JP4163564B2 - Charging member, cartridge having the same, and image forming apparatus having cartridge - Google Patents

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（式中、Ｒ¹ ，Ｒ² ，Ｒ³ は、炭素数が１〜２０のアルキル基である。）
で示される共重合体である。この共重合体は、ポリアミド単位のハード部分とポリエーテル単位のソフト部分からなるものであるが、それ自体は、公知のものである。そして、前記（Ｂ）のポリエーテルエステルアミドは、イオン導電性の高分子材料であるので、電気抵抗調整層に要求される電気抵抗値を容易に得ることができる。また、ポリエーテルエステルアミドは、マトリクスポリマー中に分子レベルで均一に分散、固定化され、そのために、導電性顔料を分散した樹脂組成物にみられるような導電性顔料の分散不良に伴う電気抵抗値のバラツキが生じない。さらに、ポリエーテルエステルアミドは、高分子材料であるので、ブリードアウトが生じ難い。
【００３２】
前記（Ｃ）の主鎖のエチレン−グリシジルメタクリレート共重合体は、低吸水性であるエチレン成分と反応基であるグリシジルメタクリレート成分からなる。エチレン単位は、（Ａ）のスチレン系樹脂との親和性が高く、また、低吸水であるので、樹脂の吸湿に伴う電気抵抗や形状の変動を抑制する。また、反応基のグリシジルメタクリレートは、（Ａ）、（Ｂ）及び（Ｃ）を溶融混練する際の加熱により、エポキシ基が（Ｂ）のポリエーテルエステルアミドのエステル基やアミノ基と反応し、（Ｂ）と強固に化学的結合をする。さらに、側鎖に含まれるアクリロニトリル成分及びスチレン成分は、（Ａ）のスチレン系樹脂との相溶性が良好であるので、（Ｃ）のグラフトコポリマーは、本来親和性の低い（Ａ）と（Ｂ）との間の相溶化剤として機能して、（Ａ）及び（Ｂ）の分散状態を均一かつ緻密化する。それ故、側鎖に含まれるアクリロニトリル成分及びスチレン成分は、（Ａ）及び（Ｂ）の分散不良に伴うウェルド部電気抵抗の変動、使用時の電気的・機械的ストレス、又は、経時・環境での体積変動により電気抵抗調整層のウェルド部分に発生するクラックを抑制することができる。そして、（Ｃ）と（Ｂ）とが充分な結合を行うためには、グリシジルメタクリレート成分の含有量が、（Ｃ）のグラフトコポリマーの１〜２０重量％である必要がある。
【００３３】
このように、電気抵抗調整層２が、（Ａ）スチレン系熱可塑性樹脂、（Ｂ）高分子型イオン導電材料、並びに、（Ｃ）主鎖にエチレン−グリシジルメタクリレート共重合体を有し、側鎖にアクリロニトリル成分及びスチレン成分の両方又はそれらの一方を有するグラフトコポリマー、を溶融混練してなる樹脂組成物で構成されていると、電気抵抗値のばらつき、トナー固着、及び、それらに伴う帯電不良を防止すると共に、機械的強度及び耐久性の優れた帯電部材を提供することができる。
【００３４】
本発明においては、前記電気抵抗調整層２の体積固有電気抵抗は、好ましくは、１０⁶ 〜１０⁹ Ωｃｍである。前記体積固有電気抵抗が１０⁹ Ωｃｍを越えると、帯電部材１０の帯電量が不足するので、均一画像を得るのに十分な帯電電位を得ることができなくなる。また、前記体積固有電気抵抗が１０⁶ Ωｃｍよりも低いと、感光体全体への電圧集中(リーク)、及び、異常放電が生じてしまう。それ故、前記電気抵抗調整層２の体積固有電気抵抗が１０⁶ 〜１０⁹ Ωｃｍであると、均一画像を得るのに十分な帯電電位を得ることができ、しかも、感光体全体への電圧集中（リーク）及び異常放電が生じることがない。また、ローラ電気抵抗の周方向偏差により部分的な画像不良が発生する場合があるので、ローラ電気抵抗の周方向偏差は、０．５オーダー以下に収める必要がある。
【００３５】
本発明においては、前記（Ａ）の配合比が、３０〜７０重量％であると共に、前記（Ｂ）の配合比が、７０〜３０重量％であり、かつ、前記（Ｃ）の配合量が、前記（Ａ）及び（Ｂ）の合計１００重量部に対して、１〜１５重量部である。このように、前記（Ａ）の配合比が、３０〜７０重量％であると共に、前記（Ｂ）の配合比が、７０〜３０重量％であり、かつ、前記（Ｃ）の配合量が、前記（Ａ）及び（Ｂ）の合計１００重量部に対して、１〜１５重量部であると、電気抵抗調整層２の体積固有電気抵抗を、好ましいとされる、１０⁶ 〜１０⁹ Ωｃｍの範囲内に調整することができる。
【００３６】
本発明においては、前記樹脂組成物は、前記（Ａ）、（Ｂ）及び（Ｃ）の混合物を二軸混練機、ニーダー等で溶融混練して均一かつ緻密に分散することによって得られる。本発明における電気抵抗調整層２は、このようにして得られた熱可塑性樹脂組成物を押出成形、射出成形等の手段で導電性支持体１の表面に被覆して、簡単に形成することができる。また、このようにして形成された電気抵抗調整層２は、任意の段階において、その表面を切削及び／又は研削加工をして、所望の表面精度とする。
【００３７】
本発明においては、前記保護層３は、アクリルシリコン樹脂、フッ素樹脂、シリコーン樹脂、アクリル樹脂、ポリアミド樹脂、ポリウレタン樹脂、ポリエステル樹脂、及び、ポリビニルブチラール樹脂から選ばれる樹脂を含有する樹脂組成物で構成されている。このような樹脂は、非粘着性において優れるので、トナー固着性に優れた帯電部材が得られる。
【００３８】
また、このような樹脂は、電気的に絶縁性であるので、単体で保護層３を形成すると、帯電ローラとしての特性が得られない。そこで、本発明においては、前記保護層３を形成する樹脂組成物は、導電性粒子を含有している。このような導電性粒子としては、例えば、酸化スズ、酸化鉄等の金属酸化物、及び、アセチレンブラック、ケッチェンブラック等のカーボンブラックが好適に用いられるが、本発明の目的に反しないかぎり、それら以外の導電性粒子であってもかまわない。
【００３９】
また、樹脂は電気的に絶縁性であるので、樹脂だけで保護層３を形成すると、帯電ローラとしての特性が得られない。そこで、前記樹脂に対してカーボン、金属酸化物等の導電粒子を分散することによって保護層３の電気抵抗を調整する。また、保護層３と電気抵抗調整層２との接着性を向上させるために、前記樹脂にイソシアネート等の反応性硬化剤を分散させてもよい。
【００４０】
このように、保護層３を形成する樹脂組成物が導電性粒子を含有していると、前記保護層３の電気抵抗値を容易に調整することができる。前記保護層３の電気抵抗値は、好ましくは、前記電気抵抗調整層２のそれよりも大きくなるように調整される。前記保護層３の電気抵抗値が前記電気抵抗調整層２のそれよりも大きくなるように調整されていると、感光体欠陥部への電圧集中、及び、異常放電（リーク）を回避することができる。ただし、前記保護層３の電気抵抗値を高くしすぎると帯電効率が低下するので、前記保護層３と前記電気抵抗調整層２との電気抵抗値の差は、１０³ Ωｃｍ以下であることが好ましい。
【００４１】
電気抵抗調整層２の上への保護層３の形成は、保護層３を構成する樹脂材料を有機溶媒に分散して塗料を作製し、これをスプレー塗装、ディッピング等の手段で被覆することにより行う。
【００４２】
本発明のプロセスカートリッジ（図２の１１０を参照。）には、請求項１〜８のいずれかに記載の帯電部材（ローラ）１０が被帯電体上に近接配置されるように設けられている。そして、本発明の画像形成装置は、このようなプロセスカートリッジを有している。このように、請求項１〜８のいずれかに記載の帯電部材１０が被帯電体上に近接配置されるように設けられたプロセスカートリッジとすると、これを有する画像形成装置は、電気抵抗値のばらつき、トナー固着、及び、それらに伴う帯電不良を防止すると共に、機械強度及び耐久性を向上させて、画像不良の発生を防止することができる。
【００４３】
本実施の形態においては、帯電部材１０を具体化した帯電ローラについて説明したが、本発明における帯電部材１０は、本発明の目的に反しない限り、帯電ローラ以外の帯電部材、例えば、ブレードのようなものであってもかまわない。
【００４４】
【実施例】
（実施例１）
（Ａ）ＡＢＳ樹脂（ＧＲ−０５００、電気化学工業製）５０重量％、（Ｂ）ポリエーテルエステルアミド（ＩＲＧＡＳＴＡＴ Ｐ１８、チバスペシャリティケミカルズ社製）５０重量％、及び、（Ｃ）エチレン−グリシジルメタクリレート−スチレン−アクリロニトリル共重合体（モディバーＡ４４００、日本油脂社製）４５重量部（前記（Ａ）及び（Ｂ）の材料の合計１００重量部に対して４５重量部）を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して、電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、アクリルシリコン樹脂（３０００ＶＨ−Ｐ、川上塗料社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなるフッ素樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００４５】
（実施例２）
実施例１と同様に形成した電気抵抗調整層の表面に、フッ素樹脂（ルミフロンＬＦ−６００、旭硝子社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなるフッ素樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００４６】
（実施例３）
実施例１と同様に形成した電気抵抗調整層の表面に、ポリアミド樹脂（ダイアミドＴ−１７１、ダイセルヒュルス社製）及びカーボンブラック（全固形分に対して１０重量％）からなる樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００４７】
（実施例４）
実施例１と同様に形成した電気抵抗調整層の表面に、ポリビニルブチラール樹脂（デンカブチラール３０００−Ｋ、電気化学工業社製）、イソシアネート硬化剤及び酸化スズ（全固形分に対して６０重量％）からなる樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００４８】
（実施例５）
（Ａ）スチレン−ブタジエン共重合体（ＨＩ−ＰＳ樹脂）（Ｈ４５０、東洋スチレン社製）５０重量％、（Ｂ）ポリエーテルエステルアミド（ＩＲＧＡＳＴＡＴ Ｐ１８、チバスペシャリティケミカルズ社製）５０重量％、及び、（Ｃ）エチレン−グリシジルメタクリレート−スチレン−アクリロニトリル共重合体（モディバーＡ４４００、日本油脂社製）４５重量部（前記（Ａ）及び（Ｂ）の材料の合計１００重量部に対して４５重量部）を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して、電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、フッ素樹脂（ルミフロンＬＦ−６００、旭硝子社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなるフッ素樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００４９】
（比較例１）
ポリプロピレン樹脂（ＭＡ０３、日本ポリケム社製）４０重量部にポリエーテルエステルアミド成分を含有するイオン導電性の高分子化合物（ＩＲＧＡＳＴＡＴ Ｐ１８、チバスペシャリティケミカルズ社製）６０重量部を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して、電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、アクリルシリコン樹脂（３０００ＶＨ−Ｐ、川上塗料社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなるフッ素樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００５０】
（比較例２）
ポリプロピレン樹脂（ＭＡ０３、日本ポリケム社製）５０重量部に四級アンモニウム塩基を含有するイオン導電性の高分子化合物（レオレックスＡＳ−１７２０、第一工業製薬社製、）５０重量部を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して、電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、フッ素樹脂（ルミフロンＬＦ−６００、旭硝子社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなるフッ素樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００５１】
（比較例３）
エピクロルヒドリンゴム（エピクロマーＣＧ、ダイソー社製）１００重量部に過塩素酸アンモニウム３重量部を配合してゴム組成物とし、このゴム組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して、電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、ポリビニルブチラール樹脂（デンカブチラール３０００−Ｋ、電気化学工業社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなる樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００５２】
（比較例４）
ＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部に導電性カーボンブラック（ケッチェンブラックＥＣ、ケッチェンブラックインターナショナル社製）１５重量部を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、ポリアミド樹脂（ダイアミドＴ−１７１、ダイセルヒュルス社製）及びカーボンブラック(全固形分に対して１０重量％)からなる樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００５３】
（比較例５）
ＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部に過塩素酸リチウム３重量部を配合して樹脂組成物とし、この樹脂組成物をステンレスからなる直径８ｍｍの芯軸に射出成形により被覆して電気抵抗調整層を形成した。次いで、この電気抵抗調整層の表面に、ポリビニルブチラール樹脂（デンカブチラール３０００−Ｋ、電気化学工業社製）、イソシアネート系硬化剤及び酸化スズ（全固形分に対して６０重量％）からなる樹脂組成物を塗布して、約１０μｍ厚の保護層を形成することにより、直径１２ｍｍの帯電ローラを得た。
【００５４】
以上、実施例１〜５及び比較例１〜５で得られた帯電ローラについて、次の試験を行った。
【００５５】
（試験１）
実施例１〜５及び比較例１〜５で得られた帯電ローラについて、成形後のローラのウェルド発生状態を目視にて確認したところ、実施例１〜５では、目視でウェルドを確認することができなかったが、比較例１、２では、ローラ軸方向に顕著なウェルドが確認された。
【００５６】
（試験２）
実施例１〜５及び比較例１〜５で得られた帯電ローラについて、ローラ電気抵抗の周方向変動状態を測定した。評価環境を２３℃６０％ＲＨとし、そして、印加電圧を５００Ｖとした。試験結果は、次の表１に示される。
【００５７】
【表１】

