JP4099113B2 - Electrophotographic carrier, developer, and image forming apparatus - Google Patents

Description

上記式中Ｒ_１は水素原子、炭素原子１〜４のアルキル基またはフェニル基、Ｒ_２およびＲ_３は水素基、炭素原子数１〜４のアルコキシ基、フェニル基、フェノキシ基、炭素原子数２〜４のアリケニル基、炭素原子数２〜４のアルケニルオキシ基、ヒドロキシ基、カルボキシル基、エチレンオキシド基、グリシジル基または下記化学式（２）で示される基である。
【００４１】
【化２】

（上記式中Ｒ_４、Ｒ_５はヒドロキシ基、カルボキシル基、炭素原子数１〜４のアルキル基、炭素原子数１〜４のアルコキシ基、炭素原子数２〜４のアルケニル基、炭素原子数２〜４のアルケニルオキシ基、フェニル基、フェノキシ基である）。 上記化学式（１）中、ｋ、ｌ、ｍ、ｎ、ｏ、ｐは１以上の整数を示す。
上記各置換基は未置換のもののほか、例えばヒドロキシ基、カルボキシル基、アルキル基、フェニル基、ハロゲン原子のような置換基を有してもよい。
【００４２】
また、該コート層には、上述の絶縁性無機粒子に代表される表面凹凸を形作る粒子の個数平均径より小さな個数平均径を持つ導電性または半導性粒子を含むことが好ましく、このような導電性または半導性粒子をコート層中に含有させることにより、キャリア抵抗値を、精度良く制御することができる。
【００４３】
また、キャリアの磁化のバランスがあまりにも悪い場合には、本発明で規定されたような前記の組成均一性を有しているか否かの如何によらず、全てのキャリアに対して過大なストレスがかかり、キャリア粒子の破砕を発生させる可能性があり、さらには静電潜像担持体面を傷付ける怖れがあるために、１０００エルステッドにおけるキャリア磁化σｂが４０〜７５ｅｍｕ／ｇである必要がある。
キャリア磁化σｂが、４０を下回る場合は、磁化が低すぎるため、キャリア全体の磁気的拘束力が弱くなる。キャリア付着防止の目的で現像材担持部の磁界を強くすると、磁気ブラシが長く剛直になるため、その先端部で大きなストレスが生じ、キャリア粒子の破砕が生じやすくなる。逆に７５を上回る場合には、現像剤担持体上のキャリア粒子密度が高くなりがちであり、粒子密集部での摺擦による過大なストレスを引き起こすことがあり、キャリア粒子破砕を効果的に抑制しつつ高画質な画像を得るための、現像条件を設定することが困難となる。
【００４４】
また、上述のようなキャリア粒子では、その組成や磁化が制限されるため、これらのキャリア粒子を用いつつ、確実にキャリア付着を抑制し高画質化を図るには、充分にキャリア粒子の電気特性、すなわち、現像時にキャリアへ掛かる静電力を制御することが好ましく、ギャップｄ（ｍｍ）の平行平板電極間に空間占有率４０％の該キャリアの磁気ブラシを形成し、ブラシと略同一方向に式（２）の交流電圧Ｅを周波数１０００Ｈｚで掛けたときの電気抵抗Ｒを、１．０×１０＾９〜１．０×１０＾１１Ω・ｃｍとすることが好ましい。
【００４５】
【数７】
電圧Ｅ（Ｖ）＝２５０×ｄ 式（２）
ただし、ｄ＝０．４０±０．０５（ｍｍ）、Ｅはピーク電圧とする。
キャリア付着は、主に、キャリア粒子の磁気的拘束力と、機械的及び静電的脱離力とのアンバランスによって発生するため、これを抑制するためには、組成均一性の確保、キャリア粒度規制並びに磁気的規制に加えて、キャリアの静電的な規制を行なうほうがよい。
該キャリアの電気抵抗Ｒが、１．０×１０＾１１Ω・ｃｍを上回る場合には、現像剤の攪拌によるトナーとキャリアの摩擦帯電によって生じた電荷が、キャリア粒子への蓄積し、像担持体上の非画像部に引き寄せられキャリア付着となりやすい。
また、該キャリアの電気抵抗Ｒが、１．０×１０＾９Ω・ｃｍを下回る場合には、キャリア粒子に誘導電荷が生じ、画像部、非画像部を問わず、キャリア付着となる。
更に、電気抵抗が低いキャリアは、像担持体上の静電潜像を掻き乱し、高画質化の妨げともなる。
【００４６】
導電性または半導性粒子としては、従来公知のもので良く、導電性粒子の例としては、鉄、金、銅等の金属；フェライト、マグネタイト等の酸化鉄；酸化ビスマス、酸化モリブデン等の酸化物；ヨウ化銀、βアルミナ等のイオン導電体；カーボンブラック等の顔料が挙げられ、半導性粒子の例としては、チタン酸バリウム、チタン酸ストロンチウム、チタン酸ランタン酸鉛等に代表される複酸化物や、酸化チタン、酸化亜鉛、酸化スズの酸素欠陥形成物（フレンケル型半導体）、不純物型欠陥形成物（ショトキー型半導体）が挙げられる。
この中でも特にカーボンブラックの一つであるファーネスブラックやアセチレンブラックを用いることにより、少量の低抵抗微粉末の添加で効果的に導電性の調整が可能であり、好ましく用いられる。
これらの低抵抗微粉末は、キャリア表面凹凸を形成するための粒子より小さくする必要があるが、およそ個数平均径で０．０１〜１μｍ程度のものが好ましく、コート層樹脂１００重量部に対して２〜３０重量部添加されることが好ましい。
【００４７】
コート層の形成法としては、従来公知の方法が使用でき、コア材粒子の表面にコート層形成液を噴霧法、浸漬法等の手段で塗布すればよい。また、コート層の厚さは０．０１〜２０μｍが好ましく、０．３〜１０μｍ程度であれば更に好ましい。
更に、このようにしてコート層を形成したキャリア粒子を加熱することによりコート層の重合反応を促進させることが好ましい。
これらのキャリア粒子の加熱保持は、コート層形成後これに引き続きコート装置内で行なっても良く、また、コート層形成後、通常の電気炉や焼成キルン等、別の加熱手段によって行なっても良い。
また、加熱保持温度は、使用するコート層材料により異なるため、一概に決められるものではないが、１２０〜３５０℃程度の温度が好ましく用いられる。このとき、加熱保持温度は、コート層樹脂の分解温度以下の温度が好ましく用いられ、２００℃程度までの上限温度であることがより好ましい。
また加熱保持時間としては、５〜１２０分間程度であることが好ましい。
【００４８】
キャリアに用いる磁性フェライトコア材は、前述のようにマンガン並びに鉄を規定の範囲で含有する限り、特に限定されるものではなく、マンガンフェライト、マンガン−マグネシウムフェライト、マンガン−ストロンチウムフェライト、マンガン−マグネシウム−ストロンチウムフェライト等の公知フェライトを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。また、コア材抵抗を制御する目的や製造安定性を高める目的などで、この他の組成成分として、例えば、Ｌｉ、Ｎａ、Ｋ、Ｃａ、Ｂａ、Ｙ、Ｔｉ、Ｚｒ、Ｖ、Ａｇ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｓｎ、Ｓｂ、Ｂｉ等の組成成分元素を一種以上配合させても良い。これらの配合量としては、総金属元素量の５原子％以下であることが好ましく、３原子％以下であることが、より好ましい。
【００４９】
また、電子写真用キャリアと、少なくとも結着樹脂及び着色剤を含むトナーを混合してなる電子写真用現像剤において、該キャリアを、上述の電子写真用キャリアとすることにより、キャリア粒子破砕やキャリア付着が抑制された、高画質化に対応できる電子写真用現像剤を得ることができる。このとき、該現像剤重量中のトナー重量は、２〜１２重量％であることが好ましく、２．５〜１０重量％であることが更に好ましい。
【００５０】
本発明に使用するトナーは、通常、電子写真用トナーとして使用されるものを、特に制限なく、使用することができる。
例えば、該電子写真用トナーに使用される結着剤樹脂の一例としては、ポリスチレン、ポリｐ−クロロスチレン、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／ビニルトルエン共重合体、スチレン／ビニルナフタレン共重合体、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／アクリル酸オクチル共重合体、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等のスチレン系共重合体；ポリアクリル酸メチル、ポリアクリル酸ブチル、ポリメタクリル酸メチル、ポリメタクリル酸ブチル等のアクリル酸エステル系単重合体やその共重合体；ポリ塩化ビニル、ポリ酢酸ビニル等のポリビニル誘導体；ポリエステル系重合体、ポリウレタン系重合体、ポリアミド系重合体、ポリイミド系重合体、ポリオール系重合体、エポキシ系重合体、テルペン系重合体、脂肪族または脂環族炭化水素樹脂、芳香族系石油樹脂などが挙げられ、単独あるいは混合して使用できるが特にこれらに限定するものではない。中でも、スチレン−アクリル系共重合樹脂、ポリエステル系樹脂、ポリオール系樹脂より選ばれる少なくとも１種以上であることが、電気特性、コスト面等から、より好ましいものである。更には、良好な定着特性を有するものとして、ポリエステル系樹脂および／またはポリオール系樹脂の使用が、一層好ましい。
【００５１】
また、該電子写真用トナーに使用される着色剤としては、従来からトナー用着色剤として使用されてきた顔料及び染料が使用でき、具体的には、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、フタロシアニングリーン、ハンザイエローＧ、ローダミン６Ｃレーキ、カルコオイルブルー、クロムイエロー、キナクリドンレッド、ベンジジンイエロー、ローズベンガル等を単独あるいは混合して用いることができる。
更に、必要により、トナー粒子自身に磁気特性を持たせるには、フェライト、マグネタイト、マグヘマイト等の酸化鉄類、鉄、コバルト、ニッケル等の金属あるいは、これらと他の金属との合金等の磁性成分を単独または混合して、トナー粒子へ含有させればよい。また、これらの成分は、着色剤成分として使用／併用することもできる。
【００５２】
また、該電子写真用現像剤に含まれるトナーは離型性物質を含むことが好ましく、これにより定着オイルを使用しないオイルレス定着を行ないつつ、該キャリアの効果により現像剤の長寿命化をも図られる。トナー中に含ませる離型性物質としては、ポリエチレンワックス、プロピレンワックス、カルナウバワックス等のワックス類が好ましく用いられるが、これらに限定されるものではない。これらの使用量としては、用いる材料の種類や定着の方法にもよるが、およそ０．５〜１０．０重量％程度の使用が好ましく、３．０〜８．０重量％程度の使用が更に好ましい。
【００５３】
トナー流動性や環境依存性改良のための添加剤としても、一般に公知のものが使用でき、例えば、酸化亜鉛、酸化錫、酸化アルミニウム、酸化チタン、酸化珪素、チタン酸ストロンチウム、チタン酸バリウム、チタン酸カルシウム、ジルコン酸ストロンチウム、ジルコン酸カルシウム、チタン酸ランタン、炭酸カルシウム、炭酸マグネシウム、マイカ、ドロマイト等の無機粉末や、これらの疎水化物が単独または混合して使用できる。この他の添加剤として、ポリテトラフルオロエチレン、テトラフルオロエチレンヘキサフルオロプロピレン共重合体、ポリフッ化ビニリデン等のフッ素樹脂微粒子をトナー表面改質剤として使用しても良い。これらは、添加する材料の種類にもよるが、トナー母体粒子１００重量部に対して、およそ０．１〜１０重量部程度を外添し、必要であれば適当な混合機により混合してトナー粒子表面に付着、凝着或いは、トナー粒子間隙で遊離した状態になるよう調整し、用いることができる。
【００５４】
この他、帯電の立ち上がりをより良くするための電荷制御剤としては、一般に知られているものが使用でき、例えば、アミノ基含有ビニル系コポリマー、四級アンモニウム塩化合物、ニグロシン染料、ポリアミン樹脂、イミダゾール化合物、アジン系染料、トリフェニルメタン系染料、グアニジン化合物、レーキ顔料等の正帯電性電荷制御剤や、カルボン酸誘導体及びこの金属塩、アルコキシレート、有機金属錯体、キレート化合物等の負帯電性電荷制御剤を、単独または混合して、トナー粒子中への混練物および／または添加物とすることができる。これら電荷制御剤を分散状態で用いる場合、キャリア粒子表面との相互作用が略均等に生じるためには、その分散径は、２．０μｍ以下であることが好ましく、１．０μｍ以下であることが更に好ましいものである。
【００５５】
本発明の現像剤中のトナー粒子製造方法としては、上述のような原材料を、二本ロール、二軸押出し混練機、一軸押出し混練機等の、公知の方法で混練し、これを機械式や気流式等の公知の粉砕、分級を行ないトナー母体粒子を作成することができる。また混練時に、着色剤や磁性体の分散状態を制御するための分散剤等を併用しても良い。更に、このトナー母体粒子は、前述の添加剤を添加し、混合機等により混合・表面改質を行なっても良い。
またこの他に、樹脂単量体や、低分子量樹脂オリゴマー等を出発原料としてトナー粒子を造粒する、いわゆる重合トナーや、分散媒中でこれと非相溶の樹脂，離型剤，着色剤といった組成物を会合させトナー粒子化する、いわゆる会合トナー等を用いても良い。
また、これらのトナー粒子の帯電電荷量は、実使用プロセスにより異なるため一概に決定できるものではないが、おおよそ、本発明の構成によるキャリア粒子との組み合わせにおいて、絶対値で３〜６０μＣ／ｇ程度の飽和電荷量であることが好ましく、更には５〜４０μＣ／ｇ程度の飽和電荷量であることが、より好ましい。
また、トナー粒子の粒径としては、重量平均径Ｄ４＝４〜１０μｍ程度であることが好ましく、トナー粒子の個数基準１０％径は、２．５μｍ以上であることが、より安定した画質を得るためには好ましい。
【００５６】
また、現像剤を摩擦することによりトナーを帯電させる摩擦帯電手段、帯電したトナーを含む現像剤を保持する内部に磁界発生手段を有する回動可能な現像剤保持体、及び静電潜像を形成する像担持体を備えた現像装置において、現像剤が上述の何れかに記載の電子写真用現像剤とし、かつ、現像剤保持体及び像担時体の近接部である現像領域近傍における、該現像剤保持体表面法線方向の磁束密度Ｂ（ｍＴ）の最大値を、式（３）の関係とすることにより、キャリア中に混在する低い磁化を持つ粒子に対しても充分な磁気的拘束力を保つことができ、かつ現像部でのキャリア磁気ブラシの状態を良好に制御できるため、キャリア付着が抑制された、高品質の画像を長期にわたって得ることができることが判明した。
【００５７】
【数８】
３５００／σｂ≦Ｂ≦１００００／σｂ 式（３）
ただし、σｂ（ｅｍｕ／ｇ）は、１０００エルステッドにおけるキャリア磁化である。
【００５８】
また、該現像装置は、像担持体と現像剤保持体の現像領域内における最近接部の間隔が０．２０〜０．８０ｍｍとする維持手段を有する現像装置であることが現像の安定性を得るためには、より好ましい。間隔が０．２０ｍｍを下回るとキャリア磁気ブラシにより、いったん現像されたトナー像が掃き取られることがあり、逆に０．８０ｍｍを上回るとベタ画像中央部より端部のトナー現像量が多くなる、いわゆるエッジ効果が発生しやすくなるため好ましくない。
【００５９】
また、これらの現像装置では、主として単位面積中の現像面積率により画像の階調性を持たせるには、現像剤担持体へ直流バイアス電圧を印加する電圧印加機構を有することが好ましく、主として単位面積あたりのトナー付着量により画像の階調性を持たせるには、該現像剤保持体へ直流電圧に交流電圧を重畳したバイアス電圧を印加する電圧印加機構を有することがより好ましい。
【００６０】
また、該現像装置は、少なくとも像担持体をクリーニングするクリーニング機構、クリーニング機構により回収したトナーを現像機構へ搬送する回収トナー搬送機構よりなるトナーリサイクル機構を備えることにより、上記の高品質画像を省資源で得ることができるため、更に好ましいものである。
【００６１】
また、複数の現像装置の像担持体上に形成した各々のトナー像を媒体上へ転写する転写手段、媒体上に転写したトナー像を定着する定着手段を有する画像形成装置において、該現像装置を上述の現像装置とすることにより、高画質な画像を得ることができる。
【００６２】
また、現像剤を摩擦することによりトナーを帯電させる摩擦帯電手段、帯電したトナーを含む現像剤を保持する内部に磁界発生手段を有する回動可能な現像剤保持体、静電潜像を形成する像担持体、現像剤及びトナーを備えたプロセスカートリッジにおいて、現像剤を本発明の電子写真用現像剤とし、かつ、現像剤保持体及び像担時体の近接部である現像領域近傍における、該現像剤保持体表面法線方向の磁束密度Ｂ（ｍＴ）の最大値を、式（３）の関係とすることにより、現像剤中のキャリア劣化を抑制しつつ、安定した現像が長期間行なえるプロセスカートリッジを得ることができる。
【００６３】
本発明の現像装置について、その主要部の概略構成図を示す図１を用いてさらに説明する。
潜像担持体である感光体ドラム（１）に対向して配設された現像装置は、現像剤担持体としての現像スリーブ（４１）、現像剤収容部材（４２）、規制部材としてのドクターブレード（４３）、支持ケース（４４）等から主に構成されている。
