Photoconductive imaging members with fluorinated polycarbonates

Abstract: An abrasion resistant photoconductive imaging member comprises a supporting substrate (1), a photogenerating layer (2) and a charge transport layer (5) comprising charge transport components (7) dispersed in a fluorinated polycarbonate (9).

Description: This invention is generally directed to imaging members. Layered imaging members are known. These imaging members can be comprised of photogenerating layers, and in contact therewith charge transport layers comprised of aryldiamines, reference U.S. Patent 4,265,990. Layered imaging members with charge transport arylamines dispersed in resin binders, like polycarbonates, such as MAKROLON®, are also known. JP-A-2 132 450 discloses imaging members having at the top a charge-transfer layer comprising a fluorine containing polycarbonate binder and a hindered phenole or amine. These known imaging members while suitable for their intended purposes can possess a number of disadvantages, such as being substantially nonresistant to cleaning, and subject to abrasion after about 25,000 imaging cycles, thereby causing undesirable copies with reduced quality. These imaging members can also be difficult to clean or require complex and expensive cleaning systems to achieve adequate cleaning. It is an object of the present invention to enable these disadvantages to be avoided, or minimized. The present invention provides an abrasion resistant photoconductive imaging member as defined in appending claim 1. An imaging member in accordance with the present invention may comprise a supporting substrate, such as aluminum, MYLAR®, titanized MYLAR® and the like, thereover a photogenerating layer comprised of known photogenerating pigments such as trigonal selenium, amorphous selenium, metal phthalocyanines like copper phthalocyanine, metal free phthalocyanines like x-metal free, vanadyl phthalocyanine, squaraines, bisazos, azos, titanyl phthalocyanines especially Type IV, and the like, optionally dispersed in a resin binder, and thereover in contact with the photogenerating layer a charge transport layer comprised of charge transport, especially hole transport components, like known aryldiamines dispersed in a fluorinated polycarbonate resin binder. An important aspect of the present invention resides in the selection of a fluorinated polycarbonate as the resin binder for the charge transport components. The selected fluorinated polycarbonates comprise poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,4-phenylenebisisopropylidene) bisphenol) carbonate; poly(4,4'-hexafluoropropylidene bisphenol-co-4,4'-(1,4-phenylenebispropylidene) bisphenol) carbonate; poly(4,4'-hexafluoroalkylidene bisphenol-co-4,4'-(1,4-phenylenebisalkylidene) bisphenol) carbonate wherein alkyl is methyl, ethyl, butyl, pentyl, hexyl, octyl, nonyl, and the like, and generally alkyl contains from 1 to about 25, and preferably from 1 to about 10 carbon atoms; poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-isopropylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,3-phenylenebisisopropylidene) bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene-2,2'-dimethyl bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-isopropylidene-2,2'-dimethyl bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,4-phenylenebisisopropylidene) bisphenol)-co-4,4'-biphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-diphenylmethylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cycloheptylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4-t-butylcyclohexylidene) bisphenol) carbonate, and poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,4-phenylenebisisopropylidene) bisphenol)-co-4,4'-dihydroxydiphenylether) carbonate. The polycarbonates for embodiments of the present invention, which are available from, for example, BASF, can be prepared by known polyesterification methods. More specifically, the polycarbonates can be prepared by the reaction of one or more, for example up to 3, and preferably 2, bisphenols with a diaryl carbonate, especially bis(aryl)carbonates, reference U.S. Patent 4,345,062, such as diphenyl carbonate; the bis(aryl)carbonate reactants are also commonly referred to as carbonic acid aromatic diesters in the presence of a catalyst, such as metal alkoxides, like titanium butoxide, titanium isopropoxide, zirconium isopropoxide; metal acetates, such as magnesium acetate, zinc acetate; tin compounds, such as dibutyltin oxide, di-n-butyltin dimethoxide, tetraborate compounds, such as tetramethyl ammonium tetraphenyl borohydride, a titanium or zirconium alkoxides, metal diacetates, organotin compounds or borohydride based compounds. The diphenylcarbonate is, in embodiments, used in molar excess with respect