US3533787A - Photoconductive elements containing polymeric binders of nuclear substituted vinyl haloarylates - Google Patents

Description

United States Patent 3,533,787 PHOTOCONDUCTIVE ELEMENTS CONTAINING POLYMERIC BINDERS OF NUCLEAR SUB- STITUTED VINYL HALOARYLATES Stewart H. Merrill and William A. Light, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New York No Drawing. Filed July 31, 1967, Ser. No. 657,069

Int. Cl. G03g 5/00 US. C]. 96-15 27 Claims ABSTRACT OF THE DISCLOSURE Photoconductive elements containing a photoconductor and a binder comprising polymers of nuclear substituted vinyl haloarylates are described. The desl'ibed elements can be sensitized and charged either negatively or positively.

This invention relates to electrophotographic elements and to binder-containing photoconductive compositions useful in such electrophotographic elements.

Binder-containing photoconductive compositions have have been widely used in the preparation of electrophotographic elements. In electrophotographic reproduction processes, these elements are utilized in the formation of latent electrostatic images. In some applications the photoconductive compositions contain an organic photoconductor and a sensitizer uniformly admixed in an inert resinous binder. Many binders are currently used in connection with a wide variety of available organic photoconductor compounds and compositions. Typical :binders are ordinary polymeric materials, e.g., phenolic resins, ketone resins, acrylic ester resins, polystyrene, etc. However, these binders usually do not impart any particular improvement in light sensitivity to the system. The light sensitivity as indicated by the electrical speed of these particular systems is ordinarily due wholly to the organic photoconductor and sensitizer.

It is therefore, an object of this invention to provide improved noval binder-containing photoconductive compositions which exhibit high light sensitivities.

It is another object to provide transparent electrophotographic elements having the high speed characteristic of the novel photoconductive compositions of this invention.

It is a further object of this invention to provide a novel photoconductive composition comprising a photoconductor and a polymeric binder.

These and other objects of this invention are accomplished by using a photoconductive composition which contains a photoconductor admixed with a binder which is a polymer of a nuclear substituted vinyl haloarylate. It has been discovered that such compositions exhibit increased light sensitivities as evidenced by greater electrical speeds. In particular, substantial increases in electrical speeds (i.e., toe and shoulder speeds) are obtained with reference to the standard H and D curve as compared to electrical speeds attainable with many other polymeric binder compositions. These increases in electrical speed are observed when the coating accepts a suitable potential (e.g., 500-600 volts) and the relative speed of the coating is determined on the basis of the reciprocal of the exposure required to reduce the potential of the surface charge by 100 volts (shoulder speed) or to 100 volts (toe speed). The reduction of the surface potential to 100 volts or below is significant in that it represents a requirement for suitable broad area development of a latent image. The relative speed at 100 volts is a measure of the ability to produce and henceforth to develop or otherwise utilize the latent image.

ice

If the photoconductor is absent from the coating and only a conventional binder is used, the surface potential does not drop to or below 100 volts and therefore no speed can be assigned to such a composition.

If an organic photoconductor is part of the coating in many conventional polymeric binders, the surface potentials of such resultant compositions usually drop below 100 volts, and thus, a definite speed can be ascertained. However, these speeds are augmented when the binders of this invention are employed.

The aryl nucleus of the polymeric binders of this invention can be substituted in either the ortho, meta or para position by any of the halogens, including chlorine, bromine, iodine and fluorine. Also, the nucleus can be substituted with more than one halogen atom. Homopolymers of the nuclear substituted haloarylates provide suitable binders, however, copolymers (particularly with vinyl acetate) are preferred.

(c) an ester linkage between the aryl moiety and the backbone of the polymer chain.

Particularly useful binders of this invention comprise polymers having repeating units of both wherein X is a halo-substituted aryl group of such as halophenyl and halonaphthyl and Y is an alkyl radical having 1-8 carbon atoms, methyl being particularly useful. These polymeric binders generally have substantial amounts of repeating units of the first type, i.e. vinylarylates. The polymer should contain at least of arylate repeating units and preferably to of such repeating units. If a copolymer is employed as the binder, the structure may be that of a block, heteroblock or random copolymer.

