JPH06135157A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material reduced in background fog due to the effect of temp. or humidity, forming a recording image having preservability against chemicals such as oils and fats, a solvent or a plasticizer and having excellent recording sensitivity. CONSTITUTION:In a thermal recording material wherein a recording layer containing a colorless or light-colored basic dye and a coupler is provided on a support, as the coupler, a zinc salt of 4-[3-(p-tolylsulfonyl)propyloxy]salicylic acid and 2,4'-dihydroxydiphenylsulfone are together 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 to a heat-sensitive recording material excellent in storage stability and recording sensitivity of recorded images.

[0002]

2. Description of the Related Art Heretofore, a heat-sensitive recording material has been well known which uses a heat energy of a heat-sensitive head or the like to develop a colorless or light-colored basic dye and a color developer. Since such a thermal recording material is relatively inexpensive and the recording equipment is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields such as thermal labels. .

In recent years, recording speeds of 10 seconds or less in A4 size for thermal fax and 120 characters / second or more for thermal printer have become possible, and there is a further demand for higher sensitivity of the thermal recording material. In addition, the use of heat-sensitive recording labels is increasing with the expansion of POS systems aimed at labor saving in the retail industry. However, since an ordinary thermosensitive recording material uses a phenol-based developer such as bisphenol A, it has a drawback that fogging occurs due to a solvent or the like, and the coloring material causes discoloration due to oils or chemicals. is doing. Therefore, for example, when touching stationery and office supplies such as water-based pens, oil-based pens, highlighters, vermilion, adhesives, glues, diazo developers, etc. or cosmetics such as hand creams, emulsions, etc. The image density was significantly reduced or discolored, which significantly impaired the commercial value. For the purpose of improving such defects, various proposals have been made such as a method of providing a protective layer on the recording layer and a method of adding a storage stability improver to the recording layer, but all of them have new defects. However, since it is not always possible to obtain a sufficiently satisfactory effect, further improvement is strongly demanded.

[0004]

DISCLOSURE OF THE INVENTION The object of the present invention is to obtain a heat-sensitive material which has less background fog due to the influence of temperature and humidity and which is excellent in the storability of a recorded image with respect to chemicals such as oils and fats, solvents or plasticizers, and recording sensitivity. To provide a recording body.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have found that a thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a developer is used as a developer.
The inventors have found that the above object can be achieved by using a zinc salt of [3- (p-tolylsulfonyl) propyloxy] salicylic acid in combination with 2,4′-dihydroxydiphenyl sulfone, and completed the present invention.

A thermosensitive recording medium using a zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid as a color developer has less background fog and is excellent in preservability of a recorded image with a plasticizer. Although it exhibits the characteristics, it has a drawback that the recording sensitivity is low and the recorded image is not easily faded by hand cream.

Therefore, in order to increase the recording sensitivity of a thermosensitive recording medium using a zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, a combination with various phenol derivatives was examined. However, there is a new defect that the background fogging is likely to occur. But,
4- [3- (p-tolylsulfonyl) propyloxy]
A heat-sensitive recording material in which a zinc salt of salicylic acid and 2,4'-dihydroxydiphenyl sulfone are used together as a developer has an effect of improving recording sensitivity without reducing whiteness.

When 2,4'-dihydroxydiphenyl sulfone is used alone as a color developer, the recording density is high, the fog on the background is not caused by an oil-based pen, and the recorded image does not easily fade even with a hand cream or the like. Although the storage stability of the recorded image is good, the recording sensitivity is low because the melting point is as high as 183 ° C. Therefore, when printing at low energy with a thermal printer, sufficient recording density cannot be obtained.

In the present invention, the ratio of the zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid to 2,4'-dihydroxydiphenylsulfone is not particularly limited, but 4- [3 -(P-
It is desirable to adjust 2,4'-dihydroxydiphenyl sulfone within a range of 5 to 500 parts by weight based on 100 parts by weight of zinc salt of tolylsulfonyl) propyloxy] salicylic acid.

The zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid is, for example,
In water or a mixed medium of water and an organic solvent, 4- [3-
A method of reacting an alkali metal salt of (p-tolylsulfonyl) propyloxy] salicylic acid with a zinc compound,
4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid and a zinc compound can be produced by a method such as wet simultaneous pulverization.

The above method has some drawbacks in operability at the time of production, but is advantageous in terms of zinc chloride yield and purity. On the other hand, the above-mentioned method has some drawbacks in terms of the yield and purity of zinc chloride, but has an advantage that a composite zinc salt can be produced very easily.

