JPH0489283A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve the preservability of high sensitivity and the stability of a developed image by adding a specific compound to the thermal coloring layer of a thermal recording material having the thermal coloring layer which contains an electron-donative colorless dye and an electron-receptive compound. CONSTITUTION:A fluoran compound shown by formula I and a compound shown by formula II are added to a thermal coloring layer provided on a support 1. The electron-donative colorless dye which can be used with the compound I is, for example, a triphenylmethanephthalide compound, a fluoran compound, etc. The electron-receptive compound is, for example, a salicylic acid derivatives the metal salt of aromatic carboxylic acid, etc. The electron-donative colorless dye, the electron-receptive compound and a sensitizer are dispersed and mixed using a mill with an aqueous water-soluble polymer solution such as polyvinylalcohol, and the thermal coating liquid is applied to a high-quality paper or synthetic paper, then is dried and the coat is smoothed using a calendar to obtain the thermally recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a heat-sensitive recording material, and more particularly to an electron-donating colorless dye and an electron-donating colorless dye that have improved color development, shelf life, and stability of colored images. The present invention relates to a heat-sensitive recording material in which a coloring layer containing an electron-accepting compound is provided on a support.

(Prior Art) Recording materials using electron-donating colorless dyes and electron-accepting compounds are already well known as pressure-sensitive paper, thermal paper, light-sensitive pressure-sensitive paper, electrically conductive thermal recording paper, thermal transfer paper, and the like. For example, British Patent No. 2,140,449, U.S. Patent No. 4,48
No. 0.052, No. 4.436,920, Special Publication No. 1983
-23992, JP-A-57-179836, JP-A No. 60
-123556, 60-123557, etc. for details. In particular, heat-sensitive recording materials are detailed in Japanese Patent Publications No. 43-4160 and Japanese Patent Publication No. 45-14039.

In recent years, there has been active research into increasing the speed and energy consumption of thermal recording systems, and many attempts have been made to improve sensitivity by using various additives and sensitizers in combination. The present inventors have also developed several compounds such as ether compounds. On the other hand, as the sensitivity of heat-sensitive recording materials becomes higher, the temperature at which color development starts of heat-sensitive recording materials tends to decrease. Therefore, when printing on heat-sensitive recording materials by facsimile or the like, or when storing them in a high-temperature environment, fogging tends to occur.

(Objective of the Invention) An object of the present invention is to provide a heat-sensitive recording material which is highly sensitive, has good printing quality, and has good shelf life and stability of colored images.

(Structure of the Invention) The object of the present invention is to provide (1) a heat-sensitive recording material in which a heat-sensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound is provided on a support; Formula [1
], and a heat-sensitive recording material characterized by containing a compound represented by the following general formula [11] (R', R2, R' represent a lower furkyl group, m is Represents an integer from 1 to 4.) (x' and x' may be the same or different, and include a hydrogen atom, a halogen atom, a lower alkyl group, a lower flukoxy group,
2 represents a direct bond or an oxygen atom, and n represents an integer of 1 to 4. ) (2) The oxalate ester compound has the following general formula (Il
This was achieved by the heat-sensitive recording material according to claim (1), which is a compound represented by (1).

(X' and X' may be the same or different and represent a hydrogen atom, a halogen atom, a lower alkyl group, or a lower flukoxy group.) The oxalate ester compound according to the present invention has an electron-donating colorless dye in its shell. as, 2-7nilino-3-methyl-6
-When using dinitylaminofluorane etc., β
-Features lower sensitivity than ether compounds such as naphthyl hensyl ether. However, it was found that when used with the fluoran compound of the present invention, the sensitivity was specifically increased and the temperature at which color development started was high.

Specific examples of the compound represented by compound (1) according to the present invention include 2-7nilino3-methyl-6-N-methyl-N-γ-ethoxypropyl7minofluorane, 2-7
Nilino 3-methyl-6-N-ethyl-N-γ-methoxybutylaminofluorane, 2-7 Nilino 3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-7 Nilino 3-Methyl-6-N-ethyl-N-β-dihydroxyethylaminofluorane 2-7
Examples include Nilino 3-methyl-6-N-ethyl-N-γ-propoxypropylaminofluoran.