感光体ドラム（１）側に開口を有する支持ケース（４４）には、内部にトナー（１０）を収容するトナー収容部としてのトナーホッパー（４５）が接合されている。トナーホッパー（４５）に隣接した、トナー（１０）とキャリア粒子とからなる現像剤（１１）を収容する現像剤収容部（４６）には、トナー粒子（１０）と現像剤（１１）を撹拌し、トナー粒子に摩擦／剥離電荷を付与するための、現像剤撹拌機構（４７）が設けられている。
【００６４】
トナーホッパー（４５）の内部には、図示しない駆動手段によって回動されるトナー供給手段としてのトナーアジテータ（４８）及びトナー補給機構（４９）が配設されている。トナーアジテータ（４８）及びトナー補給機構（４９）は、トナーホッパー（４５）内のトナー（１０）を現像剤収容部（４６）に向けて撹拌しながら送り出す。
感光体ドラム（１）とトナーホッパー（４５）との間の空間には、現像スリーブ（４１）が配設されている。図示しない駆動手段で図の矢印方向に回転駆動される現像スリーブ（４１）は、キャリア粒子による磁気ブラシを形成するために、その内部に現像機構（４）に対して相対位置不変に配設された、磁界発生手段としての図示しない磁石を有する。
現像剤収容部材（４２）の、支持ケース（４４）に取り付けられた側と対向する側には、規制部材（ドクターブレード）（４３）が一体的に取り付けられている。規制部材（ドクターブレード）（４３）は、その先端と現像スリーブ（４１）の外周面との間に一定の隙間を保った状態で配設されている。
【００６５】
上記構成により、トナーホッパー（４５）の内部からトナーアジテータ（４８）、トナー補給機構（４９）によって送り出されたトナー（１０）は、現像剤収容部（４６）へ運ばれ、現像剤撹拌機構（４７）で撹拌されることによって、所望の摩擦／剥離電荷が付与され、キャリア粒子と共に現像剤（１１）として（またはトナー粒子単独で）、現像スリーブ（４１）に担持されて感光体ドラム（１）の外周面と対向する位置まで搬送され、トナー（１０）のみが感光体ドラム（１）上に形成された静電潜像と静電的に結合することにより、感光体ドラム（１）上にトナー像が形成される。
【００６６】
図２は、本発明の現像装置を具備する画像形成装置の一例を示す断面図である。
ドラム状の像担持体（１）の周囲に、像担持体帯電部材（２）、像露光系（３）、現像機構（４）、転写機構（５）、クリーニング機構（６）および除電ランプ（７）が配置され、以下の動作で画像形成が行なわれる。
【００６７】
画像形成のための一連のプロセスについて、ネガ−ポジプロセスで説明を行なう。
有機光導電層を有する感光体（ＯＰＣ）に代表される像担持体（１）は、除電ランプ（７）で除電され、帯電チャージャーや帯電ローラーといった帯電部材（２）で均一にマイナスに帯電され、レーザー光学系（３）よって照射されるレーザー光で潜像形成（露光部電位の絶対値は、非露光部電位の絶対値より低電位となる）が行なわれる。
【００６８】
レーザー光は半導体レーザーから発せられて、高速で回転する多角柱の多面鏡（ポリゴン）等により像担持体（１）の表面を、像担持体（１）の回転軸方向に走査する。
このようにして形成された潜像が、現像手段または現像機構（４）にある現像剤担持体である現像スリーブ（４１）上に供給されたトナー粒子、またはトナー粒子及びキャリア粒子の混合物からなる現像剤により現像され、トナー可視像が形成される。
潜像の現像時には、電圧印加機構（図示せず）から現像スリーブ（４１）に、像担持体（１）の露光部と非露光部の間にある、適当な大きさの電圧またはこれに交流電圧を重畳した現像バイアスが印加される。
【００６９】
一方、転写媒体（例えば紙）（８）が、給紙機構（図示せず）から給送され、上下一対のレジストローラー（図示せず）で画像先端と同期をとって像担持体（１）と転写機構（５）との間に給送され、トナー像が転写される。
このとき、転写機構（５）には、転写バイアスとして、トナー帯電の極性と逆極性の電位が印加されることが好ましい。その後、転写媒体または中間転写媒体（８）は、像担持体（１）から分離され、転写像が得られる。
また、像担持体上に残存するトナー粒子は、クリーニング部材（６１）によって、クリーニング機構（６）内のトナー回収室（６２）へ回収される。
回収されたトナー粒子は、トナーリサイクル手段（図示せず）によって現像部および／またはトナー補給部に搬送され、必要に応じて再使用することができる。
画像形成装置としては、上述の現像装置が複数配置されたものを用い、複数の現像装置によって順次作製された色が異なる複数トナー像を順次転写材上へ転写した後、定着機構へ送り、熱等によってトナーを定着する装置であっても、あるいは同様に作製された複数のトナー像を順次一旦中間転写媒体上に順次転写した後、これを一括して紙のような転写媒体に転写後に、同様に定着する装置であっても良い。
【００７０】
また、本発明の画像形成装置に具備される像担持体としては、特にアモルファスシリコン感光体（以下、「ａ−Ｓｉ系感光体」ともいう）が有効である。
このａ−Ｓｉ系感光体は、導電性支持体を５０℃〜４００℃に加熱した後、該支持体上に真空蒸着法、スパッタリング法、イオンプレーティング法、熱ＣＶＤ法、光ＣＶＤ法、プラズマＣＶＤ法等の成膜法によってａ−Ｓｉからなる光導電層を形成し作製されるものである。
なかでもプラズマＣＶＤ法、すなわち、原料ガスを直流または高周波あるいはマイクロ波グロー放電 によって分解し、支持体上にａ−Ｓｉ堆積膜を形成する方法が好適なものとして用いられている。
【００７１】
ａ−Ｓｉ系感光体の層構成としては、例えば以下のような４種類のものがあり、図３は、層構成を説明するための模式的構成図である。
図３（ａ）に示された電子写真用感光体（５００）は、支持体（５０１）の上にａ−Ｓｉ：Ｈ，Ｘからなり光導電性を有する光導電層（５０２）が設けられたものである。
図３（ｂ）に示された電子写真用感光体（５００）は、支持体（５０１）の上に、ａ−Ｓｉ：Ｈ，Ｘからなり光導電性を有する光導電層（５０２）と、アモルファスシリコン系表面層（５０３）とから構成されたものである。
また、図３（ｃ）に示された電子写真用感光体（５００）は、支持体（５０１）の上に、ａ−Ｓｉ：Ｈ，Ｘからなり光導電性を有する光導電層（５０２）と、アモルファスシリコン系表面層（５０３）と、アモルファスシリコン系電荷注入阻止層（５０４）とから構成されたものである。
さらに、図３（ｄ）に示された電子写真用感光体（５００）は、支持体（５０１）の上に、光導電層（５０２）が設けられている。該光導電層（５０２）はａ−Ｓｉ：Ｈ，Ｘからなる電荷発生層（５０５）ならびに電荷輸送層（５０６）とからなり、その上にアモルファスシリコン系表面層（５０３）とから構成されたものである。
【００７２】
感光体を構成する支持体としては、導電性でも電気絶縁性であってもよい。
導電性支持体としては、Ａｌ、Ｃｒ、Ｍｏ、Ａｕ、Ｉｎ、Ｎｂ、Ｔｅ、Ｖ、Ｔｉ、Ｐｔ、Ｐｄ、Ｆｅ等の金属、およびこれらの合金、例えばステンレス等が挙げられる。
また、ポリエステル、ポリエチレン、ポリカーボネート、セルロースアセテート、ポリプロピレン、ポリ塩化ビニル、ポリスチレン、ポリアミド等の合成樹脂のフィルムまたはシート、ガラス、セラミック等の電気絶縁性支持体であって、少なくとも感光層を形成する側の表面を導電処理した支持体も用いることができる。
支持体の形状としては、平滑表面あるいは凹凸表面の円筒状または板状、無端ベルト状であることができ、その厚さは、所望通りの画像形成装置用感光体を形成し得るように適宜決定されるが、画像形成装置用感光体としての可撓性が要求される場合には、支持体としての機能が充分発揮できる範囲内で可能な限り薄くすることができる。しかしながら、支持体は製造上および取り扱い上、機械的強度等の点から通常は１０μｍ以上とされる。
【００７３】
本発明に用いることができるアモルファスシリコン感光体には、必要に応じて導電性支持体と光導電層との間に、導電性支持体側からの電荷の注入を阻止する働きのある電荷注入阻止層を設けるのがいっそう効果的である（図３（ｃ））。
すなわち、該電荷注入阻止層は、感光層が一定極性の帯電処理をその自由表面に受けた際、支持体側より光導電層側に電荷が注入されるのを阻止する機能を有し、逆の極性の帯電処理を受けた際にはそのような機能が発揮されない、いわゆる極性依存性を有している。そのような機能を付与するために、電荷注入阻止層には伝導性を制御する原子を光導電層に比べ比較的多く含有させる。
電荷注入阻止層の層厚は、所望の電子写真特性が得られること、及び経済的効果等の点から、好ましくは０．１〜５μｍ、より好ましくは０．３〜４μｍ、最適には０．５〜３μｍとされるのが望ましい。
【００７４】
ａ−Ｓｉ系光導電層は、必要に応じて下引き層上に形成され、光導電層（５０２）の層厚は、所望の電子写真特性が得られること及び経済的効果等の点から適宜所望にしたがって決定され、好ましくは１〜１００μｍ、より好ましくは２０〜５０μｍ、最適には２３〜４５μｍとされるのが望ましい。
【００７５】
電荷輸送層は、光導電層を機能分離した場合の電荷を輸送する機能を主として奏する層である。
この電荷輸送層は、その構成要素として少なくともシリコン原子と炭素原子と弗素原子とを含み、必要であれば水素原子、酸素原子を含むａ−ＳｉＣ（Ｈ、Ｆ、Ｏ）からなり、所望の光導電特性、特に電荷保持特性，電荷発生特性および電荷輸送特性を有する。本発明においては酸素原子を含有することが特に好ましい。
電荷輸送層の層厚は、所望の電子写真特性が得られることおよび経済的効果などの点から適宜所望にしたがって決定され、電荷輸送層については、好ましくは５〜５０μｍ、より好ましくは１０〜４０μｍ、最適には２０〜３０μｍとされるのが望ましい。
【００７６】
電荷発生層は、光導電層を機能分離した場合の電荷を発生する機能を主として奏する層である。
この電荷発生層は、構成要素として少なくともシリコン原子を含み、実質的に炭素原子を含まず、必要であれば水素原子を含むａ−Ｓｉ：Ｈから成り、所望の光導電特性、特に電荷発生特性、電荷輸送特性を有する。
電荷発生層の層厚は所望の電子写真特性が得られることおよび経済的効果等の点から適宜所望にしたがって決定され、好ましくは０．５〜１５μｍ、より好ましくは１〜１０μｍ、最適には１〜５μｍとされる。
【００７７】
本発明に用いることができるアモルファスシリコン感光体には、必要に応じて、上述のようにして支持体上に形成された光導電層の上に、さらに表面層を設けることができ、アモルファスシリコン系の表面層を形成することが好ましい。
この表面層は、自由表面を有し、主に耐湿性、連続繰り返し使用特性、電気的耐圧性、使用環境特性、耐久性において本発明の目的を達成するために設けられる。
本発明における表面層の層厚としては、通常０．０１〜３μｍ、好適には０．０５〜２μｍ、最適には０．１〜１μｍとされるのが望ましいものである。層厚が０．０１μｍよりも薄いと感光体を使用中に摩耗等の理由により表面層が失われてしまい、３μｍを超えると残留電位の増加等の電子写真特性低下がみられる。
【００７８】
本発明の画像形成装置に具備される前記定着手段は、発熱体を具備する加熱体と、前記加熱体と接触するフィルムと、前記フィルムを介して前記加熱体と圧接する加圧部材とを有し、前記フィルムと前記加圧部材の間に未定着画像を形成させた被記録材を通過させて加熱定着する定着装置であることを特徴とする。
また、ここで定着装置は、図４に示すように、定着フィルムを回転させて定着する、いわゆるサーフ定着装置である。
以下、詳説すると、定着フィルムは、エンドレスベルト状耐熱フィルムであり、該フィルムの支持回転体である駆動ローラと従動ローラと、この両ローラ間の下方に設けたヒータ支持体に保持させて固定支持させて配設した加熱体とに、張設してある。
【００７９】
従動ローラは、定着フィルムのテンションローラを兼ね、定着フィルムは駆動ローラの図中時計回転方向の回転駆動によって、時計回転方向に向かって回転駆動される。この回転駆動速度は、加圧ローラと定着フィルムが接する定着ニップ領域Ｌにおいて転写材と定着フィルムの速度が等しくなる速度に調節される。
ここで、加圧ローラは、シリコンゴム等の離型性のよいゴム弾性層を有するローラであり、反時計周りに回転しつつ、前記定着ニップ領域Ｌに対して総圧４〜１０ｋｇの当接圧をもって圧接させてある。
また定着フィルムは、耐熱性、離型性、耐久性に優れたものが好ましく、総厚１００μｍ以下、好ましくは４０μｍ以下の薄肉のものを使用する。
例えばポリイミド、ポリエーテルイミド、ＰＥＳ（ポリエーテルサルファイド）、ＰＦＡ（４フッ化エチレンバーフルオロアルキルビニルエーテル共重合体樹脂）等の耐熱樹脂の単層フィルム、或いは複合層フィルム、例えば２０μｍ厚フィルムの少なくとも画像当接面側にＰＴＦＥ（４フッ化エチレン樹脂）、ＰＦＡ等のフッ素樹脂に導電材を添加した離型性コート層を１０μｍ厚に施したものや、フッ素ゴム、シリコンゴム等の弾性層を施したものである。
本発明の画像形成装置においては、このような構成からなる定着手段を用いることによって、キャリア付着を抑制することができ、各接触部材を傷つけることなく、寿命を延ばすのに、極めて効果的である。
【００８０】
図４において、本実施形態の加熱体は、平面基板および定着ヒータから構成されており、平面基板は、アルミナ等の高熱伝導度且つ高電気抵抗率を有する材料からなっており、定着フィルムと接触する表面には抵抗発熱体で構成した定着ヒータを長手方向に設置してある。
かかる定着ヒータは、例えばＡｇ／Ｐｄ、Ｔａ_２Ｎ等の電気抵抗材料をスクリーン印刷等により線状もしくは帯状に塗工したものである。
また、前記定着ヒータの両端部には、図示しない電極が形成され、この電極間に通電することで抵抗発熱体が発熱する。
さらに、前記基板の定着ヒータが具備させてある面と逆の面にはサーミスタによって構成した定着温度センサが設けられている。
定着温度センサによって検出された基板の温度情報は図示しない制御手段に送られ、かかる制御手段により定着ヒータに供給される電力量が制御され、加熱体は所定の温度に制御される。
【００８１】
【実施例】
これより、実施例において本発明を更に詳細に説明するが、本発明は以下の実施例に限定されるものではない。また、ここで「部」は全て重量部を示す。
実施例１
（コア材製造例１）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が３５／６５となるよう混合し、ボールミルを用い、水中で４８時間湿式粉砕・分散した後乾燥して、電熱式の雰囲気焼成炉により、弱還元雰囲気下で９００℃、２時間の仮焼を行なった。
湿式粉砕は、粉砕メディアとしては１０ｍｍφのジルコニアボールをボールミルポット容積の３０ｖｏｌ％充填し、固形分を２５％となるように調整した酸化物スラリーをボールミルポット容積の２０ｖｏｌ％充填して行なった。
続いて、得られた仮焼物を粗粉砕後、再度同様の条件で、ボールミルを用い水中で２４時間湿式粉砕・分散し、マンガン鉄複合酸化物のスラリーを得た。
このスラリーに、バインダーとしてポリビニルアルコール及び分散剤を加え、スプレードライヤーを用いて造粒・乾燥し、超音波振動篩を用いて分級し、造粒粒子を作成した。
得られた造粒粒子を、電熱式の雰囲気焼成炉により、大気雰囲気下で１２００℃、４時間の本焼成して、マンガンフェライト粒子を得た。
更に、得られたマンガンフェライト粒子を、超音波振動篩を用いて分級し、コア材（１）を得た。
【００８２】
（コート処方１）
アクリル樹脂溶液（固形分＝５０重量％） ６０部
グアナミン溶液（固形分＝７０重量％） １５部
ストレートシリコーン樹脂（固形分＝２０％） １５０部
ジブチルチンジアセテート １．５部
アルミナ粒子（個数平均粒径＝０．３μｍ） １００部
カーボンブラック ６部
トルエン １５００部
上記処方をホモミキサーで３０分間分散してコート層形成用の塗工液を調整した。
【００８３】
これをコア材（１）５０００部の表面へ流動床型スプレーコート装置によりコート後、１５０℃の雰囲気温度下で、１時間加熱してキャリア（Ｃ１）を得た。キャリア（Ｃ１）の粒度分布を、マイクロトラック粒度分布計（Ｍｉｃｒｏｔｒａｃ社製 Ｍｏｄｅｌ Ｘ１００）にて測定したところ、重量平均粒径（Ｄ４）３６．５μｍ、数平均径（Ｄ１）３４．１μｍであり、１２μｍ以下のキャリア粒子が０．０８重量％であった。
また、キャリア（Ｃ１）の表面を、走査型電子顕微鏡で２０００倍に拡大し観察したところ、表面にアルミナ由来の凹凸が形成され、レーザー顕微鏡を用いて非接触で測定したキャリア表面凹凸の平均高低差は、０．３μｍであった。
次に、このキャリア（Ｃ１）の１０００エルステッドにおける磁化（σｂ）を、多試料回転式磁化測定装置（東英工業株式会社製 ＲＥＭ−１−１０型）を用いて測定したところ、６６．０ｅｍｕ／ｇであった。
続いて、キャリア（Ｃ１）の脱離試験を、以下の手順で行なった。
