusable.
Factors that affect the number of durable sheets include the image area of the document, the rubbing of the cleaning member and the developer, the pressing of the toner, carrier, and paper powder by the cleaning member, and the corona product generated during the above-described charging. When the photosensitive layer is worn, the electrostatic capacity is increased, so that the charged position is reduced. Therefore, the margin between the charging potential and the developing bias potential is reduced, and the possibility of background contamination is increased.
[0004]
Quadruple tandem color copier (a copying system using four photoconductors, charging, exposing, developing (magenta, yellow, cyan, and black developers) for each photoconductor, and a cleaning device. ), The wear of the four photoconductors varies depending on the color of the document, the image area, the amount of developer supplied, the amount of toner, and the like, in addition to the background stains. It appears as a decrease in color reproducibility.
Improving the abrasion resistance of the photoconductor assures a reduction in total cost and reliability with respect to image quality. Therefore, it is important to increase the durability of the photoconductor.
Techniques for increasing the durability of the photoreceptor include a method of forming a wear-resistant thin film on the surface of the photoreceptor, a method of forming the photosensitive layer with a wear-resistant photosensitive material, and making the outermost surface of the photosensitive layer wear-resistant. There are methods, etc.
[0005]
Hereinafter, a disclosure example for improving the durability will be described.
(1) JP-A-1-92756, JP-A-2-79047, JP-A-4-66954, and the like use a dry film-forming method such as vapor deposition and CVD on a photosensitive layer. It has high transmittance from visible light to infrared light, and has a volume resistivity (10 ¹¹ -10 ¹⁴ Ω · cm) to form uniform thin films such as a-SiC layer (amorphous silicon carbide layer), a-C layer (amorphous carbon layer), and DLC layer (Diamond Like Carbon layer) having high wear resistance. Is described.
The film hardness (Knoop hardness) of the above thin film is 500 to 2000 (kg / mm). ² ), Which is about 20 to 100 times larger than the organic material, is an effective means for increasing the durability of the photoreceptor, and achieves a durability of about 500,000 to 1,000,000 sheets even with a thin film of about 2 μm. Have been confirmed by the present inventors.
However, although the durability of the photoreceptor can be enhanced by the above-mentioned thin film, a corona product such as ozone or nitrogen oxide (NOx) generated at the time of charging may adhere or the resistance may be reduced by oxidation. In addition, since the abrasion resistance is high, there is a problem that the attached matter is not easily removed, and the image deletion occurs at a relatively early stage. In addition, when formed on a soft resin layer such as an organic photosensitive layer, pinholes and peeling are liable to occur due to the pressure contact of the blade and the action of ozone products. There are problems such as.
[0006]
(2) JP-A-06-0352220 and JP-A-08-234469 disclose conductive fine particles such as zinc oxide, titanium oxide, tin oxide, indium oxide antimony, bismuth oxide, and tin-doped indium oxide. It describes that a photosensitive member is formed using a photosensitive layer.
Abrasion resistance can be improved by dispersing an appropriate amount of conductive particles having high hardness in the photosensitive layer. Use of low-resistance fine particles is effective for charge injection charging.However, when using the contact charging method with a severe hazard, it is easy to cause image deletion, and it is quite difficult to achieve both resistance to image quality deterioration. .
[0007]
(3) JP-A-08-123053 discloses that inorganic compound particles of 0.02 to 5 μm (preferably 0.07 to 2.0 μm), for example, metal oxides such as silica, aluminum oxide, zinc oxide, and aluminum nitride It is described that a photosensitive member is constituted by using a photosensitive layer containing a substance, a metal sulfide, a metal nitride and a butadiene-based charge transport material.
This means can improve abrasion resistance by dispersing high-resistance inorganic compound particles other than silica in the photosensitive layer, and can secure charging ability. When the butadiene-based charge transporting material is contained in the photosensitive layer, the mobility of the charges can be maintained in the same manner as in the charge transporting layer. However, since trap sites are easily formed between the particles and the binder resin, the residual potential is accumulated due to repeated use, and light attenuation is deteriorated due to repeated use, and image density may gradually decrease and image unevenness may occur. . Further, when a filler having a large particle diameter is used, the sharpness of a line image is reduced, and on the other hand, there is a problem that the edge of the cleaning blade is deformed and cleaning failure is likely to occur.
When silica is used, the oxidizing effect of ozone causes a rapid reduction in the resistance of the photosensitive layer, and image deletion easily occurs even in a normal humidity environment of about 60% RH.
[0008]
(4) JP-A-08-234455 discloses that a charge-transporting layer having a thickness of 12 μm or less includes a silicone resin, a phenol resin, ₂ (Silica), Al ₂ O ₃ (Alumina), TiO ₂ It describes that a photosensitive member is composed of a photosensitive layer in which (titanium oxide) and ZnO (zinc oxide) are dispersed.
This technology achieves high abrasion resistance by using particles of a certain size, but the large particle size increases the surface roughness of the photoconductor surface layer and sharpens image edges. When the blade cleaning method is used, the edge is distorted, toner is lost, and the image quality of copy paper is likely to be degraded and the background is easily stained. There are insufficient points such as the durability of the blade cannot be maintained.
[0009]
(5) JP-A-08-146641 discloses that inorganic compound fine particles such as titanium oxide, aluminum oxide and silicon oxide having an average particle size of 0.02 to 0.5 μm are dispersed in one or two kinds of polycarbonate resins. Photosensitive layer is described
This technique is almost the same as the content described in (3), but since particles having a small particle size are used, deterioration of image quality due to the particles is small. However, in a region where the particle size is small (for example, 0.1 μm or less), the effect of the addition is difficult to be exhibited, so that the effect of increasing the durability is small.
[0010]
(6) JP-A-08-248663 discloses that a photosensitive layer having a surface roughness of 0.1 to 0.5 μm formed on a conductive support having a surface roughness of 0.01 μm to 2 μm has an average grain size. It describes that inorganic fine particles (hydrophobized silica) having a diameter of 0.05 to 0.5 μm are dispersed over a thickness of 0.05 to 15 μm.
This means makes the dispersed silica particles hydrophobic, thereby increasing durability and preventing a decrease in resolution and image deletion caused by the attachment of contaminants such as corona products.
Although the effect of repelling water droplets (large contact angle) is exhibited by making the inorganic fine particles hydrophobic, the adhesion of the corona product cannot be prevented, so that the image deletion cannot be prevented. In addition, the hydrophobic fine particles exposed on the surface of the photosensitive layer have a problem that the coating is scraped off by rubbing with a blade or the like. Improvement is almost impossible.
[0011]
Description of surface roughness of photoreceptor
The surface roughness of the photoreceptor is important for maintaining image quality. The surface roughness is influenced by applying an object having a particle size to the photosensitive layer or forming a thin film in which a granular material is dispersed. Further, as the particle size increases, the surface roughness increases. In particular, when the particle size of the filler dispersed in the photosensitive layer is about 0.7 to 1.0 μm or more, the surface roughness becomes 10 points average roughness Rz. _JIS Is about 0.8 μm to 1.5 μm, and the maximum height Rz is about 2 to 3 μm. When the surface roughness is large, the charge density on the surface of the photoreceptor is scattered, and the adhesion of the copy paper at the time of transfer is affected, so that the image lacks sharpness of the character edge. In addition, corona products accumulate between the particles, resulting in poor cleaning, which is a factor of causing image deletion.
Further, since the edge portion of the cleaning blade that abuts on the photoconductor is locally distorted, a gap is formed between the blade and the photoconductor, and toner cleaning failure occurs. If such repetition continues, the blade edge is gradually chipped, resulting in permanent cleaning failure. Therefore, the charging member is contaminated, and the copy paper is stained.
To obtain good image quality, it is desirable that the surface roughness is small, but if the surface roughness is too small, the friction coefficient between the photoconductor and the cleaning blade becomes high, and the blade edge is dragged by the photoconductor. Deformation also causes cleaning failure. As a generally used blade, for example, a strip-shaped rubber member having a JIS-A hardness of 50 to 75 degrees is used.
Since such a member is easily deformed and deformed, a small gap is formed between the member and the photosensitive member. As the toner has a higher sphericity, the toner easily slips through the gap to the charging device side and is sent out. The toner stagnates at the leading end, and the pressing against the photoconductor is likely to occur.
If such a situation continues, background contamination and crushing of the line image occur, and the cleaning blade tends to cause a constant cleaning failure, so that the blade needs to be replaced early.
[0012]
Description of roundness and straightness of photoconductor
Organic photoreceptors are mostly made by coating a photosensitive layer on a conductive support on a drum, but the outer diameter of the photoreceptor at the start of image formation is possible to provide image quality without uneven density. It is necessary to be as straight and straight as possible. This is particularly important in the case of a charging system using a charging roller.
[0013]
A conventional example relating to roundness and straightness is shown.
For example, in the case of a conductive support, Japanese Patent Application Laid-Open No. 11-143292 describes that the roundness of a photoreceptor is set to 10 to 30 (μm), and Japanese Patent Application Laid-Open No. 07-319326 discloses a circularity. It is described that the straightness is desirably set to 0.080 mm (80 μm) to 0.002 mm (2 μm), and Japanese Patent Application Laid-Open No. 2001-222129 desirably sets the straightness to 0.1 mm or less. Has been described.
[0014]
The roundness and straightness are basically controlled by the conductive support of the photoreceptor, but when heating and drying after coating the photosensitive layer, when attaching the flange to the photoreceptor, and inside the photoreceptor. When a vibration damping member is attached, the shape of the member changes to a considerable extent. It is desirable that the roundness and the straightness are smaller. The larger the larger, the more the photoreceptor rotates. When roller charging is used, charging unevenness occurs, and developing unevenness occurs in the developing unit. Therefore, it is not sufficient to hold the support only with the support, and it is important to keep the finished photoreceptor within the target value.
[0015]
Description of toner and carrier
In an image forming apparatus, a one-component developer or a two-component developer in which toner and a carrier are mixed in an appropriate amount is used to visualize an electrostatic latent image formed by charging and image exposure. . The developing method includes a magnet brush developing method, a spray developing method, a cascade developing method, a flying developing method, and the like, and the mainstream is a magnetic brush developing method.
As the carrier used for the two-component developer, a magnetic powder having a particle size of about 30 to 80 μm having a resin coating containing a charge control agent such as iron powder, ferrite, and magnetite is used. The smaller the particle size, the easier it is to obtain a high resolution. However, if the particle size is too small, the carrier is more likely to adhere to the photoreceptor, causing image loss or damage to the photoreceptor. Therefore, it is necessary to select a carrier suitable for the copying system.
[0016]
On the other hand, with the spread of color copiers in recent years, higher definition and reproducibility of images have been increasingly required, and small particles having a particle size of 4 to 8 μm are mainly used. .
The toner production method mainly includes a pulverization method and a polymerization method.
The pulverization method is a method in which additives such as a colorant and a charge control agent are melted and kneaded in a binder polymer produced by polymerization, and the resulting mass is roughly pulverized, finely pulverized, and classified by a sieve.
Although the pulverization method has an advantage that the toner can be finely divided, the cost is likely to increase because the process is complicated.
[0017]
The toner produced by the pulverization method has an irregular shape (irregular shape). In order to obtain a toner for a developer, a step of further rounding corners is added, and the particles are sieved by classification to obtain particles having a constant particle size. In a commonly used toner, since the circularity of the toner is small (square), it is difficult to uniformly charge the particles, and transfer failure is likely to occur. In addition, when pressed against the photoreceptor by the cleaning blade, there is a tendency that scratches easily occur.
In addition, even if a high resolution with good sharpness is obtained in the early stage, it is difficult to maintain, and when a copy of a copy (the second or third generation copy) is printed, the resolution becomes extremely poor, and it is not practical. There are points. For this reason, toners with even higher sphericity are being developed, but the cost is further increased, and conversion to polymerization methods is being promoted.
[0018]
The main production methods of the polymerization method include a suspension polymerization method and an emulsion polymerization method. For example, in the case of the suspension polymerization method, a binder resin is produced by homogenizing additives such as a colorant and a charge controlling agent, adding a dispersion medium and a dispersant, and polymerizing. Since the polymerization method has a simplified process, the production cost is lower than that of the pulverization method. In addition, there is an advantage that the particle diameters are relatively well uniform, and irregularly shaped particles are hardly produced (mostly spherical toner).
Most of the particles produced by the polymerization method are spherical and have almost the same particle size, so that the charge can be easily made uniform and adhere to the latent image almost faithfully. Therefore, transfer efficiency is high, high resolution is easily obtained, and image reproducibility is high. For this reason, in recent years, there are many examples in which a toner manufactured by a polymerization method having many advantages is used.
[0019]
The circularity of the spherical toner produced by the polymerization method is even larger (0.98 to 0.998) than that of the spherical pulverized toner (about 0.91 to 0.95). There is a problem that defects easily occur. Conventional cleaning blades that have been used with conventional pulverized toners use a relatively soft rubber blade with a blade hardness of about 50 to 75 degrees. At the same time, the blade edge is distorted. Further, since the friction coefficient of the photoconductor is high, the tip of the blade is caught in the photoconductor and deformed. For this reason, a slight gap is generated between the blade and the photoconductor, and the toner remaining on the cleaning blade passes through the gap between the blades, that is, a so-called toner loss occurs. This toner loss tends to increase as the spherical toner is less caught.
In a cleaning device in which the contact pressure of the blade is reduced, the cleaning may not be performed at all, and the photoconductor having a softer surface layer of the photoconductor tends to be less easily cleaned.
[0020]
Description of cleaning
There are two methods of cleaning the toner, in which one cleaning blade is installed in a reverse rotation direction (counter) or a forward rotation direction (leading) with respect to the rotation direction of the photoconductor. Depending on the condition, a cleaning brush made of polyester fiber or nylon fiber is used in combination.
Since the blade cleaning method is an advantageous method for reducing the size of an image forming apparatus, it is employed in most image forming apparatuses.
In the blade cleaning method, if the blade is installed in the counter direction with respect to the rotation direction of the photoconductor, the bite into the photoconductor increases, and the cleaning performance of the toner can be improved.
The cleaning blade cuts an elastic plate rubber having a JIS-A hardness of about 50 to 70 degrees and a rebound resilience of about 40 to 70% into a strip having a width of 1.5 mm to 3 mm, and supports a plate made of aluminum or iron. It is generally used by attaching to a substrate.
At present, polyurethane rubber for a cleaning blade generally used is easily adhered to a photoconductor made of a polycarbonate resin, and the frictional resistance between the photoconductor and the blade is extremely large.
For this reason, usually, some kind of lubricant is taken into the surface layer of the photoreceptor and is applied from the outside. When the toner rotates once, the toner also becomes a certain amount of lubricant, and it is particularly difficult to reduce the friction coefficient. As long as the photoconductor does not use a binder resin, the photoconductor can be rotated normally. However, since the coefficient of friction is not sufficiently low, when the edge of the cleaning blade comes into contact with the photoconductor, the edge portion is pulled in the rotation direction of the photoconductor, causing the edge to be distorted and causing chatter ( Vibration). At this time, since a slight gap is generated between the blade and the photoconductor, a phenomenon occurs in which the toner adhered to the photoconductor and powder such as paper powder slip through. Slippage of the toner causes toner filming and contamination of the charging member, resulting in poor charging and deterioration of image quality.
Another cause of toner slippage is that the cut width of the cleaning blade is 1.5 to 3 (mm), so that the cleaning blade is deformed by being pressed and dragged by the photoconductor, the cut surface approaches the photoconductor, and the toner is removed by the blade. When the blade is lifted by being sandwiched between the photoconductor and the normal organic photoconductor, the surface layer of the photoconductor is not made durable, the surface layer is soft, so that the edge of the blade bites, Edges may be distorted, making uniform contact impossible. From this, it can be said that the surface roughness of the photosensitive layer is preferably as small as possible and the surface roughness is as small as possible as long as the degree of adhesion to the photosensitive member does not increase.
[0021]
There are several disclosed examples of a method for satisfactorily cleaning a spherical toner.
Japanese Patent Application Laid-Open No. 2001-242758 discloses that a plurality of plate-shaped cleaning blades are adhered to each other, and a relationship between a blade A that is in contact with the photoreceptor and a rebound resilience B on a side that is not in contact is 0.1B <A. JP-A-5-265360 discloses that a plate-shaped conductive blade is used as a cleaning member, an AC bias is applied to the blade, and a toner at the time of development is used. It is described that a DC voltage having the same polarity as the electric charge to be charged is applied, and JP-A-2001-313191 uses a toner having a shape factor SF-1 of 100 to 140 and an SF-2 of 100 to 120. Japanese Patent Application Laid-Open No. 2001-305 describes that a cleaning blade in contact with a photoreceptor in a counter direction is set to have a linear pressure of 20 g / cm to 60 g / cm. No. 76 discloses that a cleaning blade having a plate shape is used, and that the surface layer of the photoreceptor contains silicon compound fine particles having an average primary particle diameter of 5 to 500 nm in an amount of 3 to 30 parts by weight based on the total weight of the solid content. Has been described.
[0022]
In order to clean toner satisfactorily, it is necessary to prevent the edge of the cleaning blade from vibrating due to rotation, to prevent the edge of the blade from being dragged by the photoreceptor, and to press the toner by the blade. It is important not to make room (the blade should be in line contact with the photoreceptor during driving, not in surface contact). For this purpose, it is necessary to take measures not to cause the cleaning blade to be resistant to the shape and deformation and also to prevent the cleaning blade from coming off. The vibration of the blade also increases the wear of the photoconductor.
Further, when the friction coefficient of the photoconductor is large, the blade is easily distorted, and the toner is easily attached to the photoconductor. Therefore, the edge portion of the blade floats, causing a toner slip-through phenomenon. Although a certain effect is recognized in the disclosed examples, there is still room for improvement in any of the methods, and there is a possibility that the cleaning property is reduced by long-term use.
[0023]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to clean even toner having an average circularity as large as 0.98 or 0.99 to such an extent that image formation is not affected. It is an object of the present invention to provide an image forming apparatus and a process unit capable of stably maintaining a certain high-quality image.
[0024]
[Means for Solving the Problems]
As a result of examining a phenomenon in which a spherical toner having a high average circularity of about 0.98 or 0.99 slips through the cleaning blade and causes poor cleaning, it has been found that the phenomenon occurs as follows.
Generally, a relatively soft elastic body having a hardness of about 70 degrees is used for the blade used for the cleaning blade. The cleaning blade abuts such that the blade edge cut into a strip shape comes into line contact with the photoconductor. When the photoreceptor rotates, the tip of the blade is dragged in the rotation direction, and the tip is crushed or twisted, causing a gap or being dragged between the photoreceptors, causing a phenomenon in which toner enters. When the photoreceptor has a large roundness and straightness (large irregularities and distortion), a large friction coefficient (or surface free energy), and a low photoconductor hardness using an organic photoreceptor, the photoreceptor rotates. It has been found that when the blade occasionally vibrates, the blade edge is likely to be distorted, twisted, floated, or the like.
When toner is removed from the cleaning blade (cleaning failure), it causes not only background contamination, but also a reduction in the life of the cleaning blade and a decrease in durability due to accelerated wear of the photoconductor. This leads to increased costs.
[0025]
As a result of earnestly studying the means for solving the above problem, it has been found that it can be achieved by implementing the following matters.
The roundness and the straightness are “20 μm” and “± 20 μm”, respectively, and the depth of “6.7% to 80%” from the surface layer of the photosensitive layer in which the thickness of the charge transport layer is “10 μm to 30 μm”. In the meantime, alumina having a primary average particle size of “0.2 μm to 0.7 μm” is dispersed by “10% by weight or more and 40% by weight or less”, and the pencil hardness Hp becomes “HB ≦ Hp <2H”, In addition, the surface roughness was measured at 10 points average roughness Rz. _JIS A photosensitive member having a height of 0.4 μm to 0.8 μm, a maximum height Rz of 1.0 μm or less, and
JIS-A hardness "80-90 degrees", contact pressure with photoreceptor "15 g / cm or more and 25 g / cm or less", shape in which the edge contacting the photoreceptor is sharply cut when viewed from the side A cleaning blade having an edge width W of “0 <W ≦ 0.5 mm” at a portion in contact with the photoconductor and capable of abutting the photoconductor in the “counter direction”;
Can be achieved by an image forming apparatus combining the above.
[0026]
Specifically, it is as follows.
That is, the above-mentioned problem is solved by (1) the present invention, wherein an electrophotographic photosensitive member, a charging device, an image exposing device, a developing device, a transfer device, a cleaning device, and a fixing device are arranged at suitable positions to perform image formation. In an image forming apparatus using indirect electrophotography, an undercoat layer, a charge generation layer, and a charge transport layer are stacked on a conductive support, and the charge transport layer is at least an organic photosensitive layer. An elastic cleaning blade, which has an acute-angled V-shaped or knife-edge shaped abutment against the electrophotographic photosensitive member and is provided for toner cleaning, is provided with an elastic cleaning blade that is abutted and arranged with respect to the electrophotographic photosensitive member. An image forming apparatus comprising: a charge transport layer constituting the electrophotographic photoreceptor, wherein the charge transport layer comprises a filler non-dispersed charge transport layer and a filler dispersed charge transport layer; (3) The image forming apparatus according to the above (1), wherein the image forming apparatus has a layer configuration, and the filler-dispersed charge transport layer occupies 6.7% to 80% of the total thickness of the charge transport layer. "The charge transport layer constituting the electrophotographic photoreceptor has a two-layer structure of a filler non-dispersed charge transport layer and a filler dispersed charge transport layer, and there is no clear interface between both layers. (4) "The amount of the filler added to the filler-dispersed charge transport layer is 10% by weight or more and 40% by weight of the total weight of the filler-dispersed charge transport layer." % Or less, wherein the average particle diameter of the filler is 0.2 μm to 0.7 μm. It is alumina and is suitable for forming an image on the outermost surface of the charge transport layer in which alumina is dispersed. The image formation according to any one of the above items (1) to (4), wherein the 10-point average roughness is 0.4 μm to 0.8 μm and the maximum roughness is 1.0 μm or less. Apparatus ", (6)" the coefficient of static friction at the start of image formation of the electrophotographic photoreceptor is 0.3 to 0.5, and the average friction coefficient after 100 sheets of image formation at the time of applying lubricant is 0.3 to 0.5 ". (5) The image forming apparatus according to any one of the above (1) to (5), "(7)" the pencil hardness (Hp ) Is HB ≦ Hp <2H, wherein the image forming apparatus according to any one of the above items (1) to (6) ”, (8)“ the electrophotographic photosensitive member at the time of image formation ” Wherein the straightness is (±) 20 μm and the roundness is 0 to 20 μm. (9) The image forming apparatus according to any one of (7) and (9), wherein the electrophotographic photosensitive member has a built-in vibration damping member, and the straightness of the electrophotographic photosensitive member during image formation is (±) 20 μm; The image forming apparatus according to any one of the above items (1) to (8), wherein the roundness is 20 μm or less, (10) “the total thickness of the charge transport layer is 10 μm. As described above, the electric field strength held by the electrophotographic photosensitive member at the development position during development is (-) 1.3 x 10 ⁵ ~ 4.5 × 10 ⁵ (V / cm), the image forming apparatus according to any one of the above items (1) to (9) ", (11)" the edge angle of the cleaning member abutting on the photosensitive member. Is an acute angle and is a rubber-like elastic body having a JIS-A hardness of 80 to 90 degrees, wherein the image forming apparatus according to the above item (1), (12), The image forming apparatus according to the above (1) or (11), wherein the contact pressure (linear pressure) of the edge contacting the photoreceptor is 15 g / cm or more and 25 g / cm or less. (13) "If the edge width of the tip end of the rubber-like elastic body abutting on the photoreceptor is W, 0 <W ≦ 0.5 mm, wherein the item (1) or ( (10) The image forming apparatus according to any one of the above items (12) to (12), and (14) the rubber. The image forming apparatus according to any one of the above (1) or (10) to (13), wherein the elastic body is a cleaning member fixed to the metal supporting base. Is done.
