This invention is generally directed to imaging members containing polycarbonates, and more specifically, the present invention is directed to multilayered photoconductive imaging members containing charge, especially hole transport binders comprised of crosslinked polycarbonates, which can be formed from the reaction of novel polycarbonates containing pendant hydroxyl groups along the polymer backbone, and functional agents comprised of, for example, isocyanates.
A number of advantages are associated with the present invention in embodiments thereof, such as excellent electrical characteristics, the provision of robust photoconductive imaging members wherein the life thereof is increased from about 170 kilocycles to over 500 kilocycles, and more specifically, from about 255 to about 510 kilocycles; compatibility with hole transport components, such as aryl amines; resistance to solvents, such as methylene chloride, tetrahydrofuran, and chlorobenzene, and substantial resistant to the disintegration of bias charging rolls. In embodiments of the present invention, the imaging members exhibit excellent cyclic/environmental stability, and substantially no adverse changes in their performance over extended time periods, and excellent resistance to mechanical abrasion, and therefore extended photoreceptor life. The aforementioned photoresponsive, or photoconductive imaging members can be positively or negatively charged when the photogenerating layer is situated between the charge transport layer and the substrate.
Processes of imaging, especially xerographic imaging and printing, including digital, are also encompassed by the present invention. More specifically, the layered photoconductive imaging members of the present invention can be selected for a number of different known imaging and printing processes including, for example, color processes, digital imaging process, digital printers, PC printers, and electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. The imaging members of the present invention are in embodiments sensitive in the wavelength region of, for example, from about 500 to about 900 nanometers, and more specifically, from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the Imaging members of this invention are useful for color xerographic systems.
Layered photoresponsive imaging members have been described in numerous U.S. patents, such as U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006, the disclosure of which is totally incorporated herein by reference, a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the ""006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
The use of perylene pigments as photoconductive substances is also known. There is thus described in Hoechst European Patent Publication 0040402, DE3019326, filed May 21, 1980, the use of N,Nxe2x80x2-disubstituted perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive substances. Specifically, there is, for example, disclosed in this publication N,Nxe2x80x2-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyl-diimide dual layered negatively charged photoreceptors with improved spectral response in the wavelength region of 400 to 700 nanometers. A similar disclosure is presented in Ernst Gunther Schlosser, Journal of Applied Photographic Engineering, Vol. 4, No. 3, page 118 (1978). There are also disclosed in U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance with this patent, the photoconductive layer is preferably formed by vapor depositing the dyestuff in a vacuum. Also, there are specifically disclosed in this patent dual layer photoreceptors with perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have spectral response in the wavelength region of from 400 to 600 nanometers. Also, in U.S. Pat. No. 4,555,463, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a chloroindium phthalocyanine photogenerating layer. In U.S. Pat. No. 4,587,189, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with, for example, a perylene, pigment photogenerating component. Both of the aforementioned patents disclose an aryl amine component, such as N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-bis(3-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine dispersed in a polycarbonate binder, as a hole transport layer. The above components, such as the photogeneraling compounds and the aryl amine charge transport, can be selected for the imaging members of the present invention.
It is a feature of the present invention to provide novel polycarbonates and imaging members thereof with many of the advantages illustrated herein, such as for example extended life, and excellent Imaging performance.
A further feature of the present invention is the provision of novel polycarbonates, and improved layered photoresponsive imaging members which are responsive to near infrared radiation exposure and which imaging members in embodiments possess excellent wear resistance.
In a further feature of the present invention there are provided imaging members containing crosslinked binder layers which are compatible with transport layer components, and more specifically, wherein the polycarbonate binder, inclusive of the crosslinked components thereof, are miscible with hole transport molecules, such as arylamines, and wherein the photoconductive imaging member possesses excellent electrical performance including high charge acceptance, low dark decay and low residual charge.
Moreover, in another feature of the present invention there are provided abrasion resistant photoconductive imaging members, and wherein the imaging member corrosive erosion by bias charging rolls and mechanical erosion by cleaning blades is avoided or minimized.
