JP2004109701A - Method and device for development and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high quality image by improving development efficiency in a developing method for performing development by arranging a developer carrier having a magnet inside oppositely from an image carrier and adhering free toner removed from a magnetic carrier to a latent image on the image carrier in a process for making a magnetic brush flow while forming the magnetic brush by a two component developer. <P>SOLUTION: There are at least one or more places where a spike of assembled magnetic carriers rises in an area in which electric field intensity E (V/m) formed in an area where a development sleeve 111c faces a photosensitive body 100 satisfies the following expression (1 expression). E≥¾(A×ρ<SB>T</SB>×d×R)/(3B<SP>1/2</SP>×ε<SB>O</SB>×v<SB>SL</SB>)¾(1 expression), however, B = T<SB>C</SB>×D<SP>3</SP>×ρ<SB>C</SB>/(100-T<SB>C</SB>)×d<SP>3</SP>×ρ<SB>T</SB>, wherein, A: a toner average electric charge amount (C/kg), T<SB>C</SB>: toner concentration (wt%), d: a toner average particle size (m), D: a magnetic carrier average particle size (m), ρ<SB>T</SB>: toner specific gravity (kg/m<SP>3</SP>), ρ<SB>C</SB>: carrier specific gravity (kg/m<SP>3</SP>), ε<SB>O</SB>= 8. 854×10<SP>-12</SP>(F/m), R: the diameter of the development sleeve 111c, and v<SB>SL</SB>: a line rate of the development sleeve 111c (m/sec). <P>COPYRIGHT: (C)2004,JPO

Description

【０１７４】
ここで、表１において、○印はトナー飛翔有り、×印はトナー飛翔無しを表し、○×印は僅かではあるが飛翔していることを示す。このようにトナー飛翔の有無を生じるのは、トナーの帯電量に分布があるためと考えられる。表１において、〇印のついた欄の条件で▲１▼式を満足している。
【０１７５】
▲１▼式の根拠は次のような考察に基づく。▲１▼式は、トナーが飛翔する条件であるので、運動を考慮した場合の、キャリアからトナーが飛び出す閾値を示す電界の式として次の▲２▼式の成立を考える必要がある。
【０１７６】
【数１】

【０１７７】
そこで先ず、キャリア上に付着したトナーには、ｖａｎ　ｄｅｒ　Ｗａａｌｓ力を無視した場合、次の▲３▼式で示すトナー−キャリア間付着力Ｆ_ｔが作用する。
【０１７８】
【数２】

【０１７９】
この付着力Ｆ_ｔより電界からの力が勝ったときトナーはキャリアから離れるから、そのときの電界Ｅは、次の▲４▼式で示される。
【０１８０】
【数３】

【０１８１】
上記の▲４▼式でｑは、▲５▼式で示される。
【０１８２】
【数４】

【０１８３】
よって、電界Ｅは次の▲６▼式で示される。
【０１８４】
【数５】

【０１８５】
定数αについて実験的に検討したところ、定数αは次の▲７▼式で示されることがわかった。
【０１８６】
【数６】

【０１８７】
▲７▼式において、ｎはキャリア１個当たりに付着しているトナー数で、均一にトナーがキャリア上に付着していると仮定した場合、トナー濃度Ｔ_Ｃにおけるｎは重量比の関係から、次の▲８▼式で示される。
【０１８８】
【数７】

