GB2248698A - Electrophotographic imaging member - Google Patents

Abstract

An electrophotographic imaging member having a supporting substrate (1), an adhesive layer (2), an electrically conductive layer (3) formed from a I-VII semiconductor, a charge blocking layer (4). and at least one photoconductive layer (6) and preferably an adhesive layer (8), a charge-generating layer (6) and a charge transporting layer (7). The adhesive layer (2) is preferably a polyester and the semiconductor layer (3) is preferably a copper or silver halide; layer (2) ensuring good adhesion of layer (3) with support. The charge generating layer (6) may be PVK-Se. <IMAGE>

Description

ELECTROPHOTOGRAPHIC IMAGING MEMBER This invention relates in general to electrophotography and, in particular, to an electrophotographic imaging member.

In electrophotography, an electrophotographic plate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging its surface. The plate is then exposed to a pattern of activating electromagnetic radiation such as light. The radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent Image may then be developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the electrophotographic plate to a support such as paper.This Imaging process may be repeated many times with reusable photoconductive insulating layers An electrophotographic Imaging member may be provided in a number of forms For example, the imaging member may be a homogeneous layer of a single material such as vitreous selenium or it may be a composite layer containing a photoconductor and another material. One type of composite Imaging member comprises a layer of finely divided particles of a photoconductive Inorganic compound dispersed in an electrically insulating organic resin binder. U S.Patent No 4,265,990 discloses a layered photoreceptor having separate photogenerating and charge transport layers The photogenerating layer Is capable of photogenerating holes and Injecting the photogenerated holes into the charge transport layer As more advanced, higher speed electrophotographic copiers, duplicators and printers were developed, degradation of Image quaiity was encountered during extended cycling. Moreover, complex, highly sophisticated duplicating and printing systems operating at very high speeds have placed stringent requirements including narrow operating limits on photoreceptors.For example, the numerous layers found In many modern photoconductive imaging members must be highly flexible, adhere well to adjacent layers, and exhibit predictable electrical characteristics within narrow operating limits to provide excellent toner images over many thousands of cycles One type of multilayered photoreceptor that has been employed as a belt in electrophotographic imaging systems comprises a substrate, a conductive layer, a blocking layer, an adhesive layer, a charge generating layer, a charge transport layer and a conductive ground strip layer adjacent to one edge of the Imaging layers.This photoreceptor may also comprise additional layers such as an anti-curl layer and an optional overcoating layer Transparent electrophotographic Imaging members are currently being developed Such transparent electrophotographic imaging members require a transparent substrate ana transparent conductive layer for rear exposure to activating electromagnetic radiation.

Conductive layers (ground planes) comprising cuprous iodide and other l-VII semiconductors such as CuBr, CuCI and the corresponding silver salts provide desirable conductive properties while maintaining the requisite transparency desired in such members. See, for example, a review article by A. Goldmann, "Band Structure and Optical Properties of Tetrahedrally Coordinated Cuand Ag- Halides," Phys. Stat. Sol. (b) 81,9-47(1977).

The use of cuprous iodide as a conductive material in electrophotographic elements is known. For example, U.S. Patents Nos. 4,082,551 to Steklenkski etal and 4,485,161 to Scozzafava et al disclose conductive layers of cuprous iodide coated on polyester substrates. U.S.

Patent No 4,661,428 to Ishida discloses an electrically conductive substrate for composite photosensitive elements which may comprise Cul. U.S. Patent No. 4,465,751 to Kawamura et al discloses a light-sensitive material comprised of a conductive layer containing cuprous iodide and a photoconductive layer.

Cuprous iodide has also been used as a photoconductive material. For example, U.S.

Patent No. 4,190,445 to Takahashi et al discloses inorganic photoconductive materials such as Cul in an insulating binder for a photoconductive layer. U.S. Patent No. 4,188,212 to Fujiwara petal discloses a photoelectric sensor comprising a photoconductive material such as Cul.

Photoconductors, especially those formed with a cuprous iodide conductive layer, will delaminate under slight flexing due to poor adhesion to the supporting substrate.

Delamination of cuprous iodide layers in the photoconductive device is frequently seen from commonly used substrate materials, for example, biaxially oriented polyester known as Mylar from du Pont or Melinex from ICI Americas, Inc. Moreover, in electrostatographic imaging systems, where transparency of the substrate and conductive layer is necessary for rear exposure to activating electromagnetic radiation, any undesired exposure to activating electromagnetic radiation or any reduction of transparency due to opacity of the supporting substrate or conductive layer will cause a reduction in performance of the photoconductive imaging member.

