JP2005043621A - Electrophotographic photoreceptor, image forming apparatus and process cartridge for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high durability electrophotographic photoreceptor which maintains a low skin friction coefficient, has good electrophotographic properties and performs stable image formation and cleaning in repetitive use, and also to provide a high quality image forming apparatus which ensures high reliability over a prolonged period of time. <P>SOLUTION: The electrophotographic photoreceptor has at least a photosensitive layer on a conductive substrate and contains in a top surface layer fine fluorocarbon resin particles (a), a copolymer resin (b) obtained by reacting an acrylic-polyol copolymer with an isocyanate compound, and inorganic conductive fine particles (c). When an average diameter of the projected images of parts of the fine fluorocarbon resin particles (a) exposed in the top surface layer to the surfaces of primary particles and secondary particles formed by aggregation of a plurality of primary particles is represented by D, the sum total of projected area ratios of particles within the range of 0.15≤D≤3 μm in the surfaces is set at ≥10%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５２】
同様にイソシアネート重合体があげられる。例えば、ＨＭＤＩ ３モルの水１モル付加物もあげられる。
【化２】

【００５３】
また、以下のようなウレトジオン、イソシアネートなども用いることができる。
【化３】

【００５４】
具体例として、ＨＭＤＩイソシアネート、ＩＰＤＩイソシアネートが挙げられる。
【化４】

【００５５】
また、
【化５】

などのイソシアネートも例示できる。
【００５６】
アクリルポリオール共重合体と１分子中に２個以上のＮＣＯ基を有するイソシアネート化合物を反応させた共重合樹脂はその反応成分の比率を合わせないと、硬化がうまくいかなかったり、残留反応基により感光体特性が非常に悪くなるため、イソシアネート化合物の量は、ＮＣＯ基とアクリルポリオール共重合体におけるＯＨ基との数の比（ＮＣＯ／ＯＨ）が０．７〜１．３の範囲になる量であることが望ましい。
これら共重合体樹脂の分子量は数平均で２，０００〜２００，０００好ましくは１０，０００〜４０，０００である。
【００５７】
感光体最表層にアクリルポリオール共重合体と１分子中に２個以上のＮＣＯ基を有するイソシアネート化合物を反応させた共重合樹脂を用いると感光体感度特性が悪くなる傾向にあるため、導電性微粒子を添加する必要がある。無機導電性微粒子の添加は、前述したように耐摩耗性の向上にも効いている。
本発明の感光体最表層に用られる無機導電性微粒子としては、銅、スズ、アルミニウム、インジウムなどの金属粉末、酸化錫、アンチモンをド−プした酸化錫、錫をド−プした酸化インジウム等の金属酸化物が挙げられるが、特に酸化錫が好適である。
酸化スズ微粒子の粒径は大きすぎると摩擦係数が上昇したり、光の透過率が小さくなってしまい、粒径が小さすぎると導電性が悪くなるため、０．１〜１．０μｍが良い。バインダー樹脂と酸化スズ微粒子の比率は、酸化スズが少ないと感度、耐摩耗性が悪くなり、酸化スズが多すぎると、膜の電気抵抗が小さくなり画像ボケが発生したり、膜が脆くなって摩耗しやすくなるため、アクリルポリオール共重合体とイソシアネート化合物を反応させた共重合樹脂に対して４０〜８０ｗｔ％が良い。
【００５８】
本発明の感光体最表層には、無機導電性微粒子以外に更に耐摩耗性を向上する目的でフィラ−材料を添加してもよい。フィラーとしては有機性フィラーと無機性フィラーがあるが、フィラーの硬度の点から無機性フィラーを用いることが耐摩耗性の向上に対し有利である。このような無機性フィラ−材料としては、シリカ、酸化チタン、アルミナ、酸化ジルコニウム、酸化ビスマス、酸化カルシウム等の金属酸化物、フッ化カルシウム、フッ化アルミニウム等の金属フッ化物、チタン酸カリウム、窒化硼素などの無機材料が挙げられる。
【００５９】
これらのフィラーは少なくとも１種の表面処理剤で表面処理させることが可能であり、そうすることがフィラーの分散性の面から好ましい。フィラーの分散性の低下は残留電位の上昇だけでなく、塗膜の透明性の低下や塗膜欠陥の発生、さらには耐摩耗性の低下をも引き起こすため、高耐久化あるいは高画質化を妨げる大きな問題に発展する可能性がある。表面処理剤としては、従来用いられている表面処理剤すべてを使用することができるが、フィラーの絶縁性を維持できる表面処理剤が好ましい。例えば、チタネート系カップリング剤、アルミニウム系カップリング剤、ジルコアルミネート系カップリング剤、高級脂肪酸等、あるいはこれらとシランカップリング剤との混合処理や、Ａｌ_２Ｏ_３、ＴｉＯ_２、ＺｒＯ_２、シリコーン、ステアリン酸アルミニウム等、あるいはそれらの混合処理がフィラーの分散性及び画像ボケの点からより好ましい。シランカップリング剤による処理は、画像ボケの影響が強くなるが、上記の表面処理剤とシランカップリング剤との混合処理を施すことによりその影響を抑制できる場合がある。表面処理量については、用いるフィラーの平均一次粒径によって異なるが、３〜３０ｗｔ％が適しており、５〜２０ｗｔ％がより好ましい。表面処理量がこれよりも少ないとフィラーの分散効果が得られず、また多すぎると残留電位の著しい上昇を引き起こす。
【００６０】
次に本発明の画像形成装置について、図を参照して説明する。
図５は、本発明の画像形成装置を説明するための概略図である。なお、下記するような変形例も本発明の範疇に属するものである。
図５に示すように、本発明に係る電子写真感光体を用いた画像形成装置は、本発明に係るドラム状の感光体１と、帯電チャージャ３と、転写前チャージャ７と、転写チャージャ１０と、分離チャージャ１１と、クリーニング前チャージャ１３などから構成されている。なお、感光体１の形状は、ドラム状の形状に限定されるものではなく、例えば、シート状、エンドレスベルト状のものであっても良い。また、各種チャージャーとしては、コロトロン、スコロトロン、固体帯電器（ソリッド・ステート・チャージャ）、帯電ローラを始めとする公知の手段を用いることができる。
転写手段としては、一般には上記の帯電器が使用できるが、図示するような転写チャージャと分離チャージャとを併用したものが効果的である。
また、画像露光部５、除電ランプ２等の光源には、蛍光灯、タングステンランプ、ハロゲンランプ、水銀灯、ナトリウム灯、発光ダイオード（ＬＥＤ）、半導体レーザー（ＬＤ）、エレクトロルミネッセンス（ＥＬ）などの発光物全般を用いることができる。そして、所望の波長域の光のみを照射するために、シャープカットフィルター、バンドパスフィルター、近赤外カットフィルター、ダイクロイックフィルター、干渉フィルター、色温度変換フィルターなどの各種フィルターを用いることもできる。
かかる光源等は、図５に示される工程の他に、光照射を併用した転写工程、除電工程、クリーニング工程、あるいは前露光などの工程を設けることにより、感光体に光を照射することができる。
【００６１】
さて、現像ユニット６により感光体１上に現像されたトナーは、転写紙９に転写されるが、全部が転写されるわけではなく、感光体１上にトナーが残存する。このようなトナーは、クリーニングブラシ１４及びクリーニングブレード１５により、感光体１より除去される。クリーニングは、クリーニングブラシ１４又はクリーニングブレード１５単独で行なわれることもあり、クリーニングブラシ１４にはファーブラシ、マグファーブラシを始めとする公知のものが用いられる。電子写真感光体に正（負）帯電を施し、画像露光を行なうと、感光体表面上には正（負）の静電潜像が形成される。これを負（正）極性のトナー（検電微粒子）で現像すれば、ポジ画像が得られるし、また正（負）極性のトナーで現像すれば、ネガ画像が得られる。かかる現像手段としては、公知の方法が適用され、また、除電手段にも公知の方法が用いられる。
【００６２】
本発明の画像形成装置は、電子写真感光体に接触して摺擦する接触部材を具備させることができる。
加圧された接触部材としては、フッ素樹脂微粒子の露出部分の摺擦を目的とした接触部材を設けても良いし、帯電ローラーなどの接触帯電部材、クリーニングブレード、クリーニングブラシなどのクリーニング部材、転写ベルト、中間転写ベルトなどの転写部材など一般的に画像形成装置に用いられる部材に加圧する機構を設けたようなものでもよい。ここでは、クリーニングブレード１５によって感光体表面を摺擦する場合を例に挙げて説明する。クリーニングブレード１５は、感光体１表面を略均等な圧力で押しながらほぼ全面を摺擦し、フッ素樹脂微粒子を均等に表面に付着させるという効果が大きく好ましい。
クリーニングブレード１５によってフッ素樹脂を被覆させる場合、クリーニングブレード１５の各種条件として、ブレード当接角１０〜３０度、当接圧力０．３〜４ｇ／ｍｍ、ブレードとして用いるゴムのゴム硬度６０〜７０度、反発弾性３０〜７０％、ヤング率３０〜６０ｋｇｆ／ｃｍ^２、厚さ１．５〜３．０ｍｍ、自由長７〜１２ｍｍ、ブレードエッジの感光体１への食い込み量０．２〜２ｍｍの範囲が好適であり、このような物性を満たす材質としてウレタンゴムブレードが特に好適である。
【００６３】
図６には、本発明による画像形成装置を用いた別のプロセスの例を示す。図６において、感光体２２は、本発明の電子写真感光体であり、駆動ローラ２３により駆動され、帯電チャージャ２０による帯電、画像露光部２１による像露光、現像（図示せず）、転写チャージャ２５を用いる転写、クリーニングブラシ２６によるクリーニング、除電ランプ２７による除電が繰返し行なわれる。
【００６４】
さらに、本発明を適用したフルカラー画像形成装置として、電子写真方式のプリンタ（以下、単にプリンタという）の一実施形態について説明する。
図７は、本実施形態に係るプリンタの概略構成図である。
図７において、潜像担持体たる感光体ドラム３６は、図中反時計回りに回転駆動されながら、その表面がコロトロンやスコロトロンなどを用いる帯電チャージャ３３によって一様帯電せしめられた後、図示しないレーザ光学装置から発せられるレーザ光Ｌの走査を受けて静電潜像を担持する。この走査はフルカラー画像をイエロー、マゼンタ、シアン及びブラックの色情報に分解した単色の画像情報に基づいてなされるため、感光体ドラム３６上にはイエロー、マゼンタ、シアン又はブラックという単色用の静電潜像が形成される。感光体ドラム３６の図中左側には、リボルバ現像ユニット３０が配設されている。これは、回転するドラム状の筺体の中にイエロー現像器、マゼンタ現像器、シアン現像器、ブラック現像器を有しており、回転によって各現像器を感光体ドラム３６に対向する現像位置に順次移動させる。なお、イエロー現像器、マゼンタ現像器、シアン現像器、ブラック現像器は、それぞれイエロートナー、マゼンタトナー、シアントナー、ブラックトナーを付着せしめて静電潜像を現像するものである。感光体ドラム３６上には、イエロー、マゼンタ、シアン、ブラック用の静電潜像が順次形成され、これらはリボルバ現像ユニット３０の各現像器によって順次現像されてイエロートナー像、マゼンタトナー像、シアントナー像、ブラックトナー像となる。
【００６５】
上記現像位置よりも感光体ドラム３６の回転下流側には中間転写ユニットが配設されている。これは、張架ローラ３９ａ、転写手段たる中間転写バイアスローラ３７、２次転写バックアップローラ３９ｂ、ベルト駆動ローラ３９ｃによって張架している中間転写ベルト３８を、ベルト駆動ローラ３９ｃの回転駆動によって図中時計回りに無端移動せしめる。感光体ドラム３６上で現像されたイエロートナー像、マゼンタトナー像、シアントナー像、ブラックトナー像は、感光体ドラム３６と中間転写ベルト３８とが接触する中間転写ニップに進入する。そして、中間転写バイアスローラ３７からのバイアスの影響を受けながら、中間転写ベルト３８上に重ね合わせて中間転写されて、４色重ね合わせトナー像となる。
【００６６】
回転に伴って中間転写ニップを通過した感光体ドラム３６表面は、ドラムクリーニングユニット３５によって転写残トナーがクリーニングされる。このドラムクリーニングユニット３５は、クリーニングバイアスが印加されるクリーニングローラによって転写残トナーをクリーニングするものであるがファーブラシ、マグファーブラシ等からなるクリーニングブラシや、クリーニングブレードなどを用いるものであってもよい。
【００６７】
転写残トナーがクリーニングされた感光体ドラム３６表面は、除電ランプ３４によって除電せしめられる。除電ランプ３４には、蛍光灯、タングステンランプ、ハロゲンランプ、水銀灯、ナトリウム灯、発光ダイオード（ＬＥＤ）、半導体レーザ（ＬＤ）、エレクトロルミネッセンス（ＥＬ）などが用いられている。また、上記レーザ光学装置の光源には半導体レーザが用いられている。これらから発せられる光については、シャープカットフィルター、バンドパスフィルター、近赤外カットフィルター、ダイクロイックフィルター、干渉フィルター、色温度変換フィルターなどの各種フィルターにより、所望の波長域だけを用いるようにしてもよい。
一方、図示しない給紙カセットから送られてきた転写紙４０を２つのローラ間に挟み込んでいるレジストローラ対４１は、転写紙４０を中間転写ベルト３８上の４色重ね合わせトナー像に重ね合わせ得るタイミングで上記２次転写ニップに向けて送り込む。中間転写ベルト３８上の４色重ね合わせトナー像は、２次転写ニップ内で紙転写バイアスローラー４３からの２次転写バイアスの影響を受けて転写紙４０上に一括して２次転写される。この２次転写により、転写紙４０上にはフルカラー画像が形成される。
【００６８】
フルカラー画像が形成された転写紙４０は、転写ベルト４２によって紙搬送ベルト４４に送られる。
搬送ベルトは４４は、転写ユニットから受け取った転写紙４０を定着装置４５内に送り込む。
定着装置４５は、送り込まれた転写紙４０を加熱ローラとバックアップローラとの当接によって形成された定着ニップに挟み込みながら搬送する。
転写紙４０上のフルカラー画像は、加熱ローラからの加熱や、定着ニップ内での加圧力の影響を受けて転写紙４０上に定着せしめられる。
【００６９】
なお、図示を省略しているが、転写ベルト４２や搬送ベルト４４には、転写紙４０を吸着させるためのバイアスが印加されている。また、転写紙４０を除電する紙除電チャージャや、各ベルト（中間転写ベルト３８、転写ベルト４２、搬送ベルト４４）を除電する３つのベルト除電チャージャが配設されている。また、中間転写ユニットは、ドラムクリーニングユニット３５と同様の構成のベルトクリーニングユニットも備えており、これによって中間転写ベルト３８上の転写残トナーをクリーニングする。
【００７０】
図８は、本実施形態に係るプリンタの変形例である。この装置は、いわゆるタンデム方式のプリンタであり、感光体ドラム５０を各色で共有させるのではなく、各色用の感光体ドラム５０Ｙ、５０Ｍ、５０Ｃ、５０Ｂｋを備えている。また、ドラムクリーニングユニット５５、除電ランプ５３、感光体ドラム５０を一様帯電せしめる帯電ローラ５４も、各色用のものを備えている。なお、図７に示したプリンタではドラム一様帯電手段として帯電チャージャ３３を設けていたが、このプリンタでは帯電ローラ５４を設けている。
タンデム方式では、各色の潜像形成や現像を並行して行うことができるため、リボルバ式よりも画像形成速度を遙かに高速化させることができる。
以上に示すような画像形成手段は、複写装置、ファクシミリ、プリンター内に固定して組み込まれていてもよいが、プロセスカートリッジの形でそれら装置内に組み込まれてもよい。プロセスカートリッジとは、感光体を内蔵し、他に帯電手段、露光手段、現像手段、転写手段、クリーニング手段、除電手段を含んだ１つの装置（部品）である。プロセスカートリッジの形状等は多く挙げられるが、一般的な例として、図９に示すものが挙げられる。かかるプロセスカートリッジは、感光体ドラム６６、帯電チャージャ６７、画像露光部６９、クリーニングブラシ６８及び現像ローラ７０などから構成されている。
【００７１】
【実施例】
以下、本発明について実施例を挙げて説明するが、本発明は実施例により制約を受けるものではない。なお、部はすべて重量部である。
＜実施例１＞
アルミニウムシリンダー上に下記組成の下引き層塗工液、電荷発生層塗工液、および電荷輸送層塗工液を、浸漬塗工によって順次塗布、乾燥し、３．５μｍの下引き層、０．２μｍの電荷発生層、２２μｍの電荷輸送層を形成した。
◎下引き層塗工液
二酸化チタン粉末 ４００部
メラミン樹脂 ６５部
アルキッド樹脂 １２０部
２−ブタノン ４００部
【００７２】
◎電荷発生層塗工液
下記構造のビスアゾ顔料 １２部
【化６】

