JPH0630967B2 - 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 between a colorless or light-colored electron-donating dye precursor and an electron-accepting compound. Regarding recording material.

(Prior Art) A so-called two-component thermal recording material utilizing a color reaction of a colorless or light-colored electron-donating dye precursor and an electron-accepting compound is disclosed in JP-B-45-14039 and JP-B-43-416.
No. 0 and the like.

The two-component color-developing heat-sensitive recording material is prepared by dispersing a colorless or light-colored electron-donating dye precursor and an electron-accepting compound in the form of fine particles, and mixing a binder or the like with these two types of heat-reactive compounds to form a binder or the like. It is coated on a support so as to be separated by, and one or both of them are melted and heated by heating to obtain a record by utilizing a coloring reaction generated. These two-component color-developing heat-sensitive recording materials have a primary color and do not require development. The quality of the paper is close to that of ordinary paper, it is easy to handle, the color density is high, and the thermosensitive recording materials of various hues can be easily used. 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 to generate a sufficient pulse density even with a short pulse width, that is, low thermal energy, for a thermal recording material, that is, There is a strong demand for improvement in thermal responsiveness, and JP-A-58-187393 and JP-A-59-670 are strongly demanded.
Various attempts have been made as disclosed in JP-A No. 83, JP-A-60-54884 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 a color image generated by a thermal reaction between the compound and an electron-accepting compound causes discoloration due to oils and fats, chemicals and the like. for that reason,
Water-based ink pens, oil-based ink pens, fluorescent pens, vermilion,
Stationery and office supplies such as adhesives, glue, diazo developer, etc.
Alternatively, when touching cosmetics such as hand creams and milky lotions, the white background portion of the heat-sensitive recording material is colored, and the colored portion is discolored, which significantly impairs the commercial value.

On the other hand, Japanese Patent Publication No.
7880, JP-A-48-30437, JP-A-48-
As disclosed in JP-A-31958, efforts have been made to provide a protective layer having chemical resistance. However, the provision of the protective layer causes a decrease in color development sensitivity and a mating with a thermal head of a thermal recording apparatus. Insufficient properties cause problems such as noise during printing and staging, poor writing properties such as stationery, and problems such as ink bleeding. It was

Further, as a method for improving discoloration of a colored image, Japanese Patent Publication No. 51-43386, JP-A No. 53-17347,
JP-A-56-72996, JP-A-59-19489
No. 1, British Patent Publication No. 2,074,335A, and the like have been attempted, but in all cases, the effect of improving discoloration is insufficient, or there is an effect, but the white background It has drawbacks such as generation of color (fog).

(Object of the Invention) It is an object of the present invention to obtain a thermosensitive recording material in which a white background portion is not colored by a solvent, a chemical or the like, and a generated color image is not easily discolored.

(Structure of the Invention) An object of the present invention is to provide a thermosensitive recording material having a thermosensitive coloring layer containing 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. In the above, it is achieved by mixing bis-hydroxycumylbenzene or bis-hydroxy-α-methylbenzylbenzene as the electron-accepting compound and one or more of salicylic acid derivative metal salts represented by the following general formula (I). It was

General formula (I) In the above formula, X and Y represent a hydrogen atom or an alkyl group, M represents an n-valent metal atom, and n represents an integer.

In the present invention, two or more kinds of electron-accepting compounds are mixed and used as described above. In the former electron-accepting compounds, the hydroxycumyl group or the hydroxy-α-methylbenzyl group has 1,4-position. Is preferred. Specific examples of preferable compounds are: 1,4-bis-p-hydroxycumylbenzene (mp.192 ° C) 1,4-bis-m-hydroxycumylbenzene (mp.180 ° C) 1,4- There is bis-p-hydroxy-α-methylbenzylbenzene (mp. 165 ° C), and 1,4-bis-p-hydroxycumylbenzene is particularly preferable. This can be obtained, for example, by reacting diisopropenylbenzene with 2 molar equivalents of phenol in the presence of an acid catalyst in a Friedel-Crafts reaction.

In the salicylic acid metal salt derivative represented by the general formula (I), in the formula, X and Y may be the same or different, each represents a hydrogen atom or an alkyl group, M represents an n-valent metal atom, and n Represents an integer. Particularly, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms are preferable, but a compound having 7 to 11 total carbon atoms (for example, salicylic acid, methylsalicylic acid) is water-soluble, and thus is a white background part. The compound having 12 or more total carbon atoms is preferable, and the compound having 15 or more total carbon atoms is particularly preferable from the viewpoint of water insolubility. The metal atom represented by M is particularly preferably zinc, aluminum, magnesium and calcium.

