JP3694681B2

JP3694681B2 - Wet image forming device

Info

Publication number: JP3694681B2
Application number: JP2002153751A
Authority: JP
Inventors: 敏齋藤
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2002-05-28
Filing date: 2002-05-28
Publication date: 2005-09-14
Anticipated expiration: 2020-09-14
Also published as: JP2002357962A

Description

【０００１】
【発明の属する技術分野】
本発明は、複写機、ファクシミリ、プリンターなどの湿式画像形成装置に係り、詳しくは、電子写真プロセスなどにより潜像が形成された潜像担持体の表面に、現像装置により液体現像剤を供給して該潜像を顕像化した後に、現像を転写材に転写する湿式画像形成装置に関するものである。
【０００２】
【従来の技術】
一般に、電子写真プロセスを用いた湿式画像形成装置としては、潜像担持体に感光体を用いるものが知られている。しかし、感光体には温度が低くなることにより、残留電位が上昇するなど、特性値が変化するものがある。この変化が出力画像に大きく影響するため、その対策として、感光体の温度が低いときには必要最低温度以上になるように加熱するなど、感光体の温度制御装置に関する発明が多数出願されている。
【０００３】
また温度により感光体の特性が変化しているのを前提として変化後の感光体特性においても良好な画像を形成し得るように、感光体の温度を検出し、検出温度に基づいて画像形成の諸条件を調整する方法も提案されている。更に、この感光体の温度を直接検出するのに代え、感光体と接触して感光体とほぼ同一の温度にされる現像液の温度を検出して、上記諸条件を調整することも提案されている（例えば、特開平１ー１６７７８０号公報参照）。
【０００４】
また、液体現像装置を用いて感光体などの潜像担持体に形成した画像を転写材に転写して画像を得る湿式画像形成装置では、転写に最低必要な量のキャリア液を残して、余剰なキャリア液をスクイズすることが行われている。余剰なキャリア液をスクイズする具体的な方法としては、スクイズロ−ラやコロナ放電器などで構成される余剰液除去手段を潜像担持体の表面に対して所定間隔をとって対向配置し、スクイズロ−ラを潜像担持体との対向領域において潜像担持体の方向と逆の方向に回転させたり、スクイズロ−ラに所定のバイアス電圧を印加したり、コロナ放電器によりトナ−と同極性のイオンを発生させて該イオンを潜像担持体へ照射したりする方法が知られている。
【０００５】
【発明が解決しようとする課題】
ところが、感光体の特性が変化しないかあるいは変化した特性に応じて画像形成条件を調整したとしても、機内温度により画像品質が低下するという不具合が発生するという問題点を発見した。
【０００６】
そこで、原因を鋭意検討したところ、上記スクイズ後にも潜像担持体の表面に付着したまま転写領域に搬送される現像液の膜厚が、現像液の温度によって異なることに起因していることが判った。具体的には温度が高くなるほど転写領域に搬送される現像液の膜厚が薄くなり、転写不良による画像濃度の低下が生じた。これは現像液の膜厚の不足で、電気泳動による転写率が低下したためと考えられる。逆に、温度が低くなるほど潜像担持体上の現像液の膜厚が厚くなり、画像流れや画像濃度の低下が生じた。これは現像液の膜厚が厚く現像液の付着量が過剰で、潜像担持体上に形成されるトナ−像を転写する際の電界強度が弱くなり、潜像担持体上のトナ−をキャリア中の電気泳動によって転写材に吸引する力が弱くなるためと考えられる。
【０００７】
また、上記湿式画像形成装置であって、転写ベルトを用いて転写材を搬送しながら転写する転写装置を有するものにおいては、感光体の特性が変化しないかあるいは変化した特性に応じて画像形成条件を調整したとしても、機内温度が低いときに、転写材における搬送方向先端の部分にトナー汚れが生じることがあり、機内温度が低いほどトナー汚れの度合いが増すという問題点を発見した。
【０００８】
そこで、原因を鋭意検討したところ、前述のように現像液の温度が比較的低いときに、比較的厚い膜厚で多量に潜像担持体の表面に付着して転写領域に搬送される現像液が、図４に示すように、転写ベルト４と感光体ドラム１との接触部に現像液の溜り１９を形成し、この現像液溜り１９に転写ベルト４上の転写材５が進入する際にその先端部に現像液溜り１９の現像液が吸収され、該先端部にトナ−汚れを生じさせていることが判った。
【０００９】
本発明は以上の問題点に鑑みなされたものであり、その目的とするところは、転写ベルトなどを用いて転写材を潜像担持体に接触させる転写装置を有する湿式画像形成装置において、転写材先端部のトナ−汚れを防止できる湿式画像形成装置を提供することである。
【００１３】
【課題を解決するための手段】
上記目的を達成するために、請求項１の湿式画像形成装置は、潜像が形成された潜像担持体の表面に、現像装置により液体現像剤を供給して該潜像を顕像化した後に、現像像を担持した潜像担持体表面に対向する転写領域を含む移動経路に沿って無短移動される転写ベルトの表面に担持した転写材を該潜像担持体表面に接触させて、該現像像を転写する湿式画像形成装置において、上記潜像担持体と上記転写ベルトとの接触部に形成される液体現像剤の溜りが、これに進入する上記転写材の先端部に許容できないトナー汚れを生じさせるほど大きくなる温度まで低下しないよう、該現像装置で現像に使用される現像液の温度を調整する温度調整手段とを設けたことを特徴とするものである。
また、請求項２の湿式画像形成装置は、請求項１の湿式画像形成装置において、上記温度調整手段を、上記現像装置に収容されている現像液を加熱する加熱装置と上記潜像担持体を加熱する加熱装置との少なくとも一方を用いて構成したことを特徴とするものである。
また、請求項３の湿式画像形成装置は、請求項１の湿式画像形成装置において、上記温度調整手段を、上記現像装置に収容されている現像液の温度を測定する第１温度測定器と、第１温度測定器の測定結果に基づいて該現像液を加熱する第１加熱装置と、上記潜像担持体の温度を測定する第２温度測定器と、第２温度測定器の測定結果に基づいて、第１加熱装置の狙いの調整温度と同一の温度になるように該潜像担持体を加熱する第２加熱装置とを用いて構成したことを特徴とするものである。
