1,3-phenylenediamine Containing Photoconductive Materials

Abstract

A new group of N,N,N',N'-substituted-1,3-phenylenediamines and an electrophotographic material comprised of a slightly conductive support and an insulating coating thereon comprised of an insulating resin, and a N,N,N',N'-substituted-1,3-phenylenediamine photoconductor. An electron-acceptor sensitizing agent can also be added to the insulating coating.

Description

BACKGROUND OF THE INVENTION

This invention relates to photographic reproduction and more particularly to a new group of organic photoconductors and to electrophotographic processes, namely processes in which an electrostatic latent image is produced by utilizing the property of photoconduction (i.e., a variable conductivity dependent on the intensity of illumination). The electrostatic latent image may be produced in a conventional exposure operation, for example by means of a lens-projected image or by contact-printing techniques, whereby a nonvisible electrostatic charge pattern (the so-called electrostatic latent image) is created on a surface, in which pattern the charge density at any point is related to the intensity of illumination obtained at the point during the exposure. The latent image may be developed (i.e., rendered visible) by means of a triboelectric powder or liquid toner. Said powder, such as a pigmented synthetic resin, fixes the resulting visible image by rendering the powder permanently adherent to a support on which the image is desired, for example in suitable cases by heating to soften or melt the powder particles. The liquid toner particles which are washed over the surface are caused to adhere permanently by the drying oil component of the liquid toner.

In electrophotographic processes the electrostatic latent image is commonly formed on the surface of a photoconductive insulating layer carried on a support. For example, material comprising such support and photoconductive layer may be charged by applying a uniform surface charge to the free surface of the photoconductive layer. The charge can be applied by conventional means such as corona discharge or the like. The charge is retained due to the substantial insulating character, i.e., the low conductivity, of the insulating layer in the dark. On exposure as described above, the photoconductive property of the layer causes the conductivity to increase in the illuminated areas to an extent which is proportional to the intensity of illumination. This results in a leakage of the surface charge in the illuminated areas while the charge in the unilluminated areas remains. This is what constitutes the aforementioned charge pattern or electrostatic latent image.

Electrophotographic processes have become of increasing importance in recent years, especially in connection with office duplicating processes. Consequently, there has been much interest aroused and much effort has been made to obtain suitable materials for making the support and photoconductive insulating layers used in such copying processes.

Attempts have been made to develop colorless organic photoconductors; however, problems have been encountered in obtaining colorless photoconductors sufficiently sensitive to be imaged using known light sources without being so sensitive as to become severely discolored by the interaction of light and oxygen during aging.

It is therefore the major objective of the present invention to provide a new group of colorless organic photoconductors that do not become appreciably discolored when exposed to light and oxygen. The invention is also directed to a new electrophotographic material which is quickly and easily imaged by exposure to commonly employed light sources.

PRIOR ART

In recent years many investigations have been made with respect to the nature of suitable photoconductive materials. Most notable among the photoconductive substances hitherto used in electrophotographic processes have been inorganic materials such as zinc oxide and selenium.

However, within the last few years the search for suitable photoconductors has been broadened to include organic chemical compounds and polymers. As a result of these searches several classes of organic compounds have been found to be useful as photoconductors; included in this group are the 2,5 bis (p-aminophenyl)-1,3,4-oxadiazoles, U.S. Pat. No. 3,189,447; 2-aryl-4-arylidene oxazolones, U.S. Pat. No. 3,072,479; substituted Schiff bases, U.S. Pat. No. 3,041,165; aryl-substituted-p and-m-phenylenediamines, U.S. Pat. Nos. 3,314,788, 3,141,770, and 3,265,496; N-disubstituted benzylideneazines, U.S. Pat. No. 3,290,147, and various other compounds, see Great Britain, Pat. No. 895,001.

U.S. Pat. No. 3,314,788 describes the use of N,N,N',N'-tetrabenzyl-p-phenylenediamines and N,N'-dibenzyl-N,N'-dialkyl substituted-p-phenylenediamines as organic photoconductors. While electrophotographic plates or sheets having coatings containing the substituted-p-phenylenediamines give good prints, it has been discovered that they discolor appreciably upon aging in the presence of light and oxygen. Upon exposure to light in the presence of oxygen the p-phenylenediamines cause the sheet to turn dark yellow or brown, thus making the electrophotographic product containing them unsuitable for use when it must be exposed to light for any period of time. However, the N,N,N',N'-substituted-1,3-phenylenediamines of the present invention have been found to be very stable and do not discolor appreciably when exposed to light and oxygen for substantial periods of time. Thus electrophotographic sheets or plates having a coating containing the substituted-1,3-phenylenediamines of the present invention can be exposed to light and oxygen for long periods of time without the coatings turning dark yellow or brown.

SUMMARY OF THE INVENTION

a. New N,N,N',N'-substituted-1,3-phenylenediamines.

