JP2004053643A - Electrophotographic developer, carrier for electrophotographic developer, and method for manufacturing the carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for an electrophotographic developer having excellent magnetic characteristics, electrification property, and developing property. <P>SOLUTION: The carrier for an electrophotographic developer is prepared by using a material comprising a metal oxide having the composition of Gd<SB>x</SB>Fe<SB>3-x</SB>O<SB>4</SB>, wherein x satisfies 0.25≤x≤1.25. <P>COPYRIGHT: (C)2004,JPO

Description

前記式中、Ｒ^１は水素原子、ハロゲン原子、ヒドロキシ基、メトキシ基、炭素数１〜４の低級アルキル基、またはアリール基（フェニル基、トリル基など）を示し、Ｒ^２は炭素数１〜４のアルキレン基、またはアリーレン基（フェニレン基など）を示す。
【００３２】
また本発明では、ストレートシリコーン樹脂を用いることができる。このようなものとしては、ＫＲ２７１、ＫＲ２７２、ＫＲ２８２、ＫＲ２５２、ＫＲ２５５、ＫＲ１５２（以上、信越化学工業社製）、ＳＲ２４００、ＳＲ２４０６（以上、東レダウコーニングシリコーン社製）などが挙げられる。
【００３３】
他には、変性シリコーン樹脂を用いることができる。このようなものとしては、エポキシ変性シリコーン、アクリル変性シリコーン、フェノール変性シリコーン、ウレタン変性シリコーン、ポリエステル変性シリコーン、アルキッド変性シリコーンなどが挙げられる。
これらには、変性シリコーン：ＫＲ−５２０８、ポリエステル変性物：ＫＲ−５２０３、アルキッド変性物：ＫＲ−２０６、ウレタン変性物：ＫＲ−３０５（以上、信越化学工業社製）、エポキシ変性物：ＳＲ２１１５、アルキッド変性物：ＳＲ２１１０（東レダウコーニングシリコーン社製）などが挙げられる。
【００３４】
また、本発明では前記シリコーン樹脂に、アミノシランカップリング剤を適量（０．００１〜３０重量％）含有させることができる。例として、以下のようなものが挙げられる。
【表１】

