JP2004037672A - Developing roller and process cartridge, and electrophotographic image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller that does not cause an image streak in a pressure contact part and maintains a high quality image over a long period. <P>SOLUTION: In the developing roller, when the surface roughness (Rz) of the roller is a(μm), and the surface roughness Rz of the pressure contact part after left for seven days in a pressure-contact stationary state on a flat plate and in 40°C and 95% RH environment is b(μm), 2≤a≤20, 2≤b≤20, and 0≤a-b≤5 are satisfied. <P>COPYRIGHT: (C)2004,JPO

Description

【０００８】
を満足することを特徴とする現像ローラに関するものである。より好ましくは、
【０００９】
【数４】

【００１０】
であるのが良い。さらに好ましくは、
【００１１】
【数５】

【００１２】
であるのが良い。また、現像ローラを、平板上で１００μｍ変形させた圧接静止状態で４０℃、９５％ＲＨ環境下で７日放置し、解放６時間後の、ローラ表面圧接部のローラ外径変形量をｃ（μｍ）とした時に、以下の式
【００１３】
【数６】

【００１４】
を満足することが好ましい。より好ましくは、
【００１５】
【数７】

【００１６】
であるのが良い。さらに好ましくは、
【００１７】
【数８】

【００１８】
であるのが良い。現像ローラの弾性層は、圧縮永久歪み０〜１０％の導電性ゴム材料からなることが好ましい。
【００１９】
現像ローラの弾性層が、シリコーンゴムを主成分とするゴム材料からなることが好ましい。
【００２０】
現像ローラの弾性層が、硬化可能なオルガノポリシロキサンと、シロキサン骨格を有する硬化剤とを用いて架橋したシリコーンゴムを主成分とするゴム材料であることが好ましい。
【００２１】
現像ローラの弾性層が、導電剤を含有し、体積抵抗率１×１０＋Ｅ３〜１×１０＋Ｅ１０Ω・ｃｍのゴム材料から形成されていることが好ましい。導電剤としては、温度や湿度の環境変化においても抵抗値が変化しにくい、電子導電系導電剤が好ましい。
【００２２】
現像ローラの表面層が、永久伸び０〜２０％の樹脂材料からなることが好ましい。
【００２３】
現像ローラの表面層を構成する樹脂材料が、架橋成分により架橋されることによってトルエン不溶性となる樹脂材料であり、現像ローラをトルエンに含浸したときの抽出率が０〜３０質量％であることが好ましい。
【００２４】
現像ローラの表面層を形成する樹脂材料の固形分１００質量部に対して、真比重０．９〜３ｇ／ｃｍ^３、平均粒子径３〜２０μｍの粗し材を１〜５０質量部含有することが好ましい。
【００２５】
現像ローラの表面層が、窒素原子を含有する樹脂材料からなることが好ましい。
【００２６】
現像ローラの表面層が電子導電系導電剤を含有することを特徴とするが好ましい。
【００２７】
本発明は電子写真画像形成装置本体に脱離可能に装着される電子写真プロセスカートリッジにおいて、カートリッジが、現像ローラを有することを特徴とする電子写真プロセスカートリッジに関するものである。
【００２８】
また、本発明は静電潜像を保持するための静電保持体及び静電保持体に当接配置される現像ローラを有する電子写真画像形成装置において、現像ローラが、前記現像ローラであることを特徴とする電子写真画像形成装置に関するものである。
【００２９】
【発明の実施の形態】
本発明は感光体に圧接し、回転して静電潜像を現像、可視化する現像ローラにおいて、現像ローラは導電性軸体上の弾性層と、その外周部に表面層を配した２層構成で形成されており、未圧接時のローラ表面の表面粗さ（Ｒｚ）をａ（μｍ）とし、平板上で１００μｍ変形させた圧接静止状態で４０℃、９５％ＲＨ環境下で７日放置し、解放６時間後の、ローラ表面圧接部の表面粗さ（Ｒｚ）をｂ（μｍ）とした時に、以下の式
【００３０】
【数９】

【００３１】
を満足することを特徴とする現像ローラに関するものである。
【００３２】
未圧接時のローラ表面の表面粗さ（Ｒｚ）ａ（μｍ）および圧接放置後のローラ表面圧接部の表面粗さ（Ｒｚ）ｂ（μｍ）を式９を満たすように調節し、弾性層の上にさらに表面層を設ける２層構造とすることによって、長期圧接によるローラの変形と表面粗さの局所的低下を抑え、現像ローラ上のトナーコート状態を均一化し、画像スジの発生を抑えることができる。
【００３３】
導電性軸体としては良好な導電性を有するものであれば、いずれのものも使用し得るが、通常はアルミニウムや鉄、ＳＵＳなどの金属製円筒体のものが用いるのが好ましい。
【００３４】
本発明によれば、まず導電性軸体上に押出成形、射出成形、注型などいずれかの方法により弾性ゴム層を設ける。この方法は、材料の特性（液状、固形、粘度など）にあわせて適宜選択することが出来る。また、寸法精度（外径、振れ、円筒度など）を向上するために、更に弾性ゴム層表面を研磨などで追加工することも可能である。次に、表面層を構成する樹脂材料、粗し材および電子導電系導電剤等をボールミル、サンドミル、液衝突型分散、超音波分散などを単独または併用して混合攪拌する。特に良好な分散を得るために超音波照射機による分散を用いるのが好ましい。架橋剤および必要により架橋触媒を添加し、攪拌することにより得られる塗料を、スプレー、ディッピング等の公知の方法で塗布し、現像ローラを作製する。
【００３５】
現像ローラを、平板上で１００μｍ変形させた圧接静止状態で４０℃、９５％ＲＨ環境下で７日放置し、解放６時間後の、ローラ表面圧接部のローラ外径変形量をｃ（μｍ）とした時に、以下の式
【００３６】
【数１０】