The new N,N,N',N'-substituted-1,3-phenylenediamine compounds of the present invention correspond to one of the ##SPC1##

In the present specification and claims, R represents 1,3-phenylene, 4-methyl-1,3-phenylene, 4-halo-1,3-phenylene, 4-ethyl-1,3-phenylene, 4-isopropyl-1,3-phenylene, 4-methoxy-1,3-phenylene, 2-halo-1,3-phenylene and 4,6-dimethyl-1,3-phenylene and Z represents benzyl, monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, tetramethylbenzyl, monohalobenzyl or dihalobenzyl; however, when R represents 1,3-phenylene, Z must represent monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, tetramethylbenzyl, monohalobenzyl, or dihalobenzyl; Z' represents a dissimilar moiety selected from the group designated by Z, and R' represents 1,3-phenylene, methyl-1,3-phenylene, 4-ethyl-1,3-phenylene, or 4-isopropyl-1,3-phenylene. The terms "alkyl" and "halo" as employed in the present specification and claims represent an alkyl moiety having from one to six carbon atoms, inclusive, and a halogen selected from the group consisting of bromine or chlorine. The new N,N,N',N'-tetrabenzyl-1,3-phenylenediamines and N,N'-dialkyl-N,N'-dibenzyl-1,3-phenylenediamines of the present invention are hereinafter referred to as substituted 1,3-phenylenediamines for the sake of convenience. These new substituted 1,3-phenylenediamines are oils, noncrystalline solids or crystalline solids which are soluble in various common organic liquids and substantially insoluble in water.

The new N,N,N',N'-tetrabenzyl-1,3-phenylenediamines of the present invention corresponding to the formula ##SPC2##

are prepared by reacting a 1,3-phenylenediamine corresponding to the formula H.sub.2 N-R-NH.sub.2 with a benzyl halide corresponding to the formula Z-X, where X represents bromine or chlorine. The reaction between the 1,3-phenylenediamine and benzyl halide takes place readily in an inert organic solvent as reaction medium and at temperatures within the range of from 40.degree. to 150.degree. C. with the production of the desired substituted 1,3-phenylenediamine product and the hydrogen halide of reaction. The temperature of the reaction mixture is maintained within the reaction temperature range for from 1 to 4 hours and conveniently until there is a substantial cessation in the production of the hydrogen halide of reaction.

The proportions of the reactants to be employed are not critical, some of the desired product being produced when the reactants are contacted together in any proportions. The reaction consumes 4 molar proportions of a benzyl halide such as benzyl chloride or benzyl bromide for each molar proportion of 1,3-phenylenediamine; however, in a preferred procedure the benzyl halide is employed in an amount slightly in excess (about 10 percent) of the stoichiometric amount necessary to react with all of the 1,3-phenylenediamine. The use of a larger excess of the benzyl halide does not adversely affect the yield or the desired product.

In carrying out the reaction, the benzyl halide and 1,3-phenylenediamine are dispersed in the inert organic reaction medium in any order or fashion. Representative inert organic liquids include ethanol, methyl cellosolve, 2-propanol, and methanol. It is preferred that the solvents be at least slightly polar in nature. Following the addition of the reactants to the reaction medium the resulting reaction mixture is heated at a temperature within the reaction temperature range. In a convenient procedure, the reaction mixture is heated at the reflux temperature of the reaction mixture. In order to obtain optimum yields, a base such as sodium hydroxide or potassium hydroxide is added to the reaction mixture in order to neutralize the reaction mixture and prevent the formation of the hydrohalide salt of the 1,3-phenylenediamine starting material. In a convenient procedure, the temperature of the reaction mixture is maintained within the reaction temperature range until there is a substantial cessation in the production of hydrogen halide byproduct as indicated by the amount of base, preferably an aqueous base, needed to neutralize the reaction mixture.

The water added to the reaction mixture with the aqueous base can be removed by azeotropic distillation with additional inert organic solvent being added to the reaction mixture to replace the solvent lost during the distillation. However, it is not necessary to remove the water from the reaction mixture as the product separates during the reaction period as an oil and can be easily isolated from the reaction mixture.

Following the reaction period, the desired product can be isolated from the reaction mixture by conventional procedures. In a convenient procedure, the oily product is separated by decantation and thereafter dissolved in an organic solvent such as acetone. The solvent solution is filtered to remove the salt byproduct formed during the neutralization procedure and cooled. During the cooling procedure, the product separates as an oil, noncrystalline solid, or crystalline solid. This product can then be further purified by such conventional procedures as washing, crystallization, distillation or recrystallization.

Mixed symmetrical substituted 1,3-phenylenediamines corresponding to the formula ##SPC3##

wherein Z is as previously described and Z' represents a dissimilar radical selected from the group comprising Z, are prepared by reacting an N,N'-disubstituted-1,3-phenylenediamine corresponding to the formula

Z-HN-R-NH-Z

with a benzyl halide corresponding to the formula Z'-X, wherein Z' represents a moiety from the group designated by Z which is different from the Z substituent on the N,N'-1,3-phenylenediamine. The N,N'-disubstituted-1,3-phenylenediamine starting material is prepared by the condensation of 1,3-phenylenediamine with the appropriate benzyl alcohol (Z-OH) according to the method of Y. Sprinzac, J. Am. Chem. Soc., 78, 3207(1956). The reaction between the N,N'-disubstituted-1,3-phenylenediamine and benzyl halide takes place in an inert organic solvent as the reaction medium and occurs readily at temperatures of from 40.degree. to 150.degree. C. and preferably at the boiling temperature of the reaction mixture. While the proportions of the reactants to be employed are not critical, optimum yields are obtained by employing the benzyl halide in an amount slightly in excess (about 10 percent) of the stoichiometric amount necessary to react with the N,N'-disubstituted-1,3-phenylenediamine. The reaction is carried out and the product isolated in the same manner as described for the other N,N,N',N'-tetrabenzyl-1,3-phenylenediamine products of the present invention.

