JP3667307B2 - Image forming apparatus - Google Patents

Description

（式中、Ｒ１、Ｒ２、Ｒ３、Ｒ４、Ｒ５、Ｒ６、Ｒ７及びＲ８は同一あるいは異なって、炭化水素基、ヒドロキシル基置換炭化水素基、基内にアミド結合及びエステル結合の少なくとも１方を有する炭化水素系の基、基内にエーテル酸素を有する炭化水素系の基、Ｏ−炭化水素基置換−３−オキシ−２−ヒドロキシプロピル基、末端ヒドロキシル基置換ポリオキシ炭化水素基、ポリオキシ炭化水素基、カルボニル基を連結基として末端炭化水素基と結合しているポリオキシ炭化水素基、同一原子団内の中心窒素原子ともう一つのＮ−置換基と共にモルホリン環、ピリジン環またはイミダゾリン環を形成する残基からなる群より選ばれる少なくとも１つの基であり、（Ａ） ^2- はＳＯ ₃ ^2- 、Ｓ ₂ Ｏ ₅ ^2- 、Ｓ ₂ Ｏ ₄ ^2- 、Ｓ ₂ Ｏ ₃ ^2- 及びＳＯ ₄ ^2- からなる群より選ばれる少なくとも１つのイオンである。）
【００１８】
以下、本発明を詳細に説明する。
【００１９】
まず、繰り返し高品位な画像を得るためには、中間転写体上の転写残現像剤を完全に除去する必要がある。転写残現像剤を完全に除去するためには、転写残現像剤が少ないほど有利であることは明らかである。すなわち、２次転写効率が高いほど、転写残現像剤の除去が容易になる。
【００２０】
本発明者らによる検討の結果、２次転写効率を向上させるためには中間転写体の抵抗値が重要な因子であることが分かった。すなわち、中間転写体の抵抗値は、下記に示す測定法にて、１×１０⁴（Ω）以上１×１０¹⁰（Ω）未満であることが好ましいことが分かった。
＜中間転写体の抵抗値の測定方法＞
（１）中間転写体と金属ロールを両者の軸が平行になるように線圧４０ｇ／ｃｍで当接させ、直流電源、抵抗器、電位差計をつなぐ（図２）。
（２）上記金属ロールを駆動回転し、これに従動する中間転写体表面の線速度が１２０ｍｍ／ｓｅｃになるように調節する。
（３）直流電源から＋１ｋＶを回路に印加し、中間転写体の下流側に挿入した適当な抵抗値Ｒ（Ω）を持つ抵抗器の、両端の電位差Ｖｒ（Ｖ）を電位差計にて測定する。
（４）以下の式に従って、中間転写体の抵抗値を算出する。
中間転写体の抵抗値（Ω）＝１０００（Ｖ）×Ｒ（Ω）÷Ｖｒ（Ｖ）
なお、特に断らない限り、測定時の雰囲気は２３℃／５５％Ｒｈとする。
【００２１】
本発明の中間転写体は、樹脂、エラストマー、ゴム等の材料からなるために、中間転写体の抵抗値を前記範囲に調整するためには、導電剤を使用する必要がある。
【００２２】
導電剤としては、従来より、カーボンブラック、金属等の導電性フィラー、界面活性剤型帯電防止剤等が用いられている。
【００２３】
しかし、カーボンブラック、金属等の導電性フィラーを用いた場合には、導電性フィラーを均一に分散することが困難であるために、ミクロ的な抵抗ムラを生じ易く、画像品位の低下を招いてしまう場合がある。また、界面活性剤型帯電防止剤を用いると、多くの場合中間転写体の抵抗値が使用環境（特に温度及び湿度）によって大きく変化してしまうために、安定した画像を得ることができない。更に、前記界面活性剤型帯電防止剤が中間転写体の表面にブリードアウトすると感光体を汚染してしまうという問題もある。
【００２４】
本発明は、溶剤可溶型導電性高分子を導電剤として用いることにより、上記の問題を解決するものである。
【００２５】
すなわち、ミクロ的な抵抗ムラを無くすためには、導電性フィラー分散系よりも、中間転写体の樹脂マトリックス中に導電剤を溶解させた系の方が、より均一に分散できるために有利である。ただし、溶剤に可溶であっても、従来より用いられているような界面活性剤型帯電防止剤では、前述のように、抵抗値の環境安定性が乏しい、感光体を汚染する、という問題があるために使用できない。
【００２６】
これに対して、本発明の中間転写体に用いる溶剤可溶型導電性高分子は、
（１）溶剤に可溶であるために中間転写体の樹脂マトリックス中に容易に均一分散することができる、
（２）周囲の環境の変化による抵抗値の変化が小さい、
（３）高分子であるために感光体を汚染しない（中間転写体の表面にブリードアウトしにくい）、という特徴がある。
【００２７】
ここで、本発明の中間転写体に用いる溶剤可溶型導電性高分子とは、以下に示す（１）及び（２）を満足するものをいう。
（１）下記に示す溶剤の少なくとも１種に、１質量％以上溶解すること。
メタノール、エタノール、イソプロピルアルコール、ベンジルアルコール、ピリジン、Ｎ−メチルピロリドン、Ｎ，Ｎ′−ジメチルホルムアミド、アセトン、メチルエチルケトン、メチルイソブチルケトン、ベンゼン、トルエン、キシレン、テトラヒドロフラン、酢酸エチル、酢酸ブチル、シクロヘキサン、ｎ−オクタン、ジエチルエーテル、ジメチルスルホキシド、ジエチレングリコール、２−メトキシエタノール、２−エトキシエタノール、２−ブトキシエタノール、フレオン１１、フレオン１２、フレオン１１２。
（２）単体での表面抵抗が１×１０¹⁰（Ω／□）以下であること。ただし、表面抵抗の測定は２３℃／５５％ＲＨで行なうものとする。
【００２８】
なお、溶剤可溶型導電性高分子が中間転写体の表面にブリードアウトして感光体を汚染することを防止するためには、分子量は大きい方が好ましい。すなわち、上記溶剤可溶型導電性高分子の分子量は４０００以上であることが好ましい。ただし、これに限られるものではない。
【００２９】
上記（１）及び（２）を満足する化合物について、本発明者らが検討を行なった結果、以下に示す化合物が、本発明の画像形成装置に用いる中間転写体を製造するにあたって好ましいことが分かった。
硫酸イオン、ピロ亜硫酸イオン、亜二チオン酸イオン、チオ硫酸イオン及び亜硫酸イオンからなる群より選ばれる少なくとも１つのイオンと、少なくとも１種の４級アンモニウムイオンを有する化合物。
【００３０】
上記化合物について説明する。この化合物は、硫酸イオン、ピロ亜硫酸イオン、亜二チオン酸イオン、チオ硫酸イオン及び亜硫酸イオンからなる群より選ばれる少なくとも１つのイオンと、少なくとも１種の４級アンモニウムイオンを有する化合物であることを特徴としており、電気陰性度の高い原子同士（硫黄及び酸素）の組み合わせからできている電子吸引性基が、４級アンモニウムイオン中に含まれる塩基性窒素化合物と結合したことによって、共鳴構造をとることが可能になり、広範囲の電子移動が起こり、導電性が発現するものと考えられる。すなわち、該化合物の主たる導電機構は電子伝導によるものであると考えられる。従って、該化合物の導電性は使用環境によらず安定している。
【００３１】
硫酸イオンと４級アンモニウムイオンとの化合物である場合の、共鳴構造式を下記構造式（１）に示す。
【００３２】
構造式（１）
【００３３】
【化２】

