Photoconductive elements containing polymeric binders

Abstract

Electrophotographic elements containing a photoconductor and a binder comprising a polymer having a naphthyl nucleus as a pendant side group extending from the backbone of the polymer chain can be sensitized and charged either positively or negatively to prepare images electrophotographically.

Description

FIELD OF INVENTION

This invention relates to novel electrophotographic elements having coatings of binder-containing photoconductive compositions.

BACKGROUND OF INVENTION

Binder-containing photoconductive compositions have been widely used in the preparation of electrophotographic elements suitable for forming latent electrostatic images. In some applications the photoconductive compositions contain an organic photoconductor and a sensitizer uniformly admixed in an inert resinous binder. Typical binders are ordinary polymeric materials, e.g., phenolic resins, acrylic ester resins, polystyrene, etc. However, these conventional 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 systems is ordinarily due wholly to the organic photoconductor and sensitizer. Other binders have been found to contribute significantly to the light sensitivity of the system. However, the selection of these polymers for incorporation into photoconductive compositions to form electrophotographic layers has preceeded on a compound-by-compound basis. Nothing has yet been discovered from the numerous binders tested which permits effective prediction and selection of particular polymers exhibiting the desired properties. To date there still exists a need for improved novel binder-containing photoconductive compositions which exhibit improved light sensitivities.

SUMMARY OF INVENTION

In accordance with this invention, electrophotographic elements and compositions are provided which contain novel polymeric binders. These compositions and elements exhibit improved electrophotographic speed resulting from the incorporation of the present binder materials.

DESCRIPTION OF PREFERRED EMBODIMENT

The objects and advantages of this invention are accomplished by using an electrophotographic element having coated thereon a photoconductive composition which contains a photoconductor admixed with a binder having repeating units represented by the following structure: ##EQU1## In this structure:

R represents

1. AN ALKYL GROUP HAVING 1 TO 18 CARBON ATOMS E.G., METHYL, ETHYL, PROPYL, BUTYL, ISOBUTYL, OCTYL, DODECYL, ETC. INCLUDING SUBSTITUTED ALKYL HAVING 1 TO 18 CARBON ATOMS WHEREIN THE SUBSTITUENTS ARE

A. alkoxy group e.g., ethoxy, methoxy, propoxy, etc.,

B. aryloxy group e.g., phenoxy, naphthoxy, etc.

C. amino group,

D. hydroxy group,

E. aryl group, e.g., benzyl, phenyl, etc.,

F. alkylamino and dialkylamino,

G. arylamino group, e.g., phenylamino, diphenylamino, N-phenyl-N-ethylamino, naphthylamino, etc.,

H. nitro group,

I. cyano group,

J. halo group,

K. alkyl substituted with an acyl group having the formula -C-R'

wherein R' is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkyl having 1 to 8 carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino e.g., diloweralkylamino, lower alkoxy having 1 to 8 carbon atoms e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy, naphthoxy, etc.; or

2. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc., including substituted aryl wherein the substituents are

a. alkoxy group, e.g., ethoxy, methoxy, propoxy, etc.,

b. aryloxy group, e.g., phenoxy, naphthoxy, phenoxy, etc.,

c. amino group,

d. hydroxy group,

e. aryl, e.g. phenyl,

f. alkylamino, e.g., dimethylamino, dipropylamino, etc.,

g. arylamino, e.g., phenylamino, N-phenyl-N-ethylamino, naphthylamino, etc.

h. nitro group,

i. cyano group,

j. halo group,

k. alkyl group, e.g., methyl, ethyl, propyl, etc.,

l. an acyl group having the formula ##EQU2## wherein R" is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having 1 to 8 carbon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl having 1 to 8 carbon atoms, e.g, methyl, ethyl, propyl, butyl, etc.; or

3. a hydrogen atom.

