Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Reexamination Certificate
2000-04-19
2002-02-12
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
C428S195100, C428S327000, C428S913000, C428S914000
Reexamination Certificate
active
06346502
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a dye-donor element for thermal dye transfer, and more particularly to the use of a transferable protection overcoat in the element for transfer to a thermal print to provide a matte surface thereon.
BACKGROUND OF THE INVENTION
In recent years, thermal transfer systems have been developed to obtain prints from pictures which have been generated electronically from a color video camera. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separated images are then converted into electrical signals. These signals are then operated on to produce cyan, magenta and yellow signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor element is placed face-to-face with a dye-receiving element. The two are then inserted between a thermal printing head and a platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heating elements and is heated up sequentially in response to one of the cyan, magenta and yellow signals. The process is then repeated for the other two colors. A color hard copy is thus obtained which corresponds to the original picture viewed on a screen. Further details of this process and an apparatus for carrying it out are contained in U.S. Pat. No. 4,621,271, the disclosure of which is hereby incorporated by reference.
Thermal prints are susceptible to retransfer of dyes to adjacent surfaces and to discoloration by fingerprints. This is due to dye being at the surface of the dye-receiving layer of the print. These dyes can be driven further into the dye-receiving layer by thermally fusing the print with either hot rollers or a thermal head. This will help to reduce dye retransfer and fingerprint susceptibility, but does not eliminate these problems. However, the application of a protection overcoat will practically eliminate these problems. This protection overcoat is applied to the receiver element by heating in a likewise manner after the dyes have been transferred. The protection overcoat will improve the stability of the image to light fade and oil from fingerprints.
The protection overcoat must adhere strongly to the top layer of the receiver element so that no imperfections exist in the transferred layer that can be observed without magnification. One such imperfection resulting from the lack of adhesion of the protection overcoat to the receiver surface is the presence of small voids or air bubbles. Bubbles are created if the temperature during transfer of the protection overcoat layer does not go above the Tg of the protection overcoat material, resulting in inadequate adhesion as the donor substrate is stripped away from the receiver.
Inadequate adhesion of the protection overcoat to the receiver can occur when the protection overcoat layer is too thick. The greater the thickness of the protection overcoat layer, the greater its mass and consequently more energy is needed to raise the temperature of the protection overcoat above its Tg.
In a thermal dye transfer printing process, it is desirable for the finished prints to compare favorably with color photographic prints in terms of image quality. The look of the final print is very dependent on the surface texture and gloss. Typically, color photographic prints are available in surface finishes ranging from very smooth, high gloss to rough, low gloss matte. However, applying a thermal image to a rough surface would result in uniformity problems and drop-outs.
If a matte finish is desired on a thermal print, it has been previously been accomplished by using matte sprays or by matte surface applications through post printing processors. However, both of these solutions are costly and add a degree of complexity to the process.
U.S. Pat. No. 5,387,573 relates to a thermal dye transfer dye-donor element with a transferable protection overcoat containing particles. However, there is a problem with this element in that it gives a high gloss surface.
JP 09/323482 relates to the use of a transfer picture image-protecting layer containing a thermoplastic resin and thermally expandable microcapsules, the thickness of the layer being from 1 to 10 &mgr;m. The additional mass of the microspheres in the protection overcoat layer requires more energy to expand the spheres as well as to effect adhesion of the polymeric layer to the receiver. However, there is a problem with this element in that imperfections such as bubbles are obtained between the protecting layer and the receiving layer.
It is the object of this invention to provide a dye-donor element for thermal dye transfer printing that can impart a matte or low gloss finish onto a receiving element. It is another object of this invention to provide a dye-donor element for thermal dye transfer printing that provides a protection layer which improves the adhesion between the protection layer and the receiving layer resulting in less defects.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with this invention which relates to a dye-donor element for thermal dye transfer comprising a support having thereon at least one dye layer area comprising an image dye in a binder and another area comprising a transferable protection layer, the transferable protection layer area being approximately equal in size to the dye layer area, wherein the transferable protection layer contains inorganic particles, a polymeric binder and unexpanded synthetic thermoplastic polymeric microspheres, the microspheres having a particle size in the unexpanded condition of from about 5 to about 20 &mgr;m, and which expand to about 20 to about 120 &mgr;m upon application of heat during transfer of the protection layer to an image-receiving layer to provide a matte surface thereon, the transferable protection layer being less than about 1 &mgr;m thick.
During application of the protection layer to the receiver element, heat from the linear thermal printing head causes the microspheres to expand to many times their original size. This causes a roughening of the surface to occur resulting in a matte or lower gloss image comparable to that obtained on a matte surface photographic paper.
It has been found that reducing the thickness of the polymer layer in a heat transferable laminate containing expandable microspheres to less than 1 &mgr;m results in an improved appearance of the laminated image at a much lower energy than that required for thicker polymer films. The low energy results in an improvement in performance since it solves the problem of the dye donor element sticking irreversibly to the receiver element resulting in printer jams and subsequent down time.
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the invention, the dye-donor element is a multicolor element comprising repeating color patches of yellow, magenta and cyan image dyes, respectively, dispersed in a binder, and a patch containing the protection layer.
In another embodiment of the invention, the protection layer is the only layer on the donor element and is used in conjunction with another dye-donor element which contains the image dyes.
In another preferred embodiment of the invention, the dye-donor element is a monochrome element and comprises repeating units of two areas, the first area comprising a layer of one image dye dispersed in a binder, and the second area comprising the protection layer.
In another preferred embodiment of the invention, the dye-donor element is a black-and-white element and comprises repeating units of two areas, the first area comprising a layer of a mixture of image dyes dispersed in a binder to produce a neutral color, and the second area comprising the protection layer.
Any expandable microspheres may be used in the invention such as those disclosed in U.S. Pat. No. 3,556,934 and 3,779,951, the disclosures of which are hereby incorporated by reference. In a preferred
Campbell Bruce C.
Hastreiter, Jr. Jacob J.
Simpson William H.
Cole Harold E.
Eastman Kodak Company
Hess Bruce H.
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