JP2005010527A - Two-component development method and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-component development method using a small particle-diameter carrier having specified distribution of the particle size and a developing unit, and to provide an image forming apparatus using the method. <P>SOLUTION: In the two-component development method to mix and stir developer while circulating it in a loop by using a developing unit, the carrier used is an electrostatic charge image developing carrier comprising magnetic core particles and a resin layer coating the particle surface. The carrier has 25 to 45 μm weight average particle size Dw, has ≥70 wt.% proportion of particles having <44 μm particle size, <1 wt.% proportion of particles of ≥62 μm, and ≤7 wt.% proportion of particles having <22 μm particle size, and shows ≥76 emu/g magnetic moment in an 1 kOe magnetic field. The distribution of charges of the toner in the two-component developer after the developer is stirred for 1 hour without replenishing or consuming the toner can be approximated to one waveform of a normal distribution function having ≤1.0 [fC/10 μm] standard deviation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４０】
正規分布関数はｘ＝μで最大となる左右対称な分布であり、その分布幅は標準偏差σの値によって決まる。σが大きくなるにつれて分布幅が大きくなり、ピーク値が下がる。正規分布関数は常に正で、ｘ→∞でｆ（ｘ）＝０、ｘ→−∞でもｆ（ｘ）＝０となる。この正規分布関数を、−∞から∞の間で積分すると１になるので、実際にこの正規分布関数で帯電量分布を近似するには、正規分布関数を整数倍αしてやる必要がある。
【００４１】
地汚れ・トナー飛散の起こるトナーも起こりにくいトナーも、ユニット投入直後（＝初期状態）については、地汚れ・トナー飛散の原因となる弱帯電トナー及び逆帯電トナーのほとんどない正常な帯電量分布が得られ、その分布は正規分布関数１波形で近似することができ、そのプロファイルはシャープである。
【００４２】
しかし、ユニットに投入した剤をトナー補給と消費を行わず攪拌するような経時の剤中のトナーの帯電量分布については、弱帯電トナーや逆帯電トナーの発生や平均値・標準偏差の変化により、帯電量分布に差が生じる。地汚れ・トナー飛散の起こりにくい良好なトナーの帯電量分布は、平均値・標準偏差の変化は起こるがその変化は小さく、逆帯電トナー及び弱帯電トナーの発生はわずかであり、経時でもユニット投入直後の剤同様に正規分布関数１波形で表現することができる。一方、地汚れ・トナー飛散の起こるトナーの帯電量分布は、平均値・標準偏差の変化が大きく、逆帯電トナー及び弱帯電トナーの発生も多く、ユニット投入直後の剤のように正規分布関数１波形で近似することができない。
【００４３】
ただし、トナーの帯電量分布が正規分布関数１波形で近似できれば、地汚れ・トナー飛散が起こらないという訳ではない。一般に、トナーの帯電量分布のプロファイルがシャープであると、同じような帯電量ｑ／ｄを有するトナーが多く存在することとなり、キャリアとトナーの接触帯電が均等に行われ、弱帯電トナーが発生しにくい。その反対に、トナーの帯電量分布のプロファイルがブロードであると、トナーの帯電量ｑ／ｄの範囲が広がり、高帯電量のトナーがキャリアから離れないためキャリアとトナーの接触帯電が均等に行われず、低帯電量トナーの増加が進む。
【００４４】
その結果、弱帯電トナー量の増加につながり、地汚れ・トナー飛散が起こりやすくなる。従って、地汚れ・トナー飛散が起こらないためには、トナーの帯電量分布が正規分布関数１波形で近似できるだけでは不十分であり、その分布のプロファイルのシャープさ、すなわち、標準偏差、弱帯電トナー量、高帯電トナー量等を規定する必要がある。
【００４５】
地汚れ・トナー飛散の起こる現像剤と起こりにくい現像剤の帯電量分布では、このようにトナー補給と消費を行わず攪拌した時の経時の剤中のトナーの帯電量分布に差があることが正規分布関数による解析で顕在化した。
【００４６】
本発明者らは、上記方法により鋭意研究を重ねた結果、実際にランニングを行わずとも、トナー補給と消費を行わず攪拌した時の経時の剤中のトナーの帯電量分布の変化について調べることで、地汚れ・トナー飛散の起こるトナーを有する現像剤と地汚れ・トナー飛散の起こりにくいトナーを有する現像剤についてその差を明確にできることを見出した。
【００４７】
特に、通常のランニングで地汚れ・トナー飛散が起こるトナーを有する現像剤については、トナー補給と消費を行わず１時間攪拌後の剤中トナーの帯電量分布について調べることで明確にできるが、低画像面積のチャートを連続して長時間画像形成するような剤ストレスの大きい特殊なモードにて地汚れ・トナー飛散が始めて起こるようなトナーを有する現像剤については、さらに５時間まで攪拌後の剤中トナーの帯電量分布について調べることで明確にできることを見出した。
【００４８】
従って、本発明は、上記目的を達成するために以下の構成を有するものである。
本発明の現像ユニットの一例を、図１に示す。図１は、現像ユニットの断面図を示している。本発明の現像ユニットは、大きくは像担持体上の静電潜像を現像するためのトナーを供給する現像スリーブ１と、この現像スリーブの軸方向に沿って二成分現像剤を混合・攪拌しながら搬送する２本の現像剤攪拌部材及び現像剤規制手段（ドクタブレード７）、上部現像ケース２、下部現像ケース３からなる。現像スリーブ１から遠い側には、第１の現像剤攪拌部材４が軸支され、近い側には第２の現像剤攪拌部材５が軸支され、第１の現像剤攪拌部材４と第２の現像剤攪拌部材５との間には、仕切り部材８が設けられている。仕切り部材８の幅方向の両側には現像剤の連絡通路が確保され、現像剤をループ状に循環するようになっている。
【００４９】
現像剤の搬送状態を図１に基づいて説明すると、現像剤は、第１の現像剤攪拌部材のある室を紙面手前側から奥側に搬送されて紙面奥側の連絡通路から第２の現像剤攪拌部材のある室へ搬送され、次いで、第２の現像剤攪拌部材のある室を紙面奥側から手前側へ搬送された後、紙面手前側の連絡通路から第１の現像剤攪拌部材のある室へ搬送されるようになっている。
【００５０】
また、図１において、現像剤規制手段（ドクタブレード）７の左側のスペースを解消して、第２の現像剤攪拌部材のある室から汲み上げられた現像剤が滞留して帯電が立ち上がらないのを防止する手段を設けてもよい。
【００５１】
本発明に使用されるキャリアは、磁性を有する芯材粒子とその表面を被覆する樹脂層とからなる。本発明のキャリアにおいて、その重量平均粒径Ｄｗは、２５μｍ〜４５μｍの範囲であり、好ましくは３０μｍ〜４５μｍである。重量平均粒径Ｄｗが前記範囲よりも大きいとキャリア付着が起こりにくいが、高画像濃度を得るためにトナー濃度を高くした場合、地汚れが急速に増大する。また、潜像のドット径が小さい場合は、ドット径のバラツキが大きくなる。なお、前記キャリア付着は、静電潜像の画像部または地肌部にキャリアが付着する現象を示す。それぞれの電界が強いほどキャリア付着しやすい。画像部がトナーが現像されることにより電界が弱められるため、地肌部に比べキャリア付着は起こりにくい。キャリア付着は、感光体ドラムや定着ローラーの傷の原因となる等の不都合を生じるので好ましくない。さらに、本発明のキャリアにおいて、４４μｍよりも小さい粒径を有する粒子の含有割合は７０重量％以上、好ましくは７５重量％以上である。
【００５２】
６２μｍ以上のキャリア粒子は３重量％未満、好ましくは１重量％未満である。６２μｍ以上の粒子の含有量が多いほど、ドット径のバラツキが大きくなる。６２μｍ以上のキャリアの重量のわずかな差が４４μｍ〜６２μｍの範囲のキャリアの重量％に大きな影響を与えているためだと考えられる。
【００５３】
２２μｍより小さい粒径を有するキャリア粒子の含有割合は７重量％以下、好ましくは３重量％以下、更に好ましくは１重量％以下である。小粒径キャリアの場合、キャリア付着しているキャリアの大部分は、２２μｍ未満の微細粒子である。
本発明者らは、重量平均粒径Ｄｗが２５μｍ〜４５μｍの小粒径キャリアにおいて、２２μｍより小さい粒子の重量比率を変化させてキャリア付着を評価したところ、２２μｍ以下の粒径を有する粒子が７重量％以下ならば大きな問題はないが、３重量％、更に１重量％にすると、キャリア付着はさらに改善されることを見出した。
同時に、１ＫＯｅにおける磁気モーメントが７６ｅｍｕ／ｇ以上とすることにより、キャリア付着は実質的に発生しなくなることも判明した。
【００５４】
本発明のキャリアは、磁性材料を粉砕し、その粉砕物粒子を所定の粒径が得られるように分級し、この分級により得られた芯材粒子の表面に樹脂被膜を形成することで得ることができる。前記分級には、風力分級やふるい分級（ふるい分け）等が包含される。キャリア芯材粒子の製造には、振動ふるいが好ましく用いられているが、従来一般的に用いられている振動ふるいでは、小粒径の粒子を分級しようとすると、そのふるい（金網）の小さな網目がすぐに詰まってしまうという不都合を生じるため、その分級のための作業性は非常に悪いものであった。
【００５５】
本発明者らは、小粒径粒子を効率良く、シャープにカットし得る方法を開発すべく種々検討したところ、ふるい機を用いて粒子を分級する際に、その金網に超音波振動を与えることにより、２２μｍ未満の小粒径粒子を効率良く、シャープにカットし得ることを見出した。
【００５６】
金網を振動させる超音波振動は、高周波電流をコンバータに供給して超音波振動に変換することにより得ることができる。この場合のコンバータは、ＰＺＴ振動子からなる。超音波振動により金網を振動させるためには、コンバータにより発生される超音波振動を、金網に固定した共振部材に伝達させる。超音波振動が伝達された共振部材は、その超音波振動により共振し、その共振部材に固定されている金網を振動させる。金網を振動させる周波数は、２０〜５０ｋＨｚ、好ましくは３０〜４０ｋＨｚである。共振部材の形状は、金網を振動させるのに適した形状であればよく、通常はリング状である。金網を振動させる振動方向は、垂直方向であるのが好ましい。
【００５７】
図２に、超音波発振器付振動ふるい機の構造図を示す。図２において、１５は振動ふるい機、１６は円筒容器、１７はスプリング、１８はベース（支持台）、１９は金網、２０は共振リング、２１は高周波電流ケーブル、２２はコンバータ、２３はリング状フレームを示す。図２に示した超音波発振器付振動ふるい機（円形ふるい機）を作動させるには、ケーブル２１を介して高周波電流をコンバータ２２に供給する。コンバータ２２に供給された高周波電流は、超音波振動に変換される。コンバータ２２で発生した超音波振動は、そのコンバータ２２が固定されている共振リング２０及びそれに連接するリング状フレーム２３を垂直方向に振動させる。この共振リング２０の振動により、共振リング２０とフレーム２３に固定されている金網１９が垂直方向に振動する。超音波発振器付振動ふるい機は市販されており、例えば、晃栄産業（株）より製品名「ウルトラソニック」として入手可能である。
【００５８】
本発明のキャリアは、磁性材料の粉砕物粒子の表面に樹脂被膜を形成して樹脂被覆粒子とした後、この樹脂被覆粒子を分級することによっても製造することができる。この場合の樹脂被覆粒子の分級は、前記した超音波発振器付振動ふるい機を用いて行うのが好ましい。
【００５９】
本発明のキャリアを構成する芯材粒子の材料としては、従来公知の各種の磁性材料が用いられる。本発明で用いるキャリア芯材粒子において、１０００エルステッド（Ｏｅ）の磁場を印加した時の磁気モーメントは、７０ｅｍｕ／ｇ以上、好ましくは７６ｅｍｕ／ｇ以上である。その上限値は特に制約されないが、通常、１５０ｅｍｕ／ｇ程度である。キャリア芯材粒子の磁気モーメントが前記範囲よりも小さくなると、キャリア付着が生じやすくなるので好ましくない。
【００６０】
前記磁気モーメントは、以下のようにして測定することができる。
Ｂ−Ｈトレーサー（ＢＨＵ−６０／理研電子（株）製）を使用し、円筒のセルにキャリア芯材粒子１．０ｇを詰めて装置にセットする。磁場を徐々に大きくし３０００エルステッドまで変化させ、次に徐々に小さくしてゼロにした後、反対向きの磁場を徐々に大きくし３０００エルステッドとする。更に徐々に磁場を小さくしてゼロにした後、最初と同じ方向に磁場をかける。このようにして、Ｂ−Ｈカーブを図示してその図より、１０００エルステッドの磁気モーメントを算出する。
【００６１】
本発明のキャリアで使用する１０００エルステッドの磁場を印加したときに、７０ｅｍｕ／ｇ以上となる芯材粒子としては、例えば、鉄、コバルトなどの強磁性体、マグネタイト、ヘマタイト、Ｌｉ系フェライト、Ｍｎ−Ｚｎ系フェライト、Ｃｕ−Ｚｎ系フェライト、Ｎｉ−Ｚｎ系フェライト、Ｂａ系フェライト、Ｍｎ系フェライトなどが挙げられる。
フェライトとは、一般に次式で表される燒結体である。
（ＭＯ）_ｘ（ＮＯ）_ｙ（Ｆｅ_２Ｏ_３）_ｚ
但し、ｘ＋ｙ＋ｚ＝１００ｍｏｌ％であって、Ｍ、ＮはそれぞれＮｉ、Ｃｕ、Ｚｎ、Ｌｉ、Ｍｇ、Ｍｎ、Ｓｒ、Ｃａなどであり、１価、２価の金属酸化物と３価の鉄酸化物との完全混合物から構成されている。
本発明において、より好ましく用いられる１０００エルステッドの磁場を印加した時の磁気モーメントが７６ｅｍｕ／ｇ以上の芯材粒子としては、例えば、鉄系、マグネタイト系、Ｍｎ−Ｍｇ−Ｓｒ系フェライト、Ｍｎ系フェライトなどが挙げられる。
【００６２】
キャリアの嵩密度が２．２ｇ／ｃｍ^３以上、より好ましくは２．３ｇ／ｃｍ^３以上であると、キャリア付着防止に有利である。嵩密度が小さい芯材は、多孔性、または表面の凹凸が大きい。嵩密度が小さいと、１ＫＯｅの磁気モーメント（ｅｍｕ／ｇ）が大きくても、１粒子あたりの実質的な磁気モーメントの値が小さくなるため、キャリア付着に対して不利である。また、凹凸が大きいと、場所によりコート樹脂の厚みが違ってきて、帯電量及び抵抗の不均一性を生じやすく、経時での耐久性、キャリア付着などに影響を与える。
【００６３】
本発明のキャリアにおいて、その抵抗（ＬｏｇＲ）は、１２．０Ωｃｍ以上、より好ましくは１３．０Ωｃｍ以上である。キャリアの抵抗が前記範囲よりも低いと、現像ギャップ（感光体と現像スリーブ間の最近接距離）が狭くなった場合、キャリアに電荷が誘導されてキャリア付着が発生し易くなる。感光体の線速度、及び、現像スリーブの線速度が大きい場合、悪化の傾向が見られる。また、ＡＣバイアスを印加する場合は顕著である。通常、カラートナー現像用キャリアは十分なトナー付着量を得るため、低抵抗なものが使用されることが一般的である。上記の抵抗範囲のキャリアは、適正なトナー帯電量のもとで使用することにより、十分な画像濃度が得られることが分かった。
【００６４】
上記キャリア抵抗率は、次の方法により測定することができる。
図３に示すように、電極間距離２ｍｍ、表面積２×４ｃｍの電極１２ａ、１２ｂを収容した弗素樹脂製容器からなるセル１１にキャリア１３を充填し、両極間に１００Ｖの直流電圧を印加し、ハイレジスタンスメーター４３２９Ａ（横河ヒューレットパッカード株式会社製）にて直流抵抗を測定し、電気抵抗率ＬｏｇＲ（Ωｃｍ）を算出する。
【００６５】
