JPH04353488A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material especially imparting strong glossiness and high recording density and excellent in preservability, recording running properties and printability. CONSTITUTION:A thermal recording material is formed by providing a thermal recording layer 1 containing a color former and a developer forming a color upon the contact with the color former and an intermediate layer 2 containing a water-soluble resin and/or a water-dispersible resin on a support and further providing an overcoat layer containing an ionizing radiation curable resin to irradiate the same with ionizing radiation. The overcoat layer contains ethylene, alpha-olefin and a cooligomer and/or an acid modified cooligomer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that is highly glossy, has a high recording density, has excellent storage stability, and has excellent recording running properties and printability.

0002

[Prior Art] Conventionally, heat-sensitive recording utilizes a color-forming reaction between a color-forming agent and a color-forming agent that develops color when it comes into contact with the color-forming agent, and a color-forming image is obtained by bringing both color-forming substances into contact with heat. The body is well known. Such thermal recording media are relatively inexpensive, the recording equipment is compact, and maintenance is relatively easy, so they are used not only as recording media for facsimiles and various computers, but also in a wide range of fields such as thermal labels. ing. However, it has problems with fingerprint resistance, solvent resistance, etc., and, for example, when the recording layer comes into contact with human sebum or solvents, the recording density decreases and unnecessary color development called background fog occurs.

[0003] As a method to eliminate such drawbacks, a method of coating an aqueous emulsion of a resin having film-forming ability and chemical resistance on the heat-sensitive recording layer (Japanese Unexamined Patent Application Publication No. 1986-54) has been proposed.
-128347), a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Utility Model Application No. 56-12535),
No. 4) 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. , a phenomenon in which the recording head and the resin layer stick together occurs during recording. Therefore, a method has been proposed in which a resin component that is cured by electron beams is applied onto the heat-sensitive recording layer and the resin component is cured by electron beams.
The storage stability of prints is still not sufficient, and the resin layer, which is cured by electron beams, has had adverse effects such as causing the heat-sensitive recording layer to develop color immediately after coating and causing discoloration of the recorded image.

[0005] As a result of studies on how to improve these drawbacks, the inventors of the present invention found that if an aqueous resin intermediate layer is provided on the heat-sensitive recording layer, and then an overcoat layer containing an electron beam curable resin is provided, recording can be improved. It was discovered that a heat-sensitive recording material with improved printing storage stability without layer fogging, a wide range of surface properties, and excellent recording properties could be obtained, and the invention was previously filed as Japanese Patent Publication No. 1-42835.

[0006]

However, in recent years, there has been an increase in the use of thermal recording media as product labels, and especially when recording at high speeds, for example in fully automatic labelers, there is a problem with the recording head and overlapping during recording. The problem of adhesion with the coating layer became clear. In this case, a possible countermeasure would be to include a silicone-based leveling agent in the overcoat layer to prevent the phenomenon of adhesion (sticking) to the recording head, but although silicone-based leveling agents are slightly effective in preventing sticking, It was found that the printability was poor. For example, good printing cannot be obtained due to poor ink transferability or poor adhesion during printing.

[0007]

[Means for Solving the Problems] The present invention provides a support with:
A heat-sensitive recording layer containing a coloring agent and a coloring agent that develops a color when in contact with the coloring agent, an intermediate layer containing a water-soluble resin and/or a water-dispersible resin, and an ionizing radiation-curable resin. A heat-sensitive recording material formed by providing an overcoat layer containing the above-mentioned material and irradiating it with ionizing radiation, characterized in that the overcoat layer contains a cooligomer of ethylene and α-olefin and/or an acid-modified product of the cooligomer. This is a heat-sensitive recording medium.

[0008]

[Function] 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, and combinations of higher fatty acid metal salts such as ferric stearate and phenols such as gallic acid. .

However, especially when applied to a combination of a basic dye and an acidic substance, the recording properties are extremely excellent, so it is particularly preferable. 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-dimethylindol-3-yl)phthalide, 3- (p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindole-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-leucoolamine, N
- diphenylmethane dyes such as 2,4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-
Spiro dyes such as dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (o- Lactam dyes such as chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran,
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-phnylaminofluorane, 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)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6
-Fluoran dyes such as methyl-7-p-butylphenylaminofluorane, etc.

