JP3826654B2

JP3826654B2 - Development device

Info

Publication number: JP3826654B2
Application number: JP2000055123A
Authority: JP
Inventors: 哲丸藤田; 浩後藤; 秀一中川; 陽子藤江; 成隆吉田
Original assignee: Konica Minolta Business Technologies Inc
Current assignee: Konica Minolta Business Technologies Inc
Priority date: 2000-03-01
Filing date: 2000-03-01
Publication date: 2006-09-27
Anticipated expiration: 2020-03-01
Also published as: JP2001242699A

Description

【０００１】
【発明の属する技術分野】
この発明は、複写機やプリンター等の画像形成装置において、像担持体に形成された静電潜像を現像するのに使用する現像装置に係り、特に、静電潜像が形成される像担持体と所要間隔を介して対向するように設けられたトナー担持体の表面にトナーを保持させ、このトナー担持体によりトナーを像担持体と対向する現像領域に導く途中において規制部材により搬送されるトナーの量を規制し、このように規制されたトナーを像担持体と対向する現像領域に導くと共に、このトナー担持体と像担持体との間に交番電界を作用させて現像を行うようにした現像装置に関するものである。
【０００２】
【従来の技術】
従来より、複写機やプリンター等の画像形成装置においては、像担持体に形成された静電潜像を現像するのに様々な現像装置が使用されており、このような現像装置としては、現像剤にキャリアとトナーとを含む２成分現像方式の現像装置の他に、キャリアを含まない現像剤を使用した１成分現像方式の現像装置が知られている。
【０００３】
また、このような１成分現像方式の現像装置においては、トナーを保持するトナー担持体を像担持体と接触するように設け、このトナー担持体によってトナーを像担持体と接触する現像領域に導いて現像を行なうようにした接触現像方式の現像装置と、トナー担持体を像担持体と所要間隔を介して対向するように設け、このトナー担持体によりトナーを像担持体と対向する現像領域に導き、トナーをトナー担持体から像担持体に飛翔させて現像を行うようにした非接触現像方式の現像装置とが知られている。
【０００４】
ここで、接触現像方式の現像装置の場合、トナーを像担持体と接触させて現像を行うため、像担持体に形成された静電潜像の再現性に優れるが、静電潜像の形成されていない非画像部分にもトナーが付着されて、形成される画像にカブリが発生する等の問題があった。
【０００５】
このため、近年においては、上記の非接触現像方式の現像装置について様々な開発が行われるようになった。
【０００６】
ここで、このような非接触現像方式の現像装置においては、一般に図１に示すように、ドラム状になった像担持体１と所要間隔を介して対向するようにトナー担持体１１を設け、このトナー担持体１１と像担持体１とを回転させると共に、このトナー担持体１１の表面に装置本体１０内に収容されたトナーｔを送り部材１２によって供給するようにしている。
【０００７】
そして、このようにトナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制すると共に摩擦帯電させ、このように規制されて摩擦帯電されたトナーｔをトナー担持体１１により像担持体１と対向する現像領域に導くと共に、トナー担持体１１に電源１４から交番電圧を印加させて、像担持体１とトナー担持体１１との間に交番電界を作用させ、トナー担持体１１の表面に保持されたトナーｔを飛翔させて像担持体１に供給し、像担持体１に形成された静電潜像を現像するようにしていた。
【０００８】
また、上記のようにトナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制すると共に摩擦帯電させるにあたり、従来においては、一般に上記の規制部材１３に電源１４からトナー担持体１１と同じ交番電圧を印加させるようにしていた。
【０００９】
ここで、上記のようにトナー担持体１１の表面に供給されたトナーｔを規制部材１３により規制すると共に摩擦帯電させると、トナーｔがこの規制部材１３によりトナー担持体１１の表面に押し付けられて、このトナーｔがトナー担持体１１の表面に強く付着されるようになった。特に、近年においては、高精細な画像を得るため、小粒径のトナーｔが使用されるようになり、このような小粒径のトナーｔにおいてはトナー担持体１１の表面への付着力が高く、上記のようにトナー担持体１１の表面に保持されたトナーｔを飛翔させて像担持体１に供給するにあたり、トナーｔが像担持体１に十分に供給されなくなり、形成される画像の濃度が低下したり、濃度むらが発生したりするという問題があった。
【００１０】
また、近年においては、特開平９−２７４３７６号公報に示されるように、トナー担持体と規制部材との間に交流電圧を印加させて交番電界を作用させ、トナーをトナー担持体と規制部材との間で飛翔させて往復動させ、これによりトナー担持体の表面に対するトナーの付着力を低減させてた、トナー担持体の表面に良好なトナーの層を形成することが提案されている。
【００１１】
しかし、このようにトナー担持体と規制部材との間に交流電圧を印加させて交番電界を作用させると、規制部材との接触によりトナーの帯電が不均一になって、逆帯電トナーや不良帯電トナーが発生し、このようなトナーが規制部材に付着して、トナー担持体の表面におけるトナーの層に筋状のむらが生じたり、また形成される画像にかぶりが発生する等の問題が生じた。
【００１２】
【発明が解決しようとする課題】
この発明は、静電潜像が形成される像担持体と所要間隔を介して対向するように設けられたトナー担持体の表面にトナーを保持させ、このトナー担持体によりトナーを像担持体と対向する現像領域に導く途中において、規制部材により搬送されるトナーの量を規制し、このように規制されたトナーを像担持体と対向する現像領域に導くと共に、このトナー担持体と像担持体との間に交番電界を作用させて現像を行うようにした非接触現像方式の現像装置における上記のような問題を解決することを課題とするものである。
【００１３】
すなわち、この発明は、上記のような現像装置において、トナー担持体によりトナーを像担持体と対向する現像領域に導く途中に、規制部材によって搬送されるトナーの量を規制するにあたり、トナーがトナー担持体の表面に強く付着されるのを抑制し、小粒径のトナーを使用した場合においても、トナー担持体の表面に対するトナーの付着力が低減されるようにし、またトナー担持体と規制部材との間に交流電圧を印加させて交番電界を作用させる場合のように、逆帯電トナーや不良帯電トナーが発生して、トナーが規制部材に付着したり、形成される画像にかぶりが発生するということもなく、十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようにすることを課題とするものである。
【００１４】
【課題を解決するための手段】
この発明における現像装置においては、上記のような課題を解決するため、静電潜像が形成される像担持体と所要間隔を介して対向するように設けられたトナー担持体の表面にトナーを保持させ、このトナー担持体によりトナーを像担持体と対向する現像領域に導く途中において規制部材により搬送されるトナーの量を規制し、このように規制されたトナーを像担持体と対向する現像領域に導くと共に、このトナー担持体と像担持体との間に交番電界を作用させて現像を行う現像装置において、上記のトナー担持体と規制部材との間にトナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させるようにしたのである。
【００１５】
