JPH04119882A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having strong gloss and excellent in printing preservability and recording characteristics by successively laminating a thermal recording layer, an intermediate layer containing a water- soluble or water-dispersible resin and an overcoat layer containing an electron beam cured resin on a support. CONSTITUTION:A thermal recording layer containing a color former and a developer forming a color upon the contact with the color former and an intermediate layer containing a water-soluble or water-dispersible resin are formed on a support in this order and two or more overcoat layers each containing an electron beam cured resin are formed on the intermediate layer to obtain a thermal recording material. As an embodiment of the water-soluble or water- dispersible resin used in the intermediate layer, there is perfectly or partially saponified polyvinyl alcohol. As the prepolymer of the electron beam cured resin forming the overcoat layers, there are poly(meth)acrylates of aliphatic, alicyclic and alaromatic divalent-hexavalent polyhydric alcohols or polyalkylene glycol.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that has high gloss and excellent printing stability.

"Prior Art" Conventionally, heat-sensitive recording utilizes a coloring reaction between a coloring agent and a coloring agent that develops color when it comes into contact with the coloring agent, and brings a recoloring substance into contact with heat to obtain a colored image. The body is well known. Such heat-sensitive recording media are relatively inexpensive, and the recording equipment is compact and relatively easy to maintain.
It is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields such as heat-sensitive labels. However, it has problems in fingerprint resistance, solvent resistance, etc., and has the disadvantage that, for example, when the recording layer comes into contact with human sebum or solvent, the recording density decreases, and unnecessary color development called background fog occurs.

As a method to overcome these drawbacks, a method is proposed in which an aqueous emulsion of a resin having film-forming ability and chemical resistance is coated on the heat-sensitive recording layer (Japanese Patent Laid-Open No. 12834/1983).
No. 7), a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Utility Model Application Publication No. 125354/1983), etc. have been proposed.

However, improvements have been accompanied by new drawbacks, and satisfactory results have not always been obtained.

For example, when applying a water-based resin coating on a heat-sensitive recording layer, it is necessary to limit the drying temperature to avoid coloring of the recording layer due to high-temperature drying, which inevitably results in insufficient curing of the resin layer and A phenomenon in which the recording head and the resin layer stick together occurs.

For this reason, a method has been proposed in which a resin component that can be cured by electron beams is applied onto the heat-sensitive recording layer, and the resin component is cured by electron beams. A resin layer that is cured by electron beams may cause adverse effects such as causing the heat-sensitive recording layer to develop color immediately after coating or causing discoloration of the recorded image.

As a result of studying ways to improve these drawbacks, the present inventors found that by providing an aqueous resin intermediate layer on the heat-sensitive recording layer and then providing an overcoat layer containing an electron beam curable resin, the recording layer can be improved. It was discovered that a heat-sensitive recording material with significantly improved printing storage stability without any problems, a wide range of surface properties, and excellent recording properties could be obtained, and an application was previously filed as Japanese Patent Publication No. 1-42835.

On the other hand, in recent years, various types of printers such as video printers that provide photographic-like high-quality images have come into use, and thermal recording materials used for printouts are also required to have better recording density and gradation. ing. For this reason, the development of heat-sensitive recording materials with excellent gradation expression using plastic films or synthetic papers as supports is progressing. Attempts have been made to provide an overcoat layer of water-based resin or the like on the recording layer. However, when a recording medium with an overcoat layer made of water-based resin is recorded using a video printer under particularly high humidity conditions, the overcoat layer tends to stick to the recording head and paper feed guide, causing jams. It became. Furthermore, the recording density itself is not necessarily satisfactory.

Therefore, as a result of intensive research into such problems, the present inventors formed a heat-sensitive recording layer on a plastic film or synthetic paper, provided an aqueous resin intermediate layer on the heat-sensitive recording layer, and then added an electron beam-curable resin. It was discovered that by providing an overcoat layer, it was possible to obtain an excellent recording medium with high recording density, excellent gradation, and storage stability, and which did not stick to the recording head even under high humidity conditions. Showa 6
It was proposed as No. 399984.

