JP2004177462A - Organic photoreceptor, image forming method, image forming apparatus, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoreceptor forming an exact electrostatic latent image with little blur and capable of faithfully developing the electrostatic latent image as a toner image, and to provide an image forming method and an image forming apparatus capable of preventing image defects such as black spots, voids, environmental memory and initial memory and capable of ensuring high-grade image quality with good image density, sharpness and gradation. <P>SOLUTION: The organic photoreceptor has a charge generating layer comprising a charge generating material of an N type pigment on a conductive support and a laminated structure of at least one or more layers having a total thickness of 5-15 μm on the charge generating layer, wherein the uppermost layer comprises fluororesin particles. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
（式中、Ｒは水素原子、ハロゲン原子、炭素数１〜１０のアルキル基、アリール基、アルコキシ基、複素環基を表す。）
上記ペリレン化合物はいくつかの結晶多形が存在するが、特にどの結晶型のものも好適に用いられる。例えばＸ線回折スペクトルのブラッグ角２θ（±０．２°）の６．３°、１２．４°、２５．３°、２７．１°にピークを有し、最大ピークが１２．４°である結晶型のものやほとんど明瞭なピークを示さないアモルファスのものも含まれる。また、キャリア発生層に用いる場合には特定の結晶型を示すペリレンを分散して用いてもよいし、蒸着等の操作により膜を形成してもかまわない。また、蒸着膜を溶媒処理等で結晶変換させることもできる。
【００３９】
次に、本発明に好ましく用いることの出来るペリレン化合物の具体例を下記に示す。
【００４０】
一般式（１）の化合物の具体例
前記一般式（１）中、Ｒ_１、Ｒ_２は同一でも異なっていても良く、下記のものが挙げられる。
【００４１】
【化３】

