JPS6374684A - Thermal recording body - Google Patents

Abstract

PURPOSE:To prevent the occurrence of fog and enhance resistance to plasticizer, oil, and water, by a method wherein a specific compound is used as a color developer and at least one of specific two sorts of phenol compounds is contained in a recording layer. CONSTITUTION:A recording layer containing a colorless or light-colored basic dye and a color developer which makes the basic dye develop a color under heat is provided. A compound shown by a formula (I) is used as the color developer, and at least one of phenol compounds shown by formulas (II) and (III) are contained in the recording layer. In the formula (I), R1-R5 represent hydrogen atom, halogen atom, C1-10 alkyl group, C1-10 alkoxyl group, benzyloxy group, aryloxy group, or hydroxyl group. In the formula (II), R6, R7, and R8 represent hydrogen atom, C1-8 alkyl group, or C5-8 cycloalkyl group, and R9, R10, R11, R12, and R13 represent hydrogen atom or C1-8 alkyl group. In the formula (III), R14, R15, and R16 represent hydrogen atom or C1-8 alkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and more particularly to a heat-sensitive recording medium with excellent storage stability of recorded images.

``Prior art'' Thermal recording materials that utilize a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to obtain a recorded image by bringing a recoloring substance into contact with heat are well known. Are known.

Such heat-sensitive recording media are relatively inexpensive, and the recording devices are compact and relatively easy to maintain, so they are used not only as recording media for facsimiles and various computers, but also in a wide range of fields.

For example, one of the fields of use is POS at retail stores, etc.
(Point of 5ales) With the expansion of systemization, the number of cases in which they are used as labels is increasing.

However, when a PoS system is introduced in a supermarket or the like, the labels often come into contact with water, plastic wrap, and oil, and as a result, the recorded image (print) on the heat-sensitive label becomes defective in color fading.

Therefore, thermal recording materials are required to have qualities such as water resistance, plasticizer resistance, and oil resistance.

``Problems to be Solved by the Invention'' In order to improve the storage stability of recorded images, methods of adding various storage improvers have been proposed, but with the improvement, the whiteness of the recording layer decreases. However, new drawbacks such as the occurrence of fogging at high temperatures have not necessarily been achieved, and therefore satisfactory results have not always been obtained.

In view of the current situation, the present inventors conducted intensive research not only on storage improvers to be contained in the recording layer but also on coloring agents.
) When used in combination, the water stability and moisture resistance of recorded images are significantly improved, color fogging does not occur, and excellent effects are obtained in terms of plasticizer resistance, oil resistance, etc. The present invention was completed based on the discovery that the present invention is possible.

"Means for Solving the Problem" The present invention provides a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent that causes the basic dye to develop color when heated. A compound represented by the following general formula [I] is used as a compound represented by the following general formula [I], and the following general formula (I) is used in the recording layer.
II) and (I) [wherein R0 to R3 are each a hydrogen atom,
It represents a halogen atom, a C+-tO alkyl group, a C1-1o alkoxyl group, a benzyloxy group, an aryloxy group, or a hydroxyl group. Note that R8 and R2 or R2 and R3 may be bonded to each other to form a ring. ] [In the formula R,,R
7 and R each represent a hydrogen atom, a C8-8 alkyl group, or a C6-8 cycloalkyl group. However, Rh,
At least one of R7 and Rs is 03~.

