JP3667059B2 - Magnetic carrier for electrophotographic developer, two-component developer and image forming method - Google Patents

Description

【００３５】
下記式（Ｉ）及び（ＩＩ）の構成単位を有するシリコーンオリゴマー又はシリコーン樹脂を生成する。
【００３６】
【外２０】

（式中、Ｒ¹ 〜Ｒ⁵ はそれぞれメチル基、エチル基又はフェニル基から選ばれる炭化水素基を表わす。）
【００３７】
シリコーンオリゴマー又はシリコーン樹脂を生成する際に下記式（ＩＩＩ）、（ＩＶ），（Ｖａ）及び（Ｖｂ）を使用しても良い。
【００３８】
【外２１】

（式中、Ｒ⁶ 及びＲ⁷ は炭素数が１以上の炭化水素基を表わす。）
【００３９】
【外２２】

【００４０】
さらに、メタクリル酸エステル又はアクリル酸エステルと下記式（ＶＩ）
【００４１】
【外２３】

（式中、Ｒ⁸ ，Ｒ⁹ 及びＲ¹⁰は同一又は異なる基でありＣＨ₃ 、ＣＨ₂ ＣＨ₃ 、ＯＣＨ₃ 又はＯＣＨ₂ ＣＨ₃ を表す。但し、Ｒ⁸ 、Ｒ⁹ 及びＲ¹⁰の少なくとも１つはＯＣＨ₃ 又はＯＣＨ₂ ＣＨ₃ である。）
で示される化合物とを反応させてオリゴマー又は樹脂を上記シリコーンオリゴマー又はシリコーン樹脂と組み合わせて使用してもよい。
【００４２】
本発明のシリコーン樹脂被覆磁性キャリアにおけるキャリア芯材としては、従来より公知のものが使用できる。例えば、鉄、コバルト等の強磁性体金属の粒子、磁性体を樹脂に分散させた粒子、マグネタイト粒子、ヘマタイト粒子、フェライト粒子等が挙げられる。好ましくは、表面をコントロールし易いフェライト粒子や鉄粒子を用いるのがよく、特にフェライト粒子が好ましい。
【００４３】
本発明におけるキャリア芯材の粒径は、個数平均粒径２０〜１００μｍが好ましく、特に３０〜６５μｍのものが好ましい。これは個数平均粒径が２０μｍ未満になると、キャリア粒子の分布において微粉が多くなり、１粒子当たりの磁化が低くなりキャリアの飛散が生じやすい。また、キャリアの個数平均粒子が１００μｍを超えると、キャリアの比表面が低下しトナーの飛散が生じやすい。また、ベタ部分の多いフルカラー画像形成では、特にベタ部の再現が低下する。
【００４４】
本発明における被覆層を形成するためのシリコーンオリゴマー又はシリコーン樹脂の溶剤としては、トルエン、キシレン、メチルエチルケトン、メチルイソブチルケトンの如き有機溶剤が挙げられる。
【００４５】
最終的に生成されたシリコーン樹脂被覆磁性キャリアの表面が上記原子組成を満たすように被覆液を調製し、磁性キャリアコアを該被覆液でコートして後、被覆層の焼結温度を通常行うよりも低い、１２０〜１７０℃で焼き付けさせるのが良い。この理由としては、１２０℃を下回る温度で焼結させると流動性が低下し、トナーに対する耐スペント性も低下する。また逆に１７０℃を上回る焼結温度であると理由は定かではないが、アクリル基又は含窒素基を酸化することによる帯電性の低下を招き、トナー飛散やカブリが生じやすくなるためである。
【００４６】
焼付装置としては、外部加熱方式又は内部加熱方式のいずれでもよく、例えば、固定式又は流動式電気炉、ロータリー式電気炉、バーナー炉でもよく、もしくはマイクロウエーブによる焼付でもよい。
【００４７】
シリコーン樹脂被覆磁性キャリア中の樹脂被覆量としては、シリコーン樹脂被覆磁性キャリア総量に対し０．１０〜５．０重量％であり、好ましくは０．１５〜２．０重量％である。
【００４８】
本発明のキャリアと組み合わせて使用するトナーとしては、重量平均粒径が９μｍ以下、好ましくは重量平均粒径３．０〜８．０μｍの範囲であることが好適である。
【００４９】
トナーの結着樹脂としては、例えば、ポリスチレン、スチレン−ブタジエン共重合体、スチレン−アクリル共重合体の如きスチレン系共重合体；エチレン−酢酸ビニル共重合体、エチレン−ビニルアルコール共重合体のようなエチレン系共重合体；フェノール系樹脂、エポキシ系樹脂、ポリアミド樹脂、ポリエステル樹脂、マレイン酸系樹脂が挙げられる。
【００５０】
これらの樹脂の中で、特に負帯電能の高いポリエステル系樹脂を用いた場合、本発明キャリアの組み合わせ効果は大きい。
【００５１】
特に、次式
【００５２】
【外２４】

（式中Ｒはエチレンまたはプロピレン基であり、ｘ，ｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２〜１０である。）で代表されるビスフェノール誘導体もしくは置換体をジオール成分とし、２価以上のカルボン酸またはその酸無水物またはその低級アルキルエステルとからなるカルボン酸成分（例えばフマル酸、マレイン酸、無水マレイン酸、フタル酸、テレフタル酸、トリメリット酸、ピロメリット酸など）とを共縮重合したポリエステル樹脂がシャープな溶融特性を有するのでより好ましい。
【００５３】
着色剤としては、非磁性トナーとしては公知の染顔料、例えばフタロシアニンブルー、インダスレンブルー、ピーコックブルー、パーマネントレッド、レーキレッド、ローダミンレーキ、ハンザイエロー、パーマネントイエロー、ベンジジンイエロー等を使用することができる。その含有量としては、ＯＨＰ用フィルムの透過性に対し敏感に反映するために、結着樹脂１００重量部に対して１２重量部以下であり、好ましくは０．５〜９重量部である。
【００５４】
本発明に使用されるトナーには、荷電制御剤をトナーに配合しても良い。荷電制御剤の添加によって現像システムに応じた最適の摩擦帯電量とすることが出来る。
【００５５】
負荷電制御剤としては、有機金属錯体及びキレート化合物が好ましい。アゾ系金属錯体、アルミニウムアセチルアセトナート、鉄（ＩＩ）アセチルアセトナート、３．５−ジーターシャリーブチルサリチル酸クロム，３，５−ジーターシャリーブチルサリチル酸アルミ、３．５−ジーターシャリーブチルサリチル酸亜鉛等を挙げることが出来る。特にアセチルアセトンの金属錯体（モノアルキル置換体及びジアルキル置換体を包含する）、サリチル酸系金属錯体（モノアルキル置換体及びジアルキル置換体を包含する）、又はそれらの塩が好ましく、特にはサリチル酸系金属錯体又は塩が好適である。
【００５６】
上述の荷電制御剤はトナーに添加する際には、結着樹脂１００重量部に対して０．１〜２０重量部、より好ましくは０．２〜１０重量部で使用することが好適である。特にカラー画像形成に使用される場合には無色若しくは淡色の荷電制御剤を使用することが好ましい。
【００５７】
本発明に使用されるトナーには、シリカ微粉末、アルミナ微粉末、酸化チタン微粉末、ポリテトラフロロエチレン微粉末、ポリビニルデンフロライド微粉末、ポリメチルメタクリレート微粉末、ポリスチレン微粉末、シリコーン微粉末の如き微粉末を混合又は添加することが好適である。トナーに対して上述した微粉末を混合又は添加することによって、トナーとキャリア、或いはトナー相互の間に微粉末が存在することになり、現像剤の流動性が向上され、且つ更に現像剤の寿命も向上されることになる。上述した微粉末の表面積としては、ＢＥＴ法による窒素吸着によった比表面積が３０ｍ² ／ｇ以上、特に５０〜４００ｍ² ／ｇの範囲のものが良好な結果が得られる。かかる微粉末の添加量は、トナーに対して０．１〜２０重量％で使用することが好適である。
【００５８】
本発明のトナーには更に熱ロール定着時の離型性を向上させる目的でポリエチレン、ポリプロピレン、マイクロクリスタリングワックス、カルナバワックス、サゾールワックル、パラフィンワックスの如きワックス成分を添加することも出来る。
【００５９】
この様な組成を有するトナーは、ビニル系熱可塑性樹脂又は非ビニル系の熱可塑性樹脂、着色剤、荷電制御剤、その他の添加剤を混合機により十分に混合してから加熱ロール、ニーダー、エクストルーダーの如き混練機を用いて溶融及び混練して樹脂類を十分に混合して樹脂類を互いに混合し、その中に顔料若しくは染料を分散させる。溶融混練物を冷却後、粉砕及び分級を行ってトナー粒子を得ることが出来る。該トナー粒子はそのままで使用することも出来るが、必要に応じた種類及び量の微粉体を外添して使用することも出来る。
【００６０】
かかる微粉末の外添処理は、ヘンシェルミキサーの如き混合機を使用して行うことが出来る。この様にして得られたトナーは本発明のキャリア粒子と混合されて二成分系現像剤とされる。上述の二成分系現像剤を形成する場合、現像プロセスにも依存するが典型的には現像剤中のトナーの割合が１〜２０重量％、より好ましくは１〜１０重量％の範囲であることが好適である。かかる二成分系現像剤のトナーの摩擦帯電量としては２０〜１００μＣ／ｇの範囲であることが好適であり、最も好ましく３０〜６０μＣ／ｇである。本発明で使用した摩擦帯電量の測定条件については後述する。
【００６１】
キャリア及びトナーの各物性の測定方法について以下に説明する。
【００６２】
キャリアの平均粒径の測定
キャリアの粒径は、光学顕微鏡によりランダムに３００個以上抽出し、ニレコ社（株）製の画像処理解析装置Ｌｕｚｅｘ３により水平方向フェレ径をもってキャリア粒径として測定するものとする。
【００６３】
トナーの粒度分布の測定
測定装置としては、コールターカウンターＴＡ−ＩＩ或いはコールターマルチサイザーＩＩ（コールター社製）を用いる。電解液は、１級塩化ナトリウムを用いて、約１％ＮａＣｌ水溶液を調製する。例えば、ＩＳＯＴＯＮ−ＩＩ（コールターサイエンティフィックジャパン社製）が使用できる。測定方法としては、前記電解水溶液１００〜１５０ｍｌ中に分散剤として、界面活性剤（好ましくはアルキルベンゼンスルホン酸塩）を、０．１〜５ｍｌ加え、さらに測定試料を２〜２０ｍｇ加える。試料を懸濁した電解液は、超音波分散器で約１〜３分間分散処理を行ない、前記測定装置により、アパーチャーとして１００μｍアパーチャーを用いて、トナー粒子の体積及び個数を各チャンネルごとに測定して、トナーの体積分布と個数分布とを算出する。それから、トナー粒子の体積分布から求めた重量基準のトナーの重量平均粒径（Ｄ４）（各チャンネルの中央値をチャンネル毎の代表値とする）を求める。
【００６４】
チャンネルとしては、２．００〜２．５２μｍ；２．５２〜３．１７μｍ；３．１７〜４．００μｍ；４．００〜５．０４μｍ；５．０４〜６．３５μｍ；６．３５〜８．００μｍ；８．００〜１０．０８μｍ；１０．０８〜１２．７０μｍ；１２．７０〜１６．００μｍ；１６．００〜２０．２０μｍ；２０．２０〜２５．４０μｍ；２５．４０〜３２．００μｍ；３２．００〜４０．３０μｍの１３チャンネルを用いる。
【００６５】
トナーの凝集度
試料（外添剤を有するトナー等）の流動特性を測定する一手段として凝集度を用いるものであり、この凝集度の値が大きいほど試料の流動性は悪いと判断する。
【００６６】
測定装置としては、デジタル振動計（デジバイブロ ＭＯＤＥＬ １３３２）を有するパウダーテスター（細川ミクロン社製）を用いる。
【００６７】
測定法としては、振動台に２００メッシュ，１００メッシュ，６０メッシュのフルイを目開の狭い順に、すなわち６０メッシュフルイが最上位にくるように２００メッシュ，１００メッシュ，６０メッシュのフルイ順に重ねてセットする。
【００６８】
このセットした６０メッシュフルイ上に正確に秤量した試料５ｇを加え、振動台への入力電圧を２１．７Ｖになるようにし、デジタル振動計の変位の値を０．１３０にし、その際に振動台の振幅が６０〜９０μｍの範囲に入るように調整し（レオスタット目盛約２．５）、約１５秒間振動を加える。その後、各フルイ上に残った試料の重量を測定して下式にもとずき凝集度を算出する。
【００６９】
【外２５】

