US3765882A

US3765882A - Heterocyclic photoconductor containing o, s or se

Info

Publication number: US3765882A
Application number: US00278303A
Authority: US
Inventors: R Virkhaus
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1972-08-07
Filing date: 1972-08-07
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

Compounds useful in electrophotography as part of photoconductive elements are disclosed having the general formula:

WHEREIN Z is a sulfur, oxygen or selenium hetero atom and R1 through R4 each represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or a halogen atom and Y represents the group -(CH CH)n-R in which n equals 0, 1 or 2 and R is an aryl radical.

Description

United States Patent [191 Virkhaus 1 HETEROCYCLIC PHOTOCONDUCTOR CONTAINING O, S OR SE [75] Inventor: Rein Virkhaus, Rochester, N .Y.

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22] Filed: Aug. 7, 1972 [21] Appl. No.: 278,303

[52] US. Cl 96/l.5, 96/l.6, 260/239 R,

260/240 D, 260/330.5, 260/346.2 [51] Int. Cl 603g 5/06 [58] Field of Search..'. 96/15, 1.6, 1 PC [56] References Cited UNITED STATES PATENTS 3,072,479 1/1963 Bethe 96/l.5 3,174,854 3/1965 Stumpf et al. 96/l.5 3,301,676 l/1967 Tomanek 96/15 [451 Oct. 16, 1973 Primary Examiner-Roland E. Martin, Jr. Attorney-Robert W. Hampton et al.

[57] ABSTRACT Compounds useful in electrophotography as part of photoconductive elements are disclosed having the general formula:

wherein Z is a sulfur, oxygen or selenium hetero atom and R through R each represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or a halogen atom and Y represents the group -(CH=CH),, R in which n equals 0, l or 2 and R is an aryl radical.

13 Claims, N0 Drawings 7 HETEROCYCLIC PHOTOCONDUCTOR CONTAINING 0, S OR SE This invention relates to electrophotography, and in particular, to photoconductive compositions and elements.

Electrophotographic imaging processes and techniques are based on the discovery that certain materials which are normally insulating become conductive during exposure to electromagnetic radiation of certain wavelengths after being electrically charged. Such materials, such may be either organic or inorganic, are termed photoconductors. They are conveniently formed into usable image-forming elements by coating a layer of the photoconductive composition, together with an electrically insulating resinous binder where necessary or desirable, onto a suitable support. Such an element will accept and retain an electrostatic'charge in the absence of actinic radiation. In use, the surface of the element is charged in the dark to a uniform potential and exposed to an imagewise pattern of actinic radiation, which selectively reduces the surface potential to produce a charge pattern corresponding to the imagewise radiation pattern. The resultant charge pattern or electrostatic latent image may be developed by contacting it with suitably charged marking particles which adhere in accordance with the charge pattern, or it may be transferred to another insulating surface upon which it is developed. The particles may then be fused or fixed to the surface by known means such as heat or solvent vapor, or they may be transferred to another surface to which they may similarlybe fixed, to produce a permanent reproduction of the original radiation pattern.

Various photoconductive insulating materials have been employed in the manufacture of electrophoto graphic elements. Nothing as yet has been discovered from the large number of different photoconductive substances tested which permits effective prediction, and therefore, selection of the particular compounds exhibiting the desired electrophotographic properties.

It is, therefore, an object of this invention to provide a novel class of photoconductors having useful photosensitivity when electrically charged.

It is another object to provide novel photoconductorcontaining compositions which exhibit improved electrical speeds.

These and other objects and advantages of this invention are accomplished through the use as photoconductors of compounds corresponding to the general formula:

wherein:

Z is a hetero atom selected from an oxygen atom, a sulfur atom and a selenium atom;

R through R may be the same or different and each represent a hydrogen atom, an alkylgroup, an aryl group, an alkoxy group, an aryloxy group or a halogen atom; and

-CH=OH)Rin which n is Y represents the group wherein:

Z isa hetero atom selected from an oxygen atom and a sulfur atom;

Y represents the group(CH=CH),,-R in which n is an integer from 0 to l; and R is phenyl radical, a methoxyphenyl radical, adi-p-tolylaminophenyl radical, a dialkylaminophenyl radical, a diphenylaminophenyl radical or a diphenylaminonaphthyl radical.

The terms alkyl, aryl, etc, as used herein, are intended to have the meanings as hereinafter set forth.

