Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-03-16
2002-02-26
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S409000
Reexamination Certificate
active
06350507
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording paper, and in particular, relates to a recording sheet for an ink jet printer, in which printing density is high and vivid; ink absorptivity is superior; light resistance, shelf-life in a room, yellow stain prevention and water resistance are excellent; fading and changing of color tone in direct sunlight can be avoided; and ink is quickly absorbed, thereby satisfying high speed printing technique requirements in the future.
The use ink jet printers is further increasing in recent years since they have characteristics such as vividness of recording images, quiet operation, ease of coloring, and the like. In order to prevent the jet nozzle from being blocked due to drying of ink, an ink which is difficult to dry must be used in the ink jet printer. As ink having this property, water-soluble ink which is dissolved or dispersed with adhesive, dye, solvent, additives, or the like, in water, is generally employed. However, a letter or an image formed on the recording sheet by employing the water-soluble ink is inferior to that of printed matter or silver halide photographs due to the use of pigment-type inks, from the viewpoint of light resistance, shelf-life in a room, water resistance, and resistance to direct sunlight.
In recent years, as ink jet printers become less expensive and high vividness and colorfulness of the printing image is anticipated, the requirements for various properties such as light resistance are gradually becoming severe. Therefore, completely satisfying these various requirements such as light resistance is an essential goal for recording sheets for ink jet printers.
In consideration of this present situation, improvement of the light resistance of recording sheets for ink jet printers is being studied. Many patent applications, for example, typified by Japanese Patent Publication No. 4(92)-15745, proposes adding metallic compounds such as magnesium oxide, magnesium carbonate, calcium oxide, calcium carbonate, or the like to improve light resistance. However, it has been confirmed that an improvement in light resistance by merely adding these metallic compounds is not sufficient and a drawback is that a decrease in vividness of images results. Additionally, with regard to conventional methods of improving yellow stain prevention of recording sheets for ink jet printers, many patents, for example, typified by Japanese Patent Unexamined Publication (Kokai) No. 8(96)-169177, are applied for. However, these improvements are not yet sufficient and are not put to practical use. Furthermore, with regard to light resistance, resistance to the room light has been studied; however, preventive methods for fading and changing of color tone in direct sunlight have not been researched sufficiently.
Therefore, an object of the present invention is to provide a superior recording sheet for an ink jet printer which sufficiently satisfies various property requirements such as light resistance of images.
SUMMARY OF THE INVENTION
According to the results that the inventors have derived from various studies with regard to a recording sheet for an ink jet printer, the various properties, such as the light resistance of images, are improved very effectively by including a specific salt in an ink receiving layer, and have thereby attained the present invention. In other words, the present invention provides a recording sheet for an ink jet printer including a water-soluble divalent or greater metallic salt. In the following, the preferred embodiments according to the present invention will be explained in detail.
The recording sheet for an ink jet printer according to the present invention is a lamination in which is provided at least one ink receiving layer on at least one surface of a base material by a providing means such as a coating method, or the like. The ink receiving layer may be provided as two layers or more. In the following, materials which consist of a base material and an ink receiving layer will be explained.
(1) Base Material
As a base material provided for coating an ink receiving layer and a back coat layer according to the present invention, a base paper which is mixed wood pulp such as chemical pulp such as LBKP, NBKP, or the like; mechanical pulp such as GP, POW, RMP, TMP, CTMP, CMP, CGP, or the like; recycled pulp such as DIP, or the like; etc.; or synthetic fiber pulp such as polyethylene fiber, or the like, as a primary component, with pigment and any type of additive which is usually employed in paper such as sizing agent, yield improving agent, strength agent, or the like, alone or in combination, as necessary, and produced by using any type of apparatus such as a fourdrinier paper machine, cylinder paper machine, twin wire paper machine, or the like; can be preferably employed. In addition, a base paper provided with starch, polyvinyl alcohol, or the like using a size press; a base paper provided with an anchor coat layer; a coated paper such as art paper, coated paper, cast coat paper, or the like, on which is provided with a coat layer on these base papers, can be preferably employed. These base papers and coated papers may provide an ink receiving layer directly, and in order to control flattening of the paper, a calender apparatus may be used such as a machine calender, TG calender, soft calender, or the like, before coating the ink receiving layer.
As a base material, a polyolefin resin layer may be provided on the surface of the above-described base paper, and synthetic resin such as polyethylene, polypropylene, polyester, nylon, rayon, polyurethane, or the like; film material comprised of mixture with these; and fiber-formed sheets of these synthetic resins may be employed.
(2) Ink Receiving Layer
(A) Pigment
In an ink receiving layer according to the present invention, generally used pigments which are insoluble or slightly soluble in water can be employed alone or in combination. For example, a white inorganic pigment such as precipitated calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomite, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudo-boehmite, aluminum hydroxide, alumina, lithopone, zeolite, hydrolytic halloysite, magnesium carbonate, magnesium hydroxide, or the like; an organic pigment such as styrene-type plastic pigment, acrylic-type plastic pigment, polyethylene, microcapsules, urea resin, melamine resin, or the like, etc., can be employed.
Of these pigments, as white pigment which is a primary component contained in an ink receiving layer, porous inorganic pigment is preferable since drying properties and absorptivity of an ink for an ink jet printer is excellent. For example, porous synthetic amorphous silica, porous magnesium carbonate, porous alumina, or the like, are preferably employed. Of these, since both printing quality and shelf-life (shelf-life in a room or in direct sunlight) are satisfied in the present invention, the precipitation type or the gel type of porous synthetic amorphous silica with a specific surface of about 200 to 600 g/m
2
can be preferably employed.
(B) Binder Resin
As binder resin contained in an ink receiving layer according to the present invention, polyvinyl alcohol, silyl modified polyvinyl alcohol, vinyl acetate, oxidized starch, etherificated starch, casein, gelatin, soybean protein; cellulosic derivative such as carboxymethyl cellulose, hydroxyethyl cellulose, or the like; conjugate diene type copolymer latex such as maleic anhydride resin, styrene-butadiene type copolymer, methylmethacrylate-butadiene copolymer, or the like; acrylic type polymer latex such as (metha)acrylic acid ester polymer, (metha)acrylic acid ester copolymer, or the like; vinylic type polymer latex such as ethylene-vinylacetate copolymer, or the like; functional group modified polymer latex comprised of monomer including functional groups such as carbox
Ishikawa Takayuki
Iwamoto Kiyoshi
Kobayashi Shinitiro
Kubota Nobuhiro
Onishi Hiroyuki
Hess Bruce H.
Scully Scott Murphy & Presser
Tomoegawa Paper Co. Ltd.
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