JP4224181B2 - Electrophotographic carrier - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、二成分系現像剤における電子写真用キャリアに関する。
【０００２】
【従来の技術】
電子写真法は、光導電現象を利用し、感光体面に静電潜像を形成し、これを現像剤で現像化し、転写用紙等に定着せしめるものである。従来より、静電潜像を可視化するためには、カスケード法や磁気ブラシ法等で知られるように、キャリアとトナーを混合した二成分系現像剤が使用されている。
【０００３】
二成分系現像剤のキャリアとして、特公昭６２−３７７８３号公報に記載されているように、Ｃｕ、Ｃｏ、ＣｕとＺｎとの組み合わせ、または、ＣｏとＣｕ、Ｚｎ及びＭｇの１〜３種との組み合わせによる磁性キャリア粒子、及び特公平５−５９４２３号公報に記載されているように、ＭｇＯ、ＺｎＯ、Ｆｅ2Ｏ3からなる電子写真用フェライトキャリアがある。
【０００４】
しかし、近年、環境面の問題から、Ｃｕ、Ｃｏ、Ｚｎ等を含まないキャリアの使用が検討されている。例えば、Ｃｕ、Ｃｏ、Ｚｎ等を含まないキャリアとして、特公平２−６０１８６号公報に記載されている、球状マグネタイト粒子よりなる電子写真用キャリアがある。
【０００５】
しかし、球状マグネタイト粒子よりなる電子写真用キャリアは、実質的に飽和磁化のコントロールが不可能で、飽和磁化が高い。このため、キャリア付着に対しては有利であるが、現像トルクが高いため、現像剤の劣化が早く、耐久性に問題があった。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、上記キャリアの問題点を解消し、Ｃｕ、Ｚｎ、Ｃｏ、Ｃｒ、Ｐｂ等の重金属を含まない成分で構成された、環境に優しく、キャリア付着が無く、耐久性に優れた電子写真用キャリアを提供することにある。
【０００７】
【課題を解決するための手段】
本発明は、下記の構成よりなるキャリアであることを特徴とする。
【０００８】
主構成成分が鉄・酸素・マグネシウムで、該マグネシウムを０．５〜１０重量％含有するコア材が樹脂被覆されている電子写真用キャリアであって、飽和磁化が５５〜８５（Ａｍ2／ｋｇ）、残留磁化が３（Ａｍ2／ｋｇ）以下、保磁力が４（ｋＡ／ｍ）以下であり、且つ飽和磁化をσｓ（Ａｍ2／ｋｇ）とし、体積基準粒度分布１％粒径をｘ１（μｍ）としたとき、σｓとｘ１が下記式を満足することを特徴とする電子写真用キャリア。
【０００９】
（１／σｓ）×７５０ ≦ ｘ１
本発明者等は、上記目的を達成するべく鋭意検討した結果、鉄・酸素以外の主構成成分として、環境に優しい成分は、マグネシウムであることを見出した。
【００１０】
本発明のコア材の構成として、最も基本的なものは、鉄・酸素・マグネシウムである。その他の成分の含有量は、合計で２重量％以下であることが望ましい。
【００１１】
マグネシウムの含有量は、０．５〜１０重量％であることが必要で、特に０．８〜８重量％の範囲であることが望ましい。飽和磁化は、５５〜８５（Ａｍ2／ｋｇ）であることが必要で、特に５８〜８３（Ａｍ2／ｋｇ）の範囲であることが望ましい。マグネシウムの含有量が少なくて、飽和磁化が高いと、現像トルクが高くなり耐久性に劣る。また、マグネシウムの含有量が多くて、飽和磁化が低いと、キャリア付着が発生する。
【００１２】
マグネシウムの含有量を多くすると飽和磁化は低下し、焼成温度を高くすると飽和磁化は高くなる。このため、焼成温度を調整することにより、マグネシウムの含有量が０．５重量％未満でも、飽和磁化が８５（Ａｍ2／ｋｇ）以下の粒子を得ることができるが、粒子の空隙量が増大し、キャリアとしては好ましくない。また、マグネシウムの含有量が、１０重量％を超えても、飽和磁化が５５（Ａｍ2／ｋｇ）以上のキャリアを得ることができるが、焼成温度が高くなり、経済性に問題が生じる。
【００１３】
また、焼成の雰囲気を調整することにより、飽和磁化は調整できる。通常、焼成は窒素雰囲気で行うが、窒素、酸素共存下で焼成することにより、飽和磁化は低くなる。しかし、残留磁化及び保磁力が高くなる欠点がある。このため、酸素分圧を調整し、残留磁化及び保磁力を調整する必要がある。
【００１４】
残留磁化は３（Ａｍ2／ｋｇ）以下にすることが必要で、特に２（Ａｍ2／ｋｇ）以下にすることが望ましい。また、保磁力は４（ｋＡ／ｍ）以下にすることが必要で、特に３（ｋＡ／ｍ）以下にすることが望ましい。残留磁化及び保磁力が高くなると、現像剤の流動性が悪化し、耐久性が悪化する。また、前記のキャリアは、通常樹脂被覆されている。
【００１５】
【発明の実施の形態】
本発明で、使用される被覆樹脂としては、例えば、シリコーン系樹脂（シリコーン樹脂及びその誘導体）、フッ素系樹脂、スチレン系樹脂、アクリル系樹脂、メタアクリル系樹脂、ポリエステル系樹脂、ポリアミド系樹脂、エポキシ系樹脂、ポリエーテル系樹脂、フェノール系樹脂等が挙げられる。これらは、単独或いは組み合わせて使用することができ、また、共重合体として使用することもでき、その使用に特に制限はない。
【００１６】
上記樹脂の被覆量は、樹脂の種類、キャリアに要求される帯電特性及び電気抵抗特性によって異なるが、キャリアの重量に対して、０．０５〜５．０重量％の範囲が望ましい。
【００１７】
次に、飽和磁化をσｓ（Ａｍ2／ｋｇ）とし、体積基準粒度分布１％粒径をｘ１（μｍ）としたとき、σｓとｘ１が、（１／σｓ）×７５０≦ｘ１、特に（１／σｓ）×１０００≦ｘ１を満足することが望ましい。さらに好ましくは、体積基準粒度分布５０％粒径をｘ５０（μｍ）としたとき、ｘ５０×０．３５≦ｘ１を満足することが望ましい。この場合、キャリア付着が防止できる。
【００１８】