The group of new N,N'-dialkyl-N,N'-dibenzyl-1,3-phenylenediamine compounds corresponding to the formula ##SPC4##

are prepared by reacting together N,N'-dialkyl-1,3-phenylenediamine and a benzyl halide corresponding to the formula Z-X, dispersed in an inert organic solvent such as ethanol, methyl cellosolve, or 2-propanol as reaction medium. The reaction proceeds readily at temperatures from 40.degree. to 150.degree. C., with the temperature of the reaction mixture being maintained within the reaction temperature range for from about 1 to 4 hours. During the reaction period, the reaction mixture is neutralized by the addition of aqueous base as previously described. Following the reaction period the desired product is isolated from the reaction mixture and further purified using the same procedures as previously described for the production of the N,N,N',N'-tetrabenzyl-1,3-phenylenediamines.

In a preferred procedure, N,N'-diethyl-N,N'-dibenzyl-1,3-phenylenediamine is prepared by ethylation of the appropriate N,N'-dibenzyl-1,3-phenylenediamine corresponding to the formula

Z-HN-R'-NH-Z.

The ethylation is carried out in an excess of the ethylating agent as reaction medium. Representative ethylating agents include triethylphosphate and diethyl sulfate.

In carrying out the reaction, the reactants are contacted together at temperatures of from 150.degree. to 250.degree. C. for from 1 to 4 hours. However, in a convenient procedure, the reaction mixture is maintained at the reflux temperature for from 1 to 4 hours. Following the reaction period, the reaction mixture is treated with an aqueous base to hydrolyze the polyphosphates formed during the reaction period and to facilitate the isolation of the desired product. During the hydrolysis procedure, the desired product separates in the reaction mixture as an oily residue which is then extracted from the reaction mixture with ether. The ether extract is then dried and fractionally distilled to obtain the desired product.

As previously stated the new substituted-1,3-phenylenediamine products of the present invention are oils, noncrystalline solids or crystalline solids. It has been found that when seed crystals for the oils and noncrystalline materials are obtained, the oils and noncrystalline products can be caused to readily crystallize. The oils and noncrystalline solids are conveniently prepared for use as photoconductors as follows: the oil or noncrystalline solid is dissolved in an organic solvent and the solvent solution washed with water to remove any salt remaining in the product. In those cases where it is found that the product does not form a crystalline solid the reaction mixture is diluted with water to remove ionic materials. The recovered oil is then washed with an alcohol such as methanol or ethanol. The washed oil is then dissolved in chloroform and the chloroform solution dried, filtered, stripped of low boiling constituents to yield the product as an oily residue. This residue can then be dissolved in an organic solvent and employed as a photoconductor as described in the present specification and claims.

Representative benzyl halides to be employed as starting materials for the production of the substituted 1,3-phenylenediamines include 4-chlorobenzyl chloride, 4-methylbenzyl chloride, 2,5-dimethylbenzyl chloride, 4-bromobenzyl bromide, 2,3,5,6-tetramethylbenzyl bromide, 2,3,4,5-tetramethylbenzyl chloride, 2-chlorobenzyl chloride, 3,4-dichlorobenzyl chloride, 3,5-dibromobenzyl bromide and 3-chlorobenzyl chloride.

b. Electrophotographic Material.

The new electrophotographic material of the present invention is comprised of a conductive support layer, being coated on at least one surface thereof with a photoconductive insulating layer, said photoconductive insulating layer being comprised of an insulating resin binder, and a substituted 1,3-phenylenediamine or N,N,N',N'-tetrabenzyl-1,3-phenylenediamine.

The substituted 1,3-phenylenediamines correspond to ##SPC5##

N,n,n',n'-tetrabenzyl-1,3-phenylenediamine and N,N'-di-o-xylylene-1,3,-phenylenediamine have been found to be useful as organic photoconductors. The new substituted 1,3-phenylenediamines, N,N'-di-o-xylylene-1,3-phenylenediamine and N,N,N',N'-tetrabenzyl-1,3-phenylenediamine will be referred to as TSMPD for the sake of convenience. The TSMPD compounds generally absorb the lower end of the ultraviolet spectrum (i.e., 3300 A. and below). Therefore, when it is desired to shift the spectral response of the electrophotographic product of the present invention to a longer wavelength, an electron-accepting sensitizing agent is added to the TSMPD-containing photoconductive layer. The sensitizer compounds serve as electron acceptors, and in addition to shifting the spectral response, these sensitizers facilitate mobile charge carrier transport, thereby increasing the efficiency of the system. Representative sensitizers are the substituted fluorene compounds such as 9-fluorenone, 2,4,7-trinitro-9-fluorenone and 2-nitrofluorene; and substituted stilbenes such as 2,4,3'-trinitrostilbene, 2,4-dinitrostilbene, and 2,4,6-trinitrostilbene and substituted benzothiazoles such as 2-styrylbenzothiazole, 3-nitrophenylbenzothiazole, 2-phenylbenzothiazole, 2-(3'-nitrophenyl)-benzothiazole, 2-(4'-dimethylamino)-benzothiazole, 4-phenylbutadienyl-2-benzothiazole, 2-styrylquinoline, p-nitroacetophenone, 1,1-dicyano-4-phenylbutadiene, 9,10-phenanthrenedione, 3,5-dinitromethyl benzoate, 2,4-dinitrophenyl sulfide, 2,4,4'-trinitrodiphenyl ether, bis(3-nitrophenyl) disulfide bis(4-chloro-2-nitrophenyl) disulfide, and cyanine dyes, such as Orthochrome T, pinacyanol, Kryptacyanine, and ethyl red.

