US3873309A

US3873309A - Imaging method using migration material

Info

Publication number: US3873309A
Application number: US322274A
Authority: US
Inventors: William L Goffe
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1970-06-18
Filing date: 1973-01-09
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25

Abstract

A method of forming a colored image wherein an imaging member is employed comprising a substrate having an overlayer of softenable material. Within the softenable material there is dispersed migration material and at the free surface of the softenable material there is provided a colored light transmitting layer of non-photoconductive material. The imaging member is uniformly electrostatically charged and exposed to an imagewise pattern of light. After exposure the softenable layer is softened to permit migration of the migration material together with the light transmitting layer directly above the migrating migration material in imagewise configuration. After the migration to the substrate of the imaging member is complete, the relatively unmigrated portions of at least the light transmitting layer is removed.

Description

I United States Patent 11 1 1111 3,873,309 Goffe Mar. 25, 1975 [54] IMAGING METHOD USING MIGRATION 3,627,526 12/1971 Donald 96/15 AT 1 3,648,607 3/1972 Gundlach 96/1 R M ER AL 3,664,834 5/1972 Amidon etal. 96/1 R Inventor: William Goffe, Webster, NY 3,720,513 3/1973 Gundlach 96/1 R Assignee: Xerox Corporation, Stamford 3,753,706 8/1973 Sankus et al. 96/] R C onn Primary ExaminerNorman G. Torchin Filed: Jan. 9, 1973 Assistant Examiner-J. P. Brammer [21] Appl. 322,274 gttogiggiaglgnt {gaze-James J. Ralabate; David C.

Related U.S. Application Data [63] Continuation of Ser. No. 47,469, June 18,1970, [57] ABSTRACT d dbdn one A method of forming a colored image wherein an 1m- [52] Us Cl 96/12 96/1 96/1 E aging member is employed comprising a substrate hav- 96/15 96/28 ing an overlayer of softenable material. Within the softenable material there is dispersed migration mate- [51] Int. Cl. G03g 13/00, G03g 13/04 [58] Field of Search 96/1 1 2 l 3 1 5 27 rial and at the free surface of the softenable material 5 j g there is provided a colored light transmitting layer of non-photoconductive material. The imaging member [56] References Cited is uniformly electrostatically charged and exposed to an imagewise pattern of light. After exposure the soft- UNITED STATES PATENTS enable layer is softened to permit migration of the mi- 3,l2l,006 2/l964 Middleton et a]. 96/].5 gration material together with the light transmitting 3,l40,l75 7/l964 Kaprellan 96/12 layer directly abov the migrating migration material g in imagewise configuration. After the migration to the 3458309 7/1969 3;; 96/l'2 substrate of the imaging member is complete, the rela- 3:520:62 7/1970 tiI ely unmigrated portions of at least the light trans. 3,556,781 11/1971 Levy et al. 96/1 R mlttmg layer is removed 3,556,783 l/l97l Kariakakis 96/1 R 3,561,957 2 1971 Perry 96/].5 35 4 Drawmg F'gures \Y v v v v.-; v Y Y Y M OQ UQ@.

IMAGING METHOD USING MIGRATION MATERIAL CROSS-REFERENCE TO RELATED APPLICATION This is a continuation of application Ser. No. 47,469, filed June 18, 1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates in general to imaging, and more specifically to migration imaging and a process for forming colored images from migration imaging members.

Recently, a migration imaging system capable of producing high quality images of high density, continuous tone and high resolution has been developed. Such migration imaging systems are disclosed in copending applications Ser. Nos. 837,780 and 873,591, both filed June 30, 1969 and are hereby expressly incorporated herein by reference. In a typical embodiment of the new migration imaging system, there is employed an imaging member comprising a substrate having an overlayer of softenable material. Within the softenable material, there is dispersed electrically photosensitive particles. Typically, a latent electrostatic image is formed, for example, by electrostatically charging the member and exposing it to a pattern ofelectromagnetic radiation to which the particles are sensitive. There is thereby formed an imgewise pattern in the imaging layer of particles which have a tendency to migrate toward the substrate. Upon reducing the resistance of the softenable layer to such migration, the particles migrate twoaward the substrate forming which is known as a migration image on or near the substrate.

One mode of developing a latent image in the migration imaging system is to contact the imaging member containing the latent image with a solvent which dissolves away the softenable layer. The photosensitive particles which have been exposed to radiation migrate through the softenable layer as it is softened and dissolved, leaving an image of migrated particles corresponding to the radiation pattern of the substrate while the softenable layer is washed away. The particle image may then be fixed to the substrate in a variety of ways known to those skilled in the art or transferred. For many preferred photosensitive particles, the image produced by the above process is a negative of the positive original, i.e., particles deposit in imagewise configuration corresponding to the areas exposed to the radiation. However, positive-to-positive systems are also possible by varying imaging parameters. Those portions of the photosensitive material which do not migrate to the substrate are washed away by the solvent with the softenable layer. As disclosed in the cope nding applications referred to above, by means of other developing techniques, the softenable layer may at least partially remain behind on the supporting substrate with or without a relatively unmigrated pattern of marking material complimentary to said migrated material.

In another imaging member embodiment, migration material is formed as a single layer over but in contact with the free surface of the softenable layer in a multilayer configuration.

"Softenable as used herein is intended to mean any material which can be rendered more permeable to migration material migrating through its bulk. Conventionally, changing permeability is accomplished by dissolving, melting and softening as by contact with heat, vapors, partial solvents and combinations thereof.

Fracturable layer or material as used herein, means any layer or material which is capable of breaking up during development, thereby permitting portions of said layer to migrate toward the substrate in image configuration. The fracturable layer may be particulate, semi-continuous or continuous in various embodiments of the migration imaging members.

Contiguous for the purpose of this invention is defined as in Websters New Collegiate Dictionary, Second Edition, I960; an actual contact; touching; also, near, though not in contact; adjoining."

In certain methods of forming the latent image, nonphotosensitive or inert, fracturable layers and particulate material may be used to form images, for example, wherein the softenable material is, in addition, photoconductive. The characteristics of the images produced are dependent on such process steps as charging, exposure and development as well as the particular combination of process steps. High density, continuous tone and high resolution are some of the image characteristics possible. The images are generally characterized as fixed or unfixed particulate images with or without a portion of the softenable layer and unmigrated portions of the layer left on the imaged member.

Previously, multicolored images have been provided by the above described migration imaging system by providing a migration imaging member having a mosaic pattern of different color areas, each area containing electrically photosensitive particles of a single color which particles also possessed essentially monochromatic sensitivity. In another polychromatic migration imaging system, photosensitive particles of different colors essentially monochromatic in sensitivity are dispersed throughout the softenable layer. Upon uniform electrostatic charging and exposure to a polychromatic image, selective migration of some of the particles in the substrate resulted in a polychromatic migration image.

In each of the previous polychromatic migration imaging systems, the migration material was required to possess the right color and, in addition, essentially monochromatic photosensitivity. There has now been discovered a migration imaging system employing panchromatic photosensitive particles as migration material to produce colored images. In addition, panchromatic photosensitive particles can now be employed to provide polychromatic images.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an imaging system which provides the above noted advantages.

It is another object of this invention to provide a novel migration imaging system.

It is another object of this invention to provide a novel migration imaging system which produces polychromatic images while employing panchromatic electrically photosensitive migration material.

It is another object of this invention to provide a migration imaging system wherein polychromatic images are formed by the migration of non-photosensitive materials of different colors.

It is yet another object of this invention to provide an imaging system capable of producing polychromatic images of high quality and excellent resolution.

It is still another object of this invention to provide novel migration imaging members.

These and other objects of this invention will be apparent from the following detailed description taken in conjunction with the attached drawings.