to the total number of moles of bisphenol employed; this excess being in the range of from about 5 percent to about 30 percent and preferentially about 10 percent. The catalyst is employed in an effective amount of, for example, from about 0.01 percent to about 1.0 percent molar relative to the bisphenol content, and preferentially in an amount of from about 0.1 to about 0.3 based on the bisphenol. This mixture is heated with stirring in a one liter steel reactor capable of maintaining a vacuum of at least as low as 1.0 mbar. The reactor should also be capable of heating to a temperature at least as high as 300°C and be equipped with a condenser for the collection of the byproducts, such as phenol, of the polymerization and the molar excess of diphenylcarbonate. Specifically, the process can be accomplished as follows: there can be added to a one liter reactor 4,4'-(1,4-phenylenebisisopropylidene) bisphenol, about 173 grams, or approximately half of a mole, and 4,4'-hexafluoroisopropylidene bisphenol, about 168 grams, or approximately half of a mole, together with a molar excess of diphenyl carbonate of about 10 percent or 235.6 grams. A catalyst, such as titanium butoxide, can be added in the amount of about 0.5 milliliter of the solid bisphenols and diphenylcarbonate melt with heating. Heating can be accomplished by an electric element heater that surrounds the reactor vessel. The monomer mixture comprised of the bisphenols and diphenylcarbonate melts in the temperature range of about 80°C to about 140°C. Upon melting, the reactor is sealed, stirring initiated, and a continuous stream of dry nitrogen gas is flushed through the reactor for 50 minutes or other effective time. The reactor temperature is raised to about 220°C over a period of about 50 minutes. This temperature is maintained while the pressure in the reactor is lowered by means of a mechanical vacuum pump. The pressure is lowered from about 1,000 mbar to about 500 mbar over a period of about 10 minutes. The pressure is then further reduced to about 0 mbar over a period of about 80 minutes. After the temperature has been maintained at 220°C for about 100 to about 180 minutes, but preferentially about 133 minutes, the progress of the reaction may be monitored by the rise in the stirrer torque, the stirrer torque increases being indicated by the millivolt signal of a HBM torque transducer and meter which rises from about 0.012 mV to between about 0.1 and 0.3 millivolt as the melt viscosity increases from about 10 centipoise to about 1,000,000 or more centipoise and the rise in the viscosity is caused by the increase in the polymer molecular weight as the reaction progresses or by the collection of the phenol byproduct, since 2 moles of phenol are produced by every mole of bisphenol that polymerizes, the extent of the polymerization can be directly followed. The temperature is then increased to about 280°C in about 10 minutes. This temperature is maintained for about 97 minutes. The temperature is then increased to about 300°C in about 10 minutes. This temperature is maintained for about 97 minutes. The reactor is then repressurized with dry nitrogen gas to atmospheric pressure and the resulting molten polymer is drawn with large forceps from the reactor bottom into a dry inert atmosphere and cut with wire cutters where it is permitted to cool to room temperature, about 25°C, to provide the product, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,4-phenylenebisisopropylidene) bisphenol) carbonate (0.5:0.5 M). The products and structures were confirmed by NMR and M n = 20,800 and M w = 57,500 for the specific aforementioned product. Subsequent to effecting purification of the product, it can be treated by the process outlined in U.S. Patent 4,921,940 whereby, for example, 10 grams of the polycarbonate product was added to 100 milliliters of dimethylformamide as the polymer solvent containing 0.25 gram of tartaric acid as the complexing component. Following stirring of the mixture for 16 hours, the resulting polymer solution was precipitated into 3 liters of rapidly stirring deionized water. The polymer was recovered by filtration and dried overnight in a vacuum oven at about 80°C. The presence of the fluorinated monomer can be confirmed by NMR to be a statistical distributed incorporation of the two comonomers. The number average molecular weight, the weight average molecular weight and the M w /M n ratio may be determined by a Waters Gel Permeation Chromatograph employing four ULTRASTYRAGEL® columns with pore sizes of 100, 500, 500, and 10 4 Angstroms and using THF (tetrahydrofuran) as a solvent. The fluorinated resin binder is present in the charge transport layer of an imaging member in various effective amounts, such as for example from