JPH11138988A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium having an excellent water resistance of a thermal color developing layer and an excellent storage stability of a recorded image. SOLUTION: In the thermal recording medium comprising a thermal color developing layer containing an electron donative compound, an electron acceptive compound and an adhesive on a support; as the adhesive, a polyurethaneionomer and an acetoacetyl modified polyvinylalcohol are used. Further, in order to enhance preservability of a recorded image against chemicals of a plasticizer resistance, oil resistance or the like, solid particles of the electron donative compound included by a polyurea or a polyurea- polyurethane are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between an electron-donating compound and an electron-accepting compound, and more particularly to a heat-sensitive recording excellent in water resistance of a heat-sensitive coloring layer and storage stability of a recorded image. It is about the body.

[0002]

2. Description of the Related Art Conventionally, a color-forming reaction between an electron-donating compound and a color-developing compound that makes contact with the electron-donating compound under heating to form a color is used, and both color-forming substances are brought into contact with each other by heating. A heat-sensitive recording medium for obtaining a color image is widely known. Such a thermosensitive recording medium is relatively inexpensive, has a compact recording device, and is easy to maintain. Therefore, it can be used not only as a recording medium for a facsimile, a word processor, various computers, but also for POS labels, ATMs, various types of computers. It is used in a wide range of fields, such as passenger tickets, parking tickets, and handy terminal applications.

[0003] With the expansion of such uses, the quality required of the heat-sensitive recording medium has also been diversified, and the number of cases in which the heat-sensitive recording medium is used outdoors has been increased. There is a demand for image stability against such factors.

As a method for improving the water resistance of the heat-sensitive coloring layer, for example, a combination of a water-soluble adhesive and a crosslinking agent or a self-crosslinking adhesive is used.
646, JP-A-49-36343, JP-A-50-30539, JP-A-52-145228, JP-A-55-159993, and JP-A-57-15993.
No. 189889. However, these methods did not provide practically sufficient water resistance. There is also a method of improving water resistance by using a hydrophobic polyvinyl acetate resin, an acrylic resin, or a styrene-butadiene resin as an adhesive for the heat-sensitive coloring layer, but sticking tends to occur during recording. There is.

[0005] Further, the conventional heat-sensitive recording medium has heat, humidity,
The color image has a disadvantage that the color image is easily erased by the influence of oil, plasticizer and the like. Thermosensitive recording media containing microcapsules containing an electron-donating compound in order to enhance the preservability of a color image are described in, for example, JP-A-57-12695 and JP-A-59-214691. Have been. However, when an oil-based liquid for dissolving the electron-donating compound is contained in the microcapsules, there is a problem in that the capsules are broken by pressure or frictional rubbing, and ground color is likely to occur.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in water resistance of a heat-sensitive coloring layer and in storage stability of a recorded image.

[0007]

Means for Solving the Problems In a heat-sensitive recording medium having a thermosensitive coloring layer containing an electron-donating compound, an electron-accepting compound and an adhesive on a support, one means for solving the above-mentioned problems is provided. As an adhesive, a polyurethane ionomer and acetoacetyl-modified polyvinyl alcohol are used. In addition, by using solid particles of an electron-donating compound encapsulated in polyurea or polyurea / polyurethane, a heat-sensitive recording material having excellent preservability against chemicals such as plasticizer resistance and oil resistance of a recorded image can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that a specific adhesive consisting of a polyurethane ionomer and acetoacetyl-modified polyvinyl alcohol is used as an adhesive for a thermosensitive coloring layer containing an electron donating compound and an electron accepting compound. The use amount thereof is preferably about 5 to 40% by weight based on the total solid content of the thermosensitive coloring layer.

The polyurethane ionomer is different from a polyurethane latex obtained by a conventional emulsion polymerization method, and is a so-called colloid-dispersed aqueous solution which is dissolved in water or dispersed in extremely fine particles without using an emulsifier. Urethane resin.

When such a polyurethane ionomer is incorporated in the heat-sensitive coloring layer, a film having excellent water resistance is formed, and it is difficult for the heat-sensitive recording surface to stick to the paper or cardboard surface particularly when wet with water. There are features,
Adhesives have the disadvantage of poor strength. On the other hand, by using acetoacetyl-modified polyvinyl alcohol in combination, it is possible to obtain a thermosensitive coloring layer having good strength of the coating film without impairing water resistance.

The ratio between the polyurethane ionomer and the acetoacetyl-modified polyvinyl alcohol is not particularly limited, but is about 10:90 to 90:10, preferably about 30:70 to 70:30.

