JP3663611B2

JP3663611B2 - Development device

Info

Publication number: JP3663611B2
Application number: JP20761996A
Authority: JP
Inventors: 純安部; 憲明山崎; 明彦野田; 新一倉本; 正太大場
Original assignee: Fuji Xerox Co Ltd; Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 1996-07-19
Filing date: 1996-07-19
Publication date: 2005-06-22
Anticipated expiration: 2016-07-19
Also published as: JPH1039624A

Description

【０００１】
【発明の属する技術分野】
本発明は、複写機、プリンター等の電子写真式の画像形成装置において用いられ、像担持体上に形成された静電潜像をトナーの付着によって可視化する現像装置に関する。
【０００２】
【従来の技術】
従来より、像担持体上に形成された潜像をトナーの付着により可視化する現像装置として、１成分現像方式又は２成分現像方式によるものが知られている。このような現像装置は、像担持体と対向する位置に回転可能な現像剤担持体を備えており、現像剤担持体上にトナー層又は２成分現像剤による磁気ブラシを形成して像担持体と対向する現像領域に搬送する。そして、現像剤担持体と像担持体との間に現像バイアス電圧を印加して電界を形成し、トナーを像担持体上の潜像に転移させるものである。
【０００３】
このような現像装置では、現像領域でトナーを像担持体上の潜像に良好に転移させるために、トナーに所定の帯電量を与える必要がある。２成分現像方式の現像装置は、トナーを摩擦帯電序列において隔たっているキャリアと混合・撹拌することで、トナーに電荷を付与するものであるが、トナーに外添された帯電制御剤が遊離してキャリア表面を汚染することがある。従って、キャリアを長期間使用するとそれらの影響によりトナーに電荷を付与することができなくなり、現像剤の交換が必要になるという欠点がある。また、トナーとキャリアとの混合比を一定に保つためのトナー濃度コントロール装置や現像剤撹拌装置を必要としたり、磁性キャリアを担持するため現像剤担持体内にマグネットを配設する必要があったりして、装置の複雑化を招くという欠点がある。
【０００４】
一方、１成分現像方式の現像装置は、これら２成分現像方式の欠点を克服することができるものとして広く利用されている。この現像装置は、現像剤担持体に弾性部材からなるブレードと呼ばれるトナー層形成部材を圧接させ、現像剤担持体上に１成分のトナー層を形成するとともに、トナー層形成部材の摩擦帯電によりトナーに電荷を付与するものである。しかし、一般にブレードによるトナー帯電能力は低く、すべてのトナーを十分に帯電することが難しく、所望の極性とは逆に帯電した所謂逆極性のトナーが存在し、その逆極性のトナーにより地かぶりが発生するという欠点がある。すなわち、ブレードでの摩擦帯電においてはトナーがブレードと接触する確率が低く、特に微小トナーは摩擦帯電されずに層形成部分を通過してしまいトナーが帯電されないことがある。そこで摩擦帯電を促進するためにトナー層形成部材のトナーへの圧接力を増加することが考えられるが、摩擦熱によりトナーのバインダー樹脂が溶融し、凝縮したトナーがブレードに詰まって、画像に白筋が発生するという問題が生じる。
【０００５】
上記のようなトナーを摩擦帯電する装置の問題点を解消するために、トナーに直接電荷を付与する現像装置が提案されている。このような方式として、例えば、実開昭６３−１３８５６０号公報に開示される現像装置や、図１４又は図１５に示す現像装置などがある。
実開昭６３−１３８５６０号公報に開示される現像装置は、現像剤担持体と対向する位置にコロナ放電器を配設し、トナー層へ所望の極性のイオンを照射してトナーに電荷を付与するものである。しかし、コロナ放電器を用いると、コロトロンワイヤーに汚れが付着し、均一な放電が得られない。また、コロトロンワイヤー近傍の空気層を電離させるための高電圧が必要であり、放電の軸方向の安定性などを考慮すると５ｋＶ以上の電圧が必要となる。さらに、放電時にオゾンの発生が多いなどの欠点もある。
【０００６】
一方、図１４に示す現像装置は、現像剤担持体２０２と、この現像剤担持体と圧接されトナー層を形成する層形成ブレード２０３と、現像剤担持体２０２と接触して、又は微小間隔をおいて支持される円筒状の帯電付与部材２０４と、現像剤担持体へトナーを供給するトナー供給部材２０５と、現像バイアス電源２０６と、トナー帯電用電源２０７とを備えている。そして、帯電付与部材２０４に電源２０７から電圧を印加して現像剤担持体２０２との間隙内で放電を発生させ、その放電現象で発生したイオン又は電子をトナーに付着させてトナーを帯電するものである。
【０００７】
また、図１５に示す現像装置は、現像剤担持体２１２と圧接するように層形成ブレード２１３を配設し、これに電源２１７からトナー帯電用の電圧を印加する。これにより層形成ブレード２１３と現像剤担持体２１２との間隙内で放電を発生させ、現像剤担持体２１２上にトナー層を形成するとともにトナーを帯電させるようにしたものである。
【０００８】
上記のような図１４又は図１５に示す現像装置は、コロナ放電器ほどの高電圧を必要とせず、さらにオゾンの発生も少ないという利点がある。このような技術として、例えば特開昭５４−１７０３０号公報、特開昭６２−２９１６７８号公報、特開昭６４−６２６７５号公報などに開示されている。
【０００９】
【発明が解決しようとする課題】
しかしながら、上記図１４又は図１５に示す現像装置では以下に示すような問題点がある。
図１４に示す現像装置では、帯電付与部材２０４に印加される電圧が放電電圧以下であると、体積抵抗率の高いトナーを使用しているため電荷誘導が十分に行われず、トナーを所望の極性に帯電することはできない。一方、印加電圧を上げることで電極からの放電現象によりトナーを帯電することが可能であるが、図１６に示すように帯電付与部材２０４と現像剤担持体２０２との間には、放電に伴う電離により電子なだれ現象が発生しており、その結果、放電領域にプラスイオンと電子又はマイナスイオンという相反する極性のものが発生する。また、図１５に示す現像装置でも同様に、層形成ブレード２１３と現像剤担持体２１２との間に電子なだれ現象が発生し、相反する極性のイオン等が発生する（図１７）。
【００１０】
従って、トナーを所望の極性（本例ではマイナス）に帯電するため電子又はマイナスイオンのいずれかをトナーに付着させようとしても、放電領域は電離現象で発生したプラスイオンと電子又はマイナスイオンで満たされているため、電離域に満たされたプラスイオンと電子又はマイナスイオンの両方ともトナーに付与されてしまう。このため、放電により帯電されたトナーは所望の極性に揃わず、逆極性トナーが発生してしまう。これが、逆極性トナーが発生してしまうメカニズムであると考えられる。ここで逆極性は、本例のようにトナーをマイナスに帯電したい場合はプラス電荷をさすが、トナーをプラス帯電する場合はマイナス電荷が逆極性である。文献「放電現象」（東京電機大学出版、本多侃士著、６４ページ）に基づいて、平行する２つの電極間に発生している電子とプラスイオンの相対密度を計算してみると、図１８に示すように、プラスイオンは陽極（現像剤担持体）の極近傍にも存在し、トナーの大きさ（７μｍ〜１０μｍ）において、電子の数千倍あることが示される。つまり、放電によりトナーをマイナスに帯電しようとした場合には、これと同時にかなりの量のプラスのトナーが発生すると考えられる。
【００１１】
例えば、「最近の電子写真現像システムとトナー材料の開発・実用化」（日本科学情報株式会社出版部、竹内学。３０３ページ）の記載と同様に、トナー粒子１個１個の極性と帯電量を分布として計測する方法によれば、上記現像装置において発生する逆極性トナーは２０ｗｔ％であった。このような逆極性のトナーが現像剤担持体の回転により現像領域に搬送されると、現像されたトナー像に地かぶりなどの画質劣化が発生し、良好な画像を得ることはできない。また、逆極性のトナーが現像剤担持体上から飛散し、機内のトナー汚染を招くという問題がある。
【００１２】
本発明は、上記のような問題点に鑑みてなされたものであり、その目的は、逆極性のトナーの発生を防止して現像剤担持体上のトナーをほぼ均一に帯電し、長期にわたり良好な画質が得られる現像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】
上記問題点を解決するために、請求項１に記載の発明に係る現像装置は、表面に静電電位の差による潜像が形成された像担持体と近接もしくは接触するように配設される現像剤担持体と、前記現像剤担持体の周面に現像剤の薄層を形成する層形成部材とを備え、前記像担持体と前記現像剤担持体とが対向する現像領域で、薄層化された前記現像剤を前記像担持体に選択的に転移させて、前記潜像を可視化する現像装置において、前記現像剤担持体上に既に現像剤の薄層が形成されている位置で該現像剤担持体と近接・対向するように配置され、前記現像剤担持体との間に電界を生じさせる電荷付与部材と、該電荷付与部材と前記現像剤担持体との間に配置され、前記電荷付与部材と前記現像剤担持体とが直接に対向する部分が生じるように貫通部分が形成されて、前記電荷付与部材の電位と前記現像剤担持体の電位との間の電位が付与される帯電制御部材とを有し、前記電荷付与部材と前記帯電制御部材との少なくとも一方は、半導電性材料からなるものであり、前記帯電制御部材は、前記電荷付与部材に直接接触して、又は絶縁体層を介して接触配置され、前記電荷付与部材と前記帯電制御部材の間に放電開始電圧以上の電圧を印加するとともに、該帯電制御部材と前記現像剤担持体との間には所定の極性のイオン又は電子が現像剤担持体側へ移動する電界を形成するように放電開始電圧以下の電圧を印加するものとする。
【００１４】
かかる現像装置では、前記電荷付与部材に印加する電圧の平均値をＶｂ（Ｖ）、前記帯電制御部材に印加する電圧の平均値をＶｍ（Ｖ）としたときに、
｜Ｖｂ｜＞｜Ｖｍ｜の条件を満たすように、電荷付与部材と帯電制御部材に独立の電圧を印加するものとし、電荷付与部材と帯電制御部材との間に放電開始電圧以上の電圧を印加するとともに、電荷付与部材と現像剤担持体との間には帯電したい極性のイオン又は電子が現像剤担持体側へ移動するように電界を形成するが、放電を生じないように電圧を設定する。
【００１５】
このような現像装置では、電荷付与部材と帯電制御部材との間に放電開始電圧以上の電圧を印加することで強い電界が形成され、両者間で放電が発生する。この放電により電離現象が発生し、電子なだれ現象によりプラスイオンと電子およびマイナスイオンが発生するが、電離域は電荷付与部材と帯電制御部材との間に限定され、帯電制御部材と現像剤担持体との間、すなわち現像剤担持体上に薄層形成されたトナーの存在している領域では電離は生じない。このため、トナー層の厚さの範囲内での電離は発生せず、プラスイオンとマイナスイオンとが生成されない。
【００１６】
一方、帯電制御部材と現像剤担持体との間には放電を開始するよりも小さい電界が形成されており、帯電制御部材と現像剤担持体との間の電界作用によって、電荷付与部材と帯電制御部材との間とその近傍に発生したプラスイオン又はマイナスイオン等のいずれか一方が現像剤担持体側に引き付けられ、現像剤担持体上に形成されたトナー層に付与される。これにより、トナーを所望の極性に帯電することが可能となる。
【００１７】
このような現像装置において、電荷付与部材と帯電制御部材とはいずれも導電性材料又は半導電性材料からなるものとすることができるが、持続的な放電を生じさせるために、いずれか一方は半導電性材料からなるものとするのが望ましい。ここで、半導電性材料とは体積抵抗が１０³ Ω・ｃｍ〜１０¹¹Ω・ｃｍ程度のものである。
帯電制御部材の形状はトナーをほぼ均一に帯電させることができるものであれば適宜に設定することが可能であり、例えば請求項２に記載の発明のように、導電性材料又は半導電性材料からなる網状部材や、請求項３に記載の発明のように、多数の小孔を有する導電性又は半導電性の薄板部材とすることができる。この帯電制御部材は電荷付与部材と微小間隙をおいて支持されてもよいし、一部が接触するように支持されるものでもよい。また、この電荷付与部材と帯電制御部材との間に、絶縁材料からなり、多数の小さな開口を有する薄い網状部材又は板状部材を介挿してもよい。
【００１８】
請求項４に記載の発明は、表面に静電電位の差による潜像が形成された像担持体と近接もしくは接触するように配設される現像剤担持体と、前記現像剤担持体の周面に現像剤の薄層を形成する層形成部材とを備え、前記像担持体と前記現像剤担持体とが対向する現像領域で、薄層化された前記現像剤を前記像担持体に選択的に転移させて、前記潜像を可視化する現像装置において、前記現像剤担持体上に既に現像剤の薄層が形成されている位置で該現像剤担持体と近接・対向するように配置され、前記現像剤担持体との間に電界を生じさせる電荷付与部材と、該電荷付与部材と前記現像剤担持体との間に配置され、前記電荷付与部材と前記現像剤担持体とが直接に対向する部分が生じるように貫通部分が形成されて、前記電荷付与部材の電位と前記現像剤担持体の電位との間の電位が付与される帯電制御部材とを有し、前記電荷付与部材は、円筒状に形成され、軸線回りに回転可能に支持されており、前記帯電制御部材は、前記電荷付与部材より径が大きい円筒状に形成され、該電荷付与部材に外挿されて、前記現像剤担持体との対向位置で内周面の一部が該電荷付与部材と接触して回転するように支持され、前記電荷付与部材と前記帯電制御部材の間に放電開始電圧以上の電圧を印加するとともに、該帯電制御部材と前記現像剤担持体との間には所定の極性のイオン又は電子が現像剤担持体側へ移動する電界を形成するように放電開始電圧以下の電圧を印加するものとする。
【００１９】
このような現像装置では、電荷付与部材、帯電制御部材及び現像剤担持体が共に回転し、電荷付与部材と帯電制御部材との接触部近傍の微小間隙で放電が発生する。そして、この放電は電荷付与部材の現像剤担持体と対向する部分に限定されるので、電荷付与部材と帯電制御部材との間で過大な電流が流れるのを防止することができる。
【００２０】
また、この現像装置では、請求項５に記載の発明のように、前記帯電制御部材が、前記電荷付与部材と前記現像剤担持体とに挟持され、前記現像剤担持体の回転に従動して回転駆動されるものとすることができる。これにより、帯電制御部材の支持構造が簡単になり、装置の大型化や複雑化を防止できる。
【００２１】
また、請求項６に記載の発明のように、前記帯電制御部材が、前記現像剤担持体と離隔するように支持され、周速度が前記現像剤担持体の周速度と差を有するように回転駆動されるものとすることもできる。これにより、帯電制御部材の電極部又は開口部とは現像剤担持体の表面と相対的に移動し、現像剤担持体上の現像剤をより均一に帯電することが可能となる。