ポリビニルブチラール ５部
２−ブタノン ２００部
シクロヘキサノン ４００部
【００７３】
◎電荷輸送層塗工液
ポリカーボネート（Ｚポリカ、帝人化成製） ８部
下記構造式の電荷輸送物質 １０部
【化７】

テトラヒドロフラン １００部
【００７４】
電荷輸送層上にさらに、下記の保護層塗工液をスプレー塗工［スプレーガン：ピースコンＰＣ３０８ オリンポス社製、エア圧：２ｋｇｆ／ｃｍ^２］を行い、１５０℃６０分間乾燥して約５μｍの保護層を形成し、電子写真感光体１を作製した。
【００７５】
◎保護層塗工液
下記組成の溶液を高速液衝突分散装置（装置名：アルティマイザーＨＪＰ−２５００５ スギノマシン社製）において、１００ＭＰａ圧力下、３０ｍｉｎ循環し、パーフロロアルコキシ（以下、ＰＦＡと省略）樹脂粒子分散液▲１▼を得た。
ＰＦＡ樹脂粒子（ＭＰＥ−０５６、三井フロロケミカル製） ３８部
分散助剤（モディパーＦ２１０ 日本油脂製） ３．８部
テトラヒドロフラン １０００部
シクロヘキサノン ３００部
【００７６】
次にアクリルポリオール共重合体であるスチレン（Ｓｔ）〜メチルメタクリレート（ＭＭＡ）〜２−ヒドロキシエチルメタクリレート（２−ＨＥＭＡ）共重合体の溶液（溶媒はセロソルブアセテートとメチルイソブチルケトンとの混合溶媒）と酸化スズ粒子（三菱金属社製）を用意した。アクリルポリオール共重合体は、モノマー構成比（重量比）Ｓｔ／ＭＭＡ／２−ＨＥＭＡ／２−ＨＥＭＡ＝２８／４２／３０を用いた。
前記Ｓｔ／ＭＭＡ／２−ＨＥＭＡ共重合体溶液（固形分） １０部
酸化スズ粒子 ９０部
をシクロヘキサノンとテトラヒドロフラン（混合溶媒重量比１００／３０）の混合溶媒で全固形分濃度２０ｗｔ％となるように配合し、１００時間ボールミル分散した。続いて、この分散液と希釈用樹脂液（上記アクリルポリオール共重合体樹脂、濃度約１０％）とＨＭＤＩ系ポリイソシアネート（スミジュールＨＴ、住友バイエルウレタン社製）とを、分散液中の酸化スズの粒子と樹脂固形分の割合が６：４、イソシアネート基とアクリルポリオール共重合体の水酸の数の比が１：１になるように混合し、分散液▲２▼を得た。
分散液▲１▼と分散液▲２▼を、表−１に示す組成比になるように混合した後、全固形分濃度が３ｗｔ％になるようにシクロヘキサノンとテトラヒドロフラン（混合溶媒重量比１００／３０）の混合溶媒で希釈し、その後、超音波を１０分間照射して調整し、保護層塗工液を得た。
【００７７】
＜実施例２〜３、比較例１＞
実施例１において、保護層の組成重量比を表−１に示すように変更した以外は同様にして、電子写真感光体２〜４を作製した。
＜比較例２＞
実施例１において、保護層塗工液を下記のように変更した以外は同様にして、電子写真感光体５を作製した。
【００７８】
下記組成の溶液を配合し高速液衝突分散装置（装置名：アルティマイザーＨＪＰ−２５００５ スギノマシン社製）において、１００ＭＰａ圧力下、３０ｍｉｎ循環し、保護層塗工液を作製した
ＰＦＡ樹脂粒子（ＭＰＥ−０５６、三井フロロケミカル製） ５５部
分散助剤（モディパーＦ２１０ 日本油脂製） ５．５部
ポリカーボネート（Ｚポリカ、帝人化成製） ３９．５部
テトラヒドロフラン ２０００部
シクロヘキサノン ６００部
【００７９】
＜実施例４〜５＞
実施例１において、保護層のイソシアネート化合物のＮＣＯ基とアクリルポリオール共重合体のＯＨ基の比を表−１に示すように変更した以外は同様にして電子写真感光体６，７を作製した。
【００８０】
＜実施例６〜７＞
実施例１において、保護層の酸化スズの添加量を表−１に示すように変更した以外は同様にして、電子写真感光体８，９を作製した。
【００８１】
＜実施例８〜９＞
実施例１において、ボールミル時間を変えることによって酸化スズの平均粒径を表−１に示すように変更した以外は同様にして、電子写真感光体１０，１１を作製した。
【００８２】
＜実施例１０〜１１＞
実施例１において、アクリルポリオール共重合体のＳｔ／ＭＭＡ／２−ＨＥＭＡ比を表−１に示すように変更した以外は同様にして、電子写真感光体１２，１３を作製した。
【００８３】
＜実施例１２〜１４＞
実施例１において、イソシアネート化合物の種類を表−１に示すように変更した以外は同様にして、電子写真感光体１４〜１６を作製した。
【００８４】
＜実施例１５＞
実施例１において、ＰＦＡ樹脂微粒子をポリテトラフルオロエチレン微粒子（ＴＬＰ１０Ｆ−１、三井フロロケミカル製）に変更した以外は同様にして、電子写真感光体１７を作製した。
【００８５】
【表１】

【００８６】
次に、本実施例に使用した重合トナーの製造例を示す。
トナー製造例１
１）単量体組成物の作製
スチレンモノマー ７０部
ｎ−ブチルメタクリレート ３０部
ポリスチレン ５部
３，５−ジ−ｔｅｒｔ−ブチルサリチル酸亜鉛塩 ２部
カーボンブラック ６部
上記の重合性単量体混合物をボールミルを用いて２４時間分散混合して単量体組成物を調製した。
２）造粒、重合
攪拌機、温度計、不活性ガス導入管及び細孔径１１０，０００Å、細孔容積０．４２ｃｃ／ｇ、１０φ×５０ｍｍの多孔質ガラス管を備えたフラスコに２％ポリビニルアルコール水溶液４００ｍｌを取り、窒素ガスを送りながら室温で攪拌を行い、反応容器中の酸素を窒素置換した。
【００８７】
ついで１）の単量体組成物１１３ｇにアゾビスイソブチルニトリル１．５６ｇを加え攪拌溶解し、ポンプを用いて多孔質ガラス管を通過させて、ポリビニルアルコール水溶液中へ加え、加え終った後ポリビニルアルコールと単量体組成物の混合物を、前記ポンプと多孔質ガラス管を用いて約１２０ｍｌ／ｍｉｎの割合で２時間循環させた後、内温を７０℃とし８時間重合させた。
その後室温まで冷却し一晩静置後、上澄液を除き水を加えて１時間攪拌後濾過、乾燥しトナーを得た。このトナーをコールターカウンターで粒子径を測定したところ、平均粒子径８．５μｍで５〜１０μｍ径の範囲にある粒子は全体の９５％であり極めて狭い粒度分布であった。
【００８８】
評価例１
トナー製造例１で得られたトナー粒子を含む懸濁液を平板上の撮像部検知帯に通過させ、ＣＣＤカメラで光学的に粒子画像を検知し、得られる投影面積の等しい相当円の周囲長を実在粒子の周囲長で除した値である平均円形度を評価した。この値はフロー式粒子像分析装置ＦＰＩＡ−２０００により平均円形度として計測することができ、具体的な測定方法としては、容器中の予め不純固形物を除去した水１００〜１５０ｍｌ中に分散剤として界面活性剤、好ましくはアルキルベンゼンスフォン酸塩を０．１〜０．５ｍｌ加え、更に測定試料を０．１〜０．５ｇ程度加え、試料を分散した懸濁液は超音波分散器で約１〜３分間分散処理を行ない、分散液濃度を３０００〜１万個／μｌとして前記装置によりトナーの形状及び分布を測定することによって得られる。これまでの検討の結果、０．９６０以上のトナーが適正な濃度の再現性のある高精細な画像を形成するのに有効であることがわかっており、より好ましくは、平均円形度が０．９８０〜１．０００である。トナー製造例１で作製したトナーの円形度は０．９８であった。
【００８９】
評価例２（二次粒子径、被覆面積比）
得られた電子写真感光体１〜１７の表面の任意の観察点１０点について、ＦＥ−ＳＥＭにより４５００倍で撮影し、得られたＳＥＭ写真を画像処理ソフト（ＩＭＡＧＥ Ｐｒｏ Ｐｌｕｓ）を用いて、フッ素樹脂微粒子の最表層膜中における一次粒子、及び一次粒子が複数個凝集して形成された二次粒子の表面に露出した部分の投影像の平均直径をＤとした場合の、０．１５≦Ｄ≦３μｍの範囲にある粒子の、表面に占める投影面積比の合計を求めた。
【００９０】
評価例３（表面摩擦係数）
得られた電子写真感光体１〜１７について、特許文献９０等にて開示されているオイラー・ベルト方式を用い表面摩擦係数を評価した。ここでいうベルトとは、中厚の上質紙で、紙すきが長手方向になるようにして、図１０に示すように、感光体の円周１／４に張架し、ベルトの一方にＷ＝１００ｇの荷重を掛け、他方にフォースゲージ（バネ秤）を設置し、フォースゲージを徐々に引っ張りながらベルトの移動を観察し、移動が開始した時点での荷重を読み取って以下の式にて計算する。なお、図１０では、荷重：１００ｇ分銅と、ベルト：Ｔｙｐｅ６２００／Ｔ目／Ａ４用紙／３０ｍｍ幅（すき目方向にカット）と、ダブルクリップ２個が使用される。また、式におけるμは摩擦係数を、Ｆは引っ張り力を、Ｗは荷重を表す。
μ＝２／π×ｌｎ（Ｆ／Ｗ） Ｗ＝１００ｇ
【００９１】
評価例４（耐久寿命Ａ）
得られた電子写真感光体１〜３及び６〜１７、比較用電子写真感光体４、５を、リコー製ｉｍａｇｉｏ Ｃｏｌｏｒ ５１００改造機（画像露光光源を６５５ｎｍの半導体レーザーに交換し潤滑剤塗布手段を除去したもの）に搭載し、連続してトータル１５万枚の印刷を行い、その際初期画像及び１５万枚印刷後の画像について評価を行った。また、初期及び１５万枚印刷後の明部電位を測定した。さらに、初期及び１５万枚印刷後での膜厚差より摩耗量の評価を行った。
【００９２】
【表２】

