US3926629A

US3926629A - Electrophotographic method and plate employing a phthaldcyanine polymer

Info

Publication number: US3926629A
Application number: US425653A
Authority: US
Inventors: John W Weigl
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1970-03-11
Filing date: 1973-12-17
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16

Abstract

A xerographic plate including a photoconductive insulating layer made from a polymer containing phthalocyanine is disclosed. A method of forming a latent electrostatic image on said plate is also disclosed.

Description

Elnited States Patent [1 1 Weigl Dec. 16, 1975 ELECTROPHOTOGRAPHIC METHOD AND PLATE EMPLOYING A PHTHALDCYANINE POLYMER [75] Inventor: John W. Weigl, W. Webster, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Dec. 17, 1973 [21] Appl. No.: 425,653

Related US. Application Data [63] Continuation-impart of Ser. No. 18,754, March 11, 1970, abandoned, which is a continuation-in-part of Ser. No. 468,983, July 1, 1965, abandoned.

[56] References Cited UNITED STATES PATENTS 3,308,444 3/1967 Ting 340/173 3,816,118 6/1974 Byrne 96/1.5

OTHER PUBLICATIONS Moser et al., Phthalocyanine Compounds, ACS monograph No. 157, 1963, PP. 69-76 and 328-336.

Primary ExaminerNorman G. Torchin Assistant ExaminerJohn R. Miller Attorney, Agent, or FirmJames J. Ralabate; Donald C. Kolasch; Anthony W. Karambelas [5 7] ABSTRACT A xerographic plate including a photoconductive insulating layer made from a polymer containing phthalocyanine is disclosed. A method of forming a latent electrostatic image on said plate is also disclosed.

12 Claims, No Drawings ELECTROPHOTOGRAPHIC METHOD AND PLATE EMPLOYING A PHTHALDCYANINE POLYMER This application is a continuation-in-part application of U.S. Ser. No. 18,754, filed on Mar. 11, 1970, now

abandoned which in turn is a continuation-in-part application of U.S. Ser. No. 468,983, filed on July I,

1965, now abandoned, the specifications of which are hereby incorporated by reference.

This invention relates to a photosensitive material and, more particularly, to such a material in polymeric form and methods for its use.

The xerographic process, as originally disclosed by Carlson in U.S. Pat. No. 2,297,691, is generally carried out by applying a uniform electrostatic charge to the photoconductive insulating layer which makes up the surface layer of a xerographic plate so as to sensitize it followed by the exposure of the charged plate to an image of activating electromagnetic radiation such as light, X-ray or the like which selectively dissipates the charge in illuminated areas leaving behind charge in the non-illuminated areas to form a latent electrostatic image. This latent image is then developed or made visible by the deposition of finely divided electroscopic marking material on the surface of the photoconductive insulating layer as a result of which the marking material conforms to the pattern of the latent image. Where the photoconductive insulating material is reusable this visible image of finely divided or powdered marking material is then transferred to a second surface, such as a sheet of paper, and fixed in place 7 thereon to form a permanent visible reproduction of the original. Where, on the other hand, a less expensive, non-reusable photoconductive insulating material is employed the toner particles may be fixed in place directly on its surface with the consequent elimination of the transfer step from the process.

In Carlsons original work coatings of anthracene, melted sulfur and the like were employed as the photoconductive insulating materials. However, these materials had low sensitivity and produced only fair images at best by todays standards. Following this initial work a great deal of development effort was expended on attempting to provide improved photoconductive insulating layers for xerographic plates resulting in the production of a number of organic photoconductors such as polyvinyl anthracene, 2,5-bis-(p-aminophenyl- (l))-l,3,4-oxadiazole; polyvinyl carbazole etc. Another major area of xerographic plate development involves the binder plate in which finely divided photoconductive materials such as cadmium sulfide, cadmium selenide, zinc sulfide, antimony sulfide, mercuric oxide, lead iodide, lead sulfide, lead telluride, lead chromate, gallium telluride and other materials are dispersed in a film forming, insulating binder to make up the photoconductive insulating layer of a xerographic plate, as more fully described in U.S. Pat. No. 3,121,006 to Middleton and Reynolds. Although certain of these materials have been found to have a limited commercial utility they suffer from various deficiencies such as low-dark resistivity, poor sensitivity,

high cost and mainly from the fact that they are not reusable to make a rapid succession of images in the copying process. Accordingly, high quality xerographic plates made with photoconductors such as elemental selenium and its alloys in the amphorous form, as described in U.S. Pat. No. 2,970,906 to Bixby, have been found to be very successful from the commercial point of view because of the fact that they can be made in very smooth layers, they are reusable and can produce high resolution images and are fairly sensible to visible light and X-rayradiation. On the other hand, this preferred xerographic plate material is fairly soft and eventually suffers surface degradation from abrasion with developing material after the production of 50,000 to 100,000 copies. In addition the amorphous form of selenium is metastable so that when plates including this type of selenium photoconductive layer are exposed to heat or certain solvent vapors they frequently are converted to inoperative crystalline forms of selenium. Even with all these drawbacks, the amorphous selenium xerographic plate is the plate of preference in this field because other photoconductors such as the photoconductive aromatic polymers and binder plates described supra generally have low sensitivity, lack of reusability, relatively low abrasion resistance, rough surface characteristics and similar deficiencies. In addition many of these materials can be sensitized only by negative and not by positive corona discharge techniques. Since negative corona discharge generates much more ozone than positive corona and since it is much more difficult to control negative corona discharge so as to uniformly charge the photoconductive layer, this also stands as the substantial drawback to the use of many of the alternatives to the amorphous selenium plate.

Other photoelectric imaging techniques also suffer from materials drawbacks in sensitivity, proper spectral response, etc.

It is therefore an object of this invention to provide a novel xerographic plate devoid of the above noted disadvantages.

Another object of this invention is to provide a reusable xerographic plate having spectral sensitivity that extends over a wide range.

Still another object of this invention is to provide a reusable xerographic plate having an extremely high level of thermal stability and resistance to solvents.

Yet another object of this invention is to provide a xerographic plate which is highly resistant to abrasion and which is mechanically strong.

Again another object of this invention is to provide a novel xerographic process employing a xerographic plate with exceptionally good imaging properties.

