JPH054444A - Thermal recording body - Google Patents

Abstract

PURPOSE:To provide the above thermal recording body, to which an overcoat layer formed, and to relate to the thermal recording body having printability on the recording surface side and available as a prepaid card in details. CONSTITUTION:In a thermal recording body, a coating layer, which mainly comprises a pigment and adhesives on one surface of a supporter and has K&N ink absorption of 10.0g/m<2> or less, is formed and a thermal recording layer containing colorless or light-colored basic dyes and a colorant and an overcoat layer using an ionizing radiation curing resin as a main component are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording material provided with an overcoat layer, and more particularly to a thermal recording material having excellent printability on the recording surface side and useful as a prepaid card.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive recording which utilizes a color reaction between a color-forming agent and a color-forming agent which develops color by contacting with the color-forming agent, by contacting both color-forming substances with heat to obtain a color-developed image. The body is well known. Since such a thermal recording material is relatively inexpensive, and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields such as thermal labels. There is.

However, the heat-sensitive recording material is poor in fingerprint resistance and solvent resistance. For example, when human sebum or a solvent comes into contact with the recording layer, the recording density is lowered, and unnecessary color development called background fog occurs. There is a drawback that causes.

As a method for solving such a drawback, a method of coating an aqueous emulsion of a resin having film forming ability and chemical resistance on a heat-sensitive recording layer (JP-A-54).
No. 128347), and a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Actual No. 56-12535).
No. 4) etc. have been proposed. However, with the improvement, new defects are accompanied, and satisfactory results are not always obtained.

For example, when an aqueous resin coating is applied on the heat-sensitive recording layer, it is necessary to limit the drying temperature in order to avoid color development of the recording layer due to high temperature drying, and inevitably the resin layer is insufficiently cured. The phenomenon that the recording head and the resin layer adhere to each other during recording occurs. Therefore, a method in which a resin component that is cured by an electron beam is applied onto the heat-sensitive recording layer or a water-soluble resin intermediate layer provided on the heat-sensitive recording layer and the resin component is cured by the electron beam (Japanese Patent Publication No. 1-42835).
No.) has been proposed.

[0006]

In recent years, there are increasing cases in which the thermal recording material is used as a prepaid card, and in that case, the card tends to be visualized, colored, and upscaled. Therefore, printing is required to have printability not only on the back surface but also on the recording surface so as to be compatible with various printing methods such as relief printing, gravure printing, offset printing, and stencil printing. In particular, the recording surface is required to have high gloss, high print density, uniform print image quality, and excellent storability under various conditions.

As described above, it is an essential condition of the thermal recording material for prepaid cards that various kinds of printing can be performed on the surface of the card. However, in the thermal recording material provided with the above-mentioned resin component which is cured by the electron beam, the overcoat layer is provided. However, the picking phenomenon occurs in which the heat-sensitive recording layer is peeled off from the support during printing.

[0008]

In view of the present situation, as a result of earnest research, the inventors of the present invention provided a pigment coating layer on a support,
The present invention has been completed by finding that the K & N ink absorption of the coating layer has a large correlation with the adhesiveness between the thermal recording layer and the coating layer.

That is, in the present invention, a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring when contacted with the dye is provided on one surface of the support, and an ionizing radiation curable resin is further provided. A thermal recording material provided with an overcoat layer as a main component, wherein a pigment and an adhesive are main components between a support and the thermal recording layer, and a K & N ink absorption amount is 10.0 g / m ² or less. A heat-sensitive recording material having a layer.

[0010]

The present invention has a significant feature in that the support is provided with a coating layer containing a pigment and an adhesive as the main components having a K & N ink absorption of 10.0 g / m ² or less as described above. is there. The K & N ink used in the present invention is used as a dedicated colored ink for measuring the ink absorbency of paper, and the absorbency is generally measured by using the K & N ink over the entire coating layer of the paper. After applying the amount, leave it for 2 minutes at room temperature, and then wipe off excess ink on the surface with gauze or waste cloth, and then measure the change in whiteness of the paper.
It is a measure of the ink absorption of paper. However, the K & N ink absorption amount in the present invention is calculated as the absorption amount per 1 m ² by measuring the ink amount actually absorbed by the paper after treating the ink in the same manner as described above.