【００３４】
４級アンモニウムイオンとしては、特に前記の一般式（１）において、Ｒ１、Ｒ２、Ｒ３、Ｒ４、Ｒ５、Ｒ６、Ｒ７及びＲ８が、炭化水素基、ヒドロキシル基置換炭化水素基、基内にアミド結合及びエステル結合の少なくとも１方を有する炭化水素系の基、基内にエーテル酸素を有する炭化水素系の基、Ｏ−炭化水素基置換−３−オキシ−２−ヒドロキシプロピル基、末端ヒドロキシル基置換ポリオキシ炭化水素基、ポリオキシ炭化水素基、カルボニル基を連結基として末端炭化水素基と結合しているポリオキシ炭化水素基、同一原子団内の中心窒素原子ともう一つのＮ−置換基と共にモルホリン環、ピリジン環またはイミダゾリン環を形成する残基からなる群より選ばれる少なくとも１つの基である場合、該化合物の導電性がいっそう増して好ましい。これは上記の官能基が、４級アンモニウムイオン中の塩基性窒素の（＋）性をより増大させ、安定化させるためであると考えられる。
【００３５】
更に、前記一般式（１）の化合物は、多価ヒドロキシ化合物との混合物にしてもよい。この場合、
（ｉ）導電付与効果がより増大する。これは、ヒドロキシル基が４級アンモニウムイオン中の塩基性窒素の（＋）性をより増大させ、安定化させるためであると考えられる。
（ii）熱安定性が向上する。
（iii ）ゴム、エラストマー、樹脂との相溶性が増す。
等、多くの優れた特徴を有するために、より好ましい。
【００３６】
なお、多価ヒドロキシ化合物の例としては、ペンタエリスリトール、ソルビトール、マンニトール、ベンジリデンソルビトール、ジ（ベンジリデン）ソルビトール、トリメチロールエタン、トリメチロールプロパン、ジ（ペンタエリスリトール）、ビスフェノールＡ、ハイドロキノン、ピロガロール等が挙げられるが、特に限定されるものではない。また、もちろん、これらを２種以上混合して用いることもできる。
【００３７】
本発明の中間転写体に用いる溶剤可溶型導電性高分子は、表面層に添加することが好ましいが、場合によっては、その下層に被覆層が有るときにはその被覆層、また弾性層に添加してもよい。
【００３８】
本発明に用いる中間転写体の弾性層及び被覆層にはゴム、エラストマー、樹脂を使用することができ、例えば、ゴム、エラストマーとしては、天然ゴム、イソプレンゴム、スチレン−ブタジエンゴム、ブタジエンゴム、ブチルゴム、エチレン−プロピレンゴム、エチレン−プロピレンターポリマー、クロロプレンゴム、クロロスルホン化ポリエチレン、塩素化ポリエチレン、アクリロニトリルブタジエンゴム、ウレタンゴム、シンジオタクチック１，２−ポリブタジエン、エピクロロヒドリンゴム、アクリルゴム、シリコーンゴム、フッ素ゴム、多硫化ゴム、ポリノルボルネンゴム、水素化ニトリルゴム、熱可塑性エラストマー（例えば、ポリスチレン系、ポリオレフィン系、ポリ塩化ビニル系、ポリウレタン系、ポリアミド系、ポリエステル系、フッ素樹脂系）を用いることができる。
【００３９】
また、樹脂としてはポリスチレン、クロロポリスチレン、ポリ−α−メチルスチレン、スチレン−ブタジエン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体（スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体及びスチレン−アクリル酸フェニル共重合体等）、スチレン−メタクリル酸エステル共重合体（スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸フェニル共重合体等）、スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体等のスチレン系樹脂（スチレンまたはスチレン置換体を含む単重合体または共重合体）、メタクリル酸メチル樹脂、メタクリル酸ブチル樹脂、アクリル酸エチル樹脂、アクリル酸ブチル樹脂、変性アクリル樹脂（シリコーン変性アクリル樹脂、塩化ビニル変性アクリル樹脂、アクリル・ウレタン樹脂等）、塩化ビニル樹脂、スチレン−酢酸ビニル共重合体、塩化ビニル−酢酸ビニル共重合体、ロジン変性マレイン酸樹脂、フェノール樹脂、エポキシ樹脂、ポリエステル樹脂、ポリエステルポリウレタン樹脂、ポリエチレン、ポリプロピレン、ポリブタジエン、ポリ塩化ビニリデン、アイオノマー樹脂、ポリウレタン樹脂、シリコーン樹脂、フッ素樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂及びポリビニルブチラール樹脂、ポリアミド樹脂、変性ポリフェニレンオキサイド樹脂等が挙げられる。
【００４０】
更に、溶剤可溶型導電性高分子を溶解するための溶媒は、前記のごとく、メタノール、エタノール、イソプロピルアルコール、ベンジルアルコール、ピリジン、Ｎ−メチルピロリドン、Ｎ，Ｎ′−ジメチルホルムアミド、アセトン、メチルエチルケトン、メチルイソブチルケトン、ベンゼン、トルエン、キシレン、テトラヒドロフラン、酢酸エチル、酢酸ブチル、シクロヘキサン、ｎ−オクタン、ジエチルエーテル、ジメチルスルホキシド、ジエチレングリコール、２−メトキシエタノール、２−エトキシエタノール、２−ブトキシエタノール、フレオン１１、フレオン１２、フレオン１１２等が挙げられるが、その他の溶剤であっても溶剤可溶型導電性高分子を溶解するものであればよく、良溶媒同士の混合溶媒はもちろんのこと、貧溶媒との混合溶媒であってもよい。
【００４１】
また、本発明の画像形成装置に用いる中間転写体を製造するにあたって、上記に示したごとくの溶剤を必ずしも使用する必要はなく、例えば、溶剤可溶型導電性高分子を直接、ゴム、エラストマー、樹脂に練り込む等の製造方法をとることも可能である。この場合には、溶剤を広義に解釈すればよい。すなわち、ゴム、エラストマー、樹脂が、溶剤可溶型導電性高分子の溶媒にあたるとみなすことができる。
【００４２】
同じく、本発明の画像形成装置に用いる中間転写体を製造するにあたって、上記の材料群の中から材料選択を行なう必要はなく、中間転写体の抵抗値が前記範囲になるようなものであれば、その他の材料を用いて製造することもできる。
【００４３】
本発明に用いる中間転写体は、例えば、円筒状の導電性支持体上に少なくともゴム、エラストマー、樹脂よりなる弾性層及び１層以上の被覆層を有するローラ形状、または、図６に示されるごとくのベルト形状と、種々の態様を目的、必要に応じて選択することができる。その例を図３〜図５に示す。
【００４４】
画像の重ね合わせの色ズレ、繰り返しの使用による耐久性を考慮すると、より好ましい本発明の態様としてはローラ形状である。各図において、１００は剛体である円筒状導電性支持体、１０１は弾性層、１０２及び１０３は被覆層、そして１０４は中間転写ベルトを示す。
【００４５】
円筒状導電性支持体としては、アルミニウム、鉄、銅及びステンレス等の金属や合金、カーボンや金属粒子等を分散した導電性樹脂等を用いることができ、その形状としては、上述したような円筒状や、円筒の中心に軸を貫通したもの、円筒の内部に補強を施したもの等が挙げられる。
【００４６】
中間転写体の弾性層の膜厚は０．５〜１０ｍｍ、更には１〜５ｍｍにすることが好ましい。また、被覆層の膜厚は、下層の弾性層の柔軟性を、更にその上層あるいは感光体表面に伝えるためには薄層、具体的には１〜５００μｍ、更には５〜２００μｍが好ましい。
【００４７】
また、第１の画像担持体としては、導電性を有する剛体ローラの表面に感光層を被覆した感光ドラム、更には該感光ドラムの少なくとも最外層に、四フッ化エチレン樹脂（ＰＴＦＥ）の微粉末を含有する感光ドラムを用いることが好ましい。特に、少なくとも表面層にＰＴＦＥの微粉末を含有する感光ドラムを用いた場合には、より高い１次転写効率が得られる。これは、ＰＴＦＥの微粉末を含有することにより、該感光ドラム最外層の表面エネルギーが低下し、トナーの離型性が向上するためではないかと考えられる。
【００４８】
ここで、本発明の画像形成装置において、より好ましい形態例として、図１に示すごとく転写残現像剤を静電的にクリーニングする画像形成装置を挙げることができる。
【００４９】
図１において、８はクリーニング用帯電部材であり、転写残現像剤を感光ドラム１と逆極性に帯電させるものである。９は転写残現像剤回収部材であり、感光ドラム１と同極性のバイアスを印加して、クリーニング用帯電部材８により帯電された先の転写残現像剤を回収するものである。
【００５０】
ここで、クリーニング用帯電部材８、転写残現像剤回収部材９は中間転写体２０と接触させながらバイアスを印加しているので、中間転写体２０の表面はこれらの部材により帯電されることになる。この電荷が減衰しない（中間転写体２０の表面電位が大きい）うちに次の画像形成ステップに入ると、感光ドラム１とのニップ部において１次転写電界が乱されるために、画像品位が低下してしまう。しかし、本発明の画像形成装置に用いる溶剤可溶型導電性高分子（特に含窒素電荷移動錯体型ポリ硼素化合物）においては、電荷の減衰が速いためにそのようなことはなく、静電的なクリーニングが可能になるものと考えられる。
【００５１】
図１において、クリーニング用帯電部材８及び転写残現像剤回収部材９は、金属ロール、導電性を有する弾性ロール、導電性を有するファーブラシ、導電性を有するブレード等、種々の形態をとることができる。
【００５２】
図１の画像形成装置において、例えば電源投入時に転写残現像剤回収部材９に感光ドラム１と逆極性のバイアスを印加して、回収容器内の転写残現像剤を帯電させ、感光ドラムのクリーニング装置１３に回収することも考えられる。この方式は、転写残現像剤の回収容器を小型化できるという利点を有している。
【００５３】
また、図１の画像形成装置においては転写残現像剤回収部材９を設けることなく、感光ドラム１を転写残現像剤回収部材としてもよい。
【００５４】
更に、図１の画像形成装置においては、感光ドラム１から中間転写体２０に現像剤９４を転写すると同時に、転写残現像剤９６を感光ドラム１に戻してもよい（以後、１次転写同時クリーニング方式と称する）。１次転写同時クリーニング方式は、クリーニングステップを特に必要としないために、スループットの低下がないという利点を有している。
【００５５】
以上のように、本発明の中間転写体は溶剤可溶型導電性高分子を含有しているために、
（１）中間転写体の抵抗ムラがない、
（２）環境による中間転写体の抵抗値の変動が小さい、
（３）感光体を汚染しない、
という特徴を有している。
【００５６】
従って、本発明の画像形成装置は、使用環境によらず、繰り返し安定した画像を得ることができるという効果を有する。
【００５７】
本発明の中間転写体は、例えば以下のようにして製造される。
【００５８】
まず、円筒状導電性支持体としての金属ロールを用意する。ゴム、エラストマー、樹脂等を金属ロール上に溶融成形、注入成形、浸漬塗工あるいはスプレー塗工等により成形することによって弾性層を設ける。次に、被覆層の材料を弾性層の上に溶融成形、注入成形、浸漬塗工あるいはスプレー塗工等により成形することによって被覆層を設ける。
【００５９】
【実施例】
以下に実施例により本発明を詳細に説明する。
（実施例１）
直径１８２ｍｍ、長さ３２０ｍｍ、厚み５ｍｍのアルミニウム製円筒状ローラ表面に下記配合のゴムコンパウンドを金型を用いてトランスファー成形することにより、厚さ５ｍｍの弾性層を有するローラを得た。
【００６０】

