US3912511A - Multicomponent organic coating of polyester, polyurethane and a humidity barrier thermoplastic resin - Google Patents

Abstract

An electrophotographic plate having a three component resin composition coating is disclosed. The coating consists of from about 16 to 71 percent film forming polyester, 16 to 71 percent moisture insensitive, film forming, organic solvent soluble resin and 5 to 35 percent polyurethane polymers. The three component resin overcoating exhibits particular utility in that it enables an electrophotographic member to function under conditions of high humidity.

Description

United States Patent Gerace et a1.

[ 1 Oct. 14, 1975 MULTICOIVIPONENT ORGANIC COATING OF POLYESTER, POLYURETHANE AND A HUlVflDITY BARRIER THERMOPLASTIC RESIN Inventors: Paul L. Gerace, Rochester; Paul R.

Handley, Webster; Rudy H. Haidle, Evanston, all of 111.

Xerox Corporation, Stamford, Conn.

Filed: Jan. 5, 1973 Appl. No.: 321,193

Related US. Application Data Continuation-impart of Ser. No. 38,467, May 18, 1970, abandoned.

Assignee:

U.S. Cl. 96/1.5 Int. Cl. G03G 5/04 Field of Search 96/l.5, 115; 117/61 References Cited UNITED STATES PATENTS 7/1964 Clark 96/1 3,159,483 12/1964 Behmenburg 96/1.5 3,312,548 4/1967 Straughan 96/1.5 3,403,019 9/1968 Stahly 96/1.5 3,639,120 2/1972 Snelling 96/1.5 3,656,949 4/1972 Honjo 96/1.5 3,682,632 8/1972 Fumiaki 96/1.5 3,736,134 5/1973 Gosselink et a1. 96/1.5

Primary Examiner-Norman G. Torchin Assistant ExaminerJohn L. Goodrow [57] ABSTRACT 7 Claims, I Drawing Figure U.S. Patent Oct. 14, 1975 3,912,511

MULTICOMPONENT ORGANIC COATING OF POLYESTER, POLYURETHANE AND A HUMIDITY BARRIER THERMOPLASTIC RESIN This application is a continuation-in-part of copending application Ser. No. 38,467, filed May 18, 1970, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to xerography and more particularly to an improved xerographic plate.

The xerographic process described in US. Pat. No. 2,297,691 to Chester F. Carlson, involves the sensitization of a xerographic plate, as by placing an electrostatic charge thereon, and the exposure sensitized plate exposed to an original image to be reproduced. The exposed plate is developed by contacting the plate surface with electrostatically charged, finely divided powder particles to produce a powder image which is either used or fixed in situ or thereafter transferred from the plate to a final support, the transferred image being fixed thereon to form the final print. If desired, the transfer step may be omitted and the image fixed to the plate itself. As originally described by Carlson, the xerographic plate consisted of a thin layer of sulfur, anthracene or anthraquinone, either singly or in combination, applied to a relatively conductive base by melting and flowing onto the base or by evaporating material onto the base which is kept at a lower temperature so as to condense the vapor.

A significant advance was made in xerography when it was discovered that vitreous selenium was highly photoconductive. A selenium xerographic plate generally comprises a metal backing plate, as aluminum, having coated on one side, as by vacuum evaporation, a layer of very high purity viteous selenium. In the dark the selenium layer has a high resistivity, but when exposed to light the resistivity is reduced many orders of magnitude, the amount depending on the intensity and wavelength of light. By reason of its high electrical resistivity in the dark the selenium layer can be charged electrostatically, which charge is retained for prolonged periods until light impinges thereon causing discharge. The outstanding ability of vitreous selenium to hold its charge for an appreciable period in the dark coupled with its high light sensitivity have made the selenium plate the standard commercial plate of xerogra phy. Such plates are costly to fabricate, but may be used a thousand or more times in the xerographic process so that the cost per image developed is small. Thus, the selenium plate requires reusability to obtain reasonable operating costs.

Another advance was made in the field of xerographic plates with the discovery of the binder plate. Such plates are described by Arthur E. Middleton in U.S. Pat. No. 2,663,636. As there described it was found that an efficient xerographic plate can be obtained by coating a relatively conductive base with a photoconductive insulating composition prepared by intimately mixing and grinding together any photoconductive insulating material, a binder of high electrical resistance and a solvent.

