JPH1120318A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording material having excellent plasticizer resistance and oil resistance. SOLUTION: In the thermal recording material comprising an electron donative dye precursor and electron acceptive compound on a support, as the acceptive compound, at least one type of a compound represented by a formula, where Z denotes any of C, N, O and S, the Z and N form a heterocycle via bivalent bond group, and the heterocycle may have a substituent.

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 which does not lose a color image obtained by heating and has excellent storage stability of a recorded image.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support having thereon a thermosensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored dye precursor and an electron-accepting compound. By heating with a hot pen, a laser beam, or the like, the dye precursor and the electron-accepting compound react instantaneously to obtain a recorded image, which is disclosed in JP-B-43-4160 and JP-B-45-14039. It has been disclosed and is widely used.

[0003] These thermal recording systems are widely used in facsimile machines, printers, labels and the like. However, such a heat-sensitive recording material generally has a disadvantage that a color-developing material is deteriorated or discolored by contact with a plasticizer and oil, so that it is particularly valuable in fields such as labels and slips. Has been significantly impaired.

[0004] In a thermal recording system using a so-called leuco dye, which is usually colorless or pale, many electron-accepting compounds have been disclosed in order to improve the decoloring phenomenon. For example, those using a metal salt of a specific salicylic acid derivative as an electron-accepting compound as disclosed in JP-A-62-169681 and those using a sulfonylurea derivative as disclosed in JP-A-5-147357 as an electron-accepting compound. A compound used as a compound and a compound using a metal salt of an N-substituted benzoic acid derivative as an electron-accepting compound as disclosed in JP-A-7-214916 and JP-A-7-290832 are known.

[0005] Those using a metal salt of the above-mentioned salicylic acid derivative have oil resistance (for example, afterimage ratio of image density after a certain period of time when salad oil is brought into contact with a coloring surface), and plasticizer resistance (for example, plasticizer). (Image retention after a certain period of time) when a wrap film containing) is brought into contact with a color-developing surface, but the color erasure cannot be avoided in a long-term test.

On the other hand, those using the sulfonylurea derivative improve the oil resistance and the plasticizer resistance of the printed image, but significantly impair the whiteness of the uncolored portion (hereinafter referred to as "background"). In addition, there are problems such as low color-forming sensitivity and lack of intended color tone.

Further, those using a metal salt of an N-substituted benzoic acid derivative have improved oil resistance and plasticizer resistance of printed images and good whiteness of the background, but are stored in a high-temperature and high-humidity atmosphere. In this case, the whiteness of the background is impaired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which is excellent in long-term storage stability of a color image such as oil resistance and plasticizer resistance.

[0009]

The problem to be solved by the present invention is to provide a thermosensitive recording material comprising a support having thereon a thermosensitive recording layer containing an electron donating dye precursor and an electron accepting compound. This has been attained by a heat-sensitive recording material comprising at least one compound represented by the general formula (1) as a receptive compound.

[0010]

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(In the formula (1), Z represents any one of C, N, O, and S, and Z and N form a heterocyclic ring via a divalent linking group, and the heterocyclic ring is a substituent. May be included.)

The compound of the present invention can be prepared by the method described in Org.
0, JP-A-9-3051, USP 4,610,9
54 ('86), JP-A-60-147735, An
n.1818 (1979), J.chem.soc. 121 2542.
(1922); Synlett 553 (1993);
It can be easily synthesized according to the method described in JP-A-7-128331.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the compound represented by the general formula (1) include the following (2) to (12), but the present invention is not limited thereto.

[0014]

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(In the formula (2), R represents a hydrogen atom, a hydroxyl group, or a carboxyl group.)

[0016]

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(In the formula (3), R represents a mercapto group, an amino group, or an alkylamino group such as a dibutylamino group.)

