JP2002137554A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material with outstanding color development sensitivity and recording medium shelf stability. SOLUTION: This thermal recording material contains 0.01-10 pts.wt. of a colorant (i), a developer (ii) of a constitution such as represented by an esterification reaction product composed of a carboxylic acid component (A) containing a (poly) 4-hydroxy benzoic acid (a) as an essential component and a polyhydroxy alcohol component (B) containing a polyhydroxy alcohol (b) which is trihydric or higher as an essential component, as represented by the described general formula (I) and an acidic cyclic phosphate compound (iii) of alkylidene bisphenols as represented by the described general formula (II), to one pt.wt. of colorant (i). (In the formula (I), p is an integer of 0-2). (In the formula (II), R1 and R2 are each a 1-8C alkyl group independently).

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 having improved color sensitivity and improved storage stability after recording. In detail, the coloring layer, a developer having a specific structure, and a specific alkylidene bisphenol acidic cyclic phosphate compound as a storage stabilizer are contained in the recording layer, so that the color development sensitivity and storage stability are excellent. Heat-sensitive recording material.

[0002]

2. Description of the Related Art A heat-sensitive recording material utilizes a color-forming reaction between an electron-donating color developing agent such as a colorless or pale-colored basic dye and an electron-accepting color developing agent. The color former and the developer, together with a sensitizer, a binder and other additives,
A heat-sensitive recording material obtained by coating the surface of a support such as paper, synthetic paper, a plastic film or a sheet is brought into contact with a heating element such as a thermal head or a hot pen in a recording apparatus and is colored black or the like.

However, the heat-sensitive recording materials described above are not satisfactory in both the color sensitivity and the storage stability of a recording material (showing a color of the recording material for recording information). Color development sensitivity and storage stability of the recording medium
It is adjusted by the material contained in the recording layer of the thermosensitive recording material such as a color developer and a sensitizer. Discoloration (ground fog) tends to occur, and long-term storage stability tends to be a problem. Further, when the storage stability is increased, the coloring sensitivity tends to be insufficient.

With respect to these heat-sensitive recording materials, for example, JP-A-56-144193, JP-A-58-188842, and JP-A-60-6, in order to improve color sensitivity.
No. 4,890, JP-A-63-252782, etc., there have been proposals for using a 4-hydroxybenzoic acid ester derivative as a color developer, and they are still used at present. However, these heat-sensitive recording materials have satisfactory color-forming sensitivity, but are not sufficient with respect to the storage stability of the recording medium, and further improvement has been desired. Furthermore, International Patent Publication No. WO 99/51444 describes that a sodium salt of a cyclic phosphate of an alkylidene bisphenol is blended with an ester reaction product (a color developer) of 4-hydroxybenzoic acid and a polyhydric alcohol. However, storage stability was not sufficiently satisfactory.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat-sensitive recording material which is excellent in coloring sensitivity and storage stability of a recording medium.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to solve the above-mentioned problems. As a result, the color former (i) was compared with (poly) 4-hydroxybenzoic acid (a). By using an esterification reaction product (e) with a polyhydric alcohol component (b) having a valence of 3 or more as a developer (ii) and using a compound (iii) of an acidic cyclic phosphate of an alkylidene bisphenol as a storage stabilizer, The present inventors have found that it is possible to obtain a recording material which is excellent in the coloring sensitivity of a recording medium and also excellent in storage stability such as heat resistance and water resistance, and has reached the present invention.

The gist of the present invention is as follows. The first invention comprises a color former (i), a carboxylic acid component (A) containing (poly) 4-hydroxybenzoic acid (a) represented by the following general formula (I) as an essential component, and a trivalent or higher carboxylic acid component. A developer (ii) having a structure represented by an esterification reaction product with a polyhydric alcohol component (B) containing a polyhydric alcohol (b) as an essential component, and represented by the following general formula (II) The acid cyclic phosphate compound (iii) of the alkylidene bisphenol is used in an amount of 0.01 to 1 part by weight based on 1 part by weight of the color former (i).
Provided is a thermosensitive recording material containing 10 parts by weight.

Embedded image (In the formula, p represents an integer of 0 to 2.)

Embedded image (Wherein, R ₁ and R ₂ each independently represent an alkyl group having 1 to 8 carbon atoms.) According to a second aspect, the esterification reaction product comprises at least (poly) 4-hydroxybenzoic acid (a) A heat-sensitive recording material according to the first invention, which comprises a structure represented by an esterification reaction product (e) of a polyhydric alcohol (b) with a trihydric or higher polyhydric alcohol (b). The third invention is characterized in that in the carboxylic acid component (A),
(Poly) 4-hydroxybenzoic acid (a) represented by the general formula (I) and (poly) 4 represented by the following general formula (III)
The present invention provides the heat-sensitive recording material according to the first or second invention, which comprises -hydroxybenzoic acid derivative (a ') in a molar ratio of 1: m (provided that 0 <m ≦ 2).

Embedded image (In the formula, q represents an integer of 0 to 2, X is a formyl group; an alkyl group having 1 to 18 carbon atoms, an alkyl group, an alkylcarbonyl group, an alkylcarbamoyl group or an alkylsulfonyl group; The number represents an aryl group, an arylcarbonyl group, an arylcarbamoyl group, an arylsulfonyl group, or an acetoacetyl group having 6 to 30.) In the fourth invention, a trihydric or higher polyhydric alcohol (b) is represented by the following general formula ( A heat-sensitive recording material according to any one of the first to third inventions, which is a compound represented by IV).

Embedded image (In the formula, n represents an integer of 0 to 9, and R ₁ and n R _{2 s} each independently represent a hydroxymethyl group, a hydroxyethyl group, or an alkyl group having 1 to 8 carbon atoms.) The invention provides the heat-sensitive recording material according to the fourth invention, wherein in the general formula (IV), R ₁ and n R ₂ are each independently a hydroxymethyl group or a hydroxyethyl group. The sixth invention is a compound of the general formula (II) wherein R ₁
And R ₂ is a tertiary butyl group.
5. A heat-sensitive recording material according to any one of the fifth aspect of the invention.
The seventh invention provides the heat-sensitive recording material according to any one of the first to sixth inventions, further comprising a sensitizer (s). The eighth invention provides the heat-sensitive recording material according to any one of the first to seventh inventions, further comprising calcium carbonate as a filler.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the thermosensitive recording material of the present invention having the above-mentioned gist will be described in more detail. The heat-sensitive recording material according to the present invention may be any heat-sensitive recording material in which a color developer, a sensitizer, and a color former are provided in a layer on a base material,
There is no restriction on the structure, manufacturing method, etc. In the present invention, 4-hydroxybenzoic acid and poly-4-hydroxybenzoic acid are referred to as (poly) 4-hydroxybenzoic acid unless otherwise required, and the 4-hydroxybenzoic acid derivative and poly-4-hydroxybenzoic acid are referred to as (poly) 4-hydroxybenzoic acid. The hydroxybenzoic acid derivative is referred to as a (poly) 4-hydroxybenzoic acid derivative.

