JPH07125427A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having a superior image reliability and a longer pot life of coating liquid by a method wherein in a thermal recording material provided with a thermal color-forming layer and a protective layer mainly composed of a resin and a crosslinking agent on a substrate, a specific alkylene imide compound is used as the crosslinking agent. CONSTITUTION:In a thermal recording material, a thermal color-forming layer mainly composed of a leuco dye and a color developer making the leuco dye produce a color under heat is provided on a substrate, and thereon a protective layer mainly composed of a resin and a crosslinking agent is provided. In this invention, as the crosslinking agent, an alkylene imide compound having a plurality of groups represented by a formula I is used. In the formula, R represents alkyl. group. As the main-component resin of the protective layer, a copolymer esp. obtained from an (anhydrous) maleic acid monomer is used. Alternatively, as the crosslinking agent, a carbodiimide compound, a methylethyl ketoxime compound having group represented by a formula II, or bis(beta- hydroxyethyl) sulfone can bee 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, and more particularly, it relates to an improvement of a heat-sensitive recording material having a heat-sensitive coloring layer which is colored by heat on a support.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a support such as paper, synthetic paper, plastic film, etc., on which a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component is provided. A colored image can be obtained by heating with a flash lamp or the like. Compared to other recording materials, this type of recording material does not require complicated processing such as development and fixing,
Not only is it used for copying books, documents, etc. due to the advantages of being able to obtain records in a short time with a relatively simple device, low noise and environmental pollution, and low cost, electronic calculators, facsimiles, It is widely used as a recording material in various fields such as ticket vending machines, labels and recorders. The thermochromic composition used for such a heat-sensitive recording material is composed of a general color former and a developer which allows the color former to develop color when heated, and the color former is, for example, a lactone, a lactam or a colorless compound having a spiropyran ring. Alternatively, a light-colored leuco dye has been conventionally used as a developer, and an organic acid or a phenolic substance has been used. The recording material obtained by combining the color-developing agent and the color-developing agent has the advantages that the color tone of the obtained image is particularly clear, the background whiteness is high, and the weather resistance of the image is excellent. Widely used.

However, this type of heat-sensitive recording material is DOA or D
When it comes into contact with a plasticizer such as OP or oils and fats, it has a defect that the image is erased and the background portion is colored.
In order to overcome these drawbacks, a protective layer has been conventionally provided on the thermosensitive coloring layer, and the components constituting this protective layer include a water-soluble resin such as polyvinyl alcohol or starch and a glyoxal or an epoxy compound. Fillers such as calcium carbonate and silica and wax have been used as cross-linking agents such as as a matching improvement aid.

Since a water-soluble resin is used for the protective layer,
Since the water resistance is low and there is a problem that the protective layer peels off when it comes into contact with water, it is usual to add a crosslinking agent. For example, polyvinyl alcohol and an epoxy compound having two or more epoxy groups or an ethyleneimine compound having two or more ethyleneimine groups are used (JP-A-60-68990), and a compound having casein and a methylol group. What was used
No. 0-193693), one using an acrylamide-acrylonitrile-carboxyl group-containing vinyl compound copolymer and an epoxy resin (JP-A-61-37467),
Polyvinyl alcohol and 2,4-dihydroxy-1,4
-Using a dioxane derivative (JP-A-62-444)
94) and bis (4-glycidyloxyphenyl) sulfone as a crosslinking agent (JP-A-62-27).
No. 0382) has been proposed. However, the pot life of the coating liquid is short, such as the viscosity of the coating liquid increasing with time and the crosslinking effect decreasing with time like ethyleneimine compounds, and conversely the pot life is long but the water resistance is high. There are drawbacks such as insufficientness.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the above problems and provides a heat-sensitive recording material which is excellent in image reliability such as water resistance, oil resistance and plasticity resistance and has a long pot life of a coating liquid. The purpose is to

[0006]

According to the present invention, a thermosensitive coloring layer containing, as a main component, a leuco dye and a developer for coloring the leuco dye by heat is provided on a support, and further thereon. A heat-sensitive recording material comprising a protective layer containing a resin and a cross-linking agent as a main component, wherein an alkyleneimide compound having a plurality of groups represented by the following chemical formula 1 is used as the cross-linking agent.