【００９３】
評価例５（耐久寿命Ｂ）
得られた電子写真感光体１〜１８、比較用電子写真感光体１〜９を、リコー製ｉｍａｇｉｏ Ｃｏｌｏｒ ５１００改造機（トナーを製造例１で作成したものに変更し画像露光光源を６５５ｎｍの半導体レーザーに交換、更に潤滑剤塗布手段を除去したもの）に搭載し、連続してトータル１５万枚の印刷を行い、その際初期画像及び１５万枚印刷後の画像について評価を行った。また、初期及び１５万枚印刷後の明部電位を測定した。さらに、初期及び１５万枚印刷後での膜厚差より摩耗量の評価を行った。
【００９４】
【表３】

【００９５】
評価例６（耐久寿命Ｃ）
得られた電子写真感光体１〜１８、比較用電子写真感光体１〜９を、リコー製ＩＰＳｉＯ Ｃｏｌｏｒ ８１００改造機（トナーを製造例１で作成したものに変更）に搭載し、連続してトータル７．５万枚の印刷を行い、その際初期画像及び７．５万枚印刷後の画像について評価を行った。また、初期及び７．５万枚印刷後の明部電位を測定した。さらに、初期及び７．５万枚印刷後での膜厚差より摩耗量の評価を行った。
【００９６】
【表４】

