JP2002086927A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive recording medium especially with excellent whiteness in relation to the heat-sensitive recoring meterial in the present invention. SOLUTION: In the heat-sensitive recording medium with an undercoat layer containing a pigment and an adhesive as main ingredients on a substrate and a heat-sensitive recording layer containing an electron donating and ordinarily colorless or light-colored dye precursor and an electron accepting compound reacting at heating and developing color of the dye precursor, at least one specified electron accepting compound is incorporated in the heat-sensitive recording layer and an organic pigment with a through-hole, an organic hollow particle with an opening part or at least one organic hollow particle having substantially no opening part as a pigment is incorporated in the undercoat layer. As the specified electron accepting compound, N-(p-toluene sulfonyl)-N '-(3-p-toluene sulfonyloxyphenyl) urea, etc., are cited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having excellent whiteness.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support provided with a thermosensitive recording layer mainly composed of an electron-donating, usually colorless or pale-colored dye precursor, and an electron-accepting developer. Yes, by heating with a thermal head, a hot pen, a laser beam, etc., a dye precursor and a developer react instantaneously to obtain a recorded image, and Japanese Patent Publication No. 43-4160,
No. 45-14039 and the like. Such a heat-sensitive recording material has the advantages that recording can be obtained with a relatively simple device, maintenance is easy, and there is no generation of noise.Measurement recorder, facsimile, printer, computer terminal, It is used in a wide range of fields such as label printing machines, boarding tickets, and ticket issuing machines.

[0003] In recent years, in recent years, receipts of gas, water, electricity, etc., financial institution ATM usage statements, various receipts, etc., financial-related recording paper, thermal recording labels for POS systems, and thermal recording tags, etc. Also, heat-sensitive recording materials have been used.

[0004] As the use and demand of the heat-sensitive recording material are expanding in various ways, the use environment is also diversifying. In particular, heat-sensitive recording materials processed into heat-sensitive recording labels, heat-sensitive recording tags, and the like are often stored in a high-temperature and high-humidity environment, and are required to have high whiteness of white paper and little discoloration together with a recorded image. I have.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to provide a heat-sensitive recording material having particularly excellent whiteness.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have invented a heat-sensitive recording material of the present invention which can solve the problems. That is, an undercoat layer containing a pigment and an adhesive as main components on a support, and an electron-accepting compound that reacts upon heating with an electron-donating usually colorless or light-colored dye precursor to form a color with the dye precursor. In a heat-sensitive recording material having a heat-sensitive recording layer containing: an organic pigment having at least one electron-accepting compound represented by the general formula 1 in the heat-sensitive recording layer; A thermosensitive recording material comprising at least one kind of organic hollow particles having a portion or organic hollow particles having substantially no opening.

Embedded image (In the formula, R ₁ and R ₂ represent a hydrogen atom or an alkyl group.)

A thermosensitive recording material characterized in that the thermosensitive recording layer contains a compound represented by the general formula (2).

Embedded image (Wherein, R _{3 to} R ₆ represent an alkyl group, X represents a hydrogen atom,
Indicates an ammonium or metal atom. )

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the contents of the present invention will be described more specifically. The heat-sensitive recording material of the present invention, on a support, an undercoat layer containing a pigment and an adhesive as main components, and a colorless or light-colored electron-donating dye precursor that reacts when heated to form the dye precursor. And a heat-sensitive recording layer containing an electron-accepting compound to be formed.

As the support used in the present invention, paper is mainly used. In addition to paper, various woven fabrics, nonwoven fabrics, synthetic resin films, synthetic resin laminated paper, synthetic paper, metal paper,
A vapor-deposited sheet or a composite sheet in which these are combined by lamination or the like can be arbitrarily used according to the purpose.

As the electron-accepting compound for coloring the dye precursor constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention, a compound represented by the following general formula 1 is used.