Yet still a further object of this invention is to provide a xerographic plate capable of extremely high resolution imaging.

Yet a further object of this invention is to provide a flexible xerographic plate.

An additional object of this invention is to provide photoresponsive polymer particles for use in various photoelectric imaging techniques.

Another object of the invention is to provide a xerographic plate which may be imaged according to conventional xerographic processes for use as a printing plate.

The foregoing objects and others which will become apparent from the following description are accomplished in accordance with this invention, generally speaking, by providing a novel xerographic plate including a photoconductive insulating layer made from a polymer containing phthalocyanine. The monomeric phthalocyanine pigment itself is a substantially xerographically conductive and, therefore, unusable material xerographically but when combined in a binder which may or may not be photoconductive, as taught in U.S. Ser. No. 518,450 to Byrne, now U.S. Pat. No. 3,816,118 this material is found not only capable of sustaining very high fields in commercial xerography but is also found to be highly photoconductive. Surprisingly, it is found, however, that when this substantially xerographically conductive and, therefore, unusable xerographic material is polymerized, i.e., just as the xerographically unusable material described by Byrne in U.S. Ser. No. 518,450 which is hereby incorporated by reference, a novel xerographically photoconductive polymeric phthalocyanine material is obtained.

As explained in greater detail hereinafter, the polymer may consist of a homopolymer of the phthalocyanine monomer or of a copolymer, terpolymer or the like of the phthalocyanine monomer with various other monomers which may be employed to impart a number of various desirable properties such as flexibility, high strength, abrasion resistance and the like to the layer. While the polymerization may be carried out by either addition, condensation or any other suitable polymerization technique, it is generally preferred that at least about 2% by weight of the recurring molecular units in the resulting polymer contain the phthalocyanine moiety so that the polymer will have the desired photoconductive response. Various polymer chain lengths ranging from as short as only a few units to extremely long polymer chains, branched chains or the like as well as cross-linked chains using the phthalocyanine either in the main chain or as a portion of the cross linking agent may be used. The phthalocyanine moiety may also be included as a pendant or terminal group on a polymer chain. This photoconductive insulating polymer may be cast, molded, extruded or otherwise formed in a selfsupporting form either as a flexible film such as a long web or an endless belt or in the form of a rigid plate or rigid cylindrical drum, as desired, depending in most instances upon the type of imaging apparatus in which it is to be employed. Depending upon the monomers with which it is crosslinked or copolymerized, the final product may be a very tough flexible film or an extremely hard abrasion resistant rigid structure. Although the ability to form the photoconductive insulating film into a self-supporting structure which can be employed as a single layer xerographic plate constitutes an important feature and advantage of the invention, it is also to be understood that the photoconductive insulating film of this invention may be deposited on any suitable supporting substrate where this is desired. Typical substrates generally used in making xerographic plates include aluminum, steel, brass, copper, glass; thin layers of aluminum, silver, gold, tin oxide, copper oxide, or other metals coated on glass; conductive and semiconductive plastics and resins, paper and other convenient materials. The use of a conductive substrate provides an additional advantage in that it serves as 'a conductive ground plane beneath the photoconductive insulating surface so as to facilitate charging of the plate when this metallic layer is connected to ground or at least to a definite potential significantly below the level of the charging source potential. Since many of the polymers which include the phthalocyanine moiety are relatively insoluble and have high melting points, it is frequently desirable to polymerize the monomer directly in situ on the substrate. It is to be noted, however, that the use of such a ground plane is not essential to the operation of the invention since self-supporting films without a conductive substrate may be pressed in contact with a grounded metal plane or a two-sided 4 charging technique may be employed in which positive charge is appliedto one side of the photoconductive insulatingfilm while negative charge is applied to its opposite surface. This technique is more fully described in U.S. Pat. No. 2,922,883.

It should also be noted that although it is preferable to produce a photoconductive polymer which is film forming so as to facilitate xerographic plate fabrication, non-film forming materials may also be employed since these can often be fabricated into a continuous layer by sintering, hot pressing or the like for plate use, and may be used directly in photoelectrophoresis.

Any suitable phthalocyanine may be used to prepare the polymeric photoconductive layer of the present invention. It may be substituted or unsubstituted both in the ring and straight chain portions. Reference is made to a book entitled Phthalocyanine Compounds by F.H. Moser and A.L. Thomas, published by The Reinhold Publishing Company, 1963 edition, for a detailed description of phthalocyanines and their syntheses. Any suitable phthalocyanine may be used in the present invention. Phthalocyanines encompassed within this invention may be described as compositions having four isoindole groups linked by four nitrogen atoms in such a manner so as to form a conjugated chain, said compositions have the general formula (C H N R,, wherein R is selected from the group consisting of hydrogen, deuterium, lithium, sodium, potassium, copper, silver, beryllium, magnesium calcium, zinc, cadmium, barium, mercury, aluminum, gallium, indium, lanthanum, neodymium, Samarium, europium, calcium, gadolinium, dysprosium, holmium, erbium, thuliumytterbium, lutecium, titanium, tin, hafnium, lead, silicon, germanium, thorium, vanadium, antimony, chromium, molybdenum, uranium, maganese, iron, cobalt, nickel, rhodium, palladium, osmium, and platinum; and n is a value of greater than 0 and equal to or less than 2. Any other suitable phthalocyanines such as ring or aliphatically substituted metallic and/or nonmetallic phthalocyanines may also be used as monomers if suitable. As above noted, any suitable phthalocyanine may be used to prepare the photoconductive layer of the present invention. Typical phthalocyanines are: aluminum phthalocyanine, aluminum antimony phthalocyanine, barium phthalocyanine, beryllium phthalocyanine, cadmium hexadecachlorophthalocyanine, cadmium phthalocyanine, calcium phthalocyanine, cerium phthalocyanine, chromium phthalocyanine, cobalt phthalocyanine, cobalt chlorophthalocyanine, copper bromochlorophthalocyanine copper 4-chlorophthalocyanine, copper 4-nitr'ophthalocyanine, copper phthalocyanine, copper phthalocyanine sulfonate, copper poly-chlorophthalocyanine, deuterophthalocyanine, dysprosium phthalocyanine, erbium phthalocyanine, europium phthalocyanine, gadolinium phthalocyanine, gallium phthalocyanine, germanium phthalocyanine, hafnium phthalocyanine, halogen substitute phthalocyanine, holmium phthalocyanine, indium phthalocyanine, iron phthalocyanine, iron polyhalophthalocyanine, lanthanum phthalocyanine, lead phthalocyanine, lead polychlorophthalocyanine, cobalt hexaphenylphthalocyanine, copper pentaphenylphthalocyanine, lithium phthalocyanine, luteciurn phthalocyanine, magnesium phthalocyanine, manganese phthalocyanine, mercury phthalocyanine, molybdenum phthalocyanine, naphthalocyanine, neodymium phthalocyanine, nickel phthalocyanine, nickel polyhalophthalocyanine, osmium phthalocyanine, palladium phthalocyanine, palladium chlorophthalocyanine, alkoxyphthalocyanine, alkylaminophthalocyanine, alkylmercaptophthalocyanine, aralkylaminophthalocyanine, aryloxyphthalocyanine, arylmercaptophthalocyanine, copper phthalocyanine piperidine, cy-

