JP4159300B2 - Image fixing apparatus and image forming apparatus - Google Patents

Description

表１は、スイープローラ７１０ａ、７１０ｂによる余剰キャリア除去の結果を示したものである。
表１に示すように、現像ローラ表面に担持される現像剤が０．８[ｍｇ／ｃｍ^２]のとき、現像ニップＮ１を通過した感光体ドラム６１０の非画像部には０．３０[ｍｇ／ｃｍ^２]のキャリア液Ｃが付着する。この感光体ドラム６１０の非画像部に付着したキャリア液Ｃは、第１スィープローラ７１０ａとの除去ニップを通過すると、その付着量が０．１５[ｍｇ／ｃｍ^２]に減少する。すなわち、感光体ドラム６１０の非画像部に付着したキャリア液Ｃのうち０．１５[ｍｇ／ｃｍ^２]が第１スィープローラ７１０ａで除去されたことになる。つまり、上記第１スィープローラ７１０ａは、現像時に感光体ドラム６１０上の非画像部に付着した余分なキャリア液Ｃの約半分程度を除去することができる。
一方、現像ニップを通過した感光体ドラム６１０の画像部には、０．６３[ｍｇ／ｃｍ^２]のキャリア液Ｃが付着する。この感光体ドラム６１０の画像部に付着したキャリア液Ｃは、第１スィープローラ７１０ａとの除去ニップを通過すると、その付着量が０．４９[ｍｇ／ｃｍ^２]に減少する。すなわち、感光体ドラム６１０の画像部に付着したキャリア液Ｃのうち０．１４[ｍｇ／ｃｍ^２]がスィープローラ４３で除去されたことになる。
そして、第１スィープローラ７１０ａで除去されたキャリア液Ｃはクリーニングブレード７１１ａで第１スィープローラ７１０ａ表面からクリーニングされて専用タンク７１３ａに収容され、その後現像剤収容タンク７０８に戻される。
【０１１５】
ここで、本実験で使用したスィープローラのゴム硬度は２０度（ＪＩＳ−Ａ）程度であるために除去ニップ内部の圧力は低い。したがって、除去ニップ内部の圧力を高めれば（例えばスィープローラのゴム硬度を５０度より高く設定する）、除去ニップを通過できるキャリア液量も制限されるため、さらに感光体ドラム６１０側へのキャリア液Ｃの付着を低減することができる。しかし、過度の圧力を感光体ドラム６１０とスィープローラとに与えると、画像部のトナー粒子もこの除去ニップを通過できなくなり、画像流れなどの不具合を生じる虞が大きい。よって、弾性層のゴム硬度の好ましい範囲は５０度（ＪＩＳ−Ａ）以下であり、より好ましくは２０度程度である。但し、弾性層のゴム硬度の数値は一例であってこの数値に限定されるものではない。
【０１１６】
次に、第２スイープローラ７１０ｂによる余剰キャリア除去の結果を説明する。第２スイープローラ７１０ｂには、既に述べたように、４００[Ｖ]の電圧を印加している。
表１に示すように、第１スィープローラ７１０ａとの除去ニップを通過した感光体ドラム６１０の非画像部には０．１５[ｍｇ／ｃｍ^２]のキャリア液Ｃが付着している。この感光体ドラム６１０の非画像部に付着したキャリア液Ｃは、第２スイープローラ７１０ｂとの除去ニップを通過すると、その付着量が０．０８[ｍｇ／ｃｍ^２]に減少する。すなわち、感光体ドラム６１０の非画像部に付着したキャリア液Ｃのうち０．０７[ｍｇ／ｃｍ^２]が第２スイープローラ７１０ｂで除去されたことになる。つまり、上記第２スイープローラ７１０ｂによっても、現像時に感光体ドラム６１０上の非画像部に付着した余分なキャリア液Ｃの約半分程度を除去することができる。
一方、現像ニップを通過した感光体ドラム６１０の画像部には、０．４９[ｍｇ／ｃｍ^２]のキャリア液Ｃが付着する。この感光体ドラム６１０の画像部に付着したキャリア液Ｃは、第２スイープローラ７１０ｂとの除去ニップを通過すると、その付着量が０．４１[ｍｇ／ｃｍ^２]に減少する。すなわち、感光体ドラム６１０の画像部に付着したキャリア液Ｃのうち０．０８[ｍｇ／ｃｍ^２]が第２スイープローラ７１０ｂで除去されたことになる。
そして、第２スイープローラ７１０ｂで除去されたキャリア液Ｃはクリーニングブレード７１１ｂで第２スイープローラ７１０ｂ表面からクリーニングされて専用タンク７１３ｂに収容され、その後現像剤収容タンク７０８に戻される。
【０１１７】
第２スイープローラ７１０ｂによる除去ニップに進入する感光体ドラム６１０表面は、既に第１スイープローラ７１０ａによって非画像部のカブリは概ね除去されている。そして、第２スイープローラ７１０ｂに印加された電圧と感光体ドラム６１０との間に生じる除去電界によって、画像部のトナーＴが感光体ドラム６１０表面に圧縮され、トナー粒子間のキャリア液体が更に除去されたのである。
【０１１８】
以上のように第１スィープローラ７１０ａ、第２スイープローラ７１０ｂによる感光体ドラム６１０上の余剰キャリア除去によって、トナーは次のように変化した。ここで、以下に説明する「画像濃度」とは形成された画像の光学濃度であり、「現像剤濃度」とは画像を構成している現像剤に対する現像剤中のトナーの重量比である。
▲１▼現像ニップにおける現像剤濃度
現像直後の感光体ドラム６１０上の画像の現像剤濃度の算出のため、その画像を構成している現像剤中のトナー重量を数２を用いて算出した。
【数２】
画像中トナー重量＝現像ローラ上現像剤塗布量×現像剤トナー濃度×現像率
現像ローラ上現像剤塗布量＝０．８[ｍｇ／ｃｍ^２]
現像剤トナー濃度＝１５[％]
現像率＝１００[％]
これによって算出した結果、現像直後の画像を構成している現像剤の現像剤濃度は１９[％]であった。
▲２▼第１スィープローラ７１０ａによるキャリア除去後の現像剤濃度
感光体ドラム６１０上の画像は、第１スィープローラ７１０ａによる除去ニップ通過後、画像濃度が９５[％]を維持できた。従って、その画像を構成している現像剤中のトナー重量は数３によって求めることができる。
【数３】
画像中トナー重量＝現像直後感光体ドラム上トナー重量×９５[％]
これによって算出した結果と上記表１の結果とから、第１スィープローラ７１０ａによるキャリア除去後の画像を構成している現像剤の現像剤濃度は２３％であった。
▲２▼第２スィープローラ７１０ｂによるキャリア除去後のトナー
更に、第２スィープローラ７１０ｂによる除去ニップ通過後、画像濃度が９５[％]を維持できた。従って、上記表１の結果より、第２スィープローラ７１０ｂによるキャリア除去後の画像を構成している現像剤の現像剤濃度は２６[％]であった。
【０１１９】
なお、第１スィープローラ７１０ａ及び第２スィープローラ７１０ｂによりカブリトナー４０ｃを効率的に除去できる。このため、感光体ドラム６１０と現像ローラ７０６との間の現像ニップでカブリトナー４０ｃが少々残留してもよく、カブリ除去電界（現像ローラ７０６に印加された現像バイアスと感光体帯電電位との電位差）を低く抑えることできる。よって、感光体ドラム６１０の帯電電位を低くすることが可能になる。このことにより、感光体ドラム６１０の耐久性向上、帯電装置の負担軽減、露光パワーの低減等、種々の利点が生じる。
また、第１スィープローラ７１０ａと第２スィープローラ７１０ｂとの電圧を上記のように設定したことによって、次のようなメリットもある。即ち、第２スィープローラ７１０ｂは、画像部のトナーを剥ぎ取ることなく、非画像部に付着したカブリトナーを回収し、また、画像部の余剰キャリアも除去できるというものである。
【０１２０】
以上のように、第１スィープローラ７１０ａ及び第２スィープローラ７１０ｂによって非画像部の液体現像剤や画像部の余剰キャリアを除去できるので、リブのない細線再現性の良い画像を感光体に形成できる。また、感光体ドラム６１０上でトナー像を形成する現像剤の現像剤濃度を上げる事が出来た。
【０１２１】
第１スィープローラ７１０ａ及び第２スィープローラ７１０ｂに印加するバイアスについては、感光体に放電を発生させなければ良い。特にそれぞれに印加する電圧の上限は、感光体とトナーの特性で決定される。また、第１スィープローラ７１０ａで除去できない非画像部のカブリを第２スィープローラ７１０ｂで除去しても良い。その場合、第２スィープローラ７１０ｂに印加するバイアスは第１スィープローラ７１０ａを通過したときのトナー像の画像部表面電位と非画像部表面電位との間に設定する。このように第１スィープローラ７１０ａで回収できない非画像部のカブリを第２スィープローラ７１０ｂで除去すれば、第１スィープローラ７１０ａで非画像部のカブリトナーを凝集した状態で回収する必要がなくなる。よって、現像剤を再利用する上で好都合となる。
【０１２２】
また、実施形態３の変形例として、第１スィープローラ７１０ａと第２スィープローラ７１０ｂとに印加するバイアスによって、それぞれ異なる作用を発揮するよう、バイアス値を設定しても良い。例えば、第１スィープローラ７１０ａには、主に感光体ドラム６１０の地肌部に付着している現像剤を引き寄せるようなバイアスを印加する。第２スィープローラ７１０ｂには、感光体ドラム６１０の画像部に付着したキャリアを付着させ、かつ画像部のトナーを感光体ドラム６１０表面に圧縮するバイアスを印加する。具体例としては、第１スィープローラ７１０ａには４５０[Ｖ]とし、非画像部に残留する感光体上の地汚れトナーおよびキャリア液を除去し、第２スィープローラ７１０ｂには５００[Ｖ]を印加し、画像部をさらに圧縮し、画像部のキャリアおよび、非画像部のキャリアを除去することが考えられる。尚、ここで示したバイアスは一例でありこれに限るものではない。第１スイープローラでは感光体ドラム６１０の地汚れを除去できる電界、第２スイープローラではキャリアを除去しつつ画像を除去しない電界をそれぞれ発生できるバイアスを印加すればよい。
【０１２３】
尚、本実施形態に記載したスィープ電界は、非画像部と画像部の画像濃度、トナーの凝集状態等の因子を満たすことができるように最適化をはかる必要があり、最適化が行われた上で、決定されるものである。また、好ましいスィープ電界の強度は、トナーの易動度によっても左右される。このため、本実施形態３に用いた現像剤では上記のような電界強度が好ましいが、異なる種類のトナーを用いた場合にはこの電界強度に限定されるものではない。現像後に現像ローラあるいはスイープローラ上に付着残留する現像剤が凝集しなければ良い。
【０１２４】
更に、液体画像形成装置の感光体ドラム６１０に当接するように中間転写体を配置し、感光体ドラム６１０上の画像部の電位との電位差が生じる電界が発生する様に中間転写体へバイアス電圧を印加する。本実施形態３では中間転写体に−３００[Ｖ]を印加することにより、良好に画像を中間転写体上に１次転写することが出来た。中間転写体は本実施形態３では中間転写ドラム８１０で説明する。
【０１２５】
なお、従来は中間転写体として、所定厚さの低抵抗の導電性部材の無端ベルトで、たとえば厚さが３０〜１５０[μｍ]で、ポリイミドやＰＥＴ（ポリエチレンテレフタレート）、ＰＶＤＦ樹脂などに導電性の物質（カーボンや金属粉等）を一定割合で混入させたものが用いられていた。ところが、上記転写紙Ｐとして普通紙等の表面の凹部が比較的大きい紙に上記従来の材質からなる中間転写ベルト８６０によって２次転写すると、次のような不具合が生じる。即ち、上述したように、中間転写ベルト８６０の表面が硬いため普通紙等の表面凹部に追従することができず、転写不良による濃度ムラ等が生じる。そこで、本実施形態に係る中間転写ドラム８１０は、普通紙等の表面の凹部に追従するように弾性体を主として構成し、転写不良が生じないようにした。
【０１２６】
図２６は、本実施形態に係る中間転写ドラム８１０の一例の説明図である。中間転写ドラム８１０は、弾性導電体と、該弾性導電体８１１が金属性のドラムに接着されたドラム８１２と、表面コート層８１３とにより構成されたものである。上記弾性導電体は、たとえばカーボンを分散させたポリウレタンゴムで構成することができる。この弾性導電体は、厚さが２００〜２０００[μｍ]、体積抵抗率が１０^３〜１０^１２[Ωｃｍ]、硬度がＪＩＳＡで１５〜８０度（Ｈｓ）であれば、所定の効果を得ることができる。また、上記表面コート層は、トナー粒子の離型性を向上させて２次転写性を向上させるとともに、２次転写後の転写紙Ｐの分離性を向上させるためのものである。たとえばフッ素系樹脂を含むコート層を５〜６０[μｍ]の厚さにコーティングして形成したものである。
【０１２７】
上記中間転写ドラム８１０は、非画像部の余剰キャリア液Ｃの付着防止に加えて、画像部のキャリア液Ｃの一部を付着防止することもできる。
【表２】

表２は、中間転写ドラム８１０への１次転写による画像及び非画像部の余剰キャリア除去の結果を示したものである。表１において、第２スイープローラ７１０ｂとのニップを通過した感光体ドラム６１０の画像部には０．４１[ｍｇ／ｃｍ^２]のキャリア液Ｃを含む現像剤が付着している。それが、中間転写ドラム８１０と感光体が形成する１次転写ニップを通過した中間転写ドラム８１０の画像部には、０．３５[ｍｇ／ｃｍ^２]のキャリア液Ｃを含む現像剤が付着する。また、この時の感光体上の画像部のトナー像は１次転写工程で、１００[％]の画像濃度を維持し、中間転写体上にトナー像を形成できた。したがって、中間転写ドラム８１０に１次転写像を形成することにより、中間転写ドラム８１０に形成されたトナー像の画像部における現像剤濃度は約３０[％]と見積もれる。
【０１２８】
これによって、中間転写ドラム８１０を用いて感光体から中間転写ドラム８１０に画像を１次転写することにより、感光体上のトナー像の画像部はキャリア液を感光体に残し、１次転写を終える。したがって、中間転写ドラム８１０上のトナー像の画像部トナー濃度を更に上昇させることができる。更に、非画像部におけるキャリア付着量も、略半分に減らすことができる。
【０１２９】
さらに中間転写体上のトナー像から、画像部あるいは非画像部に付着したキャリア液Ｃをスィープ（掃除）するために、図２２に示すように、中間転写体上除去部材としての中間転写体スィープローラ８２０を設けている。この中間転写体スィープローラ８２０は、感光体との接触点(1次転写位置)の回転方向下流側であって、現像されたトナー層を挟むように、中間転写ドラム８１０に押圧して設置されている。中間転写体スイープローラ８２０の表面は、中間転写ドラム８１０の表面と略等速で移動する。
【０１３０】
上記中間転写体スィープローラ８２０は、外周面に弾性体の弾性層が設けられている。この弾性層の材質としてはウレタンゴムを用いることができる。弾性層のゴム硬度としては、ＪＩＳ−Ａ硬度で５０度以下であることが望ましい。なお、上記弾性層の材質はウレタンゴムに限られるものではなく、溶剤で膨潤したり溶解したりしない材質であればよい。また、上記中間転写体スィープローラ８２０は、コーティングもしくはチューブにより、その表面粗さ（Ｒｚ）が３[μｍ]以下の平滑性を有するように構成されている。なお、弾性層を中間転写体スィープローラ８２０に設ける構成ではなく、弾性層を中間転写体側に設ける構成であってもよい。さらに、中間転写体を無端ベルト状部材で構成してもよい。
【０１３１】
そして、上記中間転写体スィープローラ８２０を中間転写ドラム８１０に対して適当な圧力で当接させると、弾性層が弾性変形し、除去ニップを形成する。当接圧力を調整することで除去ニップにおける表面移動方向の大きさである除去ニップ幅を調整することができる。
なお、中間転写体スィープローラ８２０の表面は、上述したように中間転写ドラム８１０の表面と略等速で移動するようになっている。従って、中間転写ドラム８１０に現像されたトナーに対して相対的に中間転写ドラム８１０の接線方向の速度ベクトルをもたせない。これにより、中間転写体スィープローラ８２０で中間転写体ドラム上のトナー画像を乱すことなく余剰なキャリア液Ｃを除去することができる。
【０１３２】
なお、上記中間転写ドラム８１０は、非画像部の余剰キャリア液の付着防止に加えて、画像部のキャリア液の一部を付着防止することもできる。表２において、中間転写ドラム８１０画像部には０．３５[ｍｇ／ｃｍ^２]のキャリア液を含む現像剤が付着する。そして、中間転写ドラム８１０と中間転写体スイープローラが形成するニップを通過した中間転写ドラム８１０の画像部には０．[ｍｇ／ｃｍ^２]のキャリア液Ｃを含む現像剤が付着する。
また、この時の感光体上の画像部トナー像は中間転写スイープ工程で、１００[％]の画像濃度を維持し、中間転写体上にトナー像を形成できた。従って、中間転写ドラム８１０に中間転写スイープすることにより、中間転写ドラム８１０に形成されたトナー像の画像部における現像剤濃度は約３５[％]と見積もれる。
以上のように、中間転写体と中間転写体スイープローラ８２０との両方を用いている。これによって、感光体ドラム６１０から中間転写体への１次転写及び中間転写体スイープローラ８２０によるキャリア除去の２段階で、中間転写体上のトナー像の画像部現像剤濃度を更に上昇させることができた。本実施形態３では、中間転写体スイープローラ８２０に印加するバイアスは中間転写ドラム８１０にトナー像を転写するための1次転写バイアス−３００[Ｖ]が印加されているので、０[Ｖ]程度で良好であった。
【０１３３】
本実施形態３においては、転写紙Ｐへの画像の定着性向上のために、定着ニップに至るまでにキャリアを除去する構成を示したものである。以上のように感光体ドラム６１０上、中間転写ニップ、中間転 写体上等の複数の箇所でキャリアを除去すると、転写紙Ｐへの２次転写の前に、既に画像部現像剤濃度を３５[％]にまで上昇させることができた。これによって、転写紙Ｐ上に２次転写した後の画像定着性が安定したものとなった。
【０１３４】
ところで、現像剤濃度の上昇は画像の定着性向上に効果がある反面、画像の転写性は低下し、転写における画像劣化の原因となることが分かった。
図２７は、現像剤濃度と転写紙Ｐへの２次転写率との関係を示したグラフである。転写率とは、１次転写後の中間転写体上の画像濃度を分子に１次転写後と２次転写後の中間転写体上の画像濃度の差をに分母にして計算したものである。グラフ中実線において、現像剤濃度が３０[％]以下のとき、転写紙Ｐ体への転写率は９０[％]程度あり、画像欠陥の少ない良好な画像が得られる。そして、現像剤濃度が上昇するのに従って、転写率が低下する。このグラフ中では、転写率が５０[％]以上であれば許容範囲である。現像剤濃度が７０[％]に達すると、転写率が許容範囲以下となり、２次転写不良が発生する。
現像剤濃度の上昇によって転写不良が発生するメカニズムは、以下のように説明することができる。本実施形態においては、現像剤中のキャリアを高引火点で高電気抵抗値を有するものを使用している。高引火点のキャリアはほとんど揮発しない。そして、本実施形態ではキャリアの引火点は、２５０[℃]以上のものを使用している。ここで、引火点の測定法はタグ密閉式、セタ密閉式、クリーブランド開放式等があり、各測定法によって測定できる温度範囲が異なっている。具体的には、タグ密閉式が０[℃]未満、こてで測定できない場合は動粘度を測定した後、セタ密閉式で０〜８０[℃]の範囲を測定する。さらにそれ以上の温度をクリーブランド開放式によって測定する。従って、本発明で用いられる引火点の測定方法はクリーブランド開放式を利用している。
そして、具体的に使用できるキャリアのその例を３つ例示しておく。東レダウコーニング社製シリコーンオイル・ＳＨ２００−５０ＣＳで引火点が３１０[℃]、東レダウコーニング社製ジメチルシリコーン・ＳＨ２００−２０ＣＳで引火点が２５５[℃]、ＳＨ２００−２０ＣＳで引火点が３２５[℃]、信越化学社製シリコーンオイル・ＫＦ９６−５０ＣＳで引火点が３１０[℃]などがある。それぞれ、引火点の計測は、クリーブランド開放式を用いて行った。
尚、高引火点のキャリアに対し、引火点の低いキャリアとしては、エクソンモービル社製アイソパーＬで引火点が６０[℃]、エクソンモービル社製アイソパーＧで引火点が４１[℃]などが知られている。これらのキャリアは本実施形態のプリンタには使用しないものとする。
現像剤はトナー粒子である顔料成分が含まれた絶縁性の樹脂（以下、定着樹脂）を上記高引火点のキャリア液中に分散している。また、キャリア液体と顔料成分を含んだ定着樹脂を、分散樹脂と呼ばれる樹脂と帯電制御剤とを適量混合したものに分散させることにより、均一分散された現像剤を得ることもある。特に顔料成分がカーボンブラックなどの電気抵抗値の低い顔料を用いた定着樹脂ではトナー粒子の外周にカーボンブラックなどの導電性粒子が存在することになる。
このような現像剤を、定着性向上のためにキャリア除去していくと、トナー粒子の外周に絶縁膜として働いていたキャリア液体が介在できず、トナーＴ同士、カーボンブラック同士がつながってトナー粒子層となる。図３１（ａ）は、トナー粒子間にキャリアＣが存在している状態、（ｂ）はトナー粒子層となった状態を示したものである。そして、このトナー粒子層が低抵抗のため、トナー粒子の絶縁性が保てなくなる。そして、例えば本実施形態のように、正帯電した液体現像剤が1次転写あるいは２次転写ニップでマイナスの転写バイアスを受けると、電荷の注入を受け、トナー粒子の極性が保てなくなる。つまり、トナーの極性が反転し、転写バイアスによる電界の働きによってトナー粒子の動きを制御することができなくなる。
【０１３５】
表３は、現像剤の電気抵抗を段階的に区切り、各範囲ごとに２次転写性を調べた結果を、転写性が良好の場合を「○」、悪い場合を「×」として示したものである。
【表３】

表中の電気抵抗の各範囲は、下限値を含み、上限値は含まない。そして、本実施形態に用いている現像剤Ａの場合、現像剤濃度が３０[％]のとき、現像剤の電気抵抗が１０^１０〜１０^１４[Ωｃｍ]、５０[％]のとき、現像剤の電気抵抗が１０^６〜１０^１０[Ωｃｍ]、７０[％]のとき、現像剤の電気抵抗が１０^３〜１０^６[Ωｃｍ]の範囲に属している。
この結果から、トナー層の電気抵抗が１０^６[Ωｃｍ]以上では２次転写性が良好であり、トナー層の電気抵抗が１０^６[Ωｃｍ]を下回ると２次転写性が悪くなることが分かった。これは、転写を行うときの、現像剤の電気抵抗が転写性を左右することとなる。また、現像剤Ａの電気抵抗は、現像剤濃度が高くなるほど低下していくことも分かった。
【０１３６】
上記結果より、現像剤中のキャリアを定着性向上のためにある程度除去しても、電気抵抗が低下しすぎないような液体現像剤であれば、定着性も良好に維持することが可能であると考えられる。そこで、現像剤濃度によって、現像剤の電気抵抗がほとんど変化しない現像剤Ｂを用いることを考えた。この現像剤Ｂは、定着樹脂の表面に顔料成分が現れない様に定着樹脂を処理したものであり、その転写性は、図２７の一点鎖線に示すような結果が得られる。従って、現像剤Ｂを用いて画像形成を行うことによって、転写性と定着性との両方を良好に保つことができる。
尚、現像剤Ｂの構造としては、例えば、分散樹脂によって定着樹脂表面に現れた顔料成分をコートしたものが考えられる。また、更に顔料成分のカーボンブラックの抵抗値を高抵抗処理したものを用いると効果的である。
【０１３７】
以上、本実施形態は、プロセススピード３００[ｍｍ／ｓｅｃ]で感光体ドラム６１０上の静電潜像を顕像化する反転現像法で実験を行なったものである。
また、本実施形態では、反転現像により画像を形成する場合について説明したが、正規現像により画像を形成することもできる。
【０１３８】
〔実施形態４〕
次に、実施形態４について説明する。
図２８は、実施形態４にかかるプリンタの概略構成図である。このプリンタは、上記実施形態３で用いた液体現像装置を各色ごとに中間転写ベルト８６０上に並列配置したものである。このように配置することによって中間転写ベルト８６０上に異なる色の画像を順次１次転写し、中間転写ベルト８６０上にフルカラー画像を形成できるようにしている。そして、カラー画像を２次転写ローラ８９０によって転写紙Ｐ上にに２次転写するカラー液体画像形成装置である。また、本実施形態４では感光体ドラム６１０Ｙ，Ｍ，Ｃ，Ｋに当接するスイープローラが１本で構成されたが、上記実施形態３のようにスイープローラを２本設けても良い。
【０１３９】
液体現像装置の構成は、実施形態３と同様なので説明を省略する。
次に、中間転写ユニットについて説明する。中間転写ユニット８００は、懸架ローラ８５１，８５２，８５３，８５４，８５５，８５６、８５７，８５８、これらの懸架ローラに張架された中間転写ベルト８６０、１次転写バイアスローラ８７０Ｋ、８７０Ｙ、８７０Ｍ、８７０Ｃ、及びクリーニングブレードを有するクリーニング装置８８０等から構成されている。
【０１４０】
上記紙転写ユニットは、２次転写バイアスローラ８９０及び２次転写バイアスローラ８９０に接続された図示しない２次転写電源等から構成されている。さらに２次転写工程に先立って中間転写ベルト８６０に中間転写体上除去部材としての中間転写体スイープローラ８２０を配置した。
【０１４１】
次に、上記中間転写ベルト８６０、１次転写バイアスローラ及び２次転写バイアスローラ等について、より具体的に説明する。上記中間転写ベルト８６０は、懸架ローラ８５１，８５２，８５３，８５４，８５５，８５６、及び感光体ドラム６１０Ｋ、６１０Ｙ、６１０Ｍ、６１０Ｃに所定の張力を有するように張架され、矢印の反時計方向に回転可能となっている。また、１次転写電荷付与手段は、例えば以下のような配置になっている。即ち、１次転写バイアスローラ８７０Ｋが感光体ドラム６１０Ｋに対向し、これら１次転写バイアスローラ８７０Ｋと感光体ドラム６１０Ｋとの間に、中間転写ベルト８６０を挟み込むような配置である。前記１次転写バイアスローラ８７０Ｋは、１次転写バイアスを与える電極ともなっており、１次転写バイアスローラ８７０Ｋには図示しない１次転写電源から所定の転写バイアスが印加される。前記懸架ローラ８５２，８５７との間に対向して、２次転写バイアスローラ８９０が配設されており、２次転写バイアスローラ８９０は、２次転写バイアスを与える電極ともなっている。２次転写バイアスローラ８９０には図示しない２次転写電源から所定の転写バイアスが印加される。
懸架ローラ８５３は中間転写体スイープローラ８２０に当接し裏面から中間転写ベルト８６０をグランドに接地している。そして、中間転写体スイープローラ８２０との間に電界を生じさせることが出来る様に、中間転写体スイープローラ８２０に図示しない除去電極によってバイアス電圧を印加した。中間転写体スイープローラ８２０に印加するバイアスはトナー粒子が中間転写ベルト８６０に圧縮される様に働く電界を発生させるものであれば良い。また、中間転写体スイープローラ８２０が対向している中間転写ベルト８６０の領域を懸架ローラ８５７と８５８との間に位置させており、１次及び２次転写ニップに形成される電界とは独立した電界を形成できるようにしている。
本実施形態４では２次転写バイアスが４色目の１次転写バイアスに影響を与えない様に懸架ローラ８５３をグランドに接地する必要があり、中間転写体スイープローラ８２０にバイアス電圧を印加する必要があった。
【０１４２】
ついで、顕像が形成された感光体ドラム６１０Ｋを回転し、感光体ドラム６１０と中間転写ベルト８６０とが当接する１次転写ニップに顕像が移動する。そして、１次転写ニップで、上記中間転写ベルト８６０１００裏面に１次転写バイアスローラ８７０Ｋを介し、正極性トナーの逆極性である負極性バイアス電圧、たとえば、−３００〜−５００[Ｖ]を印加する。この印加電圧によって発生した電界で、上記感光体ドラム６１０Ｋ上の顕像の現像剤を、中間転写ベルト８６０に引き寄せ、中間転写ベルト８６０上に転写する（１次転写）。フルカラーの画像形成動作では、イエロー現像剤、マゼンタ現像剤、シアン現像剤、ブラック現像剤の順に画像を中間転写ベルト８６０に転写してフルカラーの画像を形成する。
【０１４３】
本実施形態のプリンタは以上のように、中間転写ベルト８６０上に順次１次転写することによって形成したフルカラー画像を、転写紙Ｐに一括して２次転写する。これは、感光体ドラム６１０上の画像を転写紙Ｐ上に順次転写する直接転写方式の画像形成装置より、キャリア量を低減することが出来る。それは、中間転写ベルト８６０上に１次転写する１色目のステーション（以下、第１ステーションという）は乾いた中間転写ベルト８６０に当接するためにキャリアの転移量が多い。次の２色目以降のステーションに関しては中間転写体がウェットな状態で１次転写を行えることにより、キャリア液体の付着を低減することができる。さらに、中間転写ベルト８６０上のカラートナー像は、色が重なる部分、重ならない部分ではキャリア液の液量が異なることは明らかである。よって、中間転写体スイープローラ８２０により、トナーを中間転写ベルト８６０に圧縮することによってキャリア液を除去し、現像剤濃度を高めることが出来る。
【０１４４】
【表４】

表４は、第１ステーションに画像が存在し、その他のステーションに画像がない場合の中間転写ベルト８６０上現像剤付着量の変化を各ステーションごとに示したものである。感光体から中間転写ベルト８６０へのトナーの転写率は１００[％]であり、現像率１００[％]でスイープローラを通過しても感光体の画像は９５[％]維持される。そして、４つのステーションで転写され終えたときの中間転写ベルト８６０上の１次転写後トナー像の現像剤濃度は２１[％]と見積もれる。本実施形態４の中間転写体スイープローラ８２０により、中間転写ベルト８６０上の１次転写後トナー像はキャリア成分が０．１５[ｍｇ／ｃｍ^２]除去される。したがって中間転写体スイープローラ８２０とのスイープニップを通過した後の中間転写ベルト８６０上のトナー像は現像剤濃度が２９[％]となる。
【０１４５】
ついで、フルカラーの画像の転写された中間転写ベルト８６０を駆動し中間転写ベルト８６０と不図示の給紙部から矢印方向に搬送された記録媒体としての転写紙Ｐとが当接する２次転写ニップに画像を移動する。この２次転写ニップにおいて、転写紙Ｐ裏面に２次転写装置としての２次転写バイアスローラ８９０を介して負極性のバイアス電圧、たとえば−８００〜−２０００[Ｖ]を印加し、また、たとえば５０[Ｎ／ｃｍ^２]程度の圧力をかける。この印加電圧によって発生した電界と圧力とによって、中間転写ベルト８６０の現像剤を転写紙Ｐに引き寄せ、転写紙Ｐに一括転写する（２次転写）。本実施形態４では２次転写バイアスローラ８９０に中間転写ベルト８６０を加圧するローラを、懸架ローラ８５２，８５７の２つのローラとしたが、加圧を受けるための独立した対向ローラを配置しても良い。
【０１４６】
この後、画像（未定着画像）が転写された転写紙Ｐは、図示を省略した分離器により中間転写ベルト８６０から分離され、画像定着手段としての画像定着装置９００に搬送される。この画像定着装置９００で加熱定着処理がなされた後に装置本体から排出される。一方、２次転写後の感光体ドラム６１０Ｙ，Ｍ，Ｃ，Ｋは、除電装置で残留電荷が除電され、その表面がクリーニング装置６５０Ｙ，Ｍ，Ｃ，Ｋよってクリーニングされ、未転写現像剤が回収除去されて次の作像に備える。
本実施形態４では中間転写ベルト８６０上に中間転写体スイープローラ８２０を1本配置したが、その数に限定されるものではない。
【０１４７】
また、中間転写ベルト８６０の構成は、実施形態３の中間転写ドラム８１０の構造で説明した図２６と同じく、弾性体を設けて構成し、転写不良が生じないようにした。ただし、図２６に示した断面図では、弾性導電体８１１をドラム８１２に接着させていた。本実施形においてはベルト形状のため、弾性導電体８１１のベルト周方向への延びを防止するため、ドラム８１２部分にナイロンコードもしくはスチールコードを設けている。これらコードの形状は、例えば、直径５０〜４００[μｍ]とすることが考えられる。
【０１４８】
更に、本実施形態においては、転写紙Ｐ上の２次転写画像からも定着前にキャリアを除去できるようにしている。
図２９は、実施形態４に関するプリンタの画像定着装置の概略構成図である。この画像定着装置９００は、転写紙Ｐ搬送方向の上流側（図中右側）から下流側（図中左側）方向に順に次のものを有している。即ち、溶媒析出手段としてのプレ加熱部９１０、キャリア除去手段としてのキャリア除去部９３０、そして加熱定着手段としての加熱定着部９５０である。
【０１４９】
加熱定着部９５０は、加熱ローラ９５１と加圧ローラ９５２が互いに圧接するよう付設されている。加熱ローラ９５１にはヒータが内蔵され、心金の表面に順次所望の厚さのゴム層、耐油層（フッ化シリコンゴム層）やＲＴＶシリコンゴム層あるいはテフロン層が積層されている。一方、加圧ローラ９５２はシリコンゴムにテフロンコートされている。加熱ローラ９５１の周辺にはサーミスタ９５５および温度ヒューズ９５６が配置され、これらによって温度制御が行われる。また分離爪９５７およびクリーニングブレードが加熱ローラ９５１の表面に接触配置されている。
【０１５０】
上記プレ加熱部９１０は、転写紙Ｐのトナー像転写面にプレ加熱ヒータ９１１が接触するよう配置され、このプレ加熱ヒータ９１１には加熱手段としてハロゲンランプあるいは赤外線ヒータが用いられる。ヒータは集光された光を用いて構成されるとが好ましい。
【０１５１】
そして、転写紙Ｐ搬送方向におけるプレ加熱部９１０と加熱定着部９５０との間に位置しているのが上記キャリア除去部９３０である。このキャリア除去部９３０は、プレ加熱部９１０で加熱によってトナー像表面に析出せしめられた被析出溶媒としての析出キャリアを除去するための溶媒除去手段としてのキャリア除去ローラ９３１が設けられている。また、トナー像表面をキャリア除去ローラ９３１側に押圧する押圧手段としてのバックアップローラ９３２が設けられている。キャリア除去ローラには転写紙Ｐ表面から回収したキャリア液体を除去回収するクリーニングブレード（図示を省略）が当接し、常に付着液体のないキャリア除去ローラを転写紙Ｐ画像面に当接できるようにしている。また、上記キャリア除去ローラ９３１は、表層部がキャリア液を含浸しない材料から構成されている。更に、搬送ベルト９２１が駆動ローラ９２２、懸架ローラ９２３およびバックアップローラ９３２に懸架、駆動されている。転写紙Ｐは、図に示すように搬送ベルト９２１によって搬送され、プレ加熱ヒータ９１１の下を転写紙Ｐが通過する際にプレ加熱ヒータ９１１からの熱により転写紙Ｐが加熱され、トナー層内のキャリアが表面に析出する。転写紙Ｐは搬送ベルト９２１によってそのままキャリア除去部９３０に搬送される。
【０１５２】
次に、上記構成の画像定着装置９００を用いた画像の定着動作について説明する。未定着画像が転写された転写紙Ｐは、分離装置により中間転写ベルト８６０１００から分離され画像定着装置９００に入ると、先ずプレ加熱部９１０に達する。このとき、転写紙Ｐ画像面がヒータによって加熱され、転写紙Ｐ上の未定着画像を構成している現像剤からキャリアが未定着画像の表面に析出してくる。
表面にキャリアが析出した状態で転写紙Ｐは次にキャリア除去部９３０に進入する。キャリア除去部９３０では、転写紙Ｐ上面の析出キャリアにキャリア除去ローラ９３１が当接し、バックアップローラ９３２で転写紙Ｐ裏面からキャリア除去ローラ９３１側に押圧された状態で転写紙Ｐが通過する。この際、析出キャリアがキャリア除去ローラ９３１側に転移する。これによって、転写紙Ｐ上からは析出キャリアが除去される。
析出キャリアが除去された転写紙Ｐは、更に搬送されて加熱定着部９５０に進入する。加熱定着部９５０では、転写紙Ｐ上面即ち画像担持面に当接する加熱ローラと、転写紙Ｐ裏面から転写紙Ｐを加熱ローラ側に押圧する加圧ローラとのニップ部を転写紙Ｐが通過する。このときに、加熱及び加圧によって画像が転写紙Ｐ上に定着される。その後、画像定着装置９００から排出される。
【０１５３】
中間転写ベルト８６０上の画像は、２次転写ニップにおいて、転写率９０[％]で転写紙Ｐ上に２次転写される。従って、キャリア液が０．０４[ｍｇ／ｃｍ^２]程度中間転写ベルト８６０表面に残留することとなる。表７において、２次転写後の転写紙Ｐ上のトナー像には、キャリア液が０．３５[ｍｇ／ｃｍ^２]付着している。このときの転写紙Ｐ上の画像部における現像剤濃度は２９[％]であった。
そして、転写紙Ｐがキャリア除去ローラ９３１との対向ニップを通過すると、キャリア除去ローラ９３１によって、０．０３[ｍｇ／ｃｍ^２]のキャリアが除去され、トナーは除去されずそのまま転写紙Ｐ上に残留する。このときの転写紙Ｐ上の画像部における現像剤濃度は３２[％]となった。
これら、１次転写ニップからキャリア除去ローラ９３１によるキャリア除去までの間の、キャリア液付着量を示したものが表５である。
【表５】

【０１５４】
上記構成の画像定着装置９００によって、現像剤を構成するキャリアに不揮発性の成分が含有されていても、キャリア除去ローラ９３１で事前に除去することができる。転写紙Ｐ上の未定着画像を確実に定着させることができる。よって、加熱定着を良好に行うことができるようになる。
また、加熱定着温度も、キャリア成分を除去しているため、従来に比して低くすることが可能となる。これに加え、プレ加熱部９１０で事前に加熱した画像を加熱定着するので、加熱定着部９５０における加熱温度を１回の加熱で定着させる場合に比して低くすることが可能である。例えば、プレ加熱部と加熱定着部とにそれぞれ温度を検知する温度センサを設け、これら温度センサの検知結果に応じてヒータのＯＮ、ＯＦＦ制御を行い、プレ加熱部と加熱定着部の温度を所望の温度となるよう制御すれば良い。本実施例の場合、プレ加熱部９１０のプレ加熱ローラ９１１による加熱温度を１００〜１５０[℃]とし、加熱定着部９５０における加熱ローラによる加熱温度を１００〜１２０[℃]として、良好な定着画像を得ることができた。従って、加熱定着時間も短縮することが可能となる。
