GB2261669A

GB2261669A - Electrophotographic imaging members containing polyarylamine polyesters

Info

Publication number: GB2261669A
Application number: GB9224675A
Authority: GB
Inventors: John F Yanus; William W Limburg; Dale S Renfer
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1991-11-25
Filing date: 1992-11-25
Publication date: 1993-05-26
Anticipated expiration: 2012-11-25
Also published as: JPH05232727A; JP3189914B2; GB2261669B; GB9224675D0

Abstract

A polyarylamine polymer suitable for use in an electrophotographic imaging member is represented by the following formula: <IMAGE> wherein: n is between about 5 and about 5,000 p is between about 0 and about 5,000 X' and X'' are independently selected from a group having bifunctional linkages, Q is a divalent group derived from certain hydroxy terminated arylamine reactants, and Q' is a divalent group derived from a hydroxy terminated reactant containing the group <IMAGE> where Ar' is a phenyl, alkyl or alkyoxyphenyl group and Z is one of a specified number of aromatic groups.

Description

ELECTROPHOTOGRAPHIC IMAGING MEMBERS CONTAINING POLYARYLAMINE POLYESTERS This invention relates to polyarylamine polymers and to electrophotographic imaging members and processes utilizing such polymers.

There is a current need for long service life, flexible photoreceptors in compact imaging machines that employ small diameter support rollers for photoreceptor belt systems compressed into a very confined space. Small diameter support rollers are also highly desirable for simple, reliable copy paper stripping systems which utilize the beam strength of the copy paper to automatically remove copy paper sheets from the surface of a photoreceptor belt after toner image transfer. However, small diameter rollers, e.g less than about 0.75 inch (19 mm) diameter, raise the threshold of mechanical performance criteria for photoreceptors to such a high level that spontaneous photoreceptor belt material failure becomes a frequent event for flexible belt photoreceptors.

One type of multilayered photoreceptor that has been employed as a belt in electrophotographic imaging systems comprises a substrate, a conductive layer, a charge blocking layer a charge generating layer, and a charge transport layer. The charge transport layer often comprises an activating small molecule dispersed or dissolved in a polymeric film forming binder. Generally, the polymeric film forming binder in the transport layer is electrically inactive by itself and becomes electrically active when it contains the activating molecule. The expression "electrically active" means that the material is capable of supporting the injection of photogenerated charge carriers from the material in the charge generating layer and is capable of allowing the transport of these charge carriers through the electrically active layer in order to discharge a surface charge on the active layer.Although excellent toner images may be obtained with multilayered belt photoreceptors that are developed with dry developer powder (toner), it has been found that these same photoreceptors become unstable when employed with liquid development systems. These photoreceptors suffer from cracking, crazing, crystallization of active compounds, phase separation of activating compounds and extraction of activating compounds caused by contact with the organic carrier fluid, isoparaffinic hydrocarbons e.g. Isopar&commat;, commonly employed in liquid developer inks which, in turn, markedly degrade the mechanical integrity and electrical properties of the photoreceptor. More specifically, the organic carrier fluid of a liquid developer tends to leach out activating small molecules, such as the arylamine containing compounds typically used in the charge transport layers.The leaching process results in crystallization of the activating small molecules, such as the aforementioned arylamine compounds, onto the photoreceptor surface and subsequent migration of arylamines into the liquid developer ink. In addition, the ink vehicle, typically a Clo-c14 branched hydrocarbon, induces the formation of cracks and crazes in the photoreceptor surface. These effects lead to copy defects and shortened photoreceptor life. The degradation of the photoreceptor manifests itself as increased background and other printing defects prior to complete physical photoreceptor failure.

The leaching out of the activating small molecule also increases the susceptibility of the transport layer to solventfstress cracking when the belt is parked over a belt support roller during periods of non-use. Some carrier fluids also promote phase separation of the activating small molecules, such as arylamine compounds and their aforementioned derivatives, in the transport layers, particularly when high concentrations of the arylamine compounds are present in the transport layer binder. Phase separation of activating small molecules also adversely alters the electrical and mechanical properties of a photoreceptor. The leachant, the hole transporting molecule, may also contaminate the liquid ink lowering the overall print quality.Although flexing is normally not encountered with rigid, cylindrical, multilayered photoreceptors which utilize charge transport layers containing activating small molecules dispersed or dissolved in a polymeric film forming binder, electrical degradation is similarly encountered during development with liquid developers. Sufficient degradation of these photoreceptors by liquid developers can occur in less than eight hours of use thereby rendering the photoreceptor unsuitable for even low quality xerographic imaging purposes.