[0027]
The object of the present invention is to provide (15) the electrophotographic photosensitive member according to any one of the above items (1) to (10), a DC voltage, or a DC voltage superimposed with an AC voltage. A contact or non-contact charging device, an image exposure device for performing optical writing on an electrophotographic photosensitive member with monochromatic light, a developing device including four-color toner, and the cleaning according to any one of the above items (11) to (14). A four-tandem color copying type image forming apparatus, in which a cleaning device using members and a belt-type intermediate transfer device for transferring a toner image are respectively provided and an image is formed. .
[0028]
Further, the above object is achieved by the present invention further provides (16) the electrophotographic photoreceptor according to any one of the above (1) to (10), and the above (11) to (14). An image forming process unit comprising a cleaning blade having the content described in any one of the above items), (17), and the electrophotograph described in any one of the above items (1) to (10). And an image forming process unit comprising the cleaning blade and the developing device according to any one of the above items (11) to (14).
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
1. Copy process
A copying process using the indirect electrophotographic method according to the present invention will be described with reference to FIGS.
In the copying process, a charging device (2), an image exposure device (3), a developing device (4), a transfer device (5), a separation device (6), a cleaning device (7) ( The cleaning device (7) basically includes a cleaning blade (7-1), but may further include a cleaning brush), a fixing device (8), and copy paper (9). Is done. Although the photosensitive member (1) shown in FIG. 1 has a built-in vibration damping member (10) for suppressing a vibration sound (high frequency sound) generated when an AC voltage is superimposed on the charging device. In the case of DC charging, there is no need to particularly incorporate the DC charging.
[0030]
FIG. 2 shows the cleaning device (7) and the charging device (2) as means for reducing the friction coefficient of the surface layer of the photoconductor and improving the wear resistance, cleaning property, and transferability of the photoconductor layer. FIG. 9 is a schematic diagram in the case where a lubricant applying device (200) ((201) indicates a lubricant, and (202) indicates an application brush) is provided therebetween.
In addition to the method shown in the figure, the means for applying can also be performed by adding it to the developer, so that it is not always necessary to mount such an apparatus.
[0031]
For color electrophotographic copiers and color laser beam printers, four photoconductors, which are advantageous in terms of copying speed, and four systems of yellow (Y), magenta (M), cyan (C), and black (Bk) Although there is a four-tandem tandem type copying system using a (color) developing device, this copying device can be described with reference to FIG. 1 or FIG. 2 only by repeating four copying cycles. FIG. 3 shows an example of a tandem type copying system.
1 to 3 can also constitute an image forming apparatus as a process unit in which a photoconductor and a cleaning member, a photoconductor and a developing device and a cleaning member, and a photoconductor and a developing device are integrally formed. It is. FIG. 4 shows an example of a process unit incorporating the photoconductor, charging, transfer, and cleaning devices or members.
[0032]
The photoreceptor (1) has a structure in which an undercoat layer (or an intermediate layer) is formed on a drum-shaped conductive support, and a photosensitive layer is formed thereon. And a film thickness of about 10 to 30 μm. As the charge generation layer, any of inorganic and organic materials can be used as long as holes and electron pairs (hole / electron pairs) generated by image exposure can move normally.
In the present invention, the charge transport layer comprises a filler non-dispersed charge transport layer and a filler dispersed charge transport layer.
The filler-dispersed charge transport layer occupies 6.7 to 80% of the total thickness of the charge transport layer (non-filler-dispersed charge transport layer + filler-dispersed charge transport layer), and the filler accounts for the total weight of the filler-dispersed charge transport layer. It is dispersed in an amount of 10% by weight or more and 40% by weight or less, so that abrasion resistance and resistance to biting of the cleaning blade are achieved.
The non-filler-dispersed charge transport layer and the filler-dispersed charge transport layer are formed so that no clear interface is formed between both layers.
In the photoconductor, a removable vibration damping member for suppressing vibration noise generated at the time of charging or when the cleaning blade is rubbed can be built in such a manner as to be in close contact with the inner wall of the photoconductor. If necessary, a lubricant may be applied to the surface layer of the photosensitive layer (the lubricant may be added to the toner and applied to the photoreceptor, or the lubricant may be applied via an application brush as shown in FIG. 2). There are several methods, etc.)
[0033]
The photoreceptor (1) is charged at -350 V to -1000 V by the charging device (2). However, considering the influence of corona products, discharge breakdown, and the like, the image quality is within a range where image quality is guaranteed. The dark portion potential Vd required for formation is preferably as low as possible, and it is desirable that the dark portion potential Vd at the position of the developing device is set to a constant value in the range of -350 to -800 V.
[0034]
The charging method generates much less ozone than the corona charging method, and is a contact charging method that is environmentally advantageous or generates more corona products, but a non-contact charging method can be preferably used. The charging member used for charging includes a roller-shaped, brush-shaped, sheet-shaped member, a magnetic brush using magnetic powder, and the like, and any of them can be used in the present invention. Considering image quality, charging stability, durability and the like, a roller charging method using an elastic member is desirable.
[0035]
The roller type charging member is a SUS round bar of φ5 to φ15 (mm) on the core metal, and the elastic member for charging the photoreceptor is urethane rubber or hydrin rubber; A control material is added, and if necessary, a water repellent such as a fluororesin is added to make the specific resistance 10 ² -10 ¹² (Ω · cm) is used. The hardness is about 30 to 80 degrees in JIS-A hardness. The external dimensions are set to about φ10 to φ20 (mm) according to system conditions.
[0036]
In the case of contact charging, the hardness is desirably low in order to increase the nip and increase the stability of charging.In the case of non-contact charging, the hardness is not limited because it does not contact the photoreceptor, but hard fine powdery foreign matter When mixed, if the hardness is high, there is a high possibility that a pinhole will be formed in the photoreceptor. Therefore, it is desirable that the hardness is low including the cushioning action for the following reasons.
When a hard conductive fine powder (aluminum powder, iron powder, etc.) is stuck in the photosensitive layer and pinholes are formed in the conductive support or the undercoat layer, discharge breakdown occurs and the conductive layer becomes completely conductive. In such a situation, a current flows from the charging roller, and when a charging member having a low specific resistance is used, a black band is generated in a portion having a pinhole in the length direction of the charging member. On the other hand, if it is too high, the charging characteristics will deteriorate. ⁵ -10 ¹⁰ (Ω · cm) is used.
[0037]
In the case of using the brush charging method, one brush is made of 10 to 100 filaments / bundle of 3 to 10 denier conductive fibers (for example, fibers obtained by adding carbon, an ionic conductive agent and the like to polyester fibers), and 80 to 600 filaments. A conductive brush in which the hairs are planted at a density of 1 / mm on the support and the bristle feet are cut between 1 and 10 mm can be suitably used.
[0038]
On the other hand, when the magnetic brush charging method is used, Zn-Cu ferrite particles having an average particle diameter of 25 μm and Zn-Cu ferrite particles having an average particle diameter of 10 μm are mixed at a weight ratio of 1: 0.05. By mixing, ferrite particles having an average particle diameter of 25 μm having a peak at each average particle diameter position were coated with a medium-resistance resin layer using magnetic particles, and the coated magnetic particles were coated on a sleeve to a thickness of 1 mm. And use it as a magnetic brush.
[0039]
The charging member is applied with a DC voltage of -1100 V to -1500 V alone or a DC voltage obtained by superimposing an AC voltage of 1000 V to 2000 V / 500 Hz to 4500 Hz on a DC voltage of -500 V to -1500 V. Usually, a sine wave is generally used as the waveform of the AC voltage, but a triangular wave (or sawtooth wave) may be used.
The electric field intensity applied to the photoconductor is (-) 1.3 × 10 ⁵ ~ 4.5 × 10 ⁵ (V / cm). This electric field strength is equivalent to charging the photosensitive member of 10 to 30 μm to (−) 350 to 800 (V). If the electric field strength applied to the photoconductor during image formation is large, the probability of reaching a discharge breakdown phenomenon when pinholes occur in the photosensitive layer increases, and if the electric field strength is low, the image quality may be poor Therefore, it is important to set an appropriate electric field strength for the photosensitive layer.
[0040]
After the charging, the photoconductor (1) receives, on one or a plurality of LD (Laser Diode) elements, an original image read by a CCD (Charge Coupled Device) or a digital signal transmitted from a personal computer or the like. An image image exposure device (3) including an LED (Laser Emitting Diode) array, a convex lens, a polygon mirror, a cylindrical lens, etc. irradiates a single-wavelength light image narrowed down to a dot diameter of about 60 to 20 μm, and receives an input signal. An electrostatic latent image corresponding to the image is formed. As the LD element or the LED array, an element having an emission wavelength corresponding to the highest sensitivity region of the photoconductor is selected. Since the spot diameter can be narrowed as the emission wavelength becomes shorter, an LD element having an oscillation wavelength on the short wavelength side of about 400 to 450 nm is advantageous in obtaining a high resolution such as 1200 or 2400 dpi. It can be used mounted on a forming apparatus.
The contrast potential required for image formation is usually set at about 250 V to 600 V.
Here, the contrast potential refers to the difference [Δ (Vl−Vb)] between the bright portion potential Vl and the developing bias potential Vb. The developing bias potential Vb is set to be higher by about 100 to 150 V than the charge level Vd in consideration of the degree of background contamination due to repetitive potential fluctuations.
[0041]
To visualize the electrostatic latent image formed on the photoreceptor (1), a developing device (4) using a one-component toner (magnetic toner) or a two-component developer composed of a toner and a carrier is used. However, in the present invention, a two-component developer is mainly used.
The carrier of the two-component developer includes, for example, polyfluorocarbon to improve the chargeability, charge stability, durability, etc. of powder having magnetic properties (magnetic powder) such as iron powder, ferrite powder, and nickel powder; A resin coated with a resin such as polyvinyl chloride or polyvinylidene chloride is used. The particle size of the carrier is about 30 to 60 μm.
The particle size of the carrier affects the resolution, and the smaller the size, the higher the resolution tends to be. However, if the size is too small, the carrier tends to adhere to the photoreceptor, resulting in poor transfer of the toner image (transfer loss), When conveyed to the cleaning section, the blade is pressed against the photoconductor by the blade, so that the photoconductor surface is damaged, which also contributes to shortening the durability of the photoconductor.
On the other hand, the toner may be a toner manufactured by the above-described pulverization method and having a spherical shape by shaving off an angular area, or a spherical toner manufactured by a polymerization method (emulsion polymerization method, suspension polymerization method, etc.). A toner having a diameter of 4 to 8 μm is used, and 2 to 10 (% by weight) is mixed with the carrier.
The particle size of the toner also affects the resolution similarly to the carrier. However, if the particle size is too small, there is a concern that the toner may harm health if it scatters (environmental destruction = pollution), and the use limit is considered to be at most about 4 μm.
[0042]
When the development is completed, a voltage (or an electric field) having a polarity opposite to the charge held by the toner is applied by using the transfer device (5), and the toner image is transferred to the copy paper (9). FIG. 1 illustrates a belt-shaped transfer device (5) (the transfer belt basically includes a support base, an elastic layer, and a coating layer). A transfer device of the type can be used.
After the transfer is completed, the copy paper is separated from the photoreceptor (1) by a separating device (6) to which an AC voltage or a DC voltage on which the AC voltage is superimposed is applied, and is sent to a fixing device (8). Become a copy. The separation device (6) is generally a corona discharge device that applies a voltage obtained by superimposing an AC voltage or a DC voltage on a metal wire or a sawtooth electrode. Since the electric field intensity applied to the photoreceptor via the copy paper may be an amount such that the copy paper is separated from the photoreceptor, the amount of corona generated is small, and is not large enough to damage the photoreceptor. When the diameter of the photoreceptor is 30 mm or less, the separating device may be omitted in some cases due to the paper stiffness.
On the other hand, the toner remaining on the photoreceptor after separation of the copy paper is a cleaning blade (7-1) made of a material such as polyurethane rubber, silicone rubber, neoprene rubber, or fluoro rubber, and / or a polyethylene blade, nylon, carbon fiber, or the like. The cleaning is performed by the cleaning device (7) used in combination with the cleaning brush made of fibers, and a series of copying processes is completed.
[0043]
Next, the photoconductor will be described.
2. Photoconductor
2-1. Photoconductor outline
The photoreceptor is composed of a drum-shaped aluminum conductive support, a subbing layer, a charge generation layer, and a charge transport layer in this order. The charge transport layer is at least composed of an organic photosensitive layer.
The charge transport layer can be used alone with the organic photosensitive layer.However, in order to improve the durability of the photoreceptor and the performance of maintaining image quality, a cleaning blade and a high hardness filler Is preferably formed on the organic photosensitive layer. FIG. 5 shows a schematic view of an example having a charge transport layer composed of a filler non-dispersed charge transport layer and a filler dispersed charge transport layer. That is, the charge transport layer comprises a filler non-dispersed charge transport layer and a filler dispersed charge transport layer, and the filler dispersed charge transport layer is configured to occupy 6.7 to 80% of the total charge transport layer. Alternatively, the charge transport layer comprises a filler non-dispersed charge transport layer and a filler dispersed charge transport layer, and is formed such that no clear interface exists between both layers. The charge transport layer, which is a filler non-dispersed charge transport layer or a filler dispersed transport layer, is a layer in which a low-molecular charge transport material is dispersed with an appropriate amount of a binder resin, an antioxidant, a dispersant, and the like, or a polymer charge. The film thickness and the layer structure can be set according to the required quality of the photoreceptor.
[0044]
The first purpose of adding a filler (in the present invention, an inorganic filler composed of alumina (α type) is particularly preferably used) is to increase the hardness of the surface layer of the photoreceptor by adding an appropriate amount of the filler. Pencil hardness Hp is HB ≦ Hp <2H) By increasing abrasion resistance, the life of the photoconductor is prolonged and the image quality is stabilized. However, a significant increase in hardness may cause image deterioration such as image deletion in order to reduce wear of the photosensitive layer.
In addition, using a pencil scratch tester (surface property measuring device HEIDON-14 type manufactured by Shinto Kagaku Co., Ltd.) manufactured based on JIS K 5401 and a JIS standard pencil (Mitsubishi pencil "Uni"), weight 100 g ( (Measured weight) is defined as the pencil hardness in the present invention.
[0045]
Means for measuring hardness include scratch hardness, Vickers hardness, Knoop hardness, and the like, in addition to pencil hardness. For a filler-dispersed charge transport layer in a dispersion system, abrasion such that the photosensitive layer is rubbed by a blade ( (Abrasive wear), it is a desirable method to make a determination using a pencil hardness measurement method. High pencil hardness means that the amount of filler added is large or the particle size is large, that is, the surface roughness is large, and the image quality is reduced, and foreign substances such as corona products are easily attached. Therefore, it is not desirable that the hardness is too high.
[0046]
The second purpose is to disperse a small particle size filler on the surface of the photosensitive layer to set a suitable hardness, to suppress a large increase in the coefficient of friction, and to suppress the cleaning blade edge from penetrating into the layer. Thus, the distortion and deformation of the blade edge are reduced as much as possible, and the toner not blocked by the cleaning blade (particularly a spherical toner produced by a polymerization method having a high sphericity) is prevented from coming off the blade as much as possible. .
If the surface of the photosensitive layer is a resin layer to which no filler is added, the coefficient of friction (or free surface energy) increases due to the action of corona products, paper powder, toner components, atmospheric moisture, etc., and cleaning is performed. At this time, the blade edge cuts into the photoconductor, and is dragged in the rotation direction of the photoconductor, causing deformation and local distortion, creating a gap between the photoconductor and a factor that causes toner loss. In addition, the crushed blade presses the toner against the photoreceptor, causing further stagnation of the toner, which further increases the toner loss. However, when the surface energy (or coefficient of friction) of the surface layer of the photoreceptor is reduced by a lubricant or the like, toner loss is improved, but reduction of the surface energy alone is not sufficient.
In order to minimize this deformation and distortion, a filler is dispersed in the photosensitive layer to prevent an extreme increase in the coefficient of friction and to suppress biting.
However, since toner loss is not sufficient only by using the above-described filler-containing photoconductor, in order to improve the cleaning performance of spherical toner to a level close to 100%, even if the photoconductor is rotating, The task can be achieved by using a specific cleaning blade that maintains line contact without crushing or distortion of the blade edge and does not cause the toner to be crushed by the blade. Further, if necessary, a lubricant is applied to the surface of the photoreceptor to reduce the coefficient of friction of the surface of the photoreceptor, thereby ensuring long-term stable cleaning performance and maintaining the durability of the cleaning blade.
It should be noted that a method of changing a low-molecular-weight charge-transporting substance, which is a constituent substance of the charge-transporting layer, to a high-molecular-weight charge-transporting substance is also one means for improving abrasion resistance.
[0047]
The thickness of the photosensitive layer is desirably set to a value enough to obtain a sufficient contrast image and a thickness that can secure a contrast potential. If the contrast potential (difference between the developing bias potential and the image portion potential) is 100 V, a character image can be formed at a relatively good level, but a photographic image is not practical because of insufficient density. Not a target. In order to obtain good image forming properties, it is desirable to secure a contrast potential of at least 250 V or more.
It is preferable that the total film thickness of the photosensitive layer is set to 10 μm or more as a film thickness at which a contrast potential can be secured. If the film thickness is reduced to 10 μm or less, it is difficult to secure a sufficient charge level, and it is difficult to obtain a sufficient contrast potential. Further, unevenness in the thickness of the photosensitive layer is easily reflected on the image as it is, resulting in non-uniform image quality. On the other hand, if the thickness is too large, the dot pattern spreads in the layer, causing a reduction in sharpness and resolution, making it difficult to achieve a high-quality image.
In order to obtain an image having a higher contrast, the thickness is usually about 10 μm to 50 μm, preferably 10 μm to 30 μm.
[0048]
Hereinafter, the configuration of the photoconductor will be described.
2-2. Conductive support
First, the conductive support will be described.
Materials that can be used as the conductive support of the photoconductor include metals such as stainless steel, copper, and brass that satisfy various electrical, mechanical, and chemical properties, as well as gold, aluminum, and platinum on compressed paper, resin, and glass. And a conductive layer on which chromium or the like is deposited or sputtered, or a conductive layer in which fine particles of carbon, tin, or the like are dispersed. In view of the fact that thin cutting is easy to perform, light, advantageous for reproduction, easy to form a blocking layer, easy to obtain, and the like, aluminum, particularly an aluminum alloy such as JIS3003 is preferable.
The technologies for processing the surface of aluminum include cutting, honing, and blasting.The drum-shaped aluminum tube is cut to the required length, cut to the target outer diameter, and then super-finished. , Mirror finish, etc., to make the surface roughness 10 points average roughness Rz _JIS And then sufficiently washed until the washing solution is completely removed, and used as a conductive support for an electrophotographic photosensitive member. The roughness of the support is covered to some extent by the undercoat layer. However, if the surface roughness is as large as 10 μm or more, the undercoat layer cannot cover the unevenness. Charge injection occurs, and abnormal images such as streak patterns, white spots, and black spots on the image are likely to appear on the entire copy sheet.
Aluminum is an oxide film (Al ₂ O ₃ ) Is easy to form, but the electrical resistance for maintaining the electrophotographic characteristics is 10 ⁶ There is no particular problem as long as the value is on the order of Ω · cm or less.
The conductive support has a drum shape and an outer diameter of about φ30 to φ80 (mm) is generally used. However, in the case of a large-sized image forming apparatus, in order to cope with durability and large-volume copying, Those having an outer diameter of φ80 mm or more are used.
The thickness of aluminum is about 0.6 mm to 3 mm for a photoreceptor having an outer diameter of φ30 to φ80 (mm). Therefore, if it is not deformed at such a temperature, conductive support is required if the vibration damping member is incorporated as a means for suppressing cost and charging when using the DC voltage of the AC voltage superimposed. It is desirable that the body thickness is thin. By reducing the wall thickness, the vibration generated by the charging can be quickly transmitted to the vibration damping member, so that the vibration damping function can be effectively exhibited.
[0049]
2-3. Undercoat layer
Next, the undercoat layer will be described.
An undercoat layer is provided between the conductive support and the photosensitive layer, if necessary. The form of the undercoat layer may vary depending on the wavelength range used for the light source. For example, when used for a light source such as an LD element or an LED array having an oscillation wavelength in a long wavelength region of 650 to 780 nm, moiré occurs due to reflection of light from aluminum, so that an undercoat layer or a similar layer is used. The formation of an anti-reflection thin film is indispensable, but when an LD element having an oscillation wavelength of about 400 to 420 nm is used, the absorption near the surface layer increases, so that a lower layer as described in a specific example of the present invention is used. The pulling layer is not necessarily required, and may be a thin film having a thickness of 1 μm or less, such as alumina, or a semiconductor film that prevents hole injection. The following description is for the case where a light source having an oscillation wavelength in a long wavelength region (infrared region) is used.
The reason for forming the undercoat layer is to prevent charge injection from the support side, stabilize charging characteristics, improve adhesion, prevent moiré, improve coatability of the upper layer, reduce residual potential, etc. With the goal. Therefore, a method may be adopted in which a semiconductor film is formed to prevent injection of holes (holes) and allow electrons (electrons) to pass therethrough, and further form an intermediate layer or an undercoat layer thereon. In general, the undercoat layer is formed of a thin film containing a resin as a main component and having a high resistance so that potential decay hardly occurs within a unit time. Considering that the undercoat layer is coated with a photosensitive layer using a solvent, it is preferable that the undercoat layer be a resin having high resistance to dissolution in general organic solvents. As such a resin, polyvinyl alcohol, casein, water-soluble resin such as sodium polyacrylate, copolymerized nylon, alcohol-soluble resin such as methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, epoxy resin, etc. Curable resins that form a three-dimensional network structure are exemplified. Further, fine powders of metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like, or metal sulfides and metal nitrides may be dispersed and contained. These undercoat layers can be formed using a suitable solvent and a coating method.
Further, as the undercoat layer of the present invention, a metal oxide layer formed by using a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like by a sol-gel method or the like is also useful.
