Patent Application
20070281228
To a flask are added 46.75 grams of benzoguanamine and 129.75 ml of 37% formaldehyde solution at pH 7.9. The mixture is heated at 71° C. for 1 hour and then allowed to cool slowly to ambient temperature (23˜25° C.). The white solid is filtered, washed with methanol, and dried in vacuum oven at 50° C. to yield 30.5 grams of tetrahydroxymetlhylbenzoguanamine.
To a flask are added 27.65 grams of tetrahydroxymethylbenzoguanamine obtained above, 75 ml of butanol, and 2 ml of concentrated hydrochloric acid. The mixture is stirred at ambient temperature for 1 hour. The excess amount of the butanol is removed by evaporation under reduced pressure to yield 47.3 grams of tetrabutoxymethylbenzoguanamine.
An electrophotographic imaging member web stock is prepared by providing a 0.02 micrometer thick titanium layer coated on a biaxially oriented polyethylene naphthalate substrate (KADALEX, available from ICI Americas, Inc.) having a thickness of 3.5 mils (89 micrometers) and applying thereto, using a gravure coating technique and a solution containing 10 parts of gamma aminopropyltriethoxy silane, 10.1 parts of distilled water, 3 parts of acetic acid, 684.8 parts of 200 proof denatured alcohol and 200 parts of heptane. This layer is then allowed to dry for 5 minutes at 135° C. in a forced air oven. The resulting blocking layer has an average dry thickness of 0.05 micrometer measured with an ellipsometer.
An adhesive interface layer is then prepared by applying with extrusion process to the blocking layer a wet coating containing 5 percent by weight based on the total weight of the solution of polyester adhesive (MOR-ESTER 49,000, available from Morton International, Inc.) in a 70:30 volume ratio mixture of tetrahydrofuran:cyclohexanone. The adhesive interface layer is allowed to dry for 5 minutes at 135° C. in a forced air oven. The resulting adhesive interface layer has a dry thickness of 0.065 micrometer.
The adhesive interface layer is thereafter coated with a photogenerating layer. The photogenerating layer dispersion is prepared by introducing 0.45 part of Iupilon 200 (PC-Z 200) available from Mitsubishi Gas Chemical Corp and 50 parts of tetrahydrofuran into a glass bottle. To this solution is added 2.4 parts of hydroxygallium phthalocyanine and 300 parts of ⅛ inch (3.2 millimeter) diameter stainless steel shot. This mixture is then placed on a ball mill for 20 to 24 hours. Subsequently, 2.25 parts of PC-Z 200 is dissolved in 46.1 parts of tetrahydrofuran, then added to this OHGaPc slurry. This slurry is then placed on a shaker for 10 minutes. The resulting slurry is, thereafter, coated onto the adhesive interface by an extrusion application process to form a layer having a wet thickness of 0.25 mil. However, a strip about 10 mm wide along one edge of the substrate web bearing the blocking layer and the adhesive layer is deliberately left uncoated by any of the photogenerating layer material to facilitate adequate electrical contact by the ground strip layer that is applied later. This photogenerating layer is dried at 135° C. for 5 minutes in a forced air oven to form a dry thickness photogenerating layer having a thickness of 0.4 micrometer layer.
Onto the photogenerating layer of the imaging member web is simultaneously coated with a charge transport layer and a ground strip layer using extrusion co-coating process. The charge transport layer is prepared by introducing into an amber glass bottle a weight ratio of 1:1 N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4˜4′-diamine, and MAKROLON 5705, a polycarbonate resin having a weight average molecular weight of about 120,000 commercially available from Bayer A. G. The resulting mixture is dissolved to give a 15 percent by weight solid in 85 percent by weight methylene chloride. This solution is applied onto the photogenerator layer to form a coating which upon drying has a thickness of 29 micrometers.
The approximately 10 mm wide strip of the adhesive layer left uncoated by the photogenerator layer is coated over with a ground strip layer during the co-coating process. This ground strip layer, after drying along with the co-coated charge transport layer at 135° C. in the forced air oven for minutes, has a dried thickness of about 19 micrometers. This ground strip is electrically grounded, by conventional means such as a carbon brush contact means during conventional xerographic imaging process.