【００４２】
【化４】

【００４３】
【化５】

【００４４】
一般式（２）の化合物の具体例
前記一般式（２）中のＲ_１は一般式（１）と同一であり、Ｚは下記のものが挙げられる。
【００４５】
【化６】

【００４６】
２量体の場合には、Ｚは下記のものとなる。
【００４７】
【化７】

【００４８】
一般式（３）の化合物
【００４９】
【化８】

【００５０】
【化９】

【００５１】
【化１０】

【００５２】
【化１１】

【００５３】
【化１２】

【００５４】
上記ペリレン顔料の他にＮ型顔料としては、電気陰性度が高い官能基、例えばシアノ基等を有するアゾ顔料や多環キノン顔料が挙げられる。
【００５５】
本発明の電荷発生層には前記Ｎ型顔料の電荷発生物質とともに、該Ｎ型顔料の１０質量％未満のＰ型顔料を併用して含有させることが好ましい。Ｐ型顔料としては、前記したＰ型特性を示す顔料であればいかなる種類の電荷発生物質でもよい。例えば、フタロシアニン顔料等が挙げられる。
【００５６】
従来のデジタル複写機等に主として用いられてきたＰ型のフタロシアニン顔料の電荷発生物質は、電荷キャリアの輸送能が小さいため、電荷発生層を厚くすると残留電位の上昇や光メモリによる画像むら等を発生しやすい。そのため電荷発生層を厚くして、電荷発生物質を増大し、感度の改善や光干渉縞を防止すること、或いは導電性基体からのフリーキャリアをブロックすることは困難であった。
【００５７】
本発明の有機感光体は、導電性支持体上にＮ型顔料の電荷発生物質を含有し、膜厚が０．３〜２μｍである電荷発生層とその上に、電荷輸送物質を含有し、合計膜厚が５〜１５μｍである電荷輸送層を有する負帯電型有機感光体（負の静電潜像が形成される。）の構造を有しているが、電荷発生層の電荷発生物質はＮ型顔料を主とすることにより、電荷発生層内で発生した電子は、比較的長い距離を移動し導電性基体に導通することができる。このため、電荷発生層を比較的厚い膜厚に構成しても、電子のトラップによる残留電位の上昇は防止される。又、電荷発生層が上記範囲の膜厚をもてば、十分に顔料濃度をあげることが出来るので、デジタル画像形成で、一般的に用いられる像露光光、レーザ光やＬＥＤ光等の単波長光照射によるモアレ等の発生も防止することが出来る。その上、Ｎ型顔料が導電性基体からのフリーキャリアの注入効果が著しく、反転現像での黒ポチの発生を顕著に改善する。
【００５８】
電荷発生層の膜厚が０．３μｍ未満では顔料濃度を十分に含有することができにくいため、露光電位の低下が不十分となり画像濃度が低下したり、レーザ光の干渉防止効果が小さくなったりしやすい。一方、２．０μｍより大きいと、電荷発生層内での電荷キャリアのトラップ密度が大きくなりやすく、光メモリの増加による画像むらが発生しやすい。好ましい電荷発生層の膜厚は０．３〜１．０μｍである。
【００５９】
又、前記電荷発生層には、前記Ｎ型顔料の電荷発生物質とともに、該Ｎ型顔料の１０質量％未満のＰ型顔料を併用して含有させることが好ましい。Ｐ型顔料をＮ型顔料と併用することにより、電荷発生層の内部深くで発生した正孔キャリアを電荷輸送層との境界まで輸送し、注入することができ、正孔キャリアの電荷発生層内でのトラップが防止され、残留電位の上昇が防止される。より好ましいＰ型顔料の量は０．５〜５質量％である。１０質量％以上だと、導電性基体からのフリーキャリアの注入防止効果が劣化し、黒ポチやカブリが発生しやすい。
【００６０】
一方、電荷発生層の上には少なくとも１層以上の積層構成を有し、その膜厚の合計が５〜１５μｍで且つ最上層がフッ素系樹脂粒子を含有することを特徴とする。即ち、前記したＮ型顔料も電荷発生物質を含有する電荷発生層の上に合計膜厚が５〜１５μｍで且つ最上層がフッ素系樹脂粒子を含有する層を設けることにより、黒ポチが発生しにくく又白抜けの発生も防止され、文字画像及び中間調画像の両方とも、鮮鋭性が改良された電子写真画像を得ることが出来る。
【００６１】
上記電荷発生層上の合計膜厚が５〜１５μｍの層構造は、複数の電荷輸送層から構成し、且つ最上層の電荷輸送層にフッ素系樹脂粒子を含有させた構成が好ましい。複数の電荷輸送層で構成した合計膜厚が５〜１５μｍの層構造は、電荷発生層で発生した電荷キャリアの拡散を小さくし、微細なドットで構成された潜像を十分な電位コントラストで再現することができる。該合計膜厚が５μｍ未満だと帯電電位が不十分になりやすく、１５μｍを超えると、該電荷キャリアの拡散が大きくなり、鮮鋭性が十分に改善されない。特に、電荷輸送層の合計膜厚を８〜１４μｍの範囲で構成した場合が、鮮鋭性の改善効果がより顕著である。
【００６２】
前記最上層の電荷輸送層に含有されるフッ素系樹脂粒子とはフッ素原子を含有した樹脂粒子を意味し、例えば、四フッ化エチレン樹脂、三フッ化塩化エチレン樹脂、六フッ化エチレンプロピレン樹脂、フッ化ビニル樹脂、フッ化ビニリデン樹脂、二フッ化二塩化エチレン樹脂及びこれらの共重合体のなかから１種あるいは２種以上を適宜選択するのが好ましいが、特に、四フッ化エチレン樹脂及びフッ化ビニリデン樹脂が好ましい。フッ素系樹脂粒子の分子量や粒子の粒径は、適宜選択することができ、特に制限されるものではない。
【００６３】
最上層の電荷輸送層はバインダー樹脂中にフッ素系樹脂粒子を含有する構成が好ましく、フッ素系樹脂粒子の割合は、粒子の粒径にも影響を受けるが、最上層全質量に対し、１〜５０質量％であることが好ましく、より好ましくは５〜４０質量％である。更に、最上層には電荷輸送物質が含有されていることが好ましい。
【００６４】
本発明の最上層には、分散性、結着性や耐候性を向上させる目的でカップリング剤や酸化防止剤等の添加剤を加えてもよい。
【００６５】
最上層のフッ素系樹脂粒子の分散方法としては、ホモジナイザー、ボールミル、サンドミル、ロールミル及び超音波といった方法が挙げられる。一次粒径の粒径まで分散可能であれば特に限定されるものではない。
【００６６】
また、フッ素系樹脂粒子の分散助剤として、各種の界面活性剤、例えばクシ型グラフトポリマー等を適宜混合してもさしつかえない。
【００６７】
最上層の膜厚は０．１〜４μｍであることが好ましい。０．１μｍ未満では表面硬度や強度が十分でなく耐久性が低下し易く、４μｍを超えると現像時に潜像によって形成されるコントラストポテンシャルが劣化し易い。より好ましくは０．２〜３．０μｍである。
【００６８】
最上層はクリーニング性及び耐汚染性を満足するために低表面エネルギーであることが好ましく、水の接触角で測定される低表面エネルギー性としては９０度以上が好ましい。９０度未満では電子写真プロセスによる繰り返し使用によって表面に帯電生成物やトナー、紙からもたらされる脱落物が付着し易く、クリーニング不良や表面抵抗の低下による潜像の劣化（画像流れ）を生じ易い。より好ましくは９５度以上である。
【００６９】
以上のような構成を採用することにより、鮮鋭性を著しく改善でき、且つ電荷輸送層を薄膜化した場合に発生しやすい、黒ポチの発生や画像むら等の画像欠陥を防止し、電位性能が安定した有機感光体を提供することができる。
【００７０】
以下、上記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感光体を全て含有する。
【００７１】
本発明の電荷輸送層とは、光露光により電荷発生層で発生した電荷キャリアを有機感光体の表面に輸送する機能を有する層を意味し、該電荷輸送機能の具体的な検出は、電荷発生層と電荷輸送層を導電性支持体上に積層し、光導伝性を検知することにより確認することができる。
【００７２】
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及び電荷輸送層の感光層から構成される。最も好ましい構成としては、感光層を電荷発生層と電荷輸送層で構成する。
【００７３】
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。
【００７４】
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。
【００７５】
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。
【００７６】
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。
【００７７】
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。
【００７８】
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。
【００７９】
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。
【００８０】
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。
【００８１】
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。
【００８２】
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。
【００８３】
上記反応性有機ケイ素化合物としては下記一般式（４）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。
【００８４】
一般式（４）
（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（４）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。
【００８５】
また、一般式（４）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。
【００８６】
また、一般式（４）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（４）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。
【００８７】
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。
【００８８】
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。
【００８９】
感光層
電荷発生層
電荷発生層の電荷発生物質（ＣＧＭ）は前記したＮ型顔料を用いる。
【００９０】
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。
【００９１】
電荷輸送層
前記したように、本発明では電荷輸送層を複数の電荷輸送層から構成し、且つ最上層の電荷輸送層にフッ素系樹脂粒子を含有させた構成が好ましい。
【００９２】
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前記したフッ素系樹脂粒子や酸化防止剤等の添加剤を含有しても良い。
【００９３】
電荷輸送物質（ＣＴＭ）としては公知の正孔輸送性（Ｐ型）の電荷輸送物質（ＣＴＭ）を用いることが好ましい。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。
【００９４】
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。
【００９５】
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。
【００９６】
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。
【００９７】
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。
【００９８】
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。
【００９９】
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。
【０１００】
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。
【０１０１】
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。
【０１０２】
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。
【０１０３】
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（帯電工程）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（現像工程）２３、転写手段（転写工程）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（クリーニング工程）２６及び光除電手段（光所電荷発生工程）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には、本発明の有機感光体を使用し、図示の時計方向に駆動回転される。
【０１０４】
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（像露光工程）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）によって静電潜像が形成される。本実施の形態の一例では文字部に対して露光を行い静電潜像を形成する。
【０１０５】
本発明の画像形成方法においては、感光体上に静電潜像を形成するに際し、像露光をスポット面積が２×１０^−９ｍ^２以下の露光ビームを用いて行うことが好ましい。このような小径のビーム露光を行っても、本発明の有機感光体は、該スポット面積に対応した画像を忠実に形成することができる。より好ましいスポット面積は、０．０１×１０^−９〜１×１０^−９ｍ^２である。その結果４００ｄｐｉ（ｄｐｉ：２．５４ｃｍ当たりのドット数）以上で、２５６階調を実現するところのきわめて優れた画像品質を達成することができる。
【０１０６】
前記露光ビームのスポット面積とは該ビーム光の強度がピーク強度の１／ｅ^２以上の光強度に対応する面積で表される。
【０１０７】
用いられる露光ビームとしては半導体レーザを用いた走査光学系、及びＬＥＤや液晶シャッター等の固体スキャナー等があり、光強度分布についてもガウス分布及びローレンツ分布等があるがそれぞれのピーク強度の１／ｅ^２までの部分をスポット面積とする。
【０１０８】
感光体２１上の静電潜像は現像手段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。本発明の画像形成方法では、該現像手段に用いられる現像剤には重合トナーを用いることを特徴とする。形状や粒度分布が均一な重合トナーを本発明の有機感光体と併用することにより、より鮮鋭性が良好な電子写真画像を得ることができる。
【０１０９】
ここで、重合トナーとは、トナー用バインダーの樹脂の生成とトナー形状がバインダー樹脂の原料モノマーの重合、及びその後の化学的処理により形成されて得られるトナーを意味する。より具体的には懸濁重合、乳化重合等の重合反応と必要により、その後に行われる粒子同士の融着工程を経て得られるトナーを意味する。
【０１１０】
重合トナーは原料モノマーを水系で均一に分散した後に重合させトナーを製造することから、トナーの粒度分布、及び形状が均一なトナーが得られる。
【０１１１】
重合トナーは、懸濁重合法や、必要な添加剤の乳化液を加えた液中にて単量体を乳化重合し、微粒の重合粒子を製造し、その後に、有機溶媒、凝集剤等を添加して会合する方法で製造することができる。会合の際にトナーの構成に必要な離型剤や着色剤などの分散液と混合して会合させて調製する方法や、単量体中に離型剤や着色剤などのトナー構成成分を分散した上で乳化重合する方法などがあげられる。ここで会合とは樹脂粒子および着色剤粒子が複数個融着することを示す。
【０１１２】
即ち、重合性単量体中に着色剤や必要に応じて離型剤、荷電制御剤、さらに重合開始剤等の各種構成材料を添加し、ホモジナイザー、サンドミル、サンドグラインダー、超音波分散機などで重合性単量体に各種構成材料を溶解あるいは分散させる。この各種構成材料が溶解あるいは分散された重合性単量体を分散安定剤を含有した水系媒体中にホモミキサーやホモジナイザーなどを使用しトナーとしての所望の大きさの油滴に分散させる。その後、攪拌機構が後述の攪拌翼である反応装置へ移し、加熱することで重合反応を進行させる。反応終了後、分散安定剤を除去し、濾過、洗浄し、さらに乾燥することでトナーを調製する。
【０１１３】
また、本発明のトナーを製造する方法として樹脂粒子を水系媒体中で会合あるいは融着させて調製する方法も挙げることができる。この方法としては、特に限定されるものではないが、例えば、特開平５−２６５２５２号公報や特開平６−３２９９４７号公報、特開平９−１５９０４号公報に示す方法を挙げることができる。すなわち、樹脂粒子と着色剤などの構成材料の分散粒子、あるいは樹脂および着色剤等より構成される微粒子を複数以上会合させる方法、特に水中にてこれらを乳化剤を用いて分散した後に、臨界凝集濃度以上の凝集剤を加え塩析させると同時に、形成された重合体自体のガラス転移点温度以上で加熱融着させて融着粒子を形成しつつ徐々に粒径を成長させ、目的の粒径となったところで水を多量に加えて粒径成長を停止し、さらに加熱、攪拌しながら粒子表面を平滑にして形状を制御し、その粒子を含水状態のまま流動状態で加熱乾燥することにより、トナーを形成することができる。なお、ここにおいて凝集剤と同時に水に対して無限溶解する有機溶媒を加えてもよい。
【０１１４】
なお、本発明で用いられる形状係数等の均一なトナーを作製するための材料や製造方法、重合トナーの反応装置等については特開２０００−２１４６２９に詳細に記載されている。
【０１１５】
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。
【０１１６】
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。
【０１１７】
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。
【０１１８】
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。
【０１１９】
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。
【０１２０】
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。
【０１２１】
本発明の画像形成装置としては、上述の感光体と、現像器、クリーニング器等の構成要素をプロセスカートリッジとして一体に結合して構成し、このユニットを装置本体に対して着脱自在に構成しても良い。又、帯電器、像露光器、現像器、転写又は分離器、及びクリーニング器の少なくとも１つを感光体とともに一体に支持してプロセスカートリッジを形成し、装置本体に着脱自在の単一ユニットとし、装置本体のレールなどの案内手段を用いて着脱自在の構成としても良い。
【０１２２】
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。
【０１２３】
【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。
【０１２４】
感光体１の作製
下記の様に感光体１を作製した。
【０１２５】
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。
【０１２６】

を混合し、分散機としてサンドミルを用い、バッチ式で１０時間の分散を行い、中間層分散液を作製した。
【０１２７】
上記塗布液を用いて前記支持体上に、乾燥膜厚１．０μｍとなるよう塗布した。

を混合し、サンドミルを用いて３０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。
【０１２８】

を混合し、溶解して電荷輸送層塗布液１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塗布し、１１０℃７０分の乾燥を行い、乾燥膜厚１０μｍの電荷輸送層１を形成した。
【０１２９】

