US3533785A

US3533785A - Photoconductive compositions and elements

Info

Publication number: US3533785A
Application number: US630144A
Authority: US
Inventors: Charles J Fox; Arthur L Johnson
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1967-03-20
Filing date: 1967-03-20
Publication date: 1970-10-13
Anticipated expiration: 1987-10-13
Also published as: GB1223702A; GB1223703A; BE712429A; FR1575622A

Description

United States Patent Ofice 3,533,785 Patented Oct. 13, 1970 3,533,785 PHOTOCONDUCTIVE COMPOSITIONS AND ELEMENTS Charles J. Fox and Arthur L. Johnson, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Mar. 20, 1967, Ser. No. 630,144 Int. Cl. G03g 5/00 US. Cl. 96-15 13 Claims ABSTRACT OF THE DISCLOSURE A photoconductive composition useful in electrophotography wherein the photoconductor has the structural formula wherein Q and Q are each phenyl radicals or when taken together with the adjacent groups, form an imide ring system having 5 to 6 atoms in its nucleus. and R is selected from phenyl radicals, heterocyclic radicals or amino-containing substituents.

This invention relates to electrophotography. In particular aspects it relates to organic photoconductor-containing compositions and elements having enhanced photosensitivity when electrically charged, and to a method of preparing organic compounds which are photoconductors.

The process of xerography, as disclosed by Carlson in US. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of a normally insulating material whose electrical resistance varies with the amount of incident actinic radiation it receives during an imagewise exposure. The element, commonly termed a photoconductive element, is first given a uniform surface charge, generally in the dark after a suitable period of dark adaptation. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of the surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or electrostatic latent image remaining on the electrophotographic element is then made visible by contacting the surface with a suitable electroscopic marking material. Such marking material or toner, Whether contained in an insulating liquid or on a dry carrier, can be selected to be deposited on the exposed surface in accordance with either the charge pattern or the absence of charge pattern as desired. The deposited marking material can then be either permanently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor, or the like, or transferred to a second element to which it can similarly be fixed. Likewise, the electrostatic latent image can be transferred to a second element and developed there.

Various photoconductive insulating materials have been employed in the manufacture of electrophotographic elements. For example, selenium and selenium alloys vapor deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming binder have found wide application in present-day document copying applications.

Since the introduction of electrophotography, a great many organic compounds have also been screened for their photoconductive properties. As a result a very large number of organic compounds are known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have incorporated into photoconductive compositions. Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be' especially useful in electrophotography. Such electrophotographic elements can be exposed through a transparent base if desired, thereby providing unusual flexibility in equipment design. Such compositions, when coated as a film or layer on a suitable suport, also yield an element which is reusable; that is it can be used to form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning. Thus far, the selection of organic compounds for incorporation into photoconductor compositions to form electrophotographic layers has proceeded On a compound-bycompound or narrow class of compounds basis. Nothing has yet been discovered from the large number of different photoconductive substances tested which permits elfective prediction and therefore selection of particular compounds exhibiting the desired electrophotographic properties.

It is an object of this invention to provide novel photoconductive compositions of matter.

It is another object of this invention to provide a new class of photoconductive organic compounds.

It is yet another object of this invention to provide a novel method for preparing novel photoconductive organic compounds.

It is a further object of this invention to provide novel photoconductive elements containing at least one organic photoconductor in an amount suflicient to be useful in electrophotographic applications.

It is still a further object of this invention to provide new photoconductive elements containing an organic photoconductor that can be effectively sensitized.

These and further objects and advantages of this invention have been achieved by the discovery of the advantageous photoconductive properties of certain N-substituted imides having the structural formula:

wherein Q and Q are each substituted or unsubstituted phenyl radicals such as phenyl, aminophenyl, tolyl, halophenyl, etc., or when taken together comprise the atoms required to complete an imide ring system having 5 or 6 atoms in its nucleus which can optionally be fused to one or more substituted or unsubstituted carbocyclic ring sys tems or can be an integral part of an addition copolymer chain such as imide-styrene copolymers, imide-olefin copolymers, imide-vinyl chloride copolymers, imide-acrylonitrile copolymers, etc., and R is (1) A substituted or unsubstituted phenyl radical such as described above for Q and Q.

(2) A heterocyclic radical having 5 or 6 atoms in its heteronucleus including such hetero atoms as oxygen, nitrogen, sulfur and selenium such as quinolyl, benzothi- 3 azolyl, phthalimido, morpholino, pyrimidyl, pyridinyl, pyrazinyl, etc.,

(3) A radical having the structural formula:

wherein n can be an integer from 12 preferably an integer from 0-3 and R and R are each a hydrogen atom, an alkyl radical typically having 1-20 carbon atoms such as methyl, ethyl, propyl, hexyl, octyl, nonyl, dodecyl, etc., an aryl radical such as phenyl, naphthyl, tolyl, aminophenyl, alkoxyphenyl, halophenyl, etc., or when taken together with the nitrogen atom of the R substituent comprise the atoms necessary to complete a heterocyclic ring system having or 6 atoms in its heteronucleus which can optionally be substituted or fused at the 2- and 3-positions to a benzenoid ring system,

(4) a radical having the structural formula:

wherein n is an integer from 0-12, preferably an integer from 0-3 and Z and Z are each substituted or unsubstituted phenyl groups or when taken together with their adjacent groups can comprise the atoms required to complete an imide ring system having 5 or 6 atoms in its nucleus which can optionally be fused to one or more substituted or unsubstituted carbocyclic ring systems,

(5 A radical having the structural formula:

wherein Z and Z have the same meaning as above,

(6) A radical having the structuarl formula:

0 ll C-Z N/ ll 0 wherein Z and Z have the same meaning as above,

(7) Or a radical having the structural formula:

(CH2)x-OH=CHN R2 wherein R and R each have the same meaning as above andx is an integer from 0-10.

Suitable photoconductive imides of the invention Within the foregoing class are included in Table I. The compound number assigned is used herein in later examples to identify the named compounds. This list is exemplary only and is not presented as being limiting with respect to the scope of the invention.

Table I Compound No.: Name 1 N- 2- 1,2,3 ,4-tetrahydro-1-quin0lyl)ethyl] phthalimide.

2 N- 2-( 1,2,3,4-tetrahydro-2-methyl-l-quinolyl ethyl] phthalimide.

3 N- [2( 1,2,3 ,4-tetrahydro-2,7-dimethyl- 1- quinolyl) ethyl] phthalimide.

4 N-[3-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl)propyl]phthalimide.

5 N-[2-(N-ethyl-N-m-tolylamino) -ethyl] phthalimide.

Compound No; Name 6 N{2-[N-ethyl-N-(4-formyl-3-methyl)phenylamino]ethyl}phthalimide.