上記キャリアの低効率の調整は、芯材粒子上の被覆樹脂の抵抗調整、膜厚の制御によって可能である。また、キャリア抵抗調整のために、導電性微粉末被覆樹脂層に添加して使用することも可能である。上記導電性微粉末としては、導電性ＺｎＯ、Ａｌ等の金属または、金属酸化物粉、種々の方法で調整されたＳｎＯ_２または種々の元素をドープしたＳｎＯ_２、ＴｉＢ_２、ＺｎＢ_２、ＭｏＢ_２等のホウ化物、炭化ケイ素、ポリアセチレン、ポリパラフェニレン、ポリ（パラ−フェニレンスルフィド）ポリピロール等の導電性高分子、ファーネスブラック、アセチレンブラック、チャネルブラック等のカーボンブラック等が挙げられる。
【００６６】
これらの導電性微粉末は、以下の方法、即ち、コーティングに使用する溶媒、あるいは被覆用樹脂溶液に導電性微粉末を投入後、ボールミル、ビーズミルなどメディアを使用した分散機、あるいは高速回転する羽根を備えた攪拌機を使用することによって均一に分散することができる。
【００６７】
本発明のキャリアは、前記芯材粒子の表面に樹脂層を形成することによって製造される。樹脂層を形成するための樹脂としては、キャリアの製造に用いられている従来公知の各種のものを用いることができる。
本発明においては、下記式で表される３種の構成単位の少なくとも１種を繰り返し単位として含むシリコーン樹脂も好ましく用いることができる。
【００６８】
【化１】

【００６９】
前記式中Ｒ^１は水素原子、ハロゲン原子、ヒドロキシ基、アルコキシ基（メトキシ基、エトキシ基、プロポキシ基、ブトキシ基など）、炭素数１〜４の低級アルキル基（メチル基、エチル基、プロピル基、ブチル基など）、またはアリール基（フェニル基、トリル基など）を示し、Ｒ^２は炭素数１〜４のアルキレン基、またはアリーレン基（フェニレン基など）を示す。これらアルコキシ基、低級アルキル基、アリール基、アルキレン基およびアリーレン基は、その水素原子が他の基（ハロゲン原子、ヒドロキシ基、アルコキシ基、アリール基など）によって置換されていても良い。
【００７０】
本発明では、ストレートシリコーン樹脂を用いることができる。このようなものとしては、ＫＲ２７１、ＫＲ２７２、ＫＲ２８２、ＫＲ２５２、ＫＲ２５５、ＫＲ１５２（信越化学工業社製）、ＳＲ２４００、ＳＲ２４０６（東レダウコーニングシリコーン社製）などが挙げられる。
【００７１】
本発明では、変性シリコーン樹脂を用いることができる。このようなものとしては、エポキシ変性シリコーン、アクリル変性シリコーン、フェノール変性シリコーン、ウレタン変性シリコーン、ポリエステル変性シリコーン、アルキッド変性シリコーンなどが挙げられる。変性シリコーンの具体例としては、エポキシ変性物：ＥＳ−１００１Ｎ、アクリル変性シリコーン：ＫＲ−５２０８、ポリエステル変性物：ＫＲ−５２０３、アルキッド変性物：ＫＲ−２０６、ウレタン変性物：ＫＲ−３０５（以上、信越化学工業社製）、エポキシ変性物：ＳＲ２１１５、アルキッド変性物：ＳＲ２１１０（東レダウコーニングシリコーン）などが挙げられる。
【００７２】
本発明で使用できる前記シリコーン樹脂には、アミノシランカップリング剤を適量（０．００１〜３０重量％）含有させることができるが、このようなものとしては以下のようなものが挙げられる。

【００７３】
更に、本発明では、キャリア芯材粒子表面を被覆する樹脂として、以下に示すものを単独または上記シリコーン樹脂と混合して使用することも可能である。
ポリスチレン、クロロポリスチレン、ポリ−α−メチルスチレン、スチレン−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ブタジエン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体（スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸フェニル共重合体等）、スチレン−メタクリル酸エステル共重合体（スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−メタクリル酸フェニル共重合体等）、スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体などのスチレン系樹脂、エポキシ樹脂、ポリエステル樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、アイオノマー樹脂、ポリウレタン樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂、ポリアミド樹脂、フェノール樹脂、ポリカーボネート樹脂、メラミン樹脂などがある。
【００７４】
キャリア芯材粒子表面に樹脂層を形成するための方法としては、スプレードライ法、浸漬法、あるいはパウダーコーティング法など公知の方法が使用できる。特に、流動床型コーティング装置を用いる方法は、均一な塗布膜を形成するのに有効である。
【００７５】
キャリア芯材粒子表面上に形成する樹脂層の厚みは、通常の０．０２〜１μｍ、好ましくは０．０３〜０．８μｍである。樹脂層の厚みは極めて小さいことから、樹脂層を被覆した芯材粒子からなるキャリアとキャリア芯材粒子の粒度分布は、実質的に同じである。
【００７６】
本発明のキャリアは、磁性粉をフェノール樹脂、アクリル樹脂、ポリエステル樹脂などの公知の樹脂中に分散した形態を持つ、所謂樹脂分散キャリアであることができる。
【００７７】
本発明の現像剤は、前記キャリアとトナーとからなる。
本発明に使用されるトナーは、熱可逆性樹脂を主成分とするバインダー樹脂中に、着色剤、微粒子、そして帯電制御剤、離型剤等を含有させたものであり、従来公知の各種のトナーを用いることができる。このトナーは、重合法、造粒法などの各種のトナー製法によって作製された不定形または球形のトナーであることができる。また、磁性トナー及び非磁性トナーのいずれも使用可能である。
【００７８】
トナーのバインダー樹脂としては以下のものを、単独あるいは混合して使用できる。
スチレン系バインダー樹脂として、ポリスチレン、ポリビニルトルエン等のスチレン及びその置換体の単重合体、スチレン−ｐ−クロルスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−α−クロルメタクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体等のスチレン系共重合体；アクリル系バインダーとして、ポリメチルメタクリレート、ポリブチルメタクリレートが挙げられ、その他、ポリ塩化ビニル、ポリ酢酸ビニル、ポリエチレン、ポリプロピレン、ポリエステル、ポリウレタン、エポキシ樹脂、ポリビニルブチラール、ポリアクリル酸樹脂、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、脂肪族または脂肪族炭化水素樹脂、芳香族系石油樹脂、塩素化パラフィン、パラフィンワックスなどが挙げられる。
【００７９】
また、ポリエステル樹脂は、スチレン系やアクリル系樹脂に比して、トナー保存時の安定性を確保しつつ、より溶融粘度を低下させることが可能である。このようなポリエステル樹脂は、例えば、多価アルコールや多価フェノールなどとカルボン酸との重縮合反応によって得ることができる。
これら多価アルコールや多価フェノールなどとしては、ポリエチレングリコール、ジエチレングリコール、トリエチレングリコール、１，２−プロピレングリコール、１，３−プロピレングリコール、１，４−プロピレングリコール、ネオペンチルグリコール、１，４−ブテンジオールなどのジオール類、１，４−ビス（ヒドロキシメチル）シクロヘキサン、ビスフェノールＡ、水素添加ビスフェノールＡ、ポリオキシエチレン化ビスフェノールＡ、ポリオキシプロピレン化ビスフェノーＡなどのエーテル化ビスフェノール類、これらを炭素数３〜２２の飽和もしくは不飽和の炭化水素基で置換した二価のアルコール単位体、その他の二価のアルコール単位体、ソルビトール、１，２，３，６−ヘキサンテトロール、１，４−ソルビタン、ペンタエスリトールジペンタエスリトール、トリペンタエスリトール、蔗糖、１，２，４−ブタントリオール、１，２，５−ペンタントリオール、グリセロール、２−メチルプロパントリオール、２−メチル−１，２，４−ブタントリオール、トリメチロールエタン、トリメチロールプロパン、１，３，５−トリヒドロキシメチルベンゼン等の三価以上の単量体を挙げることができる。
【００８０】
また、ポリエステル樹脂を得るために用いられるカルボン酸としては、例えばパルミチン酸、ステアリン酸、オレイン酸等のモノカルボン酸、マレイン酸、フマール酸、メサコン酸、シトラコン酸、テレフタル酸、シクロヘキサンジカルボン酸、コハク酸、アジピン酸、セバチン酸、マロン酸、これらを炭素数３〜２２の飽和もしくは不飽和の炭化水素基で置換した２価の有機酸単量体、これらの酸の無水物、低級アルキルエステルとリノレイン酸からの二量体、１，２，４−ベンゼントリカルボン酸、１，２，５−ベンゼントリカルボン酸、２，５，７−ナフタレントリカルボン酸、１，２，４−ナフタレントリカルボン酸、１，２，４−ブタントリカルボン酸、１，２，５−ヘキサントリカルボン酸、１，３−ジカルボキシル−２−メチル−２−メチレンカルボキシプロパン、テトラ（メチレンカルボキシル）メタン、１，２，７，８−オクタンテトラカルボン酸エンボール三量体酸、これらの酸の無水物等の三価以上の多価カルボン酸単量体を挙げることができる。
【００８１】
エポキシ系樹脂としては、ビスフェノールＡとエポクロルヒドリンとの重縮合物等があり、例えば、エポミックＲ３６２、Ｒ３６４、Ｒ３６５、Ｒ３６６、Ｒ３６７、Ｒ３６９（以上三井石油化学工業（株）製）、エポトートＹＤ−０１１、ＹＤ−０１２、ＹＤ−０１４、ＹＤ−９０４、ＹＤ−０１７（以上東都化成（株）製）、エポコート１００２、１００４、１００７（以上シェル化学社製）等の市販のものが挙げられる。
【００８２】
本発明に使用される着色剤としては、カーボンブラック、ランプブラック、鉄黒、群青、ニグロシン染料、アニリンブルー、フタロシアニンブルー、ハンザイエローＧ、ローダミン６Ｇ、レーキ、カルコオイルブルー、クロムイエロー、キナクリドン、ベンジジンイエロー、ローズベンガル、トリアリルメタン系染料、モノアゾ系、ジスアゾ系、染顔料など、従来公知のいかなる染顔料をも単独あるいは混合して使用し得る。
【００８３】
また、トナーに磁性体を含有させて磁性トナーとすることも可能である。磁性体としては、鉄、コバルトなどの強磁性体、マグネタイト、ヘマタイト、Ｌｉ系フェライト、Ｍｎ−Ｚｎ系フェライト、Ｃｕ−Ｚｎ系フェライト、Ｎｉ−Ｚｎ系フェライト、Ｂａフェライトなどの微粉末が使用できる。
【００８４】
トナーの摩擦帯電性を十分に制御する目的で、いわゆる帯電制御剤、例えばモノアゾ染料の金属錯塩、ニトロフミン酸及びその塩、サリチル酸、ナフトエ塩、ジカルボン酸のＣｏ、Ｃｒ、Ｆｅ等の金属錯体、アミノ化合物、第４級アンモニウム化合物、有機染料などを含有させることができる。
【００８５】
さらにまた、本発明で用いるトナーには、必要に応じて離型剤を添加してもよい。
離型材料としては、低分子量ポリプロピレン、低分子量ポリエチレン、カルナウバワックス、マイクロクリスタリンワックス、ホホバワックス、ライスワックス、モンタン酸ワックス等を単独または混合して用いることができるが、これらに限定されるものではない。
【００８６】
トナーには、添加剤を添加することができる。良好な画像を得るためには、トナーに十分な流動性を付与することが肝要である。これには、一般に流動性向上材として疎水化された金属酸化物の微粒子や、滑剤などの微粒子を外添することが有効であり、金属酸化物、有機樹脂微粒子、金属石鹸などを添加剤として用いることが可能である。これら添加物の具体例としては、テフロン（Ｒ）、ステアリン酸亜鉛のごとき滑剤や、酸化セリウム、炭化ケイ素などの研磨剤；例えば表面を疎水化したＳｉＯ_２、ＴｉＯ_２等の無機酸化物などの流動性付与剤；ケーキング防止剤として知られるもの、および、それらの表面処理物などが挙げられる。トナーの流動性を上げるためには、特に、疎水性シリカが好ましく用いられる。
【００８７】
本発明で用いるトナーにおいて、その重量平均粒径Ｄｔは、９．０〜４．０μｍ、好ましくは８．５μｍ〜４．５μｍである。キャリアに対するトナーの割合は、キャリア１００重量部当り、トナー２〜２５重量部、好ましくは４〜１５重量部の割合である。
本発明において、キャリア、キャリア芯材及びトナーに関して言う重量平均粒径Ｄｗは、個数基準で測定された粒子の粒径分布（個数頻度と粒径との関係）に基づいて算出されたものである。この場合の重量平均粒径Ｄｗは、以下の式で表される。
Ｄｗ＝｛１／Σ（ｎＤ^３）｝×｛Σ（ｎＤ^４）｝
前記式中、Ｄは各チャネルに存在する粒子の代表粒径（μｍ）を示し、ｎは各チャネルに存在する粒子の総数を示す。
なお、チャネルとは、粒径分布図における粒径範囲を等分に分割するための長さを示すもので、本発明の場合には、２μｍの長さを採用した。また、各チャネルに存在する粒子の代表粒径としては、各チャネルに保存する粒子粒径の下限値を採用した。
粒径分布を測定するための粒度分析計としては、マイクロトラック粒度分析計（モデルＨＲＡ ９３２０−Ｘ１００：Ｈｏｎｅｗｅｌｌ社製）を用いた。
その測定条件は、以下の通りである。
（１）粒径範囲：１００〜８μｍ
（２）チャネル長さ（チャネル幅）：２μｍ
（３）チャネル数：４６
【００８８】
本発明の現像方法は、その現像剤として前記した現像剤を用いる。この場合、外部から印加する現像バイアスとして、直流電圧に交流電圧を重畳させた電圧を印加すると、画像濃度が高く、地汚れの少ない高画質を得ることができる。特に、ドット再現性、及びハイライトの再現性が良好となる。上記の現像バイアスを印加する場合、直流バイアスのみを印加する場合に比べて、実質的な現像ポテンシャル、及び地肌ポテンシャルが大きくなる。そのため、従来はキャリア付着が起こりやすかったが、本発明のキャリアによって、両立が可能となった。
【００８９】
【実施例】
以下、本発明を実施例及び比較例にて更に詳細に説明する。なお、本発明は、ここに例示される実施例及び比較例に限定されるものではない。
【００９０】
＜キャリア製造例＞
製造例１
シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）を希釈して、固形分５％のシリコーン樹脂溶液を得た。固形分に対して、３重量％のアミノシランカップリング剤 Ｈ_２Ｎ（ＣＨ_２）_３Ｓｉ（ＯＣ_２Ｈ_５）_３を添加し、流動床型コーティング装置を用いて、表１に示した性状を持つキャリア芯材粒子▲１▼（マグネタイト、１ＫＯｅの磁気モーメント７７ｅｍｕ／ｇ）５ｋｇの各粒子表面上に、上記のシリコーン樹脂溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．３８μｍ、真比重５．０ｇ／ｃｍ^３の比較用キャリアＡを得た。
【００９１】
製造例２
シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）を希釈して、固形分５％のシリコーン樹脂溶液を得た。流動床型コーティング装置を用いて、表１に示した性状を持つキャリア芯材粒子▲２▼（ＭｎＭｇＳｒ系フェライト、１ＫＯｅの磁気モーメント７７ｅｍｕ／ｇ）５ｋｇの各粒子表面上に、上記のシリコーン樹脂溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．３４μｍ、真比重５．０ｇ／ｃｍ^３の比較用キャリアＢを得た。
【００９２】
製造例３
表１の芯材粒子▲３▼（ＭｎＭｇＳｒ系フェライト、１ＫＯｅの磁気モーメント７４ｅｍｕ／ｇ）を使用する以外は、製造例２と全く同様にして、膜厚０．３２μｍ、真比重５．０ｇ／ｃｍ^３のキャリアＣを得た。
【００９３】
＜現像条件＞
実施例及び比較例においては、現像剤をループ状に循環する二成分現像剤用現像ユニット、具体的には、リコー製カラーレーザープリンタ（ＩＰＳｉＯ Ｃｏｌｏｒ８０００）用二成分現像ユニット（スリーブ径１８ｍｍ、汲み上げ量０．０７５ｇ／ｃｍ^２、ドクタギャップ０．７７５±０．０２ｍｍ）を用いて表２に示す現像条件１〜５にて評価を行った。
【００９４】
＜実施例及び比較例評価方法＞
上記Ａ〜Ｃのキャリアと現像条件１〜５の組み合わせにより、評価を行った。トナーは全てＩＰＳｉＯ Ｃｏｌｏｒ８０００用黒トナーを用い、リコー製カラーレーザープリンタ（ＩＰＳｉＯ Ｃｏｌｏｒ８０００）にて画像面積率１％の文字画像チャートで１０万枚のランニングを行い、地汚れ・トナー飛散を評価した。この時の結果を表３に示す。
なお、実施例１〜４及び比較例１〜４で使用したキャリアと現像条件の対応は、次の通りである。
実施例１・・・キャリアＡ＋現像条件４
実施例２・・・キャリアＡ＋現像条件３
実施例３・・・キャリアＡ＋現像条件２
実施例４・・・キャリアＡ＋現像条件１
比較例１・・・キャリアＡ＋現像条件５
比較例２・・・キャリアＢ＋現像条件１
比較例３・・・キャリアＣ＋現像条件１
比較例４・・・キャリアＣ＋現像条件５
