JP4163525B2 - Charging member and image forming apparatus having the same - Google Patents

Description

（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って、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、公知の樹脂である。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、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。また、前記（Ｂ）の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。
【００３０】
前記（Ｃ）のエチレン−アクリレート共重合体は、次の式
【化２】

（式中、Ｒ¹ は、Ｈ又はメチル基であり、そして、Ｒ³ は、メチル基、エチル基、又は、グリシジル基である。）
で示される共重合体であって、低吸水性であるエチレン単位と耐衝撃性に優れるアクリレート単位とから構成されるものである。そして、前記（Ｃ）のエチレン−アクリレート共重合体は、そのエチレン単位が（Ａ）のスチレン系樹脂との親和性が高く、また、そのアクリレート単位が前記（Ｂ）のポリエーテルエステルアミドと親和性が高いので、親和性の低い前記（Ａ）の共重合体と前記（Ｂ）の共重合体との間の相溶化剤として機能することができ、そのために、（Ａ）（Ｂ）の分散状態を均一にかつ緻密化することができ、また、環境安定性を向上させることができる。
【００３１】
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）ポリエーテルエステルアミド、及び、（Ｃ）エチレン−アクリレート共重合体を含有す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、環境安定性の優れた帯電部材を提供することができる。
【００３２】
本発明においては、前記電気抵抗調整層２の体積固有抵抗は、好ましくは、１０⁶ 〜１０⁹ Ωｃｍである。前記体積固有抵抗が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。
【００３３】
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、５〜１５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、５〜１５重量部であると、電気抵抗調整層２の体積固有抵抗を、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。
【００３４】
本発明においては、前記樹脂組成物は、前記（イ）、（ロ）及び（ハ）の混合物を二軸混練機、ニーダー等で溶融混練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の表面に被覆して形成する。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。
【００３５】
本発明においては、前記保護層３は、フッ素樹脂、シリコーン樹脂、アクリル樹脂、アクリルシリコン樹脂、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。
【００３６】
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。
【００３７】
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。
【００３８】
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。
【００３９】
本発明の画像形成装置においては、請求項１〜６に記載の帯電部材が被帯電体上に近接配置されている。このように、請求項１〜６に記載の帯電部材が被帯電体上に近接配置されていると、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、機械強度及び耐久性を向上させて、画像不良の発生を防止した、画像形成装置とすることができる。
【００４０】
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。
【００４１】
【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−メチルアクリレート−グリシジルメタクリレート共重合体（Ｌｏｔａｄｅｒ ＡＸ８９００、アトフィナジャパン社製）１０重量部（前記（Ａ）及び（Ｂ）の材料の合計１００重量部に対して１０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。
【００４２】
（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、ポリエステル樹脂（バイロン２０ＳＳ、東洋紡社製）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。
【００４３】
（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。
【００４４】
（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。
【００４５】
（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−メチルアクリレート−グリシジルメタクリレート共重合体（Ｌｏｔａｄｅｒ ＡＸ８９００、アトフィナジャパン社製）１０重量部（前記（Ａ）及び（Ｂ）の材料の合計１００重量部に対して１０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。
【００４６】
（比較例１）
ステンレスからなる直径８ｍｍの芯軸に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重量部を配合したゴム組成物を押出成形により被覆し、これを加硫して、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。
【００４７】
（比較例２）
ステンレスからなる直径８ｍｍの芯軸にＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部及び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重量部からなる樹脂組成物を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。
【００４８】
（比較例３）
ステンレスからなる直径８ｍｍの芯軸にＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部及び過塩素酸リチウム３重量部からなる樹脂組成物を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。
【００４９】
（比較例４）
ステンレスからなる直径８ｍｍの芯軸にＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部及び高分子型ノニオン性導電材料（ゼオスパンＡＳＮ８１００、日本ゼオン社製）３０重量部からなる樹脂組成物を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。
【００５０】
（比較例５）
ステンレスからなる直径８ｍｍの芯軸にＡＢＳ樹脂（ＧＲ−１５００、電気化学工業社製）１００重量部及び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、）３０重量部からなる樹脂組成物を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。
【００５１】
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、図２に示される画像形成装置を使用して評価を行った。
【００５２】
（試験１）
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、１００，０００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１に示される。
【００５３】
【表１】

