JP3953906B2 - Electrophotographic developer, carrier for electrophotographic development and method for producing the same - Google Patents

Description

【００５５】
［上記式中、Ｒ^１は水素原子、炭素原子１〜４のアルキル基またはフェニル基、Ｒ^２およびＲ^３は水素基、炭素原子数１〜４のアルコキシ基、フェニル基、フェノキシ基、炭素原子数２〜４のアリケニル基、炭素原子数２〜４のアルケニルオキシ基、ヒドロキシ基、カルボキシル基、エチレンオキシド基、グリシジル基または下記式で示される基である。
【化２】

式中Ｒ^４、Ｒ^５はヒドロキシ基、カルボキシル基、炭素原子数１〜４のアルキル基、炭素原子数１〜４のアルコキシ基、炭素原子数２〜４のアルケニル基、炭素原子数２〜４のアルケニルオキシ基、フェニル基またはフェノキシ基である。ｋ、ｌ、ｍ、ｎ、ｏ、ｐは１以上の整数を示す。
上記各置換基は未置換のものほか、例えばアミノ基、ヒドロキシ基、カルボキシル基、メルカプト基、アルキル基、フェニル基、エチレンオキサイド基、グリシジル基、ハロゲン原子のような置換基を有してもよい。］
【００５６】
またコート層には抵抗調整のために添加物を加えても良い。例えば抵抗調整の添加物としては、従来公知のカーボン、Ａｌ等の金属紛、各種の方法で作られたＳｎＯ_２及び種々の元素をドープしたＳｎＯ_２、ホウ化物例えばＴｉＢ_２、ＺｎＢ_２、ＭｏＢ_２、炭化ケイ素、及び導電性高分子などが挙げられる。
また、キャリア芯材粒子及び／又はコート層中には、これらの抵抗制御剤の分散性や密着性を向上する目的でシランカップリング剤、チタンカップリング剤等のカップリング剤を助剤として添加しても良い。
【００５７】
本発明で用いられるシランカップリング剤の例としては、下記一般式で示される化合物が挙げられる。
ＹＲＳｉＸ_３
（式中、Ｘはケイ素原子に結合している加水分解基でクロル基、アルコキシ基、アセトキシ基、アルキルアミノ基またはプロペノキシ基を示す。Ｙは有機マトリックスと反応する有機官能基でビニル基、メタクリル基、エポキシ基、グリシドキシ基、アミノ基またはメルカプト基を示す。Ｒは炭素数１〜２０のアルキル基またはアルキレン基を示す。）
【００５８】
このシランカップリング剤の中でも、特に負帯電性を有する現像剤を得るにはＹにアミノ基を有するアミノシランカップリング剤が好ましく、正帯電性を有する現像剤を得るにはＹにエポキシ基を有するエポキシシランカップリング剤が好ましい。
【００５９】
【実施例】
次に、本発明を製造例、実施例、比較例を用いて説明する。以下において「部」は重量部を表す。
表１にキャリア製造例の特性をまとめたものを示す。
【００６０】
（キャリア製造例１）
使用コート液：
ストレートシリコーン樹脂（固形分：２０重量％相当） ６３０部
トルエン ６３０部
アミノシラン ６部
カーボン ３部
上記に示すシリコーン樹脂溶液を流動床型コーティング装置を使用して、芯材▲１▼（Ｃｕ−Ｚｎ系フェライト、包絡係数：３．８、重量平均径：３５μｍ、２２μｍ未満の粒子：７重量％以下）５ｋｇの各粒子上に、１００℃の雰囲気下で３０ｇ／ｍｉｎの割合で塗布し、塗布後は電気炉で２５０℃、１２０分の焼成を行い膜厚０．５μｍのコートキャリアＡを得た。
【００６１】
（キャリア製造例２）
芯材▲２▼（包絡係数が１．８であることを除いては芯材▲１▼と同じ）を使用する以外はキャリア製造例１と全く同様にしてキャリアＢを得た。
【００６２】
（キャリア製造例３）
芯材▲３▼（包絡係数が８であることを除いては芯材▲１▼と同じ）を使用する以外はキャリア製造例１と全く同様にしてキャリアＣを得た。
【００６３】
（キャリア製造例４）
芯材▲４▼（２２μｍ未満の粒子の割合が５重量％以下であることを除いては芯材▲１▼と同じ）を使用する以外はキャリア製造例１と全く同様にしてキャリアＤを得た。
【００６４】
（キャリア製造例５）
芯材▲５▼（２２μｍ未満の粒子の割合が３重量％以下であることを除いては芯材▲１▼と同じ）を使用する以外はキャリア製造例１と全く同様にしてキャリアＥを得た。
【００６５】
（キャリア製造例６）
芯材▲６▼（２２μｍ未満の粒子の割合が１０重量％以下であることを除いては芯材▲１▼と同じ）を使用する以外はキャリア製造例１と全く同様にしてキャリアＦを得た。
【００６６】
（キャリア製造例７）
芯材▲７▼（キャリア芯材抵抗率（ＬｏｇＲ）が１００Ｖにおいて８．６Ω・ｃｍであることを除いては芯材▲１▼と同じ）使用する以外はキャリア製造例１と全く同様にしてキャリアＧを得た。
【００６７】
（キャリア製造例８）
芯材▲８▼（キャリア芯材の１０００Ｏｅにおける磁気モーメントが８１ｅｍｕ／ｇであることを除いては芯材▲１▼と同じ）使用する以外はキャリア製造例１と全く同様にしてキャリアＨを得た。
【００６８】
（キャリア製造例９）
芯材▲９▼（キャリア芯材の嵩密度が２．３３ｇ／ｃｍ^３であることを除いてはほぼ芯材▲１▼と同じ）使用する以外はキャリア製造例１と全く同様にしてキャリアＩを得た。
【００６９】
【表１】

【００７０】
［評価方法］
現像剤の作製：
上記コートキャリアとリコー社製の静電荷像現像用トナー（ｉｍａｇｉｏ５１００用黒トナー）を重量比で９３対７になり、総重量が７００ｇになるように混合攪拌し現像剤を作製する。
評価方法：
上記作製現像剤はリコー社製のｉｍａｇｉｏ５１００カラー複写機現像ユニットに充填し、ｉｍａｇｉｏ５１００カラー複写機を使用して評価を行った。現像ニップ部の剤密度は汲み上げ量を調整することで行い、現像スリーブの線速は感光体との線速比で調整した。
（キャリア付着評価方法）
現像バイアス（Ｖｂ）をＤＣ＝−５００Ｖに固定し、帯電電位（Ｖｄ）を−６５０、−８００、−９５０Ｖと変化させ、地肌部の現像を行った。紙に転写が完了する前に電源を落とし、感光体を取りだして付着したキャリアの量を観測した。
ここで地肌ポテンシャルとはＶｂ−Ｖｄのことである。この値が大きいほどキャリア付着が起きやすい。今回の評価では様々な条件を想定し、かなり強い地肌ポテンシャルまで印加した。各地肌ポテンシャルに対するキャリア付着の様子から以下のようなランク付けを行った。
ランク５：強い地肌ポテンシャルを印加してもキャリア付着が起きにくく、キャリア付着の余裕度が極めて高い。
ランク４：強い地肌ポテンシャルを印加すると若干キャリア付着は見られるが、キャリア付着に対して余裕度が高い。
