United States Patent (15) 3,647,432 Holstead (45) Mar. 7, 1972

(54) CARBAZOLYLMETHANEDYE SALTS 3,503,740 3/1970 De Selms et al...... 96/15 ASSENSTAERS FOR PHOTOCONDUCTOR COMPOSTIONS Primary Examiner-George F. Lesmes 72) Inventor: Colin Holstead, 37 Abbotts Road Abbotts Assistant Examiner-John C. Cooper, Langley, Walford, England Attorney-William H. J. Kline, James R. Frederick and Fred 22 Filed: Oct. 22, 1969 L. Denson 21 Appl. No.: 868,600 57 ABSTRACT 52 U.S.C...... 96/16,96/1.5, 96/1.7, Tris(9-alkylcarbazol-3-yl)methane dyes and tris(9-arylcar 260/215 bazol-3-yl)methane dyes enhance the sensitization of 51 int. Clk...... G03g S/06, G03g 5/08 photoconductive layers containing various photoconductors. 58 Field of Search...... 96/1.5-1.7; These materials are particularly useful in elements used in 260/315 electrophotographic processes. 56 References Cited 15Claims, NoDrawings UNITED STATES PATENTS 3,448,705 l/1970 Fox et al...... 96/1.6 3,647,432 1. 2 It is a further object of this invention to provide a process CARBAZOLYLMETHANEDYE SALTS ASSENSTIZERS for using novel sensitized photoconductive elements. FORPHOTOCONDUCTOR COMPOSITIONS These and other objects are accomplished by using either a This invention relates to electrophotography, and in par tris(9-alkyl carbazol-3-yl)methane dye or a tris(9-arylcar ticular to novel sensitized photoconductive compositions and bazol-3-yl)methane dye as a sensitizer for a photoconductive elements having coated thereon such compositions. composition. The carbazole nucleus of these dyes can be The process of xerography, as disclosed by Carlson in U.S. further substituted by additional groups such as alkoxy, Pat. No. 2,297,691, employs an electrophotographic element aryloxy, alkyl, acyl, halogen, etc. The use of photoconductive comprising a support material bearing a coating of a normally compositions containing the sensitizing dyes of this invention insulating material whose electrical resistance varies with the 10 in electrophotographic elements increases the speed of such amount of incident actinic radiation it receives during an elements when exposed in an electrophotographic process imagewise exposure. The element, commonly termed a compared to the speeds attainable when the sensitizer is ab photoconductive element, is first given a uniform surface sent. When the sensitizer is not present in the photoconduc charge, generally in the dark after a suitable period of dark tive layer, the resultant speed of the layer is frequently not fast adaptation. It is then exposed to a pattern of actinic radiation 15 enough to produce a developable electrostatic latent image. which has the effect of differentially reducing the potential of The preferred sensitizing dyes described herein have the fol the surface charge in accordance with the relative energy con lowing formula: tained in various parts of the radiation pattern. The dif ferential surface charge or electrostatic latent image remain ing on the electrophotographic element is then made visible 20 by contacting the surface with a suitable electroscopic mark R ing material. Such marking material or toner, whether con tained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or the absence of charge pattern as desired. 25 The deposited marking material may then be either per manently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor, or the R like, or transferred to a second element to which it may similarly be fixed. Likewise, the electrostatic latent image can 30 be transferred to a second element and developed there. Various photoconductive insulating materials have been employed in the manufacture of electrophotographic ele ments. For example, vapors of selenium and vapors of seleni um alloys deposited on a suitable support and particles of wherein: photoconductive zinc oxide held in a resinous, film-forming R represents any of the following binder have found wide application in present-day document 1. an aliphatic group having one to 18 carbon atoms e.g., copying applications. methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc. Since the introduction of electrophotography, a great many 40 including a substituted alkyl group having one to 18 car organic compounds have also been screened for their bonatoms such as photoconductive properties. As a result, a very large number a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propox of organic compounds are known to possess some degree of ymethyl, etc., photoconductivity. Many organic compounds have revealed a b. aryloxyalkyl e.g., phenoxyethyl, naphthoxymethyl, useful level of photoconduction and have been incorporated 45 phenoxypenty, etc., into photoconductive compositions. Optically clear organic c. aminoalkyl, e.g., aminobutyl, aminoethyl, photoconductor-containing elements having desirable elec aminopropyl, etc., trophotographic properties can be especially useful in elec d. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc., trophotography. Such electrophotographic elements may be e.aralkyl e.g., benzyl, phenethyl, etc., exposed through a transparent base if desired, thereby provid 50 f. alkylaminoalkyl C.9. methylaminopropyl, ing unusual flexibility in equipment design. Such composi methylaminoethyl, etc., and also including dial tions, when coated as a film or layer on a suitable support also kylaminoalkyl e.g., diethylaminoethyl, yield an element which is reusable; that is, it can be used to dimethylaminopropyl, propylaminooctyl, etc., form subsequent images after residual toner from prior images g. arylaminoalkyl, e.g., phenylaminoalkyl, diphen has been removed by transfer and/or cleaning. 55 ylaminoalkyl, N-phenyl-N-ethylaminopentyl N-phenyl Although some of the organic photoconductors comprising N-ethylaminohexyl, naphthylaminomethyl, etc., the materials described are inherently light sensitive, their h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc., degree of sensitivity is usually low and in the shortwavelength i. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyanoethyl, portion of the spectrum so that it is common practice to add materials to increase the speed and to shift the sensitivity 60 etc., toward the longer wavelength portion of the visible spectrum. j. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooc Increasing the speed and shifting the sensitivity of such tyl, etc., systems into the visible region of the spectrum has several ad k. alkyl substituted with an acyl group having the formula vantages: it makes available inexpensive and convenient light sources such as incandescent lamps; it reduces exposure time; 65 O it makes possible the recording of a wide range of colors in --R proper tonal relationship, and allows projection printing through various optical systems. By increasing the speed wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, through the use of sensitizers, photoconductors which would etc., lower alkyl having one to 8 carbon atoms e.g., methyl, otherwise have been unsatisfactory are useful in processes 70 ethyl, propyl, etc., amino including substituted amino e.g., where high speeds are required such as document copying. diloweralkylamino, lower alkoxy having one to 8 carbon It is therefore an object of this invention to provide novel atoms e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy, sensitized photoconductive elements. naphthoxy, etc.; or It is another object of this invention to provide novel sen 2. an aryl group, e.g., phenyl, naphthyl anthryl, fluorenyl, sitized photoconductive compositions. 