Specific examples of the polyurethane ionomer include, for example, Hydran HW manufactured by Dainippon Ink and Chemicals, Inc.
Series, Hydran AP series, Superflex series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and the like.

By enclosing the electron donating compound with polyurea or polyurea / polyurethane, the storage stability of the recorded image to chemicals such as plasticizer resistance and oil resistance, and the resistance to uncolored stains due to pressure or rubbing of the unrecorded portion are improved. Excellent effects can be obtained when applied. Solid particles of an electron-donating compound encapsulated in polyurea or polyurea-polyurethane (hereinafter referred to as specific solid particles)
Is obtained by emulsifying and dispersing a solution containing a polyvalent isocyanate compound as a solvent and an electron-donating compound as a solute in water, and then promoting the polymerization reaction of the polyvalent isocyanate compound.

The specific solid particles do not contain an organic solvent unlike microcapsules in which an electron-donating compound described in Japanese Patent Publication No. 4-4960 or the like is dissolved in a high-boiling solvent and the solution is encapsulated. No destruction by pressure. Therefore, the thermal recording medium of the present invention hardly generates pressure fog.

The specific solid particles can be obtained, for example, by dissolving an electron-donating compound in a polyvalent isocyanate compound, emulsifying in an oil-in-water type, and polymerizing the polyvalent isocyanate compound. The dissolution temperature at this time is preferably 50 ° C. or higher, more preferably 90 ° C. or higher. 50 ℃
If the dissolution temperature is lower, the dissolution of the electron-donating compound in the polyvalent isocyanate compound becomes insufficient, so that uniform composite fine particles may not be produced. The dissolution can also be performed under pressure using a pressure vessel.

In the present invention, this solution is cooled if necessary, and then emulsified and dispersed in an aqueous medium containing a protective colloid such as polyvinyl alcohol or a surfactant. The temperature at the time of emulsification and dispersion is not particularly limited, but is desirably set to a temperature at which isocyanate and water do not rapidly react. Further, if necessary, after adding a reactive substance such as a water-soluble polyamine, the polymer-forming raw material is polymerized by raising the temperature of the emulsion as necessary, thereby forming composite fine particles comprising an electron-donating compound and polyurea or polyurea / polyurethane. I do.

The polyvalent isocyanate compound used in the present invention forms a urea bond by reacting with an amino compound in addition to water, and forms a urethane bond by reacting with a hydroxy compound to polymerize. The polymer formed is
Polyurea or polyurea polyurethane,
The polymer-forming material used may be only a polyvalent isocyanate compound, or a mixture of a polyvalent isocyanate compound and a polyol that reacts with the polyisocyanate compound, or a polyol adduct of a polyvalent isocyanate compound,
It may be a multimer such as a biuret form or an isocyanurate form. An electron-donating compound is dissolved in these polyvalent isocyanate compounds, and this solution is emulsified and dispersed in an aqueous medium containing a protective colloid substance such as polyvinyl alcohol or a surfactant, and, if necessary, reacting with a polyamine or the like. After mixing the active substance, the emulsified dispersion is heated to polymerize the polymer-forming material to polymerize. Thereby, composite fine particles composed of the electron donating compound and the polymer substance can be formed.

The polyvalent isocyanate compound used as the polymer-forming raw material includes, for example, p-phenylene diisocyanate, 2,6-tolylene diisocyanate,
2,4-tolylene diisocyanate, naphthalene-1,
4-diisocyanate, 4,4'-diphenylmethane diisocyanate, dicyclohexylmethane-4,4'-
Diisocyanate, 3,3-trimethylcyclohexane, 3,3'-dimethyldiphenylmethane-4,4'-
Diisocyanates such as diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, cyclohexylene-1,2-diisocyanate, and cyclohexylene-1,4-diisocyanate; , 4 ', 4 "-triphenylmethane triisocyanate, toluene-2,4,6
Triisocyanates such as triisocyanate, 4,
4'-dimethyldiphenylmethane-2,2 ', 5,5'
-Tetraisocyanates such as tetraisocyanate.

Examples of the adduct of a polyvalent isocyanate and a polyol include a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of 2,4-tolylenediisocyanate, and a trimethylolpropane adduct of xylylenediisocyanate. An isocyanate prepolymer such as a hexanetriol adduct of tolylene diisocyanate can be used.

In addition, these polyvalent isocyanate compounds,
For example, a biuret of hexamethylene diisocyanate, an isocyanurate of hexamethylene diisocyanate and the like can be preferably used as the polymer-forming raw material of the present invention.

