JP4121252B2 - Electrostatic latent image developing carrier, developer, developing method and developing apparatus using the same - Google Patents

Description

（式中、Ｒは水素原子、ハロゲン原子、ヒドロキシ基、メトキシ基またはＣ₁〜Ｃ₄の低級アルキル基またはフェニル基を表わす。）
【００１５】
こうしたシリコーン樹脂の例として、たとえばストレートシリコーンとし、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、またその一部を有機化合物と、置換、付加することにより得られる変性シリコーンなどがあり、その例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。例としてはエポキシ変性：ＥＳ−１００１Ｎ、アクリル変性：ＫＲ−５２０８、ポリエステル変性：ＫＲ−５２０３、アルキッド変性：ＫＲ−２０６、ウレタン変性：ＫＲ−３０５（以上、信越化学工業社製）、エポキシ変性：ＳＲ２１１５、アルキッド変性：ＳＲ２１１０（東レ・ダウコーニング・シリコーン社製）などが代表的である。
【００１６】
皮膜を設けるキャリア芯材としては、従来公知のものが使用できる。例えば、鉄、コバルトなどの強磁性体、マグネタイト、ヘマタイト、Ｌｉ系フェライト、Ｍｎ−Ｚｎ系フェライト、Ｃｕ−Ｚｎ系フェライト、Ｎｉ−Ｚｎ系フェライト、Ｂａフェライトなどが挙げられる。キャリア芯材としては上記の磁性粒子が一般的だが、より小粒径の磁性粉をフェノール樹脂、アクリル樹脂、ポリエステル樹脂などの公知の樹脂中に分散した形態を持つ、いわゆる樹脂分散キャリアも好適に用いられる。
【００１７】
被覆樹脂の形成方法は、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。
【００１８】
また、キャリア上の凹凸はその平均高低差が０．１μｍ〜２μｍであることが好ましい。ここでいうキャリア上の凹凸は、トナーと攪拌を行った場合には、キャリアとトナーとの接触機会を増加するが、スリーブ上でトナーを保持する場合にはキャリアとトナーの接点になる凸部の曲率が小さいためにキャリアとの物理的な付着性が低くなるため、トナーの均一な帯電と、速やかな現像性を備えることができる。高低差が０．１μｍ以下では、凹凸による上記の効果が十分に期待できない。２μｍより大きい場合、凹凸の脱離や凹部内に、トナーの微粉成分の固着が発生しやすく好ましくない。
【００１９】
また、キャリア上の凸部の存在率は同様の理由から重要である。求められる表面積Ｓｃに対する凸部の存在個数ｎの割合ｎ／Ｓｃが１［μｍ ^{- ２} ］以上であることが好ましい。ｎ／Ｓｃが１［μｍ ^{- ２} ］より少ないとキャリア上のトナーが占有するキャリアの表面積に対して凸部の数が十分ではなく、先の効果を十分に期待できない。
【００２０】
凹凸の高低差と存在率の測定は例えば、電子顕微鏡観察により実施される。電子顕微鏡写真より直接、高低差を読み取ることが最も容易である。ここでいう凹凸の高低差とは、キャリアの凸部に外接する円と、キャリアの凹部に外接する円の半径の差に相当する。
【００２１】
こうした凹凸の形成は先のとおり、従来公知の皮膜形成方法で形成することができる。すなわちキャリア上に樹脂溶液を塗布、または、樹脂を構成するモノマー、オリゴマー、ポリマーの溶液を塗布し、乾燥固化、もしくは、相応の化学反応によって高分子量化もしくは、芯材表面への化学的な皮膜の析出、積層などによって皮膜を形成する際に、皮膜形成材料の一部を意図的に析出、硬化させることで可能である。最も容易には、皮膜材料溶液中に粒子状物質を分散し、これをキャリア芯材上に塗布、硬化、させることにより得られる。すなわち、凸部内部にはキャリア表面を構成する材料と異なる組成の微粒子を含有することにより、皮膜上の凹凸の形態と存在状態を任意に形成できる。
【００２２】
このとき、微粒子が芯材皮膜から突出したり、著しく、キャリア形態が球形から逸脱した異型粒子となった場合には、現像剤として使用した場合に、長時間の使用で、突出部の破損、磨耗の局所的な進行が生じやすくなる。すなわち、キャリア上の凹凸は、均一な形態と分布状態にあることが好ましい。そのためには、凸部を形成する微粒子は円形に近いことが好ましい。異方性のある形態、たとえば、針状、板状の粒子はキャリア上の凹凸を構成するための材料としては、好ましくない。すなわち該微粒子の長軸と短軸の比が１．０〜２．０の範囲であることが好ましい。
【００２３】
ここで用いられる凸部内部の微粒子は、金属紛や、種々の金属酸化物粒子などの無機微粒子が好ましく用いられ、中でも酸化ケイ素、酸化チタン、アルミナなどの金属酸化物粒子は容易に均一な微細粒径の粒子が得られ、かつ、使用する粒子によって様々な電気特性や機械的な強度が得ることができる。また、シリコーン樹脂の縮合硬化の過程で、キャリアを高温に加熱しても、微粒子が熱的に安定であることも重要である。
【００２４】
また、凸部内部の微粒子は外殻を構成するシリコーンポリマーに比べて高硬度の微粒子であることは、特に好ましい。これは、キャリア上の凸部は実質的にキャリア−キャリア間、キャリア−トナー間、キャリア−現像装置内の部材との接点部であり、この部分は凹部に比べ他部材との接触機会が多い。実質的に凹部の内部は芯材である硬質な磁性粉体であり、凸部内も、同様に高硬度の微粒子であることが好ましい。すなわちシリコーンポリマーに比べ高い硬度を持つことにより、表面の凹凸形状に由来する選択的な摩砕を防止することができる。先の金属酸化物粒子は高硬度の粒子の代表である。
【００２５】
キャリア表面の凹凸形状を均一かつ、強靭に作成することは、本キャリアの耐久性を向上させる上では重要である。キャリア上の凸部には凹部に比べて攪拌時に接線方向のストレスがかかる。攪拌により凸部の脱離や選択的な磨耗が生じると、キャリアの粉体特性や電気特性の変化を生じ、画質の変化や作像条件との不整合により、種々の画質劣化を生じてはならない。
【００２６】
強靭な凹凸に形成するためには、微粒子を包埋する樹脂層を有し、さらにその外側にキャリアの最表面を構成する樹脂層を形成することが効果的であり、好ましい。
【００２７】
すなわち、皮膜を形成する際に、まず、微粒子を含有する樹脂層（第１層）を形成し、その後、微粒子を含まない樹脂層（第２層）を積層した形態で構成することにより特に、その耐久性に優れた皮膜を容易に得ることができる。
【００２８】
また、この凹凸をさらに強固に形成し、かつ、キャリアへのトナースペントを防止するには、キャリアの外層を微粒子を含有する有機樹脂層（第１層）と微粒子を含まないシリコーン樹脂層（第２層）を積層した形態で構成とすることも好ましい。最表層のシリコーン樹脂層はキャリア皮膜の磨耗性や、トナーのスペント防止性によって好ましいものが選択されるが、そうした樹脂が必ずしも微粒子の保持性に優れるとは限らない。とくに、外層の平均厚みに対して、大きな微粒子を担持する場合には、微粒子保持の機械的強度を十分に大きくする必要があるが、シリコーン樹脂をキャリア上で熱硬化させる場合、膜の体積収縮、膜と粒子の界面強度によっては、微粒子の脱離が生じる場合がある。
【００２９】
そのため、第１層として、微粒子保持、凹凸形成および、電気抵抗の制御を主目的とした層を設け、その外層に、最表面層としてシリコーンポリマー層を設けることは好ましい。
第１層に用いる樹脂としては、従来公知のいかなる樹脂でも使用できる。
【００３０】
先に例示したとおり、公知のシリコーンポリマーを全て用いることができるが、シリコーン層の物理的な硬度を向上させることは、キャリアの磨耗耐久性を向上させる上で重要である。これは、キャリア表面を構成する材料を単一組成のシリコーンポリマーにより構成することでも、ある程度の磨耗耐性を持たせることが可能であるが、複数種のシリコーンポリマーを混合して用いることで、飛躍的に磨耗強度の向上が認められる。
【００３１】
すなわち、キャリア表面を構成する材料を従来公知のストーレートシリコーン組成のプレポリマー材料に対して、４官能アルコキシシランを混合して生成するポリマーを用いることでキャリアの磨耗強度は向上する。従来、単一のストレートシリコーンのプレポリマーを塗布し、加熱縮合させて皮膜を形成する際、プレポリマー内のＳｉ−ＯＨ間の脱水縮合による架橋構造が形成されると考えられているが、プレポリマーの分子鎖の広がりと架橋点間の立体的な距離のため、ポリマー内に未架橋のＳｉ−ＯＨが残留する。これに多官能で分子量の小さいシラン化合物をブレンドすることにより、プレポリマーの柔軟性や成膜性を低下させることなく、縮合時の緻密な架橋構造が得られるためと考えられる。一般に４官能アルコキシシランの縮合生成物はその架橋構造が緻密であるために、硬度は得られるものの、成膜性に劣るとされているが、ストレートシリコーンプレポリマー内に溶解して、成膜を行うことにより、シリコーンポリマー内の架橋密度を向上させることが可能であり、より強靭な皮膜を形成できる。
【００３２】
さらに、用いるシリコーン化合物をストレートシリコーンポリマーと、４官能アルコキシシランと３官能アルコキシシランの混合物から生成するシリコーンポリマーとにすることで、皮膜強度はさらに向上する。先と同様にストレートシリコーンプレポリマー内にさらに、多官能の低分子量ポリマーを混合して用いても架橋構造の高密度化が期待でき、また、４官能アルコキシシランのみからなる脆い縮合物の生成を抑制することができる。
【００３３】
また、皮膜の構成する材料は脱オキシム反応により加水分解されるストレートシリコーンポリマーと先の４官能アルコキシシラン、もしくは、４官能と３官能アルコキシシランからなるシリコーンプレポリマーのような脱アルコール反応をもって加水分解するシリコーンポリマーの混合物として用いることはさらに好ましい。
【００３４】
こうした、多官能アルコキシシランの添加量としては、ストレートシリコーンポリマーに対して、任意の量添加することが可能であり、好ましくは、２０％〜８０％である。
【００３５】
さらに、キャリア皮膜にはトナーとの帯電性を好適にするための種々の薬剤を含有させるできる。
【００３６】
なかでも特に、窒素を構造内に含有する有機シリコーン樹脂はその帯電性と成膜性から好ましく用いられる。窒素を構造内に含有する有機シリコーン樹脂の代表例としてはたとえば下記構造で表わされ、特にＸにアミノ基を有する、いわゆるアミノシランカップリング剤は好ましく用いられる。
【００３７】
（ただし、式中、ｎは１〜３の整数、Ｘは有機または無機物との反応性または吸着性を有する各種の官能基、及び官能基を有する飽和または不飽和の炭化水素鎖を、ＯＲはアルコキシ基を意味する。）
【００３８】
【化２】