It has been found that the K & N ink absorption amount thus calculated has a great correlation with the adhesion between the heat-sensitive recording layer and the coating layer. By the way, in a heat-sensitive recording material in which a support having a coating layer having a K & N ink absorption of more than 10.0 g / m ² is used and a heat-sensitive recording layer and an overcoat layer containing an ionizing radiation-curable resin as a main component are sequentially provided, However, when printing is performed on the recording surface side, a picking phenomenon occurs in which the thermosensitive recording layer is peeled off from the support. This is probably because when the thermosensitive recording layer is provided on the support, the binder contained in the coating liquid is absorbed by the support, the ratio of the binder in the thermosensitive recording layer is reduced, and the adhesive force of the thermosensitive recording layer is weakened.
On the other hand, the overcoat layer is a strong layer using an ionizing radiation curable resin, and since the surface smoothness is high, the contact area with the printing plate is wide, and it easily peels from the thermal recording layer during printing. it is conceivable that. In particular, a support having a coating layer having a K & N ink absorption of 5.0 g / m ² or less is preferable because it has extremely excellent printability.

In the present invention, high-quality paper, medium-quality paper, lower-grade paper, synthetic pulp-containing paper and the like are used as the support. The paper thickness is not particularly limited, but for prepaid cards, the thickness is preferably 50 to 1000 μm, and particularly preferably 100 to 500 μm. If the thickness is less than 50 μm, a prepaid card having a sufficient strength cannot be obtained, and if it exceeds 1000 μm, the production cost becomes high and the correlation with the output device becomes problematic. The papermaking method is not particularly limited, and may be either acidic papermaking or alkaline papermaking. Further, a base paper pre-coated with a size press, bill blade or the like can also be used.

In the present invention, the support is provided with a coating layer containing a pigment and an adhesive as main components, but the composition is not particularly limited. As the pigment, for example, one or more pigments for ordinary coated paper such as clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white, calcium sulfate, talc and plastic pigment are appropriately used. Used by choice.

Examples of the adhesive include proteins such as casein, soybean protein, and synthetic protein; conjugated diene copolymer latex such as styrene / butadiene copolymer, methyl methacrylate / butadiene copolymer, acrylic ester and / or Or acrylic polymer latex such as polymer or copolymer of methacrylic acid ester, vinyl polymer latex such as ethylene / vinyl acetate copolymer, or various polymer latexes containing functional groups such as carboxyl group Alkali-soluble or alkali-insoluble polymer latex modified with monomers; Synthetic resin adhesives such as polyvinyl alcohol, orfrene / maleic anhydride resin, melamine resin; starches such as positive starch and oxidized starch ; Cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, etc. Such conventional coating one or more of the paper or the like adhesive is appropriately selected and used.

The adhesive is generally added in an amount of 5 to 50 parts by weight, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the pigment. In addition, various auxiliary agents such as a defoaming agent, a colorant, a release agent, and a flow modifier are appropriately blended in the coating liquid, but as an auxiliary agent for promoting the solidification of the coating layer. For example, 0.1 to 10 parts by weight of amine, amide, polyacrylamine, etc. or a salt of polyvalent metal such as zinc, aluminum, calcium barium, etc. may be added to 100 parts by weight of the pigment.

The coating liquid is, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, which is used in the production of general coated paper.
Curtain coater, die slot coater, gravure coater, champlex coater, size press coater On-machine or off-machine provided with a coating device, the coating is carried out in one or multiple layers on a support. The solid content concentration of the coating liquid at that time is generally about 40 to 75% by weight, but in consideration of operability, the range of 45 to 70% by weight is desirable. As a method for drying the wet coating layer, various methods such as conventionally known steam heating, hot air heating, gas heater heating, electric heater heating, infrared heater heating, high frequency heating, laser heating, electron beam heating and the like can be used. It can be adopted as appropriate.