【００７０】
試料は温度２３℃，湿度６０％ＲＨの環境下で約１２時間放置したものを用い、測定環境は温度２３℃，湿度６０％ＲＨである。
【００７１】
次に、図１に示す現像装置を参照して本発明の画像形成方法を説明する。
【００７２】
静電荷像担持体（感光体）１は静電記録用絶縁ドラムあるいはα−Ｓｅ，ＣｄＳ，ＺｎＯ_２ ，ＯＰＣ，α−Ｓｉの如き光導電絶縁物質層を持つ感光ドラムもしくは感光ベルトである。静電荷像担持体１は図示しない駆動装置によって矢印ａ方向に回転される。２は静電荷像担持体１に近接もしくは接触されている現像剤担持体としての現像スリーブであり、例えばアルミニウム、ＳＵＳ３１６の如き非磁性材料で構成されている。現像スリーブ２を現像容器の左下方壁に容器長手方向に形成した横長開口に右略半周面を容器２０内へ突入させ、左略半周面に容器外へ露出させて回転自在に軸受けさせて横設してあり、矢印ｂ方向に回転駆動される。
【００７３】
３は現像スリーブ（現像剤担持体）２内に挿入し図示の位置姿勢に位置決め保持した固定磁界発生手段としての固定の永久磁石（マグネット）であり、現像スリーブ２が回転駆動されてもこの磁石３は図示の位置・姿勢にそのまま固定保持される。この磁石３はＮ極の磁極３ａ，３ｅ及び３ｄを有し、Ｓ極の磁極３ｂ及び３ｃの５磁極を有する。磁石３は永久磁石に代えて電磁石を配設してもよい。
【００７４】
４は現像スリーブ２を配設した現像剤供給器開口の上縁側に、基部を容器側壁に固定した、現像剤規制部材としての非磁性ブレードであり、例えばＳＵＳ３１６を横断面路図の如くＬ字形に曲げ加工したものである。
【００７５】
５は非磁性ブレード（現像剤規制部材）４の下面側に上面を接触させ前端面を現像剤案内面とした磁性キャリア限定部材であり、非磁性ブレード４及び磁性キャリア返し部材５などによって構成される部分が規制部である。
【００７６】
７は本発明のキャリア及びトナーを有する現像剤層である。６は非磁性トナーである。
【００７７】
１０はトナー濃度検出センサー（不図示）によって得られる出力に応じて作動するトナー補給ローラーである。センサとしては、現像剤の体積検知方式、圧電素子、インダクタンス変化検知素子、交番バイアスを利用したアンテナ方式、光学濃度を検知する方式を利用することができる。該ローラーの回転または停止によって非磁性トナー６の補給を行う。トナー６が補給されたフレッシュな現像剤は現像剤搬送スクリュー１１によって搬送されながら混合及び攪拌される。従ってこの搬送中において補給されたトナーにトリボ付与が行われる。１３はしきり板で現像器の長手方向両端部において切り欠かれており、この部分でスクリュー１１によって搬送されたフレッシュな現像剤がスクリュー１２へ受け渡される。
【００７８】
Ｓ磁極３ｄは搬送極である。現像後の回収現像剤を容器内に回収し、さらに容器内の現像剤を規制部まで搬送する。
【００７９】
３ｄ付近では、現像スリーブ２に近接して設けたスクリュー２によって搬送されてきたフレッシュな現像剤と現像後の回収現像剤とを交換する。
【００８０】
非磁性ブレード４の端部と現像スリーブ２面との距離ｄは１００〜９００μｍ、好ましくは１５０〜８００μｍである。この距離が１００μｍより小さいとキャリア粒子がこの間に詰まり現像剤層にムラを生じやすいと共に良好な現像を行うのに必要な現像剤を塗布することが出来ず濃度の薄いムラの多い現像画像しか得られない場合がある。一方、この距離が９００μｍより大きいと現像スリーブ２上へ塗布される現像剤量が増加し所定の現像剤層厚の規制が行えず、潜像担持体への磁性粒子付着が多くなると共に現像剤の循環、現像剤限定部材５による現像規制が弱まりトナーのトリボが不足しカブリしやすくなる傾向がある。
【００８１】
現像スリーブ２上の現像剤層の厚さを、現像スリーブ２と静電荷像担持体１との対向空隙距離と同様もしくは若干大きくし、現像スリーブ２に交番電圧を印加することが好ましい。空隙の距離は、５０〜８００μｍ（より好ましくは、１００〜７００μｍ）が良い。
【００８２】
バイアス電源１４により現像スリーブ２に交番電圧又は交番電圧に直流電圧を重畳した現像バイアスを印加することにより、現像スリーブ２から静電荷像担持体１０へのトナーの移動を容易にし、さらに良質の画像を形成することができる。
【００８３】
上記の印加する交番電圧としての交流電圧は１，０００〜１０，０００（好ましくは、２，０００〜８，０００）Ｖｐｐであることが好ましい。直流電圧を重畳する場合には、直流電圧を絶対値で１，０００Ｖ以下の範囲で印加することが好ましい。
【００８４】
本発明の現像剤をフルカラー画像形成方法を良好に実施し得るための画像形成装置を図２を参照しながら説明する。
【００８５】
図２に示されるカラー電子写真装置は、装置本体１の右側（図１右側）から装置本体の略中央部にわたって設けられている転写材搬送系Ｉと、装置本体１の略中央部に、上記転写材搬送系Ｉを構成している転写ドラム３１５に近接して設けられている潜像形成部ＩＩと、上記潜像形成部ＩＩと近接して配設されている現像手段（すなわち回転式現像装置）ＩＩＩとに大別される。
【００８６】
上記転写材搬送系Ｉは、以下の様な構成となっている。上記装置本体１の右壁（図２右側）に開口部が形成されており、該開口部に着脱自在な転写材供給用トレイ３０２及び３０３が一部機外に突出して配設されている。該トレイ３０２及び３０３の略直上部には給紙用ローラー３０４及び３０５が配設され、これら給紙用ローラー３０４及び３０５と左方に配された矢印Ａ方向に回転自在な転写ドラム３０５とを連係するように、給紙用ローラー３０６及び給紙ガイド３０７及び３０８が設けられている。上記転写ドラム３１５の外周面近傍には回転方向上流側から上流側に向かって当接用ローラー３０９、グリッパ３１０、転写材分離用帯電器３１１、分離爪３１２が順次配設されている。
【００８７】
上記転写ドラム３１５の内周側には転写帯電器３１３、転写材分離用帯電器３１４が配設されている。転写ドラム３１５の転写材が巻き付く部分にはポリ弗化ビニリデンの如き、ポリマーで形成されている転写シート（図示せず）が貼り付けられており、転写材は該転写シート上に静電的に密着貼り付けされている。上記転写ドラム３１５の右側上部には上記分離爪３１２と近接して搬送ベルト手段３１６が配設され、該搬送ベルト手段３１６の転写材搬送方向終端（右側）には定着装置３１８が配設されている。該定着装置３１８よりもさらに搬送方向後流には装置本体３０１の外へと延在し、装置本体３０１に対して着脱自在な排出用トレイ３１７が配設されている。
【００８８】
次に、上記潜像形成部ＩＩの構成を説明する。図２に矢印方向に回転自在な潜像担持体である感光体（例えば、ＯＰＣ感光ドラム又はＯＰＣ感光ベルト）３１９が、外周面を上記転写ドラム３１５の外周面と当接して配設されている。上記感光ドラム３１９の上方でその外周面近傍には、該感光ドラム３１９の回転方向上流側から下流側に向かって除電用帯電器３２０、クリーニング手段３２１及び一次帯電器３２３が順次配設され、さらに上記感光ドラム３１９の外周面上に静電潜像を形成するためのレーザービームスキャナのごとき像露光手段３２４、及びミラーのごとき像露光反射手段３２５が配設されている。
【００８９】
上記回転式現像装置ＩＩＩの構成は以下のごとくである。上記感光ドラム３１９の外周面と対向する位置に、回転自在な筐体（以下「回転体」という）３２６が配設され、該回転体３２６中には四種類の現像装置が周方向の四位置に搭載され、上記感光ドラム３１９の外周面上に形成された静電潜像を可視化（すなわち現像）するようになっている。上記四種類の現像装置は、それぞれイエロー現像装置３２７Ｙ、マゼンタ現像装置３２７Ｍ、シアン現像装置３２７Ｃ及びブラック現像装置３２７ＢＫを有する。
【００９０】
上記したごとき構成の画像形成装置全体のシーケンスについて、フルカラーモードの場合を例として説明する。上述した感光ドラム３１９が図２矢印方向に回転すると、該感光ドラム３１９上の感光体は一次帯電器３２３によって帯電される。図２の装置においては、各部動作速度（以下、プロセススピードとする）は１００ｍｍ／ｓｅｃ以上（例えば、１３０〜２５０ｍｍ／ｓｅｃ）である。一次帯電器３２３による感光ドラム３１９に対する帯電が行われると、原稿３２８のイエロー画像信号にて変調されたレーザー光Ｅにより画像露光が行われ、感光ドラム３１９上に静電潜像が形成され、回転体３２６の回転によりあらかじめ現像位置に定置されたイエロー現像装置３２７Ｙによって上記静電潜像の現像が行われ、イエロートナー画像が形成される。
【００９１】
給紙ガイド３０７、給紙ローラー３０６、給紙ガイド３０８を経由して搬送されてきた転写材は、所定のタイミングにてグリッパ３１０により保持され、当接用ローラー３０９と該当接用ローラー３０９と対向している電極とによって静電的に転写ドラム３１５に巻き付けられる。転写ドラム３１５は、感光ドラム３１９と同期して図２矢印方向に回転しており、イエロー現像装置３２７Ｙにより形成されたイエロートナー画像は、上記感光ドラム３１９の外周面と上記転写ドラム３１５の外周面とが当接している部位にて転写帯電器３１３によって転写材上に転写される。転写ドラム３１５はそのまま回転を継続し、次の色（図２においてはマゼンタ）の転写に備える。
【００９２】
感光ドラム３１９は、上記除電用帯電器３２０により除電され、クリーニングブレードによるクリーニング手段３２１によってクリーニングされた後、再び一次帯電器３２３によって帯電され、次のマゼンタ画像信号により画像露光が行われ、静電潜像が形成される。上記回転式現像装置は、感光ドラム３１９上にマゼンタ画像信号による像露光により静電潜像が形成される間に回転して、マゼンタ現像装置３２７Ｍを上述した所定の現像位置に配置せしめ、所定のマゼンタトナーにより現像を行う。引き続いて、上述したごときプロセスをそれぞれシアン色及びブラック色に対しても実施し、四色のトナー像の転写が終了すると、転写材上に形成された四色顕画像は各帯電器３２２及び３１４により除電され、上記グリッパ３１０による転写材の把持が解除されると共に、該転写材は、分離爪３１２によって転写ドラム３１５より分離され、搬送ベルト３１６で定着装置３１８に送られ、熱と圧力により定着され一連のフルカラープリントシーケンスが終了し、所要のフルカラープリント画像が転写材の一方の面に形成される。
【００９３】
このとき、定着装置３１８での定着動作速度は、本体のプロセススピード（例えば１６０ｍｍ／ｓｅｃ）より遅い（例えば９０ｍｍ／ｓｅｃ）で行われる。これは、トナーが二層から四層積層された未定着画像を溶融混色させる場合、十分な加熱量をトナーに与えなければならないためで、現像速度より遅い速度で定着を行うことによりトナーに対する加熱量を多くしている。
【００９４】
【実施例】
実施例１
磁性キャリアコア粒子の表面に被覆層を形成するための塗布液を下記の如く調製した。
【００９５】
キシレンに下記化合物（１）の３３モル部、下記化合物（２）の３５モル部及び下記化合物（３）の２モル部を溶解し、得られたキシレン溶液を温度７０〜８０℃に加温された温水の入っている容器に液下し、シリコーン化合物を縮重合してオリゴマーを生成した。前記構成単位（Ｉ）及び（ＩＩ）を有するシリコーンオリゴマーを生成後、下層の水層と上層のオリゴマーを溶解しているキシレン層とを分離し、第１のキシレン溶液を調製した。
【００９６】
【外２６】

【００９７】
別途、下記化合物（４）の１５モル部及び下記化合物（５）の１５モル部をキシレンに溶解し、得られたキシレン溶液にアゾ系開始剤（２，２′−ａｚｏｂｉｓｉｓｏｂｕｔｙｒｏｎｉｔｌｉｌｅ）の約３モル部を加え、液温５０〜６０℃でラジカル重合をおこない、化合物（４）と（５）との共重合体を生成し、第２のキシレン溶液を調製した。
【００９８】
【外２７】

【００９９】
次に、第１のキシレン溶液と第２のキシレン溶液とを混合し、キシレンを追加して固形分濃度が約３重量％となるように調整して塗布液Ｎｏ．１を調製した。
【０１００】
磁性キャリアコア粒子として平均粒径３５μｍの磁性フェライト粒子（商品名：Ｆ−４００；パウダーテック社製 ＰＯＷＤＥＲＴＥＣＨ ＣＯ．，ＬＴＤ）に対して流動床中で塗布液Ｎｏ．１を塗布して被覆層を有する磁性キャリアを得た。次いで、磁性キャリアを温度１５０℃で３０分間加熱処理し、磁性フェライトコア粒子表面にシリコーン樹脂の焼き付けをおこないシリコーン樹脂の０．５重量％でコーティングされている磁性キャリアＮｏ．１を得た。得られた磁性キャリアＮｏ．１の表面をＥＳＣＡで分析したところ、−ＣＯＯ−基に由来する炭素量がシリコーン樹脂を構成するケイ素量に対して３９原子％であり、フェニル基に由来する炭素量が−ＣＯＯ−基に由来する炭素量に対して１１２原子％であった。
【０１０１】
磁性キャリアＮｏ．１と、カラーレーザ複写機（キヤノン製、商品名ＣＬＣ−７００）用の負摩擦帯電性の非磁性シアントナー（重量平均粒径約８．５μｍ、凝集度１０％）、負摩擦帯電性の非磁性マゼンタトナー（重量平均粒径約８．５μｍ、凝集度１０％）、負摩擦帯電性の非磁性イエロートナー（重量平均粒径約８．５μｍ、凝集度１０％）、及び負摩擦帯電性の非磁性ブラックトナー（重量平均粒径約８．５μｍ、凝集度１０％）とをそれぞれ混合してシアン色用二成分系現像剤（トナー濃度６重量％）、マゼンタン色用二成分系現像剤（トナー濃度６重量％）、イエロー色用二成分系現像剤（トナー濃度６重量％）及びブラック色用二成分系現像剤（トナー濃度６重量％）を調製した。
【０１０２】
各色用二成分系現像剤をＯＰＣ感光ドラムを有し、現像時に現像スリーブに交流バイアスを印加しながら反転現像方式でデジタルな静電荷像を現像する方式の該カラーレーザ複写機のシアン色用現像器、マゼンタ色用現像器、イエロー色用現像器及びブラック色用現像器にそれぞれ入れ、画像面積比率２５％のオリジナル原稿を用いて常温常湿（２３℃／６０％ＲＨ）の環境下で逐次各色トナーを補給しながら、各色モノカラーモードで５万枚連続複写したところ、５万枚の耐久中画像濃度の変動が小さく、画像上カブリも無く、帯電量変化が殆どなく、且つトナー粒径が殆ど変化しない耐久安定性に優れたものであった。シアントナーの摩擦帯電量は−２７μＣ／ｇであり、マゼンタトナーの摩擦帯電量は−２６μＣ／ｇであり、イエロートナーの摩擦帯電量は−２８μＣ／ｇであり、ブラックトナーの摩擦帯電量は−２３μＣ／ｇであった。更に高温高湿（３０℃，８０％ＲＨ）と低温低湿（１５℃，１０％ＲＨ）における帯電量の差も小さいものであり帯電特性に優れ、且つ高湿下で顕著になる感光ドラム上の画像流れも全く発生していない優れた特性を示した。結果を表３に示す。
【０１０３】
実施例２
表２に示す処方にした塗布液Ｎｏ．２を使用することを除いて実施例１と同様にして磁性キャリアＮｏ．２を調製した。磁性キャリアＮｏ．２のＥＳＣＡの分析結果を表２に示す。磁性キャリアＮｏ．２を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。
【０１０４】
結果を表３に示す。５万枚後の画像濃度の変動と帯電量の変動が若干見られたものの良好なレベルであった。
【０１０５】
実施例３
組成比を変更することを除いて表１に示す処方で塗布液Ｎｏ．３を調製した。
【０１０６】
塗布液Ｎｏ．３を使用して実施例１と同様にして磁性キャリアＮｏ．３を調製した。磁性キャリアＮｏ．３のＥＳＣＡの分析結果を表２に示す。磁性キャリアＮｏ．３を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。
【０１０７】
結果を表３に示す。５万枚後の若干のカブリと現像器中のトナー粒度の変動が若干見られたものの良好なレベルであった。
【０１０８】
比較例１
化合物（１）を使用しなく、組成比を表１に変更することを除いて表１に示す処方で塗布液Ｎｏ．４を調製した。
【０１０９】
塗布液Ｎｏ．４を使用して実施例１と同様にして比較磁性キャリアＮｏ．１を調製した。比較磁性キャリアＮｏ．１のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．１を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表３に示す。
【０１１０】
５万枚後の画像濃度の変動と帯電量の変動に関して悪く、耐久安定性に欠けるものであり、環境による帯電量の変化が大きく帯電特性に劣るものであった。この理由としては−ＣＯＯ−基に由来する炭素量に対してフェニル基に由来する炭素量が少なく、電荷の拡散が十分に行われないために電荷の蓄積に依るものだと考えられる。
【０１１１】
比較例２
表２に示す処方の塗布液Ｎｏ．５を使用することを除いて実施例１と同様にして比較磁性キャリアＮｏ．２を調製した。比較磁性キャリアＮｏ．２のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．２を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。
【０１１２】
結果を表３に示す。５万枚後の画像濃度の変動と帯電量の変動及びカブリに関して悪く、耐久安定性に欠けるものであり、トナー粒度が耐久後に変化した。
【０１１３】
比較例３
組成比を変更することを除いて表１に示す処方で塗布液Ｎｏ．６を調製した。塗布液Ｎｏ．６を使用することを除いて実施例１と同様にして比較磁性キャリアＮｏ．３を調製した。比較磁性キャリアＮｏ．３のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．３を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。
【０１１４】
結果を表３に示す。５万枚後のカブリと帯電量の変動に関して悪く、耐久安定性に欠けるものであり、感光ドラム上の画像流れが発生した。
【０１１５】
比較例４
組成比を変更することを除いて表１に示す処方で塗布液Ｎｏ．７を調製した。塗布液Ｎｏ．７を使用することを除いて実施例１と同様にして比較磁性キャリアＮｏ．４を調製した。比較磁性キャリアＮｏ．４のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．４を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。
【０１１６】
結果を表３に示す。５万枚後の画像濃度の変動とカブリに関して悪く、耐久安定性に欠けるものであり、環境による帯電量の変化が大きく帯電特性に劣るものであった。この理由としては珪素量に対して−ＣＯＯ−基に由来する炭素量少なく、帯電付与能力に劣っていたためだと考えられる。
【０１１７】
比較例５
化合物（４）及び（５）を使用しなく、組成比を変更することを除いて表１に示す処方で塗布液Ｎｏ．８を調製した。塗布液Ｎｏ．８を使用することを除いて実施例１と同様にして比較磁性キャリアＮｏ．５を調製した。比較磁性キャリアＮｏ．５のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．５を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表３に示す。
【０１１８】
比較例６
化合物（１）を使用しなく、組成比を変更することを除いて表１に示す処方で塗布液Ｎｏ．９を調製した。塗布液Ｎｏ．９を使用して実施例１と同様にして比較磁性キャリアＮｏ．６を調製した。比較磁性キャリアＮｏ．６のＥＳＣＡの分析結果を表２に示す。比較磁性キャリアＮｏ．６を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表３に示す。
【０１１９】
【表１】