Although the reduction in transparency may in some cases be compensated for by increasing the intensity of the electromagnetic radiation, such increase is generally undesirable due to the amount of heat generated, as well as the greater cost to achieve higher intensity. A conductive layer which exhibits the above deficiencies is highly undesirable. However, there are few electrically conductive materials which form substantially transparent layers having desirable conductive properties.

The use of an adhesive layer between a support member and conductive layer is disclosed in U.S. Patents No. 4,024,030 to Burov et al and No. 3,880,657 to Rasch. The Burov et al patent discloses radiation sensitive elements comprising a thin metal layer attached to a substrate by an intermediate adhesive layer. A photosensitive compound in Intimate contact with the metal layer Is capable of reacting chemically with the metal layer when exposed to radiation. The Rasch patent discloses an adhesive polymeric subbing layer between a polyester dielectric support and a conducting layer. The adhesive subbing layer is a vinylidene chloride-contaming polymer, and the conductive layer is comprised of a metal intermixed with a protective inorganic oxide component.The conducting layer of metal and protective oxide is formed by vacuum codeposition to achieve an intimate physical intermixture. Transparent conductive oxide coatings may be formed by solution coating, but require an undesirable heating step of several hundred degrees Celsius that would decompose many or most polymeric substrates. Solution coating of such materials is impractical and thus not preferred.

It is an object of the invention to provide an electrophotographic imaging member .n which there is good adhesion between a supporting substrate and a conductive layer.

Accordingly, the present invention provides an electrophotographic imaging member, comprising a supporting substrate, a contiguous adhesive layer, an electrically conductive layer comprising a l-VII semiconductor and at least one photoconductive layer.

In one embodiment the electrophotographic Imam no member comprises a substantially transparent conductive layer'which exhibits greater resistance to layer delamination, -he transparent conductive layer comprising cuprous iodide.

The conductive layer may be solution coated, and does not delaminate after coating, and the adhesive between the support member and the substantially transparent conductive :ayer does not adversely affect the electrical Intensity of the Imaging member The present invention will be described further, with reference to the single Figure which is a cross-sectional view of a multilayer photoreceptor according to one embodiment of the nvention.

The electrophotographic imaging member contains an adhesive layer located between a supporting substrate and a conductive layer Tne adhesive !ayer allows for excellent adhesion between the supporting substrate and the conductive layer The conductive layer may De comprised of a substantially transparent conductive material. The adhesive layer In the embodiment of the present invention provides these benefits without adverse effects on optical.

conductive and mechanical properties of the device.

A representative structure of an electrophotographic imaging member is shown in Figure 1. This Imaging member is provided with a supporting substrate 1, an adhesive layer 2, an electrically conductive ground plane (conductive layer) 3, a hole blocking layer 4, an optional adhesive layer 5, a charge generating layer 6, and a charge transport layer 7. Optional layers such as an overcoating layer over the charge transport layer, and an antt-curl layer adjacent the substrate opposite to the imaging layers, may also be used In the device.

A description of the layers of the electrophotographic imaging member shown In =:gure 1 follows.

The Supportinq Substrate The supporting substrate 1 may be opaque or substantially transparent and may compnse numerous suitable materials having the required mechanical properties. There may be employed various resins known for this purpose including polyesters, polycarbonates, polyamides, polyurethanes, and the like. The substrate should be flexible and may have any number of different configurations such as, for example, a sheet, a scroll, an endless flexible belt, and the like. Preferably, the substrate is in the form of an end'less flexible belt and comprises a commercially available biaxially oriented polyester known as Mylar, available from E.l. du Pont de Nemours & Co, or Melinex, available from ICI Americas Inc., or Hostaphan, available from American Hoechst Corporation.Other materials for the substrate include polymeric materials such as polyvinyl fluoride, available as Tedlar from du Pont, or polyimides such as that available as Kapton from du Pont.

The thickness of the substrate layer depends on numerous factors, including mechanical performance and economic considerations. The thickness of this layer may range from about 65 micrometers to about 150 micrometers, and preferably from about 75 micrometers ro about 125 micrometers for optimum flexibility and minimum induced surface bending stress v.hen cycled around small diameter rollers, e.g, 19 millimeter diameter rollers. The substrate for a flexible belt may be of substantial thickness, for example, over 200 micrometers, or of minimum thickness, for example, less than 50 micrometers, provided there are no adverse effects on the i nal photoconductive device. The surface of the substrate layer could be cleaned prior to coating o promote greater adhesion of the deposited coating.Cleaning may be effected byexposing ne surface of the substrate layer to plasma discharge, ion bombardment, solvent treatment and the like he Adhesive Laver The adhesive layer 2 is coated onto the substrate to promote adhesion of the conductive layer to the supporting substrate. The adhesive layer may be formed from filmforming polymers such as copolyester, for example, du Pont 49,000 resin (available from E.l. du Pont de Nemours & Cho ), Vitel PE-100, Vitel PE-200, Vitel PE-200D and Vitel PE-222 (available from Goodyear Rubber & Tire Co.) and the like.

