Abstract: An electrophotographic photoconductor of the invention comprising: an conductive support; a light-sensitive layer formed on the conductive support and containing a charge generating material and a charge transport material; and a surface protective layer formed on the light-sensitive layer and made of a resin composition, wherein the resin composition constituting the surface protective layer contains an amine compound represented by the following formula (1): wherein R1 and R2 are, the same or different, each an alkyl group or an allyl group which may have a substituent or a heterocyclic residue to be formed through or not through a nitrogen atom or an oxygen atom together with the nitrogen atom to which R1 and R2 are bonded, R3 and R4 are, the same or different, each an alkyl group having a substituent and n denotes 1 or 2, provided that when n is 1, X is a hydrogen atom, a halogen atom, or an alkyl group, a hydroxyl group or a mercapto group which may have a substituent, or a ring optionally containing

Abstract: An electrophotographic photoreceptor comprising at least a photosensitive layer on an electroconductive substrate, a surface layer of the electrophotographic photoreceptor including a fluorinated alkyl group-containing copolymer having repeating units represented by the following formulae A and B, and fluorine-based resin particles: wherein in Formulae A and B, l, m and n each independently represent a integer number of 1 or more; p, q, r and s each independently represent 0 or an integer of 1 or more; t represents an integer of from 1 to 7; R1, R2, R3, and R4 each independently represent a hydrogen atom or an alkyl group; X represents an alkylene chain, a halogen-substituted alkylene chain, —S—, —O—, —NH— or a single bond; Y represents an alkylene chain, a halogen-substituted alkylene chain, —(CzH2z-1(OH))— or a single bond; and z represents an integer of 1 or more.

Abstract: The electrophotographic photoreceptor includes a substrate and a photosensitive layer disposed on the substrate, wherein a surface layer of the electrophotographic photoreceptor contains fluorine-containing polymer particles and a dispersion aid for the fluorine-containing polymer particles, and the surface layer has convex portions with diameters of from 200 ?m to 500 ?m spaced at an average interval of from 600 ?m to 950 ?m.

Abstract: An electrophotographic photoconductor includes a base, a photosensitive layer formed on the base, and an overcoat layer formed on the photosensitive layer, wherein the overcoat layer includes gallium, oxygen, and hydrogen, and the intensity ratio (IO-H/IGa-O) of a signal IO-H of an O—H bond to a signal IGa-O of a Ga—O bond in an infrared absorption spectrum is about 0.1 or more and 0.5 or less.

Abstract: Disclosed is an electrophotogaphic photoreceptor that causes little or no abrasion-derived uneven image density and does not cause scratches and image defects attributable to the occurrence of scratches even after a large volume, for example, exceeding 1,000,000 sheets of printing, and that does not cause image blurring even after printing in an environment of a high-temperature and a high-relative humidity (RH) respectively exceeding 30° C. and 80%.

Abstract: An electrophotographic photoconductor that stabilizes electrical performances and prevents generation of image faults such as memories, irrespective of types of organic materials of resin binder and charge transport material, and variation of temperature and humidity of the operation environment. An electrophotographic photoconductor includes at least a photosensitive layer formed over a conductive substrate, wherein the photosensitive layer contains a cyclohexane dimethanol-diaryl ester compound represented by the formula (I): in formula (I), each of R1 through R10 represents independently, a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group of carbon number of from 1 to 5, a substituted or unsubstituted aryl group, or a substituted or unsubstituted alkoxy group of carbon number of from 1 to 5.

Abstract: Exemplary embodiments provide materials and methods for a pen that can include a writing end for writing an image on an erasable medium and an erasing end for locally erasing an image from the erasable medium.

Abstract: Provided is an electrophotographic photosensitive member having a conductive support, an intermediate layer provided on the conductive support, and a photosensitive layer provided on the intermediate layer in which the intermediate layer contains a polyolefin resin containing a specific component at a specific mass ratio, and a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member.

Abstract: A photoreceptor including an electroconductive substrate, a photosensitive layer located overlying the electroconductive substrate, and a surface layer located overlying the photosensitive layer, the surface layer including a cross-linked material of a radical polymerizable monomer having at least 3 functional groups with no charge transport structure and a radical polymerizable compound having a charge transport structure, the surface layer having a sulfur concentration of 50 ppmw or lower.