Specific examples include N- (benzenesulfonyl) -N '-(3-benzenesulfonyloxyphenyl) urea and N- (p-toluenesulfonyl) -N'-
(3-p-toluenesulfonyloxyphenyl) urea,
N- (p-ethylbenzenesulfonyl) -N '-(3-
Examples thereof include p-ethylbenzenesulfonyloxyphenyl) urea, but the electron-accepting compound represented by the general formula 1 according to the present invention is not limited thereto, and two or more electron-accepting compounds may be used if necessary. It can also be used.

Among the electron accepting compounds represented by the general formula 1, N- (p-toluenesulfonyl) -N '-(3-p
-Toluenesulfonyloxyphenyl) urea is particularly preferably used.

The heat-sensitive recording material of the present invention contains an electron-accepting compound represented by the general formula 1. Further, one or more other electron-accepting compounds can be used in combination as long as the desired effects of the present invention are not impaired. The electron-accepting compound that can be used in combination is generally represented by an electron-accepting compound used in a pressure-sensitive recording material or a heat-sensitive recording material, but is not limited thereto. For example, phenol derivatives, aromatic carboxylic acid derivatives, N,
Examples include N'-diarylthiourea derivatives, arylsulfonylurea derivatives, polyvalent metal salts such as zinc salts of organic compounds, and benzenesulfonamide derivatives.

Specific examples include clays such as acid clay, activated clay, zeolite, bentonite and kaolin, p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy -4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 3-phenylsulfonyl-4-hydroxydiphenyl sulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenyl sulfone, 1,1-
Bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) pentane, 1,1-bis (4-hydroxyphenyl) hexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1-
Bis (4-hydroxyphenyl) cyclododecane, 2,
2-bis (4-hydroxyphenyl) propane, 2,2
-Bis (4-hydroxyphenyl) hexane, 2,2-
Bis (4-hydroxyphenyl) octane, 1,1-bis (4-hydroxyphenyl) -2-ethylhexane,
2,2-bis (3-chloro-4-hydroxyphenyl)
Propane, 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,3-di- [2- (4-hydroxyphenyl) -2-propyl] benzene, 1,3-di- [2- (3,4-dihydroxyphenyl) -2-propyl] benzene 1,4-di- [2- (4-hydroxyphenyl) -2-propyl] benzene, 4,4'-dihydroxydiphenyl ether, N- (2-hydroxyphenyl) benzenesulfonamide, N- (2-hydroxyphenyl) ) -P-toluenesulfonamide, N- (4
-Hydroxyphenyl) benzenesulfonamide, N-
(4-hydroxyphenyl) -p-toluenesulfonamide, 4,4'-dihydroxydiphenylsulfone,
2,4'-dihydroxydiphenyl sulfone, 3,3 '
-Dichloro-4,4'-dihydroxydiphenylsulfone, 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfide, 2,2-bis ( Methyl 4-hydroxyphenyl) acetate, butyl 2,2-bis (4-hydroxyphenyl) acetate, 4,4'-thiobis (2-t-butyl-5-methylphenol), benzyl p-hydroxybenzoate, p- Chlorobenzyl hydroxybenzoate, dimethyl 4-hydroxyphthalate, benzyl gallate, stearyl gallate, salicylanilide,
5-chlorosalicylanilide, novolak phenolic resin, modified terpene phenolic resin, 3,5-di-t-butylsalicylic acid, 3,5-di-t-nonylsalicylic acid,
3,5-didodecylsalicylic acid, 3-methyl-5-t-
Dodecyl salicylic acid, 5-cyclohexyl salicylic acid,
3,5-bis (α, α-dimethylbenzyl) salicylic acid, 3-methyl-5- (α-methylbenzyl) salicylic acid, and the like, and metal salts thereof such as zinc, nickel, aluminum, and calcium can be given. However, the present invention is not limited to this, and two or more kinds can be used in combination as needed.

The compound constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention is represented by Formula 2.

Specific examples include 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate and 2,2'-methylenebis (4,6-di-ter
ammonium salt of t-butylphenyl) phosphate,
Sodium salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, 2,2′-
Examples include the potassium salt of methylenebis (4,6-di-tert-butylphenyl) phosphate. However, the compound represented by the general formula 2 according to the present invention is not limited thereto, and is not limited thereto. Depending on the type, two or more types can be used in combination.

