JPH0214097A - Production of coated paper - Google Patents

Abstract

PURPOSE:To obtain a paper high in planarity, having a coating layer of high porosity, thus useful as a substrate for heat-sensitive recording use by putting a coating layer comprising a sublimable substance and a polymeric compound on a substrate followed by heating said layer to vaporize the sublimable substance to produce pores. CONSTITUTION:A coating layer comprising (A) a sublimable substance (e.g., naphthalene, camphor, p-dichlorobenzene) and (B) a polymeric compound (e.g., CMC, starch, styrene-butadiene rubber latex, polyvinyl acetate emulsion) is provided on a substrate. Thence, this coating layer is heated to temperatures lower than the melting point of the substance A to vaporize this substance A to impart said coating layer with pores, thus obtaining the objective coated paper.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing coated paper, and more particularly to a method for producing a support for heat-sensitive recording.

(Prior Art) Regarding heat-sensitive recording, many methods have been known for a long time. It is disclosed in Publication No. 443-4/40. Further, a heat-sensitive recording material entirely using a diazo compound is disclosed in Japanese Patent Application Laid-open No. 2003-111001/YORR6. In recent years, these thermal recording systems have been applied to 1) fields such as facsimiles, printers, and labels, and the needs are expanding. with this,
Heat-sensitive recording has come to be required to have characteristics that were not required in the past. One of these is the reproducibility of printed dots. In general, thermal recording paper is printed by being heated by a minute heating element of about 200 μm in size called a thermal head. At this time, being able to faithfully reproduce the shape of the minute heating element as a coloring body is what gives high print quality. It has been found that this is important for This is called total print dot reproducibility. One of the ways to improve the reproducibility of printed dots is to provide the support with heat insulation properties. That is, by providing a coating layer with a high porosity, it is possible to completely impart heat insulation properties to the support. Japanese Patent Application Publication No. 1973-/7/l.

No. 15 has an undercoat layer containing air bubbles, which makes it possible to improve the appearance of JP-A-Shojter! OF3, JP-A-5? -22 Tata Ir
No. 7 has a coating layer with a high porosity by having a foam layer. However, both have low flatness and low printed dot reproducibility. In JP-A No. 62-rrrt,
A heat-sensitive recording material having an undercoat layer containing non-expandable hollow particles is obtained. However, even if non-expandable hollow particles are used, the porosity does not become very high.

(Object of the Invention) The object of the present invention is to provide a manufacturing method for obtaining coated paper having a coating layer with high flatness and high porosity in order to obtain a heat-sensitive recording material with good dot reproducibility and high print quality. It is to be.

(Structure of the Invention) The object of the present invention is to provide a coating layer mainly composed of a sublimable substance and a polymer compound on a support, and to heat the coating layer to a temperature below the melting point of the sublimable substance. This was achieved by a coated paper manufacturing method characterized by vaporizing the sublimable substance gold and imparting voids to the coating 1@. In other words, when the coated paper obtained by this method is used as a support for a heat-sensitive recording material, it has a unique property because it has high flatness, a high porosity of the coating layer, and a heat-insulating property. It has been found that a heat-sensitive recording material with good dot reproducibility can be obtained.

The coating layer according to the invention mainly contains a sublimable substance and a polymer compound, but may also contain a crosslinking agent, a pigment, a thermofusible substance, a surfactant, and the like. The amount of polymer compound added is
It is optional depending on the type of material, but preferably 5% to ioo%, more preferably 10% to the sublimable substance.
~? θ%.

Examples of sublimable substances used in the factory of the present invention include naphthalene, camphor, baladichlorobenzene, noubenzoquinone, tranS-stilbene, ethylene glycol diphenyl ether, adamantane, and the like.

Examples of the polymer compounds used in the coating layer include water-bathable polymers and water-insoluble polymers, and seven types or a mixture of two or more types of binders may be used.

Examples of water bathing polymers include methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, and Butylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol,
Examples include carboxy-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, and polyacrylamide.

As water-insoluble polymers, synthetic rubber latex or synthetic resin emulsion is generally used, and examples include styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, and vinyl acetate emulsion. It will be done.