In preparing the photoconductive insulating layers the TSMPD compounds and the sensitizer, if utilized, are employed in association with a resin or synthetic polymer, for example: natural resins, synthetic resins (including copolymers) such as the polystyrenes or polystyrene copolymers including styrene-butadiene, styrene-butadiene-acrylonitrile; acrylates, polyvinyl acetals, polycarbonates, polyphenylene oxide, phenoxy resins, polysulfones, polyesters and other synthetic polymeric resinous materials.

The TSMPD photoconductive substances and sensitizers when used for preparation of the photoconductive insulating layer are preferably so used in solution in organic solvents, such as for example ethanol, benzene, chloroform, acetone, toluene, methylene chloride, methyl ethyl ketone or ethylene glycol monomethyl ether. Mixtures of two or more TSMPD compounds may be employed. Mixtures of solvents may also be used. It is also possible to employ the photoconductive substances in association with other organic photoconductive substances.

In producing the electrophotographic plate or sheet material of the present invention the TSMPD compound or mixture thereof is employed in an amount equivalent to from 0.01 to 200 or more percent by weight with respect to the resinous binder. In many cases the photoconductive TSMPD compound or mixture thereof may be employed at greater than 200 percent with advantageous results. The amount of TSMPD to be employed will depend upon the system in which the product is being utilized, i.e. the particularly light source, the length of exposure, the particular TSMPD compound being used, etc.

The amount of electron-acceptor sensitizing agent to be utilized will vary depending upon such factors as the sensitizer, the TSMPD, the light source and the length of exposure. The TSMPD compounds of the present invention can be employed without the use of a sensitizer at 3600 A. or below. However, it is generally desirable to employ a sensitizer to shift the spectral response. In such cases the amount employed will be within the range of from 0.01 to 20 percent by weight of the TSMPD compound.

The support may be of any material suitable for use in electrophotographic processes, for example, aluminum or other metal plates or foils, plastic foil and preferably paper sheets or webs. When paper is to be used as a support for the photoconductive layer, it is preferable that it shall have been pretreated against penetration by the coating solution, for example with methyl-cellulose in aqueous solution; polyvinyl alcohol in aqueous solution; a solution in acetone and methyl ethyl ketone of a mixed polymer of acrylic acid methyl ester and acrylonitrile; or with solutions of polyamides in aqueous alcohols or a coating containing some conductive polymer such as polyvinylbenzyltrimethylammonium chloride. Solutions of the photoconductive substances and insulating resins in organic solvents are applied to the support by known methods (for example, by spraying, reverse-roll coating, or whirl coating). Following the coating procedure, the coating thus prepared is dried.

The photoconductive layers are usually charged positively or negatively by means of a corona discharge. The light sensitivity of the thus obtained photoconductive layers lies mainly in the range of 3,000 to 7,000 A. Very good images may be obtained by a short exposure using a positive or negative to a conventional electrophotographic light source such as a high-pressure mercury vapor lamp, tungsten lamp or the like.

The latent image so produced may be developed in known fashion by the application of dry powder or liquid toner.

The following examples are merely illustrative and are not deemed to be limiting.

PREFERRED EMBODIMENTS

Example 1.

Meta-phenylenediamine (10.8 grams, 0.1 mole) and benzylchloride (50.6 grams, 0.4 mole) were dispersed in 70 ml. of methyl cellosolve. The reaction mixture thus prepared was then heated at the reflux temperature. Within a few minutes the acid salt began to precipitate in few reaction mixture. This acid salt was neutralized by the periodic addition of an aqueous sodium hydroxide (20 grams, 0.5 mole in 20 ml. of water). The refluxing of the reaction mixture was continued throughout the addition of the aqueous base. The water so added was removed by azeotropic distillation, with additional methyl cellosolve added to the reaction mixture slowly portionwise. After refluxing for one hour, 0.1 mole of benzyl chloride was added to the reaction mixture and the refluxing continued for an additional hour. Following the reaction period, the reaction period, the reaction mixture was filtered while hot to remove the precipitated sodium chloride, and the filtrate recovered. The filtrate was allowed to cool whereupon an oily product began to separate. Acetone was added to the filtrate to keep the oily product in solution. The filtrate was then cooled in an ice bath and seed crystals were added to initiate the crystallization of the desired product. The solid product was isolated by filtration and recrystallized from a solution of equal parts of acetone and ethanol. The recrystallized N,N,N',N'-tetrabenzyl-1,3-phenylenediamine was found to melt at 99-100.degree. C.

In a similar manner, the following products of the invention are prepared by reacting 1,3-phenylenediamine with the appropriate substituted benzyl chloride corresponding to the formula Z-Cl:

N,N,N',N'-tetra-(2-methylbenzyl)-1,3-phenylenediamine (m.p.164.degree.-166.degree. C.)

N,N,N',N'-tetra-(4-methylbenzyl)-1,3-phenylenediamine (m.p.101.degree.-103.degree. C.) N,N,N',N'-tetra-(2-chlorobenzyl)-1,3-phenylenediamine (m.p. 173.degree.-175.degree. C.).

N,N,N',N'-tetra-(4-chlorobenzyl)-1,3-phenylenediamine (m.p.133.degree.-135.degree. C.)

N,N,N',N'-tetra-(2,5-dimethylbenzyl)-1,3-phenylenediamine (m.p.164.degree.-167.degree. C.)

N,N,N',N'-tetra-(3,4-dichlorobenzyl)-1,3phenylenediamine (m.p.126.degree.-128 .degree. C.)