【０１８９】
▲８▼式で、ｍ：トナーの質量、ｄ：トナーの直径（粒径）、ρ_Ｔ：トナーの比重であり、Ｍ：キャリアの質量、Ｄ：キャリアの直径（粒径）、ρ_Ｃ：キャリアの比重である。また、Ｒは現像剤担持体の直径、ｖ_ＳＬは現像剤担持体の線速である。
▲６▼式に▲７▼式、▲８▼式のα、ｎなどを代入整理することで、上記▲２▼式を得る。この▲２▼式はキャリアからトナーが飛び出す電界の閾値を示すものであるから、▲２▼式より、現像を可能にする遊離トナーの発生に関する▲１▼式が導かれる。
【０１９０】
ここで、▲７▼式、▲８▼式における物理的な理由は不明であるが、この意味するところは、
Ｒ：現像剤担持体の直径が長くなるほど曲率半径は大きくなり磁気ブラシの穂立ちがなだらかになり、機械的力が弱まるため、より大きな電界が必要になる、
ｖ_ＳＬ：現像剤担持体の線速が早くなるほど、キャリア上トナーに機械的作用力が働き、キャリア上トナーの飛び出す電界は小さくなる、
ｎ：一般にＴ_Ｃが高くなると、トナー帯電量ｑは小さくなり、機械的作用力の影響が大きくなり、キャリア上トナーはより小さい電界で飛び出す。また、Ｔ_Ｃの変化でｑが変化しない場合も、ｎが大きい方が１個のトナーが飛翔したときにキャリア上に残るカウンターチャージの影響が小さいため、より小さい電界で飛び出すことが可能となる、
と考えられる。
【０１９１】
これまでの現像方法、現像装置などの説明において、現像スリーブと感光体１００との対向領域における現像態様として、▲１▼磁性キャリアの集合した穂が立ち上がる部分が１ヵ所以上存在する態様（請求項１関連）▲２▼磁性キャリアの集合した穂が立ち上がり、そして穂が寝る連続部分が少なくとも１ヵ所以上存在する態様（請求項２関連）▲３▼表面にトナーを有する磁性キャリアから、トナーを現像スリーブ１１１ｃに散布する態様（請求項５関連）▲４▼トナーを表面に有する磁性キャリアにより形成される磁気ブラシを感光体１００に摺接又は近接させて、トナーを現像させる態様（請求項８関連）▲５▼表面にトナーを有する磁性キャリアが集合した穂と、磁性キャリア表面から離脱させる遊離トナーとを含む磁気ブラシを形成し、磁性キャリアの集合した穂が立ち上がり、そして穂が寝る間にトナーを離脱させて現像し、かつ、磁気ブラシを像担持体に接触させて離脱させる遊離トナーを像担持体へ散布して現像し、かつ、磁気ブラシを像担持体に摺擦又は近接させて現像する態様（請求項１０関連）▲６▼表面にトナーを有する磁性キャリアが集合した穂と、磁性キャリア表面から離脱させる遊離トナーとを含む磁気ブラシを形成し、磁性キャリアの集合した穂が立ち上がり、さらに寝る間にトナーを離脱させて現像し、かつ、磁気ブラシを像担持体に近接させて現像する態様（請求項１２関連）について述べた。
【０１９２】
これらの現像態様において、現像スリーブ１１１ｃと感光体１００との対向領域に形成される電界強度Ｅ（Ｖ／ｍ）が、
Ｅ≧｜（Ａ・ρ_Ｔ・ｄ・Ｒ）／（３Ｂ^１／２・ε_０・ｖ_ＳＬ）｜
ただし、Ｂ＝Ｔ_Ｃ・Ｄ^３・ρ_Ｃ／（１００−Ｔ_Ｃ）・ｄ^３・ρ_Ｔ
ここで、Ａ：トナー平均帯電量（Ｃ／ｋｇ）、Ｔ_Ｃ：トナー濃度（ｗｔ％）、ｄ：トナー平均粒径（ｍ）、Ｄ：磁性キャリア平均粒径（ｍ）、ρ_Ｔ：トナー比重（ｋｇ／ｍ^３）、ρ_Ｃ：キャリア比重（ｋｇ／ｍ^３）、ε_０＝８．８５４×１０^−１２（Ｆ／ｍ）、Ｒ；現像剤担持体の直径（ｍ）、ｖ_ＳＬ：現像剤担持体の線速（ｍ／ｓｅｃ）となる領域を構成し、この領域で上記▲１▼〜▲６▼などの現像態様を実施することにより、遊離トナーの発生及びその飛翔を得て本発明の課題とする高品質の現像を得ることができた。
【０１９３】
［４］画像形成装置（請求項１７関連）
以上説明した本発明にかかる現像方法を行なう現像装置を備えた画像形成装置を例示する。この画像形成装置は、前記図１乃至図４で説明した基本構成を備えた現像装置を具備している。この現像装置は、必要に応じて、前記した内容の変更を加えて実施される。
【０１９４】
図１５は、画像形成装置の一例としてのカラー複写機の概略構成を示している。このカラー複写機は、カラー画像読取装置（以下、カラースキャナという）１、カラー画像記録装置（以下、カラープリンタという）２、給紙バンク３、図示省略の制御部等で構成されている。
【０１９５】
上記カラースキャナ１は、コンタクトガラス４上の原稿５の画像を照明ランプ６、ミラー群７ａ、７ｂ及びレンズ８を介してカラーセンサ９に結像して、原稿５のカラー画像情報を、例えばレッド（Ｒｅｄ）、グリーン（Ｇｒｅｅｎ）、ブルー（Ｂｌｕｅ）（以下、それぞれＲ、Ｇ、Ｂという）の色分解光毎に読み取り、電気的な画像信号に変換する。
【０１９６】
カラーセンサ９は、本例ではＲ、Ｇ、Ｂの色分解手段とＣＣＤ（ｃｈａｒｇｅ　ｃｏｕｐｌｅｄ　ｄｅｖｉｃｅ）のような光電変換素子で構成され、原稿４の画像を色分解した３色のカラー画像を同時に読み取っている。そして、このカラースキャナ１で得たＲ、Ｇ、Ｂの色分解画像信号強度レベルをもとにして図示しない画像処理部で色変換処理を行い、ブラック（Ｂｌａｃｋ、以下、Ｂｋという）、シアン（Ｃｙａｎ、以下、Ｃという）、マゼンタ（Ｍａｇｅｎｔａ、以下、Ｍという）、イエロー（Ｙｅｌｌｏｗ、以下、Ｙという）のカラー画像データを得る。
【０１９７】
上記Ｂｋ、Ｃ、Ｍ、Ｙのカラー画像データを得るためのカラースキャナ１の動作は次のとおりである。後述のカラープリンタ２の動作とタイミングを取ったスキャナスタ−ト信号を受けて、照明ランプ６及びミラー群７ａ、７ｂ等からなる光学系が矢印左方向へ原稿５を走査し、１回の走査毎に１色のカラー画像データを得る。この動作を合計４回繰り返すことによって、順次４色のカラー画像データを得る。そして、その都度カラープリンタ２で順次顕像化しつつ、これを重ねあわせて最終的な４色フルカラー画像を形成する。
【０１９８】
上記カラープリンタ２は、像担持体としての筒状をした感光体１００、書き込み光学ユニット１０、現像装置としてのリボルバ現像ユニット１１、中間転写装置１２、定着装置１３等で構成されている。
【０１９９】
感光体１００は矢印の反時計方向に回転し、その周りには、感光体クリ−ニング装置１４、除電ランプ１５、帯電器１０１、帯電電位検出手段としての電位センサ１６、リボルバ現像ユニット１１の選択された現像器２４（これが前記図１乃至図４で説明した現像装置１１０に相当する）、現像濃度パターン検知器１７、中間転写装置１２の中間転写ベルト１８などが配置されている。
【０２００】
また、上記書き込み光学ユニット１０は、カラースキャナ１からのカラー画像データを光信号に変換して、原稿５の画像に対応した光書き込みを行い、感光体１００に潜像を形成する。この書き込み光学ユニット１０は、光源としての半導体レーザー１９、図示しないレーザー発光駆動制御部、ポリゴンミラー２０とその回転用モ−タ２１、ｆ／θレンズ２２、反射ミラー２３などで構成されている。
【０２０１】
また、上記リボルバ現像ユニット１１は、Ｂｋ現像器２４Ｋ、Ｃ現像器２４Ｃ、Ｍ現像器２４Ｍ、Ｙ現像器２４Ｙ、及び各現像器を矢印の反時計方向に回転させる後述のリボルバ回転駆動部などで構成されている。
【０２０２】
各現像器は、感光体１００に対向して配置され、内部に磁石を有する現像スリーブ１１１ｃを備え、このスリーブ１１１ｃがトナーとトナーを保持する磁性キャリアとを含む二成分現像剤を表面に担持して、この担持した二成分現像剤を感光体１００との間の対向領域に搬送し、現像スリーブ１１１ｃと感光体１００との間に電界を印加し、感光体１００の表面上に形成されている潜像をトナーで現像する。
【０２０３】
各現像器２４内のトナーは磁性キャリアであるフェライトキャリアとの撹拌によって負極性に帯電され、また、各現像スリ−ブ１１１ｃには現像バイアス用の電源ＶＰ（図３参照）によって負の直流電圧に交流電圧が重畳された現像バイアス等が印加され、現像スリ−ブ１１１ｃが感光体１００の導電性支持体３１（図３参照）に対して所定電位にバイアスされている。前記▲１▼式を満足する電界強度はこの電源ＶＰにより与えることができる。
【０２０４】
複写機本体の待機状態では、リボルバ現像ユニット１１はＢｋ現像器２４Ｋが現像位置にセットされており、コピ−動作が開始されると、カラースキャナ１で所定のタイミングからＢｋカラー画像データの読み取りが開始し、このカラー画像データに基づきレーザー光による光書き込み、潜像形成が始まる（以下、Ｂｋ画像データによる潜像をＢｋ潜像という。Ｃ、Ｍ、Ｙについても同様）。
【０２０５】
このＢｋ潜像の先端部から現像可能とすべくＢｋ現像位置に潜像先端部が到達する前に、Ｂｋ現像スリ−ブ１１１ｃを回転開始して、Ｂｋ潜像をＢｋトナーで現像する。そして、以後Ｂｋ潜像領域の現像動作を続けるが、潜像後端部がＢｋ現像位置を通過した時点で、速やかに次の色の現像器が現像位置にくるまで、リボルバ現像ユニット１１が回転する。これは少なくとも、次の画像データによる潜像先端部が到達する前に完了させる。なお、このリボルバ現像ユニット１１については、後で詳しく説明する。
【０２０６】
また、上記中間転写装置１２は、中間転写ベルト１８、ベルトクリ−ニング装置２５、搬送ベルト３８、紙転写コロナ放電器（以下、紙転写器という）２６などで構成されている。中間転写ベルト１８は駆動ローラ１８ａ、転写対向ロ−ラ１８ｂ、クリ−ニング対向ロ−ラ１８ｃ及び従動ロ−ラ群に張架されており、図示しない駆動モ−タにより駆動制御される。
【０２０７】
この中間転写ベルト１８の材質は、ＥＴＦＥ（エチレンテトラフロロエチレン）であり、その電気抵抗は表面抵抗で１０^８〜１０^１０Ω／ｃｍ^２程度である。またベルトクリ−ニング装置２５は、入口シ−ル、ゴムブレ−ド、排出コイル、入口シ−ル及びゴムブレ−ドの接離機構等で構成されており、１色目のＢｋ画像を中間転写ベルト１８に転写した後の２、３、４色目の画像をベルト転写している間はブレード接離機構によって中間転写ベルト１８面から入口シ−ル、ブレ−ドを離間させておく。また紙転写器２６は、コロナ放電方式にてＡＣ電圧＋ＤＣ電圧、又はＤＣ電圧を印加して、中間転写ベルト１８上の重ねトナー像を記録紙２７に一括転写する。
【０２０８】
また、カラープリンタ２内の記録紙カセット２８及び給紙バンク３内の記録紙カセット３００ａ、ｂ、ｃには、各種サイズの記録紙２７が収納されており、指定されたサイズの記録紙２７のカセットから、給紙コロ３０、３１ａ、ｂ、ｃによってレジストロ−ラ対３０方向に給紙、搬送される。また、ＯＨＰ用紙や厚紙などの手差し給紙用にプリンタ２の右側面に手差しトレイ３３がある。
【０２０９】
上記構成のカラー複写機において、画像形成サイクルが開始されると、まず感光体１００は矢印の反時計方向に、中間転写ベルト１８は矢印の時計回りに図示しない駆動モ−タによって回転される。中間転写ベルト１８の回転に伴ってＢｋトナー像形成、Ｃトナー像形成、Ｍトナー像形成、Ｙトナー像形成が行われ、最終的にＢｋ、Ｃ、Ｍ、Ｙの順に中間転写ベルト１８上に重ねてトナー像が形成される。
【０２１０】
上記Ｂｋトナー像形成は次のように行われる。帯電器１０１はコロナ放電によって感光体１００を負電荷で一様帯電する。そして、半導体レーザー１９はＢｋカラー画像信号に基づいてラスタ露光を行う。このラスタ像が露光されたとき、当初一様荷電された感光体１００の露光された部分は、露光光量に比例する電荷が消失し、Ｂｋ潜像が形成される。
【０２１１】
Ｂｋ潜像にＢｋ現像スリーブ上の負帯電のＢｋトナーが接触することにより、感光体１００の電荷が残っている部分にはトナーが付着せず、電荷の無い部分つまり露光された部分にはＢｋトナーが吸着し、潜像と相似なＢｋトナー像が形成される。
【０２１２】
感光体１００上に形成されたＢｋトナー像は、感光体１００と接触状態で等速駆動している中間転写ベルト１８の表面に、ベルト転写器３４によって転写される（以下、感光体１００から中間転写ベルト１８へのトナー像転写をベルト転写という）。
【０２１３】
感光体１００上の若干の未転写残留トナーは、感光体１００の再使用に備えて感光体クリ−ニング装置１４で清掃される。ここで回収されたトナーは回収パイプを経由して図示しない排トナータンクに蓄えられる。
【０２１４】
感光体１００側ではＢｋ画像形成工程の次にＣ画像形成工程に進み、所定のタイミングでカラースキャナ１によるＣ画像データ読み取りが始まり、そのＣ画像データによるレーザー光書き込みで、Ｃ潜像形成を行う。そして、先のＢｋ潜像の後端部が通過した後で、かつＣ潜像の先端部が到達する前にリボルバー現像ユニット１１の回転動作が行われ、Ｃ現像器２４Ｃが現像位置にセットされてＣ潜像がＣトナーで現像される。
【０２１５】
以後、Ｃ潜像領域の現像を続けるが、Ｃ潜像の後端部が通過した時点で、先のＢｋ現像器２４Ｋの場合と同様にリボルバー現像ユニット１１の回転動作を行い、次のＭ現像器２４Ｍを現像位置に移動させる。これもやはり次のＭ潜像の先端部が現像位置に到達する前に完了させる。なお、Ｍ及びＹの画像形成工程については、それぞれのカラー画像データ読み取り、潜像形成、現像の動作が上述のＢＫ、Ｃの工程と同様であるので説明は省略する。
【０２１６】
上記中間転写ベルト１８には、感光体１００に順次形成するＢｋ、Ｃ、Ｍ、Ｙのトナー像を、同一面に順次位置合わせして、４色重ねのトナー像が形成され、次の転写工程において、この４色のトナー像が記録紙２７に紙転写器２６により一括転写される。
【０２１７】
上記画像形成動作を開始する時期に、記録紙２７は上記記録紙カセット又は手差しトレイのいずれかから給送され、レジストローラ対３２のニップで待機している。紙転写器２６に中間転写ベルト１８上のトナー像先端がさしかかるときに、丁度、記録紙２７の先端がこのトナー像の先端に一致するようにレジストローラ対３２が駆動され、搬送ベルト３８の助けで記録紙２７とトナー像とのレジスト合わせが行われる。
【０２１８】
記録紙５が中間転写ベルト１８上のトナー像と重ねられて正電位の紙転写器２６の上を通過する。このとき、コロナ放電電流で記録紙２７が正電荷で荷電され、トナー画像のほとんどが記録紙２７上に転写される。続いて紙転写器２６の左側に配置した図示しないＡＣ＋ＤＣコロナによる分離除電器との対向部を通過するときに、記録紙２７は除電され、中間転写ベルト１８から剥離されて、搬送ベルト２７から搬送ベルト３５に移る。
【０２１９】
中間転写ベルト１８面から４色重ねトナー像を一括転写された記録紙２７は、紙搬送ベルト３５で定着装置３６に搬送され、所定温度に制御された定着ロ−ラ３６ａと加圧ロ−ラ３６ｂのニップ部でトナー像が溶融定着され、排出ローラ対３７で装置本体外に送り出され、図示しないコピ−トレイに表向きにスタックされ、フルカラーコピーを得る。
【０２２０】
一方、ベルト転写後の感光体１００の表面は、感光体クリ−ニング装置１４（ブラシロ−ラ、ゴムブレ−ド）でクリ−ニングされ、除電ランプ１５で均一に除電される。また、記録紙２７にトナー像を転写した後の中間転写ベルト１８の表面は、ベルトクリ−ニング装置２５のブレードを再びブレ−ド接離機構で押圧することによってクリ−ニングされる。
【０２２１】
ここで、リピ−トコピ−のときは、カラースキャナ１の動作及び感光体１００への画像形成は、１枚目の４色目（Ｙ）の画像形成工程に引き続き、所定のタイミングで２枚目の１色目（Ｂｋ）の画像形成工程に進む。また、中間転写ベルト１８の方は、１枚目の４色重ねトナー像の記録紙２７への一括転写工程に引き続き、表面のベルトクリ−ニング装置２５でクリ−ニングされた領域に、２枚目のＢｋトナー像がベルト転写されるようにする。その後は、１枚目と同様動作になる。
【０２２２】
以上は、４色フルカラーコピ−を得るコピ−モ−ドであったが、３色コピ−モ−ド、２色コピ−モ−ドの場合は、指定された色と回数の分について、上記同様の動作を行うことになる。
【０２２３】
また、単色コピ−モ−ドの場合は、所定枚数が終了するまでの間、リボルバ現像ユニット１１の所定色の現像器のみを現像作動状態にして、ベルトクリ−ニング装置２５のブレ−ドを中間転写ベルト１８に押圧状態のまま連続してコピ−動作を行う。
【０２２４】
また、Ａ３サイズのフルカラーコピーモードの場合には、中間転写ベルト１８が１周するごとに１色のトナー像を形成し、４回転で４色のトナー像を形成していくのが望ましいが、装置全体を小さく、つまり中間転写ベルト１８の周長を抑え、小サイズの場合のコピースピードを確保し、かつ最大サイズのコピースピードも落さないようにするためには、中間転写ベルト１８が２周する間に１色のトナー像を形成するのが好ましい。この場合には、Ｂｋトナー像を中間転写ベルト１８に転写した後、次の中間転写ベルト１８の１周では、カラープリンタ２における現像及び転写が行われずに空回転し、その次の１周で次色のＣトナーによる現像を行い、そのＣトナー像を中間転写ベルト１８に転写するように順次行っていく。このとき現像器切り換えのためのリボルバ現像ユニット１１の回転動作は、上記空回転時に行う。
【０２２５】
本発明の画像形成装置では、遊離トナーで現像を行なう現像装置を備え、対向領域で前記▲１▼式満足する所定の電界強度のもとで、遊離トナーで現像することで、広い範囲で現像領域を設定することにより、現像されるトナーの供給量を多くすることで、機械を設計する際の現像ギャップ、現像スリーブの回転数等の許容範囲を広くすることでき、また、ソリッド部や横細線の高品位の画像、特に、カラーの画像では、ハーフトーン部の再現性の優れた画像を得る画像形成装置を提供することができる。
【０２２６】
【発明の効果】
請求項１乃至１３記載の発明では、従来の現像領域よりも広い範囲で現像領域を設定することにより、現像領域におけるトナーの現像される量を多くして、ソリッド部のベタ濃度の高い画像を得ることができる。
【０２２７】
請求項１４記載の発明では、ハーフトーン部の後端白抜けや横細線画像のカスレを防止することができる。
【０２２８】
請求項１５記載の発明では、トナーが振動するようにより激しく運動し、さらに、潜像に忠実に揃えられ高品位の画像を得ることができる。
【０２２９】
請求項１６記載の発明では、従来の現像領域よりも広い範囲で現像領域を設定することから、現像スリーブの回転数を高くしなくとも、現像されるトナーの供給量を多くする現像装置を提供することができる。
【０２３０】
請求項１７記載の発明では、広い範囲で現像領域を設定することにより、現像されるトナーの供給量を多くすることで、機械を設計する際の現像ギャップ、現像スリーブの回転数等の許容範囲を広くすることでき、また、ソリッド部や横細線の高品位の画像、特に、カラーの画像では、ハーフトーン部の再現性の優れた画像を得ることができる。
【図面の簡単な説明】
【図１】現像装置の基本構成を説明した正面図である。
【図２】現像スリーブの断面図である。
【図３】現像装置の基本構成を説明した概略構成図である。
【図４】図４（ａ）は磁力分布とその大きさ程度を示した図、図４（ｂ）は各磁石の位置関係を説明した図である。
【図５】図５（ａ）乃至（ｇ）は、磁気穂の変位と遊離トナーの発生を段階的に説明した図である。
【図６】対向領域に複数の穂立ち部を形成した例を説明した図である。
【図７】穂立ち部を拡大して模視的に示した図である。
【図８】穂立ち部を拡大して模視的に示した図である。
【図９】穂立ち部を拡大して模視的に示した図である。
【図１０】磁気穂が感光体に接触して散布状に遊離トナーが発生する状態を説明した斜視図である。
【図１１】磁気穂が感光体に摺接（又は近接）する状態を拡大して模視的に示した図である。
【図１２】穂立ち部が感光体に近接して移動する例を説明した図である。
【図１３】像担持体上でトナーに作用する静電力を模視的に説明した図である。
【図１４】像担持体上でトナーに作用する静電力を模視的に説明した図である。
【図１５】画像形成装置の概略構成を説明した図である。
【符号の説明】
ＢＲ１ａ、ＢＲ１ｂ、ＢＲ１ｃ　磁気ブラシ
ＳＰ１ａ、ＳＰ１ｂ、ＳＰ１ｃ　穂立ち部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing method, a developing device, and an image forming apparatus applicable to an electrostatic image forming process such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
(A) At present, in an image forming apparatus such as a copying machine, a printer, and a facsimile, an electrostatic latent image is formed on an image carrier (hereinafter, referred to as a “photoconductor”) having a photoconductive photosensitive layer provided on a surface thereof. (Hereinafter, referred to as a “latent image”), and the latent image is visualized using a developing device containing a developer, and the visible image is transferred to a sheet-shaped recording medium to obtain a final image. I have an image.
[0003]
As a developer housed in the developing device, a two-component developer mainly composed of a toner and a magnetic carrier (hereinafter, simply referred to as “developer”) is widely used because it is easy to colorize. . The developer is triboelectrically charged by stirring and mixing in the developing device. The toner is electrostatically attached to the surface of the magnetic carrier by the frictionally charged electrostatic charge. The magnetic carrier with the toner attached thereto is attracted and carried on a surface of a cylindrical developer carrier (hereinafter, referred to as a “developing sleeve”) having a magnet therein by a magnetic force, and the rotating developing sleeve is moved to a developing area on the rotating developing sleeve. It is transported toward.
[0004]
A magnet for development (hereinafter, referred to as a “first magnet”) is provided inside the development sleeve at the closest position where the development sleeve is closest to the photoconductor in the opposing region of the development sleeve facing the photoconductor. Will be described).
[0005]
As the developer conveyed on the developing sleeve approaches the first magnet, a large number of magnetic carriers in the developer gather along the lines of magnetic force of the first magnet to form ears or chains. Since these many ears look like a brush, they are generally referred to as a magnetic brush, and a developing method using the state of the magnetic brush is referred to as a magnetic brush development.
[0006]
In this magnetic brush development, the magnetic brush is in contact with the photoreceptor in the development area, and the magnetic carrier, which is a dielectric, increases the electric field strength between the photoreceptor and the developing sleeve, thereby causing the tip of the tip of the magnetic brush to be removed. It is considered that the toner is transferred directly from the surface of the constituting magnetic carrier to the latent image (the surface of the photoreceptor), whereby the development is performed.
[0007]
According to this idea, in the conventional magnetic brush development, a transition from the magnetic brush formed by the spikes of the magnetic carriers to the latent image occurs in a limited area of the surface of the developing sleeve centered on the closest position. In a portion where only the toner contributes to the development and there is no magnetic brush, or in a portion where the magnetic brush is not in contact with the latent image, development due to the transfer of the toner directly from the tip of the magnetic brush to the latent image cannot occur.
[0008]
In other words, the portion where the toner can be developed is a limited area where the tip of the magnetic brush is in contact with the photoreceptor. Therefore, increasing the amount of toner to be developed is not a condition other than the limited area. It was very difficult to adjust the conditions.
[0009]
(B) As a developing method for obtaining a high-density image in this limited area, a two-component developer was used to carry toner particles carried on the ears of the magnetic particles and carried on the developer carrier. A developing method for developing toner particles with an alternating electric field has been disclosed (for example, see Patent Document 1).
[0010]
In the developing method disclosed above, the developing region is a region where the magnetic particles are rubbing, and the toner particles held on the ears of the magnetic particles in this region and the toner particles on the developer carrier are not sufficient. It is difficult to obtain a high density image. In addition, since there are few ears of the magnetic particles, it is difficult to obtain a smooth high-quality image with good solid filling of the solid portion due to the electrode effect.
[0011]
(C) As another developing method, the two magnetic poles are arranged so that the developing area adjacent to the latent image carrier is sandwiched between the two magnetic poles, and the developing sleeve and the latent image carrier are arranged to be thinner than the layer thickness of the developer. There is known a non-contact inter-electrode developing method in which the gap is set to be large and the developer is jumped to perform development (for example, see Patent Document 2).
[0012]
In this development method, reproducibility of a highlight portion can be made extremely good, and a fine image can be obtained even in a halftone portion. However, the development efficiency is poor, and the density of a solid black image is insufficient. In some cases, or "fading".
[0013]
As described above, in the conventional developing method, it is necessary to further improve the quality with respect to the developing efficiency and the image density of the solid black image.
[0014]
(D) The present inventors, although not known, have proposed a new developing method as follows: "a developer carrier having a magnet therein is disposed opposite to an image carrier, and a toner is provided on the surface of the developer carrier; A two-component developer containing a magnetic carrier is carried in a layered manner, and a speed difference is provided between the developer carrier and the magnet, so that the two-component developer layer is magnetically formed at least in a region opposed to the image carrier. A developing method in which a free toner separated from a magnetic carrier in the process of flowing while forming a brush is attached to a latent image on the image carrier to be subjected to development.
[0015]
In the developing method according to the above proposed technique, development is performed with free toner, so that the area where development is performed is in direct contact with the magnetic carrier as in the above-mentioned (a) magnetic brush developing method, as described later. It can be seen that since the free toner that contributes to the development is present compared to the development performed only in the area, the development area is widened, the development amount is increased, the development efficiency is improved, and an image having a high solid density in the solid part can be obtained. Was.
[Patent Document 1]
Japanese Patent No. 2668781
[Patent Document 2]
JP-A-5-303284 ([0008] to [0009])
[0016]
[Problems to be solved by the invention]
According to the present invention, based on the developing method of the above (d), all the positions where the image carrier and the developer carrier are opposed to each other contribute to the development, so that the area developed by the toner is increased, and An object of the present invention is to provide a developing method, a developing device, and an image forming apparatus capable of obtaining a high-quality image having a high image density and a high solid black image density.
[0017]
[Means for Solving the Problems]
The present invention has the following configuration to achieve the above object.
(1). A developer carrier, which is disposed opposite the image carrier and has a magnet inside, carries a two-component developer including toner and a magnetic carrier holding the toner, and is formed between the image carrier and the developer carrier. The developing method of transporting the latent image formed on the surface of the image carrier with toner to the developing area is performed by separating the magnetic carrier having toner on the surface into ears and the magnetic carrier surface in the developing area. A developing method for forming a magnetic brush containing free toner,
The electric field intensity E (V / m) formed in the region where the image carrier and the developer carrier are opposed to each other is
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
At least one or more portions where the spikes of the magnetic carriers stand are present in the region to be formed (claim 1).
(2). A developer carrier, which is disposed opposite the image carrier and has a magnet inside, carries a two-component developer including toner and a magnetic carrier holding the toner, and is formed between the image carrier and the developer carrier. The developing method of transporting the latent image formed on the surface of the image carrier with toner to the developing area is performed by separating the magnetic carrier having toner on the surface into ears and the magnetic carrier surface in the developing area. A developing method for forming a magnetic brush containing free toner,
The electric field intensity E (V / m) formed in the region where the image carrier and the developer carrier are opposed to each other is
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
At least one or more continuous portions where the spikes of the magnetic carriers rise and lie down in the region where the spikes lie (claim 2).
(3). (1) In the developing method according to (1) or (2), when the spikes on which the magnetic carriers are gathered rise on the developer carrying member, the magnet in the developing area causes the tip of the magnetic brush to be in a developer state. The magnetic carrier on the carrier is separated from the aggregated developer layer (claim 3).
(4). (1) In the developing method according to any one of (1) to (3), the developing method may be configured such that when the ears on which the magnetic carriers are gathered fall on the developer carrier, the magnet in the developing area is used to move the tip of the magnetic brush. Is in a state of being combined with the developer layer in which the magnetic carriers on the developer carrier are gathered (claim 4).
(5). A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
In the developing method, an electric field intensity E (V / m) formed in a region where the image carrier and the developer carrier are opposed to each other is reduced.
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
The toner is spread on the image carrier from the magnetic carrier having the toner on the surface in the region to be developed and developed.
(6). In the developing method according to (5),
The developing method includes contacting a magnetic brush formed in a developing area with an image carrier to separate toner from the surface of the magnetic carrier, and dispersing the separated free toner to the image carrier to perform development. (Claim 6).
(7). In the developing method according to (5) or (6), in the developing method, the magnetic brush formed in the developing area is brought into contact with the image carrier to release the already developed toner from the image carrier. (Claim 7).
(8). A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
In the developing method, an electric field intensity E (V / m) formed in a region where the image carrier and the developer carrier are opposed to each other is reduced.
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
The toner is developed by rubbing or approaching a magnetic brush formed of a magnetic carrier having a toner on the surface thereof to the image carrier in a region to become (claim 8).
(9). (8) In the developing method described in (8), in the developing method, the magnetic brush is rubbed or brought close to the image carrier in the developing area to release the already developed toner from the image carrier. Claim 9).
(10). A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
In the developing method, an electric field intensity E (V / m) formed in a region where the image carrier and the developer carrier are opposed to each other is reduced.
