Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-12-20
2003-11-18
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S204000, C428S032100
Reexamination Certificate
active
06649252
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink jet recording element for improving the durability of an ink jet image.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant which is molecularly dispersed or solvated by a carrier medium. The carrier medium can be a liquid or a solid at room temperature. A commonly used carrier medium is water or a mixture of water and organic co-solvents. Each individual dye molecule is surrounded by molecules of the carrier medium. In dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor light-fastness. When water is used as the carrier medium, such inks also generally suffer from poor water-fastness.
DESCRIPTION OF RELATED ART
U.S. Pat. No. 6,087,051 relates to an ink jet recording element containing a protective overcoat layer of an aqueous polyurethane resin or an aqueous polyacryl resin. In addition, there are comparison examples in that patent which use a polyester resin, and the aqueous polyurethane resin and polyacryl resins are said to have advantages over the polyester resin. However, there are problems using a polyurethane resin or an aqueous polyacryl resin in that these resins have to be synthesized from virgin raw materials and the resins cannot be recycled.
It is an object of this invention to provide an ink jet recording element which has an ink jet image with improved durability. It is another object of this invention to provide an ink jet recording element containing an overcoat layer made with a material that can be made from recycled materials and is capable of being recycled.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the present invention which comprises an ink jet recording element comprising a support having thereon an image-receiving layer containing an ink jet image and an overcoat layer of a water-dispersible, hydrophobic polyester resin having the following general formula:
I
n
—P—A
m
wherein
I is an ionic group;
n is an integer from 1-3;
P is a polyester backbone;
A is an aliphatic group comprising a straight or branched chain fatty acid or triglyceride thereof having from about 6 to about 24 carbon atoms; and
m is an integer from 3-8.
It was found that the durability of an ink jet image is improved using an overcoat layer of a material that is capable of being recycled.
DETAILED DESCRIPTION OF THE INVENTION
The ionic groups I in the above formula which provide the polymer with water-dispersibility are typically derived from a carboxylic acid group which is introduced into the resin by polyacid monomers such as trimellitic anhydride, trimellitic acid, or maleic anhydride or sulfonate groups which come from monomers such as dimethyl 5-sulfoisophthalate, dimethyl 5-sulfo,1,3-benzenedicarboxylate, sulfoisophthalate ethylene glycol, dihydroxyethyl-5-sulfol, 3-benzenedicarboxylate, or from sulfonated alkenically unsaturated end groups as described in U.S. Pat. No. 5,281,630, the disclosure of which is hereby incorporated by reference. The weight percent of ionic monomers in the resin is from 1% to 20%, but 1% to 10% is preferred.
The backbone P of the polymer in the above formula is composed of polyester groups. It can be any linear or branched polyester made using polyacids and polyalcohols. The weight percent of the polyester backbone ingredients range from 30-80% of the whole resin, with the most preferred being 50-60% by weight. Examples of aromatic dicarboxylic acids useful in the backbone polyester polymer, P, employed in the invention include, but are not limited to, terephthalic, isophthalic, phthalic, and 2,6-naphthoic, succinic, glutaric, adipic, 1,4-cyclohexane dicarboxylic, maleic, fumaric, and azelaic. The polyalcohol component of the polyester can be virtually any dihydroxy functional compound. Aliphatic and alicyclic glycols would be the most useful. Useful glycols include, but are not limited to, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol, diethylene glycol, and triethylene glycol.
The backbone polyester consisting of any combination of the above polyacids and glycols may further directly include or incorporate by transesterification a multifunctional polyol selected from, but not limited to, glycerol, trimethylolpropane, erythritol, pentaerythritol, trimethylolethane, or a monosaccharide.
As noted above, A in the above formula is an aliphatic group comprising a straight or branched chain fatty acid or triglyceride thereof having from about 6 to about 24 carbon atoms, such as stearic, oleic, palmitic, lauric, linoleic, linolenic, behenic acid, or their mixtures. These can come from hydrogenated or unhydrogenated animal or vegetable oil, such as beef tallow, lard, corn oil, or soy bean oil. The weight percent of the aliphatic moiety can be 10-60%, with 20-40% by weight being the preferred amount.
In a preferred embodiment of the invention, the water-dispersible, hydrophobic polyester resin employed comprises a reaction product of 30-70% by weight of a poly(ethylene terephthalate) condensation polymer; 5-40% by weight of a hydroxy functional compound having at least two hydroxyl groups; 1-20% by weight of a carboxy functional compound having at least two carboxyl groups and 10-60% by weight of a C
6
-C
24
straight chain or branched fatty acid or triglyceride. The resin is further characterized in that the hydroxy functional compound is present at 1-3 times the equivalents of the hydrophobic moiety. The preparation of such hydrophobic polyester resins is described in detail in U.S. Pat. No. 5,958,601, the disclosure of which is hereby incorporated by reference. In another preferred embodiment, the water-dispersible, hydrophobic polyester resin comprises water-dispersed transesterified polyester, e.g., poly(ethylene terephthalate) transesterified in the presence of stearic acid and trimellitic acid, or oleic acid and trimellitic acid.
In another preferred embodiment of the invention, the water-dispersible, hydrophobic polyester as described above is physically mixed with a thermoplastic or thermosetting polymer. The thermoplastic or thermosetting polymer lends added hydrophobicity to the layer, as well as enhanced coating flexibility and serves as a diluent to the polyester component to minimize cross-linking which would deleteriously alter coating properties.
Examples of such thermoplastic or thermosetting polymers useful in the invention include, but are not limited to, carboxylated styrene butadiene, styrene/acrylate or methacrylate ester compositions containing acrylic or methacrylic acids, hydrolyzed styrene maleic anhydride copolymers, styrene maleic acid salt copolymers, styrene maleic ester copolymers, styrene (meth)acry
DeMejo Lawrence P.
Nesbitt Sandra D.
Romano, Jr. Charles E.
Cole Harold E.
Eastman Kodak Company
Schwartz Pamela R.
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