ランク３：強い地肌ポテンシャルをかけるとキャリア付着はやや見られるが、通常の使用では十分耐えうるキャリア付着余裕度。
ランク２：通常の使用の地肌ポテンシャルではキャリア付着は少ないが強い地肌ポテンシャルを印加した場合に急激に増加し、キャリア付着余裕度が劣る。
ランク１：弱い地肌ポテンシャルでもキャリア付着が起きやすく、通常の使用で問題となり、キャリア付着余裕度が劣悪。
非キャリア付着のランク付けは初期剤、Ｓ−３チャートによる５０Ｋラン、１５０Ｋラン、３００Ｋラン後に行い、経時によるキャリア付着ランクの変化を調べた。
【００７１】
（実施例１）
キャリアＡを使用し、現像剤ニップ部の剤密度が１．５ｇ／ｃｍ^３、現像スリーブ線速が４４１ｍｍ／ｓの条件で評価を行った。評価結果をまとめて表２に示す。
【００７２】
（比較例１）
キャリアＣを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期においては非キャリア付着ランクが同じである。ランニングを行うと実施例１では１５０Ｋまで非キャリア付着が悪化しないのに対し、比較例１においては５０Ｋのランで非キャリア付着が急激に悪化した。比較例１は経時に対して非キャリア付着性が極めて悪い。
【００７３】
（比較例２）
キャリアＦを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１がキャリア付着ランク３なのに対し、比較例２では１．５と非キャリア付着性が極めて悪い。キャリア付着ランクの経時に対する変化は、実施例１及び比較例２とも、３００Ｋラン後に初期のキャリア付着ランクから悪化した。比較例２は初期の非キャリア付着性が極めて悪い。
【００７４】
（実施例２）
キャリアＢを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期から１５０Ｋのランまではキャリア付着ランクが３で同じであるが、３００Ｋのランでは実施例１が１．５に下がっているのに対し、実施例２では２．５とランクの低下が少なく、実施例２の方が経時に対する非キャリア付着性が良好であることがわかる。
【００７５】
（実施例３）
キャリアＤを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において、実施例１がキャリア付着ランク３なのに対し、実施例３がランク４と初期におけるキャリア付着ランクが実施例３の方が良好であることがわかる。
【００７６】
（実施例４）
キャリアＥを使用する以外は実施例１と同じ条件で評価を行った。
実施例１及び３と比較すると初期におけるキャリア付着ランクが実施例１及び３がそれぞれランク３、４であるのに対し、実施例４はランク５と極めて良好であることがわかる。
【００７７】
（実施例５）
キャリアＧを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１ではキャリア付着がランク３なのに対し、実施例５ではランクが３．５と実施例５の方が初期のランクが良好であることがわかる。またランニングによる非キャリア付着性の変化も実施例５では３００Ｋラン後において初期に比べ１．０低下しているのに対し、実施例１では１．５も低下していて実施例５のほうが経時に対する非キャリア付着性も安定していることがわかる。
【００７８】
（実施例６）
キャリアＨを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１ではキャリア付着ランク３なのに対し、実施例６ではランクが４と実施例６の方が初期のランクが良好であることがわかる。
【００７９】
（実施例７）
キャリアＩを使用する以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１ではキャリア付着ランク３なのに対し、実施例６ではランクが３．５と実施例７の方が初期のランクが良好であることがわかる。
【００８０】
（実施例８）
現像スリーブの線速が３６７ｍｍ／ｓであること以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１ではキャリア付着ランク３なのに対し、実施例８ではランク３．５と実施例８の方が初期における非キャリア付着性が良好であることがわかる。
【００８１】
（実施例９）
現像ニップ部における現像剤密度が０．９３ｇ／ｃｍ^３であること以外は実施例１と同じ条件で評価を行った。評価結果をまとめて表２に示す。
実施例１と比較すると初期において実施例１ではキャリア付着ランク３なのに対し、実施例９ではランクが３．５と初期における非キャリア付着性が向上していることがわかる。
【００８２】
【表２】

【００８３】
【発明の効果】
包絡係数が４．５より小さい平滑な芯材を使用することにより、１つのキャリア中においてコート層厚が均一になり、経時に対するキャリア付着特性の変化が少なくなり、且つ重量平均粒径が２５〜４５μｍのコートキャリアに占める粒径２２μｍ未満のコートキャリアの量を７重量％以下にすることで良好な非キャリア付着性が得られる。すなわち、長期間にわたり、良好な非キャリア付着性が得られる電子写真現像剤用コートキャリアが得られる。
【図面の簡単な説明】
【図１】キャリア芯材の包絡係数を説明するための図である。
【図２】キャリア芯材の平滑性の違いによるコート層樹脂被覆層の均一性を説明するための図である。
【図３】キャリア芯材の抵抗率測定用セルの概略を表わした図である。
【図４】超音波発信子付き振動篩の概略を表わした図である。
【図５】画像形成装置の概略図である。
【図６】現像容器の概略図である。
【符号の説明】
（図３において）
１１ セル
１２ａ、１２ｂ 電極
１３ キャリア
（図４のおいて）
１ 振動ふるい機
２ 円筒容器
３ スプリング
４ ベース
５ 金網
６ 共振リング
７ ケーブル
８ コンバータ（振動子）
９ リング状フレーム
（図５において）
１ 書きこみユニット
２ 感光体
３ 中間転写ベルト
４ 紙転写ローラ
５ 帯電器
６ 現像ユニット
７ 定着ユニット
（図６において）
１１ 撹拌搬送スクリュー
１２ Ｔサンサ
１３ 現像ローラ
１４ 現像剤
１５ 感光体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic developer used for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like, a carrier used therefor, and a method for producing the same.
