JP2004004504A - Method and apparatus for image formation, and electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for image formation and an electrophotographic photoreceptor which prevent the occurrence of image defects such as void and illegal character by improving transfer property of toner in an image formation system using an intermediate transfer body. <P>SOLUTION: In the image forming method which develops a latent image formed on the electrophotographic receptor into a toner image and is equipped with a transfer means of transferring the toner image to a recording material or an intermediate transfer body, the development and transfer are carried while a surface energy decreasing agent is supplied to the surface of the electrophotographic receptor to suppress variance in contact angle of the electrophotographic photoreceptor at a mean value±5°. <P>COPYRIGHT: (C)2004,JPO

Description

【００９４】
指定面とは全測定面であり、本発明では５μｍ四方の測定面（ＸＹ平面）を表す。
【００９５】
全測定面Ｚは次式で求められる。
Ｚ＝Ｆ（Ｘ，Ｙ）
Ｓ_０は次式で求められる。
【００９６】
Ｓ_０＝Ｘ×Ｙ
基準面：Ｚデータの平均値をＺ_０とするとＺ＝Ｚ_０で表される面
（ＸＹ平面と平行）
Ｚ_０は次式で求められる。
【００９７】
【数２】

【００９８】
次に、このような表面形状を有する感光体の構成について記載する。
本発明の感光体の表面層には、個数平均粒径５〜５００ｎｍの微粒子を添加するのが好ましい。上記のような微粒子を添加することにより、原子間力顕微鏡を用いて測定した５μｍ四方の表面平均面粗さ（Ｒａ）が１．５ｎｍ以上、１００ｎｍ以下の表面層を作製できる。このような微粒子は前記したポリフッ化ビニリデン、ポリテトラフルオロエチレン等の表面エネルギー低下剤としての機能を有する微粒子でもよいが、個数平均粒径５〜５００ｎｍの疎水化処理を行った無機微粒子（例えば特開平８−２４８６６３号記載の）を感光体の表面層に分散、含有させて表面粗さを調整することが好ましい。又、無機微粒子を疎水化する方法としては、チタンカップリング剤・シランカップリング剤・高分子脂肪酸またはその金属塩等の疎水化処理剤により処理する方法を利用することができる。
【００９９】
無機微粒子としては、例えば、シリカ、酸化チタン、アルミナ、チタン酸バリウム、チタン酸カルシウム、チタン酸ストロンチウム、酸化亜鉛、酸化マグネシウム、酸化ジルコニウム、硫酸バリウム、炭酸バリウム、炭酸カルシウム、炭化ケイ素、窒化ケイ素、酸化クロム、ベンガラ等の微粒子が挙げられる。
【０１００】
前記したように、無機微粒子は疎水化処理が成されている方が好ましい。該疎水化処理は無機微粒子と疎水化処理剤とを高温度下で反応させて行うことができる。前記疎水化処理剤としては、特に制限はなく、例えば、ヘキサメチルジシラザン、ジメチルジクロロシラン、デシルシラン、ジアルキルジハロゲン化シラン、トリアルキルハロゲン化シラン、アルキルトリハロゲン化シラン等のシランカップリング剤やジメチルシリコンオイルなどが挙げられる。前記疎水化処理剤の量としては、前記微粒子等の種類等により異なり、一概に規定することはできないが、一般的にはその量が増せば疎水化度は高くなる。又、例えば再沈や加熱処理等により、吸湿性物質を除去するのも有効である。
【０１０１】
上記微粒子としては、ポリメタクリレート、ポリメチルメタクリレート、ポリエチレン、ポリプロピレン、ポリフッ化ビニリデン、ポリテトラフルオロエチレン等の有機微粒子でもよい。
【０１０２】
尚、上記個数平均粒径は透過型電子顕微鏡観察によって２０００倍に拡大し、ランダムに１００個の粒子を一次粒子として観察し、画像解析によってフェレ方向平均径としての測定値である。
【０１０３】
次に、本発明に好ましく用いられる感光体の層構成について記載する。
本発明において、感光体とは電子写真画像形成に用いられる電子写真感光体であり、中でも有機電子写真感光体（有機感光体）を用いた場合に本発明の効果が顕著に表れる。有機感光体とは電子写真感光体の構成に必要不可欠な電荷発生機能及び電荷輸送機能の少なくとも一方の機能を有機化合物に持たせて構成された電子写真感光体を意味し、公知の有機電荷発生物質又は有機電荷輸送物質から構成された感光体、電荷発生機能と電荷輸送機能を高分子錯体で構成した感光体等公知の有機電子写真感光体を全て含有する。
【０１０４】
本発明の表面層とは電子写真感光体を構成する各種層構成の中で単純に表面に存在する層を意味し、機能を示すものではない。即ち、電子写真感光体が円筒状基体上に中間層、電荷発生層、電荷輸送層を順に積層している場合には電荷輸送層が表面層であり、更に保護層を積層している場合は保護層が表面層となる。
【０１０５】
以下に本発明に用いられる有機感光体の層構成について記載する。
導電性基体
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、円筒状のどちらを用いても良いが、画像形成装置をコンパクトに設計するためには円筒状導電性支持体の方が好ましい。
【０１０６】
本発明の円筒状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。この真円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。
【０１０７】
導電性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。導電性基体としては常温で比抵抗１０^３Ωｃｍ以下が好ましい。
【０１０８】
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中間層を設けることもできる。
【０１０９】
本発明においては導電性支持体と前記感光層のとの接着性改良、或いは該支持体からの電荷注入を防止するために、該支持体と前記感光層の間に中間層（下引層も含む）を設けることもできる。該中間層の材料としては、ポリアミド樹脂、塩化ビニル樹脂、酢酸ビニル樹脂並びに、これらの樹脂の繰り返し単位のうちの２つ以上を含む共重合体樹脂が挙げられる。これら下引き樹脂の中で繰り返し使用に伴う残留電位増加を小さくできる樹脂としてはポリアミド樹脂が好ましい。又、これら樹脂を用いた中間層の膜厚は０．０１〜０．５μｍが好ましい。
【０１１０】
又本発明に好ましく用いられる中間層はシランカップリング剤、チタンカップリング剤等の有機金属化合物を熱硬化させた硬化性金属樹脂を用いた中間層が挙げられる。硬化性金属樹脂を用いた中間層の膜厚は、０．１〜２μｍが好ましい。
【０１１１】
又、本発明に好ましく用いられる中間層としては疎水化表面処理を行った酸化チタン微粒子（平均粒径が０．０１〜１μｍ）をポリアミド樹脂等のバインダーに分散させた中間層が挙げられる。該中間層の膜厚は、１〜１５μｍが好ましい。
【０１１２】
感光層
本発明の感光体の感光層構成は前記中間層上に電荷発生機能と電荷輸送機能を１つの層に持たせた単層構造の感光層構成でも良いが、より好ましくは感光層の機能を電荷発生層（ＣＧＬ）と電荷輸送層（ＣＴＬ）に分離した構成をとるのがよい。機能を分離した構成を取ることにより繰り返し使用に伴う残留電位増加を小さく制御でき、その他の電子写真特性を目的に合わせて制御しやすい。負帯電用の感光体では中間層の上に電荷発生層（ＣＧＬ）、その上に電荷輸送層（ＣＴＬ）の構成を取ることが好ましい。正帯電用の感光体では前記層構成の順が負帯電用感光体の場合の逆となる。本発明の最も好ましい感光層構成は前記機能分離構造を有する負帯電感光体構成である。
【０１１３】
以下に機能分離負帯電感光体の感光層構成について説明する。
電荷発生層
電荷発生層には電荷発生物質（ＣＧＭ）を含有する。その他の物質としては必要によりバインダー樹脂、その他添加剤を含有しても良い。
【０１１４】
電荷発生物質（ＣＧＭ）としては公知の電荷発生物質（ＣＧＭ）を用いることができる。例えばフタロシアニン顔料、アゾ顔料、ペリレン顔料、アズレニウム顔料などを用いることができる。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ＣＧＭは複数の分子間で安定な凝集構造をとりうる立体、電位構造を有するものであり、具体的には特定の結晶構造を有するフタロシアニン顔料、ペリレン顔料のＣＧＭが挙げられる。例えばＣｕ−Ｋα線に対するブラッグ角２θが２７．２°に最大ピークを有するチタニルフタロシアニン、同２θが１２．４に最大ピークを有するベンズイミダゾールペリレン等のＣＧＭは繰り返し使用に伴う劣化がほとんどなく、残留電位増加小さくすることができる。
【０１１５】
電荷発生層にＣＧＭの分散媒としてバインダーを用いる場合、バインダーとしては公知の樹脂を用いることができるが、最も好ましい樹脂としてはホルマール樹脂、ブチラール樹脂、シリコーン樹脂、シリコーン変性ブチラール樹脂、フェノキシ樹脂等が挙げられる。バインダー樹脂と電荷発生物質との割合は、バインダー樹脂１００質量部に対し２０〜６００質量部が好ましい。これらの樹脂を用いることにより、繰り返し使用に伴う残留電位増加を最も小さくできる。電荷発生層の膜厚は０．０１μｍ〜２μｍが好ましい。
【０１１６】
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。
【０１１７】
電荷輸送物質（ＣＴＭ）としては公知の電荷輸送物質（ＣＴＭ）を用いることができる。例えばトリフェニルアミン誘導体、ヒドラゾン化合物、スチリル化合物、ベンジジン化合物、ブタジエン化合物などを用いることができる。これら電荷輸送物質は通常、適当なバインダー樹脂中に溶解して層形成が行われる。これらの中で繰り返し使用に伴う残留電位増加を最も小さくできるＣＴＭは高移動度で、且つ組み合わされるＣＧＭとのイオン化ポテンシャル差が０．５（ｅＶ）以下の特性を有するものであり、好ましくは０．２５（ｅＶ）以下である。
【０１１８】
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。
【０１１９】
電荷輸送層（ＣＴＬ）に用いられる樹脂としては、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ＣＴＬのバインダーとして最も好ましいものはポリカーボネート樹脂である。又、電荷輸送層の膜厚は１０〜４０μｍが好ましい。
【０１２０】
保護層
必要により、感光体の保護層として、各種樹脂層を設けることができる。特に架橋系の樹脂層を設けることにより、機械的強度の強い有機感光体を得ることができる。
【０１２１】
本発明のトナー像を形成するトナーとしては、例えば磁性体を含有させて一成分磁性トナーとして使用する場合、いわゆるキャリアと混合して二成分現像剤として使用する場合、非磁性トナーを単独で使用する場合等が考えられ、いずれも好適に使用することができるが、本発明ではキャリアと混合して使用する二成分現像剤として使用することが好ましい。
【０１２２】
本発明の画像形成方法は電子写真複写機、レーザープリンター、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、下記文章中の「部」は質量部を表す。
【０１２４】
（１）感光体の作製
感光体１の作製
円筒形アルミドラム（直径：６０ｍｍφ、長さ３６２ｍｍ）上に、チタンキレート化合物「ＴＣ−７５０」（松本製薬社製）２０部、シランカップリング剤「ＫＢＭ−５０３」（信越化学社製）１３部をイソプロパノール：水＝１００：３の混合溶媒１００部に溶解した中間層液を浸漬塗布し、１５０℃；３０分加熱硬化して乾燥膜厚１．０μｍの中間層を設けた。
【０１２５】
その上に、電荷発生物質としてＸ線回折におけるブラッグ角２θが９．５度、２４．１度、２７．２度を有するチタニルフタロシアニン顔料６部、シリコン樹脂「ＫＲ−５２４０」（信越化学社製）７部、酢酸ｔ−ブチル２００部をサンドグラインダーを用いて分散した塗布液を浸漬塗布して、乾燥膜厚０．３μｍの電荷発生層を形成した。
【０１２６】
次いで電荷輸送物質（ＣＴ−１）２００部、酸化防止剤（ＡＯ−１）５部、ビスフェノールＺ型ポリカーボネート「パンライトＴＳ−２０５０」（帝人化成（株）製）３００部、疎水化処理シリカ（数平均粒径７ｎｍ）５０部、１，２−ジクロロエタン２０００部に溶解した塗布液を、電荷発生層上に円形スライドホッパーにて塗布して、乾燥膜厚２４μｍの電荷輸送層を形成し、感光体１を作製した。感光体１の平均面粗さ（Ｒａ）は２．１５ｎｍであった。
【０１２７】
【化１】

【０１２８】
感光体２の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を疎水化処理シリカ（数平均粒径４５ｎｍ）に代えて用いた他は、感光体１と同様にして感光体２を作製した。感光体２の平均面粗さ（Ｒａ）は３５．６ｎｍであった。
【０１２９】
感光体３の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を疎水化処理酸化チタン（数平均粒径３５ｎｍ）に代えて用いた他は、感光体１と同様にして感光体３を作製した。感光体３の平均面粗さ（Ｒａ）は２４．２ｎｍであった。
【０１３０】
感光体４の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を疎水化処理ジルコニア（数平均粒径６２ｎｍ）を用いた他は、感光体１と同様にして感光体４を作製した。感光体４の平均面粗さ（Ｒａ）は４８．４ｎｍであった。
【０１３１】