【００６１】
次に、該ローラ上に被覆層を得るための被覆層用塗料を下記処方により作成した。
【００６２】

【００６３】
ただし、上記塗料配合において、溶剤可溶型導電性高分子１は一般式（１）において、Ｒ１＝Ｒ４＝Ｒ５＝Ｒ８＝ＣＨ₃、Ｒ２＝Ｒ６＝Ｃ₂Ｈ₄ＯＨ、Ｒ３＝Ｒ７＝Ｃ₁₂Ｈ₂₅、Ａ＝ＳＯ₄で示される化合物である。該化合物は、分子量＝約６００、表面抵抗＝約１×１０⁴（Ω／□）である。
【００６４】
上記塗料を前記ローラにスプレー塗布し、その後１００℃で２時間加熱することにより残存溶剤を除去し、厚さ３５μｍの強靱な被覆層を有する中間転写体を得た。
【００６５】
得られた中間転写体の抵抗を、上記の＜中間転写体の抵抗値の測定方法＞に従って、各環境にて測定した。
【００６６】
次に、中間転写体を図１に示されるフルカラー電子写真装置に装着し、８０ｇ／ｍ²紙にフルカラー画像をプリントし、以下のように転写効率を定義して、転写効率の測定を行なった。
【００６７】
１次転写効率＝中間転写体上の画像濃度／（感光ドラム上の転写残画像濃度＋中間転写体上の画像濃度）×１００（％）。
【００６８】
２次転写効率＝紙上の画像濃度／（紙上の画像濃度＋中間転写体上の転写残画像濃度）×１００（％）。
【００６９】
なお、クリーニング用帯電部材８には１×１０⁸（Ω）の抵抗を持つ弾性ローラを、転写残現像剤回収部材９には１×１０²（Ω）の抵抗を持つ導電性ファーブラシを用いた。
【００７０】
次に、フルカラー画像にて５０００枚の連続プリントを行なったが、クリーニング不良に起因する画像不良は一切発生しなかった。
【００７１】
また、中間転写体の抵抗値の環境依存性が画像に与える影響を調べるために、５０００枚の連続プリントを行なう前後にて、１５℃／１０％、２３℃／５５％、３０℃／８０％の３環境（以後、３環境と略す）で画像を出力したが、全て良好な画像を得ることができた。
【００７２】
結果を表１及び表２に示す。
【００７３】
以下に本実施例の作像条件を示す。
【００７４】
感光体：ＯＰＣ感光ドラム

カラー現像剤：非磁性１成分トナー（４色共に）
１次転写電位：＋１００Ｖ
２次転写電流：＋１５μＡ
プロセススピード：１２０ｍｍ／ｓｅｃ

中間転写体と感光ドラムとの当接圧：２ｋｇｆ
中間転写体と転写ベルトとの当接圧：５ｋｇｆ
中間転写体とクリーニング用帯電部材との当接圧：１ｋｇｆ
【００７５】
（実施例２）
実施例１のゴム配合で得られた弾性層を有するローラ上に、被覆層を得るための被覆層用塗料を下記処方により作成した。
【００７６】

【００７７】
ここで、溶剤可溶型導電性高分子１とヒドロキシ化合物の共晶物は、以下のようにして製造した。
【００７８】
フラスコに溶剤可溶型導電性高分子１を１００ｇ、ヒドロキシ化合物としてペンタエリスリトールを２００ｇ、純水を９００ｇ入れ、窒素気流下で徐々に加熱しながら脱水を行ない、更に加熱して注入した純水を全て蒸発させる。この操作により、溶剤可溶型導電性高分子１とペンタエリスリトールとの共晶物を得た。
【００７９】
なお、上記の共晶物の表面抵抗は約５×１０³（Ω／□）である。
【００８０】
上記塗料を前記ローラにスプレー塗布し、その後１００℃で２時間加熱することにより残存溶剤を除去し、厚さ３０μｍの強靱な被覆層を有する中間転写体を得た。
【００８１】
得られた中間転写体の抵抗値を実施例１と同様に測定した。
【００８２】
次に、中間転写体を図１に示されるフルカラー電子写真装置に装着した。なお、クリーニング用帯電部材８は実施例１と同じものを用いたが、転写残現像剤回収部材９は使用せず、１次転写同時クリーニング方式とした。なお、バイアス電源２６からクリーニング用帯電部材８に印加した電流値は＋４０（μＡ）である。
【００８３】
また、転写効率の測定及び５０００枚の耐久試験を実施例１と同様に行なった。５０００枚耐久後もクリーニング不良に起因する画像不良は発生せず、１次転写同時クリーニングが可能であった。これは本実施例に用いた共晶物が、中間転写体の電荷の漏洩をが非常に速めているためと考えられる。なお、その他の作像条件は実施例１と同様である。
【００８４】
また、中間転写体の抵抗値の環境依存性が画像に与える影響を調べるために、５０００枚の連続プリントを行なう前後にて、３環境で画像を出力したが、全て良好な画像を得ることができた。
【００８５】
結果を表１及び表２に示す。
【００８６】
（比較例１）
実施例１のゴム配合で得られた弾性層を有するローラ上に、被覆層を得るための被覆層用塗料を下記処方により作成した。
【００８７】