In accordance with this invention, there is provided a migration imaging member comprising a substrate having an overlayer of softenable material. Within the softenable material, there is dispersed photosensitive migration material and contiguous with the free surface of the softenable layer there is provided a light transmitting layer which in one form comprises coterminous laterally adjacent areas comprising nonphotoconductive material of at least two different colors, each of the areas being transparent to light of different colors. Several variations can be made to the above described imaging member without departing from the scope of this invention. For instance, the migration material may comprise panchromatic photoconducting particles such as zinc oxide. In addition, the photosensitive migration material may be dispersed throughout the softenable material or confined to one stratum in the material as will be more fully disclosed below. Also, the nonphotoconductive light transmitting layer contiguous with the free surface of the softenable layer may comprise individual particles of light transmitting material resting upon, partially or totally embedded within the free surface of the softenable material. In addition, the light transmitting layer may comprise a mosaic pattern of various different colored particles which transmit monochromatic light of different colors. Furthermore, non-photoconductive particles can be employed in the softenable layer together with the light transmitting layer. Preferably, such non-photoconductive material may be light reflecting and thus improve the appearance of the image produced.

The above described imaging member is employed in the process of this invention by first uniformly electro statically charging the member and then exposing the free surface of the softenable layer to an imagewise pattern of light. As will be more fully described below, there is thus formed a latent electrostatic charge pattern in the softenable layer according to the transmission of light in imagewise pattern through the nonphotoconductivc layer at the free surface. The latent image is developed preferably by contacting the film with a solvent for the softenable material whereby the photosensitive migration material and the nonphotoconductive light transmitting layer directly above it, migrate toward the substrate. The nonphotoconducting layer is fracturable and migrates as a separate entity together with the migration material beneath, possibly lagging behind, moving adhead or staying with the migration material. Thus, there are two kinds ofmigrating material, the photosensitive material and the color transmitting material. The migration material and the areas of non-photoconductive light transmitting layer directly above it form a colored image on the substrate in accordance with the color of the migrated light transmitting layer. After removal of the unmigrated material and softenable layer, the image can be fixed to the substrate or transferred to a different substrate and fixed thereon.

In accordance with this invention, a full color positive image can be produced by employing the above described imaging member having a mosaic pattern of three different light transmitting materials in the light transmitting layer, each of which transmits one of the primary colors. Electrostatic charging followed by exposure to a color negative and subsequent development of the latent image produces the color image. A particularly preferred imaging member is one in which the substrate is colored black. Ofcourse, the imaging member can be prepared so as to produce one or two colors rather than three simply by forming the layer ofthe imaging member of materials which transmit one or two rather than three colors. In addition, there is no need for exact registraion such that color conversion can be achieved. That is, depending on the color and light transmitting properties ofthe light transmitting layer of the imaging member, multicolor images having different color relationships than the original can be formed.

When light transmitting layers which transmit light of only one color are employed, color separations of a full color original can be produced and a method of proofing such color separations for the preparation of printing plates can be achieved with the process of this invention. For example, an imaging member of this invention having a light transmitting layer which transmits red light only may be exposed to a full color original in accordance with the process of this invention and upon development the image produced is a direct red separation of the full color image. The process can be repeated using light transmitting layers in the blue and green colors to provide three separations which, upon superimposition, can provide a proof of the image. If the proof of the image is acceptable, the individual images either upon transfer to a different or on the same substrate can be employed to prepare printing plates to produce the multicolored image.

In general, the process of this invention involves the uniform electrostatic charging of the migration imaging member, the exposure of the member to a pattern of light to provide latent electrostatic images and the development of the latent image by one of the several methods described in the copending applications referred to above.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed disclosure of the preferred embodiments of the invention taken in conjunction with the accompanying drawings thereof, wherein:

FIG. 1A is a partially schematic cross sectional view of a binder structured migration imaging member of this invention.

FIG. 1B is a partially schematic cross sectional view of another embodiment of the binder structured migration imaging member of this invention.

FIG. 1C illustrates a partially schematic cross sectional view of the layer structured migration imaging member of this invention.

FIG. 2 illustrates a partially schematic cross sectional view of an imaging member of this invention which has been processed in accordance with the novel imaging process of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1A illustrates a typical embodiment of the binder structured migration imaging member of this invention. Imaging member 10 comprises substrate 12 having an overlayer of softenable material indicated as softenable layer 14. Dispersed within softenable layer 14 are particles of migration material 16, which depending upon the nature of the softenable layer 14, can be either photosensitive or non-photosensitive. At the free surface of softenable layer 14, there is shown in FIG. 1A light transmitting layer 18 shown as contiguous areas of materials which transmit either red (R), green (G) or blue (B) light. Preferably,'substrate 12 is coated witih a thin layer of substantially electrically conductive material 20 so as to enable convenient electrostatic charging of the imaging member. In the absence of such a conductive layer, the imaging member of this invention may reside upon a conductor connected to the electrical system of the charging means employed to apply a uniform electrostatic charge on the imaging member.

FIG. 18 illustrates another embodiment of the binder structured migration imaging member of this invention wherein substrate 12, softenable layer 14 and migration material 16 are as indicated in FIG. 1A. Light transmitting layer 22 comprises a mosaic pattern of small light transmitting particles 23 wherein discrete areas contain particles which transmit one color of light, such as red, green and blue indicated as in FIG. IA above.

FIG. 1C is an embodiment ofthe layer structured migration imaging member of this invention. In FIG. 1C there is diagramatically illustrated migration material 16 contained in a limited area of layer of softenable material 14. In the embodiment illustrated in FIG. 1C, migration material 16 can take the form ofa monolayer of a dispersion of particles confined in a small portion at or near the interface of softenable layer 14 and light transmitting layer 24. Light transmitting layer 24 provides, as does light transmitting layers 22 and 28, small areas of image forming material which are of specific visual color or colors in which areas transmit essentially monochromatic light.

FIG. 2 illustrates the preferred method of electrostatically charging imaging member 10. Corona discharge device 26 charges the upper surface of the member inducing a counter charge on substrate 12 which preferably is provided with conductive coating 20. If substrate 12 is insulating electrostatic charging can be accomplished by placing the substrate on a conductive surface or a corona discharge device can be employed of opposite polarities on opposite sides. Elements l4, l6 and 18 are as described above. After electrostatic charging, the imaging member is exposed to an imagewise pattern of actinic electromagnetic radiation. FIG. 3 illustrates the effect of an exposure to a polychromatic image on the imaging member of this invention. For purposes of illustration, each area across the surface of light transmitting layer 18 is exposed to light of a different color as follows: area i is exposed to red light, area 2 to white light, area 3 is exposed to no light or black and area 4 is exposed to red and blue light. Since the areas of layer 18 transmit only monochromatic light the panchromatic photoconductive migration material 16 below those areas not transmitting light remain unaffected while the migration material 116 under the light transmitting areas are struck by light becoming conducting.

The latent image can be developed by softening the softenable material 14 to the extent which allows the migration material not struck by light and the area of layer 18 directly above the non-light struck migration material to migrate through the softenable material toward substrate 12. After migration has proceeded to the desired extent, normally at or very near substrate 12, further development can occur such as splitting softenable layer 14 in the manner described in copending application Ser. No. 784,164 filed Dec. 16, 1968 now US. Pat. No. 3,741,757 or by washing away the ummigrated portions of layers 18 and migration material 16 by contacting the member 10 with a solvent for the softenable layer 14.

FIG. 4 illustrates an imaged migration imaging member, that is, one which has been uniformly electrostatically charged, exposed to electromagnetic radiation to which either the migration material 16 or a photoconductive softenable layer 14 is sensitive to form a latent image. The latent image is then developed by softening the softenable layer allowing migration material id to migrate toward the substrate bringing with it portions of the light transmitting layer 18 directly above the mi grating migration material. After migration, the rela tively unmigrated material has been removed as by exposing the member to a solvent for the softenable layer whereby the softenable layer and unmigrated material are washed away leaving behind the migrated migration material 16 together with portions ofthe light transmitting layer ll8 which formerly resided at the free surface of the softenable layer directly above the migrated migration material. For purposes of illustration only, the imaged member illustrated in FIG. 4 has been exposed to a reflected image of a polychromatic original document. The area of the member generally designated as l in FIG. 4 has been struck by red light. The area of light transmitting layer 18 indicated by G and B does not transmit red light, hence the migration material below those areas were not exposed to the radiation and the migration material together with the light transmitting layer directly above the migration material migrated to substrate 12. In the area of image 15 generally designated as 2, essentially white light impinged resulting in the transmission of light by all three portions of the light transmitting layer and no migration took place. In area 3 a black portion of the original image was reflected and essentially no light struck the light transmitting layer thereby permitting migration material to migrate bringing with it all three portions of the light transmitting layer. In area 4 both red and blue light struck the light transmitting layer and, therefore, the green transmitting portion of the light transmitting layer did not transmit any light and the migration material below that portion of the light transmitting area migrated bringing with it green light transmitting portion of the light transmitting layer. Upon viewing the image residing on substrate 12 of imaged member 15, one would see in area 1 a cyan color, area 2 the color of the substrate which preferably when making direct color positives from color negatives would be black, area 3 would appear white and area 4 would appear green. Other color relationships, of course, would occur when the light struck materials employed to provide the light transmitting layer were made to migrate on as can be done by modifying the process as described in copending application Ser. No. 785,l64 filed Dec. 16, 1968.