The support having the coating layer thus obtained is passed through a conventionally used finish calender for coated paper to finish the surface. As a calender, for example, Various calenders such as super calender, gross calender, soft calender, soft compact calender, etc. are used in the form of on-machine or off-machine. The water content of the coated paper before entering the nip of the calender is preferably about 3 to 10%, and the finishing speed of the calender is
Although it is largely different, a range of about 100 to 1300 m / min is desirable. Further, for the humidity control and humidification of the coated paper after the surface treatment, a water coating device by a roll, an electrostatic humidifier, a steam humidifier, etc. are installed, and various types conventionally known in the coated paper manufacturing field. It is of course possible to use a combination of technologies.

The present invention provides a support having a coating layer thus formed, which has a K & N ink absorption of 10.0 g.
/ M ² or less is used. A pigment coating layer may be provided on the back surface side, but the K & N ink absorption amount on the back surface side is not particularly limited.

A heat-sensitive recording layer is provided on a coated layer having a K & N ink absorption of 10.0 g / m ² or less. The combination of the color former and the color former contained in the heat-sensitive recording layer is not particularly limited. However, any combination can be used as long as they are brought into contact with each other by heat to cause a color reaction, for example, a combination of a colorless or light basic dye and an inorganic or organic acidic substance, stearic acid. Examples include combinations of higher fatty acid metal salts such as ferric iron and phenols such as gallic acid. However, especially when applied to a combination of a basic dye and an acidic substance, the recording characteristics are extremely excellent, and therefore it is particularly preferable.

Various types of basic dyes which are colorless or light-colored are known, and examples thereof include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2) -Dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl)-
3- (2-methylindol-3-yl) phthalide,
3,3-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) -6-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
6-Dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6
-Triallylmethane dyes such as dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leukoauramine, N-2,4,5-trichlorophenylleucoaamine, etc. Diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-
Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-
Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3- Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane,
3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
Diethylamino-6,7-dimethylfluorane, 3-
(N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino- 7-dibenzylaminofluorane, 3-diethylamino-7-N
-Methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) −
6-methyl-7-phenylaminofluorane, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N-ethyl-N-iso-amylamino)- 6-methyl-7-phenylaminofluorane, 3
-(N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylamino Fluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-dibutylamino-7-
Fluoran dyes such as (o-chlorophenylamino) fluorane and 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane.

Various kinds of inorganic or organic acidic substances that are colored by contact with a basic colorless dye are also known, and examples thereof include activated clay, acid clay, attapulgite, bentonite, colloidal silica, and aluminum silicate. Acidic substance, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol,
4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2'-dihydroxydiphenol,
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis (2
-Tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-phenylphenol, 4,4 '
-Isopropylidene diphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, benzyl 4-hydroxybenzoate, 4-
Dimethyl hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-
Butylbenzoic acid, trichlorobenzoic acid, terephthalic acid,
3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-
Benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethyl) Benzyl) salicylic acid, aromatic carboxylic acids such as 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Examples thereof include organic acidic substances such as salts with polyvalent metals.

In the heat-sensitive recording material of the present invention, the use ratio of the color former and the color former in the recording layer is appropriately selected according to the kind of the color former and the color former used. For example, a colorless or light-colored base is used. When a basic dye and an acidic substance are used, the amount of the basic dye is generally 1 to 50 parts by weight, preferably 1 part by weight.
About 10 parts by weight of an acidic substance is used.

To prepare a coating liquid containing these substances, generally, water is used as a dispersion medium, and a color former and a color former are dispersed together or separately by a stirring / grinding machine such as a ball mill, an attritor or a sand mill. , Prepared as a coating liquid.