【００３９】
また、キャリア表面を構成する材料に電気抵抗調整の目的で、下記のような物質を含有させることができる。必要に応じて１種以上のものを適当な量使用すればよい。
【００４０】
導電性ＺｎＯ、Ａｌ等の金属粉、各種の方法で作られたＳｎＯ₂及び種々の元素をドープしたＳｎＯ₂、ホウ化物、例えばＴｌＢ₂、ＺｎＢ₂、ＭｏＢ₂、炭化ケイ素及び導電性高分子（ポリアセチレン、ポリパラフェニレン、ポリ（パラ−フェニレンスルフィド）、ポリピロール）、カーボンブラック等である。
【００４１】
皮膜に最も好適なシリコーン化合物はその電気抵抗が高く、一般に高抵抗であることが知られている。そのため、皮膜抵抗の抵抗調整剤としては、その体積抵抗が１０^-6以下の粒子が少なくとも１種用いられることが好ましい。
【００４２】
また、電気抵抗調整の目的として導入される導電性微粒子は皮膜に対して十分に小さい粒径を有し、かつ、皮膜内に均一に分散しうることが重要である。これは、皮膜の凹凸形態をこれらの導電性微粒子の導入により乱すことは好ましくなく、皮膜形態による、帯電の均一化とトナー保持性と現像性に期待する効果を発現させるためには重要である。それらの条件を満たす材料としては、導電性処理された金属酸化物の微粒子やカーボンブラックなどは好ましく用いられる。
【００４３】
また、一方で、カーボンブラックなどのきわめて低抵抗な物質をシリコーン膜に分散して使用すると、皮膜の電気特性がカーボンブラックの含有量に対して敏感に変動してしまうため、その取り扱いに注意を要する。たとえば、キャリア間の電気抵抗の不均一さを生ずやすくなったり、製造工程における、わずかな工程の変動に対して得られるキャリアの特性が安定しにくいなどの、取り扱い難さを伴う。このことは、含有量の正確な管理と、皮膜内の分散性の均一化により回避できるが、皮膜内に含有する電気抵抗制御材料が導電性カーボン粒子と非導電性金属酸化物の微粒子混合して用いることによってもよい。
【００４４】
こうして得られるキャリアは二成分現像剤として用いる場合、電気抵抗測定値が１０⁷〜１０¹⁶Ωｃｍの範囲であることが好ましい。電気抵抗は、キャリアを用いる現像プロセスに応じて適切に選ばれなくてはならないが、１０⁷Ωｃｍ以下になると、現像剤担持体上に保持したキャリアのブラシ（磁気ブラシ）の穂立ち形状が画像濃度の濃淡となって目立ちやすくなり好ましくない。また、１０¹⁶Ωｃｍを超える場合、画像のエッジ部とベタ部の濃度差やライン画像とベタ画像内の濃度差を生じたりする、エッジ現像やキャリアのチャージアップによる現像能力の低下、潜像の非画像部へのキャリア現像（キャリア付着）などの不具合を生じやすくなる。
【００４５】
キャリアの電気抵抗は、２つの平行電極の間にキャリアを充填し、電極間に電位差を設けた時の電流値と印加電圧から求められる値である。具体的には、２ｍｍの間隔で平行に配置した電極を有する容器にキャリアを充填し、両極間の電位差５００Ｖでの直流抵抗を横川ヒューレットパッカード株式会社製４３２９Ａ Ｈｉｇｈ Ｒｅｓｉｓｔａｎｃｅ Ｍｅｔｅｒにて測定する。
【００４６】
また、同様の理由からキャリアの皮膜の厚さは、電気抵抗が適正範囲内になるよう、適宜設定されることが好ましいが、シリコーンは縮合反応時の体積収縮があるため皮膜厚さが厚くなるほど、皮膜内部の反応の不均一さが生じやすくなる欠点を持つ。そのため、皮膜厚さ１．０μｍ以下がより好ましい。
【００４７】
キャリア皮膜厚さの測定は、様々な方法で可能である。たとえば、用いたキャリア芯材、皮膜材料のそれぞれの比重が既知である場合には、キャリアの真比重を正確に測定することでも可能である。
【００４８】
最も容易には、電子顕微鏡でキャリア断面を測定することである。キャリアが燒結体である芯材上にシリコーン樹脂による硬化膜を設けたキャリアの場合、キャリア粒子に剪断方向に加圧して破砕することで、その破砕物から比較的容易に皮膜断面を観察することができる。ここでいう該キャリアの外殻の平均厚みとは、凹凸を含めて皮膜全体の平均的な厚みを意味する。
【００４９】
こうして得られるキャリアは実質的に非磁性体のトナーと混合して現像剤として用いられることが好ましい。トナーが磁性を有する場合、磁性キャリアと混合すると、トナーとキャリアの磁気モーメント差と比重差により、磁界中ではキャリアとトナーが分離しやすくなる。また、二成分現像で磁気ブラシを形成した場合、ブラシ先端や、キャリア粒子間の節部にトナーが凝集する現象が見られ、これは、画像へのトナー供給の不均一さの原因となり、画像の均一さ、特にハーフトーン部や微細なドットの欠落の原因になる。本発明のキャリアは非磁性トナーと混合して用いられるとき、最も好ましい画像が得られる。
【００５０】
また、同様の理由からキャリアの皮膜の厚さは、電気抵抗が適正範囲内になるよう、適宜設定されることが好ましいが、シリコーンは縮合反応時の体積収縮があるため皮膜厚さが厚くなるほど、皮膜内部の反応の不均一さが生じやすくなる欠点を持つ。そのため、皮膜厚さ１．０μｍ以下がより好ましい。
【００５１】
キャリア皮膜厚さの測定は、様々な方法で可能である。たとえば、用いたキャリア芯材、皮膜材料のそれぞれの比重が既知である場合には、キャリアの真比重を正確に測定することでも可能である。
【００５２】
最も容易には、電子顕微鏡でキャリア断面を測定することである。キャリアが燒結体である芯材上にシリコーン樹脂による硬化膜を設けたキャリアの場合、キャリア粒子に剪断方向に加圧して破砕することで、その破砕物から比較的容易に皮膜断面を観察することができる。ここでいう該キャリアの外殻の平均厚みとは、凹凸を含めて皮膜全体の平均的な厚みを意味する。
【００５３】
また、本発明のキャリアは有彩色トナー、特に、離型剤を含有する有彩色トナーにおいても、好ましい画像が得られる。有彩色トナーを用いるカラー画像形成においては、トナーは通常、減法混色の三原色（イエロー、マゼンタ、シアン、以下それぞれＹ、Ｍ、Ｃ）と黒（以下ＢＫ）の各色のトナーを用いて作成した画像を得ることから、各色のトナーが十分に溶融し、二次色を得るためには、トナーの溶融性や透明性、さらに、その画像表面の平滑性が必要であり、温度に対してシャープな溶融性と粘度変化が求められる。こうしたトナーにおいては、往々にして離型剤の必要量が多くなり、キャリアへの離型剤の付着（スペント）が問題となるが、本発明のキャリアはこうしたトナーと使用した場合においても、先の理由から良好な画像が長期にわたり維持できる。
【００５４】
本キャリア、およびキャリアを用いた現像剤が用いられる現像装置構成としては、内部に固定、もしくは、回転する磁石を配する現像剤担持体に現像剤を磁気的に保持し、この現像剤担持体を潜像担持体と対向して設けることにより、潜像担持体に現像剤を連続的に当接させ、現像剤担持体と潜像担持体の間に電位差を設けることによりトナーを潜像担持体上に現像を行うものである。
【００５５】
また、本発明のキャリア、および現像剤は従来公知の二成分電子写真方式においても、好ましく用いられるが、先に述べた理由から高いトナー供給の保持性と現像性を持つため、特に従来、キャリアを用いた二成分現像方式特有の欠点である、画像不良を回避することが可能になる。
【００５６】
すなわち、従来、現像量を確保するために、設けられた現像剤担持体の線速（Ｖｒ）、潜像担持体の線速（Ｖｐ）との間の線速差を小さく、かつ、現像剤と潜像担持体の接触幅を小さくしても、十分な画像濃度を得ることが可能であり、そのため、必然的に先の画像不良を防止することが可能となる。
【００５７】
すなわち、潜像担持体表面の移動速度Ｖｐ、現像剤担持体表面の移動速度Ｖｒ、現像剤と潜像担持体の接触幅Ｌとするとき、