Photoreceptors have been developed which comprise charge transfer complexes prepared with polymeric molecules. For example, charge transport complexes formed with polyvinyl carbazole are disclosed in US-A 4,047,948, US-A 4,346,158 and US-A 4,388,392.

Photoreceptors utilizing polyvinyl carbazole layers, as compared with current photoreceptor requirements, exhibit relatively poor xerographic performance in both electrical and mechanical properties. Polymeric arylamine molecules prepared from the condensation of disecondary amine with a di-iodo aryl compound are disclosed in European patent publication 34,425, published August 1981 and issued May 16, 1984. Since these polymers are extremely brittle and form films which are very susceptible to physical damage, their use in a flexible belt configuration is precluded. Thus, in advanced imaging systems utilizing multilayered belt photoreceptors exposed to liquid development systems, cracking and crazing have been encountered in critical charge transport layers during belt cycling.Cracks developing in charge transport layers during cycling can be manifested as print-out defects adversely affecting copy quality. Furthermore, cracks in the photoreceptor pick up toner particles which cannot be removed in the cleaning step and may be transferred to the background in subsequent prints.

In addition, crack areas are subject to delamination when contacted with blade cleaning devices thus limiting the options in electrophotographic product design. It should also be noted that the presence of an anti-curl back coating will exacerbate the propagation of cracks in brittle polymers.

Photoreceptors having charge transport layers containing small molecule arylamine compounds dispersed or dissolved in various resins such as polycarbonates are known in the art.

Similarly, photoreceptors utilizing polymeric arylamine containing molecules such as polyvinyl carbazole and polymethacrylates possessing pendant arylamines are also known. Further, condensation polymers of a di-secondary amine with a di-iodo aryl compound are described in the prior art. Moreover, various polymers derived from a reaction of certain monomers with aromatic amines such as N,N'-diphenyl-N,N'-bis(3-hydroxyphenyl)-[1,1'-biphenyll-4,4'-diamine have recently been described.

Recently photoreceptors having charge transport layers containing charge transporting arylamine polymers have been described in the patent literature. These polymers include the products of a reaction involving a dihydroxy arylamine reactant and are described, for example in US-A 4,806,443, US-A 4,806,443, US-A 4,801,517 and US-A 4,818,650. Although these polymers form excellent charge transport layers, many other polymeric derivatives of dihydroxy arylamines do not meet the numerous stringent requirements of sophisticated automatic electrophotographic systems. For example, the polymeric reaction products of dihydroxy arylamines and 1,3-diiodopropane form charge transport layers that possess very poor mechanical properties, are soft and non-robust and are of low molecular weight.

There is a continuing need for multilayered photoreceptors having improved resistance to cracking, crazing, delamination, softening, swelling, crystallization of active compounds, phase separation of active compounds and leaching of active compounds. In addition to the ink compatibility requirements, there is a requirement for stable electrical properties during cycling and mechanical toughness for long life. There also exists the need to better match the coefficient of thermal expansion of the supporting substrate in a flexible belt architecture to provide a stress free flat surface and eliminating the need for an anti-curl back coating.

It is an object of the present invention to enable some, at least, of those needs to be met.

The present invention provides a polyarylamine polymer represented by formula I

FORMULA I wherein: n is between about 5 and about 5,000 p is bet,ween about 0 and about 5,000 X' and X" are independently selected from a group having bifunctional linkages, Q is a divalent group derived from a hydroxy terminated arylamine reactant containing the group:

wherein: Ar' is selected from the group consisting of:

Z is selected from the group consisting of:

and -Ar-(X)-Ar- r r isO or 1, Aris selected from the group consisting of:

R is selected from the group consisting of -CH3, -C2 H5, -C3H7, and -C4H9, X is selected from the group consisting of::

Q' is a divalent group derived from a hydroxy terminated group, and the weight average molecular weight of the polyarylamine polymer is between about 10,000 and about 1,000,000.

The invention also provides an electrophotographic imaging member comprising a support layer and at least one electrophotoconductive layer, the imaging member comprising a polyarylamine polymer as defined above.