【００５８】
表１より、実施例１〜５の帯電ローラでは、周方向偏差が０．５オーダー以下であったが、比較例１、２、４のローラでは、周方向偏差が０．５オーダー以上になったことがわかる。
【００５９】
（試験３）
図２に示される画像形成装置を使用して、２３℃、６０％ＲＨの環境において、３００，０００枚の複写を行い、ローラ割れが発生するまでの耐久枚数を調べた。この際、帯電ローラの両端部に空隙規制部材としてスペーサテープを貼りつけ、帯電ローラと感光体との間の空隙を５０μとなるように配置させた。また、帯電ローラに印加する電圧は、ＤＣ＝−８００Ｖ、ＡＣ＝２４００Ｖpp（周波数＝２ＫＨｚ）とした。試験結果は、次の表２に示される。
【００６０】
【表２】

【００６１】
表２より次のことがわかる。即ち、実施例１〜５のローラでは、３００，０００枚の複写で割れが発生しなかったが、比較例１、２のローラでは割れが発生した。
【００６２】
（試験４）
図２に示される画像形成装置を使用して、感光体の「感光体の帯電電位」を測定し、そして、画像評価を「部分的帯電不良（画像ムラ）の有無」及び「感光体欠陥部への異常放電有無」によって行った。この際、帯電ローラの両端部に空隙規制部材としてスペーサテープを貼りつけ、帯電ローラと感光体との間の空隙を５０μとなるように配置させた。また、帯電ローラに印加する電圧は、ＤＣ＝−８００Ｖ、ＡＣ＝２４００Ｖpp（周波数＝２ＫＨｚ）とし、そして、評価環境は、２３℃６０％ＲＨとした。
そして、感光体欠陥部への電圧集中、及び、異常放電（リーク）によって生じる異常画像の有無を評価した。
次いで、１００，０００枚の連続複写を行って、ローラ表面へのトナー固着評価及び画像評価を行った。評価環境は、いずれも、２３℃５０％ＲＨとした。
以上の試験結果は、次の表３に示される。
【００６３】
【表３】

【００６４】
表３より次のことがわかる。即ち、実施例１〜５の帯電ローラは、全項目で良好な結果が得られたが、比較例３〜５のローラでは不具合が見られた。
【００６５】
前記試験３と同様に、図２に示される画像形成装置を使用して、感光体の帯電電位及び画像評価を行った。また、感光体欠陥部への電圧集中、異常放電（リーク）によって生じる異常画像の有無の評価を行った。評価環境は、１０℃１５％ＲＨ及び３０℃９０％ＲＨとした。
試験結果は、次の表４，５に示される。
【００６６】
【表４】

