JPH0615262B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material utilizing a color reaction of a colorless or light-colored electron-donating contaminant precursor and an electron-accepting compound. Regarding recording material.

(Prior Art) A color reaction between a colorless or light-colored electron-donating dye precursor and an electron-accepting compound was used. So-called two-component thermal recording materials are disclosed in JP-B-45-14039 and JP-B-43-416.
No. 0 and the like.

A two-component color-developing heat-sensitive recording material is a colorless or light-colored electron-donating dye precursor and an electron-accepting compound dispersed in the form of fine particles, and a binder or the like is mixed into the fine particles to combine these two types of heat-reactive compounds into a binder or the like. It is coated on a support so as to be separated by, and one or both of them are heated to melt and contact each other by utilizing a color development reaction to provide a record. These two-component color-developing heat-sensitive recording materials have a primary color and do not require development. Paper quality is close to regular paper, easy to handle, high color density,
It is advantageous in that it can easily be used as a heat-sensitive recording material of various coloring hues and has a great utility value. Therefore, it is most often used as a thermal recording material.

In particular, the use of thermal recording materials in the field of facsimiles, recorders and printers has been remarkable in recent years. The recording speed has been increased with the widespread use in the field of facsimiles, but the color developability of a thermosensitive recording material with a short pulse width, that is, a color density that develops at a sufficient density even with low thermal energy, that is, There is a strong demand for improvement in thermal reactivity, and JP-A-58-1873
9, JP-A-59-67083, JP-A-60-548.
Various attempts have been made as disclosed in No. 84 and the like.

On the other hand, since these heat-sensitive recording materials have a primary color development, not only heat but also the drawback that the reaction between the electron-donating dye precursor and the electron-accepting compound occurs due to the solvent, and the electron-donating dye precursor. It has a drawback that the color-developing body produced by the thermal reaction of the electron-accepting compound and the electron-accepting compound causes discoloration of brown color due to oils and fats, chemicals and the like. Therefore, when touching water-based ink pens, oil-based ink pens, fluorescent pens, vermilion flesh, adhesives, glue, stationery such as diazo developers and office supplies, or cosmetics such as hand creams and emulsions, the white background of the thermal recording material may develop color. , The color-developed part had a discolored brown color, which significantly impaired the commercial value.

On the other hand, Japanese Patent Publication No.
7880, JP-A-48-30437, JP-A-48-3
Although efforts have been made to provide a protective layer having chemical resistance as disclosed in No. 1958 and the like, the provision of the protective layer lowers the color density and causes the mating property with the thermal head of the thermal recording apparatus. Is not sufficient, causing problems such as noise caused during staging and recording, and causing problems such as bleeding of ink due to poor writing properties of stationery and the like, and complicated manufacturing processes.

Further, as a method for improving the discoloration of the color-developed image, JP-B-51-43386, JP-A-53-17347,
JP-A-56-72996, JP-A-59-194891
No. 2074335A, etc., attempts have been made, but in any case, the effect of improving discoloration is insufficient, or although there is an effect, color development (fog) on white background It has drawbacks such as occurrence.

(Object of the Invention) An object of the present invention is to obtain a heat-sensitive recording material in which the color development of a white background due to storage of a solvent / chemical or storage under high temperature and high humidity is extremely small, and a generated color image is not easily discolored.

(Object of the Invention) An object of the present invention is to provide a salicylic acid derivative or a polyvalent metal salt thereof as a colorless or light-colored electron-donating dye precursor and an electron-accepting compound that reacts with the electron-donating dye precursor to develop a color. A heat-sensitive recording material having a heat-sensitive color forming layer containing 0.01 to 5.00% by weight of the sodium salt or potassium salt of the salicylic acid derivative with respect to the salicylic acid derivative or its polyvalent metal salt. Was achieved with a thermosensitive recording material.

Preferred compounds among the salicylic acid derivative and the polyvalent metal salt thereof according to the present invention are represented by the following general formula [I].