【０１２０】
【表２】

【０１２１】
【表３】

【０１２２】
評価方法
１）画像濃度：
適正露光条件下でコピーし、Ｉ．Ｄ．の評価を、ベタ部の画像濃度をマクベス濃度計により測定してランク評価した。
【０１２３】
Ａ：濃度ムラも無く原稿濃度を非常に良く再現している
Ｂ：原稿濃度を再現している（実用上問題ないレベル）
Ｃ：不均一で濃度ムラがある（実用上問題を生じるレベル）
Ｄ：原稿濃度に比べ大きく変化している（実用できないレベル）
【０１２４】
２）画像上のカブリ：
白地画像上のトナーカブリを東京電色社製のＲＥＦＬＥＣＴＯＭＥＴＥＲ ＭＯＤＥＬ ＴＣ−６ＤＳを用い測定してランク評価した。
【０１２５】
Ａ：０．５％未満
Ｂ：０．５〜１．５％未満
Ｃ：１．５〜２．５％未満
Ｄ：２．５％以上
【０１２６】
３）帯電量の環境変動：
５０ｍｌ容量のポリエチレン容器に入れ現像剤を１５℃，湿度１０％環境下で一日放置後、５００回手で振って混合した後のトナーの帯電量Ｑ（ＬＬ）と、３０℃，湿度８０％環境下で一日放置後に５００回手で振って混合した後のトナーの帯電量Ｑ（ＨＨ）を、後述する帯電量の測定方法を用いて算出し、その差ΔＱ（＝Ｑ（ＬＬ）−Ｑ（ＨＨ））でランク評価した。
【０１２７】
Ａ：ΔＱ＝１０μＣ／ｇ未満
Ｂ：ΔＱ＝１０μＣ／ｇ以上１５μＣ／ｇ未満
Ｃ：ΔＱ＝１５μＣ／ｇ以上２０μＣ／ｇ未満
Ｄ：ΔＱ＝２０μＣ／ｇ以上
【０１２８】
４）帯電量の耐久変動：
２３℃，湿度６０％環境下で耐久初期の現像器の現像スリーブ上から採取した現像剤のトナーの帯電量Ｑ（ｓｔａｒｔ）と、５万枚後の現像器の現像スリーブ上から採取した現像剤のトナーの帯電量Ｑ（ｌａｓｔ）を、後述する帯電量の測定方法を用いて算出し、その差ΔＱ（＝Ｑ（ｓｔａｒｔ）−Ｑ（ｌａｓｔ）でランク評価した。
【０１２９】
Ａ：ΔＱ＝５μＣ／ｇ未満
Ｂ：ΔＱ＝５μＣ／ｇ以上１０μＣ／ｇ未満
Ｃ：ΔＱ＝１０μＣ／ｇ以上１５μＣ／ｇ未満
Ｄ：ΔＱ＝１５μＣ／ｇ以上
【０１３０】
５）トナー粒度の耐久変動：
２３℃，湿度６０％環境下で耐久初期の現像器中のトナーの重量平均トナー粒径Ｄ（ｓｔａｒｔ）と、５万枚後の現像器中のトナーの重量平均トナー粒径Ｄ（ｌａｓｔ）を、後述するトナー粒径の測定方法を用いて算出し、その差ΔＤ（＝Ｄ（ｓｔａｒｔ）−Ｄ（ｌａｓｔ））でランク評価した。
【０１３１】
Ａ：ΔＤ＝１μｍ未満
Ｂ：ΔＤ＝１μｍ以上２μｍ未満
Ｃ：ΔＤ＝２μｍ以上３μｍ未満
Ｄ：ΔＤ＝３μｍ以上
【０１３２】
６）感光ドラム上の画像流れ：
３０℃，湿度６０％環境下においてカラーレーザ複写機（ＣＬＣ７００）を用い、ハーフトーン画像を形成させ画質の評価を行った。
【０１３３】
Ａ：全く画像流れが見られない
Ｂ：少々見られるが実用上問題ないレベル
Ｃ：実用上問題になるレベル
Ｄ：全面に画像流れが見られ、実用不可能なレベル
【０１３４】
７）帯電量の測定：
図３は現像剤のトナーのトリボ電荷を測定する装置の説明図である。先ず、底に５００メッシュのスクリーン１０３のある金属製の測定容器１０２に、現像器のスリーブ上から採取した現像剤約０．５〜０．９ｇを入れ金属製のフタ１０４をする。このときの測定容器２全体の重量を秤りＷ_１（ｇ）とする。次に、吸引機１０１（測定容器１０２と接する部分は少なくとも絶縁体）において、吸引口１０７から吸引し同量調節弁１０６を調整して真空計１０５の圧力を２５０ｍｍＡｑとする。この状態で充分、好ましくは約２分間吸引を行いトナーを吸引除去する。このときの電位計１０９の電位をＶ（ボルト）とする。ここで１０８はコンデンサーであり容量をＣ（μＦ）とする。また、吸引後の測定容器全体の重量を秤りＷ₂ （ｇ）とする。このトナーの摩擦帯電量（μＣ／ｇ）は下式の如く計算される。
【０１３５】
トナーの摩擦帯電量（μＣ／ｇ）＝（Ｃ×Ｖ）／（Ｗ₁ −Ｗ₂ ）
【０１３６】
実施例４
シアントナーの調製
プロポキシ化ビスフェノールとフマル酸を縮合して得られたポリエステル樹脂
（結着樹脂、重量平均分子量 ２５，０００） １００重量部
フタロシアニン顔料（シアン着色剤） ４重量部
ジ−ｔｅｒｔ−ブチルサリチル酸クロム（負荷電性制御剤） ４重量部
上記材料をヘンシェルミキサーにより十分予備混合を行い、２軸式押出し機で溶融混練し、冷却後ハンマーミルを用いて約１〜２ｍｍ程度に粗粉砕し、次いでエアージェット方式による微粉砕機で微粉砕した。更に得られた微粉砕物を分級して重量平均粒径約５．８μｍの負帯電性の非磁性シアントナー粒子を得た。得られた非磁性シアントナー粒子１００重量部と疎水性酸化チタン微粉体（ＢＥＴ比表面積１００ｍ² ／ｇ）１．５重量部とを混合して負帯電性シアントナーを調製した。
【０１３７】
マゼンタトナーの調製
フタロシアニン顔料のかわりにキナクリドン系マゼンタ顔料を使用することを除いて、上記シアントナー粒子と同様にして重量平均粒径約５．８μｍの負帯電性の非磁性マゼンタトナー粒子を得た。得られた非磁性マゼンタトナー粒子１００重量部と疎水性酸化チタン微粉体（ＢＥＴ比表面積１００ｍ²／ｇ）１．５重量部とを混合して負帯電性マゼンタトナーを調製した。
【０１３８】
イエロートナーの調製
フタロシアニン顔料のかわりにイエロー着色剤（Ｃ．Ｉ．ピグメントイエロー１７）を使用することを除いて、上記シアントナー粒子と同様にして重量平均粒径約５．８μｍの負帯電性の非磁性イエロートナー粒子を得た。得られた非磁性イエロートナー粒子１００重量部と疎水性酸化チタン微粉体（ＢＥＴ比表面積１００ｍ² ／ｇ）１．５重量部とを混合して負帯電性イエロートナーを調製した。
【０１３９】
ブラックトナーの調製
フタロシアニン顔料のかわりにカーボンブラックを使用することを除いて、上記シアントナー粒子と同様にして重量平均粒径約５．８μｍの負帯電性のブラックトナー粒子を得た。得られた非磁性ブラックトナー粒子１００重量部と疎水性酸化チタン微粉体（ＢＥＴ比表面積１００ｍ²／ｇ）１．３重量部とを混合して負帯電性ブラックトナーを調製した。
【０１４０】
小粒径の上記各色トナー６重量部と実施例１で調製された磁性キャリアＮｏ．１の９４重量部とを混合して各色の二成分系現像剤を調製し、実施例１と同様にして逐次各色トナーを補給しながら単色モードで画出し試験をおこなった。結果を表４に示す。常温常湿環境下では、シアントナーの摩擦帯電量は、−３４μＣ／ｇであり、マゼンタトナーの摩擦帯電量は−３３μＣ／ｇであり、イエロートナーの摩擦帯電量は−３５μＣ／ｇであり、ブラックトナーの摩擦帯電量は−３２μＣ／ｇであった。
【０１４１】
実施例５，６、比較例７乃至１２
磁性キャリアＮｏ．２及び３、比較磁性キャリアＮｏｓ．１乃至６を使用することを除いて、実施例４と同様にして画出し試験をおこなった。結果を表４に示す。
【０１４２】
【表４】

【０１４３】
実施例７
磁性キャリアコア粒子の表面に被覆層を形成するための塗布液を下記の如く調製した。
【０１４４】
キシレンに化合物（１）の２８モル部、化合物（２）の３７モル部、化合物（３）の２モル部及び下記化合物（８）の３モル部を溶解し、得られたキシレン溶液を温度７０〜８０℃に加温された温水の入っている容器に液下し、シリコーン化合物を縮重合してオリゴマーを生成した。前記構成単位（Ｉ）及び（ＩＩ）を有するシリコーンオリゴマーを生成後、下層の水層と上層の含窒素基を有するオリゴマーを溶解しているキシレン層とを分離し、第３のキシレン溶液を調製した。
【０１４５】
【外２８】

【０１４６】
次に、実施例１と同様にして調製した化合物（４）と（５）との共重合体を溶解している第２のキシレン溶液と上記第３のキシレン溶液とを混合し、キシレンを追加して固形分濃度が約３重量％となるように調製して塗布液Ｎｏ．１０を調製した。
【０１４７】
磁性キャリアコア粒子として平均粒径３５μｍの磁性フェライト粒子（商品名：Ｆ−４００；パウダーテック社製）に対して流動床中で塗布液Ｎｏ．１０を塗布して被覆層を有する磁性キャリアを得た。次いで、磁性キャリアを温度１５０℃で３０分間加熱処理し、磁性フェライトコア粒子表面にシリコーン樹脂の焼き付け（ｓｔｉｃｋｉｎｇ）をおこないシリコーン樹脂の１．０重量％でコーティングされている磁性キャリアＮｏ．４を得た。得られた磁性キャリアＮｏ．４の表面をＥＳＣＡで分析したところ、−ＣＯＯ−基に由来する炭素量がシリコーン樹脂を構成するケイ素量に対して４０原子％であり、含窒素基に由来する窒素量が−ＣＯＯ−基に由来する炭素量に対して１原子％であった。
【０１４８】
磁性キャリアＮｏ．４を使用して実施例１と同様にして画出し試験をおこなった結果を表７に示す。
【０１４９】
５００００枚後の画像濃度の変動が小さく、画像上カブリも無く、そして帯電量変化がほとんどない耐久安定性に優れたものであった。さらに高温多湿と低温低湿における帯電量の差も小さいものであり帯電特性に優れ、且つ高湿下で顕著になる感光ドラム上の画像流れも全く発生していない優れた特性を示した。
【０１５０】
実施例８
シリコーンオリゴマーを生成する時に化合物（６）及び（７）を使用し、組成比を変更することを除いて表５に示す処方で実施例４と同様にして塗布液Ｎｏ．１１を調製した。塗布液Ｎｏ．１１を使用して実施例１と同様にして磁性キャリアＮｏ．５を調製した。磁性キャリアＮｏ．５のＥＳＣＡの分析結果を表６に示す。磁性キャリアＮｏ．５を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表７に示す。５００００枚後の画像濃度の変動と帯電量の変動が若干見られたものの好適なレベルであった。
【０１５１】
実施例９
化合物（８）のかわりに下記化合物（９）を使用し、組成比を変更することを除いて表５に示す処方で実施例４と同様にして塗布液Ｎｏ．１２を調製した。
【０１５２】
【外２９】

