JP2004004454A - Organic photoreceptor, method and apparatus for image formation, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoreceptor improved in toner transfer property and residual toner cleaning performance, and also improved in flaw resistance and image characteristics, and to provide a method and an apparatus for image formation and a process cartridge which use the organic photoreceptor. <P>SOLUTION: The organic photoreceptor has at least a photosensitive layer provided on a conductive base; the creep rate (creep rate when a Vicker's indenter is pressed in with a load of 20 mN) of the organic photoreceptor is 1 to 3.5 % and the surface roughness Ra is 0.02 to 0.1 μm. <P>COPYRIGHT: (C)2004,JPO

Description

【００３２】
一方、疎水性微粒子としては、数平均一次粒径が１０ｎｍ以上１００ｎｍ未満の疎水性無機粒子が好ましく、数平均粒径は１０ｎｍ以上９０ｎｍ以下がより好ましく、最も好ましくは１０ｎｍ以上５０ｎｍ未満である。もちろん該電荷輸送層には、この他の構成成分として、電荷輸送物質を含有している。表面層に含有される無機粒子の数平均一次粒子径が１０ｎｍ未満では感光体表面に微細な凹凸が形成されず、上記トナーの転写性、クリーニング性の改善効果が小さく、１００ｎｍ以上の無機粒子では、クリーニングブレードの摩耗が増大し、クリーニング性が低下しやすい。
【００３３】
この表面層となる電荷輸送層に前記した共重合ポリカーボネートと数平均粒径が１０ｎｍ以上１００ｎｍ未満の疎水性の無機粒子を混在させた表面層はこれらの量比を最適化することにより、前記したクリープ率が１％以上３．５％未満であり、且つ表面粗さＲａが０．０２μｍ以上０．１μｍ未満の膜物性を得ることができる。
【００３４】
本発明のクリープ率は１％以上３．５％未満であるが、２．０％以上３．２％以下がより好ましい。又表面粗さＲａは０．０２μｍ以上０．１μｍ未満であるが、０．０３μｍ以上０．０８５μｍ以下が好ましい。
【００３５】
本発明に用いられる１０ｎｍ以上１００ｎｍ未満の無機粒子としては、シリカ、酸化亜鉛、酸化チタン、酸化スズ、酸化アンチモン、酸化インジウム、酸化ビスマス、スズをドープした酸化インジウム、アンチモンやタンタルをドープした酸化スズ、酸化ジルコニウム等の微粒子を好ましく用いることができが、これらの中でもコスト、粒径の調整や表面処理の容易さ等からシリカ、特に表面を疎水化した疎水性シリカが好ましい。
【００３６】
本発明の無機粒子の数平均一次粒径は、透過型電子顕微鏡観察によって１００００倍に拡大し、ランダムに３００個の粒子を一次粒子として観察し、画像解析によりフェレ径の数平均径として測定値を算出する。
【００３７】
上記疎水性シリカの疎水化度は、メタノールに対する濡れ性の尺度（メタノールウェッタビリティ）で示される疎水化度で５０％以上のものが好ましい。疎水化度が５０％未満であると前記吸熱エネルギー変化量ΔＨが、１０Ｊ／ｇより大きくなりやすく、その結果、環境メモリを発生しやすくなり、又ブレードを傷つけクリーニング不良も発生しやすくなる。より好ましい疎水化度は６５％以上、最も好ましくは７０％以上である。
【００３８】
疎水化度を表すメタノールウェッタビリティとは、メタノールに対するシリカ微粉末の濡れ性を評価するものである。濡れ性の測定は以下の方法で行う。内容量２５０ｍｌのビーカーに入れた蒸留水５０ｍｌに、測定対象のシリカ微粉末を０．２ｇ添加して撹拌する。次にメタノールを先端が液体中に浸漬されているビュレットからゆっくり撹拌した状態でシリカ微粉末の全体が濡れるまでゆっくり滴下する。このシリカ微粉末を完全に濡らすために必要なメタノールの量をａ（ｍｌ）とした時、下記式（１）により疎水化度を算出する。
【００３９】
式（１）　　　疎水化度＝ａ／（ａ＋５０）×１００
上記疎水性シリカは、公知の湿式法もしくは乾式法で生成されたシリカ粉末をを疎水化することにより得られる。特に乾式法（ケイ素化ハロゲン化合物の蒸気相酸化）により生成されたいわゆるヒュームドシリカと称されるものを疎水化剤で処理したものが、水分吸着サイトが少なく好ましい。これは従来公知の技術によって製造されるものである。例えば四塩化ケイ素ガスの酸水素焔中における熱分解酸化反応を利用するもので、基礎となる反応式は次のようなものである。
【００４０】
ＳｉＣｌ_４＋２Ｈ_２＋Ｏ_２→ＳｉＯ_２＋４ＨＣｌ
又、この製造工程において例えば、塩化アルミニウム又は、塩化チタンなど他の金属ハロゲン化合物をケイ素ハロゲン化合物と共に用いることによってシリカと他の金属酸化物の複合微粉体を得ることも可能である。
【００４１】
シリカ粉末の疎水化処理は、シリカ微粉末を撹拌等によりクラウド状に分散させたものに、アルコール等で溶解した疎水化処理剤溶液を噴霧するか或いは気化した疎水化処理剤を接触させて付着させる乾式処理、又は、シリカ粉末を溶液中に分散させ、その中に疎水化処理剤を滴下して付着させる湿式処理等の従来公知の方法で行うことが出来る。
【００４２】
疎水化処理剤としては、公知の化合物を用いることが出来、具体例を下記に挙げる。又、これらの化合物は組み合わせて使用しても良い。
【００４３】
チタンカップリング剤としてはテトラブチルチタネート、テトラオクチルチタネート、イソプロピルトリイソステアロイルチタネート、イソプロピルトリデシルベンゼンスルフォニルチタネート及びビス（ジオクチルパイロフォスフェート）オキシアセテートチタネート等が挙げられる。
【００４４】
シランカップリング剤としてはγ−（２−アミノエチル）アミノプロピルトリメトキシシラン、γ−（２−アミノエチル）アミノプロピルメチルジメトキシシラン、γ−メタクリロキシプロピルトリメトキシシラン、Ｎ−β−ビニルベンジルアミノエチル−Ｎ−γ−アミノプロピルトリメトキシシラン塩酸塩、ヘキサメチルジシラザン、メチルトリメトキシシラン、ブチルトリメトキシシラン、イソブチルトリメトキシシラン、ヘキシルトリメトキシシラン、オクチルトリメトキシシラン、デシルトリメトキシシラン、ドデシルトリメトキシシラン、フェニルトリメトキシシラン、ｏ−メチルフェニルトリメトキシシラン及びｐ−メチルフェニルトリメトキシシラン等が挙げられる。
【００４５】
シリコーンオイルとしてはジメチルシリコーンオイル、メチルフェニルシリコーンオイル及びアミノ変性シリコーンオイル等が挙げられる。
【００４６】
これらの疎水化処理剤は、シリカ粉末に対して１〜４０質量％添加して被覆することが好ましく、３〜３０質量％がより好ましい。
【００４７】
又、上記表面疎水化剤としてハイドロジェンポリシロキサン化合物を用いてもよい。該ハイドロジェンポリシロキサン化合物の分子量は１０００〜２００００のものが一般に入手しやすく、又、黒ポチ発生防止機能も良好である。特にメチルハイドロジェンポリシロキサンを最後の表面処理に用いると良好な効果が得られる。
【００４８】
本発明では上記疎水化処理された疎水性シリカを有機感光体の表面層にバインダーと共に含有させるが表面層のシリカ粒子の割合はバインダーに対して１〜２０質量％、好ましくは２〜１５質量％、最も好ましくは２〜１０質量％で使用されるのがよい。２０質量％以上だと、感光体の吸熱エネルギー変化量ΔＨを１０Ｊ／ｇ以下にするのが難しくなり、環境メモリやトナーの転写性を低下させやすい。一方、１質量％未満だとクリーニング不良や、耐摩耗性の低下を起こしやすい。
【００４９】
又、表面層となる電荷輸送層には、上記共重合ポリカーボネートのバインダー樹脂と疎水性無機粒子以外に、電荷輸送物質や酸化防止剤が含有されることが好ましい。該電荷輸送物質はバインダー樹脂に対して５０〜１５０質量％、酸化防水剤は同様に１〜１０質量％存在させることが好ましい。
【００５０】
以上のような構成を選択採用することにより、前記した表面層の膜物性と表面粗さを実現させることができ、このような表面層を有する有機感光体は残留トナークリーニング性を改善すると同時に、耐傷性、耐摩耗性を改善し、長期に亘り鮮鋭性が良好な電子写真画像を提供することができる。
【００５１】
以下、表面層以外の本発明に適用される有機感光体の構成について記載する。本発明において、有機感光体とは電子写真感光体の構成に必要不可欠な電荷発生機能及び電荷輸送機能の少なくとも一方の機能を有機化合物に持たせて構成された電子写真感光体を意味し、公知の有機電荷発生物質又は有機電荷輸送物質から構成された感光体、電荷発生機能と電荷輸送機能を高分子錯体で構成した感光体等公知の有機電子写真感光体を全て含有する。
【００５２】
本発明の有機感光体の層構成は、基本的には導電性支持体上に電荷発生層、電荷輸送層、或いは電荷発生・電荷輸送層（電荷発生と電荷輸送の機能を同一層に有する層）等の感光層から構成され、その上に本発明の膜特性を有する表面層を塗設した構成でもよいが、最も好ましい構成としては、感光層を電荷発生層と複数の電荷輸送層で構成し、最上層の電荷輸送層を本発明の表面層とした構成である。
【００５３】
以下に本発明に用いられる具体的な感光体の構成について記載する。
導電性支持体
