JP3943514B2 - Electrophotographic developer carrier and method for producing the same - Google Patents

Description

上記式中、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、又はアリール基（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、又はアリーレン基（フェニレン基など）を示す。
【００１３】
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。その具体例としては、ＫＲ２７１、ＫＲ２７２、ＫＲ２８２、ＫＲ２５２、ＫＲ２５５、ＫＲ１５２（信越化学工業社製）、ＳＲ２４００、ＳＲ２４０６（東レダウコーニングシリコーン社製）などが挙げられる。
その他に、変性シリコーン樹脂を用いることもできる。例として、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を挙げることができ、具体例としては、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（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。
【００１４】
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％程度）含有させることができる。具体例としては次のようなものが挙げられる。

【００１５】
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で又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、クロルポリスチレン、ポリ−α−メチルスチレン、スチレン−クロルスチレン共重合体、スチレン−プロピレン共重合体、スチレン−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。
【００１６】
また、本発明では樹脂層の中に、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。このような添加剤としてはフラーレン、カーボンナノチューブ、カーボン等が挙げられる。フラーレンはＣ_６０、Ｃ_７０、Ｃ_８２、Ｃ_８４、更に高分子量のフラーレンなどを使用できる。
フラーレンや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。
フラーレンや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。
【００１７】
フラーレンの粒径は０．０１〜０．２μｍとし、好ましくは０．０１〜０．１μｍとする。粒径が０．０１μｍ未満の場合には凝集等が生じ易く、０．２μｍより大きいと分散状態が低下するため適していない。
カーボンナノチューブの形状は、直径０．０１〜０．１μｍφで、長さ０．０５〜０．５μｍとし、好ましくは直径０．０１〜０．０５μｍφで、長さ０．０５〜０．１μｍとする。直径が０．０１μｍφ、長さが０．０５μｍより小さいと凝集が生じ易く、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するため適していない。
カーボンとしては、カーボンブラック等がある。粒径は、０．０１〜０．２μｍとする。０．０１μｍより小さいと粉塵の問題があり、０．２μｍ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。
【００１８】
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、或いは被覆用樹脂溶液に投入して、ボールミル、ビーズミルなどを使用した分散機、或いは高速回転する羽根を備えた撹拌機を使用することによって均一に分散させ、この分散液をキャリア表面にスプレー塗布などによりコートする。
キャリア表面に樹脂層を形成する方法としては、スプレードライ法、浸漬法、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、均一なコート層が形成できるので適している。
コート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０．０１〜１０重量部とする必要がある。含有量が０．０１重量部より小さいと耐久性の向上が認められず、１０重量部より大きいと樹脂層が脆くなって耐久性が劣化する。
【００１９】
キャリア粒子表面上に形成する樹脂層やフラーレン、カーボンナノチューブ、カーボンを含む樹脂層の厚みは、通常０．０２〜１μｍ、好ましくは０．０３〜０．８μｍとする。厚みが０．０２μｍより薄いと耐久性の向上が十分でなく、１μｍより厚いと膜剥がれ現象が生じ、帯電特性の安定性が低下する。
被覆後のキャリア平均粒径は、重量平均粒径Ｄｗで２０〜７０μｍの範囲とし、好ましくは３０μｍ〜６０μｍの範囲とする。Ｄｗが７０μｍよりも大きいと、キャリア付着は起り難いがドット再現性が悪くなる。Ｄｗが２０μｍより小さくな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難くなる。
【００２０】
キャリア付着は、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。画像部又は地肌部の電界が強いほどキャリア付着し易い。しかし、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、地肌部に比べてキャリア付着は起り難い。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。
本発明ではこのキャリア付着の対策として、磁気特性の改良を材料面から行なったが、更に１５μｍより小さい粒径を有する粒子の含有割合を３重量％以下、好ましくは１重量％以下にすると良い。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。そこで、重量平均粒径Ｄｗが２５〜４５μｍ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く、１重量％以下とすると、キャリア付着は更に改善されることが判明した。
【００２１】
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樹脂被膜を形成することにより得ることができる。この分級には、風力分級や篩分級（篩分け）等が包含される。キャリア粒子の製造には、振動篩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篩では、小粒径の粒子を分級しようとすると、その篩（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、分級のための作業性は非常に悪いものであった。
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、篩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。金網を振動させる周波数は、２０〜５０ｋＨｚ、好ましくは３０〜４０ｋＨｚとする。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。
【００２２】
本発明では、分級した磁性粒子の表面に樹脂被膜を形成するが、磁性粒子の粉砕物粒子の表面に樹脂被膜を形成した後、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篩機を用いて行うのが好ましい。
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、カーボン等の少なくとも１種を含む樹脂層により行なう。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易くなるため、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、カーボン等の含有量と膜厚でコントロールする。
更に本発明では、金属酸化物に加えて、マグネタイト、ヘマタイト、ＭｎＭｇＳｒ系フェライト、Ｍｎ系フェライトなどの材料を１種又は２種以上組み合わせて使用してもよい。
【００２３】
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製法によって作成された不定形又は球形のトナーであり、磁性トナー及び非磁性トナーの何れも使用可能である。
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挙げられる。
【００２４】
ビニル樹脂としては、ポリスチレン、ポリ−ｐ−クロルスチレン、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独重合体：スチレン−ｐ−クロルスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−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−クロルメタクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニル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挙げられる。
【００２５】
ポリエステル樹脂としては、下記のＬ群に示したような２価のアルコールと、Ｍ群に示したような二塩基酸塩からなるものであり、更に、Ｎ群に示したような３価以上のアルコール又はカルボン酸を第三成分として加えてもよい。
Ｌ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。
【００２６】
Ｍ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、又はこれらの酸無水物若しくは低級アルコールのエステル等。
Ｎ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。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又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、エポキシ基と反応する活性水素を分子中に２個以上有する化合物とを反応してなるものなどが挙げられる。
【００２７】
トナーに用いる顔料としては以下のものが用いられる。
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。
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。
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。
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。
【００２８】
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。
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。
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挙げられる。
これらは１種又は２種以上を使用することができる。
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。
【００２９】
トナーには電荷制御剤をトナー粒子内部に配合（内添）しても良く、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できる。
トナーを正電荷性に制御するものとして、ニグロシン及び四級アンモニウム塩、イミダゾール金属錯体や塩類を、単独で或いは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。
【００３０】
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挙げられる。中でも融点が６５〜９０℃のものが好ましく、６５℃より低いとトナーの保存時のブロッキングが発生し易くなり、９０℃より高いと定着ローラー温度が低い領域でオフセットが発生し易くなる場合がある。
離型剤等の分散性を向上させるなどの目的で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種以上混合して用いても良い。
【００３１】
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。このような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。
更に、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。疎水化処理剤としては、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が挙げられる。
無機微粉体はトナーに対して０．１〜２重量％の割合で使用するのが好ましい。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％を超えると、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易い傾向がある。
【００３２】
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。粉砕法により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又は染料、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、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、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又は固着させ、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。
【００３３】
トナーの重量平均粒径は４〜１０μｍとし、更に好ましくは４〜８μｍとする。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の問題が生じ易い。また、１０μｍを超えると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。
また、重合法によりトナーを作製する方法の一例としては、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方法が挙げられる。造粒法は特に限定されない。
【００３４】
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共に、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。
ウレア変性ポリエステル系樹脂のＴｇは４０〜６５℃、好ましくは４５〜６０℃とする。その数平均分子量Ｍｎは２５００〜５００００、好ましくは２５００〜３００００とする。その重量平均分子量Ｍｗは１万〜５０万、好ましくは３万〜１０万とする。
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されている。
【００３５】
得られた乾燥後のトナーの粉体を風力分級し、上記最適な混合条件により混合機により無機微粒子などからなる添加剤を粒子表面に付着又は固着させる。また、電荷制御剤を乾燥後のトナー粉体表面に打込んで固着注入させた後、無機微粒子などからなる添加剤を粒子表面に付着又は固着させても良い。電荷制御剤を表面に打込むことによりトナーの帯電量が制御し易くなる。
混合したり、固着注入したりする手段としては、高速で回転する羽根によって粉体混合物に衝撃力を加える方法、高速気流中に粉体混合物を投入し、加速させ、粒子同士又は複合化した粒子を適当な衝突板に衝突させる方法などがある。
トナーの流動性はトナーの形状に影響されるが、トナーの平均円形度が０．９０〜０．９９である非常に球形に近いトナーの場合には流動性に優れ、シャープ性やベタ均一性に優れた高画質化を実現できる。重合法の場合、球形に近いトナーが得易い。
【００３６】
現像剤として使用する場合は、上記トナーと前述した磁性キャリアを所定の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挙げられる。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、１０〜７０重量部であることが好ましい。
また、本発明の現像剤には、実質的に悪影響を与えない範囲内で更に他の添加剤を現像性向上剤として少量用いることもできる。このような添加剤としては、例えばテフロン（登録商標）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；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；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が挙げられる。
【００３７】
【実施例】
以下、実施例及び比較例により本発明を更に具体的に説明するが、本発明はこれらの実施例により何ら限定されるものではない。なお、実施例及び比較例中の配合における部数は全て重量部である。
【００３８】
実施例１〜５、比較例１〜２
＜トナー製造＞