[Chemical 1] (Wherein R represents an alkyl group), and a copolymer obtained from a (anhydrous) maleic acid monomer is used as the main component resin of the protective layer. A heat-sensitive recording material is provided, and a heat-sensitive coloring layer mainly containing a leuco dye and a developer that makes the leuco dye color by heat is provided on a support, and a resin and a cross-linking agent are mainly formed on the heat-sensitive coloring layer. A heat-sensitive recording material comprising a protective layer as a component, wherein the heat-sensitive recording material is characterized by using a carbodiimide compound as the crosslinking agent, and further, a leuco dye and the leuco dye are provided on a support. In a heat-sensitive recording material comprising a thermosensitive coloring layer containing a color developer which is colored by heat as a main component, and further a protective layer containing a resin and a crosslinker as a main component thereon, as the crosslinking agent,
A heat-sensitive recording material characterized by using a methyl ethyl ketoxime compound having a group represented by the following chemical formula 2.

[Chemical 2] Further, a thermosensitive coloring layer mainly containing a leuco dye and a color developer capable of coloring the leuco dye by heat is provided on a support, and a resin and a cross-linking agent as main components are further provided thereon. In the heat-sensitive recording material provided with a protective layer, the bis (β-
Thermosensitive recording material characterized by using hydroxyethyl) sulfone

[Chemical 3] Will be provided.

That is, the inventors of the present invention have made extensive studies as to a protective layer comprising a resin and a cross-linking agent provided on the heat-sensitive color forming layer in the heat-sensitive recording material, and as a result, have used the above-mentioned cross-linking agent. In this case, it was found that the intended purpose could be achieved, and the present invention was completed.

Specific examples of the alkyleneimide compound having a plurality of groups represented by the above chemical formula 1 used as a crosslinking agent in the present invention include those represented by the following chemical formulas 4 and 5.

[Chemical 4]

[Chemical 5]

Specific examples of the carbodiimide compound used as the crosslinking agent in the present invention include the following. 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.

Further, specific examples of the methylethylketoxime compound having the group represented by the above chemical formula 2 used as a crosslinking agent in the present invention include those represented by the following chemical formula 6, chemical formula 7 or chemical formula 8.

[Chemical 6]

[Chemical 7]

[Chemical 8]

Furthermore, in the present invention, together with the aforementioned crosslinking agent of the present invention, conventionally used crosslinking agents such as formalin, chromium alum, glyoxal, boric acid, amine compounds, epoxy compounds, polyamide epichlorohydrin compounds, It can be used in combination with a glycidyl compound, a methylol compound, an ethyleneimine compound and the like.

Examples of the resin used in the protective layer of the present invention include polyvinyl alcohol, cellulose derivatives, starch and its derivatives, carboxyl group-modified polyvinyl alcohol, polyacrylic acid and its derivatives, styrene / acrylic acid copolymer and its derivatives. , Poly (meth) acrylamide and their derivatives, styrene / acrylic acid / acrylamide copolymer, amino group-modified polyvinyl alcohol,
Water-soluble resins such as epoxy-modified polyvinyl alcohol, polyethyleneimine, aqueous polyester, aqueous polyurethane, maleic anhydride copolymer and its derivatives, polyester, polyurethane, acrylic ester (co) polymer, styrene / acrylic copolymer Examples thereof include aqueous emulsion resins such as coalesce, epoxy resin, polyvinyl acetate, polyvinylidene chloride, polyvinyl chloride and derivatives thereof. Among these, water-soluble resins are preferable, and (modified) polyvinyl alcohol is particularly preferable, and among them, completely saponified type having a polymerization degree of 1,000 or more is preferable.

When the alkyleneimide compound is used as the crosslinking agent, the copolymer obtained from the (anhydrous) maleic acid monomer is particularly preferable as the resin for forming the protective layer.
Examples of such (anhydrous) maleic acid copolymer include isobutylene-maleic anhydride copolymer and diisobutylene-
Examples thereof include maleic anhydride copolymers and acrylic-styrene-maleic acid copolymers.