Du Pont 49,000 is a linear saturated copolyester of four diacids and ethylene glycol having a molecular weight of about 70,000 and a glass transition temperature of 32"C. Its molecular structure is represented as

0 ii HO-C-[Diacid-Ethylene glycoi*OH where n is a number which represents the degree of polymerization and gives a molecular weight of about 70,000. The ratio of diacid to ethylene glycol in the copolyester is 1:1. The diacids are terephthalic acid, isophthalic acid, adipic acid and azelaic acid in a ratio of 4:4:1:1.

Vitel PE-100 is a linear copolyester of two diacids and ethylene glycol having a molecular weight of about 50,000 and a glass transition temperature of 71"C. Its molecular structure is represented as

0 If HO-C-[Dlacid-Ethylene glycolf OH where n is a number which represents the degree of polymerization and gives a molecular weight of about 50,000. The ratio of diacid to ethylene glycol in the copolyester is 1:1. The two diacids are terephthalic acid and isophthalic acid In a ratio of 3:2.

Vitel PE-200 is a linear saturated copolyester of two diacids and two diols having a molecular weight ofabout 45,000 and a glass transition temperature of 67"C. The molecular structure is represented as

0 II HO-C-[DIacld-Diole OH where n is a number which represents the degree of polymerization and gives a molecular weight of about 45,000 The ratio of diacid to diol in the copolyester is 1:1 The two diacids are terephthalic and isophthalic acid In a ratio of 1.2:1.The two diols are ethylene glycol and 2,2dimethyl propane diol in a ratio of 1.33:1 The adhesive layer should be continuous and preferably has a dry thickness between about 0.01 micrometer and about 2 micrometers, and more preferably between about 0 05 micrometer and 0 5 micrometer At thicknesses less than about 0.01 micrometer, the adhesion oetween the substrate and the conductive layer Is poor and spontaneous delamination occurs vhen the belt Is transported over small diameter supports such as rollers and curved skid plates waving 19mm diameter of curvature. When the thickness of the adhesive layer Is greater than about 2 micrometers, excessive residual charge build-up may be observed during extended cycling.

The adhesive layer is preferably applied as a solution. Any suitable solvent or solvent mixtures may be employed to form a coating solution. Typical solvents Include tetrahydrofuran, toluene, methylene chloride, cyclohexane, and the like, and mixtures thereof. Any suitable coating technique may be utilized to mix and thereafter apply the adhesive layer coating mixture typical application techniques include spraying, dip coating, gravure coating, and the like. Drying of the deposited coating may be effected by any suitable conventional technique such as oven drying, Infrared radiation drying, air drying and the like.

ne Electrical lv Conductive Ground Plane The electrically conductive ground plane 3 may be an opaque or transparent e'ectrically conductive layer which may be formed, for example. on the adhesive layer by any suitable coating technique, such as a vacuum depositing technique. Preferably, the material can be coated from a solution. Preferred materials are the I- VII semiconductors such as Cul, CuBr, CuCI and corresponding silver salts. The l-VII semiconductors are a class of compounds formed from Group IB and Group VIIA elements of the Periodic Table.

With solution-coatable materials, for example, cuprous iodide, any suitable coating technique may be used to apply the layer, including those discussed above for application of the adhesive layer. Cuprous iodide may be dissolved in any suitable solution, for example, organic ritriles, and applied to the adhesive layer 2. The coated solution dries to form neat Cul which may be amorphous, crystalline or polycrystalline. With crystalline structures, particle sizes of the Cul may range from about 100 to about 200 Angstroms.

The conductive layer may vary in thickness over substantially wide ranges depending on the optical transparency, conductivity and flexibility desired for the electrophotoconductive member. Accordingly, for a flexible photoresponsive imaging device, the thickness of the conductive layer may be between about 0.01 micrometer and about 0.1 micrometer, and more preferably from about 0.02 micrometer to about 0.08 micrometer for an optimum combination of electrical conductivity, flexibility and light transmission.

he Charge Blocking Layer After formation of the electrically conductive ground plane layer, the blocking layer may be applied thereto. Electron blocking layers for positively charged photoreceptors allow roles from the Imaging surface of the photoreceptor to migrate toward the conductive layer. For negatively charged photoreceptors, any suitable hole blocking layer capable of forming a barrier to prevent hole injection from the conductive layer to the opposite photoconductive layer may be utilized. When a material such as cuprous iodide is used in the conductive layer, it is necessary to employ a blocking material which does not react with the material of the conductive layer. In particular, materials for the blocking layer which contain amino, imino or tertiary amine groups, such as nitrogen containing amines, may react with the conductive layer and reduce or destroy tse electrical conductivity of the conductive layer. Thus, use of these materials is not preferred unless the materials are modified to render them incapable of interacting with the conductive layer. Modification may be achieved by metal- complexing the amino, imino or tertiary amine croup of the charge blocking material.