cloalkylaminophthalocyanine, dialkylaminophthalocyanine, diaralkylaminophthalocyanine, dicycloalkylaminophthalocyanine, hexadecahydrophthalocyanine, imidomethylphthalocyanine, 1,2-naphthalocyanine, 2,3-naphthalocyanine, octaazaphthalocyanine, sulfur phthalocyanine, tetraazaphthalocyanine, tetra-4-acetylaminophthalocyanine, tetra-4-aminobenzoylphthalocyanine, tetra-4-aminophthalocyanine, tetrachloromethylphthalocyanine, tetradiazophthalocyanine, tetra-4,4-dimethyloctaazaphthalocyanine, tetra-4,S-diphenylene-dioxide phthalocyanine, tetra-4,5-diphenyloctaazaphthalocyanine, tetra- (6-methyl-benzothiazoyl) phthalocyanine, tetra-pmethylphenylaminophthalocyanine, tetra-methylphthalocyanine, tetra-naphthotriazolylphthalocyanine, tetra-4-naphthylphthalocyanine, tetra-4-nitrophthalocyanine, tetra-peri-naphthylene-4,5-octaazphthalocyanine, tetra-2,3-phenyleneoxide phthalocyanine, tetra-4-phenylooctaazaphthalocyanine, tetraphenylphthalocyanine, tetraphenylphthalocyanine tetracarboxylic acid, tetraphenylphthalocyanine tetrabarium carboxylate, tetraphenylphthalocyanine tetra-calcium carboxylate, tetrapyridylphthalocyanine, tetra-4-trifluoromethyl-mercaptophthalocyanine, tetra-4-trifluoromethylphthalocyanine 4,5-thionaphthene-octaazaphthalocyanine, platinum phthalocyanine, potassium phthalocyanine, rhodium phthalocyanine, samarium phthalocyanine, silver phthalocyanine, silicone phthalocyanine, sodium phthalocyanine, sulfonated phthalocyanine, thorium phthalocyanine, thulium phthalocyanine, tin chlorophthalocyanine, tin phthalocyanine, titanium phthalocyanine, uranium phthalocyanine, vanadium phthalocyanine, ytterbium phthalocyanine, zinc chlorophthalocyanine, zinc phthalocyanine, others described in the Moser and Thomas test, and mixtures, dimers, trimers, oligomers, polymers, copolymers or mixtures thereof.

As stated above, any suitable technique may be employed for forming the phthalocyanine polymer according to this invention. Thus, for example, a vinyl group may be attached to one of the benzene rings on the outside of the phthalocyanine ring so that a vinyl phthalocyanine monomer of the following type is produced. This monomer can be polymerized to form a polymer chain with pendant phthalocyanine of the following structure:

H H C=CH polymerize CC Pc H P0 Phthalocyanine The monomer and homopolymer structures are, of course, similar to vinyl benzene (styrene) except that it contains phthalocyanine in place of the pendant benzene ring in styrene. Like the divinyl benzene derivative of styrene, vinyl phthalocyanine can also be made in a poly-functional form. Since the phthalocyanine molecule is a cyclic structure containing four benzene rings, the di, tri and tetra-vinyl phthalocyanine can be t 6 formed be merely attaching vinyl groups to the requisite number of benzene rings. This provides an additional degree of control over the nature of the polymer which isproduced since it can be varied from relatively flexible when the. monomer is substantially all monofunctional to a highly crosslinked structure when a predominantly poly-functional monomer is employed. As stated above, the vinyl phthalocyanine monomer for example, tetra vinyl copper phthalocyanine more fully described in US. Pat. No. 2,513,098, may be copolymerized with one or more of any other suitable ethylenically unsaturated monomers eg. styrene (vinyl benzene) to form a copolymer or terpolymer therewith as described in Polymer Processes by Calvin E. Schildknecht, lnterscience Publishers Inc., 1956, and Textbook of Polymer Science by Fred W. Billmeyer, Jr., Interscience Publishers Inc., 1962. Typical ethylenically unsaturated monomers include: vinyl benzene, vinyl toluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl methyl ether, vinyl carbazole, vinyl chloride trifluoride, isobutylene, isoprene, butadiene, ethylene, propylene, acrylonitrile, methacrylonitrile, 3-methyl-butene-1, pentene-l, 2-chlorobutadiene, divinyl benzene, acrylic acid, methacrylic acid, acrylates such as methylacrylate, ethyl acrylate, butylacrylate, 2-thylhexylacrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, hexyl methacrylate, decyl-octyl methacrylate, lauryl methacrylate, stearyl methacrylate, 1,3-butylene dimethacrylate; dimethylaminoethyl methacrylate, t-butyl-aminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, methacrylami-de, N, N-diphenyl acrylamide, fumaronitrile, maleic anhydride, 2-chloroethylvinyl ether, methylchloroacrylate, cyclohexyl methacrylate, vinyl 2-ethyl-hexoate, vinyl .oleate, vinyl stearate, coumarone, indene, vinyl siloxanes, chloroprene, methylbutadiene, dimethylbutadiene, chloromethyl butadiene, isobutene and certain terpenes. As stated above, the vinyl phthalocyanine may also be introduced into the polymer structure by employing it as a crosslinking agent for any suitable unsaturated polymer. Thus, for example, they may be employed to crosslink unsaturated polyesters. Typical unsaturated polyesters include those madeby reacting unsaturated dibasic acids or anhydrides such as maleic acid, fumaric acid, chloromaleic acid, itaconic acid, citraconic acid, and mesaconic acid or their anhydrides with any suitable polyol. Typical polyols employed for this purpose include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, isopropylidene bis-(p-phenylene oxypropanol-2), and bis-phenol-A, (para, paraisopropylidene diphenol).