【００９７】
表−２、３、４の評価結果より、粉砕トナーの場合だけでなく、球形トナーにおいても感光体の最表面層に本発明の請求項の要件を満たす条件のフッ素樹脂微粒子を含有させることで、高安定な低表面摩擦係数の持続性を維持することが可能となった。また、それと同時に摩耗量についても抑制されており、耐摩耗性が大幅に向上していることが確認された。さらに、繰り返し印刷後においても明部電位上昇は少なく、クリーニング不良が発生せず高画質画像が安定に得られることが確認された。
一方、本発明の請求項の要件を満たしていない条件のフッ素樹脂微粒子を含有させた感光体やバインダー樹脂がアクリルポリオール共重合体とイソシアネート化合物を反応させた共重合樹脂でない感光体は、摩耗量が大きく、また、クリーニング不良も引き起こしていた。
【００９８】
【発明の効果】
本発明によれば、感光体最表層にフッ素樹脂微粒子を含有し、該フッ素樹脂微粒子が最表層膜中において、一次粒子、及び一次粒子が複数個凝集して形成された二次粒子の表面に露出した部分の投影像の平均直径をＤとした場合、０．１５≦Ｄ≦３μｍの範囲にある粒子の、表面に占める投影面積比の合計が１０％以上とすることで、感光体表面の摩擦係数を長期渡り低く維持することができ、トナーのクリーニング性が向上する。感光体最表層のバインダー樹脂を熱硬化樹脂とし、無機導電性微粒子を添加することにより、感光体の耐摩耗性を著しく向上させることができる。
【００９９】
すなわち、繰返し使用しても低い摩擦係数を有しながら優れた耐摩耗性を併せ持つ感光体が提供でき、長期に渡り信頼性の高い高画質画像形成装置の提供することが可能となる。
【図面の簡単な説明】
【図１】本発明の電子写真感光体の一例を示す模式断面図である。
【図２】本発明における電子写真感光体の他の構成例の一例を示す模式断面図である。
【図３】本発明における電子写真感光体の他の構成例の一例を示す模式断面図である。
【図４】本発明における電子写真感光体の他の構成例の一例を示す模式断面図である。
【図５】本発明の画像形成装置を説明するための概略図である。
【図６】本発明による画像形成装置を用いた別のプロセスの例を示す概略図である。
【図７】本発明におけるプリンタの一例を示す概略図である。
【図８】本実施形態に係るプリンタの変形例を示す概略図である。
【図９】本発明に係るプロセスカートリッジの一例を示す概略図である。
【図１０】実施例における表面摩擦係数の評価法を示す概念図である。
【符号の説明】
１，２２ 感光体
２，２７，３４，５３ 除電ランプ
３，２５，３３，６７ 帯電チャージャ
５，６９ 画像露光部
６，３０ 現像ユニット
７ 転写前チャージャ
１４，２６，６８ クリーニングブラシ１４
１５ クリーニングブレード
３６，５０，６６ 感光体ドラム
３８ 中間転写ベルト
４２ 転写ベルト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoconductor such as a copying machine, a printer, and a facsimile using an electrophotographic system, an image forming apparatus, and a process cartridge for the image forming apparatus.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a printer, and a facsimile machine using an electrophotographic system, a uniformly charged photosensitive member is irradiated with writing light modulated by image data, and the photosensitive member is irradiated on the photosensitive member. An electrostatic latent image is formed, and toner is supplied to the photosensitive member on which the electrostatic latent image is formed by a developing unit to form a toner image on the photosensitive member and develop. The image forming apparatus transfers the toner image on the photoconductor to the transfer paper (recording paper) by the transfer unit, and then fixes the toner transferred on the transfer paper by the fixing unit by heating and pressurizing, and remains on the surface of the photoconductor. The collected toner is collected by a method such as scraping with a cleaning blade at the cleaning unit.
[0003]
In an image forming apparatus using such an electrophotographic method, it has been known that, by reducing the coefficient of friction on the surface of the photoreceptor, unnecessary toner adhesion can be prevented and an image free of background stains can be obtained. It has been. In addition, a photoreceptor having a small surface friction coefficient can reduce the amount of surface wear and extend the life of the photoreceptor.
In other words, the reason for determining the life of the photoconductor is the wear of the photoconductive layer of the photoconductor. When a certain amount of the photoconductive layer is scraped off, the electrical characteristics of the photoconductor change and an appropriate image forming process can be performed. Disappear. This friction is generated in all the parts where the photoconductor and other image forming units such as the developing unit and the transfer unit are in contact with each other in the image forming process described above. It is possible to reduce the wear generated at the site and improve the life of the photoreceptor.
[0004]
Further, it is known that by reducing the coefficient of friction on the surface of the photoconductor, the transfer rate when the toner image formed on the photoconductor is transferred to the transfer target is improved. That is, since it is possible to suppress worm-eating prints and to reduce the amount of residual toner after transfer, there are also effects such as a reduction in the amount of waste toner.
Furthermore, recently, due to the demand for higher image quality of electrophotography, it has become clear that a high effect can be obtained for cleaning spherical toners produced using an emulsion polymerization method or a suspension polymerization method. ing.
In general, the toner remaining on the photosensitive member is cleaned by bringing a blade formed of rubber or the like into contact with the counter and removing the toner with the blade. However, since the spherical toner is rubbed into the contact portion between the cleaning blade and the photosensitive member and slips through, the cleaning toner often causes poor cleaning. On the other hand, by reducing the coefficient of friction on the surface of the photoconductor, it is possible to suppress slipping of the spherical toner and to suppress poor cleaning.
[0005]
As a method for reducing the coefficient of friction on the surface of the photoreceptor, an image forming apparatus having a mechanism for supplying a lubricant to the surface of the photoreceptor has been proposed and put to practical use, as proposed in Patent Document 1. It has become. However, since such a mechanism is provided around the photosensitive member, an increase in size and complexity of the apparatus cannot be avoided, and problems such as an increase in cost and deterioration in maintainability occur. Further, as a different method for reducing the coefficient of friction of the photoreceptor, it has been proposed to add a lubricant that reduces the friction coefficient to the surface layer of the photoreceptor.
Specifically, there are those proposed in Patent Documents 2 to 35 and the like.
[0006]
Known lubricants include fluorine atom-containing resins such as polytetrafluoroethylene, powders such as spherical acrylic resins, metal oxide powders such as silicon oxide and aluminum oxide, and the like. In particular, a fluorine atom-containing resin containing a large amount of fluorine atoms has a great effect as a lubricant since the surface energy is extremely small. Such a fluorine atom-containing resin is used as crystalline fine particles, and after being dispersed in a binder resin such as an acrylic resin, a polyester resin, a polyurethane resin, or a polycarbonate resin, it is formed as a surface layer or a protective layer of the photoreceptor. Be filmed.
[0007]
However, when the content of the fluororesin fine particles is relatively small, even if the initial friction coefficient of the photoreceptor surface can be reduced, if the image is repeatedly output, the friction coefficient gradually increases. Therefore, it is conceivable to increase the amount of the fluororesin fine particles added as a means for maintaining a low friction coefficient. However, the property of the fluororesin fine particles has a problem that the tendency of aggregation in the resin solution is strong and uniform dispersion is difficult.
For example, various investigations have been made and proposed for the dispersion method of fluororesin fine particles, and specific examples include Patent Documents 36 to 40.
[0008]
However, most of the fluororesin fine particle-containing surface layers produced by these methods have a relatively small content, which is insufficient to maintain a low coefficient of friction over a long period of time. Also, in Patent Document 38, which has a description with a large content, there is no description about the particle size after dispersion, and since the content of the fluororesin fine particles is high, it is easier to aggregate and difficult to finely disperse. It is believed that there is. When a coating film is formed using such a coating solution, there are many large secondary aggregated particles in the coating film, and the unevenness of the coating film surface becomes large, or the fluororesin on the coating film surface. Cause localization of fine particles. If the unevenness on the surface of the coating film becomes large, it may be considered that cleaning failure or toner image disturbance is caused. Further, the localization of the fluororesin fine particles may cause a defective cleaning because the surface of the photoreceptor coating film has microscopically high and low friction coefficient portions. Furthermore, if the secondary aggregation diameter of the fluorine fine particles is too large, the laser light is scattered on the aggregate, which may cause an abnormal image due to disturbance of the exposure latent image and insufficient potential contrast due to insufficient light quantity. is there.
[0009]
Further, in the prior art, the fluorine atom-containing resin fine particles have problems in dispersibility and agglomeration as described above, and it is difficult to form a uniform and smooth film. In addition to often having image defects such as holes, such fluorine atom-containing resin fine particles accumulate discharge products on the outermost surface as a side effect that wear hardly occurs due to its low friction coefficient in repeated use, Depending on the toner used, so-called toner filming, in which the toner resin adheres in the form of a film on the outermost surface layer of the photoreceptor, is likely to occur, and the coefficient of friction is thus greatly increased. When such a phenomenon occurs, image flow occurs in a high humidity environment.
Therefore, even when a good image was obtained under a normal environment, there was a case where image flow occurred, for example, when the usage environment changed, specifically when the humidity increased.
In addition, there were cases where abnormal images were generated due to the paper dust generated from the paper used being stuck to the surface of the photoreceptor due to repeated use.
[0010]
Furthermore, depending on the binder resin used, the fluorine atom-containing resin fine particles may increase the friction coefficient of the entire surface layer due to the high surface energy and high friction coefficient of the binder resin.
Therefore, in order to improve this, as in the claim of Patent Document 36, the design is made so that the surface roughness falls within a suitable range, or as proposed in the claim of Patent Document 37, Although it was necessary to mechanically polish the surface, all of these increased the cost of the photoreceptor.
In addition, in the case where a resin having a known lubricity is added, the amount of wear is too large if it is added alone, and it has no durability that can withstand actual use.
In this way, the friction coefficient of the photoreceptor surface using various lubricants has been reduced, but the durability of the low friction coefficient during repeated use and abnormalities under various usage environments (especially in high humidity environments) Nothing satisfying the suppression of the image and the miniaturization of the apparatus has been obtained.
[0011]
[Patent Document 1] Japanese Patent Laid-Open No. 56-142567
[Patent Document 2] JP-A-52-117134
[Patent Document 3] Japanese Patent Application Laid-Open No. 53-107841
[Patent Document 4] Japanese Patent Laid-Open No. 54-26740
[Patent Document 5] JP-A-54-27434
[Patent Document 6] Japanese Patent Laid-Open No. 54-86340
[Patent Document 7] Japanese Patent Laid-Open No. 54-143142
[Patent Document 8] JP 54-143148 A
[Patent Document 9] JP-A-56-99345
[Patent Document 10] Japanese Patent Application Laid-Open No. 56-126638
[Patent Document 11] Japanese Patent Application Laid-Open No. 57-14845
[Patent Document 12] Japanese Patent Application Laid-Open No. 57-74748
[Patent Document 13] Japanese Unexamined Patent Publication No. 57-35863
[Patent Document 14] JP-A-57-76553
[Patent Document 15] JP-A-57-201240
[Patent Document 16] JP 58-44444 A
[Patent Document 17] JP 58-70229 A
[Patent Document 18] Japanese Patent Laid-Open No. 58-102949
[Patent Document 19] Japanese Patent Laid-Open No. 58-162958
[Patent Document 20] Japanese Patent Laid-Open No. 59-197042
[Patent Document 21] Japanese Patent Laid-Open No. 62-272281
[Patent Document 22] Japanese Patent Laid-Open No. 62-272282
[Patent Document 23] Japanese Patent Laid-Open No. 63-30850
[Patent Document 24] Japanese Patent Laid-Open No. 63-56658
[Patent Document 25] Japanese Patent Laid-Open No. 63-58352
[Patent Document 26] Japanese Patent Laid-Open No. 63-58450
[Patent Document 27] JP 63-61255 A
[Patent Document 28] JP-A-63-61256
[Patent Document 29] JP-A-63-65449
[Patent Document 30] JP-A-63-65450
[Patent Document 31] JP-A-63-65451
[Patent Document 32] Japanese Patent Laid-Open No. 63-73267
[Patent Document 33] Japanese Patent Laid-Open No. 63-221355
[Patent Document 34] Japanese Unexamined Patent Publication No. 63-249152
[Patent Document 35] Japanese Patent Laid-Open No. 63-131356
[Patent Document 36] JP-A-5-045920
[Patent Document 37] JP-A-5-265243
[Patent Document 38] Japanese Patent Laid-Open No. 6-130711
[Patent Document 39] JP-A-6-332219
[Patent Document 40] JP-A-8-087125
[Patent Document 41] Japanese Patent Laid-Open No. 50-82056
[Patent Document 42] JP 54-9632 A
[Patent Document 43] Japanese Patent Laid-Open No. 54-11737
[Patent Document 44] JP-A-4-175337
[Patent Document 45] JP-A-4-183719
[Patent Document 46] Japanese Patent Laid-Open No. 6-234841
[Patent Document 47] JP-A-57-78402
[Patent Document 48] Japanese Patent Laid-Open No. 61-20953
[Patent Document 49] Japanese Patent Laid-Open No. 61-296358
[Patent Document 50] JP-A-1-134456
[Patent Document 51] JP-A-1-179164
[Patent Document 52] JP-A-3-180851
[Patent Document 53] Japanese Patent Laid-Open No. 3-180852
[Patent Document 54] Japanese Patent Laid-Open No. 3-50555
[Patent Document 55] JP-A-5-310904
[Patent Document 56] JP-A-6-234840
[Patent Document 57] Japanese Patent Laid-Open No. 63-285552
[Patent Document 58] JP-A-1-88461
[Patent Document 59] JP-A-4-264130
[Patent Document 60] JP-A-4-264131
[Patent Document 61] JP-A-4-264132
[Patent Document 62] JP-A-4-264133
[Patent Document 63] JP-A-4-289867
[Patent Document 64] JP-A-1-134457
[Patent Document 65] JP-A-2-282264
[Patent Document 66] JP-A-2-304456
[Patent Document 67] Japanese Patent Application Laid-Open No. 4-133065
[Patent Document 68] Japanese Patent Laid-Open No. 4-133066
[Patent Document 69] JP-A-5-40350
[Patent Document 70] JP-A-5-202135
[Patent Document 71] Japanese Patent Laid-Open No. 51-73888
[Patent Document 72] Japanese Patent Laid-Open No. 56-150749
[Patent Document 73] Japanese Patent Laid-Open No. 6-234836
[Patent Document 74] JP-A-6-234837
[Patent Document 75] JP-A-3-109406
[Patent Document 76] Japanese Patent Application Laid-Open No. 64-1728
[Patent Document 77] Japanese Patent Application Laid-Open No. 64-13061
[Patent Document 78] Japanese Patent Application Laid-Open No. 64-19049
[Patent Document 79] JP-A-4-11627
[Patent Document 80] JP-A-4-225014
[Patent Document 81] JP-A-4-230767
[Patent Document 82] JP-A-4-320420
[Patent Document 83] JP-A-5-232727
[Patent Document 84] Japanese Patent Laid-Open No. 7-56374
[Patent Document 85] JP-A-9-127713
[Patent Document 86] JP-A-9-222740
[Patent Document 87] JP-A-9-265197
[Patent Document 88] JP-A-9-211877
[Patent Document 89] Japanese Patent Application Laid-Open No. 9-304956
[Patent Document 90] JP-A-9-166919
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide a highly durable electrophotographic photosensitive member that solves the above problems, maintains a low surface friction coefficient, has good electrophotographic characteristics, and can perform stable image formation and cleaning during repeated use. An object of the present invention is to provide a high-quality image forming apparatus with high reliability over a long period of time.
[0013]
[Means for Solving the Problems]
Therefore, in order to achieve the above-mentioned problems, the present inventors reduced the surface friction coefficient, maintained the low friction coefficient, and provided a highly durable, high-quality outermost layer that does not cause abnormal images under any use environment. As a result of intensive studies on an electrophotographic photosensitive member having an electrophotographic photosensitive member and an image forming apparatus using the electrophotographic photosensitive member, an electrophotographic photosensitive member having at least a photosensitive layer on a conductive support,
(A) fluororesin fine particles,
(B) a copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound,
(C) inorganic conductive fine particles,
When the average diameter of the projected image of the portion exposed on the surface of the primary particles and the secondary particles formed by agglomerating a plurality of primary particles in the outermost layer film of the fluororesin fine particles is D , 0.15 ≦ D ≦ 3 μm, the total projected area ratio of the particles occupying the surface is 10% or more, so that the above-mentioned problems can be solved and cleaning can be performed even after repeated use over a long period of time. The present inventors have found that an electrophotographic photosensitive member and an image forming apparatus that can output a good image without causing defects and the like, and have reached the present invention.
Here, the average diameter of the projected image refers to a particle or an aggregate of particles observed when the surface of the outermost layer is observed from a substantially vertical direction as one particle, and the inner diameter passing through the center of gravity of the projected image is incremented by 2 degrees. It is the average value measured by.
[0014]
The electrophotographic photosensitive member having the outermost layer having such a structure has a very small coefficient of friction on the surface of the photosensitive member, and the low coefficient of friction is maintained even after repeated use. And the durability of the photoreceptor is also increased.
The reason why the electrophotographic photosensitive member having the outermost layer having such a configuration maintains a low coefficient of friction even during repeated use and maintains good cleaning properties for a long period of time is as follows.
When the average diameter of the projected image of the portion exposed to the surface of the secondary particles formed by aggregating a plurality of primary particles and primary particles first, the range not corresponding to the invention according to the claim of the present invention is D, In the case where the total projected area ratio of the particles in the range of 0.15 ≦ D ≦ 3 μm on the surface is smaller than 10% with respect to the coating film surface, the following forms can be considered.
[0015]
As the first form, when the content of the fluororesin fine particles in the surface layer is small, as the second form, most of the fluororesin fine particles (including secondary particles) exposed on the surface are 0.15 μm. When it is smaller, the third form is when most of the fluororesin fine particles exposed on the surface are larger than 3 μm.
In the first embodiment, as described above, since the low coefficient of friction of the surface cannot be maintained in repeated use, there is a possibility that it will eventually cause a cleaning failure.
In the second mode, since the average diameter of the exposed portion of the coating film surface is less than 0.15 μm and the coating film surface is dispersed only with very fine fluororesin particles, the effect on the reduction of the friction coefficient is achieved. May be insufficient, resulting in poor cleaning. That is, when considering a mechanism that improves the slip cleaning property of the toner by setting the surface of the photosensitive member to have a low friction coefficient, the area where the toner contacts the primary particles and the secondary particles of the fluororesin fine particles becomes small. For this reason, the effect that the toner slides on the surface of the photoconductor is reduced by half, which may cause a cleaning failure.
Further, in the third embodiment, since a large number of particles larger than 3 μm are exposed on the surface, the surface roughness becomes large as described above, causing cleaning failure, or electrostatic latent image due to scattering of laser light. The occurrence of abnormal images due to deterioration of sharpness, reduction in potential contrast, etc. can be considered.
[0016]