そして、この発明における現像装置のように、トナー担持体によって像担持体と対向する現像領域に搬送されるトナーの量を規制部材によって規制するにあたり、トナー担持体と規制部材との間に、トナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させると、トナー担持体と規制部材との間に交流電圧を印加させて交番電界を作用させる場合のように、逆帯電トナーや不良帯電トナーが発生して、トナーが規制部材に付着したり、形成される画像にかぶりが発生するということがない。また、トナー担持体に保持されたトナーが上記の変動電界によってトナー担持体の表面において振動し、これによりトナー担持体の表面におけるトナーの付着力が低減され、小粒径のトナーを使用した場合においても、十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようになる。
【００１６】
ここで、この発明における現像装置において、上記のようにトナー担持体と規制部材との間に、トナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させるにあたっては、トナー担持体と規制部材とに交番電圧を印加させて、トナー担持体の表面電位が規制部材の表面電位と同じ又はトナー担持体の表面電位より規制部材の表面電位がトナーの帯電極性側になるようにして、トナーをトナー担持体に付勢する方向の電界を作用させるようにすると共に、トナー担持体の表面電位と規制部材の表面電位との電位差を変動させて、トナー担持体と規制部材との間に電界強度が変化する変動電界を作用させるようにする。
【００１７】
そして、このようにトナー担持体と規制部材との間に変動電界を作用させるにあたり、変動電界におけるピークの電界強度が大きくなり過ぎると、トナー担持体と規制部材との間にリークが発生して、トナーの帯電等が適切に行えなくなるため、請求項２に示すように、トナーの帯電極性と同極性の電圧が印加された場合におけるトナー担持体の表面電位Ｖｔ１と規制部材の表面電位Ｖｒ１との最大電位差をΔＶ１＝｜Ｖｔ１−Ｖｒ１｜、トナーの帯電極性と逆極性の電圧が印加された場合におけるトナー担持体の表面電位Ｖｔ２と規制部材の表面電位Ｖｒ２との最大電位差をΔＶ２＝｜Ｖｔ２−Ｖｒ２｜、トナー担持体と規制部材との間隔をｄとした場合に、ΔＶ１／ｄ≦４０Ｖ／μｍ及びΔＶ２／ｄ≦４０Ｖ／μｍの条件を満たすようにすることが好ましい。
【００１８】
また、この発明における現像装置において、トナー担持体と規制部材との間に作用させる変動電界における電界強度の変動幅が少ないと、トナー担持体に保持されたトナーを十分に振動させて、トナー担持体の表面におけるトナーの付着力を十分に低減させることができなくなるため、請求項３に示すように、｜ΔＶ１−ΔＶ２｜／ｄ≧２Ｖ／μｍの条件を満たすようにすることが好ましい。
【００１９】
また、上記のようにトナー担持体と規制部材との間に、トナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させるにあたって、トナー担持体の表面においてトナーの均一な層が形成されるようにするためには、トナーの帯電極性と同極性の電圧が印加された場合におけるトナー担持体の表面電位Ｖｔ１と規制部材の表面電位Ｖｒ１との最大電位差ΔＶ１＝｜Ｖｔ１−Ｖｒ１｜が、トナーの帯電極性と逆極性の電圧が印加された場合におけるトナー担持体の表面電位Ｖｔ２と規制部材の表面電位Ｖｒ２との最大電位差ΔＶ２＝｜Ｖｔ２−Ｖｒ２｜より大きくなるようにし、請求項４に示すように、（ΔＶ１−ΔＶ２）／ｄ≧２Ｖ／μｍの条件を満たすようにすることが好ましい。
【００２０】
また、この発明における現像装置において、トナー担持体により像担持体と対向する現像領域に導くトナーの量を規制する規制部材を２以上設け、トナー担持体と各規制部材との間にトナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させるようにすることも可能である。
【００２１】
そして、このように２以上の規制部材を設け、トナー担持体と各規制部材との間に、トナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させると、逆帯電トナーや不良帯電トナーが発生するのが抑制されて、トナーが規制部材に付着したり、形成される画像にかぶりが発生するのがさらに抑制されると共に、トナー担持体に保持されたトナーが各規制部材との間における変動電界によりトナー担持体の表面において振動し、これによりトナー担持体の表面におけるトナーの付着力が低減され、小粒径のトナーを使用した場合においても、より十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようになる。
【００２２】
【発明の実施の形態】
以下、この発明の実施形態に係る現像装置を添付図面に基づいて具体的に説明する。
【００２３】
（実施形態１）
実施形態１における現像装置も、図２に示すように、図１に示した従来の現像装置と同様に、ドラム状になった像担持体１と所要間隔を介して対向するようにトナー担持体１１を設け、このトナー担持体１１と像担持体１とを回転させると共に、装置本体１０内に収容されたトナーｔを送り部材１２によってこのトナー担持体１１の表面に供給するようにしている。
【００２４】
そして、図３に示すように、トナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制すると共に摩擦帯電させ、このように規制されて摩擦帯電されたトナーｔをトナー担持体１１により像担持体１と対向する現像領域に導くと共に、トナー担持体１１に電源１４から交番電圧を印加させて、像担持体１とトナー担持体１１との間に交番電界を作用させ、トナー担持体１１の表面に保持されたトナーｔを飛翔させて像担持体１に供給し、像担持体１に形成された静電潜像を現像するようにしている。なお、この実施形態においては、上記のトナー担持体１１として、金属製のローラ１１ａの表面にゴム等のコート層１１ｂを設けたものを用い、また規制部材１３としては、ＳＵＳ等で構成された金属製の板材を用いるようにしている。
【００２５】
そして、この実施形態の現像装置においては、上記のようにトナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制すると共に摩擦帯電させるにあたり、図２に示すように、上記の規制部材１３に対して、電源１４からトナー担持体１１と同じ交番電圧を印加させると共に、規制部材用電源１５からトナーｔの帯電極性と同極性の直流電圧に交流電圧が重畳された交番電圧を印加させ、この規制部材１３とトナー担持体１１との間において、トナーｔをトナー担持体１１に付勢する方向の電界であって電界強度が変化する変動電界を作用させるようにしている。
【００２６】
ここで、このようにトナー担持体１１と規制部材１３との間にトナーｔをトナー担持体１１に付勢する方向の電界であって電界強度が変化する変動電界を作用させると、トナー担持体１１によって搬送されるトナーｔが規制部材１３との接触によってその帯電量が低下したり、逆極性に帯電されるということがなく、トナーｔが適切に帯電されるようになり、規制部材１３にトナーｔが付着するのが防止されると共に、トナーｔが外部に飛散したり、非画像部分に付着して形成される画像にかぶりが発生するということがない。
【００２７】
また、トナー担持体１１に保持されたトナーｔが上記の変動電界によってトナー担持体１１の表面において振動し、トナー担持体１１の表面におけるトナーｔの付着力が低減され、小粒径のトナーｔを使用した場合においても、十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようになる。
【００２８】
ここで、上記のトナーｔの帯電極性が負の場合には、例えば、上記の電源１４からトナーｔの帯電極性と同じ負の直流電圧に交流電圧が重畳された交番電圧をトナー担持体１１と規制部材１３とに印加させると共に、規制部材用電源１５から規制部材１３にトナーｔの帯電極性と同じ負の直流電圧に交流電圧が重畳された交番電圧を印加させ、図４（Ａ），（Ｂ）に示すように、トナー担持体１１の表面電位より規制部材１３の表面電位がトナーｔの帯電極性である負のマイナス側になるようにすると共に、トナーｔの帯電極性と同じ負の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ１と規制部材１３の表面電位Ｖｒ１との最大電位差ΔＶ１＝｜Ｖｔ１−Ｖｒ１｜と、トナーの帯電極性と逆極性の正の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ２と規制部材１３の表面電位Ｖｒ２との最大電位差ΔＶ２＝｜Ｖｔ２−Ｖｒ２｜とが異なるようにする。