Color developer Color developer used in the heat-sensitive recording material according to the present invention (ii)
Are a carboxylic acid component (A) containing (poly) 4-hydroxybenzoic acid (a) represented by the above general formula (I) as an essential component, and a trihydric or higher polyhydric alcohol (b) as an essential component. Having a structure represented by an esterification reaction product with a polyhydric alcohol component (B) contained as
It may be synthesized by any production method such as a condensation reaction and an exchange reaction.

In the carboxylic acid component (A), the essential component (poly) 4-hydroxybenzoic acid (a) is 4-hydroxybenzoic acid, poly-4-hydroxybenzoic acid or a mixture of these in any proportion. That is. Poly 4-hydroxybenzoic acid is produced by using 4-hydroxybenzoic acid as a raw material and performing a condensation reaction thereof. Alternatively, 4-hydroxybenzoic acid (4′-carboxy) phenyl or the like which is a dimeric compound of 4-hydroxybenzoic acid is synthesized in advance, and this is used as a raw material to cause a condensation reaction between each other or the 4-hydroxybenzoic acid. Can also be obtained.
A chain oligomer such as 4-hydroxybenzoic acid or the above dimer compound is used in the form of a free carboxylic acid when synthesizing an esterification reaction product.
It can also be used in the form of ester-forming derivatives such as acid anhydrides and lower alkyl esters.

When the (poly) 4-hydroxybenzoic acid derivative (a ′) represented by the general formula (III) is added to the carboxylic acid component (A), the softening point of the developer can be lowered, In some cases, the effect of increasing the compatibility with the sensitizer or increasing the color sensitivity may be provided. The derivative (a ′) can be added at any ratio to the carboxylic acid component (A),
It is preferable to use it in the range of 1 mol of (poly) 4-hydroxybenzoic acid (a) in the range of 0 mol (provided that 0 <m ≦ 2). When the amount of the derivative (a ') exceeds 2 mol, the color sensitivity may be insufficient.

The method for introducing the modifying group represented by X in the general formula (III) is not particularly limited. For example, the carboxylic acid group of the (poly) 4-hydroxybenzoic acid (a) represented by the general formula (I) is changed to an acid halide, an acid anhydride, a lower alkyl ester, or the like to form a (poly) 4-hydroxybenzoic acid. Ester-forming derivative (a ″) and modifier (d) for inducing a modifying group
A method of simultaneously reacting the above (a ″) with a polyhydric alcohol component (B) and a modifier (d), the above (poly) 4-hydroxybenzoic acid (a) and a polyhydric alcohol component (B) (D) with the esterification reaction product of
And the like.

Examples of the modifying group represented by X include an alkyl group having 1 to 18 carbon atoms, an alkylcarbonyl group having the alkyl group, an alkylcarbamoyl group and an alkylsulfonyl group. Examples of the alkyl group referred to herein include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, amyl, tert-amyl, hexyl, 1-ethylpentyl, heptyl,
Isoheptyl, tertiary heptyl, 1-ethylheptyl, octyl, tertiary octyl, 2-ethylhexyl, nonyl,
Examples include groups such as isononyl, decyl, dodecyl, lauryl, tridecyl, myristyl, pentadecyl, palmityl, peptadecyl, and stearyl. Other examples of the modifying group include an aryl group having 6 to 30 carbon atoms, an arylcarbonyl group having the aryl group, an arylcarbamoyl group, and an arylsulfonyl group. Examples of the aryl group referred to herein include phenyl, methylphenyl, butylphenyl, octylphenyl, naphthyl, and the like. Further, other examples of the modifying group include a formyl group and an acetoacetyl group.

Further, the carboxylic acid component (A) according to the present invention
Is an essential component (poly) 4- represented by the general formula (I).
In addition to the hydroxybenzoic acid (a), other carboxylic acids may be included, if necessary, as long as the effect as a color developer is not impaired. For example, when the storage stability of a recording medium is to be improved by increasing the molecular weight of the developer, oxalic acid, malonic acid, succinic acid, 1,3-butanedicarboxylic acid, adipic acid, azelaic acid, Sebacic acid, phthalic acid, isophthalic acid, divalent carboxylic acids such as terephthalic acid, and mixtures thereof can be used.

In the polyhydric alcohol component (B) according to the present invention, the type of the trihydric or higher polyhydric alcohol (b), which is an essential component, is not particularly limited.
Hexitols, pentitols, pentaerythritol, trimethylolethane, trimethylolpropane,
Tetramethylolpropane, glycerin, condensates of these trihydric or higher polyhydric alcohols, and condensates of these trihydric or higher polyhydric alcohols and dihydric low molecular alcohols.

As the trihydric or higher polyhydric alcohol (b), a compound represented by the general formula (IV) is particularly preferably used. In the formula, n represents an integer of 0 to 9, and R ₁ and n R ₂ each independently represent a hydroxymethyl group, a hydroxyethyl group or an alkyl group having 1 to 8 carbon atoms. A methyl group or a hydroxyethyl group is preferred. In particular, the polyhydric alcohol represented by the above general formula (IV) is preferable because a recording material having excellent coloring sensitivity and storage stability when formed into a recording medium is obtained, and particularly, pentaerythritol, trimethylolpropane and / or It is more preferable to use the condensate. As the dihydric low molecular alcohol used for the alcohol condensate, the following other polyhydric alcohols used as necessary as one component of the polyhydric alcohol component (B) can be appropriately used.

The polyhydric alcohol component (B) according to the present invention
May contain other polyhydric alcohols, if necessary, as long as the effect of the developer is not impaired. Other polyhydric alcohols include, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,
Examples thereof include 5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol and the like, or a mixture thereof. Other polyhydric alcohols are preferably used because the effect of improving the dispersibility of the color developer in the recording layer can be seen by addition.