【００９５】
地汚れ
地汚れ評価は、１０万枚ランニング後に、画像面積率６％の文字画像チャートで連続１０枚コピーし、地肌部における地汚れ発生の程度を地汚れランク１〜５までに位置付け、評価を行った。ランクが高い程地汚れが少なく、ランク５が最良である。市場で問題にならないレベルを４とし、これ以上のレベルを良好とした。
【００９６】
トナー飛散
トナー飛散評価は、１０万枚ランニング後に、プリンタ内のトナー飛散の程度をランク付け４段階で行い、◎を大変良好、○を良好、△を若干良好、×を不良とした。市場で問題にならないレベルを○とし、これ以上のレベルを良好とした。
【００９７】
＜帯電量分布評価＞
上記実施例１〜４及び比較例１〜４に対して、地汚れ・トナー飛散の評価とは別に帯電量分布の評価を行った。キャリアと現像条件の対応は、地汚れ・トナー飛散の評価時と全く同じである。トナーは全てＩＰＳｉＯ Ｃｏｌｏｒ８０００用黒トナーを用い、リコー製カラーレーザープリンタ（ＩＰＳｉＯ Ｃｏｌｏｒ８０００）にて、実施例１〜４及び比較例１〜４それぞれの現像条件に基づいてトナー補給と消費を行わずに１時間及び５時間攪拌後に、各現像剤を現像スリーブ軸方向前方側でサンプリングし、現像剤中のトナーの帯電量分布を測定し、正規分布関数による波形解析を行った。この時の結果を表３に示す。
【００９８】
【表１】

【００９９】
【表２】

【０１００】
【表３】

【０１０１】
【発明の効果】
以上説明したように、請求項１によれば、トナーとキャリアからなり、トナー濃度１〜１５％で調整された二成分現像剤を、像担持体上の静電潜像を現像する現像剤を保持する現像スリーブと、この現像スリーブの軸方向に沿って現像剤を混合・攪拌しながら搬送する、現像スリーブに遠い側に軸支された第１の現像剤攪拌部材、及び近い側に軸支された第２の現像剤攪拌部材と、これらの部材の間に設けられその両端に現像剤の連絡通路が確保された形の仕切り部材とを備えている現像ユニットを用いてループ状に循環しながら混合・攪拌する二成分現像方法において、該キャリアが磁性を有する芯材粒子と該粒子表面を被覆する樹脂層とからなる静電荷像現像用キャリアであって、該キャリアの重量平均粒径Ｄｗが２５〜４５μｍであり、該キャリア中の４４μｍよりも小さい粒径を有する粒子の含有割合が７０重量％以上で、６２μｍ以上の粒子が１重量％未満であり、２２μｍより小さい粒径を有する粒子の含有割合が７重量％以下であり、かつ、１ＫＯｅにおける磁気モーメントが７６ｅｍｕ／ｇ以上であり、該二成分現像剤をトナー補給と消費を行わず１時間攪拌後の現像剤中のトナーの帯電量分布を正規分布関数１波形で近似でき、この時の標準偏差が１．０［ｆＣ／１０μｍ］以下であることを特徴とする二成分現像方法により、現像装置を小型化でき、剤ストレスの大きい低画像面積のチャートを連続して画像形成した場合でも地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することができる。
【０１０２】
請求項２によれば、トナー補給と消費を行わず１時間攪拌した時の該二成分現像剤中のトナーの帯電量分布を正規分布関数で近似した時の標準偏差、攪拌装置ターブラミキサーの弱回転（２２ｒｐｍ）で１０分混合攪拌して作製された初期剤中のトナーの帯電量分布を正規分布関数で近似した時の標準偏差に対して＋０．２［ｆＣ／１０μｍ］以下の変化であることを特徴とする請求項１記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０３】
請求項３によれば、請求項２記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合が帯電量分布全体の０〜１０％であり、帯電量−７．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が帯電量分布全体の０〜５％であることを特徴とする請求項１または２記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０４】
請求項４によれば、請求項２記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合及び帯電量−７．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が共に帯電量分布全体の０〜５％であることを特徴とする請求項１から３のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０５】
請求項５によれば、請求項２記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合及び帯電量−７．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が共に帯電量分布全体の０〜１％であることを特徴とする請求項１から４のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０６】
請求項６によれば、トナー補給と消費を行わずさらに５時間まで攪拌後の該二成分現像剤中のトナーの帯電量分布を正規分布関数１波形で近似でき、この時の標準偏差が１．２［ｆＣ／１０μｍ］以下であることを特徴とする請求項１から５のいずれか１項に記載の二成分現像方法により、低画像面積のチャートを連続して長時間画像形成するような剤ストレスの大きい特殊なモードで画像形成した場合でも地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０７】
請求項７によれば、請求項６記載の該二成分現像剤中のトナーの帯電量分布において、トナー補給と消費を行わず５時間まで攪拌した時の現像剤中のトナーの帯電量分布を正規分布関数で近似した時の標準偏差が、攪拌装置ターブラミキサーの弱回転（２２ｒｐｍ）で１０分混合攪拌して作製された初期剤中のトナーの帯電量分布を正規分布関数で近似した時の標準偏差に対して＋０．４［ｆＣ／１０μｍ］以下の変化であることを特徴とする請求項１から６のいずれかに記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０８】
請求項８によれば、請求項６記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合及び帯電量−８．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が共に帯電量分布全体の０〜５％であることを特徴とする請求項１から７のいずれかに記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１０９】
請求項９によれば、請求項６記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合及び帯電量−８．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が共に帯電量分布全体の０〜３％であることを特徴とする請求項１から８のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１０】
請求項１０によれば、請求項６記載の該二成分現像剤中のトナーの帯電量分布において、帯電量−１．０［ｆＣ／１０μｍ］以下の弱帯電・逆帯電トナーの個数割合及び帯電量−８．０［ｆＣ／１０μｍ］以上の高帯電トナーの個数割合が共に帯電量分布全体の０〜１％であることを特徴とする請求項１から９のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１１】
請求項１１によれば、該キャリア中の２２μｍより小さい粒径を有する粒子の含有割合が、３重量％以下であることを特徴とする請求項１から１０のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１２】
請求項１２によれば、該キャリア中の２２μｍより小さい粒径を有する粒子の含有割合が、１重量％以下であることを特徴とする請求項１から１１のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１３】
請求項１３によれば、該キャリアの嵩密度が、２．２ｇ／ｃｍ^３以上であることを特徴とする請求項１から１２のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１４】
請求項１４によれば、該キャリアの抵抗（ＬｏｇＲ）が、１２Ωｃｍ以上であることを特徴とする請求項１から１３のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１５】
請求項１５によれば、該キャリアの芯材が、ＭｎＭｇＳｒ系フェライトであることを特徴とする請求項１から１４のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１６】
請求項１６によれば、該キャリアの芯材が、Ｍｎフェライトであることを特徴とする請求項１から１４のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１７】
請求項１７によれば、該キャリアの芯材が、マグネタイトであることを特徴とする請求項１から１４のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１８】
請求項１８によれば、該キャリアの被覆層が、シリコーン樹脂であることを特徴とする請求項１から１７のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１１９】
請求項１９によれば、該キャリアの樹脂層が、アミノシランカップリング剤を含有する樹脂からなることを特徴とする請求項１から１８のいずれか１項に記載の二成分現像方法により、地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像方法を提供することが可能となる。
【０１２０】
請求項２０によれば、少なくとも、磁性を有する芯材粒子と該粒子表面を被覆する樹脂層とからなる静電荷像現像用キャリアであって、該キャリアの重量平均粒径Ｄｗが２５〜４５μｍであり、該キャリア中の４４μｍよりも小さい粒径を有する粒子の含有割合が７０重量％以上で、６２μｍ以上の粒子が１重量％未満であり、２２μｍより小さい粒径を有する粒子の含有割合が７重量％以下であり、かつ、１ＫＯｅにおける磁気モーメントが７６ｅｍｕ／ｇ以上であるキャリアとトナーからなる二成分現像剤を、像担持体上の静電潜像を現像する現像剤を保持する現像スリーブと、この現像スリーブの軸方向に沿って現像剤を混合・攪拌しながら搬送する、現像スリーブに遠い側に軸支された第１の現像剤攪拌部材、及び近い側に軸支された第２の現像剤攪拌部材と、これらの部材の間に設けられその両端に現像剤の連絡通路が確保された形の仕切り部材とを備えている現像ユニットを用いてループ状に循環しながら混合・攪拌する請求項１から１９のいずれか１項に記載の二成分現像方法を用いた画像形成装置により、現像装置を小型化でき、剤ストレスの大きい低画像面積のチャートを連続して画像形成した場合でも地汚れ・トナー飛散の起こりにくい安定した画像が得られる静電荷像現像装置を提供することが可能となる。
【図面の簡単な説明】
【図１】本発明に使用する現像ユニットの１例の断面図である。
【図２】本発明に使用のキャリア芯材分級用超音波発振器付分級機の説明構造図である。
【図３】本発明に使用するキャリア電気抵抗測定用セルの斜視図である。
【図４】本発明の正規分布関数による帯電量分布の波形解析近似例の説明図である。
【符号の説明】
１ 現像スリーブ
２ 上部現像ケース
３ 下部現像ケース
４ 第１の現像剤攪拌部材
５ 第２の現像剤攪拌部材
６ 現像剤
７ 現像剤量規制手段（ドクタブレード）
８ 仕切り部材
１１ セル
１２ａ 平行平板電極
１２ｂ 平行平板電極
１３ キャリア
１５ 振動ふるい機
１６ 円筒容器
１７ スプリング
１８ ベース
１９ 金網
２０ 共振リング
２１ ケーブル
２２ コンバータ（振動子）
２３ リング状フレーム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-component developing method used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus using the two-component developing method.
[0002]
[Prior art]
In recent years, an image forming apparatus using an electrophotographic method has been rapidly colorized, and the speed has been increased. Conventionally, the two-component developing method is suitable for high-speed printing, and has been widely used in full-color image forming apparatuses because non-magnetic toner is easy to handle. However, the full-color image forming apparatus needs to have a plurality of developing devices in the apparatus, and there are drawbacks such as an increase in size and weight of the apparatus and an increase in cost compared to a monochrome machine.
[0003]
In particular, the two-component developing device must be equipped with a developer storage volume and a stirring mechanism in addition to the toner as compared with the one-component developing device. To reduce the size of the developing unit, the amount of the developer is reduced. Was essential.
[0004]
As a development unit corresponding to this, a development sleeve for supplying toner for developing an electrostatic latent image on a photosensitive drum as an image carrier, and two-component development along the axial direction of the development sleeve have been conventionally used. The developer is conveyed while being mixed and stirred, and includes a first developer stirring member pivotally supported on the side far from the developing sleeve, and a second developer stirring member pivotally supported on the near side. A developing unit configured to circulate the agent in a loop is used.
[0005]
