JP2614094B2 - 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 having an undercoat layer and having high sensitivity.

(Prior Art) Recording materials using an electron-donating dye precursor (hereinafter, referred to as a color former) and an electron-accepting compound (hereinafter, referred to as a developer) include pressure-sensitive recording paper, heat-sensitive recording paper, and photosensitive pressure-sensitive recording. It is well known as paper and heat-sensitive recording paper.

For example, British Patent No. 2140449, U.S. Pat.
No. 36920, JP-B-60-23922, JP-A-57-179836,
Nos. 60-123556 and 60-123557 are described in detail.

In recent years, there has been a strong demand for high-sensitivity thermosensitive recording materials, and for that purpose, thermosensitive recording materials having an undercoat layer have been widely used. However, the sensitivity of the heat-sensitive recording material having the undercoat layer is still insufficient, and a heat-sensitive recording material having higher sensitivity is required.

(Object of the Invention) An object of the present invention is to provide a thermosensitive recording material having high sensitivity.

(Constitution of the invention) An object of the present invention is to provide a thermosensitive recording material comprising an undercoat layer using a pigment and a binder provided on a support and a thermosensitive coloring layer provided on the undercoat layer. Wherein the undercoat layer is a layer formed by applying a coating solution containing polyvinyl alcohol and adjusted to a pH of 6.0 or more.

Conventionally, there has been known a method in which each of the thermosensitive coloring layer, the protective layer, and the undercoat layer independently contains boric acid or / and borax and polyvinyl alcohol and reacts during coating and drying to form a hardened film. Have been. But,
These have no effect on improving the sensitivity. By adding boric acid or borax and polyvinyl alcohol separately to the undercoat layer and the thermosensitive coloring layer, a hardening reaction occurs at the interface between the two layers during coating and drying, preventing the penetration of the thermosensitive coloring components into the undercoat layer. The present invention was found to be effective in improving the sensitivity, and the present invention was achieved.

The amount of boric acid or borax used in the present invention is not particularly limited, but is preferably 5% or more of polyvinyl alcohol.

In the present invention, the color former, the developer and the heat-fusible substance are dispersed in a water-soluble binder, but the binder used in the present invention is dissolved in water at 25 ° C. by 5% by weight or more. The following binders may be used in combination with polyvinyl alcohol.

Methylcellulose, carboxymethylcellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, carboxy-modified polyvinyl alcohol, polyacrylamide, vinyl acetate-polyacrylic acid copolymer And the like. These binders are used not only at the time of dispersion but also for the purpose of improving the strength of the coating film. For this purpose, styrene / butadiene copolymer, vinyl acetate copolymer, acrylonitrile / butadiene copolymer, acrylic Acid butadiene copolymer,
A latex-based binder of a synthetic polymer such as polyvinylidene chloride may be used in combination.

Examples of the color former 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-55-227253. If some of these are disclosed, as a triarylmethane compound, 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 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. Examples of the diphenylmethane compound include 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N -Halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like, and as xanthene compounds, rhodamine-B-anilinolactam, rhodamine- (p-nitrino) lactam, 2- ( Dibenzylamino) fluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6
-Dibutylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluoran, 2-anilino-3-methyl-6-N-methyl-N-
Cyclohexylaminofluoran, 2-anilino-3-
Chloro-6-diethylaminofluoran, 2-anilino-3-methyl-6-N-ethyl-N-isobutylaminofluoran, 2-anilino-6-dibutylaminofluoran, 2-anilino-3-methyl-6 N-methyl-N
-Tetrahydrofurfurylaminofluoran, 2-anilino-3-methyl-6-piperidinoaminofluoran,
2- (o-chloroanilino) -6-diethylaminofluoran, 2- (3,4-dichloroanilino) -6-diethylaminofluoran, and the like. Examples of the thiazine compound include benzoyl leucon methylene blue and p-nitrobenzyl leuco. Methylene blue and the like, and as spiro compounds, 3-methyl-spiro-dinaphthopyran,
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. .

As the color developer used in the present invention, a phenolic compound or a salicylic acid derivative and a polyvalent metal salt thereof are preferable. Examples of these phenolic compounds include 2.2'-bis (4-hydroxyphenyl) propane, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, and 1,1'-bis. (3-chloro-4-hydroxyphenyl) cyclohexane, 1,1'-bis (4-hydroxyphenyl) cyclohexane, 1.1'-bis (3-chloro-4-hydroxyphenyl) -2-ethylbutane, 4,4'- sec-isooctylidenediphenol, 4,4'-sec-butylidenediphenol, 4-tert-octylphenol, 4-p-methylphenylphenol, 4,4'-methylcyclohexylidenephenol, 4,4'-iso Pentylidene phenol,
Benzyl p-hydroxybenzoate and the like. Examples of salicylic acid derivatives include 4-pentadecylsalicylic acid, 3,5-di (α-methylbenzyl) salicylic acid, 3,5-di (ter-octyl) salicylic acid, 5-octadecylsalicylic acid,
-Α- (p-α-methylbenzylphenyl) ethyl salicylic acid, 3-α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyl Oxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4
-Octadecyloxysalicylic acid and the like, and their zinc, aluminum, calcium, copper and lead salts. These developers are preferably used in an amount of 50 to 800% by weight of the color former, more preferably 100 to 500% by weight. 50
If the amount is less than 80% by weight, color development is not sufficient, and if the amount is more than 800% by weight, no further effect can be expected, which is not preferable.

In the heat-sensitive recording material of the present invention, a heat-fusible substance can be contained in the heat-sensitive coloring layer in order to improve the thermal response. Examples of preferred heat-fusible substances include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-benzyl biphenyl, di (2-methylphenoxy) ethane,
Di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropyl Phenyl ether, 1,4-butanediol-p-tert-
Octyl phenyl ether, 1-phenoxy-2- (4
-Ethylphenoxy) ethane, 1-phenoxy-2-
(4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4
-Methoxyphenyl) ether and the like. The heat-fusible substance is used alone or in combination, and in order to obtain a sufficient thermal response, it is necessary to
It is preferably used in an amount of 10 to 200% by weight, more preferably 20 to 150% by weight.

Further, pigments, metal soaps, waxes, surfactants, antistatic agents, ultraviolet absorbers, defoamers, conductive agents, fluorescent dyes, and the like may be added as necessary.

As the pigment, calcium carbonate, barium sulfate, lithopone, wax, kaolin, silica, amorphous silica and the like are used.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, and aluminum stearate. As wax,
Paraffin wax, microcrystalline wax,
Carnauba wax, methylolsteroamide, polyethylene wax, polystyrene wax, fatty acid amide wax and the like are used alone or in combination.

As the surfactant, a sulfosuccinic acid-based alkali metal salt and a fluorine-containing surfactant are used.

Further, it is preferable to add a color erasure preventing agent to the thermosensitive coloring layer in order to prevent the color erasure of the image printing portion and to make the formed image fast. A phenol compound, particularly a hindered phenol compound, is effective as a decolorization inhibitor, for example,
1,1,3-tris (2-methyl-4-hydroxy-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, 2,2′-methylene-bis (6-tert-butyl-4-)
Methylphenol), 2,2'-methylene-bis- (6-t
ert-butyl-4-ethylphenol), 4,4'-butylidene-bis (6-tert-butyl-3-methylphenol), 4,4'-thio-bis- (3-methyl-6-tert-
Butylphenol), and the like. The phenolic compound is preferably used in an amount of 1 to 200% by weight based on the developer, more preferably 5 to 50% by weight.
% By weight.

These materials are each mixed and then applied to a support.

As the support, paper, synthetic paper, various bases and the like are used, and an undercoat layer is previously provided on the support in order to obtain high smoothness.

The undercoat layer can be of the same type as the pigment used in the thermosensitive coloring layer, and should be made using a synthetic or natural polymer compound such as styrene / butadiene latex, starch, polyvinyl alcohol, or polyacrylamide as a binder. Can be. Further, other additives may be used as needed. The applied heat-sensitive recording material is dried, subjected to a treatment such as a calender, and provided for use.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

(Examples and Comparative Examples)

(Preparation of undercoat paper) Calcined kaolin (Engelhardt; Ansilex)
93) 80g of 0.5% sodium hexametaphosphate aqueous solution 160g
Together with a homogenizer to obtain a pigment dispersion. 16 g of styrene-butadiene latex (manufactured by Sumitomo Nogatax; SN307, solid content: 48%), 80 g of a 10% aqueous solution of a water-soluble polymer shown in Table 1, and further a 10% aqueous solution of sodium hydroxide were added to the pigment dispersion. The pH was adjusted to the value shown in Table 1 to obtain a coating solution for the undercoat layer. The coating solution for undercoat was applied to high-quality paper of 50 g / m ² to 8 g / m ² and dried to prepare an undercoat paper.

(Preparation and Coating of Coating Solution for Thermosensitive Coloring Layer) 20 g of 3-diethylamino-6-methyl-7-anilinofluoran in a 5% aqueous solution of a water-soluble polymer shown in Table 1 in 100%
Disperse in a ball mill for 24-48 hours with g, average particle size 1.0
A μm dispersion was obtained. Further, 40 g of bisphenol-A and 40 g of naphthyl benzyl ether were balled together with 400 g of a 5% aqueous polymer shown in Table 1 for 24 to 48 hours. In addition, 80 g of calcium carbonate (manufactured by Shiraishi Calciul; Univer 70) was dispersed with a homogenizer together with 160 g of a 0.5% aqueous solution of sodium hexametaphosphate to obtain a pigment dispersion.

The dispersion liquids obtained as described above were mixed, and a 10% aqueous solution of the polymer shown in Table 1 was added.
% Boric acid / borax sand aqueous solution and 50 g of a 21% zinc stearate emulsion were added to obtain a coating solution for thermal paper, which was coated on the undercoated paper with a wire bar so that the dry coating amount was 7 g / m ^2. The resultant was dried in an oven at ℃ to obtain a heat-sensitive recording material of the present invention.

The heat-sensitive recording paper obtained as described above is surface-treated with a low-pressure calender, and a thermal head (KLT-216-8MPD1) manufactured by Kyocera Corporation and a heat-sensitive paper having a pressure roll of 100 kg / cm ² immediately before the head. Head voltage 24
Printing was performed with pulse widths of 8.0, 1.0, and 1.2 using a pressure roll under the conditions of V and a pulse cycle of 10 ms, and the print density was measured with a Macbeth reflection densitometer RD-918. The results are shown in Table 2.

As shown in Table 2, it can be seen that the present invention can provide a highly sensitive thermosensitive recording material.

Claims (1)

(57) [Claims] 1. A thermosensitive recording material comprising an undercoat layer using a pigment and a binder provided on a support and a thermosensitive coloring layer provided on the undercoat layer, wherein the thermosensitive coloring layer contains boric acid or borax. A thermosensitive recording material, wherein the undercoat layer is a layer formed by applying a coating solution containing polyvinyl alcohol and adjusted to pH 6.0 or higher.