JP4372396B2 - Organic photoreceptor, image forming method, image forming apparatus, and process cartridge - Google Patents

Description

【００３２】
（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。
【００３３】
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。
【００３４】
一般式（１）の化合物の具体例
前記一般式（１）中、Ｒ₁、Ｒ₂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。
【００３５】
【化３】

【００３６】
【化４】

【００３７】
【化５】

【００３８】
一般式（２）の化合物の具体例
前記一般式（２）中のＲ₁は一般式（１）と同一であり、Ｚは下記のものが挙げられる。
【００３９】
【化６】

【００４０】
２量体の場合には、Ｚは下記のものとなる。
【００４１】
【化７】

【００４２】
一般式（３）の化合物
【００４３】
【化８】

【００４４】
【化９】

【００４５】
【化１０】

【００４６】
【化１１】

【００４７】
【化１２】

【００４８】
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。
【００４９】
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。
【００５０】
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。
【００５１】
本発明の有機感光体は、導電性支持体上にＮ型顔料のペリレン系化合物及び該Ｎ型顔料に対し、０．５〜６質量％のＰ型顔料のフタロシアニン顔料を混合して含有し、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。
【００５２】
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。
【００５３】
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。
【００５４】
一方、電荷輸送層は複数の層構成にしてもよく、その膜厚の合計が５〜１５μｍであればよい。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、鮮鋭性が十分に改善されない。電荷輸送層の膜厚が５〜１０μｍの場合に、鮮鋭性の改善効果がより顕著である。
【００５５】
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。
【００５６】
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。
【００５７】
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。
【００５８】
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。
【００５９】
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。
【００６０】
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。
【００６１】
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１０³Ωｃｍ以下が好ましい。
【００６２】
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。
【００６３】
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。
【００６４】
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。
【００６５】
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。
【００６６】
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。
【００６７】
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。
【００６８】
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。
【００６９】
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。
【００７０】
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。
【００７１】
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。
【００７２】
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。
【００７３】
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。
【００７４】
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。
【００７５】
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。
【００７６】
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。
【００７７】
電荷輸送層
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。
【００７８】
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。
【００７９】
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。
【００８０】
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。
【００８１】
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。
【００８２】
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。
【００８３】
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。
【００８４】
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。
【００８５】
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。
【００８６】
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。
【００８７】
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。
【００８８】
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。
【００８９】
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。
【００９０】
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^-9ｍ²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^-9ｍ²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。
【００９１】
前記ビーム光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／ｅ²以上の光強度に対応する面積で表される。
【００９２】
用いられる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／ｅ²までの部分をスポット面積とする。
【００９３】
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。
【００９４】
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る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。
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。
【００９５】
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。
【００９６】
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。
【００９７】
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。
【００９８】
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。
【００９９】
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。
【０１００】
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。
【０１０１】
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。
【０１０２】
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。
【０１０３】
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。
【０１０４】
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。
【０１０５】
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。
【０１０６】
【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。
【０１０７】
感光体１の作製
下記の様に感光体１を作製した。
【０１０８】
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。
【０１０９】
ポリアミド樹脂ＣＭ８０００（東レ社製） １部
酸化チタンＳＭＴ５００ＳＡＳ（テイカ社製） ３部
メタノール １０部
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。
【０１１０】
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。
〈電荷発生層：ＣＧＬ〉
電荷発生物質（ＣＧＭ）
Ｎ型顔料：ペリレン顔料（Ａ） ６０部
Ｐ型顔料：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、７．５°及び２８．６°に顕著なピークを有するチタニルフタロシアニン顔料） ０．６部
ポリビニルブチラール樹脂（ＢＬ−Ｓ：積水化学社製） ７００部
２−ブタノン ２０００部
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。
【０１１１】
〈電荷輸送層：ＣＴＬ〉
電荷輸送物質（４，４′−ジメチル−４′′−（α−フェニルスチリル）トリフェニルアミン） ２２５部
ポリカーボネート（Ｚ３００：三菱ガス化学社製） ３００部
酸化防止剤（Ｉｒｇａｎｏｘ１０１０：日本チバガイギー社製） ６部
ジクロロメタン ２０００部
シリコンオイル（ＫＦ−５４：信越化学社製） １部
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塗布し、１１０℃７０分の乾燥を行い、乾燥膜厚１０μｍの電荷輸送層を形成し、感光体１を作製した。
【０１１２】
感光体２〜１０の作製
感光体１の作製において、電荷発生層（ＣＧＬ）及び電荷輸送層（ＣＴＬ）の膜厚を表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２〜１０を作製した。
【０１１３】
感光体１１〜１４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部に変更した以外は感光体１と同様にして感光体１１〜１４を作製した。
【０１１４】
感光体１５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１５を作製した。
【０１１５】
感光体１６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、７．５°及び２８．６°に顕著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１６を作製した。
【０１１６】
感光体１７の作製
感光体１の作製において、中間層の酸化チタンを除いた他は感光体１と同様にして感光体１７を作製した。
【０１１７】
上記感光体１〜１７の作製に用いたペリレン顔料Ａ〜Ｄ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。
【０１１８】
【化１３】