感光体５の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を疎水化処理アルミナ（数平均粒径１００ｎｍ）を用いた他は、感光体１と同様にして感光体５を作製した。感光体５の平均面粗さ（Ｒａ）は７２．５ｎｍであった。
【０１３２】
感光体６の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を微粉末焼結シリカ（数平均粒径０．１３μｍ）を用いた他は、感光体１と同様にして感光体６を作製した。感光体６の平均面粗さ（Ｒａ）は９６．６ｎｍであった。
【０１３３】
感光体７の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を微粉末焼結シリカ（数平均粒径０．２５μｍ）を用いた他は、感光体１と同様にして感光体７を作製した。感光体７の平均面粗さ（Ｒａ）は１１２ｎｍであった。
【０１３４】
感光体８の作製
感光体１の作製において、疎水化処理シリカ（数平均粒径１５ｎｍ）を除いた他は、感光体１と同様にして感光体８を作製した。感光体８の平均面粗さ（Ｒａ）は１．２ｎｍであった。
【０１３５】
前記感光体１〜８の作製に用いられたコロイダルシリカ等の数平均粒子径は透過型電子顕微鏡観察によって１００００倍に拡大し、ランダムに１００個の粒子を一次粒子として観察し、画像解析によってフェレ方向平均径としての測定値である。
【０１３６】
表面エネルギー低下剤Ａ〜Ｆの作製
ステアリン酸ナトリウムを水に溶解し、１５質量％液を作製した。又、硫酸亜鉛を水に溶解し、２５質量％液を作製した。直径６ｃｍのタービン羽根を有する撹拌装置付きの２リットルの受け容器を用意し、タービン羽根を３５０ｒｐｍで回転させた。この受け容器にステアリン酸ナトリウム液を投入し、液温８０℃に調整した。次に、この受け容器に８０℃にした硫酸亜鉛液を３０分かけて滴下した。ステアリン酸ナトリウムと硫酸亜鉛の当量比は０．９８とし、金属石鹸スラリー量が５００ｇとなるように混合した。全量仕込み終了後、反応時の温度状態で、１０分間熟成し、反応を終結させた。次にこのようにして得られた金属石鹸スラリーを２回水洗し、続いて水を用いて洗浄した。得られた金属石鹸ケーキを１１０℃の乾燥温度で乾燥し、１５ＭＰａの圧力で固形化した。その後３０℃８０％ＲＨの環境条件下に２４時間放置し、表１に示す含水率を変化させたステアリン酸亜鉛の固形材料（表面エネルギー低下剤Ａ〜Ｆ）を得た。これらＡ〜Ｆの含水率は１１０℃の乾燥時間を変化させて調製した。
【０１３７】
【表１】

【０１３８】
〈評価〉
図５に示したクリーニング手段を図１の中間転写体を有するデジタルカラープリンターの感光体のクリーニング手段として搭載し、該デジタルカラープリンターに感光体と表面エネルギー低下剤の組み合わせ及び中間転写体のＲｚ、クリーニングブラシの食い込み量を表２のように組み合わせ、高温高湿（３０℃８０％ＲＨ）下で、画素率８％の画像を連続してＡ４紙１０万枚プリントを行い評価した。評価項目は中抜け、文字チリの評価、ハーフトーンむら、クリーニング性評価、画像の鮮鋭性評価等である。評価項目、評価基準を下記に示す。又評価結果を表２に示す。
【０１３９】
評価項目と評価基準
感光体の接触角及び接触角のバラツキの測定
上記Ａ４紙２０００枚のプリント評価後に、本文中の方法により、純水に対する感光体表面の接触角を接触角計（ＣＡ−ＤＴ・Ａ型：協和界面科学社製）を用いて３０℃８０％ＲＨの環境下で測定した。
【０１４０】
「中抜けの発生」
文字を拡大観察し、中抜けの発生の有無を目視にて観察した。
【０１４１】
◎：１０万枚のプリント終了まで、顕著な中抜けの発生なし
○：５万枚のプリント終了まで、顕著な中抜けの発生なし
×：５万枚未満のプリントで、顕著な中抜け発生あり
「文字チリの評価」
文字を構成するドット画像に代わり、画像全面に１０％網点画像を形成し、ルーペにてドット周辺のトナー散りを観察した。
【０１４２】
ランク◎：１０万枚のプリント終了まで、トナー散りが少ない。
ランク○：５万枚のプリント終了まで、トナー散りが少ない。
【０１４３】
ランク×：５万枚未満のプリントでトナー散りが増加している。（実用上問
題のレベル）
ハーフトーンむら：１０万枚コピー終了後、ハーフトーン画像（濃度０．２近辺の均一画像）の濃度差（ΔＨＤ＝最大濃度−最小濃度）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、上記ハーフトーン画像部を同様に２０カ所、絶対画像濃度で測定し、その最大濃度−最小濃度をΔＨＤとして評価した。
【０１４４】
◎：０．０５以下（良好）
○：０．０５より大で０．１未満（実用上問題ないレベル）
×：０．１以上（実用上問題あり）
クリーニング性の評価
感光体とクリーニングブレードの摩耗によるトナーのすり抜けの発生の有無、やブレード捲れ（ブレードが反転する現象）の発生の有無を評価した。
【０１４５】
◎：１０万枚のプリント終了までトナーのすり抜け、ブレード捲れの発生なし
○：５万枚のプリント終了までトナーのすり抜け、ブレード捲れの発生なし
×：５万枚未満のプリントでトナーのすり抜け又はブレード捲れ発生あり
画像の鮮鋭性
細線の再現性、画像の鮮鋭性を高温常湿環境下（温度３３℃、相対湿度５０％）において画像を出し、文字潰れで評価した。３ポイント、５ポイントの文字画像を形成し、下記の判断基準で評価した。
【０１４６】
◎：３ポイント、５ポイントとも明瞭であり、容易に判読可能
○：３ポイントは一部判読不能、５ポイントは明瞭であり、容易に判読可能
×：３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能
その他の評価条件
画像形成のライン速度Ｌ／Ｓ：１８０ｍｍ／ｓ
感光体（６０ｍｍφ）の帯電条件：非画像部の電位は、電位センサで検知し、フィードバック制御できるようにし、その制御可能範囲は−５００Ｖ〜−９００Ｖであり、全露光した場合の感光体の表面電位は−５０〜０Ｖの範囲にした。
【０１４７】
露光条件：像露光は半導体レーザ（波長：７８０ｎｍ）を用い、８００ｄｐｉのデジタル潜像を形成した。
【０１４８】
現像条件：現像剤はＹ、Ｍ、Ｃ、Ｋ共、個数平均粒子径が７．５μｍのトナーとキャリアの２成分現像剤（トナー濃度：５質量％）であり、現像装置も２成分現像剤に対応した方式のものである。
【０１４９】
中間転写体：シームレスの無端ベルト状中間転写体７０を用い、半導電樹脂製のベルトで体積抵抗率が１×１０^８Ω・ｃｍのものを用いた。Ｒｚが０．９μｍと１．５μｍ、２．２μｍの３種類を用いた。
【０１５０】
一次転写条件
一次転写ローラ（図１の５Ｙ、５Ｍ、５Ｃ、５Ｋ（各６．０５ｍｍφ））：芯金に弾性ゴムを付した構成：表面比抵抗１×１０^６Ω、転写電圧印加
二次転写条件
中間転写体としての無端ベルト状中間転写体７０とそれを挟み込むようにバックアップローラ７４と二次転写ローラ５Ａが配置され、バックアップローラ７４の抵抗値が１×１０^６Ωであり、二次転写手段としての二次転写ローラの抵抗値が１×１０^６Ωであり定電流制御（約８０μＡ）をするようにしてある。
【０１５１】
定着はローラ内部にヒータを配置した定着ローラによる熱定着方式である。
中間転写体と感光体との最初の接触点から次色感光体との最初の接触点までの中間転写体上での距離Ｙは９５ｍｍにした。
【０１５２】
駆動ローラ７１、ガイドローラ７２，７３及び二次転写のためのバックアップローラ７４の外周長さ（円周長さ）を３１．６７ｍｍ（＝９５ｍｍ／３）にし、テンションローラ７６の外周長さを２３．７５ｍｍ（＝９５ｍｍ／４）にした。
【０１５３】
そして、一次転写ローラの外周長さを１９ｍｍ（＝９５ｍｍ／５）にした。
クリーニングブレード（感光体）：ウレタンゴムブレード
クリーニングブラシ：導電性アクリル樹脂、ブラシ毛密度（３×１０^３／ｃｍ^２）、食い込み量０．６、１．０、１．３ｍｍの３種類を用いた。
【０１５４】
二次転写ローラ（図１の５Ａ）：芯金に弾性ゴムを付した構成：転写電圧印加
クリーニングブレード（中間転写体）：ウレタンゴムブレード
【０１５５】
【表２】

【０１５６】
表２より、明らかなように、表面エネルギー低下剤を付与し、電子写真感光体の接触角のバラツキを±５°以下に小さくした本発明内の組み合わせ１〜５及び７〜１１は、本発明外の接触角のバラツキが±５°よりも大きい組み合わせ６、１２に対しては中抜け、文字チリ、鮮鋭性等の改良が顕著であり、組み合わせ１３に比してはハーフトーンむらの改善か著しい。又、表面エネルギー低下剤を付与していない組み合わせ１４に比してはほとんど全ての評価項目で改善がなされている。
【０１５７】
【発明の効果】
本発明を用いることにより、中間転写体を用いた電子写真方式のトナーの転写特性の改善を達成でき、トナー転写性の低下から発生する中抜けや文字チリ等の画像欠陥を防止でき、且つクリーニング性も良好な電子写真方式の画像形成方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態を示すカラー画像形成装置の断面構成図である。
【図２】中間転写体のクリーニング手段の一例である。
【図３】感光体と無端ベルト状中間転写体と一次転写ローラとの位置関係を示す配置図である。
【図４】バックアップローラと無端ベルト状中間転写体と二次転写ローラとの位置関係を示す配置図である。
【図５】本発明の感光体に設置されるクリーニング手段の構成図である。
【符号の説明】
１Ｙ，１Ｍ，１Ｃ，１Ｋ　感光体
２Ｙ，２Ｍ，２Ｃ，２Ｋ　帯電手段
３Ｙ，３Ｍ，３Ｃ，３Ｋ　露光手段
４Ｙ，４Ｍ，４Ｃ，４Ｋ　現像手段
５Ａ　二次転写ローラ（二次転写手段）
５Ｙ，５Ｍ，５Ｃ，５Ｋ　一次転写ローラ（一次転写手段）
６Ａ，６Ｙ，６Ｍ，６Ｃ，６Ｋ　クリーニング手段
７　無端ベルト状中間転写体ユニット
１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋ　画像形成部
６１　ブレード
６２　ブラケット
６３　支軸
７０　無端ベルト状中間転写体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming method, an image forming apparatus, and an electrophotographic photosensitive member used for a copying machine, a printer, a facsimile, and the like.
[0002]
[Prior art]
Conventionally, as a method of transferring a toner image on an electrophotographic photosensitive member (hereinafter, also simply referred to as a photosensitive member) to a recording material for a final image, a toner image formed on the electrophotographic photosensitive member is directly transferred to a recording material. The scheme is known. On the other hand, an image forming method using an intermediate transfer member is known. In this method, another transfer step is inserted in a process of transferring a toner image from an electrophotographic photosensitive member to a recording material, and the image forming method is performed from the electrophotographic photosensitive member. After the primary transfer to the intermediate transfer member, a final image is obtained by secondary transferring the primary transfer image of the intermediate transfer member to a recording material. Among these, the above-mentioned intermediate transfer method is adopted as a superimposed transfer method of each color toner image in a so-called full-color image forming apparatus that reproduces a color-separated original image by using subtractive color mixing with toners of black, cyan, magenta, yellow, and the like. Often done.
[0003]
However, in any of the above methods, when a large number of copies or prints are performed, toner filming occurs on the electrophotographic photosensitive member or the intermediate transfer member, or the surface energy of the electrophotographic photosensitive member or the intermediate transfer member increases. As a result, the adhesion to the toner increases, the transferability of the toner from the electrophotographic photosensitive member to the recording material or from the intermediate transfer member to the recording material decreases, and image defects tend to occur in the final image. In particular, in an image forming method using an intermediate transfer body, a transfer step of a primary transfer means for performing a primary transfer of a toner image from an electrophotographic photosensitive member to an intermediate transfer body and a secondary transfer for transferring a toner image from the intermediate transfer body to a recording material Due to the two transfer steps of the means transfer step, the reduced transferability significantly reduces the quality of the final image.