【００８８】
上記塗料を前記ローラにスプレー塗布し、その後１００℃で１時間加熱することにより残存溶剤を除去し、かつ被覆層に架橋を施し、厚さ２５μｍの強靱な被覆層を有する中間転写体を得た。
【００８９】
得られた中間転写体の抵抗値を実施例１と同様に測定した。
【００９０】
次に、中間転写体を図１に示されるフルカラー電子写真装置に装着し、実施例１と同様に転写効率の測定及び５０００枚のフルカラー連続プリントを行なった。中間転写体の抵抗値にムラがあるために、ハーフトーン画像にガサツキが見られた。
【００９１】
なお、クリーニング用帯電部材８及び転写残現像剤回収部材９は実施例１と同じものを用いた。作像条件も実施例１と同様である。
【００９２】
また、中間転写体の抵抗値の環境依存性が画像に与える影響を調べるために、５０００枚の連続プリントを行なう前後にて、３環境で画像を出力した。どの環境においてもハーフトーンにガサツキが見られ、その程度は５０００枚プリント後の方が悪かった。
【００９３】
結果を表１及び表２に示す。
【００９４】
（比較例２）
一般に用いられている界面活性剤型帯電防止剤の１種である、Ｎ，Ｎ′−ジ（ポリオキシエチレン）アルキルアミンを添加して、被覆層用塗料を作成した。
【００９５】

【００９６】
上記塗料を実施例１のゴム配合で得られた弾性層を有するローラ上にスプレー塗布し、その後８０℃で２時間加熱することにより残存溶剤を除去し、かつ被覆層に架橋を施し、厚さ５０μｍの強靱な被覆層を有する中間転写体を得た。
【００９７】
得られた中間転写体の抵抗値を実施例１と同様に測定した。
【００９８】
次に、中間転写体を図１に示されるフルカラー電子写真装置に装着し、実施例１と同様に転写効率の測定及び５０００枚のフルカラー連続プリントを行なった。
【００９９】
初期は良好な画像が得られたが、導電剤として用いたＮ，Ｎ′−ジ（ポリオキシエチレン）アルキルアミンが中間転写体の表面にブリードアウトしてくるために、次第に感光体を汚染し、５０００枚の連続プリントには耐えられなかった。
【０１００】
なお、クリーニング用帯電部材８及び転写残現像剤回収部材９は実施例１と同じものを用いた。作像条件も実施例１と同様である。
【０１０１】
また、中間転写体の抵抗値の環境依存性が画像に与える影響を調べるために、５０００枚の連続プリントを行なう前後にて、新しい感光ドラムを用いて３環境で画像を出力した。中間転写体の抵抗値が、特に低温／低湿環境にて非常に大きくなってしまうために、初期より１５℃／１０％の環境で転写不良が発生し、良好な画像を得ることはできなかった。
【０１０２】
結果を表１及び表２に示す。
【０１０３】
【表１】

【０１０４】
【発明の効果】
以上述べてきたように、本発明は、第１の画像担持体上に形成された画像を中間転写体に転写した後、第２の画像担持体上に更に転写する画像形成装置において、該中間転写体が溶剤可溶型導電性高分子を含有し、該溶剤可溶型導電性高分子が、前記一般式（１）で示される化合物であることを特徴とする画像形成装置である。
【０１０５】
従って、本発明の画像形成装置は、使用環境によらず、繰り返し安定した画像を得ることができるという効果を有する。
【図面の簡単な説明】
【図１】ローラ形状の中間転写体を用いたカラー画像出力装置の概略図である。
【図２】本発明に用いる中間転写体の抵抗値の測定回路図である。
【図３】本発明に用いる、弾性層を有するローラ形状の中間転写体の断面図である。
【図４】本発明に用いる、弾性層の上に被覆層を有するローラ形状の中間転写体の断面図である。
【図５】本発明に用いる、弾性層の上に複数の被覆層を有するローラ形状の中間転写体の断面図である。
【図６】本発明の実施例５に用いたカラー画像出力装置の概略図である。
【符号の説明】
１ 感光ドラム
２ １次帯電器
３ 像露光手段
６ 転写ベルト
８ クリーニング用帯電部材
９ 転写残現像剤回収部材
１０ 転写材ガイド
１１ 転写材供給ローラ
１３ 感光ドラムのクリーニング装置
１５ 定着器
２０ 中間転写体
２１ 芯金
２２ 弾性層
２６ バイアス電源
２７ バイアス電源
２８ バイアス電源
２９ バイアス電源
４１ イエロー色現像装置
４２ マゼンタ色現像装置
４３ シアン色現像装置
４４ ブラック色現像装置
６１ テンションローラ
６２ 転写ローラ
１００ 芯金
１０１ 弾性層
１０２ 被覆層
１０３ 被覆層
１０４ ベルト状中間転写体
２００ 金属ロール
２０１ 抵抗器
２０２ 電源
２０３ 電位差計
Ｐ 転写材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic method, and in particular, a transferable image (toner image) formed on a first image carrier is temporarily transferred onto an intermediate transfer member, and then a second image. The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine that obtains an image formed product by further transferring it onto a carrier.
[0002]
[Prior art]
An image forming apparatus that uses an intermediate transfer member is a color image forming device that sequentially stacks and transfers a plurality of component color images of color image information and multicolor image information, and outputs an image formed product in which color images and multicolor images are synthesized and reproduced. It is effective as an image forming apparatus, a multicolor image forming apparatus, or an image forming apparatus having a color image forming function or a multicolor image forming function, and can obtain an image having no component color misregistration (color misregistration). Is possible.
[0003]
FIG. 1 shows a schematic diagram of an example of an image forming apparatus which is a transfer apparatus using an intermediate transfer member having a roller shape.
[0004]
FIG. 1 shows a color image forming apparatus (copier or laser beam printer) using an electrophotographic process. An intermediate resistance elastic roller 20 is used as an intermediate transfer member.
[0005]
Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) that is repeatedly used as a first image bearing member, and is rotated at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. . The photosensitive drum 1 is uniformly charged to a predetermined polarity / potential by the primary charger 2 in the course of rotation, and then image exposure means (not shown) (color separation / imaging exposure optical system for color original image, image information) A first color component image (for example, a yellow component) of a target color image by receiving image exposure 3 by a scanning exposure system or the like by a laser scanner that outputs a laser beam modulated corresponding to the time-series electric digital pixel signal An electrostatic latent image corresponding to (image) is formed.
[0006]
Next, the electrostatic latent image is developed with yellow toner Y, which is the first color, by the first developing device 41 (yellow developing device). At this time, the second to fourth developing devices 42, 43, 44 (magenta, cyan, and black developing devices) are turned on and off and do not act on the photosensitive drum 1, and the yellow toner of the first color. The image is not affected by the second to fourth developing units 42 to 44. The intermediate transfer member 20 is rotationally driven in the counterclockwise direction indicated by the arrow at the same peripheral speed as that of the photosensitive drum 1.
[0007]
The intermediate transfer member 20 of this embodiment includes a pipe-shaped cored bar 21 and an elastic layer 22 formed on the outer peripheral surface thereof. The first color yellow toner image formed and supported on the photosensitive drum 1 passes through the nip portion between the photosensitive drum 1 and the intermediate transfer body 20 by the primary transfer bias applied to the intermediate transfer body 20. The intermediate transfer is sequentially performed on the outer peripheral surface of the intermediate transfer member 20 by the formed electric field. Similarly, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are sequentially superimposed and transferred onto the intermediate transfer body 20, and a composite color toner image corresponding to the target color image is obtained. Is formed.
[0008]
A primary transfer bias for sequentially superimposing and transferring toner images of the first to fourth colors from the photosensitive drum 1 to the intermediate transfer member 20 is applied from a bias power source 29 with a polarity (+) opposite to that of the toner. In the sequential transfer execution process of the first to fourth color toner images from the photosensitive drum 1 to the intermediate transfer body 20, the transfer belt 6 can be brought into and out of contact with the intermediate transfer body 20.
[0009]
The transfer belt 6 corresponds to the intermediate transfer member 20 and is arranged in parallel so as to be in contact with the lower surface portion. The transfer belt 6 is supported by a transfer roller 62 and a tension roller 61, and a desired secondary transfer bias is applied to the transfer roller 62 by a bias power supply 28, and the tension roller 61 is grounded.
[0010]
In transferring the composite color toner image superimposed and transferred onto the intermediate transfer member 20 to the transfer material P, the transfer belt 6 is brought into contact with the intermediate transfer member 20 and a transfer material supply roller 11 from a paper feed cassette (not shown). Then, the transfer material P passes through the transfer material guide 10 to the contact nip between the intermediate transfer body 20 and the transfer belt 6 at a predetermined timing, and at the same time, the secondary transfer bias is applied from the bias power source 28 to the transfer roller 62. Is done. The composite color toner image is transferred from the intermediate transfer member 20 to the transfer material P by the secondary transfer bias. The transfer material P that has received the toner image transfer is introduced into the fixing device 15 and fixed by heating.
[0011]
In a color electrophotographic apparatus having an image forming apparatus using the above-described intermediate transfer member, a second image carrier is pasted or adsorbed on a transfer drum, which is a conventional technique, and from there on the first image carrier. A color electrophotographic apparatus having an image forming apparatus for transferring an image, for example, the transfer method described in JP-A-63-301960 is superior in the following points.
(1) There is little color misregistration when the toner images of each color are superimposed.
(2) As shown in FIG. 1, the image is transferred from the intermediate transfer member without requiring any processing or control (eg, gripping, adsorbing, giving a curvature, etc.) to the second image carrier. Therefore, a wide variety of second image carriers can be selected. For example, thin paper (40 g / m, envelope, postcard, label paper, etc.)²Paper) to thick paper (200g / m²Paper), the second image bearing member can be transferred regardless of the width, length, or thickness.
[0012]
As described above, because of the advantage of using the intermediate transfer member, color copiers, color printers, and the like using this image forming apparatus are already in operation on the market.
[0013]
However, the present situation is that these image forming apparatuses make full use of the above-mentioned advantages and do not function sufficiently as apparatuses that are truly expected and satisfying users.
[0014]
[Problems to be solved by the invention]
When the above image forming apparatus is used repeatedly, the developer that has not been transferred from the intermediate transfer member to the second image carrier (hereinafter referred to as transfer residual developer) is removed from the surface of the intermediate transfer member. It is necessary to enter the next image forming step. However, in the conventional image forming apparatus using the intermediate transfer member, the transfer efficiency from the intermediate transfer member to the second image carrier (hereinafter referred to as secondary transfer efficiency) is not sufficiently high. For this reason, it becomes difficult to remove the transfer residual developer completely and stably, and the transfer residual developer appears in the next image to become a ghost image, or the transfer residual developer is formed on the surface of the intermediate transfer member. There is a problem of being accumulated and fused. The occurrence of fusion is not preferable because it causes a reduction in image quality.
[0015]
Also, depending on the type of conductive agent used for the intermediate transfer member, the resistance value of the intermediate transfer member varies greatly depending on the environment (temperature and humidity), or the conductive agent bleeds out to the surface of the intermediate transfer member to cause a photosensitive member. Therefore, it is difficult to obtain a stable image.
[0016]
An object of the present invention is to provide an image forming apparatus using an intermediate transfer member that can repeatedly obtain high-quality images regardless of the use environment.
[0017]
[Means for Solving the Problems]
  That is, the present invention provides an image forming apparatus in which an image formed on a first image carrier is transferred to an intermediate transfer member and then further transferred onto a second image carrier.
The intermediate transfer member contains a solvent-soluble conductive polymer,
The solvent-soluble conductive polymer isIt is shown by the following general formula (1)Is a compound
An image forming apparatus characterized by the above.
General formula (1)
[Chemical Formula 3]

