Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1999-03-19
2002-09-17
Hess, Bruce H. (Department: 1774)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C427S258000, C427S288000, C427S375000, C427S391000, C428S195100, C428S206000, C428S211100, C428S327000
Reexamination Certificate
active
06450633
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a coating composition and to substrates coated therewith.
The decoration of fabrics composed mainly of synthetic polymer fibers such as polyester and nylon has been accomplished for many years via dye sublimation, also referred to as dye diffusion heat transfer techniques. These techniques involve printing an image on paper or other disposable substrate and then transferring the image from the paper to the fabric. Print patterns applied to paper by such printing techniques as offset lithography contain sublimable dyes. Such dyes have been tailored to dissolve in and be retained by the synthetic polymer fibers upon heating. The print patterns are readily transferred to the fabrics by heating the paper and pressing it onto the fabric for a few seconds, typically in a heated press.
Although it is highly desirable, it has not been possible to date to use the above dye transfer techniques successfully to decorate infusible fibers such as cotton and rayon. Generally, screen printing is used to apply complex patterns directly to such fabrics. This technique works well, but is not economical for making a small number of garments (usually less than about 50) having the same pattern, since screen fabrication is quite expensive. Thus, it would be very useful if it were possible to use digital printing technology to decorate cotton, rayon or other fibers, and fabrics thereof, which are not receptive to or do not retain the colorants used in these processes.
Heat transfer papers of various constructions have been used to record images by such toner-based techniques as laser printers or laser copiers and then to transfer the images to garments such as T-shirts. These papers are generally coated with a polymer layer which will fuse to the toner particles to provide the image in the usual manner. The polymer layer then can be transferred to a fabric, using heat and pressure, and the polymer carries the image as it melts and flows into the fabric. The paper then is removed while the polymer is still fluid.
Papers of the same basic construction described above have been devised to be receptive to other marking or printing methods. For example, U.S. Pat. No. 4,773,953 to Hare describes a heat transfer paper coated with Singapore Dammar gum which is receptive to thermal ribbon printers, the wax on the ribbons being compatible with the Dammar gum coating.
U.S. Pat. No. 5,242,739 to Kronzer and Parkkila describes an image-receptive heat transfer paper having a surface coating composed of polymer particles and a binder, both of which melt to a low viscosity between 65° C. and 180° C. Optionally, a second thermoplastic coating may be positioned beneath the printable coating to assist flow of the printed material into fabrics when the product is heated and pressed in the heat transfer operation. The polymer particles can have a particle size of from 2 to 50 micrometers and comprise from 85 to 20 percent by weight of the printable coating. The thickness of the image-receptive top coating is preferably in the range of 12 to 80 micrometers.
Although the above references disclose methods of decorating fabrics via digitally printed heat transfer papers, the imaging methods are restricted to thermal wax ribbon printing or electrostatic printing. Thermal wax ribbon printing is limited to narrow formats due to problems in handling wide ribbons of the very thin type needed in this application. Color printing resolution, at 400 dpi, is not sufficient to give photographic quality images, or even flexographic quality images. The cost per page is high due to the need to use three or four ribbon panels for each print. Electrostatic printing provides a better quality image but the printers are much more expensive and more costly to maintain.
The ink jet method of printing is a rapidly growing, commercially important printing process because of its ability to produce economical, high quality, multi-colored prints. Ink jet printing is becoming the method of choice for producing colored hard copies of computer generated images consisting of graphics and fonts in both narrow and wide formats.
In general, the ink used in ink jet printing consists of an aqueous solution of one or more dyes, a humectant, and a pH buffer. These formulations are desirable because of their low cost, availability, safety, and environmental friendliness. In an ink jet printer, ink is forced through a tiny nozzle (or a series of nozzles) to form droplets which are directed toward a printing substrate. The droplets may be electrostatically charged and attracted to an oppositely charged platen behind the substrate. By means of electrically controlled deflection plates, the trajectories of the droplets can be controlled to hit the desired spot on the printing substrate. Unused droplets are deflected away from the printing substrate into a reservoir for recycling. Drop on demand printing is used for smaller, desktop printers. Drops are created by heating or compressing the inks in capillary containers, thereby ejecting them onto the substrate as it passes over the print head. The printing substrate should allow for printing of round, well-shaped dots of high optical density. The substrate should control feathering (spreading) of the ink droplets and absorb the ink vehicle rapidly (fast dry time) while adsorbing the dye at the surface to give sharp, high-density p ints. Ideally, the substrate should also “fix” the dyes (i.e., cause them to become water insoluble), so as to cause the print to be moisture and water resistant. Practically, however, it is very difficult to obtain all the above properties in a single ink jet printing substrate.
There are a large number of references which relate to ink jet printable substrates. The typical substrate is a paper or other material having an ink-receptive coating. The coating typically includes one or move pigments and a binder. Pigments which have been used, alone or in combination, include, by way of illustration only, silica; clay; calcium carbonate; talc; barium sulfate; diatomaceous earth; titanium dioxide; cation-modified non-spherical colloidal silica, in which the modifying agent is aluminum oxide, hydrous zirconium oxide, or hydrous tin oxide; calcium carbonate-compounded silica; prismatic orthorhombic aragonite calcium carbonate; alumina; aluminum silicate; calcium silicate; kaolin; magnesium silicate; magnesium oxalate; magnesium-calcium carbonate; magnesium oxide; magnesium hydroxide; high-swelling montmorillonite clay; amorphous silica particles having a coating of a Group II metal; synthetic silica; and micro-powder silica. In some instances, the pigment may have certain defined requirements, such as particle diameter, oil absorption, surface area, water absorption, refractive index, and solubility in water.
Various binders have been employed to form the ink-receptive coating. Examples of such binders include, again by way of illustration only, a mixture of esterified starch and a water-insoluble cationic polymer; an epoxy resin and a thermoplastic resin; acrylic resins and other water-soluble polymers; a mixture of an alkylquaternaryammonium (meth)acrylate polymer; poly(vinyl alcohol); polyvinylpyrrolidone or vinylpyrrolidone-vinyl acetate copolymers or mixtures thereof; an amine salt of a carboxylated acrylic resin; oxidized or esterified starch; derivatized cellulose; casein; gelatin; soybean protein; styre e-maleic anhydride resin or derivatives thereof; styrene-butadiene latex; and poly(vinyl acetate).
Additional materials have been included in the ink-receptive layer, such as a cationic polymer. Moreover, two or more layers have been employed to form the ink-receptive coating.
An inherent weakness of ink jet printing is the lack of durability of the printed images, particularly when water-based inks are employed. The water-based inks dissolve or smear easily when the images get wet. Recent advances in ink jet printing technology have provided receptive coatings which contain cationic polymers and react with the anionic dyes to i
Flack Steven D.
Hess Bruce H.
Kimberly--Clark Worldwide, Inc.
Robinson James B.
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