を混合した後ガラスビーズを用いたサンドグラインダー（（株）アメックス製）にて分散し、４−フッ化エチレン樹脂粒子分散液を調製した。
【０１３０】

を混合し、溶解して電荷輸送層塗布液２を調製した。この塗布液を前記電荷輸送層１の上に円形スライドホッパ型塗布機で塗布し、１１０℃７０分の乾燥を行い、乾燥膜厚２μｍの電荷輸送層２を形成し、感光体１を作製した。
【０１３１】
感光体２〜９の作製
感光体１の作製において、中間層の酸化チタン、電荷発生層（ＣＧＬ）の膜厚、電荷輸送層１及び２（ＣＴＬ１及び２）の膜厚及びフッ素系樹脂粒子を表１のように変化させた以外は感光体１と同様にして感光体２〜９を作製した。
【０１３２】
感光体１０〜１３の作製
感光体１の作製において、電荷発生層のペリレン顔料（Ａ）の代わりに化合物Ｂ〜ＥのＮ型顔料を用い、チタニルフタロシアニン顔料の量を３．６部に変更し、電荷輸送層２のフッ素系樹脂粒子を表１のように変更した以外は感光体１と同様にして感光体１０〜１３を作製した。
【０１３３】
感光体１４の作製
感光体１において、電荷発生層のチタニルフタロシアニン顔料（Ｆ）を除いた他は感光体１と同様にして感光体１４を作製した。
【０１３４】
感光体１５の作製
感光体１の作製において、電荷発生層のペリレン顔料（Ａ）の代わりにＰ型顔料のチタニルフタロシアニン顔料（Ｆ：Ｃｕ−Ｋα特性Ｘ線の回折角度：ブラッグ角２θで、２７．３°に最大なピークを有するチタニルフタロシアニン顔料）を用いた他は感光体１と同様にして感光体１５を作製した。
【０１３５】
感光体１６の作製
感光体１の作製において、電荷輸送層２を除いた他は同様にして感光体１６を作製した。
【０１３６】
【表１】

【０１３７】
表１中、微粒子の表面処理のＩ、Ｊ、Ｋは下記処理を示す。
Ｉ：シリカ・アルミナ処理及びメチルハイドロジェンポリシロキサン処理
Ｊ：シリカ・アルミナ処理及びオクチルトリメトキシシラン処理
Ｋ：シリカ・ジルコニア処理及びメチルトリメトキシシラン処理
Ｇ、Ｈは下記のフッ素系樹脂微粒子を示す。
【０１３８】
Ｇ：四フッ化エチレン樹脂粒子（ルブロンＬ−２、ダイキン工業（株）製）
Ｈ：三フッ化エチレン樹脂粒子（ダイフロン、ダイキン工業（株）製）
上記感光体１〜１６の作製に用いたペリレン顔料Ａ〜Ｄ、アゾ顔料Ｅ及びチタニルフタロシアニン顔料Ｆの化学構造式を下記に示す。
【０１３９】
【化１３】

【０１４０】
【化１４】

【０１４１】
《評価》
次いで、上記各感光体をコニカ製Ｓｉｔｉｏｓ７０４０デジタル複写機に搭載して、画像形成し、評価した。即ち、上記感光体を図１の構造を基本的に有するコニカ製Ｓｉｔｉｏｓ７０４０デジタル複写機（スコロトロン帯電器、半導体レーザ像露光器、反転現像手段を有する）に設定し、複写実験を行った。この実験においては図１のプロセス制御部のメモリー中に未露光部目標電位のプログラムを組み込み、自動的に現像位置の未露光部目標電位が設定されるようにデジタル複写機を改造した。
【０１４２】
《画像評価》
上記デジタル複写機に各感光体を取り付け、高温高湿（３０℃、８０％ＲＨ）環境でＡ４紙、５万枚の画素率７％の文字画像の複写を行い、スタート時及び１万枚コピー毎に白画像及びハーフトーン画像の複写を行い、黒ポチ、白抜け等の画像欠陥の有無を確認した。表２に結果を示す。
【０１４３】
尚、上記７０４０を用いたその他の評価条件は下記の条件に設定した。
帯電条件
帯電器；スコロトロン帯電器
現像位置の未露光部電位（ＶＨ）目標：−５００Ｖ
露光条件
露光部電位目標：−５０Ｖにする露光量に設定。
【０１４４】
露光ビーム：ドット密度４００ｄｐｉの像露光を行った。レーザビームスポット面積：０．８×１０^−９ｍ^２、レーザは６８０ｎｍの半導体レーザを使用
現像条件
現像剤は、体積平均粒径５０μｍの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５．３μｍ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。
【０１４５】
転写条件
転写極；コロナ帯電方式
分離条件：分離爪ユニットの分離手段を用いた
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。
【０１４６】
黒ポチ画像欠陥の評価基準
黒ポチについては、周期性が感光体の周期と一致し、目視できる黒ポチが、Ａ４サイズ当たり何個あるかで判定した。
【０１４７】
◎：０．４ｍｍ以上の黒ポチ頻度：全ての複写画像が３個／Ａ４以下（良好）
○：０．４ｍｍ以上の黒ポチ頻度：４個／Ａ４以上、１０個／Ａ４以下が１枚以上発生（実用上問題なし）
×：０．４ｍｍ以上の黒ポチ頻度：１１個／Ａ４以上が１枚以上発生（実用上問題有り）
白抜け画像欠陥の評価基準
白抜けについては、周期性が感光体の周期と一致し、目視できる白抜けが、Ａ４サイズ当たり何個あるかで判定した。
【０１４８】
◎：０．４ｍｍ以上の白抜け頻度：全ての複写画像が５個／Ａ４以下（良好）
○：０．４ｍｍ以上の白抜け頻度：６個／Ａ４以上、２０個／Ａ４以下が１枚以上発生（実用上問題なし）
×：０．４ｍｍ以上の白抜け頻度：２１個／Ａ４以上が１枚以上発生（実用上問題有り）
環境メモリ
環境メモリ：上記Ｓｉｔｉｏｓ７０４０複写機をＨＨ下に２４ｈｒ放置後、低湿低温下（ＬＬ：２０ＲＨ％、１０℃）に置き、３０分後、コピーした。オリジナル画像で０．４の濃度のハーフトーン画像を０．４の濃度にコピー、コピー画像の濃度差（ΔＨＤ＝最大濃度−最小濃度）で判定
◎：ΔＨＤが０．０５以下（良好）
○：ΔＨＤが０．０５より大で０．１未満（実用上問題なし）
×：ΔＨＤが０．１以上（実用上問題あり）
初期メモリ
感光体表面電位が初期起動時に安定せず、ΔＶ（感光体１回転目と２回転目の帯電電位の差）が大きいために発生する画像カブリの有無により評価した。
【０１４９】
◎：ΔＶがほとんどなく、カブリの発生なし（良好）
○：ΔＶが小さく、カブリが０．０１以下の濃度（目視で判別できず実用上問題なし）
△：ΔＶの発生で、カブリが０．０１より大きく０．０２以下の濃度（目視で判別しにくい、再検討要）
×：ΔＶが大きくカブリの発生が目視ではっきりと確認できる。（実用上問題あり）
画像濃度、階調性及び鮮鋭性の評価
上記評価条件を常温常湿（２０℃、６０％ＲＨ）環境に変更し、白画像から黒ベタ画像まで２０段階の階調段差を持つオリジナル画像を複写し、画像濃度と階調性を評価した。評価は複写画像の階調濃度をマクベス社製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。
【０１５０】
（画像濃度）
◎：黒ベタ部濃度が１．３以上（良好）
○：黒ベタ部濃度が１．０〜１．３未満（実用上問題なし）
△：黒ベタ部濃度が０．７〜１．０未満（再評価が必要）
×：黒ベタ部濃度が０．７未満（実用上問題あり）
（階調性）
◎：階調性が１４段階以上（良好）
○：階調性が１０〜１３段階（実用上問題なし）
△：階調性が５〜９段階（再評価が必要）
×：階調性が４段階以下（実用上問題あり）
（鮮鋭性）
画像の鮮鋭性は、環境条件の厳しい高温高湿（３０℃、８０％ＲＨ）環境において画像を出し、文字潰れで評価した。文字サイズ（ポイント）が異なる文字画像を形成し、下記の判断基準で評価した。
【０１５１】
◎：４ポイント以下の文字が明瞭であり、容易に判読可能（良好）
○：６ポイント以下の文字が明瞭であり、容易に判読可能（実用上問題なし）
△：８ポイント以下の文字が明瞭であり、容易に判読可能（再評価が必要）
×：８ポイントの文字の一部又は全部が判読不能（実用上問題あり）
【０１５２】
【表２】