(Wherein R1, R2, R3, R4, R5, R6, R7 and R8 are the same or different and have a hydrocarbon group, a hydroxyl group-substituted hydrocarbon group, and at least one of an amide bond and an ester bond in the group. Hydrocarbon group, hydrocarbon group having ether oxygen in the group, O-hydrocarbon group-substituted-3-oxy-2-hydroxypropyl group, terminal hydroxyl group-substituted polyoxyhydrocarbon group, polyoxyhydrocarbon group, Residues that form a morpholine ring, a pyridine ring or an imidazoline ring together with a polyoxyhydrocarbon group bonded to a terminal hydrocarbon group with a carbonyl group as a linking group, a central nitrogen atom in the same atomic group and another N-substituent At least one group selected from the group consisting of: (A) ^2- Is SO _Three ^2- , S ₂ O _Five ^2- , S ₂ O _Four ^2- , S ₂ O _Three ^2- And SO _Four ^2- At least one ion selected from the group consisting of )
[0018]
Hereinafter, the present invention will be described in detail.
[0019]
First, in order to repeatedly obtain a high-quality image, it is necessary to completely remove the transfer residual developer on the intermediate transfer member. Obviously, the smaller the residual transfer developer, the more advantageous in order to completely remove the residual transfer developer. That is, the higher the secondary transfer efficiency, the easier the removal of the transfer residual developer.
[0020]
As a result of studies by the present inventors, it has been found that the resistance value of the intermediate transfer member is an important factor for improving the secondary transfer efficiency. That is, the resistance value of the intermediate transfer member is 1 × 10 5 by the measurement method shown below.^Four(Ω) or more 1 × 10^TenIt was found that it was preferable to be less than (Ω).
<Method for measuring resistance value of intermediate transfer member>
(1) The intermediate transfer member and the metal roll are brought into contact with each other at a linear pressure of 40 g / cm so that both axes are parallel to each other, and a DC power source, a resistor, and a potentiometer are connected (FIG. 2).
(2) The metal roll is driven to rotate and adjusted so that the linear velocity of the surface of the intermediate transfer member following the metal roll is 120 mm / sec.
(3) Apply +1 kV from a DC power source to the circuit, and measure the potential difference Vr (V) at both ends of a resistor having an appropriate resistance value R (Ω) inserted downstream of the intermediate transfer member with a potentiometer. .
(4) The resistance value of the intermediate transfer member is calculated according to the following equation.
Resistance of intermediate transfer member (Ω) = 1000 (V) × R (Ω) ÷ Vr (V)
Unless otherwise specified, the measurement atmosphere is 23 ° C./55% Rh.
[0021]
Since the intermediate transfer member of the present invention is made of a material such as resin, elastomer, rubber or the like, it is necessary to use a conductive agent in order to adjust the resistance value of the intermediate transfer member within the above range.
[0022]
Conventionally, conductive fillers such as carbon black and metal, surfactant type antistatic agents, and the like have been used as the conductive agent.
[0023]
However, when a conductive filler such as carbon black or metal is used, it is difficult to uniformly disperse the conductive filler, so micro resistance unevenness is likely to occur, resulting in a reduction in image quality. May end up. In addition, when a surfactant type antistatic agent is used, the resistance value of the intermediate transfer member largely varies depending on the use environment (particularly temperature and humidity), so that a stable image cannot be obtained. Further, when the surfactant type antistatic agent bleeds out on the surface of the intermediate transfer member, there is a problem that the photosensitive member is contaminated.
[0024]
The present invention solves the above problems by using a solvent-soluble conductive polymer as a conductive agent.
[0025]
That is, in order to eliminate microscopic resistance unevenness, a system in which a conductive agent is dissolved in a resin matrix of an intermediate transfer member is more advantageous than a conductive filler dispersion system because it can be more uniformly dispersed. . However, even if it is soluble in the solvent, the conventional surfactant type antistatic agent has a problem that the environmental stability of the resistance value is poor and the photoreceptor is contaminated as described above. Can not be used because there is.
[0026]
In contrast, the solvent-soluble conductive polymer used in the intermediate transfer member of the present invention is
(1) Since it is soluble in a solvent, it can be easily and uniformly dispersed in the resin matrix of the intermediate transfer member.
(2) Little change in resistance due to changes in the surrounding environment,
(3) Since it is a polymer, it does not contaminate the photoreceptor (it is difficult to bleed out on the surface of the intermediate transfer member).
[0027]
Here, the solvent-soluble conductive polymer used for the intermediate transfer member of the present invention refers to those satisfying the following (1) and (2).
(1) Dissolve 1% by mass or more in at least one of the following solvents.
Methanol, ethanol, isopropyl alcohol, benzyl alcohol, pyridine, N-methylpyrrolidone, N, N'-dimethylformamide, acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, xylene, tetrahydrofuran, ethyl acetate, butyl acetate, cyclohexane, n -Octane, diethyl ether, dimethyl sulfoxide, diethylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, Freon 11, Freon 12, Freon 112.
(2) Single surface resistance of 1 × 10^Ten(Ω / □) or less. However, the surface resistance is measured at 23 ° C./55% RH.
[0028]
In order to prevent the solvent-soluble conductive polymer from bleeding out on the surface of the intermediate transfer member and contaminating the photoreceptor, it is preferable that the molecular weight is large. That is, the molecular weight of the solvent-soluble conductive polymer is preferably 4000 or more. However, the present invention is not limited to this.
[0029]
As a result of studies by the present inventors on the compounds satisfying the above (1) and (2), it has been found that the following compounds are preferable for producing the intermediate transfer member used in the image forming apparatus of the present invention. It was.
A compound having at least one ion selected from the group consisting of sulfate ion, pyrosulfite ion, dithionite ion, thiosulfate ion and sulfite ion, and at least one quaternary ammonium ion.
[0030]
The said compound is demonstrated. This compound is a compound having at least one ion selected from the group consisting of sulfate ion, pyrosulfite ion, dithionite ion, thiosulfate ion and sulfite ion, and at least one quaternary ammonium ion. It is characterized by an electron-withdrawing group made up of a combination of atoms (sulfur and oxygen) with high electronegativity, and has a resonance structure by binding to a basic nitrogen compound contained in a quaternary ammonium ion. Therefore, it is considered that a wide range of electron transfer occurs and conductivity is developed. That is, it is considered that the main conductive mechanism of the compound is due to electronic conduction. Therefore, the conductivity of the compound is stable regardless of the use environment.
[0031]
The resonance structural formula in the case of a compound of sulfate ion and quaternary ammonium ion is shown in the following structural formula (1).
[0032]
Structural formula (1)
[0033]
[Chemical 2]