On the other hand, as a developer, use of a carrier having a small particle diameter has been proposed. For example, a two-component developer having toner and a magnetic carrier is carried on a developer carrying member and conveyed to a developing unit, and a magnetic brush of the two-component developer is formed on the developer carrying member at the developing unit, In the developing method of developing the electrostatic latent image on the latent image carrier by bringing the magnetic brush into contact with the latent image carrier, the weight average particle diameter of the toner is 1 to 6 μm, and the number average particle diameter of the magnetic carrier is The saturation magnetization in a magnetic field of 100,000 Oersted is 170 to 250 emu / cm.³, And residual magnetization is 25 to 70 emu / cm³There has been proposed a developing method in which the developer carrying member has a cylindrical non-magnetic sleeve and a rotationally driven magnet contained in the sleeve (see Patent Document 1).
[0006]
Further, in the carrier for developing an electrostatic latent image in which magnetic powder is dispersed in a binder resin, the average particle size is 30 to 80 μm, and the following relational expression:
(X)²/ Σ²≧ 9.0
x: average particle diameter, σ²: Dispersion of particle size distribution
An electrostatic latent image developing carrier that satisfies the above has been proposed (see Patent Document 2).
[0007]
When this small particle size carrier is used, the following advantages are obtained.
(1) Since the surface area is large, sufficient frictional charging can be given to each toner, and the generation of low charge amount toner and reversely charged toner is reduced. As a result, scumming and toner scattering are less likely to occur, and the toner around the dots is free from dust and bleeding, and dot reproducibility is improved.
(2) Since the surface area is large and scumming and toner scattering are less likely to occur, the average charge amount of the toner can be reduced, and a sufficient image density can be obtained. Therefore, the small particle size carrier can make up for problems in using the small particle size toner, and is particularly effective in drawing out the advantages of the small particle size toner.
(3) The small particle size carrier is characterized in that it forms a dense magnetic brush and the flowability of the ears is good, so that the traces of the ears are hardly generated in the image.
As described above, the use of a small particle size carrier is effective for scumming and toner scattering, but the conventional small particle size carrier has a very big problem that carrier adhesion is likely to occur. Since it was a cause of roller scratches, it was difficult to put it to practical use.
[0008]
On the other hand, of the background dirt / toner scattering which has been a problem, the background dirt is as follows.
In the case of a two-component developer, a large amount of toner sufficient for solid development once contacts the surface of the photoreceptor in the development nip, and finally remains on the photoreceptor due to the direction and magnitude of the Coulomb force generated by the development electric field. Or return to the carrier side. If the development electric field is constant, the direction and magnitude of the Coulomb force is determined by the charge amount of the toner particles. However, since the charge amount of the toner particles actually has a distribution, the toner particles behave differently.
A developing bias is applied to the developing nip in order to reduce background contamination, and a relatively large Coulomb force that returns to the carrier side acts on many normally charged toners existing on the background in the developing nip. Therefore, background dirt is suppressed. However, for a small amount of reversely charged toner (toner having a charge opposite to the charge polarity) present in the developer, the Coulomb force acts in the direction of adhering to the photoreceptor side, so the reversely charged toner adheres to the background. Resulting in.
[0009]
In addition, weakly charged toner (toner with a very small amount of charged charge) has a small Coulomb force on the carrier side, and therefore tends to remain on the background without returning to the carrier side.
Therefore, the background stain on the electrophotographic photosensitive member is mainly caused by adhesion of the reversely charged toner and the weakly charged toner contained in the developer to the background portion. It has been considered that the cause is an increase in reversely charged toner and weakly charged toner due to insufficient stirring.
[0010]
As for toner scattering, reversely charged toner and weakly charged toner are generated and these toners are scattered by the centrifugal force formed by the rotation of the developing sleeve, etc., so that a good image free from background contamination and toner scattering can be obtained. For this purpose, it is necessary not to generate the reversely charged toner and the weakly charged toner.
[0011]
Accordingly, several methods have been disclosed as methods for reducing the reversely charged toner and the ratio of the reversely charged toner in the developer. As one of them, the toner contains at least one fluorine-containing quaternary ammonium salt compound and fluorine-containing iminium compound, and the carrier covers an inner resin layer and an inner resin layer containing a resistance control agent that covers the surface of the carrier core particles. Component for electrostatic latent image, which is a two-layer coated carrier having an inner resin layer thickness of 0.5 to 1.0 μm and a surface resin layer thickness of 0.1 to 0.5 μm By using a developer, a method has been proposed in which a charge amount distribution is sharp and uniform over a long period of time, and a stable image reproduction is possible even during continuous use or environmental changes (see Patent Document 3).
[0012]
Further, the resistance value R of the developer at an electric field strength of 500 V / cm.₅₀₀[Ω · cm] and resistance value R at an electric field strength of 2500 V / cm₂₅₀₀From [Ω · cm], Y = log (R₅₀₀) / Log (R₂₅₀₀) And the ratio X of the total amount of uncharged toner smaller than 0.2 [femt · C / μm] in the toner charge amount / particle size ratio satisfies Y> 3X / 400 + 1. Thus, there has been proposed an electrophotographic developer that can reliably prevent bleeding of an image such as front-drawing or post-drawing while maintaining a high image density (see Patent Document 4).
[0013]
Recently, however, small particle size toners have been developed for high image quality, toners with low softening points for low temperature fixing due to energy savings, and small particle size carriers have been developed. I can't do it. Further, the techniques disclosed so far have not been clarified with respect to the relationship between the charge amount distribution and the background contamination or toner scattering.
[0014]
[Patent Document 1]
JP 2000-137352 A
[Patent Document 2]
Japanese Patent Laid-Open No. 7-43951
[Patent Document 3]
JP-A-8-146663
[Patent Document 4]
JP-A-8-129268
[0015]
[Problems to be solved by the invention]
As described above, in the above prior art, a small particle size toner for high image quality, a toner with a low softening point for low temperature fixing, and a small particle size carrier have been developed. However, the technology disclosed so far has a problem that the relationship between the charge amount distribution and the background contamination or toner scattering is not clarified.