More preferably, the polyarylamine polymer is represented by the formula:

wherein: n is between about 5 and about 5,000, p is between about 0 and about 5,000, Z is selected from the group consisting of:

and -Ar-(X)-Ar- r r isOor1, Ar is selected from the group consisting of:

R is selected from the group consisting of -CH3, -C2H5, -C3 H7, and -4H9, X is selected from the group consisting of:

s is0,1 or2, Ar' is selected from the group consisting of:

X' AND X" are independently selected from a group having bifunctional linkages, Y and Y' are independently selected from a group represented by the formula:: -(CH2) t t isO, 1,2,3,or4,and Q' is independently selected from the group having bifunctional linkages consisting of:

Generally, polymeric arylamine compounds in accordance with this invention may be prepared by reacting a dihydroxy arylamine compound with a co-reactant diacid chloride compound represented by the formula:

wherein X' is selected from the group consisting of bifunctional linkages such as alkylene, arylene, substituted alkylene, substituted arylene and ether segments. Generally, the ether, alkylene and substituted alkylene bifunctional linkages contain from 1 to 25 carbon atoms.In addition a second diacid chloride compound is included in the reaction, the compound being represented by the formula

wherein X" is selected from the group consisting of bifunctional linkages such as alkylene, arylene, substituted alkylene, substituted arylene, and ether segments, and X" may be the same as X'.

Illustrative examples of substituted or unsubstituted alkylene groups include those containing from about 1 to about 25 carbon atoms, and preferably from 1 to about 10 carbon atoms, such as methylene, dimethylene, trimethylene, tetramethylene, 2,2dimethyltrimethylene, pentamethylene, hexamethylene, heptamethyl ene, and the like.

Illustrative examples of substituted or unsubstituted arylene linkages include the following:

Examples of ether segments include those containing from about 2 to about 25 carbon atoms, such as -CH2OCH2-, -CH2CH2-OCH2CH2-, -CH2CH2-OCH2-CH2CH2CH2OCH2CH2-, -CH2CH2 (OCH2CH2)2-, -CH2CH2CH(CH3)OCH2CH2-, and the like. Examples of alkyl substituents include those with from 1 to about 25 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 2-methylpentyl, hexyl, octyl, nonyl, decyl, and the like, with methyl, ethyl, propyl, and butyl being preferred. Aryl substituents include those with from 6 carbon atoms to about 24 carbon atoms, such as phenyl, tolyl, ethylphenyl, and naphthyl. The aryl groups can be substituted with alkoxy, hydroxy, halo, cyano, alkoxyalkyl, and the like.

Typical compounds represented by the above formula for the diacid chloride compound include:

4,4'-diphenylisopropylidine diacidchloride

tolylene 2,4-diacid chloride

ClOC-CH2-CH2-CH2-CH2-CH2-CH2-COCl

CIOC-(CH2)8 - COCI

In one embodiment, polymeric arylamine compounds are prepared by reacting the diacid chloride compound with a dihydroxy arylamine compound represented by the formula:

wherein: Ar, Ar', Z, Y and Y' are as defined above.

Compounds represented by the above hydroxy arylamine formula may be prepared by hydrolyzing an alkoxy arylamine. A typical process for preparing alkoxy arylamines is disclosed in Example I of US-A 4,588,666.

Typical compounds represented by the above formula for hydroxy arylamine compounds include:

Compounds represented by the above hydroxy arylamine formula where t is 0, 1, 2, 3 or 4 may be prepared by reacting an arylamine compound having the formula:

wherein: Z and Ar' are as defined above. Typical compounds represented by this formula include N,N'-diphenylbenzidine, N,N'-diphenyl-p-terphenyl diamine, N,N'-di phenyl-p,p'- diaminodiphenylether, N,N'-diphenyl-p,p'-cyclohexylidene diphenyldiamine, N,N'-diphenylp,p'-isopropyl idene diphenyldiamine, N,N'-di phenyl-p,p'-methyl idene di phenyldiami ne, and the like. This arylamine compound is reacted with an iodobenzene compound such as mbromoiodobenzene, m-chloroiodobenzene, p-chloroiodobenzene, p-bromoi od obenzene, and the like to form an intermediate product represented by the formula:

wherein: Z, Ar and Ar' are as defined above, Hal is bromine, chlorine or iodine. The bromine atoms in this intermediate product are thereafter are replaced by lithium. The resulting dilithio arylamine compound is reacted with ethylene oxide, formaldehyde, oxatane, or tetrahydrofuran. This reaction is worked up in the presence of an aqueous acid to form a hydroxy alkylene arylamine precursor represented by the formula:

wherein: Z, Ar, Ar', Y, Y' are as defined above. This hydroxy alkylene arylamine precursor is then reacted with the co-reactant diacid chloride compound to form a polymeric arylamine of this invention.

The foregoing reactions are more specifically illustrated by the following reactions:

A typical process for preparing a hydroxy alkylene arylamine is disclosed in Examples 11 and Ill of US-A 4,801,517.

Any suitable solvent may be employed to dissolve the reactants. Typical solvents include tetrahydrofuran, toluene, and the like. Satisfactory yields are achieved with reaction temperatures between about 0 C and about 20 C. The reaction temperature selected depends to some extent on the specific reactants utilized and is limited by the temperature at which a cross linking side reaction may take place. The reaction temperature may be maintained by any suitable cooling technique.