In the coating liquid, for example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride are used as an adhesive in the coating liquid. Acid copolymer salt, ethylene / acrylic acid copolymer salt,
A styrene / acrylic acid copolymer salt, a styrene / butadiene copolymer emulsion or the like is used in an amount of 10 to 40% by weight, preferably 15 to 30% by weight, based on the total solid content.

Further, various auxiliary agents can be added to the coating liquid, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. Examples thereof include dispersants, benzophenone-based and triazole-based ultraviolet absorbers, other defoaming agents, fluorescent dyes, and coloring dyes.

Lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax,
Inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay and stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, macaroic oleic acid A sensitizer such as amide and coconut fatty acid amide may be added.

The method of applying the coating liquid for the recording layer is not particularly limited and can be formed according to a conventionally known technique, for example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating. It is formed by a method of applying and drying the coating liquid by the above method. The coating amount of the coating liquid is not particularly limited, but is usually ² to 12 g / m ² , preferably 3 by dry weight.
It is in the range of about 10 to 10 g / m ² .

The heat-sensitive recording material of the present invention has an overcoat layer of ionizing radiation curable resin provided on the heat-sensitive recording layer thus obtained, and a water-soluble resin and / or a water-soluble resin is provided between the recording layer and the overcoat layer. Alternatively, when an intermediate layer of a water-dispersible resin is provided, the storage stability such as oil resistance and water resistance is improved, the glossiness is improved, and unnecessary coloring of the heat-sensitive recording layer when an overcoat layer of an ionizing radiation curing resin is provided ( It is preferable because fogging of the recording layer can be prevented.

Examples of the water-soluble resin and / or the water-dispersible resin for the intermediate layer include the following substances. Completely or partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol having acetoacetyl group introduced by reacting polyvinyl alcohol with diketene, polyvinyl alcohol and fumaric acid, phthalic anhydride, trimellitic anhydride, itaconic anhydride, etc. With an esterification product of a reaction product of a polyvalent carboxylic acid with these, or with an ethylenically unsaturated carboxylic acid such as vinyl acetate and maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid, methacrylic acid Polycarboxyl-modified polyvinyl alcohol obtained as a saponification product of a copolymer of vinyl alcohol, a sulfonic acid-modified polyvinyl alcohol obtained as a saponification product of a copolymer of vinyl acetate and an olefin sulfonic acid such as ethylene sulfonic acid and allyl sulfonic acid, or a salt thereof. , Olefin-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate with olefins such as ethylene, propylene, isobutylene, α-octene, α-dotecene, α-octadodecene, vinyl acetate and acrylonitrile, methacrylonitrile, etc. Nitrile-modified polyvinyl alcohol obtained as a saponification product of a copolymer with nitriles, amide-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate with amides such as acrylamide and methacrylamide, vinyl acetate and N -Polyvinyl alcohol such as pyrrolidone-modified polyvinyl alcohol obtained by saponifying a copolymer with vinylpyrrolidone, cellulose derivative such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose , Casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, styrene-butadiene copolymer emulsion, vinyl acetate-vinyl chloride-ethylene copolymer emulsion, methacrylate-butadiene copolymer Combined emulsion, etc.

Among these water-soluble resins and / or water-dispersible resins, various modified polyvinyl alcohols, cellulose derivatives and casein are preferable, and acetoacetylated polyvinyl alcohol and carboxy-modified polyvinyl alcohol are more preferable.

A pigment may be added to the intermediate layer in order to enhance smoothness. Specific examples of the pigment include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide,
Inorganic pigments such as silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch granules, etc. Examples include organic pigments and the like. The amount used is generally 100 for the resin component.
5 to 500 parts by weight, preferably 80 to 3 parts by weight
It is mixed in the range of about 50 parts by weight.