A particularly preferred embodiment of this invention is illustrated by the binder structured migration imaging member of FIG. 1A which is one suitable for use in the optimum chargeexpose imaging process of this invention. In all the embodiments, the softenable layer 14- is typically chemically inert and substantially electrically insulating. Softenable material 14 may be any suitable material which may be softened by liquid solvents, solvent vapors, heat or combinations thereof. Where the softenable layere is to be dissolved either during or after imaging, it should be soluble in a solvent which does not attack the marking particles.

Typical softenable materials include Staybelite Ester 10, a partially hydrogenated rosin ester, Foral Ester, a hydrogenated resin triester and Noelyne 23, an alkyd resin, all from Hercules Powder Co.; SR82, SR 84, silicon resins, both obtained from General Electric Corp.; Sucrose Benzoate, Eastman Chemical; Velsicol X-37, a polystyrene-olefin copolymer from Velsicol Chemical Corp.; Hydrogenated Piccopale lOO, a highly branched polyolefin, Piccotex 100, a copolymer of methyl styrene and vinyl toluene, Piccolastic A-75, 100 and 125,

all polystyrenes, Piccodiene 2215, a polystyrene-olefin copolymer, all from Pennsylvania Industrial Chemical Co.; Araldite 6060 and 6071, epoxy resins from CIBA Corp.; R5061A, a phenymethyl silicone resin, from Dow Corning Co.; Epon 100], a bisphenol A- epichlorohydrin epoxy resin, from Shell Chemical Corp.; and PS-2, PS-3, both polystyrenes and ET-693, a phenolformaldehyde resin, from Dow Chemical Co.; and 96-A, a custom synthesized 80/20 mole per cent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 dl/gm.

Other typical softenable materials include other custom synthesized copolymers of styrene and hexylmethacrylate, a custom synthesized polydiphenylsiloxane; a custom synthesized polyadipate; acrylic resins avialable under the trademark Acryloid from Rohm and Haas Co.; and available under the trademark Lucite from the E. l. duPont de Nemours and Co.; thermoplastic resins available under the trademark Pliolite from the Goodyear Tire and Rubber Co.; a chlorinated hydrocarbon available under the trademark Aroclor from Monsanto Chemical Co.; thermoplastic polyvinyl resins available under the trandemark Vinylite from Union Carbide Co.; other thermoplastics disclosed in Gunther, et al., US. Pat. No. 3,196,01 l; waxes and blends, mixtures and copolymers thereof.

The above group of materials is not intended to be limiting, but merely illustrative of materials for the softenable binder layer. The softenable layer may be of any suitable thickness. The thicker layers generally require a greater potential for charging. In general, a thickness up to about 16 microns has been found to be preferred.

In the preferred embodiment described above, the migration marking particles 16 are particles ofa photosensitive material. Typical such photosensitive materials include inorganic or organic photoconductive insulating materials; materials which undergo conductivity changes when photoheated, for example, see Cassiers, Photog, Sci. Engr. 4 No. 4, 199 (1960); materials which photoinject or inject when photoheated. The migration material preferably should be substantially insoluble in the softenable material and otherwise not adversely reactive therewith and have similar characteristics vis-a-vis any solvent liquid or vapor which may be used in the softening step hereof.

In the process of this invention, substantially colorless migration material are preferred and colorless light reflecting materials are still more preferred. Colorless light reflecting particles enhance the color of the image by reflecting back the light transmitted by the light transmitting layer which has migrated together with the migration material to form the final image. While migration material of various colors can be employed, they may detract from the physical appearance of the image produced. Therefore, white migration materials are preferred. Typical white light reflecting migration materials are titanium dioxide and zinc oxide.

Because of its properties of photoconductivity, color and light reflectance, zinc oxide is a particularly preferred migration material. Slightly dyed zinc oxide having an extended spectral response may also be employed.

Other organic and inorganic materials useful as migration materials are listed in the above mentioned copending applications.

Any suitable photosensitive material or mixtures of such materials may be used in carrying out the invention regardless of whether the particular material selected is organic, inorganic, is made up of one or more components in solid solution or dispersed one in the other, whether the layer is made up of different particles or made up of multiple layers of different materials.

Other materials which may be included in a photosensitive migration material include organic donoracceptor (Lewis acid-Lewis base) charge transfer complexes made up of donors such as phenolaldehyde resins, phenoxies, epoxies, polycarbonates, urethanes, styrene or the like complexed with electron acceptors such as 2,4,7-trinitro-9-fluorenone; 2,3,5,7-tetranitro- 9-fluorenone; picric acid; l,3,5-trinitro benzene; chloroanil; 2,5-dichloro-benzoquinone; anthraquinone-B- carboxylic acid 4-nitrophenol; maleic anhydride', metal halides of the metals and metalloids of groups l-B and Il-Vlll of the periodic table including, for example, aluminum chloride, zinc chloride, ferric chloride, magnesium chloride, calcium iodide, strontium bromide, chromic bromide, arsenic triiodide, magnesium bromide, stannous chloride, etc.; boron halides, such as boron trifluorides; ketones such as benzophenone and anisil, mineral acids such as sulfuric acid; organic carboxylic acids such as acetic acid and maleic acid, succinic acid, citroconic acid, sulphonic acids such as 4 toluene sulphonic acid and mixtures thereof.

As stated above any suitable photosensitive material may be employed. In the optimum embodiment of the binder structured migration imaging member, typical migration marking particles include those which are made up of only the pure photosensitive material or a sensitized form thereof, solid solutions or dispersions of the photosensitive material in a matrix such as thermoplastic or thermosetting resins, copolymers of photosensitive pigments and organic monomers, multilayered particles in which the photosensitive material is included in one of the layers and where other layers provide light filtering action in an outer layer or a fusible or solvent softenable core of resin or a core of liquid such as dye or other marking material or a core of one photosensitive material coated with an overlayer of another photosensitive material to achieve broadened spectral response. Other photosensitive structures include solutions, dispersions, or copolymers of one photosensitive material in another with or without other photosensitively inert materials. Other particle structures which may be used, if desired include those described in US. Pat. No. 2,940,847 to Kaprelian also included are photosensitive materials wherein the change caused by radiation is permanent, persistent or temporary. Also included are those particles which are thermoconductive, that is, the material is changed by the heating effects of the incident radiation.

While photoconductive particles (and photoconductive is used in its broadest sense to mean particles which show increased electrical conductivity when illuminated with electromagnetic radiation and not necessarily those which have been found to be useful in xerography in xerographic pigment-binder plate configurations) have been found to be a class of particles useful as electrically photosensitive particles in this invention and while the photoconductive effect is often sufficient in the present invention to provide an electrically photosensitive material, it does not appear to be a necessary effect.

In another preferred embodiment wherein softenable layer I4 is photosensitive, the migration material 16 of FIGS. lA-lC may be non-photosensitive particulate material which is either electrically conductive or insulating. Typical non-photosensitive or photosensitively inert materials useful in this embodiment include carbon black, garnet, iron oxide, dyed phenolic, epoxy, bitumen, resin coated particles, various insoluble dyes and pigments and combinations thereof.