[0002]
[Prior art]
Dry electrophotographic methods include a one-component developing method in which toner is charged with a developing sleeve, a blade, and the like, and a two-component developing method in which a carrier is mixed with toner and charged with the carrier. The two-component development method is mainly used for medium- and high-speed machines because the toner charging characteristics are more stable and the toner supply capability is higher than the one-component development method.
[0003]
There are two types of carriers: conductive carriers and insulating carriers. The former mainly uses oxidized or unoxidized iron powder, and has an advantage that a high developing ability can be obtained because of low carrier resistance. However, there are drawbacks in that the image quality deteriorates due to leakage of charges on the photoconductor, and carriers adhere to non-image areas due to charge injection from the carriers. For this reason, the latter insulating carrier in which a resin layer is formed on the surface of a conductive carrier has recently been widely used.
[0004]
However, even with a carrier having a resin layer, it is not sufficient to prevent carrier adhesion, and various improvement methods have been proposed. For example, as described in JP-A-7-234548, by increasing the resin coverage, A method of reducing the exposure of the carrier core material that is likely to cause charge injection is known. However, even in such a carrier with an improved resin coverage, the initial carrier adhesion is satisfactorily prevented, but it is abruptly deteriorated by running and there is no durability against carrier adhesion. In particular, the durability against carrier adhesion is extremely poor in a developing unit having a small developer capacity and a developing process having a fast sleeve linear velocity. Recently, the speed of copying has been increased, and the amount of developer to be loaded has decreased due to the downsizing of the apparatus. Therefore, the use conditions for carrier adhesion have become stricter, while the developer has been reduced due to reduced maintenance. The durability of the resin is strongly desired, and good non-carrier adhesion over a long period is strongly desired.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carrier for an electrophotographic developer and a two-component developer that hardly cause carrier adhesion over a long period of time. Still another object of the present invention is to provide a method for producing the carrier. Still another object of the present invention is to provide a developing method using the developer. Still another object of the present invention is to provide a developer container containing the developer. Still another object of the present invention is to provide an image forming apparatus equipped with the developer container.
[0006]
[Means for Solving the Problems]
The inventors of the present invention observed the carrier that caused the carrier adhesion after running, and confirmed that the core material was exposed much more than in the initial stage. When the carrier before running was analyzed for the uniformity of the coating layer (resin layer) thickness by mapping Si, the coating layer covered the entire core material, but the coating layer was thicker depending on the location in one particle. It was confirmed that the thin portions were mixed and the layer thickness was uneven. It is thought that the portion where the coat layer was thin was shaved immediately by running, and the exposure of the core material increased rapidly.
In order for the carrier adhesion to show good characteristics even with changes over time, improvement of the coating layer coverage is not prevented at all, and it is extremely important to form a uniform coating layer in one particle. It came to the idea that there is. The present invention has been made based on this.
[0007]
According to the present invention, the following electrophotographic developer, carrier for electrophotographic developer, carrier manufacturing method, developing method, developing container, and image forming apparatus are provided.
[0008]
(1)FerriteIn the carrier for an electrophotographic developer in which a resin coating layer is formed on the surface of the carrier core material,TheThe carrier has a weight average particle size of 25 to 45 μm.Yes, in the carrierParticle size less than 22μmThe content ratio of particles having a particle size of7% by weight or less,The bulk density of the carrier core material is 2.11 to 2.33 g / cm. ³ AndAnd, when the envelope coefficient A of the carrier core material is expressed by the following equation (1)1.8 ≦ A ≦ 4.0A carrier for an electrophotographic developer characterized byIs.
A = (L₁-L₂) / L₂× 100 (1)
L₁: Perimeter length of projected image of carrier core material
L₂： Envelope length of carrier core projected image
[0009]
(2) The carrier for electrophotographic developer according to (1), wherein the relationship of A <2.5 is satisfied.
[0010]
(3) The carrier for an electrophotographic developer according to any one of (1) and (2) above, wherein the carrier having a particle size of less than 22 μm is 5% by weight or less.
[0011]
(4) The carrier for an electrophotographic developer according to any one of (1) to (3), wherein a carrier having a particle size of less than 22 μm is 3% by weight or less.
[0012]
(5) The carrier for an electrophotographic developer according to any one of (1) to (4), wherein the carrier core material has a resistivity (LogR) of 8.5 Ω · cm or more.
[0013]
(6) The carrier for an electrophotographic developer according to any one of (1) to (5), wherein the carrier core has a magnetic moment of 76 emu / g or more.