更に、キャリア除去部９３０材としてローラ形状のキャリア除去ローラ３３１を使用しているので、ベルトやウェブ等の形状に比してコンパクトにでき、画像定着装置９００を小型にするのに有効である。
【０１５５】
ここで、現像剤濃度と転写紙Ｐへの画像の定着性について行った実験結果について説明する。定着性はスミア試験器（摩擦試験機I型、JISL0823）を用いて測定した。試験器は白綿布（JISL0803免号）を取り付け、画像面を往復１０回擦り、白綿布の反射画像濃度を反射画像濃度計にて画像濃度を測定するのである。測定した反射濃度からトナーの付着のない白綿布の画像濃度を減算する。この値を分子に、擦る前の記録体上の画像濃度（トナーの付着のない記録体の画像濃度を減算した）を分母にした値を定着性と読んでいる。定着性はこの値が０．１で良い定着性を示している。逆に０．４付近では手で擦った程度でトナー像が剥がれてしまい良好な定着性を示すとは言えない。
また、この定着性の試験は、上記加熱設定温度で現像剤Ａを用いて行った。トナー固形分量が一定になる様キャリア量を変えて試験を行った。転写紙Ｐはリコー製type6200を用いた。
図３０は、現像剤濃度に対する転写紙Ｐへの定着性を調べた結果を示したものである。この結果より、現像剤濃度が上昇するに従って、定着性の値が低くなり、定着性が良好になったことが分かる。一方、現像剤濃度が低下すると、定着性の値が上昇し、特に現像剤濃度が２５[％]以下で急激に定着性の値が上昇する。よって、定着性が低下したことが分かる。これより、定着ニップにおける現像剤濃度が２５[％]以上、好ましくは３０[％]以上であれば良好に定着することが出来るといえる。
尚、本実施形態においては、２次転写直後のトナー像の画像部現像剤濃度が２９[％]であり、既に良好な定着が得られる範囲に入っている。しかし、もし２次転写直後に現像剤濃度が２５[％]未満であれば、このまま定着ニップに進入すると定着性が悪くなってしまう。
しかし、本実施形態のように転写紙Ｐ上でキャリア液を除去できる構成を有している場合、定着ニップに進入する前にキャリアを除去することによって良好な定着性を得ることが可能となる。
また、画像の転写性向上のためには転写時の現像剤濃度が低い方が好ましく、画像の定着性向上のためには定着時の現像剤濃度が高い方が好ましい。この現像剤濃度に関する相反した要望にも、本実施形態４で示した定着装置を採用することで応えることができる。なぜなら、２次転写ニップまではキャリア除去を行わず、転写紙Ｐ上でキャリア除去を行った後に定着することができるためである。
【０１５６】
尚、本実施形態４においては、転写紙Ｐ上でのキャリア除去ローラ９３１を１つ設けたのみであるが、多段に設けても良い。例えば、図３に示した構成を用いて、二段でキャリア除去を行うよう構成しても良い。キャリア除去ローラを多段に設けると、１つのみ設けている場合に比して除去できるキャリアの量が多くなる。従って、キャリアの浸透しにくい材質の転写紙Ｐ上に形成された未定着画像でも、加熱定着を良好に行うことができる。またこれは結果的に、この画像定着装置９００、ひいてはプリンタに適用可能な転写紙Ｐの種類を拡大できることにもつながる。
【０１５７】
また、キャリア除去部材をベルトからなるキャリア除去ベルトで構成することもできる。キャリア除去ベルトは、キャリア液体に膨潤せず、かつ耐熱性の特性をもつ材質として、ポリイミド、ポリカーボネイトなどの樹脂フィルムで形成されたものを使用することができる。また、キャリア除去ベルト表面をクリーニングするためのクリーニングユニットを設け、ベルト表面から除去したキャリアを収容器に回収できるよう構成しても良い。キャリア除去ベルト及びクリーニングユニットの具体的な構成例としては、例えば、図５で示されている実施形態１の実施例２の定着装置が考えられる。
【０１５８】
また、本実施形態４ではキャリア除去ローラ９３１をキャリア液を含浸しない材質のものとしたが、これに代えて多孔質体で形成しキャリア液を含浸・吸収する材質のものであっても良い。例えば、ウェブなどを配置し、一度使用した面を巻取軸に巻き取っていき、最終的に供給軸に巻かれたウェブがなくなると、ウェブを交換するというものであっても良い。
【０１５９】
尚、実施形態４においては、液体現像剤Ａを用いた場合の定着性についてのみ説明したが、実施形態３と同じく現像剤Ｂを用い、現像剤濃度が多少低くても転写紙Ｐへの定着性を良好に維持することができるようにしても良い。
【０１６０】
上述した実施形態３及び４においては、画像定着装置として、加熱及び加圧による定着方法を採用しているが、本発明を適用して定着性の向上をはかることができる定着方法は、これに限るものではない。例えば、加圧定着、溶剤定着等、定着する画像を形成している現像剤中にキャリアが多く含まれていると定着性が低下してしまうような定着方法では本発明を適用することができる。
【０１６１】
以上、実施形態１及び２の構成によれば、一部もしくは全てが不揮発性である溶媒中にトナーを分散させてなる液体現像剤によって形成した画像を良好に定着させることができる。
また、溶媒除去手段としてのキャリア除去部３３０による溶媒除去後の未定着画像を上記記録媒体としての転写紙Ｐ上に加熱定着する加熱定着手段としての加熱定着部３５０を有している。よって、不揮発性溶媒が除去された後の未定着画像を加熱定着するので、十分な定着を確保できると共に、従来の液体現像剤からなる画像の定着装置に比して高速定着が可能となるという優れた効果がある。これは、未定着画像中で加熱定着に支障を来たす要因となっている不揮発性溶媒を除去した後の未定着画像を加熱定着手段によって加熱定着するからである。
また、記録媒体の画像担持面に押圧させた除去ローラとしてのキャリア除去ローラ３３１側に画像表面にある被析出溶媒を転移させて除去する構成を採用したものがある。これによって、除去ローラを用いて溶媒除去手段を容易に構成できると共に、除去ローラ表面を繰り返し溶媒除去に使用すれば、溶媒除去のための装置を小型にすることもできる。
また、記録媒体の画像担持面に押圧させた無端移動する除去ベルトとしてのキャリア除去ベルト３４９側に画像表面にある被析出溶媒を転移させて除去する構成を採用したものがある。これによって、除去ベルトを用いて溶媒除去手段を容易に構成できると共に、除去ベルト表面を無端移動させて繰り返し溶媒除去に使用することもできる。
また、上記除去ローラ又は上記除去ベルト側に転移した上記被析出溶媒を、該除去ローラ又は該除去ベルトから除去し回収する溶媒回収手段としてのクリーニングユニット３４３を設けている。この被析出溶媒にはトナー成分は含まれておらず溶媒単体となっていることが観察された。従ってそれら被析出溶媒はリサイクルが可能である。また、媒除去後の除去ローラや除去ベルトが再び画像表面の被析出溶媒の除去に利用できるようになる。そして、除去ローラや除去ベルトの溶媒除去作用を長く維持させることができるようにもなる。更に、被析出溶媒を回収できるので、回収した溶媒を新たな液体現像剤の構成材料として再利用することも可能となる。
また、上記溶媒回収手段が、上記除去ローラ又は上記除去ベルトの重力方向下部で上記被析出溶媒を回収する下部回収手段としてのクリーニングユニット３４３Ｚを有している構成を採用したものがある。除去ローラ又は除去ベルト等の溶媒除去部材に転移した溶媒のうち、次のようなものを下部回収手段で回収する。それは、溶媒除去部材の重力方向下部の領域に位置していたり、もともと重力方向下部以外の領域に位置していたものが重力によってこの溶媒除去部材を伝って重力方向下部の領域に移動してきたりしたものである。これによって、装置の駆動が長時間停止するなどにより、除去した溶媒が溶媒除去部材の重力方向下部から滴り落ちそうになった場合でも回収できるようにする。よって、除去した溶媒が溶媒除去部材の重力方向下部から滴り落ちそうになった場合でも回収できるので、装置内部を溶媒で汚染することを回避できる。
また、上記実施形態１の実施例１における変形例２いおいては、溶媒除去手段に巻き取り式のウェブを用いている。記録媒体の画像表面にある被析出溶媒をウェブ側に転移させて除去し、被析出溶媒を保持したウェブを巻取り軸により巻き取るようにしているのである。そして、被析出溶媒の除去に使用したウェブの部分を巻き取り、常に新たなウェブ部分で被析出溶媒の除去を行うことができる。よって、ウェブの巻取りが終了するまではウェブに転移した溶媒を除去しなくても溶媒除去効果を維持できる。また、これによって、ウェブから溶媒を除去するためのクリーニング手段を設ける必要がないので、装置を簡略化することもできる。
また、上記ウェブの巻き取り方向を、記録媒体表面移動方向と同方向としている。これによって、記録媒体表面の画像にかかるストレスを低減させることができるので、トナー像の欠落など画像へのダメージを低減することができる。なぜなら、記録媒体表面とこれに当接するウェブ表面とが同方向に移動していくため、逆方向に移動させる場合に比して記録媒体表面の画像にかかるストレスを低減できるからである。
【０１６２】
また、上記実施形態１及び２においては、除去ローラ、除去ベルト、又はウェブを、不織布等のような多孔質材料、又はシリコンゴムなどのような溶媒に対して吸収・膨潤性のある弾性体材料を用いて構成している。ここで、除去ローラ又は除去ベルトに対しては、不織布等のような多孔質材料、又はシリコンゴムなどのような溶媒に対して吸収・膨潤性のある弾性体材料のどちらかを用いることができる。また、ウェブに対しては不織布等のような多孔質材料を用いるものとする。これによって、被析出溶媒を効率良く除去できるので、これらの材料から構成されていない溶媒除去手段を用る場合に比して優れた定着性を得る事ができると共に、高速定着が可能となる。なぜなら、多孔質材料や弾性体材料からなる除去ローラ、除去ベルト、又はウェブ等を用いることにより、これらの材料から構成されていない溶媒除去手段を用る場合に比して効率良く被析出溶媒を除去することができるからである。
また、上記実施形態２においては、溶媒除去手段としてのキャリア除去ローラやキャリア除去ベルトなどの少なくとも表面を溶媒に対して吸収・膨潤性のない材料から構成している。よって、除去ローラや除去ベルトが溶媒に対して吸収・膨潤性のある材料から構成されている場合に比して耐久性を得ることができる。これは、溶媒を吸収・膨潤しないことにより、除去ローラや除去ベルトを構成している材料にかかるストレスが軽減されるからである。よって、吸収・膨潤性のある材料から構成されている場合に比して耐久性が高まると共に、消耗品になることも少なくなる。これと共に、回収した溶媒をこれら溶媒除去手段の表面から容易に回収できるため、定着の高速性にも優れている。これは、キャリア除去ローラやキャリア除去ベルトがキャリア液に膨潤しない材料によって形成されるので、除去キャリアを効率良くクリーニングできるからである。
また、除去ローラ、除去ベルト、又はウェブを複数設けている構成を採用したものがある。これによって、除去ローラ、除去ベルト、又はウェブを１つしか設けていない場合に比してより多くの溶媒を除去できるので、溶媒の浸透しにくい材質の記録媒体上に形成された未定着画像に対する加熱定着を良好に行うことができる。これは、複数の除去ローラ、除去ベルト、又はウェブを用いて被析出溶媒の除去を多段階に行うためである。またこれは結果的に、良好な定着ができる記録媒体を、その溶媒浸透率の範囲の面で拡大することにもなり、様々な材質の記録媒体が使用可能となる。
また、画像担持面を上記除去ローラ、除去ベルト、又はウェブ表面に押圧する押圧手段としてのバックアップローラを以下のように駆動している。即ち、除去ローラ、除去ベルト、又はウェブの記録媒体への当接面と、バックアップローラの記録媒体裏面への当接面とを、記録媒体搬送方向に略同一線速で移動させている。よって、記録媒体上の画像にストレスを与えないので、異常画像の発生を防止できる。なぜなら、記録媒体搬送方向に略同一線速で表面移動する除去ローラ、除去ベルト、又はウェブと、バックアップローラとに記録媒体を挾持搬送させつつ被析出溶媒を除去するからである。これによって、上下を挾持搬送する部材の線速が異なる場合に記録媒体上の画像に与える恐れのあるストレスを与えないようにしているのである。
また、溶媒析出位置としてのプレ加熱部３１０と、溶媒除去位置としてのキャリア除去部３３０と、加熱定着位置としての加熱定着部３５０における、上記記録媒体搬送速度を全て同一速度とすることもできる。これによって、画像を担持した記録媒体に搬送速度の変動に伴なって生じるストレスを与えないので、記録媒体のジャムや異常画像の発生を防止できる。なぜなら、記録媒体が、溶媒析出位置，溶媒除去位置，及び加熱定着位置を全て同一速度で通過するようになるからである。
また、未定着画像を記録媒体上に加熱定着する加熱定着手段としての加熱定着部３５０を設け、溶媒析出位置と、溶媒除去位置と、加熱定着位置との全てを、記録媒体を直線的に搬送する搬送経路上に設けた構成を採用したものがある。これによって、記録媒体に搬送上のストレスをかけずに溶媒析出位置と溶媒除去位置と加熱定着位置とを通過させるので、記録媒体の搬送性能を向上させることができ、溶媒析出、溶媒除去、加熱定着の各工程を精度良く行うことができる。なぜなら、記録媒体を直線的に搬送している間に、その表面の画像に溶媒析出位置と溶媒除去位置と加熱定着位置とを通過させている。このため、記録媒体が非直線的な搬送によって受けるストレスを受けずに、溶媒析出位置と溶媒除去位置と加熱定着位置とを通過するからである。
【０１６３】
また、実施形態２の実施例３において、溶媒析出手段の接触加熱部材としてのプレ加熱ローラ３１１の表面に、表面の摩擦係数が低い材料による処理を施している。よって、記録媒体上に形成された未定着画像に対して不必要にストレスを与えずに溶媒を析出することができる。
また、実施形態２の実施例４及び７において、溶媒析出手段に、非接触加熱手段としてのプレ加熱ヒータ３１３Ｘ，３１３Ｚを用いている。よって、キャリア析出部３１０において記録紙Ｐの未定着画像面に直接触れることがないため、未定着画像に不必要なストレスを与えることが避けられ、接触加熱手段を用いる場合に比してより良好な画像を得ることができる。
また、上記実施形態１の実施例２においては、加熱手段を有する１つのメインローラ３０５を設けている。そして、溶媒析出手段としてのプレ加熱部３１０、溶媒除去手段としてのキャリア除去部３３０、加熱定着手段としての加熱定着部３５０とをメインローラとこれに対向して設けられた互いに異なる対向部材とによってそれぞれ構成している。そして、記録媒体がメインローラ表面に担持されつつ移動していく間に、記録媒体表面の未定着画像から溶媒が析出され、被析出溶媒が除去され、加熱定着が行われる。これによって、溶媒析出手段と溶媒除去手段と加熱定着手段の３つの手段でそれぞれ役割をもつ部材を、１つのメインローラで構成でき、複数の部材で構成するのに比して省スペース化が実現できる。
また、上記実施形態２及び３においては、溶媒析出手段によるプレ加熱と溶媒除去手段による被析出溶媒の除去と加熱定着手段による未定着画像の加熱定着との３つの工程を行う対象としての画像が、記録媒体の両面に形成されている。これによって、記録媒体の両面に画像を形成する場合においても、トナー像の十分な定着を確保できると共に、従来の画像定着装置に比して高速定着を可能とすることができる。なぜなら、記録媒体の両面に形成された未定着画像に対して、液体現像剤中の溶媒の析出と被析出溶媒の除去と加熱定着との３つの工程を記録媒体をワンパスさせている間に行い、両面定着が完了するからである。
また、上記実施形態２及び３においては、記録媒体を両面から挟むように配設した除去ローラ又は除去ベルトを、これらの記録媒体表面への当接面が略同一線速で記録媒体搬送方向に移動するよう駆動している。そして、記録媒体搬送方向に略同一線速で表面移動する除去ローラ、又は除去ベルトの対によって、記録媒体を挾持搬送させつつ被析出溶媒を除去する。これによって、記録媒体の両面に設けられる除去ローラ、又は除去ベルトの各々に対してバックアップローラを設ける必要がなく、構成の簡略化を図ることができる。また、記録媒体の搬送部材を新たに設ける必要がなくなる。更に、上下を挾持搬送する部材の線速が記録媒体搬送方向に略同一線速であるために、記録媒体上の未定着画像に不必要なストレスを与えることがない。
また、上記実施形態２及び３においては、溶媒析出位置と溶媒除去位置と加熱定着位置とを、それぞれ記録媒体の両面で記録媒体の搬送経路における同一個所に設定している。即ち、記録媒体の未定着画像に対する液体現像剤中の溶媒の析出と被析出溶媒の除去と加熱定着とをそれぞれ、記録媒体の搬送経路における同一個所で記録媒体の両面に対して行う。よって、記録媒体上の画像の定着を表裏同時に行うので、記録媒体の両面に画像を形成した場合においても、片面に画像を形成した場合と同じ時間で画像の定着を行うことができる。また、画像定着のための記録媒体の搬送経路長も片面に画像を形成した場合と同じ長さで済むため、搬送経路の延長に起因する装置の大型化も回避することができる。
また、上記実施形態１及び２において、記録媒体の種類に応じて溶媒除去手段による溶媒除去の程度を切り替える溶媒除去程度切り替え手段としての駆動切り替え装置を設けることもできる。具体的には、溶媒を浸透させやすい材質のものからなる記録媒体に対しては溶媒除去の必要がないため、溶媒除去程度切り替え手段で溶媒除去を行わないようにする。一方、溶媒を浸透させにくい材質のものからなる記録媒体に対しては、溶媒除去を積極的に行う必要があるため、溶媒除去程度切り替え手段で、溶媒除去を最大レベルで行うように溶媒除去程度を切り替える。また、溶媒の浸透程度が上記２つの材質の間のような記録媒体に対しては、溶媒除去程度切り替え手段によって、溶媒除去を設定したいくつかのレベルの間でいずれかを選択して切り替える。これによって、記録媒体の種類に応じて溶媒除去の程度を切り替えることができるので、必要に応じて溶媒除去手段を作動させることができ、常に作動させる場合に比して溶媒除去手段を長寿命化させることができる。また、記録媒体の特性に応じて溶媒除去程度を切り替えることができるので、常に良好な定着画像を得ることができる。また、必要のないときに、溶媒除去手段の作動を休止させるので、常に作動させる場合に比して作動にかかるエネルギーコストを低減させることができる。尚、これら溶媒除去程度切り替えのための装置構造は、手動で行うようにしても良いし、装置に記録媒体の溶媒浸透率を検知するセンサ等を設け、検知結果に応じて自動的に切り替わるよう構成しても良い。
また、本実施形態１及び２の画像形成装置によれば、一部もしくは全てが不揮発性である溶媒中にトナーを分散させてなる液体現像剤によって形成した画像を良好に定着させることができる。また、高速定着が可能となるので、高速で連続的に形成した画像でも良好に定着させることができる。
【０１６４】
上記実施形態３及び４によれば、感光体ドラム６１０上と中間転写ドラム８１０上の２箇所、または中間転写ベルト８６０上と転写紙Ｐ上の２箇所でキャリア除去を行う。従って、画像の定着に先立って現像剤中のキャリアを十分に除去することができ、画像の定着性を向上させることができる。
また、実施形態３及び４によれば、定着ニップにおける現像剤中のトナー濃度を２５[％]以上としているので、図３０の結果から言えるように、画像を転写紙Ｐに良好に定着させることができる。
また、実施形態３によれば、スィープローラ７１０ａ、７１０ｂに電圧を印加することによって、感光体ドラム６１０とスィープローラ７１０ａ、７１０ｂとのニップ部に電界を発生させている。これによって、感光体ドラム６１０上の画像部のトナーを感光体ドラム６１０側に電界の力によって圧縮することができ、剥ぎ取らないようにしている。また、感光体ドラム６１０上の非画像部に付着している現像剤をスィープローラ７１０ａ側に引き寄せ、回収している。よって、感光体ドラム６１０上の余剰なキャリア液Ｃを良好に除去回収できることに加えて、非画像部に少量付着した余剰トナーまでも除去回収することができる。
また、実施形態３において、第１スィープローラ７１０ａには４５０[Ｖ]、第２スィープローラ７１０ｂには５００[Ｖ]を印加する変形例を記載した。これによって、第１スィープローラ７１０ａには、主に感光体ドラム６１０の地肌部に付着している現像剤を引き寄せる。第２スィープローラ７１０ｂには、感光体ドラム６１０の画像部に付着したキャリアを付着させ、かつ画像部のトナーを感光体ドラム６１０表面に圧縮する。つまり、第２スィープローラ７１０ｂに印加したバイアスによって、感光体ドラム６１０の画像部に付着したキャリアを積極的に第２スィープローラ７１０ｂに付着させることができる。よって、キャリアの除去回収を効率的に行うことができる。
また、実施形態３又は４においては、第１スィープローラ７１０ａや第２スィープローラ７１０ｂで除去した現像剤やキャリア液をクリーニングブレード７１１ａ、７１１ｂによってそれぞれのローラから除去する。これによって、第１スィープローラ７１０ａや第２スィープローラ７１０ｂ表面を常に現像剤やトナーの回収に使用できるようにする。よって、感光体ドラム６１０の画像部に付着したキャリアや非画像部の現像剤の除去を継続して良好に行うことができる。
また、実施形態３又は４において、ある程度のバイアスを印加した中間転写体スイープローラ８２０により、電界の力によって中間転写ドラム８１０又は中間転写ベルト８６０上の画像部のキャリア液を付着させて除去する。これによって、転写紙Ｐへの２次転写の前に中間転写体上で画像部現像剤濃度を上昇させることができ、画像定着性を安定したものとすることができる。また、実施形態４のように、中間転写ベルト８６０上でカラー画像を重ね合わせるものにおいては、重ね合わせ後の画像に対してまとめてキャリア除去を行うことが可能となる。これによって、各色ごとにキャリア除去を行う場合に比して効率よくキャリア除去を行うことができる。
また、実施形態４においては、中間転写体スイープローラ８２０が対向している中間転写ベルト８６０の領域、、１次転写ニップ、及び２次転写ニップにそれぞれ独立した電界を形成できるようにしている。即ち、同一の中間転写ベルト８６０上に、１次転写バイアス、除去バイアス、２次転写バイアスという異なった電界を形成できる。そして、１次転写電極、２次転写電極、除去電極をそれぞれ設けている。これによって、１次及び２次転写性や、現像剤とキャリアの中間転写ベルト８６０からの除去性を共に良好に得ることができる。
また、実施形態４においては、キャリア除去ローラ９３１によって転写紙Ｐ上の画像からキャリアを除去することができる。これによって、転写紙Ｐにキャリアを多く含む現像剤から形成された画像が転写されても、定着前にキャリアを除去し定着性を良好にすることができる。また、実施形態４の構成によれば、プレ加熱部９１０で事前に加熱した画像を加熱定着するので、加熱定着部９５０における加熱温度を１回の加熱で定着させる場合に比して低くすることができる。
【０１６５】
また、実施形態３及び４はいずれも、現像剤の成分であるキャリアとして、引火点が２５０[℃]以上のものを用いている。これによって、現像剤から揮発成分がほとんどなくなり、大気中に溶剤等の放出がないので無公害である。また、一般的に石油系のキャリアは危険物の指定があるが、引火点が２５０[℃]以上では危険物の指定から外れる。これは、加熱によって発火する危険性がほとんどないためであり、本実施形態においても、引火点が２５０[℃]未満の石油系のキャリアを用いるのに比して定着時の加熱に対する安全性が高いと言える。
また、実施形態３及び４はいずれも、画像部の現像剤の電気抵抗を１次及び２次転写ニップで１０^６[Ωｃｍ]以上となるようにしている。これによって、表３からも分かるように、中間転写体及び転写紙Ｐへの転写性を良好に保つことができる。
また、実施形態３及び４に現像剤Ｂを使用すると、現像剤濃度が上昇してキャリア同士が直接接触するトナー粒子層となってもほぼ絶縁性を保つことができる。このようにトナー粒子層が絶縁性のものを現像剤の材料に用いれば、高解像力を得るためにキャリア液を十分除去しトナーを圧縮しても、トナー粒子層の電気抵抗が高いためバイアスリークが発生しにくい。よって、現像剤濃度を高めることによって画像の定着性を向上させることができると共に、高解像力を得ることもできる。
また、実施形態３及び４において、感光体ドラム６１０として少なくとも表層にアモルファスシリコンを用いたアモルファスシリコン（ａ−Ｓｉ）感光体を使用することを記載している。これによれば、感光体ドラム６１０の寿命を長くできると共に安全性も高めることができる。
【０１６６】
【発明の効果】
請求項１乃至２０の画像定着装置によれば、不揮発性溶媒を用いた液体現像剤からなるトナー像の十分な定着と高速定着とを妨げる要因となる未定着画像中の溶媒を効率よく除去することができる。従って、トナー像の十分な定着を確保できると共に、従来の画像定着装置に比して高速定着を可能とすることができるという優れが効果がある。
請求項２１の画像形成装置によれば、一部もしくは全てが不揮発性である溶媒中にトナーを分散させてなる液体現像剤によって形成した画像を良好に定着させることができるという優れた効果がある。
また、高速定着が可能となるので、高速で連続的に形成した画像でも良好に定着させることができるという優れた効果もある。
【図面の簡単な説明】
【図１】実施形態１に係る画像形成装置の要部の説明図。
【図２】実施形態１の実施例１にかかる画像定着装置の説明図。
【図３】実施形態１の実施例１における変形例１にかかる画像定着装置の説明図。
【図４】実施形態１の実施例１における変形例２にかかる画像定着装置の説明図。
【図５】実施形態１の実施例２にかかる画像定着装置の説明図。
【図６】実施形態１の実施例３にかかる画像定着装置の説明図。
【図７】実施形態１の実施例４における変形例１にかかる画像定着装置の説明図。
【図８】実施形態１の実施例５における変形例２にかかる画像定着装置の説明図。
【図９】実施形態１の実施例６にかかる画像定着装置の説明図。
【図１０】実施形態２に係るプリンタの主要部の概略構成図。
【図１１】実施形態２の実施例１にかかる画像定着装置の概略構成図。
【図１２】実施形態２の実施例２にかかる画像定着装置の概略構成図。
【図１３】実施形態２の実施例２における変形例にかかる画像定着装置の概略構成図。
【図１４】ブレード式のクリーニングユニット近傍の部分拡大図。
【図１５】ローラ式のクリーニングユニット近傍の部分拡大図。
【図１６】実施形態２の実施例３にかかる画像定着装置の説明図。
【図１７】実施形態２の実施例４にかかる画像定着装置の説明図。
【図１８】実施形態２の実施例５にかかる画像定着装置の説明図。
【図１９】実施形態２の実施例６にかかる画像定着装置の説明図。
【図２０】実施形態２の実施例７にかかる画像定着装置の説明図。
【図２１】（ａ）は、転写紙Ｐの上面に未定着の画像を担持させたときの断面図。
（ｂ）は、（ａ）の転写紙Ｐを下部から加熱したときの画像を構成する液体現像剤の状態を示した断面図。
【図２２】実施形態に係る画像形成装置の要部の説明図。
【図２３】（ａ）、（ｂ）、（ｃ）は、現像ニップにおける現像剤の状態を模式的に示した図。
【図２４】（ａ）、（ｂ）は、実施形態３，４におけるスィープローラに印加するバイアスの説明図。
【図２５】実施形態３及び４の除去ニップ近傍の拡大図。
【図２６】本実施形態３に係る中間転写ドラムの一例の説明図。
【図２７】現像剤濃度と転写紙Ｐへの２次転写率との関係を示したグラフ。
【図２８】実施形態４にかかるプリンタの概略構成図。
【図２９】実施形態４に関するプリンタの画像定着装置の概略構成図。
【図３０】現像剤濃度に対する転写紙Ｐへの定着性を調べた結果を示すグラフ。
【図３１】（ａ）は、トナー粒子間にキャリアＣが存在している状態を示す図。
（ｂ）は、トナー粒子層となった状態を示す図。
【符号の説明】
１０Ｂ、Ｙ、Ｍ、Ｃ 感光体ドラム
２０Ｂ、Ｙ、Ｍ、Ｃ 一様帯電器
３０ レーザ書込装置
４０Ｂ、Ｙ、Ｍ、Ｃ 湿式現像ユニット
５０ 除電装置
６０ クリーニング装置
７０ 中間転写ユニット
７７Ｂ、Ｙ、Ｍ、Ｃ １次転写バイアスローラ
８０ 紙転写ユニット
８１ ２次転写バイアスローラ
１００ 中間転写ベルト
３００ 画像定着装置
３０５ メインローラ
３１０ プレ加熱部
３１１ プレ加熱ローラ
３１２ 押圧ローラ
３１３Ｘ，３１３Ｚ プレ加熱ヒータ
３３０ キャリア除去部
３３１，３３１ａ，３３１ｂ ブロッタローラ
３３２ バックアップローラ
３３３ ウェブ
３３７，３３７Ｘ，３３７Ｚ キャリア除去ローラ
３４０，３４０Ｘ，３４０Ｚ ブロッタベルト
３４３Ｘ，Ｚ クリーニングユニット
３４９Ｘ，３４９Ｚ キャリア除去ベルト
３５０ 加熱定着部
３５１ 加熱ローラ
３５２ 加圧ローラ
４００ 画像形成装置
４００Ｘ，４００Ｚ 画像形成ユニット
５００Ｘ，５００Ｚ 中間転写ユニット
６１０、６１０Ｙ，Ｍ，Ｃ，Ｋ 感光体ドラム
７００ 現像装置
７０４ アニロクスローラ
７０６ 現像ローラ
７０７ クリーニングブレード
７１０ａ、７１０ｂ、７１０Ｙ，Ｍ，Ｃ，Ｋ スイープローラ
７１２ スイープ部
８００ 中間転写ユニット
８１０ 中間転写ドラム
８２０ 中間転写体スイープローラ
８５１，８５２，８５３，８５４，８５５，８５６ 懸架ローラ
８６０ 中間転写ベルト
８７０Ｙ，Ｍ，Ｃ，Ｋ １次転写バイアスローラ
８８０ クリーニング装置
８９０ ２次転写バイアスローラ
９００ 画像定着装置
９１０ プレ加熱部
９３０ キャリア除去部
９５０ 加熱定着部
９５１ 加熱ローラ
９５２ 加圧ローラ
Ｐ 転写紙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image fixing apparatus used in an image forming apparatus such as a printer, a facsimile machine, and a printer, and an image forming apparatus having the image fixing apparatus. More specifically, the present invention relates to an image fixing apparatus and an image forming apparatus that heat-fix an image formed on a recording medium with a liquid developer in which colored fine particles are dispersed in a solvent.
[0002]
[Prior art]
Conventionally, there are a dry developer and a wet developer, and various image fixing apparatuses for fixing an unfixed image formed on a recording medium with the developer have been proposed depending on the type of the developer.
As a method for fixing an unfixed image formed on a recording medium with a dry developer, a method is known in which a large amount of heat is applied and a large pressure is applied to fix the image and at the same time improve the color development of a color image. ing.
On the other hand, when fixing an unfixed image formed with a wet developer, it is generally possible to fix the image while improving color development mainly by heating without applying a large pressure during image fixing. It is known that it can be done.
[0003]
The above-mentioned wet developer is one in which toner is dispersed in a solvent, which also has a volatile solvent (hereinafter referred to as a volatile solvent) and a non-volatile solvent (hereinafter referred to as a non-volatile solvent). There is. Among these, a wet developer using a non-volatile solvent does not volatilize by heating at the time of fixing. Therefore, it can be said that the wet developer is more environmentally friendly than a wet developer using a non-volatile solvent. For this reason, in recent years, development and application of a non-volatile solvent have been attempted in place of a volatile solvent.
[0004]
By the way, in the case of a wet developer using a non-volatile solvent, the solvent does not volatilize at the time of image fixing. Therefore, the presence of the solvent at the time of fixing greatly affects the fixability. That is, in the method of heat-fixing a toner image, the toner that forms a wet-developed toner image on a recording medium is softened or melted by heating. In some cases, a non-volatile solvent enters between the toner and the recording medium to prevent the toner and the recording medium from being combined. For this reason, at the time of image fixing, it is necessary to either absorb the non-volatile solvent remaining on the recording medium into the recording medium or to remove the solvent from the image surface side of the recording medium.
[0005]
In addition, the higher the residual ratio of the solvent in the toner image, the larger the heat capacity in the toner image, and the longer the time required for heat fixing.
[0006]
The applicant previously proposed a fixing device capable of removing the solvent in the toner image in Japanese Patent Application Laid-Open No. 2-71286. In this fixing device, before the toner image is heated and fixed, a blotter roller is brought into contact with the recording medium in order to reduce the residual ratio of the solvent in the unfixed toner on the recording medium. According to this fixing device, the solvent is removed by the blotter roller to reduce the residual ratio of the solvent in the unfixed toner to about 50 [%], and it is fixed well to a recording medium such as an OHP film having a low solvent absorption rate. Can be done.