Binders comprising such polymers improve the electrical speed of the photoconductive composition. Binders containing a polymer of styrene, a copolymer of vinyl benzoate and vinyl acetate, polyvinyl chloride or a polymer of vinyl chloroacetate are not as efiective in improving the electrical speed of the photoconductive compositions. However, a copolymer of vinyl bromobenzoate and vinyl acetate has an appreciable effect on the speed exhibited by the composition.

The arylate moiety can be the ester of any of the known unsaturated ring structures such as benzoate, naphthoate, etc. Exemplary of a few of the many polymers useful as binders in this invention are: poly(vinyl p-chlorobenzoate-co-vinyl acetate), poly(vinyl m-chlorobenzoate-co-vinyl acetate), poly(vinyl o-chlorobenzoateco-vinyl acetate), poly(vinyl p-bromobenzoate-co-vinyl acetate), poly(vinyl m-bromobenzoate-co-vinyl acetate), poly(vinyl o-bromobenzoate-co-vinyl acetate), poly(vinyl p-iodobenzoate-co-vinyl acetate), poly(viny1 m-iodobenzoate-co-vinyl acetate), poly(vinyl o-iodobenzoate-covinyl acetate), poly(vinyl p-fluorobenzoate-co-vinyl acetate), poly (vinyl m fluorobenzoate co vinyl acetate), poly(viny1 o-fluorobenzoate-co-vinyl acetate), poly(vinyl 5-bromo-2-naphthoate-co-vinyl acetate), poly(vinyl 4- bromo 1 naphthoate co vinyl acetate), poly(vinyl 5- bromo-l-naphthoate-co-vinyl acetate) and poly(vinyl-2, 4-dichlorobenzoate-co-vinyl acetate).

In preparing electrophotographic elements utilizing the polymeric binders of this invention the organic photoconductor is dissolved in a solution of binder and solvent and then, after thorough mixing, the composition is coated on an electrically conducting support in a wellknown manner, such as swirling, spraying, doctor blade coating, and the like.

An especially useful class of organic photoconductors is referred to herein as organic amine photoconductors. Such organic photoconductors have as a common structural feature at least one amino group. Useful organic photoconductors which can be spectrally sensitized in accordance with this invention include, therefore, arylamine compounds comprising (1) diarylamines such as diphenylamine, dinaphthylamine, N,N' diphenylbenzidine, N phenyl 1 naphthylamine; N phenyl 2 naphthylamine; N,N' diphenyl -p phenylenediamine; 2 carboxy chloro 4' methoxydiphenylamine; p anilinophenol; N,N di 2 naphthyl p phenylene diamine; 4,4 benzylidene bis -(N,N diethyl m toluidine), those described in Fox U.S. Pat. 3,240,597 issued Mar. 15, 1966, and the like, and (2) triarylamines including (a) nonpolymeric triarylamines, such as tripoly[N,4"(N,N,N' triphenylbenzidine)]; polyadipyldiamine; 4 acetyltriphenylamine, 4 hexanoyltriphenylamine; 4 lauroyltriphenylamine; 4 hexyltriphenylamine, 4 dodecyltriphenylamine, 4,4 bis(diphenylamino)benzil, 4,4 bis(diphenylamino)benzophenone, and the like, and (b) polymeric triarylamines such as poly[N,4"(N,N,N' triphenylbenzidine)]; polyadipyltriphenylamine, polysebacyltriphenylamine; polydecamethylenetriphenylamine; poly N (4 vinylphenyl) diphenylamine, poly N (vinylphenyl) a x dinapthylamine and the like. Other useful amine-type photoconductors are disclosed in U.S. Pat. 3,180,730, issued Apr. 27, 1965.