まず、試験用現像スリーブとして、リコー製カラープリンタＩＰＳｉＯ ｃｏｌｏｒ ８０００用現像スリーブを改造し、現像極のピーク磁束密度が１００ｍＴとなるようにした。
次に、この試験用現像スリーブを現像ユニットに取り付け、別途用意したモーターを用いて、スリーブ回転数を調整して、重力の３倍の遠心力（脱離力）となるように設定した（試験用現像ユニットでは、現像スリーブ径＝１８ｍｍφであったため、スリーブ回転数は、｛３（倍）×９．８（ｍ／ｓ²）×０．００９（ｍ）｝^1/2×１０００（ｍｍ）／｛１８（ｍｍ）×π｝×６０（ｓｅｃ）＝５４６ｒｐｍとした）。
現像ユニットに、試験用キャリア（Ｃ１）２５０ｇを入れ、３０分間現像スリーブを連続回転させて、現像ユニットの現像領域開口部からの組成均一性評価用の脱離キャリアを回収した。
回収した脱離キャリアをＥＰＭＡにより元素分析して、マンガン並びに鉄元素の分布を求め、キャリア粒子２００個について画像解析を行ない、個々のキャリア粒子毎のマンガン並びに鉄の原子個数基準含有率を求め、鉄元素＋マンガン元素中のマンガン元素比率の平均値並びに標準偏差を算出して、変動係数を得た。
マンガン元素比率の平均値Ｍは、０．３５であり、Ｍの０．６倍以下のマンガン元素含有率を持つキャリア粒子は、５．５個数％、Ｍの０．５倍以下のマンガン元素含有率を持つキャリア粒子は３．０個数％であった。
【００８４】
（トナー製造例１）
部分架橋ポリエステル樹脂 ７９．５部
（ビスフェノールＡのエチレンオキサイド付加アルコール、
ビスフェノールＡのプロピレンオキサイド付加アルコール、
テレフタル酸、トリメリット酸の縮合重合物）
Ｍｗ＝１５０００、ガラス転移点＝６１℃）
カーボンブラック １５部
ジ−ｔｅｒｔ―ブチルサリチル酸のジルコニウム塩 １部
カルナウバワックス；野田ワックス社製 ５部
【００８５】
上記組成の混合物を、二本ロール混練機にて３０分間混練後、機械式粉砕機・気流式分級機により粉砕・分級条件を調整し、トナー母体を得た。
更に、トナー母体１００部に対して、疎水性シリカ微粒子１部および疎水性酸化チタン微粒子１部を加えて、ヘンシェルミキサーでトータル２分間混合しトナー（Ｔ１）を得た。
トナー（Ｔ１）の粒度分布をコールターカウンターＴＡ２にて測定したところ、重量平均径Ｄ４＝６．２μｍ、累積個数分布から算出した個数基準１０％径＝２．５μｍであった。
次に、キャリア（Ｃ１）９２０部とトナー（Ｔ１）８０部を、ターブラ−ミキサーにて１分間混合し、二成分現像剤を得た。
【００８６】
この現像剤を使用して、リコー製カラープリンタＩＰＳｉＯ ｃｏｌｏｒ ８０００の改造機を用い、Ａ４版、画像面積率６％原稿３０万枚の連続画像出図試験を行ない、初期及び連続出図後の文字画像、ハーフトーン画像及びベタ画像を出力し画質評価を行なった。
このとき、現像極の磁束密度は１１０ｍＴとし、現像部における現像スリーブと感光体の最近接距離は０．６ｍｍに調整した。
画像出力時の像担持体上静電荷像は、地肌部＝−７００Ｖ、画像部＝−２００Ｖとした。また、現像スリーブには、直流電圧（−５００Ｖ）にピーク間電圧１５００Ｖ、周波数２０００Ｈｚの交流電圧を重畳した、現像バイアス電位を印加した。
画質評価としては、白紙画像及びベタ画像でのキャリア付着、文字部分の文字太り、ハーフトーン画像のボソツキおよび階調性、ベタ画像での画像濃度の安定性及び各画像でのその他不具合の有無を評価した。
初期、３０万枚後共に良好な画像品質が得られ、本発明のキャリアが、画像品質、寿命の両面で有用であることが判った。
なお、画像濃度については、マクベス濃度計（ＲＤ−９１４）を用いて計測し、その他の項目については、目視により評価した。
初期及び３０万枚後の、各評価結果について、表１−１、表１−２、表１−３に示す。
【００８７】
実施例２
（コア材製造例２）
仮焼前の、マンガン及び鉄の酸化物のボールミルによる粉砕・分散時間を、３６時間とした以外は、コア材製造例１と同様にして、コア材（２）を作成した。
コア材（２）を用いた以外は実施例１と同様にしてキャリア（Ｃ２）を得た。
キャリア（Ｃ２）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００８８】
実施例３
（コア材製造例３）
仮焼前の、マンガン及び鉄の酸化物のボールミルによる粉砕・分散時間を１２０時間とし、仮焼物粗粉砕後のボールミルによる分散時間を４８時間とした以外は、コア材製造例１と同様にして、コア材（３）を作成した。
コア材（３）を用いた以外は実施例１と同様にしてキャリア（Ｃ３）を得た。
キャリア（Ｃ３）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００８９】
実施例４
（コア材製造例４）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が１０／９０となるよう混合し、本焼成温度を１２５０℃として、弱還元雰囲気下で焼成した以外は、コア材製造例３と同様にして、コア材（４）を作成した。
コア材（４）を用いた以外は実施例１と同様にしてキャリア（Ｃ４）を得た。
キャリア（Ｃ４）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９０】
実施例５
（コア材製造例５）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が４０／６０となるよう混合した以外は、コア材製造例１と同様にして、コア材（５）を作成した。
コア材（５）を用いた以外は実施例１と同様にしてキャリア（Ｃ５）を得た。
キャリア（Ｃ５）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９１】
実施例６
（コア材製造例６）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、やや小さな平均粒子径を持つコア材（６）を得た。
コア材（６）を用いた以外は実施例１と同様にしてキャリア（Ｃ６）を得た。
キャリア（Ｃ６）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９２】
実施例７
（コア材製造例７）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、やや大きな平均粒子径を持つコア材（７）を得た。
コア材（７）を用いた以外は実施例１と同様にしてキャリア（Ｃ７）を得た。
キャリア（Ｃ７）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９３】
実施例８
（コア材製造例８）
コア材製造例１の本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、やや微粉量の多いコア材（８）を得た。
コア材（８）を用いた以外は実施例１と同様にしてキャリア（Ｃ８）を得た。
キャリア（Ｃ８）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９４】
実施例９
（コア材製造例９）
コア材製造例１の造粒・乾燥工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、粒度分布がややブロードなコア材（９）を得た。
コア材（９）を用いた以外は実施例１と同様にしてキャリア（Ｃ９）を得た。
キャリア（Ｃ９）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９５】
実施例１０
（コート処方２）
アクリル樹脂溶液（固形分＝５０重量％） ６０部
グアナミン溶液（固形分＝７０重量％） １５部
ストレートシリコーン樹脂（固形分＝２０％） １５０部
ジブチルチンジアセテート １．５部
アルミナ粒子（個数平均粒径＝０．３μｍ） ５０部
カーボンブラック ４部
トルエン １５００部
コート層形成用の塗工液として上記処方を用いた以外は実施例１と同様にしてキャリア（Ｃ１０）を得た。
キャリア（Ｃ１０）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９６】
実施例１１
（コート処方３）
アクリル樹脂溶液（固形分＝５０重量％） ６０部
グアナミン溶液（固形分＝７０重量％） １５部
ストレートシリコーン樹脂（固形分＝２０％） １５０部
ジブチルチンジアセテート １．５部
カーボンブラック １部
トルエン １５００部
コート層形成用の塗工液として上記処方を用いた以外は実施例１と同様にしてキャリア（Ｃ１１）を得た。
キャリア（Ｃ１１）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９７】
実施例１２
（コア材製造例１０）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が１０／９０となるよう混合し、本焼成温度を１２５０℃とて、強還元雰囲気下で５時間焼成した以外は、コア材製造例１と同様にして、コア材（１０）を作成した。
コア材（１０）を用いた以外は実施例１と同様にしてキャリア（Ｃ１２）を得た。
キャリア（Ｃ１２）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９８】
実施例１３
（コア材製造例１１）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が４０／６０となるよう混合した、本焼成時間を８時間とした以外は、コア材製造例１と同様にして、コア材（１１）を作成した。
コア材（１１）を用いた以外は実施例１と同様にしてキャリア（Ｃ１３）を得た。
キャリア（Ｃ１３）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【００９９】
実施例１４
（コート処方４）
アクリル樹脂溶液（固形分＝５０重量％） ６０部
グアナミン溶液（固形分＝７０重量％） １５部
ストレートシリコーン樹脂（固形分＝２０％） １５０部
ジブチルチンジアセテート １．５部
アルミナ粒子（個数平均粒径＝０．３μｍ） １００部
カーボンブラック ８部
トルエン １５００部
コート層形成用の塗工液として上記処方を用いた以外は実施例１と同様にしてキャリア（Ｃ１４）を得た。
キャリア（Ｃ１４）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１００】
実施例１５
（コート処方５）
アクリル樹脂溶液（固形分＝５０重量％） ６０部
グアナミン溶液（固形分＝７０重量％） １５部
ストレートシリコーン樹脂（固形分＝２０％） １５０部
ジブチルチンジアセテート １．５部
アルミナ粒子（個数平均粒径＝０．３μｍ） １００部
カーボンブラック ３部
トルエン １５００部
コート層形成用の塗工液として上記処方を用いた以外は実施例１と同様にしてキャリア（Ｃ１５）を得た。
キャリア（Ｃ１５）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０１】
（実施例１６、１７）
トナー製造例１の混錬物を、粉砕・分級条件を調節して、重量平均粒子径の異なるトナー母体を得た。これらをトナー製造例１と同様の方法によって外添剤を混合し、重量平均粒子径が１１μｍ、３．８μｍのトナー（Ｔ２）、（Ｔ３）を得た。
トナー（Ｔ２）、（Ｔ３）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０２】
比較例１
（コア材製造例１２）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が３５／６５となるよう混合し、ボールミルを用い、水中で１８時間湿式粉砕・分散した後乾燥して、弱還元雰囲気下で８５０℃、１時間の仮焼を行なった。
湿式粉砕は、粉砕メディアとしては１０ｍｍφのジルコニアボールをボールミルポット容積の２５ｖｏｌ％充填し、固形分を２５％となるように調整した酸化物スラリーをボールミルポット容積の２０ｖｏｌ％充填して行なった。
続いて、得られた仮焼物を、再度同様の条件で、ボールミルを用い水中で２４時間湿式粉砕・分散し、マンガン鉄複合酸化物のスラリーを得た。
このスラリーに、バインダーとしてポリビニルアルコール及び分散剤を加え、スプレードライヤーを用いて造粒・乾燥し、超音波振動篩を用いて分級し、造粒粒子を作成した。
得られた造粒粒子を、弱還元雰囲気下で１２００℃、４時間の本焼成して、マンガンフェライト粒子を得た。
更に、得られたマンガンフェライト粒子を、超音波振動篩を用いて分級し、コア材（１２）を得た。
コア材（１２）を用いた以外は実施例１と同様にしてキャリア（Ｃ１６）を得た。
キャリア（Ｃ１６）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０３】
比較例２
（コア材製造例１３）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が７／９３となるよう混合し、本焼成温度を１２５０℃とて、還元雰囲気下で５時間焼成した以外は、コア材製造例３と同様にして、コア材（１３）を作成した。
コア材（１３）を用いた以外は実施例１と同様にしてキャリア（Ｃ１７）を得た。
キャリア（Ｃ１７）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０４】
比較例３
（コア材製造例１４）
マンガン及び鉄の酸化物を、Ｍｎ／Ｆｅモル比が５０／５０となるよう混合した以外は、コア材製造例１と同様にして、コア材（１４）を作成した。
コア材（１４）を用いた以外は実施例１と同様にしてキャリア（Ｃ１８）を得た。
キャリア（Ｃ１８）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０５】
比較例４
（コア材製造例１５）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、より小さな平均粒子径を持つコア材（１５）を得た。
コア材（１５）を用いた以外は実施例１と同様にしてキャリア（Ｃ１９）を得た。
キャリア（Ｃ１９）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０６】
比較例５
（コア材製造例１６）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、より大きな平均粒子径を持つコア材（１６）を得た。
コア材（１６）を用いた以外は実施例１と同様にしてキャリア（Ｃ２０）を得た。
キャリア（Ｃ２０）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０７】
比較例６
（コア材製造例１７）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、微粉量が多いコア材（１７）を得た。
コア材（１７）を用いた以外は実施例１と同様にしてキャリア（Ｃ２１）を得た。
キャリア（Ｃ２１）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０８】
比較例７
（コア材製造例１８）
コア材製造例１の造粒工程、並びに、本焼成工程後の分級工程で、マンガンフェライト粒子の超音波振動篩による分級条件を調節し、粒度分布がブロードなコア材（１８）を得た。
コア材（１８）を用いた以外は実施例１と同様にしてキャリア（Ｃ２２）を得た。
キャリア（Ｃ２２）を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１０９】
実施例１８
二成分現像剤調整として、キャリア（Ｃ１）８５０部とトナー（Ｔ１）１５０部を、ターブラ−ミキサーにて３分間混合した以外は、実施例１と同様にして二成分現像剤を得た。
この現像剤を用いた以外は、実施例１と同様にして、各評価結果を得た。評価結果を、表１−１、表１−２、表１−３に示す。
【０１１０】
実施例１９、２０
現像スリーブの現像極のピーク磁束密度が１４０ｍＴとなるように、内部の磁石を交換し、実施例１、４と同様の画像試験を行なった。評価結果を、表１−１、表１−２、表１−３に示す。
【０１１１】
実施例２１、２２
現像スリーブの現像極のピーク磁束密度が７０ｍＴとなるように、内部の磁石を交換し、実施例１、５と同様の画像試験を行なった。評価結果を、表１−１、表１−２、表１−３に示す。
【０１１２】
実施例２３、２４
現像部における現像スリーブと感光体の最近接距離を０．１５ｍｍ、０．９ｍｍとした以外は、実施例１と同様の画像試験を行なった。評価結果を、表１−１、表１−２、表１−３に示す。
【０１１３】
実施例２５
実施例１において、現像バイアスとして直流電圧（−５００Ｖ）のみを印加し、実施例１と同様の画像評価を行なった。評価結果を、表１−１、表１−２、表１−３に示す。
評価結果（初期）
【０１１４】
【表１−１】