represents a branched alkyl group or a C2-8 cycloalkyl group. R,,R,. RI I Rl□R13 is
Each represents a hydrogen atom or an alkyl group of 01-8. ] [In the formula, RI4R15RI6 is a hydrogen atom or C
Indicates 3 to 8 alkyl groups. [Function] In the present invention, examples of the basic dye contained in the recording layer include various known colorless or light-colored basic dyes. For example, 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3 -(p-dimethylaminophenyl) -3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindole-
3-yl)-5-dimethylaminophthalide, 3.3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3゜3-bis(9-ethylcarbazol-3- yl)-6-dimethylaminophthalide,
3,3-bis(2-phenylindol-3-yl)-
6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6
- triallylmethane dyes such as dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine,
Diphenylmethane dyes such as N-2,4,5-trichlorophenylleucoauramine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran , 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzobilane, etc., rhodamine-B ani Lactam dyes such as linolactam, rhodamine (p-nitroanilino)lactam, rhodamine (O-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7 -Methoxyfluorane, 3-
Diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-
Diethylamino-6゜7-dimethylfluorane, 3-(
N-ethyl-p-toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamine-7 -Sibenzylaminofluorane, 3-diethylamino-7=N-
Methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl-p-toluidino)- 6
-Methyl-7-phenylaminofluorane, 3-(N-
Ethyl-p-)luidino)-6-methyl-7-(p-)
Luidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 3-(N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-
Pyrrolidino-6-methyl-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(0-
chlorophenylamino)fluoran, 3-dibutylamino-7-(O-chlorophenylamino)fluoran, 3
-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-diethylamino-7-(O-fluorophenylamino)fluoran, 3-dibutylamino-7-(o-fluorophenylamino)fluoran, 3
-(N-methyl-N-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-iso-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N- Methyl-N-n-hexyl)amino-6
-Methyl-7-phenylaminofluorane, 3-(N-
Ethyl-Nn-hexyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-N-β
Examples include fluoran dyes such as -ethylhexyl)amino-6-methyl-7-phenylaminofluoran. In addition, two or more types of these basic dyes can be used in combination as necessary.

As mentioned above, in the heat-sensitive recording material of the present invention, a specific 4-hydroxydiphenylsulfone compound represented by the general formula [I] is used as a coloring agent that develops color when it comes into contact with such a dye. be.

Specific examples of the coloring agent represented by general formula [1] include 4,4'-dihydroxydiphenylsulfone, 3.3
'-Dibrobenyl-4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, 4-hydroxy- 4-hydroxydiphenylsulfone derivatives such as 4'-butoxydiphenylsulfone, 3,4-dihydroxy-4'-ethyldiphenylsulfone, 3,4-dihydroxy-4'-phenoxydiphenylsulfone and 3';

4'-trimethylene-4-hydroxydiphenylsulfone, 3',4'-trimethylene-2,6-cymethyl-4
-Hydroxydiphenylsulfone, 3',4'-tetramethylene-4-hydroxydiphenylsulfone, 3',
Examples include 4-hydroxydiphenylsulfone derivatives having rings at the 3' and 4' positions, such as 4'-tetramethylene-2-methyl-4-hydroxydiphenylsulfone.

In addition, it is also possible to use ordinary coloring agents in addition to the above-mentioned specific coloring agents within a range that does not impede the effects of the present invention, such as activated clay, acpargite, colloidal silica, aluminum silicate, etc. inorganic acidic substance, 4-ter
t-Butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2.2'-dihydroxydiphenol, 4.4'-isopropylidene bis(2 -tert-butylphenol), 4,4'-5ec-butylidene diphenol,
4-phenylphenol, 4.4'-isopropylidene diphenol, 2.2'-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexylidene diphenol, 4.4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether,
4-Hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2.4.4'-)dihydroxybenzophenone, 2.2',4.4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate , propyl 4-hydroxybenzoate, 5ec-butyl 4-hydroxybenzoate, 4-
Pentyl hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate,
Phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, p-methoxybenzyl 4-hydroxybenzoate, nopolafuku type phenolic resin, phenolic compounds such as phenol polymers, benzoic acid, p-tert- Butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-5ec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid,
3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3,5
-tart-butylsalicylic acid, 3-phenyl-5
-(α,α-dimethylbenzyl)salicylic acid, 3.5-
Aromatic carboxylic acids such as di-α-methylbenzyl salicylic acid, phenolic compounds thereof, salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Examples include organic acidic substances.

In the present invention, the usage ratio of the basic dye and coloring agent is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but in general, 1 weight of the basic dye 1 to 50 parts by weight, preferably 2 to 50 parts by weight
About 10 parts by weight of coloring agent is used.