【００３５】
更に、本発明では、キャリア粒子表面を被覆する樹脂として、以下に示すものを単独または上記シリコーン樹脂と混合して使用することも可能である。
ポリスチレン、クロロポリスチレン、ポリ−α−メチルスチレン、スチレン−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ブタジエン共重合体、スチレン−塩化ビニル共重合体、スチレン−酢酸ビニル共重合体、スチレン−マレイン酸共重合体、スチレン−アクリル酸エステル共重合体（スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−アクリル酸フェニル共重合体等）スチレン−メタクリル酸エステル共重合体（スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−メタクリル酸フェニル共重合体等）スチレン−α−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル−アクリル酸エステル共重合体などのスチレン系樹脂、エポキシ樹脂、ポリエステル樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、アイオノマー樹脂、ポリウレタン樹脂、ケトン樹脂、エチレン−エチルアクリレート共重合体、キシレン樹脂、ポリアミド樹脂、フェノール樹脂、ポリカーボネート樹脂、メラミン樹脂等。
【００３６】
また、本発明では樹脂被覆層の中に、抵抗調整や耐久性向上のための添加剤を分散させても良い。添加剤としてはフラーレンまたはカーボンナノチューブ、カーボン等が上げられる。
フラーレンはＣ_６０、Ｃ_７０、Ｃ_８２、Ｃ_８４さらに高分子量のフラーレンなどを使用できる。
【００３７】
フラーレンまたはカーボンナノチューブの合成法としては、希ガス中でグラファイト棒を直接通電加熱する抵抗加熱法、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法等がある。
【００３８】
フラーレン、カーボンナノチューブは、内部空間にＬａ、Ｙ、Ｓｃなどの金属等を内包したものも使用できる。金属内包フラーレンの合成には、金属酸化物（Ｌａ_２Ｏ_３など）を含む炭素棒を用いてアーク放電を起させて合成したり、金属酸化物を含む炭素チップをるつぼ状陽極に投入してアーク放電を起させて合成したりする方法がある。
【００３９】
フラーレンの粒径は０．０１〜０．２μｍであり、好ましくは０．０１〜０．１μｍである。フラーレンの粒径が０．０１μｍ未満の場合には凝集等が生じやすく適しておらず、０．２μｍより大きい場合には分散状態が低下して適していない。
【００４０】
カーボンナノチューブの形状は、直径が０．０１〜０．１μｍφで、長さが０．０５〜０．５μｍであり、好ましくは直径が０．０１〜０．０５μｍφで、長さが０．０５〜０．１μｍである。カーボンナノチューブの直径が０．０１μｍφ、長さが０．０５μｍより小さい場合には凝集が生じやすく適しておらず、カーボンナノチューブの直径が０．１μｍφ、長さが０．５μｍより大きくなると分散の均一性が低下して適していない。
【００４１】
カーボンとしては、カーボンブラック等がある。粒径としては、０．０１〜０．２μｍである。これより小さいと粉塵の問題があり、この範囲より大きいと分散が悪くなり、均一な膜形成が難しくなる。
【００４２】
これらのフラーレン、カーボンナノチューブ、カーボン等は、コーティングに使用する溶媒、あるいは被覆用樹脂溶液に投入して、ボールミル、ビーズミルなどメディアを使用した分散機、あるいは高速回転する羽根を備えた攪拌機を使用することによって均一に分散させ、この溶液を磁性を示すキャリア粒子表面にスプレー塗布などによりコートする。
【００４３】
キャリア粒子表面に樹脂被覆層を形成する方法としては、スプレードライ法、浸漬法、あるいはパウダーコーティング法など公知の方法が使用できる。特に流動床型コーティング装置を用いる方法は、キャリアの流動床を形成し、この流動床中にスプレーする方法で、均一な樹脂被覆層が形成できるので適している。
【００４４】
樹脂被覆層の樹脂に対するフラーレン、カーボンナノチューブ、カーボンの含有量は、樹脂１００重量部に対して０．０１重量部〜１０重量部であることが必要である。フラーレン、カーボンナノチューブ、カーボンの含有量が０．０１重量部より小さい場合には、耐久性の向上が認められず、フラーレン、カーボンナノチューブ、カーボンの含有量が１０重量部より大きい場合には樹脂層が脆くなって、耐久性が劣化する。
【００４５】
キャリア粒子表面上に形成される樹脂被覆層やフラーレン、カーボンナノチューブ、カーボンを含む樹脂被覆層の厚みは、通常０．０２〜１μｍ、好ましくは０．０３〜０．８μｍである。この厚みが０．０２μｍ未満の場合には耐久性の向上が十分でなく、また１μｍを越える場合には膜はがれ現象が生じ、帯電特性の安定性が低下する。
【００４６】
本発明のキャリア（非コートキャリア、コートキャリア）の平均粒径は、重量平均粒径Ｄｗで２０μｍ〜１００μｍの範囲であり、好ましくは３０μｍ〜７０μｍの範囲である。重量平均粒径Ｄｗが１００μｍを越えると、キャリア付着が起りにくいが、ドット再現性が悪くなる。重量平均粒径Ｄｗが２０μｍ未満であるとキャリア付着が多くなると共に、トナーとの撹拌効率が悪くなりトナーの均一な帯電量が得られにくくなる。
【００４７】
キャリア付着は、既述のとおり、静電潜像の画像部又は地肌部にキャリアが付着する現象を示す。それぞれの電界が強いほどキャリアは付着し易い。画像部はトナーが現像されることにより電界が弱められる為、地肌部に比べ、キャリア付着は起こりにくい。キャリア付着は、感光体ドラムや定着ローラーの傷の原因となる等の不都合を生じるので好ましくない。
【００４８】
本発明ではこのキャリア付着の対策を考え、磁気特性の改良を材料面から行なったが、さらに１５μｍより小さい粒径を有するキャリアの含有割合は３重量％以下、好ましくは１重量％以下であるように規定した。小粒径キャリアの場合、キャリア付着しているキャリアの大部分は、１５μｍ未満の微細粒子である。本発明者らは、重量平均粒径Ｄｗが２５μｍ〜４５μｍの小粒径キャリアにおいて、１５μｍより小さい粒子の重量比率を変化させてキャリア付着を評価したところ、１５μｍ以下の粒径を有する粒子が３重量％以下ならば大きな問題はないが、更に１重量％とすると、キャリア付着は更に改善されることが判明した。
【００４９】
本発明のキャリアは、本発明の磁性材料を粉砕し、その粉砕物粒子を所定の粒径が得られるように分級し、この分級により得られた磁性粒子の表面に必要に応じて樹脂被覆層を形成することに得ることができる。この分級には、風力分級やふるい分級（ふるい分け）等が包含される。キャリア粒子の製造には、振動ふるいが好ましく用いられているが、従来一般的に用いられている振動ふるいでは、小粒径の粒子を分級しようとすると、そのふるい（金網）の小さな網目がすぐに詰まってしまうという不都合を生じるため、その分級のための作業性は非常に悪いものであった。
【００５０】
本発明者らは、小粒径粒子を効率よく、シャープにカットし得る方法を開発すべく種々検討したところ、ふるい機を用いて粒子を分級する際に、その金網に超音波振動を与えることにより、１５μｍ未満の小径粒子を効率よく、シャープにカットし得ることを見出した。金網を振動させる超音波振動は、高周波電流をコンバータに供給して超音波振動に変換することにより得ることができる。この場合のコンバータは、ＰＺＴ振動子からなる。超音波振動により金網を振動させるためには、コンバータにより発生される超音波振動を、金網に固定した共振部材に伝達させる。超音波振動が伝達された共振部材は、その超音波振動により共振し、そして、その共振部材に固定されている金網を振動させる。
金網を振動させる周波数は、２０〜５０ｋＨｚ、好ましくは３０〜４０ｋＨｚである。共振部材の形状は、金網を振動させるのに適した形状であればよく、通常はリング状である。
金網を振動させる振動方向は、垂直方向であるのが好ましい。
【００５１】
図３に超音波発振器付振動ふるい機の説明構造図を示す。
図３において、１は振動ふるい器、２は円筒容器、３はスプリング、４はベース（支持台）、５は金網、６は共振リング、７は高周波電流ケーブル、８はコンバータ、９はリング状フレームを示す。図１に示した超音波発振器付振動ふるい器（円形ふるい機）を作動させるには、ケーブル７を介して高周波電流をコンバータ８に供給する。コンバータ８に供給された高周波電流は超音波振動に変換される。コンバータ８で発生した超音波振動は、そのコンバータ８が固定されている共振リング８及びそれに連設するリング状フレーム９を垂直方向に振動させる。この共振リング６の振動により、共振リング６とフレーム９に固定されている金網５が垂直方向に振動する。
超音波発振器付きの振動ふるい機は販売されており、例えば、晃栄産業（株）より製品名「ウルトラソニック」として入手可能である。
【００５２】
本発明では、分級した磁性粒子（キャリア粒子）の表面に樹脂被覆層を形成するが、磁性粒子の粉砕物粒子の表面に樹脂被覆層を形成した後、この樹脂被覆キャリア粒子を分級することによっても製造することができる。この場合の樹脂被覆キャリア粒子の分級は、前記した超音波発振器付きの振動ふるい機を用いて行うのが好ましい。
【００５３】
本発明では、キャリアの抵抗の調整は、キャリア粒子表面上に形成するフラーレン、カーボンナノチューブ、カーボンを少なくとも１種を含む樹脂被覆層により行なう。キャリア抵抗が高すぎると、エッジ効果の副作用による白抜け現象等の異常画像が生じ、キャリア抵抗が低すぎると、ベタ画像の均一性は良くなるがキャリア付着が生じやすくなり、キャリア抵抗を実際の現像条件と合わせて適正化する必要がある。このキャリア抵抗の適正化はフラーレン、カーボンナノチューブ、カーボンの含有量と膜厚でコントロールする。
【００５４】
本発明の現像剤は、前記キャリアとトナーとからなる。
本発明に使用されるトナーは、熱可塑性樹脂を主成分とするバインダー樹脂中に、着色剤、電荷制御剤、離型剤等を含有させたものであり、従来公知の各種のトナーを用いることができる。このトナーは、粉砕法、重合法、造粒法などの各種のトナー製法によって作成された不定形または球形のトナーであり、磁性トナー及び非磁性トナーのいずれも使用可能である。
【００５５】
トナーに用いられる樹脂としては、エポキシ樹脂、ポリエステル樹脂、ポリアミド樹脂、スチレンアクリル樹脂、スチレンメタクリレート樹脂、ポリウレタン樹脂、ビニル樹脂、ポリオレフィン樹脂、スチレンブタジエン樹脂、フェノール樹脂、ブチラール樹脂、テルペン樹脂、ポリオール樹脂等がある。
【００５６】
ビニル樹脂としては、ポリスチレン、ポリ−ｐ−クロロスチレン、ポリビニルトルエンなどのスチレン及びその置換体の単重合体：スチレン−ｐ−クロロスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−ビニルナフタリン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−アクリル酸オクチル共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−メタクリル酸ブチル共重合体、スチレン−α−クロロメタクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルエチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソプレン共重合体、スチレン−アクリロニトリル−インデン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体などのスチレン系共重合体：ポリメチルメタクリレート、ポリブチルメタクリレート、ポリ塩化ビニル、ポリ酢酸ビニル等がある。
【００５７】
ポリエステル樹脂としては以下のＡ群に示したような２価のアルコールと、Ｂ群に示したような二塩基酸塩からなるものであり、さらにＣ群に示したような３価以上のアルコールあるいはカルボン酸を第三成分として加えてもよい。
【００５８】
Ａ群：エチレングリコール、トリエチレングリコール、１，２−プロピレングリコール、１，３−プロピレングリコール、１，４ブタンジオール、ネオペンチルグリコール、１，４ブテンジオール、１，４−ビス（ヒドロキシメチル）シクロヘキサン、ビスフェノールＡ、水素添加ビスフェノールＡ、ポリオキシエチレン化ビスフェノールＡ、ポリオキシプロピレン（２，２）−２，２’−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシプロピレン（３，３）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシエチレン（２，０）−２，２−ビス（４−ヒドロキシフェニル）プロパン、ポリオキシプロピレン（２，０）−２，２’−ビス（４−ヒドロキシフェニル）プロパン等。
【００５９】
Ｂ群：マレイン酸、フマール酸、メサコニン酸、シトラコン酸、イタコン酸、グルタコン酸、フタール酸、イソフタール酸、テレフタール酸、シクロヘキサンジカルボン酸、コハク酸、アジピン酸、セバチン酸、マロン酸、リノレイン酸、またはこれらの酸無水物または低級アルコールのエステル等。
【００６０】
Ｃ群：グリセリン、トリメチロールプロパン、ペンタエリスリトール等の３価以上のアルコール、トリメリト酸、ピロメリト酸等の３価以上のカルボン酸等。
【００６１】
ポリオール樹脂としては、エポキシ樹脂と、２価フェノールのアルキレンオキサイド付加物もしくはそのグリシジルエーテルとエポキシ基と反応する活性水素を分子中に１個有する化合物と、エポキシ樹脂と反応する活性水素を分子中に２個以上有する化合物を反応してなるものなどがある。
【００６２】
トナーに用いる顔料としては以下のものが用いられる。これは１種又は２種以上を使用することができる。
【００６３】
黒色顔料としては、カーボンブラック、オイルファーネスブラック、チャンネルブラック、ランプブラック、アセチレンブラック、アニリンブラック等のアジン系色素、金属塩アゾ色素、金属酸化物、複合金属酸化物が挙げられる。
【００６４】
黄色顔料としては、カドミウムイエロー、ミネラルファストイエロー、ニッケルチタンイエロー、ネーブルスイエロー、ナフトールイエローＳ、ハンザイエローＧ、ハンザイエロー１０Ｇ、ベンジジンイエローＧＲ、キノリンイエローレーキ、パーマネントイエローＮＣＧ、タートラジンレーキが挙げられる。
【００６５】
橙色顔料としては、モリブデンオレンジ、パーマネントオレンジＧＴＲ、ピラゾロンオレンジ、バルカンオレンジ、インダンスレンブリリアントオレンジＲＫ、ベンジジンオレンジＧ、インダンスレンブリリアントオレンジＧＫが挙げられる。
【００６６】
赤色顔料としては、ベンガラ、カドミウムレッド、パーマネントレッド４Ｒ、リソールレッド、ピラゾロンレッド、ウォッチングレッドカルシウム塩、レーキレッドＤ、ブリリアントカーミン６Ｂ、エオシンレーキ、ローダミンレーキＢ、アリザリンレーキ、ブリリアントカーミン３Ｂが挙げられる。
【００６７】
紫色顔料としては、ファストバイオレットＢ、メチルバイオレットレーキが挙げられる。
【００６８】
青色顔料としては、コバルトブルー、アルカリブルー、ビクトリアブルーレーキ、フタロシアニンブルー、無金属フタロシアニンブルー、フタロシアニンブルー部分塩素化物、ファーストスカイブルー、インダンスレンブルーＢＣが挙げられる。
【００６９】
緑色顔料としては、クロムグリーン、酸化クロム、ピグメントグリーンＢ、マラカイトグリーンレーキ等がある。
【００７０】
特にカラートナーにおいては、良好な顔料の均一分散が必須となり、顔料を直接大量の樹脂中に投入するのではなく、一度高濃度に顔料を分散させたマスターバッチを作製し、それを希釈する形で投入する方式が用いられている。この場合、一般的には、分散性を助けるために溶剤が使用されていたが、環境等の問題があり、本発明では水を使用して分散させた。水を使用する場合、マスターバッチ中の残水分が問題にならないように、温度コントロールが重要になる。
【００７１】
トナーには電荷制御剤をトナー粒子内部に配合（内添）してもよいし、トナー粒子と混合（外添）して用いても良い。
電荷制御剤によって、現像システムに応じた最適の電荷量コントロールが可能となり、特に本発明では、粒度分布と電荷量とのバランスを更に安定したものとすることが可能である。
トナーを正電荷性に制御するものとして、ニグロシンおよび四級アンモニウム塩、イミダゾール金属錯体や塩類を、単独あるいは２種類以上組み合わせて用いることができる。また、トナーを負電荷性に制御するものとしてサリチル酸金属錯体や塩類、有機ホウ素塩類、カリックスアレン系化合物等が用いられる。
【００７２】
また、トナーには定着時のオフセット防止のために離型剤を内添することも可能である。離型剤としては、キャンデリラワックス、カルナウバワックス、ライスワックスなどの天然ワックス、モンタンワックス、パラフィンワックス、サゾールワックス、低分子量ポリエチレン、低分子量ポリプロピレン、アルキルリン酸エステル等がある。これら離型剤の融点は６５〜９０℃であることが好ましい。この範囲より低い場合には、トナーの保存時のブロッキングが発生しやすくなり、この範囲より高い場合には定着ローラー温度が低い領域でオフセットが発生しやすくなる場合がある。
【００７３】
離型剤等の分散性を向上させるなどの目的の為に、添加剤を加えても良い。添加剤としては、スチレンアクリル樹脂、ポリエチレン樹脂、ポリスチレン樹脂、エポキシ樹脂、ポリエステル樹脂、ポリアミド樹脂、スチレンメタクリレート樹脂、ポリウレタン樹脂、ビニル樹脂、ポリオレフィン樹脂、スチレンブタジエン樹脂、フェノール樹脂、ブチラール樹脂、テルペン樹脂、ポリオール樹脂等があり、それぞれの樹脂を２種以上混合した物でも良い。
【００７４】
トナーの流動性等を改善するために、トナー表面に無機微粉体により表面処理を行なっても良い。この無機微粉体としてはＳｉ、Ｔｉ、Ａｌ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｉｎ、Ｇａ、Ｎｉ、Ｍｎ、Ｗ、Ｆｅ、Ｃｏ、Ｚｎ、Ｃｒ、Ｍｏ、Ｃｕ、Ａｇ、Ｖ、Ｚｒ等の酸化物や複合酸化物が挙げられる。これらのうち二酸化珪素（シリカ）、二酸化チタン（チタニア）、アルミナの微粒子が好適に用いられる。さらに、疎水化処理剤等により表面改質処理することが有効である。
【００７５】
疎水化処理剤の代表例としては以下のものが挙げられる。ジメチルジクロルシラン、トリメチルクロルシラン、メチルトリクロルシラン、アリルジメチルジクロルシラン、アリルフェニルジクロルシラン、ベンジルジメチルクロルシラン、ブロムメチルジメチルクロルシラン、α−クロルエチルトリクロルシラン、ｐ−クロルエチルトリクロルシラン、クロルメチルジメチルクロルシラン、クロルメチルトリクロルシラン、ヘキサフェニルジシラザン、ヘキサトリルジシラザン等。
【００７６】
無機微粉体はトナーに対して０．１〜２重量％使用されるのが好ましい。０．１重量％未満では、トナー凝集を改善する効果が乏しくなり、２重量％を超える場合は、細線間のトナー飛び散り、機内の汚染、感光体の傷や摩耗等の問題が生じやすい傾向がある。
【００７７】
トナーを作製する方法としては、粉砕法、重合法（懸濁重合、乳化重合、分散重合、乳化凝集、乳化会合等）等があるが、これらの作製法に限るものではない。
【００７８】
粉砕法にてトナーを作製する方法の一例としては、まず、前述した樹脂、着色剤としての顔料または染料、電荷制御剤、離型剤、その他の添加剤等をヘンシェルミキサーの如き混合機により充分に混合した後、バッチ式の２本ロール、バンバリーミキサーや連続式の２軸押出し機、例えば神戸製鋼所社製ＫＴＫ型２軸押出し機、東芝機械社製ＴＥＭ型２軸押出し機、ＫＣＫ社製２軸押出し機、池貝鉄工社製ＰＣＭ型２軸押出し機、栗本鉄工所社製ＫＥＸ型２軸押出し機や、連続式の１軸混練機、例えばブッス社製コ・ニーダ等の熱混練機を用いて構成材料をよく混練し、冷却後、ハンマーミル等を用いて粗粉砕し、更にジェット気流を用いた微粉砕機や機械式粉砕機により微粉砕し、旋回気流を用いた分級機やコアンダ効果を用いた分級機により所定の粒度に分級する。その後、混合機により無機粒子などからなる添加剤を粒子表面に付着もしくは固着させ、２５０メッシュ以上の篩を通過させ、粗大粒子、凝集粒子を除去しトナーを得る。
【００７９】
本トナーの重量平均粒径は４〜１０μｍであり、さらに好ましくは５〜８μｍである。重量平均粒径４μｍ未満では長期間の使用でのトナー飛散による機内の汚れ、低湿環境下での画像濃度低下、感光体クリーニング不良等という問題が生じやすい。また重量平均粒径が１０μｍを超える場合では１００μｍ以下の微小スポットの解像度が充分でなく非画像部への飛び散りも多く画像品位が劣る傾向となる。
【００８０】
また、重合法によるトナー製造の一例としては、モノマーに着色剤及び電荷制御剤等を添加したモノマー組成物を水系の媒体中で懸濁し重合させることでトナー粒子を得る。造粒法は特に限定されない。
例えば本発明のトナーは、有機溶媒中に少なくとも、イソシアネート基を含有するポリエステル系プレポリマーが溶解し、顔料系着色剤が分散し、離型剤が溶解ないし分散している油性分散液を水系媒体中に無機微粒子及び／又はポリマー微粒子の存在下で分散させるとともに、この分散液中で該プレポリマーをポリアミン及び／又は活性水素含有基を有するモノアミンと反応させてウレア基を有するウレア変性ポリエステル系樹脂を形成させ、このウレア変性ポリエステル系樹脂を含む分散液からそれに含まれる液状媒体を除去することにより得られる。
【００８１】
ウレア変性ポリエステル系樹脂において、そのＴｇは４０〜６５℃、好ましくは４５〜６０℃である。その数平均分子量Ｍｎは２５００〜５００００、好ましくは２５００〜３００００である。その重量平均分子量Ｍｗは１万〜５０万、好ましくは３万〜１０万である。
【００８２】
このトナーは、該プレポリマーと該アミンとの反応によって高分子量化されたウレア結合を有するウレア変性ポリエステル系樹脂をバインダー樹脂として含む。そして、そのバインダー樹脂中には着色剤が高分散している。
【００８３】
本発明の現像剤として使用する場合は、前述した磁性キャリアと所定の混合比率で混合することによって二成分現像剤とする。
また、磁性トナーとする場合には、トナー粒子の中に磁性体の微粒子を内添すれば良い。磁性体としては、フェライト、マグネタイト、鉄、ニッケル、コバルト、それらの合金などの強磁性体等が考えられる。磁性体の平均粒径は０．１〜１μｍが好ましい。磁性体の含有量はトナー１００重量部に対して、１０から７０重量部であることが好ましい。
【００８４】
また、本発明の現像剤には、実質的な悪影響を与えない範囲内で更に他の添加剤、例えばテフロン（Ｒ）粉末、ステアリン酸亜鉛粉末、ポリフッ化ビニリデン粉末の如き滑剤粉末；あるいは酸化セリウム粉末、炭化珪素粉末、チタン酸ストロンチウム粉末などの研磨剤；あるいは例えばカーボンブラック粉末、酸化亜鉛粉末、酸化スズ粉末等の導電性付与剤を現像性向上剤として少量用いることもできる。
【００８５】
本発明の現像方法は、その現像剤として前記した本発明の現像剤を用いる方法である。この場合、外部から印加する現像バイアスとして、直流電圧に交流電圧を重畳させた電圧を印加すると、画像濃度が高く、地汚れの少ない高画質を得ることが出来る。特に、ドット再現性、およびハイライトの再現性が良好となる。上記の現像バイアスを印加する場合、直流バイアスのみを印加する時に比べて、実質的な現像ポテンシャル、および地肌ポテンシャルが大きくなる。その為、従来はキャリア付着が起り易かったが、本発明のキャリアによって、両立が可能となった。
【００８６】
本発明の画像形成装置は、現像容器を搭載した画像形成装置において、その現像容器として、本発明の現像剤が収納された現像容器を用いたものである。この場合の画像形成装置としては、従来公知の各種のものを用いることができる。
【００８７】
【実施例】
以下、実施例をあげて本発明をさらに具体的に説明するが、これらの実施例は本発明をなんら限定するものではない。なお、以下の配合における部数は全て重量部である。
【００８８】
（実施例１〜５、および比較例１、２）
（トナー製造）
樹脂　　　　ポリエステル樹脂　　　　　１００部
顔料　　　　カーボンブラック　　　　　　１０部
帯電制御剤　サルチル酸亜鉛塩　　　　　　　２部
離型剤　　　カルナウバワックス　　　　　　５部
添加剤　　　スチレンアクリル樹脂　　　　　３部
上記原材料をミキサーで十分に混合した後、２軸押出し機により混練物温度１００℃混練機回転数１２０ｒｐｍで溶融混練した。混練物を圧延冷却後カッターミルで粗粉砕し、ジェット気流を用いた微粉砕機で粉砕後、旋回式風力分級装置を用いて、平均粒径が６．５μｍの粒度分布に分級した。さらに、母体着色粒子１００部に対して、シリカ微分末１部をスーパーミキサーにて混合して、トナーを得た。
【００８９】
（キャリア製造）
磁性材　　　Ｇｄ_ｘＦｅ_{３ − ｘ}Ｏ_４
上式において、Ｇｄ組成ｘを変化して、磁性材を作製した。
Ｇｄ組成ｘは、Ｇｄ_ｘＦｅ_{３ − ｘ}Ｏ_４において、以下のように変化した。
【表２】

