JP4138515B2 - Image forming apparatus and process cartridge - Google Patents

Description

【０１６８】
次に、下記電荷輸送層Ｂ塗工液の組成に従がって、無機フィラー（アルミナフィラー）が夫々３、５、１０、２５、３０、３５重量％になるようにそれぞれ秤量し、これと分散助剤及び溶剤を各々硝子ポットに入れてボールミルで２４時間分散させ、調整して電荷輸送層Ｂ塗工液（塗工液）を得た。
なお、上記フィラーの添加量に応じて分散助剤の配合比を変えた。配合の割合（フィラーの添加量（重量％）／分散助剤（部））は、以下の通りである。
（Ｎｏ．２）：フィラー３重量％／０．０３部、（Ｎｏ．３）：フィラー５重量％／０．０４部、（Ｎｏ．４、５）：フィラー１０、２５重量％／０．０８部、
（Ｎｏ．６）：フィラー３０重量％／０．１部、（Ｎｏ．７）：フィラー３５重量％／０．２部。
上記において、分散助剤を添加することにより、膜質の均一化が行われて残留電位の低減化に寄与するが、体積抵抗率、表面抵抗率を低下させる傾向のあることが確認された。
［電荷輸送層Ｂ塗工液］
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ７部
アルミナフィラー（住友化学工業製ＡＡ−０３、
平均一次粒径：０．３μｍ） ０．５３部〜９．３部
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：（ＢＹＫ−Ｐ１０４：
ビックケミージャパン製） ０．０３〜０．２部
【０１６９】
【化２】

【０１７０】
上記で得られた塗工液を用いて電荷輸送層Ｂを成膜した。成膜方法は、約３６０ｒｐｍで回転しながら２２μｍの膜厚を有する電荷輸送層Ａ上に、スプレーガンを１往復（送りスピード２５ｍｍ／ｓｅｃ）させて塗工を行い、１５０℃で２０分間加熱乾燥させて４層構成の感光体サンプル（Ｎｏ．２〜７）を作製した。このようにして作製した各感光体サンプル（Ｎｏ．１〜７）の表面抵抗率及び体積抵抗率を測定環境が２２〜２３℃の温度で、６５〜６７％ＲＨの相対湿度下において印加電圧５００Ｖで測定した（５００Ｖ印加１分後の参考値）。各感光体サンプルの一部構成（感光体径、電荷輸送層Ａ膜厚、電化輸送層Ｂのフィラー添加量）と表面抵抗率及び体積抵抗率を下記表１に示す。
【０１７１】
１−２ 評価用感光体サンプル（Ｎｏ．８、９）の作製
まず、φ１００ｍｍ、長さ３６０ｍｍ、肉厚１．２０ｍｍに加工された３００３系アルミニウム合金ドラムを導電性支持体とし、これを下記組成の下引き層用塗工液に浸漬して引き上げた後、１２０℃で２５分乾燥して約３．５μｍの下引き層を塗布形成した。
〔下引き層用塗工液〕
アルキッド樹脂（ベッコゾール １３０７−６０−ＥＬ：
大日本インキ化学工業社製） ６部
メラミン樹脂（スーパーベッカミン Ｇ−８２１−６０：
大日本インキ化学工業社製） ４部
酸化チタン（ＣＲ−ＥＬ：石原産業社製） ４０部
メチルエチルケトン ２００部
【０１７２】
引き続き、下記組成の電荷発生層用塗工液に浸漬後、１２０℃で２０分加熱乾燥して、０．２μｍの電荷発生層を形成した。
〔電荷発生層用塗工液〕
オキソチタニウムフタロシアニン顔料 ２部
ポリビニルブチラール（ＵＣＣ：ＸＹＨＬ） ０．２部
テトラヒドロフラン ５０部
【０１７３】
さらに、下記組成の電荷輸送層Ａ用塗工液に浸漬塗工し、１３０℃で３０分の加熱乾燥を行って、電荷輸送層Ａの膜厚が約２２μｍの電荷輸送層Ａを形成して、３層構成の有機感光体を作製した。
〔電荷輸送層Ａ用塗工液〕
下記構造式（２）の高分子電荷輸送物質 １０部
テトラヒドラフラン ４００部
シクロヘキサン ２００部
【０１７４】
【化３】

【０１７５】
次に、下記組成により、電荷輸送層Ｂ中の無機フィラー（一次平均粒径０．３μｍのαアルミナフィラー）量が夫々、電荷輸送層Ｂの１５、２５重量％になるよう調合し、これと分散助剤及び溶剤を夫々硝子ポットに入れ、ボールミルで２４時間分散させて電荷輸送層Ｂ塗工液（塗工液）を調整した。
なお、アルミナフィラーの添加量（部）が多くなるにしたがい、分散助剤の添加量を増加した。
［電荷輸送層Ｂ塗工液］
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の電荷輸送物質 ７部
アルミナフィラー（住友化学工業製ＡＡ−０３、
平均一次粒径：０．３μｍ） ３．１８部、５．７部
トラヒドロフラン ４００部
シクロヘキサノン ２００部
分散助剤：（ＢＹＫ−Ｐ１０４：
ビックケミージャパン製） ０．０４部、０．０８部
【０１７６】
【化４】

【０１７７】
得られた塗工液をスプレーガンを往復させて、約５μｍになるように電荷輸送層Ｂをスプレー塗工し、１５０℃で２０分間加熱乾燥させて、４層構成の感光体サンプルを作製した。
このようにして作製した各感光体サンプル（Ｎｏ．８、９）の表面抵抗率及び体積抵抗率を測定環境が２２〜２３℃の温度で、６５〜６７％ＲＨの相対湿度下において印加電圧５００Ｖで測定した（５００Ｖ印加１分後の参考値）。各感光体サンプルの一部構成（感光体径、電荷輸送層Ａ膜厚、電化輸送層Ｂのフィラー添加量）と表面抵抗率及び体積抵抗率を下記表１に示す。
【０１７８】
１−３ 評価用感光体サンプル（Ｎｏ．１０〜１２）の作製
φ３０ｍｍ、長さ３４０ｍｍ、肉厚０．７５ｍｍに加工された３００３系アルミニウム合金ドラムを導電性支持体として用い、これを下記組成の下引き層用塗工液に浸漬して表面に塗工を行った後、１２０℃で２０分加熱乾燥し、３．５μｍの下引き層を形成した。
〔下引き層用塗工液〕
アルキッド樹脂（ベッコゾール １３０７−６０−ＥＬ：
大日本インキ化学工業社製） ６部
メラミン樹脂（スーパーベッカミン Ｇ−８２１−６０：
大日本インキ化学工業社製） ４部
酸化チタン（ＣＲ−ＥＬ：石原産業社製） ４０部
メチルエチルケトン ２００部
【０１７９】
次に、下記組成の電荷発生層用塗工液に浸漬塗工した後、１２０℃で２０分間加熱乾燥して、０．２μｍの電荷発生層を形成した。
〔電荷発生層用塗工液〕
下記構造式（３）のビスアゾ顔料 １０部
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
【０１８０】
【化５】

【０１８１】
さらに、下記組成の電荷輸送層Ａ用塗工液を引き上げ速度条件を変化させて、電荷輸送層Ｂ上に浸積塗工し、１３０℃で２０分の加熱乾燥を行い、２２μｍの電荷輸送層Ａからなる３層構成の有機感光体を作製した。
〔電荷輸送層Ａ用塗工液〕
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ８部
テトラヒドラフラン ２００部
【０１８２】
【化６】

【０１８３】
次に、下記組成により、電荷輸送層Ｂ中の無機フィラー（一次平均粒径０．３μｍのαアルミナフィラー）量が夫々、電荷輸送層Ｂの１５、２５、３５重量％になるよう調合し、この無機フィラーと分散助剤及び溶剤を夫々硝子ポットに入れ、ボールミルで２４時間分散させて電荷輸送層Ｂ塗工液（塗工液）を得た。
［電荷輸送層Ｂ塗工液］
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ７部
アルミナフィラー（住友化学工業製ＡＡ−０３、
平均一次粒径：０．３μｍ） ４．２５部〜９．１部
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：（ＢＹＫ−Ｐ１０４：
ビックケミージャパン製） ０．０５部
【０１８４】
【化７】

【０１８５】
上記で得られた塗工液をスプレーガンを往復させて、約５μｍになるように電荷輸送層Ｂをスプレー塗工し、１５０℃２０分間加熱乾燥させて、４層構成の感光体サンプルを作製した。
このようにして作製した各感光体サンプル（Ｎｏ．１０〜１２）の表面抵抗率及び体積抵抗率を測定環境が２２〜２３℃の温度で、６５〜６７％ＲＨの相対湿度下において印加電圧５００Ｖで測定した（５００Ｖ印加１分後の参考値）。各感光体サンプルの一部構成（感光体径、電荷輸送層Ａ膜厚、電化輸送層Ｂのフィラー添加量）と表面抵抗率及び体積抵抗率を下記表１に示す。
【０１８６】
１−４ 評価用感光体サンプル（Ｎｏ．１３〜１５）の作製
φ３０ｍｍ、長さ３４０ｍｍ、肉厚０．７５ｍｍに加工された３００３系アルミニウム合金ドラムを導電性支持体として用い、これを下記組成の下引き層用塗工液に浸漬して表面に塗工を行った後、１２０℃で２０分加熱乾燥して３．５μｍの下引き層を形成した。
〔下引き層用塗工液〕
アルキッド樹脂（ベッコゾール １３０７−６０−ＥＬ：
大日本インキ化学工業社製） ６部
メラミン樹脂（スーパーベッカミン Ｇ−８２１−６０：
大日本インキ化学工業社製） ４部
酸化チタン（ＣＲ−ＥＬ：石原産業社製） ４０部
メチルエチルケトン ２００部
【０１８７】
次に、下記組成の電荷発生層用塗工液に浸漬後、１２０℃２０分加熱乾燥して０．２μｍの電荷発生層を形成した。
〔電荷発生層用塗工液〕
下記構造式（３）のビスアゾ顔料 １０部
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
【０１８８】
【化８】

【０１８９】
さらに、下記組成の電荷輸送層Ａ用塗工液に浸漬塗工し、１３０℃で２０分の加熱乾燥を行い、１５μｍ及び２２μｍの電荷輸送層Ａからなる３層構成の有機感光体を作製した。
〔電荷輸送層Ａ用塗工液〕
下記構造式（４）の高分子電荷輸送物質 ７部
テトラヒドラフラン ４００部
シクロヘキサン ２００部
【０１９０】
【化９】

【０１９１】
次に、下記組成により、電荷輸送層Ｂ中の無機フィラー（一次平均粒径０．３μｍのαアルミナフィラー）量が夫々、電荷輸送層Ｂの１５、２５、４０重量％になるよう調合し、これと分散助剤及び溶剤を夫々硝子ポットに入れ、ボールミルで２４時間分散させて電荷輸送層Ｂ塗工液（塗工液）を得た。
［電荷輸送層Ｂ塗工液］
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ７部
アルミナフィラー（住友化学工業製ＡＡ−０３、
平均一次粒径：０．３μｍ） ３．１８部〜１１．３部
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：（ＢＹＫ−Ｐ１０４：
ビックケミージャパン製） ０．０７部
【０１９２】
【化１０】

【０１９３】
上記で得られた塗工液を用い、スプレーガンによるスプレー塗工法により１往復させ、電荷輸送層Ａ上に約５μｍの電荷輸送層Ｂ塗工し、１５０℃で２０分間加熱乾燥させて４層構成の感光体サンプルを作製した。
このようにして作製した各感光体サンプル（Ｎｏ．１３〜１５）の表面抵抗率及び体積抵抗率を測定環境が２２〜２３℃の温度で、６５〜６７％ＲＨの相対湿度下において印加電圧５００Ｖで測定した（５００Ｖ印加１分後の参考値）。各感光体サンプルの一部構成（感光体径、電荷輸送層Ａ膜厚、電化輸送層Ｂのフィラー添加量）と表面抵抗率及び体積抵抗率を下記表１に示す。
【０１９４】
１−５ 評価用感光体サンプル（Ｎｏ．１６〜１８）の作製
φ３０ｍｍ、長さ３４０ｍｍ、肉厚０．７５ｍｍに加工された３００３系アルミニウム合金ドラムを導電性支持体として用い、これを下記組成の下引き層用塗工液に浸漬して表面に塗工を行った後、１２０℃で２０分加熱乾燥して３．５μｍの下引き層を形成した。
〔下引き層用塗工液〕
アルキッド樹脂（ベッコゾール １３０７−６０−ＥＬ：
大日本インキ化学工業社製） ６部
メラミン樹脂（スーパーベッカミン Ｇ−８２１−６０：
大日本インキ化学工業社製） ４部
酸化チタン（ＣＲ−ＥＬ：石原産業社製） ４０部
メチルエチルケトン ２００部
【０１９５】
次に、下記組成の電荷発生層用塗工液に浸漬後、１２０℃で２０分間加熱乾燥して０．２μｍの電荷発生層を形成した。
〔電荷発生層用塗工液〕
下記構造式（３）のビスアゾ顔料 １０部
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
【０１９６】
【化１１】

【０１９７】
さらに、下記組成の電荷輸送層Ａ用塗工液に浸漬し、その浸漬液からの引き上げ速度条件を変化させて、電荷輸送層Ｂを浸積塗工し、１３０℃で２０分の加熱乾燥を行い、２２μｍの電荷輸送層Ａからなる３層構成の有機感光体を作製した。
〔電荷輸送層Ａ用塗工液〕
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ８部
テトラヒドラフラン ２００部
【０１９８】
【化１２】

【０１９９】
次に、下記電荷輸送層Ｂ塗工液の組成に従って、一次平均粒径が０．３μｍ、０．５μｍ及び０．７μｍのαアルミナフィラーを用意し、その夫々のαアルミナフィラーと、分散助剤及び溶剤とを夫々硝子ポットに入れ、ボールミルで２４時間分散させて、電荷輸送層Ｂの２０重量％になるよう調合した電荷輸送層Ｂ塗工液（塗工液）を作製した。
［電荷輸送層Ｂ塗工液］
ビスフェノールＺ型ポリカーボネート（帝人化成社製：
Ｚポリカ Ｍｖ５万） １０部
下記構造式（１）の低分子電荷輸送物質 ７部
アルミナフィラー（住友化学工業製ＡＡ−０３〜０．７
平均一次粒径：０．３、０．５、０．７μｍ） ４．２５部
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：（ＢＹＫ−Ｐ１０４：
ビックケミージャパン製） ０．０８部
【０２００】
【化１３】

【０２０１】
上記で作製した塗工液を評価用の感光体を設置した塗工装置に装着したスプレーガンに投入したのち、１往復の噴射により、感光体上にスプレー塗工を行い、１５０℃で２０分間加熱乾燥させて約５μｍの電荷輸送層Ｂを形成し、４層構成の感光体サンプルを作製した。
このようにして作製した各感光体サンプル（Ｎｏ．１６〜１８）の表面抵抗率及び体積抵抗率を測定環境が２２〜２３℃の温度で、６５〜６７％ＲＨの相対湿度下において印加電圧５００Ｖで測定した（５００Ｖ印加１分後の参考値）。各感光体サンプルの一部構成（感光体径、電荷輸送層Ａ膜厚、電化輸送層Ｂのフィラー添加量）と表面抵抗率及び体積抵抗率を下記表１に示す。
【０２０２】
【表１】

【０２０３】
前記で作製した各感光体サンプルを用い、以下のように感光体表層への潤滑剤の付与方法及びクリーニング装置用クリーニングブラシを使用して、評価用装置（イマジオＮｅｏ６００、イプシオカラー８０００）にて評価を行った。
【０２０４】
＜感光体表層への潤滑剤の付与方法＞
重量平均粒径が約４．８μｍ、平均円形度が０．９２４の粉砕トナー（流動剤としてＳｉＯ_２を０．７％、ＴｉＯ_２を０．８％添加）に、平均粒径が０．３μｍのステアリン酸亜鉛（ＳＺ２０００：堺化学工業株式会社製）を０．０２〜０．０５重量％添加し、このトナーを用いて感光体表層（表面）に潤滑性を付与する方法を採用した。現像剤用のキャリアには、重量平均粒径５８μｍの磁性キャリア（ＦＰＣ−３００ＬＣ：パウダーテック社製）を使用した。
なお、上記以外の現像剤を使用する場合には、評価装置用の純正品を使用した。
【０２０５】
＜クリーニング装置用クリーニングブラシ＞
本発明におけるクリーニングブラシＡ（強化ループブラシ）：
繊維径１５デニール、４８フィラメント／４５０ループ、ループ長さ３ｍｍのナイロン繊維製のベルトロン（久保田織物製）を幅１０ｍｍのひも状にカットし、φ５ｍｍの真鍮製ロッド棒に巻き付け接着剤を用いて貼り付けて固定し、ループ状繊維からなるクリーニングブラシ（ループクリーニングブラシ）を作製した。次に、上記で作製したループクリーニングブラシに下記方法で樹脂被覆を行い、繊維の強度強化を図った。
繊維表面処理用の被覆樹脂として、主剤にトーヨーポリマー社の水系ウレタン接着剤メルシ５８５を使用し、硬化剤にトーヨーポリマー社のエポキシＡＤ−Ｃ−６５を用いた。被覆樹脂の粘度が４１ｍＰａ・Ｓとなるようにイオン交換水を希釈溶媒として使用した。主剤５部に対し、硬化剤（架橋剤）の添加量が５重量％になるように調整しながら１．２５部の水を添加し得られた被覆樹脂用溶液に、前記クリーニングブラシのブラシ表面より２ｍｍ浸漬させて取り出した後、１６０℃で１０分の乾燥を行った。なお、クリーニングブラシの回転方向は感光体の回転方向に倣う方向（順方向）で回転し、フリッカーバーの設置はしていない。
参考例におけるクリーニングブラシＢ（直毛ブラシ）：
直毛ブラシのクリーニングブラシは、評価用に使用した装置（イマジオＮｅｏ６００、及びイプシオ・カラー８０００）用の、いわゆる純正のブラシを夫々使用した。
【０２０６】
実施例１〜４
まず、評価用の装置（評価機）としてデジタル複合機のイマジオＮｅｏ６００（コロナ帯電器、φ１００ｍｍの感光体使用、リコー製）を用いた。前記表１に記載のＮｏ．２〜５の感光体サンプルを評価機に搭載し、連続通紙を行って作像し、５万枚後、２０万枚後の表面抵抗率、体積抵抗率、画像品質（解像度、２ドットパターン濃度ムラ）、感光層の摩耗量及び摩擦係数を評価した。作像時の感光体の表面電位は−８００Ｖに設定し、現像剤にはトナーに対し０．０２５重量％のステアリン酸亜鉛（前記ＳＺ２０００、平均粒径０．３μｍ）を添加した現像剤を使用した。
クリーニング装置用クリーニングブラシは前記作製したクリーニングブラシＡ（強化ループブラシ）を使用し、クリーニングブレードと併用する構成とした。なお、通紙ランニング中の画像パターンには画像面積が５％のチャートを使用した。また、解像度の確認にはコダック社製図票Ａ（ＪＩＳ Ｚ ６００８）を画像評価用のテストチャートに貼り付け使用した。作像環境は２２〜２４℃／６１〜６８％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表２に示す。
【０２０７】
【表２】

【０２０８】
評価に使用した感光体はいずれも、ほぼ均一に摩耗しており、研磨面も初期に近い光沢を保っていた。その結果が表面抵抗率、体積抵抗率にも現れており、画像品質における解像度や２ドットパターンの再現性も良好で均一な特性であった。また、コロナ帯電器の使用及び潤滑剤の付与効果により感光層の摩耗量も少なく、２０万枚でも感光層の膜厚には余裕があり、良好な耐久性を有することが確認された。なお、フィラー添加量が２５重量％の感光体（感光体サンプルＮｏ．５）では感光体端部に局部的にフィルミングの発生が生じ２ドットパターンにやや濃度ムラが生じたが、僅かな研磨力の強化で改善できる範疇にある。
【０２０９】
参考例１〜６
評価用の装置（評価機）としてデジタル複合機のイマジオＮｅｏ６００（コロナ帯電器、φ１００ｍｍの感光体を使用、リコー製）を用いて、前記表１に記載のＮｏ．１、５、６、７、８、９の６本の各感光体サンプルを評価機に搭載し、連続通紙を行って作像し、５万枚後、２０万枚後の表面抵抗率、体積抵抗率、画像品質（解像度、２ドットパターン濃度ムラ）、感光層の摩耗量及び摩擦係数、を評価した。作像時の感光体の表面電位を−８００Ｖに設定し、現像剤にはワックス入りの純正の現像剤を使用した。
また、クリーニングブラシは純正の直毛ブラシに交換し、クリーニングブレードと併用使用とした。なお、通紙ランニング中の画像パターンには画像面積が５％のチャートを使用した。作像環境は２４〜２７℃／６３〜７２％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表３に示す。
【０２１０】
【表３】

【０２１１】
フィラーを添加した電荷輸送層Ｂを形成していない感光体サンプル（Ｎｏ．１）では摩耗が多いために、表面抵抗率、体積抵抗率とも変化は少なく、見かけ上良好な特性を示したが、現像剤中に添加した酸化チタンやシリカなどの流動剤が感光体表面に付着し、感光体表面の荒れが生じてドットパターンに濃度ムラが生じた。
その他の感光体サンプル（Ｎｏ．５、６、７、８、９）では、クリーニングブラシが直毛タイプであり、感光体表層の摩擦係数が比較的低く、感光層を研磨する能力が無いため、フィルミングの形成がコピー枚数を重ねる毎に顕著になった。その結果、コロナ生成物の蓄積により、表面抵抗率、体積抵抗率の低下が顕著になって解像度の低下が発生した。
【０２１２】
実施例５〜９
評価用の装置（評価機）としてデジタルプリンターのイプシオカラー８０００（非接触帯電器、φ３０ｍｍの感光体を使用、リコー製）を用いて、前記表１に記載のＮｏ．１０（Ｍ）、１１（Ｃ）、１２（Ｙ），１３（Ｍ），１４（Ｃ）の５本の感光体サンプルを前記評価機に搭載し、連続通紙を行って作像し、５万枚後、１０万枚後の表面抵抗率、体積抵抗率、画像品質（シャープ性、２ドットパターン濃度ムラ）及び感光層の摩耗量、摩擦係数を評価した。
なお、括弧内のＭ、Ｃ、Ｙは、Ｍ：マゼンタステーション、Ｃ：シアンステーション、Ｙ：イエローステーションの現像位置を夫々表す。
【０２１３】
評価は２回に分けて行った。１回目はＮｏ．１０〜１２とし、２回目はＮｏ．１３、１４として、空いたステーションにはダミードラムをセットした。上記括弧内は初期にセットした現像位置であり、５０００枚毎にクリーニングブレードと共に、順にローテーションを行った。作像時の感光体の表面電位は−７００Ｖに設定し、現像剤にはステアリン酸亜鉛をトナーに対して０．０３重量％添加し、トナー濃度を５重量％として使用した。
クリーニングブラシには前記した製法により、樹脂補強したクリーニングブラシＡ（強化ループブラシ）を、イプシオ８０００用に加工して使用した。また、通紙ランニング中に使用する画像パターンには、パソコンのデータベースに入力されている５％チャートを使用し、その信号をイプシオ・カラー８０００に入力した。作像環境は２３〜２５℃／６４〜７０％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表４に示す。
【０２１４】
【表４】

【０２１５】
電荷輸送層Ｂへのフィラーの添加量が３５重量％（実施例７）の感光体サンプルは、フィラーの量が多いために、コロナ生成物のアタック量が多い割には、摩耗量が少なく、２ドットパターンに少しムラが生じたと推測される。実施例８及び９の感光体サンプルでの評価がやや思わしくなかったのは、電荷輸送層Ａに使用した高分子電荷輸送層の比抵抗に起因するためと思われる。これらのサンプルはもう少し電荷輸送層Ｂの摩耗を多くすれば、画像品質の劣化は回避できる。
上記以外のその他の感光体サンプルは、２ドットパターンの濃度ムラも良好であった。その結果は表面抵抗率、体積抵抗率の変化が夫々１桁、２桁以内であり、コロナ生成物が均一に削り取られているためであると推測される。
【０２１６】
参考例７〜１０
評価用の装置（評価機）としてデジタルプリンターのイプシオカラー８０００（非接触帯電器、φ３０ｍｍの感光体を使用、リコー製）を用いて、前記表１に記載のＮｏ．１０（Ｍ）、１２（Ｃ）、１４（Ｍ）、１５（Ｃ）の４本の感光体サンプルを２本ずつ２回に分けて、前記評価機に搭載し、連続通紙を行って作像し、５万枚後、１０万枚後の表面抵抗率、体積抵抗率、画像品質（シャープ性、２ドットパターン濃度ムラ）及び感光層の摩耗量、摩擦係数を評価した。なお、括弧内は初期にセットした現像位置で、５０００枚毎にクリーニングブレードと共に、順にローテーションを行った。Ｙ（イエロー）及びＢｋ（ブラック）ステーションには夫々ダミードラムをセットし、Ｍ（マゼンタ）とＣ（シアン）ステーションのみで評価した。作像時の感光体の表面電位は−７００Ｖに設定し、現像剤にはステアリン酸亜鉛をトナーに対して０．０３重量％添加し、トナー濃度を５重量％として使用した。
なお、クリーニングブラシにはイプシオ８０００用の純正直毛タイプクリーニングブラシを使用した。通紙ランニング中に使用する画像パターンには、パソコンのデータベースに入力されている５％チャートを使用し、その信号をイプシオ・カラー８０００に入力した。作像環境は２６〜２９℃／６８〜７４％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表５に示す。
【０２１７】
【表５】