【０１１５】
【表１−２−１】

【０１１６】
【表１−２−２】

評価結果（３０万枚後）
【０１１７】
【表１−３−１】

【０１１８】
【表１−３−２】

【０１１９】
最後に、実施例１、実施例３について、引き続き、１００万枚連続画像出図試験を行なったところ、初期画像と比較して全く遜色のない高精細・高解像度の画像が得られた。
【０１２０】
【発明の効果】
以上、詳細かつ具体的な説明から明らかなように、本発明により、実施例および比較例の対比から明らかなように、幅広い現像条件のもと、キャリア粒子の破砕に伴う周辺部材へのダメージを抑制しつつ、画像品質の変動や、画像劣化の少ない、高精細・高解像度の高品質画像を得るのに、有効な電子写真用キャリア、電子写真用二成分現像剤並びに現像方法、現像装置、画像形成装置を得られる。
【図面の簡単な説明】
【図１】本発明における現像装置主要部の概略構成図である。
【図２】本発明における現像装置を有する画像形成装置の一例を示す断面図である。
【図３】本発明における層構成を説明するための模式的構成図である。
【図４】本発明において、定着フィルムを回転させて定着する、いわゆるサーフ定着装置を示した図である。
【符号の説明】
１ 像担持体（感光体ドラム）
２ 像担持体帯電部材
３ 像露光系
４ 現像機構
５ 転写機構
６ クリーニング機構
７ 除電ランプ
８ 転写媒体
１０ トナー粒子
１１ 現像剤
４１ 現像スリーブ
４２ 現像剤収容部材
４３ ドクターブレード
４４ 支持ケース
４５ トナーホッパー
４６ 現像剤収容部
４７ 現像剤撹拌機構
４８ アジテータ
４９ トナー補給機構
５１ 転写部材、
５２ 除電ブラシ
６１ クリーニング部材
６２ トナー回収室
５００ 電子写真用感光体
５０１ 支持体
５０２ 光導電層
５０３ アモルファスシリコン系表面層
５０４ アモルファスシリコン系電荷注入阻止層
５０５ 電荷発生層
５０６ 電荷輸送層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called carrier, a two-component developer containing at least the toner and the carrier, and a developing device, a copier, and a laser, which are charge-providing members that impart charge to the toner by rubbing the toner. The present invention relates to an image forming apparatus such as a printer and a process cartridge.
[0002]
[Prior art]
In general, according to the electrophotographic method, a latent image is formed on an image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a visible image. The toner visible image thus formed is finally transferred onto a transfer medium such as paper, and then fixed on the transfer medium with heat, pressure, solvent gas, or the like to form an output image.
This electrophotographic image forming method uses a so-called two-component development method that uses friction charging generated by stirring and mixing a toner and a carrier by a method of charging a toner for visualization, and does not use a carrier. The toner is roughly classified into a so-called one-component developing system in which charge is imparted to the toner.
This one-component development method is classified into a magnetic one-component development method and a non-magnetic one-component development method depending on whether magnetic force is used for holding toner particles on the developing roller.
[0003]
Until now, printers, copiers, and multifunction devices that require high speed and image reproducibility have many two-component development methods due to demands for toner charging stability and startup, and long-term image quality stability. Many single-component development systems have been adopted for small printers, facsimiles, and the like that have been adopted and require large space saving and low cost.
Particularly in recent years, colorization of output images has progressed, and the demand for higher image quality and stabilization of image quality has become stronger than ever.
[0004]
In the two-component development method using a magnetic carrier, in order to improve the image quality, the toner particles are reduced, and more precise heading of the developer brush on the magnetic sleeve (development sleeve) of the two-component developer is realized. , Proposals have been made to reduce the particle size of the carrier to be used, and to make the developer magnetic brush formed on the developing sleeve thin, so that a more detailed latent image can be developed. Patent documents 1, 2, etc. are mentioned.
In a so-called coated carrier in which a coating layer is provided on the surface of the magnetic core material, the particle size of the magnetic carrier is usually reduced by setting the core material to a small particle size.
When the particle size of the core material becomes small, the core material may be fused in the core material manufacturing process, particularly the core material firing process, and in order to prevent this, it is necessary to strictly control the firing temperature and firing atmosphere. There is.
However, depending on the type and blending of the core material composition, the appropriate firing conditions vary greatly, resulting in variations in the firing state due to variations in the composition blending of the individual core materials, resulting in core materials that are overfired or insufficiently fired. May be mixed.
In particular, if a carrier with a core material that is not sufficiently fired is used, the carrier is crushed by the stress applied in the actual copying machine or printer, generating minute magnetic powder, resulting in image defects such as white spots and black spots, The inner contact member may be damaged.
Since such carrier particles that are easily crushed are finely crushed to generate a large number of abnormal fine particles, even if the mixing amount is extremely small, image quality and contact members are seriously damaged.
However, the relationship between the core material composition and the variation in the firing state accompanying the reduction in the particle size of the core material has not been studied so far, and the above-mentioned problems remain.
[0005]
On the other hand, when the particle size of the magnetic carrier is reduced, since the magnetization per carrier particle is reduced, the magnetic binding force on the magnetic sleeve is weakened, so that the carrier is transferred onto the image carrier, so-called. Carrier adhesion sometimes occurred.
[0006]
In order to suppress the carrier adhesion accompanying the reduction in the particle size of the carrier, a method of setting a lower limit on the carrier saturation magnetization in a developing method in which a developer contained in the developing sleeve is rotated to convey the developer (for example, Patent Documents) 3), and a method of setting a lower limit on the product of the particle size of the magnetic particles and the residual magnetization (for example, see Patent Document 4).
In other words, they also prevent the carrier having a small magnetic binding force from being transported, but since the electrostatic component is added to the carrier detachment force in the developing unit, the detachment force is restrained. Since it may exceed the force, the carrier adhesion has not been sufficiently suppressed.
Further, for example, in the method described in Patent Document 3, a value in a magnetic field of 10,000 Oersted is used as the saturation magnetization. However, in a general electrophotographic developing device, such a high magnetic field is not used. Even if the range of the publication is taken, carrier adhesion is not always sufficiently suppressed.
[0007]
In addition to this, there is also a proposal to suppress carrier adhesion by removing specific low saturation magnetization, small particle diameter, and small specific gravity carrier particles regardless of the carrier particle diameter. The properties of the obtained carrier itself have not been clarified at all, so that it is not possible to expect sufficient suppression of carrier adhesion while further uniforming of the carrier particles is required along with higher image quality (for example, patent documents) 5).
[0008]
Further, for example, a proposal that attempts to suppress carrier adhesion by defining the volume average particle diameter and particle size distribution of the carrier core material, the average void diameter, the magnetization at a magnetic field of 1 KOe, and the difference in magnetization between this and the scattered matter. (See, for example, Patent Document 6). According to the proposal, since the presence of particles having a small magnetic binding force is suppressed, it is assumed that a certain suppression effect on carrier adhesion can be obtained.
By the way, it is thought that carrier adhesion occurs due to the difference in behavior of individual carrier particles with respect to external force. In the developing method using a magnetic brush, in particular, the magnetic acting force (binding force) of each carrier particle has. It is considered that the variation greatly affects the quality of carrier adhesion.
However, in the proposal described in Patent Document 6, only the ratio of the scattered object total magnetization and the original carrier magnetization is specified, and the state of individual carrier particles directly involved in carrier adhesion is as follows. Nothing has been revealed.
That is, the proposal of Patent Document 6 is still insufficient to aim at higher image quality while suppressing carrier adhesion to a high degree.
In addition, in the proposal of Patent Document 6, carrier adhesion suppression and other effects are sought by controlling each characteristic of the carrier core material, but the carrier characteristics include mechanical and chemical properties of the coat layer in addition to the core material characteristics. In many cases, it depends on the physical, electrical, physical, and thermal characteristics, and it is not always possible to sufficiently control the carrier characteristics only by controlling the core material characteristics. In particular, since the image quality and its stability often depend on the characteristics of the carrier surface under the conditions actually used in the image forming apparatus, a coating layer is provided for further image quality improvement. It was necessary to pay close attention to carrier particles.
[0009]
In recent years, from the viewpoint of not affecting the environment from various aspects, it has been realized that units such as toner containers and toner cartridges mainly used in the one-component development system are recycled and reused. At the same time, even in the two-component development system, there is an increasing demand for a longer life of the developer.
On the other hand, from the viewpoint of reducing energy consumption, the temperature at which a toner image is fixed is becoming lower, and in order to enable fixing with lower energy, the toner is more likely to be deformed and fixed at a lower temperature. .
[0010]
Causes of deterioration of the two-component developer include (1) abrasion of the carrier surface, (2) peeling of the carrier surface coat layer, (3) crushing of the carrier, and (4) fixing of the toner component on the carrier (spent )), Deterioration of charging performance, transition from desired electrical resistance, generation of foreign matter such as debris and abrasion powder, etc. Based on these causes, decrease in image density, occurrence of background fogging, Degradation of image quality such as a decrease in resolution and physical / electrical damage of the image carrier are caused.
In order to solve the above-mentioned problems and improve the durability of the carrier, many proposals have been made with some effect so far.
Among them, as a proposal focusing on a carrier having a coating layer on the surface of the core material, a coating layer of a so-called coating carrier, a coating layer obtained by curing a polyimide varnish containing a specific bismaleimide is formed, and environmental stability is improved. To prevent background fogging and prevent peeling of the coating layer (see, for example, Patent Document 7), a resin coating layer in which resin particles and conductive fine powder are dispersedly contained in a matrix resin is provided to prevent spent by toner for a long period of time. (For example, see Patent Document 8), a spherical composite core particle composed of iron oxide particle powder and a cured phenol resin, and a coating layer composed of a phenol resin containing a cured amino group on the surface, and the content of iron oxide particles And a stable triboelectric charge and durability by specifying the amino group content (for example, see Patent Document 9), carrier By dispersing resin fine particles and conductive fine particles in the matrix resin of the child coating layer and containing 10% or more of the same resin component that constitutes the binder resin of the toner, the toner spent on the charging performance can be reduced. A coating layer is formed which is made less susceptible to influence (for example, see Patent Document 10), a polyimide resin having a repeating group containing a diorganosiloxy group, and a compound containing two or more epoxy groups in one molecule. There have been proposed ones that obtain carrier particles having a stable charge amount (for example, see Patent Document 11).
However, in these proposals, there is a case where a sufficient effect cannot be maintained even though the lifetime of the carrier particles is expected to be longer than ever while the fixing temperature is further lowered.
[0011]
For example, in the proposals described in Patent Documents 7, 8, 9, and 11, since the matrix resin alone occupies most of the surface of the carrier particles, the adherability of the toner particle component mainly depends on the surface state of the matrix resin. As a result, a sufficient function for preventing spents may not be exhibited.
In addition, when toner particles that can lower the fixing temperature are used, in the method proposed in Patent Document 10, a portion of the same component as the binder resin component of the toner on the carrier surface is likely to be a starting point for toner particle component fixation, and stirring is performed. From the initial stage, the toner charge amount may be low and unstable.
In addition, many proposals have been made to form a coat layer with a silicone resin whose surface energy is relatively low, but these also have the durability of adhesion to the carrier core material due to the low surface energy. There are problems such as lack, and sufficient durability has not yet been achieved.
[0012]
In addition, those coated with a specific resin material (for example, see Patent Document 12), those for adding various additives to the coating layer (for example, see Patent Documents 13 to 18), and further on the carrier surface The thing using what attached the additive (for example, refer patent document 19) etc. is disclosed.
Further, it is proposed to use a benzoguanamine-n-butyl alcohol-formaldehyde copolymer as a main component for a carrier coating material (see, for example, Patent Document 20), and use a cross-linked product of a melamine resin and an acrylic resin as a carrier coating material. Has been proposed (see, for example, Patent Document 21).
However, these proposals still have insufficient durability.
[0013]
Therefore, in order to improve the spent on the carrier surface of the toner, the resulting destabilization of the charge amount, and the resistance change due to the scraping of the coating resin, a proposal using a thermoplastic resin as the coating resin, and the binder resin Proposals have also been made to use a coat film containing particles larger than the film thickness (see, for example, Patent Documents 22 to 24).
[0014]
Further, as another method for maintaining the carrier coat layer characteristics, particularly the charging characteristics, a proposal has been made to disperse specific thermosetting resin fine particles in the matrix resin of the coat layer. Even when worn out, the coating layer properties were the same as in the initial stage, which was insufficient to sufficiently reduce the wear itself (see, for example, Patent Document 25).
Further, the proposal described in the above-mentioned Patent Document 8 in which the conductive fine powder is simultaneously dispersed in this configuration is not sufficient as a method for reducing the wear itself as described above.
[0015]
As explained above, the core material strength variation in the two-component developer, which is expected to improve image quality, has been drastically improved in terms of the composition and blending of individual core material particles. Obtaining a high-quality image has not been attempted so far and has been left as a very difficult task. In addition, excessive measures to prevent carrier adhesion, that is, prevention of carrier detachment from the developing sleeve at the development location are likely to cause stiffening of the formed brush of the developing brush, thus preventing carrier adhesion and development. It is also possible to form a high quality image with high image density and low background stain by optimizing the supply of toner to the electrostatic image carrier by forming the ears of the developing brush sufficiently and softly on the sleeve and updating it appropriately. It was still a very difficult task.
[0016]
[Patent Document 1]
JP 58-184157 A
[Patent Document 2]
Japanese Patent Publication No. 5-8424
[Patent Document 3]
JP 2000-137352 A
[Patent Document 4]
JP 2000-338708 A
[Patent Document 5]
JP-A-4-145451
[Patent Document 6]
Japanese Patent Laid-Open No. 2002-296846
[Patent Document 7]
JP-A-8-6308
[Patent Document 8]
Japanese Patent No. 2998633
[Patent Document 9]
Japanese Patent Laid-Open No. 9-311504
[Patent Document 10]
JP-A-10-198078
[Patent Document 11]
JP-A-10-239913
[Patent Document 12]
JP 58-108548 A
[Patent Document 13]
JP 54-1555048 A
[Patent Document 14]
JP 57-40267 A
[Patent Document 15]
JP 58-108549 A
[Patent Document 16]
JP 59-166968 A
[Patent Document 17]
Japanese Patent Publication No. 1-19584
[Patent Document 18]
JP-A-6-202381
[Patent Document 19]
Japanese Patent No. 3120460
[Patent Document 20]
JP-A-8-6307
[Patent Document 21]
Japanese Patent No. 2683624
[Patent Document 22]
JP 2001-117287 A
[Patent Document 23]
JP 2001-117288 A
[Patent Document 24]
JP 2001-188388 A
[Patent Document 25]
JP-A-9-319161
[0017]
[Problems to be solved by the invention]
Therefore, the present invention is a carrier suitable for obtaining a high-quality image without causing the carrier to be crushed by the stress in the actual machine and without causing carrier adhesion in view of the above-described current problems. The purpose is to provide.
Another object of the present invention is to provide a two-component developer capable of obtaining a high-quality image without causing carrier crushing due to stress in an actual machine and without causing carrier adhesion.
It is another object of the present invention to provide a carrier that has small carrier aging fluctuations and that maintains its characteristics for an extremely long period of time.
Another object of the present invention is to provide a two-component developer that has little variation over time and that maintains its characteristics over an extremely long period of time.
Another object of the present invention is to provide a developing method, a developing device, an image forming apparatus, and a process cartridge that are suitable for using these carriers or two-component developers and can obtain a good image over a long period of time.
[0018]
[Means for Solving the Problems]
  The above-mentioned problem is (1) an electrophotography characterized in that “a manganese-based ferrite is used as a core material and at least a coat layer is provided on the surface thereof and satisfies the following conditions 1) to 3)” Developer carrier;
1) After holding a carrier magnetically on a cylindrical sleeve having a fixed magnet inside and having a magnetic pole region having a surface magnetic flux density peak of 100 mT in a direction perpendicular to the rotation axis, the cylindrical sleeve is rotated for 30 minutes. As a result of elemental analysis by applying a desorption force three times the gravity in the direction perpendicular to the rotation axis and desorbing from the magnetic pole region having the peak magnetic flux density, the content of iron element in one carrier particle is When M1 (mol%) and the content of manganese element are M2 (mol%), the average value M of M2 / (M1 + M2) is 0.10 to 0.45, and M2 / (M1 + M2) is the average value. The number of particles less than 0.6 times M is 10% by number or less.
2) A weight average particle diameter (D4) is 25-65 micrometers, and the particle | grains of 12 micrometers or less are the ratio of 0.3 weight% or less.
3) The ratio D4 / D1 of the weight average particle diameter (D4) and the number average particle diameter (D1) is 1 to 1.3 ", (2)" The surface coat layer contains at least resin and insulating inorganic particles. The carrier for an electrophotographic developer according to the above item (1), characterized in that it comprises: (3) “the surface has irregularities, and the average height difference of the irregularities is 0.1 to 2.0 μm. The carrier for an electrophotographic developer according to the item (1) or (2), (4) “carrier magnetization σb at 1000 oersted is 40 to 75 emu / g. The carrier for an electrophotographic developer according to any one of (1) to (3) above, (5) "The carrier having a space occupation ratio of 40% between parallel plate electrodes of a gap d (mm)" Forming a magnetic brush and brushSame asThe electrical resistance R when the AC voltage E of the formula (1) is applied at a frequency of 1000 Hz in one direction is 1.0 × 10 9 to 1.0 × 10 11 Ω · cm The carrier for an electrophotographic developer according to any one of (1) to (4);
[0019]
[Expression 4]
Voltage E (V) = 250 × d Equation (2)
However, d = 0.40 ± 0.05 (mm), E is the peak voltage ”.
[0020]