【００５４】
表１より次のことがわかる。即ち、実施例１〜５のローラでは、全項目において良好な結果が得られたが、比較例１〜５のローラでは、不具合がみられた。
【００５５】
（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１００Ｖの電圧を印加した時の体積抵抗率ρＶ（Ωｃｍ）を測定した。その際における評価環境は、１０℃１５％ＲＨ、２３℃５０％ＲＨ及び３０℃９０％ＲＨとした。
評価結果は、次の表２に示される。
【００５６】
【表２】

【００５７】
表２からみると、実施例１〜５で得られた帯電ローラは、各環境下で体積固有抵抗が帯電ローラに必要な半導電性領域（１０⁶ 〜１０⁹ Ωｃｍ）を維持しているのに対し、試験１で良好な結果を示した比較例５で得られた帯電ローラは、低温低湿（１０℃１５％ＲＨ）時、及び、高温高湿（３０℃９０％ＲＨ）時にその範囲外になっている。
【００５８】
（試験３）
図２に示される画像形成装置を使用して、１０℃１５％ＲＨ及び３０℃９０％ＲＨの環境において、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。
測定結果及び評価結果は、次の表３，４に示される。
【００５９】
【表３】

【００６０】
【表４】

【００６１】
表３，４からみると、実施例１〜５で得られた帯電ローラは、各環境下で良好な結果が得られたが、試験１で良好な結果を示した比較例５で得られた帯電ローラは、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。
【００６２】
【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）ポリエーテルエステルアミド、及び、（Ｃ）エチレン−アクリレート共重合体を含有する樹脂組成物で構成されているので、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、環境安定性の優れた帯電部材を提供することができる。
【００６３】
（２）請求項２に記載された発明によれば、電気抵抗調整層の体積固有抵抗が１０⁶ 〜１０⁹ Ωｃｍであるので、均一画像を得るのに十分な帯電電位を得ることができ、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。
【００６４】
（３）請求項３に記載された発明によれば、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、５〜１５重量部であるので、電気抵抗調整層の体積固有抵抗を、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。
【００６５】
（４）請求項４に記載された発明によれば、保護層が、フッ素樹脂、シリコーン樹脂、アクリル樹脂、アクリルシリコン樹脂、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、トナー固着性に優れた帯電部材が得られる。
【００６６】
（５）請求項５に記載された発明によれば、保護層を形成する樹脂組成物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。
【００６７】
（６）請求項６に記載された発明によれば、請求項１〜６に記載の帯電部材が被帯電体上に近接配置されているので、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した、画像形成装置とすることができる。
【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】従来の帯電ローラを用いた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 a charging member for a proximity charging system that performs a charging process on a photoreceptor in an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile, and an image forming apparatus having the charging member.
[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 110 denotes a conventional charging roller type image forming apparatus. A conventional charging roller type image forming apparatus 110 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. In FIG. 2, functional units normally required in other electrophotographic processes are omitted because they are not required in this specification.
[0004]
Next, a basic image forming operation in the conventional charging roller type image forming apparatus 110 will be described.
[0005]
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.
[0006]
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.
[0007]
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.
[0008]
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.
[0009]
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.
[0010]
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.
[0011]
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).
[0012]
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.
[0013]
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.
[0014]
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.
[0015]
However, since a polymer type conductive agent containing a polyether machine such as a polyalkylene oxide that is generally used has a resistance value of about 10 ⁸ to 10 ¹¹ Ω · cm even by itself, it has a resistance higher than that of an electrolyte salt. Therefore, it is difficult to control the resistance region (approximately 10 ⁶ to 10 ⁹ Ω · cm) required for the charging roller.
[0016]
Further, 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) has been proposed.
[0017]
However, in the case of a quaternary ammonium salt-containing polymer-type conductive agent, the resistance value greatly depends on the temperature and humidity environment. Since there is a high possibility that problems such as charging failure will occur, there is a problem that prescription is difficult.
[0018]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-240076 [Patent Document 2]
[Patent Document 1] Japanese Patent Laid-Open No. 7-121009
[Problems to be solved by the invention]
The present invention aims to solve this problem.
That is, an object of the present invention is to provide a charging member having excellent environmental stability and an image forming apparatus having the same, while preventing variation in electric resistance value, toner fixation, and charging failure associated therewith. It is said.
[0020]
[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 is composed of a resin composition containing (A) a styrene-based thermoplastic resin, (B) a polyether ester amide, and (C) an ethylene-acrylate copolymer. This is a charging member.
[0021]
The invention described in claim 2 is characterized in that a volume resistivity of the electric resistance adjusting layer is 10 ⁶ to 10 ⁹ Ωcm.
[0022]
The invention described in claim 3 is the invention described in claim 1 or 2, wherein the blending ratio of (A) is 30 to 70% by weight and the blending ratio of (B) is 70. And the blending amount of (C) is 5 to 15 parts by weight with respect to 100 parts by weight of the total of (A) and (B). .
[0023]
The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein the protective layer is a fluororesin, silicone resin, acrylic resin, polyamide resin, polyurethane resin, polyester resin, polyvinyl butyral. It is comprised with the resin composition containing resin selected from resin.
[0024]
The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein the resin composition contains conductive particles.
[0025]
A sixth aspect of the present invention is an image forming apparatus in which the charging member according to any one of the first to fifth aspects is disposed in proximity to a member to be charged.
[0026]
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.
[0027]
In FIG. 1, reference numeral 10 denotes a charging member (charging roller). The charging member (charging roller) 10 has an electric resistance adjusting layer 2 and a protective layer 3 on the conductive support 1 in this order. The electrical resistance adjusting layer 2 includes (A) a styrene-based thermoplastic resin (hereinafter referred to as “PS”), (B) a polyetheresteramide (hereinafter referred to as “PEEA”), and (C). It is comprised with the resin composition containing an ethylene-acrylate copolymer (henceforth "EAC").
[0028]
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).
[0029]
The polyether ester amide of (B) has the following formula:

(In the formula, R ¹ , R ² and R ³ are alkyl groups having 1 to 20 carbon atoms.)
The copolymer is a copolymer composed of a hard part of a polyamide unit and a soft part of a polyether unit, and is a known resin per se. Since the polyether ester amide (B) is an ion conductive polymer material, it is uniformly dispersed and fixed at the molecular level in the matrix polymer, and therefore a resin composition in which a conductive pigment is dispersed. There is no variation in electrical resistance value due to poor dispersion of conductive pigments as seen in products. Further, since the polyether ester amide (B) is a polymer material, bleeding out hardly occurs.
[0030]
The ethylene-acrylate copolymer (C) has the following formula:

(In the formula, R ¹ is H or a methyl group, and R ³ is a methyl group, an ethyl group, or a glycidyl group.)
In which the ethylene unit has low water absorption and the acrylate unit has excellent impact resistance. The ethylene-acrylate copolymer (C) has a high affinity with the styrene resin having an ethylene unit (A), and the acrylate unit has an affinity with the polyether ester amide (B). Since it has high properties, it can function as a compatibilizing agent between the copolymer (A) having a low affinity and the copolymer (B). The dispersed state can be made uniform and dense, and the environmental stability can be improved.
[0031]
Thus, the electrical resistance adjusting layer 2 is composed of a resin composition containing (A) a styrene-based thermoplastic resin, (B) a polyetheresteramide, and (C) an ethylene-acrylate copolymer. In addition, it is possible to provide a charging member that is excellent in environmental stability while preventing variations in electrical resistance values, toner adhesion, and charging defects associated therewith.
[0032]
In the present invention, the volume resistivity of the electric resistance adjusting layer 2 is preferably 10 ⁶ to 10 ⁹ Ωcm. If the volume specific resistance exceeds 10 ⁹ Ωcm, the charging amount of the charging member 10 is insufficient, so that it is 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. Therefore, when the volume resistivity of the electric resistance adjusting layer 2 is 10 ⁶ to 10 ⁹ Ωcm, a charging potential sufficient for obtaining a uniform image can be obtained, and the voltage concentration on the entire photoreceptor ( Leakage) and abnormal discharge do not occur.
[0033]
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 5 to 15 parts by weight based on 100 parts by weight of the 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 resistivity of the electric resistance adjusting layer 2 is preferably in the range of 10 ⁶ to 10 ⁹ Ωcm when it is 5 to 15 parts by weight with respect to 100 parts by weight of the total of (A) and (B). Can be adjusted in.
[0034]
In the present invention, the resin composition is obtained by melt-kneading the mixture of (a), (b) and (c) with a twin-screw kneader, a kneader or the like. The electrical resistance adjusting layer 2 in the present invention is formed by coating the surface of the conductive support 1 with the thermoplastic resin composition thus obtained by means such as extrusion molding or injection molding. 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.
[0035]
In the present invention, the protective layer 3 is composed of a resin composition containing a resin selected from a fluororesin, a silicone resin, an acrylic resin, an acrylic silicon 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.
[0036]
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.
[0037]
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.
[0038]
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.
[0039]
In the image forming apparatus of the present invention, the charging member according to any one of claims 1 to 6 is disposed in proximity to the member to be charged. As described above, when the charging member according to any one of claims 1 to 6 is disposed close to the member to be charged, variation in electric resistance value, toner fixation, and charging failure associated therewith are prevented, and mechanical strength is increased. In addition, the image forming apparatus can improve the durability and prevent the occurrence of image defects.
[0040]
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.
[0041]