When the binder and photoconductor are selected from low cost materials and the backing comprises an inexpensive material such as paper, it is economically feasible to utilize a xerographic plate, only once, that is, use it as a disposable xerographic plate. However,

necessarily such a paper is significantly more expensive than non-light sensitive paper. Therefore, for high volume applications, reusability of the xerographic plate is essential no matter whether a uniform photoconductor is used or a binder composition. In a disposable binder plate, the photoconductor is selected primarily on the basis of cost, rather than on the merits of its xerographic properties. If, however, the plate is reusable, then the cost of the photoconductor is not such an overriding consideration. Thus, in present commercial xerography utilizing a reusable plate, as in the vitreous selenium plate, the photoconductive layer is generally the most expensive as well as the most easily damaged element of the plate.

In high speed, xerographic applications as described for example in US. Pat. No. 2,357,809 to C. F. Carlson it is important to apply a protective layer or coating over the photoconductive insulating material so as to extend the life of the plate. Generally, the overcoating is formed by applying a solvent solution of an organic resin to the plate surface and allowing the solution to evaporate. However, there are many highly polymerized, solvent resistant resins that cannot be applied by this method and, further, when a solvent is found for such a polymer it often has a deleterious effect upon the photoconductor. The solution to this problem was found by .l. J. Kinsella in U.S. Pat. No. 3,146,145 where there is disclosed a process involving placing a thin pellicle of highly polymerized, solvent resistant resin in contact with a photoconductive insulating layer and then subjecting the assembly to ion bombardment in a vacuum.

While various waxes, hydrocarbons, inorganic resins have been employed as a protective layer on reusable xerographic plates, they all have a similar problem in that their electrical properties change significantly at very high and very low humidities. Therefore most organic materials, particularly resins, when used as overcoatings on electrophotographic plates affect the quality of the image resolution from said plate when it is operated at humidities above about 58 percent relative humidity (RH) or below 20 percent relative humidity. This is due to the tendency of the coating composition to absorb and de-sorb moisture thereby varying its electrical behavior, i.e. the discharge properties of the plate. Thus it has been found that a common coating such as cellulose acetate which has the property of wear resistance and electrical properties at a moderate RH is not moisture insensitive in either high or low humidities. Therefore, cellulose acetate is unsuitable for use in systems requiring high image quality under such conditions.

SUMMARY OF THE INVENTION According to the present invention a three component polymer composition now has been found which not only obviates the problem of operating xerographic plates in high or low humidity but provides excellent wear resistance and suitable electrical properties for use in reusable xerography. Therefore when the three component organic resin composition of the present invention is used as an overcoating on a xerographic plate there is obtained a reusable plate characterized by wear resistance, moisture insensitivity, exceptionally easy cleaning, and overall efficiency in a repetitive xerographic process. The photoconductor in the reusable electrophotographic plate contemplated in the instant invention may be used in the form of a continuous uniform layer as in the case of vitreous selenium or may be in the form of a binder plate.

DESCRIPTION OF THE INVENTION In general, the electrophotographic plate of the instant invention comprises a photoconductive insulating surface overcoated with a thin layer of a three component organic polymer composition of the present invention. More specifically, the present invention involves the use of three organic resins whose physical and electrical properties are suitable for use as an overcoating for an electrophotographic plate. The particular components of the coating composition comprise film forming polyesters, which are well known for their physical wear resistance, film forming, organic solvent soluble resins having the property of moisture insensitivity, and certain polyurethanes, having volume resistivities in the range from "10 ohm-cm. The use of these three resins in a coating composition of the electrophotographic plate involves the discovery that certain concentration of each component resin will render a coating composition having the physical and electrical properties indigenous to each resin in the composition; that is, the final composition will be wear resistant due to its film forming polyester content, moisture insensitive due to its content of moisture insensitive, film forming, organic solvent soluble resin, and have suitable electrical properties for use in xerography due to its polyurethane content.