〔Ｖｐ：潜像担持体表面の移動速度（ｍｍ／ｓｅｃ）、
Ｖｒ：現像剤担持体表面の移動速度（ｍｍ／ｓｅｃ）、
Ｌ：現像剤と潜像担持体の接触幅（ｍｍ）〕
の範囲で画像を作像すればよい。ｋ値が０．１ｍｍ未満では画像濃度が十分に得られず、また、２ｍｍより大きいと先の画像不良が顕著になる。
【００５８】
本発明に使用されるトナーとしては、バインダー樹脂としての熱可塑性樹脂を主成分とし、着色剤、微粒子、そして帯電制御剤、離型剤等を含むものである。また、一般公知の粉砕法、重合法等の各種のトナー製法により作製されたトナーを用いることができる。
【００５９】
バインダー樹脂としては、ポリスチレン、ポリビニルトルエン等のスチレン及びその置換体の単重合体、スチレン−ｐ−クロルスチレン共重合体、スチレン−プロピレン共重合体、スチレン−ビニルトルエン共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−アクリル酸ブチル共重合体、スチレン−メタアクリル酸メチル共重合体、スチレン−メタアクリル酸エチル共重合体、スチレン−メタアクリル酸ブチル共重合体、スチレン−ｏ−クロルアクリル酸メチル共重合体、スチレン−アクリロニトリル共重合体、スチレン−ビニルメチルエーテル共重合体、スチレン−ビニルメチルケトン共重合体、スチレン−ブタジエン共重合体、スチレン−イソブチレン共重合体、スチレン−マレイン酸共重合体、スチレン−マレイン酸エステル共重合体等のスチレン系共重合体、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、ポリエチレン、ポリプロピレン、ポリエステル、ポリウレタン、エポキシ樹脂、ポリビニルブチラール、ポリアクリル酸樹脂、ロジン、変性ロジン、テルペン樹脂、フェノール樹脂、脂肪族または芳香族炭化水素樹脂、芳香族系石油樹脂、塩素化パラフィン、パラフィンワックスなどが単独あるいは混合して使用できる。
【００６０】
ポリエステル樹脂としては、アルコールと酸の重縮合反応によって得られ、例えばアルコールとしては、ポリエチレングリコール、ジエチルグリコール、トリエチレングリコール、１，２−プロピレングリコール、１，３−プロピレングリコール、１，４−プロピレングリコール、ネオペンチルグリコール、１，４−ブテンジオールなどのジオール類、１，４−ビス（ヒドロキシメチル）シクロヘキサン、ビスフェノールＡ、水素添加ビスフェノールＡ、ポリオキシエチレン化ビスフェノールＡ、ポリオキシプロピレン化ビスフェノールＡなどのエーテル化ビスフェノール類、これらを炭素数３〜２２の飽和もしくは不飽和の炭化水素基で置換した２価のアルコール単量体、その他の２価のアルコール単量体、ソルビトール、１，２，３，６−ヘキサンテトロール、１，４−サルビタン、ペンタエリスリトール、ジペンタエリスリトール、トリペンタエリスリトール、ショ糖、１，２，４−ブタントリオール、１，２，５−ペンタントリオール、グリセロール、２−メチルプロパントリオール、２−メチル−１，２，４−ブタントリオール、トリメチロールエタン、トリメチロールプロパン、１，３，５−トリヒドロキシメチルベンゼン等の３価以上の高級アルコール単量体を挙げることができる。また、ポリエステル樹脂を得るために用いられるカルボン酸としては、例えばパルミチン酸、ステアリン酸、オレイン酸等のモノカルボン酸、マレイン酸、フマール酸、メサコン酸、シトラコン酸、テレフタル酸、シクロヘキサンジカルボン酸、コハク酸、アジピン酸、セバチン酸、マロン酸、これらを炭素数３〜２２の飽和もしくは不飽和の炭化水素基で置換した２価の有機酸単量体、これらの酸の無水物、低級アルキルエステルとリノレイン酸からの二量体、１，２，４−ベンゼントリカルボン酸、１，２，５−ベンゼントリカルボン酸、２，５，７−ナフタレントリカルボン酸、１，２，４−ナフタレントリカルボン酸、１，２，４−ブタントリカルボン酸、１，２，５−ヘキサントリカルボン酸、１，３−ジカルボン酸−２−メチル−２−メチレンカルボキシプロパン、テトラ（メチレンカルボキシル）メタン、１，２，７，８−オクタンテトラカルボン酸エンボール三量体、これらの酸の無水物等、３価以上の多価カルボン酸単量体を挙げることができる。
【００６１】
さらにエポキシ樹脂としては、ビスフェノールＡとエピクロルヒドリンとの重縮合物等があり、例えば、エポミックＲ３６２、Ｒ３６４、Ｒ３６５、Ｒ３６６、Ｒ３６７、Ｒ３６９（以上三井石油化学工業社製）、エポトートＹＤ−０１１、ＹＤ−０１４、ＹＤ−９０４、ＹＤ−０１７（以上東都化成社製）、エポコート１００２、１００４、１００７（以上シェル化学社製）等の市販のものがある。
【００６２】
着色剤としては、カーボンブラック、ランプブラック、鉄黒、群青、ニグロシン染料、アニリンブルー、フタロシアニンブルー、ハンザイエローＧ、ローダミン６Ｇレーキ、カルコオイルブルー、クロムイエロー、キナクリドン、ベンジジンイエロー、ローズベンガル、トリアリルメタン系染料、モノアゾ系、ジスアゾ系、染顔料など、従来公知のいかなる染顔料をも単独あるいは混合して使用し得る。
【００６３】
また、トナーは、通常使用されるトナーと同様に摩擦帯電性を制御する目的で含有せしめる薬剤を含有していても何ら不都合はない。そうした、いわゆる極性制御剤としては、例えばモノアゾ染料の金属錯塩、ニトロフミン酸及びその塩、サリチル酸、ナフトエ酸、ジカルボン酸のＣｏ、Ｃｒ、Ｆｅ等の金属錯体等を単独または混合して用いることができるが、これらに限定されるものではない。
【００６４】
また、トナーの補給性や攪拌性、帯電特性の均一化など粉体特性としての流動性の向上のためにトナーに従来公知の流動性補助剤や種々の添加剤を用いることもできる。
【００６５】
添加物としては、例えばテフロン（登録商標）、ステアリン酸亜鉛のごとき滑剤或いは酸化セリウム、炭化ケイ素などの研磨剤、流動化剤としては代表的には酸化ケイ素、酸化チタン、酸化アルミニウムなどの酸化金属微粒子、およびその表面を疎水化した粒子であり、これらのいずれの微粉末もその表面を疎水化することによりさらに流動性の面で優れた効果をもたらす。表面を疎水化処理するためには、例えば、シランカップリング剤やシリコーンオイル、有機オイル、また、シリル化剤として一般に知られる珪素化合物を粒子表面と接触、反応させることができる。
【００６６】
疎水化剤としては、例えばクロロシラン類としては代表的にトリクロロシラン、メチルジクロロシラン、ジメチルジクロロシラン、トリメチルクロロシラン、エチルジクロロシラン、ジエチルクロロシラン、トリエチルクロロシラン、プロピルジクロロシラン、ジプロピルジクロロシラン、トリプロピルクロロシラン、などアルキルクロロシラン、フェニルクロロシランなど。そのフッソ置換体としてフルオロアルキルクロロシラン、パーフルオロアルキルクロロシランの類、シリルアミン類としては、代表的にヘキサメチルジシラザン、ジエチルアミノトリメチルシラン、ジエチルアミノトリメチルシランなど、シリルアミド類としては、代表的にN，Ｏ−ビストリメチルシリルアセトアミド、N−トリメチルシリルアセトアミド、ビストリメチルシリルトリフルオロアセトアミド、など、また、アルコキシシラン類として、メチルトリアルコキシシラン、ジメチルジアルコキシシラン、トリメチルアルコキシシラン、エチルジアルコキシシラン、ジエチルアルコキシシラン、トリエチルアルコキシシラン、プロピルトリアルコキシシラン、ジプロピルジアルコキシシラン、トリプロピルアルコキシシラン、などアルキルクロロシランや、フェニル基を有するフェニルアルコキシシランなど、また、そのフッソ置換体としてフルオロアルキルアルコキシシランの類、パーフルオロアルキルアルコキシシランの類、シリコーンオイルとして、ジメチルシリコーンオイル、およびその誘導体、フッ素置換体、ジシロキサン、ヘキサメチルジシロキサンなど、シロキサンの類など、一般公知の疎水化剤として用いられ化合物すべてが使用できる。
【００６７】
【実施例】
以下、本発明を実施例によりさらに具体的に説明する。ただし、本実施例は、本発明の一態様にすぎず、本発明はこれら実施例に拘束されない。なお、以下実施例に示す各成分量（部）はいずれも重量基準である。
【００６８】
参考例（キャリア１〜１６の製造例）
キャリア芯材としては、Ｃｕ−Ｚｎフェライト粒子（重量平均粒径５０μｍ、印加磁界１０００Ｏｅにおける磁気モーメント ６５ｅｍｕ／ｇ）を用いた。
【００６９】
（１）キャリア抵抗は、２ｍｍの間隔で平行に配置した電極を有する容器に芯材を充填し、両極間の５００Ｖでの直流抵抗を横川ヒューレットパッカード株式会社製４３２９Ａ Ｈｉｇｈ Ｒｅｓｉｓｔａｎｃｅ Ｍｅｔｅｒにて測定した。
【００７０】
（２）磁気モーメントは東英工業株式会社製 多試料回転式磁化測定装置 ＲＥＭ−１−１０を用い印加磁界１０００Ｏｅにて測定した。
【００７１】
（３）重量平均粒径はマイクロトラックで測定した重量基準で求めた径（ＤＶ）とした。
それぞれの芯材に対し次のように外層を形成して、キャリアを得た。
【００７２】
キャリア１
シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）の固形分に対して微粉体Ａとしてアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−０４ ０．４μｍ 軸比１．１）の４５ｗｔ％を、ホモジナイザーを使用して、３０分間分散し、この分散液を固形分１０ｗｔ％になるよう希釈し、分散液を得た。
【００７３】
上記それぞれの芯材５ｋｇに対して、上記の分散液を流動床型コーティング装置を用いて、１００℃の雰囲気下で、約５０ｇ／ｍｉｎの割合で塗布した。更に、３００℃で２時間加熱して、平均膜厚０．４３μｍのキャリアＡを得た。膜厚の調整はコート液量により行った。
【００７４】
キャリア２
キャリア１の製造例において、微粉体Ａとしてアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−０５ ０．５μｍ 軸比１．２）４５ｗｔ％、を用いる以外はすべて同様にしてキャリア２を得た。
【００７５】
キャリア３
キャリア１の製造例において、微粉体Ａとしてシリカ微粉体（アドマテックス株式会社製 アドマファイン ＳＯ−Ｃ３ １．０μｍ 軸比１．１）１２０ｗｔ％を、用いる以外はすべて同様にしてキャリア３を得た。
【００７６】
キャリア４
キャリア１の製造例において、微粉体Ａとしてアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−０３ ０．３μｍ 軸比１．１）３０ｗｔ％を用いる以外はすべて同様にしてキャリア４を得た。
【００７７】
キャリア５
総研化学株式会社製 アクリル微粉末 ＭＰ５５００（０．４μ 軸比１．０）をイオン交換水とメタノールの１：１混合溶液中に分散し、これに下記構造式のアミノシラン、０．１ｗｔ％メタノール溶液を混合しながら滴下した。続いて、ジメトキシジメチルシラン０．５ｗｔ％メタノール溶液を滴下した。十分に攪拌を行った後、希塩酸水溶液を滴下し、ｐＨ５を保ち、ウォーターバス中で６０℃に加温しながら４時間攪拌を行った。その後、この分散液を遠心分離と溶媒置換を繰り返し、トルエン分散液とした。シリコーン処理アクリル微粒子分散液を得た。
【００７８】
【化３】

【００７９】
この微粒子は粒径０．５μｍ、軸比１．０であった。
キャリア１の製造例において、微粉体Ａに代えて次のように作成した微粒子の８０ｗｔ％を用いる以外はすべて同様にしてキャリア５を得た。
【００８０】
キャリア６
シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）をイオン交換水とメタノールの１：１ 混合溶液に攪拌しながら滴下し、乳化した。この溶液にアンモニア水溶液を滴下し、ｐＨ１０を保ち、ウォーターバス中で６０℃に加温しながら４時間攪拌い、シリコーン微粒子分散液を得た。この微粒子は粒径０．６μｍ、軸比１．０であった。
【００８１】
キャリア１の製造例において、微粉体Ａに代えて、得られたシリコーン微粒子分散液を固形分として４５ｗｔ％相当用いる以外はすべて同様にしてキャリア６を得た。
【００８２】
キャリア７
キャリア１の製造例において、微粉体Ａに代えて微粉体（石原産業株式会社 酸化チタン ＴＴＯ−Ｄ−１ ０．３μｍ 軸比２．９）を３０ｗｔ％用いる以外はすべて同様にしてキャリア７を得た．
【００８３】
キャリア８
シリコーン樹脂溶液（ＳＲ２４１１：東レダウコーニングシリコーン社製）の固形分に対して微粉体Ａとしてアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−０３ ０．３μｍ 軸比１．１）３０ｗｔ％をホモジナイザーを使用して、３０分間分散し、この分散液を固形分５ｗｔ％になるよう希釈し、分散液Ａを得た。
【００８４】
また、別途、シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）の固形分に対してホモジナイザーを使用して、３０分間分散し、この分散液を固形分５ｗｔ％になるよう希釈し、分散液Ｂを得た。
【００８５】
芯材５ｋｇに対して、上記の分散液Ａ、分散液Ｂを流動床型コーティング装置を用いて、順次塗布し、１００℃の雰囲気下で、約５０ｇ／ｍｉｎの割合で塗布し、更に、２５０℃で２時間加熱して、平均膜厚０．４７μｍのキャリア８を得た。膜厚の調整はコート液量により行った。
【００８６】
キャリア９
アクリル樹脂溶液（日立化成社製 ヒタロイド３０１９）の固形分に対して微粉体Ａとしてアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−０３ ０．３μｍ 軸比１．１）３０ｗｔ％をホモジナイザーを使用して、３０分間分散し、この分散液を固形分５ｗｔ％になるよう希釈し、分散液Ａを得た。
【００８７】
また、別途、シリコーン樹脂（ＳＲ２４１１：東レダウコーニングシリコーン社製）の固形分に対してホモジナイザーを使用して、３０分間分散し、この分散液を固形分５ｗｔ％になるよう希釈し、分散液Ｂを得た。
【００８８】
芯材５ｋｇに対して、上記の分散液Ａ、分散液Ｂを流動床型コーティング装置を用いて、順次塗布し、１００℃の雰囲気下で、約５０ｇ／ｍｉｎの割合で塗布し、更に、２５０℃で２時間加熱して、平均膜厚０．２μｍのキャリア９を得た。膜厚の調整はコート液量により行った。
【００８９】
キャリア１０
キャリア９の製造例において樹脂分散液Ｂのシリコーン樹脂に、さらにテトラメトキシシラン１５部を混合し、それ以外はすべて同様にしてキャリア１０を得た。
【００９０】
キャリア１１
キャリア８の製造例において樹脂分散液Ｂのシリコーン樹脂に、さらに下記構造式からなる数平均分子量約５０００のシリコーンポリマーを５０部を混合し、それ以外はすべて同様にしてキャリア１１を得た。
【００９１】
キャリア１２
キャリア１０の製造例において樹脂分散液Ａおよび樹脂分散液Ｂにそれぞれ下記構造のアミノシラン化合物０．５部を加える以外はすべて同様にしてキャリア１２を得た。
【００９２】
【化４】