[0034]
  As quaternary ammonium ion, SpecialIn the general formula (1), R1, R2, R3, R4, R5, R6, R7 and R8 are a hydrocarbon group, a hydroxyl group-substituted hydrocarbon group, and at least one of an amide bond and an ester bond in the group. A hydrocarbon group having an ether oxygen in the group, an O-hydrocarbon group-substituted-3-oxy-2-hydroxypropyl group, a terminal hydroxyl group-substituted polyoxyhydrocarbon group, a polyoxyhydrocarbon Form a morpholine ring, a pyridine ring or an imidazoline ring together with a group, a polyoxyhydrocarbon group bonded to a terminal hydrocarbon group with a carbonyl group as a linking group, a central nitrogen atom in the same atomic group and another N-substituent In the case of at least one group selected from the group consisting of residues, the conductivity of the compound is further increased, which is preferable. This is considered to be because the functional group described above increases and stabilizes the (+) property of basic nitrogen in the quaternary ammonium ion.
[0035]
  Further, the compound of the general formula (1) is mixed with a polyvalent hydroxy compound.May. in this case,
(I) The conductivity imparting effect is further increased. This is presumably because the hydroxyl group increases and stabilizes the (+) nature of the basic nitrogen in the quaternary ammonium ion.
(Ii) Thermal stability is improved.
(Iii) Compatibility with rubber, elastomer and resin is increased.
It is more preferable because it has many excellent features.
[0036]
Examples of the polyvalent hydroxy compound include pentaerythritol, sorbitol, mannitol, benzylidene sorbitol, di (benzylidene) sorbitol, trimethylolethane, trimethylolpropane, di (pentaerythritol), bisphenol A, hydroquinone, pyrogallol and the like. However, it is not particularly limited. Of course, a mixture of two or more of these may be used.
[0037]
The solvent-soluble conductive polymer used in the intermediate transfer member of the present invention is preferably added to the surface layer. However, in some cases, when a coating layer is present in the lower layer, it is added to the coating layer or the elastic layer. May be.
[0038]
Rubber, elastomer, and resin can be used for the elastic layer and the coating layer of the intermediate transfer member used in the present invention. For example, natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber can be used as the rubber and elastomer. , Ethylene-propylene rubber, ethylene-propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, acrylonitrile butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, acrylic rubber, silicone rubber , Fluorinated rubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile rubber, thermoplastic elastomer (eg polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyamide, polyester It can be used system, the fluorine resin).
[0039]
The resins include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene- Acrylate ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer) Styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl chloroacrylate Copolymer, styrene-acrylonitrile-acrylic Styrenic resins such as acid ester copolymers (monopolymers or copolymers containing styrene or styrene-substituted products), methyl methacrylate resins, butyl methacrylate resins, ethyl acrylate resins, butyl acrylate resins, modified acrylic resins (Silicone-modified acrylic resin, vinyl chloride-modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, rosin-modified maleic acid resin, phenol resin, epoxy Resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, fluororesin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin Fine polyvinyl butyral resins, polyamide resins, modified polyphenylene oxide resins.
[0040]
Further, as described above, the solvent for dissolving the solvent-soluble conductive polymer is methanol, ethanol, isopropyl alcohol, benzyl alcohol, pyridine, N-methylpyrrolidone, N, N'-dimethylformamide, acetone, methyl ethyl ketone. , Methyl isobutyl ketone, benzene, toluene, xylene, tetrahydrofuran, ethyl acetate, butyl acetate, cyclohexane, n-octane, diethyl ether, dimethyl sulfoxide, diethylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, freon 11 , Freon 12, Freon 112 and the like, but other solvents may be used as long as they can dissolve the solvent-soluble conductive polymer. Or it may be a mixed solvent of.
[0041]
Further, in producing the intermediate transfer member used in the image forming apparatus of the present invention, it is not always necessary to use a solvent as described above. For example, a solvent-soluble conductive polymer is directly used as a rubber, an elastomer, It is also possible to take a manufacturing method such as kneading into a resin. In this case, the solvent may be interpreted broadly. That is, it can be considered that rubber, elastomer, and resin correspond to the solvent of the solvent-soluble conductive polymer.
[0042]
Similarly, in manufacturing the intermediate transfer member used in the image forming apparatus of the present invention, it is not necessary to select a material from the above material group, and the intermediate transfer member can have a resistance value within the above range. It can also be manufactured using other materials.
[0043]
The intermediate transfer member used in the present invention is, for example, a roller shape having at least a rubber, elastomer, resin elastic layer and one or more coating layers on a cylindrical conductive support, or as shown in FIG. The belt shape and various modes can be selected according to the purpose and necessity. Examples thereof are shown in FIGS.
[0044]
In consideration of the color misalignment of the superimposed images and durability due to repeated use, a more preferable aspect of the present invention is a roller shape. In each figure, 100 is a rigid cylindrical conductive support, 101 is an elastic layer, 102 and 103 are coating layers, and 104 is an intermediate transfer belt.
[0045]
As the cylindrical conductive support, metals or alloys such as aluminum, iron, copper and stainless steel, conductive resins in which carbon, metal particles, etc. are dispersed can be used. The shape, what penetrated the axis | shaft in the center of a cylinder, what gave reinforcement to the inside of a cylinder, etc. are mentioned.
[0046]
The film thickness of the elastic layer of the intermediate transfer member is preferably 0.5 to 10 mm, more preferably 1 to 5 mm. The film thickness of the coating layer is preferably a thin layer, specifically 1 to 500 μm, more preferably 5 to 200 μm, in order to further convey the flexibility of the lower elastic layer to the upper layer or the photoreceptor surface.
[0047]
Further, as the first image carrier, a photosensitive drum in which a photosensitive layer is coated on the surface of a conductive rigid roller, and a fine powder of tetrafluoroethylene resin (PTFE) is formed on at least the outermost layer of the photosensitive drum. It is preferable to use a photosensitive drum containing In particular, when a photosensitive drum containing at least the surface layer containing PTFE fine powder is used, higher primary transfer efficiency can be obtained. This is considered to be because the surface energy of the outermost layer of the photosensitive drum is lowered and the toner releasability is improved by containing the fine powder of PTFE.
[0048]
Here, in the image forming apparatus of the present invention, as a more preferable embodiment, an image forming apparatus that electrostatically cleans the residual transfer developer as shown in FIG. 1 can be exemplified.
[0049]
In FIG. 1, reference numeral 8 denotes a cleaning charging member that charges a transfer residual developer with a polarity opposite to that of the photosensitive drum 1. A transfer residual developer collecting member 9 applies a bias having the same polarity as that of the photosensitive drum 1 and collects the previous transfer residual developer charged by the cleaning charging member 8.
[0050]
Here, since the cleaning charging member 8 and the residual transfer developer collecting member 9 are biased while being in contact with the intermediate transfer member 20, the surface of the intermediate transfer member 20 is charged by these members. . If this charge is not attenuated (the surface potential of the intermediate transfer member 20 is large) and the next image forming step is started, the primary transfer electric field is disturbed at the nip portion with the photosensitive drum 1, so that the image quality is lowered. Resulting in. However, in the solvent-soluble conductive polymer (especially nitrogen-containing charge transfer complex type polyboron compound) used in the image forming apparatus of the present invention, the charge decay is fast, so this is not the case. It is thought that it becomes possible to perform proper cleaning.
[0051]
In FIG. 1, the cleaning charging member 8 and the residual transfer developer collecting member 9 can take various forms such as a metal roll, a conductive elastic roll, a conductive fur brush, and a conductive blade. it can.
[0052]
In the image forming apparatus of FIG. 1, for example, when the power is turned on, a bias having a polarity opposite to that of the photosensitive drum 1 is applied to the transfer residual developer collecting member 9 to charge the transfer residual developer in the collection container, thereby cleaning the photosensitive drum. It is also conceivable to collect it at 13. This method has an advantage that the transfer residual developer collecting container can be reduced in size.
[0053]
In the image forming apparatus of FIG. 1, the photosensitive drum 1 may be used as a residual transfer developer collecting member without providing the residual transfer developer collecting member 9.
[0054]
Further, in the image forming apparatus shown in FIG. 1, the developer 94 may be transferred from the photosensitive drum 1 to the intermediate transfer body 20 and the residual transfer developer 96 may be returned to the photosensitive drum 1 at the same time (hereinafter, primary transfer simultaneous cleaning). Referred to as a scheme). The primary transfer simultaneous cleaning method has an advantage that there is no decrease in throughput because a cleaning step is not particularly required.
[0055]
As described above, since the intermediate transfer member of the present invention contains a solvent-soluble conductive polymer,
(1) There is no resistance unevenness of the intermediate transfer member,
(2) The fluctuation of the resistance value of the intermediate transfer member due to the environment is small.
(3) Does not contaminate the photoreceptor.
It has the characteristics.
[0056]
Therefore, the image forming apparatus of the present invention has an effect that a stable image can be obtained repeatedly regardless of the use environment.
[0057]
The intermediate transfer member of the present invention is produced, for example, as follows.
[0058]
First, a metal roll as a cylindrical conductive support is prepared. An elastic layer is provided by molding rubber, elastomer, resin or the like on a metal roll by melt molding, injection molding, dip coating or spray coating. Next, the coating layer is provided by molding the material of the coating layer on the elastic layer by melt molding, injection molding, dip coating, spray coating, or the like.
[0059]
【Example】
Hereinafter, the present invention will be described in detail by way of examples.
Example 1
A roller having an elastic layer having a thickness of 5 mm was obtained by transfer molding a rubber compound having the following composition on the surface of an aluminum cylindrical roller having a diameter of 182 mm, a length of 320 mm, and a thickness of 5 mm using a mold.
[0060]