[0004]
That is, when the transferability of the toner is reduced in the image forming method using the intermediate transfer member, a so-called “missing portion” or “character dust” in which a part of the toner image is not transferred easily occurs. In particular, a toner image of 400 dpi (dpi is the number of dots per 2.54 cm) or more formed on the photoreceptor is liable to cause "missing" and "character dust".
[0005]
In order to improve transferability and prevent toner filming, or to improve poor cleaning, which cause "hollowness" and "character dust", fine particles are contained in the surface layer of the electrophotographic photosensitive member, and Techniques have been studied for providing irregularities, reducing the adhesion of the toner on the surface of the photoreceptor, improving the transferability, and reducing the frictional force with the blade. For example, it has been reported that an alkylsilsesquioxane resin fine particle is contained in a photosensitive layer (Patent Document 1). However, the alkyl silsesquioxane resin fine particles have a hygroscopic property, and in a high-humidity environment, the wettability of the surface of the photoreceptor, that is, the surface energy is increased, and a problem such that transferability is likely to be lowered occurs. On the other hand, an electrophotographic photoreceptor containing a fluororesin powder has been reported to reduce the surface energy of the photoreceptor surface (Patent Document 2). However, there has been a problem that sufficient surface strength cannot be obtained with fluororesin powder, and streak failure due to scratches on the photoreceptor surface is likely to occur. In addition, a technique has been disclosed in which a fatty acid metal salt is supplied to a photoreceptor surface having minute irregularities to reduce friction torque on the photoreceptor surface and improve cleaning properties (Patent Document 3). However, in the technology disclosed herein, there is no description about the technology for reducing the variation in the contact angle on the surface of the photoreceptor and for preventing the above-mentioned “hollow-out” and “character dust”.
[0006]
On the other hand, in order to improve the transferability of the intermediate transfer member, a technology has been disclosed in which a solid lubricant is supplied to the intermediate transfer member to reduce the surface energy of the intermediate transfer member (Patent Documents 4, 5, and 6). ). However, simply controlling the surface of such an intermediate transfer member is still insufficient for improving the total transferability of an image forming method using an intermediate transfer member having two transfer steps, especially at high temperatures. It has been found that further improvement is required for the formation of high-humidity or long-term copy images.
[0007]
That is, in the image forming method using the intermediate transfer member, it is necessary to reduce the surface energy of both the electrophotographic photosensitive member and the intermediate transfer member in a well-balanced manner and to improve the total transferability of both the primary transfer and the secondary transfer. It was found to be.
[0008]
[Patent Document 1]
JP-A-5-181291
[0009]
[Patent Document 2]
JP-A-63-56658
[0010]
[Patent Document 3]
JP 2001-265040 A
[0011]
[Patent Document 4]
JP-A-6-337598
[0012]
[Patent Document 5]
JP-A-6-332324
[0013]
[Patent Document 6]
JP-A-7-271142
[0014]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art, improve the transferability of toner in an image forming method using an intermediate transfer body, and prevent image defects such as voids and character dust from occurring. An object of the present invention is to provide an image forming method, an image forming apparatus, and an electrophotographic photosensitive member.
[0015]
[Means for Solving the Problems]
As a result of repeated studies on the above problems, the present inventors have found that in order to improve the transferability of the toner of the image forming system using the intermediate transfer member and to prevent image defects such as voids and character dust, an electronic device is required. By forming irregularities smaller than the toner particle size on the surface of the photoreceptor, and spreading the surface energy reducing agent uniformly on the surface of the photoreceptor, reducing the variation in the contact angle on the surface of the photoreceptor, It has been found that the object of the present invention can be achieved by minimizing the variation depending on the place at the time of development for forming an image and transfer of a toner image, and completed the present invention.
[0016]
The object of the present invention is achieved by having the following configuration.
1. An image forming method comprising: transferring a latent image formed on an electrophotographic photosensitive member to a toner image by development and transferring the toner image to a recording material or an intermediate transfer member; An image forming method, comprising applying an energy-lowering agent and performing the development and transfer while making the contact angle variation of the electrophotographic photosensitive member ± 5 ° of the average value.
[0017]
2. A primary transfer means for developing the latent image formed on the electrophotographic photosensitive member into a toner image and transferring the toner image to an intermediate transfer member; and a secondary transfer means for transferring the toner image transferred to the intermediate transfer member to a recording material. An image forming method including a secondary transfer means, wherein a surface energy reducing agent is applied to the surface of the electrophotographic photoreceptor, and the variation of the contact angle of the electrophotographic photoreceptor is adjusted to ± 5 ° of an average value while the development is performed. And an image forming method.