Further, in the coating liquid for forming the intermediate layer, a curing agent such as glyoxal, methylolmelamine, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid or ammonium chloride may be added, if necessary. Lubricants such as zinc stearate, calcium stearate, stearic acid amide, polyethylene wax, carnauba wax, paraffin wax, and ester wax, sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, and lauryl may be added as necessary. Appropriately add various surfactants such as alcohol sulfates / sodium salts, alginates, fatty acid metal salts, etc., benzophenone-based, triazole-based UV absorbers, defoamers, fluorescent dyes, coloring dyes, etc. You can also

The coating liquid for forming the intermediate layer is generally prepared as an aqueous coating liquid and, if necessary, sufficiently mixed and dispersed by a mixing / stirring machine such as a mixer, attritor, ball mill, roll mill, etc. It is coated on the heat-sensitive recording layer by the coating device. After coating, it can be cured and dried by irradiating it with ultraviolet rays or electron beams. When a curing agent is used in combination, the curing agent can be applied not only in the coating liquid that forms the intermediate layer, but also separately from the coating liquid that forms the intermediate layer. There is an advantage that a strong curing agent can be selected without having to worry about life.

The coating amount of the coating liquid for forming the intermediate layer is not particularly limited, but if it is less than 0.1 g / m ² , the desired effect of the present invention cannot be sufficiently obtained, and 20
If it exceeds g / m ² , the recording sensitivity of the thermosensitive recording medium may be remarkably reduced, so that the dry weight is generally 0.1 to 20.
g / m ^2, it is preferably adjusted in the range of about 0.5 to 10 g / m ^2.

Since a recording material having a high recording density and gloss can be obtained by further increasing the smoothness of the surface of the intermediate layer, the Bekk smoothness of the surface of the intermediate layer is 50 seconds by smoothing with a super calender or the like. As described above, it is desirable to adjust the time to 300 seconds or more.

In the heat-sensitive recording material of the present invention, an overcoat layer containing an ionizing radiation curable resin as a main component is provided on the recording layer or the intermediate layer thus formed. As an ionizing radiation curable resin forming the overcoat layer, The following prepolymers and monomers are exemplified.

Examples of the prepolymer include (a) poly (meth) acrylates of aliphatic, alicyclic, araliphatic polyhydric alcohols having 2 to 6 valences and polyalkylene glycols; (b) aliphatic, alicyclic, Poly (meth) acrylate of polyhydric alcohol obtained by adding alkylene oxide to araliphatic or aromatic polyhydric alcohol having 2 to 6 valences; (c) Poly (meth) acryloyloxyalkyl phosphate ester; (d) Polyester poly (meth) acrylate; (e) Epoxy poly (meth) acrylate; (f) Polyurethane poly (meth) acrylate; (g) Polyamide poly (meth) acrylate; (h) Polysiloxane poly (meth) acrylate; (i ) A vinyl-based or diene-based low polymer having a (meth) acryloyloxy group on a side chain and / or a terminal; (j) The oligoester according to (a) to (i) above. (Meth) acrylate modified product; and the like.

As the monomer, (a) a carboxyl group-containing monomer represented by ethylenically unsaturated mono- or polycarboxylic acid and a carboxylate group-containing alkali metal salt, ammonium salt, amine salt or the like Monomer; (b) Ethylenically unsaturated (meth) acrylamide or alkyl-substituted (meth) acrylamide, an amide group-containing monomer represented by vinyllactams such as N-vinylpyrrolidone; (c) Aliphatic or Sulfonic acid group-containing monomers represented by aromatic vinyl sulfonic acids and alkali metal salts thereof,
Sulfonate group-containing monomers such as ammonium salts and amine salts; (d) Hydroxyl group-containing monomers represented by ethylenically unsaturated ethers; (e) Dimethylaminoethyl (meth) acrylate-2-
Amino group-containing monomer such as vinyl pyridine; (f) Quaternary ammonium base-containing monomer; (g) Alkyl ester of ethylenically unsaturated carboxylic acid; (h) Nitrile group-containing monomer such as (meth) acrylonitrile (I) Styrene; (j) Esters of ethylenically unsaturated alcohols such as vinyl acetate and (meth) allyl acetate; (k) Mono (meth) acrylates of alkylene oxide addition polymers of compounds containing active hydrogen. (L) an ester group-containing bifunctional monomer represented by a diester of a polybasic acid and an unsaturated alcohol; (m) an alkylene oxide addition polymer of a compound containing active hydrogen and (meth) acrylic acid Bifunctional monomer composed of diester; (n) Bisacrylamide such as N, N-methylenebisacrylamide; (o) Divinylbenzene, divinylethylene glycol,
Bifunctional monomers such as divinyl sulfone, divinyl ether, divinyl ketone; (p) ester group-containing polyfunctional monomer represented by polyester of polycarboxylic acid and unsaturated alcohol; (q) containing active hydrogen A polyfunctional monomer composed of a polyester of an alkylene oxide addition polymer of a compound and (meth) acrylic acid; and (r) a polyfunctional unsaturated monomer such as trivinylbenzene. Two or more of the above-mentioned ionizing radiation curable resins may be used in combination.