In addition, as the undercoat layer of the present invention, Al ₂ O ₃ , An organic substance such as polyparaxylylene (Parylene = trade name of Union Carbide Co.), SnO ₂ , TiO ₂ , CeO ₂ Inorganic substances such as are provided by a vacuum thin film manufacturing method. ¹⁰ -10 ¹³ A thin film having an electrical resistance on the order of (Ω · cm) can be used favorably. The thickness of the undercoat layer is suitably from 0.1 to 20 μm, and preferably from 1 to 10 μm.
[0050]
2-4. Charge generation layer
Next, the charge generation layer will be described.
The charge generation layer is a layer containing a charge generation substance as a main component, and a binder resin is used as necessary. As the charge generation substance, there are an inorganic material and an organic material.
Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compound, and amorphous silicon. As amorphous silicon, a material in which a dangling bond is terminated with a hydrogen atom or a halogen atom, or a material in which a dangling bond is doped with a boron atom, a phosphorus atom, or the like is preferably used.
[0051]
On the other hand, as the organic material, a known material can be used. For example, phthalocyanine-based pigments such as metal phthalocyanine and metal-free phthalocyanine, azulhenium salt pigment, methine squaric acid pigment, azo pigment having a carbazole skeleton, azo pigment having a triphenylamine skeleton, azo pigment having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyryl carbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinone imine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Njigoido based pigments, and bisbenzimidazole pigments. These charge generating substances can be used alone or as a mixture of two or more kinds.
[0052]
As the binder resin used as necessary for the charge generation layer, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N- Vinyl carbazole, polyacrylamide and the like are used. These binder resins can be used alone or as a mixture of two or more. In addition, a low molecular charge transport material may be added as needed.
[0053]
Examples of the electron transporting substance include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-trione An electron accepting substance such as nitrodibenzothiophene-5,5-dioxide is exemplified. These electron transport materials can be used alone or as a mixture of two or more.
[0054]
Examples of the hole transport material include the electron donating materials shown below and are preferably used.
For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives and the like. These hole transporting substances can be used alone or as a mixture of two or more.
The charge generation layer contains a charge generation substance, a solvent, and a binder resin as main components, and may include any additives such as a sensitizer, a dispersant, a surfactant, and a silicone oil. good.
[0055]
As a method for forming the charge generation layer, a vacuum thin film preparation method and a casting method from a solution dispersion system are largely mentioned. For the former method, a vacuum evaporation method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, or the like is used, and the above-mentioned inorganic material and organic material can be favorably formed. In addition, in order to provide a charge generation layer by a casting method, if necessary, the above-mentioned inorganic or organic charge generation material is used together with a binder resin together with a binder resin such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone, or a ball mill, an attritor, or the like. It can be formed by dispersing with a sand mill or the like, diluting the dispersion liquid appropriately and applying. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like.
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.
[0056]
2-5. Charge transport layer
Next, the charge transport layer will be described.
The charge transport layer is formed to secure a surface potential required for image formation. The charge transport layer can be used in the present invention even if the organic photosensitive layer alone is used. However, in order to maintain durability and image quality of the photoreceptor, an organic photosensitive layer (non-filler dispersed charge transport layer) is further provided on the outermost surface. It is desirable to form a filler-dispersed charge transport layer to which an appropriate amount of ultrafine inorganic filler particles of high hardness is added. In the present invention, as shown in FIG. 5, the charge transporting layer is composed of a filler non-dispersed charge transporting layer and a filler dispersed charge transporting layer, and is configured such that no clear interface is formed between both charge transporting layers. By preventing a clear interface from being formed, most of the holes / electron pairs (hole / electron pairs) generated by image exposure that have moved toward the surface layer are not captured near the interface. In addition, the charge transferred to the surface layer and given by the charge can be canceled without loss of time. That is, since the optical attenuation characteristic hardly deteriorates, high-definition image quality can be reproduced. However, since the filler is dispersed, a slight loss occurs due to the amount of dispersion of the filler, the particle size, and the like.
When an interface is formed between the two charge transport layers, the movement of holes is restricted, so that the light attenuation characteristic is degraded and the residual potential is increased, so that the contrast potential is reduced and the afterimage is easily caused.
The coating means for preventing the formation of the interface can be prepared by a spray coating method when the thickness of the charge transport layer is as thin as about 10 μm. Inject the liquid and the filler-dispersed charge transport layer liquid in the other, apply the filler non-dispersed charge transport layer on the charge generation layer, and wait for the finger dry time (several minutes). What is necessary is just to apply a transport layer. When the charge transport layer is as thick as 25 μm or 30 μm, and when the filler non-dispersed charge transport layer is as thick as 20 μm, first, the filler non-dispersed charge transport layer is formed, touch dried, and further dried by heating at 120 to 130 ° C. Thereafter, the filler-dispersed charge transport layer is formed within a relatively short time, and the entire photoconductor is heated and dried at a temperature of 130 to 160 ° C. for about 10 to 60 minutes, whereby the photoconductor can be manufactured without any problem.
The charge transporting layer (filler non-dispersed charge transporting layer + filler dispersed charge transporting layer) is formed by dissolving or dispersing a mixture or copolymer containing a charge transporting component and a binder component as main components in a suitable solvent. It can be formed by coating to a required thickness and drying.
[0057]
The thickness of the charge transport layer is set to 10 to 50 μm, preferably 10 to 30 μm. The variation in the entire photosensitive layer (difference between the maximum film thickness and the minimum film thickness) is desirably set fine because the thinner the photosensitive layer is, the more easily the influence of coating unevenness is produced. Therefore, ± 10 μm for 10 μm and ± 1 μm for 30 μm Is preferably set within a range of ± 2 μm. Among these, unless the filler non-dispersed charge transport layer and the filler-dispersed charge transport layer do not have a clear interface, the tightening ratio (occupancy) of the filler-dispersed charge transport layer thickness is preferably 6.7% to 80%. It is.
As the thickness of the photosensitive layer decreases, the capacitance increases, and the electric field intensity increases. However, it is difficult to secure a high charge level. If the charge of the toner is small, the developing ability can be increased even with a photoreceptor with a small film thickness, but voltage development is inevitable for toners of small particle diameter currently used in the market at present. Therefore, a certain or more surface potential is required.
When the thickness of the photosensitive layer is reduced, the distortion of the charge transfer is reduced, so that a high-quality image can be reproduced. On the other hand, as the thickness increases, the capacitance decreases, so that a high charge level can be secured. However, when the charge moves, the charge tends to be distorted upon input of light, and the resolution tends to decrease.
When the thickness of the photosensitive layer is set to about 10 μm, the charged portion is charged only at about −450 V at most. However, if the residual potential is suppressed to about −50 V to −100 V and the developing bias potential is set to −350 V, a contrast potential of about 250 V to 300 V can be secured, so that practically problem-free image formation can be performed. It is.
The charge transport layer is formed on the charge generation layer in the order of the filler non-dispersed charge transport layer and the filler dispersed charge transport layer. This is because, when the filler-dispersed charge transport layer is in direct contact with the charge generation layer, abnormal movement of charges occurs between the filler-dispersed charge transport layer and the charge generation layer, so that a speckle pattern appears on the image. Therefore, in the region in contact with the charge generation layer, it is desirable that the charge transport layer does not disperse the filler, and it is desirable that the film thickness be at least 2 μm or more.
For the coating film, a dip coating method, a spray coating method, or the like can be used.
[0058]
The filler added to the filler-dispersed charge transport layer is spherical and has high hardness, has optical transparency, and has an electric resistance of 10%. ¹² -10 ¹³ (Ω · cm). This improves the abrasion resistance of the photosensitive layer, and the light image illuminated on the surface layer must reach the charge generation layer without scattering, while the charge does not diffuse in the horizontal direction during charging, and This is to avoid the flow and the accumulation of the residual potential as much as possible.
The filler in the filler-dispersed charge transport layer is preferably uniformly dispersed in the charge transport layer, or a layer configuration in which the concentration gradient is increased toward the surface layer, but from the viewpoint of maintaining durability, Uniform dispersion is preferred.
The amount of filler dispersed in the charge transport layer depends on the required durability (depending on abrasion, chemical and physical deterioration), and image quality (depending on the aging characteristics such as charge level, sensitivity and residual potential). To 10% by weight or more and 40% by weight or less based on the total weight of the filler-dispersed charge transport layer. When the content is less than 10% by weight, the abrasion increases rapidly. When the content is more than 40% by weight, the residual potential increases, the surface roughness of the photosensitive layer deteriorates, and toner filming easily occurs due to the surface roughness. Is suppressed, and image deletion is easily caused.
The thickness of the filler-dispersed charge transporting layer depends on the particle size and amount of the filler dispersed in the photosensitive layer, and needs to be changed depending on the durability required for the photoreceptor and image quality characteristics. From the viewpoint of durability, it is desirable that the filler-dispersed charge transport layer be thicker. However, when the amount of the filler is in the range of 10% by weight or more and 40% by weight or less, when the thickness is increased to 8 μm or more, a sharp increase in the residual potential may occur. And the image quality is affected.
On the other hand, when the film thickness is reduced, the resolution tends to be improved, but the durability is lowered. It is desirable to set the film thickness to at least 2 μm or more.
From the viewpoint of the distribution of the thickness of the filler non-dispersed charge transport layer and the filler-dispersed charge transport layer, when the charge transport layer is set within the range of 10 to 30 μm, the filler non-dispersed charge transport layer and the filler dispersed charge transport layer The thickness of the filler-dispersed charge transport layer is desirably 6.7% to 80% of the charge transport layer, unless the layer has no clear layer interface.
FIG. 6 is a graph showing a preferable thickness ratio of the charge transport layer. Good characteristics can be obtained within a line of 10 to 30 (μm) and a frame surrounded by two curves shown in FIG.
[0059]
The materials used for the charge transport layer are as follows.
Oxazole derivatives, oxadiazole derivatives, imidal derivatives, triphenylamine derivatives, α-phenylstilbene derivatives, toniphenyl methane derivatives, anthracene derivatives, and the like can be used as the low-molecular-weight charge transport material constituting the charge transport layer.
On the other hand, as the polymer charge transporting substance, the following known polymer charge transporting materials can be used. For example,
1) Polymers having a carbazole ring in the main chain and / or side chain include, for example, poly-N-vinyl carbazole, JP-A-50-82056, JP-A-54-9632, There are the compounds described in JP-A-54-11737 and JP-A-4-183719.
2) Polymers having a hydrazone structure in the main chain and / or side chain include, for example, compounds described in JP-A-57-78402 and JP-A-3-50555.
3) Examples of the polysilylene polymer include compounds described in JP-A-63-285552, JP-A-5-19497, and JP-A-5-70595.
4) Polymers having a tertiary amine structure in the main chain and / or side chain include, for example, N, N-bis (4-methylphenyl) -4-aminopolystyrene, JP-A-1-13061, JP-A-1-19049, JP-A-1-1728, JP-A-1-105260, JP-A-2-167335, JP-A-5-66598, and compound described in JP-A-5-40350 Etc.
5) Other polymers include, for example, formaldehyde polycondensates of nitropyrene and compounds described in JP-A-51-73888 and JP-A-56-150749.
[0060]
The polymer having an electron donating group used in the present invention is not only the above-mentioned polymer, but also a copolymer of a known monomer, a block polymer, a graft polymer, a star polymer, and, for example, It is also possible to use a crosslinked polymer having an electron donating group as disclosed in JP-A-3-109406.
As the polymer charge transporting material in the present invention, a polycarbonate having a triarylamine structure in the main chain and / or side chain is effectively used.
On the other hand, examples of the high molecular compound that can be used as the binder component include polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, polyester resin, polyvinyl chloride, and chloride. Vinyl / vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, polycarbonate resin (bisphenol A type, bisphenol C type, bisphenol Z type or a copolymer thereof), cellulose acetate resin, ethyl cellulose resin, polyvinyl Thermoplastic or heat of butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluorine resin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, etc. Including but of resin, but is not limited thereto. These polymer compounds can be used singly or as a mixture of two or more kinds, or copolymerized with a charge transport material.
[0061]
Examples of dispersion solvents that can be used when preparing the charge transport layer coating liquid include, for example, methyl ethyl ketone, acetone, methyl isobutyl ketone, ketones such as cyclohexanone, dioxane, tetrahydrofuran, ethers such as ethyl cellosolve, toluene, xylene and the like. Examples thereof include aromatics, halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate. However, it is desirable to avoid using a halogen-based solvent in consideration of environmental destruction.
[0062]
Next, the filler dispersed in the charge transport layer will be described.
The filler used in the present invention is an oxide insulator, and when dispersed in a binder resin, traps are easily formed at the interface between the particles and the binder resin. Therefore, when the photoreceptor is used repeatedly, the residual potential accumulates and the potential of the image portion is increased, so that the image density and the resolution are easily reduced. Therefore, an additive can be added to improve the dispersibility, uniformize the photosensitive layer, prevent the formation of traps, or reduce the trap density.
Means for imparting electric charge to the photoreceptor during image formation is performed by a charging device that is in contact with or close to the photoreceptor, and corona products such as ozone and nitrogen oxides generated during charging are applied to the photoreceptor. It attaches to the surface layer or penetrates into the photosensitive layer, lowering the electrical resistance and causing deterioration in image quality such as resolution. In order to solve this, a small amount of an antioxidant and a plasticizer can be added. However, these additives are not always necessary, and may be omitted when the charge transport layer is thin, when the amount of the filler added is small, or depending on the image system.
In the charge transporting layer to which the filler is added, a coating liquid in which a suitable amount of the filler is dispersed in a binder resin is applied to a target film thickness by using a coating method such as a spray method or a dipping method.
Filler is 10 ¹² -10 ¹⁴ (Ω · cm), desirably having water repellency and maintaining its function.
[0063]
The filler material includes an organic filler material and an inorganic filler material. Examples of the organic filler material include a fluororesin powder such as polytetrafluoroethylene, a silicone resin powder, and an amorphous carbon powder. Materials include metal powders such as copper, tin, aluminum, and indium, silica, tin oxide, zinc oxide, titanium oxide, alumina, indium oxide, antimony oxide, bismuth oxide, calcium oxide, tin oxide and tin doped with antimony. Metal oxides such as doped indium oxide; metal fluorides such as tin fluoride, calcium fluoride, and aluminum fluoride; and inorganic materials such as potassium titanate and boron nitride. Among these fillers, it is advantageous to use an inorganic material from the viewpoint of the hardness of the filler for improving the wear resistance.
In particular, titanium oxide or alumina can be desirably used in the present invention, but alumina (particularly α-type) is more preferable. These fillers can be used alone or as a mixture.
The filler material can be dispersed by using a suitable disperser together with a charge transporting substance, a binder resin, a solvent, and the like.
[0064]
If the surface roughness of the photosensitive layer increases due to the addition of the filler, the edges of the characters become jagged, and the cleaning properties of residues such as toner and paper dust deteriorate, resulting in defective cleaning. Contaminants such as corona products remain in areas where the blade does not come into contact, causing image deletion, toner filming, and chipping of the edge of the cleaning blade, and the photosensitive layer is easily damaged. Therefore, it is necessary to select a filler having a particle size with good dispersibility so that the target abrasion resistance can be achieved and good image quality can be obtained. The primary particle size of the filler dispersed in the photosensitive layer is selected from the light transmittance, abrasion resistance, surface roughness and the like of the charge transport layer.
[0065]
For example, FIG. 7 shows a measurement example of the average primary particle diameter and the average surface roughness (measured using Surfcom 1400D, Tokyo Seimitsu Co., Ltd.). The measurement sample was a photosensitive member having a diameter of 30 mm, and the charge transport layer was composed of a 22 μm non-dispersed charge transport layer and a 5 μm filler-dispersed charge transport layer in which α-alumina filler was dispersed at 25% by weight. As shown in FIG. 7, when the primary particle size of the filler is 0.2 μm to 0.7 μm, the 10-point average roughness (Rz _JIS ) And the maximum roughness Rp are both 1 μm or less, and show good numerical values in image formation and toner cleaning.
However, when the primary particle size exceeds 0.7 μm, the surface roughness tends to suddenly increase. When a filler having a primary particle size of 1.0 μm is dispersed, the 10-point average roughness (Rz _JIS ) Is 1.2 (μm) and the maximum roughness Rz is 1.5 (μm), which is a level at which the character thickening, the resolution is reduced, and the edge of the cleaning blade is slightly affected.
For this reason, it is desirable to use alumina having a particle size of 0.7 μm or less as the primary particle size to be added to the photosensitive layer. It is possible to secure.
If the surface roughness of the photoreceptor surface is too small, the cleaning blade easily adheres to the surface of the photoreceptor, and the rotation of the photoreceptor causes the blade edge to be dragged. Distortion occurs, which is a factor that causes toner loss.
In addition, the filler concentration is highest on the outermost surface side of the charge transport layer and the filler concentration gradient is provided so that the support side is lower, or the charge transport layer is formed of a plurality of layers, and the filler concentration is increased from the support side to the surface side. It is also possible to adopt a configuration in which the height is increased sequentially. When the filler is added to the charge transport layer, the amount of the filler to be added to the photosensitive layer needs to be changed depending on the required number of printing presses and image quality, the copying process used, the developer component, and the like.
[0066]
In FIG. 8, a 22 μm filler non-dispersed charge transport layer is formed on an φ30 μm aluminum drum via an undercoat layer, and an alumina filler (α-alumina) having a primary average particle size of 0.3 μm is added thereon. An example of the evaluation results of the abrasion of the photosensitive layer and the image rank in the photosensitive member having the filler-dispersed charge transport layer of about 5 μm formed by changing the amount is shown. The evaluation conditions were such that a voltage obtained by superimposing a DC voltage of -740 and an AC voltage of 1600 V / 1350 Hz was applied to the charging member for contact charging of the Ricoh Imagio MF2200 machine, and the surface potential at the developing unit position was set to -700 V. And 100,000-sheet running.
The abrasion of the photosensitive layer increases sharply as the amount of filler added decreases, and the image quality ranks (rank 5 is good, rank 1 is unacceptable, and the evaluation target is resolution, sharpness, and dot reproducibility). Has a tendency to drop below 30% by weight, but at 40% by weight, the image quality still maintains Rank 4. For this reason, the amount of the filler added to the filler-dispersed charge transport layer is desirably 40% by weight or less. The durability of more than 10,000 sheets is maintained. However, it has been confirmed that when the paper is further passed, the filming phenomenon is likely to occur from about 40% by weight. Therefore, the amount of the filler added to the photosensitive layer should be 10% by weight or more and 40% by weight or less. It is desirable to select by.
[0067]
As a means for eliminating roughness of the photosensitive layer surface and smoothing it, for example, adding a leveling agent to the charge transport layer according to the invention is an effective means. As the leveling agent, a known material can be used. However, a silicone oil-based leveling agent, which can impart a high level of smoothness in a small amount and has a small effect on electrostatic characteristics, is particularly preferable. Examples of silicone oils include dimethyl silicone oil, methyl phenyl silicone oil, methyl hydrogen polysiloxane, cyclic dimethyl polysiloxane, alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, and amino-modified silicone oil. Examples include silicone oil, mercapto-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, higher fatty acid-modified silicone oil, and higher fatty acid-containing silicone oil. In addition, it is possible to reduce unevenness depending on conditions at the time of coating and the like. For example, in dip coating, after lifting the photoreceptor, if the coating surface is still wet, cover it with a hood so that the surface is not disturbed by wind flow etc. Is done. Also, if the solvent near the surface of the coating film evaporates rapidly, only the surface is hardened and the inside of the coating film becomes fluid, and the coating film inside this film may sag and form irregularities. In a wet state, a vapor layer of a solvent is formed around the photoreceptor, and the solvent is gently volatilized, whereby leveling progresses, and unevenness is reduced and smoothed.
[0068]
Also, in spray coating, when forming a coating film by air spray, by controlling the air pressure and the air flow rate to an appropriate amount, the surface of the coating film in a fluid state is suppressed and irregularities are suppressed. It is necessary to control. Here, if the air pressure and air flow rate are too large, the surface of the coating film will be disturbed by the flow of air, while if too small, the droplets of the coating liquid will not be uniform or the atomization will be insufficient. As a result, the uniformity of the coating film is reduced. After the charge transport layer is formed, the solvent is volatilized while being rotated. If the rotation speed is too high, centrifugal force is applied to the coating film which still contains the solvent and has fluidity, so that unevenness is emphasized. On the other hand, if the rotation speed is too low, the effect of sagging due to gravity is greater than the leveling due to rotation, which may cause unevenness. Therefore, it is necessary to set the rotation speed of the photoconductor in a wet state of the coating film to an appropriate value.
Further, in spray coating, it is important that the supply of a pump for supplying a coating liquid is constant. In other words, if the supply of the liquid is not constant and has a pulsation, the pulsation directly affects the discharge amount of the liquid, so that the adhesion amount becomes uneven. Therefore, as a pump for supplying the liquid to the spray, it is preferable to use a multiple plunger pump in which pulsation is suppressed, a syringe-type super-precision discharge device, or the like.
These methods may be used alone, but by combining a plurality of them, a more effective leveling is performed and a charge transport layer with reduced unevenness is formed.
Furthermore, when the leveling is insufficient, it is also possible to wear and smooth the convex portions of the charge transport layer as a method of reducing unevenness. For example, a method in which a convex portion is detected by a film thickness meter and the portion is polished to eliminate the convex portion can be considered.
[0069]
In the present invention, in order to improve environmental resistance, and to prevent a decrease in sensitivity and a rise in residual potential, oxidation of each layer such as a charge generation layer, a charge transport layer, an undercoat layer, a protective layer, and an intermediate layer is performed. Inhibitors, plasticizers, lubricants, UV absorbers, and low molecular charge transport materials can be added. Representative materials of these compounds are described below.
[0070]
Examples of the antioxidant that can be added to each layer include the following, but are not limited thereto.
(A) Phenolic compound
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n-octadecyl-3- (4′-hydroxy-3 ′, 5 '-Di-t-butylphenol), 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-t-butylphenol) 4,4'-thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidenebis- (3-methyl-6-t-butylphenol), 1,1,3-tris- ( 2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, Tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3′-t-butylphenyl) butyric acid] Clichol esters, tocopherols and the like.
(B) paraphenylenediamines
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N, N'- Di-isopropyl-p-phenylenediamine, N, N'-dimethyl-N, N'-di-tert-butyl-p-phenylenediamine and the like.
(C) Hydroquinones
2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl ) -5-methylhydroquinone and the like.
(D) Organic sulfur compounds
Dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like. (E) Organic phosphorus compounds
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.
[0071]
Examples of the plasticizer that can be added to each layer include the following, but are not limited thereto.
(A) Phosphate ester plasticizer
Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichloroethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate and the like.
(B) Phthalate ester plasticizer
Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, dinonyl phthalate, dinononyl phthalate, phthalic acid Diisodecyl, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, methyl oleyl phthalate, octyl decyl phthalate, dibutyl fumarate, dioctyl fumarate and the like.
(C) Aromatic carboxylate plasticizer
Trioctyl trimellitate, tri-n-octyl trimellitate, octyl oxybenzoate and the like.
(D) Aliphatic dibasic ester plasticizer
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, n-octyl adipate-n-decyl, diisodecyl adipate, dicapry adipate, diazellate -2-ethylhexyl, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexyl sebacate, di-2-ethoxyethyl sebacate, dioctyl succinate, diisodecyl succinate, Dioctyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate and the like.
(E) Fatty acid ester derivatives
Butyl oleate, glycerin monooleate, methyl acetyl ricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, tributyrin and the like.
(F) Oxyacid ester plasticizer
Methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, tributyl acetyl citrate and the like.
(G) Epoxy plasticizer
Epoxidized soybean oil, epoxidized linseed oil, butyl epoxystearate, decyl epoxystearate, octyl epoxystearate, benzyl epoxystearate, dioctyl epoxyhexahydrophthalate, didecyl epoxyhexahydrophthalate, and the like.
(H) Dihydric alcohol ester plasticizer
Diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate and the like.
(I) Chlorine-containing plasticizer
Chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxy chlorinated fatty acid methyl and the like.
(J) Polyester plasticizer
Polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester, etc.
(K) sulfonic acid derivative
P-toluenesulfonamide, O-toluenesulfonamide, P-toluenesulfonethylamide, O-toluenesulfonethylamide, toluenesulfone-N-ethylamide, P-toluenesulfon-N-cyclohexylamide and the like.
(L) Citric acid derivative
Triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, acetyl tri-2-ethylhexyl acetyl citrate, n-octyldecyl acetyl citrate and the like.
(M) Other
Terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietate and the like.
[0072]
In the present invention, a lubricant can be added to each layer. Examples include, but are not limited to, the following.
(A) Hydrocarbon compounds
Liquid paraffin, paraffin wax, microwax, low-polymerized polyethylene, etc.
(B) fatty acid compound
Lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, etc.
(C) Fatty acid amide compound
Stearyl amide, palmityl amide, olein amide, methylene bis stearoamide, ethylene bis stearoamide and the like.
(D) Ester compound
Lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, and fatty acid polyglycol esters.
(E) Alcohol compounds
Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethylene glycol, polyglycerol and the like.
(F) Metal soap
Lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate and the like.
(G) Natural wax
Carnauba wax, Candelilla wax, beeswax, whale wax, Ibota wax, Montan wax, etc.
(H) Other
Silicone compounds, fluorine compounds, etc.
[0073]
Examples of the ultraviolet absorber that can be added to each layer include the following, but are not limited thereto.
(A) Benzophenone type
2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ′, 4-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone and the like.
(B) salicylate
Phenyl salicylate, 2,4-di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate and the like.
(C) Benzotriazole type
(2′-hydroxyphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy-3′-tert-butyl) -5'-methylphenyl) -5-chlorobenzotriazole
(D) cyanoacrylate-based
Ethyl-2-cyano-3,3-diphenyl acrylate, methyl-2-carbomethoxy-3- (paramethoxy) acrylate and the like.
(E) Quencher (metal complex salt)
Nickel (2,2′-thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyl dithiocarbamate, nickel dibutyl dithiocarbamate, cobalt dicyclohexyl dithiophosphate, and the like.
(F) HALS (Hindered amine)
Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6 6-tetramethylpyridine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy- 2,2,6,6-tetramethylpiperidine and the like.
There is.
[0074]
3. Roundness and straightness
As one of the factors for obtaining high quality image quality, the roundness and straightness of the photoconductor are important.
If the roundness is large, that is, if it is a distorted cylinder, the photoreceptor will rotate eccentrically, causing poor charging, poor transfer, and poor cleaning.If the straightness is large, uneven charging will occur. This causes image density and color unevenness to occur easily. In particular, in the case of a non-contact charging method in which charging is performed while maintaining a small gap around 50 μm, the method is particularly susceptible to the influence. Also, in the contact charging method, when charging is performed only by direct current, the gap between the photoconductor and the charging member immediately affects the discharge condition, and the larger the gap, the more easily charging unevenness occurs. Management of roundness and straightness is particularly important.
It is desirable that the roundness and the straightness be as small as possible, but it is not necessary that the roundness and the straightness be smaller than necessary. It is desirable that the roundness is suppressed to 0 to 20 (μm) and the straightness is controlled to ± 20 μm.
The roundness and straightness depend on the cutting of the conductive support, the heating and drying after the application of the photosensitive layer, the mounting of the flange, the built-in vibration damping member, and the like. In the method of charging the photosensitive member by superimposing an AC voltage on the charging member, a high-frequency sound (hereinafter referred to as a vibration sound) sensitive to the ear is generated at the time of charging. As one means for improving the vibration noise, a vibration damping member is built in so as to be in close contact with the inner wall of the photoconductor. In order to transmit this vibration noise to the vibration damping member without delay, the vibration of the photoconductor is required. It is desirable that the thickness of the conductive support be as thin as possible. However, there is a problem in that when the vibration damping member is built in, the mechanical strength is reduced due to the reduction in thickness.
When the conductive support is thin, it deforms due to deformation during processing, temperature during drying of the photosensitive layer, built-in vibration damping member, press-fitting when mounting the flange, etc., so that roundness and straightness cannot be guaranteed. Problems occur in image quality.
It is desirable that the roundness and straightness are small. However, according to the study results of the present invention, if the roundness is 20 μm or less and the straightness is within ± 20 μm, the charging is not performed when the contact charging member is used. Uniformization can be avoided to a level where there is no problem, and even when the cleaning brush is used, even if the toner has a large sphericity (average circularity of 0.97 or more), the cleaning property is improved to a level close to 100%. It becomes possible.
[0075]
The average circularity is, for example, selected from toner having a size of 5 μm or more, measured using a FRIP-1000 manufactured by Sysmex Corporation, and calculated by the following equation.
Average circularity = {(perimeter of a circle having the same projected area as the particle image / perimeter of particle projection imaging)} number of measured particles
The number of particles to be measured was 1,000 or more, and a particle having a diameter of 5 μm or more was used for calculation.
[0076]
9 and 11 show measurement examples of straightness measured at 13 locations in the longitudinal direction and four locations every 90 degrees in the circumferential direction of the photoreceptor having a diameter of 30 mm, and FIGS. 10 and 12 show examples of measured roundness measured at 13 locations in the longitudinal direction. Each of these photoconductors has a built-in butyl rubber-based columnar vibration damping member. In the state of a raw tube (aluminum raw tube) before the photosensitive layer is applied, the roundness is 0 to 20 μm and the straightness is straight. The degree was within ± 20 μm. 9 shows an example in which the numerical value falls within the range of ± 20 μm, FIG. 10 shows an example in which the numerical value falls within the range of 0 to 20 μm, and FIG. The straightness in FIG. 9 is within ± 20 μm and the roundness in FIG. 10 is within 20 μm, and there is no problem in image quality.
Although the straightness in FIG. 11 shows a maximum of about 40 μm at the position of 160 °, when a non-contact charging member designed to have a gap of 50 μm is used, the closest contact with the photoconductor is reduced to 10 μm. As a result, streak-like unevenness contamination occurs in the charging member, and the charging characteristics are affected. As the ramp increases, the non-contact charging member causes local contact with the photoreceptor, and when it becomes even larger, the charging member lifts up, causing the charging roller to rotate in a distorted manner, and the image quality is likely to be uneven. become.
[0077]
4. Cleaning member
For the shape of the cleaning blade generally used, a strip-shaped elastic body (polyurethane rubber) having a plate thickness of about 1.5 to 3 mm is used in view of cost, and the rubber hardness is about 75 degrees in JIS hardness. The disadvantage of this cleaning blade is that since the rubber hardness of the portion in contact with the photoreceptor is low, the blade edge is dragged in the rotating direction of the photoreceptor when sliding on the photoreceptor, so that line contact is likely to occur. For this reason, the tip of the blade is crushed, deformed, distorted, etc., and a slight gap is generated between the photoconductor and the blade, so that the toner is pinched between the blade and the photoconductor and is sent to the charging device. Occurs. That is, cleaning failure occurs. In such a situation, even if the pulverized toner has an irregular shape, the toner tends to be removed. FIG. 13 is a schematic diagram of toner loss.
[0078]
As described above, the cause of toner loss is caused by the cleaning blade edge penetrating into the photosensitive layer due to insufficient photoconductor hardness, deformation due to insufficient cleaning blade hardness, the shape and hardness of the cleaning blade, and the friction coefficient of the photoconductor surface layer. The toner pressure contact with the photoconductor at the time of sliding contact, the roundness of the photoconductor, a change in the contact pressure of the blade caused by the straightness, the sphericity of the toner, and the like.
The improvement means viewed from the cleaning blade for eliminating the toner loss, that is, the cleaning failure, is to set the shape and hardness of the cleaning blade to a suitable value, and to always keep the line contact with the photoreceptor. The goal is to make no gaps between you and your body.
Therefore, the cleaning blade needs to have a high hardness so as to maintain its shape, and a desirable numerical value is 80 to 90 degrees in JIS-A hardness.
[0079]
Abrasion of the photoreceptor contributes more when hard foreign matter such as toner, carrier, and paper powder (such as talc) is pressed by the blade or slips through the blade.
There is a concern that abrasion of the photosensitive layer may be accelerated by increasing the hardness of the cleaning blade. However, this is not due to the hardness of the cleaning blade, but rather the movement of the photoconductor, the vibration of the cleaning blade, and the penetration of toner and carrier. It seems that the factor caused by the phenomenon is large. This is when a record player is placed on a poorly-accurate record player and the diamond stylus is turned with a load of about 2 gr. When the turn is performed with extremely high precision and almost no deflection, the above-mentioned load is applied to the diamond stylus. When a load several times the load is applied, the latter is said to have much less wear on the record disc, despite the large load. In the former case, the diamond needle vibrates vigorously to the left and right, which causes the diamond needle to cut the molecules of the record with the diamond needle, which promotes wear, causing the blade to vibrate violently. In such a case, it can be interpreted that a similar phenomenon is occurring.
[0080]
In order to increase the cleaning efficiency using the current strip-shaped cleaning blade, it is possible, but not sufficient, to cope with the problem by increasing the hardness of the tip (edge) of the cleaning blade in contact with the photoconductor. In order to perform the cleaning satisfactorily, the edge shape of the cleaning blade in contact with the photoreceptor should be sharply cut into a V-shape or a knife-edge shape, and the cut angle should be θ1 as shown in FIG. A blade with a knife edge shape sharply cut at an acute angle of 15 to 40 (degrees) (a shape rotated by 180 degrees) or a blade shown in FIG. A good cleaning can be easily achieved by forming the blade in the shape of a square.
The toner stays at the blade edge, but it is important that the structure does not allow the toner to sneak under the blade. The knife-edge shape and the V-shape make the adhesion to the photoreceptor good, and even if there is a stagnation of the toner, the blade will not be crushed and will not cover the toner, so it will not sink under the blade. In addition, the blade of the toner hardly comes off.
[0081]
It is preferable that the edge portion in contact with the photoreceptor has as little width as possible, but the shape is sharply cut from the side, and the width W of the portion in contact with the photoreceptor is up to 0.5 mm. It is acceptable. That is, 0 <W ≦ 0.5 (mm). If the width is 0.5 mm or more, a small gap is formed between the photosensitive member and the photosensitive member, so that there is an opportunity for toner to sneak into the photosensitive member.
[0082]
The thickness (maximum width) of the blade used for the cleaning blade is preferably 2 to 5 mm, and the lengths L1 and L2 of the oblique cut surfaces shown in FIGS. 14 and 15 are 3 to 8 mm, preferably 3 to 8 mm. The free length L4 from the tip of the support base to the edge of the blade shown in FIGS. 16, 17 and 22 is desirably set to 3 to 6 mm. These dimensions are determined based on the installation space and the set position, but it is preferable to use a member as thick as possible from the viewpoint of maintaining the cleaning property and the cleaning property.
[0083]
As a means of fixing these tip-shaped blades, metals such as aluminum, phosphor bronze, iron and brass, resins such as polycarbonate, vinyl chloride, delrin, polyethylene terephthalate, and ceramic members such as alumina are processed into plates and casings. A cleaning blade can be attached, but a metal plate having a thickness of about 1 mm to 3 mm, such as a chromium-plated iron plate or an aluminum plate, is preferable from the characteristics of workability, toughness, no temperature deformation, and rust resistance. . As shown in FIGS. 16 to 18, means for processing the support base and attaching the blade include a method of fitting and fixing the support base in a casing shape, performing a bending process on a metal plate, and using an adhesive (double-sided tape, one-pack type). Or a two-component adhesive, hot melt adhesive, or the like), or a method of attaching a holding plate from above the blade as shown in FIGS. 19 and 20.
[0084]
As the elastic body used for the cleaning blade, there are polyurethane rubber, silicone rubber, fluorine rubber, chloroprene rubber, neoprene rubber, and the like. However, polyurethane rubber is preferably used from the viewpoint of durability, repelling resilience and cleaning properties. Polyurethane rubber is mainly composed of a polyol, an isocyanate, and a curing agent.
The polyurethane rubber is prepared by mixing a dehydrated polyol and an isocyanate, reacting the mixture at a temperature of 70 to 140 (° C.) for about 100 minutes, adding a curing agent to the prepolymer, and heating the prepolymer to 140 to 160 ° C. in advance. Place in the mold of the placed molding machine and cure for 50-60 minutes. Then, it is obtained by taking out from a metal mold | die and cutting with a cutting machine to required size.
The polyurethane rubber used for the cleaning blade is cut obliquely with a cutter or molded into a shape as shown in FIGS. 14 and 15 with a mold, and then the burrs at the portion contacting the photoreceptor are cut as shown in FIG. Then, there is a method of adjusting the thickness of the tip portion to be 0.5 mm or less.
The reason why the thickness is set to 0.5 mm or less is to minimize the penetration of the toner under the blade by expanding the surface contact, and to maintain the line contact even while the photosensitive member is rotating.
[0085]
The contact state of the cleaning blade of the shape shown in FIGS. 14, 16 and 20 fixed to the supporting base with the photoconductor is shown in FIG. 22, and the cleaning blade of the shape shown in FIGS. FIG. 23 shows the state of contact with the body. The cleaning blade is installed in a counter direction (a direction opposite to the rotation of the photoconductor) with respect to the photoconductor. By installing in the counter direction, it works so as to sneak into the photoreceptor, so that the chance of toner passing through is reduced. The contact angle θ3 (FIG. 22) to the cleaning blade photosensitive member having the shape shown in FIGS. 14, 16, and 20 can be set to an angle of 5 to 85 degrees, preferably 5 to 30 degrees. Degrees.
[0086]
On the other hand, the contact angle θ4 (FIG. 23) to the cleaning blade photoreceptor having the shape shown in FIGS. 15 and 17 can be set to an angle of 40 to 85 degrees, but is preferably 40 to 75 degrees. It is. These contact angles are appropriately set according to the size of the photoconductor and the width of the blade.
[0087]
Since the contact pressure (linear pressure) at which the edge of the blade contacts the photoconductor is higher than the hardness of a commonly used blade, the contact pressure (linear pressure) is set to 15 g / cm to 40 g / cm. However, in consideration of the cleaning property and the scratch imparted to the photoreceptor, it is preferably set to 15 g / cm or more and 25 g / cm or less. If it is 15 g / cm or less, cleaning failure may occur because the blade is hard. If the setting is higher than 25 / cm, the photoreceptor may be scratched by the blade because the hardness is higher than that of the conventional product. However, even if the setting is higher than 40 g / cm, the scratch occurs. The increased likelihood does not necessarily mean that a shallow abrasion will usually occur, but that the photoreceptor will not be immediately usable except in the case where a hard foreign matter is stuck and the blade edge is damaged.
If the roundness and straightness of the photoreceptor are within the specified values, no foreign matter adheres to the photoreceptor, and the above-mentioned condition is satisfied, the average circularity of the toner is 0.95 or more, and particularly, 0. Even with a spherical toner having a particle size of 98 or more, cleaning can be performed satisfactorily so as not to cause a practical problem.
[0088]
5. Coefficient of friction of photoreceptor and reduction method
Maintaining the friction coefficient of the photosensitive layer surface at a low level is effective for improving the wear resistance of the photosensitive layer, improving the transferability of a visualized toner image, and improving the cleaning property with a cleaning blade. That is, an effect of reducing the sliding friction pressure of the cleaning blade against the photoconductor and relaxing the adhesion of the toner to the photoconductor is provided.
As means for reducing the friction coefficient, an external addition method of applying a lubricant to the surface layer of the photoreceptor (an example of applying a lubricant scraped off with a brush to the photoreceptor is shown in FIG. 2. 202) is a coating brush) is carried out by any of the internal addition methods in which a lubricant is contained in the photosensitive layer, but the latter means that the corona product acts on the surface of the photosensitive member and seals the action of the lubricant. Therefore, the former method is superior in terms of effect. In the external addition method, a substance having lubricity, such as polytetrafluoroethylene, polyvinylidene fluoride, or zinc stearate, can be applied to the surface of the photoreceptor by direct or indirect means. As a direct method, a powdery lubricant is incorporated in a bag, or a sheet-like lubricant is applied while being rubbed on the surface of the photoreceptor. There is a method of dispersing about 0.2% or arranging a lubricant, a brush, and a photoreceptor in this order, and applying a lubricant scraped off with a brush to the photoreceptor.
[0089]
When a lubricant is applied to the photoreceptor, the coefficient of friction of 0.6 can be easily reduced to 0.2 or less with polytetrafluoroethylene. However, if the coefficient of friction is too low, the corona product adhered to the photoreceptor will not be scraped off, causing image deletion or toner adhering to the corona product film, making toner filming more likely. , Image flow may occur. Therefore, the coefficient of friction for preventing image deletion is 0.3 to 0.5 in the initial value set in the image forming apparatus, and the coefficient of friction after 100 copies is at least 0.3 or more. The upper limit is desirably 0.45 or less from the viewpoints of maintenance of cleaning properties, improvement of abrasion resistance, and maintenance of high-quality images. Of course, even if it temporarily exceeds 0.45, there is no practical problem.
[0090]
When the lubricant is not applied, the friction coefficient sharply increases even with the photoreceptor having about 0.2 at the initial stage, and the friction coefficient reaches nearly 0.6 in 20 to 30 sheets. This is because not only abrasion of the photosensitive layer but also cleaning failure and transfer failure are likely to occur.
Normally, in the case of an organic photoreceptor or a photoreceptor having a filler content of 10% by weight or less without a lubricant, the friction coefficient is about 50 sheets from the start of copying. Although it increases, the tendency is seen that the friction coefficient is less than 0.6 as the filler amount increases and the particle size increases. When the lubricant is externally added to the photoreceptor, the friction coefficient largely fluctuates due to the application means. However, if the lubricant is normally supplied and the control performance is good, the friction coefficient which has once increased also starts to decrease, and 100 to 200 sheets Can be maintained at a substantially stable level between the two. Therefore, if the coefficient of friction specifies 100 sheets, the trend of the coefficient of friction after that can be predicted to some extent.
[0091]
The coefficient of friction described in the text is calculated using the Euler belt method (an equation calculated from Euler's formula).
A photoreceptor for measurement was fixed to a pedestal, and high-quality paper (manufactured by Ricoh Co., Ltd., type 6200 paper, using vertical meshes) cut to 30 mm in width and 290 mm in length was prepared as a belt, and the high-quality paper was exposed to light. Attach a 100 gr weight to one end of the belt, attach a digital force gauge for weight measurement to the other end, slowly pull the digital force gauge, The weight is read, and the (static) coefficient of friction μs is calculated from the following equation.
(Equation 1)
μs = 2 / π × ln (F / W)
Here, μs: static friction coefficient, F: reading load, W: weight of weight, π: pi.
This measurement method (Euler-belt method) is also described in JP-A-9-166919.
[0092]
6. Method of damping photoconductor
When a DC voltage on which an AC voltage is superimposed is applied to the charging member to charge the photoconductor, the photoconductor vibrates, and a high-frequency sound called keen is generated. Further, when the friction coefficient of the photosensitive member is high, the frictional resistance with the cleaning blade increases, so that a vibration noise (sliding noise) is also generated. Since these sounds are in the frequency band (800 to 2500 Hz) most sensitive to the human ear, they pose a noise problem. Means for improving these vibration sounds can be achieved by taking measures to prevent the photosensitive member from vibrating. Means having a large vibration damping effect include a damping member having a loss tangent tan δ of 0.5 or more, preferably 0.6 or more, more preferably 0.8 or more and a thickness of 4 mm or more inside the photoreceptor. If it is closely attached to the inner wall of the photoreceptor so as to occupy 70% or more of the space length, it is possible to suppress the vibration to the extent that it does not matter. FIG. 25 shows an example of installation. FIG. 25 shows a combination of a tapered cylindrical damping member made of butyl rubber and a similarly tapered cylindrical damping member, which is easy to remove. Therefore, both the photosensitive member and the damping member can be recycled. In the example of FIG. 25, when the background noise in the evaluation room is 46 dB, the noise can be suppressed to 48 dB, and an improvement effect of 6 dB can be achieved as compared with the case where the vibration damping member is not built in (54 dB).
[0093]
The vibration sound measuring means is configured to directly superimpose a roller-shaped charging member on the photoreceptor, apply a voltage obtained by superposing an AC voltage of 1500 V / 1350 Hz on a DC voltage of -800 V, and apply a noise meter (for example, It can be confirmed by arranging an accord sound level meter type 6224) and reading the oscillation sound. Normally, if the sound pressure difference is 4 dB or less, the difference can be reduced to a level that does not matter.
In order to enhance the vibration damping effect, a member having a large loss tangent tan δ (not limited to the above-mentioned butyl rubber) is closely inserted into the inner wall of the photoreceptor so as to occupy 70% or more in the length direction and is recycled. is important.
As an improvement method other than the above, there is a method in which a liquid or gel-like object is put in a balloon-like bag and set so as to be in close contact with the inner wall of the photosensitive body.
[0094]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
<Electrophotographic photoreceptor for evaluation>
1) Preparation of photoreceptor having filler non-dispersed charge transport layer
The photoreceptor having the filler non-dispersed charge transport layer for evaluation was prepared by the following means.
Using a JIS3003 aluminum alloy drum having a diameter of 30.0 mm, a length of 340 mm and a thickness of 0.750 mm as a conductive support, a coating liquid for an undercoat layer (UL) and a coating for a charge generation layer (CGL) having the following composition: Dip coating was performed in order with the liquid, and each layer was heated and dried at 120 ° C. for 20 minutes to form a 3.5 μm undercoat layer and a 0.2 μm charge generation layer. Furthermore, after dip coating with a coating liquid for a charge transport layer (CTL), changing the pulling speed conditions, and coating the filler non-dispersed charge transport layer, heating and drying at 130 ° C. for 20 to 30 minutes was performed. An organic photoreceptor having a filler non-dispersed charge transporting layer having a thickness varied between 2 μm and 28 μm was prepared. All "parts" described below represent parts by weight.
[0095]
(Coating liquid for undercoat layer)
Alkyd resin 6 parts
(Beccosol 1307-60-EL, manufactured by Dainippon Ink and Chemicals, Inc.)
Melamine resin 4 parts
(Super Beckamine G-821-60, manufactured by Dainippon Ink and Chemicals, Inc.)
Titanium oxide (CR-EL, manufactured by Ishihara Sangyo) 40 parts
200 parts of methyl ethyl ketone
(Coating solution for charge generation layer)
Bisazo pigment of the following structure 10 parts
[0096]
Embedded image