【００９０】
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【００９１】
その後、それぞれの磁性粒子の表面に以下の条件でコート層（樹脂被覆層）を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５３μｍの樹脂コート層を形成し、キャリアを得た。それぞれの実施例及び比較例のキャリアの平均粒径と、１５μｍ未満の粒径を有するキャリアの含有割合を以下に示す。
【００９２】
【表３】

【００９３】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
また、キャリアの磁気特性を振動試料型磁力計にて測定し、飽和磁化、保磁力、キュリー温度を評価した。その結果を図１に示す。
【００９４】
（実施例６、７及び比較例３、４）
（トナー製造）
実施例１と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．２５（Ｆｅ_{１ − ｙ}Ａｌ_ｙ）_２．７５Ｏ_４
上式において、Ａｌ組成ｙを変化して、磁性材を作製した。
Ａｌ組成ｙは、Ｇｄ_０．２５（Ｆｅ_{１ − ｙ}Ａｌ_ｙ）_２．７５Ｏ_４において、以下のように変化した。
【表４】

【００９５】
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物、Ａｌ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅＡｌ酸化物の粒子を得た。
【００９６】
その後、それぞれの磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５３μｍの樹脂コート層を形成し、キャリアを得た。それぞれの実施例のキャリア平均粒径と、１５μｍ未満粒径を有するキャリアの含有割合を以下に示す。
【表５】

【００９７】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
また、キャリアの磁気特性を振動試料型磁力計にて測定し、飽和磁化、保磁力、キュリー温度を評価した。その結果を図２に示す。
【００９８】
（実施例８）
（トナー製造）
樹脂　　　　ポリエステル樹脂　　　　　１００部
顔料　　　　カーボンブラック　　　　　　１０部
帯電制御剤　サルチル酸亜鉛塩　　　　　　　２部
離型剤　　　カルナウバワックス　　　　　　５部
添加剤　　　スチレンアクリル樹脂　　　　　３部
上記原材料をミキサーで十分に混合した後、２軸押出し機により混練物温度１００℃混練機回転数１２０ｒｐｍで溶融混練した。混練物を圧延冷却後カッターミルで粗粉砕し、ジェット気流を用いた微粉砕機で粉砕後、旋回式風力分級装置を用いて、平均粒径が６．５μｍの粒度分布に分級した。さらに、母体着色粒子１００部に対して、シリカ微分末１部をスーパーミキサーにて混合して、トナーを得た。
【００９９】
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１００】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
フラーレンＣ_６０　　　　　　１部
シリコーン樹脂中に、ボールミルを用いてフラーレンＣ_６０を分散させ、この分散液を希釈して固形分５ｗｔ％の分散液を得た。フラーレンＣ_６０は、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法で作製し、平均粒径が０．０２５μｍであった。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．４μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１０１】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１０２】
（実施例９）
（トナー製造）
実施例８と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１０３】
その後、磁性粒子の表面に以下の条件でコート層を設けた。

シリコーン樹脂中に、ボールミルを用いてフラーレンＣ_６０にＣ_７０が３０％混入しているものを分散させ、この分散液を希釈して固形分５ｗｔ％の分散液を得た。フラーレンＣ_６０にＣ_７０が３０％混入しているものは、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法で作製し、平均粒径が０．０３５μｍであった。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５２μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．４μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．８重量％であった。
【０１０４】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１０５】
（実施例１０）
（トナー製造）
実施例１２と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１０６】
その後、磁性粒子の表面に以下の条件でコート層を設けた。

シリコーン樹脂中に、ボールミルを用いてカーボンナノチューブを分散させ、この分散液を希釈して固形分５ｗｔ％の分散液を得た。カーボンナノチューブは、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法で作製し、カーボンナノチューブの形状は、直径が０．０１〜０．１μｍφで、長さが０．０５〜０．５μｍであった。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５２μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．７μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．８重量％であった。
【０１０７】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１０８】
（実施例１１）
（トナー製造）
実施例１と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｃｏ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１０９】
その後、磁性粒子の表面に以下の条件でコート層を設けた。

シリコーン樹脂中に、ボールミルを用いてＣ_６０とカーボンを分散させ、この分散液を希釈して固形分５ｗｔ％の分散液を得た。Ｃ_６０は、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法で作製し、平均粒径が０．０４μｍであった。カーボンの平均粒径は０．０４μｍであった。流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．６μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１１０】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１１１】
（実施例１２）
（トナー製造）
実施例１と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１１２】
その後、磁性粒子の表面に以下の条件でコート層を設けた。

シリコーン樹脂中に、ボールミルを用いてフラーレンＣ_６０を分散させ、この分散液を希釈して固形分５ｗｔ％の分散液を得た。フラーレンＣ_６０は、希ガス中で２本のグラファイト棒の間にアーク放電を起させて合成するアーク放電法で作製し、平均粒径が０．０２５μｍであった。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５８μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．９μｍで１５μｍより小さい粒径を有する粒子の含有割合は２．８重量％であった。
【０１１３】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１１４】
（実施例１３）
（トナー製造）
実施例１と同じ。

Ｇｄ_０．５Ｆｅ_２．５Ｏ_４金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。この金属酸化物粒子にＭｎＭｇＳｒフェライト粒子を１：１の割合で投入し、混合機で混合した。
【０１１５】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５３μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．４μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１１６】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１１７】
（実施例１４）
（トナー製造）
実施例１と同じ。

Ｇｄ_０．５Ｆｅ_２．５Ｏ_４金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。この金属酸化物粒子にＭｎフェライト粒子を１：１の割合で投入し、混合機で混合した。
【０１１８】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．５μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１１９】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１２０】
（実施例１５）
（トナー製造）
実施例１と同じ。

Ｇｄ_０．５Ｆｅ_２．５Ｏ_４金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＣｏＦｅ酸化物の粒子を得た。この金属酸化物粒子にマグネタイト粒子を１：１の割合で投入し、混合機で混合した。
【０１２１】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．４μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１２２】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１２３】
（実施例１６）
（トナー製造）
実施例１と同じ。

Ｇｄ_０．５Ｆｅ_２．５Ｏ_４金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。この金属酸化物粒子にヘマタイト粒子を１：１の割合で投入し、混合機で混合した。
【０１２４】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５３μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．６μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．６重量％であった。
【０１２５】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１２６】
（実施例１７）
（トナー製造）
実施例１と同じ。
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
　上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１２７】
その後、磁性粒子の表面に以下の条件でコート層を設けた。