[0016]
Accordingly, the present invention has been made to solve the above problems, and includes a small particle size carrier having a specific particle size distribution, a developing sleeve, and first and second developer stirring members, and a developer. By using a development unit that is conveyed while mixing and stirring so that the toner circulates in a loop, the development device can be downsized, and even when images of low image area charts with high agent stress are continuously formed, the background is stained. An object of the present invention is to provide a two-component developing method capable of obtaining a stable image in which toner scattering hardly occurs and an image forming apparatus using the two-component developing method.
[0017]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, according to the first aspect of the present invention, a two-component developer comprising a toner and a carrier and adjusted at a toner concentration of 1 to 15% is developed, and an electrostatic latent image on the image carrier is developed. A developing sleeve that holds the developer to be conveyed, a first developer agitating member that is axially supported on the side far from the developing sleeve and that conveys the developer while being mixed and agitated along the axial direction of the developing sleeve; Loop using a developing unit comprising: a second developer agitating member pivotally supported on the side; and a partition member provided between these members and having a developer communication path secured at both ends thereof In a two-component development method in which mixing and stirring are performed while circulating in a state, the carrier is an electrostatic charge image developing carrier comprising magnetic core material particles and a resin layer covering the particle surface, the weight of the carrier Average particle diameter Dw is 25- The content ratio of particles having a particle diameter of 5 μm and smaller than 44 μm in the carrier is 70% by weight or more, the particle content of 62 μm or more is less than 1% by weight, and the content ratio of particles having a particle diameter of less than 22 μm Is 7% by weight or less, and the magnetic moment at 1 KOe is 76 emu / g or more. The toner charge amount distribution in the developer after stirring for 1 hour without supplying and consuming the two-component developer is shown. The two-component development method, which can be approximated by one waveform of a normal distribution function and the standard deviation at this time is 1.0 [fC / 10 μm] or less, is the main feature.
[0018]
According to the second aspect of the present invention, the standard deviation when the charge amount distribution of the toner in the two-component developer is approximated by a normal distribution function when the toner is stirred for 1 hour without replenishing and consuming toner, Change of +0.2 [fC / 10 μm] or less with respect to the standard deviation when the charge amount distribution of the toner in the initial agent prepared by mixing and stirring for 10 minutes at a low rotation (22 rpm) is approximated by a normal distribution function The two-component developing method according to claim 1 is a main feature.
[0019]
In the invention according to claim 3, in the charge amount distribution of the toner in the two-component developer according to claim 2, the number ratio of the weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less is obtained. 3. The number ratio of highly charged toner having a charge amount of −7.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution, and is 0 to 5% of the entire charge amount distribution. The two-component development method is the main feature.
[0020]
In the invention according to claim 4, in the charge amount distribution of the toner in the two-component developer according to claim 2, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less, and 4. The two-component developing method according to claim 1, wherein the number ratio of highly charged toners having a charge amount of −7.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution. Main features.
[0021]
In the invention according to claim 5, in the charge amount distribution of the toner in the two-component developer according to claim 2, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less, and 5. The two-component developing method according to claim 1, wherein the number ratio of highly charged toners having a charge amount of −7.0 [fC / 10 μm] or more is 0 to 1% of the entire charge amount distribution. Main features.
[0022]
According to the sixth aspect of the present invention, the toner charge amount distribution in the two-component developer after stirring for up to 5 hours without toner replenishment and consumption can be approximated by a normal distribution function 1 waveform, and the standard deviation at this time is 6. The two-component developing method according to claim 1, wherein the two-component developing method is 1.2 [fC / 10 μm] or less.
[0023]
According to the seventh aspect of the present invention, in the charge amount distribution of the toner in the two-component developer according to the sixth aspect, the charge amount distribution of the toner in the developer when stirring for up to 5 hours without toner replenishment and consumption. The standard deviation when approximating with the normal distribution function approximated the charge distribution of the toner in the initial agent prepared by mixing and stirring for 10 minutes at a low rotation (22 rpm) of the stirrer Turbula mixer with the normal distribution function. The two-component developing method according to any one of claims 1 to 6, which is a change of +0.4 [fC / 10 μm] or less with respect to a standard deviation of time, is a main feature.
[0024]
In the invention according to claim 8, in the charge amount distribution of the toner in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less, and The two-component development method according to any one of claims 1 to 7, wherein the ratio of the number of highly charged toners having a charge amount of -8.0 [fC / 10 µm] or more is 0 to 5% of the entire charge amount distribution. Features.
[0025]
In the invention according to claim 9, in the toner charge amount distribution in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less, and 9. The two-component developing method according to claim 1, wherein the number ratio of highly charged toners having a charge amount of −8.0 [fC / 10 μm] or more is 0 to 3% of the entire charge amount distribution. Main features.
[0026]
In the tenth aspect of the present invention, in the charge amount distribution of the toner in the two-component developer according to the sixth aspect, the number ratio of the weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and 10. The two-component developing method according to claim 1, wherein the ratio of the number of highly charged toners having a charge amount of −8.0 [fC / 10 μm] or more is 0 to 1% of the entire charge amount distribution. Main features.
[0027]
The invention according to claim 11 is characterized in that the content ratio of particles having a particle size of less than 22 μm in the carrier is 3% by weight or less, and the two-component developing method according to any one of claims 1 to 10 is mainly used. Features.
[0028]
The invention according to claim 12 is characterized in that the content ratio of particles having a particle size of less than 22 μm in the carrier is 1% by weight or less, and the two-component developing method according to any one of claims 1 to 11 is mainly used. Features.
[0029]
In the invention according to claim 13, the bulk density of the carrier is 2.2 g / cm.³The main feature is the two-component developing method according to any one of claims 1 to 12.
[0030]
The invention according to claim 14 is characterized in that the resistance (LogR) of the carrier is 12 Ωcm or more, and the two-component developing method according to any one of claims 1 to 13 is a main feature.
[0031]
The invention according to claim 15 is characterized in that the two-component development method according to any one of claims 1 to 14 is characterized in that the core material of the carrier is MnMgSr ferrite.
[0032]
The invention according to claim 16 is characterized by the two-component developing method according to any one of claims 1 to 14, wherein the core material of the carrier is Mn ferrite.
[0033]
The invention according to claim 17 is characterized in that the two-component development method according to any one of claims 1 to 14 is characterized in that the core material of the carrier is magnetite.
[0034]
The invention according to claim 18 is characterized in that the two-component developing method according to any one of claims 1 to 17 is characterized in that the coating layer of the carrier is a silicone resin.
[0035]
According to the nineteenth aspect of the present invention, the two-component developing method according to any one of the first to eighteenth aspects is mainly characterized in that the resin layer of the carrier is made of a resin containing an aminosilane coupling agent.
[0036]
The invention according to claim 20 is an electrostatic charge image developing carrier comprising at least magnetic core material particles and a resin layer covering the particle surface, and the carrier has a weight average particle diameter Dw of 25 to 45 μm. The content ratio of particles having a particle size smaller than 44 μm in the carrier is 70% by weight or more, the particle content of 62 μm or more is less than 1% by weight, and the content ratio of particles having a particle size of less than 22 μm is A developing sleeve for holding a developer for developing an electrostatic latent image on an image carrier, a two-component developer composed of a carrier and a toner having a magnetic moment of 7 wt% or less and a magnetic moment at 1 KOe of 76 emu / g or more A first developer agitating member that is axially supported on the side far from the developing sleeve, and that is axially supported on the near side for conveying the developer while mixing and stirring along the axial direction of the developing sleeve. The developer is circulated in a loop using a developing unit provided with the second developer agitating member and a partition member provided between these members and having a developer communication path secured at both ends thereof. An image forming apparatus using the two-component developing method according to any one of claims 1 to 19 which is mixed and stirred while being a main feature.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve the above-described problems of the prior art, in the present invention, a two-component developer developing unit that circulates the developer in a loop shape is used as shown in FIG. Specifically, a two-component development unit (sleeve diameter 18 mm, sleeve linear velocity 275.65 mm / sec, pumping amount 0.075 g / cm for Ricoh color laser printer (IPSiO Color 8000)²And a doctor gap (0.775 ± 0.02 mm).
The toner and carrier are adjusted to a predetermined toner concentration, put in a cylindrical container, mixed and stirred for 10 minutes at a low rotation (22 rpm) of a stirrer tumbler mixer to produce a two-component developer. The amount of charge distribution over time was measured at a total count of 3000 using a toner particle charge amount distribution measuring apparatus (E-Spart Analyzer MODEL EST-III, manufactured by Hosokawa Micron Corporation).
At this time, when we looked at the time transition of the charge distribution for the toner that causes scumming and toner scattering and the toner that hardly squeezes, analysis of the normal distribution function revealed that the time for the charge distribution of the toner that hardly causes scumming and toner scattering. The conditions for the transition became clear.
[0038]
Hereinafter, a method for analyzing the charge amount distribution using the normal distribution function will be described.
First, the toner charge amount distribution measuring apparatus (E-Spart Analyzer MODEL EST-III, manufactured by Hosokawa Micron Corporation) using a laser Doppler velocimeter is used to measure the toner charge amount distribution in the developer as a total count of 3000. A normal distribution function is approximated to the charge amount distribution obtained above. Here, the normal distribution function expression is as follows.
[0039]
[Expression 1]

[0040]
The normal distribution function is a bilaterally symmetric distribution that becomes maximum when x = μ, and the distribution width is determined by the value of the standard deviation σ. As σ increases, the distribution width increases and the peak value decreases. The normal distribution function is always positive, f (x) = 0 when x → ∞, and f (x) = 0 even when x → −∞. When this normal distribution function is integrated between −∞ and ∞, it becomes 1. Therefore, in order to actually approximate the charge amount distribution with this normal distribution function, it is necessary to multiply the normal distribution function by an integer multiple α.
[0041]
Both the toner that causes scumming and toner scattering, and the toner that hardly scatters, have a normal charge amount distribution with almost no weakly charged toner or reversely charged toner that causes scumming or toner scattering immediately after the unit is inserted (= initial state). The distribution can be approximated by a normal distribution function 1 waveform, and the profile is sharp.
[0042]
However, the charge distribution of the toner in the agent over time, such as stirring the agent charged in the unit without replenishing and consuming the toner, depends on the occurrence of weakly charged toner and reversely charged toner and the change in average value and standard deviation. A difference occurs in the charge amount distribution. The charge distribution of good toner, which is less likely to cause scumming and toner scattering, changes in the average value and standard deviation, but the change is small, the occurrence of reversely charged toner and weakly charged toner is slight, and the unit is charged even over time Similar to the agent immediately after, it can be expressed by a normal distribution function 1 waveform. On the other hand, in the toner charge amount distribution in which scumming or toner scattering occurs, the average value and the standard deviation vary greatly, and there are many occurrences of reversely charged toner and weakly charged toner. It cannot be approximated by a waveform.
[0043]
However, if the toner charge amount distribution can be approximated by a normal distribution function 1 waveform, it does not mean that the background stain and toner scattering do not occur. Generally, when the toner charge amount distribution profile is sharp, there are many toners having the same charge amount q / d, and contact charging between the carrier and the toner is performed uniformly, and weakly charged toner is generated. Hard to do. On the contrary, if the toner charge amount distribution profile is broad, the range of toner charge amount q / d is widened, and high charge amount toner is not separated from the carrier, so contact charging between the carrier and the toner is performed uniformly. However, the increase in low charge amount toner proceeds.
[0044]
As a result, the amount of weakly charged toner is increased, and background contamination and toner scattering are likely to occur. Therefore, in order not to cause scumming or toner scattering, it is not sufficient that the toner charge amount distribution can be approximated by a normal distribution function 1 waveform. The sharpness of the profile of the distribution, that is, standard deviation, weakly charged toner It is necessary to specify the amount, the amount of highly charged toner, and the like.
[0045]
There is a difference in the charge distribution of the toner in the agent over time when stirring is performed without replenishing and consuming the toner, in the developer charge distribution of the developer that causes scumming and toner scattering. It became apparent by analysis with a normal distribution function.
[0046]
As a result of intensive research by the above method, the present inventors have investigated the change in the charge distribution of the toner in the agent over time when the toner is stirred without being replenished and consumed without actually running. Thus, it has been found that the difference can be clarified between a developer having a toner that causes scumming and toner scattering and a developer having a toner that hardly causes scumming and toner scattering.
[0047]
In particular, for a developer having toner that causes scumming and toner scattering during normal running, it can be clarified by examining the toner charge amount distribution after stirring for 1 hour without toner replenishment and consumption. For a developer having a toner in which scumming or toner scattering occurs for the first time in a special mode with a large agent stress that continuously forms an image area chart for a long time, the agent after stirring for up to 5 hours It was found that this can be clarified by examining the charge amount distribution of the medium toner.