``Problem to be Solved by the Invention J'' However, even in the heat-sensitive recording material proposed earlier, when the support is paper, for example, the Benk smoothness of the intermediate layer is 5.
If it is less than 0 seconds, a highly glossy surface cannot be obtained;
If the time exceeds 00 seconds, there is a disadvantage that storage properties such as plasticizer resistance and oil resistance deteriorate.

On the other hand, when the support is a plastic film or synthetic paper, if the Bekk smoothness of the intermediate layer is less than 1600 seconds, it is difficult to obtain a highly glossy surface, and storage properties such as recording density and plasticizer resistance deteriorate. Image quality also deteriorates. Furthermore, if the time exceeds 20,000 seconds, there is also a drawback that storage properties such as surface strength and plasticizer resistance deteriorate.

Therefore, as a result of further studies in order to completely eliminate the variation in quality due to the difference in the smoothness of the intermediate layer, we found that by providing an overcoat layer containing an electron beam curing resin of 2N or more, the smoothness of the intermediate layer can be improved. It has been discovered that a heat-sensitive recording material with strong gloss and excellent printing stability and recording properties can be obtained regardless of the conditions, and the present invention has been completed.

"Means for Solving the Problems" The present invention provides a heat-sensitive recording layer containing a coloring agent and a coloring agent that develops color upon contact with the coloring agent on a support, and a water-soluble This heat-sensitive recording material is provided with an intermediate layer containing a resin or a water-dispersible resin, and further has two or more overcoat layers containing an electron beam curable resin on the intermediate layer.

"Function J" In the present invention, there are no particular limitations on the combination of the coloring agent and the coloring agent contained in the heat-sensitive recording layer, and any combination that causes a coloring reaction when the two come into contact with each other due to heat can be used. Possible. Examples include combinations of colorless or light-colored basic dyes and inorganic or organic acidic substances, combinations of higher fatty acid metal salts such as ferric stearate and phenols such as gallic acid, etc. .

However, it is particularly preferable to use a combination of a basic dye and an acidic substance because it provides extremely excellent recording properties. Various colorless to light-colored basic dyes are known, including the following.

3.3-bis(p-dimethylaminophenyl) 6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl) phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole) -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-Ethylcarbasol-3-yl)-6-cynotylaminophtha υF, 3,3-bis(2-
phenylindol-3-yl)-6-dimethylaminophthalide, 3-P-dimethylaminophenyl-3-(1
triallylmethane dyes such as -methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'bis-dimethylaminohenzhydrylhenzyl ether, N-halophenyl-leucoolamine, N-2,4, 5-t I
Diphenylmethane dyes such as J chlorophenyl leuco auramine, thiazine dyes such as hendiyl leucomethylene flu, p-nitropensoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-
Spiro-dinaphthopyran, 3-phenylsuvirocinaphthohyran, 3-benzyl-spiro-dinaphthopyran, 3
Spiro dyes such as -methyl-naphtho(6'-methoxyhenzu)spiropyran, 3-propyl-spiro-dibenzobilane, rhodamine B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (0-
Lactam dyes such as chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-6-methyl-
7-lyrolofluorane, 3-diethylamine-6,7-
Cynotylfluorane, 3-(N-ethyl-p-toluidino)-7methylfluorane, 3-diethylamino-7-
N-acetyl-N-methylaminofluorane, 3-diethylamino-'1-N-methylaminofluorane, 3-diethylamine-7-dihendylaminofluorane, 3-
Diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-N-chloroethyl-N-methylaminofluorane, 3-N-butylamino-6-methyl-7-phenylaminofluorane, 3-
N-pentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamine-7-N-diethylaminofluorane, 3-(N-ethyl-p~toluidino)
-6-methyl-7-phenylaminofluorane, 3-(
N-ethyl-p-toluidino)-6-methyl-7-(p
-Toluidino)fluoran, 3-diethylamino-6-
Methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 3-(N-ethyl-N-1so-amylamino)-6-methyl-7-tunylaminofluoran Oran,
3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-
Piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-dibutylamino-7-
Fluoran dyes such as (o-chlorophenylamino)fluoran and 3-pyrrolidino-6-methyl-7-P-butylphenylaminofluoran.

