Stock material or miscellaneous articles – Receiver for thermal transfer ink – Thermal transfer donor attached
Reexamination Certificate
2002-01-25
2004-09-14
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Receiver for thermal transfer ink
Thermal transfer donor attached
C428S032770
Reexamination Certificate
active
06790492
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a multi-color image-forming material and a multi-color image-forming process for forming a full-color image having a high resolution using laser beam. More particularly, the present invention relates to a multi-color image-forming material and a multi-color image-forming process useful for the preparation of a color proof (DDCP: direct digital color proof) or mask image in the art of printing by laser recording from digital image signal.
BACKGROUND OF THE INVENTION
In graphic art, a printing plate is made from a set of color separation films prepared from a color original through a lithographic film. In general, in order to check error in the color separation step or necessity for color correction before the final printing (actual printing), a color proof is prepared from the color separation films. A color proof is required to realize a high resolving power allowing a high reproducibility of halftone image or a high step stability. In order to obtain a color proof approximating the actual printed matter, the color proof is preferably made of the material to be used in the actual printed matter, e.g., printing paper as a substrate and pigment as a colorant. It is extremely desirable that the color proof be prepared by a dry process in the absence of developer.
As a dry process for the preparation of a color proof, a recording system for preparing a color proof directly from a digital signal has been developed with the recent spread of an electronizing system in prepressing step. Such an electronizing system is particularly adapted for the preparation of a high quality color proof and normally reproduces a halftone image having a precision of not lower than 150 lines/inch. In order to record a high quality proof from a digital signal, laser beam, which can be modulated with a digital signal and can be converged to form a fine recording beam, is used as a recording head. To this end, it is necessary that an image-forming material be developed which exhibits a high recording sensitivity to laser beam and a high resolving power allowing reproduction of a high precision halftone.
As an image-forming material to be used in the transfer image forming process using laser beam there has been known a hot-melt transfer sheet comprising a light-to-heat conversion layer which absorbs light beam to generate heat and an image-forming layer having a pigment dispersed in a hot-melt wax, binder or the like provided in this order on a support (Japanese Patent Application (Laid-Open) No. 1993-58045). In the image forming process using such an image-forming material, heat generated in the laser beam-irradiated area on the light-to-heat conversion layer causes the image-forming layer corresponding to that area to be melted and transferred to the image-receiving sheet laminated on the transfer sheet to form a transfer image on the image-receiving sheet.
Japanese Patent Application (Laid-Open) No. 1994-219052 discloses a heat transfer sheet comprising a light-to-heat conversion layer containing a light-to-heat conversion material, a heat-peeling layer having a thickness as very small as 0.03 &mgr;m to 0.3 &mgr;m, and an image-forming layer containing a colorant provided in this order on a support. When this heat transfer sheet is irradiated with laser beam, the adhesion between the image-forming layer and the light-to-heat conversion layer, which are bonded to each other with the heat-peeling layer provided interposed therebetween, is lowered to form a high precision image on the image-receiving sheet laminated on the heat transfer sheet. The image forming process using the heat transfer sheet involves so-called “ablation”. In some detail, a phenomenon is used that the area which has been irradiated with laser beam is subject to decomposition and vaporization of a part of the heat-peeling layer that weakens the adhesion between the image-forming layer and the light-to-heat conversion layer, causing the image-forming layer on the area to be transferred to the image-receiving sheet laminated on the heat transfer sheet.
These image forming processes are advantageous in that a printing paper comprising an image-receiving layer (adhesive layer) provided therein may be used as an image-receiving sheet material and a multi-color image can be easily obtained by sequentially transferring images having different colors onto the image-receiving sheet. In particular, the image-forming process using ablation is advantageous in that a high precision image can be easily obtained and is useful for the preparation of a color proof (DDCP: direct digital color proof) or a high precision mask image.
With the progress of DTP environment, CTP (Computer to Plate) system has been needed more for DDCP process proof than for proof sheet or analog process proof because it requires no step of withdrawing intermediate film. In recent years, a large-sized DDCP having a high quality, a high stability and an excellent coincidence with desired printed matter has been desired.
A laser heat transfer process allows printing with a high resolution. A laser heat transfer process has heretofore been effected in various processes such as (1) laser sublimation process, (2) laser ablation process and (3) laser melt process. However, all these processes were disadvantageous in that the resulting recorded halftone is not sharp. In some detail, the laser sublimation process (1) involves the use of a dye as a colorant and thus is disadvantageous in that the approximation to desired printed matter is insufficient. This process also involves the sublimation of a colorant and thus is disadvantageous in that the resulting halftone has a blurred contour, giving an insufficient resolution. On the other hand, the laser ablation process (2) involves the use of a pigment as a colorant and thus provides a good approximation to desired printed matter. However, this process involves the scattering of a colorant and thus is disadvantageous in that the resulting halftone has a blurred contour, giving an insufficient resolution as in the laser sublimation process. Further, the laser melt process (3) involves the flow of molten material and thus is disadvantageous in that the resulting image has no clear contour.
Moreover, when a heat transfer sheet is used particularly for color proof, it is necessary that the thickness of the image-forming layer be raised to provide the image transferred to printing paper with a required reflection OD. As a result, the heat capacity of the image-forming layer increases, causing the deterioration of the recording sensitivity and resolving power of the system.
Japanese Patent Application (Laid-Open) No. 1996-300829 and Japanese Patent Application (Laid-Open) No. 1996-300830 disclose a process which comprises controlling the color power index of carbon black to not greater than 120 or not greater than 125 to obtain a transfer image having a sufficient blackness. It is described that the coloring power index is a value determined relative to that of standard black as 100 according to ASTM N-440 and is more preferably from 30 to 100.
However, even the use of such an index gave no solution to the foregoing problems.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a large-sized DDCP having a high quality, a high stability and an excellent coincidence with desired printed matter. In some detail, the present invention has the following objects:
1) The heat transfer sheet can withstand comparison of pigment colorant with desired printed matter free from the effect (i.e., the influence) of the illuminating light source and allows transfer of thin colorant film resulting in the provision of dots with an excellent sharpness and stability;
2) The image-receiving sheet can securely receive the image-forming layer of laser energy heat transfer sheet in a stable manner;
3) An image can be transferred to printing paper and a close description of texture or accurate reproduction of paper white (high key portion) can be made according to a basis weigh
Hatakeyama Akira
Shimomura Akihiro
Yamamoto Mitsuru
Yoshinari Shinichi
LandOfFree
Multi-color image-forming material and multi-color... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-color image-forming material and multi-color..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-color image-forming material and multi-color... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3237008