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１１０ｒｐｍで溶融混練した。混練物を圧延冷却した後、カッターミルで粗粉砕し、更にジェット気流を用いた粉砕機で微粉砕した後、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。
次いで、上記母体着色粒子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。
【００３９】
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_ＸＦｅ_３−ＸＯ_４のＤｙ組成Ｘを下記のように変化させて、実施例１〜５及び比較例１〜２で用いる磁性材粒子を作製した。

各磁性材粒子は次のようにして作製した。
Ｄｙ酸化物、Ｆｅ酸化物を所定量秤量した後、ボールミルを用いて５時間混合し、電気炉にて９００℃で３時間仮焼した後、こ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にて１３００℃で５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、Ｄｙ酸化物とＦｅ酸化物からなる磁性材粒子を得た。
その後、それぞれの磁性材粒子の表面に、シリコーン樹脂からなるコート層を設けてキャリアを得た。即ち、シリコーン樹脂１００部を希釈して固形分５重量％の分散液とし、流動床型コーティング装置を用いて１００℃の雰囲気下で、上記磁性材粒子表面上に該分散液を、約４０ｇ／ｍｉｎの割合で塗布し、更に２４０℃で２時間加熱して、膜厚０．５５μｍの樹脂コート膜を形成した。
各実施例及び比較例のキャリア平均粒径（α）と、１５μｍより小さい粒径を有する粒子の含有割合（β）を次に示す。

【００４０】
上記のようにして得られたトナーとキャリアを、キャリア９７．５部に対しトナー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、耐久試験を行った。
評価項目は、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、画質上でのかぶりである。その結果を表１に示す。
また、キャリアの磁気特性を振動試料型磁力計〔東英工業（株）〕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。
【００４１】
実施例６〜７、比較例３〜４
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．２５（Ｆｅ_１−ＹＡｌ_Ｙ）_２．７５Ｏ_４のＡｌ組成Ｙを下記のように変化させて実施例６〜７及び比較例３〜４で用いる磁性材粒子を作製した。

各磁性材粒子は、Ｄｙ酸化物、Ｆｅ酸化物、Ａｌ酸化物を所定量秤量して用いた点以外は実施例１と同様にして作製し、それぞれの磁性材粒子の表面にシリコーン樹脂からなるコート層を設けてキャリアを得た。
各実施例及び比較例のキャリア平均粒径（α）と、１５μｍより小さい粒径を有する粒子の含有割合（β）を次に示す。

上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。また、キャリアの磁気特性についても実施例１と同様にして測定した。その結果を図２に示す。
【００４２】
実施例８
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．５Ｆｅ_２．５Ｏ_４の粒子を実施例１と同様にして作製し、該磁性材粒子の表面に、シリコーン樹脂とフラーレンＣ_６０の混合物を用いた点以外は実施例１と同様にしてコート層を設け、キャリアを得た。
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た平均粒径が０．０２５μｍのものを用い、シリコーン樹脂１００部中に、ボールミルを用いてフラーレンＣ_６０１部を分散させ、この分散液を希釈して固形分５重量％の分散液にして塗布した。
得られたキャリア平均粒径は３５．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４３】
実施例９
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
実施例８と同様にしてＤｙ_０．５Ｆｅ_２．５Ｏ_４からなる磁性材粒子を作製し、該磁性材粒子の表面に、シリコーン樹脂とフラーレンＣ_６０にＣ_７０が３０重量％混入しているものの混合物を用いた点以外は実施例１と同様にしてコート層を設け、キャリアを得た。
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た平均粒径が０．０３５μｍのものを用い、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５重量％の分散液にして塗布した。
得られたキャリア平均粒径は３５．８μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４４】
実施例１０
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
実施例８と同様にしてＤｙ_０．５Ｆｅ_２．５Ｏ_４からなる磁性材粒子を作製し、該磁性材粒子の表面に、シリコーン樹脂とカーボンナノチューブの混合物を用いた点以外は実施例１と同様にしてコート層を設け、キャリアを得た。
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た、直径が０．０１〜０．１μｍφで長さが０．０５〜０．５μｍのものを用い、シリコーン樹脂１００部中に、ボールミルを用いてカーボンナノチューブ１部を分散させ、この分散液を希釈して固形分５重量％の分散液にして塗布した。
得られたキャリア平均粒径は３５．８μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４５】
実施例１１
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
実施例８と同様にしてＤｙ_０．５Ｆｅ_２．５Ｏ_４からなる磁性材粒子を作製し、該磁性材粒子の表面に、シリコーン樹脂とＣ_６０及びカーボンの混合物を用いた点以外は実施例１と同様にしてコート層を設け、キャリアを得た。
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た平均粒径が０．０４μｍのものを用い、カーボンは平均粒径０．０４μｍのものを用い、シリコーン樹脂１００部中に、ボールミルを用いてＣ_６００．５部とカーボン０．５部を分散させ、この分散液を希釈して固形分５重量％の分散液にして塗布した。
得られたキャリア平均粒径は３５．８μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４６】
実施例１２
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．５Ｆｅ_２．５Ｏ_４の粒子を実施例１と同様にして作製し、該磁性材粒子とＭｎＭｇＳｒフェライト粒子を１：１の割合で混合機により混合した。次いで、該混合粒子の表面に実施例１と同様にしてシリコーン樹脂からなるコート層を設けてキャリアを得た。
得られたキャリア平均粒径は３５．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４７】
実施例１３
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．５Ｆｅ_２．５Ｏ_４の粒子を実施例１と同様にして作製し、該磁性材粒子とＭｎフェライト粒子を１：１の割合で混合機により混合した。次いで、該混合粒子の表面に実施例１と同様にしてシリコーン樹脂からなるコート層を設けてキャリアを得た。
得られたキャリア平均粒径は３５．８μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４８】
実施例１４
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．５Ｆｅ_２．５Ｏ_４の粒子を実施例１と同様にして作製し、該磁性材粒子とマグネタイト粒子を１：１の割合で混合機により混合した。次いで、該混合粒子の表面に実施例１と同様にしてシリコーン樹脂からなるコート層を設けてキャリアを得た。
得られたキャリア平均粒径は３５．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００４９】
実施例１５
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
金属酸化物磁性材Ｄｙ_０．５Ｆｅ_２．５Ｏ_４の粒子を実施例１と同様にして作製し、該磁性材粒子とヘマタイイト粒子を１：１の割合で混合機により混合した。次いで、該混合粒子の表面に実施例１と同様にしてシリコーン樹脂からなるコート層を設けてキャリアを得た。
得られたキャリア平均粒径は３５．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００５０】
実施例１６
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
実施例８と同様にしてＤｙ_０．５Ｆｅ_２．５Ｏ_４からなる磁性材粒子を作製し、該磁性材粒子の表面に、シリコーン樹脂とアミノシランカップリング剤の混合物を用いた点以外は実施例１と同様にしてコート層を設け、キャリアを得た。
上記混合物は、シリコーン樹脂１００部中に、ボールミルを用いてアミノシランカップリング剤〔Ｈ_２Ｎ（ＣＨ_２）_３Ｓｉ（ＯＣ_２Ｈ_５）_３〕５部を分散させ、この分散液を希釈して固形分５重量％の分散液にして塗布した。
得られたキャリア平均粒径は３５．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００５１】
比較例５
＜トナー製造＞
実施例１と同じ。
＜キャリア製造＞
磁性材としてＭｎＭｇＳｒフェライトを用いた点以外は、実施例１と同様にしてキャリアを作製した。キャリア平均粒径は３６．７μｍ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。
上記のようにして得られたトナーとキャリアを用い、実施例１と同様にして二成分現像剤を作製し画像評価実験、耐久試験を行った。その結果を表１に示す。
【００５２】
以上の実施例及び比較例の実験結果を下記表１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（５段階評価、５万枚コピー時）、かぶり（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、かぶりはＡからＥまでの５段階評価を行った。「Ａ：良」から「Ｅ：悪」に向って順に悪くなることを表す。
【表１】