In formula (I), X and Y may be the same or different and each represents a hydrogen atom or an alkyl group.

Particularly preferred are a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms, but compounds having a total of 7 to 11 carbon atoms (for example, salicylic acid and methylsalicylic acid) are water-soluble and are therefore white. A compound having a total carbon atom number of 12 or more is preferable, and a compound having a total carbon atom number of 15 or more is particularly preferable from the viewpoint of water insolubility. M represents an n-valent metal atom, and n represents an integer. The metal atom represented by M is particularly preferably zinc, aluminum, magnesium and calcium.

Preferred specific examples of the salicylic acid derivative according to the present invention are shown below: 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-amylsalicylic acid, 3-phenyl-5-benzylsalicylic acid, 3-phenyl-5-t-octylsalicylic acid, 3-phenyl-5
-Α-methylbenzyl salicylic 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-
Dodecyl salicylic acid, 4-n-dodecyl salicylic acid, 4
-N-pentadecylsalicylic acid, 4-n-heptadecylsalicylic acid, 5- (1,3-diphenylbutyl) -salicylic acid, 5-n-octadecylsalicylic acid, 5-dodecylsulfonylsalicylic acid, 5-dodecylsulfosalicylic acid, 3- Methyl-5-dodecylsulfosalicylic acid and the like.

Preferred specific examples of the polyvalent metal salt of salicylic acid derivative according to the present invention include zinc, aluminum, magnesium and calcium salts of the salicylic acid derivative.

Examples of the colorless or light-colored electron-donating dye precursor used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, and the like. Specific examples thereof include those described in JP-A-55-27253.

For example, as a triallyl-methane compound, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lettactone) and 3,3-bis (triaryl-l-methane) compound can be given. p-Dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl)-
3- (2-methylindol-3-yl) phthalide and the like, and as a diphenylmethane compound, 4,4'-bis-
Dimethylaminobenzhydrin benzyl ether, N-
There are halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco olamine and the like, and xanthene compounds include rhodamine-B-anilinolactam, rhodamine (p-nitrino) lactam, 2
2- (benzylamino) fluorane, 2-phenylamino-6-diethylamino-fluorane, 2- (o-chloroanilino) -6-diethylaminofluorane, 2-
(3,4-dichloroanilino) -6-diethylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-phenyl-6-diethylaminofluorane and the like, and the thiazine-based compound is benzo. There are leuco methylene blue, p-nitrobenzyl leuco methylene blue and the like. Examples of spiropyran compounds include 3-methyl-spirodinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3′-dichloro-spiro-dinaphthopyran, 3
-Benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like. These may be used alone or as a mixture.

Among them, electron-donating dye precursors of triarylmethane-based compounds (for example, crystal biolettlactone) and xanthene-based compounds are preferable because many have less fog and give a high color density. A more preferable example is a xanthene compound represented by the following general formula (II).

In the general formula (II), the group represented by R ₁ and R ₂ is preferably an alkyl group having 1 to 10 carbon atoms, and forms a ring regardless of whether it is linear or branched. Or may further have a substituent. Also 5 to 7
May form a ring containing a member heteroatom.

R ₃ represents an aryl group, preferably an aryl group having 6 to 20 carbon atoms, and particularly preferably a phenyl group and a phenyl group having a substituent. As the substituent of the phenyl group, an alkyl group having 1 to 10 carbon atoms is preferable.

X is preferably an alkyl group having 1 to 10 carbon atoms or a halogen atom.

Examples of these colorless to light-colored electron-donating dye precursors include, but are not limited to, the following compounds.