[0007]
By the way, when an image formed with a liquid developer using a non-volatile solvent as described above is heat-fixed on a recording medium, the solvent contained in the developer forming the image reduces fixability. I know. This is because when the image is heated and fixed on the recording medium, the solvent enters between the toner and the recording medium and prevents the binding between the toner and the recording medium. Therefore, in order to obtain sufficient fixability, it is required to sufficiently remove the solvent contained in the developer before fixing.
[0008]
Conventionally, in order to improve the fixability of an image, the solvent is removed before fixing, and a solvent from an unfixed image on a recording medium as described in JP-A-2-71286 and JP-A-2000-92290 is used. Various proposals have been proposed in addition to the configuration for removing the. For example, Japanese Patent Laid-Open No. 2001-305877 discloses an intermediate transfer member provided between a latent image carrier and a recording medium, and excess oil, that is, a solvent is removed from an image that is temporarily supported on the intermediate transfer member. The configuration to be removed is adopted.
In Japanese Patent Laid-Open No. 2000-250319, a conductive member is disposed in contact with the surface of a latent image carrier that is being developed and conveyed on the latent image carrier. Thus, the prewetting liquid and the solvent in the image are removed on the surface of the latent image carrier.
[0009]
As described in JP-A No. 2001-30587 and JP-A No. 2000-250319, the solvent removal for improving the fixing property is performed not only on the recording medium but also on the intermediate transfer member or the latent image carrier. It is known to do.
[0010]
In addition, the present applicant previously proposed an image fixing apparatus in Japanese Patent Application Laid-Open No. 2001-92290 in which the solvent of the wet developer can be removed during fixing. According to this publication, by applying an electric field to an unfixed toner image on a recording medium, the toner solids in the toner image are electrically urged to the surface of the recording medium, and thereby the surface of the toner image is not heated. A method and apparatus for separating and recovering a solvent is disclosed.
[0011]
[Problems to be solved by the invention]
In the fixing device proposed in the above-mentioned Japanese Patent Application Laid-Open No. 2-71286, a solvent is volatile and has a viscosity as low as 1 Cst. For this reason, even if the solvent residual ratio in the unfixed toner is about 50 [%], the fixing can be performed satisfactorily. However, when this is applied to a toner image formed with a liquid developer using a non-volatile solvent, a large amount of the solvent remains, so that the bonding between the toner and the recording medium is hindered and the fixing property becomes insufficient.
In addition, the effect of shortening the time required for heat fixing is small.
[0012]
Further, in the image fixing apparatus proposed in Japanese Patent Laid-Open No. 2001-92290, a conductive electric field roller is used as a member for applying a voltage, and a carrier is attached to the surface of the electric field roller and removed. there were. For this reason, when the carrier on the toner image is removed by applying an electric field, the carrier remaining on the toner layer and the carrier adhering to the electric field roller are each divided by about 50 [%], and the liquid recovery efficiency Was not enough. Accordingly, in order to increase the carrier recovery rate, a plurality of electric field rollers must be provided. For this reason, in addition to an increase in the number of rollers, it becomes necessary to dispose each roller with a predetermined gap, so that the apparatus becomes complicated, and the thickness of the transfer paper to be used must be limited in terms of curvature and the like. To do. Furthermore, since various new problems occur, such as the necessity of providing a cleaning device from the viewpoint of ensuring the reliability of each roller and extending the life, development of a new device is desired.
[0013]
The present inventor has found that the solvent can be separated from an unfixed toner image by heating in addition to the method of separating the solvent without heating as described in JP-A-2001-92290.
[0014]
  The present invention has been made in view of the above background.EyesThe object is to provide an image fixing apparatus and an image forming apparatus that can secure sufficient fixing and can perform high-speed fixing as compared with a conventional image fixing apparatus.
[0017]
[Means for Solving the Problems]
  In order to achieve the above object, the image fixing apparatus according to claim 1 is a non-fixed image on a recording medium formed by using a liquid developer in which toner is dispersed in a solvent that is partly or entirely non-volatile. An image fixing device for fixing an image by heating,Arranged on the opposite side of the recording medium from where the unfixed image is formed,Liquid development for forming an unfixed image on the recording mediumAgentheatingdo itDissolution in the liquid developerMediumOn the surface of the imageCome outMakePre-heatingMeans and theIt came out on the surface of the unfixed image by heating by the pre-heating means.Solvent removing means for removing the solvent from the image surface;And a heat fixing means for heat fixing the unfixed image after the solvent removal by the solvent removing means on the recording medium.
  Here, when the recording medium is made of a material having a relatively rough surface, such as general copy paper, which easily penetrates the solvent, the solvent whose viscosity has been reduced by heating penetrates into the recording medium. Even if the process is performed, a certain degree of fixability is obtained. However, since a small amount of solvent still remains in the toner image, complete fixability cannot be obtained. In addition, a recording medium made of a material that hardly permeates the solvent, for example, (PET) film such as OHP, surface-coated coated paper, art paper, etc. The fixability was very inadequate.
ContractClaim2In the image fixing apparatus,1'sIn the image fixing apparatus, the solvent removing means isUnfixed imageA removing roller having a surface abutted on the surface, and a pressing unit that presses the image carrying surface of the recording medium toward the removing roller.Unfixed aboveimageofTransfer from the surface to the removal rollerSolventIt is characterized by removingThe
  Claim3In the image fixing apparatus,1'sIn the image fixing device, the solvent removing means isUnfixed image aboveA removal belt that abuts the surface thereof and moves endlessly, and a pressing means that presses the image carrying surface of the recording medium against the surface of the removal belt,Unfixed aboveimageofTransfer from the surface to the removal beltSolventIt is characterized by removingThe
  Claim4In the image fixing apparatus,2Or3In the image fixing apparatus, the toner image is transferred to the removal roller or the removal belt side.MeltingSolvent recovery means for removing and recovering the medium from the removal roller or the removal belt is provided.The
  Claim5The invention of claim4In the image fixing apparatus, the solvent recovery means is located above the removal roller or the removal belt at the lower part in the gravity direction.MeltingIt has a lower recovery means for recovering the medium.The
  Claim6The invention of claim1'sIn the image fixing device, the solvent removing means is supported by a supply shaft in a state where one end of the web is wound, and the other end is wound by a winding shaft to move the surface of the web, and a web portion between these shafts The aboveUnfixedConfigured by contacting thethe aboveSolventUnfixedimageofIt is transferred from the surface to the web side and removed.The
  Claim7The invention of claim6In the image fixing apparatus, the web winding direction is the same as the recording medium surface moving direction.The
  Claim8The invention of claim2,3Or 6In the image fixing apparatus, the removal roller, the removal belt, or the web is configured using a porous material such as a nonwoven fabric or an elastic material that absorbs and swells with respect to a solvent such as silicon rubber. Characterized byThe
  Claim9The invention of claim2,3Or 6In this image fixing apparatus, the removal roller, the removal belt, or the web is composed of at least a metal material or a resin material that does not absorb and swell with respect to the solvent.The
  Claim10The invention of claim2,3Or 6In the image fixing apparatus, a plurality of the removing rollers, removing belts, or webs are provided.The
  Claim11The invention of claim2,3Or 6In the image fixing device, the recording medium is pressed from the back surface of the image bearing surface of the recording medium as the pressing means for pressing the image bearing surface against the removal roller, the removal belt, or the web surface. A backup roller that presses against the web is provided, and the contact surface of the removal roller, the removal belt, or the web to the recording medium, and the contact surface of the backup roller to the back surface of the recording medium are arranged in the recording medium conveyance direction. It is characterized by moving at approximately the same linear speedThe
  Claim12The invention of claim1,2,3,4,5,6,7,8,9,10Or 11In the above image fixing apparatus,Pre-heatingIn the meansheatingThe recording medium conveyance speed at the position, the solvent removing position in the solvent removing means, and the heat fixing position in the heat fixing means are all the same.The
  Claim13The invention of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11Or 12In the image fixing apparatus, there is provided a heating fixing means for fixing the unfixed image on the recording medium by heating.Pre-heatingBy meansheatingAll of the position, the solvent removal position by the solvent removing means, and the heat fixing position by the heat fixing means are provided on a conveyance path for linearly conveying the recording medium.The
  Claim14The invention of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12Or 13In the above image fixing apparatus,Pre-heatingmeansInstead ofContact heating member disposed in contact with the image forming surface of the recording mediumProvided with pre-heating means consisting ofThe surface of the contact heating member is subjected to a surface friction coefficient reduction treatment for reducing the friction coefficient of the surface.The
  Claim15The invention of claim14In the above image fixing apparatus,PreNon-contact heating means provided with heating means spaced apart from the image forming surface of the recording mediumsoCharacterized by compositionThe
  Claim16In the image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15., Pre-heating aboveMeans, and the solvent removing means,the aboveHeat fixing means,With heating meansIt is characterized by comprising a main roller and different opposing members provided opposite to the main roller.The
  Claim17The invention of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15Or 16In the above image fixing apparatus,Pre-heatingHeating by means and by the above solvent removal meansMeltingAn image as an object to be subjected to the two steps of removing the medium, or an image as an object to be subjected to the three steps of performing heat fixing of the unfixed image by the heat fixing unit in addition to the two steps is the recording medium. It is characterized by being formed on both sidesThe
  Claim18The invention of claim2, 3 or 6In the image fixing device ofAn image as an object to be subjected to the two steps of heating by the preheating unit and removal of the solvent by the solvent removing unit, or three types of heating and fixing of an unfixed image by the heating and fixing unit in addition to the two steps Images as objects to be processed are formed on both sides of the recording medium,The removal roller, the removal belt, or the web is disposed so as to sandwich the recording medium from both sides of the recording medium, and the contact surface of the removal roller, the removal belt, or the web on the surface of the recording medium, It is characterized by being moved in the recording medium conveyance direction at substantially the same linear velocity.The
  Claim19The invention of claim17 or 18In the above image fixing apparatus,Pre-heatingBy meansheatingThe position, the solvent removal position by the solvent removing means, and the heat fixing position by the heat fixing means are respectively set at the same location on the recording medium conveyance path on both sides of the recording medium.The
  Claim 20The invention of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18Or 19In the image fixing apparatus, a solvent removal degree switching means for switching the degree of the solvent removal by the solvent removal means according to the type of the recording medium is provided.
  Claims 1 to 20In the image fixing apparatus, the unfixed image on the recording medium is heated by the solvent precipitation unit to separate and deposit the solvent in the liquid developer on the upper layer of the toner image.
  FIG. 21A is a cross-sectional view when an unfixed image is carried on the upper surface of a transfer sheet P as a recording medium, and FIG. 21B is an indeterminate state when the transfer sheet P of FIG. FIG. 4 is a cross-sectional view showing a state of a liquid developer constituting a received image. As shown in FIG. 21B, when the transfer paper P is heated, the liquid developer is separated into toner and a carrier as a solvent, and the carrier liquid floats on the upper layer of the toner layer of toner solids, Penetrates on transfer paper. This is considered to be a phenomenon that occurs when the unfixed toner image on the transfer paper is heated, the resin in the toner is dissolved by heating to form a film, and the carrier liquid in the toner layer separates and precipitates. This phenomenon is conspicuous when the recording medium is made of a material that is difficult to penetrate the solvent. Then, the deposited solvent to be deposited is removed from the surface of the image by a solvent removing means, and the non-volatile solvent that causes a problem in heat fixing in the image is removed. Thereby, a non-volatile solvent is removed efficiently.
  Claim 21The image forming apparatus includes an image forming unit that forms an unfixed image on a recording medium using a liquid developer, and an image fixing unit that heat-fixes the unfixed image on the recording medium. An image forming apparatus using a liquid developer in which toner is dispersed in a solvent that is partly or entirely non-volatile as the liquid developer, wherein: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19Or 20The image fixing apparatus is used.
  Claim 21In this image forming apparatus, it is possible to secure sufficient fixing of a non-fixed image formed on a recording medium with a liquid developer in which toner is dispersed in a solvent that is partly or entirely non-volatile, and high-speed fixing is possible. The image is fixed by an image fixing device.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments 1 and 2 in which the present invention is applied to a wet electrophotographic printer (hereinafter referred to as “printer”) as an image forming apparatus will be described below.
[0020]
Embodiment 1
FIG. 1 is a schematic configuration diagram of a main part of the printer according to the first embodiment. This printer includes four sets of an image forming unit 1 as an image forming unit, an intermediate transfer unit 70, a transfer device 80, an image fixing device 300, a print control unit (not shown), a paper feed unit, and a control unit.
