Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1997-08-27
2001-06-26
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S327000, C428S331000, C428S328000, C428S329000, C428S421000, C428S447000, C428S448000, C428S449000
Reexamination Certificate
active
06251512
ABSTRACT:
TECHNICAL FIELD
This invention relates to writable and printable films and paper, particularly films and paper comprising a water absorbing layer coated on a polymeric film or paper and more particularly to films or paper having a water absorbing layer comprising a blend of crosslinked, water absorbing polymer particles, a water insoluble binder polymer, and optionally, inert particles.
BACKGROUND OF THE INVENTION
There are many transparency films that are writable in some fashion or another. Writability has been provided for these films by various means including surface treatment and application of materials onto the film substrate. Solvent based pen writability is typically not an insurmountable problem when it is necessary to write on a film. However, films that will work successfully with water based writing instruments typically have a number of deficiencies. Many configurations of films that are writable using both solvent and water-based instruments tend to use polyvinyl pyrollidone or polyvinyl alcohol as a water accepting agent. Varying chemistry is used to immobilize the water-accepting polymer to improve rubbing resistance and avoid tack of the coating. Immobilization is usually accomplished through crosslinking, inter-penetrating polymer networks, or ionic interactions.
Many constructions accept water based and solvent based inks, dry in a short time, and are resistant to pressure from moist fingers. Typically, these materials are transparent for use on an overhead projector. However, in general, these films are smooth and therefore do not accept pencil writing. Pencil writing is typically not a requirement of an overhead transparency.
Several examples of writable films have been described. These include for example, U.S. Pat. No. 5,126,194 wherein an ink jet transparency is described as having polyvinyl pyrollidone, a sulfonated polyester, a polyalkylene oxide, polyvinyl alcohol, nonylphenoxypolyglycidol, and inert particles coated onto a polyester film substrate. This construction performs well at room temperature, but the coating is not robust and durable under heat and humidity aging, and turns into a viscous liquid during heat and humidity aging.
Many coating formulations containing water-soluble polymers such as polyvinyl pyrollidone, sulfonated polyesters, or polyvinyl alcohol tend to exhibit similar problems with heat and humidity aging.
An alternative to examples of writable films as described above is examples of synthetic papers or tracing films. These papers tend to be roughened polymeric films. In JP 256607, polyester film was coated with a graft copolymer resin that is composed of an acrylic polymer as a principle chain, and a hydroxyl containing acrylic polymer as a branch chain. Acrylic polymers for the principle chain include polymers of acrylic acid, methacrylic acid, and their metal or ammonium salts. The film claims to have a good writing property, solvent resistance, adhesion of the coating layer, and surface roughness. Another example is JP 97,528/82 in which a polyester film was coated with a water-soluble cationic acrylic resin and benzophenone, which was subsequently UV cured for water resistance. Another example is JP 97,684/79, which describes a mixture of polyvinyl alcohol, a synthetic copolymer, and clay coated on PVDC (polyvinylidene chloride) primed polyester and used as a writable film.
For example, water-absorbing materials that are solvent insoluble have been described. U.S. Pat. No. 4,887,097 describes an ink jet recording medium, which contains particles of solvent insoluble resin that is capable of absorbing water in an amount of 50 times or more as much as its own weight. Examples of solvent insoluble resin particles include natural resins such as albumin, gelatin, casein, starch, cationic starch, gum arabic, and potassium alginate and synthetic resins such as polyvinyl alcohol, polyamide, polyacrylamide, quarternary polyvinyl pyrollidone, polyethyleneimine, polyvinylpyridinium halide, melamine resins, polyurethane, polyester, and sodium polyacrylate.
In WO 96/23659, a coating composition for a plastic film is described. The coating composition is made from an acrylic polymer or ionomer resin and an ink receptive particulate, such as a molecular sieve and/or a carbohydrate polymer such as cellulose, carboxymethyl cellulose, or cornstarch. The coating composition facilitates adhesion of ink to the polyolefin film and reduces the dry time of the ink to less than two minutes. The acrylic polymer contains carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, and mixtures thereof.
Some examples of writable adhesive coated products have been described. For example, U.S. Pat. No. 4,708,907 describes a writable adhesive tape consisting of a polyolefin substrate, having on one side an adhesive layer and on the opposite side a writable anti-adhesive layer. The writable anti-adhesive layer comprises 25% to 55% by weight of a chlorinated polyolefin, 20% to 50% by weight of a polyaldehyde resin together with 5% to 20% by weight of an anti-adhesive agent, and 25% by weight of a matting charge.
Another example (U.S. Pat. No. 4,985,302) describes a removable self-adhesive sheet with a writable surface. In this example, the sheet material is a polymer film selected from the group consisting of polyvinyl chloride, polypropylene, cellulose acetate, polyester, cellophane, high density polyethylene, or polyolefin coextrusion. The writable side of the sheet is coated with a mixture of a pigment, vinyl or acrylic resin, synthetic wax, epoxide stabilizer, phthallic acid esters, and the solvents ethyl acetate and ethanol.
SUMMARY OF THE INVENTION
Briefly, in one aspect of the present invention, a writable matte article is provided comprising a water-absorbing layer coated on a substrate. The water absorbing layer is a unique blend of a crosslinked, water absorbing polymer particle, a water insoluble binder polymer with good adhesion to the substrate, and optionally, inert organic or inorganic particles that impart a matte finish on at least one major surface of the substrate. Advantageously, drying times of these inks using the present invention is reduced from about 10 minutes to 10 seconds. Preferred substrates are polyester and polyolefin-based films. As used in this application “writable” would include not only hand writable articles, but also printable articles, such as those printed on a laser jet printer, impact printer or an ink jet printer.
Advantageously, the writable matte article of the present invention has paper-like writability with all types of pens and pencils and withstands heat and humidity aging with a minimum of problems.
This unique invention is particularly useful as a writable backing for an adhesive coated product such as a tape, label, tag or flag. An adhesive coated product may or may not have a release coating depending on the application. The invention is also useful as a substrate for ink jet and laser printing.
The invention has the following advantages:
The matte surface accepts pencil writing and produces a line darker than or equal to pencil writing on bond paper.
The article has a matte appearance, which is transparent for reading and copying print but rough enough to eliminate glare and ghosting during copying.
The article accepts ink from solvent-based pens without dewetting or wicking.
The article accepts ink from water-based pens without film splitting, de-wetting, or wicking compared to other polymeric films.
Water-based inks can be drawn into the coating and do not smear compared to uncoated polymeric films.
Furthermore, the coating used in the present invention has good wet strength and resists rub off during repeated writing in the same place with a water-based pen. Additionally, the coating has good dry strength when writing under pressure with a sharp pencil or fine point metal roller pen.
The coating of the present invention accepts ink jet, impact, and laser printing with good clarity and image adhesion.
REFERENCES:
patent: 3011988 (1961-12-01), Luedke et al.
patent: 331
Gustafson Frederick John
Hamer Kevin Mark
Kumar Ramesh Chand
3M Innovative Properties Company
Le Hoa T.
Peters Carolyn V.
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