7 N-[2-(N-ethyl-N-m-tolylamino)ethyl]-4- carbanilino phthalimide.

8 N-[2-(N-ethyl-N-m-tolylamino)ethyl]-3,

4,5,6-tetrachlorophthalimide.

9 N-[(N-ethyl-N-phenylamino)methyl] phthalimide.

l0 N-3-o-tolylaminopropyl phthalimide.

11 l,2-bis(phthalimido)ethane.

12 N,N-oxalyl bisphthalimide.

13 1,4-bis(phthalimido)benzene.

14 N-phenyl phthalimide.

15 N-p-diethylaminophenyl phthalimide.

16 N-p-dimethylaminophenyl phthalimide.

17 N-p-methoxyphenyl phthalimide.

18 N-p-tolyl phthalimide.

19 N-p-chlorophenyl phthalimide.

20 M... N-p-acetylphenyl phthalimide.

21 N-[4-(2-pyrimidylphenyl) ]phthalimide.

22 N-Z-benzothiazolyl phthalimide.

23 N-p-diethylaminophenyl-3,4,5,6-tetrachlorophthalimide.

24 N-[2-(1,2,3,4-tetrahydro-2,7-dimethyl-1- quinolyl) ethyl] succinimide.

25 N- 2- N-m-tolyl-N-ethylamino ethyl] succinimide.

26 N-{Z-[N-ethyl-N-(4-formyl-3-methy1) phenylamino] ethyl} succinimide.

27 N-[ (N-ethyl-N-phenylamino)methyl] succinimide.

28 N-[(N-ethyl-N-m-tolylamino)ethyl]maleimide.

29 N- [2- (N-ethyl-N-m-tolylamino ethyl 9,

10-dihydro-9,10-ethanoanthracene-11, IZ-dicarboximide.

30 N-[2-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl)ethyl]maleimide/ styrene copolymer.

31 N-[2-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl) ethyl] maleimide/ ethylene copolymer.

32 N-p-di-n-propylaminophenyl phthalimide.

33 N-p-di-n-butylaminophenyl phthalimide.

34 N-p-diphenylaminophenyl phthalimide.

35 N,N-dibenzoyl-N,N-diethyl-p-phenylenediamine.

36 N-[2-(1,2,3,4-tetrahydro-2-methyl-6-bromo-l-quinolyl)ethy1] phthalimide.

37 N-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl phthalimide.

38 N-[1,2,3,4-tetrahydro-2-methyl-l-quinolyl) methyl] phthalimide.

39 N-[2-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl)vinyl]phthalimide.

40 N-2-diphenylaminovinyl phthalimide.

41 N-[2-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl)ethyl]naphthalimide.

42 N-[2-(1,2,3,4-tetrahydro-2-methyl-1-quinolyl)ethyl]-4-bromonaphthalimide.

43 .l N-[2-(1,2,3,4-tetrahydro-2-methyl-l-quinolyl ethyl] -3-nitronaphthalimide.

44 N-(4-diethylamino-2-met hylphenyl)naphthalimide.

45 N-(4-diethylamino-2-methylphenyl)phthalimide.

46 N-(4-diethylamino-2,6-dimethylphenyl) phthalimide.

47 N-(4-diethylamino-Z-methylphenyl)-3-dimethylamino phthalimide.

48 N-m-bromophenyl phthalimide.

49 N-p-bromophenyl phthalimide.

50 N[2-(1,2,3,4-tetrahydro-2-methyl-6-di- Table IContinued Compound No.: Name methylamino-1-quinolyl)vinyl]phthalimide.

51 N-[2-(N-benzyl-N-phenylamino)vinyl] phthalimide.

52 N-morpholinovinyl phthalimide.

53 N-(4-diethylamino-2-methylphenyl)pyridine-2,3-dicarboximide.

54 N-pheny1-2,3-pyrazinedicarboximide.

55 N-(4-diethylamino-Z-ethylphenyl)phthalimide.

56 N-(4-diethylamino-2-ethylphenyl) -3-dimethylamino phthalimide.

A preferred class of compounds within the scope of Formula I which are useful in the practice of the present invention are the phthalimides; i.e., those compounds where in Formula I Q and Q form a phthalimide ring system with the adjacent groups. Especially preferred phthalimides are those having the structural formula:

Rs H C H R4 0 (II) where z is an integer from 0 through 3 and R and R are each hydrogen atoms or lower alkyl radicals typically having 1 to 8 carbon atoms such as methyl, ethyl, propyl, hexyl, octyl, etc. and those having the structural formula:

where R is a lower alkyl radical such as those shown above for R and R and R and R are each hydrogen atoms or dialkylamino or diarylamino radicals.

In general, the imides used in the practice of this invention can be prepared by Well-known methods. Typically, a suitable group containing a reactive nitrogen is converted into a primary amine, which is then condensed with an appropriate anhydride to form the corresponding imide. Representative examples illustrating this method of preparation are included in Examples 1 through 14 hereinafter. When the N-substituted imide is to be part of a copolymer chain, the copolymer can be prepared by this same procedure. In such cases, a copolymer containing the appropriate anhydride is condensed with the desired primary amine to yield the corresponding imide as an integral portion of the copolymer. Examples 6 and 7 hereinafter further illustrate this method of preparation.

However, the imides corresponding to Formula I wherein R represents the radical are advantageously prepared by a novel procedure. According to this novel procedure, an alkali metal salt of the imide is condensed with an acetal to give the imidoacetal, which is hydrolyzed to the aldehyde. The imidoaldehyde then condenses readily with a secondary amine to give an unsaturated N-substituted imide which can be reduced to the corresponding fully saturated imide photoconductor. This method of preparation is illustrated schematically in Equation 1.

wherein Q, Q, R R x, and n have the same meaning as above, R represents a lower alkyl group, M represents an alkali metal, X represents a halogen and y represents an integer from 0-11.

In the condensation reaction to produce the imidoacetal, the imide is present as an alkali metal salt, preferably a potassium salt, and the acetal is present as a haloacetal, preferably a bromoacetal. The reaction is performed in a solvent such as N,N-dimethylformarnide. The temperature and pressure at which the reaction is carried out can vary over a wide range. The reaction will proceed satisfactorily at room temperature (20 C.) and atmospheric pressure. Elevated temperatures and reflux are preferred, however, since under such conditions the reaction proceeds more rapidly. The upper temperature is generally limited by the boiling point of the solvent; higher boiling solvents permitting higher temperatures of reaction.,Ternperatures of from 50 C. to 150 C. are typical of suitable elevated temperatures. Although the reaction is normally performed at atmospheric pressure, either elevated or reduced pressures. can be employed if desired.