【００２９】
このようにすると、トナー担持体１１と規制部材１３との間には負に帯電したトナーｔをトナー担持体１１に付勢する方向の電界が作用すると共に、上記のようにΔＶ１とΔＶ２とが異なるため、トナー担持体１１と規制部材１３との間に作用する電界の電界強度が変化するようになる。
【００３０】
また、このようにΔＶ１とΔＶ２とを異ならせるにあたっては、ΔＶ１とΔＶ２の何れが大きくなっていてもよいが、規制部材１３によりトナー担持体１１の表面に均一なトナーｔの層を形成するためには、図４（Ａ），（Ｂ）に示すように、トナーｔの帯電極性と同じ負の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ１と規制部材１３の表面電位Ｖｒ１との最大電位差ΔＶ１が大きくなるようにして、トナーｔの帯電極性と同じ負の電圧が印加された場合における電界強度を、トナーの帯電極性と逆極性の正の電圧が印加された場合における電界強度より高くすることが好ましい。
【００３１】
次に、上記の実施形態１における現像装置において、上記の規制部材用電源１５から規制部材１３に印加させる電圧を変更させた実験を行い、この発明の条件を満たす場合と満たさない場合とを比較し、この発明の条件を満たす場合には、良好な画像が得られるようになることを明らかにする。
【００３２】
ここで、この実験においては、像担持体１として直径が３０ｍｍの感光体ドラムを、トナーｔとして平均粒径が８μｍの負帯電性トナーを、トナー担持体１１として金属製のローラ１１ａの表面に抵抗値が１０⁶Ωのシリコンゴムのコート層１１ｂを設けたものを、規制部材１３としてＳＵＳで構成された厚みが０．１ｍｍの板材を用いるようにした。
【００３３】
また、上記の像担持体１とトナー担持体１１との間隔を１５０μｍ、システム速度を１６０ｍｍ／ｓ、像担持体１の周速度に対するトナー担持体１１の周速度の比を１．５にし、上記の像担持体１の初期表面電位を−５５０Ｖ、露光されたべたの潜像部分の電位を−５０Ｖにし、上記のようにトナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制すると共に摩擦帯電させ、このように規制されて負に帯電されたトナーｔをトナー担持体１１により像担持体１と対向する現像領域に導くと共に、電源１４から−４００Ｖの直流電圧に周波数が２０００Ｈｚでピーク・ピーク値Ｖｐｐが１５００Ｖの矩形波からなる交流電圧をトナー担持体１１に印加させて反転現像を行うようにした。なお、上記のトナー担持体１１と規制部材１３との間隔ｄは１５μｍになっていた。
【００３４】
そして、上記のトナー担持体１１の表面に供給されたトナーｔを規制部材１３によって規制する規制部材用電源１５から規制部材１３に印加させる電圧を変更させて、トナーｔの帯電極性と同じ負の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ１と規制部材１３の表面電位Ｖｒ１との差ΔＶ１ａ（＝Ｖｔ１−Ｖｒ１）と、トナーｔの帯電極性と逆極性の正の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ２と規制部材１３の表面電位Ｖｒ２との差ΔＶ２ａ（＝Ｖｔ２−Ｖｒ２）とを下記の表１に示すように変更させ、またこの場合における、上記のΔＶ１／ｄ、ΔＶ２／ｄ及び｜ΔＶ１ａ−ΔＶ２ａ｜／ｄの値を求め、その結果を表１に合わせて示した。
【００３５】
ここで、上記のΔＶ１ａ及びΔＶ２ａがプラスの場合には、トナー担持体１１の表面電位より規制部材１３の表面電位がトナーｔの帯電極性であるマイナス側になっており、トナーｔをトナー担持体１１に付勢する方向の電界が作用する一方、ΔＶ１ａ及びΔＶ２ａがマイナスの場合には、トナー担持体１１の表面電位より規制部材１３の表面電位がトナーｔの帯電極性と逆のプラス側になって、トナーｔを規制部材１３に引き付ける方向の電界が作用するようになる。なお、ΔＶ１ａ及びΔＶ２ａがプラスの場合、｜ΔＶ１ａ−ΔＶ２ａ｜／ｄ＝｜ΔＶ１−ΔＶａ｜／ｄとなる。
【００３６】
また、上記のΔＶ１ａとΔＶ２ａの値が異なる場合には、トナー担持体１１と規制部材１３との間に電界強度が変化する変動電界が作用する一方、ΔＶ１ａとΔＶ２ａの値が同じ場合には、トナー担持体１１と規制部材１３との間に一定した電界強度の電界が作用するようになる。
【００３７】
そして、上記のようにΔＶ１ａとΔＶ２ａの値を変化させて、それぞれトナー担持体１１の表面に供給されたトナーｔを規制部材１３により規制した場合における規制部材１３へのトナー付着を調べ、また上記のように反転現像させてべた画像を形成し、形成されたべた画像におけるトナー量（ｍｇ／ｃｍ²）を求めると共に濃度むらを調べ、これらの結果を表１に合わせて示した。なお、規制部材１３へのトナー付着については、トナーが付着しなかった場合を○、付着した場合を×で示した。また、濃度むらについては、濃度むらが分からない場合を◎、濃度むらが殆どない場合を○、濃度むらが少しある場合を△、濃度むらが明確に現れた場合を×で示した。
【００３８】
【表１】

【００３９】
この結果から明らかなように、ΔＶ１ａとΔＶ２ａの何れかがマイナスになって、トナーｔを規制部材１３に引き付ける方向の電界が作用する場合には、規制部材１３にトナーｔが付着すると共に、濃度むらが発生するを十分に抑制することができず、またΔＶ１ａとΔＶ２ａとがプラスであるが、ΔＶ１ａとΔＶ２ａの値が同じで、トナー担持体１１と規制部材１３との間に一定した電界強度の電界が作用する場合には、像担持体１に十分な量のトナーｔが供給されず、形成される画像の画像濃度が低下すると共に、濃度むらが発生することを十分に抑制することができなかった。
【００４０】
これに対して、ΔＶ１ａとΔＶ２ａとがプラスであると共に、ΔＶ１ａとΔＶ２ａの値が異なって、トナー担持体１１と規制部材１３との間に、トナーｔをトナー担持体１１に付勢する方向の電界であって電界強度が変化する変動電界を作用するようにした場合には、規制部材１３にトナーｔが付着するということがなく、像担持体１に十分な量のトナーｔが供給されて、十分な画像濃度を有する画像が得られるようになると共に、濃度むらの発生も十分に抑制されるようになった。
【００４１】
特に、トナーｔの帯電極性と同極性の負の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ１と規制部材１３の表面電位Ｖｒ１との最大電位差ΔＶ１＝｜Ｖｔ１−Ｖｒ１｜が、トナーｔの帯電極性と逆極性の正の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ２と規制部材１３の表面電位Ｖｒ２との最大電位差ΔＶ２＝｜Ｖｔ２−Ｖｒ２｜よりも大きくなるようにすると、さらに濃度むらの発生が抑制されるようになった。
【００４２】
なお、上記の実験において、上記のΔＶ１やΔＶ２の値が７００Ｖになって、ΔＶ１／ｄやΔＶ２／ｄの値が４０Ｖ／μｍを越えると、トナー担持体１１と規制部材１３との間においてリークが発生した。
【００４３】
（実施形態２）
実施形態２における現像装置においても、図５に示すように、ドラム状になった像担持体１と所要間隔を介して対向するようにトナー担持体１１を設け、このトナー担持体１１と像担持体１とを回転させると共に、このトナー担持体１１の表面に装置本体１０内に収容されたトナーｔを送り部材１２によって供給するようにしている。
【００４４】
そして、この実施形態における現像装置においては、トナー担持体１１の表面に供給されたトナーｔを規制すると共に摩擦帯電させる２つの規制部材１３ａ，１３ｂを設け、この２つの規制部材１３ａ，１３ｂに対して、それぞれ電源１４からトナー担持体１１と同じ交番電圧を印加させると共に、規制部材用電源１５からトナーｔの帯電極性と同極性の直流電圧に交流電圧が重畳された交番電圧を印加させ、この２つの規制部材１３ａ，１３ｂとトナー担持体１１との間において、トナーｔをトナー担持体１１に付勢する方向の電界であって電界強度が変化する変動電界が作用するようにしている。
【００４５】
