JP3975835B2 - Electrophotographic photoreceptor, image forming method, image forming apparatus, and process cartridge - Google Patents

Description

【００２８】
（式中、Ａは単結合、炭素数１〜１０の直鎖、分岐鎖あるいは環状のアルキリデン基、アリール置換アルキリデン基、アリーレンジアルキリデン基、又は−Ｏ−，−Ｓ−，−ＣＯ−，−ＳＯ−および−ＳＯ₂−を示し、Ｒ₁、Ｒ₂、Ｒ₃及びＲ₄は水素、ハロゲン又は炭素数１〜４のアルキル基、アルケニル基を示す。）
分散安定剤の濃度は分散媒質量１００質量部に対し０．１〜２００質量部が好ましい。
【００２９】
０．１質量部未満だと粒子状重合体の分散が安定せず、又２００質量部より多いと分散安定剤同士が分散媒中で凝集しやすく、均一な粒子状重合体の生成を妨げやすい。
【００３０】
本発明の分散重合に用いられる重合性モノマーとしてはラジカル重合を進行させる重合性モノマーを用いることができる。即ち、本発明に用いられるラジカル重合性モノマーとしてはビニル系モノマーが好ましい。例えばアクリレイト，メタクリレイト，スチレン，フッ素置換されたアクリレイト，同メタクリレイト，同スチレン，ジビニルベンゼンなどのビニル系モノマーが好ましく用いられる。
【００３１】
本発明の分散重合に用いられる分散媒（溶媒）としては前記分散安定剤、重合性モノマーを溶解する溶媒が用いられる。これらの溶媒は一般に有機溶媒が用いられるが、必要により、有機溶媒同士の混合溶媒、或いは水と有機溶媒の混合溶媒を用いることも可能である。
【００３２】
本発明の分散重合に使われる有機溶媒としては、メチクロリド、エチクロリド、クロロホルム、モノクロルベンゼン、ジクロルベンゼン、テトラヒドロフラン、ジオキソラン、ジオキサン、ベンゼン、トルエン、キシレン、メシチレン、アルコール類、エステル類、ヘキサン、ヘプタン、リグロイン、ケロシン、テトラリン、ケトン類、エーテル類、ジメチルホルムアミド、アセトニトリルなどが好ましく使われる。
【００３３】
本発明の分散重合に用いられる重合開始剤としては以下のような化合物が用いられる。即ち、ＡＩＢＮ（Ａｚｏｂｉｓ−（２，４−ｄｉｍｅｔｈｙｌｖａｌｅｒｏｎｉｔｒｉｌｅ））、ＡＤＶＮ（Ａｚｏｂｉｓｉｓｏｂｕｔｙｒｏｎｉｔｒｉｌｅ）、ＡＣＰＡ（Ａｚｏｂｉｓ−（４−ｃｙａｎｏｐｅｎｔａｎｏｉｃ ａｃｉｄ））、ＡＭＢＮ（Ａｚｏｂｉｓ−（２−ｍｅｔｈｙｌｂｕｔｙｒｏｎｉｔｒｉｌｅ））、ＢＰＯ（Ｂｅｎｚｏｙｌ ｐｅｒｏｘｉｄｅ）などが好ましく用いられる。
【００３４】
本発明の分散重合には分散安定助剤（粒子状重合体を安定に分散させるための助剤）を用いることもできる。分散安定助剤としては、例えばノニオン系界面活性剤等が用いられる。
【００３５】
分散重合の重合操作
後述する合成例で具体的に示すが、分散重合は分散媒（有機溶媒）中に、分散安定剤（バインダー樹脂）、重合性モノマー、重合開始剤、必要なら分散安定助剤を均一に溶解し、又、必要によりその他の物質の存在下、（或いは必要に応じて、途中で添加しても良い）加熱などにより重合を行い、重合性モノマーの重合に伴い、均一系からの析出により、粒子状の重合体が析出し、更に該粒子状の重合体が成長して、均一な粒度分布の粒子状重合体を得ることができる。分散重合に用いられるそれぞれの成分（分散媒、分散安定剤、重合性モノマー等）はそれぞれ単一のものを用いてもよいが、２種以上のものを併用して、粒子径を制御したり、共重合体を生成させることも出来る。又、重合開始剤を２種併用して、粒度分布の広い、或いは２山ピークの粒度分布を有する粒子状重合体を生成させてもよい。
【００３６】
上記分散重合の重合系で用いられる成分の量は以下のような質量比で用いられるのが好ましい。
【００３７】
材料成分の好ましい質量比
分散安定剤：有機溶媒１００質量部に対し０．１質量部〜２００質量部
重合性モノマー：バインダー樹脂１００質量部に対し１質量部〜２００質量部
重合開始剤：モノマー１００質量部に対し０．０１質量部〜５０質量部
分散安定助剤：モノマー１００質量部に対し０．００１質量部〜１０質量部
上記のような質量比で用いることにより、分散重合を安定に進行させることが出来る。又、上記において、重合性モノマー、重合開始剤等は段階的或いは連続して重合系に添加する方法も適宜用いることができる。
【００３８】
本発明の有機微粒子の個数平均粒径は１０〜５０００ｎｍが好ましい。更に、２０〜５００ｎｍが好ましい。１０ｎｍ未満だと、クリーニング性やトナーの転写率の改良効果が少なく、５０００ｎｍより大きいと残留電位が上昇しやすく、画像濃度の低下やカブリが発生しやすい。尚、個数平均粒径は透過型電子顕微鏡観察によって有機微粒子を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算出した測定値である。
【００３９】
又、本発明では分散重合法により得られた有機微粒子溶液をそのまま塗布液として用い、該塗布液を塗布、乾燥して電子写真感光体の表面層を形成してもよいし、又、上記有機微粒子溶液に電荷輸送物質、酸化防止剤、塗布助剤等の添加剤を加えて調製し、表面層用塗布液を作製して、塗布乾燥し、電子写真感光体の表面層を形成してもよい。
【００４０】
次に、本発明の分散重合法等で得られた有機微粒子を含有する電子写真感光体の構成について記載する。
【００４１】
本発明の有機微粒子は有機感光体の表面層を形成する電荷輸送層、或いは保護層等に含有させることが好ましい。以下、本発明の重合体を表面層に用いた有機感光体を中心に説明する。
【００４２】
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いずれか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。
【００４３】
有機感光体の層構成は、特に限定はないが、電荷発生層、電荷輸送層、或いは電荷発生・電荷輸送層（電荷発生と電荷輸送の機能を同一層に有する層）等の感光層と、その上に必要によって保護層を塗設した構成をとるのが好ましい。
【００４４】
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。
【００４５】
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するのに必要な円筒状の支持体を意味し、真円度で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。
【００４６】
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。導電性支持体としては常温で比抵抗１０³Ω・ｃｍ以下が好ましい。
【００４７】
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。
【００４８】
中間層（下引き層）
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。
【００４９】
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。
【００５０】
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。
【００５１】
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。
【００５２】
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。
【００５３】
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。
【００５４】
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。
【００５５】
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。
【００５６】
電荷輸送層
電荷輸送層が有機感光体の表面層となる場合は、電荷輸送層に本発明の有機微粒子を含有させることが好ましい。
【００５７】
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。該バインダー樹脂として、ポリカーボネート等の樹脂を用い、その他の物質として、酸化防止剤等の添加剤を必要により含有させてることが好ましい。
【００５８】
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。
【００５９】
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。
【００６０】
電荷輸送層が表面層とならない場合は、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とうが挙げられる。又、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。特にポリカーボネート樹脂が電子写真特性（帯電性、感度等）を良好に保つ上で好ましい。
【００６１】
表面層（保護層）
前記した分散重合法により得られた有機微粒子溶液をそのまま表面層用塗布液として用い、該塗布液を塗布、乾燥して電子写真感光体の表面層を形成してもよいし、又上記有機微粒子溶液に電荷輸送物質、酸化防止剤、塗布助剤等の添加剤を加えて調製し、表面層用塗布液を作製して、塗布乾燥し、電子写真感光体の表面層を形成してもよい。電子写真特性（帯電性、感度等）を良好に維持する為には、表面層にも電荷輸送層、酸化防止剤等を存在させる方がより好ましい。
【００６２】
又、表面層には酸化防止剤を含有させることが好ましい。該酸化防止剤とは、その代表的なものは有機感光体中ないしは有機感光体表面に存在する自動酸化性物質に対して、光、熱、放電等の条件下で酸素の作用を防止ないし、抑制する性質を有する物質である。代表的には下記の化合物群が挙げられる。
【００６３】
【化２】