Aspects of the present invention relate to novel polycarbonates; a polycarbonate comprised of a repeating segment represented by Formula (I) 
wherein R1 is selected from the group consisting of hydrogen, alkyl, and aryl; R2 represents a divalent linkage selected from the group consisting of alkylene optionally containing one or more heteroatoms of halogen, nitrogen, oxygen, sulfur, silicon, or phosphorus, arylalkylene, and arylene; Ar1 and Ar2 each independently represent aromatic groups; and P represents a hydrogen atom, or a hydroxyl protective group; a polycarbonate wherein arylene is selected from the group consisting of 
and wherein the arylene optionally contains a substituent selected from the group consisting of hydrogen, halogen, alkyl of from 1 to about 15 carbon atoms, halogenated alkyl of 1 to about 15 carbons, or alkyl containing one or more heteroatoms of nitrogen, oxygen, sulfur, silicon, or phosphorus; a polycarbonate containing at least one repeating segment represented by Formula (II) 
wherein A is a divalent hydrocarbon optionally containing from about 2 to about 30 carbon atoms, or optionally a divalent hydrocarbon linkage containing from about 2 to about 30 carbon atoms further containing a heteroatom of oxygen, nitrogen, sulfur, silicon, or phosphorus and wherein R1 is selected from the group consisting of hydrogen, alkyl, and aryl; a polycarbonate wherein A is selected from the group comprised of 
a polycarbonate and wherein the polycarbonate is comprised of 
wherein x and y represent mole fractions such that x+y is equal to 1, and wherein the polycarbonate possesses a weight Mw average molecular weight of from about 2,000 to about 500,000; a monomer comprised of 
wherein P is a protective group selected from the group consisting of a pyranyl, a thiopyranyl, an alkoxyalkyl, an alkylsilyl, an alkylarylsilyl, an acyl, and a benzyl; a polycarbonate of the formula 
wherein x is about 0.05 and y is about 0.95; wherein x is about 0.10 and y is about 0.90; wherein x is about 0.15 and y is about 0.85; wherein x is about 0.20 and y is about 0.80; or wherein x is about 0.30 and y is about 0.70; a monomer and the alternative formulas 
a crosslinked polycarbonate wherein the polymer is alternatively 
a photoconductive imaging member comprised of a supporting substrate, a blocking layer, a photogenerating layer, and a charge transport layer, and wherein the charge transport layer comprises a hole transport component and a crosslinked polycarbonate binder; a photoconductive imaging member comprised in sequence of a supporting substrate, a photogenerating layer, a charge transport layer containing hole transport aryl amine molecules and a crosslinked polycarbonate binder, wherein the crosslinked polycarbonate is formed by reacting a hydroxyl-pendent polycarbonate with an isocyanate; a photoconductive imaging member comprised of a supporting substrate, a hole blocking layer thereover, a photogenerating layer, and a charge transport layer containing a polycarbonate with hydroxyl groups and/or crosslinked components thereof; a photoconductive imaging member wherein the photogenerating layer is comprised of photogenerating pigments dispersed in a resinous binder, which pigments are present in an amount of from about 5 percent by weight to about 95 percent by weight; a photoconductive imaging member wherein the photogenerating resinous binder is selected from the group consisting of polyesters, polyvinyl butyrals, polycarbonates, polystyrene-b-polyvinyl pyridine, and polyvinyl formals; a photoconductive imaging member wherein the charge transport layer comprises, aryl amine molecules; a photoconductive imaging member wherein the aryl amines are of the formula 