2-anilino-3-methyl-6-dimethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N
-Ethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N- (iso-propyl) aminofluorane, 2-anilino-3-methyl-6-N-methyl-N-pentylaminofur Oran, 2-anilino-3-
Methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-chloro-6-dimethylaminofluorane, 2-anilino-3- Methyl-6
-N-ethyl-N-isoamylaminofluorane, 2-
Anilino-3-methyl-6-N-methyl-N-isoamylaminofluorane, 2-anilino-3-chloro-6-
Diethylaminofluorane, 2-anilino-3-chloro-6-N-methyl-N-ethylaminofluorane, 2-
Anilino-3-chloro-6-N-methyl-N- (iso
-Propyl) aminofluorane, 2-anilino-3-chloro-6-N-methyl-N-pentylaminofluorane, 2-anilino-3-chloro-6-N-methyl-N-
Cyclohexylaminofluorane, 2-anilino-3-
Methyl-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N-
Pentylaminofluorane, 2- (p-methylanilino) -3-methyl-6-dimethylaminofluorane, 2
-(P-Methylanilino) -3-methyl-6-dimethylaminofluorane, 2- (p-methylanilino) -3-
Methyl-6-N-methyl-N-ethylaminofluorane, 2- (p-methylanilino) -3-methyl-6-N
-Methyl-N- (iso-propyl) aminofluorane, 2- (p-methylanilino) -3-methyl-6-N
-Methyl-N-pentylaminofluorane, 2- (p-
Methylanilino) -3-methyl-6-N-methyl-N-
Cyclohexylaminofluorane, 2- (p-methylarilino) -3-methyl-6-N-ethyl-N-pentylaminofluorane, 2- (p-methylanilino) -3-
Chloro-6-dimethylaminofluorane, 2- (p-methylanilino) -3-chloro-6-diethylaminofluorane, 2- (p-methylanilino) -3-chloro-6
-N-methyl-N-ethylaminofluorane, 2- (p
-Methylanilino) -3-chloro-6-N-methyl-N
-(Iso-propyl) aminofluorane, 2- (p-
Methylanilino) -3-chloro-6-N-methyl-N-
Cyclohexylaminofluorane, 2- (p-methylanilino) -3-chloro-6-N-methyl-N-pentylaminofluorane, 2- (p-methylanilino) -3-
Chloro-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-
There are furylmethylaminofluorane, 2-anilino-3-ethyl-6-N-methyl-N-furylmethylaminofluorane and the like, and these may be used alone, but color adjustment and fading of color images are possible. You may use it in mixture of 2 or more types for prevention.

In the present invention, a compound other than the present invention may be used in combination as the electron-accepting compound. Specifically, JP-A-58-18
7393, JP-A-59-67083 and the like are exemplified, and as preferable examples, compounds represented by the following general formulas (III) to (VII) are preferable.

(In the formula, X is S, O, SO ₂ , S ₂ , Represents an integer of 0 to 3, R ₁ and R ₂ represent hydrogen, an alkyl group having 1 to 8 carbon atoms, or a cycloalkyl group formed by combining R ₁ and R ₂ .