The organic solvent used in the above method is preferably one having a low solubility in water and a high solubility of the zinc salt of the aromatic carboxylic acid produced, such as aromatic compounds, halides and esters. A compound etc. are mentioned. More specifically, toluene, xylene, trichlene, ethyl acetate and the like can be exemplified. Further, as the zinc compound in preparing the zinc salt, zinc oxide, zinc hydroxide, zinc carbonate, zinc sulfate, zinc chloride and the like can be used, but zinc sulfate and zinc chloride are particularly preferable in the above method. Zinc oxide is particularly preferably used in the above method. The amount of the zinc compound used is not particularly limited, but it is desirable to use it so that it is equivalent to 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid.

In the present invention, the salicylic acid-based developer can sufficiently exhibit the desired effect if the zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid is the main component. is there.

In the heat-sensitive recording material of the present invention, various known compounds can be used as the colorless or light-colored basic dye to be contained in the heat-sensitive recording layer.
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane,
3- (N-ethyl-Np-tolyl) amino-7-N-
Methylanilinofluorane, 3-diethylamino-7-
Anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6- Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-
N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7 -Anilino Fluoran, 3
-Di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(O-chlorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n- Butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p)
-Toluidino) -6-methyl-7- (p-toluidino)
Fluorane, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3
-(N-methyl-Nn-propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4
-Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1 -(4-Pyrrolidinophenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3,3-Bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-6 -Methyl-7-chlorofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] ] Phenyl} propane,
3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

In the heat-sensitive recording material of the present invention, the ratio of the basic dye and the developer to be contained in the recording layer is such that the basic dye and the developer to be used are 4- [3-
(P-Tolylsulfonyl) propyloxy] salicylic acid zinc salt and 2,4'-dihydroxydiphenyl sulfone should be appropriately selected according to the ratio and are not particularly limited, but generally 1 part by weight of the basic dye. It is desirable to use 0.5 to 50 parts by weight, and preferably 1 to 10 parts by weight of the developer.

In the present invention, 4- [3- (p-
It is characterized by using a zinc salt of tolylsulfonyl) propyloxy] salicylic acid and 2,4'-dihydroxydiphenyl sulfone, but within the range that does not impair the effects of the present invention, for example, the following known developers It is also possible to use together. Activated clay, attapulgite, colloidal silica, inorganic acid substances such as aluminum silicate, 4,4'-dihydroxydiphenyl sulfone, 4
-Cumylphenol, hydroquinone monobenzyl ether, 4,4'-isopropylidenediphenol, 1,1
-Bis (4-hydroxyphenyl) cyclohexane,
4,4'-dihydroxydiphenyl-2,2-butane,
4,4'-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane,
2,2-bis (4-hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy) methane,
1,5-di (4-hydroxyphenylthio) -3-oxapentane, 1,1-bis (4-hydroxyphenyl)
-1-phenylethane, 1,4-bis [α-methyl-α
-(4'-hydroxyphenyl) ethyl] benzene,
1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenyl sulfide, di (4-hydroxy-3-methylphenyl) sulfine, 4-hydroxy-4 '-Methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 4-hydroxy-3'. , 4'-tetramethylene biphenyl sulfone, 3,4-dihydroxyphenyl-p-tolyl sulfone, benzyl 4-hydroxybenzoate, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, (4 -Hydroxyphenylthio)
Acetic acid-2- (4-hydroxyphenylthio) ethyl ester, di (p-hydroxyphenylthioethyl) ether, N, N'-di-m-chlorophenylthiourea, N-
Phenolic compounds such as (phenoxyethyl) -4-hydroxyphenylsulfonamide, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 5-
[P- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, aromatic carboxylic acids such as p-chlorobenzoic acid, and zinc, magnesium, aluminum, calcium, titanium, manganese of these aromatic carboxylic acids,
Examples thereof include salts with polyvalent metals such as tin and nickel, and organic acid substances such as antipyrine complex of zinc thiocyanate.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the recording layer according to the purpose. Specific examples of the sensitizer include stearic acid amide and methoxycarbonyl-.
N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide,
Dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, oxalate-di-p-methylbenzyl,
Oxalic acid-di-p-chlorobenzyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy). ) Ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane,
1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-
Methylthiophenyl benzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxy) Examples include ethoxy) benzene and 1-isopropylphenyl-2-phenylethane. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, in order to suppress the background fog caused by heat, tetrakis (1,2,2,6,6-pentamethyl-4)
It is desirable to use a hindered amine stabilizer such as -piperidinyl) -1,2,3,4-butanetetracarboxylate together. Further, a preservative improving agent may be used in combination for the purpose of further enhancing preservability of a recorded image as long as the effect is not impaired. Specific examples of such storage improvers include 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4 '-(2-methyl-2,3).
-Epoxypropyloxy) diphenyl sulfone, digylcidyl terephthalate, epoxy compounds such as bisphenol A type epoxy resin, 2,2'-methylenebis (4-
Methyl-6-tert-butylphenol), 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-)
tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol),
4,4'-thiobis (2-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert
-Butyl-m-cresol), 1,1,3-tris (2
-Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,
4'-thiobis (3-methylphenol), 4,4'-
Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',
5,5'-tetramethyldiphenyl sulfone, 2,2-
Bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) Hindered phenol compounds such as propane, 1- [α-methyl-α- (4′-
Hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene,
N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate, etc. may be mentioned.

