US3839031A

US3839031A - Electrode development migration imaging method

Info

Publication number: US3839031A
Application number: US00854596A
Authority: US
Inventors: J Sankus; A Amidon; W Goffe
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1969-09-02
Filing date: 1969-09-02
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01
Also published as: NL7013012A; BE755599A; FR2060875A5; GB1326950A; ES383314A1; CA947367A; SE7400140L; DE2043542A1; JPS4929576B1; SE369115B

Abstract

A novel migration imaging system having a migration imaging member comrpising migration material in or on a softenable layer, also having a conductive receiving layer and a system for developing migration imaging members by applying a developing medium to an imaging member and having the imaging member adjacent a development electrode.

Description

United States Patent 1191 Sankus, Jr. et al.

1451 Oct. 1, 1974 1 1 ELECTRODE DEVELOPMENT MIGRATION IMAGING METHOD [75] Inventors: Joseph G. Sankus, Jr., Fairport;

Alan B. Amidon, Penfield; William L. Goffe, Webster, all of NY.

[73] Assignee: Xerox Corporation, Rochester, NY.

[22] Filed: Sept. 2, 1969 [21] Appl. No.: 854,596

1521 Us. c1. 96/1 PS, 96/1.3 96/l.5

[51] Int. Cl 603g 13/00 [58] Field of Search 96/1.3, 1, 1.5, 1 PS [56] i References Cited UNITED STATES PATENTS 3,441,410 4/1969 Brynko 96/1 X 3,510,419 5/1970 Carreira et a1 96/1.3 X 3,512,968 5/1970 Tulagin 96/1 X 3,515,549 6/1970 Bixby 96/1 X 3,520,681 7/1970 Goffe 96/1.5 X 3,536,483 10/1970 Watanabe et a1 96/1 3,556,781 1 1971 Levy et a1. 96/1 3,556,783 1/1971 Kyriakakis 96/1 X 3,615,400 10/1971 Augostimi et 81.. 96/1 X 3,653,064 3/1972 lnone et a1 96/1 Pc 3,653,885 4 1970 Levy et a1. 96/1 3,656,990 4/1972 Goffe 117/8 3,676,117 7 1972 Kimoshita 96/1 Primary ExaminerRonald H. Smith Assistant Examiner-John R. Miller, Jr.

Attorney, Agent, or Firm-James J. Ralbate; David C. Petre; John B. Mitchell 5 7 ABSTRACT A novel migration imaging system having a migration imaging member comrpising migration material in or on a softenable layer, also having a conductive receiving layer and a system for developing migration imaging members by applying a developing medium to an imaging member and having the imaging member adjacent a development electrode.

35 Claims, 18 Drawing Figures PAIENIEMBT 1 w 3.899.031 sum 1 u 4 FIG 2b PATENIEDUET H 3.839.031

summar ly FIG 5a F/G 5b ELECTRODE DEVELOPMENT MIGRATION IMAGING METHOD BACKGROUND OF THE INVENTION This invention relates to a novel imaging system in which the recording material is selectively moved through and repelled from a softenable medium under the influence of electrical forces.

Various methods of forming visible images in response to patterns of lights and shadows are well known. Recently, palpable, visible images have often been formed by means involving the electrical properties rather than the chemical properties of various photoconductive materials. For example, a uniformly charged layer of photoconductive material is exposed to a pattern of light and shadows and the resulting electrostatic latent image pattern is used to control the selective attraction or repulsion of a marking material onto the surface of the photo-conductive layer thereby forming one type of electrostatographic image.

More recently, however, a migration imaging system capable of producing high quality images of high density, continuous tone, and high resolution has been developed. Such a migration imaging system is disclosed in copending application Ser. No. 460,377, filed June 1, 1965, now U.S. Pat. No. 3,520,681. In one embodiment of that system an imaging member comprising a substrate layer with a layer of softenable material overlying the substrate and a third layer comprising photosensitive particles overlying the softenable layer, is imaged in the following manner: a latent image is formed on the member by suitable means, for example, by uniformly electrostatically charging and exposing the uniformly charged member to a pattern of activating electromagnetic radiation. The latently imaged member is then developed by exposing it to a solvent which dissolves only the softenable layer. The photosensitive particles of the third layer which have been exposed to the radiation, migrate through the intermediate softenable layer as it is softened, depositing on the substrate an image of migrated photosensitive particles corresponding to the radiation pattern to which the member was exposed. Where the softening step is performed by simply washing the member in a suitable solvent, the material of the softenable layer along with unmigrated residual portions of the upper layer comprising photosensitive particles, are substantially completely washed away by the liquid solvent. The migrated particles imaged upon the substrate may then be fixed to the substrate. For many photosensitive particles which are preferred for use in such a migration imaging system, the image produced is a negative of a positive original. However, positive-to-positive imaging may be accomplished by varying imaging parameters and materials.

The basic imaging member used in the new migration imaging system is typically in one of three configurations: (1) a layered configuration comprising a substrate, coated with a layer of softenable material, and a fracturable and preferably particulate layer comprising photosensitive material on or embedded at the upper surface of the softenable layer; (2) a binder structure, in which the photosensitive particles are dispersed in the softenable layer overcoating the substrate; or, (3) an overcoated structure, in which a substrate is overcoated with a layer of softenable material, followed by an overlayer comprising photosensitive particles, and a second overlayer of softenable material 2 sandwiching the layer comprising photosensitive particles.