【００５３】
表１から、Ｆｅ酸化物とＤｙ酸化物を原料とする金属酸化物Ｄｙ_ＸＦｅ_３−ＸＯ_４において、Ｄｙ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る。
また、Ｄｙ_Ｘ（Ｆｅ_１−ＹＡ_Ｙ）_３−ＸＯ_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共に良好な画像品質が得られ、且つ耐久特性が非常に改善されることが分る。
図１からは、Ｄｙ組成Ｘが０．２５より小さいと保磁力Ｈｃが大きく、キャリアとして適していないことが分る。
図２からは、添加物Ａlの組成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る。
【００５４】
【発明の効果】
本発明によれば、磁気特性に優れ、高機能なコート層を持ち、キャリア付着が起き難く、帯電安定性に優れた、高画質で高耐久な電子写真現像剤用キャリアを提供できる。
【図面の簡単な説明】
【図１】Ｄｙ組成Ｘと磁気特性の関係を示す図。
【図２】添加物Ａlの組成Ｙと磁気特性の関係を示す図。
【符号の説明】
４πＭｓ 飽和磁化
Ｈｃ 保磁力
Ｔｃ キュリー温度[0001]
【Technical field】
The present invention relates to a carrier for an electrophotographic developer, a method for producing the same, an electrophotographic developer using the carrier, and a two-component developing method and apparatus using the developer.
[0002]
[Prior art]
As far as the present inventors know, there is no patent using a metal oxide made of Fe oxide and Dy oxide as a carrier. Conventionally, Ni—Zn based ferrite and Mn—Zn based ferrite described in Patent Document 1 are used as carriers. In Patent Document 2, etc., Mg—Zn-based ferrite is proposed. 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 photosensitive member increases due to the small magnetization. Further, there is Patent Document 3 as a patent for dispersing fine particles in a carrier coat layer. This patent disperses titanium dioxide powder in a resin and aims to improve image quality and improve developer life. Patent Document 4 proposes a carrier whose surface is coated with a silicone resin containing silicon carbide. The aim of the present invention is to improve the durability of the developer. However, the coating layer of the developer also plays a role of controlling electric characteristics, and it is difficult to adjust with these additives, and it is necessary to add another additive.
Conventionally, carbon has been added to the coating layer in order to adjust the resistance of the developer. For example, in Patent Document 5, the amount of carbon in the resin coat layer is defined in relation to the amount of carbon in the toner so as to prevent problems such as brush marks and toner scattering with high image quality. However, carbon cannot increase the mechanical strength of the coating layer, and its durability is limited.
[0003]
[Patent Document 1]
Japanese Examined Patent Publication No. 53-15040
[Patent Document 2]
JP 58-145621 A
[Patent Document 3]
Japanese Patent No. 2555704
[Patent Document 4]
JP 58-207054 A
[Patent Document 5]
Japanese Patent No. 2643568
[0004]
[Problems to be solved by the invention]
The present invention provides a carrier for an electrophotographic developer having an excellent magnetic property, having a highly functional coating layer, hardly causing carrier adhesion, excellent charging stability, high image quality and high durability, a method for producing the same, and the carrier It is an object of the present invention to provide an electrophotographic developer using a developer and a two-component developing method and apparatus using the developer.
[0005]
[Means for Solving the Problems]
  The above-mentioned problems are as follows:21).
  1) Fe oxide and Dy oxide as raw materialsIncludeA carrier for an electrophotographic developer, wherein a metal oxide having the following composition formula is used as a magnetic material. However,In the composition formulaA is at least one selected from Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr.
              Dy_X(Fe_1-YA_Y)_3-XO₄
                (0.25 ≦ X ≦ 1.25, 0 <Y ≦ 0.5)
  2) A resin coating layer is provided on the surface of carrier particles.1)The carrier for an electrophotographic developer according to the description.
  3) The resin coating layer is made of silicone resin2The carrier for an electrophotographic developer described in the above.
  4) The resin coating layer is made of a resin containing an aminosilane coupling agent.2Or3The carrier for an electrophotographic developer described in the above.
  5The resin coating layer includes at least one of carbon, fullerene, and carbon nanotube.2) ~4) The carrier for an electrophotographic developer according to any one of the above.
  6) The particle size of carbon or fullerene is 0.01 to 0.2 μm5The carrier for an electrophotographic developer described in the above.
  7) The shape of the carbon nanotube is 0.01 to 0.1 μm in diameter and 0.05 to 0.5 μm in length.5The carrier for an electrophotographic developer described in the above.
  8) The total content of carbon, fullerene, and carbon nanotube is 0.01 to 10 parts by weight with respect to 100 parts by weight of the resin.5) ~7) The carrier for an electrophotographic developer according to any one of the above.
  9) The carrier particles provided with the resin coating layer have a weight average particle diameter of 20 to 70 μm.8) The carrier for an electrophotographic developer according to any one of the above.
  10) The content ratio of the particles having a particle size of less than 15 μm in the carrier particles is 3% by weight or less 1) to9) The carrier for an electrophotographic developer according to any one of the above.
  111) to at least one selected from magnetite, hematite, MnMgSr ferrite and Mn ferrite in addition to metal oxide10) The carrier for an electrophotographic developer according to any one of the above.
  121) ~11An electrophotographic developer using the carrier for an electrophotographic developer according to any one of 1).
  131) ~11An electrophotographic developer, and a toner having a weight average particle diameter of 4 to 10 μm.
  141) ~11The electrophotographic developer according to any one of the above) and a toner having an average circularity of 0.90 to 0.99.
  151) ~11An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of (1) and a toner containing a release agent and an additive that aids dispersion.
  161) ~11An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of 1) and a toner prepared by a polymerization method.
  171) ~11An electrophotographic developer carrier according to any one of the above and a toner in which a pigment is dispersed in a resin without using a solvent.
  18)12) ~17And a developing method using the electrophotographic developer according to any one of the above.
  19)12) ~17The two-component developing device is characterized in that development is performed using the electrophotographic developer according to any one of the above.
  20It is produced using a fluidized bed type coating device.2) ~8) For producing a carrier for an electrophotographic developer.
  21) It is produced using a vibration sieve equipped with an ultrasonic oscillator.11The method for producing a carrier for electrophotographic development according to any one of the above.