【００３７】
を満足することが好ましい。
【００３８】
未圧接時のローラ表面の表面粗さ（Ｒｚ）ａ（μｍ）、圧接放置後のローラ表面圧接部の表面粗さ（Ｒｚ）ｂ（μｍ）およびローラ外径変形量ｃ（μｍ）を式１０を満たすように調節することによって、さらに効果的に長期圧接時のローラ変形を抑え、画像スジの発生をより効果的に抑制することができる。なお、ローラ外径変形量ｃ（μｍ）はレーザースキャンマイクロメーターＬＳ（キーエンス社製）を使用して２３℃、５５％ＲＨ環境下で１２時間放置後に測定を行なう。
【００３９】
ここで現像ローラの弾性層には、圧縮永久歪みが０〜１０％のゴム材料を用いることが好ましい。より好ましくは圧縮永久歪みは０〜６％である。圧縮永久歪みが０〜１０％のゴム材料を用いた場合、現像剤量規制部材や感光体などに長期間静止状態で圧接した場合でも現像ローラの変形により画像上スジが発生せず良好な画像特性を得ることができる。ゴム材料としては、例えば、天然ゴム、シリコーンゴム、ウレタンゴム、エチレンプロピレンゴム、ブタジエンゴム、クロロプレンゴム、ネオプレンゴム、イソプレンゴム、二トリルゴム、スチレンジエン共重合ゴム、ブチルゴム、アクリルゴム、ヒドリンゴム、多硫化ゴム、フッ素ゴム等が挙げられ、これらを２種類以上組み合わせて使用することも出来る。
【００４０】
また、ゴム材料の硬度としては、弾性ローラのローラ硬度がＡｓｋｅｒＣ硬度２０〜７０°、好ましくは３５〜５５°のものが好ましい。ここでＡｓｋｅｒＣ硬度とは、日本ゴム協会標準規格ＳＲＩＳ０１０１に準拠したアスカーＣ型スプリング式ゴム硬度計（高分子計器（株）社製）を用いて測定したローラの硬度であり、常温常湿（２３℃、５５％ＲＨ）の環境中に１２時間以上放置したローラに対して、上記硬度計を１０Ｎの力で当接させてから３０秒後の測定値とする。ローラ硬度が２０〜７０°のとき、表面層を形成した場合にしわ等の外観不良が発生せず、圧縮永久歪みが悪化しない。また、現像剤量規制部材や感光体との圧接力が増加し、摺擦によるトナー劣化を防止することができる。なお、圧縮永久歪みはテストピースを成型し、放置温度７０℃、放置時間２２時間の条件で、ＪＩＳ　Ｋ６３０１に従って測定した。
【００４１】
現像ローラの弾性層が、シリコーンゴムを主成分とするゴム材料からなることが好ましい。
【００４２】
現像ローラの弾性層にシリコーンゴムを使用することで、長期圧接によるローラ変形を抑え、画像スジの発生を抑えることができる。
【００４３】
また、シリコーンゴムは硬化可能なオルガノポリシロキサンと、シロキサン骨格を有する硬化剤を用いて架橋したものであることが好ましい。
【００４４】
硬化可能なオルガノポリシロキサンとしては例えば、ジメチルポリシロキサンまたは末端にビニル基等の硬化剤と反応する官能基を有するオルガノポリシロキサンを用いることができる。硬化可能なオルガノポリシロキサンはシリコーンゴム原料のベースポリマーであり、その分子量は特に限定されないが１０万以上１００万以下が好ましく、平均分子量はおよそ５０万程度が好ましい。また、硬化剤としてはオルガノハイドロジェンポリシロキサンを用いることができる。硬化可能なオルガノポリシロキサンのアルケニル基は、硬化剤であるオルガノハイドロジェンポリシロキサンの活性水素と反応して架橋点を形成する部位であり、その種類は特に限定されないが、活性水素との反応性が高い等の理由から、ビニル基およびアリル基の少なくとも一方であることが好ましく、ビニル基が特に好ましい。オルガノハイドロジェンポリシロキサンは、硬化工程における付加反応の架橋剤の働きをするもので、一分子中のケイ素原子結合水素原子の数は２コ以上であり、硬化反応を最適に行わせるために、３個以上のポリマーが好ましい。ポリオルガノハイドロジェンシロキサンの分子量に特に制限は無く、低分子量（オリゴマー）から高分子量まで含有される。しかし、硬化反応を最適に行わせるために、比較的低分子量のポリマーが好ましい。
【００４５】
本発明においてポリオルガノハイドロジェンシロキサンの架橋触媒として使用される塩化白金酸六水和物のかわりに、ヒドロシリル化反応において触媒作用を示す遷移金属化合物が使用できる。特に制限はないが、例えば、Ｆｅ（ＣＯ）_５、Ｃｏ（ＣＯ）_８、ＲｕＣｌ_３、ＩｒＣｌ_３、〔（オレフィン）ＰｔＣｌ_２〕_２、ビニル基含有ポリシロキサン−Ｐｔ錯体、Ｈ２ＰｔＣｌ_６・６Ｈ２Ｏ、Ｌ_３ＲｈＣｌ_３、Ｌ_２Ｎｉ（オレフィン）、Ｌ_４Ｐｄ、Ｌ_４Ｐｔ、Ｌ_２ＮｉＣｌ_２（但し、Ｌ＝ＰＰｈ_３若しくはＰＲ’_３、ここでＰｈはフェニル基、Ｒ’はアルキル基を示す）を挙げることができる。その中でも、好ましくは白金、パラジウム、ロジウム系遷移金属化合物触媒である。
【００４６】
現像ローラの弾性層が、導電剤を含有し、体積抵抗率１×１０＋Ｅ３〜１×１０＋Ｅ１０Ω・ｃｍのゴム材料から形成されていることが好ましい。ここで、弾性層材料の体積抵抗率が１×１０＋Ｅ３〜１×１０＋Ｅ１０Ω・ｃｍのとき、感光体にピンホール等の欠陥がある場合、現像バイアスがリークすることにより、横スジ画像が発生する等といった問題が発生しない。また、現像バイアスによる現像電流が微小になり、画像濃度が低下するという問題が発生しない。体積抵抗率は、テストピースとして１３０℃のオーブンに入れ２０分加熱することにより厚み１０ｍｍのゴムシートを成型し、その後２００℃のオーブンで４時間２次加硫を行ない、ハイレスタＩＰ（三菱油化社製）を用いて１００Ｖの電圧印加で測定した。体積抵抗率は、より好ましくは１×１０＋Ｅ４〜１×１０＋Ｅ９Ω・ｃｍである。
【００４７】
また、導電剤としては、温度や湿度の環境変化においても抵抗値が変化しにくい、電子導電系導電剤が好ましい。電子導電系導電剤としては、カーボンブラック、グラファイト等の炭素系物質、アルミニウム、銀、金、錫−鉛合金、銅−ニッケル合金等の金属或いは合金、酸化亜鉛、酸化チタン、酸化アルミニウム、酸化錫、酸化アンチモン、酸化インジウム、酸化銀等の金属酸化物、各種フィラーに銅、ニッケル、銀等の導電性金属めっきを施した物質等を挙げる事が出来る。
【００４８】
これら電子導電系導電剤は粉末状或いは、繊維状の形態で、単独または２種類以上を混合して使用する事が出来る。この中でもカーボンブラックは導電性の制御がしやすい、経済的であるなどの観点から使用することが好ましい。
【００４９】
現像ローラの表面層が、永久伸び０〜２０％の樹脂材料からなることが好ましい。
【００５０】
永久伸びが０〜２０％のとき、現像剤量規制部材や感光体との圧接放置により、変形した表面層が復元せず、画像スジが発生するといった問題が生じない。より好ましくは、永久伸びは０〜１０％である。なお、永久伸びは、厚さ１５０μｍのＪＩＳ２号ダンベル片を作製し、標準間距離２０ｍｍに対し２０％（４ｍｍ）伸長で保持し、常温常湿環境下に３日間、放置後開放し、静置１時間後の伸び量ｄ（ｍｍ）を測定し、以下の計算式により求めた。
【００５１】
永久伸び（％）＝伸び量ｄ（ｍｍ）／４（ｍｍ）×１００
現像ローラの表面層を構成する樹脂材料は、架橋成分により架橋されることによってトルエン不溶性となる樹脂材料であり、現像ローラをトルエンに含浸したときの抽出率が０〜３０質量％であることが好ましい。
【００５２】
表面層に架橋成分を含まない、またはトルエン抽出率が０〜３０質量％のとき、圧接による変形が回復せず、画像スジが発生するといった問題が生じない。トルエン抽出率は、より好ましくは０〜１５質量％である。
【００５３】
ここで、トルエン抽出率の測定法としては、表面層に用いる材料を幅２０ｍｍ、長さ５０ｍｍ、厚み１ｍｍのシート状に成形し、室温下にてトルエン中に３日間含浸した後取り出し、風乾１週間後の質量減量百分率を求めた。表面層に用いる、永久伸びが０〜２０％、トルエン抽出率が０〜３０％となる樹脂材料として、例えば３官能成分を含有するポリオール化合物に、２〜５個の官能基を有するイソシアネート化合物を添加し、加熱硬化することにより得られる架橋性のウレタン樹脂、またはメトキシメチル化ナイロン等の変性ナイロン樹脂を必要に応じて触媒を添加し、加熱硬化することにより得られる架橋性のナイロン樹脂が好ましい。
【００５４】
現像ローラの表面層を形成する樹脂材料の固形分１００質量部に対して、真比重０．９〜３ｇ／ｃｍ^３、平均粒子径３〜２０μｍの粗し材を１〜５０質量部含有することが好ましい。より好ましくは、粗し材の含量は３〜３０質量部であるのが良い。
【００５５】
ここで、所望の表面粗さを粗し材の凹凸で形成することにより、画像出力耐久を通じて安定した現像ローラ表面の表面粗さを得ることができ、例えば、表面粗さ（Ｒｚ）を２〜２０μｍに調整することが可能となる。平均粒子径が３〜２０μｍの粗し材を１〜５０質量部含有することによって、所望の表面の粗さが確保でき、トナーの搬送量が十分でないために、画像濃度が良好であり、画像上ムラも発生しない。平均粒子径はより好ましくは６〜１８μｍである。また、真比重が０．９〜３ｇ／ｃｍ^３の粗し材を用いることによって現像剤量規制部材や感光体との圧接放置により、圧接部における粗し材の変形が起こらず、初期の表面粗さを維持することが可能となると共にローラが適度な強度を有し、圧接による変形が起こらず、表面粗さが変化しない。真比重はより好ましくは１〜１．５ｇ／ｃｍ^３である。また、粗し材としては例えば、ナイロン粒子、アクリル粒子、シリコーンゴム粒子、ウレタンゴム粒子、炭素粒子等がられ、これらを２種類以上組み合わせて使用することも出来る。
【００５６】
表面層を形成する樹脂成分としては、マイナスに帯電する現像剤（ネガトナー）の帯電に有利な窒素原子を含有していることが好ましく、特にウレタン樹脂、ナイロン樹脂、アクリル樹脂が好ましい。
【００５７】
現像ローラの表面層が電子導電系導電剤を含有することを特徴とするが好ましい。ローラ表面層が電子導電系導電剤を含有することによって、温度や湿度の環境変化においても現像ローラの電気抵抗値を変化しにくいものとすることができる。電子導電系導電剤としては、カーボンブラック、グラファイト等の炭素系物質、アルミニウム、銀、金、錫−鉛合金、銅−ニッケル合金等の金属或いは合金、酸化亜鉛、酸化チタン、酸化アルミニウム、酸化錫、酸化アンチモン、酸化インジウム、酸化銀等の金属酸化物、各種フィラーに銅、ニッケル、銀等の導電性金属めっきを施した物質等を挙げる事が出来る。これら電子導電系導電剤は粉末状或いは、繊維状の形態で、単独または２種類以上を混合して使用する事が出来る。この中でもカーボンブラックは導電性の制御がしやすい、経済的であるなどの観点から使用することが好ましい。
【００５８】
図１は、本発明の現像ローラの概略を示したものであり、１ａは芯金、１ｂ弾性層、１ｃは表面層を示す。
【００５９】
芯金１ａは、成形時や実使用時のたわみに耐えうる強度を有すれば良く、外径４〜１０ｍｍが好ましい。より好ましくは６〜８ｍｍであるのが良い。弾性層１ｂはシリコーンゴムを主成分とする。
【００６０】
これらのゴム材料に必要に応じてカーボンブラック、グラファイト、導電性粒子、導電性ゴム等を添加したものであり、硬さ、圧縮永久歪みを考慮した場合、シリコーンゴムが好ましく、厚みは１〜６ｍｍが好ましい。より好ましくは２〜５ｍｍであるのが良い。
【００６１】
表面層１ｃは、耐摩耗性やトナー帯電性、トナー搬送性等が要求されるため、ウレタン樹脂、ナイロン樹脂、アクリル樹脂、フッ素樹脂等をメチルエチルケトン、トルエン、アルコール、水等の溶媒で適宜希釈し、導電剤としてカーボンブラックを分散し、表面粗し材を、固形分に対し１〜５０質量部、分散した後、硬化剤もしくは硬化触媒を添加し、ボールミル、サンドミル、液衝突型分散、超音波分散などを単独または併用して混合攪拌する。特に良好な分散を得るために超音波照射機による分散を用いるのが好ましい。このようにして得られた塗料を、スプレー、ディッピング等の公知の方法で塗布して現像ローラを得る。
【００６２】
表面粗し材としては、真比重０．９〜３ｇ／ｃｍ^３、平均粒子径３〜２０μｍの粗し材が好ましく、例えば、ナイロン粒子、アクリル粒子、シリコーンゴム粒子、ウレタンゴム粒子、炭素粒子等が挙げられる。被覆層の厚みは弾性層の柔軟性を損なうことなく、また摩耗性を考慮し、３〜１００μｍが好ましい。より好ましくは５〜３０μｍであるのが良い。
【００６３】
本発明は電子写真画像形成装置本体に脱離可能に装着される電子写真プロセスカートリッジに
おいて、カートリッジが、現像ローラを有することを特徴とする電子写真プロセスカートリッジに関するものである。
【００６４】
また、本発明は静電潜像を保持するための静電保持体及び静電保持体に当接配置される現像ローラを有する電子写真画像形成装置において、現像ローラが、前記現像ローラであることを特徴とする電子写真画像形成装置に関するものである。電子写真画像形成装置は図２に示すように、トナーを供給するためのトナー塗布用ローラ６、感光ドラム５を帯電させる帯電ローラ８、静電潜像を保持した感光ドラム５に対応するトナー像を形成する現像ローラ４、トナー塗布用ローラ６により現像ローラ４の表面にトナーが供給され、このトナーをより均一な薄層に整える現像ブレード７からなっており、この状態で現像ローラ４が感光ドラム５と接触しながら回転することにより、薄層に形成されたトナーが現像ローラ４から感光ドラム５の潜像に付着して、潜像が可視化するようになっている。なお、図２中１０は転写部であり、ここで紙等の記録媒体にトナー画像を転写するようになっており、また９はクリーニングブレードであり、これにより転写後に感光ドラム５表面に残留するトナーを除去するようになっている。また、図２中１１は定着ローラであり、トナーを熱と圧力で紙等の記録媒体に定着させるものである。
【００６５】
【実施例】
（実施例１）
外径８ｍｍの芯金を内径１６ｍｍの円筒状金型内に同心となるように設置し、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度３５度：体積抵抗率２×１０＋Ｅ３Ω・ｃｍ：２液性シリコーンゴム）を注入後、１３０℃のオーブンに入れ２０分加熱成型し、脱型後、２００℃のオーブンで４時間２次加硫を行ない、弾性層厚み４ｍｍのローラを得た。次いで、（ニッポランＮ５０３３：日本ポリウレタン社製）を濃度１０質量％となるように、メチルエチルケトンで希釈し、導電剤としてカーボンブラック（商品名：＃７３６０ＳＢ：東海カーボン製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対し４０質量部、表面粗し材として平均粒子径６μｍのアクリル粒子（商品名：Ｇ−８００：根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対し１０質量部添加した後、超音波照射機（８５１０（商品名）：Ｂｒａｎｓｏｎ社製）により十分に分散した塗料に、イソシアネート化合物（商品名：コロネートＬ：日本ポリウレタン社製）をポリオール１００質量部に対し１０質量部添加、先に成型したローラ上に引き上げ速度１５０ｍｍ／ｍｉｎの条件でディッピングすることにより膜厚１０μｍとなるように塗布し、８０℃のオーブンで１５分乾燥後、１４０℃のオーブンで４時間硬化し、現像ローラを得た。
（実施例２）
弾性層として、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度１５度：体積抵抗率８×１０＋Ｅ９Ω・ｃｍ：２液性シリコーンゴム）を用い、表面層に添加するイソシアネート化合物（商品名：コロネートＬ：日本ポリウレタン社製）の量を５質量部とした以外は実施例１と同様にして現像ローラを得た。
（実施例３）
弾性層として、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度６０度：体積抵抗率５×１０＋Ｅ７Ω・ｃｍ：２液性シリコーンゴム）を用い、表面粗し材として平均粒子径１５μｍのウレタン樹脂粒子（Ｃ−４００：根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加した以外は実施例１と同様にして現像ローラを得た。
（実施例４）
表面層に添加するイソシアネート化合物（商品名：コロネートＬ：日本ポリウレタン社製）の量を５質量部とし、表面粗し材として平均粒子径２０μｍの炭素粒子（商品名：ニカビーズ　ＭＳＢ：日本カーボン社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加した以外は実施例１と同様にして現像ローラを得た。
（実施例５）
表面粗し材として平均粒子径３μｍのアクリル粒子（商品名：Ｆ−５Ｐ、根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して４５質量部添加した以外は実施例１と同様にして現像ローラを得た。
（実施例６）
弾性層として、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度１０度：体積抵抗率６×１０＋Ｅ２Ω・ｃｍ：２液性シリコーンゴム）を用い、表面粗し材として平均粒子径１５μｍのウレタン樹脂粒子（商品名：Ｃ−４００：根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加したとした以外は実施例１と同様にして現像ローラを得た。
（実施例７）
弾性層として、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度３５度：体積抵抗率２×１０Ｅ＋１０Ω・ｃｍ：２液性シリコーンゴム）を用い、表面粗し材として平均粒子径２μｍの導電性ほう酸アルミニウム粒子（商品名：５２１０、三井金属社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して５０質量部添加したとした以外は実施例１と同様にして現像ローラを得た。
（実施例８）
弾性層として、液状導電性シリコーンゴム（東レダウシリコーン社製：ＡｓｋｅｒＣ硬度６５度：体積抵抗率２×１０＋Ｅ４Ω・ｃｍ：２液性シリコーンゴム）を用い、表面粗し材として平均粒子径１５μｍのウレタン樹脂粒子（Ｃ−４００：根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加したとした以外は実施例１と同様にして現像ローラを得た。
（実施例９）
表面粗し材として平均粒子径２μｍの導電性ほう酸アルミニウム粒子（５２１０：三井金属社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して５質量部添加したとした以外は実施例１と同様にして現像ローラを得た。
【００６６】
以上により作製した現像ローラの処方一覧を表１に示す。
（比較例１）
表面層に添加するイソシアネート化合物（商品名：コロネートＬ、日本ポリウレタン社製：２液性シリコーンゴム）の量を２質量部とし、表面粗し材として平均粒子径２１μｍのウレタン樹脂粒子（Ｃ−３００：根上工業社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加したとした以外は実施例１と同様にして現像ローラを得た。
（比較例２）
表面粗し材として平均粒子径１０μｍの中空多孔質アクリル粒子（商品名：Ｍ−６１０：松本油脂製薬社製）をポリオールおよび後に添加するイソシアネート化合物の総固形分量１００質量部に対して２０質量部添加した以外は実施例１と同様にして現像ローラを得た。
【００６７】
【表１】