Useful photoconductive substances capable of being spectrally sensitized in accordance with this invention are disclosed in Fox U.S. Pat. 3,265,496 issued Aug. 9, 1966, and include those represented by the following general formula:

| Q A b wherein A represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear, (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from about 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.) an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc), or a nitro group; A represents a mononuclear or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro group; Q can represent a hydrogen atom, a halogen atom or an aromatic amino group, such as ANH; b represents an integer from 1 to about 12, and G represents a hydrogen atom, a mononucleaiz ful in producing the present invention. Such photoconductors are described in U.S. Pat. 3,274,000; French Pat. 1,383,461 and in a copending application of Seus and Goldman titled Photoconductive Elements Containing Organic Photoconductors filed Apr. 3, 1967. These photoconductors include leuco bases of diaryl or triaryl methane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes, there being substituted an amine group on at least one of the aryl groups attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials.

Preferred polyaryl alkane photoconductors can be represented by the formula:

where in each of D, E and G is an aryl group and J is a hydrogen atom, an alykyl group, or an aryl group, at least one of D, E and G containing an amino substituent. The aryl groups attached to the central carbon atom are preferably phenyl groups, although naphthyl groups can also be used. Such aryl groups can contain such substituents as alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy, halogen, etc. in the ortho, meta or para positions, ortho-substituted phenyl being preferred. The aryl groups can also be joined together or cyclized to form a fluorene moiety, for example. The amino substituent can be represented by the formula wherein each L can be an alkyl group typically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having 5 to 6 atoms in the ring such as morpholino, pyridyl, pyrryl, etc. At least one of D, E, and G is preferably p-dialkylaminophenyl group. When I is an alkyl group, such an alkyl group more generally has 1 to 7 carbon atoms.

Representative useful polyarylalkane photoconductors include the compounds listed below:

TABLE A Compound No. Compound name (2) 4, 4"EiammoA-drmethylamino-Z, 2-dimethyl-triphenylme ane.

(4) 4, 4-b1s(d1cthylan1ino)-2, 2-dimethyldiphenylnaphthylmethane.

(5) h 2, 2-dimethyl-4, 4, 4-tris(dimetl1ylamino)- trlphenylmethane.

(6) 4, 4-bis (diethylamino)4-dimethylamino- 2, 2":cl1methyltriphenylmethane.

(7) 4, 4 b1s(d1ethylamin0)-2-ehl0r0-2, 2-dimethyl-4- dlmethylaminotriphenylmethane.

(8) 4, 4 -b1s(diethylamino)-4-dimethylamin0-2, 2, 2"-

trrmethyltriphenylmethane.

(11) B s(4-d ethylamrn0)-1, 1, l-triphenylcthane.

(12) BIS (4-d 1ethylam1no)tetraphenylmethane.

(13) 4, 4 -b1s(benzylethylamino)-2, 2-dimethyltrlphenylmethane.

(15) 4, 4 -b1s (drmethylamnro)1, 1, l-triphenylethane.

(1Q) 1-(4 N, N-dlmethylam1nophenyl)-l, l-diphenylethane.

(11) 4-dtmethylammotetraphenylmethane.

(18) 4d1cthyla1ni1iotetraphenylmethane.

Anothen useful class of photoconducting compounds are the 4-d1arylamino-substituted chalcones. Typical compounds of this type are low molecular weight nonpolymeric ketones having the general formula:

\sQ-crmou-ii-m wherein R and R are each phenyl radicals including substituted phenyl radicals and particularly when R is a phenyl radical having the formula:

TAB LE B Compound name Compound No.:

(1) 4, 4f-b1s(d1phenyla.mino)chalcone.

4-d1phenylamino-4-dimethylaminochalcone. -dimethylamino-4-diphenylaminoehalcone.

4, 4-bis (dimethylarninmchalcone.

4, 4bis (diethylam1no)chalcone.

. 4diethylammmt diphenylaminochalcone.

. 4, 4-bis(n-amyloxy) chalcone.

- 4, 4-bis(nitro) chalcone:

-diphenylaminochalcone.

4-dimethylaminochalcone.

-diphenylaminochalcone.