In addition, various inorganic or organic acidic substances are known that color when they come into contact with basic colorless dyes. 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(
2ter t-butylphenol), 4. 4'-5
ec-phthylidene diphenol, 4-phenylphenol, 4,4'-isopropylidene diphenol (bisphenol A), 2,2'-methylenebis (4 chlorphenol), hydroquinone, 44' cyclohexylidene diphenol, 4-hydroxy Benzyl benzoate, 4-
Phenolic compounds such as dimethyl hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenol polymer, benzoic acid, p-te
rt-methylbenzoic 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-hensylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3.5-di-tert-butylsalicylic acid , 3-phenylene, IL/-5-(α,α-dimethylhensyl)salicylic acid, aromatic carboxylic acids such as 3,5-di-α-methylhensylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids Examples include organic acidic substances such as salts with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and 4-hydroxy-4''-isopropoxydiphenylsulfone.

In the heat-sensitive recording material of the present invention, the usage ratio of the color former and the color former in the recording layer should be appropriately selected depending on the type of the color former and the color former used, and is not particularly limited. When using basic colorless dyes and acidic substances,
Generally, 1 to 50 parts by weight, preferably 1 to 10 parts by weight, of the acidic substance are used per 1 part by weight of the basic colorless dye.

To prepare a coating solution containing these substances, generally, water is used as a dispersion medium, and a coloring agent and a coloring agent are dispersed together or separately using a stirring/pulverizing machine such as a ball mill or attritor sand mill, and then the coating solution is prepared. prepared.

This coating liquid contains starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic,
Polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt,
Ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. accounts for 10 to 40% by weight of the total solids, preferably 15% by weight.
It is used in an amount of about 30% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate ester, alginates, fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, other antifoaming agents, and fluorescence. Examples include dyes, colored dyes, and the like.

In addition, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin,
Inorganic pigments such as clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay, stearamide, methylene bisamide stearate, oleic acid amide, palmitic acid amide,
Aliphatic acid amides such as matcha oleic acid amide and coconut fatty acid amide, 1,2-diphenoxyethane, 1゜2-bis(
3-methylphenokidine)ethane, 1゜2-bis(4-
Methylphenoxidine) ethane, 1゜5-bis(4-methoxyphenoxy)-3-oxabencune, ■-phenoxy 2-(4-methoxyphenoxy)ethane, 1-hensyloxynaphthalene, 2-hensyloxy Naphthalene, 1,4-bis(2-vinyloxyethoxy)henzen, etc. (7)
Esters such as dibenzyl oxalate, bis(P-chlorobenzyl) oxalate, henzyl p-benzyloxybenzoate, aromatic compounds such as p-hensyl biphenyl, m-terphenyl, and various known thermofusible substances. It can also be added as a sensitizer.

The coating method for the recording layer is not particularly limited, and it can be formed according to conventionally well-known and commonly used techniques, such as bar coating, air knife coating, rot blade coating, pure blade coating, short dwell coating, etc. It is formed by coating and drying. In addition, when a plastic film is used as a support, the coating efficiency can be increased by subjecting the surface to a treatment such as corona discharge or electron beam irradiation. The amount of coating liquid applied is also not particularly limited, but is usually 2 to 12 g/r+ (preferably 3 to 10 g/r+) in terms of dry weight.
+ (within a range of degrees)

In the heat-sensitive recording material of the present invention, an intermediate layer containing a water-soluble resin or a water-dispersible resin is first provided on the heat-sensitive recording layer thus obtained. The following substances are exemplified as the plastic resin.

