Abstract: 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.

Abstract: 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 CTM2 to a charge transporting material CTM1 within a specific range, wherein the ionization potential Ip(2) of the CTM2 is smaller than the ionization potential Ip(1) of the CTM1 in 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 ?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, ?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.

Abstract: 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<(X/Y)<0.8, where X represents the reduction in film thickness (?) per 1×107 mm of the traveling distance of the photoreceptor for black development and Y represents the reduction in film thickness (?) per 1×107 mm 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.

Abstract: An electrophotographic image forming apparatus according to the present invention includes: a multiple number of image forming stations for multiple development colors including black, each station having a photoreceptor, an exposure device, a developing device for developing each static latent image with the toner of each development color; a recording media conveyer belt conveying, along the photoreceptors, a recording medium on which a monochrome toner image is formed or a color image is formed by overlapping multiple colors of toner images, wherein each of the photoreceptors has a charge transport layer composed of a binder resin that is a blend of at least two kinds of resins, the blended ratio 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 so that the photoreceptor for black presents a greater abrasion resistance than the photoreceptors for other development colors.

Abstract: 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:—

Abstract: 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 CTM2 to a charge transporting material CTM1 within a specific range, wherein the ionization potential Ip(2) of the CTM2 is smaller than the ionization potential Ip(1) of the CTM1 in the constituent of the photosensitive layer, and thereby the electrophotographic photoreceptor has only a little reduction of image concentration.