about 25 to about 75 weight percent and preferably from about 45 to about 65 weight percent. Examples of aryl amine hole transport molecules that may be selected for photoconductive imaging members in accordance with the present invention are illustrated in U.S. Patent 4,265,990. Also, examples of charge transport molecules are illustrated in U.S. Patent 4,921,773 and the patents mentioned therein. These components are present in various effective amounts such as for example from about 75 to about 25 weight percent and preferably from about 55 to about 35 weight percent. The charge transport layers are comprised of aryl amine compounds of the formula: wherein X is selected from the group consisting of hydrogen, alkyl and halogen. A photoresponsive imaging device in accordance with the present invention may comprise (1) a supporting substrate, (2) a hole blocking layer, (3) an optional adhesive interface layer, (4) a photogenerating layer, and (5) a charge transport layer with charge transport components dispersed in a selected fluorinated polycarbonate, as defined hereinbefore. Thus, a specific photoconductive imaging member in accordance with the present invention may comprise a conductive supporting substrate, a hole blocking metal oxide layer in contact therewith, an adhesive layer, a photogenerating layer comprised, for example, of bisazo compounds, overcoated on the optional adhesive layer, and as a top layer a hole transport layer comprised of certain diamines dispersed in a selected fluorinated polycarbonate resinous matrix. The photoconductive layer composition when in contact with the hole transport layer is capable of allowing holes generated by the photogenerating layer to be transported. The photoresponsive devices described herein can be incorporated into various imaging systems such as those conventionally known as xerographic imaging processes. Additionally, imaging members in accordance with the present invention can be selected for imaging and printing systems with visible light and/or near infrared light. In that case, the photoresponsive devices may be negatively charged, exposed to light in a wavelength of from about 400 to about 800, and preferably 400 to 680 nanometers, either sequentially or simultaneously, followed by developing the resulting image and transferring to paper. By way of example only, embodiments of the invention will be described with reference to the accompanying drawing, wherein: Figure 1 illustrates a photoconductive imaging member comprising a supporting substrate 1, a photogenerating layer 2 comprised of photogenerating pigments 3 like vanadyl phthalocyanine, trigonal selenium, or titanyl phthalocyanine, especially Type IV titanyl phthalocyanine, dispersed in a resinous binder composition 4, and a charge carrier hole transport layer 5, which comprises hole transporting molecules 7 dispersed in an inactive resinous fluorinated polycarbonate binder composition 9. The supporting substrate of the imaging members may comprise an insulating material such as an inorganic or organic polymeric material, including MYLAR®, a commercially available polymer titanized MYLAR®; 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 such as aluminum, titanium, chromium, nickel, brass, or the like. The substrate may be flexible, seamless, or rigid and may have a number of different configurations, such as a plate, a cylindrical drum, a scroll, an endless flexible belt, and the like. The thickness of the substrate layer depends on a number of factors, including economic considerations, the components of the other layers, and the like. Thus, this layer may be of substantial thickness, for example up to 3.43 mm (135 mils), or of minimal thickness provided that there are no adverse effects on the system. The thickness of the substrate layer, may be in the range of from about 0.77 to 2.54 mm (3 to 100 mils). In certain embodiments, the thickness of this layer is from about 0.77 to 0.127 mm (3 mils to about 25 mils). Generally, the photogenerating layer has a thickness of from about 0.05 µm to about 10 µm or more, and preferably has a thickness of from about 0.1 µm to about 3 or, possibly, 4 µm. The thickness of this layer, however, is dependent primarily upon the photogenerating weight loading, which may vary from about 5 to 95 or, possibly, 100 percent, the components of the other layers, and the like. Optionally, resin binders for the photogeneration layer include polyester, polyvinylbutyral, and the like. Generally, photogenerating pigmens employed in the photogenerating layer may comprise selenium, metal free phthalocyanines, metal phthalocyanines, vanadyl phthalocyanines, or titanyl phthalocyanines. The photoconductive imaging member may optionally contain a hole blocking layer situated