[0018]
3. The image forming method according to claim 1 or 2, wherein the contact angle is 90 to 120 °.
[0019]
4. Any one of the above items 1 to 3, wherein the surface of the electrophotographic photosensitive member has an average surface roughness (Ra) of 1.5 μm or more and 100 nm or less as measured on a 5 μm square surface using an atomic force microscope. Item.
[0020]
5. The image forming method according to any one of Items 1 to 4, wherein the surface energy reducing agent is applied by an agent applying unit.
[0021]
6. 6. The image forming method according to any one of the above items 1 to 5, wherein the water content of the surface energy reducing agent is 5.0% by mass or less.
[0022]
7. 7. The image forming method according to any one of items 1 to 6, wherein the surface energy reducing agent is a fatty acid metal salt.
[0023]
8. 8. The image forming method according to the item 7, wherein the fatty acid metal salt is zinc stearate.
[0024]
9. 9. The image forming method according to any one of items 1 to 8, wherein the surface layer of the electrophotographic photosensitive member contains fine particles having a number average particle size of 5 nm to 500 nm.
[0025]
10. An image forming apparatus that forms an electrophotographic image by using the image forming method according to any one of the above items 1 to 9.
[0026]
11. The latent image formed on the electrophotographic photoreceptor is developed by applying a surface energy reducing agent to the surface of the electrophotographic photoreceptor and developing the latent image on the electrophotographic photoreceptor while maintaining the contact angle variation of the electrophotographic photoreceptor at an average value of ± 5 °. In an electrophotographic photosensitive member used in an image forming method provided with a transfer means for transferring the toner image to a recording material or an intermediate transfer member as an image, an average surface roughness of 5 μm square measured on the surface using an atomic force microscope. An electrophotographic photoreceptor having a thickness (Ra) of 1.5 nm or more and 100 nm or less.
[0027]
That is, by employing the above-described structure of the present invention, it is possible to prevent the occurrence of voids, character dust, and deterioration of sharpness, and to form a favorable electrophotographic image with an image forming apparatus using an intermediate transfer member.
[0028]
Hereinafter, the present invention will be described in detail.
FIG. 1 is a sectional view of a color image forming apparatus according to an embodiment of the present invention.
[0029]
This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7, a sheet feeding and conveying unit 21, And fixing means 24. An original image reading device SC is arranged above the main body A of the image forming apparatus.
[0030]
The image forming unit 10Y that forms a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a primary transfer unit that are arranged around a drum-shaped photoconductor 1Y as a first image carrier. It has a primary transfer roller 5Y and a cleaning unit 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning unit 6M. The image forming unit 10C for forming a cyan image includes a drum-shaped photoconductor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, It has cleaning means 6C. The image forming unit 10K for forming a black image includes a drum-shaped photosensitive member 1K as a first image carrier, a charging unit 2K, an exposing unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit. Has 6K.
[0031]
The endless belt-shaped intermediate transfer body unit 7 has an endless belt-shaped intermediate transfer body 70 as a semiconductive endless belt-shaped second image carrier that is wound around a plurality of rollers and rotatably supported.
[0032]
Images of each color formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5K as primary transfer means. Then, a combined color image is formed. The sheet P as a recording medium stored in the sheet cassette 20 is fed by a sheet feeding unit 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D, a registration roller 23, and as a secondary transfer unit. The sheet is conveyed to the secondary transfer roller 5A, and is secondary-transferred onto the sheet P to collectively transfer color images. The paper P to which the color image has been transferred is subjected to a fixing process by the fixing unit 24, and is held by a paper discharge roller 25 and placed on a paper discharge tray 26 outside the apparatus.
[0033]
On the other hand, after the color image is transferred onto the sheet P by the secondary transfer roller 5A as the secondary transfer unit, the residual toner is removed by the cleaning unit 6A from the endless belt-shaped intermediate transfer body 70 from which the sheet P is separated by curvature.
[0034]
During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoconductor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoconductors 1Y, 1M, and 1C only during color image formation.
[0035]
The secondary transfer roller 5A is in pressure contact with the endless belt-shaped intermediate transfer body 70 only when the sheet P passes through the secondary transfer roller 5A to perform secondary transfer.
[0036]
Further, the housing 8 can be pulled out from the apparatus main body A via the support rails 82L and 82R.
[0037]
The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer unit 7.
[0038]
The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer unit 7 is disposed on the left side of the photoconductors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can rotate around rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5K, and a cleaning unit 6A. Consists of
[0039]
FIG. 2 shows an example of a cleaning unit for the intermediate transfer member.
As shown in FIG. 2, the cleaning means 6A for the intermediate transfer member is composed of a blade 61 attached to a bracket 62 which is rotatably controlled around a support shaft 63, and changes the spring load or the weight load to change the roller. The blade pressing force to the blade 71 can be adjusted.
[0040]
The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out of the main body A by the pulling-out operation of the housing 8.
[0041]
The support rail 82 </ b> L on the left side of the housing 8 in the drawing is disposed in the space above the fixing unit 24 on the left side of the endless belt-shaped intermediate transfer body 70. The support rail 82R on the right side of the housing 8 in the drawing is disposed near the lower part of the lowermost developing unit 4K. The support rail 82R is arranged at a position that does not hinder the operation of attaching and detaching the developing units 4Y, 4M, 4C, and 4K to and from the housing 8.
[0042]
The right side of the photoconductors 1Y, 1M, 1C, and 1K of the housing 8 is surrounded by developing means 4Y, 4M, 4C, and 4K, and the lower part of the figure is a charging unit 2Y, 2M, 2C, and 2K and a cleaning unit 6Y. , 6M, 6C, 6K, etc., and the left side in the figure is surrounded by an endless belt-shaped intermediate transfer body 70.
[0043]
Among them, the photoreceptor, the cleaning unit, the charging unit and the like form one photoreceptor unit, and the developing unit and the toner replenishing device form one developing unit.
[0044]
FIG. 3 is a layout diagram showing a positional relationship among the photosensitive member, the endless belt-shaped intermediate transfer member, and the primary transfer roller. The primary transfer rollers 5Y, 5M, 5C and 5K are pressed from the back surface of the endless belt-shaped intermediate transfer body 70 as the intermediate transfer body to the respective photoconductors 1Y, 1M, 1C and 1K, as shown in the arrangement diagram of FIG. In addition, the primary transfer rollers 5Y, 5M, 5C are located downstream of the contact point between the endless belt-shaped intermediate transfer body 70 as the intermediate transfer body when not pressed and each of the photoconductors 1Y, 1M, 1C, 1K in the photoconductor rotation direction. , 5K and press them against the photoconductors 1Y, 1M, 1C, 1K. At this time, the endless belt-shaped intermediate transfer body 70 as the intermediate transfer body is bent along the outer periphery of each of the photoconductors 1Y, 1M, 1C, and 1K, and is most downstream of the contact area between the photoconductor and the endless belt-shaped intermediate transfer body 70. The primary transfer rollers 5Y, 5M, 5C, 5K are arranged on the side.
[0045]
FIG. 4 is a layout diagram showing a positional relationship among a backup roller, an endless belt-shaped intermediate transfer body, and a secondary transfer roller. As shown in the layout diagram of FIG. 4, the secondary transfer roller 5A is located between the contact center portion of the endless belt-shaped intermediate transfer member 70 as the intermediate transfer member and the backup roller 74 when not pressed by the secondary transfer roller 5A. It is also desirable that the backup roller 74 is disposed on the upstream side in the rotation direction of the backup roller 74.
[0046]
Intermediate transfer member, polyimide, polycarbonate, polymer film such as PVdF, silicone rubber, synthetic rubber such as fluorine rubber and conductive filler such as carbon black is added conductive, and the like, drum-shaped, The belt shape may be used, but the belt shape is preferable from the viewpoint of the degree of freedom in device design.
[0047]
The surface of the intermediate transfer member is preferably appropriately roughened. By setting the ten-point average roughness Rz of the intermediate transfer member to 0.5 to 2.5 μm, the surface energy reducing agent supplied to the photoconductor is taken into the surface of the intermediate transfer member, and the toner adhesion on the intermediate transfer member is reduced. This makes it easier to improve the transfer rate of the secondary transfer of the toner from the intermediate transfer member to the recording paper. In this case, the effect tends to be greater when the ten-point average roughness Rz of the intermediate transfer member is larger than the ten-point average roughness Rz of the photoconductor.
[0048]
The present invention is characterized in that a latent image on an electrophotographic photosensitive member is developed while a surface energy reducing agent is applied to the surface of the electrophotographic photosensitive member, and the latent image is visualized as a toner image. As a method of applying to the photoreceptor, there is a method of adding a surface energy reducing agent to a developer and applying the agent to the photoreceptor from the developer, but in the present invention, it is preferable to use a method different from such a method. That is, when the surface energy reducing agent is mixed with the developer, the mixing affects the charging characteristics of the toner, the developing characteristics such as fluidity, and it is difficult to achieve a sufficient mixing amount. Speaking of the relationship with the toner of the present invention, by mixing a developer with a surface energy-lowering agent, hollowing-out and the effect of preventing the occurrence of text dust are likely to be significantly reduced. It is preferable to use different means and methods.
[0049]
That is, the present invention preferably has an agent applying means for supplying a surface energy reducing agent to the surface of the electrophotographic photosensitive member. The agent applying means can be installed at an appropriate position around the electrophotographic photoreceptor, but in order to effectively use the installation space, a part of the charging means, developing means, and cleaning means shown in FIG. May be installed. Hereinafter, an example in which an agent applying unit is used in combination with a cleaning unit will be described.
[0050]
FIG. 5 is a configuration diagram of the cleaning unit provided on the photoconductor of the present invention.
The cleaning means is used as cleaning means for 6Y, 6M, 6C, 6K, etc. in FIG. The cleaning blade 66A of FIG. 5 is attached to the support member 66B. A rubber elastic body is used as a material of the cleaning blade, and urethane rubber, silicon rubber, fluorine rubber, chloropyrene rubber, butadiene rubber, and the like are known as the material. Of these, urethane rubber is another material. It is particularly preferable because it has excellent wear characteristics as compared with rubber.
[0051]
On the other hand, the support member 66B is formed of a plate-shaped metal member or a plastic member. As the metal member, a stainless steel plate, an aluminum plate, a vibration control steel plate, or the like is preferable.