【０２１８】
強化処理されていない直毛タイプのクリーニングブラシを使用した場合、感光体表面にはフィルミング現象が生じ、またコロナ生成物の蓄積、潤滑剤の堆積が生じた結果、感光体表面の摩擦係数の低減化が進行した。その結果、表面抵抗率及び、体積抵抗率は夫々、画像品質の劣化がなく良好な作像が可能な限界値である１桁ないしは２桁以上の変化を示した。その結果、画像品質の劣化が生じ、評価した感光体サンプル全てに亘って、画像流れ状態に到り悪い画像品質となった。
【０２１９】
実施例１０〜１２
評価用の装置（評価機）としてデジタルプリンターのイプシオ・カラー８０００（非接触帯電器、φ３０ｍｍの感光体を使用、リコー製）を用いて、前記表１に記載のＮｏ．１６（Ｍ）、１７（Ｃ）及び１８（Ｙ）の３本の感光体サンプルを前記評価機に搭載し、連続通紙を行って作像し、５万枚後、１０万枚後の表面抵抗率、体積抵抗率、画像品質（シャープ性、２ドットパターン濃度ムラ）及び感光層の摩耗量、摩擦係数を評価した。なお、括弧内は初期にセットした現像位置で、５０００枚毎にクリーニングブレードと共に、順にローテーションを行った。ブラック現像位置にはダミードラムをセットした。作像時の感光体の表面電位は−７００Ｖに設定し、現像剤にはステアリン酸亜鉛をトナーに対して０．０２重量％添加し、トナー濃度を５重量％として使用した。
また、クリーニングブラシには前記した製法により、樹脂補強した強化ブラシＡ（強化ループブラシ）を、イプシオ８０００用に加工して使用した。通紙ランニング中に使用する画像パターンには、パソコンのデータベースに入力されている５％チャートを使用し、その信号をイプシオ・カラー８０００に入力した。作像環境は２４〜２７℃／６４〜７１％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表６に示す。
【０２２０】
【表６】

【０２２１】
フィラーの１次平均粒径の大きさを変えた感光体サンプルでは、使用したいずれの感光体サンプルも１０万枚後でも良好な表面抵抗率、体積抵抗率を示し、感光体の表面性及び画像品質共々良好であった。
なお、フィラーの平均粒径が０．７μｍの感光体サンプル（Ｎｏ．１８）では、耐摩耗性が向上した影響による摩耗の偏り並びに表面の荒れが少し見られ、その結果、少しではあるが２ドットパターンの濃度ムラとなって現れた。摩耗量をもう少しアップさせるか、クリーニング部材の改良により、摩耗性及び画像品質の改良が期待されるが、更に偏摩耗が進行する可能性も有ることからフィラー径は０．７μｍが限度と推定される。
【０２２２】
参考例１１〜１３
評価用の装置（評価機）としてデジタルプリンターのイプシオカラー８０００（非接触帯電器、φ３０ｍｍの感光体を使用、リコー製）を用いて、前記表１に記載のＮｏ．１５（Ｍ）、１６（Ｃ）、及び１７（Ｙ）の３本の感光体サンプルを前記評価機に搭載し、連続通紙を行って作像し、５万枚後、１０万枚後の表面抵抗率、体積抵抗率、画像品質（シャープ性、２ドットパターン濃度ムラ）及び感光層の摩耗量、摩擦係数を評価した。なお、括弧内は初期にセットした現像位置で、５０００枚毎にクリーニングブレードと共に、順にローテーションを行った。ブラック現像位置にはダミードラムをセットした。作像時の感光体の表面電位は−７００Ｖに設定し、現像剤には潤滑剤を添加しないトナー濃度５重量％混合の現像剤を使用した。
クリーニングブラシには純正の直毛ブラシを使用した。通紙ランニング中に使用する画像パターンには、パソコンのデータベースに入力されている５％チャートを使用し、その信号をイプシオ・カラー８０００に入力した。作像環境は２４〜２６℃／６８〜７３％ＲＨ、表面抵抗率、体積抵抗率の測定環境は２２〜２３℃／６５〜６７％ＲＨである。評価結果を表７に示す。
【０２２３】
【表７】

