US3718462A

US3718462A - Manifold electrification process

Info

Publication number: US3718462A
Application number: US00829963A
Authority: US
Inventors: I Krohn; G Page
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1969-06-03
Filing date: 1969-06-03
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27
Also published as: JPS491213B1; GB1313712A; DE2027309A1; CA947366A

Abstract

A process for improving the imaging characteristics of electrically photosensitive material employed in the manifold layer transfer imaging process which comprises subjecting the material to an electric field of known polarity and then reversing the polarity of the field prior to the exposure of the imaging material to electromagnetic radiation to which it is sensitive.

Description

United States Patent 11 1 Krohn et al.

[ Feb. 27, 1973 MANIFOLD ELECTRIFICATION PROCESS [75] Inventors: Ivar T. Krohn; Geoffrey A. Page,

' both of Rochester, N.Y.

[73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: June 3, 1969 [211 App]. No.: 829,963

52 us. 01. ..'...96/1.3, 96/1 R, 96/15 [51] Int. Cl. ..G03g 13/22 [58] Field of Search ..96/1, 1.3, 1.5

[56] References Cited UNITED STATES PATENTS 3,041,167 6/1962 Blakney et a1. .Q ..96I1.4 X 3,355,289 11/1967 Hall et a1. ..96/l.4 3,412,242 11/1968 Giaimo 1.96/1 X 2,833,648 5/1958 Walkup ..96/1

3,268,331 Harper ..96/1 3,438,772 4/1969 Grundlach ..96/1 3,446,616 5/1969 Clark ..96/1.5 3,457,070 7/1969 Watanabe et al.... ..96/1.4 3,512,968 5/1970 Tulagin ..96/1.2

Primary Examiner-George F. Lesmes Assistant Examiner-John R. Miller Attorney-James J. Ralabate, David C. Petre and Raymond C. Loyer [5 7] ABSTRACT A process for improving the imaging characteristics of electrically photosensitive material employed in the manifold layer transfer imaging process which comprises subjecting the material to an electric field of known polarity and then reversing the polarity of the field prior to the exposure of the imaging material to electromagnetic radiation to which it is sensitive.

12 Claims, 2 Drawing Figures PATENTED Z' 7 INVENTORS lVAR T4 KROHN GEOFFREY A. PAGE @m za%w ATTORNEY MANIFOLD ELECTRIFICATION PROCESS BACKGROUND OF THE INVENTION The present invention relates to manifold layer transfer imaging and more specifically to a process which provides improved imaging characteristics of the electrically photosensitive materials employed therein.

Although color imaging techniques based on the transfer of an imaging layer have been known in the past, these techniques have always been difficult to operate because they depend on photochemical reactions and generally involve the use of distinct layer materials for the two functions of imagewise transfer and image coloration. A typical example of the complex structures and sensitive materials employed in prior art techniques is described in US. Pat. No. 3,09l,529 to Buskes. A more comprehensive discussion of prior art imaging techniques based on layer transfer may be found in copending application Ser. No. 452,641, filed May 3, 1965, in the U.S. Patent Office, now abandoned.

Copending application Ser. No. 452,641, filed May 3, 1965 now abandoned, describes an imaging system utilizing a manifold sandwich comprising an electrically photosensitive material between a pair of sheets. In this imaging system, an imaging layer is prepared by coating a layer of cohesively weak electrically photosensitive imaging material onto a substrate. In one form the imaging layer comprises an electrically photosensitive material such as metal-free phthalocyanine dispersed in a cohesively weak insulating binder. This coated substrate is called the donor. When needed, in preparation for the imaging operation, the imaging layer is activated as by contacting it with a swelling agent, solvent, or partial solvent for the material, or by heating. This step may be eliminated, of course, if the layer retains sufficient residual solvent after having been coated on the substrate from a solution or paste or if sufficiently cohesively weak to fracture in response to the application of electromagnetic radiation and electrical field. After activation a receiving sheet is laid over the surface of the imaging layer. An electric field is then applied across the imaging layer while it is exposed to a pattern of light and shadow representative of the image to be reproduced. Upon separation of the donor substrate or sheet and receiving sheet, the imaging layer fractures along the lines defined by the pattern of light and shadow to which the imaging layer has been exposed. Part of the imaging layer is transferred to one of the sheets while the remainder is retained on the other sheet so that a positive image, that is, a duplicate of the original is produced on one sheet while a negative image is produced on the other.

Copending application Ser. No. 609,058, filed Jan. 13, I967, now abandoned, described a, modified manifold imaging process wherein the electric field across the imaging layer is modified by reducing, grounding or reversing the field after image exposure of the imaging layer. By such means the image sense normally obtained in the manifold imaging process is reversed. That is, the respective sheets upon which the positive and negative image are obtained are reversed when the electric field employed during the imaging step is modified subsequent to the imaging step but prior to sandwich separation.

In the manifold imaging process the imaging layer containing the electrically photosensitive materials can be exposed in several different modes. That is, conventionally a transparent donor sheet is employed and the imaging layer is exposed through the donor sheet. In some instances it is preferred that the imaging layer be exposed from the receiver side of the manifold sandwich through a transparent receiver. Also the imaging layer can be exposed prior to being incorporated into a manifold sandwich by electrically charging a donor sheet and imaging layer, then exposing it to an imagewise pattern of light and shadow either through a transparent donor sheet or directly on the uncovered surface of the imaging layer.