R ₂ may be an ester represented by —COOR ′, and R ′ represents an alkyl group having 1 to 10 carbon atoms.
R represents a linear or branched alkyl group having 1 to 8 carbon atoms or a halogen atom. ) (Wherein, Y is _hydrogen, -CH 3, represents -OH, _{R 3} is Represents a straight-chain or branched alkyl group having 1 to 6 carbon atoms,
m, n is an integer of from 0 to 3, Z is hydrogen, halogen, -CH ₃
Represents ) (In the formula, R ₄ represents a benzyl group, a halogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.) (In the formula, R ₆ and R ₇ represent an alkyl group having 1 to 8 carbon atoms.) (In the formula, R ₈ represents an alkylene group having 1 to 5 ether bonds.) Specific examples of the compounds represented by the general formulas (III) to (VII) include 2,2-bis (4′-). Hydroxyphenyl) propane,
2,2-bis (4'-hydroxyphenyl) pentane,
2,2-bis (4'-hydroxy-3 ', 5'-dichlorophenyl) propane, 1,1-bis (4'-pydroxyphenyl) cyclohexane, 1,1-bis (4'-hydroxyphenyl) (Enyl) propane, 1,1-bis (4'-hydroxyphenyl) butane, 1,1-bis (4'hydroxyphenyl) pentane, 1,1-bis (4'-hydroxyphenyl) hexane, 1, 1-bis (4'-hydroxyphenyl) heptane, 1,1-bis (4'-hydroxyphenyl) -2-methyl-pentane, 1,1-bis (4'-hydroxyphenyl) -2-ethyl Hexane,
1,1-bis (4'-hydroxyphenyl) dodecane,
3,3-bis (4'-hydroxyphenyl) pentane,
1,2-bis (4'-hydroxyphenyl) ethane,
1,1-bis (4'-hydroxyphenyl) sulfone, 1,1-bis (4'-hydroxyphenyl) ether, 2,2-bis (4'-hydroxy-3 ', 5'-dichlorophenyl) ) Butane, phenyl 2,4-dihydroxybenzoate, phenyl 2,4-dihydroxy-4′-methylbenzoate, phenyl 2,4-dihydroxy-4′-chlorobenzoate, 2,4-dihydroxy-6-methylbenzoate Phenyl acid, 2,4,6-trihydroxybenzoic acid phenyl, 2,4-dihydroxy-6,4'-dimethylbenzoic acid phenyl, 2,4-dihydroxy-6-methyl-4'-chlorobenzoic acid phenyl, 2 Benzyl 4-dihydroxybenzoate, benzyl 2,4-dihydroxy-4'-methylbenzoate 2,4-Dihydroxy-4'-
Benzyl chlorobenzoate, 2,4-dihydroxy-6-
Benzyl methylbenzoate, benzyl 2,4,6-trihydroxybenzoate, 2,4-dihydroxy-6,4'-
Benzyl dimethyl benzoate, 2,4-dihydroxy-6
-Methyl-4'-chlorobenzoic acid benzyl, 4-hydroxybenzoic acid ethyl ester, 4-hydroxybenzoic acid propyl ester, 4-hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic acid-2 -Ethylhexyl ester, 4-hydroxy-4'-chlorobenzoic acid benzyl ester, 4-hydroxy-4'-methylbenzoic acid benzyl ester, 4-hydroxy-4'-ethylbenzoic acid benzyl ester, 3-hydroxy-m-phthalate Acid dimethyl, 3-hydroxy-m-diethyl phthalate, 3-hydroxy-m-methyl ethyl phthalate, 3-hydroxy-m-dibutyl phthalate, 3-hydroxy-o-dimethyl phthalate, 3-hydroxy-o- Diethyl phthalate,
Methyl-bis (4-hydroxyphenyl) acetate,
Examples include iso-butyl-bis (4-hydroxyphenyl) acetate.

Further, as the compound of the general formula (VII), specifically, Etc.

Preferred examples other than the electron-accepting compounds represented by the formulas (III) to (VII) are bis-hydroxycumylbenzene and bis-hydroxy-α-methylbenzylbenzenes.
1,4-bis-p-hydroxycumylbenzene, 1,4
-Bis-m-hydroxycumylbenzene, 1,3-bis-p-hydroxycumylbenzene, 1,3-m-hydroxycumylbenzene, 1,4-bis-o-hydroxycumylbenzene, 1,4 Examples thereof include, but are not limited to, -bis-p-hydroxy-α-methylbenzylbenzene and 1,3-bis-p-hydroxy-α-methylbenzylbenzene.

The electron-accepting compound is 50 to 8 of the electron-donating dye precursor.
It is preferably used in an amount of 00% by weight, more preferably 100 to 500% by weight. The salicylic acid derivative, which is an electron-accepting compound according to the present invention, and the metal salt thereof are preferably mixed in a ratio of 2000 to 10% by weight.

Moreover, you may use together 2 or more types of said electron-accepting compounds.

