EP0104626A1

EP0104626A1 - Opaque contact print copy and method of making same

Info

Publication number: EP0104626A1
Application number: EP83109494A
Authority: EP
Inventors: Manfred R. Kuehnle
Original assignee: Coulter Systems Corp
Current assignee: Coulter Systems Corp
Priority date: 1982-09-24
Filing date: 1983-09-23
Publication date: 1984-04-04
Also published as: DK437383A; AU1959083A; ES8501893A1; DK437383D0; BR8305278A; ES525892A0; JPS5979258A; ZA837105B; IL69807A0

Abstract

Method for producing an opaque contact print of at least photographic quality by transferring an electrostatically formed dry toned image reproduced from the photoconductive surface layer (22) of an electrophotographic medium onto an image receptor comprising an opaque substrate on which a coating is bonded comprising one component (the hardener) of a two component polymerizable thermosetting epoxy resin. The coating includes a composition which becomes tacky upon heating. The toner forming the toner image includes the second component of the epoxy resin of the said thermosetting epoxy polymer system. The image receptor is preheated to tackify the coating thereof, engaged (32) with the toner image carrier and separated. The toner adheres to the tacky surface. The image receptor is heated (34) to effect polymerization where the two components are present forming a hard infusible image layer. The toner includes pigments which are transparentized during the reaction to form a highly reflective enhanced image.

Description

. This invention relates generally to electrostatic transfer media for forming permanent print copies of images formed by electrostatic methods and more particularly, provides an image receptor capable of receiving a toned latent electrostatic image from an electrophotographic member or carrier forming an opaque reflective print copy thereof.
Formation of print copies electrostatically by transfer of toned electrostatic images from an electrophotographic member to a secondary carrier is advantageous in the qualities of speed, in that it employs generally chemically-free procedures, does not require skilled technicians and does not require darkroom or other special conditions and equipment. However, where a photographic quality minimum is sought, the advantages of electrostatic reproduction are offset by the resulting generally poor resolution and the considerable loss in optical density. Edge effects often characteristic of most electrostatic reproduction procedures have reduced the acceptance of electrostatic process in high resolution print making.
Various processes have been proposed for producing an image upon a substrate, including photographic processes involving actinic exposure of a photosensitive material carried on a substrate or electrostatic processes involving exposing a charged electrophotographic member having a photoconductive surface coating or layer to radiation to produce an electrostatic latent image. This latent image is rendered visible by application of dry toner particles thereto as in cascade type development, or by wet application thereto of a liquid toner suspension wherein the toner particles have electrophoretic properties.
The production of suitable print reproductions heretofore commonly requires the skill of a trained technician and the substantial expenditure of money and time. Photographic reproduction processes require controlled exposure, development, washing and fixing of a light. sensitive composition present on a support with or without the intermediate production of a negative image..
Xerographic processes have proven to be an easy and reliable technique for the production of reproductions. Notwithstanding the desirability of these imaging processes, drawbacks have been encountered in forming print reproductions in that. the adherence of the image on the transfer support leaves much to be desired. Additionally, some loss of optical density and resolution is experienced upon transfer of the toned image to a receiving member employing prior methods.
Electrophotographic processes require the provision of a suitable image carrier upon which images are formed, these carriers being required to accept an electrical charge and retain the charge sufficiently to enable an image to be formed by application of toner particles thereto. Many materials displaying photoconductivity will not accept a charge initially, and of those which may be charged, few are capable of retaining the charge thereon without leaking off or decaying so rapidly as to be almost useless. In addition .to accepting a charge and retaining the charge in darkness, the photoconductive layer is required to discharge in light areas to a degree which is fairly rapid and generally proportional to the amount of light to which the surface is exposed impinging upon the charged surface. Further, there must be retained a discernible difference between the remaining charged and uncharged layers without lateral movement of the charges.
In U.S. Patent No. 4,025,339, an electrophotographic member is provided with an outer coating of a unique photoconductive material comprising a uniform, microcrystalling, highly ordered, wholly inorganic sputtered deposits having unusual electrical and optical properties highly beneficial to the electrostatic reproduction processes. The resulting coating is electrically anisotropic; electric anisotropy effectively resulting from the field domain of each crystal of the coating Which functions independently in the charge and in the discharge mode without communicating laterally with contiguous crystals. Optical anisotropy is believed to be a result of the single crystal activity of the coating and the uniform vertical orientation of the crystals defining same. Here, during toning, the toner particles are attracted by myriads of individual fields in a magnitude of the individual field strengths of these individual fields, enabling resolution to be achieved which heretofore was unobtainable by electrostatic reproduction methods.
Using conventional electrophotographic processes it was not possible to transfer toner images to surfaces of roughened or irregular surface configuration or to surfaces of stretchable media such as inflatables. It would be advantageous to provide a method whereby the transfer of electrostatically obtained toned images could be applied to surfaces independent of their configuration. Considerable improvement over silk screen processes would be of considerable advantage.
Images normally obtainable electrophotographically are usually "flat" in appearance, lacking depth, and good perspective, i.e. being two dimensioned in character. Prints made photographically or even electrophotographically require overcoating with a clear material to produce a so-called glossy reproduction. It would be highly desirable from a finished esthetic viewpoint to provide greater depth and deeper perspective to the produced print. This would be increasingly acceptable if effected quickly without additional coatings, fixatives, etc. and, of course, performed on an automated basis at lower cost and with no loss of detail in the finished print compared with the original.
Accordingly, the invention provides a method of forming a print copy of an original image pattern characterized by the steps of providing a receptor consisting of an opaque substrate carrying a thin layer formed of one of a transparent thermosetting polymerizable resinous composition and an activator for effecting polymerization thereof, said thin layer being bonded to one surface of the substrate, forming a toner image of an original image pattern electrophotographically on an electrophotographic medium, the toner including the other one of said thermosetting polymerizable resinous composition and activator, transferring said toner image to the said thin layer on said substrate, causing localized polymerization reaction to occur only at the limited locations on the receptor where both the resinous composit ion and the activator together are present forming a permanent image on said substrate, said image being embedded just below the surface of.the thin layer but spaced above the substrate surface.
Further, the invention provides a receptor for use in practicing the above method characterized by_:the layer coating formed of the activator and the toner, the resin. The preferred embodiments of this invention now will be described, by way of example, with reference to the drawings accompanying this specification in which:

FIGURE 1 is a cross-sectional view of the image receptor constructed in accordance with the herein invention;
FIGURE 2 is a view similar to that of FIGURE 1 but showing the image receptor including the chemically reacted . toner image functioning as a finished print reproduction;.and
FIGURE 3 is a flow diagram illustrating the method of making a finished print reproduction according to the invention.

An opaque receptor for receiving a toned, electrostatically formed latent image of a pattern from a carrier thereof. The receptor comprises a substrate of opaque material and a transparent layer including one reactive component of a thermosetting epoxy resin system bonded to at least one surface of said substrate. The toner includes. the other reactive component of said system and a pigment. The carrier with its toner image is brought into engagement with the receptor coating for transfer of the toner image to the surface of said coating image carrier. The receptor . is separated and then reheated to react and form the polymer image. The toner pigment can be transparentized during heating. The product is a highly reflective print having unusually enhanced intensity, contrast and depth due to reflection of light from both the polymer portion and the interface of the unreacted transparent coating and the opaque substrate.
Toning can be effected using dry transfer or wet (electrophoretic)transfer from an electrophotographic medium. In Figure I, the image receptor 10, according to the invention, preferably comprises an opaque imperforate substrate 12 preferably formed of paper, metal, stretchable and/or inflatable media, stone, ceramics and the like having a smooth or a roughened surface.. The substrate 12 may be flexible or rigid and may have a regular or an irregular configuration. A thin layer 14 of one chemical reactant of a thermosetting polymer material is bonded to at least one surface of said substrate. The toner represented in Figure 2 by reference character 16 which defines the toned image carried by the electrophotographic medium is a second chemical reactable with the first mentioned reactant to permanentize the image under reaction conditions effected subsequent to transfer. These may be incresed or raised temperature conditions subsequent to transfer of the toned image to the image receptor. Preferably, the components are heat reactive and the image carrying image receptor is heated to effect the reaction. The process is diagrammatically represented in FIGURE 3 and described hereinafter.
Under the influence of the application of pressure while in engagement, the toner latent image is transferred in its entirety from the image carrier either wet via electrophotretic transfer or dry by heating the image receptor to make the polymer component layer tacky. The print copy then can be separated from the.carrier subsequent to cooling, with the image being retained on the surface of the layer. The resultant image receptor carrying the toner layer is reheated to carry out the desired reaction and the post transfer reaction is effected with no loss of image density, to provide a permanent, opaque print copy of the image, said copy having even higher resolution and improved depth of image than heretofore could be obtainable using conventional chemical photographic processes or other electrophotographic imaging processes.
The transfer is effected completely with no pin holes, fractures or other surface defects resulting.
Suitable materials useful as the imperforate substrate of the print medium may be paper such as printing stock, calendered or uncalendered. Preferably, the thickness of the paper sheet is from 3-to 12 mils.
The principle criteria for selection of a substrate herein is the bondability of the thermosetting polymer component layer thereto and the capability of being heated to effect the desired reaction.
Other materials suitable to function as the substrate include steel sheet, stainless steel, aluminum, stone, rubber and other stretchable materials, including inflatable media. The surface of the substrate may be smooth or roughened. Objects having irregular shapes also may receive the thermosettable layer so long as the configuration and the material does not prevent the chemical reaction to occur.
The preferred material for forming the overcoating on the substrate is the hardener activator component for epoxy type polymers which are two part systems. The epoxy resin component of such system preferably is'carried by the toner particles.
The hardener or activator component layer is coated onto the substrate using conventional coating methods. The coating is transparent and includes a carrier resin which tackifies when the coated substrate is preheated to about 40°_C. The preheating may be accomplished by passing the coated substrate past heating lamps or through a heating tunnel. Immediately subsequent to preheating, the coated image receptor is engaged with the toned image carrier, the toner image preferentially adhering to the tacky layer and is freed completely from the photoconductive surface of the image carrier. The image receptor carrying the toner image is heated further to effect the chemical reaction between the epoxy resin carried by the toner and the activator resin layer at those limited overlaid areas. No toner residue remains on the photoconductive surface of said image carrier. Subsequent to completion of said reaction,-a cooling step may be required.
The imaged areas of the image receptor comprise the polymerized epoxy polymer. The overcoated areas which are unreacted remain clear.
The finished print copy is permanent, has high gloss and high resolution. The substrate carrying the polymer layer is light-reflective, while the coating and the polymerized imaged areas preferably are transparent, the pigmented toner particles are transparentized to pass light through both the layers of generally transparent coating, the polymer pigment to reflect light in a diffuse manner, back-lighting the polymerized toner portions, increasing the intensity and furnishing the brilliance and depth sufficient to give to the viewer a pseudo three-dimensional image. This occurs whether the toners employed are black or are pigmented for color and is particularly effective where paper substrates are employed.
There appears not to be any detectable lateral image spread or change in optical density and resolving power levels on the reflective print as a result of the transfer operation or the reaction taking place between the epoxy system components.