In order to prepare a coating liquid for a recording layer containing these substances, water is generally used as a dispersion medium, and a basic dye, a color developer, and further a basic dye, a color developer, and the like are required by a stirring and crushing machine such as a ball mill, attritor, or sand mill. A sensitizer or the like added according to the above is dispersed together or separately to prepare a coating liquid.
In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, arabic gum, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer are used as adhesives. A polymer salt, an ethylene / acrylic acid copolymer salt, a styrene / acrylic acid copolymer salt, a styrene / butadiene copolymer emulsion or the like is used in an amount of 10 to 40% by weight, preferably about 15 to 30% by weight of the total solid content. To be

It is also possible to use various pigments together in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Further, various auxiliary agents can be added to the coating liquid, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. Dispersant, benzophenone type,
Examples thereof include UV absorbers such as triazole type, defoaming agents, fluorescent dyes, and coloring dyes.

In the present invention, the method for forming the heat-sensitive recording layer is not particularly limited, and the heat-sensitive recording layer can be formed according to a conventionally well-known technique, for example, air knife coating, varibar blade coating, pure blade coating. It can be formed by a method of coating and drying the coating liquid on the support by short dwell coating, curtain coating or the like. The coating amount of the coating liquid is also not particularly limited, and is usually ² to 12 g / m ² in dry weight, preferably 3 to 10 g.
The range is / m ² . As the support, paper, synthetic paper, plastic film or the like is appropriately selected and used.

In the present invention, it is possible to further improve the storability of a recorded image by providing a resin layer on the heat-sensitive recording material and / or on the back surface side, if necessary.
Further, in the field of heat-sensitive recording material manufacturing, such as providing an undercoat layer on the support to improve image quality and sensitivity, processing the back surface of the recording material into an adhesive label by processing with an adhesive, and providing a magnetic layer on the back surface of the recording material. Various known techniques can be added. Further, the image quality and the image density can be improved by performing a super calendering process after forming the recording layer.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 [Preparation of solution A] A composition comprising 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water. Was pulverized with a sand mill until the average particle diameter became 1.5 μm. [Preparation of solution B] A composition consisting of 30 parts of 2,4'-dihydroxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was pulverized by a sand mill until the average particle diameter became 1.5 µm. [Preparation of Solution C] A composition consisting of 30 parts of a zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water having an average particle diameter of 1 using a sand mill. It was pulverized to a size of 0.5 μm. [Preparation of liquid D] A composition consisting of 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized by a sand mill until the average particle diameter became 1.5 μm. did. [Formation of recording layer] A liquid 55 parts, B liquid 40 parts, C liquid 75
Part, D solution 80 parts, 10% polyvinyl alcohol aqueous solution 1
60 parts, and the recording layer coating solution obtained by mixing and stirring 25 parts of calcium carbonate, the coating amount after drying on one surface of woodfree paper of 45 g / m ² is then applied and dried so as to 4g / m ² A recording layer was formed.

Example 2 In preparation of solution A, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluorane, 3
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of-(N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane was used.

Example 3 Preparation of Solution E Tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) -1,2,3,4-butanetetracarboxylate 10 parts, 5% of methylcellulose A composition consisting of 5 parts of an aqueous solution and 40 parts of water was pulverized with a sand mill until the average particle size became 1.5 μm. [Formation of recording layer] A liquid 55 parts, B liquid 40 parts, C liquid 75
Part, liquid D 80 parts, liquid E 55 parts, 10% polyvinyl alcohol aqueous solution 160 parts, and calcium carbonate 25 parts by mixing, and a recording layer coating solution is dried on one side of a fine paper of 45 g / m ^2. A recording layer was formed by coating and drying so that the subsequent coating amount was 4 g / m ² .

Example 4 [Preparation of solution F] 10 parts of 4-benzyloxy-4 '-(2-methyl-2,3-epoxypropyloxy) diphenylsulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water. The composition was pulverized with a sand mill until the average particle size became 1.5 μm. [Formation of recording layer] A liquid 55 parts, B liquid 40 parts, C liquid 75
Part, liquid D 80 parts, liquid F 55 parts, 10% polyvinyl alcohol aqueous solution 160 parts, and calcium carbonate 25 parts by mixing, and a recording layer coating solution is dried on one side of a fine paper of 45 g / m ^2. A recording layer was formed by coating and drying so that the subsequent coating amount was 4 g / m ² .