wherein X is selected from the group consisting of alkyl and halogen; a photoconductive imaging member wherein the arylamine alkyl contains from about 1 to about 10 carbon atoms; a photoconductive imaging member wherein the arylamine alkyl contains from 1 to about 5 carbon atoms; a photoconductive imaging member wherein the arylamine alkyl is methyl, and wherein halogen is chlorine; a photoconductive imaging member wherein the aryl amine is N,Nxe2x80x2-diphenyl-N,N-bis(3-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine; a photoconductive imaging member further including an adhesive layer of a polyester with an Mw of preferably about 70,000, and an Mn of from about 25,000 to about 50,000, and preferably about 35,000; a photoconductive imaging member wherein the photogenerating layer is comprised of metal phthalocyanines, or metal free phthalocyanines; a photoconductive imaging member wherein the photogenerating layer is comprised of titanyl phthalocyanines, perylenes, or hydroxygallium phthalocyanines; a photoconductive imaging member wherein the photogenerating layer is comprised of Type V hydroxygallium phthalocyanine; a method of imaging which comprises generating an electrostatic latent image on the imaging member, developing the latent image, and transferring the developed electrostatic image to a suitable substrate; imaging members comprised of a supporting substrate thereover, a photogenerating layer of, for example, hydroxygallium phthalocyanine, and a charge transport layer containing the polycarbonates illustrated herein; a photoconductive imaging member comprised of a blocking layer, a photogenerating layer, and a charge transport layer, and wherein the charge transport layer comprises hole transport components and a crosslinked polycarbonate binder of the formula 
wherein, for example, R1 is selected from the group consisting of hydrogen, alkyl of, for example, from about 1 to about 15 carbons, a halogenated alkyl of from about 1 to about 15 carbons, an alkyl with, for example, from about 1 to about 15 carbons optionally further containing one or more heteroatoms selected, for example, from the group consisting of nitrogen, oxygen, sulfur, silicon, and phosphorus, an aryl or substituted aryl of, for example, from about 6 to about 30 carbons; R2 represents a divalent link of, for example, an alkylene with from about 1 to about 15 carbons; Ar1, Ar2, Ar3 and Ar4 each independently represent aromatic groups of from about 6 to about 30 carbons; R3 and R4 are independently selected from the group consisting of hydrogen, alkyl of from about 1 to about 15 carbons, aryl or substituted aryl of from about 6 to about 30 carbons, wherein R3 and R4 may form a combined ring structure containing from about 5 to about 20 atoms; and wherein x and y represent the mole fractions of the repeating segments with the sum of x and y being equal to about 1, and more specifically, wherein x and y can each be from about 0.03 to about 1; crosslinked polycarbonates generated from a hydroxy-pendent polycarbonate represented by the general Formula (II) 
wherein R1 is selected from the group consisting of hydrogen throughout (for example, is intended for all examples of substituents and for the number of carbon atoms), alkyl of from about 1 to about 15 carbons, a halogenated alkyl of from about 1 to about 15 carbons, an alkyl of from about 1 to about 15 carbons further containing one or more heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, silicon, and phosphorus, an aryl or substituted aryl of from about 6 to about 30 carbons; R2 represents a divalent linkage; H can be P which represents a hydrogen atom, or a hydroxyl protective group; Ar1, Ar2, Ar3 and Ar4 each independently represent aromatic groups of from about 6 to about 30 carbons; R3 and R4 are independently selected from the group consisting of hydrogen, alkyl of from about 1 to about 15 carbons, aryl or substituted aryl of from about 6 to about 30 carbons, wherein R3 and R4 may form a combined ring structure containing from about 5 to about 20 atoms, wherein x and y represent the mole fractions of the repeating segment; and wherein, for example, the weight average molecular weight, Mw, and the number average molecular weight, Mn, thereof are, for example, from about 1,000 to about 1,000,000, and more specifically, Mw is preferably from about 1,000 to about 200,000 and Mn is preferably from about 500 to about 100,000; and a monomer comprised of 
wherein P is a protective group selected from the group consisting of a pyranyl, a thiopyranyl, an alkoxyalkyl, an alkylsilyl, an alkylarylsilyl, an acyl, and a benzyl.