Among the compounds represented by the general formula 2,
The sodium salt of 2'-methylenebis (4,6-di-tert-butylphenyl) phosphate is particularly preferably used.

The electron-donating, usually colorless or light-colored dye precursor constituting the heat-sensitive recording layer of the heat-sensitive recording material of the present invention includes, in general, pressure-sensitive recording materials and dye precursors used in heat-sensitive recording materials. Representative, but not particularly limited.

Specific examples of the dye precursor include: (1) a triarylmethane compound: 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-methylindole-3-
Yl) phthalide, 3- (p-dimethylaminophenyl)
-3- (2-Phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-
Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-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, etc.

(2) Diphenylmethane compound: 4,
4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenylleuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc.

(3) Xanthene compound: rhodamine B
Anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3-diethylamino -7-chlorofluoran, 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-dibutylamino-6-methyl-7-anilinofluoran, 3-dipentylamino-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- (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-tetrahydrofurfuryl) amino-
6-methyl-7-anilinofluoran and the like,

(4) Thiazine compounds: benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.

(5) Spiro compounds: 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran,
Examples thereof include 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, and 3-propylspirobenzopyran. These dye precursors can be used in combination of two or more as necessary.

The heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention can contain a heat-fusible substance in order to improve the thermal response. In this case, 60 ° C. to 180
Those having a melting point of 80 ° C.
Those having a melting point of more preferably are used.

Specifically, stearic acid amide, N-hydroxymethyl stearic acid amide, N-stearyl stearic acid amide, ethylenebisstearic acid amide,
N-stearyl urea, benzyl-2-naphthyl ether, m-terphenyl, 4-benzylbiphenyl, 2,
2′-bis (4-methoxyphenoxy) diethyl ether, α, α′-diphenoxyxylene, bis (4-methoxyphenyl) ether, diphenyl adipate, dibenzyl oxalate, di (4-chlorobenzyl) oxalate, Dimethyl terephthalate, dibenzyl terephthalate, phenyl benzenesulfonate, bis (4-
Allyloxyphenyl) sulfone, 4-acetylacetophenone, acetoacetic anilides, fatty acid anilides,
And other known heat-fusible substances. These heat-fusible substances can be used in combination of two or more as necessary. In order to obtain a sufficient thermal response, it is preferable that the heat-fusible substance accounts for 5 to 50% by weight of the total solid content of the heat-sensitive recording layer.

The heat-sensitive recording layer constituting the heat-sensitive recording material of the present invention is obtained by mixing each dispersion obtained by finely pulverizing each color-forming component, a binder and the like, applying the mixture on a support, and drying. Can be The layer configuration of the heat-sensitive recording layer may be a single layer or a multilayer.

As the adhesive used for the heat-sensitive recording layer,
Various adhesives used in ordinary coating can be used.

Specifically, starches, hydroxymethylcellulose, methylcellulose, ethylcellulose,
Carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, polyvinylpyrrolidone, polyacrylamide, acrylamide / acrylate copolymer,
Acrylamide / acrylic acid ester / methacrylic acid terpolymer, alkaline salt of polyacrylic acid, alkaline salt of polymaleic acid, alkaline salt of styrene / maleic anhydride copolymer, alkaline salt of ethylene / maleic anhydride copolymer , A water-soluble binder such as an alkali salt of an isobutylene / maleic anhydride copolymer, a styrene / butadiene copolymer, an acrylonitrile / butadiene copolymer, a methyl acrylate / butadiene copolymer, an acrylonitrile / butadiene / styrene terpolymer Polymer, polyvinyl acetate, vinyl acetate / acrylate copolymer,
Examples include, but are not limited to, water / dispersible binders such as ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylate copolymer, and polyurethane.

In the heat-sensitive recording layer, as pigments, diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide , Barium sulfate, zinc sulfate,
Inorganic pigments such as amorphous silica, amorphous calcium silicate and colloidal silica, and organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder and nylon powder can be used.