Softenableas used herein is intended to mean any material which can be rendered more permeable thereby enabling particles to migrate through its bulk. Conventionally, changing permeability is accomplished by heat or solvent softening. Fracturable" layer or material as used herein, means any particulate, continuous, or semi-continuous layer or material which is capable of breaking up during development, thereby permitting portions of said layer to migrate towards the substrate or to be otherwise removed.

There are other systems for forming the latent image, wherein non-photosensitive or inert, fracturable layers or particulate material may be used to form said images, as described in copending application Ser. No. 483,675, tiled Aug. 30, 1965, now U.S. Pat. No. 3,656,990. In that application and copending application Ser. No. 725,676, filed May I, 1968, now abandoned, as well as the present application, a variety of methods which may be used to form the latent image upon the migration imaging member are disclosed.

Likewise, various means for developing latent images in the novel migration imaging system are known. Typi cal developing means include solvent washaway, as described above, solvent vapor softening, heat softening and combinations of these methods. In another mode of development, if the softenable layer is at least partially left behind on the substrate, it has been found that the unmigrated fracturable material remaining on the imaging member after development may be adhesively stripped off to yield complementary positive and negative images, as disclosed for example, in copending application Ser. No. 642.8 30, filed June 1 1967 now U.S. Pat. No. 3,740,216.

In new and growing areas of technology such as migration imaging systems suitable for use in the present invention, new methods, apparatus, compositions of matter, and articles'of manufacture continue to be discovered for the application of the new technology in a new mode. The present invention relates to a new and advantageous system for the development of latent images in such migration imaging systems. I

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a novel imaging system.

It is another object of this invention to provide a novel imaging system wherein marking material is selectively displaced in image configuration.

It is another object of this invention to provide a novel imaging system wherein photosensitive material is selectively displaced in image configuration.

It is another object of the invention to provide a novel imaging member.

It is another object of this invention to provide a development system for migration imaging members, which system produces high quality images of high resolution, low background, and excellent solid area coverage.

It is another object of this invention to provide images having lesser amounts of extraneous marking materials in background (non-image) areas.

It is another object of this invention to provide an imaging system capable of positive-to-positive, or positive-to-negative imaging.

It is 'yet another object of this invention to provide an imaging system capable of producing complementary negative and positive images from the same imaging member.

It is still another object of this invention to provide a migration imaging system which is more suitable for automatic imaging apparatus.

The foregoing objects and others are accomplished in accordance with this invention by the novel migration imaging system, comprising a migration imaging member comprising migration material in or on a softenable layer said member having a conductive receiving layer, and a system for developing migration imaging members comprising applying a developing medium to an imaging member and having said member adjacent a development electrode.

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:

FIGS. 1(a) and 1(1)) show partially schematic crosssectional views (a) and (b) of typical migration imaging members suitable for use in preferred embodiments of the inventive system.

FIGS. 2(a) to 2(d) illustrate process steps suitable for usein a preferred embodiment of the inventive system.

FIGS. 3(a) to 3(e) illustrate the process steps in another preferred embodiment of the present inventive system.

FIGS. 4(a) and 4(b) show cross-sectional views of preferred embodiments of the novel migration imaging member of the present invention.

FIGS. 5(a) to 5(e) illustrate the process steps in another preferred embodiment of the present inventive system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, one embodiment of an imaging member suitable for use in a migration imag ing system is shown in a partially schematic view in FIG. 1(a). This typically comprises a substrate 11 coated with a layer of softenable material 12 in which particles 13 of a suitable marking material are dispersed. Another embodiment of a migration imaging member is shown in FIG. 1(b) wherein the member 10 typically comprises substrate 11 coated with layer of softenable material 12, and fracturable or particulate layer 13 comprising migration marking material is contiguous the upper surface of the softenable layer. In various embodiments, the marking material may be coated onto, slightly embedded in, or substantially embedded in the softenable material of layer 12 at the upper surface of that layer.

The substrate and other layers of the migration imag ing member may generally be in any suitable form such as a strip, sheet, plate, coil, cylinder, drum, endless belt, circular disk or the like, depending upon the specific embodiment of the novel migration imaging system.

In various embodiments of the inventive imaging system, the preferred substrate may be electrically conductive or insulating. However, in certain embodiments the substantially electrically insulating substrate is the more preferable substrate. In addition. the substrate should be substantially insoluble in any solvent which may be used for developing such migration imaging members.

The softenable layer may be coated directly onto the insulating substrate, or alternatively, the softenable layer may be formed separately from the desired substrate and may be brought into contact with a suitable substrate during imaging. The softenable layer may comprise one or more layers of softenable material. The softenable layer should preferably be substantially electrically insulating for use in preferred modes of migration imaging by applying electrical migration forces to the migration layers; but, more conductive materials may be used in other electrical modes of the imaging system wherein a constant and replenishing supply of charges in image configuration is applied to the imaged member. The softenable layer may be of any suitable thickness. However, imaging thicker layers generally requires a greater electrostatic potential in a given mode of the migration imaging system. Thicknesses in the range of about /2 to about 16 microns have been found preferable for use in such imaging systems.

