JP2000335108A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat sensitive recording material, reduced in the generation of blushing (coloring on the surface) in the non-printed part of the heat sensitive paper and, further, excellent in high-concentration coating suitability of coating liquid upon manufacturing the heat sensitive paper. SOLUTION: A recording material is provided on a sheet type substrate with a heat sensitive recording layer containing an electron donative color developing dye, an electron acceptive developer compound for developing color while reacting under heating and an adhesive agent. In this case, an adhesive agent consisting of a dispersant of polyvinyl alcohol having mercapto group and a dispersoid of a polymer comprising least one kind of ethylenically unsaturated monomer or diene monomer capable of effecting radical polymerization is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-sensitive recording material. Further, the present invention relates to a heat-sensitive recording material which has less fog (coloration of the background portion) in a non-printed portion of the heat-sensitive paper and further has excellent suitability for high-concentration coating of a coating solution at the time of heat-sensitive paper production.

[0002]

2. Description of the Related Art Heat-sensitive recording materials comprising a heat-sensitive recording layer containing an electron-donating color-forming dye, an electron-accepting color-developing compound capable of reacting under heating to form a color, and an adhesive are well known. Have been. Such a thermosensitive recording medium is relatively inexpensive, and since the recording apparatus is compact and easy to maintain, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields. In the heat-sensitive recording material as described above, the usual adhesives include a water-soluble polymer adhesive such as polyvinyl alcohol and starch, and a styrene / butadiene copolymer latex synthesized using a low-molecular emulsifier, and an acrylic adhesive. Latex is often used. Conventionally, due to the coloring mechanism of the thermosensitive recording material, it has not been possible to dry at high temperature during the manufacturing process,
Therefore, there was a problem that the production speed did not increase.
For this purpose, it is desirable to increase the solid content concentration of the coating liquid as much as possible and to lower the viscosity in view of coating properties. Therefore, attempts have been made to use latex at a high addition level.However, when a latex synthesized with such an emulsifier is used, the coloring of an electron-donating color-forming dye by the emulsifier in the latex, so-called, There was a problem that fogging occurred and it could not be used.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and has reduced fog (coloration of the background portion) in the non-printed portion of the thermal paper. It is a further object of the present invention to provide a heat-sensitive recording material which is excellent in suitability for high-concentration coating of a coating liquid when preparing a thermal paper.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, an electron-donating color-forming dye was formed on a sheet-like support and reacted with heat to form a color. In a heat-sensitive recording material comprising a heat-sensitive recording layer comprising an electron-accepting developer compound and an adhesive, a polyvinyl alcohol having a mercapto group is used as an adhesive, and a radical polymerizable ethylenically unsaturated monomer is used. The present inventors have found that the use of an adhesive containing a polymer composed of at least one of a monomer and a diene monomer as a dispersoid has an excellent effect in the above point, and reached the present invention.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, polyvinyl alcohol used as a dispersant (hereinafter, polyvinyl alcohol may be abbreviated as PVA) must have a mercapto group. PVA having a mercapto group at only one end of such a molecule is obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer in the presence of thiolic acid by a conventional method. The production method will be described in detail below. The thiolic acid used herein includes an organic thiolic acid having a -COSH group. For example, thiolacetic acid,
Examples thereof include thiolpropionic acid, thiolbutyric acid, and thiolvaleric acid. Of these, thiolacetic acid is the most preferable because of its good decomposability. The vinyl ester monomer can be used as long as it is capable of radical polymerization. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc.
From the viewpoint of obtaining vinyl acetate, vinyl acetate is preferred.