The charge blocking layer may include polymers such as polyvinylbutyral, epoxy resins, polyesters, polysiloxanes, polyamides, polyurethanes and the like, or may be modified ritrogen-containing siloxanes or nitrogen. containing titanium compounds such as tri methoxysilyl propylene diamine, hydrolyzed trimethoxysilyl propyl ethylene diamine, N-beta (aminoethyl) gamma-amino-propyl trimethoxy silane, isopropyl 4-aminobenzene sulfonyl, di(dodecylbenzene sulfonyl) titanate, isopropyl di(4- aminobenzoyl)isostearoyl titanate, isopropyl tri(N-ethylamino-ethylamino)titanate, isopropyl trianthranil titanate, isopropyl tri(N,N.dimethyl- ethylamino)titanate, titanium-4-amino benzene sulfonate oxyacetate, titanium 4- aminobenzoate isostearate oxyacetate, [H2N(CH2)4jCH3Si(OCH3)2, (gamma-aminobutyl) methyl diethoxy- plane, (H2N(CH2)3]CH 3Si(OCH3)2, and (gamma-aminopropyl) methyl diethoxysilane, as disclosed in U.S. Patents Nos. 4,338,387, 4,286,033 and 4,291,110.

Charge blocking materials containing amino, imino or tertiary amine groups are preferably complexed with a metal, a metal ion or a metal-containing compound. Preferred metals include transition metals, for example, copper, silver, gold, nickel, palladium, platinum, cobalt, rhodium, irridium, iron, ruthenium, osmium, manganese, chromium, vanadium, titanium, zinc, cadmium, mercury, lead, main group metals, rare earth atoms, and the like. Preferably, transition metals are used which coordinate to nitrogen in the charge blocking material.

Preferably, transition metals are used which also can form 2, 3, 4, 5 and 6 coordinate species and higher coordination numbers for larger metal ions The metal ions may be provided in a solution which is added to the hydrolyzed silane solution, and chemically reacted. The resulting solution may then be coated as a charge blocking layer and dried. The dried charge blocking layer is substantially uniform throughout the layer. That is, the layer contains a uniform mixture of the complexed blocking material. Hydrolyzed silanes have the general formula

wherein R1 is an alkyiidene group containing 1 to 20 carbon atoms, R2, R3 and R7 are independently selected from the group consisting of H, a lower alkyl group containing 1 to 3 carbon atoms and a phenyl group, X is an anion of an acid or acidic salt, n is 1-4, and y is 1-4.The Imaging member is preferably prepared by depositing on the Cul conductive layer, a coating of an aqueous solution of the hydrolyzed aminosilane at a pH between about 4 and about 10, drying the reaction product layer to form a siloxane film and applying an adhesive layer, and thereafter applying electrically operative layers, such as a photogenerator layer and a hole transport layer, to the adhesive layer.

The blocking layer should be continuous and have a thickness of less than about 0.5 micrometer because greater thicknesses may lead to undesirably high residual voltage. The thickness of the charge blocking layer may range between about 0.002 micrometer and about 0.4 micrometer, and preferably ranges from about 0.02 micrometer to about 0.16 micrometers. The blocking layer may be applied by any suitable conventional technique such as spraying, dip coating, draw bar coating, gravure coating, silk screening, air knife coating, reverse roll coating, vacuum deposition, chemical treatment and the like.For convenience In obtaining thin layers, the blocking layer is preferably applied in the form of a dilute solution, with the solvent being removed after deposition of the coating by conventional techniques such as by vacuum, heating and the like Generally, a weight ratio of blocking layer material and solvent of between about 0 05: 100 to about 0.5:100 is satisfactory for spray coating.

he Optional Adhesive Layer In most cases, intermediate layers between the blocking layer and the adjacent charge generating or photogenerating layer may be desired to promote adhesion. For example, rhe optional adhesive layer 5 may be employed. If such layers are utilized, they preferably have a dry thickness between about 0.001 micrometer to about 0.2 micrometer. Typical adhesive layers include film-forming polymers such as polyester, du Pont 49,000 resin (available from E.l. du Pont de Nemours & Co.), polyvinylbutyral, polyvinylpyrrolidone, polyurethane, polymethyl methacrylate, and the like.