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
In the region where the magnetic carrier having the toner on the surface is gathered, a magnetic brush including the free toner to be detached from the surface of the magnetic carrier is formed, and the gathered ears of the magnetic carrier rise, and while the ear is sleeping The toner is released and developed, and the free toner to be released by contacting the magnetic brush with the image carrier is sprayed and developed on the image carrier, and the magnetic brush is rubbed or brought close to the image carrier. It was developed (claim 10).
(11). In the developing method described in (10), in the developing method, the magnetic brush formed in the developing area is brought into contact with the image carrier to release toner from the image carrier, and the magnetic brush is attached to the image carrier. By rubbing or approaching, the already developed toner is separated from the image carrier.
(12). A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
In the developing method, an electric field intensity E (V / m) formed in a region where the image carrier and the developer carrier are opposed to each other is reduced.
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: Linear velocity of developer carrier (m / sec)
In the area where the magnetic carrier having the toner on the surface is gathered, a magnetic brush including the free toner to be detached from the magnetic carrier surface is formed, and the magnetic carrier gathers the rising ear, and the toner is collected while sleeping. The development is performed by detaching the magnetic brush, and the development is performed by bringing the magnetic brush close to the image carrier.
(13). (12) In the developing method described in (12), in the developing method, the magnetic brush formed on the developer carrier develops the image carrier in a non-contact state.
(14). In the developing method according to any one of (1) to (13), in the developing method, a linear velocity ratio (Vs / Vp) between the developer carrier (Vs) and the image carrier (Vp) is 0.1. 9 <Vs / Vp <4.
(15). (1) In the developing method according to any one of (1) to (14), in the developing method, development is performed by an electric field applied between the image bearing member and the developer bearing member. (Claim 15).
(16). A developer carrier having a magnet therein is disposed facing the image carrier, and the developer carrier carries a two-component developer including a toner and a magnetic carrier holding the toner on the surface, In a developing device that conveys to a developing area, applies an electric field between the developer carrier and the image carrier, and develops a latent image formed on the surface of the image carrier with toner.
The developing device performs development by the developing method according to any one of (1) to (15).
(17). An image carrier having photoconductivity and forming a latent image on the surface, a charging device for charging the image carrier, and a magnetic carrier that is disposed opposite to the image carrier and holds the toner and the toner on the surface. In an image forming apparatus including a developing device that accommodates and forms a toner image on the surface of an image carrier and a transfer device that transfers a toner image formed on the surface of the image carrier to a recording member, the image forming device includes: (16) A developing device according to (16).
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
[1] Developing device
The developing method of the present invention can be performed using a developing device described below.
[1-1] Basic configuration of developing device (related to claim 16)
Here, the basic configuration of the developing device 110 that can execute the developing method described below will be described.
[0019]
In FIG. 1, a charging device 101 for charging the surface of the photoconductor 100 is provided around a cylindrical photoconductor 100 provided with a photosensitive layer on the surface. The photoconductor 100 is rotated in a counterclockwise direction indicated by an arrow in FIG. A cylindrical developing sleeve 111c having a magnet therein is disposed so as to face the photoconductor 100 and have a predetermined developing gap GP.
[0020]
The developer (consisting of the toner and the magnetic carrier as described above) is contained in the developing casing 115, and is supplied to the developing sleeve 111c by being stirred by rotation of the stirring screws 112 and 113.
[0021]
A component serving as a toner supply unit is provided at the upper part of the developing casing 115, and a toner storage unit 116 is provided. An appropriate amount corresponding to consumed toner is supplied into the developing casing 115.
[0022]
With respect to the photoconductor 100, a laser beam Lb for forming a latent image on a charging processing surface uniformly charged in advance by the charger 101 is applied to a portion downstream of the charger 101 in the rotation direction 100R of the photoconductor 100. A latent image Li is formed by irradiating a laser beam at this position. The photoreceptor 100 on which the latent image Li is formed reaches an opposing area where the developing sleeve 111c opposes, where the charged toner adheres to the latent image Li to form a toner image.
[0023]
At the upstream side in the transport direction 111R (clockwise in the figure) of the developer transported with the rotation of the developing sleeve 111c, the height of the magnetic ears by the magnetic carrier holding the toner, that is, on the developing sleeve 111 A doctor blade 114 is provided as a layer thickness regulating member for regulating the thickness of the developer layer.
[0024]
Conventionally, a plate-shaped doctor blade made of only a non-magnetic material has been used. However, the doctor blade 114 in this embodiment has a configuration in which a plate made of a magnetic material is joined to a conventional non-magnetic plate. are doing. The use of a magnetic material facilitates the formation of magnetic spikes with uniform spike height, as described later.
[0025]
In FIG. 1, a transfer device for transferring the toner image on the photoconductor 100 to the recording paper, a cleaning device for removing the residual toner on the photoconductor 100, and a static elimination for removing the residual potential on the photoconductor 100 The devices and the like are omitted.
[0026]
In such a configuration, when forming a color image, if the toner image on the photoreceptor 100 is, for example, a cyan toner image, this is transferred onto an intermediate transfer belt, and the toner images of magenta, yellow, black, etc. are sequentially formed. The images are superimposed and transferred onto the intermediate transfer belt by a similar image forming process to form a full-color toner image. The full-color toner image is transferred to recording paper conveyed from a paper feed tray (not shown), and the unfixed toner image on the recording paper is transferred to a fixing device (not shown) after the recording paper is separated from the intermediate transfer belt. Established while passing. On the other hand, the toner remaining on the photoconductor 100 without being transferred is removed and collected by the cleaning device. The photoreceptor 100 from which the residual toner has been removed is initialized by a discharging lamp, and is used for the next image forming process.
[0027]
The developing sleeve 111c forms a part of the developing roller 111 and is configured to rotate around an immobile magnet. In FIG. 2 showing the structure of the developing roller 111, the developing roller 111 has a fixed shaft 111a fixed to a developing casing 115 as an immovable member, a cylindrical magnet support 111b integrated with the fixed shaft 111a, and a magnet. It comprises a cylindrical developing sleeve 111c which covers the periphery of the support 111b via a gap, and a rotating member 111d integral with the developing sleeve 111c.
[0028]
The rotating member 111d is rotatable with respect to the fixed shaft 111a via a bearing 111e, and the rotating shaft 111d is rotationally driven by transmitting power from a rotation driving unit (not shown).
[0029]
As shown in FIG. 3, a plurality of magnets MG1a, MG1b, MG1c, MG2, MG3, MG4, MG5, MG6 (hereinafter, collectively referred to as MG) are provided at a predetermined interval on the outer peripheral portion of the magnet support 111b. ) Is fixed. The developing sleeve 111c is rotated around these magnets MG.
[0030]
As the developing sleeve 111c, a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin is used, and the cylindrical developing sleeve 111c is moved around the magnet MG by a rotation drive mechanism (not shown) in FIGS. In the example, it is rotated clockwise.
[0031]
These magnets MG form a magnetic field such that the developer is transported while raising the developer with the rotation of the developing sleeve 111c. The magnetic carriers gather to form spikes along the lines of magnetic force in the normal direction emitted from these magnets MG, and the spikes gather to form a magnetic brush. The ears and the magnetic brush are composed of a collection of magnetic carriers, and the magnetic carriers hold charged toner.
[0032]
The developing sleeve 111c is arranged close to the photoconductor 100 via a developing gap GP, and development is performed in both opposing regions. In this example, since both the photosensitive member 100 and the developing sleeve 111c have a cylindrical shape, in a facing area where the convex curved surfaces are close to each other and opposed, the distance between the developing sleeve 111c and the photosensitive member 100 is the closest. An opposing surface is formed such that the distance gradually increases as going to both sides with a certain closest position therebetween. In addition, when the photoconductor 100 is formed in a belt shape instead of a cylindrical shape, the closest approach position is similarly configured even in the case of a flat shape. In the example shown in FIGS. 1 and 2, the closest position is on a virtual line connecting the center O1 of the developing sleeve 111c and the center O2 of the photoconductor 100.
[0033]
In FIG. 3, the magnetic force distribution of these magnets is denoted by a reference sign P1a around the developing sleeve 111c, corresponding to the second magnet MG1a, the first magnet MG1b, the magnets MG1c, MG2, MG3, MG4, MG5, and MG6. , P1b, P1c, P2, P3, P4, P5, and P6 as shown schematically.
[0034]
The first magnet MG1b (magnetic force distribution P1b) is located corresponding to the closest position, is on the rotation direction 111R of the developing sleeve 111c, and is located in the rotation direction with the first magnet MG1b (magnetic force distribution P1b) interposed therebetween. The second magnet MG1a (magnetic force distribution P1a) is located on the upstream side, and the magnet MG1c (magnetic force distribution P1c) is located on the downstream side.
[0035]
Further, on the rotation direction 111R of the developing sleeve 111c and downstream of the magnet MG1c (magnetic distribution P1c) in the rotational direction, the magnet MG3 (magnetic distribution P3), the magnet MG4 (magnetic distribution P4), and the magnet MG5 (magnetic distribution). Distribution P5) and magnet MG6 (magnetic force distribution P6) are located in this order. Among them, the second magnet MG1a (magnetic force distribution P1a), the first magnet MG1b (magnetic force distribution P1b), and the magnet MG1c (magnetic force distribution P1c) are located in a region where the developing sleeve 111c and the photoconductor 100 face each other. ing.
[0036]
The developing method of the present invention using the developing device 110 is an operation mode from the rising of the magnetic brush formed by at least the second magnet MG1a (magnetic force distribution P1a) and the first magnet MG1b (magnetic force distribution P1b) to sleep. Perform using.
[0037]
The magnet MG1c (magnetic force distribution P1c) indicates the half width of the magnetic force formed by the adjacent first magnet MG1b (magnetic force distribution P1b), and the magnet MG6 (magnetic force distribution P6) indicates the width of the adjacent second magnet MG1a (magnetic force distribution P1a). The half width of the magnetic force to be formed is regulated to a predetermined narrow width so that the above-described operation mode of the magnetic brush is effectively performed for development. Thereby, the developing performance can be improved.
[0038]
In FIG. 4A, in this example, all the magnets MG are adjacent to each other, thereby regulating the half width of the magnetic force formed by the magnets. The value of the half width of the magnetic force formed by the magnet is set so as to effectively perform the above function.
[0039]
By narrowing the half width of the magnetic force formed by the magnet, the operation of raising the ears and sleeping is performed rapidly (quickly), and the magnetic brush moves jerkingly. For this reason, it is considered that the movement of the magnetic brush is accelerated, and a disturbance effect such as disturbing of the shape of the ear is generated, so that separation and flying of the toner from the magnetic carrier are likely to occur. In addition, since the time during which the developer is in contact with the photoreceptor can be shortened, it is considered that the induction of the counter charge to the magnetic carrier hardly occurs.
[0040]
The magnet MG4 (magnetic force distribution P4) has a function of pumping the developer onto the developing sleeve 111c. The magnet MG3 (magnetic force distribution P3) is a pole for cutting ears. The magnet 2, the magnet 5, and the magnet 6 (magnetic force distributions P2, P5, P6) have a function of transporting the developer pumped onto the developing sleeve 111c to the opposing area.
[0041]
The center of each of the magnets MG1a (magnetic force distribution P1a), MG1b (P1b), MG1c (P1c), MG2 (P2), MG3 (P3), MG4 (P4), MG5 (P5), and MG6 (P6) is located at the center of the developing sleeve. They are arranged radially.
[0042]
In this example, the magnets are configured with eight poles, and three magnets (magnets MG1a, MG1b, and MG1c) are provided in a region where the developing sleeve 111c and the photoconductor 100 are opposed to each other. May be provided with four or more magnets. In order to improve the developer pumping property and the solid black image follow-up property, the number of magnets may be increased from the magnet P3 to the doctor blade 114 so that the number of poles may be 10 or 12.
[0043]
The second magnets MG1a, MG1b, MG1c are composed of magnets having small cross sections arranged in this order from the upstream side in the rotation direction 111R of the developing sleeve 111c, and these magnets are made of a rare earth metal alloy. A samarium alloy magnet, particularly a samarium cobalt alloy magnet, can also be used. Among the rare earth metal alloy magnets, a typical iron neodymium boron alloy magnet has a maximum energy product of 358 kJ / m.³And the maximum energy product of the iron-neodymium boron alloy bonded magnet is 80 kJ / m³Before and after.
[0044]
With such a magnet, unlike a conventional magnet, a necessary magnetic force on the surface of the developing roller can be secured even if the size is considerably reduced. If it is permissible to increase the diameter of the developing sleeve to a certain extent, a conventional ferrite magnet or ferrite bonded magnet is used, and the magnet tip formed toward the developing sleeve is made thinner to reduce the magnetic force generated by the magnet. It is possible to narrow the half width.
[0045]
In this example, as shown in FIG. 4A, the first magnet MG1b, the magnet MG2, the magnet MG3, and the magnet MG6 form an N pole, and the magnets MGa, MG1c, and MG5 form an S pole. For example, as the first magnet MG1b, a magnet having a normal magnetic force of 85 mT or more on the developing roller was used. For example, it has been confirmed that if the magnetic force is 60 mT or more, no abnormal image such as the adhesion of a magnetic carrier is generated. In the case of a magnetic force smaller than this, magnetic carrier adhesion occurred.
[0046]
Each magnet width of the second magnet MG1a, the first magnet MG1b, and the magnet MG1c was 2 mm. At this time, the half width of the magnetic force of the magnetic force distribution P1b was 16 °. Further, it was confirmed that the half width of the magnetic force was further reduced by reducing the width of the magnet. The half width of the magnetic force of the magnetic force distribution P1b by the first magnet MG1b when using the 1.6 mm width was 12 °.
[0047]
In FIG. 4B showing a positional relationship between the first magnet MG1b, the second magnet MG1a, and the magnet MG1c, the half width of each magnetic force of the magnetic force distributions P1a and P1c is set to 35 ° or less. The half width of the magnetic force in this portion cannot be set to be relatively narrow as in the magnetic force distribution P1b because the half width of the magnetic force of the magnetic force distributions P2 and P6 located outside is large.
[0048]
Regarding the positional relationship between the first magnet MG1b, the second magnet MG1a, and the magnet MG1c, the included angle between the second magnet MG1a and the magnet MG1c on both sides of the first magnet MG1b is set to 30 ° or less. In the above example, the included angle is set to 22 ° in order to set the half width in the magnetic force distribution P1b to 16 °. Further, the included angle of the inflection point (0 mT: the point at which the magnetic force changes from the N pole to the S pole and the magnetic pole changes from the N pole to the S pole and from the S pole to the N pole) by the magnets MG1a and MG1c and the magnets MG2 and MG6 outside each of the magnets is set to 120 ° or less. ing.
[0049]
In the developing device 110, as shown in FIG. 3, the fixed shaft 111a is connected to a grounded power source VP for bias. The voltage of the power supply VP connected to the fixed shaft 111a is applied to the developing sleeve 111c via the conductive bearing 111e and the conductive rotating member 111d shown in FIG. On the other hand, in FIG. 3, the lowermost conductive support 31 constituting the photoconductor 100 is grounded.
[0050]
In this way, an electric field for moving the toner separated from the magnetic carrier to the photoconductor 100 side is formed in the facing region, and the toner is moved toward the photoconductor 100 side.
[0051]
As described above with reference to FIGS. 1 to 4, the developing sleeve 111 c is provided to face the photoreceptor 100 and has a magnet MG therein, and the developing sleeve 111 c includes the toner and the magnetic carrier holding the toner. The developer containing the developer is carried on the surface, and the carried developer is conveyed to a region facing the photoconductor 100, and an electric field is applied between the developing sleeve 111 c and the photoconductor 100, and the surface of the photoconductor 100 is A developing device 110 that develops the latent image Li formed thereon with toner is configured. The developing method of the present invention can be performed using the developing device 110.
[0052]
Note that the developing device of the present embodiment is an example in which the developing device is combined with an image forming device of a method of writing with a laser beam Lb. The charging device 101 uniformly applies a negative charge on the photoreceptor 100 and exposes the character portion with a laser beam Lb to reduce the amount of writing, so that the character portion (latent image Li) having a reduced potential is applied. A so-called reversal development system in which development is performed with a negative polarity toner is employed. This is just an example, and the polarity of the charged charge placed on the photoconductor 100 is not a significant problem in the developing method of the present invention.
[0053]
In the developing device 110, a developing sleeve 111c having a magnet MG therein is disposed so as to face the photoconductor 100, and a developer containing a toner and a magnetic carrier is carried on the surface of the sleeve 111c in a layered manner. By rotating the developing sleeve 111c with respect to the magnet MG, a speed difference is given between the developing sleeve 111c and the inter-magnet MG, and the developer layer is formed by using this speed difference while forming the magnetic brush at least in the facing region. It is assumed that the toner is caused to flow, and the free toner released from the magnetic carrier in the course of the flow is attached to the latent image Li on the photoconductor 100 and is used for development.