【００２１】
【作用】
請求項１の湿式画像形成装置においては、前述の図４に示す現像液溜りが、これに進入する転写材先端部に許容できない程のトナ−汚れを生じさせる程度になってしまう、現像液の温度を予め実験などにより求めておく。そして、温度調整手段により、現像装置で現像に使用される現像液の温度がこの温度まで低下しないように調整する。
ここで、前述のように現像装置で現像に使用される現像液の温度が高過ぎても、転写領域に搬送される現像液の膜厚が薄くなり過ぎて画像品質が低下するので、このような不具合が発生しないように現像液の上限温度を予め求めておいて、上記温度調整手段をこのような上限温度を越えないように制御したり、必要に応じて冷却装置を追加して設け、該冷却装置を必要に応じて作動させるようにしても良い。
請求項２の湿式画像形成装置においては、上記現像装置に収容されている現像液を加熱する加熱装置と上記潜像担持体を加熱する加熱装置との少なくとも一方を用いて現像装置で現像に使用される現像液の温度を調整する。このうち、潜像担持体を加熱する加熱装置は、潜像担持体を介して、該潜像担持体に供給された現像液を加熱する。
ここで、請求項２の発明の様態として、現像装置に収容されている現像液を加熱する加熱装置のみを設けて、該現像装置内での現像液の温度を所定温度に制御しても、潜像担持体の温度と現像装置内の現像液温度との差が大きい場合、具体的には潜像担持体の温度が比較的低温の場合、現像装置から潜像担持体に供給された後、潜像担持体との間の熱交換で現像液の温度が低下してしまう恐れがある。この温度低下により上記下限温度を下回った状態で上記スクイズを受けるなどして比較的多量の現像液が転写領域に搬送されると、上記液溜りの現像液量が増えて転写材先端部のトナー汚れが許容範囲を越える恐れがある。
そこで、請求項３の湿式画像形成装置においては、第１温度測定器で上記現像装置に収容されている現像液の温度を測定し、その測定結果に基づいて必要に応じて第１加熱装置により該現像装置に収容されてる現像液を加熱するとともに、第２温度測定器で潜像担持体の温度を測定し、その測定結果に基づいて必要に応じて第２加熱装置により潜像担持体を加熱して潜像担持体を、現像液の狙いの調整温度と同一の温度にする。これにより、現像装置から潜像担持体に供給された後の現像液の温度が、潜像担持体との間の熱交換で低下して、上記下限温度を下回らないようにする。
【００２６】
【発明の実施の形態】
〔実施例１〕
以下、本発明を湿式画像形成装置である電子写真複写機（以下、複写機という）に適用した実施例について説明する。図１は本実施例に係る複写機の概略断面図である。まず本図を用いて複写機全体の概略について説明する。
潜像担持体である感光体ドラム１は、複写時には図示されていない駆動装置により一定速度で矢印方向ａに回転駆動され、コロナ放電機からなる帯電チャージャ２により均一に帯電された後、感光体ドラム１上を図示されていない露光装置により画像信号に基づいて変調されたレ−ザ−光３が走査し、原稿像が投影されて、その露光光により静電潜像が形成され、図示しないイレ−サにより作像領域外が除電される。
感光体ドラム１上の静電潜像は現像装置によりトナ−像として顕像化され、このトナ−像は、図示されていない給紙装置から送り込まれ、転写材搬送装置としての転写ベルト４に静電的に吸着させて搬送した転写材としての転写紙５に、転写チャージャ（転写チャ−ジャに代え、転写電極や転写ロ−ラを用いてもよい）６からなる転写装置によって転写される。
感光体ドラム１は転写紙５の分離後に、クリ−ニング装置であるクリ−ニングユニット７により残留トナ−が除去され、除電ランプからなる除電器８により残留電位が除去されて、次の複写に備える。
【００２７】
上記湿式現像装置は、感光体ドラム１の側方に配置され、かつ、現像容器に回動自在に支持されていてそれぞれ矢印方向ｂ、ｃに駆動される現像ロ−ラ９及びスクイズロ−ラ１０などを備えた現像器１１と、該現像器で使用される現像液、具体的にはキャリア液中にトナーが分散された現像液を収容する現像液タンク１２とからなっている。現像器１１内の現像ロ−ラ９は感光体ドラム１の表面と微小間隔を置いて対向するように位置決めされている。現像ロ−ラ９は図示しない駆動装置により矢印ｂのように感光体ドラム１と逆方向に、かつ感光体ドラム１より速い周速で駆動され、上記スクイズロ−ラ１０は図示しない駆動装置により矢印ｃのように感光体ドラム１と同方向に、所定の周速で駆動される。各ロ−ラには、それぞれの基端縁部を現像容器に固定されたスクレ−パ−１３、１４の先端縁部がそれぞれ当接させられている。そして、この現像器の現像ローラ９上に、ポンプにより汲み上げられた現像液タンク１２からの現像液が供給され、かつ現像に使用されなかった現像液が現像器１１内から現像液タンク１２に回収されることにより、現像器１１と現像液タンク１２との間で現像液が循環されている。
【００２８】
現像容器内に供給された現像液は、図示しないバッファ−においてロ−ラ軸方向に振り分けられてスクレ−パ−１３と現像ロ−ラ９とで形成される現像液溜り部に滞留した後、現像ロ−ラ９の回転によって感光体ドラム１表面に供給され、感光体ドラム１表面に形成されている静電潜像を可視像化する。現像ロ−ラ９表面に付着している現像液はスクレ−パ−１３によって掻き落とされる。現像ロ−ラ９によって供給された現像液は、液膜として感光体ドラム１表面に付着して転写位置に向けて移動する。そして、スクイズロ−ラ１０によって余剰の現像液が除去されて適当な厚さの液膜に制御された後に転写領域に搬送される。この感光体ドラム１上の液膜はスクイズロ−ラ１０と感光体ドラム１とのギャップなどの機械条件などにより変えることができる。なお、本実施例では感光体ドラム１とスクイズロ−ラ１０とのギャップは約６０μｍであり、感光体ドラム１は７５mm/secの線速で回転している。
【００２９】
なお、この複写機は、上記感光体ドラム１上方には、該感光体ドラム１と同様に転写ベルト４の表面に対向する図示を省略した感光体ドラムが複数配設され、各感光体ドラムの周囲には、上記感光体ドラム１と同様に、クリ−ニングユニット、帯電チャージャ、露光装置、イレーサ、現像装置、転写チャージャなどが配設され、各現像装置には互いに異なる色の現像液が収容されている。これにより、上記転写ベルト４による転写紙搬送方向で最も上流側に配設された上記感光体からのトナー像転写につづき、順次、同方向下流側に配設された感光体ドラムから各色トナー像が、転写紙５に転写され、これにより、カラ−画像を形成するようになっている。カラー画像が形成された転写紙は、転写ベルト４から分離され、図示を省略した乾燥装置で乾燥された後に機外に排出される。