シリコーン樹脂１００部中に、５部のアミノシランカップリング剤Ｈ_２Ｎ（ＣＨ_２）_３Ｓｉ（ＯＣ_２Ｈ_５）_３を添加し、ボールミルを使用して分散し、この分散液を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２３０℃で２時間加熱して、膜厚０．５１μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．１μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．６重量％であった。
【０１２８】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１２９】
（実施例１８）
（トナー製造）
樹脂　　　　ポリエステル樹脂　　　　　　　　　　　　　　　１００部
顔料　　　　銅フタロシアニンブルー顔料（Ｃ．Ｉ．ヒ゜ク゛メントフ゛ルー１５：３）　５部
帯電制御剤　サルチル酸亜鉛塩　　　　　　　　　　　　　　　　　２部
離型剤　　　カルナウバワックス　　　　　　　　　　　　　　　　５部
上記原材料をミキサーで十分に混合した後、２軸押出し機により混練物温度１００℃、混練機回転数１２０ｒｐｍで溶融混練した。混練物を圧延冷却後カッターミルで粗粉砕し、ジェット気流を用いた微粉砕機で粉砕後、旋回式風力分級装置を用いて、平均粒径が６．５μｍの粒度分布に分級した。
【０１３０】
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１３１】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート膜を形成し、キャリアを得た。キャリア平均粒径は３５．５μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．７重量％であった。
【０１３２】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１３３】
（実施例１９）
（トナー製造）
樹脂　　　　　　ポリエステル樹脂　　　　　　　　　　　　　１００部
マスターバッチ　銅フタロシアニンブルー顔料とポリエステル樹脂（１：１）からなる混練物（水を用いて混練）　１０部
帯電制御剤　　　サルチル酸亜鉛塩　　　　　　　　　　　　　　　２部
離型剤　　　　　カルナウバワックス　　　　　　　　　　　　　　５部
上記原材料をミキサーで十分に混合した後、２軸押出し機により混練物温度１００℃、混練機回転数１２０ｒｐｍで溶融混練した。混練物を圧延冷却後カッターミルで粗粉砕し、ジェット気流を用いた微粉砕機で粉砕後、旋回式風力分級装置を用いて、平均粒径が６．５μｍの粒度分布に分級した。
【０１３４】
（キャリア製造）
磁性材　　　Ｇｄ_０．５Ｆｅ_２．５Ｏ_４
上記金属酸化物は、以下の条件で作製した。
Ｇｄ酸化物、Ｆｅ酸化物を所定量に秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼し、その仮焼物をボールミルに投入し、粉砕した。得られた粉末を粉末プレス機にて圧力成形して板状にし、この成形物を電気炉等にて１３００℃で３時間焼成した。この焼成物をカッターで切断し、粗粉砕、微粉砕し、分級機により所定の粒度に分級して、ＧｄＦｅ酸化物の粒子を得た。
【０１３５】
その後、磁性粒子の表面に以下の条件でコート層を設けた。
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３５．７μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．６重量％であった。
【０１３６】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１３７】
（比較例５）
（トナー製造）
樹脂　　　　ポリエステル樹脂　　　　　１００部
顔料　　　　カーボンブラック　　　　　　１０部
帯電制御剤　サルチル酸亜鉛塩　　　　　　　１部
離型剤　　　カルナウバワックス　　　　　　５部
添加剤　　　スチレンアクリル樹脂　　　　　３部
上記原材料をミキサーで十分に混合した後、２軸押出し機により混練物温度１００℃、混練機回転数１２０ｒｐｍで溶融混練した。混練物を圧延冷却後カッターミルで粗粉砕し、ジェット気流を用いた微粉砕機で粉砕後、旋回式風力分級装置を用いて、平均粒径が６．５μｍの粒度分布に分級した。さらに、母体着色粒子１００部に対して、シリカ微粉末１部をスーパーミキサーにて混合して、トナーを得た。
【０１３８】
（キャリア製造）
磁性材　　　ＭｎＭｇＳｒフェライト
コート層　　シリコーン樹脂　　　　　１００部
シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３６．２μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．６重量％であった。
【０１３９】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１４０】
（比較例６）
（トナー製造）
比較例１と同じ。

シリコーン樹脂を希釈して固形分５ｗｔ％の分散液を得た。
流動床型コーティング装置を用いて、磁性粒子表面上に上記の希釈した分散溶液を、１００℃の雰囲気下で約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５４μｍの樹脂コート層を形成し、キャリアを得た。キャリア平均粒径は３６．３μｍで、１５μｍ未満の粒径を有するキャリアの含有割合は２．６重量％であった。
【０１４１】
上記作製法で得られたトナーとキャリアをキャリア９７．５部に対し、２．５部の割合で混合し、二成分現像剤を作製した。
得られた現像剤を潜像担持体がＯＰＣドラム感光体でクリーニング方式がブレードクリーニングである複写機にセットし、画像評価実験、耐久試験を行なった。
評価は、画像特性として画像濃度、シャープ性及びベタ均一性、耐久特性として帯電量の耐久試験時の変化、キャリア付着の評価、画質上でのかぶりを評価した。その結果は表６のようになる。
【０１４２】
以上の実施例及び比較例の実験結果を下表６に示す。
評価項目は、画像特性として画像濃度、シャープ性（５段階評価）、ベタ均一性（５段階評価）、耐久特性として耐久試験時のトナー帯電量変化（初期のトナー帯電量、５万枚コピー時のトナー帯電量）、キャリア付着の評価（５段階評価、５万枚コピー時）、かぶりの評価（５段階評価、５万枚コピー時）である。
シャープ性、ベタ均一性、キャリア付着、かぶりの評価は５段階評価でＡ：良→Ｅ：悪と表す。
【表６】

