Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-03-13
2002-12-24
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S212000
Reexamination Certificate
active
06497940
ABSTRACT:
FIELD OF INVENTION
The present invention is related to transparent media for ink printing. More specifically, this invention is related to a transparent media and a process for forming the media. The media has superior clarity, resistance to scratching and excellent adhesion to phase change inks.
BACKGROUND OF THE INVENTION
Transparent films which display information are widely used throughout many different industries and for many applications. Typically, a positive image is formed by placing an ink or pigment onto a transparent plastic sheet. The image is then displayed by projection or by light transmission.
Many methods are available for printing a positive image onto a transparent plastic sheet. Ink jet printers, and their associated ink formulations, are well advanced technically; and aqueous ink jet printers represent a respectable share of the total printing market. Aqueous ink jet printing is particularly advantageous for printing text or images where the printed area covers a small portion of the area of the transparent sheet. However, aqueous ink jet printing is less suitable for printing large areas of a transparent plastic sheet since a large volume of solvent must be removed from the media. The volume of solvent increases with image density which leads a skilled artisan away from ink jet printing for high optical density, large print area applications.
Phase change ink printing corrects many of the deficiencies of aqueous ink jet printing. A high optical density can be obtained and large areas can be printed without evaporation of solvent. The impact of phase change ink printing in the market place has been impeded due to the lack of a suitable transparent media. Media designed for use with aqueous or other solvent based ink jet printers is unsuitable due to the large coating weight of the ink receptive layer which is required to absorb the ink solvent. Furthermore, the coatings used for aqueous or solvent ink jet media do not provide adequate adhesion for the phase change ink composition. Thus, there is a need for a media which will take full advantage of the properties offered by phase change ink printing.
Compositions described in commonly assigned U.S. Pat. No. 5,756,226 demonstrate adequate performance when used with phase change ink jet printing methods. Improvements in ink adhesion are still desired to insure adequate adhesion between the ink and the media. An overcoat comprising a softer polymer mixture is demonstrated herein to provide superior adhesion.
Japanese unexamined Patent Appl. Kokai 6-32046 teaches the addition of up to 10%, by weight, of a zirconium compound to improve the print quality. Japanese unexamined Patent Application Kokai 4-364,947 utilizes TiO
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in a similar manner. The transparency of the coated layer is compromised by the addition of zirconium or titanium solids rendering the film unsuitable for use as a transparent media. Japanese unexamined Patent Appl. Kokai 4-201,286 teaches media which is suitable for aqueous ink jet printing yet the surface is susceptible to scratching. High scratch susceptibility renders a media unacceptable for use in automatic printing devices and for high quality printing applications.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved media for use with phase change ink printing.
It is a particular object of the present invention to provide a media which has improved resistance to surface scratching and improved adhesion with phase change inks.
A particular advantage offered by the present invention is the clarity which can be obtained and the suitability for use as a transparency media. The present invention is superior for printing applications requiring high clarity in unprinted areas.
These and other advantages, as will be apparent from the teachings herein, is demonstrated in a phase change ink recording media comprising: a polyethylene terephthalate support; a 1-15 mg/dm
2
lower receptor layer coated on the support wherein the lower receptor layer comprises: silica; and at least one polymer chosen from a set consisting of polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, methylcellulose and gelatin; wherein a total weight of the polymer and the silica is 82-97%, by weight, silica and 3-18%, by weight, polymer; and an upper receptive layer coated on said lower receptor layer wherein said upper receptor layer comprises: 32-70%, by weight, matrix polymer; 15-62%, by weight, inorganic particulate material; and 5-53%, by weight, soft polymer mixture.
The advantages offered by the present invention are particularly well suited for use with phase change inks. The superiority of the media is demonstrated in a process for forming a printed image comprising the steps of:
i) heating a solid phase change ink to form a liquid phase change ink;
ii) applying the liquid phase change ink to a transfer surface in a pattern;
iii) cooling the liquid phase change ink on the transfer surface to form an image of the pattern;
iv) transferring the solid image to a receptor comprising:
a 1-10 mil thick polyethylene terephthalate support; and
a 1-15 mg/dm
2
lower receptor layer coated on the support wherein the lower receptor layer comprises:
a fibrous, branched silica with a particle size of no more than 0.3 &mgr;m; and
a polymer chosen from a set consisting of polyvinyl alcohol, polyacrylamide and gelatin; and
v) fixing the solid image to the receptor.
A preferred method for forming a transparent recording material for phase change ink recording comprising the steps of: making an aqueous coating solution comprising: water; a binder composition comprising: at least one polymer chosen from a group consisting of polyvinyl alcohol, polyacrylamide, methyl cellulose, polyvinyl pyrrolidone and gelatin; and an inorganic particulate material with an average particle size of no more than 0.3 &mgr;m wherein the inorganic particulate material represents at least 82%, by weight, and no more than 97%, by weight, of a combined coating weight of the polymer and the inorganic particulate material taken together; wherein the aqueous coating solution has an ionic conductivity of no more than 0.6 mS at 25° C.; applying the coating solution to a polyethyleneterephthalate support in a sufficient amount that the inorganic particulate material and said polymer taken together weigh 1-15 mg/dm
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; removing the water from the coating solution.
DETAILED DESCRIPTION OF THE INVENTION
The inventive media comprises a support with a receptive layer coated thereon. The receptive layer preferably comprises a lower receptive layer coated on the support and an upper receptive layer coated on the lower receptive layer. Throughout the specification “lower receptive layer” refers to the layer closest to the support and “upper receptive layer” refers to the layer furthest from the support. “Receptive layer” refers to the layer which includes a lower receptive layer and optionally an upper receptive layer.
The lower receptive layer comprises a binder and an inorganic particulate material. The binder comprises at least one water soluble polymer. The prefered water soluble polymers are chosen based on low ionic content and the presence of groups capable of adhering to silica. The water soluble polymer is most preferably chosen from polyvinyl alcohol, acrylates, hydrolyzed polyacrylamide, methyl cellulose, polyvinyl pyrrolidone, gelatin and copolymers thereof. Copolymers and grafted polymers are suitable provided they are water soluble or water dispersable and dry to a clear coat. Particularly suitable copolymers comprise acrylic acid/vinyl pyrrolidone copolymers and urethane/acrylate copolymers. More preferably, the binder comprises at least one polymer chosen from a group consisting of polyvinyl alcohol, polyvinyl pyrrolidone and gelatin. Most preferably, the binder comprises polymerized monomer chosen from vinyl alcohol, acrylamide, vinyl pyrrolidone and combinations thereof.
Throughout the specification, percentages of lower receptive layer components will be presented based on the combined weight of the polymers
Apple Bernard Allan
Chandler, Jr. John Thomas
Jones Richard Roy
Siqueira Jose A
Thomas, Jr. Jule William
AGFA Corporation
Guy Joseph T.
Hess Bruce H.
Nexsen Pruet Jacobs & Pollard LLC
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