Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-06-26
2001-01-09
Davis, Jenna (Department: 1771)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S235000, C347S114000, C347S153000, C399S342000, C428S041400, C428S041800, C428S354000
Reexamination Certificate
active
06171422
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to elements for electrographic imaging. More particularly, this invention relates to elements for electrographic imaging comprising an electrically conductive polymeric release layer and to their use in forming color images.
BACKGROUND OF THE INVENTION
In electrographic imaging a latent image of electric charge is formed on a surface of a carrier. Toner particles that are attracted to the charge are applied to the surface of the carrier to render the latent image visible. The toned image is fixed, either by fusing the toner particles to the surface of the carrier, or by first transferring the toned image to a receptor and fusing, or otherwise permanently affixing, the particles to the receptor.
The latent image is produced by imagewise deposition of electrical charge onto the carrier surface. Typically, charged styli, arranged in linear arrays across the width of a moving dielectric surface, are used to create the latent image. Such processes are disclosed, for example, in Helmberger, U.S. Pat. No. 4,007,489; Doggett, U.S. Pat. No. 4,731,542; and St. John, U.S. Pat. No. 4,569,584.
After the latent image has been created on the surface of the carrier, toner is applied to produce a toned image. The toner is fixed to the surface of the carrier by heat fusing, or, if the toner is dispersed in a liquid, by drying and then, optionally, by heat fusing. When fixing is by drying only, the image is comparatively fragile and can be damaged by physical contact, abrasion, and the like.
Because color electrography needs only a carrier comprising a dielectric layer over a conductive support, it has, from its inception, been used for applications in which large size images are needed, such as for store graphics, posters, signs, banners, and other out-of-doors advertisements. In these applications the need for image protection is intense. Consequently, the color electrographic art has, from the outset, endeavored to protect the image.
One well-known way of protecting the image is to overlaminate the image with a permanent transparent protective film to form a laminate consisting of, in order, the carrier, the image, and the transparent protective film. In this method, the image is both fixed and protected between the original carrier and the transparent protective film in a single step.
In overlamination, the original carrier becomes an integral component of the final product. The carrier typically comprises a conductive base paper, which is unsuited for outdoor uses, even when protected by the overlaminated transparent protective film. Thus, overlamination is generally not suitable for preparing images for outdoor applications.
Another way of using the image, which avoids having the conductive base as part of the final product, is to laminate a receptor onto the toner that forms the image and then remove and discard the original carrier. In a second step, a permanent protective transparent film is laminated to the image and receptor, to form an element comprising the receptor, the toner image, and the permanent protective transparent film. The toner image is fixed and protected between the receptor and the permanent protective transparent film in two steps. This process is described in Chou, U.S. Pat. No. 5,262,259.
An alternative way that avoids having the conductive base as part of the final product is to laminate a receptor onto the surface of the dielectric layer which contains the toner that forms the image. Then the conductive base is removed and discarded, leaving behind the dielectric layer. This forms a product, comprising the receptor, the toner image, and the dielectric layer, in which the dielectric layer now serves as a protective layer. The image is fixed and protected between the dielectric layer and the receptor in a single step. Electrographic elements useful in this process are disclosed in Cahill, U.S. Pat. Nos. 5,414,502 and 5,483,321.
If the imaged and toned dielectric layer is to be transferred to provide a protective layer for the image, the dielectric layer must be able to release from the conductive base. To enhance release, a non-conductive release layer has been provided between the dielectric layer and the conductive base, increasing the cost and manufacturing complexity for the elements and lowering the density of the image. Therefore, to reduce manufacturing cost and improve image density, a need exists for electrographic imaging elements that do not comprise a separate release layer.
SUMMARY OF THE INVENTION
The invention is an imaging element comprising a support structure and an imaging layer structure wherein the support structure is removably adhered to the imaging layer structure and wherein the support structure comprises an electrically conductive polymeric release layer having tailored optical and surface release properties. The electrically conductive release layer comprises, in polymerized form:
(A) 1 to 80 weight parts of a polymerizable, ethylenically unsaturated ammonium precursor;
(B) 0.1 to 10 weight parts of a polymerizable, ethylenically unsaturated, organo-silicone precursor;
(C) 5 to 95 weight parts of a multifunctional polymerizable precursor containing at least two polymerizable, ethylenically unsaturated functional groups;
(D) 0 to 60 weight parts of a polymerizable, ethylenically unsaturated acidic precursor containing at least one carboxylic acid group; and
(E) 0 to 90 weight parts of a monofunctional precursor containing one polymerizable, ethylenically unsaturated functional group.
The electrically conductive polymeric release layer has a thickness of about 1 to 20 microns, an electrical resistance between about 1×10
5
&OHgr;/□ and 1×10
8
&OHgr;/□, and a surface energy of between 20 and 40 dynes/cm
2
.
In another embodiment, the invention is a method for forming an image using an imaging element of this invention.
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Bennett Everett Wyman
Cahill Douglas Allan
Shi Weitong
Sporbert Edward William
Taylor Alan Richard
Davis Jenna
Ratner & Prestia
Rexam Graphics Inc.
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