【０２２４】
評価に使用した感光体サンプルはいずれもフィルミング現象が生じ、感光体表面はいずれも薄く灰色がかった色を呈した。その結果、コロナ生成物、紙粉などの汚染物質の除去が行われず（摩耗量が少ない）、感光体の内部へのコロナ生成物の侵入が行われ、結果的に表面抵抗率、体積抵抗率の大幅な低下を起こし、画像品質の劣化が生じた。参考例１１に記載の感光体サンプルＮｏ．１５の場合は、電荷輸送層Ａに他の比較感光体サンプルより、窒素酸化物の影響を受け易い高分子輸送層を使用したため、抵抗率が大きく低下し、常湿環境より少し高めの環境（〜７３％ＲＨ）でも画像流れが起こり、全面２ドットパターンの画像も画像流れが大きな濃淡差となった。
【０２２５】
【発明の効果】
本発明によれば、樹脂層で被覆強化された強化ループブラシ（ループ状繊維からなるクリーニングブラシ）を備えた特定のクリーニング装置と、感光層の最外層（電荷輸送層Ｂ）にフィラーを分散して適切な量に削り取られるように調節された耐久性を備えた感光体との構成により、常に感光体表層面を清浄な状態に維持して表面抵抗率（σｓ）を１×１０¹⁵〜１×１０¹⁷Ω、体積抵抗率（ρｖ）を１×１０¹³〜５×１０¹⁵Ω・ｃｍに調整すると共に、作像中における感光層表面の摩擦係数を０．２〜０．４（オイラーベルト方式で測定）に調整することによって、長期的に画像ムラがなく良好なシャープ性と高解像度な高品位画像形成が達成される。
また、作像開始時と５万枚作像後における表面抵抗率及び体積抵抗率の値が好適な範囲内に調整され、しかも変動値（表面抵抗率：１桁以内、体積抵抗率：２桁以内）が適正かつ厳しく規定されるため、高品位画像を長期に亘って作像することが可能である。
表面抵抗率及び体積抵抗率の測定用の電極（円電極とリング電極）として、インジウム箔を使用することにより、ドラム形状のような曲率を有する感光体（測定試料）でも切断加工などを施すことなく、そのままの状態で感光体表面に容易に密着付設することができる。そのため、正確で安定した表面抵抗率及び体積抵抗率が測定でき、実際の状況把握が可能となり、所定の制御範囲に抵抗率を制御することができる。また、感光体（測定試料）を加工する必要がないため、再使用が可能となる。
更に、強化ループ繊維の表面被覆材（樹脂層）として、水系のウレタン系樹脂（主剤）＋エポキシ系化合物（硬化剤）を使用することにより、耐久性と均一な研磨能力を有するループグブラシが得られる。この強化ループグブラシを用いることにより、感光体表面に付着したトナー等の残留粉体の除去、感光体表面に固着し始めた汚染物質を薄く均一に除去することが可能となり、感光体表面を常に清浄に保つことができる。
また、感光層を電荷発生層と電荷輸送層との２層構成の機能分離型とすることにより、良好な帯電特性と良好な感度が得られ、高品位画像を形成することが可能となる。
更に、電荷輸送層は、無機フィラーを分散しない電荷輸送層Ａと無機フィラーを分散した電荷輸送層Ｂとから構成される。フィラーを分散した電荷輸送層Ｂを設けることにより、感光体表面研削に対する耐久性を向上して適正な摩耗量に調整し、またフィラーを分散しない電荷輸送層Ａ（電荷発生層と電荷輸送層Ｂとの間に介在）を設けることによって異常な電荷移動を防ぎ、安定した高品位画像を形成することが可能となる。
更にまた、潤滑剤として微粒なステアリン酸亜鉛もしくはポリテトラフルオロエチレン（ＰＴＦＥ）の何れか１種を感光体表面に付与して摩擦係数を調整（作像中の摩擦係数：０．２〜０．４）することにより、感光層の摩耗を抑制し、シャープ性の良好な均一性の高い画像品質を維持することが可能となる。
また、各種帯電手段に合わせて感光体の電荷輸送層Ｂに分散するフィラー量を調整することにより、各帯電における化学的ハザ−ドレベル（大、小）に対応することができるため、感光体の耐久性を最適にすることが可能となる。そして、高画像品質を得る画像形成装置の幅広い設計を可能とする。
更に、感光体と帯電装置（帯電部材等）との配置間隔や環境条件（湿度等）に応じて、最適な印加電圧方式（直流電圧、交流電圧を重畳した直流電圧）を選択することができるため、高画像品質を提供するための要求に応じた幅広い画像形成装置の設計を可能とする。
また、感光層を構成する最外電荷輸送層にフィラーを分散してなる電子写真感光体と、帯電装置、現像装置、あるいはクリーニング装置（強化ループブラシを備える）から選ばれる少なくとも１つの装置とを一体に支持した画像形成装置本体に着脱自在なプロセスカートリッジとすることにより、画像装置をコンパクトに構成することができる他、簡単で且つ着実なメンテナンス作業を可能とすると共に、更に部品の交換を容易とし、総合的なコストダウンが図れる。しかも、プロセスカートリッジの交換だけで簡単に元の高品位画像に復させることが可能である。
【図面の簡単な説明】
【図１】実施の形態において複写プロセスを説明するための本発明に係る画像形成装置の基本的な構成例を示す概略構成図である。
【図２】マゼンタ、シアン、イエロー、ブラックの現像装置を配設した４連タンデム型フルカラー方式の画像形成装置構成例を説明するための概略模式図である。
【図３】画像形成装置本体に着脱可能なプロセスカートリッジの一例を示す概略模式図である。
【図４】画像形成装置本体に着脱可能なプロセスカートリッジの別の例を示す概略模式図である。
【図５】本発明における電子写真感光体の基本的な構成例（導電性支持体／下引き層／感光層から構成）を示す概略模式図である。
【図６】本発明における電子写真感光層が電荷発生層と電荷輸送層との機能分離型構成により形成される例を示す概略模式図である。
【図７】図６における電荷輸送層が電荷輸送層Ａ（無機フィラー非分散層）と電荷輸送層Ｂ（無機フィラー分散層）とから構成される例を示す概略模式図である。
【図８】本発明のクリーニングブラシ（強化ループブラシ）とクリーニングブレードから構成されるクリーニング装置を示す概略模式図である。
【図９】本発明の基体布とループ状繊維からなるクリーニングブラシの形態を示す概略模式図である。
【図１０】本発明における表面低抵抗率及び体積抵抗率を測定するための電極形状と寸法を説明するための概略模式図である
【図１１】曲率を有するドラム形状の電子写真感光体表面に電極を密着付設した様子を示す概略模式図である。
【図１２】インジウム電極を付設した電子写真感光体の表面抵抗率を測定する場合の測定治具と電圧印加状態を示す概略回路図である。
【図１３】インジウム電極を付設した電子写真感光体の体積抵抗率を測定する場合の測定治具と電圧印加状態を示す概略回路図である。
【図１４】電荷発生層Ａ上に膜厚の異なる電荷輸送層Ｂを形成した感光体サンプルＡ(５μｍ)と感光体サンプルＢ(３μｍ)の表面抵抗率の印加電圧依存性を示す図である。
【図１５】電荷発生層Ａ上に膜厚の異なる電荷輸送層Ｂを形成した感光体サンプルＡ(５μｍ)と感光体サンプルＢ(３μｍ)の体積抵抗率の印加電圧依存性を示す図である。
【図１６】感光体サンプルＡのフィラー量を20％に変えたサンプルの初期と５万枚通紙ランニング後(強化ループブラシ)の体積抵抗率の印加電圧依存性を示す図である。
【図１７】図１６のサンプルの低電荷輸送物質を高電荷輸送物質に変えたサンプルの初期と５万枚通紙ランニング後(直毛ブラシ)の体積抵抗率の印加電圧依存性を示す図である。
【図１８】感光体サンプルＡのフィラー量を20％に変えたサンプルの初期と５万枚通紙ランニング後(強化ループブラシ)の表面抵抗率の印加電圧依存性を示す図である。
【図１９】図１８のサンプルの低電荷輸送物質を高電荷輸送物質に変えたサンプルの初期と５万通紙ランニング後(直毛ブラシ)の表面抵抗率の印加電圧依存性を示す図である。
【図２０】各種抵抗率を変えた感光体サンプルの体積抵抗率に対する帯電々位低下量の依存性を示す図である。
【図２１】各種抵抗率を変えた感光体サンプルの体積抵抗率に対する解像度の依存性を示す図である。
【図２２】各種抵抗率を変えた感光体サンプルの表面抵抗率に対する解像度の依存性を示す図である。
【符号の説明】
１ 電子写真用感光体（感光体）
２ 帯電装置
２−１ 帯電部材
２−２ 高圧電源回路
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 クリーニングブラシ
７−２ クリーニングブレード
８ 定着装置
９ 被転写体（コピー用紙）
２１ 導電性支持体
２２ 下引き層
２３ 感光層
２４ 電荷発生層
２５ 電荷輸送層
２５ａ 電荷輸送層Ａ
２５ｂ 電荷輸送層Ｂ
２００ 潤滑剤塗布装置
２０１ 潤滑剤
２０２ 塗布ブラシ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and a process cartridge capable of high-quality image formation over a long period of time. Specifically, the present invention relates to an electrophotographic photosensitive member having a function-separated type photosensitive layer in which a filler is dispersed in a charge transport layer. The present invention relates to an image forming apparatus which is equipped with a specific cleaning device for adjusting to a suitable surface resistivity and volume resistivity and performs image formation while maintaining a low friction coefficient, and a process cartridge which can be attached to and detached from the image forming device.
[0002]
[Prior art]
An electrophotographic photosensitive member (hereinafter referred to as a photosensitive member) is charged, the charged surface is exposed to an image to form an electrostatic latent image, the electrostatic latent image is visualized as a toner image, and the toner image is copied. 2. Description of the Related Art Image forming apparatuses that use indirect electrophotography that transfers to a transfer medium such as paper have been known.
The image forming apparatus is configured as a main means such as a facsimile, a laser printer, and a copying machine. For image formation, a charging device (such as corona charging, contact charging with a roller or a brush, or non-contact charging arranged at a distance of 30 to 250 μm) or an image exposure device (for example, LD , Exposure means for irradiating a photosensitive member with a dot pattern using an LED array as a light source), developing device (developing means using a one-component or two-component developer magnet brush or flying method), transfer device (corona, roller, belt, etc.) Each device of the image forming apparatus provided with a transfer device), a cleaning device (blade cleaning, brush cleaning, a cleaning device combining the above two cleaning members), a static eliminator (corona discharge, a brush, light, etc.). Are performed in order.
[0003]
In image formation, charging (charging) is first performed on the photosensitive member by a charging device. Such a charging device includes a grid, a metal wire such as a tungsten wire or a nickel wire having a diameter of about 40 to 80 μm stretched in the shield case in the length direction of the photosensitive member, or a SUS sawtooth shape. A corona charging device that charges by applying a DC voltage of about −4000 to −6500 V to the electrode plate, or 10^Five -10¹²Direct current obtained by superimposing a DC voltage of −800 to −2000 V or a DC voltage of −500 to −2000 V to an AC voltage of 1000 to 2500 V / 600 to 2500 Hz on a charging member such as a roller or a brush having a resistance of about Ω · cm. A contact charging device for charging by applying a voltage, or a non-contact charging device for charging by applying a DC voltage or a DC voltage on which an AC voltage is superposed, with a charging member disposed about 30 to 250 μm away from the photoreceptor. It is used. The surface of the photoreceptor is set to a surface potential necessary for image formation using these charging devices, for example, 400 to 1000 V in absolute value. Note that a function-separated organic photoreceptor formed in the order of a charge generation layer and a charge transport layer that are generally used is negatively charged.
[0004]
All of the above-described charging devices are charging systems that involve discharge during charging, and therefore ozone (O.sub._Three), Nitrogen oxides (NOx), and the like (hereinafter, these substances generated from the charging device are referred to as corona products).
Chemical effects (corresponding to image flow and electrophotographic characteristic deterioration) of the corona product generated by the charging device on the photoreceptor are known in the prior art, but the degree of influence varies depending on the charging method. . Looking at the degree of influence of the charging method due to image flow or the like, roughly, the non-contact charging method ≧ the contact charging method ≧ the corona charging method, the order is reverse to the generation amounts of ozone and nitrogen oxides.
[0005]
In the case of the corona charging method, the charging efficiency (charging level with respect to the input voltage) greatly depends on the shape, size, discharge electrode used, and the like. In the corona charging method with good charging efficiency, ozone is obviously generated more than in the contact charging method, but the influence of chemical and physical hazards can be minimized as in the above order. Therefore, when a corona charging system charging device is used, the durability of the photoreceptor can be greatly extended.
When the corona charging method is used, the clear reason why the hazard to the photoconductor is low is unknown, but since it is away from the photoconductor, the substances that affect the process (halfway) disappear and decrease. This is presumably because the energy given to the photoconductor as a whole is low, the bonding force with the surface of the photoconductor becomes weak, and it is relatively easy to remove with a developer or the like.
[0006]
In the case of a contact or non-contact charging device, the amount of pollutants generated is small, but the distance to the photoconductor is very close, so the energy is large and the adhesion of the pollutants to the photoconductor surface is large. It is estimated that it will be difficult to remove.
Ozone is known as a strong oxidizing substance, and when it acts on the surface of the photosensitive layer, it oxidizes the surface of the photosensitive member to lower the electrical resistance (lower resistance) and further cuts the molecular structure of the photosensitive layer. This reduces the charging characteristics and sensitivity of the photoreceptor. However, because ozone adheres to an object and decomposes into oxygen molecules and oxygen atoms (which eventually becomes oxygen), the action time as ozone is relatively short, and the continuous effect is less than that of nitrogen oxides. Low.
[0007]
On the other hand, nitrogen oxides adhere to the surface of the photosensitive layer and penetrate into the photosensitive layer, thereby reducing the electrical resistance of the entire photoconductor, and the influence continues until the nitrogen oxides are removed.
If the corona product adheres to the surface of the photoconductor and absorbs moisture and is rubbed with a blade or developer, the corona product is stretched, so the range of reduction in electrical resistance (reduction in resistance) on the photoconductor surface is expanded. As a result, the resolution is lowered and the image flow area is enlarged over the entire surface.
[0008]
Further, when toner components (resin, wax, colorant, etc.) or paper dust (binder resin, talc, etc.) are attached, a filming phenomenon occurs on the surface of the photoreceptor, and resolution and image flow are more likely to occur. In addition, background contamination and density unevenness are caused, and further, the wear of the photosensitive layer is promoted.
[0009]
In the initial stage, even if corona products such as ozone and nitrogen oxides are attached, it is a transparent thin layer of dots or islands that does not penetrate immediately into the interior, but gradually becomes gradually internal by repeated use. Therefore, if appropriate measures are taken to eliminate corona products adhering to the surface at an early stage, damage can be minimized. However, the corona product is a very thin film that is strongly adsorbed on the surface of the photoconductor, and it cannot be scraped off at the edge of the cleaning blade, so that it is not easy to remove only the corona product. .
[0010]
As a countermeasure for eliminating the influence of the corona product and maintaining the image quality, a method of decomposing and invalidating the corona product generated by charging on the photosensitive member (for example, refer to Patent Document 1) or moisture. There is a method for reducing the influence of the image quality so that the image quality is not deteriorated. However, there is a limit that the effective period is short for the countermeasures with antioxidants, etc., and the means of applying antioxidants to the surface of the photoreceptor gradually deteriorates the function, and the effect stops at a relatively early stage. is there. Further, when it is applied excessively, the surface resistivity is lowered, and conversely, image deterioration is liable to occur.
[0011]
Alternatively, the method of containing a fluororesin in the protective layer (for example, see Patent Document 2) aims to suppress the adsorption of the corona product, but the corona product adheres indiscriminately on the photoreceptor. If it enters the recess, it is almost impossible to eliminate it with a normal cleaning device, and the problem that the adhesion gradually spreads and it is difficult to suppress the image flow still remains.
[0012]
A method of heating the photosensitive member (see, for example, Patent Document 3) is a method in which the image flow is affected by the influence of humidity and is caused by this. There is continuity of effect. However, in addition to the need to add a new heating source, there is a disadvantage (disadvantage) that a significant cost increase occurs due to the risk of burns and the need to take measures against heat.
[0013]
Further, the main cause of resolution reduction and image flow is a corona product. As described above, it is known that paper dust, a toner component, and the like other than the corona product adhere to the photoconductor. If the paper dust (talc or binder resin) or toner component adhering to the photoreceptor is not removed, it accumulates and eventually a filming film is formed. Therefore, it is not possible to maintain a sufficiently high quality image by removing only the corona product.
In general, there is a fact (phenomenon) that an image is less likely to flow in a photoconductor with much wear, and this is because the electrical resistance decreases (corresponding to low resistance) along with contaminants such as corona products, paper dust, and filming films. It is considered that resolution reduction and image flow do not occur because the photosensitized layer is scraped off. However, there is a problem that the durability of the photosensitive member is lowered due to much wear. For this reason, measures have been proposed regarding methods for scraping the photosensitive layer together with corona products, paper dust, filming, and the like.
[0014]
For example, the amount of wear on the surface of the photoconductor is controlled between the transfer process and the charging process (charge direct injection charging method using a magnetic brush) using a rubbing means such as a brush, a roller, or a web (100,000). A method is disclosed in which image blurring and flow are not generated even in a high humidity environment by adjusting to 0.1 to 1.0 μm per sheet. (For example, refer to Patent Document 4).
However, in the case of this method, since the photoconductor protective layer whose wearability is enhanced by adding conductive fine particles (filler) is formed on the surface of the photoconductor, the charge transport layer is formed on the outermost layer. The surface roughness is larger than that of a normal photoreceptor. Therefore, when the above-described nylon fiber brush (for example, a nylon fiber brush having a length of 5 mm) is used as a rubbing means for the photoreceptor having a protective layer with enhanced wear resistance, it adheres to the surface of the photoreceptor and is extremely It is not easy to polish a non-uniform corona product with a thin film. In addition, even if it is scraped, it becomes non-uniformly shaved, resulting in a surface state with poor uniformity. For this reason, there is a risk that the corona product cannot be sufficiently removed and image flow is caused. The roller-like and web-like rubbing means are more prone to wear because the scraping is reduced.
[0015]
Alternatively, as another method, an electrophotographic photosensitive member provided with a protective layer containing one or more organic silicate films can be appropriately selected at the time of charging, or a cleaning blade such as urethane rubber or silicon rubber can be used as a polishing means. Wear per 1000 revolutions by adjusting the pressure contact force or by using cerium oxide or strontium titanate with a particle size of 0.005 to 2 nm when a polishing apparatus (polishing roller, polishing pad, etc.) is provided. A method for adjusting the rate (5 nm or more and 30 nm or less) and cleaning the surface is disclosed (for example, see Patent Document 5).
However, in this method, when the applied voltage of the charging device is set to a high value, the corona product is increased and the photosensitive layer is chemically deteriorated. As a result, wear is promoted. There is a concern that durability will be lost.
[0016]
On the other hand, the means for controlling wear with a cleaning blade is effective to some extent for organic photoconductors that are subject to wear. However, when the surface of the photoconductor is hardened, the corona product that adheres will come into contact with the cleaning blade. It is difficult to remove even if the pressure is increased. On the other hand, the cleaning blade may be distorted or damaged (the edge of the part in contact with the photoconductor may be jagged), or the surface of the photoconductor may be scratched. Therefore, the durability of the photoreceptor is deteriorated. Further, when inorganic fine particles or the like are added to the developing means, there is a high possibility that the charging characteristics (Q / M) of the developer will be abnormal.
[0017]
In general, an organic photoconductor has a small hardness and is relatively brittle, so that it is easy to wear, and in the case of a photoconductor having a film thickness of about 30 μm, it has only a durability of about 50,000 to 100,000 sheets. Therefore, when removing a contaminant such as a corona product adhering to the surface of the photosensitive layer or a filming film, it is ideally desirable to remove only the corona product, but this is actually a difficult technique. For this reason, since it is inevitable that the photosensitive layer includes the photosensitive layer, how to keep the grinding amount to the minimum necessary is the key to maintaining the durability of the photosensitive member.
When the photosensitive layer is heavily worn, the electrophotographic characteristics are deteriorated (for example, the charging level is lowered, the sensitivity is lowered, and the background is soiled). That is, in order to maintain the characteristics of the photoreceptor for a long period of time, it is necessary to take measures for improving durability.
[0018]
As a measure for improving the surface hardness for improving the durability of such a photoreceptor, for example, 40% by weight of conductive fine particles such as zinc oxide, titanium oxide, tin oxide, antimony indium oxide, bismuth oxide, and tin-doped indium oxide are used. A method of forming the photosensitive layer dispersed as described above is disclosed (for example, see Patent Document 6).
Among the above materials, the durability of zinc oxide is low, but the other fillers can be expected to improve durability by being dispersed in the photosensitive layer. However, since the dispersion amount of the inorganic filler is as large as 40% by weight or more, the surface roughness tends to increase. For this reason, corona products, paper dust, and the like are likely to accumulate in the dents and are difficult to remove, so that the electrical resistance of the photoreceptor surface layer tends to decrease. In particular, when using a low melting point toner to which a large amount of wax is added, there is a problem that filming is likely to occur in combination with the problem due to the large amount of filler added. It is easy to cause image flow.
[0019]
Furthermore, in order to improve wear resistance, at least one selected from metal oxides such as titanium oxide, aluminum oxide, silicon oxide, metal sulfides, and metal nitrides having an average particle size of 0.02 to 0.5 μm. Is disclosed in which a photosensitive layer is dispersed in a polycarbonate resin having a molecular weight of 40,000 or more (0.5 to 30% of the total solid weight of the surface layer) (see, for example, Patent Document 7).
The above method is effective in improving the wear resistance and ensuring the charging ability when the inorganic compound particles having high electrical resistance excluding silica are dispersed in the photosensitive layer. By including a butadiene-based charge transporting material in the photosensitive layer, the charge mobility can be maintained in the same manner as the charge transporting layer, so that problems related to charging and sensitivity can be solved to some extent.
However, trapping sites are easily formed between the particles and the binder resin. Therefore, if the particles are simply contained, the residual potential is accumulated by repeated use, resulting in deterioration of light attenuation, and gradually reducing image density and image unevenness. Sometimes. In addition, when a filler having a large particle size is used, the sharpness of the line image is reduced. On the other hand, the surface roughness of the photosensitive member is increased, and the difference between the maximum value and the minimum value is larger than the particle size of the toner. Leading to poor cleaning. In addition, there is a problem that the edge of the cleaning blade is easily deformed and the toner and the corona product are liable to be poorly cleaned. Further, when a filler having a small particle diameter of 0.1 μm or less is used, the wear resistance cannot be improved. When silica is used, the abrasion resistance is increased, but due to the oxidizing action by ozone, the photosensitive layer is rapidly reduced in resistance, and the image flow is reduced even in a normal humidity environment of about 60% RH. Therefore, a heat source for heating the photoreceptor to about 45 to 55 ° C. is essential. That is, it is necessary to install a heating device such as a drum heater that avoids image flow.
[0020]
Furthermore, inorganic fine particles having an average particle diameter of 0.05 to 0.5 μm are formed on 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. A method of dispersing (hydrophobized silica) is disclosed (for example, see Patent Document 8).
In this method, the effect of repelling water droplets (a large contact angle) is manifested by hydrophobizing the inorganic fine particles, but it is not possible to prevent the corona product from adhering, and therefore, the image flow cannot be prevented. In addition, the inorganic fine particles that have been subjected to hydrophobic treatment on the surface of the photosensitive layer can be scraped off by rubbing with a blade or the like. In addition, since silica has a decrease in electrical resistance due to the action of ozone, image flow is hardly improved. Impossible.
[0021]
In order to establish a high-quality image, it is important to maintain a surface resistivity and volume resistivity in a suitable range so that a corona product film or a filming film is not formed on the photoreceptor. For this purpose, a method and means for accurately measuring the resistivity are required. The resistivity tends to vary in the measured value depending on the measurement means and measurement environment. Therefore, it is necessary to define an appropriate measurement means and measurement environment that have high repeatability and can obtain actual values.
[0022]
As a general method for measuring surface resistivity and volume resistivity, there are the following static measurement methods. For example, (1) a method of measuring a specific resistance by forming a comb electrode pattern (electrode spacing 200 to 300 μm) of a gold electrode on a photoconductor as a sample to be measured by a vacuum deposition method or the like (for example, Non-Patent Document 1) (2) Using a pre-made surface / volume resistivity measuring device, a circular electrode (main electrode) and a ring electrode are placed on the sample, a voltage is applied between the electrodes, and the flowing current Is converted into resistivity (for example, see Non-Patent Document 2).
[0023]
The method (1) lacks simplicity, but has good adhesion to the sample because the electrode (a gold electrode is generally used) is directly deposited on the sample. Therefore, since the current flows uniformly, there is little loss and the repeated measurement value is relatively stable. However, since the electrodes are formed by vacuum deposition, the surface state of the photoreceptor changes, and there is a problem that a value far from the actual value can be obtained. For this reason, it is impossible to accurately grasp the surface resistivity and volume resistivity generated by the corona product.
[0024]
In the case of the measurement method (2), the measurement can be easily performed. However, since the measurement is performed by placing the metal electrode on the sample, in the case of irregularities in the shape of the sample or in the case of a drum-shaped sample having a curvature, the electrode can be physically brought into close contact with the sample. Because it is not possible to measure correctly. In addition, when a commercially available measuring jig (with a wide electrode interval of about 10 mm) is used, the resistance value of the photosensitive member is large and the current value is extremely small even when shielding is sufficiently performed (10^-13-10^-17A) Therefore, there is a problem that current fluctuation becomes large and accurate measurement cannot be performed.
[0025]
Specifically, as a means for measuring the surface resistivity (σs) or the volume resistivity (ρv), other than using an existing measurement jig (for example, a sample box for ultra-high resistance measurement, TR42, R12704A: manufactured by Advantest) In addition, there is a method of using mercury, liquid gallium, gold foil, or the like as an electrode material.
However, these electrode materials are difficult to handle, mercury is a dangerous poison and dangerous, and it takes a considerable amount of time to prepare a drum-shaped photoconductor with curvature, and it is easy There is a problem that it cannot be measured, and gold is expensive and easily damaged during processing, so that adhesion to the organic photoreceptor is almost impossible. In the case of liquid gallium, it is necessary to heat it to about 25 ° C. to make gallium into a liquid. After the measurement, a part of the electrode material remains in a ball shape on the photoconductor, and the photoconductor is used again. In some cases, there is an inconvenience of image defects.
[0026]
In order to maintain a high-quality image for a long period of time, it is necessary that the electrostatic latent image does not collapse until the development is completed. For this purpose, the surface resistivity and volume resistivity of the photoconductor are suitable. It must be adjusted to a numerical range.
If the surface resistivity is low, the charge formed on the surface of the photoreceptor spreads in all directions and the charge pattern is destroyed. Further, when the volume resistivity is low, a charge spread occurs in the photosensitive layer in the process of forming the electrostatic latent image, and a correct charge pattern cannot be formed. This phenomenon becomes worse as the resistivity is lower, and the image appears as a phenomenon such as character thickening, sharpness deterioration, and contrast reduction.
[0027]
As the photoconductor is vulnerable to contamination by ultraviolet rays, ozone, oil, etc., metal chips, etc., as a protective layer (forming a 0.05 to 20 μm resin film made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, etc.) Surface resistivity is 10¹¹A method of providing a protective layer of Ω or more is disclosed. (For example, refer to Patent Document 9). In addition, although the surface resistivity of a protective layer is described, there is no description of a measuring method and volume resistivity.
By forming a protective layer, it is reasonable to avoid the influence of oil and chips, but the electrostatic latent image for image formation is formed on the surface of the photoconductor. In any case, the image quality is inevitably degraded when the is damaged. Since the measurement method is not specified, it is unclear which measurement means measured the surface resistivity. But 10¹¹Ω is clearly too low, and there is a possibility that the image quality will be sweet from the first image. In order to maintain stable image quality, at least 10¹³Ω or more, preferably 10¹⁴Ω is necessary, and it cannot be said that the range of surface resistivity is sufficient. Since almost all of the protective layer material is an insulator, accumulation of residual potential gradually increases and image quality deteriorates, which is not preferable as a protective layer material.
[0028]
On the other hand, in order to maintain the surface resistivity and the volume resistivity, cleaning means for cleaning the residual powder on the surface of the photoreceptor is important. Cleaning devices include a cleaning brush or a cleaning blade alone, or a combination of a cleaning brush and a cleaning blade, which are selectively used according to the developer, the photoreceptor, the copy amount, and the like.
The cleaning brush is basically installed for cleaning the residual powder after transfer on the photosensitive member, and generally does not have a function for removing film-like foreign matters such as filming. However, it is possible to wear it little by little by rubbing. As the material of the cleaning brush, fibers having good durability such as nylon fibers, polyester fibers, acrylic fibers, carbon fibers, chemical fibers, and inorganic fibers are used.
[0029]
For example, for a loop-shaped brush, the thickness of the raw yarn is 250d / 25F to 300d / 15F, the loop length is 2 to 4 mm, and the loop density is 50 to 100 (loop / cm²) Is disclosed (for example, see Patent Document 10). In the text, d represents denier and F represents a filament.
The cleaning performance of the loop brush is better than that of a straight brush, and toner tends to enter between the fibers and the cleaning performance tends to decrease due to clogging. Some improvement is possible by increasing the recycling power to the agent. Compared to straight hair brushes, the residual powder cleaning ability and filming film grinding ability are higher with the loop brush, but it is insufficient to improve the image flow.
[0030]
On the other hand, the blade cleaning method is an advantageous method for downsizing the image forming apparatus. In the blade cleaning method, if the blade is installed in the counter direction with respect to the rotation direction of the photoconductor, the biting into the photoconductor is increased, so that the toner cleaning performance is improved.
For cleaning blades, a rubber plate with a JIS-A hardness of about 50 to 90 degrees and a rebound resilience of about 30 to 60% is usually cut into strips with a width of 1.5 mm to 3 mm to form a plate made of aluminum or iron. Used by attaching to a support substrate.
There are two types of cleaning blades that are installed by installing one cleaning blade in the reverse rotation direction (counter) or forward rotation direction (leading) with respect to the rotation direction of the photosensitive member. The blade cleaning method is simpler than the brush method, and is an advantageous method for downsizing the image forming apparatus.
[0031]
However, in the blade cleaning method, if the blade is installed in the counter direction with respect to the rotation direction of the photoconductor, the biting into the photoconductor is increased and the toner cleaning performance can be improved, but the friction coefficient of the surface of the photoconductor is not small. Then, there is a problem that the cleaning blade bites into the photoconductor and the photoconductor is locked, not only the photoconductor is damaged but also the apparatus is broken. In addition, even when the photoconductor rotates, there is a problem that the photoconductor is abnormally scraped and damaged due to the large frictional resistance between the cleaning blade and the photoconductor, and the edge of the blade is pulled in the rotation direction of the photoconductor, A stick-slip phenomenon occurs in which a gap is generated between the photosensitive member and the photosensitive member. At this time, the toner comes out and causes a cleaning failure, which causes a filming film to be formed.
[0032]
As described above, in many image forming apparatuses, charging means, copy paper, and a developer are used to form an image. These always act on the photoconductor at the time of image formation, and the amount of action surely increases with the amount of copying, and the influence increases as the amount of copying increases. The charging means contains corona products such as ozone and nitrogen oxides (NOx), talc and binder resin from copy paper, and additives such as pigments, dyes, resins, and wax from the developer. By adhering, a low electric resistance layer is formed on the surface of the photoreceptor, thereby causing a reduction in image quality such as resolution reduction and image flow.
Measures are taken to avoid the influence of these formations and to achieve a high-quality image, an appropriate surface resistivity and / or volume resistivity of the photoreceptor for maintaining a high-quality image, etc. However, even if the prior art is effective at the beginning, the surface of the photoreceptor is lowered when used over a long period of time, and the surface resistivity and volume resistivity cannot be maintained. For this reason, development of a corresponding technology is desired.
[0033]
[Patent Document 1]
JP 2000-305291 A
[Patent Document 2]
JP 2000-206724 A
[Patent Document 3]
JP 2001-75461 A
[Patent Document 4]
JP-A-10-254291 ([0017] lines 4-7, [0015] lines 2-4)
[Patent Document 5]
JP 2001-249478 A ([0011] lines 6 to 7)
[Patent Document 6]
JP 08-234469 A ([0018], [0019])
[Patent Document 7]
Japanese Patent Application Laid-Open No. 08-146641 ([Claim 2], [Claim 3], [0009], [0013])
[Patent Document 8]
JP 08-248663 A ([Claim 1], [Claim 2])
[Patent Document 9]
Japanese Patent No. 2562144
[Patent Document 10]
Japanese Patent No. 2619424
[Non-Patent Document 1]
Nakatani, “Electrophotographic characteristics of phthalocyanine-PVK laminated photoreceptor”, Journal of Electrophotographic Society, Vol. 23, No. 1, p. 3-P. 4 (1984)
[Non-Patent Document 2]
“Electrical Engineering Handbook”, edited by the Institute of Electrical Engineers of Japan (P.275-P.276, Chapter 7, FIG. 76, FIG. 77)
[0034]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and its object is to provide corona products such as ozone and nitrogen oxides (NOx) generated by charging means while ensuring the durability of the electrophotographic photosensitive member. Alternatively, remove talc from the copy paper, binder resin or pigment from the developer, dye, resin, wax, and other substances adhering to the surface of the photoconductor, and accurately measure the surface resistivity and volume resistivity of the photoconductor. Based on this, image formation that can maintain a good state at all times and can create a high-quality image with good sharpness and high resolution without any image unevenness by maintaining a favorable friction coefficient over a long period of time. An apparatus and a process cartridge are provided.
[0035]
[Means for Solving the Problems]
As a result of diligent studies to solve the above-mentioned problems, a specific cleaning provided with a reinforced loop brush that sequentially and uniformly polishes a corona product having a high adhesive force that is generated on the surface of the photosensitive member during charging, every charging cycle. And a photosensitive member having durability adjusted so that surface abrasion does not proceed more than necessary even when polished by adding an inorganic filler to the photosensitive layer (scraped in an appropriate amount) Therefore, the surface of the photoconductor layer is always kept new and clean, the surface resistivity and volume resistivity are controlled to appropriate values, and a lubricant is applied on the photoconductor surface to reduce the friction coefficient. By adjusting and maintaining it within a suitable range, it is possible to suppress photoreceptor surface abnormalities due to the developer carrier, to prevent excessive abrasion due to polishing, to prevent deterioration of the cleaning blade, or to prevent deterioration of the cleaning property. Etc. is achieved, long term image unevenness without good sharpness and high resolution high-quality image formation has led to the present invention found to be achieved.
Hereinafter, the present invention will be specifically described.
[0036]
  According to the first aspect of the present invention, the surface of an electrophotographic photosensitive member provided with a photosensitive layer in which a filler is dispersed in an outermost charge transporting layer of a constituent layer provided on a conductive support is sequentially contacted or disposed in proximity. The electrostatic latent image is formed by an image exposure device, the electrostatic latent image is visualized as a toner image by a developing device, and the toner image is transferred to the transfer object under voltage application by a transfer device. A cleaning brush comprising a loop-like fiber to remove residual powder and adhering foreign matter on the surface of the electrophotographic photosensitive member.And a cleaning bladeAn image forming apparatus for cleaning by rubbing with a cleaning device comprising:
  Looped fiber surface of the cleaning brushWas formed by coating and curing a two-component resin liquid containing a water-based urethane resin as the main ingredient and an epoxy compound as a curing agent.The resin layer is coated and reinforced, and the surface resistivity (σs) of the photosensitive layer is 1 × 10.¹⁵~ 1x10¹⁷Ω and volume resistivity (ρv) is 1 × 10¹³~ 5x10¹⁵In addition to being adjusted to Ω · cm, the coefficient of friction of the photosensitive layer surface during image formation is adjusted to 0.2 to 0.4 (measured by the Euler belt method). is there.
[0037]
  The structure of claim 1, that is, the specific cleaning means provided with the reinforced loop brush, and durability so that the surface wear does not progress more than necessary even when polished by adding an inorganic filler and is scraped off in an appropriate amount. Due to the structure with the improved photoconductor, the surface of the photoconductor is uniformly and satisfactorily cleaned, the entire surface of the photoconductor is always kept clean, and the coefficient of friction is suitably adjusted, so that image unevenness is achieved. It is possible to form a high-quality image with good sharpness and high resolution over a long period of time.
According to a second aspect of the present invention, the loop-shaped fiber is an acrylic fiber containing conductive fine particles, a nylon fiber containing conductive fine particles, or a polyester fiber containing conductive fine particles. It is.
According to the configuration of claim 2, since the water-based urethane resin (main agent) and the epoxy compound (curing agent) are used as the coating material on the surface of the loop-shaped fiber, there is a concern about environmental pollution. The reinforced loop brush coated and cured with this two-component resin liquid is excellent in both durability and uniform polishing ability. For this reason, it is possible to remove residual powder such as toner adhering to the surface of the photoconductor by the loop brush subjected to this resin coating treatment, and to remove the contaminants that have started to adhere to the surface of the photoconductor thinly and uniformly. Always kept clean. As a result, there is little uneven wear of the photosensitive layer, it is possible to maintain a good surface resistivity and volume resistivity (suppress degradation to a minimum), and to form a high-quality image over a long period of time. Become.
[0038]
  Claim 3According to the present invention, the difference between the surface resistivity (σs) at the start of image formation of the photosensitive layer and the surface resistivity (σs) after image formation of 50,000 sheets is that the room temperature is 22 to 23 ° C. and the relative humidity is 65 to 67%. The measurement condition of the applied voltage 500500V is within one digit, and the surface resistivity (σs) is 1 × 10¹⁵~ 1x10¹⁷The image forming apparatus according to claim 1, wherein the image forming apparatus is Ω.
[0039]
  Claim 4According to the present invention, the difference between the volume resistivity (ρv) at the start of image formation of the photosensitive layer and the volume resistivity (ρv) after image formation of 50,000 sheets is that the room temperature is 22 to 23 ° C. and the relative humidity is 65 to 67%. The measurement condition of applied voltage 500V is within 2 digits, and the volume resistivity (ρv) is 1 × 10¹³~ 5x10¹⁵The image forming apparatus according to claim 1, wherein the image forming apparatus is Ω · cm.
[0040]
  Claims 3 and 4Since the surface resistivity or volume resistivity value at the start of image formation (initial stage) and after the image formation of a large number of sheets is controlled within a suitable range, and the fluctuation value is appropriately and strictly defined, A quality image can be created over a long period of time. In addition, the surface resistivity and volume resistivity of the photoconductor tend to gradually deteriorate with repeated imaging, but there is little change on photoconductors with high stability and stable characteristics, and is affected by ozone and nitrogen oxides. Since easy-to-follow photosensitive members tend to show a large change in the initial stage, it is possible to determine whether the image forming state is good or not by measuring the difference in resistivity between them.
[0046]
  Claim 5According to the present invention, the electrophotographic photosensitive member has an undercoat layer and a photosensitive layer sequentially formed on at least a drum-shaped conductive support, and the photosensitive layer has a two-layer structure of a charge generation layer and a charge transport layer. The image forming apparatus according to claim 1.
[0047]
  Claim 5By adopting this function separation type configuration, the design of the electrophotographic characteristics can be facilitated, and better charging characteristics and better sensitivity can be obtained. This makes it possible to form a high-quality image using an organic material for the charge transport layer.
[0048]
  Claim 6The present invention is characterized in that the charge transport layer further comprises a charge transport layer A in which inorganic filler is not dispersed and a charge transport layer B in which inorganic filler is dispersed.Claim 5The image forming apparatus described in the above.
[0049]
  Claim 7In the invention, the average particle size of the inorganic filler dispersed in the charge transport layer B is 0.3 to 0.7 μm, and the content of the inorganic filler isOf the charge transport layer B2 to 35% by weightClaim 6The image forming apparatus described in the above.
[0050]
  Claims 6 and 7According to the configuration, by providing the charge transport layer B in which the filler is dispersed, the charge transport layer A is adjusted so as to improve durability against the surface grinding of the photoreceptor and to have an appropriate amount of wear, and in which the filler is not dispersed. Is interposed between the charge generation layer and the charge transport layer B, abnormal charge transfer is prevented, and a stable high-quality image can be formed. From the viewpoint of stable high-quality image formation and long life of the photoreceptor, the content of the filler may be reduced when the corona charging method is used, and the filler may be increased when a contact or non-contact charging device is used. desirable.
[0051]
  Claim 8According to the invention, the friction coefficient is adjusted by applying one or two of zinc stearate or polytetrafluoroethylene (PTFE) to the surface of the photoreceptor. An image forming apparatus according to claim 1.
[0052]
  Claim 8According to the configuration, by applying fine zinc stearate and / or polytetrafluoroethylene (PTFE) (minimum necessary), the coefficient of friction of the photoreceptor surface that gradually increases in the image forming process is suitably reduced. Therefore, the friction coefficient during image formation can be adjusted to 0.2 to 0.4, so that the wear of the photosensitive layer can be suppressed, and image formation with good sharpness and high image quality is possible. It becomes.
[0053]
  Claim 9According to the present invention, the surface of the electrophotographic photosensitive member can be charged by a corona charging method, a contact charging method using a charging roller, or a non-contact charging method using a charging device disposed close to the electrophotographic photosensitive member. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed by any one of the methods.
[0054]
  Claim 9According to the present invention, by adjusting the amount of filler dispersed in the charge transport layer B in the present invention, it is possible to cope with the difference (large and small) in the chemical hazard level in charging, and to various charging means. In addition, the durability of the photoconductor can be ensured. In addition, a wide range of image forming apparatuses can be designed to provide high image quality.
[0055]
  Claim 10In the invention, the charging performed by any one of the above methods is performed by any one of a method of applying a DC voltage to the charging member or a method of applying a DC voltage superimposed with an AC voltage. DoClaim 9The image forming apparatus described in the above.
[0056]
  Claim 10According to this configuration, it is possible to select an optimum charging means according to the arrangement interval between the photosensitive member and the charging device (charging member or the like) and environmental conditions (humidity or the like). For example, when stability of image quality is required, a method of applying a DC voltage on which an AC voltage is superimposed is selected. Make it possible.
[0057]
  Claim 11The invention includes an electrophotographic photosensitive member having a photosensitive layer in which a filler is dispersed in an outermost charge transporting layer of a constituent layer provided on a conductive support, a charging device, a developing device,as well asCleaning brush made of looped fibersAnd a cleaning bladeA process cartridge detachably attached to an image forming apparatus main body integrally supporting at least one apparatus selected from cleaning apparatuses comprising:
  Looped fiber surface of the cleaning brushWas formed by coating and curing a two-component resin liquid containing a water-based urethane resin as the main ingredient and an epoxy compound as a curing agent.The resin layer is coated and reinforced, and the surface resistivity (σs) of the photosensitive layer is 1 × 10.¹⁵~ 1x10¹⁷Ω and volume resistivity (ρv) is 1 × 10¹³~ 5x10¹⁵In addition to being adjusted to Ω · cm, the coefficient of friction of the photosensitive layer surface during image formation is adjusted to 0.2 to 0.4 (measured by the Euler belt method).RupuIt is a process cartridge.
[0060]
  According to a twelfth aspect of the present invention, the loop fiber is an acrylic fiber containing conductive fine particles, a nylon fiber containing conductive fine particles, or a polyester fiber containing conductive fine particles. Is a process cartridge.
[0061]
  Claim 13According to the present invention, the surface of the electrophotographic photosensitive member can be charged by a corona charging method, a contact charging method using a charging roller, or a non-contact charging method using a charging device disposed close to the electrophotographic photosensitive member. It is performed by any one methodClaim 11Is a process cartridge.
[0062]
  Claims 11-13In addition to making the image device compact, it is possible to perform a simple and steady maintenance work, and further facilitate the replacement of parts, so that the total cost can be reduced. The image quality can be reduced and the image quality can be stabilized (replacement of the original high-quality image can be easily achieved by simply replacing the process cartridge).).
[0063]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention includes an image forming apparatus and a copying process, an electrophotographic photosensitive member, a cleaning member (cleaning brush and cleaning blade), a friction coefficient of the photosensitive member and its reduction, charging, surface resistivity, volume resistivity and a measuring method thereof. Embodiments of the present invention will be sequentially described with reference to the drawings.
<Image forming apparatus and copying process>
FIG. 1 shows a schematic configuration diagram of an image forming apparatus using an indirect electrophotographic method (basic configuration example). In the image forming apparatus of FIG. 1, a charging device 2, an image exposure device 3, a developing device 4, a transfer device 5, a separation device 6, and a cleaning device 7 are arranged in this order on the periphery of the photoreceptor 1. The transfer body 9 (copy paper, OHP sheet, etc.) is arranged (system using the Carlson process). The cleaning device 7 includes a cleaning brush 7-1 and a cleaning blade 7-2.
[0064]
In FIG. 1, a lubricant application device 200 (201: lubricant, 202: application brush) for reducing the surface friction coefficient of the photoreceptor 1 is disposed between the cleaning device 7 and the charging device 2. However, the lubricant application device 200 is not necessary when a method of adding a lubricant to the photosensitive layer 1 or a method of adding it to the developer is used.
Although not shown, the photosensitive member 1 may include a damping member for suppressing vibration noise (high-frequency sound) generated when an AC voltage is superimposed on the charging device 2. it can. In addition, at least from the charging process to the transfer process of the copying process, it is necessary to perform an image forming process in a state where at least all light is blocked.
The outline of the image forming apparatus will be described below in accordance with the copying process.
[0065]
The photoreceptor 1 used in the present invention has a configuration in which an undercoat layer and then a photosensitive layer are formed on a drum-like conductive support made of a material such as aluminum. The photosensitive layer is a function-separated type photoconductor further comprising a charge generation layer and a charge transport layer. The charging polarity when forming the electrostatic latent image is negative.
The charge transport layer is composed of a charge transport layer in which no filler is dispersed (referred to as charge transport layer A) and a charge transport layer in which an inorganic filler is dispersed (referred to as charge transport layer B). The reason why the filler is dispersed in the charge transport layer B is to prevent deterioration of electrophotographic characteristics (for example, charging characteristics, sensitivity, etc.) by suppressing the photoconductor from being worn more than necessary (electrical, mechanical) This is for the purpose of improving stability. In addition, when a cleaning blade is used, biting into the photosensitive layer is reduced to reduce edge distortion of the blade and to prevent toner cleaning failure. That is, it is a suitable means for maintaining a high-quality image over a long period of time.
[0066]
The charge transport layer has a two-layer structure because it has a high resistivity (10¹²-10¹⁴This is because the residual potential is increased by adding a filler of (Ω · cm), and the deterioration of image quality (image density, resolution, etc.) due to accumulation is suppressed as much as possible. However, it is desirable to change the amount of filler added depending on the charging means, and it is preferable to use a small amount in the corona charging method described later and to increase it in the contact charging method or the non-contact charging method. This is to cope with a difference in hazard given to the photoreceptor.
The filler dispersed in the charge transport layer B is preferably α-alumina, but may be metal oxide fine particles such as titanium oxide. However, silica (SiO₂It is not preferable to disperse fillers that tend to be reduced in resistance by ozone as in the case of resolution retention characteristics.
[0067]
By using the charging device 2 (adopting any one of a corona charging method, a contact charging method, and a non-contact charging method arranged several tens of micrometers away from the photosensitive member 1), the photosensitive member 1 is necessary for image formation. Charged to surface potential. A high voltage power supply circuit 2-2 is connected to the charging member 2-1 in FIG. The high-voltage power supply circuit 2-2 includes a circuit that generates either a DC voltage or a DC voltage on which an AC voltage is superimposed.
The roller-type charging member 2-1 shown in FIG. 1 is manufactured, for example, by covering a core of a SUS round bar having a diameter of 5 mm to 15 mm with an elastic member. The elastic member that charges the photosensitive member is added with a resistance control material such as conductive carbon, carbon fiber powder, or ionic conductive agent in epichlorohydrin rubber or urethane rubber, and if necessary, water repellent such as fluorine resin. To increase the volume resistance to 10^Five-10¹⁴Those adjusted to Ω · cm are used. The applied volume resistivity needs to be changed between the contact charging member and the non-contact charging member.
[0068]
In the case of a non-contact charging member, the volume resistivity of the outermost surface is 10^Five-10⁸In the case of a contact charging member, the volume resistivity of the outermost surface is 10 Ω · cm.¹²-10¹⁴It is set to Ω · cm. This is because there is a gap between the charging member and the photosensitive member, so that the charging start voltage (Vth) is shifted to the higher side and the charging efficiency is different. In order to perform uniform charging, the volume resistivity of the charging member is Need to be low. However, if the volume resistivity is lowered too much, it causes discharge breakdown.^FiveIt is desirable to make it Ω · cm or more.
The final outer diameter of the charging member 2-1 is set according to system conditions, but is usually about φ10 to φ20 (mm). In order to obtain good image forming properties, it is desirable that the contrast potential is at least 250 V or more, and the charging potential for this purpose is preferably -400 V to -800 V.
[0069]
On the surface of the photosensitive member 1 that has been charged, an original image read by a CCD (charge coupled device) or a digital signal transmitted from a personal computer or the like is provided with one or a plurality of LD (Laser Diode) elements or LEDs. (Laser Emitting Diode) An image exposure apparatus 3 composed of an array, a convex lens, a polygon mirror, a cylindrical lens or the like irradiates a single-wavelength optical image narrowed down to a dot diameter of about 60 to 20 μm, and responds to an input signal. An electrostatic latent image is formed.
For the LD element or LED array (wavelength: 780 to 400 nm), an element having an oscillation wavelength at or near the highest sensitivity region of the photoreceptor is selected. Since the spot diameter can be narrowed as the oscillation wavelength becomes shorter, an LD element having an oscillation wavelength on the short wavelength side of about 400 to 450 nm is advantageous when obtaining a high resolution such as 1200 dpi or 2400 dpi.
[0070]
The electrostatic latent image is visualized by the developing device 4. There are one-component and two-component developers. In the present invention, a two-component developer (carrier and toner) is used for development.
As a carrier used in a two-component developer, for example, polyfluorinated carbon to improve the charging property, charging stability, durability, etc. of magnetic powder (magnetic powder) such as iron, ferrite and nickel A material 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 resolution, the better the resolution. However, when the carrier particle size is too small, the carrier is attracted by the electrostatic force of the photoconductor and tends to adhere to the photoconductor. For this reason, toner image transfer failure (transfer omission) occurs, or the blade is pressed against the photoconductor by being transported to the cleaning unit. As a result, the photoconductor surface is damaged and the surface roughness is increased, resulting in deterioration of image quality. In addition, the corona product may enter the uneven portion and cause the image to flow, which may contribute to shortening the durability of the photoreceptor.
[0071]
On the other hand, as the toner, toner produced by a pulverization method and then spheroidized by scraping off the angular portions of the particles (average circularity of 0.9 to 0.94) or polymerization method (emulsion polymerization method, suspension weight) A spherical toner (average circularity is 0.95 to 1.0) having a weight average particle diameter of 4 to 8 μm, which is manufactured by a legal method, etc., and 2 to 10% by weight based on the carrier as a two-component developer. Used by mixing.
The particle size of the toner affects the resolution as well as the carrier. However, if it is too small, it will easily scatter, and will float in the atmosphere for a long time. It is desirable to remove the fine particles of about 1 to 3 μm.
[0072]
Next, the transfer device 5 (corona discharge type, roller, belt type, or the like) to which a positive voltage is applied is transferred to a transfer target 9 (copy paper, OHP sheet, etc.) conveyed from the cassette, and is separated by the separation device 6. The transfer target 9 is separated from the photosensitive member 1 and sent to the fixing device 8 to be a hard copy. Residual powder such as toner on the photoreceptor 1 is cleaned by the cleaning device 7.
The cleaning brush 7-1 of the cleaning device 7 according to the present invention is subjected to a resin coating process such that a contaminant such as a corona product attached to the photosensitive member 1 is polished into an extremely thin layer (reinforced loop brush). The surface of the brush (processed fiber) is always in contact with the photoreceptor 1. The photosensitive member 1 after being polished and removed of contaminants is subjected to a process in which most of the polished powder and residual powder are cleaned by the cleaning blade 7-2.
[0073]
After the cleaning, the lubricant is applied thinly on the surface of the photoreceptor 1 by the lubricant application device 200, and the increased friction coefficient is lowered to a predetermined level (0.2 to 0.4). The surface is sufficiently smoothed. By the operation of applying the cleaning brush 7-1 and the lubricant 201, the surface resistivity (σs) and the volume resistivity (ρv) of the photosensitive member 1 are maintained and controlled in a suitable range. Note that the method of applying the lubricant is not limited to the method of the lubricant applying device 200 described above, and is a method of applying via a cleaning brush or a charging roller, or when developing the lubricant dispersed in the developer. There is a method of giving, and any method may be used in the present invention.
The friction coefficient during image formation after applying the lubricant is preferably 0.2 to 0.4. At the start of image formation (at the start), it may be temporarily smaller than 0.2 or larger than 0.4.
[0074]
Various effects other than the above can be obtained by applying the lubricant in this manner. For example, improvement in cleaning performance (especially effective in the case of a spherical toner having a circularity close to 1.0), suppression of deformation (distortion) of the cleaning member, relaxation of toner adhesion to the photosensitive member, prevention of sharpness deterioration, reduction of the photosensitive layer For example, wear suppression. However, if the coefficient of friction is too low, faithful development with respect to the electrostatic latent image is hindered, and the grinding force of the corona product adhering to the photoreceptor is lacking, which causes a reduction in resolution and image flow.
[0075]
A series of copying cycles is completed by the above-described charging-cleaning- (applying lubricant), and the next copying process is repeated again.
Note that the copying process described with reference to FIG. 1 can also be applied to a full-color image forming apparatus. Although not shown, in a full-color electrophotographic copying machine or color laser beam printer, four systems (colors) of magenta (M), cyan (C), yellow (Y), and black (Bk) are used on one photosensitive member. ) Developing device, or a four-photosensitive member and magenta (M), cyan (C), yellow (Y), and black (Bk) as shown in the schematic diagram of FIG. There is a quadruple tandem type copying type image forming apparatus in which four systems (colors) of developing devices are arranged.
Further, by combining two or more of the photoconductor 1, the charging device 2, the developing device 4, the cleaning brush 7-1 and the cleaning blade 7-2 shown in FIG. The process cartridge can be detachably attached to the image forming apparatus main body as illustrated in the schematic diagrams of FIGS. 3 and 4.
Hereinafter, the configuration of the photosensitive member (photosensitive member, cleaning brush, charging (surface resistivity, volume resistivity, friction coefficient, etc.) in the image forming apparatus of the present invention will be described in detail for each item.
[0076]
<Photoconductor>
The basic structure of the photoreceptor is as shown in the schematic diagram of FIG. 5, and an undercoat layer 22 and a photosensitive layer 23 are formed in this order on a conductive support 21 (for example, made of drum-shaped aluminum). .
The photosensitive layer 23 of the photoreceptor used in the present invention further has a function-separated type photosensitive layer configuration of a charge generation layer 24 and a charge transport layer 25 as shown in the schematic schematic diagram of FIG. Further, the charge transport layer 25 in FIG. 6 is composed of a charge transport layer A (inorganic filler non-dispersed layer) 25a and a charge transport layer B (inorganic filler dispersed layer) 25b as shown in the schematic schematic diagram of FIG. Has been. At least an organic material is used for the charge transport layer 25 shown in FIG. The reason why the function separation type is used is that it is easy to design the electrophotographic characteristics of the photoreceptor, and good charging characteristics and sensitivity can be obtained.
The charge transport layer A25a and the charge transport layer B25b are composed of a low molecular charge transport material, a binder resin, and a layer in which an appropriate amount of an antioxidant or a dispersant is dispersed as required, or a polymer charge transport material, The film thickness and the layer configuration are set according to the quality required for the photoreceptor 1.
[0077]
The total film thickness of the charge transport layer is preferably set to 10 μm to 30 μm. If the film thickness is thinner than 10 μm, a sufficient light / dark potential difference necessary for image formation cannot be secured, and only a poor image can be obtained. In the case of being produced by the dip coating method, the photosensitive layer is not uniformly formed, so that the image quality is likely to be non-uniform due to film thickness unevenness. On the other hand, when the film thickness is greater than 30 μm, the dot pattern spreads in the layer, causing a reduction in sharpness and a reduction in resolution, making it difficult to achieve formation of a high-quality image. Usually, the film thickness is set in consideration of durability, optical characteristics, and electrical characteristics.
[0078]
<Conductive support>
Examples of members that can be used as the conductive support 21 (FIGS. 5, 6, and 7) of the photosensitive member 1 include not only metals such as stainless steel, copper, and brass that satisfy various electrical, mechanical, and chemical characteristics, but also compressed paper, A conductive layer is formed by vapor deposition or sputtering of gold, aluminum, platinum, chromium, or the like on a resin or glass, and further, a conductive layer in which fine particles such as carbon or tin are dispersed is applied. Aluminum, especially aluminum alloys such as Alloy No. 3003 (JIS H 4000), considering that it is thin and easy to cut, light and advantageous for recycling, and that it is easy to form a blocking layer and is easily available. Is preferred.
Techniques for processing the surface of aluminum include cutting, honing, and blasting. After cutting the drum-shaped aluminum tube to the required length by these processing techniques and cutting it to the target outer diameter, the surface roughness is set to 10-point average roughness Rz by super finishing and mirror finishing._JISAnd is washed sufficiently until the cleaning solution is completely removed, and used as a conductive support for an electrophotographic photosensitive member. 10-point average roughness Rz of support_JISIn general, when the thickness is 10 μm or less, an abnormal image due to the surface roughness of the support can be suppressed to a level that does not cause a problem in practice.
[0079]
The shape of the conductive support 21 is desirably a drum shape, and the outer diameter is generally about 30 mm to 100 mm. For a photoreceptor having an outer diameter of φ30 to φ100 (mm), the thickness of aluminum is about 0.6 mm to 3 mm. In the case of an organic photoreceptor, the processing temperature during heat drying is 120 to 160 ° C. and the processing time is about 10 to 60 minutes. Is desirable. In addition to being advantageous in terms of cost by reducing the wall thickness, the temperature is easily applied even when the photosensitive layer is heated and dried.
There is a merit that it is easy to suppress a decrease in (effect).
However, if the wall is too thin, it may be deformed when the flange is mounted or when the damping member is built in, so that the shape and dimensions of these members must be sufficiently controlled. In other words, when the outer diameter is deformed, a slight deviation from those members occurs when charging and the blade come into contact with each other, thereby affecting non-uniform charging and cleaning properties. The variation of the outer diameter of the conductive support is evaluated by items such as roundness, straightness, and single touch, but it is desirable that these numerical values are all small.
[0080]
<Underlayer>
An undercoat layer 22 is provided between the conductive support 21 and the photosensitive layer 23 as necessary. The form of the undercoat layer 22 can be changed depending on the wavelength range of the light source used. For example, when an LD element or LED array having an oscillation wavelength in a long wavelength region of 650 to 780 nm is used as a light source, moire due to reflection of light from aluminum is generated, so the undercoat layer 22 is indispensable. However, when an LD element having an oscillation wavelength of about 400 to 420 nm is used, the absorption near the surface layer increases, and as described in the specific examples of the present invention (FIGS. 5, 6, and 7). The undercoat layer 22 is not necessarily required, and may be a thin film of 1 μm or less such as alumina or a semiconductor film that prevents hole injection. However, it is desirable to be opaque.
[0081]
The reason for forming the undercoat layer 22 is to prevent charge injection from the conductive support 21 side, stabilize charging characteristics, improve adhesion, prevent moire, improve coatability of the upper layer, reduce residual potential, etc. Objective. Therefore, a method may be employed in which a semiconductor film that prevents injection of holes (holes) and allows electrons (electrons) to pass therethrough is formed, and an intermediate layer or undercoat layer 22 is further formed thereon. In general, the undercoat layer 22 is high enough not to cause potential decay within a unit time.ElectricalA thin film mainly composed of a resin having resistance is formed. Since the photosensitive layer 23 is applied and formed on the undercoat layer 22 using a solution containing a solvent thereon, it is desirable to use a resin having a high solvent resistance (dissolution resistance) with respect to a general organic solvent. .
Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resins, alkyd-melamine resins, and epoxy resins. Examples thereof include curable resins that form a three-dimensional network structure. Further, for example, metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide, or fine powders such as metal sulfides and metal nitrides may be dispersed and contained. These undercoat layers can be formed using an appropriate solvent and coating method.
[0082]
Further, as the undercoat layer 22 (FIGS. 5, 6 and 7) of the present invention, a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like is used, for example, a metal oxide layer by a sol-gel method or the like. A method of forming is also useful.
In addition, as the undercoat layer 22 of the present invention, Al₂O_ThreeOr an organic material such as polyparaxylylene (Parylene: trade name of Union Carbide), or SnO₂TiO₂, CeO₂10 provided with an inorganic material such as a vacuum thin film manufacturing method.^Ten-10¹³A thin film having an electrical resistance (volume low efficiency) on the order of Ω · cm can be used satisfactorily. The thickness of the undercoat layer is suitably from 0.1 to 20 μm, preferably from 0.5 to 10 μm.
[0083]
<Charge generation layer>
Next, the charge generation layer 24 (FIGS. 6 and 7) will be described. The charge generation material used for the charge generation layer 24 includes an inorganic material and an organic material.
Inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, amorphous silicon, and the like. In the case of amorphous silicon, those obtained by terminating dangling bonds with hydrogen atoms and halogen atoms, or those doped with boron atoms, phosphorus atoms, etc. are preferably used.
On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzo An azo pigment having a thiophene skeleton, an azo pigment having a fluorenone skeleton, an azo pigment having an oxadiazol skeleton, an azo pigment having a bisstilbene skeleton, an azo pigment having a distyryl oxadiazol skeleton, and a distyrylcarbazole skeleton Azo pigments, perylene pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Njigoido pigments, bisbenzimidazo - such as Le based pigments. These charge generation materials can be used alone or as a mixture of two or more.
[0084]
Examples of the binder resin used for the charge generation layer 24 are polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl. Formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide and the like can be mentioned. These binder resins can be used alone or as a mixture of two or more. Further, a low molecular charge transport material (electron transport material or hole transport material) may be added as necessary.
[0085]
Examples of the electron transporting material include chloroanil, bromoanil, 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-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.
[0086]
Examples of the hole transporting material include the following electron donating materials and are used favorably.
For example, oxazol derivatives, oxadiazol derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene , Styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazol derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials can be used alone or as a mixture of two or more.
[0087]
The charge generation layer 24 is mainly composed of a charge generation material, a solvent, and a binder resin, and may include additives such as a sensitizer, a dispersant, a surfactant, and silicone oil. Good.
Examples of the method for forming the charge generation layer 24 include a vacuum thin film manufacturing method and a casting method from a solution dispersion system. As the vacuum thin film preparation method, vacuum deposition method, glow discharge decomposition method, ion plating method, sputtering method, reactive sputtering method, CVD method, etc. are used, and it is formed well by the inorganic materials and organic materials mentioned above. it can. Further, in order to provide a charge generation layer by a casting method, a ball mill using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone together with a binder resin if necessary with the inorganic or organic charge generation material described above, It can be formed by dispersing with an attritor, a sand mill or the like, and applying the solution after diluting the dispersion appropriately. The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.
[0088]
The film thickness of the charge generation layer 24 provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm. Usually, it is applied to a thickness of 0.1 to 0.3 μm. If the film thickness is too thin, poor sensitivity occurs, but if it is too thick, light attenuation deterioration due to space charge and a residual potential increase occur, leading to image quality deterioration such as image density reduction and resolution reduction.