X, when taken singly, represents a naphthyl containing moiety having one of the following structures: ##EQU3##

wherein R.sub.1 is a lower alkylene group having 1 to 8 carbon atoms such as methylene, ethylene, propylene, tetramethylene, pentamethylene, neopentylene, etc.;

Ar is a naphthyl group or a substituted naphthyl group wherein the substituents are

a. alkoxy group of 1 to about 4 carbon atoms e.g. ethoxy, methoxy, propoxy, etc.,

b. aryloxy group, e.g. phenoxy, naphthoxy, etc.,

c. amino group,

d. hydroxy group,

e. alkylamino, of 1 to about 4 carbon atoms in each alkyl moiety e.g. methyl, ethyl, etc. and e.g. diethylamino, dipropylamino, etc.,

f. arylamino, e.g. phenylamino, diphenylamino, N-phenyl-N-ethylamino, etc.,

g. nitro group,

h. cyano group,

i. halo group,

j. alkyl group of 1 to about 6 carbon atoms, e.g. ethyl, methyl, propyl, etc.; and

Y is an oxygen atom or a sulfur atom.

X.sub.1, when taken singly, represents a hydrogen atom.

X and X.sub.1, when taken together, represent a 1,8-naphthylene group as, for example, in polyacenaphthylene.

In a preferred embodiment of this invention electrophotographic elements are provided which have a binder of the type described above wherein:

R represents an alkyl group of 1 to about 8 carbon atoms, a hydrogen atom, a phenyl group or a naphthyl group;

X represents a naphthyl containing moiety having the structure: ##EQU4## in which Ar is a naphthyl group and R.sub.1 is a lower alkylene group having 1 to about 4 carbon atoms;

X is a hydrogen atom; and

Y is an oxygen atom.

The resinous binder of this invention can contain, in addition to those repeating units set forth above, repeating units having the following structure: ##EQU5## wherein R.sub.2 is a lower alkyl group having 1 to 8 carbon atoms such as methyl, ethyl, propyl, neopentyl, butyl, isobutyl, etc.

Typical classes of polymers containing the above repeating units are poly(vinyl naphthoate-co-vinyl ester), poly(vinyl naphthoxyalkyl carboxylate-co-vinyl ester), poly(vinyl naphthylalkyl carboxylate-co-vinyl ester), poly(vinyl naphthiaalkyl carboxylate-co-vinyl ester), polymers of naphthyl ketones and aldehydes, etc.

Particularly useful binders according to this invention are resins represented by Formula A (above) wherein X represents one of the following structures: ##SPC1##

wherein R.sub.1 is the same as defined above.

Additional suitable binders for the elements described herein are resins containing the repeating units of A with repeating units derived from vinyl acetate i.e. ##EQU6##

Exemplary of a few of the many resins useful as binders in this invention are listed in Table I below.

Table I ______________________________________ I 2-Phenyl-2'-acetonaphthone-formaldehyde resin II 2'-Butyronaphthone-formaldehyde resin III 2'-Acetonaphthone-formaldehyde resin IV Poly(vinyl 2-naphthoate) V Poly(vinyl 2-naphthylacetate) VI Poly(vinyl 2-naphthoxyacetate) VII Poly(vinyl 2-naphthiaacetate) VIII Poly(vinyl 2-naphthoate-co-vinyl acetate) IX Poly(vinyl 2-naphthylacetate-co-vinyl acetate) X Poly(vinyl 2-naphthoxyacetate-co-vinyl acetate) XI Poly(vinyl 2-naphthiaacetate-co-vinyl acetate) XII Poly(vinyl 1-naphthoate-co-vinyl acetate) XIII Poly(vinylnaphthalene) XIV Poly(acenaphthylene) ______________________________________

As described previously, the binders of this invention can comprise homopolymers having repeating unit A above or copolymers having repeating units of A and B. The copolymer can be either a block or random copolymer and contains at least 2 percent of repeating unit A.