Hydrolysis of the imidoacetal to the imidoaldehyde is generally effected with formic acid in the presence of a mineral acid such as hydrochloric acid. The reaction will proceed satisfactorily under ambient conditions (room temperature and atmospheric pressure). Elevated temperatures up to C. are preferred for this reaction.

Condensation of the imidoaldehyde with a secondary amine is performed in an organic solvent such as benzene, toluene, etc. The temperature and pressure can vary over a wide range. As in the case of the condensation to the imidoacetal, this reaction will proceed at room temperature and atmospheric pressure. Elevated temperatures are preferred, the upper temperature limit being controlled generally by the boiling point of the solvent. Temperatures up to C. are typical of suitable temperatures for this reaction. Reduced or elevated pressures can be employed.

The unsaturated imide can be converted to the saturated N-substituted imide by standard hydrogenation procedures. For example, the unsaturated N-substituted imide can be contacted with hydrogen at elevated temperature and pressure in the presence of a catalyst such as carbonized platinum or finely divided platinum or nickel.

This novel method of preparation is further illustrated in Examples 15 and 16, hereinafter.

This novel method of preparing certain of the N-substituted imides of this invention yields a novel class of compounds which could not be easily obtained by prior art processes, These compounds are the unsaturated N- substituted imides generally represented by structural Formula IV in Equation I above. As compounds of this formula are photoconductors per so they can be incorporated in suitable coating compositions for use in the practice of this invention. The unsaturated imides also find use as intermediates in the preparation of the fully saturated imide photoconductors, being reduced to compounds of Formula V as indicated in Equation I.

Included among other novel N-substituted imides of this invention are compounds having the structural formula:

ll R4 (VI) where n is an integer from 0 to 12, preferably an integer from 0 to 3, T is a substituted or unsubstituted phenylene or naphthylene radical, R is a lower alkyl radical as defined above, and X is a hydrogen atom or a halogen atom, preferably a bromine atom; and compounds having the structural formula:

where T is a substituted or unsubstituted phenylene or naphthylene radical, R is as defined above, and R is a dialkylamino radical, diarylamino radical, keto radical, alkoxy radical, alkyl radical, or halogen atom.

Compounds of Formulas VI and VII can be prepared by known methods such as condensation of a primary amine with an anhydride as described above; compounds of Formula VI can also be prepared by the novel reaction illustrated by Equation 1.

In preparing electrophotographic elements utilizing the photoconductive compounds of this invention, the photoconductive composition can be formulated and coated with or without a binder. When a binder is employed, the compound is dissolved in a solution of binder and solvent and then, after thorough mixing, the composition is coated on an electrically conducting support in a well-known manner, such as swirling, spraying, doctor-blade coating, and the like.

Preferred binders for use in preparing the photoconductive layers comprise polymers having fairly high dielectric strength which are good electrically insulating film-forming vehicles. Materials of this type comprise styrene-butadiene copolymers; silicone resins; styrenealkyd resins; silicone-alkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chloride acrylonitrile copolymers; poly(vinyl acetals) such as poly(vinyl butyral); polyacrylic and methacrylic esters, such as poly(methylmethacrylate), poly(n-butylmethacrylate), poly(isobutyl methacrylate), and the like; polystyrene; nitrated polystyrene; polymethylstyrene; isobutylene polymers; polyesters, such as poly- (alkylene terephthalates); phenol-formaldehyde resins; ketone resins; poly-amides; and polydiarylalkanes such as polycarbonates and polythiocarbonates. Methods of making resins of this type have been extensively described, for example, styrene-alkyd resins can be prepared according to the method described in U.S. Pats. 2,361,019 and 2,258,423. Suitable resins of the type contemplated for use in the preparation of photoconductive layers are sold under such trade names as Vitel PE-lOl, Cymac, Piccopale 100, Lexan and Saran F220. Other types of binders which can be used in the photoconductive layers of the invention include such materials as parafiin, mineral waxes, and the like.

Solvents useful for preparing coating compositions with the compounds of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride; ethylene chloride; and the like; ethers such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the compounds disclosed herein useful results are obtained Where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be widely varied in accordance with usual practice. In those cases where a binder is employed, it is normally required that the photoconductive material be present in an amount from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferrred weight range for the photoconductive material in the coating composition is from about 10 weight percent to about 60 weight percent.

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

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

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

The photoconductive layers of the invention can also be sensitized by the addition of effective amounts of sensitizing compounds to exhibit improved electrophotosensitivity. Sensitizing compounds useful with the photoconductive compounds of the present invention can be selected from a wide variety of materials including such materials as pyrylium, thiapyrylium, and selenapyrylium dye salts disclosed in Van Allan et al. U.S. Pat. 3,250,615; fiuorenes, such as 7,12-di0xo 13 dibenzo(a,h)fiuorene, 5,10-dioxo-4a,l1-diazabenzo(b)fluorene, 3,13-dioxo-7-ox adibenzo(b,g)fluorene, and the like; aromatic nitro compounds of the kinds described in U.S. Pat. 2,610,120; anthrones like those disclosed in U.S. Pat. 2,670,285; quinones, U.S. Pat. 2,670,286; benzophenones U.S. Pat. 2,670,287; thiazoles U.S. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid,

and salicyclic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine, carbocyanine, merocyanine, diarylmethane, thiazine, azine, oxazine, xanthcne, phthalein, acridine, azo, anthraquinone dyes and the like and mixtures thereof. The sensitizers preferred for use with the compounds of this invention are selected from pyrylium and thiapyrylium salts, fiuorenes, carboxylic acids and triphenylmethane dyes.

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

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

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust or powder and generally comprise a pigment in a resinous carrier called a toner. A preferred method of applying such a toner to a latent electrostatic image for solid area development is by the use of a mag netic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S. Pats: 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,- 063; 2,984,163; 3,040,704; 3,117,884; and Reissue 25,-

779. Liquid development of thelatent electrostatic image can also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, US. Pat. 2,296,691 and in Australian Pat. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to'a second support such as paper which would then become the final print after developing and fusing or fusing respectively. Techniques of the types indicated are well known in the art and have been described in a number of US. and foreign patents, such as US. Pats. 2,297,691 and 2,551,582 and in RCA Review, vol. 15 (1954) pages 469-484.

