JPH0229381A - Thermal sensitive recording medium - Google Patents

Abstract

PURPOSE:To improve preservation stability of a recorded image without new disadvantage such as feasible occurrence of a color fog by incorporating at least one type of compound represented by a specific formula in a thermal sensitive recording layer. CONSTITUTION:In a thermal sensitive recording medium which utilizes a coloring reaction of colorless or pale basic dye with a colorant coloring in contact with the dye, at least one type of compound represented by a general formula (I) is contained in a heat sensitive recording layer. In the formula, R1, R2, R3, R4, R5 and R6 are respectively hydrogen, halogen, C1-C5 alkyl group or C1-C5 alkoxy group which may be the same or different. The mixing ratio is such that 1-1000 pts.wt. of the compound is used with respect to 100 pts.wt. of the colorant. The ratio of the basic dye to the colorant is generally 100-700 pts.wt. of the colorant to the 100 pts.wt. of the dye, an the coating amount is 2-12g/m<2> based on drying weight.

Description

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

(Prior Art) Conventionally, heat-sensitive recording materials are well known, which utilize a reaction between a colorless or light-colored basic dye and a coloring agent to bring the two coloring substances into contact with each other using heat to obtain a recorded image. .

However, such heat-sensitive recording materials generally have a problem in that the recorded images do not have sufficient storage stability and discolor over time. Particularly under high temperature conditions or under high temperature conditions, recorded images disappear within a relatively short period of time, so there is currently a strong demand for improvement.

(Problems to be Solved by the Invention) In order to improve the storage stability of recorded images, heat-sensitive recording materials to which various storage improvers are added have been proposed, but the improvement causes a decrease in whiteness. Since new drawbacks such as these are also involved, satisfactory results have not always been obtained.

In view of the current situation, the inventors of the present invention have conducted extensive research into a preservability improver to be contained in the recording layer, and have found that the general formula (I
) has been found to be effective in terms of the storage stability of recorded images without any new drawbacks such as the tendency to cause color fogging,
The present invention has now been completed.

(Means for Solving the Problems) The present invention provides a thermosensitive recording medium that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color upon contact with the dye. This is a heat-sensitive recording material characterized in that the layer contains at least one compound represented by the following general formula (I).

[In the formula, R1, Rt, Rs, Ra, Rs and R4 may be the same or different, and each represents hydrogen, halogen, an alkyl group of C, %C, or CI.=Cs
represents an alkoxyl group. ] (Function) Examples of the compound represented by the general formula (I') include 1
-[α-methyl-α-(4′-hydroxyphenyl)ethyl]=4-(α′,α′-bis(4#-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-(
4'-hydroxyphenyl)ethyl)-3-(α', α
'-Bis(4#-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-(3',5'-dimethyl-
4'-hydroxyphenyl)ethyl)-4-(α'
α′-bis(3″,5′-dimethyl-4″-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-
(3'-methyl-4'hydroxyphenyl)ethyl]-
4-(α',α-bis(3'-methyl-4#-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-(3',5'-dichloro-4'
-hydroxyphenyl)ethyl)-4-(α′ α′
-bis(3',5'-dichloro-41-hydroxyphenyl)ethyl]benzene, ■-[α-methyl-α-(3
'-Methoxy-4'-hydroxyphenyl)ethyl)-
Examples include 4-(α′α′-bis(3#-methoxy-4″-hydroxyphenyl)ethyl)benzene.The above compounds may be used in combination of two or more types.
Recording storage stability is improved by incorporating the compound represented by I) into the heat-sensitive recording layer, and the compounding ratio is generally 1 part by weight of the above compound per 100 parts by weight of the coloring agent.
About 1000 parts by weight, preferably 10 to 300 parts by weight is used.

In the present invention, the following are exemplified as colorless or light-colored basic dyes constituting the recording layer of the thermosensitive recording material.

3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(I,2 -dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-
3-(2-methylindol-3-yl)phthalide, 3
,3-bis(I,2-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis(I゜2
-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazole-
3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-P-dimethylaminophenyl-
Triallylmethane dyes such as 3-(I-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'
-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4
, diphenylmethane dyes such as 5-trichlorophenylleucoauramine, benzoylleucomethylene blue,
Thiazine dyes such as p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-
Ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)
Spiro dyes such as spiropyran, 3-propyl-spiro-dibenzopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (0-chloroanilino) lactam, 3-dimethylamino- 7-methoxyfluorane, 3
-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 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-diethylamino-7-dibenzylaminofluoran Orane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N
-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3
-(N-ethyl-p-)luidino)-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-p-
1 luidino)-6-methyl-7-(p-)luidino)fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3 -diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluorane, 3-
Pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-( o-
chlorophenylamino)fluoran, 3-dibutylamino-7-(0-chlorophenylamino)fluoran, 3
-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 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-isoamyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-hexyl)amino-6
-Methyl-7-phenylaminofluorane, 3-(N-
Ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7
-phenylaminofluorane, 3-(N-ethyl-N-
Fluoran dyes such as (cyclopentyl)amino-6-methyl-7-phenylaminofluorane, etc. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