本発明の感光体に用いられる導電性支持体としてはシート状或いは円筒状の導電性支持体が用いられる。
【００５４】
本発明の円筒状の導電性支持体とは回転することによりエンドレスに画像を形成できるに必要な円筒状の支持体を意味し、真直度で０．１ｍｍ以下、振れ０．１ｍｍ以下の範囲にある導電性の支持体が好ましい。この真直度及び振れの範囲を超えると、良好な画像形成が困難になる。
【００５５】
導電性支持体の材料としてはアルミニウム、ニッケルなどの金属ドラム、又はアルミニウム、酸化錫、酸化インジュウムなどを蒸着したプラスチックドラム、又は導電性物質を塗布した紙・プラスチックドラムを使用することができる。導電性支持体としては常温で比抵抗１０^３Ωｃｍ以下が好ましい。
【００５６】
本発明で用いられる導電性支持体は、その表面に封孔処理されたアルマイト膜が形成されたものを用いても良い。アルマイト処理は、通常例えばクロム酸、硫酸、シュウ酸、リン酸、硼酸、スルファミン酸等の酸性浴中で行われるが、硫酸中での陽極酸化処理が最も好ましい結果を与える。硫酸中での陽極酸化処理の場合、硫酸濃度は１００〜２００ｇ／ｌ、アルミニウムイオン濃度は１〜１０ｇ／ｌ、液温は２０℃前後、印加電圧は約２０Ｖで行うのが好ましいが、これに限定されるものではない。又、陽極酸化被膜の平均膜厚は、通常２０μｍ以下、特に１０μｍ以下が好ましい。
【００５７】
中間層
本発明においては導電性支持体と感光層の間に、バリヤー機能を備えた前記した中間層を設けることが好ましい。
【００５８】
本発明の中間層には前記した吸水率が小さいバインダー樹脂中に酸化チタンを含有させることが好ましい。該酸化チタン粒子の平均粒径は、数平均一次粒径で１０ｎｍ以上４００ｎｍ以下の範囲が良く、１５ｎｍ〜２００ｎｍが好ましい。１０ｎｍ未満では中間層によるモアレ発生の防止効果が小さい。一方、４００ｎｍより大きいと、中間層塗布液の酸化チタン粒子の沈降が発生しやすく、その結果中間層中の酸化チタン粒子の均一分散性が悪く、又黒ポチも増加しやすい。数平均一次粒径が前記範囲の酸化チタン粒子を用いた中間層塗布液は分散安定性が良好で、且つこのような塗布液から形成された中間層は黒ポチ発生防止機能の他、環境特性が良好で、且つ耐クラッキング性を有する。
【００５９】
本発明に用いられる酸化チタン粒子の形状は、樹枝状、針状および粒状等の形状があり、このような形状の酸化チタン粒子は、例えば酸化チタン粒子では、結晶型としては、アナターゼ型、ルチル型及びアモルファス型等があるが、いずれの結晶型のものを用いてもよく、また２種以上の結晶型を混合して用いてもよい。その中でもルチル型で且つ粒状のものが最も良い。
【００６０】
本発明の酸化チタン粒子は表面処理されていることが好ましく、表面処理の１つは、複数回の表面処理を行い、かつ該複数回の表面処理の中で、最後の表面処理が反応性有機ケイ素化合物を用いた表面処理を行うものである。また、該複数回の表面処理の中で、少なくとも１回の表面処理がアルミナ、シリカ、及びジルコニアから選ばれる少なくとも１種類以上の表面処理を行い、最後に反応性有機ケイ素化合物を用いた表面処理を行うことが好ましい。
【００６１】
尚、アルミナ処理、シリカ処理、ジルコニア処理とは酸化チタン粒子表面にアルミナ、シリカ、或いはジルコニアを析出させる処理を云い、これらの表面に析出したアルミナ、シリカ、ジルコニアにはアルミナ、シリカ、ジルコニアの水和物も含まれる。又、反応性有機ケイ素化合物の表面処理とは、処理液に反応性有機ケイ素化合物を用いることを意味する。
【００６２】
この様に、酸化チタン粒子の様な酸化チタン粒子の表面処理を少なくとも２回以上行うことにより、酸化チタン粒子表面が均一に表面被覆（処理）され、該表面処理された酸化チタン粒子を中間層に用いると、中間層内における酸化チタン粒子等の酸化チタン粒子の分散性が良好で、かつ黒ポチ等の画像欠陥を発生させない良好な感光体を得ることができるのである。
【００６３】
上記反応性有機ケイ素化合物としては下記一般式（１）で表される化合物が挙げられるが、酸化チタン表面の水酸基等の反応性基と縮合反応をする化合物であれば、下記化合物に限定されない。
【００６４】
一般式（１）
（Ｒ）_ｎ−Ｓｉ−（Ｘ）_４−ｎ
（式中、Ｓｉはケイ素原子、Ｒは該ケイ素原子に炭素が直接結合した形の有機基を表し、Ｘは加水分解性基を表し、ｎは０〜３の整数を表す。）
一般式（１）で表される有機ケイ素化合物において、Ｒで示されるケイ素に炭素が直接結合した形の有機基としては、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、オクチル、ドデシル等のアルキル基、フェニル、トリル、ナフチル、ビフェニル等のアリール基、γ−グリシドキシプロピル、β−（３，４−エポキシシクロヘキシル）エチル等の含エポキシ基、γ−アクリロキシプロピル、γ−メタアクリロキシプロピルの含（メタ）アクリロイル基、γ−ヒドロキシプロピル、２，３−ジヒドロキシプロピルオキシプロピル等の含水酸基、ビニル、プロペニル等の含ビニル基、γ−メルカプトプロピル等の含メルカプト基、γ−アミノプロピル、Ｎ−β（アミノエチル）−γ−アミノプロピル等の含アミノ基、γ−クロロプロピル、１，１，１−トリフロオロプロピル、ノナフルオロヘキシル、パーフルオロオクチルエチル等の含ハロゲン基、その他ニトロ、シアノ置換アルキル基を挙げられる。また、Ｘの加水分解性基としてはメトキシ、エトキシ等のアルコキシ基、ハロゲン基、アシルオキシ基が挙げられる。
【００６５】
また、一般式（１）で表される有機ケイ素化合物は、単独でも良いし、２種以上組み合わせて使用しても良い。
【００６６】
また、一般式（１）で表される有機ケイ素化合物の具体的化合物で、ｎが２以上の場合、複数のＲは同一でも異なっていても良い。同様に、ｎが２以下の場合、複数のＸは同一でも異なっていても良い。又、一般式（１）で表される有機ケイ素化合物を２種以上を用いるとき、Ｒ及びＸはそれぞれの化合物間で同一でも良く、異なっていても良い。
【００６７】
又、表面処理に用いる好ましい反応性有機ケイ素化合物としてはポリシロキサン化合物が挙げられる。該ポリシロキサン化合物の分子量は１０００〜２００００のものが一般に入手しやすく、又、黒ポチ発生防止機能も良好である。
【００６８】
特にメチルハイドロジェンポリシロキサンを最後の表面処理に用いると良好な効果が得られる。
【００６９】
感光層
電荷発生層
電荷発生層には電荷発生物質（ＣＧＭ）を含有する。その他の物質としては必要によりバインダー樹脂、その他添加剤を含有しても良い。
【００７０】
本発明の有機感光体には、電荷発生物質として、例えば、他のフタロシアニン顔料、アゾ顔料、ペリレン顔料、アズレニウム顔料などを単独で或いは併用して用いることができる。
【００７１】
電荷発生層にＣＧＭの分散媒としてバインダーを用いる場合、バインダーとしては公知の樹脂を用いることができるが、最も好ましい樹脂としてはホルマール樹脂、ブチラール樹脂、シリコーン樹脂、シリコーン変性ブチラール樹脂、フェノキシ樹脂等が挙げられる。バインダー樹脂と電荷発生物質との割合は、バインダー樹脂１００質量部に対し２０〜６００質量部が好ましい。これらの樹脂を用いることにより、繰り返し使用に伴う残留電位増加を最も小さくできる。電荷発生層の膜厚は０．１μｍ〜２μｍが好ましい。
【００７２】
電荷輸送層
本発明の電荷輸送層は複数の電荷輸送層の構成を有する。最上層の電荷輸送層については前記したが、最上層以外の電荷輸送層は公知の電荷輸送層の構成を採用することができる。
【００７３】
電荷輸送層には電荷輸送物質（ＣＴＭ）及びＣＴＭを分散し製膜するバインダー樹脂を含有する。その他の物質としては必要により酸化防止剤等の添加剤を含有しても良い。
【００７４】
電荷輸送物質（ＣＴＭ）としては公知の電荷輸送物質（ＣＴＭ）を用いることができる。例えばトリフェニルアミン誘導体、ヒドラゾン化合物、スチリル化合物、ベンジジン化合物、ブタジエン化合物などを用いることができる。これら電荷輸送物質は通常、適当なバインダー樹脂中に溶解して層形成が行われる。これらの中で繰り返し使用に伴う残留電位増加を最も小さくできるＣＴＭは高移動度で、且つ組み合わされるＣＧＭとのイオン化ポテンシャル差が０．５（ｅＶ）以下の特性を有するものであり、好ましくは０．３０（ｅＶ）以下である。
【００７５】
ＣＧＭ、ＣＴＭのイオン化ポテンシャルは表面分析装置ＡＣ−１（理研計器社製）で測定される。
【００７６】
電荷輸送層（ＣＴＬ）に用いられるバインダー樹脂としては熱可塑性樹脂、熱硬化性樹脂いずれの樹脂かを問わない。例えばポリスチレン、アクリル樹脂、メタクリル樹脂、塩化ビニル樹脂、酢酸ビニル樹脂、ポリビニルブチラール樹脂、エポキシ樹脂、ポリウレタン樹脂、フェノール樹脂、ポリエステル樹脂、アルキッド樹脂、ポリカーボネート樹脂、シリコーン樹脂、メラミン樹脂並びに、これらの樹脂の繰り返し単位構造のうちの２つ以上を含む共重合体樹脂。又これらの絶縁性樹脂の他、ポリ−Ｎ−ビニルカルバゾール等の高分子有機半導体が挙げられる。これらの中で吸水率が小さく、ＣＴＭの分散性、電子写真特性が良好なポリカーボネート樹脂が最も好ましい。
【００７７】
バインダー樹脂と電荷輸送物質との割合は、バインダー樹脂１００質量部に対し５０〜２００質量部が好ましい。
【００７８】
又、複数の電荷輸送層の膜厚の合計は１０〜５０μｍが好ましい。膜厚が１０μｍ未満だと帯電電位が不十分になりやすく、５０μｍを超えると、鮮鋭性が劣化しやすい。
【００７９】