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

This invention is further illustrated by the following examples, of which Examples 1-17 illustrate methods by which the N-substituted imides of this invention can be prepared.

EXAMPLE 1 Preparation of N-[2-(1,2,3,4-tetrathydro-2-methyl-1- quinolyl)ethyl]phthalimide (Compound 2) A solution 224 g. (2.15 moles) of sodium bisulfite in 330 ml. of water was kept at 30 C. and treated with 190 g. of 35-40% aqueous formaldehyde. One milliliter of Igepal CA-730 (an alkyl phenoxy polyoxyethylene ethanol which is a nonionic surfactant marketed by General Aniline & Film Corp.) was added and the mixture was stirred until solution was complete. The solution was warmed to room temperature and 294 g. (2 moles) of 1,2,3,4-tetrahydroquinaldine was added. The mixture was stirred for one hour at room temperature and thereafter at 75-80 C. until solution was complete. It was then treated with a solution of 131 g. (2 moles) of potassium cyanide in 200 ml. of Water and heated at 7080 C. for an additional 2 hours. After cooling to room temperature, the aqueous layer was extracted with two ml. portions of benzene. The combined organic extracts were dried over anhydrous sodium sulfate and the solvent was then removed. The residual oil was distilled to obtain 244.4 g. of N cyanomethyl 1,2,3,4 tetrahydroquinaldine, B.P. 132.5 C./0.5 mm., n =l.5706. A mixture of 244.4 g. (1.32 moles) of N-cyanomethyl-l,2,3,4-tetrahydroquinaldine, 500 ml. of isopropanol, 13.2 g. of Raney nickel, and ml. of anhydrous ammonia was shaken in a stainless steel autoclave under 2000 p.s.i. of hydrogen at 100 C. for two hours. The catalyst was then removed by filtration and the residue was distilled to obtain 150 gof N-(2-aminoethyl)-1,2,3,4-tetrahydroquinaldine, B.P. 130 C./2.4 mm. A mixture of 19 g. (0.1 mole) of N- (Z-aminoethyl)-1,2,3,4-tetrahydroquinaldine and 14.8 g. (0.1 mole) of phthalic anhydride was heated at 150 C. for one hour. The resulting oil was poured, while hot, into 150 ml. of ethyl alcohol. The yellow, solid N-[2-(1, 2,3,4 tetrahydro 2 methyl 1-quinolyl)ethyl]phthalimide, 26.5 g., M.P. 122-124 C., was collected and dried.

Analysis.Calcd. (percent): C, 74.6; H, 5.9; N, 9.2; mol. wt. 306. Found (percent): C, 72.6; H, 5.6; N, 9.1; mol. wt. 297.

N-[2-(l,2,3,4 tetrahydro 1 quinolyl)ethyl]phthalimide (Compound 1) was also prepared according to the procedure of this example.

EXAMPLE 2 Preparation of N-[3-(1,2,3,4-tetrathydro-2-methyl- 1-quino1oy1)propyl]phathalimide (Compound 4) A solution of 29.4 g. (0.2 mole) of 1,2,3,4-tetrahydroquinaldine in g. of glacial acetic acid at 125 C. was treated dropwise with 20 g. (0.37 mole) of acrylonitrile with stirring. The resulting solution was heated under reflux for 6 hours and then neutralized in the cold with a saturated solution of potassium carbonate. The resulting mixture was extracted three times with 100 ml. portions of chloroform and the combined extracts were dried over anhydrous calcium chloride and distilled to obtain 14.5 g. of N-cyanoethyl-l,2,3,4-tetrahydroquinaldine, B.P. 124-l29 C./0.4 mm., n :1.5637, which was reduced and condensed with phthalic anhydride in the manner described in Example 1 to obtain the title compound.

Analysis.Calcd. (percent): C, 75.0; H, 6.3; N, 8.7. Found (percent): C, 72.3; H, 6.1; N, 8.6.

EXAMPLE 3 Preparation of N-(p-diethylaminophenyl)phtalimide (Compound 15) A mixture of 14.8 g. (0.1 mole) of phthalic anhydride and 16.4 g. (0.1 mole) of p-diethylaminoaniline was heated at 150 C. for one hour. The resulting product was recrystallized'from 1:1 isopropanol: chloroform to give 18.1 g. of orange crystals, M.P. 218-22l C.

Analysis.-'Calcd. (percent): C, 73.5; H, 6.3; N, 8.7; mol. wt., 294. Found (percent): C, 73.4; H, 6.0; N, 9.6; mol. wt., 300.

The other N-aryl phthalimides described herein were prepared in the same manner.

EXAMPLE 4 Preparation of l,2-bis(phthalimido)ethane (Compound 11) A mixture of 17.5 g. (0.1 mole) of potassium phthalimide, 25.4 g. (0.1 mole of N-(2-bromoethyl)phthalimide, and 60 ml. of dimethylformamide was heated at 140-150" C. for 17 hours with stirring. The resulting solution was cooled to room temperature and poured into 2.5 l. of water to give 25.9 g. of the title compound as a yellow solid, M.P. 232-235 C.

Analysis.Calcd. (percent): C, 67.0; H, 3.7; N, 8.7; mol wt., 322. Found (percent): C, 67.2; H, 3.6; N, 8.7; mol. wt., 305.

EXAMPLE 5 Preparation of N,N-oxalyl bisphthalimide (Compound 12) A slurry of g. (0.2 mole) of potassium phthalimide in 150 ml. of methylene chloride was treated dropwise with 12.7 g. (0.1 mole) of oxalyl chloride with stirring. The resulting mixture was heated under reflux for 7 hours and then diluted with 200 ml. of water and 100 ml. of methylene chloride. The white, solid product was collected on a filter. Yield, 24.2 g.; M.P., 247-250 C.

12 Analysis.-Calcd. (percent): C, 61.6; H, 2.3; N, 8.0. Found (percent): C, 61.0; H, 2.5; N, 8.0.

EXAMPLE 6 Preparation of a copolymer of styrene and N-[2-( 1,2,3, 4-tetrahydro-2-methyl- 1 -quinolyl ethyl] maleimide (Compound 30) A solution containing 10.1 g. (0.05 mole) of a styrenemaleic anhydride copolymer (Lustrex 410, sold by Monsanto Chemical Co.) and 9.5 g. (0.05 mole) of N- (2-aminoethyl)-l,2,3,4-tetrahydroquinaldine in g. of dimethylformamide was heated at 150 C. for four hours. The resulting solution was cooled, and added dropwise to isopropanol to precipitate the title compound which was collected, washed with isopropanol, and dried. Yield: 12 g.