[0048]
Accordingly, the present invention has the following configuration in order to achieve the above object.
An example of the developing unit of the present invention is shown in FIG. FIG. 1 shows a sectional view of the developing unit. The developing unit of the present invention generally mixes and agitates a developing sleeve 1 that supplies toner for developing an electrostatic latent image on an image carrier, and a two-component developer along the axial direction of the developing sleeve. The two developer agitating members and the developer regulating means (doctor blade 7), the upper developing case 2 and the lower developing case 3 are conveyed. A first developer agitating member 4 is pivotally supported on the side far from the developing sleeve 1, and a second developer agitating member 5 is pivotally supported on the near side, and the first developer agitating member 4 and the second developer agitating member 4 are supported. A partition member 8 is provided between the developer agitating member 5. A developer communication path is secured on both sides of the partition member 8 in the width direction, and the developer is circulated in a loop.
[0049]
The developer transport state will be described with reference to FIG. 1. The developer is transported from the front side to the back side in the chamber where the first developer agitating member is located, and the second development is performed from the communication path on the back side. After the second developer agitating member is conveyed from the back side to the front side of the paper, the first developer agitating member is conveyed from the communication path on the front side of the paper. It is transported to a certain room.
[0050]
Further, in FIG. 1, the space on the left side of the developer regulating means (doctor blade) 7 is eliminated, and the developer pumped up from the chamber with the second developer agitating member stays and charging does not rise. Means for preventing this may be provided.
[0051]
The carrier used in the present invention comprises magnetic core particles and a resin layer covering the surface. In the carrier of the present invention, the weight average particle diameter Dw is in the range of 25 μm to 45 μm, preferably 30 μm to 45 μm. When the weight average particle diameter Dw is larger than the above range, carrier adhesion hardly occurs. However, when the toner concentration is increased in order to obtain a high image density, scumming increases rapidly. In addition, when the dot diameter of the latent image is small, the variation in the dot diameter increases. The carrier adhesion indicates a phenomenon that the carrier adheres to the image portion or the background portion of the electrostatic latent image. The stronger each electric field, the easier the carrier adheres. Since the electric field is weakened by developing toner in the image area, carrier adhesion is less likely to occur compared to the background area. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller. Furthermore, in the carrier of the present invention, the content ratio of particles having a particle size smaller than 44 μm is 70% by weight or more, preferably 75% by weight or more.
[0052]
Carrier particles of 62 μm or more are less than 3% by weight, preferably less than 1% by weight. As the content of particles of 62 μm or more increases, the variation in dot diameter increases. This is probably because a slight difference in the weight of carriers of 62 μm or more has a great influence on the carrier weight% in the range of 44 μm to 62 μm.
[0053]
The content of carrier particles having a particle size of less than 22 μm is 7% by weight or less, preferably 3% by weight or less, and more preferably 1% by weight or less. In the case of a small particle size carrier, most of the carrier adhering to the carrier is a fine particle of less than 22 μm.
The present inventors evaluated carrier adhesion in a small particle size carrier having a weight average particle size Dw of 25 μm to 45 μm by changing the weight ratio of particles smaller than 22 μm. As a result, 7 particles having a particle size of 22 μm or less were observed. It has been found that there is no major problem if it is less than or equal to% by weight, but carrier adhesion is further improved if it is made 3% by weight and further 1% by weight.
At the same time, it was also found that carrier adhesion does not substantially occur when the magnetic moment at 1 KOe is 76 emu / g or more.
[0054]
The carrier of the present invention is obtained by pulverizing a magnetic material, classifying the pulverized particles so as to obtain a predetermined particle size, and forming a resin film on the surface of the core material particles obtained by the classification. Can do. The classification includes wind classification, sieve classification (sieving), and the like. Vibrating sieves are preferably used for the production of carrier core particles. However, in the case of conventional vibrating sieves, when trying to classify particles with a small particle size, the meshes with small sieves (wire meshes) are used. However, the workability for the classification was very bad.
[0055]
The inventors of the present invention have made various studies in order to develop a method capable of efficiently and sharply cutting small-sized particles. When the particles are classified using a sieving machine, ultrasonic vibration is applied to the wire mesh. Thus, it has been found that small particle diameter particles of less than 22 μm can be efficiently and sharply cut.
[0056]
The ultrasonic vibration that vibrates the wire mesh can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. The converter in this case consists of a PZT vibrator. In order to vibrate the wire mesh by ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to a resonance member fixed to the wire mesh. The resonance member to which the ultrasonic vibration is transmitted resonates by the ultrasonic vibration, and vibrates the metal mesh fixed to the resonance member. The frequency for vibrating the wire mesh is 20 to 50 kHz, preferably 30 to 40 kHz. The shape of the resonance member may be any shape suitable for vibrating the wire mesh, and is usually a ring shape. The vibration direction for vibrating the wire mesh is preferably a vertical direction.
[0057]
FIG. 2 is a structural diagram of a vibration sieve machine with an ultrasonic oscillator. In FIG. 2, 15 is a vibrating screen, 16 is a cylindrical container, 17 is a spring, 18 is a base (support), 19 is a wire mesh, 20 is a resonant ring, 21 is a high-frequency current cable, 22 is a converter, and 23 is a ring. Indicates a frame. In order to operate the vibration sieving machine with an ultrasonic oscillator (circular sieving machine) shown in FIG. 2, a high frequency current is supplied to the converter 22 via the cable 21. The high frequency current supplied to the converter 22 is converted into ultrasonic vibration. The ultrasonic vibration generated in the converter 22 vibrates the resonant ring 20 to which the converter 22 is fixed and the ring-shaped frame 23 connected thereto in the vertical direction. Due to the vibration of the resonance ring 20, the metal mesh 19 fixed to the resonance ring 20 and the frame 23 vibrates in the vertical direction. The vibration sieve machine with an ultrasonic oscillator is commercially available, and can be obtained as, for example, the product name “Ultrasonic” from Sakae Sangyo Co., Ltd.
[0058]
The carrier of the present invention can also be produced by forming a resin film on the surface of pulverized particles of magnetic material to form resin-coated particles, and then classifying the resin-coated particles. In this case, the classification of the resin-coated particles is preferably performed using the above-described vibration sieving machine with an ultrasonic oscillator.
[0059]
As the material for the core particles constituting the carrier of the present invention, various conventionally known magnetic materials are used. In the carrier core particles used in the present invention, the magnetic moment when a magnetic field of 1000 oersted (Oe) is applied is 70 emu / g or more, preferably 76 emu / g or more. The upper limit is not particularly limited, but is usually about 150 emu / g. If the magnetic moment of the carrier core particles is smaller than the above range, carrier adhesion tends to occur, which is not preferable.
[0060]
The magnetic moment can be measured as follows.
A BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.) is used, and 1.0 g of carrier core particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersted. After gradually reducing the magnetic field to zero, the magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated and the magnetic moment of 1000 oersted is calculated from the figure.
[0061]
Examples of the core particles that are 70 emu / g or more when a 1000 oersted magnetic field used in the carrier of the present invention is applied include, for example, ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn- Examples thereof include Zn-based ferrite, Cu—Zn-based ferrite, Ni—Zn-based ferrite, Ba-based ferrite, and Mn-based ferrite.
Ferrite is a sintered body generally represented by the following formula.
(MO)_x(NO)_y(Fe₂O₃)_z
However, x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., and monovalent, divalent metal oxide and trivalent iron oxide. And consists of a complete mixture.
In the present invention, the core particles having a magnetic moment of 76 emu / g or more when a magnetic field of 1000 oersted is more preferably used are, for example, iron-based, magnetite-based, Mn-Mg-Sr-based ferrite, Mn-based ferrite. Etc.
[0062]
The bulk density of the carrier is 2.2 g / cm³Or more, more preferably 2.3 g / cm³The above is advantageous in preventing carrier adhesion. A core material having a low bulk density is porous or has large surface irregularities. If the bulk density is small, even if the magnetic moment (emu / g) of 1 KOe is large, the value of the substantial magnetic moment per particle is small, which is disadvantageous for carrier adhesion. Also, if the unevenness is large, the thickness of the coating resin varies depending on the location, and the charge amount and the resistance are likely to be non-uniform, affecting the durability over time and the carrier adhesion.
[0063]
In the carrier of the present invention, the resistance (LogR) is 12.0 Ωcm or more, more preferably 13.0 Ωcm or more. When the resistance of the carrier is lower than the above range, when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charges are induced in the carrier and carrier adhesion is likely to occur. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. In general, a color toner developing carrier is generally used with a low resistance in order to obtain a sufficient toner adhesion amount. It has been found that a sufficient image density can be obtained by using a carrier having the above resistance range under an appropriate toner charge amount.
[0064]
The carrier resistivity can be measured by the following method.
As shown in FIG. 3, a cell 11 made of a fluororesin container containing electrodes 12a and 12b having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier 13, and a DC voltage of 100 V is applied between both electrodes, DC resistance is measured with a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Co., Ltd.), and an electrical resistivity LogR (Ωcm) is calculated.
[0065]
The low efficiency of the carrier can be adjusted by adjusting the resistance of the coating resin on the core particles and controlling the film thickness. Moreover, it is also possible to add to the conductive fine powder coating resin layer and use it for carrier resistance adjustment. Examples of the conductive fine powder include conductive metals such as ZnO and Al, metal oxide powders, and SnO prepared by various methods.₂Or SnO doped with various elements₂TiB₂ZnB₂, MoB₂And boric compounds such as silicon carbide, polyacetylene, polyparaphenylene, poly (para-phenylene sulfide) polypyrrole and the like, and carbon black such as furnace black, acetylene black, and channel black.
[0066]
These conductive fine powders can be obtained by the following methods: a dispersing machine using a medium such as a ball mill or a bead mill after the conductive fine powder is put into a solvent used for coating or a resin solution for coating, or a blade rotating at high speed. Can be uniformly dispersed.
[0067]
The carrier of the present invention is produced by forming a resin layer on the surface of the core material particles. As the resin for forming the resin layer, various conventionally known resins used for carrier production can be used.
In the present invention, a silicone resin containing at least one of three structural units represented by the following formula as a repeating unit can also be preferably used.
[0068]
[Chemical 1]

[0069]
R in the above formula¹Is a hydrogen atom, halogen atom, hydroxy group, alkoxy group (methoxy group, ethoxy group, propoxy group, butoxy group, etc.), lower alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, propyl group, butyl group, etc.) Or an aryl group (phenyl group, tolyl group, etc.), and R²Represents an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group). These alkoxy groups, lower alkyl groups, aryl groups, alkylene groups, and arylene groups may have their hydrogen atoms replaced by other groups (halogen atoms, hydroxy groups, alkoxy groups, aryl groups, etc.).
[0070]
In the present invention, a straight silicone resin can be used. Examples thereof include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone).
[0071]
In the present invention, a modified silicone resin can be used. Examples of such materials include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone. Specific examples of the modified silicone include epoxy modified product: ES-1001N, acrylic modified silicone: KR-5208, polyester modified product: KR-5203, alkyd modified product: KR-206, urethane modified product: KR-305 (above, Shin-Etsu Chemical Co., Ltd.), epoxy modified product: SR2115, alkyd modified product: SR2110 (Toray Dow Corning Silicone), and the like.
[0072]
The silicone resin that can be used in the present invention can contain an appropriate amount (0.001 to 30% by weight) of an aminosilane coupling agent. Examples of such a silicone resin include the following.

[0073]
Furthermore, in the present invention, as the resin for coating the surface of the carrier core particles, the following can be used alone or mixed with the above silicone resin.
Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer) Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer, etc.) Styrenic resins such as styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.
[0074]
As a method for forming the resin layer on the surface of the carrier core particles, a known method such as a spray drying method, a dipping method, or a powder coating method can be used. In particular, the method using a fluidized bed type coating apparatus is effective for forming a uniform coating film.
[0075]
The thickness of the resin layer formed on the surface of the carrier core material particles is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. Since the thickness of the resin layer is extremely small, the particle size distributions of the carrier made of core material particles covering the resin layer and the carrier core material particles are substantially the same.
[0076]
The carrier of the present invention can be a so-called resin dispersion carrier having a form in which magnetic powder is dispersed in a known resin such as a phenol resin, an acrylic resin, or a polyester resin.
[0077]
The developer of the present invention comprises the carrier and toner.
The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent and the like in a binder resin mainly composed of a thermoreversible resin. Toner can be used. This toner can be an amorphous or spherical toner produced by various toner production methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.
[0078]
As the binder resin for the toner, the following can be used alone or in combination.