Completely saponified or partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol into which an acetoacetyl group has been introduced by reacting polyvinyl alcohol with diketene, etc., polyvinyl alcohol and fumaric acid, phthalic anhydride, trimellitic anhydride, itaconic anhydride, etc. reaction products with polyhydric carboxylic acids or esterified products of these reactions, as well as vinyl acetate and ethylenically unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid, and methacrylic acid. carboxy-modified polyvinyl alcohol obtained as a saponified copolymer of sulfonic acid-modified polyvinyl alcohol obtained as a saponified copolymer of vinyl acetate and an olefin sulfonic acid such as ethylene sulfonic acid or allyl sulfonic acid or a salt thereof; Olefin-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate and olefins such as ethylene, propylene, isobutylene, α-octene, α-tothycene, α-octadodecene, etc.; vinyl acetate and nitriles such as acrylonitrile and methacrylaterile; Nitrile-modified polyvinyl alcohol obtained as a saponified copolymer with vinyl acetate and acrylamide,
Amide-modified polyvinyl alcohol obtained by saponifying a copolymer with amides such as methacrylamide, pyrrolidone-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate and N-vinylpyrrolidone, methylcellulose, ethylcellulose, hydroxyl Cellulose derivatives such as ethyl cellulose and carboxymethyl cellulose, casein, gum arabic, starches such as oxidized starch, etherified starch, dialdehyde starch, and esterified starch, styrene-butadiene copolymer emulsion, vinyl acetate-vinyl chloride-ethylene copolymer Coalescence emulsion, methacrylate-butadiene copolymer emulsion, etc.

Among these water-soluble resins or water-dispersible resins, various modified polyvinyl alcohols, cellulose derivatives, and casein are preferred, and acetoacetylated polyvinyl alcohol and carboxy-modified polyvinyl alcohol are particularly preferred. The amount of water-soluble resin or water-dispersible resin used is not particularly limited, but is preferably 10 to 50% by weight based on the total solid content in the coating liquid, preferably 15 to 40fi.
It is used at about 1%.

Pigments can be added to the intermediate layer to increase smoothness. Specific examples of pigments include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide,
Inorganic pigments such as aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, fired clay, colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea/formalin resin filler, raw starch granules, etc. is exemplified. The amount used is generally 5 parts by weight per 100 parts by weight of the resin component.
It is blended in an amount of about 500 parts by weight, preferably about 80 to 350 parts by weight.

Furthermore, curing agents such as glyoxal, methylolmelamine, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, ammonium chloride, etc. are added to the coating solution forming the intermediate layer as necessary. If necessary, lubricants such as zinc stearate, calcium stearate, stearamide, polyethylene wax, carnauba wax, paraffin wax, and ester wax, sodium dioctyl sulfosuccinate, sodium dodecyl hensensulfonate, lauryl alcohol sulfate ester, etc. Various auxiliary agents such as surfactants such as sodium salts, alginates, and fatty acid metal salts, ultraviolet absorbers such as hensifenones and triazoles, antifoaming agents, fluorescent dyes, and colored dyes may also be added as appropriate.

The coating liquid for forming the intermediate layer is generally prepared as an aqueous coating liquid, and after being thoroughly mixed and dispersed using a mixer, attritor, ball mill, roll mill, etc. as necessary, various known coating methods are used. It is applied onto the heat-sensitive recording layer by a device. After coating, it can also be cured and dried by irradiation with ultraviolet rays or electron beams.

In addition, when using a curing agent together, 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 no need to worry about pot life, and there is an advantage of being able to select a strong hardening agent.

The coating amount of the coating liquid forming the intermediate layer is not particularly limited, but if it is less than 0.1 g/rrr, the desired effect of the present invention cannot be sufficiently obtained;
In general, the dry weight is 0.1 to 20 g/vo, as there is a risk that the recording sensitivity of the thermal recording medium will be significantly reduced if it exceeds
It is preferably adjusted within a range of about 0.5 to iog/M.

Further, if necessary, it is possible to further improve the storage stability by providing a coat layer similar to the intermediate layer on the back side of the heat-sensitive recording material. Furthermore, various known techniques in the field of heat-sensitive recording material production may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

Two or more overcoat layers containing an electron beam curable resin are provided on the intermediate layer thus formed, and the following prepolymers and monomers are exemplified as the electron beam curable resin forming the overcoat layer.