[0052]
In the present invention, it is preferable that the tip of the cleaning blade that is in pressure contact with the surface of the photoconductor is pressed in a state in which a load is applied in a direction opposite to the rotation direction of the photoconductor (counter direction). As shown in FIG. 5, it is preferable that the distal end portion of the cleaning blade forms a pressing surface when pressed against the photosensitive member.
[0053]
Preferred values of the contact load P and the contact angle θ of the cleaning blade on the photoconductor are P = 5 to 40 N / m and θ = 5 to 35 °.
[0054]
The contact load P is a vector value in the normal direction of the pressing force P ′ when the cleaning blade 66A is brought into contact with the photosensitive drum 1.
[0055]
Is the angle between the tangent line X at the contact point A of the photoconductor and the blade before deformation (indicated by a dotted line in the drawing). 66E is a rotation shaft that allows the support member to rotate, and 66G is a load spring.
[0056]
The free length L of the cleaning blade represents the length of the tip of the blade before deformation from the position of the end B of the support member 66B as shown in FIG. A preferred value of the free length is L = 6 to 15 mm. The thickness t of the cleaning blade is preferably 0.5 to 10 mm. Here, the thickness of the cleaning blade of the present invention indicates a direction perpendicular to the bonding surface of the support member 66B as shown in FIG.
[0057]
A brush roll 66C also serving as an agent applying means is used as the cleaning means in FIG. The brush roll has a function of removing the toner adhered to the photoconductor 1 and a function of collecting the toner removed by the cleaning blade 66A, and also has a function as an agent applying means for supplying a surface energy reducing agent to the photoconductor. That is, the brush roll comes into contact with the photoreceptor 1, and at the contact portion, the traveling direction rotates in the same direction as the photoreceptor, thereby removing the toner and paper dust on the photoreceptor and removing the toner removed by the cleaning blade 66A. And collected by the transfer screw 66J. In the path during this time, it is preferable to remove a removed substance such as toner transferred from the photoreceptor 1 to the brush roll 66C by bringing the flicker 66I as a removing unit into contact with the brush roll 66C. Further, the toner attached to the flicker is removed by a scraper 66D, and the toner is collected by a transport screw 66J. The collected toner is taken out as waste, or is conveyed to a developing device via a toner recycling pipe (not shown) to be reused. As a material for the flicker 66I, a metal tube such as stainless steel or aluminum is preferably used. On the other hand, as the scraper 66D, an elastic plate such as a phosphor bronze plate, a polyethylene terephthalate plate, or a polycarbonate plate is used, and it is preferable that the tip is brought into contact with a counter system in which the tip forms an acute angle with the rotation direction of the flicker.
[0058]
Also, a surface energy reducing agent (solid material such as zinc stearate) 66K is attached to the brush roll by pressing with a spring load 66S. A surface energy reducing agent is supplied to the surface.
[0059]
A conductive or semiconductive brush roll is used as the brush roll 66C.
[0060]
Although any material can be used as the material of the brush of the brush roll used in the present invention, it is preferable to use a fiber-forming polymer having hydrophobicity and a high dielectric constant. Examples of such a polymer include rayon, nylon, polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, and vinylidene chloride. -Acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol formaldehyde resin, styrene-alkyd resin, polyvinyl acetal (for example, polyvinyl acetal) Butyral) and the like. These binder resins can be used alone or as a mixture of two or more. Particularly preferred are rayon, nylon, polyester, acrylic resin and polypropylene.
[0061]
The brush may be a conductive or anti-conductive brush, and may be a material in which a low-resistance substance such as carbon is contained in a constituent material and adjusted to an arbitrary specific resistance.
[0062]
The specific resistance of the brush bristles of the brush roll is measured at room temperature and normal humidity (temperature 26 ° C., relative humidity 50%) with a voltage of 500 V applied to both ends of a single 10 cm long bristles. ¹ Ωcm-10 ⁶ Those within the range of Ωcm are preferred.
[0063]
That is, the brush roll is made of 10 core material such as stainless steel. ¹ Ωcm-10 ⁶ It is preferable to use conductive or semiconductive brush bristles having a specific resistance of Ωcm. 10 ¹ If the specific resistance is lower than Ωcm, banding or the like due to discharge is likely to occur. Also, 10 ⁶ If it is higher than Ωcm, the potential difference from the photoreceptor becomes low, and cleaning failure easily occurs.
[0064]
The thickness of one brush bristles used for the brush roll is preferably 5 to 20 denier. If it is less than 5 denier, there is no sufficient rubbing force, so that the surface deposits cannot be removed. On the other hand, if it is larger than 20 denier, the brush becomes rigid, so that the surface of the photoreceptor is damaged and abrasion proceeds, thereby shortening the life of the photoreceptor.
[0065]
The term “denier” as used herein is a numerical value obtained by measuring the mass of the brush bristles (fibers) constituting the brush in a length of 9000 m in g (gram) units.
[0066]
The brush bristle density of the brush is 4.5 × 10 ² / Cm ² ~ 2.0 × 10 ⁴ / Cm ² (The number of brush hairs per square centimeter). 4.5 × 10 ² / Cm ² If it is less than, the rigidity is low, the rubbing force is weak, and the rubbing is uneven, so that it is impossible to uniformly remove the attached matter. 2.0 × 10 ⁴ / Cm ² If it is larger, the photoreceptor will be worn because it becomes rigid and the rubbing force will be strong, and a defective image such as a black stripe due to fog or a scratch due to a decrease in sensitivity will occur.
[0067]
The bite amount of the brush roll used in the present invention into the photoreceptor is preferably set to 0.4 to 1.5 mm. This biting amount means a load on the brush generated by the relative movement between the photosensitive drum and the brush roll. This load corresponds to the rubbing force received from the brush when viewed from the photoconductor drum, and defining the range means that the photoconductor needs to be rubbed with an appropriate force.
[0068]
This biting amount refers to the length of biting into the interior when it is assumed that when the brush abuts on the photoreceptor, the brush bristles do not bend on the surface of the photoreceptor but enter the interior linearly.
[0069]
In the photoreceptor to which the surface energy reducing agent is supplied, since the abrasion force of the surface of the photoreceptor by the brush is small, if the bite amount is smaller than 0.4 mm, the application of the surface energy reducing agent to the photoreceptor surface is not sufficient, Uneven transfer of toner occurs, and defects such as uneven image occur. On the other hand, if it is larger than 1.5 mm, the brush is too rubbing on the photoreceptor surface, so that it is difficult to form a uniform film of the surface energy reducing agent on the photoreceptor, which also causes uneven transfer of toner. This is a problem because a streak failure occurs on an image.
[0070]
As the core material of the roll portion used in the brush roll of the present invention, metals such as stainless steel and aluminum, paper, and plastics are mainly used, but are not limited thereto.
[0071]
The brush roll used in the present invention preferably has a configuration in which a brush is provided on the surface of a columnar core material via an adhesive layer.
[0072]
It is preferable that the brush roll rotates so that the contact portion moves in the same direction as the surface of the photoconductor. When the contact portion moves in the opposite direction, if excessive toner is present on the surface of the photoconductor, the toner removed by the brush roll may spill out and stain the recording paper or the apparatus.
[0073]
When the photoreceptor and the brush roll move in the same direction as described above, the surface speed ratio of the two is preferably a value within the range of 1: 1.1 to 1: 2. If the rotation speed of the brush roll is lower than that of the photoconductor, the toner removal ability of the brush roll is reduced and cleaning failure is likely to occur. If the rotation speed of the brush roll is higher than the photoconductor, the toner removal capability becomes excessive and blade bounding or turning over occurs. Easier to do.
[0074]
The present invention is characterized in that, in the image forming apparatus having the intermediate transfer member as described above, in order to apply the surface energy reducing agent to the surface of the electrophotographic photosensitive member, the agent applying means is brought into contact with the surface of the electrophotographic photosensitive member. And
[0075]
Here, the surface energy lowering agent refers to a substance that is attached to the surface of the electrophotographic photosensitive member and reduces the surface energy of the electrophotographic photosensitive member. A material that increases the contact angle (contact angle with pure water) by 1 ° or more.
[0076]
Contact angle and contact angle variation measurement
The contact angle in the present invention refers to the contact angle of the surface of the photoreceptor with pure water. The contact angle of the photoreceptor is measured by using a contact angle meter (CA-DT.A type: manufactured by Kyowa Interface Science Co., Ltd.) under an environment of 30 ° C. and 80% RH.
[0077]
The variation of the contact angle is measured in an environment of 30 ° C. and 80% RH. The measurement is performed at the time when the photoreceptor is adapted to image formation and the surface energy reducing agent is sufficiently applied to the surface of the photoreceptor (at least after 1000 or more repeated image formation). A total of 12 measurement points were measured at three points at a central portion of the cylindrical photoreceptor and at 5 cm from the left and right ends, each at 90 ° in the circumferential direction, and the average value was used as the contact angle of the present invention. The value that deviated most positively or negatively from this average value was taken as the value of the variation.
[0078]
In the present invention, the variation in the contact angle of the photoconductor is preferably ± 5 °, more preferably ± 4 °, and most preferably ± 3 °. If the variation in the contact angle exceeds the range of ± 5 °, halftone unevenness is likely to occur, and hollow spots and character dust are likely to occur.
[0079]
In the present invention, the contact angle is increased by applying a surface energy reducing agent to the surface of the photoreceptor, and the contact angle is preferably in the range of 90 to 120 °. If the angle is less than 90 °, the effect of preventing hollowing and character dust is small, and if it is more than 120 °, defects other than the variation in the contact angle tend to increase. That is, no suitable material has been found for a surface energy lowering agent that makes the contact angle larger than 120 °, and when such a material is applied to an electrophotographic photosensitive member, the electrophotographic image tends to be deteriorated.
[0080]
Further, in the present invention, a surface energy reducing agent is applied to the surface of the electrophotographic photoreceptor so that the variation of the contact angle of the electrophotographic photoreceptor is set to ± 5 ° of the average value, and the above-described agent applying means and the like are used. Is to continuously supply the surface energy reducing agent during the electrophotographic image formation and supply the same to the surface of the photoreceptor during operation. Can be maintained. The term “continuously supplied” means that the supply may be always performed from the start to the end of the image formation.However, the supply may be temporarily stopped at the start or the end of the image formation. If the supply is excessive, the supply may be temporarily interrupted even during image formation.