Although usable images are obtained by the various imaging modes and image sense reversal procedures, a great variety of image quality is observed between different electrically photosensitive materials. That is, some materials provide reduced image quality when subjected to field reversal after imaging while other materials may provide inferior image quality or require large amounts of light when exposed from the receiver side of the manifold sandwich. A process has been discovered which improves the quality of images ob tained from such imaging materials when exposed from the receiver side of the manifold sandwich or subjected to field reversal after imagewise exposure.

SUMMARY OF THE INVENTION An object of this invention is to provide a layer transfer imaging process wherein images of improved quality are obtained.

Another object of this invention is to provide a manifold layer transfer imaging process wherein high quality images are obtained when the imaging layer is exposed through the receiver side of the manifold sandwich.

Another object of this invention is to provide a manifold imaging process wherein images of improved quality are obtained with image sense reversal techniques.

Another object of this invention is to provide a process for improving the imaging characteristics of electrically photosensitive material employed in the manifold imaging process.

In accordance with this invention, electrically photosensitive imaging materials are subjected to an electrification treatment which comprises subjecting the material to an electrical field of known polarity while in the dark and subsequently reversing the electrical field while still in the dark. After field reversal the imaging material may be image exposed from the receiver side of the manifold sandwich to produce improved quality images. In addition, the imaging material provides improved quality images of reversed image sense when subjected to such techniques as field modification as described in copending application Ser. No. 609,058 referred toabove and excess exposure to electromagnetic radiation as described in copending application Ser. No. 609,124 filed Jan. 13, 1967, now abandoned, both applications being incorporated herein by reference.

Previously, some of the electrically photosensitive materials useful in the manifold imaging process provided high quality images in the various imaging modes and image reversal techniques whereas other electrically photosensitive materials provided images of varying quality dependent upon the imaging mode employed in the manifold imaging process. In accordance with the process of this invention, the electrically photosensitive materials useful in the manifold imaging process are rendered versatile in that high quality images are produced even when exposed to imagewise light from the receiver side of imaging layer and when image sense reversal techniques are employed.

The electrification treatment of this invention involves subjecting a material to an electric field. The electric field is provided by means known to the art to subject an area to an electric field. Thus, the electrically photosensitive material can be incorporated into a manifold sandwich and subjected in the dark to an electric field by placing the sandwich between a pair of electrodes. The polarity of the electric field between the electrodes is then reversed and, providing the receiver side electrode receiver sheets are transparent, the electrically photosensitive material can then be exposed to a pattern of electromagnetic radiation to which it is sensitive. Preferably the receiver is removed with the field still applied and a fresh receiver placed over the imaging layer prior to reversing the polarity of the field. The electric field can also be provided by employing an electrically insulating material in at least one of the sheets forming the manifold sandwich and producing a static charge in the insulating sheet. By employing the insulating sheets, which retain an electric charge, the manifold sandwich can be passed between and in contact with charge bearing members such as electrically charged rollers whereby an electric charge is transferred to the static sheets. Field reversal is accomplished by passing the manifold sandwich through two such charge bearing members prior to exposing the electrically photosensitive imaging material to a pattern of electromagnetic radiation. Thus, the static charge is developed by providing an electrical charge bearing member in electrical communication with the electrically insulating layer.

The electric field employed in the process of this invention is desirably in the range of from 2,000 to 10,000 volts per mil across the imaging layer. Preferably the electric field is in the range of from about 3,000 to 7,000 volts per mi]. The reversed field is usually of the same strength as the initial electric field. To attain such electric field with static charges in insulating layers, a potential of from about 5,000 to about 20,000 volts in the charge bearing member is usually employed. Higher voltages can be employed but are not desirable.

In one form, the process of this invention can be accomplished by passing a donor, that is, a substrate having coated thereon an electrically photosensitive imaging material, between a pair of roller electrodes or into the ionization area of corona discharge device and then incorporating the donor into a manifold sandwich and subjecting the imaging layer to a reversed electrical field. The static charges retained in insulating donor and receiver sheets are sufficient to provide an electric field across the sandwich during subsequent image exposure and sandwich separation steps in the manifold imaging process.

When combined with the manifold imaging process, the means employed to provide the electrical field for the treatment process of this invention can also be employed to provide the electric field in the manifold imaging process. The electrodes employed may comprise any suitable conductive material and may be flexible or rigid. Typical conductive materials include metals such as aluminum, brass, steel, copper, nickel, zinc, etc., metallic coatings on plastic substrates, rubber rendered conductive by the inclusion of a suitable material therein or paper rendered conductive by the inclusion of a suitable material therein or through conditioning in a humid atmosphere to insure the presence therein of sufficient water content to render the material conductive. Such electrodes are, for example, conductive rollers or corona discharge devices as described in U.S. Pat. No. 2,588,699 to Carlson and U.S. Pat. No. 2,777,957 to Walkup, U.S. Pat. No. 2,885,556 to Gundlach or by using conductive rollers as described in U.S. Pat. No. 2,980,834 to Tregay et al. Other means of transmitting a static charge will occur to those skilled in the art.

In the manifold imaging process wherein the imaging layer is exposed to activating electromagnetic radiation while positioned between the electrodes which establish the electrical field across the sandwich, one of the electrodes must be at least partially transparent. The transparent conductive electrode may be made with any suitable conductive transparent material and may be flexible or rigid. Typical conductive transparent materials include: cellophane, conductively coated glass, such as tin or indium oxide coated glass, aluminum coated glass, or similar coatings on plastic substrates. NESA, a tin oxide coated glass, available from Pittsburgh Plate Glass Company is preferred because it is a good conductor, highly transparent and is readily available. In the process of this invention wherein the donor and/or receiver is composed of conductive material, each may also be used as the electrode by which the imaging layer is subjected to an electric field. That is, either one or both of the donor sheet and receiver sheets may serve a dual function in the process of this invention.