In addition, it is possible to co-exist with a monomer copolymerizable with a vinyl ester in a range that does not impair the gist of the present invention. For example, olefins such as ethylene, propylene, 1-butene, isobutene, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate Acrylates such as t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-methacrylate
Propyl, n-butyl methacrylate, i-methacrylate
Methacrylates such as butyl, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether , Vinyl ethers such as t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chlorides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetate; Allyl compounds such as allyl, fumaric acid,
Maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, carboxyl group-containing compounds such as trimellitic anhydride or itaconic anhydride and esters thereof, ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid,
Examples thereof include sulfonic acid group-containing compounds such as 2-acrylamide-2-methylpropanesulfonic acid, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate. The amount of the monomer is preferably 5 mol% or less.

In the presence of thiolic acid, the polymerization of vinyl monomers mainly composed of vinyl esters such as vinyl acetate is carried out in the presence of a radical polymerization initiator, in a bulk polymerization method, in a solution polymerization method, or in a suspension polymerization method. Although any method such as a polymerization method and an emulsion polymerization method can be used, a solution polymerization method using methanol as a solvent is most advantageous industrially. The amount and method of addition of the thiolic acid to the polymerization system during the polymerization are not particularly limited, and are appropriately selected depending on the physical properties of the intended polyvinyl ester polymer. As the polymerization method, a known method such as a batch method, a semi-continuous method, or a continuous method can be employed. Examples of the radical polymerization initiator include, for example, 2,
Known radical polymerization initiators such as 2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), benzoyl peroxide, and carbonate carbonate can be used, An azo initiator such as 2,2'-azobisisobutyronitrile is preferred because it is easy to handle. Further, radiation, electron beam, and the like can also be used. The polymerization temperature is determined by the physical properties of the desired modified PVA, and is usually selected from the range of 10 to 90 ° C. The initiator used at that time is appropriately selected according to the polymerization temperature. After polymerization for a predetermined time, unpolymerized vinyl esters are removed by a usual method to obtain a cationically modified polyvinyl ester-based polymer having a thiolate group at a terminal.

The polyvinyl ester-based polymer thus obtained is saponified by a conventional method, but is preferably saponified in an alcohol solution, especially a methanol solution. As the alcohol, not only an anhydride but also a small amount of a water-containing alcohol may be used according to the purpose, and an organic solvent such as methyl acetate or ethyl acetate may be optionally contained. The saponification temperature is usually selected from the range of 10 to 90 ° C. As the saponification catalyst, for example, alkaline catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate and potassium methylate are preferable, and the amount of the catalyst used is appropriately determined according to the degree of saponification degree and the amount of water. It is used in a molar ratio of 0.001 or more, preferably 0.002 or more, based on the ester unit. If the amount of alkali is too large, it becomes difficult to remove the remaining alkali from the polymer, which is not preferable because the polymer is colored, and the molar ratio is preferably 0.2 or less. When the polyvinyl ester polymer contains a component that reacts with an alkali catalyst such as a carboxyl group or its ester group and consumes an alkali, the alkali catalyst is used in an amount corresponding to the consumed amount.

By the above-mentioned saponification reaction, thiol is added to the terminal.
The polyvinyl ester polymer having an acid ester group
Terminal thiolate ester and main chain vinyl ester bond
It is saponified, the polymer ends are mercapto groups, and the main chain is
Nyl alcohol, but the main chain vinyl ester unit
The degree of saponification is appropriately selected according to the purpose of use. Saponification
The polymer precipitated after the reaction is washed with, for example, methanol.
Purification by a known method such as
By removing impurities such as alkali metal salts and drying
It can usually be obtained as a white powder. As described above, the present invention
Polymerization Having Mercapto Group at Terminal Used in Polymer
The method for producing the polymer was described, but the modified PVA-based polymer
The viscosity average degree of polymerization of the body (hereinafter abbreviated as degree of polymerization) is 50
~ 150,000, and 100 ~ 20
000 is preferable, and 100 to 10,000 is more preferable.
No. The degree of polymerization of PVA is JIS-K6726.
Of the polymer purified after re-saponification,
Viscosity determined by the following formula from intrinsic viscosity [η] measured at ℃
It is represented by the average degree of polymerization (P). P = ([η] × 10³/8.29)^{(1 / 0.62)}  When the degree of polymerization is less than 50 or greater than 8000,
Stable polymer fine particles cannot be obtained. Mercapto of the present invention
The degree of saponification of a modified PVA-based polymer having a
Although it depends on the type of group, it cannot be said unconditionally.
And 40 to 99.99 mol% in terms of paper strength
It is preferably 50 to 99.9 mol%, more preferably
And more preferably 60 to 99.5 mol%.