The reaction time depends upon the reaction temperatures and the reactants used.

Satisfactory results have been achieved with reaction times between about 40 minutes to about 90 minutes. For practical purposes, sufficient degree of polymerization is achieved by the time the reaction product layer is viscous.

One may readily determine whether sufficient reaction product has been formed by monitoring the increase in solution viscosity. An abrupt change in viscosity is noted as the polymerization is nearing completion. Typical polymeric arylamine compounds used in electrophotographic imaging members in accordance with this invention include, for example:

The "n" in the first appearing formula (FORMULA I) herein is defined as between about 5 and about 5,000. For the final polymers, "n' is defined as representing a number sufficient to achieve a weight average molecular weight of between about 20,000 and about 500,000 as represented in FORMULA I.

The following is an illustrative reaction between a specific diacid chloride compound and a specific dlhydroxy arylamine compound:

The following Is still another illustrative reaction between another specific diacid chloride compound and a specific dlhydroxy arylamine compound:

The following is an illustrative reaction between a preferred specific diacid chloride compound and a specific dihydroxy arylamine compound:

wherein the value of n was between about 40 and about 100. This polymer formed a viscous solution in tetrahydrofuran at a 10 percent by weight polymer concentration thereby further indicating that the material was a high molecular weight condensation polymer of between about 20,000 and about 500,000.

Multilayered photoconductive devices were fabricated with these polymers by applying methylene chloride solutions of the polymers to aluminum substrates bearing a 0.5 micrometer thick vapor deposited amorphous selenium layer. The deposited charge transport layers were then dried to a 15 micrometer thickness. These photoconductors were corona charged to a negative potential and thereafter discharged with a monochromatic light source of 4330 A wavelength. These photoreceptor devices exhibited low dark decay, high mobility and low residual charge.

High hole mobility is a requirement for hole transporting materials to enable the rapid cycling characteristics of modern photoreceptors. Substituents on the transporting moiety should be such that an undesirable perturbation of the electronic environment, affecting its transporting ability, does not occur. Substituents that reduce mobility are those which withdraw electron density from the transporting moiety. Examples of these electronegative substituents include, NO2, CN, CF3, > C= 0, etc. Transport polymers in which the connective linkage places an electronegative group in conjugation with the active transport moiety will exhibit poorer mobilities.

The arylamine transporting moieties of polymers in accordance with this invention are rather rigid units, e.g. tetraphenylbenzidine, triphenylamine and they like. When incorporated in polymeric structures, this unit can be considered a rigid-rod unit (RRU). In condensation polymers, rigid-rod structures result in polymers of impaired flexibility, reduced adhesion and a tendency to crack. Counterbalancing this in part is the cohesiveness inherent in most condensation polymers due to the presence of dipole-dipole interaction (in this case the dipole associated with the carbonyl unit). Polymers in accordance with the present invention possess a flexible unit (FLU) to reduce the brittleness and improve other mechanical properties of the resultant polymer.The flexible units (FLU) in charge transporting polymers in accordance with this invention are derived from the diacid chloride compound represented by the generic formula above. In=-diethylene glycol diacid chloride, triethylene glycol diacid chloride and trans-1,4-cyclohexylene diacid chloride-1,6-hexane, the presence of ether units and/or methylene units imparts a substantial degree of flexibility because it possesses minimal hindrance to bond rotation. Generally, for those applications in which greater flexibility is required, polymers derived from diacid chlorides containing ether units and/or methylene units are preferred whereas for those applications in which greater hardness or creep resistance is required, polymers derived from diacid chlorides containing aromatic rings and Jor double bond units are preferred. Thus, it is possible to tailor the physical properties to the intended use.

The following structures illustrate and compare poiyester structures derived from diacid chlorides containing aromatic rings and/or double bond units with polyester structures derived from diacid chlorides containing ether units and/or methylene units. The rigid-rod units (RRU) of the arylamine moiety are represented by rectangles and rigid units associated with specific diacid chlorides are shown as crosshatched rectangles. The flexible units (FLU) derived from diacid chlorides are shown as springs.

o 0 II II C RRU AROMATIC OR RRU DOUBLE BONDED o 0 O O L (I II 0-C C-0 AROMATIC OR z DOUBLE BONDED O METHYLENIC O II OR ETHER -0 ç RRU FLU RRU r---------------------------~~----~~~~~~~~~~ I O METHYLENIC OR 1l OR ETHER II C 0-C FLU m z and m are between about 5 and about 5,000.Thus, the flexible units (FLU) of a polymer in accordance with this invention reduce the brittleness and improve other mechanical properties such as tensile toughness whereas the modulus and hardness are increased with polymers derived from diacid chlorides containing aromatic rings and/or double bonds.