[0006]
Hereinafter, the present invention will be described in detail.
In order to realize high image quality, it is necessary to have excellent dot reproducibility, uniformity of image density, image contrast, and the like. For that purpose, the effect of reducing the particle size of the carrier is very large, and the realization of the reduction of the particle size of the carrier is the most important. 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 has a magnetic surface (development characteristics, conveyance force, stirring force), an electrical surface (development characteristics, charging characteristics), and a mechanical surface (durability, charging stability, photoconductor wear). Optimization) is required. When the particle size of the carrier is reduced, all the conditions of the magnetic, electrical, and mechanical aspects change, and these conditions are optimized again, including the materials and other aspects. The need is coming out. In particular, in terms of magnetic properties, the magnetic force of a single carrier is reduced by reducing the particle size of the carrier, so that it acts on a small electrostatic force or mechanical force, leaving extra space. The phenomenon that the carrier adheres easily occurs. As a countermeasure, even if the carrier is small, it is necessary to increase the magnetic force, and it is necessary to increase the saturation magnetization more than ever. In order to increase the saturation magnetization, it is necessary to use a material composed of atoms with high magnetic ability, and a metal oxide material composed of Fe oxide and Dy oxide having a large saturation magnetization is an optimal material and is used as a carrier. Suitable for
[0007]
The carrier for an electrophotographic developer according to the present invention is characterized by using the metal oxide having the above specific composition using Fe oxide and Dy oxide as raw materials, whereby optimum magnetic properties can be obtained, and small particles Even in the case of a diameter carrier, carrier adhesion can be prevented.
FIG. 1 shows changes in the magnetic properties of the metal oxide having the specific composition with respect to the Dy composition X (see Examples 1 to 5 and Comparative Examples 1 and 2 to be described later). The metal oxide depends on the Dy composition. The magnetic properties change very steeply. In particular, the saturation magnetization changes drastically, and as the Dy composition X increases, the saturation magnetization decreases, and becomes almost zero at X = 1.5. Further, the coercive force decreases as the Dy composition X increases and becomes 500 Oe or less. The Curie temperature decreases as the Dy composition X increases, and reaches 0 ° C. near X = 1.5. Therefore, the composition range that can be used as a carrier is a composition range of 0.25 ≦ X ≦ 1.25. When X is smaller than 0.25, the saturation magnetization is large, and an abnormal image such as a toner brush trace appears and cannot be used as a carrier.
[0008]
In the present invention, at least one additive A selected from Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr is added to the metal oxide having the specific composition. May be added.
With the additive A, the magnetic properties can be adjusted, and the stability of the material can be improved. However, if the amount of addition increases, the magnetic properties deteriorate and segregation of the additive occurs._0.25(Fe_1-YA_Y)_2.75O₄Therefore, it is necessary to satisfy 0 <Y ≦ 0.5. When the composition Y is larger than 0.5, the Curie temperature Tc is lowered, which is not preferable as a carrier.
[0009]
In addition, in order to achieve optimization of development characteristics, it is necessary to devise measures that allow electrical optimization. To achieve this, adjustment of the electrical characteristics of the carrier, that is, a coat layer on the carrier surface is required. The resistance adjustment is important. In the present invention, carbon, fullerene, carbon nanotubes, etc., which have excellent mechanical wear characteristics, are used as the resistance adjusting material. By coating a resin containing these materials, the carrier resistance is simply adjusted. The durability of the carrier itself was improved.
As described above, according to the present invention, there is provided a long-lasting and highly durable carrier that does not adhere to a carrier even with a small particle diameter, stabilizes the charging characteristics and developing characteristics of the toner, and can realize high image quality indefinitely. be able to.
[0010]
As a method for producing a metal oxide using Fe oxide, Dy oxide, or the like as raw materials, there is a method using a solid phase reaction of these oxides or the like.
That is, Fe oxide, Dy oxide, additives and the like are weighed and mixed using a ball mill. Next, it is calcined at 600 to 1000 ° C. for 2 to 5 hours with an electric furnace or the like, and the calcined product is put into a ball mill and pulverized for about 12 hours. A binder is added to the obtained powder, and it is spray-dried in a heated atmosphere and granulated, and this molded product is fired at 1100 to 1300 ° C. for 2 to 5 hours in an electric furnace or the like. The fired product is coarsely pulverized, finely pulverized, and classified into a predetermined particle size by a classifier to obtain metal oxide particles composed of Fe oxide, Dy oxide, additives, and the like.
[0011]
When a magnetic field of 1000 oersted (Oe) is applied to the carrier particles used in the present invention, the magnetic moment of the particles is preferably 70 emu / g or more, more preferably 80 emu / g or more, and the upper limit is not particularly limited. About 250 emu / g. If the magnetic moment is less than 70 emu / g, carrier adhesion tends to occur, and if it exceeds 250 emu / g, the head of the magnetic brush appears on the image, which is not suitable.
The magnetic moment can be measured by a BH curve tracer or VSM. For example, using a BH curve tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier core particles are packed in a cylindrical cell and set in an apparatus, and a BH hysteresis curve is measured. From the characteristics, a magnetic moment of 1000 oersted is obtained.
[0012]
The carrier of the present invention usually forms a resin layer on the surface of the carrier particles. Although various conventionally well-known things used for manufacture of a carrier can be used as resin, For example, the silicone resin containing the repeating unit represented by a following formula is suitable.
[Chemical 1]