[0014]
(7) According to any one of (1) to (6) aboveIn the method for producing a carrier for electrophotographic development, (i) a step of forming a resin film on the surface of a carrier core material comprising pulverized particles of a magnetic material to obtain resin-coated particles; (ii) the resin-coated particles; And a step of obtaining a carrier having a weight average particle diameter of 25 to 45 μm and a content ratio of particles having a particle diameter of less than 22 μm of 7% by weight or less by classification. Carrier manufacturing method.
[0015]
(8)The method for producing a carrier for an electrophotographic developer according to (7), wherein a vibration sieving machine equipped with an ultrasonic oscillator is used to classify the resin-coated particles.
[0016]
(9)The method for producing a carrier for an electrophotographic developer according to (8) above, wherein the vibration sieve machine with an ultrasonic oscillator has a structure for transmitting ultrasonic vibrations to a wire mesh surface by a resonance ring installed in the sieve machine.
[0017]
(10)An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of the above (1) to (6) and a toner.
[0022]
(15) In the developer container in which the developer is stored, the developer is0)A developer container, which is the electrophotographic developer described in 1.
[0023]
(16) An image forming apparatus equipped with a developer container, wherein the developer container is the developer container described in (15) above.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
The carrier for an electrophotographic developer of the present invention has a relationship of A <4.5 when the envelope coefficient A of the carrier core material is expressed by the equation (1), and the weight average particle diameter of the carrier core material is Particles having a particle size of 25 to 45 μm and less than 22 μm are 7% by weight or less. In the present invention, the coefficient defined by the equation (1) is introduced as a coefficient representing the smoothness of the carrier core material, and this coefficient is called an envelope coefficient.
A = (L₁-L₂) / L₂× 100 (1)
L₁: Perimeter length of projected image of carrier core material
L₂： Envelope length of carrier core projected image
[0025]
L₁Is the outer peripheral length of the carrier core projection as shown by the solid line in FIG.₂Is the length of the envelope of the carrier core projection as shown by the dotted line in FIG. L₁And L₂The smaller the difference, the less the unevenness. In the coefficient defined by the above equation, the closer to 0, the smaller the surface unevenness, which means smoother.
[0026]
L above₁, L₂Can be measured by the following method.
The carrier core material is photographed with a scanning electron microscope (Hitachi S-2700) at a magnification of 300 times. The image is loaded into a personal computer and analyzed using Image-Pro (Media).₁Select Perimeter in the measurement item and select L₂Is Perim. Select (convex) and measure.
300 arbitrarily selected carrier core materials are measured, and the average value is adopted.
[0027]
When a resin is coated on a core material with many irregularities, as shown in FIG. 2 (b), the resin liquid tends to accumulate in the recessed portion, and conversely, the convex portion becomes insufficient and the coating layer becomes thin. In the carrier, the layer thickness is non-uniform. The thin part of the coat layer was exposed to the core material surface immediately due to wear, and the carrier adhesion with time deteriorated rapidly. On the other hand, a core material with a smooth surface with few irregularities has no place where the resin liquid is unevenly distributed as shown in FIG. 2A, and the coat layer becomes uniform in one carrier. Compared with the coated carrier of the core material with many irregularities, exposure of the core material background portion with time was very small, and the carrier adhesion with time was good. As a result of intensive studies, it has been found that when a core material having an envelope coefficient smaller than 4.5 is used, there is little deterioration in carrier adhesion over time.
[0028]
The carrier core material in the present invention has a weight average particle diameter of 25 to 45 μm. Here, even when a core material having a smooth core material surface as described above was used, the use of a carrier having a small average particle diameter deteriorated non-carrier adhesion from the beginning. Analysis of the carrier-attached carrier reveals that the coat layer is uniform and the core carrier is a good coat carrier with little exposure of the core material, but it is found that there are many fine powders having a small particle size of less than 22 μm, and the amount of fine powder in the carrier is small. I confirmed it was important. In the carrier particle size distribution, the non-carrier adhesion was also improved by making the particles having a particle size of less than 22 μm 7% by weight or less.
[0029]
This is considered to be because when the carrier particle size is small, the magnetic moment per carrier is small, the magnetic binding force on the developing sleeve is weakened, and carrier adhesion is likely to occur even when the background is not exposed.
[0030]
Moreover, good non-carrier adhesion was obtained over a long period of time by using a coated carrier having a smooth surface of the carrier core material and a particle size distribution with a small amount of fine powder.
[0031]
In the present invention, it is more preferable that the envelope coefficient is smaller than 2.5. Even when the envelope coefficient is less than 4.5, the carrier non-adhesiveness with respect to time is good, but by making it smaller than 2.5, the good non-carrier adhesiveness is maintained for a longer period of time.
[0032]
In the present invention, the carrier particles having a particle size of less than 22 μm are more preferably 5% by weight or less, and still more preferably 3% by weight or less. Such carrier adhesion of fine powder occurs even if the coat layer is uniform and the core material background is not exposed, and the content is preferably small. Even if it is 7% by weight or less, the amount of carrier adhesion that can be practically tolerated is achieved, but if it is 5% by weight or less, further improvement is achieved, and if it is 3% by weight or less, extremely good non-carrier adhesion is exhibited.
[0033]
More preferably, the carrier core material has an electrical resistivity (log R) of 8.5 Ω · cm or more. Even if the electrical resistivity (log R) of the carrier core material is less than 8.5 Ω · cm, there is no practical problem, but by setting it to 8.5 Ω · cm or more, better non-carrier adhesion characteristics can be obtained over a long period of time. Even when the surface of the carrier core material is exposed due to wear of the coat layer, coating unevenness, or the like, by increasing the resistance of the carrier core material itself, charge injection is suppressed and carrier adhesion characteristics are improved. The upper limit of the electrical resistivity is preferably about 13 Ω · cm. If the resistance is further increased, the resistance may be higher than that of the coat layer, and resistance control by the coat layer may be difficult.