中間層、電荷発生層、電荷輸送層等の層形成に用いられる溶媒又は分散媒としては、ｎ−ブチルアミン、ジエチルアミン、エチレンジアミン、イソプロパノールアミン、トリエタノールアミン、トリエチレンジアミン、Ｎ，Ｎ−ジメチルホルムアミド、アセトン、メチルエチルケトン、メチルイソプロピルケトン、シクロヘキサノン、ベンゼン、トルエン、キシレン、クロロホルム、ジクロロメタン、１，２−ジクロロエタン、１，２−ジクロロプロパン、１，１，２−トリクロロエタン、１，１，１−トリクロロエタン、トリクロロエチレン、テトラクロロエタン、テトラヒドロフラン、ジオキソラン、ジオキサン、メタノール、エタノール、ブタノール、イソプロパノール、酢酸エチル、酢酸ブチル、ジメチルスルホキシド、メチルセロソルブ等が挙げられる。本発明はこれらに限定されるものではないが、ジクロロメタン、１，２−ジクロロエタン、メチルエチルケトン等が好ましく用いられる。また、これらの溶媒は単独或いは２種以上の混合溶媒として用いることもできる。
【００８０】
次に有機感光体を製造するための塗布加工方法としては、浸漬塗布、スプレー塗布、円形量規制型塗布等の塗布加工法が用いられるが、感光層の上層側の塗布加工は下層の膜を極力溶解させないため、又、均一塗布加工を達成するためスプレー塗布又は円形量規制型（円形スライドホッパ型がその代表例）塗布等の塗布加工方法を用いるのが好ましい。なお保護層は前記円形量規制型塗布加工方法を用いるのが最も好ましい。前記円形量規制型塗布については例えば特開昭５８−１８９０６１号公報に詳細に記載されている。
【００８１】
次に、本発明の有機感光体を用いた画像形成装置について説明する。
図１に示す画像形成装置１は、デジタル方式による画像形成装置であって、画像読取り部Ａ、画像処理部Ｂ、画像形成部Ｃ、転写紙搬送手段としての転写紙搬送部Ｄから構成されている。
【００８２】
画像読取り部Ａの上部には原稿を自動搬送する自動原稿送り手段が設けられていて、原稿載置台１１上に載置された原稿は原稿搬送ローラ１２によって１枚宛分離搬送され読み取り位置１３ａにて画像の読み取りが行われる。原稿読み取りが終了した原稿は原稿搬送ローラ１２によって原稿排紙皿１４上に排出される。
【００８３】
一方、プラテンガラス１３上に置かれた場合の原稿の画像は走査光学系を構成する照明ランプ及び第１ミラーから成る第１ミラーユニット１５の速度ｖによる読み取り動作と、Ｖ字状に位置した第２ミラー及び第３ミラーから成る第２ミラーユニット１６の同方向への速度ｖ／２による移動によって読み取られる。
【００８４】
読み取られた画像は、投影レンズ１７を通してラインセンサである撮像素子ＣＣＤの受光面に結像される。撮像素子ＣＣＤ上に結像されたライン状の光学像は順次電気信号（輝度信号）に光電変換されたのちＡ／Ｄ変換を行い、画像処理部Ｂにおいて濃度変換、フィルタ処理などの処理が施された後、画像データは一旦メモリに記憶される。
【００８５】
画像形成部Ｃでは、画像形成ユニットとして、像担持体であるドラム状の感光体２１と、その外周に、該感光体２１を帯電させる帯電手段２２、帯電した感光体の表面電位を検出する電位検出手段２２０、現像手段２３、転写手段である転写搬送ベルト装置４５、前記感光体２１のクリーニング装置２６及び光除電手段としてのＰＣＬ（プレチャージランプ）２７が各々動作順に配置されている。また、現像手段２３の下流側には感光体２１上に現像されたパッチ像の反射濃度を測定する反射濃度検出手段２２２が設けられている。感光体２１は、光導電性化合物をドラム基体上に塗布形成したもので、例えば有機感光体２１Ａ（ＯＰＣと略称される）や更にはハードコートしたＨＣ有機感光体２１Ｂが好ましく使用され、図示の時計方向に駆動回転される。
【００８６】
回転する感光体２１へは帯電手段２２による一様帯電がなされた後、像露光手段としての露光光学系３０により画像処理部Ｂのメモリから呼び出された画像信号に基づいた像露光が行われる。書き込み手段である像露光手段としての露光光学系３０は図示しないレーザダイオードを発光光源とし、回転するポリゴンミラー３１、ｆθレンズ３４、シリンドリカルレンズ３５を経て反射ミラー３２により光路が曲げられ主走査がなされるもので、感光体２１に対してＡｏの位置において像露光が行われ、感光体２１の回転（副走査）によって潜像が形成される。本実施の形態の一例では文字部に対して露光を行い潜像を形成する。
【００８７】
感光体２１上の潜像は現像手段２３によって反転現像が行われ、感光体２１の表面に可視像のトナー像が形成される。転写紙搬送部Ｄでは、画像形成ユニットの下方に異なるサイズの転写紙Ｐが収納された転写紙収納手段としての給紙ユニット４１（Ａ）、４１（Ｂ）、４１（Ｃ）が設けられ、また側方には手差し給紙を行う手差し給紙ユニット４２が設けられていて、それらの何れかから選択された転写紙Ｐは案内ローラ４３によって搬送路４０に沿って給紙され、給紙される転写紙Ｐの傾きと偏りの修正を行うレジストローラ対４４によって転写紙Ｐは一時停止を行ったのち再給紙が行われ、搬送路４０、転写前ローラ４３ａ、給紙経路４６及び進入ガイド板４７に案内され、感光体２１上のトナー画像が転写位置Ｂｏにおいて転写極２４及び分離極２５によって転写搬送ベルト装置４５の転写搬送ベルト４５４に載置搬送されながら転写紙Ｐに転写され、該転写紙Ｐは感光体２１面より分離し、転写搬送ベルト装置４５により定着手段５０に搬送される。
【００８８】
定着手段５０は定着ローラ５１と加圧ローラ５２とを有しており、転写紙Ｐを定着ローラ５１と加圧ローラ５２との間を通過させることにより、加熱、加圧によってトナーを定着させる。トナー画像の定着を終えた転写紙Ｐは排紙トレイ６４上に排出される。
【００８９】
以上は転写紙の片側への画像形成を行う状態を説明したものであるが、両面複写の場合は排紙切換部材１７０が切り替わり、転写紙案内部１７７が開放され、転写紙Ｐは破線矢印の方向に搬送される。
【００９０】
更に、搬送機構１７８により転写紙Ｐは下方に搬送され、転写紙反転部１７９によりスイッチバックさせられ、転写紙Ｐの後端部は先端部となって両面複写用給紙ユニット１３０内に搬送される。
【００９１】
転写紙Ｐは両面複写用給紙ユニット１３０に設けられた搬送ガイド１３１を給紙方向に移動し、給紙ローラ１３２で転写紙Ｐを再給紙し、転写紙Ｐを搬送路４０に案内する。
【００９２】
再び、上述したように感光体２１方向に転写紙Ｐを搬送し、転写紙Ｐの裏面にトナー画像を転写し、定着手段５０で定着した後、排紙トレイ６４に排紙する。
【００９３】
図２は分離爪ユニットの平面図、その側面図である図３、更には図４の分離爪の側面図に示すように、有機感光体上への分離爪２５２の当接荷重を切り換えることで、コピー初期の爪傷を低減し、黒スジ発生を防止するようにした。
【００９４】
しかし、爪傷低減のために分離爪２５２の当接荷重を低くしすぎると転写紙Ｐを有機感光体２１から分離できなくなってＪＡＭが発生するので、当接荷重は好適な範囲に設定する必要がある。
【００９５】
次に、分離爪２５２の有機感光体２１に対する当接荷重を適切に切り換える当接荷重切換手段２６０について説明する。
【００９６】
当接荷重切換手段２６０は分離爪２５２と、それを付勢するトルクバネ２５５と、分離爪２５２を有機感光体２１に当接してその当接荷重を調節したり解除したりする当接解除板２６１と、それを取り付けたシャフト２６２に直結したロータリ式の直流ソレノイド２６５から構成されている。
【００９７】
そして、分離爪２５２はその回動軸２５３を軸受２５４に枢支されてトルクバネ２５５で付勢されており、ロータリ式の直流ソレノイド２６５の通電が切られ、該直流ソレノイド２６５に直結して軸受２６４に回転可能に枢支されているシャフト２６２がバネ力によって戻されて回動すると、該シャフト２６２に取り付けられた当接解除板２６１が下がって分離爪２５２が有機感光体２１の表面に当接し、シャフト２６２が通電されて元の位置に戻ると当接解除板２６１が上がって分離爪２５２の当接を離し当接は解除される。
【００９８】
また、直流ソレノイド２６５に印加する電圧を切り換えて当接解除板２６１と分離爪２５２との間の接触圧を変更することで、分離爪２５２と有機感光体２１との間の当接荷重を減殺して切り換えることができる。
【００９９】
前述のように、当接荷重切換手段２６０における分離爪２５２の有機感光体２１への当接荷重の切り換え動作は、直流ソレノイド２６５に印加する電圧を切り換えて行われる。即ち、直流ソレノイド２６５の印加電圧値により、当接解除板２６１が分離爪２５２に当てる位置で該分離爪２５２に掛ける接触圧が、トルクバネ２５５による分離爪２５２の付勢力を減殺させ、有機感光体２１に対する分離爪２５２の当接荷重を適正な所定値に調節して切り換え可能になる。
【０１００】
尚、前記分離爪２５２と前記有機感光体２１の表面との間の当接荷重は、０．９８〜７．８４ｍＮの範囲の中から選定されて適正な調節値に設定されるのが好ましい。
【０１０１】
一方、固定基板２７１に取り付けられたステッピングモータ２７２が同じく前記固定基板２７１に取り付けられた歯車２７３，２７４，２７５，２７６を介して分離爪ユニット２５０の基板２５１に取り付けられたラック歯車２６７に噛み合い、基板２５１は固定基板２７１のガイド２７１Ａに沿って左右５ｍｍ程度の範囲内で任意の設定位置に移動して停止できるようにしてある。このようにして分離爪２５２と有機感光体２１との当接位置は幅方向に変えられるようにし、長期間幅方向が同じ状態で当接することを避けることが好ましい。
【０１０２】
本発明の有機感光体は電子写真複写機、レーザプリンター、ＬＥＤプリンター及び液晶シャッター式プリンター等の電子写真装置一般に適応するが、更に、電子写真技術を応用したディスプレー、記録、軽印刷、製版及びファクシミリ等の装置にも幅広く適用することができる。
【０１０３】
【実施例】
以下、実施例をあげて本発明を詳細に説明するが、本発明の様態はこれに限定されない。尚、下記文中「部」とは「質量部」を表す。
【０１０４】
感光体１の作製
下記の様に感光体１を作製した。
【０１０５】
直径１００ｍｍφ、長さ３４６ｍｍの円筒形アルミニウム支持体の表面を切削加工し、表面粗さＲｚ＝１．５（μｍ）の導電性支持体を用意した。
〈中間層〉
下記中間層分散液を同じ混合溶媒にて二倍に希釈し、一夜静置後に濾過（フィルター；日本ポール社製リジメッシュ５μｍフィルター）し、中間層塗布液を作製した。
【０１０６】