75 etc., including a substituted aryl group such as 3,647,432 3 4 a. alkoxyaryl, e.g., ethoxyphenyl, methoxyphenyl, 5. substituted acyl such as those having the formula propoxynaphthyl, etc., b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl, phenoxynaphthyl, etc. - i. c. aminoaryl, e.g., aminophenyl, aminonaphthyl, aminoanthryl, etc., wherein R is hydroxy, halogen, e.g., chlorine, bromine, etc., d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydrogen, aryl e.g., phenyl, naphthyl, etc., amino including hydroxyanthryl, etc., substituted amino e.g., diloweralkylamino, lower alkoxy hav e. biphenylyl, ing one to 8 carbon atoms e.g., butoxy, methoxy, etc., aryloxy f. alkylaminoaryl, C-9., methylaminophenyl, 10 e.g., phenoxy, naphthoxy, etc., alkyl e.g., methyl, ethyl, methylaminonaphthyl, etc. and also including dial propyl, etc.; kylaminoaryl, e.g., diethylaminophenyl, 6. halogen such as chlorine, bromine, fluorine, or iodine; dipropylaminophenyl, etc., and arylaminoaryl, e.g., phenylaminophenyl, diphen X represents an acid anion such as a halide e.g., chloride, g. 5 bromide, fluoride, iodide, perchlorate, tetrafluoroborate, ylaminophenyl, N-phenyl-N-ethylaminophenyl, sulfamate, thiocyanate, p-toluenesulfonate, methyl sulfate, naphthylaminophenyl, etc., etc. h. nitroaryl e.g., nitrophenyl, nitronaphthyl, nitroanthryl, Typical dyes which belong to the herein described general etc., class of sensitizing compounds include the following: i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl, 20 cyanoanthry, etc., TABLE I j. haloary, e.g., chlorophenyl, bromophenyl, I. Tris(9-methylcarbazol-3-yl)methane dye chloronaphthyl, etc., II. Tris(9-methyl-6-methoxycarbazol-3-yl)methane dye k. aryl substituted with an acyl group having the formula III. Tris(9-methyl-6-phenoxycarbazol-3-yl)methane dye 25 IV. Tris(6,9-dimethylcarbazol-3-yl)methane dye V. Tris(6-acetyl-9-methylcarbazol-3-yl)methane dye -- VI. Tris(6-chloro-9-methylcarbazol-3-yl)methane dye wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, VII. Tris(9-ethylcarbazol-3-yl)methane dye etc., amino including substituted amino, e.g., dilloweral 30 VIII. Tris(9-ethyl-6-methoxycarbazol-3-yl)methane dye kylamino, lower alkoxy having one to 8 carbon atoms, e.g., IX. Tris(9-ethyl-6-phenoxycarbazol-3-yl)methane dye butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc., X. Tris(6,9-diethylcarbazol-3-yl)methane dye lower alkyl having one to 8 carbon atoms, e.g., methyl, ethyl, XI. Tris(6-acetyl-9-ethylcarbazol-3-yl)methane dye propyl, butyl, etc., XII. Tris(6-chloro-9-ethylcarbazol-3-yl)methane dye 1. alkaryl, e.g., tolyl, ethylphenyl, propyl, naphthyl, etc.; 35 XIII. Tris(9-phenylcarbazol-3-yl)methane dye R represents any of the following: XIV. Tris(9-phenyl-6-methoxycarbazol-3-yl)methane dye 1. an alkoxy group having one to 18 carbon atoms, e.g., XV. Tris(9-phenyl-6-phenoxycarbazol-3-yl)methane dye methoxy, ethoxy, propoxy, butoxy, etc.; XVI. Tris(6-acetyl-9-phenylcarbazol-3-yl)methane dye 2. an aryloxy group e.g., phenoxy, naphthoxy, etc.; XVII. Tris(6-chloro-9-phenylcarbazol-3-yl)methane dye 3. an aliphatic group having one to 18 carbon atoms e.g., 40 XVIII. Tris(6-methyl-9-phenylcarbazol-3-yl)methane dye methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc., Electrophotographic elements of the invention can be including a substituted alkyl group having one to 18 car prepared with any photoconductive compound and the sen bonatoms such as sitizers of this invention in the usual manner, i.e., by blending a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propox a dispersion or solution of the photoconductive compound ymethyl, etc., 45 together with a binder, when necessary or desirable, and coat b. aryloxyalkyl e.g., phenoxyethyl, naphthoxymethyl, ing or forming a self-supporting layer with the photoconduc phenoxypentyl, etc., tive composition. Generally, a suitable amount of the sensitiz c. aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl, ing compound is mixed with the photoconductive coating etc., composition so that, after thorough mixing, the sensitizing d. hydroxyalkyl e.g., hydroxypropy, hydroxyoctyl, etc., 50 compound is uniformly distributed throughout the desired e.aralkyl e.g., benzyl, phenethyl, etc., layer of the coated element. The amount of sensitizer that can f. alkylaminoalkyl e.g., methylaminopropyl, be added to a photoconductor-incorporating layer to give ef methylaminoethyl, etc., and also including dial fective increases in speed can vary widely. The optimum con kylaminoalkyl C-9., diethylaminoethyl, centration in any given case will vary with the specific dimethylaminopropyl, propylaminooctyl, etc., 55 photoconductor and sensitizing compound used. In general, g. arylaminoalkyl, e.g., phenylaminoalkyl, diphen substantial speed gains can be obtained where an appropriate ylaminoalkyl, N-phenyl-N-ethylaminopentyl, N-phen sensitizer is added in a concentration range from about 0.000 yl-N-ethylaminohexyl, naphthylaminomethyl, etc., to about 30 percent by weight of the film-forming coating h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc., composition. Normally, a sensitizer is added to the coating 60 composition in an amount of from about 0.005 to about 5.0 i. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyanoethyl, percent by weight of the total coating composition. j. haloalkyl,etc., e.g., chloromethyl, bromopentyl, chloroocw The sensitizers of this invention improve the electrical tyl, etc., speeds of compositions containing a wide variety of photocon k. alkyl substituted with an acyl group having the formula ductors including inorganic photoconductors such as zinc ox 65 ide, titanium dioxide, cadmium sulfide and the like and or ganic photoconductors including organometallic photocon in ductors. Mixtures of two or more photoconductors are also useful. wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, Typical additional photoconductors useful with the binders 70 etc., lower alkyl having one to 8 carbon atoms e.g., methyl, of A.this Arylamine invention are photoconductors described below. including substituted and ethyl, propyl, etc., amino including substituted amino e.g., unsubstituted arylamines, diarylamines, nonpolymeric tri dilloweralkylamino, loweralkoxy having one to 8 carbon atoms arylamines and polymeric triarylamines such as those e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, described in U.S. Pat. Nos. 3,240,597 and 3,180,730. etc., 4. hydrogen; 75 B. Photoconductors represented by the formula 3,647,432 5 6 