【０１１９】
【化１４】

【０１２０】
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）をベースとした評価機を用い、該複写機に感光体１〜１７を搭載し評価した。画像評価の環境条件は高温高湿：ＨＨ（３０℃、８０％ＲＨ）条件、低温低湿：ＬＬ（１０℃、２０％ＲＨ）条件で各１０万枚の複写を行った。複写は、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。評価項目及び評価基準を下記に示す。
【０１２１】
評価項目及び評価基準
解像度（各１０万枚コピー終了後に文字画像で解像度を評価）
◎：４ポイント以下の文字が明瞭であり、容易に判読可能
○：６ポイント以下の文字が明瞭であり、容易に判読可能
△：８ポイント以下の文字が明瞭であり、容易に判読可能
×：８ポイントの文字の一部又は全部が判読不能
光干渉による画像むら
レーザ光の干渉による画像むらの発生をハーフトーン画像上で評価
◎：光干渉による画像むらは発生せず
○：光干渉による画像むらは発生しているが、画像むらの濃度差が０．０２以下で実用性に支障なし
×：画像むらの濃度差が０．０２より大きい光干渉による画像むらは発生している
露光メモリによる画像むら
ＨＨ及びＬＬの各１０万枚複写後に文字画像と続いてハーフトーン画像を連続複写し、ハーフトーン画像上に残像としての文字画像が発生しているかを評価した。
【０１２２】
◎：ハーフトーン画像上に文字画像の発生なし
○：ハーフトーン画像上にわずかに画像むらは発生しているが、文字画像と判別不能で実用性に支障なし
×：ハーフトーン画像上にはっきりと文字画像の発生が見られる
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）
ＨＨ、ＬＬの１０万枚複写終了後に評価した
◎：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
カブリ：ベタ白画像部の濃度で判定
マクベス反射濃度計「ＲＤ−９１８」を用いて、印字されていないコピー用紙（白紙）の濃度を２０カ所、絶対画像濃度で測定し、その平均値を白紙濃度とする。次に、画像形成がなされた評価用紙の白地部分を同様に２０カ所、絶対画像濃度で測定し、その平均濃度から前記白紙濃度を引いた値をカブリ濃度として評価した。
【０１２３】
◎：０．００５以下（良好）
○：０．００５より大で、０．０１以下（実用上問題ないレベル）
×：０．０１より大（明らかに、実用上問題あり）
黒ポチ
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。
【０１２４】
◎：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）
電位性能
ＨＨ、ＬＬ条件の１０万枚複写前後で帯電電位と露光電位を測定し、帯電電位の変動量（ΔＶＨ＝初期−１０万枚複写後）、露光電位の変動量（ΔＶＬ＝初期−１０万枚複写後）を評価した
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。
【０１２５】
帯電条件
帯電器；スコロトロン帯電器、初期帯電電位を−５００Ｖ
露光条件
露光部電位を−５０Ｖにする露光量に設定。
【０１２６】
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^-9ｍ²、レーザは６８０ｎｍの半導体レーザを使用
現像条件
ＤＣバイアス；−４００Ｖ
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。
【０１２７】
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
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。
【０１２８】
評価結果を表１、表２に示した。
【０１２９】
【表１】