4-dimethylaminochalcone:

The photoconductive layers of the invention can also be sensitized by the addition of eflective amounts of sensitizing compounds to exhibit improved electrophotosensitivity. Sensitizing compounds useful with the photoconductive compounds of the present invention can be selected from a wide variety of materials, including such materials as pyrylium, thiapyrylium, and selenapyrylium dye salts disclosed in Van Allan et a1. U. S. Pat. 3,250,- 615; fluorenes, such as 7,12-dioxo-13-dibenzo(a,h)fluorene, 5,10-dioxo-4a,11-diazabenzo(b)fluorcne, 3,13-dioxo- 7-oxadibenzo(b,g)fluorene, and the like; aromatic nitro compounds of the kinds described in U.S. Pat. 2,610,120; anthrones like those disclosed in U.S. Pat. 2,670,284; quinones, U.S. Pat. 2,670,286; benzophenones U.S. Pat. 2,670,287; thiazoles U.S. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid, and salicyclic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine, carbocyanine, merocyanine, diarylmethane, thiazine, azine, axozine, xanthene, phthalein, acridine, azo, anthraquinone dyes and the like and mixtures thereof. The sensitizers preferred for use with the compounds of this invention are selected from pyrylium and thiapyrylium salts, fluorenes, carboxylic acids and triphenylmethane dyes.

Where a sensitizing compound is employed with the binder and organic photoconductor to form a sensitized electro-photographic element, it is the normal practice to mix a suitable amount of the sensitizing compound with the coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed in the coated element. Other methods of incorporating the sensitizer or the effect of the sensitizer may, however, be employed consistent with the practice of this invention. In preparing the photoconductive layers, no sensitizing compound is required to give photoconductivity in the layers which contain the photoconducting substances of this invention, therefore, no sensitizer is required in a particular photoconductive layer. However, since relatively minor amounts of sensitizing compound give substantial improvement in speed in such layers, the sensitizer is preferred. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective in creases in speed can vary widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 30 percent by weight based on the weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount by weight from about 0.005 to about 5.0 percent by weight of the total coating composition.

Solvents useful for preparing coating compositions with the binders of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; Z-butanone; chlorinated hydrocarbons such as methylene chloride; ethylene chloride; and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageusly be employed in the practice of this invention.

In preparing the coating compositions utilizing the binders disclosed herein useful results are obtained where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be Widely varied in accordance with usual practice. It is normally required that the photoconductive material be preesnt in an amount ranging from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductive material in the coating composition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a wet coating thickness in the range of about 0.001 inch to about 0.01 inch is useful in the practice of the invention. A preferred range of coating thickness is from about 0.002 inch to about 0.006 inch before drying although such thicknesses can vary widely depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for coating the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, paper (at a relative humidity above 20 percent); aluminum-paper laminates; metal foils, such as aluminum foil, zinc foil, etc; metal plates, such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as nickel or aluminum and the like.

An especially useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer. Such conducting layers and methods for their optimum preparation and use are disclosed in U.S. 3,007,- 901 and 3,267,807.

The compositions of the present invention can be employed in photoconuctive elements useful in any of the well known electrophotographic processes which require photoncductive layers. One such process is the xerographic process. In a process of this type, an electrophotographic element held in the dark, is given a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipatcd from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as for example, by a contact-printing technique, or by lens projection of an image, or reflex or bireflex techniques and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charge or uncharged areas rendered visible, by treatment with medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to a latent electrostatic image for solid are development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following US. Pats: 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,063; 2,984,163; 3,040,704; 3,117,884; and reissue Re. 25,779. Liquid development of the latent electrostatic image may also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are Widely known and have been described in the patent literature, for example, US. Pat. 2,297,691 and in Australian Pat. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing respectively. Techniques of the type indicated are Well known in the art and have been described in a number of US. and foreign patents, such as US. Pats. 2,297,691 and 2,551,582, and in RCA Review, vol. (1954) pages 469-484.

The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconductive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting support. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material between layers or overcoated or interposed between the photoconductive layer or sensitizing layer and the conducting layer. It is also possible to adjust the position of the support and the conducting layer placing a photoconductor layer over a support and coating the exposed face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations differing from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographic element.

The invention is further illustrated by the following examples which include preferred embodiments thereof.