he Charge Generating Layer Any suitable charge generating (photogenerating) layer 6 may be applied to the blocking layer. If an optional adhesive layer is applied to the blocking layer, then the photogenerating layer is coated to that adhesive layer. Examples of materials for ohotogenerating layers include inorganic photoconductive particles such as amorphous selenium, trigonal selenium, and selenium alloys selected from the group consisting of selenium-tellurium, selenium-tellurium-arsenic, selenium arsenide; and phthalocyanine pigment such as the X-form of metal-free phthalocyanine described in U.S.Patent No. 3,357,989; metal phthalocyanines such as vanadyl phthalocyani ne and copper phthalocyanine; dibromoanthanthrone; squaryl ium; quinacridones such as those available from du Pont under the tradename Monastral Red, Monastral Violet and Monastral Red Y; dibromo anthanthrone pigments such as those available under the trade names Vat orange 1 and Vat orange 3; benzimidazole perylene; substituted 2,4- diaminotriazines such as those disclosed in U.S. Patent No. 3,442,781; polynuclear aromatic quinones such as those available from Allied Chemical Corporation under the trade name Indofast Double Scarlet, Indofast Violet Lake B, Indofast Brilliant Scarlet and Indofast Orange; and the like, dispersed in a film forming polymeric binder.Multi-photogenerating layer compositions may be utilized where a photoconductive layer enhances or reduces the properties of the photogenerating layer. Examples of this type of configuration are described in U.S. Patent No. 4,415,639.

Other suitable photogenerating materials known in the art may also be utilized, If desired.

Charge generating layers comprising a photoconductive material such as vanadyl phthalocyanine, titanyl phthalocyanine, metal-free phthalocyanine, benzimidazole perylene, amorphous selenium, trigonal selenium, selenium alloys such as selenium-tellurium, selenium-telluriumarsenic, selenium arsenide, and the like and mixtures thereof are especially preferred because of their sensitivity to white light. Vanadyl phthalocyanine, titanyl phthalocyanine, metal-free phthalocyanine and tellurium alloys are also preferred because these materials provide the additional benefit of being sensitive to infra-red light.

Any suitable polymeric film-forming binder material may be employed as the matrix in the photogenerating layer. Typical polymeric film-forming materials include those described, for example, In U.S. Patent No. 3,121,006. If an adhesive layer is used between the blocking and photogenerating layers, the binder Dolymer should adhere well to the adhesive layer, dissolve in a solvent which also dissolves the upper surface of the adhesive layer and be miscible with the copolyester of the adhesive layer to form a polymer blend zone. Typical solvents Include tetrahydrofuran, cyclohexanone, methylene chloride, 1,1,1 -trichloroethane, 1,1,2- trichloroethane, trichloroethylene, toluene, and the like, and mixtures thereof. Mixtures of solvents may be utilized to control evaporation range. For example, satisfactory results may be achieved with a tetrahydrofuran to toluene ratio of between about 90:10 and about 10:90 by weight. Generally, the combination of photogenerating pigment, binder polymer and solvent should form uniform dispersions of the photogenerating pigment in the charge generating layer coating composition. Typical combinations include polyvinylcarbazole, trigonal selenium and tetrahydrofuran; phenoxy resin, trigonal selenium and toluene; and polycarbonate resin, vanadyl phthalocyanine and methylene chloride. The solvent for the charge generating layer binder polymer should dissolve the polymer binder utilized in the charge generating layer and be capable of dispersing the photogenerating pigment particles present in the charge generating layer.

The photogenerating composition or pigment may be present in the resinous binder composition in various amounts. Generally, from about 5 percent by volume to about 90 percent by volume of the photogenerating pigment is dispersed in about 10 percent by volume to about 90 percent by volume of the resinous blinder. Preferably from about 20 percent by volume to about 30 percent by volume of the photogenerating pigment is dispersed in about 70 percent by volume to about 80 percent by volume of the resinous binder composition. In one embodiment about 8 percent by volume of the photogenerating pigment is dispersed in about 92 percent by volume of the resinous binder composition.

The photogenerating layer generally ranges in thickness from about 0.1 micrometer to about 5.0 micrometers, preferably from about 0.3 micrometer to about 3 micrometers. The photogenerating layer thickness is related to binder content. Higher binder content compositions generally require thicker layers for photogeneration. Thicknesses outside these ranges can be selected, providing the objectives of the present invention are achieved.