Any suitable technique may be employed for forming the vinyl phthalocyanine monomer; for example, bromo phthalonitrile may be used to replace all or a part of the phthalonitrile used in the conventional synthesis of phthalocyanine. The vinyl or allyl groups may then be added at the bromine substitution point by Grignard synthesis. By using one part bromo phthalonitrile to 3 parts unsubstituted phthalonitrile the monomer produced is monofunctionall on the average, while increases in the percentage of bromophthalonitrile tend to increase the functionality of the monomer. With this type of monomer the phthalocyanine molecule may be produced in either the metal or metal-free form. Thus, for example, by heating bromophthalic anhydride with copper cyanide, the brominated copper phthalocyanine is produced.

Condensation is another technique for forming a polymer including the phthalocyanine molecule. For example by condensing nitrophthalonitirle or nitrophthalic anhydride to produce a metal or metal-free phthalocyanine with nitro groups and thenzreducing these nitro groups to amino groups a monomer is formed. Although some phthalonitrile or phthalic anhydride may be employed which does not contain the nitro group so as to control the functionality of the phthalocyanine produced by this condensation, at least half of the starting material should contain the nitro group so as to produce a difunctional monomer. This monomer is then condensed with any suitable polyfunctional acid to form a polyamide. Typical dibasic saturated acids include succinic, glutaric, adipic, pimelic, suberic azelaic and sebacic acids. The diamino phthalocyanine may also be introduced into the polymer by using them to cure and crosslink epoxy resins. The diamino phthalocyanine described above in connection with the formation of a polyamide may also be employed to form a polyurea by condensing it with a diisocyanate. Another condensation type reaction may be performed by condensing copper phthalocyanine with dichlorostyrene, more fully described in U.S. Pat. No. 2,513,098.

The phthalocyanine molecule may also be produced in the form of a difunctional acid by initially condensing it from a starting material including at least half methyl phthalonitrile and then oxidizing the methyl groups with perrnaganate to form carboxyl groups after the phthalocyanine molecule is formed. This then, can be condensed with any suitable diamine or polyamine to form a polyamide or with any suitable diol or polyol to form a polyester utilizing techniques more fully described in BR No. 1,060,086 as well as with diisocyanates to form polyureas.

In another phthalocyanine polymerization, metal phthalocyanines are employed having a valence of 4 or more. In this way the central metal atom will have at least two additional bonding sites to which there may be added various functional groups which can also be employed for bonding the phthalocyanine molecule into a polymeric chain. Metals such as titanium, tin, silicon, germanium and lead are typical of the metals with the required valence. The production of diols of this type are described in U.S. Pat. No. 3,094,536 which describes the formation of dihydroxy silicon phthalocyanine and U.S. Pat. No. 3,094,535 which' describes the formation of dihydroxy germanium phthalocyanine. This type of molecule may be polymerized by splitting out water from the hydroxyl groups on two adjacent molecules to form an oxygen bridge across them or the molecules may be condensed with dibasic acids to form a polyester with diisocyanates to form a urethane etc.

Block copolymers of various types may also be formed which include the phthalocyanine molecule. In

tion generally yields polymers limited to the trimer,

stage, oxidation of at least two of the terminal cyano groups can be carried out to produce a diisocyanate which can then be condensed with a diol such as 1,4- butanediol to produce a urethane polymer. Other short chain phthalocyanine polymers such as those in the Moser book identified as'type 3 polymers in which adjacent phthalocyanine molecules share a common benzene ring and which contain terminal carboxyl groups, may also be employed to form longer polymers by subsequent condensation with diisocyanates to form polyurea, with diols to form polyesters, etc.

Although any suitable polymerization technique may be employed for forming polymers according to this invention, glow discharge polymerization of the type generally described in U.S. Pat. No. 2,932,591 to Goodman is a preferred polymerization technique where a film is to be formed because of the highly uniform and stable film of extremely uniform electrical properties which it is capable of forming, directly on the desired substrate. This technique may, for example, be employed to polymerize phthalocyanine with liable peripheral substituents such as alkyl, carboxy, amino, amide and the like so that these can be attacked by glow discharge ionization and cross linked to each other or through additional monomers which are introduced into the discharge system such as chloroform, formaldehyde, ammonia, fluorinated hydrocarbons and many others. Other in situ polymerization techniques may also be used for film making applications while almost any technique can be used to make the particles.

Film thicknesses of up to about microns may be employed in forming the electrophotographic member of the present invention; Film thicknesses of about 10-25 microns are preferred because they more nearly satisfy the requirements of the present invention. Any suitable coating technique for forming the photoconductive film of the present invention may be employed in addition to the in situ polymerization technique disclosed herein. Typical methods of coating include: flow coating, bar coating, dip coating, Mayer rod draw down, and glow discharge and other vacuum evaporation techniques. It should be understood, however, that whatever method is employed to either cost or form the polymerized phthalocyanine materials into the photoconductive film of the present invention, uniformity of thickness and surface smoothness are to be controlled so that they conform to those accepted electrophotographic standards well-known in the art. The coating of the photo-conductive material of the present invention should be uniformly deposited in those thicknesses specified to a tolerance of 25% and preferably to a tolerance of 10% of nominal thickness. The surface smoothness of the photoconductive member of the present invention should be such that conventionally known particulate developers having particle sizes from about 2 to 10 microns can be readily removed therefrom.

