Abstract: An electrophotographic apparatus includes an electrophotographic photosensitive member, a charging device, an image exposure device, a developing device, a transfer device, and a control device. The control device stops rotation of the electrophotographic photosensitive member after a region of the electrophotographic photosensitive member, which region opposes the transfer device at the time when operation of the transfer device is stopped while the rotation of the electrophotographic photosensitive member is not stopped, passes, by at least one revolution, a position opposing the charging device which is running. The electrophotographic apparatus requires no idle rotation, makes high speed processing possible, suppresses negative and positive ghosting, and suppresses variations in electric characteristics and in image densities between first and second copying operations, thereby enabling images of high quality to be prepared quickly and simply.

Abstract: A process for producing an electrophotographic photoreceptor comprising a conductive substrate having thereon an underlayer and further thereon a photoconductive layer, the process comprising the steps of: applying a coating composition comprising at least one of a zirconium alkoxide, a zirconium chelate compound, and a silane coupling agent on a conductive substrate; drying it to form an underlayer; atomizing a mixed solution comprising a water-compatible organic solvent and water to bring it into contact with the underlayer; and forming a photoconductive layer on the underlayer.

Abstract: An electrophotographic photoreceptor comprising a photosensitive layer containing granular trigonal selenium which has a mean particle diameter of not more than 5 .mu.m and which has absorption peaks in the X-ray diffraction spectrum using CuK.alpha. characteristic X-rays at Bragg angles (2.degree..theta..+-.0.2.degree.) of 23.5.degree., 29.7.degree., 41.4.degree., and 45.4.degree., is disclosed, which has high photosensitivity and low residual potential, maintains its potential characteristics in a stable manner on repeated use, and exhibits sufficient photosensitivity even when applied to high-speed copying.

Abstract: An electrophotographic photoreceptor comprising a conductive substrate having thereon a photosensitive layer is disclosed, said photosensitive layer containing, as a binder resin, a polycarbonate resin comprising at least a repeating unit represented by formula (I): ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 each represent a hydrogen atom, a halogen atom, an alkyl group having from 1 to 5 carbon atoms, a cycloalkyl group having from 5 to 7 carbon atoms or a phenyl group; and R.sub.5 and R.sub.6 are taken together to form a 5- to 8-membered carbonaceous ring substituted with at least two alkyl groups each having from 1 to 5 carbon atoms. The photoreceptor has high mechanical durability and satisfactory surface smoothness, resistance against reduction in image quality and sensitivity, and stability against environmental change and repeated use.

Abstract: An electrophotographic photoreceptor comprising an electrically conductive substrate having thereon a subbing layer and a photosensitive layer in sequence, wherein the subbing layer is a layer formed by using a hydrolyzable compound, the layer having a residual organic group content of at least 25 mol % based on the total organic group content of the hydrolyzable compound used, or (ii) by coating a solution of the hydrolyzable compound in an organic solvent in which the hydrolyzable compound has been hydrolyzed to a degree of at least 50%. The coating composition exhibits satisfactory film-forming properties to form a subbing layer without causing cracks which thereby provides an electrophotographic photoreceptor with excellent stability on repeated use.

Abstract: A method for determining a termination time of the step of dispersing a coating composition for a photosensitive layer, containing a binder resin, a powdery charge generating material and a solvent, is disclosed, which comprises (i) providing coating (I) on a substrate by coating the coating composition, following by drying, (ii) providing coating (II) on a substrate by dispersing the coating composition using a dispersion medium to fine the powdery charge generating material, followed by drying, (iii) measuring absorbances of coating (I) at two wavelengths within a short wavelength region and a long wavelength region, respectively, of the spectral absorption wavelength of the charge generating material, (iv) measuring absorbances of coating (II) at the two wavelengthes within the short wavelength region and the long wavelength region, respectively, and (v) calculating spectral absorbance ratios of coatings (I) and (II), respectively, from the following equation: ##EQU1## wherein the dispersing of the coating

Abstract: An electrophotographic photoreceptor comprising a conductive substrate having thereon a photosensitive layer as the uppermost layer, in which the photosensitive layer contains two charge transporting materials different in ionization potential, a charge transporting material having a higher ionization potential is present in the amount equimolar to or in an amount less than the equimolar amount to the other charge transporting material having a lower ionization potential.

Abstract: An electrophotographic photoreceptor comprising a conductive substrate having thereon a charge generating layer comprising a binder resin having dispersed therein a charge generating material and a charge transporting layer containing a charge transporting material is disclosed, wherein the ionization potential of the binder resin, I.sub.pb, the ionization potential of the charge generating material, I.sub.pg, and the ionization potential of the charge transporting material, I.sub.pt, satisfy the following relationship:I.sub.pg .ltoreq.I.sub.pb <I.sub.pt orI.sub.pt <I.sub.pb .ltoreq.I.sub.pg.The photoreceptor has high photosensitivity and excellent environmental stability.

Abstract: An electrophotographic photoreceptor comprising a conductive substrate having thereon at least a charge generating layer and a charge transporting layer is disclosed, in which said charge generating layer is a deposited film of a subliming organic pigment and has an iron content of not more than 100 ppm and a sulfur content of not more than 500 ppm. The electrophotographic photoreceptor has high photosensitivity, high chargeability, small dark decay, low residual potential, and excellent durability.

Abstract: A novel method for preparing an electrophotographic photoreceptor is disclosed, which comprises laminating a charge generating layer and a charge transporting layer in this order on an electrically conductive substrate via an undercoating layer, wherein the coating solution for said undercoating layer contains an alkoxide coupling agent represented by formula (I), an aliphatic alcohol solvent containing at least the same number of carbon atoms as in the alkoxy group in said alkoxide coupling agent, and at least one compound selected from the group consisting of aromatic solvents, ethylene glycols and propylene glycols:X.sub.m --m--(OR.sub.1).sub.N (I)wherein R.sub.

Abstract: An electrophotographic photoreceptor is disclosed, comprising a substrate having thereon at least an electric charge generating layer and an electric charge transporting layer, characterized in that the electric charge generating layer is formed from a coating solution which is prepared by dispersing an electric charge generating material and an acid in a binder resin solution. Useful acids are inorganic acids, including hydrochloric acid, sulfuric acid, hydrobromic acid and phosphoric acid, and organic acids, including formic acid, acetic acid, propionic acid, butryric acid, lactic acid, benzoic acid and sulfonic acid. This material has an increased sensitivity and thus can be effectively used in copying machines.

Abstract: A novel electrophotographic photoreceptor is disclosed, comprising an undercoating layer provided on an electrically conductive substrate having thereon a light-sensitive layer, wherein the undercoating layer is obtained by coating a solution of a composition comprising zirconium and silicon or a solution of a mixture of a zirconium acetyl acetonate compound and a silane coupling agent, the silicon content in the composition comprising zirconium and silicon is in the range of 5 to 35 mol % based on the total amount of zirconium and silicon, and the hardened undercoating layer obtained from the zirconium acetyl acetonate compound and silane coupling agent is a layer having a hardening degree of 1.2 or less.

Abstract: An electrophotographic photoreceptor which employs a photosensitive layer including a binder resin and an organic pigment as a charge generating material which has been subjected to an acid pasting treatment. The sulfur content of the organic pigment is maintained at 500 ppm or less to achieve a stable high chargeability and low dark decay coefficient.