In the above formula, R¹Represents 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 (such as a phenyl group or a tolyl group), and R²Represents an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group).
[0013]
In the present invention, a straight silicone resin can be used. Specific examples thereof include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone), and the like.
In addition, a modified silicone resin can also be used. Examples include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, alkyd-modified silicone, etc. Specific examples include modified silicone: KR-5208, polyester-modified product: KR -5203, alkyd modified product: KR-206, urethane modified product: KR-305 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), epoxy modified product: SR2115, alkyd modified product: SR2110 (above, manufactured by Toray Dow Corning Silicone), etc. Is mentioned.
[0014]
In the present invention, the silicone resin may contain an appropriate amount (about 0.001 to 30% by weight) of an aminosilane coupling agent. Specific examples include the following.

[0015]
Furthermore, in the present invention, as the resin for coating the carrier particle surface, the following can be used alone or mixed with the silicone resin.
Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer) Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer, etc.) Styrenic resins such as styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.
[0016]
In the present invention, an additive for adjusting resistance and improving durability may be dispersed in the resin layer. Examples of such additives include fullerene, carbon nanotube, and carbon. Fullerene is C₆₀, C₇₀, C₈₂, C₈₄Furthermore, a high molecular weight fullerene can be used.
Fullerenes and carbon nanotubes can be synthesized by a resistance heating method in which a graphite rod is directly heated in a rare gas or an arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas. is there.
As the fullerene or carbon nanotube, a material in which a metal such as La, Y, or Sc is included in the internal space can be used. For the synthesis of metal-encapsulated fullerene, a metal oxide (La₂O₃And the like, or a carbon rod containing a metal oxide is synthesized by injecting a carbon chip containing a metal oxide into a crucible anode to cause the arc discharge.
[0017]
The particle size of fullerene is 0.01 to 0.2 μm, preferably 0.01 to 0.1 μm. When the particle size is less than 0.01 μm, aggregation or the like is likely to occur. When the particle size is greater than 0.2 μm, the dispersion state is lowered, which is not suitable.
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 0.1 μm in length. . Aggregation tends to occur when the diameter is smaller than 0.01 μmφ and the length is smaller than 0.05 μm, and when the diameter is larger than 0.1 μmφ and the length is larger than 0.5 μm, the uniformity of dispersion is lowered.
Examples of carbon include carbon black. The particle size is 0.01 to 0.2 μm. If it is smaller than 0.01 μm, there is a problem of dust, and if it is larger than 0.2 μm, the dispersion becomes worse and it becomes difficult to form a uniform film.
[0018]
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 ball mill, a bead mill or the like, or a stirrer equipped with a blade rotating at high speed is used. Then, the dispersion is coated uniformly on the surface of the carrier by spray coating or the like.
As a method for forming the resin layer on the carrier surface, a known method such as a spray drying method, a dipping method, or a powder coating method can be used. In particular, a method using a fluidized bed type coating apparatus is suitable because a uniform coated layer can be formed by forming a fluidized bed of a carrier and spraying it into the fluidized bed.
The content of fullerene, carbon nanotube, and carbon with respect to the resin of the coat layer needs to be 0.01 to 10 parts by weight with respect to 100 parts by weight of the resin. When the content is less than 0.01 parts by weight, no improvement in durability is observed. When the content is more than 10 parts by weight, the resin layer becomes brittle and the durability deteriorates.
[0019]
The thickness of the resin layer or fullerene, carbon nanotube, or carbon-containing resin layer formed on the carrier particle surface is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. When the thickness is less than 0.02 μm, the durability is not sufficiently improved. When the thickness is more than 1 μm, a film peeling phenomenon occurs and the stability of the charging characteristics is lowered.
The carrier average particle diameter after coating is in the range of 20 to 70 μm, preferably in the range of 30 to 60 μm, as the weight average particle diameter Dw. When Dw is larger than 70 μm, carrier adhesion hardly occurs, but dot reproducibility is deteriorated. When Dw is smaller than 20 μm, the carrier adhesion increases and the stirring efficiency with the toner becomes poor, and it becomes difficult to obtain a uniform charge amount of the toner.
[0020]
Carrier adhesion indicates a phenomenon in which a carrier adheres to an image portion or a background portion of an electrostatic latent image. The stronger the electric field in the image area or background area, the easier the carrier adheres. However, since the electric field is weakened by developing the toner in the image portion, carrier adhesion is less likely to occur compared to the background portion. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller.
In the present invention, as a countermeasure against the carrier adhesion, the magnetic characteristics are improved from the material side. However, the content ratio of particles having a particle diameter smaller than 15 μm is preferably 3% by weight or less, preferably 1% by weight or less. In the case of a small particle size carrier, the majority of the carrier adhering to the carrier is fine particles of less than 15 μm. Therefore, when the carrier adhesion was evaluated by changing the weight ratio of particles smaller than 15 μm in a small particle carrier having a weight average particle diameter Dw of 25 to 45 μm, if particles having a particle diameter of 15 μm or less were 3 wt% or less, It was found that there was no major problem and carrier adhesion was further improved when the content was 1% by weight or less.
[0021]
The carrier of the present invention is obtained by pulverizing the magnetic material of the present invention, classifying the pulverized particles so as to obtain a predetermined particle size, and forming a resin film on the surface of the magnetic particles obtained by the classification. Obtainable. This classification includes wind classification, sieve classification (sieving), and the like. Vibrating sieves are preferably used for the production of carrier particles. However, in the conventional vibrating sieves, when trying to classify particles with a small particle size, the small mesh of the sieve (metal mesh) is immediately present. Therefore, the workability for classification was very bad.
The inventors of the present invention have made various studies in order to develop a method capable of efficiently and sharply cutting small-sized particles. When the particles are classified using a sieve, ultrasonic vibration is applied to the wire mesh. Thus, it has been found that small diameter particles of less than 15 μm can be efficiently and sharply cut. The frequency for vibrating the wire mesh is 20 to 50 kHz, preferably 30 to 40 kHz. The shape of the resonance member may be any shape suitable for vibrating the wire mesh, and is usually a ring shape.
[0022]
In the present invention, a resin film is formed on the surface of the classified magnetic particles, but it can also be produced by classifying the resin-coated carrier particles after forming a resin film on the surface of the pulverized particles of magnetic particles. . In this case, the classification of the resin-coated carrier particles is preferably performed using the above-described vibratory sieve with an ultrasonic oscillator.
In the present invention, the resistance of the carrier is adjusted by a resin layer containing at least one of fullerene, carbon nanotube, carbon and the like formed on the surface of the carrier particle. If the carrier resistance is too high, abnormal images such as white spots due to side effects of the edge effect will be generated. If the carrier resistance is too low, the uniformity of the solid image will be improved but carrier adhesion will easily occur. It is necessary to optimize the development conditions. The optimization of the carrier resistance is controlled by the content and film thickness of fullerene, carbon nanotube, carbon and the like.
Furthermore, in the present invention, in addition to the metal oxide, materials such as magnetite, hematite, MnMgSr ferrite, and Mn ferrite may be used alone or in combination.
[0023]
The developer of the present invention comprises the carrier and toner.
The toner used in the present invention contains a colorant, a charge control agent, a release agent, etc. in a binder resin mainly composed of a thermoplastic resin, and various conventionally known toners are used. Can do. This toner is an amorphous or spherical toner prepared by various production methods such as a pulverization method, a polymerization method, and a granulation method, and either a magnetic toner or a non-magnetic toner can be used.
Resins used for toner include 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. Is mentioned.
[0024]
As the vinyl resin, styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, and homopolymers thereof: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic copolymer Acid methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinylethyl ester Ter 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 copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.
[0025]
The polyester resin is composed of a dihydric alcohol as shown in the following L group and a dibasic acid salt as shown in the M group, and more than trivalent as shown in the N group. Alcohol or carboxylic acid may be added as a third component.