In addition to using the polymeric films of this invention as the sole component of the photoconductive insulating layer of a xerographic plate, these polymers may have compatible (or suitable) organic or inorganic photoconductive materials dissolved or dispersed therein to form a composite plate structure as described, for example, in U.S. Pat. No. 3,121,007 and many other references. In addition, dyes and other sensitizing agents, as known in the art, may also be employed in conjunction with these photoconductive 9 polymers.

The use of the photoconductive polymers of this invention is not restricted to xerographic plates alone for these materials whether used alone or in conjunction with other organic or inorganic photoconductors and/or sensitizing agents may be used in photoelectric imaging systems requiring particulate photosensitive materials. In this case the polymers may be formed into relatively hard, brittle layers by controlling the types and amounts of comonomers used, degree of crosslinking, etc. Then after formation, the polymeric films may be broken up into small particle size or ifcomonomers are so selected that the polymer is initially formed as a powder, this grinding operation may be totally avoided.

Particles of this type may, for example, be used in a system where a layer of these particles is deposited on the surface of a soluble insulating film. The particle covered surface is then electrically charged as by corona discharge of the type described above and exposed to an image to be reproduced. Since the particles are separate from each other and supported on an insulating surface, charge cannot move freely through the system upon exposure even though the exposure does render the photosensitive particles more conductive. This exposure then only allows the charge to move into the bulk of exposed particles while the remainder of the charge on the unexposed particles remains on their surfaces. Since the insulating film itself is deposited on a grounded conductive backing, there is a force of attraction between all of the particles and this backing. When the particle covered imaging layer is dipped into a solvent, such as cyclohexane, the insulating layer is softened and the particles selectively migrate to the underlying substrate to produce an image. This process is more fully described in U.S. Pat. Nos 3,384,488; 3,384,565; and 3,384,566 having a common assignee and reference is made to these patents for a more detailed teaching of this process.

In another application of the particulate polymer according to this invention, the particles are suspended in an insulating liquid between a pair of electrodes at least one of which is optically transparent. When the suspension is exposed to the image to be reproduced with actinic light and an electric field is applied across the electrodes, the exposed particles migrate to one or the other of the electrode surfaces so that upon separation of the two electrodes a particle image corresponding to the optical image is formed. This process is more fully described in U.S. Pat. application Ser. 384,681, filed July 23, 1964, abandoned in favor of a continuation-in-part application, now issued as U.S. Pat. No. 3,384,566.

The invention having been generally described above the following specific examples of preferred embodiments of the invention, are now given in further illustrations thereof. All parts in the Examples are taken by weight unless otherwise indicated.

EXAMPLE I One mol of vinyl phthalocyanine and 20 mols of acrylonitrile are vaporized in a vacuum sublimator and sent into a glow discharge chamber of the type described by Bradley and Hammes (Electro Chemical Society Journal, 110, Jan., 1963, p. The monomers are then copolymerized in situ utilizing those techniques more fully described in U.S. Pat. No. r

2,932,591 at about 400 volts at 25 k Hz and a pressure of less than about 10 ton on a flexible aluminum foil plastic laminated belt to a thickness of about 50 microns. This belt is then positively charged by subjecting it to corona discharge from a discharge electrode of the type described in U.S. Pat. No. 2,836,725 to Vyverberg, while the aluminum is connected to ground, exposed to an image and developed with a conventional xerographic cascade development system which is more fully described in U.S. Pat. No. 2,618,552 to Wise. The image may be transferred to paper in utilizing conventional techniques and toner residues may be removed to permit cyclic reimaging of the photoreceptor. This film produces good quality images and adheres well to the aluminum showing no signs of flaking off after repeated flexing.

EXAMPLE II A copolymer made up from one mol vinyl phthalocyanine to each 20 mols of acrylonitrile is polymerized in situ on a flexible aluminum foil belt to a thickness of about 50 microns. This belt is then positively charged by subjecting it to corona discharge from a discharge electrode of the type described in U.S. Pat. No. 2,836,725 to Vyverberg, and exposed to an image and developed with a conventional xerographic cascade development system which is more fully described in U.S. Pat. No. 2,618,552 to Wise. This film produces a good quality image and adheres well to the aluminum showing no signs of flaking off after repeated flexing.

EXAMPLE III One mol of vinyl phthalocyanine, l7 mols of vinyl chloride and 5 moles of vinyl acetate are vaporized in a vacuum sublimator. The monomers are sent into a glow discharge chamber of the type described by Bradley & Hammes (Electro Chemical Society Journal, 110, Jan., 1963, p. 15) where they are polymerized to form a terpolymer in situ on a stainless steel belt utilizing techniques as in Example I employing a voltage of about 500 volts at 25 k Hz, an electrode spacing of about 12.5 mm and a pressure of about 10 torr. The terpolymer so produced is tested according to the procedure of Example I with similar results except that the polymer is more flexible and produces better quality images.

EXAMPLE IV A terpolymer polymerized from one mol vinyl phthalocyanine, l7 mols vinyl chloride and 5 mols vinyl acetate on a stainless steel belt is tested according to the procedure of Example I with similar results except that the polymer is more flexible and produces better quality images.

EXAMPLE V To a stainless steel, stirred, 1 gal. autoclave is added 2 l. deaerated distilled water, 3.0 g. methyl cellulose (e.g., Methocel MC25, Dow Chemical Co.), 2.0 g. lauroyl peroxide, 7.0 g. trichloroethylene, 205 g. distilled vinyl acetate, and 790 g. vinyl chloride. The vinyl chloride can be conveniently added after the other ingredients are sealed in the autoclave by condensing about 840 g. of vinyl chloride into a stainless steel cylinder equipped with inlet and outlet valves. The excess vinyl chloride is then pressured into the autoclave with nitrogen. After 50 g. of vinyl chloride has been allowed to distill from the autoclave into an isopropanol -Dry Ice trap, the autoclave is rescaled, heated to C., and stirring is started. Subsequent additions of vinyl chloride can be made in a similar Approximate Amount of time after Increment vinyl chloride preceding addition I 90 g. 2.5 hr.* 2 75 g. 0.75 3 65 g. 0.75 4 50 g. 0.75

*time after initial charge reached 60C After the fourth increment, polymerization is allowed to proceed until an overall reaction time of 10 hr. has elapsed, at which about 1 kg. of poly(vinyl chloride-covinyl acetate) is obtained which is collected on a filter, washed with methanol, and dried. This copolymer is quite uniform in composition with 13-l5 weight per cent vinyl acetate and an inherent viscosity of about 0.55 (0.5% solution in cyclohexanone at 30C.).