【０１５３】
塗布液Ｎｏ．１２を使用して実施例１と同様にして磁性キャリアＮｏ．６を調製した。磁性キャリアＮｏ．６のＥＳＣＡの分析結果を表６に示す。磁性キャリアＮｏ．６を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表７に示す。５００００枚後の画像濃度の変動と帯電量の変動が若干見られたものの好適なレベルであった。
【０１５４】
比較例１３乃至１８
表５に示す処方の塗布液Ｎｏｓ．１３乃至１７を使用して実施例１と同様にして比較磁性キャリアＮｏｓ．７乃至１１を調製した。比較磁性キャリアＮｏｓ．７乃至１１のＥＳＣＡの分析結果を表６に示す。比較磁性キャリアＮｏｓ．７乃至１１を使用し、実施例１と同様にして各色現像剤を調製し、実施例１と同様にして評価した。結果を表７に示す。比較例１３では、５００００枚後の画像濃度の変動と帯電量の変動及びカブリに関して悪く、耐久安定性に欠けるものであり、環境による帯電量の変化が大きく帯電特性に劣るものであった。この理由としてはケイ素量に対して−ＣＯＯ−基に由来する炭素量が少なく、帯電付与能力に劣っていたためだと考えられる。
【０１５５】
比較例１４では、５００００枚後の画像濃度の変動と帯電量の変動及びカブリに関して悪く、耐久安定性に欠けるものであり、感光ドラム上の画像流れも悪いレベルであった。
【０１５６】
比較例１５では、５００００枚後の画像濃度の変動と帯電量の変動及びカブリが著しく悪く耐久安定性に欠けるものであった。この理由としては−ＣＯＯ−基に由来する炭素量に対して窒素量が多く、電荷の拡散が十分に行われないために電荷の蓄積に依るものだと考えられる。
【０１５７】
比較例１６では、５００００枚後の画像濃度の変動と帯電量の変動及びカブリが著しく悪く耐久安定性に欠けるものであった。この理由としては−ＣＯＯ−基に由来する炭素量に対して窒素量が少なく、帯電速度に非常に乏しく電荷付与能力が低いことに依るものだと考えられる。
【０１５８】
【表５】

【０１５９】
【表６】

【０１６０】
【表７】

【０１６１】
実施例１０乃至１２及び比較例１９乃至２３
実施例４で調製した重量平均粒径５．８μｍの小粒径の各色トナーと、磁性キャリアＮｏｓ．４乃至６及び比較磁性キャリアＮｏｓ．７乃至１１を使用し、実施例１と同様にして画出し試験をおこなった。結果を表８に示す。
【０１６２】
【表８】

【０１６３】
【発明の効果】
本発明のキャリアを用いた現像剤は、摩擦帯電において環境安定性及び耐久安定性に優れ、且つ画像濃度を十分に満足しつつカブリのない、そして画像流れのない優れた画質を、５００００枚後も安定して得ることができる。
【図面の簡単な説明】
【図１】本発明の画像形成方法を実施するための画像形成装置の一具体例を示す概略的説明図である。
【図２】本発明の画像形成方法をフルカラー画像形成に適用するためのフルカラー複写機の一具体例を示す概略的説明図である。
【図３】二成分系現像剤におけるトナーの摩擦帯電量を測定するための測定装置の説明図である。
【図４】シリコーン樹脂で被覆された本発明の磁性キャリアのＥＳＣＡのチャートの一例を示す図である。
【図５】ＥＳＣＡのチャートの一例を示す図である。
【図６】ＥＳＣＡのチャートの一例を示す図である。
【図７】ＥＳＣＡのチャートの一例を示す図である。
【符号の説明】
１ 静電荷像担持体（感光ドラム又は感光ベルト）
２ 現像剤担持体（現像スリーブ）
３ 磁石
１４ バイアス電源
１０１ 吸引機
１０２ 測定容器
１０３ 導電性スクリーン
１０４ フタ
１０５ 真空計
１０６ 同量調節弁
１０７ 吸引口
１０８ コンデンサ
１０９ 電位計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carrier used in an electrophotographic developer used for developing an electrostatic image such as electrophotography, electrostatic recording, and electrostatic printing, a two-component developer having the carrier, and the developer. The present invention relates to an image forming method to be used.
[0002]
[Prior art]
It is well known in the art to form and develop an image on the surface of a photoconductive material by electrostatic means.
[0003]
Numerous methods are known as described in US Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748. In general, a photoconductive material is used, and an electrostatic image is formed on the photoreceptor by various means, and then a toner image is formed on the electrostatic image by attaching toner.
[0004]
Next, the toner is transferred to the surface of an image support such as paper as necessary, and then fixed by heating, pressing, heating and pressing, or solvent vapor to obtain a copy or a printer. When the toner image is transferred, a process for removing the remaining toner from the photoreceptor is usually provided.
[0005]
Examples of a method for developing an electrostatic image using toner include a powder cloud method described in US Pat. No. 2,221,776 and a method described in US Pat. No. 2,618,552. Cascade development method, magnetic brush method described in US Pat. No. 2,874,063, and method using conductive magnetic toner described in US Pat. No. 3,909,258, developer There is a development method in which a bias electric field composed of an alternating current component and a direct current component is applied to a carrier (developing sleeve) to perform development (disclosed in Japanese Patent Laid-Open No. 62-63970).
[0006]
In the magnetic brush development method, magnetic carrier particles such as steel and ferrite are used, and a two-component developer composed of toner and magnetic carrier particles is held by a magnet contained in a developing sleeve, and developed by the magnetic field of the magnet. The agent is arranged in a brush shape on the developing sleeve. When this magnetic brush is connected to the electrostatic charge image surface of the photoconductive layer, only the toner is attracted from the magnetic brush to the electrostatic charge image, and the electrostatic charge image is developed.
[0007]
Carriers constituting the two-component developer applied to the magnetic brush developing method are roughly classified into conductive carriers and insulating carriers. As the conductive carrier, oxidized or unoxidized iron powder is usually used. The two-component developer having an iron powder carrier has a problem that the triboelectric chargeability with respect to the toner is unstable and fogging is likely to occur in the toner image. That is, as the developer is used, the toner particles adhere to the surface of the iron powder carrier particles and easily accumulate (spent toner). As a result, the electric resistance of the iron powder carrier particles increases and the magnetic brush And the triboelectric charging property of the iron powder carrier to the toner becomes unstable. As a result, the image density of the formed toner image decreases and fogging increases. Therefore, when copying continuously with an electrophotographic apparatus using a two-component developer containing an iron powder carrier, the developer deteriorates in a few times, so it is necessary to replace the developer early, After all, the cost is high.
[0008]
A typical example of the insulating carrier is a carrier in which the surface of a carrier core made of a ferromagnetic material such as iron, nickel, or ferrite is uniformly coated with an insulating resin. In a two-component developer using an insulating resin-coated carrier, toner particles are significantly less fused to the carrier surface than in the case of a conductive non-coated carrier, and at the same time, the triboelectric chargeability between the toner and the carrier is controlled. This is advantageous in that it is suitable for a high-speed electronic copying machine in that it is easy to do and has excellent durability and long service life.
[0009]
Appropriate chargeability, impact resistance, wear resistance, good adhesion between carrier core and coating resin, and uniformity of charge distribution on the surface of carrier particles are important characteristics required for insulating resin-coated carriers. Can be mentioned.
[0010]
In an insulating resin-coated carrier, there has been a proposal for improving durability by using a resin having a small surface energy as a coating layer in order to prevent the carrier from being spun due to toner fusion.
[0011]
Carriers coated with a silicone resin are less likely to be spent, and are said to have a long life as a developer. However, since the ability of the carrier to impart charge to the toner is weak, a toner image with a lot of fog is likely to be formed. The toner was scattered a lot, causing the inside of the machine to be contaminated, and image defects were likely to occur.
[0012]
In order to overcome the above problems, Japanese Patent Laid-Open No. 55-157751 proposes using a resin-modified silicone resin as a coating resin.
[0013]
Further, JP-A-1-147478 proposes a carrier coated with a silicone resin containing an aminosilane coupling agent. However, when the weight average diameter of the toner is as small as 9 μm or less, the charge controllability to the toner is insufficient even with these carriers, and in particular, fog is likely to occur in a room temperature and low humidity environment. An improved career is awaited.
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a carrier for an electrophotographic developer that solves the above problems.
[0015]
An object of the present invention is to provide a carrier for an electrophotographic developer having a resin coating layer that is excellent in adhesion to carrier core particles and excellent in charge imparting ability to toner.
[0016]
An object of the present invention is to provide a carrier for an electrophotographic developer which is excellent in durability of a large number of sheets and excellent in environmental stability.
[0017]
An object of the present invention is to provide a carrier for an electrophotographic developer that has a high charge imparting ability even with a negative frictionally chargeable nonmagnetic toner having a small average particle diameter and is excellent in charge controllability.
[0018]
A further object of the present invention is to provide a two-component developer having the carrier and toner.
[0019]
Another object of the present invention is to provide an image forming method using the two-component developer.
[0020]
[Means for Solving the Problems]
  The present invention is a magnetic carrier for electrophotographic development comprising a magnetic carrier core particle and a silicone resin coating the magnetic carrier core particle,
  The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
  (I) The amount of carbon derived from —COO— groups is determined by ESCA relative to the amount of silicon derived from silicone resin.15-65Atomic percent, and
  (Ii) In the measurement by ESCA, at least when the silicone resin does not have a nitrogen-containing group, the carbon amount derived from the phenyl group is larger than the carbon amount derived from the —COO— group.10-200If the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. The present invention relates to a characteristic magnetic carrier for an electrophotographic developer.
[0021]
  Furthermore, the present invention provides a two-component developer having a toner and a magnetic carrier, wherein the magnetic carrier has a magnetic carrier core particle and a silicone resin coating the magnetic carrier core particle,
  The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
  (I) The amount of carbon derived from the —COO— group as measured by ESCA is relative to the amount of silicon constituting the silicone resin.15-65Atomic percent, and
  (Ii) In the measurement by ESCA, at least when the silicone resin does not have a nitrogen-containing group, the carbon amount derived from the phenyl group is larger than the carbon amount derived from the —COO— group.10-200If the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. The present invention relates to a two-component developer.
[0022]
  Furthermore, the present invention forms an electrostatic charge image on the photoreceptor,
  A magnetic brush of a two-component developer is formed on the developer carrier that contains the magnetic field generating means,
  An image forming method for developing an electrostatic charge image with a magnetic brush formed on a developer carrying member to form a toner image on a photoreceptor,
  The two-component developer has a toner and a magnetic carrier, and the magnetic carrier has a magnetic carrier core particle and a silicone resin covering the magnetic carrier core particle;
  The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
  (I) The amount of carbon derived from the —COO— group as measured by ESCA is relative to the amount of silicon constituting the silicone resin.15-65Atomic percent, and
  (Ii) In the measurement by ESCA, at least when the silicone resin does not have a nitrogen-containing group, the carbon amount derived from the phenyl group is larger than the carbon amount derived from the —COO— group.10-200If the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. The present invention relates to a characteristic image forming method.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have found that a carrier having excellent characteristics can be provided by paying attention to the surface composition that greatly affects various physical properties of the carrier and considering the abundance ratio of atoms derived from the functional group. In the present invention, the above problem is solved by controlling the amount of silicon contained in the resin coating layer of the carrier, the amount of benzene rings, or the amount of nitrogen-containing groups, and the amount of -COO-groups. Can also improve.
[0024]
In the present invention, the measurement of atomic composition by ELECTRON SPECTROSCORY FOR CHEMICAL ANALYSIS (ESCA) can be performed by, for example, PHYSICAL ELECTRONICS, INC. Using a MODEL-5600ci, a monochrome X-ray source (A1Kα, 14 kV-350 W), an aperture size diameter of 800 μm, and an extraction angle of 75 are used.
[0025]
In the present invention, in the analysis of the surface of the silicone resin-coated carrier by ESCA, the silicon atom constituting the silicone resin is measured at 102.0 eV ± 0.5 eV, and the carbon atom of the —COO— group is The measurement target is 289.0 eV ± 0.5 eV, the carbon atom of the phenyl group is 291.7 eV ± 0.5 eV, and the nitrogen atom of the nitrogen-containing group is 400.0 eV ±. A measurement object is set at 0.5 eV. Magnetic carrier no. The ESCA chart for 2 is shown in FIGS.
[0026]
In the magnetic carrier of the present invention, the silicone resin coating layer is measured by ESCA (the amount of carbon derived from —COO— groups contained in the silicone resin / the amount of silicon constituting the silicone resin) × 100 of 10 to 70 atomic% ( More preferably, the condition of 15 to 65 atomic%) is satisfied. In the silicone resin coating layer, when the —COO— group is absent or small (the amount of carbon derived from the —COO— group / the amount of silicon) × 100 <10 atomic%, the silicone resin coating layer is thickened. Even if the insulation is improved to suppress the leakage of charge, the toner (particularly, the small particle diameter toner having a weight average particle diameter of 9 μm or less) cannot be sufficiently charged, and the dot reproducibility of the digital latent image is not achieved. Inferior to environmental stability. Conversely, if the amount of —COO— groups increases, such as (carbon amount derived from —COO— groups / silicon amount) × 100> 70 atomic%, the effect of suppressing the image flow decreases, and the release of the surface of the silicone resin coating layer further occurs. As a result, the toner spent tends to occur and the durability of a large number of sheets decreases. Resin-coated carrier that does not cause image flow, has sufficient charge imparting ability and environmental stability, and has sufficient durability by having -COO-group and silicon present in an appropriate ratio in the silicone resin coating layer Is obtained.
[0027]
Furthermore, the silicone resin coating layer has a value of 0.1 to 300 atomic% as measured by ESCA (the amount of carbon derived from the phenyl group contained in the silicone resin / the amount of carbon derived from the —COO— group contained in the silicone resin) × 100. The condition of (more preferably 10 to 200 atomic%) is satisfied.
[0028]
By making the carbon amount derived from the phenyl group of the coating layer present at a specific ratio with respect to the carbon amount derived from the -COO- group, the development efficiency is good, the charging property is excellent, and the charge is remarkable especially under low humidity. An extremely long-life silicone resin-coated carrier that does not cause a decrease in durable concentration due to up can be provided.
[0029]
The reason for this is not clear, but by making the amount of carbon derived from the phenyl group and the amount of carbon derived from the —COO— group present at a certain ratio, the balance between charge application and charge diffusion can be balanced. It is presumed that a good magnetic developability can be achieved and a long-life coated magnetic carrier can be obtained. When the amount of carbon derived from the phenyl group is absent or small [(the amount of carbon derived from the phenyl group) / (the amount of carbon derived from the —COO— group)] × 100 <0.1 atomic%, It is presumed that the endurance density decreases due to charge-up due to the fact that the degree of charge diffusion becomes dull and the charge accumulates with endurance. Conversely, when [(carbon amount derived from phenyl group) / (carbon amount derived from —COO-group)] × 100> 300 atomic%, the developability deteriorates, and the particle size distribution of the toner changes with durability. When toner particles having a large particle diameter increase in the developing device, the image quality is deteriorated. By providing a carbon amount derived from a phenyl group and a carbon amount derived from a -COO- group at an appropriate ratio in the coating layer, a coated carrier having good developability and further sufficient durability is obtained. Can do.
[0030]
The silicone resin coating layer had a value of [(nitrogen derived from nitrogen-containing group contained in silicone resin / carbon amount derived from —COO-group contained in silicone resin)] × 100 as measured by ESCA. A satisfactory silicone resin-coated magnetic carrier can be provided even when the condition of 01 to 10 atomic% (more preferably, 0.1 to 5 atomic%) is satisfied.
[0031]
When the nitrogen amount is present at a certain ratio to the carbon amount of -COO-, it provides an extremely long-life carrier that is excellent in charge rising and does not cause a decrease in the durability concentration due to significant charge-up, particularly under low humidity. I can.
[0032]
The reason for this is not clear, but by making the amount of nitrogen present at a specific ratio to the amount of carbon in —COO—, charge application and diffusion can be performed well, and a long-life coated magnet coated with a silicone resin. Carrier can get. When there are no or few nitrogen-containing groups (nitrogen amount / carbon amount derived from —COO— group) × 100 <0.01 atomic%, charge application is low, and charge diffusion is increased, As a result, the charging speed becomes slow, and adverse phenomena such as toner scattering and fogging tend to occur. Conversely, when (nitrogen amount—carbon amount derived from COO—group) × 100> 10 atomic%, the degree of charge diffusion decreases, and charges accumulate with durability, resulting in a decrease in durability concentration due to charge-up. End up.
[0033]
Examples of the silicone resin used in the present invention include those having the above-described surface composition, such as methacrylic acid ester-modified silicone resin, acrylic ester-modified silicone resin, styrene-acrylic ester-modified silicone resin, and styrene-methacrylic ester-modified. Examples thereof include silicone resins, amino-modified silicone resins, dimethyl silicone resins, diphenyl silicone resins, epoxy-modified silicone resins, and methylphenyl silicone resins. These may be used alone or in combination.
[0034]
[Outside 19]

