Incremental printing of symbolic information – Thermal marking apparatus or processes – With transfer medium or driving means therefor
Reexamination Certificate
2002-09-11
2004-11-16
Feggins, K. (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
With transfer medium or driving means therefor
Reexamination Certificate
active
06819348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal transfer film and particularly to a thermal transfer film which can yield a thermally transferred print possessing excellent fastness or resistance properties such as excellent abrasion resistance, lightfastness, and alteration preventive property, is less likely to cause damage to an object, is free from a deterioration in quality of the print, and does not incur an increase in production cost, a process for producing the thermal transfer film, a method for image formation using the thermal transfer film, and an image formed object.
2. Prior Art
Thermal transfer can easily record variable information and thus is extensively used in a wide variety of applications. The thermal transfer is a method which comprises the steps of: putting a thermal transfer film, comprising a colorant layer provided on a substrate, on top of an object optionally provided with a receptive layer; pressing the assembly between a heating device, such as a thermal head, and a platen roll; and selectively heating the heating device in its heating portion according to image information to transfer the colorant contained in the colorant layer on the thermal transfer film onto the object, whereby an image is recorded on the object. Thermal transfer methods are roughly classified into thermal ink transfer (hot melt-type thermal transfer) and thermal dye sublimation transfer (sublimation-type thermal transfer).
The thermal ink transfer is a method for image formation wherein a thermal transfer film bearing thereon a heat-fusion ink layer is heated by the above heating means and the component of the softened heat-fusion ink layer is transferred onto an object such as natural fiber paper or plastic sheet to form an image. The heat-fusion ink layer used herein is formed of a dispersion of a colorant, such as a pigment, in a binder, such as heat-fusion wax or resin and is supported on a substrate such as a plastic film. The formed image has high density and high sharpness, and this method is suitable for recording binary images such as characters and line drawings.
On the other hand, the thermal dye sublimation transfer is a method for image formation wherein a thermal transfer film bearing thereon a sublimable dye layer is heated by the above heating means to sublimate and transfer the sublimable dye contained in the dye layer onto a receptive layer provided on an object, whereby an image is formed on the object. The sublimable dye layer used herein is formed of a solution or dispersion of a sublimable dye used as the colorant in a binder resin and is supported on a substrate film such as a plastic film. According to this method, since the amount of the dye transferred can be regulated dot by dot according to the quantity of energy applied to a heating device, such as a thermal head, the reproduction of gradation can be realized by varying the density.
Thus, the thermal ink transfer method and the thermal dye sublimation transfer method have respective features, that is, the thermal ink transfer method can easily and clearly form images of characters, numerals and the like, while the thermal dye sublimation transfer method is excellent in gradation rendering and can form images such as a photograph-like image of a face in a faithful, clear manner.
Images formed by the above thermal transfer methods, independently of whether the images have been formed by the thermal ink transfer method or the thermal dye sublimation transfer method, are unsatisfactory in fastness or resistance properties such as abrasion resistance, lightfastness, and alteration preventive property. To cope with the unsatisfactory fastness or resistance properties, a protective layer has hitherto been formed on the image. For example, Japanese Patent Laid-Open No. 159795/1991 describes that information such as images and letters are formed on a card substrate and a transparent protective layer is provided on at least a part of the surface of the information. In this case, two or more protective layers are transferred so that they overlap with each other and are different from each other in transfer area. At least one of the protective layers contains a brightening agent and/or an ultraviolet absorber. In this method, however, since the transfer of the protective layer is carried out twice or more, damage to the object is large. Further, the number of steps (transfer) necessary for preparing a print is large, and a great deal of time is required. Therefore, for example, a deterioration in print quality and an increase in production cost are disadvantageously likely to occur.
Japanese Patent Laid-Open No. 177249/2000 describes a record produced by forming a color image on recording paper and forming a transparent image of a transparent ink on the color image and further discloses that an overcoat is formed between the color image and the transparent image. The claimed advantage of the record is to improve the weathering resistance and abrasion resistance of the color image and to permit the transparent image on the color image to be viewed by the reflection of light according to the angle of the line of sight to the transparent image recorded face. Also in this case, however, since the transfer onto the color image on the recording paper is carried out a plurality of times, that is, since the transparent image and the overcoat are transferred onto the color image on the recording paper, damage to the object is large. Further, the number of steps (transfer) necessary for preparing a print is large, and a great deal of time is required. Therefore, for example, a deterioration in print quality and an increase in production cost are disadvantageously likely to occur.
SUMMARY OF THE INVENTION
The present invention has been made with a view to solving the above problems of the prior art, and it is an object of the present invention to provide a thermal transfer film which can yield a thermally transferred print possessing excellent fastness or resistance properties such as excellent abrasion resistance, lightfastness, and alteration preventive property, is less likely to cause damage to an object, is free from a deterioration in quality of the print, and does not incur an increase in production cost, a method for image formation using the thermal transfer film, and an image formed object.
The above object can be attained by a thermal transfer film comprising: a substrate; and one or a plurality of layers including a thermal transfer layer provided on one side of the substrate, the thermal transfer layer being located on the uppermost surface of the thermal transfer film, a convex being provided on a part of the thermal transfer layer.
According to a preferred embodiment of the present invention, the thermal transfer layer comprises mainly of a thermoplastic resin having a glass transition temperature of 50 to 120° C. The use of this resin can provide good transferability and fixation onto an object.
More preferably, the thermoplastic resin is selected from a polyester resin having a number average molecular weight of 2000 to 30000, a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 150 to 500, and a homopolymer or copolymer, of a methacrylate base monomer, having a weight average molecular weight of 20000 to 60000. The use of this resin can improve the function of the thermal transfer layer, after transfer onto the object, as the protective layer, that is, can improve fastness or resistance properties such as abrasion resistance, lightfastness, and alteration preventive property.
In another embodiment of the thermal transfer film according to the present invention, a release layer is provided between the substrate and the thermal transfer layer, and the release layer is not separable from the substrate side. The provision of the release layer can improve the transferability of the thermal transfer layer.
Preferably, a peel layer is provided between the substrate and the thermal transfer layer, and the peel layer is separa
Aso Kenichi
Tamura Yoshihiko
Dai Nippon Printing Co. Ltd.
Feggins K.
Parkhurst & Wendel L.L.P.
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