Group L: 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.
[0026]
Group M: 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, linolenic acid, or These acid anhydrides or esters of lower alcohols.
Group N: Trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid. The polyol resin includes an epoxy resin, an alkylene oxide adduct of dihydric phenol or its glycidyl ether, a compound having one active hydrogen in the molecule that reacts with an epoxy group, and an active hydrogen that reacts with an epoxy group in the molecule. And the like obtained by reacting with a compound having two or more compounds.
[0027]
The following pigments are used for the toner.
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.
Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. .
Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.
Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.
[0028]
Examples of purple pigments include fast violet B and methyl violet lake.
Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC.
Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.
These can use 1 type (s) or 2 or more types.
Especially for color toners, uniform dispersion of good pigments is essential. Instead of putting pigments directly into a large amount of resin, a master batch in which pigments are once dispersed at a high concentration is prepared and diluted. The method of throwing in is used. In this case, a solvent is generally used to assist dispersibility. However, there is a problem of environment and the like, and in the present invention, water is used for dispersion. When water is used, temperature control is important so that residual moisture in the masterbatch does not become a problem.
[0029]
In the toner, a charge control agent may be blended (internally added) inside the toner particles, or may be mixed (externally added) with the toner particles. The charge control agent makes it possible to optimally control the amount of charge according to the development system. In particular, in the present invention, the balance between the particle size distribution and the amount of charge can be further stabilized.
For controlling the toner to be positively charged, nigrosine, a quaternary ammonium salt, an imidazole metal complex and salts can be used alone or in combination of two or more. Further, salicylic acid metal complexes, salts, organic boron salts, calixarene compounds, and the like are used for controlling the toner to be negatively charged.
[0030]
In addition, 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, sazol wax, low molecular weight polyethylene, low molecular weight polypropylene, and alkyl phosphate ester. Among them, a melting point of 65 to 90 ° C. is preferable. When the temperature is lower than 65 ° C., blocking during storage of the toner is likely to occur, and when it is higher than 90 ° C., offset may be easily generated in a region where the fixing roller temperature is low. .
An additive may be added for the purpose of improving the dispersibility of a release agent or 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 two or more of these resins may be mixed and used.
[0031]
In order to improve the fluidity and the like of the toner, the toner surface may be surface-treated with inorganic fine powder. Examples of such inorganic fine powder include Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, and Zr. And oxides and composite oxides. Of these, fine particles of silicon dioxide (silica), titanium dioxide (titania), and alumina are preferably used.
Furthermore, it is effective to perform a surface modification treatment with a hydrophobizing agent or the like. Hydrophobing agents include dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, Examples thereof include p-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane, and the like.
The inorganic fine powder is preferably used at a ratio of 0.1 to 2% by weight based on the toner. If it is less than 0.1% by weight, the effect of improving the toner aggregation is poor, and if it exceeds 2% by weight, there is a tendency to cause problems such as toner scattering between fine wires, contamination in the machine, scratches and abrasion of the photoreceptor. .
[0032]
Examples of methods for producing the toner include pulverization methods and polymerization methods (suspension polymerization, emulsion polymerization, dispersion polymerization, emulsion aggregation, emulsion association, etc.), but are not limited to these production methods. 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, other additives, etc. are sufficiently mixed by a mixer such as a Henschel mixer. After that, a batch type two roll, a Banbury mixer and a continuous type twin screw extruder (for example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd., KCK 2) Thermal kneaders such as axial extruders, PCM type twin screw extruders manufactured by Ikekai Tekko Co., Ltd., KEX type twin screw extruders manufactured by Kurimoto Iron Works Co., Ltd. ), And after cooling, coarsely pulverize using a hammer mill or the like, and further finely pulverize using a fine pulverizer or mechanical pulverizer using a jet stream, and a classifier using a swirl stream Or a classifier using the Coanda effect Classifying the 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 passed through a sieve of 250 mesh or more to remove coarse particles and aggregated particles to obtain a toner.
[0033]
The weight average particle diameter of the toner is 4 to 10 μm, more preferably 4 to 8 μm. If the thickness is less than 4 μm, problems such as contamination inside the machine due to toner scattering during long-term use, image density reduction in a low-humidity environment, and poor photoreceptor cleaning are likely to occur. On the other hand, when the thickness exceeds 10 μm, the resolution of minute spots of 100 μm or less is not sufficient, and the scattering to the non-image portion is large and the image quality tends to be inferior.
Further, as an example of a method for producing a toner by a polymerization method, there is a method in which a monomer composition in which a colorant, a charge control agent and the like are added to a monomer is suspended in an aqueous medium and polymerized. The granulation method is not particularly limited.
[0034]
For example, in the toner of the present invention, an oily dispersion in which at least a polyester-based prepolymer containing an isocyanate group is dissolved in an organic solvent, a pigment-based colorant is dispersed, and a release agent is dissolved or dispersed in an aqueous medium. A urea-modified polyester resin having a urea group by dispersing in the presence of inorganic fine particles and / or fine polymer particles and reacting the prepolymer with a polyamine and / or a monoamine having an active hydrogen-containing group in the dispersion. And a liquid medium contained therein is removed from the dispersion containing the urea-modified polyester resin.
The Tg of the urea-modified polyester resin is 40 to 65 ° C, preferably 45 to 60 ° C. The number average molecular weight Mn is 2500-50000, preferably 2500-30000. The weight average molecular weight Mw is 10,000 to 500,000, preferably 30,000 to 100,000.
This toner contains, as a binder resin, a urea-modified polyester resin having a urea bond that has been increased in molecular weight by the reaction between the prepolymer and the amine. And the colorant is highly dispersed in the binder resin.
[0035]
The obtained toner powder after drying is air-classified, and an additive composed of inorganic fine particles or the like is adhered or fixed to the particle surface by a mixer under the optimum mixing conditions. Alternatively, the charge control agent may be applied to the surface of the dried toner powder and fixedly injected, and then an additive composed of inorganic fine particles may be adhered or fixed to the particle surface. The charge amount of the toner can be easily controlled by driving the charge control agent onto the surface.
As a means for mixing or fixing and injecting, a method of applying an impact force to the powder mixture with a blade rotating at high speed, a powder mixture is charged into a high-speed air stream, accelerated, and particles or composite particles There is a method of colliding with a suitable collision plate.
The fluidity of the toner is affected by the shape of the toner, but in the case of a very nearly spherical toner having an average circularity of 0.90 to 0.99, the fluidity is excellent, and sharpness and solid uniformity. Excellent image quality can be achieved. In the case of the polymerization method, it is easy to obtain toner having a nearly spherical shape.
[0036]
When used as a developer, the toner and the magnetic carrier described above are mixed at a predetermined ratio to obtain a two-component developer.
Further, when the magnetic toner is used, magnetic particles may be internally added to the toner particles. Examples of the magnetic material include ferromagnetic materials such as ferrite, magnetite, iron, nickel, cobalt, and alloys thereof. The average particle size of the magnetic material is preferably 0.1 to 1 μm. The content of the magnetic material is preferably 10 to 70 parts by weight with respect to 100 parts by weight of the toner.
In the developer of the present invention, other additives can be used in small amounts as a developability improver within a range that does not substantially adversely affect the developer. Examples of such additives include lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder and polyvinylidene fluoride powder; abrasives such as cerium oxide powder, silicon carbide powder and strontium titanate powder; carbon black powder And conductivity imparting agents such as zinc oxide powder and tin oxide powder.
[0037]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these Examples. In addition, all the parts in the mixing | blending in an Example and a comparative example are a weight part.
[0038]
Examples 1-5, Comparative Examples 1-2
<Toner production>