Examples of crosslinking agents that can be used in the coating layer include water bathable initial condensation resins such as N-methylol urea, N-methylol melamine, urea-formalin, benzoguanamine-formalin, and acetoguanamine-formalin, and dialdehyde compounds such as glyoxal and glutaraldehyde. , colloidal silica, inorganic crosslinking agents such as ferric acid and silica sand, polyacrylic acid, methyl vinyl ether-maleic acid copolymer, isobutylene-maleic anhydride copolymer, and the like.

As the pigment that can be used in the coating layer, organic or inorganic pigments can be used. Preferred specific examples include calcium carbonate, sulfated barium, titanium oxide, Merck, waxite, kaolin, calcined kaolin, aluminum hydroxide, amorphous silica, urea-formalin resin powder, polyethylene resin powder, and the like.

Next, a typical manufacturing method of the present invention will be described.

Methods for producing the coating solution for the undercoat layer, which mainly consists of a sublimable substance and a polymer compound, include a method in which a sublimable substance is solidly dispersed and mixed with a polymer compound bath solution (or a polymer dispersion), and a sublimation method. There are methods such as making a homogeneous solution of a chemical substance and a polymer compound.

The coating liquid is applied to a support and dried. The amount of the undercoat layer is preferably 2 to 3 oy/m<2>. After drying, the sublimable substance is sublimated at a temperature below the melting point of the sublimable substance to obtain a void layer gold.

The sublimation temperature is preferably lower than the softening point of the polymer compound. Further, depending on the case, sublimation may be performed under reduced pressure.

(Examples of the Invention) Examples are shown below, but the present invention is not limited thereto. Each heat-sensitive recording material was prepared by applying a heat-sensitive coating liquid to each coated paper with a dry coating amount of As'/m". It was coated with a wire parser and dried in an oven at 10°C.

(Preparation of heat-sensitive coating liquid) λ-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane as a color former, bisphenol A as a color developer, β-naphthylbenzyl ether as a sensitizer, 202 and 100f each. ! % polyvinyl alcohol (Clan PVA-10j) aqueous solution in a ball mill for one day to make the volume average particle size 3 μm or less.

As the pigment, order calcium (Unibur 7゜Shiraishi Kogyo) was used, and it was dispersed with a homogenizer together with rot-@hexamethalin powder soda Q and 1 toy of J% bath solution. Each of the dispersion co-anilino 3-methyl-6-N-methyl-N-7 chlorohexylaminofluorane dispersion Q/jf and bisphenol A prepared as above.
Dispersion ioy, β-naphthylbenzyl ether dispersion 1
0? , calcium carbonate dispersion/jf, and further added 21% zinc stearate emulsion 31 to obtain a heat-sensitive coating liquid.

(Example〕 Naphthalene gold was used as the sublimable substance.

Naphthalene 20? The particles were dispersed in a ball mill with a 5% f/00 S' polyvinyl alcohol (CranPVA-10j) water bath solution for one day and a night to make the volume average particle size 3 μm or less. In addition, as a polymer compound, 70% silanol modified PVA (Clan PVA-几210!r)! 0? ,3
0% colloidal silica (Snowtex 30) 209 was added to obtain an ω solution.

The coating liquid obtained in this way has a grammage! Dry coating amount on high-quality paper of 09/m2 is /0? /m 2 using a wire parser and dried in an oven at RO 0C. This coated paper was further left in an oven at 70''C for 30 seconds to sublimate the naphthalene to obtain coated paper.

When a cross-sectional photograph of this coated paper was taken, it was found that a layer with high flatness and voids was formed. (The porosity was approximately jO%) (Comparative Example 1) Spiroglycol (Mitsubishi Gas Chemical Exhibition, melting point/ff'C) was used instead of naphthalene in the example to obtain coated paper.

When a cross-sectional photograph of this coated paper was taken, a layer with almost no voids was formed. (The porosity is about 10%) (Comparative Example 2) A coated paper was obtained without putting it in an oven at 70oC in the example.

When a cross-sectional photograph of this coated paper was taken, a layer with almost no voids was formed. (The porosity is approximately 10%) The color density of each thermal recording material was measured using a color density total Macbeth e meter printed using a printing tester manufactured by Kicera at a printing energy of JOrnJ/m2.

All of the above results are shown in Table 1.

Claims (1)

[Claims] A coating layer mainly composed of a sublimable substance and a polymer compound is provided on a support, and the coating layer is heated to a temperature below the melting point of the sublimable substance to vaporize the sublimable substance. A method for producing coated paper characterized by providing voids in the coating layer.