In addition, the above-described problem is solved by (6) “the carrier for an electrophotographic developer according to any one of (1) to (5)” above and a toner containing at least a binder resin and a colorant. Electrophotographic developer obtained by mixing ”, (7)“ Electrophotographic developer according to item (6) above, wherein the toner weight is 2 to 12% by weight ”, (8)“ The developer for electrophotography as described in (6) or (7) above, wherein the toner contains a releasable substance, (9) “Weight average particle diameter of the toner is 4 It is achieved by the electrophotographic developer according to any one of (6) to (8) above, which is 10 μm to 10 μm.
[0021]
In addition, the above-mentioned problem is (10) “A friction charging means for charging toner by rubbing the toner and the carrier, and a rotatable magnetic field generating means inside the carrier and the developer containing the charged toner. An electrophotographic carrier according to any one of (1) to (5) above, comprising at least a developing device having a developer holding means and an image carrier for forming an electrostatic latent image. In the image forming apparatus used, the maximum value of the magnetic flux density B (mT) in the normal direction of the surface of the developer holding member in the vicinity of the developing region, which is the adjacent portion of the developer holding member and the image carrier, is expressed by the formula An electrophotographic image forming apparatus satisfying (3);
[0022]
[Expression 1]
  3500 / σb ≦ B ≦ 10000 / σb Formula (3)
  Where σb (emu / g) is the carrier magnetization at 1000 oersted. (11) In the above item (10), there is provided a maintaining means in which the distance between the closest portions in the development region of the image carrier and the developer holder is 0.30 to 0.80 mm. The electrophotographic image forming apparatus described in the above item (12), wherein the electrophotographic image forming apparatus includes a voltage applying mechanism for applying a DC bias voltage to the developer holding member (10) or (11). Electrophotographic image forming apparatus ”, (13)“ A voltage application mechanism for applying a bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing holder ”(10) or (11) (14) “Toner resizer comprising at least a cleaning mechanism for cleaning the image carrier and a recovered toner transport mechanism for transporting the toner recovered by the cleaning mechanism to the developing mechanism”. The electrophotographic image forming apparatus according to any one of (10) to (13) above, (15) “sequentially provided on the image carrier by a plurality of developing devices. Any one of (10) to (14) above, further comprising: a transfer unit that transfers each formed toner image onto the medium; and a fixing unit that fixes the toner image transferred onto the medium. The electrophotographic image forming apparatus according to (16), ”(16)“ a heating member provided with a heating element, a film in contact with the heating body, and a pressure member in pressure contact with the heating body through the film; The electrophotographic image forming apparatus as described in (15) above, (17) “The image carrier is an amorphous silicon photoconductor. Any of items 10) to (16) It is achieved by an electrophotographic image forming apparatus "described.
[0023]
  Further, the above-described problem is (18) “a frictional charging mechanism for charging toner by rubbing the toner and the carrier, and a rotation having a magnetic field generating means inside the developer holding the carrier and the charged toner. And a developer holding member capable of forming an electrostatic latent imageThe carrier for an electrophotographic developer according to any one of (1) to (5) is used.In the process cartridge, the maximum value of the magnetic flux density B (mT) in the normal direction of the surface of the developer holding member in the vicinity of the developing region, which is the vicinity of the developer holding member and the image carrier, is expressed by the formula ( 3) Process cartridge characterized by satisfying ;
[0024]
[Expression 2]
  3500 / σb ≦ B ≦ 10000 / σb Formula (3)
  However, σb (emu / g) is carrier magnetization at 1000 oersted.
”, (19)“ Process cartridge according to item (18), wherein the developer for electrophotography according to any of items (6) to (9) ”is stored”. Is achieved.
[0025]
In the electrophotographic carrier of the present invention, the strength of the individual carrier particle core material is highly controlled, and the carrier adhesion is also suppressed, so that the lifetime of the electrophotographic carrier is extremely long without damaging various members in contact with the carrier in the image forming apparatus. Can be extended.
Therefore, taking the case where the image carrier is an amorphous silicon photoconductor as an example, with a conventional developer, the surface is slightly polished and exposed so that the scratched portion cannot be repaired. When the electrophotographic carrier of the present invention is used, such a situation does not occur, and as a fixing means, a film disposed between the heating body and the pressure member so as to be in contact with the heating body is used. Even in the case of a so-called film fixing method (belt fixing method) in which an unfixed image is pressed against a heating body by a pressure member, in the case of the electrophotographic carrier of the present invention, It has the advantage that damage can be effectively prevented.
[0026]
Hereinafter, the present invention will be described in detail.
As a result of intensive studies to solve the problems of the prior art described above, the present inventors have found that a carrier for an electrophotographic developer in which manganese-based ferrite is used as a core material and at least a coat layer is provided on the surface thereof. In addition, it was confirmed that what satisfies the following conditions 1) to 3) combined with and satisfies the following conditions 1) to 3) was extremely remarkably effective in improving the image quality over a wide range of development conditions while suppressing carrier crushing. It came to create. 1) After holding a carrier magnetically on a cylindrical sleeve having a fixed magnet inside and having a magnetic pole region having a surface magnetic flux density peak of 100 mT in a direction perpendicular to the rotation axis, the cylindrical sleeve is rotated for 30 minutes. As a result of elemental analysis by applying a desorption force three times the gravity in the direction perpendicular to the rotation axis and desorbing from the magnetic pole region having the peak magnetic flux density, the content of iron element in one carrier particle is When M1 (mol%) and the content of manganese element are M2 (mol%), the average value M of M2 / (M1 + M2) is 0.10 to 0.45, and M2 / (M1 + M2) is the average value. The number of particles less than 0.6 times M is 10% by number or less.
2) The weight average particle diameter (D4) is 25 to 65 μm, and the ratio of particles of 12 μm or less is 0.3% by weight or less.
3) The ratio D4 / D1 of the weight average particle diameter (D4) and the number average particle diameter (D1) is 1 to 1.3.
[0027]
The action or mechanism that solves the problem of carrier crushing by the above-described electrophotographic developer carrier that satisfies such conditions is presumed as follows.
First, when considering the factors that cause the carrier particles to be crushed, the so-called doctor blade, which is a regulating member for stirring the toner and the carrier in the developing device and forming a homogeneous magnetic brush on the developer carrier Includes a core material that is not sufficiently fired due to stress such as rubbing by a magnetic pole or a striking force when a magnetic brush caused by a magnetic pole comes into contact with an image carrier, and that has a weak binding force between grain boundaries of raw material particles that form the core material It is considered that the particles are selectively crushed from the carrier particles.
Such carrier particles containing a core material that is not sufficiently fired are not sufficiently promoted to coalesce the core material raw materials, so that they tend to have low magnetization, and are easily concentrated by applying the above-described desorption force. It is thought. Therefore, in order to concentrate the carrier that is not sufficiently baked, for example, the carrier is put into a developing device having a developing sleeve in which the magnetic flux density in the developing region is a specified value, and the sleeve rotational speed is obtained so as to obtain a desired detachment force. It is sufficient to carry out carrier desorption for a predetermined time, and it is possible to carry out relatively easily and reliably.
In addition, it is reasonable to think that the desorbed material that was not held by the magnetic binding force is related to the state of the carrier particles that are included in the original carrier and are insufficiently fired.
[0028]
In particular, in the so-called manganese-based ferrite containing manganese and iron elements used in the present invention, it is considered that the nonuniformity of the metal element composition tends to appear directly as variation in carrier particle magnetization.
The reason is presumed as follows.
In manganese-based ferrites, manganese and iron elements can have relatively close ionic radii, so that they generally have a turbulent spinel structure. Tetrahedral holes and octahedral holes formed by close packing of oxygen atoms are Randomly occupied by manganese and iron atoms.
In such a random occupation state, the magnetic action due to the lattice structure is relatively dilute, and it is considered that the magnetic characteristics of manganese and iron elements are likely to appear strongly. Therefore, it can be considered that the nonuniformity of the metal element composition in individual carrier particles is a direct factor of variation in carrier particle magnetic properties (magnetization). At the same time, the heterogeneity of the metal element composition is directly related to the heterogeneity of the formation state of the metal double oxide such as manganese ferrite, and directly affects the temperature required for the grain boundary formation in the core material firing process. It is considered that it contributes to the influence of the firing state.
[0029]
The condition 1) will be described.
As is clear from the above explanation, in order to eliminate carrier particles having inferior mechanical strength in the process of producing the core material, it is important to make the composition of the core material sufficiently uniform, that is, the condition 1 ), The average value M of M2 / (M1 + M2) is 0.10, where M1 (mol%) is the content of iron element in one carrier particle and M2 (mol%) is the content of manganese element. It is ˜0.45, and M2 / (M1 + M2) is less than 10% by number of particles having an average value M less than 0.6 times, thereby suppressing carrier particle strength variation and suppressing carrier particle crushing. Therefore, it was confirmed that it was necessary as a first condition for suppressing the crushing of carrier particles.
When M is 0.10 to 0.45 and M2 / (M1 + M2) is less than 0.6 times the average value M, the number of particles exceeds 10% by number, as described above, insufficient firing. The core material is mixed, which adversely affects the image defects associated with the pulverization of the carrier particles and the physical and electrical defects on the contact member.
A uniform composition is better, but eliminating M2 / (M1 + M2) particles less than 0.6 times the average value M requires, for example, a very long time for mixing raw materials when preparing the core material. Therefore, it is not practical in production. Therefore, 0.01 to 10% by number of the particles is sufficient, and 8% by number or less is more preferable.
Further, it is more preferable that the number of particles having M2 / (M1 + M2) less than 0.5 times the average value M is 5% by number or less.
[0030]
When the amount of the iron element composing the carrier particles is M1, and the amount of the manganese element is M2, the manganese element ratio of both is expressed by M2 / (M1 + M2). It is necessary to be 10 to 0.45.
If it exceeds 0.45, it will be difficult to obtain sufficient magnetization for use as a carrier. On the other hand, if it is less than 0.10, the amount of oxygen defects will be reduced due to slight changes in the firing atmosphere during the creation of the magnetic ferrite core material. Since it becomes easy to change and it becomes difficult to control the firing conditions, it becomes difficult to control the core material strength.
[0031]
The condition 2) will be described.
As described above, it is preferable that the carrier particle size is small in order to improve the image quality. However, if the carrier particle is too small, the composition variation of individual carrier particles tends to be large. In order to ensure the strength of the carrier particle core material and improve the image quality, the weight average diameter (D4) is 25 μm to 65 μm, and for the same reason, particles of 12 μm or less are 0.3% by weight. By maintaining the following, the strength of the carrier particle core material can be reliably maintained.
[0032]
Further, condition 3) will be described.
The carrier particle size distribution is sharpened and the carrier particle size is made uniform. Specifically, the ratio D4 / D1 of the weight average diameter (D4) and number average diameter (D1) of the carrier is defined as 1 to 1.3. Thus, the external force applied to the individual carrier particles can be made more uniform, the carrier particles can be further crushed, and a wide range of image forming conditions corresponding to high image quality can be employed.
[0033]
When D4 / D1 exceeds 1.3, the carrier particle size distribution becomes broad, and thus there is a tendency for individual carrier particle core materials to vary in the firing state. Increasing the number of carrier particle core materials with a large particle size contributes greatly to an increase in the value of D4 / D1, even if the number is small, and the carrier particle core material with a large particle size inhibits the proper development brush heading. As a result, it becomes easy to form rough and hardened ears, and an excessive stress is applied to the carrier particles in the developing portion.
On the other hand, if the number of small-diameter carriers increases, even if the number is large, it does not contribute much to the increase in the value of D4 / D1, but when the proportion of small-diameter carriers increases, carrier adhesion is suppressed. As a development condition, it is necessary to form a magnetic field that can sufficiently restrain even the carrier particles having a small magnetization. For this reason, the binding force of the carrier particles having a larger magnetization becomes too strong, and the appropriate hardness is obtained. In addition to the difficulty in forming the magnetic brush, excessive stress is applied to the carrier particles and the developer, which promotes deterioration of the carrier particles.
Therefore, in the present invention, by setting each carrier characteristic within the above range, the suppression of carrier particle core material crushing and the formation of a high-quality image can be made highly compatible under a wide range of development conditions. .
[0034]
In addition, in order to make the wear resistance and spent resistance of the carrier coat layer more reliable and to suppress fluctuations in carrier characteristics (especially carrier charge imparting ability and / or carrier resistance) over time, It was also found that the average height difference is more preferably 0.1 to 2.0 μm, and more preferably 0.2 to 1.0 μm. Thereby, the time-dependent change of the electrostatic force applied to the carrier particles as the desorption force at the developing portion is suppressed, and the effect of suppressing the carrier particle crushing can be obtained even after the output of a large number of sheets as in the initial stage.
[0035]
Further, insulating inorganic particles can be preferably used as the particles. The insulating inorganic particles are not particularly limited, and aluminum oxide, silicon oxide, calcium carbonate, talc, clay, quartz glass, aluminosilicate glass, mica pieces, zirconium oxide, mullite, sialon, steatite, forte Known insulator powder particles such as stellite, cordierite, beryllium oxide, and silicon nitride can be used, but are not limited thereto. In particular, the inclusion of at least an aluminum element and / or a silicon element component typified by aluminum oxide or silicon oxide in the insulating inorganic particles as a constituent unit can further suppress the detachment of the particles from the coating layer. It is possible to suppress the initial carrier resistance variation with time more reliably.
[0036]
Moreover, in order to form the unevenness | corrugation derived from particle | grains reliably in a carrier surface, it is preferable that content of particle | grains is 20 to 90 weight% of a coating film composition component. When the particle content is less than 20% by weight of the composition component of the coat layer, even if an uneven structure can be formed on the surface of the carrier, the structure tends to be gentle. It may not be able to fully demonstrate. On the other hand, when the particle content exceeds 90% by weight of the coating layer composition component, the uneven structure may become brittle, and the initial uneven structure may not be maintained for a long period of time. The particle content is more preferably 25 to 80% by weight.
[0037]
As a resin for forming the coat layer of the carrier, it can be used without any particular limitation, such as polyolefin (for example, polyethylene, polypropylene, etc.) and modified products thereof, styrene, acrylic resin, acrylonitrile, vinyl acetate, vinyl alcohol, chloride. Crosslinkable copolymers containing vinyl, vinyl carbazole, vinyl ether, etc .; silicone resins comprising organosiloxane bonds or modified products thereof (for example, modified products with alkyd resins, polyester resins, epoxy resins, polyurethane, etc.); polyamides; polyesters; polyurethanes; Examples include polycarbonate, urea resin, melamine resin, benzoguanamine resin, epoxy resin, polyimide resin, and derivatives thereof.
Above all, in order to reliably fix the insulating inorganic particles as described above in the carrier coat layer and to better prevent the detachment of the inorganic particles due to friction, the resin of the coat layer has at least an acrylic portion as a structural unit. It is preferable to include. Thereby, the detachment | desorption by friction of said inorganic particle can be suppressed very effectively, and the uneven structure of a carrier surface can be maintained over a long period of time. Furthermore, the acrylic resin preferably has a glass transition temperature (Tg) of 20 to 100 ° C, more preferably 25 to 80 ° C. By setting the Tg of the resin within this range, it is considered that the coating layer resin has an appropriate elasticity and reduces the impact received by the carrier when the developer is triboelectrically charged, thereby preventing the coating layer from being damaged.
[0038]
In addition, by using a cross-linked product of the acrylic resin and amino resin as the coating layer resin, it is possible to prevent fusion between resins, so-called blocking, which tends to occur when the acrylic resin is used alone while maintaining appropriate elasticity. This is even more preferable.
As the amino resin, conventionally known amino resins can be used, and among them, guanamine and melamine can be used more preferably because the charge imparting ability of the carrier can be improved. If it is necessary to appropriately control the charge imparting ability of the carrier, guanamine and / or melamine may be used in combination with another amino resin.
[0039]
Furthermore, since the above-mentioned coat layer resin contains a silicone portion as a structural unit, the surface energy itself of the carrier surface can be lowered and the occurrence of toner spent itself can be suppressed, so that the carrier characteristics can be further improved. Can be maintained for a long time.
The constituent unit of the silicone part preferably includes at least one of a methyltrisiloxane unit, a dimethyldisiloxane unit, and a trimethylsiloxane unit, and the silicone part may be chemically bonded to another coating layer resin. It may be in a blended state or may be a multilayer. Moreover, when it is multilayered, it is preferable that a silicone part is located in the outermost layer at least.
In the case of a blend or multilayer structure, it is preferable to use a silicone resin and / or a modified product thereof. For example, among any conventionally known silicone resins, heat that can take a three-dimensional network structure is preferable. A curable silicone resin can be used, and examples thereof include a straight silicone consisting only of an organosiloxane bond represented by the following chemical formula (1) and a silicone resin modified with alkyd, polyester, epoxy, urethane and the like.
[0040]
[Chemical 1]