[0081]
By the way, examples of the surface energy reducing agent include fatty acid metal salts and fluorine-based resins, and these materials tend to have a high water content under high-temperature and high-humidity conditions due to hydrophilic groups and impurity components in the material. . When the water content is large, these surface energy reducing agents are not uniformly spread on the surface of the photoreceptor, and the contact angle tends to vary depending on the location, and the above-mentioned effect of the present invention cannot be sufficiently exerted. The surface energy lowering agent used in the present invention has a water content of 5.0% by mass or less under an environment of 30 ° C. and 80% RH under the conditions of high temperature and high humidity, so that the contact angle on the surface of the photoreceptor is reduced to an average value. It has the effect of making it smaller within ± 5 °.
[0082]
The surface energy reducing agent is not limited to a material such as a fatty acid metal salt or a fluororesin, as long as it increases the contact angle (contact angle with pure water) on the surface of the electrophotographic photosensitive member by 1 ° or more.
[0083]
As the surface energy lowering agent used in the present invention, a fatty acid metal salt is most preferable as a material having spreadability on the surface of the photoreceptor and uniform film forming performance. The metal salt of a fatty acid is preferably a metal salt of a saturated or unsaturated fatty acid having 10 or more carbon atoms. Examples include aluminum stearate, indium stearate, gallium stearate, zinc stearate, lithium stearate, magnesium stearate, sodium stearate, aluminum palmitate, aluminum oleate, and the like, and more preferably metal stearate. .
[0084]
Among the above-mentioned fatty acid metal salts, a fatty acid metal salt having a high outflow rate of a flow tester has a high cleavage property, and can form a layer of a fatty acid metal salt more effectively on the surface of the photoreceptor of the present invention. The range of outflow velocity is 1 × 10 ^-7 More than 1 × 10 ^-1 The following is preferable, and 5 × 10 ^-4 More than 1 × 10 ^-2 It is most preferred that: The outflow velocity of the flow tester was measured using a Shimadzu flow tester “CFT-500” (manufactured by Shimadzu Corporation).
[0085]
As another example of the solid material, a fluororesin powder such as polyvinylidene fluoride and polytetrafluoroethylene is preferable. It is preferable that these solid materials are used in the form of a plate or a rod by applying pressure as necessary.
[0086]
On the other hand, the moisture content was measured by placing this material in a petri dish in the case of a surface energy lowering agent, leaving the material at 30 ° C. and 80% RH for 24 hours, and then using a Karl Fischer moisture content meter (manufactured by Kyoto Electronics Industry Co., Ltd .; MKA- 3p).
[0087]
The surface energy lowering agent of the present invention can be adjusted to a water content of 5.0% by mass or less by controlling a hydrophilic component or impurities in the material, for example, by purifying or hydrophobizing the material to obtain a high temperature and high humidity (30 ° C., 80% RH) ) In addition to reducing the amount of water below, it can be achieved by mixing a water regulator and drying at high temperature. The water content of the water content is preferably 0.01 to 5.0% by mass, and more preferably 0.05 to 3.0% by mass. If it is less than 0.01% by mass, it is rather susceptible to environmental fluctuations due to temperature rise during copying, especially humidity due to the location of the image carrier, and it is difficult to select a material or to perform hydrophobic treatment. If the content is more than 5.0% by mass, hollow spots and character dust easily occur.
[0088]
In the present invention, it is preferable that the surface of an electrophotographic photoreceptor (hereinafter, also simply referred to as a photoreceptor) is provided with very small irregularities in comparison with the thickness of the photosensitive layer and the size of the toner. That is, the present invention provides an electrophotographic photoreceptor having a surface layer having an average surface roughness (Ra) of 1.5 nm or more and 100 nm or less as measured on a 5 μm square using an atomic force microscope. Supplying an energy-lowering agent, effectively forming a thin film of the surface-energy-lowering agent uniformly on the surface of the photoreceptor, minimizing variations due to the position of the contact angle, preventing character blemishes and dropouts, and excellent sharpness An electrophotographic image can be obtained.
[0089]
Hereinafter, specific means for realizing an electrophotographic photoreceptor having a surface layer whose average surface roughness (Ra) of 5 μm square measured by using an atomic force microscope is 1.5 nm or more and 100 nm or less will be described below. Describe.
[0090]
The photoreceptor surface roughness of the present invention is measured using an atomic force microscope. This measuring method will be described below.
[0091]
Atomic force microscope (AFM): scanning probe microscope SPI3800N, multifunctional unit SPA400 (manufactured by Seiko Instruments Inc.)
Measurement mode: Dynamic force mode (DFM mode)
Cantilever: SI-DF20 (silicon spring constant 20 N / m, natural frequency
135KHz)
Measurement area: 5 × 5 μm
The DFM mode is a mode in which the cantilever is vibrated at a certain frequency (a frequency unique to the cantilever), and the approaching sample is intermittently contacted to reduce the vibration amplitude to display the surface shape. In the DFM mode, the measurement is performed without contacting the surface of the photoconductor, so that the measurement can be performed without damaging the surface of the photoconductor while maintaining the original shape.
[0092]
Average surface roughness (Ra): A value obtained by extending the center line roughness Ra defined in JIS B601 three-dimensionally so that it can be applied to a measurement surface, and is a value obtained by averaging the absolute value of the deviation from the reference surface to the specified surface. And is represented by the following equation.
[0093]
(Equation 1)

[0094]
The designated surface is the entire measurement surface, and in the present invention, represents a 5 μm square measurement surface (XY plane).
[0095]
The total measurement plane Z is obtained by the following equation.
Z = F (X, Y)
S ₀ Is obtained by the following equation.
[0096]
S ₀ = X × Y
Reference plane: Z data average value is Z ₀ Then Z = Z ₀ Surface represented by
(Parallel to the XY plane)
Z ₀ Is obtained by the following equation.
[0097]
(Equation 2)

[0098]
Next, the configuration of the photoconductor having such a surface shape will be described.
It is preferable to add fine particles having a number average particle size of 5 to 500 nm to the surface layer of the photoreceptor of the present invention. By adding the fine particles as described above, a surface layer having a surface average surface roughness (Ra) of 1.5 nm or more and 100 nm or less measured on a 5 μm square by using an atomic force microscope can be produced. Such fine particles may be fine particles having a function as a surface energy lowering agent such as polyvinylidene fluoride and polytetrafluoroethylene, but inorganic fine particles having a number average particle diameter of 5 to 500 nm that have been subjected to a hydrophobic treatment (for example, It is preferable that the surface roughness is adjusted by dispersing and containing (described in JP-A-8-248663) in the surface layer of the photoreceptor. As a method for hydrophobizing the inorganic fine particles, a method of treating with a hydrophobizing agent such as a titanium coupling agent, a silane coupling agent, a high molecular fatty acid or a metal salt thereof can be used.
[0099]
As the inorganic fine particles, for example, silica, titanium oxide, alumina, barium titanate, calcium titanate, strontium titanate, zinc oxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride, Fine particles such as chromium oxide and red iron oxide are exemplified.
[0100]
As described above, it is preferable that the inorganic fine particles have been subjected to a hydrophobic treatment. The hydrophobizing treatment can be performed by reacting the inorganic fine particles and the hydrophobizing agent at a high temperature. The hydrophobizing agent is not particularly limited and includes, for example, silane coupling agents such as hexamethyldisilazane, dimethyldichlorosilane, decylsilane, dialkyldihalogenated silane, trialkylhalogenated silane, and alkyltrihalogenated silane, and dimethyl coupling agent. Silicone oil and the like. The amount of the hydrophobizing agent varies depending on the type of the fine particles and the like, and cannot be specified unconditionally. In general, however, as the amount increases, the degree of hydrophobicity increases. It is also effective to remove the hygroscopic substance by, for example, reprecipitation or heat treatment.
[0101]
As the fine particles, organic fine particles such as polymethacrylate, polymethyl methacrylate, polyethylene, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene may be used.
[0102]
The number average particle diameter is a value measured as an average diameter in the Feret direction by observing 100 particles at random as primary particles by magnifying 2000 times by transmission electron microscope observation and analyzing the image.
[0103]
Next, the layer constitution of the photoreceptor preferably used in the present invention will be described.
In the present invention, the photoreceptor is an electrophotographic photoreceptor used for forming an electrophotographic image. In particular, when an organic electrophotographic photoreceptor (organic photoreceptor) is used, the effect of the present invention is remarkably exhibited. 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 a known organic charge generation. It includes all known organic electrophotographic photoreceptors such as a photoreceptor composed of a substance or an organic charge transporting substance, and a photoreceptor having a charge generation function and a charge transporting function composed of a polymer complex.
[0104]
The surface layer of the present invention simply means a layer existing on the surface among various layer constitutions constituting the electrophotographic photosensitive member, and does not show a function. That is, when the electrophotographic photoreceptor has an intermediate layer, a charge generation layer, and a charge transport layer sequentially laminated on a cylindrical substrate, the charge transport layer is a surface layer, and further, a protective layer is laminated. The protective layer becomes the surface layer.
[0105]
Hereinafter, the layer structure of the organic photoreceptor used in the present invention will be described.
Conductive substrate
Conductive support
As the conductive support used for the photoreceptor of the present invention, either a sheet-like or a cylindrical support may be used, but a cylindrical conductive support is more preferable for designing a compact image forming apparatus.
[0106]
The cylindrical conductive support of the present invention means a cylindrical support necessary for forming an image endlessly by rotating, and has a straightness of 0.1 mm or less and a runout of 0.1 mm or less. Conductive supports are preferred. Exceeding the ranges of the roundness and the shake make it difficult to form a good image.
[0107]
As the conductive material, 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. As a conductive substrate, it has a specific resistance of 10 at room temperature. ³ Ωcm or less is preferable.
[0108]
Middle class
In the present invention, an intermediate layer having a barrier function may be provided between the conductive support and the photosensitive layer.