The 85% vinyl chloride and 15% of vinyl acetate copolymer is then hydrolyzed in about a by weight sodium methoxide in tetrahydrofuran solution by refluxing at about 65C. until the hydrolysis is completed as measured by a gas chromatograph sample. A vinyl alcohol and 5% vinyl acetate terpolymer with vinyl chloride is thus obtained.

To about 60 grams (1 mol) of molten urea in a 1000 cc flask is added about 55 grams (0.25 mol) of pyromellitic dianhydride. The system is heated to about 120C, at which temperature considerable gas evolution occurrs. When frothing abates, about 0.1 gram of ammonium molybdate is added and heating is continued. At a temperature of about 190C., about 10 grams (0.1 mol) of CuCl is added. Continued heating results in the development of an intense green color in the vicinity of about 210C. Temperature is held between 210 and 230C. for about 2 minutes, at the end of which time a thick grainy paste forms.

After cooling, the paste, which is now hardened, is broken up and repeatedly washed with boiling water until the washings show no cloudiness on cooling in ice. The residue is then dried several hours at about 125C. and is found to weigh about 55 grams, representing a 73% yield based on the pyromellitic dianhydride.

The crude product is further purified by dissolving it in 10 times its weight of concentrated sulfuric acid at room temperature. The solution is filtered through 2 layers of 1 l2 weave glass cloth and then poured slowly with vigorous stirring into a lO-fold volume of water. The flocculent bluegreen precipitate is filtered off and washed with water until the washings are neutral. The product is dried for several hours at about 125C. and ground to pass 200 mesh. The yield from crude product is found to be 90%.

About twenty-five grams of the phthalocyanine octacarboxyl acid so produced is condensed with about 10 grams of the terpolymer in xylene by refluxing with para toluene sulfonic acid for about 5 hours. The polymer is then purified by precipitation in methanol redissolving in tetrahydrofuran and precipitating again. Twenty percent by weight of the completed polymer is 12 dissolved in a 1 to l ketone to toluene solvent and coated on an aluminum foil belt and tested according to the procedure of Example I after drying. Here again, a flexible and fairly tough coating is produced with sensitivity about /2 asgood as that of the film of Example III.

EXAMPLE VI A dichlorobenzene solution of a terpolymer made up of 3% by weight vinyl acetate, 5.7% by weight vinyl alcohol and the remainder vinyl chloride is condensed with an excess of copper phthalocyanine monosulfonic acid chloride so that pendent copper phthalocyanine molecules are attached to the original vinyl alcohol units of the polymer through an ester linkage. Twenty percent by weight of the completed polymer is dissolved in a 1 to l ketone to toluene solvent and coated on an aluminum foil belt and tested according to the procedure of Example I after drying. Here again, a flexible and fairly tough coating is produced with sensitivity about /2 as good as that of the film of Example III.

EXAMPLE VII Tetraaminophthalocyanine is prepared by condensing 4 moles of nitrophthalonitrile and reducing by dithionite utilizing techniques more fully described in Moser and Thomas. This product is blended with an epichlorohydrin/bisphenol A type epoxy resin with an epoxide equivalent of about 500 in a ratio of about 15 parts by weight of tetraaminophthalocyanine to each parts by weight of the epoxy resin. After a cure of about 3 hours at about 200F. on a thin aluminum sheet, an extremely hard and fairly flexible coating is produced. Testing in accordance with the procedure of Example I indicates that the plate has the highest level of sensitivity of any of those tested.

EXAMPLE VIII A tetraaminophthalocyanine (having an average functionality of four) produced by the reduction of tetranitrophthalocyanine is blended with an epichlorohydrin/bisphenol A-type epoxy resin with an expoxy resin with an epoxide equivalent of 500 in a ratio of 15 parts by weight of tetraaminophthalocyanine to each 100 parts by weight of the epoxy resin. After a cure of 3 hours at 200F on a thin aluminum sheet, an extremely hard and fairly flexible coating is produced. Testing in accordance with the procedure of Example I indicates that the plate has the highest level of sensitivity of any of those tested.

EXAMPLE IX About 34.8 grams of suberic acid is condensed with about 57.6 grams of polyaminophthalocyanine in dichlorobenzene at a temperature of about 250C. to form a polyamide resin. A thin aluminum sheet is passed through the reaction mixture to form a coating thereon. The coating so formed is a fairly flexible tough coating with a sensitivity slightly better than that of Example I when tested according to the procedure I described in Example 1.

EXAMPLE X About 34.8 grams of suberic acid are condensed with about 57.6 grams of polyaminophthalocyanine in dichlorobenzene to form a polyamide resin on a thin aluminum sheet. This forms a fairly flexible tough coating with a sensitivity slightly better than that of the Example I coating when tested according to the procedure described in that Example.

EXAMPLE XI EXAMPLE XII About 50 grams of phthalocyanine dicarboxylic acid and about 17 grams of suberic acid are condensed with about 66 grams of glycerol and about 4 grams of methanol as a chain terminator. The polymer s condensed on a flexible aluminum sheet and tested according to the procedure of Example I. A very tough coating with good adhesion and fairly high photosensitivity is produced.

EXAMPLE XIII Formaldehyde is bubbled through a solution of tetraaminophthalocyanine in benzene with refluxing. 1,6- hexamethylene diisocyanate is added in molar equivalents to the reaction product at the reflux for about 3 hours. A brass foil is passed through the reaction mixture and tested according to those procedures outlined in Example I. A tough and extremely flexible coating is produced with sensitivity about equal to that of Example IX.

EXAMPLE XIV A polymer produced by condensing dimethylol phthalocyanine with 1,6-hexamethylene diisocyanate on a brass foil is tested according to the procedure of Example I. A tough and extremely flexible coating is produced with sensitivity about equal to that of Example IX.