An anticurl coating is prepared by combining 8.82 parts of polycarbonate resin (MAKROLON 5705, available from Bayer A G), 0.72 part of polyester resin (VITEL PE-200, available from Goodyear Tire and Rubber Company) and 90.1 parts of methylene chloride in a glass container to form a coating solution containing 8.9 percent solids. The container is covered tightly and placed on a roll mill for about 24 hours until the polycarbonate and polyester are dissolved in the methylene chloride to form the anticurl coating solution. The anticurl coating solution is then applied to the rear surface (side opposite the photogenerator layer and charge transport layer) of the imaging member web stock, again by extrusion coating process, and dried at 135° C. for about 5 minutes in the forced air oven to produce a dried film thickness of about 17 micrometers. The resulted photoconductor sheet is used for applying an overcoat layer of the present invention.
An overcoat coating solution is prepared as follow: One part of a hydroxyl-containing polymer, 0.6 part of a benzoguanamine curing agent, 0.8 part of a charge transport compound, and 0.016 part of an acid catalyst are dissolved in 7.2 parts of 1-methoxy-2-propanol as a solvent at room temperature (about 20° C. to about 25° C.). The mixture is filtered through a 0.45 micron filter to form a coating solution. The coating composition is then applied using a 0.125 mil Bird bar applicator onto the charge transport layer of the photoconductor sheet, and cured at 125° C. for 5 minutes. The result is an imaging member having an overcoating layer thickness of about 3 microns.
An imaging member was fabricated in the same manner as described above except that the overcoating layer is omitted. This imaging member is used as a control.
The imaging members of Examples 2-7 and Comparative Example are tested for their electrostatographic sensitivity and cycling stability in a scanner. The scanner is known in the industry and equipped with means to rotate the drum while it is electrically charged and discharged. The charge on the sample is monitored through use of electrostatic probes placed at precise positions around the circumference of the device. The samples in this Example are charged to a negative potential of 500 Volts. As the device rotates, the initial charging potential is measured by voltage probe 1. The sample is then exposed to monochromatic radiation of known intensity, and the surface potential measured by voltage probes 2 and 3. Finally, the sample is exposed to an erase lamp of appropriate intensity and wavelength and any residual potential is measure by voltage probe 4. The process is repeated under the control of the scanner's computer, and the data is stored in the computer. The PIDC (photo induced discharge curve) is obtained by plotting the potentials at voltage probes 2 and 3 as a function of the light energy. The testing results are summarized in Table 1. All photoreceptors with an overcoat layer show comparable PIDC characteristics as the control device.
Image deletion tests are also conducted on the imaging members of Examples 2-7 and Comparative Example. The test is conducted by laminating a strip (about 8 inch×1.5 inch) of the overcoated imaging member of Examples 2-7 and a strip (about 8 inch×1.5 inch) of the reference imaging member of Comparative Example on the photoreceptor drum of a Xerox DOCUCENTRE 12 office machine using conductive adhesive tape. The tape is used to hold the laminated strips in place and also to provide electrical contact between the conductive layer in each of the two strips and the drum metal base. The drum configuration is then mounted in an axial scanner equipped with a scorotron charging element and an erase laser bar. The scanner allows for the repetitive charging and discharging of the drum configuration by means of rotating the drum at a rate of 150 cycles per minute between the scorotron (where the drum surface in close proximity to the scorotron gets charged to a potential of about 750 volts) and discharged by means of exposure to the laser beam. The cycling is carried in ambient conditions for a total of about 170,000 cycles. Following cycling, the drum configurations are then removed from the axial scanner and mounted in a Xerox DOCUCENTRE 12 office machine. The machine is then used to print a variable-width multiple-lined print pattern on 11″×17″ standard white paper. The printed pattern is then examined visually on the paper for line blurriness. A comparison between print patterns produced by drum areas laminated by a strip of the overcoated imaging member of Examples 2-7 and a strip of the reference imagine member of Comparative Example is then done. The testing showed that the imaging member of Examples 2-6 were very resistant to image deletion, exhibiting stable performce over 170,000 cycles. The imaging members of Comparative Example and Example 7 showed exhibited image deletion after about 50,000 cycles.
The craking resistance test of the imaging members was conducted using a in-house testing fixture. The degree of cracking was estimated under optical microscopoic technique. The results indicate that the imaging members having an overcoat layer possess much improved cracking resistance with respect to the control.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