[0018]

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(In the formula (4), R represents an alkylthio group such as a mercapto group, a trimethylsilylmethyl group or a methylthio group, or an arylthio group such as a 2-thiadiazolyl group.
In the formula (5), R represents an alkyl group such as a methyl group and an aryl group such as a phenyl group. )

[0020]

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[0021]

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(In the formula (7), R ₁ and R ₂ represent a hydrogen atom or an alkyl group such as a methyl group. In the formula (8), R represents an alkoxy group such as a methyloxy group or an ethyloxy group.
In the formula (9), R represents an alkyl group such as a methyl group or an aryl group such as a phenyl group. )

[0023]

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(In the formula (10), R ₁ and R ₂ represent a hydrogen atom or a mercapto group.)

[0025]

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[0026]

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The preferred amount of the compound represented by the general formula (1) is 50% by weight or more based on the electron-donating dye precursor.
000% by weight or less, more preferably 100% by weight
Not less than 500% by weight. These compounds can be used alone or in combination of two or more. It can be used in combination with a conventionally known electron-accepting compound comprising a phenol or an organic acid as long as the desired effect is not impaired.

The generally colorless or light-colored electron-donating dye precursor according to the present invention is typified by known compounds generally used in pressure-sensitive recording paper and heat-sensitive recording paper, but is not particularly limited. . Specific examples include, for example, the following, but the present invention is not limited thereto.

(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-
Yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5 -Dimethylaminophthalide, 3-p
-Dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

(2) Diphenylmethane compounds 4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like.

(3) Xanthene compounds rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3- Diethylamino-7-phenylfluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3 -Diethylamino-7
-(2-chloroanilino) fluoran,

3-Diethylamino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl- 7-anilinofluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Phenethylfluoran, 3-diethylamino-7- (4
-Nitroanilino) fluoran, 3-dibutylamino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamyl) amino-6 Methyl-7-anilinofluoran, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluoran and the like.

(4) Thiazine compounds Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like.

(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like.

The above usually colorless to light-colored electron-donating dye precursors may be used alone or in combination of two or more.

As a specific example of the method for producing the heat-sensitive recording material of the present invention, there is a method of forming a heat-sensitive recording layer by applying the compound of the present invention and a dye precursor as main components onto a support.

The method for preparing a coating liquid for incorporating the compound of the present invention and the electron-donating dye precursor into the heat-sensitive recording layer includes:
A method in which each compound is dispersed in a dispersion medium and then mixed, a method in which each compound is mixed and then dispersed in a dispersion medium,
A method of dissolving each compound by heating and homogenizing, cooling, and dispersing the compound in a dispersion medium may be mentioned, but it is not specified. At the time of dispersion, a dispersant may be used if necessary. When water is the dispersion medium, examples of the dispersant include water-soluble polymers such as polyvinyl alcohol and various surfactants.

It is also possible to add a binder to the heat-sensitive recording layer for the purpose of improving the strength of the heat-sensitive recording layer. Specific examples of the binder include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acryl. Water-soluble polymers such as acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid Ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer,
Latexes such as methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene / vinylidene chloride copolymer, polyvinylidene chloride and the like are mentioned. It is not limited.

Further, as an additive for adjusting the color development sensitivity of the heat-sensitive recording layer, a heat-fusible substance can be contained in the heat-sensitive recording material. Those having a melting point of 60 ° C to 200 ° C are preferred, and those having a melting point of 80 ° C to 180 ° C are particularly preferred. A sensitizer used in general thermosensitive recording paper can also be used. These compounds include waxes such as N-hydroxymethyl stearamide, behenamide, stearamide, palmitamide, naphthol derivatives such as 2-benzyloxynaphthalene, p-benzylbiphenyl, 4-allyloxybiphenyl Biphenyl derivatives such as 1,2-bis (3-methylphenoxy) ethane, and 2,2′-bis (4
-Methoxyphenoxy) diethyl ether, bis (4-
Polyether compounds such as methoxyphenyl) ether,
Examples thereof include carbonic acid or oxalic acid diester derivatives such as diphenyl carbonate, dibenzyl oxalate, and bis (p-methylbenzyl) oxalate, and two or more kinds thereof may be added in combination.

As the support used in the heat-sensitive recording material of the present invention, paper, various nonwoven fabrics, woven fabrics, synthetic resin films such as polyethylene terephthalate and polypropylene, paper laminated with synthetic resins such as polyethylene and polypropylene, synthetic paper, Metal foil, glass or the like, or a composite sheet combining these can be used arbitrarily according to the purpose, but is not limited thereto, and they may be opaque, translucent or transparent. Good. In order to make the background appear white or another specific color, a white pigment, a colored dye or a bubble may be contained in or on the support. Especially when performing water-based coating on films, etc., when the hydrophilicity of the support is small and it is difficult to apply the heat-sensitive recording layer, the same water-soluble polymer as that used for the surface hydrophilization treatment by corona discharge or the binder May be applied to the surface of the support for easy adhesion treatment.

The layer structure of the heat-sensitive recording material of the present invention may be only the heat-sensitive recording layer. If necessary, a protective layer may be provided on the heat-sensitive recording layer, or an intermediate layer containing at least one of a water-soluble polymer, white or colored dye or hollow particles between the heat-sensitive recording layer and the support. Can also be provided. In this case, the protective layer and / or the intermediate layer may be composed of two or three or more layers. The heat-sensitive recording layer may be a multilayer of two or more layers by containing each component one by one or changing the mixing ratio for each layer. Further, a material capable of recording information electrically, optically, and magnetically may be included in the heat-sensitive recording layer and / or on the surface opposite to the surface on which the other layer and / or the heat-sensitive recording layer is provided. . Further, a back coat layer may be provided on the surface opposite to the surface on which the heat-sensitive recording layer is provided for the purpose of preventing blocking, curling, and preventing electrification.

The method for producing the heat-sensitive recording material of the present invention by coating each of the above-mentioned layers on the support in the present invention is not particularly limited, and it can be produced by a conventional method. For example, a smearing device such as an air knife coater, a blade coater, a bar coater, and a curtain coater, and various printing machines using a method such as lithographic, letterpress, intaglio, flexo, gravure, screen, and hot melt can be used. In addition to the usual drying process, UV irradiation and
Each layer can be held on the support by EB irradiation.

The heat-sensitive recording layer is prepared by mixing each dispersion obtained by pulverizing each component, coating and drying on a support, and mixing each solution obtained by dissolving each component in a solvent. And a method of coating and drying on a support. Drying conditions vary depending on a dispersion medium or solvent such as water. In addition, there is a method in which the components are mixed and heated to melt a fusible component, and the mixture is heated and applied.

The thermal recording layer and / or the protective layer and / or the intermediate layer include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, Pigments such as urea-formalin resin, and other higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearamide, and caster wax for the purpose of preventing head abrasion and sticking. And a dispersing agent such as sodium dioctyl sulfosuccinate, a surfactant, a fluorescent dye and the like.

[0045]

The present invention will be described in more detail with reference to the following examples. Parts and percentages in the examples are on a weight basis.

Example 1 (A) Preparation of Thermal Sensitive Coating Solution 20 parts of 3-dibutylamino-6-methyl-7-anilinofluorane was added to a 1.25% aqueous solution of polyvinyl alcohol 8
The average particle size is 1.
Pulverized to 5 μm or less, and the dye precursor dispersion (A
Liquid). Next, 20 parts of the exemplified compound (3-3) is pulverized together with 80 parts of a 1.25% aqueous solution of polyvinyl alcohol using a paint conditioner until the average particle size becomes 1.5 μm or less to obtain an electron accepting compound dispersion liquid (liquid B). Was. Further, 20 parts of benzyloxynaphthalene and 1.25
Similarly, 80 parts of an aqueous solution of polyvinyl alcohol was crushed until the average particle size became 1.5 μm or less, and a sensitizer dispersion (C
Liquid). To 35 parts of solution A, 70 parts of solution B, and 70 parts of solution C, 100 parts of 30% calcium carbonate, 10 parts of a 40% aqueous solution of zinc stearate, and 57 parts of a 10% aqueous solution of polyvinyl alcohol were added and mixed well. To prepare a heat-sensitive coating solution.

(B) Preparation of heat-sensitive recording material The heat-sensitive coating solution prepared in (A) is smear-dried on a high-quality paper so that the solid content is 3.4 g / m ^2, and then processed by a super calender to obtain heat-sensitive coating. A recording material was obtained.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that Exemplified Compound (2-1) was used instead of Exemplified Compound (3-3) used in Example 1.

Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that Exemplified Compound (3-1) was used instead of Exemplified Compound (3-3) used in Example 1.

Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that Exemplified Compound (4-1) was used instead of Exemplified Compound (3-3) used in Example 1.

Comparative Example 1 In place of the exemplified compound (3-3) used in Example 1,
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) was used.

Comparative Example 2 In place of the exemplified compound (3-3) used in Example 1, 4
-A heat-sensitive recording material was obtained in the same manner as in Example 1, except that benzyl hydroxyhydroxyate was used.

Comparative Example 3 In place of the exemplary compound (3-3) used in Example 1, 4
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that -isopropyloxy-4'-hydroxydiphenylsulfone was used.

Test 1 (Background Whiteness) The heat-sensitive recording materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were measured for whiteness by a Hunter whiteness meter using a blue filter.

Test 2 (Color Test) The heat-sensitive recording materials obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to an applied pulse using a thermal facsimile printing tester TH-PMD manufactured by Okura Electric with a print head LH4409 manufactured by TDK. Printing was performed under an applied voltage of 20.5 volts in 1.2 milliseconds, and the density of a color image was measured using a Macbeth densitometer (RD-918).

Test 3 (Plasticizer resistance test-image stability) A core material (160 mmφ) was wound so that the printing surface of the heat-sensitive recording material was on the top, and a wrap film made of polyvinylidene chloride [Mitsuhito (Manufactured by Pressure Chemical Co., Ltd.) was wound three times and left at 40 ° C. for 24 hours. The larger the value, the better the storage stability.

[0057]

A = (C / B) × 100 A: Image residual ratio (%) B: Image density before test C: Image density after test

Test 4 (Plasticizer resistance test-background stability) A heat-sensitive recording material was wound around a core material (160 mmφ) so that the printed surface was facing upward, and a wrap film made of polyvinylidene chloride [Mitsuhito Pressure chemical Co., Ltd.] was wound three times and left at 40 ° C. for 24 hours, and the whiteness of the background was measured in the same manner as in Test 1.

Test 5 (Oil resistance test) Edible salad oil was applied to the image area of the colored heat-sensitive recording material.
The image remaining ratio after standing at room temperature for 24 hours was determined by the above-mentioned formula (1). As in Test 3, the larger the value, the better the oil resistance.

Tests 1 of Examples 1-4 and Comparative Examples 1-3
Table 1 shows the results of No. 5.

[0061]

[Table 1]

[0062]

As is clear from Table 1, the present invention makes it possible to provide a heat-sensitive recording material having excellent plasticizer resistance and oil resistance.

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support having thereon a thermosensitive recording layer containing an electron-donating dye precursor and an electron-accepting compound, wherein the electron-accepting compound is represented by the general formula (1):
A heat-sensitive recording material comprising at least one compound represented by the formula: Embedded image (In the formula (1), Z represents any one of C, N, O, and S, and Z and N form a heterocyclic ring via a divalent linking group, and the heterocyclic ring has a substituent. May be.) 2. A heat-sensitive recording material comprising at least one compound according to claim 1 having a pKa of 2 or more and 12 or less.