In the protective layer of the present invention, the above resin,
In addition to the cross-linking agent, if necessary, an auxiliary additive component commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance (or a lubricant), a pressure color-developing inhibitor, etc. are used in combination. be able to. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide,
Inorganic fine powders such as aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium and silica, as well as urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin and other organic materials Mention may be made of fine powders of the system. Examples of the heat-fusible substance include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate esters, higher linear glycols, 3 Examples thereof include those having a melting point of about 50 to 200 ° C. such as 1,4-epoxy-dialkyl hexahydrophthalate, higher ketones, p-benzylbiphenyl and other heat-fusible organic compounds.

As the method of developing color by heat used in the present invention, a method utilizing a color reaction between a leuco dye and a developer, a method utilizing a reaction between a diazo compound and a coupler, and a reaction between an isocyanate and an amine are utilized. There are things to do. Since the characteristic of the present invention is the protective layer of the heat-sensitive recording material, the color forming method is not particularly limited. Hereinafter, as a thermal recording system, a system using a general leuco dye will be described.

In the present invention, the leuco dyes used in the thermosensitive coloring layer may be used alone or in admixture of two or more.
As such leuco dyes, those applied to this type of heat-sensitive material are arbitrarily applied, for example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophtalide-based, etc. Leuco compounds of dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl)-
Phthalide, 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-
Dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,
7-Dimethylfluorane, 3-N-methyl-N-isobutyl-6-
Methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 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-
Chloranilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o -Chloranilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino ) Fluoran, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-
3'-methoxy-benzoindolino-spiropyran, 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
-Morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethyl) Anilino) fluorane, 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- (pn-butylanilino) fluorane, 3-
(N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro ( 9,3 ')-6'-Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-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-
N-ethyl-N-isobutyl-6-methyl-7-anilinofluorane and the like.

Further, as the color developer used in the thermosensitive color developing layer of the present invention, various electron-accepting compounds which develop the above leuco dye upon contact, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic compounds Acids and metal salts thereof are preferably applied, and specific examples thereof include those shown below.

4,4'-isopropylidene bisphenol,
4,4'-isopropylidene bis (o-methylphenol),
4,4'-Secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-cyclohexylidene diphenol, 4,4'-
Isopropylidene bis (2-chlorophenol), 2,2'-
Methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-2-methylphenol), 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-methylphenol), 4,4'-
Diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate , Benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-Oxapentane, 1,3-bis (4-hydroxyphenylthio) -propane, 1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1- Futoe acid, 1-hydroxy-2-naphthoic acid, zinc hydroxynaphthoic acid, aluminum, metal salts such as calcium,
Bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3
-Bis (4-hydroxycumyl) benzene, 1,4-bis (4-
(Hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,3'-diallyl-4,4'-diphenol sulfone,
α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, etc.

In order to produce the heat-sensitive recording material of the present invention,
When the leuco dye and the color developer are bound and supported on the support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyacrylic acid sodium -Da, 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, soda alginate, gelatin, other water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylic acid, Polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene /
Emulsion such as vinyl acetate copolymer, latex such as styrene / butadiene copolymer and styrene / butadiene / acrylic copolymer.

In the heat-sensitive color developing layer of the present invention, an auxiliary additive component, such as a filler, a surface active agent, a heat agent, or the like, which is commonly used in heat-sensitive recording materials of this type, may be added together with the leuco dye and the color developer. 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 the same as those exemplified in relation to the protective layer.

In the present invention, an undercoat layer may be provided between the support and the thermosensitive color developing layer, if necessary. In this case, the above-mentioned filler, binder, heat-fusible substance, surfactant or the like can be used as a component constituting the undercoat layer. Further, in the present invention, the protective layer may be composed of two or more layers, or a back coat layer may be provided.

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 label sheet utilizing the above-described excellent color-developed image and stability of the background portion,
It can be advantageously used as a heat-sensitive recording type magnetic ticket paper. In the case of a heat-sensitive recording type label sheet, one side of the support is provided with the above-mentioned protective layer and the heat-sensitive coloring layer containing the leuco dye and the color developer, and the other side of the support is provided with an adhesive layer. It is sufficient to provide a release mount, and in the case of 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.