【００６７】
【表５】

【００６８】
表４，５より次のことがわかる。即ち、実施例１〜５の帯電ローラは、各環境下で良好な結果が得られたが、比較例２〜５は低温低湿（１０℃１５％ＲＨ）時、及び、高温高湿（３０℃９０％ＲＨ）時に画像上の不具合が見られた。
【００６９】
【発明の効果】
（１）請求項１に記載された発明によれば、電気抵抗調整層が、（Ａ）スチレン系熱可塑性樹脂、（Ｂ）高分子型イオン導電材料、並びに、（Ｃ）主鎖にエチレン−グリシジルメタクリレート共重合体を有し、側鎖にアクリロニトリル成分及びスチレン成分の両方又はそれらの一方を有するグラフトコポリマー、を溶融混練してなる樹脂組成物で構成されていると、電気抵抗値のばらつき、トナー固着、及び、それらに伴う帯電不良を防止すると共に、機械的強度及び耐久性の優れた帯電部材を提供することができる。
【００７０】
（２）請求項２に記載された発明によれば、高分子型イオン導電材料がポリエーテルエステルアミドを含有する化合物であるので、電気抵抗調整層に要求される電気抵抗値を容易に得ることができる。また、ポリエーテルエステルアミドがマトリクスポリマー中に分子レベルで均一に分散、固定化され、そのために、導電性顔料を分散した樹脂組成物にみられるような導電性顔料の分散不良に伴う電気抵抗値のバラツキが生じない。さらに、ポリエーテルエステルアミドは高分子材料であるので、ブリードアウトも生じ難い。
【００７１】
（３）請求項３に記載された発明によれば、グリシジルメタクリレート成分の含有量がグラフトコポリマーの１〜２０重量％であるので、本来親和性の低い（Ａ）と（Ｂ）との間の相溶化剤として機能して、（Ａ）及び（Ｂ）の分散状態を均一かつ緻密化し、そのために、側鎖に含まれるアクリロニトリル成分及びスチレン成分は、（Ａ）及び（Ｂ）の分散不良に伴うウェルド部電気抵抗の変動、使用時の電気的・機械的ストレス、又は、経時・環境での体積変動により電気抵抗調整層のウェルド部分に発生するクラックを抑制することができる。
【００７２】
（４）請求項４に記載された発明によれば、（Ａ）の配合比が、３０〜７０重量％であると共に、（Ｂ）の配合比が、７０〜３０重量％であり、かつ、（Ｃ）の配合量が、（Ａ）及び（Ｂ）の合計１００重量部に対して、１〜１５重量部であるので、電気抵抗調整層２の体積固有電気抵抗を、好ましいとされる、１０⁶ 〜１０⁹ Ωｃｍの範囲内に調整することができる。
【００７３】
（５）請求項５に記載された発明によれば、保護層の電気抵抗値が電気抵抗調整層のそれよりも大きくなるように調整されているので、感光体欠陥部への電圧集中、及び、異常放電（リーク）を回避することができる。
（６）請求項６に記載された発明によれば、保護層と電気抵抗調整層との電気抵抗値の差が１０³ Ωｃｍ以下であるので、帯電効率の低下を防ぐことができる。
【００７４】
（７）請求項７に記載された発明によれば、保護層が導電性粒子を含有しているので、保護層の電気抵抗値を容易に調整することができる。
（８）請求項８に記載された発明によれば、保護層がアクリルシリコン樹脂、フッ素樹脂、シリコーン樹脂、アクリル樹脂、ポリアミド樹脂、ポリウレタン樹脂、ポリエステル樹脂、及び、ポリビニルブチラール樹脂から選ばれる樹脂を含有する樹脂組成物で構成されているので、このような樹脂が非粘着性において優れていることにより、トナー固着性に優れた帯電部材が得られる。
【００７５】
（９）請求項９，１０に記載された発明によれば、請求項１〜８のいずれかに記載の帯電部材が被帯電体上に近接配置されるように設けられたプロセスカートリッジとするので、これを有する画像形成装置は、電気抵抗値のばらつき、トナー固着、及び、それらに伴う帯電不良を防止すると共に、機械強度及び耐久性を向上させて、画像不良の発生を防止することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態を示す帯電ローラの断面図である。
【図２】従来の帯電ローラ方式の画像形成装置の説明図である。
【符号の説明】
１ 導電性支持体
２ 電気抵抗調整層
３ 保護層
１０ 帯電部材（帯電ローラ）[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, a facsimile, and the like, a charging member that is disposed in the vicinity of a photosensitive member and performs a charging process, a cartridge having the charging member, and an image forming apparatus having the cartridge.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile, a charging roller is generally used as a charging member that performs a charging process on a photosensitive member. FIG. 2 is an explanatory diagram of an image forming apparatus having a conventional charging roller.
[0003]
In FIG. 2, reference numeral 111 denotes a conventional charging roller type image forming apparatus. A conventional charging roller type image forming apparatus 111 includes a photosensitive drum 101 on which an electrostatic latent image is formed, a charging roller 102 that performs charging processing in contact with the photosensitive drum 101, an exposure unit 103 such as a laser beam, and a photosensitive member. A developing roller 104 for attaching toner to the electrostatic latent image on the photosensitive drum 101, a power pack 105 for applying a DC voltage to the charging roller 102, and a transfer roller for transferring the toner image on the photosensitive drum 101 to the recording paper 107. 106, a cleaning device 108 for cleaning the photosensitive drum 101 after the transfer process, and a surface potential meter 109 for measuring the surface potential of the photosensitive drum 101. The conventional charging roller type image forming apparatus 111 is a process cartridge attaching / detaching type. In other words, in the image forming apparatus 111, four process devices, that is, the photosensitive drum 101, the charging roller 102, the developing roller 104, and the cleaning device 108, are collectively provided as a process cartridge 110 that is detachable from the main body. ing. The process cartridge 110 only needs to include at least the photosensitive drum 101 and the charging roller 102. The process cartridge 110 is connected to the drive system and the electrical system on the main body side by being mounted on the image forming apparatus 111 in a predetermined manner.
[0004]
Next, a basic image forming operation in the conventional charging roller type image forming apparatus 111 will be described.
When a DC voltage is supplied from the power pack 105 to the charging roller 102 in contact with the photosensitive drum 101, the surface of the photosensitive drum 101 is uniformly charged at a high potential. Immediately thereafter, when image light is irradiated onto the surface of the photosensitive drum 101 by the exposure unit 103, the potential of the irradiated portion of the photosensitive drum 101 is lowered. It is known that such a charging mechanism to the surface of the photosensitive drum 101 by the charging roller 102 is a discharge according to Paschen's law in a minute space between the charging roller 102 and the photosensitive drum 101.
[0005]
Since the image light has a light amount distribution according to white / black of the image, when the image light is irradiated, the potential distribution corresponding to the recorded image on the surface of the photosensitive drum 101 by the irradiation of the image light, that is, An electrostatic latent image is formed. When the portion of the photosensitive drum 101 on which the electrostatic latent image is formed in this way passes through the developing roller 104, toner adheres according to the level of the potential, and a toner image that visualizes the electrostatic image is formed. Is done. The recording paper 107 is conveyed by a registration roller (not shown) at a predetermined timing to the portion of the photosensitive drum 101 where the toner image is formed, and overlaps the toner image. Then, after the toner image is transferred onto the recording paper by the transfer roller 106, the recording paper 107 is separated from the photosensitive drum 101. The separated recording paper 107 is conveyed through a conveyance path, heated and fixed by a fixing unit (not shown), and then discharged outside the apparatus. When the transfer is completed in this manner, the surface of the photosensitive drum 101 is cleaned by the cleaning device 108, and the residual charge is removed by a quenching lamp (not shown), so that the next image forming process is performed. Prepared for.
[0006]
As a charging method using a charging roller, a contact charging method in which a roller is brought into contact with a photosensitive member is generally used.
(1) The substance constituting the charging roller oozes out from the charging roller, and this adheres to the surface of the object to be charged and leaves a charging roller mark.
(2) When an AC voltage is applied to the charging roller, the charging roller that is in contact with the member to be charged vibrates, so that a charging noise is generated.
(3) Since the toner on the photosensitive member adheres to the charging roller (particularly, the above-described oozing causes toner adhesion more easily), so that the charging performance of the charging roller is reduced,
(4) the substance constituting the charging roller adheres to the photoreceptor, and
(5) The charging roller is permanently deformed when the photosensitive member is stopped for a long time.
There was a problem.
[0007]
As a technique for solving such a problem, a proximity charging method (see Patent Document 1) in which a charging roller is brought close to a photosensitive member has been proposed. In this proximity charging method, the photosensitive member is charged by applying a voltage to the charging roller with the charging roller facing the photosensitive member at a closest distance (0.005 to 0.3 mm). Charging method. In this proximity charging method, the roller and the photosensitive member are not in contact with each other, which has been a problem in the conventional contact charging method, (a) the substance constituting the charging roller adheres to the photosensitive member, and (B) There is no problem that the photoreceptor is permanently deformed when stopped for a long time. In this proximity charging method, the amount of toner that adheres to the charging roller is reduced, so that the toner on the photosensitive member is less likely to adhere to the charging roller, and the charging performance of the charging roller does not deteriorate.
[0008]
The required characteristics of the charging roller used in the proximity charging method are different from those of the charging roller used in the conventional contact charging method. A charging roller generally used in the contact charging system has a structure in which an elastic body such as vulcanized rubber is coated around a cored bar. Therefore, in the contact charging method, the photosensitive member is uniformly charged, so that it is necessary that the charging roller uniformly contacts the photosensitive member.
[0009]