D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula: wherein Z represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl 10 group having from one to about six carbon atoms (e.g., wherein R and R are each phenyl radicals including sub methyl, ethyl, propyl, butyl, etc.), an alkoxy group having stituted phenyl radicals, R. preferably having the formula: from one to about six carbon atoms (e.g. methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group; Z' represents a mononuclear or polynuclear monovalent or polynuclear 15 - -N monovalent aromatic radical, either fused or linear (e.g., N phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent (D-NC R aromatic radical wherein said substituent can comprise a member, such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl 20 group having from one to about six carbon atoms (e.g., wherein Ra and R4 are each aryl radicals, aliphatic residues of methyl, ethyl, propyl, butyl, etc.), an alkoxy group having one to 12 carbon atoms such as alkyl radicals preferably hav from one to about six carbon atoms (e.g., methoxy, propoxy, ing one to four carbon atoms, or hydrogen; particularly ad pentoxy, etc.) or a nitro group, Q can represent a hydrogen vantageous results being obtained when R is a phenyl radical atom or an aromatic amino group, such as Z'NH-; b 25 including a substituted phenyl radical and where R is diphen represents an integer from one to about 12, and L represents a ylaminophenyl, dimethylaminophenyl or phenyl, these materi hydrogen atom, a mononuclear or polynuclear aromatic radi als being more fully described in Fox Application U.S. Ser. cal, either fused or linear (e.g., phenyl, naphthyl, biphenyl, No. 613,846, now U.S. Pat. No. 3,526,501. etc.), a substituted aromatic radical wherein said substituent E. Nonionic cycloheptenyl compounds which may be sub comprises an alkyl group, an alkoxy group, an acyl group, or a 30 stituted with substituents such as: nitro group, or a poly(4'-vinylphenyl) group which is bonded 1. an aryl radical including substituted as well as unsub to the nitrogen atom by a carbon atom of the phenyl group, stituted aryl radicals, these materials being more fully described in U.S. Pat. No. 2. a hydroxy radical, 3. an azido radical, 3,265,496.C. Polyarylalkane photoconductors including leuco bases of 35 4. a heterocyclic radical having five to six atoms in the diaryl or triarylmethane dye salts, 1,1,1-triarylalkanes heterocyclic nucleus and at least one hetero nitrogen wherein the alkane moiety has at least two carbon atoms atom, and including substituted and unsubstituted and tetraarylmethanes having an amino group substituted heterocyclic radicals, and in at least one of the aryl nuclei attached to the alkane 5. an oxygen linked cycloheptenyl moiety. and methane moieties of the latter two classes of 40 The substitution on the cycloheptenyl nucleus occurs at an un saturated carbon atom when the cycloheptenyl moiety is a photoconductors which are nonleuco base materials; and conjugated triene with no aromatic structure fused thereto. also other polyarylalkanes included by the formula: However, if there is at least one aromatic structure fused to the cycloheptenyl moiety, then the substituents are attached D 45 to a saturated carbon atom. Additional photoconductors within this class are included in one of the following formulas: J--EG

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 50 of D, E and G containing an amino substituent, the aryl groups attached to the central carbon atom being preferably phenyl groups, although naphthyl groups can also be used including substituted aryl groups containing substituents such as alkyl and alkoxy typically having one to eight carbon atoms, 55 where E. and G can be either: hydroxy, halogen, etc., in the ortho, meta or para positions, 1. a phenyl radical, ortho-substituted phenyl being preferred; the aryl groups can 2. a naphthyl radical, also be joined together or cyclized to form a fluorene moiety, 3. a heterocyclic radical having five to six atoms in the for example; the amino substituent can be represented by the heterocyclic nucleus and at least one hetero nitrogen 60 aton, formula 4. a hydroxyl radical, or 5. an oxygen containing radical having a structure such that -N the resultant cycloheptenyl compound is a symmetrical N R ether; wherein each R can be an alkyl group typically having one to 65 D, can be any of the substituents defined for E and G above eight carbon atoms, a hydrogen atom, an aryl group, or and is attached to a carbon atom in the cycloheptenyl nucleus together the necessary atoms to form a heterocyclic amino having a double bond; (Rs and Rio), (R and R), (Rs and group typically having five to six atoms in the ring such as Rs), and (R and Rs) are together the necessary atoms to morpholino, pyridyl, pyrryl, etc.; at least one of D, E and G complete a benzene ring fused to the cycloheptenyl nucleus; preferably being a p-dialkyl-aminophenyl group, when J is an 70 these compounds being more fully described in U.S. Ser. No. alkyl group, such an alkyl group more generally has one to 654,091 filed July 18, 1967, now U.S. Pat. No. 3,533,786. seven carbon atoms, these materials being more fully F. Compounds containing an described in U.S. Pat. No. 3,274,000, French Pat. No. 1,383,461 and in U.S. Ser. No. 627,857 filed Apr. 3, 1967 by Y-NY Seus and Goldman. 75 / N 3,647,432 8 atoms. These organic photoconductors are more fully nucleus including: described in U.S. Ser. No. 664,642 filed Aug. 31, 1967, 1. unsubstituted and substituted N,N-bicarbazyls contain now U.S. Pat. No. 3,527,602. ing the substituents in either or both carbazolyl nuclei H. Triarylamines in which at least one of the aryl radicals is such as: substituted by either a vinyl radical or a vinylene radical a, an alkyl radical including a substituted alkyl radical having at least one active hydrogen-containing group. such as a haloalkyl or an alkoxyalkyl radical, The phrase "vinylene radical" includes substituted as well b. a phenyl radical including a substituted phenyl radi as unsubstituted vinylene radicals and also includes those cal such as a naphthyl, an aminophenyl or a hydrox radicals having at least one and as many as three repeat yphenyl radical, 10 ing units of vinylene groups such as -(CH = CH) c. a halogen atom, wherein n is an integer of from one to three. Groups d. an amino radical including substituted as well as un which contain active hydrogen are well known in the art, substituted amino radicals such as an alkylamino or a the definition of this term being set forth in several text phenylalkylamino radical, books such as "Advanced Organic Chemistry," R. C. e. an alkoxy radical, 15 Fuson, pp. 154-157, John Wiley & Sons, 1950. The term f, a hydroxyl radical, "active hydrogen-containing group' as used herein in g. a cyano radical, cludes those compounds encompassed by the discussion h, a heterocyclic radical such as a pyrazolyl carbazolyl in the textbook cited above and in addition includes those or a pyridyl radical; or compounds