Coating processes – Transfer or copy sheet making – Coating opposite sides or forming plural or nonuniform coats
Reexamination Certificate
2002-04-30
2004-11-23
Schilling, Richard L. (Department: 1752)
Coating processes
Transfer or copy sheet making
Coating opposite sides or forming plural or nonuniform coats
C430S338000, C430S961000, C503S200000, C503S207000
Reexamination Certificate
active
06821556
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat-sensitive recording material utilizing the color-forming reaction between a leuco dye and a developer, and in particular relates to such a heat-sensitive recording material with a protective layer having better gloss, as well as a method for its production.
BACKGROUND ART
Heat-sensitive recording materials which make use of the color forming reaction of a leuco dye with a developer induced by heat are relatively inexpensive, and recording devices for these materials are compact and easy to maintain. Consequently such recording materials are widely used as recording media for facsimile systems, various computers and other application.
With the expansion of the scope of application of such heat-sensitive recording materials, there is a demand for a heat-sensitive recording material which has higher grade gloss. However, attempts to increase the gloss of the protective layer of heat-sensitive recording materials often cause sticking of the protective layer to the thermal heads of printers during recording, failing to obtain uniform record images, or result in inadequate runnability during recording.
In order to improve water resistance, runnability during recording and chemical resistance of the heat-sensitive recording material, Japanese Unexamined Patent Applications (Kokai) H5-69665, H5-318926, and H6-171237 disclose heat-sensitive recording materials comprising a resin-based protective layer which is obtained by applying to the heat-sensitive recording layer a protective layer aqueous coating composition containing a latex with a core/shell structure, and then drying the coating. However, the gloss of the protective layers of these heat-sensitive recording materials needs to be improved.
In order to improve the gloss of the protective layer, Japanese Unexamined Patent Publication (Kokai) 2000-71617 discloses a heat-sensitive recording material in which a protective layer is formed by applying a protective layer aqueous coating composition containing a latex with a core/shell structure to a high-smoothness film or a metal surface having a chromium-plated mirror finish, which is separate from the support, drying the coating to form a protective layer, and then laminating the protective layer onto the heat-sensitive recording layer. However, the productivity and manufacturing costs are problematic.
An object of the present invention is to provide a heat-sensitive recording material having excellent gloss and excellent sticking resistance and water resistance.
DISCLOSURE OF THE INVENTION
In heat-sensitive recording materials which comprise a heat-sensitive recording layer containing a leuco dye and a developer on a support and a protective layer comprising a resin in the form of a film, the present invention uses, as a means for achieving the aforementioned object, a protective layer which is obtained by applying a protective layer aqueous coating composition comprising at least resin particles having a core/shell structure to the heat-sensitive recording layer and drying the coating, the resin in the form of a film formed from the resin particles with the core/shell structure in the resulting protective layer being present in an amount of not less than 80 mass % relative to the total amount of solids of the protective layer, and the protective layer having a gloss (based on JIS P 8142) of not less than 80%.
Specifically, the present invention provides a heat-sensitive recording material characterized in that it comprises (a) a support, (b) a heat-sensitive recording layer comprising a leuco dye and a developer, and (c) a protective layer comprising a resin in the form of a film and formed on the heat-sensitive recording layer, the protective layer being obtained by coating the heat-sensitive recording layer with a protective layer aqueous coating composition comprising at least resin particles having a core/shell structure, and then drying the coating, wherein the resin in the form of a film formed of the resin particles having a core/shell structure is present in an amount of not less than 80 mass % of the total solids of the protective layer, and the protective layer having a gloss (based on JIS P 8142) of not less than 80%.
The present invention also provides a heat-sensitive recording material characterized in that it comprises (i) a support, (ii) a heat-sensitive recording layer comprising a leuco dye and a developer, (iii) an interlayer comprising a film-forming resin and formed on the heat-sensitive recording layer, and (iv) a protective layer comprising a resin in the form of a film, the protective layer being obtained by coating the interlayer with a protective layer aqueous coating composition comprising at least resin particles having a core/shell structure, and then drying the coating, wherein the resin in the form of a film formed of the resin particles having a core/shell structure is present in an amount of not less than 80 mass % of the total solids of the protective layer, and the protective layer having a gloss (based on JIS P 8142) of not less than 80%.
The present invention also provides a process for producing a heat-sensitive recording material comprising (a) a support, (b) a heat-sensitive recording layer comprising a leuco dye and a developer, and (c) a protective layer comprising a resin in the form of a film and formed on the heat-sensitive recording layer, wherein the protective layer having a gloss (based on JIS P 8142) of not less than 80%, the process being characterized in that it comprises coating the heat-sensitive recording layer with a protective layer aqueous coating composition comprising resin particles having a core/shell structure in an amount of not less than 80 mass % of the total solids of the protective layer aqueous coating composition, and then drying the coating.
Furthermore, the present invention provides a process for producing a heat-sensitive recording material comprising (i) a support, (ii) a heat-sensitive recording layer comprising a leuco dye and a developer, (iii) an interlayer comprising a film-forming resin and formed on the heat-sensitive recording layer, and (iv) a protective layer comprising a resin in the form of a film and formed on the interlayer, wherein the protective layer has a gloss (based on JIS P 8142) of not less than 80%, the process being characterized in that it comprises the steps of:
forming a recording material comprising the support and the heat-sensitive recording layer,
coating the heat-sensitive recording layer with an interlayer coating composition comprising a film-forming resin and then drying the coating composition to form the interlayer, and
coating the interlayer with a protective layer aqueous coating composition comprising at least resin particles having a core/shell structure, the protective layer aqueous coating composition comprising the resin particles with a core/shell structure in an amount of not less than 80 mass % of the total solids of the protective layer aqueous coating composition, and then drying the coating.
The present invention will be described below in detail.
Protective Layer
<Protective Layer Gloss>
As described above, the heat-sensitive recording material of the present invention is characterized in that the protective layer is obtained by coating the heat-sensitive recording layer with a protective layer aqueous coating composition comprising resin particles with a core/shell structure, and then drying the coating, wherein the resin in the form of a film formed of the resin particles having a core/shell structure (specific resin) is present in an amount of not less than 80 mass % relative to the total solids of the protective layer, and wherein the protective layer has a gloss (based on JIS P 8142) of not less than 80%.
A means for ensuring that the protective film of the present invention has a gloss of not less than 80% is, for example, to form a protective layer by coating the heat-sensitive recording layer with a protective layer aqueous coating composition containing resin particles with a core/shell
Ishida Koichi
Isu Yutaka
Tsuchida Hideki
Watanabe Kazuo
Kubovcik & Kubovcik
OJI Paper Co. Ltd.
Schilling Richard L.
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