[0054]
[1-2] Speed difference
As a means for giving a speed difference between the developing sleeve 111c and the MG between the magnets, the magnet MG is immobilized and the developing sleeve 111c is rotated in the above example. However, the present invention is not limited to this. By rotating the developing sleeve 111c and the magnet MG between the magnets, it is possible to perform the same development, and to rotate the developing sleeve 111c and the magnet MG in opposite directions.
[0055]
[1-3] Development gap
The developing gap GP in which the magnetic carrier particle size is 5 is the distance between the photosensitive member 100 and the developing sleeve 111. The developing gap GP is a type in which the tip of the magnetic brush is brought into contact with the photosensitive member 100, a non-contact type, and even in these types, Is determined according to individual specific conditions, depending on various conditions such as whether to dispose them corresponding to the closest position or to displace them.
[0056]
[1-4] Developer
A stirring screw 112 for pumping the developer in the developing casing 115 to the developing sleeve 111c while stirring the developer in the developing casing 115 is provided in a region of the developing sleeve 111c opposite to the photoconductor 100. The developer in the developing casing 115 is composed of a toner T and a magnetic carrier C. The developer is mixed and stirred by stirring screws 112 and 113 rotated by a driving unit (not shown), and the toner T is frictionally charged. At this time, the toner charge amount (q / m) is -5 to -60 C / g, preferably -10 to -30 C / g.
[0057]
Examples of the magnetic carrier C include metals such as iron, nickel, and cobalt or alloys of these and other metals, oxides such as magnetite, γ-hematite, chromium dioxide, copper zinc ferrite, and manganese zinc ferrite; Ferromagnetic particles such as a Heusler alloy such as aluminum can be used.
[0058]
Further, the ferromagnetic particles may be covered with a styrene-acrylic, silicone, fluorine-based resin, or the like. These can be appropriately selected in consideration of the chargeability with the toner T. A charge control agent, a conductive substance, and the like may be added to the resin that coats the magnetic particles.
[0059]
Further, the magnetic particles may be dispersed in a styrene-acrylic or polyester resin. The saturation magnetization of the ferromagnetic material is preferably 45 to 85 emu / g. If it is less than 45 emu / g, since the intensity of the saturation magnetization is low, the transportability decreases, and the adhesion of the magnetic carrier to the photoconductor 100 increases. If it exceeds 85 emu / g, the intensity of the saturation magnetization is high, so that the magnetic brush becomes strong, the scavenging effect is strong, and a scavenge mark is generated in the halftone portion, thereby deteriorating the image quality.
[0060]
As the toner T, a toner having at least a thermoplastic resin and pigments of carbon black, copper phthalocyanine, quinacridone, and bisazo is used. As the resin, a styrene-acrylic or polyester resin is preferable. In addition, a wax such as polypropylene and an alloy-containing dye for controlling the charge amount of the toner can be internally added as a fixing aid. Furthermore, oxides, nitrides, carbides and the like of surface-treated silica, alumina, titanium oxide and the like may be externally added. Further, a fatty acid metal salt, resin fine particles and the like may be externally added together.
[0061]
[1-5] Description of ears, magnetic brushes, and spikes (related to claims 1-4)
As shown in FIGS. 1, 3 and 4, etc., magnetic force distributions P1a, P1b, P1c, P2, P3, P4, P5, and P6 are formed from the outer peripheral surface of the developing sleeve 111c by a magnet MG provided therein. It is formed radially.
[0062]
Due to the rotation of the developing sleeve 111c, the developer is carried on the developing sleeve 111c and is conveyed together with the developing sleeve 111c. When the developer passes through each magnetic force distribution in this transport process, there is a phenomenon that magnetic spikes in which magnetic carriers are gathered in a spike shape rise from the developer layer on the developing sleeve 111c, and the magnetic spikes fall asleep. Here, the magnetic spikes are formed along the normal magnetic field lines in the magnetic force distribution.
[0063]
Here, FIG. 5 schematically illustrates a change of the magnetic force distribution shown in FIG. 1 by focusing on a magnetic force formed by a developer passing through an arbitrary magnetic force distribution, for example, a magnetic force distribution P1a. , The magnetic spikes, the free toner, the spikes and the like will be described.
[0064]
In FIG. 5, normal magnetic lines of force formed in the magnetic force distribution P1a are schematically indicated by reference numerals (1) to (7). These normal magnetic force lines (1) to (7) are such that as the normal magnetic force line (1) is oriented substantially in the tangential direction of the developing sleeve 111c and the numbers of the normal magnetic force lines (2) to (3) advance. The rising angle is increased, and becomes substantially perpendicular to the peripheral surface of the developing sleeve 111c at the normal magnetic force line (4), so that the developing state is the highest.
[0065]
The normal magnetic field lines (5), (6), and (7) are symmetrically set to the normal magnetic field lines (3), (2), and (1) at the time of the above-described rising with the normal magnetic field lines (4) as the axis of symmetry. In the normal magnetic field line (7), the developing sleeve 111c is slanted to near the tangential direction of the developing sleeve 111c. The normal magnetic force line {circle around (4)} matches the line segment connecting the center O1 and the center O2 in FIG.
[0066]
These normal magnetic lines of force {1} to {7} are formed at fixed positions outward from the surface of the developing sleeve 111c. The developer carried on the developing sleeve 111c and transported together with the developing sleeve 111c forms a layer on the developing sleeve 111c, but is not shown in FIG. 5 to avoid complexity. Further, the toner T is held by electrostatic force in the magnetic carrier CC, but it is not shown because it becomes complicated when individually shown.
[0067]
When the developer layer on the developing sleeve 111c moves together with the developing sleeve 111c and approaches the magnetic force distribution P1a, as shown in FIG. 5A, the magnetic carrier CC gathers in a spike shape along the normal magnetic force line (1). It rises separately from the developer layer as ears (or magnetic brushes on which magnetic ears are gathered).
[0068]
That is, when the magnetic spikes (simply called spikes) in which the magnetic carriers CC are gathered rise on the developing sleeve 111c, the tips of the magnetic brushes are gathered by the magnets in the developing area by the magnets in the developing area. As a result, the toner T separates from the magnetic carrier CC and becomes free toner as described below.
[0069]
The magnetic ear forms a spike when viewed from the axial longitudinal direction of the developing sleeve 111c, and is formed facing the magnet MG1a in the longitudinal direction of the developing sleeve 111c, which is a direction in which the magnetic ear penetrates the paper surface.
[0070]
As shown in FIG. 5A, when the magnetic carrier CC rises from the developer layer along the normal magnetic force line {circle around (1)}, the toner T separates from the magnetic carrier CC. In this way, the toner T released from the magnetic carrier and released into the space is released into the space on the rising side of the magnetic chain (the back side of the magnetic chain facing the peripheral surface of the developing sleeve 111c).
[0071]
The free toner contributes to the development, and if at least one or more portions where the spikes of the magnetic carrier stand are at least one portion, the free toner is generated, so that the development can be performed.
[0072]
When the magnetic ears rise from the developer layer, the developer is displaced also on the developer layer side, and the displacement causes the toner to be released from the magnetic carrier also from the developer layer side, thereby generating free toner T. The generation of the free toner T will be described later with reference to FIGS.
[0073]
It should be noted that the toner is separated from the magnetic carrier CC and becomes a free toner T in the developer layer between the adjacent magnetic brushes, that is, in the portion where the spike does not rise, and is used for development.
[0074]
Such free toner T is generated when the image portion of the photoreceptor 100 (the portion exposed after charging, that is, the latent image Li portion) is in the opposing region, and flies to the image portion, and the non-image portion ( The free toner T was not generated when the uncharged portion (which was charged) was in the facing region.
[0075]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5A, the shape and position of the magnetic chain changes from the normal magnetic force line (1) to the normal magnetic force line (2). The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly detached from the magnetic carrier CC, and is released toward the rising side of the magnetic ear (upstream in the rotation direction 111R of the magnetic ear) to become free toner.
[0076]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5B, the shape and position of the magnetic chain changes from the normal magnetic force line (2) to the normal magnetic force line (3). The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly detached from the magnetic carrier CC and released toward the rising side of the magnetic chain (downstream in the rotation direction 111R of the magnetic chain) to become free toner.
[0077]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5C, the shape and position of the magnetic spikes are changed so that the magnetic spikes extend from the normal magnetic force line (3) to the normal magnetic force line (4). It is in a state of rising most upright from the peripheral surface of 111c. The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly detached from the magnetic carrier CC, released around the tip of the magnetic chain, and becomes free toner.
[0078]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5D, the shape and position of the magnetic chain change along the normal magnetic force line (5). The normal magnetic field line (5) is located adjacent to the downstream side in the rotation direction 111R with respect to the normal magnetic field line (4), and is formed to be inclined toward the downstream side (side down) as the distance from the peripheral surface of the developing sleeve 111c increases. Therefore, the magnetic spikes are formed along this shape.
[0079]
The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly released from the magnetic carrier CC and is discharged to the opposite side (upstream in the rotation direction 111R of the magnetic spike) of the magnetic spike and the vicinity of the tip of the magnetic spike. It becomes a free toner.
[0080]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5E, the magnetic spikes are formed so as to follow the normal magnetic force lines (6) whose sleeping degree is increased from the normal magnetic force lines (5). And change the position. The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly released from the magnetic carrier CC and is discharged to the opposite side (downstream in the rotation direction 111R of the magnetic chain) of the magnetic chain and the vicinity of the tip of the magnetic chain. It becomes a free toner.
[0081]
As the rotation of the developing sleeve 111c further progresses from the state shown in FIG. 5F, the shape and position of the magnetic chain change so as to follow the magnetic force line {circle around (7)} from which the magnetic force line {circle around (6)} is further increased. . The state of the magnetic ear after this change is shown in FIG. In the course of this change, the toner T is newly released from the magnetic carrier CC and is released into the space on the side where the magnetic ears lie (back side opposite to the peripheral surface of the developing sleeve 111c).
[0082]
Although the rotation of the developing sleeve 111c further advances from the state shown in FIG. 5G, although not shown, the magnetic brushes and the magnetic brushes on which the magnetic brushes are gathered are formed on the peripheral surface of the developing sleeve 111c when lying down. The toner is separated from the magnetic carrier also from the developer layer side by this displacement, and free toner is generated.
[0083]
That is, when the magnetic spikes (spikes) in which the magnetic carriers CC are gathered on the developing sleeve 111c lie, the magnets in the developing area cause the tip of the magnetic brush in which the magnetic spikes are gathered to gather the magnetic carriers CC on the developing sleeve 111c. The developer layer is brought into a state of being combined with the developer layer, and at that time, free toner is generated (related to claim 4).
[0084]
FIG. 5 schematically shows the displacement and the state of generation of free toner by focusing on only one magnetic spike, so that the magnetic force is applied to only one of the normal magnetic force lines (1) to (7). It looks as if the spikes are formed and only this is displaced, but in reality, the magnetic spikes are formed simultaneously along each of the magnetic force lines (1) to (7), and the developing sleeve 111c With rotation, magnetic spikes are successively displaced to adjacent normal magnetic force lines, and the toner is detached from the magnetic carrier in the course of the flow accompanied by the displacement, and the detached free toner is used for development.
[0085]
In the example of FIG. 5, a magnetic brush is formed by a set of magnetic ears formed along the normal magnetic lines of force {1} to {7}. In this example, the magnetic spike rises in the opposing area, and the area around the developing sleeve until the magnetic spike lies down is the spike.
[0086]
Here, the continuous portion from when the magnetic ears rise and the magnetic ears lie down is defined as a portion of the developer on the developing sleeve 111c by the magnetic force of the magnet MG in the process of transporting the developer on the developing sleeve 111c. The period from when the tip of the magnetic spike separates from the layer to the time when the tip of the magnetic spike comes together with the developer layer on the developing sleeve 111c, and mainly the morphological change of the magnetic spike during this period Accordingly, the toner held on the magnetic carrier is separated from the magnetic carrier. If one or more such continuous portions exist, the free toner released from the magnetic carrier can contribute to the development (related to claim 2).
[0087]
In other words, a set of magnetic spikes formed along a number of normal magnetic lines of force in one magnetic force distribution is called a magnetic brush, and a set of magnetic spikes around the developing sleeve 111c where the magnetic spikes constituting the magnetic brush are located is located. The area is a spike portion, and development is performed using free toner separated from a magnetic carrier of a magnetic brush (magnetic spike) formed in the spike portion.
[0088]
The magnetic force distribution, P1a, the magnetic spike, the magnetic brush, the spike portion and the like have been described above. However, the magnetic force distribution P1b, the magnetic force distribution P1c, and the magnetic spike, the magnetic brush, the spike similar to the magnetic force distribution P1a in the facing region. A part or the like is formed.
[0089]
A large amount of free toner is generated in accordance with the change in the shape of the magnetic spike. Since the free toner is present in a large amount around the magnetic brush (magnetic spike), the free toner can be used for development. The development efficiency can be improved as compared with a development method in which toner is directly transferred from a carrier to a latent image.
[0090]
As described above, the form change of the magnetic spike causing the free toner is achieved by narrowing the half-value width of the magnetic force formed by the magnet so that the spike rises, and the operation of sleeping is performed rapidly (fastly), and the magnetic brush is jerky. It is thought that the movement is largely due to the phenomenon of movement.
[0091]
The developing device described above is provided with a configuration for performing the developing method of the present invention described below, so that the developing region is set in a wider range than the conventional developing region. It is possible to provide a developing device that increases the supply amount of toner to be developed without increasing the linear velocity ratio (Vs / Vp) between the linear velocity (Vs) and the linear velocity (Vp) of the photoconductor 100.
[0092]
[2] Development method
In the developing method of the present invention, at least one spike portion of the magnetic brush is formed in the facing region. Since the diameter of the developing sleeve 111c is smaller than the diameter of the photoreceptor 100, the facing region is a region of “diameter width × length in the axial direction” corresponding to the projected area of the developing sleeve 111c at the maximum. It turns out that.
[0093]
However, in this example, as shown in FIG. 1, the case 115 has a configuration surrounding the developing sleeve 111c, and the toner adhering to the latent image on the photoconductor from the developing sleeve side in the maximum facing area is considered. Only a necessary portion that does not obstruct the flight path is opened, and the developing sleeve 111c and the photoconductor 100 directly face each other through this opening.
[0094]
In the developing method of the present embodiment, the dimension of the opening 115a of the case 115 in the rotation direction 111R is made smaller than that of the maximum facing area in order to prevent toner scattering. For this reason, the photosensitive member 100 and the developing sleeve 111c directly oppose each other in a limited opposing area limited by the opening 115a and smaller than the maximum opposing area.
[0095]
In the developing method of the present invention, the developing region is formed in the developer regardless of the state in which the magnetic spikes in which the magnetic carriers gather form a magnetic brush or a thin developer layer on the developing sleeve 111c. The area where the toner T is developed toward the photoconductor 100 is defined.
[0096]
In the following embodiment, a description will be given of a development mode performed in a limited facing region that is a range of the opening 115a.
[0097]
When the developing sleeve 111c rotates in the rotation direction 111R under the magnet arrangement and magnetic force distribution shown in FIGS. 1, 3, and 4 shown as the basic configuration, the developer pumped up by the magnetic force distribution P4 is The passing amount is regulated to be constant by passing through the doctor gap of the doctor blade 114 portion, and the doctor blade 114 is conveyed in the rotational direction by the magnetic force distribution P6 (because the doctor blade 114 is in the middle of the magnetic force distribution P5), and the above-described restriction is applied. (Hereinafter simply referred to as an opposing region).
[0098]
Magnetic force distributions P1a, P1b, and P1c are formed in the facing region, and a magnetic brush is formed in these magnetic force distribution portions. In accordance with the rotation of the developing sleeve 111c, the developer flows while forming a magnetic brush, The toner is transferred to the latent image in the developing region in the facing region and development is performed, and almost all of the remaining developer after the development is removed at P3, which is the ear-cut pole, and falls to the stirring screw 112 side.
[0099]
FIG. 6 shows a magnetic brush, a spike portion, and the like based on the basic configuration of the developing device shown in FIGS. In FIG. 6, the magnetic brushes in the magnetic force distributions P1a, P1b, and P1c are indicated by reference numerals BR1a, BR1b, and BR1c, respectively. In these magnetic brushes, magnetic spikes as described in FIG. 5 are gathered along a number of normal magnetic force lines {1} to {circle around (7)}. Is flowing while holding the toner, and in the course of this flow, the toner is separated from the magnetic carrier to generate free toner.