【００２２】
請求項７に記載の発明に係る現像装置では、前記帯電制御部材が、前記電荷付与部材の表面上に絶縁性層を介して積層された導電性層又は半導電性層によって形成されている。これにより、電荷付与部材と帯電制御部材と間でのリーク現象が防止され、安定した放電によりトナーを良好に帯電させることができる。また、帯電制御部材と帯電付与部材とを一体とすることで、装置の大型化や複雑化を防止できる。ここで、上記絶縁性層は体積抵抗が１０¹²Ω・ｃｍ程度以上の材料で形成された層である。
【００２３】
また、この現像装置では、請求項８に記載の発明のように、前記電荷付与部材が、前記層形成部材と一体となるように支持されるものとすることができる。これにより、層形成部材によって現像剤担持体上に現像剤層が形成されるとともに、電荷付与部材の近傍で放電を発生させることができる。このため、現像剤層の形成とともに現像剤を帯電させることが可能となり、装置の大型化や複雑化を防止できる。
【００２４】
請求項９に記載の発明は、表面に静電電位の差による潜像が形成された像担持体と近接もしくは接触するように配設される現像剤担持体と、前記現像剤担持体の周面に現像剤の薄層を形成する層形成部材とを備え、前記像担持体と前記現像剤担持体とが対向する現像領域で、薄層化された前記現像剤を前記像担持体に選択的に転移させて、前記潜像を可視化する現像装置において、前記現像剤担持体上に既に現像剤の薄層が形成されている位置で該現像剤担持体と近接・対向するように配置され、前記現像剤担持体との間に電界を生じさせる電荷付与部材と、該電荷付与部材と前記現像剤担持体との間に配置され、前記電荷付与部材と前記現像剤担持体とが直接に対向する部分が生じるように貫通部分が形成されて、前記電荷付与部材の電位と前記現像剤担持体の電位との間の電位が付与される帯電制御部材とを有し、前記帯電制御部材は、前記電荷付与部材の表面上に絶縁性層を介して積層された導電性層又は半導電性層によって形成されており、前記電荷付与部材が、回転可能な円筒状部材又は周回可能な無端ベルト状部材からなり、該電荷付与部材の周速度が、前記現像剤担持体の周速度と差を生じるように駆動されるものであり、前記電荷付与部材と前記帯電制御部材の間に放電開始電圧以上の電圧を印加するとともに、該帯電制御部材と前記現像剤担持体との間には所定の極性のイオン又は電子が現像剤担持体側へ移動する電界を形成するように放電開始電圧以下の電圧を印加するものとする。
このような装置では、帯電制御部材である電極層と現像剤担持体の表面が相対的に移動し、放電は微視的には均一に生じてはいないが、現像剤担持体上の現像剤をより均一に帯電することが可能となる。
【００２５】
また、請求項１０に記載の発明に係る現像装置では、前記帯電制御部材の少なくとも一部が半導電性材料又は絶縁性材料で被覆されているものとすることができる。これにより、電荷付与部材と帯電制御部材との間又は帯電制御部材と現像剤担持体との間でリーク現象や電荷付与部材表面の電位低下による帯電性不良が発生するのが防止され、トナーを良好に帯電させることができる。
【００２６】
なお、上記現像装置では、電荷付与部材と被帯電体である現像剤担持体との間に帯電制御部材を配置することで、イオン等を発生する電離領域を帯電付与部材側に制限するものであるが、従来帯電器として使われるスコロトロン帯電器も、本発明と似た構成を取る。すなわち、スコロトロン帯電器では、放電ワイヤーは本発明の帯電付与部材であり、被帯電体は感光体や現像剤担持体であり、また本発明の帯電制御部材は放電ワイヤーと被帯電体との間に配設されるスクリーングリッド電極に相当すると考えることもできる。しかしながら、スコロトロン帯電器では、放電ワイヤーの直径が３０〜１００μｍと小さいため、帯電制御部材がなくても、放電ワイヤーがそれを囲むシールド電極及び被帯電体との間で発生させる電界はワイヤー近傍のみで電離を引き起こし、シールドと被帯電体の近傍ではイオン又は電子が移動するのみである。つまり、スクリーングリッド電極は、帯電しようとする極性のイオン又は電子の移動を制限して被帯電体の帯電電位が一定になる働きをしており、放電による電離領域を制御する働きは積極的にはない。これに対して本願発明は、２つの微小な電極間における電界を電離領域と電子やイオンの移動領域とに分離する働きを有しており、被帯電体付近で帯電しようとする極性と逆極性のイオンが多量に発生するのを制限するもので、機能が従来のスコロトロン帯電器と全く異なっている。
【００２７】
【発明の実施の形態】
以下、本発明の実施の形態を図に基づいて説明する。
図１は、請求項１、請求項２、請求項４又は請求項５に記載の発明の一実施形態である現像装置を示す概略構成図である。
この現像装置は、表面に帯電電位の差による潜像を形成することができる像担持体１との対向位置に設けられており、ハウジング１０内に、像担持体１と近接対向し表面にトナーを付着して搬送する現像剤担持体２と、この現像剤担持体上のトナーを規制してトナー層を形成する層形成部材３と、トナーを撹拌するとともに現像剤担持体２にトナーを供給する撹拌供給部材４と、現像剤担持体２と対向して配置され、この対向位置に放電を生じさせる電荷付与部材５と、この電荷付与部材５と現像剤担持体２との間に配置され、これらの間に生じる放電の電離領域を制限する帯電制御部材６とを備えている。さらに、現像剤担持体２と像担持体１との間に現像用の電圧を印加する現像用電源７と、現像剤担持体２と電荷付与部材５との間にトナー帯電用の電圧を印加するトナー帯電用電源８と、帯電制御部材６に電離領域を制限するための電圧を印加する帯電制御用電源９とを備えている。
【００２８】
上記現像剤担持体２は、回転可能に支持され、現像用電源７からトナーと同極性の約−２００Ｖの直流電圧が印加されるものである。これにより、現像剤担持体２と像担持体１との間に電界が形成され、トナーが像担持体１上の潜像に転移されるようになっている。この現像剤担持体は、アルミニウムやステンレスの丸棒やパイプを切削加工した後、外周面にサンドブラスト、液体ホーニング、エメリー研磨等の機械加工を施すか、或いは化学腐食を施すことによりＲａ＝０．１〜５．０μｍ程度の凹凸を形成したものである。また、アルミニウムやステンレスの丸棒やパイプを切削加工した後に、導電粉を分散させた樹脂層を形成したものでもよい。本例の現像剤担持体２はΦ２０ｍｍとなっており、アルミニウムのパイプを切削加工した後、外周面にサンドブラスト陽極酸化処理を施したものが用いられている。また、現像用電源７から印加される電圧は、現像性能を確保するため直流電圧と交流電圧とを重畳した電圧としてもよい。
【００２９】
上記層形成部材３は、厚さ０．０３〜０．３ｍｍ程度のステンレスの板バネに、導電性粉を分散させたＳｉゴムやＥＰＤＭゴムからなる圧接部材を加硫接着したものであり、現像剤担持体２への接触圧力は５〜１００ｇ／ｃｍ程度に設定されている。また、ゴムの硬度は２０〜８０度のものが使用可能であり、好ましくは３０〜６０度が適している。このような層形成部材３で圧接されることにより、現像剤担持体２上に５〜３０μｍ程度のトナー層が形成されるようになっている。
【００３０】
上記電荷付与部材５は、円筒状に形成され、軸線回りに回転可能に支持されている。この電荷付与部材５は、イオン導電体を含んだもの、もしくはゴムに導電性微粒子を配合したものであり、体積抵抗率が１０⁵ 〜１０¹⁰Ω・ｃｍ程度のものである。この体積抵抗率は、特に１０⁷ 〜１０⁸ Ω・ｃｍ程度が望ましい。
【００３１】
上記帯電制御部材６は、線径５０μｍ、ピッチ１２７μｍのステンレスのメッシュ状部材からなり、電荷付与部材５より径が大きい円筒状に形成されている。この帯電制御部材６は、電荷付与部材５に外挿され、該電荷付与部材５と現像剤担持体２とに挟持されており、現像剤担持体２との対向位置で内周面の一部が電荷付与部材５と接触して回転するようになっている。このとき、帯電制御部材６は現像剤担持体２の回転に従動して回転駆動される。
【００３２】
また、現像剤担持体２上のトナーを負極性に帯電するためには、電荷付与部材５と帯電制御部材６との間には放電を開始するように電界を形成し、帯電制御部材６と現像剤担持体２との間には放電を生じない程度に勾配の小さい電界であって、負電荷を現像剤担持体側に引き付ける方向の電界を形成する。このため、帯電制御部材６と現像剤担持体２との電位の関係は、例えば以下の関係に保たれている。
（現像剤担持体電位）−（帯電制御部材電位）＝１００Ｖ
【００３３】
また、帯電付与部材５と帯電制御部材６との電位の関係は、以下の関係に保たれている。
（帯電制御部材電位）−（電荷付与部材電位）＝１０００Ｖ
なお、これらの部材の電位は電荷付与部材５と現像剤担持体２との間隔、帯電制御部材６の構造・厚さ等によって適宜決定されるものである。また、電荷付与部材５、帯電制御部材６、および現像剤担持体２が、それぞれ間隙をおいて設けられるときにはこれらの間隙の大きさも考慮して定められる。本例では、現像剤担持体２には電源７から−２００Ｖの電圧が印加され、帯電制御部材６には電源９から−３００Ｖの電圧が印加され、電荷付与部材５のシャフトには電源８から−１３００Ｖの電圧が印加されている。
【００３４】
なお、上記現像装置で用いられる現像剤は一成分系のトナーであり、スチレン樹脂、アクリル樹脂若しくはポリエステル樹脂等の各種熱可塑性樹脂中に顔料や含金属アゾ染料等の極性制御剤を分散し、粉砕、分級により３〜２０μｍ（平均粒径７μｍ）の大きさにしたものである。また電荷制御剤が添加され、負極性の電荷が付与されている。電荷制御剤としては、疎水化処理したシリカ、アルミナ、チタン等の０．１μｍ以下の微粒子が用いられるが、疎水性シリカが最も望ましい。またトナーの流動性助剤が外添されている。
なお、上記像担持体１としてはセレン系感光体や有機感光体が用いられ、像担持体１と現像剤担持体２とは接触してもよいし、あるいは１００μｍ〜４００μｍ程度の間隙をおいて対向させてもよい。
【００３５】
このような現像装置では、撹拌供給部材４の回転によりハウジング１０内のトナーが撹拌され、現像剤担持体２に供給される。現像剤担持体２の表面付近のトナーは現像剤担持体２の回転により層形成部材３との対向位置へ搬送され、層形成部材３の押圧力により現像剤担持体２上にトナー層が形成される。その後、トナー層は電荷付与部材５及び帯電制御部材６との対向位置に搬送される。このとき、電荷付与部材５と帯電制御部材６との間、及び帯電制御部材６と現像剤担持体２との間には上記のような電圧が印加されており、これらが対向する領域に電界が形成される。このとき、現像剤担持体上のトナーが帯電される状態を図２及び図３を用いて説明する。
【００３６】
電荷付与部材５と現像剤担持体２との間に電制御部材６が入らないときの電位分布はこの間隙内でほぼ均一な電界となるが、帯電制御部材６が間に入り、これに電圧が印加されることにより、図３（ａ）に示すように電界が歪み、不均一な電界となる。図３（ｂ）は、図３（ａ）中の直線Ａ−Ａ′に沿った電位変化を示したものであり、これにＰａｓｃｈｅｎの放電開始電界の勾配Ｂを重ねると、接点Ｃより電界が大きい電荷付与部材５の側のみが放電可能であり、現像剤担持体２の側の電界は放電開始電界より小さいため電離しない。従って、図２に示すように電荷付与部材５の付近では放電に伴う電離によりマイナスイオン又は電子の他にプラスイオンが発生するが、現像剤担持体２の近傍では電離が発生せず、帯電制御部材６と現像剤担持体２との間の電界作用によりマイナスイオン又は電子が現像剤担持体に引き付けられる。そして、この電荷が現像剤担持体上のトナーに付着し、トナーが帯電される。従って、電離にともなって発生するプラスイオンは電荷付与部材５の側でのみ存在し、電荷付与部材５へ吸着されるが、現像剤担持体２上のトナーに付着することはない。このように、電荷付与部材５と現像剤担持体２との間にメッシュ状の帯電制御部材６を配置することにより、電離領域がトナーから離れた場所に限定されるので、逆極性トナーの発生が抑制される。
【００３７】
このようにして均一な電荷が付与されたトナー層は、現像剤担持体２の回転により像担持体１と対向する現像領域に搬送される。そして、現像剤担持体２と像担持体１との間に形成される現像電界により、上記トナーが像担持体１の潜像に転移して現像が行われる。
【００３８】
このような現像装置において、トナーの帯電効果を確認したところ、トナーは−７μＣ／ｇから−１２μＣ／ｇに帯電され、逆極性のトナーは０．１ｗｔ％以下であり、良好な帯電性が得られた。
【００３９】
なお、上記現像装置では、帯電制御部材が回転するのに伴って軸方向に移動することがあるため、電荷付与部材の中央部分の径を太くしてもよい。また、現像剤担持体と逆方向にテンションロール部材を設け、そのロールの軸方向における中央部分の径を太くしてもよい。
【００４０】
図４は、請求項１、請求項４又は請求項５に記載の発明の一実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置は、上記図１に示す現像装置とほぼ同じ構成であるが、図４（ｂ）に示すように、帯電制御部材１６がフォトエッチング、エレクトロフォーミング、レーザー加工などにより作成した、多数の円形小孔１６ａを有する導電性フィルムからなる。この帯電制御部材１６は、現像剤担持体１２と接触し、現像剤担持体２の駆動により帯電制御部材１６が従動回転するとともに、この帯電制御部材１６の回転により電荷付与部材１５が回転するようになっている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００４１】
このような現像装置では、電荷付与部材１５と帯電制御部材１６との間の電界により放電現象が生じ、プラスイオンとマイナスイオン又は電子が発生するとともに、帯電制御部材１６と現像剤担持体１２との間の電界によりマイナスイオン又は電子が現像剤担持体１２上に引き付けられる。これにより、現像剤担持体２上のトナーに負極性の電荷が与えられ、トナーが均一に帯電される。
【００４２】
上記現像装置では、帯電制御部材１６が円筒形状であるため連続的に回転が可能であり、現像剤を効率的に帯電することが可能である。また帯電制御部材１６が電荷付与部材１５の一部にのみ接触しているため、現像剤に近接していない部分すなわち現像剤の帯電に寄与されない部分での放電は発生せず、装置全体としての放電量が少なくなる。このため、必要な電流が少なくて済み、電源の小型化及び低コスト化が可能である。また、放電量が少ないため放電生成物、例えばオゾンなどの発生量を抑えることができる。また、現像剤の帯電に必要な放電現象は、電荷付与部材１５と帯電制御部材１６との接触もしくは近接部分により十分に確保されるため、現像剤の帯電能力が損なわれることはない。
【００４３】
このような現像装置において、帯電制御部材１６に印加する電圧を−３００Ｖ、電荷付与部材１５に印加する電圧を−１３００Ｖ、及び現像剤担持体１２に印加する電圧を−２００Ｖに設定してトナーの帯電テストを行ったところ、逆極性のトナーは０．１ｗｔ％以下であり、良好な帯電性が得られることが確認された。