【００３０】
次に、本実施例において、温度などの変化により感光体ドラム１表面に付着して転写領域に搬送される現像液の膜厚が変わっても、感光体ドラム１上のトナー像を転写紙５に良好に転写できるようにするための構成について説明する。
本実施例の複写機は、現像液の膜厚が変わっても、感光体ドラム１上のトナー像を転写紙５に良好に転写できるように、上記現像装置を通過して転写領域に搬送される感光体ドラム１上の現像液の膜厚を測定し、測定した膜厚に応じて転写チャージャ６に供給する電流を制御する。この液膜測定のため、図示の例では現像装置と転写部との間で感光体ドラム１の表面に対向するように表面電位計１５が配設されている。この表面電位計１５がマイクロプロセッサなどからなる制御部１６に接続され、また該制御部１６に転写電流可変の転写チャージャ６用の電源回路１７も接続されている。
【００３１】
そして、上記制御部１６内の図示を省略した記憶装置には、表面電位計１５の出力と、該出力に対応した適正な転写電流値との対応関係に関するデータが例えばデータテーブルの形で記憶され、かつ、該関係及び表面電位計１５の出力を用いて上記転写用電源回路１７の制御値を切り換える制御プログラムが記憶されている。
【００３２】
ここで、上記対応関係に関するデータは、例えば次のような実験によりあらかじめ求めておく。すなわち、所定の表面電位の感光体ドラム１上に形成する現像液の膜厚を異ならせ、この膜厚が形成される感光体ドラム１の対向面に設けた表面電位計１５によって、各膜厚毎に該現像液膜を介して感光体ドラム１の電位を測定するとともに、その膜厚において良好な転写を行える転写チャ−ジャ６用の転写電流又は転写電圧を求める。この測定表面電位と、それに対応する適正な転写電界を得るための転写電流値又は転写電圧値との関係を、例えばデータテーブルの形で記憶させておく。
【００３３】
また、上記対応関係に関する制御プログラムとしては、除電器８で除電され、かつ帯電チャ−ジャ２による帯電を受けてない感光体表面部分、又は除電器８による除電、帯電チャージャ２による帯電、及び露光装置による露光３のすべてを受けている感光体表面部分、つまり感光体ドラム１の地肌部（白部）相当の電位部分を形成し、該表面部分を作動中の現像器を通過させて現像液を付着させた後に表面電位計１５に対向させて、この対向時の表面電位計１５の出力と、上記データテーブルなどの形で記憶されている関係とを用いて、転写電流可変の転写チャージャ６用の電源回路１７の制御値を切り換える制御プログラムを用いることができる。
【００３４】
以上の構成において、本実施例の湿式画像形成装置では、表面電位計１５によって測定された電位に基づき転写電流可変の転写チャージャ６用の電源回路１７を制御して良好な転写が行える転写電流又は転写電圧を転写チャージャ６に供給するよう調整するので、温度などの変化により感光体ドラム１表面に付着して転写領域に搬送される現像液の膜厚が変わっても、感光体ドラム１上のトナー像を転写紙５に良好に転写することができる。
【００３５】
なお、感光体ドラム１は疲労により一様な電位が低下する傾向があるので、この疲労を表面電位を測定することによって検出し、疲労を補うために帯電チャージャ−２の電圧または電流を上げたり、現像バイアスを下げたりする方法が知られている。本実施例における表面電位計１５は、現像液が付着していない感光体ドラム１表面部分を測定することにより、現像液膜に影響されずに感光体表面電位を測定することも可能であるので、所定の疲労検出用の電位状態にした感光体表面部分を、不作動にした現像器１１を通過させた後に上記表面電位計１５に対向させ、該表面部分の検出結果を上記疲労検出に使用しても良い。
【００３６】
以上の実施例においては、感光体ドラム１に付着して転写領域に搬送される現像液の膜厚を表面電位計１５などからなる膜厚測定器で測定したが、これに代え、現像装置で使用される現像液の温度から上記膜厚を推測して、その膜厚に応じた適正な転写電流又は転写電圧を転写チャージャ６に供給するようにして良い。
【００３７】
例えば、図２は、図１の複写機における現像液の温度と感光体ドラム１に形成されるスクイズ後の現像液の膜厚との関係を、同膜厚を縦軸に取り、同温度を横軸に取って示すグラフである。特性線ａは感光体ドラム１表面の線速Ｖｐに対するスクイズローラ表面の線速Ｖｒの線速比Ｖｒ／Ｖｐが３．０の場合、特性線ｂは同線速比Ｖｒ／Ｖｐが２．５の場合、特性線ｃは同線速比Ｖｒ／Ｖｐが２．０の場合の実験結果を示す（感光体ドラムの線速は７５mm/sec）。各線速比においても、いずれも現像液の温度が高くなるほど液膜が薄くなる一定の傾向があることが判る。そこで、実際に複写機に採用する線速比において、上記温度と上記膜厚との一定の関係をあらかじめ実験など求めておくことにより、上記温度の検出から上記膜厚を推定することができる。よって、各膜厚毎に、その膜厚で適正な転写電界を形成するための転写電流又は転写電圧もあらかじめ実験などにより求めておけば、上記温度を測定することにより、適正な転写電界を形成するための転写電流又は転写電圧を決定することができる。また、上記温度と、その温度で適正な転写電界を形成するための転写電流又は転写電圧との関係をあらかじめ実験などにより求めておけば、上記温度を測定することにより、直接適正な転写電流又は転写電圧を決定することができる。
【００３８】
そして、例えば図１に示すように、上記現像液で使用する現像液の温度を、例えば現像液タンク１２内で測定する温度測定器１８を、該現像液タンク１２に付設し、この温度測定器１８を、転写電流可変の転写チャージャ６用の電源回路１７が接続された制御部１６に接続し、上記実施例と同様、該制御部１６の記憶装置に測定温度と適正転写電流との関係に関するデータテーブルや、測定温度及び該データテーブルを用いて上記転写用電源回路１７の制御値を切り換える制御プログラムを記憶させておくと、適宜転写電流の切換え制御を行うことができる。
【００３９】
〔実施例２〕