R in the above formula₁Is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R₂And R₃Is a hydrogen group, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a hydroxy group, a carboxyl group, an ethylene oxide group, A glycidyl group or a group represented by the following chemical formula (2).
[0041]
[Chemical formula 2]

(In the above formula, R₄, R₅Is a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a phenyl group A phenoxy group). In the above chemical formula (1), k, l, m, n, o, and p are integers of 1 or more.
Each of the above substituents may have a substituent such as a hydroxy group, a carboxyl group, an alkyl group, a phenyl group, or a halogen atom in addition to an unsubstituted one.
[0042]
The coating layer preferably contains conductive or semiconductive particles having a number average diameter smaller than the number average diameter of the particles that form the surface irregularities represented by the above-described insulating inorganic particles. By containing conductive or semiconductive particles in the coat layer, the carrier resistance value can be controlled with high accuracy.
[0043]
In addition, when the balance of magnetization of carriers is too bad, excessive stress is applied to all carriers regardless of whether or not the compositional uniformity as defined in the present invention is present. The carrier magnetization σb at 1000 oersted needs to be 40 to 75 emu / g, since there is a possibility that the carrier particles may be crushed and the surface of the electrostatic latent image carrier may be damaged.
When the carrier magnetization σb is less than 40, since the magnetization is too low, the magnetic binding force of the entire carrier becomes weak. When the magnetic field of the developer carrying portion is increased for the purpose of preventing carrier adhesion, the magnetic brush becomes long and rigid, so that a large stress is generated at the tip portion, and the carrier particles are easily crushed. On the other hand, if it exceeds 75, the carrier particle density on the developer carrier tends to be high, which may cause excessive stress due to rubbing at the particle dense portion, effectively suppressing carrier particle crushing. However, it is difficult to set development conditions for obtaining a high-quality image.
[0044]
In addition, since the composition and magnetization of the carrier particles as described above are limited, the electrical characteristics of the carrier particles are sufficient to reliably suppress carrier adhesion and improve image quality while using these carrier particles. That is, it is preferable to control the electrostatic force applied to the carrier at the time of development. A magnetic brush of the carrier having a space occupancy of 40% is formed between parallel plate electrodes with a gap d (mm), and the formula is set in the same direction as the brush. The electric resistance R when the AC voltage E of (2) is applied at a frequency of 1000 Hz is preferably 1.0 × 10 9 to 1.0 × 10 11 Ω · cm.
[0045]
[Expression 7]
Voltage E (V) = 250 × d Equation (2)
However, d = 0.40 ± 0.05 (mm) and E is a peak voltage.
Carrier adhesion occurs mainly due to an imbalance between the magnetic binding force of carrier particles and the mechanical and electrostatic detachment forces. To suppress this, ensuring composition uniformity, carrier particle size, etc. In addition to regulation and magnetic regulation, it is better to carry out electrostatic regulation of the carrier.
When the electric resistance R of the carrier exceeds 1.0 × 10 ^ 11 Ω · cm, the charge generated by frictional charging between the toner and the carrier due to the stirring of the developer accumulates on the carrier particles, and the image carrier It is attracted to the upper non-image area and tends to adhere to the carrier.
Further, when the electric resistance R of the carrier is less than 1.0 × 10 9 Ω · cm, an induced charge is generated in the carrier particle, and the carrier adheres regardless of the image portion or the non-image portion.
Further, the carrier having a low electric resistance disturbs the electrostatic latent image on the image carrier, and hinders high image quality.
[0046]
As the conductive or semiconductive particles, conventionally known particles may be used. Examples of the conductive particles include metals such as iron, gold, and copper; iron oxides such as ferrite and magnetite; oxidation such as bismuth oxide and molybdenum oxide. Materials: Ion conductors such as silver iodide and β-alumina; pigments such as carbon black are exemplified, and examples of the semiconductive particles are represented by barium titanate, strontium titanate, lead lanthanum titanate, etc. Examples include double oxides, titanium oxide, zinc oxide, tin oxide oxygen defect formations (Frenkel type semiconductors), and impurity type defect formations (Schottky type semiconductors).
Among these, furnace black or acetylene black, which is one of carbon blacks, can be effectively used because the conductivity can be adjusted effectively by adding a small amount of low-resistance fine powder.
These low-resistance fine powders need to be smaller than the particles for forming the carrier surface irregularities, but those having a number average diameter of about 0.01 to 1 μm are preferable, with respect to 100 parts by weight of the coating layer resin. It is preferable to add 2 to 30 parts by weight.
[0047]
As a method for forming the coat layer, a conventionally known method can be used, and the coat layer forming liquid may be applied to the surface of the core material particles by means such as spraying or dipping. The thickness of the coat layer is preferably 0.01 to 20 μm, and more preferably about 0.3 to 10 μm.
Furthermore, it is preferable to accelerate the polymerization reaction of the coat layer by heating the carrier particles on which the coat layer is formed in this way.
The heating and holding of these carrier particles may be performed in the coating apparatus after the formation of the coat layer, or may be performed by another heating means such as a normal electric furnace or a firing kiln after the formation of the coat layer. .
Further, the heating and holding temperature varies depending on the coating layer material to be used, and is not generally determined, but a temperature of about 120 to 350 ° C. is preferably used. At this time, the heating and holding temperature is preferably a temperature equal to or lower than the decomposition temperature of the coat layer resin, and more preferably an upper limit temperature up to about 200 ° C.
The heating and holding time is preferably about 5 to 120 minutes.
[0048]
The magnetic ferrite core material used for the carrier is not particularly limited as long as it contains manganese and iron in the specified range as described above. Manganese ferrite, manganese-magnesium ferrite, manganese-strontium ferrite, manganese-magnesium- Known ferrites such as strontium ferrite can be used, but are not limited thereto. Further, for the purpose of controlling the core material resistance and the purpose of improving the production stability, other composition components include, for example, Li, Na, K, Ca, Ba, Y, Ti, Zr, V, Ag, Ni, One or more compositional component elements such as Cu, Zn, Al, Sn, Sb, and Bi may be blended. As these compounding quantities, it is preferable that it is 5 atomic% or less of the total amount of metal elements, and it is more preferable that it is 3 atomic% or less.
[0049]
In addition, in an electrophotographic developer obtained by mixing an electrophotographic carrier and a toner containing at least a binder resin and a colorant, the carrier is used as the above-described electrophotographic carrier, whereby carrier particle crushing or carrier It is possible to obtain an electrophotographic developer capable of dealing with high image quality, in which adhesion is suppressed. At this time, the toner weight in the developer weight is preferably 2 to 12% by weight, and more preferably 2.5 to 10% by weight.
[0050]
As the toner used in the present invention, those usually used as an electrophotographic toner can be used without any particular limitation.
For example, as an example of a binder resin used in the electrophotographic toner, styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene and the like, and a substituted homopolymer thereof; styrene / p-chlorostyrene copolymer Polymer, styrene / propylene copolymer, styrene / vinyl toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer Styrene / octyl 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 keto Styrene copolymers such as copolymers, styrene / butadiene copolymers, styrene / isoprene copolymers, styrene / maleic acid copolymers; polymethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polymethacryl Acrylic acid ester homopolymers such as butyl acid and copolymers thereof; polyvinyl derivatives such as polyvinyl chloride and polyvinyl acetate; polyester polymers, polyurethane polymers, polyamide polymers, polyimide polymers, polyols Polymer, epoxy polymer, terpene polymer, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, etc., which can be used alone or in combination, but are not particularly limited thereto. . Of these, at least one selected from styrene-acrylic copolymer resins, polyester resins, and polyol resins is more preferable in terms of electrical characteristics, cost, and the like. Furthermore, it is more preferable to use a polyester-based resin and / or a polyol-based resin as having good fixing characteristics.
[0051]
As the colorant used in the electrophotographic toner, pigments and dyes conventionally used as toner colorants can be used. Specifically, carbon black, lamp black, iron black, ultramarine blue, Nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6C lake, calco oil blue, chrome yellow, quinacridone red, benzidine yellow, rose bengal and the like can be used alone or in combination.
Further, if necessary, in order to give the toner particles magnetic properties, magnetic components such as iron oxides such as ferrite, magnetite and maghemite, metals such as iron, cobalt and nickel, or alloys of these with other metals. May be contained alone or in combination in the toner particles. Moreover, these components can also be used / used together as a colorant component.
[0052]
In addition, the toner contained in the electrophotographic developer preferably contains a releasable substance, which makes it possible to extend the life of the developer by the effect of the carrier while performing oilless fixing without using fixing oil. Figured. As the releasable substance contained in the toner, waxes such as polyethylene wax, propylene wax and carnauba wax are preferably used, but are not limited thereto. The amount used is preferably about 0.5 to 10.0% by weight, more preferably about 3.0 to 8.0% by weight, although it depends on the type of material used and the fixing method. preferable.
[0053]
As additives for improving toner fluidity and environment dependency, generally known additives can be used. For example, zinc oxide, tin oxide, aluminum oxide, titanium oxide, silicon oxide, strontium titanate, barium titanate, titanium Inorganic powders such as calcium oxide, strontium zirconate, calcium zirconate, lanthanum titanate, calcium carbonate, magnesium carbonate, mica and dolomite, and hydrophobized products thereof can be used alone or in combination. As other additives, fluororesin fine particles such as polytetrafluoroethylene, tetrafluoroethylene hexafluoropropylene copolymer, and polyvinylidene fluoride may be used as the toner surface modifier. Depending on the type of material to be added, about 0.1 to 10 parts by weight is externally added to 100 parts by weight of the toner base particles, and if necessary, the toner is mixed with an appropriate mixer. It can be adjusted and used so that it adheres to, adheres to the particle surface, or is released in the toner particle gap.
[0054]
In addition, generally known charge control agents for improving the rising of charge can be used, such as amino group-containing vinyl copolymers, quaternary ammonium salt compounds, nigrosine dyes, polyamine resins, imidazoles. Positive charge control agents such as compounds, azine dyes, triphenylmethane dyes, guanidine compounds, lake pigments, and negative charge charges such as carboxylic acid derivatives and their metal salts, alkoxylates, organometallic complexes, chelate compounds The control agent can be used alone or mixed to form a kneaded product and / or additive into the toner particles. When these charge control agents are used in a dispersed state, the dispersion diameter is preferably 2.0 μm or less, and preferably 1.0 μm or less in order for the interaction with the carrier particle surface to occur substantially evenly. Further preferred.
[0055]
As a method for producing toner particles in the developer of the present invention, the raw materials as described above are kneaded by a known method such as a two-roll, twin-screw extrusion kneader, or single-screw extrusion kneader. The toner base particles can be prepared by performing known pulverization and classification such as an airflow method. Further, at the time of kneading, a colorant or a dispersant for controlling the dispersion state of the magnetic material may be used in combination. Further, the toner base particles may be mixed and surface-modified with a mixer or the like by adding the aforementioned additives.
In addition to this, a so-called polymerized toner that granulates toner particles using a resin monomer, a low-molecular-weight resin oligomer, or the like as a starting material, or a resin, release agent, or colorant that is incompatible with this in a dispersion medium. A so-called associative toner that associates such a composition to form toner particles may be used.
In addition, although the charge amount of these toner particles varies depending on the actual use process, it cannot be determined unconditionally. However, in the combination with the carrier particles according to the configuration of the present invention, the absolute value is about 3 to 60 μC / g. The saturated charge amount is preferably about 5 to 40 μC / g, and more preferably about 5 to 40 μC / g.
The particle diameter of the toner particles is preferably about weight average diameter D4 = 4 to 10 μm, and the toner particle number-based 10% diameter is 2.5 μm or more to obtain more stable image quality. It is preferable for this purpose.
[0056]
Further, friction charging means for charging the toner by rubbing the developer, a rotatable developer holding body having a magnetic field generating means for holding the developer containing the charged toner, and an electrostatic latent image are formed. In the developing device provided with the image carrier, the developer is the electrophotographic developer described in any one of the above, and in the vicinity of the developing region which is a proximity portion of the developer holder and the image carrier. By setting the maximum value of the magnetic flux density B (mT) in the normal direction of the developer holder surface to the relationship of the formula (3), sufficient magnetic restraint can be achieved even for particles with low magnetization mixed in the carrier. It was found that a high-quality image with suppressed carrier adhesion can be obtained over a long period of time because the force can be maintained and the state of the carrier magnetic brush in the developing unit can be controlled well.
[0057]
[Equation 8]
      3500 / σb ≦ B ≦ 10000 / σb Formula (3)
  However, σb (emu / g) is carrier magnetization at 1000 oersted.
[0058]
In addition, the developing device is a developing device having a maintaining unit in which the distance between the closest portions in the developing region of the image carrier and the developer holding member is 0.20 to 0.80 mm. More preferred for obtaining. If the interval is less than 0.20 mm, the toner image once developed may be swept away by the carrier magnetic brush. Conversely, if the interval exceeds 0.80 mm, the toner development amount at the end of the solid image becomes larger than the central portion. This is not preferable because a so-called edge effect is likely to occur.
[0059]
Further, in these developing devices, in order to give the gradation of the image mainly by the development area ratio in the unit area, it is preferable to have a voltage application mechanism for applying a DC bias voltage to the developer carrying member. In order to provide gradation of the image by the toner adhesion amount per area, it is more preferable to have a voltage application mechanism that applies a bias voltage in which an AC voltage is superimposed on a DC voltage to the developer holder.
[0060]
Further, the developing device includes a toner recycling mechanism including at least a cleaning mechanism for cleaning the image carrier, and a collected toner transport mechanism for transporting the toner collected by the cleaning mechanism to the developing mechanism, so that the high quality image can be saved. Since it can be obtained with resources, it is more preferable.
[0061]
An image forming apparatus having a transfer unit that transfers each toner image formed on an image carrier of a plurality of developing devices onto a medium, and a fixing unit that fixes the toner images transferred onto the medium. By using the above-described developing device, a high-quality image can be obtained.
[0062]
Further, friction charging means for charging the toner by rubbing the developer, a rotatable developer holding body having a magnetic field generating means inside the developer containing the charged toner, and an electrostatic latent image are formed. In a process cartridge including an image carrier, a developer, and toner, the developer is the electrophotographic developer of the present invention, and the developer holding member and the image carrier are in the vicinity of the development region in the vicinity. By setting the maximum value of the magnetic flux density B (mT) in the direction normal to the surface of the developer holder to the relationship of Expression (3), stable development can be performed for a long time while suppressing carrier deterioration in the developer. A process cartridge can be obtained.
[0063]
The developing device of the present invention will be further described with reference to FIG.
The developing device disposed opposite to the photosensitive drum (1) as a latent image carrier has a developing sleeve (41) as a developer carrier, a developer accommodating member (42), and a doctor blade as a regulating member. (43), mainly a support case (44) and the like.
To a support case (44) having an opening on the side of the photosensitive drum (1), a toner hopper (45) as a toner containing portion for containing the toner (10) is joined. In the developer accommodating portion (46) that accommodates the developer (11) composed of toner (10) and carrier particles adjacent to the toner hopper (45), the toner particles (10) and the developer (11) are agitated. In addition, a developer stirring mechanism (47) is provided for imparting friction / release charges to the toner particles.
[0064]
Inside the toner hopper (45), a toner agitator (48) and a toner replenishing mechanism (49) are disposed as toner supplying means rotated by a driving means (not shown). The toner agitator (48) and the toner replenishing mechanism (49) send out the toner (10) in the toner hopper (45) toward the developer container (46) while stirring.
A developing sleeve (41) is disposed in a space between the photosensitive drum (1) and the toner hopper (45). The developing sleeve (41) that is rotationally driven in the direction of the arrow in the figure by a driving means (not shown) is disposed in the interior thereof so as not to change relative position with respect to the developing mechanism (4) in order to form a magnetic brush made of carrier particles. In addition, it has a magnet (not shown) as magnetic field generating means.
A regulating member (doctor blade) (43) is integrally attached to the side of the developer accommodating member (42) facing the side attached to the support case (44). The restricting member (doctor blade) (43) is disposed in a state where a certain gap is maintained between the tip thereof and the outer peripheral surface of the developing sleeve (41).
[0065]
With the above configuration, the toner (10) sent out from the inside of the toner hopper (45) by the toner agitator (48) and the toner replenishing mechanism (49) is carried to the developer accommodating portion (46), and the developer agitating mechanism ( 47), the desired friction / peeling charge is imparted, and is carried on the developing sleeve (41) as a developer (11) (or toner particles alone) together with carrier particles, and the photosensitive drum (1). ) To the position facing the outer peripheral surface, and only the toner (10) is electrostatically coupled to the electrostatic latent image formed on the photosensitive drum (1), so that the photosensitive drum (1) A toner image is formed.
[0066]
FIG. 2 is a cross-sectional view showing an example of an image forming apparatus including the developing device of the present invention.
Around the drum-shaped image carrier (1), an image carrier charging member (2), an image exposure system (3), a developing mechanism (4), a transfer mechanism (5), a cleaning mechanism (6), and a charge eliminating lamp ( 7) is arranged, and image formation is performed by the following operation.
[0067]
A series of processes for image formation will be described using a negative-positive process.
An image carrier (1) represented by a photoconductor (OPC) having an organic photoconductive layer is neutralized by a static elimination lamp (7) and is uniformly negatively charged by a charging member (2) such as a charging charger or a charging roller. Then, latent image formation (the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential) is performed with the laser light irradiated by the laser optical system (3).
[0068]
Laser light is emitted from a semiconductor laser, and the surface of the image carrier (1) is scanned in the direction of the rotation axis of the image carrier (1) by a polygonal polygon mirror (polygon) that rotates at high speed.
The latent image formed in this way consists of toner particles or a mixture of toner particles and carrier particles supplied on the developing sleeve (41) which is a developer carrying member in the developing means or developing mechanism (4). Development with a developer forms a visible toner image.
At the time of developing the latent image, a voltage of an appropriate magnitude between the exposed portion and the non-exposed portion of the image carrier (1) or AC is applied to the developing sleeve (41) from a voltage application mechanism (not shown). A developing bias with a superimposed voltage is applied.
[0069]
On the other hand, a transfer medium (for example, paper) (8) is fed from a paper feed mechanism (not shown) and is synchronized with the leading edge of the image by a pair of upper and lower registration rollers (not shown). And the transfer mechanism (5) to transfer the toner image.
At this time, it is preferable that a potential having a polarity opposite to the polarity of toner charging is applied to the transfer mechanism (5) as a transfer bias. Thereafter, the transfer medium or intermediate transfer medium (8) is separated from the image carrier (1) to obtain a transfer image.
The toner particles remaining on the image carrier are collected by the cleaning member (61) into the toner collecting chamber (62) in the cleaning mechanism (6).
The collected toner particles are conveyed to a developing unit and / or a toner replenishing unit by a toner recycling means (not shown), and can be reused as necessary.
As the image forming apparatus, an apparatus in which a plurality of the developing devices described above are arranged is used, and a plurality of toner images, which are sequentially produced by the plurality of developing devices, are sequentially transferred onto a transfer material, and then sent to a fixing mechanism to be heated. Even after a plurality of toner images produced in the same manner are sequentially and sequentially transferred onto an intermediate transfer medium, and then collectively transferred to a transfer medium such as paper, Similarly, a fixing device may be used.
[0070]
In addition, an amorphous silicon photoconductor (hereinafter also referred to as “a-Si photoconductor”) is particularly effective as the image carrier provided in the image forming apparatus of the present invention.
In this a-Si photoconductor, a conductive support is heated to 50 ° C. to 400 ° C., and then a vacuum deposition method, a sputtering method, an ion plating method, a thermal CVD method, a photo CVD method, a plasma is formed on the support. The photoconductive layer made of a-Si is formed by a film forming method such as a CVD method.
Among them, a plasma CVD method, that is, a method in which a source gas is decomposed by direct current, high frequency or microwave glow discharge to form an a-Si deposited film on a support is preferably used.
[0071]
As the layer configuration of the a-Si-based photoreceptor, there are, for example, the following four types, and FIG. 3 is a schematic configuration diagram for explaining the layer configuration.
In the electrophotographic photoreceptor (500) shown in FIG. 3 (a), a photoconductive layer (502) made of a-Si: H, X and having photoconductivity is provided on a support (501). It is a thing.
The electrophotographic photosensitive member (500) shown in FIG. 3B has a photoconductive layer (502) made of a-Si: H, X and having photoconductivity on a support (501). And an amorphous silicon-based surface layer (503).
In addition, the electrophotographic photosensitive member (500) shown in FIG. 3C has a photoconductive layer (502) made of a-Si: H, X and having photoconductivity on a support (501). And an amorphous silicon-based surface layer (503) and an amorphous silicon-based charge injection blocking layer (504).
Furthermore, the electrophotographic photoreceptor (500) shown in FIG. 3D is provided with a photoconductive layer (502) on a support (501). The photoconductive layer (502) comprises a charge generation layer (505) and a charge transport layer (506) made of a-Si: H, X, and an amorphous silicon-based surface layer (503) thereon. Is.
[0072]
The support constituting the photoreceptor may be conductive or electrically insulating.
Examples of the conductive support include metals such as Al, Cr, Mo, Au, In, Nb, Te, V, Ti, Pt, Pd, and Fe, and alloys thereof such as stainless steel.
In addition, a film or sheet of synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, polyamide, or the like, an electrically insulating support such as glass or ceramic, and at least the side on which the photosensitive layer is formed It is also possible to use a support whose surface is subjected to a conductive treatment.
The shape of the support may be a cylindrical or plate-like or endless belt with a smooth or uneven surface, and its thickness is determined as appropriate so that a desired photoreceptor for an image forming apparatus can be formed. However, when flexibility as a photoreceptor for an image forming apparatus is required, it can be made as thin as possible within a range in which the function as a support can be sufficiently exhibited. However, the support is usually 10 μm or more from the viewpoints of manufacturing and handling, such as mechanical strength.
[0073]
The amorphous silicon photosensitive member that can be used in the present invention includes a charge injection blocking layer that functions to prevent charge injection from the conductive support side between the conductive support and the photoconductive layer, if necessary. It is more effective to provide (Fig. 3 (c)).