That is, softenable layer 14, of FIGS. 1AllC may comprise a photosensitive or photoconductive material, as disclosed in copending application Ser. No. 553,837, filed May 13, 1966 incorporated herein by reference. The migration imaging process of the present invention can be performed using this imaging member with any of the imaging techniques described herein. For example, when the imaging member having a photoconductive softenable layer I4 is used in the imaging process, the photoconductive softenable layer 14 becomes conductive in the light struck areas shown in FIG. 2 thereby permitting discharge of the structure in the light struck areas, which removes charge formerly available to the marking particles in those areas, and thereby eliminates electric fields across the member in said areas. In this way an electrostatic latent image is typically formed on the imaging member. This image may then be developed by softening the softenable layer in one of the modes previously described, for example, by solvent liquid wash-away of the relatively unmigrated material and softenable layer. As the softenable layer softens during development, the migration material In in FIGS. lAlC, which had retained charge after exposure, migrate to the surface of substrate l2. In addition, the migration material may be omitted completely from the imaging members of the invention employing photoconductive softenable layer l4. Although not preferred, the light transmitting layer alone can be caused to migrate selectively after light exposure to provide an informational color image with out the presence of migration material of any sort.

The softenable layer may comprise any photoconductive material which is capable of being softened so as to permit the marking particles to migrate toward the substrate during image formation. While the layer may be softened by heat, it is preferable that the softening be accomplished by a solvent liquid which does not attack the migration material, but which removes the softenable layer and unneeded portions of the marking material during imaging, leaving only those particles forming the image on the plate at the conclusion of the imaging steps. The solution layer may comprise, for example, organic photoconductors in a resin, soluble photoconductive polymers, charge transfer complexes III) of certain aromatic resins with Lewis acids and mixtures thereof. Typical organic photoconductors include anthracene, 2,5-bis-(p-aminophenyl)- l ,3,4-oxadiazole; 2-aryl-4-arylidene-oxazolones; 4,5- diphenylimidazolidinone; 2,5-bis-(p-aminophenyl)- 1,3,4-triazoles, l,3-diphenyl-tetrahydrominidazoles, 1,2,3-triazines, l,2,5,6-tetruazacycloctetranes- (2,4,6,8); quinazolines; 6-hydroxy-2-phenyl-3-(pdimethyl aminophenyl)-2-benzofurane; thiazolidones; triphenylamines; and mixtures thereof. Typical aromatic resins which may be sensitized with Lewis acids include: polyvinyl-carbazole, epoxy resins, phenoxy resins, phenol-formaldehyde resins, polystyrenes, polycarbonates, polysulfones. polyphenylenc oxide and mixtures thereof. Typical Lewis acids which may be used to sensitize the above resins include 2,4,7-trinitro- 9-fluorenone; 4,4-(dimethyl-amino) benzophenone; chloranil; 1,3,5-trinitrobenzene, and mixtures thereof.

Surprisingly, it has been found that almost any sort of marking material is suitable for use as the migration material 16 in a photoconductive softenable layer. Any sort of inert, conductive, insulating, photosensitive or photosensitively inert material will satisfactorily perform the function of migration material 16. Typical materials include pigments, both organic and inorganic, such as: titanium dioxide, powdered iron, iron oxide, barium sulfate, carbon phthalocyanine, graphite, dyes, garnet, tungsten, other organic materials capable of being formed into particles, the photosensitive and inert materials named above as suitable in various other embodiments of the member and mixtures of any of these materials.

The surprising result that any sort of migration marking particle and mixtures of any combination of marking particles perform most satisfactorily in the migration imaging system of this invention is not unique to the photoconductive binder member just described. Mixtures of the various marking materials perform satisfactorily in all the imaging member embodiments when such members are used in an appropriate mode of the imaging system. That is, it has been found that mixtures of various inert, conductive, insulating, photosensitive and/or photosensitively inert migration materials migrate in response to appropriate imagewise migration force just as the individual materials migrate in embodiments having a single migration material.

The support member or substrate 12 may be electrically conductive or insulating. Conductive substrates as illustrated in the embodiment described with FIG. 1, generally facilitate the charging or sensitization of the member according to the optimum electrical-optical mode of the invention and typically may be of copper, brass, nickel, zinc, chromium, stainless steel, conductive plastics and rubbers, aluminum, steel, cadmium silver, gold or paper rendered conductive by the inclusion of a suitable chemical therein or through conditioning in a humid atmosphere to ensure the presence therein of sufficient water content to render the material conductive. The substrate may be in any form such as the metallic strip, sheet, coil, cylinder, drum, moebius strip, circular disc, or the like. If desired, the conductive substrate may be coated on an insulator such as paper glass or plastic. One example of this type of sub strate comprises NESA glass, which is a substantially transparent tin oxide coated glass available from Pittsburgh Plate Glass Co. Another typical substrate comprises aluminized Mylar which is made up of a Mylar polyester film available from the E. I. duPont de Nemours Co., Inc., having a thin, substantially transparent aluminum coating. Another typical substrate comprises Mylar coated with copper iodide. Other substrates include conductive resin coated films such as Dow Resin 261 1-7 (Dow Chemical Company) or Conductive Polymer 261 (Calgon Corporation). It is, therefore, clear that where it is desirable to view the migration imaged member as a transparency using transmitted light, that a suitable, substantially transparent substrate is used. Of course, hard copy images suitable for viewing with reflected light may similarly be produced on any suitable opaque substrate.

Although the migration imaging members described in FIGS. 1A-1C are shown on supporting substrate 12, it will be appreciated that in various modes of the inventive imaging system, binder matrix layers comprising marking material 16 dispersed in softenable layer 14 may themselves be sufficiently self-supporting to allow their preparation separate from the imaging substrate. Such self-supporting imaging members may be imaged by processes involving selectively softening only portions of the area of thickness of the softenable material while the unsoftened portions thereof maintain sufficient integrity to continue to support the member. Typically such a migration imaging binder matrix is placed in contact with a suitable, desired substrate before or during the migration imaging process.

In another particularly preferred embodiment of the binder structured imaging member, an imaging member like that shown in FIGS. 1A1C comprises softenable matrix 14 having photosensitive marking material 16 dispersed therein, and the softenable matrix is coated directly onto substrate 12 which is a dielectric or non-conductive support member. Any dielectric or insulating material is typically suitable for the substrate in this embodiment of the invention, for example, Mylar polyester film, available from duPont, in thicknesses up to about 3 mils is a particularly preferred insulating substrate. Any other insulating material compatible with the other materials used and suitable in the process steps of the inventive system may be used as the insulating substrate. For example, films of polyethylene terephthalate, polycarbonate, polysulfone, polyphenylene oxide, cellulose acetate, cellulose triacetate, cellulose nitrate, vinyl chloride, vinyl acetate; acrylic esters, such as methyl methacrylate, vinyl butyral, vinyl formal, polyvinylcarbazole, rubber, chlorinated rubber, acrylonitrile resin rubber, polyamides, polyimides, coated and impregnated materials such as waxed paper, shellac coated cloth, epxoy impregnated cloth, glass, fibrous glass cloth and combinations thereof. As before, the substrate may be either opaque or transparent, depending upon the way in which the finally imaged member is to be imaged and viewed.

Imaging processes using the binder structure imaging member having an insulating substrate may be accomplished by any of the methods described later herein for use with the imaging member having the conductive substrate, by additionally placing the insulating substrate ofthis imaging member in contact with a conductive member, typically grounded, and then creating the imagewise migration force across the imaging member, for example, by charging with a corona charge device. Alternatively, other methods known in the art of xerography for charging xerographic plates having insulating backings may also be applied. For example, the imaging member having the insulating substrate may be moved between two corona charging devices thereby simultaneously charging both surfaces to opposite potentials. This last described method is often referred to as double-sided charging.

Any suitable method of creating a multiplicity of areas of different color which transmits light of different color may be used to provide the light transmitting layers 18, 22 and 24. For example, the color areas may be printed by conventional multicolor printing means such as gravure rollers or by conventional lithography. For example, three gravure rollers having registering groove patterns each containing a light transmitting material of a single color may be passed over the previously prepared softenable layer depositing a continuous pattern of alternating areas of different colors which areas transmit light of different colors. For example, three half tone screens may be prepared one for each of the different color patterns so that when each plate is inked with a different color pattern, patterns will be printed on the softenable layer in registration. Typical of the printing techniques which may be used are those described in Practical Photo-lithography by C. M. Willy, Pittman, and Sons, Ltd., London, 1952 and in Photography and Plate Making for Photo- Lithography," I. H. Sayre, Lithographic Text Book Publishing Company, Chicago, 1944. Also, the areas could be provided by spraying the colored light transmitting material through stencils onto the softenable layer.

