Record receiver having plural interactive leaves or a colorless – Having plural interactive leaves
Reexamination Certificate
1999-04-05
2001-08-28
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having plural interactive leaves
C428S323000
Reexamination Certificate
active
06281166
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to thermal dye diffusion printing.
Thermal dye diffusion printing is a non-impact electronic printing process which is capable of giving near photographic quality prints. An image is formed by using a thermal head to transfer dye from a color ribbon into a surface of a receiver. The head consists of a line of individually addressable heated elements which are fed appropriate electrical pulses to generate the quantity of heat required to provide the amount of dye transfer needed to reproduce the corresponding pixel in the image. The surface temperature of the thermal head typically is 350° C. and the duration of the heating pulse typically is up to 10 milliseconds. The depth of shade is governed by the length of the heating pulse and a full color image is built up in the normal way by transfer of the primary colors on top of each other.
In general, both the ribbon and the receiver have very smooth surfaces. The active layer of the ribbon consists of a solid solution of dye in a binder. The receiver typically consists of a polymer coating on a paper or other supporting material; the coating is designed to be receptive to the dye and to release smoothly from the ribbon, or dye layer after printing.
The receiver is supported on a platen roller and the thermal head is pressed against the surface of the ribbon. The two media are held together under a pressure of between 10 and 100 atmospheres. As the surfaces are very smooth, there is no air gap between the media in the region where the thermal head is applying maximum pressure. Dye is transferred by phase transfer and diffusion; the dye which is dissolved in the dye layer partitions into the receiver coating by a molecular diffusion process. Once dye is in the receiver coating, it is free to continue diffusing further into the coating as long as the thermal head temperature remains sufficiently high. At all stages, the dye molecules are surrounded by a polymer matrix; transfer occurs from one polymer phase to another without sublimation taking place.
Because the dyes are always constrained by polymer molecules, the dye diffusion process is very well controlled. The build up of color is well defined and sideways diffusion cannot occur, as is possible in the air gap of a sublimation process.
While films have the requisite degree of smoothness, the accumulation of a static charge on the film may occur during the printing process which leads to the attraction of dust particles on the surfaces of the film. The presence of dust on a receiver coating prevents intimate contact over the entire area of the thermal printing head which results in imperfections in the printed image. While papers generally do not suffer from static charge build up, image quality may be reduced. In addition, transfer of the printed image to another substrate may be adversely affected by the use of a paper carrier or support for the receiver coating. Accordingly, there is a need for improved thermal dye diffusion substrates, particularly for substrates intended to be used as a heat transfer material.
SUMMARY OF THE INVENTION
The present invention addresses some of the difficulties and problems discussed above by providing a coating suitable for receiving an image by dye diffusion printing. The coating includes a thermoplastic polymer having a glass transition temperature of at least about 30° C. For example, the thermoplastic polymer may have a glass transition temperature of at least about 40° C. As another example, At the thermoplastic polymer may be a vinyl chloride-acrylate copolymer.
The coating also includes a powdered plastficizer having aeliagpoint of at least about 80° C. For example, the plasticizer may be an aromatic carboxylic acid ester. As another example, the plasticizer may be cyclohexane dimethanol dibenzoate. As a further example, the average particle size of the powdered plasticizer may be no greater than about 20 micrometers. The weight ratio of the thermoplastic polymer to the plasticizer typically is in a range of friom about 80:20 to about 40:60. For example, the weight ratio of the thermoplastic polymer to the plasticizer may be from about 70:30 to about 50:50.
Finally, the coating includes a release agent. The release agent may be present in a range of from about 0.5 to about 10 percent by weight, based on the dry weight of the coating
The present invention also provides a coated substrate suitable for receiving an image by dye diffusion printing. The coated substrate includes a flexible first layer which has first and second surfaces and is selected from the group consisting of films, fibrous sheet-like materials, and combinations thereof. For example, the first layer may be a film. As another example, the first layer may be a fibrous sheet-like material.
The present invention further provides a coated substrate suitable for receiving an image by dye diffusion printing which includes a flexible first layer as just described; a second layer overlaying the first surface of the first layer, which second layer comprises a first thermoplastic polymer having a glass transition temperature of at least about 30° C. and a first powdered plasticizer having a melting point of at least about 80° C.; and a third layer overlaying the second layer, which third layer includes a second thermoplastic polymer having a glass transition temperature of at least about 30° C., a second powdered plasticizer having a melting point of at least about 80° C., and a release agent.
The first layer has a basis weight of from about 50 to about 200 grams per square meter. For example, the first layer may be a film. As a further example, the first layer may a fibrous sheet-like material. The second layer has a basis weight of from about 0.5 to about 10 grams per square meter, and the third layer has a basis weight of from about 0.5 to about 10 grams per square meter.
The weight ratio of first thermoplastic polymer to first plasticizer is in a range of from about 80:20 to about 40:60 and the weight ratio of second thermoplastic polymer to second plasticizer is in a range of from about 80:20 to about 40:60. The release agent is present in the third layer in a range of from about 0.5 to about 10 percent by weight, based on the weight of the third layer coating.
By way of illustration only, the first thermoplastic polymer may have a glass transition temperature of at least about 40° C. For example, the first thermoplastic polymer may be a vinyl chloride-acrylate copolymer. Similarly, the second thermoplastic polymer may have a glass transition temperature of at least about 40° C. and may be a vinyl chloride-acrylate copolymer. The first powdered plasticizer may be an aromatic carboxylic acid ester, such as cyclohexane dimethanol dibenzoate. The average particle size of the first powdered plasticizer may be, for example, no greater than about 20 micrometers. In like manner, the second powdered plasticizer may an aromatic carboxylic acid ester, such as cyclohexane dimethanol dibenzoate and may have an average particle size no greater than about 20 micrometers.
Finally, the present invention provides a coating composition which is an aqueous dispersion of a thermoplastic polymer having a glass transition temperature of at least about 30° C., a powdered plasticizer having a melting point of at least about 80° C., and a release agent. The weight ratio of thermoplastic polymer to powdered plasticizer is in a range of from about 80:20 to about 40:60, on a dry weight basis, and the release agent is present in a range of from about 0.5 to about 10 percent by weight, on a dry weight basis, based on the weight of the solids content. The aqueous dispersion contains from about 10 to about 50 percent by weight solids.
By way of example, the thermoplastic polymer may have a glass transition temperature of at least about 40° C. As another example, the thermoplastic polymer may be a vinyl chloride-acrylate copolymer. As a further example, the powdered plasticizer may be an aromatic carboxylic acid ester, such as cyclohexane dimethanol
Flack Steven D.
Hess Bruce H.
Kimberly-Clark Worldwide
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