次に、本発明の他の実施例に係る複写機について説明する。本実施例の複写機は、転写ベルト４を用いて転写紙５を感光体ドラム１表面に接触させて転写紙５にトナー像を転写するにあたり、図４に示すような転写ベルト４と感光体ドラム１との接触部に形成されるトナー溜り１９により、許容範囲を越えた転写紙５先端部のトナ−汚れが生じないようにするものである。図３は本実施例に係る複写機の概略断面図である。この複写機の概略は、前述の図１の複写機と同様であるので、同一部材に同一の符号を付して説明を省略する。
【００４０】
この複写機においては、前述の図２のグラフに示すように現像液の温度が低くなりすぎて転写領域に搬送される現像液の膜厚が厚くなりすぎる結果、図４に示すような感光体ドラム１と転写ベルト４の接触部の現像液溜り１９が大きくなりすぎて、上記転写紙５先端部のトナー汚れが発生するのを防止するため、現像液タンク１２内に収容する現像液の温度を測定する温度測定器１８を設け、また、現像装置内に温度を調節するためのヒータ２０を設けてある。そしてマイクロプロセッサなどからなる制御部１６の記憶装置に、あらかじめ実験などにより求めておいた上記接触部の現像液溜り１９が転写紙５先端部に許容できない程のトナ−汚れを生じさせる程度になってしまう現像液の温度の下限値を下回らない一定の範囲内に維持されるように必要に応じて上記ヒータ２０を作動させるヒータ制御プログラムを記憶させておく。この感度制御の範囲の上限としては、例えば前述の温度の上昇し過ぎによる現像液膜厚の減少で画質低下が生じない上限温度を用いることができる。
【００４１】
本実施例の複写機においては、現像液タンク１２内の現像液温度を温度測定器１８で測定し、現像液タンク１２内の現像液を加熱するヒータ２０を必要に応じて作動させて、現像液タンク１２内の現像液の温度を、上記温度範囲内に制御するので、転写紙５先端部のトナー汚れが許容範囲を越えず、かつ、転写領域に搬送される現像液不足による画質低下も生じない。
【００４２】
なお、上記接触部の現像液溜り１９が転写紙５先端部に許容できない程のトナ−汚れを生じさせる程度になってしまう現像液の温度の下限値よりも、転写領域に搬送される現像液膜厚が大きすぎて、画像流れなどが生じはじめる現像液温度の方が高温である場合には、該現像液温度を上記温度制御範囲の下限値として用いることが望ましい。これによれば、転写紙５先端部のトナー汚れなどを防止できるとともに、上記画像流れも防止できる。
【００４３】
以上の実施例２の複写機においては、現像液タンク１２内に収容されている現像液の温度を測定し、かつ該タンク１２内の現像液をヒータ２０で加熱するようにしたが、これに代え、図３に示すように感光体ドラム１の温度を測定する温度測定器を例えば感光体ドラム１内に設け、かつ、該感光体ドラム１を加熱するヒータ２１を例えば感光体ドラム１内に設け、これらにより、感光体ドラム１の温度を、所定の温度範囲内に制御し、該感光体ドラム１に供給されながら、現像器１１と現像液タンク１２との間を循環する現像液の温度を所定温度に制御するようにしても良い。この場合には、現像ローラ９により感光体ドラム１に供給され該感光体ドラム１に付着してスクイズローラ１０との対向部まで搬送される現像液を、感光体ドラム１を介して直接加熱するので、スクイズローラ１０通過後の現像液の膜厚を直接的に管理できる。
【００４４】
更に、現像液タンク１２についての温度測定及び加熱と、感光体ドラム１についての感度測定及び加熱との両方を、互いに同一の温度を狙いの制御温度にして行っても良い。これによれば、現像液タンク１２内における現像液の温度と感光体ドラム１表面上、特にスクイズ時の現像液の温度との間のバラツキを最小にできるので、スクイズ後の感光体ドラム１表面の現像液膜厚を良好に管理できる。また現像液タンク１２と感光体ドラム１の両方にヒータ１８、２１を設けたので、複写機のメイン電源投入後のウォーミングアップ中に両ヒータ１８、２１を作動させることにより、所定のスクイズ後現像液膜を実現できる装置状態に立ち上げることができる。
【００４８】
【発明の効果】
請求項１乃至３の湿式画像形成装置によれば、現像液の温度を測定し、この測定結果に基づいて、温度調整手段により、現像装置で現像に使用される現像液の温度が、転写材先端部に許容できない程のトナ−汚れを生じさせる程度になってしまう現像液の温度まで低下しないように調整するので、許容できない程の転写材先端部のトナ−汚れを防止できる。
特に、請求項３の湿式画像形成装置によれば、現像装置に収容される現像液の温度と潜像担持体の温度とを互いに同一になるようにそれぞれ調整するので、現像装置から潜像担持体に供給された後の現像液の温度が、潜像担持体との間の熱交換で低下して、上記下限温度を下回るような事態を防止できる。また装置電源投入時に現像装置と潜像担持体の両方において加熱装置を作動させることにより、迅速に、装置を立ち上げることができる。
【図面の簡単な説明】
【図１】本発明の実施例に係る複写機の概略断面図。
【図２】本発明の他の実施例に係る複写機の概略断面図。
【図３】現像液の温度と感光体ドラムに形成される液膜の厚さとの関係を示すグラフ。
【図４】従来の複写機における不具合の説明図。
【符号の説明】
１感光体ドラム
２帯電チャ−ジャ
３露光レ−ザ−光
４転写ベルト
５転写紙
６転写チャ−ジャ
７クリ−ニングユニット
８除電ランプ
９現像ロ−ラ
１０スクイズロ−ラ
１１現像器
１２現像タンク
１３スクレ−パ−
１４スクレ−パ−
１５表面電位計
１６制御部
１７転写チャ−ジャ電源
１８現像液温度測定器
１９現像液溜り
２０ヒ−タ
２１ヒ−タ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wet image forming apparatus such as a copying machine, a facsimile machine, and a printer. Specifically, a liquid developer is supplied to a surface of a latent image carrier on which a latent image is formed by an electrophotographic process by a developing device. In particular, the present invention relates to a wet image forming apparatus in which development is transferred to a transfer material after the latent image is visualized.