【０１３０】
【表２】

【０１３１】
表１中の、ＣＧＭ欄のＡ〜Ｆは前記したペリレン顔料Ａ〜Ｄ及びチタニルフタロシアニン顔料Ｆを示す。
【０１３２】
表１の電位性能評価ではＮ型及びＰ型顔料を含有し、膜厚以外は同一処方の感光体１〜１０を比較評価すると、電荷発生層の膜厚変化（感光体１、４、５、６、９、１０間の比較）による電位特性は膜厚が０．５μｍ近辺で最も安定な電位特性を示し、０．５μｍより薄くても、厚くても電位特性は、徐々に低下する様子が見られる。特に、膜厚が本発明外の０．２μｍ及び２．２μｍの感光体９，１０は、電位性能の変化が大きい。一方電荷輸送層の膜厚変化（感光体１，２、３、４、７、８間の比較）による電位変化は膜厚が４μｍの感光体７は、感光体全体の膜厚が薄いことから、帯電電位が−５００Ｖに達せず、帯電電位変動（ΔＶＨ）も大きい。膜厚が１６μｍの感光体８も露光電位変動（ΔＶＬ）が少し大きくなっている。又、Ｎ型顔料のみの感光体１５では帯電電位変動（ΔＶＨ）が若干劣化しており、Ｐ型顔料のみの感光体１６では帯電電位変動（ΔＶＨ）が著しく劣化している。又中間層から酸化チタンを除いた感光体１７では、露光電位の変動（ΔＶＬ）が少し大きくなっている。又、Ｎ型顔料の種類の変化（感光体１、１１、１２、１３、１４間の比較）では、ペリレン顔料（Ａ）を用いた感光体１が最も安定した電位性能を示し、アゾ顔料（Ｅ）の感光体１４がもっとも安定性が劣っている。次に表２から、電荷発生物質にＮ型顔料のペリレン系化合物及び該Ｎ型顔料に対し、０．５〜６質量％のＰ型顔料のフタロシアニン顔料を混合して用い、膜厚が０．３〜２μｍ電荷輸送層の膜厚が５〜１５μｍの条件を満たした感光体１〜６、１１〜１３は解像度が改善され、且つ光干渉やメモリによる画像むらの発生や黒ポチ等の画像欠陥の発生もなく、電位性能も安定して、各評価項目において、良好な特性を示している（但し、感光体１７は画像濃度が低下している）が、本発明外の感光体７（電荷輸送層が４μｍ）では、カブリ、黒ポチの発生が多く、解像度も低下している。感光体８（電荷輸送層が１６μｍ）では解像度の改善効果が不十分であり、光干渉による画像むらも発生している。感光体９（電荷発生層が０．２μｍ）では、画像濃度が低下し、光干渉による画像むらも発生しており、感光体１０（電荷発生層が２．２μｍ）では、露光メモリによる画像むらが発生し、画像濃度も低下し、解像度が低下している。又、電荷発生層がＰ型顔料のみの感光体１６ではカブリや黒ポチが発生し、光干渉及びメモリによる画像むらも発生している。
【０１３３】
【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、鮮鋭性が著しく改善され、且つ光干渉や露光メモリによる画像むらや黒ポチ等の画像欠陥も発生しない良好な電子写真画像を提供することができる。
【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。
【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]
BACKGROUND 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 photoreceptors have been widely used for electrophotographic photoreceptors. Organic photoreceptors have advantages over other photoreceptors, such as easy development of materials suitable for various exposure light sources from visible light to infrared light, the ability to select materials that are free from environmental pollution, and low manufacturing costs. However, there are disadvantages such as poor mechanical strength and chemical durability, deterioration of the electrostatic characteristics of the photosensitive member when a large number of sheets are printed, and generation of scratches on the surface.
[0003]
That is, the surface of an organic photoreceptor (hereinafter also simply referred to as a photoreceptor) is directly applied with electrical and mechanical external forces by charging means, developing means, transfer means, cleaning means, etc., so durability against them is required. The
[0004]
Specifically, durability against the generation of abrasion or scratches on the surface of the photoreceptor due to friction, surface degradation due to active oxygen such as ozone generated during corona charging, nitrogen oxide, and the like is required.
[0005]
In order to solve the above-mentioned problems of mechanical and chemical durability, the organic photoconductor 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 A configuration in which the active gas does not easily permeate and the charge transport layer has a thickness greater than 20 μm is often used.
[0006]
As another approach, a technique such as installing a high-strength protective layer on the surface of the photoreceptor has been studied. For example, JP-A-6-118681 reports the use of a curable silicone resin as a protective layer of a photoreceptor. However, the method of thickening the charge transport layer as described above or the method of providing a high-strength protective layer has a problem that carriers generated in the charge generation layer diffuse laterally until reaching the surface, such as sharpness. Problems arise. In the field of digital copiers, the demand for higher image quality is increasing 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 tends to cause carrier diffusion. I can't.
[0007]
In order to faithfully reproduce the image information as an electrostatic latent image, it is necessary to ensure a sufficient potential contrast between the exposed and unexposed areas. This is because the generated carriers are not diffused until they reach the surface charge. It is important to hold down. The Journal of the Imaging Society of Japan, Vol. 38, No. 4, page 296 shows that the latent image degradation of a high-density image becomes electrostatic when the ratio D / μ between the diffusion constant (D) and the drift mobility (μ) of the charge transport layer increases. It is described that the effect of diffusion on the latent image cannot be ignored, and that the deterioration of the latent image increases as the thickness of the charge transport layer increases.
[0008]
Further, an organic photoreceptor that has a thin charge transport layer and prevents diffusion of an electrostatic latent image has already been proposed in JP-A-5-119503. However, these proposed organic photoreceptors still cannot be a sufficient solution in terms of durability of the photoreceptor. That is, in the case of a photosensitive member having a thin photosensitive layer, the electric field strength per unit film thickness increases when a charging potential is applied when forming an electrostatic latent image, and black spots are generated by injecting free carriers from the conductive substrate. Defects and fog are likely to occur. For such problems, a wide range of measures have been taken to prevent free carrier injection by installing an intermediate layer or anodizing the surface of a conductive substrate to form an insulating layer. For example, Japanese Patent Application No. 2000-394650 proposes a photoreceptor in which the photosensitive layer is made thin and the intermediate layer contains titanium oxide particles.
[0009]
However, in the above-described countermeasures, if a photosensitive member having a thin photosensitive layer is used and the electric field strength is increased, repeated use is likely to cause image defects such as an increase in residual potential, image memory, and black spots. It has been found.
[0010]
Conventionally, in order to improve the image quality of digital images, it has been proposed to use toner having a smaller particle size or a sharper particle size distribution. However, in the examination results of the present inventors, these toners are used. However, it has been found that if the organic photoreceptor does not scatter the above-described toner and the electrostatic latent image cannot be reproduced sharply, the effect of reducing the toner particle size and improving the particle size distribution cannot be fully utilized.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems, and an organic photoreceptor capable of forming an accurate electrostatic latent image with small blur and faithfully developing the electrostatic latent image as a toner image. It is to provide an organic photoreceptor capable of preventing image defects such as black spots and image memories and ensuring high-quality image quality, and an image forming method and image formation using the photoreceptor And a process cartridge used in the image forming apparatus.
[0012]
[Means for Solving the Problems]