Examples of R1 include suitable substituents such as a hydrogen atom; alkyl with 1 to about 30 carbon atoms, such as methyl, ethyl, propyl, butyl, iso-propyl, tert-butyl and the like; aryl with 6 to about 30 carbon atoms, such as phenyl, naphthyl, phenaphthyl, biphenyl, and the like. The alkyl group may contain halogen atoms such as fluoride, chloride, or bromide. Illustrative examples of halogenated alkyl are fluoromethyl, fluoroethyl, perfluoropropyl, fluorobutyl, fluoropentyl, chloromethyl, chloroethyl, and the like.
Examples of divalent linkages include suitable substituents such as alkylene, arylene, alkylenearyl groups, and more specifically, alkylene with 1 to about 30 carbon atoms, and more specifically, about 1 to about 10, such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, and the like; arylene with 6 to about 30 carbon atoms, such as phenylene, biphenylene, naphthalene, and the like; and alkylenearyl containing from about 13 to about 60 carbon atoms, such as methylenephenyl, methylenediphenyl, ethylenephenyl, propylenephenyl, and the like.
Examples of R3 and R4 include suitable substituents such as a hydrogen atom; alkyl having 1 to about 30 carbon atoms, such as methyl, ethyl, propyl, butyl, iso-propyl, tert-butyl and the like; substituted alkyl including halogen, such as fluoride, chloride, and bromide, and alkoxy, such as methoxy, ethoxy, propoxy, iso-propoxy, butoxy and the like. Typical examples of substituted alkyl include fluoromethyl, fluoroethyl, fluoropropyl, chlorobutyl, methoxymethyl, ethoxymethyl and the like. Examples of aryl include those with 6 to about 30 carbon atoms, such as phenyl, biphenyl, naphthyl, and the like; and substituted aryl with 6 to about 30 carbon atoms. Illustrative examples of substituted aryl are methylphenyl, ethylphenyl, propylphenyl, butylphenyl, dimethylphenyl, trimethylphenyl, tetramethylphenyl and the like. The substituted aryl may additionally contain halogen atoms such as fluoride, chloride, or bromide. Illustrative examples include trifluoromethylphenyl, chlorophenyl, perfluorophenyl, fluorophenyl, dichlorophenyl, and the like. Illustrative examples of the ring structures R3 and R7 include cyclopropyl, cyclobutyl, cyclohexyl, cyclopentyl, cyclooctyl, and the like.
Examples of Ar1, Ar2, Ar3, and Ar4 and the substituted derivatives thereof with alkyl or halogen include aryl with 6 to about 60 carbon atoms, such as phenyl, biphenyl, naphthyl, methylenephenyl, dimethylenephenyl, binaphthyl and the like. Aryl may contain an alkyl substituent such as methyl, ethyl, isopropyl and the like; a halogen substituent such as fluorine, chlorine, or bromine. Illustrative examples of halogenated aryl are fluorophenyl, perfluorophenyl, fluoromethylphenyl, fluoropropylphenyl, chlorophenyl, dichlorophenyl, and the like.
Illustrative examples of hydroxyl-pendent polycarbonates are represented by (IIa) through (IIj) wherein x and y are the molar fractions of the repeating monomer units such that the sum of x+y is, for example, equal to 1, and more specifically, wherein x represents the number of repeating segments, such as a number of from about 0.01 to about 1, and yet more specifically, from about 0.03 to about 0.99. 
In embodiments, the present invention relates to the provision of a polycarbonate, especially crosslinked polycarbonate, binder illustrated herein. More specifically, the crosslinked polycarbonate (III) can be formed from the reaction of a hydroxyl-pendent polycarbonate of Formula (II) with a curing agent of, for example, a diisocyanate, ONC-L-NCO, and which reaction is illustrated in Scheme (I) 
wherein R1, R2, R3, R4, Ar3 and Ar4 are as illustrated herein; and wherein L represents a divalent linkage of, for example, from about 1 to about 30 carbon atoms, and preferably from about 3 to about 15 carbon atoms. Diisocyanate examples include 1,6-diisocyanatohexane, 1,4-diisocyanatobutane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, 1,5-diisocyanoto-2-methylpentane, trimethyl-1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, trans-1,4-cyclohexenediisocyanate, 4,4xe2x80x2-methylenebis(cyclohexylisocyanate), isophoronediisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, 4,4xe2x80x2-methylenebis(2,6-diethylphenylisocyanate), or 4,4xe2x80x2-oxybis(phenylisocyanate), and the like.