Materials suitable for use as softenable layers and marking materials in such migration imaging systems, are more fully discussed in copending applications Ser. No. 725,676, filed May I, 1968, now abandoned, and Ser. No. 634,757, filed Apr. 28, 1967, now abandoned. Marking materials suitable for use in migration imaging members may be insulating, conductive, magnetic, or photosensitive in various embodiments of the imaging member. In the preferred electro-optical mode of migration imaging, the migration marking material is typically electrically photosensitive.

The electrically photosensitive material or particles, portions of which migrate during image formation, may comprise any suitable electrically photosensitive material which is not readily soluble in any of the media used to soften the softenable layer during development of the migration imaging member. Preferably, photosensitive materials in particle form should be about 0.01 to about 3 microns in size and optimally about 0.5 to about 1 microns in size for optimum resolution and otherwise high quality images according to this invent1on.

Electrically photosensitive particles as used herein refers to any particles which when dispersed in a softenable, electrically insulating binder or matrix layer as described herein, in response to electrical charging, imagewise exposure to activating radiation, and contact with suitable softening media, are caused to selectively deposit in positive or negative image configuration on a substrate or on an appropriate receiving layer.

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. Apparently the necessary effect according to the invention is the selective relocation of charge into, within or out of the material or particles, said relocation being effected by light acting on the bulk or surface of the electrically photosensitive material, by exposing said material or particle to activating radiation which may specifically include photoconductive effects, photoinjection, photoemission, photochemical effects and others which cause said selective relocation of charge.

Materials typically suitable for use as insulating substrates include films of polystyrene; cellulose acetate; polyester films such as polyethylene terephthalate film (e.g., Mylar available from Dupont); polyamide films such as those prepared from caprolactam Nylon 66; polyolefin films such as extruded polyethylene or biaxially oriented polypropylene; films prepared from polyacrylonitrile and copolymers thereof; plastic coated papers; acrylic sheets such as Lucite; glass; films of polytetrafluoroethylene and poly chloro-fluoro ethylene resins such as Duponts Teflon and 3Ms Kel-F; mixtures and combinations of the above, and other insulating materials generally known in the art.

Particularly satisfactory insulators include Mylar polyester film available from the E. I. duPont deNemours Co., Inc., usually used in a thickness from about 2 to 5 mils; and polyethylene coated paper available under the tradename Polygleam available from Crocker-Hamilton Division of Weyerhaeuser Corporation.

Materials typically suitable for use as electrically conductive substrates include: 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. If desired, the conductive substrate may be coated on an insulator such as paper, glass, or plastic. One example of this type of substrate comprises NESA glass, which is 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 deNemours Co., Inc., having a thin, substantially transparent aluminum coating. Another typical substrate comprises Mylar coated with copper iodide. Others include conductive resin coated films such as Dow Resin 2611-7 (Dow Chemical Company) or Conductive Polymer 261 (Calgon Corporation).

The imaging method illustrated in FIG. 2 includes an optional precharging step as first disclosed in copending application Ser. No. 645,192, filed June 12, 1967, now abandoned. It is seen in FIG. 2(a), that the imaging member 10 comprising marking particles 13, which are here electrically photosensitive particles, dispersed in softenable layer 12 coated on a substantially electrically insulating substrate 11, is placed upon a grounded conductive member 14 and the imaging member is charged with a negative polarity at 15 while being uniformly flooded with activating electromagnetic radiation, light for example, from source 16. In FIG. 2(b), the source of activating radiation,.here light, has been removed, and a positive electrostatic charge is then applied to surface 17 of the imaging member by a corona charging device 18 or other equivalent means while maintaining the imaging member in darkroom conditions as disclosed in Steinhilper US. Pat. No.

2,955,938. In FIG. 2(0), the charged imaging member is exposed to a pattern of activating electromagnetic radiation, such as light, exposing the charged imaging member in areas 20 and leaving it unexposed in areas 21, thereby forming an electrostatic latent image or other electrical latent image which may be developed by any suitable development technique.

An electrical latent image is intended to mean any electrical imagewise migration force acting on the charged marking materials in the present system. This includes electrostatic latent images" which are well known in the xerographic arts and are detectable with equipment such as a Monroe Electrometer, available from Monroe Electronics, Webster, N.Y., which measures surface potentials and differences in surface potential to a sensitivity of about -5 volts. The latent images formed in the electrical-optical mode of the present invention are typically not readily detectable by such electrometric techniques. In contrast to an electrostatic latent image, for example as found in commercial xerographic processes using an amorphous selenium photoconductor where surface potentials in image areas typically differ by at least about 600 volts,

the latent images formed in the preferred chargeexpose mode of the present system typically show no readily detectable change in the electrostatic or cou lombic force after exposure, although migration in image configuration still occurs when the softenable material is softened.

FIG. 2(d) illustrates the imaged migration imaging member being developed by exposure to liquid solvent 22 in a system including novel development electrode 23 of the present inventive system. The development electrode may be grounded, or electrically biased. Development electrode 23 enhances the removal of unmigrated marking particles from background areas 24 of an imaged migration imaging member, thereby facilitating production of sharp, positive images 25 of excellent resolution, low background, and excellent solid area coverage upon the substrate ofthe imaging memher.

It will be appreciated that through the use of selected materials, the sequence of the charging polarities may be reversed thereby utilizing a positive charge first and a negative charge second. In addition, the surface of the imaging member may optionally be flooded with light following the optional initial charging step rather than simultaneously with it, while still achieving the desired result of uniform charging.