In the present invention, it is necessary that the compound [1] accounts for 50% by weight or more of the electron-donating colorless dye. Under the above-mentioned conditions, it can be used in combination with other electron-donating colorless dyes. Examples of electron-donating colorless dyes that can be used in combination are shown below.

Examples of electron-donating colorless dyes include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucoolamine compounds, rhodamine lactam compounds, triphenylmethane compounds, There are various compounds such as triazene compounds, spiropyran compounds, and fluorene compounds. Specific examples of phthalides can be found in U.S. reissued patent specification cylinder 2.
3゜024, U.S. Patent Specification No. 3.491,111, U.S. Patent No. 3,491,112, U.S. Patent No. 3,491゜116
No. 3,509,174, and specific examples of fluorans are given in U.S. Pat.
, No. 627.787, No. 3641.011, No. 3,462.828, No. 3,681,390, No. ¥3,920,510, No. 3,959,571 ,
Specific examples of spiropyrans can be found in U.S. Patent Specification No. 3,971.
No. 808, pyridine and pyrazine compounds are described in U.S. Patent Specification No. 3,775,424, U.S. Pat.
, No. 869, No. 4,246,318, and specific examples of fluorene compounds are described in Japanese Patent Application No. 61-240989.

Among these, 2-7 arylamino-3-H, halogen-, alkyl-, or 1-alkoxy-6-substituted 7-minofluorane which produces black color is particularly effective.

Specific examples include 2-7nilino-3-methyl-6-ethylaminofluorane and 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane.

2-p-Chloroanilino-3-methyl-6-sibutylaminofluorane, 2-anilino-3-methyl-6-sioctylaminofluorane, 2-7nilino-3-di-6-dinithylaminofluorane , 2-7nilino3-methyl-6-N-ethyl-N-iso7mil7minofluorane, 2-7nilino3-methyl-6-N-ethyl-N-
Dodecylaminofluorane, 2-7nilino-3-methoxy-6-sibutylaminofluorane, 2-O-chloroanilino-6-sibutylaminofluorane, 2-p-ri0
Port 7 Nilino-3-ethyl-6-N-ethyl-N-isoamylaminofluorane, 2-〇-chloroanilino 6-
p-butylanilinofluorane, 2-7nilino-3-pentadecyl-6-diethylaminofluorane, 2-7nilino-3-ethyl-6-sibutylaminofluorane, 2
-O-Toluidino-3-methyl-6-diitubrobylaminofluorane, 2-7nilino-3-methyl-6-N-
Inbutyl-N-ethylaminofluorane, 2-7nilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluorane.

Examples include 2-7nilino-3-chloro-6-N-ethyl-N-isoamylaminofluorane.

Next, specific examples of the compound represented by compound [11] according to the present invention will be shown.

Oxalic acid dibenzyl ester, oxalic acid di(p-methylbenzyl) ester, oxalic acid di(p-chlorobenzyl) ester, oxalic acid di(m-methylhensyl) ester, oxalic acid di(p-ethylbenzyl) ester, oxalate acid cy(p-methoxybenzyl) ester, oxalic acid bis(β-phenoxyethyl) ester, oxalic acid bis(β-0-chlorophenoxyethyl) ester, oxalic acid bis(β-p-chlorophenoxyethyl) ester,
Oxalate bis(β-p-ethylphenoxyethyl) ester, oxalate bis(β-m-methoxyphenoxyethyl) ester, oxalate bis(β-p-methoxyphenoxyethyl) ester, oxalate bis(4-phenoxybutyl) ester ) esters, etc. In particular, the compound (I
I+ ) oxalic acid dibenzyl ester, oxalic acid di(p-methylbenzyl) ester,
Oxalic acid di(p-chlorobenzyl) ester, oxalic acid di(m-methylbenzyl) ester, oxalic acid di(p-
Ethylbenzyl) ester and oxalic acid di(p-methoxybenzyl) ester are preferred.