Using the PVA polymer having a mercapto group obtained by the above method as a dispersion stabilizer for polymerization, the (co) polymerization of an ethylenically unsaturated monomer or a diene monomer is carried out. In order to obtain an aqueous polymer (dispersoid) dispersion, known polymerization methods such as an emulsion polymerization method, a dispersion polymerization method, and a suspension polymerization method can be employed. The aqueous polymer dispersion thus obtained can be suitably used as an adhesive, and the polymer obtained by dehydrating the aqueous polymer dispersion by coagulation filtration or drying is disassembled or crushed. Powdered fine particles can also be used as the adhesive. From the viewpoint of the average particle size and the production of the obtained polymer fine particles, the aqueous polymer dispersion of the present invention is obtained by using a PVA-based polymer having a mercapto group as a dispersion stabilizer for emulsion polymerization, and using an ethylenically unsaturated monomer. An aqueous polymer emulsion obtained by carrying out emulsion (co) polymerization of a polymer or a diene monomer is particularly preferred.

In carrying out the emulsification (co) polymerization of an ethylenically unsaturated monomer or a diene monomer using the modified PVA-based polymer of the present invention as a dispersion stabilizer for emulsion polymerization, water, emulsification, By temporarily or continuously adding the above monomers in the presence of a dispersion stabilizer for polymerization and a polymerization initiator,
Any of ordinary emulsion polymerization methods such as heating and stirring can be carried out, and a monomer having a PVA having a mercapto group in advance can be used.
A method of continuously adding a mixture emulsified with an A-based polymer aqueous solution can also be carried out.

The ethylenically unsaturated monomers in the present invention include olefins such as ethylene, propylene and isobutene, vinyl chloride, vinylidene chloride, vinyl fluoride, and the like.
Halogenated olefins such as vinylidene fluoride, vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, vinyl esters such as vinyl pivalate, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, I-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-acrylate
Acrylates such as -butyl, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, and n-methacrylate Butyl, i-butyl methacrylate, t-butyl methacrylate, methacrylic acid 2
Methacrylic acid esters such as ethylhexyl, dodecyl methacrylate, octadecyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, acrylamide-2-methylpropanesulfonic acid and acrylamide-based monosodium salt thereof Dimers, acrylonitrile,
Nitriles such as methacrylonitrile, allyl compounds such as allyl acetate and allyl chloride, styrene-based monomers such as styrene, α-methylstyrene, P-methylstyrenesulfonic acid and its sodium and potassium salts, and other N-vinyl Pyrrolidone and the like, and diene monomers include butadiene, isoprene, chloroprene and the like. These monomers may be used alone or in combination of two or more. Particularly, diene copolymers such as styrene / butadiene copolymer latex, acrylonitrile / butadiene copolymer latex, and ethyl methacrylate / butadiene copolymer latex are used. A polymer latex or an acrylic copolymer latex such as an acrylate / vinyl acetate copolymer latex is preferably used.

The amount of the dispersion stabilizer for emulsion polymerization comprising the PVA polymer having a mercapto group of the present invention is as follows.
Depending on the degree of polymerization of the PVA-based polymer, the degree of saponification, and the required resin concentration of the emulsion, it is usually 0.2 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the monomer. Department. When the amount of the PVA-based polymer is less than 0.2 part by weight per 100 parts by weight of the monomer, the polymerization stability and the chemical stability are reduced, and the characteristics of the PVA-protected colloid-based aqueous emulsion are characteristic. However, the mechanical stability is also impaired, and the value as an emulsion is lost, which is not preferable. On the other hand, if the amount of the PVA-based polymer exceeds 20 parts by weight, the viscosity of the emulsion becomes high, and it is difficult to increase the concentration.