【０１４３】
表２から、Ｆｅ酸化物とＧｄ酸化物からなるＧｄ_ｘＦｅ_{３ − ｘ}Ｏ_４金属酸化物において、Ｇｄ組成ｘが０．２５≦ｘ≦１．２５のときキャリア付着などの異常画質がなく、高画質で、耐久性も優れていることが分かる。また、Ｇｄ_ｘ（Ｆｅ_{１ − ｙ}Ａｌ_ｙ）_{３ − ｘ}Ｏ_４でのＡｌ組成ｙは０≦ｙ≦０．５のとき高画質であるが、０．５より大きくなると磁気特性が低下し、全ての画像品質が低下することが分かる。また、フラーレン、カーボンナノチューブ、カーボン等を含有する樹脂被覆層を設けたことにより、トナー帯電特性が安定し、画像濃度及びシャープ性ともに良好な画像品質が得られ、なお且つ耐久特性が非常に改良されることが分かる。
【０１４４】
Ｇｄ_ｘＦｅ_{３ − ｘ}Ｏ_４において、Ｇｄ組成ｘを変化したときの磁気特性の変化を図１に示す。（実施例１〜７）Ｇｄ組成ｘが１以下のとき、保磁力Ｈｃが大きく、キャリアとして適していないことが分かる。
また、Ｇｄ_０．５（Ｆｅ_{１ − ｙ}Ａｌ_ｙ）_２．５Ｏ_４において、Ａｌ組成ｙを変化したときの磁気特性の変化を図２に示す。Ａｌ組成ｙが０．５より大きくなると、キュリー温度Ｔｃが低下し、キャリアとして適していないことが分かる。
【０１４５】
【発明の効果】
本発明は、キャリア材料としてＦｅ酸化物とＧｄ酸化物からなるＧｄ_ｘＦｅ_{３ − ｘ}Ｏ_４（０．２５＜ｘ≦１．２５）金属酸化物を用いることにより、小粒径でもキャリア付着がなく、高画質で帯電特性の安定した高耐久性な電子写真現像剤用キャリアを提供することが出来る。
【図面の簡単な説明】
【図１】Ｇｄ_ｘＦｅ_{３ − ｘ}Ｏ_４でｘの値を変化させたときの磁気特性を表わした図である。
【図２】Ｇｄ_０．５（Ｆｅ_{１ − ｙ}Ａｌ_ｙ）_２．５Ｏ_４でｙの値を変化させたときの磁気特性を表わした図である。
【図３】超音波発信器付振動ふるい機の説明図である。
【符号の説明】
１　振動ふるい機
２　円筒容器
３　スプリング
４　ベース
５　金網
６　共振リング
７　ケーブル
８　コンバータ（振動子）
９　リング状フレーム[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic developer used for electrostatic image development in electrophotography, electrostatic recording, electrostatic printing, and the like, a carrier for the electrophotographic developer, and a method for manufacturing the carrier.
[0002]
[Prior art]
Generally, in image forming methods such as electrophotography, electrostatography, and electrostatic printing, an electrostatic latent image formed on a latent image carrier (photoconductor, electrostatic recording body) is called toner. A method in which the electroconductive fine particles are adhered and visualized is adopted. For development, a method using a two-component developer obtained by mixing a toner and a carrier and a method using a one-component developer containing no carrier are known.
[0003]
The two-component developer used in the former developing method is required to be a mixture of an appropriately charged toner and a carrier, but the developing method using this two-component developer is relatively stable and good. Although an image can be obtained, there is a disadvantage that carrier deterioration and a change in the mixing ratio between the toner and the carrier are likely to occur. On the other hand, the latter one-component developer does not have the disadvantage of the former, but has a disadvantage that the charging property is difficult to stabilize. Each of the two-component developer and the one-component developer has both advantages and disadvantages. At present, however, two-component developers are often used due to the ease of toner charging.
[0004]
Carriers used in such a two-component developer are roughly classified into a coated carrier having a coating layer on the surface and an uncoated carrier having no coating layer on the surface. Filming of the toner on the carrier surface is performed. Prevention, formation of a uniform carrier surface, prevention of surface oxidation, prevention of deterioration in moisture sensitivity, extension of the life of the developer, prevention of carrier adhesion to the surface of the latent image carrier, protection of the latent image carrier from scratches or abrasion by the carrier, For the purpose of controlling the charge polarity or adjusting the charge amount, a coat carrier provided with a hard and high-strength coating layer by coating with an appropriate resin material is often used.
[0005]
Generally, Ni-Zn ferrite, Mn-Zn ferrite (Japanese Patent Publication No. 53-15040, etc.), and Mg-Zn ferrite (Japanese Patent Application Laid-Open No. 58-145621, etc.) are used or proposed as carriers. However, the saturation magnetization of these carriers is not so high. In particular, when the particle size is small, there is a problem that the carrier adhesion to the photoreceptor increases because the magnetization is small.
[0006]
It is also known to disperse fine particles in a carrier coat layer (resin coating layer). For example, Japanese Patent No. 2555704 attempts to improve the image quality and improve the life of the developer by dispersing titanium dioxide powder in a resin. Further, Japanese Patent Application Laid-Open No. 58-207054 attempts to improve the durability of the developer by coating the carrier surface with a silicone resin containing silicon carbide. However, the carrier coat layer also has a role of controlling electric characteristics, and it is difficult to adjust these additives, and it is necessary to add another additive.
[0007]
Also, conventionally, carbon has been added to the carrier coat layer in order to adjust the resistance of the developer. For example, in Japanese Patent No. 2643568, the amount of carbon in the carrier coat layer is defined in relation to the amount of carbon in the toner, with the aim of achieving high image quality and avoiding problems such as brush marks and toner scattering. I have. However, carbon cannot increase the mechanical strength of the carrier coat layer, and has a limit in durability.
[0008]
By the way, in order to achieve high image quality of an image, it is necessary that dot reproducibility, image density uniformity, image contrast, and the like be excellent. For that purpose, the effect of reducing the particle size of the carrier is very large, and realizing the reduction of the particle size of the carrier is of utmost importance. Further, in order to realize high image quality, it is necessary to prevent abnormal images such as carrier adhesion, toner scattering, magnetic brush patterns and white spots. In the electrophotographic process, the carrier is a magnetic surface (development characteristics, transport force, stirring force), an electrical surface (development characteristics, charging characteristics), and a mechanical surface (durability, charging stability, abrasion of the photoreceptor). Optimization) is needed.
[0009]
When the particle size of the carrier becomes smaller, all the conditions of the magnetic, electrical, and mechanical surfaces change, and these conditions are optimized again including the surface of the material. The need is coming out. In particular, in terms of magnetic properties, as the particle size of the carrier becomes smaller, the magnetic force of one carrier becomes smaller, so that it acts on a minute electrostatic force or a mechanical force, and The phenomenon of carrier adhesion is likely to occur.
[0010]
As a countermeasure, it is necessary to increase the magnetic force even if the carrier is small. It is necessary to increase the saturation magnetization more than ever.
[0011]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a long life and a high durability, which can stably maintain toner charging characteristics and development characteristics and realize high image quality forever without causing carrier adhesion even with a small particle diameter. The purpose is to provide.
[0012]
[Means for Solving the Problems]
The present inventors have studied the carrier for an electrophotographic developer from various angles, and as a result, have found that an FeGd oxide material having a specific composition exhibits high saturation magnetization which is favorable for the carrier. In addition, in order to optimize the development characteristics, it is necessary to devise a device that enables electrical optimization. To achieve this, adjustment of the electrical characteristics of the carrier (that is, resistance adjustment in the carrier coat layer) is required. Importantly, fullerene, carbon nanotube, and the like are useful as the resistance adjusting material, and these materials are excellent in mechanical wear characteristics and can improve durability characteristics. The present invention has been made based on these findings.
[0013]
According to the present invention, the above object is achieved by the following (1) to (9).
(1) A carrier for an electrophotographic developer, wherein a material comprising a metal oxide having the following composition is used.
Gd _x Fe _{3 - x} O ₄
(In the formula, 0.25 ≦ x ≦ 1.25.)
[0014]
(2) A carrier for an electrophotographic developer, wherein a material composed of a metal oxide having the following composition is used.
_{Gd x (Fe 1 - y A} y) 3 - x O 4
(Where A is at least one selected from Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr, and 0.25 ≦ x ≦ 1.25; 0 ≦ y ≦ 0.5.)
[0015]
(3) A carrier for an electrophotographic developer, wherein a resin coating layer is provided on the surface of the carrier particles according to (1) or (2).
This resin coating layer preferably contains at least one of carbon, fullerene and carbon nanotube.
[0016]
(4) A carrier for an electrophotographic developer, wherein the carrier particles comprising the metal oxide of (1), (2) or (3) have an average particle size of 20 to 100 μm.
[0017]
(5) A carrier for an electrophotographic developer, wherein the content of the carrier having a particle size of less than 15 μm in the carrier is 3% by weight or less.
[0018]
(6) A carrier for an electrophotographic developer, wherein the carrier particle material (1) to (4) contains at least one of MnMgSr ferrite, Mn ferrite, magnetine, and hematite.
[0019]
(7) The carrier for an electrophotographic developer, wherein the resin coating layer of (3) to (6) is a silicone resin.
[0020]
(8) The carrier for an electrophotographic developer, wherein the resin coating layer of (1) to (7) is a resin containing an aminosilane coupling agent.
[0021]
(9) An electrophotographic developer comprising the carrier of (1) to (8) and a toner. This toner preferably has an average particle size of 4 to 10 μm, and preferably contains a releasing agent and an additive for assisting dispersion therein.
Further, the toner is preferably prepared by a polymerization method or prepared by dispersing a pigment in a resin without using a solvent.
[0022]
(10) The carriers (3) to (8) are prepared using a fluidized bed type coating apparatus, and the carriers (1) to (8) are prepared using a vibration sieving machine with an ultrasonic oscillator. A method for producing a carrier for electrophotographic development, characterized by comprising:
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
In the present invention, a metal oxide made of an FeGd oxide having a high saturation magnetization is used as a magnetic material, so that even when a small particle size carrier is used, carrier adhesion does not occur. In addition, a carrier configuration in which the surface of the carrier is coated with a resin containing one or more types of carbon, fullerene, and carbon nanotubes has been proposed to not only adjust the carrier resistance but also improve the durability of the carrier itself.
Therefore, a carrier having a high-performance coating layer having excellent magnetic properties can be realized, and a carrier with low carrier adhesion, high charge stability, high image quality and high durability can be realized.
[0024]
In the present invention, a metal oxide composed of an Fe oxide and a Gd oxide is used as a carrier material, and in terms of composition, the Gd composition x needs to satisfy 0.25 ≦ x ≦ 1.25 in the following formula. It is.
Gd _x Fe _{3 - x} O ₄
(In the formula, 0.25 ≦ x ≦ 1.25.)
[0025]
Further, in the present invention, an additive A comprising at least one selected from the group consisting of Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr may be added to the oxide. good. The additive composition y needs to satisfy 0 ≦ y ≦ 0.5 in the following formula.
_{Gd x (Fe 1 - y A} y) 3 - x O 4
(In the formula, 0.25 ≦ x ≦ 1.25 and 0 ≦ y ≦ 0.5.)
These additives can adjust the magnetic properties and improve the stability of the material. However, when the addition amount is large (y exceeds 0.5 in the above formula), the magnetic properties are deteriorated, and the segregation phenomenon of the additives occurs, which is not suitable.
[0026]
FIG. 1 shows the change in magnetic properties of the FeGd oxide of the present invention with respect to the Gd composition x. The magnetic properties of this metal oxide change very steeply in accordance with the Gd composition. In particular, the saturation magnetization greatly changes. As the Gd composition x increases, the saturation magnetization decreases, and becomes almost zero when x = 1.5. Further, the coercive force becomes 500 Oe or less and decreases as the Gd composition x increases. The Curie temperature decreases as the Gd composition x increases, and reaches 0 ° C. near x = 1.5. Therefore, the composition range that can be used as the carrier is a composition range of 0.25 ≦ x ≦ 1.25. If x is smaller than 0.25, an abnormal image such as a toner brush earmark appears due to a large saturation magnetization, and cannot be used as a carrier.
[0027]
As a method for producing a metal oxide composed of an FeGd oxide or the like, there is a method of producing a metal oxide utilizing a solid-phase reaction between an Fe oxide and a Gd oxide or the like.
That is, Fe oxide, Gd oxide, additives, and the like are weighed and mixed using a ball mill. Next, it was calcined at 600 to 1000 ° C. for 2 to 5 hours by an electric furnace or the like, and the calcined product was put into a ball mill and ground for about 12 hours. A binder was added to the obtained powder, and the mixture was spray-dried and granulated in a heated atmosphere, and the molded product was fired in an electric furnace or the like at 1100 to 1300 ° C for 2 to 5 hours. The calcined product is roughly pulverized and finely pulverized, and classified into a predetermined particle size by a classifier to obtain particles of a metal oxide composed of an Fe oxide, a Gd oxide, additives, and the like.
[0028]
In the carrier particles used in the present invention, the magnetic moment when a magnetic field of 1,000 Oersted (Oe) is applied is 70 emu / g or more, preferably 80 emu / g or more. g. If the magnetic moment of the carrier particles (carrier core material particles) is less than 70 emu / g, carrier adhesion is likely to occur. If the magnetic moment exceeds 300 emu / g, ears of the magnetic brush appear on the image, and It may not be suitable.
[0029]
The magnetic moment can be measured by a BH curve tracer, a VSM, or the like. For example, using a BH curve tracer (BHU-60 / manufactured by RIKEN ELECTRONICS CO., LTD.), 1.0 g of carrier core material particles are packed in a cylindrical cell and set in an apparatus, and a BH hysteresis curve is measured. A magnetic moment of 1000 Oe is obtained from the characteristics.
[0030]
The carrier of the present invention may be manufactured by forming a resin coating layer on the surface of the carrier particles, and in this case, various types of conventionally known resins used for manufacturing the carrier may be used. Can be.
For example, a silicone resin containing any one or two or more of the repeating units represented by the following formulas (a), (b), and (c) is suitable for the present invention, and can be used.
[0031]
Embedded image

In the above formula, R ¹ represents a hydrogen atom, a halogen atom, a hydroxy group, a methoxy group, a lower alkyl group having 1 to 4 carbon atoms, or an aryl group (phenyl group, tolyl group, etc.), and R ² has 1 to 1 carbon atoms. 4 represents an alkylene group or an arylene group (such as a phenylene group).
[0032]
In the present invention, a straight silicone resin can be used. Examples of such a material include KR271, KR272, KR282, KR252, KR255, and KR152 (all manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, and SR2406 (all manufactured by Dow Corning Toray Silicone Co., Ltd.).
[0033]
Alternatively, a modified silicone resin can be used. Examples of such a material include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone.
These include modified silicone: KR-5208, modified polyester: KR-5203, modified alkyd: KR-206, modified urethane: KR-305 (all manufactured by Shin-Etsu Chemical Co., Ltd.), modified epoxy: SR2115, Modified alkyd: SR2110 (manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like.
[0034]
In the present invention, the silicone resin may contain an aminosilane coupling agent in an appropriate amount (0.001 to 30% by weight). Examples include the following.
[Table 1]