The present resinous binders are prepared by methods known to those skilled in the art. The naphthoneformaldehyde resins are prepared by condensing the appropriate naphthone with formaldehyde. The vinyl naphthoate/vinyl acetate polymers are prepared by treating a suspension in pyridine of polY(vinyl alcohol), which may or may not contain some residual vinyl acetate or other desired vinyl ester units, with a slight excess of the appropriate naphthyl-containing acid derivative, e.g. naphthoyl chloride, naphthiaacetyl chloride. When there are no vinyl acetate units present, a homopolymer having the desired pendant side groups is formed. The reaction is carried out at about 50.degree.C. The polymer is recovered by precipitation in water and is purified by reprecipitation in methanol from methylene chloride solution.

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

The novel polymeric binders of this invention improve the electrical speeds of compositions containing a wide variety of photoconductors including inorganic photoconductors such as zinc oxide, titanium dioxide, cadmium sulfide and the like and organic photoconductors including organometallic photoconductors. Mixtures of two or more photoconductors are also useful.

The organic photoconductors employed in the elements and the method of our invention can be essentially any of the organic photoconductors or mixtures thereof which are suitable for use in electrophotography.

Examples of useful organic photoconductors include the following:

A. Arylamine photoconductors including substituted and unsubstituted arylamines, diarylamines, nonpolymeric triarylamines and polymeric triarylamines such as those described in U.S. Pat. Nos. 3,240,597 and 3,180,730.

B. Photoconductors represented by the formula ##EQU7## wherein Z and Z' are aromatic radicals, Q is a hydrogen atom or an aromatic amino group, such as Z'NH-; b is an integer from 1 to about 12, and L is a hydrogen atom or an aromatic radical, these materials being more fully described in U.S. Pat. NO. 3,265,496

C. Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials; and also other polyarylalkanes included by the formula: ##EQU8## wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, these materials being more fully described in U.S. Pat. No. 3,274,000; French Pat. No. 1,383,461 and in U.S. Pat. No. 3,542,544, issued Nov. 24, 1970. D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula: ##EQU9## wherein R.sub.1 and R.sub.2 are each phenyl radicals including substituted phenyl radicals, these materials being more fully described in Fox U.S. Pat. No. 3,526,501 issued Sept. 1, 1970 and other chalcones as disclosed in U.S. Pat. No. 3,265,497.

E. Non-ionic cycloheptenyl compounds which may be substituted with substituents such as aryl, hydroxy, azido, nitrogen heterocycles, or oxycycloheptenyl; these compounds being more fully described in U.S. Pat. No. 3,533,786 issued Oct. 13, 1970.

F. Compounds containing an >N - N< nucleus, including N,N-bicarbazyls and tetra-substituted hydrazines, which compounds are more fully described in U.S. Pat. No. 3,542,546 issued Nov. 24, 1970.

G. Organic compounds having a 3,3'-bis-aryl-2-pyrazoline nucleus which is substituted in either five-member ring with the same or different substituents. These organic photoconductors are more fully described in U.S. Pat. No. 3,527,602 issued Sept. 8, 1970.

H. Triarylamines in which at least one of the aryl radicals is substitued by an active hydrogen-containing group or a vinyl or vinylene radical having at least one active hydrogen-containing group. These materials are more fully described in U.S. Pat. No. 3,658,520, issued Apr. 25, 1972.

I. Organic-metallic compounds having at least one amino-aryl substituent attached to a Group IVa or Group Va metal atom such as silicon, germanium, tin and lead from Group IVa and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted in the metallo nucleus with a wide variety of substituents but at least one of the substituents must be an amino-aryl radical. These materials are described in U.S. Pat. No. 3,647,429, issued Mar. 7, 1972.

J. Polymeric organic photoconductors such as poly-N-vinylcarbazoles and related vinyl polymers, such materials being disclosed for example, in U.S. Pat. Nos. 3,037,861; 3,155,503; 3,418,116; 3,421,891 and 3,232,755.