As a result of studying the above problems, we have improved the sharpness using an organic photoconductor, and with reversal development at a high electric field strength (reversal development under conditions where the amount of charge per unit area of the photoconductor is increased). In order to prevent the occurrence of black spots and image memory that are likely to occur, the organophotoreceptor has a functional separation structure of the charge generation layer and the charge transport layer, the thickness of the charge transport layer that forms the surface layer is reduced, and In order to prevent diffusion and at the same time prevent injection of free carriers from the conductive substrate, which is facilitated by thinning the charge transport layer, use a substance capable of blocking injection of free carriers in the charge generation material of the charge generation layer, and The present invention has been completed by discovering that it is important to make it possible to transport charge carriers (holes and electrons) generated in the charge generation layer.
[0013]
Further, when an electrophotographic image is formed by using such an organic photoreceptor and a toner having a uniform shape factor and particle size distribution, an electrophotographic image with higher sharpness and higher image quality can be obtained.
[0014]
  That is, the object of the present invention is achieved by having the following configuration.
  1. In an organic photoreceptor in which a charge generation layer and at least one charge transport layer are laminated in this order on a conductive support, titanium oxide particles are contained in a binder resin between the conductive support and the charge generation layer. An intermediate layer is provided, and the charge generation layer is an N-type pigment perylene compoundAnd 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment to the N-type pigmentAn organic photoreceptor comprising: a charge transport layer containing a charge transport material, wherein the total thickness of the charge transport layer is from 5 to 15 μm.
[0017]
  2. The perylene compound is a 3,4,9,10-tetracarboxylic imide derivative represented by the general formulas (1) to (3) and a mixture thereof.1The organophotoreceptor described.
[0018]
  3. In an image forming method in which an electrostatic latent image formed on an organic photoreceptor is converted into a toner image in a development process, the toner image is transferred to a transfer material, and then toner remaining on the organic photoreceptor is removed in a cleaning process. The organic photoreceptor is formed by laminating a charge generation layer and at least one charge transport layer in this order on a conductive support, and titanium oxide particles in a binder resin between the conductive support and the charge generation layer. A perylene compound in which the charge generation layer is an N-type pigmentAnd 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment to the N-type pigmentAn image forming method, comprising: a film thickness of 0.3 to 2 μm, and a charge transport layer having a total film thickness of 5 to 15 μm or less, wherein the toner used in the developing step is a polymerized toner.
[0019]
  4. The formation of the electrostatic latent image has an exposure spot area of 2 × 10.^-9(M²) The exposure is performed by the following exposure beam exposure3The image forming method described in 1.
[0020]
  5. Said3Or4An image forming apparatus that forms an electrophotographic image using the image forming method described in 1.
[0021]
  6. 1 aboveOr 2The organic photoconductor described in 1) is combined with any one of a charging unit, an image exposure unit, a developing unit, and a cleaning unit, and is designed to be freely taken in and out of an image forming apparatus. Process cartridge.
[0022]
  That is, the organic photoreceptor of the present invention is an organic photoreceptor in which a charge generation layer and at least one charge transport layer are laminated in this order on a conductive support, and the gap between the conductive support and the charge generation layer. An intermediate layer containing titanium oxide particles in a binder resin is provided, and the charge generation layer is an N-type pigment perylene compound.And 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment to the N-type pigmentThe charge transport layer contains a charge transport material, and the total thickness of the charge transport layer is 5 to 15 μm.
[0023]
Since the organophotoreceptor of the present invention has the above-described configuration, the resolution of the character image is remarkably improved, and halftone image unevenness and black spots that are likely to occur with a thin-layer photoreceptor are not generated. For both halftone images, an electrophotographic image with improved sharpness can be obtained.
[0024]
The image forming method of the present invention is further improved by developing the electrostatic latent image on the organic photoreceptor having the above-described configuration using a polymerized toner having a uniform shape factor and particle size distribution as described below. A high-quality electrophotographic image having sharpness can be provided for a long time.
[0025]
That is, the organic photoreceptor of the present invention has a structure in which a charge generation layer and a charge transport layer are laminated in this order, and the charge generation layer contains an N-type pigment charge generation material.
[0026]
Here, the method for discriminating between 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 is formed on the conductive support (the charge generation layer is formed using a dispersion in which 50% by mass of a pigment is dispersed in a binder). The charge generation layer is charged to a negative polarity, and the light attenuation characteristic is evaluated. In addition, the light attenuation characteristics are similarly evaluated by charging to positive polarity.
[0027]
The N-type pigment is a pigment whose light attenuation when negatively charged is larger than that when positively charged in the above evaluation.
A P-type pigment is a pigment whose light attenuation when charged positively is larger than that when charged negatively in the above evaluation.
[0028]
  As an N-type pigment charge generating substance, it exhibits the above-mentioned N-type characteristics.Perylene compoundsCharge generation materialContain asAmong them, examples of charge generating materials for N-type pigments that are particularly preferably used include perylene, 1-nitroperylene, 1,12-o-phenyleneperylene, 1,3,7,9-tetraacetoxyperylene, and the like.AndAmong these, 3,4,9,10-tetracarboxylic imide derivatives are preferable, and those represented by the structural formulas of the general formulas (1) to (3) are particularly preferably used.
[0029]
The structure may be symmetric or asymmetric. As seen 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 those produced as a mixture at the time of synthesis may be used as they are.
[0030]
Among these perylene compounds, the perylene compound represented by the general formula (3) is most preferably used, and among them, the perylene compound represented by the following structural formula is most preferable.
[0031]
[Chemical formula 2]