Therefore, in the heat-sensitive recording material of the present invention, the general formulas [II] and [III] are combined with the specific coloring agent as described above.
At least one specific phenol compound represented by formula (II) is contained in the recording layer. Specific examples of the phenol compound represented by the general formula (II) include l, 1°3-tris, (2-methyl-4-
hydroxy-5-tert-butylphenyl)butane,
1,1,3-tris(2-ethyl-4-hydroxy-5
-tert-butylphenyl)butane, 1,1.3-)
Lis(2-methyl-4-hydroxy-5-tert-butylphenyl)propane, 1,1.3-)lis(3゜5
-tert-butyl-4-hydroxyphenyl)
Butane, 1,1.3-)lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1.
3-tris(2-ethyl-4-hydroxy-5-cyclohexylphenyl)butane, 1.1.3-)lis(2-
Methyl-4-hydroxy-5-cyclohexylphenyl)propane, 1゜1.3-tris(2-methyl-4-hydroxy-5-cyclopentylphenyl)butane, 1,
1゜3-tris(2-ethyl-4-hydroxy-5-cyclopentylphenyl)butane, 1,1,3-tris(
Examples include 2-methyl-4-hydroxy-5-cyclopentylphenyl)propane.

Specific examples of the phenol compound represented by the general formula (III) include bis(3-tert-butyl-4-hydroxy-6-methylphenyl) sulfide,
Bis(4-hydroxy-3,5-dimethylphenyl) sulfide, bis(3-methyl-4-hydroxyphenyl) sulfide, bis(3-tert-butyl-4-hydroxy-5-methylphenyl) sulfide, bis(3-tert-butyl-4-hydroxy-5-methylphenyl) sulfide, −
methyl-4-hydroxy-6-ituprobylphenyl)
Examples thereof include sulfide, bis(3-isopropyl-4-hydroxy-6-methylphenyl) sulfide, and bis(4-hydroxy-3,6-dimethylphenyl) sulfide.

The amount of the phenol compound represented by these general formulas (n) and (II[) depends on the amount of the phenol compound used,
The amount may be adjusted as appropriate depending on the type of basic dye and coloring agent, but it is generally desirable to use about 0.05 to 5 parts by weight per 1 part by weight of the dye.

Coating liquids containing these substances are generally prepared using water as a dispersion medium. The phenolic compounds represented by the general formulas (II) and (I[) may be added to the coating liquid as an aqueous dispersion, or may be added and dispersed in the process of dispersing the dye or coloring agent. good.

Coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene, etc. as binders. Maleic anhydride copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion,
Urea resin, melamine resin, amide resin, etc. account for 1% of the total solid content.
It is used in an amount of 0 to 701i, preferably about 15 to 50% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid as necessary, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate ester, IJium salt, fatty acid metal. Dispersants such as salts, ultraviolet absorbers such as benzophenone, other foaming agents, fluorescent dyes, coloring dyes, etc. are added as appropriate.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc, calcium carbonate, calcined gel,
Inorganic pigments such as titanium oxide, diatomaceous earth, particulate anhydrous silica, and activated clay may also be added.

Furthermore, a sensitizer can also be used in combination depending on the purpose. Specific examples of sensitizers include stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, fatty acid amides such as coconut fatty acid amide, and 2,2'-methylenebis(4-methyl-6-tert).
-butylphenol), 4,4'-butylidene bis(6
-tert-butyl-3-methylphenol), 2.2
Hindered phenols such as '-methylenebis(4-ethyl-5-tert-butylphenol), 2,4-di-tert-butyl-3-methylphenol! , 2-(2
UV absorbers such as '-hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, 1,2-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 1 -Phenoxy-2-(4-methylphenoxy)ethane, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, and various known thermofusible substances etc.

The amount of sensitizer used is not particularly limited, but generally color former 1
It is desirable to adjust the amount within a range of about 4 parts by weight or less.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and may be formed, for example, by a method of applying and drying a coating liquid by air knife coating, blade coating, or the like. Further, the amount of the coating liquid to be applied is not particularly limited, and is usually prepared in a dry weight range of 2 to 12 g/m, preferably 3 to 10 g/rd.

Since the heat-sensitive recording material of the present invention contains a combination of the above-mentioned specific coloring agent and a phenol compound in the recording layer, it has excellent recorded image preservation properties such as water resistance, moisture resistance, plasticizer resistance, and oil resistance. However, in order to further enhance these characteristics, an overcoat layer mainly composed of a water-soluble polymer compound or the like may be provided on the recording layer.