The electrification treatment of electrically photosensitive materials in accordance with this invention can be conveniently employed in conjunction with the manifold layer transfer imaging process. The imaging process employes an electric field across the imaging layer at some point in the process prior to the separation of the manifold sandwich. Although the electrification treatment can be performed on electrically photosensitive materials at some point in time and location and remote from the manifold imaging process, the electrification treatment is conveniently performed in conjunction with the imaging process. Thus, a donor sheet having an imaging layer coated thereon can, immediately after the reversed potential is applied be imagewise exposed to electromagnetic radiation to which. it is sensitive and further processed in accordance with the manifold imaging process to provide negative and positive copies of the original image.

The process of this invention can be employed to improve any suitable electrically photosensitive material. Typical organic electrically photosensitive materials include: quinacridones such as 2,9-dimethyl quinacridone, 4,11-dimethyl quinacridone, 2,10-dichloro- 6,13-dihydro-quinacridone, 2,9-dimethoxy-6,13- dihydro quinacridone, 2,4,9,1l-tetrachloro-quinacridone, and solid solutions of quinacridones and other compositions as described in U.S. Pat. No. 3,160,510; carboxamides such as: N-2"-pyridyl-8,13- dioxodinaphtho-(2,1-2',3 ')-furan-6-carboxamide, N- 2"-(l ",3",5"-triazyl-8,l3-dioxodinaphtho-(2,1-2

' ,3 )-furan-6-carboxamide, anthra-( 2,1 )-naphtho-( 2,3 d )-furan-9 ,14-dione-7-(2'-methyl-phenyl) carboxamide; carboxanilides such as: 8,13-dioxodinaphtho- (2,1-2',3 ')-furan-6-carbox-p-methoxy-ani1ide, 8,13- dioxodinaphtho-( 2, l -2 ,3 )-furan-6-carbox-pmethylanilide, 8,13-dioxodinaphtho-(2,l-2',3 )furan- 6-carbox-p-cyanoanilide; triazines such as: 2,4- diamino-triazine, 2,4-di (1'-anthraquinonyl-amino)-6- l '-pyrenyl )-triazine, 2,4-di( l '-anthraquinonyl amino)-6-(1"-naphthyl)-triazine, 2,4-di (l'-naphthylamino)-6-(l'-perylenyl)-triazine, 2,4,6-tri (l',1",1"'- pyrenyl) triazine, 2,4,6-tri (l,l",1"' -pyrenyl) triazine; benzopyrrocolines such as: 2,3-phthaloyl-7,8- benzo-pyrrocoline, 1-cyano-2,3-phtha1oyo-7,8- benzopyrrocoline, l-cyano-2,3-phtha1ocy-5 -nitro-7 ,8- benzopyrrocoline, l-cyano-2,3-phthaloyl-5-acetamido- 7,8-benzopyrrocoline; anthraquinones such as: 1,5-bis- (beta-phenylethylamino) anthraquinone, l,5-bis-(3'- methoxypropylamino) anthraquinone, 1 ,5-bis (benzylamino) anthraquinone, 1,5-bis (phenylbutylamino) anthraquinone, 1,2,5,6-di(c,c-diphenyl)- triazole-anthraquinone, 4-(2'-hydroxyphenylmethoxyamino) anthraquinone; azo compounds such as: 2,4,6- tris(N-ethyl-N-hydroxyethyl-p-aminophenylazo) phloroglucinol, l ,3 ,5 ,7-tetra-hydroxy-2,4,6,8-tetra (N- methyl-N-hydroxyethyl-p-amino-phenylazo) naphthalene, 1,3 ,5-trihydroxy-2,4,6-tri (3 '-nitro-N- methyl-N-hydroxymethyl-4'-aminophenylazo) benzene, 3-methyl-1-phenyl-4-(3' pyrenylazo)-2- pyrazolin-S -one, 1-( 3 '-pyrenylazo )-2-hydroxy-3- naphthanilide, 1-( 3-pyrenylazo )-2-naphthol, l-( 3 pyrenylazo )-2-hydroxypyrene, l-( 3 'pyreny1azo)-2- hydroxy-3-methyl-xanthene, 2,4,6-tris (3'-pyrenylazo) phloroglucinol, 2,4,6-tris (l-phen-anthrenylazo) phloroglucinol, l-(2-methoxy-5 '-nitro-phenylazo)-2- hydroxy-3'nitro-3-naphthanilide; salts and lakes of compounds derived from 9-phenylxanthene, such as: phosphotongstomolybdic lake of 3,6-bis (ethylaminoy 9,2'-carboxyphenyl xanthenonium chloride, barium salt of 3-2-toluidineamino-6-2"-methy1-4"- sulphophenyl-amino-9-2 '-carboxyphenylxanthene; phosphomolybdic lake of 3,6-bis (ethylamino)-2,7- dimethyl-9,2'-carbethoxy-phenylxanthenonium chloride; dioxazines such as: 2,9-dibenzoyl-6,l3- dichloro-triphenodioxazine, 2,9-diacetyl6,13- dichloro-triphenodioxazine, 3 ,10-dibenzoylamino-2 ,9- diisopropoxy-6 l 3-dichlorotriphenodioxazine, 2,9- difuroyl-6,13-dichlorotripheno-dioxazine; lakes of fluorescein dyes, such as: lead lake of 2,7-dinitro-4,5- dibromo fluorescein, lead lake of 2,4,5,7-tetrabromo fluorescein, aluminum lake of 2,4,5,7-tetrabromo- 10,ll,l2,13-tetrachloro fluorescein; bisazo compositions such as: N,N-di[l-(l'-naphthy1azo)-2-hydroxy- B-naphthyl] adipdiamide, N,N'-di-l-(1 -naphthylazo 2-hydroxy-8-naphthyl succindiamide, bis-4,4'-(2"- hydroxy-B"N,N-diterephthala-mide-l-naphthylazo) biphenyl, 3,3'-methoxy-4,4'-diphenyl-bis (1"-azo-2"- hydroxy-3"-naphth-anilide); pyrenes such as: 1,3,6,8- tetra-cyanopyrene, l,3-dicyano-6,8-dibromo-pyrene, 1 ,3 ,6,8-tetraaminopyrene, 1-cyano-6-nitropyrene; phthalocyanines such as: beta-form metal free phthalocyanine, copper phthalocyanine, tetrachloro phthalocyanine, the x form of metal-free phthalocyanine as described in U.S. Pat. No. 3,357,989; metal salts and lakes of azo dyes, such as: calcium lake of 6-bromo-1 (1 '-sulfo-2-naphthylazo)-2-naphthol, barium salt of 6- cyano-1( l '-sulfo-2-naphthylazo )-2-naphthol, calcium lake of 1-(2'-azonaphthalene-l'-sulfonic acid)-2- naphthol, calcium lake of 1-(4 -ethyl-5 chloroazobenzene-Z'-sulfonic acid)-2-hydroxy-3- naphthoic acid; and mixtures thereof.