In the present invention, a sensitizer can be used in combination with compound (I+). Examples of sensitizers that can be used in combination are:
Compounds disclosed in JP-A-58-57989, JP-A-58-87094, JP-A-63-39375 and the like can be mentioned. Representative examples include aromatic ethers (particularly benzyl ethers and di(substituted phenoxy)alkanes), esters and/or aliphatic amides, ureidos, and aromatic amides or ureidos.

As the electron-accepting compound according to the present invention, salicylic acid derivatives, metal salts of aromatic carboxylic acids, phenol derivatives, phenol resins, novolak resins, metal-treated novolak resins, metal complexes, acid clay, bentonite, and the like are used.

Examples of these are Special Publication No. 9309 of 1972 and Special Publication No. 1 of 1973.
No. 4039, JP-A-52-140483, JP-A-48
-51510, JP-A-57-210886, JP-A-58-87089, JP-A-59-11286, JP-A-60-176795, JP-A-61-95988, etc.

Some examples of these include 4-tert-butylphenol, 4-phenylphenol, and 4-hydroxydiphenoxide-α-naphthol.

β-naphthol, hexyl-4-hydroxyhenzoate, 2,2'-dihydroxybiphenyl.

2.2-bis(4-hydroxyphenyl)propane (bisphenol A), 4.4'-isopropylidenebis(2-methylphenol), 1.1'-bis-(3-chloro-4-hydroxyphenyl)cyclohexane , 1.
1-bis(3-chloro-4-hydroxyphenyl)-2
-Ethylbutane.

4.4'-Secondary octylidenzyphenol + 4-tart-octylphenol.

4.4'-5ac-butylidene diphenol, 4-p-
Methylphenylphenol, 4.4'-isopentylidenephenol, 4.4'-methylcyclohexylidenediphenol, bis(3-7ly-4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-3'4
' Dimethylphenylsulfone, 4-hydroxy-4
'-isopropoxydiphenylsulfone, 4-hydroxy-4'propoxydiphenylsulfone, 4-hydroxy-4'-ethoxydiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone .

4-Hydroxy-4'-ethyldiphenylsulfone, 4
-Hydroxy-4'-isopropyldiphenylsulfone, 4-hydroxy-4'-propyldiphenylsulfone, 4-hydroxy-4'-isopropyldiphenylsulfone, 4-hydroxy-41-fluorodiphenylsulfone,
4-hydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 1,4-bis-(4'
-hydroxycumyl)benzene, 113-bis-(4
'-Hydroxycumyl)benzene, 4,4'thiobis(
6-tert-butyl-3-methylphenol), 4.
4'-dihydroxydiphenyl sulfone, hydroquinone monobenzyl ether.

4-hydroxybenzophenone, 2.4-dihydroxybenzophenone, polyvinylbenzyloxycarponylphenol, 2.4.4'-1-lyhydroxybenzophenone, 2.2', 4.4'tetrahydroxybenzophenone, 4-hydroxy Phthalic acid, methyl dimethyl-4-hydroxybenzoate, 2,4.4'-trihythmO
xydiphenylsulfone, 1,5-bis-p-hydroxyphenylpentane, 1,6-pis-p-humanOxyphenoxyhexane, tolyl 4-hydroxybenzoate,
4-Hydroxybenzoic acid α-phenylbenzyl ester, phenylpropyl 4-human Oxybenzoate, phenethyl 4-hydroxybenzoate.

p-chlorobenzyl 4-hydroxybenzoate.

4-Hydroxybenzoic acid-ρ-methoxybenzyl.