The mixing ratio of each raw material for obtaining the developer (ii) according to the present invention is not particularly limited, but usually, preferably, the hydroxyl group of the trihydric or higher polyhydric alcohol (b) is used. With respect to the number of moles, the sum of the number of moles of the carboxyl group of (poly) 4-hydroxybenzoic acid (a) and the optionally used modified (poly) 4-hydroxybenzoic acid derivative (a ') is 0. It is used in the range of 0.5 to 3 times. If the sum of the number of moles of the carboxyl groups of the (poly) 4-hydroxybenzoic acid (a) and the modified (poly) 4-hydroxybenzoic acid derivative (a ′) is less than 0.5, the polyhydric alcohol (b) And the above-mentioned (poly) 4-hydroxybenzoic acid (a) and the modified poly-4-hydroxybenzoic acid derivative, and the content of the ester group obtained by the reaction of (a ′) becomes low, and the color sensitivity tends to be insufficient. . Also, 3
If it exceeds twice, unreacted (poly) 4-hydroxybenzoic acid (a) or modified (poly) benzoic acid derivative (a ') remains, and there is a tendency for background fog to occur. In the present invention, the developer (ii) contains at least the esterification reaction product (e) of the trihydric or higher polyhydric alcohol (b) and the (poly) 4-hydroxybenzoic acid (a). Carboxylic acid component including (poly) 4-hydroxybenzoic acid (a), optionally added modified poly-4-hydroxybenzoic acid derivative (a '), and other polyvalent carboxylic acid components An ester reaction product of (A), a trihydric or higher polyhydric alcohol (b) and a polyhydric alcohol component (B) containing another polyhydric alcohol component may be used. )

Further, in the color developer according to the heat-sensitive recording material of the present invention, 1 mol of the (poly) 4-hydroxybenzoic acid (a) represented by the general formula (I) is used with respect to 1 mol of the general formula (III). The molar ratio of the (poly) 4-hydroxybenzoic acid derivative (a ′) represented by the formula (1) is not particularly limited, but is preferably in the range of 0.01 to 2. The molar ratio is 0.
If it is less than 01, the background fog tends to occur easily,
If it exceeds 2, the coloring sensitivity tends to be insufficient.

The amount of the developer obtained by the ester reaction is particularly limited because it varies depending on the required properties such as recording suitability and the type and amount of the color former or other additives used in combination. Although not particularly limited, usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, is used per 1 part by weight of the color former. If the amount of the developer is less than 0.01 part by weight, the color sensitivity may be insufficient, and if the amount is more than 10 parts by weight, the effect may not be further increased. It is uneconomical.

Acidic cyclic phosphate compounds of alkylidene bisphenols In the present invention, acidic cyclic phosphate compounds of alkylidene bisphenols represented by the general formula (II) (ii)
i) is used as a storage stabilizer and is used in combination with a color developer. Compound (iii) is usually produced by reacting phosphorus trichloride or phosphorus oxychloride with 2,2′-alkylidene phenol, hydrolyzing it to form a cyclic acidic phosphate, and then oxidizing as necessary. Is done. After the production, it is filtered and dried to obtain the desired product, and if necessary, crushed and used as a storage stabilizer.

In the compound represented by the general formula (II), the alkyl group having 1 to 8 carbon atoms represented by R ₁ and R ₂ includes methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, Tert-butyl, isobutyl, amyl, tertiary amyl, hexyl, 1-ethylpentyl, heptyl,
Isoheptyl, tertiary heptyl, 1-ethylheptyl, octyl, tertiary octyl, 2-ethylhexyl and the like can be mentioned. More specifically, the following compound No. 1 to No. 3
Is mentioned.

[0023]

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[0024]

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[0025]

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The addition amount of the compound (iii) is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 1 part by weight of the color former. If the amount is less than 0.01 part by weight, the storage stability effect becomes insufficient, and if the amount exceeds 10 parts by weight, the effect may not be further increased, which is uneconomical.

The heat-sensitive recording material of the present invention may contain, as necessary, fillers, pigments, additives such as calcium carbonate, talc, titanium dioxide, zinc white, metal soap, and a sensitizer (s) as described below. Metal salts of organic acids and the like can be added. A part of the compound (iii) may react with a metal compound in a filler, a pigment, an additive or a sensitizer (s) to form a metal salt of an alkylidene bisphenol cyclic phosphate. Even in this case, as long as the acidic cyclic phosphate compound remains in the above range, the effect of the present invention, that is, the effect as a storage stabilizer after recording is not affected at all.

Sensitizer When the recording material is a heat-sensitive recording material, one or two or more sensitizers (s) can be used in combination in order to enhance color development sensitivity. Examples of the sensitizer (s) include zinc acetate, zinc octylate, zinc laurate, zinc stearate, zinc oleate, zinc behenate, zinc benzoate, zinc salt of dodecyl salicylate, calcium stearate, and magnesium stearate. And metal salts of organic acids such as aluminum stearate; stearamide, beheninamide, methylolamide stearate, stearoyl urea, acetanilide, acetotoluide, acetoacetic anilide, acetoacetic-o-chloroanilide, benzoylacetic anilide, benzoic acid Amide compounds such as stearylamide, ethylenebisstearic acid amide and hexamethylenebisoctylamide;
1,2-bis (3,4-dimethylphenyl) ethane, m
Terphenyl, 1,2-diphenoxyethane, 1,2
-Bis (3-methylphenoxy) ethane, p-benzylbiphenyl, p-benzyloxybiphenyl, diphenyl carbonate, bis (4-methylphenyl) carbonate, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis ( 4-chlorobenzyl) oxalate, phenyl 1-hydroxy-2-naphthalenecarboxylate, benzyl 1-hydroxy-2-naphthalenecarboxylate, phenyl 3-hydroxy-2-naphthalenecarboxylate, methylenebenzoate, 1,4-bis (2 -Vinyloxyethoxy) benzene, 2-benzyloxynaphthalene, 4-benzyloxybenzoyl benzyl, dimethylphthalate, dibenzyl terephthalate, dimethyl terephthalate, diethyl terephthalate, dibutyl terephthalate,
Di (2-hydroxyethyl) terephthalate, (2-hydroxypropyl) terephthalate, dibenzoylmethane,
Diphenyl sulfone, p-toluenesulfonic acid anilide, 4-methylphenoxy-p-biphenyl, 4-chlorophenylphenyl sulfone and the like can be used. Of these, dimethyl terephthalate, diethyl terephthalate, dibutyl terephthalate, di (2-hydroxyethyl) terephthalate, (2-hydroxypropyl) terephthalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) ) Oxalate, acetoacetic acid-o-chloroanilide, diphenyl sulfone, stearic acid amide, methylolamide stearate and the like are preferably used.

These sensitizers are usually used as a color former (i)
(Also referred to as a coloring substance or a dye.) 0.01 to 10 parts by weight per 1 part by weight is used. Sensitizer 0.01
If the amount is less than 10 parts by weight, the effect of addition cannot be obtained. Conversely, if the amount exceeds 10 parts by weight, the sensitivity is hardly improved, and the storage stability effect is rather reduced. When a sensitizer is used as a raw material, it can be used separately from the above other raw materials,
It can be used as a raw material after being melt-mixed with a developer in advance.