Typical inorganic electrically photosensitive materials include cadmium sulfide, cadmium sulfoselenide, zinc oxide, zinc sulfide, sulphur selenium, mercuric sulfide, lead oxide, lead sulfide, cadmium selenide, titanium dioxide, indium trioxide and the like.

In addition to the aforementioned organic materials, other organic materials which may be employed in the imaging layer include polyvinylcarbazole; 2,4-bis (4,4'- diethyl-amino-phenyl)-1 ,3 ,4-oxidiazole; N-isopropylcarbazole and the like. Other electrically photosensitive materials useful in the process of this invention are listed in copending application Ser. No. 708,380, filed Feb. 26, 1968 which is incorporated herein by reference.

It is also to be understood that the electrically photosensitive particles themselves may consist of any suitable one or more of the aforementioned electrically photosensitive materials, either organic or inorganic, dispersed in, in solid solution in, or copolymerized with, any suitable insulating resin whether or not the resin itself is photosensitive. This particular type of particle may be particularly desirable to facilitate dispersion of the particle, to prevent undesirable reactions between the binder and the photosensitive material or between the photosensitive and the activator and for similar purposes. Typical resins of this type include polyethylene, polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinyl chlorides, polyvinyl acetates, polystyrene, polysiloxanes,

chlorinates rubbers, polyacrylonitrile, epoxies, phenolics, hydrocarbon resins and other natural resins such as resin derivatives as well as mixtures and copolymers thereof.

The x form phthalocyanine is preferred because of its excellent photosensitivity although any suitable phthalocyanine may be used to prepare the imaging layer of this invention. The phthalocyanine used may be in any suitable crystal form. 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 synthesis. As above noted, any suitable phthalocyanine may be used to prepare the photoconductive layer of the present invention. Typical phthalocyanines are listed in copending application Ser. No. 708,380 referred to above.

The basic physical property desired in the imaging layer of the manifold imaging process is that it be frangible as prepared or after having been suitably activated. That is, the layer must be sufficiently weak structurally so that the application of electrical field combined with the action of actinic radiation on the electrically photosensitive materials will fracture the imaging layer upon separation of the manifold sandwich. Further, the layer must respond to the application of field, the strength of which is below that field strength which will cause electrical breakdown or arcing across the imaging layer. Another term for cohesively weak, therefore, would be field fracturable.

Although the imaging layer must be cohesively weak in order to fracture in imagewise configuration in the manifold imaging process, the electrically photosensitive material to be treated in accordance with the electrification treatment of this invention need not be cohesively weak. The electrically photosensitive material to be treated may be incorporated into an imaging layer and treated in accordance with the process of this invention without rendering the layer cohesively weak. After treatment by the process of this invention, the layer may be rendered cohesively weak by the application thereto of an activator as will be more fully described below.

The imaging layer serves as the photoresponsive element of the system as well as the colorant for the final image produced. Other colorants such as dyes and pigments may be added to the imaging layer so as to intensify or modify the color of the final images produced when color is important. Preferably, the imaging layer is selected so as to have a high level of response while at the same time being intensely colored so that a high contrast image can be formed by the high gamma system of this invention. The imaging layer may be homogeneous comprising, for example, a solid solution of two or more pigments. The imaging layer may also be heterogeneous comprising, for example, pigment particles dispersed in a binder.

One technique for achieving low cohesive strength in the imaging layer is to employ relatively weak, low molecular weight materials therein. Thus, for example, in a single component homogeneous imaging layer, a monomeric compound or a low molecular weight polymer complexed with a Lewis acid to impart a high level of photoresponse to the layer may be employed. Similarly, when a homogeneous layer utilizing two or more components in solid solution is selected to make up the imaging layer, either one or both of the components of the solid solution may be a low molecular weight material so that the layer has the desired low level of cohesive strength. This approach may also be taken in connection with the heterogeneous imaging layer. Although the binder material in the heterogeneous system may in itself be photosensitive, it does not necessarily have this property. Materials may be selected for use as this binder material solely on the basis of physical properties without regard to their photosensitivity. This is also true of the two component homogeneous system where photoinsensitive materials with the desired physical properties can be used. Any other technique for achieving low cohesive strength in the imaging layer may also be employed. For example, suitable blends of incompatible materials such as a blend of a polysiloxane resin with a polyacrylic ester resin may be used either as the binder layer in a heterogeneous system or in conjunction with a homogeneous system in which the photoresponsive material may be either one of the incompatible components (complexed with a Lewis acid) or a separate and additional component of the layer. The thickness of the imaging layer whether homogeneous or heterogeneous ranges from about 0.2 microns to about 10 microns generally about 0.5 microns to about 5 microns and preferably about 2 microns.