【００６４】
【化３】

【００６５】
【化４】

【００６６】
【化５】

【００６７】
中間層、感光層、保護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。
【００６８】
次に本発明の電子写真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。なお本発明の樹脂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。
【００６９】
次に、本発明の画像形成装置について説明する。
図２は本発明の画像形成方法の１例としての画像形成装置の断面図である。
【００７０】
図２に於いて５０は像担持体である感光体ドラム（感光体）で、有機感光層をドラム上に塗布し、その上に本発明の樹脂層を塗設した感光体で、接地されて時計方向に駆動回転される。５２はスコロトロンの帯電器（帯電手段）で、感光体ドラム５０周面に対し一様な帯電をコロナ放電によって与えられる。この帯電器５２による帯電に先だって、前画像形成での感光体の履歴をなくすために発光ダイオード等を用いた帯電前露光部５１による露光を行って感光体周面の除電をしてもよい。
【００７１】
感光体への一様帯電の後、像露光手段としての像露光器５３により画像信号に基づいた像露光が行われる。この図の像露光器５３は図示しないレーザーダイオードを露光光源とする。回転するポリゴンミラー５３１、ｆθレンズ等を経て反射ミラー５３２により光路を曲げられた光により感光体ドラム上の走査がなされ、静電潜像が形成される。
【００７２】
ここで本発明の反転現像プロセスとは帯電器５２により、感光体表面を一様に帯電し、像露光が行われた領域、即ち感光体の露光部電位（露光部領域）を現像工程（手段）により、顕像化する画像形成方法である。一方未露光部電位は現像スリーブ５４１に印加される現像バイアス電位により現像されない。
【００７３】
その静電潜像は次いで現像手段としての現像器５４で現像される。感光体ドラム５０周縁にはトナーとキャリアとから成る現像剤を内蔵した現像器５４が設けられていて、マグネットを内蔵し現像剤を保持して回転する現像スリーブ５４１によって現像が行われる。現像器５４内部は現像剤攪拌搬送部材５４４、５４３、搬送量規制部材５４２等から構成されており、現像剤は攪拌、搬送されて現像スリーブに供給されるが、その供給量は該搬送量規制部材５４２により制御される。該現像剤の搬送量は適用される有機電子写真感光体の線速及び現像剤比重によっても異なるが、一般的には２０〜２００ｍｇ／ｃｍ²の範囲である。
【００７４】
現像剤は、例えば前述のフェライトをコアとしてそのまわりに絶縁性樹脂をコーティングしたキャリアと、前述のスチレンアクリル系樹脂を主材料としてカーボンブラック等の着色剤と荷電制御剤と本発明の低分子量ポリオレフィンからなる着色粒子に、シリカ、酸化チタン等を外添したトナーとからなるもので、現像剤は搬送量規制部材によって層厚を規制されて現像域へと搬送され、現像が行われる。この時通常は感光体ドラム５０と現像スリーブ５４１の間に直流バイアス、必要に応じて交流バイアス電圧をかけて現像が行われる。また、現像剤は感光体に対して接触あるいは非接触の状態で現像される。感光体の電位測定は電位センサー５４７を図２のように現像位置上部に設けて行う。
【００７５】
記録紙Ｐは画像形成後、転写のタイミングの整った時点で給紙ローラー５７の回転作動により転写域へと給紙される。
【００７６】
転写域においては転写のタイミングに同期して感光体ドラム５０の周面に転写電極（転写手段：転写器）５８が作動し、給紙された記録紙Ｐにトナーと反対極性の帯電を与えてトナーを転写する。
【００７７】
次いで記録紙Ｐは分離電極（分離器）５９によって除電がなされ、感光体ドラム５０の周面により分離して定着装置６０に搬送され、熱ローラー６０１と圧着ローラー６０２の加熱、加圧によってトナーを溶着したのち排紙ローラー６１を介して装置外部に排出される。なお前記の転写電極５８及び分離電極５９は記録紙Ｐの通過後、一次作動を中止し、次なるトナー像の形成に備える。図２では転写電極５８にコロトロンの転写帯電極を用いている。転写電極の設定条件としては、感光体のプロセススピード（周速）等により異なり一概に規定することはできないが、例えば、転写電流としては＋１００〜＋４００μＡ、転写電圧としては＋５００〜＋２０００Ｖを設定値とすることができる。
【００７８】
一方記録紙Ｐを分離した後の感光体ドラム５０は、クリーニング器（クリーニング手段）６２のブレード６２１の圧接により残留トナーを除去・清掃し、再び帯電前露光部５１による除電と帯電器５２による帯電を受けて次なる画像形成のプロセスに入る。
【００７９】
尚、７０は感光体、帯電器、転写器、分離器及びクリーニング器が一体化されている着脱可能なプロセスカートリッジである。
【００８０】
本発明の有機電子写真感光体は電子写真複写機、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。
【００８１】
【実施例】
以下実施例をあげて詳細な説明を行うが、本発明はこれらに限定されるものではない。尚、下記文中「部」とは「質量部」を表す。
【００８２】

上記組成を窒素雰囲気下、約６５℃で１０時間攪拌し重合した。重合の結果得られた分散重合体（有機微粒子：個数平均粒径５０ｎｍ）の固形分濃度を１，３ジオキソランで８％に調整した後、下記の電荷輸送物質等を添加し表面層用塗布液１とした。
【００８３】
［４−（２，２−ジフェニルビニル）フェニル］−ジ−ｐ−トリルアミン
９．０部
２，６−ジ−ｔ−ブチル−４−フェニルフェノール ０．１８部
（合成例２）
ポリカーボネート「ユーピロンＺ２００」（三菱瓦斯化学社製）
１０．０部
１Ｈ，１Ｈ，１１Ｈ−エイコサフロロウンデシルアクリレイト ３．０部
アゾビス−（２−メチルブチロニトリル） ０．１５部
トルエン ９０．０部
上記組成を窒素雰囲気下、約７０℃で１０時間攪拌し重合した。重合の結果得られた分散重合体（有機微粒子：個数平均粒径３０ｎｍ）の固形分濃度をトルエンで７％に調整した後、下記の電荷輸送物質等を添加し表面層用塗布液２とした。
【００８４】

上記組成を窒素雰囲気下、約７０℃で１０時間攪拌し重合した。重合の結果得られた分散重合体（有機微粒子：個数平均粒径１２０ｎｍ）の固形分濃度を１，２ジクロロエタンで６．５％に調整した後、下記の電荷輸送物質等を添加し表面層用塗布液３とした。
【００８５】
［４−（２，２−ジフェニルビニル）フェニル］−ジ−トリルアミン
６．７部
２，６−ジ−ｔ−ブチル−４−フェニルフェノール ０．１３４部
（合成例４）
ポリカーボネート「ＴＳ２０５０」（帝人化成（株）製） ５．０部
ポリカーボネート「ユーピロンＺ２００」（三菱瓦斯化学社製）５．０部
１Ｈ，１Ｈ，７Ｈ−ドデカフロロヘプチルアクリレート ５．０部
ジビニルベンゼン ０．１部
アゾビス−（２−メチルブチロニトリル） ０．１部
１，３ジオキソラン ８０．０部
上記組成を窒素雰囲気下、約７０℃で１０時間攪拌し重合した。重合の結果得られた分散重合体（有機微粒子：個数平均粒径９０ｎｍ）の固形分濃度を１，２ジクロロエタンで６％に調整した後、下記の物質を添加し表面層用塗布液４とした。
【００８６】

上記組成を窒素雰囲気下、約７５℃で１０時間攪拌し重合した。重合の結果得られた分散重合体（有機微粒子：個数平均粒径７０ｎｍ）の固形分濃度を１，２ジクロロエタンで５％に調整した後、下記の物質を添加し表面層用塗布液５とした。
【００８７】