The term alkyl refers to any aliphatic group having one to 18 carbon atoms, e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc, including a substituted alkyl group having one to 18 carbon atoms with such substituents as an alkoxy radical, an aryloxy radical, an amino radical, a hydroxy radical, an aryl radical, an alkylamino radical, an arylamino radical, a nitro radical, a cyano radical, a halogen atom, an acyl radical having the formula:

wherein R is hydroxy, hydrogen, aryl, lower alkyl having one to eight carbon atoms, amino including substituted amino, lower alkoxy having one to eight carbon atoms, aryloxy, etc.

The term aryl group'refers to an aromatic group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc. including a substituted aryl group having such substituents as an alkoxy radical, an aryloxy radical, an aminoradical, a hydroxy radical, an alkylamino radical, an arylamino radical, a nitro radical, a cyano radical, a halogen atom, as well as an acyl group having the formula:

wherein R is hydroxy, halogen, hydrogen, aryl, amino, including substituted amino, lower alkoxy having one to eight carbona'toms, aryloxy, lower alkyl having one to eight carbon atoms.

An amino group is a group having the formula:

wherein R and R are the same or different including hydrogen, lower alkyl having one to eight carbon atoms such as ethyl, propyl, butyl, etc, aryl such as phenyl, naphthyl, etc, or halogen, e.g., chlorine, bromine, etc.

An alkoxygroup is a group having from one to about 18 carbon atoms in the alkyl moiety, e.g., methoxy, propoxy, octoxy, dodecyloxy, octadecyloxy, etc.

An aryloxy group is a group such as phenoxy, naphthoxy, and the like.

Representative photoconductors corresponding to the above formulas including the following:

A. 2-benzylidenebenzofb] thiophen-3-one B. 2-(p-dimethylaminobenzylidene)benzo[b] thiophen-3-one C. 2-(p-diethylaminobenzylidene)benzo [b] thiophen-3-one 1 D. 2-(p-diphenylaminobenzylidene)benzo ['b} thiophen-3-one E. Z-(p-dimethylaminocinnamylidene)benzo [b] thiophen-3-one F. Z-(p-methoxybenzylidene)benzo [b] thiophen- 3-one G. 2-(p-diphenylamino-o-methoxybenzylidene)- benzo [b] thiophen-3-one l3-dibenzo(a,h )fluorene, 5,10-dioxo-4a, l ldiazabenzo(b )fluorene, 3 l 3-dioxo-7-oxadibenzo (b,g)- fluorene, and the like; aggregate type sensitizers of the type described in Light'Belgian Patent 705,1 l 7, dated Apr. 16, 1968; aromatic nitro compounds of the kinds described in U.S. Pat. No. 2,6l0,l; anthrones as 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, and salicyclic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine (including carbocyanine), merocyanine, diarylmethane, thiazine, azine, oxazine, 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 dye salts,

binder and organic photoconductor to form a sensitized electrophotographic element, it is the normal H. 2-(p-di-p-tolylaminobenzylidene)benzo [b] thiophen-3-one J. 2-(4-diphenylamino-l-naphthylidene)benzo {b} thiophen-3-one While the above-described compounds are preferred, certain modifications produce compounds which are suitable for use in electrophotography. Exemplary of such modifications would be the compounds having the above formulas (a) wherein the hetero atom is substituted by certain hetero groups such as SO, SO NI-I, NR and NAr wherein R and Ar represent an alkyl and an aryl radical, respectively, as described above and (b) wherein the size of the heterocyclic ring itself maybe increased from 5 to 6 members. Also, the positions of the hetero atom or group, the =0 and the =CI-I-Y in or on the heterocyclic ring may be'located in an alternative position. Another modification is that the R through R substituents of the benzene ring may together complete an optionally substituted heterocyclic or carbocyclic fused ring system, such as naphthyl, phenanthryl, anthryl, benzonaphthyl, quinolyl, quinazolyl, etc. v

Electrophotographic elements of the invention can be prepared with the photoconductive compounds of the invention in the usual manner, i.e., by blending a dispersion or solution of a photoconductive compound together with a binder;-when necessary or desirable, and coating or forming a self-supporting layer with'the photoconductor-containing material. Mixtures of the photoconductors'described herein can be employed. Likewise, other photoconductors known in the art such as those described in Light British Patent 'No. 1,153,506, dated May 29, 1969, can be combined with the present photoconductors.