(a) Aliphatic, alicyclic, araliphatic di- to hexavalent polyhydric alcohol and poly(meth)acrylate of polyalkylene glycol; (b) Aliphatic, alicyclic, araliphatic, aromatic di- to 6
(C) poly(meth)acryloyloxyalkyl phosphate; (d) polyester poly(meth)acrylate;
(e) Epoxy poly(meth)acrylate;
Polyurethane poly(meth)acrylate; (6) Polyamide poly(meth)acrylate; (iii) Polysiloxane poly(meth)acrylate; (i) Vinyl-based or diene having (meth)acryloyloxy group in side chain and/or terminal Prepolymers such as (j) oligoester (meth)acrylate modified products described in (a) to (i) above; and monomers such as (a) ethylenically unsaturated mono- or polycarboxylic acids, etc. Carboxyl group-containing monomers and their alkali metal salts, ammonium salts, amine salts, and other carboxylic acid group-containing monomers; (b) Ethylenically unsaturated (meth)acrylamide or alkyl-substituted (meth)acrylamide , amide group-containing monomers represented by vinyl lactams such as N-vinylpyrrolidone; (C) sulfonic acid group-containing monomers represented by aliphatic or aromatic vinyl sulfonic acids and their alkali metal salts; , ammonium salts, amine salts, and other sulfonic acid group-containing monomers; (d) Hydroxyl group-containing monomers represented by ethylenically unsaturated ethers; (e) Dimethylaminoethyl (meth)acrylate-2-vinylpyridine amino group-containing monomers such as
Monomers containing quaternary ammonium bases; (alkyl esters of ethylenically unsaturated carboxylic acids; (c) monomers containing nitrile groups such as (meth)acrylonitrile; (i) styrene; (j) vinyl acetate, acetic acid ( Esters of ethylenically unsaturated alcohols such as meth)allyl; tentative) mono(meth)acrylates of alkylene oxide addition polymers of compounds containing active hydrogen; (1) Typical examples are diesters of polybasic acids and unsaturated alcohols. (e) A bifunctional monomer consisting of a diester of an alkylene oxide addition polymer of an active hydrogen-containing compound and (meth)acrylic acid; (n) N, N- Bisacrylamides such as methylenebisacrylamide; (0) Bifunctional monomers such as divinylbenzene, divinylethylene glycol, divinylsulfone, divinyl ether, and divinyl ketone; (p) Typical examples include polyesters of polycarboxylic acids and unsaturated alcohols. (q) A polyfunctional monomer consisting of a polyester of an alkylene oxide addition polymer of a compound containing active hydrogen and (meth)acrylic acid; (r) A polyfunctional monomer containing trivinylhenzene; polyfunctional unsaturated monomers such as

etc.

In addition to the above-mentioned electron beam curable prepolymers and monomers, the resin component may contain, for example, non-electron beam curable resins, antifoaming agents,
Additives such as rehering agents, lubricants, surfactants, desensitizers, ultraviolet absorbers, fluorescent dyes, colored dyes, pigments, fluorescent pigments, and colored pigments can be added as appropriate.

Examples of the non-electron beam curable resin include acrylic resin, silicone resin, acrylic resin, fluororesin, butyral resin, and the like.

The resin components as described above are thoroughly mixed using a suitable mixer such as a mixer, and then coated on the intermediate layer by various known methods. You can also make adjustments. Further, although the coating amount is not necessarily limited, if it is less than 0.1 g/rd, the desired effect of the present invention cannot be expected, and if the coating amount is more than 20 g/rd, the recording sensitivity of the resulting recording medium may decrease. Because of this, the overall overcoat layer is 0.1~
20 g/n (more preferably 0.3 to 10 g/n)
It is desirable to adjust within a range of about rrr.

Incidentally, in order to improve the adhesion between the intermediate layer and the overcoat layer, the surface of the intermediate layer may be subjected to corona treatment if necessary.

In the present invention, two or more overcoat layers are provided, and the overcoat layers are cured by electron beam irradiation. For example, when providing two overcoat layers, the first overcoat layer is first applied and semi-cured or completely cured by electron beam irradiation, then the second overcoat i is applied, and the It is cured by irradiation, or after the two overcoat layers are applied, the two overcoat layers are simultaneously cured by irradiation with an electron beam.

In this case, the resin composition of the first overcoat layer and the resin composition of the second overcoat layer may be the same or completely different.

In addition, to improve the adhesion between overcoat layers,
Corona treatment may be performed if necessary.