【００８８】
【化６】

【００８９】
感光体１の作製
下記のようにして感光体１を作製した。
【００９０】
直径８０ｍｍの円筒形アルミニウム製導電性基体上に、下記の中間層塗布液を浸漬塗布して、乾燥膜厚４．０μｍの中間層を形成した。
【００９１】
〈中間層塗布液〉
ポリアミド樹脂「ＣＭ８０００」（東レ社製） １０．０部
酸化チタン「ＳＭＴ５００ＳＡＳ」（テイカ社製） ３０．０部
メタノール １００．０部
上記を循環式湿式分散機（ディスパーマットＳＬＣ１２ＥＸ；ＶＭＡ ＧＥＴＺＭＡＮＮ社製）を用いて分散した。
【００９２】
前記中間層上に下記の電荷発生層塗布液を、浸漬塗布して、乾燥膜厚０．３μｍの電荷発生層を形成した。
【００９３】

上記を混合しサンドグラインダーにて分散した。
【００９４】
前記電荷発生層上に、下記の電荷輸送層塗布液、次いで前記の表面層用塗布液１を円形スライドホッパーにて連続塗布して、１１０℃；６０分加熱硬化し、乾燥膜厚２０μｍの電荷輸送層及び乾燥膜厚５．０μｍの表面層を形成した。
【００９５】

感光体２〜５の作製
感光体１の作製において、表面層用塗布液１の代わりに表面層用塗布液２〜５を用いた他は同様にして感光体２〜５を作製した。
【００９６】
感光体６の作製（比較感光体）
表面層用塗布液１の代わりに下記組成の表面層用塗布液６を用いた以外は感光体１と同様にして感光体６を作製した。
【００９７】

感光体７の作製（比較感光体）
表面層用塗布液１の代わりに下記組成の表面層用塗布液７を用いた以外は感光体１と同様にして感光体７を作製した。
【００９８】
表面層用塗布液７の作製（特開平８−３２８２８７号実施例１）
まず、フッ素系樹脂粒子分散液を調製するために、２５０℃で加熱処理を行った４−フッ化エチレン樹脂２００質量部、ポリカーボネート樹脂２００質量部、モノクロルベンゼン６００質量部、フッ素系クシ型グラフトポリマー（商品名ＧＦ３００、東亜合成化学（株）製）８質量部を充分に混合した後ガラスビ−ズを用いたサンドグラインダー（（株）アメックス製）にて分散し、４−フッ化エチレン樹脂粒子分散液（個数平均粒径：３１０ｎｍ）を調製した。
【００９９】
次に［４−（２，２−ジフェニルビニル）フェニル］−ジ−ｐ−トリルアミン１２００質量部、ポリカーボネート樹脂８００質量部、上記４−フッ化エチレン樹脂粒子分散液１５００質量部をモノクロルベンゼン５０００質量部、ジクロロメタン３０００質量部に溶解混合し、表面層用塗布液７を調製した。この表面層用塗布液７を表面層用塗布液１の代わりに用いた以外は感光体１と同様にして感光体７を作製した。
【０１００】
評価
表面層の有機微粒子の凝集率：Ｎの評価
厚さ０．３±０．１μｍの感光体表面層の切片を作製し、該切片断面の２万倍拡大写真（透過型電子顕微鏡写真）を撮影し、該拡大写真の任意の場所５カ所を選定し、各場所の５×５ｃｍ²の画像面積内の有機粒子とその凝集粒子を数えて凝集率を計算した。
【０１０１】
複写機を用いた評価
評価機としてコニカ社製デジタル複写機Ｋｏｎｉｃａ「Ｓｉｔｉｏｓ７０７５」（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し、プリント速度７５枚／ｍｉｎ）を用い、該複写機に感光体１〜７を搭載し評価した。クリーニング性及び画像評価は、画素率が７％の文字画像、人物顔写真、ベタ白画像、ベタ黒画像がそれぞれ１／４等分にあるオリジナル画像をＡ４中性紙にコピーして行った。コピー条件は最も厳しいと思われる高温高湿環境（３０℃、８０％ＲＨ）にて連続２０万枚コピー行いハーフトーン、ベタ白画像、ベタ黒画像を評価した。但し、コピー開始前に、感光体表面にセッティングパウダーをまぶし、感光体とクリーニングブレードをなじませた後２０万枚のコピーを行った。評価項目及び評価基準を下記に示す。
【０１０２】
評価項目及び評価基準
画像濃度（マクベス社製ＲＤ−９１８を使用して測定。紙の反射濃度を「０」とした相対反射濃度で測定した。初期と２０万枚コピー後の両方で評価）
◎：初期と２０万枚コピー後の両方共１．２以上：良好
○：初期と２０万枚コピー後の両方共１．０以上：実用上問題ないレベル
×：初期と２０万枚コピー後の少なくとも一方が１．０未満：実用上問題となるレベル
カブリ：ベタ白画像濃度で判定
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。
【０１０３】
◎：初期と２０万枚コピー後の両方共０．００５以下（良好）
○：初期と２０万枚コピー後の両方共０．０１以下（実用上問題ないレベル）
×：初期と２０万枚コピー後の少なくとも一方が０．０１より大（明らかに、実用上問題あり）
鮮鋭性
細線の再現性、画像の先鋭性を２０万枚コピー終了後、文字画像を出し、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。
【０１０４】
◎：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ポイントは判読可能
×：３ポイントは殆ど判読不能、５ポイントも一部あるいは全部が判読不能
トナー転写率
下記式により転写率（％）を求めた。但し、転写率を求める際には、クリーニングユニットから回収されたトナーは現像器に戻さず、袋に取った。
【０１０５】
転写率（％）＝｛１−（回収トナーの質量／消費トナーの質量）｝×１００
クリーニング性（１０万及び２０万枚コピー終了後にＡ３紙に連続１０枚コピーを行い、ベタ白部でのクリーニング不良の発生の有無で判定）
◎：２０万枚までトナーのすり抜け発生なし
○：１０万枚までトナーのすり抜け発生なし
×：１０万枚未満でトナーのすり抜け発生
画像ボケ
◎：２０万枚まで発生なし
○：１５万枚まで発生なし
×：１０万枚以下で発生
クリーニングブレードの起動トルク測定
初期（ｓ）及び２０万枚コピー後（ｅ）に、ドラムカートリッジを用い、複写機本体のドラム軸に連結したトルクゲージ（ＭＯＤＥＬ ６ＢＴＧ：ＴＯＨＮＩＣＨＩ社製）を回転させて起動トルクを測定した。測定は５回行い、平均値を採用した。
【０１０６】
表面接触角測定
感光体の表面接触角は純水に対する接触角を接触角計（ＣＡ−ＤＴ・Ａ型：協和界面科学社製）を用いて測定した。接触角が小さいと感光体表面の劣化が進行したり、トナーや紙粉等の付着が発生しやすく、９０〜１２０°がよい。
【０１０７】
感光体膜厚減耗量
減耗量は実写評価開始時と２０万枚コピー終了時に測定した感光体の平均膜厚の差分を求め、膜厚減耗量とした。
【０１０８】
膜厚測定法
感光層の膜厚は均一膜厚部分をランダムに１０ケ所測定し、その平均値を感光層の膜厚とする。膜厚測定器は渦電流方式の膜厚測定器ＥＤＤＹ５６０Ｃ（ＨＥＬＭＵＴ ＦＩＳＣＨＥＲ ＧＭＢＴＥ ＣＯ社製）を用いて行い、実写試験前後の感光層膜厚の差を膜厚減耗量とする。
【０１０９】
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。
【０１１０】
帯電条件
帯電器；スコロトロン帯電器、初期帯電電位を−７５０Ｖ
露光条件
露光部電位を−５０Ｖにする露光量に設定。
【０１１１】
現像条件
ＤＣバイアス；−５５０Ｖ
現像剤は、フェライトをコアとして絶縁性樹脂をコーティングしたキャリアとスチレンアクリル系樹脂を主材料としてカーボンブラック等の着色剤と荷電制御剤と本発明の低分子量ポリオレフィンからなる着色粒子に、シリカ、酸化チタン等を外添したトナーの現像剤を使用
転写条件
転写極；コロナ帯電方式
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（Ｎ／ｍ）となるように重り荷重方式で当接した。
【０１１２】
評価結果を表１に示した。
【０１１３】
【表１】