4-hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic acid-m-chlorobenzyl ester, 4-hydroxybenzoic acid-β-phenethyl ester, 4-hydroxy-2',4'-dimethyldiphenylsulfone β-phenethyl ester Serinate, cinnamyl orselinate, orselic acid-〇-chlorophenoxyethyl ester, 0-ethylphenoxyethyl orselinate, o-phenylphenoxyethyl orselinate, m
-phenylphenoxyethyl orseline), 2.
4-dihydroxybenzoic acid-β-3'-t-butyl-
4'-hydroxyphenoxyethyl ester, 1-t-
Butyl-4-ρ-hydroxyphenylsulfonyloxybenzene, 4-N-benzylsulfamoylphenol, 2,4-dihydroxybenzoic acid-β-phenoxyethyl ester, 2,4-dihydroxy-6-methylbenzoic acid benzyl ester, Methyl bis-4-hydroxyphenylacetate.

Ditolylthiourea, 4,4'-diacetyldiphenylthiourea, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 2-phenyl-5- (α,α-dimethylbenzyl)salicylic acid, 3.5-di(α-methylbenzyl)salicylic acid, 5
-t-octylsalicylic acid, 3,5-di-t-butylsalicylic acid, 3-chloro-5-cumylsalicylic acid, 3-methyl-5-t-octylsalicylic acid, 3-methyl-5-
α-Methylbenzylsalicylic acid, 3-methyl-5-cumylsalicylic acid, 3.5-di-t-7milsalicylic acid, 3
-Phenyl-5-benzylsalicylic acid, 3-phenyl-
5-t-octylsalicylic acid, 3-phenyl-5-α-
Methylbenzylsalicylic acid, 3,5-di-t-octylsalicylic acid, 3,5-bis(α-methylbenzyl)salicylic acid, 3,5-dicumylsalicylic acid, 4-methyl-5
-(α-Methylbenzyl)salicylic acid.

4-Methyl-5-cumylsalicylic acid, 3-(α-methylbenzyl)-6-methylsalicylic acid, 3-(α-methylbenzyl)-6-phenylsalicylic acid.

3-triphenylmethylsalicylic acid, 3-diphenylmethylsalicylic acid, 4-n-dodecylsalicylic acid, 4-t
-dodecylsalicylic acid, 4-n-dodecylsalicylic acid,
4-n-pentadecylsalicylic acid, 4-n-heptadecylsalicylic acid, 5-(1,3-diphenylbutyl)-salicylic acid, 5-n-octadecylsalicylic acid, 4-pentadecylsalicylic acid, 315-bis(α-methylbenzyl ) salicylic acid, 3,5-bis-t-octylsalicylic acid, 5-octadecylsalicylic acid, 5-α-(p-α-
Methylbenzylphenyl)ethylsalicylic acid, 3-α-
Methylbenzyl-5-t-octylsalicylic acid, 5-tetradecylsalicylic acid.

4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-octyloxysalicylic acid, 4-
Decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-tetradecyloxysalicylic acid, 4-pentadecyloxysalicylic acid.

4-hexadecyloxysalicylic acid, 4-octadecyloxysalicylic acid, 4-icosyloxysalicylic acid, 4
-Tri7contyloxysalicylic acid.

4-oleyloxysalicylic acid, 4-β-phenethyloxysalicylic acid, 4-β-dodecyloxyethoxysalicylic acid, 4-(12-chlorododecyl)oxysalicylic acid, 4-β-N-stear0ylaminoethoxysalicylic acid, 4-β -N-Mylinutoyl 7minoethoxysalicylic acid, 4-β-perfluorohexylethoxysalicylic acid, 4-dodecyloxy-5-chlorosalicylic acid, 4-dodecyloxy-5-methylsalicylic acid, 4-dodecyloxy-6-methylsalicylic acid, 4 -dodecyloxy-6
-Phenylsalicylic acid, 4-methoxy-6-dodecyloxysalicylic acid. 6-octazosyloxysalicylic acid,
4-pt-octylphenyloxysalicylic acid, 4-
p-dodecyloxyphenyloxysalicylic acid, 4-p
-chlorophenoxy-6-butylsalicylic acid, 4-p-
Phenylphenoxysalicylic acid, 4-p-N-myristoylcarbamoylphenyloxysalicylic acid.

4-β-p-methoxaldiphnidiphenoxyethoxysalicylic acid benzyloxy-6-dodecyloxysalicylic acid,
5-dodecylsulfonylsalicylic acid.