The novel imaging system of the present invention differs from former migration imaging systems and particularly from former migration imaging development systems in that in the advantageous system of the present invention unmigrated marking par'ticlesare repelled from the imaging member and attracted to the development electrode, whereas in former systems, the primarymovement of marking particles was the movement of particles in unexposed imaged areas'of the migration imaging member toward the substrate of said member. In the inventive system as shown and described in FIG. 2, during the optional charging step with ambient light as illustrated in FIG.2(a) it is believed that negative charge carriers are forced to interface 19 between the softenable layer and the substantially insulating substrate, and that such charges are trapped there by the attraction of the opposite charge in the conductive, grounded member '14. When the source of activating radiation, here light, is removed, it is believed that negative carriers are trapped at interface 19. Then, during the positive charging step illustrated in FIG. 2(b) it is believed that corresponding negative charge from the conductive ground allows the imaging member to be positively charged at the surface, and negatively charged at interface 19. During the exposure step illustrated in FIG. 2(c), the charges trapped on the imaging member during the charging steps are dissipated in the background areas as the imaging member is affected by the activating radiation, here light.

Migration imaging members have typically been developed by exposure to liquid solvents, vaporous solvents, or exposure to heat, sufficient to soften the softenable layer of the imaging member. In former development systems, the primary movement of marking particles was, typically, the movement of particles in the unexposed imaged areas toward the substrate of the migration imaging member. However, suprisingly, the

advantageous system of the present invention by its imagewise repulsion process gives rise to positive images upon the substrate of the imaging member. Quite unexpectedly it is found that there is an imagewise repulsion of charged particles from the illuminated background areas of the imaged member to the grounded development electrode. In this process the marking particles which are freed from the matrix of the softenable layer by the action of the solvent upon said softenable layer, are observed to quickly migrate away from the migration imaging member and adhere to the grounded development electrode. In this way substantially all of the marking particles in the illuminated background areas of the imaged member are removed from the member itself, leaving a positive image of excellent quality upon the substrate of the imaging member. The present system is most advantageous in that there is an even lesser tendency than in earlier systems for unmigrated marking particles to remain in background areas of the imaged member.

The development electrode 23 illustrated in FIG. 2(d) may be made of any suitable conductive material. The obvious limitation is that the electrode be substantially unaffected by the solvent being used for the development of the imaging member. Aluminum, copper, stainless steel, and other metallic conductors, tin oxide coated NESA glass available from Pittsburg Plate Glass Co., metallized Mylar film available from Dupont, paper coated with evaporated aluminum or conductive resin compositions, and even highly humidified papers and cellophane films are suitable for use as electrode materials in the present invention. The development electrode is typically electrically grounded or electrically biased in order to promote the development process. Electrical biases in the range of about -200 volts are suitable for use in the inventive system. Depending upon the specific materials used, either positive or negative polarity may be applied to the development electrode.

FIG. 3 illustrates the process steps in another preferred embodiment of the advantageous imaging system of the present invention. In FIG. 3(a), a migration imaging member such as that illustrated in FIG. 1, is negatively charged by corona charging device 26 in the presence of light 27. The light is then removed, and as shown in FIG. 3( b), the imaging member is positively charged by corona device 28. The charged imaging member then remains positively charged at its upper surface 29, and negatively charged at the interface 30 between the'softenable material 12 and the substrate 11. In FIG. 3(a), the positively charged imaging member is shown being exposed to a Iight-and-shadow image with light impinging upon the member at 31, and the unexposed imaged areas remaining charged at 32. FIG. 3(d) shows an imaged member to which conductive receiving layer 33 has been applied, and to which a developing medium is being applied through said conductive receiving layer by means of roller 34. It will be understood that the developing medium may be ap- I plied by any one of a variety of means including the illustrated solvent roller, a solvent spray system, a solvent bath, various means for applying vaporous solvents, or various means for applying heat. It will 'be appreciated that the developing medium will typically be sufficiently electrically resistant to permit migration of the marking material before the imaging member is discharged.

In the development step illustrated in FIG. 3(d), the conductive receiving sheet is electrically grounded or electrically biased and performs the function of the development electrode illustrated in FIG. 2(d).

After the application of the development medium which softens the softenable layer of the imaging member, in the presence of the development electrode which is here in the form of the conductive receiving sheet, said receiving sheet is removed from the migration imaging member as shown in FIG. 3(e), andin this mode of the advantageous migration imaging system, the positive image 35 is adhered to the conductive receiving layer 33. The substrate 11, which in the embodiment illustrated in FIG. 2, supported the positive image, here supports the negative image 36 corresponding to the positive image 35 which has been transferred to the conductive receiving layer 33. Surprisingly, when the development electrode, here the conductive receiving layer, is itself in contact with the imaging member, the image produced on the substrate of the member is a negative of the original, and the image on the receiving layer is the positive image.

Where the conductive receiving sheet is in contact with the exposed imaging member, the spacing between the charged migration marking particles and the receiving sheet becomes small compared to the spacing between the charged particles and the induced counter-charge at the substrate interface with the softenable material. Therefore it is believed that the capacitance between the particles and the conductive receiving sheet becomes larger than the capacitance between the charged particle and its corresponding induced counter-charge. Hence, the electric field lines of force are re-directed from particle to receiving sheet in proportion to this capacitance ratio, and the particle is then attracted to the receiving sheet, thereby producing a positive image of a positive original on the receiving sheet. This theory is believed to explain the image reversal in the process illustrated in FIG. 2 as compared with the process illustrated in FIG. 3.