[0089]
<Charge transport layer>
Next, the charge transport layer 25 (FIGS. 6 and 7) will be described. The charge transport layer 25 is formed to ensure a surface potential necessary for image formation. The charge transport layer 25 can of course be used alone as an organic photosensitive layer, but it is preferable to subject the surface of the organic photosensitive member to abrasion resistance in order to maintain the durability and image quality of the photosensitive member. In the present invention, a method of incorporating (adding) a high hardness inorganic filler in the depth direction from the outermost surface of the charge transport layer 25, that is, in the thickness direction is adopted. The filler in the charge transport layer B25b is preferably either uniformly dispersed in the charge transport layer or a layer structure in which the concentration gradient is increased toward the surface layer, but it is uniform from the viewpoint of maintaining durability. Dispersion is preferred. As shown in FIG. 7, the charge transport layer A25a is formed, and the charge transport layer B25b to which an inorganic filler is added is stacked to a thickness of about 2 to 10 μm (usually about 3 to 10 μm). A layer is formed.
[0090]
As described above, the charge transport layer 25 is formed on the charge generation layer 24 in the order of the charge transport layer A and the charge transport layer B. This is because the charge transport layer B25b is in direct contact with the charge generation layer 24. This is because an abnormal movement of charge occurs between the charge transport layer B25b and the charge generation layer 24, and a spotted pattern appears in the image. Accordingly, the charge transport layer A25a in which the filler is not dispersed in the region in contact with the charge generation layer 24 is desirable, and the film thickness is preferably at least 2 μm. As the coating means, a dip coating method, a spray coating method, or the like can be used.
[0091]
The charge transport layer A25a and the charge transport layer B25b must be configured such that no interface (barrier) exists between them. If an interface (barrier) exists, the movement of holes is restricted, thereby deteriorating the light attenuation characteristics and increasing the residual potential, thereby deteriorating electrophotographic characteristics such as a decrease in contrast potential and afterimage. By preventing the formation of an interface (barrier), the hole-electron pairs generated in the vicinity of the interface between the charge generation layer 24 and the charge transport layer 25 are immediately separated and the movement of holes is inhibited by the interface (barrier). Without reaching the surface layer, a normal electrostatic latent image can be formed by canceling the surface charge (-).
[0092]
However, since the filler is dispersed, some loss due to the amount of filler dispersed, particle size, etc., for example, dimming, light diffusion, variation in charge distribution, etc. occurs, but when added in a suitable range This is a negligible range, and there is no practical problem.
In order to prevent the formation of an interface between the charge transport layer A25a and the charge transport layer B25b, after the charge transport layer A25a is applied and touch-drying time (several minutes), oxidation or some kind of precipitation occurs. The charge transport layer B25b may be applied within the range (preferably within 1 to 2 days). After coating, the photoreceptor can be prepared by heating and drying the entire photoreceptor at a temperature of 130 to 160 ° C. for about 10 to 60 minutes.
[0093]
The total film thickness of the charge transport layer 25 (charge transport layer A + charge transport layer B) is set to 10 to 30 μm. The smaller the variation of the entire photosensitive layer (difference between the maximum film thickness and the minimum film thickness), the smaller the coating thickness. Since the influence of unevenness is likely to occur, it is desirable to set finely, and it is preferable to set within a range of ± 1 μm for 10 μm and within a range of ± 2 μm for 30 μm.
As the film thickness of the charge transport layer 25 decreases, the capacitance increases and the electric field strength increases, but it is difficult to ensure a sufficient charge level. If the charge possessed by the toner is small, it is possible to increase the developing ability even with a thin film photoconductor, but voltage development is unavoidable with the small particle size toner that is currently used in the market. For this reason, a certain surface potential is required.
[0094]
Note that if the thickness of the charge transport layer is reduced, distortion at the time of movement of holes is reduced, so that a high-quality image can be reproduced. On the other hand, the thicker the thickness, the smaller the electrostatic capacity, so that a high charge level is secured, which is advantageous for obtaining a high-contrast image, but when the charge moves, it is distorted when light is input and the resolution is reduced. descend. When the thickness of the charge transport layer is about 10 μm, the charge level is charged only at around −450V. However, if the residual potential is suppressed to about -50V to -100V and the developing bias potential is set to -350V, the contrast potential can be secured to about 250V to 300V, so that it is possible to perform image formation with no practical problem. .
[0095]
The film thickness of the charge transport layer B25b is desirably changed depending on the durability and image quality characteristics required for the photoreceptor. From the viewpoint of durability, it is desirable that the charge transport layer B has a certain thickness. However, as the thickness increases, the optical characteristics and electrical characteristics deteriorate, and this causes a decrease in resolution and an increase in residual potential. Image quality is degraded. Therefore, it is necessary to suppress the film thickness within a range in which the required image quality can be maintained.
Further, the ratio of the thickness of the charge transport layer B in the total charge transport layer is preferably 6.7 to 80% (however, the thickness of the entire charge transport layer is preferably 10 to 30 μm).
The maximum film thickness when the amount of filler added is in the range of 2 to 35% by weight is about 8 to 10 μm, and the minimum film thickness is set according to the required durability, but usually it is set to about 3 to 6 μm. Good image quality can be maintained in terms of durability.
[0096]
The amount of filler added to the charge transport layer B depends on the charging method and required durability (depending on wear, chemical and physical deterioration), or image quality (charge level, sensitivity, residual potential, etc.) Affected by). A desirable addition amount is 2 to 35% by weight, preferably 3 to 30% by weight, based on the total weight of the charge transport layer B. However, it is desirable to change the filler to be included depending on the charging means, and in the corona charging method with relatively little chemical hazard, the filler should be small, and in the contact or non-contact charging method with large chemical hazard, a larger amount of filler may be contained. desirable.
[0097]
For example, when the corona charging method is used, the amount of filler added is desirably 2 to 20% by weight. When the amount is less than 2% by weight, the photosensitive layer is heavily worn, and an abnormal image is likely to occur due to the sticking of a carrier. On the other hand, when the amount is more than 20% by weight, it is difficult to physically wear, so that an abnormality such as filming is likely to occur. Usually, about 3 to 10% by weight can provide sufficient practicality.
In the case of the contact charging method or the non-contact charging method, it is desired to be 15 to 35% by weight, preferably 15 to 30% by weight. In this case, the chemical deterioration mainly imparted to the charge transport layer by the charging means is larger than that in the corona charging method, so it is better to increase the amount of filler added. However, if the amount is too large, the polishing ability of the cleaning brush will be exceeded, so it is best to set it to 35% by weight, preferably 30% by weight or less. When the addition amount is large, the polishing ability of the cleaning brush becomes insufficient, and a filming phenomenon occurs, and abnormalities such as an image flow phenomenon and image density unevenness are likely to occur.
[0098]
The amount of filler added as described above is not applicable when a normal cleaning brush is used, and exhibits a great effect when using a loop brush (reinforced loop brush) with enhanced polishing ability as described in the present invention. .
If the amount of filler added is increased, the polishing ability of the cleaning brush can be increased, or other means of promoting polishing can be considered, but abnormal images due to the polished filler, uneven wear, cleaning blade damage, etc. Since it tends to occur and the durability of not only the photoconductor but also the cleaning blade is reduced, it is not a preferable means.
[0099]
Filler materials include organic filler materials and inorganic filler materials.
Examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, amorphous carbon powder, and the like, and inorganic filler materials include copper, tin, aluminum, and indium. Metal powders such as silica, tin oxide, zinc oxide, titanium oxide, alumina, indium oxide, antimony oxide, bismuth oxide, calcium oxide, tin oxide doped with antimony, indium oxide doped with tin, etc. Examples thereof include inorganic materials such as oxides, metal fluorides such as tin fluoride, calcium fluoride, and aluminum fluoride, potassium titanate, and boron nitride. Among these fillers, it is advantageous to use an inorganic material in terms of hardness to improve wear resistance.
[0100]
In particular, titanium oxide or alumina can be desirably used in the present invention, but alumina (especially α type) is more preferable. Alumina has the second highest hardness after diamond, relatively good translucency, good dispersibility in resin, strong oxide film, and a specific resistance of 10¹³-10¹⁵It is around Ω · cm. Furthermore, since it has water repellency, environmental stability is excellent. Accordingly, when used as a filler for a photoreceptor, stable photoreceptor characteristics are exhibited even when used for a long time.
The filler material can be dispersed together with a charge transport substance, a binder resin, a solvent, and the like using an appropriate disperser.
[0101]
When the surface roughness of the photosensitive layer increases due to the addition of the filler, the edge of the character becomes jagged, and the cleaning property of the residue such as toner and paper dust is deteriorated, which may cause a problem of defective cleaning. Contaminants such as corona products remain in areas where the blades do not come into contact, causing an image flow, and toner filming, and further, the edge of the cleaning blade is missing, and the photosensitive layer is easily damaged.
For this reason, it is necessary to select a filler having a particle size with good dispersibility so that the target wear resistance can be achieved and good image quality can be obtained. The primary particle size of the filler dispersed in the photosensitive layer is determined from the light transmittance, wear resistance, surface roughness, etc. of the charge transport layer.
[0102]
If the average particle size of the filler to be dispersed is in the range of 0.2 to 1.0 μm, there is no problem with short-term imaging, but in the long term, a narrower range will yield a high-quality image. The average particle size is desirably 0.3 to 0.7 μm, preferably 0.3 to 0.5 μm. The reason for defining the size of the filler to be dispersed is to balance the surface roughness and durability. However, in order to improve durability, it is necessary to reduce the friction coefficient (or free surface energy) of the surface of the photoreceptor with a lubricant or the like. The surface roughness of the photoreceptor surface is 10-point average roughness Rz_JISIt is desirable that the thickness is 0.3 to 1.0 μm and the maximum height Rz is 0.4 to 1.5 μm.
[0103]
The filler added to the charge transport layer B25b is spherical and has high hardness, optical transparency, and a volume resistivity of 10^Ten-10¹⁵About Ω · cm, preferably 10¹²-10¹⁴It is preferably Ω · cm, water repellency, and its function is maintained. If the volume resistivity is low, charge retention becomes difficult and the resolution is reduced. If the volume resistivity is too high, the residual potential is increased, the image potential is increased, and the contrast potential is decreased. A high image density cannot be obtained, and the image has a lot of unevenness.
[0104]
The filler (metal oxide such as titanium oxide and alumina) in the present invention is an insulator, and when dispersed in the binder resin, traps are easily formed at the interface between the particles and the binder resin. For this reason, when the photoreceptor is used repeatedly, there is a concern that the residual potential accumulates, leading to an increase in image portion potential, resulting in a decrease in image density and resolution. In this case, the dispersibility is improved. It is possible to add an additive that makes the photosensitive layer uniform and inhibits trap formation or reduces trap density.
[0105]
In addition, the charge applied to the surface of the photoconductor in image formation is performed by a charging device placed in contact with or close to the photoconductor. As described above, the generation of corona such as ozone and nitrogen oxides generated during this charging is performed. Objects adhere to the surface of the photoreceptor or enter the photosensitive layer to reduce the electrical resistance, resulting in a reduction in image quality such as a reduction in resolution. In order to avoid or eliminate this, a small amount of an antioxidant or a plasticizer can be added to the charge transport layer 25. However, these additives are not always necessary, and may be left unadded when the charge transport layer 25 is thin, when the amount of filler added is small, or depending on the image system.
In the charge transport layer B25b to which a filler is added, a coating liquid in which an appropriate amount of filler is dispersed in a binder resin is applied to a target film thickness using a coating method such as a spray method or a dipping method.
[0106]
Examples of the low molecular charge transport material constituting the charge transport layer 25 (6, 7) include oxazole derivatives, oxadiazole derivatives, imidazoles derivatives, triphenylamine derivatives, α-phenylstilbene derivatives, toniphenylmethane derivatives, anthracene derivatives, and the like. Can be used.
On the other hand, as the charge transport layer 25 polymer charge transport material, the following known polymer charge transport materials can be used.
(1) As a polymer having a carbazole ring in the main chain and / or side chain, for example, poly-N-vinylcarbazole and other known compounds (for example, JP-A-50-82056, JP-A-Shosho). No. 54-9632, JP 54-11737, JP 4183719, and the like.
(2) As a polymer having a hydrazone structure in the main chain and / or side chain, there are known compounds (for example, compounds described in JP-A-57-78402 and JP-A-3-50555).
(3) As polysilylene polymers, there are known compounds (for example, compounds described in JP-A-63-285552, JP-A-5-19497, JP-A-5-70595, etc.).
(4) As a polymer having a tertiary amine structure in the main chain and / or side chain, N, N-bis (4-methylphenyl) -4-aminopolystyrene or a known compound (for example, JP-A-1-13061). No. 1, JP-A-1-19049, JP-A-1-1728, JP-A-1-105260, JP-A-2-167335, JP-A-5-66598, JP-A-5-40350. And the like.
(5) Examples of other polymers include formaldehyde condensation polymers of nitropyrene and known compounds (for example, compounds described in JP-A Nos. 51-73888 and 56-150749).
[0107]
The polymer having an electron donating group used in the present invention is not limited to the above-mentioned polymer, but a copolymer of a known monomer, a block polymer, a graft polymer, a star polymer, or a known electron donation. It is also possible to use a crosslinked polymer having a functional group (for example, JP-A-3-109406).
Further, as the polymer charge transport material in the present invention, a polycarbonate having a triarylamine structure in the main chain and / or side chain is effectively used.
[0108]
On the other hand, examples of the polymer 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 copolymers thereof), cellulose acetate resin, ethyl cellulose resin, polyvinyl Thermoplastics such as butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluorine resin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, etc. Include thermosetting resin, but is not limited thereto. These polymer compounds can be used singly or as a mixture of two or more kinds and copolymerized with a charge transport material.
[0109]
Examples of the dispersion solvent that can be used in preparing the charge transport layer coating solution include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone, ethers such as dioxane, tetrahydrofuran, and ethyl cellosolve, and aromatics such as toluene and xylene. Examples thereof include halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate, but it is desirable to avoid the use of halogen solvents in consideration of the influence on the environment.
[0110]
In the charge transport layer 25 (FIGS. 6 and 7) according to the present invention, it is effective to add, for example, a leveling agent as a means for smoothening the surface of the photosensitive layer by eliminating the roughness. As the leveling agent, a known material can be used, but a silicone oil-based leveling agent that can impart a high level of smoothness in a small amount and has a small influence on electrostatic characteristics is particularly preferable.
Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen polysiloxane, cyclic dimethylpolysiloxane, alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, amino-modified 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.
[0111]
It is also possible to reduce the unevenness depending on the coating conditions. For example, in dip coating, when the surface of the coating film is still wet after it has been lifted, unevenness is reduced by covering it with a hood so that the surface is not disturbed by the flow of wind. Is done. Also, if the solvent near the coating surface suddenly volatilizes, only the surface hardens and the inside of the coating film becomes fluid, and the coating film inside may sag and form irregularities. By forming a vapor layer of solvent around the photoconductor in a wet state and volatilizing the solvent gently, leveling proceeds, and the unevenness is reduced and smoothed.
[0112]
In addition, in spray coating, when forming a coating film by air spray, by controlling the air pressure and air flow to an appropriate amount, surface irregularities can be suppressed while the coating film is in a fluid state. It is necessary to suppress. Here, if the air pressure and air flow rate are too large, the surface of the coating will be disturbed by the air flow, and conversely if it is too small, the coating liquid droplets may not be uniform or atomization may be insufficient. As a result, the uniformity of the coating film is reduced. In addition, after the charge transport layer B25b is formed, the solvent is volatilized while rotating, but if the rotation speed at this time is too high, the coating film that still contains the solvent and has fluidity is subjected to centrifugal force and the unevenness is emphasized. Is done. On the other hand, if the rotational speed is too low, the influence of dripping due to gravity is superior to the leveling due to rotation, which causes unevenness. For this reason, it is necessary to set the rotation speed of the photoreceptor in a wet state to an appropriate value.
[0113]
Further, in spray coating, it is important that the liquid feeding of a pump that supplies the coating liquid is constant. That is, if the supply of the liquid is not constant and has pulsation, it directly affects the discharge amount of the liquid, resulting in unevenness in the adhesion amount. Therefore, as a pump for supplying liquid to the spray, it is preferable to use a multiple plunger pump with reduced pulsation, a syringe-type ultra-precise discharge device, or the like. The devices in these methods may be used singly, but by combining a plurality of devices, a charge transport layer with more effective leveling and reduced unevenness is formed. Further, when leveling is insufficient, it is possible to wear the convex portions of the charge transport layer and wear them as a method for reducing the irregularities. For example, a method of detecting the convex portion with a film thickness meter and polishing the portion to eliminate the convex portion can be considered.
[0114]
In the present invention, each component layer (for example, a charge generation layer, a charge transport layer, an undercoat layer, a protective layer, an intermediate layer, etc.) is used for improving the environmental resistance and for the purpose of preventing a decrease in sensitivity and an increase in residual potential. ), An antioxidant, a plasticizer, a lubricant, an ultraviolet absorber, and a low molecular charge transport material can be added. The typical material example of these compounds is described below.
[0115]
Examples of the antioxidant that can be added to each layer include, but are not limited to, the following.
(A) Phenolic compounds
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-tert-butylphenol), 4,4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol) ), 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-) t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di-) -Butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] cricol ester, tocopherols Such.
(B) Laphenylenediamines
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-t-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) Organophosphorus compounds
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.
[0116]
Next, examples of the plasticizer that can be added to each layer include, but are not limited to, the following.
(A) Phosphate ester plasticizer
Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichlorethyl 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, diisononyl 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, etc.
(C) Aromatic carboxylic ester plasticizer
Trioctyl trimellitic acid, tri-n-octyl trimellitic acid, octyl oxybenzoate, and the like.
(D) Aliphatic dibasic acid ester plasticizer
Dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, n-octyl-n-decyl adipate, diisodecyl adipate, dicapryl adipate, diazeline 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, glycerol monooleate, methyl acetylricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, tributyrin and the like.
(F) Oxyester 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 epoxy stearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxy stearate, dioctyl epoxy hexahydrophthalate, didecyl epoxy hexahydrophthalate and the like.
(H) Dihydric alcohol ester plasticizer
Diethylene glycol dibenzoate, triethylene glycol di-2-ethylbutyrate, etc.
(I) Chlorine-containing plasticizer
Chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxychlorinated fatty acid methyl, etc.
(J) Polyester plasticizer
Polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester, etc.
(K) Sulfonic acid derivative
P-toluenesulfonamide, O-toluenesulfonamide, P-toluenesulfoneethylamide, O-toluenesulfoneethylamide, toluenesulfone-N-ethylamide, P-toluenesulfone-N-cyclohexylamide and the like.
(L) Citric acid derivative
Triethyl citrate, triethyl citrate citrate, tributyl citrate, tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, acetyl citrate-n-octyldecyl and the like.
(M) Other
Terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietate and the like.
[0117]
In the present invention, a lubricant can be added to each layer. Examples thereof include those shown below, but are not limited thereto.
(A) Hydrocarbon compounds
Liquid paraffin, paraffin wax, microwax, low-polymerized polyethylene, etc.
(B) Fatty acid compounds
Lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, etc.
(C) Fatty acid amide compounds
Stearylamide, palmitylamide, oleinamide, methylenebisstearamide, ethylenebisstearamide, etc.
(D) Ester compound
Lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, fatty acid polyglycol esters, and the like.
(E) Alcohol compounds
Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethylene glycol, polyglycerol, etc.
(F) Metal soap
Lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate, etc.
(G) Natural wax
Carnauba wax, candelilla wax, beeswax, whale wax, ibotarou, montan wax, etc.
(H) Other
Silicone compounds, fluorine compounds, etc.
[0118]
Examples of the ultraviolet absorber that can be added to each layer include, but are not limited to, the following.
(A) Benzophenone series
2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ′, 4-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and the like.
(B) Salsylate type
Phenyl salsylate, 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′-hydroxy3′-tertiarybutyl 5) '-Methylphenyl) 5-chlorobenzotriazole and the like.
(D) Cyanoacrylate type
Ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate, and the like.
(E) Quencher (metal complex)
Nickel (2,2′thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyldithiocarbamate, nickel dibutyldithiocarbamate, cobalt dicyclohexyldithiophosphate 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.
[0119]
<Cleaning member (cleaning brush and cleaning blade)>
As shown in the schematic configuration diagram of FIG. 1 and the schematic schematic diagram of FIG. 8, the cleaning device 7 according to the present invention includes a cleaning brush 7-1 and a cleaning blade 7-2. There are mainly two types of brush shapes used for the cleaning brush 7-1: straight hair (cut pile brush) and loop (loop brush). In the present invention, the cleaning brush is made of a loop-like fiber. A brush (loop brush) is used.
The purpose of using the loop brush is that the loop-shaped fiber as shown in the schematic diagram of FIG. 9 is more in surface contact (contact) with the photoconductor than the normal straight cut pile brush. This is because they can be slid evenly on the fiber surface, and the photoconductor is hardly rubbed and has good cleaning properties and durability.
[0120]
In general, the surface of a photoreceptor with low hardness is rubbed against a cleaning blade, a cleaning brush, or a developer, resulting in greater or lesser scratches on the surface, but when a straight-haired cut pile brush is used. , The cut surface of the fiber tip that rotates at a rotation speed of about 100 to 250 rpm hits the photoconductor, so that scratches (fine scratches) appear compared to the loop brush, and abnormal images (white spots, black spots) become over time. It easily reduces the life of the photoreceptor. On the other hand, in the case of a loop brush, since the surface of the photoreceptor is rubbed with the fiber's belly or back portion, deep scratches are less likely to occur, and the scratches are shallow and uniform. It is difficult to achieve non-uniform density, and the occurrence rate of abnormal images is small.
[0121]
The amount of loop brush biting into the photoreceptor is preferably 1 to 2 mm. If it is installed unevenly, it causes uneven wear on the brush as well as the photosensitive layer. The rotation direction may be either the counter direction or the reading direction, but is preferably the reading direction (the direction of the arrow in FIG. 8, the direction opposite to the rotation of the photosensitive member). This is because the photosensitive layer can be easily scraped when the counter direction is set, and uneven wear of the photosensitive layer is easily caused. However, when scraping is small, the counter direction is also an effective means, and when the amount of filler dispersed in the charge transport layer (charge transport layer B25b) is large, the toner discharge force, the brush rotation speed, and the brush bite If the amount etc. is optimized, the rotation in the counter direction also increases the effectiveness.
[0122]
Further, the present invention is characterized in that a flicker bar that is generally provided in order to remove toner adhering to the brush is not provided. This is because when a flicker bar is attached, in the case of a loop brush, the fiber is easily damaged, the toner is likely to be unevenly removed, the toner is easily pushed into the back of the fiber, and the toner is not easily burned. This is because, for example, it becomes easy to occur, causing uneven wear on the photoreceptor.
[0123]
The material of the loop brush used for cleaning includes nylon fiber, acrylic fiber, polyester fiber, carbon fiber, etc. (textile manufacturers are Unitika, Toray, Kanebo, Kuraray, Mitsubishi Rayon, etc.).
The fiber diameter of the fiber used for the cleaning brush (loop brush) is 10 to 20 (denier), the density is 24 to 48 filaments / 450 loops, and the loop length (fiber length) is 2 to 5 mm. The denier is a value calculated by the following formula (1) (see :).
Denier = Yarn weight (g) x 9000 / Yarn length (m) (1)
Loop brushes that can be suitably used in the present invention include acrylic fibers such as SA-7 (Toray Industries, Inc.), nylon beltlons ([nylon fiber, Kanebo, Type 931, 961, etc.), polyester beltrons [polyester fibers] Fiber, Kanebo, type B31, etc.].
[0124]
As a method for producing a cleaning brush (loop brush) having loop-shaped fibers as shown in FIG. 9, a loop brush cut into strips (strings) is formed directly on a core bar or a coating layer having a low electrical resistance. A method is generally provided in which a layer is spirally wound from above without any gap and fixed so as not to be displaced. The fixing means may be an adhesive or may be fixed using an adhesive member such as a double-sided adhesive tape. By adopting such a manufacturing method, it is possible to maintain stable cleaning properties without deviation and without unevenness.
The production method is simple and can be produced in a short time. If a double-sided pressure-sensitive adhesive tape is used, the cored bar can be reused. However, in most cases, since the cleaning brush is used for a long period of time, fixing with an adhesive is desirable.
[0125]
Usually, the cleaning brush is rubbed with the photoconductor, and frictional charging occurs, so that toner tends to adhere and the cleaning property gradually decreases. Therefore, it is desirable that the electric resistance of the brush is controlled. Conductive treatment is usually performed at the fiber production stage, and a method of filling the fiber with a conductive substance, for example, fibers mixed with metal fine particles such as conductive carbon, tin, gold, titanium when the fiber resin is in a molten state. It becomes. Alternatively, the conductive fibers and the fibers may be mixed after weaving. However, if the resistance is too low, discharge from the photoconductor occurs and causes an abnormal image.^Five-10^TenA medium to high resistance of about Ω · cm is desirable.
SA-7 and Beltron are both electrically conductive and have self-discharge capability even when charged, so that they can be detached from the brush after copying even if toner is electrostatically adsorbed. . In the case of Veltron, conductive fine particles such as carbon are incorporated inside, and in SA-7, carbon is dispersed. The tendency for static elimination to be higher in Beltron than in SA-7 is seen. However, it has been confirmed that the discharge characteristics of a single unit require several seconds to several tens of seconds for electric charges to be discharged.
When the cleaning brush is used, the brush and a core material (metal, conductive resin, or the like) are electrically coupled, and the core material is grounded (grounded) or a voltage is applied to the housing. Normally, grounding is sufficient.
[0126]
Since the amount of filler added to the photosensitive layer (charge transport layer B) increases and the surface roughness tends to increase, the polishing ability of the photosensitive layer by the cleaning device decreases. Accordingly, filming is more likely to occur and image quality is deteriorated. Therefore, in order to reliably prevent the filming film from being formed on the photosensitive layer, it is desirable to polish the film before forming a continuous film on the photosensitive layer.
In the case of a material that is difficult to wear, such as filming, it cannot be completely removed by a straight brush (cut pile brush), and even a simple loop-shaped brush does not have sufficient removal capability. Therefore, as in the present invention, a brush made of loop-like fibers (loop brush) is coated with a resin to form a reinforced loop brush, which is formed on the surface of the photoreceptor without being worn more than necessary by improving the polishing ability. It is necessary to surely polish (scrap) the formation (buds) of the filming every cycle.
[0127]
As a means for polishing the photosensitive layer, the method using an abrasive or the like causes much wear and is not practical. The polishing means can be reliably performed by the cleaning brush rather than the cleaning blade. In order to add polishing means to the cleaning brush, it is necessary to perform a treatment for increasing the polishing strength on the outer wall of the fiber as in the present invention.
In order to polish the filming layer uniformly and extremely thinly by a simple method, it is preferable to coat the loop fiber with a resin that increases the polishing effect and with a material that does not promote polishing more than necessary. . As the covering material, it is necessary to use a material that does not easily wear and does not transfer to the photoconductor and does not chemically affect the photoconductor.
For example, a metal such as tungsten, tin, or aluminum, an amorphous carbon film, silicon, or the like is coated by a method such as coating with an acrylic, epoxy, or urethane resin, a CVD method, a vacuum deposition method, or a sputtering method. There are methods. In the present invention, a water-based urethane adhesive (for example, Merci 585 manufactured by Toyo Polymer Co., Ltd.) having a viscosity of 5 to 500 (mPa · S) is used as the main material, and an epoxy compound (for example, AD-C-65 manufactured by the same company) is cured. A two-component type as an agent can be preferably used. The coating method may be performed by laying the loop brush sideways, immersing the fiber in a resin solution by 2 to 3 mm so that the solution reaches the inside of the fiber, and heat drying. In the case of the above resin, there is no concern about pollution because a liquid such as ion exchange water or distilled water is used as the solvent.
[0128]
The average wear amount for polishing the photosensitive layer with the cleaning brush is desirably 0.05 to 0.5 μm per 10,000 sheets in the case of a φ30 mm photosensitive member (value converted to A4 size paper).
For example, an image is formed by combining a φ100 mm photoreceptor formed with a charge transport layer B (5 μm) added with 5% by weight of an α-alumina filler having an average particle size of 0.3 μm, a corona charging device, and a reinforced loop brush. When Imagio Neo600 (made by Ricoh) is used, the wear amount is 0.06 to 0.075 μm / 10,000 when the friction coefficient (friction coefficient during image formation) is maintained between 0.33 and 0.38. Even after 200,000 sheets have passed, there is no image flow in an environment of 30 ° C./90% RH. The friction coefficient (initial value) at the start of image formation (at the start) was 0.41.
Incidentally, the surface resistivity at the end of image formation of 200,000 sheets in this case is 1.2 × 10¹⁶Ω, volume resistivity is 6.6 × 10¹⁴The resistivity was very good at Ω · cm.
[0129]
Furthermore, adjustment of the amount of wear of the photosensitive layer is achieved with the aid of a lubricant. That is, the wear amount of the photosensitive layer can be adjusted by applying a lubricant and controlling the coefficient of friction of the surface of the photoreceptor to 0.2 to 0.4 over the entire surface.
If the wear amount is less than 0.05 μm, uneven polishing tends to occur in some cases, and a streak image flow may occur locally. On the other hand, when the amount of wear is greater than 0.5 μm, the image quality problem is small, but since the wear is large, durability cannot be maintained and large-scale copying is performed. Forced to replace early. However, when filming occurs and the friction coefficient increases or the friction coefficient decreases abnormally, wear is suppressed. It should be noted that less wear is desirable if the image quality can be maintained.
[0130]
<Coefficient of friction and reduction of photoreceptor>
Maintaining the coefficient of friction on the surface of the photosensitive layer at a low level improves the abrasion resistance of the photosensitive layer, improves the transferability of the visualized toner image, improves the cleaning performance by the cleaning blade, prevents damage to the cleaning member edge, etc. It is valid. That is, there is an effect of reducing the rubbing pressure of the cleaning blade against the photosensitive member and reducing the adhesion force of the toner to the photosensitive member. (Provides a relaxing action). Therefore, the surface of the photoreceptor is less likely to be scratched, and after the toner or carrier is sufficiently removed (damped) by the cleaning blade, the surface of the photoreceptor is rubbed only by the cleaning blade, and the lubricant is further applied by applying a lubricant. Abrasion can be reduced.
[0131]
As means for reducing the friction coefficient, a method of scraping the lubricant with a cleaning brush and applying the lubricant to the photosensitive member (see FIG. 1), a method of adding the lubricant to the developer, or a lubricating liquid is used for the photosensitive member. For example, an external addition method of applying a lubricant to the surface of the photoreceptor, such as a method of applying to the surface, or an internal addition method of adding a lubricant to the surface of the photoreceptor. The internal addition method is a method of reducing the friction coefficient of the surface by adding a lubricant to the surface layer of the photoreceptor by several% to several tens%. When the addition amount is small (for example, about 5% of polytetrafluoroethylene is added), the corona product may act on the surface of the photoreceptor to inhibit the action of the lubricant. .4) It is difficult to maintain the friction coefficient, but when added in a large amount (for example, 50% or more), the friction coefficient can be lowered to about 0.2 to 0.3, and the predetermined friction is obtained. The coefficient can be maintained stably. This method is effective in that no incidental facilities are required.
[0132]
In the case of the external addition method, since it is possible to always supply the lubricant from the outside, this is an effective means for maintaining high durability of the photoreceptor. In the external addition method, a material such as polytetrafluoroethylene, polyvinylidene fluoride, and zinc stearate showing lubricity can be applied directly or indirectly to the surface of the photoreceptor.
As a direct method, a powdered lubricant is applied in a bag having a coarse texture (such as gauze), or a sheet-like lubricant is applied while being rubbed against the surface of the photoreceptor. and so on. Further, as an indirect method, a method in which a lubricant is dispersed in an amount of 0.01 to 0.5% by weight in the toner, or a lubricant that is brought into contact with a cleaning brush and scraped with the brush is used. For example, there is a method of applying powder to the photoreceptor.
[0133]
When polytetrafluoroethylene is applied to the photoreceptor as a lubricant, the friction coefficient can be easily lowered from about 0.6 to about 0.2. However, generally, if the coefficient of friction is too low, the corona product adhering to the photoreceptor cannot be scraped off, causing image flow or toner adhering to the corona product film. Toner filming is likely to occur, and image flow may occur. However, in the case of the present invention, since the corona product is removed by the cleaning brush, even if it is lowered to 0.3 or less, the image does not flow. However, if the friction coefficient is too low, the ability of the corona product to be removed by the brush will be extremely reduced, the development may be affected, and characters may become thin due to toner sliding, so the friction coefficient is 0.2. Desirably, it is desirable that the upper limit is not higher than 0.4. That is, the range is preferably 0.2 to 0.4.
[0134]
In addition, the friction coefficient described in the text is calculated using the Euler belt method (formula calculated based on Euler's formula). This method is carried out as follows, but is easy to measure, can be performed regardless of the diameter of the photoreceptor, and is excellent in repeated stability. In addition, the measurement environment in this invention is 20-24 degreeC / 61-65% RH.
Measurement method: A photoconductor for measurement is fixed to a pedestal, and a high-quality paper of 85 μm in thickness (made by Ricoh, type 6200 paper, vertical mesh) cut to a width of 30 mm and a length of 290 mm is prepared as a belt. Is placed on the photoconductor, a 100gr weight is attached to one end of the belt, a digital force gauge for weight measurement is attached to the other end, the digital force gauge is pulled slowly, and the belt starts moving. The time weight is read, and the (static) friction coefficient (μs) is calculated from the following equation (2).
μs = 2 / π × ln (F / W) (2)
In the above formula, μs: coefficient of static friction, F: reading load, W: weight of weight, and π: circumference ratio.
[0135]
Next, the cleaning blade 7-2 (FIGS. 1 and 8) used in combination with the cleaning brush 7-1 (enhanced loop brush) provided in the cleaning device of the present invention has a plate thickness of 1.5 to 1.5. 3 mm, polyurethane rubber having a JIS hardness of 75 to 90 degrees and a rebound resilience of about 30 to 60% is cut into strips (or sheets) and fixed to an aluminum or iron support substrate using an adhesive. A member such as a knife edge that does not contact the surface of the photosensitive member and does not contact the surface and has a substantially line contact can be used.
[0136]
The cleaning blade 7-2 is a means for completely and cleanly removing residual powder (toner, paper powder, corona product, filler, dust, etc.) that could not be removed by the cleaning brush 7-1. It needs to be cleaned regardless of the surface condition on the layer.
The cleaning blade 7-2 is installed in the counter direction with respect to the photosensitive member, applies contact pressure (press) so that the amount of biting is about 0.5 to 2 mm, and is as shown in the schematic schematic diagram of FIG. In addition, a strip-shaped blade is used, and this is fixed so as to have an acute angle with respect to the tangent to the photoreceptor 1. In this case, the contact angle is 15 to 40 degrees, and the free length from the tip of the support to the tip of the cleaning blade 7-2 is set to 3 to 8 mm. If the frictional resistance between the photosensitive member 1 and the cleaning blade 7-2 is large, the edge portion that contacts the photosensitive member 1 is dragged in the rotational direction of the photosensitive member 1 and locally twisted, and the edge is in a line contact state. Surface contact is likely to occur. For this reason, a slight gap is generated between the photosensitive member 1 and the cleaning blade 7-2, and the toner is sandwiched between the cleaning blade 7-2 and the photosensitive member 1 to cause toner omission. In order to prevent this, it is necessary to reduce the coefficient of friction of the photosensitive layer surface by suitable means.
[0137]
The shape of the tip of the cleaning blade 7-2 (blade) is excellent in the cleaning property by reducing the coefficient of friction of the photosensitive member to around 0.3 even in the case of the above-described strip-shaped sheet cut at 90 degrees. Can be maintained. On the other hand, when the friction coefficient is larger than 0.5, in order to maintain a good cleaning property, it is an effective means to make the blade tip part a knife edge.
In the case of a knife edge shape, it is desirable that the rubber hardness used for the blade is high, and a rubber blade of about 80 to 90 degrees is used. When the hardness is high, the photosensitive layer is easily worn, but the durability of the photosensitive layer is not deteriorated by increasing the hardness of the photosensitive surface with which the blade contacts with a filler. The angle of the knife edge tip may be in the range of 30 to 90 degrees, preferably 30 to 60 degrees. The free length is 2 to 8 mm, preferably 3 to 6 mm.
[0138]
As means for fixing these cleaning blades 7-2, metal such as aluminum, phosphor bronze, iron and brass, resin such as polycarbonate, vinyl chloride, delrin and polyethylene terephthalate, and ceramic members such as alumina are processed into a plate or casing. A cleaning blade can be attached, but because of its workability, toughness, and the absence of temperature deformation and rust, it has a thickness of 1 to 3 mm, such as a chrome-plated iron plate or aluminum plate. Is preferred. As a means for processing the support substrate and attaching the blade, a method of fitting and fixing to a casing-like support substrate, bending a metal plate, and adhesive (double-sided tape, one-component or two-component adhesive, There is a method of attaching and fixing using a hot melt adhesive or the like.
As a method for processing a knife-edge blade, the tip portion is cut obliquely or is produced by a technique such as mold forming.
[0139]
In the case of polyurethane rubber, the main raw materials are polyol, isocyanate and curing agent. For example, a molding machine in which a dehydrated polyol and an isocyanate are mixed and a curing agent is added to a prepolymer obtained by reacting at a temperature of 70 to 140 ° C. for about 100 minutes and heated to 140 to 160 ° C. in advance. And curing for 50-60 minutes. Then, the rubber | gum for blades is obtained by taking out from a metal mold | die and cutting to a required magnitude | size with a cutter. In the mold manufacturing method using this mold, the target blade can be manufactured relatively easily if only the mold is manufactured.
The polyurethane rubber used in the cleaning blade is cut at the tip with a cutting machine at an angle, or after cutting into a knife edge with a metal mold, and then the burrs at the edge that contacts the photoconductor are accurately cut in a straight line. The thickness is adjusted to 0.5 mm or less.
[0140]
The contact pressure (linear pressure) when the edge of the cleaning blade 7-2 (blade) contacts the photosensitive member 1 is preferably set to 15 to 40 g / cm. In consideration of scratches and the like, it is preferably set to 15 to 25 g / cm. When the linear pressure is lower than 15 g / cm, when a blade having a high hardness (JIS-A hardness) is used as the blade, the blade and the photosensitive member 1 may be exposed even if there is a small amount of foreign matter depending on the surface roughness of the photoreceptor 1. There is a possibility that a gap is generated between the bodies 1 and cleaning failure occurs. On the other hand, when the linear pressure is higher than 25 g / cm, since the blade has a higher hardness than that of a conventionally used product, the photosensitive member 1 may be scratched by the blade. Even if the linear pressure is set to 40 g / cm or higher, the possibility of scratching is increased. Usually, only a shallow rubbing scratch is introduced, and a hard foreign object is pierced and the blade edge is scratched. It does not mean that it cannot be used immediately except for.
[0141]
When the cleaning blade 7-2 according to the present invention is used, it is possible to satisfactorily clean even a spherical toner having an average circularity of 0.95 or more, particularly 0.98 or more.
Further, if the cleaning blade has been used for a long time, the edge portion in contact with the photosensitive member is chipped, and cleaning failure is likely to occur. This is particularly noticeable in the case of a photoreceptor to which a filler is added. In order to prevent chipping, it is important to reduce the friction coefficient on the surface of the photosensitive member as in the present invention and reduce the burden on the blade as much as possible.
[0142]
<Charging>
Examples of charging means for forming an image on the photosensitive member include a corona charging method, a contact charging method, and a non-contact charging method in which charging is performed while maintaining a gap (Gap) of 30 μm to 100 μm between the photosensitive member and the charging member. However, any charging method can be used in the present invention.
As described above, the charging member 2-1 of FIG. 1 is connected to the high voltage power supply circuit 2-2 that generates either a DC voltage or a DC voltage on which an AC voltage is superimposed.
The corona charging device is charged by applying a DC voltage of −4000 to −6000 V. In the contact charging and non-contact charging methods, charging is performed according to Paschen's law. If the voltage applied to the charging member is equal to or lower than the charging start voltage (Vth), no discharge is performed and charging is not performed. The charging start voltage (Vth) is lowest during contact charging, and the start voltage (Vth) increases as the interval (Gap) increases. That is, the charging efficiency is lowered. The conditions of the applied voltage for setting the charging voltage to -400 to -800 V are -1000 V to -2000 V in the case of DC voltage driving, and the DC voltage is -450 to in the case of DC voltage driving in which AC voltage is superimposed. At -900 V, the AC voltage (sine wave or triangular wave) is set to 700 V to 2000 V / 800 to 2500 Hz. Applying a DC voltage superimposed with an AC voltage can cause uneven charging due to unstable discharge characteristics when there is a gap between the photoconductor and the charging member or when the humidity is high, resulting in image unevenness. This is effective for maintaining a uniform image for a long time.
[0143]
Since the corona charging method generates a large amount of ozone, it is necessary to sufficiently perform ozone treatment with activated carbon, activated carbon fiber, etc., but the chemical hazard given to the photoreceptor is less than the contact charging method depending on the design means. Is possible. Therefore, the durability of the photoconductor can be greatly extended by performing appropriate processing. Further, since it has a follow-up property to charging as compared with the contact charging method, it is useful for a large-sized image forming apparatus having a high peripheral speed. As the discharge electrode, a tungsten wire having a thickness of 40 to 80 μm, a sawtooth electrode made of stainless steel having a thickness of 0.1 to 0.2 mm, and the like can be used.
[0144]
Both the contact and non-contact charging methods are charging methods that involve discharge. However, because the applied voltage is low, the generation of ozone is as low as around 0.1 ppm. There is no odor that leaks out. However, since contact charging is a discharge in the vicinity of the photoconductor, the chemical hazard received by the photoconductor may be greater than that of the corona charging method. For this reason, the wear of the photosensitive layer is also affected, and the wear tends to be larger than that of the corona charging method. Therefore, it is essential to take measures against the abrasion resistance of the photoreceptor, and in the present invention, it is possible to cope with the increase in the amount of filler as described above.
[0145]
The charging member can be roughly classified into three shapes: a roller, a brush, and a blade. The roller charging method is preferable in consideration of durability, uniform charging, image quality, workability, and the like.
The difference between the contact charging method and the non-contact charging method is that the contact charging method has no gap with the photoconductor (0 μm), and the non-contact charging method has not only a difference of 30 to 100 μm, but also the hardness and charging of usable members. There are also differences in the resistance values of the members. The interval (Gap) of 30 to 100 μm is preferably 50 to 80 μm. If the gap is 30 μm or more, even if the roundness or straightness of the photosensitive member and the charging member is 20 μm, which is the limit that causes charging unevenness, the photosensitive member and the charging member do not contact the photosensitive member. The contamination caused by can be avoided to some extent. In the range of 50 to 80 μm, since the average carrier of the developer is 30 to 60 μm, there is a thickness of the photosensitive layer even when one carrier adheres to the photosensitive member and is pressed against the photosensitive member by the charging roller. Therefore, it means the minimum gap that does not cause discharge breakdown. Further, since the charging uniformity is easily lost as the gap increases, the applied voltage and frequency must be increased. Therefore, it is necessary to suppress the upper limit of the gap, but the gap of 80 μm is the minimum gap that can achieve charging uniformity by slightly increasing the electric field condition applied to the charging member.
[0146]
In the contact charging method, a member having a JIS-A hardness of about 30 to 80 degrees is mainly used, but a non-contact charging member has a JIS-A hardness of about 90 degrees or more. Can be used. That is, in the case of a non-contact charging member, the surface facing the photoreceptor is made of a rubber-like or dense sponge elastic resistor having a thickness of 0.5 to 5 mm, and the other region is made of metal. Is also possible.
[0147]
The electric resistance value (resistance value) is different between the contact charging method and the non-contact charging method, and the resistance value of the member used in the contact charging method is set higher. This is because there is no distance to the photoconductor (0 μm), so that even if the resistance value is high, charging can be performed sufficiently. It is possible to reduce the area.
Specifically, in the case of a contact charging member, the volume resistivity is 10 on the surface facing the photoreceptor.¹²-10¹⁴A high-resistance layer having a thickness of about 1 to 3 mm and having flexibility to earn a nip between the core metal and the high-resistance layer 10^Five-10⁹It consists of a medium resistance layer of Ω · cm. The hardness of the medium resistance layer is 30 to 75 degrees in terms of JIS-A hardness, and the high resistance layer is also about 60 to 80 degrees.
[0148]
Furthermore, the surface roughness of the charging member 2-1 is rougher than the surface roughness of the contact charging member, and the 10-point average roughness Rz._JISIs about 25 to 80 μm, it is advantageous for improving uniform charging and charging efficiency. It is preferable to use an elastic member having a JIS-A hardness of about 30 to 90 degrees. In the case of the contact charging method, it is desirable to take a large nip (1 to 5 mm) in order to increase charging stability and charging efficiency. The contact charging member uses an elastic member having low hardness, but the non-contact charging member has an advantage that the charging efficiency is deteriorated because the nip cannot be obtained, but is not limited to the hardness of the charging member used.
[0149]
On the other hand, in the case of a non-contact charging member, the resistance layer facing the photosensitive member has 10^Five-10⁸Use an elastic member with medium resistance of Ω · cm. Except for the cored bar, members of all layers or medium resistance layers may be used, or members having different hardness and resistance values such as contact charging members may be used. The thickness of the medium resistance layer may be about 1 to 3 mm, and the others may be metal. A charging member having a JIS hardness of 30 to 90 degrees can be used, but a member of 60 to 85 degrees is usually used.
[0150]
For the elastic member of the resistance layer, rubber products such as urethane rubber, epichlorohydrin rubber, chloroprene rubber, silicone rubber, fluorine rubber, etc., conductive carbon, activated carbon fiber, metal powder such as tin, gold, titanium, ion conductive agent, etc. Although an appropriate amount of a resistance control agent is used, epichlorohydrin rubber is used in the present invention.
This is because epichlorohydrin rubber can obtain a medium resistance without adding carbon or the like, and since no carbon is added, the electrical resistance is hardly affected by the environment. However, in order to further reduce the resistance, it may be necessary to add conductive carbon or the like. In the case of the contact charging member, in order to make it difficult for the toner or the like to adhere, a fluororesin and silica are added to the epichlorohydrin rubber as a protective layer on the outermost layer, the releasability is improved, and the electric resistance is 100 VDC applied. 10¹²-10¹⁴Set to be in Ω · cm.
The surface roughness of the charging member is finer for the contact charging member and rougher for the non-contact charging member. This is to ensure good chargeability, and the 10-point average roughness Rz_JISHowever, the contact charging member is set to 10 to 100 μm, and the non-contact charging member is set to 20 to 200 μm.
[0151]
In the case of the contact charging method, since there is no distance from the photoconductor (interval of 0 μm), the charging efficiency is high even when the resistance of the charging member is increased, and the applied voltage can be set lower than in the non-contact charging method. For this reason, the generation amount of ozone and NOx is reduced, and in terms of image quality, an abnormal image is less likely to reach other parts even if there is a pinhole. Therefore, high quality image formation can be performed.
[0152]
On the other hand, in the case of the non-contact charging method, since there is a gap of several tens of μm, the applied voltage becomes high. Therefore, ozone generation is about three times that of the contact charging method, but there is almost no amount of leakage to the outside and there is no environmental impact. Less. Therefore, although it is advantageous in terms of discharge breakdown and contamination of the charging member, the same precautions as in the rapid charging method are necessary when a hard foreign material such as metal or the electric field strength is high. Image quality is equivalent to the contact charging method.
[0153]
<Surface resistivity and volume resistivity and measurement method thereof>
The surface resistivity (σs) and volume resistivity (ρv) of the photoreceptor can be measured by using an electrode as shown in the schematic schematic diagram of FIG. For example, an indium foil (thickness of about 0.1 mm) is punched out with a jig such as a punch, a circular electrode (main electrode) with a diameter of φ5.2 mm, and a ring electrode (a guard electrode or a pair with an outer diameter of 11.5 mm and an inner diameter of 7 mm). Electrode) is prepared, and measured on a photoreceptor (drum-shaped or cut sample) with a complete adhesion in the form shown in the schematic diagram of FIG.
[0154]
The surface resistivity and volume resistivity are measured using a measuring jig such as the schematic circuit diagram shown in FIG. The circuit includes a DC power supply and an ammeter (10^-14A or less can be measured, for example, a Kessley electrometer 617) is connected, the applied voltage is set to 100 to 500 V, the current after 1 minute of voltage application is read, and the following formulas (3) and (4) respectively. Then, the surface resistivity and volume resistivity are calculated (Reference: The Institute of Electrical Engineers of Japan: Electrical Engineering Handbook, P.275-P.276). The measurement environment is a temperature of 22 to 23 ° C. and a relative humidity of 65 to 67% RH.
Surface resistivity σs = P / g × Rs = 22.1293 Rs (Ω) (3)
Volume resistivity ρv = (A / d) × Rv = (0.212 / d) × Rv = (Ω · cm) (4)
In the above formula, A: main electrode area, d: photosensitive layer thickness, P: circumferential length determined from the distance from the center of the main electrode to the center of the main electrode and the ring electrode, g: main electrode and ring Electrode spacing, Rs, Rv: applied voltage / dark current (1 minute value).
[0155]
The indium foil used in the present invention is a soft metal, has malleability, and can be easily adhered even in the case of a resin photoconductor such as an organic photoconductor. There is an advantage that there is nothing. For this reason, even a photoconductor sample having a curvature like a drum can be freely measured regardless of the normal humidity or high humidity environment. That is, indium foil is a very suitable and highly effective material for measuring surface resistivity and volume resistivity, and when measured using this, there is no need to measure by cutting the photoreceptor sample. In the required environment (for example, with the sample after image formation as it is), resistivity (surface resistivity and volume resistivity) can be measured, and it has the great merit of high reproducibility. ing.
[0156]
The means for attaching the electrodes to the photoconductor is to use a spatula with a round shape by placing the electrode material on the photoconductor while observing with a magnifying glass so that the dimensions between the electrodes are uniform, and then placing a medicine wrapping paper on the electrode material. Lightly press with a jig like this, and finally press the edge part of the electrode lightly so that it fits in the surface of the object to be measured to improve the adhesion. The measurement circuit uses a measurement jig as shown in FIG. 12 and FIG. 13 in which a phosphor bronze plate having a thickness of 0.1 mm cut to a width of 1 to 2 mm is wired in advance as a lead electrode, and this lead electrode (phosphor bronze). Plate) is connected so as to lightly contact the indium electrode, and a DC power source and a microammeter are connected via a measuring jig. At this time, a positive (+) voltage is applied to the main electrode. For the plate supporting the phosphor bronze plate, an insulating material such as an acrylic plate having a thickness of 3 to 5 mm is used.
[0157]
When the surface resistivity is low, after the electrostatic latent image is formed and before the development is completed, the potential is diffused according to the surface resistance value, resulting in a decrease in resolution and image flow. In addition, when the volume resistivity is low, resolution reduction and image flow occur in the process of forming an electrostatic latent image, and in particular, image flow in a high humidity environment of 80% RH or 90% RH is inevitable.
FIG. 14 to FIG. 15 show measurement examples of initial surface resistivity and volume resistivity of an imaged photoreceptor sample measured in an environment of room temperature 22 to 23 ° C. and relative humidity 65 to 67% RH.
The photoconductor sample used is a photoconductor having a 0.75 mm aluminum support having a diameter of 30 mm as a support. Sample A is a 22 μm charge transport layer A in which a polycarbonate resin (bisphenol Z) and a low charge transport material are mixed on a 0.2 μm charge generation layer, and 25 wt% α-alumina in the charge transport layer A material. It consists of an added 5 μm charge transport layer B. Sample B has a 22 μm charge transport layer A made of a polymer charge transport material on a 0.2 μm charge generation layer, and 3 μm of 25 μ% of α-alumina added to the material of the charge transport layer A. It consists of a charge transport layer B. Image formation of these photoreceptor samples was carried out by mounting on an IMAGIO MF200 machine (manufactured by Ricoh, roller charging system, cleaning blade system). For evaluation of resolution, Kodak company chart A (JIS Z 6008) was used as a chart.
[0158]
FIG. 14 is a measurement example of the surface resistivity. Sample A had a resolution of 7.1 lines / mm, and Sample B had a resolution of 2.0 to 2.5 lines / mm. Sample A has a surface resistivity of 4.3 × 10¹⁶Ω, and the surface resistivity of sample B is 8 × 10¹⁵Ω, the difference is within one digit. In the case of the volume resistivity shown in FIG. 15, the volume resistivity when 500 V is applied is 10 for sample A.¹⁴Ω · cm order is shown, but sample B is 10¹¹The resistivity is low on the order of Ω · cm, and the difference is three digits, which is clearly low as a level.
Surface resistivity 10¹⁵Ω falls within a suitable range and is judged to be a satisfactory level, but the volume resistivity is 10¹¹The level is as low as Ω · cm, and this level is clearly a category in which the resolution is degraded, and the image is completely lost in a high humidity environment. That is, this is an example that does not satisfy both the characteristics of surface resistivity and volume resistivity. In this case, formation of a high-quality image is not realized. In addition, when the surface resistivity shows a change exceeding one digit, the image deterioration is surely caused in a high humidity environment.
[0159]
Next, FIGS. 16 and 17 show measurement examples of volume resistivity before and after the 50,000-sheet passing run. About the above
FIG. 16 shows a measurement example of volume resistivity when a reinforced loop brush with a resin coating is used as a cleaning brush and a photoconductor sample having a diameter of 30 mm in which 20 wt% of α-alumina is added to the charge transport layer B of the sample A configuration. It is. In this sample, the volume resistivity at the time of applying 500 V is 3.5 × 10 5 even after 50,000 images are formed.¹⁴Good characteristics such as Ω · cm. The change from the initial volume resistivity is about one digit, and the resolution is 6.3 to 8.0 lines / mm even after 50,000 images are formed. showed that.
On the other hand, FIG. 17 shows an example of volume resistivity measurement using a nylon fiber straight hair brush as the cleaning brush and using a φ30 mm photoconductor sample in which 20 wt% of α-alumina is added to the charge transport layer B of the sample B configuration. It is. Initially the characteristics are almost flat with respect to the applied voltage, and the volume resistivity when 500 V is applied is 5 × 10 5.¹⁴Ω · cm was good, but the measurement after 50,000 sheets was 2.4 × 10¹¹This is an example in which Ω · cm shows a decrease of 3 digits, the image flow becomes remarkable during image formation, and finally a resolution (not resolved) of 2.0 (lines / m) or less is shown.
[0160]
FIGS. 18 and 19 show measurement examples of the surface resistivity when the same photoreceptor sample as that used in FIGS. 16 and 17 is used.
In the sample of FIG. 18, the surface resistivity level is 10¹⁶On the order of Ω, the change before and after running paper is slight, whereas the sample in FIG.¹⁵It decreases to Ω order, and it is confirmed that the change is about an order of magnitude when 500 V is applied. When the photoconductor sample having a large change was measured in an environment of 30 ° C./90% RH, the surface resistivity was 10 due to the influence of moisture absorption of the pollutant.⁸-10⁹It was observed that the resistance dropped to Ω.
[0161]
FIG. 20 is a graph showing dependency of the charge level drop (ΔVd) on the volume resistivity of the photoconductor when a photoconductor sample having various volume resistances with the same layer structure as the sample A is prepared and measured. (Graph). As the volume resistivity increases, the amount of decrease in charge level decreases and 1 × 10¹³Above Ω · cm, the amount of decrease is minimum. That is, 1 × 10¹³If it is Ω · cm or more, the charge level repeated decrease ΔVd is the lowest (good).
FIG. 21 is a graph showing the dependence of the resolution on the volume resistivity of the photoreceptor when measurement is performed with the main electrode set to +500 V as in FIG. It can be seen that the resolution also improves as the volume resistivity increases. From these graphs, the volume resistivity range is 1 × 10.¹³It can be seen that Ω · cm or more is necessary. But 5x10¹⁵If it is higher than Ω · cm, the movement of carriers (in this case, holes) in the photosensitive layer becomes dull, so that the light attenuation characteristic is affected and the image forming characteristic is deteriorated. Therefore, the upper limit is preferably 5 × 10¹⁵There is no problem if it is Ω · cm.
From the above, the preferred range of volume resistivity (ρv) is 1 × 10¹³~ 5x10¹⁵Ω · cm. Further, it is desirable that the volume resistivity change width after passing 50,000 sheets (converted to φ30 mm photoreceptor) is within two digits. In a state exceeding this, the image quality deteriorates, and a low volume resistance value causes a decrease in resolution even in a normal humidity environment.
[0162]
FIG. 22 is a graph showing the dependence of the resolution on the surface resistivity of the photoreceptor when measured with the main electrode set at + 500V. Surface resistivity is 1 × 10¹⁵The resolution decreases below Ω, but 1 × 10¹⁵Ω ～ 1 × 10¹⁷Ω shows a good resolution of 6.3 lines / mm or more.
The upper limit of the numerical value is not as strict as the volume resistivity, and even if it is high, problems are unlikely to occur. The only problem that arises is the limit on the instrument. 10 in practice¹⁸Ω or 10¹⁹It is difficult to make a sample of Ω, but if it is made, the influence of triboelectric charge cannot be ignored, and charge transfer from the higher potential of the electrostatic latent image to the lower potential occurs. There is a possibility that the latent image is disturbed and the resolution is lost locally. Actually 1x10¹⁷If it is Ω, there is no problem at all.
Therefore, the surface resistivity (σs) is 1 × 10¹⁵~ 1x10¹⁷Ω is desirable. Further, it is desirable that the change width of the surface resistivity after passing 50,000 sheets (converted to φ30 mm photoreceptor) is within one digit. That is, in order to maintain a high quality image, it is necessary to maintain the surface resistivity.
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
[0163]
【Example】
Various evaluation photoreceptor samples (Nos. 1 to 19) of the present invention were prepared by the following procedure, and a cleaning brush composed of the photoreceptor sample and looped fibers was used as an image forming apparatus, that is, Imagio Neo600 (corona charger, φ100 mm). Are mounted on Ricoh) and Ipsio Color 8000 (non-contact charger, φ30 mm photoconductor, manufactured by Ricoh), surface resistivity, volume resistivity, image quality (resolution, sharpness, 2 (Dot pattern density unevenness), the abrasion amount of the photosensitive layer, and the friction coefficient were evaluated. In the following description, “parts” represent parts by weight.
[0164]
1. Preparation example of photoconductor sample for evaluation
1-1 Preparation of photoconductor sample for evaluation (No. 1 to 7)
First, a 3003 series aluminum alloy drum processed to φ100 mm, length 360 mm, and wall thickness 1.20 mm was used as a conductive support, and this was dipped in an undercoat layer coating solution having the following composition and then pulled up. It was dried at 25 ° C. for 25 minutes, and an undercoat layer of about 3.5 μm was formed by coating.
[Coating liquid for undercoat layer]
Alkyd resin (Beccosol 1307-60-EL:
Dainippon Ink & Chemicals, Inc.) 6 parts
Melamine resin (Super Becamine G-821-60:
Dainippon Ink & Chemicals, Inc.) 4 parts
Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) 40 parts
200 parts of methyl ethyl ketone
[0165]
Subsequently, the film was immersed in a charge generation layer coating solution having the following composition, and then heated and dried at 120 ° C. for 20 minutes to form a 0.2 μm charge generation layer.
[Coating liquid for charge generation layer]
Oxotitanium phthalocyanine pigment 2 parts
Polyvinyl butyral (UCC: XYHL) 0.2 part
50 parts of tetrahydrofuran
[0166]
Furthermore, the film thickness is 28 μm (No. 1) or 22 μm (No. 2 to 7) by immersing in the coating liquid for charge transport layer A having the following composition and adjusting the pulling rate from the immersion liquid. The charge transport layer A was applied and formed as described above, and was heat-dried at 130 ° C. for 30 minutes to produce a three-layer organic photoreceptor.
The film thickness is an average value obtained by measuring 13 points at an interval of 20 mm starting from 60 mm from the left end of the drum using a Fischer eddy current film thickness meter (type mms).
[Coating liquid for charge transport layer A]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of low molecular charge transport material of the following structural formula (1)
200 parts of tetrahydrafuran
[0167]
[Chemical 1]