[0032]
(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 perylene compound has several crystal polymorphs, but any crystal form is particularly suitable. For example, the X-ray diffraction spectrum has peaks at Bragg angles 2θ (± 0.2 °) of 6.3 °, 12.4 °, 25.3 °, 27.1 °, and the maximum peak is 12.4 °. Some crystal types and amorphous ones showing almost no clear peak are also included. When used for the carrier generation layer, perylene having a specific crystal type may be dispersed and used, or a film may be formed by an operation such as vapor deposition. Further, the deposited film can be crystal-converted by solvent treatment or the like.
[0033]
Next, specific examples of perylene compounds that can be preferably used in the present invention are shown below.
[0034]
Specific examples of compounds of general formula (1)
In the general formula (1), R₁, R₂May be the same or different and include the following.
[0035]
[Chemical 3]

[0036]
[Formula 4]

[0037]
[Chemical formula 5]

[0038]
Specific examples of compounds of general formula (2)
R in the general formula (2)₁Is the same as in general formula (1), and Z includes the following.
[0039]
[Chemical 6]

[0040]
In the case of a dimer, Z is as follows.
[0041]
[Chemical 7]

[0042]
Compound of general formula (3)
[0043]
[Chemical 8]

[0044]
[Chemical 9]

[0045]
Embedded image

[0046]
Embedded image

[0047]
Embedded image

[0048]
In addition to the perylene pigment, N-type pigments include azo pigments and polycyclic quinone pigments having a functional group with high electronegativity, such as a cyano group.
[0049]
The charge generation layer of the present invention preferably contains a P-type pigment of less than 10% by mass of the N-type pigment in combination with the N-type pigment charge-generating substance. As the P-type pigment, any kind of charge generating substance may be used as long as the pigment exhibits the P-type characteristics described above. Examples thereof include phthalocyanine pigments.
[0050]
The charge generation material of P-type phthalocyanine pigment, which has been mainly used in conventional digital copiers, has a small charge carrier transport capability, so increasing the thickness of the charge generation layer causes an increase in residual potential and uneven image due to optical memory. It's easy to do. For this reason, it has been difficult to increase the thickness of the charge generation layer, increase the charge generation material, improve sensitivity, prevent optical interference fringes, or block free carriers from the conductive substrate.
[0051]
  The organophotoreceptor of the present invention comprises an N-type pigment on a conductive support.To the perylene compound and the N-type pigment, 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment is mixed.A negative charge-type organic photoreceptor containing a charge generation layer having a film thickness of 0.3 to 2 μm and a charge transport layer on the charge generation layer having a total film thickness of 5 to 15 μm (negative The charge generation material of the charge generation layer is mainly an N-type pigment, so that electrons generated in the charge generation layer are relatively It can move a long distance and conduct to a conductive substrate. For this reason, even if the charge generation layer is formed with a relatively thick film thickness, an increase in residual potential due to electron trapping is prevented. In addition, if the charge generation layer has a film thickness in the above range, the pigment concentration can be sufficiently increased, so that a single wavelength such as image exposure light, laser light, LED light, etc. that is generally used in digital image formation. Generation of 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.
[0052]
If the thickness of the charge generation layer is less than 0.3 μm, it is difficult to contain the pigment concentration sufficiently, so that the exposure potential is not sufficiently lowered, the image density is lowered, and the laser beam interference prevention effect is reduced. It's easy to do. On the other hand, if it is larger than 2.0 μm, the charge carrier trap density in the charge generation layer tends to increase, and image unevenness due to an increase in optical memory tends to occur. A preferred thickness of the charge generation layer is 0.3 to 1.0 μm.
[0053]
The charge generation layer preferably contains a P-type pigment of less than 10% by mass of the N-type pigment together with the N-type pigment charge-generating substance. By using a P-type pigment together with an N-type pigment, hole carriers generated deep inside the charge generation layer can be transported to the boundary with the charge transport layer and injected, Trapping is prevented, and a rise in residual potential is prevented. A more preferable amount of P-type pigment is 0.5 to 5% by mass. If it is 10% by mass or more, the effect of preventing free carrier injection from the conductive substrate deteriorates and black spots and fog are likely to occur.
[0054]
On the other hand, the charge transport layer may be composed of a plurality of layers, and the total thickness may be 5 to 15 μm. When the film thickness is less than 5 μm, the charged potential tends to be insufficient, and when it exceeds 15 μm, the sharpness is not sufficiently improved. When the thickness of the charge transport layer is 5 to 10 μm, the sharpness improving effect is more remarkable.
[0055]
By adopting the above configuration, sharpness can be remarkably improved, and image defects such as black spots and image unevenness that are likely to occur when the charge transport layer is made thin are prevented, and potential performance is improved. A stable organic photoreceptor can be provided.
[0056]
The constitution of the organic photoreceptor applied to the present invention other than the above will be described below.
In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic photoconductors such as a photoconductor composed of an organic charge generating material or an organic charge transport material, a photoconductor composed of a polymer complex with a charge generating function and a charge transport function are contained.
[0057]
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, and the specific detection of the charge transport function is charge generation. It can be confirmed by laminating a layer and a charge transport layer on a conductive support and detecting the optical conductivity.
[0058]
The layer structure of the organic photoreceptor of the present invention is basically composed of a photosensitive layer of a charge generation layer and a charge transport layer on a conductive support. In the most preferred configuration, the photosensitive layer is composed of a charge generation layer and a charge transport layer.
[0059]
Hereinafter, a specific configuration of the photoreceptor used in the present invention will be described.
Conductive support
As the conductive support used in the photoreceptor of the present invention, a sheet-like or cylindrical conductive support is used.
[0060]
The cylindrical conductive support of the present invention means a cylindrical support necessary for forming an endless image by rotating, and the straightness is in the range of 0.1 mm or less and the deflection is 0.1 mm or less. Certain conductive supports are preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.
[0061]
As a material for the conductive support, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide, or the like, or a paper / plastic drum coated with a conductive substance can be used. As a conductive support, the specific resistance is 10 at room temperature.^ThreeΩcm or less is preferable.
[0062]
As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing 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 film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.
[0063]
Middle class
In the present invention, it is preferable to provide the above-described intermediate layer having a barrier function between the conductive support and the photosensitive layer.
[0064]
The intermediate layer of the present invention preferably contains titanium oxide in the binder resin having a small water absorption rate. The average particle diameter of the titanium oxide particles is preferably in the range of 10 nm to 400 nm in terms of number average primary particle diameter, and is 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, the titanium oxide particles in the intermediate layer coating solution are likely to settle, and as a result, the uniform dispersibility of the titanium oxide particles in the intermediate layer is poor, and the black spots are likely to increase. An intermediate layer coating liquid using titanium oxide particles having a number average primary particle size in the above range has good dispersion stability, and the intermediate layer formed from such a coating liquid has an environmental characteristic in addition to the function of preventing the occurrence of black spots. Is good and has cracking resistance.
[0065]
The shape of the titanium oxide particles used in the present invention includes a dendritic shape, a needle shape, a granular shape, and the like. The titanium oxide particles having such a shape are, for example, titanium oxide particles, anatase type, rutile as crystal types. There are types, amorphous types, and the like. Any crystal type may be used, or two or more crystal types may be mixed and used. Among them, the rutile type and granular type are the best.
[0066]
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 surface treatment is a reactive organic in the plurality of surface treatments. Surface treatment using a silicon compound is performed. In addition, at least one of the surface treatments is at least one surface treatment selected from alumina, silica, and zirconia, and finally a surface treatment using a reactive organosilicon compound. It is preferable to carry out.
[0067]
Alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of titanium oxide particles, and alumina, silica, and zirconia deposited on these surfaces are water of alumina, silica, zirconia Japanese products are also included. The surface treatment of the reactive organosilicon compound means using a reactive organosilicon compound in the treatment liquid.
[0068]
In this way, the surface treatment of the titanium oxide particles such as titanium oxide particles is performed at least twice, so that the surface of the titanium oxide particles is uniformly coated (treated), and the surface-treated titanium oxide particles are used as the intermediate layer. When used in the present invention, it is possible to obtain a good photoconductor having good dispersibility of titanium oxide particles such as titanium oxide particles in the intermediate layer and causing no image defects such as black spots.
[0069]
The reactive organic silicon compound includes a compound represented by the following general formula (4), but is not limited to the following compound as long as it is a compound that undergoes a condensation reaction with a reactive group such as a hydroxyl group on the titanium oxide surface.
[0070]
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), the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl. Group, aryl group such as phenyl, tolyl, naphthyl, biphenyl, epoxy-containing group such as γ-glycidoxypropyl, β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl, γ-methacryloxypropyl (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, Amino-containing groups 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 alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.
[0071]
Moreover, the organosilicon compound represented by General formula (4) may be individual, and may be used in combination of 2 or more type.
[0072]
Moreover, in the specific compound of the organosilicon compound represented by the general formula (4), when n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by General formula (4), R and X may be the same between each compound, and may differ.
[0073]
Moreover, a polysiloxane compound is mentioned as a preferable reactive organosilicon compound used for surface treatment. The polysiloxane compound having a molecular weight of 1000 to 20000 is generally easily available, and has a good function to prevent occurrence of black spots.
[0074]
In particular, when methylhydrogenpolysiloxane is used for the final surface treatment, a good effect can be obtained.
[0075]
Photosensitive layer
Charge generation layer
The aforementioned N-type pigment is used as the charge generation material (CGM) of the charge generation layer.
[0076]