K. Any other organic compound which exhibits photoconductive properties such as those set forth in Australian Pat. No. 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

triphenylamine

4,4'-diethylamino-2,2'-dimethyltriphenylmethane

4,4'-benzylidene-bis(N,N-diethyl-m-toluidine)

4',4"-diamino-4-dimethylamino-2',2"-dimethyltriphenylmethane

4',4"-bis(diethylamino)-2,6-dichloro-2',2"-dimethyltriphenylmethane

2',2"-dimethyl-4,4',4"-tris(dimethylamino)-triphenylmethane

4',4"-bis(diethylamino)-4-dimethylamino-2,2',2"-trimethyltriphenylmethane

4',4"-bis(dimethylamino)-2', 2"-dimethyl-4-methoxytriphenylmethane

bis(4-diethylamino)tetraphenylmethane

4,4'-bis(diphenylamino)chalcone

tetra-4-tolylhydrazine

poly-N-vinylcarbazole

monobrominated poly-N-vinylcarbazole

dibrominated poly-N-vinylcarbazole

N,n'-bicarbazyl

3,3'-bis(1,5-diphenyl-2-pyrazoline

1,5-diphenyl-3-[3'-(1'-p-tolyl-5'-phenyl)-2'-pyrazolyl]2-2-pyrazoline

p-diphenylaminostyrene

p-diphenylaminocinnamic acid

triphenyl-p-dimethylaminophenylstannane

triphenyl-p-diethylaminophenylplumbane

tetra-p-diethylaminophenylplumbane

phenyl-tri(p-diethylaminophenyl)stannane

tetra-p-diethylaminophenylgermane

p-diethylaminophenylarsine

The photoconductive layers of the invention can be sensitized by the addition of effective 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 dye salts including thiapyrylium dye salts and selenapyrylium dye salts disclosed in VanAllan et al, U.S. Pat. No. 3,250,615; fluorenes, such as 7,12-dioxo-13-dibenzo-(a,h)fluorene, 5,10-dioxo-4a,11-diazabenzo(b)fluorene, 3,13-dioxo-7-oxadibenzo(b,g)fluorene, and the like; aggregate-type sensitizers of the type described in Light, Belgian Pat. No. 705,117 dated Apr. 16, 1968; aromatic nitro compounds of the kinds described in U.S. Pat. No. 2,610,120; anthrones like those disclosed in U.S. Pat. No. 2,670,284; quinones, U.S. Pat. No. 2,670,286; benzophenones, U.S. Pat. No. 2,670,287; thiazoles, U.S. Pat. No. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid, trichloroacetic acid and salicyclic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine (including carbocyanine), nitro-substituted cyanines, styryls, anils, merocyanine, diarylmethane, thiazine, azine, oxazine, xanthone, 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 1. pyrylium salts including selenapyrylium salts and thiapyrylium salts and 2. cyanine dyes including carbocyanine dyes.

Although typically no sensitizer is required to impact photoconductivity to the photosensitive layer, since relatively minor amounts of sensitizing compound give substantial immprovement in speed in such layers, the sensitizer is preferred. The amount of sensitizer that can be added to a photoconductor-containing layer to give effective increases 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. Generally, a senitizer 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 present invention can include a wide variety of organic solvents for the components of the coating composition such as

1. aromatic hydrocarbons, and substituted aromatic hydrocarbons e.g. benzene, toluene, xylene, mesityene, etc.;

2. ketones such as acetone, 2-butanone, etc.;

3. halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, ethylene chloride, etc.;

4. ethers including cyclic ethers such as tetrahydrofuran and dioxane; and

5. mixtures of the above.

In preparing the coating compositions 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 typically required that the photoconductive material be present 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. 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 will vary depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, various conducting papers; 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 silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating a transparent film support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. A suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of a maleic anhydridevinyl acetate copolymer, cuprous iodide and the like. Such conducting layers and methods for their optimum preparation and use are disclosed in U.S. Pat. Nos. 3,007,901; 3,245,833; and 3,267,807.