In the heat-sensitive recording material according to the present invention, a heat-fusible substance may be contained in the heat-sensitive color forming layer in order to improve its thermal response.

As an example of a preferable heat fusible substance, the following general formula (VIII)
The compounds represented by (XIII) to (XIII) are mentioned.

R ₅ NHCONH ₂ (XI) R ₆ CONH-R ₇ (XII) In the formula, R _{1 to} R ₄ are each a phenyl group, a benzyl group,
And R ₅ and R ₆ each represent an alkyl group having 12 or more and 24 or less carbon atoms, and R ₇ represents hydrogen or a phenyl group.

When the phenyl group or benzyl group represented by R _{1 to} R ₄ in the general formulas (VIII) to (X ^II ) is substituted with a lower alkyl group, the number of carbon atoms is 1 or more and 8 or less, preferably 1 or 3 It is the following. When it is substituted with a halogen atom, fluorine is preferable. Also, the formula (X)
In, R ₄ ′ represents hydrogen or a hydroxyl group.

In the formula (XIII), R ₈ represents a divalent group, preferably an alkylene group, an alkylene group having a carbonyl group, an alkyl group having a halogen atom, an alkylene group having an unsaturated bond, more preferably an alkylene group or an ether. An alkylene group having a bond is shown.

X, Y, Z, X ', Y'and Z'may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyloxycarbonyl group or an aralkyloxycarbonyl group,
A represents O or S.

The compounds of the general formulas (VIII) to (XIII) have a melting point of 70 ° C.
The melting point is preferably 150 ° C or higher and 150 ° C or lower, more preferably 80 ° C or higher and 130 ° C or lower. Specifically, benzyl p-benzyloxybenzoate (mp.119
C), β-naphthyl benzyl ether (mp. 105)
C.), stearic acid amide (mp.108 ° C.), palmitic acid amide (mp.103 ° C.), N-phenyl aeric acid amide (mp.96 ° C.), N-stearyl urea (m
p. 110 ° C.), β-naphthoic acid phenyl ester (m
p. 92 ° C.), 1-hydroxy-2-naphthoic acid phenyl ester (mp. 92 ° C.), β-naphthol (p-chlorobenzyl) ether (mp. 115 ° C.), β-naphthol (p-methylbenzyl) ether ( mp.96
C), α-naphthyl benzyl ether (mp. 76).
° C), 1,4-butanediol-p-methylphenyl ether (mp. 93 ° C), 1,4-propanediol-
p-methylphenyl ether (mp. 93 ° C), 1,4
-Butanediol-p-isopropylphenyl ether (mp. 79 ° C), 1,4-butanediol-pt-
Octyl phenyl ether (mp. 99 ° C), 2-phenoxy-1-p-tolyl-oxy-ethane (mp. 10)
4 ° C.), 1-phenoxy-2- (4-ethylphenoxy) ethane (mp. 106 ° C.), 1-phenoxy-2-
(4-chlorophenoxy) ethane (mp. 77 ° C),
1,4-butanediol phenyl ether (mp.98
C) diethylene glycol bis (4-methoxy-phenyl) ether (mp. 101 C), and the like.

The heat-fusible substances may be used alone or in combination, and in order to obtain a sufficient thermal response, it is preferable to use 10 to 200% by weight based on the electron-accepting compound. The preferred amount used is 20 to 150% by weight.

In the recording layer of the heat-sensitive recording material of the present invention, a water-soluble binder is added. As these binders, compounds that are soluble in 5% by weight or more in water at 25 ° C. are preferable, and specifically, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches (including modified starch), gelatin, arabic. Rubber, casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, carboxy-modified polyvinyl alcohol, polyacrylamide, vinyl acetate Examples thereof include saponified products of polyacrylic acid copolymers.

These binders may be used as a dispersant for finely dispersing an electron-donating dye precursor, an electron-accepting compound, a heat-fusible substance, and the compound according to the present invention.