本発明での飽和磁化、残留磁化、保磁力の測定は、東英工業（株）製の振動型磁力計ＶＳＭＰ−１Ｓ型を用いる。サンプルは測定用カプセル（０．０５６５ｃｃ）に充填し、磁場１．１（ＭＡ／ｍ）で測定する。また、本発明での体積基準粒度分布の測定は、ＳＹＭＰＡＴＥＣ社製のレーザー回折式粒度分布測定装置を用いる。体積基準粒度分布１％粒径、及び体積基準粒度分布５０％粒径は、得られた体積基準粒度分布を、粒径の小さい方から積算して算出する。
【００１９】
本発明のキャリアは、トナーと混合して、二成分現像剤として用いられる。トナーは、結着樹脂中に着色剤等を分散させたもので、結着樹脂としては、ポリスチレン系樹脂、スチレン−アクリル系樹脂、ポリエステル系樹脂、エポキシ系樹脂等が挙げられる。
【００２０】
【実施例】
以下、本発明を実施例により説明する。尚、本発明は、以下の実施例に限られるものではない。
実施例１
ヘマタイトに、酸化マグネシウムをマグネシウム含有量５．０重量％になるよう配合し、次に、バインダー（ポリビニルアルコール）１．５重量％及び分散剤０．５重量％を添加し、スラリー濃度５０重量％になるよう水を加えた。これを、三井鉱山（株）製のアトライターで１時間湿式粉砕混合し、スラリーを作成した。
【００２１】
該スラリーをスプレードライヤーで造粒乾燥し、次に電気炉で、窒素雰囲気下、１４６０℃で５時間焼成し、振動フルイで分級を行ない、芯材キャリアを得た。得られた芯材キャリア１０００重量部に対し、メチル系シリコーン樹脂（東レダウコーニング（株）製のＳＲ２４１０）７５重量部をトルエンで希釈して被覆樹脂溶液を調製し、この樹脂溶液を流動コーティング装置を用いて、上記芯材キャリアにスプレーコートした。その後、流動層にて、２５０℃で６０分間の熱処理を行い、本発明のキャリアを得た。得られたキャリアのマグネシウム含有量は５．０重量％、飽和磁化は５７（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は５５（μｍ）、体積基準粒度分布５０％粒径は１２５（μｍ）であった。
【００２２】
このようにして得られた樹脂被覆キャリア１０００重量部に対して、市販のトナー５５重量部を５リットルのＶ型ブレンダーで３０分間混合して二成分現像剤を得た。この現像剤を用い、市販の複写機で連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例２
ヘマタイトに、酸化マグネシウムをマグネシウム含有量１．０重量％になるよう配合し、分級条件以外は実施例１と同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は１．０重量％、飽和磁化は８４（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は５９（μｍ）、体積基準粒度分布５０％粒径は１４０（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例３
マグネタイトに、酸化マグネシウムをマグネシウム含有量４．６重量％になるよう配合し、実施例１と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は４．６重量％、飽和磁化は５８（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は２０（μｍ）、体積基準粒度分布５０％粒径は５３（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例４
マグネタイトに、酸化マグネシウムをマグネシウム含有量１．３重量％になるよう配合し、実施例１と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は１．３重量％、飽和磁化は８２（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は１４（μｍ）、体積基準粒度分布５０％粒径は３５（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例５
マグネタイトに、酸化マグネシウムをマグネシウム含有量２．５重量％になるよう配合し、実施例１と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は２．５重量％、飽和磁化は７４（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は２２（μｍ）、体積基準粒度分布５０％粒径は５０（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例６
マグネタイトに、酸化マグネシウムをマグネシウム含有量２．０重量％になるよう配合し、実施例１と同様な方法でスラリーを得た。スラリーをスプレードライヤーで造粒乾燥し、次に、電気炉で、窒素＋酸素雰囲気下、１４６０℃で焼成し、振動フルイで分級を行い、芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は２．０重量％、飽和磁化は７５（Ａｍ2／ｋｇ）、残留磁化は２（Ａｍ2／ｋｇ）、保磁力は２（ｋＡ／ｍ）、体積基準粒度分布１％粒径は５２（μｍ）、体積基準粒度分布５０％粒径は１１５（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
実施例７
マグネタイトに、酸化マグネシウムをマグネシウム含有量２．５重量％になるよう配合し、実施例６と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は２．５重量％、飽和磁化は７２（Ａｍ2／ｋｇ）、残留磁化は２（Ａｍ2／ｋｇ）、保磁力は２（ｋＡ／ｍ）、体積基準粒度分布１％粒径は１９（μｍ）、体積基準粒度分布５０％粒径は４０（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、２０万枚後においても初期の画質と大差なく、キャリア付着もなく、カブリも少なく、画像濃度の高い画像が得られた。