分散機としてサンドミルを用いて、バッチ式で１０時間の分散を行った。
【０１０７】
上記塗布液を用いて前記支持体上に、乾燥膜厚２μｍとなるよう塗布した。

を混合し、サンドミルを用いて１０時間分散し、電荷発生層塗布液を調製した。この塗布液を前記中間層の上に浸漬塗布法で塗布し、乾燥膜厚０．３μｍの電荷発生層を形成した。
【０１０８】

を混合し、溶解して電荷輸送層塗布液を調製した。この塗布液を前記電荷発生層の上に浸漬塗布法で乾燥膜厚２０μｍの電荷輸送層を形成した。
【０１０９】

を混合し、超音波を照射できる循環分散装置にて循環分散を行い、表面層塗布液を調製した。この塗布液を前記電荷輸送層の上に円型量規制型塗布法により乾燥膜厚５μｍになるように塗布し、１１０℃で７０分間の乾燥を行い、感光体１を作製した。
【０１１０】
感光体２〜１５の作製
感光体１において第二電荷輸送層のポリカーボネート及び疎水性シリカを表１のように変化させた他は感光体１と同様にして感光体２〜１５を作製した。
【０１１１】
【表１】

【０１１２】
表中、ＰＣ−４は下記構造のポリカーボネートを示す。
【０１１３】
【化２】

【０１１４】
評価
１．表面粗さＲａ
Ｒａは粗さ曲線からその平均線の方向に基準長さだけ抜き取り、この抜き取り部分の平均線の方向にＸ軸を、縦倍率の方向にＹ軸を取り、粗さ曲線をｙ＝ｆ（ｘ）で表したときに、次の式によって求められ値をマイクロメートル（μｍ）で表したものをいう。
【０１１５】
Ｒａ＝１／ｌ∫_０ ^ｌ｜ｆ（ｘ）｜ｄｘ
ｌは基準長さ
本発明ではｌが２．５ｍｍ、カットオフ値は０．０８ｍｍとする。
【０１１６】
測定機は表面粗さ計（小坂研究所社製　Ｓｕｒｆｃｏｒｄｅｒ　ＳＥ−３０Ｈ）で測定した。但し、誤差範囲内で同一の結果を生じる測定器であれば、他の測定器を用いても良い。
【０１１７】
表面粗さの測定条件
測定速度（Ｄｒｉｖｅ　ｓｐｅｅｄ：０．１ｍｍ／秒）
測定針直径（Ｓｔｙｌｕｓ：２μｍ）
２．クリープ率の測定
使用機器：フィッシャースコープＨ１００Ｖ（微小硬さ測定装置）フィッシャー・インストルメンツ社製
使用圧子：ダイアモンド　ビッカース圧子
負荷条件：４ｍＮ／ｓｅｃの速度で有機感光体の表面からビッカース圧子を押し込む
負荷時間：５ｓｅｃ
保持時間：５ｓｅｃ
除荷条件：負荷と同じ速度で負荷を除く
測定試料
アルミ平板上に前記した感光体と同様に中間層、電荷発生層、第一電荷輸送層、第二電荷輸送層を設け、同じ条件で乾燥させ作製した試料をＨ１００Ｖ機に固定し、試料に対して垂直にビッカース圧子を押し込み測定。
【０１１８】
測定は圧子負荷（５ｓｅｃ）、荷重保持（５ｓｅｃ：この間の変形量の割合がクリープ率）、除荷の手順で行う。
【０１１９】
クリープ率の求め方
ＣＨＵ（クリープ率）＝｛（ｈ２−ｈ１）／ｈ１｝×１００（％）
ｈ１：負荷荷重（２０ｍＮ）に達した時（負荷開始から５秒後）の押し込み深さ
ｈ２：保持（５ｓｅｃ）後の押し込み深さ
３．画像評価
評価機としてコニカ社製デジタル複写機Ｋｏｎｉｃａ７０７５（コロナ帯電、レーザ露光、反転現像、静電転写、爪分離、ブレードクリーニング、クリーニング補助ブラシローラー採用プロセスを有する）を用い、該複写機に感光体１〜１５を搭載し評価した。クリーニング性及び画像評価は、画素率が７％の文字画像、人物顔写真、ベタ白画像、ベタ黒画像がそれぞれ１／４等分にあるオリジナル画像をＡ４中性紙に複写して行った。複写条件は最も厳しいと思われる高温高湿環境（３０℃、８０％ＲＨ）にて連続２０万コピー行いハーフトーン、ベタ白画像、ベタ黒画像を評価した。
【０１２０】
評価項目及び評価基準
画像濃度（マクベス社製ＲＤ−９１８を使用して測定。紙の反射濃度を「０」とした相対反射濃度で測定した）
◎：１．２以上：良好
○：０．８以上：実用上問題ないレベル
×：０．８未満：実用上問題となるレベル
鮮鋭性（２０万枚コピー終了後に文字画像で鮮鋭性を評価）
３ポイント、５ポイントの文字画像を形成し、下記の判断基準で評価した。
【０１２１】
◎：３ポイント、５ポイントとも明瞭であり、容易に判読可能
○：３ポイントは一部判読不能、５ポイントは明瞭であり、容易に判読可能
×：３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能
トナーの転写性（２０万枚コピー終了後、感光体上に６０ｍｇ／ｃｍ^２の画像を形成し、転写紙に転写された単位面積当たりの付着量（ｆｍｇ／ｃｍ^２）を測定し、以下の計算により転写率を算定した。）
トナーの転写率＝（ｆ／６０）×１００
◎：トナーの転写率８５％以上：良好
○：トナーの転写率６５〜８４％以上：実用上問題ないレベル
×：トナーの転写率６４％以下：実用上問題となるレベル
クリーニング性（１０万及び２０万コピー終了後にＡ３紙に連続１０枚複写を行い、ベタ白部でのクリーニング不良の発生の有無で判定）
◎：２０万枚ですり抜け発生なし
○：１０万枚まですり抜け発生なし
×：１０万枚未満ですり抜け発生
耐傷性（２０万枚のコピー画像を全数検査し、分離爪による画像傷の発生の有無の確認、及び感光体表面の分離爪による傷の発生の有無をコピー１万枚毎に検査した。）
◎：感光体表面にもコピー画像にも分離爪による傷の発生なし
○：感光体表面には弱い傷発生があるが、コピー画像には分離爪による傷の発生なし
×：感光体表面にははっきりした傷発生があり、コピー画像にも分離爪による
傷の発生あり
その他評価条件
尚、上記７０７５を用いたその他の評価条件は下記の条件に設定した。
【０１２２】
帯電条件
帯電器；スコロトロン帯電器、初期帯電電位を−７５０Ｖ
露光条件
露光部電位を−５０Ｖにする露光量に設定。
【０１２３】
現像条件
ＤＣバイアス；−５５０Ｖ
現像剤は、フェライトをコアとして絶縁性樹脂をコーティングしたキャリアとスチレンアクリル系樹脂を主材料としてカーボンブラック等の着色剤と荷電制御剤と低分子量ポリオレフィンからなる重合法で作製した体積平均粒径７．３μｍの着色粒子に、シリカ、酸化チタンを外添したトナーの現像剤を使用した。
【０１２４】
転写条件
転写極；コロナ帯電方式
分離条件
図２〜図４で説明した分離爪ユニットの分離手段を用いた。
【０１２５】
分離爪の材質：ベースの材質がポリアミドイミド（ＰＡＩ）であり、それにポリテトラフルオロエチレン（ＰＴＦＥ）をコートしたもの
感光体への当接荷重：５．６ｍＮ
クリーニング条件
クリーニング部に硬度７０°、反発弾性６５％、厚さ２（ｍｍ）、自由長９ｍｍのクリーニングブレードをカウンター方向に線圧１８（ｇ／ｃｍ）となるように重り荷重方式で当接した。
【０１２６】
評価結果を表２に示した。
【０１２７】
【表２】