When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized.
[0077]
Charge transport layer
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. Other substances may contain additives such as antioxidants as necessary.
[0078]
As the charge transport material (CTM), a known hole transport property (P-type) charge transport material (CTM) is preferably used. For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM capable of minimizing 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, preferably 0 .30 (eV) or less.
[0079]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0080]
The binder resin used for the charge transport layer (CTL) may be either 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, phenol 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, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.
[0081]
The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.
[0082]
Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers 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, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents may be used alone or as a mixed solvent of two or more.
[0083]
Next, as a coating processing method for manufacturing the organic photoreceptor, a coating processing method such as dip coating, spray coating, circular amount regulation type coating, etc. is used. In order to prevent dissolution as much as possible, and in order to achieve uniform coating processing, it is preferable to use a coating processing method such as spray coating or circular amount regulation type (circular slide hopper type is a typical example). It is most preferable to use the circular amount regulation type coating method for the protective layer. The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.
[0084]
Next, an image forming apparatus using the organic photoreceptor of the present invention will be described.
An 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. Yes.
[0085]
An automatic document feeder that automatically conveys the document is provided above the image reading unit A. The document placed on the document table 11 is separated and conveyed by the document conveyance roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.
[0086]
On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.
[0087]
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 line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.
[0088]
In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the color, developing means (development process) 23, transfer / conveying belt device 45 as transfer means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and photostatic means (photo-site charge). PCLs (precharge lamps) 27 as generating steps) are arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. The photoconductor 21 uses the organic photoconductor of the present invention and is driven to rotate in the clockwise direction as shown.
[0089]
After the rotating photosensitive member 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 an exposure optical system 30 as an image exposure unit (image exposure step). Exposure is performed. An exposure optical system 30 as an image exposure means as a writing means uses a laser diode (not shown) as a light source, and passes through a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35, and an optical path is bent by a reflection mirror 32 to perform main scanning. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.
[0090]
In the image forming method of the present invention, when an electrostatic latent image is formed on a photoreceptor, image exposure is performed with a spot area of 2 × 10.^-9m²It is preferable to use the following exposure beam. Even when such 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 preferable spot area is 0.01 × 10.^-9~ 1x10^-9m²It is. As a result, it is possible to achieve extremely excellent image quality that achieves 256 gradations at 400 dpi (dpi: the number of dots per 2.54 cm) or more.
[0091]
The spot area of the light beam is 1 / e of the peak light intensity.²It is represented by an area corresponding to the above light intensity.
[0092]
Examples of the light beam used include a scanning optical system using a semiconductor laser, and a solid state scanner such as an LED or a liquid crystal shutter. The light intensity distribution includes a Gaussian distribution and a Lorentz distribution, but 1 / e of each peak intensity.²The area up to is the spot area.
[0093]
The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method of the present invention, a polymerized toner is used as a developer used in the developing unit. By using a polymerized toner having a uniform shape and particle size distribution in combination with the organic photoreceptor of the present invention, an electrophotographic image with better sharpness can be obtained.
[0094]
Here, the polymerized toner means a toner obtained by forming a toner binder resin and forming a toner shape by polymerization of a raw material monomer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a subsequent step of fusing particles.
Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then producing the toner, a toner having a uniform toner particle size distribution and shape can be obtained.
[0095]
The polymerized toner is produced by emulsion polymerization of monomers in a suspension polymerization method or in a solution to which an emulsion of necessary additives is added to produce fine polymer particles, and then an organic solvent, an aggregating agent, etc. It can manufacture by the method of adding and associating. A method of preparing by mixing 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 a toner component such as a release agent and a colorant dispersed in the monomer And a method of emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.
[0096]
That is, various constituent materials such as a colorant and, if necessary, a release agent, a charge control agent, and a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, a sand grinder, an ultrasonic disperser, etc. Various constituent materials are dissolved or dispersed in the polymerizable monomer. The polymerizable monomer in which these various constituent materials are dissolved or dispersed is dispersed in oil droplets having a desired size as a toner in an aqueous medium containing a dispersion stabilizer using a homomixer or a homogenizer. Thereafter, the stirring mechanism is transferred to a reactor that is a stirring blade described later, and the polymerization reaction is advanced by heating. After completion of the reaction, the dispersion stabilizer is removed, filtered, washed, and dried to prepare a toner.
[0097]
Further, as a method for 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. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, a method of associating a plurality of fine particles composed of resin particles and colorants, etc., or particles composed of resin and colorant, in particular, after dispersing them in water using an emulsifier, the critical aggregation concentration The above flocculant is added for salting out, and at the same time, the formed polymer itself is heated and fused at a temperature higher than the glass transition temperature to gradually grow the particle size while forming fused particles. Then, a large amount of water was added to stop the particle size growth, and the particle surface was smoothed while heating and stirring to control the shape, and the particles were heated and dried in a fluidized state while containing water, whereby a toner was obtained. Can be formed. Here, an organic solvent that is infinitely soluble in water may be added simultaneously with the flocculant.
[0098]
Note that materials and manufacturing methods for producing a uniform toner such as a shape factor used in the present invention, a polymerization toner reaction device, and the like are described in detail in JP-A-2000-214629.
[0099]
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 for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by the registration roller pair 44 that corrects the inclination and bias of the transfer paper P, and then re-feeded. The transport path 40, the pre-transfer roller 43a, the paper feed path 46, and the entry guide Guided by the plate 47, the toner image on the photosensitive member 21 is transferred onto the transfer paper P while being transferred to the transfer conveyance belt 454 of the transfer conveyance 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.
[0100]
The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.
[0101]
The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper 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.
[0102]
Further, the transfer paper P is transported downward by the transport mechanism 178 and switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The
[0103]
The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .
[0104]
Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.
[0105]
The organophotoreceptor of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also displays, recordings, light printing, plate making and facsimiles using electrophotographic technology. The present invention can be widely applied to such devices.
[0106]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means “part by mass”.
[0107]
Production of photoreceptor 1
Photoreceptor 1 was produced as follows.
[0108]
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, and allowed to stand overnight, followed by filtration (filter; rigesh mesh 5 μm filter manufactured by Nihon Pall) to prepare an intermediate layer coating solution.
[0109]
1 part of polyamide resin CM8000 (Toray Industries, Inc.)
Titanium oxide SMT500SAS (manufactured by Teika) 3 parts
10 parts of methanol
Were mixed using a sand mill as a disperser, and batch-type dispersion was performed for 10 hours to prepare an intermediate layer dispersion.
[0110]
It apply | coated so that it might become a dry film thickness of 2 micrometers on the said support body using the said coating liquid.
<Charge generation layer: CGL>
Charge generation material (CGM)
N-type pigment: 60 parts of perylene pigment (A)
P type pigment: titanyl phthalocyanine pigment (F: diffraction angle of Cu-Kα characteristic X-ray: titanyl phthalocyanine pigment having remarkable peaks at 7.5 ° and 28.6 ° at Bragg angle 2θ) 0.6 parts
700 parts of polyvinyl butyral resin (BL-S: manufactured by Sekisui Chemical Co., Ltd.)
2-butanone 2000 parts
Were mixed for 30 hours using a sand mill 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.
[0111]
<Charge transport layer: CTL>
225 parts of charge transport material (4,4′-dimethyl-4 ″-(α-phenylstyryl) triphenylamine)
300 parts of polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company)
Antioxidant (Irganox 1010: Nihon Ciba Geigy) 6 parts
2000 parts of dichloromethane
Silicon oil (KF-54: Shin-Etsu Chemical Co., Ltd.) 1 part
Were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method and dried at 110 ° C. for 70 minutes to form a charge transport layer having a dry film thickness of 10 μm.
[0112]
Production of photoconductors 2 to 10
Photoconductors 2 to 10 were prepared in the same manner as the photoconductor 1 except that the film thicknesses of the charge generation layer (CGL) and the charge transport layer (CTL) were changed as shown in Table 1 in preparation of the photoconductor 1.
[0113]
Preparation of photoreceptors 11-14
Similar to Photoreceptor 1 except that the N-type pigments of Compounds B to E were used in place of the perylene pigment (A) in the charge generation layer and the amount of titanyl phthalocyanine pigment was changed to 3.6 parts. Thus, photoconductors 11 to 14 were produced.
[0114]
Production of photoconductor 15
A photoconductor 15 was produced in the same manner as the photoconductor 1 except that the titanyl phthalocyanine pigment (F) in the charge generation layer of the photoconductor 1 was removed.
[0115]
Production of photoconductor 16
In the production of the photoreceptor 1, a titanyl phthalocyanine pigment of P type pigment (F: Cu-Kα characteristic X-ray diffraction angle: Bragg angle 2θ, 7.5 ° and 28 ° instead of the perylene pigment (A) of the charge generation layer. Photoconductor 16 was prepared in the same manner as Photoconductor 1, except that a titanyl phthalocyanine pigment having a remarkable peak at 6 ° was used.
[0116]
Production of photoconductor 17
Photoconductor 17 was prepared in the same manner as Photoreceptor 1 except that the intermediate layer of titanium oxide was removed.
[0117]
The chemical structural formulas of perylene pigments A to D and titanyl phthalocyanine pigment F used for the production of the photoreceptors 1 to 17 are shown below.
[0118]
Embedded image