EXAMPLE 1 1.5 grams of poly(vinyl m-bromobenzoate-co-vinyl acetate) binder containing 88% on a molar basis of the vinyl bromobenzoate, 0.5 gram of 4,4'benzylidine-bis (N,N-diethyl-m-toluidine) photoconductor and .02 gram of 2,4-di 4-ethoxyphenyl -6- 4-n-amyloxystryl) pyrylium fluoroborate sensitizer are dissolved in 15.6 grams of methylene chloride by stirring the solids in the solvent for one hour at room temperature. The resulting solution is hand coated at a weat coating thickness of 0.004 inch on a conducting layer comprising the sodium salt of a carboxyester lactone, such as described in US. 3,120,028, which in turn is coated on a cellulose acetate film base. The coating block is maintained at a temperature of F. This electrophotographic element is charged under positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts. It is then subjected to exposure from behind a stepped density gray scale to a 3000 K. tungsten source. The exposure causes reduction of the surface po tential of the element under each step of the gray scale from its initial potential, V to some lower potential, V, whose exact value depends on the actual amount of exposure in meter-candle-seconds received by the area. The results of the measurements are plotted on a graph of surface potential V vs. log exposure for each step. The shoulder speed is the numerical expression of 10 multiplied by the reciprocal of the exposure in meter-candleseconds required to reduce the 600 volt charged surface potential by volts. The toe speed is the numerical expression of 10 multiplied by the reciprocal of the exposure in meteI-candle-seconds required to reduce the 600 volt charged surface potential to 100 volts. This coating is found to have a positive shoulder speed of 1600 and 100 v. toe speed of 110. Similar results are obtained when 0.5 gram of bis(4 diethylamino)-1,1,1-triphenylethane or 0.5 gram of bis(4-diethylamino)-tetraphenylmethane are used as photoconductors in place of the 4,4- benZylidine-bis (N,N-diethyl-m-toluidine) EXAMPLE 2 The purpose of this example is to show the desirability of having a halogen substituted aryl nucleus. This example is identical to Example 1 except the binder employed is 1.5 grams of poly(vinyl benzoate-co-vinyl acetate). The coating has a positive shoulder speed of 500 and 100 v. toe speed of 28.

EXAMPLE 3 The purpose of this example is to show the desirability of having an ester linkage between the aryl moiety and the backbone of the polymer chain, i.e. the employment of an arylate as opposed to an aryl group. 1.5 grams of (poly-p-iodostyrene), 0.5 gram of 4,4'-benzylidine-bis(N, N-diethyl-m-toulidine) and 0.04 gram of 2,4-di(4- ethoxyphenyl)-6-(4-n-amyloxystyryl) pyrylium fluoroborate are dissolved in 15.6 grams of methylene chloride by stirring the solids in the solvent for one hour at room temperature. The resulting solution is hand coated at a wet coating thickness of 0.004 inch on the conducting layer of Example 1, which is in turn coated on cellulose acetate film base. The coating block is maintained at a temperature of 90 F. during coating. The coating has a shoulder speed of and a 100 v. toe speed of 32. The polymeric binder can be prepared by iodinating polystyrene by the method of Braun, Makromolekular Chemie, 30, 85 (1959).

EXAMPLE 4 The purpose of this example is to show the desirability of having an aryl moiety present. This example is identical to Example 1 except the binder employed is 1.5 grams of polyvinyl chloroacetate. The coating could only be charged to 80 volts and therefore no shoulder speed or 100 v. toe speed were attainable.

The following Examples 5-15 are identical to Example 1 except for the binder employed. 1.5 grams of various binders are used in each of the following examples. In each case a significant improvement is noted in the 100 v. toe speeds and the shoulder speeds over those exhibited in Examples 24. Example 16 represents a polymeric binder not included in the present invention and no im' provement is noted.