【０１５３】
表２から明らかなように、本発明の感光体の条件（Ｎ型顔料の電荷発生物質を含有する電荷発生層及び合計膜厚が５〜１５μｍ電荷輸送層、且つ最上層の電荷輸送層がフッ素系樹脂粒子を含有する感光体）Ｎｏ．１〜３、６〜１４は黒ポチ、白抜け、環境メモリ、初期メモリ、画像濃度、階調性、鮮鋭性の各評価項目とも、本発明外の感光体Ｎｏ．４、５、１５、１６に対し、良好な結果を達成している。特に、ペリレン顔料ＡのＮ型顔料を用い、最上層の電荷輸送層がフッ素系樹脂粒子を含有する感光体（Ｎｏ．１〜３、６〜９、１４）は改善効果が著しい。一方、電荷輸送層の合計膜厚が１６μｍの感光体４は環境メモリ、初期メモリが劣り、鮮鋭性も低下しており、電荷輸送層の合計膜厚が４μｍの感光体５は帯電電位が目標の５００Ｖに達せず、画質が全体に低下している。又、電荷発生物質がＰ型顔料のみの感光体１５は環境メモリ、初期メモリが劣り、鮮鋭性も低下している。又、最上層の電荷輸送層がフッ素系樹脂粒子を含有していない感光体１６は黒ポチ、白抜けが多発し、鮮鋭性も低下している。
【０１５４】
【発明の効果】
本発明の有機感光体を用いることにより、黒ポチ、白抜け、環境メモリ、初期メモリ等の画像欠陥の発生が少なく、且つ、高い画像濃度及び高階調性の電子写真画像が得られる。又、本発明の有機感光体を用いた良好な電子写真画像を形成できる画像形成方法、画像形成装置を提供することが出来る。
【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。
【符号の説明】
１ 画像形成装置
２１ 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[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, organic photoconductors have been widely used as electrophotographic photoconductors. Organic photoreceptors have advantages over other photoreceptors such as easy development of materials corresponding to various exposure light sources from visible light to infrared light, selection of materials without environmental pollution, and low manufacturing cost. However, disadvantages include poor mechanical strength and poor chemical durability, deterioration of the electrostatic characteristics of the photoreceptor at the time of printing a large number of sheets, and generation of surface scratches.
[0003]
That is, since an electrical or mechanical external force is directly applied to the surface of an organic photoreceptor (hereinafter, also simply referred to as a photoreceptor) by a charging unit, a developing unit, a transfer unit, a cleaning unit, and the like, durability against these is required. You.
[0004]
Specifically, the photoreceptor is required to have durability against abrasion and scratches on the surface of the photoreceptor due to friction, active oxygen such as ozone generated during corona charging, surface deterioration due to nitrogen oxides, and the like.
[0005]
In order to solve the problems of mechanical and chemical durability as described above, the organic photoreceptor has a layer structure of a charge generation layer and a charge transport layer, and the charge transport layer of the surface layer has high strength and high charge. In many cases, a uniform layer hardly permeates the active gas and the thickness of the charge transport layer is set to be larger than 20 μm.
[0006]
Further, as another approach, a technique of providing a high-strength protective layer on the surface of the photoreceptor has been studied. For example, it is reported that a curable silicone resin is used as a protective layer of a photoreceptor (Patent Document 1). However, the method of thickening the charge transport layer and the method of providing a high-strength protective layer as described above have a problem that carriers generated in the charge generation layer diffuse laterally before reaching the surface, and sharpness and the like are disadvantageous. Problem. In the field of digital copiers, there is a growing demand for higher image quality, and high-resolution image formation is being studied. In this way, a good electrostatic latent image can be obtained with a layer structure or protective layer that easily causes carrier diffusion. Can not.
[0007]
In order to faithfully reproduce image information as an electrostatic latent image, it is necessary to ensure a sufficient potential contrast between the exposed and unexposed portions. This is because diffusion of carriers until the generated carriers reach the surface charge is performed. It is important to control. The latent image deterioration of a high-density image is caused by the fact that when the ratio D / μ between the diffusion constant (D) and the drift mobility (μ) of the charge transport layer increases, the effect of diffusion to the electrostatic latent image cannot be ignored, It has been reported that the latent image degradation increases as the layer thickness increases (Non-Patent Document 1).
[0008]
Further, an organic photoreceptor in which the charge transport layer is made thinner to prevent diffusion of an electrostatic latent image has already been proposed (Patent Document 2). However, when these proposed organic photoreceptors are actually formed using an electrophotographic image forming apparatus, an unclear image having a reduced image density tends to appear. This is because, when the organic photoreceptor is made thinner, the capacitance of the photosensitive layer becomes smaller, the charging potential decreases, and as a result, the developability decreases and the image density decreases. In particular, when a developer using a toner having a small particle diameter is used to obtain high image quality, the developability is reduced, the image density in reversal development is not sufficient, and a character image or a photographic image with sharpness is obtained. There is a problem that it is difficult to be performed.
[0009]
In order to recover this decrease in the developing property, it is effective to apply an increased amount of charge per unit area to the thinned organic photoreceptor to increase the electric field intensity per unit thickness of the photoreceptor. . However, when the electric field intensity per unit film thickness of the photoreceptor is increased, image defects such as black spots and white spots on the contrary tend to increase in reversal development. That is, black spots are likely to occur due to injection of free carriers from the conductive support. That is, when the electric field intensity per unit film thickness of the photoreceptor is increased, the injection of charges irrelevant to the image from the conductive support constituting the photoreceptor increases with the increase in the electric field intensity of the photoreceptor. Image defects are likely to occur. As a method for improving the black spots, a wide range of measures have been taken to prevent the injection of free carriers by providing an intermediate layer or anodizing the surface of the conductive substrate to form an insulating layer. For example, there has been proposed a photoreceptor in which the thickness of a photosensitive layer is reduced, and an intermediate layer contains titanium oxide particles (Patent Document 3). However, in the reversal development in which the electric field intensity is increased, the above-mentioned method cannot sufficiently prevent black spots.
[0010]
Also, if the amount of electric charge per unit area increases in order to increase the electric field strength per unit film thickness of the photoconductor, image unevenness (hereinafter referred to as environmental memory) due to environmental fluctuations in temperature and humidity, and photoconductor surface potential Are not stable at the time of initial startup, ΔV (difference in charging potential between the first rotation and the second rotation of the photoconductor) increases (hereinafter, referred to as an initial memory), and fog tends to occur.
[0011]
On the other hand, when the surface charge of the photoreceptor is increased and the electric field intensity per unit film thickness is increased, the adhesion of foreign substances on the photoreceptor surface is increased, and the white spot is generated in the reversal development, which is opposite to the above-mentioned black spot. An image defect is generated, and the sharpness is easily reduced. The white spot is considered to be caused by filming of the fine toner or the like on the surface of the photoreceptor, and is caused by the surface charge not disappearing in the exposed portion. When the surface charge of the photoreceptor increases, the Coulomb force between the toner and the photoreceptor increases. It is considered that the cleaning property is reduced and white spots are liable to occur as the value increases. In addition, when a small particle diameter toner is used, this white spot is likely to occur as the surface area of the toner increases.
[0012]
[Patent Document 1]
JP-A-6-118681
[Patent Document 2]
JP-A-5-119503
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2002-196522
[Non-patent document 1]
The Imaging Society of Japan, Vol. 38, No. 4, page 296
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide an organic photoreceptor that forms an accurate electrostatic latent image with a small blur and that can faithfully visualize the electrostatic latent image as a toner image. And an image forming method capable of preventing image defects such as black spots and white spots, environmental memory, initial memory, etc., and ensuring high quality image quality with good image density, sharpness, and gradation. An object of the present invention is to provide an image forming apparatus.
[0017]
[Means for Solving the Problems]
As a result of repeated investigations on the above problems, we have improved the sharpness using an organic photoreceptor and performed reversal development at high electric field strength (reversal development under the condition of increasing the amount of charge per unit area of the photoreceptor). To prevent the occurrence of image defects such as black spots and white spots, which are likely to occur, the organic photoreceptor should have a function-separated configuration of the charge generation layer and the charge transport layer, and the thickness of the charge transport layer forming the surface layer should be reduced. In addition, it is necessary to prevent the diffusion of carriers, and at the same time, to prevent image defects such as black spots, white spots, environmental memory, and initial memory, which are likely to occur at high electric field strength. Therefore, in order to prevent the injection of free carriers from the conductive substrate, which is facilitated by the thinning of the charge transport layer, the injection of free carriers into the charge generation material of the charge generation layer can be blocked, and the potential characteristics are stabilized. The present inventors have discovered that it is important to use a substance and reduce the surface energy of the photoreceptor to reduce the adhesion of foreign substances that cause white spots, and completed the present invention.
[0018]
That is, the present invention, by having the following configuration, prevents the occurrence of image defects such as black spots, white spots, and image unevenness due to changes in temperature and humidity, and is excellent in image density, sharpness, and gradation. High quality electrophotographic images can be obtained. That is, the object of the present invention is achieved by having the following configuration.
[0019]
1. A charge generation layer containing a charge generation substance of an N-type pigment on a conductive support; and a laminated structure of at least one layer having a total film thickness of 5 to 15 μm on the charge generation layer, and the uppermost layer is made of fluorine. An organic photoreceptor characterized by containing resin particles.
[0020]
2. A charge generation layer containing an N-type pigment and 10% by mass or less of a P-type pigment charge generation substance based on the N-type pigment on the conductive support, and at least 1 layer having a total film thickness of 5 to 15 μm on the charge generation layer; An organic photoreceptor having a laminated structure of at least two layers, wherein the uppermost layer contains fluorine resin particles.
[0021]
3. 3. The organic photoconductor according to the above item 1 or 2, wherein the N-type pigment is a perylene compound pigment.
[0022]
4. Wherein the perylene-based compound is a 3,4,9,10-tetracarboxylic imide derivative represented by the general formulas (1) to (3) and a mixture thereof. 2. The organic photoreceptor according to claim 1.
[0023]
5. The organic photoreceptor according to any one of the above items 1 to 4, further comprising an intermediate layer containing inorganic particles between the conductive support and the charge generation layer.
[0024]
6. An image forming method comprising forming an electrophotographic image using the organic photoreceptor according to any one of the above items 1 to 5.
[0025]
7. 7. An image forming apparatus for forming an electrophotographic image by using the image forming method according to the above item 6.
[0026]
8. 6. The organic photoreceptor according to any one of 1 to 5, charging means for uniformly charging the organic photoreceptor, a latent image forming means for forming an electrostatic latent image on the charged organic photoreceptor, Developing means for visualizing the electrostatic latent image on the organic photoreceptor, transfer means for transferring the toner image visualized on the organic photoreceptor onto a transfer material, and electric charge on the organic photoreceptor after the transfer And at least one of cleaning means for removing residual toner on the organic photoreceptor after transfer is integrally supported, and can be detachably attached to the image forming apparatus main body. Characteristic process cartridge.
[0027]
Hereinafter, the present invention will be described in detail.
That is, the organic photoreceptor of the present invention has a laminated structure of a charge generation layer containing a charge generation substance of an N-type pigment on a conductive support and at least one layer having a total film thickness of 5 to 15 μm on the charge generation layer. And the uppermost layer contains fluorine resin particles.
[0028]
Further, the organic photoreceptor of the present invention comprises an N-type pigment on a conductive support and a charge-generating layer containing 10% by mass or less of a charge-generating substance of a P-type pigment with respect to the N-type pigment. It has a laminated structure of at least one layer having a thickness of 5 to 15 μm, and the uppermost layer contains fluorine resin particles.
[0029]
In the present invention, since the organic photoreceptor has the above-described configuration, even when an image is formed by reversal development under a high electric field strength, black spots are hardly generated and white spots are prevented from being generated. Generation of memory can be prevented, and an electrophotographic image with improved sharpness can be obtained for both the character image and the halftone image.
[0030]
Hereinafter, the organic photoreceptor used in the present invention will be described.
The organic photoreceptor used in the present invention contains a charge generating substance of a charge generating layer N-type pigment.
[0031]
Here, the method for determining the N-type pigment and the P-type pigment of the present invention will be described.
A charge generation layer having a thickness of 10 μm (a charge generation layer is formed using a dispersion in which a pigment is dispersed in a binder by 50% by mass) is formed on a conductive support. The charge generation layer is negatively charged, and the light attenuation characteristics are evaluated. In addition, the light-attenuating characteristics are similarly evaluated by charging to a positive polarity.
[0032]
The N-type pigment is a pigment in the above evaluation in which the light decay when charged negatively is greater than the light decay when charged positively.
[0033]
The P-type pigment is a pigment in the above evaluation in which the light decay when charged positively is greater than the light decay when charged negatively.
[0034]
As the charge generating substance of the N-type pigment, any kind of charge generating substance may be used as long as the charge generating substance exhibits the above-described N-type characteristics. Among them, perylene is preferably used as the charge generating substance of the N-type pigment. , 1-nitroperylene, 1,12-o-phenyleneperylene, 1,3,7,9-tetraacetoxyperylene and the like, among which 3,4,9,10-tetracarboximide derivatives are preferred, Those represented by the structural formulas of the general formulas (1) to (3) are particularly preferably used.
[0035]
The structure may be symmetric or asymmetric. As shown in the general formula (3), cis type and trans type are also included. These isomers may be used alone by synthesis or subsequent separation operation, or may be used as they are as a mixture during synthesis.
[0036]
Among these perylene compounds, a perylene compound represented by the general formula (3) is most preferably used, and a perylene compound represented by the following structural formula is most preferred.
[0037]
Embedded image