[0035]
A silicone oligomer or silicone resin having structural units of the following formulas (I) and (II) is produced.
[0036]
[Outside 20]

(Wherein R¹ ~ R^Five Each represents a hydrocarbon group selected from a methyl group, an ethyl group and a phenyl group. )
[0037]
In producing the silicone oligomer or silicone resin, the following formulas (III), (IV), (Va) and (Vb) may be used.
[0038]
[Outside 21]

(Wherein R⁶ And R⁷ Represents a hydrocarbon group having 1 or more carbon atoms. )
[0039]
[Outside 22]

[0040]
Further, methacrylic acid ester or acrylic acid ester and the following formula (VI)
[0041]
[Outside 23]

(Wherein R⁸ , R⁹ And R^TenAre the same or different groups and CH_Three , CH₂ CH_Three , OCH_Three Or OCH₂ CH_Three Represents. However, R⁸ , R⁹ And R^TenAt least one of the OCH_Three Or OCH₂ CH_Three It is. )
The oligomer or resin may be used in combination with the silicone oligomer or silicone resin by reacting with the compound represented by
[0042]
As the carrier core material in the silicone resin-coated magnetic carrier of the present invention, conventionally known ones can be used. Examples thereof include particles of a ferromagnetic metal such as iron and cobalt, particles obtained by dispersing a magnetic material in a resin, magnetite particles, hematite particles, and ferrite particles. Preferably, ferrite particles or iron particles whose surface can be easily controlled are used, and ferrite particles are particularly preferable.
[0043]
The particle diameter of the carrier core material in the present invention is preferably a number average particle diameter of 20 to 100 μm, particularly preferably 30 to 65 μm. When the number average particle diameter is less than 20 μm, the amount of fine particles increases in the carrier particle distribution, the magnetization per particle is lowered, and carrier scattering is likely to occur. On the other hand, when the number average particle of the carrier exceeds 100 μm, the specific surface of the carrier is lowered and the toner is likely to be scattered. In addition, in full-color image formation with many solid portions, the reproduction of solid portions is particularly deteriorated.
[0044]
Examples of the solvent for the silicone oligomer or silicone resin for forming the coating layer in the present invention include organic solvents such as toluene, xylene, methyl ethyl ketone, and methyl isobutyl ketone.
[0045]
The coating liquid is prepared so that the surface of the finally produced silicone resin-coated magnetic carrier satisfies the above atomic composition, the magnetic carrier core is coated with the coating liquid, and then the sintering temperature of the coating layer is normally performed. It is good to bake at 120-170 degreeC which is low. The reason for this is that when sintering is performed at a temperature lower than 120 ° C., the fluidity is lowered and the spent resistance against the toner is also lowered. Conversely, the reason is that the sintering temperature is higher than 170 ° C., but the reason is that the chargeability is lowered by oxidizing the acrylic group or the nitrogen-containing group, and toner scattering and fogging are likely to occur.
[0046]
The baking apparatus may be either an external heating system or an internal heating system, and may be, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking.
[0047]
The resin coating amount in the silicone resin-coated magnetic carrier is 0.10 to 5.0% by weight, preferably 0.15 to 2.0% by weight, based on the total amount of the silicone resin-coated magnetic carrier.
[0048]
The toner used in combination with the carrier of the present invention preferably has a weight average particle diameter of 9 μm or less, and preferably a weight average particle diameter of 3.0 to 8.0 μm.
[0049]
Examples of toner binder resins include styrene copolymers such as polystyrene, styrene-butadiene copolymers, and styrene-acrylic copolymers; ethylene-vinyl acetate copolymers and ethylene-vinyl alcohol copolymers. Examples of such ethylene copolymers include phenolic resins, epoxy resins, polyamide resins, polyester resins, and maleic acid resins.
[0050]
Among these resins, particularly when a polyester resin having a high negative chargeability is used, the combination effect of the carrier of the present invention is great.
[0051]
In particular, the following formula
[0052]
[Outside 24]

(Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10). Carboxylic acid component consisting of a divalent or higher carboxylic acid or its acid anhydride or its lower alkyl ester (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) A polyester resin obtained by co-condensation with is preferable because it has sharp melting characteristics.
[0053]
As the colorant, known dyes and pigments such as phthalocyanine blue, indanthrene blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used as the non-magnetic toner. . The content is 12 parts by weight or less, preferably 0.5 to 9 parts by weight with respect to 100 parts by weight of the binder resin in order to reflect sensitively to the transparency of the OHP film.
[0054]
In the toner used in the present invention, a charge control agent may be added to the toner. By adding the charge control agent, the optimum triboelectric charge amount according to the development system can be obtained.
[0055]
As the negative charge control agent, an organometallic complex and a chelate compound are preferable. Azo-based metal complexes, aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3.5-ditertiary butylsalicylate, 3,5-ditertiary butylsalicylate aluminum, 3.5-zetary butylsalicylate zinc, etc. I can do it. In particular, metal complexes of acetylacetone (including monoalkyl-substituted and dialkyl-substituted products), salicylic acid-based metal complexes (including monoalkyl-substituted and dialkyl-substituted products), or salts thereof are preferable, and salicylic acid-based metal complexes are particularly preferable. Or a salt is suitable.
[0056]
When the above-mentioned charge control agent is added to the toner, it is preferably used in an amount of 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the binder resin. In particular, when used for color image formation, it is preferable to use a colorless or light-colored charge control agent.
[0057]
The toner used in the present invention includes silica fine powder, alumina fine powder, titanium oxide fine powder, polytetrafluoroethylene fine powder, polyvinyldenfluoride fine powder, polymethyl methacrylate fine powder, polystyrene fine powder, and silicone fine powder. It is preferable to mix or add such a fine powder. By mixing or adding the above-described fine powder to the toner, the fine powder exists between the toner and the carrier or between the toners, the flowability of the developer is improved, and the life of the developer is further increased. Will also be improved. As the surface area of the fine powder described above, the specific surface area by nitrogen adsorption by the BET method is 30 m.² / G or more, especially 50-400m² Good results are obtained in the range of / g. The addition amount of such fine powder is preferably 0.1 to 20% by weight based on the toner.
[0058]
To the toner of the present invention, a wax component such as polyethylene, polypropylene, microcrystalline wax, carnauba wax, sazol waffle and paraffin wax may be added for the purpose of improving releasability at the time of fixing with a hot roll.
[0059]
A toner having such a composition is obtained by thoroughly mixing a vinyl-type thermoplastic resin or a non-vinyl-type thermoplastic resin, a colorant, a charge control agent, and other additives with a mixer, and then heating rolls, kneaders, extenders. It is melted and kneaded using a kneader such as a ruder, and the resins are sufficiently mixed to mix the resins with each other, and the pigment or dye is dispersed therein. After the melt-kneaded product is cooled, the toner particles can be obtained by pulverization and classification. The toner particles can be used as they are, but they can be used by adding externally a kind and amount of fine powder as required.
[0060]
The external addition treatment of the fine powder can be performed using a mixer such as a Henschel mixer. The toner thus obtained is mixed with the carrier particles of the present invention to form a two-component developer. When forming the above-mentioned two-component developer, the ratio of the toner in the developer is typically in the range of 1 to 20% by weight, more preferably 1 to 10% by weight, depending on the development process. Is preferred. The toner triboelectric charge amount of such a two-component developer is preferably in the range of 20 to 100 μC / g, and most preferably 30 to 60 μC / g. The measurement conditions of the triboelectric charge amount used in the present invention will be described later.
[0061]
A method for measuring the physical properties of the carrier and the toner will be described below.
[0062]
Measurement of average particle size of carrier
The particle size of the carrier is extracted 300 or more randomly by an optical microscope, and measured as the carrier particle size with a horizontal ferret diameter by an image processing analyzer Luzex 3 manufactured by Nireco Corporation.
[0063]
Measurement of toner particle size distribution
As a measuring device, Coulter Counter TA-II or Coulter Multisizer II (manufactured by Coulter Inc.) is used. As the electrolyte, first grade sodium chloride is used to prepare an approximately 1% NaCl aqueous solution. For example, ISOTON-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of toner particles are measured for each channel by using the 100 μm aperture as the aperture. Thus, the toner volume distribution and number distribution are calculated. Then, the weight-based toner weight average particle diameter (D4) obtained from the volume distribution of the toner particles (the median value of each channel is a representative value for each channel) is obtained.
[0064]
As channels, 2.00 to 2.52 μm; 2.52 to 3.17 μm; 3.17 to 4.00 μm; 4.00 to 5.04 μm; 5.04 to 6.35 μm; 6.35 to 8. 00μm; 8.00 to 10.08 μm; 10.08 to 12.70 μm; 12.70 to 16.00 μm; 16.00 to 20.20 μm; 20.20 to 25.40 μm; 25.40 to 32.00 μm; 13 channels of 32.00-40.30 μm are used.
[0065]
Toner cohesion
The degree of aggregation is used as one means for measuring the flow characteristics of a sample (such as a toner having an external additive). The larger the value of the degree of aggregation, the worse the fluidity of the sample.
[0066]
As a measuring device, a powder tester (manufactured by Hosokawa Micron Corporation) having a digital vibrometer (Digivibro Model 1332) is used.
[0067]
As a measurement method, 200 mesh, 100 mesh, and 60 mesh sieves are placed on the shaking table in the order of narrow opening, that is, the meshes of 200 mesh, 100 mesh, and 60 mesh are overlapped in order of the highest mesh. To do.
[0068]
5 g of accurately weighed sample is added to the set 60 mesh sieve, the input voltage to the shaking table is set to 21.7 V, and the displacement value of the digital shaking meter is set to 0.130. Is adjusted to fall within the range of 60 to 90 μm (rheostat scale about 2.5), and vibration is applied for about 15 seconds. Thereafter, the weight of the sample remaining on each sieve is measured, and the degree of aggregation is calculated based on the following equation.
[0069]
[Outside 25]