Analysis.Calcd. for C H N O (percent): C, 77.0; H, 6.9; N. 7.5. Found (percent): C, 76.2; H, 6.8; N, 6.5.

EXAMPLE 7 Preparation of a copolymer of ethylene and N-[2-(1,2,3,4- tetrahydro-Z-methyl- 1 -quinolyl) ethyl] maleimide (Compound 3 1) The title compound was prepared by the procedure described in the preceding example from a 1:1 ethylene: maleic anhydride copolymer (DX 840-11 sold by Monsanto Chemical Co.) and N-(2-aminoethyl)-l,2,3,4-tetrahydroquinaldine. Yield: 8.3 g.

Analysis.-Calcd. for C H N O (percent): C, 72.8; H, 7.1; N, 9.5. Found (percent): C, 70.3; H, 7.2; N, 9.0-9.2.

EXAMPLE 8 Preparation of N-(p-dipropylaminophenyl)phthalimide (Compound 32) A stirred solution of 21.9 g. (0.124 mole) of N,N-dipropylaniline in 75 ml. of a 1:1 mixture of concentrated hydrochloric acid and water at 0 C. was treated dropwise with a solution (at 0 C.) of 9.0 g. (0.124 mole) of sodium nitrite in 35 ml. of water. During the addition the temperature was maintained below 5 C. by external cooling. The precipitate of p-nitroso-N,N-dipropylaniline hydrochloride was collected, washed with a 1:1 mixture of water and concentrated hydrochloric acid and neutralized with concentrated ammonium hydroxide. Yield: 17 g. of green solid, M.P. 45-46 C.

Analysis.Calcd. for C H N O (percent): C, 70.0; H, 8.7; N, 13.6; mol. wt. 206. Found (percent): C, 70.0; H, 9.0; N, 13.7; mol. wt. 205.

A solution of 14.0 g. (0.068 mole) of p-nitrOs0-N,N- dipropylaniline in 150 ml. of ethanol was shaken for 10 minutes with palladium under 57 pounds per square inch of hydrogen at room temperature. The reaction was essentially complete in 2 minutes during which time the temperature increased to 50 C. and the pressure dropped to 22 p.s.i. The catalyst was then removed by filtration and the mixture was distilled to obtain 9.9 g. of N,N- dipropyl-p-phenylenediamine as a light oil, B.P. 90- 99 C./0.15 mm.

Analysis.-Calcd. for C H N (percent): C, 75.0; H, 10.4; N, 14.6. Found (percent): C, 73.9; H, 10.4; N, 14.4.

A mixture of 9.6 g. (0.05 mole) of N,N-dipropyl-pphenylenediamine and 7.4 g. (0.05 mole) of phthalic anhydride was stirred at 150 C. for one hour. The resulting mixture was poured with stirring into 300 ml. of isopropanol and the precipitate collected and recrystallized from 200 ml. of isopropanol. Compound 32, N-(p-dipropylaminophenyl)phthalimide, was obtained as orange crystals. Yield: 9.2 g., M.P. -130 C.

AnaIysis.Calcd. for C H N O (percent): C, 74.5; H, 6.8; N, 8.7; mol. wt. 322. Found (percent): C, 74.2; H, 6.5; N, 8.6; mol. wt. 320.

Compound 33, N-(p-dibutylaminophenyl)phthalimide,

N-(p-diphenylaminophenyl)phthalimide (Compound 34) A mixture of 35.1 g. (0.2 mole) of diphenylamine, 49.8 g. (0.2 mole) of 1-iodo-4-nitrobenzene, 27.6 g. (0.2 mole) of anhydrous potassium carbonate, 1 g. of copper powder, and 200 ml. of nitrobenzene was heated under reflux for 24 hours. The nitrobenzene was then removed by steam distillation and the residue was washed with water, dissolved in 400 ml. of benzene, and filtered. Removal of the benzene afforded a dark residue which was distilled at 170 210 C./ 101.4. There was obtained 17.2 g. of yellow-orange pnitrotriphenylarnine following recrystallization from absolute alcohol. M.P. 144.5- 146 C.

Analysis.Calcd. for C H N O (percent): C, 74.5; H, 4.8; N, 9.7; mol. wt. 290. Found (percent): C, 74.5; H, 5.2; N, 9.5; mol. wt. 293.

A solution of 15.7 g. (0.054 mole) of p-nitrotriphenylamine in 150 ml. of 1,4-dioxane was shaken for 1 hour with palladium under 56 p.s.i. of hydrogen at room temperature. The temperature remained constant as the pressure dropped to p.s.i. The product was precipitated in water and recrystallized .irom absolute alcohol. There was obtained 5.3 g. of N,N-diphenyl-p-phenylenediamine as a white solid, M.P. 144-145 C.

Analysis.-Calcd. for C H N (percent): C, 83.0; H, 6.2; N, 10.8; mol. Wt. 260. Found (percent): C, 82.5; H, 6.3; N, 10.8; mol. wt. 262.

A solution of 3.5 g. (0.0135 mole) of N,N-diphenylp-phenylenediamine and 2.0 g. (0.0135 mole) of phthalic anhydride in 50 ml. of dimethylformamide was heated under reflux for 6 hours. The product was precipitated in 4 l. of water and then recrystallized from 600 ml. of isopropanol. There was obtained 3.5 g. of N-(p-diphenylaminophenyl)phthalimide (Compound 34) as a yellow solid, M.P. 205 C.

Analysis.Calcd. for C H N O (percent): C, 80.0; H, 4.6; N, 7.2. Found (percent): C, 80.0; H, 4.5; N, 6.7.

EXAMPLE 10 N,N-dibenzoyl-N,N'-diethyl-p-phenylenediamine (Compound 35) A solution of 16.4 g. (0.1 mole) of distilled N,N- diethyl-p-phenylenediamine in 100 ml. of pyridine was added dropwise to 28.0 g. (0.2 mole) of distilled benzoyl chloride while stirring in a nitrogen atmosphere. The resulting mixture was heated for 1.5 hours on a steam bath and then heated at 150 C. until all the pyridine distilled otf. The remaining material was shaken with 250 ml. of methylene chloride and filtered. The filtrate was washed four times with 200 ml. portions of water and dried over anhydrous calcium chloride. The solvent was removed under reduced pressure and the resulting brown solid was recrystallized first from 125 ml. of absolute alcohol and then from 200 ml. of absolute alcohol. The product was dried in a vacuum oven at 50 C. to yield 5.5 g. of yellow powdery material, M.P. 164-166 C.

