Mita Industrial Co., Ltd.

Masahide Inoue

Koichi Tsuyama

Yoshitake Shimizu

Tetsuya Nakano

Naruo Yabe

Teruaki Teratani

Seijiro Ishimaru

Takeshi Arakawa

Yutaka Aso

Mitsushi Kuroki

Mamoru Kato

Ryo Fujisawa

Koji Murata

Hidenori Asada

Mikiko Tamori

Kouichi Tsuyama

Seijirou Ishimaru

The present invention relates to a recycle developing process which comprises developing an electrostatic image formed on a photosensitive material with a starting developer filled in a developing vessel, transferring the toner image to a predetermined paper, recovering the toner remaining on the photosensitive material by a cleaning means, and repeating the developing procedure while replenishing a virgin toner and the toner recovered by the cleaning means into the developing vessel; wherein the virgin toner to be replenished into the developing vessel is that which is fulfilled in a container wherein a rotating roller is provided in an opening portion at a lower portion has a flowability, shown as a fallen amount of the toner at a time of falling via the rotating roller for a certain fixed time, of 50 to 70% based on the toner in the starting developer. According to this process, an abrupt decrease in the properties of the developer due to the mixing of the recovered toner can be relaxed. As a result, a stable image free from fogging or toner scattering can be formed by the recycle developing process.

Recycle developing process

A recycle developing method utilizes the steps of (1) providing a developing vessel containing a starting developer composed of an electroscopic toner and a magnetic carrier; (2) transferring toner from the developing vessel to a photosensitive material having an electrostatic latent image formed thereon; (3) transferring a portion of the toner on the photosensitive material to a paper to form a toner image on the paper; (4) recovering toner remaining on the photosensitive material after the aforementioned portion of toner is transferred to the paper to form a toner image thereon; and (5) repeating steps (2)-(4) while replenishing toner in the developing vessel by the sub-steps of: (5a) supplying toner recovered in step (4) to the developing vessel, and (5b) supplying a virgin toner, having a higher chargeability than the electroscopic toner in the starting developer, to the developing vessel, to form a mixed toner in the developing vessel. An absolute value of the average charge quantity of the mixed toner is greater than the absolute value of the average charge quantity of the electroscopic toner in the starting developer plus 10 .mu.C/g. Apparatus to effect the process is also disclosed.

Recycle developing method and apparatus

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 two-component developer comprising a magnetic carrier having a carbon black-containing resin-coating layer and a toner composed of a carbon black-containing resin composition is disclosed. A styrene resin, an acrylic resin or a styrene-acrylic copolymer resin is selected as each of the carrier-coating resin and the toner-forming resin, and the carbon black content A in the carrier-coating layer and the carbon black content B in the toner-forming layer satisfy requirements represented by the following formulae: ##STR1## Namely, by adjusting the carbon black contents A and B within specific ranges relatively to each other, a two-component developer which is well-balanced between the frictional chargeability characteristic and the electric resistance is provided.

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

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.

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Nara, Japan

Masahide Inoue