【０１２８】
クリープ率、表面粗さＲａ共本発明の範囲にある感光体１〜５及び１０〜１５は画像濃度、トナーの転写性、鮮鋭性、クリーニング性、耐傷性の各評価項目において、良好な特性を示しているが、本発明外の感光体６（クリープ率：３．６２）ではクリーニング性、耐傷性が劣り、感光体９（クリープ率：０．８２）では、画像濃度、鮮鋭性、クリーニング性が低下している。又、感光体７（表面粗さＲａ：０．２５μｍ）はクリーニング性が劣り、感光体８（表面粗さＲａ：０．００９μｍ）ではトナーの転写性、画像濃度が低下している。
【０１２９】
【発明の効果】
実施例からも明らかなように、本発明の構成を有する有機感光体を用いることにより、高温高湿下で、多数枚のコピーを行ってもトナーの転写性、残留トナークリーニング性を改善すると同時に、耐傷性を改善し、鮮鋭性の良好な電子写真画像を作製することができる。
【図面の簡単な説明】
【図１】本発明の画像形成装置の機能が組み込まれた概略図である。
【図２】分離爪ユニットの平面図である。
【図３】分離爪ユニットの側面図である。
【図４】分離爪の側面図である。
【符号の説明】
１　画像形成装置
２１　感光体
２１Ａ　有機感光体
２１Ｂ　ＨＣ有機感光体
２２　帯電手段
２３　現像手段
２４　転写極
２５　分離極
２６　クリーニング装置
３０　露光光学系
４５　転写搬送ベルト装置
５０　定着手段
２５０　分離爪ユニット
２５１　基板
２５２　分離爪
２５５　トルクバネ
２６０　当接荷重切換手段
２６１　当接解除板
２６２　シャフト
２６５　直流ソレノイド
２７１　固定基板
２７１Ａ　ガイド
２７２　ステッピングモータ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic photoreceptor used in the field of copying machines and printers, and an image forming method, an image forming apparatus, and a process cartridge using the organic photoreceptor.
[0002]
[Prior art]
In recent years, as an electrophotographic photosensitive member, an electrophotographic photosensitive member containing an organic photoconductive material is most widely used. Organic photoreceptors (hereinafter also referred to as photoreceptors) are easy to develop materials corresponding to various exposure light sources from visible light to infrared light, can select materials without environmental pollution, and have low manufacturing costs. Although it is an advantage to the photoconductor, it has a large adhesive force with the toner formed from the same organic substance, easily causes toner filming on the photoconductor, and has a low mechanical strength. This means that the photoreceptor surface is deteriorated or damaged during copying or printing.
[0003]
As a method for improving the cleaning properties of the residual toner on the organic photoreceptor and the abrasion resistance of the organic photoreceptor as described above, silica particles are contained in the outermost surface layer of the photoreceptor to increase the mechanical strength of the photoreceptor surface. It is reported that durability can be improved (Patent Documents 1, 2, and 3). Further, hydrophobic silica particles obtained by treating the silica particles with a silane coupling agent or the like are contained in the outermost surface layer of the photoreceptor, thereby increasing the mechanical strength of the photoreceptor and imparting lubricating properties to enhance the photoreceptor. It is reported that a durable photoreceptor can be obtained (Patent Documents 4, 5, and 6).
[0004]
Further, as a problem for improving the durability of the organic photoreceptor, it has been strongly demanded to suppress abrasion of a cleaning blade or the like due to abrasion. As an approach therefor, a technique of reducing the frictional force with a blade by including fine particles on the surface of the photoconductor has been studied. For example, it has been reported that an alkylsilsesquioxane resin fine particle is contained in a photosensitive layer (Patent Document 7).
[0005]
However, the addition of such submicron-order fine particles does not always improve the cleaning performance of the toner, but increases the surface roughness of the photoconductor and promotes chipping and wear of the edge of the cleaning blade. There is a problem that defects easily occur.
[0006]
For the chipping of the edge of the cleaning blade as described above, a method of adding inorganic particles such as hydrophobized silica particles to the surface layer of the photoreceptor, configuring the surface roughness in a specific range, and making cleaning easier. Proposed. For example, a patent has been disclosed in which the average surface roughness Ra of 5 μm square is set to 1.5 to 100 nm (Patent Document 8).
[0007]
However, in the organic photoreceptor, as an important durability inhibiting factor along with abrasion, susceptibility to scratches by sharp substances such as separation claws is cited. This is because not only the sharp particles such as talc contained in the material such as the developer and the transfer material, or the separation claw of the transfer material causes deep scratches on the surface of the photoreceptor, but also deteriorates the cleaning property, For example, at locations where the frequency of contact locally is high, such as the contact position of the separation claw, streaks appear in the halftone image.
[0008]
[Patent Document 1]
JP-A-56-117245
[0009]
[Patent Document 2]
JP-A-63-91666
[0010]
[Patent Document 3]
JP-A-1-205171
[0011]
[Patent Document 4]
JP-A-57-176057
[0012]
[Patent Document 5]
JP-A-61-117558
[0013]
[Patent Document 6]
JP-A-3-155558
[0014]
[Patent Document 7]
JP-A-5-181291
[0015]
[Patent Document 8]
JP 2001-265040 A
[0016]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned problems of the related art. That is, an object of the present invention is to improve the transferability of the toner on the photoconductor and the cleaning property of the residual toner, and at the same time, to improve the scratch resistance of the photoconductor, and to provide an organic photoconductor capable of producing an electrophotographic image having good sharpness. An object of the present invention is to provide an image forming method, an image forming apparatus, and a process cartridge using the organic photoreceptor.
[0017]
[Means for Solving the Problems]
The object of the present invention is achieved by having the following configuration.
[0018]
1. In an organic photoreceptor having at least a photosensitive layer provided on a conductive support, the organic photoreceptor has a creep rate (creep rate when a Vickers indenter is pushed in with a load of 20 mN) of 1% or more and less than 3.5%. And an organic photoreceptor having a surface roughness Ra of not less than 0.02 μm and less than 0.1 μm.
[0019]
2. An organic photoreceptor having a charge generation layer on a conductive support and a charge transport layer laminated thereon, wherein the charge transport layer is composed of a plurality of layers, one of which is a surface layer, and The creep rate of the body (creep rate when the Vickers indenter is pushed in with a load of 20 mN) is 1% or more and less than 3.5%, and the surface roughness Ra is 0.02 μm or more and less than 0.1 μm. Organic photoreceptor.
[0020]
3. 3. The organic photoreceptor according to the above item 2, wherein the surface layer is a layer containing inorganic particles having a number average particle diameter of 1 nm or more and less than 100 nm.
[0021]
4. 4. The organic photoreceptor according to the above item 3, wherein the inorganic particles are hydrophobic silica.
[0022]
5. 5. The organic photoconductor according to any one of items 2 to 4, wherein a binder of the surface layer is a copolymerized polycarbonate resin.
[0023]
6. 6. Using the organic photoreceptor according to any one of 1 to 5, forming an electrophotographic image through at least each of a charging step, an image exposure step, a development step, a transfer step, a separation step, and a cleaning step. An image forming method comprising:
[0024]
7. 7. An image forming apparatus for forming an electrophotographic image by using the image forming method according to the above item 6.
[0025]
8. 6. The organic photoreceptor according to any one of 1 to 5, wherein one of a charging device, an image exposure device, a developing device, and a cleaning device is integrally combined, and is freely inserted into and removed from the image forming apparatus. A process cartridge characterized by being designed.
[0026]
That is, the organic photoreceptor of the present invention has a creep rate (creep rate when a Vickers indenter is pushed in with a load of 20 mN) of the organic photoreceptor having at least a photosensitive layer provided on a conductive support. % Or more and less than 3.5%, and the surface roughness Ra is 0.02 μm or more and less than 0.1 μm.
[0027]
Further, the organic photoreceptor of the present invention is an organic photoreceptor having a charge generation layer on a conductive support and a charge transport layer laminated thereon, wherein the charge transport layer is composed of a plurality of layers. The upper layer is the surface layer of the organic photoreceptor, and the creep rate (creep rate when the Vickers indenter is pushed in with a load of 20 mN) of 1% or more to less than 3.5%, and the surface roughness Ra Is not less than 0.02 μm and less than 0.1 μm.
[0028]
The organic photoreceptor of the present invention having the above-described configuration improves toner transferability, residual toner cleaning properties, scratch resistance, and the like. Hereinafter, the present invention will be described in detail in embodiments.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
The organic photoreceptor of the present invention is configured by optimizing the viscoelastic properties from the surface of the photoreceptor, that is, a certain plastic deformation (1%) against a constant load indenter (20 mN load) applied from the photoreceptor surface. The above-described properties are imparted to the organic photoreceptor and the surface roughness Ra is set to 0.02 μm or more and less than 0.1 μm, thereby improving the transferability and the residual toner cleaning property of the toner as described above. At the same time, it is possible to form an electrophotographic image having improved scratch resistance and excellent sharpness and the like.
[0030]
A specific organic photoreceptor having a creep rate and a surface roughness Ra of the present invention includes a charge generation layer on a conductive support and a plurality of charge transport layers thereon. It is preferable that the surface layer is used, and the layer contains a highly elastic binder resin and hydrophobic inorganic fine particles. Examples of the binder resin having high elasticity include the following copolymerized polycarbonate.
[0031]
Embedded image