That is, the charge injection blocking layer has a function of blocking charge injection from the support side to the photoconductive layer side when the photosensitive layer is subjected to charging treatment with a constant polarity on its free surface. It has a so-called polarity dependency that does not exhibit such a function when subjected to a polar charging process. In order to provide such a function, the charge injection blocking layer contains a relatively large number of atoms for controlling conductivity as compared with the photoconductive layer.
The thickness of the charge injection blocking layer is preferably from 0.1 to 5 μm, more preferably from 0.3 to 4 μm, and most preferably from the viewpoint of obtaining desired electrophotographic characteristics and economic effects. It is desirable to be 5 to 3 μm.
[0074]
The a-Si-based photoconductive layer is formed on the undercoat layer as necessary, and the thickness of the photoconductive layer (502) is appropriately determined from the viewpoint of obtaining desired electrophotographic characteristics and economic effects. It is determined as desired, and is preferably 1 to 100 μm, more preferably 20 to 50 μm, and most preferably 23 to 45 μm.
[0075]
The charge transport layer is a layer mainly having a function of transporting charges when the photoconductive layer is functionally separated.
The charge transport layer includes at least silicon atoms, carbon atoms, and fluorine atoms as constituent elements, and is formed of a-SiC (H, F, O) including hydrogen atoms and oxygen atoms as required. It has conductive properties, particularly charge retention properties, charge generation properties, and charge transport properties. In the present invention, it is particularly preferable to contain an oxygen atom.
The layer thickness of the charge transport layer is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic characteristics and economic effects. The charge transport layer is preferably 5 to 50 μm, more preferably 10 to 40 μm. Optimally, the thickness is desirably 20 to 30 μm.
[0076]
The charge generation layer is a layer mainly having a function of generating charges when the photoconductive layer is functionally separated.
This charge generation layer is composed of a-Si: H containing at least silicon atoms as components and substantially no carbon atoms and, if necessary, hydrogen atoms, and has desired photoconductive properties, particularly charge generation properties. Have charge transport properties.
The layer thickness of the charge generation layer is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic characteristics and economic effects, etc., preferably 0.5 to 15 μm, more preferably 1 to 10 μm, optimally 1 ˜5 μm.
[0077]
The amorphous silicon photoconductor that can be used in the present invention can be further provided with a surface layer on the photoconductive layer formed on the support as described above, if necessary. It is preferable to form a surface layer.
This surface layer has a free surface, and is provided to achieve the object of the present invention mainly in moisture resistance, continuous repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability.
The thickness of the surface layer in the present invention is usually 0.01 to 3 μm, preferably 0.05 to 2 μm, and most preferably 0.1 to 1 μm. If the layer thickness is less than 0.01 μm, the surface layer is lost due to wear or the like during use of the photoreceptor, and if it exceeds 3 μm, electrophotographic characteristics such as an increase in residual potential are observed.
[0078]
The fixing unit included in the image forming apparatus of the present invention includes a heating body including a heating element, a film that contacts the heating body, and a pressure member that press-contacts the heating body via the film. And a fixing device that heats and fixes a recording material on which an unfixed image is formed between the film and the pressure member.
Here, the fixing device is a so-called surf fixing device in which a fixing film is rotated and fixed as shown in FIG.
In detail, the fixing film is an endless belt-like heat-resistant film, and is fixed and supported by a driving roller and a driven roller, which are supporting rotating members of the film, and a heater support provided below the rollers. It is stretched around the heating element disposed.
[0079]
The driven roller also serves as a tension roller for the fixing film, and the fixing film is rotationally driven in the clockwise direction by the rotational driving of the driving roller in the clockwise direction in the drawing. This rotational driving speed is adjusted to a speed at which the transfer material and the fixing film are equal in the fixing nip region L where the pressure roller and the fixing film are in contact with each other.
Here, the pressure roller is a roller having a rubber elastic layer having good releasability such as silicon rubber, and abutting with a total pressure of 4 to 10 kg against the fixing nip region L while rotating counterclockwise. It is pressed with pressure.
The fixing film preferably has excellent heat resistance, releasability and durability, and a thin film having a total thickness of 100 μm or less, preferably 40 μm or less is used.
For example, at least an image of a single layer film of a heat-resistant resin such as polyimide, polyetherimide, PES (polyether sulfide), PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), or a composite layer film, for example, a 20 μm thick film The contact surface is coated with a release coating layer of PTFE (tetrafluoroethylene resin), PFA or other fluororesin added with a conductive material to a thickness of 10 μm, or an elastic layer such as fluororubber or silicon rubber. It is a thing.
In the image forming apparatus of the present invention, by using the fixing unit having such a configuration, it is possible to suppress carrier adhesion, and it is extremely effective in extending the life without damaging each contact member. .
[0080]
In FIG. 4, the heating body of the present embodiment is composed of a flat substrate and a fixing heater, and the flat substrate is made of a material having high thermal conductivity and high electrical resistivity such as alumina and is in contact with the fixing film. A fixing heater composed of a resistance heating element is installed on the surface to be longitudinally arranged.
Such a fixing heater is, for example, Ag / Pd, Ta₂An electric resistance material such as N is applied in a linear or belt shape by screen printing or the like.
In addition, electrodes (not shown) are formed at both ends of the fixing heater, and the resistance heating element generates heat when energized between the electrodes.
Furthermore, a fixing temperature sensor constituted by a thermistor is provided on the surface of the substrate opposite to the surface provided with the fixing heater.
The temperature information of the substrate detected by the fixing temperature sensor is sent to a control unit (not shown), and the amount of electric power supplied to the fixing heater is controlled by the control unit, and the heating body is controlled to a predetermined temperature.
[0081]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example. Here, “parts” are all parts by weight.
Example 1
(Core material production example 1)
Manganese and iron oxides were mixed so that the molar ratio of Mn / Fe was 35/65, wet-ground and dispersed in water for 48 hours using a ball mill, dried, and then weakened in an electrothermal atmosphere firing furnace. Precalcination was performed at 900 ° C. for 2 hours in a reducing atmosphere.
Wet pulverization was performed by filling 10 vol. Of zirconia balls as a pulverization medium with 30 vol% of the ball mill pot volume, and filling the oxide slurry adjusted to a solid content of 25% with 20 vol% of the ball mill pot volume.
Subsequently, the obtained calcined product was roughly pulverized and then wet pulverized and dispersed in water again for 24 hours under the same conditions to obtain a manganese iron composite oxide slurry.
To this slurry, polyvinyl alcohol and a dispersant were added as a binder, granulated and dried using a spray dryer, and classified using an ultrasonic vibration sieve to prepare granulated particles.
The obtained granulated particles were subjected to main firing at 1200 ° C. for 4 hours in an air atmosphere by an electrothermal atmosphere firing furnace to obtain manganese ferrite particles.
Furthermore, the obtained manganese ferrite particles were classified using an ultrasonic vibration sieve to obtain a core material (1).
[0082]
(Coat formula 1)
Acrylic resin solution (solid content = 50% by weight) 60 parts
Guanamin solution (solid content = 70% by weight) 15 parts
150 parts of straight silicone resin (solid content = 20%)
Dibutyltin diacetate 1.5 parts
100 parts of alumina particles (number average particle size = 0.3 μm)
Carbon black 6 parts
1500 parts of toluene
The above formulation was dispersed with a homomixer for 30 minutes to prepare a coating solution for forming a coat layer.
[0083]
This was coated on the surface of 5000 parts of the core material (1) with a fluidized bed spray coater, and then heated at 150 ° C. for 1 hour to obtain a carrier (C1). When the particle size distribution of the carrier (C1) was measured with a Microtrac particle size distribution analyzer (Model X100 manufactured by Microtrac), the weight average particle diameter (D4) was 36.5 μm, and the number average diameter (D1) was 34.1 μm. Carrier particles of 12 μm or less were 0.08% by weight.
Further, when the surface of the carrier (C1) was observed with a scanning electron microscope at a magnification of 2000 times, irregularities derived from alumina were formed on the surface, and the average height of the carrier surface irregularities measured in a non-contact manner using a laser microscope. The difference was 0.3 μm.
Next, when the magnetization (σb) at 1000 oersted of this carrier (C1) was measured using a multi-sample rotational magnetization measuring device (REM-1-10 type manufactured by Toei Kogyo Co., Ltd.), 66.0 emu / g.
Subsequently, a carrier (C1) desorption test was performed according to the following procedure.
First, a development sleeve for a color printer IPSiO color 8000 manufactured by Ricoh was modified as a test development sleeve so that the peak magnetic flux density of the development pole was 100 mT.
Next, the developing sleeve for this test was attached to the developing unit, and the rotational speed of the sleeve was adjusted using a separately prepared motor so that the centrifugal force (detachment force) was three times the gravity (test). In the developing unit for developing, since the developing sleeve diameter was 18 mmφ, the sleeve rotation speed was {3 (times) × 9.8 (m / s²) × 0.009 (m)}^1/2× 1000 (mm) / {18 (mm) × π} × 60 (sec) = 546 rpm).
250 g of the test carrier (C1) was placed in the developing unit, and the developing sleeve was continuously rotated for 30 minutes to recover the release carrier for composition uniformity evaluation from the developing region opening of the developing unit.
The recovered desorbed carriers are subjected to elemental analysis by EPMA to determine the distribution of manganese and iron elements, image analysis is performed on 200 carrier particles, and the atomic number reference content of manganese and iron for each individual carrier particle is determined. The average value and the standard deviation of the ratio of manganese element in the iron element + manganese element were calculated, and the coefficient of variation was obtained.
The average value M of the manganese element ratio is 0.35, and the carrier particles having a manganese element content of 0.6 times or less of M are 5.5% by number, and the manganese element content is 0.5 times or less of M. The number of carrier particles having a rate was 3.0% by number.
[0084]
(Toner Production Example 1)
Partially cross-linked polyester resin 79.5 parts
(Bisphenol A ethylene oxide addition alcohol,
Propylene oxide addition alcohol of bisphenol A,
Condensation polymer of terephthalic acid and trimellitic acid)
(Mw = 15000, glass transition point = 61 ° C.)
Carbon black 15 parts
1 part of zirconium salt of di-tert-butylsalicylic acid
Carnauba wax; Noda Wax 5 parts
[0085]
The mixture having the above composition was kneaded for 30 minutes with a two-roll kneader, and then pulverized and classified using a mechanical pulverizer / airflow classifier to obtain a toner base.
Further, 1 part of hydrophobic silica fine particles and 1 part of hydrophobic titanium oxide fine particles were added to 100 parts of the toner base, and mixed for a total of 2 minutes with a Henschel mixer to obtain a toner (T1).
When the particle size distribution of the toner (T1) was measured with a Coulter counter TA2, the weight average diameter D4 = 6.2 μm and the number-based 10% diameter calculated from the cumulative number distribution = 2.5 μm.
Next, 920 parts of carrier (C1) and 80 parts of toner (T1) were mixed for 1 minute with a turbula mixer to obtain a two-component developer.
[0086]
Using this developer, a Ricoh color printer IPSiO color 8000 was used to perform a continuous image drawing test on an A4 size, 300% original image with a 6% image area ratio. Images, halftone images and solid images were output for image quality evaluation.
At this time, the magnetic flux density of the developing pole was 110 mT, and the closest distance between the developing sleeve and the photosensitive member in the developing portion was adjusted to 0.6 mm.
The electrostatic charge image on the image carrier at the time of image output was set to background portion = −700V and image portion = −200V. Further, a developing bias potential in which an AC voltage with a peak-to-peak voltage of 1500 V and a frequency of 2000 Hz was superimposed on a DC voltage (−500 V) was applied to the developing sleeve.
For image quality evaluation, carrier adhesion in blank images and solid images, character thickening of characters, blur and gradation of halftone images, stability of image density in solid images, and other defects in each image evaluated.
Initially, good image quality was obtained both after 300,000 sheets, and it was found that the carrier of the present invention was useful in both image quality and lifetime.
The image density was measured using a Macbeth densitometer (RD-914), and the other items were visually evaluated.
The evaluation results at the initial stage and after 300,000 sheets are shown in Table 1-1, Table 1-2, and Table 1-3.
[0087]
Example 2
(Core material production example 2)
A core material (2) was prepared in the same manner as in the core material production example 1 except that the pulverization / dispersion time of the manganese and iron oxides before calcination was 36 hours.
A carrier (C2) was obtained in the same manner as in Example 1 except that the core material (2) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C2). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0088]
Example 3
(Core material production example 3)
Manganese and iron oxides before calcination were pulverized and dispersed by a ball mill for 120 hours, and the dispersion time by a ball mill after calcination coarse pulverization was 48 hours. A core material (3) was prepared.
A carrier (C3) was obtained in the same manner as in Example 1 except that the core material (3) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C3). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0089]
Example 4
(Core material production example 4)
Manganese and iron oxides were mixed so that the molar ratio of Mn / Fe was 10/90, the main firing temperature was 1250 ° C., and fired in a weak reducing atmosphere as in the core material production example 3. A core material (4) was prepared.
A carrier (C4) was obtained in the same manner as in Example 1 except that the core material (4) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C4). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0090]
Example 5
(Core material production example 5)
A core material (5) was prepared in the same manner as in Core material production example 1 except that manganese and iron oxides were mixed so that the Mn / Fe molar ratio was 40/60.
A carrier (C5) was obtained in the same manner as in Example 1 except that the core material (5) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C5). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0091]
Example 6
(Core material production example 6)
In the granulation step of the core material production example 1 and the classification step after the main baking step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve are adjusted to obtain the core material (6) having a slightly small average particle diameter. It was.
A carrier (C6) was obtained in the same manner as in Example 1 except that the core material (6) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C6). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0092]
Example 7
(Core material production example 7)
In the granulation step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve are adjusted to obtain the core material (7) having a slightly large average particle diameter. It was.
A carrier (C7) was obtained in the same manner as in Example 1 except that the core material (7) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C7). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0093]
Example 8
(Core material production example 8)
In the classification step after the main firing step of Core Material Production Example 1, the classification conditions of the manganese ferrite particles with an ultrasonic vibration sieve were adjusted to obtain a core material (8) having a slightly larger amount of fine powder.
A carrier (C8) was obtained in the same manner as in Example 1 except that the core material (8) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C8). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0094]
Example 9
(Core material production example 9)
In the granulation / drying step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve are adjusted, and the core material (9) having a slightly broad particle size distribution Obtained.
A carrier (C9) was obtained in the same manner as in Example 1 except that the core material (9) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C9). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0095]
Example 10
(Coat prescription 2)
Acrylic resin solution (solid content = 50% by weight) 60 parts
Guanamin solution (solid content = 70% by weight) 15 parts
150 parts of straight silicone resin (solid content = 20%)
Dibutyltin diacetate 1.5 parts
50 parts of alumina particles (number average particle size = 0.3 μm)
Carbon black 4 parts
1500 parts of toluene
A carrier (C10) was obtained in the same manner as in Example 1 except that the above formulation was used as a coating solution for forming a coat layer.
Each evaluation result was obtained like Example 1 except having used carrier (C10). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0096]
Example 11
(Coat prescription 3)
Acrylic resin solution (solid content = 50% by weight) 60 parts
Guanamin solution (solid content = 70% by weight) 15 parts
150 parts of straight silicone resin (solid content = 20%)
Dibutyltin diacetate 1.5 parts
Carbon black 1 part
1500 parts of toluene
A carrier (C11) was obtained in the same manner as in Example 1 except that the above formulation was used as a coating solution for forming a coat layer.
Each evaluation result was obtained like Example 1 except having used carrier (C11). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0097]
Example 12
(Core material production example 10)
Manganese and iron oxides were mixed so that the molar ratio of Mn / Fe was 10/90, the main firing temperature was 1250 ° C., and fired in a strong reducing atmosphere for 5 hours. Similarly, a core material (10) was prepared.
A carrier (C12) was obtained in the same manner as in Example 1 except that the core material (10) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C12). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0098]
Example 13
(Core material production example 11)
The core material (11) was prepared in the same manner as in Core Material Production Example 1 except that manganese and iron oxides were mixed so that the Mn / Fe molar ratio was 40/60, and the main firing time was 8 hours. Created.
A carrier (C13) was obtained in the same manner as in Example 1 except that the core material (11) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C13). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0099]
Example 14
(Coat prescription 4)
Acrylic resin solution (solid content = 50% by weight) 60 parts
Guanamin solution (solid content = 70% by weight) 15 parts
150 parts of straight silicone resin (solid content = 20%)
Dibutyltin diacetate 1.5 parts
100 parts of alumina particles (number average particle size = 0.3 μm)
Carbon black 8 parts
1500 parts of toluene
A carrier (C14) was obtained in the same manner as in Example 1 except that the above formulation was used as a coating solution for forming a coat layer.
Each evaluation result was obtained like Example 1 except having used carrier (C14). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0100]
Example 15
(Coat prescription 5)
Acrylic resin solution (solid content = 50% by weight) 60 parts
Guanamin solution (solid content = 70% by weight) 15 parts
150 parts of straight silicone resin (solid content = 20%)
Dibutyltin diacetate 1.5 parts
100 parts of alumina particles (number average particle size = 0.3 μm)
Carbon black 3 parts
1500 parts of toluene
A carrier (C15) was obtained in the same manner as in Example 1 except that the above formulation was used as a coating solution for forming a coat layer.
Each evaluation result was obtained like Example 1 except having used carrier (C15). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0101]
(Examples 16 and 17)
The kneaded product of Toner Production Example 1 was subjected to pulverization / classification conditions to obtain toner bases having different weight average particle diameters. These were mixed with external additives by the same method as in Toner Production Example 1 to obtain toners (T2) and (T3) having a weight average particle diameter of 11 μm and 3.8 μm.
Each evaluation result was obtained in the same manner as in Example 1 except that the toners (T2) and (T3) were used. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0102]
Comparative Example 1
(Core material production example 12)
Manganese and iron oxides were mixed so that the molar ratio of Mn / Fe was 35/65, and were wet pulverized and dispersed in water for 18 hours using a ball mill, followed by drying and 850 ° C., 1 Temporary firing was performed.
The wet pulverization was performed by filling 10 vol. Of zirconia balls as a pulverization medium with a volume of 25 vol% of the ball mill pot volume, and filling an oxide slurry adjusted to a solid content of 25% with a volume of 20 vol% of the ball mill pot volume.
Subsequently, the obtained calcined product was wet-ground and dispersed in water again for 24 hours under the same conditions to obtain a manganese iron composite oxide slurry.
To this slurry, polyvinyl alcohol and a dispersant were added as a binder, granulated and dried using a spray dryer, and classified using an ultrasonic vibration sieve to prepare granulated particles.
The obtained granulated particles were subjected to main firing at 1200 ° C. for 4 hours in a weak reducing atmosphere to obtain manganese ferrite particles.
Furthermore, the obtained manganese ferrite particles were classified using an ultrasonic vibration sieve to obtain a core material (12).
A carrier (C16) was obtained in the same manner as in Example 1 except that the core material (12) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C16). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0103]
Comparative Example 2
(Core material production example 13)
Manganese and iron oxides were mixed so that the Mn / Fe molar ratio was 7/93, the main firing temperature was 1250 ° C., and fired in a reducing atmosphere for 5 hours. Thus, a core material (13) was prepared.
A carrier (C17) was obtained in the same manner as in Example 1 except that the core material (13) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C17). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0104]
Comparative Example 3
(Core material production example 14)
A core material (14) was prepared in the same manner as in the core material production example 1 except that manganese and iron oxides were mixed so that the Mn / Fe molar ratio was 50/50.
A carrier (C18) was obtained in the same manner as in Example 1 except that the core material (14) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C18). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0105]
Comparative Example 4
(Core material production example 15)
In the granulation step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve are adjusted to obtain the core material (15) having a smaller average particle diameter. It was.
A carrier (C19) was obtained in the same manner as in Example 1 except that the core material (15) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C19). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0106]
Comparative Example 5
(Core material production example 16)
In the granulation step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve are adjusted to obtain the core material (16) having a larger average particle size. It was.
A carrier (C20) was obtained in the same manner as in Example 1 except that the core material (16) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C20). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0107]
Comparative Example 6
(Core material production example 17)
In the granulation step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve were adjusted to obtain a core material (17) with a large amount of fine powder.
A carrier (C21) was obtained in the same manner as in Example 1 except that the core material (17) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C21). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0108]
Comparative Example 7
(Core material production example 18)
In the granulation step of the core material production example 1 and the classification step after the main firing step, the classification conditions of the manganese ferrite particles by the ultrasonic vibration sieve were adjusted to obtain a core material (18) having a broad particle size distribution.
A carrier (C22) was obtained in the same manner as in Example 1 except that the core material (18) was used.
Each evaluation result was obtained like Example 1 except having used carrier (C22). The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0109]
Example 18
As a two-component developer adjustment, a two-component developer was obtained in the same manner as in Example 1 except that 850 parts of the carrier (C1) and 150 parts of the toner (T1) were mixed for 3 minutes with a turbula mixer.
Each evaluation result was obtained in the same manner as in Example 1 except that this developer was used. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0110]
Examples 19 and 20
The same image test as in Examples 1 and 4 was performed by replacing the internal magnet so that the peak magnetic flux density of the developing pole of the developing sleeve was 140 mT. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0111]
Examples 21 and 22
The same image test as in Examples 1 and 5 was performed by replacing the internal magnet so that the peak magnetic flux density of the developing pole of the developing sleeve was 70 mT. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0112]
Examples 23 and 24
An image test was performed in the same manner as in Example 1 except that the closest distance between the developing sleeve and the photosensitive member in the developing unit was 0.15 mm and 0.9 mm. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
[0113]
Example 25
In Example 1, only a DC voltage (−500 V) was applied as the developing bias, and the same image evaluation as in Example 1 was performed. The evaluation results are shown in Table 1-1, Table 1-2, and Table 1-3.
Evaluation result (initial)
[0114]
[Table 1-1]