Further, if necessary, the recording layer of the heat-sensitive recording material of the present invention, a pigment, a water-insoluble binder, a metal soap, wax,
Add a surfactant or the like.

As the pigment, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax, kaolin, aluminum hydroxide, silica, amorphous silica, etc. are used, but light calcium carbonate, kaolin, surface treatment Amorphous silica and aluminum hydroxide are preferred.

As the water-insoluble binder, synthetic rubber latex or synthetic resin emulsion is generally used, and styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, etc. are used. . In order to prevent fogging of the heat-sensitive recording material, the amount of the rubber latex or the surfactant in the emulsion is preferably as small as possible, and so-called soap-free rubber latex or emulsion is preferable.

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

As waxes, emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polyethylene wax, and the like are used.

As the surfactant, a sulfosuccinic acid-based alkali metal salt, a fluorine-containing surfactant or the like is used.

In the heat-sensitive recording material according to the present invention, it is preferable that the heat-sensitive color forming layer contains a compound that prevents decoloration in order to prevent decoloration of the printed image and to make the generated image fast.

A phenol derivative, particularly a hindered phenol compound, is effective as the decoloring inhibitor. Examples of preferable anti-decoloring agents include compounds represented by the following general formulas (XIV) to (XVIII).

(In the formula, R ₁ is a branched alkyl group having 3 to 8 carbon atoms, R ₂ is hydrogen or a branched alkyl group having 3 to 8 carbon atoms, and R ₃ is hydrogen or an alkyl group having 1 to 3 carbon atoms. , R ₄ is hydrogen or an alkyl group having 1 to 8 carbon atoms, R ₅ , R ₆ , and R ₇ are hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ₈ is hydrogen or an alkyl group having 1 to 8 carbon atoms. .) (In the formula, R ₁ and R ₃ represent a branched alkyl group having 3 to 8 carbon atoms, R ₂ and R ₄ represent an alkyl group having 1 to 8 carbon atoms, and X represents S, O, SO ₂ , S ₂ It represents a diclopentylene group or a cyclohexylene group, n represents an integer of 0 to 3, R ₅ and R ₆ represent hydrogen or an alkyl group having 1 to 8 carbon atoms. ) (In the formula, R ₁ and R ₄ are branched alkyl groups having 3 to 8 carbon atoms, and R ₂ , R ₃ , R ₅ , and R ₆ are hydrogen or an alkyl group having 1 to 8 carbon atoms.

Y is S, O, SO ₂ , S ₂ , And m is an integer of 0 to 3, R ₇ and R ₈ represent hydrogen or an alkyl group having 1 to 8 carbon atoms, or a cyclic pentamethylene group formed by combining R ₇ and R ₈ . ) (In the formula, R ₁ and R ₂ are branched alkyl groups having 3 to 8 carbon atoms, Z is —NH—, —O (CH ₂ ) _n is — (where n is 1
~ Represents an integer of 5), i represents an integer of 1 to 4. However, when i = 1, W is an alkyl group having 1 to 18 carbon atoms, when i = 2, W is S,
O, (Wherein R ₃ and R ₄ represent hydrogen or an alkyl group having 1 to 8 carbon atoms, j represents an integer of 0 to 8), and when i = 3, W is (Wherein R ₅ represents hydrogen or an alkyl group having 1 to 8 carbon atoms), and when i = 4, W is Represents ) Representative examples of the phenol derivatives represented by the above general formulas (XV) to (XVIII) are shown.

(A) The phenol derivative represented by the general formula (XV) includes 1,1,3-tris (2-methyl-4-hydroxy-5)
-Tert-butylphenyl) butane, 1,1,3-tris (2-ethyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (3,5-di-tert.
-Butyl-4-hydroxyphenyl) butane, 1,1,
3-tris (2-methyl-4-hydroxy-5-tert-
Butylphenyl) propane and the like.

