Mita Industrial Co., Ltd.

Tdk Corporation

Koichi Tsuyama

Masahide Inoue

Yoshitake Shimizu

Tetsuya Nakano

Naruo Yabe

Teruaki Teratani

Seijiro Ishimaru

Mitsushi Kuroki

Koji Murata

Hiroshi Harada

Mamoru Kato

Takeshi Arakawa

Yutaka Aso

Hidenori Asada

Seijirou Ishimaru

A developing method using a compact machine such as a copying machine for personal use, etc., employs a two component-type magnetic developing agent with small diameter photosensitive drum and small diameter developing sleeve. In order to eliminate toner falling from the drum and/or sleeve to increase toner transfer efficiency and reduce fogging, the developing agent conveying sleeve is provided with a curvature (mm.sup.-1) of from 0.2 to 0.05. The toner is specifically designed for use in the method and includes magnetic fine particles having a saturation magnetization of not smaller than 70 emu/g and hydrophobic fine silica particles added to fixing resin particles containing a coloring agent.

Developing method using a developing agent conveying sleeve of a small

The developer in accordance with the present invention includes toner, and a carrier having a core material the surface of which is coated with a coating layer made of a polymer, the coating layer having a resistance value sufficient to minimize the counter electric charge remaining in the coating layer, and the toner having any of characteristic values required for preventing a counter electric charge remaining in the coating layer from being increased. The use of the developer of the present invention not only prevents the occurrence of so-called carrier scattering, to thereby prevent blanking, but also produces an image of high quality having a high initial image density.

Two-component developer

The present invention provides an electrophotographic toner having rheology characteristics, under the conditions of measuring frequency of 1 Hz and measuring distortion of 1 degree, such that:

Electrophotographic toner having improved low temperature fixing

A toner composition comprising a binder resin having dispersed therein additives including a colorant and a charge control agent, wherein said additives are present as agglomerates having an average sectional area of from 1.4 to 1.7 .mu.m.sup.2 in a section of toner particles, the total sectional area of the agglomerates in the section of toner particles ranging from 1.5 to 1.8%, or wherein said colorant and charge control agent are present as agglomerates having an average sectional area of from 1.4 to 1.7 .mu.m.sup.2 in a section of toner particles, and said composition has such rheological characteristics that a dissipation factor (tan .delta.) is from 0.95 to 1.25 when a storage elastic modulus (G') is 10.sup.4 dyne/cm.sup.2.

Toner composition

The present invention provides a start developer wherein an output voltage of a sensor in the start developer having a particular toner density is not less than 0.9 times an output voltage of the sensor in a developer having the same toner density in a time period during which image characteristics are stabilized after repeating image formation by an image forming apparatus and is less than a threshold value at which the supply of toner is started and a method of controlling the toner density using the start developer. According to the present invention, good images can be always formed irrespective of the variation in characteristics between sensors in image forming apparatuses and from the early stage of image formation to the stable time period.

Start developer and method of controlling toner density

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

The present invention provides an electrophotographic developer comprising (i) a toner containing a fixing resin in which the content of an acrylic component is limited to a predetermined range, or a toner of which surface dye density is limited to a predetermined range, and (ii) a carrier coated with a coating resin containing, as an acrylic component, dodecyl methacrylate or 2-hydroxyethyl acrylate. In the electrophotographic developer of the present invention, the electric charging characteristics are always stable.

Electrophotographic developer comprising resin coated carrier

The present invention provides an electrophotographic developer comprising (i) a toner containing, as a fixing resin, a styrene-acrylic copolymer presenting a gel permeation chromatogram showing a molecular-weight distribution in which the detection-starting molecular weight and the detection-ending molecular weight are respectively located in specific ranges, and (ii) a carrier coated with a coating resin which is a styrene-acrylic copolymer containing at least 2-hydroxyethyl acrylate. Even though repeatedly agitated in the developing device, the electrophotographic developer of the present invention is not deteriorated and assures good durability and long life-time.

Electrophotographic developer

A start developer is described which includes a toner and a carrier, present in a predetermined ratio. The carrier spent amount is adjusted so that it is not less than 0.010% in terms of the amount of carbon, as measured with a carbon analyzer. With this start developer, good quality images may be formed throughout the copying operation, from the initial image forming stage to the repeated image forming stage and through the stabilized image forming stage.

Start developer

Magnetic carrier for use in electrophotographic development takes the form of ferrite core particles each having a resinous coating. Ferrite core particles having a limited particle size distribution are coated with a resinous composition based on a copolymer consisting essentially of ethyl methacrylate, 15 to 25% by weight of styrene, up to 2% by weight of dodecyl methacrylate, and up to 2% by weight of 2-hydroxyethyl acrylate. The magnetic carrier particles have a resistance of 8.5.times.10.sup.7 to 2.2.times.10.sup.9 .OMEGA.. This carrier has a sharp distribution of electric charge and a quick rise of charging performance. The coating is tough enough to impart durability to the carrier.

Electrophotographic development magnetic resin coated carrier

Disclosed is a process for developing an electrostatic latent image, which comprises forming a magnetic brush of a two-component type developer comprising a toner and a magnetic carrier on a developing sleeve and bringing the magnetic brush into sliding contact with a photosensitive drum, wherein a spike-cutting plate is arranged along the developing sleeve to adjust the spike length of the magnetic brush, a detecting mechanism is arranged in a development apparatus to detect the concentration of the toner by measuring the permeability of the developer, the magnetic carrier used has a saturation magnetization not higher than 50 emu/g but not lower than 40 emu/g, and the ratio (do/dl) of the distance (do) between the spike-cutting plate and the developing sleeve to the distance (dl) between the photosensitive drum and the developing sleeve is set in the range of from 0.80 to 0.85, whereby the toner concentration is detected by the detecting mechanism and the development is carried out at a predetermined toner concentration.

Developing process

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:

A toner composition is disclosed which comprises a mixture of toner particles with finely powdered acylic polymer, and finely powdered silica dispersed in the mixture, wherein the finely powdered acrylic polymer is present in an amount of 0.05 to 0.15 parts by weight per 100 parts by weight of the toner particles and the weight ratio of silica to acrylic polymer is within the range of 1 to 5:1. Also disclosed is a method for preparing the toner composition.

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Kobe, Japan

Koichi Tsuyama