between the supporting substrate and the photogenerating layer. This layer may comprise metal oxides, such as aluminum oxide and the like, or materials such as silanes, nylons, and the like. The primary purpose of this layer is to prevent hole injection from the substrate during and after charging. Typically, this layer is of a thickness of less than about 0.05 µm (500 Angstroms), for example in the range of from about 0.005 µm to about 0.03 µm (5 to about 300 Angstroms), although it may be as thick as 3 µm in some instances. In addition, the photoconductive imaging member may also optionally contain an adhesive interface layer situated between the hole blocking layer and the photogenerating layer. This layer may comprise a polymeric material such as polyester, like Polyester-100, polyvinyl butyral, polyvinyl pyrrolidone, and the like. Typically, this layer is, for example, of a thickness of less than about 0.9 µm preferably less than about 0.6 µm, although a thickness range of from about 0.05 to about 1 µm is generally suitable. In an embodiment, the photoconductive imaging member of the present invention is comprised of (1) a conductive supporting substrate of MYLAR® with a thickness of 75 µm and a conductive vacuum deposited layer of titanium with a thickness of 0.02 µm; (2) a hole blocking layer of N-methyl-3-aminopropyltrimethoxysilane with a thickness of 0.1 µm; (3) an adhesive layer of 49,000 Polyester (obtained from E.I. DuPont Chemical) with a thickness of 0.05 micron; (4) a photogeneration layer of a dispersion of trigonal selenium with a thickness of 1 µm; and (5) a charge transport layer with a thickness of 20 µm of an aryl amine dispersed in a resin binder of fluorinated polycarbonate of Example I below. In another embodiment the charge transport layer has a thickness in the range from 5 to 50 µm. Imaging members in accordance with the present invention can exhibit excellent xerographic properties. For example, values for dark development potential (V ddp ) can range from about -400 to about -975 Volts. Preferred ranges for dark development potential are usually about -400 to -900 volts with -800 volts being especially preferred. High dark development potentials permit high contrast potentials, which result in images of high quality with essentially no background development. Imaging members in accordance with the present invention can also exhibit low dark decay values of, for example, about -50 volts per second or less. Low dark decay values can be of importance for developing high quality images since dark decay measures the amount of charge that disappears after charging of the photoreceptor, and a large difference in charge between exposed and unexposed areas of the photoreceptor results in images with high contrast. Acceptable values for dark decay vary depending on the design of the imaging apparatus in which the imaging members are contained. This dark decay may be as high as-100 volts per second with -50 volts and -10 to -20 volts per second being preferred. Residual potential values (V R ) for certain imaging members in accordance with the present invention are excellent, ranging from, for example, about -5 volts to about -50 volts. Residual potential is a measure of the amount of charge remaining on the imaging member after erasure by exposure to light and prior to imaging. Residual potentials of -5 to -20 are considered very exceptional. Photosensitivity values for imaging members in accordance with the present invention in embodiments thereof are acceptable and in some instances excellent, and can be, for example, from about 4 to about 25 ergs per square centimeter. Acceptable photosensitivity values vary depending on the design of the imaging apparatus in which the imaging members are contained; thus in some instances, values as high as 40 or 50 are acceptable, and values of about 5 can be preferred. A method of generating images with a photoconductive imaging member in accordance with the invention comprises the steps of generating an electrostatic image on the photoconductive imaging member, subsequently developing the electrostatic image with known developer compositions comprised of resin particles, pigment particles, additives, including charge control agents and carrier particles, reference U.S. Patents 4,558,108; 4,560,535; 3,590,000; 4,264,672; 3,900,588 and 3,849,182, transferring the developed electrostatic image to a suitable substrate, and permanently affixing the transferred image to the substrate. Imaging members in accordance with the present invention can be prepared by a number of different known processes. In one process, the vanadyl phthalocyanine photogenerator is coated onto a supporting substrate with a Bird applicator, for example, followed by the solution