The four sets of image forming units 1 are composed of a photosensitive drum 10, a developing device 40, and the like. The developer of the developing device 40Y of the image forming unit 1Y is a yellow developer, the developer of the developing device 40M of the image forming unit 1M is a magenta developer, and the developer of the developing device 40C of the image forming unit 1C is a cyan developer. The developer of the developing device 40B of the part 1B is a black developer. A full color image can be formed by performing corresponding image exposure on each of the photosensitive drums 10. These developers are carriers that are mixed and dispersed by a ball mill, three rolls, etc. in the examples disclosed in JP-A-3-98084, JP-A-3-200264, JP-A-3-225356, JP-A-3-291671, etc. A solvent (hereinafter referred to as carrier) is used as the solvent according to the present invention. A liquid developer is formed by dispersing toner as colored fine particles in the carrier. Some or all of these carriers are non-volatile. In addition, the liquid developer according to the present embodiment was adjusted to a high viscosity liquid developer (hereinafter referred to as a developer) having a toner solid content of about 15 to 20 [%] and having a viscosity of 100 to 1000 mPa · s. .
Since the four sets of image forming units 1 have the same configuration, the image forming unit 1B using a black developer will be described.
[0021]
The image forming unit 1B includes a photosensitive drum 10B as a latent image carrier, a uniform charger 20B, a laser writing device 30 that irradiates a laser beam LB, a wet developing unit 40B as a developing unit, and a discharging unit. A static eliminator 50B is provided. Further, a photoreceptor cleaning device 60B having a cleaning blade is also provided. The uniform charger 20B and the laser writing device 30 constitute a latent image forming unit.
[0022]
The wet developing unit 40B includes a developing roller 41B as a developer carrying member, a developing tank 42B for storing a liquid developer, a drawing roller 43B disposed so as to be immersed in the liquid developer in the developing tank 42B, and the like. It is configured. Furthermore, a measuring roller 44B for thinning the liquid developer pumped from the pumping roller 43B and applying it to the developing roller 41B is also provided.
The liquid developer is a high-viscosity liquid developer in which toner particles as a visualization substance are dispersed at a high concentration in a liquid carrier that is an insulating liquid.
[0023]
The intermediate transfer unit 70 includes suspension rollers 71, 72, 73, 74, 75, and 76, an intermediate transfer belt 100 stretched around the suspension rollers 71, 72, 73, 74, 75, and the like. Yes. Further, it also includes a primary transfer bias roller 77B, 77Y, 77M, 77C, a cleaning device 79 having a cleaning blade, and the like.
[0024]
The paper transfer unit 80 includes a secondary transfer bias roller 81 and a secondary transfer power source (not shown) connected to the secondary transfer bias roller 81.
[0025]
Next, the intermediate transfer belt, the primary transfer bias roller, the secondary transfer bias roller, and the like will be described more specifically.
The intermediate transfer belt 100 is stretched around the suspension rollers 71, 72, 73, 74, 75, and 76 and the photosensitive drums 10B, 10Y, 10M, and 10C so as to have a predetermined tension, and is counterclockwise as indicated by an arrow. It can be rotated. Further, as a primary transfer charge applying unit, for example, a primary transfer bias roller 77B faces the photosensitive drum 10B, and the intermediate transfer belt 100 is sandwiched between the primary transfer bias roller 77B and the photosensitive drum 10B. It has become the arrangement. The primary transfer bias roller 77B also serves as an electrode for applying a primary transfer bias, and a predetermined transfer bias is applied to the primary transfer bias roller 77B from a primary transfer power source (not shown).
A secondary transfer bias roller 81 is disposed facing the suspension roller 73, and the secondary transfer bias roller 81 also serves as an electrode for applying a secondary transfer bias. A predetermined transfer bias is applied to the secondary transfer bias roller 81 from a secondary transfer power source (not shown).
[0026]
Next, the operation of the wet electrophotographic printer according to this embodiment will be described.
As shown in FIG. 1, the photosensitive drum 10B is uniformly charged by the uniform charger 20B while being driven to rotate in the direction of the arrow, and then the laser beam LB from the laser writing device 30 is irradiated to irradiate the photosensitive drum 10B. An electrostatic latent image is formed on the surface. On the other hand, the liquid developer adhering to the scooping roller 43B immersed in the high-viscosity liquid developer in the developing tank 42B is uniformly on the developing roller 41B via the metering roller 44B, for example, about 0.5 to 20 [μm]. Applied to a thickness of
Then, the developing roller 41B is brought into contact with the photosensitive drum 10B, the toner in the liquid developer is transferred to the electrostatic latent image formed on the surface of the photosensitive drum 10B by the electric field, and developed. Form.
[0027]
Next, the photosensitive drum 10B on which the visible image is formed is rotated and moved to a primary transfer portion where the photosensitive drum 10B and the intermediate transfer belt 100 abut.
In the primary transfer portion, a negative bias voltage, for example, −300 to −500 [V], which is the reverse polarity of the positive toner is applied to the back surface of the intermediate transfer belt 100 via the primary transfer bias roller 77B. Then, the developer of the visible image on the photosensitive drum 10B is attracted to the intermediate transfer belt 100 by the electric field generated by the applied voltage, and is transferred onto the intermediate transfer belt 100 (primary transfer). In the full-color image forming operation, an image is transferred to the intermediate transfer belt 100 in the order of yellow developer, magenta developer, cyan developer, and black developer to form a full-color image.
[0028]
Next, the intermediate transfer belt 100 to which the full-color image has been transferred is rotated, and the secondary transfer in which the intermediate transfer belt 100 and the transfer paper P as a recording medium conveyed in the direction of the arrow from a paper supply unit (not shown) abuts. Move to the part. In the secondary transfer portion, a negative bias voltage, for example, −800 to −2000 [V] is applied to the back surface of the transfer paper P via the secondary transfer bias roller 81, and for example, 50 N / cm.²Apply a certain amount of pressure. The developer of the intermediate transfer belt 100 is attracted to the transfer paper P by the electric field and pressure generated by the applied voltage, and is collectively transferred to the transfer paper P (secondary transfer). As described above, the intermediate transfer unit 70 and the transfer device 80 constitute transfer means.
[0029]
Thereafter, the transfer paper P onto which the image (unfixed image) has been transferred is separated from the intermediate transfer belt 100 by the separating device 85, and after being subjected to heat fixing processing by the image fixing device 300 as an image fixing means, from the apparatus main body. Discharged. On the other hand, after the secondary transfer, the photosensitive drum 10B is charged with residual charges by the static eliminator 50B, the surface thereof is cleaned by the cleaning device 60B, the untransferred developer is collected and removed, and is prepared for the next image formation.
[0030]
By the way, when a carrier that is at least partially non-volatile is used as the developer used in this embodiment, the carrier does not volatilize during image fixing. Greatly affects. Therefore, at the time of image fixing, it is necessary to either absorb the non-volatile carrier remaining on the transfer paper P into the transfer paper P or to remove the carrier from the image carrying surface side of the transfer paper P. .
[0031]
In Examples 1 and 2 below, an image fixing device 300 that is a characteristic part of Embodiment 1 will be described.
[Example 1]
FIG. 2 is an explanatory diagram of the image fixing apparatus 300 according to the first embodiment. The image fixing apparatus 300 includes a pre-heating unit 310 as a solvent precipitation unit and a carrier removal unit as a solvent removal unit in order from an upstream side (right side in the figure) to a downstream side (left side in the figure) in the transfer paper P conveyance direction. 330 and a heat fixing unit 350 as heat fixing means.
[0032]
The heat fixing unit 350 is attached so that the heating roller 351 and the pressure roller 352 are in pressure contact with each other. The heating roller 351 has a built-in heater, and a rubber layer, an oil-resistant layer (fluorinated silicon rubber layer), an RTV silicon rubber layer, or a Teflon (registered trademark) layer having a desired thickness are sequentially laminated on the surface of the mandrel. Yes. On the other hand, the pressure roller 352 is coated with silicone rubber with Teflon (registered trademark). The cam surface of the pressure cam 353 is pressed against the shaft portion of the pressure roller 352 by the urging force of the spring 354, so that a predetermined pressure action is applied to the pressure roller 353. A thermistor 355 and a thermal fuse 356 are disposed around the heating roller 351, and temperature control is performed by these. A separation claw 357 and a cleaning pad 358 are disposed in contact with the surface of the heating roller 351.
[0033]
The pre-heating unit 310 is disposed so that the pre-heating roller 311 contacts the opposite side of the transfer paper P from the toner image transfer surface, and the pre-heating roller 311 has a built-in heater as a heating means. Two pressing rollers 312 are disposed on the toner image carrier surface side to press the transfer paper P against the pre-heating roller 311 so as to be in close contact therewith. A cleaning pad 314 for cleaning toner adhering to the surface of the pre-heating roller 311 is disposed in contact therewith. A cleaning roller 315 is disposed in contact with the pressing roller 312.
[0034]
The carrier removing unit 330 is located between the pre-heating unit 310 and the heat fixing unit 350 in the transfer paper P conveyance direction. The carrier removing unit 330 is provided with a member for absorbing and removing the precipitated carrier as a solvent to be deposited that has been deposited on the surface of the toner image by heating by the preheating unit 310. That is, a blotter roller 331 serving as a removing roller that contacts the surface of the toner image and a backup roller 332 serving as a pressing unit that presses the surface of the toner image toward the blotter roller 331 are provided. Further, the blotter roller 331 has a surface layer portion made of a porous elastic material.
[0035]
  Next, an image fixing operation using the image fixing apparatus 300 having the above configuration will be described.
  The transfer paper P onto which the unfixed image has been transferred is separated from the intermediate transfer belt 100 by the separation device 85 and enters the image fixing device 300, and first reaches the preheating unit 310. At this time, the developer constituting the unfixed image on the transfer paper P is heated by the pre-heating roller 311 in contact with the back surface of the transfer paper P, and the carrier isSeparateOn the surface of the imageOutCome(Hereinafter, this is referred to as “deposition” of the carrier, and the carrier that appears on the surface is referred to as “deposition carrier”.).
  Next, the transfer paper P enters the carrier removing unit 330 with the carrier deposited on the surface. In the carrier removing unit 330, the precipitated carrier is transferred to the blotter roller 331 side. This is performed when the transfer paper P passes while the blotter roller 331 comes into contact with the deposition carrier on the upper surface of the transfer paper P and is pressed from the back surface of the transfer paper P to the blotter roller 331 side by the backup roller 332. As a result, the deposited carrier is removed from the transfer paper P.
  The transfer paper P from which the precipitation carrier has been removed is further conveyed and enters the heat fixing unit 350. The heating and fixing unit 350 is heated when passing through a nip portion between a heating roller that contacts the upper surface of the transfer paper P, that is, the image carrying surface, and a pressure roller that presses the transfer paper P toward the heating roller from the rear surface of the transfer paper P. The image is fixed on the transfer paper P by pressing. Then, the image is discharged from the image fixing device 300.
[0036]
With the image fixing apparatus 300 having the above configuration, even if a non-volatile component is contained in the carrier constituting the developer, it can be removed in advance by the blotter roller 331, so that an unfixed image on the transfer paper P can be reliably obtained. Can be fixed.
In addition, since the carrier fixing component is removed, the heat fixing temperature can be lowered as compared with the conventional case, and in addition, the heat fixing temperature in the heat fixing unit 350 is fixed by one heating. And can be lowered. This is for heating and fixing an image heated in advance by the preheating unit 310. For example, a temperature sensor that detects the temperature is provided in each of the pre-heating unit and the heat-fixing unit, and the heaters are turned on and off according to the detection results of these temperature sensors, and the temperatures of the pre-heating unit and the heat-fixing unit are desired What is necessary is just to control so that it may become. In the case of the present embodiment, a good fixed image is obtained by setting the heating temperature by the pre-heating roller 311 of the pre-heating unit 310 to 100 to 150 [° C.] and the heating temperature by the heating roller in the heating and fixing unit 350 to 100 to 120 [° C.]. Could get. Accordingly, it is possible to shorten the heat fixing time.
Further, since the roller-shaped blotter roller 331 is used as a carrier removing member in the carrier removing unit 330, it can be made compact compared to the shape of a belt, web, etc., and is effective in reducing the size of the image fixing device 300. is there.
In addition, since the blotter roller 331 is formed of a porous elastic material, the carrier can be efficiently removed, which is effective for excellent fixing performance and high-speed fixing.
[0037]
[Modification 1]
Next, as a modified example of the first embodiment, a first modified example in which blotter rollers are provided in multiple stages in the carrier removing unit 330 will be described.
FIG. 3 is an explanatory diagram of the image fixing device 300 according to the first modification. The carrier removing unit 330 of this apparatus is provided with two blotter rollers 331a, b and backup rollers 332a, b provided to face the blotter rollers 331a, b. Since the other structure is the same as that of the image fixing apparatus 300 of the first embodiment, description thereof is omitted.
[0038]
When the unfixed image on the transfer paper P is fixed using the image fixing device 300, the transfer paper P enters the carrier removal unit 330 with the carrier deposited on the surface. In the carrier removal unit 330, the two blotter rollers 331a and 331b sequentially contact the deposition carrier on the upper surface of the transfer paper P. Most of the precipitation carrier is first removed by the blotter roller 331a, and if there is any remaining precipitation carrier that cannot be removed, it is removed by the next blotter roller 331b. Thereby, it is possible to reliably remove the precipitation carrier as compared with the case where only one blotter roller is provided.
The transfer paper P from which the precipitation carrier has been removed is heated and fixed with an unfixed image by the heat fixing unit 350 and discharged from the image fixing device 300 as in the first embodiment.
[0039]
If the blotter rollers are provided in multiple stages as in the first modification, the amount of solvent that can be removed is larger than when only one blotter roller is provided. Therefore, it is possible to satisfactorily heat and fix the image formed on the transfer paper P made of a material that hardly penetrates the solvent. As a result, this also leads to an increase in the types of transfer paper P that can be applied to the image fixing device 300 and, in turn, the printer.
[0040]
[Modification 2]
Next, as another modified example of the first embodiment, a second modified example in which the web 333 is provided in the carrier removing unit 330 will be described.
FIG. 4 is an explanatory diagram of an image fixing device 300 according to the second modification. The carrier removing unit 330 of this apparatus uses a web 333 made of a material having good hygroscopicity instead of the blotter roller 331 of the first embodiment and the first modification. One end of the web 333 is wound and supported by the supply shaft 334, and the other end is wound by the winding shaft 335 to move the surface of the web 333, and the web 333 portion between these shafts is pressed against the transfer paper P Then, the deposition carrier on the transfer paper P is wiped away. In the second modification as well, the other structure is the same as that of the image fixing apparatus 300 of the first embodiment, and a description thereof will be omitted.
[0041]
When the image on the transfer paper P is fixed using the image fixing device 300, the transfer paper P enters the carrier removing unit 330 with the carrier deposited on the surface. In the carrier removing unit 330, the deposition carrier on the upper surface of the transfer paper P pressed to the web 333 side by the backup roller 332 contacts the web 333. The precipitated carrier is transferred to the web 333 and removed. At this time, the cleaning surface once used is wound up by the winding shaft. The cleaning surface that has been used once is wound around the winding shaft and is not reused. When the web 333 is used up, the web 333 is replaced with a new one. In this example, the winding direction is the same as the transfer paper P surface movement direction, that is, the transfer paper P transport direction.
[0042]
When the precipitation carrier is removed using the web 333 as in the second modification, the precipitation carrier can always be removed at a new web 333 portion. Therefore, the removal effect can be maintained without removing the carrier transferred to the web 333 until the winding of the web 333 is completed. Further, there is no need to provide a cleaning device for the web 333.
Further, the winding direction is set so that the surface of the transfer paper P and the surface of the web 333 in contact with the surface of the transfer paper P move in the same direction. Therefore, the stress applied to the image on the surface of the transfer paper P can be reduced as compared with the case where the images are not set in the same direction, and damage to the image such as missing images can be reduced.
[0043]
Next, an image fixing apparatus 300 according to the second embodiment will be described.
[Example 2]
FIG. 5 is an explanatory diagram of the image fixing apparatus 300 according to the second embodiment. The image fixing apparatus 300 uses a blotter belt 340 as a removal belt whose surface moves endlessly at a carrier removal unit 330. Also, a main roller 305 having a heater 305h (for example, a halogen heater) is provided, and a pre-heating unit 310, a carrier removing unit 330, and a heat fixing unit 350 are formed on the surface of the main roller 305 sequentially from the upstream side in the roller rotation direction. is doing.
The carrier removing unit 330 stretches the blotter belt 340 around the pressing rubber roller 341 and the two tension rollers 342, and presses the blotter belt 340 against the main roller 305 by the pressing rubber roller 341. The blotter belt 340 and the three rollers 341 and 342 constitute an opposing member. The blotter belt 340 is made of an elastic material such as urethane, hydrin, or polyimide as a material having silicon rubber or micro cells and having porous and heat-resistant characteristics. In addition, a cleaning unit 343 as a solvent recovery unit is provided at a position facing the tension roller of the blotter belt 340. The cleaning unit includes a cleaning blade 344 that contacts the blotter belt 340 and a container 345 that stores the carrier scraped off by the blade.
In the pre-heating unit 310, an opposing member is provided to face the main roller 305, which includes two pressing rollers 312 that press the transfer paper P against the main roller 305 and closely contact the main roller 305 and a cleaning roller 315 that cleans the pressing roller 312. ing. The pressing roller 312 contacts the main roller 305 with a bearing having an outer diameter that is larger than the pressing roller 312 of both rollers (not shown) by a pressure greater than that of the main roller 305 with respect to the main roller 305. A gap is formed by contact. This takes into consideration that the transfer paper P is in contact with or close to the main roller, and also takes into account that the transfer paper P is transported well even when the transfer paper P is thick. Further, the pressing roller 312 is provided with Teflon (registered trademark) having a small surface energy so that the toner image does not easily adhere to the surface. Instead of providing Teflon (registered trademark), emery paper having irregularities in the surface shape and having a tip of 1 to 100 [μm] may be wound around the surface of the pressing roller 312 in a spiral.
In the heat fixing unit 350, a fixing roller 360 with a built-in heater 360h is provided as an opposing member so as to face the main roller 305.
[0044]
An image fixing operation using the image fixing apparatus 300 having the above configuration will be described.
The transfer paper P separated from the intermediate transfer belt 100 by the separating device 85 and entering the image fixing device 300 first reaches the preheating unit 310. At this time, the main roller 305 with which the back surface of the transfer paper P abuts is heated at about 140 [° C.], the developer constituting the unfixed image I on the transfer paper P is heated, and the carrier is deposited on the surface of the image. Come on.
With the carrier deposited on the surface, the transfer paper P is carried and conveyed by the main roller 305 and enters the carrier removing unit 330. In the carrier removing unit 330, the blotter belt 340 comes into contact with the deposition carrier on the upper surface of the transfer paper P. The precipitated carrier is transferred to the blotter belt 340 side and removed.
The transfer paper P from which the precipitation carrier is removed is further carried and conveyed by the main roller 305 and enters the heat fixing unit 350. In the heat fixing unit 350, the image I is fixed on the transfer paper P by heating and pressurization of about 140 [° C.] by the fixing roller 360 in contact with the upper surface of the transfer paper P and the main roller 305 in contact with the back surface. Then, the image is discharged from the image fixing device 300.
[0045]
In addition, since the image after removing the precipitation carrier is originally fixed, the heating temperature in the heat fixing unit 350 can be performed at a low temperature of about 100 to 120 [° C.]. However, in this embodiment, unlike the first embodiment, the heater that heats the back surface of the transfer paper by the pre-heating unit and the heat-fixing unit is the heater 305h built in the main roller 305. Yes. Thus, when the heat fixing temperature is 140 [° C.], there is an advantage that a good fixed image can be obtained even when the transfer paper P is thick.
[0046]
On the other hand, the blotter belt 340 holding the precipitation carrier is driven by a tension roller 342 having a belt driving function. Then, the carrier is scraped off at the contact position with the cleaning blade 344 and used again to remove the precipitated carrier on the transfer paper P. The scraped carrier is accommodated in the container 345.
In addition, it was observed that the precipitation carrier contained no toner component and was a carrier alone, and the toner component was observed to be melted by heating and bound to the paper fiber of the transfer paper. Therefore, these precipitation carriers are recyclable because they can be recycled.
[0047]
In the image fixing apparatus 300 of the second embodiment, while the transfer paper P is carried and conveyed on one main roller 305, the carrier is deposited from the unfixed image on the surface of the transfer paper P, the precipitated carrier is removed, and heating is performed. Fixing is in progress. Therefore, the main roller 305 and one of the three functions of the pre-heating roller 311 of the pre-heating unit 310, the backup roller 332 of the carrier removing unit 330, and the pressure roller 352 of the heat-fixing unit 350 in the first embodiment can be achieved. it can. As a result, space can be saved as compared with the case where a plurality of members are provided as in the first embodiment, and the image fixing device 300 can be downsized.
In Example 2, the precipitation carrier transferred to the blotter belt 340 can be removed from the belt, and the blotter belt 340 can be used again to remove the precipitation carrier. Therefore, the carrier removing action of the blotter belt 340 can be maintained for a long time. Further, the precipitation carrier recovered in the container can be reused as a constituent material of a new liquid developer.
Furthermore, since the blotter belt 340 of Example 2 is formed of a porous elastic material, it can absorb the precipitated carrier efficiently, and is effective for excellent fixing properties and high-speed fixing.
In the second embodiment, an example in which the blotter belt 340 is used as the carrier removing member is shown. However, the same effect can be obtained by using the above-described blotter roller or web.
[0048]
Example 3
FIG. 6 is an explanatory diagram of the image fixing apparatus 300 according to the third embodiment. The image fixing apparatus 300 includes a preheating unit 310 as a solvent precipitation unit and a carrier removal unit as a carrier removal unit in order from the upstream side (right side in the drawing) to the downstream side (left side in the drawing) in the transfer paper P conveyance direction. 330 and a heat fixing unit 350 as heat fixing means.
[0049]
The heat fixing unit 350 is attached so that the heating roller 351 and the pressure roller 352 are in pressure contact with each other. The heating roller 351 includes a heater, and a rubber layer, an oil resistant layer (silicon fluoride rubber layer), an RTV silicon rubber layer, or a Teflon layer having a desired thickness are sequentially laminated on the surface of the core metal. On the other hand, the pressure roller 352 is Teflon coated on silicon rubber. A cam surface of a pressure cam (not shown) is brought into pressure contact with the shaft portion of the pressure roller 352 by a biasing force of a spring (not shown) so that a predetermined pressure action is applied to the pressure roller 352. It has become.
[0050]
The pre-heating unit 310 is provided with a pre-heating roller 311 as a contact heating member that comes into contact with the toner image transfer surface side of the transfer paper P. A pressure roller 312 is provided. A halogen lamp or an infrared heater is used as a heating means for the pre-heating roller 311. Furthermore, the surface of the pre-heating roller 311 has high heat resistance such as fluorine coating or PVFE coating so that the toner image formed on the transfer paper P is not unnecessarily stressed, and the surface friction coefficient. It is preferable that treatment with a material having a low value is performed.
[0051]
The carrier removing unit 330 is located between the pre-heating unit 310 and the heat fixing unit 350 in the transfer paper P conveyance direction. The carrier removing unit 330 absorbs and removes the deposited carrier as a solvent to be deposited that has been deposited on the surface of the toner image by heating by the preheating unit 310. For this purpose, a carrier removal roller 331 that contacts the surface of the toner image and a backup roller 332 as a pressing unit that presses the toner image surface toward the carrier removal roller 331 are provided.
[0052]
In the third embodiment, the carrier removal roller 331 is formed of a material that does not impregnate the carrier liquid in the surface layer portion. For example, a metal roller or a resin material that does not swell in a carrier liquid such as polyimide can be used. Further, a cleaning unit 343 as a solvent recovery unit is provided at a position facing the carrier removal roller 331. The cleaning unit 343 includes a cleaning blade 344 that contacts the carrier removal roller 331 and a container 345 that stores the carrier scraped off by the blade.
[0053]
Next, an image fixing operation using the image fixing apparatus 300 having the configuration of the third embodiment will be described.
The transfer paper P onto which the unfixed image has been transferred is separated from the intermediate transfer belt 100 by the separation device 85 and enters the image fixing device 300, and first reaches the preheating unit 310. At this time, the developer constituting the unfixed image on the transfer paper P is heated by the preheating roller 311 on the transfer paper P image surface, and the carrier is deposited on the surface of the unfixed image. Next, the transfer paper P enters the carrier removing unit 330 with the carrier deposited on the surface. In the carrier removal unit 330, the carrier removal roller 331 comes into contact with the deposited carrier on the upper surface of the transfer paper P, and the transfer paper P passes through the state where the backup roller 332 is pressed from the back surface of the transfer paper P toward the carrier removal roller 331. At this time, the precipitated carrier is transferred to the carrier removing roller 331 side. As a result, the deposited carrier is removed from the transfer paper P. The transfer paper P from which the precipitation carrier has been removed is further conveyed and enters the heat fixing unit 350. The heat fixing unit 350 passes through a nip portion between a heating roller 351 that contacts the upper surface of the transfer paper P, that is, the image carrying surface, and a pressure roller 352 that presses the transfer paper P from the back surface of the transfer paper P toward the heating roller 351. At this time, the image is fixed on the transfer paper P by heating and pressing. Then, the image is discharged from the image fixing device 300.
[0054]
Even if the carrier constituting the developer contains a non-volatile component by the image fixing device 300 having the above configuration, it can be removed in advance by the carrier removing roller 331, so that the unfixed image on the transfer paper P can be removed. It can be reliably fixed. In addition, since the carrier fixing component is removed, the heat fixing temperature can be lowered as compared with the prior art. In addition, the image heated in advance by the preheating unit 310 is heat fixed. Accordingly, the heating temperature in the heat fixing unit 350 can be lowered as compared with the case of fixing by one heating. For example, a temperature sensor that detects the temperature is provided in each of the pre-heating unit and the heat-fixing unit, and the heaters are turned on and off according to the detection results of these temperature sensors, and the temperatures of the pre-heating unit and the heat-fixing unit are desired What is necessary is just to control so that it may become. In the case of this embodiment, the heating temperature by the heater 311 of the pre-heating unit 310 is set to 100 to 150 [° C.], and the heating temperature by the heating roller in the heating fixing unit 350 is set to 100 to 120 [° C.] to obtain a good fixed image. I was able to. Accordingly, it is possible to shorten the heat fixing time. Further, since the roller-shaped carrier removing roller 331 is used as the material of the carrier removing unit 330, it can be made compact compared to the shape of a belt, a web or the like, and is effective in reducing the size of the image fixing device 300.
[0055]
Next, an image fixing apparatus 300 according to the fourth embodiment will be described.
Example 4
FIG. 7 is an explanatory diagram of the image fixing apparatus 300 according to the fourth embodiment. The image fixing apparatus 300 uses a heater 320 which is a non-contact heating means such as a halogen heater or an infrared heater instead of the heating roller as the heating means of the pre-heating unit 310 in the third embodiment.
The conveyor belt 321 is configured to be suspended and driven by a drive roller 322, a suspension roller 323, and a backup roller 332 of the carrier removing unit 330. The transfer paper P is transported by the transport belt 321 as shown in the figure, and when the transfer paper P passes under the heater 320 arranged at a distance of several centimeters from the transfer paper P, the transfer paper P The transfer paper P is heated by the radiant heat. As a result, carriers in the toner layer are deposited on the surface. The transfer paper P is directly transported to the carrier removal unit 330 by the transport belt 321, and the carrier deposited on the surface of the toner layer of the transfer paper P is removed by being pressed against the carrier removal roller 331 by the backup roller 332.
According to the fourth embodiment, since the carrier deposition portion 310 does not directly touch the unfixed image surface of the transfer paper P, unnecessary stress can be avoided from being applied to the unfixed image, and a better image can be obtained. It is done.
[0056]
Next, an image fixing apparatus 300 according to Example 5 will be described.
Example 5
FIG. 8 is an explanatory diagram of the image fixing apparatus 300 according to the fifth embodiment. The image fixing apparatus 300 uses a carrier removal belt 349 whose surface is moved endlessly at the carrier removal unit 330. The carrier removing unit 330 stretches the carrier removing belt 349 around the pressing rubber roller 341 and the two tension rollers 342, and presses the carrier removing belt 349 against the backup roller 332 by the pressing rubber roller 341.
The carrier removal belt 349 is formed of a resin film such as polyimide as a material that does not swell in the carrier liquid and has heat resistance. Further, a cleaning unit 343 as a solvent recovery unit is provided at a position of the carrier removal belt 349 facing the tension roller. The cleaning unit includes a cleaning blade 344 that contacts the carrier removal belt 349 and a container 345 that stores the carrier scraped off by the blade.