Among these dyes, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-isoamyl), amino-6-methyl-7-phenylaminofluorane, and -dibutylamino-7-
(o-chlorophenylamino)fluoran, in combination with the specific substance of the present invention, can provide a heat-sensitive recording medium that not only has particularly high whiteness and excellent storage stability of recorded images, but also has excellent recording density. , more preferably used.

Furthermore, various compounds are known as coloring agents used in combination with the above-mentioned basic dyes, and the following are exemplified.

4-tert-butylphenol, α-naphthol, β
-naphthol, 4-acetylphenol, 4-ter
t-octylphenol, 4.4'-5ec-butylidene diphenol, 4-phenylphenol, 4.4'-
Dihydroxy-diphenylmethane, 4゜4'-isopropylidenediphenol, hydroquinone, 4.4'-cyclohexylidenediphenol, 4.4'-(I,3
-dimethylbutylidene) bisphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol),
4.4'-Dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-
Hydroxy-3',4'-trimethylene diphenyl sulfone, 4-hydroxy-3',4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis(3-allyl-4-hydroxy phenyl) sulfone, 1,3-di(2-(4-hydroxyphenyl)-2-propyl)benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl ester, 4-hydroxybenzophenone, 2.4- Dihydroxybenzophenone, 2,4
．． 4'-1-dihydroxybenzophenone, 2.2'
, 4.4'-tetrahydroxybenzophenone, 4
-dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-5e
c-Butyl, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, 4-hydroxy phenethyl benzoate,
Phenolic compounds such as 4-hydroxybenzomp-chlorobenzyl, p-methoxybenzyl 4-hydroxybenzoate, novolac type phenolic resin, phenol polymer, 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, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-t
ert-butylsalicylic acid, 3-benzylsalicylic acid,
3-(α-methylbenzyl)salicylic acid, 3-chloro-
5-(α-methylbenzyl)salicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,
Aromatic carboxylic acids such as 5-di-α-methylbenzyl salicylic acid, and combinations of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. Organic acidic substances such as salts, etc. Of course, two or more of the above coloring agents can be used in combination as necessary. Especially 4-
When hydroxybenzoic acid esters are used as coloring agents, the storage stability of recorded images is significantly improved by the compound represented by general formula (I). Further, the use of 4-hydroxybenzoic acid esters has the advantage that a heat-sensitive recording material with excellent whiteness can be obtained.

The ratio of the basic dye and coloring agent to be used is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but is generally based on 100 parts by weight of the basic dye. 100-700 parts by weight, preferably 150-4
About 0.00 parts by weight of coloring agent is used.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
It is prepared by dispersing the dye, the compound represented by the general formula (I), and the coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, sand, or mill.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. It is blended in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight. Various auxiliary agents can be added to the coating liquid.
Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

Furthermore, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added to improve the adhesion of residue to the recording head. Furthermore, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, or the like may be added to prevent sticking from contact with a recording device or a recording head.

Further, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, 2,2'-methylene bis(4
-methyl-5-tert-butylphenol), 4.4
'-Butylidenebis(6-tert-butyl-3-methylphenol), 1.1.3-1-lis(2-methyl-
Hindered phenols such as 4-hydroxy-5-tert-butylphenyl)butane, p-benzylbiphenyl, 1.2-bis(phenoxy)ethane, 1.2-bis(4-methylphenoxy)ethane, 1.2 -Bis(3-
Ethers such as methylphenoxy)ethane, 2-naphthol benzyl ether, dibenzyl terephthalate, 1
-Esters such as hydroxy-2naphthoic acid phenyl ester L2-(2'-hydroxy-5'-methylphenyl)benzotriazole, ultraviolet absorbers such as 2-hydroxy-4-benzyloxybenzophenone, and various known thermoplastic Melting substances can also be used in combination as exacerbating agents.

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

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques.For example, a coating liquid for the heat-sensitive recording layer is coated on a support. A recording layer is formed by coating and drying using a suitable coating device such as an air knife coater, blade coater, bar coater, gravure coater, or curtain coater.