[0035]
Further, in the present invention, as the resin for coating the surface of the carrier particles, the following resin may be used alone or in combination with the above silicone resin.
Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer Polymer, styrene-phenyl acrylate copolymer) styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene -Phenyl methacrylate copolymer) Styrene resins such as len-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylate copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.
[0036]
In the present invention, an additive for adjusting the resistance and improving the durability may be dispersed in the resin coating layer. Examples of the additive include fullerene, carbon nanotube, and carbon.
As the fullerene, C ₆₀ , C ₇₀ , C ₈₂ , C ₈₄ and a high molecular weight fullerene can be used.
[0037]
As a method for synthesizing fullerenes or carbon nanotubes, there are a resistance heating method in which a graphite rod is directly heated by heating in a rare gas, and an arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas to synthesize. is there.
[0038]
As the fullerenes and carbon nanotubes, those in which a metal such as La, Y, Sc or the like is included in the internal space can be used. To synthesize a metal-encapsulated fullerene, an arc discharge is generated using a carbon rod containing a metal oxide (eg, La ₂ O ₃ ), or a carbon chip containing the metal oxide is put into a crucible-shaped anode. There is a method of causing an arc discharge to synthesize.
[0039]
The particle size of the fullerene is 0.01 to 0.2 μm, preferably 0.01 to 0.1 μm. If the particle size of the fullerene is less than 0.01 μm, aggregation or the like is likely to occur, and if it is more than 0.2 μm, the dispersion state is reduced and the composition is not suitable.
[0040]
The shape of the carbon nanotube is 0.01 to 0.1 μm in diameter and 0.05 to 0.5 μm in length, preferably 0.01 to 0.05 μm in diameter and 0.05 to 0.05 μm in length. 0.1 μm. When the diameter of the carbon nanotube is less than 0.01 μmφ and the length is less than 0.05 μm, aggregation is likely to occur, and the carbon nanotube is not suitable. It is not suitable because of its poor quality.
[0041]
Examples of carbon include carbon black. The particle size is 0.01 to 0.2 μm. If it is smaller than this range, there is a problem of dust. If it is larger than this range, dispersion becomes worse, and it becomes difficult to form a uniform film.
[0042]
These fullerenes, carbon nanotubes, carbon, etc. are put into a solvent used for coating or a resin solution for coating, and a disperser using a medium such as a ball mill or a bead mill, or a stirrer equipped with high-speed rotating blades is used. In this manner, the solution is uniformly dispersed, and the solution is coated on the surface of carrier particles exhibiting magnetism by spray coating or the like.
[0043]
As a method for forming the resin coating layer on the surface of the carrier particles, a known method such as a spray drying method, an immersion method, or a powder coating method can be used. In particular, a method using a fluidized bed type coating apparatus is suitable since a uniform resin coating layer can be formed by forming a fluidized bed of a carrier and spraying the fluidized bed.
[0044]
The content of fullerene, carbon nanotube, and carbon to the resin in the resin coating layer must be 0.01 to 10 parts by weight based on 100 parts by weight of the resin. When the content of fullerene, carbon nanotube, and carbon is less than 0.01 part by weight, no improvement in durability is observed, and when the content of fullerene, carbon nanotube, and carbon is greater than 10 parts by weight, the resin layer Becomes brittle and the durability deteriorates.
[0045]
The thickness of the resin coating layer formed on the surface of the carrier particles and the resin coating layer containing fullerene, carbon nanotube, and carbon is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. If the thickness is less than 0.02 μm, the durability is not sufficiently improved, and if it exceeds 1 μm, the film peels off and the stability of the charging characteristics decreases.
[0046]
The average particle size of the carrier (uncoated carrier, coated carrier) of the present invention is in the range of 20 μm to 100 μm, and preferably in the range of 30 μm to 70 μm in terms of weight average particle size Dw. When the weight average particle diameter Dw exceeds 100 μm, carrier adhesion hardly occurs, but dot reproducibility deteriorates. When the weight average particle diameter Dw is less than 20 μm, the carrier adhesion increases, the stirring efficiency with the toner is deteriorated, and it is difficult to obtain a uniform charge amount of the toner.
[0047]
As described above, the carrier adhesion indicates a phenomenon that the carrier adheres to the image portion or the background portion of the electrostatic latent image. Carriers are more likely to adhere as the respective electric fields are stronger. Since the electric field is weakened in the image area by developing the toner, carrier adhesion is less likely to occur than in the background area. Carrier adhesion is not preferable because it causes inconvenience such as causing damage to the photosensitive drum and the fixing roller.
[0048]
In the present invention, the magnetic properties are improved from the viewpoint of the material in consideration of the carrier adhesion, but the content of the carrier having a particle size smaller than 15 μm seems to be 3% by weight or less, preferably 1% by weight or less. Stipulated. In the case of a small particle size carrier, the majority of the carrier adhering to the carrier are fine particles of less than 15 μm. The present inventors evaluated the carrier adhesion by changing the weight ratio of particles smaller than 15 μm in a small particle size carrier having a weight average particle size Dw of 25 μm to 45 μm. It is found that there is no major problem if the amount is less than 1% by weight.
[0049]
The carrier of the present invention is obtained by pulverizing the magnetic material of the present invention, classifying the pulverized product particles so as to obtain a predetermined particle size, and optionally coating a resin coating layer on the surface of the magnetic particles obtained by the classification. Is formed. This classification includes air classification and sieving classification (sieving). A vibrating sieve is preferably used for the production of carrier particles. However, with a vibrating sieve generally used in the past, when trying to classify particles having a small particle size, a small mesh of the sieve (wire mesh) is immediately formed. Therefore, the workability for classification is very poor.
[0050]
The present inventors have conducted various studies to develop a method capable of efficiently cutting small-sized particles sharply, and when classifying particles using a sieving machine, applying ultrasonic vibration to the wire mesh. As a result, it has been found that small particles of less than 15 μm can be efficiently and sharply cut. Ultrasonic vibration that vibrates the wire mesh can be obtained by supplying a high-frequency current to a converter and converting it into ultrasonic vibration. The converter in this case is composed of a PZT vibrator. In order to vibrate the metal net by the ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to a resonance member fixed to the metal net. The resonance member to which the ultrasonic vibration has been transmitted resonates due to the ultrasonic vibration, and vibrates the wire net fixed to the resonance member.
The frequency at which the wire net is vibrated is 20 to 50 kHz, preferably 30 to 40 kHz. The shape of the resonance member may be any shape as long as it is suitable for vibrating the wire mesh, and is usually a ring shape.
The vibration direction for vibrating the wire mesh is preferably a vertical direction.
[0051]
FIG. 3 shows an explanatory structural view of a vibration sieve with an ultrasonic oscillator.
In FIG. 3, 1 is a vibrating sieve, 2 is a cylindrical container, 3 is a spring, 4 is a base (support), 5 is a wire mesh, 6 is a resonance ring, 7 is a high-frequency current cable, 8 is a converter, and 9 is a ring shape. Indicates a frame. To operate the vibrating sieve (circular sieve) with the ultrasonic oscillator shown in FIG. 1, a high-frequency current is supplied to the converter 8 via the cable 7. The high-frequency current supplied to the converter 8 is converted into an ultrasonic vibration. The ultrasonic vibration generated by the converter 8 causes the resonance ring 8 to which the converter 8 is fixed and the ring-shaped frame 9 connected thereto to vibrate in the vertical direction. The vibration of the resonance ring 6 causes the resonance ring 6 and the wire mesh 5 fixed to the frame 9 to vibrate in the vertical direction.
A vibration sieving machine with an ultrasonic oscillator is sold, for example, available from Koei Sangyo Co., Ltd. under the product name "Ultrasonic".
[0052]
In the present invention, the resin coating layer is formed on the surface of the classified magnetic particles (carrier particles). After forming the resin coating layer on the surface of the pulverized magnetic particles, the resin-coated carrier particles are classified. Can also be manufactured. In this case, the classification of the resin-coated carrier particles is preferably performed using the above-described vibration sieve equipped with an ultrasonic oscillator.
[0053]
In the present invention, the adjustment of the resistance of the carrier is performed by a resin coating layer containing at least one of fullerene, carbon nanotube, and carbon formed on the surface of the carrier particles. If the carrier resistance is too high, an abnormal image such as a white spot phenomenon due to the side effect of the edge effect occurs.If the carrier resistance is too low, the uniformity of the solid image is improved, but the carrier adhesion easily occurs, and the carrier resistance is reduced. It is necessary to optimize it according to the development conditions. The optimization of the carrier resistance is controlled by the content and film thickness of fullerene, carbon nanotube, and carbon.
[0054]
The developer of the present invention comprises the carrier and the toner.
The toner used in the present invention is a binder resin containing a thermoplastic resin as a main component, a coloring agent, a charge control agent, a release agent, and the like, and various conventionally known toners may be used. Can be. This toner is an irregular or spherical toner produced by various toner production methods such as a pulverization method, a polymerization method, and a granulation method, and any of a magnetic toner and a non-magnetic toner can be used.
[0055]
As the resin used for the toner, epoxy resin, polyester resin, polyamide resin, styrene acrylic resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, polyol resin, etc. There is.
[0056]
Examples of the vinyl resin include styrene such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene, and homopolymers of substituted styrenes: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, and styrene-vinyltoluene copolymer. Polymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacryl Methyl acrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl acetate Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene-based copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.
[0057]
The polyester resin is composed of a dihydric alcohol as shown in Group A below and a dibasic acid salt as shown in Group B, and a trivalent or higher alcohol as shown in Group C or A carboxylic acid may be added as a third component.
[0058]
Group A: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4 butanediol, neopentyl glycol, 1,4 butenediol, 1,4-bis (hydroxymethyl) cyclohexane , Bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2,2) -2,2'-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -2,2′-bis (4 -Hydroxyphenyl) propane and the like.
[0059]
Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, linoleic acid, or Esters of these acid anhydrides or lower alcohols.
[0060]
Group C: trihydric or higher alcohol such as glycerin, trimethylolpropane, pentaerythritol and the like, and trivalent or higher carboxylic acid such as trimellitic acid and pyromellitic acid.
[0061]
As the polyol resin, an epoxy resin, a compound having one alkylene oxide adduct of dihydric phenol or its glycidyl ether and one active hydrogen in the molecule that reacts with the epoxy group, and an active hydrogen reacting with the epoxy resin in the molecule. There are compounds obtained by reacting two or more compounds.
[0062]
The following pigments are used for the toner. One or more of these can be used.
[0063]
Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides.
[0064]
Examples of the yellow pigment include cadmium yellow, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hanza yellow G, Hanza yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. .
[0065]
Examples of orange pigments include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.
[0066]
Examples of the red pigment include bengara, cadmium red, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B.
[0067]
Examples of purple pigments include Fast Violet B and Methyl Violet Lake.
[0068]
Examples of the blue pigment include cobalt blue, alkali blue, Victoria Blue Lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, and indanthrene blue BC.
[0069]
Green pigments include chrome green, chromium oxide, pigment green B, malachite green lake, and the like.
[0070]
Particularly in the case of color toners, it is essential to disperse good pigments uniformly.Instead of directly charging pigments into a large amount of resin, a masterbatch in which pigments are once dispersed at a high concentration is prepared and diluted. Is used. In this case, a solvent is generally used to help dispersibility, but there are environmental problems and the like, and in the present invention, water is used to disperse. When water is used, temperature control is important so that residual moisture in the masterbatch does not matter.
[0071]
In the toner, a charge control agent may be blended (internally added) inside the toner particles, or may be used as a mixture (externally added) with the toner particles.
The charge control agent makes it possible to control the charge amount optimally according to the development system. In particular, in the present invention, the balance between the particle size distribution and the charge amount can be further stabilized.
Nigrosine, a quaternary ammonium salt, an imidazole metal complex or salts can be used alone or in combination of two or more to control the toner to have a positive charge. Further, a metal salicylate complex, salts, organic boron salts, calixarene-based compounds, and the like are used to control the toner to have a negative charge.
[0072]
Further, a release agent can be internally added to the toner to prevent offset during fixing. Examples of the release agent include natural waxes such as candelilla wax, carnauba wax and rice wax, montan wax, paraffin wax, sasol wax, low molecular weight polyethylene, low molecular weight polypropylene, alkyl phosphate and the like. The melting point of these release agents is preferably from 65 to 90 ° C. If the temperature is lower than this range, blocking during storage of the toner tends to occur. If the temperature is higher than this range, offset may easily occur in a region where the temperature of the fixing roller is low.
[0073]
An additive may be added for the purpose of improving the dispersibility of the release agent and the like. As additives, styrene acrylic resin, polyethylene resin, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, There are polyol resins and the like, and a mixture of two or more of each resin may be used.
[0074]
In order to improve the fluidity or the like of the toner, the surface of the toner may be subjected to a surface treatment with an inorganic fine powder. As the inorganic fine powder, oxidation of Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, Zr, etc. And composite oxides. Among them, fine particles of silicon dioxide (silica), titanium dioxide (titania), and alumina are preferably used. Further, it is effective to perform a surface modification treatment with a hydrophobizing agent or the like.
[0075]
The following are typical examples of the hydrophobizing agent. Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane and the like.
[0076]
The inorganic fine powder is preferably used in an amount of 0.1 to 2% by weight based on the toner. If it is less than 0.1% by weight, the effect of improving toner aggregation is poor. If it exceeds 2% by weight, problems such as toner scattering between fine lines, contamination inside the machine, scratches and abrasion of the photoreceptor tend to occur. is there.
[0077]
Methods for producing the toner include a pulverization method and a polymerization method (suspension polymerization, emulsion polymerization, dispersion polymerization, emulsion aggregation, emulsion association, etc.), but are not limited to these production methods.
[0078]
As an example of a method for producing a toner by a pulverization method, first, the above-mentioned resin, a pigment or dye as a colorant, a charge control agent, a release agent, and other additives are sufficiently mixed by a mixer such as a Henschel mixer. After mixing, batch-type two rolls, Banbury mixer and continuous twin-screw extruder, for example, KTK twin-screw extruder manufactured by Kobe Steel, TEM twin-screw extruder manufactured by Toshiba Machine Co., Ltd., manufactured by KCK A twin-screw extruder, a PCM-type twin-screw extruder manufactured by Ikegai Iron Works, a KEX-type twin-screw extruder manufactured by Kurimoto Iron Works, and a hot kneader such as a continuous single-screw kneader such as a co-kneader manufactured by Buss. After kneading the components well, cool and coarsely pulverize using a hammer mill or the like, further pulverize with a fine pulverizer using a jet stream or a mechanical pulverizer, and a classifier or a Coanda using a swirling stream. Classifier using effects Ri is classified to a predetermined particle size. Thereafter, an additive composed of inorganic particles or the like is adhered or fixed to the particle surface by a mixer, and is passed through a sieve of 250 mesh or more to remove coarse particles and aggregated particles to obtain a toner.
[0079]
The weight average particle size of the toner is 4 to 10 μm, and more preferably 5 to 8 μm. If the weight average particle diameter is less than 4 μm, problems such as contamination inside the apparatus due to toner scattering during long-term use, a decrease in image density in a low-humidity environment, and poor cleaning of the photoconductor tend to occur. When the weight average particle size exceeds 10 μm, the resolution of the fine spots of 100 μm or less is not sufficient, and the fine spots tend to be scattered to non-image portions, resulting in poor image quality.
[0080]
Further, as an example of toner production by a polymerization method, toner particles are obtained by suspending and polymerizing a monomer composition in which a colorant, a charge control agent, and the like are added to a monomer in an aqueous medium. The granulation method is not particularly limited.
For example, the toner of the present invention is obtained by dissolving at least an isocyanate group-containing polyester prepolymer in an organic solvent, dispersing a pigment colorant, and dissolving or dispersing a release agent in an aqueous medium. Urea-modified polyester resin having a urea group by dispersing the prepolymer in the dispersion in the presence of inorganic fine particles and / or polymer fine particles and reacting the prepolymer with a polyamine and / or a monoamine having an active hydrogen-containing group in the dispersion. Is formed, and the liquid medium contained therein is removed from the dispersion containing the urea-modified polyester resin.
[0081]
The urea-modified polyester resin has a Tg of 40 to 65 ° C, preferably 45 to 60 ° C. Its number average molecular weight Mn is 2,500 to 50,000, preferably 2,500 to 30,000. Its weight average molecular weight Mw is 10,000 to 500,000, preferably 30,000 to 100,000.
[0082]
This toner contains, as a binder resin, a urea-modified polyester-based resin having a urea bond and having a high molecular weight by a reaction between the prepolymer and the amine. The coloring agent is highly dispersed in the binder resin.
[0083]
When used as the developer of the present invention, a two-component developer is obtained by mixing the above-described magnetic carrier with a predetermined mixing ratio.
When a magnetic toner is used, fine particles of a magnetic substance may be internally added to the toner particles. As the magnetic material, a ferromagnetic material such as ferrite, magnetite, iron, nickel, cobalt, or an alloy thereof can be considered. The average particle size of the magnetic material is preferably 0.1 to 1 μm. The content of the magnetic substance is preferably from 10 to 70 parts by weight based on 100 parts by weight of the toner.
[0084]
The developer of the present invention may further contain other additives within a range that does not substantially adversely affect the lubricant, for example, a lubricant powder such as Teflon (R) powder, zinc stearate powder, polyvinylidene fluoride powder; Abrasives such as powder, silicon carbide powder and strontium titanate powder; or a small amount of a conductivity-imparting agent such as carbon black powder, zinc oxide powder and tin oxide powder can also be used as a developability improver.
[0085]
The developing method of the present invention is a method using the above-mentioned developer of the present invention as the developer. In this case, when a voltage in which an AC voltage is superimposed on a DC voltage is applied as a developing bias applied from the outside, high image density and high image quality with less background smear can be obtained. In particular, dot reproducibility and highlight reproducibility are improved. When the above-described developing bias is applied, the substantial developing potential and the background potential become larger than when only the DC bias is applied. For this reason, conventionally, the carrier was likely to adhere, but the carrier of the present invention has made compatibility possible.
[0086]
The image forming apparatus of the present invention is an image forming apparatus equipped with a developing container, wherein a developing container containing the developer of the present invention is used as the developing container. As the image forming apparatus in this case, various conventionally known apparatuses can be used.
[0087]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but these examples do not limit the present invention at all. All parts in the following formulations are parts by weight.
[0088]
(Examples 1 to 5 and Comparative Examples 1 and 2)
(Toner production)
Resin Polyester resin 100 parts Pigment carbon black 10 parts Charge control agent Zinc salicylate 2 parts Release agent Carnauba wax 5 parts Additives Styrene acrylic resin 3 parts After thoroughly mixing the above raw materials with a mixer, using a twin screw extruder The kneaded material was melt-kneaded at a kneading temperature of 100 ° C. at a kneader rotation speed of 120 rpm. The kneaded product was rolled and cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a revolving air classifier. Further, 1 part of silica differential powder was mixed with 100 parts of the base colored particles using a super mixer to obtain a toner.
[0089]
(Carrier manufacturing)
Magnetic material Gd _x Fe _{3 - x} O ₄
In the above formula, the magnetic material was manufactured by changing the Gd composition x.
Gd composition x _is, Gd x _{Fe 3 -} In x _{O 4,} were changed as follows.
[Table 2]