[0100]
The magnetic brush is composed of a number of magnetic ears and occupies a space. The space region indicated by the magnetic spikes is referred to as a brush spike. The ears of the magnetic brushes BR1, BR2, BR3 are indicated by ears SP1a, SP1b, SP1c, respectively. Thus, there are three spikes in the facing area. In this example, the magnetic brush BR1b is in contact with the photoconductor 100, and the magnetic brush BR1a is not in contact with the photoconductor 100.
[0101]
The spike portion SP1b is formed by a first magnet MG1b (magnetic force distribution P1b) located corresponding to the closest position to the photoconductor 100, and the spike portion SP1a is larger than the spike portion SP1b. It is formed by a second magnet MG1a (magnetic force distribution P1a) arranged on the upstream side in the rotation direction 111R (same as the developer conveyance direction).
[0102]
In the example shown in FIG. 6, three raised portions SP1a, SP1b, and SP1c are formed in the facing region. When developing the toner by generating free toner from the magnetic brushes at these spikes, the spike SP1a at the most upstream position of the spikes and the spike SP1b at the closest position. If the toner is sufficiently attached to the portion where the image is to be attached, the toner is saturated, and therefore, the development is scarcely performed in the spike SP1c located downstream of the spike SP1b.
[0103]
When the electric field applied between the developing sleeve 111c and the photoreceptor 100 is an alternating electric field, the vibration of the toner occurs on the downstream side of the spike portion SP1b, the potential of the toner is adjusted to the latent image potential, and the toner adheres. .
[0104]
In this example, an example in which the spike portion SP1c actually exists is shown because the half width of the first magnet MG1b (magnetic force distribution P1b) is set at the closest position with a narrow half width. The first magnet MG1b (magnetic force distribution P1b) must be provided adjacent to the first magnet MG1b (magnetic force distribution P1b). Therefore, the first magnet MG1b (magnetic force distribution P1b) automatically causes the ears to be raised. SPc has occurred.
[0105]
For example, by changing the configuration of the magnet MG, changing the diameter of the developing sleeve, or changing the shape and size of the case 115, only the spike portions SP1a and SP1b are present in the configuration shown in FIG. Alternatively, the object of the present invention can be attained if at least one spike portion can be formed on the upstream side of the opposed region including the vicinity of the closest position.
[0106]
As shown in FIGS. 1 to 4 and 6, {circle around (1)} three poles (magnets MG1a, MG1b, MG1c) are arranged in the facing region and the other five poles (magnets MG2, MG3, MG4, MG5, MG6) In the opposite region, a developing device using three poles to form three raised portions using a developing roller with magnets of eight poles in total, and (2) the closest position to the photoconductor in the opposite region Has only one magnet (instead of the three magnets MG1a, MG1b, MG1c in this example, a single magnet), and the other magnetic poles have the five poles (magnets MG2, MG3, MG4, MG5, MG6). The results were compared with those of a developing device provided with a developing roller having a configuration in which all the six poles were arranged in accordance with MG4, MG5, and MG6, and only one spike was formed in the facing region. The result of the development by the development device of Compared to development result by the apparatus, solid black follow-up property is good, the image quality of the roughness-rear blank area of the image was also improved.
[0107]
In the developing device of the above item (2), the half width of the magnetic force of the magnet coming closest to the photoconductor is 21 °, and only this one pole exists in the area facing the photoconductor. Further, the development gaps and the pumping amounts of the developing devices of the above (1) and (2) were the same.
[0108]
Further, in the developing method of the present invention, one of the two ears is formed by the first magnet MG1b, which is a magnet that forms the ears in the opposing region and is located closest to the photoconductor 100. Another spike portion SP1a is formed by the second magnet MG1a disposed at a position upstream of the spike portion SP1b in the developer transport direction (rotation direction 111c). By doing so, the developer can be effectively developed by using the developer conveying path process until the facing distance gradually narrows and finally reaches the closest position, and free toner is generated during this time.
The details of the developing method will be described below.
[2-1] Development method of contacting
This example is a developing method in which at least one magnetic brush formed in the facing region is brought into contact with the photoconductor 100, and the example has already been described with reference to FIG.
[0109]
According to the developing method of the present embodiment, since the magnetic brush is brought into contact with the photoconductor 100, the development with the free toner and the toner on the carrier at the tip of the magnetic brush are rubbed or close to the photoconductor. The toner developed on the photoreceptor 100 is separated by the magnetic carrier at the tip of the magnetic brush by the so-called contact development, in which the toner directly adheres to the latent image. A developing method for obtaining a high quality image which is smooth with good solid filling, has less fogging in non-image portions, and has excellent sharpness of horizontal fine lines and characters.
[0110]
[2-1.1] Example in which center of ear stand is set to closest position
In FIG. 6, among the two magnetic brushes formed in the facing region, the spike portion SP1b of one magnetic brush BR1b is located at the closest position, and the magnetic brush is in contact with the photoconductor 100, and the other one is different. The spike portions SP1a of the two magnetic brushes BR1a are located upstream of the closest position and are separated from the photoconductor 100.
[0111]
In such a developing method using the raised portions, the distance between the developing sleeve 111c and the photoconductor 100 gradually decreases, and the toner is conveyed to the photosensitive member 100 by using a developer conveying path process until reaching the closest position. Then, the toner developed on the photoreceptor 100 is separated by the magnetic brush BR1b, whereby a high-quality image having a high solid density and excellent horizontal fine lines and sharpness of characters can be obtained.
[0112]
[2-1.1a] Development mode
6, the magnetic brush BR1b is in contact with the photoconductor 100, and the magnetic brush BR1a is not in contact with the photoconductor 100. FIG. 7 is an enlarged view showing the state of the magnetic brush in the region from the spike portion SP1a to the spike portion SP1b in FIG.
[0113]
In FIG. 7, the state of the magnetic brush and the state of the knurl in the development area d corresponding to the ridge portions SP1a and SP1b are observed and schematically shown.
In FIG. 7, an area A0 until the magnetic ears rise and lie down is observed corresponding to a certain area corresponding to the uppermost stream position of the developing area. In the region A0, the magnetic carrier distribution in the developer causes the magnetic carriers CC in the developer to form a magnetic chain by aggregating a plurality of magnetic carriers CC while having the toner T on the surface. This is a region from the time when the ears of the magnetic carrier CC rise to the time when the magnetic carrier CC falls to the side of the developing sleeve 111c.
[0114]
In FIG. 7, in a certain area adjacent to the downstream side of the area A0, an area A1 where the magnetic brushes of the magnetic brush BR1b start to rise is correspondingly observed. This region A1 is a region where the ears of the magnetic carrier CC start to rise, and the magnetic carrier CC in the developer approaching the vicinity of the magnetic force distribution P1b has a plurality of magnetic carriers CC gathering while having the toner T on the surface. Magnetic spikes, and the spikes of the magnetic carrier CC start to rise along the normal magnetic field lines.
[0115]
In a certain area adjacent to the downstream side of the area A1 in the developing area, an area B where the rising magnetic spike contacts the photoconductor 100 is observed. Further, a region C where the magnetic ears in contact with the region B are in sliding contact with the photosensitive member 100 in a certain region on the downstream side of the region B is observed.
[0116]
In FIG. 6, the area A0, the area A1, the area B, and the area C exist, and the area C corresponds to the closest position. In another example, the area B, the area B, C may not exist, or the positional relationship of these areas A0, A1, B, and C with respect to the closest position may be shifted. In addition, the length of the magnetic spikes is not uniform, and the atmosphere of the magnetic field is not constant (in addition, the magnetic characteristics of the magnetic carriers have a distribution, and the number of carriers forming the magnetic spikes is not uniform. The position (region) where the magnetic ear contacts the photoconductor 100 changes.
[0117]
(A) Development in area A0 (related to claims 1 and 2)
In FIG. 8 schematically showing a state from the rising of the ears of the magnetic carrier CC to the falling of the ears in the region A0, on the developing sleeve 111c corresponding to the position where the second magnet MG1a is arranged, Irrespective of the polarity of the second magnet MG1a, a magnetic brush BR1a is formed, and the magnetic brushes are formed between the magnets corresponding to the portion where the magnetic ears start to rise (for example, between the magnet MG6 and the second magnet MG1a, or the second magnet MG1a). On the developing sleeve 111c corresponding to the area between the first and second magnets MG1b), the developer is pressed against the developing sleeve 111c because the layer of the developer has a strong tangential magnetic force.
[0118]
As shown in FIG. 8, the magnetic carriers CC previously confined in the developer layer of the group of magnetic carriers CC have a magnetic force with each other. Although small, the magnets adjacent to each other have opposite poles, so that the tangential magnetic force of the developing sleeve is large, so that this forms a developer layer which is a group of magnetic carriers CC thinner between the magnets than the one on the magnet. Forced to keep the magnetic carrier CC in the population of the developer layer.
[0119]
When the developer layer comes to a position corresponding to the magnet P1a, some magnetic carriers CC gather to form magnetic spikes and rise. The number of magnetic carriers CC gathered to form the magnetic ears is generally determined by the amount of developer passing through the doctor blade 114. In addition, the magnetic properties of the magnetic carrier CC and the magnetic force of the magnet Is determined by the size and inclination of the line of magnetic force depending on the size of the magnet, the shape of the magnet, and the manner of arrangement.
[0120]
Further, since the magnet P1a is fixed, but the developing sleeve 111c is rotating, the angle and magnitude of the magnetic force lines at the position of the magnetic chain that has started rising also change. At this time, since the magnetic responsiveness of the magnetic carrier CC is delayed, the magnetic brush is not immediately aligned in the shape along the line of magnetic force. Although it escapes and rises, a large magnetic field of the magnet acts, the magnetic polarities of all the magnetic carriers CC are in the same direction, and repulsive forces act on each other. As a result, the developer layer of the magnetic carrier CC is suddenly broken, and the magnetic spikes of the magnetic carrier CC rise as magnetic brushes.
[0121]
Therefore, when the magnetic carrier CC forms magnetic spikes and rises, the space where the toner T is confined in the group of the magnetic carriers CC is released, and further, the toner T is adsorbed on the surface of the magnetic carrier CC. When a large centrifugal force acts on the toner T, the toner T separates from the surface of the magnetic carrier CC, and the developing space is released to become free toner T.
[0122]
Further, the magnetic spike does not rise or sleep at a constant speed due to a change in the magnetic field, but has acceleration. For this reason, an inertial force acts on the toner T, so that the toner T is separated from the surface of the magnetic carrier CC and released into the developing space in a continuous portion until the toner T rises and lays down, and becomes free toner T. Further, the free toner T detached from the surface of the magnetic carrier CC can be easily moved by a developing electric field or the like because no electrostatic or physical adhesive force acts on the magnetic carrier CC.
[0123]
(B) Development in the area A1 (related to claim 1)
A description will be given with reference to FIG. 9 showing a state of a region A1 where the magnetic spikes of the magnetic carrier CC start rising. The toner T on the surface of the magnetic carrier CC is formed by the powder characteristics such as the particle size of the magnetic carrier CC, the magnetic characteristics such as the saturation magnetization intensity, the magnetic characteristics such as the saturation magnetization intensity of the magnet, and the morphological characteristics such as width and shape. The acting force can be controlled to generate the free toner T.
[0124]
Since the free toner T is generated when the magnetic spikes start to rise at the upstream side of the spike portion SP1b shown in FIG. 9, the amount of the toner T attached to the latent image Li on the photoconductor 100 can be increased. A developing method having high developability can be obtained.
[0125]
As described above, by generating the free toner T that can be developed even with a low electric field in the area A1, a so-called developing method having high developability can be obtained. The behavior of the magnetic carrier CC and the toner T in the region A0 and the region A1 as described above was determined by the inventors of the present invention using a stereo microscope (Olympus: SZH10) and a high-speed camera (Photron: FASTCAM-). Ultima-I²) Is confirmed by an image photographed at a photographing speed of 9000 to 40500 frames / sec. Further, the same is confirmed in the regions B and C described below.
[0126]
(C) Development by region B (related to claims 5 and 6)
In the area B, the magnetic brush (magnetic brush) is brought into contact with the photoreceptor 100, and when this contact is made, the toner is detached from the magnetic carrier in a scattered manner (in a sprinkling state) to generate free toner. The free toner is used for development.
[0127]
That is, the magnetic brush formed in the developing area is brought into contact with the photoreceptor 100 (image carrier) to separate the toner from the surface of the magnetic carrier, and the separated free toner is spread on the developing sleeve 111c and developed ( Claims 5 and 6)
In this example, as shown in FIG. 10, free toner is sprinkled from the magnetic carrier CC having the toner T on the surface so that the toner T is sprayed on the photoconductor 100, and the free toner is used for development. is there. The manner in which the toner T is scattered on the photoconductor 100 is caused by strong contact of the magnetic chain constituting the magnetic brush with the photoconductor 100.
[0128]
The site where the free toner is generated by separating the toner in a scattered manner is the vicinity including the closest position. The distance between the developing sleeve 111c and the photoconductor 100 is narrowest at the closest position, and the distance gradually increases as the distance between the developing sleeve 111c and the photosensitive member 100 increases. On the other hand, since the spike portion SP1b is formed around the closest approach area, the magnetic brush contacts the photoconductor 100 for the first time near the upstream side of the closest approach position, and generates free toner in a scattered manner. The portion where the free toner is generated in a scattered manner includes a slight displacement of the position closest to the closest position due to the development gap, the height of the ears of the magnetic brush, and the like. Further, since there is a particle size distribution and a magnetic characteristic distribution of the magnetic carrier, there are variations in the positions where the ears are raised. This is because the portion where the free toner is generated by detaching the toner in a scattered manner is in the vicinity including the closest position.
[0129]
FIG. 10 schematically shows a region B where the magnetic spikes of the magnetic carrier CC strongly contact the photoconductor 100. On the developing sleeve 111c, the size of the magnetic chain formed by the aggregation of the magnetic carriers CC in the region B, particularly the height thereof, depends on the powder characteristics such as the particle size of the magnetic carrier CC and the saturation magnetization as described above. And the magnetic characteristics such as the intensity of the saturation magnetization of the developing main magnet, and the morphological characteristics such as the width and shape.
[0130]
Therefore, in the region B, the magnetic spikes of the magnetic carrier CC on the developing sleeve 111c are moving at substantially the same speed as the developing sleeve 111c, except that they slide on the developing sleeve 111c. Therefore, when the height of the magnetic spike of the magnetic carrier CC is higher than the distance between the developing sleeve 111c and the photoconductor 100, the speed at which the tip of the magnetic spike rises along the magnetic force line of the first magnet MG1b and the developing speed The photosensitive drum 100 is strongly contacted at both peripheral speeds of the sleeve 111c.
[0131]
Even if the magnetic spike of the magnetic carrier CC completely rises before strongly contacting the photoconductor 100, the developing sleeve 111c has a cylindrical shape, so that the developing sleeve 111c gradually moves from the developing sleeve 111c toward the closest position. The distance to 100 is narrowed, and the closest position (the position on the imaginary line connecting the center O1 and the center O2) is the shortest. Therefore, the magnetic chain moves in the direction of gradually narrowing. Therefore, when the height of the magnetic chain is larger than the closest part between the developing sleeve 111c and the photoconductor 100, the magnetic chain increases the peripheral speed of the developing sleeve 111c in the vicinity including the closest position. From above, the photoconductor 100 strongly contacts the photoconductor 100 in a direction indicated by an arrow F at a speed equal to or higher than the speed offset by the peripheral speed of the photoconductor 100.
[0132]
During this contact, the toner T electrostatically attached to the magnetic carrier CC is separated from the surface of the magnetic carrier CC by impact. Observation of the state of the toner T at the time of this detachment shows that a large amount of the toner T is scattered from the magnetic carrier CC constituting the magnetic spikes. Is described as having separated the toner.
[0133]
As described above, the free toner separated and released in the form of a scatter is applied to the inertial force of the movement due to the centrifugal force, the electric field due to the latent image Li on the surface of the photoconductor 100, and applied between the developing sleeve 111 and the photoconductor 100. The electric field moves toward the photoconductor 100 as shown by an arrow F1 and adheres to the latent image Li to perform development.
[0134]
In this developing method, the toner is formed by a large amount of free toner which is separated and released in a scattered manner through contact of the magnetic chain to the photoconductor 100, that is, a large amount of scattered toner generated in a space very close to the photoconductor. And developing performance can be improved.
[0135]