Abstract: The presently disclosed embodiments relate in general to electrostatography comprising improved features in the flexible imaging member that enhance function when used in the electrostatographic imaging system. These embodiments pertain, more particularly, to a structurally simplified curl-free flexible electrostatographic imaging member belt containing a stress/strain free ground strip layer and stress/strain free imaging layer(s) to improve dynamic belt cyclic motion quality and extend service life.

Abstract: The present invention provides an image forming apparatus which is equipped with at least a latent electrostatic image forming unit, a developing unit, a transferring unit, and a fixing unit, wherein the transferring unit is configured to apply a positive electric potential to a visible image formed on the latent electrostatic image bearing member via a recording medium, the latent electrostatic image member has a surface layer which comprises a hardened material hardened by irradiating at least a trifunctional or more radical polymerizable compound having no charge transporting structure, a radical polymerizable compound having a charge transporting structure, and a reactive silicone compound having any one of an acryloyloxy group and a methacryloyloxy group, and the concentration of the reactive silicone compound is varied in between the surface part and the innerlayer part of the surface layer.

Abstract: An electrophotographic photosensitive member includes a photoconductive layer and, provided on the photoconductive layer, a surface layer containing a hydrogenated amorphous silicon carbide. A ratio of the number of carbon atoms (C) to the sum of the number of silicon atoms (Si) and number of carbon atoms (C), C/(Si+C), in the surface layer is from 0.61 or more to 0.75 or less, and the sum of atom density of the silicon atoms and atom density of the carbon atoms in the surface layer is 6.60×1022 atom/cm3 or more.

Abstract: Exemplary embodiments provide materials and methods for an electrostatic charging member including a conductive substrate; a base layer disposed over the conductive substrate, the base layer comprising an elastomeric material and a semiconductive material; and a protective outer layer disposed over the base layer, the protective outer layer comprising a polymeric resin and a plurality of conductive particles, wherein the outer protective layer has a surface resistivity ranging from about 105 O/sq to about 1013 O/sq.

Abstract: An organic photoreceptor is disclosed, comprising, on an electrically conductive support, a photosensitive layer and a protective layer containing metal oxide particles produced by a plasma method, and the protective layer being formed by curing a composition containing the metal oxide particles and a curable compound. There is also disclosed a preparation method of the organic photoreceptor.

Abstract: Disclosed is an electrophotographic imaging member that includes a substrate; a charge generating layer; a charge transport layer; and a protective overcoat layer having a polyol binder; a hole transport material; an acid catalyst; a leveling agent; and no melamine formaldehyde curing agent or cross-linking additive. Also disclosed is a process for forming a photoreceptor that includes providing a substrate; applying to it a charge generating layer, charge transport layer; and protective over coating layer having a polyol binder; a hole transport material; an acid catalyst; a leveling agent; and no melamine formaldehyde curing agent or cross-linking additive. Additionally provided is a method of forming an image with the disclosed electrophotographic imaging member.

Abstract: The invention provides an electrophotographic photoreceptor having at least a conductive substrate and a photosensitive layer formed on the conductive substrate wherein the outermost surface layer of the photoreceptor is composed of a cured material containing at least one compound represented by the formula (I) and a surfactant that contains, in the molecule thereof, at least one structure selected from (A) a structure that is obtained by polymerizing an acrylic monomer having a fluorine atom, (B) a structure having a carbon-carbon double bond and a fluorine atom, (C) an alkyleneoxide structure, and (D) a structure having a carbon-carbon triple bond and a hydroxy group. In formula (I), Q is an organic group having a valency of n and having hole transportability, R is a hydrogen atom or an alkyl group, L is a divalent organic group, n is 1 or more, and j is 0 or 1.

Abstract: A developing roller has a mandrel, an elastic layer and a cover layer as a surface layer. The cover layer includes a silicon oxide film containing a carbon atom chemically bonded to a silicon atom. In the silicon oxide film, the proportion of the total number of the elements of silicon, oxygen, carbon and hydrogen to the number of all detected elements, as detected with a high-frequency glow discharge light-emission surface analysis method, is 90% or more. The silicon oxide film has an abundance ratio of an oxygen atom chemically bonded to a silicon atom to silicon atoms, (O/Si), of 0.65 or more but 1.95 or less and an abundance ratio of a carbon atom chemically bonded to a silicon atom to silicon atoms, (C/Si), of 0.05 or more but 1.65 or less, and has a ratio of the maximum value to the minimum value of the (C/Si) in a thickness direction of the cover layer, of 1.50 to 33.00.