比較例１
ヘマタイトに、酸化マグネシウムをマグネシウム含有量１０．５重量％になるよう配合し、実施例１と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は１０．５重量％、飽和磁化は５２（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は２２（μｍ）、体積基準粒度分布５０％粒径は５０（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、初期からキャリア付着が発生した。
比較例２
芯材キャリアにマグネタイト（ヘガネス社製）を使用した以外は、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は０重量％、飽和磁化は９０（Ａｍ2／ｋｇ）、残留磁化は２（Ａｍ2／ｋｇ）、保磁力は２（ｋＡ／ｍ）、体積基準粒度分布１％粒径は５２（μｍ）、体積基準粒度分布５０％粒径は１１５（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、１０万枚後において、カブリが発生した。
比較例３
マグネタイトに酸化マグネシウムをマグネシウム含有量２．５重量％になるよう配合し、実施例１と同様な方法でスラリーを得た。スラリーをスプレードライヤーで、造粒乾燥し、次に電気炉で、窒素＋酸素雰囲気下、１４６０℃で、焼成し、振動フルイで、分級を行い、芯材キャリアを得た。芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は２．５重量％、飽和磁化は６８（Ａｍ2／ｋｇ）、残留磁化は４（Ａｍ2／ｋｇ）、保持力は５（ｋＡ／ｍ）、体積基準粒度分布１％粒径は１９（μｍ）、体積基準粒度分布５０％粒径は４０（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、キャリア付着は発生しなかったが、１５万枚後において、カブリが発生した。
比較例４
ヘマタイトに、酸化マグネシウムをマグネシウム含有量２．５重量％になるよう配合し、実施例１と分級条件以外は同様な方法で芯材キャリアを得、実施例１と同様な方法で、樹脂被覆キャリアを得た。得られたキャリアのマグネシウム含有量は２．５重量％、飽和磁化は７５（Ａｍ2／ｋｇ）、残留磁化は１（Ａｍ2／ｋｇ）、保磁力は１（ｋＡ／ｍ）、体積基準粒度分布１％粒径は９（μｍ）、体積基準粒度分布５０％粒径は３５（μｍ）であった。実施例１と同様な方法で、二成分現像剤を得、連続実写テストを行った。その結果、初期からキャリア付着が発生した。
【００２３】
以上の実施例と比較例をまとめた結果を表１に示す。また、図１の本発明のマグネシウム含有量と飽和磁化の関係を示す図に、実施例と比較例の結果を記入し、図２の本発明の飽和磁化とｘ１の関係を示す図に、実施例と比較例の結果を記入した。図１の太線で囲まれた部分と、図２の太線の内側の部分を合わせた範囲が、本発明の範囲である。
【００２４】
【表１】
【発明の効果】
以上説明したように、本発明によれば、Ｃｕ、Ｚｎ、Ｃｏ等の重金属による環境汚染を防ぎ、キャリア付着がなく、耐久性に優れた電子写真用キャリアを得ることができる。
【図面の簡単な説明】
【図１】本発明のマグネシウム含有量と飽和磁化の関係を示した図である。
【図２】本発明の飽和磁化とｘ１の関係を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic carrier in a two-component developer.
[0002]
[Prior art]
Electrophotography uses a photoconductive phenomenon to form an electrostatic latent image on the surface of a photoreceptor, which is developed with a developer and fixed on a transfer sheet or the like. Conventionally, in order to visualize an electrostatic latent image, a two-component developer in which a carrier and a toner are mixed is used, as is known by a cascade method, a magnetic brush method, or the like.
[0003]
As a carrier of a two-component developer, as described in JP-B-62-37783, Cu, Co, a combination of Cu and Zn, or 1 to 3 types of Co, Cu, Zn and Mg As described in Japanese Patent Publication No. 5-59423, there is a ferrite carrier for electrophotography made of MgO, ZnO, and Fe 2 O 3 .
[0004]