The particular concentration necessary to arrive at the necessary properties of the instant overcoating are from about 16 to 71 percent by weight of the moisture insensitive, film forming organic solvent soluble resin, from about 16 to 71 percent polyester, and from about 5 to percent polyurethane having a volume resistivity of from about 10" to 10 ohm-cm. It is found that a composition outside of these concentrations results in the absence or weakening of one of the three properties necessary for the organic xerographic coating. Particularly critical is the control of the electrical properties of the coating by addition of the proper amount of polyurethane. The electrical requirement necessary is that sufficient charge dissipation be accomplished through the layer of the coating without sufficient lateral conductivity to produce image degradation in the xerographic imaging process. If there is too much polyurethane in the three component composition, the coating is laterally conductive while too little renders the coating insulating with regard to charge dissipation through the layer. This will be discussed more fully hereinafter.

The particular moisture insensitive, organic solvent soluble film forming resins which can be used in the three component composition of the present invention include many thermoplastic resins. Typically effective resins include polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyisobutylene, and copolymers thereof. Preferred resins in the three component resin composition of the instant invention are vinyl copolymers and copolymers of vinylidene chloride and acrylonitrile.

The film forming polyesters which can be used in the three component compositions of the instant invention are those comprised of aromatic dicarboxylic acids with glycols. As a class, these can be described as aromatic, solvent soluble, thermoplastic linear polyester polymers. Typical products would be polymers or copolymers of terephthalic and isophthalic acids with ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol and hexamethylene glycol. The preferred composition would be a copolymer of terephthalic and isophthalic acids with ethylene glycol. One example of a typical polyester is Vitel PE200, which is a high molecular weight, linear polyester solution resin manufactured by the Chemical Division of Goodyear Tire and Rubber Company. It is a copolymer of terephthalic and isophthalic acids with ethylene glycol.

The polyurethane resins to be used in the three component resin composition of the present invention include any polyurethane elastomer which has a volume resistivity of from about 10 to 10 ohm-cm and is prepared by the basic reaction of an isocyanate with an alcohol or an ester. Typical of those polyurethanes to be used within the purview of the present invention include those prepared by the reaction of toluene diisocyanate or diphenylmethane-4,4'-diisocyanate with any alcohol. One example of a typical polyurethane is Vithane TPU123 which is a thermoplastic solvent soluble polyester-based polyurethane elastomer manufactured by the Chemical Division of Goodyear Tire and Rubber Company. Another typical polyurethane is Estane 5702-F2 having a similar composition to Vithane TPU123, and which is manufactured by the B. F. Goodrich Company.

DESCRIPTION OF THE DRAWINGS FIG. 1 represents the xerographic plate according to the instant invention.

As shown the figure illustrates a xerographic plate 10, which comprises an electrically conductive base 1 1 having coated at least one side thereof a layer of photoconductive insulating material 12. The photoconductive insulating layer-may comprise selenium, selenium alloys, organic photoconductor material, or a binder layer such as that illustrated in US. Pat. No. 2,663,636 to Middleton. On top of the photoconductive insulating layer is the three component resin composition of the present invention designated as 13. The composition as described hereinbefore comprises polyester resin,

moisture insensitive, film forming, organic solvent soluble polymer, and polyurethane resin. The thickness of the three component overcoating of the present invention may range from about 0.5 to 5 microns.

To illustrate the instant invention 60 grams of Saran F310, a copolymer of vinylidene chloride and acrylonitrile, produced by the Dow Chemical Company of Midland, Michigan is dissolved in 1000 milliliters of cyclohexanone and 1500 milliliters of ethoxy-ethanol with stirring over a 2 hour period. A gram portion of a film forming polyester produced by the Goodyear Company of Akron, Ohio, under the tradename Vitel PE 200 is dissolved in a mixture of 800 milliliters of toluene and 1200 milliliters of cyclohexanone by stirring over a 3 hour period. A solution of polyurethane is then effected by slowly adding 35 grams of a polyurethane elastomer produced by Goodyear Company of Akron, Ohio, under the tradename TPU 123, and having a volume resistivity of about 10 ohm-cm., in 700 milliliters of dimethyl formamide over a two hour period until complete solution takes place. The three solutions are added together and additional solvent is added when.

necessary to prevent reprecipitation of one of the resins. When a xerographic selenium drum is dip coated with the resulting solution, a thin coating is formed which physically resembles a pattern of differentially phased dots dispersed in a binder. The resulting xerographic plate comprises an aluminum substrate, a layer of amorphous selenium of about 20 microns thick and a 2 micron thick layer of a three component resin composition of the present invention. It is found that the three component resin overcoated xerographic plate of the present invention can be imaged in humidity conditions of from about 6 to 95 percent relative humidity.