The heat-sensitive recording layer has a head wear prevention,
For the purpose of preventing sticking, etc., zinc stearate,
Higher fatty acid metal salts such as calcium stearate; higher fatty acid amides such as stearic acid amide; lubricants such as paraffin, polyethylene wax, polyethylene oxide, and caster wax; and anionic and nonionic high molecular weight agents as dispersing / wetting agents For the purpose of improving the light resistance, a surfactant, a benzophenone-based or benzotriazole-based ultraviolet absorber, a fluorescent dye, an antifoaming agent, and the like are added as necessary.

The method for forming the heat-sensitive recording layer is not particularly limited, and it can be formed according to a conventionally known technique. Specific examples include letterpress, lithographic, flexo,
Including various printing methods such as gravure, air knife coating,
A heat-sensitive recording layer can be formed by applying a coating solution to a support by a method such as rod blade coating, bar coating, blade coating, gravure coating, curtain coating, or E-bar coating, and drying. .

The coating amount of the heat-sensitive recording layer is usually 0.1 to 2.0 g / m ^{2 as} the coating amount of the dye precursor. 0.1g / m ²
If the amount is smaller than this, a sufficient recorded image cannot be obtained,
Further, if the amount exceeds 2.0 g / m ² , no improvement in thermal responsiveness is observed, which is disadvantageous in cost.

The organic pigment constituting the undercoat layer of the heat-sensitive recording material of the present invention is preferably an organic pigment having through holes, organic hollow particles having openings, or organic hollow particles having substantially no openings. .

The organic pigment having a through-hole may have at least one through-hole in the pigment particles. Organic pigments having such through-holes, for example, sodium hydroxide, ammonium hydroxide, potassium hydroxide, resin particles dissolved in alkaline water such as triethylamine and the like as a core material while synthesizing a resin that is not dissolved in alkaline water around it. It is obtained by eluting the core substance with alkaline water.

The resin particles dissolved in the alkaline water include, for example, at least one of hydrophobic monomers such as styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. And copolymer particles obtained by emulsion polymerization of at least one of a vinyl monomer of an unsaturated carboxylic acid such as itaconic acid and crotonic acid. The unsaturated carboxylic acid monomer is preferably about 10 to 50% by weight based on all monomers.

Examples of the resin that is not dissolved in alkaline water include:
Examples thereof include those obtained by polymerizing at least one of the above-mentioned hydrophobic monomers. Above all, by using a resin containing styrene as a main component as a monomer, an effect that a decrease in the density of a recording portion with time is small can be obtained. Further, as long as the vinyl monomer is not dissolved in alkaline water, at least one of the above-mentioned vinyl monomers of unsaturated carboxylic acids may be copolymerized.

When the volume average particle size of the organic pigment having through holes is less than 0.1 μm, the density of the undercoat layer is increased, the thermal conductivity is increased, and the sensitivity may be reduced. There is a risk of producing cake. On the other hand, if the volume average particle size exceeds 2.0 μm, the undercoat layer will not be formed uniformly, and a decrease in image quality or a decrease in surface strength will be caused. Is about 0.2 to 1.5 μm.

The hollow organic particles having an opening have a characteristic structure of having an opening which can be obtained by cutting a part of the hollow organic particles in a plane. Can be taken. The average maximum diameter of the organic hollow particles having such openings is generally 0.3 to 5 μm,
Preferably it is 0.5 to 3 μm. The ratio of the average equivalent diameter of the opening to the average maximum diameter of the particles is generally 25 to 1
00%, preferably 60-95%.