[0168]
Next, according to the composition of the following charge transport layer B coating solution, each inorganic filler (alumina filler) was weighed to be 3, 5, 10, 25, 30, 35% by weight, respectively, The dispersion aid and the solvent were each placed in a glass pot, dispersed with a ball mill for 24 hours, and adjusted to obtain a charge transport layer B coating solution (coating solution).
The mixing ratio of the dispersion aid was changed according to the amount of the filler added. The blending ratio (filler addition amount (% by weight) / dispersion aid (parts)) is as follows.
(No. 2): Filler 3% by weight / 0.03 part, (No. 3): Filler 5% by weight / 0.04 part, (No. 4, 5): Filler 10, 25% by weight / 0.08 Part,
(No. 6): Filler 30% by weight / 0.1 part, (No. 7): Filler 35% by weight / 0.2 part.
In the above, it was confirmed that by adding a dispersion aid, the film quality is made uniform and contributes to the reduction of the residual potential, but the volume resistivity and surface resistivity tend to be lowered.
[Charge transport layer B coating solution]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of low molecular charge transport material of the following structural formula (1)
Alumina filler (AA-03, manufactured by Sumitomo Chemical Co., Ltd.)
(Average primary particle size: 0.3 μm) 0.53 to 9.3 parts
Tetrahydrofuran 400 parts
200 parts of cyclohexanone
Dispersing aid: (BYK-P104:
Made by Big Chemie Japan) 0.03-0.2 parts
[0169]
[Chemical 2]