Further, in the region B, the toner that has already adhered to the photoconductor 100 is separated from the photoconductor 100 by the contact of the magnetic brush that has come into contact with the photoconductor 100, and is again attached to the magnetic carrier CC. As a result, the toner T developed in the non-image area or the low-potential image area in the developing area (opposite area) on the upstream side in the rotation direction 111R with respect to the area C shown in FIG. Is obtained (related to claim 7).
[0136]
(D) Development in region C
The developing method will be described with reference to FIG. 11, which schematically shows the state of development in the area C. An electric field for developing the toner T is applied between the developing sleeve 111c and the photoconductor 100 by the power supply VP shown in FIG. This electric field intensity is strongest in the area C located at the closest position in this example.
[0137]
In the area C, the magnetic brush of the magnetic carrier CC in the spike portion SP1b is conveyed on the developing sleeve 111 while rubbing against the photoconductor 100, and the magnetic carrier CC is applied by the electric field applied between the developing sleeve 111c and the photoconductor 100. From the CC, the toner T adheres to the latent image Li on the photoreceptor 100 and development is performed. In this development, the free toner already released from the magnetic carrier CC and existing in the vicinity of the magnetic carrier CC moves to and adheres to the latent image Li by the action of the electric field, and the toner directly from the magnetic carrier CC to the latent image. It is considered that both of the attached toner are included.
[0138]
In the area C, under the contact state of the magnetic brush in contact with the photosensitive member 100 in the vicinity including the closest position, the toner already attached on the photosensitive member 100 is removed from the photosensitive member 100 by magnetic force. The toner T is detached by the brush rubbing, detached from the previously developed photoreceptor 100, and adhered onto the magnetic carrier CC again. As a result, in the development in the region C, the developed toner T is pulled back to the non-image portion or the low-potential image portion, so that a high-quality image is obtained. Note that there is a magnetic brush that passes the magnetic brush close to the photoconductor 100, and performs a developing function similar to the magnetic brush to some extent (related to claims 8 and 9).
[0139]
That is, in the region C, the toner T on the magnetic carrier CC having a space opened to the photoconductor 100 side is caused by the electric field between the photoconductor 100 and the developing sleeve 111 and between the photoconductor 100 and the magnetic carrier CC. The latent image Li on the photoconductor 100 is developed by the generated electric field.
[0140]
On the other hand, the toner T present on the surface due to the development in the development region on the upstream side in the rotation direction 111R from the region C shown in FIG. To move while rubbing against the toner T that has been developed earlier, catching up on the previously developed toner T, making strong contact with the toner T, and the electrostatic Coulomb force generated by being charged to opposite polarities. It is adsorbed on the surface of the carrier CC and is separated from the photoconductor 100.
[0141]
In this case, mainly in the non-image area on the photoconductor 100, the electrostatic charge by the charging device 101 is small, and the electric field for adsorbing the toner T to the photoconductor 100 is small. Many T can be released. For this reason, it is possible to prevent the background from being stained in the non-image portion and obtain a high-quality image.
[0142]
(E) Development through areas A0 to C
In the development through the areas A0 to C, the two-component developer layer is caused to flow while forming a magnetic brush at least in an area facing the photoreceptor 100, and is developed with the free toner separated from the magnetic carrier in the process of the flow. In addition, this is an example of a developing method in which the magnetic brush is brought into contact with the photoconductor 100 to develop with the free toner detached from the magnetic carrier in a scattered manner, and the magnetic brush is rubbed against the photoconductor 100.
[0143]
That is, in the region A0 and the region A1, the magnetic carriers CC gather to form magnetic spikes, and the toner T is separated from the magnetic carrier CC during the period from the rise to the fall of the spikes to form free toner T. Since an electric field for development is applied between the developing sleeve 111c and the photoconductor 100 by the power supply VP (see FIG. 3), the free toner T is developed toward the photoconductor 100 by the action of the electric field.
[0144]
Further, in the region B, the magnetic spikes of the magnetic carrier CC further come into contact with the photoconductor 100, and the free toner generated by detaching the toner T from the magnetic carrier CC in a scattered manner is scattered on the photoconductor 100, so The latent image Li of the body 100 is developed.
[0145]
Further, by this contact, the toner T on the photoreceptor 100 that has been developed previously is adsorbed and collected on the magnetic carrier CC again. As a result, the toner T developed on the non-image portion or the low-potential image portion in the developing region on the upstream side in the rotation direction 111R from the region C shown in FIG. 7 is pulled back, so that a high-quality image is obtained.
[0146]
Further, in the area C, the magnetic carrier CC at the tip of the magnetic brush rubs against the photoconductor 100, and the electric field applied from the power supply VP causes the magnetic carrier CC to move from the magnetic carrier CC and the free toner T to form the latent image Li on the photoconductor 100. Develop. Further, by this rubbing, the toner T is detached from the photoreceptor 100 that has been previously developed, and adheres again on the magnetic carrier CC. Thus, in the development in the area C shown in FIG. 7, the toner T developed in the non-image area or the low-potential image area is pulled back from the photoconductor 100 to the magnetic carrier CC, so that a high-quality image is obtained. 11). In some cases, by appropriately setting the developing gap, after the application in the region C, the developing is performed in such a manner that the magnetic brush is in close proximity to the photoconductor 100 instead of sliding.
[0147]
In other words, the developing method according to the present embodiment includes a two-component developing sleeve 111c disposed opposite to the photoreceptor 100 and having a magnet therein, including a toner T and a magnetic carrier CC holding the toner T. In the developing method in which the developer is carried on the surface, is conveyed to a development area formed between the photoconductor 100, and the latent image Li formed on the surface of the photoconductor 100 is developed with the toner T, the developing sleeve 111c is Then, the magnetic spikes on which the magnetic carriers CC having the toner T on the surface are gathered rise, and the toner T is detached and developed while the magnetic spikes lie down, and the magnetic brush formed in the development area is strongly applied to the photoreceptor 100. This is a developing method in which the toner T is sprayed on the photoconductor 100 to be brought into contact with the photoconductor 100 for development, and the magnetic carrier CC in the development area is rubbed or brought close to the photoconductor 100 for development.
[0148]
As described above, in the developing method of the present embodiment, the movement mode of the magnetic carrier CC is controlled by focusing on a region where the movement mode of the magnetic carrier CC is characteristic in the surface of the developing sleeve 111c facing the photoconductor 100. (1) Development with free toner generated in the process of flowing while forming the magnetic brush, (2) Development with free toner generated by dispersing from the magnetic carrier when the magnetic brush comes into contact with the photoreceptor (3) development performed by rubbing or bringing the magnetic carrier CC in the development area into or close to the photoconductor 100; (4) magnetic brush in which the toner T on the photoconductor 100 that has been developed earlier has contacted the photoconductor 100 The amount of toner on the photoreceptor 100 can be increased by developing, for example, adsorbed on the magnetic carrier CC and collected again on the magnetic carrier CC, and a high-quality image can be obtained.
[0149]
According to the developing method of the present invention, a developing sleeve 111 disposed opposite to the photoreceptor 100 and having a magnet inside carries a two-component developer containing a toner T and a magnetic carrier C holding the toner T on the surface. In the developing method of transporting the latent image Li formed on the surface of the photoconductor 100 with the toner T to the developing region formed between the photoconductor 100 and the developing sleeve 111, the developing sleeve 111 The magnetic spikes in which the magnetic carriers CC having the toner T are gathered rise, and the toner T is released and developed while the spikes lie down, and the magnetic brush formed in the development area is brought into strong contact with the photoconductor 100, This is a developing method in which toner T is sprayed on the photoconductor 100 for development, and the magnetic carrier CC in the development area is rubbed against the photoconductor 100 for development.
[2-2] Non-contact developing method (claims 12 and 13)
The developing method of the present embodiment is a developing method in which the spikes of the magnetic brush are developed on the photoreceptor 100 in the facing region using the free toner in a non-contact state. Such a non-contact state can be constituted by a balance between the developing gap GP, the amount of the developer pumped up, that is, the doctor gap, the magnetic force of the magnet present in the facing region, the particle diameter of the magnetic carrier, the saturation magnetic moment, and the like. it can.
[0150]
According to the developing method of the present embodiment, since the magnetic brush is not in contact with the photoreceptor 100, there is provided a developing method that does not have roughness in a halftone portion and obtains an image with excellent horizontal thin lines and excellent sharpness of characters. be able to.
[0151]
The developing method of the present invention is characterized in that in FIG. 12, the magnetic brush on the developing sleeve 111c is developed in a non-contact state in which the magnetic brush ears do not come into contact with the photoconductor 100.
[0152]
In the developing method of this example, the developing sleeve 111c causes the developer to flow while forming a magnetic brush in the developing area, and in the course of this flow, the magnetic spikes in which the magnetic carriers CC having the toner T on the surface are gathered, Then, the toner T is released while the magnetic ears are sleeping, and the toner T is released from the surface of the magnetic carrier CC to generate free toner T, which is developed with the free toner. Further, in the developing method, a magnetic carrier CC of a magnetic brush (magnetic brush) is brought close to the photoconductor 100 in a region where the developing sleeve 111c and the photoconductor 100 face each other.
[0153]
In the above, the magnetic brushes on the developing sleeve 111c are kept in a non-contact state without contact with the photoconductor 100, and the magnetic brushes BR1a and BR1b are not in contact with the photoconductor 100 in the proximity area [A0] corresponding to the area A0. As described in FIG. 5, FIG. 8, FIG. 9, etc., the toner T is released and the free toner T is generated while the magnetic spikes of the magnetic carrier CC rise and the magnetic spikes lie down. .
[0154]
Further, in the area [A0], while the magnetic brush is being conveyed through the developing sleeve 111c, the tip of the magnetic brush moves close to the photoconductor 100, so that the toner T on the magnetic carrier CC becomes a latent image Li. , And fly and develop.
[0155]
Further, while the magnetic brush is being transported together with the developing sleeve 111c, the toner T already attached to the latent image Li on the photoconductor 100 can be released even if the tip of the magnetic brush is brought close to the photoconductor 100. Therefore, the amount of toner adhered does not decrease, and the image quality does not decrease.
[0156]
[2-3] Speed difference (related to claim 14)
In the above-described developing method, the linear velocity ratio (Vs / Vp) between the linear velocity (Vs) of the developing sleeve 111c and the linear velocity (Vp) of the photoconductor 100 is set in the range of 0.9 <Vs / Vp <4. .
[0157]
The developing sleeve 111c and the photoconductor 100 rotate in the same direction in the facing region. Even if the linear velocity of the developing sleeve 111c is lower than the linear velocity of the photoconductor 100, that is, even if the linear velocity ratio (Vs / Vp) is 1 or less, there is sufficient toner T to be detached from the surface of the magnetic carrier CC. It is possible to maintain a large amount.
[0158]
A linear velocity ratio (Vs / Vp) with a linear velocity ratio greater than 0.9 increases the amount of toner T developed by the rotation of the developing sleeve 111, so that an image with a high image density can be obtained. Depending on the amount of the free toner T, there is a possibility that the linear velocity ratio can be further reduced.
[0159]
Further, in the area C shown in FIG. 7, when the magnetic brush rubs or approaches the photoconductor 100, the number of times that the magnetic brush contacts the magnetic spikes of the magnetic carrier CC increases, so that the amount of toner detached from the photoconductor 100 increases. In particular, when the linear velocity ratio (Vs / Vp) is 4 or more, the trailing edge white spots in the halftone portion and blurring of the horizontal fine line image increase, so that the linear velocity ratio (Vs / Vp) is preferably less than 4. .
[0160]
[2-4] Development bias (related to claim 15)
In the above-described developing method, the free toner is developed by the electric field applied between the photoconductors 100 of the developing sleeve 111c.
FIG. 13 is a diagram schematically illustrating a development state when a DC power supply is used as the power supply VP in FIG. 3 and a DC electric field is applied in the reversal development method. In the photoreceptor 100 using an organic pigment as a carrier generating material, an image is generally formed with a negatively charged toner by being charged to a negative polarity in many cases. However, in the developing method, the polarity of the charged charge placed on the photoconductor 100 is not a significant problem.
[0161]
In the case of writing with the laser beam Lb, the character portion is exposed to reduce the writing amount, so that the charged charges in this portion are neutralized by holes generated from the carrier generating material, and as shown in FIG. The image portion potential, which is the potential of the portion (character portion), decreases.
[0162]
By applying a DC voltage biased to the negative side by the power supply VP connected to the developing sleeve 111c in FIG. 3 to the image portion having the lowered potential, the free toner of negative polarity and the toner held by the magnetic carrier CC (FIG. 13 and 14, a vector directed toward the developing sleeve 111c or the image portion acts on the toner T).
[0163]
In FIG. 13, even if toner is present in the non-image area on the photoconductor 100, the toner is reliably separated from the non-image area due to the action of the vector from the non-image area to the developing sleeve 111c. Is prevented.
[0164]
The developing method of the present invention is based on the powder characteristics such as the particle size of the carrier CC, the magnetic characteristics such as the saturation magnetization intensity, the magnetic characteristics such as the saturation magnetization intensity of the magnet, and the morphological characteristics such as width and shape. By controlling the force acting on the toner T on the surface, the free toner T can be generated. Further, by forming a magnetic brush that generates the free toner T, the amount of toner attached to the latent image Li on the photoconductor 100 can be increased, and a so-called developing method with high developability can be obtained.
[0165]
FIG. 14 shows a case where an alternating voltage power supply is used as the power supply VP in FIG. 3, and more specifically, a power supply which generates a voltage in which DC and AC are superimposed is used to make the electric field of the developing bias an alternating electric field. FIG. 3 is a diagram schematically illustrating a development state in a reversal development method.
[0166]
As described above, an alternating electric field can be applied to the portion where the photoconductor 100 and the developing sleeve 111c face each other. In the developing method of the present embodiment, the bias electric field applied to the developing sleeve 111c is particularly preferably an alternating electric field generated by superimposing DC and AC.
[0167]
In FIG. 14, similarly to the case of the DC electric field described above, for example, the negative polarity toner T is developed by the electric field applied between the developing sleeve 111c and the photoconductor 100.
[0168]
Also in this case, since the magnetic carrier CC on the developing sleeve 111c is a dielectric material, the magnetic field in which the photoconductor 100 and the magnetic carrier CC are gathered further adheres to the magnetic carrier CC by further strengthening the electric field. Is developed into the latent image Li on the photoconductor 100. Further, by the application of the alternating electric field, the toner T on the photosensitive member 100 is developed and moves so as to vibrate, and the latent image Li is gradually aligned with the latent image Li to obtain a high-quality image. Also, in this case, if the ears of the magnetic brush are close to the photoconductor 100, an electric field emphasized by the magnetic carrier CC is generated. It is possible to obtain a high-quality image that is faithfully aligned with Li.
[0169]
That is, since the alternating electric field deviated to the negative side is applied as the developing bias electric field, in the image portion, the free toner T surely reaches the image portion while receiving the action of the strong and weak vector toward the image portion. Even if it is present in the non-image portion, it is reliably separated from the non-image portion while receiving the action of the strong and weak vectors from the non-image portion side to the developing sleeve 111c side, thereby preventing background contamination.
[0170]
[3] Electric field strength formed in the facing region (related to claims 1, 2, 5, 8, 10, and 12)
The inventors of the present invention used the above-described stereo microscope (Olympus: SZH10) and a high-speed camera (Photron: FASTCAM-Ultima-I).²), The development region front area A₀In the vicinity of the toner, the average toner charge A (C / kg) and the toner density_C(Wt%), toner average particle diameter d (m), magnetic carrier average particle diameter D (m), developer carrier diameter R (m), developer carrier linear velocity v_SL(M / sec) as a parameter, and as shown in Table 1 below, as shown in Table 1 below, in order for toner to fly from the carrier for development, the electric field intensity E at the flying position P was expressed by the following equation (1). It was found that it was necessary to satisfy the condition of (Expression).
[0171]
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜ ・ ・ ・ ・ ▲ 1 ▼ type
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: The linear velocity (m / sec) of the developer carrying member.
[0172]
In Table 1, ρ_T= 1250, ρ_C= 5000, the shortest distance from the flying position P to the image carrier surface (corresponding to the photoconductor 100 in the above example) is L (m) on the developer carrier (corresponding to the developing sleeve 111c in the above example), and the developing electric field An alternating electric field in which a rectangular wave having a DC component of -500 V and an AC component of Vp-p: 800 V and a frequency of 4.5 kHz was superimposed was applied to the developer carrier, and the image carrier was operated at an image portion potential of -100 V. . The shooting speed is 18,000 frames / sec.
[0173]
[Table 1]