[0109]
In the present invention, in order to improve the adhesion between the conductive support and the photosensitive layer, or to prevent charge injection from the support, an intermediate layer (an undercoat layer is also provided) between the support and the photosensitive layer. ) Can be provided. Examples of the material for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of the repeating units of these resins. Among these undercoating resins, a polyamide resin is preferable as a resin capable of reducing an increase in residual potential due to repeated use. The thickness of the intermediate layer using these resins is preferably 0.01 to 0.5 μm.
[0110]
The intermediate layer preferably used in the present invention includes an intermediate layer using a curable metal resin obtained by thermally curing an organic metal compound such as a silane coupling agent and a titanium coupling agent. The thickness of the intermediate layer using the curable metal resin is preferably 0.1 to 2 μm.
[0111]
The intermediate layer preferably used in the present invention is an intermediate layer in which titanium oxide fine particles (average particle diameter: 0.01 to 1 μm) subjected to a hydrophobic surface treatment are dispersed in a binder such as a polyamide resin. The thickness of the intermediate layer is preferably from 1 to 15 μm.
[0112]
Photosensitive layer
The photosensitive layer structure of the photoreceptor of the present invention may have a single-layer structure in which a charge generation function and a charge transport function are provided in one layer on the intermediate layer. It is preferable to adopt a configuration separated into a generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which functions are separated, an increase in residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoreceptor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the case of a positively charged photoreceptor, the order of the layer configuration is opposite to that in the case of a negatively charged photoreceptor. The most preferable constitution of the photosensitive layer of the present invention is a constitution of a negatively charged photoreceptor having the function separation structure.
[0113]
The configuration of the photosensitive layer of the function-separated negatively charged photoconductor will be described below.
Charge generation layer
The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.
[0114]
As the charge generation material (CGM), a known charge generation material (CGM) can be used. For example, phthalocyanine pigments, azo pigments, perylene pigments, azurenium pigments and the like can be used. Among these, CGM which can minimize the increase in residual potential due to repeated use has a steric and potential structure capable of forming a stable aggregated structure among a plurality of molecules, and specifically, a phthalocyanine having a specific crystal structure And CGM of a perylene pigment. For example, CGMs such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu-Kα radiation, and benzimidazole perylene having a maximum peak at a 2θ of 12.4 have almost no deterioration due to repeated use, and remain intact. The potential increase can be reduced.
[0115]
In the case where a binder is used as a dispersion medium of CGM in the charge generation layer, a known resin can be used as the binder, but the most preferable resin is a formal resin, a butyral resin, a silicone resin, a silicone-modified butyral resin, a phenoxy resin, and the like. No. The ratio between the binder resin and the charge generating substance is preferably from 20 to 600 parts by mass per 100 parts by mass of the binder resin. By using these resins, an increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.
[0116]
Charge transport layer
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses the CTM and forms a film. As other substances, additives such as antioxidants may be contained as necessary.
[0117]
As the charge transport material (CTM), a known charge transport material (CTM) can be used. For example, triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds and the like can be used. These charge transporting substances are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM that can minimize the increase in residual potential due to repeated use has a high mobility and an ionization potential difference from the combined CGM of 0.5 (eV) or less, and is preferably 0. .25 (eV) or less.
[0118]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0119]
Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resins, silicone resins, melamine resins, and copolymer resins containing two or more of the repeating units of these resins. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinyl carbazole may be used. The most preferred binder for these CTLs is a polycarbonate resin. The thickness of the charge transport layer is preferably from 10 to 40 μm.
[0120]
Protective layer
If necessary, various resin layers can be provided as a protective layer of the photoconductor. In particular, by providing a crosslinked resin layer, an organic photoreceptor having high mechanical strength can be obtained.
[0121]
As the toner for forming the toner image of the present invention, for example, when a magnetic substance is contained and used as a one-component magnetic toner, when mixed with a so-called carrier and used as a two-component developer, a non-magnetic toner is used alone. It is possible to use any of them. However, in the present invention, it is preferable to use as a two-component developer to be mixed with a carrier.
[0122]
The image forming method of the present invention is generally applicable to electrophotographic apparatuses such as an electrophotographic copying machine, a laser printer, an LED printer, and a liquid crystal shutter printer, and further includes a display, recording, light printing, plate making and facsimile to which electrophotographic technology is 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. Note that “parts” in the following text represents parts by mass.
[0124]
(1) Production of photoreceptor
Production of photoconductor 1
On a cylindrical aluminum drum (diameter: 60 mmφ, length 362 mm), 20 parts of a titanium chelate compound “TC-750” (manufactured by Matsumoto Pharmaceutical Co., Ltd.) and 13 parts of a silane coupling agent “KBM-503” (manufactured by Shin-Etsu Chemical Co., Ltd.) Was dissolved in 100 parts of a mixed solvent of isopropanol: water = 100: 3, dip-coated, and heated and cured at 150 ° C. for 30 minutes to form an intermediate layer having a dry film thickness of 1.0 μm.
[0125]
On top of this, 6 parts of a titanyl phthalocyanine pigment having a Bragg angle 2θ in X-ray diffraction of 9.5 degrees, 24.1 degrees, and 27.2 degrees as a charge generating substance, and a silicon resin “KR-5240” (manufactured by Shin-Etsu Chemical Co., Ltd.) 7) and a coating liquid in which 200 parts of t-butyl acetate was dispersed using a sand grinder was applied by dip coating to form a charge generation layer having a dry film thickness of 0.3 μm.
[0126]
Next, 200 parts of a charge transporting substance (CT-1), 5 parts of an antioxidant (AO-1), 300 parts of bisphenol Z-type polycarbonate “PANLITE TS-2050” (manufactured by Teijin Chemicals Ltd.), and hydrophobically treated silica ( A coating solution dissolved in 50 parts of (number average particle diameter 7 nm) and 2,000 parts of 1,2-dichloroethane was applied on the charge generation layer with a circular slide hopper to form a charge transport layer having a dry film thickness of 24 μm. A body 1 was produced. The average surface roughness (Ra) of the photoreceptor 1 was 2.15 nm.
[0127]
Embedded image

[0128]
Production of photoconductor 2
Photoreceptor 2 was prepared in the same manner as photoreceptor 1 except that hydrophobized silica (number average particle diameter 15 nm) was used in place of hydrophobized silica (number average particle diameter 45 nm). did. The average surface roughness (Ra) of the photoreceptor 2 was 35.6 nm.
[0129]
Production of photoconductor 3
In the production of the photoreceptor 1, the photoreceptor 3 was prepared in the same manner as the photoreceptor 1, except that the hydrophobized silica (number average particle diameter 15 nm) was used instead of the hydrophobized titanium oxide (number average particle diameter 35 nm). Produced. The average surface roughness (Ra) of the photoreceptor 3 was 24.2 nm.
[0130]
Production of photoconductor 4
Photoreceptor 4 was prepared in the same manner as photoreceptor 1 except that hydrophobized silica (number average particle diameter 15 nm) was used and hydrophobized zirconia (number average particle diameter 62 nm) was used. The average surface roughness (Ra) of the photoreceptor 4 was 48.4 nm.
[0131]
Production of photoconductor 5
Photoreceptor 5 was prepared in the same manner as photoreceptor 1 except that hydrophobized silica (number average particle diameter 15 nm) was used for hydrophobized alumina (number average particle diameter 100 nm). The average surface roughness (Ra) of the photoreceptor 5 was 72.5 nm.
[0132]
Production of photoconductor 6
Photoreceptor 6 was prepared in the same manner as photoreceptor 1 except that hydrophobized silica (number average particle diameter 15 nm) was used as fine powder sintered silica (number average particle diameter 0.13 μm). Produced. The average surface roughness (Ra) of the photoreceptor 6 was 96.6 nm.
[0133]
Production of photoconductor 7
Photoreceptor 7 was fabricated in the same manner as photoreceptor 1 except that hydrophobized silica (number average particle size 15 nm) was used as fine powder sintered silica (number average particle size 0.25 μm). Produced. The average surface roughness (Ra) of the photoreceptor 7 was 112 nm.
[0134]
Production of photoconductor 8
Photoreceptor 8 was prepared in the same manner as photoreceptor 1, except that hydrophobic treated silica (number average particle diameter 15 nm) was omitted. The average surface roughness (Ra) of the photoreceptor 8 was 1.2 nm.
[0135]
The number average particle diameter of the colloidal silica and the like used for producing the photoconductors 1 to 8 was magnified 10000 times by transmission electron microscope observation, 100 particles were randomly observed as primary particles, and ferrite was analyzed by image analysis. It is a measured value as an average diameter in the direction.
[0136]
Preparation of Surface Energy Lowering Agents AF
Sodium stearate was dissolved in water to prepare a 15% by mass liquid. In addition, zinc sulfate was dissolved in water to prepare a 25% by mass liquid. A 2 liter receiving vessel with a stirring device having a turbine blade with a diameter of 6 cm was prepared, and the turbine blade was rotated at 350 rpm. A sodium stearate solution was charged into the receiving container, and the solution temperature was adjusted to 80 ° C. Next, a zinc sulfate solution at 80 ° C. was dropped into the receiving container over 30 minutes. The equivalent ratio of sodium stearate to zinc sulfate was set to 0.98, and the mixture was mixed so that the amount of the metal soap slurry became 500 g. After the completion of the preparation, the mixture was aged for 10 minutes at the temperature at the time of the reaction to terminate the reaction. Next, the metal soap slurry thus obtained was washed twice with water, and subsequently washed with water. The obtained metal soap cake was dried at a drying temperature of 110 ° C and solidified at a pressure of 15 MPa. Thereafter, the mixture was allowed to stand for 24 hours under an environment condition of 30 ° C. and 80% RH to obtain solid materials of zinc stearate (surface energy lowering agents A to F) having different moisture contents shown in Table 1. The water content of these A to F was prepared by changing the drying time at 110 ° C.