[0002]
[Prior art]
In general, as a wet image forming apparatus using an electrophotographic process, an apparatus using a photosensitive member as a latent image carrier is known. However, there are some photoconductors whose characteristic values change, for example, the residual potential increases as the temperature decreases. Since this change greatly affects the output image, a number of inventions relating to the temperature control device for the photoconductor have been filed as countermeasures, such as heating the photoconductor to a temperature higher than the required minimum temperature when the temperature is low.
[0003]
In addition, on the assumption that the characteristics of the photoconductor change depending on the temperature, the temperature of the photoconductor is detected so that a good image can be formed even in the changed photoconductor characteristics, and image formation is performed based on the detected temperature. A method of adjusting various conditions has also been proposed. Further, instead of directly detecting the temperature of the photoconductor, it is also proposed to adjust the above-mentioned conditions by detecting the temperature of the developing solution that is brought into contact with the photoconductor and brought to substantially the same temperature as the photoconductor. (See, for example, JP-A-1-167780).
[0004]
In addition, in a wet image forming apparatus that obtains an image by transferring an image formed on a latent image carrier such as a photoconductor to a transfer material using a liquid developing device, a surplus of carrier liquid is left with a minimum amount necessary for transfer. A squeeze of a suitable carrier liquid is performed. As a specific method for squeezing the surplus carrier liquid, surplus liquid removing means composed of a squeeze roller, a corona discharger, or the like is disposed facing the surface of the latent image carrier at a predetermined interval, -Rotate the roller in the opposite direction to the latent image carrier in the area facing the latent image carrier, apply a predetermined bias voltage to the squeeze roller, or use the corona discharger to have the same polarity as the toner A method of generating ions and irradiating the latent image carrier with the ions is known.
[0005]
[Problems to be solved by the invention]
However, a problem has been found that even if the image forming conditions are not changed or the image forming conditions are adjusted in accordance with the changed characteristics, there is a problem that the image quality deteriorates due to the temperature inside the apparatus.
[0006]
As a result of intensive investigation of the cause, the film thickness of the developer transported to the transfer region while adhering to the surface of the latent image carrier after the squeeze varies depending on the temperature of the developer. understood. Specifically, as the temperature is increased, the film thickness of the developer conveyed to the transfer region is reduced, and the image density is lowered due to transfer failure. This is presumably because the transfer rate by electrophoresis was lowered due to insufficient film thickness of the developer. Conversely, the lower the temperature, the thicker the developer film on the latent image carrier, resulting in a decrease in image flow and image density. This is because the developer film thickness is large and the developer adhesion amount is excessive, the electric field strength when transferring the toner image formed on the latent image carrier is weakened, and the toner on the latent image carrier is removed. This is presumably because the force attracted to the transfer material is weakened by electrophoresis in the carrier.
[0007]
In addition, in the above-described wet image forming apparatus having a transfer device that transfers a transfer material using a transfer belt, the characteristics of the photoconductor are not changed or image forming conditions are changed according to the changed characteristics. Even when the in-machine temperature is adjusted, when the temperature inside the apparatus is low, toner contamination may occur at the tip of the transfer material in the transport direction, and the degree of toner contamination increases as the in-machine temperature decreases.
[0008]
As a result of intensive investigation of the cause, when the temperature of the developing solution is relatively low as described above, the developing solution that adheres to the surface of the latent image carrier in a large amount with a relatively thick film thickness and is conveyed to the transfer region. However, as shown in FIG. 4, a developer reservoir 19 is formed in the contact portion between the transfer belt 4 and the photosensitive drum 1, and the transfer material 5 on the transfer belt 4 enters the developer reservoir 19. It was found that the developer in the developer reservoir 19 was absorbed at the tip, causing toner stains at the tip.
[0009]
The present invention has been made in view of the above problems, it is an purpose of that, in the wet-type image forming apparatus having a transfer device for contacting the latent image bearing member transfer material by using a transfer belt, It is an object of the present invention to provide a wet image forming apparatus capable of preventing toner stains at a transfer material front end.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the wet image forming apparatus according to claim 1 visualizes the latent image by supplying a liquid developer to the surface of the latent image carrier on which the latent image is formed by a developing device. After that, the transfer material carried on the surface of the transfer belt moved shortly along the moving path including the transfer region facing the surface of the latent image carrier carrying the developed image is brought into contact with the surface of the latent image carrier, In the wet image forming apparatus for transferring the developed image, the liquid developer pool formed at the contact portion between the latent image carrier and the transfer belt is unacceptable toner at the front end portion of the transfer material entering the liquid developer. A temperature adjusting means for adjusting the temperature of the developer used for development in the developing device is provided so as not to decrease to a temperature that becomes so large as to cause contamination .
According to a second aspect of the present invention, there is provided the wet image forming apparatus according to the first aspect, wherein the temperature adjusting means includes a heating device for heating a developer contained in the developing device and the latent image carrier. It is characterized by using at least one of the heating device for heating.
The wet image forming apparatus according to claim 3 is the wet image forming apparatus according to claim 1 , wherein the temperature adjusting unit includes a first temperature measuring device that measures the temperature of the developer contained in the developing device, Based on the first heating device for heating the developer based on the measurement result of the first temperature measuring device, the second temperature measuring device for measuring the temperature of the latent image carrier, and the measurement result of the second temperature measuring device. The second heating device is used to heat the latent image carrier so that the temperature is the same as the target adjustment temperature of the first heating device.
[0021]
[Action]
In the wet image forming apparatus of the first aspect, the developer pool shown in FIG. 4 described above causes an unacceptable toner stain at the leading edge of the transfer material entering the developer. previously obtained in advance by experiment temperature. Then, the temperature adjusting means is adjusted so that the temperature of the developer used for development in the developing device does not decrease to this temperature .
Here, as described above, even if the temperature of the developer used for development in the developing device is too high, the film thickness of the developer conveyed to the transfer region becomes too thin and the image quality deteriorates. The upper limit temperature of the developer is obtained in advance so as not to cause a problem, and the temperature adjusting means is controlled so as not to exceed the upper limit temperature, or a cooling device is additionally provided as necessary. You may make it operate this cooling device as needed.