このようにすると、トナー担持体１１によって搬送されるトナーｔが各規制部材１３ａ，１３ｂとの接触によって適切に帯電されるようになると共に、トナー担持体１１に保持されたトナーｔが各規制部材１３ａ，１３ｂとの間における上記の変動電界により、それぞれトナー担持体１１の表面において振動し、トナー担持体１１の表面におけるトナーｔの付着力が低減されるようになる。
【００４６】
そして、このように各規制部材１３ａ，１３ｂにより規制されて摩擦帯電されたトナーｔを、トナー担持体１１により像担持体１と対向する現像領域に導くと共に、トナー担持体１１に電源１４から交番電圧を印加させて、像担持体１とトナー担持体１１との間に交番電界を作用させ、トナー担持体１１の表面に保持されたトナーｔを飛翔させて像担持体１に供給し、像担持体１に形成された静電潜像を現像するようにしている。
【００４７】
このようにして現像を行うと、上記のようにトナーｔが各規制部材１３ａ，１３ｂとの接触によって適切に帯電されるようになり、トナーｔが外部に飛散したり、非画像部分に付着して形成される画像にかぶりが発生するのが抑制されると共に、トナー担持体１１の表面におけるトナーｔの付着力が低減され、小粒径のトナーｔを使用した場合においても、十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようになる。
【００４８】
次に、この実施形態２の現像装置を用いて、上記の実施形態１の現像装置と同様に実験を行った。
【００４９】
ここで、この実験においては、規制部材用電源１５から各規制部材１３ａ，１３ｂに印加させる電圧を適切に設定し、トナーｔの帯電極性と同じ負の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ１と各規制部材１３ａ，１３ｂの表面電位Ｖｒ１との差ΔＶ１ａ（＝Ｖｔ１−Ｖｒ１）が２００Ｖ、トナーｔの帯電極性と逆極性の正の電圧が印加された場合におけるトナー担持体１１の表面電位Ｖｔ２と各規制部材１３ａ，１３ｂの表面電位Ｖｒ２との差ΔＶ２ａ（＝Ｖｔ２−Ｖｒ２）が１００Ｖになるようにし、それ以外は、上記の実施形態１の現像装置における実験と同様にして反転現像を行った。
【００５０】
そして、上記のようにトナー担持体１１の表面に供給されたトナーｔを各規制部材１３ａ，１３ｂにより規制した場合における各規制部材１３ａ，１３ｂへのトナー付着を調べたところ、各規制部材１３ａ，１３ｂにトナーｔが付着するということはなかった。
【００５１】
また、上記のように反転現像させてべた画像を形成した場合、べた画像におけるトナー量は０．６３ｍｇ／ｃｍ²であり、十分な画像濃度を有する画像が得られると共に、濃度むらが発生するということもなく、さらに形成された画像にがぶりが発生するのがより一層抑制された。
【００５２】
【発明の効果】
以上詳述したように、この発明における現像装置においては、トナー担持体によって像担持体と対向する現像領域に搬送されるトナーの量を規制部材によって規制するにあたり、トナー担持体と規制部材との間に、トナーをトナー担持体に付勢する方向の電界であって電界強度が変化する変動電界を作用させるようにしたため、逆帯電トナーや不良帯電トナーが発生して、トナーが規制部材に付着したり、形成される画像にかぶりが発生するということがなく、また上記の変動電界によって、トナーがトナー担持体の表面において振動し、これによりトナー担持体の表面におけるトナーの付着力が低減され、小粒径のトナーを使用した場合においても、十分な画像濃度を有すると共に濃度むらのない良好な画像が得られるようになった。
【図面の簡単な説明】
【図１】従来の現像装置を用いて、像担持体の表面に形成された静電潜像を現像する状態を示した概略説明図である。
【図２】この発明の実施形態１に係る現像装置を用いて、像担持体の表面に形成された静電潜像を現像する状態を示した概略説明図である。
【図３】同実施形態に係る現像装置において、トナー担持体に保持されたトナーの量を規制部材によって規制する状態を示した部分拡大説明図である。
【図４】同実施形態に係る現像装置において、トナー担持体の表面電位と規制部材の表面電位の変化を示した図、及びトナー担持体の表面電位と規制部材の表面電位の電位差の変化を示した図である。
【図５】この発明の実施形態２に係る現像装置を用いて、像担持体の表面に形成された静電潜像を現像する状態を示した概略説明図である。
【符号の説明】
１像担持体
１１トナー担持体
１３，１３ａ，１３ｂ規制部材
１４電源
１５規制部材用電源
ｔトナー
ｄ規制部材とトナー担持体との間隔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device used to develop an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly to an image carrier on which an electrostatic latent image is formed. The toner is held on the surface of the toner carrying member provided to face the body with a predetermined interval, and the toner is conveyed by the regulating member in the middle of guiding the toner to the developing area facing the image carrying member. The amount of toner is regulated, and the regulated toner is guided to a development region facing the image carrier, and development is performed by applying an alternating electric field between the toner carrier and the image carrier. The developing device.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices are used to develop an electrostatic latent image formed on an image carrier. In addition to a two-component developing type developing device including a carrier and a toner in a developer, a one-component developing type developing device using a developer not including a carrier is known.
[0003]
In such a one-component developing type developing device, a toner carrier for holding toner is provided so as to be in contact with the image carrier, and the toner is guided to the developing region in contact with the image carrier. A contact developing type developing device adapted to perform development, and a toner carrier to be opposed to the image carrier via a required interval, and the toner carrier causes the toner to be placed in a development region facing the image carrier. There is known a non-contact developing type developing device in which development is performed by flying toner from a toner carrier to an image carrier.