Further, the amount of the coating liquid to be applied is not particularly limited (generally adjusted in the range of 2 to 12 g/rrr, preferably 3 to 10 g/r+i in terms of dry weight).

Note that it is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, etc. A protective layer may be provided on the back side of the support, or an undercoat layer may be provided between the support and the heat-sensitive recording layer. Of course, it is also possible to provide a heat-sensitive recording material, and various known techniques in the field of heat-sensitive recording material manufacturing, such as applying adhesive processing, can be added.

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

In addition, parts in the chest and percentages indicate parts by weight and percentages by weight, respectively, unless otherwise specified.

Example 1 ■ Preparation of Solution A 3-(N-Ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane 10 parts Methylcellulose 5% aqueous solution 5 parts Water
40 parts This composition was grinded with a sand grinder until the average particle size was 2.0 μm.
It was crushed until it was.

■Preparation of Solution B Benzyl 4-hydroxybenzoate 20 parts Methylcellulose 5% aqueous solution 5 parts Water
55 parts of this composition was ground with a sand grinder until the average particle size was 2.0 μm.

■ C wave preparation 1-[α-methyl-α-(4'-hydroxyphenyl)
7 parts methylcellulose 5% aqueous solution 3 parts water
25 parts This composition was ground with a sand grinder until the average particle size was 2.0 μm.
It was crushed until it was.

■ Formation of recording layer 55 parts of liquid A, 80 parts of liquid B, 35 parts of liquid C, silicon oxide pigment (
Oil absorption amount 180mj! /100 g), 50 parts of a 20% polyvinyl alcohol aqueous solution, and 10 parts of water were mixed and stirred. The resulting coating liquid was applied onto a base paper having a basis weight of 50 g/rf so that the coated amount after drying was 6 g/rrf and dried to obtain a heat-sensitive recording paper.

Example 2 In the preparation of 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl)-4-(α′α′-bis(
4#-hydroxyphenyl)ethyl] instead of benzene, 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl)-3-(α′α′-bis(4″-hydroxyphenyl)ethyl] A thermosensitive recording paper was obtained in the same manner as in Example 1 except that benzene was used.

Example 3 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl)-4-Cα′α′-bis(4
Instead of #-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-(3'5'-dimethyl-
4'-hydroxyphenyl)ethyl)-4-(α', α
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that '-bis(3'5#-dimethyl-42-hydroxyphenyl)ethyl]benzene was used.

Example 4 ■ Preparation of Solution D 3-(N-Ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane 10 parts 1.2-di(3-methylphenoxy)ethane 25 parts Methylcellulose 5% aqueous solution 5 parts water
50 parts of this composition was ground to an average particle size of 2.0 μm using a sand grinder.
It was crushed until it was.

■ Preparation of F solution 4.4'-, isopropylidenediphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts This composition was ground with a sand grinder until the average particle size was 2.0 μm.
It was crushed until it was.

■ Preparation of F solution 1-[α-methyl-α-(4'-hydroxyphenyl)
7 parts methylcellulose 5% aqueous solution 3 parts water
25 parts This composition was ground with a sand grinder until the average particle size was 2.0 μm.
It was crushed until it was.

■ 90 parts of recording layer forming liquid, 80 parts of liquid E, 35 parts of liquid F, silicon oxide pigment (
Oil absorption amount 180mj! /100 g) 15 parts, 50 parts of a 2% polyvinyl alcohol aqueous solution, and 10 parts of water were mixed and stirred. The resulting coating liquid was applied onto a base paper having a basis weight of 50 g/rrr so that the coated amount after drying was 6 g/rrr, and dried to obtain a heat-sensitive recording paper.

Example 5 In the preparation of liquid F, 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl]-4 to [α′α′-bis(
4#-hydroxyphenyl)ethyl]benzene, 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl)-3-[α′α′-bis(4″-hydroxyphenyl)ethyl ] A thermosensitive recording paper was obtained in the same manner as in Example 4 except that benzene was used.

Example 6 In the preparation of liquid F, 1-[α-methyl-α-(4′-hydroxyphenyl)ethyl)-4-(α′α′-bis(
1-[α-methyl-α-(3′ 5′-dimethyl-4′-hydroxyphenyl)ethyl)-4-(α′
A thermal recording paper was obtained in the same manner as in Example 4, except that , α'-bis(3"5"-dimethyl-4#-hydroxyphenyl)ethyl]benzene was used.

Example 7 ■ Preparation of liquid G 10 parts of 3-dibutylamino-6-methyl-7-phenylaminofluorane 1,2-di(
3-Methylphenoxy)ethane 25 parts Methylcellulose 5% aqueous solution 5 parts Water
50 parts of this composition was ground to an average particle size of 2.0 μm using a sand grinder.
It was crushed until it was.