EXAMPLE 1:

An electrophotographic master comprising a substrate carrying a photoconductive coating applied thereto in accordance with the teachings of U.S. Patent 4,025,339 is charged with a negative corona, exposed to the image pattern of an original document and toned with a selected toner. If the toner employed comprises toner particles in insulating liquid suspension, a drying step is required to produce a dry toner image. The toner employed for this example is known as and includes as a part thereof, an epoxy resin component.
A sheet of paper is coated with an epoxy hardener = (activator) such as Versamid 115 to form 2 to 5 A thick layer (in dry state) bonded to a surface of the sheet.
The epoxy activator resin is coated from a methyl ethyl ketone solution thereof (15 percent solids) and the methyl ethyl ketone solvent evaporated. The activator resin coated paper sheet was heated to a surface temperature between 40 and 50°C and the heated layer, now tacky, was brought into engagement with the toner image carried on the photoconductive coating of the electrophotographic member.
The toner image is transferred completely to the resin layer. The image receptor then is heated to about 80°C whereupon the reaction between epoxy carried by the toner is reacted chemically with the underlying resin coating to complete the polymerization and provide the opaque back reflective print. The heating also transparentizes the the toner pigment to provide greater depth to the print than heretofore experienced with electrostatically obtained print copies.
An example of an applicable epoxy resin/hardener system is as follows:

Resin: Epon 1007, Epon being a trademark of Shell.
Hardener: Versamid 115, Versamid being a trademark of General Mills Chemicals, Inc., Minneapolis, Mn.