[0061]
Next, a coating material for a coating layer for obtaining a coating layer on the roller was prepared according to the following formulation.
[0062]

[0063]
However, in the coating composition, the solvent-soluble conductive polymer 1 is R1 = R4 = R5 = R8 = CH in the general formula (1)._Three, R2 = R6 = C₂H_FourOH, R3 = R7 = C₁₂H_{twenty five}, A = SO_FourIt is a compound shown by these. The compound has a molecular weight of about 600 and a surface resistance of about 1 × 10^Four(Ω / □).
[0064]
The coating material was sprayed onto the roller and then heated at 100 ° C. for 2 hours to remove the residual solvent, and an intermediate transfer member having a tough coating layer with a thickness of 35 μm was obtained.
[0065]
The resistance of the obtained intermediate transfer member was measured in each environment according to the above <Method for measuring resistance value of intermediate transfer member>.
[0066]
Next, the intermediate transfer member is mounted on the full-color electrophotographic apparatus shown in FIG.²A full color image was printed on paper, the transfer efficiency was defined as follows, and the transfer efficiency was measured.
[0067]
Primary transfer efficiency = image density on the intermediate transfer member / (transfer residual image density on the photosensitive drum + image density on the intermediate transfer member) × 100 (%).
[0068]
Secondary transfer efficiency = image density on paper / (image density on paper + transfer residual image density on intermediate transfer member) × 100 (%).
[0069]
The cleaning charging member 8 is 1 × 10⁸An elastic roller having a resistance of (Ω) is applied to the transfer residual developer collecting member 9 by 1 × 10.²A conductive fur brush having a resistance of (Ω) was used.
[0070]
Next, continuous printing of 5,000 sheets was performed with a full-color image, but no image defect due to poor cleaning occurred.
[0071]
Further, in order to investigate the influence of the environmental dependency of the resistance value of the intermediate transfer member on the image, before and after continuous printing of 5000 sheets, 15 ° C./10%, 23 ° C./55%, 30 ° C./80%. Images were output in these three environments (hereinafter abbreviated as three environments), but all of them could obtain good images.
[0072]
The results are shown in Tables 1 and 2.
[0073]
The image forming conditions of this embodiment are shown below.
[0074]
Photoconductor: OPC photosensitive drum

Color developer: Non-magnetic one-component toner (both four colors)
Primary transfer potential: + 100V
Secondary transfer current: +15 μA
Process speed: 120mm / sec

Contact pressure between the intermediate transfer member and the photosensitive drum: 2 kgf
Contact pressure between intermediate transfer member and transfer belt: 5 kgf
Contact pressure between intermediate transfer member and cleaning charging member: 1 kgf
[0075]
(Example 2)
On the roller having the elastic layer obtained by the rubber composition of Example 1, a coating material for coating layer for obtaining a coating layer was prepared according to the following formulation.
[0076]

[0077]
Here, the eutectic of the solvent-soluble conductive polymer 1 and the hydroxy compound was produced as follows.
[0078]
Put 100 g of solvent-soluble conductive polymer 1 in a flask, 200 g of pentaerythritol as a hydroxy compound, and 900 g of pure water, perform dehydration while gradually heating in a nitrogen stream, and further add pure water injected by heating. Evaporate all. By this operation, a eutectic of solvent-soluble conductive polymer 1 and pentaerythritol was obtained.
[0079]
The surface resistance of the eutectic is about 5 × 10^Three(Ω / □).
[0080]
The paint was spray-applied to the roller and then heated at 100 ° C. for 2 hours to remove the residual solvent, thereby obtaining an intermediate transfer member having a tough coating layer having a thickness of 30 μm.
[0081]
The resistance value of the obtained intermediate transfer member was measured in the same manner as in Example 1.
[0082]
Next, the intermediate transfer member was mounted on the full-color electrophotographic apparatus shown in FIG. The cleaning charging member 8 was the same as in Example 1, but the transfer residual developer collecting member 9 was not used, and the primary transfer simultaneous cleaning method was used. The current value applied from the bias power source 26 to the cleaning charging member 8 is +40 (μA).
[0083]
Further, the measurement of the transfer efficiency and the endurance test for 5000 sheets were carried out in the same manner as in Example 1. Even after the endurance of 5,000 sheets, there was no image defect due to poor cleaning, and primary transfer simultaneous cleaning was possible. This is presumably because the eutectic used in this example has a very rapid charge leakage of the intermediate transfer member. Other image forming conditions are the same as those in the first embodiment.
[0084]
In addition, in order to investigate the influence of the environmental dependency of the resistance value of the intermediate transfer member on the image, images were output in three environments before and after the continuous printing of 5000 sheets. did it.
[0085]
The results are shown in Tables 1 and 2.
[0086]
(Comparative Example 1)
On the roller having the elastic layer obtained by the rubber composition of Example 1, a coating material for coating layer for obtaining a coating layer was prepared according to the following formulation.
[0087]

