Sharp Kabushiki Kaisha Corporation

Yuriko Shindoh

Kazushige Morita

Yoshihide Shimoda

Hiroko Ishibashi

Masanori Matsumoto

A multiple number of image forming stations are provided for multiple development colors including black. Each station having a photoreceptor. Each one of the photoreceptors has a charge transport layer including a binder resin that is a blend of at least two kinds of resins. The blended ration of at least two kinds of binder resins for the photoreceptor for black is made different from that of the binder resins for the photoreceptors for the other development colors. The photoreceptor for black presents a greater abrasion resistance than the photoreceptors for the other development colors. This structure makes it possible to use all the photoreceptors for back and colors, for and within, a concurrent period.

Color image forming apparatus

An electrophotographic photoreceptor, in which the increase of VL is controlled below 15 V by controlling the content ratio M (ppm) of a charge transporting material CTMto a charge transporting material CTMwithin a specific range, wherein the ionization potential Ip(2) of the CTMis smaller than the ionization potential Ip(1) of the CTMin the constituent of the photosensitive layer, and thereby the electrophotographic photoreceptor has only a little reduction of image concentration. A method for producing an electrophotographic photoreceptor having &#x394;VL which is controlled below 15 V, wherein, in a case where the ionization potential of the charge transporting material used in the previous run of production is small, &#x394;VL can be set below 15 V by using, in the next production, a dip coating liquid, which comprises, as a constitutive material, a charge transporting material in which the difference between the ionization potential of the current material and that of the previous material is set below 0.25 eV.

Electrophotographic photoreceptor and production method thereof

An electrophotographic color image forming apparatus including a multiple number of photoreceptors for multiple development colors including black, is constructed such that the photoreceptors satisfy the following relation:0.5&#x3c;()&#x3c;0.8,where X represents the reduction in film thickness (&#x212b;) per 1&#xd7;10mm of the traveling distance of the photoreceptor for black development and Y represents the reduction in film thickness (&#x212b;) per 1&#xd7;10mm of the traveling distance of the photoreceptors for the other development colors. This limitation is aimed at differentiating the abrasion resistance of the photoreceptors between that for black and that for colors and designating the reduced amounts of the film thickness per unit traveling distance to fall within the predetermined ranges, whereby it is possible to prevent the drum for black development, which is used most frequently, alone, from being worn away at an earlier time. Accordingly, both the drums for black and for colors can be replaced at approximately the same time, to the maintenance cost can be reduced.

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Yamatokoriyama, Japan

Yuriko Shindoh