The general scope and nature of the invention having been set forth the following examples are given as typical illustrations of the invention and are not by way of limitation.

EXAMPLE I The three component resin composition of the present invention is prepared in the following manner: An 80 gram portion of Goodyear Vite] polyester 200 is dissolved in a solution of 240 milliliters (mls.) of methylethyl-ketone, 240 mls. of 2-methoxy ethyl acetate, 220 mls. of toluene, 1200 mls. of xylene and 800 mls. of cyclohexanone by stirring over a three hour period.

A second solution is prepared by dissolving 25 grams of solid TPU 123, a polyurethane manufactured by the Goodyear Company, and 667 milliliters of dimethylformamide. Complete solution also takes place over a three hour period by slowly adding and stirring the solid polyurethane and dimethyl formamide (DMF) over the three hour period.

A third solution is prepared by dissolving 50 grams of Saran F310, a copolymer of vinylidene chloride and acrylonitrile, manufactured by the Dow Chemical Company of Midland, Michigan, in a thousand mls. of cyclohexanone and 1533 mls. of 2-ethoxy ethanol. Solution again is obtained by stirring over a three hour period the solvent system containing Saran.

After complete solution of the various resins is completed in the three hour mixing period, the polyurethane solution and the Saran solution are then added together and stirred for a period of one hour. During this time there is no indication of reprecipitation of either resin. Thereafter the polyester solution is added to the polyurethane-Saran mixture which results in a cloudy solution thereby indicated reprecipitation. Thereupon 6400 mls. of toluene is slowly added along with 1600 milliliters of dimethylformamide (DMF) where upon complete dissolution of the three resins is affected.

A xerographic flat plate comprising an aluminum substrate overcoated with a 60 micron layer of an arsenic-selenium alloy, having a composition of 0.5 percent arsenic, 99.5 percent selenium which is halogen doped with 10 parts per million chlorine, is prepared in the conventional manner as outlined in US. Pat. No. 3,312,548 to Straughan. The plate is then dip coated with the three component resin solution prepared above by means ofa dip coating apparatus and dried in an exhausted laminar flow hood. There results a xerographic plate having approximately a two micron overcoating comprising the three resins which were prepared in solution above. Physically, the three component resin overcoating appears as a dot pattern of differentially phased spheres dispersed in a matrix.

EXAMPLE n A solution of cellulose acetate is prepared by dissolving grams of cellulose acetate in 2000 mls. of ethylene-dichloride. A xerographic flat plate having the same composition as that of Example I is dip coated in the cellulose acetate solution using a Fisher Paine coater and dried in an exhausted laminar flow hood. There results a xerographic plate having a two micron layer of cellulose acetate overcoating.

EXAMPLE III The plates prepared in Examples I and II were then placed in a controlled environment having a relative humidity of 60 percent and stored under these conditions for a period of 2 days. Both plates were then removed and placed in a xerographic copy apparatus sold by Xerox Corporation under the tradename Model D Processor under a controlled RH of 60 percent where they are charged to 800 volts and exposed to a standard pattern. The xerographic copy produced by the plate prepared in Example I showed excellent reproduction, especially with respect to the resolution of the lines in the pattern. The copies made by the plate prepared in Example II, however, demonstrate a degradation of image quality indicating lateral conductivity of the overcoating caused by the high moisture environment.

The plate prepared in Example I also indicated good adhesion to the surface of the photoreceptor in that it could not be removed by adhered cellophane tape. It also demonstrated good wear resistance by withstanding 10,000 dynel brush abrasion cycles.

In an effort to further exhibit the superiority of the three component overcoating of the present invention, xerographic plates were made using overcoatings of the three components separately, and two xerographic plates were made containing an overcoating of the present invention. These plates were then tested to compare and evaluate x-ray image resolution, transfer of toner image, and the cleaning qualities of the plates. The test procedures and test data are as follows:

TEST PROCEDURES FOR X-RAY IMAGE RESOLUTION, TRANSFER AND CLEANING Plate Structures Five xerographic plates are made according to the method set forth in Example I. The plates comprise a micron vitreous layer of 99.66 weight percent selenium 0.34 weight percent arsenic contained on a 9% inch X 14% inch X 0.081 inch aluminum plates. Plates designated Nos. 1A, 2A and 3A are overcoated with a 1 micron layer of polyurethane, vinylidene chlorideacrylonitrile copolymer (Tradename Saran F-3l0), and polyester, respectively. Plate 4A is overcoated with a one micron layer of 10 percent polyurethane balance 1.6 parts polyester to 1.0 parts vinylidene chloride-acrylonitrile copolymer. Plate 5A is overcoated with a one micron layer of 16 percent polyurethane balance 1.6 parts polyester to 1.0 parts vinylidene chloride-acrylonitrile copolymer. Both plates 4A and 5A are directed to a three component overcoating of the present invention, while plates 1A, 2A and 3A are overcoated with 100 percent of a single component of the three components of the overcoating composition of the invention.

X-Ray Image Resolution Test An overcoated test plate is inserted into an updated Xerox Model D Processing Unit and scorotron charged to 1600 volts positive potential. The plate is covered to prevent light exposure and transferred while so charged to a Picker Model 815 X-ray Unit. The plate is then ex posed through an aluminum step wedge test target to 25.5 KVP radiation for 400 milliamp seconds. The aluminum step wedge target contains line pairs and grid patterns in a range from 2 to 10. The higher the number of lines and grids observed, the better the resolution. If none of the patterns are discernible, the resolution is said to be zero. Normally the resolution patterns are read with the aid of 4X eyepiece magnification.

Image Transfer Test ferred image is permanently affixed to the paper by means of heat or methylene chloride vapor fusing.

Cleaning Test The photoreceptor plate is then cleaned by inserting it into brush cleaning apparatus whereupon it comes into contact with a rotating dynel brush at the entrance. The cleaning must be accomplished by 2 passes of the brush over the plate. One pass occurs as the plate is inserted into the apparatus and the other pass as the plate is removed. The cleaned plate is then visually inspected for the presence of residual toner.

The results of the x-ray resolution, image transfer and cleaning tests are tabulated in Table I.

As shown in Table I, the three component overcoatings of the present invention (plates 4A and 5A) exhibit superior properties with regard to x-ray image resolution, transfer of toner image, and cleaning, while the three components, when used separately as overcoatings (plates 1A, 2A and 3A), are inferior in at least one of the three tests.

In order to demonstrate the degree of abrasion resistance which the three component overcoatings of the present invention exhibit over the components of the overcoating separately, the following tests are carried out:

ABRASION RESISTANCE TEST CONDITIONS Eight plates numbered 18, 2B, 3B and 58 (there are two No. lBs, two No. 2Bs, etc.), respectively, are made by coating a glass plate with a thin layer of the overcoating material only. The plate numbers correspond to the overcoating material used under the heading plate structure in Exhibit II. The plates are made and tested as follows:

Two 2 inch by 2 inch glass plates are each dip coated with the appropriate overcoating material. The coating thickness is roughly one micron. One sample of each of the overcoated plates is then separately tested by abrading with a sand dropping device (Gardner Falling Sand Abraser, Gardner Labs, Inc., Bethesda, Md.) in which Ottawa sand is dropped from a height of about 36 inches onto the appropriate plate which is placed at an angle of about 45 to the falling sand. By the impact of the sand particles, a very small amount of the overcoating material is worn off the substrate. In addition, the surface of the overcoating exhibits some pit marks and scratches which are also formed by the abrading sand. The more resistant coatings show less marks, of course, after the sand test. The degree of surface deterioration can be measured by a haze meter. The haze meter measures the percent of light transmitted which is deviated from the incident beam by forward scattering. The more pitmarks a surface has, the more light is scattered, therefore, the higher the reading on the haze meter. An unabraded sample with a smooth surface shows a very low haze value. Therefore, the percentage of haze which is produced by the sand is the measure of the abrasion resistance of the coating.

TABLE I COMPARATIVE DATA Image Resolution Plate No.* Overcoating Component X-Ray Exposure Transfer of Toner Image Cleaning of Plate 1A All polyurethane 3 fair Requires Additional Requires Additional Process Step (i.e. Process Step (Le. Reverse Charging) Negative Preelean) 2A All Vinylidene 0 poor Good Cannot be Cleaned Chloride-Acrylonitrile Initially Toner (Saran F-3l0) Will Not Come Off Overcoating 3A All polyester 3 fair Good Good 4A Present Invention 4 good Good Good (10% Polyurethane Balance 1.6 Parts Polyester to 1.0 Parts Vinylidene Chloride-Acrylonitrile Copolymer) 5A Present Invention 6 excellent Good Good (16% Polyurethane Balance 1.6 Parts Polyester to 10 Parts Vinylidene Chloride-Aerylonitrile Copolymer) Each plate contains a I30 micron layer M99136 weight percent selenium 0.34 weight percent arsenic on a 9V4" X 14%" aluminum substrate. Each plate has a different overcoating component about I micron in thickness.