A photoconductive imaging member may be prepared by providing a substrate having an electrically conductive surface, applying a charge blocking layer on the electrically conductive surface, applying a charge generation layer on the blocking layer and applying a charge transport layer on the charge generation layer. If desired, the charge transport layer may be applied to the electrically conductive surface and the charge generation layer may thereafter be applied to the charge transport layer. A polymeric arylamine in accordance with this invention is present in at least the charge generation layer or the charge transport layer.

When the photoconductive imaging member is employed in liquid development systems, the polymeric arylamine of this invention is preferably present in at least the outermost layer of the imaging member.

The substrate, electrically conductive surface, charge blocking layer, and optional adhesive layer are well know in the art of electrostatographic imaging and described, for example in US-A 4,806,443,4,806,444, 4,801,517 and 4,818,650.

Any suitable photogenerating layer may be applied to the blocking layer or intermediate layer if one is employed, which can then be overcoated with a contiguous hole transport layer as described. Examples of photogenerating layers include inorganic amorphous photoconductive films, inorganic photoconductive particles, and organic photoconductive particles described for example in US-A 3,357,989, US-A 3,442,781, US-A 4,587,189 and US-A 4,415,63. Other suitable photogenerating materials known in the art may also be utilized, if desired.

Numerous inactive resin materials may be employed in the photogenerating binder layer including those described, for example, in US-A 3,121,006. Typical organic resinous binders include thermoplastic and thermosetting resins.

Active carrier transporting resin may also be employed as the binder in the photogenerating layer. These resins are particularly usefui where the concentration of carrier generating pigment particles is low and the thickness of the carrier generation layer is substantially thicker than about 0.7 micrometer. The active resin commonly used as a binder is polyvinylcarbazole whose function is to transport carriers which would otherwise be trapped in the layer.

Electrically active polymeric amines in accordance with this invention can be employed in the generation layer replacing the polyvinylcarbazole binder or any other active or inactive binder. Thus, for example, all of the active resin materials to be employed in the generator layer may be replaced by electrically active polymeric arylamines in accordance with this invention.

The photogenerating composition or pigment is present in the resinous binder composition in various amounts, generally, however, 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 95 percent by volume of the resinous binder, and 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.

For embodiments in which the photogenerating layers do not contain a resinous binder, the photogenerating layer may comprise any suitable, well known homogeneous photogenerating material. Typical homogeneous photogenerating materials include inorganic photoconductive compounds such as amorphous selenium, selenium alloys selected such as selenium-tellurium, selenium-tellurium-arsenic, and selenium arsenide and organic materials such as vanadyl phthalocyanine, chlorindium phthalocyanine.

The photogenerating layer containing photoconductive compositions and/or pigments and the resinous binder material generally ranges in thickness of from about 0.1 micrometer to about 5 micrometers, and preferably has a thickness of 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.

The active charge transport layer comprises a polymeric aryl amine in accordance with this invention capable of supporting the injection of photo-generated holes from the charge generation layer and allowing the transport of these holes through the transport layer to selectively discharge the surface charge. When the photogenerating layer is sandwiched between the conductive layer and the active charge transport layer, the transport layer not only serves to transport holes, but also protects the photoconductive layer from abrasion or chemical attack and therefore extends the operating life of the electrophotographic 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.

Therefore, the charge transport layer is substantially transparent to radiation in a region in which the photoconductor is to be used. Thus, the active charge transport layer is a substantially non-photoconductive material which supports the injection of photogenerated holes from the generation layer. The active transport layer is normally transparent when exposure is effected through the active layer to ensure that most of the incident radiation is utilized by the underlying charge carrier generator layer for efficient photogeneration. When used with a transparent substrate, imagewise exposure may be accomplished through the substrate with all light passing through the substrate. In this case, the active transport material need not be transmitting in the wavelength region of use. The charge transport layer in conjunction with the generation layer is a material which is an insulator to the extent that an electrostatic charge placed on the transport layer is not conducted in the absence of illumination.