N,N,N',N'-tetra-(3-methylbenzyl)-1,3-phenylenediamine (oil)

N,N,N',N'-tetra-(3,4-dimethylbenzyl)-1,3-phenylenediamine (oil)

N,N,N',N'-tetra-(2,3,5,6-tetramethylbenzyl)-1,3-phenylenediamine (m.p.129.degree.-149.degree. C.)

N,N,N',N'-tetra-(2,4,6-trimethylbenzyl)-1,3-phenylenediamine (m.p.183.degree.-193.degree. C.).

In other similar procedures, the following new compounds of the present invention are prepared by reacting (a) 4-methyl-1,3-phenylenediamine; or (b) 4-chloro-1,3-phenylenediamine; or (c) 4-isopropyl-1,3-phenylenediamine; or (d) 4-methoxy-1,3-phenylenediamine; or (e) 2-chloro-1,3-phenylenediamine; or (f) 4,5-dimenthyl-1,3-phenylenediamine with the appropriate substituted benzyl chloride.

a. N,N,N',N'-tetrabenzyl-4-methyl-1,3-phenylenediamine (m.p.94.degree.-97.degree. C.)

N,N,N',N'-tetra-(2-methylbenzyl)-4-methyl-1,3-phenylenediamine (m.p.117.degree.-119.degree. C.)

N,N,N',N'-tetra-(4-chlorobenzyl)-4methyl-1,3-phenylenediamine (m.p. 110.degree.-111.degree. C.)

N,N,N',N'-tetra-(2,5-dimethylbenzyl)-4-methyl-1,3-phenylenediamine (m.p. 158.degree.160.degree. C.)

b. N,N,N',N'-tetrabenzyl-(4-chloro-1,3-phenylenediamine) (m.p. 107.5.degree.-109.5.degree. C.)

N,N,N',N'-tetra-(2-methylbenzyl)-4-chloro-1,3-phenylenediamine (m.p. 129.degree.-132.degree. C.)

N,N,N',N'-tetra-(2,5-dimethylbenzyl)-4-chloro-1,3-phenylenediamine (m.p. 158.degree.-160.degree. C.)

c. N,N,N',N'-tetrabenzyl-(4-isopropyl-1,3-phenylenediamine) (m.p.112.degree.-114.degree. C.)

N,N,N',N'-tetra-(2-chlorobenzyl)-4-isopropyl-1,3-phenylenediamine (m.p. 134.degree.-137.degree. C.)

N,N,N',N'-tetra-(4-methylbenzyl)-4-isopropyl-1,3-phenylenediamine (oil)

d. N,N,N',N'-tetrabenzyl-(4-methoxy-1,3-phenylenediamine) (m.p. 115.degree.-117.degree. C.)

e. N,N,N',N'-tetrabenzyl-(2-chloro-1,3-phenylenediamine) (m.p. 106.degree.-108.degree. C.)

f. N,N,N',N'-tetrabenzyl-(4,5-dimethyl-1,3-phenylenediamine) (oil)

Example 2.

N,N'-diisopropyl-1,3-phenylenediamine (4grams, 0.0021 mole) and 2,5-dimethylbenzyl chloride (7.16 grams, 0.0046 mole) were dispersed in 20 milliliters of ethanol. The reaction mixture thus prepared was heated at the reflux temperature for 1.5 hours. During the reflux period the reaction mixture was periodically neutralized by the addition of aqueous sodium hydroxide. Following the reaction period, the reaction mixture was filtered while hot and the filtrate cooled. The oily product which separated from the filtrate was washed with water and ethanol. The oily product was then dissolved in chloroform, dried over sodium sulfate, and distilled under reduced pressure to remove the low-boiling constituents and obtain the N,N'-diisopropyl-N,N'-di-(2,5-dimethylbenzyl)-1,3-phenylenediamine product as an oil.

In further operations, using the procedure set forth in the previous paragraph the following compounds of the present invention are prepared:

N,N'-di-sec.-butyl-N,N'-dibenzyl-1,3-phenylenediamine (oil) by reacting together N,N'-di-sec.-butyl-1,3-phenylenediamine and benzyl chloride.

N,N'-di-sec.-butyl-N,N'-di(2-chlorobenzyl) phenylenediamine (an oil) by reacting together N,N'-di-sec.-butyl-1,3-phenylenediamine and 2-chlorobenzyl chloride.

N,N'-diisopropyl-N,N'-dibenzyl-1,3-phenylenediamine (an oil) by reacting together N,N'-diisopropyl-1,3-phenylenediamine and benzyl chloride.

Example 3.

N,N'-dicyclohexyl-1,3-phenylenediamine (10 grams, 0.037 mole) and 2,5-dimethylbenzyl chloride (15.5 grams, 0.1 mole) were dispersed in 25 milliliters of methyl cellosolve and the reaction mixture thus prepared heated at the reflux temperature for 2 hours. During the reflux period, aqueous sodium hydroxide (4 grams in 7 milliliters of water) was added periodically to neutralize the reaction mixture. Following the reflux period, 10 milliters of methyl cellosolve was added to the reaction mixture and the mixture filtered while hot. The filtrate thus obtained was allowed to cool whereupon the N,N'-dicyclohexyl-1,3-phenylenediamine product separated as an oil. This oily product was collected by decantation, washed with ethanol and water and dissolved in chloroform. This chloroform solution was evaporated to dryness to obtain the N,N'-dicyclohexyl-N,N'-di-(2,5-dimethylbenzyl-1,3-phenylenediamine product as a glassy noncrystalline solid.