Any suitable and conventional technique may be utilized to mix and thereafter apply the photogenerating layer coating mixture to the previously applied blocking layer (or dried adhesive layer, if used). Typical appiication techniques include spraying, dip coating, roll coating, wire wound rod coating, and the like. Drying of the deposited coating may be effected by any suitable conventional technique such as oven drying, infrared radiation drying, air drying and the like, to remove substantially all of the solvents utilized in applying the coating.

ne Charge Transport Layer The charge transport layer 7 may comprise any suitable transparent organic polymer or non-polymeric material capable of supporting the injection of photo- generated holes or eiectrons from the charge generating layer and allowing the transport of these holes or electrons through the organic layer to selectively discharge the surface charge The charge transport layer not only serves to transport holes or electrons, but also protects the photoconductive layer from abrasion or chemical attack, and therefore extends the operating iife of the photoreceptor imaging member. The charge transport layer should exhibit negligible, if any, discharge when exposed to a wavelength of light useful in xerography, e.g. 4000 Angstroms to 9000 Angstroms.

he charge transport layer is normally transparent in a wavelength region in which the photoconductor is to be used when exposure is effected therethrough to ensure that most of the incident radiation is utilized by the underlying charge generating layer. When used with a transparent substrate, imagewise exposure or erasure may be accomplished through the substrate with all light passing through the substrate. In this case, the charge transport material need not transmit light in the wavelength region of use. The charge transport layer in conjunction with rne charge generating layer is an insulator to the extent that an electrostatic charge placed on the charge transport layer is not conducted in the absence of illumination.

The charge transport layer may comprise activating compounds or charge transport molecules dispersed in normally electrically inactive film-forming polymeric materials for making these materials electrically active. These charge transport molecules may be added to polymeric materials which are incapable of supporting the injection of photogenerated holes and incapable of allowing the transport of these holes. An especially preferred transport layer employed in multilayer photoconductors comprises from about 25 percent to about 75 percent by weight of at least one charge-transporting aromatic amine, and about 75 percent to about 25 percentby weight of a polymeric film-forming resin in which the aromatic amine is soluble.

The charge transport layer is preferably formed from a mixture comprising at least one aromatic amine compound of the formula:

wherein R1 and R2 are each an aromatic group selected from the group consisting of a substituted or unsubstituted phenyl group, naphthyl group, and polyphenyl group and R3 is selected from the group consisting of a substituted or unsubstituted aryl group, an alkyl group having from 1 to 18 carbon atoms and a cycloaliphatic group having from 3 to 18 carbon atoms. The substituents should be free from electron-withdrawing groups such as NO2 groups, CN groups, and the like.

Typical aromatic amine compounds that are represented by this structural formula include: I. Triphenyl amines such as:

B s and po y t a y am nes such as

B a am e e he ha

B a ky a yam e u ha

A preferred aromatic amine compound has the general formula:

wherein R1 and R2 are defined above, and R4 is selected from the group consisting of a substituted or unsubstituted biphenyl group, a diphenyl ether group, an alkyl group having from 1 to 18 carbon atoms, and a cycloaliphatic group having from 3 to 12 carbon atoms. The substituents should be free from electron-withdrawing groups such as NO2 groups, CN groups, and the like.

Examples of charge-transporting aromatic amines represented by the structural formulae above include triphenyimethane, bis(4-diethylamine-2.methylphenyl)phenylmethane; 4-4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane; N,N'-bls(alkylphenyl)-( 1,1 '-biphenyl)-4,4'- diamine wherein the alkyl is, for example, methyl, ethyl, propyl, n-butyl, etc.; N,N'-diphenyl-N,N'bis(3- methylphenyl)-(1,1'biphenyl)-4,4'-diamine; and the like, dispersed in an inactive resin binder.

Any suitable inactive resin binder soluble in methylene chloride or other suitable solvents may be employed. Typical inactive resin binders soluble in methylene chloride include polycarbonate resin, polyvinylcarbazole, polyester, poiyarylate, polyacrylate, polyether, polysulfone, and the like. Molecular weights can vary from about 20,000 to about 1,500,000.

Other solvents that may dissolve these binders include tetrahydrofuran, toluene, trichloroethylene, 1,1 ,2-trichloroethane, 1,1, 1-trichloroethane, and the like.

The preferred electrically inactive resin materials are polycarbonate resins having a molecular weight from about 20,000 to about 120,000, more preferably from about 50,000 to about 100,000. The materials most preferred as the electrically inactive resin material are poly(4,4'-dipropylidene-diphenylene carbonate) with a molecular weight of from about 35,000 to about 40,000, available as Lexan 145 from General Electric Company; poly(4,4'.isopropylidene.

diphenylene carbonate) with a molecular weight of from about 40,000 to about 45,000, available as Lexan 141 from General Electric Company; a polycarbonate resin having a molecular weight of from about 50,000 to about 100,000, available as Makrolon from Farbenfabricken Bayer A.G.; a polycarbonate resin having a molecular weight of from about 20,000 to about 50,000, available as melon from Mobay Chemical Company; polyether carbonates; and 4,4'-cyclohexylidene diphenyl polycarbonate. Methylene chloride solvent is a desirable component of the charge transport layer coating mixture for adequate dissolving of all the components and for its low boiling point.