Abstract: The presently disclosed embodiments relate in general to electrophotographic imaging members, such as layered photoreceptor structures, and processes for making and using the same. More particularly, the embodiments pertain to the incorporation of an ozone quenching compound into the charge transport layer to quench the corona effluents and protect the polycarbonate binder of the charge transport layer from being attacked by ozone species, thereby enhancing wear resistance and fatigue cracking.

Abstract: Disclosed is an organic photoreceptor, which is composed of a photosensitive layer and a protective layer, provided on an electric conductive support, and the protective layer contains a composition obtained by hardening reaction of ?-alumina particles treated with a compound having a reactive functional group with a hardenable compound. A manufacturing method thereof is also disclosed.

Abstract: An electrophotographic photoreceptor including a conductive substrate, a photosensitive layer, and a surface layer, which satisfies the following inequations: 0.005<WRa(LMH)<0.03??(i) 0.010<WRa(LHH)<0.03??(ii) 0.005<WRa(LML)<0.20??(iii) WRa(LLH)>WRa(LMH)??(iv) WRa(LLH)>WRa(LHH)??(v) wherein WRa (?m) represents a center-line average roughness of frequency components LHH, LHL, LMH, LML, LLH, and LLL that are obtained by subjecting a one-dimensional data array of a surface profile of the electrophotographic photoreceptor to wavelet transformation multiresolution analysis so as to be separated into 6 frequency components; thinning a one-dimensional data array of the lowest frequency component so that the number of data array is reduced to 1/40; and subjecting the thinned one-dimensional data array to wavelet transformation multiresolution analysis so as to be separated into the 6 frequency components LHH, LHL, LMH, LML, LLH, and LLL.

Abstract: An electrophotographic photoreceptor comprising: a conductive substrate; a photosensitive layer formed on the conductive substrate; and an outermost surface layer that is a layer made of a cured material of a composition including at least one compound represented by the following formula (I) and at least one compound having charge transportability and an azo group: wherein in formula (I), F represents an n-valent organic group having a hole transporting property, R represents a hydrogen atom or an alkyl group, L represents a divalent organic group, n represents an integer of 1 or more, and j represents 0 or 1.

Abstract: A charging member is provided having a support, a conductive elastic layer formed on the support and a surface layer formed on the conductive elastic layer. The surface layer contains a polysiloxane having at least one of structures represented by the following formulas (1a1), (1a2), (1b1) and (1b2): Toners and external additives used in the toners clinging to the charging member surface can be minimized even through repeated use over a long period of time, thus the charging member can perform stable charging and image reproduction even when used in the DC contact charging method.

Abstract: The present invention provides an electrophotographic photoreceptor including a photosensitive layer on a conductive substrate, an outermost layer of the electrophotographic photoreceptor including a cured film of a composition which includes at least one charge transporting compound (a) having a charge transporting skeleton and at least two structural units represented by R—O—CO—CR??CH—R? in the same molecule, and at least one polycarbonate resin; a ratio (IA/IC) of an absorption peak intensity (IA) resulting from stretching vibration of a carbonyl group originating from the structural unit represented by R—O—CO—CR??CH—R? of the charge transporting compound (a) to an absorption peak intensity (IC) resulting from stretching vibration of a carbonyl group originating from the polycarbonate resin in an IR absorption spectrum of the outermost layer being from about 0.5 to about 10, and a width at half maximum of the absorption peak of the absorption peak intensity (IA) being about 25 cm?1 or more.

Abstract: The invention provides an electrophotographic photoreceptor having comprising at least an electrically conductive substrate and a photo-sensitive layer provided on the conductive substrate, the outermost layer is being a cured film of comprising a composition containing at least one compound (a) having a triphenylamine structure and four or more methacryloyl groups in one and the same molecule.