coating of the charge transport layer, and thereafter drying in, for example, an oven. The following Examples are being supplied to illustrate the present invention further. Parts and percentages are by weight unless otherwise indicated. EXAMPLE I POLYMERIZATION The reactor employed was a 1 liter stainless steel reactor equipped with a helical coil stirrer and a double mechanical seal. It was driven by a 0.5 horsepower motor with a 30:1 gear reduction. A torque meter was part of the stirrer drive. The reactor was heated electrically. The pressure was monitored by both pressure transducer and pirani gauge. The temperature was monitored by platinum RTDs. The pressure and temperature were precisely controlled and profiled by a Fischer and Porter Chameleon controller. A specially designed condenser ensured the monitoring of the efficient condensation of phenol and diphenylcarbonate. A proportioning valve and a rotary oil pump provided controlled variations in reactor pressure. To this reactor was added bisphenol P (4,4'-(1,4-phenylenebisisopropylidene) bisphenol), 173.1 grams, 0.5 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 168.1 grams, 0.5 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The reactor was sealed and the temperature raised to about 220°C. The pressure was then lowered to about 500 millibars in the space of about 10 minutes. Phenol began to collect in the condenser as the pressure neared 500 millibars. The rate of pressure decrease was slowed so that about 80 minutes was required to reach a pressure below 2 millibars. After a total of 170 minutes at 220°C, the temperature was raised to 260°C and held there for about 67 minutes. The temperature was then raised to and retained at 280°C for about 97 minutes and then to 300°C for a further 120 minutes. The molten polymer was then drawn out of the reactor into a dry nitrogen atmosphere to cool. The obtained polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,4-phenylenebisisopropylidene) bisphenol) carbonate (0.5:0.5) had a T g of 155°C as determined on a DuPont Instruments DSC 10. The GPC molecular weight averages were determined on a Waters chromatography system using a 0.01 µm (100 Å), two 0.05 µm (500 Å) and a 10 µm (10 4 Å) Waters ULTRASTRYRAGEL® columns calibrated with narrow molecular weight polystryrene standards and found to be M n = 20,800 and M w = 57,500. NMR confirms the structure. Ten grams of the polymer were added to 100 milliliters of DMF containing 0.25 gram of tartaric acid and stirred overnight, about 18 hours. The polymer solution was precipitated into 1.5 liters of rapidly stirred deionized water. The polymer in quantitative yield was subsequently dried and evaluated as a charge transport matrix polymer in a photoreceptor. EXAMPLE II The process of Example I was repeated with the following changes in the temperature profile: total time at 220°C was lowered to 133 minutes, the temperature plateau at 260°C was eliminated, the time at 280°C remained at 97 minutes, and the time at 300°C was reduced to 97 minutes. The polymer produced had a T g of 161°C and GPC molecular weight averages of M n = 29,300 and M w = 87,800. EXAMPLE III (Comparative) The process of Example II was repeated with the following reactants bisphenol AP (4,4'-(1-phenylethylidene) bisphenol), 143.5 grams, 0.5 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 168.1 grams, 0.5 moles; and diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer product poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1-phenylethylidene) bisphenol) carbonate (0.5:0.5 M) had a T g of 178°C and GPC molecular weight averages of M n = 27.600 and M w = 70,900. EXAMPLE IV The process of Example II was repeated with the following reagents bisphenol Z (4,4'-cyclohexylidene bisphenol), 134.0 grams, 0.5 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 168.1 grams, 0.5 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer product poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene bisphenol) carbonate (0.5:0.5 M) had a T g of 170°C and GPC molecular weight averages of M n = 27.700 and M w = 120,000. EXAMPLE V The process of Example II was repeated with the following reactants bisphenol Z (4,4'-cyclohexylidene bisphenol), 67.0 grams, 0.25 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 252.2 grams, 0.75 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene bisphenol) carbonate (0.75:0.25 M) had a T g of 173°C and GPC molecular weight averages of M n = 27,800 and M w = 56,700. EXAMPLE VI The process of Example II was repeated with the following reagents bisphenol Z (4,4'-cyclohexylidene bisphenol), 201.0 grams, 0.75 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 84.1 grams, 0.25 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene bisphenol) carbonate (0.25:0.75 M) had a Tg of 175°C and GPC molecular weight averages of M n = 29,200 and M w = 75,900. EXAMPLE VII The process of Example II was repeated with the following reagents bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 180.8 grams, 0.54 moles; diphenylcarbonate, 126.7 grams, 0.59 moles; and titanium butoxide, 0.25 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol) carbonate had a Tg of 170°C and GPC molecular weight averages of M n = 30,900 and M w = 68,900. EXAMPLE VIII The method of Example II was repeated with the following reagents bisphenol A (4,4'-isopropylidenebisphenol), 114.1 grams, 0.5 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 168.1 grams, 0.5 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-isopropylidene bisphenol) carbonate (0.5:0.5 M) had a Tg of 158°C and GPC molecular weight averages of M n = 28,700 and M w = 62,200. EXAMPLE IX The method of Example II was repeated with the following reagents bisphenol M (4,4'-(1,3-phenylenebisisopropylidene) bisphenol), 173.1 grams, 0.5 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 168.1 grams, 0.5 moles; diphenylcarbonate, 235.6 grams, 1.1 moles; and titanium butoxide, 0.5 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,3-phenylenebisisopropylidene) bisphenol)) carbonate (0.5:0.5 M) had a T g of 121°C and GPC molecular weight averages of M n = 28,200 and M w = 59,300. EXAMPLE X The process of Example II was repeated except that a 100 milliliter stainless steel reactor was used along with the following reagents bisphenol P (4,4'-(1,4-phenylenebisisopropylidene) bisphenol), 13.0 grams, 0.0375 moles; bisphenol AF (4,4'-hexafluoroisopropylidene bisphenol), 8.4 grams, 0.025 moles; 4,4'-biphenol, 7.0 grams, 0.0375 moles; diphenylcarbonate, 23.6 grams, 0.11 moles; and titanium butoxide, 0.05 milliliter. The polymer poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,4-phenylenebisisopropylidene) bisphenol)-co-4,4'-biphenol) carbonate (0.25:0.375:0.375 M) had a T g of 147°C and GPC molecular weight averages of M n = 14,400 and M w = 32,300. EXAMPLE XI A layered photoresponsive imaging member comprised of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD) molecularly dispersed in the fluorinated polymer binder of Example I as the hole transport layer, and a trigonal selenium generator layer was fabricated as follows: A dispersion of trigonal selenium and poly(N-vinyl carbazole) was prepared by ball milling 1.6 grams of trigonal selenium and 1.6 grams of poly(N-vinyl carbazole) in 14 milliliters each of tetrahydrofuran and toluene. Ten grams of the resulting slurry were then diluted with a solution of 0.24 gram of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl)-4,4'-diamine (TPD) in 5 milliliters each of tetrahydrofuran and toluene. A 1.5 micron thick photogenerator layer was fabricated by coating the above dispersion onto an aluminized MYLAR® substrate, thickness of 75 microns, with a Bird film applicator, followed by drying in a forced air oven at 135°C for 5 minutes. A solution for the charge transport layer was then prepared by dissolving 0.8 gram of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD), and 1.2 grams of the polymer binder of Example I in 10 milliliters of methylene chloride. This solution was then coated over the photogenerator layer by means of a Bird film applicator. The resulting member was then dried in a forced air oven at 135°C for 20 minutes, resulting in a 20 micron thick charge transport layer. A solution for a charge transport layer of a control imaging member was then prepared by dissolving 0.8 gram of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD), 1.2 grams of bisphenol A polycarbonate (MAKROLON 5705®) in 10 milliliters of methylene chloride. This solution was then coated over the above photogenerator layer by means of a Bird film applicator. The resulting layered photoconductive imaging member was then dried in a forced air oven at 135°C for 20 minutes, resulting in a 20 micron thick charge transport layer. A wear test fixture was set up to measure the relative wear and wear rates of charge transport layers subjected to toner interactions and blade cleaning. The two photoresponsive imaging members fabricated as described above were used by wrapping around and taping onto an aluminum drum in the test fixture. The drum speed controlled by a motor can be varied and is usually maintained at about 55 rpm during the test. Toner is supplied continuously from a hopper and cleaning of the residual toner on the imaging member was achieved by a cleaning blade. The typical test conditions during a wear test are described as follows: Toner: 46.7 percent of polystyrene/n-butylacrylate copolymer (58/42), 49.6 percent of cubic magnetite BL220, 1.0 