【００９３】
キャリア１３
キャリア１１の製造例において用いるアミノシランを下記構造のアミノシラン化合物とする以外はすべて同様にしてキャリア１３を得た。
Ｈ₂Ｎ（ＣＨ₂）₃Ｓｉ（ＯＣ₂Ｈ₅）₃
【００９４】
キャリア１４
キャリア１１の製造例において樹脂分散液Ａおよび樹脂分散液Ｂにさらに導電性酸化チタン（石原産業製 EＴ−３００W ０．０３μｍ 体積抵抗３０Ωｃｍ）の１０部を加え、アミノシランの添加量を０．７部とする以外は同様に分散して用いる以外はすべて同様にしてキャリア１４を得た。
【００９５】
キャリア１５
キャリア１２の製造例において樹脂分散液Ａおよび樹脂分散液Ｂにさらに導電性カーボン（ライオンアクゾ社製、ケッチェンブラックＥＣ−ＤＪ６００）１部を加え、アミノシランの添加量を１．５部とする以外は同様に分散して用いる以外はすべて同様にしてキャリア１５を得た。
【００９６】
キャリア１６
キャリア１２の製造例において樹脂分散液Ａおよび樹脂分散液Ｂにさらに導電性カーボン（ライオンアクゾ社製、ケッチェンブラックＥＣ−ＤＪ６００）０．５部と導電性酸化チタン（石原産業製 EＴ−３００W）５部を加えアミノシランの添加量を１．５部とする以外は同様に分散して用いる以外はすべて同様にしてキャリア１６を得た。
【００９８】
【表１】

【００９９】
トナーＡ（トナーの製造例）
ポリエステル樹脂 ６０部
スチレンアクリル樹脂 ２５部
カルナウバワックス１号品 ５部
カーボンブラック（三菱化学 ＃４４） １０部
含クロムアゾ化合物（保土ヶ谷化学 Ｔ−７７） ３部
【０１００】
以上の物質をブレンダーにて十分に混合した後、２軸式押出し機にて溶融混練し、放冷後カッターミルで粗粉砕し、ついでジェット気流式微粉砕機で微粉砕し、さらに風力分級機で重量平均粒径６．８μｍのトナー母粒子を得た。
【０１０１】
またトナー母粒子１００部に対し、疎水性シリカ微粒子（Ｒ９７２日本アエロジル社製）０．７部、疎水性酸化チタン（ＭＴ１５０Ａ イソブチルトリメトキシシラン処理品疎水化処理 テイカ株式会社製）０．１部を加え、ヘンシェルミキサーで混合し同様に風櫛してトナーＡを得た。
このトナーの個数平均径６．２μｍ、体積平均径７．４μｍであった。
【０１０２】
（評価方法）
実施例１
リコー製複写機ｉｍａｇｉｏ ＭＦ４５７０に、先のキャリア１、９５ｗｔ％、トナーＡ５ｗｔ％からなる現像剤を装填し、トナーを補給しながら、画像面積率６％の文字画像チャートを使用して１００万枚の作像試験を行った。
このときに、感光体帯電電位は−８５０Ｖとし、現像剤担持ローラの印加電圧は−６００Ｖとした。
作像試験の間、逐次、次のようなプリンタ画像を出力し、評価を行った。また、現像スリーブ上から現像剤を少量取出し、現像剤の帯電量を測定した。
【０１０３】
飽和ＩＤ ：黒ベタ画像を出力し、紙面上の任意の３点について、マクベス反射濃度計による画像濃度を測定し、その平均値とする。
◎：１．４以上（大変良好）
○：１．３〜１．４（良好）
△：１．２〜１．３（若干不良）
×：１．２未満（不良）（×は許容不可のレベル）
【０１０４】
ハーフトーン均一性：主走査、副走査共に６００ｄｏｔ／ｉｎｃｈ、１５０ｌｉｎｅ／ｉｎｃｈにて網点画像パターン（１６階調）を出力し、ドット抜け及び階調性、濃度均一性を４段階で目視評価した。
◎：大変良好
○：良好
△：若干不良
×：不良（×は許容不可のレベル）
【０１０５】
画像不良 ：マクベス反射濃度計による画像濃度＝０．２、０．８のハーフトーン部（１ｃｍ×１ｃｍ）が通紙方向に、一定間隔で並ぶ、画像チャートを出力し、ハーフトーン部後端部の濃度低下を４段階で目視評価した。
◎：大変良好
○：良好
△：若干不良
×：不良（×は許容不可のレベル）
評価結果は表２に記載する。
【０１０６】
実施例２〜１６
用いる現像剤を表１のとおりとして、実施例１と同様に評価を行った。評価結果は表２に記載する。
【０１０７】
実施例１７
実施例１において、リコー製複写機ｉｍａｇｉｏ ＭＦ４５７０の現像スリーブローラーのＰＣに近接する磁極幅を変更して、Ｌ＝０．２ｍｍとなる条件とし、Ｖｒ＝４１４ｍｍ／ｓｅｃ、Ｖｐ＝２３０ｍｍ／ｓｅｃとして、現像を行った。このときのｋ＝０．１６ｍｍであった。磁極幅の変更ＭＦ４５７０の最近接極を３極に分割し、中心極とその上下の極とが反対磁極となるようにした。
【０１０８】
先のキャリア１の９５部、トナーＡ５部からなる現像剤を装填し、トナーを補給しながら、画像面積率６％の文字画像チャートを使用して１０万枚の作像試験を行った。
このときに、感光体帯電電位は−８５０Ｖとし、現像剤担持ローラの印加電圧は−６００Ｖとした。
【０１０９】
作像試験の間、逐次、次のようなプリンタ画像を出力し、評価を行った。また、現像スリーブ上から現像剤を少量取出し、現像剤の帯電量を測定した。評価結果は表２に記載する。
【０１１０】
実施例１８
実施例１７と同様にリコー製Ｉｍａｇｉｏ ＭＦ４５７０の現像剤担持ローラー内の潜像担持体と最近接する磁石の着磁幅を変更し、Ｌ値１ｍｍとなるように調整した。この装置においては、Ｖｐ＝２３０ｍｍ／ｓｅｃ、Ｖｒ＝５７５ｍｍ／ｓｅｃであり、ｋ＝L・（（Ｖｒ／Ｖｐ）−１））＝１．５ｍｍであった。
同様に画像評価を行った。評価結果は表２に記載する。
【０１１１】
実施例１９
リコー製Ｉｍａｇｉｏ ＭＦ４５７０の現像剤担持ローラー内の潜像担持体と最近接する磁石の着磁幅を変更し、Ｌ値０．４ｍｍとなるように調整した。この装置においては、Ｖｐ＝２３０ｍｍ／ｓｅｃ、Ｖｒ＝５７５ｍｍ／ｓｅｃであり、ｋ＝L・（（Ｖｒ／Ｖｐ）−１））＝０．６ｍｍであった。
同様に画像評価を行った。評価結果は表２に記載する。
【０１１２】
比較例１
キャリアの製造例１において微粉体Ａを用いずに、同様にしてキャリア１７を作成した。このキャリアを実施例と同様に耐久性評価を行った。結果を表２にあわせて記載する。このキャリアは著しい帯電量の低下が認められ、地肌かぶりが発生した。
【０１１３】
比較例２
キャリアの製造例１において微粉体Ａの変わりにアルミナ微粉体（住友化学工業製 スミコランダム ＡＡ−２ ３μｍ 軸比１．１）を用いてキャリア１８を作成した。このキャリアを実施例と同様にして耐久性評価を行った。結果を表２にあわせて記載する。このキャリアは特に、経時でハーフトーン均一性の低下が著しく、画像濃度が低下していった。五万枚通紙後のキャリアを電子顕微鏡で観察すると、表面の突起の脱離痕が多数見うけられた。
【０１１４】
比較例３
キャリアの製造例１において用いる芯材を重量平均径８２μｍの鉄粉粒子（印加磁界１０００Ｏｅにおける磁気モーメント９０ｅｍｕ／ｇ、不定形）を用いる以外はすべて同様にしてキャリア１９作成した。
【０１１５】
このキャリアを実施例と同様に耐久性評価を行った。結果を表２にあわせて記載する。このキャリアは初期から画像濃度が低く、ハーフトーン部の均一性に掛ける画像であった。また、画像上の通紙方向にスジ状の掃き目が見られた。また、画像不良の発生が顕著であった。
【０１１６】
【表２】