[0034]
The carrier resistivity can be measured by the following method.
[0035]
As shown in FIG. 3, a cell 13 made of a fluororesin container containing electrodes 12a and 12b having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier 13, and a DC voltage of 100 V is applied between both electrodes, The DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HLVLVWDQFH 0HWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), and the electrical resistivity LogR (Ωcm) is calculated.
[0036]
More preferably, it is desirable that the magnetic moment of the carrier core material is 76 emu / g or more. By setting it to 76 emu / g or more, the binding force of the carrier with respect to the developing sleeve is strengthened, and the occurrence of carrier adhesion can be further prevented. The upper limit value of the magnetic moment of the carrier core material is not particularly limited, but is usually about 150 emu / g.
[0037]
The magnetic moment can be measured as follows.
Using a B-H tracer (BHU-60, manufactured by Riken Denshi), 1.0 g of the carrier core material is packed in a cylindrical cell and set in the apparatus. The magnetic field is gradually increased to 3000 oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.
[0038]
More preferably, the bulk density of the carrier core material is 2.2 g / cm.³The above is desirable. A core material having a small bulk density is porous and has large irregularities on the surface. In the case of porosity, even if the magnetic moment of 1000 Oe is large, the substantial magnetic moment per particle is small, which is disadvantageous for non-carrier adhesion, and the bulk density is 2.2 g / cm 2.³By making it above, better non-carrier adhesion is exhibited. The upper limit of the bulk density of the carrier core material is 3.0 g / cm because the filling rate is only about 74% even when the spherical particles having the same particle diameter are closely packed.³Any degree is acceptable.
[0039]
The carrier of the present invention can be obtained by pulverizing a magnetic material, classifying the pulverized particles so as to obtain a predetermined particle size, and forming a resin film on the surface of the core material obtained by the classification. it can.
[0040]
The classification includes wind classification, sieve classification (sieving), and the like. Vibrating sieves are preferably used for the production of carrier core materials. However, in the case of conventional vibrating sieves, when trying to classify particles having a small particle size, the mesh of the sieve (metal mesh) is small. Since the problem of clogging immediately occurs, the workability for the classification is very bad.
[0041]
The inventors of the present invention have made various studies in order to develop a method capable of efficiently and sharply cutting small-sized particles. When the particles are classified using a sieving machine, ultrasonic vibration is applied to the wire mesh. Thus, it has been found that small diameter particles of less than 22 μm can be cut efficiently and sharply.
[0042]
The ultrasonic vibration that vibrates the wire mesh can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. The converter in this case consists of a PZT vibrator. In order to vibrate the wire mesh by ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to a resonance member fixed to the wire mesh. The resonance member to which the ultrasonic vibration is transmitted resonates by the ultrasonic vibration, and vibrates the wire mesh fixed to the resonance member.
The frequency for vibrating the wire mesh is 20 to 50 kHz, preferably 30 to 40 kHz. The shape of the resonance member may be any shape suitable for vibrating the wire mesh, and is usually a ring shape.
The vibration direction for vibrating the wire mesh is preferably a vertical direction.
[0043]
FIG. 4 is an explanatory structural diagram of a vibration sieve with an ultrasonic oscillator.
In FIG. 4, 1 is a vibration sieve, 2 is a cylindrical container, 3 is a spring, 4 is a base (support), 5 is a wire mesh, 6 is a resonant ring, 7 is a high-frequency current cable, 8 is a converter, and 9 is a ring shape. Indicates a frame. In order to operate the vibration sieve with an ultrasonic oscillator (circular sieve) shown in FIG. 1, a high-frequency current is supplied to the converter 8 via the cable 7. The high frequency current supplied to the converter 8 is converted into ultrasonic vibration. The ultrasonic vibration generated in the converter 8 vibrates the resonance ring 8 to which the converter 8 is fixed and the ring-shaped frame 9 connected thereto in the vertical direction. Due to the vibration of the resonance ring 6, the metal mesh 5 fixed to the resonance ring 6 and the frame 9 vibrates in the vertical direction.
[0044]
Vibrating sieve machines equipped with an ultrasonic oscillator are commercially available, and are available, for example, as “Ultrasonic” as a product name from Kanei Sangyo Co., Ltd.
[0045]
The carrier of the present invention can also be produced by forming a resin film on the surface of pulverized particles of a magnetic material to form resin-coated particles, and then classifying the resin-coated particles. In this case, the classification of the resin-coated particles (carrier particles) is preferably performed using the above-described vibration sieving machine equipped with an ultrasonic oscillator.
[0046]
As a developing method using the carrier, the linear velocity of the developing sleeve is preferably 400 mm / s or less. Even if the sleeve linear velocity is higher than 400 mm / s, it shows carrier adhesion characteristics that can withstand normal use. However, by making the sleeve linear velocity 400 mm / s or less, the centrifugal force applied to the carrier of the magnetic brush is reduced, and the carrier The binding force on the sleeve increases, and the occurrence of carrier adhesion can be further suppressed. The lower limit of the sleeve linear velocity is about 100 mm / s because the developing ability is lowered.
[0047]
More preferably, as a developing method using the carrier, the developer filling density at the closest portion of the photoreceptor and the developing sleeve is 1.2 g / cm.³The following is desirable. As the packing density increases, carriers are also deposited in places where the magnetic force is relatively weak, that is, carrier adhesion. Although there is no problem in practical use, the packing density is 1.2 g / cm.³By lowering to the following, the carrier adhesion is prevented and better non-carrier adhesion is exhibited. In addition, since the developer supply amount decreases, the packing density is 0.7 g / cm.³Larger is preferred.