In addition, supplemental sensitizing materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the present photoconductive compositions when it is desirable to produce the characteristic effect of such materials. Sensitizing compounds useful with the photoconductive compounds of the present invention can be selected from a wide variety of materials, for example, pyrylium dye salts, including thiapyrylium dye salts and selenapyrylium dye salts as disclosed in VanAllan et al U.S. Pat. No. 3,250,615; fluorenes, such as 7,12-dioxopractice 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 effects 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, 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 photoconductorincorpor'ating 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, increases in speed 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. Typically, 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 thetotal coating composition.

Preferred binders for use in preparing the present photoconductive layers are film-forming, hydrophobic v polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles..Materials of this type include styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; sili- 'cone-alkyd resins; soly-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chlorideacrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly(vinyl acetals), such as poly(vinyl butyral); polyacrylic and meth- .acrylic esters, such as poly(methyl methacrylate), po-

ly(n-butyl methacrylate), poly(isobutyl methacrylate), etc; polystyrene, nitrated polystyrene; polymethylstyrene; isobutylene polymers; polyesters, such as poly[etphenyl)terephthalate];'copolymers of vinyl haloarying resins of this type have been described in the prior art, for example, styrene-alkyd resins can be prepared according to the method described in U.S. Pats. Nos. 2,361,019 and 2,258,423.

Suitable resins of the type contemplated for use in the photo-conductive layers of the invention are sold under such trade-names as Vitel PE-lOl, Cymac, Piccopale 100, Saran F220, Lexan 105 and Lexan 145. Other types of binders which can be used in the photoconductive layers of the invention include such materials as paraffin, mineral waxes, etc.

Solvents useful for preparing coating compositions with the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-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 advantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the photoconducting compounds 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. Typically, the photoconductive material is 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 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. 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 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 layer such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like. An especially useful conducting support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. A suitable conducting coatingcan be prepared from the sodium salt of a carboxyester lactone and the like. Such conducting layers and methods for their optimum preparation and use are disclosed in U.S. Pats. 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. 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 dissipated from the surface of the layer by imagewise exposure to light, thereby forming a latent electrostatic image in the photoconductive layer.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, using any of the liquid or dry developer 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 possibleto 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. 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 following examples are included for a further understanding of this invention.

EXAMPLE 1 Preparation of 2-(p-diphenylaminobenzylidene)- benzo[b]thiophen-3-one (Compound D) To an ethanol solution of 1.5 grams (0.01 mole) of benzo[b]thiophen-3 '2l-l-one and 2.7 grams (0.01 mole) of p-diphenylaminobenzaldehydeare added 1.5 ml. of concentrated sulfuric acid. A deep red color appears. The solution is sitrred for 40 minutes while being maintained at an elevated temperature and therafter is cooled to room temperature. A yield of 4.2 grams of deep orange crystals is obtained. Recrystallization from carbon tetrachloride andthen from petroleum ether gives a product having a melting point range of 188-1 C.

Analysis C- H N S Calculated: 79.97 4.72 3. 5 7.9 Found: 79.8 5.0 3.5 7.8

EXAMPLE 2 Preparation of 2-(p-dimethylaminocinnamulidene)- benzo[b]thiophen-3-one (Compound E) The procedure of Example 1 is followed using an equimolar portion (1.75 grams) of pdimethylaminocinnamaldehyde in place of the pdiphenylaminobenzaldehyde. The solution is refluxed with stirring for 35 minutes, to yield a tan precipitate. The product is collected and purified by washing in turn in water, dilute sodium hydroxide (10 percent), and finally water again to yield 2.0 grams of deep pur- 'tolylaminobenzaldehyde ple needles having a melting point range of Analysis c H N Calculated: 74.24 5.57 4.56 10.43 Found: 74.2 5.6 4.5 10.4

EXAMPLE 3 Preparation of 2-(p-di-p-tolylaminobenzylidene)- benzo[b]thiophen-3-one (Compound H) The procedure of Example 1 is followed using an equimolar portion (3 .0 grams) of di-pin place of the pdiphenylaminob'enzaldehyde. The resulting product is recrystallized from ethyl acetate to give 3.5 grams of magenta crystals having a melting point range of from 193-l95C.