【００６８】
「ｐｈｒ」はポリオール１００質量部に対して使用するコロネート量の質量部を表す。
【００６９】
上記弾性層に用いるゴム材料を用いて、テストピースを成型し、ＪＩＳ　Ｋ６３０１に従い圧縮永久歪みを測定した。また、ローラ成型と同じ加熱条件で厚み１０ｍｍのゴムシートを成型し、体積抵抗率をハイレスタＩＰ（三菱油化社製）を用いて１００Ｖの電圧印加で測定した。また、弾性層をローラとして成型後、荷重１０ＮにてローラのＡｓｋｅｒＣ硬度を測定した。次いで、表面層に用いる材料を用いて、厚さ１５０μｍのＪＩＳ２号ダンベル片を作製し、標準間距離２０ｍｍに対し２０％（４ｍｍ）伸長で保持し、常温常湿環境下に３日間、放置後開放し、静置１時間後の伸び量ｄ（ｍｍ）を測定し、以下の計算式により求めた。
【００７０】
永久伸び（％）＝伸び量ｄ（ｍｍ）／４（ｍｍ）×１００
次に表面層に用いる材料を幅２０ｍｍ、長さ５０ｍｍ、厚み１ｍｍのシート状に成形し、室温下にてトルエン中に３日間含浸した後、取り出し風乾１週間後の質量減量百分率を求め、トルエン抽出率とした。
【００７１】
以上により作製した現像ローラを、感光体に変形量１００μｍとなるように圧接し、高温高湿環境（４０℃／９５％ＲＨ）下に７日間放置した後、解放６時間後に表面粗さ計（サーフコーダーＳＥ−３４００：小坂研究所社製）を用いて、圧接部と非圧接部の軸方向の十点平均表面粗さ（Ｒｚ）を測定した。また、ローラ周方向にレーザースキャンマイクロメーターＬＳ（キーエンス社製）を用いて外径を測定し、圧接部の変形量を求めた。更に、カラーレーザープリンターを用いてベタ画像を出力し、画像濃度、現像ローラ周期の画像スジを目視により評価した。また、非画像域に直径０．２ｍｍのピンホールを配した感光体を用い、カラーレーザープリンターにてハーフトーン画像の出力を行い、ピンホール部の横スジを目視により判定した。結果を表２、３に示す。
【００７２】
【表２】