[0170]
A charge transport layer B was formed using the coating solution obtained above. The film is formed by applying a spray gun to the charge transport layer A having a film thickness of 22 μm while revolving at about 360 rpm with one reciprocation (feed speed 25 mm / sec), and drying by heating at 150 ° C. for 20 minutes. Thus, a photoreceptor sample (Nos. 2 to 7) having a four-layer structure was produced. The surface resistivity and volume resistivity of each of the photoreceptor samples (Nos. 1 to 7) thus produced were measured at an environment of 22 to 23 ° C. and an applied voltage of 500 V under a relative humidity of 65 to 67% RH. (Reference value 1 minute after application of 500 V). Table 1 below shows the partial configuration (photoconductor diameter, charge transport layer A film thickness, filler addition amount of the electrification transport layer B), surface resistivity, and volume resistivity of each photoconductor sample.
[0171]
1-2 Preparation of evaluation photoreceptor sample (No. 8, 9)
First, a 3003 series aluminum alloy drum processed to φ100 mm, length 360 mm, and wall thickness 1.20 mm was used as a conductive support, and this was dipped in an undercoat layer coating solution having the following composition and then pulled up. An undercoat layer of about 3.5 μm was formed by coating at 25 ° C. for 25 minutes.
[Coating liquid for undercoat layer]
Alkyd resin (Beccosol 1307-60-EL:
Dainippon Ink & Chemicals, Inc.) 6 parts
Melamine resin (Super Becamine G-821-60:
Dainippon Ink & Chemicals, Inc.) 4 parts
Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) 40 parts
200 parts of methyl ethyl ketone
[0172]
Subsequently, the film was immersed in a charge generation layer coating solution having the following composition, and then heated and dried at 120 ° C. for 20 minutes to form a 0.2 μm charge generation layer.
[Coating liquid for charge generation layer]
Oxotitanium phthalocyanine pigment 2 parts
Polyvinyl butyral (UCC: XYHL) 0.2 part
50 parts of tetrahydrofuran
[0173]
Furthermore, it is dip coated in a coating solution for charge transport layer A having the following composition, and is heated and dried at 130 ° C. for 30 minutes to form charge transport layer A having a thickness of about 22 μm. A three-layer organic photoreceptor was prepared.
[Coating liquid for charge transport layer A]
10 parts of a polymer charge transport material of the following structural formula (2)
400 parts of tetrahydrafuran
200 parts of cyclohexane
[0174]
[Chemical 3]