【００４４】
図５は、請求項１、請求項４又は請求項６に記載の発明の一実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置では、図５（ａ）に示すように、電荷付与部材２５は円筒状の半導電性部材であるが、両端部に設けられたトラッキングロール２７により現像剤担持体２２と微小間隙をおいて支持されている。帯電制御部材２６は、図５（ｂ）に示すように、多数の長円状の小孔２６ａを長手方向に配列した導電性フィルムからなり、電荷付与部材２５より径が太い円筒状に形成され、この電荷付与部材２５に外挿されている。また、この帯電制御部材２６は、現像剤担持体２２と接触しないように、両端部でバネ部材により現像剤担持体２２とは逆方向に付勢されている。したがって、帯電制御部材２６は内周面の一部が電荷付与部材２５と接触しており、電荷付与部材２５の回転に従動して帯電制御部材２６が回転するようになっている。このとき、帯電制御部材２６の周速度が現像剤担持体２２の周速度と差を有するように回転駆動される。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００４５】
このような現像装置では、帯電制御部材２６が現像剤担持体と離隔して回転可能であり、周速差によって現像剤担持体２２の表面と相対的に移動し、帯電制御部材２６の開口の形状による帯電むらの発生を低減することができる。さらに、帯電制御部材２６の周速度が現像剤担持体２２の周速度と差を有するように回転駆動されているので、帯電制御部材２６の電極部分と小孔との両箇所が現像剤担持体２２の表面と対向することになり、現像剤をほぼ均一に帯電することができる。
【００４６】
図６は、本願発明に係る現像装置とほぼ同じ効果が得られる他の現像装置の帯電制御部材付近の構成を参考に示す拡大図である。
この現像装置は、帯電制御部材３６が多数の小孔を有する導電性の薄板部材からなり、電荷付与部材３５は帯電制御部材３６とほぼ同じ面積を有する板状の電極からなる。この帯電制御部材３６は、両端部に設けられたトラッキング部材３７により電荷付与部材３５と微小間隔をおいて離隔されるとともに、現像剤担持体３２と近接・対向するように支持されている。
また、上記現像装置では、帯電制御部材３６の小孔が直径約８０μｍで、電極部分となる小孔間の最小幅は約３０μｍに形成されており、電荷付与部材３５が現像剤担持体３２に対向しても現像剤担持体付近で放電が発生しないような電圧が印加される設定となっている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００４７】
このような現像装置では、電荷付与部材３５と帯電制御部材３６との微小間隙で放電を発生させることができ、この放電現象により発生した電子又はマイナスイオンのみが現像剤担持体３２上のトナーに付与され、トナーが帯電される。このような現像装置では、電荷付与部材３５と帯電制御部材３６との支持構造が簡単であるので、装置全体の小型化及びコストの低減が可能となる。
なお、本例では、帯電制御部材３６と電荷付与部材３５との間隙をトラッキング部材３７により保持しているが、現像装置に設けられた位置決め部材に取り付けるような構成としてもよい。
【００４８】
図７は、請求項１又は請求項７に記載の発明の第１の実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置では、電荷付与部材４５が図７（ａ）に示すような円筒状の部材であり、周面に半導電性フィルム層４５ａが形成されている。帯電制御部材４６は、図７（ｂ）に示すように、半導電性フィルム層４５ａの表面上に絶縁性層４７を介して積層された導電性層によって形成されている。この帯電制御部材４６は、図７（ｃ）に示すような多数の円形小孔４６ａを有する導電性層を、無電界めっきやレーザ加工などの方法により形成したものであり、この導電性層に電源４９から約−３００Ｖの電圧が印加されるようなっている。また、半導電性フィルム層４５ａの背面側には給電部材４５ｂが配設されており、この給電部材４５ｂを介して電源４９から約−１３００Ｖの電圧が印加されるようになっている。上記帯電制御部材４６は、上記のように円形小孔を有するものに限らず、ストライプ状に導電性層を形成したもの等、様々な態様のものとすることができる。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００４９】
このような現像装置では、半導電性フィルム層を有する電荷付与部材４５と、絶縁層４７を介して積層された帯電制御部材４６との間に放電が発生し、電離現象により電子又はマイナスイオンとプラスイオンとが発生する。このうち電子又はマイナスイオンのみが現像剤担持体４２との間に生じる電界により引き付けられ、現像剤担持体上のトナーに付与される。
このような現像装置では、電荷付与部材４５と帯電制御部材４６との間に絶縁性層が介在されているので、両者間のリーク現象、電荷付与部材４５の表面電位の低下、および両者間で過大な電流が流れるのを防止することができる。また、両者間での放電領域を拡大することが可能となり、現像剤の帯電効率を向上することができる。
【００５０】
このような現像装置において帯電テストを行ったところ、逆極性トナーは０．１ｗｔ％以下となり、良好な帯電性が得られることが確認された。また、電荷付与部材４５と帯電制御部材４６とが一体の部材として形成されているので、装置の簡略化や低コスト化を図ることができる。なお、上記現像装置において、電荷付与部材４５が有する半導電性フィルム層４５ａは、半導電性のゴム層であってもよい。
【００５１】
図８は、請求項１又は請求項７に記載の発明の第２の実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置は、電荷付与部材５５が半導電性フィルムで形成されており、一方の端部が固定され、もう一方が現像剤担持体５２の表面と当接するように支持されている。また、帯電制御部材５６は、図７に示す構成と同様に電荷付与部材５５の表面上に絶縁性層５７を介して積層されており、現像剤担持体５２と近接して対向する位置に形成されている。さらに、電荷付与部材５５の背面側には、該電荷付与部材５５に電圧を印加する給電部材６０が設けられている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００５２】
このような現像装置では、電荷付与部材５５と帯電制御部材５６との間に放電現象により電離が発生するが、帯電制御部材５６と現像剤担持体３２との間の電界の作用により電子又はマイナスイオンのみが現像剤担持体５２に引き付けられる。このため、現像剤担持体上のトナーをほぼ均一に帯電することができる。また、電荷付与部材５５と帯電制御部材５６とが一体の部材として形成されるので、装置の簡略化や低コスト化を図ることができる。
【００５３】
図９は、請求項１又は請求項７に記載の発明の第３の実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置は、電荷付与部材６５が半導電性フィルムで形成されており、その両端部が固定支持されている。また、帯電制御部材６６は、電荷付与部材６５の表面上に絶縁性層６７を介して積層されており、該帯電制御部材６６が現像剤担持体６２と微小間隔をおいて離隔するように支持されている。また、電荷付与部材６５の背面側には給電部材７０が設けられている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００５４】
このような現像装置でも上記と同様に、現像剤担持体上のトナーをほぼ均一に帯電することができる。さらに、電荷付与部材６５及び帯電制御部材６６の構成及び支持構造が簡単であり、装置の小型化や低コスト化を図ることができる。
【００５５】
図１０は、請求項１、請求項７又は請求項９に記載の発明の一実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置では、電荷付与部材７５が可撓性を有する半導電性フィルムからなり、円筒形状に形成されている。この電荷付与部材７５の周面上には絶縁性層７７を介して積層された導電性層からなる帯電制御部材７６を備えている。また、電荷付与部材７５の内周面側には現像剤担持体７２と対向する位置に給電部材８０が配設されており、電荷付与部材と当接して所定の電位を付与するようになっている。さらに、この電荷付与部材７５の内面と当接するように３つの支持ローラＲ₁ ，Ｒ₂ ，Ｒ₃ が配設され、これらによって周回可能に支持されている。そして、電荷付与部材７５の周速度が現像剤担持体７２の周速度と差を生じるように駆動される。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００５６】
このような現像装置では、電荷付与部材７５が周回可能に支持されているので、帯電制御部材７６の形状による帯電むらがなくなり、現像剤を好適な電位に帯電することが可能となる。また、電荷付与部材７５の周速度が現像剤担持体７２の周速度と差を生じるように駆動されているので、帯電制御部材７６の電極部又は非電極部と対向する現像剤担持体表面の位置が移動し、現像剤をほぼ均一に帯電することができる。
【００５７】
また、上記現像装置では、帯電制御部材７６と現像剤担持体７２とを非接触に支持しているが、両者が接触するように支持してもよい。このとき、電荷付与部材７５が可撓性を有するため、現像剤担持体と接触した際に現像剤に与える機械的ストレスを低減することが可能となる。また、現像剤担持体７２と接触させた際には、帯電制御部材の表面にトナーの粒径以下の微小開口部を有する保護膜を設けるとよい。この保護膜は離型性のよい材料で形成されていることが好ましく、例えばフッ素樹脂などを用いることができる。これにより、トナーが帯電制御部材に付着するのを防止することができ、より均一な帯電が得られる。
【００５８】
図１１は、請求項１、請求項７又は請求項８に記載の発明の第１の実施形態である現像装置を示す概略構成図である。
この現像装置では、現像剤担持体８２上にトナー層を形成する層形成部材８３と電荷付与部材８５とが一体となるように支持されたものであり、層形成部材８３の表面に給電部材９０が装着され、この給電部材９０上に電荷付与部材８５が設けられている。また、電荷付与部材８５の表面には絶縁性層８７が形成されており、この絶縁性層を介して導電性の帯電制御部材８６が積層されている。
【００５９】
上記層形成部材８３は板状の保持部材８３ａとこれに接着された弾性部材８３ｂとを有し、層形成部材８３が現像剤担持体８２に圧接されるように支持されている。層形成部材８３の先端部は現像剤担持体８２の回転方向に対して上流側に向けて配置されており、現像剤担持体８２上のトナーが層形成部材８３との圧接部を通過することによりトナー量が規制されるようになっている。
また、上記電荷付与部材８５及び帯電制御部材８６は、弾性部材８３ｂ表面の現像剤担持体８２との接触部より支持端側に形成されており、帯電制御部材８６が現像剤担持体８２と離隔して対向するように設けられている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００６０】
このような現像装置では、現像剤担持体８２の回転によりトナーが層形成部材８３との圧接部を通過し、現像剤担持体８２上にトナー層が形成される。そして、このトナー層は帯電制御部材８６との対向位置を通過し、電荷付与部材８５と帯電制御部材８６との間の放電現象により発生したマイナスイオン及びプラスイオン等のうち、電子又はマイナスイオンのみが現像剤担持体８２との間に生じる電界によりトナーに付与される。
【００６１】
このような現像装置を用いてトナーの帯電性能を確認したところ、逆極性トナーは０．１ｗｔ％以下となり、良好な結果が得られた。また、電荷付与部材８５と層形成部材８３とが一体として支持されているので、装置の小型化や低コスト化を図ることができる。
【００６２】
図１２は、請求項１、請求項７又は請求項８に記載の発明の第２の実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置では、給電部材が層形成部材９３の保持部材９３ａを兼ねており、弾性部材９３ｂに並列して半導電性材料からなる電荷付与部材９５が形成されている。また、この電荷付与部材９５の表面上には絶縁性層９７が形成されており、この絶縁性層を介して導電性の帯電制御部材９６が積層されている。この帯電制御部材９６は、現像剤担持体９２と離隔して対向するように設けられている。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００６３】
このような現像装置では、層形成部材９３により現像剤担持体９２上にトナー層が形成されるとともに、このトナー層は帯電制御部材９６との対向位置を通過する。このとき、電荷付与部材９５と帯電制御部材９６との間の放電現象により発生したマイナスイオン及びプラスイオン等のうち、電子又はマイナスイオンのみが現像剤担持体９２との間に生じる電界によりトナーに付与される。このため、トナーをほぼ均一に帯電することができる。
【００６４】
図１３は、請求項１、請求項７又は請求項８に記載の発明の第３の実施形態である現像装置の帯電制御部材付近の構成を示す拡大図である。
この現像装置は、導電性の保持部材１０３の先端部に、板状の半導電性材料からなる電荷付与部材１０５が装着されており、これがトナー層形成部材を兼ねている。この電荷付与部材１０５の表面上には絶縁性層１０７を介して導電性の帯電制御部材１０６が積層されている。また、帯電制御部材１０６の表面にはトナーの粒径以下の微小開口部を有する保護膜１０１が形成されている。この保護膜には例えばフッ素樹脂などが用いられる。
なお、この現像装置の他の構成は上記図１に示す現像装置と同じである。
【００６５】
この現像装置では、電荷付与部材１０５が現像剤担持体１０２に圧接されることにより現像剤担持体１０２上にトナー層が形成されるとともに、このトナー層に、電荷付与部材１０５と帯電制御部材１０６との間の放電現象により発生したイオン等のうち、電子又はマイナスイオンのみが付与される。このため、トナーをほぼ均一な極性に帯電することができる。また、帯電制御部材１０６の表面には保護膜１０１が形成されているので、トナーが帯電制御部材に付着するのを防止することができ、より均一な帯電が得られる。
【００６６】
なお、以上に説明した実施形態の現像装置において、導電性の帯電制御部材が電荷付与部材又は現像剤担持体と直接に接触する場合には、帯電付与部材の表面に絶縁性材の被覆層を設けてもよい。この被覆層によって電荷付与部材の電位の変動や電荷のリーク現象を低減することができ、トナーをより均一に帯電することができる。
【００６７】
【実施例】
本願発明に係る現像装置のトナー帯電性能を確認するために、下記の条件にて長時間のプリントテストを行った結果について説明する。この実験では、現像装置は図４と同じ構成のものが用いられている。