As the polymerization initiator, those known for emulsion polymerization can be used. Further, a redox system using a mercapto group of the PVA-based polymer and a water-soluble oxidizing agent such as potassium bromate, potassium persulfate, ammonium persulfate, hydrogen peroxide, or cumene hydroperoxide is also possible. Under normal polymerization conditions, a radical is not generated alone, but is decomposed only by a redox reaction with a mercapto group at the terminal of the PVA-based polymer to generate a radical. Therefore, the PVA-based polymer and the block copolymer are separated. It is preferable because it is effectively formed, and as a result, the effect of stabilizing the emulsion is increased. It is also possible to use a method in which potassium bromate is used at the start of polymerization, and then another polymerization initiator or an oxidizing agent, preferably hydrogen peroxide, is additionally added.

The PV having a mercapto group in the present invention
In carrying out emulsion (co) polymerization using a dispersant comprising an A-based polymer, it is preferable that the polymerization system is acidic. This is because, under basic conditions, the mercapto group, which exhibits extremely active reactivity in radical polymerization, ionically adds to the double bond of the monomer, and the rate of disappearance is large, so that the polymerization efficiency is significantly reduced. Although it depends on the type of unsaturated monomer, it is preferable that all operations are performed at pH 6 or lower, preferably pH 4 or lower. In the present invention, the dispersant comprising a PVA-based polymer having a mercapto group is preferably used alone, but a conventionally known anionic, nonionic, cationic surfactant or water-soluble polymer compound may be used. It can also be used appropriately as long as the effects of the present invention are not impaired.

In the present invention, the following are exemplified as the electron-donating color-forming dye and the electron-accepting color developing compound constituting the heat-sensitive recording layer.

As the electron-donating color-forming dye to be contained in the heat-sensitive recording layer, a triarylmethane compound may be used.
3,3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalite}, diphenylmethane compounds such as 4,4′-bis-dimethylaminobenzhydrin benzyl ether, N-2,4,5-trichlorophenyl Leuco auramine, as a xanthene compound, rhodamine B-anilinoactam, 3-diethylamino-7-
Butylaminofluoran, 3-diethylamino-7-
(2-chloroanilino) fluoran, 3-piperidino-
6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl-7-anilinofluoran, 3
-Cyclohexyl-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-
7- (β-ethoxyethyl) aminofluoran, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-isoamyl-
(N-ethylamino) -6-methyl-anilinofluoran and the like. These coloring dyes may be used alone or in combination of two or more.

Examples of the electron-accepting color developing compound that can be used in the present invention include phenol derivatives and aromatic carboxylic acid derivatives. When these are specifically exemplified, phenols include p-octylphenol and p-te
rt-butylphenol, p-phenylphenol,
2,2′-bis (p-hydroxyphenyl) propane,
2,2′-bis (p-hydroxyphenyl) pentane,
1,1′-bis (p-hydroxyphenyl) hexane,
2,2′-bis (p-hydroxyphenyl) hexane,
2,2′-bis (p-hydroxy-3,5-dichlorophenyl) propane, dihydroxydiphenyl ether,
4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like. . Examples of the aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-methylbenzylsalicylic acid, and polyvalent of the carboxylic acid. Metal salts and the like. These color developing compounds may be used alone or in combination of two or more.

Further, in the heat-sensitive recording layer, a sensitizer, a water-soluble polymer, an inorganic or organic pigment, a wax, a metal soap, and if necessary, a preservability improver, an ultraviolet absorber, a fluorescent dye, a colorant, etc. Can be appropriately blended. As a sensitizer for improving the sensitivity of the heat-sensitive recording material, for example, parabenzyl biphenyl, dibenzyl terephthalate,
Phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate, 1,2
-Di (3-methylphenoxy) ethane, di-p-oxalate
-Chlorobenzyl, di-p-methylbenzyl oxalate,
1,2-bis (3,4-dimethylphenyl) ethane and the like can be used.