[0137]
[Table 1]

[0138]
<Evaluation>
The cleaning unit shown in FIG. 5 is mounted as a cleaning unit for the photoreceptor of the digital color printer having the intermediate transfer body of FIG. 1, and the digital color printer is provided with a combination of the photoreceptor and the surface energy reducing agent and the Rz of the intermediate transfer body. The cleaning brushes were combined as shown in Table 2, and 100,000 sheets of A4 paper were continuously printed at 8% pixel rate under high temperature and high humidity (30 ° C., 80% RH) for evaluation. The evaluation items are evaluation of hollowness, character dust, halftone unevenness, cleaning property evaluation, image sharpness evaluation, and the like. The evaluation items and evaluation criteria are shown below. Table 2 shows the evaluation results.
[0139]
Evaluation items and evaluation criteria
Measurement of contact angle and contact angle variation of photoreceptor
After the print evaluation of 2,000 A4 papers, the contact angle of the photoreceptor surface to pure water was measured at 30 ° C. 80% using a contact angle meter (CA-DT · A type: manufactured by Kyowa Interface Science Co., Ltd.) by the method described in the text. It was measured in an environment of RH.
[0140]
"Omission"
The characters were observed under magnification, and the presence or absence of voids was visually observed.
[0141]
：: No noticeable hollowing occurred until printing of 100,000 sheets
：: No noticeable hollowing occurred until 50,000 prints were completed
×: Prints of less than 50,000 prints have noticeable hollow holes
"Evaluation of character chile"
Instead of a dot image constituting a character, a 10% halftone image was formed on the entire image, and toner scattering around the dots was observed with a loupe.
[0142]
Rank A: toner scattering is small until printing of 100,000 sheets is completed.
Rank ：: toner scattering is small until printing of 50,000 sheets is completed.
[0143]
Rank x: Toner scattering is increased in prints of less than 50,000 sheets. (Practical question
Title level)
Halftone unevenness: After completion of 100,000 copies, judgment is made based on the density difference (ΔHD = maximum density−minimum density) of the halftone image (uniform image having a density of around 0.2).
Using a Macbeth reflection densitometer “RD-918”, the density of unprinted copy paper (blank paper) is measured at 20 locations in absolute image density, and the average value is defined as the blank paper density. Next, the above halftone image portion was similarly measured in absolute image density at 20 places, and the maximum density-minimum density was evaluated as ΔHD.
[0144]
◎: 0.05 or less (good)
：: Greater than 0.05 and less than 0.1 (no problem in practical use)
×: 0.1 or more (problematic in practical use)
Evaluation of cleaning performance
The presence or absence of toner slippage due to abrasion of the photoreceptor and the cleaning blade, and the occurrence of blade turning (blade inversion phenomenon) were evaluated.
[0145]
：: No toner slippage and blade curling occurred until 100,000 sheets were printed
：: No toner slippage and blade curling occurred until 50,000 sheets were printed
X: Toner slip-through or blade curling occurred with less than 50,000 prints
Image sharpness
The reproducibility of the fine line and the sharpness of the image were evaluated in a high-temperature and normal-humidity environment (temperature: 33 ° C., relative humidity: 50%) by character collapse. Three-point and five-point character images were formed and evaluated according to the following criteria.
[0146]
：: 3 points and 5 points are clear and easily legible
：: 3 points are partially unreadable, 5 points are clear and easily readable
×: 3 points almost illegible, 5 points partially or completely illegible
Other evaluation conditions
Line speed L / S for image formation: 180 mm / s
Charging condition of photoconductor (60 mmφ): The potential of the non-image area is detected by a potential sensor, and feedback control is performed. The controllable range is −500 V to −900 V, and the surface of the photoconductor when fully exposed The potential was in the range of -50 to 0V.
[0147]
Exposure conditions: For image exposure, a semiconductor laser (wavelength: 780 nm) was used to form a 800 dpi digital latent image.
[0148]
Developing conditions: The developer is a two-component developer of toner and carrier (toner concentration: 5% by mass) having a number average particle diameter of 7.5 μm for all of Y, M, C, and K, and the developing device is also a two-component developer. It is a method corresponding to.
[0149]
Intermediate transfer member: A seamless endless belt-shaped intermediate transfer member 70 is used, and a semiconductive resin belt having a volume resistivity of 1 × 10 ⁸ Ω · cm was used. Three types having Rz of 0.9 μm, 1.5 μm, and 2.2 μm were used.
[0150]
Primary transfer conditions
Primary transfer roller (5Y, 5M, 5C, 5K (6.05 mmφ each) in FIG. 1): A structure in which a cored bar is provided with elastic rubber: Surface specific resistance 1 × 10 ⁶ Ω, transfer voltage applied
Secondary transfer conditions
An endless belt-shaped intermediate transfer member 70 as an intermediate transfer member, and a backup roller 74 and a secondary transfer roller 5A are disposed so as to sandwich the intermediate transfer member 70, and the resistance value of the backup roller 74 is 1 × 10 ⁶ Ω, and the resistance value of the secondary transfer roller as the secondary transfer means is 1 × 10 ⁶ Ω so that constant current control (about 80 μA) is performed.
[0151]
The fixing is a heat fixing method using a fixing roller in which a heater is arranged inside the roller.
The distance Y on the intermediate transfer member from the first contact point between the intermediate transfer member and the photosensitive member to the first contact point with the next color photosensitive member was 95 mm.
[0152]
The outer peripheral length (circumferential length) of the driving roller 71, the guide rollers 72 and 73, and the backup roller 74 for the secondary transfer is set to 31.67 mm (= 95 mm / 3), and the outer peripheral length of the tension roller 76 is set to 23. 0.75 mm (= 95 mm / 4).
[0153]
Then, the outer peripheral length of the primary transfer roller was set to 19 mm (= 95 mm / 5).
Cleaning blade (photoreceptor): urethane rubber blade
Cleaning brush: conductive acrylic resin, brush bristle density (3 × 10 ³ / Cm ² ), And three types with a bite amount of 0.6, 1.0, and 1.3 mm.
[0154]
Secondary transfer roller (5A in FIG. 1): Configuration in which elastic rubber is attached to a core metal: Transfer voltage application
Cleaning blade (intermediate transfer member): Urethane rubber blade
[0155]
[Table 2]

[0156]
As is clear from Table 2, the combinations 1 to 5 and 7 to 11 in the present invention in which the surface energy reducing agent was applied to reduce the variation in the contact angle of the electrophotographic photoreceptor to ± 5 ° or less. For combinations 6 and 12 in which the variation of the outside contact angle is larger than ± 5 °, the improvement of the hollowness, character dust, sharpness, etc. is remarkable, and the halftone unevenness is improved compared to the combination 13. Remarkable. In addition, almost all the evaluation items are improved as compared with the combination 14 to which the surface energy reducing agent is not added.
[0157]
【The invention's effect】
By using the present invention, it is possible to improve the transfer characteristics of an electrophotographic toner using an intermediate transfer member, prevent image defects such as voids and character dust caused by a decrease in toner transferability, and perform cleaning. It is possible to provide an image forming method of an electrophotographic system having good properties.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an example of a cleaning unit for an intermediate transfer member.
FIG. 3 is a layout diagram illustrating a positional relationship among a photoconductor, an endless belt-shaped intermediate transfer body, and a primary transfer roller.
FIG. 4 is a layout diagram illustrating a positional relationship among a backup roller, an endless belt-shaped intermediate transfer member, and a secondary transfer roller.
FIG. 5 is a configuration diagram of a cleaning unit installed on the photoconductor of the present invention.
[Explanation of symbols]
1Y, 1M, 1C, 1K photoreceptor
2Y, 2M, 2C, 2K Charging means
3Y, 3M, 3C, 3K exposure means
4Y, 4M, 4C, 4K developing means
5A secondary transfer roller (secondary transfer means)
5Y, 5M, 5C, 5K primary transfer roller (primary transfer means)
6A, 6Y, 6M, 6C, 6K Cleaning means
7 Endless belt-shaped intermediate transfer unit
10Y, 10M, 10C, 10K Image forming unit
61 blade
62 bracket
63 spindle
70 Endless belt-shaped intermediate transfer body

Claims (11)

An image forming method comprising: transferring a latent image formed on an electrophotographic photosensitive member to a toner image by development and transferring the toner image to a recording material or an intermediate transfer member; An image forming method, comprising applying an energy-lowering agent and performing the development and transfer while making the contact angle variation of the electrophotographic photosensitive member ± 5 ° of the average value. A primary transfer means for developing the latent image formed on the electrophotographic photosensitive member into a toner image and transferring the toner image to an intermediate transfer member; and a secondary transfer means for transferring the toner image transferred to the intermediate transfer member to a recording material. An image forming method including a secondary transfer means, wherein a surface energy reducing agent is applied to the surface of the electrophotographic photoreceptor, and the variation of the contact angle of the electrophotographic photoreceptor is adjusted to ± 5 ° of an average value while the development is performed. And an image forming method. The image forming method according to claim 1, wherein the contact angle is 90 to 120 °. The average surface roughness (Ra) of 5 μm square measured on the surface of the electrophotographic photoreceptor using an atomic force microscope is 1.5 nm or more and 100 nm or less. Item 2. The image forming method according to Item 1. The image forming method according to claim 1, wherein the surface energy reducing agent is applied by an agent applying unit. The image forming method according to any one of claims 1 to 5, wherein the water content of the surface energy lowering agent is 5.0% by mass or less. The image forming method according to any one of claims 1 to 6, wherein the surface energy reducing agent is a metal salt of a fatty acid. The image forming method according to claim 7, wherein the fatty acid metal salt is zinc stearate. The image forming method according to claim 1, wherein the surface layer of the electrophotographic photosensitive member contains fine particles having a number average particle size of 5 nm to 500 nm. An image forming apparatus that forms an electrophotographic image by using the image forming method according to claim 1. The latent image formed on the electrophotographic photoreceptor is developed by applying a surface energy reducing agent to the surface of the electrophotographic photoreceptor and developing the latent image on the electrophotographic photoreceptor while maintaining the contact angle variation of the electrophotographic photoreceptor at an average value of ± 5 °. In an electrophotographic photosensitive member used in an image forming method provided with a transfer means for transferring the toner image to a recording material or an intermediate transfer member as an image, an average surface roughness of 5 μm square measured on the surface using an atomic force microscope. An electrophotographic photoreceptor having a thickness (Ra) of 1.5 nm or more and 100 nm or less.

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