In the specific test, a sample of each of the different overcoating compositions is abraded by milliliters of falling sand. Then these samples, together with identical control samples of each composition which had not been abraded, are measured with a Werner and Pfleiderer Corporation Model TRBI Haze Meter. These results are tabulated in Table II. The abraded samples showed an increase in haze value, and by calculating the difference in haze value from abraded and unabraded samples of each composition. Plate 58 of the present invention showed the least abrasion, a 2 percent increase in haze value, while the polyester showed a 3.5 percent increase, the Saran an 8.5 percent increase and the polyurethane a 10 percent increase.

TABLE II COMPARATIVE DATA Abrasion Resistance Increase In Haze After Abrasion Plate No. Plate Structure With respect to abrasion resistance data shown in Table II, the plate designated 58 has the overcoating of the present invention, and when compared to plates 1B, 2B and 3B, which employ overcoatings of the three component separately, the abrasion, or increase in haze after abrasion, was extremely low in case of, the three component overcoating. When each of the three overcoating components are used separately, however, (plates 13, 2B and 3B) they exhibit significant abrasion or increase in haze after abrasion.

The solvent system for the three component resin coating composition of the present invention may comprise any of the commercially available solvents well known to those skilled in the art. These include such solvents as methyl-ethyl-ketone, 2-ethoxy ethyl acetate, toluene, xylene, cyclohexanone, dimethylformamide, and Z-ethoxy ethanol. Complexity of the solvent system results from parameters such a temperature and quantity of the ultimate composition and techniques for simplification by using multiple quantities of presently available solvents is well known to those skilled in the art.

Without intending to limit the scope or spirit of the present three component resin coating composition by proposing a theory, an explanation is speculated as to the function of the present composition under conditions of high or low humidity. It is well known that under conditions of high humidity most resin compositions undergo significant increase in both their lateral and vertical conductivity; that is, charge dissipation occurs both across and through the overcoating. It is believed, however, that the present three component resin composition undergoes virtually no change in either its vertical or lateral conductivity at high or low humidities. It is speculated that this phenomena is due to the nature of the three component composition in that the differentially phased clots, hereinbefore re ferred to, are spheres of polyurethane distributed throughout the film matrix. Because the particles of polyurethane remain relatively protected by the binder film the electrical properties of the overcoating remain relatively unchanges at low or high humidities.

It is further speculated, without intention of limitation, that in the function of the three component resin composition of the present invention the spheres of dispersed polyurethane conduct charges through the resin overcoating. Therefore upon charging a three component overcoated xerographic plate, the charge is dissipated through the thickness of the overcoating layer and remains at the interface of the overcoating and photoreceptor layer. Upon exposure the charges in the illuminated area will then be dissipated through the photoreceptor layer while those unexposed areas would retain charges at the interface. Because the thickness of the layer is no more than about 5 microns, no difficulty of electroscopic particle development is presented.

Selenium being the photoconductor of choice in commercial xerography, it is preferred to use the instant three component resin overcoating with selenium. However, the nature of the photoconductive insulating layer is not critical so that the coating may be used with any photoconductive insulating material such as selenium alloys (Se-Te, Se-As, etc.), anthracene, and other continuous films in binder plates described hereinbefore. As is wellknown in the xerographic art, any electrically conductive support layer may be used for the photoconductive insulating layer. Alloy selenium plates are often constructed in a layer structure where a thin alloy layer, as for example, selenium-tellurium, or selenium-arsenic, is coated on a layer of vitreous selenium thus combining excellent photoresponse of the alloy with the excellent electrical characteristics of uiteous selenium. Such plates are described for example in U.S. Pat. No. 2,803,541 to Paris. In addition, the three component resin composition of the present invention may be used in any xerographic plates known to those skilled in the art. Such plates are described as to preparation, composition, thickness, and other parameters, for example, in U.S. Pat. No. 2,803,542 to Ullrich; U.S. Pat. No. 2,803,541 to Paris; U.S. Pat. No. 2,745,327 to Mengali; U.S. Pat. No. 2,863,768 to Schaffert; U.S. Pat. No. 2,970,906 to Bixby; and aforesaid patents to Middleton and Reynolds.

