Incremental printing of symbolic information – Thermal marking apparatus or processes – Density control
Reexamination Certificate
1999-02-01
2001-04-03
Le, N. (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Density control
C347S191000
Reexamination Certificate
active
06211894
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image forming method in which an image is formed by employing thermal transfer, and more specifically to a technology for the improvement in the keeping quality of a transferred image without deteriorating the surface characteristics of the image receiving sheet.
BACKGROUND OF THE INVENTION
As a multicolor or single-color image forming technology, this technology has been known in that an ink sheet containing a sublimable dye is in contact with an image-receiving layer of a image-receiving element and is heated by a thermal head, etc. so that the sublimable dye is transferred imagewise to the image-receiving layer.
In such the transferred image forming technology, the sublimable dye employed in the ink sheet plays an important roles, and image preservation quality is not sufficient from the conventional sublimable dye. As for improving this problem it is disclosed in Japanese Patent Publication Open to Public Inspection Nos. 59-78893, 59-109394, 60-2398 etc. that a metal chelate is formed by allowing a metal ion-containing compound (metal source) to react with a thermally transferable dye which is capable of chelate reaction (post chelate dye) to form a dye image.
It has been known that the image preservation quality of the post chelate sublimable dye image is improved as a chelation ratio becomes higher which is obtained by allowing a post chelate dye supplied from the ink sheet to react with the metal source in the image-receiving layer.
As a method to increase the chelation ratio, a technology has been proposed in that an image formed by transfer is treated at high temperature employing a thermostat or another heating device (Japanese Patent Publication Open to Public Inspection No. 4-89292 and Japanese Patent Application No. 5-258397). However, in this method, there is a disadvantage since another device is required in addition to a thermal transfer printer and further two steps-working is required for forming image with inferior handling. In this method, cost becomes higher since a sheet form protective material is necessary attaching between the image receiving sheet and roller and press plate to avoid contamination of the roller and press plate by dye transfer in the heating procedure.
A method heating the image formed by thermal transfer recording, a method employing thermal head is proposed. For example, it is disclosed in Japanese Patent Publication 4-55870, employing a sublimation transfer paper having dye areas of each color and an area having no coating, a transferred image receiving sheet is heated again through the non-coated area by means of a thermal head after the dye transfer. This method is advantageous because the re-heating is carried out within a same apparatus as the thermal transfer recording apparatus.
In case that the re-heating is carried out employing a thermal head with the same applied energy as that is applied when dye transferring with the maximum density, the image receiving layer or support is deteriorate so that an original surface characteristics of the image receiving sheet is lost, uneven band image appears at the high density area or sticking occurred at worst due to reducing the slippability between the image receiving layer and ink layer or back side of ink sheet and thermal head, because an excess energy all energy for dye transfer is used for the re-heating. For this reason the applied energy is set at lower condition than that gives maximum density of dye transfer. When the applied energy is reduced to avoid the phenomenon mentioned above, chelation of the post chelate dye is not performed sufficiently and the preservation quality of the obtained image becomes reduced.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a technology to dissolve such problem mentioned above, and to improve the preservation quality of a thermally transferred image formed on an image-receiving layer without reducing the original surface characteristics of image receiving sheet as itself, fusion of the image receiving layer with ink layer, sticking between back side of ink layer and thermal head or occurrence of uneven image.
The invention and its embodiment are described.
An ink sheet used in the present invention comprises an ink layer containing a thermal transfer dye provided on a support. An image-receiving element comprises, provided on a support, an image-receiving layer which accepts the thermal transfer dye.
The image forming process comprises the following steps;
An image-receiving layer of an image-receiving element having the image-receiving layer and an ink layer of the ink sheet are brought into contact and are subjected to imagewise-heating by a thermal head and the dye of the ink sheet is transferred to the image-receiving layer to form an image on the image-receiving layer,
the image receiving element in which a transferred image was formed is subjected re-heating by a thermal head through a thin film material which is brought into contact to an image forming surface of the image receiving sheet,
wherein pulse supplying period per one line of the thermal head of re-heating is shorter than that of the thermal head of imagewise heating, and supplying energy to the thermal head of re-heating is lower than that of the thermal head of imagewise heating which gives maximum density.
The pulse supplying period per one line of the thermal head of re-heating is preferably 65 to 95% of that of the thermal head of imagewise heating.
The supplying energy to the thermal head of re-heating is preferably 40 to 80% of that of the thermal head of imagewise heating which gives maximum density.
In one of the preferable embodiment the ink layer contains a thermally transfer dye precursor, and the image receiving layer contains a dye fixing compound capable of forming a dye by reacting with the dye thermally transfer dye precursor.
The preferable example of the thermally transfer dye precursor is a thermally transfer dye capable of chelation. The preferable example of the dye fixing compound is a metal ion containing compound capable of chelating with the thermally transfer dye capable of chelation.
In one of the preferable embodiment the ink layer contains a dye capable of chelating as the thermal transfer dye. The image receiving layer preferably contains a metal ion containing compound which reacts with the dye capable of chelating.
The thin film material preferably comprises a layer containing a metal ion containing compound.
In one of the embodiment of the invention, the thin film material is provided in a part of the ink layer. In this case, the ink sheet comprises dye-containing region and the thin film material region. The dye-containing region is composed of, for example, an yellow dye-containing region, a magenta dye-containing region and a cyan dye-containing region, and the thin film material region is formed next those dye-containing regions.
The thin film material preferably comprises a releasing agent.
REFERENCES:
patent: 5634731 (1997-06-01), Kita et al.
patent: 6-155778 (1994-06-01), None
Fukumuro Kaori
Mano Shigeru
Watanabe Hiroshi
Yamaya Yorihiro
Bierman Jordan B.
Bierman, Muserlian and Lucas, LLP
Konica Corporation
Le N.
Vo Anh T. N.
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