(B) Examples of the phenol derivative represented by the general formula (XVI) include 2,2'-methylene-bis (6-tert-butyl-4-methylphenol) and 2,2'-methylene-bis (6-te).
rt-butyl-4-ethylphenol) and the like.

Examples of the phenol derivative represented by the general formula (XVII) (C) include 4,4′-butylidene-bis (6-tert-butyl-3-
Methylphenol) 4,4'-thio-bis (3-methyl-6-tert-butylphenol).

(D) As the phenol derivative represented by the general formula (XVIII), Etc.

The amount of the phenol compound represented by the general formulas (XV) to (XVIII) used is 1 to 200 with respect to the electron accepting compound.
It is preferably used in an amount of 5% by weight, more preferably 5 to 50% by weight.

(Examples of the Invention) Examples are shown above, but the present invention is not limited thereto. Weight% unless otherwise specified in the examples
Indicates.

The thermal response is from Fujitsu Limited High Speed Factory FF-200.
No. 3 was used to copy a test chart No. 3 of the Institute of Image Electronics Engineers of Japan, and the density was measured with a Macbeth RD-918 type densitometer.

The storability of heat-sensitive recording materials at high temperature and humidity is
Under conditions of 0 ° C., 30% RH) and humidity resistance (40 ° C., 90% RH), the uncolored thermosensitive recording material and the thermosensitive recording material colored by the above method were stored for 24 hours, and white areas before and after that were stored. The fog density, the density of the color-developed part, and the density of the sample developed after storage were measured with a Macbeth RD-918 type densitometer.

In addition, the preservability of the density of the color-developed part is (density after storage: density immediately after color development) × 100 (displayed in%)
Indicated by.

Table 1 shows the electron-accepting compounds used in the thermosensitive coloring layer according to the present invention. A mixture obtained by mixing the compounds in the ratios shown in the table is hereinafter referred to as a mixture of electron-accepting compounds.

Table 2 shows the materials used for the thermosensitive coloring layer according to the present invention.
20 g of each of the electron-donating dye precursor, the mixture of electron-accepting compounds, the heat-fusible substance, and the decoloring inhibitor are 5% of 100 g.
Disperse with a polyvinyl alcohol (Kuraray PVA-105) aqueous solution in a ball mill all day and night to obtain a volume average particle size of 3
It was set to μ or less.

The pigment was used by dispersing 80 g with a homogenizer together with 160 g of a 0.5% sodium hexametaphosphate solution. 5 g of the electron-donating dye precursor dispersion liquid, 10 g of the electron-accepting compound dispersion liquid, 5 g of the heat-fusible substance dispersion liquid, 2 g of the decoloring inhibitor dispersion liquid, and the pigment dispersion liquid were prepared as described above. The mixture was mixed at a ratio of 22 g, and 3 g of emulsion of 21% zinc stearate and 5 g of a 2% aqueous solution of sodium di (2-ethylhexyl) -sulfosuccinate were added to obtain a coating liquid.

The coating liquid thus obtained was coated on a high-quality paper having a basis weight of 50 g / m ^{2 with} a wire bar so that the dry coating amount was 7 g / m ² , and dried in an oven at 50 ° C. to obtain a heat-sensitive recording material. Obtained.

(Comparative columns 1 to 11) Examples 1 to 11 except that the sodium salt or potassium salt of salicylic acid derivative is not added in Examples 1 to 11.
A heat-sensitive recording material was obtained in the same manner as in.

Table 3 shows the test results.

Claims (1)

[Claims] 1. A thermosensitive coloring layer containing a salicylic acid derivative or a polyvalent metal salt thereof as an electron-accepting compound that reacts with a colorless or light-colored electron-donating dye precursor and the electron-donating dye precursor. In the heat-sensitive recording material, the sodium salt or potassium salt of the salicylic acid derivative is added to the salicylic acid derivative or its polyvalent metal salt in an amount of 0.
A heat-sensitive recording material, characterized in that it comprises from 01 to 5.00% by weight.