In the resin component, in addition to the above-mentioned prepolymers and monomers, if necessary, calcium carbonate, barium carbonate, zinc carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, sulfuric acid. Inorganic pigments such as barium, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, etc., pigments obtained by surface-treating these inorganic pigments with organic acids, styrene microballs, nylon powder, polyethylene powder, urea.
Formalin resin powder, cellulose acetate powder, polymethylmethacrylate powder, fluorine resin powder,
Add appropriate additives such as epoxy resin powder, benzoguanamine resin powder, organic pigments such as raw starch granules, non-electron beam curing resin, defoaming agent, leveling agent, lubricant, surfactant, plasticizer, ultraviolet absorber, etc. You can

Further, a heat-sensitive recording material having a wide range of surface properties from a matte tone to a strong gloss can be formed by adjusting the kinds and blending ratios of various additives. Also,
Examples of the non-electron beam curable resin include acrylic resin, silicon resin, alkyd resin, fluororesin, butyral resin and the like.

The resin component as described above is thoroughly mixed by a suitable mixing stirrer such as a mixer, and then coated on the recording layer or the intermediate layer by various known methods. If necessary, the resin component may be added. It is also possible to adjust the viscosity by heating. Further, the coating amount is not necessarily limited,
If it is less than 0.1 g / m ² , the desired effect of the present invention cannot be expected, and if the coating amount is more than 20 g / m ² , the recording sensitivity of the obtained recording medium may be lowered, so that 0.1 to 2 is used.
0 g / m ^2, more preferably it is desirable to adjust the range of about 1 to 10 g / m ^2.

The resin layer formed on the recording layer or the intermediate layer is cured by irradiation with ionizing radiation. Examples of the ionizing radiation include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X rays.
Examples include lines. Since α rays, β rays, γ rays, and X rays are accompanied by problems such as danger to the human body, electron rays and ultraviolet rays, which are easy to handle and are widely used industrially, are preferably used.

When an electron beam is used, the amount of the electron beam irradiated is 0.1 to 15 Mrad, more preferably 0.5 to 1 Mrad.
A range of about 0 Mrad is desirable. By the way, 0.1 Mrad
If it is less than 1, the resin component cannot be sufficiently cured, and 1
Excessive electron beam irradiation exceeding 5 Mrad may cause coloration or discoloration of the thermosensitive recording medium, and may cause a decrease in paper strength when the support is paper. As an electron beam irradiation method, for example, a scanning method, a curtain beam method, a broad beam method, or the like can be adopted, and an accelerating voltage for irradiation is preferably about 100 to 300 KV.

When ultraviolet rays are used, it is necessary to add a sensitizer to the coating composition, which is 0.2 to 10% by weight, preferably 0.5 to 5% by weight, based on the resin component. % Is added. Further, as a light source for irradiating ultraviolet rays, an ultraviolet lamp, a xenon lamp, a tungsten lamp or the like is used, and ultraviolet rays having an intensity of about 5000 to 8000 μW / cm are preferably irradiated.