EXAMPLE XV Phosgene is bubbled through a mixture of molar equivalents of dihydroxy germanium phthalocyanine made according to Example V of U.S. Pat. No. 3,094,535 and 1,4-butanediol at a termperature of about 50C. for about 1 hour in a pyridine bath to form a block copolymer. The polymer so obtained is coated on an aluminum foils sheet and tested according to the procedures outlined in Example I. A strongly adherent coating is produced with a sensitivity about /2 that of Example I.

EXAMPLE XVI A polymer made by condensing dihydroxy germanium phthalocyanine made according to Example V of US. Pat. No. 3,094,535 with 1,4-butanediol is coated on an aluminum foil sheet and tested according to the procedure of Example I. A strongly adherent coating is produced with a sensitivity about /2 that of Example I.

EXAMPLE XVII Phthalocyanine octacarboxylic acid prepared in the manner as described in Example III is vaporized in a vacuum sublimator. The vaporized monomer is then sent into a glow discharge chamber and polymerized is situ on an aluminum sheet using those techniques outlined in Example I. Apparently the glow discharge ionization attacks the carboxyl groups in such a way that the adjacent groups come together by some type of condensation reaction thereby forming a crosslinked polymer on the substrate. The material produced has a vitreous appearance, fairly high photosensitivity, strong adhesion to the substrate and good mechanical strength but is less flexible than the films produced according to the foregoing Examples when tested in accordance with those techniques outlined in Example I.

EXAMPLE XVIII A phthalocyanine tetracarboxylic acid produced by first condensing methyl phthalonitrile and then oxidizing the methyl groups to produce carboxyl groups is employed as a starting monomer. This monomer is polymerized on an aluminum sheet by glow discharge of the type described in the aforementioned patent to Goodman. Apparently the glow discharge ionization attacks the carboxyl groups in such a way that the adjacent groups come together by some type of conden sation reaction thereby forming a crosslinked polymer on the substrate. The material produced has a vitreous appearance, fairly high photosensitivity, strong adhesion to the substrate and good mechanical strength but is less flexible than the films produced according to the foregoing Examples.

EXAMPLE XIX About 10 millimoles (900 mg.) of 1,4-butanediol are mixed with about 8 millimoles (980 mg.) of maleic anhydride and reacted at about 180C to form a low molecular weight oligomeric polyester. This polyester is stirred vigorously with about 2 millimoles (1.86 grams) of sym-o ctacarboxy phthalocyanine (the synthesis of which is later described) at 180200C for a period of about six hours, to produce a low-molecular weight mixed polyester comprising about 10 mole percent of phthalocyanine groups. The product is cooled to room temperature, and mixed with about 10 millimoles (1.04 g) of purified styrene monomer in the presence of about 0.1 millimoles (24 mg) of the catalyst benzoyl peroxide. This mixture is now coated immediately (while still in a fluid state) on a degreased bright aluminum base by means of a Bird coater (a coating device supplied by Gardner Laboratory) with about a 1 mil blade gap setting. The dark bluish-green coating gradually hardens, presumably as a result of a cross-linking reaction between the styrene and the phthalocyanine containing polyester. After about two hours at room temperature, the reaction is substantially complete, and the phthalocyanine copolymer coating has hardened sufficiently to be ready for use in electrophotography. The coating is the charged, exposed, and developed utilizing techniques as in Example I resulting in an image of good quality. v

The sym-oxtacarboxy phthalocyanine is prepared, as follows:

About 5.0 g. of pyromellitic dianhydride (EK Cat.

About 26.0 g. of urea,

About 4.7 g. of ammonium molybdate (tetrahydrate) and About ml. o-cichlorobenzene are mixed,

stirred vigorously, heated-to about 160C, and held at 160C for about minutes. The reaction product is cooled to about 40C and solids are collected by filtration. The filter cake is washed copiously with water, followed by ethanol, benzene and ethanol, then suction dried.

The product is purified as follows: the solid is dissolved in ice-cold concentrated H 50 and filtered (sintered glass funnel). The filtrate is poured onto an ice-water mixture, with vigorous stirring. The resultant mixture is allowed to stand over night, and the solids are then collected by filtration. The green solid is washed with acetone and then methanol, suction-dried, and extracted with methanol in Soxhlet apparatus. The extracted solid is air dried producing a yield of about 4 grams.

EXAMPLE XX The synthesis of octacarboxy phthalocyanine is repeated essentially as described in Example XIX except that the mole equivalent (4.6 m.moles, or 620 mg) of CuCl is added to the initial reaction mixture. The resultant copper octacarboxy phthalocyanine may be used to make a photoconductive styrenated polyester analgous to the one described in the immediately preceding example. The appearance and xerographic performance of the photoconductive polymeric layer produced are similar to the corresponding properties of the metal-free phthalocyanine polymer when tested in accordance with techniques as employed in Example I.

The term phthalocyanine when used in the following claims is intended to include metal and metal-free phthalocyanine whether substituted or not. Reference is made to the Moser text cited above and to the many references cited therein for a teaching of phthalocyanine compound preparation techniques.

Although specific materials and conditions are set forth in the above Examples, these are merely illustrative of the present invention. Various other materials such as any of the typical phthalocyanine compounds polymerized together or copolymerized with other materials in various polymer configurations as set out above, which are suitable may be substituted for the materials in the Examples with similar results. The films of this invention may also have other materials mixed, dispersed, copolymerized or otherwise added thereto to enhance, sensitize, synergize or otherwise modify the properties thereof.

Although the present examples were specific in terms. of conditions and materials used, any of the above listed typical materials may be substituted when suitable in the above examples with similar results. In addition to the steps used to carry out the process of the present invention, other steps or modifications may be used if desirable. For example, during the development step a field may be applied which permits toner to deposit on areas which bear electrostatic images to be developed and substantially eliminates deposition of the toner in nonimage areas thus appreciably reducing background. In addition, other materials may be incorporated in the system of the present invention which will enhance, synergize or otherwise desirably affect the properties of the systems for their present use. For example, chemically reactive groups which may improve the mechanical and electrical properties of the monomer or polymer of the present invention may be chemically combined as desired.

Anyone skilled in the art will have other modifications occur to him based on the teachings of the present invention. These modifications are intended to be encompassed within the scope of this invention.