The compositions of the present invention can be employed in photoconductive elements useful in any of the well known electrophotographic processes which require photoconductive layers, and the present compositions can be used in electrophotographic elements of 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 by 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. Configuration differing from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographic element.

The following Examples are included for a further understanding of the invention.

EXAMPLE 1

A solution of 1.5 g of poly(vinyl 1-naphthoate-co-vinyl acetate) (88/12 molar ratio) as the binder, 0.5 g of 4,4'-benzylidenebis(N,N-diethyl-m-toluidine) as the photoconductor and 0.02 g of 2,4-di(4-ethoxyphenyl)-6-(4-amyloxystyryl)pyrylium fluoroborate as the sensitizer in 15.6 g of methylene chloride is hand coated at a wet thickness of 0.004 inch on a conducting layer comprising the sodium salt of a carboxyester lactone, such as described in U.S. Pat. No. 3,102,028 which in turn is coated on a cellulose acetate support. The coating block is maintained at a temperature of 90.degree.F. After drying the 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 3,000.degree.K. tungsten source. The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential, V.sub.o, 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.sup.4 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential by 100 volts. The toe speed is the numerical expression of 10.sup.4 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential to 100 volts. This coating is found to have a positive 100 V. toe speed of 63 and a shoulder speed of 900.

EXAMPLE 2

Example 1 is repeated except the binder employed is poly(vinyl 2-naphthoate-co-vinyl acetate). The shoulder speed is 630 and the toe speed is 50.

EXAMPLE 3

Example 1 is repeated except the binder employed is poly(vinyl 2-naphthoxyacetate-co-vinyl acetate). The shoulder speed is 1800 and the toe speed is 200.

EXAMPLE 4

Example 1 is repeated except the element is charged negatively. Good shoulder and toe speeds are obtained.

EXAMPLE 5

Coating compositions containing the binders set forth in the following Table III are prepared and 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. The quality of the reproduction of the pattern in each instance is set forth in the following Table III:

Table III ______________________________________ Polymeric Binder No. Quality of Reproduction (from Table I) ______________________________________ I Good II Good III Good IV Good V Good VI Good VII Good VIII Good IX Good X Good XI Good XII Good XIII Good XIV Good ______________________________________

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.

Claims

We claim:

1. An electrophotographic element comprising an electrically conductive support having coated thereon a photoconductive composition comprising at least about 10 weight percent photoconductor and a polymeric binder having repeating units represented by the following structure: ##EQU10## wherein R represents A. an alkyl group having 1 to 18 carbon atoms,

B. an aryl group, or

C. a hydrogen atom; and

X is a naphthyl-containing moiety having a formula selected from the following: ##EQU11## wherein R.sub.1 is a lower alkylene group having 1 to 8 carbon atoms,

Ar is a naphthyl group or a substituted naphthyl group wherein the substituents are selected from the group consisting of alkoxy group, aryloxy group, amino group, hydroxy group, alkylamino, arylamino, nitro group, cyano group, halo group, and alkyl group, and

Y is an oxygen atom or a sulfur atom.

2. The electrophotographic element of claim 1 wherein the photoconductive composition contains a sensitizing amount of a sensitizer for said photoconductor.

3. The electrophotographic element of claim 1 wherein X is ##EQU12## and Ar is a naphthyl group.

4. The electrophotographic element of claim 1 wherein X is ##EQU13## and Ar is a naphthyl group.

5. The electrophotographic element of claim 1 wherein X is ##EQU14## Ar is a naphthyl group and R.sub.1 is a lower alkylene group.

6. The electrophotographic element of claim 1 wherein X is ##EQU15## R.sub.1 is lower alkylene group, Y is oxygen atom or sulfur atom and Ar is a napthyl group.