【００７３】
【表３】

【００７４】
表から明らかな様に、実施例１〜５および７〜９では画像スジが発生していない。比較例１、２では圧接による表面粗さの変化により、画像スジが発生した。
【００７５】
【発明の効果】
本発明によれば、ローラ表面の表面粗さ（Ｒｚ）をａ（μｍ）とし、平板上に圧接静止状態で４０℃９５％ＲＨ環境に７日放置した後の、圧接部の表面粗さＲｚをｂ（μｍ）とした時に、２≦ａ≦２０かつ２≦ｂ≦２０かつ０≦ａ−ｂ≦５を満足する現像ローラは、圧接部における画像スジの発生がなく、高品質の画像を長期にわたり維持することが可能となる。
【図面の簡単な説明】
【図１】本発明の現像ローラの使用形態の一例の説明図である。
【図２】本発明の現像ローラを利用したレーザープリンタの構成を示す概念図である。
【符号の説明】
１ａ　　芯金
１ｂ　　弾性層
１ｃ　　表面層
４　　現像ローラ
５　　感光ドラム
６　　トナー塗布用ローラ
７　　現像ブレード
８　　帯電ローラ
９　　クリーニングブレード
１０　　転写ローラ
１１　　定着ローラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing roller used in an electrophotographic apparatus and an electrophotographic image forming apparatus using the same.
[0002]
[Prior art]
In recent years, OA equipment such as copiers and printers has been improved in image quality. With the development process of visualizing an electrostatic latent image on a photoconductor with toner, an elastic material is used as a developing roller and a photoconductor is used for the photoconductor. There has been proposed a contact development system in which development is performed by pressing uniformly. In this contact development, the developing roller is made of an elastic material in order to ensure a uniform pressure contact width with the photoconductor, and the surface of the developing roller has an appropriate surface roughness for conveying an appropriate amount of toner. Is required. In particular, when a non-magnetic one-component toner is used, the toner on the developing roller is a thin layer, and the surface roughness (Rz) of the roller surface needs to be adjusted to about 2 to 20 μm. Further, in order to always maintain the surface roughness during use, a measure is taken to form irregularities by adding particles or the like to the surface layer.
[0003]
However, since the developing roller in the contact developing method is pressed against the developer amount regulating member or the photosensitive member in a stationary state for a long period of time, the trace of the pressing occurs as a streak of the developing roller cycle on an image. Occurs. Possible causes include permanent deformation of the surface layer and permanent deformation of the elastic layer.Therefore, a material having low compression set such as silicone rubber or urethane rubber is used for the elastic layer, and crosslinkable urethane is used for the surface layer. Resin, nylon resin and the like are used.
[0004]
[Problems to be solved by the invention]
However, in the case of a developing roller composed of an elastic layer and a surface layer formed on the outer periphery thereof, even when a material having a low compression set is used as the elastic layer, a streak is generated on an image when the material is pressed in a stationary state for a long time. There's a problem. The first cause is that even when the deformation of the elastic layer is reduced, the deformation of the surface layer increases the amount of deformation due to the pressure contact as the developing roller. The second cause is that the unevenness formed in the surface layer is flattened by long-term pressing, and the toner coating state is locally changed.
[0005]
Therefore, an object of the present invention is to provide an electrophotographic apparatus, in which a developing roller that presses against a photoreceptor to visualize a developer suppresses deformation of the roller and local decrease in surface roughness due to long-term pressing, and reduces toner coating on the developing roller. The purpose is to make the state uniform and suppress the occurrence of image streaks.
[0006]
[Means for Solving the Problems]
The present invention relates to a developing roller in which an electrostatic latent image is developed and visualized by being pressed against and rotated by a photoreceptor, wherein the developing roller has a two-layer structure in which an elastic layer on a conductive shaft and a surface layer are arranged on the outer periphery thereof. The surface roughness (Rz) of the roller surface when not pressed is a (μm), and the roller is left standing at 40 ° C., 95% RH environment for 7 days in a pressure-contact stationary state deformed by 100 μm on a plate. When the surface roughness (Rz) of the roller surface pressure contact portion after 6 hours of release is represented by b (μm), the following equation is obtained.
[0007]
[Equation 3]