[0032]
On the other hand, the hydrophobic fine particles are preferably hydrophobic inorganic particles having a number average primary particle diameter of 10 nm or more and less than 100 nm, more preferably 10 nm or more and 90 nm or less, and most preferably 10 nm or more and less than 50 nm. Of course, the charge transport layer contains a charge transport substance as another component. If the number average primary particle diameter of the inorganic particles contained in the surface layer is less than 10 nm, fine irregularities are not formed on the surface of the photoreceptor, and the effect of improving the transferability and cleaning properties of the toner is small. As a result, the wear of the cleaning blade increases, and the cleaning property tends to decrease.
[0033]
The surface layer in which the above-mentioned copolymerized polycarbonate and the hydrophobic inorganic particles having a number average particle diameter of 10 nm or more and less than 100 nm are mixed in the charge transport layer serving as the surface layer is described above by optimizing the quantitative ratio thereof. A film property having a creep rate of 1% or more and less than 3.5% and a surface roughness Ra of 0.02 μm or more and less than 0.1 μm can be obtained.
[0034]
The creep rate of the present invention is 1% or more and less than 3.5%, but is more preferably 2.0% or more and 3.2% or less. The surface roughness Ra is not less than 0.02 μm and less than 0.1 μm, but preferably not less than 0.03 μm and not more than 0.085 μm.
[0035]
The inorganic particles having a size of 10 nm or more and less than 100 nm used in the present invention include silica, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony and tantalum-doped tin oxide. And fine particles such as zirconium oxide can be preferably used. Among them, silica, particularly hydrophobic silica whose surface is hydrophobized, is preferred from the viewpoints of cost, adjustment of particle size, ease of surface treatment, and the like.
[0036]
The number average primary particle size of the inorganic particles of the present invention is magnified 10,000 times by transmission electron microscopy, randomly observes 300 particles as primary particles, and measures the number average particle size of Feret diameter by image analysis. Is calculated.
[0037]
The hydrophobicity of the above-mentioned hydrophobic silica is preferably 50% or more in terms of the degree of hydrophobicity indicated by a measure of methanol wettability (methanol wettability). If the degree of hydrophobicity is less than 50%, the amount of change in endothermic energy ΔH tends to be larger than 10 J / g, and as a result, an environmental memory is easily generated, and the blade is damaged and cleaning failure is also easily generated. A more preferred degree of hydrophobicity is 65% or more, most preferably 70% or more.
[0038]
The methanol wettability representing the degree of hydrophobicity is to evaluate the wettability of the silica fine powder with methanol. The wettability is measured by the following method. 0.2 g of the silica fine powder to be measured is added to 50 ml of distilled water placed in a 250 ml beaker and stirred. Next, methanol is slowly added dropwise from a burette whose tip is immersed in the liquid until the whole silica fine powder is wet with stirring. Assuming that the amount of methanol necessary for completely wetting the silica fine powder is a (ml), the degree of hydrophobicity is calculated by the following equation (1).
[0039]
Formula (1) degree of hydrophobicity = a / (a + 50) × 100
The hydrophobic silica can be obtained by hydrophobizing silica powder produced by a known wet method or dry method. In particular, a so-called fumed silica produced by a dry method (vapor phase oxidation of a silicified halogen compound) treated with a hydrophobizing agent is preferable because it has few moisture adsorption sites. This is manufactured by a conventionally known technique. For example, it utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is as follows.
[0040]
SiCl₄+ 2H₂+ O₂→ SiO₂+4 HCl
In this production step, for example, a composite fine powder of silica and another metal oxide can be obtained by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide.
[0041]
Hydrophobization treatment of silica powder is performed by spraying a hydrophobizing agent solution dissolved with alcohol or the like on a silica fine powder dispersed in a cloud shape by stirring or by contacting a vaporized hydrophobizing agent. A conventionally known method such as a dry treatment in which a silica powder is dispersed in a solution and a wet treatment in which a hydrophobic treatment agent is dropped and adhered thereto is applied.
[0042]
Known compounds can be used as the hydrophobizing agent, and specific examples are shown below. These compounds may be used in combination.
[0043]
Examples of the titanium coupling agent include tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate and bis (dioctyl pyrophosphate) oxyacetate titanate.
[0044]
As the silane coupling agent, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-vinylbenzylamino Ethyl-N-γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyl Examples include trimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane.
[0045]
Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.
[0046]
These hydrophobizing agents are preferably coated by adding 1 to 40% by mass based on the silica powder, and more preferably 3 to 30% by mass.
[0047]
Further, a hydrogen polysiloxane compound may be used as the surface hydrophobizing agent. The hydrogen polysiloxane compound having a molecular weight of 1,000 to 20,000 is generally easily available and has a good black spot prevention function. In particular, when methyl hydrogen polysiloxane is used for the final surface treatment, a good effect can be obtained.
[0048]
In the present invention, the hydrophobic layer subjected to the hydrophobic treatment is contained in the surface layer of the organic photoreceptor together with the binder. The proportion of the silica particles in the surface layer is 1 to 20% by mass, preferably 2 to 15% by mass, based on the binder. , Most preferably from 2 to 10% by weight. If the amount is 20% by mass or more, it is difficult to reduce the amount of change in endothermic energy ΔH of the photoconductor to 10 J / g or less, and it is easy to reduce environmental memory and transferability of toner. On the other hand, if it is less than 1% by mass, poor cleaning and a decrease in wear resistance are likely to occur.
[0049]
The charge transport layer serving as the surface layer preferably contains a charge transport substance and an antioxidant, in addition to the binder resin of the copolymerized polycarbonate and the hydrophobic inorganic particles. It is preferable that the charge transporting substance is present in an amount of 50 to 150% by mass relative to the binder resin, and the oxidizing waterproofing agent is also present in an amount of 1 to 10% by mass.
[0050]
By selectively adopting the configuration as described above, the film physical properties and surface roughness of the surface layer can be realized, and the organic photoconductor having such a surface layer improves the residual toner cleaning property, An electrophotographic image having improved scratch resistance and abrasion resistance and excellent sharpness over a long period of time can be provided.
[0051]
Hereinafter, the configuration of the organic photoreceptor applied to the invention other than the surface layer will be described. In the present invention, the organic photoreceptor refers to an electrophotographic photoreceptor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function, which are indispensable for the configuration of the electrophotographic photoreceptor. And all known organic electrophotographic photoreceptors, such as a photoreceptor composed of an organic charge generating substance or an organic charge transporting substance, and a photoreceptor having a charge generating function and a charge transporting function formed of a polymer complex.
[0052]
The layer constitution of the organic photoreceptor of the present invention basically comprises a charge generation layer, a charge transport layer, or a charge generation / charge transport layer (a layer having the functions of charge generation and charge transport in the same layer) on a conductive support. And the like, and a surface layer having the film characteristics of the present invention may be applied thereon. However, the most preferable constitution is that the photosensitive layer comprises a charge generation layer and a plurality of charge transport layers. The uppermost charge transport layer is the surface layer of the present invention.
[0053]
Hereinafter, a specific configuration of the photoconductor used in the present invention will be described.
Conductive support
As the conductive support used in the photoreceptor of the present invention, a sheet-shaped or cylindrical conductive support is used.
[0054]
The cylindrical conductive support of the present invention means a cylindrical support required to be able to form an image endlessly by rotation, and has a straightness of 0.1 mm or less and a runout of 0.1 mm or less. Certain conductive supports are preferred. Exceeding the ranges of straightness and runout makes it difficult to form a good image.
[0055]
As a material for the conductive support, a metal drum such as aluminum or nickel, a plastic drum on which aluminum, tin oxide, indium oxide, or the like is deposited, or a paper / plastic drum coated with a conductive substance can be used. The conductive support has a specific resistance of 10 at room temperature.³Ωcm or less is preferable.
[0056]
The conductive support used in the present invention may have a surface on which a sealed alumite film is formed. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, and sulfamic acid. Anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodic oxidation treatment in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average thickness of the anodic oxide coating is usually 20 μm or less, particularly preferably 10 μm or less.
[0057]
Middle class
In the present invention, it is preferable to provide the above-mentioned intermediate layer having a barrier function between the conductive support and the photosensitive layer.
[0058]
The intermediate layer of the present invention preferably contains titanium oxide in the binder resin having a small water absorption. The average particle diameter of the titanium oxide particles is preferably in the range of 10 nm or more and 400 nm or less as a number average primary particle diameter, and more preferably 15 nm to 200 nm. If it is less than 10 nm, the effect of preventing the occurrence of moire by the intermediate layer is small. On the other hand, if it is larger than 400 nm, sedimentation of the titanium oxide particles in the coating liquid for the intermediate layer tends to occur, and as a result, the uniform dispersibility of the titanium oxide particles in the intermediate layer is poor, and black spots tend to increase. The coating solution for the intermediate layer using titanium oxide particles having a number average primary particle diameter in the above range has good dispersion stability, and the intermediate layer formed from such a coating solution has a function of preventing the occurrence of black spots and environmental characteristics. Is good and has cracking resistance.
[0059]
The shape of the titanium oxide particles used in the present invention includes dendritic, needle-like and granular shapes, and the titanium oxide particles having such a shape are, for example, titanium oxide particles, as anatase type, rutile as a crystal type. There are a crystal type and an amorphous type, and any crystal type may be used, or a mixture of two or more crystal types may be used. Among them, the rutile type and granular type are the best.
[0060]
The titanium oxide particles of the present invention are preferably surface-treated, and one of the surface treatments is a plurality of surface treatments, and the last one of the plurality of surface treatments is a reactive organic compound. The surface treatment using a silicon compound is performed. Further, among the plurality of surface treatments, at least one surface treatment performs at least one or more surface treatments selected from alumina, silica, and zirconia, and finally, a surface treatment using a reactive organosilicon compound. Is preferably performed.
[0061]
The alumina treatment, the silica treatment, and the zirconia treatment refer to a treatment for depositing alumina, silica, or zirconia on the surface of the titanium oxide particles. Japanese foods are also included. Further, the surface treatment of the reactive organosilicon compound means to use the reactive organosilicon compound in the treatment solution.
[0062]
In this way, by performing the surface treatment of the titanium oxide particles such as the titanium oxide particles at least twice or more, the surface of the titanium oxide particles is uniformly coated (treated), and the surface-treated titanium oxide particles are transferred to the intermediate layer. In this case, it is possible to obtain a good photoreceptor having good dispersibility of titanium oxide particles such as titanium oxide particles in the intermediate layer and free from image defects such as black spots.
[0063]
Examples of the reactive organosilicon compound include compounds represented by the following general formula (1), but are not limited to the following compounds as long as they are compounds that undergo a condensation reaction with a reactive group such as a hydroxyl group on the surface of titanium oxide.
[0064]
General formula (1)
(R)_n-Si- (X)_4-n
(In the formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3.)
In the organosilicon compound represented by the general formula (1), examples of the organic group in which carbon represented by R is directly bonded to silicon include alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, and dodecyl. Groups, aryl groups such as phenyl, tolyl, naphthyl, and biphenyl; epoxy-containing groups such as γ-glycidoxypropyl and β- (3,4-epoxycyclohexyl) ethyl; γ-acryloxypropyl; γ-methacryloxypropyl A (meth) acryloyl group, a hydrous group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, a vinyl group such as vinyl and propenyl, a mercapto group such as γ-mercaptopropyl, γ-aminopropyl, An amino-containing group such as N-β (aminoethyl) -γ-aminopropyl, γ-chloropropyl, , 1,1-tri fluoroalkyl propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include an alkoxy group such as methoxy and ethoxy, a halogen group, and an acyloxy group.
[0065]
The organosilicon compound represented by the general formula (1) may be used alone or in combination of two or more.
[0066]