The diisocyanate amount selected is, for example, from about 0.1 to about 5 equivalents of the hydroxyl group contained in the polycarbonate; the curing reaction can be accomplished by heating at, for example, about room temperature (25xc2x0 C.) to about 200xc2x0 C., and preferably from about 50xc2x0 C. to about 140xc2x0 C. Optionally a catalyst can be added to assist the crosslinking reaction. Catalyst examples include amines, tin compounds, zinc compounds and the like, with specific examples being triethylamine, tributylamine, dibutyltin diacetate, zinc octate, and the like. The hydroxyl polycarbonates, therefore, can be crosslinked by reacting with isocyanates, and which crosslinked polycarbonate products provide chemical and mechanical wear resistance without altering substantially the electrical performance, and therefore, are used to extend the life of photoresponsive imagining members.
The hydroxyl-pendent polycarbonates (II) can be prepared by known interfacial phosgenation, interfacial or solution polycondensation. More specifically, the polycarbonates can be prepared by the interfacial polycondensation method according to Scheme (II) wherein the substituents, such as R, x and y, are as illustrated herein. 
Typically, the processes for the preparation of the polycarbonates are initiated with the preparation of tetrahydropyranyl ether (THP) protected hydroxyl bisphenol monomer (VI), followed by interfacial polycondensation of the protected hydroxyl bisphenol and bischloroformate (V) optionally with other suitable bisphenols (IV) to produce the THP protected hydroxyl polycarbonate (II-P), and then followed by removing the THP protecting group to provide the hydroxyl polycarbonate (III). The hydroxyl group is protected by a THP group which could prevent it from reacting with the bischloroformate to interrupt the polymer formation. Specifically, the monomer can be prepared by the following method as shown in Scheme (III): 4,4-bis(4-hydroxyphenyl)valeric acid (VII) is refluxed in methanol with concentrated sulfuric acid as the catalyst to provide methyl 4,4-bis(4-hydroxyphenyl)valerate (VIII). Methyl 4,4-bis(4-hydroxylphenyl)valerate (IX) is reacted with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and chlorotrimethylsilane (TMSCl), then reduced by lithium aluminum hydride (LiAlH4) to provide 4,4-bis(4-hydroxyphenyl)valeric alcohol (VIII). 4,4-Bis(4-hydroxyphenyl)valeric alcohol (VIII) is reacted with dihydropyran (DHP) to produce the desired monomer, THP protected 4,4-bis(4-hydroxyphenyl)valeric alcohol (VI). 
More specifically, the hydroxy-pendent polycarbonates (II) can be prepared by the following method. A mixture of THP-protected 4,4-bis(4-hydroxyphenyl)valeric alcohol (VI) and optionally other bisphenol monomers, such as 4,4-cyclohexylidenebisphenol, an aqueous inorganic base solution, such as sodium hydroxide, and an organic solvent, such as dichloromethane, a suitable amount of a phase transfer catalyst, such as benzyltriethylammonium chloride, is stirred at room temperature (25xc2x0 C.). To the mixture is added a dichloromethane solution containing a bischloroformate, such as 4,4-cyclohexylidenebisphenol bischloroformate. A catalyst, such as triethylamine, tributylamine or the like, can be added to further accelerate the reaction. The interfacial polycondensation is generally accomplished by heating at a temperature of from 0xc2x0 C. to about 100xc2x0 C., and preferably from room temperature (25xc2x0 C.) to about 50xc2x0 C.; the reaction time is generally from about 10 minutes to about 3 hours. The polymeric product obtained can be purified by dissolving it in an organic solvent, such as dichloromethane or tetrahydrofuran (THF), and then precipitating in methanol. Product structures can be confirmed by NMR and IR spectroscopy. The number and weight average molecular weights of the polymer and the Mw/Mn can be obtained by a Waters Gel Permeation Chromatograph (GPC) employing four ULTRASTYRAGEL(copyright) columns with pore sizes of 100, 500, 500, and 104 Angstroms and using THF as a solvent.