The organic hollow particles having openings used in the present invention usually have a thick-walled portion having a multilayered polymer structure. As an example of the production method, the following steps (1) to (7) And a multistage polymerization method. (1) Nucleic acid polymer particles are prepared by copolymerizing a monomer mixture of 30 to 65% by weight of an acidic group-containing monomer and 70 to 35% by weight of a monomer copolymerizable therewith,
(2) In the presence of the polymer particles, 10 to 35% by weight of an acidic group-containing monomer and a monomer 90 copolymerizable therewith.
By co-polymerizing the monomer mixture with about 65% by weight, a core polymer substantially surrounding the nucleus polymer particles is formed. The content ratio of the body is equal to or smaller than the content ratio of the acidic group-containing monomer in the nuclear polymer),
(3) In the presence of the core / core polymer particles, 1 to 12% by weight of an acidic group-containing monomer and a monomer 9 copolymerizable therewith
By copolymerizing the monomer mixture with 9 to 88% by weight, at least one intermediate polymer layer substantially surrounding the core polymer particles is formed. An aromatic vinyl monomer is used alone or in an amount of 0.5% by weight or less of an acidic group-containing monomer and an aromatic copolymerizable therewith in the presence of a polymer particle having an intermediate layer polymer formed thereon. By copolymerizing a monomer mixture comprising at least 99.5% by weight of a vinyl monomer, an outer layer polymer substantially surrounding the intermediate layer polymer was formed. A base is added to the aqueous dispersion containing the polymer particles having a layer structure to adjust the pH of the dispersion to 7 or more to form voids in the polymer particles. (6) Then, if desired, The pH was adjusted to less than 7, and the aqueous dispersion was treated with aromatic vinyl. Monomers alone or with the addition of an aromatic vinyl monomer 90 wt% or more and this monomer copolymerizable consisting of 10 wt% or less monomer mixture,
The outermost layer polymer is formed around the outer layer polymer by polymerizing in the presence of the polymer particles having the at least four-layer structure, and then (7) the obtained polymer particle dispersion is dried. .

The organic hollow particles having substantially no openings include, for example, monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, methyl acrylate, ethyl acrylate, methyl methacrylate, acrylonitrile and styrene. And particles having a shell made of a resin such as a resin or a copolymer resin containing these monomers as a main component. The average particle size of the pigment is about 0.5 to 20 μm, preferably about 0.5 to 3 μm. The hollowness of the organic hollow particles (the ratio of the volume of the voids in the particles to the total volume of the particles) is preferably about 50 to 98%.

The amount of the organic pigment used in the undercoat layer in the present invention is not particularly limited, but is preferably 20 to 95% by weight based on the total solid content of the undercoat layer. If the used amount is less than 20% by weight, head residues are generated, and if it exceeds 95% by weight, stick trouble may occur at the time of printing, and 40 to 95% by weight is more preferable.

Further, other known pigments can be contained in the undercoat layer as long as the desired effects of the present invention are not impaired. Examples of such pigments include organic pigments such as nylon resin fillers, urea-formalin resin fillers, hollow resin particle fillers, and inorganic pigments such as calcium carbonate, aluminum hydroxide, kaolin, calcined kaolin, silica, and aluminum silicate compounds. .

Examples of the adhesive used in combination with the specific organic pigment in the undercoat layer include starches, hydroxymethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium alginate, and polyvinylpyrrolidone. , Polyacrylamide, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali of styrene / maleic anhydride copolymer Water-soluble resins such as salts, alkali salts of ethylene / maleic anhydride copolymers, alkali salts of isobutylene / maleic anhydride copolymers, and styrene / butadiene copolymers, Nitrile / butadiene copolymer, methyl / butadiene acrylate copolymers, acrylonitrile / butadiene / styrene terpolymer, polyvinyl acetate, vinyl acetate / acrylic acid ester copolymer,
Water-dispersible resins such as ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylate copolymer, and polyurethane can be used.

With respect to the total solid content of the undercoat layer, the amount of the specific organic pigment and the adhesive used is 30 to 40%.
About 95% by weight and about 5 to 35% by weight of the adhesive are preferable.

The undercoat layer is prepared by, for example, using water as a medium, mixing and stirring an organic pigment, an adhesive, and, if necessary, an auxiliary with an undercoat layer. There 1 to 30 g / m ^2, more preferably formed by coating and drying so that 3 to 20 g / m ² approximately. As the auxiliaries contained in the undercoat layer coating solution, known pigments, surfactants,
Examples include a coloring dye, a fluorescent dye, a lubricant, and an ultraviolet absorber.