Polyvinyl butyral 2 parts
200 parts of 2-butanone
Cyclohexanone 400 parts
(Filler non-dispersed charge transport layer coating solution)
Bisphenol Z-type polycarbonate 10 parts
(Made by Teijin Chemicals: Z-Polyka Mv50,000)
8 parts of low molecular charge transport material having the following structure
[0097]
Embedded image

200 parts of tetrahydrafuran
[0098]
2) Production of photoreceptor having filler-dispersed charge transport layer
The organic photoreceptor coated with the filler non-dispersed charge transport layer was dried by heating and then cooled, and subsequently, the filler dispersed charge transport layer was applied to a thickness of 2 to 10 μm by a spray coating method.
The reason why the filler-dispersed charge transport layer was subsequently applied after cooling was that the interface was dissolved by the solvent and a clear interface was not formed, but there was almost no problem if left overnight. However, if left for several weeks, oxidation causes a local barrier, which tends to adversely affect image quality.
On the filler non-dispersed charge transport layer, a binder resin (bisphenol Z-type polycarbonate resin) described below and a low molecular charge transport material (donor) having a primary particle size of 0.2, 0.3, 0.5, 0.7 And 5 μm of inorganic filler (α-alumina) of 1 μm are prepared, each inorganic filler, a dispersing aid and a solvent are put into a glass pot, and dispersed for 24 hours by a ball mill to prepare a coating liquid, and a spray method is used. And reciprocated 1 to 5 times to apply a filler-dispersed charge transport layer. After touch drying, the coating was dried by heating at 150 ° C. for 20 minutes to prepare an electrophotographic photosensitive member for evaluation having a filler-dispersed charge transport layer.
[0099]
[Filler-dispersed charge transport layer coating liquid] (Examples of filler addition amount of 25% by weight)
Bisphenol Z-type polycarbonate 10 parts
(Made by Teijin Chemicals: Z-Polyka Mv50,000)
7 parts of charge transport material of the following structural formula
[0100]
Embedded image