In a similar procedure, the N,N'-dibenzyl-N,N'-dicyclohexyl-1,3-phenylenediamine (oil) was prepared by reacting N,N'-dicyclohexyl-1,3-phenylenediamine with benzyl chloride.

Example 4.

n,n'-dibenzyl-1,3-phenylenediamine (10 grams, 0.035 mole) and 2,5-dimethylbenzyl chloride (12.5 grams, 0.08 mole) were dispersed in 50 milliliters of isopropanol and the resulting mixture heated at the reflux temperature for 2.5 hours. Aqueous potassium hydroxide was periodically added to the reaction mixture. Following the reflux period the oil which separated in the reaction mixture during the reflux period was taken up in hot acetone and the hot acetone solution was filtered. The filtrate was then allowed to cool, whereupon the N,N'-dibenzyl-N,N'-di-(2,5-dimethylbenzyl)-1,3-phenylenediamine product precipitated as a crystalline solid. This solid product was recrystallized from an acetone-ethanol mixture and the recrystallized product found to melt at 124.degree.-126.degree. C.

Example 5.

N,N'-dibenzyl-1,3-phenylenediamine (25 grams, 0.087 mole) and triethyl phosphate (15.9 grams, 0.087 mole) were placed in a reaction vessel and heated until the exothermic reaction started, whereupon the heat was removed. The reaction was allowed to proceed for about 10 minutes and then -phenylenediamine was heated at the reflux temperature for about 50 minutes. Following the reflux period, aqueous sodium hydroxide (12 grams NaOH in 50 ml. of water) was added to the reaction mixture and the mixture thereafter heated for 1 hour. During the heating period an oily product separated in the aqueous mixture. Following this heating period the aqueous mixture and oily product were allowed to cool. The oily product was then extracted with diethyl ether, the ether layer washed with water, dried over sodium sulfate and fractionally distilled. The N,N'-diethyl-N,N'-dibenzyl-1,3-phenylenediamine product distilled over at 225.degree.-235.degree. C. at 0.1 mm. of mercury.

Example 6.

A photoconductive insulating coating was prepared by mixing

Toluene 11 .9 liters Polystyrene (Dow Chemical Co. 2 .3 kilograms styron 666u) N,N,N',N'-tetrabenzyl-1,3- 1 0.6 kilogram phenylenediamine 9,10-phenanthrenedione 4grams (dissolved in 200 milliliters of chloroform)

The above-listed constituents were thoroughly mixed to provide a uniform coating composition. This coating composition was applied by means of a reverse-coil coater to one side of a 34-pound paper base stock having on each side thereof a 10-pound base coating of clay, titanium dioxide, polyvinyl alcohol and electrically conductive polyvinyl benzyl trimethyl ammonium chloride. The photoconductive insulating coating was applied in an amount equivalent to 5 pounds dry weight of coating per ream (25 inches X 38 inches--500 sheets). This paper yielded a clear image upon exposure using 200-watt high-pressure mercury light source (microfilm projection exposure) for 5 seconds. The imaged paper was very stable showing barely discernable discoloration after 30 minutes in a Fade-ometer Microfilm projection exposures were effected using silver, Kalvar and diazo microfilms.

In another operation, a photoconductive coating varying from the above described coating only by having 4 grams of 2,4,3'-trinitrostilbene in place of the 9,10-phenanthrenedione was prepared and coated on the same body stock. This paper yielded a clear image which did not discolor appreciably when placed in the Fade-ometer for 30 minutes.

Example 7.

N,N,N',N'-tetra-(2-methylbenzyl)-1,3-phenylenediamine (0.25 grams), tetramethylthiuram disulfide, toner set, (0.07 grams) and 2-styrylbenzothiazole (0.03 gram) were dissolved in 20 grams of a polymer solution comprised of polystyrene (Dow Chemical Company, Styron 666U) dissolved in 108 milliliters of chloroform. The coating composition was mixed thoroughly and thereafter applied to a paper base sheet by means of a No. 20 Meyer bar. The coating was then dried, charged by means of a corona discharge and imaged through a transparency by means of a high-pressure mercury vapor lamp for a period of 10 seconds. The imaged surface was then treated with a standard, commercial liquid toner. A sample of the paper thus produced was placed in the Fade-ometer for 30 minutes with only very slight discoloration.

Example 8.

A coating composition is prepared by mixing 1 part by weight of N,N,N',N'-tetra-(4-methylbenzyl)-1,3-phenylenediamine, 3 parts by weight of polysulfone P-4700 (manufactured by the Union Carbide Corporation), 0.0005 part by weight of 2,4,3'-trinitrostilbene, and 15 parts by weight of toluene as a solvent. This coating composition is applied to a suitable paper substrate which has been base-coated with 8 pounds (dry weight) per ream (25 inches X 38 inches--500 sheets) of a coating comprised of 70 parts by weight of polyvinyl alcohol, 20 parts by weight of calcium carbonate and 10 parts by weight of polyvinyl benzyl trimethyl ammonium chloride.

A positive print is made by negatively charging the coated paper by means of a corona discharge, and subsequently exposing the paper sheet through a positive transparency to a high-pressure mercury light source at 22 cm. for 4 seconds.

The latent electrostatic image thus produced is developed by applying thereto a dry, positively charged thermoplastic resinous toner (comprising carbon black particles coated with thermoplastic resin). The toner thus applied is attracted to the latent image areas producing a visible image which is permanently fixed by heating the thermoplastic toner on the sheet surface at a temperature of 100.degree.--130.degree. C for short time which solidly fuses the toner.