[0070]
The sample used was left at a temperature of 23 ° C. and a humidity of 60% RH for about 12 hours, and the measurement environment was a temperature of 23 ° C. and a humidity of 60% RH.
[0071]
Next, the image forming method of the present invention will be described with reference to the developing device shown in FIG.
[0072]
An electrostatic charge image carrier (photoconductor) 1 is an electrostatic recording insulating drum or α-Se, CdS, ZnO.₂  , OPC, α-Si, a photosensitive drum or photosensitive belt having a photoconductive insulating material layer. The electrostatic image carrier 1 is rotated in the direction of arrow a by a driving device (not shown). Reference numeral 2 denotes a developing sleeve as a developer carrying member that is in proximity to or in contact with the electrostatic charge image carrying member 1 and is made of a nonmagnetic material such as aluminum or SUS316. The developing sleeve 2 is protruded into the container 20 through a laterally long opening formed in the longitudinal direction of the container on the lower left wall of the developing container. The developing sleeve 2 is exposed to the outside of the container on the substantially left semicircular surface and is rotatably supported. And is rotationally driven in the direction of arrow b.
[0073]
Reference numeral 3 denotes a fixed permanent magnet (magnet) which is inserted into the developing sleeve (developer carrying member) 2 and is positioned and held in the position and orientation shown in the drawing, and this magnet even when the developing sleeve 2 is driven to rotate. 3 is fixed and held as it is in the illustrated position and orientation. The magnet 3 has N-pole magnetic poles 3a, 3e, and 3d, and has five S-pole magnetic poles 3b and 3c. The magnet 3 may be an electromagnet instead of a permanent magnet.
[0074]
Reference numeral 4 denotes a non-magnetic blade as a developer regulating member having a base fixed to the container side wall on the upper edge side of the developer supply opening in which the developing sleeve 2 is disposed. For example, SUS316 is L-shaped as shown in a cross-sectional view. Bending process.
[0075]
Reference numeral 5 denotes a magnetic carrier limiting member having an upper surface in contact with the lower surface side of a nonmagnetic blade (developer regulating member) 4 and having a front end surface as a developer guide surface. The magnetic carrier limiting member 5 includes a nonmagnetic blade 4 and a magnetic carrier return member 5. This is the regulation section.
[0076]
Reference numeral 7 denotes a developer layer having the carrier and toner of the present invention. Reference numeral 6 denotes a non-magnetic toner.
[0077]
Reference numeral 10 denotes a toner supply roller that operates according to an output obtained by a toner density detection sensor (not shown). As the sensor, a developer volume detection method, a piezoelectric element, an inductance change detection element, an antenna method using an alternating bias, and a method for detecting optical density can be used. The nonmagnetic toner 6 is supplied by rotating or stopping the roller. The fresh developer replenished with the toner 6 is mixed and stirred while being conveyed by the developer conveying screw 11. Therefore, tribo is applied to the toner replenished during the conveyance. A threshold plate 13 is cut out at both ends in the longitudinal direction of the developing device, and the fresh developer conveyed by the screw 11 is transferred to the screw 12 at this portion.
[0078]
The S magnetic pole 3d is a transport pole. The collected developer after development is collected in a container, and the developer in the container is further transported to a regulating portion.
[0079]
In the vicinity of 3d, the fresh developer conveyed by the screw 2 provided close to the developing sleeve 2 and the recovered developer after development are exchanged.
[0080]
The distance d between the end of the nonmagnetic blade 4 and the surface of the developing sleeve 2 is 100 to 900 μm, preferably 150 to 800 μm. If this distance is smaller than 100 μm, the carrier particles are clogged in the meantime, and the developer layer is likely to be uneven, and the developer necessary for good development cannot be applied, and only a developed image with a small density and unevenness can be obtained. It may not be possible. On the other hand, if the distance is greater than 900 μm, the amount of developer applied onto the developing sleeve 2 increases, the predetermined developer layer thickness cannot be regulated, and magnetic particles adhere to the latent image carrier and the developer increases. And the development restriction by the developer limiting member 5 is weakened, and the toner tribo is insufficient and tends to be fogged.
[0081]
It is preferable to apply an alternating voltage to the developing sleeve 2 by making the thickness of the developer layer on the developing sleeve 2 the same as or slightly larger than the opposing gap distance between the developing sleeve 2 and the electrostatic charge image carrier 1. The distance of the gap is preferably 50 to 800 μm (more preferably 100 to 700 μm).
[0082]
A bias power supply 14 applies an alternating voltage or a developing bias in which a DC voltage is superimposed on the alternating voltage to the developing sleeve 2 to facilitate the movement of toner from the developing sleeve 2 to the electrostatic charge image carrier 10, and a higher quality image. Can be formed.
[0083]
The alternating voltage as the alternating voltage to be applied is preferably 1,000 to 10,000 (preferably 2,000 to 8,000) Vpp. When superimposing a DC voltage, it is preferable to apply the DC voltage in an absolute value range of 1,000 V or less.
[0084]
An image forming apparatus for satisfactorily implementing the full color image forming method using the developer of the present invention will be described with reference to FIG.
[0085]
The color electrophotographic apparatus shown in FIG. 2 includes the transfer material conveying system I provided from the right side (right side of FIG. 1) of the apparatus main body 1 to the substantially central part of the apparatus main body, A latent image forming unit II provided in the vicinity of the transfer drum 315 constituting the transfer material conveying system I, and a developing unit (that is, a rotary developing unit) provided in the vicinity of the latent image forming unit II. Apparatus) III.
[0086]
The transfer material transport system I has the following configuration. An opening is formed in the right wall (right side in FIG. 2) of the apparatus main body 1, and transfer material supply trays 302 and 303 detachably attached to the opening are partly disposed outside the apparatus. Feeding rollers 304 and 305 are disposed substantially directly above the trays 302 and 303. The feeding rollers 304 and 305 and a transfer drum 305 that is arranged on the left and is rotatable in the direction of arrow A are provided. A paper feed roller 306 and paper feed guides 307 and 308 are provided so as to be linked. Near the outer peripheral surface of the transfer drum 315, an abutting roller 309, a gripper 310, a transfer material separating charger 311 and a separating claw 312 are sequentially arranged from the upstream side to the upstream side in the rotational direction.
[0087]
A transfer charger 313 and a transfer material separation charger 314 are disposed on the inner peripheral side of the transfer drum 315. A transfer sheet (not shown) made of a polymer such as polyvinylidene fluoride is attached to a portion of the transfer drum 315 around which the transfer material is wound, and the transfer material is electrostatically placed on the transfer sheet. It is stuck on. Conveying belt means 316 is disposed on the upper right side of the transfer drum 315 in the vicinity of the separation claw 312, and a fixing device 318 is disposed at the end (right side) of the conveying belt means 316 in the transfer material conveying direction. Yes. A discharge tray 317, which extends outside the apparatus main body 301 and is detachable from the apparatus main body 301, is arranged further downstream of the fixing device 318 in the transport direction.
[0088]
Next, the configuration of the latent image forming unit II will be described. In FIG. 2, a photosensitive member (eg, an OPC photosensitive drum or an OPC photosensitive belt) 319 that is a latent image carrier that can rotate in the direction of the arrow is disposed with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 315. . Above the photosensitive drum 319, in the vicinity of the outer peripheral surface thereof, a static elimination charger 320, a cleaning unit 321 and a primary charger 323 are sequentially arranged from the upstream side to the downstream side in the rotation direction of the photosensitive drum 319. An image exposure unit 324 such as a laser beam scanner for forming an electrostatic latent image and an image exposure reflection unit 325 such as a mirror are provided on the outer peripheral surface of the photosensitive drum 319.
[0089]
The configuration of the rotary developing device III is as follows. A rotatable housing (hereinafter referred to as a “rotating body”) 326 is disposed at a position facing the outer peripheral surface of the photosensitive drum 319, and four types of developing devices are provided in the rotating body 326 at four positions in the circumferential direction. The electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 319 is visualized (that is, developed). The four types of developing devices include a yellow developing device 327Y, a magenta developing device 327M, a cyan developing device 327C, and a black developing device 327BK, respectively.
[0090]
The sequence of the entire image forming apparatus configured as described above will be described by taking the case of the full color mode as an example. When the photosensitive drum 319 described above rotates in the direction of the arrow in FIG. 2, the photosensitive member on the photosensitive drum 319 is charged by the primary charger 323. In the apparatus of FIG. 2, the operation speed of each part (hereinafter referred to as process speed) is 100 mm / sec or more (for example, 130 to 250 mm / sec). When the photosensitive drum 319 is charged by the primary charger 323, image exposure is performed by the laser beam E modulated by the yellow image signal of the document 328, and an electrostatic latent image is formed on the photosensitive drum 319, and rotated. The electrostatic latent image is developed by the yellow developing device 327Y previously set at the developing position by the rotation of the body 326, and a yellow toner image is formed.
[0091]
The transfer material conveyed via the paper feed guide 307, the paper feed roller 306, and the paper feed guide 308 is held by the gripper 310 at a predetermined timing, and faces the contact roller 309 and the corresponding contact roller 309. It is wound around the transfer drum 315 electrostatically by the electrode being operated. The transfer drum 315 rotates in the direction of the arrow in FIG. 2 in synchronization with the photosensitive drum 319, and the yellow toner image formed by the yellow developing device 327 </ b> Y has an outer peripheral surface of the photosensitive drum 319 and an outer peripheral surface of the transfer drum 315. Is transferred onto the transfer material by the transfer charger 313 at the site where the contact is made. The transfer drum 315 continues to rotate to prepare for the transfer of the next color (magenta in FIG. 2).
[0092]
The photosensitive drum 319 is neutralized by the static elimination charger 320, cleaned by the cleaning means 321 by the cleaning blade, and then charged again by the primary charger 323, and image exposure is performed by the next magenta image signal. A latent image is formed. The rotary developing device is rotated while an electrostatic latent image is formed on the photosensitive drum 319 by image exposure based on a magenta image signal, and the magenta developing device 327M is disposed at the predetermined developing position described above. Develop with magenta toner. Subsequently, the above-described processes are performed for cyan and black colors, respectively, and when the transfer of the four-color toner images is completed, the four-color visible images formed on the transfer material are transferred to the chargers 322 and 314, respectively. The transfer material is discharged by the gripper 310, and the transfer material is released from the transfer drum 315 by the separation claw 312 and sent to the fixing device 318 by the conveyor belt 316, and is fixed by heat and pressure. Then, a series of full color print sequences are completed, and a required full color print image is formed on one surface of the transfer material.
[0093]
At this time, the fixing operation speed in the fixing device 318 is performed at a slower speed (for example, 90 mm / sec) than the process speed (for example, 160 mm / sec) of the main body. This is because when an unfixed image in which two to four layers of toner are laminated is melted and mixed, a sufficient amount of heating must be given to the toner, so that the toner is heated by fixing at a speed slower than the developing speed. The amount is increased.
[0094]
【Example】
Example 1
A coating solution for forming a coating layer on the surface of the magnetic carrier core particles was prepared as follows.
[0095]
33 parts by mole of the following compound (1), 35 parts by mole of the following compound (2) and 2 parts by mole of the following compound (3) are dissolved in xylene, and the resulting xylene solution is heated to a temperature of 70 to 80 ° C. The solution was poured into a container containing warm water and the silicone compound was subjected to condensation polymerization to produce an oligomer. After producing the silicone oligomer having the structural units (I) and (II), the lower aqueous layer and the xylene layer dissolving the upper oligomer were separated to prepare a first xylene solution.
[0096]
[Outside 26]

[0097]
Separately, 15 mol parts of the following compound (4) and 15 mol parts of the following compound (5) are dissolved in xylene, and about 3 mol parts of an azo initiator (2,2′-azobisisobutyronitrile) are dissolved in the resulting xylene solution. And radical polymerization was carried out at a liquid temperature of 50 to 60 ° C. to produce a copolymer of the compounds (4) and (5) to prepare a second xylene solution.
[0098]
[Outside 27]

[0099]
Next, the first xylene solution and the second xylene solution are mixed, and xylene is added to adjust the solid content concentration to about 3% by weight. 1 was prepared.
[0100]
As a magnetic carrier core particle, a magnetic ferrite particle having an average particle size of 35 μm (trade name: F-400; POWDERTECH CO., LTD, manufactured by Powder Tech Co., Ltd.) was applied in a fluidized bed. 1 was applied to obtain a magnetic carrier having a coating layer. Next, the magnetic carrier was heat-treated at a temperature of 150 ° C. for 30 minutes, and the surface of the magnetic ferrite core particles was baked with a silicone resin and coated with 0.5% by weight of the silicone resin. 1 was obtained. The obtained magnetic carrier No. When the surface of 1 was analyzed by ESCA, the amount of carbon derived from —COO— groups was 39 atomic% with respect to the amount of silicon constituting the silicone resin, and the amount of carbon derived from phenyl groups was derived from —COO— groups. It was 112 atomic% with respect to the carbon amount to do.
[0101]
Magnetic carrier No. 1, a non-magnetic cyan toner (weight average particle size of about 8.5 μm, aggregation degree 10%) for negative friction charge for color laser copying machine (product name CLC-700, manufactured by Canon) Magnetic magenta toner (weight average particle size of about 8.5 μm, aggregation degree of 10%), negative friction chargeable non-magnetic yellow toner (weight average particle diameter of about 8.5 μm, aggregation degree of 10%), and negative friction chargeability Non-magnetic black toner (weight average particle diameter of about 8.5 μm, aggregation degree of 10%) was mixed with each other to prepare a cyan two-component developer (toner concentration 6% by weight) and a magentan two-component developer ( Toner concentration 6% by weight), yellow two-component developer (toner concentration 6% by weight) and black two-component developer (toner concentration 6% by weight) were prepared.
[0102]
Development for cyan color of the color laser copying machine having a two-component developer for each color having an OPC photosensitive drum and developing a digital electrostatic charge image by a reversal development method while applying an AC bias to the developing sleeve during development , Magenta color developer unit, yellow color developer unit, and black color developer unit, using an original document with an image area ratio of 25%, in an environment of normal temperature and humidity (23 ° C / 60% RH). When 50,000 sheets were continuously copied in each color mono color mode while replenishing each color toner, the fluctuation of the image density during the durability of 50,000 sheets was small, there was no fogging on the image, there was almost no change in charge amount, and the toner particle size Was excellent in durability stability with almost no change. The triboelectric charge amount of cyan toner is −27 μC / g, the triboelectric charge amount of magenta toner is −26 μC / g, the triboelectric charge amount of yellow toner is −28 μC / g, and the triboelectric charge amount of black toner is − It was 23 μC / g. Furthermore, the difference in charge amount between high temperature and high humidity (30 ° C., 80% RH) and low temperature and low humidity (15 ° C., 10% RH) is also small, and it has excellent charging characteristics and becomes noticeable under high humidity. Excellent characteristics with no image flow occurred. The results are shown in Table 3.
[0103]
Example 2
Coating liquid No. having the formulation shown in Table 2 was used. 2 except that the magnetic carrier No. 2 was used in the same manner as in Example 1. 2 was prepared. Magnetic carrier No. Table 2 shows the results of ESCA analysis of No. 2. Magnetic carrier No. Each color developer was prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1.
[0104]
The results are shown in Table 3. The image density after 50,000 sheets was slightly changed and the charge amount was slightly changed, but it was a good level.
[0105]
Example 3
Except for changing the composition ratio, the coating liquid No. 3 was prepared.
[0106]
Coating liquid No. 3 is used in the same manner as in Example 1 to obtain the magnetic carrier No. 3 was prepared. Magnetic carrier No. The analysis results of 3 ESCA are shown in Table 2. Magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1.
[0107]
The results are shown in Table 3. Although a slight fog after 50,000 sheets and a slight change in the toner particle size in the developing device were observed, the level was good.
[0108]
Comparative Example 1
Except for not using the compound (1) and changing the composition ratio to Table 1, the coating solution No. 4 was prepared.
[0109]
Coating liquid No. 4 was used in the same manner as in Example 1, and the comparative magnetic carrier No. 1 was prepared. Comparative magnetic carrier No. Table 2 shows the results of analysis of 1 ESCA. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 3.
[0110]
The change in image density after 50,000 sheets and the change in charge amount were poor and lacked in durability stability, and the change in charge amount due to the environment was large and the charge characteristics were inferior. The reason for this is considered to be due to the accumulation of charge because the amount of carbon derived from the phenyl group is less than the amount of carbon derived from the —COO— group, and the charge is not sufficiently diffused.
[0111]
Comparative Example 2
The coating liquid No. Comparative magnetic carrier No. 5 was used in the same manner as in Example 1 except that No. 5 was used. 2 was prepared. Comparative magnetic carrier No. Table 2 shows the results of ESCA analysis of No. 2. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1.
[0112]
The results are shown in Table 3. The image density after 50,000 sheets, the fluctuation of the charge amount and the fog were poor and the durability stability was poor, and the toner particle size changed after the endurance.
[0113]
Comparative Example 3
Except for changing the composition ratio, the coating liquid No. 6 was prepared. Coating liquid No. 6 was used in the same manner as in Example 1 except that the comparative magnetic carrier No. 6 was used. 3 was prepared. Comparative magnetic carrier No. The analysis results of 3 ESCA are shown in Table 2. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1.
[0114]
The results are shown in Table 3. It was bad in terms of fog and fluctuation of the charge amount after 50,000 sheets and lacked durability stability, and image flow on the photosensitive drum occurred.
[0115]
Comparative Example 4
Except for changing the composition ratio, the coating liquid No. 7 was prepared. Coating liquid No. Comparative magnetic carrier No. 7 was used in the same manner as in Example 1 except that No. 7 was used. 4 was prepared. Comparative magnetic carrier No. The analysis results of 4 ESCA are shown in Table 2. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1.
[0116]
The results are shown in Table 3. The image density fluctuation and fogging after 50,000 sheets were poor and lacked durability stability, and the change in charge amount due to the environment was large and the charging characteristics were inferior. This is considered to be because the amount of carbon derived from the —COO— group was small relative to the amount of silicon, and the charge imparting ability was poor.
[0117]
Comparative Example 5
The coating liquid No. 1 was prepared according to the formulation shown in Table 1 except that the compounds (4) and (5) were not used and the composition ratio was changed. 8 was prepared. Coating liquid No. Comparative magnetic carrier No. 8 was used in the same manner as in Example 1 except that No. 8 was used. 5 was prepared. Comparative magnetic carrier No. The analysis results of 5 ESCA are shown in Table 2. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 3.
[0118]
Comparative Example 6
Except for not using the compound (1) and changing the composition ratio, the coating liquid No. 9 was prepared. Coating liquid No. 9 was used in the same manner as in Example 1, and the comparative magnetic carrier No. 6 was prepared. Comparative magnetic carrier No. The analysis results of 6 ESCA are shown in Table 2. Comparative magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 3.
[0119]
[Table 1]