The THP-protected hydroxyl polycarbonate obtained was stirred and heated with an acid or a salt, such as hydrochloric acid, toluenesulfonic acid, pyridinium toluenesulfonate and the like, and alcohol, such as methanol, ethanol, propanol and the like, in an organic solvent, such as methylenechloride, tetrahydrofuran or the like. The temperature was controlled at from about 30xc2x0 C. to about 100xc2x0 C., and preferably, from about 40xc2x0 C. to about 70xc2x0 C.; reaction time is, for example, for about 6 to about 72 hours, and preferably for about 12 to about 24 hours. The completion of the reaction was monitored by the disappearance of the singlet at xcex4 4.5 ppm on the 1H NMR spectrum, and the resulting hydroxyl polycarbonate was precipitated into methanol, collected by filtration and dried at 70xc2x0 C. under vacuum. The number and weight molecular weight of the resulting hydroxyl polycarbonate can be obtained by GPC to determine if there has been a change in the molecular weight of the product after converting from the THP-protected hydroxyl polycarbonate to a hydroxyl polycarbonate.
The substrate layers selected for the imaging members of the present invention can be opaque or substantially transparent, and may comprise any suitable material having the requisite mechanical properties. Thus, the substrate may comprise a layer of insulating material including inorganic or organic polymeric materials, such as MYLAR(copyright) a commercially available polymer, MYLAR(copyright) containing titanium, a layer of an organic or inorganic material having a semiconductive surface layer, such as indium tin oxide, or aluminum arranged thereon, or a conductive material inclusive of aluminum, chromium, nickel, brass or the like. The substrate may be flexible, seamless, or rigid, and may have a number of many different configurations, such as for example a plate, a cylindrical drum, a scroll, an endless flexible belt, and the like. In one embodiment, the substrate is in the form of a seamless flexible belt. In some situations, it may be desirable to coat on the back of the substrate, particularly when the substrate is a flexible organic polymeric material, an anticurl layer, such as for example polycarbonate materials commercially available as MAKROLON(copyright).
The thickness of the substrate layer depends on many factors, including economical considerations, thus this layer may be of substantial thickness, for example in excess of about 3,000 microns, or of a minimum thickness. In embodiments, the thickness of this layer is from about 75 microns to about 300 microns, and more specifically, from about 70 to about 150 microns.
The photogenerating layer can contain known photogenerating pigments, such as metal phthalocyanines, metal free phthalocyanines, hydroxygallium phthalocyanines, perylenes, especially bis(benzimidazo)perylene, titanyl phthalocyanines, and the like, and more specifically, vanadyl phthalocyanines, Type V hydroxygallium phthalocyanines, and inorganic components, such as selenium, especially trigonal selenium. The photogenerating pigment can be dispersed in a resin binder or alternatively no resin binder is needed. Generally, the thickness of the photogenerator layer depends on a number of factors, including the thicknesses of the other layers and the amount of photogenerator material contained in the photogenerating layers. Accordingly, this layer can be of a thickness of, for example, from about 0.05 micron to about 10 microns, and more specifically, from about 0.25 micron to about 3 microns when, for example, the photogenerator compositions are present in an amount of from about 30 to about 75 percent by volume. The maximum thickness of the layer in an embodiment is dependent primarily upon factors, such as photosensitivity, electrical properties and mechanical considerations. The photogenerating layer binder resin, present in various suitable amounts, for example from about 1 to about 50, and more specifically, from about 1 to about 10 weight percent, may be selected from a number of known polymers, such as poly(vinyl butyral), poly(vinyl carbazole), polyesters, polycarbonates, poly(vinyl chloride), polyacrylates and methacrylates, copolymers of vinyl chloride and vinyl acetate, phenoxy resins, polyurethanes, poly(vinyl alcohol), polyacrylonitrile, polystyrene, and the like. In embodiments of the present invention, it is desirable to select a coating solvent that does not substantially disturb or adversely effect the other previously coated layers of the device. Examples of solvents that can be selected for use as coating solvents for the photogenerator layer are ketones, alcohols, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, ethers, amines, amides, esters, and the like. Specific examples are cyclohexanone, acetone, methyl ethyl ketone, methanol, ethanol, butanol, amyl alcohol, toluene, xylene, chlorobenzene, carbon tetrachloride, chloroform, methylene chloride, trichloroethylene, tetrahydrofuran, dioxane, diethyl ether, dimethyl formamide, dimethyl acetamide, butyl acetate, ethyl acetate, methoxyethyl acetate, and the like.
