JP2008188926A - Heat-sensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sensitive recording material excellent in color-forming capability prone to make fewer and smaller dark spots in the background due to heat and humidity which enables excellent developed image in preservation stability, especially in resistance to heat and humidity and to a plasticizer. <P>SOLUTION: The heat-sensitive recording material having on its supporting body a heat-sensitive color-forming layer including an achromatic or a hypochromic color-forming compound and a color-developing compound which can thermally develop the color-forming compound is characterized in that the heat-sensitive color-forming layer includes a maleic acid denatured propylene copolymer as an adhesive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to a heat-sensitive recording material having excellent color developability and excellent storage stability of background fog and color images against dry heat and wet heat after color recording.

  In general, heat-sensitive recording materials are obtained by dispersing a leuco dye and a developer such as a phenolic substance separately into fine particles, and then mixing both of them together with additives such as a binder, a sensitizer, a filler, and a lubricant. Is applied to paper, film, synthetic paper, etc., and color recording is obtained by a chemical reaction that occurs when one or both of the leuco dye and the developer is melted and contacted by heating. . For the color development of such a heat-sensitive recording material, a thermal printer or the like with a built-in thermal head is used. Compared to other recording methods, this thermal recording method is (1) no noise during recording, (2) no need for development, fixing, etc. (3) maintenance-free, (4) machine relatively Due to its low cost, it is widely used in the facsimile field, the output of computers, the field of printers such as calculators, the field of medical measurement recorders, the field of automatic ticket machines, the field of thermal recording labels, and the like.

In recent years, the use of labels, boarding tickets, coupon tickets, etc. has increased with the establishment of POS systems in retail stores and supermarkets, and automation systems for transportation facilities. In these applications, preservability such as water resistance, plasticizer resistance, and oil resistance of recorded images (prints, images, patterns) generated by touching water, wraps, plastic sheets, oil, fat, etc. is an essential condition. is there. Among them, various types of wrap films have recently been used for wraps, and it is strongly desired to improve resistance to plasticizers. At the same time, the demand for high-speed recording has further increased, and the development of heat-sensitive recording materials that can sufficiently support high-speed recording is strongly desired. The disadvantage that a background fog occurs at the time of storage or storage is likely to appear. Thus, it is desired to improve the stability of the unrecorded portion (unused portion) of the heat-sensitive recording material.
Various attempts have been made to heat-sensitive recording materials that have less background fogging under such high-temperature and high-humidity environmental conditions and have good storage stability of various recorded images. For example, when 2,4′-dihydroxydiphenylsulfone is used as a color developing compound in Documents 1 to 3 and the like, it is disclosed that there is an improvement effect such as heat resistance of white paper or background fogging, various image storage stability, It is still insufficient in terms of satisfying the quality required for high quality or long-term use.

JP-A-6-1069 Japanese Patent No. 2745172 Japanese Patent Publication No.7-12749

  The object of the present invention is to solve the above-mentioned drawbacks of the prior art. That is, it is an object of the present invention to provide a heat-sensitive recording material that has excellent color developability, has little background fogging against dry heat and wet heat after color recording, and has excellent storage stability of color images.

  The present inventor has completed the present invention as a result of various studies to achieve the above object.

That is, the present invention
(1)
In a heat-sensitive recording material provided with a heat-sensitive color-developing layer containing a normally colorless or light-color-colorable compound and a color developing compound capable of developing the color-forming compound when heated, the heat-sensitive color developing layer is an adhesive. A heat-sensitive recording material comprising a maleic acid-modified propylene copolymer as
(2)
As a color developing compound capable of developing a color developing compound when heated, bis (3-allyl-4-hydroxyphenyl) sulfone, the following formula (1),

(In formula (1), R ¹ represents an alkyl group or cyclohexyl group having 4 or less carbon atoms, and R ² represents an alkyl group having 4 or less carbon atoms).
Following formula (2),

Following formula (3),

Or the following formula (4),

A heat-sensitive recording material as described in (1) above, which is used in combination with any of the compounds represented by:
About.

  A heat-sensitive recording material having excellent color developability, little background fog against dry heat and wet heat after color recording, and excellent storage stability of color images was obtained.