The total amount of electron beam irradiation is preferably in the range of 15 Mrad or less. Incidentally, excessive electron beam irradiation exceeding 15 Mrad may cause color development or discoloration of the thermosensitive recording material.

As the electron beam irradiation method, for example, scanning method, curtain beam method, broad beam method, etc. can be adopted, and the acceleration voltage during irradiation is 100 to 300 KV.
The degree is appropriate.

Further, the recording density and recording density unevenness can be further improved by smoothing the recording body provided with the overcoat layer using a super calender or the like.

"Example" The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these.

Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 1 ■ Lacquer preparation A 3-(N-cyclohexyl-N-methylamino)6-methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% water-soluble i 5 parts water
30 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of Solution B Hensyl 4-hydroxybenzoate 20 parts Methylcellulose 5% aqueous solution 5 parts Water
55 parts of this composition was ground in a Santo mill until the average particle size was 3 μm.

(2) Formation of Recording Layer 45 parts of liquid A, 80 parts of liquid B, 50 parts of a 20% oxidized starch aqueous solution, and 10 parts of water were mixed and stirred to prepare a coating liquid.

The obtained coating liquid was applied and dried on a base paper of 50 g/n so that the coated amount after drying was 6 g/n, to obtain a heat-sensitive recording material.

■ Formation of intermediate layer On the recording layer of the obtained heat-sensitive recording material, a coating liquid having the following composition is applied so that the coating amount after drying is 4 g/m, and dried, and the Bekk smoothness is 45 seconds. A thermosensitive recording medium was obtained.

Acetoacetylated polyvinyl alcohol (product name: Z-
1000 parts of an 8% aqueous solution of calcium carbonate (trade name: Laughton 180O, manufactured by Bihoku Funka Co., Ltd.) 100 parts water
100 parts of the mixture was then smoothed using a super calender to prepare a heat-sensitive recording material having an intermediate layer having a Bekk smoothness of 500 seconds.

■ Formation of overcoat layer Polyacrylate (trade name: 78E204,
Mobil Oil Co., Ltd.) was applied at a dry coating amount of 2 g/pot, and an electron curtain type electron beam irradiation device (C
B: Type 150, manufactured by ESI) to cure the resin component with an irradiation dose of 2 Mrad, and then apply the same polyacrylate in a similar manner to a dry coating amount of 2 g/rrf. The resin component was cured by treatment with the same electron curtain type electron beam irradiation device at an irradiation dose of 3 Mrad to obtain a thermosensitive recording material having two overcoat layers of electron beam cured resin.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1, except that the surface of the intermediate layer was not smoothed and two overcoat layers were provided directly on the intermediate layer having a Bekk smoothness of 45 seconds.

Example 3 In Example 1, the Bekk smoothness of the intermediate layer surface was 2000.
A heat-sensitive recording material having two overcoat layers was obtained in the same manner except that it was subjected to super calender treatment so that the heat-sensitive recording material had two overcoat layers.

Example 4 In Example 1, 80 g/r+ synthetic paper (trade name: Yupo, manufactured by Tamago Yuka Co., Ltd.) was used as the support instead of the 50 g/n base paper, and the surface of the intermediate layer was smoothed. degree is 50
A heat-sensitive recording material having two overcoat layers was obtained in the same manner except that it was subjected to a super calender treatment so that the heating time was 0.00 seconds.

Example 5 A thermosensitive recording material was obtained in the same manner as in Example 4, except that the surface of the intermediate layer was not smoothed and two overcoat layers were provided directly on the intermediate layer having a Heck smoothness of 150 seconds.

Example 6 In Example 4, the Bekk smoothness of the surface of the intermediate layer was 3000.
A heat-sensitive recording material having two overcoat layers was obtained in the same manner except that it was subjected to supercalender treatment so that the heating time was 0 seconds.

Example 7 In Example 4, oligoester acrylate (trade name: M-8030) was used to form the 20th overcoat layer.
A heat-sensitive recording material having two overcoat layers was obtained in the same manner, except that a heat-sensitive recording material (manufactured by Toagosei Kagaku Co., Ltd.) was used.