Coloring Agent The coloring agent (i) used in the recording layer of the heat-sensitive recording material of the present invention may be any of various well-known dyes, which are usually colorless or pale, and are used in general recording materials and the like. Is not particularly limited as long as it is Specific examples of these color formers include: (i) 3,3-bis (p-dimethylaminophenyl)-
6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (2-phenyl-3-indolyl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethyl-3-indolyl) phthalide, 3,
3-bis (9-ethyl-3-carbazolyl) -5-dimethylaminophthalide, 3,3-bis (2-phenyl-3
-Indolyl) -5-dimethylaminophthalide, 3-
(4-diethylaminophenyl) -3- (1-ethyl-
2-methylindol-3-yl) phthalide, 3,3-
Bis [2- (4-dimethylaminophenyl) -2- (4
-Methoxyphenyl) vinyl] -4,5,6,7-tetrachlorophthalide and other triarylmethane compounds;

(Ii) diphenylmethane compounds such as 4,4-bis (dimethylamino) benzhydrin benzyl ether and N-2,4,5-trichlorophenylleuco auramine; (iii) rhodamine-β-anilinolactam , 3- (N
-Methyl-N-cyclohexylamino) -6-methyl-
7-anilinofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-
(2-chloroanilino) fluoran, 3-diethylamino-7- (2-fluoroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7- (2,4-dimethylanilino) fluoran, 3-diethylamino-7-
Dibenzylaminofluoran, 3-diethylamino-6
-Chloro-7- (β-ethoxyethylamino) fluoran, 3-diethylamino-6-chloro-7- (γ-chloropropylamino) fluoran, 3- (N-ethyl-N
-Isoamylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-ethoxyethylamino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-N-tetrahydrofurfurylamino) -6
Methyl-7-anilinofluoran, 3-dibutylamino-7- (2-chloroanilino) fluoran, 3- (N-
Ethyl-N-tolylamino) -6-methyl-7-anilinofluoran, 3- (N, N-dibutylamino) -6
Methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (4
Xanthene-based compounds such as -anilino) anilino-6-methyl-7-chlorofluoran;

(Iv) benzoylleucomethylene blue,
thiazine compounds such as p-nitrobenzoyl leucomethylene blue; (v) 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran And spiro compounds such as 3-propylspirodibenzopyran; (vi) other 3,5 ', 6-tris (dimethylamino)
-Spiro [9H-fluorene-9,1 '-(3'H)-
Isobenzofuran] -3′-one, 1,1-bis [2-
(4-dimethylaminophenyl) -2- (4-methoxyphenyl) ethenyl] -4,5,6,7-tetrachloro (3H) isobenzofuran-3-one, 3- (4-diethylamino-2-ethoxyphenyl) ) -3- (1-Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl-2-methylindole-3-
Il) -4-azaphthalide, phenoxazine derivatives and the like, and these dyes can be used in combination of several kinds.

Of these examples (i) to (vi), 3-
(N, N-dibutylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran and the like are preferably used. The recording material of the present invention may optionally contain a chelating color former such as aliphatic ferric iron.

Other Developers When it is necessary to further increase the color development sensitivity in the heat-sensitive recording material of the present invention, if necessary, other well-known developers such as phenolic, carboxylic acid or metal-based ones may be used. One or more colorants can be used in combination. The amount of the developer (ii) of the present invention can be reduced by using these other developers in combination.

Examples of the other color developing agents include, for example, p-octylphenol, p-tert-butylphenol, p-phenylphenol, p-hydroxyacetophenone, α
-Naphthol, β-naphthol, p-tert-octylcatechol, 2,2′-dihydroxybiphenyl, bisphenol A, 1,1-bis (p-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) heptane , 2,2-bis-((3-methyl-4-hydroxyphenyl) propane), 2,2-bis- (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5 -Dichloro-4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3,4-dihydroxyphenyl) sulfone, 2,
4'-dihydroxydiphenyl sulfone, 1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4
-Hydroxyphenyl) ether, bis [2- (4-hydroxyphenylthio) ethoxy] methane, 4- (4-
Isopropoxybenzenesulfonyl) phenol, 4-
Dimethyl hydroxyphthalate, butyl bis (4-hydroxyphenyl) acetate, benzyl p-hydroxybenzoate, 3,5-ditert-butylsalicylic acid, 2,4-dihydroxybenzanilide, 2,4-dihydroxy-2′-
Methoxybenzanilide, 2,4-dihydroxy-
2 ′, 4′-dimethylbenzanilide, 2,4-dihydroxy-2′-methoxy-5′-methylbenzanilide, bis (4- (2,4-dihydroxyphenylcarbonylamino) -3-methoxyphenyl) methane, Examples include phenols such as 4-methylbenzenesulfonic acid-2-hydroxyanilide, phenolic resins such as novolak phenol, resorcinols, organic carboxylic acids such as benzoic acid, and metal salts such as zinc salicylate. It is preferable to use a coloring agent.

Other Storage Stabilizers In the heat-sensitive recording material of the present invention, one or more other storage stabilizers may be used as a raw material for the recording layer, if necessary. Examples of the other storage stabilizer include 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,1
3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-butylidenebis (2-tert-butyl-5-methylphenol), 4,4 '
-Thiobis (2-tert-butyl-5-methylphenol), 2,2'-thiobis (6-tert-butyl-4-methylphenol), 2,2'-methylenebis (6-tert-butyl-4-methylphenol) Hindered phenol compounds such as phenol), 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenylsulfone, sodium-
2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and the like. These storage stabilizers are usually preferably 0.01 to 10 parts by weight per 1 part by weight of a color former (dye). Parts by weight are used. When the other storage stabilizer is less than 0.01 part by weight, the effect of addition cannot be obtained and 1
When used in excess of 0 parts by weight, the sensitivity hardly improves, but the storage stability effect decreases.

Heat-sensitive recording material In the heat-sensitive recording material of the present invention, the color developing agent, storage stabilizer, sensitizer and the like used are usually mixed with a grinding machine such as a ball mill, an attritor, a sand grinder or an appropriate emulsifying device. It is made into fine particles, and is further prepared as a coating liquid by adding various additives according to the purpose.

[0038] The coating solution usually contains polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,
Polyvinylpyrrolidone, polyacrylamide, starch, styrene-maleic anhydride copolymer, vinyl acetate-
Binders such as maleic anhydride copolymer, styrene-butadiene copolymer or modified products thereof; fillers such as kaolin, silica, diatomaceous earth, talc, titanium dioxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, melamine, etc. It is compounded, but in addition to this, metal soaps,
Amides, waxes, light stabilizers, water-proofing agents, dispersants, defoamers and the like can be used as needed.

The heat-sensitive recording material may be provided with an overcoat layer for the purpose of imparting a higher storage stability, and may be provided with an undercoat layer for improving the color sensitivity.