Analysis.-Calcd. for C H N O (percent): C, 77.4; H, 6.5; N, 7.5; mol. wt. 372. Found (percent): C, 76.8; H, 6.7; N, 7.2; mol. wt. 375.

EXAMPLE 11 N- [2- 6-'bromo-1,2,3 ,4-tetrahydro-2-methyll-quinolyl) ethyl]phthalimide (Compound 36) A solution of 16 g. (0.05 mole) of N-[2-(1,2,3,4-tetrahydro-2-methyl-1-quinolyl)ethyl]phthalimide (Compound 2) in 80 ml. of benzene was heated to boiling and treated dropwise over a 45 minute period with 8.8 g. (0.055 mole) of bromine. The resulting mixture was heated under reflux for 20 minutes. The solid which separated on cooling to room temperature was filtered, washed with benzene,

and dried in vacuo at 58 C. There was obtained 19.6 g. of tan solid, M.P. 169.5-17l C. Fifteen grams of this solid was recrystallized from a mixture of 1840 ml. of ethanol and 700 ml. of water to obtain 9 g. of yellowbrown solid, M.P. 156.5-157.5 C. This was recrystallized from 225 m1. of a 60:40 ethanol-chloroform mixture. There was obtained 3.8 g. of yellow crystals, M.P. 157- 158.5 C.

Analysis.-Calcd. for C H BrN O (percent): C, 60.2; H, 4.8; Br, 20.0; N, 7.0. Found (percent): C, 60.2; H, 3.2; Er, 20.2; N, 6.9.

EXAMPLE 12 Preparation of N-[2-(1,2,3,4-tetrahydro-2-methyl-1- quinolyl) phthalimide (Compound 37) A solution of 14.7 g. (0.01 mole) of 1,2,3,4-tetrahydroquinaldine in 300 m1. of glacial acetic acid was treated dropwise over a 10 minute period with a solution of 12 g. (0.174 mole) of sodium nitrite in 30 ml. of water while stirring at room temperature. Stirring was continued for an additional hour and the resulting solution was poured with stirring into 4 l. of water. The precipitated oil was extracted with 50 ml. of chloroform and the extract was washed with water and dried over anhydrous magnesium sulfate. Removal of the chloroform by evaporation in vacuo yielded 8.1 g. of N-nitroso 1,2,3,4 tetrahydroquinaldine as a light brown oil.

Analysis.-Calcd. for C H N O (percent): C, 68.1; H, 6.8; N, 15.9. Found (percent): C, 67.2; H, 6.8; N,

A rapidly stirred suspension of 11.1 g. (0.17 mole) of zinc dust in 25 ml. of water was treated dropwise at 20 C. with a solution of 8.0 g. (0.046 mole) of N- nitroso 1,2,3,4 tetrahydroquinaldine in 25 ml. of acetic acid. Stirring was continued for 1.5 hours at room temperature. The unreacted zinc was filtered ofii, washed with 60 ml. of warm 5% hydrochloric acid, and the combined filtrates were treated with 140 ml. of 40% sodium hydroxide and then extracted with two ml. portions of chloroform. The combined extracts were washed with water and dried over anhydrous magnesium sulfate. Removal of the solvent in vacuo yielded 3.1 g. of N-amino 1,2,3,4 tetrahydroquinaldine as a light brown oil.

Analysis.Calcd. for C H N (percent): C, 74.1; H, 8.6. Found (percent): C, 75.4; H, 8.5.

A mixture of 2.95 g. (0.018 mole) of N-amino-1,2,3,4-

tetrahydroquinaldine and 2.7 g. (0.018 mole) of phthalic N- [2- 1,2,3,4-tetrahydro-2-methyll-quinolyl methyl] phthalimide (Compound 3 8) A mixture of 14.7 g. (0.1 mole) of l,2,3,4 tetrahydroquinaldine, 17.7 g. (0.1 mole) of hydroxymethylphthalimide, and 50 ml. of ethanol was heated under reflux for 18 hours. The resulting red solution was filtered and the filtrate was allowed to stand at room temperature overnight. The yellow-orange solid which separated was recrystallized from ml. of ethanol. (Initially, an oil separated which crystallized on standing for 4 days.) The product was dissolved in 125 ml. of hot ethanol and then allowed to cool to room temperature. The supernatant liquid was removed from the oil which separated. On standing overnight the liquid yielded 5.2 g. of yellow crystals, M.P. 121-1235 C.

EXAMPLE 14 Preparation of N-[2 methyl-4-diethylamino)phenyl] 3-dimethylaminophthalimide (Compound 47) A mixture of 43.5 g. (0.2 mole) of 3-aminophthalic acid hydrochloride, 43.9 g. (0.2 mole) of 2-amino-5- diethylaminotoluene hydrochloride, and 600 ml. of glacial acetic acid was heated under reflux for 8 hours. The solvent was removed from the yellow solution by evaporation in vacuo at a bath temperature of 50 C. The resulting viscous residue was dissolved in 150 ml. of ethanol and precipitated in 3 liters of ether. The yellow solid was triturated with ether, filtered, and dried in air at 60 C. to obtain 71.5 g. of N-[(2-methyl-4-diethylamino)phenyl]-3-aminophthalimide hydrochloride as a yellow solid, M.P. 121-155 C. A mixture of 35.9 g. (0.1 mole) of N-[(2-methyl 4 diethylamino)phenyl]-3- aminophthalimide and 50 ml. of dimethyl sulfate was heated under reflux for 30 minutes. The resulting hot solution was poured, with stirring, into 600 ml. of water and allowed to stand for 1.5 hours, The pH of the solution was then adjusted to 5.0 with concentrated sodium hydroxide. The solid which precipitated was washed thoroughly with water and dried in air at 40 C. to obtain 22.1 g. of orange solid. This was then recrystallized four times from methanol to yield 2.8 g. of N-[ (Z-methyl- 4-diethylamino)phenyl] 3 aminophthalimide as a yellow solid, M.P. 129.5131.5 C.

Analysis.Calcd for C H N O (percent): C, 71.8; H, 7.1; N, 12.0. Found (percent): C, 71.4; H, 6.9; N,

The following three examples illustrate a novel method of preparation of certain unsaturated imides which can be readily hydrogenated to give the saturated counterparts.