The light transmitting layer may be contiguous or slightly, partially or substantially embedded in the softenable material at the surface of the softenable material. The light transmitting layer is typically a fracturable layer of particulate material or a semi-continuous layer which is capable of breaking up into discrete particles ofthe size of an image element or less during migration imaging development. The thickness of the light transmitting layer is in the range of from about 0.01 to about 4.0 microns although thicker layers of up to 5 microns have been found to give good results for some materials.

The light transmitting layer can comprise any nonphotosensitive material which transmits light, preferably of only one color or principle wave length. Typical materials are dyed plastic particles and organic pigments. Other materials will be obvious to those skilled in the art. Should the commercially available material not be of the prioer particle size, ball milling can be employed to provide the proper size. Light transmitting materials include transparent pigments which, although photoconductive, can be considered inert in the present process due to their low sensitivity to light as compared to the sensitivity of the photosensitive migration material or photosensitive softenable material. Of course, the light transmitting layers, like the migration material, is substantially inert or insoluble in the softening agents employed to soften the softenable layer.

Any suitable photosensitively inert particles as herein defined may be used in the course of the present invention. Typical materials include dyed resinous substitutents such as polyolefins, for example, polyethylene, polypropylene, polybutylene, vinyl compounds such as polyvinylchloride, polyvinyl acetate, polyvinyl fluoride, polystyrene, polyvinyl alcohol, polyvinylbutyral. polyvinyl carbazole, polyvinyl ethers and ketones, esters such as polyethylene terephthalate, polymethyl methacrylate, the above stated polyvinyl acetate, fluorocarbons such as tetrafluoroethylene, the above stated polyvinyl fluoride, polyvinylidenefluoride, polychlorotrifluoroethylene, phenolic resins such as phenolformaldehyde, phenol-furfural, amino resins such as ureaformaldehyde and melamine-formaldehyde, epoxy resins such as epichlorohydrin, polyurethane resins, polycarbonate resins, polyamide resins, styrene-butadiene copolymers and silicone resins. Representative organic pigments include the chemically quasineutral compounds which include nitro, azo and polynuclear classes of materials. Exemplary of the nitro compounds are Lithol Fast Yellow GG (C.l. l4) and Pigment Chlorine GG (C.l. l3). Exemplary of the azo compounds are Paranitroaniline Red (p-nitro-aniline), Toluidine Red R (2-nitro-p-toluidine)), Fire Red (2-chloro-4- nitroaniline), Red Toner (4-chloro-2-nitroaniline), Permatone Orange (2,4-dinitroaniline)-Permanent Red FRLL (2,5-dichloroaniline, Permanent Bordeaux F3R (4-nitro-o-anisidine (5-nitro-2-aminoanisole), Permanent Rubine RBH [5-chloro-o-toluidine (4- chloro-2-aminotoluene)], Vulcan Fast pigments such as Orange GG (3,3'-dimethoxybenzidine), Yellow R (o-toluidine), Yellow GR (3,3'-dichlorobenzidine), and Yellow 50 (2,2 '-dichloro-5,5'-dimethoxybenzidine). Exemplary of the polynuclear compounds are anthraquinones which include helio Fast Yellow 6 GL (l-(o-hydroxybenzamido) anthraquinone), C.I. ll27, Algol Pink R (l-benzamido-4-hydroxyanthraquinone), C.l. 1128, lndanthrene Blue RS, C1. 1106, Caledon Jade Green, C.l. llOl, Indigo, C.l. 1177, Thioindigo Red B, C]. 1207, and Indanthrene Red Violet RH, C.l. 1212. Inorganic pigments such as titanium dioxide, white lead, iron oxide, chromium oxide, lead chromate, zinc chromate, cadmium yellow, cadmium red, antimony dioxide, magnesium silicate, calcium carbonate and gypsum silicate may be utilized.

Other chemically reactive compounds which may be considered in this family of materials include colored organic compounds which are chemically reactive and require corresponding processing to produce the insolubility and other properties required. Cationic dyes used in the pigment industry such as Auramine, a diphenylmethane having a Cil. No. 655, tri-aryl methanes such as Malachite Green, C.l. 657, Brilliant Green, Cl. 662, Methyl Violet B, Cl. 680, Thoduline Blue 6G, Cl. 658, xanthenes such as Rhodamine B, Cl. 749, thiazoles such as Thioflavine T, C.l. 8l5 may be included in this category. Various anionic derivatives which in clude organic coloring materials capable of producing metallic derivatives suitable for use as pigments cuch as Pigment Green B the iron chelate of l-nitroso-2- naphthol, Naphthol Green B, the sulfo derivative of Pigment Green B prepared by nitrosating 2-naphthol-6- sulfonic acid and reacting the product under controlled conditions with ferrous sulphate, Naphthol Yellow S, C. I. 10, a nitro compound the pigment counterpart of which is a brilliant yellow known as Indian Yellow. The sodium, calcium, strontium and barium salts of certain azo pigments such as Lithol Red R (2-amino-l-naphtholenesulfonic acid), Lake Red C amine, (2-amino-5-chloro-p-toluenesulfonic acid), Lake Red D (anthranilic acid), alkaline earth and manganese salts of Lithol Rubine B (6-amino-m-toluenesulfonic acid), Lake Bordeaux B (Z-amino- 1 -naphthalenesulfonic acid), Lithol Red 2G (2-amino-5-chloro-p-toluenesulfonic acid and Permanent Red 28 (6-amino-4- chloro-m-toluenesulfonic acid) are further exemplary materials. Xanthene derivatives converted to brilliant reds of a bluish undertone by precipitation with soluble lead salts and metallic derivatives of anthraquinones and phthalocyanine pigments have also been found suitable. The pigments herein enumerated may be used either alone or in conjunction with the above listed resin particles so that one may have a resin particle, a pigment particle or a combination of the two to produce a pigmented resin particle. In addition, various dyed resins may also be used in conjunction with the present invention which would include many resinous materials similar to those stated above in combination whith a dye stuff such as azo dyes, acridine dyes, azine dyes, ketone amine dyes, metallized azomethine dyes, methine dyes, nitro dyes, nitroso dyes, oxazine dyes, quinoline dyes, thiazine dyes, triarylmethane dyes, xanthene dyes, sulphur dyes, anthraquinone dyes, indigold dyes and phthalocyanine dyes. Other miscellaneous materials such as ceramic glass oxides, various chemical synthetic particles such as silicates, zeolites, hydroxides, sulfates, iodates, various metal particles encapsulated with a resinous shell, and liquid materials which can be encapsulated with both natural and synthetic resins have been found suitable. When desirable, any of the above materials may be encapsulated or lightly coated with a plastic material or resin to render the particle more insulating at the time of imaging. As is apparent, almost any inert particle insulating in nature or at least capable of retaining a charge for the length of time required for imaging will satisfy the requirements of the present invention.

When light transmitting layer 22 is employed, a preferred average particle size is in the range of about the same as employed for the migration material 16. That is, migration material 16 has a particle size in the range of from about 0.01 to about 2.0 microns to yield images of optimum resolution and high density compared to migration layers having larger particles. For optimum resultant image density, the particles should not be over about 0.7 microns in average particle size. Layers of migration material such as that illustrated in FlG. 1C preferably should have a thickness ranging from about the thickness of the smallest element of migration material in the layer to about twice the thickness of the largest element in the layer. It should be recognized that the particles may not all be packed tightly together laterally or vertically so that some of the thickness of layer 24 and migration material 16 may constitute softenable material.

The thickness of softenable material 14 including the light transmitting layer is typically in the range of from about /.2 to about 16 microns thick. If the layer is thinner than about /2 micron, excessive background may result upon development while layers thicker than about 16 microns may require relatively long development time resulting in lower image contrast and density. The imaging process by which the imaging members of this invention are employed typically comprises the following steps. First, a typical imaging member as illustrated in FlG. lA-lC is provided and an imagewise migration force which is typically an electrical field interacting with the charged particles is placed across the thickness of the imaging member. The softenable layer is then softened by the application of any suitable softening medium. As the softenable layer is softened, the

15 migration marking material migrates in imagewise configuration towards the surface of the substrate.