7. An electrophotographic element comprising an electrically conductive support having coated thereon a photoconductive composition comprising at least 10 weight percent photoconductor and a polymeric binder having:

I. repeating units represented by the following structure: ##EQU16## wherein R represents A. an alkyl group having 1 to 18 carbon atoms,

B. an aryl group, or

C. a hydrogen atom;

X is a naphthyl-containing moiety having a formula selected from the following: ##EQU17## wherein R.sub.1 is a lower alkylene group having 1 to 8 carbon atoms,

Ar is a naphthyl group or a substituted naphthyl group wherein the substituents are selected from the group consisting of alkoxy group, aryloxy group, amino group, hydroxy group, alkylamino, arylamino, nitro group, cyano group, halo group, and alkyl group, and

Y is an oxygen atom or a sulfur atom;

X.sub.1, when taken singly, represents a hydrogen atom; and

X and X.sub.1, when taken together, represent a 1,8-naphthylene group; and

II. repeating units represented by the following structure. ##EQU18## wherein R.sub.2 is a lower alkyl group.

8. An electrophotograhic element comprising an electrically conductive support having coated thereon a photoconductive composition comprising at least 10 weight percent organic photoconductor and a polymeric binder having repeating units represented by the following structure: ##EQU19## wherein R is selected from the group consisting of an aryl group, an alkyl group having from 1 to about 18 carbon atoms, and a hydrogen atom,

X is a naphthyl containing moiety selected from the group consisting of ##EQU20## and R.sub.1 is a lower alkylene group.

9. The electrophotographic element of claim 8 wherein X is ##SPC2##

10. The electrophotographic element of claim 8 wherein X is ##SPC3##

11. The electrophotographic element of claim 8 wherien X is ##SPC4##

and R.sub.1 is a lower alkylene group.

12. The electrophotographic element of claim 8 wherein X is ##SPC5##

and R.sub.1 is a lower alkylene group.

13. An electrophotographic element comprising an electrically conductive support having coated thereon a photoconductive composition comprising at least 10 weight percent organic photoconductor and a polymeric binder having:

I. repeating units represented by the following structure: ##EQU21## wherein R is selected from the group consisting of an aryl group, an alkyl group and a hydrogen atom,

X is a naphthyl or naphthyl containing moiety selected from the group consisting of ##EQU22## and R.sub.1 is a lower alkylene group; and II. repeating units represented by the following structure: ##EQU23## wherein R.sub.2 is a lower alkyl group.

14. An electrophotographic element comprising an electrically conductive support having coated thereon a photoconductive composition comprising at least 10 weight percent organic photoconductor and a polymeric binder having repeating units represented by the following structure: ##EQU24## wherein R is an alkyl group of 1 to about 8 carbon atoms, a hydrogen atom, a phenyl group or a naphthyl group; and X is a naphthyl containing moiety having the structure: ##EQU25## wherein Ar is naphthyl group and R.sub.1 is a lower alkylene group having 1 to about 4 carbon atoms.

15. An electrophotographic element comprising an electrically conducting support having coated thereon a photoconductive composition comprising from about 10 to about 60 weight percent of an organic photoconductor, 0.005 to about 5.0 weight percent of sensitizer for said photoconductor and poly(vinyl 1-naphthoate-co-vinyl acetate) as a binder.

16. An electrophotograhic element comprising an electrically conducting support having coated thereon a photoconductive composition comprising from about 10 to about 60 weight percent of an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(vinyl 2-naphthoate-co-vinyl acetate) as a binder.

17. An electrophotograhpic element comprising an electrically conducting support having coated thereon a photoconductive composition comprising from about 10 to about 60 weight percent of an organic photoconductor, 0.005 to about 5.0 weight percent of a sensitizer for said photoconductor and poly(vinyl 2-naphthoxyacetate-co-vinyl acetate) as a binder.