JPH09263049A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistance against a plasticizer, heat resistance and water resisting property by using a core-shell emulsion in the presence of an acrylic polymer or an acrylic copolymer seed emulsion, as resin and a carbodiimide as a crosslinking agent, in a recording material consisting of a protecting layer formed on a thermosensitive recording layer. SOLUTION: In a thermosensitive recording material consisting of a protecting layer containing resin and a crosslinking agent formed on a thermosensitive recording layer, a core-shell emulsion obtained by polymerizing acrylamide and/or methacrylamide in the presence of an acrylic polymer or an acrylic copolymer seed emulsion is used as resin, while a carbodiimide compound is used as a crosslinking agent. In addition, this resin has a glass transition point Tg of at least 15 deg.C for the core part and a glass transition point Tg of at least 150 deg.C for the shell part. Further, pigment is used and the pigment/resin ratio is 1 or less. Besides, the oil absorption amount of the pigment is 250cc/100g or less and the average grain diameter thereof is 3μm or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly to improvement of a heat-sensitive recording material in which a heat-sensitive recording layer which is colored by heat is provided on a support.

[0002]

2. Description of the Related Art Generally, a thermosensitive recording material having a thermosensitive coloring layer containing a thermochromic composition as a main component on a support such as paper or film is used for a thermal head, a thermal pen, a laser beam, a strobe lamp, etc. A colored image can be obtained by heating. Compared with other recording materials, this type of recording material has advantages that it does not require complicated operations and devices at the time of recording, can record in a short time, generates little noise and environmental pollution, and has low cost. Therefore, in addition to being used for copying books and documents, it is also used as a versatile recording material for facsimiles, electronic computers, recorders, labels, ticket vending machines, and the like. The thermochromic composition used for such a heat-sensitive recording material is generally composed of a color former and a developer that allows the color former to develop color when heated.
For example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used as a color former, and an organic acid or a phenolic substance is conventionally used as a color developer. The recording material in which the color former and the developer are combined has the advantage that the color tone of the obtained image is particularly clear, the whiteness of the background is high, and the weather resistance of the image is excellent. Widely used.

However, in this type of heat-sensitive recording material, the image disappears when it is brought into contact with water or a plasticizer such as DOA or DOP, or the white part is colored by a solvent such as oil, ethanol or ethyl acetate, and the image reliability is high. There is a drawback that is inferior to. As a solution to these problems, it has been proposed to provide a protective layer on the heat-sensitive recording layer (JP-A-54-128347).
No. JP-A-54-3594). For such a protective layer, it has been proposed that a water-soluble resin such as polyvinyl alcohol and its modified type, starch and its modified type, and the like are effective in order to enhance oil resistance and plasticizer resistance (Japanese Patent Application Laid-Open No. 2000-242242). JP-A-56-126193, JP-A-56-1399.
No. 3), a water-soluble resin is mainly used. Further, it has been proposed to use a copolymer emulsion as a protective layer (Japanese Patent Laid-Open No. 5-69665). However, the protective layer using such a water-soluble resin often lacks water resistance, and a method of curing the protective layer by using a cross-linking agent together (JP-A-57-188392) is often used. . Many crosslinking agents have been proposed, but insufficient problems remain. For example, it has been proposed to use a glycidyl-based cross-linking agent (JP-A-57-188392), which is excellent in oil resistance and matching resistance (fouling of a thermal head), but it has poor reactivity and is water resistant. Is not enough.

A protective layer using a glyoxydyl-based cross-linking agent as an amino compound (JP-A-64-61287) is excellent in water resistance and chemical resistance, but it is not suitable for use as a food label because it produces formalin. . Furthermore, with respect to the cross-linking agent containing an amino group, the protective layer is changed, the aziridine-based cross-linking agent is unstable in an aqueous solution, and the glycidylamine-based cross-linking agent has a problem such as generation of formalin. Use of epoxy-based cross-linking agent (JP-A-49-3
6343, JP-A-60-68990, JP-A-5-3
No. 18926) has been proposed, but those having an aromatic ring are inferior in plasticizer resistance, and glycol type ones have problems such as heat resistance and background coloration. In addition, these methods have the drawbacks of lowering the sensitivity and matching with the thermal head (adhesion of dust, fading of printing, etc.).

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the above-mentioned problems, is excellent in plasticizer resistance, heat resistance and water resistance, has a high coloring density, and is capable of erasing color in a recording area and coloring in a non-printing area. It is an object of the present invention to provide a heat-sensitive recording material which is also excellent in prevention and is also excellent in matching property with a thermal head and in sticking.