When n is 2 or more in the specific compound of the organosilicon compound represented by the general formula (1), a plurality of Rs may be the same or different. Similarly, when n is 2 or less, a plurality of Xs may be the same or different. When two or more organosilicon compounds represented by the general formula (1) are used, R and X may be the same or different between the respective compounds.
[0067]
A preferred reactive organosilicon compound used for the surface treatment is a polysiloxane compound. The polysiloxane compound having a molecular weight of 1,000 to 20,000 is generally easily available, and has a good black spot prevention function.
[0068]
In particular, when methyl hydrogen polysiloxane is used for the final surface treatment, a good effect can be obtained.
[0069]
Photosensitive layer
Charge generation layer
The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.
[0070]
In the organic photoreceptor of the present invention, for example, other phthalocyanine pigments, azo pigments, perylene pigments, azurenium pigments and the like can be used alone or in combination as charge generation substances.
[0071]
In the case where a binder is used as a dispersion medium of CGM in the charge generation layer, a known resin can be used as the binder. No. The ratio between the binder resin and the charge generating substance is preferably from 20 to 600 parts by mass per 100 parts by mass of the binder resin. By using these resins, an increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably from 0.1 μm to 2 μm.
[0072]
Charge transport layer
The charge transport layer of the present invention has a configuration of a plurality of charge transport layers. Although the charge transport layer of the uppermost layer has been described above, the charge transport layers other than the uppermost layer can adopt a known structure of the charge transport layer.
[0073]
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses the CTM and forms a film. As other substances, additives such as antioxidants may be contained as necessary.
[0074]
As the charge transport material (CTM), a known charge transport material (CTM) can be used. For example, triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds and the like can be used. These charge transporting substances are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM that can minimize the increase in residual potential due to repeated use has a high mobility and an ionization potential difference from the combined CGM of 0.5 (eV) or less, and is preferably 0. .30 (eV) or less.
[0075]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0076]
The binder resin used for the charge transport layer (CTL) does not matter whether it is a thermoplastic resin or a thermosetting resin. For example, polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinyl carbazole may be used. Among them, a polycarbonate resin having a small water absorption, good dispersibility of CTM and good electrophotographic properties is most preferable.
[0077]
The ratio of the binder resin to the charge transporting material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.
[0078]
The total thickness of the plurality of charge transport layers is preferably from 10 to 50 μm. If the film thickness is less than 10 μm, the charging potential tends to be insufficient, and if it exceeds 50 μm, the sharpness tends to deteriorate.
[0079]
Solvents or dispersion media used for forming layers such as an intermediate layer, a charge generation layer, and a charge transport layer include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, and acetone. , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolan, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although the present invention is not limited to these, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone and the like are preferably used. In addition, these solvents can be used alone or as a mixed solvent of two or more kinds.
[0080]
Next, as a coating processing method for manufacturing an organic photoreceptor, a coating processing method such as dip coating, spray coating, circular amount control type coating or the like is used. It is preferable to use a coating processing method such as spray coating or circular amount control type (a typical example is a circular slide hopper type) coating so as not to dissolve as much as possible and to achieve uniform coating processing. It is most preferable that the protective layer be formed by the above-mentioned circular amount-regulating coating method. The circular amount control type coating is described in detail in, for example, JP-A-58-189061.
[0081]
Next, an image forming apparatus using the organic photoreceptor of the present invention will be described.
The image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. I have.
[0082]
An automatic document feeder for automatically transporting a document is provided above the image reading unit A. The document placed on the document table 11 is separated and transported one by one by a document transport roller 12, and is moved to a reading position 13a. Image is read. The document for which reading of the document has been completed is discharged onto the document discharge tray 14 by the document conveying roller 12.
[0083]
On the other hand, when the image of the original placed on the platen glass 13 is read at a speed v of a first mirror unit 15 including an illumination lamp and a first mirror constituting a scanning optical system, and a V-shaped second image is read. Reading is performed by moving the second mirror unit 16 including the second mirror and the third mirror in the same direction at the speed v / 2.
[0084]
The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The linear optical image formed on the image sensor CCD is sequentially subjected to A / D conversion after being photoelectrically converted into an electric signal (luminance signal), and subjected to processing such as density conversion and filter processing in an image processing unit B. After that, the image data is temporarily stored in the memory.
[0085]
In the image forming unit C, a drum-shaped photosensitive member 21 serving as an image carrier is provided as an image forming unit, and a charging unit 22 for charging the photosensitive member 21 is provided on the outer periphery thereof. A detecting unit 220, a developing unit 23, a transfer / conveying belt device 45 as a transferring unit, a cleaning device 26 for the photoconductor 21, and a PCL (precharge lamp) 27 as a light removing unit are arranged in the order of operation. On the downstream side of the developing unit 23, there is provided a reflection density detecting unit 222 for measuring the reflection density of the patch image developed on the photoconductor 21. The photoreceptor 21 is formed by coating a photoconductive compound on a drum substrate. For example, an organic photoreceptor 21A (abbreviated as OPC) or a hard organic HC photoreceptor 21B is preferably used. It is driven and rotated clockwise.
[0086]
After the rotating photoconductor 21 is uniformly charged by the charging unit 22, the exposure optical system 30 as the image exposure unit performs image exposure based on the image signal called from the memory of the image processing unit B. The exposure optical system 30 serving as an image exposure means as a writing means uses a laser diode (not shown) as a light emitting light source, and the optical path is bent by a reflection mirror 32 via a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35, and main scanning is performed. In this case, image exposure is performed on the photoconductor 21 at the position of Ao, and a latent image is formed by rotation (sub-scan) of the photoconductor 21. In an example of the present embodiment, a latent image is formed by exposing a character portion.
[0087]
The latent image on the photoconductor 21 is subjected to reversal development by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means in which transfer papers P of different sizes are stored. A manual paper feed unit 42 for performing manual paper feed is provided on the side, and the transfer paper P selected from any of them is fed along a transport path 40 by guide rollers 43 and fed. The transfer paper P is temporarily stopped by a pair of registration rollers 44 that corrects the inclination and deviation of the transfer paper P, and then re-fed, and the conveyance path 40, the pre-transfer roller 43a, the paper supply path 46, and the entry guide The toner image on the photoreceptor 21 is guided by the plate 47 and is transferred onto the transfer paper P while being placed and transported on the transfer transport belt 454 of the transfer transport belt device 45 by the transfer pole 24 and the separation pole 25 at the transfer position Bo. Transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.
[0088]
The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. The transfer paper P is passed between the fixing roller 51 and the pressure roller 52 to fix the toner by heating and pressing. The transfer paper P on which the toner image has been fixed is discharged onto the discharge tray 64.
[0089]
The above is a description of a state in which image formation is performed on one side of transfer paper. In the case of duplex copying, the discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.
[0090]
Further, the transfer paper P is transported downward by the transport mechanism 178, is switched back by the transfer paper reversing unit 179, and the rear end of the transfer paper P is transported into the double-sided copy paper supply unit 130 as the leading end. You.
[0091]
The transfer paper P is moved in the paper feeding direction by a conveyance guide 131 provided in the two-sided copy paper supply unit 130, the transfer paper P is fed again by the paper feed roller 132, and the transfer paper P is guided to the conveyance path 40. .
[0092]
Again, as described above, the transfer paper P is transported in the direction of the photoconductor 21, the toner image is transferred to the back surface of the transfer paper P, and is fixed by the fixing unit 50, and then discharged to the discharge tray 64.
[0093]
FIG. 2 is a plan view of the separation claw unit, and FIG. 3 is a side view of the separation claw unit. Further, as shown in a side view of the separation claw in FIG. 4, the contact load of the separation claw 252 on the organic photoconductor is switched. The nail scratches at the beginning of copying were reduced, and the occurrence of black streaks was prevented.
[0094]
However, if the contact load of the separation claw 252 is too low to reduce nail scratches, the transfer paper P cannot be separated from the organic photoreceptor 21 and JAM occurs, so the contact load needs to be set in a suitable range. There is.
[0095]
Next, the contact load switching means 260 for appropriately switching the contact load of the separation claw 252 to the organic photoconductor 21 will be described.
[0096]
The contact load switching means 260 includes a separation claw 252, a torque spring 255 for urging the separation claw 252, and a contact release plate 261 for contacting the separation claw 252 with the organic photoconductor 21 to adjust or release the contact load. And a rotary type DC solenoid 265 directly connected to a shaft 262 to which it is attached.
[0097]
The separation claw 252 has its rotating shaft 253 pivotally supported by a bearing 254 and is urged by a torque spring 255. The energization of the rotary type DC solenoid 265 is cut off, and the separation claw 252 is directly connected to the DC solenoid 265. When the shaft 262, which is rotatably supported on the shaft 262, is returned by the spring force and rotates, the contact release plate 261 attached to the shaft 262 is lowered, and the separation claw 252 comes into contact with the surface of the organic photoreceptor 21. When the shaft 262 is energized and returns to the original position, the contact release plate 261 is raised to release the contact of the separation claw 252 and release the contact.
[0098]
Further, by switching the voltage applied to the DC solenoid 265 to change the contact pressure between the contact release plate 261 and the separation claw 252, the contact load between the separation claw 252 and the organic photoconductor 21 is reduced. Can be switched.
[0099]
As described above, the operation of switching the contact load of the separation claw 252 on the organic photoconductor 21 in the contact load switching means 260 is performed by switching the voltage applied to the DC solenoid 265. That is, due to the applied voltage value of the DC solenoid 265, the contact pressure applied to the separation claw 252 at the position where the contact release plate 261 contacts the separation claw 252 reduces the urging force of the separation claw 252 by the torque spring 255, and the organic photosensitive member The contact load of the separation claw 252 with respect to 21 can be adjusted to an appropriate predetermined value and switched.
[0100]
The contact load between the separation claw 252 and the surface of the organic photoreceptor 21 is preferably selected from the range of 0.98 to 7.84 mN and set to an appropriate adjustment value.
[0101]
On the other hand, the stepping motor 272 attached to the fixed board 271 meshes with the rack gear 267 attached to the board 251 of the separation claw unit 250 via the gears 273, 274, 275, 276 also attached to the fixed board 271. The substrate 251 can be moved to an arbitrary set position within a range of about 5 mm left and right along the guide 271A of the fixed substrate 271 and can be stopped. In this manner, it is preferable that the contact position between the separation claw 252 and the organic photoreceptor 21 be changed in the width direction so as to avoid the contact in the same width direction for a long time.
[0102]
The organic photoreceptor of the present invention is generally applicable to electrophotographic apparatuses such as an electrophotographic copying machine, a laser printer, an LED printer, and a liquid crystal shutter printer, but is further applied to a display, recording, light printing, plate making and facsimile to which electrophotographic technology is applied. Etc. can be widely applied.
[0103]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but embodiments of the present invention are not limited thereto. In the following description, “parts” means “parts by mass”.
[0104]
Production of photoconductor 1
Photoconductor 1 was prepared as follows.
[0105]
The surface of a cylindrical aluminum support having a diameter of 100 mmφ and a length of 346 mm was cut to prepare a conductive support having a surface roughness Rz = 1.5 (μm).
<Intermediate layer>
The following intermediate layer dispersion was diluted twice with the same mixed solvent, allowed to stand overnight, and then filtered (filter; Rigimesh 5 μm filter manufactured by Pall Corporation) to prepare an intermediate layer coating solution.
[0106]

