Mita Industrial Co., Ltd.

Mitsushi Kuroki

Naruo Yabe

Akihiro Watanabe

Yoshitake Shimizu

Masahide Inoue

Koichi Tsuyama

Tetsuya Nakano

Yoshihisa Kuramae

Tsutomu Uezono

Noriaki Tsubota

Shoji Tomita

Toshio Nishino

Katsumi Oyama

In an electrophotographic toner, by using as the binder resin a styrene/acrylic resin in which in the gel permeation chromatogram, a high molecular weight peak value appears in a molecular weight region higher than 1.times.10.sup.5, a low molecular weight peak value appears in a molecular weight region of from 2.times.10.sup.4 to 500, a minimum value appears halfways between the two peaks and the ratio (V/P) of the area of the valley to the peak area is lower than 0.3, the internal cohesive force of the binder resin for the toner can be prominently improved while maintaining the low-temperature fixing property and offset resistance at high levels, and pulverization of the toner and formation of the spent toner can be prevented during the developing operation and the durability of the toner can be improved.

Electrophotographic toner

A two-component developer for use in dry development of electrostatic charge pattern, comprising a mixture of magnetic carrier particles and electroscopic toner particles, characterized in that said magnetic carrier particles have a relaxation time B (msec) satisfying the equation 0&lt;B&lt;20 when they are situated in a dynamic state and said developer has a relaxation time A (msec) satisfying the equation: 0.35B+11&lt;A&lt;0.35B+14 when it is situated in a dynamic state.

Two-component developer for use in dry development of electrostatic

Disclosed are a two-component type developer for use in the electrophotography or electrostatic printing, which comprises a magnetic carrier and a toner, and a process for the preparation thereof. This developer has a dynamic resistivity (Rd) lower than the dynamic resistivity (Rc) of the magnetic carrier. This developer is prepared by mixing a toner with a magnetic carrier so that the dynamic resistivity (Rd) of the formed developer is lower than the dynamic resistivity (Rc) of the magnetic carrier. This developer is capable of realizing an excellent reproducibility of a fine line image and a high density of a solid image area simultaneously.

Developer and process for preparation thereof

A developing process excellent in the reproducibility of images is disclosed. In reproducing multiple fine lines, the line width can be kept uniform in the respective lines and front end chipping or rear end chipping can be prevented, and a high-density and high-quality image can be formed, by comprehensively setting developing conditions so that the relaxation time measured under dynamic conditions in an electric circuit comprising a developing sleeve, a surface of a photosensitive material and a developing layer interposed therebetween is set within a certain range; carrying out the sliding contact between the magnetic brush of the developer and the surface of the photosensitive material so that the frequency of the contact of a carrier with the photosensitive material is set within a certain range; or establishing a specific relation among the rotation number of the developing sleeve, the saturation magnetization of the magnetic carrier and the flux density of magnetic poles in the developing sleeve or further setting the contacting frequency of the carrier within a certain range.

Developing process excellent in image reproducibility

Disclosed is a toner for developing a statically charged image, which comprises a fixing resin and, dispersed therein, a colorant and a charge-controlling dye. This toner is characterized in that the tangent (tan .delta.) of the loss angle is in the range of from 0.95 to 1.25 when the storage modulus of elasticity (G') is 10.sup.4 dyne/cm.sup.2. The toner having such rheological characteristics has an excellent fixing property, a high offset resistance, a capacity of forming an image having a high quality and a good durability.

Toner for developing statically charged images and process for

Disclosed are a toner for developing a statically charged image and a process for the preparation thereof. If a toner for developing a statically charged image, comprising a binder resin and, dispersed therein, a colorant and a charge-controlling dye, is prepared so that it has a particle size distribution satisfying the requirement represented by the following formula:

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Kumamoto, Japan

Mitsushi Kuroki