[0010] Various inorganic or organic acidic substances are also known that color when they come into contact with basic colorless dyes. For example, activated clay, acid clay, attapulgite, bentonite, colloidal silica, aluminum silicate, etc. Acidic substances, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-
Octylcatechol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis(4-methyl-6-te
rt-butylphenol), 4,4'-isopropylidene bis(2-tert-butylphenol), 4,4'
-sec-butylidenediphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol
(bisphenol A), 2,2'-methylenebis (
4-chlorophenol), hydroquinone, 4,4'-
Phenolic compounds such as cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak type phenolic resin, phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlor Benzoic 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-t
ert-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-dimethylbenzyl)salicylic acid, 3,5-di-α
- aromatic carboxylic acids such as methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium,
Examples include organic acidic substances such as salts with polyvalent metals such as titanium, manganese, tin, and nickel.

[0011] In the heat-sensitive recording material of the present invention, the ratio of the coloring agent and coloring agent used in the recording layer should be appropriately selected depending on the type of coloring agent and coloring agent used, and is not particularly limited. However, for example, when using a colorless or light-colored basic dye and an acidic substance, the acidic substance is generally used in an amount of about 1 to 50 parts by weight, preferably about 1 to 10 parts by weight, per 1 part by weight of the basic dye. .

[0012] To prepare a coating solution containing these substances, the coloring agent and the coloring agent are generally dispersed together or separately using water as a dispersion medium and using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill. , prepared as a coating liquid. 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 as adhesives. 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 to 30% by weight.
About % by weight is used.

Furthermore, various auxiliary agents can be added to the coating liquid, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, alginate, fatty acid metal salt. Dispersants such as benzophenone,
Examples include triazole-based ultraviolet absorbers, other antifoaming agents, fluorescent dyes, and colored dyes.

If necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, and fine particulate anhydrous silica may be used. , inorganic pigments such as activated clay, and sensitizers such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, matcha oleic acid amide, coconut fatty acid amide, etc. can also be added.

Supports include paper such as high-quality paper, art paper, and coated paper, plastic films such as polyethylene, polyester, polyvinyl chloride, polystyrene, and nylon, and sheets and films obtained by laminating paper with plastic. Synthetic paper produced by the fiber method or the fiber method is used. 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, rod 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 improved by subjecting the surface to a treatment such as corona discharge or electron beam irradiation. The amount of the coating liquid to be applied is also not particularly limited, but is usually in the range of about 2 to 12 g/m2, preferably about 3 to 10 g/m2 in terms of dry weight.

In the heat-sensitive recording material of the present invention, an intermediate layer is first provided on the heat-sensitive recording layer thus obtained.
Examples of the water-soluble resin and/or water-dispersible resin used in the intermediate layer include the following substances. 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 olefin sulfonic acid or its salt such as ethylene sulfonic acid or allyl sulfonic acid; Olefin-modified polyvinyl alcohol obtained by saponifying copolymers of vinyl acetate and olefins such as ethylene, propylene, isobutylene, α-octene, α-dotecene, α-octadodecene, etc.; Nitrile-modified polyvinyl alcohol obtained as a saponified product of a copolymer with nitriles, amide-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate and an amide such as acrylamide or methacrylamide, vinyl acetate and N- Cellulose derivatives such as pyrrolidone-modified polyvinyl alcohol, methylcellulose, ethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose obtained by saponifying a copolymer with vinylpyrrolidone,
casein, gum arabic, oxidized starch, etherified starch,
Starches such as dialdehyde starch and esterified starch, styrene-butadiene copolymer emulsion, vinyl acetate-vinyl chloride-ethylene copolymer emulsion, methacrylate-butadiene copolymer emulsion, and the like.

Among these water-soluble resins and/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. Pigments can be added to the intermediate layer to increase smoothness. Specific examples of pigments include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, and styrene microballs. , nylon powder, polyethylene powder,
Examples include urea/formalin resin fillers, organic pigments such as raw starch granules, and the like. The amount used is generally 5 to 500 parts by weight, preferably 80 to 350 parts by weight, based on 100 parts by weight of the resin component.

[0018] Further, in the coating liquid forming the intermediate layer, curing agents such as glyoxal, methylolmelamine, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, ammonium chloride, etc. are added 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 dodecylbenzenesulfonate, and lauryl may be added. Various auxiliary agents such as surfactants such as alcohol sulfate/sodium salts, alginates, fatty acid metal salts, ultraviolet absorbers such as benzophenone type and triazole type, antifoaming agents, fluorescent dyes, and coloring dyes may be added as appropriate. You can also do it.