[0119]
Embedded image

[0120]
Image evaluation
Using an evaluation machine based on Konica 7075, a Konica digital copying machine (with corona charging, laser exposure, reversal development, electrostatic transfer, nail separation, blade cleaning, cleaning auxiliary brush roller adoption process) as an evaluation machine The photoreceptors 1 to 17 were mounted on the machine and evaluated. The environmental conditions for image evaluation were high-temperature and high-humidity: HH (30 ° C., 80% RH) conditions, and low-temperature low-humidity: LL (10 ° C., 20% RH) conditions. Copying was performed by copying an original image in which a character image having a pixel ratio of 7%, a human face photo, a solid white image, and a solid black image are each equally divided into A4 neutral paper. Evaluation items and evaluation criteria are shown below.
[0121]
Evaluation items and evaluation criteria
Resolution (Evaluate resolution with text image after each 100,000 copies are completed)
◎: Characters of 4 points or less are clear and easily readable
○: Characters of 6 points or less are clear and easily readable
Δ: Characters of 8 points or less are clear and easily readable
×: Some or all of the 8-point characters are illegible
Image unevenness due to optical interference
Evaluation of image unevenness due to laser light interference on halftone images
A: Image unevenness due to optical interference does not occur
○: Image unevenness due to light interference occurs, but there is no problem in practicality because the difference in image unevenness is 0.02 or less.
X: Image unevenness due to light interference in which the density difference of image unevenness is greater than 0.02
Image unevenness due to exposure memory
After copying 100,000 sheets of HH and LL, a character image and then a halftone image were continuously copied to evaluate whether a character image as an afterimage was generated on the halftone image.
[0122]
A: No character image is generated on the halftone image
○: Slight image unevenness occurs on the halftone image, but it cannot be distinguished from the character image and there is no hindrance to practicality
X: Generation of a character image is clearly seen on a halftone image
Image density (measured using Macbeth RD-918. Measured with a relative reflection density where the paper reflection density was "0")
Evaluated after copying 100,000 copies of HH and LL
A: 1.2 or more: Good
○: 0.8 or more: Level that does not cause any practical problems
×: Less than 0.8: a level causing a practical problem
Fog: Judged by density of solid white image
Using a Macbeth reflection densitometer “RD-918”, the density of unprinted copy paper (white paper) is measured at 20 locations in absolute image density, and the average value is defined as the white paper density. Next, the white portion of the evaluation paper on which the image was formed was similarly measured at 20 locations at the absolute image density, and the value obtained by subtracting the white paper density from the average density was evaluated as the fog density.
[0123]
A: 0.005 or less (good)
○: Greater than 0.005 and 0.01 or less (a level that is not problematic for practical use)
×: Greater than 0.01 (apparently problematic in practical use)
Black pot
For black spots, the periodicity coincided with the period of the photoreceptor, and it was determined how many black spots per A4 size were visible.
[0124]
: Black spot frequency of 0.4 mm or more Frequency: All 3 copies / A4 or less (good)
○: Black spot frequency of 0.4 mm or more Frequency: 4 / A4 or more, 10 / A4 or less occurred (no problem in practical use)
×: Black spot frequency of 0.4 mm or more Frequency: 11 / A4 or more occurs (practical problem)
Potential performance
The charging potential and the exposure potential are measured before and after copying 100,000 sheets under HH and LL conditions, the amount of change in charging potential (ΔVH = initial−after 100,000 copies), and the amount of change in exposure potential (ΔVL = initial−100,000 sheets). Evaluated after copying)
Other evaluation conditions
In addition, the other evaluation conditions using said 7075 were set to the following conditions.
[0125]
Charging conditions
Charger: Scorotron charger, initial charge potential of -500V
Exposure conditions
Set the exposure amount so that the potential of the exposed area is -50V.
[0126]
Exposure beam: Image exposure with a dot density of 400 dpi was performed. Laser beam spot area: 0.8 × 10^-9m²The laser uses a 680nm semiconductor laser
Development conditions
DC bias; -400V
The developer is a volume-average particle diameter produced by a polymerization method comprising a carrier coated with an insulating resin with ferrite as a core, a styrene acrylic resin as a main material, a carbon black colorant, a charge control agent, and a low molecular weight polyolefin. A toner developer in which silica and titanium oxide were externally added to 3 μm colored particles was used.
[0127]
Transcription conditions
Transfer pole; corona charging method
Separation conditions
Using the separation means of the separation claw unit
Separation claw material: Base material is polyamideimide (PAI), coated with polytetrafluoroethylene (PTFE)
Contact load on 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 that the linear pressure was 18 (g / cm) in the counter direction.
[0128]
The evaluation results are shown in Tables 1 and 2.
[0129]
[Table 1]