The heat-sensitive recording material of the present invention is used to further improve the chemical resistance of the recording portion or to improve the recording running property.
A protective layer is formed on the heat-sensitive recording layer. Such a protective layer,
As a main component, a water-soluble resin or a water-dispersible resin having a film-forming property, and while the adhesive is dissolved or dispersed, if necessary, the above-mentioned ultraviolet absorber, and an auxiliary agent which can be added to the heat-sensitive recording layer are added. and a protective layer coating solution prepared by heat-sensitive recording layer, the coating amount after drying 0.2 to 10 g / m ^2, coating and drying as more preferably a 0.5 to 5 g / m ² approximately Formed.

The water-soluble resin or water-dispersible resin of the protective layer is appropriately selected from conventionally known water-soluble polymers or water-dispersible resins. That is, examples of the water-soluble resin include polyvinyl alcohol, modified polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxyethylcellulose, methylcellulose, ethylcellulose and carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, acrylamide /
Acrylic ester copolymer, acrylamide / acrylic ester / methacrylic acid terpolymer, alkali salt of polyacrylic acid, alkali salt of polymaleic acid, alkali salt of styrene / maleic anhydride copolymer, ethylene /
Alkaline salt of maleic anhydride copolymer, isobutylene /
An alkali salt of a maleic anhydride copolymer, sodium alginate, gelatin, casein, an acid neutralized product of chitosan, and the like can be used.

Examples of the water dispersible resin include styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, acrylonitrile / butadiene / styrene terpolymer,
Polyvinyl acetate, vinyl acetate / acrylate copolymer, ethylene / vinyl acetate copolymer, polyacrylate, styrene / acrylate copolymer, polyurethane and the like can be used.

Among them, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and diacetone-modified polyvinyl alcohol are preferably used as the water-soluble resin for the protective layer because they can form a strong film.

Further, the protective layer may contain a pigment for the purpose of improving the recording running property, the writing property and the like. Specific examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, heavy calcium carbonate, precipitated calcium carbonate, magnesium carbonate, zinc oxide, aluminum oxide, aluminum hydroxide, magnesium hydroxide, titanium dioxide, barium sulfate, and sulfuric acid. Inorganic pigments such as zinc, amorphous silica, amorphous calcium silicate and colloidal silica, organic pigments such as melamine resin filler, urea-formalin resin filler, polyethylene powder and nylon powder can be used.

For the purpose of improving recording running properties such as head abrasion prevention and sticking prevention, higher protective metal layers such as zinc stearate and calcium stearate, higher fatty acid amides such as stearic acid amide, paraffin and polyethylene are provided on the protective layer. Lubricants such as wax, oxidized polyethylene and caster wax are added as needed.

The method for forming the undercoat layer and the protective layer is not particularly limited, either, and can be formed according to conventionally known techniques. Specific examples include various printing methods, air knife coating, rod blade coating, bar coating, blade coating, gravure coating, curtain coating, and E-bar coating. And can be formed by drying.

In the heat-sensitive recording material of the present invention,
If necessary, a protective layer (barrier) may be provided on the back side, an adhesive layer may be provided, an optional information recording layer such as a magnetic recording layer, an ink jet recording layer, or the like. And the like.

[0054]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. still,
All copies shown in the examples are on a weight basis.

Example 1 (1) Preparation of Coating Liquid for Undercoat Layer Organic pigment having 20% opening (V1005 manufactured by Zeon Corporation) 500 parts 50% styrene butadiene latex 24 parts

The above composition was mixed, water was added so that the concentration of the undercoat layer coating solution was 30% aqueous solution, and the mixture was sufficiently stirred to prepare an undercoat layer coating solution.

(2) Preparation of coating liquid for heat-sensitive recording layer Dispersions A to H were obtained by the following method.

