Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-03-10
2002-09-10
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S211100, C428S331000, C428S423300
Reexamination Certificate
active
06447883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink-jet recording media having an ink-receptive coating comprising a hydrophilic, water-insoluble polyurethane resin, silica and water-dispersible alumina. The media are capable of absorbing large volumes of aqueous-based ink to provide images having good color gamut, color density and water-fastness.
2. Brief Description of the Related Art
Recently, it has become more popular to used wide format ink-jet printers for printing large format materials such as signs, posters, banners, and advertising displays for indoor and outdoor applications. Typically, the recording medium comprises a base substrate coated with an ink-receptive coating. If the printed image or text is intended for viewing by reflected light, the substrate is typically an opaque paper or film. If the printed image or text is intended for viewing by transmitted light, the substrate is typically a transparent or translucent film.
“Back-lit” films are typically translucent films, where the image (and text) is viewed by means of a light source placed behind the imaged surface of the films. Back-lit films are commonly used for high impact lighted signs, vending and game machine displays, and trade-show displays. For these applications, it is important that the substrate and coatings be durable and have good weather-resistance, particularly water-fastness and light stability.
Traditionally, most inks used in ink-jet printing devices have consisted of molecular dyes carried in an aqueous-based solvent or ink vehicle containing a substantial amount of water. Water-miscible solvents and trace amounts of high-boiling solvents such as glycol or glycol ethers may also be present in the fluid. During imaging (i.e., printing), molecular dyes from the ink penetrate into the ink-receptive coating, leaving solvent to evaporate off the surface of the imaged media. Today, pigmented inks are replacing molecular dye-based inks. Pigmented-based inks have better light stability than molecular dye-based inks which is important for imaged media that are displayed outdoors. Pigmented inks comprise a pigmented colorant carried in an aqueous-based ink vehicle. Unlike molecular dyes, pigmented colorants generally bind to the surface of the film or paper, i.e., recording medium. In order to obtain an image having good color gamut and high color density that does not smear, the recording medium should absorb the ink quickly, while retaining or insolubilizing the colorants on its surface.
The industry is constantly seeking to develop ink-jet recording media having improved ink-receptive coatings.
For example, Viola, U.S. Pat. No. 4,578,285 discloses a transparent ink-jet printing substrate comprising a transparent support carrying an ink-receptive layer comprising at least 70 weight percent polyurethane and 5 to 30 weight percent of a polymer selected from the group consisting of poly(vinyl pyrrolidone), vinyl pyrrolidone/vinyl acetate copolymer, poly(ethylene oxide), gelatin, and poly(acrylic acid). The patent further discloses that in order to prevent front-to-back blocking of the printing substrates and to improve slippage in the printer, the ink-receptive layer may contain about 0 to 0.5% by weight silica.
Romano et al., U.S. Pat. No. 5,605,750 discloses an opaque image-recording element for an ink-jet printer comprising an opaque substrate having on its surface a lower layer of a solvent-absorbing microporous material and an upper layer of a porous, pseudo-boehmite. The microporous layer comprises: (a) a matrix of a substantially water-insoluble thermoplastic organic polymer such as, for example, polyolefins, polyesters, polyamides, polyurethanes, polyureas, poly(vinyl halides), poly(vinylidene halides), polystyrenes, poly(vinyl esters), and polycarbonates; (b) finely divided substantially water-insoluble filler particles such as, for example, silica, mica, and clay; and (c) a network of interconnecting pores.
It would be desirable to have an ink-jet recording medium with an ink-receptive coating that could absorb large volumes of aqueous-based pigmented ink to form an image having good color gamut, color density and water-fastness. The present invention provides such ink-jet recording media.
SUMMARY OF THE INVENTION
The present invention relates to an ink-jet recording medium comprising a substrate having an ink-receptive layer coated thereon. The ink-receptive layer comprises silica, water-dispersible alumina and a hydrophilic, water-insoluble polyurethane resin capable of absorbing at least 200% by weight of water based on the weight of said resin. Preferably, the layer further comprises a metal salt.
Typically, the polyurethane resin comprises at least 25 wt. % the silica particulate comprises at least 25 wt. % and the water-dispersible alumina particulate comprises about 1 to about 10 wt. % of the layer based on the weight of the layer. Preferably, the layer comprises about 30 to about 60 wt. % polyurethane resin and about 30 to about 70 wt. % silica particulate.
Preferably, the silica particulate has a particle size in the range of about 4 to about 10 microns and a surface area of at least 300 m
2
/g. Preferably, the water-dispersible alumina comprises at least 90 wt. % aluminum hydrate.
The substrate may be a paper or film. Translucent films are preferred for use as back-lit films.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an ink-jet recording medium comprising a substrate having an ink-receptive coating prepared from an aqueous-based solution.
The porous ink-receptive coating comprises a hydrophilic, water-insoluble polyurethane resin that is capable of absorbing at least 200% by weight water based on the weight of the resin.
Suitable hydrophilic, water-insoluble polyurethanes include, for example, carboxylated, polyester-type, and polyether-type polyurethanes that are capable of absorbing at least 200% by weight water. As shown in the following examples, it has been found that not all polyurethane resins are suitable for use in the present invention. Suitable polyurethanes may be in the form of a dispersion or solution having a solids content of about 20% or greater. Commercially-available suitable polyurethane resins include IJ-40 and IJ-150 available from Espirit Chemical Company (Sarasota, Fla.).
Silica particles useful in the present invention include amorphous precipitated silica and silica gel particles. The polyurethane resin may be filled with silica particulate, i.e., it may be commercially produced and sold with silica particulate dispersed within the resin. Alternatively, the silica particulate may be added to the ink-receptive coating formulations of this invention as a separate ingredient. Typically, the size of the silica particles is in the range of about 2 &mgr;m to about 15 &mgr;m. Preferably, the silica has a particle size of about 4 to about 10 &mgr;m and a surface area of at least 300 m
2
/g. Suitable silica particles are commercially available, for example, GASIL IJ-35 silica gel available from Crossfield Company (Joilet, Ill.) may be used. Silica particles having relatively high surface areas should be used to enhance the ink absorption capabilities of the coating.
The ink-receptive coating further contains water-dispersible alumina to enhance image quality. The alumina also improves the strength and water-fastness of the coating. Preferably, the water-dispersible alumina comprises at least 90 wt. % aluminum hydrate. As shown in the following examples, when no water-dispersible alumina is present in the coating, the quality of the image is only fair with significant inter-color bleeding and ink cracking visible. Suitable water-dispersible alumina include DISPERAL SOL P2, available from CONDEA Vista Company (Houston, Tex.).
As shown in the following examples, it is important that the ink-receptive coating contain a polyurethane resin having a water-absorption capacity of at least 200 wt. %, silica and water-dispersible alumina in order to obtain high quality prints having good color gamut, col
Chen Tao
Glass Odette M.
Arkwright Incorporated
Hess Bruce H.
LandOfFree
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