As the overcoat layer, for example,
An epoxy compound formed by applying a photo-curable resin, an electron beam-curable resin, or a thermosetting resin and then curing to form a film, or by coating a latex or water-soluble polymer capable of forming a film. A crosslinking agent or a curing agent such as the above may be used in combination. Any known method may be used for coating, and the thickness of the coat layer is not limited at all, and is appropriately selected so as to obtain desired performance. Examples of the undercoat layer include, for example, a layer containing an inorganic pigment and / or an organic pigment and an adhesive as main components,
A layer mainly composed of an expandable filler and an adhesive; a layer mainly composed of a granular and / or fibrous inorganic and / or organic hollow material and an adhesive; a water-soluble polymer or a water-dispersible polymer compound By using a material having excellent heat insulating properties, such as a foamed layer formed of a coating solution obtained by mechanically foaming an aqueous solution containing, color development with a small amount of energy becomes possible. Also in the undercoat layer, the coating method and the thickness of the coat layer are not particularly limited, and are appropriately selected so as to obtain desired performance.

Further, the heat-sensitive recording medium has a particularly high light resistance,
When the storage stability of the background portion is required, one or more known hindered amine light stabilizers and / or ultraviolet absorbers are added to the heat-sensitive recording layer and / or the overcoat layer. You can also.

The hindered amine light stabilizer includes:
For example, 2,2,6,6-tetramethyl-4-piperidyl benzoate, N- (2,2,6,6-tetramethyl-4-piperidyl) dodecylsuccinimide, 1-
[(3,5-di-tert-butyl-4-hydroxyphenyl)
Propionyloxyethyl] -2,2,6,6-tetramethyl-4-piperidyl- (3,5-di-tert-butyl-4
-Hydroxyphenyl) propionate, bis (2,
2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4) -Piperidyl) -2-butyl-2-
(3,5-ditert-butyl-4-hydroxybenzyl) malonate, N, N-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine, tetra (2,2,6 6-tetramethyl-4-piperidyl) butanetetracarboxylate, tetra (1,2,2,
6,6-pentamethyl-4-piperidyl) butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) di (tridecyl) butanetetracarboxylate, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) di (tridecyl) butanetetracarboxylate, 3,9-bis [1,1-dimethyl-2- {tris (2,2,6,6-tetramethyl-4)
-Piperidyloxycarbonyloxy) butylcarbonyloxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [1,1-
Dimethyl-2- {tris (1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyloxy) butylcarbonyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane , 1,5,8,
12-tetrakis [4,6-bis {N- (2,2,6,
6-tetramethyl-4-piperidyl) butylamino｝-
1,3,5-triazin-2-yl] -1,5,8,1
2-tetraazadodecane, 1- (2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / dimethyl succinate condensate, 2-tert-octylamino-4,6-dicyclo-s -Triazine / N, N-bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine condensate, N, N′-bis (2
2,6,6-tetramethyl-4-piperidyl) hexamethylenediamine / dibromoethane condensate.

Further, as the ultraviolet absorber, for example,
2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-
2-hydroxybenzophenones such as octoxybenzophenone and 5,5'-methylenebis (2-hydroxy-4-methoxybenzophenone); 2- (2-hydroxy-5-methylphenyl) benzotriazole,
(2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-ditert-butylphenyl) -5-chlorobenzotriazole,
-(2-hydroxy-3-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3,5-dicumylphenyl) benzotriazole, 2,2'-methylenebis (4 -Third octyl-6
-Benzotriazolylphenol), polyethylene glycol ester of 2- (2-hydroxy-3-tert-butyl-5-carboxyphenyl) benzotriazole, 2
-[2-hydroxy-3- (2-acryloyloxyethyl) -5-methylphenyl] benzotriazole,
-[2-hydroxy-3- (2-methacryloyloxyethyl) -5-tert-butylphenyl] benzotriazole, 2- [2-hydroxy-3- (2-methacryloyloxyethyl) -5-tert-octylphenyl] Benzotriazole, 2- [2-hydroxy-3- (2-methacryloyloxyethyl) -5-tert-butylphenyl]-
5-chlorobenzotriazole, 2- [2-hydroxy-5- (2-methacryloyloxyethyl) phenyl]
Benzotriazole, 2- [2-hydroxy-3-tert-butyl-5- (2-methacryloyloxyethyl) phenyl] benzotriazole, 2- [2-hydroxy-3
-Tert-amyl-5- (2-methacryloyloxyethyl) phenyl] benzotriazole, 2- [2-hydroxy-3-tert-butyl-5- (3-methacryloyloxypropyl) phenyl] -5-chlorobenzotriazole, 2- [2-hydroxy-4- (2-methacryloyloxymethyl) phenyl] benzotriazole, 2-
[2-hydroxy-4- (3-methacryloyloxy-
2- (2-hydroxyphenyl) benzotriazoles such as 2- (2-hydroxypropyl) phenyl] benzotriazole and 2- [2-hydroxy-4- (3-methacryloyloxypropyl) phenyl] benzotriazole; -4-methoxyphenyl)-
4,6-diphenyl-1,3,5-triazine, 2-
(2-hydroxy-4-hexyloxyphenyl) -4,
6-diphenyl-1,3,5-triazine, 2- (2-
(Hydroxy-4-octoxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [2-hydroxy-4- (3-C12-13 mixed alkoxy-2) -Hydroxypropoxy) phenyl]
-4,6-bis (2,4-dimethylphenyl) -1,
3,5-triazine, 2- [2-hydroxy-4- (2
-Acryloyloxyethoxy) phenyl] -4,6-
Bis (4-methylphenyl) -1,3,5-triazine, 2- (2,4-dihydroxy-3-allylphenyl) -4,6-bis (2,4-dimethylphenyl)-
1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-hexyloxyphenyl)-
2- (2-hydroxyphenyl) -4,6-diaryl-1,3,5-triazines such as 1,3,5-triazine; phenyl salicylate, resorcinol monobenzoate, 2,4-di-tert-butylphenyl- Benzoates such as 3,5-di-tert-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate; 2-ethyl-2'-ethoxyoxanilide, 2-ethoxy- Substituted oxanilides such as 4'-dodecyl oxanilide; ethyl-α-cyano-
Cyanoacrylates such as β, β-diphenylacrylate, methyl-2-cyano-3-methyl-3- (p-methoxyphenyl) acrylate; various metal salts or metal chelates, particularly nickel or chromium salts or chelates But 2- (2-hydroxyphenyl) benzotriazoles are particularly preferred.

The light stabilizer and the ultraviolet absorber are added in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 1 part by weight of the color former (i). If the amount is less than 10 parts by weight, the stabilizing effect cannot be sufficiently obtained. If the amount is more than 10 parts by weight, not only is it wasteful but also the physical properties of the coating film may be adversely affected.