percent of P51, an aluminum salt, charge control additive obtained from Hodogaya Chemical of Japan, 2.5 percent of 660P Wax (polypropylene obtained from Sanyo of Japan) and 0.2 percent of AEROSIL R972®. Blade: Xerox imaging device 1065 cleaning blade Drum speed: 55 rpm Number of cycles: 50,000 A new cleaning blade was used in each test. The blade force was about 30 grams/centimeter and was adjusted by a micrometer mounted on the blade holder. The wear was determined as the loss in thickness of the charge transport layer and was the difference in thickness of the charge transport layer before and after the wear test. The wear was expressed in nanometers. The wear rate was obtained by dividing the wear by the number of cycles and is expressed as nanometers/K cycle. The wear rate was normalized and was independent of any variations in the total number of cycles of the wear tests. The data obtained was shown in Table 1 wherein the reduced wear of the polymer of Example I with respect to the control was shown. The wear test results shown on Table 1 indicates that a polymer binder of Example 1, when used in the charge transport layer of the photoreceptor device, exhibited a wear rate of about 12 nanometers/K cycle which was half the wear rate obtained with bisphenol A polycarbonate (MAKROLON 5705®) (control photoreceptor) tested under similar conditions. Effect of Polymer Binder on the Wear of CTL (Charge Transport Layer) Polymer Binder Sample # Wear in 50,000 Cycles µm Wear Rate nm/K Cycle MAKROLON 5705® Control 1.2 24 Example I Polymer 0.6 12 Example III Polymer (comparative) 1.5 30 EXAMPLE XII The layered photoresponsive imaging members of Example XI were tested electrically as follows: The xerographic electrical properties of the aforementioned imaging members of Example XI were determined by electrostatically charging the surfaces thereof with a corona discharge source until the surface potentials, as measured by a capacitively coupled probe attached to an electrometer, attained an initial value V o of about -800 volts. After resting for 0.5 second in the dark, the charged members reached a surface potential of V ddp , dark development potential, and each member was then exposed to light from a filtered Xenon lamp with a XBO 150 watt bulb. A reduction in surface potential to a V bg value, background potential, due to photodischarge effect was observed. The background potential was reduced by exposing with a light intensity about 10 times greater than the expose energy. The resulting potential on the imaging member was designated as the residual potential, Vr. The dark decay in volt/second was calculated as (V o -V ddp )/0.5. The percent of photodischarge was calculated as 100 percent (V ddp -V bg )/V ddp . The desired wavelength and energy of the expose light was determined by the type of filters placed in front of the lamp. The broad band white light (400 to 700 nanometers) photosensitivity of these imaging members were measured by using an infrared cut-off filter whereas the monochromatic light photosensitivity was determined using narrow band-pass filter. The photosensitivity of the imaging members is usually provided in terms of the amount of expose energy in erg/cm 2 , designated as E 1/2 , required to achieve 50 percent of photodischarge from the dark development potential. The higher the photosensitivity, the smaller is the E 1/2 value. The devices were subjected to 1,000 cycles of repeated charging, discharging and erase to determine the cycling stability. Changes in V ddp V bg , V res are indicated as ΔV ddp , ΔV bg , ΔV res . A summary of the results of the electrical testing of the imaging members of Example XI is shown on Table 2. For the imaging member based on the fluorinated polycarbonate of Example I as the binder, the acceptance potential was -800 volts, the residual potential was -20 volts and the photosensitivity (E 1/2 ) was 2.3 ergs/cm 2 . The results obtained with the control imaging member based on bisphenol A polycarbonate (MAKROLON 5705®) as the polymer binder and shown on Table 2 indicate that the acceptance potential was -800 volts, the residual potential was -22 volts and the photosensitivity was 2.1 ergs/cm 2 . The imaging members were subjected to 1,000 cycles of repeated charging, discharging and erase and exhibit excellent cycling stability as shown on Table 2. The results indicate excellent cycling stability with the polymer binder of Example I. This demonstrates the potential of this class of polymer binders to be used as lower wear resistant binders in the charge transport layer for photoresponsive imaging members. Xerographic Cycling Stability - Fluorinated Polycarbonate Xerographic Parameters Control Device MAKROLON 5705 ® as Binder Fluorinated Polycarbonate of Example I as