[0006]

Means for Solving the Problems As a result of intensive studies made by the present inventors, the above-mentioned problems can be solved by using a combination of a specific resin and a crosslinking agent in a thermal recording material having a protective layer containing a resin and a crosslinking agent. The present invention has been found to be solved by the present invention. That is, the present invention is the following (1) to (6).

(1) In a thermosensitive recording material in which a thermosensitive recording layer which is colored by heat is provided on a support, and a protective layer containing a resin and a crosslinking agent is further provided on the thermosensitive recording layer, the resin is an acrylic resin. A core-shell type emulsion obtained by polymerizing acrylamide and / or methacrylamide in the presence of a seed emulsion of a polymer or a copolymer,
And a thermosensitive recording material characterized in that the crosslinking agent is a carbodiimide compound. (2) The heat-sensitive recording material according to (1) above, wherein the glass transition point Tg of the core portion of the resin is 15 ° C. or higher. (3) The glass transition point Tg of the shell portion of the resin is 150 ° C.
The heat-sensitive recording material as described in (1) above, which is the above.

(4) Glass transition point Tg of the core of the resin
Is 15 ° C or higher and the glass transition point Tg of the shell is 15
The thermosensitive recording material according to (1) above, which has a temperature of 0 ° C. or higher. (5) The heat-sensitive recording material as described in (1) to (4) above, which further contains a pigment and has a pigment / resin ratio of 1 or less. (6) The heat-sensitive recording material as described in (5) above, wherein the pigment has an oil absorption of 250 cc / 100 g or less and an average particle diameter of 3 μm or less.

The resin used in the protective layer of the heat-sensitive recording material of the present invention is a core-shell type emulsion obtained by polymerizing acrylamide and / or methacrylamide in the presence of a seed emulsion of an acrylic polymer or copolymer. It is a polymer resin. Since the copolymer resin is of a function-separated type, it exerts favorable effects in terms of barrier properties and head matching properties. The copolymer resin can be produced by a conventional method. Further, in the core portion of the resin,
It is preferable to use acrylonitrile, and further Tg
Is preferably 15 ° C or higher. Further, it is preferable to use at least one of acrylamide and / or methacrylamide in the shell portion of the resin, and to select other vinyl monomer so that Tg is 150 ° C. or higher. As described above, the copolymer resins used in these protective layers may be copolymerized with other copolymerizable monomers in combination, if necessary, in producing them.

The resins used in the protective layer of the present invention are those mentioned above, but it is also possible to use these in combination with the resins conventionally used in the protective layer. As the resin that can be used in combination, generally known natural resins (for example, sodium alginate, starch, casein, cellulose) and synthetic resins can be optionally used. Among them, polyvinyl alcohol, polycarboxylic acid compounds, polyacrylamide and modifications thereof The product or derivative is good in reactivity with aziridine and film-forming property. The modified product or derivative means a compound containing polyvinyl alcohol, a polycarboxylic acid compound, and polyacrylamide, and copolymerized or graft-polymerized with other components, or bound to a functional group as a pendant. Further, among polyvinyl alcohol (PVA), epoxy group-modified PVA, silanol group-modified PV
A, acetoacetyl group-modified PVA, acrylamide-modified PVA, butyralized PVA-maleic acid copolymer, N
-Methylolurethane-modified PVA, amino group-modified PVA and fully saponified PVA show good results. Complete saponification P
VA preferably has a saponification degree of 80% or more. Particularly favorable is epoxy group-modified PVA. Among the polycarboxylic acid compounds, styrene-acrylic acid copolymer,
Acrylic ester-acrylic acid copolymer, styrene-
Acrylic ester-acrylic acid copolymer, styrene-
Maleic acid copolymers, isobutylene-maleic anhydride copolymers and their derivatives, and styrene-acrylic acid-acrylamide copolymers are preferred. Particularly preferred are isobutylene-maleic anhydride copolymers and their derivatives or styrene-acrylamide copolymers. Furthermore, polyethyleneimine, water-based polyester, water-based polyurethane,
Examples thereof include aqueous emulsion resins such as polyesters, polyurethanes, acrylate (co) polymers, epoxy resins, polyvinyl acetate, polyvinylidene chloride, polyvinyl chloride and derivatives thereof.