【００６８】
上記条件にてプリントテストを行ったところ、従来問題であった、地かぶりや、逆極性トナーによる機内へのトナー飛散の発生はなく、維持性に優れていることが確認された。
【００６９】
【発明の効果】
以上説明したように、請求項１に記載の発明に係る現像装置では、電荷付与部材と帯電制御部材との間の放電現象によりプラスイオンとマイナスイオン等の両方が発生するが、帯電制御部材と現像剤担持体との間では電子なだれ現象は起こらず、電界の作用によってプラスイオン又はマイナスイオン等のいずれか一方が現像剤担持体側に引き付けられて現像剤担持体上のトナーをほぼ均一に帯電することが可能となる。
【００７０】
また、請求項２又は請求項３に記載の現像装置では、帯電制御部材の形状が適切に設定されているので、帯電制御部材の形状に起因する帯電むらの発生を極力抑えることができる。
【００７１】
また、請求項４に記載の発明に係る現像装置では、電荷付与部材、帯電制御部材及び現像剤担持体が共に回転し、電荷付与部材と帯電制御部材との接触部近傍の微小間隙で放電が発生するので、各部材間に過大な電流が流れたり、リーク現象が発生するのを抑制することができ、現像剤担持体上の現像剤を好適に帯電することができる。
【００７２】
また、請求項５に記載の発明に係る現像装置では、帯電制御部材が電荷付与部材と現像剤担持体とに挟持され、現像剤担持体の回転に従動して回転駆動されるので、帯電制御部材の支持構造が簡単になり、装置の大型化や複雑化を防止できる。
【００７３】
請求項６に記載の発明に係る現像装置では、帯電制御部材の電極部又は非電極部が現像剤担持体の表面に対して移動するようになっているので、現像剤担持体上の現像剤をより均一に帯電することができる。
【００７４】
請求項７に記載の発明に係る現像装置では、電荷付与部材と帯電制御部材との間に絶縁性層が介在されているので、両者間でのリーク現象が防止され、トナーを均一かつ良好に帯電させることができる。また、帯電制御部材と帯電付与部材とを一体とすることで、装置の大型化や複雑化を防止することができる。
【００７５】
請求項８に記載の発明に係る現像装置では、電荷付与部材が層形成部材と一体となるように支持されているので、現像剤担持体上の現像剤層の形成とともに現像剤を帯電させることが可能となり、装置を簡略化することができる。
【００７６】
請求項９に記載の発明に係る現像装置では、帯電制御部材の電極層又は該電極層が形成されていない部分とが現像剤担持体の表面と対向し、相対的に移動するので、現像剤担持体上の現像剤をより均一に帯電することができる。
【００７７】
請求項１０に記載の発明に係る現像装置では、電荷付与部材の少なくとも一部が半導電性材料又は絶縁性材料で被覆されているので、電荷付与部材と帯電制御部材との間、もしくは帯電制御部材と現像剤担持体との間でのリーク現象が防止され、トナーを良好に帯電させることができる。
【図面の簡単な説明】
【図１】請求項１、請求項２、請求項４又は請求項５に記載の発明の一実施形態である現像装置を示す概略構成図である。
【図２】上記現像装置において、現像剤担持体上の現像剤が帯電されるメカニズムを示す図である。
【図３】上記現像装置の電荷付与部材と現像剤担持体との間の電位分布を示す図である。
【図４】請求項１、請求項４又は請求項５に記載の発明の他の実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図５】請求項１、請求項４又は請求項６に記載の発明の一実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図６】請求項１又は請求項３に記載の発明の一実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図７】請求項１又は請求項７に記載の発明の第１の実施形態である現像装置の帯電制御部材を示す概略構成図である。
【図８】請求項１又は請求項７に記載の発明の第２の実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図９】請求項１又は請求項７に記載の発明の第３の実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図１０】請求項１、請求項７又は請求項９に記載の発明の一実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図１１】請求項１、請求項７又は請求項８に記載の発明の第１の実施形態である現像装置を示す概略構成図である。
【図１２】請求項１、請求項７又は請求項８に記載の発明の第２の実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図１３】請求項１、請求項７、請求項８に記載の発明の第３の実施形態である現像装置の電荷付与部材および帯電制御部材を示す部分構成図である。
【図１４】従来の現像装置の一例を示す概略構成図である。
【図１５】従来の現像装置の他の例を示す概略構成図である。
【図１６】従来の現像装置の現像剤担持体上の現像剤の帯電される状態を示す図である。
【図１７】従来の現像装置の現像剤担持体上の現像剤の帯電される状態を示す図である。
【図１８】上記現像装置の現像剤帯電付与部材と現像剤担持体との間の電荷密度を示す図である。
【符号の説明】
１像担持体
２現像剤担持体
３層形成部材
４現像剤供給部材
５電荷付与部材
６帯電制御部材
７現像用電源
８、１８、２８、３８、４８、５８、６８、７８トナー帯電用電源
９、１９、２９、３９、４９、５９、６９、７９帯電制御用電源
１０ハウジング
１５、２５、３５、４５、５５、６５、７５電荷付与部材
１６、２６、３６、４６、５６、６６、７６帯電制御部材
４７、５７、６７、７７、８７、９７、１０７絶縁性層
６０、７０、８０、９０給電部材
８３、９３層形成部材
８５、９５、１０５電荷付与部材
８６、９６、１０６帯電制御部材
８８、９８、１０８トナー帯電用電源
８９、９９、１０９帯電制御用電源
１０１保護膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device that is used in an electrophotographic image forming apparatus such as a copying machine or a printer and visualizes an electrostatic latent image formed on an image carrier by adhesion of toner.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a developing device using a one-component developing method or a two-component developing method is known as a developing device that visualizes a latent image formed on an image carrier by adhesion of toner. Such a developing device includes a rotatable developer carrier at a position facing the image carrier, and forms a magnetic brush with a toner layer or a two-component developer on the developer carrier to form an image carrier. And conveyed to the developing area facing. A developing bias voltage is applied between the developer carrier and the image carrier to form an electric field, and the toner is transferred to a latent image on the image carrier.
[0003]
In such a developing device, it is necessary to give a predetermined amount of charge to the toner in order to satisfactorily transfer the toner to the latent image on the image carrier in the developing region. The two-component developing system develops a toner by mixing and agitating the toner with a carrier separated in the triboelectric charge sequence, and imparts a charge to the toner. However, the charge control agent added to the toner is released. May contaminate the carrier surface. Therefore, when the carrier is used for a long period of time, it becomes impossible to impart charge to the toner due to the influence thereof, and there is a disadvantage that the developer needs to be replaced. In addition, a toner concentration control device and a developer agitating device for keeping the mixing ratio of the toner and the carrier constant are required, and a magnet needs to be arranged in the developer carrying body to carry the magnetic carrier. Therefore, there is a drawback that the apparatus becomes complicated.
[0004]
On the other hand, one-component development type development apparatuses are widely used as devices that can overcome the disadvantages of these two-component development methods. In this developing device, a toner layer forming member called a blade made of an elastic member is brought into pressure contact with the developer carrying member to form a one-component toner layer on the developer carrying member, and the toner is formed by frictional charging of the toner layer forming member. The charge is imparted to. However, in general, the toner charging ability of the blade is low, and it is difficult to sufficiently charge all the toners, and there is a so-called reverse polarity toner that is oppositely charged to the desired polarity. There is a disadvantage that it occurs. That is, in the frictional charging with the blade, there is a low probability that the toner comes into contact with the blade. In particular, the fine toner may not pass through the layer forming portion without being frictionally charged, and the toner may not be charged. In order to promote frictional charging, it is conceivable to increase the pressure contact force of the toner layer forming member to the toner. However, the binder resin of the toner is melted by frictional heat, and the condensed toner is clogged in the blade, and the image is whitened. The problem of streaking occurs.
[0005]
In order to solve the problems of the apparatus for frictionally charging the toner as described above, a developing apparatus that directly applies a charge to the toner has been proposed. Examples of such a system include a developing device disclosed in Japanese Utility Model Publication No. 63-138560 and a developing device shown in FIG.
The developing device disclosed in Japanese Utility Model Laid-Open No. 63-138560 is provided with a corona discharger at a position facing the developer carrying member and irradiating the toner layer with ions of a desired polarity to give the toner a charge. To do. However, when a corona discharger is used, dirt is attached to the corotron wire and uniform discharge cannot be obtained. In addition, a high voltage for ionizing the air layer in the vicinity of the corotron wire is necessary, and a voltage of 5 kV or more is necessary in consideration of the stability in the axial direction of the discharge. Furthermore, there are also disadvantages such as the generation of ozone during discharge.
[0006]
On the other hand, the developing device shown in FIG. 14 is in contact with the developer carrier 202, the layer forming blade 203 that is pressed against the developer carrier to form a toner layer, and the developer carrier 202, or at a small interval. A cylindrical charge applying member 204 supported by the toner supply member 205, a toner supply member 205 that supplies toner to the developer carrying member, a developing bias power source 206, and a toner charging power source 207. Then, a voltage is applied from the power source 207 to the charging member 204 to generate a discharge in the gap with the developer carrier 202, and the toner is charged by attaching ions or electrons generated by the discharge phenomenon to the toner. It is.
[0007]
In the developing device shown in FIG. 15, a layer forming blade 213 is disposed so as to be in pressure contact with the developer carrying member 212, and a voltage for charging the toner is applied from the power source 217 thereto. As a result, a discharge is generated in the gap between the layer forming blade 213 and the developer carrying member 212 to form a toner layer on the developer carrying member 212 and to charge the toner.
[0008]
The developing device shown in FIG. 14 or 15 as described above has an advantage that it does not require a voltage as high as that of a corona discharger, and that ozone is less generated. Such techniques are disclosed in, for example, Japanese Patent Laid-Open Nos. 54-17030, 62-291678, 64-62675, and the like.
[0009]
[Problems to be solved by the invention]
However, the developing apparatus shown in FIG. 14 or 15 has the following problems.
In the developing device shown in FIG. 14, if the voltage applied to the charging member 204 is equal to or lower than the discharge voltage, since the toner having a high volume resistivity is used, charge induction is not sufficiently performed, and the toner has a desired polarity. Cannot be charged. On the other hand, it is possible to charge the toner due to the discharge phenomenon from the electrodes by increasing the applied voltage, but as shown in FIG. 16, there is a discharge between the charging member 204 and the developer carrier 202 due to the discharge. An avalanche phenomenon occurs due to ionization, and as a result, positive ions and electrons or negative ions having opposite polarities are generated in the discharge region. Similarly, in the developing device shown in FIG. 15, an avalanche phenomenon occurs between the layer forming blade 213 and the developer carrier 212, and ions having opposite polarities are generated (FIG. 17).
[0010]
Therefore, in order to charge the toner to a desired polarity (in this example, minus), even if either electrons or minus ions are attached to the toner, the discharge region is filled with positive ions generated by ionization and electrons or minus ions. Therefore, both positive ions and electrons or negative ions filled in the ionization region are imparted to the toner. For this reason, the toner charged by the discharge is not aligned with a desired polarity, and reverse polarity toner is generated. This is considered to be a mechanism in which reverse polarity toner is generated. Here, the reverse polarity indicates a positive charge when the toner is to be negatively charged as in this example, but the negative charge is a reverse polarity when the toner is positively charged. Based on the document “Discharge Phenomenon” (Tokyo Denki University Press, page 64 by Honda, page 64), the relative density of electrons and positive ions generated between two parallel electrodes is calculated. As shown in FIG. 18, positive ions are also present in the immediate vicinity of the anode (developer carrier), which indicates that the number of electrons is several thousand times that of electrons in the toner size (7 μm to 10 μm). That is, when the toner is negatively charged by discharging, a considerable amount of positive toner is considered to be generated at the same time.
[0011]
For example, as described in “Recent development and commercialization of electrophotographic development systems and toner materials” (Japan Science Information Co., Ltd., Manabu Takeuchi, page 303), the polarity and charge amount of each toner particle According to the method of measuring as a distribution, the reverse polarity toner generated in the developing device was 20 wt%. When such a reverse polarity toner is conveyed to the development area by the rotation of the developer carrying member, the developed toner image is deteriorated in image quality such as ground fog, and a good image cannot be obtained. Further, there is a problem that toner of reverse polarity is scattered from the developer carrying member and causes toner contamination in the apparatus.
[0012]
The present invention has been made in view of the above-described problems, and its object is to prevent the generation of toner of reverse polarity and to charge the toner on the developer carrying member substantially uniformly and to improve the quality over a long period of time. It is an object of the present invention to provide a developing device capable of obtaining a high image quality.
[0013]
[Means for Solving the Problems]
  In order to solve the above problems, the developing device according to the first aspect of the present invention is disposed so as to be close to or in contact with an image carrier having a latent image formed on the surface due to a difference in electrostatic potential. A developer carrying member; and a layer forming member that forms a thin layer of the developer on a peripheral surface of the developer carrying member, wherein the image carrier and the developer carrying member are opposed to each other in a developing region. In a developing device that visualizes the latent image by selectively transferring the converted developer to the image carrier, the developer is formed at a position where a thin layer of developer is already formed on the developer carrier. A charge-providing member that is disposed so as to be close to and opposed to the developer-carrying member, and that generates an electric field between the developer-carrying member and the charge-carrying member and the developer-carrying member,A penetrating part is formed so that a part where the charge imparting member and the developer carrying member directly face each other is formed,A charge control member to which a potential between the potential of the charge imparting member and the developer carrying member is imparted; at least one of the charge imparting member and the charge control member is a semiconductive material The charge control member is disposed in direct contact with the charge applying member or via an insulator layer, and has a discharge start voltage or higher between the charge applying member and the charge control member. In addition to applying a voltage, a voltage equal to or lower than the discharge start voltage is applied between the charge control member and the developer carrier so as to form an electric field in which ions or electrons of a predetermined polarity move toward the developer carrier. It shall be.
[0014]
In such a developing device, when the average value of the voltage applied to the charge applying member is Vb (V) and the average value of the voltage applied to the charge control member is Vm (V),
An independent voltage is applied to the charge applying member and the charge control member so as to satisfy the condition of | Vb |> | Vm |, and a voltage equal to or higher than the discharge start voltage is applied between the charge applying member and the charge control member. In addition, an electric field is formed between the charge imparting member and the developer carrier so that polar ions or electrons to be charged move toward the developer carrier, but a voltage is set so as not to cause discharge.
[0015]
In such a developing device, a strong electric field is formed by applying a voltage equal to or higher than the discharge start voltage between the charge imparting member and the charge control member, and a discharge is generated between the two. This discharge causes an ionization phenomenon, and an electron avalanche phenomenon generates positive ions, electrons, and negative ions, but the ionization region is limited between the charge imparting member and the charge control member, and the charge control member and the developer carrier. In other words, ionization does not occur in the region where the toner formed in a thin layer on the developer carrying member exists. For this reason, ionization within the thickness range of the toner layer does not occur, and positive ions and negative ions are not generated.
[0016]
On the other hand, an electric field smaller than that at which discharge starts is formed between the charge control member and the developer carrying member, and the electric field action between the charge control member and the developer carrying member causes the charge applying member and the developer carrying member to be charged. Either positive ions or negative ions generated between and in the vicinity of the control member are attracted to the developer carrier and applied to the toner layer formed on the developer carrier. This makes it possible to charge the toner to a desired polarity.
[0017]
In such a developing device, both the charge imparting member and the charge control member can be made of a conductive material or a semiconductive material. It is desirable to be made of a semiconductive material. Here, the semiconductive material has a volume resistance of 10^Three Ω · cm to 10¹¹It is about Ω · cm.
The shape of the charge control member can be appropriately set as long as the toner can be charged almost uniformly. For example, as in the invention according to claim 2, a conductive material or a semiconductive material can be used. And a conductive or semiconductive thin plate member having a large number of small holes, as in the invention described in claim 3. The charge control member may be supported with a small gap from the charge imparting member, or may be supported so that a part thereof is in contact. Further, a thin net-like member or plate-like member made of an insulating material and having a large number of small openings may be interposed between the charge imparting member and the charge control member.
[0018]
  According to a fourth aspect of the present invention, there is provided a developer carrier disposed so as to be close to or in contact with an image carrier on which a latent image due to a difference in electrostatic potential is formed on a surface, and a periphery of the developer carrier. And a layer forming member for forming a thin layer of developer on the surface, and the developer having a thin layer is selected as the image carrier in a development region where the image carrier and the developer carrier face each other. In the developing device for visualizing the latent image by moving the developer, the developer carrying member is disposed so as to be close to and opposed to the developer carrying member at a position where a thin layer of the developer is already formed on the developer carrying member. A charge-providing member for generating an electric field between the developer-carrying member and the charge-carrying member and the developer-carrying member,A penetrating part is formed so that a part where the charge imparting member and the developer carrying member directly face each other is formed,A charge control member to which a potential between the potential of the charge imparting member and the developer carrying member is imparted, and the charge imparting member is formed in a cylindrical shape and is rotatably supported around an axis. The charge control member is formed in a cylindrical shape having a larger diameter than the charge imparting member, and is externally attached to the charge imparting member so as to be a part of the inner peripheral surface at a position facing the developer carrier. Is applied so as to rotate in contact with the charge applying member, and a voltage equal to or higher than a discharge start voltage is applied between the charge applying member and the charge control member, and the charge control member and the developer carrier In the meantime, a voltage equal to or lower than the discharge start voltage is applied so as to form an electric field in which ions or electrons of a predetermined polarity move toward the developer carrying member.
[0019]
In such a developing device, the charge imparting member, the charge control member, and the developer carrying member rotate together, and discharge occurs in a minute gap near the contact portion between the charge imparting member and the charge control member. Since this discharge is limited to the portion of the charge imparting member facing the developer carrier, it is possible to prevent an excessive current from flowing between the charge imparting member and the charge control member.
[0020]
In the developing device, as in the invention described in claim 5, the charge control member is sandwiched between the charge applying member and the developer carrier, and is driven by the rotation of the developer carrier. It can be rotationally driven. This simplifies the support structure of the charge control member, and prevents the apparatus from becoming large and complicated.
[0021]
According to a sixth aspect of the present invention, the charge control member is supported so as to be separated from the developer carrying member, and is rotated so that a peripheral speed is different from a peripheral speed of the developer carrying member. It can also be driven. As a result, the electrode portion or the opening of the charge control member moves relative to the surface of the developer carrier, and the developer on the developer carrier can be more uniformly charged.
[0022]
In the developing device according to the seventh aspect of the invention, the charge control member is formed of a conductive layer or a semiconductive layer laminated on the surface of the charge imparting member via an insulating layer. As a result, a leakage phenomenon between the charge imparting member and the charge control member is prevented, and the toner can be charged satisfactorily by stable discharge. Further, by integrating the charge control member and the charge imparting member, it is possible to prevent the apparatus from becoming large and complicated. Here, the insulating layer has a volume resistance of 10¹²It is a layer formed of a material of about Ω · cm or more.
[0023]
In the developing device, as in the invention described in claim 8, the charge imparting member can be supported so as to be integrated with the layer forming member. As a result, a developer layer is formed on the developer carrier by the layer forming member, and a discharge can be generated in the vicinity of the charge imparting member. For this reason, it becomes possible to charge the developer together with the formation of the developer layer, and it is possible to prevent the apparatus from becoming large and complicated.
[0024]
  According to a ninth aspect of the present invention, there is provided a developer carrier disposed so as to be close to or in contact with an image carrier on which a latent image due to a difference in electrostatic potential is formed on a surface, and a periphery of the developer carrier. And a layer forming member for forming a thin layer of developer on the surface, and the developer having a thin layer is selected as the image carrier in a development region where the image carrier and the developer carrier face each other. In the developing device for visualizing the latent image by moving the developer, the developer carrying member is disposed so as to be close to and opposed to the developer carrying member at a position where a thin layer of the developer is already formed on the developer carrying member. A charge-providing member for generating an electric field between the developer-carrying member and the charge-carrying member and the developer-carrying member,A penetrating part is formed so that a part where the charge imparting member and the developer carrying member directly face each other is formed,A charge control member to which a potential between the potential of the charge imparting member and the potential of the developer carrying member is imparted, and the charge control member is interposed on the surface of the charge imparting member via an insulating layer. Formed by a conductive layer or a semiconductive layer laminated, and the charge imparting member is composed of a rotatable cylindrical member or a revolving endless belt-like member, and the peripheral speed of the charge imparting member is It is driven so as to produce a difference from the peripheral speed of the developer carrier, and a voltage equal to or higher than a discharge start voltage is applied between the charge applying member and the charge control member, and the charge control member and the charge control member A voltage equal to or lower than the discharge start voltage is applied between the developer carrying member and the developer carrying member so as to form an electric field in which ions or electrons of a predetermined polarity move toward the developer carrying member.
  In such an apparatus, the electrode layer as the charge control member and the surface of the developer carrying member move relatively, and the discharge is not generated microscopically uniformly, but the developer on the developer carrying member Can be more uniformly charged.
[0025]
In the developing device according to the tenth aspect, at least a part of the charge control member may be covered with a semiconductive material or an insulating material. As a result, it is possible to prevent a leakage phenomenon between the charge applying member and the charge control member or between the charge control member and the developer carrying member and a charging failure due to a decrease in the potential of the surface of the charge applying member. It can be charged well.
[0026]
In the developing device, an ionization region that generates ions and the like is limited to the charge applying member side by disposing a charge control member between the charge applying member and the developer carrying member that is a charged object. However, the scorotron charger used as a conventional charger also has a configuration similar to that of the present invention. That is, in the scorotron charger, the discharge wire is the charge imparting member of the present invention, the member to be charged is a photosensitive member or a developer carrier, and the charge control member of the present invention is between the discharge wire and the member to be charged. It can also be considered that it corresponds to a screen grid electrode arranged in the above. However, since the diameter of the discharge wire is as small as 30 to 100 μm in the scorotron charger, even if there is no charge control member, the electric field generated between the shield electrode and the object to be charged by the discharge wire is only in the vicinity of the wire. Causes ionization, and only ions or electrons move near the shield and the object to be charged. In other words, the screen grid electrode functions to limit the movement of ions or electrons of the polarity to be charged to make the charged potential of the charged object constant, and actively works to control the ionization region due to discharge. There is no. On the other hand, the present invention has a function of separating the electric field between two minute electrodes into an ionization region and a movement region of electrons and ions, and the polarity opposite to the polarity to be charged near the charged body The function is completely different from that of the conventional scorotron charger.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 1, claim 2, claim 4, or claim 5.
This developing device is provided at a position facing the image carrier 1 capable of forming a latent image due to a difference in charging potential on the surface, and is in close proximity to the image carrier 1 in the housing 10 and has toner on the surface. A developer carrying body 2 that adheres and conveys the toner, a layer forming member 3 that regulates the toner on the developer carrying body to form a toner layer, and stirs the toner and supplies the toner to the developer carrying body 2 The agitation supply member 4 and the developer carrier 2 are disposed opposite to each other, and a charge imparting member 5 that generates a discharge at the opposed position, and between the charge imparting member 5 and the developer carrier 2. And a charge control member 6 for limiting the ionization region of the discharge generated between them. Further, a developing power source 7 for applying a developing voltage between the developer carrier 2 and the image carrier 1 and a toner charging voltage between the developer carrier 2 and the charge imparting member 5 are applied. And a charging control power source 9 for applying a voltage for limiting the ionization region to the charging control member 6.
[0028]
The developer carrier 2 is rotatably supported, and a DC voltage of about −200 V having the same polarity as the toner is applied from the developing power source 7. As a result, an electric field is formed between the developer carrier 2 and the image carrier 1, and the toner is transferred to the latent image on the image carrier 1. In this developer carrier, after cutting a round bar or pipe made of aluminum or stainless steel, the outer peripheral surface is subjected to mechanical processing such as sand blasting, liquid honing, emery polishing, or chemical corrosion or Ra = 0. Concavities and convexities of about 1 to 5.0 μm are formed. Alternatively, a resin layer in which conductive powder is dispersed may be formed after cutting a round bar or pipe made of aluminum or stainless steel. The developer carrier 2 of this example has a diameter of 20 mm, and an aluminum pipe that has been subjected to sandblast anodizing treatment after cutting an aluminum pipe is used. Further, the voltage applied from the developing power source 7 may be a voltage obtained by superimposing a DC voltage and an AC voltage in order to ensure development performance.
[0029]
The layer forming member 3 is obtained by vulcanizing and bonding a pressure contact member made of Si rubber or EPDM rubber in which conductive powder is dispersed to a stainless steel plate spring having a thickness of about 0.03 to 0.3 mm. The contact pressure to the agent carrier 2 is set to about 5 to 100 g / cm. Further, rubber having a hardness of 20 to 80 degrees can be used, and preferably 30 to 60 degrees is suitable. By pressing with the layer forming member 3, a toner layer of about 5 to 30 μm is formed on the developer carrier 2.
[0030]
The charge applying member 5 is formed in a cylindrical shape and is supported so as to be rotatable around an axis. The charge imparting member 5 includes an ionic conductor, or is obtained by blending conductive fine particles with rubber, and has a volume resistivity of 10^Five -10^TenIt is about Ω · cm. This volume resistivity is especially 10⁷ -10⁸ About Ω · cm is desirable.
[0031]
The charge control member 6 is made of a stainless mesh member having a wire diameter of 50 μm and a pitch of 127 μm, and is formed in a cylindrical shape having a diameter larger than that of the charge applying member 5. The charge control member 6 is extrapolated to the charge applying member 5 and is sandwiched between the charge applying member 5 and the developer carrier 2, and a part of the inner peripheral surface at a position facing the developer carrier 2. Is rotated in contact with the charge applying member 5. At this time, the charge control member 6 is driven to rotate following the rotation of the developer carrier 2.
[0032]
In addition, in order to charge the toner on the developer carrier 2 negatively, an electric field is formed between the charge applying member 5 and the charge control member 6 so as to start discharge, An electric field having a small gradient so as not to generate discharge between the developer carrying member 2 and a direction in which a negative charge is attracted to the developer carrying member side is formed. For this reason, the potential relationship between the charge control member 6 and the developer carrier 2 is maintained, for example, as follows.
(Developer carrier potential)-(Charge control member potential) = 100V
[0033]
Further, the relationship between the potentials of the charge applying member 5 and the charge control member 6 is maintained as follows.
(Charge control member potential)-(Charge imparting member potential) = 1000 V
The potentials of these members are appropriately determined depending on the distance between the charge imparting member 5 and the developer carrier 2, the structure and thickness of the charge control member 6, and the like. Further, when the charge imparting member 5, the charge control member 6, and the developer carrier 2 are provided with gaps, the sizes of these gaps are determined in consideration. In this example, a voltage of −200 V is applied from the power source 7 to the developer carrier 2, a voltage of −300 V is applied from the power source 9 to the charging control member 6, and a power source 8 is applied to the shaft of the charge applying member 5. A voltage of -1300 V is applied.
[0034]
The developer used in the developing device is a one-component toner, and a polarity control agent such as a pigment or a metal-containing azo dye is dispersed in various thermoplastic resins such as a styrene resin, an acrylic resin, or a polyester resin. The size is 3 to 20 μm (average particle size 7 μm) by pulverization and classification. Further, a charge control agent is added to give a negative charge. As the charge control agent, fine particles of 0.1 μm or less such as hydrophobized silica, alumina, titanium and the like are used, and hydrophobic silica is most desirable. Further, a toner flow aid is externally added.
The image carrier 1 is a selenium photoreceptor or an organic photoreceptor, and the image carrier 1 and the developer carrier 2 may be in contact with each other, or a gap of about 100 μm to 400 μm is provided. You may make it oppose.
[0035]
In such a developing device, the toner in the housing 10 is agitated by the rotation of the agitation supply member 4 and is supplied to the developer carrier 2. The toner near the surface of the developer carrier 2 is conveyed to a position facing the layer forming member 3 by the rotation of the developer carrier 2, and a toner layer is formed on the developer carrier 2 by the pressing force of the layer forming member 3. Is done. Thereafter, the toner layer is conveyed to a position facing the charge applying member 5 and the charge control member 6. At this time, the voltage as described above is applied between the charge applying member 5 and the charge control member 6 and between the charge control member 6 and the developer carrier 2, and an electric field is applied to a region where they face each other. Is formed. At this time, the state in which the toner on the developer carrying member is charged will be described with reference to FIGS.
[0036]
The electric potential distribution when the electric control member 6 does not enter between the charge applying member 5 and the developer carrier 2 becomes a substantially uniform electric field in the gap, but the charge control member 6 is interposed between the electric charge control member 6 and the voltage. Is applied, the electric field is distorted as shown in FIG. 3A, resulting in a non-uniform electric field. FIG. 3B shows the potential change along the straight line AA ′ in FIG. 3A. When this is overlaid with the Paschen discharge start electric field gradient B, the electric field is generated from the contact C. Only the large charge imparting member 5 side can be discharged, and the electric field on the developer carrier 2 side is smaller than the discharge start electric field, so it is not ionized. Therefore, as shown in FIG. 2, negative ions or positive ions are generated in the vicinity of the charge imparting member 5 due to the ionization accompanying the discharge, but no ionization occurs in the vicinity of the developer carrier 2, and the charge control is performed. Negative ions or electrons are attracted to the developer carrier by the electric field effect between the member 6 and the developer carrier 2. Then, this charge adheres to the toner on the developer carrying member, and the toner is charged. Accordingly, the positive ions generated as a result of ionization exist only on the charge imparting member 5 side and are adsorbed to the charge imparting member 5, but do not adhere to the toner on the developer carrier 2. As described above, by arranging the mesh-shaped charge control member 6 between the charge imparting member 5 and the developer carrier 2, the ionization region is limited to a place away from the toner, and therefore, the generation of the reverse polarity toner is generated. Is suppressed.
[0037]
The toner layer to which a uniform charge has been applied in this way is conveyed to a development area facing the image carrier 1 by the rotation of the developer carrier 2. The toner is transferred to the latent image on the image carrier 1 and developed by a developing electric field formed between the developer carrier 2 and the image carrier 1.
[0038]
When the charging effect of the toner was confirmed in such a developing device, the toner was charged from −7 μC / g to −12 μC / g, and the toner of reverse polarity was 0.1 wt% or less, and good chargeability was obtained. It was.
[0039]
In the developing device, since the charge control member may move in the axial direction as it rotates, the diameter of the central portion of the charge applying member may be increased. Further, a tension roll member may be provided in the direction opposite to the developer carrying member, and the diameter of the central portion in the axial direction of the roll may be increased.
[0040]
FIG. 4 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to one embodiment of the invention according to claim 1, claim 4 or claim 5.
This developing device has substantially the same configuration as the developing device shown in FIG. 1, but as shown in FIG. 4 (b), the charging control member 16 is produced by a number of photoetching, electroforming, laser processing, etc. It consists of a conductive film having circular small holes 16a. The charge control member 16 comes into contact with the developer carrier 12, and the charge control member 16 is driven to rotate by driving the developer carrier 2, and the charge applying member 15 is rotated by the rotation of the charge control member 16. It has become.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0041]
In such a developing device, a discharge phenomenon occurs due to the electric field between the charge applying member 15 and the charge control member 16, and positive ions, negative ions, or electrons are generated, and the charge control member 16, the developer carrier 12, and the like. The negative ions or electrons are attracted onto the developer carrier 12 by the electric field between them. As a result, a negative charge is applied to the toner on the developer carrier 2 and the toner is uniformly charged.