[0008]
And a developing roller satisfying the following conditions. More preferably,
[0009]
(Equation 4)

[0010]
It is good. More preferably,
[0011]
(Equation 5)

[0012]
It is good. Further, the developing roller was allowed to stand for 7 days in an environment of 40 ° C. and 95% RH in a pressure contact stationary state in which the developing roller was deformed by 100 μm on a flat plate. μm), the following equation
[0013]
(Equation 6)

[0014]
Is preferably satisfied. More preferably,
[0015]
(Equation 7)

[0016]
It is good. More preferably,
[0017]
(Equation 8)

[0018]
It is good. The elastic layer of the developing roller is preferably made of a conductive rubber material having a compression set of 0 to 10%.
[0019]
The elastic layer of the developing roller is preferably made of a rubber material containing silicone rubber as a main component.
[0020]
The elastic layer of the developing roller is preferably made of a rubber material mainly composed of silicone rubber crosslinked using a curable organopolysiloxane and a curing agent having a siloxane skeleton.
[0021]
It is preferable that the elastic layer of the developing roller contains a conductive agent and is formed of a rubber material having a volume resistivity of 1 × 10 + E3 to 1 × 10 + E10Ω · cm. As the conductive agent, an electronic conductive type conductive agent whose resistance value does not easily change even when the environment changes in temperature or humidity is preferable.
[0022]
The surface layer of the developing roller is preferably made of a resin material having a permanent elongation of 0 to 20%.
[0023]
The resin material constituting the surface layer of the developing roller is a resin material which becomes insoluble in toluene by being cross-linked by a cross-linking component, and the extraction rate when the developing roller is impregnated with toluene is 0 to 30% by mass. preferable.
[0024]
True specific gravity of 0.9 to 3 g / cm with respect to 100 parts by mass of the solid content of the resin material forming the surface layer of the developing roller ³ It is preferable to contain 1 to 50 parts by mass of a roughening material having an average particle size of 3 to 20 μm.
[0025]
It is preferable that the surface layer of the developing roller is made of a resin material containing a nitrogen atom.
[0026]
It is preferable that the surface layer of the developing roller contains an electronic conductive agent.
[0027]
The present invention relates to an electrophotographic process cartridge detachably mounted on an electrophotographic image forming apparatus main body, wherein the cartridge has a developing roller.
[0028]
Further, according to the present invention, in an electrophotographic image forming apparatus having an electrostatic holding member for holding an electrostatic latent image and a developing roller disposed in contact with the electrostatic holding member, the developing roller is the developing roller. And an electrophotographic image forming apparatus.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a developing roller in which an electrostatic latent image is developed and visualized by being pressed against and rotated by a photoreceptor, wherein the developing roller has a two-layer structure in which an elastic layer on a conductive shaft and a surface layer are arranged on the outer periphery thereof. The surface roughness (Rz) of the roller surface when not pressed is a (μm), and the roller is left standing at 40 ° C., 95% RH environment for 7 days in a pressure-contact stationary state deformed on a flat plate by 100 μm. When the surface roughness (Rz) of the roller surface pressure contact portion after 6 hours of release is represented by b (μm), the following equation is obtained.
[0030]
(Equation 9)

[0031]
And a developing roller satisfying the following conditions.
[0032]
The surface roughness (Rz) a (μm) of the roller surface when not pressed and the surface roughness (Rz) b (μm) of the pressed portion of the roller surface after pressure contact were adjusted so as to satisfy Equation 9, and the elastic layer A two-layer structure with an additional surface layer suppresses roller deformation and local reduction in surface roughness due to long-term pressure contact, uniformizes the toner coating state on the developing roller, and suppresses image streaks. Can be.
[0033]
Any conductive shaft can be used as long as it has good conductivity. However, it is usually preferable to use a metal cylindrical body such as aluminum, iron, and SUS.
[0034]
According to the present invention, first, an elastic rubber layer is provided on a conductive shaft by any method such as extrusion molding, injection molding, and casting. This method can be appropriately selected according to the characteristics (liquid, solid, viscosity, etc.) of the material. Further, in order to improve the dimensional accuracy (outer diameter, runout, cylindricity, etc.), it is possible to further process the surface of the elastic rubber layer by polishing or the like. Next, a resin material, a roughening material, an electronic conductive agent, and the like constituting the surface layer are mixed and stirred using a ball mill, a sand mill, a liquid collision type dispersion, an ultrasonic dispersion, or the like alone or in combination. In order to obtain particularly good dispersion, it is preferable to use dispersion by an ultrasonic irradiation machine. A coating material obtained by adding a cross-linking agent and, if necessary, a cross-linking catalyst and stirring is applied by a known method such as spraying or dipping to prepare a developing roller.
[0035]
The developing roller was allowed to stand for 7 days in an environment of 95% RH at 40 ° C. in a pressure-contact stationary state in which the developing roller was deformed by 100 μm on a flat plate. And the following equation
[0036]
(Equation 10)