In the proximity charging method, when a charging roller formed of an elastic body such as vulcanized rubber is used, the following problems occur.
(1) Since a gap is formed between the photosensitive member and the charging roller, it is necessary to interpose a gap holding member such as a spacer in the non-image area at both ends of the charging roller, but the charging roller formed of an elastic body Then, since it is difficult to make the gap uniform due to the deformation of the elastic body, fluctuations in the charging potential and image unevenness due to it occur.
(2) Since the vulcanized rubber material constituting the elastic body tends to sag and deform over time, the voids change over time.
[0010]
In order to eliminate such problems, it is conceivable to use a thermoplastic resin that is an inelastic material. As a result, the gap between the photoconductor and the charging roller can be made uniform. It is known that the charging mechanism on the surface of the photosensitive drum by the charging roller is a discharge according to Paschen's law in a minute discharge between the charging roller and the photosensitive drum. In order to obtain the function of holding the photosensitive drum at a predetermined charging potential, it is necessary to control the electric resistance value of the thermoplastic resin to a semiconductive region (about 10 ⁶ to 10 ⁹ Ωcm).
[0011]
As a method of controlling the electrical resistance value, there is a method of dispersing a conductive pigment such as carbon black in a thermoplastic resin. However, when an attempt is made to set the electrical resistance adjustment layer in the semiconductive region using a conductive pigment, since the variation in electrical resistance value increases, partial charging failure occurs, and as a result, image defects occur. There was a problem.
[0012]
On the other hand, as another means for controlling the electric resistance value, there is a method using an ion conductive material, that is, an electrolyte salt such as a Li salt. Since the ion conductive material is dispersed at the molecular level in the matrix resin, the electric resistance value variation is small compared to the above-mentioned one in which the conductive pigment is dispersed. It did not matter. However, since the electrolyte salt has a low molecular weight, it tends to bleed out on the surface of the matrix resin. For this reason, when the bleed out to the surface of the charging roller, toner sticking occurs and image defects occur. There was a problem of letting.
[0013]
In order to avoid bleed out, it is conceivable to use a high molecular weight ion conductive material. In this case, the ion conductive material is dispersed and fixed in the matrix resin, and bleeding out to the surface hardly occurs. As a charging member with little bleed-out over time, a polymer obtained by polymerizing a vinyl monomer having a quaternary ammonium base, a vinyl monomer having a hydroxyl group, and a crosslinkable monomer (Patent Document 2) Have been proposed).
[0014]
However, in the case of a quaternary ammonium salt-containing polymer-type conductive agent, the electrical resistance value is highly dependent on the temperature and humidity environment, and depending on the addition ratio and the temperature and humidity environment, abnormal discharge due to lower electrical resistance, Since there is a high possibility that problems such as charging failure associated with resistance will occur, there is a problem that prescription is difficult.
[0015]
In such a polymer composite, a remarkable weld is generated at the time of molding mainly due to poor compatibility between the constituent resins, and the strength of the weld portion is reduced or the electric resistance value fluctuates. There was a problem to do. In addition, due to this decrease in strength, when a resin with low mechanical strength or poor compatibility is used as the matrix resin, electrical resistance due to electrical / mechanical stress during use or volume fluctuations over time / environment There was a problem that cracks occurred in the weld portion of the adjustment layer. In addition, there is a problem that the electric resistance variation in the weld portion causes a defect of partial image failure.
[0016]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-240076 [Patent Document 2]
[Patent Document 1] Japanese Patent Laid-Open No. 7-121209
[Problems to be solved by the invention]
The present invention aims to solve this problem.
That is, the present invention prevents a variation in electrical resistance, toner adhesion, and charging failure associated therewith, and a charging member having excellent mechanical strength and durability, a cartridge having the charging member, and an image having the cartridge. An object is to provide a forming apparatus.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 includes an electric resistance adjusting layer formed on the conductive support and a protective layer coated on the surface of the electric resistance adjusting layer. In the charging member, the electrical resistance adjusting layer has (A) a styrene-based thermoplastic resin, (B) a polymer ion conductive material, and (C) an ethylene-glycidyl methacrylate copolymer in the main chain. A charging member comprising a resin composition obtained by melt-kneading a graft copolymer having both or one of an acrylonitrile component and a styrene component in a chain.
[0019]
The invention described in claim 2 is characterized in that, in the invention described in claim 1, the polymer ion conductive material is a compound containing a polyether ester amide.
[0020]
The invention described in claim 3 is the invention described in claim 1 or 2, wherein the content of the glycidyl methacrylate component is 1 to 20% by weight of the graft copolymer.
[0021]
The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the blending ratios of (A) and (B) are 30 to 70% by weight and 70 to 30% by weight, respectively. %, And the blending amount of (C) is 1 to 15 parts by weight with respect to 100 parts by weight of the total of (A) and (B).
[0022]
The invention described in claim 5 is the invention described in any one of claims 1 to 4, characterized in that an electrical resistance value of the protective layer is larger than an electrical resistance value of the electrical resistance adjusting layer. To do.
[0023]
The invention described in claim 6 is the invention described in any one of claims 1 to 5, wherein a difference in electric resistance value between the protective layer and the electric resistance adjusting layer is 10 ³ Ω · cm or less. It is characterized by this.
[0024]
The invention described in claim 7 is the invention described in any one of claims 1 to 6, wherein the protective layer contains conductive particles.
[0025]
The invention described in claim 8 is the invention described in any one of claims 1 to 7, wherein the protective layer is an acrylic silicon resin, a fluororesin, a silicone resin, an acrylic resin, a polyamide resin, a polyurethane resin, a polyester. It is comprised with the resin composition containing resin chosen from resin and polyvinyl butyral resin.
[0026]
According to a ninth aspect of the present invention, there is provided a process cartridge characterized in that the charging member according to any of the first to eighth aspects is provided so as to be disposed close to a member to be charged.
[0027]
According to a tenth aspect of the present invention, there is provided an image forming apparatus including the process cartridge according to the ninth aspect.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a charging roller showing an embodiment of the present invention.
[0029]
In FIG. 1, reference numeral 10 denotes a charging member (charging roller). The charging member (charging roller) 10 includes an electric resistance adjusting layer 2 formed on the conductive support 1 and a protective layer 3 covered on the surface of the electric resistance adjusting layer 2. The electrical resistance adjusting layer 2 has (A) a styrene-based thermoplastic resin, (B) a polymer ion conductive material, and (C) an ethylene-glycidyl methacrylate copolymer in the main chain. And a graft copolymer having either or both of an acrylonitrile component and a styrene component, and a resin composition obtained by melt-kneading.
[0030]
The (A) styrenic thermoplastic resin is a styrene polymer or copolymer, for example, polystyrene (PS), styrene-butadiene copolymer (HI-PS), styrene-acrylonitrile copolymer (AS). Or a styrene-butadiene-acrylonitrile copolymer (ABS).
[0031]
The polymer ion conductive material (B) is preferably a polyether ester amide having the following formula:

(In the formula, R ¹ , R ² and R ³ are alkyl groups having 1 to 20 carbon atoms.)
It is a copolymer shown by these. This copolymer is composed of a hard part of a polyamide unit and a soft part of a polyether unit, which is known per se. Since the polyether ester amide (B) is an ion conductive polymer material, the electrical resistance value required for the electrical resistance adjusting layer can be easily obtained. In addition, the polyether ester amide is uniformly dispersed and fixed at the molecular level in the matrix polymer, and as a result, the electrical resistance associated with poor dispersion of the conductive pigment as seen in a resin composition in which the conductive pigment is dispersed. There is no variation in value. Furthermore, since polyether ester amide is a polymer material, bleeding out hardly occurs.
[0032]
The main chain ethylene-glycidyl methacrylate copolymer (C) comprises an ethylene component having low water absorption and a glycidyl methacrylate component as a reactive group. The ethylene unit has a high affinity with the styrene-based resin (A) and has a low water absorption, and therefore suppresses electrical resistance and shape fluctuations associated with moisture absorption of the resin. The glycidyl methacrylate of the reactive group reacts with the ester group or amino group of the polyether ester amide of (B) by heating when melt kneading (A), (B) and (C), A strong chemical bond with (B). Furthermore, since the acrylonitrile component and the styrene component contained in the side chain have good compatibility with the styrene resin of (A), the graft copolymer of (C) is inherently low in affinity with (A) and (B ) To make the dispersion state of (A) and (B) uniform and dense. Therefore, the acrylonitrile component and styrene component contained in the side chain are affected by fluctuations in the electrical resistance of the weld due to poor dispersion of (A) and (B), electrical / mechanical stress during use, or over time / environment. Cracks generated in the weld portion of the electric resistance adjusting layer due to the volume fluctuation can be suppressed. And in order for (C) and (B) to perform sufficient coupling | bonding, content of a glycidyl methacrylate component needs to be 1-20 weight% of the graft copolymer of (C).
[0033]
Thus, the electrical resistance adjusting layer 2 has (A) a styrene thermoplastic resin, (B) a polymer ion conductive material, and (C) an ethylene-glycidyl methacrylate copolymer in the main chain, When it is composed of a resin composition obtained by melt-kneading a graft copolymer having both or one of acrylonitrile component and styrene component in the chain, variation in electric resistance value, toner fixation, and charging failure associated therewith In addition, it is possible to provide a charging member having excellent mechanical strength and durability.
[0034]
In the present invention, the volume specific electric resistance of the electric resistance adjusting layer 2 is preferably 10 ⁶ to 10 ⁹ Ωcm. If the volume specific electric resistance exceeds 10 ⁹ Ωcm, the charging amount of the charging member 10 is insufficient, and it becomes impossible to obtain a charging potential sufficient for obtaining a uniform image. On the other hand, if the volume resistivity is lower than 10 ⁶ Ωcm, voltage concentration (leakage) and abnormal discharge occur on the entire photoreceptor. Thus, the volume electrical resistivity of the electrical resistance adjusting layer 2 is 10 ⁶ to 10 ⁹ [Omega] cm, to obtain a uniform image can be obtained a sufficient charging potential, moreover, voltage concentration to the entire photoconductor (Leakage) and abnormal discharge do not occur. Further, since a partial image defect may occur due to the circumferential deviation of the roller electrical resistance, the circumferential deviation of the roller electrical resistance needs to be within 0.5 order.
[0035]
In the present invention, the blending ratio of (A) is 30 to 70% by weight, the blending ratio of (B) is 70 to 30% by weight, and the blending amount of (C) is , And 1 to 15 parts by weight per 100 parts by weight in total of (A) and (B). Thus, the blending ratio of (A) is 30 to 70% by weight, the blending ratio of (B) is 70 to 30% by weight, and the blending amount of (C) is The volume specific electric resistance of the electric resistance adjusting layer 2 is preferably 10 ⁶ to 10 ⁹ Ωcm when the amount is 1 to 15 parts by weight relative to 100 parts by weight of the total of (A) and (B). Can be adjusted within the range.
[0036]
In the present invention, the resin composition is obtained by melting and kneading the mixture of (A), (B) and (C) with a biaxial kneader, a kneader or the like and uniformly and densely dispersing the mixture. The electrical resistance adjusting layer 2 in the present invention can be easily formed by coating the surface of the conductive support 1 with the thermoplastic resin composition thus obtained by means of extrusion molding, injection molding or the like. it can. Further, the electrical resistance adjusting layer 2 formed in this way is subjected to cutting and / or grinding processing at a desired stage to obtain a desired surface accuracy.
[0037]
In the present invention, the protective layer 3 is composed of a resin composition containing a resin selected from an acrylic silicon resin, a fluororesin, a silicone resin, an acrylic resin, a polyamide resin, a polyurethane resin, a polyester resin, and a polyvinyl butyral resin. Has been. Since such a resin is excellent in non-adhesiveness, a charging member excellent in toner fixing property can be obtained.
[0038]
Further, since such a resin is electrically insulating, if the protective layer 3 is formed alone, the characteristics as a charging roller cannot be obtained. Therefore, in the present invention, the resin composition forming the protective layer 3 contains conductive particles. As such conductive particles, for example, metal oxides such as tin oxide and iron oxide, and carbon black such as acetylene black and ketjen black are preferably used. Other conductive particles may be used.
[0039]
Further, since the resin is electrically insulating, if the protective layer 3 is formed only from the resin, the characteristics as the charging roller cannot be obtained. Therefore, the electrical resistance of the protective layer 3 is adjusted by dispersing conductive particles such as carbon and metal oxide in the resin. In order to improve the adhesion between the protective layer 3 and the electrical resistance adjusting layer 2, a reactive curing agent such as isocyanate may be dispersed in the resin.
[0040]
Thus, when the resin composition forming the protective layer 3 contains conductive particles, the electrical resistance value of the protective layer 3 can be easily adjusted. The electric resistance value of the protective layer 3 is preferably adjusted to be larger than that of the electric resistance adjusting layer 2. If the electrical resistance value of the protective layer 3 is adjusted to be larger than that of the electrical resistance adjustment layer 2, voltage concentration and abnormal discharge (leakage) on the photosensitive member defect portion can be avoided. it can. However, if the electrical resistance value of the protective layer 3 is too high, charging efficiency is lowered. Therefore, the difference in electrical resistance value between the protective layer 3 and the electrical resistance adjustment layer 2 may be 10 ³ Ωcm or less. preferable.
[0041]
The protective layer 3 is formed on the electric resistance adjusting layer 2 by dispersing the resin material constituting the protective layer 3 in an organic solvent to prepare a paint, which is then coated by means such as spray coating or dipping. Do.
[0042]
In the process cartridge of the present invention (see 110 in FIG. 2), the charging member (roller) 10 according to any one of claims 1 to 8 is provided so as to be disposed close to the member to be charged. . The image forming apparatus of the present invention has such a process cartridge. Thus, when the charging member 10 according to any one of claims 1 to 8 is a process cartridge provided so as to be disposed close to a member to be charged, the image forming apparatus having the process cartridge has an electric resistance value. In addition to preventing variations, toner adhesion, and charging defects associated therewith, it is possible to improve mechanical strength and durability and prevent image defects.
[0043]