Examples of water-soluble polymer compounds used in the overcoat layer include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein, sodium alginate, Examples include polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane resin, urea resin, melamine resin, polyamide resin, epichlorohydrinated polyamide resin, and the like. Of course, two or more of these polymer compounds may be used in combination.

Note that among these water-soluble polymer compounds, acetoacetyl group-modified polyvinyl alcohol is particularly preferably used because it exhibits excellent effects when combined with the specific substance of the present invention.

Pigments can be added to the overcoat layer as necessary to improve printability and sticking. Specific examples of pigments include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc,
Examples include inorganic pigments such as kaolin, clay, calcined resin, and colloidal silica, and organic pigments such as styrene microballs, nylon paratar, polyethylene powder, urea/formalin resin filler, and raw starch granules.

The amount used is generally 5 to 100 parts by weight of the resin component.
It is desirable to adjust the amount within a range of about 500 parts by weight.

Furthermore, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants such as sodium dioctyl sulfosuccinate may be added to coating liquids containing water-soluble polymer compounds as the main component. Various auxiliary agents such as agents (dispersants, lubricants) and antifoaming agents can also be added as appropriate.

In addition, to further improve water resistance, glyoxal,
Hardening agents such as boric acid, dialdehyde starch, and epoxy compounds can also be added.

In the present invention, the coating liquid forming the overcoat layer is
Generally, it is prepared as an aqueous coating solution, and after being thoroughly mixed and dispersed using a mixer, attritor, ball mill, roll mill, or other mixing/stirring machine as required, it is coated onto the heat-sensitive recording layer using a suitable coating device. The coating amount is not particularly limited, but if the dry weight exceeds 20g1rd, the recording sensitivity of the heat-sensitive recording medium may decrease significantly, so it is generally 0.1 to 20 g/m, preferably 0.5 to Log/m.
It is desirable to adjust within a range of approximately rd.

Thus, the heat-sensitive recording material of the present invention having an overcoat layer provided on the recording layer does not cause color fog and exhibits extremely excellent recorded image retention even under severe conditions.

Note that, if necessary, it is also possible to further improve the storage stability by providing a protective layer on the back side of the heat-sensitive recording material. Furthermore, various known techniques in the field of heat-sensitive recording material production may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

As the support, paper, plastic film, synthetic paper, etc. can be used, but paper is most preferably used in terms of cost, coatability, etc.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 ■ Preparation of liquid A 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of B solution 4-hydroxy-4'-methyldiphenylsulfone
20 parts methylcellulose
5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of liquid C 1.1.3-) Lis(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane 10 parts Bis(3tert-butyl-4-hydroxy-6=methylphenyl) sulfide 10 parts Methylcellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

(2) Formation of Recording Layer 55 parts of liquid A, 80 parts of liquid B, 55 parts of liquid C, 50 parts of a 15% aqueous polyvinyl alcohol solution, and 10 parts of calcium carbonate were mixed and stirred to prepare a coating liquid. The obtained coating liquid was 50g/n? A heat-sensitive recording material was obtained by coating and drying the mixture on base paper so that the coating amount after drying was 6 g/m.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1, except that 4-hydroxy-4'-isopropyloxydiphenylsulfone was used instead of 4-hydroxy-4'-methyldiphenylsulfone in the preparation of liquid B. Ta.

Example 3 In preparing liquid C, 1,1,3-tris(2-methyl-
Same as Example 1 except that 1.1.3-)lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of 4-hydroxy-5-tert-butylphenyl)butane. A thermosensitive recording medium was obtained.

Example 4 In preparing liquid C, bis(3-tert-butyl-4-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that bis(3-methyl-4-hydroxyphenyl) sulfide was used instead of hydroxy-6-methylphenyl) sulfide.

Comparative Examples 1 and 2 Thermosensitive recording bodies were obtained in the same manner as in Examples 1 and 2, except that liquid C was not used in forming the recording layer.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used in place of 4-hydroxy-4'-methyldiphenylsulfone in the BWLiJl formation.

The following evaluation tests were conducted on the seven types of heat-sensitive recording bodies thus obtained, and the results are listed in Table 1.

[Whiteness]

In order to evaluate the degree of color fog, the whiteness of the recording layer was measured using a Hunter whiteness meter.

[Color density]

The color density of the recorded image obtained by printing with a thermal printer was measured with a Macbeth densitometer (manufactured by Macbeth, Model RD-100R).