Styrene binder resins such as polystyrene, polyvinyltoluene and other styrene and substituted homopolymers, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-acrylic Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer , Styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Coalescence, styrene-malein Copolymers, Styrene copolymers such as styrene-maleic acid ester copolymers; As acrylic binders, polymethyl methacrylate and polybutyl methacrylate can be mentioned, as well as polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, Polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. It is done.
[0079]
In addition, the polyester resin can further reduce the melt viscosity while ensuring the stability during storage of the toner, as compared with the styrene or acrylic resin. Such a polyester resin can be obtained, for example, by a polycondensation reaction between a polyhydric alcohol or a polyhydric phenol and a carboxylic acid.
Examples of these polyhydric alcohols and polyhydric phenols include polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4- Diols such as butenediol, etherified bisphenols such as 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, etc. Divalent alcohol units substituted with 3-22 saturated or unsaturated hydrocarbon groups, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan , Bae Taesitol dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2 , 4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and other trivalent or higher monomers.
[0080]
Examples of the carboxylic acid used to obtain the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, and succinic acid. Acids, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters and Dimer from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl 2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, anhydrides of these acids, etc. The body can be mentioned.
[0081]
Epoxy resins include polycondensates of bisphenol A and epochrohydrin. For example, Epomic R362, R364, R365, R366, R367, R369 (manufactured by Mitsui Petrochemical Co., Ltd.), Epoto YD Commercially available products such as −011, YD-012, YD-014, YD-904, YD-017 (manufactured by Tohto Kasei Co., Ltd.), Epocoat 1002, 1004, 1007 (manufactured by Shell Chemical Co., Ltd.), and the like.
[0082]
Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G, lake, calco oil blue, chrome yellow, quinacridone, and benzidine. Any conventionally known dyes such as yellow, rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in combination.
[0083]
It is also possible to make a magnetic toner by adding a magnetic material to the toner. As the magnetic substance, ferromagnetic powders such as iron and cobalt, fine powders such as magnetite, hematite, Li ferrite, Mn—Zn ferrite, Cu—Zn ferrite, Ni—Zn ferrite and Ba ferrite can be used.
[0084]
For the purpose of sufficiently controlling the triboelectric chargeability of the toner, so-called charge control agents such as metal complexes of monoazo dyes, nitrohumic acid and salts thereof, salicylic acid, naphthoic salts, metal complexes of dicarboxylic acids such as Co, Cr, Fe, amino A compound, a quaternary ammonium compound, an organic dye, and the like can be contained.
[0085]
Furthermore, a release agent may be added to the toner used in the present invention as necessary.
As the release material, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination, but are not limited thereto. is not.
[0086]
Additives can be added to the toner. In order to obtain a good image, it is important to impart sufficient fluidity to the toner. For this purpose, it is generally effective to externally add hydrophobized metal oxide fine particles and fine particles such as lubricants as fluidity improvers, and metal oxides, organic resin fine particles, metal soaps and the like as additives. It is possible to use. Specific examples of these additives include lubricants such as Teflon (R) and zinc stearate, abrasives such as cerium oxide and silicon carbide; for example, SiO having a hydrophobic surface.₂TiO₂Fluidity imparting agents such as inorganic oxides such as those known as anti-caking agents and surface treated products thereof. In order to increase the fluidity of the toner, hydrophobic silica is particularly preferably used.
[0087]
In the toner used in the present invention, the weight average particle diameter Dt is 9.0 to 4.0 μm, preferably 8.5 μm to 4.5 μm. The ratio of the toner to the carrier is 2 to 25 parts by weight, preferably 4 to 15 parts by weight, per 100 parts by weight of the carrier.
In the present invention, the weight average particle diameter Dw referred to for the carrier, the carrier core material, and the toner is calculated based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on the basis of the number. . The weight average particle diameter Dw in this case is represented by the following formula.
Dw = {1 / Σ (nD³)} × {Σ (nD⁴)}
In the above formula, D represents the representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel.
The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. In the present invention, a length of 2 μm is adopted. Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size stored in each channel was adopted.
As a particle size analyzer for measuring the particle size distribution, a Microtrac particle size analyzer (model HRA 9320-X100: manufactured by Honeywell) was used.
The measurement conditions are as follows.
(1) Particle size range: 100-8 μm
(2) Channel length (channel width): 2 μm
(3) Number of channels: 46
[0088]
The developing method of the present invention uses the developer described above as the developer. In this case, when a voltage obtained by superimposing an AC voltage on a DC voltage is applied as a developing bias applied from the outside, a high image quality with a high image density and a low background stain can be obtained. In particular, dot reproducibility and highlight reproducibility are good. When the above developing bias is applied, the substantial developing potential and the background potential become larger than when only the DC bias is applied. Therefore, conventionally, carrier adhesion was easy to occur, but the carrier of the present invention made it possible to achieve both.
[0089]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, this invention is not limited to the Example and comparative example which are illustrated here.
[0090]
<Example of carrier production>
Production Example 1
Silicone resin (SR2411: manufactured by Toray Dow Corning Silicone) was diluted to obtain a silicone resin solution having a solid content of 5%. 3% by weight aminosilane coupling agent H based on solids₂N (CH₂)₃Si (OC₂H₅)₃Using a fluidized bed type coating apparatus, carrier silicone material particles {circle around (1)} (magnetite, 1 KOe magnetic moment of 77 emu / g) having the properties shown in Table 1 are coated on the surface of each of the above-mentioned silicones. The resin solution was applied at a rate of about 40 g / min in an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to obtain a film thickness of 0.38 μm and a true specific gravity of 5.0 g / cm.³The carrier A for comparison was obtained.
[0091]
Production Example 2
Silicone resin (SR2411: manufactured by Toray Dow Corning Silicone) was diluted to obtain a silicone resin solution having a solid content of 5%. Using a fluidized bed type coating apparatus, carrier core material particles having the properties shown in Table 1 (2) (MnMgSr ferrite, 1 KOe magnetic moment 77 emu / g) on each particle surface of 5 kg, the above silicone resin solution Is applied at a rate of about 40 g / min in an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to obtain a film thickness of 0.34 μm and a true specific gravity of 5.0 g / cm.³Carrier B for comparison was obtained.
[0092]
Production Example 3
Except for using the core particle (3) in Table 1 (MnMgSr ferrite, 1 KOe magnetic moment 74 emu / g), the film thickness is 0.32 μm and the true specific gravity is 5.0 g / cm in the same manner as in Production Example 2.³Carrier C was obtained.
[0093]
<Development conditions>
In Examples and Comparative Examples, a developing unit for two-component developer that circulates the developer in a loop shape, specifically, a two-component developing unit for a Ricoh color laser printer (IPSiO Color 8000) (sleeve diameter 18 mm, pumping amount). 0.075 g / cm²Evaluation was performed under development conditions 1 to 5 shown in Table 2 using a doctor gap of 0.775 ± 0.02 mm.
[0094]
<Example and Comparative Example Evaluation Method>
Evaluation was performed by the combination of the carriers A to C and the development conditions 1 to 5. As the toner, black toner for IPSiO Color 8000 was used, and 100,000 sheets were run on a character image chart with an image area ratio of 1% using a Ricoh color laser printer (IPSiO Color 8000) to evaluate scumming and toner scattering. The results at this time are shown in Table 3.
The correspondence between the carriers used in Examples 1 to 4 and Comparative Examples 1 to 4 and the development conditions is as follows.
Example 1 Carrier A + Development condition 4
Example 2 Carrier A + Development condition 3
Example 3 Carrier A + Development condition 2
Example 4 Carrier A + Development condition 1
Comparative Example 1 Carrier A + Developing condition 5
Comparative Example 2 ... Carrier B + Developing condition 1
Comparative Example 3 ... Carrier C + Developing condition 1
Comparative Example 4 Carrier C + Development condition 5
[0095]
Dirt
The background evaluation was performed after 100,000 sheets were run and 10 consecutive copies were made using a character image chart with an image area ratio of 6%. . The higher the rank, the less soiling, and rank 5 is the best. The level that does not cause a problem in the market was set to 4, and the level beyond this was set to be good.
[0096]
Toner scattering
In the toner scattering evaluation, after running 100,000 sheets, the degree of toner scattering in the printer was ranked in four stages, with ◎ being very good, ○ being good, Δ being slightly good, and × being bad. A level that does not cause a problem in the market was rated as “good”, and a level higher than this was considered good.
[0097]
<Electric charge distribution evaluation>
For the above Examples 1 to 4 and Comparative Examples 1 to 4, the charge amount distribution was evaluated separately from the background contamination and toner scattering. The correspondence between the carrier and the development conditions is exactly the same as in the evaluation of background contamination / toner scattering. All the toner is black toner for IPSiO Color 8000, and it is 1 without using the Ricoh color laser printer (IPSiO Color 8000) based on the development conditions of Examples 1 to 4 and Comparative Examples 1 to 4, respectively. After stirring for 5 hours and 5 hours, each developer was sampled on the front side in the axial direction of the developing sleeve, the charge amount distribution of the toner in the developer was measured, and waveform analysis was performed using a normal distribution function. The results at this time are shown in Table 3.
[0098]
[Table 1]

[0099]
[Table 2]

[0100]
[Table 3]

[0101]
【The invention's effect】
As described above, according to the first aspect, the two-component developer composed of the toner and the carrier and adjusted with the toner concentration of 1 to 15% is used, and the developer for developing the electrostatic latent image on the image carrier is used. A developing sleeve to be held, a first developer agitating member pivotally supported on the side far from the developing sleeve, and transported while mixing and stirring the developer along the axial direction of the developing sleeve, and a shaft supported on the near side The developer is circulated in a loop using a developing unit that includes the second developer agitating member and a partition member provided between these members and having a developer communication path secured at both ends thereof. In the two-component development method in which mixing and stirring are performed, the carrier is an electrostatic charge image developing carrier comprising magnetic core material particles and a resin layer covering the particle surface, and the carrier has a weight average particle diameter Dw Is 25 to 45 μm The content ratio of particles having a particle size smaller than 44 μm in the carrier is 70% by weight or more, the particle content of 62 μm or more is less than 1% by weight, and the content ratio of particles having a particle size of less than 22 μm is 7% by weight. The magnetic moment at 1 KOe is 76 emu / g or more, and the charge distribution of the toner in the developer after stirring for 1 hour without supplying and consuming the two-component developer is a normal distribution function 1 The two-component development method can be approximated by a waveform, and the standard deviation at this time is 1.0 [fC / 10 μm] or less, so that the developing device can be miniaturized and a chart of a low image area with a large agent stress can be obtained. It is possible to provide a method for developing an electrostatic charge image that can provide a stable image in which scumming and toner scattering hardly occur even when images are continuously formed.
[0102]
According to the second aspect of the present invention, the standard deviation when the toner charge amount distribution in the two-component developer is approximated by a normal distribution function when stirring for 1 hour without toner replenishment and consumption, With a change of +0.2 [fC / 10 μm] or less with respect to the standard deviation when the charge amount distribution of the toner in the initial agent prepared by mixing and stirring for 10 minutes at low rotation (22 rpm) is approximated by a normal distribution function According to the two-component developing method of claim 1, it is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering are unlikely to occur.
[0103]
According to claim 3, in the charge amount distribution of the toner in the two-component developer according to claim 2, the proportion of the number of weakly charged / reversely charged toners with a charge amount of −1.0 [fC / 10 μm] or less is charged. The number ratio of highly charged toner having a charge amount of −7.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution, and is 0 to 10% of the entire amount distribution. Alternatively, it is possible to provide a method for developing an electrostatic image that can provide a stable image in which background contamination and toner scattering hardly occur by the two-component development method described in 2.
[0104]
According to claim 4, in the charge amount distribution of the toner in the two-component developer according to claim 2, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and the charge amount 4. The number ratio of highly charged toners having an amount of −7.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution. By the component developing method, it is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering hardly occur.
[0105]
According to claim 5, in the charge amount distribution of the toner in the two-component developer according to claim 2, the number ratio of the weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and the charge 5. The number ratio of highly charged toners having an amount of −7.0 [fC / 10 μm] or more is 0 to 1% of the entire charge amount distribution. By the component developing method, it is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering hardly occur.
[0106]
According to the sixth aspect of the present invention, the toner charge amount distribution in the two-component developer after stirring for up to 5 hours without toner replenishment and consumption can be approximated by a normal distribution function 1 waveform, and the standard deviation at this time is 1 .2 [fC / 10 μm] or less, wherein the two-component development method according to any one of claims 1 to 5 continuously forms a chart with a low image area for a long time. It is possible to provide an electrostatic image developing method capable of obtaining a stable image in which background contamination and toner scattering hardly occur even when an image is formed in a special mode having a large agent stress.
