Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-21
2003-04-01
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S057000, C525S056000
Reexamination Certificate
active
06541567
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a coating composition for ink-receiving layer formation improved in the fixability and water resistance of inks and a process for producing the same. More particularly, this invention provides a coating composition which, when applied to a substrate such as, e.g., a plastic film, synthetic paper knitted or woven fabric, nonwoven fabric, paper, or metal, gives an ink-receiving layer satisfactory in printability and the fixability and water resistance of inks in ink-jet printing, and further provides a process for producing the composition.
BACKGROUND ART
Ink-jet recording is much utilized recently in various facsimile telegraphs and printers because of its advantages, for example, that high-speed recording is possible, that the impact noise is slight because the printing head does not come into contact with the printing substrate, that various printing substrates including plain paper are usable, and that color recording is possible.
The printed images are required to be high-contrast clear images free from ink running. Because of this, in the case where a printing substrate other than paper, such as a plastic film or synthetic paper, is used, an ink-receiving layer is formed on a surface of the substrate by coating. An ink-receiving layer is required to quickly absorb an ink, fix the absorbed ink, and impart water resistance to the print surface.
Ink-receiving layers have been proposed which contain a cationic compound as an ink fixative so as to meet those requirements. For example, a recording medium comprising a poly(vinyl acetal) resin and a cationic compound as essential components is proposed in Unexamined Published Japanese Patent Application 7-61113. Furthermore, an ink-receiving layer comprising a mixture of poly(vinyl alcohol), polyvinylpyrrolidone, and a vinyl acetate homopolymer and/or a vinyl acetate copolymer and, incorporated in the mixture, a quaternary ammonium compound is proposed in Unexamined Published Japanese Patent Application 7-68926.
However, the above-described techniques still have unsolved problems concerning ink running, etc. attributable to insufficient adhesion to the printing substrate and the insufficient water resistance of the film. In addition, no ink-receiving layer has been obtained so far which is fully satisfactory in ink drying property.
An object of the present invention is to obtain a coating composition eliminating the problems described above and giving an ink-receiving layer for ink-jet recording which is satisfactory in transparency, ink absorbing properties, and the fixability and water resistance of inks.
DISCLOSURE OF THE INVENTION
The present inventors made intensive studies in order to eliminate the above-described problems and, as a result, have achieved the present invention.
The present invention discloses a coating composition for forming an ink-receiving layer showing satisfactory ink absorbing properties, enabling the formation of clear images free from ink running, and excellent in the fixability and water resistance of inks, which comprises: an anionic graft polymer (1) obtained by graft-polymerizing (C) from 100 to 60 wt % at least one hydrophilic radical-polymerizable vinyl monomer and from 0 to 40 wt % other copolymerizable vinyl monomer(s) in an aqueous solution or dispersion comprising a mixture of (A) from 100 to 10 wt % water-compatible polyester resin having an average molecular weight of from 4,000 to 30,000 and from 0 to 90 wt % aqueous urethane resin and (B) a poly(vinyl alcohol) having a degree of saponification of from 75 to 100% and a degree of polymerization of from 500 to 5,000; and a modified cationic polymer (2) obtained by mixing (D) a copolymer of from 10 to 100 wt % at least one radical-polymerizable vinyl monomer having a cationic quaternary ammonium salt group as a side chain and from 90 to 0 wt % other copolymerizable vinyl monomer(s) with (E) a poly(vinyl alcohol) having a degree of saponification of from 75 to 100% and a degree of polymerization of from 500 to 5,000. The present invention further discloses a process for producing the coating composition.
It is generally known that in ink-receiving layers for ink-jet recording, enhanced ink absorbing properties result in reduced water resistance and, conversely, improved water resistance results in reduced ink absorbing properties and impaired ink drying properties to arouse problems such as reduced image quality due to ink running or beading.
In order to eliminate such problems, the present inventors previously proposed the formation of an ink-receiving layer having a two-layer structure composed of anionic and cationic layers. However, the inventors have lately found that the properties of the two-layer structure can be attained with a single fluid. The present invention has been achieved based on this finding.
The composition of the present invention is a coating composition which is a single fluid wherein the anionic polymer in which a hydrophilic vinyl monomer has been graft-polymerized coexists with the cationic polymer surrounded by a poly(vinyl alcohol).
BEST MODES FOR CARRYING OUT THE INVENTION
The present invention will be explained below in detail.
The water-compatible polyester resin used in the present invention is a polyester resin having an average molecular weight of from 4,000 to 30,000.
The water-compatible polyester resin for use in the present invention may be produced by subjecting a dicarboxylic acid and a diol to esterification (transesterification) and polycondensation by a known production technique. However, methods for this production should not be limited in any way.
The dicarboxylic acid ingredient preferably consists mainly of an aromatic dicarboxylic acid, such as terephthalic acid, isophthalic acid, phthalic acid, or naphthalenedicarboxylic acid, or of an ester thereof. This is because use of such dicarboxylic acids has an advantage that the aromatic nuclei of the acids have a high affinity for hydrophobic plastics to thereby improve adhesiveness. In particular, a water-compatible polyester resin produced from terephthalic acid shows tenacious adhesion to molded objects of poly(ethylene terephthalate) type polyesters and is hence a preferred water-compatible polyester resin.
An aromatic dicarboxylic acid such as those shown above or an ester thereof is preferred as the dicarboxylic acid ingredient used for forming the water-compatible polyester resin for use in the present invention. However, an aliphatic dicarboxylic acid such as adipic acid, succinic acid, sebacic acid, or dodecanedioic acid, an alicyclic dicarboxylic acid such as cyclohexyldicarboxylic acid, a hydroxycarboxylic acid such as hydroxybenzoic acid, or an ester of any of these acids may be used, besides those aromatic ingredients, as the dicarboxylic acid ingredient or as a part thereof.
In the case of using an ester, it is a lower-alkyl ester, e.g., a methyl ester or ethyl ester. These esters may be monoesters or diesters.
On the other hand, the diol ingredient to be used may be ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, or a bisphenol.
The water-compatible polyester resin of the present invention is produced through polymerization in such a manner that the molecule thereof contains sulfonic salt groups or carboxylic salt groups as hydrophilic groups so as to impart water solubility or water dispersibility to the resin.
Examples of techniques for incorporating a sulfonic salt include a method in which a dicarboxylic acid component such as, e.g., a 5-sodiumsulfoisophthalate is used as part of the dicarboxylic acid ingredient. The use amount thereof is preferably from 2 to 15 mol % based on the dicarboxylic acid ingredient.
Examples of techniques for incorporating a carboxylic salt include a method in which a polyester containing a carboxylic acid is prepared, for example, by using a polycarboxylic acid containing three or more carboxyl groups as an acid ingredient to be condensed in polyester resin production or by grafting a polymeri
Murata Sakae
Nakatani Masaru
Nishita Hayato
Riku Shuichiro
Fish & Richardson P.C.
Lee Rip A.
Takamatsu Oil & Fat Co., Ltd.
Wu David W.
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