An especially preferred multilayer photoconductor comprises a charge generating layer comprising a binder layer of photoconductive material and a contiguous hole transport layer of a polycarbonate resin material having a molecular weight of from about 20,000 to about 120,000, having dispersed therein from about 25 to about 75 percent by weight of one or more compounds having the formula::

wherein X is selected from the group consisting of an alkyl group, having from 1 to about 4 carbon atoms, and chlorine, the photoconductive layer exhibiting the capability of photogeneration of holes and injection of the holes, the hole transport layer being substantially nonabsorbing in the spectral region at which the photoconductive layer generates and injects photogenerated holes but being capable of supporting the injection of photogenerated holes from the photoconducti ve layer and transporting the holes through the hole transport layer.

The thickness of the charge transport layer may range from about 10 micrometers to about 50 micrometers, and preferably from about 20 micrometers to about 35 micrometers.

Optimum thicknesses may range from about 23 micrometers to about 31 micrometers.

The invention will be further illustrated in the following, non-limiting examples, it being understood that these examples are intended to be illustrative only and that the invention is not intended to be limited to the materials, conditions, process parameters, and the like recited herein.

COMPARATIVE EXAMPLE I A 1.2% cuprous iodide solution in butyronitrile (CH3 (CH,)2CN) (Aldrich) is sprayed with an automatic spray gun (Binks No. 61) upon a rotating 3 mii polyester substrate (Mylar available from du Pont). This coating is dried in a forced air oven at lOOC for 5 minutes to obtain a dry thickness of 0.06 micrometer.

A solution of 1.5% copper complex with hydrolyzed gamma-aminopropyl triethoxysilane in 90 parts ethanol/l0 parts water is sprayed upon the cuprous iodide conductive layer. A thickness of 0.08 micrometer is obtained upon drying in a forced air oven at 100"C for 15 minutes.

A phenoxy selenium slurry as described in U.S. Patent No. 4,439,507 to Pan et al is sprayed with an automatic spray gun (Binks No. 61) upon the copper complex silane layer to a thickness of 0.5 micrometer. This layer is dried at 1 for 15 minutes in a forced air oven.

A charge transport layer as described in U.S. Patent No. 4.439,507 is sprayed with an electrostatic automatic spray gun (Binks) to a thickness of 20 micrometers. This layer is dried at 80"C for 15 minutes and then at 1 250C for S minutes.

The device is 1800 peel strength tested. The observed strength is approximately 3 gcm.

EXAMPLE II The same procedure described in Comparative Example I is followed except that prior to spraying of the conductive cuprous iodide layer, an adhesive layer is sprayed with an automatic spray gun (Binks No. 61) upon a rotating 3 mil polyester (Mylar available from du Pont) sleeve. The composition of the adhesive solution is 0.5g du Pont 49,000 polyester, 80 parts by weight tetrahydrofuran available from Aldrich, and 19.5 parts by weight cyclohexanone available from Aldrich. The thickness of this layer is 0.03 micrometer after drying in a forced air oven at 1 OO"C for 5 minutes.

The observed 1800 peel strength is 100g-cm.

COMPARATIVE EXAMPLE Ill A solution of 1.2% cuprous iodide is hand coated upon a sheet of 3 mi thick polyester (Melinex from 1CI) with a 0.5 mil gapped Bird coater. The layer is dried in a forced air oven for 30 minutes at 80"C. The thickness is estimated to be 0.05 micrometer by ellipsometry.

A blocking layer of 2% copper complex hydrolyzed silane In a solvent mixture of 90 parts ethanol and 10 parts water is coated upon the previously applied cuprous iodide layer. The layer is dried at 1 000C for 15 minutes and has a thickness of 1.2 micrometers.

An adhesive solution of 0.5% 49,000 polyester from du Pont in a mixture of 80 parts tetrahydrofuran (Aldrich) and 20 parts cyclohexanone is hand coated with a 0.5 mii gapped Bird coater upon the previously applied blocking layer. The layer is dried for 15 minutes at 100"C in a forced air oven. The thickness is 0.05 micrometer.