The imaging member is conveniently electrostatically charged. The electrostatic charging step is typically accomplished by means of a corona charging head which scans the upper surface of the binder structure and deposits the uniform charge on its upper surface as it passes over the structure. During the electrostatic charging step, the substrate is typically electrically grounded for preferred results. Typical corona charging methods and devices are described in the patent to Walkup US. Pat. No. 2,777,957 and Carlson US. Pat. No. 2,588,699. Corona charging is preferred because of its ease and because of the consistency in quality of the images produced when corona charging is employed. However, any suitable source of corona charging may be used including radioactive sources as described in Dessauer, Mott and Bogdonoff, Photo Eng. 6, 250 (1955). Other charging techniques known to those skilled in the art may also be employed.

After the surface of the imaging member has been uniformly charged, the member is exposed to a pattern of activating electromagnetic radiation. Following exposure, the charged imaging member supports a pattern of electrostatic charge in imagewise configuration typically conforming to a negative of the selective pattern of activating electromagnetic radiation to which the charged member was exposed.

The image may be developed by immersing the member in a solvent liquid contained in any suitable bath or tank. Developing time is relatively short and is in the range of from 1 to 20 seconds at which time the previously charged photosensitive particles 16 which have not been exposed to radiation migrates through the softenable material 14 as it is softened and dissolved. Such migration is accomplished by portions of the light transmitting layer directly above the migrating material. Unmigrated migration material 16 and unmigrated portions of the light transmitting layer are washed away from the developing image member and the solvent bath.

The developed image is suitable for viewing on the substrate of the imaging member or it can be transferred by means known to the art and fixed to another substrate. For example, methods of fixing migration images to substrates are disclosed in copending application Ser. No, 590,959, filed Oct. 3l, 1966, now abandoned. and Ser. No. 695,214, filed Jan. 2, 1968, now abandoned.

ln solvent development the imaging member bearing the latent electrostatic image may simply be held for a few seconds in the vapors of a solvent for a softenable material 14. Usually the vapors eminate from a container holding the solvent liquids. The member to be developed is suspended for a few seconds at a predetermined point above the liquid to allow the vapor to rise and contact the member. The vapor softens the softenable layer 14 and allows migration material 16 together with those portions of the light transmitting layer directly above to migrate to the substrate of the imaging member.

The imaging member containing the latent electrostatic image can also be developed by heating the soft-- enable material to an extent which softens softenable layer 14 allowing the above mentioned migration to take place. Exposure to heat is usually for a short time such as from 1 to about seconds or longer depending upon the intensity and type of heating used. The time for development also depends upon the nature of softenable material 14, its viscosity and other characteristics. It has been found to be preferred to heat the member to a temperature in the range of from about 50C to about 150C for about 1 to about 10 seconds to produce optimum quality images. Generally, temperatures in the range of from C to l50C are usually sufficient with heating time in the range of a few seconds. A more detailed description of heat, vapor and liquid development modes is contained in aforementioned copending application Ser. No. 837,591 which is incorporated herein by reference.

It has also been found that relatively non-migrated areas of migration material 16 and light tramsmitting layer may be removed by abrasion to yield a more readily visible image. In addition, relatively unmigrated portions of light transmitting layer may be removed by contacting the surface of the imaging member containing the migrated image with a sheet having a pressure sensitive adhesive thereon such as Scotch Brand acetate tape and then stripping away the tape from the imaging member. The pressure sensitive adhesive will carry with it those particles remaining on the surface of softenable material 14 and a small portion of softenable material. As mentioned above, development can occur by splitting the softenable layer in accordance with the procedure described in copending application Ser. No. 784,l64 filed Dec. 16, 1968, now US. Pat. No. 3,741,757.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples describe specific embodiments of methods of producing color images using the process of this invention. Parts and percentages are by weight unless otherwise indicated. The following examples should be considered to describe preferred embodiments of the process of this invention.

EXAMPLE I The mixture of three light transmitting materials is prepared by mixing finely divided dyes resin particles available under the tradename Radiant Color Resin from Hercules Corp. designated P6000G-red; Rl03G- green and Rl03G-blue. These particles are then mixed with glass beads having an average diameter of about 50 microns. A plate is prepared by dissolving about two parts of Silicone Resin R-507l, available from Dow Corning Corporation in about 50 parts toluene added to the solution. About one part of ground zinc oxide having an average particle size of less than 1 micron for each two parts ofSilicone Resin R-507l is added to the solution. The zinc oxide particles are thoroughly dispersed in the solution and the solution is flow coated onto the conductive surface of an aluminized Mylar film to a dry thickness of about 7.5 microns. The mixture of light transmitting particles and glass beads is then cascaded across the firm surface of the dried film. A uniform particle layer across the surface is produced. Alternatively, the imaging member can be prepared by successive cascadings of only one pigment at a time. This layer is more firmly attached to the resin surface by heating the plate to about 65C for about 3 minutes. The plate is cooled to room temperature and then charged to a negative potential to about 250 volts by corona discharge as described by Carlson in US. Pat.

No. 2,588,699. The plate is then exposed to a Kodachrome color negative transparency. Total exposure is about l fcs foot-candle seconds through the transparency. The plate is then developed by dipping it into a container containing Toluene. After a few seconds in the solvent, the imaging member is removed. The resulting image on the imaging member is a color positive of the original consisting of portions of the light transmitting layer residing over particles of zinc oxides on the Mylar substrate.

EXAMPLE II Three separate plates are prepared by the method described in Example I employing a different single dyed resin as the light transmitting layer of each member. Thereby, there is prepared imaging members having light transmitting layers of red, green and blue respectively. Each of the thus prepared imaging members are charged to a potential of 250 volts in the dark and then exposed to a Kodachrome positive transparency for a total incident energy of 100 foot-candle seconds on each plate. There is thus formed the latent electrostatic images conforming to the red, green and blue separations of the image due to the fact that each area of the light transmitting layer transmits light of one color only. The imaged members are then developed by immersing them in 1,1,1 trichloroethane whereupon the zinc oxide migration material together with those portions of the light transmitting layer directly above the migrating particles migrate and adhere to the substrate in the non-light struck areas of each member while the relatively unmigrated material is washed away as the softenable material dissolves. There is thus produced three color separations of the image. The three separations are then projected in registration on the same screen and viewed in transmitted light revealing a reconstruction of the original colored image.

EXAMPLE Ill A strip of aluminized Mylar consisting of an about 75 micron layer of Mylar overcoated with a submicron layer of aluminum, which has an about 2 micron rollcoated overlayer of a softenable Staybelite Ester l0 thereon, is fixed to the bottom of a rectangular about 2 by 6 by 4 inch brass container. The container is rotated about its horizontal axis and cascaded with a mixture of about 0.12 grams of Florence Green Seal zinc oxide particles dyes with about 0.03 grams of Rhodamine B per about 8 grams of zinc oxide, and about 50 grams of about 50 micron diameter glass beads. This mixture consisting of carrier beads and zinc oxide particles, is cascaded over the aluminized Mylar strip held to the bottom of the container for 10 rotations 0r cascades. The strip is removed from the container and heated to about 80C for about 2 minutes, refixed in the container and cascaded again. This cycle is repeated about 6 times after which a zinc oxide layer has been formed with the zinc oxide particles dispersed approximately halfway through the upper thickness of the softenable Styabelite plastic.

A mixture oflight transmitting particles as described in Example I is placed over the surface of the Staybelite' plastic in accordance with the procedure of Example I. The thus prepared imaging member is then charged to a negative potential of 190 volts by corona discharge as described in Example I and then exposed to a positive three color image for a total incident exposure of 260 foot-candle seconds. This image is developed by dipping the imaging member into a reservoir of Sohio Odorless Solvent 3440, a kerosene fraction available from the Standard Oil Company. A negative color image of the original is seen on the Mylar strip.

EXAMPLE IV The procedure of Example I is repeated with the exception that the light transmitting layer is applied as described in Example 11 to three different Mylar strips prepared as in Example III. Each of the imaging members are exposed and developed as described in Example II yielding three color separations of the original image.