The ratio of photosensitive pigment to binder by weight in the heterogeneous system may range from about 10 to l to about 1 to 10 respectively, but it has generally been found that properties in the range of from about 1 to 4 to about 2 to 1 respectively produce the best results and, accordingly, this constitutes a preferred range.

The binder material in the heterogeneous imaging layer or the material used in conjunction with the electrically photosensitive materials in the homogeneous layer, where applicable, may comprise any suitable cohesively weak insulating material or materials which can be rendered cohesively weak. Typical materials include: microcrystalline waxes such as: Sunoco 1290, Sunoco 5825, Sunoco 985, all available from Sun Oil Co.; Paraflint RG, available from the Moore and Munger Company; paraffin waxes such as: Sunoco 5512, Sunoco 3425, available from Sun Oil Co.; Sohio Paraowax available from Standard Oil of Ohio; waxes made from hydrogenated oils such as: Capital City 1380 wax, available from Capitol City Products, Co. Columbus, Ohio; Caster Wax L-2790, available from Baker Caster Oil Co.; Vitikote L-304, available from Duro Commodities; polyethylenes such as: Eastman Epolene N-l l, Eastman Epolene C-l2, available from Eastman Chemical Products Co.; Polyethylene DYJT, Polyethylene DYLT, Polyethylene DYDT, all available from Union Carbide Corp.; Marlex TR 822, Marlex 1478, available from Phillips Petroleum Co.; Epolene C-l3, Epolene C-l0, available from Eastman Chemical Products, Co.; Polyethylene AC8, Polyethylene AC612, Polyethylene AC324, available from Allied Chemicals; modified styrenes such as: Piccotex 75, Piccotex 100, Piccotex 120, available from Pennsylvania Industrial Chemical; Vinylacetate-ethylene copolymers such as: Elvax Resin 210, Elvax Resin 310, Elvax Resin 420, available from E. l. duPont de Nemours 81. Co., lnc., Vistanex Ml-l, Vistanex L-80, available from Enjay Chemical Co.; vinyl chloride-vinyl acetate copolymers such as: Vinylite VYLF, available from Union Carbide Corp.; styrene-vinyl toluene copolymers; polypropylenes; and mixtures thereof. The use of an insulating binder is preferred because it allows for the use of a larger range of electrically photosensitive pigments.

A mixtureof microcrystalline wax and polyethylene is preferred because it is cohesively weak and an insulator.

Where the imaging layer is not sufficiently cohesively weak to allow imagewise fracture, it is desirable to include an activation step in the process of this invention. The activation step may take many forms such as heating the imaging layer thus reducing its cohesive strength or applying a substance to the surface of the imaging layer or including a substance in the imaging layer which substance lowers the cohesive strength of the layer or aids in lowering the cohesive strength. The substance so employed is termed an activator. Preferably, the activator should have a high resistivity so as to prevent electrical breakdown of the manifold sandwich. Accordingly, it will generally be found to be desirable to purify commercial grades of activators so as to remove impurities which might impart a higher level of conductivity. This may be accomplished by running the fluids through a clay column or by employing any other suitable purification technique. Generally speaking, the activator may consist of any suitable material having the aforementioned properties. For purposes of this specification and the appended claims, the term activator shall be understood to include not only materials which are conventionally termed solvents but also those which are partial solvents, swelling agents or softening agents for the imaging layer. The activator can be applied at any point in the process prior to separation of the manifold sandwich.

It is generally preferable that the activator have a relatively low boiling point so that fixing of the resulting image can be accomplished upon evaporation of the activator. If desired, fixing of the image can be accomplished more quickly with mold heating at most. It is to be understood, however, that the invention is not limited to the use of these relatively volatile activators. In fact, very high boiling point non-volatile activators including silicone oils such as dimethyl-polysiloxanes and very high boiling point long chain aliphatic hydrocarbon oils ordinarily used as transformer oils such as Wemco-C transformer oil, available from Westinghouse Electric Co., have also been successfully utilized in the imaging process. Although these less volatile activators do not dry off by evaporation, image fixing can be accomplished contacting the final image with an absorbent sheet such as paper which absorbs the activator fluid. In short, any suitable volatile or non-volatile activator may be employed. Typical activators include Sohio Odorless Solvent 3440, an aliphatic (kerosene) hydrocarbon fraction, available from Standard Oil Co. of Ohio, carbon tetrachloride, petroleum ether, Freon 2114 (tetrafluorotetrachloropropane), other halogenated hydrocarbons such as chloroform, methylene chloride, trichloroethylene, perchloroethylene, chlorobenzene, trichloromonofluoromethane, trichlorotrifluoroethane, trichlorotrifluoroethane, ethers such as diethyl ether, diisopropyl ether, dioxane tetrahydrofuran, ethyleneglycol monoethyl ether, aromatic and aliphatic hydrocarbons such as benzene, toluene, xylene, hexane, cyclohexane, gasoline, mineral spirits and white mineral oil, vegetable oils such as coconut oil, babussu oil, palm oil, olive oil, castor oil, peanut oil and neatsfoot oil, decane, dodecane and mixtures thereof. Sohio Odorless Solvent 3440 is preferred because it is odorless, nontoxic and has a relatively high flash point.