■ Preparation of H solution 4-hydroxy-4'-isopropoxydiphenylsulfone 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground with a sand grinder until the average particle size was 2.0 μm.

■ ■ Wave preparation 1-[α-methyl-α-(4'-hydroxyphenyl)
7 parts methylcellulose 5% aqueous solution 3 parts water
25 parts This composition was ground with a sand grinder until the average particle size was 2.0 μm.
It was crushed until it was.

■ Formation of recording layer 90 parts of G liquid, 80 parts of H liquid, 35 parts of I liquid, silicon oxide pigment (
Oil absorption: 180 mI2/100 g) 15 parts, 50 parts of a 20% polyvinyl alcohol aqueous solution, and 10 parts of water were mixed and stirred. The obtained coating liquid was applied onto a base paper having a basis weight of 50 g/rf so that the coated amount after drying was 6 g/rrf and dried to obtain a heat-sensitive recording paper.

Example 8 3-dibutylamino-6-methyl-7 in G liquid preparation
A thermosensitive recording paper was obtained in the same manner as in Example 7 except that 3-dibutylamino-7-(o-chlorophenylamino)fluoran was used instead of -phenylaminofluoran.

Comparative Example I A thermosensitive recording paper was obtained in the same manner as in Example 1 except that Liquid C was not used.

Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 4 except that liquid F was not used.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 7 except that the liquid (1) was not used.

Comparative Example 4 A thermosensitive recording paper was obtained in the same manner as in Example 8 except that the liquid (1) was not used.

Comparative Example 5 ■J lacquer preparation 1.1.3-tris(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane 7 parts methylcellulose 5% aqueous solution 3 parts water
25 parts of this composition was ground with a sand grinder until the average particle size was 2.0 μm.

(2) Formation of Recording Layer A thermosensitive recording paper was obtained in the same manner as in Example 7, except that 35 parts of the above J liquid was used instead of 35 parts of the I liquid in forming the recording layer.

Comparative Example 6 ■ Preparation of K solution 1.1.3-tris(2-methyl-4-hydroxy-5
-cyclohexylphenyl)butane 7 parts methylcellulose 5% aqueous solution 3 parts water
25 parts of this composition was ground with a sand grinder until the average particle size was 2.0 parts.

(2) Formation of recording layer A thermosensitive recording paper was obtained in the same manner as in Example 7 except that 35 parts of the above liquid was used instead of 35 parts of liquid (1) in forming the recording layer.

The following evaluation tests were conducted on the 14 types of heat-sensitive recording paper thus obtained.

[Whiteness]

The whiteness of the thermal recording paper was measured using a Hunter whiteness meter. The results are shown in Table 2.

[Recording density]

Transfer thermal recording paper to thermal facsimile (Hitachi HIFAX-40
Record the recorded density (DI) using a Macbeth densitometer (RD-100R model, using an amber filter).
The results are shown in Table 1.

[Moisture resistance]

After printing, the thermal recording paper was left in an atmosphere of 40'C and 90% RH for 24 hours, and then the recording density (D,) was measured again using a Macbeth densitometer. Table 1 also shows the recording density residual rate (%) according to the following formula.

Recording density residual rate = Dt /D, xI Q□ [Temperature resistance] Next, after printing, the thermal recording paper was left in an atmosphere of 60°C, 110%R)I for 24 hours, and then tested again using a Macbeth densitometer. The recording density (D,) of the printed area was measured.

Further, the recording density residual rate=Ds/DIX100 was determined and the results are listed in Table 1.

[Fog color development]

Heat-sensitive recording paper in an atmosphere of 40℃ and 90%RH or 60℃
After being left in an atmosphere of 10% RH for 24 hours, the fog color density of the white paper portion was measured using a Macbeth densitometer. The results are shown in Table 2.

Table 1 Table 2 (/JijikanI Day Pressure (Effect)) The heat-sensitive recording material of the present invention has excellent recording storage stability, and moreover, there is almost no occurrence of fogging or coloring due to the improved recording storage stability. Ta.

Claims (1)

[Claims] In a heat-sensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color when it comes into contact with the dye, the heat-sensitive recording layer contains the following general formula ( A thermosensitive recording material characterized by containing at least one compound represented by I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [In the formula, R_1, R_2, R_3, R_4, R_5 and R
_6 may be the same or different, and each represents hydrogen, a halogen, an alkyl group of C_1 to C_5, or an alkoxyl group of C_1 to C_5. ]