There is no problem in adding a preservability improver to supplement the preservability. As such a preservability improver, phenolic and epoxy compounds are effective, and for example, 1,3,5-tris (4-t-butyl-3-
Hydroxy-2-, 6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl- 4-hydroxy-5-cyclohexylphenyl) butane, 1,1-bis (2-methyl-4-
(Hydroxy-5-t-butylphenyl) butane, 4,
4 ′-(1-phenylethylidene) bisphenol,
4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisphenol, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol,
Examples include phenol novolak type epoxy, halogen-substituted phenol novolak type epoxy resin, orthocresol novolak epoxy resin, epoxy compound of phenol-modified xylene resin, hydroquinone diglycidyl ether, and the like. Further, one or more of these compounds may be used in combination.

These can be prepared by using water as a dispersion medium, and using various types of wet pulverizers such as a sand grinder, an attritor, a ball mill and a cobo mill to obtain polyvinyl alcohol,
Polyacrylamide, carboxymethylcellulose, and other water-soluble polymer compounds such as styrene-maleic anhydride copolymer salt and the like, and dispersed with a surfactant and the like to form a dispersion, which is then used to prepare a heat-sensitive recording layer paint. Can be

Examples of the water-soluble polymer include polyvinyl alcohol (including modified polyvinyl alcohol such as carboxy-modified polyvinyl alcohol and silane-modified polyvinyl alcohol), starches (including modified starch), casein, gelatin, glue, polyacrylamide, and hydroxy. Ethyl cellulose, methyl cellulose, styrene-maleic anhydride copolymer salt, ethylene-maleic anhydride copolymer salt, isobutylene-maleic anhydride copolymer salt and the like can be mentioned.

Examples of pigments include calcium carbonate, clay, talc, titanium oxide, magnesium carbonate, zinc oxide, aluminum silicate, calcium silicate, silica,
Examples include inorganic pigments such as aluminum hydroxide, and in addition, starch granules, flour, silicone resin, urea / formalin resin, phenolic resin, melamine / formalin resin, epoxy resin, polystyrene resin, and the like can be used in combination. .

Examples of waxes and metal soaps include paraffin wax, carnarava wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylenebisstearic acid amide, higher fatty acid ester, and higher fatty acid. Examples include polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate, and the like.

In addition, various additives such as a crosslinking agent, an oil repellent, an antifoaming agent, a viscosity modifier, a surfactant, a fluorescent dye, and a coloring agent may be added as long as the effects of the present invention are not impaired. It is also possible to provide an overcoat layer on the heat-sensitive recording layer of the present invention. The overcoat layer includes, in addition to a water-soluble polymer (for example, the above-described water-soluble polymer and modified PVA) for imparting oil resistance and plasticizer resistance, a pigment for mainly suppressing sticking with a thermal head, Crosslinking agents, waxes, metal soaps and the like can be used.

The coating solution of the composition thus obtained is preferably used in a solid content range of 20 to 60% by weight.
In particular, even when the concentration is high, streaking during coating is unlikely to occur, as is clear from the examples described later.

The support material used in the present invention is not particularly limited, and for example, paper, synthetic fiber paper, synthetic resin film and the like can be conveniently used. Further, in the present invention, a back layer can be provided for suppressing permeation of oil or plasticizer from the back surface or for controlling curl. In addition, various modifications such as providing an undercoat layer below the heat-sensitive recording layer as needed can be used.