It is contemplated that the epoxy resin can comprise the overcoating composition bonded to the opaque substrare and accordingly, the hardener would be incorporated in the toner particles at the time of formation.
Some hardener can be incorporated in the epoxy resin during the formation of the toner particles in an amount (quantity) insufficient to effect complete crosslinking, but sufficient to aid in achieving penetration of the softened resin when the heating occurs after image transfer is completed.
The electrophotographic medium represented by the member 20 in FIGURE 3 has a photoconductive surface 22 bonded thereto according to the method disclosed in U.S. Patent 4,025,339. Member 20 is brought to a charging station 24 whereat corona generating device 26 applies a charge potential thereon of a magnitude sufficient to enable formation of a charge gradient latent image which may be toned with toner comprising electroscopic particles to render the invisible latent charge image visible.
The member 20 is advanced to an imaging or exposure station to receive a projected image applied to the charged surface 22 from a projector 28 or the like, establishing a latent charge image thereon.
The exposed member 20 is advanced to the toning station 30 whereat the latent image is rendered visible by application of electroscopic toner particles 1₆, here containing one of the reactive chemical components. The member 20 carrying the toned image is brought to transfer station 32 where it is dried in preparation for transfer to the receptor 10.
The receptor 10 is formed by coating the substrate 12 here with a layer of the epoxy resin hardener (activator) component 14. The receptor 10 then is heated to soften the coating 14 and brought with the overcoat in softened condition sufficiently tacky to receive and preferentially hold the toner image at the transfer station. Pressure such as applied by a heated roller or unheated roller, e.g. formed of stainless steel may be applied simultaneously with transfer and/or the heating stage after transfer.
The receptor 10 carrying the transferred toner image on the overcoat is brought to aheating station 34 where the polymerization takes place at the location where both components are in contact which react to produce the finished print. The toner particles also contain a pigment which is transparentized during the second heating period.
Transfer of the toner image is complete and the photoconductive surface of the electrophotographic member is washed with a solvent, if necessary, to remove any epoxy resin hardener (activator) component present, leaving the member 20 ready for reuse.
The finished print functions as an excellent reflective print giving fine depth and perspective to the viewer, increased intensity and contrast.

Claims

1. A method of forming a print copy of an original image pattern characterized by the steps of:

1) providing a receptor consisting of an opaque substrate carrying a thin layer formed of one of a transparent thermosetting polymerizable resinous composition and an activator for effecting polymerization thereof, said thin layer being bonded to one surface of the substrate,

2) forming a toner image of an original image pattern electrophotographically on an electrophotographic medium, the toner including the other one of said thermosetting polymerizable resinous composition and activator,

3) transferring said toner image to the said thin layer on said substrate,

4) causing localized polymerization reaction to occur only at the limited locations on the receptor where both the resinous composition and the activator together are present forming a permanent image on said substrate, said image being embedded just below the surface of the thin layer but spaced above the substrate surface.

2. The method according to claim 1 characterized in that the toner includes an epoxy resin composition and the coating includes the activator for said epoxy resin.

3. The method according to claim 1 or 2 also characterized in that the toner/includes the activator in quantity insufficient to effect complete crosslinking of the epoxy resin composition.

4. The method according to any one of claims 1, 2 or 3 characterized by the step of heating the receptor after transfer of the toner image thereto.

5. The method according to any one of claims 1 to 4 characterized in that the polymerization is effected by heat and localized-application of pressure.

6. The method according to any one of claims 1 to 5 characterized in that the toner image is transferred electrophoretically to the coated substrate and dried.

7. The method according to any one of claims 1 to 5 characterized in that the toner image is transferred electrophoretically to the coated substrate and dried and the toner image is transferred as a dry image.

8. The method according to any one of claims 1 to 7 characterized by the step of preheating the coated substrate before transfer of the toner image thereto and effecting the localized polymerization subsequent to the transfer of said toner image to the preheated coated substrate.

9. The method according to any one of claims 1 to 8 characterized in that the reacted toner particles are planar and are embedded below the surface of the coating.

10. The method according to any one of claims 1 to 9 characterized in that the activator is removed from the untoned areas subsequent to completion of the localized polymerization at the toned areas.

11. The method according to any one of claims 1 to 10 characterized in that the substrate is opaque.

12. The method according to any one of claims 1 to 11 characterized in that the activator is incorporated in a binder capable of being made tacky by heat.

- 13. The method according to any one of claims 1 to 12 characterized in that the substrate is formed of paper and/or metal sheet material.

14. A receptor for use in practicing the method of any one of claims 1 to 13 characterized by a substrate, a thin layer of a polymerizable resinous composition bonded to a surface of said substrate, said layer capable of receiving a toner image from the carrier wherein the toner includes an activator for effecting localized polymerization of said resinous composition to form a permanent image embedded in said layer below the top surface thereof.

15. A receptor for use in practicing the method of any one of claims 1 to 13 characterized by a substrate, a thin layer bonded to a surface of said substrate, and formed of an activator reactable with a polymerizable resinous thermosetting composition and said layer capable of receiving a toner image from the carrier, said toner particles forming the toner image carrying a polymerizable resinous thermosetting composition reactable with said activator for effecting localized crosslinked polymerization of said resinous composition to form a fixed permanent image.

16. The receptor according to claim 15 characterized in that the toner particles include an activator for the resinous composition in quantity insufficient to completely polymerize said resin.

17. The receptor according to any one of claims 14 to 16 characterized in that said substrate is opaque.