[0042]
In the developing device, since the charging control member 16 has a cylindrical shape, it can be continuously rotated, and the developer can be charged efficiently. In addition, since the charge control member 16 is in contact with only a part of the charge applying member 15, no discharge occurs in a portion that is not close to the developer, that is, a portion that does not contribute to the charging of the developer. The amount of discharge is reduced. For this reason, less current is required, and the power supply can be reduced in size and cost. Further, since the discharge amount is small, the generation amount of discharge products such as ozone can be suppressed. In addition, since the discharge phenomenon necessary for charging the developer is sufficiently ensured by the contact or proximity between the charge imparting member 15 and the charge control member 16, the charging ability of the developer is not impaired.
[0043]
In such a developing device, the voltage applied to the charge control member 16 is set to -300 V, the voltage applied to the charge applying member 15 is set to -1300 V, and the voltage applied to the developer carrying member 12 is set to -200 V. As a result of a charging test, the toner having a reverse polarity was 0.1 wt% or less, and it was confirmed that good chargeability was obtained.
[0044]
FIG. 5 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to an embodiment of the invention described in claim 1, claim 4, or claim 6.
In this developing device, as shown in FIG. 5 (a), the charge applying member 25 is a cylindrical semiconductive member. However, the tracking roller 27 provided at both ends separates the developer carrier 22 from the minute gap. Is supported. As shown in FIG. 5 (b), the charge control member 26 is made of a conductive film in which a large number of oval small holes 26 a are arranged in the longitudinal direction, and is formed in a cylindrical shape having a diameter larger than that of the charge applying member 25. The charge applying member 25 is extrapolated. Further, the charge control member 26 is biased in the opposite direction to the developer carrier 22 by spring members at both ends so as not to contact the developer carrier 22. Therefore, a part of the inner peripheral surface of the charge control member 26 is in contact with the charge applying member 25, and the charge control member 26 rotates as the charge applying member 25 rotates. At this time, the charge control member 26 is driven to rotate so that the peripheral speed of the charge control member 26 is different from the peripheral speed of the developer carrier 22.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0045]
In such a developing device, the charge control member 26 can rotate apart from the developer carrier, and moves relative to the surface of the developer carrier 22 due to the difference in peripheral speed, and the charge control member 26 opens. The occurrence of uneven charging due to the shape can be reduced. Further, since the peripheral speed of the charge control member 26 is rotationally driven so as to have a difference from the peripheral speed of the developer carrier 22, both the electrode portion and the small hole of the charge control member 26 are located at the developer carrier. Therefore, the developer can be charged almost uniformly.
[0046]
  FIG.FIG. 6 is an enlarged view showing a configuration in the vicinity of a charge control member of another developing device that can obtain substantially the same effect as the developing device according to the present invention.
  In the developing device, the charge control member 36 is formed of a conductive thin plate member having a large number of small holes, and the charge applying member 35 is formed of a plate-like electrode having substantially the same area as the charge control member 36. The charge control member 36 is separated from the charge applying member 35 by a tracking member 37 provided at both ends, and is supported so as to be close to and opposed to the developer carrier 32.
  In the developing device, the small hole of the charging control member 36 has a diameter of about 80 μm, and the minimum width between the small holes serving as electrode portions is about 30 μm. The charge applying member 35 is formed on the developer carrier 32. A voltage is set to apply a voltage that does not generate a discharge in the vicinity of the developer carrying member even when facing each other.
  The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0047]
In such a developing device, discharge can be generated in a minute gap between the charge applying member 35 and the charge control member 36, and only electrons or negative ions generated by this discharge phenomenon are applied to the toner on the developer carrier 32. Applied to charge the toner. In such a developing device, since the support structure of the charge imparting member 35 and the charge control member 36 is simple, the entire device can be reduced in size and cost.
In this example, the gap between the charge control member 36 and the charge applying member 35 is held by the tracking member 37, but may be configured to be attached to a positioning member provided in the developing device.
[0048]
FIG. 7 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to the first embodiment of the invention described in claim 1 or claim 7.
In this developing device, the charge imparting member 45 is a cylindrical member as shown in FIG. 7A, and a semiconductive film layer 45a is formed on the peripheral surface. As shown in FIG. 7B, the charge control member 46 is formed of a conductive layer laminated on the surface of the semiconductive film layer 45a with an insulating layer 47 interposed therebetween. The charge control member 46 is formed by forming a conductive layer having a large number of small circular holes 46a as shown in FIG. 7C by a method such as electroless plating or laser processing. A voltage of about −300 V is applied from the power source 49. In addition, a power supply member 45b is disposed on the back side of the semiconductive film layer 45a, and a voltage of about -1300 V is applied from the power source 49 via the power supply member 45b. The charge control member 46 is not limited to the one having the circular small holes as described above, and may be various forms such as one having a conductive layer formed in a stripe shape.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0049]
In such a developing device, discharge occurs between the charge imparting member 45 having the semiconductive film layer and the charge control member 46 laminated via the insulating layer 47, and electrons or negative ions are generated due to the ionization phenomenon. Positive ions are generated. Of these, only electrons or negative ions are attracted by the electric field generated between the developer carrier 42 and applied to the toner on the developer carrier.
In such a developing device, since an insulating layer is interposed between the charge applying member 45 and the charge control member 46, a leakage phenomenon between them, a decrease in the surface potential of the charge applying member 45, and between them An excessive current can be prevented from flowing. In addition, it is possible to expand the discharge area between the two, and the charging efficiency of the developer can be improved.
[0050]
When a charging test was performed in such a developing apparatus, the reverse polarity toner was 0.1 wt% or less, and it was confirmed that good chargeability was obtained. In addition, since the charge imparting member 45 and the charge control member 46 are formed as an integral member, the apparatus can be simplified and the cost can be reduced. In the developing device, the semiconductive film layer 45a included in the charge applying member 45 may be a semiconductive rubber layer.
[0051]
FIG. 8 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to the second embodiment of the invention described in claim 1 or claim 7.
In this developing device, the charge imparting member 55 is formed of a semiconductive film, one end is fixed, and the other is supported so as to contact the surface of the developer carrier 52. Similarly to the configuration shown in FIG. 7, the charge control member 56 is laminated on the surface of the charge imparting member 55 via an insulating layer 57 and is formed at a position facing the developer carrier 52 in the vicinity. Has been. Furthermore, a power supply member 60 that applies a voltage to the charge application member 55 is provided on the back side of the charge application member 55.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0052]
In such a developing device, ionization occurs between the charge applying member 55 and the charge control member 56 due to a discharge phenomenon, but electrons or minus is generated by the action of the electric field between the charge control member 56 and the developer carrier 32. Only ions are attracted to the developer carrier 52. For this reason, the toner on the developer carrying member can be charged almost uniformly. Further, since the charge imparting member 55 and the charge control member 56 are formed as an integral member, the apparatus can be simplified and the cost can be reduced.
[0053]
FIG. 9 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to the third embodiment of the invention described in claim 1 or claim 7.
In this developing device, the charge imparting member 65 is formed of a semiconductive film, and both ends thereof are fixedly supported. The charge control member 66 is laminated on the surface of the charge imparting member 65 via an insulating layer 67, and is supported so that the charge control member 66 is separated from the developer carrier 62 at a minute interval. Has been. A power supply member 70 is provided on the back side of the charge applying member 65.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0054]
In such a developing device, the toner on the developer carrying member can be charged almost uniformly as described above. Furthermore, the configuration and support structure of the charge applying member 65 and the charge control member 66 are simple, and the apparatus can be reduced in size and cost.
[0055]
FIG. 10 is an enlarged view showing a configuration in the vicinity of the charge control member of the developing device according to one embodiment of the invention according to claim 1, claim 7 or claim 9.
In this developing device, the charge imparting member 75 is made of a flexible semiconductive film and is formed in a cylindrical shape. On the peripheral surface of the charge imparting member 75, a charge control member 76 made of a conductive layer laminated via an insulating layer 77 is provided. In addition, a power supply member 80 is disposed on the inner peripheral surface side of the charge applying member 75 at a position facing the developer carrying member 72, and a predetermined potential is applied by contacting the charge applying member. Yes. Further, the three support rollers R are in contact with the inner surface of the charge applying member 75.₁ , R₂ , R_Three Are arranged, and are supported so as to be able to go around. The peripheral speed of the charge applying member 75 is driven so as to make a difference from the peripheral speed of the developer carrier 72.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0056]
In such a developing device, since the charge applying member 75 is supported so as to be able to rotate, there is no uneven charging due to the shape of the charge control member 76, and the developer can be charged to a suitable potential. Further, since the peripheral speed of the charge imparting member 75 is driven so as to make a difference from the peripheral speed of the developer carrier 72, the surface of the developer carrier facing the electrode portion or the non-electrode portion of the charge control member 76 is driven. The position moves, and the developer can be charged almost uniformly.
[0057]
In the developing device, the charge control member 76 and the developer carrier 72 are supported in a non-contact manner, but may be supported so that they are in contact with each other. At this time, since the charge imparting member 75 has flexibility, it is possible to reduce mechanical stress applied to the developer when it comes into contact with the developer carrier. Further, when being brought into contact with the developer carrying member 72, it is preferable to provide a protective film having a microscopic opening smaller than the particle size of the toner on the surface of the charge control member. This protective film is preferably formed of a material having good releasability, and for example, a fluororesin can be used. As a result, the toner can be prevented from adhering to the charge control member, and a more uniform charge can be obtained.
[0058]
FIG. 11 is a schematic configuration diagram showing a developing device according to the first embodiment of the invention described in claim 1, claim 7, or claim 8.
In this developing apparatus, a layer forming member 83 for forming a toner layer and a charge imparting member 85 are supported on the developer carrier 82 so as to be integrated, and the power supply member 90 is provided on the surface of the layer forming member 83. And a charge providing member 85 is provided on the power supply member 90. In addition, an insulating layer 87 is formed on the surface of the charge imparting member 85, and a conductive charge control member 86 is laminated via the insulating layer.
[0059]
The layer forming member 83 includes a plate-like holding member 83 a and an elastic member 83 b bonded thereto, and is supported so that the layer forming member 83 is pressed against the developer carrier 82. The tip of the layer forming member 83 is arranged upstream with respect to the rotation direction of the developer carrying member 82, and the toner on the developer carrying member 82 passes through the pressure contact portion with the layer forming member 83. Thus, the toner amount is regulated.
Further, the charge applying member 85 and the charge control member 86 are formed on the support end side from the contact portion with the developer carrier 82 on the surface of the elastic member 83b, and the charge control member 86 is separated from the developer carrier 82. So as to face each other.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0060]
In such a developing device, the toner passes through the pressure contact portion with the layer forming member 83 by the rotation of the developer carrier 82, and a toner layer is formed on the developer carrier 82. The toner layer passes through a position facing the charge control member 86, and only electrons or negative ions among negative ions and positive ions generated by a discharge phenomenon between the charge applying member 85 and the charge control member 86 are provided. Is applied to the toner by an electric field generated between the developer carrier 82 and the toner.
[0061]
When the charging performance of the toner was confirmed using such a developing device, the reverse polarity toner was 0.1 wt% or less, and a good result was obtained. In addition, since the charge imparting member 85 and the layer forming member 83 are integrally supported, the apparatus can be reduced in size and cost.
[0062]
FIG. 12 is an enlarged view showing the configuration in the vicinity of the charge control member of the developing device according to the second embodiment of the invention described in claim 1, claim 7 or claim 8.
In this developing device, the power supply member also serves as the holding member 93a of the layer forming member 93, and a charge imparting member 95 made of a semiconductive material is formed in parallel with the elastic member 93b. In addition, an insulating layer 97 is formed on the surface of the charge imparting member 95, and a conductive charge control member 96 is laminated via the insulating layer. The charge control member 96 is provided so as to face the developer carrier 92 with a distance.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0063]
In such a developing device, a toner layer is formed on the developer carrier 92 by the layer forming member 93, and this toner layer passes through a position facing the charge control member 96. At this time, among the negative ions and positive ions generated by the discharge phenomenon between the charge applying member 95 and the charge control member 96, only electrons or negative ions are generated in the toner by the electric field generated between the developer carrier 92 and the like. Is granted. For this reason, the toner can be charged almost uniformly.
[0064]
FIG. 13 is an enlarged view showing the configuration in the vicinity of the charge control member of the developing device according to the third embodiment of the invention described in claim 1, claim 7 or claim 8.
In this developing device, a charge imparting member 105 made of a plate-like semiconductive material is attached to the tip of a conductive holding member 103, which also serves as a toner layer forming member. A conductive charge control member 106 is laminated on the surface of the charge applying member 105 via an insulating layer 107. In addition, a protective film 101 having a minute opening smaller than the particle size of the toner is formed on the surface of the charge control member 106. For example, a fluororesin is used for the protective film.
The other configuration of the developing device is the same as that of the developing device shown in FIG.
[0065]
In this developing apparatus, the charge imparting member 105 is pressed against the developer carrier 102 to form a toner layer on the developer carrier 102, and the charge imparting member 105 and the charge control member 106 are formed on the toner layer. Among the ions and the like generated by the discharge phenomenon between them, only electrons or negative ions are given. For this reason, the toner can be charged to a substantially uniform polarity. Further, since the protective film 101 is formed on the surface of the charge control member 106, it is possible to prevent the toner from adhering to the charge control member, and a more uniform charge can be obtained.
[0066]
In the developing device of the embodiment described above, when the conductive charge control member is in direct contact with the charge imparting member or the developer carrier, a coating layer of an insulating material is provided on the surface of the charge imparting member. It may be provided. By this coating layer, fluctuations in the potential of the charge applying member and charge leakage can be reduced, and the toner can be charged more uniformly.
[0067]
【Example】
In order to confirm the toner charging performance of the developing device according to the present invention, the results of a long-time print test under the following conditions will be described. In this experiment, a developing device having the same configuration as that in FIG. 4 is used.