[0088]
The coating material was spray-coated on the roller and then heated at 100 ° C. for 1 hour to remove the residual solvent, and the coating layer was crosslinked to obtain an intermediate transfer member having a tough coating layer having a thickness of 25 μm. .
[0089]
The resistance value of the obtained intermediate transfer member was measured in the same manner as in Example 1.
[0090]
Next, the intermediate transfer member was mounted on the full-color electrophotographic apparatus shown in FIG. 1, and the transfer efficiency was measured and 5000 full-color continuous prints were performed in the same manner as in Example 1. Since the resistance value of the intermediate transfer member was uneven, the halftone image was gritty.
[0091]
The cleaning charging member 8 and the transfer residual developer collecting member 9 were the same as those in Example 1. The image forming conditions are the same as in the first embodiment.
[0092]
Further, in order to investigate the influence of the environmental dependency of the resistance value of the intermediate transfer member on the image, images were output in three environments before and after continuous printing of 5000 sheets. In any environment, the halftone was gritty, and the degree was worse after printing 5000 sheets.
[0093]
The results are shown in Tables 1 and 2.
[0094]
(Comparative Example 2)
A coating for a coating layer was prepared by adding N, N′-di (polyoxyethylene) alkylamine, which is one of surfactant type antistatic agents that are generally used.
[0095]

[0096]
The paint is spray-coated on a roller having an elastic layer obtained by blending the rubber of Example 1, and then the remaining solvent is removed by heating at 80 ° C. for 2 hours, and the coating layer is crosslinked to obtain a thickness. An intermediate transfer member having a tough coating layer of 50 μm was obtained.
[0097]
The resistance value of the obtained intermediate transfer member was measured in the same manner as in Example 1.
[0098]
Next, the intermediate transfer member was mounted on the full-color electrophotographic apparatus shown in FIG. 1, and the transfer efficiency was measured and 5000 full-color continuous prints were performed in the same manner as in Example 1.
[0099]
Initially, good images were obtained, but the N, N'-di (polyoxyethylene) alkylamine used as the conductive agent bleeds out to the surface of the intermediate transfer member, which gradually contaminates the photoreceptor. It could not withstand 5000 continuous prints.
[0100]
The cleaning charging member 8 and the transfer residual developer collecting member 9 were the same as those in Example 1. The image forming conditions are the same as in the first embodiment.
[0101]
Further, in order to investigate the influence of the environmental dependency of the resistance value of the intermediate transfer member on the image, images were output in three environments using a new photosensitive drum before and after continuous printing of 5000 sheets. Since the resistance value of the intermediate transfer member becomes very large particularly in a low temperature / low humidity environment, transfer failure occurred in an environment of 15 ° C./10% from the initial stage, and a good image could not be obtained. .
[0102]
The results are shown in Tables 1 and 2.
[0103]
[Table 1]

[0104]
【The invention's effect】
  As described above, the present invention provides an image forming apparatus in which an image formed on a first image carrier is transferred to an intermediate transfer member and then further transferred onto a second image carrier. The transfer body contains a solvent-soluble conductive polymer, and the solvent-soluble conductive polymer isShown by the general formula (1)An image forming apparatus comprising a compound.
[0105]
Therefore, the image forming apparatus of the present invention has an effect that a stable image can be obtained repeatedly regardless of the use environment.
[Brief description of the drawings]
FIG. 1 is a schematic view of a color image output apparatus using a roller-shaped intermediate transfer member.
FIG. 2 is a measurement circuit diagram of a resistance value of an intermediate transfer member used in the present invention.
FIG. 3 is a cross-sectional view of a roller-shaped intermediate transfer member having an elastic layer used in the present invention.
FIG. 4 is a cross-sectional view of a roller-shaped intermediate transfer member having a coating layer on an elastic layer used in the present invention.
FIG. 5 is a cross-sectional view of a roller-shaped intermediate transfer member having a plurality of coating layers on an elastic layer used in the present invention.
FIG. 6 is a schematic diagram of a color image output apparatus used in Embodiment 5 of the present invention.
[Explanation of symbols]
1 Photosensitive drum
2 Primary charger
3 Image exposure means
6 Transfer belt
8 Charging member for cleaning
9 Transfer residual developer recovery member
10 Transfer material guide
11 Transfer material supply roller
13 Photosensitive drum cleaning device
15 Fixing device
20 Intermediate transfer member
21 Core
22 Elastic layer
26 Bias power supply
27 Bias power supply
28 Bias power supply
29 Bias power supply
41 Yellow color developing device
42 Magenta color developing device
43 Cyan developing device
44 Black color developing device
61 Tension roller
62 Transfer roller
100 cored bar
101 Elastic layer
102 coating layer
103 coating layer
104 belt-shaped intermediate transfer member
200 Metal roll
201 resistors
202 power supply
203 Potentiometer
P transfer material

Claims (6)

In the image forming apparatus for transferring the image formed on the first image carrier to the intermediate transfer member, and further transferring the image to the second image carrier.
The intermediate transfer member contains a solvent-soluble conductive polymer,
The image-forming apparatus, wherein the solvent-soluble conductive polymer is a compound represented by the following general formula (1) .
General formula (1)

(Wherein R1, R2, R3, R4, R5, R6, R7 and R8 are the same or different and have a hydrocarbon group, a hydroxyl group-substituted hydrocarbon group, and at least one of an amide bond and an ester bond in the group. Hydrocarbon group, hydrocarbon group having ether oxygen in the group, O-hydrocarbon group-substituted-3-oxy-2-hydroxypropyl group, terminal hydroxyl group-substituted polyoxyhydrocarbon group, polyoxyhydrocarbon group, Residues that form a morpholine ring, a pyridine ring or an imidazoline ring together with a polyoxyhydrocarbon group bonded to a terminal hydrocarbon group with a carbonyl group as a linking group, a central nitrogen atom in the same atomic group and another N-substituent at least one group selected from the group consisting of, (a) ² is _{^{SO 3 2-, S 2 O 5}} 2-, S 2 O 4 2-, S 2 O 3 2- and SO ₄ ^2- Na At least one ion selected from the group.) In the image forming apparatus for transferring the image formed on the first image carrier to the intermediate transfer member, and further transferring the image to the second image carrier.
The intermediate transfer member contains a solvent-soluble conductive polymer,
The solvent-soluble conductive polymer comprises at least one ion selected from the group consisting of sulfate ion, pyrosulfite ion, dithionite ion, thiosulfate ion and sulfite ion, and at least one quaternary ammonium ion. And a mixture of a polyvalent hydroxy compound
An image forming apparatus. The first image bearing member, a photosensitive drum having a photosensitive layer on a conductive rigid roller onto the image according to claim 1 or 2 intermediate transfer member having an elastic layer and a coating layer on a conductive rigid roller on Forming equipment. The first image bearing member, a photosensitive drum having a photosensitive layer on a conductive rigid roller on, the image forming apparatus according to claim 1 or 2 intermediate transfer member is a belt shape. The first image carrier is a photosensitive drum having a photosensitive layer on a conductive rigid roller, and at least a surface layer of the photosensitive drum contains a fine powder of tetrafluoroethylene resin (PTFE). 5. The image forming apparatus according to 3 or 4 . The image forming apparatus is an image forming apparatus for cleaning the intermediate transfer member by applying a charge to the residual transfer developer that has not been transferred from the intermediate transfer member to the second image carrier using a cleaning charging member. the image forming apparatus according to any one of a claims 1-5.

Images