Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-08-28
2003-05-20
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
Reexamination Certificate
active
06565951
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording sheet. More particularly, the present invention relates to an ink jet recording sheet having an enhanced capability of recording clear ink images at a high recording speed and a high resistance to blotting of ink.
2. Description of the Related Art
Currently, in the field of ink jet recording, due to the development of an ink jet color printer suitable for preparing colored hard copies at a high speed, it has become possible to obtain an ink jet print having a high image clarity and a high printing quality. Nevertheless, to further improve the print quality, chroma, appearance and clarity of images, a new recording sheet having an enhanced performance is required. Especially, due to the development of an ink jet printing system with high printing speed, resolution and chroma, the ink-jet recording material is required to have further enhanced properties, for example, enhanced ink-absorption speed, a high ink-absorption capacity and a regular ink-blotting property. To meet to these requirements, various types of recording sheets having an ink-receiving layer formed on a surface of a substrate have been produced.
For example, Japanese Unexamined Patent Publication No. 55-51585 discloses a coating layer comprising amorphous silica particles (having a particle size of 0.1 to 10.0 &mgr;m) and a polymeric binder formed on a substrate.
Japanese Unexamined Patent Publication No. 56-148584 discloses a recording sheet having an ink receiving layer formed on a surface of a substrate and comprising a porous inorganic pigment, for example, natural zeolite, synthetic zeolite, diatomaceous earth, fine particulate silicic acid or synthetic mica, which has a function of absorbing and holding a coloring material on a surface of a substrate.
Nevertheless, these conventional recording sheets are disadvantageous in that when the ink receiving layer is formed in a small amount, the printed ink spreads irregularly and blots on the surfaces of the recording sheets, and when the ink-receiving layer is formed in a large amount, the ink receiving layer is easily peeled off and a fine powder is formed on and scattered from the surface, even though the spreading and blotting of the ink can be prevented.
To solve the above-mentioned problem, an attempt was made to provide a recording sheet provided with an ink receiving layer containing an increased amount of a binder resin and having an enhanced mechanical strength. However, this type of recording sheet is disadvantageous in that the ink receiving layer exhibits an insufficient ink-absorbing capacity, and the printed ink spreads irregularly on the ink receiving layer and thus the resultant image quality is unsatisfactory. Therefore, it is difficult to provide a satisfactory resolution or reproduction of halftone colors.
Also, Japanese Unexamined Patent Publication No. 62-288,076 discloses a binder resin having an enhanced strength and comprising a water insoluble polymer resin prepared by reacting polyvinyl alcohol with acrylic acid and methyl methacrylate. However, since this water-insoluble polymer resin is anionic, and the main components of the ink are also anionic, the anionic ink is not easily and stably fixed to the ink-receiving layer formed from the anionic, water-insoluble polymer resin. Also, if the water-insoluble polymer resin is contained too large an amount in the ink receiving layer, the ink bleeds out with the lapse of time. Further, if the content of the water-insoluble polymer resin in the ink receiving layer is too small, the bonding strength-enhancing effect of the resin is insufficient.
As mentioned above, although various attempts have been made to produce ink jet recording sheets, it has not yet been possible to realize a new type of ink jet recording sheet having a satisfactory resistance to ink-blotting, a high ink-absorbing capacity, an excellent surface strength and the capability to form colored images with a high brightness.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink jet recording sheet capable of recording clear images at a high recording speed without ink-blotting, in an ink jet recording system such as, for example an ink jet printer or an ink jet plotter, and having an excellent surface strength.
Another object of the present invention is to provide an ink jet recording sheet useful for an ink jet recording system for printing images such as letters, characters and pictures by using an aqueous ink, having a high ink-absorbing speed, a high resistance to blotting and spreading of ink dots, and a satisfactory capability of forming ink images having a high color brightness, a good dot shape and a high sharpness at the edges of the images, and thus being capable of recording the ink images with high resolution at high speed.
The above-mentioned objects can be attained by the ink jet recording sheet of the present invention, in which a substrate and an ink receiving layer are formed on at least one surface of the substrate and comprise a pigment and a binder,
wherein
the binder comprises (1) a self-emulsifying cationic resin consisting essentially of at least one water-insoluble acrylic copolymer having a cationic functional group, produced without using an emulsifying agent and capable of being emulsified in water without using an emulsifying agent; (2) an water-soluble non-ionic polymeric material comprising at least one member selected from the group consisting of polyvinyl alcohol, silanol group-modified polyvinyl alcohols, starch and oxidized starches; and (3) a water-soluble cationic resin comprising at least one member-selected from the group consisting of polydimethyldiallyl ammonium chloride, polyallylamine and polyoxypropylenemethyldiethyl ammonium chloride having 9 oxypropylene chain groups per molecule,
the self-emulsifying cationic resin (1) is present in a content of 5 to 70% by weight based on the total weight of the binder, and
the ink receiving layer contains no emulsifying agent.
Also, in the ink jet recording sheet of the present invention, the water-insoluble acrylic copolymer having cationic functional group is preferably a copolymerization product of at least one acrylic monomer selected from the group consisting of alkyl acrylates having 4 to 21 carbon atoms and alkyl methacrylates having 5 to 22 carbon atoms with at least one cationic, ethylenically unsaturated monomer having at least one cationic group selected from tert-amino groups and quaternary ammonium salt groups.
Further, in the ink jet recording sheet of the present invention, the pigment preferably comprises at least one white pigment selected from the group consisting of amorphous synthetic silica, alumina, hydrated alumina sol, aluminum silicate, magnesium silicate, precipitated calcium carbonate, ground calcium carbonate, calcium silicate, aluminum hydroxide, zeolite, calcined clay, kaolin clay, talc, white carbon and organic (plastic) pigments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Generally speaking, in the preparation of an aqueous emulsion or latex of a conventional water-insoluble acrylic copolymer resin, an anionic, cationic, nonionic or polymeric emulsifying agent is used to stably emulsify or disperse the resin in water. However, it has became clear that the emulsifying agent causes the adhesion of the resultant coating layer, formed from the resin latex or emulsion, to the substrate and the water-resistance of the coating layer to be greatly reduced. Also, it has become clear that the emulsifying agent affects the surface tension of the ink applied to the coating layer so that the ink easily blots and spreads irregularly on the surface of the coating layer.
To remove the above-mentioned disadvantages, in the ink jet recording sheet of the present invention, the ink receiving layer comprises, as a binder, a self-emulsifying cationic resin consisting essentially of at least one water-insoluble acrylic copolymer having cationic functional groups, produced without using an emulsifying agen
Kondo Hiromasa
Okumura Yoshitaka
Sugiyama Naonobu
Grendzynski Michael
Hess Bruce H.
OJI Paper Co. Ltd.
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