It is to be understood that various modifications known to those skilled in the art can be made to the present, three component resin composition without departing from the spirit of the invention. For example, substances may be added to enhance or synergize the properties of the three component resin composition coating.

What is claimed is:

1. An electrophotographic plate comprising:

a. a photoconductive insulating layer contained on a conductive substrate, and

b. an organic polymer coating composition overlaying the said photoconductive layer, said coating composition comprising from about 16 to 71 percent of a film forming polyester; about 16 to 71 percent of a moisture insensitive, film forming or- 5. The plate of claim 1 in which the moisture insensitive, film forming, organic solvent soluble resin is a copolymer of vinylidene chloride and acrylonitrile and the polyurethane has a volume resistivity of from about 10 to 10 ohm-cm.

6. The plate of claim 1 in which the polymers are present in the composition of from about 51 percent film forming polyester, about 32 percent moisture insensitive film forming, organic solvent soluble resin, and about 17 percent polyurethane resin.

7. The plate of claim 1 in which the thickness of the polymer overcoating is from about 0.5 to 5 microns.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIQN DATED October 14 1975 INVENTOR(S) Paul L. Gerace, Paul R. Handley Rudy H. Haidle It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 36, delete "viteous" and insert -vitreous-.

Column 2, line 44, delete "de-sorb" and insert --desorb-.

Column 9, Table II, Plate No. 5, delete "vinylidend" and insert vinylidene-.

Column 9, line 49, delete methyl-ethyl-ketone" and insert -methylethylketone.

Column 10, line 9, delete. "unchanges" and insert unchanged-.

Column 10, line 33, delete "wellknown" and insert well known.

Column 10, line 41, delete uiteous" and insert vitreous-.

Signed and Scaled this twenty- D 3) Of January 19 76 [SEAL] A ttes t:

RUTH Cr MASON C. MARSHALL DANN Arresting Officer Commissioner oj'Patents and Trademarks

Claims (7)

1. AN ELECTROPHOTOGRAPHIC PLATE COMPRISING: A. A PHOTOCONDUCTIVE INSULATINGG LAYER CONTAINED ON A CONDUCTIVE SUBSTRATE, AND B. AN ORGANIC POLYMER COATING COMPOSITION OVERLAYING THE SAID PHOTOCONDUCTIVE LAYER, SAID COATING COMPOSITION COMPRISING FROM ABOUT 16 TO 7U PERCENT OF A FILM FORMING POLYESTER, ABOUT 16 TO 71 PERCENT OF A MOISTURE INSENSITIVE, FILM FORMING ORGANIC SOLVENT SOLUBLE THERMOPLASTIC RESIN SELECTED FROM THE GROIP CONSISTING OF POLYVINYL CHLORIDE, POLYVINYL FLUORIDE, POLYVINYLIDENE CHLORIDE, POLYISOBUTYLENE, AND COPOLYMERS THEREOF, AND FROM ABOUT 5 TO 35 PERCENT OF A POLYURETHANE RESIN, WITH SAID POLYURETHANE RESIN HAVING A VOLUME RESISTIVITY OF FROM 10**11 TO 10**13 OHM-CM.

2. The plate of claim 1 in which the photoconductive insulating material is amorphous selenium.

3. The plate of claim 1 in which the photoconductive insulating material is an arsenic-selenium alloy.

4. The plate of claim 3 in which the alloy is doped with a halogen.

5. The plate of claim 1 in which the moisture insensitive, film forming, organic solvent soluble resin is a copolymer of vinylidene chloride and acrylonitrile and the polyurethane has a volume resistivity of from about 1011 to 1013 ohm-cm.

6. The plate of claim 1 in which the polymers are present in the composition of from about 51 percent film forming polyester, about 32 percent moisture insensitive film forming, organic solvent soluble resin, and about 17 percent polyurethane resin.

7. The plate of claim 1 in which the thickness of the polymer overcoating is from about 0.5 to 5 microns.

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