[0048]
The developer filling density in the developing nip here is a value obtained by dividing the pumping amount by the developing gap (distance between the closest portion of the photosensitive member and the developing sleeve). The pumping amount is 1 cm before entering the developing area after passing the doctor blade when the machine is forcibly stopped after stirring the developing sleeve for 60 seconds at the process speed used.³Per gram of developer.
[0049]
The developing container filled with the developer of the present invention is accommodated in a developing portion of an image forming apparatus represented by, for example, an electrophotographic apparatus. FIG. 5 is a schematic view of an example of an image forming apparatus, and FIG. 6 is a schematic view of a developing container.
[0050]
Although it does not restrict | limit especially as a raw material of a carrier core material, a conventionally well-known magnetic particle can be used. For example, magnetite, hematite, Li-based ferrite, Cu-Zn-based ferrite, Mn-Zn-based ferrite, Ni-Zn-based ferrite, Ba ferrite, iron, cobalt, nickel and the like can be mentioned.
[0051]
The core material having a magnetic moment of 76 emu / g or more when a magnetic field of 1000 Oe used more preferably in the present invention is a magnetite-based, Mn-Mg-Sr-based, Mn-based ferrite or the like.
[0052]
The carrier coat layer is not particularly limited, and a conventionally known one can be used. For example, polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polystyrene, acrylic (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl Polyvinyls and polyvinylidene resins such as ethers and polybiliketones; vinyl chloride-vinyl acetate copolymers; silicone resins composed of organosiloxane bonds or modified products thereof (for example, modified products using alkyd resins, polyester resins, epoxy resins, polyurethanes, etc.); Perhydropolysilazane or modified products thereof (including partially oxidized products); polytetrafluoroethylene, polyvinyl fluoride, polyvinyl fluoride Den, fluorine resins such as polychlorotrifluoroethylene, polyamides, polyesters, polyurethanes, polycarbonates, urea resins, melamine resins, benzoguanamine resins, epoxy resins and the like. Among them, as a preferable coating layer material for satisfying the constituent requirements of the present invention, a silicone resin or a modified product thereof, a fluorine resin, particularly a silicone resin or a modified product thereof is more preferable.
[0053]
The silicone resin may be any conventionally known silicone resin, and includes straight silicone consisting only of an organosiloxane bond represented by the following formula and a silicone resin modified with alkyd, polyester, epoxy, urethane or the like. It is done.
[0054]
[Chemical 1]

[0055]
[In the above formula, R¹Is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R²And R³Is a hydrogen group, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a hydroxy group, a carboxyl group, an ethylene oxide group, A glycidyl group or a group represented by the following formula.
[Chemical 2]

Where R⁴, R⁵Is a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a phenyl group Or a phenoxy group. k, l, m, n, o, and p are integers of 1 or more.
Each of the above substituents may have a substituent such as an amino group, a hydroxy group, a carboxyl group, a mercapto group, an alkyl group, a phenyl group, an ethylene oxide group, a glycidyl group, or a halogen atom in addition to an unsubstituted one. . ]
[0056]
An additive may be added to the coating layer for adjusting the resistance. For example, as an additive for resistance adjustment, conventionally known carbon, metal powder such as Al, SnO made by various methods₂And SnO doped with various elements₂Borides such as TiB₂ZnB₂, MoB₂, Silicon carbide, and conductive polymer.
In addition, a coupling agent such as a silane coupling agent or a titanium coupling agent is added as an auxiliary agent to the carrier core particles and / or the coating layer in order to improve the dispersibility and adhesion of these resistance control agents. You may do it.
[0057]
Examples of the silane coupling agent used in the present invention include compounds represented by the following general formula.
YRSiX₃
(In the formula, X is a hydrolyzable group bonded to a silicon atom and represents a chloro group, an alkoxy group, an acetoxy group, an alkylamino group, or a propenoxy group. Y is an organic functional group that reacts with an organic matrix, such as a vinyl group, A group, an epoxy group, a glycidoxy group, an amino group, or a mercapto group, and R represents an alkyl group or an alkylene group having 1 to 20 carbon atoms.)
[0058]
Among these silane coupling agents, an aminosilane coupling agent having an amino group in Y is preferable for obtaining a negatively charged developer, and Y has an epoxy group in order to obtain a positively charged developer. Epoxy silane coupling agents are preferred.
[0059]
【Example】
Next, this invention is demonstrated using a manufacture example, an Example, and a comparative example. In the following, “parts” represents parts by weight.
Table 1 summarizes the characteristics of carrier production examples.
[0060]
(Carrier production example 1)
Used coating solution:
Straight silicone resin (solid content: equivalent to 20% by weight) 630 parts
630 parts of toluene
Aminosilane 6 parts
Carbon 3 parts
Using the fluidized bed type coating device, the silicone resin solution shown above was used as a core material (1) (Cu—Zn ferrite, envelope coefficient: 3.8, weight average diameter: 35 μm, particles less than 22 μm: 7% by weight The following is applied to each particle of 5 kg at a rate of 30 g / min in an atmosphere of 100 ° C. After coating, the carrier is baked at 250 ° C. for 120 minutes in an electric furnace to obtain a coat carrier A having a thickness of 0.5 μm. It was.
[0061]
(Carrier production example 2)
Carrier B was obtained in exactly the same manner as Carrier Production Example 1, except that core material (2) (same as core material (1) except that the envelope coefficient was 1.8) was used.
[0062]
(Carrier production example 3)
Carrier C was obtained in exactly the same manner as Carrier Production Example 1 except that core material (3) (same as core material (1) except that the envelope coefficient was 8) was used.
[0063]
(Carrier Production Example 4)
Carrier D was obtained in exactly the same manner as Carrier Production Example 1, except that core (4) (same as core (1) except that the proportion of particles less than 22 μm was 5% by weight or less) was used. It was.