[0027]

The present invention will now be described in more detail by way of examples. The following parts and% are based on weight.

Examples 1 to 5 and Comparative Examples 1 to 4 [Formation of Thermosensitive Coloring Layer] Mixtures having the following compositions were pulverized and dispersed by a sand grinder for 2 to 4 hours, and [A
Solution] and [B Solution] were prepared. [Solution A] 3- (N-methyl-N-cyclohexyl) amino-6-10 parts Methyl-7-anilinofluorane 10% aqueous solution of polyvinyl alcohol 10 parts Water 80 parts [Solution B] 4-hydroxyphenyl-4 '-Isopropoxyphenyl sulfone 10 parts Calcium carbonate 10 parts 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexyl 5 parts phenyl) butane 10% aqueous solution of polyvinyl alcohol 20 parts water 55 parts Both liquid A and liquid B were dispersed in a sand mill for 24 hours to obtain each dispersion liquid, and the weight ratio was [liquid A]: [liquid B].
= 1: 3 to prepare a thermosensitive color developing layer coating solution by mixing and stirring, and dried on commercial high-quality paper, the coating amount is 50 g / m ² basis weight,
It was coated and dried so that the dry weight was 5 g / m ² , to obtain a paper coated with a thermosensitive coloring layer.

[Formation of Protective Layer] [Liquid C] Kaolin 10 parts Polyvinyl alcohol 10% aqueous solution 10 parts Water 80 parts [Liquid C] was dispersed in a sand mill for 15 hours to obtain a kaolin dispersion liquid. [D ₁ liquid] to [D ₅ liquid], [E ₁ liquid] to [E ₄ liquid] Kaolin dispersion liquid 20 parts Resin (as shown in Table 1) 10% aqueous solution 40 parts Crosslinking agent (as shown in Table 1) 10% aqueous solution (dispersion) 49 parts 1 part water [D ₁ liquid] - [D ₅ liquid] or [E ₁ solution] - [E ₄ liquid] each said thermosensitive coloring layer has been formed paper and the dry weight is 3g / M ²
And dried to form a protective layer. Further, surface treatment was performed with a super calendar to obtain heat-sensitive recording materials of Examples 1-5 and Comparative Examples 1-4.

[0030]

[Table 1]

With respect to the heat-sensitive recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 4, the plasticizer resistance, water resistance, liquidity, and liquid-aging effect were measured by the methods described below. The results are shown in Table 2. -Plasticizer resistance Using a heat block, a density of 1.3 on a Macbeth densitometer
Applying DOA to the color developed at 0, 30 ° C, 16
After a period of time, the density was measured with a Macbeth densitometer. -Water resistance After standing 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, Δ: Slightly peeling occurs ×: Poor with peeling-Liquid property After preparing the protective layer forming liquid, leave it at 30 ° C. for 16 hours, and then remove the liquid. The viscosity was evaluated. ○ ... Good liquidity ・ Efficacy test of liquid over time After preparation of the protective layer forming liquid, after leaving at 30 ° C. for 16 hours, 30
After standing for a period of time, each liquid was evaluated for the protective layer forming ability when the protective layer was provided in the same procedure as described above. ○ ・ ・ ・ Good, △ ・ ・ ・ Slightly inferior, × ・ ・ ・ Poor

[0032]

[Table 2]

As is apparent from Examples 1 to 5 and Comparative Examples 1 to 4, the protective layer in the heat-sensitive recording material of the present invention was used as a cross-linking agent for forming the protective layer. The pot life of the forming liquid is long,
Moreover, the obtained thermal recording material has excellent plasticizer resistance and water resistance. In particular, when a copolymer obtained from a (anhydrous) maleic acid monomer is used as the resin forming the protective layer, the pot life is further improved.