In the heat-sensitive recording material of the present invention, by providing a protective layer in which a resin is further combined with a crosslinking agent, water resistance, plasticizer resistance and heat resistance are excellent. Moreover, the following are mentioned as a specific example of the carbodiimide compound used as a crosslinking agent in this invention. R-N = C = N- R 1 ( wherein, R: R ¹ is an alkyl group which may be substituted or an aryl group) such Gunze Sangyo are commercially, UC
ARLNK XL25SE, Gunze industry, UCARLN
K XL27HS and the like can be mentioned.

As the pigment used as an optional component in the present invention, conventionally known pigments can be used. For example, silicon dioxide, calcium silicate, magnesium silicate, aluminum silicate, zinc silicate, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax stone, kaolin, aluminum hydroxide, calcined kaolin, etc. Examples thereof include inorganic pigments, urea formalin resins, and organic pigments such as polyethylene powder.

The ratio of pigment to resin is 1 or less. The pigment preferably has an oil absorption of 250 cc / 100 g or less and an average particle size of 3 μm or less. In the protective layer of the present invention, in addition to the resin, the cross-linking agent, and the pigment, if necessary, an auxiliary additive component that is commonly used in this type of heat-sensitive recording material,
For example, a surfactant, an ultraviolet absorber, a heat-fusible substance (or a lubricant), a pressure color-developing inhibitor, etc. can be used in combination. As a method of coloring with heat used in the present invention,
There are those that utilize the color development reaction between the leuco dye and the color developer, those that utilize the reaction of the diazo compound and coupler, and those that utilize the reaction of the isocyanate and amine. Since the feature of the present invention resides in the protective layer of the heat-sensitive recording material, the color forming method is not particularly limited. Hereinafter, the thermal recording method using a general leuco dye will be described.

The leuco dyes used in the heat-sensitive recording layer of the present invention are applied singly or as a mixture of two or more kinds. As such leuco dyes, those applied to this kind of heat-sensitive material are arbitrarily applied. For example, leuco compounds such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spirobiran-based, indolinophtalide-based dyes are preferably used. Specific examples of such leuco dyes include, for example, those shown below.

That is, 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3- Screw (p-
Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6
-Chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-
Chlorfluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane,
3-diethylamino-7,8-benzfluoran, 3-
Diethylamino-6-methyl-7-chlorofluorane,
3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- [N- (3'- Trifluoromethylphenyl) amino] -6-diethylaminofluorane, 2- [3,6-bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoate lactam], 3-diethylamino-6-methyl-7-
(M-Trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-di-n-butylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N, n -Amylamino-6-methyl-7-anilinofluorane, 3-N-
Methyl-N-cyclohexylamino-6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoylleuco methylene blue ,
6'-chloro-8'-methoxy-benzoindolinose spirobilane, 6'-promo-3'-methoxy-benzoindolino-spirobilan, 3- (2'-hydroxy-
4'-Dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3-
(2'methoxy-5'-nitrophenyl) phthalide, 3
-(2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3- (N-ethyl-N-tetrahydrofuru Furyl) amino-6-methyl-
7-anilinofluorane, 3-N-ethyl-N- (2-
(Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-morpholino-7-
(N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-m-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-
7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-
5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α
-Phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino)
Fluoran, 3-diethylamino-5-methyl-7-
(Α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3
-(N-methyltoluidino) -7- (pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran,
3-di-n-butylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6'-dimethylaminophthalide, 3- (N -Benzyl-N-cyclohexylamino)
-5,6-benzo-7-α-naphthylamino-4'-promofluorane, 3-diethylamino-6-chloro-7
-Anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluoran,
3-N-methyl-N-isopropyl-6-methyl-7-
Anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluorane, 3 -Morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethyl) Anilino) Fluoran, 3-
Pyrrolidino-7- (di-P-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7
-(Α-phenylethylamino) fluorane, 3- (N
-Ethyl-P-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o
-Methoxycarbonylphenylamino) fluorane, 3
-Diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (p-N-butylanilino) ) Fluoran, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 3-
(N-benzyl-N-cyclohexylamino) -5.6
-Benz-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-(-2-ethoxypropyl) amino-6 -Methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5 '-
Benzofluorane, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- { 1,1-bis (P-dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-phenyl Ethylene-2-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-Dimethylamino-2'-methoxy) -3- (1 "-p-dimethylaminophenyl-1" -p-chlorophenyl-
1 ", 3" -butadiene-4 "-yl) benzophthalide, 3- (4'-dimethylamino-2'-benzyloxy) -3- (1" -p-dimethylaminophenyl-1 "
-Phenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide 3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, 3,3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl} -4,5,6,7-tetrachlorophthalide, 3-bis {1,1-bis (4-pyrrolidinophenyl ) Ethylene-2-yl} -5,6-dichloro-4,7-dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) -1-p- Tolylsulfonylmethane and the like.