5.7 parts of alumina filler (25% by weight)
(Sumitomo Chemical Industries AA-02 to AA-10,
Average primary particle size: 0.2 to 1.0 μm, specific resistance ≒ 2.5 × 10 ¹² Ω ・ cm)
400 parts of tetrahydrofuran
Cyclohexanone 200 parts
Dispersing aid 0.08 parts
(BYK-P104 made by Big Chemie Japan)
Table 1 shows a list of characteristics of the produced photoreceptor.
[0101]
[Table 1]

[0102]
<Charging member>
1) Charging member for contact charging
In the charging member according to the embodiment of the present invention, carbon was uniformly dispersed in a 6 mm brass lot rod, and the electric resistance was 6 × 10 ⁵ Epichlorohydrin rubber adjusted to Ω · cm (when 100 VDC is applied) is applied so as to have a thickness of 3 mm and polished, and carbon, silica and fluororesin are dispersed on the epichlorohydrin rubber to form an electric resistance of (3 to 5) x 10 ⁸ Epichlorohydrin rubber prepared so as to have a resistivity of Ω · cm (when 100 VDC is applied) is uniformly applied to a thickness of 1 mm to form a shape of φ14 mm × 314 mm (effective charging width: 312 mm). (Used for electrophotocopier Imagio MF2200)
[0103]
2) Charging member for non-contact charging
8mm brass lot rod with electric resistance (4-6) × 10 ⁵ Epichlorohydrin rubber in which carbon, silica, and fluororesin dispersed at Ω · cm (when 100 VDC is applied) is applied to a brass lot rod having a diameter of 6 mm so that the thickness becomes 1 mm. Φ10 mm × 327 mm (effective charging width: 308 mm) Was prepared. A non-contact charging member was prepared in which 1.5 mm inward from both ends of the charging member was attached with PET (polyethylene terephthalate) cut into a rhombus having a thickness of 49 μm, a width of 8 mm and a length of 31 mm, and used as a spacer. The distance between the photosensitive member and the charging member was 53 μm on average. (Used for the color laser beam printer IPSIOR 8000)
[0104]
<Damping member>
A butyl rubber having a loss tangent tan δ of 0.8 was used as a material of the vibration damping material, and was manufactured by die molding.
The dimensions of the elastic body A after the formation are cylindrical with a thick part of φ24.7 mm, a thin part of φ12.7 mm, and a concave part (φ22 mm, depth 6 mm) for a flange electrode in the center of the thick part. The elastic member B was a cylindrical damping member having a thin portion of 2 mmt, a thick portion of 8 mmt, and an outer shape of 28.2 mm. The length of each of the elastic bodies A and B was 312 mm. The inner diameter of the photoconductor is 28.5 mm.
Before being inserted into the photoreceptor, a fluorine-based lubricant (PTFE powder, manufactured by Lubron L-5, manufactured by Daikin Industries, Ltd.) is applied to the nonwoven fabric on the outer side of the elastic body A and the outer side of the elastic body B, and is applied almost uniformly to the nonwoven fabric. The elastic body B was inserted into the photoreceptor on which was set, and then the elastic body A was inserted. After completely inserting the elastic body A while tapping lightly, the opposite flange was set. The setting state on the photoconductor is as shown in FIG.
[0105]
<Method of reducing friction coefficient of photoconductor surface layer>
In the present invention, a method is employed in which 0.02% by weight of zinc stearate is added to the toner to provide a lubricant to the surface layer of the photoreceptor via the developer.
[0106]
<Developer = carrier + toner>
As the carrier, a magnetic carrier (FPC-300LC) having a weight average particle size of 58 μm was used.
Spherical toner (yellow, magenta, cyan, black) having a weight average particle size of about 4.6 μm and an average circularity of 0.981 to 0.987 produced by an emulsion polymerization method is referred to as a toner [1].
The toner having a weight average particle size of 6.3 μm and an average circularity of 0.914 produced by a pulverization method is referred to as a toner [2].
These toners were added at a ratio of 5% by weight to the carrier to form a developer.
These toners contain 0.02% by weight of zinc stearate as a means for reducing the friction coefficient of the photoconductor surface layer.
[0107]
<Cleaning blade>
Cleaning blade [1]
Four types of polyurethane rubber cleaning blades having JIS-A hardnesses of 74 degrees, 81 degrees, 87 degrees, and 92 degrees were produced by molding. The dimensions after the formation are a trapezoidal shape (the shape is as shown in FIG. 21) having a plate thickness of 2.8 mm, a height of 15 mm, a length of 320 mm, and a length of the oblique cut portion of 4 mm. The burr at the contact portion with the photoreceptor was cut, and the width of the cut portion was about 0.3 mm. The measurement of JIS-A hardness used TECLOCK GS-701N manufactured according to JIS K6301.
Two-part epoxy adhesive with a diagonally cut portion facing upstream (transfer device side) in the rotation direction of the photoconductor on a 363 mm long iron plate obtained by bending the blade to a thickness of 0.8 mm and an angle of 8 degrees. An adhesive (Araldite 8254-01 Bantico) was used to bond the free length to 5 mm to complete the cleaning member. (Used for electrophotocopier Imagio MF2200)
[0108]
Cleaning blade [2]
A polyurethane rubber cleaning blade having a JIS-A hardness of 87 degrees was produced by a mold. The dimensions after the formation are a trapezoidal shape having a plate thickness of 2.8 mm, a height of 10 mm, a length of 325 mm, and a length of the oblique cut portion of 3 mm. The edge of the contact portion with the photoconductor was cut off burrs, and the width of the cut portion was about 0.2 mm. The shape is as shown in FIG. The measurement of JIS-A hardness used TECLOCK GS-701N manufactured according to JIS K6301.
An obliquely cut portion of the blade is rotated in the direction of rotation of the photoreceptor using a two-part epoxy adhesive (Araldite 8254-01 Bantico) on a 325 mm iron plate obtained by bending the blade at a right angle with a plate thickness of 0.8 mm. The cleaning member was completed by bonding so that the free length was 4.5 mm in the upstream direction (toward the transfer device). (Used for the color laser beam printer IPSIOR 8000)
[0109]
<Evaluation method>
As an evaluation machine for the photoconductor and the cleaning blade, a dry charging type incorporating a process unit in which a photoconductor, a developing device, and a cleaning blade are integrated with a contact charging system using an LD element with an oscillation wavelength of a light source of 655 nm. An electrophotographic copier (Imagio MF2200, manufactured by Ricoh) and a non-contact charging type, a quadruple tandem type color laser beam printer [CLBP] (Ipsiocolor 8000, with a built-in process unit integrating a photoconductor and a cleaning blade) Ricoh) was prepared.
The electrophotographic copier (Imagio MF2200, manufactured by Ricoh) prepared for evaluation uses a high-voltage power supply (type HV-255, manufactured by Nagano Aichi Electric Co.) that can superimpose an AC voltage because the high-voltage power supply to the charging device is a DC voltage. It was prepared separately and evaluated while switching to the standard setting DC power supply.
When applying an AC superimposed DC voltage to the charging member, the AC voltage was fixed at 1500 V / 1350 Hz, the DC voltage was adjusted, and the dark portion potential at the developing device position was set.
The color laser beam printer was used in the standard setting (default) state and evaluated.
The evaluation number was 50,000 sheets (A4 size) for each A4 size, and the film thickness of the initial photosensitive layer and the film thickness after 50,000 sheets were measured using an eddy current film thickness meter (Fisher type MMS). The wear amount of the layer was evaluated.
Pencil hardness was measured by using a pencil scratch tester (surface property measuring device HEIDON-14 type, manufactured by Shinto Kagaku Co., Ltd.) and a JIS standard pencil (Mitsubishi Pencil "Uni") manufactured based on JIS K5401. Using a weight of 100 g, the photoreceptor prepared for measurement was cut into a size of 50 × 80 (mm) and measured.
The roundness and straightness were measured using a surface roughness contour shape integrated measuring instrument (Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd.) at 13 locations in the longitudinal direction of the photoreceptor and at 4 locations every 90 degrees in the circumferential direction.
The coefficient of friction was measured by fixing the photoreceptor to be measured to a pedestal and using a high-quality paper (manufactured by Ricoh Co., Ltd., type 6200 paper, using vertical grain) as a belt with a width of 30 mm, a length of 290 mm and a thickness of 85 μm Is placed in the circumferential direction of the photoreceptor, a 100 gr weight is attached to one end of the belt, a digital force gauge for weight measurement is attached to the other end, and the digital force gauge is slowly pulled to move the belt. The weight at the start was read, and the (static) friction coefficient μs was calculated from the following equation derived from Euler's method.
μs = 2 / π × ln (F / W)
Where μs: coefficient of static friction, F: reading load, W: weight of weight, π: pi
When the image quality evaluation is performed using an electrophotographic copying machine, the image quality evaluation uses a test sheet (manufactured by Kodak) prepared in accordance with JISZ 6008 to evaluate the resolution, and a Ricoh test prepared separately. The reproducibility of the dot pattern and the evaluation of the background stain were carried out on the chart.
On the other hand, in the case of evaluation using a color laser beam printer, various patterns input to a separately prepared personal computer were used to evaluate the resolution, the reproducibility of the dot pattern, noise, color unevenness, and the like.
The originals during paper running other than during the evaluation use an image pattern with an image area of 6% in both evaluation machines, and paper running was performed in an environment of 22 to 24 (° C.) / 58 to 65 (% RH).
The evaluation was carried out at the initial stage, after 100 sheets (measurement of friction coefficient only), and after 50,000 sheets.
[0110]
Examples 1-4
As a photoconductor for evaluation, No. 1 shown in Table 1 was used. 4 (Example 1), 5 (Example 2), No. 5 6 (Example 3), 7 (Example 4) was used. Each of the photoconductors mounted on the electrophotographic copying machine prepared for evaluation has a vibration damping member having a high loss tangent tan δ of 0.8 as shown in FIG. The degree and straightness satisfy 0 to 20 μm and ± 20 μm, respectively.
The electric field strength at the position of the developing device applied to the photosensitive member 4.5 × 10 for 4 samples ⁵ V / cm, No. 3.04 × 10 for 5 samples ⁵ V / cm, No. 2.33 × 10 for 6 samples ⁵ V / cm, No. 7 × 2 × 10 ⁵ V / cm, 50,000 sheets of paper running were performed.
The photoreceptor sample was formed on a non-dispersed charge transporting layer coated with four different film thicknesses between 2 and 28 (μm) on the charge generation layer. Alumina was added so as to be 25% by weight of the filler-dispersed charge transport layer, and laminated to a thickness of 2 to 8 μm.
The ratio of the film thickness of the filler-dispersed charge transport layer to the charge transport layer is 80% to 6.7%. The 10-point average roughness of the photoreceptor was on the order of 0.48 μm, and the pencil hardness was HB to H.
[0111]
A cleaning blade prepared by adjusting the hardness of these photoconductors to 81 degrees is mounted on the photoconductor unit of the electrophotographic copying machine for evaluation so that the contact pressure against the photoconductor becomes 24.0 g / cm. I set it.
As the toner, a black toner having an average circularity of 0.981 to 0.987 was used, and 5% by weight was mixed with the carrier. The lubricant (zinc stearate) was not added to the toner.
Table 2 shows the evaluation results.
[0112]
In each of the samples in which the ratio of the film thickness of the filler-dispersed charge transport layer used in the examples was 6.7% to 80%, the image quality was good, and although not described in the table, 7.1 to 9 A high resolution of 0.0 lines / mm was exhibited, and the halftone reproducibility was also good. On the other hand, when a toner having a high average circularity was used, leakage was observed to such an extent that the charging member was slightly stained, but no effect was observed on the image, and no practical problem occurred. In addition, since the effect of using a high-hardness blade is high in cleaning properties, the toner passing under the blade may be blocked, so that a light abrasion scratch caused by the blade which does not appear on the image on the photoreceptor may be prevented. Although it occurred, no deep scratch was observed.
[0113]
[Table 2]