[0068]
When a print test was performed under the above conditions, it was confirmed that there was no occurrence of ground fogging or toner scattering into the machine due to reverse polarity toner, which was a problem in the past, and it was excellent in maintainability.
[0069]
【The invention's effect】
As described above, in the developing device according to the first aspect of the present invention, both positive ions and negative ions are generated by the discharge phenomenon between the charge imparting member and the charge control member. An avalanche phenomenon does not occur with the developer carrier, and either positive ions or negative ions are attracted to the developer carrier by the action of the electric field, and the toner on the developer carrier is charged almost uniformly. It becomes possible to do.
[0070]
Further, in the developing device according to claim 2 or 3, since the shape of the charge control member is appropriately set, the occurrence of uneven charging due to the shape of the charge control member can be suppressed as much as possible.
[0071]
In the developing device according to the fourth aspect of the present invention, the charge imparting member, the charge control member, and the developer carrying member rotate together, and discharge occurs in a minute gap near the contact portion between the charge imparting member and the charge control member. Therefore, it is possible to prevent an excessive current from flowing between the members and the occurrence of a leak phenomenon, and the developer on the developer carrying member can be suitably charged.
[0072]
In the developing device according to the fifth aspect of the present invention, the charge control member is sandwiched between the charge imparting member and the developer carrier, and is driven to rotate by the rotation of the developer carrier. The support structure of the member is simplified, and the apparatus can be prevented from becoming large and complicated.
[0073]
In the developing device according to the sixth aspect of the invention, the electrode portion or the non-electrode portion of the charge control member is moved with respect to the surface of the developer carrying member. Can be more uniformly charged.
[0074]
In the developing device according to the seventh aspect of the invention, since the insulating layer is interposed between the charge imparting member and the charge control member, the leakage phenomenon between them is prevented, and the toner is uniformly and satisfactorily improved. Can be charged. Further, by integrating the charge control member and the charge imparting member, it is possible to prevent the apparatus from becoming large and complicated.
[0075]
In the developing device according to the eighth aspect of the invention, since the charge imparting member is supported so as to be integrated with the layer forming member, the developer is charged together with the formation of the developer layer on the developer carrying member. And the apparatus can be simplified.
[0076]
In the developing device according to the ninth aspect of the invention, the electrode layer of the charge control member or the portion where the electrode layer is not formed is opposed to the surface of the developer carrying member and moves relatively. The developer on the carrier can be more uniformly charged.
[0077]
In the developing device according to the tenth aspect of the present invention, since at least a part of the charge imparting member is coated with a semiconductive material or an insulating material, the charge imparting member and the charge control member or between the charge control members Leakage between the member and the developer carrying member is prevented, and the toner can be charged satisfactorily.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 1, claim 2, claim 4 or claim 5;
FIG. 2 is a diagram illustrating a mechanism in which a developer on a developer carrying member is charged in the developing device.
FIG. 3 is a diagram illustrating a potential distribution between a charge imparting member and a developer carrier of the developing device.
FIG. 4 is a partial configuration diagram illustrating a charge imparting member and a charge control member of a developing device according to another embodiment of the invention described in claim 1, claim 4, or claim 5.
FIG. 5 is a partial configuration diagram showing a charge imparting member and a charge control member of a developing device according to an embodiment of the invention as set forth in claim 1, claim 4 or claim 6;
FIG. 6 is a partial configuration diagram illustrating a charge imparting member and a charge control member of a developing device according to an embodiment of the invention described in claim 1 or claim 3;
FIG. 7 is a schematic configuration diagram illustrating a charge control member of a developing device according to a first embodiment of the invention described in claim 1 or claim 7;
FIG. 8 is a partial configuration diagram illustrating a charge imparting member and a charge control member of a developing device according to a second embodiment of the invention described in claim 1 or claim 7;
FIG. 9 is a partial configuration diagram illustrating a charge imparting member and a charge control member of a developing device according to a third embodiment of the invention described in claim 1 or claim 7;
FIG. 10 is a partial configuration diagram showing a charge imparting member and a charge control member of a developing device according to an embodiment of the invention according to claim 1, claim 7 or claim 9;
FIG. 11 is a schematic configuration diagram illustrating a developing device according to a first embodiment of the invention according to claim 1, claim 7, or claim 8.
FIG. 12 is a partial configuration diagram showing a charge imparting member and a charge control member of a developing device according to a second embodiment of the invention as set forth in claim 1, claim 7, or claim 8.
FIG. 13 is a partial configuration diagram showing a charge imparting member and a charge control member of a developing device according to a third embodiment of the invention as set forth in claims 1, 7, and 8.
FIG. 14 is a schematic configuration diagram illustrating an example of a conventional developing device.
FIG. 15 is a schematic configuration diagram illustrating another example of a conventional developing device.
FIG. 16 is a diagram illustrating a state in which a developer on a developer carrier of a conventional developing device is charged.
FIG. 17 is a diagram illustrating a state in which a developer on a developer carrier of a conventional developing device is charged.
FIG. 18 is a diagram illustrating a charge density between a developer charge imparting member and a developer carrier of the developing device.
[Explanation of symbols]
1 Image carrier
2 Developer carrier
3 layer forming member
4 Developer supply member
5 Charge imparting members
6 Charge control member
7 Power supply for development
8, 18, 28, 38, 48, 58, 68, 78 Toner power supply
9, 19, 29, 39, 49, 59, 69, 79 Charge control power supply
10 Housing
15, 25, 35, 45, 55, 65, 75 Charge applying member
16, 26, 36, 46, 56, 66, 76 Charge control member
47, 57, 67, 77, 87, 97, 107 Insulating layer
60, 70, 80, 90 Power supply member
83, 93 Layer forming member
85, 95, 105 Charge imparting member
86, 96, 106 Charge control member
88, 98, 108 Toner charging power supply
89, 99, 109 Charge control power supply
101 Protective film