EXAMPLE N- [2-( 1,2,3,4-tetrahydro-2-methyll-quinolinyl) vinyl]phthalimide (Compound 3) A mixture of 18.5 g. (0.1 mole) of phthalimide potassium salt, 16.9 g. (0.1 mole) of bromoacetaldehyde dimethylacetal, and 125 ml. of N,N-dimethylformamide was stirred under reflux for 18 hours. The resulting mixture was filtered while hot and the filtrate was poured immediately into 4 l. of water with stirring. This mixture was allowed to stand for one hour. The white solid which separated was collected, washed with water, and dried at 40 C. A 16 g. yield of phthalimidoacetaldehyde dimethylacetal, M.P. l06l08.5 C. was obtained. A mixture of 10 g. (0.02 mole) of phthalimidoacetaldehyde dimethylacetal, ml. of 90% formic acid and 10 m1. of concentrated hydrochloric acid was heated on a steam bath for 45 minutes. The resulting solution was diluted with 90 ml. of water, treated with decolorizing carbon, and filtered. The filtrate was concentrated in vacuo at 20 C. for 4 hours. The white solid obtained was collected, washed with water, and dried at C. to yield 3.4 g. of phthalimidoacetaldehyde, M.P. 114 115.5 C. A mixture of 28.4 g. (0.15 mole) of phthalimidoacetaldehyde, 22.0 g. (0.15 mole) of 1,2,3,4-tetrahydroquinaldine, and 500 ml. of benzene was heated under reflux for 17 hours during which time 2.4 ml. of water was collected from azeotropic distillation. The red solid obtained on removal of the solvent in vacuo at C. was recrystallized from acetonitrile to obtain 28.2 g. of N-[2 (1,2,3,4-tetrahydro-2-methyl-l-quinolyl) vinyl]phthalimide (Compound 39) as a red crystalline solid, M.P. 138.5-140"; e=1.93 10 (298 m 141x10 (342 m Absorption extends to 560 111,14 but there are no maxima in the visible region.

Alzalysis.-Calcd. for C H N O' (percent): C, 75.5; 1-1', 5.7; N, 8.8. Found (percent): C, 75.8; H, 5.6; N, 8.8.

1 6 EXAMPLE 16 Novel preparation of N-[2-(1,2,3,4-tetrahydro-2-methyl- 1-quinolyl)ethyl]phthalimide (Compound 2) A mixture of 7.9 g. (0.025 mole) of N-[2-(1,2,3,4- tetrahydro-Z-methyl-1-quinolyl)vinyl]phthalimide, 2 g. of 10% palladium-on-charcoal, and 140 ml. of 3A alcohol was shaken in a stainless steel autoclave under 60 p.s.i. of hydrogen at 60 C. for 3 hours. The reaction mixture was cooled to room temperature and the solid product was collected and dried at 60 C. A total of 3.2 g. of yellow solid, M.P. 118.5 C., was obtained.

EXAMPLE 17 The following compounds were prepared in the manner of Example 15 from phthalimidoacetaldehyde and the appropriate secondary amine:

TABLE 1 Number Name M.P. C.)

40 N-(2-diphenylarninovinybphthalimide 109. 5111 50 N[2 (2-methyl-6-di.methylamino-1,2,3,4 152-153. 5

tetrahydroquinolybvinyl] phthalimide. 51 N-[2(N-phenyl-N-benzyl)aminovmyl] 136. 5-138. 5

phthalimide. 52 N-[2-(N-morpholino)vinynphthahmide 172-176 The use of the compounds in this invention will now be described by reference to the following examples, wherein the sensitizers referred to are identified as follows:

EXAMPLE 18 Solutions each containing one of the photoconducting imides designated Compounds 1 thru 49, 53, and 54 were made for coating on a support material by mixing 0. 15 part of the imide with 0.002 part of Sensitizer A and dissolving these together with 0.5 part by weight of a resinous polyester binder with suitable stirring in dichloromethane The resultant mixtures were then each handcoated on an aluminum-laminated paper support. The polyester used is a copolymer of terephthalic acid and a glycol mixture comprising a 9:1 wt. ratio of 2,2-bis[4- ('fl-hydroxyethoxy)phenyl]propane and ethylene glycol. The wet coating thickness on the support was 0.004 inch. After drying, each electrophotographic element was employed in a standard xerographic process which included charging under a positive corona and exposure from behind a positive-appearing line transparency to a 3000 K. tungsten source of ZO-foot-candle illuminance at the exposure surface. The coated surface of the element was dusted with an electrostatically attractable powder having optical density according to the method and materials described in US. Pat. 2,297,691. Images were obtained in every case.

EXAMPLE 19 Elements prepared according to Example 18 containing photoconductors as tabulated herein and containing Sensitizer A and a control element containing photoconductor and binder alone were tested by the following procedure. Each element was charged under positive corona source until the surface potential, as measured by an electrometer probe, reached 600 volts. The elements were then individually exposed to a light source in the manner of Example 18, with the exception that the positive transparency was replaced by a stepped density gray scale. The actual positive electrical H and D speeds of each element was determined in the following manner. Each element was electrostatically charged under a corona source until the surface potential, as measured by an electrometer probe, reached about 600 volts. The charged element was then exposed to a light source through a transparent stepped density gray scale. The exposure caused reduction of the surface potential of the element under each step of the gray scale from its initial potential, V to some lower potential, V, whose exact value depended on the actual amount of exposure in meter-candle-seconds received by the area. The results of these measurements were then plotted on a graph of surface potential V vs. log exposure for each step. The actual positive speed of the element can then be expressed in terms of the reciprocal of the exposure required to reduce the surface potential to any arbitrarily selected value. In Table 2, the actual positive speed is the numerical expression of 10 divided by the exposure in metercandle-seconds required to reduce the 600-volt charged surface potential by 100 volts.

TABLE 2 Speed No sensitizer Sensitizer A Conipound Number:

03 OOOOQIWNOWODOOQOQO EXAMPLE 20 The procedure of Example 19 was repeated, with the exception that the sensitizer used was Sensitizer B. The results are presented in Table 3.

TABLE 3 Speed No sensitizer Sensitizer A The procedure of Example 19 was repeated with the exception that the sensitizer used was Sensitizer C. The results are presented in Table 4.

TABLE 4 Speed No sensitizer Sensitizer C Com ound Number:

EXAMPLE 22 The procedure and sensitizer of Example 21 were followed with the exception that polarity of initial charging was negative. The results are presented in Table 5.

TABLE 5 Speed No sensitizer Sensitizer C EXAMPLE 23 The procedure of Example 19 was followed, with the exception that the sensitizer used was Sensitizer D. The results are presented in Table 6.