【０１１７】
【発明の効果】
以上のように、本発明のごとく、キャリアの表面性状と組成を微細に制御することによって、長期間の使用においても画像濃度の変動や、画像の均一性に変化のない、耐久性に優れたキャリアを提供できる。また、二成分現像特有の画像不良のない、優れた画質のキャリア、現像剤および現像方法、装置を提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carrier and a developer used in an electrophotographic system, an electrostatic latent image developing method using the same, and a developing device using the same.
[0002]
[Prior art]
Various studies have been made on the improvement of durability and image reproducibility of electrostatic image developing apparatuses such as copying machines and printers using an electrophotographic system.
[0003]
The electrophotographic method includes a two-component development method using a two-component developer composed of a magnetic carrier and a toner, and a one-component development method in which development is performed by holding a magnetic or nonmagnetic toner in a thin layer on a toner carrier. Although it can be roughly divided into two types, the two-component development method uses a fine particle carrier with a large surface area compared to the one-component development method, so it is easy to supply toner at high speed and make the toner chargeability uniform. It is known that it is advantageous for high speed and high image quality. However, on the other hand, the carrier stays in the apparatus and repeats friction with the toner, so that there is a problem that the surface state of the carrier changes with time of use and the image quality changes. This is because the substance derived from the toner adheres to the carrier and becomes contaminated, so that the original chargeability cannot be obtained (toner spent), and in the case of an insulating carrier, the film formed on the surface of the carrier is worn out. There are two major causes of the change in the electrical resistance of the carrier. In particular, in two-component development, the carrier is held in the gap between the latent image carrier and the developer carrier corresponding to the counter electrode to form a development electric field. It has been a problem that the image quality changes with the aging of the carrier.
[0004]
As an example of preventing the toner spent on the carrier with respect to these problems, JP-A-60-186844 shows a silicone resin, and JP-A-64-13560 shows that a fluororesin is used as a film. Providing such a low surface energy substance as a carrier film is the most widely used method for preventing toner spent, and it is practically the only way to prevent it. Even if it is used, the spent deterrent effect is not perfect, and there is a need for a coating material and structure that can withstand long-term use. As an example of trying to improve the problem by the shape of the carrier, Japanese Patent Application Laid-Open No. 5-34991 shows the bulk density of the carrier, and the surface irregularity of the carrier core material prevents the carrier from being charged and spent. It is shown. In JP-A-7-98521, there is an example in which attention is paid to the unevenness of the carrier by specifying the ratio of the specific surface area measured from the air permeation method of the carrier and the surface area calculated from the average particle diameter. However, what is shown in these inventions is an example of a ferrite core material that has been used in the past, and defines physical properties derived from the surface shape and deformed shape of the carrier core material that is a sintered body. In addition, since the conventional acrylic resin is used for the coating material, the conventional problem remains with respect to the toner spent property. On the other hand, in JP-A-9-319161, JP-A-9-269614, and JP-A-10-186731, a film in which fine particles and a conductivity-imparting material are dispersed is provided in a resin matrix of a low surface energy substance, and the spent resistance and film strength are provided. Although it has been shown to control the electrical characteristics, the film is strengthened with fine particles, so there remains a problem with the wear of the continuous phase of the film, and the fine particles in the film are exposed on the surface. In some cases, this may cause toner spent on the portion and non-uniform charge amount.
[0005]
By the way, in the two-component development using such a carrier as a magnetic brush, a linear speed difference is provided between the moving speed of the latent image carrier and the moving speed of the developer carrier in order to ensure a sufficient development amount. However, it is known that the linear velocity difference between the latent image carrier and the developer carrier causes an image abnormality peculiar to the two-component development. The image abnormality referred to here is a decrease in image density at the rear end of the solid image portion, an image missing at the rear end of the halftone image, or an image at the boundary between the solid image and the halftone image. It means concentration change. All of these appear at locations where the latent image potential differs, and at the boundary of the image density where the latent image potential changes discontinuously and rapidly. This is because the developer moves so as to rub the latent image in the development area, so that the toner in the magnetic brush moves while the developer passes through the latent image, and the electrostatic capacitance that is originally a dielectric is reduced. It is considered that the developer layer is caused by a transient phenomenon when the developer layer passes through different discontinuous development electric fields. Hereinafter, such an image abnormality caused by the discontinuity of the latent image is referred to as an image defect.
[0006]
[Problems to be solved by the invention]
The present invention is to provide means for solving the above-mentioned conventional problems. That is, it is an object of the present invention to provide a carrier having no change in image quality even after long-term use, a developer using the carrier, a developing method using the carrier, and a developing device. It is another object of the present invention to provide a carrier capable of fine line reproducibility and uniform reproducibility of small-diameter dots and having excellent resolution, a developer using the carrier, a developing method, and a developing device.
[0007]
[Means for Solving the Problems]
  The above object can be achieved by the present invention described below.
  That is, a carrier having magnetically spherical particles and an outer shell layer provided so as to cover it, the outer shell layer having irregularities, and the outermost surface being coated with a silicone resin film A carrier for developing an electrostatic latent image. The carrier for developing an electrostatic latent image has an average height difference of unevenness of 0.1 μm to 2 μm in the carrier. Further, the ratio n / Sc of the number n of convex portions to the surface area Sc of the carrier is 1 / n.[Μm ^{- 2} ]That is the carrier.
[0008]
In this way, the surface of the carrier is coated with a silicone resin film having relatively excellent characteristics with respect to the toner spent, and fine irregularities are provided on the surface, thereby increasing the chance of contact charging between the carrier and the toner. Uniformity and, in addition, the toner is held on fine protrusions on the carrier, reducing the adhesion between the toner and the carrier due to van der Waals force, and increasing the electrostatic adhesion instead. Can do. As a result, in the development area, the toner exhibits a quick response to the development electric field, and improves the agitation and transportability when the developer is triboelectrically charged. In addition, the surface of the carrier is a low surface energy substance, which can provide a stable negative chargeability to the toner. Therefore, as the adherence of the spent substance derived from the toner decreases, the carrier contamination progresses at a slower rate, and the film wear rate also decreases. Improved.
[0009]
Further, the convex portion of the outer shell layer contains fine particles having a composition different from that of the material constituting the carrier surface, and the ratio of the major axis to the minor axis of the fine particles is in the range of 1 to 2.0. That is, the unevenness controlled uniformly is provided irrespective of the surface property of the core material while substantially maintaining the shape of the core material. In addition, the structure of the protrusions provides a uniform and smooth surface property by embedding spherical hard metal oxide fine particles inside, and mechanical destruction such as detachment and breakage of the protrusions derived from the shape. To prevent. Further, by providing a resin layer embedding the fine particles constituting the convex portion and a resin layer constituting the outermost surface of the carrier on the outer side, the detachment of the convex portion is prevented.
[0010]
Moreover, as a silicone polymer which comprises a carrier surface, a precise | minute crosslinked structure can be built in the membrane | film | coat, and film | membrane intensity | strength can be strengthened. Further, various conductive fine particles and a low-resistance substance such as carbon are contained in the film in order to provide appropriate electric resistance and charge imparting ability.
[0011]
In this way, by providing a finely controlled shape on the surface of the carrier and selecting an appropriate material for the outer shell layer, the charge imparting ability, toner adhesion, and electrical properties are controlled. The carrier can achieve the above purpose, has a long life, and achieves both developability suitable for the two-component development system and toner retention.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the invention are described in further detail.
The carrier has a form in which a layer corresponding to the outer shell is provided on the surface of the magnetic powder corresponding to the inner core so that the charging property with the toner and the developing property are appropriate. The outer shell has a form in which fine and uniform irregularities are provided on the surface of a substantially spherical core material. The surface of each part of the unevenness is all covered with a resin layer having a uniform composition. This resin layer prevents toner spent, and also has good chargeability, toner retention, toner development. It is preferable to have both properties. Among these, a silicone polymer is preferable because it has a suitable electrical resistance and low surface energy, and has a film forming property that uniformly covers fine irregularities.
[0013]
The silicone polymer here is a polymer having Si—O as a basic repeating unit, and includes a silicone resin containing a repeating unit represented by the following general formula.
[0014]
[Chemical 1]

(In the formula, R is a hydrogen atom, a halogen atom, a hydroxy group, a methoxy group or C₁~ C_FourRepresents a lower alkyl group or a phenyl group. )
[0015]
Examples of such silicone resins include straight silicone, KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone), and some of them are organic There are compounds, modified silicones obtained by substitution and addition, and examples thereof include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, alkyd-modified silicone and the like. Examples include epoxy modification: ES-1001N, acrylic modification: KR-5208, polyester modification: KR-5203, alkyd modification: KR-206, urethane modification: KR-305 (manufactured by Shin-Etsu Chemical Co., Ltd.), epoxy modification: SR2115, alkyd modification: SR2110 (manufactured by Toray Dow Corning Silicone) and the like are typical.
[0016]
A conventionally well-known thing can be used as a carrier core material which provides a membrane | film | coat. Examples thereof include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn—Zn-based ferrite, Cu—Zn-based ferrite, Ni—Zn-based ferrite, and Ba ferrite. As the carrier core material, the above-mentioned magnetic particles are generally used, but a so-called resin-dispersed carrier having a form in which a magnetic powder having a smaller particle diameter is dispersed in a known resin such as a phenol resin, an acrylic resin, or a polyester resin is also suitable. Used.
[0017]
As a method for forming the coating resin, a known method such as a spray drying method, a dipping method, or a powder coating method can be used.
[0018]
The unevenness on the carrier preferably has an average height difference of 0.1 μm to 2 μm. The unevenness on the carrier mentioned here increases the chance of contact between the carrier and the toner when the toner is agitated. However, when the toner is held on the sleeve, the unevenness becomes a contact between the carrier and the toner. Therefore, since the physical adhesion to the carrier is low, the toner can be uniformly charged and rapidly developable. When the height difference is 0.1 μm or less, the above-described effect due to the unevenness cannot be sufficiently expected. When it is larger than 2 μm, it is not preferable because the fine powder component of the toner is likely to be detached and the fine powder component is easily fixed in the concave portion.
[0019]
  Moreover, the presence rate of the convex part on a carrier is important for the same reason. The ratio n / Sc of the number n of convex portions to the required surface area Sc is 1.[Μm ^{- 2} ]The above is preferable. n / Sc is 1[Μm ^{- 2} ]If less, the carrier on the carrier will occupyAThe number of convex portions is not sufficient with respect to the surface area, and the above effect cannot be expected sufficiently.
[0020]
  The measurement of the height difference and the abundance ratio of the unevenness is performed, for example, by observation with an electron microscope. It is easiest to read the height difference directly from the electron micrograph. What is the difference in height of the unevenness here?A circle circumscribing the convex part of the carrier and a circle circumscribing the concave part of the carrierCorresponds to the difference in radius.
[0021]
As described above, such irregularities can be formed by a conventionally known film forming method. In other words, a resin solution is applied on the carrier, or a monomer, oligomer, or polymer solution constituting the resin is applied, dried and solidified, or increased in molecular weight by a corresponding chemical reaction, or chemically coated on the surface of the core material. It is possible to intentionally deposit and harden a part of the film-forming material when forming a film by deposition, lamination, or the like. Most easily, it is obtained by dispersing a particulate substance in a coating material solution, and applying, curing, and curing on a carrier core material. That is, by containing fine particles having a composition different from that of the material constituting the carrier surface inside the convex portion, the shape and state of the irregularities on the film can be arbitrarily formed.
[0022]
At this time, if the fine particles protrude from the core material film, or if the carrier shape becomes irregularly shaped particles that deviate from the spherical shape, the protrusions may be damaged or worn after prolonged use when used as a developer. The local progression of is likely to occur. That is, the unevenness on the carrier is preferably in a uniform form and distributed state. For that purpose, it is preferable that the fine particles forming the convex portion are nearly circular. Anisotropic forms such as needle-like and plate-like particles are not preferable as a material for forming irregularities on the carrier. That is, the ratio of the major axis to the minor axis of the fine particles is preferably in the range of 1.0 to 2.0.
[0023]
The fine particles inside the convex portions used here are preferably metal fine particles and inorganic fine particles such as various metal oxide particles. Among them, metal oxide particles such as silicon oxide, titanium oxide, and alumina are easily and uniformly fine. Particles having a particle size can be obtained, and various electrical properties and mechanical strength can be obtained depending on the particles used. It is also important that the fine particles are thermally stable even when the carrier is heated to a high temperature during the condensation curing of the silicone resin.
[0024]
  Further, it is particularly preferable that the fine particles inside the convex portion are fine particles having a hardness higher than that of the silicone polymer constituting the outer shell. This is because the convex portion on the carrier is substantially a contact portion between the carrier and the carrier, between the carrier and the toner, and with the member in the carrier and the developing device, and this portion has more opportunities to contact with other members than the concave portion. . The inside of the recess is essentially a hard magnet that is the core materialpowderIt is preferable that the convex portion is also a fine particle having a high hardness. That is, by having a higher hardness than that of the silicone polymer, it is possible to prevent selective attrition derived from the uneven shape of the surface. The above metal oxide particles are representative of high hardness particles.
[0025]
Creating an uneven shape on the carrier surface uniformly and toughly is important for improving the durability of the carrier. The convex portion on the carrier is subjected to tangential stress during stirring as compared with the concave portion. When the agitation causes the detachment of the protrusions and the selective wear, the powder characteristics and electrical characteristics of the carrier change, and various image quality degradations may occur due to inconsistencies with image quality changes and imaging conditions. Don't be.
[0026]
In order to form strong irregularities, it is effective and preferable to have a resin layer in which fine particles are embedded, and further to form a resin layer constituting the outermost surface of the carrier on the outer side.
[0027]
That is, when forming a film, first, by forming a resin layer (first layer) containing fine particles, and then laminating a resin layer (second layer) not containing fine particles, A film having excellent durability can be easily obtained.
[0028]
Further, in order to form the unevenness more firmly and prevent toner spent on the carrier, the outer layer of the carrier is composed of an organic resin layer (first layer) containing fine particles and a silicone resin layer (first layer containing no fine particles). It is also preferable to make it a configuration in which two layers are laminated. The outermost silicone resin layer is preferably selected depending on the wear resistance of the carrier film and the spent resistance of the toner, but such a resin is not always excellent in the retention of fine particles. In particular, when carrying large particles with respect to the average thickness of the outer layer, it is necessary to sufficiently increase the mechanical strength of the particles, but when silicone resin is thermally cured on a carrier, the volumetric shrinkage of the film Depending on the interfacial strength between the film and the particles, fine particles may be detached.
[0029]
Therefore, it is preferable to provide a layer mainly for fine particle retention, unevenness formation, and control of electric resistance as the first layer, and to provide a silicone polymer layer as the outermost layer in the outer layer.
As the resin used for the first layer, any conventionally known resin can be used.
[0030]
As illustrated above, all known silicone polymers can be used, but improving the physical hardness of the silicone layer is important for improving the wear durability of the carrier. Even if the material constituting the carrier surface is composed of a single composition silicone polymer, it can have a certain level of wear resistance. In particular, an improvement in wear strength is observed.
[0031]
That is, the wear strength of the carrier is improved by using a polymer that is formed by mixing a tetrafunctional alkoxysilane with a conventionally known prepolymer material having a stratified silicone composition as a material constituting the carrier surface. Conventionally, when a single straight silicone prepolymer is applied and heat-condensed to form a film, it is considered that a crosslinked structure is formed by dehydration condensation between Si-OH in the prepolymer. Uncrosslinked Si—OH remains in the polymer due to the spread of the molecular chain of the polymer and the steric distance between the crosslinking points. By blending this with a polyfunctional silane compound having a low molecular weight, it is considered that a dense cross-linked structure at the time of condensation can be obtained without deteriorating the flexibility and film-forming property of the prepolymer. In general, the condensation product of a tetrafunctional alkoxysilane has a dense cross-linked structure, so that the hardness can be obtained, but it is inferior in film formability. However, it is dissolved in a straight silicone prepolymer to form a film. By carrying out, it is possible to improve the crosslinking density in the silicone polymer, and to form a tougher film.
[0032]
Furthermore, the film strength is further improved by using a straight silicone polymer and a silicone polymer produced from a mixture of a tetrafunctional alkoxysilane and a trifunctional alkoxysilane as the silicone compound to be used. In the same way as above, even if a polyfunctional low molecular weight polymer is further mixed in the straight silicone prepolymer, a high density of the crosslinked structure can be expected, and the formation of a brittle condensate consisting only of tetrafunctional alkoxysilanes can be expected. Can be suppressed.
[0033]
The material of the coating is hydrolyzed by dealcoholization reaction such as straight silicone polymer hydrolyzed by deoxime reaction and the previous tetrafunctional alkoxysilane, or silicone prepolymer composed of tetrafunctional and trifunctional alkoxysilane. More preferably, it is used as a mixture of silicone polymers.
[0034]
As an addition amount of such a polyfunctional alkoxysilane, it is possible to add an arbitrary amount with respect to the straight silicone polymer, and it is preferably 20% to 80%.
[0035]
Further, the carrier film can contain various chemicals for making the charging property with the toner suitable.
[0036]
In particular, an organic silicone resin containing nitrogen in the structure is preferably used because of its chargeability and film formability. As a typical example of the organic silicone resin containing nitrogen in the structure, for example, a so-called aminosilane coupling agent represented by the following structure and having an amino group in X is preferably used.
[0037]
(Wherein, n is an integer of 1 to 3, X is a reactive or adsorptive functional group with an organic or inorganic substance, and a saturated or unsaturated hydrocarbon chain having a functional group, OR is Means an alkoxy group.)
[0038]
[Chemical 2]