Binder Vddp (V) -800 -800 E 1/2 (ergs/cm 2 ) 2.1 2.3 V residual (V) 22 20 Cyclic data No. of cycles 1,000 1,000 ΔV ddp (V) -36 -40 ΔV bkg (V) 5 0 ΔV residual (V) 10 10 EXAMPLE XIII A photoresponsive imaging member comprised of a polymer binder of Example I as the resinous binder in the charge transport layer and vanadyl phthalocyanine as the photogenerator was prepared as follows: A titanized MYLAR® substrate with a thickness of about 75 microns comprised of MYLAR® with a thickness of 75 microns and titanium film with a thickness of 0.02 micron was obtained from Martin Processing Inc. The titanium film was coated with a solution of 1 milliliter of 3-aminopropyltrimethoxysilane in 100 milliliters of ethanol. The coating was heated at 110°C for 10 minutes resulting in the formation of a 0.1 micron thick polysilane layer. The polysilane layer is a hole blocking layer and prevents the injection of holes from the titanium film and blocks the flow of holes into the charge generation layer. The polysilane layer is used to obtain the desired initial surface charge potential of about -800 volts for this imaging member. A dispersion of a photogenerator prepared by ball milling a mixture of 0.07 gram of vanadyl phthalocyanine and 0.13 gram of Vitel PE-200 polyester (Goodyear) in 12 milliliters of methylene chloride for 24 hours was coated by means of a Bird film applicator on top of the polysilane layer. After drying the coating in a forced air oven at 135°C for 10 minutes, a 0.5 micron thick vanadyl phthalocyanine photogenerating layer with 35 percent by weight of vanadyl phthalocyanine and 65 percent by weight of polyester was obtained. A solution for the charge transport layer was then prepared by dissolving 0.8 gram of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD), 1.2 grams of fluorinated polycarbonate of Example I in 10 milliliters of methylene chloride. This solution was then coated over the photogenerator layer by means of a Bird film applicator. The resulting layered photoconductive imaging member was then dried in a forced air oven at 135°C for 20 minutes resulting in a 20 µm (micron) thick charge transport layer. The above fabricated imaging member was tested electrically in accordance with the procedure of Example XII. Specifically, this imaging member was negatively charged to 800 volts and discharged when exposed to monochromatic light of a wavelength of 830 nanometers. The half decay exposure sensitivity for this device was 8 ergs/cm 2 and the residual potential was 15 volts. The electrical properties of this imaging member remained essentially unchanged after 1,000 cycles of repeated charging and discharging.

Claims: An abrasion resistant photoconductive imaging member comprising a supporting substrate (1), a photogenerating layer (2) and a charge transport layer (5) comprising charge transport components (7) dispersed in a fluorinated polycarbonate (9) selected from the group consisting of poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,4-phenylenebisisopropylidene) bisphenol) carbonate, poly(4,4'-hexafluorioisopropylidene bisphenol-co-4,4'-(1,4-phenylenebispropylidene) bisphenol) carbonate, poly(4,4'-hexafluoroalkylidene bisphenol-co-4,4'-(1,4-phenylenebisalkylidene) bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene bisphenol)carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-isopropylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-(1,3-phenylenebisisopropylidene) bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cyclohexylidene-2,2'-dimethyl bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-isopropylidene-2,2'-dimethyl bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,4-phenylenebisisopropylidene) bisphenol)-co-4,4'-bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-diphenylmethylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4,4'-cycloheptylidene bisphenol) carbonate, poly(4,4'-hexafluoroisopropylidene bisphenol-co-4-t-butylcyclohexylidene bisphenol) carbonate, and poly(4,4'-hexafluoroisopropylidene bisphenol-co-(4,4'-(1,4-phenylenebisisopropylidene) bisphenol)-co-4,4'-dihydroxydiphenylether)carbonate and wherein the charge transport components are comprised of aryl amine molecules of the formula wherein X is selected from the group consisting of hydrogen, alkyl and halogen. A photoconductive imaging member in accordance with claim 1, wherein the charge transport components comprise hole transport molecules. A photoconductive imaging member in accordance with claim 1 or claim 2, wherein the charge transport layer has a thickness in the range of from 5 to 50 µm.

Inventors: MURTI DASARAO K, ODELL PETER G, MURTI, DASARAO K., ODELL, PETER G.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1993
Main classification: G03G5
IPC codes: G03G5