  The heat-sensitive recording material of the present invention is a heat-sensitive recording material provided with a heat-sensitive color-developing layer containing a normally colorless or light-colorable color-forming compound and a color developing compound capable of color-forming the color-forming compound when heated on a support. The thermosensitive coloring layer contains maleic acid-modified propylene copolymer as an adhesive.

 The maleic acid-modified propylene copolymer used in the present invention is represented, for example, by the following formula (5).

(In Formula (5), l represents a number from 200 to 1200, m represents a number from 10 to 400, and n represents a number from 1 to 50. Also, x and y represent a hydrogen atom, Li, Na, K, Represents NH ₄ or alkanolamine.)
The maleic acid-modified propylene copolymer represented by the formula (5) is a compound having monomer main components composed of propylene and maleic acid, and a molecular weight of 5,000 to 1,000,000, preferably 30,000 to 100,000.
Although it is known that maleic acid-modified polypropylene can be used in various applications such as a dispersant, a hot melt adhesive, and a paint additive, it has not been known so far that it can be used as a heat-sensitive recording material. Examples of the compound of the above formula (5) include TP-007M, TP-001M manufactured by UMG ABS Co., Ltd., and these compounds can be preferably used.
The compound of the above formula (5) is used by being contained in the thermosensitive coloring layer.

  As the color developing compound (developer), any of the compounds described below can be used, but the bis (3-allyl-4-hydroxyphenyl) sulfone and the formulas represented by the above formulas (1) to (4) can be used. It is more preferable to use any one of the colorants in combination. By using the compound of the above formula (5) and these developers in combination, a heat-sensitive recording material excellent in the effects of the present invention, that is, various storability of a recorded image, in particular, wet heat resistance and plasticizer resistance is obtained. be able to.

Specific examples of the compound represented by the formula (1) include 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (in the formula (1), R ¹ is t -Butyl, a compound in which R ² is methyl), 1,1,3-tris (2-ethyl-4-hydroxy-5-t-butylphenyl) butane (in the formula (1), R ¹ is t-butyl, R ² Is an ethyl compound), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane (a compound in which R ¹ is cyclohexyl and R ² is methyl in formula (1)), and the like. . These are, for example, made by Adeka, trade name: Adeka Stub AO-30 or Yoshitomi Pharmaceutical, trade name: Yoshinox 930 (a compound in which R ¹ is t-butyl and R ² is methyl), or Adeka Arcles DH -43 (a compound in which R ¹ is cyclohexyl and R ² is methyl in formula (1)) or the like can be obtained from the market.
It is known that Adeka Stab AO-30 and Adeka Arcles DH-43 can be used as storage stabilizers for applications such as thermal recording paper, and Yoshinox 930 can be generally used as an antioxidant.

Moreover, the compound shown by Formula (2) can be obtained from the market as a product name: D-90 etc. by Nippon Soda Co., Ltd., for example. D-90 is a compound in which z is 2 in the above formula (2), and can be preferably used in the present invention.
Further, it is known that D-90 can be used as a developer for applications such as thermal recording paper.

Further, the compound represented by the formula (3) can be obtained from the market as, for example, an Adeka product name: developer UU.
The developer UU can be used as a developer for applications such as thermal recording paper, and is known to be a mixture of positional isomers at the substitution position of the methyl group in the above formula (3).

Moreover, the compound shown by Formula (4) can be obtained from the market as a product name: NTZ-95 etc. made from Nippon Soda.
It is known that NTZ-95 can be used as a storage stabilizer for applications such as thermal recording paper.

In forming the thermosensitive coloring layer in the present invention, the color developing compound is usually 1 to 50% by weight, preferably 5 to 30% by weight, the color developing compound and any of the compounds represented by the formulas (1) to (4). Is generally 1 to 70% by weight, preferably 10 to 50% by weight, sensitizer is 0 to 80% by weight, and maleic acid-modified propylene copolymer is usually 1 to 90% by weight, preferably 2 to 30% by weight. The filler is usually used in an amount of 0 to 80% by weight, and other lubricants, surfactants, antifoaming agents, ultraviolet absorbers and the like are each used in an arbitrary ratio, for example, usually 0 to 30% by weight. In addition, the said weight% is a weight ratio of each component which occupies in a thermosensitive coloring layer. As a more preferred embodiment, among the compositions as described above, the use amount of each of the maleic acid-modified propylene copolymer is 0.5 to 30 times, preferably 1 to 10 with respect to the chromogenic compound 1 in the weight ratio. In the range of the double weight ratio, the total amount of the color developing compound and the compounds represented by formulas (1) to (4) is usually 0.5 to 20 times, more preferably 1 to 5 times the weight ratio. Used in each range. Developer: Any one of the compounds represented by formulas (1) to (4) is used in a weight ratio range of 9: 1 to 1: 9, preferably 9: 1 to 5: 5.
In the heat-sensitive recording material of the present invention, other publicly known or publicly used adhesives or other additives may be used in combination.