[0057]
An image fixing operation using the image fixing apparatus 300 having the above configuration will be described. The transfer paper P separated from the intermediate transfer belt 100 by the separating device 85 and entering the image fixing device 300 first reaches the preheating unit 310. At this time, the heating roller 311 with which the image surface of the transfer paper P abuts is heated at about 140 [° C.], the developer constituting the unfixed image on the transfer paper P is heated, and the carrier liquid is unfixed image. Precipitates on the surface.
With the carrier deposited on the surface, the transfer paper P is carried and conveyed by the heating roller 311 and the pressure roller 312 of the preheating unit 310 and enters the carrier removal unit 330. In the carrier removal unit 330, the carrier removal belt 349 comes into contact with the deposition carrier on the upper surface of the transfer paper P. The precipitated carrier is transferred to the carrier removing belt 349 side and removed.
The transfer paper P from which the precipitated carrier has been removed is further carried and conveyed by the carrier removal belt 349 and the backup roller 332 and enters the heat fixing unit 350. In the heat fixing unit 350, the image I is fixed on the transfer paper P by heating and pressurization of about 140 ° C. by the heating roller 351 that contacts the upper surface of the transfer paper P and the pressure roller 352 that contacts the back surface. Then, the image is discharged from the image fixing device 300. In this case, since the image after removing the precipitated carrier is fixed, the heating temperature in the heat fixing unit 350 can be performed at a low temperature of about 100 to 120 [° C.].
On the other hand, the carrier removal belt 349 holding the precipitation carrier is driven by a tension roller 342 having a belt driving function, and the carrier is scraped off at a contact position with the cleaning blade 344. Then, it is used again to remove the precipitated carrier on the transfer paper P. The scraped carrier is accommodated in the container 345.
In addition, it was observed that the precipitation carrier contained no toner component and was a carrier alone, and the toner component was observed to be melted by heating and bound to the paper fiber of the transfer paper. Therefore, these precipitation carriers are recyclable because they can be recycled.
[0058]
In the fifth embodiment, the precipitated carrier transferred to the carrier removing belt 349 is removed from the belt 340, and this carrier removing belt 349 can be used again for removing the precipitated carrier. Therefore, the carrier removing action of the carrier removing belt 349 can be maintained for a long time. Further, the precipitation carrier collected in the container 345 can be reused as a constituent material of a new liquid developer.
Furthermore, since the carrier removal belt 349 of Example 5 is formed of a material that does not swell in the carrier liquid and has heat resistance, the removal carrier can be efficiently cleaned and also has excellent durability, so that it is particularly high speed. Effective for fixing.
[0059]
Next, an image fixing apparatus 300 according to Embodiment 6 will be described.
Example 6
The image fixing apparatus 300 in FIG. 9 uses a heating unit 320 such as a halogen heater or an infrared heater as a non-contact heating unit as a heating unit of the pre-heating unit 310 in the sixth embodiment, instead of a heating roller.
The conveyor belt 321 is configured to be suspended and driven by a drive roller 322, a suspension roller 323, and a backup roller 332 of the carrier removing unit 330. The transfer paper P is transported by the transport belt 321 as shown in the figure, and when the transfer paper P passes under the preheater 320 disposed away from the transfer paper P, the radiation from the preheater 320 is emitted. The transfer paper P is heated by heat. As a result, carriers in the toner layer are deposited on the surface. The transfer paper P is directly transported to the carrier removing unit 330 by the transport belt 321, and the carrier deposited on the surface of the toner layer of the transfer paper P is removed by being pressed against the carrier removal belt 349 by the backup roller 332.
[0060]
According to the sixth embodiment, since the carrier deposition portion 310 does not directly touch the unfixed image surface of the transfer paper P, it is possible to avoid applying unnecessary stress to the unfixed image and obtain a better image. It is done.
[0061]
In Examples 1 to 6 related to the first embodiment, the carrier removal unit 330 sets the surface movement linear velocity of the blotter roller 331, the blotter belt 340, or the web 333 in contact with the upper surface of the transfer paper P as follows. Also good. That is, the linear velocity is set to be approximately the same as the linear velocity of the surface of the backup roller 332 or the main roller 305 that contacts the lower surface of the transfer paper P. As a result, it is possible to prevent stress that may be applied to the image on the transfer paper P when the linear speeds of the members that are held and conveyed by the upper and lower sides are different, and to generate an abnormal image due to such stress. Can be prevented.
[0062]
In Examples 1 to 6 related to the first embodiment, the transfer paper P may pass through the pre-heating unit 310, the carrier removing unit 330, and the heating and fixing unit 350 all at the same speed. As a result, it is possible to prevent the transfer paper P carrying the image from being subjected to the stress caused by the fluctuation of the conveyance speed, and to prevent the transfer paper P from being jammed due to the stress caused by the fluctuation of the conveyance speed. Generation of abnormal images can be prevented.
[0063]
Further, in Examples 1 to 6 relating to the first embodiment, there is no need for a carrier for the transfer paper P made of a material that easily penetrates the carrier. Therefore, a drive switching device may be provided as a carrier removal degree switching means for switching whether to operate the carrier removal unit 330 according to the type of transfer paper P.
The precipitation of the carrier due to the heating of the preheating unit 310 is conspicuous in, for example, a coated paper when the material of the transfer paper P is not easily penetrated by the carrier. This is because the paper fiber is covered with clay or resin on the surface layer of the coated paper and the carrier is difficult to penetrate. Then, the deposited carrier is diffused to the toner layer and the transfer paper P with the lapse of time as it is, leading to a poor fixing property. In this case, the carrier is removed to some extent only by the heat fixing unit 350, but it is difficult to ensure sufficient fixing performance.
On the other hand, the transfer paper P that easily penetrates the carrier can obtain good fixing performance only by the heat fixing unit 350. Therefore, the driving of the carrier removing unit 330 is switched according to the carrier penetration rate of the transfer paper P.
[0064]
For example, in the case of the carrier removing unit 330 provided with the web 333 shown in FIG. 4, the backup roller 332 and the stretching roller 336 that stretches the web 333 from the upper part of the web 333 are movable up and down. When the carrier removal is performed, the backup roller 332 and the stretching roller 336 are moved in a direction approaching each other (ON direction in the drawing), and when the carrier removal is not performed, they are separated from each other (OFF direction in the drawing). The drive is controlled so as to be moved. This can be performed, for example, by moving a roller by driving and controlling a cam or the like provided on the roller shaft with a solenoid based on a signal on panel operation. This switching may be performed manually, or a sensor for detecting the carrier penetration rate of the transfer paper P may be provided in the apparatus so that the switching is automatically performed according to the detection result.
[0065]
Further, the carrier removing unit 330 provided with the carrier removing roller 331 shown in FIG. The carrier removal roller 331 can be moved up and down, and when performing carrier removal, the carrier removal roller 331 is moved in a direction approaching the backup roller 332, and when carrier removal is not performed, drive control is performed so that the carrier removal roller 331 is moved away. .
[0066]
As described above, it is necessary to remove the carrier from the transfer paper P made of a material that hardly penetrates the carrier and not remove the carrier from the transfer paper P that easily penetrates the carrier. Only when the carrier removal unit 330 can be operated. This can extend the life of the carrier removal unit 330 compared to the case where the carrier removal is always operated. Further, the energy cost for operation can be reduced as compared with the case where the operation is always performed.
Further, for the transfer paper P having a carrier penetration level between the two materials, if the carrier removal level can be switched at several levels, the transfer paper P can be flexibly changed according to the material of the transfer paper P. Carrier removal can be performed.
[0067]
In the second modification of the first embodiment, the surface once used of the web 333 is wound around the winding shaft, and the web 333 is eventually replaced when the web 333 wound around the supply shaft disappears. It was a product. For this reason, periodic replacement is required, and maintenance is troublesome. On the other hand, in the apparatus using the one whose cleaning surface moves endlessly as in the first embodiment, the first modification thereof, and the second to sixth embodiments, the cleaning surface is cleaned, and the surface once used is reused. By using it, there is an advantage that almost no replacement is required, and maintenance is not troublesome.
[0068]
In the first to sixth embodiments described above, the apparatus configured to deposit and remove the carrier from the unfixed image carried on one side of the transfer paper P has been described. In this case, if a device that performs image formation on both sides is provided with a solvent removal member so as to come into contact with both sides of the transfer paper P, a good fixed image can be obtained.
[0069]
[Embodiment 2]
Next, Embodiment 2 applied to a printer which is a double-sided transfer type image forming apparatus that forms images on both sides will be described.
FIG. 10 is a schematic configuration diagram of a main part of the printer according to the second embodiment. The printer includes a pair of image forming units 100X and 100Z, intermediate transfer units 200X and 200Z, an image fixing device 300, a reading unit, a paper feeding unit, and a control unit (not shown).
The image forming units 100X and 100Z are provided with photosensitive drums 10X and 10Z, uniform chargers 20X and 20Z, optical writing devices 30X and 30Z, and wet developing units 40X and 40Z as developing means. Further, a static elimination device (not shown), photoconductor cleaning devices 60X and 60Z, and the like are also provided. After the toner images formed by the pair of image forming units 100X and 100Z form toner images on both sides of the transfer paper P through the secondary transfer unit, the images are fixed simultaneously on both sides by the image fixing device 300. It has come to be.
The developer used in this embodiment is also the same liquid developer as that in the first embodiment.
[0070]
The intermediate transfer units 200X and 200Z oppose the intermediate transfer rollers 201X and 201Z provided to face the photosensitive drums 10X and 10Z, respectively, and the intermediate transfer rollers 201X and 201Z through the transfer paper conveyance path. The secondary transfer bias rollers 202X and 202Z provided, and a secondary transfer power source (not shown) connected to the secondary transfer bias roller are provided. The intermediate transfer rollers 201X and 201Z are provided with an intermediate resistance rubber layer on the surface of a metal roller so that a bias can be applied. As a result, a primary transfer electric field is formed between the photosensitive drum and the intermediate transfer rollers 201X and 201Z. A secondary transfer electric field is formed between the two intermediate transfer rollers 201X and 201Z and the secondary transfer bias rollers 202X and 202Z, respectively.
Since the image fixing device is a characteristic part of the present embodiment, it will be described in detail later.
[0071]
An image forming process using the printer of the second embodiment will be described.
The process of forming a visible image on the photoconductive drums 10X and 10Z is the same as that in the first embodiment. However, in the second embodiment, the photosensitive drum 10X located on the upper side of the two photosensitive drums 10X and 10Z installed in both the upper and lower directions of the transfer paper conveyance path has no contact with the upper surface of the transfer paper. A transfer image is formed. Further, an image for transfer onto the lower surface of the transfer paper is formed on the photosensitive drum 10Z located at the lower part.
Then, the photosensitive drums 10X and 10Z are further rotated to convey the visible image to the primary transfer nip facing the intermediate transfer rollers 201X and 201Z. At this position, the toner images on the photosensitive drums 10X and 10Z are primarily transferred to the intermediate transfer rollers 201X and 201Z by a primary transfer electric field between the photosensitive drum and the intermediate transfer rollers 201X and 201Z. Further, the primary transfer toner images on the intermediate transfer rollers 201X and 201Z are secondarily transferred by a secondary transfer electric field between the intermediate transfer rollers 201X and 201Z and the secondary transfer bias rollers 202X and 202Z. This secondary transfer is performed on both the front and back sides of the transfer paper P that is conveyed to the secondary transfer nip at the correct timing.
[0072]
Next, an image fixing apparatus 300 that is a characteristic part of the present embodiment for fixing an unfixed toner image that has been secondarily transferred onto both surfaces of a transfer sheet will be described below as Examples 1, 2, and modifications thereof. To do.
[Example 1]
FIG. 11 is a schematic configuration diagram of an image fixing apparatus according to Example 1 of Embodiment 2. The image fixing device 300 includes a pre-heating unit 310 having pre-heating roller pairs 311X and 311Z, a carrier removing unit 330 having carrier-removing roller pairs 337X and 337Z, and a heat-fixing unit 350 having fixing roller pairs 360X and 360Z. Then, the transfer paper P is conveyed in the direction of the arrow between the respective roller pairs.
[0073]
The carrier removing roller pair 337X and 337Z is formed of a porous elastic body having at least a micro cell on the roller surface and a porous heat resistance characteristic. Examples of the porous elastic body include materials such as PTFE, cellulose acetate, and polycarbonate having a hole diameter of about 0.1 [μm] to 1.0 [μm] and a thickness of about 50 [μm] to 300 [μm], Alternatively, an elastic body such as urethane, hydrin, or polyimide is used. The microcell of this material has a function of holding the absorbed carrier liquid. These materials are preferably lipophilic materials that absorb and swell the carrier liquid. The carrier removal roller pair 337X and 337Z are provided with cleaning units 343X and 343Z as solvent recovery means, respectively.
[0074]
Next, the operation in the first embodiment will be described.
The transfer paper P conveyed to the pre-heating unit 310 first enters between the pre-heating roller pairs 311X and 311Z and is heated. Here, the pre-heating roller pair 311X, 311Z is heated to about 120 to 150 [° C.] by a heater built in the roller. The transfer paper P that has entered the pair of pre-heating rollers 311X and 311Z is heated from both sides, and the resin in the toner image formed on both sides is turned into a film, so that the carrier liquid contained in the toner image is deposited and partially Penetrates into the transfer paper P, and the rest floats on the upper surface of the toner image.
FIG. 21 illustrates this state, but the amount of carrier liquid that penetrates into the transfer paper P differs depending on the type of the transfer paper P, and the coated paper has a surface coated as compared with a general copy paper. Etc., the permeation amount is slight, and most of them are deposited on the upper surface of the toner image. The carrier liquid floating on the upper surface of the toner image is absorbed by the absorbing material formed on the roller surface while the transfer paper P passes between the next-stage carrier removal roller pair 337X and 337Z. One of the carrier removal rollers has a role of the other pressing means, and the transfer paper is pressed against the pair of removal rollers 337X and 337Z so that the carrier liquid is easily absorbed. The carrier liquid absorbed by the carrier removal roller pair 337X and 337Z is collected by the cleaning units 343X and 343Z attached to the carrier removal roller pair 337X and 337Z, respectively, so that the carrier liquid of the carrier removal roller pair 337X and 337Z is collected. Absorption capacity is maintained. Further, since the carrier liquid collected by the cleaning units 343X and 343Z is in a substantially clear state, it can be reused.
Thereafter, the transfer paper P passes between the pair of fixing rollers 360X and 360Z, and the toner image on the transfer paper P is completely fixed on both the front and back sides.
[0075]
Conventionally, in a fixing device that does not have the carrier removal unit 330, a heating temperature of 180 [deg.] C. to 200 [[deg.] C.] or higher is required to follow high-speed printing. However, according to the configuration in which the carrier removing unit 330 is provided as in the present embodiment, it has been confirmed that sufficient fixability can be obtained even when the temperature of the pair of fixing rollers 360X and 360Z is about 120 [° C.]. This is because, in addition to the effect of removing the excess carrier liquid by providing the carrier removing unit 330, the temperature of the transfer paper at the time of fixing can be increased efficiently by the structure of heating from both sides of the transfer paper at the same time. Even if the heating temperature of the pair 360X, 360Z is greatly reduced as compared with the conventional case, the fixing can be sufficiently performed. As described above, in this embodiment, there is an excellent effect that the high-speed followability can be improved and the power consumption can be significantly reduced.
Further, since the transfer paper P can be linearly conveyed by using the roller arrangement as shown in FIG. 11, the transfer paper conveyance performance can be improved and the occurrence of paper jam can be prevented. Can do. Further, each of the three steps of carrier deposition, removal, and heat fixing can be performed with high accuracy, and the reliability of the apparatus is improved.
Furthermore, the pre-heating unit 310 that is the solvent deposition position, the carrier removal unit 330 that is the solvent removal position, and the heating and fixing unit 350 that is the heating and fixing position are placed on the same portion of the transfer paper conveyance path on both sides of the transfer paper. Set. As a result, the three steps for fixing the image such as carrier deposition, removal, and heat fixing can be performed simultaneously on the front and back of the transfer paper. Can be shortened.
[0076]
[Example 2]
FIG. 12 is a schematic configuration diagram of an image fixing apparatus according to Example 2 of Embodiment 2. The same symbols as those in FIG. 11 have the same functions as those described in the first embodiment. In FIG. 12, blotter belts 340 </ b> X and 340 </ b> Z as removal belts whose surfaces endlessly move are used for the carrier removal unit 330. The blotter belts 340X and 340Z are stretched around the pressing rubber rollers 341X and 341Z and the two tension rollers 342X and 342Z, respectively. The blotter belts 340X and 340Z are formed of an elastic body of a porous material having at least a micro cell on the surface and a porous and heat resistant characteristic. Specifically, the same material as that used for the above-described roller is used. Further, as shown in the figure, cleaning units 343X and 343Z are attached to the blotter belts 340X and 340Z, respectively, so that the carrier liquid is recovered. By using such an endless belt-like configuration, the area of the absorbent material can be increased, and there is an effect of increasing the absorption efficiency of the carrier liquid, and the blotter belt in Example 2 of Embodiment 1 is used. The effect similar to the effect acquired by can be acquired. Furthermore, the same effect as that obtained by the simultaneous double-side fixing and linear conveyance in Example 1 of Embodiment 2 can be obtained.
[0077]
[Modification]
FIG. 13 is a schematic configuration diagram of an image fixing device according to a modification of Example 2 of the second embodiment. In FIG. 13, the blotter belts 340X and 340Z are respectively stretched between two pressing rubber rollers 341X and 341Z and one tension roller 342X and 342Z. The blotter belts 340X and 340Z are pressed against the front and back of the transfer paper P by the two pressing rubber rollers 341X and 341Z, respectively, and the transfer paper P of the blotter belts 340X and 340Z and the transfer paper P of the second embodiment shown in FIG. The contact nip width is increased. Further, except for the arrangement of the pressing rubber rollers 341X and 341Z and one tension roller 342X and 342Z, the description is omitted because it is the same as the second embodiment shown in FIG.
[0078]
According to the modification of the second embodiment, the contact nip width of the blotter belts 340X and 340Z with the transfer paper P can be increased as compared with the first and second embodiments in the second embodiment. Can be further enhanced.
Note that the configuration in which the nip width of the blotter belt is increased as in this modification can also be applied to a configuration in which an image is fixed on one side of a transfer sheet as in the first embodiment.
[0079]
Details of the cleaning units 343X and 343Z applicable to the second embodiment will be described below by taking as an example a case where the cleaning units 343X and 343Z are used in a modification of the image fixing device 300 shown in FIG.
FIG. 14 is a partially enlarged view of the vicinity of the cleaning unit provided on the blotter belt 340X located at the top. The blotter belt 340X is driven by one pressing rubber roller 341X, and a cleaning blade 344X provided in the cleaning unit 343X is disposed to abut against the driving pressing rubber roller 341X with the blotter belt 340X interposed therebetween. The carrier liquid absorbed by the blotter belt 340X is scraped by the cleaning blade 344X and collected in the container 345X. The recovered carrier liquid is guided to a recovery bottle not described from the drain port 346X.
[0080]
FIG. 15 is a partially enlarged view of the vicinity of the cleaning unit 343X provided on the lower blotter belt 340Z. The cleaning unit 343Z is different from the configuration of the cleaning unit 343X shown in FIG. In FIG. 15, a cleaning unit 343Z includes a cleaning roller 347Z that is pressed against a tension roller 342Z that drives the blotter belt 340Z by a pressing means (not shown), and a recovery for abutting against the cleaning roller 347Z to recover the carrier liquid. Blade 348Z. The blotter belt 340Z that has absorbed the carrier liquid is compressed between the tension roller 342Z and the cleaning roller 347Z, and the carrier liquid absorbed by the blotter belt 340Z is squeezed out. Thereafter, the carrier liquid adhering to the cleaning roller 347Z is scraped off by the recovery blade 348Z and recovered from the drain port 346Z.
[0081]
By the way, in a state where the image fixing device 300 is stopped for a long time, the carrier liquid contained in the blotter belts 340X and 340Z gradually moves downward due to gravity, and finally dripped directly below to contaminate the surroundings. There is a risk of malfunction. In order to cope with this problem, as shown in FIGS. 11 to 13, each of the first and second examples and the modified example of the second embodiment is the cleaning unit located at least in the lower part in the gravity direction of the cleaning units 343 </ b> X and 343 </ b> Z. The unit 343Z is arranged as follows. That is, of the blotter belts 340X and 340Z, it is disposed directly below the blotter belt 340Z at the lower part in the direction of gravity, and serves as a lower recovery means. By placing the cleaning unit in this position, even if the apparatus stops for a long time and carrier liquid dripping from the blotter belts 340X and 340Z, it can be received, and the inside of the apparatus is contaminated with the carrier liquid. It can be avoided. The cleaning unit used at this time may be either a blade type as shown in FIG. 14 or a roller type as shown in FIG.
[0082]
Example 3
FIG. 16 is an explanatory diagram of an image fixing apparatus 300 according to Example 3 of the second embodiment. In the third embodiment, the pre-heating unit 310 is disposed at a position facing the pair of pre-heating rollers 311X and 311Z through the transfer paper P so that both the front and back surfaces of the transfer paper P are in contact with each other. In these pre-heating roller pairs 311X and 311Z, a halogen lamp or an infrared heater as a heating means is used. Here, since the pre-heating roller pairs 311X and 311Z are heated from both sides of the recording paper P at the same time, the heating amount per roller can be suppressed lower than when heating from one side of the recording paper P. Therefore, it is possible to reduce energy consumption and shorten the time required for fixing.
Further, the surface of the pre-heating rollers 311X and 311Z is subjected to a surface friction coefficient reduction process for reducing the surface friction coefficient. Specifically, surface treatment with a material having high heat resistance and low surface energy such as a fluorine-based coating material is performed. This prevents unnecessary stress on the toner image formed on the transfer paper P.
[0083]
A carrier removing unit 330 is provided between the preheating unit 310 and the heat fixing unit 350 in the transfer paper P conveyance direction. The carrier removal unit 330 is provided with carrier removal roller pairs 338X and 338Z so as to be pressed against each other from both sides of the transfer paper P, and the transfer paper P is conveyed to the heat fixing unit 350 while being sandwiched between the roller pairs. The surface layer portion of the carrier removal roller pair 338X, 338Z is made of a material that does not absorb or swell with respect to the carrier liquid. For example, a metal roller or a resin material that does not swell in the carrier liquid such as polyimide or polycarbonate is used. It has been.
The carrier removal roller pair 338X and 338Z are provided with cleaning units 343 and 343Z as solvent recovery means at positions facing the respective rollers. These cleaning units 343 and 343Z 'are composed of cleaning blades 344X and 344Z that are in contact with the carrier removal rollers 338X and 338Z, respectively, and containers 345X and 345Z that store carriers scraped off by the blades.
The heat fixing unit 350 is attached such that a pair of heat and pressure rollers 360X and 360Z for heat fixing both surfaces of the transfer paper P are in pressure contact with each other.
[0084]
As described above, according to the third example of the second embodiment, since the pre-heating rollers 311X and 311Z subjected to the surface friction coefficient reduction process are used, the toner image formed on the transfer paper P is unnecessarily stressed. No longer give. Further, unfixed images formed on both sides of the recording paper P can be fixed simultaneously. As a result, a better fixed image can be obtained in a short time.
[0085]
Next, an image fixing apparatus 300 according to Example 4 of Embodiment 2 will be described.
Example 4
FIG. 17 is an explanatory diagram of an image fixing apparatus 300 according to Example 4 of the second embodiment. In the fourth embodiment, a non-contact heating member is provided as a heating unit of the pre-heating unit 310 in place of the contact heating member such as the heating roller pair 311X and 311Z in the third embodiment. Specifically, non-contact preheating heaters 313X and 313Z such as halogen heaters or infrared heaters are used.
According to the fourth embodiment, since the carrier deposition portion 310 does not directly touch the unfixed image surface of the recording paper P, unnecessary stress can be avoided from being applied to the unfixed image. Better images can be obtained.
Further, since the pre-heating heaters 313X and 313Z are heated from both sides of the recording paper P at the same time, the heating amount per heater can be suppressed lower than when heating from one side of the recording paper P. Thus, a great effect can be obtained in reducing energy consumption and shortening the time required for fixing.
[0086]
Next, an image fixing apparatus 300 according to Example 5 of Embodiment 2 will be described.
Example 5
FIG. 18 is an explanatory diagram of an image fixing apparatus 300 according to Example 5 of the second embodiment. In the fifth embodiment, the carrier removing unit 330 in the seventh embodiment is configured by a pair of carrier removing belts 349X and 349Z provided at positions facing each other from both surfaces of the transfer paper P. The carrier removal belt 349X is stretched by a pressing rubber roller 341X and two tension rollers 342X. The carrier removal belt 349Z is stretched by a pressing rubber roller 341Z and two tension rollers 342Z.
The carrier removing belt pair 349X, 349Z is urged so as to press each other by pressing rubber rollers 341X, 341Z so as to sandwich the transfer paper P from both sides. When the transfer paper P passes with both sides pressed by these removal belts, the carrier deposited from the unfixed images on both sides of the transfer paper P is transferred to the carrier removal belts 349X and 349Z, and the transfer paper P Precipitated carriers are removed from both sides. Subsequently, the transfer paper P is conveyed to the heat fixing unit 350 while being sandwiched between these belt pairs. The carrier removal belt pair 349X, 349Z in the fifth embodiment is made of a material that is not impregnated with a carrier liquid. For example, a metal material or a resin material that does not swell in a carrier liquid such as polyimide or polycarbonate is used. Yes.
[0087]
Next, an image fixing apparatus 300 according to Example 6 of Embodiment 2 will be described.
Example 6
FIG. 19 is an explanatory diagram of an image fixing apparatus 300 according to Example 6 of Embodiment 2. In the sixth embodiment, the carrier removal belt 349X is suspended from the pre-heating roller pair 311X, the pressing roller 341X, and the tension roller 342X. Similarly, the carrier removing belt 349Z is suspended by the pre-heating roller 311Z, the pressing roller 341Z, and the tension roller 342Z, and the transfer paper P is conveyed between these belts.
According to the configuration of the sixth embodiment, the preheating rollers 311X and 311Z can also be used as the stretching roller for stretching the carrier removal belts 349X and 349Z. Therefore, the number of rollers can be reduced, and the apparatus can be reduced in size as compared with the case where the rollers are not shared.
[0088]
Next, an image fixing apparatus 300 according to Example 7 in Embodiment 2 will be described.
Example 7
FIG. 20 is an explanatory diagram of an image fixing apparatus 300 according to Example 7 of the second embodiment. In the seventh embodiment, the non-contact heating member is provided instead of the heating roller of the fifth embodiment as the heating means of the preheating unit 310. Specifically, non-contact preheating heaters 313X and 313Z such as halogen heaters or infrared heaters are used. Other configurations are the same as those in the fifth embodiment.
[0089]
As in the seventh embodiment, by using the preheating heaters 313X and 313Z as the non-contact heating members for the preheating unit 310, it is possible to avoid applying unnecessary stress to the unfixed image.
[0090]
In the second embodiment as well, as in the first embodiment, a drive switching device may be provided as a carrier removal degree switching unit that switches and controls the operation state of the carrier removal unit 330 according to the type of transfer paper P.
[0091]
[Embodiment 3]
Next, Embodiment 3 will be described.
FIG. 22 is a schematic configuration diagram of a printer according to the third embodiment. In the figure, this image forming apparatus includes a charger 620 around the photosensitive drum 610 as a latent image carrier, an exposure device (not shown) that irradiates the photosensitive drum 610 with an exposure L, a developing device 700, an intermediate transfer drum 810, and the like. A transfer device 800, a static elimination lamp 640, a cleaning device 650, and the like.
As the material of the photosensitive drum 610, amorphous silicon (a-Si), organic photosensitive member (OPC), or the like can be used.
In addition to the corona discharger as shown in FIG. 22, the charger 20 may be of a type in which a charging roller to which a charging bias is applied is brought into contact with the photosensitive drum 610.
In the exposure apparatus, an arrayed LED, a laser having a scanning optical system, a light image from a document illuminated by a printer, or the like can be used.
[0092]
The transfer device applies a voltage to the intermediate transfer drum 810 in order to generate a transfer electric field that generates a potential difference between the intermediate transfer drum 810 disposed so as to contact the photosensitive drum 610 and the potential of the image portion on the photosensitive member. It has a power supply (not shown). During image formation, the intermediate transfer drum 810 is rotated in the direction of the arrow in the figure. The contact position between the intermediate transfer drum 810 and the photosensitive drum 610 is a primary transfer nip. The toner image that has entered the transfer nip with the rotation of the photosensitive drum 610 is primarily transferred onto the intermediate transfer drum 81031 under the action of the transfer electric field and nip pressure. The toner image primarily transferred in this way is secondarily transferred to the transfer paper P in a region not shown.