[0174]
Here, in Table 1, the mark “有 り” indicates that the toner is flying, the mark “X” indicates that the toner is not flying, and the mark “○” indicates that the toner is slightly flying. The reason for the presence / absence of the toner flying is considered to be due to the distribution of the charge amount of the toner. In Table 1, Expression (1) is satisfied under the conditions in the column marked with a triangle.
[0175]
The basis of equation (1) is based on the following considerations. Since the expression (1) is a condition under which the toner flies, it is necessary to consider the following expression (2) as an electric field expression that indicates a threshold value at which the toner jumps out of the carrier in consideration of the movement.
[0176]
(Equation 1)

[0177]
Therefore, first, when the van der Wals force is ignored, the toner-carrier adhesion force F expressed by the following equation (3) is applied to the toner adhered on the carrier._tWorks.
[0178]
(Equation 2)

[0179]
This adhesive force F_tWhen the force from the electric field wins, the toner separates from the carrier, and the electric field E at that time is expressed by the following equation (4).
[0180]
(Equation 3)

[0181]
In the above equation (4), q is expressed by the equation (5).
[0182]
(Equation 4)

[0183]
Therefore, the electric field E is expressed by the following equation (6).
[0184]
(Equation 5)

[0185]
When the constant α was experimentally examined, it was found that the constant α was expressed by the following equation (7).
[0186]
(Equation 6)

[0187]
In the equation (7), n is the number of toners adhering to one carrier, and assuming that the toner is uniformly adhering to the carrier, the toner density T_CIs represented by the following equation (8) from the relation of the weight ratio.
[0188]
(Equation 7)