It is therefore seen that in the preferred embodiment of the present migration imaging system illustrated in FIG. 3, the conductive receiving layer 33 is itself typically not substantially soluble in the development medium used, and it is also sufficiently conductive to perform the function of the development electrode in the development system. It is also most advantageous for ample fixing methods and materials are disclosed in copending applications Ser. No. 590,959, filed Oct. 31, 1966, now abandoned, and Ser. No. 695,214, filed Jan. 2, 1968, now abandoned.

FIG. 4 illustrates novel imaging members for use in another preferred embodiment of the present inventive system. The novel migration imaging member in FIG.

4(a) comprises substrate 11 supporting softenable layer l2 wherein marking particles 13 are dispersed. and conductive receiving layer 33 overlying the matrix of softenable layer and marking particles. In Fig. 4(b) the novel migration imaging member comprises substrate 11 supporting softenable layer 12(i) over which fracturable layer 13 of marking material is coated or embedded. This embodiment further includes a second softenable layer 12 (ii) coated over marking material 13. Conductive receiving layer 33 overlies the softenable layers 12(ii).

Materials suitable for use in the substrate, softenable layer, and marking material portions of the novel migration imaging member are the same as those described as suitable for use in the migration imaging member illustrated in FIG. 1 above.

Materials which have been found suitable for use as conductive receiving layer 33 in the novel imaging member in the advantageous system of the present invention include conductive papers such as 48 l electrostatic base stock, 60 No., West Virginia Pulp and Paper Company; Conductive Copy Base A No. 7850-8, from Crocker Hamilton Papers, a division of Weyerhauser Corporation; moistened 914 Bond, Xerox Corporation; Zinc Oxide Paper, Bruning Pre- 1 mium, Charles Bruning Company; Polyvinyl Alcohol OS Base, type P-1096, 1997-0, 45No., Standard color, Lot No. 18949, Crocker Hamilton; Conductive Base Copy C, No. 168118, L-01-41-2, 45 No., Crocker Hamilton; Conductive Copy Base, D-ll9- 13-2, 39 No., 69330, Crocker Hamilton; Conductive Copy Base A, No. 63678, K-0l-40-2, 45 No., Crocker Hamilton; and electroconductive papers (containing silver treated glass fiber) from P. J. Schweitzer Division of Kimberly Clark Company having surface resistivities in the range of about 2 to about 500 megaohms per square; and any other suitable conductive, preferably porous material. Conductive receiving layers having resistances of less than about 10 ohm-cm, and thicknesses less than about 200 microns are preferred for use in the present system.

In FIG. 5 yet another preferred embodiment of the advantageous invention of the present system is illustrated using the novel migration imaging member illustrated in FIG. 4. FIGS. 5(a) and (b) illustrate the double charging procedure already described in conjunction with FIGS. 2(a) and (b), and 3(a) and (b). In FIG. 5(0), the novel migration imaging member already charged as illustrated in FIGS. 5(a) and (b), is shown being imaged by exposure through the substantially transparent base material 38. In FIG. 5(d), the developing medium is being applied as discussed in conjunction with FIG. 3(d), and in FIG. 5(e), the complementary negative and positive images are shown being separated, with the positive image adhering to the conductive receiving layer. and the corresponding negative image remaining on the substantially insulating substrate, as discussed with respect to FIG. 3(e).

Yet another preferred embodiment of the advantageous system of the present invention uses the process steps essentially the same as those shown in FIG. 5, except that the novel migration imaging member is exposed through a conductive receiving layer which is substantially transparent. It will be appreciated that a receiving layer for use in this process must necessarily be transparent to allow sufficient light or other electromagnetic radiation to pass therethrough so that a sharp image is formed by the unexposed areas on the imaging member. As in other embodiments of the advantageous system of the present invention, the softening step and the separation step may be performed by any suitable means.

The following examples further specifically define the advantageous migration imaging system of the present invention. The parts and percentages are by weight unless otherwise indicated. The examples below are intended to illustrate various preferred embodiments of the imaging system of the present invention.

EXAMPLE I A migration imaging member suitable for use in the present inventive system is constructed using a matrix of photosensitive particles in a softenable material, said matrix consisting of an about 1:3 ratio of x-form metalfree phthalocyanine to Piccopale -SF, a petroleum hydrocarbon resin with a color of G-lO on the Gardner scale, which is available from Pennsylvania Industrial Chemical Co., and said matrix is ground in a long-chain saturated aliphatic hydrocarbon liquid, boiling point 3 l5350F., lsopar G solvent, available from Humble Oil Co., thoroughly mixed on a paint shaker, and coated onto an insulating Mylar polyester film, available from E. l. duPont deNemours and Co., Inc., of about 3 mils in thickness. The imaging member is then dried for 10 minutes at about 50C.

The above imaging member is then laid on an electrically grounded conductive base plate, with the exposed side of the Mylar film in contact'with the conductive base plate. In ambient illumination, the imaging member on the conductive base plate is negatively charged.