In the present embodiment, the charging roller in which the charging member 10 is embodied has been described. However, the charging member 10 in the present invention may be a charging member other than the charging roller, such as a blade, as long as it does not contradict the purpose of the present invention. It doesn't matter if it's something.
[0044]
【Example】
(Example 1)
(A) ABS resin (GR-0500, manufactured by Denki Kagaku Kogyo) 50% by weight, (B) polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) 50% by weight, and (C) ethylene-glycidyl methacrylate- Styrene-acrylonitrile copolymer (Modiva A4400, manufactured by NOF Corporation) 45 parts by weight (45 parts by weight with respect to the total of 100 parts by weight of the materials (A) and (B)) was blended to form a resin composition, This resin composition was coated on a core shaft made of stainless steel with a diameter of 8 mm by injection molding to form an electric resistance adjusting layer. Next, a fluororesin composition comprising an acrylic silicon resin (3000 VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight with respect to the total solid content) is formed on the surface of the electric resistance adjusting layer. Coating was performed to form a protective layer having a thickness of about 10 μm, thereby obtaining a charging roller having a diameter of 12 mm.
[0045]
(Example 2)
Fluorine made of fluororesin (Lumiflon LF-600, manufactured by Asahi Glass Co., Ltd.), isocyanate curing agent and tin oxide (60% by weight based on the total solid content) on the surface of the electrical resistance adjusting layer formed in the same manner as in Example 1. By applying the resin composition to form a protective layer having a thickness of about 10 μm, a charging roller having a diameter of 12 mm was obtained.
[0046]
(Example 3)
On the surface of the electrical resistance adjusting layer formed in the same manner as in Example 1, a resin composition comprising a polyamide resin (Daiamide T-171, manufactured by Daicel Huls) and carbon black (10% by weight with respect to the total solid content) Coating was performed to form a protective layer having a thickness of about 10 μm, thereby obtaining a charging roller having a diameter of 12 mm.
[0047]
Example 4
Polyvinyl butyral resin (Denka Butyral 3000-K, manufactured by Denki Kagaku Kogyo Co., Ltd.), isocyanate curing agent and tin oxide (60% by weight based on the total solid content) on the surface of the electric resistance adjusting layer formed in the same manner as in Example 1. A charging roller having a diameter of 12 mm was obtained by applying a resin composition comprising: a protective layer having a thickness of about 10 μm.
[0048]
(Example 5)
(A) 50% by weight of styrene-butadiene copolymer (HI-PS resin) (H450, manufactured by Toyo Styrene Co., Ltd.), (B) 50% by weight of polyetheresteramide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals Co., Ltd.), and (C) 45 parts by weight of an ethylene-glycidyl methacrylate-styrene-acrylonitrile copolymer (Modiva A4400, manufactured by NOF Corporation) (45 parts by weight with respect to a total of 100 parts by weight of the materials (A) and (B)) The resin composition was blended to form a resin composition, and this resin composition was coated on a core shaft made of stainless steel with a diameter of 8 mm by injection molding to form an electric resistance adjusting layer. Next, a fluororesin composition comprising a fluororesin (Lumiflon LF-600, manufactured by Asahi Glass Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight with respect to the total solid content) is applied to the surface of the electrical resistance adjusting layer. Thus, a charging roller having a diameter of 12 mm was obtained by forming a protective layer having a thickness of about 10 μm.
[0049]
(Comparative Example 1)
A resin composition is prepared by blending 40 parts by weight of a polypropylene resin (MA03, manufactured by Nippon Polychem) with 60 parts by weight of an ion conductive polymer compound (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) containing a polyetheresteramide component. The resin composition was coated on an 8 mm diameter core shaft made of stainless steel by injection molding to form an electric resistance adjusting layer. Next, a fluororesin composition comprising an acrylic silicon resin (3000 VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight with respect to the total solid content) is formed on the surface of the electric resistance adjusting layer. Coating was performed to form a protective layer having a thickness of about 10 μm, thereby obtaining a charging roller having a diameter of 12 mm.
[0050]
(Comparative Example 2)
50 parts by weight of an ion conductive polymer compound containing a quaternary ammonium base (ROLEX AS-1720, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is blended with 50 parts by weight of a polypropylene resin (MA03, manufactured by Nippon Polychem). A resin composition was formed, and this resin composition was coated on a core shaft made of stainless steel with a diameter of 8 mm by injection molding to form an electric resistance adjusting layer. Next, a fluororesin composition comprising a fluororesin (Lumiflon LF-600, manufactured by Asahi Glass Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight with respect to the total solid content) is applied to the surface of the electrical resistance adjusting layer. Thus, a charging roller having a diameter of 12 mm was obtained by forming a protective layer having a thickness of about 10 μm.
[0051]
(Comparative Example 3)
100 parts by weight of epichlorohydrin rubber (Epichromer CG, manufactured by Daiso Corporation) is blended with 3 parts by weight of ammonium perchlorate to form a rubber composition, and this rubber composition is coated on a core shaft made of stainless steel with a diameter of 8 mm by injection molding. Then, an electric resistance adjusting layer was formed. Next, on the surface of the electric resistance adjusting layer, a resin composition comprising a polyvinyl butyral resin (Denka Butyral 3000-K, manufactured by Denki Kagaku Kogyo Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight based on the total solid content). A charging roller having a diameter of 12 mm was obtained by applying the product to form a protective layer having a thickness of about 10 μm.
[0052]
(Comparative Example 4)
100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 15 parts by weight of conductive carbon black (Ketjen Black EC, manufactured by Ketjen Black International) are blended to form a resin composition. Was coated by injection molding on an 8 mm diameter core shaft made of stainless steel to form an electric resistance adjusting layer. Next, a resin composition composed of polyamide resin (Daiamide T-171, manufactured by Daicel Huls) and carbon black (10% by weight with respect to the total solid content) is applied to the surface of the electric resistance adjusting layer, and about By forming a protective layer having a thickness of 10 μm, a charging roller having a diameter of 12 mm was obtained.
[0053]
(Comparative Example 5)
3 parts by weight of lithium perchlorate is blended with 100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo Co., Ltd.) to obtain a resin composition, and this resin composition is formed by injection molding on a core shaft made of stainless steel with a diameter of 8 mm. An electric resistance adjusting layer was formed by coating. Next, on the surface of the electric resistance adjusting layer, a resin composition comprising a polyvinyl butyral resin (Denka Butyral 3000-K, manufactured by Denki Kagaku Kogyo Co., Ltd.), an isocyanate curing agent and tin oxide (60% by weight based on the total solid content). A charging roller having a diameter of 12 mm was obtained by applying the product to form a protective layer having a thickness of about 10 μm.
[0054]
As described above, the following tests were performed on the charging rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 5.
[0055]
(Test 1)
Regarding the charging rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 5, when the weld occurrence state of the roller after molding was visually confirmed, in Examples 1 to 5, it is possible to visually confirm the weld. Although it was not possible, in Comparative Examples 1 and 2, a remarkable weld was confirmed in the roller axial direction.
[0056]
(Test 2)
For the charging rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 5, the circumferential variation state of the roller electrical resistance was measured. The evaluation environment was 23 ° C. and 60% RH, and the applied voltage was 500V. The test results are shown in Table 1 below.
[0057]
[Table 1]

