Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Reexamination Certificate
1999-04-30
2001-02-06
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
C428S320200
Reexamination Certificate
active
06184181
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for controlling the gloss of a thermal dye transfer image using expandable microspheres.
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.
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. Nos. 3,556,934 and 3,779,951 disclose the use of microspheres in a paper and subjecting it to temperatures sufficient to cause the particles to expand within the paper sheet. However, there is no disclosure in these patents of using such microspheres in a dye-donor element for a thermal dye transfer system.
U.S. Pat. No. 5,387,573 relates to the a dye-donor element with a transferable protection overcoat containing particles in order to reduce iridescence. However, there is a problem with these particles in that they do not appreciably roughen the receiver surface to reduce the image gloss.
It is the object of this invention to provide a process for controlling the gloss of a thermal dye transfer image.
SUMMARY OF THE INVENTION
This and other objects are achieved in accordance with this invention which relates to a process of controlling the gloss of a thermal dye transfer image comprising:
(a) imagewise-heating a dye-donor element comprising a support having thereon a dye layer comprising an image dye in a binder, the dye-donor being in contact with a dye-receiving element, thereby transferring a dye image to an image-receiving layer of the dye-receiving element to form the dye transfer image; and
(b) thermally transferring a protection layer on top of the transferred dye image, the protection layer being applied from an element which contains unexpanded synthetic thermoplastic polymeric microspheres, the microspheres having a particle size in the unexpanded condition of from about 5 to about 20 &mgr;m, the protection layer being transferred using a given energy level in order to expand the microspheres until a desired gloss level is obtained.
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. By controlling the printing energy, a wide range of glosses can be created using the same donor ribbon.
DETAILED DESCRIPTION OF THE INVENTION
By use of the invention, a printer can be programmed to provide a given energy level during transfer of the protection layer. This energy level will correspond to a desired gloss level in the final print without changing the donor ribbon or receiver. Thus, the invention provides a very simple way to obtain different gloss levels in a thermal transfer print.
In general, the minimum energy level for transferring the protection layer is at least about 2.4 joules/cm
2
. A preferred range for the energy level is from about 2.4 joules/cm
2
to about 3.6 joules/cm
2
.
In a preferred embodiment of the invention, the dye-donor element employed in the process of the invention 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 employed 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 employed 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 employed 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. Nos. 3,556,934 and 3,779,951 discussed above. In a preferred embodiment of the invention, the expandable microspheres are white, spherically-formed, hollow particles of a thermoplastic shell encapsulating a low-boiling, vaporizable substance, such as a gas, which acts as a blowing agent. When the unexpanded microspheres are heated, the thermoplastic shell softens and the encapsulated blowing agent expands, building pressure. This results in expansion of the microsphere. This results in expansion of the microsphere. Unexpanded microspheres have an initial average diameter of 6 to 35 &mgr;m (based on weight average) depending on grade. After expansion they reach average diameters of 20 to 120 &mgr;m.
The expandable microspheres employed in the invention may be formed by encapsulating propane, butane or any other low-boiling, vaporizable substance into a microcapsule of a thermoplastic resin such as a vinylidene chloride-acrylonitrile copolymer, a methacrylic acid ester-acrylonitrile copolymer or a vinylidene chloride-acrylic acid ester copolymer. These microspheres are available commercially as Expancel® Microspheres 551 DU, 461 DU, 551-20 DU and 461-20 DU (Expancel Inc.)
The amount of the microspheres employed in the invention ranges from about 10 to about 200% by weight of the polymer used in the protection layer. This coverage is from about 0.05 g/m
2
to about 1 g/m
2
, preferably about 0.25 g/m
2
to about 0.5 g/m
2
.
The present invention provides a protection overcoat layer
Campbell Bruce C.
Gray Maurice L.
Lum Kin K.
Cole Harold E.
Eastman Kodak Company
Hess Bruce H.
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