Examples include 5-dodecylsulfosalicylic acid and 3-methyl-5dodecylsulfosalicylic acid.

The electron-accepting compound is an electron-donating colorless dye of 50 to 80
It is preferable to use 0 weight X, more preferably 1
00 to 500% by weight. Further, two or more of the above electron-accepting compounds may be used in combination.

Next, a typical method for producing a heat-sensitive coloring layer of the present invention will be described.

The electron-donating colorless dye, the electron-accepting compound, and the sensitizer are dispersed to a size of several microns or less together with an aqueous solution of a water-soluble polymer such as polyvinyl alcohol using a ball mill, sand mill, or the like. The sensitizer is added to either the electron-donating colorless dye or the electron-accepting compound, or both, and is dispersed simultaneously, or in some cases, a eutectic product is prepared in advance with the electron-donating colorless dye or the electron-accepting compound. , may be dispersed.

These dispersions are mixed after dispersion, and pigments and
Add surfactant, binder, metal soap, wax, antioxidant, ultraviolet absorber, etc. to make a heat-sensitive coating liquid.

The obtained heat-sensitive coating liquid is coated and dried on high-quality paper, high-quality paper with an undercoat layer, synthetic paper, plastic film, etc., and then smoothed by calendering to obtain the desired heat-sensitive recording material. In this case, it is particularly preferable to use a support having a smoothness defined by JIS-8119 of 500 seconds or more, particularly 800 seconds or more from the viewpoint of dot reproducibility. To obtain a support with a smoothness of 500 seconds or more, ■ Use a material with high smoothness such as synthetic paper or plastic film ■ Provide an undercoat layer containing pigment as the main component on the support ■ Super calender There are methods such as increasing the smoothness of the support by using .

The binder is preferably a compound that dissolves 5% by weight or more in water at 25°C, and specifically, polyvinyl alcohol (including modified polyvinyl alcohols such as carboxy-modified, itaconic acid-modified, maleic acid-modified, and silica-modified polyvinyl alcohols). , methylcellulose, carboxymethylcellulose, starches (including modified starches), gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, polyacrylamide, saponified vinyl acetate-polyacrylic acid copolymer, etc. can be given. These binders are used not only for dispersion but also for the purpose of improving coating film strength. A synthetic polymer latex binder such as acid methyl butadiene copolymer or polyvinylidene chloride may also be used.

Further, a crosslinking agent suitable for the binder may be added depending on the type of the binder, if necessary.

Pigments include calcium carbonate, barium sulfate, lithopone, waxite, kaolin, silica, amorphous silica, and the like.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like.

Furthermore, an antistatic agent, an antifoaming agent, a conductive agent, a fluorescent dye, a coloring dye, etc. may be added as necessary.

The coated heat-sensitive recording material is dried and subjected to a process such as a calender before being used.

Further, a protective layer may be provided on the heat-sensitive coloring layer if necessary. As the protective layer, any one known as a protective layer for heat-sensitive recording materials can be used.

Furthermore, if necessary, a back coat layer may be provided on the opposite side of the support of the heat-sensitive recording material from the heat-sensitive coloring layer. As the back coat layer, any material known as a back coat layer for heat-sensitive recording materials can be used.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the Examples.

(Example-1) 2-7nilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane was used as an electron-donating color dye, and bisphenol A was used as an electron-accepting compound.
, oxalic acid di(p-methylpencyl) ester as a sensitizer, 209 was dispersed in a ball mill overnight with a 5% polyvinyl alcohol (Kuraray PVA-105) aqueous solution of 1009, and the average particle size was reduced to 1.5 μm or less. A dispersion was obtained. Further, calcium carbonate 809 was dispersed with a 0.5% sodium hexametaphosphate solution 1609 using a homogenizer to obtain a pigment dispersion.