[0175]
  Next, the amount of inorganic filler (α-alumina filler having a primary average particle size of 0.3 μm) in the charge transport layer B is respectively determined by the following composition., ElectricPrepare 15% to 25% by weight of the load transport layer B, add the dispersion aid and solvent to a glass pot, and disperse them with a ball mill for 24 hours to obtain the charge transport layer B coating liquid (coating liquid). It was adjusted.
  In addition, as the addition amount (part) of the alumina filler increased, the addition amount of the dispersion aid was increased.
[Charge transport layer B coating solution]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of charge transport material of the following structural formula (1)
Alumina filler (AA-03, manufactured by Sumitomo Chemical Co., Ltd.)
(Average primary particle size: 0.3 μm) 3.18 parts, 5.7 parts
400 parts of trahydrofuran
200 parts of cyclohexanone
Dispersing aid: (BYK-P104:
Made by Big Chemie Japan) 0.04 parts, 0.08 parts
[0176]
[Formula 4]

[0177]
The resulting coating solution was reciprocated with a spray gun, and the charge transport layer B was spray-coated so as to have a thickness of about 5 μm, followed by heating and drying at 150 ° C. for 20 minutes to prepare a photoconductor sample having a four-layer structure. .
The surface resistivity and volume resistivity of each of the photoreceptor samples (Nos. 8 and 9) thus produced were measured at an environment of 22 to 23 ° C. and an applied voltage of 500 V under a relative humidity of 65 to 67% RH. (Reference value 1 minute after application of 500 V). Table 1 below shows the partial configuration (photoconductor diameter, charge transport layer A film thickness, filler addition amount of the electrification transport layer B), surface resistivity, and volume resistivity of each photoconductor sample.
[0178]
1-3 Preparation of evaluation photoreceptor sample (No. 10-12)
3003 series aluminum alloy drum processed to φ30mm, length 340mm, wall thickness 0.75mm is used as a conductive support, and this is immersed in the undercoat layer coating solution and coated on the surface. And then dried by heating at 120 ° C. for 20 minutes to form a 3.5 μm undercoat layer.
[Coating liquid for undercoat layer]
Alkyd resin (Beccosol 1307-60-EL:
Dainippon Ink & Chemicals, Inc.) 6 parts
Melamine resin (Super Becamine G-821-60:
Dainippon Ink & Chemicals, Inc.) 4 parts
Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) 40 parts
200 parts of methyl ethyl ketone
[0179]
Next, after dip-coating in a coating solution for charge generation layer having the following composition, it was dried by heating at 120 ° C. for 20 minutes to form a 0.2 μm charge generation layer.
[Coating liquid for charge generation layer]
10 parts of bisazo pigment of the following structural formula (3)
Polyvinyl butyral 2 parts
2-butanone 200 parts
400 parts of cyclohexanone
[0180]
[Chemical formula 5]

[0181]
Further, the coating liquid for charge transport layer A having the following composition was pulled up and the speed condition was changed, dip-coated on charge transport layer B, heat-dried at 130 ° C. for 20 minutes, and 22 μm charge transport layer A three-layer organic photoreceptor consisting of A was prepared.
[Coating liquid for charge transport layer A]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
8 parts of low molecular charge transport material of the following structural formula (1)
200 parts of tetrahydrafuran
[0182]
[Chemical 6]

[0183]
  Next, the amount of inorganic filler (α-alumina filler having a primary average particle size of 0.3 μm) in the charge transport layer B is respectively determined by the following composition., ElectricThe inorganic filler, the dispersion aid and the solvent are respectively mixed in a glass pot and dispersed in a ball mill for 24 hours, and the charge transport layer B coating liquid (coating liquid (coating) is prepared. Working solution).
[Charge transport layer B coating solution]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of low molecular charge transport material of the following structural formula (1)
Alumina filler (AA-03, manufactured by Sumitomo Chemical Co., Ltd.)
(Average primary particle size: 0.3 μm) 4.25 parts to 9.1 parts
Tetrahydrofuran 400 parts
200 parts of cyclohexanone
Dispersing aid: (BYK-P104:
0.05 parts made by Big Chemie Japan)
[0184]
[Chemical 7]

[0185]
The coating liquid obtained above is reciprocated with a spray gun, and the charge transport layer B is spray-coated so as to have a thickness of about 5 μm, and dried by heating at 150 ° C. for 20 minutes to produce a 4-layer photoconductor sample. did.
The surface resistivity and volume resistivity of each of the photoreceptor samples (Nos. 10 to 12) produced in this manner were measured at a temperature of 22 to 23 ° C. and an applied voltage of 500 V under a relative humidity of 65 to 67% RH. (Reference value 1 minute after application of 500 V). Table 1 below shows the partial configuration (photoconductor diameter, charge transport layer A film thickness, filler addition amount of the electrification transport layer B), surface resistivity, and volume resistivity of each photoconductor sample.
[0186]
1-4 Preparation of evaluation photoreceptor sample (No. 13 to 15)
3003 series aluminum alloy drum processed to φ30mm, length 340mm, wall thickness 0.75mm is used as a conductive support, and this is immersed in the undercoat layer coating solution and coated on the surface. And then dried by heating at 120 ° C. for 20 minutes to form an undercoat layer of 3.5 μm.
[Coating liquid for undercoat layer]
Alkyd resin (Beccosol 1307-60-EL:
Dainippon Ink & Chemicals, Inc.) 6 parts
Melamine resin (Super Becamine G-821-60:
Dainippon Ink & Chemicals, Inc.) 4 parts
Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) 40 parts
200 parts of methyl ethyl ketone
[0187]
Next, after being immersed in a coating solution for charge generation layer having the following composition, it was dried by heating at 120 ° C. for 20 minutes to form a 0.2 μm charge generation layer.
[Coating liquid for charge generation layer]
10 parts of bisazo pigment of the following structural formula (3)
Polyvinyl butyral 2 parts
2-butanone 200 parts
400 parts of cyclohexanone
[0188]
[Chemical 8]

[0189]
Furthermore, it was dip-coated in a coating solution for charge transport layer A having the following composition, and heat-dried at 130 ° C. for 20 minutes to produce an organic photoreceptor having a three-layer structure composed of 15 μm and 22 μm charge transport layer A. .
[Coating liquid for charge transport layer A]
7 parts of polymer charge transport material of the following structural formula (4)
400 parts of tetrahydrafuran
200 parts of cyclohexane
[0190]
[Chemical 9]

[0191]
  Next, the amount of inorganic filler (α-alumina filler having a primary average particle size of 0.3 μm) in the charge transport layer B is respectively determined by the following composition., ElectricThe charge transport layer B was mixed at 15, 25, and 40% by weight, and the dispersion aid and solvent were placed in a glass pot and dispersed in a ball mill for 24 hours. )
[Charge transport layer B coating solution]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of low molecular charge transport material of the following structural formula (1)
Alumina filler (AA-03, manufactured by Sumitomo Chemical Co., Ltd.)
(Average primary particle size: 0.3 μm) 3.18 parts to 11.3 parts
Tetrahydrofuran 400 parts
200 parts of cyclohexanone
Dispersing aid: (BYK-P104:
0.07 parts made by Big Chemie Japan)
[0192]
[Chemical Formula 10]

[0193]
Using the coating solution obtained above, it is reciprocated once by a spray coating method using a spray gun, and about 5 μm of the charge transport layer B is coated on the charge transport layer A, followed by heating and drying at 150 ° C. for 20 minutes to form four layers. A photoconductor sample having the structure was prepared.
The surface resistivity and volume resistivity of each of the photoreceptor samples (Nos. 13 to 15) thus produced were measured at a temperature of 22 to 23 ° C. and an applied voltage of 500 V under a relative humidity of 65 to 67% RH. (Reference value 1 minute after application of 500 V). Table 1 below shows the partial configuration (photoconductor diameter, charge transport layer A film thickness, filler addition amount of the electrification transport layer B), surface resistivity, and volume resistivity of each photoconductor sample.
[0194]
1-5 Preparation of evaluation photoreceptor sample (No. 16 to 18)
3003 series aluminum alloy drum processed to φ30mm, length 340mm, wall thickness 0.75mm is used as a conductive support, and this is immersed in the undercoat layer coating solution and coated on the surface. And then dried by heating at 120 ° C. for 20 minutes to form an undercoat layer of 3.5 μm.
[Coating liquid for undercoat layer]
Alkyd resin (Beccosol 1307-60-EL:
Dainippon Ink & Chemicals, Inc.) 6 parts
Melamine resin (Super Becamine G-821-60:
Dainippon Ink & Chemicals, Inc.) 4 parts
Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) 40 parts
200 parts of methyl ethyl ketone
[0195]
Next, after being immersed in a coating solution for charge generation layer having the following composition, it was dried by heating at 120 ° C. for 20 minutes to form a 0.2 μm charge generation layer.
[Coating liquid for charge generation layer]
10 parts of bisazo pigment of the following structural formula (3)
Polyvinyl butyral 2 parts
2-butanone 200 parts
400 parts of cyclohexanone
[0196]
Embedded image

[0197]
Furthermore, it is immersed in the coating liquid for charge transport layer A having the following composition, the pulling speed condition from the immersion liquid is changed, the charge transport layer B is dip-coated, and heat drying at 130 ° C. for 20 minutes. Then, an organic photoreceptor having a three-layer structure consisting of a 22 μm charge transport layer A was produced.
[Coating liquid for charge transport layer A]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
8 parts of low molecular charge transport material of the following structural formula (1)
200 parts of tetrahydrafuran
[0198]
Embedded image

[0199]
  Next, α-alumina fillers having primary average particle sizes of 0.3 μm, 0.5 μm, and 0.7 μm are prepared according to the composition of the following charge transport layer B coating solution, and each α-alumina filler and dispersion aid are prepared. And solvent are placed in a glass pot, and dispersed in a ball mill for 24 hours., ElectricA charge transport layer B coating solution (coating solution) prepared so as to be 20% by weight of the load transport layer B was prepared.
[Charge transport layer B coating solution]
Bisphenol Z-type polycarbonate (manufactured by Teijin Chemicals:
Z Polica Mv50,000) 10 copies
7 parts of low molecular charge transport material of the following structural formula (1)
Alumina filler (AA-03-0.7 manufactured by Sumitomo Chemical Co., Ltd.)
(Average primary particle size: 0.3, 0.5, 0.7 μm) 4.25 parts
Tetrahydrofuran 400 parts
200 parts of cyclohexanone
Dispersing aid: (BYK-P104:
0.08 parts made by Big Chemie Japan)
[0200]
Embedded image

[0201]
The coating solution prepared above is put into a spray gun mounted on a coating apparatus provided with a photoconductor for evaluation, and spray coating is performed on the photoconductor by one reciprocating jet, at 150 ° C. for 20 minutes. Heat drying was performed to form a charge transport layer B having a thickness of about 5 μm, thereby preparing a photoconductor sample having a four-layer structure.
The surface resistivity and volume resistivity of each of the photoreceptor samples (Nos. 16 to 18) thus produced were measured at an environment of 22 to 23 ° C. and an applied voltage of 500 V under a relative humidity of 65 to 67% RH. (Reference value 1 minute after application of 500 V). Table 1 below shows the partial configuration (photoconductor diameter, charge transport layer A film thickness, filler addition amount of the electrification transport layer B), surface resistivity, and volume resistivity of each photoconductor sample.
[0202]
[Table 1]

[0203]
Using each of the photoconductor samples prepared above, evaluation was performed with an evaluation device (Imagio Neo600, Ipsio Color 8000) using a method for applying a lubricant to the surface of the photoconductor and a cleaning brush for a cleaning device as follows. Went.
[0204]
<Method for Applying Lubricant to Photoreceptor Surface Layer>
A pulverized toner having a weight average particle diameter of about 4.8 μm and an average circularity of 0.924 (SiO 2 as a flow agent)₂0.7%, TiO₂Is added in an amount of 0.02 to 0.05% by weight of zinc stearate (SZ2000: manufactured by Sakai Chemical Industry Co., Ltd.). A method of imparting lubricity to the surface layer (surface) was adopted. As the carrier for the developer, a magnetic carrier (FPC-300LC: manufactured by Powdertech) having a weight average particle diameter of 58 μm was used.
When a developer other than the above was used, a genuine product for the evaluation device was used.
[0205]
<Cleaning brush for cleaning device>
Cleaning brush A (reinforced loop brush) in the present invention:
Nylon fiber beltlon (made by Kubota Textile) with a fiber diameter of 15 denier, 48 filaments / 450 loops, and loop length of 3 mm is cut into a string with a width of 10 mm, wrapped around a φ5 mm brass rod and pasted using an adhesive Then, a cleaning brush (loop cleaning brush) made of looped fibers was produced. Next, the loop cleaning brush produced above was coated with a resin by the following method to enhance the strength of the fiber.
As a coating resin for fiber surface treatment, Toyo Polymer's water-based urethane adhesive Merci 585 was used as the main agent, and Toyo Polymer's epoxy AD-C-65 was used as the curing agent. Ion exchange water was used as a dilution solvent so that the viscosity of the coating resin was 41 mPa · S. The brush surface of the cleaning brush was added to a coating resin solution obtained by adding 1.25 parts of water while adjusting the amount of the curing agent (crosslinking agent) to 5% by weight with respect to 5 parts of the main agent. Then, after 2 mm immersion, the product was dried at 160 ° C. for 10 minutes. The rotation direction of the cleaning brush rotates in a direction (forward direction) that follows the rotation direction of the photosensitive member, and no flicker bar is installed.
Cleaning brush B (straight hair brush) in the reference example:
As the straight brush cleaning brushes, so-called genuine brushes for the devices used for evaluation (Imagio Neo600 and Ypsio Color 8000) were used.
[0206]
Examples 1-4
First, as an evaluation apparatus (evaluation machine), an Imagio Neo 600 (corona charger, φ100 mm photoconductor, manufactured by Ricoh Co., Ltd.), which is a digital multifunction machine, was used. No. in Table 1 above. 2 to 5 photoconductor samples are mounted on an evaluation machine, and images are formed by continuously passing paper. After 50,000 sheets and 200,000 sheets, surface resistivity, volume resistivity, and image quality (resolution, two-dot pattern) Density unevenness), the abrasion amount of the photosensitive layer, and the friction coefficient were evaluated. The surface potential of the photoreceptor during image formation is set to -800 V, and a developer added with 0.025% by weight of zinc stearate (SZ2000, average particle size: 0.3 μm) is used as a developer. did.
The cleaning brush for the cleaning device uses the produced cleaning brush A (reinforced loop brush) and is configured to be used in combination with the cleaning blade. A chart having an image area of 5% was used as an image pattern during paper running. For confirmation of the resolution, Kodak drafting sheet A (JIS Z 6008) was attached to a test chart for image evaluation. The image forming environment is 22 to 24 ° C./61 to 68% RH, and the measurement environment for surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. The evaluation results are shown in Table 2.
[0207]
[Table 2]