[0107]
According to claim 7, in the toner charge amount distribution in the two-component developer according to claim 6, the toner charge amount distribution in the developer when stirring up to 5 hours without toner replenishment and consumption is performed. When the standard deviation when approximated by the normal distribution function is approximated by the normal distribution function, the toner charge amount distribution in the initial agent prepared by mixing and stirring for 10 minutes at a low rotation (22 rpm) of the stirrer tumbler mixer 7. The two-component development method according to claim 1, wherein the change is less than +0.4 [fC / 10 μm] with respect to the standard deviation of the image, and the background and the toner scattering are less likely to occur. It is possible to provide a method for developing an electrostatic image that can obtain an image.
[0108]
According to claim 8, in the charge amount distribution of the toner in the two-component developer according to claim 6, the number ratio of the weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and the charge 8. The two-component development according to claim 1, wherein the number ratio of the highly charged toner having an amount of −8.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution. By this method, it is possible to provide a method for developing an electrostatic image that can obtain a stable image in which background contamination and toner scattering hardly occur.
[0109]
According to claim 9, in the charge amount distribution of the toner in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and the charge amount The number ratio of highly charged toners having an amount of −8.0 [fC / 10 μm] or more is 0 to 3% of the entire charge amount distribution. By the component developing method, it is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering hardly occur.
[0110]
According to the tenth aspect, in the charge amount distribution of the toner in the two-component developer according to the sixth aspect, the number ratio of the weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and the charge amount The number ratio of the highly charged toner having an amount of −8.0 [fC / 10 μm] or more is 0% to 1% of the entire charge amount distribution. By the component developing method, it is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering hardly occur.
[0111]
11. The two-component according to claim 1, wherein a content ratio of particles having a particle size smaller than 22 μm in the carrier is 3% by weight or less. By the developing method, it is possible to provide an electrostatic image developing method capable of obtaining a stable image in which background contamination and toner scattering are unlikely to occur.
[0112]
According to Claim 12, the content ratio of particles having a particle size smaller than 22 µm in the carrier is 1% by weight or less, The two-component according to any one of Claims 1 to 11 By the developing method, it is possible to provide an electrostatic image developing method capable of obtaining a stable image in which background contamination and toner scattering are unlikely to occur.
[0113]
According to claim 13, the bulk density of the carrier is 2.2 g / cm.³13. An electrostatic charge image developing method capable of obtaining a stable image in which background contamination and toner scattering are unlikely to occur by the two-component developing method according to claim 1, wherein the two-component developing method according to claim 1 is used. Is possible.
[0114]
According to Claim 14, the resistance (LogR) of the carrier is 12 Ωcm or more, and the two-component developing method according to any one of Claims 1 to 13 can cause scumming and toner scattering. It is possible to provide an electrostatic image developing method capable of obtaining a stable image that hardly occurs.
[0115]
According to claim 15, the core material of the carrier is MnMgSr ferrite, and the two-component developing method according to any one of claims 1 to 14 causes scumming and toner scattering. It is possible to provide a method for developing an electrostatic image that can obtain a difficult and stable image.
[0116]
According to the sixteenth aspect, the carrier core material is Mn ferrite, and the two-component developing method according to any one of the first to fourteenth aspects makes it difficult to cause background contamination and toner scattering. It is possible to provide a method for developing an electrostatic image capable of obtaining a stable image.
[0117]
According to Claim 17, the core material of the carrier is magnetite, and the two-component development method according to any one of Claims 1 to 14 makes it possible to prevent background contamination and toner scattering. It is possible to provide a method for developing an electrostatic image that can obtain an image.
[0118]
According to claim 18, the carrier coating layer is made of silicone resin, and the two-component developing method according to any one of claims 1 to 17 makes it difficult for dirt and toner scattering to occur. It is possible to provide a method for developing an electrostatic image capable of obtaining a stable image.
[0119]
According to claim 19, the carrier layer is made of a resin containing an aminosilane coupling agent, and the background stain is caused by the two-component developing method according to any one of claims 1 to 18. It is possible to provide an electrostatic charge image developing method capable of obtaining a stable image in which toner scattering is unlikely to occur.
[0120]
According to claim 20, there is provided an electrostatic charge image developing carrier comprising at least core particles having magnetism and a resin layer covering the particle surface, wherein the carrier has a weight average particle diameter Dw of 25 to 45 μm. The content ratio of particles having a particle size smaller than 44 μm in the carrier is 70% by weight or more, the particle content of 62 μm or more is less than 1% by weight, and the content ratio of particles having a particle size of less than 22 μm is 7%. A developing sleeve for holding a two-component developer composed of a carrier and a toner having a magnetic moment of not more than% by weight and a magnetic moment at 1 KOe of 76 emu / g or more, and a developer for developing an electrostatic latent image on an image carrier; The first developer agitating member that is axially supported on the side far from the developing sleeve, and that is axially supported on the near side, conveys the developer while mixing and stirring along the axial direction of the developing sleeve. 2 while mixing in a loop using a developing unit provided with a developer agitating member 2 and a partition member provided between these members and having a developer communication path secured at both ends thereof. The image forming apparatus using the two-component developing method according to any one of claims 1 to 19, wherein the developing apparatus can be reduced in size, and a chart of a low image area with a large agent stress is continuously formed. Even in such a case, it is possible to provide an electrostatic charge image developing device that can obtain a stable image in which scumming and toner scattering hardly occur.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a developing unit used in the present invention.
FIG. 2 is an explanatory structural diagram of a classifier with an ultrasonic oscillator for carrier core material classification used in the present invention.
FIG. 3 is a perspective view of a cell for measuring carrier electric resistance used in the present invention.
FIG. 4 is an explanatory diagram of a waveform analysis approximation example of a charge amount distribution by a normal distribution function of the present invention.
[Explanation of symbols]
1 Development sleeve
2 Upper development case
3 Lower development case
4 First developer stirring member
5 Second developer stirring member
6 Developer
7 Developer amount regulating means (doctor blade)
8 Partition members
11 cells
12a Parallel plate electrode
12b Parallel plate electrode
13 Career
15 Vibrating sieve machine
16 Cylindrical container
17 Spring
18 base
19 Wire mesh
20 Resonant ring
21 cable
22 Converter (vibrator)
23 Ring-shaped frame

Claims (20)

A two-component developer comprising a toner and a carrier and adjusted at a toner concentration of 1 to 15%, a developing sleeve for holding a developer for developing an electrostatic latent image on the image carrier, and an axial direction of the developing sleeve A first developer agitating member pivotally supported on the side far from the developing sleeve, a second developer agitating member pivotally supported on the near side, and conveying the developer along the mixing / stirring In the two-component development method, the carrier is mixed and stirred while being circulated in a loop using a developing unit provided between the members and provided with a partition member having a developer communication path secured at both ends thereof. Is an electrostatic charge image developing carrier comprising magnetic core material particles and a resin layer covering the particle surface, the carrier having a weight average particle diameter Dw of 25 to 45 μm, from 44 μm in the carrier Smaller particle size The content ratio of particles having a particle size of 70% by weight or more, the particle size of 62 μm or more is less than 1% by weight, the content ratio of particles having a particle size of less than 22 μm is 7% by weight or less, and the magnetic moment at 1 KOe Is equal to or greater than 76 emu / g, and the toner charge amount distribution in the developer after stirring for 1 hour without toner replenishment and consumption of the two-component developer can be approximated by a normal distribution function 1 waveform, and the standard deviation at this time Is 1.0 [fC / 10 μm] or less. Standard deviation when the toner charge amount distribution in the two-component developer is approximated by a normal distribution function when the toner is stirred for 1 hour without toner replenishment and consumption, and 10 when the stirrer is slightly rotated (22 rpm). It is a change of +0.2 [fC / 10 μm] or less with respect to a standard deviation when a toner charge amount distribution in an initial agent prepared by partial mixing and stirring is approximated by a normal distribution function. Item 2. The two-component developing method according to Item 1. 3. The toner charge amount distribution in the two-component developer according to claim 2, wherein the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less is 0 to 10 in the entire charge amount distribution. 3. The two-component development according to claim 1, wherein the ratio of the number of highly charged toners having a charge amount of −7.0 [fC / 10 μm] or more is 0 to 5% of the entire charge amount distribution. Method. 3. The toner charge amount distribution in the two-component developer according to claim 2, wherein the number of weakly charged / reversely charged toners with a charge amount of −1.0 [fC / 10 μm] or less and a charge amount of −7.0 [fC]. The two-component developing method according to any one of claims 1 to 3, wherein the ratio of the number of highly charged toners equal to or greater than / 10 µm is 0 to 5% of the entire charge amount distribution. 3. The toner charge amount distribution in the two-component developer according to claim 2, wherein the number of weakly charged / reversely charged toners with a charge amount of −1.0 [fC / 10 μm] or less and a charge amount of −7.0 [fC]. The two-component developing method according to any one of claims 1 to 4, wherein the ratio of the number of highly charged toners of / 10 μm] or more is 0 to 1% of the entire charge amount distribution. The toner charge amount distribution in the two-component developer after stirring for up to 5 hours without toner replenishment and consumption can be approximated by a normal distribution function 1 waveform, and the standard deviation at this time is 1.2 [fC / 10 μm] 6. The two-component developing method according to claim 1, wherein the two-component developing method is as follows. 7. The toner charge amount distribution in the two-component developer according to claim 6, wherein the toner charge amount distribution in the developer when stirring up to 5 hours without toner replenishment and consumption is approximated by a normal distribution function. The standard deviation of the toner is +0 with respect to the standard deviation when the charge distribution of the toner in the initial agent prepared by mixing and stirring for 10 minutes at a low rotation (22 rpm) of a stirrer tumbler mixer is approximated by a normal distribution function. The two-component developing method according to claim 1, wherein the change is 4 [fC / 10 μm] or less. In the toner charge amount distribution in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and a charge amount of −8.0 [fC The two-component developing method according to any one of claims 1 to 7, wherein the ratio of the number of highly charged toners of / 10 μm or more is 0 to 5% of the entire charge amount distribution. In the toner charge amount distribution in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and a charge amount of −8.0 [fC The two-component developing method according to any one of claims 1 to 8, wherein the ratio of the number of highly charged toners of / 10 μm or more is 0 to 3% of the entire charge amount distribution. In the toner charge amount distribution in the two-component developer according to claim 6, the number ratio of weakly charged / reversely charged toner having a charge amount of −1.0 [fC / 10 μm] or less and a charge amount of −8.0 [fC The two-component developing method according to claim 1, wherein the ratio of the number of highly charged toners of / 10 μm or more is 0 to 1% of the entire charge amount distribution. 11. The two-component developing method according to claim 1, wherein a content ratio of particles having a particle diameter of less than 22 μm in the carrier is 3% by weight or less. 12. The two-component developing method according to claim 1, wherein a content ratio of particles having a particle diameter of less than 22 μm in the carrier is 1% by weight or less. The two-component developing method according to claim 1, wherein the carrier has a bulk density of 2.2 g / cm ³ or more. 14. The two-component developing method according to claim 1, wherein the resistance (Log R) of the carrier is 12 Ωcm or more. The two-component developing method according to claim 1, wherein the core material of the carrier is MnMgSr ferrite. The two-component developing method according to claim 1, wherein the core material of the carrier is Mn ferrite. The two-component developing method according to any one of claims 1 to 14, wherein the core material of the carrier is magnetite. The two-component developing method according to any one of claims 1 to 17, wherein the coating layer of the carrier is a silicone resin. The two-component developing method according to any one of claims 1 to 18, wherein the resin layer of the carrier is made of a resin containing an aminosilane coupling agent. An electrostatic charge image developing carrier comprising at least magnetic core material particles and a resin layer covering the particle surface, the carrier having a weight average particle diameter Dw of 25 to 45 μm, and 44 μm in the carrier The content ratio of particles having a smaller particle size is 70% by weight or more, the particle content of 62 μm or more is less than 1% by weight, the content ratio of particles having a particle size of less than 22 μm is 7% by weight or less, and A two-component developer comprising a carrier and a toner having a magnetic moment of 76 emu / g or more at 1 KOe, a developing sleeve for holding a developer for developing an electrostatic latent image on the image carrier, and an axial direction of the developing sleeve The first developer agitating member pivotally supported on the side far from the developing sleeve and the second developer agitating member pivotally supported on the near side are conveyed while mixing and stirring the developer. 20. Mixing and stirring while circulating in a loop using a developing unit provided between these members and a partition member having a developer communication path secured at both ends thereof. An image forming apparatus using the two-component developing method according to any one of the above.

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