Comparative Example 1 In Example 1, to form an overcoat layer, polyacrylate (trade name: 78E204, manufactured by Mobil Oil Co., Ltd.) was applied on the intermediate layer at a dry coating amount of 5 g/rl (electron curtain type electronic Line irradiation device (CB
A heat-sensitive recording material was obtained in the same manner, except that the resin component was cured by treatment with an irradiation dose of 3 Mrad, and one overcoat layer of electron beam-curable resin was used.

Comparative Example 2 In Example 2, a thermosensitive recording material having one overcoat layer of electron beam curing resin was obtained in the same manner as in Comparative Example 1.

Comparative Example 3 In Example 3, a thermosensitive recording material having one overcoat layer of electron beam curing resin was obtained in the same manner as in Comparative Example 1.

Comparative Example 4 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the overcoat layer was not provided on the intermediate layer.

Comparative Example 5 In Example 4, a thermosensitive recording material having one overcoat layer of electron beam curing resin was obtained in the same manner as in Comparative Example 1.

Comparative Example 6 In Example 5, a thermosensitive recording material having one overcoat layer of electron beam curing resin was obtained in the same manner as in Comparative Example 1.

Comparative Example 7 In Example 6, a thermosensitive recording material having one overcoat layer of electron beam curing resin was obtained in the same manner as in Comparative Example 1.

Comparative Example 8 A thermosensitive recording material was obtained in the same manner as in Example 4 except that the overcoat layer was not provided on the intermediate layer.

Of the 15 types of heat-sensitive recording materials obtained in this way, 7 types whose support was paper
20"C12kg/cm2.10 seconds), and for eight types whose support was synthetic paper, the print color was developed using a Sony video printer UP-103, and the initial print color density was measured using a Machess densitometer (manufactured by Macbeth Co., Ltd., RD-103). 10
The results are shown in Table 1.

Furthermore, for paper supports, the plasticizer resistance and oil resistance shown below were evaluated as print storage properties, and the results are shown in Table 1.

When the support was made of synthetic paper, the plasticizer resistance, adhesiveness and surface strength of the coating layer shown below were evaluated, and the results are shown in Table 1.

Table 1 also shows the glossiness of the surface of the heat-sensitive recording material before printing color development.

Rankamei Oita: Polypropylene pipe (40mmφ pipe) is wrapped with vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) three times, and a heat-sensitive recording material with colored print is placed on top of it, with the colored side of the print facing out. Then, a vinyl chloride wrap film was wrapped five times over it, and the print density after 72 hours was measured using a Maches densitometer.

(The larger the number, the better the plasticizer resistance.) JtJ
1 standing: 0.05 cc of salad oil was dropped onto the recording layer surface of the heat-sensitive recording material that had been colored and spread uniformly over the surface, and after being left for 24 hours, the print density was measured.

(The larger the number, the better the oil resistance.) Coating I: After dropping 0.05 ml of water onto the coated surface of the heat-sensitive recording material, the coated surfaces of the same heat-sensitive recording material are overlapped, and 20 g
/ c n (after being treated for 1 minute under pressure, peeled off,
The state of peeling on the surface was visually determined.

○: No abnormality in the coated layer ×: Peeling of the coated layer Surface stringency: Cellophane tape (manufactured by NITTO) was adhered to the surface of the coated layer and then peeled off to visually determine the peeling state of the surface layer.

○: No abnormality in the surface layer ×; Peeling of surface layer Measurements were made with a variable angle photometer at an angle of incidence of 60 degrees.

(The larger the number, the higher the gloss.) Table 1 (d) Coating layer tackiness (e) Surface strength ([) Glossiness "Effect" As is clear from the results in Table 1, the thermal recording of the present invention The body was a heat-sensitive recording material with high gloss and excellent printing stability.

Claims (1)

[Scope of Claims] A heat-sensitive recording layer containing a color former and a color former that develops a color when in contact with the color former is provided on a support, and a water-soluble resin or a water-dispersible resin is provided on the heat-sensitive recording layer. 1. A heat-sensitive recording material comprising an intermediate layer containing an electron beam curable resin, and two or more overcoat layers containing an electron beam curable resin formed on the intermediate layer.