[0130]
[Table 2]

[0131]
In Table 1, A to F in the CGM column indicate the perylene pigments A to D and the titanyl phthalocyanine pigment F described above.
[0132]
  In the potential performance evaluation of Table 1, N-type and P-type pigments were contained, and when the photoconductors 1 to 10 having the same formulation other than the film thickness were compared and evaluated, the change in the film thickness of the charge generation layer (photoconductors 1, 4, 5, 6, 9, and 10) shows the most stable potential characteristic when the film thickness is near 0.5 μm, and the potential characteristic gradually decreases even if it is thinner or thicker than 0.5 μm. It can be seen. In particular, the photoreceptors 9 and 10 having a film thickness of 0.2 μm and 2.2 μm outside the present invention have a large change in potential performance. On the other hand, the potential change due to the change in the thickness of the charge transport layer (comparison between the photoconductors 1, 2, 3, 4, 7, and 8) is that the photoconductor 7 having a film thickness of 4 μm is thin in the entire photoconductor. The charging potential does not reach −500 V, and the charging potential fluctuation (ΔVH) is large. The photosensitive member 8 having a film thickness of 16 μm also has a slightly larger exposure potential fluctuation (ΔVL). Further, the charge potential fluctuation (ΔVH) is slightly deteriorated in the photoconductor 15 only with the N-type pigment, and the charge potential fluctuation (ΔVH) is remarkably deteriorated in the photoconductor 16 with only the P-type pigment. Further, in the photoreceptor 17 from which the titanium oxide is removed from the intermediate layer, the exposure potential fluctuation (ΔVL) is slightly increased. In addition, in the change in the type of N-type pigment (comparison between photoreceptors 1, 11, 12, 13, and 14), the photoreceptor 1 using the perylene pigment (A) showed the most stable potential performance, and the azo pigment ( The photoreceptor 14 of E) is the least stable. Next, from Table 2, the charge generation material is an N-type pigment.A 0.5 to 6 mass% P-type pigment phthalocyanine pigment is mixed with the perylene compound and the N-type pigment.The photoreceptors 1 to 6 and 11 to 1 satisfy the condition that the film thickness of the charge transport layer is 5 to 15 μm.3Has improved resolution, no image interference due to optical interference or memory, no image defects such as black spots, etc., stable potential performance, and shows good characteristics in each evaluation item (however, The image density of the photoconductor 17 is low), but in the photoconductor 7 outside the present invention (the charge transport layer is 4 μm), fog and black spots are frequently generated and the resolution is also low. The photoreceptor 8 (with a charge transport layer of 16 μm) has an insufficient resolution improvement effect, and image unevenness due to light interference also occurs. In the photoreceptor 9 (the charge generation layer is 0.2 μm), the image density is reduced and image unevenness due to light interference is also generated. In the photoreceptor 10 (the charge generation layer is 2.2 μm), the image unevenness due to the exposure memory is generated. Occurs, the image density also decreases, and the resolution decreases. Further, fog and black spots occur on the photoconductor 16 whose charge generation layer is only a P-type pigment, and optical interference and image unevenness due to memory also occur.
[0133]
【The invention's effect】
As is clear from the examples, by using the organic photoreceptor having the structure of the present invention, sharpness is remarkably improved, and image defects such as image interference due to light interference and exposure memory and black defects are not generated. An electrophotographic image can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view in which functions of an image forming apparatus of the present invention are incorporated.
[Explanation of symbols]
1 Image forming device
21 photoconductor
22 Charging means
23 Development means
24 Transfer pole
25 Separation pole
26 Cleaning device
30 Exposure optics
45 Transfer conveyor belt device
50 Fixing means
250 Separating claw unit

Claims (6)

In an organic photoreceptor in which a charge generation layer and at least one charge transport layer are laminated in this order on a conductive support, titanium oxide particles are contained in a binder resin between the conductive support and the charge generation layer. An intermediate layer is provided, and the charge generation layer contains an N-type pigment perylene compound and the N-type pigment mixed with 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment. 0.3 to 2 μm, the charge transport layer contains a charge transport material, and the total thickness of the charge transport layer is 5 to 15 μm. 2. The perylene compound is a 3,4,9,10-tetracarboxylic imide derivative represented by the following general formulas (1) to (3) and a mixture thereof: Organic photoreceptor.

(Wherein R ₁ , R ₂ Each represents a hydrogen atom, a substituted or unsubstituted alkyl group, cycloalkyl group, aryl group, alkoxy group, alkylamino group, dialkylamino group, benzyl group, phenethyl group, or heterocyclic group. In addition, when forming a multimer, R ₁ , R ₂ May be a 1,4-phenylene group. Z represents an atomic group necessary for forming a substituted or unsubstituted heterocyclic ring. ) In an image forming method in which an electrostatic latent image formed on an organic photoreceptor is converted into a toner image in a development process, the toner image is transferred to a transfer material, and then toner remaining on the organic photoreceptor is removed in a cleaning process. The organic photoreceptor is formed by laminating a charge generation layer and at least one charge transport layer in this order on a conductive support, and titanium oxide particles in a binder resin between the conductive support and the charge generation layer. A charge generating layer containing an N-type pigment perylene compound and 0.5 to 6% by mass of a P-type pigment phthalocyanine pigment mixed with the N-type pigment, An image forming method, wherein the thickness is 0.3 to 2 μm, the total thickness of the charge transport layer is 5 to 15 μm, and the toner used in the developing step is a polymerized toner. The formation of the electrostatic latent image has an exposure spot area of 2 × 10. ^-9 (M ² 4. The image forming method according to claim 3, wherein the image forming method is performed by exposure with the following exposure beam. An image forming apparatus for forming an electrophotographic image using the image forming method according to claim 3. The organic photoreceptor according to claim 1 or 2 is used, and any one of a charging unit, an image exposure unit, a developing unit, and a cleaning unit is integrally combined, and is designed to be freely taken in and out of the image forming apparatus. A process cartridge characterized by that.

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