[0090]
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0091]
Thereafter, a coating layer (resin coating layer) was provided on the surface of each magnetic particle under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A resin coat layer of 0.53 μm was formed to obtain a carrier. The average particle size of the carriers of the respective Examples and Comparative Examples and the content ratio of the carriers having a particle size of less than 15 μm are shown below.
[0092]
[Table 3]

[0093]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
The magnetic properties of the carrier were measured with a vibrating sample magnetometer, and the saturation magnetization, coercive force, and Curie temperature were evaluated. The result is shown in FIG.
[0094]
(Examples 6, 7 and Comparative Examples 3, 4)
(Toner production)
Same as Example 1.
(Carrier manufacturing)
Magnetic material _{Gd 0.25 (Fe 1 - y Al} y) 2.75 O 4
In the above formula, a magnetic material was manufactured by changing the Al composition y.
Al composition y _is, Gd 0.25 - in _{(Fe 1 y Al y) 2.75} O 4, were changed as follows.
[Table 4]

[0095]
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide, Fe oxide and Al oxide, they are mixed for 5 hours using a ball mill, and calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product is put into a ball mill. Crushed. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified into a predetermined particle size by a classifier to obtain particles of GdFeAl oxide.
[0096]
Thereafter, a coat layer was provided on the surface of each magnetic particle under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A resin coat layer of 0.53 μm was formed to obtain a carrier. The average particle diameter of the carrier and the content ratio of the carrier having a particle diameter of less than 15 μm in each example are shown below.
[Table 5]

[0097]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
The magnetic properties of the carrier were measured with a vibrating sample magnetometer, and the saturation magnetization, coercive force, and Curie temperature were evaluated. The result is shown in FIG.
[0098]
(Example 8)
(Toner production)
Resin Polyester resin 100 parts Pigment carbon black 10 parts Charge control agent Zinc salicylate 2 parts Release agent Carnauba wax 5 parts Additives Styrene acrylic resin 3 parts After thoroughly mixing the above raw materials with a mixer, using a twin screw extruder The kneaded material was melt-kneaded at a kneading temperature of 100 ° C. at a kneader rotation speed of 120 rpm. The kneaded product was rolled and cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a revolving air classifier. Further, 1 part of silica differential powder was mixed with 100 parts of the base colored particles using a super mixer to obtain a toner.
[0099]
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0100]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
The coating layer silicone resin 100 parts in fullerene C _{60 1} parts of a silicone resin, using a ball mill to disperse the fullerene C _60, a solid content of 5 wt% of the dispersion to dilute the dispersion. Fullerene C ₆₀ is produced by the arc discharge method of synthesizing by causing an arc discharge between two graphite rods rare gas, the average particle size was 0.025 .mu.m.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.4 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0101]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0102]
(Example 9)
(Toner production)
Same as Example 8.
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0103]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.

In a silicone resin, C ₇₀ to fullerene C ₆₀ with a ball mill was the dispersing those mixed 30%, a solid content of 5 wt% of the dispersion to dilute the dispersion. Fullerene C ₆₀ containing 30% of C ₇₀ was produced by an arc discharge method in which an arc discharge was generated between two graphite rods in a rare gas and synthesized, and the average particle size was 0.035 μm. Met.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.52 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.4 μm, and the content of the carrier having a particle size of less than 15 μm was 2.8% by weight.
[0104]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0105]
(Example 10)
(Toner production)
Same as Example 12.
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0106]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.

The carbon nanotubes were dispersed in the silicone resin using a ball mill, and this dispersion was diluted to obtain a dispersion having a solid content of 5 wt%. Carbon nanotubes are produced by an arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas, and the carbon nanotubes are formed in a shape having a diameter of 0.01 to 0.1 μmφ and a length of 0.01 μmφ. Was 0.05 to 0.5 μm.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.52 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.7 μm, and the content of the carrier having a particle size of less than 15 μm was 2.8% by weight.
[0107]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0108]
(Example 11)
(Toner production)
Same as Example 1.
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After the Co oxide and the Fe oxide were weighed to a predetermined amount, they were mixed using a ball mill for 5 hours, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0109]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.

In a silicone resin, a ball mill to disperse the C ₆₀ and carbon, to yield the solid content 5 wt% of the dispersion to dilute the dispersion. C ₆₀ is produced by the arc discharge method of synthesizing by causing an arc discharge between two graphite rods rare gas, the average particle diameter was 0.04 .mu.m. The average particle size of the carbon was 0.04 μm. Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.6 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0110]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0111]
(Example 12)
(Toner production)
Same as Example 1.
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0112]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.

In a silicone resin, using a ball mill to disperse the fullerene C _60, a solid content of 5 wt% of the dispersion to dilute the dispersion. Fullerene C ₆₀ is produced by the arc discharge method of synthesizing by causing an arc discharge between two graphite rods rare gas, the average particle size was 0.025 .mu.m.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A resin coat layer of 0.58 μm was formed to obtain a carrier. The average particle size of the carrier was 35.9 μm, and the content of particles having a particle size smaller than 15 μm was 2.8% by weight.
[0113]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0114]
(Example 13)
(Toner production)
Same as Example 1.