[0120]
[Table 2]

[0121]
[Table 3]

[0122]
Evaluation methods
1) Image density:
Copy under proper exposure conditions. D. In the evaluation, the solid image density was measured with a Macbeth densitometer, and the rank was evaluated.
[0123]
A: The original density is reproduced very well without density unevenness.
B: The document density is reproduced (a level with no practical problem).
C: non-uniform and uneven density (a level causing practical problems)
D: Changed greatly compared to the original density (unusable level)
[0124]
2) Fog on the image:
The toner fog on the white background image was measured using a REFLECTOMETER MODEL TC-6DS manufactured by Tokyo Denshoku Co., Ltd., and rank evaluation was performed.
[0125]
A: Less than 0.5%
B: Less than 0.5 to 1.5%
C: Less than 1.5 to 2.5%
D: 2.5% or more
[0126]
3) Environmental variation of charge amount:
The toner is charged in a 50 ml capacity polyethylene container at 15 ° C. and 10% humidity for one day and then mixed by shaking by hand 500 times, and the toner charge amount Q (LL) is 30 ° C. and 80% humidity. The charge amount Q (HH) of the toner after being shaken and mixed by hand 500 times after being left in the environment for one day is calculated using a charge amount measurement method described later, and the difference ΔQ (= Q (LL) − Q (HH)) was evaluated for rank.
[0127]
A: ΔQ = less than 10 μC / g
B: ΔQ = 10 μC / g or more and less than 15 μC / g
C: ΔQ = 15 μC / g or more and less than 20 μC / g
D: ΔQ = 20 μC / g or more
[0128]
4) Durability fluctuation of charge amount:
The toner charge amount Q (start) of the developer collected from the developing sleeve of the developing device in the initial stage of durability at 23 ° C. and 60% humidity, and the developer collected from the developing sleeve of the developing device after 50,000 sheets The toner charge amount Q (last) was calculated using a charge amount measurement method described later, and rank evaluation was performed using the difference ΔQ (= Q (start) −Q (last)).
[0129]
A: ΔQ = less than 5 μC / g
B: ΔQ = 5 μC / g or more and less than 10 μC / g
C: ΔQ = 10 μC / g or more and less than 15 μC / g
D: ΔQ = 15 μC / g or more
[0130]
5) Durability fluctuation of toner particle size:
The weight average toner particle size D (start) of the toner in the developing device in the initial stage of durability under the environment of 23 ° C. and 60% humidity, and the weight average toner particle size D (last) of the toner in the developing device after 50,000 sheets The toner particle size was calculated using a toner particle diameter measuring method described later, and the rank was evaluated by the difference ΔD (= D (start) −D (last)).
[0131]
A: ΔD = 1 less than 1 μm
B: ΔD = 1 to 2 μm
C: ΔD = 2 μm or more and less than 3 μm
D: ΔD = 3 μm or more
[0132]
6) Image flow on the photosensitive drum:
A halftone image was formed using a color laser copying machine (CLC700) in an environment of 30 ° C. and humidity of 60%, and the image quality was evaluated.
[0133]
A: No image flow is seen
B: A level that can be seen a little but has no practical problem
C: Practical problem level
D: Image flow is seen on the entire surface, impractical level
[0134]
7) Measurement of charge amount:
FIG. 3 is an explanatory diagram of an apparatus for measuring the tribo charge of the developer toner. First, about 0.5 to 0.9 g of the developer collected from the sleeve of the developing device is placed in a metal measuring container 102 having a 500 mesh screen 103 at the bottom, and a metal lid 104 is formed. Weigh the entire measurement container 2 at this time W₁(G). Next, in the suction machine 101 (at least the insulator is in contact with the measurement container 102), the suction is performed through the suction port 107 and the same amount control valve 106 is adjusted to set the pressure of the vacuum gauge 105 to 250 mmAq. In this state, the toner is sucked and removed by suction for about 2 minutes. The potential of the electrometer 109 at this time is set to V (volt). Here, 108 is a capacitor, and the capacity is C (μF). Also, weigh the entire measurement container after suction.₂ (G). The triboelectric charge amount (μC / g) of the toner is calculated by the following equation.
[0135]
Toner triboelectric charge amount (μC / g) = (C × V) / (W₁ -W₂ )
[0136]
Example 4
Preparation of cyan toner
Polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid
(Binder resin, weight average molecular weight 25,000) 100 parts by weight
4 parts by weight of phthalocyanine pigment (cyan colorant)
Di-tert-butylsalicylic acid chromium (negative charge control agent) 4 parts by weight
The above materials are sufficiently premixed with a Henschel mixer, melt-kneaded with a twin-screw extruder, cooled and roughly ground to about 1 to 2 mm using a hammer mill, and then finely ground with an air jet type fine grinding machine. did. Further, the obtained finely pulverized product was classified to obtain negatively charged nonmagnetic cyan toner particles having a weight average particle diameter of about 5.8 μm. 100 parts by weight of the obtained nonmagnetic cyan toner particles and hydrophobic titanium oxide fine powder (BET specific surface area of 100 m)² / G) A negatively chargeable cyan toner was prepared by mixing 1.5 parts by weight.
[0137]
Preparation of magenta toner
Except for using a quinacridone-based magenta pigment instead of the phthalocyanine pigment, negatively charged nonmagnetic magenta toner particles having a weight average particle diameter of about 5.8 μm were obtained in the same manner as the cyan toner particles. 100 parts by weight of the obtained nonmagnetic magenta toner particles and hydrophobic titanium oxide fine powder (BET specific surface area of 100 m)²/ G) A negatively chargeable magenta toner was prepared by mixing 1.5 parts by weight.
[0138]
Preparation of yellow toner
A negatively chargeable non-magnetic yellow toner having a weight average particle diameter of about 5.8 μm in the same manner as the cyan toner particles except that a yellow colorant (CI Pigment Yellow 17) is used in place of the phthalocyanine pigment. Particles were obtained. 100 parts by weight of the obtained nonmagnetic yellow toner particles and hydrophobic titanium oxide fine powder (BET specific surface area of 100 m)² / G) A negatively chargeable yellow toner was prepared by mixing 1.5 parts by weight.
[0139]
Preparation of black toner
Negatively charged black toner particles having a weight average particle diameter of about 5.8 μm were obtained in the same manner as the cyan toner particles except that carbon black was used in place of the phthalocyanine pigment. 100 parts by weight of the obtained nonmagnetic black toner particles and hydrophobic titanium oxide fine powder (BET specific surface area of 100 m)²/ G) A negatively chargeable black toner was prepared by mixing 1.3 parts by weight.
[0140]
6 parts by weight of each color toner having a small particle diameter and the magnetic carrier No. prepared in Example 1 were used. A two-component developer of each color was prepared by mixing with 94 parts by weight of No. 1, and an image formation test was conducted in the single color mode while replenishing each color toner in the same manner as in Example 1. The results are shown in Table 4. Under a normal temperature and humidity environment, the triboelectric charge amount of cyan toner is −34 μC / g, the triboelectric charge amount of magenta toner is −33 μC / g, and the triboelectric charge amount of yellow toner is −35 μC / g, The triboelectric charge amount of the black toner was −32 μC / g.
[0141]
Examples 5 and 6 and Comparative Examples 7 to 12
Magnetic carrier No. 2 and 3, comparative magnetic carrier Nos. The image-drawing test was conducted in the same manner as in Example 4 except that 1 to 6 were used. The results are shown in Table 4.
[0142]
[Table 4]

[0143]
Example 7
A coating solution for forming a coating layer on the surface of the magnetic carrier core particles was prepared as follows.
[0144]
In xylene, 28 mol parts of the compound (1), 37 mol parts of the compound (2), 2 mol parts of the compound (3) and 3 mol parts of the following compound (8) were dissolved. The solution was poured into a container containing warm water heated to ˜80 ° C., and a silicone compound was subjected to condensation polymerization to produce an oligomer. After the formation of the silicone oligomer having the structural units (I) and (II), the lower aqueous layer and the xylene layer in which the upper nitrogen-containing oligomer is dissolved are separated to prepare a third xylene solution. did.
[0145]
[Outside 28]

[0146]
Next, the second xylene solution dissolving the copolymer of the compounds (4) and (5) prepared in the same manner as in Example 1 is mixed with the third xylene solution, and xylene is added. The solid content concentration was adjusted to about 3% by weight and the coating solution No. 10 was prepared.
[0147]
As a magnetic carrier core particle, a magnetic ferrite particle having an average particle diameter of 35 μm (trade name: F-400; manufactured by Powdertech Co., Ltd.) was applied to a coating solution No. 10 was applied to obtain a magnetic carrier having a coating layer. Next, the magnetic carrier was heated at a temperature of 150 ° C. for 30 minutes, the surface of the magnetic ferrite core particles was baked with a silicone resin, and the magnetic carrier No. 1 coated with 1.0% by weight of the silicone resin was coated. 4 was obtained. The obtained magnetic carrier No. When the surface of No. 4 was analyzed by ESCA, the amount of carbon derived from the —COO— group was 40 atomic% with respect to the amount of silicon constituting the silicone resin, and the amount of nitrogen derived from the nitrogen-containing group was changed to —COO— group. It was 1 atomic% with respect to the amount of carbon derived.
[0148]
Magnetic carrier No. Table 7 shows the results of the image output test using 4 in the same manner as in Example 1.
[0149]
The change in image density after 50,000 sheets was small, there was no fogging on the image, and there was almost no change in charge amount, and the durability stability was excellent. Further, the difference in charge amount between high temperature and high humidity and low temperature and low humidity was small, and the charge characteristics were excellent, and the image characteristics on the photosensitive drum that became remarkable under high humidity were not generated at all.
[0150]
Example 8
In the same manner as in Example 4 except that the compounds (6) and (7) were used when the silicone oligomer was produced and the composition ratio was changed, the coating solution No. 11 was prepared. Coating liquid No. 11 was used in the same manner as in Example 1 to obtain the magnetic carrier No. 5 was prepared. Magnetic carrier No. The analysis results of 5 ESCA are shown in Table 6. Magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 7. Although there were some fluctuations in image density after 50,000 sheets and fluctuations in charge amount, they were at suitable levels.
[0151]
Example 9
The following compound (9) was used in place of the compound (8), and the coating solution No. 1 was prepared in the same manner as in Example 4 except that the composition ratio was changed. 12 was prepared.
[0152]
[Outside 29]

[0153]
Coating liquid No. 12 was used in the same manner as in Example 1 to obtain the magnetic carrier No. 6 was prepared. Magnetic carrier No. The analysis results of 6 ESCA are shown in Table 6. Magnetic carrier No. Each color developer was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 7. Although there were some fluctuations in image density after 50,000 sheets and fluctuations in charge amount, they were at suitable levels.
[0154]
Comparative Examples 13 to 18
Coating solution Nos. 13 to 17 were used in the same manner as in Example 1 to produce the comparative magnetic carrier Nos. 7 to 11 were prepared. Comparative magnetic carrier Nos. Table 6 shows the results of ESCA analysis of 7 to 11. Comparative magnetic carrier Nos. Each color developer was prepared in the same manner as in Example 1 using 7 to 11, and evaluated in the same manner as in Example 1. The results are shown in Table 7. In Comparative Example 13, the image density variation after 50000 sheets, the variation in charge amount and fogging were poor, and durability stability was poor, and the change in the charge amount due to the environment was large and the charging characteristics were inferior. The reason is considered to be that the amount of carbon derived from the —COO— group was small relative to the amount of silicon, and the charge imparting ability was poor.
[0155]
In Comparative Example 14, the image density fluctuation after 50000 sheets, the charge amount fluctuation and fogging were poor, the durability stability was poor, and the image flow on the photosensitive drum was also at a bad level.
[0156]
In Comparative Example 15, the image density fluctuation after 50000 sheets, the charge amount fluctuation and fogging were remarkably poor and lacked in durability stability. The reason for this is thought to be that the amount of nitrogen is larger than the amount of carbon derived from the —COO— group, and the charge is not sufficiently diffused, so that it depends on charge accumulation.
[0157]
In Comparative Example 16, the image density fluctuation after 50000 sheets, the charge amount fluctuation and fogging were remarkably poor and lacked in durability stability. The reason for this is considered to be that the amount of nitrogen is small relative to the amount of carbon derived from the —COO— group, the charging speed is very poor, and the charge imparting ability is low.
[0158]
[Table 5]

[0159]
[Table 6]

[0160]
[Table 7]

[0161]
Examples 10 to 12 and Comparative Examples 19 to 23
Each color toner having a small particle diameter of 5.8 μm prepared in Example 4 and a magnetic carrier Nos. 4 to 6 and the comparative magnetic carrier Nos. 7 to 11 were used and an image output test was conducted in the same manner as in Example 1. The results are shown in Table 8.
[0162]
[Table 8]