[0028]

The present invention will be described in more detail with reference to examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 (a) Preparation of emulsion In a heat-resistant autoclave equipped with a nitrogen inlet and a thermometer, PVA having a terminal mercapto group (polymerization degree: 300;
Degree of saponification 92.0 mol%, mercapto group content 6.5 ×
^10-5 equivalents / g) of a 4% aqueous solution (100 parts) was charged and adjusted to pH = 4.0 with dilute sulfuric acid. Then, styrene 60
Part and 40 parts of butadiene from a heat-resistant meter and pressurized to 70 ° C
Then, 25 parts of a 2% aqueous solution of potassium persulfate was injected under pressure to initiate polymerization. The internal pressure decreased from 4.6 kg / cm ^{2 as the} polymerization progressed, and after 20 hours, the internal pressure was 0.4 kg / cm ^2.
m ^{2 and the} polymerization rate was determined to be 99.0%.
The resulting styrene / butadiene copolymer emulsion had a solid content of 45.5% and a viscosity at 20 ° C. of 140 m
It was stable with Pa · s and an average particle diameter of 0.4 μm.

(B) Formation of heat-sensitive recording layer (1) Preparation of color-forming dye dispersion A; component amount (parts by weight) 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilino 40 parts of fluoran, 40 parts of a 10% aqueous solution of polyvinyl alcohol (Kuraray PVA105), and 20 parts of water. (2) Preparation of developer B; component amount (parts by weight) 40 parts of 4,4'-dihydroxyphenylsulfone; 40 parts of a 10% aqueous solution of polyvinyl alcohol (Kuraray PVA105) and 20 parts of water (3) Preparation of sensitizer dispersion C; component amount (parts by weight) 40 parts of di-p-methylbenzyl oxalate, polyvinyl alcohol (Kuraray PVA105) ) 10% aqueous solution 40
Parts, water 20 parts (4) Preparation of hydroquinone glycidyl ether dispersion D; component amount (parts by weight) Hydroquinone glycidyl ether 20 parts, 10% aqueous solution 20 of polyvinyl alcohol (Kuraray PVA105) 20
Part, water 40 parts These compositions were each separately prepared using a 1 mm-diameter glass bead and a vertical sand mill (manufactured by Imex Co., Ltd.).
(Sand grinder) until the average particle diameter was 0.8 μm. Thereafter, for the dispersion A, the diameter of the dispersion A was further increased to 0.
Using 3 mm zirconia beads, dispersion was performed to 0.38 μm using a diamond fine mill (manufactured by Mitsubishi Heavy Industries, Ltd.). (5) Preparation of pigment dispersion E; component amount (parts by weight) 40 parts of light calcium carbonate (Brilliant 105, Shiraishi Kogyo Co., Ltd.) and 60 parts of a 0.7% aqueous solution of sodium hexametaphosphate. This composition was dispersed with a Cowles disperser. (6) Preparation of Dispersions F and G As dispersions F and G, an aqueous dispersion of 20% zinc stearate and an aqueous dispersion of 20% stearamide were prepared.

Each of the compositions obtained in the above (1) to (6) and the emulsion obtained in the above (A) are mixed with an adhesive so that the weight ratio of the solid components is A: B: C: D: E: F. : G: corn starch (Oji Ace A: manufactured by Oji Corn Starch Co., Ltd.): styrene-butadiene copolymer = 10: 2
0: 20: 5: 20: 2: 2: 10: 11 were blended to obtain a coating liquid (concentration: 45%). Apply this coating solution with a basis weight of 5
0 g / m ² of high-quality paper with a coating amount of 7.5 g / m ² after drying
^The composition was coated with a rod blade (manufactured by Ishikawajima-Harima Kogyo Co., Ltd.) so as to obtain No. ^2, and high-concentration coatability (generation of streaks) was observed.
Table 1 shows the results. Further, after coating, it was dried to form a heat-sensitive recording layer to obtain a heat-sensitive recording material. After smoothing the thus obtained heat-sensitive recording material with a super calender,
The ground color development and oil resistance tests were examined.