In the present invention, it is particularly desirable to use dicyclohexylmethane-4,4'-diisocyanate having low viscosity and good workability.

As the polyol compound used for the polymer-forming raw material, for example, ethylene glycol, 1,3-
Propanediol, 1,4-butanediol, 1,8-
Octanediol, propylene glycol, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethyleneglycol, 1,2,2 Aliphatic polyols such as 6-trihydroxyhexane, pentaerythritol and glycerin, aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-bis (2-hydroxyethoxy) benzene, and alkylenes Condensation products with oxides, p-xylylene glycol,
Hydroxy groups such as m-xylylene glycol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol, ethylene oxide adduct of 4,4'-isopropylidenediphenol, and 2-hydroxyacrylate An acrylate having a group is exemplified.

Examples of the polyamine compound used for the polymer-forming raw material include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-phenylenediamine, m-phenylenediamine, piperazine, and the like.
2-methylpiperazine, 2,5-dimethylpiperazine,
Examples thereof include 2-hydroxytrimethylenediamine, diethylenetriamine, triethylenetriamine, triethylenetetramine, diethylaminopropylamine, tetraethylenepentamine, and amine adducts of epoxy compounds.

Further, a tin compound, a polyamide compound, an epoxy compound and the like may be used in combination as long as the object of the present invention is not impaired. When a polyamine compound is used, it is more preferable to use an aliphatic polyamine compound from the viewpoint that light resistance is not reduced.

In the present invention, an organic compound having a melting point of about 40 to 150.degree. C. and a boiling point of 150.degree. C. or more is used in addition to the electron-donating compound as a solute at the time of preparing specific solid particles for the purpose of increasing color development sensitivity. be able to. As such organic compounds, aromatic ketone compounds, aromatic ether compounds, and aromatic cyclic ester compounds can be preferably used.
Specific examples are shown below.

The aromatic ketone compound is benzophenone, and the aromatic ether compound is 1,2-di (m
Examples of -tolyloxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, and aromatic cyclic ester compounds include coumarin and phthalide. These organic compounds may be used alone or in combination of two or more.

The weight ratio of the electron donating compound to the polyvalent isocyanate compound in the specific solid particles is such that the polyvalent isocyanate compound is 20 to 2,000 parts by weight based on 100 parts by weight of the electron donating compound. And more preferably 100 to 500 parts by weight. If the amount of the polyvalent isocyanate compound is less than 20 parts, the background fog and the storage stability due to the pressure of the heat-sensitive recording medium are poor, which is not preferable. In addition, when the polyvalent isocyanate compound is 2000
Exceeding the number of parts is not preferred because the color sensitivity of the thermosensitive recording medium is reduced.

Emulsifiers used for preparing specific solid particles include water-soluble polymers such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, sulfone-modified polyvinyl alcohol, methylcellulose, carboxymethylcellulose, and styrene-maleic anhydride copolymer salts. , And various surfactants can be used. If necessary, an antifoaming agent or the like may be used.

The average particle diameter of the specific solid particles is 0.05
To 3.0 μm, more preferably,
It is 0.1 to 1.5 μm. Average particle size is 0.05μm
If it is smaller, the storage stability of the colored portion with respect to oil, plasticizer, and the like may be deteriorated. If the average particle diameter is larger than 3.0 μm, the color-forming sensitivity is reduced, so that it is necessary to excessively apply energy to the thermal head in order to obtain the color of the composite fine particles, which is not preferable.

The inclusion of an ultraviolet absorber in specific solid particles is preferred from the viewpoint of light resistance, and particularly, 2- (2-
A benzotriazole-based ultraviolet absorber such as (hydroxy-5-methylphenyl) -2H-benzotriazole has an effect of improving not only light resistance of a color image but also color sensitivity, and can be preferably used.

As the electron-donating compound contained in the thermosensitive coloring layer, a leuco dye such as triaryl, diphenylmethane, thiazine, spiro, lactam or fluoran can be preferably used. Such an electron donating compound gives a unique color tone upon contact with an electron accepting compound, and the color tone is black, red,
It ranges from magenta, orange, blue, green, and yellow.