The coating of the photogenerator layers in embodiments of the present invention can be accomplished with spray, dip or wire-bar methods such that the final dry thickness of the photogenerator layer is, for example, from about 0.01 to about 30 microns, and more specifically, from about 0.1 to about 3 microns after being dried at, for example, about 40xc2x0 C. to about 150xc2x0 C. for about 15 to about 90 minutes.
Illustrative examples of polymeric binder materials that can be selected for the photogenerator layer are as indicated herein, and include those polymers as disclosed in U.S. Pat. No. 3,121,006, the disclosure of which is totally incorporated herein by reference. In general, the effective amount of polymer binder that is utilized in the photogenerator layer is from about 0 to about 95 percent by weight, and preferably from about 25 to about 60 percent by weight of the photogenerator layer.
As optional adhesives usually in contact with the supporting substrate layer, there can be selected various known substances inclusive of polyesters, polyamides, poly(vinyl butyral), poly(vinyl alcohol), polyurethane and polyacrylonitrile. This layer is, for example, of a thickness of from about 0.001 micron to about 1 micron. Optionally, this layer may contain effective suitable amounts, for example from about 1 to about 10 weight percent, of conductive and nonconductive particles, such as zinc oxide, titanium dioxide, silicon nitride, carbon black, and the like, to provide, for example, in embodiments of the present invention desirable electrical and optical properties.
The charge transport layer can be comprised of known hole transports, such as aryl amines, and which generally is of a thickness of from about 5 microns to about 80 microns, and preferably is of a thickness of from about 10 microns to about 44 microns, and which aryl amines include molecules of the following formula 
wherein X is an alkyl group, a halogen, or mixtures thereof, especially those substituents selected from the group consisting of Cl and CH3.
Examples of specific aryl amines are N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-bis(alkylphenyl)-1,1-biphenyl-4,4xe2x80x2-diamine wherein alkyl is selected from the group consisting of methyl, ethyl, propyl, butyl, hexyl, and the like; and N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-bis(halophenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine wherein the halo substituent is preferably a chloro substituent. Other known charge transport layer molecules can be selected, reference for example U.S. Pat. Nos. 4,921,773 and 4,464,450, the disclosures of which are totally incorporated herein by reference.
Generally, the transport layer contains from about 10 to about 75 percent by weight of the charge transport material, and more specifically, from about 35 percent to about 50 percent of this material.
Also, included within the scope of the present invention are methods of imaging and printing with the photoresponsive devices illustrated herein. These methods generally involve the formation of an electrostatic latent image on the imaging member, followed by developing the image with a toner composition comprised, for example, of thermoplastic resin, colorant, such as pigment, charge additive, and surface additives, reference U.S. Pat. Nos. 4,560,635; 4,298,697 and 4,338,390, the disclosures of which are totally incorporated herein by reference, subsequently transferring the image to a suitable substrate, and permanently affixing the image thereto. In those environments wherein the device is to be used in a printing mode, the imaging method involves the same steps with the exception that the exposure step can be accomplished with a laser device or image bar.