Claims

A developer carrier disposed so as to be close to or in contact with an image carrier on which a latent image due to a difference in electrostatic potential is formed on the surface;
A layer forming member for forming a thin layer of developer on the peripheral surface of the developer carrying member,
In a developing device for visualizing the latent image by selectively transferring the thinned developer to the image carrier in a development region where the image carrier and the developer carrier are opposed to each other.
Electric charge is applied to the developer carrier at a position where a thin layer of developer has already been formed so as to be close to and opposed to the developer carrier, and to generate an electric field between the developer carrier and the developer carrier. Members,
A penetrating portion is formed between the charge imparting member and the developer carrying member so that a portion where the charge imparting member and the developer carrier are directly opposed to each other is formed . A charge control member to which a potential between a potential and the potential of the developer carrying member is applied;
At least one of the charge imparting member and the charge control member is made of a semiconductive material,
The charge control member is disposed in direct contact with the charge imparting member or through an insulator layer,
A voltage equal to or higher than a discharge start voltage is applied between the charge applying member and the charge control member, and ions or electrons having a predetermined polarity are placed between the charge control member and the developer carrier on the developer carrier side. A developing device, wherein a voltage equal to or lower than a discharge start voltage is applied so as to form an electric field that moves toward the surface.

The developing device according to claim 1,
The developing device according to claim 1, wherein the charge control member is a mesh member made of a conductive material or a semiconductive material.

The developing device according to claim 1,
The developing device according to claim 1, wherein the charge control member is a conductive or semiconductive thin plate member having a large number of small holes.

A developer carrier disposed so as to be close to or in contact with an image carrier on which a latent image due to a difference in electrostatic potential is formed on the surface;
A layer forming member for forming a thin layer of developer on the peripheral surface of the developer carrying member,
In a developing device for visualizing the latent image by selectively transferring the thinned developer to the image carrier in a development region where the image carrier and the developer carrier are opposed to each other.
Electric charge is applied to the developer carrier at a position where a thin layer of developer has already been formed so as to be close to and opposed to the developer carrier, and to generate an electric field between the developer carrier and the developer carrier. Members,
A penetrating portion is formed between the charge imparting member and the developer carrying member so that a portion where the charge imparting member and the developer carrier are directly opposed to each other is formed . A charge control member to which a potential between a potential and the potential of the developer carrying member is applied;
The charge imparting member is formed in a cylindrical shape and is supported so as to be rotatable around an axis.
The charge control member is formed in a cylindrical shape having a diameter larger than that of the charge applying member, and is externally attached to the charge applying member so that a part of the inner peripheral surface is provided with the charge at a position facing the developer carrying member. Supported to rotate in contact with the member,
A voltage equal to or higher than a discharge start voltage is applied between the charge applying member and the charge control member, and ions or electrons having a predetermined polarity are placed between the charge control member and the developer carrier on the developer carrier side. A developing device, wherein a voltage equal to or lower than a discharge start voltage is applied so as to form an electric field that moves toward the surface.

The developing device according to claim 4,
The developing device, wherein the charge control member is sandwiched between the charge imparting member and the developer carrying member, and is driven to rotate following the rotation of the developer carrying member.

The developing device according to claim 4,
The charge control member is supported so as to be separated from the developer carrying member, and is driven to rotate so that a peripheral speed is different from a peripheral speed of the developer carrying member. .

The developing device according to claim 1,
The developing device, wherein the charge control member is formed of a conductive layer or a semiconductive layer laminated on a surface of the charge imparting member via an insulating layer.

The developing device according to claim 7,
The developing device, wherein the charge applying member is supported so as to be integrated with the layer forming member.

A developer carrier disposed so as to be close to or in contact with an image carrier on which a latent image due to a difference in electrostatic potential is formed on the surface;
A layer forming member for forming a thin layer of developer on the peripheral surface of the developer carrying member,
In a developing device for visualizing the latent image by selectively transferring the thinned developer to the image carrier in a development region where the image carrier and the developer carrier are opposed to each other.
Electric charge is applied to the developer carrier at a position where a thin layer of developer has already been formed so as to be close to and opposed to the developer carrier, and to generate an electric field between the developer carrier and the developer carrier. Members,
A penetrating portion is formed between the charge imparting member and the developer carrying member so that a portion where the charge imparting member and the developer carrier are directly opposed to each other is formed . A charge control member to which a potential between a potential and the potential of the developer carrying member is applied;
The charge control member is formed of a conductive layer or a semiconductive layer laminated on the surface of the charge imparting member via an insulating layer,
The charge imparting member is a rotatable cylindrical member or an endless belt-like member that can be rotated, and is driven so that the peripheral speed of the charge imparting member is different from the peripheral speed of the developer carrier. And
A voltage equal to or higher than a discharge start voltage is applied between the charge applying member and the charge control member, and ions or electrons having a predetermined polarity are placed between the charge control member and the developer carrier on the developer carrier side. A developing device, wherein a voltage equal to or lower than a discharge start voltage is applied so as to form an electric field that moves toward the surface.

In the developing device according to any one of claims 1 to 9 ,
A developing device, wherein at least a part of the charge control member is coated with a semiconductive material or an insulating material.