Abstract: An image forming apparatus including an image bearing member having an electroconductive substrate on which are provided at least a photosensitive layer and a protection layer, in that sequence, a charging device that charges the surface of the image bearing member to form a latent electrostatic image thereon, a development device that develops the latent electrostatic image with a development agent containing toner to obtain a developed toner image, a cleaning device that removes toner remaining on the surface of the image bearing member and a lubricant material applicator that applies a lubricant material to the surface of the image bearing member, the protection layer containing a cured resin and a filler and the surface form of the protection layer having an arithmetical mean waviness Wa of from 0.05 to 0.3 ?m and an average length WSm of profile elements of from 0.5 to 1.5 mm, which are obtained from a waviness profile obtained by filtering a coarse component with a ?c profile filter of 0.

Abstract: According to an aspect of the invention, an electrophotographic photoreceptor including a conductive substrate and a photosensitive layer provided on a surface of the conductive substrate is provided. In the electrophotographic photoreceptor, an outermost layer of the photosensitive layer containing a crosslinked product formed from at least one charge transporting material having at least one substituent selected from the group consisting of —OH, —OCH3, —NH2, —SH, and —COOH, an acidic substance, and at least one compound selected from the group consisting of compounds represented by the following formula (A) and compounds represented by the following formula (B).

Abstract: Present embodiments pertain to an improved electrostatographic imaging member having low contact friction surfaces to ease sliding mechanical interaction and suppressing abrasion/wear failure and methods of preparing thereof. The improved imaging member has layers comprising one or two low surface energy polymeric materials that enhance the physical and mechanical functions and reduce the layers surface contact friction of the imaging member to extend service life.

Abstract: An electrophotographic photoreceptor comprises: an electroconductive support; and a photosensitive layer on the electroconductive support, wherein the photosensitive layer having a dynamic hardness of from 20×109 to 150×109 N/m2 and an elastic deformation ratio of from 15 to 80%.

Abstract: The present invention provides an electrophotographic photoconductor having a support, at least an intermediate layer, and a photosensitive layer, the intermediate layer and photosensitive layer being laid in this order over the support, wherein the intermediate layer comprises an amorphous oxide semiconductor.

Abstract: A imaging member, such as a photoreceptor, comprising a capped structured organic film comprising a plurality of segments and a plurality of linkers arranged as a covalent organic framework, wherein the structured organic film may be a multi-segment thick structured organic film.

Abstract: The presently disclosed embodiments are directed generally to an improved electrostatographic imaging member in which the overcoat layer comprises cross-linkable polyester resins. The overcoat layer not only provides wear resistance, but it also provides higher charge transport efficiency and therefore better photoelectrical properties. In addition, the polyesters can cross-link with a variety of resins and thus provide good adhesion as well.

Abstract: A photoreceptor including an electroconductive substrate, a photosensitive layer located overlying the electroconductive substrate, and a surface layer located overlying the photosensitive layer, wherein the surface layer is a cross linked surface layer comprising filler particulates on which linear scar is formed along the circumference direction, and the filler particulates form concave portions on a groove formed by the linear scar, and wherein the ten point average roughness Rz along the direction of the rotation axis of the photoreceptor measured on the circumference surface thereof is from 0.17 to 2.00 ?m and the average distance Sm of concavities and convexities along the direction of the rotation axis of the photoreceptor measured on the circumference surface thereof is from 20 to 500 ?m, and the ten point average roughness Rz along the circumference direction of the photoreceptor measured on the circumference surface thereof is from 0.13 to 0.

Abstract: Present embodiments pertain to an improved electrostatographic imaging member having low contact friction surfaces to ease sliding mechanical interaction and suppressing abrasion/wear failure and methods of preparing thereof. The improved imaging member has layers comprising one or two low surface energy polymeric materials that enhance the physical and mechanical functions and reduce the layers surface contact friction of the imaging member to extend service life.

Abstract: To provide an electrophotographic photoconductor that has a layer containing a compound represented by the following general formula (1), and an image forming apparatus using the electrophotographic photoconductor. where R1 and R2 independently represent any one of a hydrogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted cycloalkyl group and substituted or unsubstituted aralkyl group, and R3, R4, R5, R6, R7, R8, R9 and R10 independently represent any one of a hydrogen atom, halogen atom, cyano group, nitro group, amino group, hydroxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted cycloalkyl group and substituted or unsubstituted aralkyl group.