However, in recent years, due to environmental problems, the use of carriers that do not contain Cu, Co, Zn, or the like has been studied. For example, as a carrier that does not contain Cu, Co, Zn, etc., there is an electrophotographic carrier made of spherical magnetite particles described in Japanese Patent Publication No. 2-60186.
[0005]
However, the carrier for electrophotography made of spherical magnetite particles cannot substantially control the saturation magnetization and has a high saturation magnetization. For this reason, it is advantageous for carrier adhesion, but since the developing torque is high, the developer is rapidly deteriorated and there is a problem in durability.
[0006]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the carrier and to be composed of components not containing heavy metals such as Cu, Zn, Co, Cr, Pb, etc., which are environmentally friendly, have no carrier adhesion, and have excellent durability. It is to provide a carrier for electrophotography.
[0007]
[Means for Solving the Problems]
The present invention is a carrier having the following configuration.
[0008]
An electrophotographic carrier in which main components are iron, oxygen, and magnesium, and a core material containing 0.5 to 10% by weight of magnesium is coated with a resin, and has a saturation magnetization of 55 to 85 (Am 2 / kg ), The residual magnetization is 3 (Am 2 / kg) or less, the coercive force is 4 (kA / m) or less, the saturation magnetization is σs (Am 2 / kg), and the volume-based particle size distribution 1% particle size is x1 A carrier for electrophotography, wherein σs and x1 satisfy the following formula when (μm) is satisfied.
[0009]
(1 / σs) × 750 ≦ x1
As a result of intensive studies to achieve the above object, the present inventors have found that an environmentally friendly component is magnesium as the main component other than iron and oxygen.
[0010]
The most basic configuration of the core material of the present invention is iron, oxygen, and magnesium. The total content of other components is preferably 2% by weight or less.
[0011]
The magnesium content is required to be 0.5 to 10% by weight, and particularly preferably in the range of 0.8 to 8% by weight. The saturation magnetization needs to be 55 to 85 (Am 2 / kg), and is particularly preferably in the range of 58 to 83 (Am 2 / kg). If the magnesium content is low and the saturation magnetization is high, the development torque becomes high and the durability is poor. Further, when the content of magnesium is large and the saturation magnetization is low, carrier adhesion occurs.
[0012]
Increasing the magnesium content decreases the saturation magnetization, and increasing the firing temperature increases the saturation magnetization. Therefore, by adjusting the firing temperature, particles having a saturation magnetization of 85 (Am 2 / kg) or less can be obtained even when the magnesium content is less than 0.5% by weight, but the void volume of the particles is increased. However, it is not preferable as a carrier. Further, even if the magnesium content exceeds 10% by weight, a carrier having a saturation magnetization of 55 (Am 2 / kg) or more can be obtained, but the firing temperature becomes high, resulting in a problem in economy.
[0013]
Further, the saturation magnetization can be adjusted by adjusting the firing atmosphere. Usually, firing is performed in a nitrogen atmosphere, but saturation magnetization is lowered by firing in the presence of nitrogen and oxygen. However, there is a drawback that the residual magnetization and the coercive force are increased. For this reason, it is necessary to adjust the oxygen partial pressure and adjust the residual magnetization and the coercive force.
[0014]
The residual magnetization needs to be 3 (Am 2 / kg) or less, and particularly preferably 2 (Am 2 / kg) or less. Further, the coercive force needs to be 4 (kA / m) or less, and particularly preferably 3 (kA / m) or less. When the residual magnetization and the coercive force are increased, the fluidity of the developer is deteriorated and the durability is deteriorated. The carrier is usually coated with a resin.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the coating resin used in the present invention include silicone resins (silicone resins and derivatives thereof), fluorine resins, styrene resins, acrylic resins, methacrylic resins, polyester resins, polyamide resins, An epoxy resin, a polyether resin, a phenol resin, etc. are mentioned. These can be used alone or in combination, and can also be used as a copolymer, and the use thereof is not particularly limited.
[0016]
The coating amount of the resin varies depending on the type of resin, charging characteristics and electrical resistance characteristics required for the carrier, but is preferably in the range of 0.05 to 5.0% by weight with respect to the weight of the carrier.
[0017]
Next, when the saturation magnetization is σs (Am 2 / kg) and the volume-based particle size distribution 1% particle size is x1 (μm), σs and x1 are (1 / σs) × 750 ≦ x1, particularly (1 / Σs) × 1000 ≦ x1 is preferably satisfied. More preferably, it is desirable to satisfy x50 × 0.35 ≦ x1 when the 50% volume-based particle size distribution is x50 (μm). In this case, carrier adhesion can be prevented.
[0018]
For measurement of saturation magnetization, residual magnetization, and coercive force in the present invention, a vibration type magnetometer VSMP-1S manufactured by Toei Kogyo Co., Ltd. is used. The sample is filled in a measurement capsule (0.0565 cc) and measured with a magnetic field of 1.1 (MA / m). The volume-based particle size distribution in the present invention is measured using a laser diffraction particle size distribution measuring device manufactured by SYMPATEC. The volume-based particle size distribution 1% particle size and the volume-based
[0019]
The carrier of the present invention is mixed with toner and used as a two-component developer. The toner is obtained by dispersing a colorant or the like in a binder resin. Examples of the binder resin include polystyrene resins, styrene-acrylic resins, polyester resins, and epoxy resins.
[0020]
【Example】
Hereinafter, the present invention will be described with reference to examples. The present invention is not limited to the following examples.
Example 1
Hematite is blended with magnesium oxide so that the magnesium content is 5.0% by weight, and then 1.5% by weight of binder (polyvinyl alcohol) and 0.5% by weight of dispersant are added, and the slurry concentration is 50% by weight. Water was added to become. This was wet pulverized and mixed for 1 hour with an attritor manufactured by Mitsui Mining Co., Ltd. to prepare a slurry.
[0021]
The slurry was granulated and dried with a spray dryer, then fired in an electric furnace at 1460 ° C. for 5 hours in a nitrogen atmosphere, and classified with a vibration sieve to obtain a core carrier. A coating resin solution is prepared by diluting 75 parts by weight of methyl-based silicone resin (SR2410 manufactured by Toray Dow Corning Co., Ltd.) with toluene with respect to 1000 parts by weight of the obtained core material carrier. Was used to spray coat the core material carrier. Thereafter, heat treatment was performed at 250 ° C. for 60 minutes in the fluidized bed to obtain the carrier of the present invention. The obtained carrier has a magnesium content of 5.0% by weight, a saturation magnetization of 57 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 55 (μm), and the volume-based
[0022]
A two-component developer was obtained by mixing 55 parts by weight of a commercially available toner with a 5-liter V-type blender for 30 minutes with respect to 1000 parts by weight of the resin-coated carrier thus obtained. Using this developer, a continuous live-action test was conducted with a commercially available copying machine. As a result, even after 200,000 sheets, an image having a high image density was obtained with no significant difference from the initial image quality, no carrier adhesion, little fogging.