3. The wet image forming apparatus according to claim 2, wherein at least one of a heating device for heating the developer contained in the developing device and a heating device for heating the latent image carrier is used for development in the developing device. Adjust the temperature of the developer. Among these, the heating device for heating the latent image carrier heats the developer supplied to the latent image carrier through the latent image carrier.
Here, as an aspect of the invention of claim 2, even if only a heating device for heating the developer contained in the developing device is provided and the temperature of the developer in the developing device is controlled to a predetermined temperature, When the difference between the temperature of the latent image carrier and the developing solution temperature in the developing device is large, specifically, when the temperature of the latent image carrier is relatively low, after being supplied from the developing device to the latent image carrier There is a risk that the temperature of the developer is lowered by heat exchange with the latent image carrier. When a relatively large amount of developer is conveyed to the transfer area, for example, by receiving the squeeze while the temperature is below the lower limit temperature due to this temperature drop, the amount of developer in the liquid pool increases and the toner at the tip of the transfer material increases. Contamination may exceed the allowable range.
Therefore, in the wet image forming apparatus according to the third aspect, the temperature of the developer contained in the developing device is measured by the first temperature measuring device, and the first heating device is used as necessary based on the measurement result. The developer contained in the developing device is heated, the temperature of the latent image carrier is measured by a second temperature measuring device, and the latent image carrier is removed by the second heating device as necessary based on the measurement result. The latent image carrier is heated to the same temperature as the target adjustment temperature of the developer. As a result, the temperature of the developer after being supplied from the developing device to the latent image carrier is lowered by heat exchange with the latent image carrier so that it does not fall below the lower limit temperature.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is a wet image forming apparatus will be described. FIG. 1 is a schematic sectional view of a copying machine according to this embodiment. First, an outline of the entire copying machine will be described with reference to FIG.
A photosensitive drum 1 serving as a latent image carrier is rotationally driven in a direction indicated by an arrow a at a constant speed by a driving device (not shown) during copying, and is uniformly charged by a charging charger 2 composed of a corona discharge machine. A laser beam 3 modulated based on an image signal is scanned on the drum 1 by an exposure device (not shown), a document image is projected, and an electrostatic latent image is formed by the exposure light, not shown. The eraser neutralizes the outside of the image forming area.
The electrostatic latent image on the photosensitive drum 1 is visualized as a toner image by a developing device, and this toner image is fed from a paper feeding device (not shown) and is transferred to a transfer belt 4 as a transfer material conveying device. The image is transferred to a transfer sheet 5 as a transfer material electrostatically attracted and conveyed by a transfer device including a transfer charger 6 (a transfer electrode or a transfer roller may be used in place of the transfer charger). .
After the transfer sheet 5 is separated from the photosensitive drum 1, the residual toner is removed by a cleaning unit 7 which is a cleaning device, and the residual potential is removed by a static eliminator 8 consisting of a static elimination lamp. Prepare.
[0027]
The wet developing device is disposed on the side of the photosensitive drum 1 and is rotatably supported by the developing container and is driven in the arrow directions b and c, respectively, and a developing roller 9 and a squeeze roller 10. And a developer tank 12 containing a developer used in the developer, specifically, a developer in which toner is dispersed in a carrier liquid. The developing roller 9 in the developing device 11 is positioned so as to face the surface of the photosensitive drum 1 with a minute gap. The developing roller 9 is driven by a driving device (not shown) in a direction opposite to the photosensitive drum 1 as indicated by an arrow b and at a peripheral speed faster than the photosensitive drum 1, and the squeeze roller 10 is driven by an arrow (not shown). It is driven at a predetermined peripheral speed in the same direction as the photosensitive drum 1 as shown in c. The end edges of the scrapers 13 and 14 whose base edges are fixed to the developing container are brought into contact with the rollers. Then, the developer from the developer tank 12 pumped up by the pump is supplied onto the developing roller 9 of the developer, and the developer not used for development is collected from the developer 11 to the developer tank 12. As a result, the developer is circulated between the developing device 11 and the developer tank 12.
[0028]
The developer supplied into the developer container is distributed in the roller axial direction in a buffer (not shown) and stays in the developer reservoir formed by the scraper 13 and the developer roller 9. The electrostatic latent image formed on the surface of the photosensitive drum 1 is visualized by being supplied to the surface of the photosensitive drum 1 by the rotation of the developing roller 9. The developer adhering to the surface of the developing roller 9 is scraped off by the scraper 13. The developer supplied by the developing roller 9 adheres to the surface of the photosensitive drum 1 as a liquid film and moves toward the transfer position. Then, the excess developer is removed by the squeeze roller 10 and controlled to a liquid film having an appropriate thickness, and then conveyed to the transfer region. The liquid film on the photosensitive drum 1 can be changed according to mechanical conditions such as a gap between the squeeze roller 10 and the photosensitive drum 1. In this embodiment, the gap between the photosensitive drum 1 and the squeeze roller 10 is about 60 μm, and the photosensitive drum 1 rotates at a linear speed of 75 mm / sec.
[0029]
In this copying machine, a plurality of photosensitive drums (not shown) facing the surface of the transfer belt 4 are arranged above the photosensitive drum 1 in the same manner as the photosensitive drum 1. Similar to the photosensitive drum 1, a cleaning unit, a charging charger, an exposure device, an eraser, a developing device, a transfer charger, and the like are disposed around the developing drum. Has been. Thus, following the transfer of the toner image from the photoconductor disposed on the most upstream side in the transfer sheet conveying direction by the transfer belt 4, each color toner image is sequentially transferred from the photoconductive drum disposed on the downstream side in the same direction. Is transferred to the transfer paper 5, thereby forming a color image. The transfer paper on which the color image is formed is separated from the transfer belt 4, dried by a drying device (not shown), and then discharged outside the apparatus.
[0030]
Next, in this embodiment, even if the film thickness of the developer that adheres to the surface of the photosensitive drum 1 and is conveyed to the transfer region changes due to a change in temperature or the like, the toner image on the photosensitive drum 1 is transferred to the transfer paper 5. A configuration for enabling good transfer to be described.
The copying machine of this embodiment is conveyed to the transfer area through the developing device so that the toner image on the photosensitive drum 1 can be satisfactorily transferred to the transfer paper 5 even if the film thickness of the developer changes. The film thickness of the developer on the photosensitive drum 1 is measured, and the current supplied to the transfer charger 6 is controlled according to the measured film thickness. For this liquid film measurement, in the illustrated example, a surface electrometer 15 is disposed between the developing device and the transfer unit so as to face the surface of the photosensitive drum 1. The surface potentiometer 15 is connected to a control unit 16 such as a microprocessor, and a power supply circuit 17 for the transfer charger 6 having a variable transfer current is connected to the control unit 16.