In the present technology, the developer is an electron-accepting compound which develops the leuco dye when contacted,
For example, phenolic compounds, thiophenolic compounds,
A thiourea derivative, an organic acid and a metal salt thereof can be used, and specific examples thereof include, but are not limited to, those shown below.

4,4'-isopropylidene diphenyl, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisdenol 4,4'-isopropylidene bis (2-) Tert-butylphenol), zinc p-nitrobenzoate, 1,
3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid,
2,2- (3,4′-dihydroxydiphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4- [β- (p-methoxyphenoxy) ethoxy] salicylic acid, 1,7-bis (4 -Hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -5-oxapentaso, phthalic acid monobenzyl ester monocalcium acid,
4,4'-Cyclohexylidene diphenol, 4,4 '
-Isopropylidene bis (2-chlorophenol),
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6
-Tert-butyl-2-methyl) phenol, 1,
1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4 ′ -Thiobis (6-tert-butyl-2-methyl) phenol, 4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-pentyloxy-4'-hydroxydiphenyl sulfone, 4,4 '-Diphenol sulfoxide, isopropyl P-hydroxybenzoate,
Benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N′-diphenylthiourea,
N, N'-di (m-chlorophenyl) thiourea, salicylanilide, methyl bis- (4-hydroxyphenyl) acetate, bis- (4-hydroxyphenyl) benzyl acetate, 1,3-bis (4-hydroxycumyl) )benzene,
1,4-bis (4-hydroxycumyl) benzene, 2,
4'-diphenol sulfone, 2,2'-diallyl-
4,4'-diphenol sulfone, 3,4-dihydroxyphenyl-4'-methyldiphenyl sulfone, zinc 1-acetyloxy-2-naphthoate, zinc 2-acetyloxy-1-naphthoate, 2-acetyloxy- Zinc 3-naphthoate, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrapromobisphenol A, tetrapromobisphenol S, 4,4′-thiobis (2-methyl) Phenol), 4,4′-thiobis (2-chlorophenol) and the like.

In order to produce the thermal recording material of the present technology,
When the leuco dye and the color developer are bonded to the support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

That is, polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic. Acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. Others, such as polyvinyl acetate, polyurethane, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, etc. Emissions and styrene / butadiene copolymer, styrene / butadiene / latex such as acrylic copolymer.

Further, in the heat-sensitive recording layer of the present invention, together with the above-mentioned leuco dye and color developer, auxiliary additives, such as fillers, surfactants, and heat agents, which are commonly used in heat-sensitive recording materials of this type are used, if necessary. A fusible substance (or a lubricant), a pressure color-developing inhibitor, etc. can be used in combination. In this case, specific examples of the filler and the heat-fusible substance include those similar to those exemplified in relation to the protective layer.

In the present invention, an undercoat layer may be provided between the support and the thermosensitive recording layer. In this case, the resin and the crosslinking agent used in the protective layer are preferably used as the main components of the undercoat layer. With such a configuration, water resistance and chemical resistance to water and chemicals leached from the back surface of the support are excellent. Further, in the present invention, a back coat layer can be provided on the back surface of the support, but in this case, it is desirable to use the resin and the crosslinking agent used in the protective layer as the main components. With such a configuration, it is possible to effectively prevent water or chemicals from leaching from the back surface of the support. Furthermore,
In the present invention, it is possible to form the protective layer in two or more layers.

The heat-sensitive recording material of the present invention is used in various fields. In particular, the heat-sensitive recording type label sheet and the heat-sensitive recording type magnetic sheet are utilized by utilizing the above-mentioned excellent color image and stability of the background. It can be advantageously used as paper.
In the case of a thermal recording type label sheet, one side of the support,
The above-mentioned protective layer and the heat-sensitive recording layer containing the leuco dye and the developer are provided, on the other surface of the support, a release mount may be provided via an adhesive layer, and in the case of a magnetic ticket paper, Instead of the release mount, a magnetic recording layer containing a ferromagnetic material and a binder as main components may be provided.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to Examples and Comparative Examples. The following parts and percentages are all based on weight. Examples 1 to 11 and Comparative Examples 1 to 3 <Formation of Thermosensitive Recording Layer> Mixtures having the following compositions were pulverized and dispersed by a sand glider for 2 to 4 hours, and [A
Liquid] and [Liquid B].