Example 5 [Formation of recording layer] A liquid 55 parts, B liquid 25 parts, C liquid 90
Part, liquid D 80 parts, liquid E 55 parts, 10% polyvinyl alcohol aqueous solution 160 parts, and calcium carbonate 25 parts by mixing, and a recording layer coating solution is dried on one side of a fine paper of 45 g / m ^2. A recording layer was formed by coating and drying so that the subsequent coating amount was 4 g / m ² .

Example 6 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 2-naphthylbenzyl ether 20 was used in place of 20 parts of 1,2-di (3-methylphenoxy) ethane in the preparation of solution D. Got

Example 7 [Preparation of liquid G] Calcined clay [Product name: Ansilex, E
Manufactured by MC, oil absorption: 110 ml / 100 g] 100 parts,
A composition consisting of 100 parts of a 10% aqueous solution of polyvinyl alcohol and 200 parts of water was mixed and stirred to obtain a coating liquid for the undercoat layer. [Preparation of thermal recording material] On one side of a high-quality paper of 45 g / m ² ,
The solution G was applied and dried so that the applied amount after drying was 8 g / m ^2, and the coating material for recording layer prepared in the same manner as in Example 1 was applied so that the applied amount after drying was 4 g / m ^2. After drying, a super calender treatment was performed to obtain a heat sensitive recording material.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40 parts of C liquid was used instead of 40 parts of B liquid in the formation of the recording layer of Example 1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 75 parts of solution B was used instead of 75 parts of solution C in the formation of the recording layer of Example 1.

Comparative Example 3 In the same manner as in Example 1 except that 30 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone was used in place of 30 parts of 2,4'-dihydroxydiphenyl sulfone in the preparation of the liquid B. A thermosensitive recording medium was obtained.

Comparative Example 4 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 30 parts of 4,4'-dihydroxydiphenylsulfone was used in place of 30 parts of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. Got

Comparative Example 5 In the preparation of solution C, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid was added instead of 30 parts of zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 30 parts of zinc salt was used.

Comparative Example 6 In the preparation of solution C, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl was used instead of 30 parts of zinc salt of 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 30 parts of zinc salicylate was used.

The 13 types of heat-sensitive recording materials thus obtained were subjected to the following evaluation tests, and the results are shown in [Table 1]. [Whiteness] In order to evaluate the degree of color fog, the whiteness of the recording layer was measured with a Hunter whiteness meter. [Color density] Thermal recording material evaluation machine [Product name: TH-PM
D, manufactured by Okura Electric Co., Ltd.], each of the thermosensitive recording media was colored with an applied voltage of 24 V and a pulse time of 2 ms, and the color density of the obtained recorded image was measured with a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.]. Measured in visual mode. [Oil resistance] Edible oil was dropped on the heat-sensitive recording material on which the color was printed, and the state of the printing was visually evaluated after standing for 24 hours. [Solvent resistance] A yellow oil-based magic ink was used to write on a heat-sensitive recording material on which printing was performed, and the state of subsequent printing was visually evaluated. [Hand cream resistance] A hand cream was applied on the heat-sensitive recording material on which the print color was formed, and the state of the print after that was visually evaluated. [Plasticizer resistance] 3 vinyl chloride wrap film (Mitsui Toatsu Chemicals, Inc.) on polypropylene pipe (40 mmφ pipe)
Double wrap, sandwich the heat-sensitive recording material with the printed color on it so that the printed surface is on the outside, and wrap the vinyl chloride wrap film in three layers on top of it and wrap it at 30 ° C for 24 hours.
The plasticizer resistance was evaluated from the print density after leaving for a period of time. [Heat resistance] As a background fogging acceleration test, a heat-sensitive recording material before printing was treated under a drying condition of 60 ° C. for 24 hours,
The degree of fogging was visually evaluated. [Moisture resistance] The thermal recording material before printing was treated for 24 hours under the conditions of 50 ° C. and 75% RH, and then the degree of fogging was visually evaluated. [Evaluation criteria] Oil resistance, solvent resistance, hand cream resistance,
The evaluation criteria for plasticizer resistance, heat resistance and moisture resistance were as follows. ◎ −−−−− ○ −−−−− △ −−−−− × Excellent Excellent Inferior

[0038]

[Table 1]

[0039]

As is clear from the results shown in Table 1, the heat-sensitive recording materials of the present invention are excellent in storage stability of recorded images, particularly oil resistance, plasticizer resistance and solvent resistance, and have recording sensitivity. It was also an excellent thermal recording material.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a developer, wherein 4- [3- (p-tolylsulfonyl) is used as the developer.
A heat-sensitive recording material comprising a combination of a zinc salt of propyloxy] salicylic acid and 2,4'-dihydroxydiphenyl sulfone.