Background fog: The coated paper prepared by the above method was placed in a thermo-hygrostat adjusted to 40 ° C. and 90% RH.
After 4 hours, the background fog of the blank portion was measured with a Macbeth reflection densitometer (RD-914, manufactured by Macbeth).

Oil resistance: Commercial high-speed facsimile UF60
Recording was performed in a copy mode using (manufactured by Matsushita Dentsu Co., Ltd.), a few drops of edible soybean oil were dropped on the printed part, and after 24 hours, the soybean oil was wiped off with gauze, and the degree of decoloration of the printed part was visually determined. Table 1 shows the results.

Example 2 In the styrene-butadiene copolymer emulsion of Example 1, instead of 100 parts of a 4% aqueous solution of polyvinyl alcohol having a terminal mercapto group, PVA having a terminal mercapto group (polymerization degree 500, saponification degree 500) 88.0 mol%, mercapto group content 3.2 × 10 ⁻⁵
Styrene-butadiene copolymer emulsion was obtained in the same manner as in Example 1 except that 100 parts of a 2% aqueous solution (equivalent / g) and 2 parts of an anionic emulsifier (Aerosol-OT; manufactured by Mitsui Cyanamid) were used (solid content). Concentration 45.
1%, viscosity 100 mPa · s). This emulsion was evaluated in the same manner as in Example 1.

Example 3 PVA having a mercapto group at the end in a pressure-resistant autoclave equipped with a nitrogen inlet and a thermometer (polymerization degree: 500, saponification degree: 92.0 mol%, mercapto group content: 3.3 × 1)
0 ^-5 eq / g) 2% aqueous solution of 120 parts of a nonionic emulsifier (NONPOL 200: manufactured by Sanyo Chemical) were charged 2 parts,
The pH was adjusted to 3.5 with dilute sulfuric acid. Next, 10 parts of vinyl acetate and 10 parts of 2-ethylhexyl acrylate were charged. Then, after the temperature was raised to 60 ° C. and the atmosphere was replaced with nitrogen, ethylene was injected under pressure up to 50 kg / m ² ,
The polymerization was initiated using a Rongalit redox initiator. After the polymerization started, 40 parts of vinyl acetate and 40 parts of 2-ethylhexyl acrylate were continuously added over 2 hours. The polymerization was completed in 4 hours, and the solid content was 46.
A stable ethylene-vinyl acetate-2-ethylhexyl acrylate copolymer emulsion having a viscosity of 0% and a viscosity of 130 mPa · s at 20 ° C. and an average particle size of 0.25 μm was obtained.
This emulsion was evaluated in the same manner as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the emulsion of Example 1 was replaced with 4 parts of an anionic emulsifier (Sandet BL: manufactured by Sanyo Chemical Co., Ltd.) instead of polyvinyl alcohol having a mercapto group at the end. A styrene / butadiene copolymer emulsion was obtained (solid content: 45%, viscosity: 90%).
mPa · s). This emulsion was evaluated in the same manner as in Example 1.

[0037]

[Table 1]

[0038]

According to the present invention, there is provided a heat-sensitive recording material which has less fog (coloration of the background portion) in the non-printed area of the heat-sensitive paper and has excellent suitability for high-concentration coating of a coating liquid at the time of heat-sensitive paper production. can get.

Claims (2)

[Claims] 1. A heat-sensitive recording layer comprising a sheet-like support provided with a heat-sensitive recording layer containing an electron-donating color-forming dye, an electron-accepting color-developing compound capable of reacting under heating to form a color, and an adhesive. In a recording material, an adhesive in which polyvinyl alcohol having a mercapto group is used as a dispersant and a polymer comprising at least one kind of radically polymerizable ethylenically unsaturated monomer or diene monomer is used as a dispersoid. A heat-sensitive recording material characterized by using: 2. The heat-sensitive recording material according to claim 1, wherein the adhesive is an aqueous polymer dispersion.