which contain groups which are hydrolyzable 2. tetra-substituted hydrazines containing substituents 20 to active hydrogen-containing groups. Typical active which are substituted or unsubstituted phenyl radicals, hydrogen-containing groups substituted on the vinylene or heterocyclic radicals having five to six atoms in the radical of the triarylamine include: hetero nucleus, suitable results being obtained when all 1. carboxy radicals, four substituents are not unsubstituted phenyl radicals, 2. hydroxy radicals, i.e., if at least one substituent is a substituted phenyl 25 3. ethynyl radicals, radical or a heterocyclic radical having five to six atoms 4. ester radicals (e.g., in the hetero nucleus. Other tetra-substituted hydrazines include those having the following formula: O D G1 30 --ora YN-N 1. N wherein Ra is alkyl or aryl) including cyclic ester radicals E1 J. (e.g., wherein D, E, G and J, are each either: O a. a substituted phenyl radical such as a naphthyl radi 35 cal, an alkyl phenyl radical, a halophenyl radical, a --or, hydroxyphenyl radical, a haloalkylphenyl radical or a hydroxyalkylphenyl radical, or wherein R. is a cyclic alkylene radical connected to a b. a heterocyclic radical such as an imidazolyl radical, a vinylene combination such as is found in coumarin deriva furyl radical, or a pyrazolyl radical. In addition J and 40 tives), E can also be. 5. carboxylic acid anhydride radicals, c. an unsubstituted phenyl radical. 6. semicarbazono radicals, Especially preferred are those tetra-substituted hydrazines 7. cyano radicals, wherein both D and G are either substituted phenyl radicals 8. acyl halide radicals (e.g., or heterocyclic radicals. These compounds are more fully 45 described in U.S. Ser. No. 673,962 filed Oct. 9, 1967, now O U.S.G. Pat.Organic No. 3,542,546. compounds having a 3,3'-bis-aryl-2-pyrazoline -(-C) nucleus which is substituted in either five-member ring with the same or different substituents. The one and five 50 , etc.), and positions on both pyrazoline rings can be substituted by 9. amido radicals (e.g., an aryl moiety including unsubstituted as well as sub Ris stituted aryl substituents such as alkoxyaryl, alkaryl, al - -N kaminoaryl, carboxyaryl, hydroxyaryl and haloaryl. The Ris 4-position can contain hydrogen or unsubstituted as well 55 wherein Ris is a hydrogen atom, an alkyl group or an aryl as substituted alkyl and aryl radicals such as alkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl, alkoxyalkyl, group). aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Other active hydrogen-containing groups include substituted Other photoconductors in this class are represented by and unsubstituted alkylidyne oximido radicals. Photoconduc 60 tors included in this class can be represented by the following the following structure: structure:

65

wherein: wherein: D, D, J, and Ja' can be either a phenyl radical including a 70 1. Art and Ar, are each a phenyl radical including a sub substituted phenyl radical such as a tolyl radical or a stituted phenyl radical such as a halophenyl radical, an naphthyl radical including a substituted naphthyl radical, alkyl phenyl radical or an aminophenyl radical, E, E, Ga, Ga", La and La can be any of the substituents set 2. Ars is an arylene radical including a substituted arylene forth above and in addition can be either a hydrogen radical such as a phenylene radical or a naphthylene radi atom or an alkyl radical containing one to eight carbon 75 cal, 3,647,432 10 3. Re and R are each hydrogen, a phenyl radical including Ara a substituted phenyl radical or a lower alkyl radical preferably having one to eight carbon atoms, N-Ar-x. 4. X is either: Ars a. an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a car boxylic acid anhydride radical, an ester radical, a cyano radical, a hydroxy radical, a semicarbazono radical, an wherein: ethynyl radical, or a methylidyne oximido radical, or a. Ar and Ars are each a phenyl radical including a sub b. hydrogen, provided that when X is hydrogen Rs and 10 stituted phenyl radical such as a halophenyl radical, an R17 are also hydrogen, and 5. n is an integer of one to alkyl phenyl radical or an amino phenyl radical, three. b. Are is an arylene radical including a substituted arylene The arylene nucleus can be substituted in any position by the radical such as a phenylene radical or a naphthylene radi vinyl or vinylene moiety. However, when Ara is phenylene, cal, and particularly good results are obtained if the substitution oc 15 c. X is an active hydrogen-containing group such as a car curs in the para position. These materials are more fully boxy radical, an acyl halide radical, an amido radical, a described in U.S. Ser. No. 706,800 filed Feb. 20, 1968. carboxylic acid anhydride radical, an ester radical, a I. Triarylamines in which at least one of the aryl radicals is cyano radical, a semicarbazono radical, a hydroxy radi substituted by an active hydrogen-containing group. The cal, an ethynyl radical, a methylidyne oximido radical or a term "active hydrogen-containing group' has the same 20 phenylene carboxy radical. meaning as set forth above and again includes those com These materials are more fully described in U.S. Ser. No. 706,780 filed Feb. 20, 1968. pounds encompassed by the discussion in the textbook J. Organometallic compounds having at least one amino and additionally includes those compounds which contain aryl substituent attached to a Group IVa or Group Va groups which are hydrolyzable to active hydrogen-con 25 metal atom. The metallic substituents of this class of or taining groups. Typical active hydrogen-containing ganic photoconductors are Group IVa or Group Va groups which are substituted on an aryl radical of the tri metals in accordance with the Periodic Table of the Ele arylamine include: ments (Handbook of Chemistry and Physics, 38th edi 1. carboxy radicals, tion, pp. 394-95) and include silicon, germanium, tin and 2. hydroxy radicals, lead from Group IVa and phosphorus, arsenic, antimony 3. ethynyl radicals, and bismuth from Group Va. These materials can be sub 4. ester radicals (e.g., stituted in the metallo nucleus with a wide variety of sub stituents but at least one of the substituents must be an O amino-aryl radical. The amino radical can be positioned --or, 35 anywhere on the aromatic nucleus, but best results are obtained if the aryl moiety is a phenyl radical having the wherein Rus is an alkyl or an aryl group), amino group in the four or para position. Typical sub 5. lower alkylene hydroxy radicals (e.g., having one to eight stituents attached to the metal nucleus include the follow carbon atoms), ing: 6. carboxylic acid anhydride radicals, 40 1. a hydrogen, sulfur or oxygen atom, 7. lower alkylene carboxy radicals (e.g., having two to eight 2. an alkyl radical, carbon atoms), 3. an aryl radical including unsubstituted as well as sub 8. cyano radicals, stituted aryl radicals such as aminoaryl alkylaryl and 9. acyl halide radicals (e.g., haloaryl, 45 4. an oxygen-containing radical such as an alkoxy or aryloxy O radical, 5. an amino radical including unsubstituted and substituted -(-C), amino radicals such as mono- and diarylamino and mono , etc.), and dialkylamino radicals, 10. amido radicals (e.g., 50 6. a heterocyclic radical, and R19 7. a Group IVa or Va organo metallic radical. Photoconduc --- tors included in this class can be represented by the fol Y. lowing structures: wherein Rus is a hydrogen atom, an alkyl group or an aryl 55 group), 11. lower alkylidyne oximido radicals having 1 to 8 carbon I atoms including substituted alkylidyne oximido radicals (1) T-A-Ma-D, (e.g., Gs 60 --NOH R20 (2) wherein Rois hydrogen or a lower alkyl radical), 12. semicarbazono radicals, and 65 13. arylene carboxy radicals including substituted arylene (3) carboxy radicals (e.g., -- Q5 D Es Es 70 (4) T-Ar-Ma-Ma-A r-T