Then in darkness, the imaging member still on the conductive base plate is recharged positively. The charged imaging member is then exposed to a pattern of lightand-shadow images illuminated to about 0.8 fcs (footcandle-seconds) of tungsten illumination. The imaging member then supporting an electrostatic latent image is developed by immersion in xylene solvent while the side of the imaging member supporting the migration material is closely spaced adjacent to a grounded metal electrode within the solvent bath.

This imaging member and process gives sharp, clean positive images with very low background, on the original Mylar substrate, and corresponding negative images on the development electrode.

EXAMPLE II A migration imaging member suitable for use in a preferred embodiment of the present inventive system is produced using a sheet of Polygleam polyethylene coated paper from Crocker Hamilton Papers Division, Weyerhauser Paper Company, Fitchburg, Mass, as the insulating substrate. The Polygleam substrate is coated with a layer of a micro-imaging matrix comprising about a 1:3 ratio of x-form metal-free phthalocyanine to Piccopale 70-SF (thermoplastic hydrocarbon resin) which is ground in lsopar G solvent, and thoroughly mixed on a paint shaker. The matrix coating is applied using an 0.0005 inch Bird applicator bar and a mechanical drive unit from Gardner Laboratories, lnc. The migration imaging member is then air dried for half an hour.

The imaging member is then charged negatively in the presence of ambient illumination. Then in darkness, the imaging member is charged positively. Next the charged imaging member is exposed to a light-andshadow image of about 20 fcs (foot-candle-seconds) of light produced from a tungsten filament at about 2,800K projected through a positive transparency. A sheet of water vapor pre-moistened 914 Xerox bond paper (Xerox Corp., Rochester, N.Y.) is placed in contact with the side of the migration imaging member containing the migration material, and the developing solvent, Freon 1 l3, trifluoro trichloroethane, manufactured by E. l. duPont deNemours and Co., Wilmington, Delaware, is applied through the conductive receiving sheet. A type 72Q inch diameter, 4 inch wide, gravure roller, available from Parmarco lnc., Roselle, N. J is passed over the receiving sheet once with moderate manual pressure. The receiving sheet is then separated from the imaging member.

A positive image is obtained on the conductive receiving sheet, and a corresponding negative pattern remains on the Polygleam substrate of the imaging member. Upon drying, the sharp, positive image on the conductive receiving sheet becomes fixed within and to the receiving sheet. The negative image on the Polygleam substrate of the imaging member remains unfixed due to the nearly complete removal of the matrix binder in the development step.

EXAMPLE III A migration imaging member is prepared and processed as in Example 1, except the exposure step is performed through the transparent Mylar substrate which is in contact with the electrically grounded'conductive base plate which is a sheet of substantially transparent tin oxide coated NESA glass available from the Pittsburgh Plate Glass Co.

EXAMPLE IV A migration imaging member suitable for use in a preferred embodiment of the inventive system is produced using a matrix of photosensitive particles in a softenable material, said matrix comprising about 10 grams of elemental selenium alloyed with arsenic (two percent by weight of arsenic), about 5 grams of a copolymer of hexylmethylacrylate and styrene and about 13 grams of toluene, which is milled in a ball mill jar with flint balls of size 000 for about 96 hours. The milling balls arethen removed from the solution, and the matrix solution is coated onto a Mylar polyester substrate,,available from duPont, with a Gardner Draw This imaging member is then imaged by the process of Example 1, and is developed by immersing it for a few seconds adjacent a grounded metal electrode in a trichloroethylene bath. This imaging member and process gives sharp, clean images with very low background.

EXAMPLE V A migration imaging member is prepared using the binder matrix described in Example ll coated onto an electrically conductive aluminized Mylar film, an aluminum coated polyester film available from duPont, as the substrate. This imaging member is charged. exposed and developed as in Example ll, using a sheet of pre-moistened 914 Xerox bond paper as the conductive receiving sheet and Freon l 13, trifluoro trichloroethane solvent as the developing medium. Images similar to those produced in Example [I are produced by this system.

Although specific components, proportions and procedures have been stated in the above description of the preferred embodiments of the novel migration imaging system, other suitable materials, as listed above, may be used with similar results. In addition, it may be that other substances exist or may be discovered, that have some or enough of the properties of the particular substances described herein to be used as substitutes, or that other materials and procedures may be employed to synergize, enhance or otherwise modify the novel migration imaging system.

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

What is claimed is: a

1. An imaging method comprising:

providing an imaging member comprising a substrate supporting a layer of substantially electrically insulating softenable material containing migration marking material, said softenable material capable of having its resistance to migration of migration marking material decreased sufficiently to allow migration of migration marking material in depth in said softenable layer,

forming an electrical latent image on said member,

and thereafter placing an electrically conductive receiving layer in contact with the softenable layer of the imaging member, said electrically conductive receiving layer being electrically biased or electrically grounded, and

developing said member by decreasing the resistance of the softenable material to migration of migration marking material in depth in the softenable material at least sufficient to allow migration of migration marking material at least in depth in said softenable material whereby the migration marking material selectively migrates in a first image configuration toward said conductive receiving sheet and in a second image configuration complementary to said first image configuration toward said substrate.