Specific examples of the electron donating compound include, for example, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) Amino-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n
-Pentyl) amino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluoran, 3-diethylamino-7
-(O-fluorophenylamino) fluoran, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-ani Linofluoran, 3- (N
-Ethyl-N-tetrahydrofurfurylamino) -6
Methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-ethoxyanilinofluoran, 3-pyrrolidino-6-methyl A leuco dye having a black color tone, such as -7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, or 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluoran;

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylamino Phthalide, 3-
Diethylamino-7-dibenzylamino-benzo [a]
Leuco dye having a blue color tone such as fluoran, 3- (N-ethyl-Np-tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino- Leuco dye having a green color tone such as 7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane , 3-diethylamino-
Leuco dyes having a red color tone such as 7,8-benzofluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, and 3-diethylamino-6,8-dimethylfluoran.

Specific examples of the electron-accepting compound include, for example, 4,4'-isopropylidenediphenol, bis (2
-Tert-butylphenol), 4,4'-cyclohexylidenediphenol, 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3- Allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 3,4-dihydroxyphenyl-4 '
-Methylphenyl sulfone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
1,4-bis [(4-hydroxyphenyl) isopropylidene] benzene, benzyl 4-hydroxybenzoate,
4-hydroxybenzoic acid-p-methoxybenzyl, a phenolic compound such as a novolak type phenol resin, a phenol polymer, 4- [2- (p-methoxyphenoxy)
Ethyloxy] zinc salicylate, 4- [3- (p-tolylsulfonyl) propyloxy] zinc salicylate, 5-
[P- (2-p-methoxyphenoxyethoxy) cumyl] zinc salt of an aromatic carboxylic acid such as zinc salicylate, N
-P-tolylsulfonyl-N'-phenylurea, 4,
Compounds having a sulfamide bond in the molecule such as 4'-bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane are exemplified.

In the thermosensitive coloring layer, pigments such as kaolin, calcium carbonate, amorphous silica, titanium oxide, aluminum hydroxide, calcined kaolin, zinc oxide, stearic acid amide, ethylene bisstearic acid amide, m-terphenyl, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, dibenzyl terephthalate, phenyl 1-hydroxynaphthoate, 1,2-di- (3-methylphenoxy) ) Sensitizers such as ethane, 1,2-diphenoxyethane, 1-phenoxy-2-naphthoxyethane, p-benzylbiphenyl, and 1,1,3-tris (2-
Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, N,
N′-di-2-naphthyl-p-phenylenediamine,
Preservative improvers such as sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate, carnauba wax, montan wax, paraffin wax, microcrystalline wax, polyethylene wax, etc., zinc stearate , Calcium stearate and the like, and a fluorescent dye, a coloring dye, a surfactant, a water-proofing agent and the like can also be added.

The heat-sensitive coloring layer is generally formed by using water as a medium,
The average particle diameter is about 0.1 to 3 μm by a pulverizer such as Domill.
Electron-donating compound or specific solid finely dispersed
Combine the particles with colorants, adhesives and, if necessary, sensitizers,
Thermosensitive coloring layer obtained by mixing and stirring the solubility improver and auxiliary agent
The coating amount after drying the coating solution for application on a support is 2 to 20 g /
m ^Two, Preferably 3 to 10 g / m^TwoPaint to the extent
The cloth is formed by drying.

Examples of the adhesive contained in the coating solution for the thermosensitive coloring layer include polyvinyl alcohol and derivatives thereof,
Starch and derivatives thereof, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, polyvinylpyrrolidone, acrylamide-
Water solubility of acrylate copolymer, acrylamide-acrylate-methacrylate copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin and derivatives thereof Polymeric materials, and polyvinyl acetate,
Emulsions such as polyurethane, polyacrylic acid, polyacrylate, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer A latex of a water-insoluble polymer such as a coalescence can be used.

As the support, for example, high quality paper (acid paper,
Neutral paper), medium paper, coated paper, art paper, cast coated paper, glassine paper, resin laminated paper, polyolefin synthetic paper, synthetic fiber paper, nonwoven fabric, synthetic resin film, etc., as well as various transparent supports It can be appropriately selected and used.

In the present invention, an undercoat layer for improving the recording sensitivity is provided between the support and the thermosensitive coloring layer, or a protective layer for further improving the recording running property and preservability is provided on the thermosensitive coloring layer. Conventionally known techniques for producing a thermosensitive recording medium, such as performing a super calender treatment after forming each layer or providing an adhesive layer on the back surface side of the support, can also be provided.

The method for forming each of the above layers on the support includes known coating methods such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dip method, a bar method, and an extrusion method. Either may be used. Further, it is also possible to suppress the penetration of oil or plasticizer from the back surface of the recording material, or to provide a back layer for curl control on the back surface of the support.