E wherein D and E are phenyl or lower alkyl radicals. (5) Photoconductors included in this class can be represented by 75 the following structure: - Gs J 3,647,432 1. 12 4',4'-bis(diethylamino)-2,6-dichloro-2',2'-dimethyl (6) 4',4'-bis(diethylamino)-2',2'-dimethyldiphenylnaphthyltriphenylmethane - &J a 2,2'-dimethyl-4,4',4'-tris(dimethylamino)triphenylmethamethane where Es, Gs, L5 and Qs can be: ne a, a hydrogen atom, 4'-bis(diethylamino)-4-dimethylamino-2',2'-dimethyl b. an aryl radical including unsubstituted as well as sub triphenylmethane stituted aryl radicals such as a phenyl radical, a naphthyl 4',4'-bis(diethylamino)-2-chloro-2',2'-dimethyl-4- radical, a dialkylamino phenyl radical, or a di 10 dimethylaminotriphenylmethane arylaminophenyl radical, 4',4'-bis(diethylamino)-4-dimethylamino-2,2',2'- c. an alkyl radical having one to eight carbon atoms, trimethyltriphenylmethane d. an alkoxy radical having one to eight carbon atoms, 4',4'-bis(dimethylamino)-2-chloro-2',2'-dimethyltriphen e. an aryloxy radical such as a phenoxy radical, ylmethane 15 4',4'-bis(dimethylamino)-2',2'-dimethyl-4-methox f. an amino radical having the formula ytriphenylmethane bis(4-diethylamino)-1,1,1-triphenylethane bis(4-diethylamino)tetraphenylmethane N R22 ..',4'-bis(benzylethylamino)-2',2'-dimethyltriphenyl wherein R2 and R22 can be hydrogen atoms or alkyl radicals 4',4'-bis(diethylamino)-2',2'-diethoxytriphenylmethanemethane having one to 8 carbon atoms, or 4,4'-bis(dimethylamino)-1,1,1-triphenylethane g. a heterocyclic radical having five to six atoms in the 1-(4-N,N-dimethylaminophenyl)-1,1-diphenylethane hetero nucleus including at least one nitrogen atom such 4-dimethylaminotetraphenylmethane as a triazolyl, a pyridyl radical, etc., 25 4-diethylaminotetraphenylmethane T is an amino radical such as an alkylamino radical having 4,4'-bis(diphenylamino)chalcone one to eight carbon atoms or an arylamino radical such as 4-diphenylamino-4'-dimethylaminochalcone a phenylamino radical; 4-dimethylamino-4'-diphenylaminochalcone Are is an aromatic radical such as phenyl ornaphthyl; 4,4'-bis(dimethylamino)chalcone Ma and Ma are the same or different Group IV metals; 4,4'-bis(diethylamino)chalcone M is a Group Va metal; 4-diethylamine-4'-diphenylaminochalcone Ds can be any of the substituents set forth above for Es, Gs, 4-diphenylaminochalcone Ls and Qs and in addition can be a Group IVa or 4-dimethylaminochalcone ganometallic radical or, when taken with E, an oxygen 4'-diphenylaminochalcone atom or a sulfur atom; 35 4'-dimethylaminochalcone Js can be any of the substituents set forth above for Es, Gs, bis-(5-(5H-dibenzo(a,d)cycloheptenyl)ether Ls and Os and in addition can be when taken with E, an 5-hydroxy-5H-dibenzo(a,d)cycloheptene oxygen atom or a sulfur atom. These materials are 1-(5-(5H-dibenzo(a,d)cycloheptenyl)-4,5-dicar described in U.S. Ser. No. 650,664 filed July 3, 1967. bomethoxy-1,2,3-triazole K. Any other organic compound which exhibits photocon 40 1-(5-(5H-dibenzo(a,dicycloheptenyl)-4,5-dibenzoyl ductive properties such as 9-alkylcarbazoles and 9-aryl 1,2,3-triazole carbazoles and also those set forth in Australian Pat. No. 5-azido-5H-dibenzoad cycloheptene 248,402. 1-(5-(10,1 1-dihydro-5H-dibenzo(a,d)cycloheptenyl)-4,5- Representative organic photoconductors useful in this in dicarbomethoxy-1,2,3-triazole vention include the compounds listed below: 45 1-(5-(10,11-dihydro-5H-dibenzo(a,d)cycloheptenyl)-4,5- dibenzoyl-1,2,3-triazole TABLE 4-(5-(5H-dibenzo(a,dcycloheptenyl)-N,N- diphenylamine dimethylaniline dinaphthylamine N,N-diethyl-3-methyl-4-5-(5H-dibenzo(a,d)cyclohepteny N,N'-diphenylbenzidine 50 l)aniline N-phenyl-1-naphthylamine 4-5-(5H-dibenzo(a,d)cycloheptenyl)-1- N-phenyl-2-naphthylamine dimethylaminonaphthalene N,N'-diphenyl-p-phenylenediamine N,N-diethyl-3-methyl-4-5-(10,11-dihydro-5H. 2-carboxy-5-chloro-4'-methoxydiphenylamine dibenzoa,d)-cycloheptenyl)aniline p-anilinophenol 55 3-(4-dimethylaminopheynl)-1,3,5-cycloheptatriene N,N'-di-2-naphthyl-p-phenylenediamine 3-(4-diethylamino-2-methylphenyl)-1,3,5-cycloheptatriene 4,4'-benzylidene-bis-(N,N-dimethyl-m-toluidine) 3-(4-dimethylaminonaphthyl)-1,3,5-cycloheptatriene triphenylamine N,N-diethyl-3-methyl-4-(5-(5H-dibenzo(a,d)cyclohepteny N,N,N',N'-tetraphenyl-m-phenylenediamine l)aniline 4-acetyltriphenylamine 60 tetra-a-naphthylhydrazine 4-hexanoyltriphenylamine tetra(3-methyl-4-hydroxyphenyl)hydrazine 4-lauroyltriphenylamine tetra(m-hydroxyethylphenyl)hydrazine 4-hexyltriphenylamine tetra(2-methyl-5-chloroethylphenyl)hydrazine 4-dodecyltriphenylamine tetra(2-methyl-5-hydroxyphenyl)hydrazine 4,4'-bis(diphenylamino)benzil 65 tetra(1-imidazolyl) hydrazine 4,4'-bis(diphenylamino)benzophenone N,N-di-o-naphthyl-N',N'-di(3-methyl-4-hydroxyphen poly(N,4'-(N,N',N'-triphenylbenzidine)) yl)hydrazine polyadipyltriphenylamine N-3-furyl-N-(2-methyl-4-hydroxyphenyl)-N',N'-di-e- polysebacyltriphenylamine naphthylhydrazine polydecamethylenetriphenylamine 70 tetra-g-naphthylhydrazine poly-N-(4-vinylphenyl)diphenylamine N,N'-di-3-naphthyl-N,N'-diphenylhydrazine poly-N-(vinylphenyl)-a,a'-dinaphthylamine tetra-4-tolylhydrazine 4,4'-benzylidene-bis(N,N-diethyl-m-toluidine) N,N'-diphenyl-N,N'-di(3-methyl-4-hydroxyphen 4',4'-diamino-4-dimethylamino-2',2'-dimethyltriphenyl yl)hydrazine - methane 75 N,N'-diphenyl-N,N'-di-p-chlorophenyl hydrazine 3,647,432 13 14 phenyltri-(2-methyl-5-hydroxyphenyl)hydrazine 3-p-diphenylaminophenylpropionic acid N,N'-bicarbazyl 4-formyltriphenylamine semicarbazone cyclotetrakis(3,9-carbazolylene) triphenyl-p-diethylaminophenylsilane 6-(3-carbazolyl)-cyclotetrakis(3,9-carbazolylene) methyl-diphenyl-p-diethylaminophenylsilane 6-(9-carbazolyl)-cyclotetrakis(3,9-carbazolylene) triphenyl-p-diethylaminophenylgermane 3,3'-bis(3-carbazolyl)-9,9'-bicarbazolyl triphenyl-p-dimethylaminophenylstannane 3-(3-carbazolyl)-9-(9-carbazolyl carbazole triphenyl-p-diethylaminophenylstannane 3-(9-carbazolyl)-9,9'-bicarbazolyl diphenyl-di-(p-diethylaminophenyl)stannane 3,3'-diethyl-9,9'-bicarbazolyl triphenyl-p-diethylaminophenylplumbane 3,3'-diphenyl-9,9'-bicarbazolyl 10 tetra-p-diethylaminophenylplumbane 3,3'-dichloro-9,9'-bicarbazolyl phenyl-di-(p-diethylaminophenyl)phosphine 