TABLE 6 Speed No sensitizer Sensitizer D Compound Number:

EXAMPLE 24 The procedure and sensitizer of Example 2.3 were followed, with the exception that the polarity of initial charging was negative. The results are presented in Table 7.

TABLE 7 Speed No sensitizer Sensitizer D Comfipound Number:

EXAMPLE 25 The procedure of Example 19 was followed, with the exception that the sensitizer used was Sensitizer E. The results are presented in Table -8.

TABLE 8 Speed N0 sensitizer Sensitizer E Conpound N umber:

EXAMPLE 26.

The procedure and sensitizer of Example 25 were used, with the exception that the polarity of initial charging was negative. The results are presented in Table 9.

TABLE 9 Speed No sensitizer Sensitizer E Compound Number- The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be elfected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photoconductive composition for use in electrophotographic image-forming processes comprising a sensitizing compound and a photoconductor which is an N- substituted imide having the structural formula:

' li Q-C wherein:

(a) Q and Q are each selected from the group consisting of phenyl radicals and, when taken together with the adjacent groups, the atoms necessary to complete an imide ring system having to 6 atoms in its nucleus, and,

(b) R is selected from the group consisting of (1) phenyl radicals, (2) heterocyclic radicals, (3) radicals having the structural formula:

where n is an integer from 0 through 12, and R and R are each selected from the group consisting of hydrogen atoms, alkyl radicals, aryl radicals, and, when taken together with the nitrogen atom of said R radical, the atoms necessary to complete a heterocyclic ring system having 5 to 6 atoms in its nucleus, (4) radicals having the structural formula:

where n is an integer from 0 through 12, and Z and Z are each selected from the group consisting of phenyl radicals and, when taken together with the adjacent groups, the atoms necessary to complete an imide ring system having 5 to 6 atoms in its nucleus,

(5') radicals having the structural formula:

where Z and Z are each as defined above, (6) radicals having the structural formula:

20 where Z and Z are each as defined above, and (7) radicals having the structural formula:

where x is an integer from 0 through 10, and R and R are each as defined above. 2. A photoconductive composition comprising a sensitizing compound and a photoconductor which is an N- substituted imide having the structural formula:

R1 at N Re (I where R is a lower alkyl radical, and R and R are each selected from the group consisting of hydrogen atoms and dialkylamino and diarylamino radicals.

4. A photoconductive composition as defined in claim 1 wherein Q and Q when taken together with the adjacent groups form a phthalimide ring system.

5. The photoconductive composition as defined in claim 1 wherein the sensitizing compound is selected from the group consisting of pyrylium and thiapyrylium sensitizing compounds.

6. The photoconductive composition as defined in claim 1 wherein the sensitizing compound is selected from the group consisting of 2,6-bis(ethylphenyl)-4-(4-n-amyloxyphenyl) thiapyrylium perchlorate, 2,4-bis(4-ethoxyphenyl)-6-(4-n-amyloxystyryl) pyrylium fluoroborate, 2,4- bis(4 ethylphenyl)-6-(4-styrylstyry1)pyrylium perchlorate, 2,4,7-trinitrofluorenone, Crystal Violet, and Rhodamine B.

7. An electrophotographic element comprising a conducting support and a photoconductive layer of a composition comprising an N-substituted imide having the structural formula:

wherein:

(a) Q and Q are each selected from the group consisting of phenyl radicals and, when taken together with the adjacent groups, the atoms necessary to complete an imide ring system having 5 to 6 atoms in its nucleus, and

21 (b) R is selected from the group consisting of (l) phenyl radicals, (2) heterocyclic radicals, (3) radicals having the structural formula:

(CH2),,N

where n is an integer from through 12, and R and R are each selected from the group consisting of hydrogen atoms, alkyl radicals, aryl radicals, and, when taken together with the nitrogen atom of said R radical, the atoms necessary to complete a heterocyclic ring system having to 6 atoms in its nucleus, (4) radicals having the structural formula:

it o-z -(CH2)nN where n is an integer from 0 through 12, and Z and Z are each selected from the group consisting of phenyl radicals and, when taken together with the adjacent groups, the atoms necessary to complete an imide ring system having 5 to 6 members in its nucleus,

(5) radicals having the structural formula:

0 o o i Jz t t N where Z and Z are each as defined above, (6) radicals having the structural formula:

O-Z' ll 0 where Z and Z are each as defined above, and (7) radicals having the structural formula:

where x is an integer from 0 through 10, and R and R are each as defined above. 8. An electrophotographic element as defined in claim 7 wherein the photoconductive composition includes a sensitizing compound.

9. An electrophotographic element as defined in claim 8 wherein in the photoconductive composition Q and Q when taken together with the adjacent groups form a phthalimide ring system.

10. An electrophotographic element comprising a conducting support having coated thereon a layer of a photoconductive composition comprising a sensitizing compound and an N-substituted imide selected from the group consisting of compounds having the structural formula:

where z is an integer from 0 through 3 and R and R are each selected from the group consisting of hydrogen atoms and lower alkyl radicals, and compounds having the structural formula:

where R is a lower alkyl radical, and R and R are each selected from the group consisting of hydrogen atoms and dialkylamino and diarylamino radicals.

11. A photoconductive element as defined in claim 10 wherein the sensitizing compound is selected from the group consisting of pyrylium and thiapyrylium sensitizing compounds.

12. A photoconductive element as defined in claim 10 wherein the sensitizing compound is selected from the group consisting of 2,6bis(ethylphenyl)-4-(4-n-arnyloxyphenyl)thiapyryliurn perchlorate, 2,4 bis(4 ethoxyphenyl)-6- (4-n-amyloxystyryl)pyrylium fiuoroborate, 2,4- bis(4-ethylphenyl)-6-(4-styrylstyryl) pyrylium perchlorate, 2,4,7-trinitrofluorenone, Crystal Violet, and Rhodamine B.

13. A photoconductive element comprising a conductive support having coated thereon a layer of a photoconductive composition comprising N-[2-l,2,3,4-tetrahydro 2-methyl 1 quinolyl)ethyl]phthalimide as a photoconductor sensitized with 2,4-bis(4-ethylphenyl)-6-(4-styrylstyry1)pyrylium perchlorate.

References Cited UNITED STATES PATENTS 2,729,673 1/ 1956 Prichard 260-326 X 3,250,615 5/1966 Van Allan et a1. 96-1 3,316,087 4/1967 Munder et a1. 961

GEORGE F. LESMES, Primary Examiner M. B. WITTENBERG, Assistant Examiner US. Cl. X.R. 96-16; 260326