EXAMPLES V AND VI The procedures of Examples II and III are repeated with the exception that the latent images are developed by first exposing the softenable layers to vapors of 1,1,1 trichloroethane and then, while softened, contacting the layer with a clear film of Mylar in accordance with the procedure of Example I of copending application Ser. No. 784,164 filed Dec. 16, 1968, now US. Pat. No. 3,741,757. Upon separation of the two films, the soft-enable layer splits yielding an image on the imaging member substrate.

EXAMPLE VII An imaging member is prepared by first mixing together thoroughly in a weight ratio of 2 to l a silicone resin available under the tradename R-5061A from the Goodyear Rubber Company and zinc oxide having an average particle size of less than 1 micron. The zinc oxide contains 0.025% by weight manganese naphthenate. An aluminized Mylar film is coated with the mixture as described in Example I to provide a film over the Mylar of 7.5 microns thickness after drying at 50C for 1 hour. A light transmitting layer comprising dyed resin particles is then placed over the film in accordance with the procedure of Example I. The thus prepared imaging member is charged by means of corona discharge to a negative potential of 250 volts and exposed to a multicolor light image for a total incident exposure of foot-candle seconds by reflected light from a tungsten incandescent light source at 2,800K color temperature. The image is developed by dipping the member into carbon tetrachloride liquid.

EXAMPLE VIII The procedure of Example 11 is repeated except that the imaging member is initially charged by corona discharge to a positive potential of 250 volts and after exposure is charged to a negative potential of 250 volts. By this procedure the previously charged areas are brought to zero potential while the uncharged areas are negatively charged. Upon development of the image in accordance with the procedure of Example II, images are obtained on the substrate which are complimentary to the images obtained in Example II.

Although specific components and proportions have been stated in the above description of the preferred embodiments of the migration imaging system employing a binder structured imaging member, other suitable materials and variations in the various steps in the system as listed herein, may be used with satisfactory results and various degrees of quality. In addition, other materials and steps may be added to those used herein and variations may be madse in the process to synergize, enhance or otherwise modify the properties of the invention. For example, the solvents, binder materials, photosensitive materials and other marking materials, which are used and disclosed in the above mentioned copending applications, can be employed in the various imaging members of this invention described above. In addition, more than one marking material may be used in the same imaging structure, either mixed together or in separate layers in the imaging member. Another modification employs adding dyes to the marking material or to the softenable materials to enhance the sensitivity of the imaging structure or to change its imaging sense from positive-to-negative, to positive-to-positive. The light transmitting layer can comprise a plurality of separate layers which together transmit light of one color. For example, a dual layer structure of cyan colored material which absorbs red light over a yellow colored material which absorbs blue light will transmit only green light. Likewise, a dual layer structure of a magenta colored layer which absorbs green light over a cyan colored layer will transmit only blue light. Other combinations will occur to those skilled in the art.

It will be understood that various other changes in the details, materials, steps and arrangements of elements, which have been herein described and illustrated in order to explain the nature of the invention will occur to and may be made by those skilled in the art, upon a reading of this disclosure, and such changes are intended to be included within the principle and scope of this invention.

What is claimed is:

1. An imaging method comprising:

a. providing an imaging member comprising an overlayer of softenable material on an opaque substrate, said softenable material having migration material dispersed at least in part in said softenable layer, and a fracturable electrically insulating light transmitting layer comprising individual laterally adjacent alternating areas of at least two colors, each of said alternating areas transmitting light of one of the three visual primary colors red, green and blue, said light transmitting layer contacting said softenable material and contiguous the surface of said softenable material opposite the softenable material surface contacting said substrate, said light transmitting layer being relatively nonphotoconductive as compared to the photoconductive material below said light transmitting layer and wherein at least one of said migration material and said softenable material is photoconductive, said softenable material capable of having its resistance to migration of migration material and material from said light transmitting layer decreased sufficiently to allow migration of areas of said light transmitting layer and migration material in depth in in said softenable material;

b. eleetrostatically charging said imaging member;

c. exposing said photoconductive material through said light transmitting layer to an image pattern of activating electromagnetic radiation;

(1. developing said imaging member by decreasing the resistance to migration of migration material and material from said light transmitting layer in depth in the softenable layer at least sufficent to allow imagewise migration of migration material and material from said light transmitting layer comprising imagewise areas of said light transmitting layer directly over said migration material whereby said migration material and material from said light transmitting layer migrate in imagewise configuration in depth in said softenable material; and

e. removing the unmigrated portion of said light transmitting layer from said imaging member.

2. An imaging method according to claim 1 wherein said light transmitting layer is nonphotoconductive.

3. An imaging method according to claim 1 wherein said light transmitting layer comprises materials which are visually colored red, green and blue.

4. An imaging method according to claim 1 wherein said light transmitting layer is between from about 0.01 to about 5.0 microns thick.

5. An imaging method according to claim 1 wherein said softenable material has dispersed throughout migration material.

6. An imaging method according to claim 1 wherein said softenable material is a thermoplastic material.

7. An imaging method according to claim 1 wherein said migration material is a monolayer of dispersed migration material contiguous the interface of said softenable material and light transmitting layer and between said light transmitting layer and said substrate.

8. An imaging method according to claim 1 wherein said migration material is white.

9. An imaging method according to claim 1 wherein said migration mateial comprises particles of an average particle size from about 0.01 to about 2 microns and wherein said softenable layer is betwen from about V2 to about 16 microns thick.

10. An imaging method according to claim 1 wherein said migration material is selected from the group consisting of titanium dioxide and zinc oxide.

11. An imaging method according to claim wherein said migration material is zinc oxide.

12. An imaging method according to claim 1 wherein said substrate is black.

13. An imaging method according to claim 1 wherein said substrate is coated with a layer of electrically conductive material.

14. An imaging method according to claim 1 wherein said developing is accomplished by softening said softenable material by exposing said member to vapors of a solvent for said softenable layer.

15. An imaging method according to claim 1 wherein said developing is accomplished by softening said softenable material by heating said member.

16. An imaging method according to claim 1 wherein said developing and removing steps (d) and (e) are accomplished by contacting said member with a solvent for said softenable layer.

17. An imaging method according to claim 1 wherein the softenable material. unmigrated migration material and unmigrated light transmitting layer are removed by contact with a solvent liquid which dissolves said softenable layer and washes away said unmigrated material.

18. An imaging method according to claim 1 wherein said unmigrated migration material and unmigrated light transmitting layer are removed by abrasion to yield a visible image.

19. An imaging method according to claim 1 wherein said unmigrated migration material and unmigrated light transmitting layer are removed by splitting said softenable material by means of contacting said material while softened with a substrate and contacting the opposite side of said material with a receiver material and removing the substrate.

20. An imaging method according to claim 1 wherein said softenable layer has dispersed throughout said layer photoconductive migration material and contiguous the surface of said softenable layer a fracturable electrically insulating light transmitting layer comprising individual laterally adjacent areas of nonphotoconductive material in a mosaic pattern visually colored red, green and blue, each of said areas transmitting light of one of the three visual primary colors red, green and blue.

21. An imaging method according to claim including the step of immersing said imaging member in a solvent for said softenable layer whereby said softenable layer is substantially removed from said substrate together with relatively unmigrated migration material and light transmitting layer.

22. An imaging method comprising:

a. providing an imaging member comprising an overlayer of photoconductive softenable material on an opaque substrate and contacting said photoconductive softenable layer and contiguous one surface thereof and spaced apart from said opaque substrate a fracturable, electrically insulating light transmitting layer comprising individual laterally adjacent alternating areas of at least two colors, each of said alternating areas transmitting light of one of the three visual primary colors red. green and blue, said light transmitting layer being relatively non-photoconductive as compared to the photoconductive softenable layer, said photoconductive softenable material capable of having its resistance to migration of material from said light transmitting layer decreased sufficiently to allow migration of areas of said light transmitting layer in depth in said photoconductive softenable material;

b. electrostatically charging said member;

c. exposing said photoconductive softenable layer through said light transmitting layer to an image pattern of activating electromagnetic radiation;

d. developing said imaging member by decreasing the resistance to migration of said light transmitting layer in depth in the softenable layer at least sufficient to allow imagewise migration of said light transmitting layer at least in depth in said photoconductive softenable layer whereby said material from said light transmitting layer migrates in imagewise configuration in depth in said softenable material; and

e. removing the unmigrated portion of said light transmitting layer from said member.