Therefore, as shown in the present invention, the average diameter of the projected image of the portion exposed to the surface of the primary particles and the secondary particles formed by agglomerating a plurality of primary particles in the outermost surface layer of the fluororesin fine particles is D In this case, it is essential that the total ratio of the projected area ratio of the particles in the range of 0.15 ≦ D ≦ 3 μm to the surface is 10% or more.
[0017]
Furthermore, in this invention, it is included as one of the more preferable aspects that fluororesin microparticles | fine-particles contained in the outermost layer are 20 vol%-60 vol%.
Even if the outermost layer is reduced due to wear, the existing secondary layer is formed by forming a coating so that the content of the fluororesin fine particles is in the above range and the secondary particles are delocalized in the outermost layer. Since the particles are sequentially exposed, the total projected area ratio occupying the surface is always in the preferred range, and since the fluororesin fine particles are not present more than necessary, the mechanical strength of the outermost layer is also kept in the preferred range. Therefore, a decrease in wear resistance is also suppressed.
Furthermore, according to the present invention, the outermost layer is made to contain conductive fine particles using a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound having two or more NCO groups in one molecule as a binder resin. Abrasion resistance can be remarkably improved. The binder resin is a cross-linked resin, and is strong against mechanical deterioration due to its three-dimensional structure, and further to resin degradation on the outermost surface of the photoreceptor due to charging hazard, and also has a higher hardness than organic materials. The mechanical strength can be further improved by adding functional fine particles. That is, it is possible to provide a photoconductor having a low friction coefficient and excellent wear resistance even after repeated use, and to provide a high-quality image forming apparatus with high reliability over a long period of time.
[0018]
A copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound having two or more NCO groups in one molecule may not be cured successfully unless the ratio of the reaction components is matched, or may be sensitive to residual reactive groups. Since the body properties become very poor, the amount of the isocyanate compound is such that the ratio of the number of NCO groups to the OH groups in the acrylic polyol copolymer (NCO / OH) is in the range of 0.7 to 1.3. It is desirable to be.
When a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound having two or more NCO groups in one molecule is used, the sensitivity characteristic of the photosensitive member tends to be deteriorated. Therefore, it is necessary to add conductive fine particles. is there. The addition of inorganic conductive fine particles is also effective in improving the wear resistance as described above. As the inorganic conductive fine particles, tin oxide is suitable. If the particle size of the tin oxide fine particles is too large, the friction coefficient increases or the light transmittance decreases. If the particle size is too small, the conductivity is poor. Therefore, 0.1 to 1.0 μm is preferable. The ratio between the binder resin and tin oxide fine particles is low in sensitivity and wear resistance when there is little tin oxide, and when there is too much tin oxide, the electrical resistance of the film becomes small and image blurring occurs or the film becomes brittle. Since it becomes easy to wear, 40-80 wt% is good with respect to the copolymer resin which made the acrylic polyol copolymer and the isocyanate compound react.
[0019]
Furthermore, the present invention provides an image forming apparatus and an image forming method having at least the electrophotographic photosensitive member, the charging unit, the exposure unit, and the transfer unit of the present invention. As a result, the low coefficient of friction of the surface of the photosensitive member is maintained even after repeated use over a long period of time. For example, even if spherical toner is used, poor cleaning is unlikely to occur. Is less likely to occur and a good image can be obtained for a long time.
[0020]
According to the present invention, there is also provided an image forming apparatus comprising a contact member that contacts and rubs at least the surface of the electrophotographic photosensitive member while pressing the surface of the image forming apparatus. There are provided an image forming apparatus and an image forming method having a configuration in which the fluororesin fine particles contained therein are extended and covered on the surface of the outermost layer by the contact member.
A urethane rubber blade is particularly preferable as the material of the contact member that comes into contact because of the sustainability of the above effect.
As a result, the surface area with a low coefficient of friction is increased, so that the effect of reducing the coefficient of friction is remarkably improved, and the cleaning property and wear resistance are remarkably increased. Although this effect is not clearly understood, the following mechanism is conceivable.
[0021]
When the contact member rubs the outermost layer on which the fluororesin fine particles are exposed, the exposed portion of the fluororesin fine particles extends in the rubbing direction to cover the surface of the photoreceptor where the fluororesin fine particles are not present. At this time, as the surface of the outermost layer of the electrophotographic photosensitive member of the present invention, particles having a suitable size are present almost uniformly in a suitable range, so that the content of the fluororesin fine particles is not increased. The surface where fine particles are not present can be coated over almost the entire region, and placed over the entire surface of the photoreceptor, so that a low coefficient of friction can be expressed substantially uniformly. Furthermore, even if the outermost layer wears out, the inner fluororesin fine particles are deposited, so that it is possible to maintain a surface with a low coefficient of friction over a long period of time, maintaining a high level of cleaning performance and image quality. A high-quality image free from abnormal images such as a flow can be obtained over a long period of time.
When the surface of the photoreceptor rubbed with the SEM image was actually observed, the appearance of the fluororesin covering the surface due to the above phenomenon was observed.
[0022]
The present invention also provides a tandem image forming apparatus and an image forming method having at least a plurality of electrophotographic photoreceptors, charging means, exposure means, and transfer means.
As a result, a good full-color image can be obtained at a very high speed as compared with the one-drum type image forming apparatus.
[0023]
Further, according to the present invention, the intermediate transfer means for primarily transferring the toner image developed on the electrophotographic photosensitive member onto the intermediate transfer member and then secondary transferring the toner image on the intermediate transfer member onto the recording material. An image forming apparatus having a plurality of color toner images sequentially superimposed on an intermediate transfer member to form a color image, and the color image is secondarily transferred onto a recording material in a batch to thereby prevent color misregistration. A suppressed and good image is provided. Further, the layout through the intermediate transfer member improves the degree of freedom of layout in the image forming apparatus, and achieves downsizing of the apparatus and improvement in maintainability.
[0024]
The present invention also provides a process cartridge for an image forming apparatus comprising at least one of a charging unit, an exposure unit, a developing unit, and a transfer unit and the electrophotographic photosensitive member of the present invention.
As a result, the electrophotographic photosensitive member and other process members can be easily replaced in a short time, so that the time required for maintenance can be shortened and the cost can be reduced. Further, since the process member and the electrophotographic photosensitive member are integrated, there are also advantages such as improvement in the accuracy of the mounting position.
[0025]
That is, the present invention is as follows.
(1) In an electrophotographic photoreceptor having at least a photosensitive layer on a conductive support,
(A) fluororesin fine particles,
(B) a copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound,
(C) inorganic conductive fine particles,
The average diameter of the projected image of the portion exposed to the surface of the primary particles and the secondary particles formed by agglomerating a plurality of primary particles in the outermost surface layer film of the fluororesin fine particles (a) is D. An electrophotographic photosensitive member, wherein the total projected area ratio occupying the surface of the particles in the range of 0.15 ≦ D ≦ 3 μm is 10% or more,
(2) The proportion of the fluororesin fine particles (a) in the outermost layer is 20 vol% to 60 vol%, The electrophotographic photosensitive member according to (1),
(3) The copolymer resin (b)
(B-1) an acrylic polyol copolymer,
(B-2) an isocyanate compound having two or more NCO groups in one molecule;
The amount of the isocyanate compound (b-2) in the copolymer resin (b) is the amount of the NCO group and the OH group in the acrylic polyol copolymer (b-1). The electrophotographic photosensitive member according to (1) or (2) above, wherein the ratio (NCO / OH) of the number is in an amount ranging from 0.7 to 1.3,
(4) The inorganic conductive fine particles (c) are tin oxide fine particles, and the average particle size thereof is 0.1 to 1.0 μm, as described in any one of (1) to (3) above Electrophotographic photoreceptors,
(5) The weight ratio of the inorganic conductive fine particles (c) and the copolymer resin (b) contained in the outermost surface layer of the photoreceptor is
0.4 ≦ b / (b + c) ≦ 0.8
The electrophotographic photosensitive member according to any one of (1) to (4) above,
(6) The above (1) to (5), wherein the acrylic polyol copolymer is a methyl methacrylate-2-hydroxyethyl methacrylate copolymer or a styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer. The electrophotographic photoreceptor according to any one of
[0026]
(7) In an image forming apparatus having at least an electrophotographic photosensitive member, a charging unit, an exposing unit, and a transferring unit, the electrophotographic photosensitive member according to any one of (1) to (6). An image forming apparatus,
(8) The image forming apparatus as described in (7) above, wherein the shape of the toner used for image formation is spherical.
(9) The contact member that contacts the surface of the photosensitive member is at least one from a charging roller, a cleaning blade, a cleaning brush, an intermediate transfer belt, and a contact member that is only intended to extend fluororesin fine particles on the surface of the photosensitive member. The image forming apparatus according to (7) or (8), wherein two or more are selected,
(10) The image according to any one of (7) to (9), wherein the image forming apparatus is a tandem type having a plurality of electrophotographic photosensitive members, a charging unit, a developing unit, and a transfer unit. Forming equipment,
(11) Intermediate transfer means for primary transfer of the toner image developed on the electrophotographic photosensitive member onto the intermediate transfer member by the image forming apparatus and then secondary transfer of the toner image on the intermediate transfer member onto the recording material An image forming apparatus comprising: a plurality of color toner images sequentially superimposed on an intermediate transfer member to form a color image; and the color image is secondary-transferred collectively onto a recording material. (7) to (10), the image forming apparatus according to any one of
(12) For an image forming apparatus comprising at least one of a charging unit, an exposure unit, a developing unit, a cleaning unit, and a transfer unit and the electrophotographic photosensitive member according to any one of (1) to (6). Process cartridge,
Is provided.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of an electrophotographic photosensitive member of the present invention, and shows an electrophotographic photosensitive member having a structure in which a photosensitive layer is provided on a conductive support. 2, 3 and 4 show other examples of the structure of the electrophotographic photosensitive member according to the present invention. FIG. 2 shows a function separation type electrophotographic photosensitive member in which the photosensitive layer is composed of a charge generation layer (CGL) and a charge transport layer (CTL). FIG. 3 shows a conductive support and a function separation type. 2 shows an electrophotographic photosensitive member having an undercoat layer interposed between the photosensitive layer and the photosensitive layer. FIG. 4 shows an electrophotographic photosensitive member in which a protective layer is further formed on the photosensitive layer of the type shown in FIG. The electrophotographic photosensitive member according to the present invention may have other layers other than the above as long as it has at least a photosensitive layer on a conductive support, and the type of the photosensitive layer. May be combined arbitrarily.
[0028]
The conductive support used in the electrophotographic photosensitive member in the present invention includes a conductor or an insulator subjected to a conductive treatment, for example, a metal such as Al, Ni, Fe, Cu, Au, or an alloy thereof, polyester Insulating substrate such as polycarbonate, polyimide, glass, etc., metal such as Al, Ag, Au or In ₂ O ₃ , SnO ₂ A resin substrate in which a thin film of a conductive material such as carbon black, graphite, Al, Cu, Ni or the like is uniformly dispersed in a resin, and a conductive glass powder is uniformly dispersed to impart conductivity to the resin, Paper or the like that has been subjected to conductive treatment can be used. The shape of the conductive support is not particularly limited, and any of a plate shape, a drum shape, and a belt shape can be used. However, when a belt-like support is used, it is necessary to provide a driving roller and a driven roller inside. While the equipment is complicated and large, there are advantages such as increased flexibility in layout. However, when forming a protective layer, there is a possibility that cracks called cracks may occur on the surface due to insufficient flexibility of the protective layer, which may cause granular background stains. It is done. For this reason, a drum-like member having high rigidity is preferably used as the support.
[0029]
An undercoat layer may be provided between the conductive support and the photosensitive layer as necessary. Such an undercoat layer is provided for the purpose of improving adhesiveness, preventing moire, improving the coatability of the upper layer, and reducing residual potential. The undercoat layer generally contains a resin as a main component, but these resins are resins having high solubility resistance to general organic solvents in consideration of applying a photosensitive layer thereon with a solvent. It is desirable to be. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resins, alkyd-melamine resins, and epoxy resins. Examples thereof include curable resins that form a three-dimensional network structure. Further, fine powders such as metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like, or metal sulfides and metal nitrides may be added. These undercoat layers can be formed by a common coating method using an appropriate solvent.
Further, as the undercoat layer, a metal oxide layer formed by using, for example, a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like is also useful.
In addition, as such an undercoat layer, Al ₂ O ₃ Anodic oxidation, organic materials such as polyparaxylylene (parylene), SnO ₂ TiO ₂ , ITO, CeO ₂ An inorganic material such as the above may be provided by a vacuum thin film manufacturing method.
The thickness of the undercoat layer is suitably about 0.1 to 5 μm.
[0030]
As the kind of the photosensitive layer used in the electrophotographic photosensitive member of the present invention, any of Se type, OPC type and the like can be applied. Examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, and selenium-arsenic compounds. In particular, environmentally friendly and inexpensive OPC is good. Of these, the OPC system will be briefly described below.
The photosensitive layer in the present invention may be either a single layer type or a laminated type, but here, a laminated type will be described. First, the charge generation layer will be described.
[0031]
The charge generation layer is a layer mainly composed of a charge generation material, and a binder resin may be used as necessary. As the charge generation material, inorganic materials and organic materials can be used.
Examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, and selenium-arsenic compounds.
On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having carbazole skeleton, azo pigments having triphenylamine skeleton, azo pigments having diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having fluorenone skeleton, azo pigments having oxadiazole skeleton, azo pigments having bis-stilbene skeleton, azo pigments having distyryl oxadiazole skeleton, azo pigments having distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Goido based pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.
[0032]
As a binder resin used as necessary for the charge generation layer, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, Polyacrylamide or the like is used. These binder resins can be used alone or as a mixture of two or more.
Moreover, you may add a charge transport substance as needed. In addition to the binder resin described above, a polymer charge transporting material is also preferably used as the binder resin for the charge generation layer.
[0033]
As a method for forming the charge generation layer, a vacuum thin film preparation method and a casting method from a solution dispersion system can be largely mentioned.
Examples of the former method include a glow discharge polymerization method, a vacuum deposition method, a CVD method, a sputtering method, a reactive sputtering method, an ion plating method, and an accelerated ion injection method. This vacuum thin film manufacturing method can satisfactorily form the inorganic material or organic material described above.
In addition, in order to provide the charge generation layer by the latter casting method, a ball mill using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, butanone together with a binder resin, if necessary, the inorganic or organic charge generation material described above, It can be formed by dispersing with an attritor, sand mill or the like, and applying the solution after diluting the dispersion appropriately. The application can be performed using a commonly used method such as a dip coating method, spray coating, or bead coating.
The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm.
[0034]
The charge transport layer is a layer intended to hold a charged charge and to couple the charge generated and separated in the charge generation layer by exposure to the charged charge that has been held. In order to achieve the purpose of holding the charged charge, it is required that the electric resistance is high. Further, in order to achieve the purpose of obtaining a high surface potential with the charged charge that has been held, it is required that the dielectric constant is small and the charge mobility is good.
