Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2002-02-14
2004-05-18
Hess, B. Hamilton (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C503S227000
Reexamination Certificate
active
06737152
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a protective layer transfer sheet and a print, and more particularly to a protective layer transfer sheet which can impart excellent fastness properties to a print comprising an image provided on a substrate, and a print provided with an image having excellent fastness properties.
BACKGROUND ART
Printing methods, which have hitherto been extensively used for image formation, include: a sublimation dye thermal transfer method wherein a dye contained in a colorant layer is transferred by thermal sublimation and diffusion onto an image-receiving sheet; a thermal ink transfer method wherein a colorant layer is melt and softened upon heating and as such is transferred onto an image-receiving sheet; an ink jet recording method; and electrophotography.
Regarding the sublimation dye thermal transfer method among these printing methods, a method has been proposed which comprises: providing a thermal transfer sheet produced by melting or dispersing a sublimable dye as a recording material in a binder resin and supporting the melted or dispersed sublimable dye on a substrate sheet such as a polyester film to form a dye layer; putting the thermal transfer sheet on top of an object dyeable with a sublimable dye, for example, an image-receiving sheet, such as paper or a plastic film provided with a dye-receptive layer; and thermally transferring dyes by sublimation from the thermal transfer sheet onto the image-receiving sheet to form various full-color images.
In this case, a thermal head in a printer is used as heating means, and a large number of heat quantity-regulated color dots of three or four colors are transferred onto an image-receiving sheet by heating for a very short period of time to reproduce a full-color image of an original by the large number of color dots.
Images formed in this way are very clear and highly transparent, because the colorant used is a dye. Accordingly, the images have excellent reproduction of intermediate colors and gradation and have the same quality as images formed by conventional offset printing and gravure printing. Further, the above method can produce images having high quality comparable with full-color photographic images.
At the present time, a thermal transfer recording method is extensively used as a simple printing method. The thermal transfer recording method can simply form various images and thus is utilized in the preparation of prints, in which the number of times of printing may be relatively small, for example, in the preparation of ID cards and photographs for business, or in printers of personal computers or video printers.
In the sublimation dye thermal transfer method, the amount of the dye transferred can be controlled dot by dot according to the quantity of energy applied to the thermal transfer sheet. Therefore, excellent halftone images can be formed. Unlike a conventional printing ink, however, the colorant is not a pigment but a dye having a relatively low molecular weight and, in addition, does not contain any vehicle. For this reason, the formed images are disadvantageously inferior in fastness properties, such as lightfastness, weathering resistance, and abrasion resistance, to images formed using conventional printing ink.
Further, prints formed by ink jet recording are disadvantageously poor in fastness to solutions usually found in general households, such as water and alcohols, that is, fastness to water, chemicals, solvents and the like. In addition, for example, upon contact of prints, for example, with plasticizer-containing card cases, file sheets, or plastic erasers, images are blurred, or otherwise, dyes are transferred onto these contacted materials. That is, these prints disadvantageously have poor plasticizer resistance.
A method for solving the above problem is to form a protective layer by transfer onto the formed image. In this method wherein a protective layer is formed by transfer, when sublimation transfer is used, the same thermal head as used in the formation of images can be used in the formation of the protective layer. Therefore, as compared with lamination or pouching of a molding film, the protective layer can be formed by transfer by means of a simpler device at a lower cost. This method, however, is disadvantageous in that the plasticizer resistance of the prints with a protective layer formed thereon is unsatisfactory. In particular, when a print, in which a protective layer has been thermally transferred onto an image-receiving sheet with an image formed thereon, is stored in contact with a plasticizer-containing card case, file sheet, plastic eraser or other material, dyes constituting the image in the print are transferred onto the contacted material, such as cases. This disadvantageously contaminates the cases or lowers the density of the print. Further, when the print is taken out of the case in which the print is in contact with a plasticizer-containing card case, file sheet, plastic eraser or other material, the image is disadvantageously broken.
Poor plasticizer resistance of the print with a protective layer formed thereon by sublimation transfer is considered attributable to the following fact. Specifically, the contamination of the case occurs due to the formation of cracks in the protective layer through which dyes are transferred to the case side, and the breaking of the image occurs due to fusing between the protective layer and the case. When a protective layer formed of a highly flexible resin or a hydrophilic resin is adopted in consideration of these points, good plasticizer resistance could be imparted to the print. This protective layer, however, has a problem with fastness to water, alcohols and the like and, in addition, requires high energy for transfer.
Accordingly, it is an object of the present invention to solve the above problems of the prior art and to provide a protective layer transfer sheet that can form by transfer a protective layer which possesses high weathering resistance and, when formed by transfer onto an image, can prevent a dye in the image from being transferred or fused to a vinyl chloride case, can prevent the dye constituting the image being faded upon exposure to light, and thus can impart excellent fastness properties to a print.
It is another object of the present invention to provide a print having an image possessing excellent fastness properties.
DISCLOSURE OF THE INVENTION
The object of the present invention can be attained by a protective layer transfer sheet comprising: a substrate sheet; and a thermally transferable protective layer provided on at least a part of one side of the substrate sheet, said protective layer being formed of a laminate having a multilayer structure comprising at least a layer composed mainly of an acrylic resin and a layer composed mainly of a polyester resin provided in that order on the substrate sheet.
The acrylic resin is preferably an acrylic copolymer composed mainly of polymethyl methacrylate.
Preferably, the polyester resin comprises an alicyclic compound contained in at least one of a diol component and an acid component, and/or has, in one molecular chain, one or more aromatic dicarboxylic acids containing a sulfonic acid substituent or a group of a salt thereof.
The alicyclic compound in the polyester resin is preferably tricyclodecanemethanol, cyclohexanedicarboxylic acid, cyclohexanedimethanol, or cyclohexanediol.
The protective layer transfer sheet may further comprise a release layer between the protective layer and the substrate sheet.
The protective layer transfer sheet may further comprise an adhesive layer stacked on the protective layer.
The layer composed mainly of the polyester resin and/or the adhesive layer may contain an ultraviolet absorber.
In the protective layer transfer sheet, an organic filler and/or an inorganic filler may be contained in an outermost surface layer provided on the substrate sheet in its side remote from the protective layer.
According to another aspect of the present invention, there is provided a print comprising: a
Hirota Kenichi
Suzuki Shino
Dai Nippon Printing Co. Ltd.
Hess B. Hamilton
Parkhurst & Wendel L.L.P.
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