The above-mentioned heat-sensitive recording material is particularly useful in various recording fields such as recording paper for measurement, computers, facsimile machines, telex, vending machines such as tickets, prepaid cards, labels, receipts and the like.

[0046]

The present invention will be described in more detail with reference to Production Examples (Synthesis Examples), Examples and Comparative Examples. However, the scope of the present invention is not limited at all by the following examples.

(Production Example 1) Synthesis of Developer Test Sample A A 100 ml round bottom flask was charged with 12.7 g of dipentaerythritol, 48.4 g of 4-hydroxybenzoic acid, and 0.43 g of tetraisopropoxytitanate.
The reaction was performed at 0 ° C. for 4 hours. After cooling, it was dissolved in 300 ml of ethyl acetate, washed with water and separated into oil and water. After the solvent was distilled off, the residue was dissolved in 50 g of ethanol, and activated carbon and silica gel were added to adsorb impurities. A solution obtained by filtering and excluding activated carbon and silica gel was dropped into 150 g of toluene to precipitate crystals, and 39.98 g of white crystals (82% yield).
I got This was designated as developer test sample A.

(Production Example 2) Synthesis of Developer Test Sample B A 500-ml round bottom flask was charged with 55.25 g of 4-hydroxybenzoic acid, 45.39 g of DCC (dicyclohexylcarbodiimide), and 200 ml of ethyl acetate. The reaction was carried out at 77 ° C. for 2 hours. After cooling, the precipitate was removed by filtration, and the solvent was distilled off to obtain a crude crystal. The crude crystals were purified using a silica gel column using a mixed solvent of hexane / ethyl acetate = 8/2 as a mobile phase,
26.05 g (50.5% yield) of the intermediate (4'-carboxy) phenyl 4-hydroxybenzoate was obtained.
Subsequently, 26.05 g of the obtained (4'-carboxy) phenyl 4-hydroxybenzoate, 4.32 g of dipentaerythritol, 0.3 g of p-toluenesulfonic acid and 30 g of 4-methylanisole were charged, and the mixture was placed under a nitrogen stream. 1
The reaction was carried out at 75 ° C. for 3 hours. After confirming that 1.9 g of water had distilled out into the water separator, the mixture was cooled. After cooling, it was dissolved in 100 ml of ethyl acetate, washed three times with 80 ml of diluted alkaline water and three times with 80 ml of water, and separated into oil and water. Take the organic layer,
After the solvent was distilled off, the residue was dissolved in 150 g of ethanol, and activated carbon and silica gel were added to adsorb impurities.
The activated carbon and silica gel were removed by filtration, and the solid obtained by distilling off the solvent was pulverized to obtain 19.6 g (yield 68%) of a slightly yellowish white powder. This was designated as a developer test sample B.

(Production Example 3) Synthesis of Developer Test Sample C In a 200 ml round bottom flask, 12.7 g of dipentaerythritol, 62.15 g of 4-hydroxybenzoic acid, 0.1 g of sulfuric acid and 50 g of 4-methylanisole were placed. The mixture was charged and reacted at 175 ° C. for 3 hours under a nitrogen stream. After confirming that 8.1 g of water had distilled out into the water separator, the mixture was cooled. After cooling, it was dissolved in 150 ml of ethyl acetate, washed three times with 100 ml of diluted alkaline water and three times with 100 ml of water, and separated into oil and water. After the organic layer was removed and the solvent was distilled off, the residue was dissolved in 300 g of ethanol, and activated carbon and silica gel were added to adsorb impurities. The activated carbon and silica gel were removed by filtration, and the solid obtained by distilling off the solvent was pulverized to obtain 50.10 g (yield 75%) of a slightly yellowish white powder. This was used as a developer test sample C.

(Synthesis of Intermediate (1) Consisting of Esterification Reaction Product (e) between Essential Components) In a 1000 ml round bottom flask, 230 g of Solvesso 150 ^™ (manufactured by Esso, aromatic solvent), 25.4 g of pentaerythritol, 4-hydroxybenzoic acid
5 g and sulfuric acid 0.25 g were charged and reacted at 190 ° C. for 5 hours while distilling off generated water. After cooling, washing with water and distilling off the solvent, the residue was dissolved in 100 g of ethanol, and Kyoward 500 (manufactured by Kyowa Chemical Industry Co., Ltd., acid adsorbent: Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O) ), Activated carbon,
4 g of each silica gel was added and stirred for 30 minutes. The solid was filtered, and the filtrate was dropped into 200 g of toluene to precipitate crystals, thereby obtaining 135 g of an intermediate, which was a white crystal having a softening point of about 115 ° C. (peak top temperature according to DTA) and a number average molecular weight of 2030.

(Synthesis of Intermediate (2) Consisting of Esterification Product (e) between Essential Components) In a 1000 ml round bottom flask, 230 g of aromatic Solvesso 150 ^™ , tetratrimethylolpropane
3 g, 83.0 g of 4-hydroxybenzoic acid, sulfuric acid 0.3
0 g, and distilling off generated water at 190 ° C.
Allowed to react for hours. After cooling, washing with water and distilling off the solvent,
The residue is dissolved in 100 g of ethanol, and Kyoward 5
00 ^TM , activated carbon and silica gel were added in amounts of 4 g each,
For a minute. The solid content was filtered, and the filtrate was 200 g of toluene.
At a temperature of about 100 ° C. (DT
A), and 127 g of a white crystal having a number average molecular weight of 1560 was obtained.

(Production Example 4) Synthesis of Developer Test Sample D The above intermediate (1) was placed in a 200 ml round bottom flask.
5 g, diethylene glycol dimethyl ether 60.0
g, acetic anhydride 6.12 g, and 100 ° C. for 3 hours.
Further, the reaction was carried out at 190 ° C. for 1 hour. The solvent was exchanged for ethanol, and this solution was added dropwise to toluene. The solid obtained was dried, and its softening point: about 106 ° C., IR absorption wave number: 1715c
m ^-1 , 1320 cm ^-1 , 1100 cm ^-1 (derived from aromatic ester), 1760 cm ^-1 , 1195 cm ^-1 (derived from acetate group) 1380 cm ^-1 , 620 cm
^-1 (from higher phenols), 1110 cm ^-1 (derived from ether) to give 19.3g of developer test sample D having a number average molecular weight 2305. PMR ( ¹ HNM)
R) was measured. As a result of calculation from the number of ring protons and the number of protons of the modifying group, the ratio of unmodified phenolic OH group to modified phenolic OH (unmodified-modified ratio) was 1.
0: 1.0.