Abstract: A photoreceptor charge transport layer containing a film-forming material or binder with a higher Tg and a symmetric charge transport molecule is described.

Abstract: An image bearing member having an electroconductive substrate, a photosensitive layer overlying the electroconductive layer, and a cross-linked surface layer overlying the photosensitive layer, which contains a cross-linked polymer and a first compound consisting essentially of a nitrogen atom and a phenyl group, biphenyl group, and condensed polycyclic hydrocarbon group, or a second compound consisting essentially of a nitrogen atom and hydrogen atoms, halogen atoms, alkyl groups, alkoxy groups, or aryl groups, substituted or non-substituted alkyl groups, substituted or non-substituted alkoxy groups, substituted or non-substituted aralkyl groups, substituted or non-substituted aryl group, substituted or non-substituted alkylene groups, cyano groups, nitro groups, or —OCO?CH2R16, in which R16 represents a hydrogen atom, a substituted or non-substituted alkyl group, a substituted or non-substituted alkoxy group, or a substituted or non-substituted aryl group.

Abstract: A polycarbonate polymer includes: a monomer unit represented by a formula (1A) below; and a monomer unit represented by a formula (2). A haze of a solution that is obtained by dissolving the polycarbonate polymer in THF (tetrahydrofuran) at a concentration of 10 mass % is 5% or less (according to JIS K7105, optical path length of 10 mm). In the formula (1A), R and R? each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; n1 is an integer in a range of 2 to 4; and n2 is an integer in a range of 25 to 220; and in the formula (2), Ar represents a divalent aromatic group.

Abstract: An electrophotographic photoreceptor is provided with a conductive support; a photosensitive layer provided on the conductive support; and a surface layer provided on the photosensitive layer, wherein the surface layer contains a reaction product of surface-treated inorganic fine particles which are applied with a surface treatment with a metal oxide and a surface treatment with a compound having a polymerizable functional group.

Abstract: To provide an electrophotographic photoconductor that comprises a support and a cross-linked layer formed over the support, wherein the cross-linked layer comprises at least light curable of radically polymerizable compound, the difference of maximum value of the post-exposure electrical potential and minimum value of the post-exposure electrical potential when writing is conducted under the condition that image static power is 0.53 mW, exposure energy is 4.0 erg/cm2 for the electrophotographic photoconductor is within 30V.

Abstract: An overcoat containing a copolymer of a first propylene monomer and a second hydrophilic monomer provides superior wear resistance and low torque to a photoreceptor.

Abstract: An electrophotographic photoconductor including: an outermost layer, wherein the outermost layer comprises an amino group-containing acryl-modified polyorganosiloxane, wherein the amino group-containing acryl-modified polyorganosiloxane is a copolymer in which a polyorganosiloxane represented by the following structural formula (1) and an acrylic monomer are graft-polymerized

Abstract: An electrophotographic image forming method is disclosed. The method includes electrically charging a photoreceptor, imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor, supplying a lubricant on a surface of the photoreceptor, and developing the latent image with a toner so that a toner image is formed on the photoreceptor, transferring the toner image and cleaning the photoreceptor, in which the photoreceptor has an electro-conductive substrate, a photosensitive layer and a protective layer containing inorganic particles, a ratio RSm/D50 of an average length of surface roughness profile element in the direction making a right angle with the driving direction of the photoreceptor RSm (?m) to a number-based median diameter of the toner D50 is from 0.4 to 2.0, and a skewness of the surface roughness profile of the photoreceptor in the direction making a right angle with the driving direction of the photoreceptor Rsk is from ?3.0 to 0.0.

Abstract: An electrophotographic photoreceptor includes: an electrophotographic photoreceptor body containing a cylindrical electroconductive substrate having openings at both ends in an axial direction, the cylindrical electroconductive substrate having a thickness of approximately 2 mm or more at a center portion in an axial direction and having a socket joint portion on each of inner surfaces of both end portions in an axial direction; and a photosensitive layer provided on an outer surface of the electroconductive substrate; and a support member fit in the openings of the electroconductive substrate, having an fitting portion which has an outer diameter that is larger than a diameter of the opening by a range of from approximately 0.01 mm to approximately 0.1 mm, the fitting portion being press-fit into the opening.