[0004]
Here, in the case of a contact developing type developing device, since development is performed by bringing toner into contact with the image carrier, the electrostatic latent image formed on the image carrier is excellent in reproducibility. There is a problem that toner is adhered to a non-image portion that is not formed, and fogging occurs in the formed image.
[0005]
For this reason, in recent years, various developments have been made on the above-described non-contact developing type developing apparatus.
[0006]
Here, in such a non-contact developing type developing apparatus, generally, as shown in FIG. 1, a toner carrier 11 is provided so as to face the drum-shaped image carrier 1 with a required interval, The toner carrier 11 and the image carrier 1 are rotated, and the toner t accommodated in the apparatus main body 10 is supplied to the surface of the toner carrier 11 by the feeding member 12.
[0007]
The toner t thus supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 and frictionally charged, and the toner t thus regulated and frictionally charged is image-bearing by the toner carrier 11. 1 is applied to the toner carrier 11 and an alternating voltage is applied to the toner carrier 11 from the power source 14 to cause an alternating electric field to act between the image carrier 1 and the toner carrier 11. The toner t held on the image carrier 1 is ejected and supplied to the image carrier 1, and the electrostatic latent image formed on the image carrier 1 is developed.
[0008]
Further, as described above, when the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 and frictionally charged, conventionally, the regulating member 13 is generally connected to the toner carrier 11 from the power source 14. The same alternating voltage was applied.
[0009]
When the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 and frictionally charged as described above, the toner t is pressed against the surface of the toner carrier 11 by the regulating member 13. The toner t is strongly attached to the surface of the toner carrier 11. Particularly in recent years, in order to obtain a high-definition image, a toner t having a small particle diameter has been used, and the toner t having such a small particle diameter has an adhesion force to the surface of the toner carrier 11. When the toner t held on the surface of the toner carrier 11 is made to fly and is supplied to the image carrier 1 as described above, the toner t is not sufficiently supplied to the image carrier 1 and the image to be formed There has been a problem that the density is lowered or uneven density occurs.
[0010]
In recent years, as disclosed in Japanese Patent Application Laid-Open No. 9-274376, an alternating voltage is applied between a toner carrier and a regulating member to apply an alternating electric field, and the toner is separated from the toner carrier and the regulating member. It has been proposed that a good toner layer is formed on the surface of the toner carrying member that has been reciprocated by flying between them, thereby reducing the adhesion of the toner to the surface of the toner carrying member.
[0011]
However, if an alternating voltage is applied between the toner carrier and the regulating member in this way and an alternating electric field is applied, the toner becomes non-uniform due to contact with the regulating member, and reversely charged toner or defective charging Toner is generated, and such toner adheres to the regulating member, causing problems such as streaky irregularities in the toner layer on the surface of the toner carrying member and fogging in the formed image. .
[0012]
[Problems to be solved by the invention]
According to the present invention, toner is held on the surface of a toner carrier provided so as to face an image carrier on which an electrostatic latent image is formed with a predetermined interval therebetween, and the toner is separated from the image carrier by the toner carrier. The amount of toner conveyed by the regulating member is regulated on the way to the opposite developing area, and the regulated toner is guided to the developing area facing the image carrier, and the toner carrier and the image carrier. It is an object of the present invention to solve the above-described problems in a non-contact developing system developing apparatus in which an alternating electric field is applied to the developing device.
[0013]
That is, according to the present invention, in the developing device as described above, when the amount of toner conveyed by the regulating member is regulated while the toner is guided by the toner carrier to the development area facing the image carrier, Suppressing strong adhesion to the surface of the carrier, and even when a small particle size toner is used, the adhesion force of the toner to the surface of the toner carrier is reduced, and the toner carrier and the regulating member As in the case of applying an alternating electric field by applying an alternating voltage between the toner and the toner, reversely charged toner or defectively charged toner is generated, and the toner adheres to the regulating member, or the formed image is fogged. In other words, it is an object to obtain a good image having a sufficient image density and having no density unevenness.
[0014]
[Means for Solving the Problems]
In the developing device of the present invention, in order to solve the above-described problems, the toner is applied to the surface of the toner carrier provided so as to face the image carrier on which the electrostatic latent image is formed with a predetermined interval. The amount of toner transported by the regulating member is regulated while the toner carrying member is held and the toner is guided to the developing region facing the image bearing member, and the toner thus regulated is opposed to the image bearing member. In a developing device that conducts development by applying an alternating electric field between the toner carrier and the image carrier and energizing the toner between the toner carrier and the regulating member. In other words, a fluctuating electric field that changes the electric field strength is applied.
[0015]
As in the developing device according to the present invention, when the amount of toner conveyed to the developing region facing the image carrier by the toner carrier is regulated by the regulating member, the toner is interposed between the toner carrier and the regulating member. When a fluctuating electric field whose electric field intensity changes is applied to the toner carrying member, an alternating voltage is applied between the toner carrying member and the regulating member to apply an alternating electric field. In addition, reversely charged toner and defectively charged toner are not generated, and the toner does not adhere to the regulating member and fogging does not occur in the formed image. In addition, when the toner held on the toner carrier vibrates on the surface of the toner carrier due to the above-described fluctuation electric field, the adhesion force of the toner on the surface of the toner carrier is reduced, and a toner having a small particle diameter is used. In this case, a good image having a sufficient image density and having no density unevenness can be obtained.
[0016]
Here, in the developing device according to the present invention, as described above, a fluctuating electric field, which is an electric field in a direction in which the toner is urged to the toner carrier, is applied between the toner carrier and the regulating member. In this case, an alternating voltage is applied to the toner carrier and the regulating member so that the surface potential of the toner carrier is the same as the surface potential of the regulating member or the surface potential of the regulating member is greater than the charging potential of the toner. The toner carrier is made to act as an electric field in the direction in which the toner is urged to the toner carrier, and the potential difference between the surface potential of the toner carrier and the surface potential of the regulating member is changed. A fluctuating electric field whose electric field strength changes is applied between the control member and the regulating member.
[0017]
Then, when the variable electric field acts between the toner carrier and the regulating member in this way, if the peak electric field strength in the varying electric field becomes too large, a leak occurs between the toner carrier and the regulating member. Since the toner cannot be charged properly, the surface potential Vt1 of the toner carrier and the surface potential Vr1 of the regulating member when a voltage having the same polarity as the toner charging polarity is applied, as shown in claim 2. ΔV1 = | Vt1−Vr1 |, and the maximum potential difference between the surface potential Vt2 of the toner carrier and the surface potential Vr2 of the regulating member when a voltage having a polarity opposite to the charging polarity of the toner is applied is ΔV2 = | Vt2 −Vr2 |, and satisfying the conditions of ΔV1 / d ≦ 40 V / μm and ΔV2 / d ≦ 40 V / μm, where d is the distance between the toner carrier and the regulating member. Door is preferable.
[0018]
Further, in the developing device according to the present invention, when the fluctuation range of the electric field strength in the fluctuating electric field acting between the toner carrying member and the regulating member is small, the toner held on the toner carrying member is sufficiently vibrated to cause the toner carrying Since the adhesion force of the toner on the surface of the body cannot be sufficiently reduced, it is preferable to satisfy the condition of | ΔV1−ΔV2 | / d ≧ 2V / μm as shown in claim 3.