Binder Example Poly(vinyl pch1orobenzoateeoviny1 acetate) Poly(viny1 m-chlorobenzoate-covinyl acetate)- Poly(vinyl p-fluorobenzoatecovinyl acetate)- 8. Poly(vinyl o-bromobenzoate-covinyl acetate) 9.-. Poly(vinyl p-bromobenzoatecovinyl acetate) Poly(viny1o-iodobenzoate-covinyl acetate) 11 Poly(vinyl m-iodobenzoate coviuyl acetate).

12.- Poly(vinyl p-iodobenzoate-covinyl acetate 13 Po1y(viny1 5-bromo-2-napl1thoateeovmyl acetate 1L. Poly(vinyl 4-bromo-1-naphthoatecovinyl acetat 15.- Poly (vinyl 5-bromo-1-naphthoate-covinyl acetate) Electrical speed Shoulder To 16 Butvar B-76 (Trade name for poly(vinyl butyral distributed by Shawinigan Products Corporation.

EXAMPLE 17 A dope containing 1.5 g. of polyvinyl m-bromobenzoate-co-vinyl acetate, 0.5 g. of 4,4-bis(diphenylamino) chalcone, 0.04 g. of 2,4(4 ethoxyphenyD-6-(4-amyloxystyryl)pyrylium fluoroborate and 15.6 g. of methylene chloride are coated and tested in the manner described in Example 1. The coating has a positive 100 v. toe speed of 400 and a negative 100 v. toe speed of 90.

EXAMPLE 18 EXAMPLE 19 Example 18 is repeated except that 6,6'-dichloro-l,1', 3,3 tetraphenylimidazo[4,5-b]quinoxalinocarbocyanine p-toluenesulfonate is employed as the sensitizer in place of the one used in the preceding example. The coating has a positive 100 v. toe speed of 1600 and a negative 100 v. toe speed of 250.

EXAMPLE 20 The coating compositions of Examples 1, 5X15, and 17-19 are again coated in the manner described in Example 1. In a darkened room, the surface of each of the photoconductive layers so prepared is charged to a potential of about +600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 meter-candles for 12 seconds. The resulting electrostatic latent image is developed in the usual manner by cascading over the surface of the layer a mixture of negatively charged black thermoplastic toner particles and glass beads. A good reproduction of the pattern results in each instance.

The vinyl ester copolymers used as binders in accordance with the invention in the above examples can be made by treating a suspension in pyridine of poly(vinyl alcohol) containing approximately 12% residual vinyl acetate units (DuPont Elevanol 52-22) with a small excess of the appropriate aryl acid chloride at 50 C. The polymer is recovered by precipitation in water and is purified by reprecipitation in methanol from methylene chloride solution.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising an organic photoconductor and a binder, said binder being selected from the group consisting of homoploymers of a monovinyl haloarylate and copolymers of at least 75 mole percent of monovinyl haloarylate and up to 25 mole percent of a monovinyl alkanoate.

2. The electrophotographic element of claim 1 wherein the binder is a copolymer of a nuclear substituted vinyl haloarylate and vinyl acetate.

3. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising an organic photoconductor and a binder comprising a polymer containing at least 75 mole percent of repeating units of wherein X is a halo-substituted aryl group and Y is an alkyl radical having 1-8 carbon atoms.

4. The electrophotographic element of claim 3 wherein the photoconductive composition contains a sensitizer selected from the group consisting of carbocyanine, pyrylium, thiapyrylium and selenapyrylium dye salts.

5. The electrophotographic element of claim 3 wherein the binder is poly(vinyl bromobenzoate-co-vinyl acetate).

6. The electrophotographic element of claim 3 wherein the binder is poly(vinyl chlorobenzoate-co-vinyl acetate).

7. The electrophotographic element of claim 3 wherein the binder is poly(vinyl fluoro'benzoate-co-vinyl acetate).

8. The electrophotographic element of claim 3 wherein the binder is poly(vinyl iodobenzoate-co-vinyl acetate).

9. The electrophotographic element of claim 3 wherein the binder is poly(viny1 bromonaphthoate-co-vinyl acetate).

10. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising an organic photoconductor, a sensitizer and a binder, said binder being a copolymer of at least 75 mole percent of a nuclear substituted monovinyl haloarylate and up to 25 mole percent of vinyl acetate.