[0031]
In the storage device (not shown) in the control unit 16, data relating to the correspondence between the output of the surface electrometer 15 and an appropriate transfer current value corresponding to the output is stored in the form of a data table, for example. In addition, a control program for switching the control value of the transfer power supply circuit 17 using the relationship and the output of the surface electrometer 15 is stored.
[0032]
Here, the data relating to the correspondence relationship is obtained in advance by, for example, the following experiment. That is, the film thickness of the developer formed on the photosensitive drum 1 having a predetermined surface potential is varied, and each film thickness is measured by the surface potential meter 15 provided on the opposite surface of the photosensitive drum 1 where the film thickness is formed. Each time the potential of the photosensitive drum 1 is measured via the developer film, a transfer current or transfer voltage for the transfer charger 6 that can perform good transfer at the film thickness is obtained. The relationship between the measured surface potential and the transfer current value or transfer voltage value for obtaining an appropriate transfer electric field corresponding to the measured surface potential is stored, for example, in the form of a data table.
[0033]
As a control program related to the above correspondence, the surface portion of the photosensitive member that has been neutralized by the static eliminator 8 and has not been charged by the charging charger 2, or static elimination by the static eliminator 8, charging by the charging charger 2, and exposure. A photosensitive member surface portion that has undergone all of the exposure 3 by the apparatus, that is, a potential portion corresponding to the background portion (white portion) of the photosensitive drum 1 is formed, and the surface portion is passed through a developing device in operation, and a developing solution Is applied to the surface potential meter 15 and the transfer charger 6 with variable transfer current is used by using the output of the surface potential meter 15 at the time of facing and the relationship stored in the form of the data table or the like. A control program for switching the control value of the power supply circuit 17 can be used.
[0034]
In the above configuration, in the wet image forming apparatus of the present embodiment, the transfer current or the transfer current that can perform good transfer by controlling the power supply circuit 17 for the transfer charger 6 with variable transfer current based on the potential measured by the surface potentiometer 15. Since the transfer voltage is adjusted to be supplied to the transfer charger 6, even if the film thickness of the developer that adheres to the surface of the photosensitive drum 1 and is transported to the transfer region changes due to a change in temperature or the like, the transfer voltage on the photosensitive drum 1 is changed. The toner image can be satisfactorily transferred to the transfer paper 5.
[0035]
Since the photosensitive drum 1 tends to have a uniform potential that decreases due to fatigue, this fatigue is detected by measuring the surface potential, and the voltage or current of the charger 2 is increased to compensate for the fatigue. A method for lowering the developing bias is known. The surface potential meter 15 in this embodiment can measure the surface potential of the photoreceptor without being affected by the developer film by measuring the surface portion of the photoreceptor drum 1 where the developer is not attached. Then, the surface portion of the photoreceptor in a predetermined fatigue detection potential state is made to face the surface potential meter 15 after passing through the deactivated developing device 11, and the detection result of the surface portion is used for the fatigue detection. You may do it.
[0036]
In the above embodiment, the film thickness of the developer that adheres to the photosensitive drum 1 and is conveyed to the transfer region is measured by a film thickness measuring device including the surface potentiometer 15 or the like. The film thickness may be estimated from the temperature of the developer used, and an appropriate transfer current or transfer voltage corresponding to the film thickness may be supplied to the transfer charger 6.
[0037]
For example, FIG. 2 shows the relationship between the temperature of the developer in the copying machine of FIG. 1 and the film thickness of the developer after squeezing formed on the photosensitive drum 1, and the same film thickness is plotted on the vertical axis. It is a graph taken along the horizontal axis. The characteristic line a indicates that the linear speed ratio Vr / Vp of the linear speed Vr of the squeeze roller surface to the linear speed Vp of the surface of the photosensitive drum 1 is 3.0, and the characteristic line b has the linear speed ratio Vr / Vp of 2.5. In this case, the characteristic line c shows the experimental result when the linear velocity ratio Vr / Vp is 2.0 (the linear velocity of the photosensitive drum is 75 mm / sec). It can be seen that at each linear velocity ratio, the liquid film tends to become thinner as the temperature of the developer increases. Therefore, the film thickness can be estimated from the detection of the temperature by previously obtaining a certain relationship between the temperature and the film thickness in the linear speed ratio actually employed in the copying machine. Therefore, if the transfer current or transfer voltage for forming an appropriate transfer electric field for each film thickness is obtained in advance by experiments or the like, an appropriate transfer electric field can be formed by measuring the above temperature. A transfer current or a transfer voltage can be determined. Also, if the relationship between the temperature and the transfer current or transfer voltage for forming an appropriate transfer electric field at that temperature is obtained in advance by experiments or the like, the appropriate transfer current or The transfer voltage can be determined.
[0038]
For example, as shown in FIG. 1, a temperature measuring device 18 for measuring the temperature of the developing solution used in the developing solution, for example, in the developing solution tank 12 is attached to the developing solution tank 12, and this temperature measuring device is provided. 18 is connected to the control unit 16 to which the power supply circuit 17 for the transfer charger 6 having a variable transfer current is connected. Similarly to the above-described embodiment, the storage device of the control unit 16 relates to the relationship between the measured temperature and the appropriate transfer current. If a control program for switching the control value of the transfer power supply circuit 17 is stored using the data table, the measured temperature, and the data table, transfer current switching control can be appropriately performed.
[0039]
[Example 2]
Next, a copying machine according to another embodiment of the present invention will be described. In the copying machine of this embodiment, when transferring the toner image onto the transfer paper 5 by bringing the transfer paper 5 into contact with the surface of the photoconductor drum 1 using the transfer belt 4, the transfer belt 4 and the photoconductor as shown in FIG. The toner reservoir 19 formed at the contact portion with the drum 1 prevents toner stains at the leading end of the transfer paper 5 from exceeding the allowable range. FIG. 3 is a schematic sectional view of the copying machine according to the present embodiment. Since the outline of the copying machine is the same as that of the copying machine of FIG. 1 described above, the same members are denoted by the same reference numerals and description thereof is omitted.