[0039]
Moreover, the following substances can be contained in the material constituting the carrier surface for the purpose of adjusting electric resistance. An appropriate amount of one or more kinds may be used as necessary.
[0040]
Metal powder such as conductive ZnO and Al, SnO made by various methods₂And SnO doped with various elements₂Borides such as TlB₂ZnB₂, MoB₂, Silicon carbide and conductive polymers (polyacetylene, polyparaphenylene, poly (para-phenylene sulfide), polypyrrole), carbon black, and the like.
[0041]
The most suitable silicone compound for the film has a high electric resistance and is generally known to have a high resistance. Therefore, as a resistance modifier for film resistance, its volume resistance is 10^-6Preferably, at least one of the following particles is used.
[0042]
Further, it is important that the conductive fine particles introduced for the purpose of adjusting the electric resistance have a sufficiently small particle diameter with respect to the film and can be uniformly dispersed in the film. It is not preferable to disturb the uneven shape of the film by the introduction of these conductive fine particles, and it is important for the effect of the film form to be expected to achieve uniform charge, toner retention and developability. . As a material satisfying these conditions, conductively treated metal oxide fine particles, carbon black, and the like are preferably used.
[0043]
On the other hand, if an extremely low resistance material such as carbon black is dispersed in a silicone film, the electrical properties of the film will change sensitively with respect to the carbon black content, so handle with care. Cost. For example, it is difficult to handle, such as non-uniformity of electrical resistance between carriers is likely to occur, and characteristics of carriers obtained with respect to slight process variations in the manufacturing process are difficult to stabilize. This can be avoided by accurately controlling the content and making the dispersibility uniform in the film, but the electrical resistance control material contained in the film is a mixture of conductive carbon particles and non-conductive metal oxide particles. May be used.
[0044]
When the carrier thus obtained is used as a two-component developer, the measured electric resistance is 10⁷-10¹⁶A range of Ωcm is preferable. The electrical resistance must be selected appropriately according to the development process using the carrier.⁷If it is Ωcm or less, the spike shape of the carrier brush (magnetic brush) held on the developer carrier is not preferable because it becomes conspicuous as the density of the image becomes dark. 10¹⁶If it exceeds Ωcm, it may cause a density difference between the edge part and the solid part of the image or a density difference between the line image and the solid part image, a decrease in developing ability due to edge development or carrier charge-up, or to a non-image part of the latent image It is easy to cause problems such as carrier development (carrier adhesion).
[0045]
The electric resistance of the carrier is a value obtained from a current value and an applied voltage when a carrier is filled between two parallel electrodes and a potential difference is provided between the electrodes. Specifically, a container having electrodes arranged in parallel at an interval of 2 mm is filled with a carrier, and a direct current resistance at a potential difference of 500 V between the two electrodes is measured with a 4329A High Resistance Meter manufactured by Yokogawa Hewlett-Packard Co., Ltd.
[0046]
For the same reason, the thickness of the carrier film is preferably set as appropriate so that the electric resistance is within an appropriate range. However, as silicone has a volume shrinkage during the condensation reaction, the film thickness increases. , There is a drawback that non-uniform reaction within the film tends to occur. Therefore, the film thickness is more preferably 1.0 μm or less.
[0047]
The thickness of the carrier film can be measured by various methods. For example, when the specific gravity of each of the used carrier core material and coating material is known, it is possible to accurately measure the true specific gravity of the carrier.
[0048]
The easiest is to measure the carrier cross section with an electron microscope. In the case of a carrier in which a cured film made of a silicone resin is provided on a core material in which the carrier is a sintered body, the cross section of the coating can be observed relatively easily from the crushed material by crushing the carrier particles by applying pressure in the shear direction. Can do. Here, the average thickness of the outer shell of the carrier means the average thickness of the entire film including irregularities.
[0049]
The carrier thus obtained is preferably mixed with a non-magnetic toner and used as a developer. When the toner has magnetism, when mixed with a magnetic carrier, the carrier and the toner are easily separated in a magnetic field due to the magnetic moment difference and specific gravity difference between the toner and the carrier. In addition, when a magnetic brush is formed by two-component development, there is a phenomenon in which toner aggregates at the brush tip and at a node between carrier particles, which causes uneven toner supply to the image. Uniformity, particularly missing halftone portions and fine dots. When the carrier of the present invention is used in combination with a nonmagnetic toner, the most preferable image is obtained.
[0050]
For the same reason, the thickness of the carrier film is preferably set as appropriate so that the electric resistance is within an appropriate range. However, as silicone has a volume shrinkage during the condensation reaction, the film thickness increases. , There is a drawback that non-uniform reaction within the film tends to occur. Therefore, the film thickness is more preferably 1.0 μm or less.
[0051]
The thickness of the carrier film can be measured by various methods. For example, when the specific gravity of each of the used carrier core material and coating material is known, it is possible to accurately measure the true specific gravity of the carrier.
[0052]
The easiest is to measure the carrier cross section with an electron microscope. In the case of a carrier in which a cured film made of a silicone resin is provided on a core material in which the carrier is a sintered body, the cross section of the coating can be observed relatively easily from the crushed material by crushing the carrier particles by applying pressure in the shear direction. Can do. Here, the average thickness of the outer shell of the carrier means the average thickness of the entire film including irregularities.
[0053]
The carrier of the present invention can provide a preferable image even with a chromatic toner, particularly a chromatic toner containing a release agent. In color image formation using chromatic color toner, the toner is usually an image created using subtractive color mixing of three primary colors (yellow, magenta, cyan, hereinafter Y, M, C respectively) and black (hereinafter BK) toner. Therefore, in order to sufficiently melt the toner of each color and obtain a secondary color, the toner must have meltability and transparency as well as smoothness of the image surface, and is sharp with respect to temperature. The meltability and viscosity change are required. In such toners, the required amount of the release agent is often increased, and adhesion of the release agent to the carrier (spent) becomes a problem. However, even when the carrier of the present invention is used with such toners, For this reason, a good image can be maintained over a long period of time.
[0054]
As a developing device configuration in which the carrier and the developer using the carrier are used, the developer is magnetically held on a developer carrier having a magnet fixed or rotating inside, and the developer carrier is provided. Is provided opposite the latent image carrier so that the developer is continuously brought into contact with the latent image carrier and a potential difference is provided between the developer carrier and the latent image carrier so that the toner is carried on the latent image carrier. Development is performed on the body.
[0055]
The carrier and the developer of the present invention are also preferably used in a conventionally known two-component electrophotographic system. However, since the toner and the developer have high retention and developability for the reasons described above, the carrier and the developer are conventionally used. It is possible to avoid image defects, which are disadvantages peculiar to the two-component development system using.
[0056]
That is, conventionally, in order to ensure the development amount, the difference between the linear velocity (Vr) of the provided developer carrier and the linear velocity (Vp) of the latent image carrier is small, and the developer Even if the contact width between the latent image carrier and the latent image carrier is reduced, a sufficient image density can be obtained. Therefore, it is inevitably possible to prevent the previous image defect.
[0057]
That is, when the moving speed Vp of the latent image carrier surface, the moving speed Vr of the developer carrier surface, and the contact width L between the developer and the latent image carrier,