[0019]
In addition, when a fluctuating electric field that changes the electric field strength is applied between the toner carrying member and the regulating member in the direction in which the toner is urged to the toner carrying member, In order to form a uniform toner layer, the maximum potential difference ΔV1 between the surface potential Vt1 of the toner carrier and the surface potential Vr1 of the regulating member when a voltage having the same polarity as the charging polarity of the toner is applied. = | Vt1-Vr1 | is larger than the maximum potential difference ΔV2 = | Vt2-Vr2 | between the surface potential Vt2 of the toner carrier and the surface potential Vr2 of the regulating member when a voltage having a polarity opposite to the charging polarity of the toner is applied. As shown in claim 4, it is preferable to satisfy the condition of (ΔV1−ΔV2) / d ≧ 2V / μm.
[0020]
Further, in the developing device according to the present invention, two or more regulating members for regulating the amount of toner guided to the developing area facing the image carrier by the toner carrier are provided, and the toner is placed between the toner carrier and each regulating member. It is also possible to apply a fluctuating electric field that is an electric field in a direction in which the carrier is urged and whose electric field strength changes.
[0021]
In this way, two or more regulating members are provided, and an electric field in the direction in which the toner is urged to the toner carrying member and a varying electric field whose electric field strength changes is applied between the toner carrying member and each regulating member. As a result, the occurrence of reversely charged toner and defectively charged toner is suppressed, and the toner is further prevented from adhering to the regulating member and fogging in the formed image, and is also held on the toner carrier. The toner vibrates on the surface of the toner carrying member due to the fluctuating electric field between each regulating member, thereby reducing the adhesion force of the toner on the surface of the toner carrying member, and even when using a small particle size toner, A good image having a sufficient image density and no density unevenness can be obtained.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.
[0023]
(Embodiment 1)
As in the conventional developing device shown in FIG. 1, the developing device in Embodiment 1 also has a toner carrier so as to face the drum-like image carrier 1 with a required interval, as shown in FIG. 11, the toner carrier 11 and the image carrier 1 are rotated, and the toner t accommodated in the apparatus main body 10 is supplied to the surface of the toner carrier 11 by the feed member 12.
[0024]
Then, as shown in FIG. 3, the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 and frictionally charged, and the toner t thus regulated and frictionally charged is fed to the toner carrier 11. To the developing area facing the image carrier 1 and an alternating voltage is applied to the toner carrier 11 from the power source 14 to cause an alternating electric field to act between the image carrier 1 and the toner carrier 11, and The toner t held on the surface of the body 11 is made to fly and supplied to the image carrier 1, and the electrostatic latent image formed on the image carrier 1 is developed. In this embodiment, the toner carrier 11 is a metal roller 11a provided with a coating layer 11b made of rubber or the like, and the regulating member 13 is made of SUS or the like. A metal plate is used.
[0025]
In the developing device of this embodiment, as described above, when the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 and frictionally charged, as shown in FIG. The same alternating voltage as the toner carrier 11 is applied from the power source 14 to the member 13, and the alternating voltage in which the alternating voltage is superimposed on the direct current voltage having the same polarity as the charging polarity of the toner t is applied from the power supply 15 for the regulating member. Thus, a fluctuating electric field that is an electric field in a direction in which the toner t is urged to the toner carrier 11 and whose electric field strength changes is applied between the regulating member 13 and the toner carrier 11.
[0026]
Here, when the electric field in the direction in which the toner t is urged to the toner carrier 11 between the toner carrier 11 and the regulating member 13 as described above and a fluctuating electric field that changes the electric field strength is applied, the toner carrier The toner t transported by the toner 11 does not decrease in charge amount due to contact with the regulating member 13 or is charged to the opposite polarity, so that the toner t is appropriately charged. The toner t is prevented from adhering, and the toner t does not scatter to the outside or the image formed by adhering to the non-image portion is not fogged.
[0027]
Further, the toner t held on the toner carrier 11 vibrates on the surface of the toner carrier 11 due to the above-mentioned fluctuation electric field, and the adhesion force of the toner t on the surface of the toner carrier 11 is reduced, so that the toner t having a small particle diameter is obtained. Even in the case of using, a good image having a sufficient image density and having no density unevenness can be obtained.
[0028]
Here, when the charging polarity of the toner t is negative, for example, an alternating voltage in which an AC voltage is superimposed on the negative DC voltage same as the charging polarity of the toner t from the power source 14 is applied to the toner carrier 11. 4A and 4B, an alternating voltage in which an AC voltage is superimposed on a negative DC voltage that is the same as the charging polarity of the toner t is applied from the power supply 15 for the regulating member to the regulating member 13. As shown in B), the surface potential of the regulating member 13 is set to a negative minus side that is the charging polarity of the toner t with respect to the surface potential of the toner carrier 11, and the negative voltage that is the same as the charging polarity of the toner t is used. Is applied, a maximum potential difference ΔV1 = | Vt1−Vr1 | between the surface potential Vt1 of the toner carrying member 11 and the surface potential Vr1 of the regulating member 13 and a positive voltage having a polarity opposite to the charging polarity of the toner is applied. Place Vt2-Vr2 | | and is made different maximum potential difference [Delta] V2 = the surface potential Vr2 of the surface potential Vt2 and the regulating member 13 of the toner carrying member 11 in.
[0029]
As a result, an electric field in a direction for urging the negatively charged toner t against the toner carrier 11 acts between the toner carrier 11 and the regulating member 13, and ΔV1 and ΔV2 are generated as described above. Therefore, the electric field strength of the electric field acting between the toner carrier 11 and the regulating member 13 changes.
[0030]
In order to make ΔV1 and ΔV2 different from each other, either ΔV1 or ΔV2 may be large. However, in order to form a uniform toner t layer on the surface of the toner carrier 11 by the regulating member 13. 4A and 4B, the surface potential Vt1 of the toner carrier 11 and the surface potential Vr1 of the regulating member 13 when a negative voltage that is the same as the charging polarity of the toner t is applied. The electric field strength when a negative voltage that is the same as the charging polarity of the toner t is applied so as to increase the maximum potential difference ΔV1 of the toner, and the electric field strength when a positive voltage that is opposite in polarity to the charging polarity of the toner is applied. It is preferable to make it higher.
[0031]
Next, in the developing device according to the first embodiment, an experiment was performed in which the voltage applied to the regulating member 13 from the regulating member power source 15 was changed, and the case where the condition of the present invention was not satisfied was compared with the case where the condition was not satisfied. It is clarified that when the conditions of the present invention are satisfied, a good image can be obtained.
[0032]
Here, in this experiment, a photosensitive drum having a diameter of 30 mm as the image carrier 1, a negatively chargeable toner having an average particle diameter of 8 μm as the toner t, and the surface of the metal roller 11 a as the toner carrier 11. Resistance value is 10 ⁶ A plate material having a thickness of 0.1 mm made of SUS was used as the regulating member 13 in which the coating layer 11b of Ω silicon rubber was provided.