[0038]
(In the formula, R represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, an alkoxy group, or a heterocyclic group.)
The above-mentioned perylene compound has several crystal polymorphs, and in particular, any crystal form is suitably used. For example, the X-ray diffraction spectrum has peaks at 6.3 °, 12.4 °, 25.3 °, and 27.1 ° of the Bragg angle 2θ (± 0.2 °), and the maximum peak is 12.4 °. Also included are those of a certain crystalline type and those of an amorphous type showing almost no clear peak. When used for the carrier generation layer, perylene exhibiting a specific crystal form may be dispersed and used, or a film may be formed by an operation such as vapor deposition. Further, the deposited film can be converted into a crystal by a solvent treatment or the like.
[0039]
Next, specific examples of perylene compounds that can be preferably used in the present invention are shown below.
[0040]
Specific examples of the compound of the general formula (1) In the general formula (1), R ₁ and R ₂ may be the same or different, and examples thereof include the following.
[0041]
Embedded image

[0042]
Embedded image

[0043]
Embedded image

[0044]
Specific examples of the compound of the general formula (2) In the general formula (2), R ₁ is the same as the general formula (1), and Z includes the following.
[0045]
Embedded image

[0046]
In the case of a dimer, Z is as follows.
[0047]
Embedded image

[0048]
Compound of general formula (3)
Embedded image

[0050]
Embedded image

[0051]
Embedded image

[0052]
Embedded image

[0053]
Embedded image

[0054]
In addition to the perylene pigment, examples of the N-type pigment include an azo pigment and a polycyclic quinone pigment having a functional group having a high electronegativity, for example, a cyano group.
[0055]
The charge generation layer of the present invention preferably contains a charge generation substance of the N-type pigment in combination with a P-type pigment of less than 10% by mass of the N-type pigment. As the P-type pigment, any kind of charge-generating substance may be used as long as it has the above-mentioned P-type characteristics. Examples include phthalocyanine pigments.
[0056]
The charge-generating substance of P-type phthalocyanine pigment, which is mainly used in conventional digital copiers and the like, has a small charge carrier transport ability. Therefore, when the charge-generating layer is thickened, the residual potential rises and image unevenness due to optical memory occurs. It's easy to do. Therefore, it has been difficult to increase the thickness of the charge generation layer to increase the amount of the charge generation substance, improve sensitivity, prevent optical interference fringes, or block free carriers from the conductive substrate.
[0057]
The organic photoreceptor of the present invention contains a charge generating substance of an N-type pigment on a conductive support, a charge generating layer having a thickness of 0.3 to 2 μm, and a charge transporting substance thereon, It has a structure of a negatively charged organic photoreceptor having a charge transport layer having a total film thickness of 5 to 15 μm (a negative electrostatic latent image is formed). By mainly using an N-type pigment, electrons generated in the charge generation layer can travel a relatively long distance and conduct to the conductive substrate. For this reason, even if the charge generation layer is formed to have a relatively large thickness, an increase in the residual potential due to trapping of electrons is prevented. When the charge generation layer has a thickness in the above range, the pigment concentration can be sufficiently increased, so that a single wavelength of image exposure light, laser light, LED light, or the like generally used in digital image formation can be used. Moire or the like due to light irradiation can also be prevented. In addition, the N-type pigment has a remarkable effect of injecting free carriers from the conductive substrate, and remarkably improves the occurrence of black spots in reversal development.
[0058]
When the thickness of the charge generation layer is less than 0.3 μm, it is difficult to sufficiently contain the pigment concentration, so that the exposure potential is insufficiently reduced to lower the image density or the effect of preventing laser light interference from being reduced. It's easy to do. On the other hand, if it is larger than 2.0 μm, the trap density of charge carriers in the charge generation layer tends to increase, and image unevenness due to an increase in optical memory tends to occur. The preferred thickness of the charge generation layer is 0.3 to 1.0 μm.
[0059]
Further, it is preferable that the charge generation layer contains a charge generation substance of the N-type pigment in combination with a P-type pigment of less than 10% by mass of the N-type pigment. By using a P-type pigment together with an N-type pigment, hole carriers generated deep inside the charge generation layer can be transported and injected to the boundary with the charge transport layer, and the hole carriers can be injected into the charge generation layer. Is prevented, and a rise in the residual potential is prevented. A more preferred amount of the P-type pigment is 0.5 to 5% by mass. If the content is 10% by mass or more, the effect of preventing free carriers from being injected from the conductive substrate is deteriorated, and black spots and fog are easily generated.
[0060]
On the other hand, the charge generation layer has a laminated structure of at least one layer, the total thickness thereof is 5 to 15 μm, and the uppermost layer contains fluorine resin particles. That is, by providing a layer having a total film thickness of 5 to 15 μm and an uppermost layer containing fluorine-based resin particles on the charge generation layer containing the charge generation substance, black spots are generated. It is also possible to obtain an electrophotographic image in which sharpness is improved for both a character image and a halftone image, since it is difficult to prevent white spots from occurring.
[0061]
The layer structure having a total thickness of 5 to 15 μm on the charge generation layer is preferably composed of a plurality of charge transport layers, and the uppermost charge transport layer contains fluorine resin particles. The layer structure composed of multiple charge transport layers with a total film thickness of 5 to 15 μm reduces diffusion of charge carriers generated in the charge generation layer and reproduces a latent image composed of fine dots with sufficient potential contrast can do. If the total thickness is less than 5 μm, the charging potential tends to be insufficient. If the total thickness exceeds 15 μm, the diffusion of the charge carriers increases, and the sharpness is not sufficiently improved. In particular, when the total thickness of the charge transport layer is in the range of 8 to 14 μm, the effect of improving sharpness is more remarkable.
[0062]
The fluorine-based resin particles contained in the uppermost charge transport layer means resin particles containing fluorine atoms, for example, ethylene tetrafluoride resin, ethylene trifluoride chloride resin, hexafluoroethylene propylene resin, It is preferable to appropriately select one or more of vinyl fluoride resins, vinylidene fluoride resins, ethylene difluoride ethylene chloride resins and copolymers thereof, and in particular, ethylene tetrafluoride resins and fluorocarbon resins. Vinylidene fluoride resins are preferred. The molecular weight and particle size of the fluororesin particles can be appropriately selected and are not particularly limited.
[0063]
The charge transport layer of the uppermost layer preferably has a structure containing fluorine-based resin particles in the binder resin, and the ratio of the fluorine-based resin particles is also affected by the particle diameter of the particles. It is preferably 50% by mass, more preferably 5 to 40% by mass. Further, the uppermost layer preferably contains a charge transporting substance.
[0064]
Additives such as coupling agents and antioxidants may be added to the uppermost layer of the present invention for the purpose of improving dispersibility, binding properties and weather resistance.
[0065]
Examples of the method for dispersing the fluorine-based resin particles in the uppermost layer include a method such as a homogenizer, a ball mill, a sand mill, a roll mill, and ultrasonic waves. There is no particular limitation as long as the particles can be dispersed to the primary particle size.
[0066]
In addition, various surfactants such as comb-type graft polymers may be appropriately mixed as a dispersing aid for the fluororesin particles.
[0067]
The thickness of the uppermost layer is preferably 0.1 to 4 μm. If the thickness is less than 0.1 μm, the surface hardness and strength are not sufficient, and the durability tends to decrease. If the thickness exceeds 4 μm, the contrast potential formed by a latent image during development tends to deteriorate. More preferably, it is 0.2 to 3.0 μm.
[0068]
The uppermost layer preferably has a low surface energy in order to satisfy the cleaning property and the stain resistance, and the low surface energy measured by the contact angle of water is preferably 90 degrees or more. If the angle is less than 90 degrees, a charge product, toner, or falling off from paper is likely to adhere to the surface due to repeated use in an electrophotographic process, and a latent image is likely to be degraded (image deletion) due to poor cleaning or reduced surface resistance. It is more preferably at least 95 degrees.
[0069]
By adopting the above configuration, sharpness can be remarkably improved, and image defects such as generation of black spots and image unevenness, which are likely to occur when the charge transport layer is thinned, are prevented. A stable organic photoreceptor can be provided.
[0070]
Hereinafter, the configuration of the organic photoconductor applied to the present invention other than the above 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 photoconductors such as a photoconductor composed of an organic charge-generating substance or an organic charge-transport substance, and a photoconductor composed of a polymer complex having a charge generation function and a charge transport function.
[0071]
The charge transport layer of the present invention means a layer having a function of transporting charge carriers generated in the charge generation layer by light exposure to the surface of the organic photoreceptor. It can be confirmed by laminating the layer and the charge transport layer on a conductive support and detecting photoconductivity.
[0072]
The layer constitution of the organic photoreceptor of the present invention basically comprises a photosensitive layer of a charge generation layer and a charge transport layer on a conductive support. Most preferably, the photosensitive layer comprises a charge generation layer and a charge transport layer.
[0073]
Hereinafter, a specific configuration of the photoconductor used in the present invention will be described.
Conductive Support A sheet-like or cylindrical conductive support is used as the conductive support used in the photoreceptor of the present invention.
[0074]
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.
[0075]
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 or plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.
[0076]
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.
[0077]