[Vp: moving speed of surface of latent image carrier (mm / sec),
Vr: moving speed of developer developer surface (mm / sec),
L: contact width between developer and latent image carrier (mm)]
It is sufficient to create an image within the range. If the k value is less than 0.1 mm, a sufficient image density cannot be obtained, and if it is greater than 2 mm, the above-mentioned image defect becomes remarkable.
[0058]
The toner used in the present invention is mainly composed of a thermoplastic resin as a binder resin, and contains a colorant, fine particles, a charge control agent, a release agent and the like. In addition, toners produced by various toner production methods such as generally known pulverization methods and polymerization methods can be used.
[0059]
As binder resin, styrene such as polystyrene and polyvinyltoluene and homopolymers thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-acrylic acid Methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer Polymer, styrene-o-chloromethyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isobutylene Copolymer, styrene-maleic acid Polymer, styrene copolymer such as styrene-maleic acid ester copolymer, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, poly Acrylic resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination.
[0060]
The polyester resin is obtained by a polycondensation reaction between an alcohol and an acid. Examples of the alcohol include polyethylene glycol, diethyl glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-propylene. Diols such as glycol, neopentyl glycol, 1,4-butenediol, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, etc. Etherified bisphenols, divalent alcohol monomers substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, other divalent alcohol monomers, sorbitol, 1,2,3 , 6 Hexanetetrol, 1,4-sarbitane, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, Mention may be made of trihydric or higher alcohol monomers such as 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene. Examples of the carboxylic acid used to obtain the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, and succinic acid. Acids, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters and Dimer from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxylic acid-2-methyl Trivalent or higher polyvalent carboxylic acid monomers such as 2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer, anhydrides of these acids, etc. Can be mentioned.
[0061]
Further, examples of the epoxy resin include a polycondensate of bisphenol A and epichlorohydrin. For example, Epomic R362, R364, R365, R366, R367, R369 (manufactured by Mitsui Petrochemical Co., Ltd.), Epototo YD-011, YD- There are commercially available products such as 014, YD-904, YD-017 (manufactured by Tohto Kasei Co., Ltd.) and Epocoat 1002, 1004, 1007 (manufactured by Shell Chemical Co., Ltd.).
[0062]
Colorants include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallyl. Any conventionally known dyes and pigments such as methane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in combination.
[0063]
Further, the toner does not have any inconvenience even if it contains a drug to be contained for the purpose of controlling the triboelectric chargeability as in the case of the toner that is usually used. As such so-called polarity control agents, for example, metal complexes of monoazo dyes, nitrohumic acid and its salts, metal complexes of salicylic acid, naphthoic acid, dicarboxylic acid such as Co, Cr, Fe, etc. can be used alone or in combination. However, it is not limited to these.
[0064]
In addition, conventionally known fluidity aids and various additives may be used for the toner in order to improve fluidity as powder characteristics such as toner replenishment property, agitation property, and charging property uniformity.
[0065]
  As an additive, for example, Teflon(Registered trademark)Lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, and fluidizing agents typically include metal oxide fine particles such as silicon oxide, titanium oxide and aluminum oxide, and particles whose surfaces are hydrophobized. In addition, any of these fine powders has an excellent effect in terms of fluidity by hydrophobizing the surface. In order to hydrophobize the surface, for example, a silane coupling agent, silicone oil, organic oil, or a silicon compound generally known as a silylating agent can be brought into contact with and reacted with the particle surface.
[0066]
As the hydrophobizing agent, for example, chlorosilanes typically include trichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, ethyldichlorosilane, diethylchlorosilane, triethylchlorosilane, propyldichlorosilane, dipropyldichlorosilane, and tripropylchlorosilane. , Such as alkylchlorosilane, phenylchlorosilane and so on. Fluoroalkyl chlorosilanes, perfluoroalkyl chlorosilanes, silylamines typically include hexamethyldisilazane, diethylaminotrimethylsilane, diethylaminotrimethylsilane, and the like, and silylamides typically include N, O- Bistrimethylsilylacetamide, N-trimethylsilylacetamide, bistrimethylsilyltrifluoroacetamide, etc. Also, as alkoxysilanes, methyltrialkoxysilane, dimethyldialkoxysilane, trimethylalkoxysilane, ethyldialkoxysilane, diethylalkoxysilane, triethylalkoxysilane , Propyltrialkoxysilane, dipropyldialkoxysilane, tripropylalkoxysilane, etc. Fluorosilane, phenylalkoxysilane having a phenyl group, fluoroalkylalkoxysilanes as perfluoro substituents, perfluoroalkylalkoxysilanes, dimethylsilicone oil as silicone oils, derivatives thereof, and fluorine-substituted substances , Disiloxane, hexamethyldisiloxane, and the like, and siloxanes can be used as generally known hydrophobizing agents.
[0067]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, this example is only one embodiment of the present invention, and the present invention is not limited to these examples. In addition, each component amount (part) shown in the following examples is based on weight.
[0068]
Reference example (production example of carriers 1 to 16)
As the carrier core material, Cu—Zn ferrite particles (weight average particle diameter 50 μm, magnetic moment 65 emu / g in applied magnetic field 1000 Oe) were used.
[0069]
(1) The carrier resistance was measured by using a 4329A High Resistance Meter manufactured by Yokogawa Hewlett-Packard Co., Ltd., with a core material filled in a container having electrodes arranged in parallel at an interval of 2 mm, and the DC resistance at 500 V between the two electrodes.
[0070]
(2) The magnetic moment was measured with an applied magnetic field of 1000 Oe using a multi-sample rotational magnetization measuring device REM-1-10 manufactured by Toei Kogyo Co., Ltd.
[0071]
(3) The weight average particle diameter was a diameter (DV) obtained on the basis of weight measured with Microtrac.
An outer layer was formed on each core material as follows to obtain a carrier.
[0072]
Career 1
45 wt% of alumina fine powder (Sumitomo Chemical AA-04 0.4 μm axial ratio 1.1) made of alumina fine powder A as a fine powder A with respect to the solid content of silicone resin (SR2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) Was used for 30 minutes, and this dispersion was diluted to a solid content of 10 wt% to obtain a dispersion.
[0073]
The above dispersion was applied to 5 kg of each of the above core materials at a rate of about 50 g / min in an atmosphere at 100 ° C. using a fluid bed type coating apparatus. Furthermore, it heated at 300 degreeC for 2 hours, and obtained the carrier A with an average film thickness of 0.43 micrometer. The film thickness was adjusted depending on the amount of the coating solution.
[0074]
Career 2
  In the production example of the carrier 1, alumina fine powder (Sumitomo Chemical AA-05 0.5 μm axial ratio 1.2 manufactured by Sumitomo Chemical Co., Ltd.) 45 wt.%The carrier 2 was obtained in the same manner except that.
[0075]
Career 3
Carrier 3 was obtained in the same manner except that 120 wt% of silica fine powder (Admafine SO-C3 1.0 μm axial ratio 1.1) manufactured by Admatechs Co., Ltd. was used as fine powder A in the carrier 1 production example. .
[0076]
Carrier 4
Carrier 4 was obtained in the same manner except that 30 wt% of alumina fine powder (Sumitomo Chemical AA-03 0.3 μm axial ratio 1.1) manufactured by Sumitomo Chemical Co., Ltd. was used as fine powder A in the production example of carrier 1.
[0077]
Carrier 5
Acrylic fine powder MP5500 (0.4 μ axial ratio 1.0) manufactured by Soken Chemical Co., Ltd. is dispersed in a 1: 1 mixed solution of ion-exchanged water and methanol, and this is followed by aminosilane having the following structural formula, 0.1 wt% methanol solution Was added dropwise while mixing. Subsequently, a 0.5 wt% methanol solution of dimethoxydimethylsilane was added dropwise. After sufficiently stirring, a dilute hydrochloric acid aqueous solution was added dropwise to maintain pH 5, and stirring was performed for 4 hours while heating to 60 ° C. in a water bath. Thereafter, this dispersion was repeatedly centrifuged and solvent substitution was performed to obtain a toluene dispersion. A silicone-treated acrylic fine particle dispersion was obtained.
[0078]
[Chemical 3]

[0079]
The fine particles had a particle size of 0.5 μm and an axial ratio of 1.0.
The carrier 5 was obtained in the same manner as in the production example of the carrier 1 except that 80 wt% of the fine particles prepared as follows were used instead of the fine powder A.
[0080]
Career 6
Silicone resin (SR2411: manufactured by Toray Dow Corning Silicone) was added dropwise to a 1: 1 mixed solution of ion-exchanged water and methanol with stirring to emulsify. An aqueous ammonia solution was added dropwise to this solution, and the pH was maintained at 10. The mixture was stirred for 4 hours while heating to 60 ° C. in a water bath to obtain a silicone fine particle dispersion. The fine particles had a particle size of 0.6 μm and an axial ratio of 1.0.
[0081]
In the production example of Carrier 1, Carrier 6 was obtained in the same manner except that instead of fine powder A, the obtained silicone fine particle dispersion was used corresponding to 45 wt% as the solid content.
[0082]
Carrier 7
In the production example of carrier 1, carrier 7 was obtained in the same manner except that 30 wt% of fine powder (Ishihara Sangyo Co., Ltd., titanium oxide TTO-D-1 0.3 μm axial ratio 2.9) was used instead of fine powder A. It was.
[0083]
Career 8
Use a homogenizer for 30 wt% of alumina fine powder (Sumitomo Chemical AA-03 0.3 μm axial ratio 1.1) as fine powder A based on the solid content of the silicone resin solution (SR2411: manufactured by Toray Dow Corning Silicone). The dispersion was used for 30 minutes, and this dispersion was diluted to a solid content of 5 wt% to obtain dispersion A.
[0084]
Separately, the solid content of the silicone resin (SR2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) was dispersed for 30 minutes using a homogenizer, and this dispersion was diluted to a solid content of 5 wt%. Got.
[0085]
  With respect to 5 kg of the core material, the above dispersion A and dispersion B are sequentially applied using a fluidized bed coating apparatus, and are applied at a rate of about 50 g / min in an atmosphere of 100 ° C., and 250 Heat for 2 hours at ℃, average film thickness0.47μm carrier8Got. The film thickness was adjusted depending on the amount of the coating solution.
[0086]
Career 9
Using a homogenizer, 30% by weight of alumina fine powder (Sumitomo Chemical AA-03 0.3 μm axial ratio 1.1) made of alumina as fine powder A is used for the solid content of the acrylic resin solution (Hitaloid 3019, manufactured by Hitachi Chemical Co., Ltd.). For 30 minutes, and this dispersion was diluted to a solid content of 5 wt% to obtain Dispersion A.
[0087]
Separately, a solid content of a silicone resin (SR2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) is dispersed for 30 minutes using a homogenizer, and this dispersion is diluted to a solid content of 5 wt%. Got.
[0088]
With respect to 5 kg of the core material, the above dispersion A and dispersion B are sequentially applied using a fluidized bed coating apparatus, and are applied at a rate of about 50 g / min in an atmosphere of 100 ° C., and 250 The carrier 9 having an average film thickness of 0.2 μm was obtained by heating at a temperature of 2 ° C. for 2 hours. The film thickness was adjusted depending on the amount of the coating solution.
[0089]
Carrier 10
In the production example of carrier 9, 15 parts of tetramethoxysilane was further mixed with the silicone resin of resin dispersion B, and carrier 10 was obtained in the same manner except that.
[0090]
Carrier 11
In Production Example of Carrier 8, 50 parts of a silicone polymer having a number average molecular weight of about 5000 having the following structural formula was further mixed with the silicone resin of Resin Dispersion B, and Carrier 11 was obtained in the same manner except that.
[0091]
Carrier 12
Carrier 12 was obtained in the same manner except that 0.5 part of an aminosilane compound having the following structure was added to resin dispersion A and resin dispersion B in the production example of carrier 10.
[0092]
[Formula 4]

[0093]
Carrier 13
Carrier 13 was obtained in the same manner except that the aminosilane used in the production example of carrier 11 was an aminosilane compound having the following structure.
H₂N (CH₂)_ThreeSi (OC₂H_Five)_Three
[0094]
Career 14
In the production example of carrier 11, 10 parts of conductive titanium oxide (ET-300W 0.03 μm, volume resistance 30 Ωcm, manufactured by Ishihara Sangyo Co., Ltd.) is further added to resin dispersion A and resin dispersion B, and the amount of aminosilane added is 0.7 parts. The carrier 14 was obtained in the same manner except that it was dispersed and used in the same manner.
[0095]
Career 15
In addition to adding 1 part of conductive carbon (made by Lion Akzo, Ketjen Black EC-DJ600) to resin dispersion A and resin dispersion B in the production example of carrier 12, the addition amount of aminosilane is 1.5 parts. The carrier 15 was obtained in the same manner except that they were dispersed and used in the same manner.
[0096]
Carrier 16
In the production example of the carrier 12, 0.5 parts of conductive carbon (made by Lion Akzo, Ketjen Black EC-DJ600) and conductive titanium oxide (ET-300W made by Ishihara Sangyo) are added to the resin dispersion A and the resin dispersion B. Carrier 16 was obtained in the same manner except that 5 parts were added and the amount of aminosilane added was 1.5 parts, except that the dispersion was similarly used.
[0098]
[Table 1]