4,4'-bis(diethylamino)-9,9'-bicarbazolyl bis(p-diethylaminophenyl)phosphine oxide 3,3'-diethoxy-9,9'-bicarbazolyl tri-p-dimethylaminophenylarsine 1, 1'-dihydroxy-9,9'-bicarbazolyl tri-p-diethylaminophenylarsine 2,2'-dicyano-9,9'-bicarbazolyl 15 2-methyl-4-dimethylaminophenylarsine oxide tetra(p-diethylaminophenyl)hydrazine tri-p-diethylaminophenylbismuthine 3,3'-bis(1,5-diphenyl-2-pyrazoline) methyl-di-(p-diethylaminophenyl)arsine 3,3'-bis(1-p-tolyl-5-phenyl-2-pyrazoline) methyl-di-(p-diethylaminophenyl)phosphine 3,3'-bis(1,5-1-naphthyl)-2-pyrazoline) phenyl-tri(p-diethylaminophenyl)stannane 20 methyl-tri(p-diethylaminophenyl)stannane 1,5-diphenyl-3-3'-(1'-p-tolyl-5'-phenyl)-2'-pyrazolyl)-2- tetra-p-diethylaminophenylgermane 3,3'-bis(1,5-diphenyl-4,5-dimethyl-2-pyrazoline)pyrazoline - diphenyl-p-diethylaminophenylsilane 3,3'-bis(1,4,5-triphenyl-2-pyrazoline) p-diethylaminophenylarsine 3,3'-bis(1,5-di-p-tolyl-4-methoxy-2-pyrazoline) tetrakis-(diphenyl-(p-diethylaminophenyl)plumbyl 3,3'-bis(1,5-diphenyl-4-dimethylamino-2-pyrazoline) 25 methane 3,3'-bis 1,5-diphenyl-4-(p-chlorophenyl)-2-pyrazoline) tetrakis-diphenyl-(p-diethylaminophenyl)stannyl)stan 3,3'-bis(1,5-diphenyl-4,5-di-(p-diethylaminophenyl)-2- bis-phenyl-(p-diethylaminophenyl)ale dibismuthine 3,3'-bis(1,5-diphenyl-4-(p-methoxyphenyl)-5-ethyl-2-pyrazoline) tri-(p-diethylaminophenyl)phosphine sulfide pyrazoline) 30 di-(p-diethylaminophenyl)thioxotin 3,3'-bis(1,5-diphenyl-4-chloromethyl-2-pyrazoline) 9-methylcarbazole 1,5-diphenyl-4,5-dimethyl-3-(3'-(1'-p-tolyl-4'-diethyl-5' 9-ethylcarbazole 5'-methylphenyl)-2'-pyrazolyl)-2-pyrazoline 9-phenylcarbazole 4-(p-diphenylaminophenyl)-3-buten-1-yne Preferred binders for use in preparing the present p-diphenylaminostyrene 35 photoconductive layers are film-forming, hydrophobic ethyl p-diphenylaminocinnamate polymeric binders having fairly high dielectric strength which methyl p-diphenylaminocinnamate are good electrically insulating film-forming vehicles. p-diphenylaminocinnamoyl chloride Typical of these materials are: p-diphenylaminocinnamic acid N,N-diphenylamide I. Natural resins including gelatin, cellulose ester derivatives p-diphenylaminocinnamic acid anhydride 40 such as alkyl esters of carboxylated cellulose, hydroxy 3-(p-diphenylaminophenyl)-2-butenoic acid ethyl cellulose, carboxymethyl cellulose, carboxy methyl bis(p-diphenylaminobenzal)succinic acid hydroxyethyl cellulose, etc.; 4-N,N-bis(p-bromophenyl)aminocinnamic acid II. Vinyl resins including 1-(4-diphenylamino)naphthacrylic acid a. polyvinyl esters such as a vinyl acetate resin, a 45 copolymer of vinyl acetate and crotonic acid, a p-diphenylaminocinnamic acid copolymer of vinyl acetate with an ester of vinyl al p-diphenylaminocinnamonitrile cohol and a higher aliphatic carboxylic acid such as 7-diphenylamino coumarin lauric acid or stearic acid, polyvinyl stearate, a p-diphenylaminophenylvinylacrylicp-diphenylaminobenzylp'-diphenylaminocinnamate acid copolymer of vinyl acetate and maleic acid, a 7-(p-diphenylaminostyryl)coumarin 50 poly(vinylhaloarylate) such as poly(vinyl-m- p-diphenylaminocinnamyl alcohol bromobenzoate) or poly(vinyl-n-bromobenzoate-covi 4-diphenylaminocinnamaldehyde semicarbazone nyl acetate), a terpolymer of vinylbutyral with vinyl al O-p-diphenylaminocinnamoyl p'-diphenylaminobenzal cohol and vinyl acetate, a terpolymer of vinyl formal with vinyl alcohol and vinyl acetate, etc.; dehyde oxime 55 b. vinyl chloride and vinylidene chloride polymers such as p-diphenylaminocinnamaldehyde1,3-bis(p-diphenylaminophenyl)-2-propen-1-ol oxime a poly(vinylchloride), a copolymer of vinyl chloride methyl p-diphenylaminobenzoate and vinyl isobutyl ether, a copolymer of vinylidene N,N-diphenylanthranilic acid chloride and acrylonitrile, a terpolymer of vinyl 3-p-diphenylaminophenyl-1-propanol chloride, vinyl acetate and vinyl alcohol, poly(viny 4-acetyltriphenylamine semicarbazone 60 lidene chloride) a terpolymer of vinyl chloride, vinyl ethyl 2,6-diphenyl-4-(p-diphenylaminophenyl)benzoate acetate and maleic anhydride, a copolymer of vinyl 1-(p-diphenylaminophenyl)-1-hydroxy-3-butyne chloride and vinyl acetate, etc.; 4-hydroxymethyltriphenylamine c. styrene polymers such as a polystyrene, a nitrated 1-(p-diphenylaminophenyl)ethanol polystyrene, a copolymer of styrene and monoisobutyl 4-hydroxytriphenylamine 65 maleate, a copolymer of styrene with methacrylic acid, 2-hydroxytriphenylamine a copolymer of styrene and butadiene, a copolymer of 4-formyltriphenylamine oxime dimethylitaconate and styrene, polymethylstyrene, 4-acetyltriphenylamine oxime etc.; 1-(p-diphenylaminophenyl)hexanol d. methacrylic acid ester polymers such as a poly(alkyl 1-(p-diphenylaminophenyl)dodecanol 70 methacrylate), etc.; p-diphenylaminobenzoic acid anhydride e. polyolefins such as chlorinated polyethylene, 4-cyanotriphenylamine chlorinated polypropylene, poly(isobutylene), etc.; p-diphenylaminobenzoic acid N,N-diphenylamide f. poly(vinyl acetals) such as a poly(vinyl butyral), etc.; p-diphenylaminobenzoic acid and p-diphenylaminobenzoyl chloride 75 g. poly(vinyl alcohol); 3,647,432 15 16 III. Polycondensates including tional film supports such as cellulose acetate, poly(ethylene a. a polyester of 1,3-disulfobenzene and 2,2-bis(4- terephthalate), polystyrene and the like conducting supports. hydroxyphenyl)propane; An especially useful conducting support can be prepared by b. a polyester of diphenyl-p,p'-disulphonic acid and 2,2- coating a transparent film support material such as bis(4-hydroxyphenyl)propane; poly(ethylene terephthalate) with a layer containing a c. a polyester of 4,4'-dicarboxyphenyl ether and 2,2- semiconductor dispersed in a resin. A suitable conducting bis(4-hydroxyphenyl)propane; coating can be prepared from the sodium salt of a carboxy d. a polyester of 2,2-bis(4-hydroxyphenyl)-propane and ester lactone of a maleic anhydride-vinyl acetate copolymer, fumaric acid; cuprous iodide and the like. Such conducting layers and e. pentaerythrite phthalate; O methods for their optimum preparation and use are disclosed f. resinous terpene polybasic acid; in U.S. Pat. Nos. 3,007,901, 3,245,833 and 3,267,807. g. a polyester of phosphoric acid and hydroquinone; The compositions of the present invention can be employed h. polyphosphites; in photoconductive elements useful in any of the well known i. polyester of neopentylglycol and isophthalic acid; electrophotographic processes which require photoconduc j. polycarbonates including polythiocarbonates such as 15 tive layers. One such process is the xerographic process. In a the polycarbonate of 2,2-bis(4-hydroxyphen process of this type, an electrophotographic element held in yl)propane; the dark, is given a blanket electrostatic charge by placing it k. polyester of isophthalic acid, 2,2-bis-4-6-hydrox under a corona discharge to give a uniform charge to the sur yethoxy)phenyl propane and ethylene glycol; face of the photoconductive layer. This charge is retained by l. polyester of terephthalic acid, 2,2-bis-4-g-hydrox 20 the layer owing to