[0163]
【The invention's effect】
The developer using the carrier of the present invention is excellent in environmental stability and durability stability in triboelectric charging, and has excellent image quality with no fog and no image blur while sufficiently satisfying the image density, after 50,000 sheets. Can also be obtained stably.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a specific example of an image forming apparatus for carrying out an image forming method of the present invention.
FIG. 2 is a schematic explanatory view showing a specific example of a full-color copying machine for applying the image forming method of the present invention to full-color image formation.
FIG. 3 is an explanatory diagram of a measuring apparatus for measuring the triboelectric charge amount of toner in a two-component developer.
FIG. 4 is a diagram showing an example of an ESCA chart of the magnetic carrier of the present invention coated with a silicone resin.
FIG. 5 is a diagram showing an example of an ESCA chart.
FIG. 6 is a diagram showing an example of an ESCA chart.
FIG. 7 is a diagram showing an example of an ESCA chart.
[Explanation of symbols]
1 Electrostatic charge image carrier (photosensitive drum or photosensitive belt)
2 Developer carrier (Development sleeve)
3 Magnet
14 Bias power supply
101 Suction machine
102 Measuring container
103 conductive screen
104 lid
105 Vacuum gauge
106 Same amount control valve
107 Suction port
108 capacitors
109 electrometer

Claims (56)

A magnetic carrier for electrophotographic development comprising a magnetic carrier core particle and a silicone resin coating the magnetic carrier core particle;
The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
(I) The amount of carbon derived from the —COO— group is 15 to 65 atomic% relative to the amount of silicon derived from the silicone resin, as measured by ESCA, and
(Ii) Whether the carbon amount derived from the phenyl group is 10 to 200 atomic% with respect to the carbon amount derived from the —COO— group when the silicone resin does not have a nitrogen-containing group, as measured by ESCA. Or when the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. Magnetic carrier for developer.   The silicone resin has a carbon amount derived from —COO— groups of 15 to 65 atomic% relative to the silicon amount derived from silicone resin as measured by ESCA, and the nitrogen amount derived from nitrogen-containing groups is —COO—. The magnetic carrier according to claim 1, which is 0.1 to 5 atomic% with respect to the amount of carbon derived from the group. Silicone resin, -COO- group has three functional groups of the phenyl group and a nitrogen-containing group, a 0.1 to 300 atomic% based on the amount of carbon derived from the full Eniru group, and a nitrogen-containing The magnetic carrier according to claim 1 or 2, wherein the amount of nitrogen derived from the group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the -COO- group.   The silicone resin has a carbon amount derived from the —COO— group of 15 to 65 atomic% relative to the silicon amount derived from the silicone resin as measured by ESCA, and the carbon amount derived from the phenyl group is a —COO— group. The nitrogen amount derived from the nitrogen-containing group is from 10 to 200 atomic% with respect to the carbon amount derived from the nitrogen, and the nitrogen amount derived from the nitrogen-containing group is from 0.1 to 5 atomic% with respect to the carbon amount derived from the —COO— group. Magnetic carrier of any one of 1 to 3. Silicone resins are represented by the following formulas (I) and (II)
[Outside 1]

(Wherein R ^{1 to} R ⁵ each represent a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), and the silicone resin has an ester group and a phenyl group as functional groups. The magnetic carrier according to claim 1, comprising: Silicone resins are represented by the following formulas (I) and (II)
[Outside 2]

(Wherein R ^{1 to} R ⁵ each represents a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), the silicone resin has an ester group and the following formula as functional groups (VII) or (VIII)
[Outside 3]

[Outside 4]

The magnetic carrier according to claim 1, which has a nitrogen-containing group represented by the formula: The silicone resin has a phenyl group and the following formula (VI)
[Outside 5]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. The magnetic carrier according to claim 1, which has an ester group derived from a compound represented by the formula: The silicone resin has a nitrogen-containing group and the following formula (VI)
[Outside 6]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. The magnetic carrier according to claim 1, which has an ester group derived from a compound represented by the formula:   The magnetic carrier according to any one of claims 1 to 8, wherein the silicone resin has an ester group derived from a copolymer of a methacrylic acid ester and the compound represented by the formula (VI).   The magnetic carrier according to any one of claims 1 to 9, wherein the silicone resin has an ester group derived from a copolymer of an acrylate ester and the compound represented by the formula (VI).   The magnetic carrier according to any one of claims 1 to 10, wherein the magnetic carrier core particles are coated with 0.10 to 5.0% by weight of a silicone resin.   The magnetic carrier according to any one of claims 1 to 11, wherein the magnetic carrier core particles are coated with 0.15 to 2.0% by weight of a silicone resin.   The magnetic carrier according to any one of claims 1 to 12, wherein the magnetic carrier has an average particle diameter of 20 to 100 µm.   The magnetic carrier according to claim 1, wherein the magnetic carrier has an average particle diameter of 30 to 65 μm.   The magnetic carrier according to any one of claims 1 to 14, wherein the silicone resin is subjected to a baking treatment at a temperature of 120 to 170 ° C on the magnetic carrier core particles. In a two-component developer having a toner and a magnetic carrier, the magnetic carrier has a magnetic carrier core particle and a silicone resin covering the magnetic carrier core particle,
The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
(I) The amount of carbon derived from the —COO— group is 15 to 65 atomic% relative to the amount of silicon constituting the silicone resin, as measured by ESCA, and
(Ii) Whether the carbon amount derived from the phenyl group is 10 to 200 atomic% with respect to the carbon amount derived from the —COO— group when the silicone resin does not have a nitrogen-containing group, as measured by ESCA. Or when the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. Developer.   The two-component developer according to claim 16, wherein the toner has a negative frictional charging property with respect to the magnetic carrier.   The two-component developer according to claim 16 or 17, wherein the toner has a triboelectric charge amount of -20 to -100 µc / g with respect to the magnetic carrier.   The two-component developer according to claim 16 or 17, wherein the toner has a triboelectric charge amount of -30 to -60 µc / g with respect to the magnetic carrier.   The two-component developer according to any one of claims 16 to 19, wherein the toner has a weight average particle size of 9.0 µm or less, and the magnetic carrier has an average particle size of 20 to 100 µm.   The two-component developer according to claim 16, wherein the toner has a weight average particle diameter of 3.0 to 8.0 μm, and the magnetic carrier has an average particle diameter of 30 to 65 μm.   The silicone resin has a carbon amount derived from -COO- groups as measured by ESCA of 15 to 65 atomic% with respect to the silicon amount derived from the silicone resin, and the nitrogen amount derived from nitrogen is -COO-groups. The two-component developer according to any one of claims 16 to 21, which is 0.1 to 5 atomic% with respect to the amount of carbon derived from the above. Silicone resin, -COO- group has three functional groups of the phenyl group and a nitrogen-containing group, a 0.1 to 300 atomic% based on the amount of carbon derived from the full Eniru group, and a nitrogen-containing The two-component developer according to any one of claims 16 to 22, wherein the nitrogen amount derived from the group is 0.01 to 10 atomic% with respect to the carbon amount derived from the -COO- group.   The silicone resin has a carbon amount derived from the —COO— group of 15 to 65 atomic% relative to the silicon amount derived from the silicone resin as measured by ESCA, and the carbon amount derived from the phenyl group is a —COO— group. The nitrogen amount derived from the nitrogen-containing group is from 10 to 200 atomic% with respect to the carbon amount derived from the nitrogen, and the nitrogen amount derived from the nitrogen-containing group is from 0.1 to 5 atomic% with respect to the carbon amount derived from the —COO— group The two-component developer according to any one of 16 to 23. Silicone resins are represented by the following formulas (I) and (II)
[Outside 7]

(Wherein R ^{1 to} R ⁵ each represent a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), and the silicone resin has an ester group and a phenyl group as functional groups. The two-component developer according to any one of claims 16 to 24. Silicone resins are represented by the following formulas (I) and (II)
[Outside 8]

(Wherein R ^{1 to} R ⁵ each represents a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), the silicone resin has an ester group and the following formula as functional groups (VII) or (VIII)
[Outside 9]

[Outside 10]

The two-component developer according to any one of claims 16 to 25, which has a nitrogen-containing group represented by: The silicone resin has a phenyl group and the following formula (VI)
[Outside 11]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. 27. The two-component developer according to any one of claims 16 to 26, which has an ester group derived from a compound represented by the formula: The silicone resin has a nitrogen-containing group and the following formula (VI)
[Outside 12]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. The two-component developer according to any one of claims 16 to 27, which has an ester group derived from a compound represented by   The two-component developer according to any one of claims 16 to 28, wherein the silicone resin has an ester group derived from a copolymer of a methacrylic acid ester and the compound represented by the formula (VI).   30. The two-component developer according to claim 16, wherein the silicone resin has an ester group derived from a copolymer of an acrylate ester and the compound represented by the formula (VI).   31. The two-component developer according to claim 16, wherein the magnetic carrier core particles are coated with 0.10 to 5.0% by weight of a silicone resin.   32. The two-component developer according to claim 16, wherein the magnetic carrier core particles are coated with 0.15 to 2.0% by weight of a silicone resin.   The two-component developer according to any one of claims 16 to 32, wherein the magnetic carrier has an average particle diameter of 20 to 100 µm.   The two-component developer according to any one of claims 16 to 32, wherein the magnetic carrier has an average particle size of 30 to 65 µm.   The two-component developer according to any one of claims 16 to 34, wherein the silicone resin is subjected to a baking treatment at a temperature of 120 to 170 ° C on the magnetic carrier core particles. Forming an electrostatic charge image on the photoreceptor,
A magnetic brush of a two-component developer is formed on the developer carrier that contains the magnetic field generating means,
An image forming method for developing an electrostatic charge image with a magnetic brush formed on a developer carrying member to form a toner image on a photoreceptor,
The two-component developer has a toner and a magnetic carrier, and the magnetic carrier has a magnetic carrier core particle and a silicone resin covering the magnetic carrier core particle;
The silicone resin has (a) a —COO— group and (b) at least a phenyl group or a nitrogen-containing group,
(I) The amount of carbon derived from the —COO— group is 15 to 65 atomic% relative to the amount of silicon constituting the silicone resin, as measured by ESCA, and
(Ii) Whether the carbon amount derived from the phenyl group is 10 to 200 atomic% with respect to the carbon amount derived from the —COO— group when the silicone resin does not have a nitrogen-containing group, as measured by ESCA. Or when the silicone resin has a nitrogen-containing group, the amount of nitrogen derived from the nitrogen-containing group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group. Method.   37. The image forming method according to claim 36, wherein the electrostatic charge image is a digital electrostatic charge image, and the electrostatic charge image is developed with a two-component developer by a reversal development method while applying an AC bias to the developer carrying member.   38. The image forming method according to claim 36 or 37, wherein the toner has a negative frictional charging property with respect to the magnetic carrier.   39. The image forming method according to claim 36, wherein the toner has a triboelectric charge amount of -20 to -100 [mu] c / g with respect to the magnetic carrier.   40. The image forming method according to claim 36, wherein the toner has a triboelectric charge amount of −30 to −60 μc / g with respect to the magnetic carrier.   41. The image forming method according to claim 36, wherein the toner has a weight average particle diameter of 9.0 [mu] m or less, and the magnetic carrier has an average particle diameter of 20 to 100 [mu] m.   41. The image forming method according to claim 36, wherein the toner has a weight average particle diameter of 3.0 to 8.0 [mu] m or less, and the magnetic carrier has an average particle diameter of 30 to 65 [mu] m.   The silicone resin has a carbon amount derived from —COO— groups of 15 to 65 atomic% relative to the silicon amount derived from silicone resin as measured by ESCA, and the nitrogen amount derived from nitrogen-containing groups is —COO—. 43. The image forming method according to any one of claims 36 to 42, wherein the content is 0.1 to 5 atomic% with respect to the amount of carbon derived from the group. Silicone resin, -COO- group has three functional groups of the phenyl group and a nitrogen-containing group, a 0.1 to 300 atomic% based on the amount of carbon derived from the full Eniru group, and a nitrogen-containing 44. The image forming method according to claim 36, wherein the amount of nitrogen derived from the group is 0.01 to 10 atomic% with respect to the amount of carbon derived from the —COO— group.   The silicone resin has a carbon amount derived from the —COO— group of 15 to 65 atomic% relative to the silicon amount derived from the silicone resin as measured by ESCA, and the carbon amount derived from the phenyl group is a —COO— group. The nitrogen amount derived from the nitrogen-containing group is from 10 to 200 atomic% with respect to the carbon amount derived from the nitrogen, and the nitrogen amount derived from the nitrogen-containing group is from 0.1 to 5 atomic% with respect to the carbon amount derived from the —COO— group. The image forming method of any one of 36 to 44. Silicone resins are represented by the following formulas (I) and (II)
[Outside 13]

(Wherein R ^{1 to} R ⁵ each represent a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), and the silicone resin has an ester group and a phenyl group as functional groups. The image forming method according to claim 36, comprising: Silicone resins are represented by the following formulas (I) and (II)
[Outside 14]

(Wherein R ^{1 to} R ⁵ each represents a hydrocarbon group selected from a methyl group, an ethyl group or a phenyl group), the silicone resin has an ester group and the following formula as functional groups (VII) or (VIII)
[Outside 15]

[Outside 16]

47. The image forming method according to claim 36, which has a nitrogen-containing group represented by The silicone resin has a phenyl group and the following formula (VI)
[Outside 17]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. 48. The image forming method according to claim 36, which has an ester group derived from a compound represented by The silicone resin has a nitrogen-containing group and the following formula (VI)
[Outside 18]

(Wherein R ⁸ , R ⁹ and R ¹⁰ are the same or different groups and represent CH 3, CH 2 CH 3, OCH 3 or OCH 2 CH 3, provided that at least one of R ⁸ , R ⁹ and R ¹⁰ is OCH 3 or OCH 2 CH 3. 49. The image forming method according to claim 36, which has an ester group derived from a compound represented by formula (1):   50. The image forming method according to claim 36, wherein the silicone resin has an ester group derived from a copolymer of a methacrylic acid ester and the compound represented by formula (VI).   51. The image forming method according to claim 36, wherein the silicone resin has an ester group derived from a copolymer of an acrylate ester and the compound represented by formula (VI).   52. The image forming method according to claim 36, wherein the magnetic carrier core particles are coated with 0.10 to 5.0% by weight of a silicone resin.   52. The image forming method according to claim 36, wherein the magnetic carrier core particles are coated with 0.15 to 2.0% by weight of a silicone resin.   54. The image forming method according to claim 36, wherein the magnetic carrier has an average particle diameter of 20 to 100 [mu] m.   54. The image forming method according to claim 36, wherein the magnetic carrier has an average particle diameter of 30 to 65 [mu] m.   56. The image forming method according to claim 36, wherein the silicone resin is subjected to a baking treatment at a temperature of 120 to 170 [deg.] C. with respect to the magnetic carrier core particles.

Images