[0041]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited by these examples. In each example and comparative example, "part" and "%"
Indicates “parts by weight” and “% by weight”, respectively.

Example 1 (1) Preparation of Support Canadian Standard Freeness (CSF) 480
100 parts of hardwood bleached kraft pulp beaten ml, from 10 parts of talc, petroleum resin sizing agent 0.3 parts, form regulating the paper stock obtained by adding 0.5 parts of aluminum sulfate, the basis weight 64 g / m ² Paper was made. The base paper was coated with a 2% solution of polyvinyl alcohol by a size press. The coating amount was 0.8 g / m ² (dry). Oken type smoothness (J.TAPPI No.5) is 50 on machine calendar
A smoothing treatment was performed so that the time became seconds, and a support was obtained.

(2) Preparation of coating liquid for undercoat layer 50 parts of calcined kaolin having an oil absorption of 110 ml / 100 g, 1 part of a 40% aqueous solution of sodium polyacrylate, and 50 parts of water
Parts, 30 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.), 10 parts of styrene-butadiene-based latex (trade name: L-1571, solid concentration 48%, manufactured by Asahi Kasei Corporation), 40 parts of glyoxal
% Aqueous solution was mixed and stirred to obtain a coating liquid for an undercoat layer.

(3) Preparation of Material Used for Thermosensitive Coloring Layer <Preparation of Liquid A (Solid Particle Dispersion of Electron Donating Compound Encapsulated in Polyurea / Polyurethane)> 3-Di (n- Pentyl) amino-6-methyl-
Dicyclohexylmethane-4,4′-diisocyanate 10 obtained by heating 5 parts of 7-anilinofluoran to 120 ° C.
Part and hexamethylene diisocyanate biuret body 5
Of the mixed solution, and the solution was cooled to 35 ° C., and then 8% polyvinyl alcohol (trade name: PVA2)
17EE, manufactured by Kuraray Co., Ltd.), gradually added to 150 parts of an aqueous solution, and emulsified and dispersed by stirring with a homogenizer at a rotation speed of 12000 rpm. A 1.0 μm solution A was obtained.

<Preparation of Liquid B (Dispersion of Electron Donating Compound)> 3-Di (n-pentyl) amino-6-methyl-7-
A composition consisting of 50 parts of anilinofluoran, 20 parts of a 20% aqueous solution of a sulfone group-modified polyvinyl alcohol, and 60 parts of water was prepared by using an ultra-viscomil with an average particle diameter of 1.
The mixture was pulverized to 0 μm to obtain a liquid B.

<Preparation of Liquid C (Dispersion of Electron-Accepting Compound)> 40 parts of 4,4'-isopropylidenediphenol,
20% aqueous solution of sulfone-modified polyvinyl alcohol 20
The composition consisting of 60 parts by weight of water and 60 parts of water was pulverized using an Ultraviscomiler until the average particle diameter became 0.9 μm to obtain a liquid C.

(4) Preparation of coating solution for thermosensitive coloring layer 120 parts of solution A, 70 parts of solution C, 40 parts of light calcium carbonate
% Dispersion 60 parts, zinc stearate (trade name: Hydrine Z-8, solid concentration 36%, manufactured by Chukyo Yushi Co., Ltd.), 14 parts, paraffin wax (trade name: Hydrin D-336, solid concentration 36%, Chukyo Yushi Co., Ltd.) 10 parts, polyurethane ionomer (trade name: Hydran AP-30F, solid concentration 30%, manufactured by Dainippon Ink and Chemicals, Inc.) 25 parts, acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200, Nippon Gosei) 12% of chemical industry
A composition comprising 30 parts of an aqueous solution was mixed and stirred to obtain a coating solution for a thermosensitive coloring layer.

(5) Preparation of heat-sensitive recording medium On one surface of the support, a coating liquid for an undercoat layer is applied and dried with a bevel blade coater so that the coated amount after drying is 9 g / m ^2, and then dried. After forming a layer, the coating solution for the heat-sensitive coloring layer is applied and dried on the undercoat layer using a Meyer bar so that the coating amount after drying is 8 g / m ² to form a heat-sensitive coloring layer. A heat-sensitive recording material was obtained by performing a smoothing process using a super calendar so that the Oken-type smoothness was 800 seconds.

Example 2 In the preparation of the coating solution for the thermosensitive coloring layer of Example 1, a polyurethane ionomer (trade name:
In the same manner as in Example 1 except that 25 parts of Hydran AP-30F) was replaced by 25 parts of a polyurethane ionomer (trade name: Hydran AP-40, solid concentration 30%, manufactured by Dainippon Ink and Chemicals, Inc.) A recording was obtained.