* In the table, μ represents the friction coefficient, and the suffix “0” indicates initial, 0.1K indicates 100 sheets, and 50K indicates 50,000 sheets. The abrasion amount is a value obtained by subtracting the film thickness after 50,000 sheets from the initial film thickness of the photosensitive layer, and is an average value at 13 points (the same applies to the following examples). ○ in the judgment indicates good (the same applies to the following examples).
[0114]
Examples 5 to 6
Photoconductor sample No. 5 (Example 5) and No. 5 Using the sample of Example 6 (Example 6) and the pulverized toner having an average circularity of 0.91, the same evaluation as in Examples 1 to 4 was performed. The electric field intensity applied to the photoreceptor 3.04 × 10 at 5 ⁵ V / cm, No. 2.33 × 10 for 6 ⁵ V / cm. Table 3 shows the results.
[0115]
When the pulverized toner having a low circularity was used, the blade of the toner was hardly removed, and extremely good cleaning property was exhibited. In addition, the resolution was as good as 6.3 to 8 lines / mm, and there was no density unevenness. Although the abrasion of the photosensitive layer was slightly larger than when the polymerized toner was used, the use of the 8 μm filler-dispersed charge transporting layer enabled high image quality and high durability.
[0116]
[Table 3]

◎ in the judgment indicates excellent (the same applies to the following examples).
[0117]
Examples 7 to 9
A toner obtained by adding 0.03% by weight of zinc stearate having an average particle diameter of 0.3 μm as a lubricant to a black toner having an average circularity of 0.981 to 0.987 produced by an emulsion polymerization method, and a carrier (FPC- 300LC) was used in an amount of 5% by weight. On the other hand, as a photoreceptor, No. 1 having no built-in damping member 5 (Example 7); 6 (Example 8), Using Example 7 (Example 9), photoreceptor evaluation was performed in the same manner as in Examples 1 to 4. Table 4 shows the results. Each of these photoconductors has a roundness of 0 to 20 μm and a straightness of ± 20 μm.
[0118]
By adding a very small amount of lubricant to the toner, the effect of reducing the friction coefficient of the photoconductor was brought about. As a result, the adhesion of the toner to the photoreceptor is weakened, the image quality is improved, especially the transfer efficiency is increased, the residual toner on the photoreceptor is reduced, and good cleaning performance is obtained. Showed that the improvement effect was further improved than the results of Examples 2 to 4. The resolution was the same as in Examples 2 to 4, but sharper. The wear of the photosensitive layer was improved because the coefficient of friction was reduced, and the wear was further reduced.
[0119]
[Table 4]

[0120]
Comparative Examples 1 to 5
No. 1 described in Table 1. 1 (Comparative Example 1) and No. 1 No. 2 (Comparative Example 2), a photoconductor of the filler non-dispersed charge transport layer, No. 3 (Comparative Example 3), 6 (Comparative Example 4) and No. 6 Using the sample No. 7 (Comparative Example 5), a cleaning blade was used as a strip-shaped polyurethane blade (width 2 mm × 13 mm × 320 mm, free length) which is standardly installed in an electrophotographic copying machine for evaluation having a JIS-A hardness of 77 degrees. 8.5 mm), and 50,000 sheets of paper running were performed.
The electric field strength at the developing device position with respect to the photoconductor 3.18 × 10 for 1 ⁵ V / cm, No. 2.86 × 10 for 2 ⁵ V / cm, No. 5.8 × 10 for 3 ⁵ V / cm, No. 2.33 × 10 for 6 ⁵ V / cm, No. 7 is 2 × 10 ⁵ V / cm was set respectively. The toner used for the developer is a lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987, and uses a developer added at 5% by weight to a carrier (FPC-300LC). did.
Other conditions were performed by the methods described in Examples 1 to 4. Table 5 shows the results.
[0121]
No. In the case where the thickness ratio of the filler-dispersed charge transport layer is as large as 0.83 as in the case of the photoconductor of No. 3, the resolution and the residual potential must be controlled unless the thickness of the filler-dispersed charge transport layer is at most 8 μm. Therefore, the film thickness of the filler non-dispersed charge transport layer must be reduced. In such a situation, the electric field strength increases due to the increase in the capacitance, the surface potential required for image formation decreases, the image density is low, and the cleaning property is insufficient. This resulted in poor image quality.
No. In the photoreceptors other than the photoreceptor 3, the spherical toner produced by the emulsion polymerization method having a high average filler sphericity is insufficiently cleaned by a strip-shaped cleaning blade. In particular, the photoreceptor (No. In Nos. 1 and 2), there was a tendency for the cleaning failure to worsen. Due to the cleaning failure, a remarkable stain was formed on the charging member in a belt shape, and a slight streak was confirmed in the halftone image.
It is considered that the photoreceptor having only the filler non-dispersed charge transport layer has a low photosensitive layer hardness (B in pencil hardness) and a high friction coefficient (0.6 or more). It is understood that the reason why the cleaning failure occurred even in the photoreceptor having the photoconductor was due to the distortion of the blade edge as described above.
In addition, No. 1 of only the filler non-dispersed charge transport layer. 1 and No. The photoreceptor No. 2 suffers from abrasion and insufficient durability. In addition, the silica or titanium oxide added as a fluidizing agent for the toner in the developer penetrates into the photosensitive layer (sticks). This caused unevenness in the halftone image.
[0122]
[Table 5]

In the table, x means that it has no practicality due to poor cleaning and poor image quality.
[0123]
Examples 10 to 13
A photoconductor for evaluation was prepared by changing the amount of filler dispersion in the filler-dispersed charge transport layer. The photoreceptor samples used were No. 1 in Table 1. 8 to No. In No. 13, the amount of filler dispersion in the filler-dispersed charge transporting layer was no. In No. 8, 10% by weight (HB) (Example 10); In No. 9, 20% by weight (HB) (Example 11). In No. 10, 30% by weight (H) (Example 12); In No. 11, the content was 40% by weight (H) (Example 13). The value in parentheses is the pencil hardness. These photoconductors have built-in vibration damping members made of butyl rubber having a loss tangent tan δ of 0.8, and the roundness and straightness are both within a range of 20 μm and ± 20 μm.
Α-Alumina having an average particle size of 0.5 μm was used as a filler for improving pencil hardness, the thickness of the charge transport layer was 27 μm, and the thickness of the filler-dispersed charge transport layer was 5 μm. At this time, the electric field intensity at the developing device position is 2.2 × 10 ⁵ V / cm.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added to a carrier (FPC-300LC) in an amount of 5% by weight is charged into a developing unit. did. As the cleaning blade, a blade of the type shown in FIG. 20 sharply cut at an acute angle of JIS-A hardness of 81 degrees is set at a contact pressure (linear pressure) of 24 g / cm, and 50,000 sheets of paper are passed by an electrophotographic copying machine. A running evaluation was performed.
As shown in Table 1, the surface roughness of the sample satisfies a 10-point average surface roughness of 0.4 to 0.8. Table 6 shows the results.
The cleaning property is slightly poor when the filler dispersion amount is about 10% by weight, but when the filler dispersion amount is 20% by weight, the cleaning property is maintained to an extent that there is almost no problem. The image quality is preferably 20 or 30% by weight, and if the amount of filler dispersion is small, the charging roller is contaminated due to a decrease in cleaning properties. If the filler is 40% by weight, abrasion is suppressed. Was not sufficient, and a local decrease in resolution (4.0 to 4.5 lines / mm) occurred.
That is, it is determined that the preferable range of the filler addition amount is good except for 10% by weight and 40% by weight.
[0124]
[Table 6]

In the table, Δ means that there is a slight problem in cleaning properties and image quality at the time of evaluation of 50,000 sheets. (The same applies to the following examples)
[0125]
Examples 14 to 17
A photoreceptor for evaluation having a primary average particle size of 0.2 to 0.7 μm dispersed in the filler-dispersed charge transport layer was prepared. The photoreceptor samples used were No. 1 in Table 1. 12-No. In No. 15, the primary particle size of the α-alumina filler in the filler-dispersed charge transporting layer was No. 1, respectively. In No. 12, 0.2 μm (HB) (Example 14). In No. 13, 0.3 μm (H) (Example 15). In No. 14, 0.5 μm (HB) (Example 16). In No. 15, the thickness was 0.7 μm (H) (Example 17). The value in parentheses is the pencil hardness. These photoconductors have built-in vibration damping members made of butyl rubber having a loss tangent tan δ of 0.8, and the roundness and straightness are all within the range of 0 to 20 μm and ± 20 μm.
The amount of the filler added was 25% by weight, the thickness of the charge transport layer was 27 μm, and the thickness of the filler-dispersed charge transport layer was 5 μm. At this time, the electric field intensity at the developing device position is 2.2 × 10 ⁵ V / cm. As for the surface roughness, the 10-point average roughness is 0.4 μm to 0.8 μm, and the maximum roughness is 1.0 μm or less.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added to a carrier (FPC-300LC) in an amount of 5% by weight is charged into a developing unit. did. As the cleaning blade, a blade of the type shown in FIG. 22 sharply cut at an acute angle of JIS-A hardness of 81 degrees is set at a contact pressure (linear pressure) of 24 g / cm, and 50,000 sheets of paper are passed by an electrophotographic copying machine. A running evaluation was performed. Table 7 shows the evaluation results.
By changing the primary average particle size in the filler-dispersed charge transport layer, the surface roughness changes, but all of the samples within the above range of the surface roughness have good cleaning properties and image quality.
[0126]
[Table 7]

[0127]
Comparative Examples 6 to 8
Photoconductors for evaluation were prepared in which the dispersion amount of the primary average particle size of 1.0 μm dispersed in the filler-dispersed charge transport layer was changed to 20, 30, and 40% by weight. The photoreceptor samples used were No. 1 in Table 1. 16-No. In No. 18, the amount of dispersion of the α-alumina filler in the filler-dispersed charge transporting layer was no. No. 16, 20% by weight (H) (Comparative Example 6); No. 17, 30% by weight (2H) (Comparative Example 7); In No. 18, the content was 40% by weight (2H) (Comparative Example 8). The value in parentheses is the pencil hardness. These photoconductors have built-in vibration damping members made of butyl rubber having a loss tangent tan δ of 0.8, and the roundness and straightness are both within a range of 20 μm and ± 20 μm.
The amount of the filler added was 25% by weight, the thickness of the charge transport layer was 27 μm, and the thickness of the filler-dispersed charge transport layer was 5 μm. At this time, the electric field intensity at the developing device position is 2.2 × 10 ⁵ V / cm. Regarding the surface roughness, the 10-point average roughness is 0.8 μm or more and the maximum roughness is 1.0 μm or more.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added at 5% by weight to a carrier (FPC-300LC) is charged into a developing unit. did. As the cleaning blade, a blade of the type shown in FIG. 23 sharply cut at an acute angle of JIS-A hardness of 81 degrees is set at a contact pressure (linear pressure) of 24 g / cm, and 50,000 sheets of paper are passed by an electrophotographic copying machine. A running evaluation was performed. Table 8 shows the evaluation results.
Even if the primary average particle size of the filler is 1.0 μm, there is a tendency that the surface roughness is suppressed to a low level by reducing the dispersion amount. In addition, both the image quality and the image quality tend to be affected. Further, as the amount of dispersion increased, the surface roughness increased, and the cleaning property and the image quality deteriorated.
[0128]
[Table 8]

[0129]
Examples 18 to 19
No. 1 described in Table 1. Two photosensitive members equivalent to 15 were prepared, and a polyurethane rubber blade having a JIS hardness of 81 degrees (Example 18) and 87 degrees (Example 19) was set on the photosensitive member unit, and the contact pressure (linear pressure) was set. Was set to 24 g / cm, and a running evaluation of 50,000 sheets was performed by an electrophotographic copying machine.
The filler in the filler-dispersed charge transport layer has an average particle size of 0.7 μm α-alumina, the amount added is 25% by weight, the thickness of the charge transport layer is 27 μm, and the thickness of the filler-dispersed charge transport layer is 5 μm. The electric field intensity applied to the photoconductor at the position of the developing device was 2.2 × 10 ⁵ V / cm. Regarding the surface roughness, the 10-point average roughness is 0.8 μm or more and the maximum roughness is 1.0 μm or more.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added at 5% by weight to a carrier (FPC-300LC) is charged into a developing unit. did. Table 9 shows the evaluation results.
With both the JIS-A hardness blades of 81 and 87 degrees, almost no toner loss was confirmed, and there was no effect on the image, and the image quality was good.
[0130]
[Table 9]

[0131]
Comparative Examples 8 to 9
No. 1 described in Table 1. Two photosensitive members equivalent to 15 were prepared, and a polyurethane rubber blade having a JIS hardness of 74 degrees (Comparative Example 8) and 92 degrees (Comparative Example 9) was set on the photosensitive member unit, and the contact pressure (linear pressure) was set. Was set to 24 g / cm, and a running evaluation of 50,000 sheets was performed by an electrophotographic copying machine.
The filler in the filler-dispersed charge transport layer was α-alumina having an average particle size of 0.7 μm, the amount added was 25% by weight, the thickness of the charge transport layer was 27 μm, and the thickness of the filler-dispersed charge transport layer was 5 μm. is there. The electric field intensity applied to the photoconductor at the position of the developing device was 2.2 × 10 ⁵ V / cm. Regarding the surface roughness, the 10-point average roughness is 0.8 μm or more and the maximum roughness is 1.0 μm or more.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added at 5% by weight to a carrier (FPC-300LC) is charged into a developing unit. did. Table 10 shows the evaluation results.
As a result of the evaluation, the blades having JIS-A hardness of 74 degrees and 92 degrees were not good results. When the hardness was low, the cleaning blade was better than the conventional strip-shaped cleaning blade. However, a toner detachment phenomenon occurred, toner adhered to the charging roller, and a slight streak pattern occurred in the halftone image.
On the other hand, when the hardness is as large as 92 degrees, the toner removal is better than that of the blade having a hardness of 74 degrees, but the toner adheres slightly on the photoreceptor and the toner adheres thinly on the charging member. However, at the point of time of 50,000 sheets, the influence on the image was so small that a halftone image had a slight difference in shading.
[0132]
[Table 10]