Specific examples of the metal salt of the salicylic acid derivative represented by the general formula (I) include 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-dodecylsalicylic acid , 4-n-pentadecyl salicylic acid, 4-n
Metal salts such as heptadecyl salicylic acid, 5- (1,3-diphenylbutyl) -salicylic acid, 5-n-octadecyl salicylic acid, 5-dodecyl sulfonyl salicylic acid, 5-dodecyl sulfosalicylic acid, 3-methyl-5-dodecyl sulfosalicylic acid is there.

The mixing ratio of bis-hydroxycumylbenzene or bis-hydroxy-α-methylbenzylbenzene, which is an electron-accepting compound according to the present invention, and the metal salt of the salicylic acid derivative represented by the general formula (I) is It is preferable to add 5 to 150% by weight of a metal salt of the salicylic acid derivative represented by the general formula (I) to millbenzene or bis-hydroxy-α-methylbenzylbenzene. Among them, 10 to 80% is particularly preferable.

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.

Examples of some of these are 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet lettactone) and 3,3-bis as the triarylmethane compounds. (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
-(Dibenzylamino) 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, and spiropyran compounds include 3-methyl-spirodinaphthopyran, 3-ethyl-spirodinaphthopyran, 3,3′-dichloro-spiro-dinaphthopyran, 3
-Benzylspirodinaphthopyran, 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, the triarylmethane-based compound (for example, crystal bio lettactone) and the electron-donating dye precursor of the xanthene-based compound 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 formula, R ₁ and R ₂ represent an alkyl group or a cycloalkyl group having 1 to 10 carbon atoms, R ₃ represents an aryl group, and X represents an alkyl group having 1 to 10 carbon atoms or a halogen atom.) In (II), the alkyl group represented by R ₁ and R ₂ may be linear or branched, and may further have a substituent. The aryl group represented by R ₃ preferably has 6 to 20 carbon atoms, and is preferably a phenyl group or a phenyl group having a substituent. As the substituent of the phenyl group, an alkyl group having 1 to 10 carbon atoms is preferable.

Among the electron-donating dye precursors represented by the general formula (II), particularly preferable ones are represented by the following general formula (III).

(In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 10 carbon atoms;
_{4 represents} a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and X represents an alkyl group having 1 to 8 carbon atoms or a chlorine atom. In the above general formula (III), the alkyl group represented by R ₁ and R ₂ may form a ring and may further have a substituent. In the above general formula (III), a compound in which X is a methyl group or a chlorine atom is particularly preferable. 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-pentylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-3-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-diethylaminofluorane, 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-methylanilino)
-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-pentylaminofluorane, 2-
(P-Methylanilino) -3-chloro-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-
Methyl-6-N-methyl-N-furylmethylaminofluorane, 2-anilino-3-ethyl-6-N-methyl-
There are N-furylmethylaminofluorane and the like, and these may be used alone, but two or more kinds may be mixed and used in order to adjust the color tone and prevent fading of the color image.

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 examples of preferable heat fusible substances, the following general formula (IV)
Examples include compounds represented by (IX).

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 (IV) to (VI) is substituted with a lower alkyl group, the carbon number thereof is 1 or more and 8 or less, preferably 1 or more and 3 or less. Is. When it is substituted with a halogen atom, fluorine is preferable. Also, R _'4 in the formula (VI) represents a hydrogen or a hydroxyl group.

In the formula (IX), R ₈ represents a divalent group, preferably an alkylene group, an alkylene group having a carbonyl group, an alkylene 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. Also, X, Y, Z, X ', Y',
Z'may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyloxycarbonyl group or an aralkyloxycarbonyl group.

The compounds of the general formulas (IV) to (IX) preferably have a melting point of 70 ° C or higher and 150 ° C or lower, and more preferably a melting point of 80 ° C or higher and 130 ° C or lower. Specifically, benzyl p-benzyloxybenzoate (mp.119 ° C) β-naphthylbenzyl ether (mp.105 ° C) stearic acid amide (mp.108 ° C) palmitic acid amide (mp.103 ° C) N-phenylaline Acid amide (mp. 96 ° C) N-stearyl urea (mp. 110 ° C) β-naphthoic acid phenyl ester (mp. 92 ° C) 1-hydroxy-2-naphthoic acid phenyl ester (m
p. 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) 1,4-butanediol-p-isopropylphenyl (mp.79 ° C) 1,4-butanediol-pt-octylphenyl ether (mp.99 ° C) 2-phenoxy-1-p-tolyl -Oxyethane (m
p. 104 ° 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.

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

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

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. Further, it is preferable to mix and disperse zinc oxide when the zinc salt of the electron-accepting compound according to the present invention is dispersed, because a higher effect of improving discoloration of an image can be obtained.

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 emulsions of zinc stearate, calcium stearate and aluminum stearate are used.

As waxes, emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene 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.

(Examples of the Invention) Examples will be shown below, but the present invention is not limited thereto. Weight% unless otherwise specified in the examples
Represents

(Examples 1 to 9) Table 1 shows materials used for the thermosensitive coloring layer according to the present invention.
20 g of each of the electron-donating dye precursor, the electron-accepting compound, and the heat-fusible substance was dispersed in a ball mill together with 100 g of a 5% aqueous solution of polyvinyl alcohol (Kuraray PVA-105) for a whole day and night to give a volume average particle diameter of 3 μm or less. did. As for the pigment, 80 g of sodium hexametaphosphate 0.5% solution 160
It was dispersed in a homogenizer together with g and used.

Each of the dispersions prepared as described above was prepared as follows: 5 g of an electron-donating dye precursor dispersion, 10 g of an electron-accepting compound (I) dispersion, and an electron-accepting compound (II) dispersion.
2 g, 2 g, 3 g in Examples 3 to 5, 6 g in Examples 6 to 9, 5 g of the dispersion of the heat-fusible substance, 22 g of the dispersion of the pigment, and 21% of stearic acid. Zinc emulsion and 2% (2-ethylhexyl)-
A coating liquid obtained by adding 5 g of an aqueous solution of sodium sulfosuccinate was applied to a high-quality paper having a basis weight of 50 g / m ² to give a dry coating amount of 6 g.
/ M ² was applied with a wire bar and dried in an oven at 50 ° C for 5 minutes, and a calendering treatment was performed to finish the surface smoothness to 500 seconds (bek).

(Comparative Examples 1-2) In Examples 1-2, except that only the electron-accepting compound (I) was used and the electron-accepting compound (II) was not added, the coating liquid was prepared. Thermal recording paper was obtained in the same manner as in 2).

(Comparative Examples 3 to 5) In Examples 3 to 5, except that the electron-accepting compound (I) was not used and only the electron-accepting compound (II) was used to prepare the coating liquid. Thermal recording paper was obtained in the same manner as 5).

(Comparative Examples 6 to 9) In Examples 6 to 9, as the electron accepting compound [second
Thermal recording papers were obtained in the same manner as in Examples 6 to 9 except that the compounds shown in Table] were used (the amount used was the same amount as the electron-accepting compound (I)).

The thermal responsiveness is Fujitsu Limited's high speed fax machine FF-20.
00, Test Chart No. 3 of the Institute of Image Electronics Engineers of Japan was copied, and the density was measured by a Macbeth RD-918 type densitometer.

On the other hand, the chemical resistance is ethanol, ethyl acetate, polyethylene glycol (600), castor oil, paraffin oil (100 seconds), diazo developer (Ricoh Company, Recopy S
D) was impregnated in each of the papers, and the papers were superposed on the color-developing surface of the resulting thermosensitive recording paper, and the degree of fog was evaluated in three grades of good, good and bad. Also, a 120 ° C hot pen (50
Using heat-sensitive recording paper colored at 0 g / cm for 5 seconds, heat resistance (60 ° C, 30% RH), humidity resistance (40 ° C, 90%)
The fog density and the density of the color-developed part before and after storage for 24 hours under the condition of (RH) were measured by a Macbeth RD-918 type densitometer. The storability of the density of the color-developed part was expressed by (density after storage / density immediately after color development) × 100 (displayed in%).

The above results are shown in Table 3.

Claims (1)

[Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer containing a colorless to 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 comprising a mixture of bis-hydroxycumylbenzene or bis-hydroxy-α-methylbenzylbenzene and one or more salicylic acid derivative metal salts represented by the following general formula (I). General formula (I) In the above formula, X and Y represent a hydrogen atom or an alkyl group, M represents an n-valent metal atom, and n represents an integer.