Heat transfer sheet

Details Heat transfer sheet Heat transfer sheet

1992-05-21

1994-07-19

Hess, B. Hamilton

Record receiver having plural interactive leaves or a colorless

Having plural interactive leaves

428195, 428913, 428914, B41M 5035, B41M 538

Patent

active

053309600

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a dye useful for heat transfer printing and a heat transfer sheet comprising the dye. More specifically, the present invention relates to a heat transfer sheet capable of producing an image which is excellent in color density, sharpness and fastness properties, and in particular, an image which is excellent in resistance to light (fastness to light) and is free from migration to the reverse side of an image-receiving sheet.


BACKGROUND ART

Heretofore, a variety of heat transfer printing methods have been known. Of these methods, a sublimation-type heat transfer printing method is now prevailing. In this method, a heat transfer sheet comprising as a coloring agent (printing agent) a sublimable dye which is retained by a substrate sheet such as paper is superposed on a heat transfer image-receiving sheet such as polyester woven cloth which can be dyed with the sublimable dye, and thermal energy is applied imagewise to the back surface of the heat transfer sheet to transfer the sublimable dye to the heat transfer image-receiving sheet, thereby producing an image on the image-receiving sheet.
Recently, there has been proposed a heat transfer printing method of the sublimation type, capable of producing various full-colored images on an image-receiving sheet such as a sheet of paper or a plastic film. In this method, a thermal head of a printer is employed as a heat application means, and a large number of dots in three or four colors are transferred to the image-receiving sheet in an extremely short heat application time. A full-colored image can thus be successfully reproduced on the image-receiving sheet.
The image thus obtained is very sharp and excellent in transparency because a dye is used as a coloring agent. Therefore, the heat transfer printing method of this type can produce an excellent half-tone image with continuous gradation, comparable to an image obtained by offset printing or gravure printing. Moreover, the quality of the image is as high as that of a full-colored photograph.
However, the image produced by the above heat transfer printing method is poor in both color density (image density) and resistance to light. This is a serious problem in this method.
To conduct high-speed printing, it is required that thermal energy be applied to the heat transfer sheet in an extremely short time of several seconds or less. However, both the sublimable dye contained in the heat transfer sheet and the heat transfer image-receiving sheet are not thoroughly heated within such a short heat application time. The resulting image, therefore, cannot have a sufficiently high density.
A sublimable dye which is excellent in sublimation ability has been developed in order to successfully conduct high-speed printing. In general, however, a highly sublimable dye has a low molecular weight. Fro this reason, an image produced on an image-receiving sheet using such a dye is poor in resistance to light, and the color of the image fades easily.
To solve the above problem, a sublimable dye having a relatively high molecular weight may be employed. Such a sublimable dye, however, cannot sublime instantly when heat is applied thereto, so that an image having a satisfactorily high density cannot be obtained by the above high-speed printing method.
Accordingly, an object of the present invention is to provide a dye and a heat transfer sheet for use in a heat transfer printing method employing a sublimable dye, capable of producing an image which has a sufficiently high density and is excellent in sharpness, fastness properties, and, in particular, resistance to light.


DISCLOSURE OF THE INVENTION

The above object can be accomplished by the below-described invention. Namely, the present invention provides a dye for heat transfer printing (hereinafter may be referred to simply as a dye) having the following formula (I), and a heat transfer sheet comprising (i) a substrate sheet and (ii) a dye layer comprising a dye having formula (I), provided on one surface of the substrate s

REFERENCES:
patent: 4062845 (1977-12-01), Schefczik
patent: 4080331 (1978-03-01), Brack

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