  The color-forming compound used in the present invention is not particularly limited as long as it is generally used for pressure-sensitive recording paper and heat-sensitive recording paper. Examples of chromogenic compounds that can be used include fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like.

  Specific examples of the fluorane compound include 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl- N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N -Isobutylamino) -6-methyl-7-anilinofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluorane, 3- (N- Ethyl-N-hexylamino) -6-methyl-7-anilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino)- -Methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-chloroanilino) Fluorane, 3-diethylamino-6-methyl-7- (p-fluoroanilino) fluorane, 3- [N-ethyl-N- (p-tolyl) amino] -6-methyl-7-anilinofluorane, 3 -Diethylamino-6-methyl-7- (p-toluidino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- ( o-fluoroanilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-diethylamino 7- (3,4-dichloroanilino) fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-ethoxyethylaminofluorane, 3-diethylamino-6- Chloro-7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-octylfluorane, 3- [N-ethyl-N- (p -Tolyl) amino] -6-methyl-7-phenethylfluorane and the like.

  Specific examples of the triarylmethane compound include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone or CVL), 3,3-bis. (P-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2 -Methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) ) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, , 3-Bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3- (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylamino And phenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide.

Further, specific examples of the above spiro compounds include, for example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3- Propylspirobenzopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8′-methoxyspiro (indoline-2,2′-benzopyran) and the like are diphenylmethane compounds Specific examples of these include, for example, N-halophenyl-leucooramine, 4,4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-trichlorophenylleucooramine, and the like of thiazine compounds. Specific examples include, for example, benzoylleucomethylene blue, p-nitrobenzoy Specific examples of lactam compounds such as leucomethylene blue include rhodamine B anilinolactam and rhodamine Bp-chloroanilinolactam, and specific examples of fluorene compounds include 3,6-bis (dimethyl). Amino) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide, 3,6-bis (dimethylamino) fluorene spiro (9,3 ′)-6′-pyrrolidinophthalide, 3-dimethylamino- 6-diethylaminofluorene spiro (9,3 ′)-6′-pyrrolidinophthalide and the like.
These color forming compounds are used alone or in combination.

  The color developing compound is not particularly limited as long as it is generally used for pressure-sensitive recording paper and heat-sensitive recording paper. For example, α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, pt-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p -Hydroxyphenyl) propane (also known as bisphenol A or BPA), 2,2-bis (p-hydroxyphenyl) butane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 4,4'-thiobisphenol, 4, 4'-cyclo-hexylidene diphenol, 2,2'-bis (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidenebis (2-t-butylphenol), 2,2 ' -Methylenebis (4-chlorophenol), 4,4'-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-methoxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, 4-hydroxy-4 ′ -Ethoxydiphenylsulfone, 4-hydroxy-4'-butoxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate, bis ( 4-hydroxyphenyl) phenolic compounds such as benzyl acetate, 2,4-dihydroxy-2′-methoxybenzanilide, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, 4-hydroxy F Aromatic carboxylic acid derivatives, aromatic carboxylic acid or polyvalent metal thereof such as dimethyl oxalate, ethyl 5-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid Examples include salts.

  Specific examples of sensitizers (thermofusible compounds) that can be used in the present invention include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, and acetylated products of aromatic amines. , Naphthalene derivatives, aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, sulfone derivatives, etc., solid at room temperature, more preferably about 60 ° C. or higher Those having a melting point of 5 can be used.