[0064]
(Carrier production example 5)
Carrier E was obtained in exactly the same manner as Carrier Production Example 1, except that core material (5) (same as core material (1) except that the proportion of particles less than 22 μm was 3% by weight or less) was used. It was.
[0065]
(Carrier Production Example 6)
Carrier F was obtained in exactly the same manner as Carrier Production Example 1 except that core material (6) (same as core material (1) except that the proportion of particles less than 22 μm was 10% by weight or less) was used. It was.
[0066]
(Carrier Production Example 7)
Core material (7) (Same as core material (1) except that carrier core material resistivity (LogR) is 8.6 Ω · cm at 100 V) Carrier G was obtained.
[0067]
(Carrier Production Example 8)
Core material (8) (Same as core material (1) except that the magnetic moment at 1000 Oe of the carrier core material is 81 emu / g) It was.
[0068]
(Carrier production example 9)
Core material (9) (bulk density of carrier core material is 2.33 g / cm³The carrier I was obtained in exactly the same manner as in the carrier production example 1 except that it was substantially the same as the core material (1) except for the above.
[0069]
[Table 1]

[0070]
[Evaluation methods]
Developer development:
The developer is prepared by mixing and stirring the coat carrier and the electrostatic charge image developing toner (black toner for imgio 5100) manufactured by Ricoh Co. so that the weight ratio is 93: 7 and the total weight is 700 g.
Evaluation methods:
The developer prepared above was filled in an imgio 5100 color copying machine developing unit manufactured by Ricoh Co., Ltd. and evaluated using an imagio 5100 color copying machine. The agent density in the developing nip was adjusted by adjusting the pumping amount, and the linear velocity of the developing sleeve was adjusted by the linear velocity ratio with the photosensitive member.
(Carrier adhesion evaluation method)
The development bias (Vb) was fixed at DC = −500 V, and the charging potential (Vd) was changed to −650, −800, and −950 V to develop the background portion. Before the transfer to the paper was completed, the power was turned off, the photoconductor was taken out, and the amount of attached carrier was observed.
Here, the background potential is Vb−Vd. The larger this value, the easier the carrier adhesion occurs. In this evaluation, various conditions were assumed and a very strong background potential was applied. The following rankings were performed based on the carrier's adherence to the skin potential of each region.
Rank 5: Carrier adhesion hardly occurs even when a strong background potential is applied, and the margin for carrier adhesion is extremely high.
Rank 4: Although a slight carrier adhesion is observed when a strong background potential is applied, the margin for carrier adhesion is high.
Rank 3: Carrier adhesion is slightly seen when a strong ground potential is applied, but the carrier adhesion margin that can withstand normal use.
Rank 2: Although the carrier adhesion is small in the normal use of the background potential, it increases rapidly when a strong background potential is applied, and the carrier adhesion margin is inferior.
Rank 1: Carrier adhesion is likely to occur even with a weak ground potential, which causes a problem in normal use, and the carrier adhesion margin is poor.
The ranking of non-carrier adhesion was performed after 50K run, 150K run, and 300K run according to the initial agent, S-3 chart, and the change in carrier adhesion rank with time was examined.
[0071]
Example 1
Using carrier A, the developer density in the developer nip is 1.5 g / cm³The evaluation was performed under the condition that the developing sleeve linear velocity was 441 mm / s. The evaluation results are summarized in Table 2.
[0072]
(Comparative Example 1)
Evaluation was performed under the same conditions as in Example 1 except that carrier C was used. The evaluation results are summarized in Table 2.
Compared with Example 1, the non-carrier adhesion rank is the same in the initial stage. When running, in Example 1, non-carrier adhesion did not deteriorate up to 150K, whereas in Comparative Example 1, non-carrier adhesion deteriorated rapidly after 50K run. Comparative Example 1 has very poor non-carrier adhesion over time.
[0073]
(Comparative Example 2)
Evaluation was performed under the same conditions as in Example 1 except that carrier F was used. The evaluation results are summarized in Table 2.
Compared with Example 1, in Example 1, Example 1 has a carrier adhesion rank of 3, whereas Comparative Example 2 has an extremely poor non-carrier adhesion of 1.5. The change in the carrier adhesion rank with time deteriorated from the initial carrier adhesion rank after 300 K run in both Example 1 and Comparative Example 2. Comparative Example 2 has very poor initial non-carrier adhesion.
[0074]
(Example 2)
Evaluation was performed under the same conditions as in Example 1 except that carrier B was used. The evaluation results are summarized in Table 2.
Compared with Example 1, the carrier adhesion rank is the same at 3 from the initial run up to 150K, but in Example 300, Example 1 drops to 1.5 in the 300K run, whereas in Example 2, the carrier adhesion rank is 2.5. It can be seen that there is little decrease in rank, and Example 2 has better non-carrier adhesion over time.
[0075]
(Example 3)
Evaluation was performed under the same conditions as in Example 1 except that carrier D was used. The evaluation results are summarized in Table 2.
Compared to Example 1, it can be seen that Example 1 has a carrier adhesion rank of 3 in the initial stage, whereas Example 3 has a better carrier adhesion rank in Example 3 and Rank 3 in Example 3.
[0076]
(Example 4)
Evaluation was performed under the same conditions as in Example 1 except that carrier E was used.
Compared with Examples 1 and 3, it can be seen that the carrier adhesion rank at the initial stage is extremely good with Rank 5 while Examples 1 and 3 are Ranks 3 and 4 respectively.
[0077]
(Example 5)
The evaluation was performed under the same conditions as in Example 1 except that the carrier G was used. The evaluation results are summarized in Table 2.
Compared with Example 1, it can be seen that carrier adhesion in Example 1 is rank 3 in the initial stage, whereas in Example 5, the rank is 3.5 and Example 5 has a better initial rank. Further, the change in non-carrier adhesion due to running was also decreased by 1.0 in Example 5 after the 300 K run compared to the initial value, but in Example 1, it was also decreased by 1.5. It can be seen that the non-carrier adhesion to is also stable.