Example 3 In the preparation of the coating solution for the thermosensitive coloring layer of Example 1, a polyurethane ionomer (trade name:
(Hydran AP-30F) was carried out in the same manner as in Example 1 except that 25 parts were changed to 15 parts, and 30 parts of a 12% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200) was changed to 40 parts. A thermosensitive recording medium was obtained.

Comparative Example 1 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 20 parts of Solution B was used instead of 120 parts of Solution A in the preparation of the coating solution for the thermosensitive coloring layer of Example 1. Obtained.

[Comparative Example 2] In the preparation of the coating solution for the thermosensitive coloring layer of Example 1, a polyurethane ionomer (trade name:
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 60 parts of a 12% aqueous solution of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200) was used instead of 25 parts of Hydran AP-30F). Was.

Comparative Example 3 12% of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200) was prepared in the preparation of the coating solution for the thermosensitive coloring layer of Example 1.
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 12 parts of a polyurethane ionomer (Hydran AP-30F) was used instead of 30 parts of the aqueous solution.

Comparative Example 4 12% of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200) was prepared in the preparation of the coating solution for the thermosensitive coloring layer of Example 1.
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 36 parts of a 10% aqueous solution of polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.) was used instead of 30 parts of the aqueous solution.

Comparative Example 5 In the preparation of the coating solution for the thermosensitive coloring layer of Example 1, 12% of acetoacetyl-modified polyvinyl alcohol (trade name: Gosefimer Z-200) was used.
A thermosensitive recording medium was obtained in the same manner as in Example 1, except that 45 parts of an 8% aqueous solution of silicon-modified polyvinyl alcohol (trade name: R-1130, manufactured by Kuraray Co., Ltd.) was used instead of 30 parts of the aqueous solution.

With respect to the thus obtained thermosensitive recording medium,
The following evaluation tests were performed, and the obtained results are shown in Table 1.

[Recording sensitivity] Thermal printing tester (trade name:
Using a TH-PMD (manufactured by Okura Electric Co., Ltd.), each thermosensitive recording medium was recorded at an applied energy of 0.4 mJ / dot, and the recording density of the obtained recording portion and the unrecorded portion (background portion) Macbeth densitometer ( (Trade name: RD-914, manufactured by Macbeth) in the visual mode.

[Plasticizer Resistance] A vinylidene chloride film containing a plasticizer was layered on the heat-sensitive recording medium recorded as described above. After leaving the film at 20 ° C. for 4 days, the density of the recording portion was measured with a Macbeth densitometer.

[Oil resistance] After the heat-sensitive recording medium recorded above was immersed in salad oil at 20 ° C for 12 hours, the oil was wiped off, and the density of the recording portion was measured with a Macbeth densitometer.

[Water resistance] The heat-sensitive recording medium was immersed in water at 20 ° C. for 2 seconds, immediately after being lifted out of the water, the heat-sensitive recording surface was stuck on high-quality paper, air-dried, and then the high-temperature recording medium was peeled off from the high-quality paper and blocked. Was evaluated organoleptically as follows. <Evaluation Criteria> A: No blocking occurred. ：: At the time of peeling, slight sticking is recognized, but there is no peeling of the recording surface. X: The recording surface is blocking.

[Scratch resistance] The recording surface of the heat-sensitive recording medium was rubbed with a nail, and the degree of color development was visually determined as follows. <Evaluation criteria> ：: Almost no color development. X: It shows that clear color development is seen.

[Coating film strength] After attaching a cellophane tape to the recording surface of the thermosensitive recording medium, the tape was peeled off, and the state of the coating film taken on the tape was visually determined as follows. <Evaluation Criteria> A: No coating film is taken on the tape. ：: The coating film was slightly removed on the tape. X: The coating film is almost removed on the tape.

[0063]

[Table 1]

[0064]

As shown in Table 1, the heat-sensitive recording material of the present invention has excellent water resistance and excellent image stability after printing.

Claims (2)

[Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing an electron donating compound, an electron accepting compound and an adhesive on a support, wherein the adhesive is a polyurethane ionomer or an acetoacetyl-modified polyvinyl alcohol. Characterized thermal recording medium. 2. The thermosensitive recording medium according to claim 1, wherein the electron donating compound is a solid particle encapsulated in polyurea or polyurea / polyurethane.