[0058]
From Table 1, in the charging rollers of Examples 1 to 5, the circumferential deviation was 0.5 orders or less, but in the rollers of Comparative Examples 1, 2, and 4, the circumferential deviation was 0.5 orders or more. I understand that.
[0059]
(Test 3)
Using the image forming apparatus shown in FIG. 2, 300,000 copies were made in an environment of 23 ° C. and 60% RH, and the number of durable sheets until a roller crack occurred was examined. At this time, a spacer tape as a gap regulating member was attached to both ends of the charging roller, and the gap between the charging roller and the photosensitive member was arranged to be 50 μm. The voltage applied to the charging roller was DC = −800 V and AC = 2400 Vpp (frequency = 2 KHz). The test results are shown in Table 2 below.
[0060]
[Table 2]

[0061]
Table 2 shows the following. That is, in the rollers of Examples 1 to 5, no cracks occurred in 300,000 copies, but in the rollers of Comparative Examples 1 and 2, cracks occurred.
[0062]
(Test 4)
Using the image forming apparatus shown in FIG. 2, the “charge potential of the photoconductor” of the photoconductor is measured, and the image evaluation is performed based on “the presence / absence of partial charging failure (image unevenness)” and “photoconductor defect portion”. It was done according to the presence or absence of abnormal discharge. At this time, a spacer tape as a gap regulating member was attached to both ends of the charging roller, and the gap between the charging roller and the photosensitive member was arranged to be 50 μm. The voltage applied to the charging roller was DC = −800 V, AC = 2400 Vpp (frequency = 2 KHz), and the evaluation environment was 23 ° C. and 60% RH.
Then, the presence or absence of an abnormal image caused by voltage concentration on the photosensitive member defect portion and abnormal discharge (leakage) was evaluated.
Subsequently, continuous copying of 100,000 sheets was performed, and toner adhesion evaluation and image evaluation on the roller surface were performed. The evaluation environments were all 23 ° C. and 50% RH.
The above test results are shown in Table 3 below.
[0063]
[Table 3]