[0093]
As the transfer device, an endless intermediate transfer belt 860 may be used instead of the intermediate transfer drum 810 as in the present embodiment. As a transfer method, a method using an electrostatic roller such as the transfer roller 32, a method using corona discharge, an adhesion transfer method, a thermal transfer method, or the like can be used.
[0094]
A case where an image is formed by reversal development in the image forming apparatus having the above configuration will be described. The photosensitive drum 610 is rotationally driven in the arrow direction at a constant speed during copying by a driving means such as a motor (not shown). Then, after being uniformly charged to about 600 [V] in the dark by the charger 20, the exposure device irradiates a light image corresponding to the image, and the electrostatic latent image is carried on the outer peripheral surface of the photosensitive drum 610. Is done. Thereafter, the electrostatic latent image is developed by being attached with charged toner while passing through a portion of the developing device 100.
[0095]
The toner image formed on the photosensitive drum 610 is transferred onto the transfer paper P by a transfer device. Thereafter, the residual charge on the surface of the photosensitive drum 610 is discharged from the photosensitive drum 610 by the charge removal lamp 640. Then, the toner remaining on the surface of the photosensitive drum 610 is removed by the cleaning device 650. Thereafter, before charging by the charger 620 in the next image forming process, the removal of the residual potential on the surface of the photosensitive drum 610 is again removed by a neutralizing lamp (not shown) as necessary.
[0096]
Further, the transfer paper P onto which the toner image has been transferred passes through a fixing device (not shown) to fix the toner to the transfer paper P. Then, the transfer paper P on which the toner image is fixed is discharged from the fixing device to the outside through a paper discharge path. As the fixing device, for example, a fixing method such as heat and pressure fixing, solvent fixing or pressure fixing can be used.
[0097]
The developer used in the image forming apparatus of the present embodiment is a low-viscosity and low-concentration liquid developer that is generally commercially available and used, for example, an insulating liquid called Isopar (trade name: manufactured by ExxonMobil). It is not a low-viscosity liquid developer of about 1 cSt containing toner of a concentration of about 1 [wt%] in the carrier, but a high-viscosity high-concentration liquid developer. The highly viscous and high concentration liquid developer uses a carrier having high insulation properties such as silicone oil, normal paraffin, IsoparM (trade name: manufactured by ExxonMobil), vegetable oil, mineral oil, and the like as a solvent. The solvent contains a toner having a concentration of about 5 to 40 [wt%], and is a liquid developer having a viscosity of about 100 to 5000 [cSt]. Further, the particle diameter of the toner is similarly adjusted from submicron to about 6 [μm].
[0098]
Now, as in the third embodiment, an image developed using a developer containing a non-volatile solvent may have a lower fixability as the solvent content is higher during fixing on the transfer paper P. I understood. This is not limited to the case where the fixing method is by heat and pressure fixing, but it can be said that various fixing methods such as solvent fixing and pressure fixing have different degrees.
Therefore, in the third embodiment, the non-volatile solvent in the image is sufficiently removed prior to fixing the image so that the fixing property of the image can be improved. The features of this embodiment will be described below.
[0099]
First, the developing device 700, which is one of the features of the present embodiment, will be described.
The developing device 700 includes a developing unit 709 including a tank unit 701, stirring screws 702 and 703, anilox roller 704, a regulating blade 705, a developing roller 706, a cleaning blade 707, a feedback unit 708, and the like, and an image carrier top removal member. Sweep rollers 710a and 710b, and a sweep unit 712 including cleaning blades 711a and 711b.
[0100]
The developing roller 706 and the sweep roller 710 are provided with cleaning blades 707 and 711 made of metal blades or rubber blades, respectively. A roller-type cleaning member may be used instead of each cleaning blade. The anilox roller 704 is provided with a regulating blade 705.
[0101]
In particular, by forming the development nip, it is possible to secure a certain development time for the developer toner to move and adhere to the photosensitive drum 610 by the development electric field in the development area. Moreover, the nip width which is the magnitude | size of the surface moving direction in each nip part can be adjusted by adjusting a contact pressure.
[0102]
In the conventional electrophotographic printer, each nip width is set to be the product of the linear velocity of each roller and the development time constant or more. Here, the development time constant is a time required until the development amount is saturated, and is obtained by dividing the nip width by the process speed. For example, if the nip width is 3 [mm] and the process speed is 300 [mm / sec], the development time constant is 10 [msec].
In the present embodiment, the development time constant is set smaller than the development time. Thus, the developer that has not been developed on the photoreceptor can be collected by the developing roller cleaning device without agglomerating.
[0103]
During the developing operation, a thin layer of developer is formed on the developing roller 706 by the anilox roller 704. At this time, the thickness of the developer applied on the developing roller is 1 [cm on the surface of the developing roller.²The pigment content in the toner carried per unit is set to 4 [μg] or more and 40 [μg] or less. For this purpose, a thin layer of developer was applied to a thickness of 5 to 10 [μm]. This is because the amount of developer is 1 [cm on the surface of the developing roller.²When the pigment content in the toner carried per unit is smaller than 4 [μg], a sufficient amount of pigment does not move to the image portion of the latent image formed on the photosensitive drum 610, and the image portion This is because the image density may be reduced. In addition, 1 [cm] on the surface of the developing roller 706²When the pigment content in the toner carried per unit is larger than 40 [μg], the coloring degree of the excess toner remaining on the background portion of the photosensitive drum 610 after development (hereinafter referred to as a non-image portion) becomes high. This is because the image may be fogged. In this embodiment, the thickness of the developer layer applied on the developing roller is set to 8 [μm], and the film thickness of the photosensitive drum 610 is set to 30 [μm].
[0104]
The developer thin layer formed on the surface of the developing roller passes through a developing nip formed by the photosensitive drum 610 and the developing roller.
In general, in an electrophotographic developing device, the surface moving speed of the developing roller is set faster than the surface moving speed of the photosensitive member in order to send sufficient toner to a region where the photosensitive member and the developing device face each other. For this reason, since the toner has a high moving speed with respect to the surface of the photosensitive member, a positional deviation occurs between the toner and the latent image, and the leading edge of the image is blurred or the balance between the vertical and horizontal lines is poor. Appear. This phenomenon is also seen in wet development. In the printer according to the present embodiment, the surface of the developing roller and the surface of the photosensitive drum 610 move at substantially constant speed, and the velocity vector in the tangential direction of the photosensitive drum 610 is not given relative to the toner. Therefore, the above phenomenon does not occur.
[0105]
A developing bias voltage (500 [V]) lower than the photoreceptor surface potential (600 [V]) is applied to the developing roller, and the image surface exposed to 50 [V] or less by the exposure device 3 is exposed. A developing electric field is generated between the two. FIGS. 23A and 23B are views schematically showing the state of the developer in the development nip.
In the image portion of the photoconductive drum 610, as shown in FIG. 23A, the toner T in the developer moves to the photoconductive drum 610 by the electric field to visualize the latent image. On the other hand, in the non-image portion, as shown in FIG. 23B, the non-image portion remaining in the non-image portion due to an electric field formed by the developing bias potential and the photoreceptor potential (hereinafter referred to as a non-image portion electric field). The image portion residual toner T is attracted to the surface of the developing roller. As a result, only a part of the toner T remains in the non-image portion and is almost collected by the developing roller.
[0106]
However, as shown in FIG. 23B, a small amount of carrier liquid C adheres to the non-image portion of the photosensitive drum 610 that has passed through the developing nip. The carrier liquid C is transferred to the transfer paper P, or the carrier liquid that has not been transferred to the transfer paper P is removed by a cleaning device and discarded. As described above, since the carrier liquid C adhering to the non-image portion of the photosensitive drum 610 is excessively consumed, this increases the running cost of the apparatus. Although it is desirable to prevent the carrier liquid C from adhering to the non-image area of the photosensitive drum 610, it is difficult to prevent the carrier liquid C from adhering to the non-image area at all.
[0107]
Therefore, in the printer according to the present embodiment, two sweep rollers 710a and 710b are provided as shown in FIG. 22 in order to sweep the carrier liquid C adhering to the non-image portion of the photosensitive drum 610. . These sweep rollers 710a and 710b are disposed downstream of the developing roller 706 in the rotation direction of the photosensitive drum 610 so as to sandwich the toner layer that is sequentially developed in the drum rotation direction. These sweep rollers 710a and 710b are pressed against the photoconductive drum 610, and the surface thereof moves at a substantially constant speed in the same direction as the photoconductive surface movement direction at a portion facing the surface of the photoconductive drum 610.
[0108]
The sweep rollers 710a and 710b have a cylindrical shape, and an elastic layer 43a made of an elastic body having conductivity is provided on the outer peripheral surface thereof. Urethane rubber can be used as the material of the elastic layer 43a. The rubber hardness of the elastic layer 43a is preferably 50 degrees or less in terms of JIS-A hardness. The material of the elastic layer 43a is not limited to urethane rubber, and any material that does not swell or dissolve with a solvent may be used. The sweep rollers 710a and 710b are configured to have a smoothness with a surface roughness (Rz) of 3 [μm] or less by coating or a tube. Note that the elastic layer 43a may be configured to be provided on the photoreceptor side instead of the configuration provided with the sweep rollers 710a and 710b. Further, the photoreceptor may be composed of an endless belt-like member.
[0109]
When the sweep rollers 710a and 710b are brought into contact with the photosensitive drum 610 with an appropriate pressure, the elastic layer 43a is elastically deformed to form a removal nip. By adjusting the contact pressure, the removal nip width, which is the size of the removal nip in the surface moving direction, can be adjusted.
Note that the surfaces of the sweep rollers 710a and 710b move at substantially constant speed in the same direction as the surface of the photosensitive drum 610 as described above. Accordingly, the velocity vector in the tangential direction of the photosensitive drum 610 is not provided relative to the toner T developed on the photosensitive drum 610. Thus, excess carrier liquid can be removed without disturbing the toner image on the photosensitive drum 610 by the sweep rollers 710a and 710b.
[0110]
Further, a predetermined bias is applied to each of the sweep rollers 710a and 710b. FIG. 24A is an explanatory diagram of a bias (hereinafter referred to as a sweep potential) applied to the sweep rollers 710a and 710b in the present embodiment. A voltage is applied to the sweep rollers 710a and 710b so as to be a potential between the non-image portion potential of the photosensitive drum 610 and the image portion potential. Assuming that the potentials applied to the sweep rollers 710a and 710b are Vdr1 and Vdr2, the relationship between the potentials is as shown in Equation 1.
[Expression 1]
Photoconductor non-image portion potential> Developing roller potential> Vdr1> Vdr2> Photoconductor image portion potential In this embodiment, the photoreceptor non-image portion potential is 600 [V], the developing roller potential is 500 [V], and Vdr1 is 450. [V] and Vdr2 were set to 400 [V]. The photoreceptor image portion potential is 50 [V] or less.
[0111]
By applying a voltage to the sweep rollers 710a and 710b as described above, the following effects are obtained at the nip portion between the photosensitive drum 610 and the sweep rollers 710a and 710b. The toner in the image area on the photoconductive drum 610 is compressed by the electric field to the photoconductive drum 610 and is not peeled off. Further, the developer adhering to the non-image area on the photosensitive drum 610 is attracted to the sweep roller 710a side by the force of the electric field and collected. Therefore, by providing the sweep rollers 710a and 710b, it is possible to remove and collect excess carrier liquid C on the photosensitive drum 610, and to remove and collect even a small amount of excess toner adhering to the non-image area.
As shown in FIG. 23C, a part of the toner T adhering to the non-image portion on the photosensitive drum 610 remains on the photosensitive drum 610 side without moving to the surface of the developing roller 706 in the developing nip. And cause fogging. The sweep rollers 710a and 710b can remove and collect toner T (hereinafter referred to as “fogging toner”) that causes fogging.
[0112]
FIG. 25 is an enlarged view of the vicinity of the removal nip, schematically showing a state in which the carrier liquid C adhering to the non-image portion of the photosensitive drum 610 is removed by the upstream sweep roller 710a. As shown in the figure, when the developer carried on the surface of the developing roller 706 passes through the developing nip N1, the carrier liquid adheres to the non-image portion of the photosensitive drum 610. At this time, the developer composed of the toner T and the carrier adheres to the image portion of the photosensitive drum 610. Then, when the carrier liquid C adhering to the non-image portion of the photosensitive drum 610 passes through the removal nip with the sweep roller 710a, it is divided into one that remains on the surface of the photosensitive drum 610 and one that transfers to the surface of the sweep roller 710a. . That is, the amount of carrier liquid C adhering to the non-image portion of the photosensitive drum 610 is removed from the surface of the photosensitive drum 610 by the amount transferred to the sweep roller 710a. The carrier liquid C removed by the sweep roller 710 a is cleaned from the surface of the sweep roller 710 a by the cleaning member and returned to the developer storage tank 708.
Here, the developer storage tank includes a supply unit 708a that stores liquid developer to be supplied to the anilox roller 704, and a recovery unit 708b that collects residual toner removed from the development roller and the sweep roller 710a. It has become. The supply unit 708a and the recovery unit 708b are provided side by side through a gear pump (not shown). In the case of FIG. 25, the collection unit 708b is positioned below the cleaning blade provided on the developing roller and the sweep roller 710a. As a result, the residual toner that remains on the developing roller 706 without being used for development and the non-image portion residual toner that is attracted from the surface of the photosensitive drum 610 by the sweep roller 710a and removed by the cleaning blade is collected in the collecting unit 708b. Is done. Then, it is conveyed again to the supply unit by the gear pump and can be reused for development. Thus, a residual toner recycling mechanism and a residual toner recycling mechanism on the removal member are configured. As a result, the consumption of the carrier liquid C can be reduced and the running cost can be reduced as compared with the case where the sweep roller 710a is not provided.
In FIG. 25, the carrier liquid cleaned from the surface of the sweep roller 710a falls down as it is, and is directly accommodated in the same recovery unit 708b as the undeveloped developer removed from the surface of the developing roller. . This is an example, and in the present embodiment, the carrier liquid cleaned from the two sweep rollers 710a and 710b is temporarily stored in the dedicated tanks 713a and 713b (see FIG. 22). The dedicated tanks 713a and 713b are returned to the developer storage tank 708.
The sweep roller 710a removes and collects a part of the carrier liquid C in the image portion in addition to the removal of the excess carrier liquid C in the non-image portion. The carrier liquid C is also adhered to the image portion of the photosensitive drum 610 that has passed through the developing nip together with the toner T. When the surface of the image portion of the photosensitive drum 610 passes through the removal nip with the sweep roller 710a, a part of the carrier liquid C adhering to the image portion of the photosensitive drum 610 is transferred to the sweep roller 710a side.
[0113]
The sweep rollers 710a and 710b for removing the excess carrier liquid on the surface of the photosensitive drum 610 as described above are provided in two stages in this embodiment. How the carrier liquid is removed in this way will be specifically described below with the upstream sweep roller 710a as the first sweep roller and the downstream sweep roller 710b as the second sweep roller. The specifications of the sweep rollers 710a and 710b and the photosensitive drum 610 used to obtain the following results are as follows. The outer diameter of the sweep rollers 710a and 710b was set to φ24 [mm], the rubber hardness of the elastic layer 43a was set to 20 degrees (JIS-A), and the outer diameter of the photosensitive drum 610 was set to φ80 mm. The removal nip width between the sweep rollers 710a and 710b and the photosensitive drum 610 was set to 2 [mm].
[0114]
[Table 1]

Table 1 shows the result of excess carrier removal by the sweep rollers 710a and 710b.
As shown in Table 1, the developer carried on the surface of the developing roller is 0.8 [mg / cm²], The non-image portion of the photosensitive drum 610 that has passed through the developing nip N1 is 0.30 [mg / cm²The carrier liquid C is attached. When the carrier liquid C adhering to the non-image portion of the photosensitive drum 610 passes through the removal nip with the first sweep roller 710a, the adhering amount is 0.15 [mg / cm.²] To decrease. That is, 0.15 [mg / cm] of the carrier liquid C adhering to the non-image portion of the photosensitive drum 610.²] Is removed by the first sweep roller 710a. That is, the first sweep roller 710a can remove about half of the excess carrier liquid C adhering to the non-image portion on the photosensitive drum 610 during development.
On the other hand, the image portion of the photoconductive drum 610 that has passed through the development nip has 0.63 [mg / cm²The carrier liquid C is attached. When the carrier liquid C adhering to the image portion of the photosensitive drum 610 passes through the removal nip with the first sweep roller 710a, the adhering amount is 0.49 [mg / cm.²] To decrease. That is, 0.14 [mg / cm] of the carrier liquid C adhering to the image portion of the photosensitive drum 610.²] Is removed by the sweep roller 43.
The carrier liquid C removed by the first sweep roller 710a is cleaned from the surface of the first sweep roller 710a by the cleaning blade 711a and stored in the dedicated tank 713a, and then returned to the developer storage tank 708.
[0115]
Here, since the rubber hardness of the sweep roller used in this experiment is about 20 degrees (JIS-A), the pressure inside the removal nip is low. Therefore, if the pressure inside the removal nip is increased (for example, the rubber hardness of the sweep roller is set higher than 50 degrees), the amount of carrier liquid that can pass through the removal nip is also limited. C adhesion can be reduced. However, if excessive pressure is applied to the photosensitive drum 610 and the sweep roller, the toner particles in the image area cannot pass through the removal nip, and there is a high possibility of causing problems such as image flow. Therefore, the preferable range of the rubber hardness of the elastic layer is 50 degrees (JIS-A) or less, more preferably about 20 degrees. However, the numerical value of the rubber hardness of the elastic layer is an example, and is not limited to this numerical value.
[0116]
Next, the result of excess carrier removal by the second sweep roller 710b will be described. As described above, a voltage of 400 [V] is applied to the second sweep roller 710b.
As shown in Table 1, the non-image portion of the photosensitive drum 610 that has passed through the removal nip with the first sweep roller 710a is 0.15 [mg / cm²The carrier liquid C is attached. When the carrier liquid C adhering to the non-image portion of the photosensitive drum 610 passes through the removal nip with the second sweep roller 710b, the adhering amount is 0.08 [mg / cm.²] To decrease. That is, 0.07 [mg / cm] of the carrier liquid C adhering to the non-image portion of the photosensitive drum 610.²] Is removed by the second sweep roller 710b. That is, the second sweep roller 710b can also remove about half of the excess carrier liquid C adhering to the non-image area on the photosensitive drum 610 during development.
On the other hand, the image portion of the photosensitive drum 610 that has passed through the development nip has 0.49 [mg / cm²The carrier liquid C is attached. When the carrier liquid C adhering to the image portion of the photosensitive drum 610 passes through the removal nip with the second sweep roller 710b, the adhering amount is 0.41 [mg / cm.²] To decrease. That is, 0.08 [mg / cm] of the carrier liquid C adhering to the image portion of the photosensitive drum 610.²] Is removed by the second sweep roller 710b.
The carrier liquid C removed by the second sweep roller 710b is cleaned from the surface of the second sweep roller 710b by the cleaning blade 711b and stored in the dedicated tank 713b, and then returned to the developer storage tank 708.
[0117]
On the surface of the photosensitive drum 610 entering the removal nip by the second sweep roller 710b, the fog of the non-image portion has already been substantially removed by the first sweep roller 710a. Then, the removal electric field generated between the voltage applied to the second sweep roller 710b and the photosensitive drum 610 compresses the toner T in the image area onto the surface of the photosensitive drum 610, and further removes the carrier liquid between the toner particles. It was done.
[0118]
As described above, the toner is changed as follows by removing the excess carrier on the photosensitive drum 610 by the first sweep roller 710a and the second sweep roller 710b. Here, “image density” described below is an optical density of the formed image, and “developer density” is a weight ratio of the toner in the developer to the developer constituting the image.
(1) Developer concentration at the development nip
In order to calculate the developer concentration of the image on the photosensitive drum 610 immediately after development, the toner weight in the developer constituting the image was calculated using Equation 2.
[Expression 2]
Toner weight in image = developer application amount on developing roller × developer toner concentration × development rate
Developer application amount on developing roller = 0.8 [mg / cm²]
Developer toner concentration = 15 [%]
Development rate = 100 [%]
As a result of the calculation, the developer concentration of the developer constituting the image immediately after development was 19 [%].
(2) Developer concentration after carrier removal by the first sweep roller 710a
The image density of the image on the photosensitive drum 610 could be maintained at 95 [%] after passing through the removal nip by the first sweep roller 710a. Therefore, the toner weight in the developer constituting the image can be obtained by Equation 3.
[Equation 3]
Toner weight in image = toner weight on photosensitive drum immediately after development × 95 [%]
From the results calculated in this way and the results shown in Table 1 above, the developer concentration of the developer constituting the image after carrier removal by the first sweep roller 710a was 23%.
(2) Toner after carrier removal by the second sweep roller 710b
Further, after passing through the removal nip by the second sweep roller 710b, the image density was maintained at 95 [%]. Therefore, from the results shown in Table 1, the developer concentration of the developer constituting the image after the carrier removal by the second sweep roller 710b was 26 [%].
[0119]
The fog toner 40c can be efficiently removed by the first sweep roller 710a and the second sweep roller 710b. Therefore, a slight amount of fog toner 40c may remain in the developing nip between the photosensitive drum 610 and the developing roller 706, and a fog removing electric field (potential difference between the developing bias applied to the developing roller 706 and the photosensitive member charging potential). ) Can be kept low. Therefore, the charging potential of the photosensitive drum 610 can be lowered. As a result, various advantages such as an improvement in durability of the photosensitive drum 610, a reduction in the burden on the charging device, and a reduction in exposure power occur.
In addition, by setting the voltages of the first sweep roller 710a and the second sweep roller 710b as described above, there are the following advantages. That is, the second sweep roller 710b collects the fog toner attached to the non-image portion without removing the toner on the image portion, and can also remove the excess carrier on the image portion.
[0120]
As described above, since the liquid developer in the non-image area and the excess carrier in the image area can be removed by the first sweep roller 710a and the second sweep roller 710b, an image with good reproducibility of fine lines without ribs can be formed on the photoconductor. . Further, the developer concentration of the developer that forms a toner image on the photosensitive drum 610 can be increased.
[0121]
As for the bias applied to the first sweep roller 710a and the second sweep roller 710b, it is sufficient that no discharge is generated in the photosensitive member. In particular, the upper limit of the voltage applied to each is determined by the characteristics of the photoreceptor and toner. Further, the fog of the non-image portion that cannot be removed by the first sweep roller 710a may be removed by the second sweep roller 710b. In this case, the bias applied to the second sweep roller 710b is set between the image portion surface potential and the non-image portion surface potential of the toner image when passing through the first sweep roller 710a. Thus, if the fog of the non-image portion that cannot be collected by the first sweep roller 710a is removed by the second sweep roller 710b, it is not necessary to collect the fog toner of the non-image portion by the first sweep roller 710a. Therefore, it is convenient to reuse the developer.
[0122]
Further, as a modification of the third embodiment, the bias value may be set so as to exhibit different actions depending on the bias applied to the first sweep roller 710a and the second sweep roller 710b. For example, a bias is applied to the first sweep roller 710 a so as to attract the developer mainly attached to the background portion of the photosensitive drum 610. The second sweep roller 710b is applied with a bias for adhering the carrier adhering to the image portion of the photosensitive drum 610 and compressing the toner of the image portion onto the surface of the photosensitive drum 610. As a specific example, the first sweep roller 710a is set to 450 [V], the ground toner and the carrier liquid remaining on the non-image portion are removed, and the second sweep roller 710b is set to 500 [V]. It is conceivable to apply and further compress the image portion to remove the carrier of the image portion and the carrier of the non-image portion. The bias shown here is only an example, and the present invention is not limited to this. A bias that can generate an electric field that can remove the background contamination of the photosensitive drum 610 with the first sweep roller, and an electric field that does not remove the image while removing the carrier may be applied with the second sweep roller.
[0123]
Note that the sweep electric field described in the present embodiment needs to be optimized so as to satisfy factors such as the image density of the non-image area and the image area, the toner aggregation state, and the like. It is to be determined above. Further, the preferred strength of the sweep electric field depends on the mobility of the toner. For this reason, the electric field strength as described above is preferable in the developer used in Embodiment 3, but the electric field strength is not limited to the case where different types of toner are used. It is sufficient that the developer remaining on the developing roller or the sweep roller after development does not aggregate.
[0124]
Further, an intermediate transfer member is disposed so as to contact the photosensitive drum 610 of the liquid image forming apparatus, and a bias voltage is applied to the intermediate transfer member so as to generate an electric field that generates a potential difference from the potential of the image portion on the photosensitive drum 610. Apply. In the third embodiment, by applying −300 [V] to the intermediate transfer member, it was possible to perform primary transfer of the image onto the intermediate transfer member satisfactorily. The intermediate transfer member will be described with an intermediate transfer drum 810 in the third embodiment.
[0125]
Conventionally, as an intermediate transfer member, an endless belt of a low-resistance conductive member having a predetermined thickness, for example, having a thickness of 30 to 150 [μm], is conductive to polyimide, PET (polyethylene terephthalate), PVDF resin, or the like. These materials (carbon, metal powder, etc.) were mixed at a constant rate. However, if the transfer paper P is secondarily transferred to a paper having a relatively large concave portion on the surface, such as plain paper, by the intermediate transfer belt 860 made of the conventional material, the following problems occur. That is, as described above, since the surface of the intermediate transfer belt 860 is hard, it cannot follow the surface recesses of plain paper or the like, resulting in density unevenness due to transfer failure. Therefore, the intermediate transfer drum 810 according to the present embodiment is mainly composed of an elastic body so as to follow the concave portion on the surface of plain paper or the like so as not to cause transfer defects.
[0126]
FIG. 26 is an explanatory diagram of an example of the intermediate transfer drum 810 according to the present embodiment. The intermediate transfer drum 810 includes an elastic conductor, a drum 812 in which the elastic conductor 811 is bonded to a metallic drum, and a surface coat layer 813. The elastic conductor can be made of, for example, polyurethane rubber in which carbon is dispersed. This elastic conductor has a thickness of 200 to 2000 [μm] and a volume resistivity of 10³-10¹²If [Ωcm] and the hardness is 15 to 80 degrees (Hs) by JISA, a predetermined effect can be obtained. The surface coat layer is for improving the releasability of toner particles to improve the secondary transfer property and improving the separation property of the transfer paper P after the secondary transfer. For example, a coating layer containing a fluorine-based resin is formed by coating to a thickness of 5 to 60 [μm].
[0127]
The intermediate transfer drum 810 can also prevent part of the carrier liquid C in the image area from adhering to the non-image area in addition to preventing the excess carrier liquid C from adhering.
[Table 2]

Table 2 shows the result of removing the excess carrier from the image and the non-image portion by the primary transfer to the intermediate transfer drum 810. In Table 1, the image portion of the photosensitive drum 610 that has passed through the nip with the second sweep roller 710b is 0.41 [mg / cm²The developer containing the carrier liquid C is attached. The image portion of the intermediate transfer drum 810 that has passed through the primary transfer nip formed by the intermediate transfer drum 810 and the photosensitive member has 0.35 [mg / cm²The developer containing the carrier liquid C is attached. Further, at this time, the toner image of the image portion on the photoconductor was maintained at an image density of 100% in the primary transfer step, and a toner image could be formed on the intermediate transfer body. Therefore, by forming the primary transfer image on the intermediate transfer drum 810, the developer concentration in the image portion of the toner image formed on the intermediate transfer drum 810 can be estimated to be about 30 [%].
[0128]
As a result, the image is primarily transferred from the photoconductor to the intermediate transfer drum 810 using the intermediate transfer drum 810, whereby the image portion of the toner image on the photoconductor leaves the carrier liquid on the photoconductor to complete the primary transfer. . Therefore, the toner density of the image portion of the toner image on the intermediate transfer drum 810 can be further increased. Furthermore, the carrier adhesion amount in the non-image area can be reduced to almost half.
[0129]
Further, in order to sweep (clean) the carrier liquid C adhering to the image portion or the non-image portion from the toner image on the intermediate transfer member, as shown in FIG. 22, the intermediate transfer member sweep as an intermediate transfer member removing member is used. A roller 820 is provided. The intermediate transfer member sweep roller 820 is installed on the intermediate transfer drum 810 in such a manner that it is downstream in the rotation direction of the contact point (primary transfer position) with the photosensitive member and sandwiches the developed toner layer. ing. The surface of the intermediate transfer member sweep roller 820 moves at substantially the same speed as the surface of the intermediate transfer drum 810.