[0208]
All of the photoconductors used for the evaluation were worn almost uniformly, and the polished surface maintained the gloss near the initial stage. The results also appeared in the surface resistivity and the volume resistivity, and the resolution in image quality and the reproducibility of the 2-dot pattern were good and uniform characteristics. Further, it was confirmed that the wear amount of the photosensitive layer was small due to the use of the corona charger and the effect of applying the lubricant, and even with 200,000 sheets, the photosensitive layer had a sufficient film thickness and had good durability. Incidentally, in the photosensitive member (photosensitive member sample No. 5) in which the filler addition amount is 25% by weight, filming occurred locally at the end of the photosensitive member, and density unevenness slightly occurred in the 2-dot pattern. It is in the category that can be improved by strengthening power.
[0209]
Reference Examples 1-6
As an evaluation apparatus (evaluation machine), an Imagio Neo600 (corona charger, using a photoconductor of φ100 mm, manufactured by Ricoh Co., Ltd.) as a digital multifunction machine was used. Each photoconductor sample of 1, 5, 6, 7, 8, 9 is mounted on an evaluation machine, and images are formed by continuous paper passing. After 50,000 sheets, surface resistivity after 200,000 sheets, Volume resistivity, image quality (resolution, 2 dot pattern density unevenness), abrasion amount and friction coefficient of the photosensitive layer were evaluated. The surface potential of the photoreceptor during image formation was set to -800 V, and a genuine developer containing wax was used as the developer.
The cleaning brush was replaced with a genuine straight-hair brush and used in combination with a cleaning blade. A chart having an image area of 5% was used as an image pattern during paper running. The image forming environment is 24 to 27 ° C./63 to 72% RH, and the measurement environment for surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. The evaluation results are shown in Table 3.
[0210]
[Table 3]

[0211]
In the photoreceptor sample (No. 1) in which the charge transport layer B to which the filler was added was not formed, the surface resistivity and the volume resistivity were little changed because of much wear, and apparently good characteristics were shown. Fluid agents such as titanium oxide and silica added to the developer adhere to the surface of the photoconductor, causing the surface of the photoconductor to become rough, resulting in a dot pattern.concentrationUnevenness occurred.
In the other photoreceptor samples (No. 5, 6, 7, 8, 9), the cleaning brush is a straight hair type, the coefficient of friction of the photoreceptor surface layer is relatively low, and there is no ability to polish the photoreceptor layer. The formation of filming became more noticeable each time the number of copies was increased. As a result, due to the accumulation of corona products, the decrease in surface resistivity and volume resistivity became remarkable, resulting in a decrease in resolution.
[0212]
Examples 5-9
As an evaluation apparatus (evaluation machine), a digital printer Ipsio Color 8000 (non-contact charger, φ30 mm photoconductor, manufactured by Ricoh) was used. Five photoconductor samples 10 (M), 11 (C), 12 (Y), 13 (M), and 14 (C) are mounted on the evaluation machine, and images are formed by continuous paper passing. After 10,000 sheets, the surface resistivity, volume resistivity, image quality (sharpness, 2-dot pattern density unevenness), photosensitive layer wear amount, and friction coefficient after 100,000 sheets were evaluated.
Note that M, C, and Y in parentheses represent development positions of M: magenta station, C: cyan station, and Y: yellow station, respectively.
[0213]
Evaluation was performed in two steps. No. 1 10 to 12, and No. 2 for the second time. Dummy drums were set in the empty stations as 13 and 14. The development position set in the parenthesis is the initial development position, and rotation was performed sequentially with a cleaning blade every 5000 sheets. The surface potential of the photoreceptor during image formation was set to -700 V, and 0.03 wt% of zinc stearate was added to the developer as the developer, and the toner concentration was 5 wt%.
As the cleaning brush, the resin-reinforced cleaning brush A (reinforced loop brush) was processed for Ypsio 8000 by the above-described manufacturing method. In addition, a 5% chart inputted in a personal computer database was used as an image pattern to be used during the paper running, and the signal was inputted into an Ipsio color 8000. The imaging environment is 23 to 25 ° C./64 to 70% RH, and the measurement environment for surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. The evaluation results are shown in Table 4.
[0214]
[Table 4]

[0215]
The photoreceptor sample in which the amount of filler added to the charge transport layer B is 35% by weight (Example 7) has a large amount of filler. Therefore, the amount of wear is small for a large amount of attack of the corona product. It is estimated that a slight unevenness occurred in the 2-dot pattern. The reason why the evaluation with the photoreceptor samples of Examples 8 and 9 was somewhat unsatisfactory was due to the specific resistance of the polymer charge transport layer used for the charge transport layer A. These samples can avoid deterioration of image quality if the wear of the charge transport layer B is increased a little.
Other photoreceptor samples other than those described above also had good 2 dot pattern density unevenness. The results are presumed to be because the changes in the surface resistivity and the volume resistivity are within 1 digit and 2 digits, respectively, and the corona product is evenly shaved off.
[0216]
Reference Examples 7-10
As an evaluation apparatus (evaluation machine), a digital printer Ipsio Color 8000 (non-contact charger, φ30 mm photoconductor, manufactured by Ricoh) was used. Four photoconductor samples of 10 (M), 12 (C), 14 (M), and 15 (C) were divided into two portions twice and mounted on the evaluation machine, and the paper was continuously passed through. Then, the surface resistivity, volume resistivity, image quality (sharpness, 2 dot pattern density unevenness), photosensitive layer wear amount, and friction coefficient after 50,000 sheets were evaluated. The development position set in the parenthesis is the development position set in the initial stage, and the rotation was sequentially performed together with the cleaning blade every 5000 sheets. A dummy drum was set in each of the Y (yellow) and Bk (black) stations, and the evaluation was performed only in the M (magenta) and C (cyan) stations. The surface potential of the photoreceptor during image formation was set to -700 V, and 0.03 wt% of zinc stearate was added to the developer as the developer, and the toner concentration was 5 wt%.
In addition, the genuine straight hair type cleaning brush for Ypsio 8000 was used for the cleaning brush. For the image pattern used during the paper running, a 5% chart inputted in the database of the personal computer was used, and the signal was inputted into the Ypsio Color 8000. The image forming environment is 26 to 29 ° C./68 to 74% RH, and the measurement environment for surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. The evaluation results are shown in Table 5.
[0217]
[Table 5]

[0218]
When a straight hair type cleaning brush that has not been reinforced is used, filming occurs on the surface of the photoconductor, and corona products accumulate and lubricant accumulates. Reduction progressed. As a result, the surface resistivity and the volume resistivity each showed a change of one digit or two digits, which is a limit value capable of good image formation without deterioration in image quality. As a result, the image quality deteriorated, and the image flow state was reached over all the evaluated photoreceptor samples, resulting in poor image quality.
[0219]
Examples 10-12
As an evaluation apparatus (evaluation machine), an Ipsio Color 8000 (non-contact charger, photoconductor with a diameter of 30 mm, manufactured by Ricoh) of a digital printer was used. Three photoreceptor samples of 16 (M), 17 (C), and 18 (Y) are mounted on the evaluation machine, and images are formed by continuous paper passing, and the surface after 50,000 sheets and 100,000 sheets Resistivity, volume resistivity, image quality (sharpness, 2 dot pattern density unevenness), photosensitive layer wear, and friction coefficient were evaluated. The development position set in the parenthesis is the development position set in the initial stage, and the rotation was sequentially performed together with the cleaning blade every 5000 sheets. A dummy drum was set at the black development position. The surface potential of the photoreceptor during image formation was set to -700 V, and 0.02% by weight of zinc stearate was added to the developer as a developer, and the toner concentration was 5% by weight.
Further, as the cleaning brush, the reinforcing brush A (reinforced loop brush) reinforced with resin was processed for the Ypsio 8000 by the above-described manufacturing method. For the image pattern used during the paper running, a 5% chart inputted in the database of the personal computer was used, and the signal was inputted into the Ypsio Color 8000. The image forming environment is 24 to 27 ° C./64 to 71% RH, and the measurement environment for surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. The evaluation results are shown in Table 6.
[0220]
[Table 6]

[0221]
In the photoreceptor sample in which the size of the primary average particle diameter of the filler was changed, any of the photoreceptor samples used showed good surface resistivity and volume resistivity even after 100,000 sheets. Both quality were good.
Incidentally, in the photoreceptor sample (No. 18) having an average particle diameter of the filler of 0.7 μm, wear unevenness and surface roughness due to the effect of improved wear resistance were slightly observed, and as a result, although slightly, 2 Dot patternconcentrationAppeared as uneven. The wear amount and image quality are expected to be improved by increasing the amount of wear a little or by improving the cleaning member, but it is estimated that 0.7 μm is the limit for the filler diameter because there is a possibility that uneven wear may further progress. The
[0222]
Reference Examples 11-13
As an evaluation apparatus (evaluation machine), a digital printer Ipsio Color 8000 (non-contact charger, φ30 mm photoconductor, manufactured by Ricoh) was used. Three photoconductor samples of 15 (M), 16 (C), and 17 (Y) are mounted on the evaluation machine, and images are formed by continuous paper passing, after 50,000 sheets and after 100,000 sheets. The surface resistivity, the volume resistivity, the image quality (sharpness, 2 dot pattern density unevenness), the abrasion amount of the photosensitive layer, and the friction coefficient were evaluated. The development position set in the parenthesis is the development position set in the initial stage, and the rotation was sequentially performed together with the cleaning blade every 5000 sheets. A dummy drum was set at the black development position. The surface potential of the photosensitive member at the time of image formation was set to -700 V, and a developer having a toner concentration of 5% by weight without adding a lubricant was used as the developer.
A pure straight brush was used as the cleaning brush. For the image pattern used during the paper running, a 5% chart inputted in the database of the personal computer was used, and the signal was inputted into the Ypsio Color 8000. The image forming environment is 24 to 26 ° C./68 to 73% RH, and the measurement environment of the surface resistivity and volume resistivity is 22 to 23 ° C./65 to 67% RH. Table 7 shows the evaluation results.
[0223]
[Table 7]

[0224]
All of the photoreceptor samples used for the evaluation had filming phenomenon, and the photoreceptor surfaces all had a light grayish color. As a result, corona products, paper dust and other contaminants are not removed (the amount of wear is small), and the corona products penetrate into the interior of the photoconductor, resulting in surface resistivity and volume resistivity. The image quality deteriorated and the image quality deteriorated. The photoreceptor sample No. described in Reference Example 11 was used. In the case of 15, the polymer transport layer that is more susceptible to the influence of nitrogen oxides than the other comparative photoconductor samples was used for the charge transport layer A, so that the resistivity decreased greatly and the environment (a little higher than the normal humidity environment ( Even at 73% RH), the image flow occurred, and the image of the entire 2-dot pattern also showed a large light / dark difference.
[0225]
【The invention's effect】
According to the present invention, a filler is dispersed in a specific cleaning device having a reinforced loop brush (cleaning brush made of loop-like fibers) reinforced with a resin layer and the outermost layer (charge transport layer B) of the photosensitive layer. Therefore, the surface resistivity (σs) of 1 × 10 is maintained by always maintaining the surface of the photoconductor in a clean state by the configuration with the photoconductor having durability adjusted so as to be scraped to an appropriate amount.¹⁵~ 1x10¹⁷Ω, volume resistivity (ρv) 1 × 10¹³~ 5x10¹⁵By adjusting to Ω · cm and adjusting the coefficient of friction of the photosensitive layer surface during image formation to 0.2 to 0.4 (measured by Euler belt method), there is no image unevenness over the long term and good sharpness High-definition image formation with high resolution is achieved.
In addition, the values of surface resistivity and volume resistivity at the start of image formation and after image formation of 50,000 sheets are adjusted within suitable ranges, and fluctuation values (surface resistivity: within one digit, volume resistivity: two digits) Can be formed over a long period of time.
By using an indium foil as an electrode for measuring surface resistivity and volume resistivity (circular electrode and ring electrode), a photosensitive member (measurement sample) having a curvature like a drum shape can also be cut. And can be easily attached to the surface of the photoreceptor as it is. Therefore, accurate and stable surface resistivity and volume resistivity can be measured, an actual situation can be grasped, and the resistivity can be controlled within a predetermined control range. Further, since it is not necessary to process the photoconductor (measurement sample), it can be reused.
Furthermore, a loop brush having durability and uniform polishing ability can be obtained by using a water-based urethane resin (main agent) + epoxy compound (curing agent) as the surface covering material (resin layer) of the reinforcing loop fiber. . By using this reinforced loop brush, it is possible to remove residual powder such as toner adhering to the surface of the photoconductor, and to remove the contaminants that have started to adhere to the photoconductor surface thinly and evenly. Can be kept in.
In addition, when the photosensitive layer is a two-layer functional separation type composed of a charge generation layer and a charge transport layer, good charging characteristics and good sensitivity can be obtained, and a high-quality image can be formed.
Further, the charge transport layer is composed of a charge transport layer A in which the inorganic filler is not dispersed and a charge transport layer B in which the inorganic filler is dispersed. By providing the charge transport layer B in which the filler is dispersed, the durability against photoconductor surface grinding is improved and adjusted to an appropriate wear amount, and the charge transport layer A (charge generation layer and charge transport layer B in which the filler is not dispersed). Therefore, it is possible to prevent abnormal charge movement and form a stable high-quality image.
Furthermore, the friction coefficient is adjusted by applying any one of fine zinc stearate or polytetrafluoroethylene (PTFE) as a lubricant to the surface of the photoreceptor (friction coefficient during image formation: 0.2 to 0. 0). 4), it is possible to suppress the abrasion of the photosensitive layer and to maintain a uniform image quality with good sharpness.
Further, by adjusting the amount of filler dispersed in the charge transport layer B of the photoconductor according to various charging means, it is possible to cope with the chemical hazard level (large and small) in each charge. It becomes possible to optimize the durability. In addition, a wide range of image forming apparatuses that can obtain high image quality can be designed.
Furthermore, an optimum applied voltage method (DC voltage or DC voltage on which AC voltage is superimposed) can be selected according to the arrangement interval between the photoreceptor and the charging device (charging member, etc.) and environmental conditions (humidity, etc.). Therefore, it is possible to design a wide range of image forming apparatuses that meet the demand for providing high image quality.
Further, an electrophotographic photosensitive member in which a filler is dispersed in the outermost charge transport layer constituting the photosensitive layer, and at least one device selected from a charging device, a developing device, or a cleaning device (including a reinforcing loop brush). By using a process cartridge that can be attached to and detached from the image forming apparatus main body that is integrally supported, the image apparatus can be made compact, and simple and steady maintenance work can be performed, and parts can be easily replaced. And overall cost reduction. Moreover, it is possible to easily restore the original high-quality image simply by replacing the process cartridge.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a basic configuration example of an image forming apparatus according to the present invention for explaining a copying process in an embodiment.
FIG. 2 is a schematic diagram for explaining a configuration example of a quadruple tandem type full-color image forming apparatus provided with magenta, cyan, yellow, and black developing devices.
FIG. 3 is a schematic diagram illustrating an example of a process cartridge that can be attached to and detached from an image forming apparatus main body.
FIG. 4 is a schematic diagram illustrating another example of a process cartridge that can be attached to and detached from the image forming apparatus main body.
FIG. 5 is a schematic diagram showing a basic configuration example of an electrophotographic photoreceptor in the present invention (constructed from a conductive support / undercoat layer / photosensitive layer).
FIG. 6 is a schematic diagram showing an example in which an electrophotographic photosensitive layer according to the present invention is formed by a function-separated configuration of a charge generation layer and a charge transport layer.
7 is a schematic diagram illustrating an example in which the charge transport layer in FIG. 6 includes a charge transport layer A (inorganic filler non-dispersed layer) and a charge transport layer B (inorganic filler dispersed layer).
FIG. 8 is a schematic diagram showing a cleaning device including a cleaning brush (enhanced loop brush) and a cleaning blade according to the present invention.
FIG. 9 is a schematic diagram showing the form of a cleaning brush made of a base cloth and looped fibers according to the present invention.
FIG. 10 is a schematic diagram for explaining electrode shapes and dimensions for measuring the low surface resistivity and volume resistivity in the present invention.
FIG. 11 is a schematic diagram showing a state in which electrodes are closely attached to the surface of a drum-shaped electrophotographic photosensitive member having a curvature.
FIG. 12 is a schematic circuit diagram showing a measuring jig and a voltage application state when measuring the surface resistivity of an electrophotographic photosensitive member provided with an indium electrode.
FIG. 13 is a schematic circuit diagram showing a measuring jig and a voltage application state when measuring the volume resistivity of an electrophotographic photosensitive member provided with an indium electrode.
14 is a graph showing the applied voltage dependence of the surface resistivity of photoreceptor sample A (5 μm) and photoreceptor sample B (3 μm) in which charge transport layers B having different thicknesses are formed on the charge generation layer A. FIG. .
FIG. 15 is a graph showing the applied voltage dependence of the volume resistivity of photoreceptor sample A (5 μm) and photoreceptor sample B (3 μm) in which charge transport layers B having different thicknesses are formed on the charge generation layer A. .
FIG. 16 is a graph showing the applied voltage dependence of the volume resistivity of the sample of the photoreceptor sample A with the filler amount changed to 20% and after running 50,000 sheets (reinforced loop brush).
17 is a graph showing the applied voltage dependence of the volume resistivity of the sample of FIG. 16 in which the low charge transport material is changed to the high charge transport material and after running 50,000 sheets (straight hair brush). is there.
FIG. 18 is a diagram showing the applied voltage dependence of the surface resistivity of the sample of the photoreceptor sample A with the filler amount changed to 20% and after running 50,000 sheets (reinforced loop brush).
19 is a graph showing the applied voltage dependence of the surface resistivity of the sample of FIG. 18 in which the low charge transport material is changed to the high charge transport material and after running 50,000 sheets of paper (straight hair brush). .
FIG. 20 is a diagram showing the dependence of the amount of decrease in charge level on the volume resistivity of a photoreceptor sample with various resistivity changed.
FIG. 21 is a graph showing the dependence of resolution on the volume resistivity of a photoreceptor sample with various resistivity changed.
FIG. 22 is a graph showing the dependency of resolution on the surface resistivity of a photoreceptor sample with various resistivity changed.
[Explanation of symbols]
1 Photoconductor for electrophotography (photoconductor)
2 Charging device
2-1 Charging member
2-2 High voltage power circuit
3 Image exposure equipment
4 Development device
5 Transfer device
6 Separation device
7 Cleaning device
7-1 Cleaning brush
7-2 Cleaning blade
8 Fixing device
9 Transfer object (copy paper)
21 Conductive support
22 Underlayer
23 Photosensitive layer
24 Charge generation layer
25 Charge transport layer
25a Charge transport layer A
25b Charge transport layer B
200 Lubricant coating device
201 Lubricant
202 Application brush

Claims (13)

The surface of the electrophotographic photosensitive member provided with a photosensitive layer in which a filler is dispersed in the outermost charge transporting layer of the constituent layer provided on the conductive support is sequentially charged by a charging device arranged in contact or close proximity. Then, an electrostatic latent image is formed by an image exposure device, the electrostatic latent image is visualized as a toner image by a developing device, the toner image is transferred to a transfer medium under voltage application by a transfer device, and a fixing device is used. Image formation in which a hard copy is made by heat fixing, and residual powder and adhered foreign matter on the surface of the electrophotographic photosensitive member are cleaned by rubbing with a cleaning device having a cleaning brush and a cleaning blade made of looped fibers. A device,
The surface of the loop-like fiber of the cleaning brush is reinforced with a resin layer formed by coating and curing a two-component resin liquid containing an aqueous urethane resin as a main component and an epoxy compound as a curing agent. The surface resistivity (σs) of the film is adjusted to 1 × 10 ¹⁵ to 1 × 10 ¹⁷ Ω and the volume resistivity (ρv) is adjusted to 1 × 10 ^{13 to} 5 × 10 ¹⁵ Ω · cm, and light sensitivity during image formation An image forming apparatus, wherein a friction coefficient of a layer surface is adjusted to 0.2 to 0.4 (measured by Euler belt method). The image forming apparatus according to claim 1, wherein the loop-shaped fiber is an acrylic fiber containing conductive fine particles, a nylon fiber containing conductive fine particles, or a polyester fiber containing conductive fine particles. The difference between the surface resistivity (σs) at the start of image formation of the photosensitive layer and the surface resistivity (σs) after image formation of 50,000 sheets is room temperature 22 to 23 ° C., relative humidity 65 to 67%, and applied voltage 500 V. The image forming apparatus according to claim 1, wherein the measurement condition is within one digit and the surface resistivity (σs) is 1 × 10 ¹⁵ to 1 × 10 ¹⁷ Ω. The difference between the volume resistivity (ρv) at the start of image formation of the photosensitive layer and the volume resistivity (ρv) after image formation of 50,000 sheets is room temperature 22 to 23 ° C., relative humidity 65 to 67%, and applied voltage 500 V. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus has a volume resistivity (ρv) of 1 × 10 ^{13 to} 5 × 10 ¹⁵ Ω · cm.   In the electrophotographic photoreceptor, an undercoat layer and a photosensitive layer are sequentially formed on at least a drum-shaped conductive support, and the photosensitive layer has a two-layer structure of a charge generation layer and a charge transport layer. The image forming apparatus according to claim 1. 6. The image forming apparatus according to claim 5 , wherein the charge transport layer further comprises a charge transport layer A in which inorganic filler is not dispersed and a charge transport layer B in which inorganic filler is dispersed. The inorganic filler dispersed in the charge transport layer B has an average particle size of 0.3 to 0.7 μm, and the content of the inorganic filler is 2 to 35% by weight of the charge transport layer B. The image forming apparatus according to claim 6 .   2. The friction coefficient according to claim 1, wherein the friction coefficient is adjusted by applying one or two of zinc stearate and polytetrafluoroethylene (PTFE) to the surface of the photoreceptor. The image forming apparatus described.   The surface of the electrophotographic photosensitive member can be charged by any one of a corona charging method, a contact charging method using a charging roller, or a non-contact charging method using a charging device disposed in proximity to the electrophotographic photosensitive member. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed by a method. The charging carried out by any method, a method for applying a DC voltage to the charging member according to claim 9, characterized in that it is carried out by any one method of how or applying a DC voltage obtained by superposing an AC voltage, The image forming apparatus described in 1. An electrophotographic photosensitive member provided with a photosensitive layer in which a filler is dispersed in an outermost charge transporting layer of a constituent layer provided on a conductive support, a charging device, a developing device, and a cleaning brush made of looped fibers ; A process cartridge detachably attached to an image forming apparatus main body integrally supporting at least one apparatus selected from cleaning apparatuses provided with a cleaning blade ;
The surface of the loop-like fiber of the cleaning brush is reinforced with a resin layer formed by coating and curing a two-component resin liquid containing an aqueous urethane resin as a main component and an epoxy compound as a curing agent. The surface resistivity (σs) of the film is adjusted to 1 × 10 ¹⁵ to 1 × 10 ¹⁷ Ω and the volume resistivity (ρv) is adjusted to 1 × 10 ^{13 to} 5 × 10 ¹⁵ Ω · cm. A process cartridge characterized in that a friction coefficient of a layer surface is adjusted to 0.2 to 0.4 (measured by an Euler belt method). 12. The process cartridge according to claim 11, wherein the loop fiber is an acrylic fiber containing conductive fine particles, a nylon fiber containing conductive fine particles, or a polyester fiber containing conductive fine particles. The surface of the electrophotographic photosensitive member can be charged by any one of a corona charging method, a contact charging method using a charging roller, or a non-contact charging method using a charging device disposed in proximity to the electrophotographic photosensitive member. The process cartridge according to claim 11 , wherein the process cartridge is performed by a method.

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