The electron beam irradiation method described above is most preferably used because it has higher productivity than the ultraviolet irradiation method, there is no problem of odor and coloring due to addition of a sensitizer, and a uniform crosslinked structure is easily obtained. .

The thermal recording material of the present invention having the overcoat layer thus obtained can be further subjected to smoothing treatment with a super calender or the like to improve recording density and recording density unevenness.

[0047]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 [Formation of coating layer] 70 parts of kaolin as a pigment and heavy carbonic acid
20 parts calcium, 10 parts satin white, as an adhesive
Phosphoesterified starch 3 parts (solid content) and styrene
A coating liquid consisting of 11 parts of Tadiene latex (solid content)
Adjust it and air-dry it on one side of the 180 μm thick base paper.
If coater, dry weight is 25g / m²Painted to be
After covering and drying, put on a super calender and K &
N ink absorption is 3g / m ²Support with single-sided coating layer
Got the body

[Preparation of Solution A] A composition comprising 10 parts of 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 5 parts of a 5% aqueous solution of methylcellulose and 30 parts of water was sand-milled until the average particle size became 3 μm. Crushed.

[Preparation of Solution B] Benzyl 4-hydroxybenzoate 20 parts, 5% aqueous solution of methylcellulose 5 parts, water 55
The composition consisting of 1 part was pulverized with a sand mill until the average particle size became 3 μm.

[Formation of Recording Layer] 45 parts of solution A, 80 parts of solution B, 50 parts of 20% aqueous solution of oxidized starch, and 10 parts of water were mixed and stirred on the coated layer of the support having a single-sided coated layer. The coating liquid prepared as described above was applied and dried so that the coating amount after drying was 5 g / m ^2, and a thermosensitive recording layer was provided.

[Formation of Intermediate Layer] On the obtained heat-sensitive recording layer, acetoacetylated polyvinyl alcohol (trade name:
Z-200, Nippon Synthetic Chemical Industry Co., Ltd.) 8% aqueous solution 1000
Parts, calcium carbonate (trade name: Softon 1800, Bihoku Powder Co., Ltd.) 100 parts, and water 100 parts so that the coating amount after drying is 4 g / m ² and then dried. After smoothing with a render, a thermosensitive recording medium having an intermediate layer having a Bekk smoothness of 500 seconds was obtained.

[Formation of Overcoat Layer] A mixture of prepolymers of polyester polyacrylate and polyurethane polyacrylate (trade name: 78E20) is formed on the intermediate layer.
4, Mobil Oil Co., Ltd.) to a dry coating amount of 3 g / m ² and treated with an electron curtain type electron beam irradiation device (CB: 150 type, manufactured by ESI) at an irradiation dose of 1.5 Mrad. Thus, the resin component was cured to obtain a thermal recording material having an overcoat layer.

Example 2 In forming a coating layer, the coating liquid was applied to both sides of a base paper having a paper thickness of 180 μm with an air knife coater so that the dry weight was 2 per side.
The coated paper was coated at 5 g / m ² and dried, and then supercalendered to obtain a double-sided gloss-finished coated paper with 70% gloss and good visual smoothness. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that a recording layer was provided on one surface of the coating layer to prepare the heat-sensitive recording material.

Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the intermediate layer was not provided on the recording layer.

Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 2 except that the intermediate layer was not provided on the recording layer.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the base paper was not provided with a coating layer and the recording layer was provided directly. In addition, K & of coating layer
The N ink absorption was 16 g / m ² .

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as Comparative Example 1 except that the overcoat layer was not provided.

Comparative Example 3 In the formation of the coating layer of Example 1, the phosphoric acid esterified starch in the coating liquid was reduced to 1 part (solid content) and the styrene-butadiene latex was reduced to 3 parts (solid content). A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the coating liquid was adjusted by still,
The K & N ink absorption of the pigment coated layer was 11 g / m ² .