Intermediate layer 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.
[0078]
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 a number average primary particle diameter of 10 nm or more and 400 nm or less, 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.
[0079]
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 type and an amorphous type, and any type may be used, or two or more types may be mixed and used. Among them, the rutile type and granular type are the best.
[0080]
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.
[0081]
The alumina treatment, the silica treatment, and the zirconia treatment refer to a treatment for depositing alumina, silica, or zirconia on the surface of titanium oxide particles, and the alumina, silica, and zirconia deposited on these surfaces include water of alumina, silica, and zirconia. 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.
[0082]
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.
[0083]
Examples of the reactive organosilicon compound include compounds represented by the following general formula (4), 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.
[0084]
General formula (4)
(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 (4), 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 hydroxyl group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, a vinyl group such as vinyl and propenyl, a mercapto group such as γ-mercaptopropyl, a 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.
[0085]
The organosilicon compound represented by the general formula (4) may be used alone or in combination of two or more.
[0086]
When n is 2 or more in the specific compound of the organosilicon compound represented by the general formula (4), 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 (4) are used, R and X may be the same or different between the respective compounds.
[0087]
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.
[0088]
In particular, when methyl hydrogen polysiloxane is used for the final surface treatment, a good effect can be obtained.
[0089]
Photosensitive layer charge generation layer The charge generation material (CGM) of the charge generation layer uses the N-type pigment described above.
[0090]
In the case where a binder is used as the CGM dispersion medium 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.
[0091]
Charge Transport Layer As described above, in the present invention, the charge transport layer is preferably composed of a plurality of charge transport layers, and the uppermost charge transport layer preferably contains fluorine-based resin particles.
[0092]
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 the above-mentioned fluororesin particles and antioxidants may be contained as necessary.
[0093]
As the charge transporting substance (CTM), a known hole transporting (P-type) charge transporting substance (CTM) is preferably 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 a characteristic that the ionization potential difference with the CGM to be combined is 0.5 (eV) or less, and is preferably 0. .30 (eV) or less.
[0094]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0095]
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 CTM dispersibility and good electrophotographic properties is most preferable.
[0096]
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.
[0097]
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.
[0098]
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.
[0099]
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.
[0100]
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.
[0101]
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.
[0102]
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.
[0103]
In the image forming section C, a drum-shaped photosensitive member 21 serving as an image carrier, a charging unit (charging step) 22 for charging the photosensitive member 21, and a surface potential of the charged photosensitive member Detecting means 220, a developing means (developing step) 23, a transfer / conveying belt device 45 as a transferring means (transfer step), a cleaning device (cleaning step) 26 for the photoreceptor 21, and a light removing means (optical charge) A PCL (precharge lamp) 27 as a generation step) is 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 uses the organic photoreceptor of the present invention and is driven and rotated clockwise in the drawing.
[0104]
After the rotating photoconductor 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by the exposure optical system 30 as an image exposure unit (image exposure step). Exposure is performed. 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. The image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by the rotation (sub-scan) of the photoconductor 21. In one example of the present embodiment, a character portion is exposed to form an electrostatic latent image.
[0105]
In the image forming method of the present invention, when forming an electrostatic latent image on the photosensitive member, it is preferable to perform image exposure using an exposure beam having a spot area of 2 × 10 ⁻⁹ m ² or less. Even if such a small-diameter beam exposure is performed, the organic photoreceptor of the present invention can faithfully form an image corresponding to the spot area. A more preferred spot area is 0.01 × 10 ⁻⁹ to 1 × 10 ⁻⁹ m ² . As a result, at 400 dpi (dpi: the number of dots per 2.54 cm) or more, it is possible to achieve an extremely excellent image quality for realizing 256 gradations.
[0106]
The spot area of the exposure beam is represented by an area corresponding to a light intensity of 1 / e ² or more of the peak intensity of the light beam.
[0107]
As the exposure beam used, there are a scanning optical system using a semiconductor laser, a solid-state scanner such as an LED or a liquid crystal shutter, and the like, and the light intensity distribution also has a Gaussian distribution, a Lorentz distribution, and the like, but 1 / e of each peak intensity. ^The area up to ² is the spot area.
[0108]
The electrostatic 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. The image forming method of the present invention is characterized in that a polymerized toner is used as a developer used in the developing unit. By using a polymerized toner having a uniform shape and a uniform particle size distribution together with the organic photoreceptor of the present invention, an electrophotographic image having better sharpness can be obtained.
[0109]
Here, the term “polymerized toner” refers to a toner obtained by forming a toner binder resin and forming the toner shape by polymerization of a raw material monomer of the binder resin and a subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization and emulsion polymerization and, if necessary, a subsequent step of fusing particles together.
[0110]
Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then polymerizing the same, a toner having a uniform particle size distribution and shape can be obtained.
[0111]
Polymerized toners are prepared by suspension polymerization or emulsion polymerization of monomers in a liquid to which an emulsion of necessary additives is added to produce fine polymerized particles. It can be produced by a method of adding and associating. A method of preparing by associating with a dispersion liquid such as a release agent and a colorant necessary for the composition of the toner at the time of association, and dispersing toner components such as a release agent and a colorant in a monomer. And then emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.
[0112]
That is, various constituent materials such as a colorant and a releasing agent as needed, a charge control agent, and a polymerization initiator are added to the polymerizable monomer. Various constituent materials are dissolved or dispersed in the polymerizable monomer. The polymerizable monomer in which the various constituent materials are dissolved or dispersed is dispersed in an aqueous medium containing a dispersion stabilizer into oil droplets having a desired size as a toner by using a homomixer or a homogenizer. Thereafter, the stirring mechanism is moved to a reaction device, which is a stirring blade described below, and heated to cause the polymerization reaction to proceed. After completion of the reaction, the dispersion stabilizer is removed, filtered, washed, and dried to prepare a toner.
[0113]
Further, as a method of producing the toner of the present invention, a method of preparing by associating or fusing resin particles in an aqueous medium can also be mentioned. Although this method is not particularly limited, for example, the methods described in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904 can be exemplified. That is, a method of associating a plurality of resin particles and dispersed particles of a constituent material such as a colorant, or a fine particle composed of a resin and a colorant, particularly, after dispersing these in water using an emulsifier, the critical aggregation concentration At the same time as adding the above flocculant and salting out, the formed polymer itself is heated and fused at a temperature equal to or higher than the glass transition temperature to gradually grow the particle size while forming fused particles, and the desired particle size is obtained. When a large amount of water is added, the particle size growth is stopped by adding a large amount of water, and the shape of the particles is controlled by heating and stirring to smooth the surface of the particles. Can be formed. Here, an organic solvent infinitely soluble in water may be added together with the coagulant.
[0114]
The materials and manufacturing method for producing a toner having a uniform shape factor and the like used in the present invention, a reactor for a polymerized toner, and the like are described in detail in JP-A-2000-214629.
[0115]
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.
[0116]
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.
[0117]
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.
[0118]
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.
[0119]
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. .
[0120]
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.
[0121]
As the image forming apparatus of the present invention, the above-described photoconductor, a developing device, a cleaning device, and other components are integrally combined as a process cartridge, and this unit is configured to be detachable from the apparatus main body. Is also good. Also, a process cartridge is formed by integrally supporting at least one of a charging device, an image exposing device, a developing device, a transfer or separation device, and a cleaning device together with a photoreceptor, as a single unit detachable from the apparatus body, It may be configured to be detachable using a guide means such as a rail of the apparatus body.
[0122]
The organic photoreceptor of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copiers, laser printers, LED printers, and liquid crystal shutter printers. In addition, displays, recording, light printing, plate making and facsimile using electrophotographic technology are applied. Etc. can be widely applied.
[0123]
【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”.
[0124]
Preparation of Photoconductor 1 Photoconductor 1 was prepared as described below.
[0125]
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 filtered (filter; Rigimesh 5 μm filter manufactured by Pall Corporation) to prepare an intermediate layer coating solution.
[0126]