[0133]
Example 20
No. 1 in Table 1 was used as a photoconductor for evaluation. Four photoconductors 6 (for magenta (M), yellow (Y), cyan (C), and black (Bk)) were prepared. As the cleaning blade, a blade having a JIS-A hardness of 87 and having a sharp cut shape as shown in FIG. 20 was attached to the photoreceptor unit at a contact pressure (linear pressure) of 21.5 g / cm.
0.03% by weight of zinc stearate having an average particle diameter of 0.3 μm added to M, Y, C, and Bk toners manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987, Used a magnetic powder (FPC-300LC) having a weight average particle size of 58 μm, and a developer having a concentration of 5% by weight was charged into the developing unit.
The photoconductor unit and the developing device are mounted on a color laser beam printer prepared for evaluation, and the electric field intensity applied to the photoconductor at the developing position is 2.5 × 10 ⁵ The running evaluation of 50,000 sheets was performed with V / cm. Table 11 shows the results. The results for magenta (M), yellow (Y), cyan (C), and black (Bk) are shown from the top of the table.
Since all of the toner contained a lubricant, the cleaning property of the toner was good and no sign of toner filming was observed. One dot reproducibility was also good, and there was no bleeding between dots, showing good color reproducibility.
[0134]
[Table 11]

[0135]
Comparative Examples 10 to 12
As a photoreceptor sample for evaluation, No. 1 shown in Table 1 was used. 19 (Comparative Example 10); 20 (Comparative Example 11); 21 (Comparative Example 12) was prepared. No. Measurement results of the straightness and roundness of the 19 photoconductors are shown in FIGS. 26 and 27. Although the roundness satisfies 0 to 20 (μm), the straightness greatly deviates from +20 μm and indicates +35 μm. No. 20, no. Although not shown, the photoreceptor 21 has a roundness of 22 to 24 μm and a straightness of +30 to 45 μm, which is far from +20 μm.
As the cleaning blade, a polyurethane rubber blade having a JIS hardness of 87 degrees and having a shape shown in FIG. 22 (width of the tip end edge: 0.2 mm) is set on the photoconductor unit, and the contact pressure (linear pressure) is reduced to 30 g / cm. After setting, the running evaluation of 50,000 sheets was performed by the electrophotographic copying machine.
The filler in the filler-dispersed charge transport layer is α-alumina having an average particle size of 0.3 μm (No. 19, 20) and 0.5 μm (No. 21), and the added amount is 25% by weight. The film thickness was 20 μm (No. 19) and 27 μm (No. 20, 21), and the film thickness of the filler-dispersed charge transport layer was 5 μm. The electric field intensity at the position of the developing device applied to this photoconductor is represented by 19 × 3 × 10 samples ⁵ V / cm, No. 2.2 × 10 samples of 20, 21 ⁵ V / cm. The surface roughness is about 0.5 μm in terms of 10-point average roughness, and the maximum roughness is about 0.7 μm.
A lubricant non-dispersed black toner manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is used as a toner, and a developer added to a carrier (FPC-300LC) in an amount of 5% by weight is charged into a developing unit. did. Table 12 shows the evaluation results.
When the roundness and straightness of the photoreceptor are large, it means that the photoreceptor is distorted.However, since the distance between the photoreceptor and the charging member and the distance between the photoreceptor and the cleaning member become uneven, charging unevenness is caused. In addition, it causes cleaning failure (toner missing). In the sample of Comparative Example 10, the roundness is in the range of 0 to 20 μm. However, since the straightness was greatly changed, toner loss occurred locally, and filming and abrasion occurred in a streak shape. In addition, the charging roller was stained, and the image was slightly uneven. On the other hand, in Comparative Examples 11 and 12, since both roundness and straightness were large, poor cleaning properties and light density unevenness occurred on the copied image, and there was a locally low resolution area of 5.6 lines / area. Further, a slight background stain was observed.
[0136]
[Table 12]

[0137]
Examples 21 to 22
No. 1 described in Table 1. No. 1 photoconductor (Example 21—no filler added, film thickness 22 μm); The photoreceptor No. 2 (Example 22-no filler added) was used. The pencil hardness was B in all cases. These photoconductors do not have a built-in damping member. Both roundness and straightness are within the range of 20 μm and ± 20 μm.
The electric field strength at the position of the developing device applied to the photoreceptor is no. 2.7 × 10 for one sample ⁵ V / cm, No. 2.14 × 10 for 2 samples ⁵ V / cm. This is the electric field strength corresponding to the surface potential of the photoconductor -600V.
A black toner in which 0.03% of a lubricant manufactured by an emulsion polymerization method having an average circularity of 0.981 to 0.987 is dispersed, and 5% by weight is added to a carrier (FPC-300LC). Was put into the developing unit. As the cleaning blade, a blade of the type shown in FIG. 20 sharply cut at an acute angle of JIS-A hardness of 87 degrees is set at a contact pressure (linear pressure) of 22 g / cm, and 50,000 sheets of paper are passed by an electrophotographic copying machine. A running evaluation was performed.
As shown in Table 1, the surface roughness of the sample was 0.09 to 0.1 in terms of 10-point average surface roughness. Table 13 shows the results.
When the charge transport layer is a filler non-dispersed charge transport layer to which no filler is added, the surface of the photosensitive layer is in a soft state. It was clearly in a better condition than the conventional strip-shaped cleaning blade.
[0138]
[Table 13]

[0139]
【The invention's effect】
As apparent from the detailed and specific description above, according to the configuration of claims 1 to 3 of the present invention, the filler non-dispersed charge transport layer in which the filler is not dispersed and the filler dispersed charge transport layer in which the filler is dispersed. The ratio of the film thickness of the filler-dispersed charge transport layer to the film thickness of the photosensitive layer is 6.7% to 80%, and the tip of the cleaning member used for cleaning is sharply cut at an acute angle. Combined with an elastic body having a part, toner can be sent to the charging member by surface contact, which was a problem in the conventional strip shape, and local distortion can be ignored, so cleaning failure is practical It can be improved to a level where there is no problem. Further, according to the configuration of claim 4, since the filler concentration in the filler-dispersed charge transport layer is set to 10% by weight or more and 40% by weight or less of the total weight of the filler-dispersed charge transport layer, the filler can be used while being appropriately worn, Contaminants adhering to the photoreceptor are also appropriately shaved and abnormal adhesion is suppressed. As a result, compared to the conventional photoreceptor without a filler-dispersed charge transport layer, high durability (abrasion resistance of the photosensitive layer and difficulty in generating scratches) can be achieved, and a stable image without density unevenness can be obtained. Quality can be provided for a long time. In addition, the increase in the hardness of the photosensitive layer relieves the biting of the edge of the cleaning blade. In addition, since a cleaning blade having a high hardness is used, the toner has a large average circularity due to a small edge distortion. However, there is an advantage that the toner is hardly removed. According to the constitution of claim 5, when an alumina filler having a primary particle size of 0.2 to 0.7 μm is dispersed in the filler-dispersed charge transport layer, the 10-point average roughness of the photosensitive layer is 0.4 to 0.8 μm. When the maximum roughness is within 1.0 μm, the edge of the blade is prevented from penetrating into the photosensitive layer, so that local distortion of the edge is less likely to occur. In addition, since the surface layer of the photosensitive layer is flat, a gap is hardly formed between the blade and the photosensitive layer. Therefore, even a spherical toner produced by a polymerization method having a high average circularity can be cleaned well. Since the cleaning edge has less pain, the durability of the cleaning blade is also improved. According to the structure of the sixth aspect, by lowering the friction coefficient of the surface layer of the photosensitive layer, the adhesion of the toner to the photosensitive layer is reduced, so that the cleaning property of the toner is improved and the transfer efficiency of the toner image is improved. Therefore, local image omission is eliminated. Further, since the load on the cleaning blade is reduced, the durability of the cleaning blade can be extended. Further, since the frictional resistance between the cleaning blade and the photosensitive member is reduced, the vibration noise is reduced, and the noise is eliminated. According to the configuration of claim 7, by setting the hardness of the filler-dispersed charge transporting layer to HB ≦ Hp <2H in pencil hardness Hp, appropriate wear resistance is achieved. Although this improves the durability of the photoreceptor, the photoreceptor has a small amount of abrasion, and even if a low-resistance substance such as a corona product adheres to it, the abrasion is moderate. It is possible to minimize the deterioration of the image, which is caused by the accompanying or the corona product adhesion. According to the eighth and ninth aspects of the present invention, when the roundness at the time of image formation is 0 to 20 (μm) and the straightness is ± 20 μm, even when a contact charging member and a non-contact charging member are used, Stable charging can be performed, and an image with uniformity can be provided. Further, the total thickness of the photosensitive layer is set to 10 μm or more and 30 μm or less, and the electric field strength is set to 1.3 × 10 5. ⁵ ~ 4.0 × 10 ⁵ (V / cm), it is possible to obtain a copy image with good sharpness and resolution and no background stain. In addition, the image quality is stable because discharge breakdown is difficult. Further, by setting the hardness of the cleaning blade at a JIS-A hardness of 80 to 90 degrees higher than usual by the configuration of claim 11, the blade is less likely to be distorted or vibrated, so that the cleaning blade is in close contact with the photoreceptor. Nature is achieved. As a result, the frequency of the toner passing under the blade is greatly reduced, so that the cleaning property can be improved, and the stability and the image quality can be maintained satisfactorily. Further, by setting the contact pressure (linear pressure) of the cleaning blade to 20 to 25 (g / cm) according to the configuration of the twelfth aspect, even if a cleaning blade having a high hardness is used, the photosensitive member is deeply damaged. It is possible to maintain good cleaning performance without adding a mark. Further, since there is no damage, wear of the blade edge is small and high durability can be maintained. According to the structure of the thirteenth aspect, by setting the edge of the leading end of the cleaning blade in contact with the photosensitive layer to 0 to 0.5 mm, uniform adhesion to the photosensitive member can be achieved, so that good cleaning can be achieved. It can demonstrate its properties. Further, by fixing the cleaning member to a hard metal support, a stable contact with the photoconductor can be guaranteed, so that a stable image quality can be obtained. According to the configuration of the fifteenth aspect, the photosensitive member and the cleaning blade described above can be used in a four-tandem color image forming apparatus without any problem. The photoconductor and the cleaning blade according to the present invention are configured as a process unit in which the photoconductor and the cleaning blade are integrally configured, and a process unit in which the photoconductor, the cleaning blade, and the developing device are integrally configured. Since it can be incorporated in the image forming apparatus, the work efficiency of assembling and the like is improved, and it is advantageous in maintenance and reproduction such as parts replacement and cleaning.
[Brief description of the drawings]
FIG. 1 is a schematic view of an image forming apparatus illustrating a copying process used in the present invention.
FIG. 2 is another schematic view of the image forming apparatus illustrating a copying process used in the present invention.
FIG. 3 is a schematic view of a quadruple tandem type color laser beam printer of the present invention.
FIG. 4 shows an example of a process unit of the present invention.
FIG. 5 is a schematic diagram illustrating a configuration of an electrophotographic photosensitive member used in the present invention.
FIG. 6 is a graph showing a preferable thickness ratio of a filler-dispersed charge transport layer constituting the charge transport layer.
FIG. 7 is an example of a graph showing the dependency of the surface roughness of the filler-dispersed charge transport layer on the average primary particle size of the inorganic filler (α-alumina).
FIG. 8 is a graph showing the relationship between the photosensitive layer wear amount and the image quality rank depending on the amount of filler added to the filler-dispersed charge transport layer.
FIG. 9 is an example of measuring the straightness of a photosensitive member having a built-in vibration damping member.
FIG. 10 is an example of measuring the roundness of a photosensitive member having a built-in vibration damping member.
FIG. 11 is another example of straightness measurement of a photoreceptor incorporating a vibration damping member.
FIG. 12 is another example of the roundness measurement of the photoconductor incorporating the vibration damping member.
FIG. 13 is a schematic diagram illustrating toner removal by a conventional cleaning blade.
FIG. 14 is a cross-sectional view of the cleaning blade as viewed from the side.
FIG. 15 is another cross-sectional view of the cleaning blade as viewed from the side.
FIG. 16 is a schematic diagram illustrating a state in which a cleaning blade is fixed to a support base.
FIG. 17 is another schematic diagram illustrating a state in which the cleaning blade is fixed to a support base.
FIG. 18 is another schematic diagram illustrating a state in which the cleaning blade is fixed to a support base.
FIG. 19 is another schematic view illustrating a state in which the cleaning blade is fixed to the supporting base.
FIG. 20 is another schematic diagram illustrating a state in which the cleaning blade is fixed to a support base.
FIG. 21 is a schematic diagram illustrating a situation in which burrs on a contact surface of a cleaning blade manufactured by die molding with a photoconductor are cut.
FIG. 22 is a schematic diagram illustrating a state in which a cleaning blade is in contact with a photoconductor and a free length from a support base to a tip of the blade.
FIG. 23 is another schematic diagram illustrating a state in which the cleaning blade is in contact with the photoconductor and a free length from the support base to the tip of the blade.
FIG. 24 is a schematic diagram illustrating a state of toner cleaning by the cleaning blade of the present invention.
FIG. 25 is a schematic view showing a state in which a vibration damping member is built in the photoconductor.
FIG. 26 shows the results of measuring the straightness of a photoconductor including a vibration damping member used in Comparative Example 10.
FIG. 27 shows a result of measuring the roundness of a photoconductor incorporating a vibration damping member used in Comparative Example 10.
[Explanation of symbols]
1: Photoreceptor for electrophotography (photoreceptor)
2: Charging device
3: Image exposure device
4: Developing device
5: transfer device
6: Separation device
7: Cleaning device
7-1: Cleaning blade
8: Fixing device
9: Copy paper
10: Damping member
200: Lubricant application device
201: Lubricant
202: Lubricant application brush

Claims (17)

An electrophotographic photoreceptor, a charging device, an image exposing device, a developing device, a transfer device, a cleaning device, and a fixing device are arranged at suitable positions to form an image. An undercoat layer, a charge generation layer, and a charge transport layer are laminated on a porous support, and the charge transport layer is at least an organic photosensitive layer, and is in contact with the electrophotographic photosensitive member and is subjected to toner cleaning. An image forming apparatus comprising: a resilient cleaning blade having a V-shaped or knife-edge-shaped tip having a sharp angle, and a counter-contact and disposed with respect to the electrophotographic photosensitive member. The charge transport layer constituting the electrophotographic photosensitive member has a two-layer structure of a non-filler-dispersed charge transport layer and a filler-dispersed charge transport layer, and the filler-dispersed charge transport layer has a total thickness of 6.7 of the charge transport layer. The image forming apparatus according to claim 1, wherein the image forming apparatus occupies about 80% to 80%. The charge transport layer constituting the electrophotographic photoreceptor has a two-layer structure of a filler non-dispersed charge transport layer and a filler dispersed charge transport layer, and a clear interface does not exist between both layers. The image forming apparatus according to claim 1. The amount of the filler added to the filler-dispersed charge transport layer is 10% by weight or more and 40% by weight or less of the total weight of the filler-dispersed charge transport layer. Image forming apparatus. The filler has an average particle diameter of 0.2 μm to 0.7 μm, and has a 10-point average roughness of 0.4 μm to 0.8 μm at the time of image formation on the outermost surface of the charge transport layer in which the alumina is dispersed. The image forming apparatus according to claim 1, wherein the thickness is 1.0 μm or less. The static friction coefficient at the start of image formation of the electrophotographic photosensitive member is 0.3 to 0.5, and the average friction coefficient after 100 sheets of image formation when the lubricant is applied is 0.3 to 0.45. The image forming apparatus according to claim 1, wherein: The image forming apparatus according to claim 1, wherein a pencil hardness (Hp) in a surface layer of the filler-dispersed charge transport layer satisfies HB ≦ Hp <2H. 8. The image forming apparatus according to claim 1, wherein a straightness of the electrophotographic photosensitive member during image formation is (±) 20 μm and a roundness is 0 to 20 μm. 9. The electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member has a built-in vibration damping member, and has a straightness of (±) 20 μm and a circularity of 20 μm or less during image formation. An image forming apparatus according to any one of the above. The total thickness of the charge transport layer is 10 μm or more and 30 μm or less, and the electric field strength held by the electrophotographic photosensitive member at the development position during development is (−) 1.3 × 10 ^{5 to} 4.5 × 10 ^5. (V / cm). The image forming apparatus according to claim 1, wherein 2. The image forming apparatus according to claim 1, wherein an edge angle of the cleaning member in contact with the photoconductor is an acute angle, and the cleaning member is a rubber-like elastic body having a JIS-A hardness of 80 to 90 degrees. The image forming apparatus according to claim 1, wherein a contact pressure (linear pressure) of an edge of the rubber-like elastic body that contacts the electrophotographic photosensitive member is 15 g / cm or more and 25 g / cm or less. . 13. The image forming apparatus according to claim 1, wherein, when an edge width of a front end portion of the rubber-like elastic body contacting the photoconductor is W, 0 <W ≦ 0.5 mm. Image forming device. 14. The image forming apparatus according to claim 1, wherein the rubber-like elastic body is a cleaning member fixed to a metal supporting base. An electrophotographic photoreceptor according to any one of claims 1 to 10, a contact or non-contact charging device to which a DC voltage or a DC voltage superimposed with an AC voltage can be applied, and an image to be photo-written on the electrophotographic photoreceptor with monochromatic light. 15. An image forming apparatus comprising: an exposure device; a developing device including four color toner; a cleaning device using the cleaning member according to claim 11; and a belt-type intermediate transfer device for transferring a toner image. Tandem color copying system image forming apparatus. An image forming process unit comprising: the electrophotographic photosensitive member according to any one of claims 1 to 10; and the cleaning blade according to any one of claims 11 to 14. An image forming process unit comprising: the electrophotographic photosensitive member according to claim 1; and the cleaning blade and the developing device according to claim 11.

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