[0033]
Further, the distance between the image carrier 1 and the toner carrier 11 is 150 μm, the system speed is 160 mm / s, and the ratio of the peripheral speed of the toner carrier 11 to the peripheral speed of the image carrier 1 is 1.5. The initial surface potential of the image carrier 1 is −550 V, the potential of the exposed latent image portion is −50 V, and the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 as described above. At the same time, the toner t, which is triboelectrically charged and regulated in this way, is guided to the developing region facing the image carrier 1 by the toner carrier 11, and the frequency from the power source 14 to a DC voltage of −400 V is 2000 Hz. Then, an AC voltage composed of a rectangular wave having a peak-to-peak value Vpp of 1500 V is applied to the toner carrier 11 to perform reversal development. The distance d between the toner carrier 11 and the regulating member 13 was 15 μm.
[0034]
Then, the voltage applied to the regulating member 13 from the regulating member power source 15 regulating the toner t supplied to the surface of the toner carrier 11 by the regulating member 13 is changed, and the negative polarity is the same as the charging polarity of the toner t. When a voltage is applied, a difference ΔV1a (= Vt1−Vr1) between the surface potential Vt1 of the toner carrier 11 and the surface potential Vr1 of the regulating member 13, and a positive voltage having a polarity opposite to the charging polarity of the toner t is applied. In this case, the difference ΔV2a (= Vt2−Vr2) between the surface potential Vt2 of the toner carrier 11 and the surface potential Vr2 of the regulating member 13 is changed as shown in Table 1 below. In this case, the above ΔV1 is changed. The values of / d, ΔV2 / d and | ΔV1a−ΔV2a | / d were determined, and the results are shown in Table 1.
[0035]
Here, when ΔV1a and ΔV2a are positive, the surface potential of the regulating member 13 is more negative than the surface potential of the toner carrier 11, and the toner t is replaced with the toner carrier. In the case where ΔV1a and ΔV2a are negative, the surface potential of the regulating member 13 is on the positive side opposite to the charging polarity of the toner t. Thus, an electric field in a direction to attract the toner t to the regulating member 13 acts. When ΔV1a and ΔV2a are positive, | ΔV1a−ΔV2a | / d = | ΔV1−ΔVa | / d.
[0036]
Further, when the values of ΔV1a and ΔV2a are different from each other, a fluctuating electric field that changes the electric field strength acts between the toner carrier 11 and the regulating member 13, while when the values of ΔV1a and ΔV2a are the same, An electric field having a constant electric field strength acts between the toner carrier 11 and the regulating member 13.
[0037]
Then, by changing the values of ΔV1a and ΔV2a as described above, the toner adhesion to the regulating member 13 when the toner t supplied to the surface of the toner carrier 11 is regulated by the regulating member 13 is examined. In this way, a solid image is formed by reversal development, and the toner amount (mg / cm in the solid image formed) ² ) And the density unevenness were examined, and the results are shown in Table 1. Regarding the toner adhesion to the regulating member 13, the case where the toner did not adhere is indicated by ◯, and the case where the toner adheres was indicated by ×. Concentration unevenness is indicated by ◎ when the density unevenness is not known, ◯ when there is almost no density unevenness, Δ when there is little density unevenness, and × when the density unevenness clearly appears.
[0038]
[Table 1]

[0039]
As is apparent from this result, when either ΔV1a or ΔV2a becomes negative and an electric field in the direction of attracting toner t to the regulating member 13 acts, the toner t adheres to the regulating member 13 and the density is increased. The occurrence of unevenness cannot be sufficiently suppressed, and ΔV1a and ΔV2a are positive, but the values of ΔV1a and ΔV2a are the same, and a constant electric field strength is present between the toner carrier 11 and the regulating member 13. When the electric field acts on the image carrier 1, a sufficient amount of toner t is not supplied to the image carrier 1, so that the image density of the formed image is lowered and density unevenness is sufficiently suppressed. could not.
[0040]
On the other hand, ΔV1a and ΔV2a are positive and ΔV1a and ΔV2a are different from each other, and the toner t is biased toward the toner carrier 11 between the toner carrier 11 and the regulating member 13. When a fluctuating electric field that changes the electric field strength is applied, the toner t does not adhere to the regulating member 13, and a sufficient amount of toner t is supplied to the image carrier 1. As a result, an image having a sufficient image density can be obtained, and the occurrence of density unevenness can be sufficiently suppressed.
[0041]
In particular, the maximum potential difference ΔV1 = | Vt1−Vr1 | between the surface potential Vt1 of the toner carrier 11 and the surface potential Vr1 of the regulating member 13 when a negative voltage having the same polarity as the charging polarity of the toner t is applied. When a positive voltage having a polarity opposite to the charging polarity of t is applied, the maximum potential difference ΔV2 = | Vt2−Vr2 | between the surface potential Vt2 of the toner carrier 11 and the surface potential Vr2 of the regulating member 13 is larger. As a result, the occurrence of density unevenness was further suppressed.
[0042]
In the above experiment, when the values of ΔV1 and ΔV2 become 700V and the values of ΔV1 / d and ΔV2 / d exceed 40V / μm, leakage occurs between the toner carrier 11 and the regulating member 13. There has occurred.
[0043]
(Embodiment 2)
Also in the developing device according to the second embodiment, as shown in FIG. 5, a toner carrier 11 is provided so as to face the drum-shaped image carrier 1 with a predetermined interval, and the toner carrier 11 and the image carrier are provided. While rotating the body 1, the toner t accommodated in the apparatus main body 10 is supplied to the surface of the toner carrier 11 by the feeding member 12.
[0044]
In the developing device in this embodiment, two regulating members 13a and 13b that regulate and frictionally charge the toner t supplied to the surface of the toner carrying member 11 are provided, and the two regulating members 13a and 13b are provided with respect to the two regulating members 13a and 13b. Then, the same alternating voltage as that of the toner carrier 11 is applied from the power source 14, and the alternating voltage in which the alternating voltage is superimposed on the direct current voltage having the same polarity as the charging polarity of the toner t is applied from the regulating member power source 15. Between the two regulating members 13a and 13b and the toner carrier 11, an electric field in the direction in which the toner t is urged toward the toner carrier 11 and a fluctuating electric field that changes the electric field strength acts.
[0045]
In this way, the toner t transported by the toner carrier 11 is appropriately charged by the contact with the regulating members 13a and 13b, and the toner t held on the toner carrying member 11 is transformed into the regulating members. The fluctuating electric field between 13a and 13b vibrates on the surface of the toner carrier 11, and the adhesion force of the toner t on the surface of the toner carrier 11 is reduced.
[0046]
The toner t regulated by the regulating members 13a and 13b and frictionally charged as described above is guided to the developing area facing the image carrier 1 by the toner carrier 11 and is alternately connected to the toner carrier 11 from the power source 14. A voltage is applied to cause an alternating electric field to act between the image carrier 1 and the toner carrier 11, and the toner t held on the surface of the toner carrier 11 is made to fly and supplied to the image carrier 1. The electrostatic latent image formed on the carrier 1 is developed.