The transport material comprising a hole transporting small molecule-inactive resin binder composition may be entirely replaced with 100 percent of a polymeric arylamine compound in accordance with this invention. In addition, the binder used in a charge generating layer may be replaced with 100 percent of a polymeric arylamine compound in accordance with this invention. The use of a polymeric arylamine as the transport layer does not necessitate nor preclude the use of a polymeric arylamine as the binder in the charge generator layer. Additionally, its use as the charge generator layer binder does not necessitate nor preclude the use of a polymeric arylamine as the charge transport layer.When a polymeric arylamine is used as the active binder in the the charge generator layer, it can be present in the range of between abqut 10 percent by volume and about 95 percent by volume, and preferably between about 20 percent by volume to about 30 percent by volume, the balance of which being made up of the photogenerating pigment. Any arylamine unit in the polymeric-hole transporting compound should be free from electron withdrawing substituents such as NO2 groups, CN groups, > C=O and the like which is directly bonded to the arylamine unit. The hole transporting small molecule-inactive resin binder composition may be entirely replaced with 100 percent of a polymeric arylamine compound in accordance with this invention.

Any suitable solvent may be employed to apply the transport layer material to the underlying layer. Typical solvents include methylene chloride, toluene, tetrahydrofuran, and the like. The selection of the solvent is determined in part by the coating method and the solvent characteristics of the other functional layers in the photoresponsive device. Methylene chloride solvent is a particularly desirable component of the charge transport layer coating mixture for adequate dissolution of all the components and for its low boiling point.

Any suitable and conventional technique may be utilized to mix and thereafter apply the charge transport layer coating mixture to the underlying surface, e.g. charge generating layer. Typical application 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, infra-red radiation drying, air drying and the like.

Generally, the thickness of the hole transport layer is between about 5 to about 100 micrometers, but thicknesses outside this range can also be used. The hole transport layer should be an insulator to the extent that the electrostatic charge placed on the hole transport layer is not conducted in the absence of illumination at a rate sufficient to prevent formation and retention of an electrostatic latent image thereon. In general, the ratio of the thickness of the hole transport layer to the charge generator layer is preferably maintained from about 2:1 to 200:1 and in some instances as great as 400:1.

Optionally, an overcoat layer may also be utilized to improve resistance to abrasion.

In some cases a back coating may be applied to the side opposite the photoreceptor to provide flatness and/or abrasion resistance.

An electrophotographic member containing an electrically active polymer arylamine in accordance with the present invention in at least the generator or transport layer may be employed in any suitable and conventional electrophotographic imaging process which utilizes charging prior to imagewise exposure to activating electromagnetic radiation.

An electrophotographic member in accordance with the present invention exhibits greater resistance to cracking, crazing, crystallization of arylamine compounds, phase separation of arylamine compounds and leaching of arylamine compounds during cycling if exposed to a xerographic liquid developer.

Embodiments of the invention will now be described in detail in the following examples, which are intended to be illustrative. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE I Into a 250 milliliter three-necked round bottom flask equipped with a mechanical stirrer, an argon gas inlet, a thermometer and a dropping funnel was placed 10.4 grams N,N-diphenyl N,N-bis-(3-hydroxyphenyl)-11,1 biphenyl] 4,4-diamine (0.02 mole), 100 milliliters tetrahydrofuran and 8.4 milliliters triethylamine (0.06 mole). The contents of the flask were cooled with a water bath and the temperature was maintained at 15"C throughout the dropwise addition of 3.6 milliliters double distilled suberoyl chloride (0.02 mole) dissolved in 50 milliliters tetrahydrofuran. A colorless precipitate of triethylamine hydrochloride formed after approximately 5 drops of acid chloride solution had been added. After 60 minutes, the addition was complete and the viscous mixture allowed to stir for 15 minutes.The polymer solution was filtered to remove the triethylamine hydrochloride. The colorless polymer solution was precipitated into methanol, filtered and dried. Yield was 12.1 grams MW 66,000.

Purification: In a 250 milliliter Erlenmeyer flask, 10 grams of crudespolymer was mixed with 100 milliliters tetrahydrofuran. The mixture was agitated with a magnetic stirrer until the polymer was completely dissolved. While stirring was maintained, 4 grams F-20 alumina (Alcoa) was added. After 90 minutes, the polymer solution was filtered, precipitated into methanol and dried. Yield was 9.7 grams.

EXAMPLE II Into a 250 milliliter three-necked round bottom flask equipped with a mechanical stirrer, an argon gas inlet, a thermometer and a dropping funnel was placed 10.4 grams N,Ndiphenyl N,N-bis-(3-hydrnxyphenyl)-(1,1 biphenyl] 4,4-diamine (0.02 mole), 100 milliliters tetrahydrofuran and 8.4 milliliters triethylamine (0.06 mole). The contents of the flask were cooled with a water bath and the temperature was maintained at 15"C throughout the dropwise addition of 4.9 milliliters double distilled azelaoyl chloride (0.02 mole) dissolved in 50 milliliters tetrahydrofuran. A colorless precipitate of triethylamine hydrochloride formed after approximately 5 drops of acid chloride solution had been added. After 60 minutes, the addition was complete and the viscous mixture was allowed to stir for 15 minutes. The polymer solution was filtered to remove the triethylamine hydrochloride. The colorless polymer solution was precipitated into methanol, filtered and dried. Yield was 12.0 grams MW 67,000.