The clear print thus prepared shows no appreciable discoloration when placed in a Fade-ometer for 30 minutes. developing produced the positively

In another variation of the procedures of this example, all steps are repeated as described above except that the coated paper is positively charged, and the developing toner is negatively charged. Clear images are produced when the positively charged paper is developed with the negative toner.

It is a unique characteristic of the coatings of the present invention that in addition to the clear images obtained by oppositely charged electrophotographic sheets and toner, excellent results may be obtained by employing sheets and toner having like charges. Thus, positively charged paper and positive toner may be employed in one variation, and negatively charged paper and negative toner in yet another. Both of these like charged combinations produce clear, sharp images with no appreciable discoloration in light and oxygen for substantial periods of time.

Example 9.

In another example, a coating composition is prepared by mixing 2 parts by weight of tetrabenzyl-1,3-phenylenediamine, 3 parts by weight of polyvinyl butyral (Butvar B-76, manufactured by the Monsanto Chemical Company) as a resinous binder, 0.002 parts by weight of a sensitizing dye (ethyl red), and 15 parts by weight of a solvent for the above composition, which solvent component is comprised of 9 parts by weight of toluene and 6 parts by weight of methyl ethyl ketone.

This coating composition is applied to one side of a web of bleached paper bodystock having a basis weight of 40 pounds per ream, and previously coated with 8 pounds (dry weight) per ream of the base coating described in Example 8.

The paper sheet thus coated is negatively charged by means of a corona discharge, and charged sheet is then exposed through a positive transparency to a 60-watt tungsten lamp at a distance of 22 cm. for 15 seconds.

The latent image thus produced in selected areas of the copy sheet is developed by applying to the exposed surface a positively charged liquid toner comprised of an oxidizing oil which has been intimately admixed with a colored body (carbon black), this composition having been dispersed in a strongly insulating liquid (deodorized kerosene). The particles of oil and carbon black are attracted to the laten image areas in the exposed sheet, and a clear, sharp visible image is produced. No heat-fusing step is necessary in this method as the oil quickly hardens and adheres permanently upon exposure to air.

The thus produced is placed in a Fade-ometer for 60 minutes with only very slight discoloration.

Example 10.

The various TSMPD compounds and sensitizers listed below were made into coating compositions by dissolving 0.5 gram of the TSMPD and 1.5 grams of polystyrene in 12 milliliters of chloroform. In the resulting solution the sensitizer was dissolved in a quantity expressed as percent weight based on the weight of TSMPD present. In each case the solution was spread on a paper base sheet by means of a No. 20 Meyer bar, about 3 to 4 pounds dry weight per ream, being applied. ---------------------------------------------------------------------------

Amount of TSMPD Compounds Sensitizer Sensitizer in % of TSMPD N,N,N',N'-tetra(2,5-dimethyl benzyl)-4-methyl-1,3-phenylenediamine 2-styrylbenzothiazole 2% N,N,N',N'-tetrabenzyl-4-isopropyl-1,3-phenylenediamine 2-styrylkenzothiazole 2% N,N,N',N'-tetrabenzyl-4-methoxy-1,3-phenylenediamine 2-styrylbenzothiazole 2% N,N'-dicyclohexyl-N,N'-dibenzyl-1,3-phenylenediamine 9,10-phenanthrenedione 0.5 N,N'-diethyl-N,N'-dibenzyl-1,3-phenylenediamine 9,10-phenanthrenedione 0.5 N,N,N',N'-tetrabenzyl-1,3-phenylenediamine 2,4-dinitrostilbene 1 N,N,N',N'-tetrabenzyl-1,3-phenylenediamine 2-strylbenzothiazole 1 N,N'-dibenzyl-N,N'-(2,5dimethyl benzyl)-1,3-phenylenediamine 9,10-phenanthrenedione 0.5 N,N,N',N'-tetra(3,4-dichloro-benzyl)-1,3-phenylenediamine 2-styrylbenzothiazole 2 N,N,N',N'-tetra(2-methyl benzyl)-1,3-phenylenediamine 2-styrylbenzothiazole 2 N,N,N',N'-tetra(4-chloro-benzyl)-4-methyl-1,3-phenylenediamine 2-styrylbenzothiazole 2 __________________________________________________________________________

Each of these sheets was charged negatively by a corona discharge, imaged through a positive transparency by means of ultraviolet light for 5 seconds. The image was then developed with a positive liquid toner. All sheets gave a clean well-defined image which did not discolor appreciably when placed in a Fade-ometer for 30 minutes.

Example 11.

In further operations a photoconductive coating was prepared by combining N,N,N',N'-tetra-(2,5-dimethylbenzyl)-1,3-phenylenediamine (0.5 gram), polyvinyl butyral (21.5 grams of a solution comprised of 12 grams of polymer in 108 ml. chloroform) and 2-(-4-diethylaminobenzylidene)-picoline methiodide. The coating thus prepared was applied to the base stock described in example 6 by means of a No. 20 Meyer bar. The sheet was charged to 800 volts and showed little dark decay and retained 15 volts after 10 seconds of exposure to visible light. No discoloration was observed after 15 minutes in the Fade-ometer.

The Fade-ometer employed to test the electrophotographic materials of the present invention is an Atlas Color Fade-ometer, Type FDA-R sold by Atlas Electric Devices Company.

The starting 1,3-phenylenediamine and benzyl halide starting materials employed in the present invention are all produced in accordance with procedures well known in the art.