  Specific examples of the above waxes include, for example, wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, oxidized polyethylene, etc., and higher fatty acids such as stearic acid, behenic acid, etc. Examples of fatty acid amides include stearic acid amide, oleic acid amide, N-methyl stearic acid amide, erucic acid amide, methylol behenic acid amide, methylene bis stearic acid amide, and ethylene bis stearic acid amide. For example, stearic acid anilide, linoleic acid anilide, etc., acetylated products of aromatic amines such as acetotoluizide, and naphthalene derivatives such as 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1- Examples of aromatic ethers such as droxynaphthoic acid phenyl ester include 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4 -Methoxyphenoxy) ethane, 1,2-bis (3,4-dimethylphenyl) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1 1,2-diphenoxymethylbenzene and the like, as the aromatic carboxylic acid derivative, for example, p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester and the like are aromatic sulfonic acid ester derivatives. For example, p-toluenesulfonic acid phenyl ester, phenyl Tylene sulfonate, 4-methylphenyl mesitylene sulfonate, etc. are carbonic acid or oxalic acid diester derivatives such as diphenyl carbonate, oxalic acid dibenzyl ester, oxalic acid di (4-chlorobenzyl) ester, oxalic acid di (4- Methylbenzyl) esters include biphenyl derivatives such as p-benzylbiphenyl and p-allyloxybiphenyl, terphenyl derivatives such as m-terphenyl, and sulfone derivatives such as diphenylsulfone. , Respectively.

  Specific examples of the adhesive that can be used in the present invention include, for example, celluloses such as methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, and cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, and sulfonic acid. Group-modified polyvinyl alcohol, silyl group-modified polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer, iso (or Water-soluble polymers such as alkali salts of diiso) butylene / maleic anhydride copolymers, or (meth) acrylic acid ester copolymers, styrene / ( ) Acrylate ester copolymer, polyurethane, polyester polyurethane, polyether polyurethane, polyvinyl acetate, ethylene / vinyl acetate copolymer, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polyvinylidene chloride, polystyrene, Styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, acrylonitrile / butadiene (NB) copolymer, carboxylated acrylonitrile / butadiene (NB) ) Hydrophobic polymer emulsions such as copolymers and composite particles of colloidal silica and (meth) acrylic resin.

  Specific examples of the filler that can be used in the present invention include, for example, calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, and polystyrene resin. And urea-formalin resin.

Further, various additives other than those described above can be used in the present invention. Examples of other additives that can be used include zinc stearate and calcium stearate for the purpose of preventing thermal head wear and sticking, for example. Higher fatty acid metal salts, such as phenol derivatives for imparting antioxidant or anti-aging effects, benzophenone compounds, benzotriazole compounds and other ultraviolet absorbers, various surfactants, antifoaming agents and the like.

Using the material, the heat-sensitive recording material of the present invention is prepared, for example, by the following method. That is, a color forming compound, a color developing compound, and a compound represented by the formulas (1) to (4) are separately separated from each other by a conventional method, together with a binder or other additives as necessary. After pulverizing and dispersing with a disperser such as (usually using water as a medium when pulverizing and dispersing in a wet manner), the mixture is mixed, and a maleic acid-modified propylene copolymer is added to prepare a thermosensitive coloring layer coating solution. A bar coater, a blade coater, etc., which is usually prepared on a support such as paper (plain paper, high-quality paper, coated paper, etc.), plastic sheet, synthetic paper, etc., at a normal dry weight of 1 to 20 g / m ^2. To obtain the heat-sensitive recording material of the present invention. Further, if necessary, an intermediate layer may be provided between the thermosensitive coloring layer and the support, or an overcoat layer (protective layer) may be provided on the thermosensitive coloring layer.
The intermediate layer and overcoat layer (protective layer) are pulverized and dispersed as necessary together with, for example, the adhesive as described above or other additives as necessary, as in the preparation of the coating solution for the thermosensitive coloring layer. The coating solution for the intermediate layer or the coating solution for the overcoat layer (protective layer) is applied by drying so that the weight is usually about 0.1 to 10 g / m ² and dried.

  The heat-sensitive material of the present invention, which usually further contains a colorless or light-coloring compound, a color developing compound, a maleic acid-modified propylene copolymer, and more preferably any one of the compounds represented by formulas (1) to (4). The recording material is excellent in color developability, has little background fog against dry heat and wet heat after color recording, and has excellent color image storage stability, in particular heat and heat resistance and plasticizer resistance, compared to conventionally known materials. Yes.