2. The method of claim 1 wherein the conductive receiving layer is permeable to a fluid solvent.

3. An imaging method comprising:

providing an imaging member comprising a substrate supporting a layer of solvent soluble electrically insulating material containing migration marking material,

forming an electrical latent image on said imaging member,

providing an electrode closely spaced adjacent the free surface of said layer of solvent soluble electrically insulating material, said electrode being electrically grounded or electrically biased without an insulating blocking layer between said imaging member and said electrode, and

providing a liquid solvent for said solvent soluble material between said layer of said solvent soluble material and said electrode whereby migration marking material selectively migrates in a first imagewise configuration toward said substrate and in a second imagewise configuration complementary to said first imagewise configuration toward said electrode.

4. The method of claim 3 wherein said substrate is substantially electrically insulating.

5. The method of claim 4 wherein the migration marking material is particulate material and said particulate migration marking material is dispersed throughout the layer of solvent soluble material.

6. The method of claim '4 wherein the migration marking material is in the form of a fracturable layer of migration marking material contiguous the surface of the layer of the solvent soluble material spaced apart from the substrate.

7. The method of claim 6 wherein the imaging member additionally comprises a second layer of solvent soluble electrically insulating material overlying the fracturable layer of migration marking material.

8. The method of claim 3 wherein the solvent is provided between the layer of solvent soluble material and the electrode by placing said imaging member and said electrode in a volume of said solvent.

9. The method of claim 4 wherein the migration marking material comprises electrically photosensitive material.

10. The method of claim wherein the migration marking material comprises electrically photosensitive material.

11. The method of claim 9 wherein the electrical latent image is provided by steps comprising substantially uniformly electrostatically charging the surface of the imaging member, and imagewise exposing said member with an image pattern of activating electromagnetic radiation.

12. The method of claim 10 wherein the electrical latent image is provided by steps comprising substantially uniformly electrostatically' charging the surface of the imaging member with a charge of a first polarity, and imagewise exposing said member with an image pattern of activating electromagnetic radiation.

13. The method of claim 12 wherein before performing the charge and expose steps of claim 12the imaging member is pre-charged by steps comprising:

contacting the electrically insulating substrate to an electrically grounded electrically conductive member, and

substantially uniformly electrostatically charging said member with a charge of opposite polarity from said first polarity, while simultaneously substantially uniformly flooding said member with activating electromagnetic radiation.

14. The method of claim 12 wherein the migration marking material in the imagewise unexposed areas of the imaging member migrate in said first imagewise configuration toward the electrically insulating sub: strate, and the migration marking material in the imagewise exposed areas of the imaging member migrate in said second imagewise configuration complementary to said first imagewise configuration toward said electrode.

15. The method of claim 3 wherein said layer of solvent soluble material is of a thickness in the range between about /z'and about 16 microns.

16. The method of claim 3 wherein said migration marking material is particulate material of average particle size in the range between about 0.01 and about 3 microns.

17. The method of claim 16 wherein said particulate migration marking material is of average particle size in the range between about 0.5 and about 1 micron.

18. The method of claim 1 wherein said substrate is substantially electrically insulating.

19. The method of claim 1 wherein said substrate is substantially electrically conductive.

20. The method of claim 1 wherein said substrate is substantially transparent.

21. The method of claim 1 wherein the migration marking material is particulate material and said particulate migration marking material is dispersed throughout the layer of softenable material.

22. The method of claim 1 wherein the migration marking material is in the form of a fracturable layer of migration marking material contiguous the surface of the layer of softenable material spaced apart from the substrate.

23. The method of claim 22 wherein the imaging member additionally comprises a second layer of substantially electrically insulating softenable material overlying the fracturable layer of migration marking material.

24. The method of claim 1 wherein the migration marking material comprises electrically photosensitive material. v

25. The method of claim 24 wherein the electrical latent image is provided by steps comprising substantially uniformly electrostatically charging the surface of the imaging member with a charge of one polarity and imagewise exposing said member with an image pattern of activating electromagnetic radiation.

26. The method of claim 24 wherein said layer of substantially electrically insulating softenable material is of a thickness in the range between about /2 and about 16 microns.

27. The method of claim 1 wherein said migration marking material is particulate material of average particle size in the range between about 0.01 and about 3 microns.

28. The method of claim 27 wherein said particulate material is of aveage particle size in the range between about 0.05 and about 1 micron.

29. The method of claim 1 wherein said member is developed by applying a liquid solvent for said softenable material to the imaging member whereby portions of said electrically insulating layer and selective portions of said migration marking material are removed and selective other portions of said migration marking material migrate at least in depth toward said substrate.

30. The method of claim 1 wherein said member is developed by applying a vaporous solvent for said softenable material to the imaging member, said vaporous solvent being at'least capable of softening said softenable material to allow migration of said migration marking material.

31. The method of claim 1 wherein said member is developed by heating the softenable material sufficiently to soften the softenable material to allow migration of said migration marking material.

32. The method of claim 25 wherein the substrate is substantially electrically insulating and the migration marking material comprising electrically photosensitive material is dispersed throughout the layer of softenable material and wherein before performing the charge and exposesteps of claim 25, the imaging member is precharged'by steps comprising:

contacting the electrically insulating substrate to an electrically grounded electrically conductive member. and

substantially uniformly electrostatically charging said member with a charge of opposite polarity from the said one polarity of charge used in the subsequent charge step, while simultaneously substantially uniformly flooding said member with activating electromagnetic radiation.