Analysis C l-l N S Calculated: 80.34 5.3 3.2 7.4 Found: 80.3 5.4 3.1 7.2

EXAMPLE 4 Analysis C H N S Calculated: 77.22 4.86 3.2! 7.36 Found: 77.! 4.9 3.1 7.l

EXAMPLE 5 Preparation of 2-(4-diphenylamino-l-naphthyliden ey benzo[b]thiophen-3-one (Compound J) The procedure of Example 1 is followed using an equimolar portion (3.23 grams) of 4-diphenylamino-1- naphthy-aldehyde in place of the pdiphenylaminobenzaldehyde. The resulting product is recyrstallized from ethyl acetate to give 3 .5 grams of an orange solid having a melting point range of l84-187" C.

Analysis C H N 8 Calculated: 8!.73 4. 4 3.l 7.0 Found: 8L8 4.7 2.9- 7.1

The other compounds used in preparing the photoconductive compositions and elements of the invention are prepared according to procedures described in-the literature. For example, Compounds A, B and F appear. in Zh. Obst. Khim. 3l (1), 17 (1961), while a compound similar to Compound C appears in Latvijas PSR Zinatu Akad. Vestis, Khim. Sci. (3), 385(1963).

EXAMPLE 6 A composition in the form of a dope consisting of the following materials is coated at a wet thickness of 150 microns on a poly(ethylene terephthalate)'film support bearing a conductive layer comprising vapor deposited nickel:

Photoconductor see below 0.25 g. Binder poly(4,4'-isopropylidenebisphenyleneoxyethylene-coethylene terephthalate 1.00 g.

Sensitizer 2,6-bis(4ethylphenyl)-4- (4-n-amyloxyphenyl)thiapyrylium perchlorate 0.0 Dichloromethane 9 .6

l g. 0 g.

The support is held on a coating block maintained at a temperature of about 32C during coating and until the solvent is removed. In a darkened room, the surface of the photoconductive layer 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 patternof opaque and light-transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 metercandles for 12 seconds. The resulting electrostatic charge pattern is developed by cascading over the surface of the layer negatively charged black thermoplastic toner particles on glass bead carriers. The quality of the images reproduced using the various photoconductors described herein are set forth in the following table:

TABLE I Photoconductor none IO' H UO IP The elements containing the photoconductors indicated in Table 11 below are then recharged under a positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts. They are then exposed from behind a stepped density gray scale to a 3000K tungsten source. The exposurecauses reduction of the surface potentials of the elements under each step of the gray scale from their initial potential, V,,, to some lower potential, V, whose exact value depends on the actual amount of exposure received by the areas. 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 -104 multiplied by the reciprocal of the exposure in meter-candle-seconds required to reduce the 600 volt charged surface potential by volts. The elements have speeds as thus measured as indicated in Table II.

TABLE II Speed Photoconductor B EXAMPLE 7 hour at room temperature. The two solutions are then incorporated into a photoconductor-containing coating solution to form a coating dope for each of the photoconductors listed in Table III below. The photoconductor-containing solution is prepared according to the following composition:

Lexan 145 0.25 g. Photoconductor 025 g. Solution 1 4.50 gv Solution 2 7.70 g.

Each of the coating dopes thus produced is coated as in Example 6 to form photoconductive elements. Each element is then charged in turn positively and negatively and exposed as in Example 6 through a stepped density gray scale. Speeds are obtained for both positive and negative charging in the manner previously described, and are listed in Table III.

When each of the elements listed in Table III is charged imagewise in a manner similar to that used in Example 6, except that the light intensity is reduced by a power of 10, and developed in the same manner, a good reproduction is obtained in each case.

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

I claim:

1. An electrophotographic element comprising a conductive support bearing a layer of a photoconductive composition comprising an organic film-forming electrically insulating polymeric binder and an organic photoconductor having the formula:

Y represents the group /CH=CH)R in which n is an integer from 0 to 2 and R is an aryl group. 2. An electrophotographic element according to claim 1 wherein Z is a sulfur atom.

3. An electrophotographic element according to claim 2 wherein R through R are each hydrogen atoms.

4. An electrophotographic element comprising an electrically conductive support bearing a photoconductive composition comprising an electrically insulating film-forming polymeric binder and an organic photoconductor having the formula:

whereini Y represents the group is an integer from 0 to 1; and R is sel e cted from the group consisting of a phenyl radical, a methoxyphenyl radical, a diphenylaminophenyl radical, a

dialkylaminophenyl radical, a phenylaminonaphthyl radical, and a diphenylamino-o-methoxyphenyl.