<Dispersion A> 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluoran 20
0 g was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfone group-modified polyvinyl alcohol and 600 g of water, and pulverized with a bead mill until the average particle diameter became 1 μm to obtain a dispersion A.

<Dispersion B> 200 g of N- (p-toluenesulfonyl) -N ′-(3-p-toluenesulfonyloxyphenyl) urea was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonated polyvinyl alcohol and 600 g of water. Then, the mixture was pulverized with a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion B.

<Dispersion C> 200 g of 2,2-bis (4-hydroxyphenyl) propane was dispersed in a mixture of 200 g of a 10% aqueous solution of a polyvinyl alcohol modified with a sulfone group and 600 g of water, and the average particle diameter was 0.7 μm using a bead mill.
To obtain a dispersion C.

<Dispersion D> 200 g of 4-hydroxy-4'-isopropoxydiphenylsulfone was dissolved in 200 g of a 10% sulfone group-modified polyvinyl alcohol aqueous solution,
The mixture was dispersed in 0 g of the mixture, and pulverized by a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion D.

<Dispersion E> 200 g of sodium-2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate was dispersed in a mixture of 200 g of a 10% aqueous solution of a sulfonated polyvinyl alcohol and 600 g of water. The mixture was pulverized with a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion E.

<Dispersion F> 2- (2-hydroxy-5-
Methylphenyl) benzotriazole 200g 10%
200 g of a sulfone group-modified polyvinyl alcohol aqueous solution,
It was dispersed in a mixture of 600 g of water, and pulverized by a bead mill until the average particle diameter became 0.7 μm, to obtain a dispersion F.

<Dispersion G>2,2'-methylenebis [4
-(1,1,3,3-tetramethylbutyl) -6-benzotriazolyl) phenol], 200 g of a 10% aqueous solution of a polyvinyl alcohol modified with a sulfone group, and 60 g of water.
The mixture was dispersed in 0 g of the mixture, and pulverized by a bead mill until the average particle diameter became 0.7 μm to obtain a dispersion G.

<Dispersion H> 200 g of aluminum hydroxide
800 g of a 0.5% aqueous solution of sodium polyacrylate
The resulting mixture was stirred in a homomixer for 10 minutes to obtain a dispersion H.

The dispersions A to H were mixed at the following ratios, and water was added so that the concentration of the heat-sensitive coating solution became a 15% aqueous solution. The mixture was sufficiently stirred to prepare a heat-sensitive recording layer coating solution. Dispersion A 30 parts Dispersion B 70 parts Dispersion F 1 part Dispersion G 1 part Dispersion H 50 parts 40% zinc stearate dispersion 10 parts 10% completely saponified PVA aqueous solution 40 parts

(3) Preparation of Thermosensitive Recording Material On one side of a high-quality neutral paper having a basis weight of 40 g / m ² , the solid content of the undercoat layer coating solution prepared in (1) was 10 g / m ² , The undercoat layer and the heat-sensitive recording layer were formed by sequentially applying and drying the coating solution for the heat-sensitive recording layer prepared in 2) so that the coating amount of the solid content of the coating solution of the dye precursor was 0.3 g / m ^2. Thus, a heat-sensitive recording material was produced.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the composition of the undercoat layer coating liquid in Example 1 was changed to the following composition. Organic pigment having 20% through-holes (Mitsui Chemicals Co., Ltd. 2000 TX) 500 parts 50% styrene butadiene latex 24 parts

Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the composition of the undercoat layer coating liquid in Example 1 was changed to the following composition. 20% hollow particulate organic pigment (Rohm & Haas Lowhage HP-91) 500 parts 50% styrene butadiene latex 24 parts

Example 4 The same procedure as in Example 1 was carried out except that the composition of the undercoat layer coating liquid in Example 1 was changed to the composition shown below, and then heated and foamed for 3 minutes with a dryer at 150 ° C. to form an undercoat layer. In the same manner, a heat-sensitive recording material was obtained. Foamable plastic filler (Micropart F30 manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 500 parts 50% styrene butadiene latex 24 parts