23. An imaging method according to claim 22 wherein said light transmitting layer is nonphotoconductive.

24. An imaging method according to claim 22 wherein said light transmitting layer comprises materials which are visually colored red, green and blue.

25. An imaging method according to claim 22 wherein the light transmitting layer is between from about 0.01 to about 5.0 microns thick.

26. An imaging method according to claim 22 wherein said substrate is coated with a layer of electrically conductive material.

27. An imaging method according to claim 22 wherein said softenable material is a thermoplastic material.

28. An imaging method according to claim 22 wherein said developing is accomplished by softening said softenable material by exposing said member to vapors of a solvent for said softenable layer.

29. An imaging method according to claim 22 wherein said developing is accomplished by softening said softenable material by heating said member.

30. An imaging method according to claim 22 wherein said developing and removing steps (d) and (e) are accomplished by contacting said member with a solvent for said softenable layer.

3]. An imaging method according to claim 22 wherein the softenable material and unmigrated light transmitting layer are removed by contact with solvent liquid and which dissolves said softenable layer.

32. An imaging method according to claim 22 wherein said unmigrated light transmitting layer is removed by abrasion of said imaging member to yield a visible image.

33. An imaging method according to claim 22 wherein said unmigrated light transmitting layer is removed by splitting said softenable material by means of contacting said material while softened with a substrate and contacting the opposite side of said material with a receiver material and removing the substrate.

34. An imaging method according to claim 22 wherein said light transmitting layer comprising individual laterally adjacent areas of non-photoconductive material in a mosaic pattern visually colored red, green and blue, each of said areas transmitting light of one of the three visual primary colors red, green and blue.

35. An imaging method according to claim 34 including the step of immersing said imaging member in a solvent for said softenable layer whereby said softenable layer is substantially removed from said substrate together with unmigrated light transmitting layer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,873,309

DATED 1 March 25, 1975 |NvENT0 5 1 William L. Goffe it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 53, delete "adhead" and insert"ahead--" Column 4, line 11, delete "registraion" and insert-- "registration"--.

Column 5, line 8, delete "witih" and insert--"with"--.

Column 7, line 3, delete "layere" and insert-"layer"--.

Signal and Sealed this twenty-eight D ay Of October 1 975 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Parents and Trademarks

Claims

1. AN IMAGING METHOD COMPRISING: A. PROVIDING AN IMAGING MEMBER COMPRISING AN OVERLAYER OF SOFTENABLE MATERIAL ON AN OPAQUE SUBSTRATE, SAID SOFTENABLE MATERIAL HAVING MIGRATION MATERIAL DISPERSED AT LEAST IN PART IN SAID SOFTENABLE LAYER, AND A FRACTURABLE ELECTRICALLY INSULATING LIGHT TRANSMITTING LAYER COMPRISING INDIVIDUAL LATERALLY ADJACENT ALTERNATING AREAS OF AT LEAST TWO COLORS, EACH OF SAID ALTERNATING AREAS TRANSMITTING LIGHT OF ONE OF THE THREE VISUAL PRIMARY COLORS RED, GREEN AND BLUE, SAID LIGHT TRANSMITTING LAYER CONTACTING SAID SOFTENABLE MATERIAL AND CONTIGUOUS THE SURFACE OF SAID SOFTENABLE MATERIAL OPPOSITE THE SOFTENABLE MATERIAL SURFACE CONTACTING SAID SUBSTRATE, SAID LIGHT TRANSMITTING LAYER BEING RELATIVELY NON-PHOTOCONDUCTIVE AS COMPARED TO THE PHOTOCONDUCTIVE MATERIAL BELOW SAID LIGHT TRANSMITTING LAYER AND WHEREIN AT LEAST ONE OF SAID MIGRATION MATERIAL AND SAID SOFTENABLE MATERIAL IS PHOTOCONDUCTIVE, SAID SOFTENABLE MATERIAL CAPABLE OF HAVING ITS RESISTANCE TO ALLOW MIGRATION OF MIGRATION MATERIAL AND MATERIAL FROM SAID LIGHT TRANSMITTING LAYER DECREASED SUFFICIENTLY TO ALLOW MIGRATION OF AREAS OF SAID LIGHT TRANSMITTING LAYER AND MITRATION MATERIAL IN DEPTH IN IN SAID SOFTENABLE MATERIAL; B. ELECTROSTATICALLY CHARGING SAID IMAGING MEMBER; C. EXPOSING SAID PHOTOCONDUCTIVE MATERIAL THROUGH SAID LIGHT TRANSMITTING LAYER TO AN IMAGE PATTERN OF ACTIVATING ELECTROMAGNETIC RADIATION; D. DEVELOPING SAID IMAGING MEMBER BY DECREASING THE RESISTANCE TO MIGRATION OF MIGRATION MATERIAL AND MATERIAL FROM SAID LIGHT TRANSMITTING LAYER IN DEPTH IN THE SOFTENABLE LAYER AT LEAST SUFFICIENT TO ALLOW IMAGEWISE MIGRATION OF MIGRATION MATERIAL AND MATERIAL FROM SAID LIGHT TRANSMITTING LAYER COMPRISING IMAGEWISE AREAS OF SAID LIGHT TRANSMITTING LAYER DIRECTLY OVER SAID MIGRATION MATERIAL WHEREBY SAID MIGRATION MATERIAL AND MATERIAL FROM SAID LIGHT TRANSMITTING LAYER MIGRATE IN IMAGEWISE CONFIGURATION IN DEPTH IN SAID SOFTENABLE MATERIAL; AND E. REMOVING THE UNMIGRATED PORTION OF SAID LIGHT TRANSMITTING LAYER FROM SAID IMGAGING MEMBER.

9. An imaging method according to claim 1 wherein said migration mateial comprises particles of an average particle size from about 0.01 to about 2 microns and wherein said softenable layer is betwen from about 1/2 to about 16 microns thick.

11. An imaging method according to claim 10 wherein said migration material is zinc oxide.

12. An imaging method according to claim 1 wherein said substrate is black.

17. An imaging method according to claim 1 wherein the softenable material, unmigrated migration material and unmigrated light transmitting layer are removed by contact with a solvent liquid which dissolves said softenable layer and washes away said unmigrated material.

20. An imaging method according to claim 1 wherein said softenable layer has dispersed throughout said layer photoconductive migration material and contiguous the surface of said softenable layer a fracturable electrically insulating light transmitting layer comprising individual laterally adjacent areas of non-photoconductive material in a mosaic pattern visually colored red, green and blue, each of said areas transmitting light of one of the three visual primary colors red, green and blue.

21. An imaging method according to claim 20 including the step of immersing said imaging member in a solvent for said softenable layer whereby said softenable layer is substantially removed from said substrate together with relatively unmigrated migration material and light transmitting layer.

22. An imaging method comprising: a. providing an imaging member comprising an overlayer of photoconductive softenable material on an opaque substrate and contacting said photoconductive softenable layer and contiguous one surface thereof and spaced apart from said opaque substrate a fracturable, electrically insulating light transmitting layer comprising individual laterally adjacent alternating areas of at least two colors, each of said alternating areas transmitting light of one of the three visual primary colors red, green and blue, said light transmitting layer being relatively non-photoconductive as compared to the photoconductive softenable layer, said photoconductive softenable material capable of having its resistance to migration of material from said light transmitting layer decreased sufficiently to allow migration of areas of said light transmitting layer in depth in said photoconductive softenable material; b. electrostatically charging said member; c. exposing said photoconductive softenable layer through said light transmitting layer to an image pattern of activating electromagnetic radiation; d. developing said imaging member by decreasing the resistance to migration of said light transmitting layer in depth in the softenable layer at least sufficient to allow imagewise migration of said light transmitting layer at least in depth in said photoconductive softenable layer whereby said material from said light transmitting layer migrates in imagewise configuration in depth in said softenable material; and e. removing the unmigrated portion of said light transmitting layer from said member.

31. An imaging method according to claim 22 wherein the softenable material and unmigrated light transmitting layer are removed by contact with solvent liquid and which dissolves said softenable layer.