Purification: In a 250 milliliter Erlenmeyer flask, 10 grams of crude,polymer was mixed with 100 milliliters tetrahydrofuran. The mixture was agitated with a magnetic stirrer until the polymer was completely dissolved. While stirring was maintained, 4 grams F-20 alumina (Alcoa) was added. After 90 minutes, the polymer solution was filtered, precipitated into methanol and dried. Yield was 9.7grams.

EXAMPLE Ill Into a 250 milliliter three-necked round bottom flask equipped with a mechanical stirrer, an argon gas inlet, a thermometer and a dropping funnel was placed 15.6 grams N,N'diphenyl N,N'-bis-(3-hydroxyphenyl)-[1 ,1' biphenyl] 4,4'-diamine (0.03 mole), 100 milliliters tetrahydrofuran and 12.6 milliliters triethylamine (0.09 mole). The contents of the flask were cooled with a water bath and the temperature was maintained at 150C throughout the dropwise addition of 6.4 milliliters double distilled sebacoyl chloride (0.03 mole) dissolved in 50 milliliters tetrahydrofuran. A colorless precipitate of triethylamine hydrochloride formed after approximately.5 drops of acid chloride solution had been added. After 60 minutes, the addition was complete and the viscous mixture allowed to stir for 15 minutes.The polymer solution was filtered to remove the triethylamine hydrochloride. The colorless polymer solution was precipitated into methanol, filtered and dried. Yield was 19.3 grams, MW 103,000.

EXAMPLE iV Into a 250 milliliter three-necked round bottom flask equipped with a mechanical stirrer, an argon gas inlet, a thermometer and a dropping funnel was placed 15.6 grams N,N'diphenyl N,N-bis-(3-hydrnxyphenyl)-(1,1 biphenyll 4,4-diamine (0.03 mole), 100 milliliters tetrahydrofuran and 12.6 milliliters triethylamine (0.09 mole). The contents of the flask were cooled with a water bath and the temperature was maintained at 15"C throughout the dropwise addition of 7.5 milliliters double distilled dodecyloyl chloride (0.03 mole) dissolved in 50 milliliters tetrahydrofuran. A colorless precipitate of triethylamine hydrochloride formed after approximately 5 drops of acid chloride solution had been added. After 60 minutes, the addition was complete and the viscous mixture allowed to stir for 15 minutes.The polymer solution was filtered to remove the triethylamine hydrochloride. The colorless polymer solution was precipitated into methanol, filtered and dried. Yield was 19.6 grams, MW 110,000.

Purification: In a 250 milliliter Erlenmeyer flask, 10 grams of crudespolymer was mixed with 100 milliliters tetrahydrofuran. The mixture was agitated with a magnetic stirrer until the polymer was completely dissolved. While stirring was maintained, 4 grams F-20 alumina (Alcoa) was added. After 90 minutes, the polymer solution was filtered, precipitated into methanol and dried. Yield was 9.7grams.

EXAMPLE V Preparation of a photosensitive member utilizing a polymer in accordance with this invention: An epoxy phenolic barrier layer about 0.5 micrometer thick was formed on a 3 mi aluminum substrate by dip coating. A 1 micrometer thick layer of amorphous selenium was the vacuum evaporated on the coated aluminum substrate by a conventional vacuum deposition technique such as the technique disclosed in Bixby in U.S. Pat. Nos. 2,753,278 and 2,970,906.

This vacuum deposition was carried out at a vacuum of 10-6 Torr while the substrate was maintained at a temperature of about 50 C. during the vacuum deposition. A charge transport layer was prepared by dissolving 10 milliliters of tetrahydrofuran and 1.5 grams of the polymer, as prepared in Example Ill. A layer of this mixture was formed on the amorphous selenium layer using a Bird film applicator. The coating was then vacuum dried a 40 C for 18 hours to form a 22 micrometer thick dry layer of the charge transport polymer. The plate was tested for its photoconductive property by first negatively corona charging to a field of 50 volts/micrometer and exposing to a blue light flash of 4330 Angstrom wavelength, 2 microseconds duration and 25 ergs/cm2 light intensity.The device discharged to a very low potential of less than 50 volts indicating good photoconductive properties.