【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-methyl acrylate- Glycidyl methacrylate copolymer (Lotader AX8900, manufactured by Atofina Japan) 10 parts by weight (10 parts by weight with respect to the total of 100 parts by weight of the materials (A) and (B)) is used as 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 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.
[0042]
(Example 2)
A resin composition composed of a polyester resin (Byron 20SS, manufactured by Toyobo Co., Ltd.) and tin oxide (60% by weight based on the total solid content) was applied to the surface of the electrical resistance adjusting layer formed in the same manner as in Example 1. A charging roller having a diameter of 12 mm was obtained by forming a protective layer having a thickness of about 10 μm.
[0043]
(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.
[0044]
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.
[0045]
(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) 10 parts by weight of ethylene-methyl acrylate-glycidyl methacrylate copolymer (Lotader AX8900, manufactured by Atofina Japan) (10 parts by weight with respect to 100 parts by weight of the total 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.
[0046]
(Comparative Example 1)
A rubber composition in which 3 parts by weight of ammonium perchlorate is blended with 100 parts by weight of epichlorohydrin rubber (Epichromer CG, manufactured by Daiso Co., Ltd.) on a core shaft having a diameter of 8 mm made of stainless steel by extrusion molding is vulcanized. An electric resistance adjusting layer was formed. Next, 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) on the surface of the electric resistance adjusting layer. Was applied to form a protective layer having a thickness of about 10 μm to obtain a charging roller having a diameter of 12 mm.
[0047]
(Comparative Example 2)
Resin composition comprising a stainless steel core shaft of 8 mm in diameter and 100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo) and 15 parts by weight of conductive carbon black (Ketjen Black EC, manufactured by Ketjen Black International). The product was coated by injection molding 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.
[0048]
(Comparative Example 3)
An electric resistance adjusting layer is formed by coating a resin composition consisting of 100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 3 parts by weight of lithium perchlorate on an 8 mm diameter core shaft made of stainless steel by injection molding. 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.
[0049]
(Comparative Example 4)
A resin composition comprising a stainless steel shaft of 8 mm in diameter and 100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo) and 30 parts by weight of a polymer type nonionic conductive material (Zeospan ASN8100, manufactured by Nippon Zeon). Was coated by injection molding to form an electric resistance adjusting layer. 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.
[0050]
(Comparative Example 5)
An ion conductive polymer compound (ROLEX AS-1720, Daiichi Kogyo) containing 100 parts by weight of ABS resin (GR-1500, manufactured by Denki Kagaku Kogyo Co., Ltd.) and a quaternary ammonium base on a 8 mm diameter core shaft made of stainless steel. A resin composition comprising 30 parts by weight of a pharmaceutical company) was coated by injection molding to form an electric resistance adjusting layer. 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.
[0051]
As described above, the charging rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were evaluated using the image forming apparatus shown in FIG.
[0052]
(Test 1)
Using the image forming apparatus shown in FIG. 2, 100,000 copies were made in an environment of 23 ° C. and 60% RH, and the durable number of 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 1 below.
[0053]
[Table 1]

[0054]
Table 1 shows the following. That is, in the rollers of Examples 1 to 5, good results were obtained in all items, but in the rollers of Comparative Examples 1 to 5, defects were observed.
[0055]
(Test 2)
Volume resistivity ρV (Ωcm) when a voltage of 100 V was applied to the charging rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 5 was measured. The evaluation environment at that time was 10 ° C. 15% RH, 23 ° C. 50% RH, and 30 ° C. 90% RH.
The evaluation results are shown in Table 2 below.
[0056]
[Table 2]