Using a sand mill as a disperser, dispersion was performed for 10 hours in a batch system.
[0107]
Using the above-mentioned coating solution, coating was performed on the support so as to have a dry film thickness of 2 μm.

Was mixed using a sand mill and dispersed for 10 hours to prepare a charge generation layer coating solution. This coating solution was applied on the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.
[0108]

Were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer to form a charge transport layer having a dry film thickness of 20 μm by a dip coating method.
[0109]

Were mixed and circulated and dispersed in a circulating dispersion apparatus capable of irradiating ultrasonic waves to prepare a surface layer coating liquid. This coating solution was applied onto the charge transport layer by a circular amount control type coating method so as to have a dry film thickness of 5 μm, and dried at 110 ° C. for 70 minutes to produce a photoreceptor 1.
[0110]
Production of photoreceptors 2 to 15
Photoconductors 2 to 15 were produced in the same manner as photoconductor 1, except that the polycarbonate and hydrophobic silica of the second charge transport layer in photoconductor 1 were changed as shown in Table 1.
[0111]
[Table 1]

[0112]
In the table, PC-4 indicates a polycarbonate having the following structure.
[0113]
Embedded image

[0114]
Evaluation
1. Surface roughness Ra
Ra is extracted from the roughness curve by a reference length in the direction of the average line, the X axis is taken in the direction of the average line of the extracted portion, the Y axis is taken in the direction of the vertical magnification, and the roughness curve is expressed as y = f (x ) Means a value obtained by the following equation and expressed in micrometers (μm).
[0115]
Ra = 1 / l∫₀ ^l| F (x) | dx
l is the reference length
In the present invention, 1 is 2.5 mm, and the cutoff value is 0.08 mm.
[0116]
The measurement was performed with a surface roughness meter (Sulfcoder SE-30H manufactured by Kosaka Laboratories). However, any other measuring device that produces the same result within the error range may be used.
[0117]
Surface roughness measurement conditions
Measurement speed (Drive speed: 0.1 mm / sec)
Measurement needle diameter (Stylus: 2 μm)
2. Measuring creep rate
Equipment used: Fisher scope H100V (micro hardness measurement device) manufactured by Fisher Instruments
Indenter used: Diamond Vickers indenter
Load condition: Vickers indenter is pushed in from the surface of the organic photoreceptor at a speed of 4 mN / sec.
Load time: 5 sec
Retention time: 5 sec
Unloading conditions: remove the load at the same speed as the load
Measurement sample
An intermediate layer, a charge generation layer, a first charge transport layer, and a second charge transport layer were provided on an aluminum plate in the same manner as the above-described photoreceptor, and a sample prepared by drying under the same conditions was fixed to an H100V machine. Press the Vickers indenter vertically to measure.
[0118]
The measurement is performed by the procedure of indenter load (5 sec), load holding (5 sec: the rate of deformation during this time is the creep rate), and unloading.
[0119]
How to find the creep rate
CHU (creep rate) = {(h2−h1) / h1} × 100 (%)
h1: Depth of indentation when the applied load (20 mN) is reached (5 seconds after the start of loading)
h2: Depression depth after holding (5 sec)
3. Image evaluation
A Konica 7075 digital copying machine manufactured by Konica Corp. (having a corona charging, laser exposure, reversal development, electrostatic transfer, nail separation, blade cleaning, cleaning auxiliary brush roller adoption process) was used as an evaluation machine. 15 was mounted and evaluated. The cleaning performance and the image evaluation were performed by copying an original image in which a character image having a pixel ratio of 7%, a photograph of a person's face, a solid white image, and a solid black image were each equal to 1/4 on A4 neutral paper. The copying conditions were 200,000 copies continuously in a high-temperature and high-humidity environment (30 ° C., 80% RH) considered to be the most severe, and halftone, solid white image and solid black image were evaluated.
[0120]
Evaluation items and evaluation criteria
Image density (measured using Macbeth RD-918. Measured by relative reflection density with the reflection density of paper set to "0")
◎: 1.2 or more: good
：: 0.8 or more: no problem in practical use
×: Less than 0.8: Practically problematic level
Sharpness (Evaluation of sharpness in character images after copying 200,000 sheets)
Three-point and five-point character images were formed and evaluated according to the following criteria.
[0121]
：: 3 points and 5 points are clear and easily legible
：: 3 points are partially unreadable, 5 points are clear and easily readable
×: 3 points almost illegible, 5 points partially or completely illegible
Transferability of toner (after 200,000 copies, 60 mg / cm²Is formed, and the amount of adhesion per unit area transferred to the transfer paper (fmg / cm²) Was measured, and the transfer rate was calculated by the following calculation. )
Toner transfer rate = (f / 60) × 100
：: toner transfer rate of 85% or more: good
：: Toner transfer rate of 65 to 84% or more: a level at which there is no practical problem
×: Toner transfer rate of 64% or less: Level that poses a problem in practical use
Cleanability (10 continuous copies on A3 paper after 100,000 and 200,000 copies are completed, and judgment is made based on whether or not cleaning failure has occurred in solid white areas)
◎: No slippage occurred with 200,000 sheets
：: No slippage occurred up to 100,000 sheets
×: Occurrence of slippage with less than 100,000 sheets
Scratch resistance (All copies of 200,000 copies were inspected to determine whether or not image scratches were generated by the separation nails, and whether or not scratches were generated by the separation nails on the photoreceptor surface were inspected every 10,000 copies.)
：: No scratches caused by separation nails on both photoconductor surface and copy image
○: There is a slight scratch on the photoreceptor surface, but no scratch on the copy image due to the separation nail.
×: Clear scratches were found on the photoreceptor surface, and the copy image was also caused by separation nails
Scratch occurs
Other evaluation conditions
Other evaluation conditions using the above 7075 were set to the following conditions.
[0122]
Charging conditions
Charger: Scorotron charger, initial charging potential is -750V
Exposure conditions
The exposure amount is set so that the exposure portion potential is -50V.
[0123]
Development conditions
DC bias; -550V
The developer is a carrier coated with an insulating resin with ferrite as a core, a styrene acrylic resin as a main material, a colorant such as carbon black, a charge control agent, and a volume average particle diameter of 7 prepared by a polymerization method comprising a low molecular weight polyolefin. A toner developer in which silica and titanium oxide were externally added to 0.3 μm colored particles was used.
[0124]
Transfer conditions
Transfer pole; corona charging method
Separation conditions
The separation means of the separation claw unit described with reference to FIGS.
[0125]
Separating claw material: Polyamideimide (PAI) base material coated with polytetrafluoroethylene (PTFE)
Contact load to photoconductor: 5.6 mN
Cleaning conditions
A cleaning blade having a hardness of 70 °, a rebound resilience of 65%, a thickness of 2 (mm) and a free length of 9 mm was brought into contact with the cleaning portion by a weight load method so as to have a linear pressure of 18 (g / cm) in the counter direction.
[0126]
The evaluation results are shown in Table 2.
[0127]
[Table 2]

[0128]
The photoreceptors 1 to 5 and 10 to 15 having the creep rate and the surface roughness Ra both within the range of the present invention have excellent characteristics in each evaluation item of image density, toner transferability, sharpness, cleaning property and scratch resistance. As shown, the photoreceptor 6 (creep ratio: 3.62) outside the present invention was inferior in cleaning performance and scratch resistance, and the photoreceptor 9 (creep ratio: 0.82) was poor in image density, sharpness, and cleaning performance. Is declining. The photoreceptor 7 (surface roughness Ra: 0.25 μm) has poor cleaning properties, and the photoreceptor 8 (surface roughness Ra: 0.009 μm) has reduced toner transferability and image density.
[0129]
【The invention's effect】
As is clear from the examples, by using the organic photoreceptor having the structure of the present invention, the transferability of the toner and the cleaning performance of the residual toner can be improved even when a large number of copies are made under high temperature and high humidity. In addition, it is possible to produce an electrophotographic image having improved scratch resistance and good sharpness.
[Brief description of the drawings]
FIG. 1 is a schematic diagram in which functions of an image forming apparatus of the present invention are incorporated.
FIG. 2 is a plan view of a separation claw unit.
FIG. 3 is a side view of the separation claw unit.
FIG. 4 is a side view of the separation claw.
[Explanation of symbols]
1 Image forming apparatus
21 photoconductor
21A Organic photoreceptor
21B @ HC organic photoreceptor
22 charging means
23 developing means
24mm transfer pole
25 ° separation pole
26 cleaning device
30 ° exposure optical system
45 ° transfer conveyor belt device
50 ° fixing means
250 separation claw unit
251 substrate
252 separation claw
255 ° torque spring
260 ° contact load switching means
261 Contact release plate
262 shaft
265 ° DC solenoid
271 fixed board
271A Guide
272 stepper motor

Claims (8)

In an organic photoreceptor having at least a photosensitive layer provided on a conductive support, the organic photoreceptor has a creep rate (creep rate when a Vickers indenter is pushed in with a load of 20 mN) of 1% or more and less than 3.5%. And an organic photoreceptor having a surface roughness Ra of not less than 0.02 μm and less than 0.1 μm. An organic photoreceptor having a charge generation layer on a conductive support and a charge transport layer laminated thereon, wherein the charge transport layer is composed of a plurality of layers, one of which is a surface layer, and The creep rate of the body (creep rate when the Vickers indenter is pushed in with a load of 20 mN) is 1% or more and less than 3.5%, and the surface roughness Ra is 0.02 μm or more and less than 0.1 μm. Organic photoreceptor. The organic photoreceptor according to claim 2, wherein the surface layer is a layer containing inorganic particles having a number average particle diameter of 1 nm or more and less than 100 nm. The organic photoconductor according to claim 3, wherein the inorganic particles are hydrophobic silica. The organic photoconductor according to any one of claims 2 to 4, wherein the binder of the surface layer is a copolymer polycarbonate resin. An electrophotographic image is formed using the organic photoreceptor according to any one of claims 1 to 5 through at least a charging step, an image exposure step, a developing step, a transfer step, a separation step, and a cleaning step. An image forming method, comprising: An image forming apparatus that forms an electrophotographic image using the image forming method according to claim 6. The organic photoreceptor according to claim 1, wherein one of a charger, an image exposing unit, a developing unit, and a cleaning unit is integrally combined, and is freely inserted into and removed from the image forming apparatus. A process cartridge characterized by being designed for.

Images