The N,N'-dialkyl-1,3-phenylenediamine starting materials are prepared by a modification of the Jones and Cowie method (German Pat. No. 927,165). The modified procedure comprises reacting a ketone such as acetone, methyl ethyl ketone, cyclohexanone and the like with a 1,3-phenylenediamine in the presence of platinum oxide as a catalyst. The reaction is carried out for 8 hours in an excess of the ketone as reaction medium in a high-pressure reactor at a temperature of 160.degree. C. and under hydrogen at a pressure of 300 pounds per square inch.

Example12.

1,3-phenylenediamine (2.80 grams, 0.26 mole) and .alpha.,.alpha.' dichloro-o-xylene (10 grams, 0.057 mole) were dispersed with stirring in 40 milliliters of methyl cellosolve. The reaction mixture was heated at 90.degree. C. for 1 hour. During the heating period aqueous sodium hydroxide was periodically added to the reaction mixture. The product precipitated as a crystalline solid in the reaction mixture during the heating period. The reaction mixture was filtered and the filter cake washed with water to remove the salts, and remaining solid product was recrystallized from chloroform-ethanol mixture. The recrystallized N,N'-di-o-xylylene-1,3-phenylenediamine product was found to melt at 232.degree.-235.degree. C.

Claims

We claim:

1. An electrophotographic material comprising a relatively more conductive support having a photoconductive insulating layer thereon which comprises a photoconductor selected from the class consisting of N,N'-di-o-xylylene-1,3-phenylenediamine and substituted 1,3-phenylenediamines having the general formula: ##SPC6##

wherein R is a divalent arylene group selected from the class consisting of 1,3-phenylene; 4-methyl-1-3,phenylene; 4-ethyl-1,3-phenylene; 4-halo-1,3phenylene; 4-isopropylene-1,3-phenylene;4-methoxy-1,3phenylene; 2-halo-1,3-phenylene; and 4,6-dimethyl-1,3-phenylene; R' is a divalent arylene group selected from the class consisting of 1,3-phenylene; 4-methyl-1,3-phenylene; 4-ethyl-1,3-phenylene and 4-isopropyl-1,3-phenylene; Z is an aralkyl group selected from the class consisting of benzyl, monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, monohalobenzyl and dihalobenzyl; and "alkyl" represents an alkyl group containing from one to six carbon atoms.

2. An electrophotographic material as claimed in claim 1 wherein the insulating layer contains an electron-acceptor sensitizing agent.

3. An electrophotographic material as claimed in claim 2 wherein the photoconductive insulating layer comprises a photoconductor having the general formula ##SPC7##

wherein R is a divalent arylene group selected from the class consisting of 1,3-phenylene, 4-methyl-1,3-phenylene, 4-ethyl-1,3-phenylene, 4-halo-1,3-phenylene, 4-isopropyl-1,3-phenylene, 4-methyloxy-1,3-phenylene, 2-halo-1,3-phenylene and 4,6-dimethyl-1,3-phenylene and Z is an aralkyl group selected from the class consisting of benzyl, monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, tetramethylbenzyl, monohalobenzyl and dihalobenzyl.

4. An electrophotographic material as claimed in claim 3 wherein the photoconductive insulating layer comprises a photoconductor having the general formula ##SPC8##

wherein R is a divalent arylene group selected from the class consisting of 1,3-phenylene, 4-methyl-1,3-phenylene, 4-ethyl-1,3-phenylene, 4-halo-1,3-phenylene, 4-isopropyl-1,3-phenylene, 4-methyoxy-1,3-phenylene, 2-halo-1,3-phenylene and 4,6-dimethyl-1,3-phenylene; Z is an aralkyl group selected from the class consisting of benzyl, monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, and tetramethylbenzyl, monohalobenzyl and dihalobenzyl; and Z' is a dissimilar aralkyl group selected from the group designated by Z.

5. An electrophotographic material as claimed in claim 2 wherein the photoconductive insulating layer comprises a photoconductor having the general formula ##SPC9##

wherein R' is a divalent arylene group selected from the class consisting of 1,3-phenylene, 4-methyl-1,3-phenylene, 4-ethyl-1,3-phenylene and 4-isopropyl-1,3-phenylene; Z is an aralky group selected from the class consisting of benzyl, monomethylbenzyl, dimethylbenzyl, trimethylbenzyl, tetramethylbenzyl, monohalobenzyl and dihalobenzyl; and "alkyl" represents an alkyl group containing from one to six carbon atoms.

6. An electrophotographic material as claimed in claim 2 wherein the electron acceptor is 9,10-phenanthrenedione.

7. An electrophotographic material as claimed in claim 3 wherein the photoconductor is N,N,N',N'-tetrabenzyl-1,3-phenylenediamine and the electron acceptor is 9,10-phenanthrenedione.

8. An electrophotographic material as claimed in claim 2 wherein the electron acceptor is 9-fluorenone, 2,4,7-trinitrofluorenone, or 2-nitrofluorenone.

9. An electrophotographic material as claimed in claim 3 wherein the photoconductor is N,N,N',N'-tetra-(4-methylbenzyl)-1,3-phenylenediamine or N,N,N',N'-tetra(2,5-dimethylbenzyl)-1,3-phenylenediamine.

10. An electrophotographic material as claimed in claim 2 wherein the electron acceptor is 2,4,3'-trinitrostilbene, 2,4-dinitrostilbene or 2,4,6-trinitrostilbene.