Although the imaging layers may be prepared as selfsupporting films, normally these layers are coated onto a sheet referred to above as the donor sheet or substrate. For convenience the combination of imaging layer and donor sheet is referred to as the donor. When employing a binder, the electrically photosensitive material can be mixed in the binder material by conventional means for blending solids as by ball milling. After blending the ingredients of the imaging layer, the

desired amount is coated on a substrate. In a particularly preferred form of the invention an imaging layer comprising the electrically photosensitive material dispersed in a binder is coated onto a transparent, electrically insulating donor sheet.

The imaging layer may be supplied in any color desired either by taking advantage of the natural color of the photosensitive material or binder materials in the imaging layer or by the use of additional dyes and pigments therein whether photoresponsive or not and, of course, various combinations of these photoresponsive and non-photoresponsive colorants may be used in the imaging layer so as to produce the desired color.

The donor sheet and receiver sheet may comprise any suitable electrically insulating or electrically conducting material. Insulating materials are preferred since they allow the use of high strength polymeric materials. Typical insulating materials include polyethylene, polypropylene, polyethylene, terephthalate, cellulose acetate, paper, plastic coated paper such as polyethylene coated paper, vinyl chloride-vinylidene chloride copolymers and mixtures thereof. Mylar (a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid available from E. I. duPont de Nemours & Co., Inc.) is preferred because of its durability and excellent insulative properties. Not only does the use of this type of high strength polymer provide a strong substrate for the positive and negative images formed on the donor substrate and receiver sheet but, in addition, it provides an electrical barrier between the electrodes and the imag ing layer which tends to inhibit electrical breakdown of the system while subjecting the manifold sandwich to an electrical field. The donor sheet and receiver sheet may each be selected from different materials. Thus a manifold sandwich can be prepared by employing an insulating donor sheet while a conductive material is employed as a receiver sheet.

A visible light source, an ultraviolet light source or any other suitable source of electromagnetic radiation may be used to expose the imaging layer of this invention. The electrically photosensitive material is chosen so as to be responsive to the wavelength of the electromagnetic radiation used. It is to be noted that different electrically photosensitive materials have different spectral responses and that the spectral response of many electrically photosensitive materials may be modified by dye sensitization so as to either increase or narrow the spectral response of a material to a peak or to broaden it to make it more panchromatic in its response.

After subjecting the imaging layer to the electrification treatment of this invention, the imaging can be exposed to electromagnetic radiation either prior to forming the manifold sandwich or after the formation of the manifold sandwich. Of course, if the imaging layer is exposed to electromagnetic radiation after sandwich formation, the receiver sheet must be transparent to such radiation. In most instances, by exposing the imaging layer from the receiver side, the positive image is formed on the receiver sheet. That is, the illuminated portions of the imaging layer adhere to the donor sheet and the non-illuminated areas of the imaging layer adhere to the receiver sheet. In addition, the activation step can be included at any point in the manifold imaging process prior to the separation of the sandwich.

DESCRIPTION OF THE DRAWINGS The advantages of this improved method of imaging will become apparent upon consideration of the detailed disclosure of the invention especially when in conjunction with the accompanying drawing wherein:

FIG. 1 is a side sectional view of a manifold sandwich.

FIG. 2 is a side sectional view diagramatically illustrating the process steps of a preferred embodiment of the process of this invention.

Referring now to FIG. 1, there is shown donor sheet 11 upon which there is resting an imaging layer generally indicated as 12 comprising electrically photosensitive particles 13 dispersed in an insulating binder 14. Over imaging layer 12 is laid a receiver sheet 16.

Referring now to FIG. 2, there is shown the optional activation step. Although the activator may be applied by any suitable techniques such as with a brush, with a smooth or rough surfaced roller, by flow coating, by vapor condensation or the like, FIG. 2 shows the activator fluid 20 being sprayed onto imaging layer 22 from container 24. Following the deposition'of this activator fluid, imaging layer 22 supported by donor sheet 26 proceeds in the direction shown by the arrow into contact with receiver sheet 28 which is supplied by roll 30. In certain instances the activation step may be omitted. Thus, for example, a manifold sandwich may be supplied wherein imaging layer 22 is initially fabricated to have a low cohesive strength so that activation may be omitted and receiver sheet 16 may be placed on the surface of imaging layer 12 directly. It is generally preferably, however, to include an activation step on the process because this allows the stronger imaging layers for purposes of handling prior to the actual imaging operation.

After receiver sheet 28 has been placed on imaging layer 22, an electrical field is applied across the manifold sandwich through

electrodes

32 and 34 which are connected to potential source 36 and resistor 38. Although FIG. 2 shows the manifold sandwich coming in contact with either

electrode

32 or 34, they may contact one or both electrodes when the electrical field is applied depending upon the type of electrode employed. Preferably the sandwich will contact at least one electrode to serve as a guide.