[0130]
The intermediate transfer body sweep roller 820 is provided with an elastic layer of an elastic body on the outer peripheral surface. Urethane rubber can be used as the material of the elastic layer. The rubber hardness of the elastic layer is desirably 50 degrees or less in terms of JIS-A hardness. The material of the elastic layer is not limited to urethane rubber, and any material that does not swell or dissolve with a solvent may be used. Further, the intermediate transfer member sweep roller 820 is configured to have a smoothness with a surface roughness (Rz) of 3 [μm] or less by coating or a tube. Instead of the configuration in which the elastic layer is provided on the intermediate transfer member sweep roller 820, a configuration in which the elastic layer is provided on the intermediate transfer member side may be employed. Further, the intermediate transfer member may be composed of an endless belt-like member.
[0131]
When the intermediate transfer member sweep roller 820 is brought into contact with the intermediate transfer drum 810 with an appropriate pressure, the elastic layer is elastically deformed to form a removal nip. By adjusting the contact pressure, the removal nip width, which is the size of the removal nip in the surface moving direction, can be adjusted.
Note that the surface of the intermediate transfer member sweep roller 820 moves at substantially the same speed as the surface of the intermediate transfer drum 810 as described above. Therefore, the velocity vector in the tangential direction of the intermediate transfer drum 810 cannot be given relative to the toner developed on the intermediate transfer drum 810. Accordingly, the excess carrier liquid C can be removed without disturbing the toner image on the intermediate transfer drum with the intermediate transfer member sweep roller 820.
[0132]
Note that the intermediate transfer drum 810 can also prevent a part of the carrier liquid in the image portion from being attached in addition to preventing the excess carrier liquid from adhering to the non-image portion. In Table 2, the image area of the intermediate transfer drum 810 is 0.35 [mg / cm²The developer containing the carrier liquid adheres. The image portion of the intermediate transfer drum 810 that has passed through the nip formed by the intermediate transfer drum 810 and the intermediate transfer member sweep roller is set to 0. [mg / cm²The developer containing the carrier liquid C is attached.
Further, at this time, the image portion toner image on the photoconductor was maintained at an image density of 100% in the intermediate transfer sweep process, and a toner image could be formed on the intermediate transfer body. Accordingly, the developer density in the image portion of the toner image formed on the intermediate transfer drum 810 is estimated to be about 35 [%] by performing the intermediate transfer sweep on the intermediate transfer drum 810.
As described above, both the intermediate transfer member and the intermediate transfer member sweep roller 820 are used. As a result, the image portion developer density of the toner image on the intermediate transfer member can be further increased in two stages, that is, primary transfer from the photosensitive drum 610 to the intermediate transfer member and carrier removal by the intermediate transfer member sweep roller 820. did it. In the third embodiment, since the primary transfer bias −300 [V] for transferring the toner image to the intermediate transfer drum 810 is applied as the bias applied to the intermediate transfer member sweep roller 820, about 0 [V]. It was good.
[0133]
In the third embodiment, in order to improve the fixability of the image on the transfer paper P, a configuration in which the carrier is removed before reaching the fixing nip is shown. As described above, when the carrier is removed at a plurality of locations on the photosensitive drum 610, the intermediate transfer nip, the intermediate transfer member, and the like, before the secondary transfer onto the transfer paper P, the image portion developer concentration is already set to 35. It was possible to increase to [%]. As a result, the image fixing property after secondary transfer onto the transfer paper P became stable.
[0134]
By the way, it has been found that an increase in developer concentration is effective in improving the fixability of the image, but the transferability of the image is lowered, which causes image deterioration during transfer.
FIG. 27 is a graph showing the relationship between the developer concentration and the secondary transfer rate to the transfer paper P. The transfer rate is calculated using the image density on the intermediate transfer body after the primary transfer as a molecule and the difference in image density on the intermediate transfer body after the primary transfer and after the secondary transfer as a denominator. In the solid line in the graph, when the developer concentration is 30 [%] or less, the transfer rate to the transfer paper P body is about 90 [%], and a good image with few image defects can be obtained. As the developer concentration increases, the transfer rate decreases. In this graph, if the transfer rate is 50% or more, it is an allowable range. When the developer concentration reaches 70 [%], the transfer rate becomes less than the allowable range, and secondary transfer failure occurs.
The mechanism by which transfer failure occurs due to an increase in developer concentration can be explained as follows. In this embodiment, a carrier having a high electric resistance value at a high flash point is used as the carrier in the developer. High flash point carriers hardly volatilize. In this embodiment, the flash point of the carrier is 250 [° C.] or higher. Here, the flash point measurement method includes a tag sealing type, a seta sealing type, a Cleveland open type, and the like, and the temperature range that can be measured by each measuring method is different. Specifically, if the tag sealing type is less than 0 [° C.] and cannot be measured with a trowel, the kinematic viscosity is measured, and then the range of 0 to 80 [° C.] is measured with the seta sealing type. Further temperatures are measured by the Cleveland open method. Therefore, the flash point measurement method used in the present invention uses the Cleveland open type.
Three examples of carriers that can be specifically used are given below. Toray Dow Corning Silicone Oil SH200-50CS has a flash point of 310 [° C], Toray Dow Corning Dimethyl Silicone SH200-20CS has a flash point of 255 [° C], and SH200-20CS has a flash point of 325 [° C]. ], Shin-Etsu Chemical's silicone oil KF96-50CS has a flash point of 310 [° C]. Each flash point was measured using the Cleveland open type.
Note that carriers with a low flash point compared to carriers with a high flash point are Isopar L made by ExxonMobil with a flash point of 60 [° C], Isopar G made by ExxonMobil with a flash point of 41 [° C], etc. It has been. These carriers are not used in the printer of this embodiment.
In the developer, an insulating resin (hereinafter referred to as a fixing resin) containing a pigment component as toner particles is dispersed in the carrier liquid having the high flash point. Further, a uniformly dispersed developer may be obtained by dispersing a fixing resin containing a carrier liquid and a pigment component in a mixture of an appropriate amount of a resin called a dispersion resin and a charge control agent. In particular, in a fixing resin using a pigment having a low electrical resistance value such as carbon black, conductive particles such as carbon black are present on the outer periphery of the toner particles.
When such a developer is removed to improve the fixability, the carrier liquid that worked as an insulating film cannot be interposed on the outer periphery of the toner particles, and the toner T and the carbon black are connected to each other. Become a layer. FIG. 31A shows a state where the carrier C exists between the toner particles, and FIG. 31B shows a state where the toner particle layer is formed. Since the toner particle layer has a low resistance, the insulating properties of the toner particles cannot be maintained. For example, as in this embodiment, when a positively charged liquid developer receives a negative transfer bias at the primary transfer or secondary transfer nip, the charge is injected and the polarity of the toner particles cannot be maintained. That is, the polarity of the toner is reversed, and the movement of the toner particles cannot be controlled by the action of the electric field due to the transfer bias.
[0135]
Table 3 shows the results of examining the secondary transferability for each range by dividing the electrical resistance of the developer step by step. The results are shown as “◯” when the transferability is good and “X” when the transferability is bad. It is.
[Table 3]

Each range of electrical resistance in the table includes a lower limit value and does not include an upper limit value. In the case of the developer A used in this embodiment, when the developer concentration is 30 [%], the electric resistance of the developer is 10¹⁰-10¹⁴When [Ωcm] and 50 [%], the electric resistance of the developer is 10⁶-10¹⁰When [Ωcm] and 70 [%], the electric resistance of the developer is 10³-10⁶It belongs to the range of [Ωcm].
From this result, the electric resistance of the toner layer is 10⁶Above [Ωcm], the secondary transferability is good and the electric resistance of the toner layer is 10⁶It was found that the secondary transferability deteriorates below [Ωcm]. This is because the electric resistance of the developer when transferring is affected by transferability. It was also found that the electrical resistance of developer A decreases as the developer concentration increases.
[0136]
From the above results, even if the carrier in the developer is removed to some extent to improve the fixability, it is possible to maintain good fixability as long as the liquid developer does not decrease the electric resistance too much. it is conceivable that. Therefore, it was considered to use Developer B whose electric resistance of the developer hardly changes depending on the developer concentration. This developer B is obtained by treating the fixing resin so that the pigment component does not appear on the surface of the fixing resin, and the transfer property is as shown by the one-dot chain line in FIG. Therefore, by performing image formation using the developer B, both transferability and fixability can be kept good.
As the structure of the developer B, for example, a structure in which a pigment component appearing on the surface of the fixing resin is coated with a dispersion resin can be considered. Furthermore, it is effective to use a pigment component having a resistance value of carbon black subjected to high resistance treatment.
[0137]
As described above, in the present embodiment, the experiment was performed by the reversal development method that visualizes the electrostatic latent image on the photosensitive drum 610 at a process speed of 300 [mm / sec].
In this embodiment, the case where an image is formed by reversal development has been described. However, an image can also be formed by regular development.
[0138]
[Embodiment 4]
Next, Embodiment 4 will be described.
FIG. 28 is a schematic configuration diagram of a printer according to the fourth embodiment. In this printer, the liquid developing devices used in the third embodiment are arranged in parallel on the intermediate transfer belt 860 for each color. With this arrangement, different color images are sequentially transferred onto the intermediate transfer belt 860 in order to form a full-color image on the intermediate transfer belt 860. A color liquid image forming apparatus that secondarily transfers a color image onto a transfer sheet P by a secondary transfer roller 890. Further, in the fourth embodiment, one sweep roller that contacts the photosensitive drums 610Y, M, C, and K is configured, but two sweep rollers may be provided as in the third embodiment.
[0139]
Since the configuration of the liquid developing apparatus is the same as that of the third embodiment, the description thereof is omitted.
Next, the intermediate transfer unit will be described. The intermediate transfer unit 800 includes suspension rollers 851, 852, 853, 854, 855, 856, 857, and 858, an intermediate transfer belt 860 stretched around these suspension rollers, and primary transfer bias rollers 870K, 870Y, 870M, and 870C. And a cleaning device 880 having a cleaning blade.
[0140]
The paper transfer unit includes a secondary transfer bias roller 890 and a secondary transfer power source (not shown) connected to the secondary transfer bias roller 890. Further, prior to the secondary transfer step, an intermediate transfer member sweep roller 820 as an intermediate transfer member removal member is disposed on the intermediate transfer belt 860.
[0141]
Next, the intermediate transfer belt 860, the primary transfer bias roller, the secondary transfer bias roller, and the like will be described more specifically. The intermediate transfer belt 860 is stretched around the suspension rollers 851, 852, 853, 854, 855, and 856 and the photosensitive drums 610K, 610Y, 610M, and 610C so as to have a predetermined tension, and is counterclockwise as indicated by an arrow. It can be rotated. Further, the primary transfer charge applying means is arranged as follows, for example. That is, the primary transfer bias roller 870K is opposed to the photosensitive drum 610K, and the intermediate transfer belt 860 is sandwiched between the primary transfer bias roller 870K and the photosensitive drum 610K. The primary transfer bias roller 870K also serves as an electrode for applying a primary transfer bias, and a predetermined transfer bias is applied to the primary transfer bias roller 870K from a primary transfer power source (not shown). A secondary transfer bias roller 890 is disposed facing the suspension rollers 852 and 857, and the secondary transfer bias roller 890 also serves as an electrode for applying a secondary transfer bias. A predetermined transfer bias is applied to the secondary transfer bias roller 890 from a secondary transfer power source (not shown).
The suspension roller 853 is in contact with the intermediate transfer member sweep roller 820 and grounds the intermediate transfer belt 860 from the back surface. Then, a bias voltage was applied to the intermediate transfer member sweep roller 820 by a removal electrode (not shown) so that an electric field could be generated between the intermediate transfer member sweep roller 820 and the intermediate transfer member sweep roller 820. Any bias may be applied to the intermediate transfer member sweep roller 820 as long as it generates an electric field that works so that the toner particles are compressed by the intermediate transfer belt 860. The region of the intermediate transfer belt 860 that the intermediate transfer member sweep roller 820 faces is positioned between the suspension rollers 857 and 858 and is independent of the electric field formed in the primary and secondary transfer nips. An electric field can be formed.
In the fourth embodiment, it is necessary to ground the suspension roller 853 to the ground so that the secondary transfer bias does not affect the primary transfer bias of the fourth color, and it is necessary to apply a bias voltage to the intermediate transfer member sweep roller 820. there were.
[0142]
Next, the photosensitive drum 610K on which the visible image is formed is rotated, and the visible image moves to the primary transfer nip where the photosensitive drum 610 and the intermediate transfer belt 860 are in contact with each other. Then, at the primary transfer nip, a negative bias voltage, for example, −300 to −500 [V], which is the reverse polarity of the positive toner is applied to the back surface of the intermediate transfer belt 860100 via the primary transfer bias roller 870K. . The developer of the visible image on the photosensitive drum 610K is attracted to the intermediate transfer belt 860 and transferred onto the intermediate transfer belt 860 by the electric field generated by the applied voltage (primary transfer). In the full-color image forming operation, an image is transferred to the intermediate transfer belt 860 in the order of yellow developer, magenta developer, cyan developer, and black developer to form a full-color image.
[0143]
As described above, the printer of the present embodiment performs a secondary transfer of the full-color image formed by sequentially transferring the image onto the intermediate transfer belt 860 sequentially onto the transfer paper P. This can reduce the amount of carrier compared to the direct transfer type image forming apparatus that sequentially transfers the image on the photosensitive drum 610 onto the transfer paper P. This is because the first color station (hereinafter referred to as the first station) that performs the primary transfer onto the intermediate transfer belt 860 abuts on the dry intermediate transfer belt 860, so that the carrier transfer amount is large. For the second and subsequent stations, the primary transfer can be performed while the intermediate transfer body is wet, so that the adhesion of the carrier liquid can be reduced. Further, it is apparent that the color toner images on the intermediate transfer belt 860 have different amounts of carrier liquid at portions where colors overlap and portions where colors do not overlap. Therefore, the carrier liquid can be removed by compressing the toner onto the intermediate transfer belt 860 by the intermediate transfer body sweep roller 820, and the developer concentration can be increased.
[0144]
[Table 4]

Table 4 shows changes in the amount of developer attached on the intermediate transfer belt 860 for each station when there is an image at the first station and no image at the other stations. The transfer rate of the toner from the photoconductor to the intermediate transfer belt 860 is 100 [%], and the image on the photoconductor is maintained at 95 [%] even when passing through the sweep roller at a development rate of 100 [%]. The developer density of the toner image after the primary transfer on the intermediate transfer belt 860 when the transfer is completed at the four stations is estimated to be 21 [%]. By the intermediate transfer member sweep roller 820 of the fourth embodiment, the toner component after the primary transfer on the intermediate transfer belt 860 has a carrier component of 0.15 [mg / cm].²] Removed. Therefore, the toner density on the intermediate transfer belt 860 after passing through the sweep nip with the intermediate transfer member sweep roller 820 has a developer concentration of 29 [%].
[0145]
Next, the intermediate transfer belt 860 to which the full-color image has been transferred is driven to enter the secondary transfer nip where the intermediate transfer belt 860 and the transfer paper P as a recording medium conveyed in the direction of the arrow from the paper supply unit (not shown) abut. Move the image. In this secondary transfer nip, a negative bias voltage, for example, −800 to −2000 [V] is applied to the back surface of the transfer paper P via a secondary transfer bias roller 890 as a secondary transfer device, and for example, 50 [N / cm²] Apply some pressure. By the electric field and pressure generated by the applied voltage, the developer on the intermediate transfer belt 860 is attracted to the transfer paper P and transferred onto the transfer paper P (secondary transfer). In the fourth embodiment, the rollers that press the intermediate transfer belt 860 to the secondary transfer bias roller 890 are the two rollers of the suspension rollers 852 and 857, but an independent counter roller for receiving the pressure may be disposed. good.
[0146]
Thereafter, the transfer paper P onto which the image (unfixed image) has been transferred is separated from the intermediate transfer belt 860 by a separator (not shown) and conveyed to an image fixing device 900 as an image fixing unit. After the image fixing apparatus 900 is heated and fixed, it is discharged from the apparatus main body. On the other hand, after the secondary transfer, the photosensitive drums 610Y, 610, M, C, and K are charged with residual charges by a static eliminator, and their surfaces are cleaned by cleaning devices 650Y, 650, M, C, and K, and untransferred developer is collected. Removed to prepare for the next image.
In the fourth embodiment, one intermediate transfer member sweep roller 820 is disposed on the intermediate transfer belt 860, but the number is not limited thereto.
[0147]
Further, the configuration of the intermediate transfer belt 860 is configured by providing an elastic body in the same manner as in FIG. 26 described in the structure of the intermediate transfer drum 810 of Embodiment 3, so that transfer defects do not occur. However, in the cross-sectional view shown in FIG. 26, the elastic conductor 811 is bonded to the drum 812. In this embodiment, because of the belt shape, a nylon cord or a steel cord is provided in the drum 812 portion in order to prevent the elastic conductor 811 from extending in the belt circumferential direction. The shape of these cords is considered to be, for example, 50 to 400 [μm] in diameter.
[0148]
Further, in the present embodiment, the carrier can be removed from the secondary transfer image on the transfer paper P before fixing.
FIG. 29 is a schematic configuration diagram of an image fixing device of a printer according to the fourth embodiment. This image fixing device 900 has the following in order from the upstream side (right side in the figure) to the downstream side (left side in the figure) in the transfer paper P conveyance direction. That is, a pre-heating unit 910 as a solvent precipitation unit, a carrier removal unit 930 as a carrier removal unit, and a heating fixing unit 950 as a heating fixing unit.
[0149]
The heat fixing unit 950 is attached so that the heat roller 951 and the pressure roller 952 are in pressure contact with each other. The heating roller 951 includes a heater, and a rubber layer, an oil resistant layer (fluorinated silicon rubber layer), an RTV silicon rubber layer, or a Teflon layer having a desired thickness are sequentially laminated on the surface of the mandrel. On the other hand, the pressure roller 952 is Teflon coated on silicon rubber. A thermistor 955 and a thermal fuse 956 are arranged around the heating roller 951, and temperature control is performed by these. A separation claw 957 and a cleaning blade are disposed in contact with the surface of the heating roller 951.
[0150]
The preheating unit 910 is arranged so that a preheater heater 911 is in contact with the toner image transfer surface of the transfer paper P, and the preheater 911 uses a halogen lamp or an infrared heater as a heating unit. It is preferable that the heater is configured using condensed light.
[0151]
The carrier removing unit 930 is located between the pre-heating unit 910 and the heat fixing unit 950 in the transfer paper P conveyance direction. The carrier removing unit 930 is provided with a carrier removing roller 931 as a solvent removing unit for removing a precipitated carrier as a solvent to be deposited that has been deposited on the toner image surface by heating by the pre-heating unit 910. In addition, a backup roller 932 is provided as a pressing unit that presses the toner image surface toward the carrier removal roller 931. A cleaning blade (not shown) that removes and collects the carrier liquid collected from the surface of the transfer paper P abuts on the carrier removal roller so that the carrier removal roller without adhering liquid can always abut against the image surface of the transfer paper P. Yes. The carrier removal roller 931 is made of a material whose surface layer portion does not impregnate the carrier liquid. Further, the conveyance belt 921 is suspended and driven by the drive roller 922, the suspension roller 923 and the backup roller 932. As shown in the figure, the transfer paper P is transported by a transport belt 921, and when the transfer paper P passes under the preheater 911, the transfer paper P is heated by heat from the preheater 911, and the toner layer Carrier is deposited on the surface. The transfer paper P is directly conveyed to the carrier removing unit 930 by the conveyance belt 921.
[0152]
Next, an image fixing operation using the image fixing apparatus 900 configured as described above will be described. The transfer paper P on which the unfixed image has been transferred is separated from the intermediate transfer belt 860100 by the separation device and enters the image fixing device 900, and first reaches the preheating unit 910. At this time, the image surface of the transfer paper P is heated by the heater, and the carrier is deposited on the surface of the unfixed image from the developer constituting the unfixed image on the transfer paper P.
Next, the transfer paper P enters the carrier removing unit 930 with the carrier deposited on the surface. In the carrier removal unit 930, the carrier removal roller 931 comes into contact with the deposited carrier on the upper surface of the transfer paper P, and the transfer paper P passes through the state where the back-up roller 932 is pressed from the back surface of the transfer paper P toward the carrier removal roller 931. At this time, the precipitated carrier is transferred to the carrier removing roller 931 side. As a result, the deposited carrier is removed from the transfer paper P.
The transfer paper P from which the precipitation carrier is removed is further conveyed and enters the heat fixing unit 950. In the heat fixing unit 950, the transfer paper P passes through a nip portion between a heating roller that contacts the upper surface of the transfer paper P, that is, the image carrying surface, and a pressure roller that presses the transfer paper P toward the heating roller from the rear surface of the transfer paper P. . At this time, the image is fixed on the transfer paper P by heating and pressing. Thereafter, the image is discharged from the image fixing apparatus 900.
[0153]
The image on the intermediate transfer belt 860 is secondarily transferred onto the transfer paper P at a transfer rate of 90% in the secondary transfer nip. Accordingly, the carrier liquid is 0.04 [mg / cm.²] Remains on the surface of the intermediate transfer belt 860. In Table 7, the carrier liquid is 0.35 [mg / cm] on the toner image on the transfer paper P after the secondary transfer.²] Adhering. At this time, the developer concentration in the image area on the transfer paper P was 29 [%].
When the transfer paper P passes through the opposite nip with the carrier removal roller 931, the carrier removal roller 931 causes 0.03 [mg / cm²] Is removed, and the toner remains on the transfer paper P without being removed. At this time, the developer concentration in the image area on the transfer paper P was 32 [%].
Table 5 shows the carrier liquid adhesion amount from the primary transfer nip to the carrier removal by the carrier removal roller 931.
[Table 5]

[0154]
With the image fixing apparatus 900 having the above-described configuration, even if a non-volatile component is contained in the carrier constituting the developer, it can be removed in advance by the carrier removing roller 931. An unfixed image on the transfer paper P can be reliably fixed. Therefore, heat fixing can be performed satisfactorily.
Further, since the carrier component is removed, the heat fixing temperature can be lowered as compared with the prior art. In addition, since the image heated in advance by the pre-heating unit 910 is heat-fixed, the heating temperature in the heat-fixing unit 950 can be lowered as compared with the case of fixing by one heating. For example, a temperature sensor that detects the temperature is provided in each of the pre-heating unit and the heat-fixing unit, and the heaters are turned on and off according to the detection results of these temperature sensors, and the temperatures of the pre-heating unit and the heat-fixing unit are desired What is necessary is just to control so that it may become. In the case of this embodiment, the fixing temperature is set to 100 to 150 [° C.] by the pre-heating roller 911 of the pre-heating unit 910 and the heating temperature by the heating roller in the heating and fixing unit 950 is set to 100 to 120 [° C.]. Could get. Accordingly, it is possible to shorten the heat fixing time.
Further, since the roller-shaped carrier removing roller 331 is used as the material of the carrier removing unit 930, it can be made compact compared to the shape of a belt, a web, or the like, which is effective for reducing the size of the image fixing device 900.
[0155]
Here, the results of experiments conducted on the developer concentration and the fixability of the image on the transfer paper P will be described. Fixability was measured using a smear tester (friction tester type I, JISL0823). The tester is attached with a white cotton cloth (JISL0803), rubbed the image surface 10 times, and the reflected image density of the white cotton cloth is measured with a reflection image densitometer. The image density of the white cotton cloth without toner adhesion is subtracted from the measured reflection density. Using this value as the numerator, the value obtained by setting the image density on the recording medium before rubbing (subtracting the image density of the recording medium without toner adhesion) as the denominator is read as fixability. This value is 0.1, indicating good fixability. On the contrary, in the vicinity of 0.4, the toner image is peeled off by rubbing by hand, and it cannot be said that good fixability is exhibited.
Further, this fixability test was performed using the developer A at the heating set temperature. The test was conducted by changing the carrier amount so that the toner solid content was constant. As the transfer paper P, type 6200 made by Ricoh was used.
FIG. 30 shows the result of examining the fixing property to the transfer paper P with respect to the developer concentration. From this result, it can be seen that as the developer concentration increases, the fixability value decreases and the fixability is improved. On the other hand, when the developer concentration is lowered, the fixability value is increased. Particularly, when the developer concentration is 25% or less, the fixability value is rapidly increased. Therefore, it can be seen that the fixability is lowered. From this, it can be said that fixing can be satisfactorily performed when the developer concentration in the fixing nip is 25% or more, preferably 30% or more.
In the present embodiment, the image portion developer concentration of the toner image immediately after the secondary transfer is 29 [%], which is already in a range where good fixing can be obtained. However, if the developer concentration is less than 25 [%] immediately after the secondary transfer, the fixability deteriorates if the developer enters the fixing nip as it is.
However, when the carrier liquid can be removed on the transfer paper P as in the present embodiment, it is possible to obtain good fixability by removing the carrier before entering the fixing nip. .
In order to improve the transferability of the image, a lower developer concentration at the time of transfer is preferable, and in order to improve the fixability of the image, a higher developer concentration at the time of fixing is preferable. The conflicting demands regarding the developer concentration can be met by adopting the fixing device shown in the fourth embodiment. This is because the carrier removal is not performed up to the secondary transfer nip, and the fixing can be performed after the carrier removal on the transfer paper P.
[0156]
In the fourth embodiment, only one carrier removal roller 931 is provided on the transfer paper P, but it may be provided in multiple stages. For example, the configuration shown in FIG. 3 may be used to perform carrier removal in two stages. If the carrier removing rollers are provided in multiple stages, the amount of carriers that can be removed is larger than when only one carrier removing roller is provided. Therefore, even with an unfixed image formed on the transfer paper P made of a material that hardly penetrates the carrier, heat fixing can be performed satisfactorily. As a result, this also leads to an increase in the types of transfer paper P that can be applied to the image fixing apparatus 900 and, in turn, the printer.
[0157]
Further, the carrier removing member can be constituted by a carrier removing belt made of a belt. As the carrier removal belt, a material formed of a resin film such as polyimide or polycarbonate can be used as a material that does not swell in the carrier liquid and has heat resistance characteristics. Further, a cleaning unit for cleaning the surface of the carrier removal belt may be provided so that the carrier removed from the belt surface can be collected in the container. As a specific configuration example of the carrier removal belt and the cleaning unit, for example, the fixing device of Example 2 of Embodiment 1 shown in FIG. 5 can be considered.
[0158]
In the fourth embodiment, the carrier removing roller 931 is made of a material that does not impregnate the carrier liquid. Alternatively, the carrier removing roller 931 may be made of a porous material that is impregnated / absorbed with the carrier liquid. For example, a web or the like may be disposed, and a surface once used may be wound around a winding shaft, and the web may be replaced when the web finally wound around the supply shaft disappears.
[0159]
In the fourth embodiment, only the fixing property when the liquid developer A is used has been described. However, the developer B is used as in the third embodiment, and the fixing to the transfer paper P is performed even if the developer concentration is somewhat low. It is also possible to maintain good properties.
[0160]
In Embodiments 3 and 4 described above, a fixing method by heating and pressurization is adopted as the image fixing device. However, a fixing method that can improve the fixing property by applying the present invention is described here. It is not limited. For example, the present invention can be applied to a fixing method such as pressure fixing, solvent fixing, or the like in which the fixing property is lowered if a large amount of carrier is contained in the developer forming the image to be fixed. .
[0161]
As described above, according to the configurations of Embodiments 1 and 2, it is possible to satisfactorily fix an image formed with a liquid developer obtained by dispersing toner in a solvent that is partially or entirely non-volatile.
Further, the image forming apparatus includes a heat fixing unit 350 as a heat fixing unit that heat-fixes an unfixed image after removal of the solvent by the carrier removing unit 330 as a solvent removing unit onto the transfer paper P as the recording medium. Therefore, since the unfixed image after the non-volatile solvent is removed is heat-fixed, sufficient fixing can be secured and high-speed fixing can be achieved as compared with an image fixing device made of a conventional liquid developer. Has an excellent effect. This is because the non-fixed image after removing the non-volatile solvent, which is a factor that hinders heat fixing in the unfixed image, is heat-fixed by the heat-fixing means.
In addition, there is a configuration in which the solvent to be deposited on the image surface is transferred to the carrier removing roller 331 side as a removing roller pressed against the image carrying surface of the recording medium and removed. As a result, the solvent removal means can be easily configured using the removal roller, and if the surface of the removal roller is repeatedly used for removing the solvent, the apparatus for removing the solvent can be reduced in size.