The charge transport layer for satisfying these requirements is composed of a charge transport material and a binder resin used as necessary. Such a charge transport layer can be formed by dissolving or dispersing these charge transport materials and a binder resin in an appropriate solvent, and applying and drying them. If necessary, an appropriate amount of additives such as a plasticizer, an antioxidant, and a leveling agent can be added to the charge transport layer in addition to the charge transport material and the binder resin.
Examples of the charge transport material include a hole transport material and an electron transport material.
[0035]
Examples of the electron transport material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.
[0036]
Examples of the hole transporting material include the electron donating materials shown below and are used favorably. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline , Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials can be used alone or as a mixture of two or more.
[0037]
Further, the polymer charge transporting material may have the following structure.
(A) a polymer having a carbazole ring
Examples thereof include poly-N-vinylcarbazole, compounds described in Patent Documents 41 to 46, and the like.
(B) a polymer having a hydrazone structure
For example, the compounds described in Patent Documents 47 to 56 are exemplified.
(C) Polysilylene polymer
For example, the compounds described in Patent Documents 57 to 63 are exemplified.
(D) a polymer having a triarylamine structure
Examples thereof include N, N-bis (4-methylphenyl) -4-aminopolystyrene, compounds described in Patent Documents 64-70, and the like.
(E) Other polymers
Examples include formaldehyde condensation polymers of nitropyrene, compounds described in Patent Documents 71 to 74, and the like.
[0038]
The polymer having an electron donating group used in the present invention is not limited to the above polymer, but also a copolymer of a known monomer, a block polymer, a graft polymer, a star polymer, or a patent document, for example. It is also possible to use a crosslinked polymer having an electron donating group as disclosed in JP-A-75.
In addition, examples of polycarbonates, polyurethanes, polyesters, and polyethers having a triarylamine structure that are further useful as the polymer charge transporting material used in the present invention include compounds described in Patent Documents 76 to 89. .
[0039]
Furthermore, examples of the binder resin that can be used in the charge transport layer include polycarbonate, polyester, methacrylic resin, acrylic resin, polyethylene, vinyl chloride, vinyl acetate, polystyrene, phenol resin, epoxy resin, polyurethane, acrylic polyol copolymer and isocyanate. A copolymer resin obtained by reacting a compound, polyvinylidene chloride, alkyd resin, silicone resin, polyvinyl carbazole, polyvinyl butyral, polyvinyl formal, polyacrylate, polyacrylamide, phenoxy resin, or the like is used. These binder resins can be used alone or as a mixture of two or more.
The film thickness of the charge transport layer is suitably about 5 to 100 μm. However, due to the recent demand for higher image quality, it has been attempted to make the charge transport layer thinner and achieve higher image quality of 1200 dpi or more. For this purpose, a thickness of about 5 to 30 μm is more preferable.
Additives such as other antioxidants and plasticizers used for rubbers, plastics, fats and the like may be added to the charge transport layer in the present invention.
Furthermore, a leveling agent may be added in the charge transport layer. Examples of such leveling agents include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain, and the amount used is 100 parts by weight of binder resin. From 0 to 1 part by weight is appropriate.
As the coating method, a commonly used method such as a dip coating method, spray coating, or bead coating method can be used.
[0040]
Further, when the charge transport layer is the outermost layer of the photoreceptor, at least the charge transport layer contains fluororesin fine particles, a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound, and inorganic conductive fine particles.
When the fluororesin fine particles are contained in the charge transport layer, it is preferable to increase the content in the vicinity of the surface of the charge transport layer in order to obtain the effect of reducing the friction coefficient more efficiently. That is, the fluororesin fine particles exposed mainly on the surface of the photoreceptor are the ones that exert the effect of reducing the friction coefficient, and the film that can no longer function as an electrophotographic photoreceptor due to wear of the charge transport layer due to repeated use. The fluororesin fine particles contained therein may be wasted, and may adversely affect the electrophotographic characteristics of the photoreceptor. As a method for producing an electrophotographic photosensitive member containing a large amount of fluororesin fine particles in the vicinity of the surface of the charge transport layer, for example, after applying a coating liquid for forming a charge transport layer that does not contain fluororesin fine particles, A method such as applying the applied charge transport layer forming coating solution is conceivable.
For example, specifically, a first charge transport layer is first formed on a charge generation layer using a coating liquid for forming a charge transport layer that does not contain fluororesin fine particles, and the content of fluororesin fine particles is formed thereon. By forming the second charge transport layer using the charge transport layer forming coating solution and drying it, a charge transport layer containing a large amount of fluororesin fine particles on the surface can be formed.
[0041]
Next, the case where the photosensitive layer has a single layer structure will be described.
When a single-layer photosensitive layer is provided by a casting method, in many cases, such a single-layer photosensitive layer is obtained by dissolving or dispersing a charge generating substance, a low molecular weight molecule, and a polymer charge transporting substance in an appropriate solvent, and applying and drying the solution. Can be formed. As the charge generating substance and the charge transporting substance, the materials described above can be used.
In addition, a plasticizer can be added to the single-layer photosensitive layer as necessary. Furthermore, as the binder resin that can be used as necessary, the binder resins mentioned above for the charge transport layer can be used as they are. In addition, the binder resin mentioned in the charge generation layer may be mixed and used.
Further, when the single-layer photosensitive layer is the outermost layer of the photosensitive member, at least the single-layer photosensitive layer contains a fluororesin fine particle, a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound, and inorganic conductive fine particles. contains.
As a result, the same effect as that of the charge transport layer described above can be obtained.
Further, as in the case of the above-described charge transport layer, it is preferable to increase the content of the fluororesin fine particles in the vicinity of the surface, and the same production method can be used for this method.
The thickness of the photosensitive layer of the single-layer photoreceptor is suitably about 5 to 100 μm.
[0042]
In the photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer. Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, aryl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, Known resins such as polybutylene terephthalate, polycarbonate, a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound, and an epoxy resin can be used.
When the protective layer is used, since the protective layer is the outermost layer, the protective layer contains at least fluororesin fine particles, a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound, and inorganic conductive fine particles. The protective layer is mainly intended for functional separation. In the present invention, by containing the fluororesin fine particles in a suitable dispersed state, the low friction coefficient is maintained even after repeated use over a long period of time, and the wear resistance is improved. Furthermore, since the protective layer is provided on the photosensitive layer with a relatively small film thickness, the influence on the electrical characteristics of the photoreceptor is relatively small, and the content is higher than that in the case where the charge transport layer contains fluororesin fine particles. There are advantages such that it can be made large, and it can be clearly separated from the charge transport layer by using a prescription specialized for low friction coefficient and wear resistance.
In addition, the inclusion of a charge transport material in the protective layer is very useful for suppressing the electrical characteristics of the photoreceptor, in particular, the deterioration of photosensitivity during repeated use and the increase in residual potential. This is considered to be because the charge can be smoothly transferred to the surface of the photoreceptor by providing the protective layer also with charge transportability. As such a charge transporting substance, the charge transporting substance used in the charge transporting layer mentioned above can be used.
Furthermore, various additives may be added to the protective layer of the electrophotographic photoreceptor according to the present invention for the purpose of improving adhesiveness, smoothness, and chemical stability.
[0043]
The protective layer according to the present invention is formed on the photosensitive layer using a conventional coating method such as dip coating, spray coating, blade coating, knife coating or the like. In particular, dip coating and spray coating are advantageous in terms of mass productivity and coating film quality.
However, since the dispersion state of the fluororesin fine particles on the surface of the photoconductor also changes depending on various conditions in coating, the setting of conditions for coating is very important.
For example, in spray coating, first, the coating liquid conditions include solid content concentration, in the case of a mixed solvent, its type and mixing ratio, and the spray device conditions include the coating liquid discharge rate, fog The air pressure, the distance between the spray tip and the surface of the coated part, the moving speed of the surface of the coated object, the number of overcoating, etc. are increased. For example, when a protective layer having a desired film thickness is formed by reducing the discharge amount of the coating liquid and increasing the number of repeated coatings, the coating film is formed in a dry state, and conversely, the discharge amount is increased. If the number of overcoating is reduced, a coating film is formed in a wetter state. Thus, it can be considered that even if one state of the coating film being applied is taken, the state of the surface fluororesin fine particles is affected. Therefore, it is necessary to study various coating conditions so that the surface fluororesin fine particles are in a state as in the present invention and to grasp a suitable range.
The thickness of the protective layer thus obtained is suitably in the range of 0.1 to 15 μm, more preferably 1 to 10 μm.
[0044]
In the photoreceptor of the present invention, an intermediate layer can be provided between the photosensitive layer and the protective layer. In the intermediate layer, a binder resin is generally used as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a generally used coating method as described above is employed. In addition, about 0.05-2 micrometers is suitable for the thickness of an intermediate | middle layer.
[0045]
The size of the secondary particle diameter of the fluororesin fine particles in the outermost surface layer of the photoreceptor of the present invention should be 0.15 to 3 μm and the surface should be coated with an area ratio of 10% or more, more preferably The size of the secondary particles is 0.3 to 1.5 μm. If the secondary particles exceed this range, the above-mentioned toner contact surface shortage may occur or abnormal images due to laser light scattering may be caused. Moreover, when the surface coverage is 10% or less in terms of area ratio, the low surface friction coefficient when viewed microscopically becomes insufficient.
The content of the fluororesin fine particles on the outermost layer of the photoreceptor is preferably 20 vol% to 60 vol%, and needs to be dispersed and exposed on the surface so as to fall within the scope of the invention according to the claims of the present invention. There is. If the content is less than 20 vol%, the projected area ratio of the fine particles exposed on the surface may be reduced, the sustainability of the low friction coefficient may be reduced, and if the content is greater than 60 vol%, It is considered that the binder resin content is inevitably reduced and the mechanical strength of the coating film is lowered.
[0046]
Next, observation by a scanning electron microscope (SEM) will be described as an example of a method for calculating the average diameter and area ratio of the projected image of the portion where the fluororesin fine particles of the present invention are exposed on the surface. This is not limited as long as the exposure state can be observed.
The surface of the electrophotographic photosensitive member in which the fluororesin fine particles are dispersed is photographed with an SEM, and the fluororesin fine particle image displayed in the obtained SEM image is analyzed using an image analyzer, The number, area ratio, etc. can be obtained. At this time, since the image obtained as the SEM image is projected from a substantially vertical direction of the surface, the projected image of the fluororesin fine particles is also a projected image in the vertical direction. Here, the average diameter of the projected image is an average value obtained by measuring the inner diameter passing through the center of gravity in increments of 2 degrees with respect to the projected image in which particles or aggregates of particles seen when observed are regarded as one particle.
[0047]
The image analysis device is capable of binaryly distinguishing the projection image of the fluororesin fine particles from the surrounding binder resin, and the condition that secondary particles in which a plurality of primary particles are aggregated can be approximated as large particles. It is necessary to be able to select. Furthermore, it is necessary to provide a program that can calculate at least the average diameter and the area ratio for each projected image of the fluororesin fine particles. As such an image analysis apparatus, a dedicated apparatus such as a high-detail image analysis system IP-1000 (manufactured by Asahi Engineering Co., Ltd.), a computer in which image analysis software Image-Pro Plus (manufactured by Planetron Co., Ltd.) is installed, or the like is used. Can do.
When the acceleration voltage is high, the SEM image may be obtained as image information up to the inside of the vicinity of the surface. In a system in which fluorine fine particles are dispersed in a binder resin, if the acceleration voltage is high, it may be observed through the fluororesin fine particles that are not exposed on the surface and are present near the surface. It is necessary to adjust so that the fluororesin fine particles exposed on the surface are projected.
For example, when a field emission scanning electron microscope S-4200 (manufactured by Hitachi, Ltd.) is used as the SEM, the acceleration voltage is preferably about 2 kv to 6 kv, but this depends on the device and the material of the photoreceptor. It is necessary to adjust accordingly.
The surface SEM image obtained in this way is taken into image analysis software, and the average diameter and area ratio of the individual fluororesin fine particles counted in the observation range are calculated. Can be observed.
[0048]
Examples of the fluororesin fine particles used for the outermost surface layer of the photoreceptor of the present invention include, for example, tetrafluoroethylene resin fine particles, perfluoroalkoxy resin fine particles, trifluorinated ethylene resin fine particles, hexafluoroethylene propylene resin fine particles, and vinyl fluoride resin. Fine particles, vinylidene fluoride resin fine particles, ethylene fluoride dichloride resin fine particles and copolymers thereof, and the like, and one or more of these are appropriately selected. Perfluoroalkoxy resin fine particles are preferable, and those having an average primary particle size in the range of 0.1 to 0.3 μm are preferable.
The fluororesin fine particles can be dispersed together with at least an organic solvent using a conventional method such as an attritor, a sand mill, a vibration mill, or an ultrasonic wave. Among these, dispersion by a ball mill or a vibration mill in which impurities from the outside are little mixed is more preferable from the viewpoint of dispersibility. As the material of the media used, all media such as zirconia, alumina, and agate that have been used in the past can be used. However, zirconia is particularly preferable from the viewpoint of the effect on the dispersibility of the fluororesin fine particles. More preferred. In some cases, dispersibility may be further increased by combining these dispersion methods. Moreover, it is not preferable that the primary particle diameter of the fluororesin fine particles is too large or too small to satisfy the average diameter of the preferred primary particles and secondary particles of the present invention. The particle size can be 0.1 to 10 μm, preferably 0.05 to 2.0 μm, and the particle size can be adjusted by a dispersion treatment described later as required.
Further, a dispersant may be added to the resin for the purpose of controlling the dispersibility of the fluororesin fine particles. As such a dispersant, a fluorine-based surfactant, a graft polymer, a block polymer, a coupling agent, and the like can be used.
[0049]
The acrylic polyol copolymer used for the outermost surface layer of the photoreceptor of the present invention is not limited to the following, but is methyl methacrylate (abbreviated as “MMA”)-2-hydroxyethyl methacrylate (abbreviated as “2-HEMA”). A copolymer or styrene (abbreviated as “St”)-MMA-2-HEMA copolymer is particularly desirable. When the copolymer is a MMA-2-HEMA copolymer, the content of 2-HEMA is 15 to 45% by weight, preferably 25 to 45% by weight, more preferably 30 to 40% by weight. Used. When the copolymer is a St-MMA-2-HEMA copolymer, the content of 2-HEMA is 15 to 45% by weight, preferably 25 to 45% by weight, more preferably 30 to 40% by weight. %, And the remaining St and MMA have a MMA / St weight ratio of about 8/2 or more.
[0050]
Examples of the isocyanate compound having two or more NCO groups in one molecule used in the present invention include hexamethylene diisocyanate [HMDI], lysine diisocyanate [LDI], trimethylhexamethylene diisocyanate [TMDI], and dimer acid diisocyanate [DDI]. Aliphatic diisocyanates: 4,4′-methylenebis (cyclohexyl isocyanate) [hydrogenated MDI], methylcyclohexane-2,4- (2,6) diisocyanate [hydrogenated TDI], 1,3- (isocyanatomethyl) cyclohexane Cycloaliphatic diisocyanates such as [hydrogenated XDI]; aromatic diisocyanates such as xylylene diisocyanate [XDI], metaxylylene diisocyanate [MXDI], and isophorone diisocyanate [IPDI] And diisocyanate monomers such as
Polyisocyanates obtained by reacting the above isocyanate compounds with polyhydric alcohols can also be used. Furthermore, a modified polyisocyanate may be used depending on the purpose. Examples thereof also include polyisocyanates obtained by selecting trimethylolpropane [TMP] as the polyhydric alcohol, selecting HMDI or hydrogen IPDI as the diisocyanate, and reacting them.
[0051]
[Chemical 1]