EXAMPLE Vl A charge transport layer is prepared by dissolving 10 milliliters of tetrahydrofuran and 1.5 grams of the polymer, as prepared in Example II. A layer of this mixture is formed, on an aluminum substrate having thereon a 0.2 micrometer As2Se3 layer, using a Bird film applicator. The coating is then vacuum dried at 100" C for one hour to form a 22 micrometer thick dry layer of the charge transporting polyester. The plate is tested for its photoconductive property by first negatively corona charging to a field of 50 volts/micron and exposing to a blue light flash of 4330 Angstrom wavelength, 2 microseconds duration, and 25 erg/cm2 light intensity. The device is expected to discharge to a very low potential of less than 50 volts which would indicate good photoconductive properties. The member is then subjected to a cyclic operation of charge expose and erase cycles in a scanner, and is expected to be stable even after 20,000 cycles of essentially continuous operation.

Claims

CLAIMS:

1. A polyarylalnine polymer represented by the formula:

FORMULA I wherein: n is between about 5 and about 5,000 p is between about 0 and about 5,000 X' and X" are independently selected from a group having bifunctional linkages, Q is a divalent group derived from a hydroxy terminated arylamine reactant containing the group:

wherein: Ar' is selected from the group consisting of:

Z is selected from the group consisting of:

and -Ar-(X)-Ar- and r isOor 1, Aris selected from the group consisting of:

R is selected from the group consisting of -CH3, -C2H5, -C3H7, and -C4H9, X is selected from the group consisting of::

2. Apolymer according to Claim 1, represented by the formula:

and -Ar-(X)-Ar- r r isOor1, Ar is selected from the group consisting of:

R is selected from the group consisting of-CH3, -C2H5, -C3H7, and -C4H9, X is selected from the group consisting of:

s is0, 1 or2, Ar' is selected from the group consisting of:

X' AND X" are independently selected from a group having bifunctional linkages, Y and Y' are independently selected from a group represented by the formula: -(CH2)- t t isO, 1,2,3,or4,and Q' is independently selected from the group having bifunctional linkages consisting of::

3. A polymer according to Claim 1 or Claim 2, which is the reaction product of a dihydroxy arylamine compound and a co-reactant di-acidchloride compound represented by the formula:

wherein X' is a bifunctional linkage containing from 1 to 25 carbon atoms.

4. A polymer according to Claim 3, wherein an additional dihydroxy compound is included in said reaction, said additional dihydroxy compound being selected from the following representative group:

5. A polymer according to Claim 4, wherein said hydroxy group terminated monomer produces a weight average molecular weight polymer of between about 50,000 and about 500,000.

6. A polymer according to any one of the preceding claims, substantially as described herein.

7. An electrostatographic imaging member comprising a support layer and at least one electrophotoconductive layer, said imaging member comprising a polyarylamine polymer according to any one of the preceding claims.

8. An electrostatographic imaging member according to Claim 1 wherein said imaging member comprises a charge generating layer and a charge transport layer.

9. An electrostatographic imaging member according to Claim 8 wherein said charge transport layer comprises said polyarylamine polymer.

10. An electrostatographic imaging member according to Claim 8 or claim 9, wherein said charge generating layer comprises said polyarylamine polymer.

11. An electrostatographic imaging member according to any one of Claims 8 to 10, wherein said imaging member comprises a blocking layer between said charge generating layer and said support layer.

12. An electrostatographic imaging member according to any one of Claims 8 to 11, wherein said imaging member comprises a protective overcoating comprising said polyarylamine polymer.

13. An electrostatographic imaging member according to any one of claims 7 to 12, substantially as described herein.

14. An electrophotographic imaging process comprising forming an electrostatic latent image on the imaging surface of an electrostatographic imaging member according to any one of claims 7 to 13, and contacting said imaging surface with a developer comprising electrostatically attractable marking particles whereby said electrostatically attractable marking particles deposit on said imaging surface in conformance with said electrostatic latent image to form a marking particle image.

15. An electrophotographic imaging process according to claim 14, wherein said developer is a liquid developer.

16. An electrophotographic imaging process according to claim 15, wherein said liquid developer comprises an organic carrier fluid.

17. An electrophotographic imaging process according to any one of claims 14 to 16, including transfering said marking particle deposit to a receiving member.

18. An electrophotographic imaging process according to claim 17 including repeating said forming, contacting and transfering steps at least once.

19. An electrophotographic imaging process according to claim 14, wherein the charge transport layer of the imaging member is substantially transparent to radiation in the region in which said imaging member is exposed during electrophotographic imaging and capable of supporting the injection of photo-generated holes from said charge generating layer and transporting said holes through said charge transport layer to selectively discharge an electrostatic charge on said imaging surface to form said electrostatic latent image.

20. An electrophotographic imaging process according to any one of claims 14 to 19, substantially as described herein.