5. An electrophotographic element according to claim 4 wherein the organic photoconductor is selected from the group consisting of 2-(pdiphenylaminobenzylidene)-benzo-[b]thiophen-3-one, 2-(p-di-p-tolylaminobenzylidene)-benzo[b]-thiophen- 3-one, 2-(p-dimethylaminocinnamylidene)-benzo[b]- thiophen-3-one, 2-(p-diphenylamino-omethoxybenzylidene)-benzo-[b]thiophen-3-one, 2-(4-' diphenylamino-l -naphthylidene )-benzo-[b]thiophen- 3 -one, 2-( p-phenylbenzylidene)-benzo[b]thiophen- 3 -one, 2-(p-diethylaminobenzylidene)benzo[blthiophen-3 -one, and

2-(p-methoxybenzylidene)- benzo[b]thiophen-3-one. I

6. An electrophotographic element according to claim 4 wherein the photoconductive composition is selected from the group consisting diphenylaminobenzylidene)-benzo[b]-thiophen-3-one and 2-(p-di-p-tolylaminobenzylidene)-benzo[b]- thiophen-3-one.

7. An electrophotographic element according to claim 1 wherein the photoconductive composition comprises from about 0.005 percent to about 5- percent by weight based on said photoconductive composition of a sensitizer for said composition. 7

8. In an electrophotographic process wherein an electrostatic charge pattern is formed on an electrophotographic element, the improvement wherein said element is the element of claim 4. i

9. A 2-(p-diphenylaminobenzylidene)benzo[b]thiophen-3-one.

10. A 2-(p-dimethylaminocinnamylidene)benzo[b]- thiophen-3-one.

11. A 2-(p-diphenylamino-o-methoxybenzylidene)- benzo[b]thiophen-3-one.

12. A 2-(4-diphenylamino-l-naphthylidene)benzo[b]-thiophen-3-one.

13. A 2-(p-di-p-tolylaminobenzylidene)benzo[b]- thiophen-S-one.

Claims

2. An electrophotographic element according to claim 1 wherein Z is a sulfur atom.
3. An electrophotographic element according to claim 2 wherein R1 through R4 are each hydrogen atoms.
4. An electrophotographic element comprising an electrically conductive support bearing a photoconductive composition comprising an electrically insulating film-forming polymeric binder and an organic photoconductor having the formula:
5. An electrophotographic element according to claim 4 wherein the organic photoconductor is selected from the group consisting of 2-(p-diphenylaminobenzylidene)-benzo-(b)thiophen-3-one, 2-(p-di-p-tolylaminobenzylidene)-benzo(b)-thiophen-3-one, 2-(p-dimethylaminocinnamylidene)-benzo(b)-thiophen-3-one, 2-(p-diphenylamino-o-methoxybenzylidene)-benzo-(b)thiophen-3-one, 2-(4-diphenylamino-1-naphthylidene)-benzo-(b)thiophen-3-one, 2-(p-phenylbenzylidene)-benzo(b)thiophen-3-one, 2-(p-diethylaminobenzylidene)benzo(b)thiophen-3-one, and 2-(p-methoxybenzylidene)-benzo(b)thiophen-3-one.
6. An electrophotographic element according to claim 4 wherein the photoconductive composition is selected from the group consisting of 2-(p-diphenylaminobenzylidene)-benzo(b)-thiophen-3-one and 2-(p-di-p-tolylaminobenzylidene)-benzo(b)-thiophen-3-one.
7. An electrophotographic element according to claim 1 wherein the photoconductive composition comprises from about 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer for said composition.
8. In an electrophotographic process wherein an electrostatic charge pattern is formed on an electrophotographic element, the improvement wherein said element is the element of claim 4.
9. A 2-(p-diphenylaminobenzylidene)benzo(b)thiophen-3-one.
10. A 2-(p-dimethylaminocinnamylidene)benzo(b)-thiophen-3-one.
11. A 2-(p-diphenylamino-o-methoxybenzylidene)-benzo(b)thiophen-3-one.
12. A 2-(4-diphenylamino-1-naphthylidene)benzo(b)-thiophen-3-one.
13. A 2-(p-di-p-tolylaminobenzylidene)benzo(b)-thiophen-3-one.