[0047]
When the development is performed in this manner, the toner t is appropriately charged by the contact with the regulating members 13a and 13b as described above, and the toner t is scattered to the outside or attached to the non-image portion. As a result, it is possible to suppress the occurrence of fog in the formed image, and to reduce the adhesion force of the toner t on the surface of the toner carrier 11, so that a sufficient image density can be obtained even when the toner t having a small particle diameter is used. As a result, it is possible to obtain a good image having non-uniform density.
[0048]
Next, using the developing device of the second embodiment, an experiment was performed in the same manner as the developing device of the first embodiment.
[0049]
Here, in this experiment, the toner carrier 11 in the case where the voltage applied from the power supply 15 for the regulating member to each regulating member 13a, 13b is appropriately set and a negative voltage equal to the charging polarity of the toner t is applied. The toner carrier 11 when the difference ΔV1a (= Vt1−Vr1) between the surface potential Vt1 of the toner and the surface potential Vr1 of each regulating member 13a, 13b is 200 V, and a positive voltage having a polarity opposite to the charging polarity of the toner t is applied The difference ΔV2a (= Vt2−Vr2) between the surface potential Vt2 and the surface potential Vr2 of each of the regulating members 13a and 13b is set to 100 V, and other than that, the same as the experiment in the developing device of the first embodiment. Reversal development was performed.
[0050]
Then, when the toner t supplied to the surface of the toner carrier 11 as described above is regulated by the regulating members 13a and 13b, the adhesion of the toner to the regulating members 13a and 13b is examined. The toner t did not adhere to 13b.
[0051]
Further, when a solid image is formed by reversal development as described above, the toner amount in the solid image is 0.63 mg / cm. ² Thus, an image having a sufficient image density was obtained, density unevenness did not occur, and the occurrence of fogging was further suppressed in the formed image.
[0052]
【The invention's effect】
As described in detail above, in the developing device according to the present invention, when the amount of toner conveyed to the developing region facing the image carrier by the toner carrier is regulated by the regulating member, In the meantime, a fluctuating electric field that is an electric field in the direction in which the toner is urged to the toner carrier and the electric field strength changes is applied, so that a reversely charged toner or a defectively charged toner is generated and the toner adheres to the regulating member. And the image formed is not fogged, and the fluctuation electric field causes the toner to vibrate on the surface of the toner carrier, thereby reducing the adhesion force of the toner on the surface of the toner carrier. Even when a toner having a small particle diameter is used, a good image having a sufficient image density and no density unevenness can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a state in which an electrostatic latent image formed on the surface of an image carrier is developed using a conventional developing device.
FIG. 2 is a schematic explanatory view showing a state where an electrostatic latent image formed on the surface of an image carrier is developed using the developing device according to Embodiment 1 of the present invention.
FIG. 3 is a partially enlarged explanatory view showing a state in which the amount of toner held on the toner carrier is regulated by a regulating member in the developing device according to the embodiment.
FIG. 4 is a diagram showing changes in the surface potential of the toner carrier and the surface potential of the regulating member in the developing device according to the embodiment, and shows changes in the potential difference between the surface potential of the toner carrier and the surface potential of the regulating member; FIG.
FIG. 5 is a schematic explanatory view showing a state where an electrostatic latent image formed on the surface of an image carrier is developed using a developing device according to Embodiment 2 of the present invention.
[Explanation of symbols]
1 Image carrier
11 Toner carrier
13, 13a, 13b Restriction member
14 Power supply
15 Power supply for regulating member
t Toner
d Distance between the regulating member and the toner carrier

Claims

The toner is held on the surface of the toner carrier provided to face the image carrier on which the electrostatic latent image is formed with a predetermined interval, and the developing region where the toner is opposed to the image carrier by the toner carrier. The amount of toner conveyed by the regulating member is regulated in the middle of guiding to the toner, and the regulated toner is guided to the developing area facing the image carrier, and the alternating between the toner carrier and the image carrier. In a developing device that performs development by applying an electric field, a fluctuating electric field that changes the electric field strength is applied between the toner carrier and the regulating member in the direction in which the toner is urged to the toner carrier. A developing device.

2. The developing device according to claim 1, wherein an alternating voltage is applied to each of the toner carrier and the regulating member, and the surface potential of the toner carrier is the same as the surface potential of the regulating member or the surface potential of the toner carrier. The surface potential of the regulating member is on the charging polarity side of the toner, and the maximum potential difference between the surface potential Vt1 of the toner carrier and the surface potential Vr1 of the regulating member when a voltage having the same polarity as the charging polarity of the toner is applied. ΔV1 = | Vt1−Vr1 |, and the maximum potential difference between the surface potential Vt2 of the toner carrier and the surface potential Vr2 of the regulating member when a voltage having a polarity opposite to the charging polarity of the toner is applied is ΔV2 = | Vt2−Vr2 | A developing device that satisfies the conditions of ΔV1 / d ≦ 40 V / μm and ΔV2 / d ≦ 40 V / μm, where d is the distance between the toner carrier and the regulating member

3. The developing device according to claim 1, wherein an alternating voltage is applied to the toner carrier and the regulating member, and the surface potential of the toner carrier is the same as the surface potential of the regulating member or the surface potential of the toner carrier. The surface potential of the regulating member is closer to the charging polarity side of the toner, and the maximum potential difference between the surface potential Vt1 of the toner carrier and the surface potential Vr1 of the regulating member when a voltage having the same polarity as the charging polarity of the toner is applied. ΔV1 = | Vt1−Vr1 |, and the maximum potential difference between the surface potential Vt2 of the toner carrier and the surface potential Vr2 of the regulating member when a voltage having a polarity opposite to the charging polarity of the toner is applied is ΔV2 = | Vt2−Vr2 | A developing device characterized by satisfying a condition of | ΔV1−ΔV2 | / d ≧ 2V / μm, where d is a distance between the toner carrier and the regulating member.

4. The developing device according to claim 1, wherein an alternating voltage is applied to the toner carrier and the regulating member, and the surface potential of the toner carrier is the same as the surface potential of the regulating member or the toner The surface potential of the regulating member is closer to the charging polarity side of the toner than the surface potential of the carrier, and the surface potential Vt1 of the toner carrier and the surface potential of the regulating member when a voltage having the same polarity as the charging polarity of the toner is applied. The maximum potential difference from Vr1 is ΔV1 = | Vt1−Vr1 |, and the maximum potential difference between the surface potential Vt2 of the toner carrying member and the surface potential Vr2 of the regulating member when a voltage having a polarity opposite to the charging polarity of the toner is applied is ΔV2 = | Vt2−Vr2 |, and a developing device characterized by satisfying the condition of (ΔV1−ΔV2) / d ≧ 2V / μm, where d is the distance between the toner carrier and the regulating member.

The toner is held on the surface of the toner carrier provided so as to face the image carrier on which the electrostatic latent image is formed with a predetermined interval, and the development region where the toner is opposed to the image carrier by the toner carrier. The amount of toner conveyed by the regulating member is regulated in the middle of guiding to the toner, and the regulated toner is guided to the developing area facing the image carrier, and the alternating between the toner carrier and the image carrier. In a developing device that performs development by applying an electric field, two or more restriction members are provided, and an electric field in a direction in which toner is urged to the toner carrier between the toner carrier and each of the restriction members. A developing device characterized in that a fluctuating electric field is applied.