Alternatively, the charging electrode may be a corona discharge device or a friction charging device such as a furcovered roller. The sign of the charge as shown on

electrodes

32 and 34 may also be reversed, electrode 32 being made negative and electrode 34 being made positive. In FIG. 2 both donor sheet 26 and receiver sheet 28 are electrically insulating thus retaining a static charge after being subjected to the electric field by

electrodes

32 and 34. After passing through

electrodes

32 and 34, the manifold sandwich proceeds in the direction of the arrow; and, as the sandwich passes between guide rollers 40, receiver sheet 28 is rolled up on take-up roller 42 leaving the imaging layer 22 on donor sheet 26 since the electrical field is placed upon the manifold sandwich while in the darkllmaging layer 22 residing on donor sheet 26 proceeds in the direction of the arrow into contact with a second receiver sheet 44 supplied from supply roll 46. The reformed manifold sandwich proceeds between

electrodes

48 and 50 which are connected to a second potential source 52 through resistor 54. As before,

electrodes

48 and 50 preferably contact the manifold sandwich thus imparting an electrical charge to the electrically insulating donor and receiver sheets and may alternatively be a corona discharge device, a roller electrode or a friction charging device such as a furcovered roller. It is noted that the sign of the charge on

electrodes

48 and 50 are reversed from the sign of the charge on

electrodes

32 and 34 whereby the imaging material is subjected to an electric field or reversed polarity prior to being exposed to activating electromagnetic radiation.

After passing through

electrodes

48 and 50 and retaining an electric charge of the sign shown on the electrodes for the donor and receiver sheet respectively, the manifold sandwich is exposed to activating electromagnetic radiation 56 which is in this case white incandescent light. After image-wise exposure to the activating electromagnetic radiation, the manifold sandwich then passes roller 58 which acts as a guide for the manifold sandwich and as a bearing point for the stripping apart of the receiver and donor sheets. Alternatively, roller 58 may be a sharp edge, a rod or a wire. Upon separation of donor sheet 26 and receiver sheet 44, imaging layer 22 fractures along the edges of exposed areas and at the surface where it had adhered to donor sheet 26. Accordingly, once separation is complete, the exposed portions of imaging layer 22 are retained on one of the

sheets

26 and 28 while the unexposed portions are retained on the other sheet thus providing a positive image on one sheet and a negative image on the other sheet.

If a relatively volatile activator is employed, such as petroleum ether or carbontetrachloride, fixing of the image occurs almost instanteously after separation of the sheets of 26 and 28 because the relatively small quantity of activator in imaging layer 22 evaporates quickly. With somewhat less volatile activators, such as Sohio Odorless Solvent 3440 or Freon 214 described above, fixing may be accelerated by blowing air over the images or warming them to about F. With the less volatile activators, such as transformer oil, fixing is accomplished by absorption of the activator into another layer such as paper. Many other fixing techniques and methods for protecting the image such as overcoating, laminating with a transparent sheet and the like will occur to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples further specifically illustrate the present invention. The examples below are intended to illustrate various preferred embodiments of the improved imaging method. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I A commercial metal-free phthalocyanine is first purified by o-dichlorobenzene extraction to remove organic impurities. Since this extraction step yields the less sensitive beta crystalline form, the desired x form is obtained by dissolving about lOO grams of beta in approximately 600 cc. of sulfuric acid precipitating it by pouring the solution into about 3,000 cc. of ice water and washing with water to neutrality. The thus purified alpha phthalocyanine is then salt milled for 6 days and desalted by slurrying in distilled water, vacuum filtering, water washing and finally methanol washing until the initial filtrate is clear. After vacuum drying to remove residual methanol, the x form phthalocyanine thus produced is used to prepare the imaging layer according to the following procedure: About grams of the x form phthalocyanine is added to about 5 grams of Algol Yellow GC, l,2,S,6-di(C,C-diphenyl) thiazoleanthraquinone, C. I. No. 67300, available from General Dyestuffs, and about 2.8 grams of purified Watchung Red B, l-(4'-methyl-5'-chloroazobenzene-2-sulfonic acid)-2-hydroxy-3-naphthoic acid, C. I. No. 15865, available from E. I. duPont de Nemours & Co., which is purified as follows: approximately 240 grams of the Watchung Red B is slurried in about 2,400 milliliters of Sohio Odorless Solvent 3440, a mixture of kerosene fractions available from the Standard Oil Company of Ohio. The slurry is then heated to a temperature of about 65C. and held there for about one-half hour. The slurry is then filtered through a glass sintered filter. The solids are then reslurried with petroleum ether (90 to 120C.) available from Matheson, Coleman and Bell Division of the Matheson Company, East Rutherford, New Jersey and filtered through a glass sintered filter. The solids are then dried in an oven at about 50C.

About 8 grams of Sunoco Microcrystalline Wax Grade 5825 having an ASTM-D-l27 melting point of 151F. and about 2 grams of Paraflint R. G., a low molecular weight paraffinic material, available from the Moore & Monger Company, New York City and about 320 milliliters of petroleum ether (90 to 120C.) and about 40 milliliters of Sohio Odorless Solvent 3440 are placed with the pigments in a glass jar containing t z-inch flint pebbles. The mixture is then milled by revolving the glass jar at about 70 r.p.m. for about 16 hours. The mixture is then heated for approximately 2 hours at about 45C. and allowed to cool to room temperature. The mixture is then ready for coating on the donor substrate. The paste-like mixture is then coated in subdued green light or 2-mil Mylar (a polyester formed by the condensation reaction between ethylene glycol and tetrephthalic acid available from E. I. du- Pont de Nemours & Co., Inc.) with a No. 36 wire wound drawdown rod to produce a coating thickness when dried of approximately 7% microns. The coating and two mil Mylar sheet is then dried in the dark at a temperature of about 33C. for one-half hour. The coating is activated by applying thereto Sohio Odorless Solvent 3440 by means of a soft brush and a 2-mil thick Mylar receiver sheet is laid over the activated imaging layer.