Also, there is a configuration in which the solvent to be deposited on the image surface is transferred and removed to the carrier removal belt 349 as an endlessly moving removal belt pressed against the image carrying surface of the recording medium. Accordingly, the solvent removal means can be easily configured using the removal belt, and the removal belt surface can be moved endlessly and used repeatedly for solvent removal.
Further, a cleaning unit 343 is provided as a solvent recovery unit that removes and recovers the solvent to be deposited transferred to the removal roller or the removal belt from the removal roller or the removal belt. It was observed that the solvent to be deposited does not contain a toner component and is a solvent alone. Therefore, these deposition solvents can be recycled. In addition, the removal roller and the removal belt after removing the medium can be used again for removing the solvent to be deposited on the image surface. And the solvent removal action of a removal roller or a removal belt can also be maintained long. Further, since the solvent to be precipitated can be recovered, the recovered solvent can be reused as a constituent material for a new liquid developer.
Further, there is a configuration in which the solvent recovery means has a cleaning unit 343Z as a lower recovery means for recovering the solvent to be deposited at the lower part in the gravity direction of the removal roller or the removal belt. Of the solvent transferred to the solvent removing member such as the removing roller or the removing belt, the following is collected by the lower collecting means. It was located in the lower region of the solvent removal member in the direction of gravity, or what was originally located in a region other than the lower part of the direction of gravity moved to this lower region in the direction of gravity through this solvent removal member. Is. As a result, the removed solvent can be recovered even if the solvent is about to drip from the lower part in the direction of gravity of the solvent removing member due to the device being stopped for a long time. Therefore, since it can collect | recover even when the removed solvent is about to drip from the gravity direction lower part of a solvent removal member, it can avoid contaminating the inside of an apparatus with a solvent.
Moreover, in the modification 2 in Example 1 of the said Embodiment 1, the winding-type web is used for the solvent removal means. The solvent to be deposited on the image surface of the recording medium is transferred to the web side and removed, and the web holding the solvent to be deposited is wound around the winding shaft. And the part of the web used for the removal of the deposition solvent can be wound up, and the removal of the deposition solvent can always be performed at a new web part. Therefore, the solvent removal effect can be maintained without removing the solvent transferred to the web until the web winding is completed. This also eliminates the need for a cleaning means for removing the solvent from the web, thus simplifying the apparatus.
The web winding direction is the same as the recording medium surface moving direction. As a result, the stress applied to the image on the surface of the recording medium can be reduced, so that damage to the image such as missing toner images can be reduced. This is because the recording medium surface and the web surface in contact with the recording medium surface move in the same direction, so that the stress applied to the image on the recording medium surface can be reduced as compared with the case of moving in the opposite direction.
[0162]
In the first and second embodiments, the removal roller, the removal belt, or the web is made of a porous material such as a nonwoven fabric, or an elastic material that absorbs and swells with respect to a solvent such as silicon rubber. It is configured using. Here, for the removal roller or the removal belt, either a porous material such as a nonwoven fabric or an elastic material that absorbs and swells with respect to a solvent such as silicon rubber can be used. . In addition, a porous material such as a nonwoven fabric is used for the web. As a result, the solvent to be precipitated can be removed efficiently, so that excellent fixing properties can be obtained as compared with the case of using a solvent removing means not composed of these materials, and high-speed fixing is possible. This is because by using a removal roller, a removal belt, a web, or the like made of a porous material or an elastic material, the solvent to be precipitated can be efficiently removed compared with the case of using a solvent removal means that is not composed of these materials. This is because it can be removed.
In the second embodiment, at least the surface of the carrier removal roller, the carrier removal belt or the like as the solvent removal means is made of a material that does not absorb and swell with respect to the solvent. Therefore, durability can be obtained as compared with the case where the removal roller and the removal belt are made of a material that absorbs and swells with respect to the solvent. This is because the stress applied to the material constituting the removal roller and the removal belt is reduced by not absorbing and swelling the solvent. Therefore, the durability is increased as compared with the case where the material is made of an absorbent / swellable material, and the number of consumables is reduced. At the same time, since the recovered solvent can be easily recovered from the surface of the solvent removing means, the fixing speed is excellent. This is because the carrier removal roller and the carrier removal belt are formed of a material that does not swell in the carrier liquid, so that the removal carrier can be efficiently cleaned.
Further, there is a configuration in which a plurality of removal rollers, removal belts, or webs are provided. As a result, more solvent can be removed as compared with the case where only one removing roller, removing belt, or web is provided, so that an unfixed image formed on a recording medium made of a material that hardly penetrates the solvent can be removed. Heat fixing can be performed satisfactorily. This is because the solvent to be deposited is removed in multiple stages using a plurality of removal rollers, a removal belt, or a web. As a result, the recording medium capable of good fixing is expanded in terms of the range of the solvent penetration rate, and recording media of various materials can be used.
Further, a backup roller as a pressing means for pressing the image carrying surface against the removal roller, the removal belt, or the web surface is driven as follows. That is, the contact surface of the removal roller, the removal belt, or the web with the recording medium and the contact surface of the backup roller with the back surface of the recording medium are moved at substantially the same linear velocity in the recording medium conveyance direction. Therefore, since no stress is applied to the image on the recording medium, the occurrence of an abnormal image can be prevented. This is because the solvent to be deposited is removed while the recording medium is held and conveyed by the removal roller, the removal belt, or the web, and the backup roller, whose surfaces move at substantially the same linear speed in the recording medium conveyance direction. This prevents stress that may be applied to the image on the recording medium when the linear speeds of the members that are held and conveyed by the upper and lower sides are different.
In addition, the recording medium conveyance speeds in the pre-heating unit 310 as the solvent deposition position, the carrier removal unit 330 as the solvent removal position, and the heat fixing unit 350 as the heat fixing position can all be the same speed. As a result, the recording medium carrying the image is not subjected to the stress caused by the fluctuation of the conveyance speed, so that it is possible to prevent the recording medium from jamming or abnormal images. This is because the recording medium passes through the solvent deposition position, the solvent removal position, and the heat fixing position all at the same speed.
In addition, a heat fixing unit 350 is provided as a heat fixing unit that heat-fixes an unfixed image on the recording medium, and the recording medium is linearly conveyed at all of the solvent deposition position, the solvent removal position, and the heat fixing position. Some of them employ a configuration provided on the transport path. This allows the recording medium to pass through the solvent deposition position, the solvent removal position, and the heat fixing position without applying any stress on the recording medium, thereby improving the recording medium conveyance performance. Each process of fixing can be performed with high accuracy. This is because the solvent deposition position, the solvent removal position, and the heat fixing position are passed through the image on the surface while the recording medium is conveyed linearly. For this reason, the recording medium passes through the solvent deposition position, the solvent removal position, and the heat fixing position without being subjected to the stress received by the non-linear conveyance.
[0163]
Further, in Example 3 of Embodiment 2, the surface of the pre-heating roller 311 as a contact heating member of the solvent precipitation unit is treated with a material having a low surface friction coefficient. Therefore, the solvent can be deposited without unnecessarily stressing the unfixed image formed on the recording medium.
In Examples 4 and 7 of Embodiment 2, preheating heaters 313X and 313Z as non-contact heating means are used as the solvent precipitation means. Therefore, since the carrier deposition portion 310 does not directly touch the unfixed image surface of the recording paper P, unnecessary stress is avoided from being applied to the unfixed image, which is better than when the contact heating means is used. Can be obtained.
In Example 2 of Embodiment 1 described above, one main roller 305 having heating means is provided. A pre-heating unit 310 as a solvent precipitation unit, a carrier removal unit 330 as a solvent removal unit, and a heating and fixing unit 350 as a heating and fixing unit are provided by a main roller and different opposing members provided to face the main roller. Each is composed. While the recording medium moves while being carried on the main roller surface, the solvent is precipitated from the unfixed image on the surface of the recording medium, the solvent to be deposited is removed, and heat fixing is performed. As a result, the members that play the role of the three means of the solvent precipitation means, the solvent removal means, and the heat fixing means can be configured by one main roller, and space saving is realized compared to the configuration of a plurality of members. it can.
In the second and third embodiments, an image as an object to be subjected to the three steps of preheating by the solvent precipitating unit, removal of the solvent to be deposited by the solvent removing unit, and heat fixing of the unfixed image by the heat fixing unit. It is formed on both sides of the recording medium. As a result, even when images are formed on both sides of the recording medium, sufficient fixing of the toner image can be ensured and high-speed fixing can be achieved as compared with a conventional image fixing apparatus. This is because, for the unfixed images formed on both sides of the recording medium, the three steps of precipitation of the solvent in the liquid developer, removal of the solvent to be deposited, and heat fixing are performed while the recording medium is in one pass. This is because the double-sided fixing is completed.
In the second and third embodiments, the removal roller or the removal belt disposed so as to sandwich the recording medium from both sides has a contact surface with the surface of the recording medium at substantially the same linear velocity in the recording medium conveyance direction. Driven to move. Then, the solvent to be deposited is removed while the recording medium is held and conveyed by a pair of a removing roller or a removing belt whose surface moves in the recording medium conveying direction at substantially the same linear velocity. Accordingly, it is not necessary to provide a backup roller for each of the removal roller or the removal belt provided on both sides of the recording medium, and the configuration can be simplified. Further, it is not necessary to newly provide a recording medium conveying member. Furthermore, since the linear velocity of the member that is held and conveyed up and down is substantially the same linear velocity in the recording medium conveyance direction, unnecessary stress is not applied to the unfixed image on the recording medium.
In the second and third embodiments, the solvent deposition position, the solvent removal position, and the heat fixing position are set at the same location on the recording medium conveyance path on both sides of the recording medium. That is, the deposition of the solvent in the liquid developer, the removal of the solvent to be deposited, and the heat fixing with respect to the unfixed image on the recording medium are performed on both sides of the recording medium at the same location in the recording medium conveyance path. Therefore, since the image on the recording medium is fixed on both sides, the image can be fixed in the same time as when the image is formed on one side even when the image is formed on both sides of the recording medium. Further, since the conveyance path length of the recording medium for image fixing is the same as that when an image is formed on one side, it is possible to avoid an increase in the size of the apparatus due to the extension of the conveyance path.
In the first and second embodiments, a drive switching device as a solvent removal degree switching unit that switches the degree of solvent removal by the solvent removal unit according to the type of the recording medium may be provided. Specifically, since it is not necessary to remove the solvent for a recording medium made of a material that easily penetrates the solvent, the solvent removal is not performed by the solvent removal degree switching means. On the other hand, for recording media made of materials that are difficult to permeate the solvent, it is necessary to positively remove the solvent. Therefore, the solvent removal degree switching means is used to remove the solvent at the maximum level. Switch. Further, for a recording medium whose solvent penetration is between the two materials, the solvent removal degree switching means selects and switches between several levels set for solvent removal. As a result, the degree of solvent removal can be switched according to the type of recording medium, so that the solvent removal means can be operated as necessary, and the life of the solvent removal means can be extended compared to the case where it is always activated. Can be made. In addition, since the degree of solvent removal can be switched according to the characteristics of the recording medium, a good fixed image can always be obtained. Further, since the operation of the solvent removing means is stopped when it is not necessary, the energy cost for the operation can be reduced as compared with the case where it is always operated. The structure of the apparatus for switching the degree of solvent removal may be performed manually, or a sensor for detecting the solvent penetration rate of the recording medium is provided in the apparatus so that the apparatus is automatically switched according to the detection result. It may be configured.
Further, according to the image forming apparatuses of Embodiments 1 and 2, it is possible to satisfactorily fix an image formed with a liquid developer obtained by dispersing toner in a solvent that is partly or entirely non-volatile. Further, since high-speed fixing is possible, even images formed continuously at high speed can be fixed well.
[0164]
According to the third and fourth embodiments, the carrier is removed at two places on the photosensitive drum 610 and the intermediate transfer drum 810 or at two places on the intermediate transfer belt 860 and the transfer paper P. Therefore, the carrier in the developer can be sufficiently removed prior to fixing the image, and the fixing property of the image can be improved.
Further, according to the third and fourth embodiments, the toner concentration in the developer at the fixing nip is set to 25 [%] or more. Therefore, as can be seen from the result of FIG. Can do.
According to the third embodiment, an electric field is generated in the nip portion between the photosensitive drum 610 and the sweep rollers 710a and 710b by applying a voltage to the sweep rollers 710a and 710b. As a result, the toner in the image area on the photosensitive drum 610 can be compressed to the photosensitive drum 610 side by the force of the electric field and is not peeled off. Further, the developer adhering to the non-image portion on the photosensitive drum 610 is drawn to the sweep roller 710a side and collected. Therefore, in addition to being able to satisfactorily remove and collect the surplus carrier liquid C on the photosensitive drum 610, it is possible to remove and collect even a small amount of excess toner adhering to the non-image area.
In the third embodiment, a modification example is described in which 450 [V] is applied to the first sweep roller 710a and 500 [V] is applied to the second sweep roller 710b. As a result, the developer adhering mainly to the background portion of the photosensitive drum 610 is attracted to the first sweep roller 710a. The carrier that adheres to the image portion of the photosensitive drum 610 is attached to the second sweep roller 710b, and the toner in the image portion is compressed onto the surface of the photosensitive drum 610. That is, the carrier applied to the image portion of the photosensitive drum 610 can be positively attached to the second sweep roller 710b by the bias applied to the second sweep roller 710b. Therefore, the carrier can be removed and collected efficiently.
In the third or fourth embodiment, the developer and the carrier liquid removed by the first sweep roller 710a and the second sweep roller 710b are removed from the respective rollers by the cleaning blades 711a and 711b. As a result, the surfaces of the first sweep roller 710a and the second sweep roller 710b can always be used for collecting developer and toner. Therefore, the carrier attached to the image portion of the photosensitive drum 610 and the developer in the non-image portion can be removed continuously and satisfactorily.
In the third or fourth embodiment, the intermediate transfer body sweep roller 820 to which a certain amount of bias is applied causes the carrier liquid in the image portion on the intermediate transfer drum 810 or the intermediate transfer belt 860 to be attached and removed by the force of the electric field. As a result, the developer density of the image area can be increased on the intermediate transfer body before the secondary transfer onto the transfer paper P, and the image fixability can be stabilized. Further, in the case where color images are superimposed on the intermediate transfer belt 860 as in the fourth embodiment, it is possible to perform carrier removal collectively on the superimposed images. Thus, carrier removal can be performed more efficiently than when carrier removal is performed for each color.
In the fourth embodiment, an independent electric field can be formed in each of the region of the intermediate transfer belt 860, the primary transfer nip, and the secondary transfer nip that the intermediate transfer member sweep roller 820 faces. That is, different electric fields such as a primary transfer bias, a removal bias, and a secondary transfer bias can be formed on the same intermediate transfer belt 860. A primary transfer electrode, a secondary transfer electrode, and a removal electrode are provided. This makes it possible to obtain both primary and secondary transfer properties and developer and carrier removability from the intermediate transfer belt 860.
In the fourth embodiment, the carrier can be removed from the image on the transfer paper P by the carrier removal roller 931. As a result, even if an image formed from a developer containing a large amount of carrier is transferred to the transfer paper P, the carrier can be removed before fixing to improve the fixing property. Further, according to the configuration of the fourth embodiment, the image heated in advance by the pre-heating unit 910 is heat-fixed, so that the heating temperature in the heat-fixing unit 950 is lower than that in the case of fixing by one heating. Can do.
[0165]
In the third and fourth embodiments, a carrier having a flash point of 250 [° C.] or more is used as a carrier that is a component of the developer. As a result, almost no volatile components are left in the developer, and no solvent is released into the atmosphere. In general, petroleum-based carriers are designated as dangerous goods. However, if the flash point is 250 [° C.] or higher, they are not designated as dangerous goods. This is because there is almost no risk of ignition by heating, and in this embodiment as well, the safety against heating at the time of fixing is higher than when a petroleum carrier having a flash point of less than 250 [° C.] is used. It can be said that it is expensive.
In both Embodiments 3 and 4, the electrical resistance of the developer in the image area is 10 at the primary and secondary transfer nips.⁶[Ωcm] or more is set. As a result, as can be seen from Table 3, the transferability to the intermediate transfer member and the transfer paper P can be kept good.
In addition, when the developer B is used in the third and fourth embodiments, even if the developer concentration is increased and the toner particle layer is brought into direct contact with the carriers, the insulating property can be maintained substantially. In this way, if an insulating toner particle layer is used as the developer material, even if the carrier liquid is sufficiently removed and the toner is compressed in order to obtain a high resolution, the toner particle layer has a high electric resistance, so that a bias leak occurs. Is unlikely to occur. Therefore, by increasing the developer concentration, image fixability can be improved and high resolution can be obtained.
In Embodiments 3 and 4, it is described that an amorphous silicon (a-Si) photoreceptor using amorphous silicon at least on the surface layer is used as the photoreceptor drum 610. According to this, the life of the photosensitive drum 610 can be extended and the safety can be improved.
[0166]
【The invention's effect】
  Claims 1 to 20According to this image fixing apparatus, it is possible to efficiently remove the solvent in the unfixed image, which is a factor that hinders sufficient fixing and high-speed fixing of a toner image made of a liquid developer using a non-volatile solvent. Therefore, there is an advantage that sufficient fixing of the toner image can be secured and high-speed fixing can be achieved as compared with the conventional image fixing apparatus.
  Claim 21According to this image forming apparatus, there is an excellent effect that it is possible to satisfactorily fix an image formed by a liquid developer obtained by dispersing toner in a solvent that is partially or entirely non-volatile.
  Further, since high-speed fixing is possible, there is an excellent effect that even images formed continuously at high speed can be fixed well.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part of an image forming apparatus according to a first embodiment.
FIG. 2 is an explanatory diagram of an image fixing apparatus according to Example 1 of Embodiment 1.
3 is an explanatory diagram of an image fixing device according to a first modification of the first embodiment of the first embodiment. FIG.
4 is an explanatory diagram of an image fixing apparatus according to a second modification of the first embodiment of the first embodiment. FIG.
5 is an explanatory diagram of an image fixing apparatus according to Example 2 of Embodiment 1. FIG.
6 is an explanatory diagram of an image fixing device according to Example 3 of Embodiment 1. FIG.
FIG. 7 is an explanatory diagram of an image fixing device according to a first modification of the fourth embodiment of the first embodiment.
FIG. 8 is an explanatory diagram of an image fixing device according to a second modification of the fifth example of the first embodiment.
9 is an explanatory diagram of an image fixing apparatus according to Example 6 of Embodiment 1. FIG.
FIG. 10 is a schematic configuration diagram of a main part of a printer according to a second embodiment.
11 is a schematic configuration diagram of an image fixing device according to Example 1 of Embodiment 2. FIG.
12 is a schematic configuration diagram of an image fixing apparatus according to Example 2 of Embodiment 2. FIG.
FIG. 13 is a schematic configuration diagram of an image fixing device according to a modification of Example 2 of the second embodiment.
FIG. 14 is a partially enlarged view of the vicinity of a blade-type cleaning unit.
FIG. 15 is a partially enlarged view of the vicinity of a roller-type cleaning unit.
16 is an explanatory diagram of an image fixing apparatus according to Example 3 of Embodiment 2. FIG.
17 is an explanatory diagram of an image fixing apparatus according to Example 4 of Embodiment 2. FIG.
18 is an explanatory diagram of an image fixing device according to Example 5 of Embodiment 2. FIG.
19 is an explanatory diagram of an image fixing device according to Example 6 of Embodiment 2. FIG.
20 is an explanatory diagram of an image fixing apparatus according to Example 7 of Embodiment 2. FIG.
21A is a cross-sectional view when an unfixed image is carried on the upper surface of the transfer paper P. FIG.
(B) is a sectional view showing a state of a liquid developer constituting an image when the transfer paper P of (a) is heated from below.
FIG. 22 is an explanatory diagram of a main part of the image forming apparatus according to the embodiment.
FIGS. 23A, 23B, and 23C are diagrams schematically illustrating a state of a developer in a development nip.
24A and 24B are explanatory views of a bias applied to the sweep roller in the third and fourth embodiments.
FIG. 25 is an enlarged view of the vicinity of the removal nip of the third and fourth embodiments.
FIG. 26 is an explanatory diagram of an example of an intermediate transfer drum according to the third embodiment.
FIG. 27 is a graph showing the relationship between the developer concentration and the secondary transfer rate to the transfer paper P.
FIG. 28 is a schematic configuration diagram of a printer according to a fourth embodiment.
FIG. 29 is a schematic configuration diagram of an image fixing device of a printer according to a fourth embodiment.
FIG. 30 is a graph showing the result of examining the fixing property to the transfer paper P with respect to the developer concentration.
FIG. 31A is a diagram illustrating a state in which a carrier C exists between toner particles.
FIG. 4B is a diagram illustrating a state where a toner particle layer is formed.
[Explanation of symbols]
10B, Y, M, C Photosensitive drum
20B, Y, M, C Uniform charger
30 Laser writing device
40B, Y, M, C Wet development unit
50 Static eliminator
60 Cleaning device
70 Intermediate transfer unit
77B, Y, M, C Primary transfer bias roller
80 Paper transfer unit
81 Secondary transfer bias roller
100 Intermediate transfer belt
300 Image fixing device
305 Main roller
310 Pre-heating unit
311 Pre-heating roller
312 Press roller
313X, 313Z Pre-heater
330 Carrier removal unit
331, 331a, 331b Blotter roller
332 Backup roller
333 Web
337, 337X, 337Z Carrier removal roller
340, 340X, 340Z Blotter belt
343X, Z Cleaning unit
349X, 349Z Carrier removal belt
350 Heat fixing part
351 Heating roller
352 Pressure roller
400 Image forming apparatus
400X, 400Z Image forming unit
500X, 500Z intermediate transfer unit
610, 610Y, M, C, K Photosensitive drum
700 Developing device
704 Anilox Roller
706 Development roller
707 Cleaning blade
710a, 710b, 710Y, M, C, K Sweep roller
712 sweep part
800 Intermediate transfer unit
810 Intermediate transfer drum
820 Intermediate transfer member sweep roller
851,852,853,854,855,856 Suspension roller
860 Intermediate transfer belt
870Y, M, C, K Primary transfer bias roller
880 Cleaning device
890 Secondary transfer bias roller
900 Image fixing device
910 Pre-heating unit
930 Carrier removal unit
950 Heat fixing part
951 Heating roller
952 Pressure roller
P transfer paper

Claims (21)

An image fixing apparatus that heat-fixes an unfixed image on a recording medium formed using a liquid developer obtained by dispersing toner in a solvent that is partially or entirely non-volatile,
The as unfixed image of the recording medium is formed is arranged on the opposite side, the Solvent of the liquid developer heated in the liquid developer for forming an unfixed image on the recording medium Pre-heating means for bringing it out on the surface of the image;
A solvent removing means for removing the solvent that has appeared on the surface of the unfixed image by heating by the preheating means ;
An image fixing apparatus comprising: a heat fixing unit that heat-fixes an unfixed image from which the solvent has been removed by the solvent removing unit on the recording medium . An image fixing apparatus 請 Motomeko 1,
A removal roller having a surface abutting against the unfixed image ;
A pressing means for pressing the image carrying surface of the recording medium toward the removal roller,
An image fixing apparatus, wherein the solvent is removed by transferring from the surface of the unfixed image to the removal roller side. The image fixing device according to claim 1 .
A removal belt that makes the surface contact the unfixed image and moves endlessly;
A pressing means for pressing the image bearing surface of the recording medium against the surface of the removal belt;
An image fixing device, wherein the solvent is removed by transferring from the surface of the unfixed image to the removal belt side. The image fixing device according to claim 2 or 3 ,
Image fixing apparatus characterized by the Ki溶 medium on metastasized to the removing roller or the removal belt side, provided with solvent recovery means for recovering removed from the removing roller or the removal belt. The image fixing device according to claim 4 .
The solvent recovery means, an image fixing apparatus characterized by having a lower recovery means for recovering on Ki溶 medium in the gravity direction lower portion of the removing roller or the removal belt. The image fixing device according to claim 1 .
The solvent removing means is supported by the supply shaft in a state where one end of the web is wound, and the other end is wound by the winding shaft to move the surface of the web so that the web portion between the shafts is unfixed . Composed by abutting,
Image fixing apparatus characterized by removing the solvent was transferred to the web side from the surface of the unfixed images. The image fixing device according to claim 6 .
An image fixing apparatus, wherein the web is wound in the same direction as the recording medium surface moving direction. The image fixing device according to claim 2, 3 or 6 ,
The removal roller, the removal belt, or the web,
An image fixing apparatus comprising a porous material such as a nonwoven fabric or an elastic material that absorbs and swells with respect to a solvent such as silicon rubber. The image fixing device according to claim 2, 3 or 6 ,
The removal roller, the removal belt, or the web,
An image fixing device, wherein at least the surface is made of a metal material or a resin material that does not absorb or swell with respect to the solvent. The image fixing device according to claim 2, 3 or 6 ,
An image fixing apparatus comprising a plurality of the removing roller, the removing belt, or the web. The image fixing device according to claim 2, 3 or 6 ,
As a pressing means for pressing the image carrying surface against the removal roller, removal belt, or web surface, a backup roller that presses the recording medium against the removal roller, removal belt, or web from the back side of the image carrying surface of the recording medium. Provided,
The contact surface of the removal roller, the removal belt, or the web to the recording medium and the contact surface of the backup roller to the back surface of the recording medium are moved at substantially the same linear speed in the recording medium conveyance direction. An image fixing device. The image fixing device according to claim 1, 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 or 11 .
A heating position in the pre-heating means, and the solvent removed position in the solvent removal means, in a heat fixing position in the heat fixing means, an image fixing apparatus characterized in that all of the above recording medium conveying speed and the same speed. The image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 .
Providing a heat fixing means for heat fixing the unfixed image on the recording medium;
Wherein a heating position by the pre-heating means, and solvent removal position by the solvent removal means, that all of the heat fixing position by the heat fixing means, provided on a conveyance path for linearly conveying the recording medium An image fixing device. The image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13 .
In place of the preheating means , a preheating means comprising a contact heating member disposed in contact with the image forming surface of the recording medium is provided , and a surface for reducing the friction coefficient of the surface on the surface of the contact heating member An image fixing device having undergone a friction coefficient reduction process. The image fixing device according to claim 14 .
An image fixing apparatus, wherein the pre -heating means is constituted by a non-contact heating means disposed away from the image forming surface of the recording medium. The image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 .
Image, wherein the said pre-heating means, and said solvent removing means, and said heat fixing means, by being configured respectively by different opposing member to each other which is disposed to be opposed to the main roller and the main roller having a heating means Fixing device. The image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 , 14 , 15 , or 16 .
Image as an object to perform two steps of the removal of by that Solvent to heating and the solvent removing means according to the pre-heating means, or in addition to the two steps of heat-fixing the unfixed image by the heat fixing means An image fixing apparatus, wherein images as targets for performing the three steps are formed on both sides of the recording medium. The image fixing device according to claim 2, 3 or 6 .
An image as an object to be subjected to the two steps of heating by the preheating unit and removal of the solvent by the solvent removing unit, or three types of heating and fixing of an unfixed image by the heating and fixing unit in addition to the two steps Images as objects to be processed are formed on both sides of the recording medium,
The removal roller, the removal belt, or the web is disposed so as to sandwich the recording medium from both sides of the recording medium, and the contact surface of the removal roller, the removal belt, or the web on the surface of the recording medium, An image fixing apparatus which is moved in the recording medium conveyance direction at substantially the same linear velocity. The image fixing device according to claim 17 or 18 ,
The heating position by the pre-heating means, the solvent removal position by the solvent removing means, and the heating and fixing position by the heating and fixing means are respectively set at the same location on the recording medium conveyance path on both sides of the recording medium. An image fixing device. In the image fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 , 16 , 17 , 18 , or 19 .
An image fixing apparatus comprising: a solvent removal degree switching unit that switches the degree of solvent removal by the solvent removal unit according to the type of the recording medium. Image forming means for forming an unfixed image using a liquid developer on a recording medium;
Image fixing means for heating and fixing the unfixed image on the recording medium,
In the image forming apparatus using the liquid developer obtained by dispersing toner in a solvent that is partly or entirely non-volatile as the liquid developer,
The image fixing means according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 , 16, 17 , 18 , 19 , or 20 as the image fixing means. An image forming apparatus using the apparatus .

Images