Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1998-02-02
2001-05-01
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S195100, C428S409000, C428S500000, C428S522000
Reexamination Certificate
active
06224971
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink-jet recording sheet and a liquid coating composition for forming a recording layer to prepare an ink-jet recording sheet. More particularly, the invention relates to a liquid coating composition suitable for forming, on the surface of a substrate sheet, an ink-receptive layer for ink-jet recording having high water resistance, excellent transparency, good ink absorptivity and good color developability as well as little stickiness not to cause a disadvantageous phenomenon of blocking of sheets.
It is a widely practiced convenient procedure in recent years to prepare posters and other printed materials for presentation by printing out patterns and images formed and stored in computer memories by utilizing a printer operated by the computer along with increasing prevalence of the computer technologies. The printers employed in these technologies include dot-impact printers, laser printers, thermal printers, ink-jet printers and the like, of which ink-jet printers and ink-jet plotters are most widely employed because these machines have advantages that printing-out can be performed with little machine noise, printing-out in full color can be performed therewith and the running cost for printing out is low.
The paper sheet used in printing in an ink-jet printer or ink-jet plotter can be a sheet of plain paper or coated paper but, besides, a recording sheet which is a plastic film provided with an ink-receptive layer on at least one surface of a substrate can also be used. Recording sheets of this type are widely used in the preparation of posters having colored images because the printed material obtained by printing out on such a recording sheet is excellent in the gloss of the surface. The paper size required in such printing is increasing to reach the A3 to A0 size to exceed the A4 size most widely used in the preparation of general documents.
Various coating compositions have been proposed heretofore for forming such an ink-receptive layer on a substrate to prepare an ink-jet recording sheet. For example, Japanese Patent Publication 6-427 proposes a coating composition comprising a polyvinyl alcohol and polyvinylpyrrolidone. Japanese Patent Kokai 7-40646 discloses a double-coated ink-jet recording sheet of which the undercoating layer contains a polyvinylpyrrolidone and the overcoating layer contains a polyvinyl alcohol. Due to the hydrophilicity of these polymers, however, the ink-receptive layer has low water-resistance so that use of the recording sheets outdoors or under a highly humid atmosphere is limited along with a disadvantage of blocking of the sheets stacked one on the other.
Various proposals have been made with an object to overcome the above described problems and disadvantages of the ink-jet recording sheets in the prior art. For example, Japanese Patent Kokai 61-188183 discloses an ink-jet recording sheet having an overall linear transmittance of at least 30%, of which the ink-receptive layer contains from 5 to 50% by weight of colloidal silica particles having a particle diameter not exceeding 80 nm. Japanese Patent Kokai 63-178173 proposes a substrate of an ink-jet recording sheet which is a film of a polyvinyl alcohol modified with acetoacetyl groups and admixed with an organic adjuvant compound selected from aldehyde compounds, amine compounds and epoxy compounds.
The above described ink-jet recording sheets have respective defects in several respects. Namely, the ink-receptive layer containing colloidal silica particles is defective in the low water resistance because the resinous ingredient forming the ink-receptive layer is a water-soluble resin such as polyvinyl alcohol and polyvinylpyrrolidone. The ink-jet recording sheet having an ink-receptive layer based on a substrate of an acetoacetyl-modified polyvinyl alcohol containing an organic adjuvant compound is defective because of the low ink receptivity as well as poor pattern reproducibility and color development.
SUMMARY OF THE INVENTION
The primary object of the present invention accordingly is, by overcoming the above described problems and disadvantages in the prior art, to provide an ink-jet recording sheet of which the ink-receptive layer is highly water-resistant and excellently transparent, exhibits good ink absorption and color development and is free from tackiness on the surface not to cause blocking of the sheets.
The above mentioned ink-receptive layer as desired is obtained by using a liquid coating composition which comprises, as a uniform blend in an aqueous medium, which is water or a mixture of water and ethyl alcohol:
(A) an acetoacetylated polyvinyl alcohol;
(B) a polyvinylpyrrolidone resin; and
(C) an acidic aqueous dispersion of a colloidal silica, of which the weight proportion of the component (A) to component (C) is in the range from 9:1 to 6:4 on a solid basis and the weight proportion of the total amount of the component (A) and component (C) to component (B) is in the range from 9:1 to 6:4 on a solid basis.
Accordingly, the ink-jet recording sheet of the invention is a web material comprising:
(1) a substrate film; and
(2) an ink-receptive coating layer on at least one surface of the substrate film formed from the above defined liquid coating composition.
The above defined ink-jet recording sheet of the invention optionally further comprises:
(3) an overcoating layer having permeability to an ink as formed from a coating composition comprising a hydrophilic resin and a surface roughening agent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The liquid coating composition of the present invention for forming the ink-receptive layer of the ink-jet recording sheet contains, as a film-forming resinous ingredient, an acetoacetylated polyvinyl alcohol resin as the component (A), which preferably has a degree of polymerization in the range from 500 to 2500 or, more preferably, from 1000 to 2000 in view of the balance of various properties of the coating composition and the ink-receptive layer formed therefrom. When the degree of polymerization of the resin is too low, the ink-receptive layer formed from the coating composition is poor in fixing of the ink and in the water resistance while, when the degree of polymerization thereof is too high, the liquid coating composition has an unduly high viscosity and the water resistance of the ink-receptive layer is too high to exhibit good ink absorption. The degree of saponification of the acetoacetylated polyvinyl alcohol resin is in the range from 75 to 99% or, preferably, from 85 to 95% in order to exhibit adequate ink absorptivity. When the degree of saponification is too low, sufficient ink absorption can not be obtained. The degree of substitution of the polyvinyl alcohol resin by the acetoacetyl groups is in the range from 1 to 20% or, preferably, from 2 to 10% relative to the overall monomeric units of the polymer. When the degree of substitution is too low, the ink-receptive layer formed from the coating composition cannot be imparted with fully improved water resistance while, when the degree of substitution is too high, the water resistance of the ink-receptive layer is too high to exhibit good ink absorption.
The acetoacetylated polyvinyl alcohol resin can be prepared by a variety of procedures without particular limitations. For example, a completely or partially saponified polyvinyl alcohol is subjected to an addition reaction with diketene. Alternatively, a partially saponified polyvinyl alcohol is subjected to an ester exchange reaction with an acetoacetic acid ester.
The component (B) in the inventive liquid coating composition is a polyvinylpyrrolidone resin having a weight-average molecular weight of at least 40,000 or, preferably, in the range from 600,000 to 2,800,000. When the molecular weight of the polyvinylpyrrolidone resin is too low, the ink-receptive layer formed from the coating composition containing the same would be poor in fixing of the ink.
The component (C) in the inventive liquid coating composition is a colloidal silica in the form
Fukuhara Kuniaki
Sakazume Naoki
Suzuki Sachiko
Tomizawa Tadashi
Schwartz Pamela R.
Somar Corporation
Wenderoth , Lind & Ponack, L.L.P.
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