[Solution A] 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane 10 parts 10% aqueous solution of polyvinyl alcohol 10 parts water 80 parts [Solution B] 4-hydroxy Phenyl-4'-isopropoxyphenyl sulfone 10 parts Calcium carbonate 10 parts 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl) phenylbutane 5 parts 10% aqueous solution of polyvinyl alcohol 20 parts water Further, both [Liquid A] and [Liquid B] were dispersed in a sand mill for 24 hours to obtain respective dispersions, and the weight ratio was [Liquid A]: [Liquid B] =
A thermal recording layer coating solution was prepared by mixing and agitating so as to be 1: 3, dried on a commercially available high-quality paper, and then coated and dried so that the basis weight was 50 g / m ² and the dry weight was 5 g / m ^2. A paper coated with a heat-sensitive recording layer was obtained.

<Formation of Protective Layer> A mixture having the following composition was prepared by using the resin, the cross-linking agent, the pigment type and the pigment addition part shown in Table 1. Resin 20% Aqueous dispersion or aqueous solution 100 parts Cross-linking agent 10% Aqueous dispersion or aqueous solution 10 parts Pigment 20% Dispersion or water X parts The recording layer on the above-mentioned thermal recording layer-formed quality paper, the back side of the quality paper or the quality paper 3g dry weight between heat sensitive recording layer and
/ M ² so as to be coated and dried to form a predetermined layer, thereby manufacturing Examples 1 to 11 and Comparative Examples 1 to 3. The resin used is an acrylic polymer having a core portion containing acrylonitrile and an acrylic polymer having a shell portion containing methacrylic acid and / or acrylamide.

[0026]

[Table 1]

The following tests were conducted on Examples 1 to 11 and Comparative Examples 1 to 3, and the results are shown in Table 2. <Color development characteristics> With a printing device manufactured by Matsushita Co., Ltd., 0.6 W,
Printed at 1.2 msec, Macbeth Densitometer RD-
The concentration was measured at 914.

<Water resistance> After being left at 40 ° C. for 16 hours, it was immersed in water for 16 hours and rubbed with a finger to evaluate the peeled state. ◯: Good without peeling △: Slight peeling occurred ×: Poor peeling and poor <Heat resistance> 70 samples measured by Macbeth densitometer
After standing at ℃ for 1 hour, measure again with a Macbeth densitometer, and check whether there is color development on the background before and after standing. The background density before the test was 0.07. <Plasticizer resistance> A commercially available polywrap was adhered to the sample printed as described above, and the residual ratio of the concentration was measured when the sample was left at 40 ° C for 24 hours.

<Dust adhesion> 30 with a thermal printer
After printing for km, the adhesion of dust on the thermal head was observed. ◎… No adhesion, no problem with printing ○… Some adhesion, but no problem with printing ×… Significant adhesion, problem with printing

[0030]

[Table 2]

[0031]

As is apparent from Table 2, the heat-sensitive recording material of the present invention is a core-shell type emulsion obtained by polymerizing acrylamide and / or methacrylamide in the presence of a seed emulsion of an acrylic (co) polymer. Since a copolymer resin is used and a protective layer using a carbodiimide compound as a cross-linking agent is provided thereon, the water resistance, heat resistance and plasticizer resistance are excellent. In addition, an oil absorption of 250 cc / 100 g or less as a pigment, and an average particle size of 3 μm
When it is m or less, the head matching property (waste adhesion), the plasticizer resistance, and the color development property are excellent.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takeshi Kajikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A heat-sensitive recording material comprising a support, a heat-sensitive recording layer which is colored by heat, and a protective layer containing a resin and a cross-linking agent, the resin being an acrylic resin. A heat-sensitive recording material, which is a core-shell type emulsion obtained by polymerizing acrylamide and / or methacrylamide in the presence of a seed emulsion of a polymer or a copolymer, and wherein the crosslinking agent is a carbodiimide compound. 2. The glass transition point Tg of the core of the resin is 1
The heat-sensitive recording material according to claim 1, which has a temperature of 5 ° C or higher. 3. The heat-sensitive recording material according to claim 1, wherein the shell portion of the resin has a glass transition point Tg of 150 ° C. or higher. 4. The glass transition point Tg of the core portion of the resin is 1
5 ℃ or higher, and glass transition point Tg of shell is 150 ℃
The heat-sensitive recording material according to claim 1, which is the above. 5. A pigment / resin ratio of 1 when used in combination with a pigment.
5. The heat-sensitive recording material according to claim 1, wherein: 6. The oil absorption of the pigment is 250 cc / 100 g.
6. The heat-sensitive recording material according to claim 5, wherein the average particle diameter is 3 μm or less.