[0040]
In this copying machine, as shown in the graph of FIG. 2 described above, the temperature of the developer becomes too low and the film thickness of the developer conveyed to the transfer region becomes too thick. In order to prevent the developer pool 19 at the contact portion between the drum 1 and the transfer belt 4 from becoming too large and causing toner contamination at the front end of the transfer paper 5, the temperature of the developer stored in the developer tank 12 is prevented. And a heater 20 for adjusting the temperature is provided in the developing device. Then, in the storage device of the control unit 16 composed of a microprocessor or the like, the developer pool 19 at the contact portion, which has been obtained in advance by experiments or the like, causes an unacceptable toner stain at the leading end of the transfer paper 5. A heater control program for operating the heater 20 as necessary is stored so as to be maintained within a certain range that does not fall below the lower limit of the developer temperature. As the upper limit of the sensitivity control range, for example, the upper limit temperature at which the image quality does not deteriorate due to the decrease in the developer film thickness due to the excessive increase in temperature can be used.
[0041]
In the copying machine of this embodiment, the temperature of the developer in the developer tank 12 is measured by the temperature measuring device 18, and the heater 20 for heating the developer in the developer tank 12 is operated as necessary to develop. Since the temperature of the developer in the liquid tank 12 is controlled within the above temperature range, the toner contamination at the front end of the transfer paper 5 does not exceed the allowable range, and the image quality is also deteriorated due to a shortage of developer conveyed to the transfer area. Does not occur.
[0042]
Note that the developer transported to the transfer region is lower than the lower limit value of the developer temperature at which the developer reservoir 19 at the contact portion causes unacceptable toner stains at the leading end of the transfer paper 5. When the developer temperature at which image thickness starts to occur due to the film thickness being too large, it is desirable to use the developer temperature as the lower limit of the temperature control range. According to this, it is possible to prevent toner smearing at the front end of the transfer paper 5 and to prevent the above-described image flow.
[0043]
In the copying machine of the second embodiment, the temperature of the developer contained in the developer tank 12 is measured and the developer in the tank 12 is heated by the heater 20, Instead, as shown in FIG. 3, a temperature measuring device for measuring the temperature of the photosensitive drum 1 is provided in the photosensitive drum 1, for example, and a heater 21 for heating the photosensitive drum 1 is provided in the photosensitive drum 1, for example. The temperature of the developing solution circulating between the developing device 11 and the developing solution tank 12 while being supplied to the photosensitive drum 1 is controlled by controlling the temperature of the photosensitive drum 1 within the predetermined temperature range. May be controlled to a predetermined temperature. In this case, the developer supplied to the photosensitive drum 1 by the developing roller 9 and attached to the photosensitive drum 1 and transported to a portion facing the squeeze roller 10 is directly heated via the photosensitive drum 1. Therefore, the film thickness of the developer after passing through the squeeze roller 10 can be directly managed.
[0044]
Further, both the temperature measurement and heating for the developer tank 12 and the sensitivity measurement and heating for the photosensitive drum 1 may be performed with the same temperature as the target control temperature. According to this, since the variation between the temperature of the developer in the developer tank 12 and the surface of the photosensitive drum 1, particularly the temperature of the developer during squeeze can be minimized, the surface of the photosensitive drum 1 after squeezing. The film thickness of the developer can be managed well. Further, since the heaters 18 and 21 are provided in both the developer tank 12 and the photosensitive drum 1, by operating both heaters 18 and 21 during warming up after the main power supply of the copying machine is turned on, a predetermined post-squeezed developer solution is provided. It is possible to start up an apparatus state that can realize a film.
[0048]
【The invention's effect】
According to the wet image forming apparatus of the first to third aspects, the temperature of the developer is measured, and based on the measurement result, the temperature of the developer used for the development in the developing device is determined by the temperature adjusting unit. Since the adjustment is made so as not to lower the temperature of the developer so as to cause an unacceptable toner stain at the front end portion, an unacceptable toner stain at the front end portion of the transfer material can be prevented.
In particular, according to the wet image forming apparatus of the third aspect, the temperature of the developer contained in the developing device and the temperature of the latent image carrier are adjusted to be equal to each other. It is possible to prevent a situation in which the temperature of the developer after being supplied to the body is lowered by heat exchange with the latent image carrier and falls below the lower limit temperature. Further, the apparatus can be quickly started up by operating the heating device in both the developing device and the latent image carrier when the apparatus is turned on.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a copying machine according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a copying machine according to another embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the temperature of a developing solution and the thickness of a liquid film formed on a photosensitive drum.
FIG. 4 is an explanatory diagram of a problem in a conventional copying machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging charger 3 Exposure laser beam 4 Transfer belt 5 Transfer paper 6 Transfer charger 7 Cleaning unit 8 Static elimination lamp 9 Developing roller 10 Squeeze roller 11 Developer 12 Developing tank 13 Scraper
14 Scraper
15 Surface potential meter 16 Control unit 17 Transfer charger power supply 18 Developer temperature measuring device 19 Developer reservoir 20 Heater 21 Heater

Claims

After a latent image is formed on the surface of the latent image carrier on which the latent image is formed by supplying a liquid developer by a developing device to visualize the latent image, a transfer region facing the surface of the latent image carrier carrying the developed image is formed. In a wet image forming apparatus for transferring a developed image by bringing a transfer material carried on the surface of a transfer belt moved shortly along a moving path in contact with the surface of the latent image carrier,
The liquid developer pool formed at the contact portion between the latent image carrier and the transfer belt does not drop to a temperature that is so large that unacceptable toner contamination occurs at the leading end of the transfer material entering the latent image carrier. As described above, a wet image forming apparatus comprising temperature adjusting means for adjusting the temperature of a developer used for development in the developing device.

2. The temperature adjusting means according to claim 1 , wherein at least one of a heating device for heating the developer contained in the developing device and a heating device for heating the latent image carrier is used. Wet image forming apparatus.

A first temperature measuring device for measuring the temperature of the developer contained in the developing device; and a first heating device for heating the developer based on a measurement result of the first temperature measuring device. And a second temperature measuring device for measuring the temperature of the latent image carrier, and the latent image so as to have the same temperature as the target adjustment temperature of the first heating device, based on the measurement result of the second temperature measuring device. The wet image forming apparatus according to claim 1 , wherein the wet image forming apparatus is configured using a second heating device that heats the carrier.