the substantial dark insulating property of yethoxy)phenyl and ethylene glycol; the layer, i.e., the low conductivity of the layer in the dark. m. polyester of ethylene glycol, neopentyl, glycol, The electrostatic charge formed on the surface of the terephthalic acid and isophthalic acid; photoconductive layer is then selectively dissipated from the n. polyamides; 25 surface of the layer by imagewise exposure to light by means o. ketone resins; and of a conventional exposure operation such as for example, by p. phenolformaldehyde resins; a contact-printing technique, or by lens projection of an IV. Silicone resins; image, or reflex or bireflex techniques and the like, to thereby V. Alkyd resins including styrene-alkyd resins, silicone form a latent electrostatic image in the photoconductive layer. alkyd resins, soya-alkyd resins, etc.; and 30 Exposing the surface in this manner forms a pattern of electro VI. Polyamides. static charge by virtue of the fact that light energy striking the V. Paraffin. photoconductor causes the electrostatic charge in the light VIII. Mineral waxes. struck areas to be conducted away from the surface in propor Solvents useful for preparing coating compositions with the tion to the intensity of the illumination in a particular area. use of the present invention can include a wide variety of 35 The charge pattern produced by exposure is then developed organic solvents for the components of the coating com or transferred to another surface and developed there, i.e., position. Typical solvents include either the charge or uncharged areas rendered visible, by 1. aromatic hydrocarbons such as benzene, naphthalene, treatment with a medium comprising electrostati-cally respon etc., including substituted aromatic hydrocarbons such as sive particles having optical density. The developing electro toluene, xylene, mesitylene, etc.; 40 statically responsive particles can be in the form of a dust, or 2. ketones such as acetone, 2-butanone, methylethylketone, powder and generally comprise a pigment in a resinous carrier etc., called a toner. A preferred method of applying such a toner to 3. halogenated aliphatic hydrocarbons such as methylene a latent electrostatic image for solid area development is by chloride, chloroform, ethylene chloride, etc.; the use of a magnetic brush. Methods of forming and using a 4. ethers including cyclic ethers such as tetrahydrofuran, 45 magnetic brush toner applicator are described in the following ethylether; and U.S. Pat. Nos. 2,786,439; 2,786,440; 2,786,441; 2,811,465; 5. mixtures of the above. 2,874,063; 2,984, 163; 3,040,704; 3,117,884 and reissue Re. In preparing the coating compositions utilizing the No. 24,779. Liquid development of the latent electrostatic photoconducting compounds disclosed herein useful results image may also be used. In liquid development the developing are obtained where the photoconductive substance is present 50 particles are carried to the image-bearing surface in an electri in an amount equal to at least about 1 weight percent of the cally insulating liquid carrier. Methods of development of this coating composition. The upper limit in the amount of type are widely known and have been described in the patent photoconductive material present can be widely varied in ac literature, for example, U.S. Pat. No. 2,297,691 and in Aus cordance with usual practice. It is normally required that the tralian Pat. No. 212,315. In dry developing processes the most photoconductive material be present in an amount ranging 55 widely used method of obtaining a permanent record is from about 1 weight percent of the coating composition to achieved by selecting a developing particle which has as one about 99 weight percent of the coating composition. A of its components a low-melting resin. Heating the powder preferred weight range for the photoconductive material in image then causes the resin to melt or fuse into or on the ele the coating composition is from about 10 weight percent to ment. The powder is, therefore, caused to adhere permanently about 60 weight percent. 60 to the surface of the photoconductive layer. In other cases, a Coating thicknesses of the photoconductive composition on transfer of the charge image or powder image formed on the a support can vary widely. Normally, a wet coating thickness photoconductive layer can be made to a second support such 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 as paper which would then become the final print after 65 developing and fusing or fusing respectively. Techniques of thickness is from about 0.002 inch to about 0.006 inch before the type indicated are well known in the art and have been drying although such thicknesses can vary widely depending described in a number of U.S. and foreign patents, such as on the particular application desired for the electrophoto U.S. Pat, NOs. 2,297,691 and 2,551,582, and in "RCA graphic element. Review,' vol. 15 (1954) pages 469-484. Suitable supporting materials for the photoconductive The compositions of the present invention can be used in layers of the present invention can include any of the electri 70 electrophotographic elements having many structural varia cally conducting supports, for example, various conducting tions. For example, the photoconductive composition can be papers; aluminum-paper laminates; metal foils, such as alu coated in the form of single layers or multiple layers on a suita minum foil, zinc foil, etc.; metal plates such as aluminum, ble opaque or transparent conducting support. Likewise, the copper,metal layers zinc, such brass, as andsilver, galvanized nickel or plates; aluminum vapor on deposited conven- 75 layers can be contiguous or spaced having layers of insulating 3,647,432 17 8 material or other photoconductive material between layers or amount of the unreacted corresponding carbazole. Since the overcoated or interposed between the photoconductive layer unreacted carbazole (i.e., N-alkylcarbazole or N-arylcar or sensitizing layer and the conducting layer. It is also possible bazole) is a photoconductor, the entire reaction product can to adjust the position of the support and the conducting layer be coated as a photoconductive layer without having to go by placing a photoconductor layer over a support and coating 5 through cumbersome purification procedures. This advantage the exposed face of the support or the exposed or overcoated makes the preparation and use of the herein described sen face of the photoconductor with a conducting layer. Configu sitizing dyes very attractive. A typical preparation is set forth below. rations differing from those contained in the examples can be EXAMPLE 5 useful or even preferred for the same or different application 10 Oxalyl chloride (0.1 mole) is added with stirring at room for the electrophotographic element. temperature to a solution of N-methylcarbazole (0.1 mole) in The following examples are included for a further un dry methylene chloride (400 ml.) containing finely ground derstanding of this