Abstract: The present invention provides an electrophotographic photosensitive member in which a photoconductive layer is an amorphous layer that contains a silicon atom as a main component, and a surface layer contains an aluminum atom, a zinc atom and an oxygen atom so as to satisfy Expression (1) and Expression (2): 3.0?100{y/(x+y)}?7.0??(1), and 1.05?z/(1.50x+y)?1.20??(2), in Expression (1) and Expression (2), x represents atom % of the aluminum atom contained in the surface layer, y represents atom % of the zinc atom contained in the surface layer, and z represents atom % of the oxygen atom contained in the surface layer.

Abstract: The present invention provides an electrophotographic photoconductor which includes at least a photosensitive layer and a surface protective layer over a support, wherein the surface protective layer contains a filler, a charge transporting material and a specific compound; and the photosensitive layer contains at least a charge transporting material; the charge transporting material contained in the photosensitive layer has an oxidation potential lower than the oxidation potential of the charge transporting material contained in the surface protective layer and is a specific compound.

Abstract: The present invention provides a method for manufacturing an electrophotographic photosensitive member including a step of forming a first surface layer and a second surface layer of the electrophotographic photosensitive member by supplying a source gas into a reaction vessel so that C2/S2, which are respectively flow rates of CH4 and SiH4 flowing when the second surface layer is formed, can be 3 or more and 25 or less, and C1/S1, which are respectively flow rates of CH4 and SiH4 flowing when the first surface layer is formed, can be C2/S2 or more but 60 or less. The method includes an additional step of adjusting the high-frequency power so that P2>P1 can be satisfied, which are high-frequency powers respectively when the second surface layer is formed and when the first surface layer is formed, and C/(Si+C) of the first surface layer and C/(Si+C) of the second surface layer can be 0.50 or more and 0.80 or less.

Abstract: An image forming apparatus including an image bearing member which has an electroconductive substrate, a photosensitive layer overlying the electroconductive substrate and a cross-linked resin surface layer overlying the photosensitive layer and bears a latent electrostatic image on the surface thereof, an application device to apply a solid lubricant to the image bearing member; a charging device to charge the surface of the image bearing member, an irradiation device to irradiate the surface of the image bearing member with light to form the latent electrostatic image thereon, a development device to develop the latent electrostatic with toner to obtain a developed image, a transfer device to transfer the developed image to a recording medium, and; a cleaning device to clean the surface of the image bearing member, wherein the cross-linked resin surface layer includes a cross-linked body of trimethylol propane triacrylate and particulates including silicon and an average diameter of agglomeration areas of t

Abstract: An electrophotographic photoreceptor includes an electrically conductive substrate, an organic photosensitive layer and a surface layer laminated in this order. The surface layer includes at least gallium (Ga) and oxygen (O) as constituent elements thereof, and has a thickness of 0.2 ?m to 1.5 ?m, and a microhardness of 2 GPa to 15 GPa.

Abstract: An image bearing member including an electroconductive substrate, a charge generating layer located overlying the electroconductive substrate, a charge transport layer located overlying the charge generating layer, the charge transport layer comprising a charge transport material and a protective layer having a thickness of from 3 to 15 ?m located overlying the charge transport layer, wherein the density of the charge transport material in the protective layer at depth of 2 ?m from the surface of the charge transport layer satisfies the following relationship: 10(%)?(Charge transport material)/{(Radical polymerizable monomer having a charge transport structure)+(Radical polymerizable monomer having no charge transport structure)+(Charge transport material)}×100?30(%).

Abstract: An aromatic silicon-containing compound has the formula: Ar—[X-L-SiRn(OR?)3-n]m where Ar represents an aromatic group, X represents a divalent or trivalent group; L represents a divalent linking group; R represents a hydrogen atom, an alkyl group or an aryl group; R? represents an alkyl group having 1 to 5 carbon atoms; n is an integer of from 0 to 2; and m is an integer of from 1 to 5. The aromatic silicon-containing compound can be used in electrophotographic photoreceptors, particularly in outmost protective layers of such electrophotographic photoreceptors.