Example 2
Hematite is blended with magnesium oxide to a magnesium content of 1.0% by weight, and a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions. In the same manner as in Example 1, a resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 1.0% by weight, a saturation magnetization of 84 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 59 (μm), and the volume-based
Example 3
Magnesium oxide is blended with magnetite so that the magnesium content is 4.6% by weight, and a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions. In the same manner as in Example 1, the resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 4.6% by weight, a saturation magnetization of 58 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 20 (μm), and the volume-based
Example 4
Magnesium is mixed with magnesium oxide so that the magnesium content is 1.3% by weight, and a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions. In the same manner as in Example 1, the resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 1.3% by weight, a saturation magnetization of 82 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 14 (μm), and the volume-based
Example 5
Magnesium is mixed with magnesium oxide so that the magnesium content is 2.5% by weight, a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions, and the resin-coated carrier is obtained in the same manner as in Example 1. Got. The obtained carrier has a magnesium content of 2.5% by weight, a saturation magnetization of 74 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 22 (μm), and the volume-based
Example 6
Magnesium oxide was blended with magnetite so that the magnesium content was 2.0 wt%, and a slurry was obtained in the same manner as in Example 1. The slurry is granulated and dried with a spray dryer, then fired at 1460 ° C. in a nitrogen + oxygen atmosphere in an electric furnace, classified with a vibrating sieve to obtain a core carrier, and the same method as in Example 1 A resin-coated carrier was obtained. The obtained carrier has a magnesium content of 2.0% by weight, a saturation magnetization of 75 (Am 2 / kg), a residual magnetization of 2 (Am 2 / kg), a coercive force of 2 (kA / m), and a volume-based particle size The distribution 1% particle size was 52 (μm), and the volume-based
Example 7
Magnesium is blended with magnesium oxide so that the magnesium content is 2.5% by weight, and a core material carrier is obtained in the same manner as in Example 6 except for the classification conditions. In the same manner as in Example 1, the resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 2.5% by weight, a saturation magnetization of 72 (Am 2 / kg), a residual magnetization of 2 (Am 2 / kg), a coercive force of 2 (kA / m), and a volume-based particle size The distribution 1% particle size was 19 (μm), and the volume-based
Comparative Example 1
Hematite is blended with magnesium oxide to a magnesium content of 10.5% by weight, and a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions. In the same manner as in Example 1, a resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 10.5% by weight, a saturation magnetization of 52 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 22 (μm), and the volume-based
Comparative Example 2
A resin-coated carrier was obtained in the same manner as in Example 1 except that magnetite (manufactured by Höganäs) was used for the core material carrier. The obtained carrier has a magnesium content of 0% by weight, a saturation magnetization of 90 (Am 2 / kg), a residual magnetization of 2 (Am 2 / kg), a coercive force of 2 (kA / m), and a volume-based particle size distribution 1 The% particle size was 52 (μm), and the volume-based
Comparative Example 3
Magnesium oxide was blended with magnetite so that the magnesium content was 2.5% by weight, and a slurry was obtained in the same manner as in Example 1. The slurry was granulated and dried with a spray dryer, then baked in an electric furnace at 1460 ° C. in a nitrogen + oxygen atmosphere, and classified with a vibration sieve to obtain a core carrier. A core material carrier was obtained, and a resin-coated carrier was obtained in the same manner as in Example 1. The obtained carrier has a magnesium content of 2.5% by weight, a saturation magnetization of 68 (Am 2 / kg), a residual magnetization of 4 (Am 2 / kg), a holding force of 5 (kA / m), and a volume-based particle size The distribution 1% particle size was 19 (μm), and the volume-based
Comparative Example 4
Hematite is blended with magnesium oxide to a magnesium content of 2.5% by weight, and a core material carrier is obtained in the same manner as in Example 1 except for the classification conditions. In the same manner as in Example 1, a resin-coated carrier is obtained. Got. The obtained carrier has a magnesium content of 2.5% by weight, a saturation magnetization of 75 (Am 2 / kg), a residual magnetization of 1 (Am 2 / kg), a coercive force of 1 (kA / m), and a volume-based particle size The distribution 1% particle size was 9 (μm), and the volume-based
[0023]
Table 1 shows a summary of the above examples and comparative examples. In addition, the results of Examples and Comparative Examples are entered in the graph showing the relationship between the magnesium content and the saturation magnetization of the present invention in FIG. 1, and the graph showing the relationship between the saturation magnetization and x1 in the present invention in FIG. The results of examples and comparative examples were entered. A range in which the portion surrounded by the thick line in FIG. 1 and the portion inside the thick line in FIG. 2 are combined is the range of the present invention.