invention. zinc chloride (0.2 mole). The mixture is refluxed on a steam EXAMPLE bath for 44 hours. The product is poured into ice water (200 A composition in the form of a dope consisting of the fol 15 ml.) containing hydrochloric acid (5 ml.) and stirred for 1 lowing materials is coated at a wet thickness of 0.004 inch on a hour. After filtration, the supernatent liquid is washed re poly(ethylene terephthalate) film support having a conducting peatedly with water until it is pale blue. The methylene layer of the sodium salt of a carboxyester resin lactone: chloride is distilled off and the product recovered. It has a Photoconductor N-methylcarbazole 0.5g. melting point of 83-85 C. About 90 to 95 percent of this Polymeric Binder Vitel 101, a polyester resin sold by product is found to be a mixture of N-methylcarbazole (about Goodyear Tire and Rubber 90 percent) and tris(4-methylcarbazol-3-yl) methane Company comprising poly(4,4'- chloride salt (about 3 percent). Each component is isolated by isopropylidenebisplenoxyethyl-co chromatography on activated alumina. ethylene terephthalate) 1.5 g. EXAMPLE 6 Sensitizer 25 (see Table li) 0.001 g. Example 1 is repeated except that both the sensitizer and Solvent Dichloromethane 9.6 g. photoconductor are replaced with the product mixture of Ex The coating block is maintained at 90°F. until the solvent is ample 5. A good reproduction is obtained when the exposed removed. In a darkened room, the surface of the photocon element is developed. 9 ductive layer so prepared is charged to a potential of about The invention has been described in detail with particular 600 volts under a corona charger. The layer is then covered 30 reference to preferred embodiments thereof, but, it will be un with a transparent sheet bearing a pattern of opaque and light derstood that variations and modifications can be effected transmitting areas and exposed to the radiation from an incan within the spirit and scope of the invention. descent lamp with an illumination intensity of about 75 meter I claim: candles for 12 seconds. The resulting electrostatic latent 1. An electrophotographic element comprising a support image is developed by cascading over the surface of the layer 35 having coated thereon a layer of a photoconductive composi negatively charged black thermoplastic toner particles on tion comprising a polymeric film-forming binder, a photocon ductor and a sensitizer selected from the group consisting of a glass bead carriers. The quality of the image reproduced using tris(9-alkylcarbazol-3-yl) methane dye salt and a tris(9-aryl various sensitizers described herein is set forth in the following carbazol-3-yl)Methane dye salt. tabie. 40 2. The element of claim 1 wherein the photoconductor is an TABLE II organic photoconductor. 3. An electrophotographic element comprising a support Sensitizer image Quality Good having coated thereon a layer of a photoconductive composi I Good 45 tion comprising a polymeric film-forming binder, an organic IV Good photoconductor and a sensitizer having the formula: EXAMPLE 2 Example 1 is repeated using N-ethyl carbazole as the photoconductor. The quality of the images reproduced using R various sensitizers is set forth in Table III. 50 N (BN TABLE III R X Sensitizer image Quality WI Good VIII Good 55 N C X Good EXAMPLE 3 R2 R2 Example 1 is repeated using triphenylamine as the NN N photoconductor. In each instance a good reproduction is ob 60 R. R1 tained. EXAMPLE 4 Example 1 is repeated except no sensitizer is used. No developable latent electrostatic image is obtained. wherein The novel sensitizers described herein can be prepared by 65 R is selected from the group consisting of an alkyl group any one of several methods. One method involves reacting ox and an aryl group, alyl chloride with the appropriate substituted carbazole in the R is selected from the group consisting of an alkoxy group, presence of zinc chloride. Another synthesis involves reacting an aryloxy group, an alkyl group, a hydrogen atom, an an appropriate di(carbazol-3-yl) ketone with a corresponding acyl group and a halogen atom and substituted carbazole in the presence of phosphorus ox 70 X is an anion. ychloride. A third method of preparation is to react a cor 4. The element of claim 3 wherein R is an alkyl group. responding substituted carbazole with carbon tetrachloride in 5. The element of claim 3 wherein R is an aryl group. the presence of aluminum chloride. In any of the synthesis 6. The element of claim 3 wherein the organic photocon mentioned above, the reaction product contains one of the ductor is selected from the group consisting of an N-arylcar sensitizing dyes described herein together with a substantial 75 bazole and an N-alkylcarbazole. 3,647,432 19 20 7. An electrophotographic element comprising a support dye salt. having coated thereon a layer of a photoconductive composi 10. The element of claim 9 wherein the organic photocon tion comprising: ductor11. isA an N-ethylphotoconductive carbazole. composition comprising a a. from about 10 percent to about 60 percent by weight photoconductor and a sensitizer selected from the group con based on said photoconductive composition of an organic sisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a photoconductor, tris(9-arylcarbazol-3-yl)methane dye salt. b. a film-forming polymeric binder for said photoconductor 12. The composition of claim 11 wherein the photoconduc and tor is an organic photoconductor. c. from about 0.005 percent to about 5 percent by weight 13. The composition of claim 11 further comprising a based on said photoconductive composition of a sen O polymeric film-forming binder for said photoconductor and sitizer comprising a tris(9-methylcarbazol-3-yl)methane said sensitizer. dye salt. 14. A photoconductive composition comprising an N-sub 8. The element of claim 7 wherein the organic photocon stituted carbazole photoconductor and a sensitizer selected ductor is an N-methyl carbazole. from the group consisting of a tris(9-alkylcarbazol-3- 9. An electrophotographic element comprising a support 15 yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane having coated thereon a layer of a photoconductive composi dye salt. tion comprising: 15. In an electrophotographic process where an electro a. from about 10 percent to about 60 percent by weight static charge pattern is formed on an electrophotographic ele based on said photoconductive composition of an organic 20 ment, the improvement characterized in that said photocon photoconductor, - ductive element has a photoconductive layer comprising a b. a film-forming polymeric binder for said photoconductor photoconductor and a sensitizer selected from the group con and sisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a c. from about 0.005 percent to about 5 percent by weight tris(9-arylcarbazol-3-yl)methane dye salt. based on said photoconductive composition of a sen sk ck sk sk ck sitizer comprising a tris(9-ethylcarbazol-3-yl)methane 25

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