The following seven kinds of quality tests were conducted on the thus obtained seven kinds of thermal recording materials, and the results are shown in Table 1.

(1) Initial printing color density The thermosensitive recording medium was subjected to a thermal inclination tester (manufactured by Toyo Seiki: Condition 120).
Image recording was performed at ² ° C., 2 kg / cm ² , 10 seconds), and the maximum color density of the obtained recorded image was measured by a Macbeth densitometer (Macbeth RD-100R type).

(2) Plasticizer resistance test A polyvinyl chloride wrap film (manufactured by Mitsui Toatsu Kagaku Co., Ltd.) was wound around a polypropylene pipe (40 mm diameter pipe) in three layers, and the color was printed by a thermal gradient tester. The heat-sensitive recording material was sandwiched so that the color-developed surface of the print was on the outside, and a vinyl chloride wrap film was wrapped around it five times. The print density after 72 hours was measured by a Macbeth densitometer. (The larger the value, the better the plastic resistance.)

(3) Oil resistance test 0.05 cc of salad oil was applied to the recording layer surface of the heat-sensitive recording material on which the color was printed.
Was dropped to spread evenly on the surface, and the print density after standing for 24 hours was measured with a Macbeth densitometer. (The larger the value, the better the oil resistance.)

(4) Water-Resistant Printing The print density after the color-developed thermosensitive recording medium was left in water for 15 hours was measured with a Macbeth densitometer. (The higher the value, the better the water resistance.)

(5) Glossiness The glossiness of the surface of the thermosensitive recording medium is measured by a goniophotometer (MURAKAM).
I COLOR RAB. Made, gloss meter GM-
3D) with an incident angle of 60 degrees. (The higher the number, the higher the gloss.)

(6) Rub dyeing Using a friction tester for hard labor (manufactured by Toyo Seiki Co., Ltd .: conditional contact load of 200 g, reciprocating frequency of 10 times), using No. 400 sandpaper instead of white cotton cloth, heat-sensitive recording The surface of the recording layer of the body was rubbed, and the degree of color development was visually judged. Criteria for visual judgment ◎: Almost no color developed: Some color developed ×: Color developed

(7) Image quality A thermosensitive recording medium was measured with a thermal inclination tester (conditions: 80 ° C., 2 kg / cm ² ,
Image recording was performed for 10 seconds), and the highest color density portion of the obtained recorded image was visually determined. Criteria for visual judgment: Uniform and no uneven coloring. Δ: Some uneven coloring. X: There is uneven coloring.

(8) Picking strength With a RI printing machine (manufactured by Ming Seisakusho), TOKA SHIKI
SO CHEMICAL INDUSTRY CO. , L
After repeatedly printing SD Super Deluxe 50 Red B ink manufactured by TD several times, the peeling state of the recording layer surface was visually determined. Criteria for visual judgment: Almost no peeled part is seen. X: Many peeled parts are seen.

[0069]

[Table 1]

[0070]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention is excellent in picking strength on the thermosensitive recording surface.
It is a thermal recording material for a prepaid card having strong gloss, high print recording density, and excellent rubbing, image quality and storage stability.

Claims (4)

[Claims] 1. A heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring when contacted with the dye is provided on one surface of the support, and further contains an ionizing radiation curable resin as a main component. In a heat-sensitive recording material provided with an overcoat layer, a pigment and an adhesive are main components between the support and the heat-sensitive recording layer, and K
& N A thermal recording material provided with a coating layer having an ink absorption of 10.0 g / m ² or less. 2. The heat-sensitive recording material according to claim 1, wherein the support has a thickness of 50 to 1000 μm. 3. The heat-sensitive recording material according to claim 1, wherein an intermediate layer containing a water-soluble resin and / or a water-dispersible resin is provided between the heat-sensitive recording layer and the overcoat layer. 4. The thermal recording material according to claim 1, which is a thermal recording material for a prepaid card.