[0115]
[Table 1-2-1]

[0116]
[Table 1-2-2]

Evaluation result (after 300,000 sheets)
[0117]
[Table 1-3-1]

[0118]
[Table 1-3-2]

[0119]
Finally, a continuous image drawing test of 1 million sheets was continuously performed for Example 1 and Example 3. As a result, a high-definition and high-resolution image completely comparable to the initial image was obtained.
[0120]
【The invention's effect】
As is apparent from the detailed and specific description above, according to the present invention, as is clear from the comparison between the examples and the comparative examples, damage to peripheral members due to the crushing of the carrier particles can be reduced under a wide range of development conditions. An electrophotographic carrier, an electrophotographic two-component developer, a developing method, a developing device, which are effective for obtaining a high-definition and high-resolution high-quality image with little fluctuation in image quality and image deterioration An image forming apparatus can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a developing device according to the present invention.
FIG. 2 is a cross-sectional view illustrating an example of an image forming apparatus having a developing device according to the present invention.
FIG. 3 is a schematic configuration diagram for explaining a layer configuration in the present invention.
FIG. 4 is a view showing a so-called surf fixing device that rotates and fixes a fixing film in the present invention.
[Explanation of symbols]
1 Image carrier (photosensitive drum)
2 Image carrier charging member
3 Image exposure system
4 Development mechanism
5 Transcription mechanism
6 Cleaning mechanism
7 Static elimination lamp
8 Transfer media
10 Toner particles
11 Developer
41 Development sleeve
42 Developer accommodating member
43 Doctor Blade
44 Support case
45 Toner Hopper
46 Developer container
47 Developer stirring mechanism
48 Agitator
49 Toner supply mechanism
51 transfer member,
52 Static elimination brush
61 Cleaning member
62 Toner recovery chamber
500 Photoconductor for electrophotography
501 Support
502 Photoconductive layer
503 Amorphous silicon surface layer
504 Amorphous silicon charge injection blocking layer
505 Charge generation layer
506 Charge transport layer

Claims (19)

A carrier for an electrophotographic developer, characterized in that manganese-based ferrite is used as a core material, and at least a coat layer is provided on the surface thereof, and satisfies the following conditions 1) to 3).
1) After holding a carrier magnetically on a cylindrical sleeve having a fixed magnet inside and having a magnetic pole region having a surface magnetic flux density peak of 100 mT in a direction perpendicular to the rotation axis, the cylindrical sleeve is rotated for 30 minutes. As a result of elemental analysis by applying a desorption force three times the gravity in the direction perpendicular to the rotation axis and desorbing from the magnetic pole region having the peak magnetic flux density, the content of iron element in one carrier particle is When M1 (mol%) and the content of manganese element are M2 (mol%), the average value M of M2 / (M1 + M2) is 0.10 to 0.45, and M2 / (M1 + M2) is the average value. The number of particles less than 0.6 times M is 10% by number or less.
2) A weight average particle diameter (D4) is 25-65 micrometers, and the particle | grains of 12 micrometers or less are the ratio of 0.3 weight% or less.
3) The ratio D4 / D1 of the weight average particle diameter (D4) and the number average particle diameter (D1) is 1 to 1.3.   2. The carrier for an electrophotographic developer according to claim 1, wherein the coating layer on the surface contains at least a resin and insulating inorganic particles.   The carrier for an electrophotographic developer according to claim 1, wherein the surface has irregularities, and the average height difference of the irregularities is 0.1 to 2.0 μm.   The carrier for an electrophotographic developer according to any one of claims 1 to 3, wherein the carrier magnetization σb at 1000 oersted is 40 to 75 emu / g. An electric resistance R when a magnetic brush of the carrier having a space occupancy of 40% is formed between parallel plate electrodes with a gap d (mm) and the AC voltage E of Formula (1) is applied at a frequency of 1000 Hz in the same direction as the brush. The carrier for an electrophotographic developer according to claim 1, wherein the carrier is 1.0 × 10 9 to 1.0 × 10 11 Ω · cm.

However, d = 0.40 ± 0.05 (mm), E is a peak voltage.   An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 5 and a toner containing at least a binder resin and a colorant.   7. The electrophotographic developer according to claim 6, wherein the toner weight is 2 to 12% by weight.   The electrophotographic developer according to claim 6, wherein the toner contains a releasable substance.   9. The electrophotographic developer according to claim 5, wherein the toner has a weight average particle diameter of 4 to 10 [mu] m. A developing device comprising a frictional charging means for charging the toner by rubbing the toner and the carrier, and a rotatable developer holding means having a magnetic field generating means inside the carrier and the developer containing the charged toner; An image forming apparatus comprising at least an image carrier for forming an electrostatic latent image, wherein the electrophotographic carrier according to any one of claims 1 to 5 is used, comprising a developer holder and an image carrier. An electrophotographic image forming apparatus, wherein a maximum value of a magnetic flux density B (mT) in a direction normal to the surface of the developer holding member in the vicinity of a developing region which is a proximity portion satisfies the formula (3).

However, σb (emu / g) is carrier magnetization at 1000 oersted.   The electrophotographic image forming apparatus according to claim 10, further comprising a maintaining unit configured such that a distance between closest portions in a developing region of the image carrier and the developer holding member is 0.20 to 0.80 mm.   12. The electrophotographic image forming apparatus according to claim 10, further comprising a voltage application mechanism that applies a DC bias voltage to the developer holder.   12. The electrophotographic image forming apparatus according to claim 10, further comprising a voltage application mechanism that applies a bias voltage obtained by superimposing an AC voltage on a DC voltage to the developer holder.   14. A toner recycling mechanism comprising at least a cleaning mechanism for cleaning the image carrier and a recovered toner transport mechanism for transporting toner recovered by the cleaning mechanism to the developing mechanism. Electrophotographic image forming apparatus.   11. The apparatus according to claim 10, further comprising: a transfer unit that transfers each toner image sequentially formed on the image carrier by a plurality of developing devices onto the medium; and a fixing unit that fixes the toner image transferred onto the medium. The electrophotographic image forming apparatus according to any one of 14.   16. The fixing unit includes a heating body having a heating element, a film in contact with the heating body, and a pressure member in pressure contact with the heating body through the film. The electrophotographic image forming apparatus described in 1.   17. The electrophotographic image forming apparatus according to claim 10, wherein the image carrier is an amorphous silicon photoconductor. A triboelectric charging mechanism that charges toner by rubbing the toner and the carrier, a rotatable developer holder having a magnetic field generating means inside the carrier and the developer containing the charged toner, and an electrostatic latent image are formed. A process cartridge using the electrophotographic developer carrier according to any one of Claims 1 to 5, wherein the development is a proximity portion of the developer holder and the image carrier. A process cartridge characterized in that the maximum value of the magnetic flux density B (mT) in the normal direction of the surface of the developer holder in the vicinity of the region satisfies the formula (3).

However, σb (emu / g) is carrier magnetization at 1000 oersted.   The process cartridge according to claim 18, wherein the electrophotographic developer according to claim 6 is accommodated.

Images