  The present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In the examples, “part” means part by weight, “%” in the description of the solution means “% by weight”, and the medium is water.

Example 1
(Formation of thermosensitive coloring layer)
A mixture of the following composition was pulverized and dispersed using a sand grinder so that the average particle size was 1 μm or less to prepare [A] solution, [B] solution, and [C] solution, respectively.

[A] Liquid: 25 parts of 3-dibutylamino-6-methyl-7-anilinofluorane
20 parts of 25% PVA aqueous solution
Water 55 parts [B] liquid: bis (3-allyl-4-hydroxyphenyl) sulfone 25 parts
20 parts of 25% PVA aqueous solution
Water 55 parts [C] liquid: compound represented by formula (1) (manufactured by ADEKA CORPORATION, trade name:
Adeka Arcles DH-43) 25 parts
20 parts of 25% PVA aqueous solution
55 parts of water

Subsequently, each liquid obtained above and the following chemicals are mixed at the following ratio to prepare a thermosensitive color-developing layer coating liquid, and the weight upon drying becomes 10 g / m ² on a high-quality paper having a basis weight of 50 g / m ^2. Thus, a heat-sensitive coloring layer was formed by coating and drying.
[A] Liquid 16 parts [B] Liquid 30 parts [C] Liquid 15 parts 50% calcium carbonate aqueous dispersion 16 parts 30% Maleic acid-modified propylene copolymer emulsion (trade name;
TP-007M, UMG ABS Co., Ltd.) 12 parts

(Formation of protective layer)
Next, a protective layer coating solution having the following ratio was applied on the thermosensitive coloring layer so that the weight upon drying was 2 g / m ² and dried to obtain the thermosensitive recording material of the present invention having a protective layer.
40% styrene / acrylic ester copolymer emulsion 20 parts 5% bentonite aqueous dispersion 40 parts 30% zinc stearate aqueous dispersion 3 parts

Example 2
The compound represented by formula (2) instead of the compound represented by formula (1) of the liquid [C] in Example 1 (ADEKA ARKLES DH-43) (trade name: D-90, manufactured by Nippon Soda Co., Ltd.) The heat-sensitive recording material of the present invention with a protective layer was obtained in the same manner as in Example 1 except that

Example 3
In place of the compound (Adeka Arcles DH-43) represented by the formula (1) in the liquid [C] of Example 1, the compound represented by the formula (3) (trade name: UU, manufactured by Adeka Co., Ltd.) was used. A heat-sensitive recording material of the present invention with a protective layer was obtained in the same manner as in Example 1 except that.

Example 4
In place of the compound (Adeka Arcles DH-43) represented by the formula (1) in the liquid [C] of Example 1, a compound represented by the formula (4) (manufactured by Nippon Soda Co., Ltd., trade name: NTZ-95) The heat-sensitive recording material of the present invention with a protective layer was obtained in the same manner as in Example 1 except that

Example 5
Instead of the 30% maleic acid-modified propylene copolymer emulsion of Example 1 (trade name: TP-007M, manufactured by UMG ABS), 30% maleic acid-modified propylene copolymer emulsion (trade name: TP-001M, A thermosensitive recording material of the present invention with a protective layer was obtained in the same manner as in Example 1 except that UMG ABS Co., Ltd. was used.

Comparative Example 1
A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that the [C] solution of Example 1 was not used.

Comparative Example 2
A comparative heat-sensitive recording material was obtained in the same manner as in Example 1 except that a 50% carboxylated SB copolymer emulsion was used in place of the 30% maleic acid-modified propylene copolymer emulsion of Example 1.

  Tables 1 and 2 show quality performance tables of the heat-sensitive recording material of the present invention obtained as described above.

