JPH089267B2 - Thermal recording material - Google Patents

Description

The present invention relates to a heat-sensitive recording material, and more specifically, it utilizes a color reaction of a colorless or light-colored electron-donating dye precursor and an electron-accepting compound. The present invention relates to a thermosensitive 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-43-4160. It is disclosed.

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 by heating and a recording reaction is performed by utilizing a coloring reaction generated by contact.

Since these heat-sensitive recording materials are the primary colors, 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 and the electron-donating dye. It has a defect that the color-developing body formed by the thermal reaction with the accepting compound causes browning due to fats and oils, chemicals and the like. Therefore, when touching stationery and office supplies such as water-based ink pens, oil-based ink pens, fluorescent pens, vermilion flesh, adhesives, glues, diazo developers, and cosmetics such as hand creams and emulsions, the white background of the thermosensitive recording material develops color. And the color-developing part caused browning, which significantly impaired the commercial value.

On the other hand, Japanese Patent Publication No.
As disclosed in Japanese Patent Publication No. 880, Japanese Patent Publication No. 30437/1988, Japanese Patent Publication No. 31958/1988, efforts have been made to provide a protective layer having chemical resistance, but the provision of the protective layer has resulted in color sensitivity. Deterioration, insufficient mating with the thermal head of the thermal recording device, causing problems such as staking and noise at the time of recording, and poor writing performance on stationery, etc., causing problems such as ink bleeding. Not only that, but it also had many drawbacks such as complicated manufacturing processes.

Also, as a method for improving the discoloration of the color image,
JP-B-51-43386, JP-A-53-17347, JP-A-56-72
996, JP-A-59-194891, British Patent Publication 2,074,3
Although attempts such as those disclosed in No. 35A and the like have been made, they all have an insufficient effect of improving discoloration, or have some drawbacks such as the occurrence of white background color (fog). are doing.

Attempts have been made to use a salicylic acid derivative and a metal salt thereof as a means for preventing the coloration of a white background and the discoloration of the formed color image due to a solvent, a chemical or the like.

Further, in order to bring it closer to plain paper, it is essential to improve the storage stability under high temperature and high humidity. When the thermal recording paper is stored in a place where the temperature and humidity are extremely high, such as in a warehouse in the summer or in a car, the printed part is discolored and the white background is fogged, which lowers the commercial value.

(Effects of the Invention) An object of the present invention is to obtain a heat-sensitive recording material in which a white background portion is not colored by a solvent, a chemical or the like, and a formed color image is not easily discolored even under high temperature and high humidity.

(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 to light-colored electron-donating dye precursor and an electron-accepting compound that reacts with the electron-donating dye precursor to develop a color. And a salicylic acid derivative represented by the following general formula (I), or a metal salt thereof is mixed with a metal oxide in advance, heated, dispersed, and applied.

In the above formula, R represents an alkyl group having 12 to 18 carbon atoms or an aralkyl group, which may have a substituent. X represents a hydrogen atom or M _{1 / n} . However, M represents an n-valent metal atom, and n represents an integer.

As the metal atom represented by M, zinc, aluminum and calcium are particularly preferable.

As the metal oxide used when mixed with the salicylic acid derivative and heated, zinc oxide, aluminum oxide, magnesium oxide, and calcium oxide are particularly preferable. When using a salicylic acid derivative metal salt, it is preferable to use the same metal oxide as the metal salt.

The heating temperature is preferably equal to or lower than the melting point of the salicylic acid derivative or its metal salt, and particularly preferably 5 ° C. to 10 ° C. below the melting point.

The heating time is preferably 30 minutes or longer, more preferably 2 hours or longer. The amount of metal oxide added is 5 for salicylic acid derivatives.
˜100% by weight, more preferably 20 to 50% by weight.

Specific examples of salicylic acid derivatives and metal salts thereof include 4-n-dodecylsalicylic acid, 4-t-dothesylsalicylic acid, 4-n-pentadecylsalicylic acid, and 4-n-.
Heptadecyl salicylic acid, 4- (1,3-diphenylbutyl) -salicylic acid, 4-n-octadecyl salicylic acid,
Examples include 4-dodecylsulfonylsalicylic acid and 4-dodecylsulfosalicylic acid.

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 include those described in JP-A-55-27253.

As an example of some of these, as a triarylmethane compound, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (that is, crystal violet letolactone), 3,3-bis (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-
Dimethylaminobenzohydrin benzyl ether, N-
There are halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco olamine and the like, and as the xanthene compound, 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. There are leuco methylene blue, p-nitrobenzyl leuco methylene blue and the like, and spiropyran compounds include 3-methyl-spiro-dinaphthopyran, 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, 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 1 to 10 carbon atoms.
Represents an alkyl group or a halogen atom. In the general formula (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, R 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 general formula (III), the alkyl groups represented by R ₁ and R ₂ may form a ring or may be a heterocycle. Further, it may 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-pentylamino Fluoran, 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-ethyl-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-N-pentylaminofluorane, 2- (p-methylanilino) -3-chloro-6-
N-ethyl-N-pentylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylaminofluorane, 2-anilino-3-ethyl-6-N-methyl-N- There are tetrahydrofurfurylaminofluorane, 2-anilino-3-methyl-N-ethyl-N-tetrahydrofurfurylaminofluorane and the like, and these may be used alone, but the color residue and color image It is possible to mix two or more kinds to prevent the color fading, but two or more kinds may be mixed to adjust the color tone and prevent the color development image from fading.

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 (IV)
Examples include compounds represented by (IX) to (IX).

R ₅ NHCONH ₂ (VII) R ₆ CONH-R ₇ (VIII) In the formula, R _{1 to} R ₄ each represent a phenyl group, a benzyl group, and a lower alkyl or halogen-substituted product thereof, and R ₅ and R ₆ represent Each represents an alkyl group having 12 to 24 carbon atoms, and R ₇ represents hydrogen or a phenyl group.

Further, 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. Further, in the formula (VI), R ₄ ′ represents 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) have a melting point of 70 ° C or higher.
It is preferably 150 ° C or lower, and more preferably
Melting point is 80 ° C or higher and 130 ° C or lower. Specifically, benzyl p-benzyloxybenzoate, β-naphthylbenzyl ether, stearic acid amide, palmitic acid amide, N
-Phenyl ethynyl acid amide, N-stearyl urea, β
-Naphthoic acid phenyl ester, 1-hydroxy-2-
Naphthoic acid phenyl ester, β-naphthol (p-chlorobenzyl) ether, β-taphthol (p-methylbenzyl) ether, α-naphthylbenzyl ether,
1,4-butanediol-p-methylphenyl ether,
1,4-propanediol-p-methylphenyl ether, 1,4-propanediol-p-isopropylphenyl ether, 1,4-butanediol-pt-octylphenyl ether, 2-phenoxy-1- p-tolyl-
Oxy-ethane, 1-phenoxy-2- (4-ethylphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4-methoxy-)
Phenyl) ether, and the like.

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

Water-soluble binders are 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, polyacrylamide, saponified products of vinyl acetate and polyacrylic acid copolymers, etc. can give.

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 soft calcium carbonate, kaolin, surface-treated Crystalline 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 browning of the 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 zinc stearate, calcium stearate, emulsion of aluminum stearate and the like are used.

As waxes, emulsions such as paraffin wax, microcristan 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.

In the present invention, salicylic acid or a metal salt thereof used as an electron-accepting compound is mixed with a metal oxide and heated, or after being dispersed alone or together with other materials, it is coated on a support.

In this case, water or an organic solvent is used as the dispersion medium, and water is particularly preferable.

As a dispersion method, a material placed in water or an organic solvent is adjusted using a disperser such as a ball mill so that the material particle diameter is 5 μm or less.

The coating liquid is applied and dried on a support such as neutral paper, high-quality paper, coated paper, synthetic paper, PET or other plastic film. When adjusting the coating liquid, all components may be mixed and pulverized at the same time from the beginning, or may be pulverized and dispersed separately in an appropriate combination and then mixed.

(Examples of the Invention) Examples will be shown below, but the present invention is not limited thereto.

In the examples, unless otherwise specified,% means% by weight.

(Examples 1 to 5) Table 1 shows materials used for the thermosensitive coloring layer of each example according to the present invention.

100 g of the electron-accepting compound was mixed with 20 g of zinc oxide, and after acidification, heat treatment was performed at 125 ° C. for 2 hours in an electric furnace before use.

20 g of each of the electron-donating dye precursor, the electron-accepting compound, and the heat-fusible substance were dispersed in a ball mill together with 100 g of an aqueous solution of 5% polyvinyl alcohol (Kuraray PVA105) for one day to obtain a volume average particle diameter of 3 μm. The pigment was used by dispersing 80 g with a 0.5% solution of sodium hexametaphosphate (160 g) in a homogenizer.

The respective dispersions dispersed as described above were mixed at a ratio of an electron-donating dye precursor dispersion 5g, an electron-accepting compound dispersion 12g, a thermoplastic material dispersion 5g, and a pigment dispersion 22g, and stearic acid was added. 4 g of zinc emulsion and 2% of (2
5 g of an aqueous solution of -ethylhexyl) -sodium sulfosuccinate was added to obtain a coating liquid. The coating liquid dry coating amount on a high-quality paper having a basis weight of 50 g / m ² and was coated with a wire bar such that the 6 g / m ^2, and dried 5 minutes at 50 ° C. oven, the surface smoothness performs Kiyarenda process Finished to be 500 seconds (bet).

(Comparative Examples 1 to 5) The electron-accepting compound in Examples 1 to 5 was changed to the compound shown in Table 2 and the electron-accepting compounds of 1 to 4 were 20 g of zinc oxide per 100 g of the electron-accepting compound. Was added, mixed and pulverized, and then heat-treated in an electric furnace to obtain a heat-sensitive recording material in the same manner as in Example.

The thermal responsiveness is Fujitsu Limited's high-speed fax machine FF-2000.
A copy of 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, chemical resistance is ethanol, ethyl acetate, polyethylene glycol (600), castor oil, paraffin oil (100 seconds), diazo developer (Ricoh Company, Ricopy SD)
Each of them was impregnated with paper and superposed on the coloring surface of the thermosensitive recording paper obtained by the above method, and the degree of fog in the white background and decolorization (discolored brown) of the colored image was extremely excellent (almost changed). None), Excellent (a slight change is recognized), Practical Use (fog color development or image erasing occurs, but image can be read), No (fog color development or image erasing causes image deterioration) The evaluation was carried out in four stages (very difficult to read).

In addition, heat resistance (60 ° C, 30% RH) using thermosensitive recording paper colored with a 120 ° C hot pen (pressure 500g / cm ² , 5 seconds).
The fog density of the white background and the density of the color development part before and after storing for 24 hours under the condition of humidity resistance (40 ° C, 90% RH) are Macbeth RD
It was measured with a -918 densitometer. The storability of the density of the color-developed portion was expressed by (density after storage / density immediately after color development) × 100 (displayed in%).

The results are shown in Table 3. From the results shown in the table, the heat-sensitive recording material according to the present invention has a high thermal response, not only a high-density image can be obtained, but also fog color development due to chemicals or decoloration of a printed image does not occur, which is very excellent. It turns out that it has performance.

Claims (1)

[Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer containing an electron-donating dye precursor and an electron-accepting compound, wherein a salicylic acid derivative represented by the following general formula (I) or a metal salt thereof is prepared in advance as a metal oxide. A heat-sensitive recording material characterized by being mixed, heated, dispersed and applied. (In the formula, R represents an alkyl group having 12 to 18 carbon atoms or an aralkyl group, and X represents a hydrogen atom or M _{1 / n} .
However, M represents an n-valent metal atom, and n represents an integer.)