Each of the dispersions prepared as described above was mixed into an electron-donating colorless dye dispersion 59, an electron-accepting compound dispersion 09, an oxalic acid di(p-methylbenzyl) ester dispersion 109, and a calcium carbonate dispersion 59. Mix at a ratio of 21
A heat-sensitive coating liquid was obtained by adding 39% zinc stearate emulsion. This heat-sensitive coloring layer coating solution has a basis weight of 50c+/m2.
The mixture was coated onto high-quality paper using a wire parser so that the dry weight of the coated layer was 597 mm, and dried at 50° C. for 1 minute to obtain heat-sensitive recording paper.

(Example-2) Instead of using 2-7nilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane in Example-1, 2-7nilino-3-methyl-6- A thermal recording paper was obtained in the same manner except that a thermal coating liquid was prepared using N-methyl-N-γ-ethoxypropyl 7minofluorane.

(Example 3) In the preparation of Example 1, 1. A heat-sensitive recording paper was obtained in the same manner except that a heat-sensitive coating liquid was prepared.

(Example 4) A thermosensitive coating was prepared in the same manner as in Example 1, except that oxalic acid cihensyl ester was used instead of oxalic acid cyhensyl ester. I got the recording paper.

(Comparative Example-1) Instead of using 2-7nilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane in Example-1, 2-7nilino-3-methyl-6- A thermal recording paper was obtained in the same manner except that N-methyl-N-cyclohexylaminofluorane was used to prepare the thermal coating liquid.

(Comparative Example-2) Instead of using 2-7nilino-3-methyl-6-N-ethyl-N-γ-dihydroxypropylaminofluorane in Example-1, 2-7nilino-3-methyl-6 - A thermosensitive recording paper was obtained in the same manner except that a thermosensitive coating liquid was prepared using diethylaminofluoran.

(Comparative Example-3) Thermal recording was carried out in the same manner as in Example-1, except that β-naphthylhensyl ether was used instead of sinuate di(p-methylhensyl) ester to prepare the heat-sensitive coating liquid. Got paper.

(Comparative Example-4) Instead of using 2-7nilino-3-methyl-6-N-ethyl-N-γ-ethoxypropyl-7minofluorane in Example-1, 2-7nilino-3-methyl-6-diethylamino A thermal recording paper was obtained in the same manner except that fluoran was used and β-naphthylbenzyl ether was used instead of oxalic acid di(p-methylbenzyl) ester to prepare a thermal coating liquid.

The surface of the thermal recording paper obtained as described above was treated with a calender, and the smoothness was 300±5 as Beck smoothness.
The temperature was adjusted to 0 seconds to obtain a heat-sensitive recording material.

The thermal recording paper was evaluated as follows.

■Color density is determined by Kyocera thermal head (KLT-2+)
6-8MPD +) and 9/c to 100 just before the head
Using a thermal printing tester with a pressure roll of m2, printing was performed at a pulse width of 0.6ms using the pressure roll under the conditions of a head voltage of 24■ and a pulse cycle of 10m5, and the print density and the density of the white background were measured. Macbeth reflection densitometer R
Measured with D-918.

■Heat resistance is the density of the white area when stored for 24 hours in an environment of 60°C and 30% RH using the Macbeth reflection densitometer RD-91.
Measured at 8.

The above results are shown in the table below.

As shown in the table, it can be seen that the heat-sensitive recording material according to the present invention exhibits good printing J degree even at low energy, has little fog, and has good heat resistance.

Claims (2)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound is provided on a support, the heat-sensitive coloring layer contains a fluoran compound represented by the following general formula [I]. A heat-sensitive recording material characterized in that it further contains a compound represented by the following general formula [II]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] (R^1, R^2, R^3 represent lower alkyl groups, m
represents an integer from 1 to 4. ) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [II] (X^1 and X^2 may be the same or different, hydrogen atom, halogen atom, lower alkyl group, lower alkoxy group, Z is a direct bond or represents an oxygen atom, and n represents an integer from 1 to 4.) (2) The heat-sensitive recording material according to claim (1), wherein the oxalate ester compound is a compound represented by the following general formula [III]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [III] (X^3 and X^4 may be the same or different and represent a hydrogen atom, a halogen atom, a lower alkyl group, or a lower alkoxy group.)