[0189]
In equation (8), m: mass of toner, d: diameter (particle size) of toner, ρ_T: Specific gravity of toner, M: mass of carrier, D: diameter (particle size) of carrier, ρ_C: Specific gravity of carrier. R is the diameter of the developer carrier, v_SLIs the linear velocity of the developer carrying member.
The above equation (2) is obtained by substituting α, n and the like in equations (7) and (8) into equation (6). Since the expression (2) indicates the threshold value of the electric field at which the toner jumps out of the carrier, the expression (1) is derived from the expression (2) regarding the generation of free toner that enables development.
[0190]
Here, the physical reason in equations (7) and (8) is unknown, but this means that
R: As the diameter of the developer carrying member becomes longer, the radius of curvature becomes larger, the spikes of the magnetic brush become gentler, and the mechanical force becomes weaker, so that a larger electric field is required.
v_SL: As the linear velocity of the developer carrying member increases, the mechanical force acts on the toner on the carrier, and the electric field of the toner on the carrier decreases.
n: generally T_CIncreases, the toner charge amount q decreases, the effect of the mechanical action force increases, and the toner on the carrier jumps out with a smaller electric field. Also, T_CAlso, when q does not change due to the change of the above, since the influence of the counter charge remaining on the carrier when one toner flies is small when n is large, it is possible to fly out with a smaller electric field.
it is conceivable that.
[0191]
In the description of the developing method and the developing device so far, the developing mode in the area where the developing sleeve and the photoreceptor 100 are opposed to each other is as follows. (1 related) (2) An aspect in which the collected spikes of the magnetic carrier rise, and there is at least one continuous portion where the spikes lie down (related to claim 2) (3) Develop toner from a magnetic carrier having toner on its surface (4) A mode in which a magnetic brush formed of a magnetic carrier having a toner on its surface is slid on or close to the photosensitive member 100 to develop the toner (related to claim 8). (5) A magnetic brush including a spike on which magnetic carriers having a toner on the surface are collected and a free toner detached from the surface of the magnetic carrier. The spikes of the magnetic carrier rise, and the toner is released and developed while the spikes lie down, and the magnetic toner is brought into contact with the image carrier and the free toner to be released is sprayed on the image carrier. Developing and developing by rubbing or approaching the magnetic brush to the image carrier (related to claim 10) (6) Spikes in which magnetic carriers having toner on the surface are gathered, and detachable from the magnetic carrier surface A magnetic brush containing toner and a magnetic brush is formed, the spikes of the magnetic carrier rise, and the toner is released and developed while lying down, and the magnetic brush is brought close to the image carrier to develop. Related).
[0192]
In these developing modes, the electric field intensity E (V / m) formed in the region where the developing sleeve 111c and the photoconductor 100 face each other is:
E ≧ | (A · ρ_T・ D ・ R) / (3B^1/2・ Ε₀・ V_SL) ｜
Where B = T_C・ D³・ Ρ_C/ (100-T_C) ・ D³・ Ρ_T
Here, A: average toner charge (C / kg), T_C: Average toner particle diameter (m), D: average magnetic carrier particle diameter (m), ρ_T: Specific gravity of toner (kg / m³), Ρ_C: Carrier specific gravity (kg / m³), Ε₀= 8.854 × 10^-12(F / m), R; diameter (m) of developer carrier, v_SL: An area where the linear velocity (m / sec) of the developer carrying member is formed, and the development mode such as the above (1) to (6) is performed in this area to obtain the generation of the free toner and its flying. As a result, high-quality development, which is the object of the present invention, could be obtained.
[0193]
[4] Image forming apparatus (related to claim 17)
An image forming apparatus provided with a developing device for performing the developing method according to the present invention described above will be exemplified. This image forming apparatus includes a developing device having the basic configuration described with reference to FIGS. This developing device is implemented by changing the contents described above as necessary.
[0194]
FIG. 15 shows a schematic configuration of a color copying machine as an example of an image forming apparatus. The color copying machine includes a color image reading device (hereinafter, referred to as a color scanner) 1, a color image recording device (hereinafter, referred to as a color printer) 2, a paper feed bank 3, a control unit (not shown), and the like.
[0195]
The color scanner 1 forms an image of an original 5 on a contact glass 4 on a color sensor 9 via an illumination lamp 6, mirror groups 7a and 7b, and a lens 8, and converts color image information of the original 5 into, for example, red. (Red), green (Green), and blue (Blue) (hereinafter, referred to as R, G, and B, respectively) are read for each color separation light, and are converted into electrical image signals.
[0196]
In this example, the color sensor 9 is composed of R, G, and B color separation means and a photoelectric conversion element such as a CCD (charge coupled device), and simultaneously reads three color images obtained by performing color separation on the image of the document 4. ing. Then, a color conversion process is performed by an image processing unit (not shown) based on the R, G, and B color separation image signal intensity levels obtained by the color scanner 1, and black (Black, hereinafter Bk) and cyan ( Color image data of cyan (hereinafter, referred to as C), magenta (hereinafter, referred to as M), and yellow (Yellow, hereinafter, referred to as Y) are obtained.
[0197]
The operation of the color scanner 1 for obtaining the color image data of Bk, C, M, and Y is as follows. Upon receiving a scanner start signal that is timed with the operation of the color printer 2 described later, an optical system including an illumination lamp 6 and mirror groups 7a and 7b scans the original 5 in the left direction of the arrow, and performs one scan. One color image data is obtained every time. By repeating this operation four times in total, color image data of four colors is sequentially obtained. Then, each time the color printer 2 sequentially visualizes the images and superimposes them to form a final four-color full-color image.
[0198]
The color printer 2 includes a cylindrical photoconductor 100 as an image carrier, a writing optical unit 10, a revolver developing unit 11 as a developing device, an intermediate transfer device 12, a fixing device 13, and the like.
[0199]
The photoreceptor 100 rotates in the counterclockwise direction indicated by the arrow. Around the photoreceptor cleaning device 14, a static elimination lamp 15, a charger 101, a potential sensor 16 as a charging potential detecting unit, and a revolver developing unit 11 are selected. A developing device 24 (which corresponds to the developing device 110 described with reference to FIGS. 1 to 4), a development density pattern detector 17, an intermediate transfer belt 18 of the intermediate transfer device 12, and the like are arranged.
[0200]
The writing optical unit 10 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the image of the original 5, and forms a latent image on the photoconductor 100. The writing optical unit 10 includes a semiconductor laser 19 as a light source, a laser emission drive control unit (not shown), a polygon mirror 20, a motor 21 for rotating the polygon mirror 20, an f / θ lens 22, a reflection mirror 23, and the like.
[0201]
Further, the revolver developing unit 11 includes a Bk developing unit 24K, a C developing unit 24C, an M developing unit 24M, a Y developing unit 24Y, and a revolver rotation drive unit which rotates each developing unit in a counterclockwise direction indicated by an arrow, and the like. It is configured.
[0202]
Each developing device includes a developing sleeve 111c having a magnet therein, which is disposed to face the photoreceptor 100, and the sleeve 111c supports a two-component developer including a toner and a magnetic carrier holding the toner on the surface. Then, the carried two-component developer is conveyed to a region facing the photoconductor 100, and an electric field is applied between the developing sleeve 111 c and the photoconductor 100 to form the two-component developer on the surface of the photoconductor 100. The latent image is developed with toner.
[0203]
The toner in each developing unit 24 is charged to a negative polarity by stirring with a ferrite carrier which is a magnetic carrier, and a negative DC voltage is applied to each developing sleeve 111c by a power supply VP for developing bias (see FIG. 3). The developing sleeve 111c is biased to a predetermined potential with respect to the conductive support 31 (see FIG. 3) of the photoreceptor 100. The electric field intensity satisfying the above equation (1) can be given by this power supply VP.
[0204]
In the standby state of the copying machine main body, the Bk developing unit 24K of the revolver developing unit 11 is set at the developing position, and when the copying operation is started, the color scanner 1 starts reading the Bk color image data from a predetermined timing. Then, based on this color image data, optical writing with a laser beam and latent image formation start (hereinafter, a latent image based on Bk image data is referred to as a Bk latent image. The same applies to C, M, and Y).
[0205]
Before the front end of the latent image reaches the Bk development position so that development can be performed from the front end of the Bk latent image, the rotation of the Bk development sleeve 111c is started to develop the Bk latent image with Bk toner. Thereafter, the developing operation of the Bk latent image area is continued, but when the rear end of the latent image passes the Bk developing position, the revolver developing unit 11 is rotated until the developing device for the next color comes to the developing position immediately. I do. This is completed at least before the leading end of the latent image based on the next image data arrives. The revolver developing unit 11 will be described later in detail.
[0206]
The intermediate transfer device 12 includes an intermediate transfer belt 18, a belt cleaning device 25, a transport belt 38, a paper transfer corona discharger (hereinafter, referred to as a paper transfer device) 26, and the like. The intermediate transfer belt 18 is stretched around a driving roller 18a, a transfer opposing roller 18b, a cleaning opposing roller 18c, and a driven roller group, and is driven and controlled by a driving motor (not shown).
[0207]
The material of the intermediate transfer belt 18 is ETFE (ethylene tetrafluoroethylene), and its electrical resistance is 10⁸-10¹⁰Ω / cm²It is about. The belt cleaning device 25 includes an entrance seal, a rubber blade, a discharge coil, an entrance seal, a mechanism for contacting and separating the rubber blade, and the like. The first color Bk image is transferred to the intermediate transfer belt 18. While the second, third and fourth color images are being transferred to the belt, the entrance seal and the blade are separated from the surface of the intermediate transfer belt 18 by a blade contact / separation mechanism. The paper transfer unit 26 applies an AC voltage + DC voltage or a DC voltage by a corona discharge method, and collectively transfers the superimposed toner image on the intermediate transfer belt 18 to the recording paper 27.
[0208]
The recording paper cassette 28 of the color printer 2 and the recording paper cassettes 300a, 300b, and 300c of the paper supply bank 3 store recording papers 27 of various sizes. Paper is fed from the cassette in the direction of the pair of registration rollers 30 by paper feed rollers 30, 31a, b, and c, and is conveyed. A manual tray 33 is provided on the right side of the printer 2 for manually feeding OHP paper or thick paper.
[0209]
In the color copier having the above-described structure, when the image forming cycle is started, first, the photosensitive member 100 is rotated counterclockwise by an arrow and the intermediate transfer belt 18 is rotated clockwise by an arrow by a driving motor (not shown). The formation of the Bk toner image, the formation of the C toner image, the formation of the M toner image, and the formation of the Y toner image are performed with the rotation of the intermediate transfer belt 18, and finally the Bk, C, M, and Y are formed on the intermediate transfer belt 18 in this order. A toner image is formed overlapping.
[0210]
The formation of the Bk toner image is performed as follows. The charger 101 uniformly charges the photosensitive member 100 with negative charges by corona discharge. Then, the semiconductor laser 19 performs raster exposure based on the Bk color image signal. When this raster image is exposed, the exposed portion of the photoreceptor 100 that is initially uniformly charged loses the charge proportional to the amount of exposure light, and a Bk latent image is formed.
[0211]
When the negatively charged Bk toner on the Bk developing sleeve comes into contact with the Bk latent image, the toner does not adhere to the portion where the charge of the photoconductor 100 remains, and the Bk toner does not adhere to the portion without charge, that is, the exposed portion. The toner is attracted, and a Bk toner image similar to the latent image is formed.
[0212]
The Bk toner image formed on the photoconductor 100 is transferred to the surface of the intermediate transfer belt 18 that is driven at a constant speed in a state of contact with the photoconductor 100 by a belt transfer device 34 (hereinafter, the intermediate image is transferred from the photoconductor 100 to the intermediate (Transfer of the toner image to the transfer belt 18 is referred to as belt transfer.)
[0213]
Some untransferred residual toner on the photoconductor 100 is cleaned by the photoconductor cleaning device 14 in preparation for reuse of the photoconductor 100. The collected toner is stored in a waste toner tank (not shown) via a collection pipe.
[0214]
On the photoconductor 100 side, the process proceeds to the C image forming process after the Bk image forming process, and the C image data reading by the color scanner 1 starts at a predetermined timing, and the C latent image is formed by laser light writing based on the C image data. . Then, after the rear end of the previous Bk latent image has passed and before the front end of the C latent image has reached, the rotating operation of the revolver developing unit 11 is performed, and the C developing device 24C is set to the developing position. Thus, the C latent image is developed with the C toner.
[0215]
Thereafter, the development of the C latent image area is continued, but when the rear end of the C latent image passes, the revolver developing unit 11 is rotated as in the case of the Bk developing unit 24K, and the next M development is performed. The container 24M is moved to the developing position. This is also completed before the leading end of the next M latent image reaches the developing position. In the M and Y image forming processes, the operations of reading the color image data, forming the latent image, and developing are the same as those of the above-described processes of BK and C, and thus the description is omitted.
[0216]
The Bk, C, M, and Y toner images sequentially formed on the photoreceptor 100 are sequentially aligned on the same surface on the intermediate transfer belt 18 to form a four-color superimposed toner image. , The four color toner images are collectively transferred to the recording paper 27 by the paper transfer unit 26.
[0219]
At the time when the image forming operation is started, the recording paper 27 is fed from either the recording paper cassette or the manual feed tray, and stands by at the nip of the registration roller pair 32. When the leading end of the toner image on the intermediate transfer belt 18 approaches the paper transfer unit 26, the registration roller pair 32 is driven so that the leading end of the recording paper 27 coincides with the leading end of the toner image. Then, registration of the recording paper 27 with the toner image is performed.
[0218]
The recording paper 5 is superimposed on the toner image on the intermediate transfer belt 18 and passes over a positive potential paper transfer unit 26. At this time, the recording paper 27 is charged with a positive charge by the corona discharge current, and most of the toner image is transferred onto the recording paper 27. Subsequently, when the recording paper 27 passes through a portion opposed to a separation static eliminator by an AC + DC corona (not shown) disposed on the left side of the paper transfer device 26, the recording paper 27 is neutralized, separated from the intermediate transfer belt 18, and transported from the transport belt 27. Move to belt 35.
[0219]
The recording paper 27 on which the four-color superimposed toner image is collectively transferred from the surface of the intermediate transfer belt 18 is conveyed to a fixing device 36 by a paper conveying belt 35, and a fixing roller 36a controlled to a predetermined temperature and a pressure roller. The toner image is melted and fixed at the nip portion 36b, sent out of the apparatus main body by the discharge roller pair 37, and stacked face up on a copy tray (not shown) to obtain a full color copy.
[0220]
On the other hand, the surface of the photoconductor 100 after the belt transfer is cleaned by a photoconductor cleaning device 14 (brush roller, rubber blade), and is uniformly discharged by a discharge lamp 15. The surface of the intermediate transfer belt 18 after the transfer of the toner image onto the recording paper 27 is cleaned by pressing the blade of the belt cleaning device 25 again with the blade contact / separation mechanism.
[0221]
Here, in the case of the repeat copy, the operation of the color scanner 1 and the image formation on the photosensitive member 100 are performed at a predetermined timing following the image formation process of the fourth color (Y) of the first sheet. The process proceeds to the first color (Bk) image forming process. Further, the intermediate transfer belt 18 has a second sheet in the area cleaned by the belt cleaning device 25 on the front surface following the batch transfer step of the first four-color superimposed toner image onto the recording paper 27. Bk toner image is transferred to the belt. Thereafter, the operation is the same as that of the first sheet.
[0222]
The above is a copy mode for obtaining a four-color full-color copy. However, in the case of a three-color copy mode and a two-color copy mode, the above-described operations are performed for the designated color and the number of times. A similar operation is performed.
[0223]
In the case of the single-color copy mode, only the developing unit of the predetermined color of the revolver developing unit 11 is in the developing operation state until the predetermined number of sheets is completed, and the blade of the belt cleaning device 25 is moved to the intermediate position. The copying operation is continuously performed with the transfer belt 18 being pressed.
[0224]
In the case of the full-color copy mode of A3 size, it is desirable to form a one-color toner image each time the intermediate transfer belt 18 makes one rotation, and to form a four-color toner image by four rotations. In order to reduce the size of the entire apparatus, that is, to reduce the peripheral length of the intermediate transfer belt 18, secure the copy speed in the case of a small size, and not to reduce the copy speed of the maximum size, the intermediate transfer belt 18 must be 2 It is preferable to form a one-color toner image during the rotation. In this case, after the Bk toner image is transferred to the intermediate transfer belt 18, in the next rotation of the intermediate transfer belt 18, the color printer 2 idles without performing development and transfer, and in the next rotation, Development is performed with the C toner of the next color, and the C toner image is sequentially transferred to the intermediate transfer belt 18. At this time, the rotation operation of the revolver developing unit 11 for switching the developing device is performed during the idle rotation.
[0225]
The image forming apparatus of the present invention is provided with a developing device that performs development with free toner, and develops with free toner under the predetermined electric field strength that satisfies the above formula (1) in the opposing area, so that the development can be performed over a wide range. By setting the area, the supply amount of the toner to be developed is increased, so that the allowable range of the developing gap, the number of rotations of the developing sleeve, and the like in designing the machine can be widened. In the case of a thin line high-quality image, particularly, a color image, an image forming apparatus that can obtain an image with excellent reproducibility of a halftone portion can be provided.
[0226]
【The invention's effect】
According to the first to thirteenth aspects of the present invention, by setting the development area in a wider range than the conventional development area, the amount of toner to be developed in the development area is increased, and an image having a high solid density in a solid portion is obtained. Obtainable.
[0227]
According to the fourteenth aspect of the present invention, it is possible to prevent a trailing edge white spot in a halftone portion and blurring of a horizontal thin line image.
[0228]
According to the fifteenth aspect of the present invention, the toner moves more violently so as to vibrate, and further, a high-quality image can be obtained which is faithfully aligned with the latent image.
[0229]
According to the sixteenth aspect of the present invention, a developing device is provided in which the developing area is set in a wider range than the conventional developing area, so that the supply amount of the toner to be developed is increased without increasing the rotation speed of the developing sleeve. can do.
[0230]
According to the present invention, by setting the developing area in a wide range, the supply amount of the toner to be developed is increased, so that the allowable range of the developing gap, the rotational speed of the developing sleeve, and the like when designing the machine. In the case of a high-quality image of a solid portion or a horizontal thin line, particularly, a color image, an image having excellent halftone portion reproducibility can be obtained.
[Brief description of the drawings]
FIG. 1 is a front view illustrating a basic configuration of a developing device.
FIG. 2 is a sectional view of a developing sleeve.
FIG. 3 is a schematic configuration diagram illustrating a basic configuration of a developing device.
FIG. 4A is a diagram illustrating a magnetic force distribution and its magnitude, and FIG. 4B is a diagram illustrating a positional relationship between magnets.
FIGS. 5 (a) to 5 (g) are diagrams illustrating the displacement of the magnetic chain and the generation of loose toner in a stepwise manner.
FIG. 6 is a diagram illustrating an example in which a plurality of spikes are formed in a facing region.
FIG. 7 is an enlarged view schematically showing an upright portion.
FIG. 8 is an enlarged view schematically showing a spike portion.
FIG. 9 is a diagram schematically showing an enlarged earing portion.
FIG. 10 is a perspective view illustrating a state in which loose toner is generated in a scattered manner when a magnetic spike comes into contact with a photoconductor.
FIG. 11 is an enlarged view schematically showing a state in which a magnetic ear slides (or approaches) a photoconductor.
FIG. 12 is a diagram illustrating an example in which a spike moves toward a photoconductor.
FIG. 13 is a diagram schematically illustrating an electrostatic force acting on a toner on an image carrier.
FIG. 14 is a diagram schematically illustrating an electrostatic force acting on a toner on an image carrier.
FIG. 15 is a diagram illustrating a schematic configuration of an image forming apparatus.
[Explanation of symbols]
BR1a, BR1b, BR1c Magnetic brush
SP1a, SP1b, SP1c @ Hot Stand

Claims (17)

A developer carrier, which is disposed opposite the image carrier and has a magnet inside, carries a two-component developer including toner and a magnetic carrier holding the toner, and is formed between the image carrier and the developer carrier. The developing method of transporting the latent image formed on the surface of the image carrier with toner to the developing area is performed by separating the magnetic carrier having toner on the surface into ears and the magnetic carrier surface in the developing area. A developing method for forming a magnetic brush containing free toner,
Field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε 0 · v SL ) ｜
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
Wherein at least one or more portions where the spikes of the magnetic carrier stand are present in the region to be formed. A developer carrier, which is disposed opposite the image carrier and has a magnet inside, carries a two-component developer including toner and a magnetic carrier holding the toner, and is formed between the image carrier and the developer carrier. The developing method of transporting the latent image formed on the surface of the image carrier with toner to the developing area is performed by separating the magnetic carrier having toner on the surface into ears and the magnetic carrier surface in the developing area. A developing method for forming a magnetic brush containing free toner,
Field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε 0 · v SL ) ｜
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
Wherein the spikes in which the magnetic carriers are gathered rise in a region to be formed and at least one or more continuous portions where the spikes lie are present. The developing method according to claim 1, wherein
In the developing method, when the spikes on which the magnetic carriers gather on the developer carrier rise, the tip of the magnetic brush is separated from the developer layer on which the magnetic carriers gather on the developer carrier by a magnet in the developing area. A developing method characterized in that the developing method is performed. The developing method according to claim 1, wherein
In the developing method, when the ears on which the magnetic carriers are gathered fall on the developer carrier, the tip of the magnetic brush is moved together with the developer layer on the developer carrier on which the magnetic carriers are gathered by the magnet in the developing area. A developing method, wherein A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
The developing method, the electric field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε ₀ · v _SL ) |
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
Developing a toner from a magnetic carrier having a toner on its surface by spraying the toner on an image carrier in a region to be developed. The developing method according to claim 5,
The developing method includes contacting a magnetic brush formed in a developing area with an image carrier to separate toner from the surface of the magnetic carrier, and spraying the separated free toner to the image carrier to perform development. Characteristic development method. The developing method according to claim 5, wherein
The developing method is characterized in that a magnetic brush formed in a developing area is brought into contact with an image carrier to release already developed toner from the image carrier. A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
The developing method, the electric field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε ₀ · v _SL ) |
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
Developing a toner by rubbing or bringing a magnetic brush formed of a magnetic carrier having a toner on its surface into contact with an image carrier in a region to be formed. The developing method according to claim 8,
The developing method is characterized in that a magnetic brush is rubbed or brought into contact with an image carrier in a developing area to release already developed toner from the image carrier. A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
The developing method, the electric field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε ₀ · v _SL ) |
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
In the region where the magnetic carrier having the toner on the surface is gathered, a magnetic brush including the free toner to be detached from the surface of the magnetic carrier is formed, and the gathered ears of the magnetic carrier rise, and while the ear is sleeping The toner is released and developed, and the free toner to be released by contacting the magnetic brush with the image carrier is sprayed and developed on the image carrier, and the magnetic brush is rubbed or brought close to the image carrier. A developing method characterized by developing. The developing method according to claim 10,
In the developing method, the magnetic brush formed in the developing area is brought into contact with the image carrier to release the toner from the image carrier, and the magnetic brush is rubbed or brought close to the image carrier, and the toner is already developed. A developing method, wherein the toner is released from the image carrier. A developer carrier having a magnet therein, which is disposed opposite to the image carrier, carries a two-component developer including toner and a magnetic carrier holding the toner on the surface, and is formed between the developer and the image carrier. In a developing method of transporting the latent image formed on the surface of the image carrier with toner,
The developing method, the electric field intensity is formed in the region opposed to the image bearing member and the developer carrying member E (V / m) is _{E ≧ | (A · ρ T} · d · R) / (3B 1/2 · ε ₀ · v _SL ) |
^{_{However, B = T C · D 3}} · ρ C / (100-T C) · d 3 · ρ T
Here, A: average toner charge (C / kg), T _C : toner concentration (wt%), d: average toner particle size (m), D: average magnetic carrier particle size (m), ρ _T : toner Specific gravity (kg / m ³ ), ρ _C : carrier specific gravity (kg / m ³ ), ε ₀ = 8.854 × 10 ⁻¹² (F / m), R: diameter of developer carrier (m), v _SL : Linear velocity of developer carrier (m / sec)
In the area where the magnetic carrier having the toner on the surface is gathered, a magnetic brush including a free toner to be detached from the surface of the magnetic carrier is formed. A developing method, wherein the developing is performed by detaching the magnetic brush and the magnetic brush is brought close to the image carrier. The developing method according to claim 12,
In the developing method, the magnetic brush formed on the developer carrier develops the image carrier in a non-contact state. The developing method according to any one of claims 1 to 13,
In the developing method, a linear velocity ratio (Vs / Vp) between the developer carrier (Vs) and the image carrier (Vp) is in a range of 0.9 <Vs / Vp <4. Method. The developing method according to any one of claims 1 to 14,
In the developing method, the developing is performed by an electric field applied between the image carrier and the developer carrier, and the electric field is an alternating electric field. A developer carrier having a magnet therein is disposed facing the image carrier, and the developer carrier carries a two-component developer including a toner and a magnetic carrier holding the toner on the surface, In a developing device that conveys to a developing area, applies an electric field between the developer carrier and the image carrier, and develops a latent image formed on the surface of the image carrier with toner.
A developing device for performing development by the developing method according to claim 1. An image carrier having photoconductivity and forming a latent image on the surface, a charging device for charging the image carrier, and a magnetic carrier arranged to face the image carrier and holding toner and toner on the surface. An image forming apparatus having a developing device for storing and forming a toner image on the surface of the image carrier and a transfer device for transferring the toner image formed on the surface of the image carrier to a recording member,
An image forming apparatus comprising the developing device according to claim 16.

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