[0037]
Is preferably satisfied.
[0038]
The surface roughness (Rz) a (μm) of the roller surface when not pressed, the surface roughness (Rz) b (μm) of the pressed portion of the roller surface after pressing and standing, and the roller outer diameter deformation amount c (μm) are expressed by the following equation (10). By adjusting so as to satisfy the condition, roller deformation during long-term pressing can be more effectively suppressed, and the occurrence of image streaks can be more effectively suppressed. Note that the roller outer diameter deformation c (μm) is measured after standing for 12 hours at 23 ° C. and 55% RH using a laser scan micrometer LS (manufactured by Keyence Corporation).
[0039]
Here, it is preferable to use a rubber material having a compression set of 0 to 10% for the elastic layer of the developing roller. More preferably, the compression set is from 0 to 6%. When a rubber material having a compression set of 0 to 10% is used, even when pressed against a developer amount regulating member or a photoreceptor in a stationary state for a long period of time, a streak on an image due to deformation of a developing roller does not occur, resulting in a good image. Properties can be obtained. Examples of the rubber material include natural rubber, silicone rubber, urethane rubber, ethylene propylene rubber, butadiene rubber, chloroprene rubber, neoprene rubber, isoprene rubber, nitrile rubber, styrene diene copolymer rubber, butyl rubber, acrylic rubber, hydrin rubber, and polysulfide. Rubber, fluororubber and the like can be mentioned, and these can be used in combination of two or more kinds.
[0040]
The rubber material preferably has an elastic roller having an AskerC hardness of 20 to 70 °, preferably 35 to 55 °. Here, the AskerC hardness is the hardness of a roller measured using an Asker C-type spring-type rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) based on the Japan Rubber Association Standard SRIS0101, and is normal temperature and normal humidity (23 (30 ° C., 55% RH) for 30 hours after the hardness tester was brought into contact with the roller left for 12 hours or more under an environment of 10 N. When the roller hardness is 20 to 70 °, appearance defects such as wrinkles do not occur when the surface layer is formed, and compression set does not deteriorate. In addition, the pressure contact force with the developer amount regulating member and the photoconductor increases, and toner deterioration due to rubbing can be prevented. The compression set was measured according to JIS K6301 under the conditions of molding a test piece, leaving at 70 ° C. and leaving for 22 hours.
[0041]
The elastic layer of the developing roller is preferably made of a rubber material containing silicone rubber as a main component.
[0042]
By using silicone rubber for the elastic layer of the developing roller, it is possible to suppress roller deformation due to long-term pressure contact and to suppress occurrence of image streaks.
[0043]
Further, the silicone rubber is preferably cross-linked by using a curable organopolysiloxane and a curing agent having a siloxane skeleton.
[0044]
As the curable organopolysiloxane, for example, dimethylpolysiloxane or an organopolysiloxane having a functional group which reacts with a curing agent such as a vinyl group at a terminal can be used. The curable organopolysiloxane is a base polymer of a silicone rubber raw material, and its molecular weight is not particularly limited, but is preferably 100,000 to 1,000,000, and the average molecular weight is preferably about 500,000. In addition, an organohydrogenpolysiloxane can be used as a curing agent. The alkenyl group of the curable organopolysiloxane is a site that forms a cross-linking point by reacting with the active hydrogen of the organohydrogenpolysiloxane as a curing agent, and the type thereof is not particularly limited. For example, at least one of a vinyl group and an allyl group is preferable, and a vinyl group is particularly preferable. The organohydrogenpolysiloxane acts as a crosslinking agent for the addition reaction in the curing step, and the number of silicon-bonded hydrogen atoms in one molecule is 2 or more. Three or more polymers are preferred. There is no particular limitation on the molecular weight of the polyorganohydrogensiloxane, and it is contained from low molecular weight (oligomer) to high molecular weight. However, in order to optimize the curing reaction, a polymer having a relatively low molecular weight is preferable.
[0045]
In the present invention, instead of chloroplatinic acid hexahydrate used as a crosslinking catalyst for polyorganohydrogensiloxane, a transition metal compound having a catalytic action in a hydrosilylation reaction can be used. Although there is no particular limitation, for example, Fe (CO) ₅ , Co (CO) ₈ , RuCl ₃ , IrCl ₃ , [(Olefin) PtCl ₂ ] ₂ , Vinyl group-containing polysiloxane-Pt complex, H2PtCl ₆ ・ 6H2O, L ₃ RhCl ₃ , L ₂ Ni (olefin), L ₄ Pd, L ₄ Pt, L ₂ NiCl ₂ (However, L = PPh ₃ Or PR ' ₃ Wherein Ph represents a phenyl group and R 'represents an alkyl group). Among them, preferred are platinum, palladium and rhodium-based transition metal compound catalysts.
[0046]
It is preferable that the elastic layer of the developing roller contains a conductive agent and is formed of a rubber material having a volume resistivity of 1 × 10 + E3 to 1 × 10 + E10Ω · cm. Here, when the volume resistivity of the elastic layer material is 1 × 10 + E3 to 1 × 10 + E10 Ω · cm, if there is a defect such as a pinhole in the photoconductor, the development bias leaks to generate a horizontal streak image. Such a problem does not occur. Further, the problem that the developing current due to the developing bias becomes small and the image density decreases does not occur. The volume resistivity was determined by placing a test piece in a 130 ° C. oven and heating for 20 minutes to form a rubber sheet having a thickness of 10 mm, and then performing secondary vulcanization in a 200 ° C. oven for 4 hours. (Manufactured by the company) and a voltage of 100 V was applied. The volume resistivity is more preferably 1 × 10 + E4 to 1 × 10 + E9Ω · cm.
[0047]
Further, as the conductive agent, an electronic conductive type conductive agent, whose resistance value does not easily change even when the environment changes in temperature or humidity, is preferable. Examples of the electronic conductive agent include carbon materials such as carbon black and graphite, metals and alloys such as aluminum, silver, gold, tin-lead alloy, and copper-nickel alloy, zinc oxide, titanium oxide, aluminum oxide, and tin oxide. And metal oxides such as antimony oxide, indium oxide and silver oxide, and substances obtained by plating various fillers with conductive metal plating such as copper, nickel and silver.
[0048]
These electronic conductive agents can be used alone or in combination of two or more in the form of a powder or a fiber. Among them, it is preferable to use carbon black from the viewpoint of easy control of conductivity, economy and the like.
[0049]
The surface layer of the developing roller is preferably made of a resin material having a permanent elongation of 0 to 20%.
[0050]
When the permanent elongation is 0 to 20%, the problem that the deformed surface layer is not restored and image streaks occur due to being left in pressure contact with the developer amount regulating member or the photosensitive member does not occur. More preferably, the permanent elongation is between 0 and 10%. For the permanent elongation, a JIS No. 2 dumbbell piece having a thickness of 150 μm was prepared, held at 20% (4 mm) elongation with respect to a standard distance of 20 mm, opened at room temperature and normal humidity for 3 days, opened after standing, and allowed to stand. The elongation d (mm) after one hour was measured and determined by the following formula.
[0051]
Permanent elongation (%) = Elongation d (mm) / 4 (mm) × 100
The resin material constituting the surface layer of the developing roller is a resin material that becomes insoluble in toluene by being crosslinked by a crosslinking component, and the extraction rate when the developing roller is impregnated with toluene is 0 to 30% by mass. preferable.
[0052]
When the surface layer does not contain a cross-linking component or when the toluene extraction ratio is 0 to 30% by mass, there is no problem that deformation due to pressure welding is not recovered and image streaks are generated. The toluene extraction rate is more preferably 0 to 15% by mass.
[0053]
Here, as a method for measuring the toluene extraction rate, the material used for the surface layer was formed into a sheet having a width of 20 mm, a length of 50 mm, and a thickness of 1 mm, impregnated in toluene at room temperature for 3 days, taken out, and air-dried. The weight loss percentage after a week was determined. As a resin material used for the surface layer and having a permanent elongation of 0 to 20% and a toluene extraction rate of 0 to 30%, for example, an isocyanate compound having 2 to 5 functional groups is added to a polyol compound containing a trifunctional component. A cross-linkable urethane resin obtained by adding and heat-curing a cross-linkable urethane resin, or a modified nylon resin such as methoxymethylated nylon, a catalyst is added as necessary, and a cross-linkable nylon resin obtained by heat-curing is preferable. .
[0054]
True specific gravity of 0.9 to 3 g / cm with respect to 100 parts by mass of the solid content of the resin material forming the surface layer of the developing roller ³ It is preferable to contain 1 to 50 parts by mass of a roughening material having an average particle size of 3 to 20 μm. More preferably, the content of the roughening material is 3 to 30 parts by mass.
[0055]
Here, by forming the desired surface roughness with the roughness of the roughening material, a stable surface roughness of the developing roller surface can be obtained through image output durability. For example, the surface roughness (Rz) is 2 to 2. It can be adjusted to 20 μm. By containing 1 to 50 parts by mass of a roughening material having an average particle size of 3 to 20 μm, a desired surface roughness can be ensured, and a sufficient amount of toner is conveyed. No upper unevenness occurs. The average particle size is more preferably from 6 to 18 μm. The true specific gravity is 0.9 to 3 g / cm. ³ By using a roughened material, the roughened material is not deformed at the press-contacted portion due to being left in pressure contact with the developer amount regulating member and the photoconductor, so that the initial surface roughness can be maintained and the roller can be maintained. It has moderate strength, does not deform due to pressure welding, and does not change its surface roughness. The true specific gravity is more preferably 1 to 1.5 g / cm. ³ It is. Examples of the roughening material include nylon particles, acrylic particles, silicone rubber particles, urethane rubber particles, carbon particles, and the like, and two or more of these can be used in combination.
[0056]
The resin component forming the surface layer preferably contains a nitrogen atom that is advantageous for charging a negatively charged developer (negative toner), and particularly preferably a urethane resin, a nylon resin, and an acrylic resin.
[0057]
It is preferable that the surface layer of the developing roller contains an electronic conductive agent. When the roller surface layer contains an electronic conductive agent, the electric resistance value of the developing roller can be made hard to change even when the environment changes in temperature or humidity. Examples of the electronic conductive agent include carbon materials such as carbon black and graphite, metals and alloys such as aluminum, silver, gold, tin-lead alloy, and copper-nickel alloy, zinc oxide, titanium oxide, aluminum oxide, and tin oxide. And metal oxides such as antimony oxide, indium oxide and silver oxide, and substances obtained by plating various fillers with conductive metal plating such as copper, nickel and silver. These electronic conductive agents can be used alone or in combination of two or more in the form of a powder or a fiber. Among them, it is preferable to use carbon black from the viewpoint of easy control of conductivity, economy and the like.
[0058]
FIG. 1 schematically shows the developing roller of the present invention, wherein 1a denotes a cored bar, 1b an elastic layer, and 1c denotes a surface layer.
[0059]
The core bar 1a only needs to have a strength that can withstand deflection during molding or actual use, and preferably has an outer diameter of 4 to 10 mm. More preferably, it is 6 to 8 mm. The elastic layer 1b contains silicone rubber as a main component.
[0060]
If necessary, carbon black, graphite, conductive particles, conductive rubber, etc. are added to these rubber materials, and in consideration of hardness and compression set, silicone rubber is preferable, and the thickness is 1 to 6 mm. Is preferred. More preferably, it is 2 to 5 mm.
[0061]
Since the surface layer 1c is required to have abrasion resistance, toner chargeability, toner transportability, and the like, urethane resin, nylon resin, acrylic resin, fluororesin, or the like is appropriately diluted with a solvent such as methyl ethyl ketone, toluene, alcohol, or water. After dispersing carbon black as a conductive agent, dispersing a surface roughening material in an amount of 1 to 50 parts by mass based on the solid content, adding a curing agent or a curing catalyst, and using a ball mill, a sand mill, a liquid collision type dispersion, and ultrasonic waves. The dispersion or the like is used alone or in combination, and the mixture is stirred. In order to obtain particularly good dispersion, it is preferable to use dispersion by an ultrasonic irradiation machine. The coating material thus obtained is applied by a known method such as spraying or dipping to obtain a developing roller.
[0062]
As surface roughening material, true specific gravity 0.9-3 g / cm ³ Rough material having an average particle diameter of 3 to 20 μm is preferable, and examples thereof include nylon particles, acrylic particles, silicone rubber particles, urethane rubber particles, and carbon particles. The thickness of the coating layer is preferably 3 to 100 μm in consideration of abrasion without impairing the flexibility of the elastic layer. More preferably, the thickness is 5 to 30 μm.
[0063]
The present invention relates to an electrophotographic process cartridge detachably mounted on an electrophotographic image forming apparatus main body.
The present invention relates to an electrophotographic process cartridge, wherein the cartridge has a developing roller.
[0064]
Further, according to the present invention, in an electrophotographic image forming apparatus having an electrostatic holding member for holding an electrostatic latent image and a developing roller disposed in contact with the electrostatic holding member, the developing roller is the developing roller. And an electrophotographic image forming apparatus. As shown in FIG. 2, the electrophotographic image forming apparatus includes a toner application roller 6 for supplying toner, a charging roller 8 for charging the photosensitive drum 5, and a toner image corresponding to the photosensitive drum 5 holding the electrostatic latent image. A toner is supplied to the surface of the developing roller 4 by a developing roller 4 and a toner applying roller 6 which forms the toner, and a developing blade 7 for adjusting the toner to a more uniform thin layer is formed. By rotating while being in contact with the drum 5, the toner formed in a thin layer adheres from the developing roller 4 to the latent image on the photosensitive drum 5, and the latent image is visualized. In FIG. 2, reference numeral 10 denotes a transfer unit, which transfers a toner image to a recording medium such as paper. Reference numeral 9 denotes a cleaning blade, which remains on the surface of the photosensitive drum 5 after the transfer. The toner is removed. In FIG. 2, reference numeral 11 denotes a fixing roller for fixing the toner to a recording medium such as paper by heat and pressure.
[0065]
【Example】
(Example 1)
A core metal having an outer diameter of 8 mm is placed concentrically in a cylindrical mold having an inner diameter of 16 mm, and a liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd., AskerC hardness 35 degrees: volume resistivity 2 × 10 + E3Ω · cm: After injecting the two-component silicone rubber), it was placed in an oven at 130 ° C. and heat-molded for 20 minutes. After demolding, secondary vulcanization was performed in an oven at 200 ° C. for 4 hours to obtain a roller having an elastic layer thickness of 4 mm. Next, (Nipporan N5033: manufactured by Nippon Polyurethane) is diluted with methyl ethyl ketone so as to have a concentration of 10% by mass, and carbon black (trade name: # 7360SB: manufactured by Tokai Carbon) as a conductive agent is a polyol and an isocyanate compound to be added later. 40 parts by mass with respect to 100 parts by mass of the total solid content of the acrylic resin (trade name: G-800: manufactured by Negami Industry Co., Ltd.) having an average particle diameter of 6 μm as a surface roughening agent, and the total solid content of the isocyanate compound to be added later After adding 10 parts by mass to 100 parts by mass, an isocyanate compound (trade name: Coronate L: manufactured by Nippon Polyurethane Co., Ltd.) was added to a coating material sufficiently dispersed by an ultrasonic irradiator (8510 (trade name): manufactured by Branson). 10 parts by mass were added to 100 parts by mass of the polyol, and The film was dipped on a roller at a pulling rate of 150 mm / min to form a film having a thickness of 10 μm, dried in an oven at 80 ° C. for 15 minutes, and then cured in an oven at 140 ° C. for 4 hours to obtain a developing roller. .
(Example 2)
As the elastic layer, a liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd .: AskerC hardness 15 degrees: volume resistivity 8 × 10 + E9Ω · cm: two-liquid silicone rubber) is used, and an isocyanate compound (trade name: A developing roller was obtained in the same manner as in Example 1 except that the amount of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) was changed to 5 parts by mass.
(Example 3)
As the elastic layer, a liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd .: AskerC hardness 60 degrees: volume resistivity 5 × 10 + E7Ω · cm: two-liquid silicone rubber) is used, and urethane having an average particle diameter of 15 μm is used as a surface roughening material. A developing roller was obtained in the same manner as in Example 1 except that resin particles (C-400: manufactured by Negami Kogyo KK) were added in an amount of 20 parts by mass relative to 100 parts by mass of the total solid content of the polyol and the isocyanate compound to be added later.
(Example 4)
The amount of the isocyanate compound (trade name: Coronate L: manufactured by Nippon Polyurethane Co.) to be added to the surface layer is 5 parts by mass, and carbon particles having an average particle diameter of 20 μm (trade name: Nicabeads MSB: manufactured by Nippon Carbon Co., Ltd.) ) Was added in the same manner as in Example 1 except that 20 parts by mass of the polyol and 100 parts by mass of the total solid content of the isocyanate compound to be added later were added.
(Example 5)
Acrylic particles having an average particle diameter of 3 μm (trade name: F-5P, manufactured by Negami Industry Co., Ltd.) were added as a surface roughening agent to the polyol and 45 parts by mass based on 100 parts by mass of the total solid content of the isocyanate compound added later. A developing roller was obtained in the same manner as in Example 1.
(Example 6)
As the elastic layer, liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd .: AskerC hardness 10 degrees: volume resistivity 6 × 10 + E2Ω · cm: two-liquid silicone rubber) is used, and urethane having an average particle diameter of 15 μm is used as a surface roughening material. Developed in the same manner as in Example 1 except that resin particles (trade name: C-400: manufactured by Negami Industry Co., Ltd.) were added in an amount of 20 parts by mass based on 100 parts by mass of the total solid content of the polyol and the isocyanate compound added later. Roller was obtained.
(Example 7)
As the elastic layer, a liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd .: AskerC hardness 35 degrees: volume resistivity 2 × 10E + 10Ω · cm: two-liquid silicone rubber) is used, and a conductive material having an average particle diameter of 2 μm is used as a surface roughening material. The development was performed in the same manner as in Example 1 except that 50 parts by mass of the basic aluminum borate particles (trade name: 5210, manufactured by Mitsui Kinzoku Co., Ltd.) were added to 100 parts by mass of the total solid content of the polyol and the isocyanate compound added later. Roller was obtained.
(Example 8)
As the elastic layer, a liquid conductive silicone rubber (manufactured by Toray Dow Silicone Co., Ltd .: Asker C hardness 65 degrees: volume resistivity 2 × 10 + E4Ω · cm: two-liquid silicone rubber) is used, and urethane having an average particle diameter of 15 μm is used as a surface roughening material. A developing roller was obtained in the same manner as in Example 1 except that resin particles (C-400: manufactured by Negami Kogyo KK) were added in an amount of 20 parts by mass based on 100 parts by mass of the total solid content of the polyol and the isocyanate compound added later. Was.
(Example 9)
Except that conductive aluminum borate particles having an average particle diameter of 2 μm (5210: manufactured by Mitsui Kinzoku Co., Ltd.) were added as a surface roughening material in an amount of 5 parts by mass based on 100 parts by mass of the total solid content of the polyol and the isocyanate compound added later. A developing roller was obtained in the same manner as in Example 1.
[0066]
Table 1 shows a list of prescriptions of the developing roller manufactured as described above.
(Comparative Example 1)
The amount of an isocyanate compound (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd .: two-part silicone rubber) to be added to the surface layer was 2 parts by mass, and urethane resin particles (C-300) having an average particle diameter of 21 μm as a surface roughening material. : Negami Kogyo Co., Ltd.) was obtained in the same manner as in Example 1 except that 20 parts by mass was added to 100 parts by mass of the total solid content of the polyol and the isocyanate compound to be added later.
(Comparative Example 2)
Hollow porous acrylic particles (trade name: M-610: manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) having an average particle diameter of 10 μm as a surface roughening material are 20 parts by mass based on 100 parts by mass of the total solid content of the polyol and the isocyanate compound added later. A developing roller was obtained in the same manner as in Example 1 except for adding the developing roller.
[0067]
[Table 1]