[0078]
(Example 6)
The evaluation was performed under the same conditions as in Example 1 except that carrier H was used. The evaluation results are summarized in Table 2.
Compared to Example 1, it can be seen that in Example 1, the carrier adhesion rank is 3 in the initial stage, whereas in Example 6, the rank is 4 and Example 6 has a better initial rank.
[0079]
(Example 7)
Evaluation was performed under the same conditions as in Example 1 except that Carrier I was used. The evaluation results are summarized in Table 2.
Compared to Example 1, it can be seen that in Example 1, the carrier adhesion rank is 3 in the initial stage, whereas in Example 6, the rank is 3.5 and Example 7 has a better initial rank.
[0080]
(Example 8)
Evaluation was performed under the same conditions as in Example 1 except that the linear velocity of the developing sleeve was 367 mm / s. The evaluation results are summarized in Table 2.
Compared to Example 1, it can be seen that in Example 1, the carrier adhesion rank is 3 in the initial stage, whereas in Example 8, Rank 3.5 and Example 8 have better initial non-carrier adhesion.
[0081]
Example 9
Developer density at the development nip is 0.93 g / cm³The evaluation was performed under the same conditions as in Example 1 except that. The evaluation results are summarized in Table 2.
Compared with Example 1, it can be seen that Example 1 has a carrier adhesion rank of 3 in the initial stage, while Example 9 has a rank of 3.5, which improves the non-carrier adhesion in the initial stage.
[0082]
[Table 2]

[0083]
【The invention's effect】
By using a smooth core material having an envelope coefficient of less than 4.5, the coating layer thickness becomes uniform in one carrier, the change in carrier adhesion characteristics with time is reduced, and the weight average particle size is 25 to 25. By setting the amount of the coat carrier having a particle diameter of less than 22 μm in the 45 μm coat carrier to 7% by weight or less, good non-carrier adhesion can be obtained. That is, a coated carrier for an electrophotographic developer capable of obtaining good non-carrier adhesion over a long period of time can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an envelope coefficient of a carrier core material.
FIG. 2 is a view for explaining uniformity of a coating layer resin coating layer due to a difference in smoothness of a carrier core material.
FIG. 3 is a diagram showing an outline of a cell for measuring resistivity of a carrier core material.
FIG. 4 is a diagram showing an outline of a vibrating sieve with an ultrasonic transmitter.
FIG. 5 is a schematic diagram of an image forming apparatus.
FIG. 6 is a schematic view of a developing container.
[Explanation of symbols]
(In Fig. 3)
11 cells
12a, 12b electrode
13 Career
(In Fig. 4)
1 Vibrating sieve machine
2 Cylindrical container
3 Spring
4 base
5 Wire mesh
6 Resonant ring
7 Cable
8 Converter (vibrator)
9 Ring frame
(In FIG. 5)
1 Writing unit
2 Photoconductor
3 Intermediate transfer belt
4 Paper transfer roller
5 Charger
6 Development unit
7 Fixing unit
(In FIG. 6)
11 Stirring conveying screw
12 T Sansa
13 Developing roller
14 Developer
15 photoconductor

Claims (12)

In the carrier for an electrophotographic developer in which a resin coating layer is formed on the surface of a ferrite carrier core material, the carrier has a weight average particle size of 25 to 45 μm, and particles having a particle size of less than 22 μm in the carrier. The content ratio is 7% by weight or less, the bulk density of the carrier core material is 2.11 to 2.33 g / cm ³ , and the envelope coefficient A of the carrier core material is expressed by the following formula (1). Then, a carrier for an electrophotographic developer satisfying a relationship of 1.8 ≦ A ≦ 4.0.
A = (L ₁ −L ₂ ) / L ₂ × 100 (1)
L ₁ : Perimeter length of carrier core material projection image L ₂ : Length of envelope of carrier core material projection image   The carrier for an electrophotographic developer according to claim 1, wherein an envelope coefficient A of the carrier core material satisfies a relationship of A <2.5.   The carrier for an electrophotographic developer according to any one of claims 1 to 2, wherein the content ratio of particles having a particle size of less than 22 µm in the carrier is 5% by weight or less.   3. The carrier for an electrophotographic developer according to claim 1, wherein a content ratio of particles having a particle size of less than 22 μm in the carrier is 3% by weight or less.   The carrier for an electrophotographic developer according to claim 1, wherein the carrier core material has a resistivity (Log R) of 8.5 Ω · cm or more.   The carrier for an electrophotographic developer according to any one of claims 1 to 5, wherein the carrier core has a magnetic moment of 76 emu / g or more.   7. The method for producing a carrier for electrophotographic development according to claim 1, wherein (i) a resin coating is formed on a surface of a carrier core material comprising pulverized particles of a magnetic material to obtain resin-coated particles. And (ii) obtaining a carrier having a weight average particle diameter of 25 to 45 μm and a content ratio of particles having a particle diameter of less than 22 μm of 7% by weight or less by classifying the resin-coated particles. A method for producing a carrier for an electrophotographic developer, comprising:   The method for producing a carrier for an electrophotographic developer according to claim 7, wherein a vibration sieving machine equipped with an ultrasonic oscillator is used to classify the resin-coated particles.   9. The method for producing a carrier for an electrophotographic developer according to claim 8, wherein the vibration sieving machine with an ultrasonic oscillator has a structure for transmitting ultrasonic vibrations to a wire mesh surface by a resonance ring installed in the sieving machine.   An electrophotographic developer comprising the carrier for an electrophotographic developer according to claim 1 and a toner. 11. A developer container containing the developer, wherein the developer is the electrophotographic developer according to claim 10. An image forming apparatus equipped with a developer container, wherein the developer container is the developer container according to claim 11.

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