Gd _0.5 Fe _2.5 O ₄ metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles. MnMgSr ferrite particles were added to the metal oxide particles at a ratio of 1: 1 and mixed by a mixer.
[0115]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A resin coat layer of 0.53 μm was formed to obtain a carrier. The average particle size of the carrier was 35.4 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0116]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0117]
(Example 14)
(Toner production)
Same as Example 1.

Gd _0.5 Fe _2.5 O ₄ metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles. Mn ferrite particles were added to the metal oxide particles at a ratio of 1: 1 and mixed by a mixer.
[0118]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.5 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0119]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0120]
(Example 15)
(Toner production)
Same as Example 1.

Gd _0.5 Fe _2.5 O ₄ metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized and finely pulverized, and classified to a predetermined particle size by a classifier to obtain CoFe oxide particles. Magnetite particles were added to the metal oxide particles at a ratio of 1: 1 and mixed with a mixer.
[0121]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.4 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0122]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0123]
(Example 16)
(Toner production)
Same as Example 1.

Gd _0.5 Fe _2.5 O ₄ metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles. Hematite particles were added to the metal oxide particles at a ratio of 1: 1 and mixed by a mixer.
[0124]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A resin coat layer of 0.53 μm was formed to obtain a carrier. The average particle size of the carrier was 35.6 μm, and the content of the carrier having a particle size of less than 15 μm was 2.6% by weight.
[0125]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0126]
(Example 17)
(Toner production)
Same as Example 1.
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0127]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.

In 100 parts of silicone resin, 5 parts of aminosilane coupling agent H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ was added and dispersed using a ball mill. A 5 wt% dispersion was obtained.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 230 ° C. for 2 hours to form a film. A resin coat layer of 0.51 μm was formed to obtain a carrier. The average particle size of the carrier was 35.1 μm, and the content of the carrier having a particle size of less than 15 μm was 2.6% by weight.
[0128]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0129]
(Example 18)
(Toner production)
Resin Polyester resin 100 parts Pigment Copper phthalocyanine blue pigment (C.I. Fluorescent Blue 15: 3) 5 parts Charge control agent Zinc salicylate 2 parts Release agent Carnauba wax 5 parts After the above raw materials are sufficiently mixed with a mixer The mixture was melt-kneaded with a twin-screw extruder at a kneaded material temperature of 100 ° C. and a kneader rotation speed of 120 rpm. The kneaded product was rolled and cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a revolving air classifier.
[0130]
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0131]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat film was formed to obtain a carrier. The average particle size of the carrier was 35.5 μm, and the content of the carrier having a particle size of less than 15 μm was 2.7% by weight.
[0132]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0133]
(Example 19)
(Toner production)
Resin Polyester resin 100 parts Masterbatch Kneaded product composed of copper phthalocyanine blue pigment and polyester resin (1: 1) (kneaded with water) 10 parts Charge control agent Zinc salicylate 2 parts Release agent Carnauba wax 5 parts After sufficiently mixing the raw materials with a mixer, the mixture was melt-kneaded with a twin-screw extruder at a kneaded material temperature of 100 ° C. and a kneader rotation speed of 120 rpm. The kneaded product was rolled and cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a revolving air classifier.
[0134]
(Carrier manufacturing)
Magnetic material Gd _0.5 Fe _2.5 O ₄
The metal oxide was produced under the following conditions.
After weighing a predetermined amount of Gd oxide and Fe oxide, they were mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and the calcined product was put into a ball mill and pulverized. The obtained powder was pressed into a plate by a powder press, and the formed product was fired at 1300 ° C. for 3 hours in an electric furnace or the like. This calcined product was cut with a cutter, roughly pulverized, finely pulverized, and classified to a predetermined particle size by a classifier to obtain GdFe oxide particles.
[0135]
Thereafter, a coat layer was provided on the surface of the magnetic particles under the following conditions.
Coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 35.7 μm, and the content of the carrier having a particle size of less than 15 μm was 2.6% by weight.
[0136]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0137]
(Comparative Example 5)
(Toner production)
Resin Polyester resin 100 parts Pigment carbon black 10 parts Charge control agent Zinc salicylate 1 part Mold release agent Carnauba wax 5 parts Additives Styrene acrylic resin 3 parts After thoroughly mixing the above raw materials with a mixer, using a twin screw extruder Melt kneading was performed at a kneaded material temperature of 100 ° C. and a kneader rotation speed of 120 rpm. The kneaded product was rolled and cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a revolving air classifier. Further, 1 part of silica fine powder was mixed with 100 parts of the base colored particles by a super mixer to obtain a toner.
[0138]
(Carrier manufacturing)
Magnetic material MnMgSr ferrite coat layer Silicone resin 100 parts Silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 36.2 μm, and the content of the carrier having a particle size of less than 15 μm was 2.6% by weight.
[0139]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0140]
(Comparative Example 6)
(Toner production)
Same as Comparative Example 1.

The silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight.
Using a fluidized bed type coating apparatus, the above-mentioned diluted dispersion solution was applied on the surface of the magnetic particles at a rate of about 40 g / min under an atmosphere of 100 ° C., and further heated at 240 ° C. for 2 hours to form a film. A 0.54 μm resin coat layer was formed to obtain a carrier. The average particle size of the carrier was 36.3 μm, and the content of the carrier having a particle size of less than 15 μm was 2.6% by weight.
[0141]
The toner and carrier obtained by the above method were mixed in a ratio of 2.5 parts to 97.5 parts of the carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier was an OPC drum photosensitive member and the cleaning method was blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation was performed by evaluating image density, sharpness and solid uniformity as image characteristics, change in charge amount during a durability test, evaluation of carrier adhesion, and fog on image quality as durability characteristics. The results are as shown in Table 6.
[0142]
The experimental results of the above Examples and Comparative Examples are shown in Table 6 below.
Evaluation items include image density, sharpness (5-grade evaluation) and solid uniformity (5-grade evaluation) as image characteristics, and change in toner charge amount during the durability test (initial toner charge amount when copying 50,000 sheets) as durability characteristics. Of the toner), evaluation of carrier adhesion (5 levels evaluation, 50,000 copies), and fog evaluation (5 levels evaluation, 50,000 copies).
Evaluation of sharpness, solid uniformity, carrier adhesion, and fogging is expressed by A: good → E: bad in five-grade evaluation.
[Table 6]

[0143]
From Table 2, _Gd x _{Fe 3} consisting of Fe oxide and Gd oxide _- In x _{O 4} metal oxide, Gd composition x no abnormality quality such as carrier adhesion when 0.25 ≦ x ≦ 1.25, It can be seen that the image quality is high and the durability is excellent. _{Further, Gd x (Fe 1 - y} Al y) 3 - Although Al composition y in x _{O 4} is a high quality when 0 ≦ y ≦ 0.5, reduces the larger the magnetic properties than 0.5, It can be seen that all image quality is reduced. In addition, by providing a resin coating layer containing fullerenes, carbon nanotubes, carbon, etc., the toner charging characteristics are stable, good image quality is obtained in both image density and sharpness, and the durability characteristics are greatly improved. It is understood that it is done.
[0144]
Gd _x Fe _{3 -} In _x O _4, shows a change in magnetic characteristics when changing the composition of Gd x in FIG. (Examples 1 to 7) It can be seen that when the Gd composition x is 1 or less, the coercive force Hc is large and not suitable as a carrier.
_Further, Gd _{0.5 -} In _{(Fe 1 y Al y) 2.5} O 4, shows a change in magnetic characteristics when changing the Al composition y in FIG. When the Al composition y is larger than 0.5, the Curie temperature Tc decreases, and it is found that the Curie temperature Tc is not suitable as a carrier.
[0145]
【The invention's effect】
The present invention, _Gd x _{Fe 3} consisting of Fe oxide and Gd oxide as a carrier material _- by using _{x O 4 (0.25 <x ≦} 1.25) metal oxide, the carrier attachment even in small particle size In addition, it is possible to provide a highly durable electrophotographic developer carrier having high image quality and stable charging characteristics.
[Brief description of the drawings]
It is a diagram showing the magnetic characteristics when changing the value of x at x _{O 4 -} [1] _Gd x _{Fe 3.}
It is a diagram showing the magnetic characteristics when changing the value of y in _{- (y Al y Fe 1)} 2.5 O 4 [2] _Gd 0.5.
FIG. 3 is an explanatory view of a vibration sieve with an ultrasonic transmitter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vibration sieve machine 2 Cylindrical container 3 Spring 4 Base 5 Wire mesh 6 Resonance ring 7 Cable 8 Converter (vibrator)
9 Ring frame

Claims (21)

A carrier for an electrophotographic developer, wherein a material comprising a metal oxide having the following composition is used.
Gd _x Fe _{3 - x} O ₄
(In the formula, 0.25 ≦ x ≦ 1.25.) A carrier for an electrophotographic developer, wherein a material comprising a metal oxide having the following composition is used.
_{Gd x (Fe 1 - y A} y) 3 - x O 4
(Where A is at least one selected from Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr, and 0.25 ≦ x ≦ 1.25; 0 ≦ y ≦ 0.5.) A carrier for an electrophotographic developer, wherein a carrier coating layer is provided on the surface of carrier particles made of the material according to claim 1. 3. A carrier for an electrophotographic developer, wherein a carrier coating layer containing at least one of carbon, fullerene and carbon nanotube is provided on the surface of carrier particles made of the material according to claim 1. 5. The carrier for an electrophotographic developer according to claim 4, wherein the particle size of carbon and fullerene is 0.01 to 0.2 [mu] m. 5. The carrier for an electrophotographic developer according to claim 4, wherein the carbon nanotube has a shape of 0.01 to 0.1 [mu] m and a length of 0.05 to 0.5 [mu] m. The carrier according to any one of claims 4 to 6, wherein the content of carbon, fullerene, and carbon nanotube is 0.01 to 10 parts by weight based on 100 parts by weight of the resin. Agent carrier. The carrier according to any one of claims 1 to 7, wherein the metal oxide particles have an average particle diameter of 20 to 100 µm. 9. The carrier for an electrophotographic developer according to claim 1, wherein the proportion of the carrier having a particle size of less than 15 [mu] m in the carrier is 3% by weight or less. The carrier according to any one of claims 1 to 9, wherein the carrier particle material contains at least one of MnMgSr ferrite, Mn ferrite, magnetite, and hematite. The carrier for an electrophotographic developer according to claim 3, wherein the resin coating layer is a silicone resin. 12. The carrier for an electrophotographic developer according to claim 3, wherein the resin coating layer is a resin containing an aminosilane coupling agent. An electrophotographic developer comprising the carrier according to claim 1 and a toner. 14. The developer according to claim 13, wherein the toner has an average particle diameter of 4 to 10 [mu] m. 15. The electrophotographic developer according to claim 13, wherein the toner contains a release agent and / or a dispersion aid. 16. The developer according to claim 13, wherein the toner is produced by a polymerization method. The developer according to any one of claims 13 to 15, wherein the toner is prepared by dispersing a pigment in a resin without using a solvent. A two-component developing method, comprising developing using the developer according to claim 13. A two-component developing apparatus, wherein development is performed using the developer according to claim 13. A method for producing a carrier for electrophotographic development, wherein the carrier according to any one of claims 3 to 12 is produced using a fluidized bed coating apparatus. A method for producing a carrier for electrophotographic development, wherein the carrier according to any one of claims 1 to 12 is produced using a vibration sieve equipped with an ultrasonic oscillator.

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