Example 5 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the following amount of the dispersion E was added in the preparation of the coating solution for the heat-sensitive recording layer of Example 1. Dispersion E 7 parts

Example 6 On the heat-sensitive recording layer of the heat-sensitive recording material obtained in Example 1, a coating solution for a protective layer having the following composition was applied so that the coating amount of the solid content was 2 g / m ^2. Example 1 except for drying and providing a protective layer
A heat-sensitive recording material was obtained in the same manner as described above. 10% acetoacetyl-modified polyvinyl alcohol (Coacefimer Z-200, manufactured by Nippon Synthetic Chemical Industry) 300 parts Kaolin (UW-90, manufactured by Engelhardtart) 65 parts 10% glyoxal aqueous solution 3 parts 40% zinc stearate 5 parts Water 150 parts

Comparative Example 1 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the composition of the undercoat layer coating liquid in Example 1 was changed to the following composition. Calcined kaolin 100 parts 50% styrene butadiene latex 24 parts Water 400 parts

Comparative Example 2 In the preparation of the heat-sensitive recording layer coating liquid of Comparative Example 1, the dispersion B
Was changed to Dispersion C to obtain a thermosensitive recording material in the same manner as in Comparative Example 1.

Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 2, except that Dispersion B was changed to Dispersion C in the preparation of the heat-sensitive recording layer coating solution of Example 2.

Comparative Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 2, except that the dispersion B was changed to the dispersion D in the preparation of the coating solution for the heat-sensitive recording layer in Example 2.

The heat-sensitive recording materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were calendered so that the Beck smoothness of the coated surface of the heat-sensitive recording layer was 300 to 800 seconds.
The following evaluation was provided. Table 1 shows the evaluation results.

[Brightness test] Using a digital hunter reflectometer (amber filter) manufactured by Toyo Seiki Seisaku-sho, Ltd., immediately after the preparation of the heat-sensitive recording material, at 40 ° C., 90%, 60 ° C. and 80 ° C. The whiteness after storage treatment for 24 hours was measured. The higher the value, the better the whiteness.

[0079]

[Table 1]

As is clear from Table 1 above, Examples 1 to
No. 6 is excellent in whiteness as compared with Comparative Examples 1 to 4. It contains an electron-accepting compound represented by the general formula 1, and an organic pigment having a through hole, an organic hollow particle having an opening, or an organic hollow particle having substantially no opening as a pigment in an undercoat layer. It depends.

[0081]

According to the present invention, an undercoat layer containing a pigment and an adhesive as main components on a support, and an electron-donating, usually colorless or pale-colored dye precursor, which reacts upon heating to form an electron acceptor which develops the color of the dye precursor A thermosensitive recording material having a thermosensitive recording layer containing a thermosensitive compound, an organic compound having at least one electron-accepting compound represented by the general formula 1 in the thermosensitive recording layer, and an organic pigment having through holes as a pigment in the undercoat layer. By containing at least one pigment, organic hollow particles having openings, or organic hollow particles having substantially no openings, it has become possible to obtain a thermosensitive recording material having excellent whiteness.

Claims (2)

[Claims] 1. An electron-accepting layer, on a support, which reacts with an undercoating layer containing a pigment and an adhesive as main components and an electron-donating, usually colorless or pale-colored dye precursor upon heating to form the dye precursor. A thermosensitive recording material having a thermosensitive recording layer containing a thermosensitive compound, an organic compound having at least one electron-accepting compound represented by the general formula 1 in the thermosensitive recording layer, and an organic pigment having through holes as a pigment in the undercoat layer. A thermosensitive recording material comprising at least one pigment, organic hollow particles having openings, or organic hollow particles having substantially no openings. Embedded image (In the formula, R ₁ and R ₂ represent a hydrogen atom or an alkyl group.) 2. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer contains a compound represented by the formula (2). Embedded image (Wherein, R _{3 to} R ₆ represent an alkyl group, X represents a hydrogen atom,
Indicates an ammonium or metal atom. )