[0064]
Table 3 shows the following. That is, the charging rollers of Examples 1 to 5 gave good results in all items, but the rollers of Comparative Examples 3 to 5 showed defects.
[0065]
As in Test 3, the image forming apparatus shown in FIG. 2 was used to evaluate the charged potential of the photoreceptor and image evaluation. In addition, the presence or absence of an abnormal image caused by voltage concentration on the photosensitive member defect portion or abnormal discharge (leakage) was evaluated. The evaluation environment was 10 ° C. 15% RH and 30 ° C. 90% RH.
The test results are shown in the following Tables 4 and 5.
[0066]
[Table 4]

[0067]
[Table 5]

[0068]
Tables 4 and 5 show the following. That is, in the charging rollers of Examples 1 to 5, good results were obtained in each environment, but Comparative Examples 2 to 5 were at low temperature and low humidity (10 ° C. and 15% RH) and at high temperature and high humidity (30 ° C. (90% RH), an image defect was observed.
[0069]
【The invention's effect】
(1) According to the invention described in claim 1, the electric resistance adjusting layer comprises (A) a styrenic thermoplastic resin, (B) a polymer type ion conductive material, and (C) an ethylene- When the resin composition is formed by melt-kneading a graft copolymer having a glycidyl methacrylate copolymer and having both or one of an acrylonitrile component and a styrene component in the side chain, variation in electrical resistance value, It is possible to provide a charging member that is excellent in mechanical strength and durability, as well as preventing toner fixation and charging failure associated therewith.
[0070]
(2) According to the invention described in claim 2, since the polymer ion conductive material is a compound containing polyether ester amide, the electric resistance value required for the electric resistance adjusting layer can be easily obtained. Can do. In addition, the polyether ester amide is uniformly dispersed and fixed at the molecular level in the matrix polymer, and as a result, the electrical resistance value due to poor dispersion of the conductive pigment as seen in a resin composition in which the conductive pigment is dispersed. This variation does not occur. Furthermore, since the polyether ester amide is a polymer material, bleeding out hardly occurs.
[0071]
(3) According to the invention described in claim 3, since the content of the glycidyl methacrylate component is 1 to 20% by weight of the graft copolymer, it is originally between (A) and (B) having a low affinity. It functions as a compatibilizing agent, and the dispersion state of (A) and (B) is made uniform and dense. Therefore, the acrylonitrile component and the styrene component contained in the side chain are poorly dispersed in (A) and (B). Accompanying fluctuations in the electrical resistance of the weld portion, electrical / mechanical stress during use, or cracks occurring in the weld portion of the electrical resistance adjustment layer due to volume fluctuations over time and in the environment can be suppressed.
[0072]
(4) According to the invention described in claim 4, the blending ratio of (A) is 30 to 70% by weight, the blending ratio of (B) is 70 to 30% by weight, and Since the blending amount of (C) is 1 to 15 parts by weight with respect to a total of 100 parts by weight of (A) and (B), the volume specific electrical resistance of the electrical resistance adjusting layer 2 is preferred. It can be adjusted within the range of 10 ⁶ to 10 ⁹ Ωcm.
[0073]
(5) According to the invention described in claim 5, since the electric resistance value of the protective layer is adjusted to be larger than that of the electric resistance adjusting layer, voltage concentration on the photosensitive member defect portion, and Abnormal discharge (leakage) can be avoided.
(6) According to the invention described in claim 6, since the difference in electrical resistance value between the protective layer and the electrical resistance adjusting layer is 10 ³ Ωcm or less, it is possible to prevent the charging efficiency from being lowered.
[0074]
(7) According to the invention described in claim 7, since the protective layer contains conductive particles, the electrical resistance value of the protective layer can be easily adjusted.
(8) According to the invention described in claim 8, the protective layer is a resin selected from an acrylic silicon resin, a fluororesin, a silicone resin, an acrylic resin, a polyamide resin, a polyurethane resin, a polyester resin, and a polyvinyl butyral resin. Since the resin composition is contained, such a resin is excellent in non-adhesiveness, whereby a charging member excellent in toner fixing property can be obtained.
[0075]
(9) According to the invention described in claims 9 and 10, since the charging member according to any one of claims 1 to 8 is a process cartridge provided so as to be disposed close to the member to be charged. The image forming apparatus having this can prevent variation in electrical resistance value, toner adhesion, and charging failure associated therewith, and improve mechanical strength and durability, thereby preventing the occurrence of image defects. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a charging roller showing an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a conventional charging roller type image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Electrical resistance adjustment layer 3 Protective layer 10 Charging member (charging roller)

Claims (10)

In a charging member having an electric resistance adjusting layer formed on a conductive support and a protective layer coated on the surface of the electric resistance adjusting layer, the electric resistance adjusting layer comprises (A) a styrene-based thermoplastic A resin, (B) a polymer type ion conductive material, and (C) a graft copolymer having an ethylene-glycidyl methacrylate copolymer in the main chain and having both or one of an acrylonitrile component and a styrene component in the side chain, A charging member comprising a resin composition obtained by melting and kneading a resin. The charging member according to claim 1, wherein the polymer ion conductive material is a compound containing a polyether ester amide. The charging member according to claim 1 or 2, wherein the content of the glycidyl methacrylate component is 1 to 20% by weight of the graft copolymer. The blending ratios of (A) and (B) are 30 to 70% by weight and 70 to 30% by weight, respectively, and the blending amount of (C) is a total of 100 of (A) and (B). The charging member according to claim 1, wherein the charging member is 1 to 15 parts by weight with respect to parts by weight. The charging member according to claim 1, wherein an electric resistance value of the protective layer is larger than an electric resistance value of the electric resistance adjusting layer. The charging member according to claim 1, wherein a difference in electric resistance value between the protective layer and the electric resistance adjusting layer is 10 ³ Ω · cm or less. The charging member according to claim 1, wherein the protective layer contains conductive particles. The protective layer is composed of a resin composition containing a resin selected from an acrylic silicon resin, a fluorine resin, a silicone resin, an acrylic resin, a polyamide resin, a polyurethane resin, a polyester resin, and a polyvinyl butyral resin. The charging member according to claim 1. 9. A process cartridge, wherein the charging member according to claim 1 is provided so as to be disposed close to a member to be charged. An image forming apparatus comprising the process cartridge according to claim 9.

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