(Preparation Example 5) Synthesis of Developer Test Sample E A developer test sample E was obtained in the same manner as in Preparation Example 4, except that the amount of acetic anhydride was changed to 3.06 g. Softening point: about 110 ° C, IR absorption wave number: 1715 cm ^-1 ,
1320cm ^-1, 1100cm ^-1 (from above aromatic ester), 1760cm ^-1, 1195cm ^-1 (derived from more acetate groups) 1380 cm ^-1, (from higher phenols) 620 cm ^-1, (from ether) 1110 cm ^-1 ,
The number average molecular weight is 2170, and the unmodified-modified ratio is 1.0: 0.
33.

(Production Example 6) Synthesis of Developer Test Sample F The developer test sample F was obtained in the same manner as in Production Examples 4 and 5 except that the amount of acetic anhydride was changed to 1.53 g. Softening point: about 113 ° C., IR absorption wave number: 1715 cm ⁻¹ ,
1320cm ^-1, 1100cm ^-1 (from above aromatic ester), 1760cm ^-1, 1195cm ^-1 (derived from more acetate groups) 1380 cm ^-1, (from higher phenols) 620 cm ^-1, (from ether) 1110 cm ^-1 ,
The number average molecular weight is 2090, and the unmodified-modified ratio is 1.0: 0.
11.

(Production Example 7) Synthesis of Developer Test Sample G The above intermediate (1) 9.7 was placed in a 100 ml round bottom flask.
5 g, diethylene glycol dimethyl ether 30.0
g, 1.33 g of diketene, 3 drops of pyridine were added, and the mixture was stirred for 30 minutes and reacted at 100 ° C. for 3 hours.
The solvent was exchanged for ethanol, this solution was added dropwise to toluene, and the solid obtained was dried. The softening point was about 110 ° C., and the IR absorption wave numbers were 1715 cm ⁻¹ , 1320 cm ⁻¹ and 1100 cm.
^-1 (above derived from aromatic ester), 1600 cm ^-1 , 17
55cm ^-1 (above derived from acetoacetate group) 1380
cm ^-1 , 620 cm ^-1 (derived from phenols), 11
9.9 g of a developer test sample G having a size of 10 cm ^-1 (derived from ether) and a number average molecular weight of 2,300 was obtained. The unmodified-acetoacetyl group modification ratio was 1.0: 0.33.

(Production Example 8) Synthesis of Developer Test Sample H In a 100 ml round bottom flask, 9.7 of the above intermediate (1) was added.
5 g, diethylene glycol dimethyl ether 30.0
g, 1.88 g of phenyl isocyanate, 3 drops of pyridine were added, and the mixture was stirred for 30 minutes and reacted at 100 ° C. for 3 hours. The solvent was exchanged for ethanol, and this solution was added dropwise to toluene. The solid obtained was dried and had a softening point of about 111.
° C, IR absorption wave number: 1715 cm ^-1 , 1320 cm ^-1 ,
1100 cm ^-1 (derived from aromatic ester), 1685
cm ^-1, 1495cm ^-1 (or phenylcarbamoyl group derived) 1380 cm ^-1, (from higher phenols) 620 cm ^-1, 1110 cm ^-1 (derived from ether), 10 a developer test sample H having a number average molecular weight 2410. 2 g were obtained. Unmodified-phenylcarbamoyl group modification ratio is 1.0: 0.3
3.

(Production Example 9) Synthesis of Developer Test Sample I The above intermediate (2) was placed in a 100 ml round bottom flask.
3 g, diethylene glycol dimethyl ether 30.0
g and 1.50 g of acetic anhydride, and reacted at 100 ° C. for 3 hours. After further reacting at 190 ° C. for 1 hour, the solvent was exchanged for ethanol, the solution was added dropwise to toluene, and the solid obtained was dried. Softening point: about 93 ° C., IR absorption wave number:
1715 cm ^-1 , 1320 cm ^-1 , 1100 cm ^-1 (derived from aromatic ester), 1760 cm ^-1 , 1195c
m ^-1 (derived from acetate group) 1375 cm ^-1 , 61
0 cm ^-1 (derived from phenols), 1115 cm
^-1 (from ether), 1380 cm ^-1 , 620 cm
9.8 g of a developer test sample I having an average molecular weight of 1640 ( ^-1 from phenols). The unmodified-acetyl group modification ratio is 1.0: 0.33.

[Example 1 Series] (Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-7) 3
5 g of (N, N-dibutylamino) -6-methyl-7-anilinofluoran was added to 25 g of a 10% by weight aqueous solution of polyvinyl alcohol, and sufficiently pulverized with a ball mill to obtain a dispersion 1 of the color former (i). A. Further, 5 g of bis (4-methylbenzyl) oxalate was sufficiently pulverized in a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 1-B of the sensitizer (s). Next, 5 g of each of the various color developer test samples obtained above was sufficiently pulverized with a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 1 of various color developers (ii).
C was obtained. Further, the compound N among the acidic cyclic phosphate compounds (iii) of alkylidene bisphenols
o. 3g was sufficiently pulverized in a ball mill together with 25g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 1-D of a storage stabilizer.

The above dispersions 1-A, 1-B, 1-C and 1
-D was mixed in a weight ratio of 1: 2: 1.5: 0.5, and 50 g of the mixture was mixed with 12.5% of calcium carbonate as an additive.
g, and sufficiently dispersed to obtain a coating liquid.
It was coated on a 0 g / m ² base paper at a dry thickness of 16 μm and dried to obtain a thermosensitive recording material. However, the blending of the storage stabilizer dispersion 1-D in Example 1-4, Example 1-5, and Comparative Examples 1-1 to 1-3 is as shown in Table 1. In Comparative Examples 1-4 to 1-7, a developer test sample A was used, and as an additive for improving storage stability, Comparative Compound No. 1 to Comparative Compound No. 4 were blended respectively.

[0060]

Embedded image

[0061]

Embedded image

[0062]

Embedded image

[0063]

Embedded image

Using the obtained heat-sensitive recording material, the color density and the background density (initial density) of a recorded image printed with a pulse width of 0.8 msec using a thermal printing apparatus (TH-PMD: manufactured by Okura Electric Co., Ltd.) ) Was measured using a Macbeth densitometer (model RD-933, manufactured by Macbeth). In order to examine the storage stability of the colored thermosensitive recording medium after recording, a heat-resistant storage stability test (under 80 ° C.,
4 hours storage), humidity resistance storage stability test (40 ° C, 90% R)
H, 24 hours), storage stability test (immersion at room temperature,
24 hours), and the density of the printed portion and the background portion was measured.
The results of these measurements are shown in Table 1.