Table 1
Quality performance test
Background 1) Color density 2) Heat resistance 3) Moist heat resistance 4)
Example 1 0.04 1.38 0.04 / 1.37 0.05 / 1.37
Example 2 0.04 1.35 0.04 / 1.35 0.05 / 1.34
Example 3 0.04 1.36 0.04 / 1.34 0.05 / 1.33
Example 4 0.04 1.36 0.04 / 1.35 0.05 / 1.34
Example 5 0.04 1.35 0.04 / 1.34 0.05 / 1.35
Comparative Example 1 0.04 1.40 0.05 / 1.39 0.05 / 1.37
Comparative Example 2 0.04 1.39 0.04 / 1.28 0.05 / 0.88

Table 2
Quality performance test
Plasticizer resistance 5) Plasticizer resistance 6)
Example 1 0.04 / 1.38 1.27
Example 2 0.04 / 1.35 1.30
Example 3 0.04 / 1.34 1.33
Example 4 0.04 / 1.35 1.32
Example 5 0.04 / 1.35 1.21
Comparative Example 1 0.05 / 1.30 0.78
Comparative Example 2 0.04 / 1.28 1.05

1) Background: A value (Macbeth reflection density) obtained by printing with a commercially available thermal printer (Ishida L-2000) and measuring an uncolored portion of the sample with a Macbeth reflection densitometer (RD-914 type, manufactured by Macbeth).
2) Color density: Macbeth reflection density of the image portion of the sample developed with the printer.
3) Heat resistance: Macbeth reflection density of the uncolored portion and the image portion after the sample developed with the printer was left in a thermostat at 60 ° C. for 24 hours.
4) Moisture and heat resistance: Macbeth reflection density of the uncolored portion and the image portion after the sample developed with the printer was left in a humidity chamber at 40 ° C. and 90% relative humidity for 24 hours.
5) Plasticizer resistance: A PVC wrap film was applied to both sides of the sample developed with the above-mentioned printer, and a non-colored portion and an image portion after 24 hours at 40 ° C. under a load of 0.098 MPa (300 g / cm ² ) Macbeth reflection density.
6) Plasticizer resistance: Water was dropped on the sample developed with the above printer and a nylon film (commercially available) was placed on the surface, and a load of 0.0294 MPa (300 gf / cm ² ) was applied at 40 ° C. for 48 hours. Macbeth reflection density of the image part.
The Macbeth reflection density indicates that the larger the numerical value, the higher the coloring density. Therefore, it is preferable that the image portion has a large value.

As is apparent from Tables 1 and 2, the heat-sensitive recording material of the present invention is excellent in color developability, has little color development on the background due to heat and wet heat, and is excellent in storage stability of color images, particularly in resistance to moist heat and plasticizers. Give the results.
Specifically, in the Macbeth reflection density of the image portion of the heat and moisture resistance 4), Examples 1 to 5 of the present invention are 1.33 to 1.37, whereas Comparative Example 2 is 0.88. A clear fading was observed in the recorded image of Comparative Example 2.
Further, in the Macbeth reflection density of the image portion of the plasticizer resistance 6), Examples 1 to 5 of the present invention are 1.21 to 1.33, whereas Comparative Examples 1 and 2 are 0.78 respectively. And 1.05, and clear fading was observed in the recorded images of the comparative examples.
As described above, maleic acid-modified propylene copolymer is usually used as a heat-sensitive color developing layer as a color developing compound, a color developing compound and a color developing compound as an adhesive, and bis (3-allyl as a color developing compound. The thermal recording material of the present invention containing -4-hydroxyphenyl) sulfone and any one of the compounds represented by the above formulas (1) to (4) is a compound represented by the formulas (1) to (4). Compared to Comparative Example 1 that does not contain any of the above and Comparative Example 2 that does not contain maleic acid-modified propylene copolymer as an adhesive, it showed clear storage stability of recorded images in wet heat resistance and plasticizer resistance. .

Claims (2)

In a heat-sensitive recording material provided with a heat-sensitive color-developing layer containing a normally colorless or light-color-colorable compound and a color developing compound capable of developing the color-forming compound when heated, the heat-sensitive color developing layer is an adhesive. And a maleic acid-modified propylene copolymer. As a color developing compound capable of developing a color developing compound when heated, bis (3-allyl-4-hydroxyphenyl) sulfone, the following formula (1),

(In formula (1), R ¹ represents an alkyl group or cyclohexyl group having 4 or less carbon atoms, and R ² represents an alkyl group having 4 or less carbon atoms).
Following formula (2),

Following formula (3),

Or the following formula (4),

The heat-sensitive recording material according to claim 1, which is used in combination with any of the compounds represented by: