JPS62280073A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain excellent color forming property and water resistance, by specifying the degree of esterification of an alkali salt of a styrene-maleate copolymer constituting a protective layer to a given value or larger. CONSTITUTION:A thermal color forming layer comprising a colorless or light- colored electron-donative dye precursor and an electron-acceptive compound capable of a color reaction with the dye precursor and a protective layer comprising an alkali salt of a styrene-maleate copolymer as a main constituent are provided in a laminated state. The alkali salt of the copolymer has a degree of esterification of at least 50%. The maleate used for the copolymer is preferably one having up to 10 carbon atoms in an ester moiety, e.g., methyl maleate, ethyl maleate, propyl maleate or isobutyl maleate. A binder used in the protective layer may be polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose or a vinyl acetate emulsion.

Description

DETAILED DESCRIPTION OF THE INVENTION V. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a thermal recording material, particularly to a thermal recording material excellent in color development and water resistance.

[Conventional technology]

So-called two-component thermal recording materials that utilize the color reaction between a colorless or light-colored electron-donating dye precursor and an electron-accepting compound are disclosed in Japanese Patent Publication Nos. 45-14039 and 43-416.
It is disclosed in No. 0, etc. Two-component color-forming thermosensitive materials are produced by dispersing a colorless or light-colored electron-donating dye precursor and an electron-accepting compound in the form of fine particles, and then mixing these with a binder to bind these two types of heat-reactive compounds. etc., and coated on the support so as to be isolated, while
Both of them are melted by heating, and the coloring reaction that occurs when they come into contact is used to record.

These two-component color-forming thermal recording materials are: ■-subsequent color development and no need for development, ■Paper quality similar to general paper, ■Easy handling, ■High color density, and ■Various color hues. It has advantages such as being able to easily produce thermal recording materials, and has great utility value. For this reason, it is most commonly used as a thermal recording material. In particular, the use of thermal recording materials in the fields of facsimiles, recorders, and printers has been remarkable in recent years. As its use in the field of facsimile has spread, recording speeds have been increased, but even for thermosensitive materials, there is a strong need to improve color development, that is, thermal responsiveness to short pulses, that is, low energy. It has been requested.

On the other hand, since these thermal recording materials are primary color-forming, they have the disadvantage that the electron-donating dye precursor and the electron-accepting compound react not only with heat but also with solvents and the like.

This is because all of these thermal recording materials are organic substances.
This is because they have high solubility in solvents, and therefore reactions occur in the solvents. Therefore, when it comes into contact with stationery containing solvents, such as water-based ink pens, oil-based ink pens, fluorescent pens, diazo developers, adhesives, or glues, the white area of thermal paper may become colored or the printed area may become discolored. This resulted in a significant loss of product value.

On the other hand, conventionally, on the heat-sensitive coloring layer,
No. 7880, JP-A-48-50457, JP-A-48-
Efforts have been made to provide a K, solvent-resistant protective layer as disclosed in Japanese Patent No. 31958 and the like.

[Problem that the invention seeks to solve]

Various binders are known for use in the protective layer, but thermal recording materials using styrene-maleic acid ester copolymer alkali salt as the binder for the protective layer include triethanolamine-triethylene glycol, etc. Even if you touch a highlighter containing a solvent of but,
Generally, these heat-sensitive paper materials have the disadvantage that they have insufficient water resistance, and if they are stacked with other paper while still wet, they will adhere to each other, and a countermeasure is desired.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a thermal recording material which uses a styrene-maleic acid ester copolymer alkali salt as a binder for a protective layer, and which has strong water resistance.

[Means for solving problems]

The object of the present invention is to provide a heat-sensitive coloring layer containing a normally colorless to light-colored electron-donating dye precursor and an electron-accepting compound that develops a color by reacting with the electron-donating dye precursor, and a styrene-maleic acid ester. A thermosensitive paper material formed by laminating a protective layer containing a copolymer alkali salt as a main component, characterized in that the styrene-maleic acid ester copolymer alkali salt has an esterification degree of 50 or more. Achieved through editorial materials.

The present invention will be explained in detail below.

The thermal recording material of the present invention basically consists of a base paper (preferably neutral paper) and a thermal coloring layer and a protective layer provided thereon.

The feature of the present invention is that the degree of esterification is 2>r50% as a binder for the protective layer provided on the heat-sensitive coloring layer.
There are books containing alkali salts of the above-mentioned styrene-maleate copolymers, such as sodium salts, potassium salts, ammonium salts, and the coexistence of these salts. The molecular weight of the copolymer salt is preferably from 30,000 to 250,000, and particularly preferably from Bn, ooo to 15CL000.

As mentioned above, salts of styrene-maleic acid ester copolymers have conventionally been used as protective layers for thermal recording paper, but all of these have a degree of esterification of about 10 to 30% and are poor in water resistance. However, it has been found that when an esterification degree of 50% or more is used, water resistance is significantly improved without impairing recording performance (coloring performance).

In the alkali salt of a styrene-maleate ester copolymer having an esterification degree of 50 or more according to the present invention, the maleate ester used in the copolymerization is preferably one in which the number of carbon atoms in the ester moiety is 10 or less. Particularly preferred examples include methyl maleate, ethyl maleate, flobyl maleate, and isobutyl maleate.

The binder used in the protective layer in the present invention may consist only of the above-mentioned copolymer salt, but may also be used in combination with other polymers. Specifically, polyvinyl alcohol, methylcellulose, starch, carboxymethylcellulose, diisobutylene/-maleic acid copolymer, polyamide resin, polyacrylamide resin, gelatin, casein, gum arabic, styrene-butadiene rubber latex, acrylonitrile-butadiene rubber. Latex, vinyl acetate emulsion, etc. are used.

When the binder of the present invention is used in combination with other polymers, it is necessary that the salt of the styrene-maleate ester copolymer be present in an amount of at least 30%.

These components are dispersed or dissolved using a solvent such as water, and then applied onto the heat-sensitive coloring layer described later and dried to form a protective layer.

Incidentally, the protective layer and the thermosensitive color forming layer may be applied separately or at the same time.

The thermosensitive coloring layer in the present invention is made by dispersing a colorless or light-colored electron-donating dye precursor (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a color developer) in a binder together with additives if necessary. It is something.

As the color forming agent used in the present invention, triarylmethane compounds, diphenylmethane compounds, xanthine compounds, thiazine compounds, spiropyran compounds, etc. are used. To illustrate some of these, triarylmethane compounds include he-3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone), he-3-bis(p-dimethyl aminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,3-dimethylindole-3
-yl) phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl) phthalide, etc. Diphenylmethane compounds include 4.
4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoolamine, N-2
, 4,5-trichlorophenylleucoolamine, etc., are suitable xanthine compounds such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine B (p-chloroanilino)lactam, 2-dibenzylamino -6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2
-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane, 2-o-chloroanilino-6-
Diethylaminofluorane, 2-m-chloroanilino-
6-Dinithylaminofluorane, 2-(3,4-dichloroanilino)-6-diethylaminofluorane, 2
-octylamino-6-diethylaminofluorane, 2
-dihexylamino-6-jethylaminofluorane,
2-m-trifluoromethylanilino-6-diethylaminofluorane, 2-butylamino-3-chloro-6-diethylaminofluorane, 2-ethoxyethylamino-
3-chloro-6-diethylaminofluorane, 2-p-
Chloroanilino-3-methyl-6-sibutylaminofluorane, 2-anilino-3-methyl-6-sioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6 -diethylaminofluorane, 2-anilino-3-methyl-
6-cyphenylaminofluorane, 2-phenyl-6-
diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane,
2-anilino-3-methyl-5-chloro-6-diethylaminofluorane% 2-anilino-3-methyl-6-
ethylamino-7-methylfluorane, 2-anilino-3-methoxy-6-sibutylaminofluorane, 2-
o-chloroanilino-6-sibutylaminofluorane,
2-p-chloroanilino-3-ethoxy-6-M-ethyl-N-isoamylaminofluorane% 2-o-chloroanilino-6-p-butylanilinofluorane, 2-
Anilino-3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl-6-sibutylaminofluorane, 2-anilino-3-ethyl-6-N-x
f-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-γ-methoxypropylaminofluorane, 2-anilino-3-chloro-6
-N-ethyl-N-isoamylaminofluorane, etc.; examples of dithiazine compounds include benzoylleucomethylene blue; examples of spiro compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 43'- Cyclolose birodinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)spiropyran,
Examples include 3-7' lopilose spirodibenzobilane.

These may be used alone or in combination.

Further, examples of color developers used in the present invention include phenolic compounds, organic acids or metal salts thereof, oxybenzoic acid esters, etc. Phenol compounds are particularly preferred because the amount thereof can be small, and among them, bisphenol compounds are preferred. is preferable.

Further, oxybenzoic acid ester is preferable because it easily produces high print density.

These compounds are disclosed in Japanese Patent Publication No. 45-14039,
It is disclosed in Japanese Patent Publication No. 51-29830. Specifically, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4-hydroxybenzoate, 42'-dihydroxybiphenyl, 2,
2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-isopropylidene bis(2-
methylphenol), 1,1-bis-(3-chloro-4
-hydroxyphenyl)cyclohexane, 1°1-bis-(3-chloro-4-hydroxyphenyl)-2-ethylbutane%4.4'-Secondary-isobutylidene diphenol, 1,1-bis-(4-hydroxyphenyl) phenyl)
Cyclohexane, 1,4-his(4'-hydroxycumyl)benzene, 4-hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic acid 13. Fragrance: -m-chlorobenzyl ester, 4-hydroxybenzoic acid β-phenethyl ester, 4-hydroxy-λj4r-dimethylphenylsulfone, 1-t-butyl-4-p-hydroxyphenylsulfonyloxybenzene% 4-M-benzyl Examples include sulfamoylphenol, 2,4-dihydroxybenzoic acid-β-phenoxyethyl ester, and λ4-dihydroxy-6-methylbenzoic acid benzyl ester.

In the present invention, in order to improve thermal responsiveness, a sensitizer can be included in the thermosensitive coloring layer together with the color former and developer.

As the sensitizer, an organic compound having a melting point of 70° C. or more and 150° C. or less and having good compatibility with a color former or developer is preferable.
Specific examples include compounds represented by the following general formulas (IX) to ('M).

R, N H00N H, (Xll) R4CONH-R? (X[[
1) In the formula, R1 to R4 each represent a phenyl group, a benzyl group, and a lower alkyl or hydroxy or alkoxy substituted product thereof, and RIb
R11 each represents an alkyl group having 12 to 24 carbon atoms, and Rγ represents hydrogen or a phenyl group.

Further, when the phenyl group or benzyl group represented by R to R4 in general formulas (IX) to (M) is substituted with a lower alkyl group, the number of carbon atoms thereof is 1 to 8, preferably 1 to 3. It is as follows. In addition, when it is substituted with hydrogen, it is preferably chlorine or fluorine.

Z Z' In the formula, R8 represents a divalent group, preferably an alkylene group, an alkylene group having an ether bond, an alkylene group having a carbonyl group, an alkylene group having a gen atom,
An alkylene group having an unsaturated bond, more preferably an alkylene group or an alkylene group having an ether bond. In addition, X, Y%z1X', Y', and Z' may be the same or different, and represent a hydrogen atom, an alkyl group, a lower alkoxy group,
Indicates a lower aralkyl group, a halogen atom, an alkyloxycarbonyl group, and an aralkyloxycarbonyl group.

Also, are Q and Q' oxygen atoms or sulfur atoms, respectively? show.

The compounds of the general formulas (■) to (XN') have a melting point of 70°C
The melting point is preferably 80°C or more and 130°C or less, more preferably 150°C or less.

Specifically, benzyl p-benzyloxybenzoate, β
~ Naphthylbenzyl ether, stearic acid amide, palmimic acid amide, N-phenyl stearic acid amide,
N-stearylurea, β-naphthoic acid phenyl ester % 1-hydroxy-2-naphthoic acid phenyl ester, β-naphthol (P-chlorobenzyl) ether, β
-Naphthol (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-phthanediol p
-Methyl phenyl ether, t4-propanediol-
p-methylphenyl ether, 1,4-7'tanediol-p-isopropylphenyl ether, 1,4-butanediol-pt-octylphenyl ether, 2-
Fe/xy-1-p-)lyluoxyethane% 1-
7 enoxy 2-(4-ethylphenoxy)ethane, 1
-7 enoxy 2-(4-chlorophenoxy)ethane,
t4-Butanediol phenyl ether 1,2-bis(
Examples include 4-methoxyphenylthio)ethane.

The thermofusible substances exemplified as the sensitizers may be used alone or in a mixture, and in order to obtain sufficient thermal responsiveness, 10 to 20% by weight of the sensitizer should be used. The amount used is preferably 20 to 150% by weight.

In the present invention, the color forming agent, color developer, and if necessary sensitizer are dispersed together with a binder such as a water-soluble polymer compound using a solvent such as water, and a support such as paper or plastic film is dispersed. It is coated and dried to form a heat-sensitive coloring layer.

Water-soluble polymer compounds used as binders include:
polyvinyl alcohol, and droxyethyl cellulose,
Hydroxyglobil cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, polyacrylic acid amide, starch derivative, casein,
Examples include gelatin, carboxymethylcellulose, methylcellulose, and the like.

In addition, in order to impart water resistance to these water-soluble polymer compounds, water-resisting agents (gelling agents, cross-linking agents) are added, and emulsions of hydrophobic polymers, specifically styrene-butadiene rubber latex, acrylic A resin emulsion or the like can also be added.

The thermosensitive coloring layer of the present invention may contain various additives for various purposes in addition to the above-mentioned components.

Examples of additives include inorganic pigments and waxes to prevent staining of the recording head during recording, fatty acids and metal soaps to improve releasability from the head.

Specifically, pigments include kaolin, calcined kaolin, talc, waxite, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate,
IbF) such as titanium oxide, barium carbonate, urea-formalin filler, cellulose filler, etc.; waxes include paraffin wax, cowna wax, microcrystalline wax, polyethylene wax, and higher fatty acid esters.

Examples of the metal soap include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

In the present invention, the heat-sensitive coloring layer is provided on a support, and the protective layer is further provided thereon to obtain a heat-sensitive paper material.

In the present invention, a water-resistant agent such as a pigment, a metal soap, or a wax may be added to the protective layer for the purpose of improving the matching property with the thermal bed during printing and improving the water resistance of the protective layer.

The amount of the pigment added is preferably 15 to 4 times the total weight of the polymer, particularly preferably a8 to &5 times. If the amount added is less than the above amount, it is ineffective in improving head matching properties, and if the amount added is more than the above amount, the sensitivity will be significantly lowered and the commercial value will be impaired. Examples of pigments used include zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, waxite, kaolin, aluminum hydroxide, silica, amorphous silica, and colloidal silica.

As metal soaps, higher fatty acid metal salts are used, such as zinc stearate and calcium stearate.

Emulsions such as aluminum stearate are used, and zinc stearate is particularly preferred. The amount added is preferably α5 to 20, particularly preferably 1 to 10%, based on the total weight of the protective layer. As the wax, emulsion wax such as paraffin wax, microcrystalline wax, carnauba wax, methylol aeramide, stearic acid amide, polyethylene wax, polystyrene wax, etc. is used, and the amount added is preferably 1 to 20% of the total weight of the protective layer. , particularly preferably 1 to 10%.

Further, when coating the protective layer on the heat-sensitive coloring layer, a surfactant may be added to obtain a uniform protective layer. As surfactants, sulfosuccinic acid alkali metal salts,
Fluorine-containing surfactants etc. may cause irritation. Specifically, di(2-ethylhexyl)sulfosuccinic acid, di(n-
There are sodium salts such as hexyl sulfosuccinic acid, ammonium salts, etc., but most anionic surfactants are effective.

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

Examples 1 to 5 Crystal violet lactone, benzyl parahydroxybenzoate, ado stearate, 1゜1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 5 of 201i100F each It was dispersed in a ball mill overnight with an aqueous solution of excellent polyvinyl alcohol (Kuraray PV Mu 105) to have a volume average particle size of 3 μm or less.

Pigment is 80f sodium hexametaphosphate [L5% solution 1
It was used after being dispersed with a homogenizer together with 60f. Each of the dispersions prepared as described above was mixed with crystal violet lactone dispersion 5at, benzyl A-hydroxybenzoate dispersion 10f, and stearamide dispersion 5? % 1
．． 1.5-)lis(2-methyl-4hydroxy-5-t
ert-butylphenyl)butane dispersion 21. A coating liquid obtained by mixing 22f of pigment dispersion liquid and further adding 21% emulsion 3f of zinc stearate and 51 aqueous solution of sodium di(2-ethylhexyl)-sulfosuccinate, has a basis weight of s. Coat with a wire bar on o y/J high-quality paper so that the dry coating amount is 517 m2,
It was dried in an oven at 50°C to obtain a heat-sensitive coloring layer.

On the thermosensitive coloring layer obtained by the above method, kaolin (Kaobrite: Georgia Basifik Co., Ltd.) dispersion 15F (dispersion liquid is the same as the above thermosensitive coloring layer) is added to 5-modified solution 1001 of the polymer shown in Table 1. ), 4 tons of zinc stearate emulsion 21, and 1 f 1 aqueous solution of sodium di-(2-ethyl)sulfosuccinate were mixed to give a dry weight of 217 m''. After applying with a wire bar and drying in an oven at 50℃.

A pressure treatment was carried out using a pressure device consisting of a combination of a hard chrome plated roll and a hard rubber reel (shore hardness: SO) to obtain heat-sensitive recording paper.

Comparative Examples 1 to 3 A thermosensitive coloring layer was coated in the same manner as in the examples, using the binder shown in Table 1 for the protective layer, and a thermosensitive recording paper was obtained.

The obtained thermosensitive recording paper was tested for water resistance using the following method.

0.5 μt of water was dropped onto the surface of the thermosensitive recording paper, the base paper was placed on top of it, and after air drying for 1 hour, it was peeled off and the strength of adhesion between the recording paper and the base paper was examined. Do not adhere to highly water resistant materials.

The evaluation results are shown in Table 1.

〔Effect of the invention〕

As is clear from the above results, when an alkali salt of a styrene-maleate copolymer having a degree of esterification of 50 or more is used as a binder for the protective layer according to the present invention, the degree of esterification is 50 or more. It can be seen that the water resistance of the thermal recording paper is improved compared to when the following materials are used.

Procedural amendment July 3rd, 1986

Claims (1)

[Claims] Usually, a heat-sensitive coloring layer containing a colorless or light-colored electron-donating dye precursor and an electron-accepting compound that develops color by reacting with the electron-donating dye precursor, and a styrene-maleate copolymer alkali salt are used. 1. A heat-sensitive recording material comprising a protective layer laminated as a main component, characterized in that a styrene-maleic acid ester copolymer alkali salt has an esterification degree of 50% or more.