Were mixed, and the mixture was dispersed in a batch system for 10 hours using a sand mill as a dispersing machine to prepare an intermediate layer dispersion.
[0127]
Using the above coating solution, coating was performed on the support so as to have a dry film thickness of 1.0 μm.

And mixed with a sand mill for 30 hours to prepare a charge generation layer coating solution. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.
[0128]

Was mixed and dissolved to prepare a charge transport layer coating solution 1. This coating solution was applied on the charge generation layer by a dip coating method, and dried at 110 ° C. for 70 minutes to form a charge transport layer 1 having a dry film thickness of 10 μm.
[0129]

Was mixed with a sand grinder using glass beads (manufactured by Amex Co., Ltd.) to prepare a dispersion of 4-fluoroethylene resin particles.
[0130]

Was mixed and dissolved to prepare a charge transport layer coating solution 2. This coating solution was applied onto the charge transport layer 1 by a circular slide hopper type coater, and dried at 110 ° C. for 70 minutes to form a charge transport layer 2 having a dry film thickness of 2 μm. .
[0131]
Preparation of Photoconductors 2 to 9 In the preparation of the photoconductor 1, the titanium oxide of the intermediate layer, the film thickness of the charge generation layer (CGL), the film thickness of the charge transport layers 1 and 2 (CTL1 and 2), and the fluorine-based resin particles were used. Photoconductors 2 to 9 were produced in the same manner as Photoconductor 1, except that the photoconductors were changed as shown in Table 1.
[0132]
Preparation of Photoconductors 10 to 13 In the preparation of Photoconductor 1, N-type pigments of Compounds B to E were used in place of the perylene pigment (A) of the charge generation layer, and the amount of the titanyl phthalocyanine pigment was changed to 3.6 parts. Photoconductors 10 to 13 were produced in the same manner as the photoconductor 1, except that the fluorine-based resin particles of the charge transport layer 2 were changed as shown in Table 1.
[0133]
Preparation of Photoreceptor 14 Photoreceptor 14 was prepared in the same manner as for Photoreceptor 1, except that the titanyl phthalocyanine pigment (F) in the charge generation layer was omitted.
[0134]
Preparation of Photoreceptor 15 In the preparation of Photoreceptor 1, instead of the perylene pigment (A) of the charge generation layer, a titanyl phthalocyanine pigment (F: Cu-Kα characteristic X-ray diffraction angle: Photoconductor 15 was prepared in the same manner as Photoconductor 1, except that a titanyl phthalocyanine pigment having a maximum peak at 0.3 ° was used.
[0135]
Preparation of Photoreceptor 16 Photoreceptor 16 was prepared in the same manner as in preparation of photoreceptor 1 except that charge transport layer 2 was omitted.
[0136]
[Table 1]

[0137]
In Table 1, I, J, and K of the surface treatment of the fine particles indicate the following treatments.
I: Silica-alumina treatment and methylhydrogenpolysiloxane treatment J: Silica-alumina treatment and octyltrimethoxysilane treatment K: Silica-zirconia treatment and methyltrimethoxysilane treatment G and H indicate the following fluororesin fine particles.
[0138]
G: ethylene tetrafluoride resin particles (Lubron L-2, manufactured by Daikin Industries, Ltd.)
H: ethylene trifluoride resin particles (DAIFRON, manufactured by Daikin Industries, Ltd.)
The chemical structural formulas of the perylene pigments A to D, the azo pigment E, and the titanyl phthalocyanine pigment F used for producing the above photoconductors 1 to 16 are shown below.
[0139]
Embedded image