A polyvinylcarbazole (PVK)-selenium layer is prepared according to the procedures of U.S. Patent No. 4,464,450 and is hand coated onto the adhesive layer with a 0.5 mil gapped Bird coater. The layer is dried at 1000C for 15 minutes in a forced air oven. he thickness of this layer is 1 8 micrometers.

A charge transport layer is also prepared according to U.S. Patent No. 4,464,450 and is hand coated with a 4.5 mil gapped Bird coater. After drying at 80"C for 10 minutes and at 1250C for 15 minutes, the thickness of the device is observed to be 28 micrometers.

The 1800 peel strength of the device is observed to be 3 g-cm.

EXAMPLE IV The same procedure is followed as in Comparative Example Ill except that an adhesive layer is coated prior to the coating of the conductive cuprous iodide layer. An adhesive solution is prepared containing 0.5% 49,000 polyester (du Pont) in a mixture of 80 parts tetrahydrofuran (Aldrich) and 20 parts cyclohexanone. The solution is coated with a 0.5 mil gapped Bird coated After drying for 15 minutes in a forced air oven, a thickness of 0.05 micrometer is observed.

The 1800 peel strength is observed to be more than 100 g-cm.

The layers of each of the above Examples and the observed 1800 peel strength are set forth in Table I below The results of Table I show that devices having the adhesive layer of the present invention provide a much higher peel strength than the Comparative Examples which do not have the adhesive layer.

TABLE I Charge Charge 180 peel Adhesive Conductive Blocking Adhesive generating transport strength Example Substrate layer layer layer layer layer layer (g-cm) I PET --- CuI copper --- phenoxy/ polycarbonate- #3 (Control) polyester complex selenium aryl amine silane II PET 49,000 CuI copper --- phenoxy/ polycarbonate- 100 polyester polyester complex selenium aryl amine (du Pont) silane III PET --- CuI copper 49,000 PVK/ polycarbonate- #3 (Control) polyester complex polyester selenium aryl amine silane (du Pont) IV PET 49,000 CuI copper 49,000 PVK/ polycarbonate- > 100 polyester polyester complex polyester selenium aryl amine (du Pont) silane (du Pont) Although the invention has been described with reference to specific preferred embodiments, it is not intended to be limited thereto. Rather, those skilled in the art will recognize that variations and modifications may be made therein.

Claims (13)

CLAIMS:

1. An electrophotographic imaging member, comprising a supporting substrate, a contiguous adhesive layer, an electrically conductive layer comprising a l-VII semiconductor and a= least one photoconductive layer.

2. An imaging member according to claim 1, wherein said l-VII semiconductor is selected from the group consisting of Cul, CuBr, CuCI, Agl, AgSr and AgCI

3. An imaging member according to claim 1, wherein said l-VII semiconductor is cJprous iodide.

4. An imaging member according to any one of claims 1 to 3, wherein said adhes. ve layer comprises a polyester.

S An imaging member according to claim 4, wherein said polyester is a copolyester.

6 An imaging member according to any one of claims 1 to 5, wherein said aging member is substantially transparent to electromagnetic radiation

7. An Imaging member according to any one of claims 1 to 6, wherein said at -east one photoconductive layer Is comprised of a charge transport layer and a charge generating layer

8. An imaging member according to any one of claims 1 to 7, further comprising a charge blocking layer between said conductive layer and said at least one photoconductive layer.

9. An imaging member according to claims 8, further comprising a second adhesive layer between said charge blocking layer and said at least one photoconductive layer.

10. An imaging member according to any one of claims 1 to 9, wherein said supoorting substrate comprises at least one material selected from the group consisting of biaxially of vented polyester, polyvinyl fluoride, and polyimide

11. An electrophotographic imaging member, comprising a supporting substrate, a conductive layer comprised of a l-VII semiconductor, an adhesive layer, between the supporting substrate and the conductive layer, comprised of a copolyester, a charge blocking layer, a charge generating layer, and a charge transport layer.

12. An imaging member according to claim 11, wherein said l-VII semiconductor is selected from the group consisting of Cul, CuBr, CuCI, Agl, AgBr and AgCI.

13. An imaging member according to claim 11 wherein said l-VII semiconductor Is cuprous iodide 14 An imaging member according to any one of claims 11 to 13, wherein said mating member is substantially transparent to electromagnetic radiation.

15 An imaging member according to any one of claims 11 to 14, further comprising a second adhesive layer between said charge blocking layer and said charge transport layer 16 An imaging member according to any one of claims 11 to 15, wherein said supporting substrate comprises at least one material selected from the group consisting of biaxially oriented polyester, polyvinyl fluoride, and polyimide 17 An electrophotographic imaging member substantially as hereinbefore described with reference to, and as rilustrated in, the accompanying Figure