Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-12-23
2002-09-10
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S331000
Reexamination Certificate
active
06447881
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a recording sheet having an ink-receiving layer, which comprises a substrate sheet made of, for example, a resin such as PET or polyvinyl chloride, paper, steel, fabrics or cloths, and an ink-receiving layer formed thereon. More particularly, the invention relates to a recording sheet having an ink-receiving layer, on which images of uniform density and high sharpness can be printed without bleeding and which is able to provide a printed matter having not only excellent water resistance, weathering resistance and fading resistance but also sufficient strength.
The present invention also relates to a coating liquid for forming the ink-receiving layer.
BACKGROUND OF THE INVENTION
An ink-jet printing method has advantages such that the method can provide printing matter of good image qualities similar to those obtained by a conventional multi-color printing method or color photographic method, that it is easy to adapt the ink-jet printing method to a high speed printing and a multi-color printing, and that even in case where the number of copies per one set is not so large, printing can be made at a lower cost as compared with conventional printing methods. Therefore, the ink-jet printing method has rapidly come into wide use in various purposes.
In the ink-jet printing method, however, an aqueous ink is used to print on a recording sheet which is generally obtained by coating a substrate sheet with a water-soluble polymer such as polyvinyl alcohol to form an ink-receiving layer. Therefore, this method has a problem that the printed recording sheet has poor water resistance to lead to deterioration of the image quality when the printed recording sheet is placed in a high-humidity environment or is wet. There is another problem that a highly sharp and accurate printed image cannot be obtained because such a conventionally used recording sheet does not have a sufficient ink absorbtion capacity.
In order to solve the above problems, recording sheets having an ink-receiving layer which contains fine particles of silica, alumna or the like and which is formed on a substrate sheet have been proposed.
For example, Japanese Patent Laid-Open Publication No. 149475/1987 discloses a recording sheet having an ink-receiving layer containing spherical particles of silica having an average particle diameter of 1 to 50 &mgr;m. Japanese Patent Publication No. 24906/1991 discloses a recording medium having an ink-receiving layer containing a cationic hydrated aluminum oxide. Japanese Patent Publication No. 19037/1992 discloses a recording medium having an ink-receiving layer containing a cationic colloidal silica. Japanese Patent Laid-Open Publication No. 115984/1992 discloses a recording sheet wherein a substrate is provided with a layer of pseudo-boehmite alumina on which a layer of porous silica is further provided. Japanese Patent Laid-Open Publication No. 55829/1994 discloses a recording sheet wherein a substrate is provided with a layer of porous silica particles having an average particle diameter of 2 to 50 &mgr;m, an average pore diameter of 8 to 50 nm and a pore volume of 0.8 to 2.5 cc/g on which a pseudo-boehmite porous layer obtained by drying an alumina sol is further provided.
Most of the recording sheets mentioned above are intended to be used for printing with dye-based inks. Since the dye-based inks are poor in weathering resistance, the resulting printed matter has drawbacks of discoloration or fading caused by exposure to ultraviolet light, oxygen or ozone. Such drawbacks are conspicuously brought about especially when the printed matter is used outdoors.
For the above reasons, pigment-based inks exhibiting excellent weathering resistance have come to be used even in the ink-jet printing method.
However, the pigment particles usually have diameter of 10 to 500 nm, and the conventional ink-receiving layers do not have pores capable of absorbing such large particles effectively, so that the pigment particles are hardly absorbed by the ink-receiving layer and then remain on the surface of the layer. Thus, there is a further problem that the printed recording sheets have insufficient water resistance or insufficient abrasion resistance and the pigment particles may come off by rubbing, thereby resulting in removal of the color component.
The present invention has been made to solve such problems associated with the prior art as described above, and it is an object of the invention to provide a recording sheet having an ink-receiving layer, which has excellent printability such that images of uniform density and high sharpness can be printed thereon without bleeding, and which has not only excellent water resistance, weathering resistance and fading resistance, but also sufficient strength.
It is another object of the invention to provide a recording sheet having an ink-receiving layer, which is particularly preferable for high-speed printing using an ink-jet method, which is employable not only with dye-based inks but also with pigment-based inks, and which is favorably used, for example, as a recording sheet for a large-sized color printer made from white PET or art paper, and also as a recording sheet with a substrate having no absorbing capacity and requiring transparency.
It is a further object of the invention to provide a coating liquid for forming the ink-receiving layer.
SUMMARY OF THE INVENTION
The recording sheet having an ink-receiving layer according to the invention is a recording sheet which comprises a substrate sheet and an ink-receiving layer containing oxide particles formed on the substrate sheet, wherein the ink-receiving layer has pores having a diameter in the range of 3.4 to 2,000 nm, the pore volume of pores having a diameter of 3.4 to 30 nm is in the range of 0.2 to 1.8 ml/g, preferably 0.5 to 1.5 ml/g, and the pore volume of pores having a diameter of 30 to 2,000 nm is in the range of 0.1 to 1.5 ml/g, preferably 0.2 to 1.2 ml/g.
It is preferable that the oxide particles have an average diameter in the range of 2 to 1,000 nm and are a mixture of hydrophobic oxide particles whose surfaces have been made hydrophobic and hydrophilic oxide particles whose surfaces have not been made hydrophobic.
It is also preferable that the weight ratio of the hydrophobic oxide particles to the hydrophilic oxide particles in the mixture is in the range of 0.01 to 9.
The oxide particles are preferably silica particles or composite oxide particles comprising a silica component.
The coating liquid for forming an ink-receiving layer according to the invention is a coating liquid which comprises oxide particles, a binder and a dispersion medium consisting of water and/or an organic solvent, said oxide particles and said binder being dispersed in the dispersion medium, wherein the oxide particles have an average particle diameter of 2 to 1,000 nm and are a mixture of hydrophobic oxide particles whose surfaces have been made hydrophobic and hydrophilic oxide particles whose surfaces have not been made hydrophobic, and the hydrophobic oxide particles and the hydrophilic oxide particles are agglomerate particles.
DETAILED DESCRIPTION OF THE INVENTION
The recording sheet having an ink-receiving layer according to the invention is described in detail hereinafter.
Recording Sheet Having Ink-recording Layer
The recording sheet having an ink-receiving layer according to the invention comprises a substrate sheet and an ink-receiving layer formed on the substrate sheet.
Substrate Sheet
The substrate sheet is described below.
There is no specific limitation on the substrate sheet for use in the invention, and, for example, films of resins such as PET and polyvinyl chloride, various types of paper, steel plates, fabrics and cloths.
Ink-receiving Layer
The ink-receiving layer of the recording sheet of the invention is described below.
The ink-receiving layer formed on the substrate sheet comprises oxide particles and a binder.
Oxide Particles
The oxide particles for use in the invention have an average particle diameter of usually 2 to 1,0
Komatsu Michio
Nakai Mitsuru
Nishida Hiroyasu
Catalysts & Chemicals Industries Co. Ltd.
Schwartz Pamela R.
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