[0057]
From Table 2, the charging rollers obtained in Examples 1 to 5 maintain a semiconductive region (10 ⁶ to 10 ⁹ Ωcm) whose volume resistivity is necessary for the charging roller in each environment. On the other hand, the charging roller obtained in Comparative Example 5, which showed good results in Test 1, was out of the range at low temperature and low humidity (10 ° C, 15% RH) and at high temperature and high humidity (30 ° C, 90% RH) It has become.
[0058]
(Test 3)
Using the image forming apparatus shown in FIG. 2, in the environment of 10 ° C. and 15% RH and 30 ° C. and 90% RH, the “charge potential of the photoconductor” of the photoconductor was measured, and the image evaluation This was performed according to “presence / absence of charging failure (image unevenness)” and “presence / absence of abnormal discharge to the defective portion of the photoreceptor”.
The measurement results and evaluation results are shown in the following Tables 3 and 4.
[0059]
[Table 3]

[0060]
[Table 4]

[0061]
As can be seen from Tables 3 and 4, the charging rollers obtained in Examples 1 to 5 obtained good results in each environment, but were obtained in Comparative Example 5 that showed good results in Test 1. The charging roller showed defects on the image at low temperature and low humidity (10 ° C., 15% RH) and at high temperature and high humidity (30 ° C., 90% RH).
[0062]
【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 polyether ester amide, and (C) an ethylene-acrylate copolymer. Therefore, it is possible to provide a charging member having excellent environmental stability as well as preventing variation in electric resistance, toner fixation, and charging failure associated therewith.
[0063]
(2) According to the invention described in claim 2, since the volume resistivity of the electric resistance adjusting layer is 10 ⁶ to 10 ⁹ Ωcm, a charging potential sufficient to obtain a uniform image can be obtained, In addition, voltage concentration (leakage) and abnormal discharge on the entire photoconductor do not occur.
[0064]
(3) According to the invention described in claim 3, the blending ratio of (A) is 30 to 70% by weight, and the blending ratio of (B) is 70 to 30% by weight. And since the compounding quantity of said (C) is 5-15 weight part with respect to a total of 100 weight part of said (A) and (B), it is supposed that the volume specific resistance of an electrical resistance adjustment layer is preferable. Can be adjusted within a range of 10 ⁶ to 10 ⁹ Ωcm.
[0065]
(4) According to the invention described in claim 4, the protective layer is a resin selected from a fluororesin, a silicone resin, an acrylic resin, an acrylic silicon resin, a polyamide resin, a polyurethane resin, a polyester resin, and a polyvinyl butyral resin. Therefore, a charging member excellent in toner fixing property can be obtained.
[0066]
(5) According to the invention described in claim 5, since the resin composition forming the protective layer contains conductive particles, the electrical resistance value of the protective layer can be easily adjusted.
[0067]
(6) According to the invention described in claim 6, since the charging member according to claims 1 to 6 is disposed close to the member to be charged, variation in electric resistance value, toner fixation, and the like In addition to preventing charging defects associated with the image forming apparatus, it is possible to provide an image forming apparatus in which mechanical strength and durability are improved to prevent 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 an image forming apparatus using a conventional charging roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Electrical resistance adjustment layer 3 Protective layer 10 Charging member (charging roller)

Claims (6)

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 charging member comprising a resin composition containing a resin, (B) a polyetheresteramide, and (C) an ethylene-acrylate copolymer. 2. The charging member according to claim 1, wherein the electric resistivity adjusting layer has a volume specific resistance of 10 ⁶ to 10 ⁹ Ωcm. 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 (A). The charging member according to claim 1, wherein the charging member is 5 to 15 parts by weight with respect to a total of 100 parts by weight of (B). The protective layer is composed of a resin composition containing a resin selected from a fluororesin, a silicone resin, an acrylic resin, a polyamide resin, a polyurethane resin, a polyester resin, and a polyvinyl butyral resin. 4. The charging member according to any one of 3. The charging member according to claim 1, wherein the resin composition contains conductive particles. An image forming apparatus, wherein the charging member according to any one of claims 1 to 5 is disposed close to a member to be charged.

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