33. The method of claim 1 comprising separating the receiving sheet and the imaging member.

34. The method of claim 29 comprising separating the receiving sheet and the imaging member.

35. The method of claim 29 wherein said electrically insulating layer and said selective portions of said migration marking material are substantially removed and said selective other portions of said migration marking material are deposited on said substrate in image con-

Claims

1. AN IMAGING METHOD COMPRISING: PROVIDING AN IMAGING MEMBER COMPRISING A SUBSTRATE SUPPORTING A LAYER OF SUBSTANTIALLY ELECTRICALLY INSULATING SOFTENABLE MATERIAL CONTAINING MIGRATION MARKING MATERIAL, SAID SOFTENABLE MATERIAL CAPABLE OF HAVING ITS RESISTANCE TO MIGRATION OF MIGRATION MARKING MATERIAL DECREASED SUFFICIENTLY TO ALLOW MIGRATION OF MIGRATION MARKING MATERIAL IN DEPTH IN SAID SOFTENABLE LAYER, FORMING AN ELECTRICAL LATEN IMAGE ON SAID MEMBER, AND THEREAFTER PLACING AN ELECTRICALLY CONDUCTIVE RECEIVING LAYER IN CONTACT WITH THE SOFTENABLE LAYER OF THE IMAGING MEMBER, SAID ELECTRICALLY CONDUCTIVE RECEIVING LAYER BEING ELECTRICALLY BIASES OR ELECTRICALLY GROUNDED, AND DEVELOPING SAID MEMBER BY DECREASING THE RESISTANCE OF THE SOFTENABLE MATERIAL TO MIGRATION OF MIGRATION MARKING MATERIAL IN DEPTH IN THE SOFTENABLE MATERIAL AT LEAST SUFFICIENT TO ALLOW MIGRATION OF MIGRATION MARKING MATERIAL AT LEAST IN DEPTH IN SAID SOFTENABLE MATERIAL WHEREBY THE MIGRATION MARKING SELECTIVELY MIGRATES IN A FIRST IMGAGE CONFIGURATION TOWARD SAID CONDUCTIVE RECEIVING SHEET AND IN A SECOND IMAGE CONFIGURATION COMPLEMENTARY TO SAID FIRST IMAGE CONFIGURATION TOWARD SAID SUBSTRATE.

3. An imaging method comprising: providing an imaging member comprising a substrate supporting a layer of solvent soluble electrically insulating material containing migration marking material, forming an electrical latent image on said imaging member, providing an electrode closely spaced adjacent the free surface of said layer of solvent soluble electrically insulating material, said electrode being electrically grounded or electrically biased without an insulating blocking layer between said imaging member and said electrode, and providing a liquid solvent for said solvent soluble material between said layer of said solvent soluble material and said electrode whereby migration marking material selectively migrates in a first imagewise configuration toward said substrate and in a second imagewise configuration complementary to said first imagewise configuration toward said electrode.

6. The method of claim 4 wherein the migration marking material is in the form of a fracturable layer of migration marking material contiguous the surfAce of the layer of the solvent soluble material spaced apart from the substrate.

10. The method of claim 5 wherein the migration marking material comprises electrically photosensitive material.

12. The method of claim 10 wherein the electrical latent image is provided by steps comprising substantially uniformly electrostatically charging the surface of the imaging member with a charge of a first polarity, and imagewise exposing said member with an image pattern of activating electromagnetic radiation.

13. The method of claim 12 wherein before performing the charge and expose steps of claim 12 the imaging member is pre-charged by steps comprising: contacting the electrically insulating substrate to an electrically grounded electrically conductive member, and substantially uniformly electrostatically charging said member with a charge of opposite polarity from said first polarity, while simultaneously substantially uniformly flooding said member with activating electromagnetic radiation.

14. The method of claim 12 wherein the migration marking material in the imagewise unexposed areas of the imaging member migrate in said first imagewise configuration toward the electrically insulating substrate, and the migration marking material in the imagewise exposed areas of the imaging member migrate in said second imagewise configuration complementary to said first imagewise configuration toward said electrode.

15. The method of claim 3 wherein said layer of solvent soluble material is of a thickness in the range between about 1/2 and about 16 microns.

20. The method of claim 1 wherein said substrate is substantially transparent.

24. The method of claim 1 wherein the migration marking material comprises electrically photosensitive material.

26. The method of claim 24 wherein said layer of substantially electrically insulating softenable material is of a thickness in the range between about 1/2 and about 16 microns.

30. The method of claim 1 wherein said member is developed by applying a vaporous solvent for said softenable material to the imaging member, said vaporous solvent being at least capable of softening said softenable material to allow migration of said migration marking material.

32. The method of claim 25 wherein the substrate is substantially electrically insulating and the migration marking material comprising electrically photosensitive material is dispersed throughout the layer of softenable material and wherein before performing the charge and expose steps of claim 25, the imaging member is pre-charged by steps comprising: contacting the electrically insulating substrate to an electrically grounded electrically conductive member, and substantially uniformly electrostatically charging said member with a charge of opposite polarity from the said one polarity of charge used in the subsequent charge step, while simultaneously substantially uniformly flooding said member with activating electromagnetic radiation.

35. The method of claim 29 wherein said electrically insulating layer and said selective portions of said migration marking material are substantially removed and said selective other portions of said migration marking material are deposited on said substrate in image configuration.