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 110 rpm. The kneaded product is rolled and cooled, then coarsely pulverized with a cutter mill, further pulverized with a pulverizer using a jet stream, and then classified into a particle size distribution having an average particle size of 6.5 μm using a swirling air classifier. did.
Next, 1 part of silica powder was mixed with 100 parts of the base colored particles with a super mixer to obtain a toner.
[0039]
<Carrier manufacturing>
Metal oxide magnetic material Dy_XFe_3-XO₄Magnetic material particles used in Examples 1 to 5 and Comparative Examples 1 and 2 were prepared by changing the Dy composition X of the following.

Each magnetic material particle was produced as follows.
Dy oxide and Fe oxide were weighed in predetermined amounts, mixed for 5 hours using a ball mill, calcined at 900 ° C. for 3 hours in an electric furnace, and then the calcined product was put into a ball mill and pulverized. The obtained powder was pressure-molded with a powder press to form a plate, and the molded product was fired at 1300 ° C. for 5 hours in an electric furnace. The fired product was cut with a cutter, coarsely pulverized, finely pulverized, and classified into a predetermined particle size by a classifier to obtain magnetic material particles composed of Dy oxide and Fe oxide.
Thereafter, a coat layer made of a silicone resin was provided on the surface of each magnetic material particle to obtain a carrier. That is, 100 parts of a silicone resin was diluted to obtain a dispersion having a solid content of 5% by weight, and the dispersion was applied to the surface of the magnetic material particles at a temperature of about 40 g / s in an atmosphere of 100 ° C. using a fluid bed type coating apparatus. The resin was applied at a rate of min and further heated at 240 ° C. for 2 hours to form a resin coat film having a thickness of 0.55 μm.
The carrier average particle diameter (α) of each Example and Comparative Example and the content ratio (β) of particles having a particle diameter smaller than 15 μm are shown below.

[0040]
The toner and the carrier obtained as described above were mixed at a ratio of 2.5 parts of toner to 97.5 parts of carrier to prepare a two-component developer.
The obtained developer was set in a copying machine in which the latent image carrier is an OPC drum photoreceptor and the cleaning method is blade cleaning, and an image evaluation experiment and a durability test were performed.
The evaluation items are image density, sharpness and solid uniformity as image characteristics, changes in charge amount during durability tests, evaluation of carrier adhesion, and fogging on image quality as durability characteristics. The results are shown in Table 1.
Further, the magnetic properties of the carrier were measured with a vibrating sample magnetometer [Toei Kogyo Co., Ltd.], and the saturation magnetization, coercive force, and Curie temperature were evaluated. The result is shown in FIG.
[0041]
Examples 6-7, Comparative Examples 3-4
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.25(Fe_1-YAl_Y)_2.75O₄Magnetic material particles used in Examples 6 to 7 and Comparative Examples 3 to 4 were prepared by changing the Al composition Y of the following.

Each magnetic material particle was prepared in the same manner as in Example 1 except that a predetermined amount of Dy oxide, Fe oxide, and Al oxide was used, and the surface of each magnetic material particle was made of a silicone resin. A coat layer was provided to obtain a carrier.
The carrier average particle diameter (α) of each Example and Comparative Example and the content ratio (β) of particles having a particle diameter smaller than 15 μm are shown below.

Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1. The carrier magnetic properties were also measured in the same manner as in Example 1. The result is shown in FIG.
[0042]
Example 8
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.5Fe_2.5O₄Were produced in the same manner as in Example 1, and a silicone resin and fullerene C were formed on the surface of the magnetic material particles.₆₀A carrier was obtained by providing a coat layer in the same manner as in Example 1 except that the above mixture was used.
Fullerene C₆₀Uses an arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas and has an average particle size of 0.025 μm, and a ball mill is used in 100 parts of a silicone resin. Fullerene C₆₀One part was dispersed, and the dispersion was diluted to a dispersion having a solid content of 5% by weight and applied.
The obtained carrier average particle diameter was 35.7 μm, and the content ratio of particles having a particle diameter smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0043]
Example 9
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Dy as in Example 8._0.5Fe_2.5O₄The magnetic material particles are made of a silicone resin and fullerene C on the surface of the magnetic material particles.₆₀To C₇₀A carrier layer was obtained by providing a coat layer in the same manner as in Example 1 except that a mixture containing 30% by weight was used.
Fullerene C₆₀To C₇₀Is mixed with 30% of the average particle size of 0.035 μm produced by the arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas. Inside, fullerene C using a ball mill₆₀To C₇₀Was dispersed and the dispersion was diluted to a dispersion having a solid content of 5% by weight and applied.
The obtained carrier average particle size was 35.8 μm, and the content ratio of particles having a particle size smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0044]
Example 10
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Dy as in Example 8._0.5Fe_2.5O₄A magnetic material particle comprising the above was prepared, and a coating layer was provided on the surface of the magnetic material particle in the same manner as in Example 1 except that a mixture of a silicone resin and a carbon nanotube was used to obtain a carrier.
Carbon nanotubes were produced by an arc discharge method in which an arc discharge was generated between two graphite rods in a rare gas, and the diameter was 0.01 to 0.1 μmφ and the length was 0.05 to 0.00. A carbon nanotube having a particle size of 5 μm was used, and 1 part of carbon nanotubes was dispersed in 100 parts of silicone resin using a ball mill, and this dispersion was diluted to a dispersion having a solid content of 5% by weight.
The obtained carrier average particle size was 35.8 μm, and the content ratio of particles having a particle size smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0045]
Example 11
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Dy as in Example 8._0.5Fe_2.5O₄The magnetic material particles are made of silicon resin and C on the surface of the magnetic material particles.₆₀A coating layer was provided in the same manner as in Example 1 except that a mixture of carbon and carbon was used to obtain a carrier.
C₆₀Uses an average particle size of 0.04 μm produced by an arc discharge method in which an arc discharge is generated between two graphite rods in a rare gas, and carbon has an average particle size of 0.04 μm. And 100 parts of silicone resin with C using a ball mill.₆₀0.5 part and 0.5 part of carbon were dispersed, and this dispersion was diluted to give a dispersion having a solid content of 5% by weight.
The obtained carrier average particle size was 35.8 μm, and the content ratio of particles having a particle size smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0046]
Example 12
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.5Fe_2.5O₄Were produced in the same manner as in Example 1, and the magnetic material particles and MnMgSr ferrite particles were mixed at a ratio of 1: 1 by a mixer. Next, a coating layer made of a silicone resin was provided on the surface of the mixed particles in the same manner as in Example 1 to obtain a carrier.
The obtained carrier average particle diameter was 35.7 μm, and the content ratio of particles having a particle diameter smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0047]
Example 13
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.5Fe_2.5O₄Were produced in the same manner as in Example 1, and the magnetic material particles and Mn ferrite particles were mixed at a ratio of 1: 1 by a mixer. Next, a coating layer made of a silicone resin was provided on the surface of the mixed particles in the same manner as in Example 1 to obtain a carrier.
The obtained carrier average particle size was 35.8 μm, and the content ratio of particles having a particle size smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0048]
Example 14
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.5Fe_2.5O₄Were produced in the same manner as in Example 1, and the magnetic material particles and magnetite particles were mixed at a ratio of 1: 1 by a mixer. Next, a coating layer made of a silicone resin was provided on the surface of the mixed particles in the same manner as in Example 1 to obtain a carrier.
The obtained carrier average particle diameter was 35.7 μm, and the content ratio of particles having a particle diameter smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0049]
Example 15
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Metal oxide magnetic material Dy_0.5Fe_2.5O₄Were prepared in the same manner as in Example 1, and the magnetic material particles and hematite particles were mixed at a ratio of 1: 1 by a mixer. Next, a coating layer made of a silicone resin was provided on the surface of the mixed particles in the same manner as in Example 1 to obtain a carrier.
The obtained carrier average particle diameter was 35.7 μm, and the content ratio of particles having a particle diameter smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0050]
Example 16
<Toner production>
Same as Example 1.
<Carrier manufacturing>
Dy as in Example 8._0.5Fe_2.5O₄A magnetic material particle comprising the above was prepared, and a coating layer was provided on the surface of the magnetic material particle in the same manner as in Example 1 except that a mixture of a silicone resin and an aminosilane coupling agent was used to obtain a carrier.
The above mixture was mixed with 100 parts of silicone resin using an aminosilane coupling agent [H₂N (CH₂)₃Si (OC₂H₅)₃5 parts were dispersed, and this dispersion was diluted to give a 5% solids dispersion.
The obtained carrier average particle diameter was 35.7 μm, and the content ratio of particles having a particle diameter smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0051]
Comparative Example 5
<Toner production>
Same as Example 1.
<Carrier manufacturing>
A carrier was produced in the same manner as in Example 1 except that MnMgSr ferrite was used as the magnetic material. The carrier average particle size was 36.7 μm, and the content ratio of particles having a particle size smaller than 15 μm was 2.8% by weight.
Using the toner and carrier obtained as described above, a two-component developer was prepared in the same manner as in Example 1, and an image evaluation experiment and a durability test were performed. The results are shown in Table 1.
[0052]
The experimental results of the above examples and comparative examples are shown in Table 1 below.
Evaluation items are image density, sharpness (five-step evaluation), solid uniformity (five-step 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 Toner charge amount), carrier adhesion (five-step evaluation, 50,000 copies), and fog (five-step evaluation, 50,000 copies).
Sharpness, solid uniformity, carrier adhesion, and fogging were evaluated in five stages from A to E. It shows that it becomes worse in order from “A: good” to “E: bad”.
[Table 1]