[0052]
Similarly, an isocyanate polymer is mentioned. For example, HMDI 3 mol water 1 mol adduct is also mentioned.
[Chemical 2]

[0053]
Moreover, the following uretdione, isocyanate, etc. can also be used.
[Chemical 3]

[0054]
Specific examples include HMDI isocyanate and IPDI isocyanate.
[Formula 4]

[0055]
Also,
[Chemical formula 5]

An isocyanate such as can also be exemplified.
[0056]
A copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound having two or more NCO groups in one molecule may not be cured successfully unless the ratio of the reaction components is matched, or may be sensitive to residual reactive groups. Since the body properties become very poor, the amount of the isocyanate compound is such that the ratio of the number of NCO groups to the OH groups in the acrylic polyol copolymer (NCO / OH) is in the range of 0.7 to 1.3. It is desirable to be.
The molecular weight of these copolymer resins is 2,000 to 200,000, preferably 10,000 to 40,000 on a number average basis.
[0057]
The use of a copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound having two or more NCO groups in one molecule as the outermost layer of the photoreceptor tends to deteriorate the sensitivity characteristics of the photoreceptor. Need to be added. The addition of inorganic conductive fine particles is also effective in improving the wear resistance as described above.
Examples of the inorganic conductive fine particles used in the outermost surface layer of the photoreceptor of the present invention include metal powders such as copper, tin, aluminum, and indium, tin oxide, tin oxide doped with antimony, tin oxide doped indium oxide, and the like. In particular, tin oxide is preferable.
If the particle size of the tin oxide fine particles is too large, the friction coefficient increases or the light transmittance decreases, and if the particle size is too small, the conductivity deteriorates, so 0.1 to 1.0 μm is preferable. The ratio between the binder resin and tin oxide fine particles is low in sensitivity and wear resistance when there is little tin oxide, and when there is too much tin oxide, the electrical resistance of the film becomes small and image blurring occurs or the film becomes brittle. Since it becomes easy to wear, 40-80 wt% is good with respect to the copolymer resin which made the acrylic polyol copolymer and the isocyanate compound react.
[0058]
In addition to the inorganic conductive fine particles, a filler material may be added to the outermost layer of the photoreceptor of the present invention for the purpose of further improving the wear resistance. As the filler, there are an organic filler and an inorganic filler. From the viewpoint of the hardness of the filler, the use of the inorganic filler is advantageous for improving the wear resistance. Examples of such inorganic filler materials include metal oxides such as silica, titanium oxide, alumina, zirconium oxide, bismuth oxide and calcium oxide, metal fluorides such as calcium fluoride and aluminum fluoride, potassium titanate, and nitride. Inorganic materials such as boron are exemplified.
[0059]
These fillers can be surface-treated with at least one surface treatment agent, and it is preferable to do so from the viewpoint of dispersibility of the filler. Decreasing the dispersibility of the filler not only increases the residual potential, but also decreases the transparency of the coating, causes defects in the coating, and decreases the wear resistance. It can develop into a big problem. As the surface treatment agent, all conventionally used surface treatment agents can be used, but a surface treatment agent capable of maintaining the insulating properties of the filler is preferable. For example, titanate coupling agents, aluminum coupling agents, zircoaluminate coupling agents, higher fatty acids, etc., or mixed treatment of these with silane coupling agents, Al ₂ O ₃ TiO ₂ , ZrO ₂ , Silicone, aluminum stearate, etc., or a mixture thereof is more preferable from the viewpoint of filler dispersibility and image blur. The treatment with the silane coupling agent is strongly influenced by image blur, but the influence may be suppressed by performing a mixing treatment of the surface treatment agent and the silane coupling agent. The surface treatment amount varies depending on the average primary particle size of the filler used, but is preferably 3 to 30 wt%, more preferably 5 to 20 wt%. If the surface treatment amount is less than this, the filler dispersing effect cannot be obtained, and if the surface treatment amount is too much, the residual potential is significantly increased.
[0060]
Next, the image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 5 is a schematic view for explaining the image forming apparatus of the present invention. Note that the following modifications also belong to the category of the present invention.
As shown in FIG. 5, the image forming apparatus using the electrophotographic photosensitive member according to the present invention includes a drum-shaped photosensitive member 1, a charging charger 3, a pre-transfer charger 7, and a transfer charger 10. , A separation charger 11 and a pre-cleaning charger 13. The shape of the photoreceptor 1 is not limited to a drum shape, and may be, for example, a sheet shape or an endless belt shape. As various chargers, known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller can be used.
As the transfer means, the above charger can be generally used, but a combination of a transfer charger and a separation charger as shown in the figure is effective.
The light source such as the image exposure unit 5 and the charge removal lamp 2 emits light such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL). All things can be used. Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.
Such a light source or the like can irradiate the photoreceptor with light by providing a transfer step, a static elimination step, a cleaning step, or a pre-exposure step in combination with light irradiation in addition to the steps shown in FIG. .
[0061]
The toner developed on the photosensitive member 1 by the developing unit 6 is transferred to the transfer paper 9, but not all is transferred, and the toner remains on the photosensitive member 1. Such toner is removed from the photoreceptor 1 by the cleaning brush 14 and the cleaning blade 15. Cleaning may be performed by the cleaning brush 14 or the cleaning blade 15 alone, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush 14. When the electrophotographic photosensitive member is positively (negatively) charged and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. A positive image can be obtained by developing this with negative (positive) toner (electrodetection fine particles), and a negative image can be obtained by developing with positive (negative) toner. As this developing means, a known method is applied, and a known method is also used as the charge eliminating means.
[0062]
The image forming apparatus of the present invention can include a contact member that contacts and rubs against the electrophotographic photosensitive member.
As the pressed contact member, a contact member for rubbing the exposed portion of the fluororesin fine particles may be provided, a contact charging member such as a charging roller, a cleaning member such as a cleaning blade or a cleaning brush, a transfer A mechanism for applying pressure to a member generally used in an image forming apparatus such as a transfer member such as a belt or an intermediate transfer belt may be provided. Here, a case where the surface of the photoreceptor is rubbed with the cleaning blade 15 will be described as an example. The cleaning blade 15 has a great effect in that the surface of the photosensitive member 1 is rubbed on the entire surface while pressing the surface of the photosensitive member 1 with a substantially uniform pressure, and the fluororesin fine particles are evenly adhered to the surface.
When coating the fluororesin with the cleaning blade 15, various conditions of the cleaning blade 15 include a blade contact angle of 10 to 30 degrees, a contact pressure of 0.3 to 4 g / mm, and rubber hardness of the rubber used as the blade of 60 to 70 degrees. , Rebound resilience 30-70%, Young's modulus 30-60kgf / cm ² A thickness of 1.5 to 3.0 mm, a free length of 7 to 12 mm, and a blade edge biting amount of 0.2 to 2 mm are suitable, and a urethane rubber blade as a material satisfying such physical properties Is particularly preferred.
[0063]
FIG. 6 shows an example of another process using the image forming apparatus according to the present invention. In FIG. 6, a photoconductor 22 is an electrophotographic photoconductor of the present invention, which is driven by a driving roller 23, charged by a charging charger 20, image exposure by an image exposure unit 21, development (not shown), and transfer charger 25. , Transfer using the cleaning, cleaning by the cleaning brush 26, and static elimination by the static elimination lamp 27 are repeated.
[0064]
An embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as a full-color image forming apparatus to which the present invention is applied.
FIG. 7 is a schematic configuration diagram of the printer according to the present embodiment.
In FIG. 7, a photosensitive drum 36, which is a latent image carrier, is rotated counterclockwise in the drawing, and its surface is uniformly charged by a charging charger 33 using a corotron or a scorotron, and then a laser (not shown). An electrostatic latent image is carried in response to scanning with laser light L emitted from the optical device. Since this scanning is performed based on single-color image information obtained by decomposing a full-color image into yellow, magenta, cyan, and black color information, a single-color electrostatic image of yellow, magenta, cyan, or black is formed on the photosensitive drum 36. A latent image is formed. A revolver developing unit 30 is disposed on the left side of the photosensitive drum 36 in the drawing. This has a yellow developing unit, a magenta developing unit, a cyan developing unit, and a black developing unit in a rotating drum-shaped casing, and each developing unit is sequentially moved to a developing position facing the photosensitive drum 36 by rotation. Move. The yellow developer, magenta developer, cyan developer, and black developer are for developing an electrostatic latent image by attaching yellow toner, magenta toner, cyan toner, and black toner, respectively. On the photosensitive drum 36, electrostatic latent images for yellow, magenta, cyan, and black are sequentially formed, and these are sequentially developed by the developing units of the revolver developing unit 30 to be yellow toner images, magenta toner images, cyan. A toner image and a black toner image are obtained.
[0065]
An intermediate transfer unit is disposed on the downstream side of the photosensitive drum 36 from the development position. This is because the intermediate transfer belt 38 stretched by a tension roller 39a, an intermediate transfer bias roller 37 as a transfer means, a secondary transfer backup roller 39b, and a belt drive roller 39c is driven by rotation of the belt drive roller 39c. Move endlessly clockwise. The yellow toner image, magenta toner image, cyan toner image, and black toner image developed on the photosensitive drum 36 enter an intermediate transfer nip where the photosensitive drum 36 and the intermediate transfer belt 38 are in contact with each other. Then, while being influenced by the bias from the intermediate transfer bias roller 37, the toner image is superimposed on the intermediate transfer belt 38 and intermediately transferred to form a four-color superimposed toner image.
[0066]
The surface of the photosensitive drum 36 that has passed through the intermediate transfer nip with the rotation is cleaned of the transfer residual toner by the drum cleaning unit 35. The drum cleaning unit 35 is for cleaning the transfer residual toner by a cleaning roller to which a cleaning bias is applied. However, a cleaning brush made of a fur brush, a mag fur brush, or a cleaning blade may be used. .
[0067]
The surface of the photosensitive drum 36 from which the transfer residual toner has been cleaned is discharged by the discharging lamp 34. As the charge removal lamp 34, a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), an electroluminescence (EL), or the like is used. A semiconductor laser is used as the light source of the laser optical device. About the light emitted from these, only a desired wavelength range may be used by various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter. .
On the other hand, the registration roller pair 41 sandwiching the transfer paper 40 sent from a paper feed cassette (not shown) between the two rollers can superimpose the transfer paper 40 on the four-color superimposed toner image on the intermediate transfer belt 38. It feeds toward the secondary transfer nip at the timing. The four-color superimposed toner image on the intermediate transfer belt 38 is secondary-transferred collectively onto the transfer paper 40 under the influence of the secondary transfer bias from the paper transfer bias roller 43 in the secondary transfer nip. A full color image is formed on the transfer paper 40 by this secondary transfer.
[0068]
The transfer paper 40 on which the full color image is formed is sent to the paper transport belt 44 by the transfer belt 42.
The conveying belt 44 feeds the transfer paper 40 received from the transfer unit into the fixing device 45.
The fixing device 45 conveys the transferred transfer paper 40 while being sandwiched in a fixing nip formed by the contact between the heating roller and the backup roller.
The full-color image on the transfer paper 40 is fixed on the transfer paper 40 under the influence of heating from the heating roller and pressure applied in the fixing nip.
[0069]
Although not shown, a bias for attracting the transfer paper 40 is applied to the transfer belt 42 and the conveyance belt 44. In addition, a paper neutralization charger that neutralizes the transfer paper 40 and three belt neutralization chargers that neutralize each belt (intermediate transfer belt 38, transfer belt 42, and conveyance belt 44) are provided. The intermediate transfer unit also includes a belt cleaning unit having the same configuration as that of the drum cleaning unit 35, thereby cleaning the transfer residual toner on the intermediate transfer belt 38.
[0070]
FIG. 8 shows a modification of the printer according to this embodiment. This apparatus is a so-called tandem printer, and does not share the photosensitive drum 50 for each color, but includes photosensitive drums 50Y, 50M, 50C, and 50Bk for the respective colors. The drum cleaning unit 55, the charge eliminating lamp 53, and the charging roller 54 for uniformly charging the photosensitive drum 50 are also provided for each color. In the printer shown in FIG. 7, the charging charger 33 is provided as the drum uniform charging means, but in this printer, the charging roller 54 is provided.
In the tandem system, latent image formation and development of each color can be performed in parallel, so that the image formation speed can be made much faster than the revolver system.
The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. The process cartridge is a single device (part) that contains a photosensitive member and includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a charge eliminating unit. There are many shapes and the like of the process cartridge, but a general example is shown in FIG. The process cartridge includes a photosensitive drum 66, a charging charger 67, an image exposure unit 69, a cleaning brush 68, a developing roller 70, and the like.
[0071]
【Example】
Hereinafter, although an example is given and the present invention is explained, the present invention is not restricted by an example. All parts are parts by weight.
<Example 1>
An undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following composition are sequentially applied onto an aluminum cylinder by dip coating and dried to obtain a 3.5 μm undercoat layer, 0. A 2 μm charge generation layer and a 22 μm charge transport layer were formed.
◎ Undercoat layer coating solution
400 parts of titanium dioxide powder
65 parts of melamine resin
120 parts alkyd resin
2-butanone 400 parts
[0072]
◎ Charge generation layer coating solution
12 parts of bisazo pigment with the following structure
[Chemical 6]

Polyvinyl butyral 5 parts
2-butanone 200 parts
400 parts of cyclohexanone
[0073]
◎ Charge transport layer coating solution
Polycarbonate (Z polycarbonate, manufactured by Teijin Kasei) 8 parts
10 parts of charge transport material of the following structural formula
[Chemical 7]

Tetrahydrofuran 100 parts
[0074]
Further, the following protective layer coating solution is spray-coated on the charge transport layer [spray gun: Peacecon PC308, manufactured by Olympus, air pressure: 2 kgf / cm ² The film was dried at 150 ° C. for 60 minutes to form a protective layer of about 5 μm, and the electrophotographic photosensitive member 1 was produced.
[0075]
◎ Protective layer coating solution
A solution having the following composition was circulated for 30 minutes under a 100 MPa pressure in a high-speed liquid collision dispersion device (device name: ULTIMIZER HJP-25005, manufactured by Sugino Machine Co., Ltd.), and perfluoroalkoxy (hereinafter abbreviated as PFA) resin particle dispersion ▲ 1 I got ▼.
38 parts of PFA resin particles (MPE-056, manufactured by Mitsui Fluorochemicals)
Dispersing aid (Modiper F210, manufactured by NOF Corporation) 3.8 parts
1000 parts of tetrahydrofuran
300 parts of cyclohexanone
[0076]
Next, a solution of styrene (St) to methyl methacrylate (MMA) to 2-hydroxyethyl methacrylate (2-HEMA) copolymer which is an acrylic polyol copolymer (the solvent is a mixed solvent of cellosolve acetate and methyl isobutyl ketone) Tin oxide particles (manufactured by Mitsubishi Metal Corporation) were prepared. As the acrylic polyol copolymer, a monomer constitution ratio (weight ratio) St / MMA / 2-HEMA / 2-HEMA = 28/42/30 was used.
10 parts of the above St / MMA / 2-HEMA copolymer solution (solid content)
90 parts of tin oxide particles
Was mixed with a mixed solvent of cyclohexanone and tetrahydrofuran (mixed solvent weight ratio 100/30) so that the total solid content concentration was 20 wt%, and dispersed in a ball mill for 100 hours. Subsequently, the dispersion, the resin liquid for dilution (the above-mentioned acrylic polyol copolymer resin, concentration of about 10%), and HMDI polyisocyanate (Sumijoule HT, manufactured by Sumitomo Bayer Urethane Co., Ltd.) are mixed with tin oxide in the dispersion. The mixture was mixed so that the ratio of the particles and the solid content of the resin was 6: 4, and the ratio of the number of hydroxyl groups of the isocyanate group and the acrylic polyol copolymer was 1: 1, whereby a dispersion (2) was obtained.
Dispersion liquid (1) and dispersion liquid (2) were mixed so as to have the composition ratio shown in Table 1, and then cyclohexanone and tetrahydrofuran (mixed solvent weight ratio 100/30) were adjusted so that the total solid content concentration became 3 wt%. ), And then adjusted by irradiation with ultrasonic waves for 10 minutes to obtain a protective layer coating solution.
[0077]
<Examples 2-3, Comparative Example 1>
In Example 1, electrophotographic photosensitive members 2 to 4 were produced in the same manner except that the composition weight ratio of the protective layer was changed as shown in Table-1.
<Comparative example 2>
An electrophotographic photosensitive member 5 was produced in the same manner as in Example 1 except that the protective layer coating solution was changed as follows.
[0078]
A solution having the following composition was blended and circulated for 30 minutes under a pressure of 100 MPa in a high-speed liquid collision dispersion device (device name: ULTIMIZER HJP-25005, manufactured by Sugino Machine Co., Ltd.) to prepare a protective layer coating solution.
55 parts of PFA resin particles (MPE-056, manufactured by Mitsui Fluorochemicals)
Dispersing aid (Modiper F210, manufactured by NOF Corporation) 5.5 parts
Polycarbonate (Z Polyca, Teijin Chemicals) 39.5 parts
Tetrahydrofuran 2000 parts
600 parts of cyclohexanone
[0079]
<Examples 4 to 5>
Electrophotographic photoreceptors 6 and 7 were produced in the same manner as in Example 1 except that the ratio of the NCO group of the isocyanate compound of the protective layer to the OH group of the acrylic polyol copolymer was changed as shown in Table-1.
[0080]
<Examples 6 to 7>
Electrophotographic photoreceptors 8 and 9 were produced in the same manner as in Example 1 except that the amount of tin oxide added to the protective layer was changed as shown in Table 1.
[0081]
<Examples 8 to 9>
Electrophotographic photoreceptors 10 and 11 were produced in the same manner as in Example 1 except that the average particle diameter of tin oxide was changed as shown in Table 1 by changing the ball mill time.
[0082]
<Examples 10 to 11>
Electrophotographic photoreceptors 12 and 13 were produced in the same manner as in Example 1, except that the St / MMA / 2-HEMA ratio of the acrylic polyol copolymer was changed as shown in Table-1.
[0083]
<Examples 12 to 14>
Electrophotographic photoreceptors 14 to 16 were produced in the same manner as in Example 1 except that the type of isocyanate compound was changed as shown in Table 1.
[0084]
<Example 15>
An electrophotographic photoreceptor 17 was produced in the same manner as in Example 1, except that the PFA resin fine particles were changed to polytetrafluoroethylene fine particles (TLP10F-1, manufactured by Mitsui Fluorochemicals).
[0085]
[Table 1]