11. The electrophotographic element of claim 1 wherein the photoconductor is selected from the group consisting of polyaryl alkanes having at least one amino aryl group and 4-diarylamino-substituted chalcones.

12. The electrophotographic element of claim 10 wherein the sensitizer is selected from the group consisting of carboeyanine, pyrylium, thiapyrylium and selenapyrylium dye salts.

13. The electrophotographic element of claim 10 wherein the binder is a poly(vinyl m-bromobenzoate-covinyl acetate).

14. The electrophotographic element of claim 10 wherein the binder is poly(vinyl p-iodobenzoate-co-vinyl acetate).

15. The electrophotographic element of claim 10 wherein the binder is poly(vinyl p-fiuorobenzoate-co-vinyl acetate).

16. The electrophotographic element of claim 10 wherein the binder is poly(vinyl o-bromobenzoate-co-vinyl acetate).

17. The electrophotographic element of claim 10 wherein the binder is poly(vinyl p-bromobenzoate-covinyl acetate).

18. The electrophotographic element of claim 10 wherein the binder is poly(vinyl o-iodobenzoate-co-vinyl acetate).

19. The electrophotographic element of claim 10 wherein the binder is poly(vinyl m-iodobenzoate-co-vinyl acetate).

20. The electrophotographic element of claim 10 wherein the binder is po1y(vinyl S-bromo-Z-naphthoatecovinyl acetate).

21. The electrophotographic element of claim 10 wherein the binder is poly(vinyl-4-bromo-1-naphthoate-covinyl acetate).

22. The electrophotographic element of claim 10 wherein the bidner is poly(vinyl-5-bromo-l-naphthoate-co-vinyl acetate).

23. The electrophotographic element of claim wherein the binder is poly(vinyl-2,4-dichlorobenzoate-co-vinyl acetate).

24. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4- benzylidinebis(N,N-diethyl-m-toluidine) as an organic photoconductor, 0.005 to about 5.0 weight percent 2,4- di 4-ethoxyphenyl -6- 4-n-amyloxystyryl pyrylium flouroborate as a sensitizer and po1y(vinyl rn-bromobenzoateco-vinyl acetate) containing at least 75% repeating units of vinyl m-bromobenzoate as a binder.

25. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4-

bis(diphenylamino)chalcone as an organic photoconductor, 0.005 to about 5.0 weight percent 2,4-(4-ethoxyphenyl)-6-(4-amyloxystyryl) pyrlium fluoroborate as a sensitizer and poly(vinyl m-bromo benzoate-co-vinyl acetate) containing at least 75 repeating units of vinyl mbromobenzoate as a binder.

26. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising 10 to about weight percent of 4,4-bis (diphenylamino) chalcone as an organic photoconductor, 0.005 to about 5.0 weight percent 6-chloro-1-methyl-1, 2',3'-triphenylimidazo[4,5 b]quinoXalino-3' indolocarbocyanine p-toluenesulfonate as a sensitizer and poly (vinyl m-bromobenzoate-co-vinyl acetate) containing at least repeating units of vinyl m-bromobenzoate as a binder.

27. An electrophotographic element comprising a support having coated thereon a photoconductive composition comprising 10 to about 60 weight percent of 4,4-bis (diphenylamino)chalcone as an organic photoconductor, 0.005 to about 5.0 weight percent 6,6'-dichloro-1,1',3,3'- tetraphenylimidazo{4,5 b]quinoxalinocarbocyanine p toluenesulfonate as a sensitizer and poly(vinyl m-bromobenzoate-co-vinyl acetate) containing at least 75% repeating units of vinyl m-bromobenzoate as a binder.

References Cited UNITED STATES PATENTS 2,465,316 3/1949 Mowry et al 260-476 3,125,447 3/1964 Stewart 961 3,245,786 4/1966 Cassiers et al. 961 3,265,497 8/1966 Kosche 961.1

GEORGE F. LESMES, Primary Examiner M. B. WITTENBERG, Assistant Examiner US. Cl. X.R.