[0068]
"Phr" represents parts by mass of the coronate used with respect to 100 parts by mass of the polyol.
[0069]
A test piece was molded using the rubber material used for the elastic layer, and the compression set was measured according to JIS K6301. Also, a rubber sheet having a thickness of 10 mm was molded under the same heating conditions as the roller molding, and the volume resistivity was measured using Hiresta IP (manufactured by Mitsubishi Yuka Co., Ltd.) by applying a voltage of 100 V. Further, after molding the elastic layer as a roller, AskerC hardness of the roller was measured under a load of 10N. Next, a JIS No. 2 dumbbell piece having a thickness of 150 μm was prepared using the material used for the surface layer, and was held at 20% (4 mm) extension with respect to a standard distance of 20 mm. It was opened and the amount of elongation d (mm) after one hour of standing was measured, and determined by the following formula.
[0070]
Permanent elongation (%) = elongation d (mm) / 4 (mm) x 100
Next, the material used for the surface layer was formed into a sheet having a width of 20 mm, a length of 50 mm, and a thickness of 1 mm. The sheet was immersed in toluene at room temperature for 3 days, and then taken out. The extraction rate was used.
[0071]
The developing roller manufactured as described above was pressed against the photoreceptor so as to have a deformation amount of 100 μm, left in a high-temperature and high-humidity environment (40 ° C./95% RH) for 7 days, and 6 hours after release, a surface roughness meter ( Using a surf coder SE-3400 (manufactured by Kosaka Laboratory Co., Ltd.), the ten-point average surface roughness (Rz) in the axial direction of the pressed portion and the non-pressed portion was measured. The outer diameter was measured using a laser scan micrometer LS (manufactured by Keyence Corporation) in the circumferential direction of the roller, and the amount of deformation of the pressed portion was determined. Further, a solid image was output using a color laser printer, and the image density and the image stripe of the developing roller cycle were visually evaluated. Further, a halftone image was output by a color laser printer using a photoreceptor having a pinhole having a diameter of 0.2 mm in the non-image area, and the horizontal streak of the pinhole was visually determined. The results are shown in Tables 2 and 3.
[0072]
[Table 2]