[0086]
Next, production examples of the polymerized toner used in this example are shown.
Toner production example 1
1) Preparation of monomer composition
70 parts of styrene monomer
30 parts of n-butyl methacrylate
5 parts of polystyrene
2,5-di-tert-butylsalicylic acid zinc salt 2 parts
Carbon black 6 parts
The above polymerizable monomer mixture was dispersed and mixed for 24 hours using a ball mill to prepare a monomer composition.
2) Granulation and polymerization
Into a flask equipped with a stirrer, thermometer, inert gas introduction tube and a porous glass tube with a pore diameter of 110,000 kg, a pore volume of 0.42 cc / g, 10φ × 50 mm, 400 ml of 2% polyvinyl alcohol aqueous solution was taken, and nitrogen gas Was stirred at room temperature, and oxygen in the reaction vessel was replaced with nitrogen.
[0087]
Next, 1.56 g of azobisisobutylnitrile was added to 113 g of the monomer composition of 1), dissolved by stirring, passed through a porous glass tube using a pump, added into an aqueous polyvinyl alcohol solution, and after addition, polyvinyl alcohol The monomer composition was circulated at a rate of about 120 ml / min for 2 hours using the pump and the porous glass tube, and then the internal temperature was set to 70 ° C. and polymerization was performed for 8 hours.
After cooling to room temperature and allowing to stand overnight, the supernatant was removed, water was added, the mixture was stirred for 1 hour, filtered and dried to obtain a toner. When the particle diameter of this toner was measured with a Coulter counter, the average particle diameter was 8.5 μm, and the particles in the range of 5 to 10 μm were 95% of the total, and the particle size distribution was extremely narrow.
[0088]
Evaluation Example 1
The suspension containing the toner particles obtained in Toner Production Example 1 is passed through an imaging unit detection zone on a flat plate, the particle image is optically detected by a CCD camera, and the perimeter of an equivalent circle having the same projected area is obtained. The average circularity, which is a value obtained by dividing by the perimeter of real particles, was evaluated. This value can be measured as an average circularity by a flow type particle image analyzer FPIA-2000. As a specific measurement method, as a dispersant in 100 to 150 ml of water from which impure solids have been removed in advance. A surfactant, preferably alkylbenzene sulfonate, is added in an amount of 0.1 to 0.5 ml, and a sample to be measured is further added in an amount of about 0.1 to 0.5 g. It is obtained by performing dispersion treatment for ˜3 minutes and measuring the shape and distribution of the toner with the above apparatus at a dispersion concentration of 3000 to 10,000 / μl. As a result of the examination so far, it has been found that a toner having 0.960 or more is effective for forming a high-definition image having a reproducibility with an appropriate density. 980 to 1.000. The circularity of the toner produced in Toner Production Example 1 was 0.98.
[0089]
Evaluation Example 2 (Secondary particle diameter, coating area ratio)
Ten arbitrary observation points on the surface of the obtained electrophotographic photosensitive members 1 to 17 were photographed at 4500 times by FE-SEM, and the obtained SEM photograph was obtained using image processing software (IMAGE Pro Plus). 0.15 ≦ D, where D is the average diameter of the projected image of the primary particles in the outermost layer film of the resin fine particles and the exposed portions of the secondary particles formed by agglomerating a plurality of primary particles. The total projected area ratio of the particles in the range of ≦ 3 μm on the surface was determined.
[0090]
Evaluation example 3 (surface friction coefficient)
About the obtained electrophotographic photoreceptors 1-17, the surface friction coefficient was evaluated using the Euler belt system currently disclosed by patent document 90 grade | etc.,. As used herein, the belt is a medium-quality high-quality paper, and is stretched around the circumference of the photoconductor, as shown in FIG. Apply a load of 100 g, install a force gauge (spring balance) on the other side, observe the movement of the belt while gradually pulling the force gauge, read the load when the movement started, and calculate with the following formula . In FIG. 10, a load: 100 g weight, a belt: Type 6200 / T / A4 paper / 30 mm width (cut in the direction of the gap), and two double clips are used. In the equation, μ represents a friction coefficient, F represents a tensile force, and W represents a load.
μ = 2 / π × ln (F / W) W = 100 g
[0091]
Evaluation Example 4 (Durability Life A)
The obtained electrophotographic photoreceptors 1 to 3 and 6 to 17 and the comparative electrophotographic photoreceptors 4 and 5 were replaced with Ricoh's imgio Color 5100 remodeling machine (the image exposure light source was replaced with a 655 nm semiconductor laser, and the lubricant application means was replaced. A total of 150,000 sheets were continuously printed, and the initial image and the image after 150,000 sheets were evaluated at that time. Further, the light portion potential at the initial stage and after printing 150,000 sheets was measured. Furthermore, the amount of wear was evaluated from the difference in film thickness at the initial stage and after printing 150,000 sheets.
[0092]
[Table 2]

[0093]
Evaluation example 5 (endurance life B)
The obtained electrophotographic photoconductors 1 to 18 and comparative electrophotographic photoconductors 1 to 9 were modified from Ricoh's imgio Color 5100 machine (the toner was changed to that prepared in Production Example 1 and the image exposure light source was a semiconductor laser having a wavelength of 655 nm. In addition, a total of 150,000 sheets were printed continuously, and the initial image and the image after 150,000 sheets were evaluated. Further, the light portion potential at the initial stage and after printing 150,000 sheets was measured. Furthermore, the amount of wear was evaluated from the difference in film thickness at the initial stage and after printing 150,000 sheets.
[0094]
[Table 3]

[0095]
Evaluation example 6 (endurance life C)
The obtained electrophotographic photoreceptors 1 to 18 and comparative electrophotographic photoreceptors 1 to 9 are mounted on a Ricoh IPSiO Color 8100 remodeling machine (the toner is changed to that prepared in Production Example 1), and the total is continuously obtained. 75,000 sheets were printed, and the initial image and the image after printing 75,000 sheets were evaluated. Further, the light portion potential at the initial stage and after printing 75,000 sheets was measured. Furthermore, the amount of wear was evaluated from the difference in film thickness at the initial stage and after printing 75,000 sheets.
[0096]
[Table 4]

[0097]
From the evaluation results of Tables 2, 3, and 4, the fluororesin fine particles satisfying the requirements of the claims of the present invention are contained in the outermost surface layer of the photoreceptor not only in the case of the pulverized toner but also in the spherical toner. It has become possible to maintain a highly stable and low surface friction coefficient. At the same time, the amount of wear was suppressed and it was confirmed that the wear resistance was greatly improved. Further, it was confirmed that even after repeated printing, the bright portion potential rises little, and no defective cleaning occurs and a high-quality image can be obtained stably.
On the other hand, a photoconductor containing fluororesin fine particles that do not satisfy the requirements of the claims of the present invention and a photoconductor that is not a copolymer resin obtained by reacting an acrylic polyol copolymer and an isocyanate compound as a binder resin have a wear amount. In addition, the cleaning was poor.
[0098]
【The invention's effect】
According to the present invention, the outermost surface layer of the photoreceptor contains fluororesin fine particles, and the fluororesin fine particles are formed on the surface of the secondary particles formed by agglomerating a plurality of primary particles and primary particles in the outermost layer film. When the average diameter of the projected image of the exposed portion is D, the total projected area ratio of the particles in the range of 0.15 ≦ D ≦ 3 μm to the surface is 10% or more. The friction coefficient can be kept low for a long period of time, and the toner cleaning property is improved. By using a thermosetting resin as the binder resin on the outermost layer of the photoreceptor and adding inorganic conductive fine particles, the abrasion resistance of the photoreceptor can be remarkably improved.
[0099]
That is, it is possible to provide a photoconductor having a low friction coefficient and excellent wear resistance even after repeated use, and to provide a highly reliable high-quality image forming apparatus for a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an electrophotographic photosensitive member of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of another configuration example of the electrophotographic photosensitive member in the present invention.
FIG. 3 is a schematic cross-sectional view showing an example of another configuration example of the electrophotographic photosensitive member in the present invention.
FIG. 4 is a schematic cross-sectional view showing an example of another configuration example of the electrophotographic photosensitive member in the present invention.
FIG. 5 is a schematic diagram for explaining an image forming apparatus of the present invention.
FIG. 6 is a schematic view showing another example of the process using the image forming apparatus according to the present invention.
FIG. 7 is a schematic diagram illustrating an example of a printer according to the present invention.
FIG. 8 is a schematic diagram illustrating a modification of the printer according to the present embodiment.
FIG. 9 is a schematic view showing an example of a process cartridge according to the present invention.
FIG. 10 is a conceptual diagram showing a method for evaluating a surface friction coefficient in Examples.
[Explanation of symbols]
1,22 photoconductor
2,27,34,53 Static elimination lamp
3, 25, 33, 67 Charger charger
5,69 Image exposure unit
6,30 Development unit
7 Charger before transfer
14, 26, 68 Cleaning brush 14
15 Cleaning blade
36, 50, 66 Photosensitive drum
38 Intermediate transfer belt
42 Transfer belt

Claims (12)

In an electrophotographic photoreceptor having at least a photosensitive layer on a conductive support, (a) fluororesin fine particles on the outermost layer of the electrophotographic photoreceptor,
(B) a copolymer resin obtained by reacting an acrylic polyol copolymer with an isocyanate compound,
(C) inorganic conductive fine particles,
The average diameter of the projected image of the portion of the fluororesin fine particles (a) exposed on the surface of the primary particles and the secondary particles formed by agglomerating a plurality of primary particles in the outermost layer film is D. In this case, the total of the projected area ratios on the surface of the grains in the range of 0.15 ≦ D ≦ 3 μm is 10% or more. The electrophotographic photosensitive member according to claim 1, wherein the proportion of the fluororesin fine particles (a) in the outermost layer is 20 vol% to 60 vol%. The copolymer resin (b) is
(B-1) an acrylic polyol copolymer,
(B-2) an isocyanate compound having two or more NCO groups in one molecule;
The amount of the isocyanate compound (b-2) in the copolymer resin (b) is the amount of NCO groups and OH groups in the acrylic polyol copolymer (b-1). The electrophotographic photosensitive member according to claim 1 or 2, wherein the number ratio (NCO / OH) is in an amount ranging from 0.7 to 1.3. The electrophotographic photosensitive member according to claim 1, wherein the inorganic conductive fine particles (c) are tin oxide fine particles having an average particle size of 0.1 to 1.0 μm. The weight ratio of the inorganic conductive fine particles (c) and the copolymer resin (b) contained in the outermost surface layer of the photoreceptor is
0.4 ≦ b / (b + c) ≦ 0.8
The electrophotographic photosensitive member according to claim 1, wherein: The acrylic polyol copolymer is a methyl methacrylate-2-hydroxyethyl methacrylate copolymer or a styrene-methyl methacrylate-2-hydroxyethyl methacrylate copolymer. Electrophotographic photoreceptor. An image forming apparatus comprising at least an electrophotographic photosensitive member, a charging unit, an exposing unit, and a transferring unit, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to claim 1. 8. The image forming apparatus according to claim 7, wherein the toner used for image formation has a spherical shape. In an image forming apparatus comprising an abutting member that contacts the surface of an electrophotographic photoreceptor while applying pressure, only the charging roller, cleaning blade, cleaning brush, intermediate transfer belt, and fluororesin fine particles on the surface of the photoreceptor are extended. 9. The image forming apparatus according to claim 7, further comprising at least one contact member from the contact member for the purpose. The image forming apparatus according to claim 7, wherein the image forming apparatus is a tandem type having a plurality of electrophotographic photosensitive members, a charging unit, a developing unit, and a transfer unit. An image having intermediate transfer means for primary transfer of the toner image developed on the electrophotographic photosensitive member onto the intermediate transfer member by the image forming apparatus and then secondary transfer of the toner image on the intermediate transfer member onto the recording material. 8. A forming apparatus, wherein a color image is formed by sequentially superposing a plurality of color toner images on an intermediate transfer member, and the color image is secondarily transferred collectively onto a recording material. The image forming apparatus according to any one of 10. A process cartridge for an image forming apparatus, comprising at least one of a charging unit, an exposure unit, a developing unit, a cleaning unit, and a transfer unit and the electrophotographic photosensitive member according to claim 1.

Images