[0024]
[Table 1]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain an electrophotographic carrier that is excellent in durability because it prevents environmental contamination by heavy metals such as Cu, Zn, and Co, has no carrier adhesion.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between magnesium content and saturation magnetization of the present invention.
FIG. 2 is a diagram showing a relationship between saturation magnetization and x1 of the present invention.
Claims (2)
（１／σｓ）×７５０ ≦ ｘ１ （１） For electrophotography in which the main constituents are iron, oxygen, and magnesium, the total content of other components is 2% by weight or less, and the core material containing 0.5 to 10% by weight of magnesium is resin-coated. The carrier has a saturation magnetization of 55 to 85 (Am 2 / kg), a residual magnetization of 3 (Am 2 / kg) or less, a coercive force of 4 (kA / m) or less, and a saturation magnetization of σs (Am 2 / kg), and σs and x1 satisfy the following formula (1) when the volume-based particle size distribution 1% particle size is x1 (μm).
(1 / σs) × 750 ≦ x1 (1)
ｘ５０×０．３５≦ｘ１x50 × 0.35 ≦ x1 （２）(2)
（式中、ｘ５０は体積基準粒度分布５０％粒径（μｍ）である。）(In the formula, x50 is a volume-based particle size distribution 50% particle size (μm).)
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|---|---|---|---|
| JP33765399A JP4224181B2 (en) | 1999-11-29 | 1999-11-29 | Electrophotographic carrier |
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| JP33765399A JP4224181B2 (en) | 1999-11-29 | 1999-11-29 | Electrophotographic carrier |
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| JP2007322731A Division JP4700677B2 (en) | 2007-12-14 | 2007-12-14 | Electrophotographic carrier |
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| JP4540668B2 (en) * | 2003-03-31 | 2010-09-08 | 関東電化工業株式会社 | Mg-based ferrite material, carrier for electrophotographic development containing the ferrite material, and developer containing the carrier |
| JP4596452B2 (en) | 2004-04-20 | 2010-12-08 | 株式会社巴川製紙所 | Resin-coated carrier for electrophotography and two-component developer for electrophotography using the same |
| US7452651B2 (en) | 2004-11-05 | 2008-11-18 | Canon Kabushiki Kaisha | Carrier, two-component developer, and image forming method |
| JP4534061B2 (en) * | 2005-05-11 | 2010-09-01 | Ｄｏｗａエレクトロニクス株式会社 | Method for producing ferrite particles of carrier powder core material for electrophotographic development |
| JP4817390B2 (en) | 2007-01-16 | 2011-11-16 | パウダーテック株式会社 | Ferrite carrier core material for electrophotographic developer, ferrite carrier and electrophotographic developer |
| JP5307414B2 (en) * | 2008-02-07 | 2013-10-02 | Ｄｏｗａエレクトロニクス株式会社 | Magnetic carrier core material for electrophotographic developer, magnetic carrier for electrophotographic developer, and method for producing electrophotographic developer |
| JP2010164829A (en) | 2009-01-16 | 2010-07-29 | Fuji Xerox Co Ltd | Electrostatic image developing carrier, electrostatic image developer, process cartridge, image forming method, and image forming apparatus |
| JP2010210975A (en) * | 2009-03-11 | 2010-09-24 | Fuji Xerox Co Ltd | Carrier for developing electrostatic charge image and method of producing the same, electrostatic charge image developer, process cartridge, image forming method, and image forming apparatus |
| JP5446593B2 (en) | 2009-08-24 | 2014-03-19 | 富士ゼロックス株式会社 | Electrostatic image developing carrier, electrostatic image developer, process cartridge, image forming method, and image forming apparatus |
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