Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Spatial relationship specified between color-former and...
Reexamination Certificate
1999-10-28
2002-06-25
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Spatial relationship specified between color-former and...
C427S152000, C503S200000
Reexamination Certificate
active
06410479
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thermally sensitive recording medium whose preservability, printability and glossiness are improved.
DESCRIPTION OF THE PRIOR ART
Generally, a thermally sensitive recording medium having a thermally sensitive layer mainly composed by colorless or pale colored dye precursor which is an electron donating dye precursor (hereinafter shortened to a dye precursor) and a color developer which develops color by a chemical reaction with the dye precursor when heated, is disclosed in Japanese Patent Publication 45-14035 and is widely and practically used. For a recording means of a thermally sensitive recording medium, a thermal printer in which a thermal head is built in is used. This recording method is superior to the conventional ordinary recording methods from the view points of noiseless recording, no need of development and fixing procedures, maintenance free, relatively cheap and compact and very clear image. Therefore, this procedure is widely used in the fields of facsimile and computer, various kinds of measuring equipment and labels.
However, in a case of a conventional thermal recording medium, since only a thermally sensitive recording layer whose main components are dye precursor, color developer and fixing agent is coated on the surface of substrate, the resistances against light, water, heat, plasicizer and oil are not stable and the color change by aging at preservation is pointed out as a problem. Further, in a case of this type of thermal recording medium, the glossiness of image part and non-image part is not considered.
To solve the problem of the conventional thermally sensitive recording medium, a method of forming a protecting layer over the surface of thermally sensitive recording layer has been suggested. For example, the method to use hydrophobic emulsion of high polymer compound is disclosed in Japanese patent Laid Open Publication 56-146794 or the method to form an intermediate layer of water soluble high polymer compound or hydrophobic emulsion of high polymer compound and then to form a surface layer by oil type coating composed by hydrophobic high polymer compound over above mentioned intermediate layer is disclosed in Japanese Patent Laid Open Publication 58-199189. In these methods, the preservative property of the image is improved, however, the glossiness is very low.
In general, UV varnish is coated over the surface of the thermally sensitive recording medium to provide the lustrous property, however, this method has several problems. That is, since the thermally sensitive recording medium by this method generates stickiness during the printing procedure, it is not suited to use with a thermal head. Further, the fixing of ink on this thermally sensitive recording medium is not good and the printing property of it is not sufficient. In Japanese Patent Laid Open Publication 1-178486, the thermally sensitive recording medium having an intermediate layer composed by water soluble high polymer, pigment and cross-linking agent on the thermally sensitive recording layer, further having a glossing layer composed by lustrous hydrophobic high polymer compound and a slipping agent on the intermediate layer is described. However, since this glossing layer is coated using solvent, the working efficiency for coating is very bad and is not sufficient for practical use.
Further, in Japanese Patent Laid Open Publication 2-169292, the thermally sensitive recording medium on which a protecting layer mainly composed by wax, resin, inorganic pigment smaller than 0.5 &mgr;m average diameter or composed mainly by resin and inorganic pigment smaller than 0.5 &mgr;m average diameter is disclosed. And, in Japanese Patent Laid Open Publication 2-175281, the lustrous thermally sensitive recording medium which has protecting layer composed by silica whose average diameter is smaller than 0.05 &mgr;m and/or calcium carbonate and water soluble binder is disclosed. If any of these protecting layers is formed, and printed by a thermal head, glossiness of the surface is deteriorated and sometimes a problem of sticking is generated. Further, in Japanese Patent Laid Open Publication 1-122483, the thermally sensitive recording medium which forms a protecting layer on the thermally sensitive recording layer mainly composed of water soluble resin formed on a substrate, and whose surface glossiness based on JIS-P-8142 is bigger than 40(GS(75°))% is described. However, when this thermally sensitive recording medium is printed by thermal head, sometimes there is a problem that the glossiness is hurt.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to solve above mentioned problems and to provide a thermally sensitive recording medium whose suitability for a thermal head and suitability for printing is improved.
The inventors of this invention, have conducted an intensive study and have found that a thermally sensitive recording medium which has good image preserving ability and glossiness can be obtained by forming a glossing layer mainly composed by an inorganic pigment and a fixing composition having heatproof sticking tendency which does not cause sticking at higher temperature on a thermally sensitive recording layer formed on the substrate, and accomplished the present invention.
That is, a thermally sensitive recording medium of this invention is characterized by forming a glossiness layer containing mainly an inorganic pigment and a fixing composition which does not cause sticking at higher temperature than 200° C. on the thermally sensitive recording medium formed on a substrate, and the surface glossiness based on JIS-P-8142 (an angle of incidence and an angle of reflection is 75°) of the glossiness layer is higher than 50%. If more improved image preservative ability and glossiness are required, it is effective to form an intermediate layer between the thermally sensitive recording layer and a glossiness layer composed mainly by inorganic pigment and fixing composition.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as the example of an inorganic pigment used in the glossiness layer or in the intermediate layer, the compound which does not hurt the property as the thermally sensitive recording medium and glossiness can be used. As the concrete example, metal oxide such as silica, colloidal silica, titania, zirconia, alumina, antimony pentaoxide or zinc oxide, metal carbonate such as calcium carbonate or magnesium carbonate, aluminum hydroxide and barium sulfate can be mentioned, however, it is not intended to be limited to these pigments. These compounds can be used singly or in combination. Especially among these compounds, colloidal silica and barium sulfate are very useful to obtain an excellent lustrous surface because the primary particles of these compounds are stable and do not form flocks, further the refractive index of these particles is comparatively low. And, the dispersion of colloidal silica and barium sulfate is very stable and hardly forms a precipitate, further since fine particles of these compounds can be dispersed in comparatively high concentration, the coating amount can be adjusted to higher level and has high work efficiency. Therefore, these compounds are desirably used.
In this invention the property of fixing composition which does not cause sticking at higher temperature than 200° C. is measured by following method.
(1) On paper of 60g/m
2
density and 74 &mgr;m thickness, the fixing composition is coated by 20 g/m
2
, left for 5 minutes in an oven of 110° C. and the coated layer of fixing composition is completely hardened.
(2) The obtained coated paper is cut to 4 cm×8 cm size and doubled up so that the coated surface with fixing composition is contacted. Thus the specimen of 4 cm×4 cm size is prepared.
(3) The specimen is placed on a hot plate heated to 200° C. and a weight of 500 g (whose base diameter is 4 cm) is placed on the specimen for 5 seconds. Then the specimen is cooled down to room temperature, and checked whether the contacte
Fukuchi Tadakazu
Hamada Kaoru
Imai Daisuke
Kimura Yoshihide
Ogawa Hidenori
Hess Bruce H.
Nippon Paper Industries Co Ltd
Sherman & Shalloway
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