〔water resistance〕

After printing, the heat-sensitive recording material was immersed in water and left at room temperature for 48 hours, after which the water resistance was evaluated from the print density.

[Plasticizer resistance]

A polypropylene pipe (40 mm diameter) was wrapped three times with divinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.), and a heat-sensitive recording material with colored print was placed on top of it, sandwiched so that the colored side of the print was on the outside. A vinyl chloride wrap film was wrapped three times over it, and the plasticizer resistance was evaluated from the print density after being left at room temperature for 12 hours.

[Water resistance to plasticizers]

The colored heat-sensitive recording material was lightly wetted with water and then evaluated in the same manner as the plasticizer resistance described above to determine its water resistance to plasticizers.

〔Oil resistance〕

After printing, several drops of cottonseed oil were dropped onto the printed colored area of the heat-sensitive recording material, and after 24 hours, it was wiped off with gauze, and the oil resistance was evaluated from the print density.

Example 5 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 1.

■ Formation of overcoat layer 100 parts of a 10% aqueous solution of polyvinyl alcohol (product name: PVA-110, manufactured by Kuraray Co., Ltd.), 20 parts of calcium carbonate
A coating liquid obtained by mixing and stirring 50 parts of water and 50 parts of water is coated and dried on the recording layer of the above heat-sensitive recording material so that the coating amount after drying is 6 g/rrl to obtain a heat-sensitive recording material having an overcoat layer. I got it.

Comparative example 4 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 1.

(2) Formation of overcoat layer A thermosensitive recording material having an overcoat layer was obtained in the same manner as in Example 5 except that the above thermosensitive recording material was used.

Comparative example 5 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Example 3.

(2) Formation of overcoat layer A thermosensitive recording material having an overcoat layer was obtained in the same manner as in Example 5 except that the above thermosensitive recording material was used.

The three types of heat-sensitive recording materials thus obtained were subjected to the same evaluation tests as described above, except that the plasticizer resistance and water plasticizer resistance were evaluated using the following methods, and the results are listed in Table 2.

[Plasticizer resistance]

Wrap vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) three times around a polypropylene pipe (40 Tsuru φ pipe), sandwich the heat-sensitive recording material with colored print on it so that the colored side of the print is on the outside, and then A vinyl chloride wrap film was wrapped three times over it, and the plasticizer resistance was evaluated from the print density after being left at 40° C. for 24 hours.

[Water resistance to plasticizers]

The colored heat-sensitive recording material was lightly wetted with water and then evaluated in the same manner as the plasticizer resistance described above to determine its water resistance to plasticizers.

Table 1 Table 2 "Effects" As is clear from the results in Tables 1 and 2, the heat-sensitive recording material of the present invention has excellent storage stability of recorded images, especially water resistance and plasticizer resistance. It was an excellent recording medium with a remarkable improvement in oil resistance, etc., and no color fog was observed.

Claims (2)

[Claims] (1) In a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent that causes the basic dye to develop color when heated, the coloring agent is expressed by the following general formula [I]. and the following general formula [
1. A heat-sensitive recording material containing at least one of the phenolic compounds represented by [II] and [III]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [In the formula, R_1 to R_5 are hydrogen atoms, halogen atoms, alkyl groups of C_1_ to _1_0, and C_1_ to _
1_0 represents an alkoxyl group, benzyloxy group, aryloxy group, or hydroxyl group. Note that R_1 and R_2 or R_2 and R_3 may be combined with each other to form a ring. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [II] [In the formula, R_6, R_7, and R_8 are hydrogen atoms, respectively.
It represents an alkyl group of C_1_ to_8 or a cycloalkyl group of C_5_ to_8. However, at least one of R_6, R_7, and R_8 represents a branched alkyl group of C_3_ to_8 or a cycloalkyl group of C_5_ to_8. R_9 and R_1_0R_1_1R_1_2R_1_3 each represent a hydrogen atom or an alkyl group of C_1_ to_9. ] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [III] [In the formula, R_1_4R_1_5R_1_6 each represent a hydrogen atom or an alkyl group of C_1_ to_6. ] (2) The heat-sensitive recording material according to claim (1), which has an overcoat layer above the recording layer.