【０１１４】
表１から明らかなように、本発明の分散重合法により得られた重合体を表面層に有する感光体１〜５は良好な画像特性、トナー転写率、クリーニング特性を示している。又、感光体１〜５は分散重合法による重合体を有しない表面層の感光体６に比し、クリーニングブレードの起動トルクが小さく、高い安定性を示している。凝集率が本発明のものより低い感光体６は初期の起動トルクが大きく、本発明範囲より凝集率の大きな感光体７は２０万コピー後の起動トルクが大きい。感光体の膜厚減耗量も感光体１〜５は感光体６に比し小さくなっている。又感光体６は鮮鋭性、トナー転写率、クリーニング性も感光体１〜５に比し劣っている。感光体７は表面層の有機微粒子の凝集率が７７％であることから、表面層の膜物性が均一でなく、膜厚減耗量も大きく、画像濃度の低下も発生している。又、鮮鋭性、クリーニング性も感光体１〜５に比し劣っている。
【０１１５】
【発明の効果】
本発明により、画像品質を向上させ、且つ環境依存性を低減できる高耐久の電子写真感光体を提供すること、更に、トナーのクリーニング性能がよく、画像ボケのないすぐれた電子写真感光体を提供すること、更に高湿環境でも鮮明な画像を得ることが出来る電子写真感光体を提供すること、該電子写真感光体を用いた画像形成方法、画像形成装置及びプロセスカートリッジを提供することが出来る。
【図面の簡単な説明】
【図１】凝集率について説明した図である。
【図２】本発明の画像形成方法の１例としての画像形成装置の断面図である。
【符号の説明】
５０ 感光体ドラム（又は感光体）
５１ 帯電前露光部
５２ 帯電器
５３ 像露光器
５４ 現像器
５４１ 現像スリーブ
５４３，５４４ 現像剤攪拌搬送部材
５４７ 電位センサー
５７ 給紙ローラー
５８ 転写電極
５９ 分離電極（分離器）
６０ 定着装置
６１ 排紙ローラー
６２ クリーニング器
７０ プロセスカートリッジ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member, an image forming method, an image forming apparatus, and a process cartridge used in the field of copying machines and printers.
[0002]
[Prior art]
In recent years, organic photoconductors containing organic photoconductive materials have been most widely used as electrophotographic photoconductors. Organic photoconductors have advantages over other photoconductors, such as easy development of materials suitable for various exposure light sources from visible light to infrared light, the ability to select materials without environmental pollution, and low manufacturing costs. It is. However, the mechanical strength is weak, and the surface layer of the photoreceptor is easily deteriorated or scratched when copying or printing a large number of sheets.
[0003]
In order to improve the durability, which is regarded as a problem of the organic photoreceptor as described above, it has been strongly demanded to suppress wear caused by abrasion of a cleaning blade or the like. As an approach for this purpose, a technique has been studied in which fine particles are contained on the surface of the photoreceptor to reduce the frictional force with the blade. For example, Japanese Patent Laid-Open No. 5-181291 reports that the photosensitive layer contains alkylsilsesquioxane resin fine particles. However, the alkylsilsesquioxane resin fine particles have a hygroscopic property, so that the wettability of the surface of the photoconductor increases in a high humidity environment, the resolution decreases, the frictional force with the blade increases, and the blade squeals occur. There is a problem. On the other hand, JP-A-63-56658 reports a photosensitive layer containing a fluororesin powder in the photosensitive layer. However, the fluororesin powder has a problem that sufficient surface strength cannot be obtained, and streak failure due to scratches on the surface of the photoreceptor is liable to occur.
[0004]
As a result of studying this problem, it is effective to introduce fluorine atom-containing groups to the particle surface to improve the wettability of the particle, and to improve the wettability of the fine particles themselves to suppress blade noise. In addition to the above, it has been found that it is important to uniformly disperse the particles in the photosensitive layer. When a fluorine atom-containing group is introduced, the wettability of the particle surface is lowered, and in particular NO causing the image blur etc. ₂ Although there is a tendency to suppress the adsorption of electrophiles such as fog and image blur, which has been a problem, the conventional fluorine atom-containing particle technology simultaneously satisfies the wettability and uniform dispersibility of the particles. As a result, the surface strength of the photoconductor and the problem of image blur cannot be sufficiently achieved, and image characteristics such as image blur and durability are not satisfied at the same time. Furthermore, it has been found that if the uniform dispersibility of the fluorine atom-containing particles is not achieved, image defects such as image blur will not be improved.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and provides a highly durable electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) that can improve image quality and reduce environmental dependency. The present invention provides an electrophotographic photoreceptor excellent in toner cleaning performance and excellent in image blur, and further providing an electrophotographic photoreceptor capable of obtaining a clear image even in a high humidity environment. An object is to provide an image forming method, an image forming apparatus, and a process cartridge using a body.
[0006]
[Means for Solving the Problems]
The object of the present invention is achieved by adopting the following configuration.
[0007]
1. An electrophotographic photosensitive member comprising a layer containing organic fine particles having an aggregation ratio: N (%) in the following range on a conductive support.
[0008]
10 <N ≦ 70
2. In an electrophotographic photosensitive member having an intermediate layer, a charge generation layer, a charge transport layer, and a surface layer on a conductive support, the surface layer contains organic fine particles having an aggregation ratio of N (%) in the following range. An electrophotographic photosensitive member.
[0009]
10 <N ≦ 70
3. 3. The electrophotographic photosensitive member according to 1 or 2, wherein the organic fine particles have a number average particle diameter of 10 to 5000 nm.
[0010]
4). 4. The electrophotographic photosensitive member according to any one of items 1 to 3, wherein the organic fine particles are synthesized by a dispersion polymerization method.
[0011]
5). 5. The electrophotographic photosensitive member according to any one of items 1 to 4, wherein a contact angle of the surface of the electrophotographic photosensitive member with respect to pure water is 90 to 120 °.
[0012]
6). 6. An image forming method comprising forming an electrophotographic image using the electrophotographic photosensitive member according to any one of 1 to 5 above.
[0013]
7). An image forming apparatus that forms an electrophotographic image using the image forming method described in 6 above.
[0014]
8). The image forming apparatus includes at least one of the electrophotographic photosensitive member according to any one of 1 to 5 and at least one of a charger, an image exposure unit, a developing unit, a transfer unit, and a cleaning unit. A process cartridge configured to be detachable.
[0015]
The present invention modifies the surface of the electrophotographic photosensitive member by coagulating organic fine particles to some extent in the layer forming the surface layer of the electrophotographic photosensitive member, thereby improving image characteristics such as image blur and mechanical strength. An electrophotographic photosensitive member that achieves both of the above has been achieved.
[0016]
That is, the present invention is characterized in that the layer forming the surface layer of the electrophotographic photosensitive member contains organic fine particles in a specific aggregation state in which the aggregation rate: N (%) is greater than 10% and 70% or less. To do. An electrophotographic photosensitive member having such a surface layer can be provided with high image quality and high durability characteristics in which image characteristics such as image blur and the mechanical strength are compatible. Furthermore, if the agglomeration rate falls within this range, the blade torque fluctuation does not change much compared with the initial value after 200,000 copies, and the drive is extremely stable, contributing to improvement in image quality and stability in cleaning, It was found that the durability of the cleaning blade was also improved. If the agglomeration rate is 10% or less, it is uniformly dispersed, so the initial torque increases. If the agglomeration rate exceeds 70%, the surface and internal distribution tend to be different and concentrate on the surface. This is because the torque after 200,000 copies increases.
[0017]
In any case, if the agglomeration rate is 10% or less, image blurring occurs, the polishing property is not sufficient, and cleaning and transfer defects are likely to occur. If it exceeds 70%, image defects, scratches, and removal of agglomerated powder are eliminated. Increase in image contamination and decrease in image sharpness due to separation.
[0018]
The aggregation rate will be described with reference to FIG.
The aggregation rate of the present invention is the number of independent fine particles in which organic fine particles are completely separated and dispersed as primary particles (in FIG. 1, (1-6), (10-15), (20) are independent fine particles). x is 13) The number of aggregated particles in which two or more microparticles are in an aggregated state is represented by y (in FIG. 1, (7-9), (16, 17), (18, 19) are aggregated microparticles, and y is 3). Then, the aggregation rate is expressed by the following formula.
[0019]
N (%) = 100y / (x + y) = 100 × 3 / (13 + 3) = 18.8
In actual measurement, calculation is performed based on the above-mentioned determination criteria based on an electron micrograph. At this time, the specific measurement method and the number of samples may be a method that does not vary, and is not particularly limited, but an example of a typical method is used in the examples described later.
[0020]
The aggregation rate N of the present invention is more than 10% and 70% or less, preferably 15 to 60%, more preferably 20 to 50%.
[0021]
Aggregation rate of organic fine particles contained in the surface layer of the present invention: N is more than 10% and 70% or less, and the organic fine particles dispersed at such an aggregation rate are known as the conventionally known organic fine particle-containing electrophotographic photosensitive member. Are clearly distinguished.
[0022]
In order to disperse and contain organic fine particles having an aggregation rate of more than 10% and not more than 70% in the surface layer of the electrophotographic photosensitive member of the present invention, the conventional technique of dispersing solid fine particles in a binder resin is incomplete. A technique for producing a dispersion of solid fine particles is required. In the present invention, a fine particle dispersion preparation technique using a dispersion polymerization method is used as the dispersion preparation technique. Hereinafter, a fine particle dispersion preparation technique by a dispersion polymerization method will be described.
[0023]
The dispersion polymerization method of the present invention is a dispersion stabilizer and an organic solvent in which a polymerizable monomer is dissolved. As the polymerization of the polymerizable monomer proceeds, the polymer is precipitated, and a polymer is produced as a particulate dispersion polymer. More specifically, it refers to a polymerization method for obtaining a product. Specifically, it is a “dispersion polymerization method” described in pages 34 to 45 of Soichi Muroi Publishing Co., Ltd.
[0024]
In the dispersion polymerization method, the polymerizable monomer, dispersion stabilizer, polymerization initiator, dispersion medium (solvent) and the like are necessary as the polymerization system component for proceeding the polymerization. Describe.
[0025]
The dispersion stabilizer used for the dispersion polymerization needs to stably disperse the particulate polymer precipitated from the dispersion medium, and is preferably an amphiphilic polymer having an affinity for both the dispersion medium and the particulate polymer. In addition to this, in the present invention, it is preferable to use a polymer that does not deteriorate the electrophotographic characteristics (chargeability, sensitivity, etc.). Various polymers such as polycarbonate, polyester, and polyamide are used as dispersion stabilizers used in dispersion polymerization. Among these, polymers that are preferably used have good effects on both amphiphilicity and electrophotographic characteristics. And polycarbonate resins having a repeating unit having the carbonate structure shown.
[0026]
For example, a polymer or copolymer of a repeating unit having a carbonate structure represented by the following general formula (1) is preferable.
[0027]
[Chemical 1]

[0028]
(In the formula, A represents a single bond, a linear, branched or cyclic alkylidene group having 1 to 10 carbon atoms, an aryl-substituted alkylidene group, an arylene alkylidene group, or —O—, —S—, —CO—, — SO- and -SO ₂ − Indicates R ₁ , R ₂ , R _Three And R _Four Represents hydrogen, halogen, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group. )
The concentration of the dispersion stabilizer is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the dispersion medium.
[0029]
When the amount is less than 0.1 parts by mass, the dispersion of the particulate polymer is not stable. When the amount is more than 200 parts by mass, the dispersion stabilizers tend to aggregate in the dispersion medium, and the formation of a uniform particulate polymer is likely to be hindered. .
[0030]
As the polymerizable monomer used in the dispersion polymerization of the present invention, a polymerizable monomer that promotes radical polymerization can be used. That is, the radical polymerizable monomer used in the present invention is preferably a vinyl monomer. For example, vinyl monomers such as acrylate, methacrylate, styrene, fluorine-substituted acrylate, methacrylate, styrene, and divinylbenzene are preferably used.
[0031]
As the dispersion medium (solvent) used in the dispersion polymerization of the present invention, the dispersion stabilizer and a solvent capable of dissolving the polymerizable monomer are used. These solvents are generally organic solvents, but if necessary, a mixed solvent of organic solvents or a mixed solvent of water and an organic solvent can be used.
[0032]
Examples of the organic solvent used in the dispersion polymerization of the present invention include methyl chloride, ethyl chloride, chloroform, monochlorobenzene, dichlorobenzene, tetrahydrofuran, dioxolane, dioxane, benzene, toluene, xylene, mesitylene, alcohols, esters, hexane, heptane, Ligroin, kerosene, tetralin, ketones, ethers, dimethylformamide, acetonitrile and the like are preferably used.
[0033]
As the polymerization initiator used in the dispersion polymerization of the present invention, the following compounds are used. That is, AIBN (Azobis- (2,4-dimethylvaleronitilele)), ADVN (Azobisisobutyronitril), ACPA (Azobis- (4-cyanopenticic acid)), AMBN (Azobis- (BitropyB)) Preferably used.
[0034]
In the dispersion polymerization of the present invention, a dispersion stabilizing aid (auxiliary for stably dispersing the particulate polymer) can also be used. As the dispersion stabilizing aid, for example, a nonionic surfactant or the like is used.
[0035]
Polymerization operation of dispersion polymerization
As specifically shown in the synthesis examples described later, in dispersion polymerization, a dispersion stabilizer (binder resin), a polymerizable monomer, a polymerization initiator, and, if necessary, a dispersion stabilization aid are uniformly dissolved in a dispersion medium (organic solvent). In addition, if necessary, polymerization may be performed by heating in the presence of other substances (or may be added in the middle, if necessary), and particles are precipitated by precipitation from a homogeneous system as the polymerizable monomer is polymerized. A particulate polymer is precipitated, and the particulate polymer is further grown to obtain a particulate polymer having a uniform particle size distribution. Each component (dispersion medium, dispersion stabilizer, polymerizable monomer, etc.) used in the dispersion polymerization may be a single component, but two or more types may be used in combination to control the particle size. A copolymer can also be produced. Further, two kinds of polymerization initiators may be used in combination to form a particulate polymer having a wide particle size distribution or a double peak particle size distribution.
[0036]
The amount of the component used in the dispersion polymerization system is preferably used in the following mass ratio.
[0037]
Preferred mass ratio of material components
Dispersion stabilizer: 0.1 mass part-200 mass parts with respect to 100 mass parts of organic solvents
Polymerizable monomer: 1 part by mass to 200 parts by mass with respect to 100 parts by mass of the binder resin
Polymerization initiator: 0.01 parts by mass to 50 parts by mass with respect to 100 parts by mass of the monomer
Dispersion stabilizing aid: 0.001 to 10 parts by weight per 100 parts by weight of monomer
By using the mass ratio as described above, the dispersion polymerization can proceed stably. In the above, a method of adding a polymerizable monomer, a polymerization initiator and the like to the polymerization system stepwise or continuously can also be used as appropriate.
[0038]
The number average particle size of the organic fine particles of the present invention is preferably 10 to 5000 nm. Furthermore, 20-500 nm is preferable. If the thickness is less than 10 nm, the effect of improving the cleaning property and the toner transfer rate is small. If the thickness is more than 5000 nm, the residual potential is likely to increase, and the image density is likely to be lowered or fogged. The number average particle diameter is a measured value obtained by magnifying organic fine particles 2000 times by transmission electron microscope observation, observing 100 particles randomly as primary particles, and calculating the average diameter in the ferret direction by image analysis.
[0039]
In the present invention, the organic fine particle solution obtained by the dispersion polymerization method may be used as a coating solution as it is, and the coating solution may be applied and dried to form the surface layer of the electrophotographic photosensitive member. It can be prepared by adding additives such as charge transport materials, antioxidants, and coating aids to the fine particle solution to prepare a coating solution for the surface layer, coating and drying, and forming the surface layer of the electrophotographic photoreceptor. Good.
[0040]
Next, the constitution of the electrophotographic photosensitive member containing the organic fine particles obtained by the dispersion polymerization method of the present invention will be described.
[0041]
The organic fine particles of the present invention are preferably contained in a charge transport layer or a protective layer that forms the surface layer of the organic photoreceptor. Hereinafter, the organic photoreceptor using the polymer of the present invention for the surface layer will be mainly described.
[0042]
In the present invention, the organic photoconductor means an electrophotographic photoconductor configured to have an organic compound having either a charge generation function or a charge transport function essential for the configuration of the electrophotographic photoconductor, It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of a known organic charge generating material or organic charge transport material, a photoreceptor composed of a polymer complex with a charge generating function and a charge transport function.
[0043]
The layer structure of the organic photoreceptor is not particularly limited, and a photosensitive layer such as a charge generation layer, a charge transport layer, or a charge generation / charge transport layer (a layer having a function of charge generation and charge transport), It is preferable to take a configuration in which a protective layer is coated thereon as necessary.
[0044]
Conductive support
The conductive support used in the photoreceptor of the present invention may be either a sheet or a cylinder, but a cylindrical conductive support is more preferable for designing an image forming apparatus in a compact manner.
[0045]
Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity within a range of 0.1 mm or less in roundness and 0.1 mm or less in runout. A sex support is preferred. Exceeding the roundness and shake range makes it difficult to form a good image.
[0046]
As the conductive material, 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. ^Three Ω · cm or less is preferable.
[0047]
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 treatment in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / L, the aluminum ion concentration is 1 to 10 g / L, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.
[0048]
Middle layer (undercoat layer)
In the present invention, an intermediate layer having a barrier function may be provided between the conductive support and the photosensitive layer.
[0049]
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 (including an undercoat layer) is provided between the support and the photosensitive layer. Including) can also 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 these resin repeating units. Of these subbing resins, a polyamide resin is preferable as a resin capable of reducing the increase in residual potential due to repeated use. The film thickness of the intermediate layer using these resins is preferably 0.01 to 0.5 μm.
[0050]
Examples of the intermediate layer preferably used in the present invention include an intermediate layer using a curable metal resin obtained by thermally curing an organic metal compound such as a silane coupling agent or a titanium coupling agent. As for the film thickness of the intermediate | middle layer using curable metal resin, 0.1-2 micrometers is preferable.
[0051]
Further, the intermediate layer preferably used in the present invention includes an intermediate layer in which titanium oxide fine particles (average particle diameter: 0.01 to 1 μm) subjected to hydrophobic surface treatment are dispersed in a binder such as polyamide resin. The thickness of the intermediate layer is preferably 1 to 15 μm.
[0052]
Photosensitive layer
The photosensitive layer configuration of the photoreceptor of the present invention may be a single layer photosensitive layer configuration in which a charge generation function and a charge transport function are provided on one layer on the intermediate layer. It is preferable that the generation layer (CGL) and the charge transport layer (CTL) be separated. By adopting a configuration in which the functions are separated, an increase in the 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 photoconductor, 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 positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.
[0053]
The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.
Charge generation layer
The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.
[0054]
A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments. For example, CGM such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu-Kα ray and benzimidazole perylene having a maximum peak at 2θ of 12.4 has little deterioration due to repeated use. Potential increase can be reduced.
[0055]
When a binder is used as a 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. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.
[0056]
Charge transport layer
When the charge transport layer is the surface layer of the organic photoreceptor, it is preferable that the charge transport layer contains the organic fine particles of the present invention.
[0057]
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. It is preferable that a resin such as polycarbonate is used as the binder resin and an additive such as an antioxidant is contained as necessary as other substances.
[0058]
A known charge transport material (CTM) can be used as the charge transport material (CTM). 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 .25 (eV) or less.
[0059]
The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).
[0060]
When the charge transport layer does not become a surface layer, 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, and polyurethane resin. Phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of repeating units of these resins. Moreover, high molecular organic semiconductors, such as poly-N-vinyl carbazole, are mentioned. In particular, a polycarbonate resin is preferable for maintaining good electrophotographic characteristics (chargeability, sensitivity, etc.).
[0061]
Surface layer (protective layer)
The organic fine particle solution obtained by the above dispersion polymerization method may be used as it is as the surface layer coating solution, and the coating solution may be applied and dried to form the surface layer of the electrophotographic photosensitive member. The solution may be prepared by adding additives such as a charge transport substance, an antioxidant, and a coating aid to prepare a surface layer coating solution, which may be coated and dried to form the surface layer of the electrophotographic photoreceptor. . In order to maintain good electrophotographic characteristics (chargeability, sensitivity, etc.), it is more preferable that a charge transport layer, an antioxidant and the like are also present in the surface layer.
[0062]
The surface layer preferably contains an antioxidant. Typical examples of the antioxidants are those that prevent the action of oxygen under conditions of light, heat, discharge, etc. on auto-oxidizing substances present in the organic photoreceptor or on the surface of the organic photoreceptor, It is a substance that has the property of inhibiting. Typical examples include the following compound groups.
[0063]
[Chemical formula 2]

[0064]
[Chemical 3]

[0065]
[Formula 4]

[0066]
[Chemical formula 5]

[0067]
Solvents or dispersion media used for forming layers such as intermediate layers, photosensitive layers and protective layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, 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 cellosolve, etc. 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.
[0068]
Next, as a coating processing method for producing the electrophotographic photosensitive member of the present invention, a coating processing method such as dip coating, spray coating, circular amount regulation type coating or the like is used. In order to prevent the lower layer film from being dissolved as much as possible, and 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 that the resin layer of the present invention uses the circular amount regulation type coating method. The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.
[0069]
Next, the image forming apparatus of the present invention will be described.
FIG. 2 is a cross-sectional view of an image forming apparatus as an example of the image forming method of the present invention.
[0070]
In FIG. 2, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an image bearing member, which is a photosensitive member coated with an organic photosensitive layer on the drum and coated with the resin layer of the present invention. Driven and rotated clockwise. Reference numeral 52 denotes a scorotron charger (charging means) for uniformly charging the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, the peripheral surface of the photosensitive member may be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.
[0071]
After uniform charging of the photoreceptor, image exposure based on the image signal is performed by an image exposure unit 53 as an image exposure unit. The image exposure unit 53 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by the light whose optical path is bent by the reflection mirror 532 through the rotating polygon mirror 531 and the fθ lens, and an electrostatic latent image is formed.
[0072]
Here, the reversal development process of the present invention means that the surface of the photosensitive member is uniformly charged by the charger 52 and the image-exposed region, that is, the exposed portion potential (exposed portion region) of the photosensitive member is developed. ) To form an image. On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.
[0073]
The electrostatic latent image is then developed by a developing device 54 as developing means. A developing device 54 containing a developer composed of toner and carrier is provided on the periphery of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer. The inside of the developing device 54 is composed of developer agitating / conveying members 544 and 543, a conveying amount regulating member 542, and the like, and the developer is agitated and conveyed and supplied to the developing sleeve. Controlled by member 542. The amount of the developer transported varies depending on the linear velocity of the applied organic electrophotographic photosensitive member and the specific gravity of the developer, but is generally 20 to 200 mg / cm. ² Range.
[0074]
The developer includes, for example, a carrier in which the above ferrite is used as a core and an insulating resin is coated around the carrier, a colorant such as carbon black, a charge control agent, and the low molecular weight polyolefin of the present invention, which is mainly composed of the above styrene acrylic resin. The developer is made up of a toner obtained by externally adding silica, titanium oxide or the like to the colored particles, and the developer is transported to the development zone with the layer thickness regulated by the transport amount regulating member, and development is performed. At this time, usually, development is performed by applying a DC bias between the photosensitive drum 50 and the developing sleeve 541 and, if necessary, an AC bias voltage. Further, the developer is developed in contact with or not in contact with the photoreceptor. The potential of the photoconductor is measured by providing a potential sensor 547 above the development position as shown in FIG.
[0075]
The recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is ready after the image formation.
[0076]
In the transfer area, a transfer electrode (transfer means: transfer device) 58 is operated on the peripheral surface of the photosensitive drum 50 in synchronization with the transfer timing, and the charged recording paper P is charged with a polarity opposite to that of the toner. Transfer the toner.
[0077]
Next, the recording paper P is neutralized by a separation electrode (separator) 59, separated by the peripheral surface of the photosensitive drum 50 and conveyed to the fixing device 60, and the toner is removed by heating and pressurization of the heat roller 601 and the pressure roller 602. After the welding, the sheet is discharged to the outside of the apparatus via the sheet discharge roller 61. The transfer electrode 58 and the separation electrode 59 stop the primary operation after passing through the recording paper P, and prepare for the next toner image formation. In FIG. 2, a transfer band electrode of corotron is used as the transfer electrode 58. The transfer electrode setting conditions vary depending on the process speed (peripheral speed) of the photosensitive member and cannot be specified. For example, the transfer current is set to +100 to +400 μA, and the transfer voltage is set to +500 to +2000 V. can do.
[0078]
On the other hand, after the recording paper P is separated, the photosensitive drum 50 removes and cleans residual toner by pressure contact of the blade 621 of the cleaning device (cleaning means) 62, and again performs charge removal by the pre-charge exposure unit 51 and charging by the charger 52. Then, the next image forming process is started.
[0079]
Reference numeral 70 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated.
[0080]
The organic electrophotographic photosensitive member 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 using electrophotographic technology. It can also be widely applied to apparatuses such as facsimiles.
[0081]
【Example】
EXAMPLES Hereinafter, although an Example is given and detailed description is given, this invention is not limited to these. In the following text, “part” means “part by mass”.
[0082]

The above composition was stirred and polymerized in a nitrogen atmosphere at about 65 ° C. for 10 hours. After adjusting the solid content concentration of the dispersion polymer (organic fine particles: number average particle size 50 nm) obtained as a result of polymerization to 8% with 1,3 dioxolane, the following charge transporting substance and the like are added, and the coating solution for the surface layer It was set to 1.
[0083]
[4- (2,2-diphenylvinyl) phenyl] -di-p-tolylamine
9.0 parts
2,6-di-tert-butyl-4-phenylphenol 0.18 parts
(Synthesis Example 2)
Polycarbonate “Iupilon Z200” (Mitsubishi Gas Chemical Co., Ltd.)
10.0 parts
1H, 1H, 11H- D Icosafluoroundecyl acrylate 3.0 parts
Azobis- (2-methylbutyronitrile) 0.15 parts
Toluene 90.0 parts
The above composition was stirred and polymerized in a nitrogen atmosphere at about 70 ° C. for 10 hours. After adjusting the solid content concentration of the dispersion polymer (organic fine particles: number average particle size 30 nm) obtained as a result of the polymerization to 7% with toluene, the following charge transporting material and the like were added to obtain a coating solution 2 for the surface layer. .
[0084]

The above composition was stirred and polymerized in a nitrogen atmosphere at about 70 ° C. for 10 hours. After adjusting the solid content concentration of the dispersion polymer (organic fine particles: number average particle size 120 nm) obtained as a result of polymerization to 6.5% with 1,2 dichloroethane, the following charge transporting material and the like are added to the surface layer. It was set as the coating liquid 3.
[0085]
[4- (2,2-diphenylvinyl) phenyl] -di-tolylamine
6.7 parts
2,34-di-tert-butyl-4-phenylphenol 0.134 parts
(Synthesis Example 4)
Polycarbonate “TS2050” (manufactured by Teijin Chemicals Ltd.) 5.0 parts
Polycarbonate "Iupilon Z200" (manufactured by Mitsubishi Gas Chemical Company) 5.0 parts
1H, 1H, 7H-Dodecafluoro Heptyl Acrylate 5.0 parts
Divinylbenzene 0.1 part
Azobis- (2-methylbutyronitrile) 0.1 part
1,3 dioxolane 80.0 parts
The above composition was stirred and polymerized in a nitrogen atmosphere at about 70 ° C. for 10 hours. After the solid content concentration of the dispersion polymer (organic fine particles: number average particle size 90 nm) obtained as a result of the polymerization was adjusted to 6% with 1,2 dichloroethane, the following substances were added to obtain a surface layer coating solution 4. .
[0086]

The above composition was stirred and polymerized at about 75 ° C. for 10 hours in a nitrogen atmosphere. After the solid content concentration of the dispersion polymer (organic fine particles: number average particle size 70 nm) obtained as a result of the polymerization was adjusted to 5% with 1,2 dichloroethane, the following substances were added to obtain a surface layer coating solution 5. .
[0087]

[0088]
[Chemical 6]

[0089]
Production of photoreceptor 1
Photoreceptor 1 was produced as follows.
[0090]
The following intermediate layer coating solution was dip-coated on a cylindrical aluminum conductive substrate having a diameter of 80 mm to form an intermediate layer having a dry film thickness of 4.0 μm.
[0091]
<Intermediate layer coating solution>
Polyamide resin “CM8000” (Toray Industries, Inc.) 10.0 parts
Titanium oxide “SMT500SAS” (manufactured by Teica) 30.0 parts
Methanol 100.0 parts
The above was dispersed using a circulation type wet disperser (Dispermat SLC12EX; manufactured by VMA GETZMANN).
[0092]
On the intermediate layer, the following charge generation layer coating solution was dip coated to form a charge generation layer having a dry film thickness of 0.3 μm.
[0093]

The above was mixed and dispersed with a sand grinder.
[0094]
On the charge generation layer, the following charge transport layer coating solution and then the above surface layer coating solution 1 are continuously applied with a circular slide hopper, and cured by heating at 110 ° C. for 60 minutes, and a dry film thickness of 20 μm. Table of transport layer and dry film thickness 5.0 μm Face layer Formed.
[0095]

Production of photoconductors 2 to 5
Photoconductors 2 to 5 were prepared in the same manner except that surface layer coating solutions 2 to 5 were used instead of surface layer coating solution 1 in the production of photoconductor 1.
[0096]
Production of photoconductor 6 (comparative photoconductor)
A photoconductor 6 was produced in the same manner as the photoconductor 1 except that the surface layer coating solution 6 having the following composition was used instead of the surface layer coating solution 1.
[0097]

Preparation of photoconductor 7 (comparative photoconductor)
A photoconductor 7 was produced in the same manner as the photoconductor 1 except that the surface layer coating solution 7 having the following composition was used instead of the surface layer coating solution 1.
[0098]
Production of surface layer coating solution 7 (Example 1 of JP-A-8-328287)
First, 200 parts by mass of 4-fluoroethylene resin, 200 parts by mass of polycarbonate resin, 600 parts by mass of monochlorobenzene, 600 parts by mass of monochlorobenzene, which were heat-treated at 250 ° C. to prepare a fluorine resin particle dispersion, fluorine type comb type graft polymer (Product name GF300, manufactured by Toa Gosei Chemical Co., Ltd.) 8 parts by mass was thoroughly mixed and then dispersed in a sand grinder (made by Amex Co., Ltd.) using glass beads, and dispersed in 4-fluoroethylene resin particles A liquid (number average particle diameter: 310 nm) was prepared.
[0099]
Next, 1200 parts by mass of [4- (2,2-diphenylvinyl) phenyl] -di-p-tolylamine, 800 parts by mass of polycarbonate resin, and 1500 parts by mass of the 4-fluoroethylene resin particle dispersion were mixed with 5000 parts by mass of monochlorobenzene. Then, it was dissolved and mixed in 3000 parts by mass of dichloromethane to prepare a surface layer coating solution 7. A photoconductor 7 was produced in the same manner as the photoconductor 1 except that this surface layer coating solution 7 was used instead of the surface layer coating solution 1.
[0100]
Evaluation
Aggregation rate of organic fine particles in surface layer: evaluation of N
A slice of the surface layer of the photosensitive member having a thickness of 0.3 ± 0.1 μm was prepared, and a 20,000 times magnified photograph (transmission electron micrograph) of the section of the slice was taken. Select, 5 x 5 cm at each location ² Aggregation rate was calculated by counting organic particles and their agglomerated particles within the image area.
[0101]
Evaluation using a copier
Konica digital copying machine Konica “Sitios 7075” as an evaluation machine (corona charging, laser exposure, reverse development, electrostatic transfer, nail separation, blade cleaning, cleaning auxiliary brush roller adoption process, printing speed 75 sheets / min) The photoconductors 1 to 7 were mounted on the copying machine and evaluated. The cleaning performance and image evaluation were 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 equally divided into A4 neutral paper. In a high temperature and high humidity environment (30 ° C., 80% RH) considered to be the harshest copy conditions, continuous 200,000 copies were made, and halftone, solid white image, and solid black image were evaluated. However, before the start of copying, setting powder was applied to the surface of the photosensitive member, and after the photosensitive member and the cleaning blade were blended, 200,000 copies were made. Evaluation items and evaluation criteria are shown below.
[0102]
Evaluation items and evaluation criteria
Image density (measured using Macbeth RD-918. Measured with a relative reflection density of “0” as the paper reflection density. Evaluated both initially and after 200,000 copies)
A: 1.2 or more after initial copy and 200,000 copies: Good
○: 1.0 or more both after initial copy and after 200,000 copies: Level with no practical problem
×: At least one of the initial and 200,000 copies after copying is less than 1.0: a level causing a practical problem
Fog: Judged by solid white image density
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.
[0103]
A: 0.005 or less (good) for both initial and 200,000 copies
○: 0.01 or less both at the initial stage and after copying 200,000 sheets (a level with no practical problem)
X: At least one after the initial and 200,000 copies is larger than 0.01 (apparently there is a practical problem)
Sharpness
The reproducibility of fine lines and the sharpness of the image were evaluated after the character image was cut out after the completion of 200,000 copies. 3-point and 5-point character images were formed and evaluated according to the following criteria.
[0104]
◎: 3 points and 5 points are clear and easy to read
○: 3 points are partially unreadable, 5 points are clear and easily readable
△: 3 points are almost unreadable 5 points are readable
×: 3 points are almost unreadable 5 points are partially or completely unreadable
Toner transfer rate
The transfer rate (%) was determined by the following formula. However, when obtaining the transfer rate, the toner collected from the cleaning unit was not returned to the developing unit but was taken in a bag.
[0105]
Transfer rate (%) = {1− (mass of collected toner / mass of consumed toner)} × 100
Cleanability (Determining whether or not there is a defective cleaning in the solid white area by making continuous 10 copies on A3 paper after the completion of 100,000 and 200,000 copies)
A: No toner slipping up to 200,000 sheets
○: No toner slipping up to 100,000 sheets
X: Toner slipping occurs when less than 100,000 sheets
Image blur
A: No occurrence up to 200,000 sheets
○: No occurrence up to 150,000
×: Generated at 100,000 sheets or less
Measurement of starting torque of cleaning blade
At the initial stage (s) and after 200,000 copies (e), a starting torque was measured using a drum cartridge by rotating a torque gauge (MODEL 6BTG: manufactured by TOHNICHI) connected to the drum shaft of the copying machine main body. The measurement was performed 5 times and the average value was adopted.
[0106]
Surface contact angle measurement
The surface contact angle of the photoreceptor was measured using a contact angle meter (CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.) with respect to pure water. When the contact angle is small, the surface of the photoreceptor is likely to deteriorate or toner or paper dust adheres easily.
[0107]
Photoreceptor film thickness reduction
The amount of wear was determined by obtaining the difference in the average film thickness of the photoconductor measured at the start of evaluation of live-action and at the end of copying 200,000 sheets.
[0108]
Film thickness measurement method
As for the film thickness of the photosensitive layer, 10 portions of the uniform film thickness are randomly measured, and the average value is defined as the film thickness of the photosensitive layer. The film thickness measuring device is an eddy current type film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO).
[0109]
Other evaluation conditions
The other evaluation conditions using 7075 were set to the following conditions.
[0110]
Charging conditions
Charger: Scorotron charger, initial charge potential of -750V
Exposure conditions
Set the exposure amount so that the potential of the exposed area is -50V.
[0111]
Development conditions
DC bias; -550V
The developer consists of a carrier coated with an insulating resin with ferrite as the core, a styrene acrylic resin as a main material, a coloring agent such as carbon black, a charge control agent, and colored particles comprising the low molecular weight polyolefin of the present invention, silica, oxidation Uses toner developer with external addition of titanium, etc.
Transcription conditions
Transfer pole; corona charging method
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 (N / m) in the counter direction.
[0112]
The evaluation results are shown in Table 1.
[0113]
[Table 1]

[0114]
As is apparent from Table 1, the photoreceptors 1 to 5 having the polymer obtained by the dispersion polymerization method of the present invention in the surface layer exhibit good image characteristics, toner transfer rate, and cleaning characteristics. In addition, the photosensitive members 1 to 5 have a smaller starting torque of the cleaning blade and exhibit high stability as compared with the photosensitive member 6 having a surface layer that does not have a polymer obtained by the dispersion polymerization method. The photosensitive member 6 having a lower aggregation rate than that of the present invention has a large initial starting torque, and the photosensitive member 7 having a larger aggregation rate than the range of the present invention has a large starting torque after 200,000 copies. The amount of wear of the photoconductor is also smaller for the photoconductors 1 to 5 than for the photoconductor 6. The photoconductor 6 is also inferior to the photoconductors 1 to 5 in terms of sharpness, toner transfer rate, and cleaning properties. Since the photoconductor 7 has an organic fine particle aggregation rate of 77% in the surface layer, the film physical properties of the surface layer are not uniform, the film thickness is reduced, and the image density is also reduced. Also, sharpness and cleaning properties are inferior to those of the photoreceptors 1 to 5.
[0115]
【The invention's effect】
The present invention provides a highly durable electrophotographic photoreceptor capable of improving image quality and reducing environmental dependency, and further providing an excellent electrophotographic photoreceptor having good toner cleaning performance and no image blur. In addition, it is possible to provide an electrophotographic photosensitive member capable of obtaining a clear image even in a high humidity environment, and to provide an image forming method, an image forming apparatus, and a process cartridge using the electrophotographic photosensitive member.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an aggregation rate.
FIG. 2 is a cross-sectional view of an image forming apparatus as an example of the image forming method of the present invention.
[Explanation of symbols]
50 photoconductor drum (or photoconductor)
51 Pre-charge exposure section
52 Charger
53 Image exposure unit
54 Developer
541 Development Sleeve
543,544 Developer stirring and conveying member
547 Potential sensor
57 Feed roller
58 Transfer electrode
59 Separation electrode (separator)
60 Fixing device
61 Paper discharge roller
62 Cleaning device
70 Process cartridge

Claims (8)

An electrophotographic photosensitive member comprising a layer containing organic fine particles having an aggregation ratio: N (%) in the following range on a conductive support.
10 <N ≦ 70 In an electrophotographic photosensitive member having an intermediate layer, a charge generation layer, a charge transport layer, and a surface layer on a conductive support, the surface layer contains organic fine particles having an aggregation ratio of N (%) in the following range. An electrophotographic photosensitive member.
10 <N ≦ 70 The electrophotographic photosensitive member according to claim 1 or 2, wherein the organic fine particles have a number average particle diameter of 10 to 5000 nm. The electrophotographic photosensitive member according to claim 1, wherein the organic fine particles are synthesized by a dispersion polymerization method. The electrophotographic photosensitive member according to claim 1, wherein a contact angle of the surface of the electrophotographic photosensitive member with respect to pure water is 90 to 120 °. An image forming method, wherein an electrophotographic image is formed using the electrophotographic photosensitive member according to claim 1. An image forming apparatus for forming an electrophotographic image using the image forming method according to claim 6. An electrophotographic photosensitive member according to any one of claims 1 to 5 and at least one of a charger, an image exposure device, a developing device, a transfer device, and a cleaning device are integrated, and the image forming apparatus includes: A process cartridge configured to be detachable.

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