[0073]
[Table 3]

[0074]
As is clear from the table, no image streaks occurred in Examples 1 to 5 and 7 to 9. In Comparative Examples 1 and 2, an image streak occurred due to a change in surface roughness due to pressure welding.
[0075]
【The invention's effect】
According to the present invention, the surface roughness (Rz) of the roller surface is defined as a (μm), and the surface roughness Rz of the press-contact portion after standing on a flat plate in a 40 ° C. 95% RH environment for 7 days in a stationary state. When b is in μm, the developing roller satisfying 2 ≦ a ≦ 20, 2 ≦ b ≦ 20 and 0 ≦ ab ≦ 5 has no image streaks in the press-contact portion, and can produce a high quality image. It can be maintained for a long time.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an example of a usage mode of a developing roller of the present invention.
FIG. 2 is a conceptual diagram showing a configuration of a laser printer using a developing roller of the present invention.
[Explanation of symbols]
1a Core
1b Elastic layer
1c Surface layer
4 Developing roller
5 Photosensitive drum
6. Toner application roller
7 Developing blade
8 Charging roller
9 Cleaning blade
10 Transfer roller
11 Fixing roller

Claims (13)

In a developing roller which is pressed against a photoreceptor and rotates to develop and visualize an electrostatic latent image, the developing roller is formed of a two-layer structure in which an elastic layer on a conductive shaft and a surface layer are arranged on an outer peripheral portion thereof. The surface roughness (Rz) of the roller surface when not pressed is a (μm), and the roller is left standing at 40 ° C., 95% RH environment for 7 days in a pressure-contact stationary state deformed on a flat plate by 100 μm, and released. When the surface roughness (Rz) of the roller surface pressure contact portion after time is represented by b (μm), the following equation is obtained.

A developing roller that satisfies the following. The developing roller was left for 7 days in an environment of 40 ° C. and 95% RH in a pressure-contact stationary state in which the developing roller was deformed 100 μm on a flat plate. ) And the following formula

The developing roller according to claim 1, wherein the following condition is satisfied. 3. The developing roller according to claim 1, wherein the elastic layer of the developing roller is made of a conductive rubber material having a compression set of 0 to 10%. The developing roller according to any one of claims 1 to 3, wherein the elastic layer of the developing roller is made of a rubber material containing silicone rubber as a main component. 5. The method according to claim 1, wherein the elastic layer of the developing roller is made of a rubber material whose main component is a silicone rubber obtained by crosslinking a curable organopolysiloxane with a curing agent having a siloxane skeleton. 2. The developing roller according to claim 1. The elastic layer of the developing roller contains an electronic conductive agent, and is formed of a rubber material having a volume resistivity of 1 × 10 + E3 to 1 × 10 + E10Ω · cm. 2. The developing roller according to claim 1. The developing roller according to claim 1, wherein a surface layer of the developing roller is made of a resin material having a permanent elongation of 0 to 20%. The resin material constituting the surface layer of the developing roller is a resin material which becomes insoluble in toluene by being cross-linked by a cross-linking component, and has an extraction rate of 0 to 30% by mass when the developing roller is impregnated with toluene. The developing roller according to any one of claims 1 to 7, wherein the developing roller is provided. 1 to 50 parts by mass of a roughening material having a true specific gravity of 0.9 to ³ g / cm ³ and an average particle diameter of ³ to 20 μm with respect to 100 parts by mass of the solid content of the resin material forming the surface layer of the developing roller The developing roller according to any one of claims 1 to 8, wherein the developing is performed. The developing roller according to any one of claims 1 to 9, wherein a surface layer of the developing roller is made of a resin material containing nitrogen atoms. The developing roller according to claim 1, wherein a surface layer of the developing roller contains an electronic conductive agent. An electrophotographic process cartridge detachably mounted on an electrophotographic image forming apparatus main body, wherein the cartridge includes the developing roller according to claim 1. . 12. An electrophotographic image forming apparatus having an electrostatic holding member for holding an electrostatic latent image and a developing roller disposed in contact with the electrostatic holding member, wherein the developing roller is any one of claims 1 to 11. 13. An electrophotographic image forming apparatus, which is the developing roller according to the above item.

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