[0053]
From Table 1, metal oxide Dy using Fe oxide and Dy oxide as raw materials_XFe_3-XO₄In FIG. 5, it can be seen that when the Dy composition X is 0.25 ≦ X ≦ 1.25, there is no abnormal image quality such as carrier adhesion, high image quality, and excellent durability.
Dy_X(Fe_1-YA_Y)_3-XO₄The Al composition Y has a high image quality when 0 <Y ≦ 0.5. However, when the Al composition Y is greater than 0.5, the magnetic properties are degraded, and all the image quality is degraded.
In addition, by providing a resin coating layer containing fullerene, carbon nanotubes, carbon, etc., toner charging characteristics are stabilized, good image quality in both image density and sharpness is obtained, and durability characteristics are greatly improved. I understand that.
From FIG. 1, it can be seen that when the Dy composition X is smaller than 0.25, the coercive force Hc is large and it is not suitable as a carrier.
From FIG. 2, it can be seen that when the composition Y of the additive Al is larger than 0.5, the Curie temperature Tc is lowered and is not suitable as a carrier.
[0054]
【The invention's effect】
According to the present invention, it is possible to provide a high-quality and highly durable carrier for an electrophotographic developer that has an excellent magnetic property, has a highly functional coating layer, hardly adheres to a carrier, has excellent charging stability.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between Dy composition X and magnetic properties.
FIG. 2 is a graph showing the relationship between the composition Y of the additive Al and the magnetic properties.
[Explanation of symbols]
4πMs saturation magnetization
Hc coercivity
Tc Curie temperature

Claims (21)

Fe oxide, an electrophotographic developer carrier, characterized in that using a Dy oxide a metal oxide of the following composition formula containing as a raw material as a magnetic material. However, A in the composition formula is at least one selected from Mg, Al, Si, Ti, Cr, Mn, Co, Ni, Cu, Zn, Ga, and Sr.
_{Dy X (Fe 1-Y A} Y) 3-X O 4
(0.25 ≦ X ≦ 1.25, 0 <Y ≦ 0.5) The carrier for an electrophotographic developer according to claim 1, characterized in that a resin coating layer on the carrier particle surface. 3. The carrier for an electrophotographic developer according to claim 2, wherein the resin coating layer is made of a silicone resin. Claim 2 or 3 for an electrophotographic developer carrier according resin coating layer is characterized by comprising a resin containing an aminosilane coupling agent. The carrier for an electrophotographic developer according to any one of claims 2 to 4 , wherein the resin coating layer contains at least one of carbon, fullerene, and carbon nanotube. 6. The carrier for an electrophotographic developer according to claim 5 , wherein the particle size of carbon or fullerene is 0.01 to 0.2 [mu] m. 6. The carrier for an electrophotographic developer according to claim 5 , wherein the shape of the carbon nanotube is 0.01 to 0.1 [mu] m in diameter and 0.05 to 0.5 [mu] m in length. The carrier for an electrophotographic developer according to any one of claims 5 to 7 , wherein the total content of carbon, fullerene, and carbon nanotube is 0.01 to 10 parts by weight with respect to 100 parts by weight of the resin. The carrier for an electrophotographic developer according to any one of claims 1 to 8 , wherein the carrier particles provided with the resin coating layer have a weight average particle diameter of 20 to 70 µm. The carrier for an electrophotographic developer according to any one of claims 1 to 9 , wherein a content ratio of particles having a particle diameter of less than 15 µm in the carrier particles is 3% by weight or less. In addition to metal oxides, magnetite, hematite, MnMgSr ferrite, an electrophotographic developer according to any one of claims 1-10, characterized by containing at least one selected from Mn ferrite For carrier. An electrophotographic developer using the carrier for an electrophotographic developer according to any one of claims 1 to 11 . An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 11 and a toner having a weight average particle diameter of 4 to 10 µm. An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 11 and a toner having an average circularity of 0.90 to 0.99. An electrophotographic developer comprising: the carrier for an electrophotographic developer according to any one of claims 1 to 11 ; and a toner containing therein a release agent and an additive that aids dispersion. An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 11 and a toner prepared by a polymerization method. An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 11 and a toner in which a pigment is dispersed in a resin without using a solvent. Development using the electrophotographic developer according to any one of claims 12 to 17 , wherein the two-component developing method. A two-component developing apparatus, wherein development is performed using the electrophotographic developer according to any one of claims 12 to 17 . The method for producing a carrier for an electrophotographic developer according to any one of claims 2 to 8 , wherein the carrier is produced using a fluidized bed type coating apparatus. The method for producing a carrier for electrophotographic development according to any one of claims 1 to 11 , wherein the carrier is produced using a vibration sieve equipped with an ultrasonic oscillator.

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