[0065]

[Table 1]

[Example 2 Series] (Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-5) 3
5 g of-(N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran and 25 g of a 10% by weight aqueous solution of polyvinyl alcohol are sufficiently pulverized by a ball mill to prepare a dispersion 2-A of the color former (i). I got Also, 5 g of a sensitizer bis (4-methylbenzyl) oxalate is prepared,
A sensitizer (s) dispersion liquid 2 was sufficiently pulverized with a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol.
B was obtained. Next, 5 g of each developer test sample obtained above
Is thoroughly pulverized with a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 2 of the developer (ii).
-C was obtained. Further, among the acid cyclic phosphate compounds (iii) of the alkylidene bisphenols, the compound No. 5 g of No. 3 together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol was sufficiently pulverized with a ball mill to obtain a dispersion 2-D of a storage stabilizer. However, for the comparative example, a developer or a storage stabilizer as shown in Table 2 was used. The dispersions 2-A, 2-B, 2-C and 2-D were mixed in a ratio of 1: 2:
1.5 were mixed in a weight ratio of 0.5, a mixture 50g to the addition of calcium carbonate 12.5 g, well dispersed as a coating liquid, the thickness of the coating solution to the paper based on the 50g / m ² 16μ
m and dried to obtain a heat-sensitive recording material. Using the obtained thermosensitive recording medium, the same test as in the series of Example 1 was performed. Table 2 shows the results of these measurements.

[0067]

[Table 2]

[Example 3 Series] (Examples 3-1 to 3-4 and Comparative Examples 3-1 to 3-4) 3
5 g of-(N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran and 25 g of a 10% by weight aqueous solution of polyvinyl alcohol are sufficiently pulverized by a ball mill to prepare a dispersion 3-A of the color former (i). I got In addition, 5 g of a sensitizer dimethyl terephthalate was prepared and sufficiently pulverized with a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 2-B of the sensitizer (s). Next, 5 g of each developer test sample obtained above was sufficiently pulverized in a ball mill together with 25 g of a 10% by weight aqueous solution of polyvinyl alcohol to obtain a dispersion 3-C of the developer (ii). Further, among the acid cyclic phosphate compounds (iii) of the alkylidene bisphenols, the compound No. 3
2.5 g of a 10% by weight aqueous solution of polyvinyl alcohol 2
5 g together with a ball mill was sufficiently pulverized to obtain a storage stabilizer dispersion 3-D. However, for the comparative example, Table 3
The developer or the storage stabilizer shown in Table 1 was used. Dispersion 3 above
-A, 3-B, 3-C and 3-D at 1: 2: 1.5:
The mixture was mixed at a weight ratio of 0.5, and 12.5 g of calcium carbonate was added to 50 g of the mixture, and the mixture was sufficiently dispersed to form a coating liquid. The coating liquid was applied to a base paper of 50 g / m ^{2 at} a thickness of 16 μm. And dried to obtain a thermosensitive recording material. Using the obtained heat-sensitive recording medium, the same tests as those in Examples 1 and 2 were performed. Table 3 shows the results of these measurements.

[0069]

[Table 3]

[Example 4 Series] (Examples 4-1 to 4-5) The developer in the dispersion 3-C was used as a developer test sample A, and the sensitizer in the dispersion 3-B was shown in Table 4. The test was conducted in the same manner as in Example 3 series, except that the test was replaced with the test described in Example 3. Table 4 shows the results.

[0071]

[Table 4]

As is apparent from the above Examples and Comparative Examples, when a cyclic phosphate hydroxide of an alkylidene bisphenol was used as the color developer and the specific storage stabilizer according to the present invention, the initial color development sensitivity was low. It is excellent and excellent in storage stability, and it is clear that even after the storage test, the discoloration of the colored portion and the background fog are extremely small. In comparison, when the specific alkylidene bisphenol cyclic phosphate hydroxide according to the present invention is not blended or when the alkylidene bisphenol cyclic phosphate sodium salt is blended, the initial color development sensitivity has no problem, The storage stability of the thermosensitive recording medium is not satisfactory.

[0073]

The color developer and the alkylidene bisphenol phosphate hydroxide according to the present invention are contained in the heat-sensitive recording layer, so that the color-sensitive portion is excellent in color-forming sensitivity and the discoloration of the color-developed portion and the background portion of the heat-sensitive recording material is small. A thermosensitive recording material having excellent stability can be obtained.

Claims (8)

[Claims] 1. A color former (i), a carboxylic acid component (A) containing (poly) 4-hydroxybenzoic acid (a) represented by the following general formula (I) as an essential component, and a trivalent or more polycarboxylic acid component: (Ii) having a structure represented by an esterification reaction product with a polyhydric alcohol component (B) containing a polyhydric alcohol (b) as an essential component, and an alkylidene represented by the following general formula (II) The acid cyclic phosphate compound (iii) of a bisphenol is added in an amount of 0.01 to 1 part by weight of the color former (i).
A heat-sensitive recording material containing from 10 to 10 parts by weight. Embedded image (In the formula, p represents an integer of 0 to 2.) (In the formula, R ₁ and R ₂ each independently represent an alkyl group having 1 to 8 carbon atoms.) 2. A structure wherein the esterification reaction product is represented by an esterification reaction product (e) of at least (poly) 4-hydroxybenzoic acid (a) and a trihydric or higher polyhydric alcohol (b). The heat-sensitive recording material according to claim 1, comprising: 3. A (poly) 4-hydroxybenzoic acid (a) represented by the general formula (I) and a (poly) 4 represented by the following general formula (III) in the carboxylic acid component (A). −
Hydroxybenzoic acid derivative (a ′) and 1: m (provided that
The heat-sensitive recording material according to claim 1, wherein the thermosensitive recording material is contained in a molar ratio of 0 <m ≦ 2). Embedded image (In the formula, q represents an integer of 0 to 2, X is a formyl group; an alkyl group having 1 to 18 carbon atoms, an alkyl group, an alkylcarbonyl group, an alkylcarbamoyl group or an alkylsulfonyl group; The number represents an aryl group, an arylcarbonyl group, an arylcarbamoyl group, an arylsulfonyl group, or an acetoacetyl group having 6 to 30.) 4. The heat-sensitive recording material according to claim 1, wherein the trihydric or higher polyhydric alcohol (b) is a compound represented by the following general formula (IV). Embedded image (In the formula, n represents an integer of 0 to 9, and R ₁ and n R _{2 s} each independently represent a hydroxymethyl group, a hydroxyethyl group, or an alkyl group having 1 to 8 carbon atoms.) 5. The heat-sensitive recording material according to claim 4, wherein in the general formula (IV), R ₁ and n R ₂ are each independently a hydroxymethyl group or a hydroxyethyl group. 6. The heat-sensitive recording material according to claim ₁ , wherein R ₁ and R ₂ in the formula (II) are tert-butyl groups. 7. The heat-sensitive recording material according to claim 1, further comprising a sensitizer (s). 8. The heat-sensitive recording material according to claim 1, further comprising calcium carbonate as a filler.