What is claimed is:

l. A method of forming a latent electrostatic image comprising charging a photoconductive insulating layer said layer comprising a polymer in which at least about 2% by weight of its recurring molecular units include a phthalocyanine molecule and exposing said charged layer to a pattern of actinic electromagnetic radiation.

2. The method as defined in claim 1 further comprising developing said latent electrostatic image with a finely divided electroscopic marking material.

3. A method of forming a latent electrostatic image comprising charging a photoconductive insulating layer said layer comprising a polymer in which at least about 2% by weight of its monomeric precursor comprises phthalocyanine with an ethylenically unsaturated substituent and exposing said charged layer to a pattern of actinic electromagnetic radiation.

4. A method of forming a latent electrostatic image comprising charging a photoconductive insulating layer said layer comprising a polymer condensed from at least about 2% by weight of phthalocyanine which is at least difunctionally substituted and exposing said charged layer to a pattern of actinic electromagnetic radiation.

5. A method of forming a latent electrostatic image comprising charging a photoconductive insulating layer comprising a polymer in which at least about 2% by weight of the recurring molecular units of said polymer include the phthalocyanine molecule and and in which said phthalocyanine containing units are arranged together in groups of at least two so as to form a block copolymer with a second and distinct recurring molecular unit and exposing said charged layer to a pattern of actinic electromagnetic radiation.

6. A method of forming a latent electrostatic image comprising charging a photoconductive insulting layer said layer comprising a polymer in which at least about 2% by weight of said polymer comprises groups which are pendant from a main polymer chain, said pendant groups including the phthalocyanine molecule and exposing said charged layer to a pattern of actinic electromagnetic radiation.

7. A method of photoelectrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between a pair of electrodes, at least one of said electrodes being at least partly transparent, said suspension comprising a plurality of finely divided polymeric particles in which at least about 2% by weight of the recurring molecular units include a phthalocyanine molecule, said particles being suspended in an insulating carrier liquid and simultaneously exposing said suspension to an image through said transparent electrode with a source of activating electromagnetic radiation whereby a pigment image made up of migrated particles is formed on one of said electrodes and separating said electrodes.

8. A method of imaging comprising uniformly charging the surface of an imaging layer said imaging layer comprising a layer of photoconductive insulating particles on a soluble, electrically insulating resin surface over a conductive base layer, said photoconductive insulating particles comprising a polymer in which at least about 2% by weight of its recurring molecular units include a phthalocyanine molecule, exposing the 17 photoconductive insulating particles of said imaging member to a pattern of actinic electromagnetic radiation corresponding to an image to be reproduced and contacting said imaging member with a solvent for said resin whereby particles selectively migrate to the underlying substrate to produce an image.

9 A xerographic plate comprising an electrophotographic film of a polymer in which at least one of the recurring molecular units includes the phthalocyanine molecule, said polymer comprising at least one recurring molecular unit in addition to the unit including phthalocyanine, said additional unit being characterized in that it imparts flexibility and toughness to the interpolymer which it forms with said phthalocyanine including unit.

10. The xerographic plate as defined in claim 9 wherein said film is deposited in the thickness up to 80 18 microns to a tolerance plus or minus 25% of nominal thickness.

11. A xerographic plate comprising an electrophotographic film comprising one member selected from the group consisting of phthalocyanine copolymers and terpolymers, in which at least about 2% by weight of the recurring molecular units of said copolymers and terpolymer include a phthalocyanine molecule, said film having a thickness of up to microns uniformly deposited to a tolerance of i 25 percent of nominal thickness.

12. The xerographic plate as defined in claim 11 wherein said film is coated on electrically conductive substrate to a thickness of up to 80 microns to a tolerance of i 25 percent of nominal thickness.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,926,629

DATED December 16, 1975 |NVENTOR(5) 1 John W. Weigl It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the title both on the cover page and at the top of column 1, please delete "Phthaldcyanine" and substitute -Phthalocyanine-.

In Claim 11, column 18, line 9, delete "terpolymer' and substitute -terpolymers.

Signed and Scaled this RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner of Parents and Trademarks

Claims

1. A method of forming a latent electrostatic image comprising charging a photoconductive insulating layer said layer comprising a polymer in which at least about 2% by weight of its recurring molecular units include a phthalocyanine molecule and exposing said charged layer to a pattern of actinic electromagnetic radiation.

8. A method of imaging comprising uniformly charging the surface of an imaging layer said imaging layer comprising a layer of photoconductive insulating particles on a soluble, electrically insulating resin surface over a conductive base layer, said photoconductive insulating parTicles comprising a polymer in which at least about 2% by weight of its recurring molecular units include a phthalocyanine molecule, exposing the photoconductive insulating particles of said imaging member to a pattern of actinic electromagnetic radiation corresponding to an image to be reproduced and contacting said imaging member with a solvent for said resin whereby particles selectively migrate to the underlying substrate to produce an image.

9. A XEROGRAPHIC PLATE COMPRISING AN ELECTROPHOTOGRAPHIC FILM OF A POLYMER IN WHICH AT LEAST ONE OF THE REDUCING MOLECULAR UNITS INCLUDES THE PHTHALOCYANINE MOLECULE, SAID POLYMER COMPRISING AT LEAST ONE RECURRING MOLECULAR UNIT IN ADDITON TO THE UNIT INCLUDING PHTHALOCYANINE, SAID ADDITIONAL UNIT BEING CHARACTERIZED IN THAT IT IMPARTS FLEXIBILITY AND TOUGHNESS TO THE INTERPOLYMER WHICH IT FORMS WITH SAID PHTHALOCYANINE INCLUDING UNITS.

10. The xerographic plate as defined in claim 9 wherein said film is deposited in the thickness up to 80 microns to a tolerance plus or minus 25% of nominal thickness.

11. A xerographic plate comprising an electrophotographic film comprising one member selected from the group consisting of phthalocyanine copolymers and terpolymers, in which at least about 2% by weight of the recurring molecular units of said copolymers and terpolymer include a phthalocyanine molecule, said film having a thickness of up to 80 microns uniformly deposited to a tolerance of + or - 25 percent of nominal thickness.

12. The xerographic plate as defined in claim 11 wherein said film is coated on electrically conductive substrate to a thickness of up to 80 microns to a tolerance of + or - 25 percent of nominal thickness.