The thus formed manifold sandwich is then placed receiver side down on the tin oxide surface of a NESA glass electrode and a black conductive paper electrode is laid over the donor side of the sandwich. The electrodes are connected to a 9,000 volt d.c. power supply in series with a 5,500 megohm resistor with the donor side electrode being made the positive and the receiver side electrode being made the negative electrode. A

potential of about 9,000 volts is applied between the electrodes in the dark. With the potential applied, the donor sheet accompanied by the imaging layer is removed from the receiver sheet and the receiver sheet on the NESA glass is replaced by a fresh 2-mil Mylar receiver sheet. The leads to the power supply from the electrodes are switched so as to make the donor side electrode negative and the receiver side electrode positive and the same voltage is again applied while in the dark. With about 9,000 volts applied a white incandescent light image is projected upwards through the transparent glass electrode and the receiver sheet with an illumination of approximately 0.1 foot-candles applied for 5 seconds for a total incident energy of about 0.5 foot-candle seconds. The donor sheet together with the opaque electrode is peeled from the manifold sandwich thus fracturing the imaging layer in imagewise configuration yielding a pair of excellent quality images with a duplicate of the original on the receiver sheet and a reversal or negative image on the donor sheet.

EXAMPLE II The procedure of Example I is repeated except that after imagewise exposure the polarity of the electric field is reversed again and the sandwich separated under the reversed field. A pair of excellent quality images are produced with a positive image residing on the donor sheet and a negative image on the receiver sheet.

Although specific components and proportions have been stated in the above description of preferred embodiments of the invention, other typical materials as listed above if suitable may be used with similar results. In addition, other materials may be added to the mixture to synergize, enhance or otherwise modify the properties of the imaging layer. For example, various dyes, spectral sensitizer, or electrical sensitizers such as Lewis acids may be added to the several layers.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

l. An imaging process comprising the steps of:

a. providing an electrically photosensitive imaging layer sandwiched between a donor sheet and a transparent receiver sheet;

. subjecting said imaging layer to an electric field of known polarity.

. reversing the polarity of said electric field in the absence of electromagnetic radiation to which said imaging layer is sensitive;

. subsequent to reversal of the polarity of said electric field exposing said imaging layer to an imagewise pattern of electromagnetic radiation to which said layer is sensitive through said transparent receiver;

. separating said sandwich while under an electric field whereby said imaging .layer fractures in imagewise configuration with the exposed portion of said imaging layer adhering to one of said donor and receiver sheets and the unexposed portion adhering to the other sheet provided that the imaging layer is structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which it is sensitive upon the separation of the sandwich.

2. The process of claim 1 further including the step of modifying the polarity of said electric field subsequent to imagewise exposure of the imaging layer wherein said modification involves reversing or reducing said field whereby the exposed and unexposed portions of said imaging layer reverse adhesion.

3. The process of claim 1 further including the step of rendering said layer structurally fracturable in response to the combined effect of an applied electric field and exposure to electromagnetic radiation by applying thereto an activating amount of an activator for said layer.

4. The process of claim 1 wherein the electrically photosensitive material is an organic material.

5. The process of claim 4 wherein the electrically photosensitive material is phthalocyanine.

6. The method of claim 1 wherein the electrically photosensitive material is dispersed in an insulating .binder.

7. The method of claim 1 wherein the electric field is in the range of from about 2,000 volts per mil to about 10,000 volts per mil.

8. The process of claim 2 wherein the electrically photosensitive imaging material is dispersed in an insulating binder.

9. The process of claim 8 further including the step of rendering said layer structurally fracturable in response to the combined effect of an applied electric field and exposure to electromagnetic radiation by applying thereto an activating amount of an activator for said layer.

10. The process of claim 8 wherein the electrically photosensitive material is phthalocyanine.

11. The process of claim 1 wherein said donor and receiver sheets are electrically insulating and said electric fields are provided by electrostatic charges residing in said sheets.

12. The process of claim 1 further including the step of continuing exposure of said imaging layer after the exposed and unexposed portions of said imaging layer adhere to one of said donor and receiver sheets until the exposed and unexposed portions of the imaging layer reverse said adhesion to said sheets.

Claims

2. The process of claim 1 further including the step of modifying the polarity of said electric field subsequent to imagewise exposure of the imaging layer wherein said modification involves reversing or reducing said field whereby the exposed and unexposed portions of said imaging layer reverse adhesion.
3. The process of claim 1 further including the step of rendering said layer structurally fracturable in response to the combined effect of an applied electric field and exposure to electromagnetic radiation by applying thereto an activating amount of an activator for said layer.
4. The process of claim 1 wherein the electrically photosensitive material is an organic material.
5. The process of claim 4 wherein the electrically photosensitive material is phthalocyanine.
6. The method of claim 1 wherein the electrically photosensitive material is dispersed in an insulating binder.
7. The method of claim 1 wherein the electric field is in the range of from about 2,000 volts per mil to about 10,000 volts per mil.
8. The process of claim 2 wherein the electrically photosensitive imaging material is dispersed in an insulating binder.
9. The process of claim 8 further including the step of rendering said layer structurally fracturable in response to the combined effect of an applied electric field and exposure to electromagnetic radiation by applying thereto an activating amount of an activator for said layer.
10. The process of claim 8 wherein the electrically photosensitive material is phthalocyanine.
11. The process of claim 1 wherein said donor and receiver sheets are electrically insulating and said electric fields are provided by electrostatic charges residing in said sheets.
12. The process of claim 1 further including the step of continuing exposure of said imaging layer after the exposed and unexposed portions of said imaging layer adhere to one of said donor and receiver sheets until the exposed and unexposed poRtions of the imaging layer reverse said adhesion to said sheets.