[0140]
Embedded image

[0141]
《Evaluation》
Next, each of the above photoconductors was mounted on a Konica Sitios 7040 digital copying machine, and images were formed and evaluated. That is, the photoreceptor was set to a Konica Sitios 7040 digital copying machine (having a scorotron charger, a semiconductor laser image exposure device, and a reversal developing means) basically having the structure shown in FIG. 1, and a copying experiment was performed. In this experiment, the program of the unexposed portion target potential was incorporated in the memory of the process control section in FIG. 1, and the digital copying machine was modified so that the unexposed portion target potential at the developing position was automatically set.
[0142]
《Image evaluation》
Attach each photoreceptor to the above digital copying machine, copy A4 paper, 50,000 sheets of character images with 7% pixel rate in a high temperature and high humidity (30 ° C., 80% RH) environment, start and copy 10,000 sheets Each time, a white image and a halftone image were copied, and the presence or absence of image defects such as black spots and white spots was confirmed. Table 2 shows the results.
[0143]
Other evaluation conditions using the above 7040 were set to the following conditions.
Charging condition Charger: Unexposed portion potential (VH) at scorotron charger development position Target: -500V
Exposure conditions Exposure portion potential target: Set to an exposure amount to be -50V.
[0144]
Exposure beam: Image exposure with a dot density of 400 dpi was performed. Laser beam spot area: 0.8 × 10 ⁻⁹ m ² , laser using a semiconductor laser of 680 nm Developing conditions The developer is a carrier coated with an insulating resin with ferrite having a volume average particle diameter of 50 μm as a core and a styrene acrylic resin. A toner developer in which silica and titanium oxide are externally added to colored particles having a volume average particle diameter of 5.3 μm prepared by a polymerization method comprising a resin as a main material, a colorant of carbon black, a charge control agent, and a low molecular weight polyolefin, is used. used.
[0145]
Transfer condition Transfer pole; Corona charging method Separation condition: Cleaning condition using separation means of separation claw unit 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 is countered in the cleaning section. Was contacted by a weight load method so as to have a linear pressure of 18 (g / cm).
[0146]
Black Spot Image Defect Evaluation Criteria Regarding black spots, the periodicity coincided with the period of the photoconductor, and the number of visible black spots per A4 size was determined.
[0147]
：: Frequency of black spots of 0.4 mm or more: All copied images are 3 copies / A4 or less (good)
：: Black spots of 0.4 mm or more Frequency: 1 or more of 4 / A4 or more and 10 / A4 or less (no problem in practical use)
×: Black spots of 0.4 mm or more Frequency: 11 pieces / A4 or more 1 sheet or more (problem in practice)
With respect to the evaluation criterion for white image defects, the periodicity coincided with the period of the photoreceptor, and the number of visible white spots per A4 size was determined.
[0148]
：: White spot frequency of 0.4 mm or more: 5 copies of all copied images / A4 or less (good)
：: White spot frequency of 0.4 mm or more: 1 or more of 6 / A4 or more and 20 / A4 or less (no problem in practical use)
×: White spot frequency of 0.4 mm or more: 21 pieces / A4 or more occurred one or more sheets (a problem in practical use)
Environmental Memory Environmental Memory: The above-mentioned Styos 7040 copying machine was left under HH for 24 hours, then placed under low humidity and low temperature (LL: 20 RH%, 10 ° C.), and copied after 30 minutes. A halftone image having a density of 0.4 is copied to a density of 0.4 in the original image, and a determination is made based on a density difference (ΔHD = maximum density−minimum density) of the copied image ◎: ΔHD is 0.05 or less (good)
：: ΔHD is larger than 0.05 and smaller than 0.1 (no problem in practical use)
×: ΔHD is 0.1 or more (there is a problem in practical use)
The evaluation was made based on the presence or absence of image fogging that occurred because the initial memory photoconductor surface potential was not stable at the initial startup and ΔV (the difference between the charging potentials of the first and second rotations of the photoconductor) was large.
[0149]
A: Almost no ΔV and no fog (good)
：: Density of ΔV is small and fog is not more than 0.01 (there is no practical problem because it cannot be visually discriminated)
Δ: Density of fog greater than 0.01 and not more than 0.02 due to occurrence of ΔV (it is difficult to determine visually and reconsideration is required)
×: ΔV is large and fogging can be clearly confirmed visually. (There is a problem in practical use)
Evaluation of Image Density, Gradation and Sharpness The above evaluation conditions were changed to a normal temperature and normal humidity (20 ° C., 60% RH) environment, and an original image having 20 gradation steps from a white image to a solid black image was copied. Then, the image density and the gradation were evaluated. In the evaluation, the gradation density of the copied image was measured using RD-918 manufactured by Macbeth. The relative reflection density was measured with the reflection density of the paper being "0".
[0150]
(Image density)
A: Black solid portion density of 1.3 or more (good)
：: Black solid portion density of 1.0 to less than 1.3 (no problem in practical use)
Δ: Black solid portion density of 0.7 to less than 1.0 (re-evaluation required)
×: Density of black solid portion is less than 0.7 (practical problem)
(Gradation)
：: 14 or more gradations (good)
：: 10 to 13 gradations (no problem in practical use)
Δ: 5 to 9 gradations (re-evaluation required)
×: Gradation of 4 steps or less (problematic in practice)
(Sharpness)
The sharpness of the image was evaluated by forming an image in a high-temperature and high-humidity (30 ° C., 80% RH) environment under severe environmental conditions and evaluating the character collapse. Character images having different character sizes (points) were formed and evaluated according to the following criteria.
[0151]
◎: Characters of 4 points or less are clear and easily legible (good)
：: Characters of 6 points or less are clear and easily legible (no problem in practical use)
△: Characters of 8 points or less are clear and easily legible (re-evaluation required)
×: Some or all of the 8-point characters are illegible (practical problem)
[0152]
[Table 2]

[0153]
As is clear from Table 2, the conditions of the photoreceptor of the present invention (the charge generation layer containing the charge generation substance of the N-type pigment, the charge transport layer having a total film thickness of 5 to 15 μm, and the uppermost charge transport layer being fluorine) Photoconductor containing resin particles) Nos. 1 to 3 and 6 to 14 are the evaluation items of the photoconductor No. other than the present invention in each of the evaluation items of black spots, white spots, environmental memory, initial memory, image density, gradation, and sharpness. Good results were achieved for 4, 5, 15, and 16. In particular, the photoconductors (Nos. 1-3, 6-9, and 14) using an N-type pigment of perylene pigment A and having the uppermost charge transport layer containing fluorine-based resin particles have a remarkable improvement effect. On the other hand, the photoreceptor 4 having a charge transport layer having a total thickness of 16 μm has poor environmental memory and initial memory, and has a reduced sharpness. The photoreceptor 5 having a charge transport layer having a total thickness of 4 μm has a target charging potential. Of 500 V, and the image quality is reduced as a whole. Further, the photoreceptor 15 having only the P-type pigment as the charge generating substance is inferior in environmental memory and initial memory, and has low sharpness. The photosensitive member 16 in which the uppermost charge transport layer does not contain fluorine resin particles has many black spots and white spots, and the sharpness is also reduced.
[0154]
【The invention's effect】
By using the organic photoreceptor of the present invention, the generation of image defects such as black spots, white spots, environmental memory, and initial memory can be reduced, and an electrophotographic image with high image density and high gradation can be obtained. Further, it is possible to provide an image forming method and an image forming apparatus capable of forming a good electrophotographic image using the organic photoreceptor of the present invention.
[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.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 image forming apparatus 21 photoreceptor 22 charging means 23 developing means 24 transfer pole 25 separation pole 26 cleaning apparatus 30 exposure optical system 45 transfer and transport belt apparatus 50 fixing means 250 separation claw unit

Claims (8)

A charge generation layer containing a charge generation substance of an N-type pigment on a conductive support; and a laminated structure of at least one layer having a total film thickness of 5 to 15 μm on the charge generation layer, and the uppermost layer is made of fluorine. An organic photoreceptor characterized by containing resin particles. A charge generation layer containing an N-type pigment and 10% by mass or less of a P-type pigment charge generation substance based on the N-type pigment on the conductive support, and at least 1 layer having a total thickness of 5 to 15 μm on the charge generation layer An organic photoreceptor having a laminated structure of at least two layers, wherein the uppermost layer contains fluorine resin particles. 3. The organic photoconductor according to claim 1, wherein the N-type pigment is a perylene compound pigment. The perylene-based compound is a 3,4,9,10-tetracarboximide derivative represented by the following general formulas (1) to (3) and a mixture thereof: The organic photoreceptor according to any one of the preceding claims.

(Wherein R ₁ and R ₂ are each a hydrogen atom, a substituted or unsubstituted alkyl group, cycloalkyl group, aryl group, alkoxy group, alkylamino group, dialkylamino group, benzyl group, phenethyl group, heterocyclic ring In the case of forming a multimer, R ₁ and R ₂ may be 1,4-phenylene groups, and Z represents a group of atoms necessary to form a substituted or unsubstituted heterocyclic ring.) The organic photoconductor according to any one of claims 1 to 4, further comprising an intermediate layer containing inorganic particles between the conductive support and the charge generation layer. An image forming method comprising forming an electrophotographic image using the organic photoreceptor according to claim 1. An image forming apparatus that forms an electrophotographic image by using the image forming method according to claim 6. An organic photoreceptor according to claim 1, charging means for uniformly charging the organic photoreceptor, a latent image forming means for forming an electrostatic latent image on the charged organic photoreceptor, Developing means for visualizing the electrostatic latent image on the organic photoreceptor, transfer means for transferring the toner image visualized on the organic photoreceptor onto a transfer material, At least one of a charge removing means for removing charge and a cleaning means for removing toner remaining on the organic photoreceptor after transfer is integrally supported, and can be detachably attached to the image forming apparatus main body. A process cartridge.

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