Examples 6 to 17 and Comparative Examples 5 to 8 [Formation of protective layer] [F liquid] 10 parts of silica 10% aqueous solution of polyvinyl alcohol 10 parts water 80 parts [F liquid] dispersed for 15 hours in a sand mill, A silica dispersion was obtained. [G ₁ liquid] - [G ₄ liquid], [H ₁ liquid] - [H ₄ solution], [J ₁
Liquid] - [J ₄ liquid], [K ₁ liquid] - [K ₄ liquid] Silica Dispersion 20 parts of the resin (Table 3 as described) of 10% aqueous solution of 40 parts of crosslinking agent (Table 3 as described) of 10% aqueous solution obtained (dispersion) with parts 1 part water 49 [G ₁ liquid] - [K ₄ liquid], example 6 to 17 in the same manner as in example 1-5, the heat-sensitive recording material of Comparative example 5-8 It was

[0035]

[Table 3]

The thermosensitive recording materials obtained in Examples 6 to 17 and Comparative Examples 5 to 6 were measured for plasticizer resistance, water resistance and liquid resistance by the methods described below. The results are shown in Table 4. -Plasticizer resistance Same as Examples 1-5-Water resistance Same as Examples 1-5-Liquidity The coating liquid was applied on the thermosensitive color developing layer again at 30 ° C for 24 hours, and the viscosity of the liquid. A similar liquidity test was carried out and compared with the sample obtained from the liquid immediately after preparation. ○ ・ ・ ・ Same as immediately after compounding △ ・ ・ ・ Slightly inferior to immediately after compounding × ・ ・ ・ Inferior to immediately after compounding

[0037]

[Table 4]

As is clear from Examples 6 to 17 and Comparative Examples 5 to 8, a carbodiimide compound, a methylethylketoxime compound, or bis (β-hydroxyethyl) was used as the crosslinking agent for forming the protective layer in the heat-sensitive recording material of the present invention. ) By using sulfone, the protective layer-forming liquid has a long pot life, and the resulting heat-sensitive recording material has excellent plasticity and water resistance.

[0039]

The heat-sensitive recording material of the present invention mainly comprises a resin and a crosslinking agent selected from an alkyleneimide compound, a carbodiimide compound, a methylethylketoxime compound, or bis (β-hydroxyethyl) sulfone on the heat-sensitive color forming layer. By providing a protective layer as a component, excellent image reliability such as plasticizer resistance and good water resistance, and by using the crosslinking agent, the pot life of the protective layer forming coating solution is improved. long. Furthermore, when an alkylene imide compound is used as the crosslinking agent, the pot life of the coating liquid is further extended by using a copolymer composed of (anhydrous) maleic acid monomer for the resin.

Claims (5)

[Claims] 1. A thermosensitive coloring layer containing, as a main component, a leuco dye and a color developer capable of coloring the leuco dye by heat is provided on a support, and further a protective film containing a resin and a cross-linking agent as the main components is further provided thereon. A heat-sensitive recording material having a layer, wherein an alkyleneimide compound having a plurality of groups represented by the following chemical formula 1 is used as the crosslinking agent. [Chemical 1] (In the formula, R represents an alkyl group.) 2. The heat-sensitive recording material according to claim 1, wherein a copolymer obtained from a (anhydrous) maleic acid monomer is used as a main component resin of the protective layer. 3. A thermosensitive coloring layer containing, as a main component, a leuco dye and a color developer capable of coloring the leuco dye by heat is provided on a support, and a protective film containing a resin and a crosslinking agent as a main component is further provided thereon. A heat-sensitive recording material comprising a layer, wherein a carbodiimide compound is used as the crosslinking agent. 4. A thermosensitive coloring layer containing, as a main component, a leuco dye and a color developer capable of coloring the leuco dye by heat, is provided on a support, and a protective layer containing a resin and a crosslinking agent as the main components is further provided thereon. A thermal recording material comprising a layer, wherein a methyl ethyl ketoxime compound having a group represented by the following chemical formula 2 is used as the crosslinking agent. [Chemical 2] 5. A thermosensitive coloring layer containing, as a main component, a leuco dye and a color developer capable of coloring the leuco dye by heat is provided on a support, and further a resin and a crosslinking agent are contained as the main components on the layer. A heat-sensitive recording material comprising a protective layer, wherein bis (β-hydroxyethyl) sulfone represented by the following chemical formula 3 is used as the crosslinking agent. [Chemical 3]