[0099]
Toner A (Example of toner production)
60 parts of polyester resin
25 parts of styrene acrylic resin
Carnauba wax No.1 product 5 parts
Carbon black (Mitsubishi Chemical # 44) 10 parts
Chromium-containing azo compound (Hodogaya Chemical T-77) 3 parts
[0100]
After thoroughly mixing the above substances with a blender, melt and knead with a twin-screw extruder, allow to cool, coarsely pulverize with a cutter mill, then finely pulverize with a jet airflow fine pulverizer, and further with an air classifier Toner mother particles having a weight average particle diameter of 6.8 μm were obtained.
[0101]
In addition, 0.7 parts of hydrophobic silica fine particles (manufactured by Nippon Aerosil Co., Ltd. R972) and 0.1 parts of hydrophobic titanium oxide (manufactured by MT150A isobutyltrimethoxysilane treated product, hydrophobized by Teika Co., Ltd.) are added to 100 parts of toner base particles. In addition, the toner A was obtained by mixing with a Henschel mixer and wind combing in the same manner.
This toner had a number average diameter of 6.2 μm and a volume average diameter of 7.4 μm.
[0102]
(Evaluation methods)
Example 1
The Ricoh copier imagio MF4570 is loaded with a developer consisting of the previous carrier 1, 95 wt% and toner A 5 wt%. While replenishing the toner, 1 million sheets are printed using a character image chart with an image area ratio of 6%. An imaging test was conducted.
At this time, the photosensitive member charging potential was −850 V, and the applied voltage of the developer carrying roller was −600 V.
During the image formation test, the following printer images were sequentially output and evaluated. Further, a small amount of the developer was taken out from the developing sleeve, and the charge amount of the developer was measured.
[0103]
Saturation ID: A black solid image is output, and the image density is measured with a Macbeth reflection densitometer at any three points on the paper, and the average value is obtained.
A: 1.4 or higher (very good)
○: 1.3 to 1.4 (good)
Δ: 1.2-1.3 (slightly poor)
×: Less than 1.2 (defect) (× is an unacceptable level)
[0104]
Halftone uniformity: A halftone dot image pattern (16 gradations) was output at 600 dots / inch and 150 line / inch for both main scanning and sub-scanning, and dot omission, gradation, and density uniformity were visually evaluated in four stages. .
A: Very good
○: Good
Δ: Slightly poor
×: Defect (× is an unacceptable level)
[0105]
Image defect: Image density measured by Macbeth reflection densitometer = 0.2, 0.8 halftone part (1 cm × 1 cm) is arranged at regular intervals in the paper passing direction. The decrease in the concentration was visually evaluated in four stages.
A: Very good
○: Good
Δ: Slightly poor
×: Defect (× is an unacceptable level)
The evaluation results are shown in Table 2.
[0106]
Examples 2-16
Evaluation was performed in the same manner as in Example 1 except that the developers used were as shown in Table 1. The evaluation results are shown in Table 2.
[0107]
Example 17
In Example 1, the magnetic pole width adjacent to the PC of the developing sleeve roller of the Ricoh copier imagio MF4570 is changed to be a condition that L = 0.2 mm, Vr = 414 mm / sec, Vp = 230 mm / sec, Development was performed. At this time, k = 0.16 mm. Change of magnetic pole width The closest pole of MF4570 was divided into three poles so that the central pole and the upper and lower poles were opposite to each other.
[0108]
An image forming test was conducted on 100,000 sheets using a character image chart with an image area ratio of 6% while loading a developer consisting of 95 parts of the carrier 1 and 5 parts of toner A and replenishing the toner.
At this time, the photosensitive member charging potential was −850 V, and the applied voltage of the developer carrying roller was −600 V.
[0109]
During the image formation test, the following printer images were sequentially output and evaluated. Further, a small amount of the developer was taken out from the developing sleeve, and the charge amount of the developer was measured. The evaluation results are shown in Table 2.
[0110]
Example 18
In the same manner as in Example 17, the magnetization width of the magnet closest to the latent image carrier in the developer carrying roller of Ricoh's Imagio MF4570 was changed and adjusted so as to have an L value of 1 mm. In this apparatus, Vp = 230 mm / sec, Vr = 575 mm / sec, and k = L · ((Vr / Vp) −1)) = 1.5 mm.
Similarly, image evaluation was performed. The evaluation results are shown in Table 2.
[0111]
Example 19
The magnetization width of the magnet closest to the latent image carrier in the developer carrying roller of Ricoh's Imagio MF4570 was changed and adjusted so as to have an L value of 0.4 mm. In this apparatus, Vp = 230 mm / sec, Vr = 575 mm / sec, and k = L · ((Vr / Vp) −1)) = 0.6 mm.
Similarly, image evaluation was performed. The evaluation results are shown in Table 2.
[0112]
Comparative Example 1
  In the carrier production example 1, the fine powder A is not used and the carrier is similarly treated.17It was created. The durability of this carrier was evaluated in the same manner as in the examples. The results are listed in Table 2. This carrier was found to have a significant decrease in charge amount, and a background fog occurred.
[0113]
Comparative Example 2
  In carrier production example 1, instead of fine powder A, a fine alumina powder (Sumitomo Chemical manufactured by Sumiko Random AA-2 3 μm axial ratio 1.1) was used as a carrier.18It was created. The durability of this carrier was evaluated in the same manner as in the example. The results are listed in Table 2. In particular, with this carrier, the halftone uniformity was significantly reduced over time, and the image density was lowered. When the carrier after passing 50,000 sheets was observed with an electron microscope, a large number of traces of protrusions on the surface were observed.
[0114]
Comparative Example 3
  The carrier used in Carrier Production Example 1 was the same except that iron powder particles having a weight average diameter of 82 μm (magnetic moment 90 emu / g at an applied magnetic field of 1000 Oe, irregular shape) were used.19Created.
[0115]
The durability of this carrier was evaluated in the same manner as in the examples. The results are listed in Table 2. This carrier was an image having a low image density from the beginning and being subjected to the uniformity of the halftone portion. In addition, streaky sweeps were observed in the paper passing direction on the image. Further, the occurrence of image defects was remarkable.
[0116]
[Table 2]

[0117]
【The invention's effect】
As described above, as in the present invention, by controlling the surface properties and composition of the carrier finely, it has excellent durability with no fluctuation in image density and no change in image uniformity even during long-term use. Can provide a career. In addition, it is possible to provide an excellent image quality carrier, developer, developing method and apparatus free from image defects peculiar to two-component development.

Claims (27)

It is a carrier having an outer shell layer provided in a form covering the spherical particles having magnetism, and the outer shell layer has irregularities based on fine particles encapsulated in the layer, and the outermost surface is silicone. A carrier for developing an electrostatic latent image , which is coated with a resin film and satisfies the following conditions .
(A) The average height difference of the irregularities is 0.1 μm to 2.0 μm
(B) The ratio n / Sc of the number n of convex portions to the surface area Sc determined from the carrier particle size is 1.0 to 14.15 [μm ⁻² ].   2. The electrostatic latent image developing carrier according to claim 1, wherein fine particles having a composition different from that of the material constituting the outermost surface of the carrier are contained in the convex portion of the outer shell layer. 3. The electrostatic latent image developing carrier according to claim 1, wherein the ratio of the major axis to the minor axis of the fine particles is in the range of 1 to 2 . An electrostatic latent image developing carrier according to any one of claims 1 to 3, the convex portion inside the particles is characterized in that the metal oxide fine particles.   5. The electrostatic latent image developing carrier according to claim 4, wherein the fine particles inside the convex portions are fine particles having a hardness higher than that of the silicone resin constituting the outer shell. Has a resin layer containing the fine particles on the magnetic particles include the electrostatic latent according to any one of claims 1 to 5, characterized by having a resin layer constituting the outermost surface of the carrier on the outside Image development carrier. The outer layer of the carrier has a form in which an organic resin layer (first layer) and the silicone resin layer containing no fine particles and (second layer) laminated containing fine particles, electrostatic latent according to any one of claims 1 to 6 Image development carrier. An electrostatic latent image developing carrier according to any one of claims 1 to 7, the material constituting the shell layer of the carrier is characterized in that it is composed of a plurality of kinds of the silicone resin. An electrostatic latent image developing carrier according to any one of claims 1 to 8, the material constituting the shell layer of the carrier is characterized in that it is a silicone resin to produce a mixture of straight silicone resin and a tetrafunctional alkoxysilane . Claim material constituting the shell layer of the carrier is characterized in that the straight silicone resin is a polymer produced from a mixture of a silicone resin to produce a mixture of tetrafunctional alkoxysilane and a trifunctional alkoxysilane 1-9 The electrostatic latent image developing carrier according to any one of the above. According to claim 9 or 10, wherein the material constituting the shell layer of the carrier is a polymer consisting of an alkoxysilane compound is hydrolyzed by a straight silicone resin and dealcoholization reaction is hydrolyzed by deoximation reaction Carrier for electrostatic latent image development. The carrier for developing an electrostatic latent image according to any one of claims 1 to 11 , wherein the outer shell layer of the carrier contains a charge adjusting material. 13. The electrostatic latent image developing carrier according to claim 12 , wherein the charge control material contained in the outer shell layer of the carrier is an organic silicone compound having nitrogen in the structure. The carrier for developing an electrostatic latent image according to any one of claims 1 to 13 , wherein the outer shell layer of the carrier contains an electric resistance control material. 15. The electrostatic latent image developing carrier according to claim 14, wherein the electrical resistance control material is in the form of particles having at least a volume resistance of 1 × 10 ⁶ Ωcm or less. 16. The electrostatic latent image development according to claim 15, wherein an average particle diameter of the electric resistance control material is smaller than that of the fine particles included in the convex portions and is 1/10 or less of an average film thickness of the outer shell layer. For carrier. 15. The electrostatic latent image developing carrier according to claim 14, wherein at least the electric resistance control material is conductive carbon. The carrier for developing an electrostatic latent image according to any one of claims 14 to 16 , wherein at least the electric resistance control material is metal oxide particles subjected to a conductive treatment. The electrostatic latent image developing carrier according to any one of claims 14 to 17 , wherein the electric resistance control material is conductive carbon particles and conductive metal oxide fine particles. The electrostatic latent image developing carrier according to any one of claims 1 to 19 , wherein a measured electric resistance value of the carrier is in a range of 10 ⁷ to 10 ¹⁶ Ωcm. An electrostatic latent image developing carrier according to any one of claims 1 to 20, the average thickness of the shell layer of the carrier is equal to or is 1.0μm or less. A method for developing an electrostatic latent image, comprising using a developer comprising the carrier according to any one of claims 1 to 21 and a non-magnetic toner. The method of developing an electrostatic latent image according to claim 22, wherein the non-magnetic toner is a chromatic toner containing a releasing agent. Electrostatic latent image developer, characterized in that consists of a carrier according to claim 1 to 21, wherein the non-magnetic toner.   25. The developer for developing an electrostatic latent image according to claim 24, wherein the non-magnetic toner is a chromatic toner containing a release agent. A developer carrier provided opposite to the latent image carrier, and magnetically holding a developer comprising a magnetic carrier and toner that is substantially non-magnetic on the developer carrier, A carrier used in a developing device that develops toner on a latent image carrier by causing a developer to continuously contact the latent image carrier and providing a potential difference between the developer carrier and the latent image carrier. A developing device comprising the carrier according to any one of claims 1 to 21 . At least an electrostatic latent image bearing member according to claim 26, provided facing the developer carrying member for carrying a developer comprising a carrier and a toner having magnetic, and developer carrying member surface, and the latent image bearing member surface Is a developing method in which the toner is developed on the latent image carrier while relatively moving at different speeds. The moving speed Vp of the surface of the latent image carrier, the moving speed Vr of the surface of the developer carrier, the developer and the latent When the contact width L of the image carrier is set,
k = L · ((Vr / Vp) −1)) [mm]
0.1 [mm] ≤ k ≤ 2 [mm] (1)
[Vp: moving speed of surface of latent image carrier (mm / sec),
Vr: moving speed of developer developer surface (mm / sec),
L: contact width between developer and latent image carrier (mm)]
The developing device.