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 mixing/stirring machine such as a mixer, attritor, ball mill, or roll mill as necessary, the coating liquid is prepared using various known methods. It is applied onto the heat-sensitive recording layer using a coating device. After coating, it can also be cured and dried by irradiation with ultraviolet rays or electron beams. 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 life expectancy and there is an advantage of being able to select a strong hardening agent.

[0020] The coating amount of the coating liquid forming the intermediate layer is not particularly limited, but if it is less than 0.1 g/m2, the desired effect of the present invention cannot be sufficiently obtained;
If it exceeds 0 g/m2, the recording sensitivity of the heat-sensitive recording medium may be significantly reduced, so it is generally 0.1 to 0.1 in terms of dry weight.
It is adjusted within a range of about 20 g/m2, preferably from 0.5 to 10 g/m2.

[0021] If necessary, it is also possible to further improve the storage stability by providing a similar coating 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. By increasing the smoothness of the surface of the intermediate layer, a recording medium with high recording density and gloss can be obtained. 500 for synthetic paper
It is desirable to adjust the time to at least 160 seconds, more preferably at least 1600 seconds, and when the support is paper, at least 50 seconds, more preferably at least 300 seconds. In the heat-sensitive recording material of the present invention, an overcoat layer containing an ionizing radiation-curable resin and a cooligomer of ethylene and α-olefin and/or an acid-modified product thereof is provided on the intermediate layer thus formed.

[0022] As the ionizing radiation-curable resin forming the overcoat layer, the following prepolymers and monomers are exemplified. (a) Poly(meth) of aliphatic, alicyclic, araliphatic di- to hexavalent polyhydric alcohol and polyalkylene glycol
Acrylate; (b) aliphatic, alicyclic, aromatic aliphatic,
Poly(meth)acrylate of polyhydric alcohol in the form of adding alkylene oxide to aromatic di- to hexavalent polyhydric alcohol; (c) Poly(meth)acryloyloxyalkyl phosphate; (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) Vinyl-based or diene-based low polymer having (meth)acryloyloxy groups in the side chain and/or terminal; (j)
Oligoester (meth) described in (a) to (i) above
Prepolymers such as acrylate modified products.

Monomers include (a) carboxyl group-containing monomers represented by ethylenically unsaturated mono- or polycarboxylic acids, and carboxylic acid group-containing monomers such as alkali metal salts, ammonium salts, and amine salts thereof; Monomer; (b) An amide group-containing monomer represented by ethylenically unsaturated (meth)acrylamide or alkyl-substituted (meth)acrylamide, vinyl lactams such as N-vinylpyrrolidone; (c) Aliphatic or Sulfonic acid group-containing monomers represented by aromatic vinyl sulfonic acids and their alkali metal salts, ammonium salts, amine salts; (d) Sulfonic acid group-containing monomers represented by ethylenically unsaturated ethers, etc. hydroxyl group-containing monomer; (e) amino group-containing monomer such as dimethylaminoethyl (meth)acrylate-2-vinylpyridine; (f) quaternary ammonium base-containing monomer; (g) ethylenically unsaturated Alkyl ester of 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) of alkylene oxide addition polymers of compounds containing active hydrogen.
Acrylates; (l) Bifunctional monomers containing ester groups represented by diesters of polybasic acids and unsaturated alcohols; (m) Alkylene oxide addition polymers of active hydrogen-containing compounds and (meth)acrylic acid A bifunctional monomer consisting of a diester with;

(n) Bisacrylamides such as N,N-methylenebisacrylamide; (o) divinylbenzene, divinylethylene glycol, divinylsulfone,
Difunctional monomers such as divinyl ether and divinyl ketone;
(p) Ester group-containing polyfunctional monomer represented by polyester of polycarboxylic acid and unsaturated alcohol; (q)
Polyfunctional monomers made of polyesters of alkylene oxide addition polymers of active hydrogen-containing compounds and (meth)acrylic acid; (r) polyfunctional unsaturated monomers such as trivinylbenzene; and the like. In addition, two or more types of the above-mentioned ionizing radiation-curable resins may be used in combination.

In the heat-sensitive recording material of the present invention, the above-mentioned ionizing radiation-curable resin contains a cooligomer of ethylene and α-olefin and/or an acid-modified product thereof. As for [chemical 1]
Compounds represented by are preferred. Moreover, those whose compatibility with the resin is improved by modifying them with various acids may also be used. For example, [Chem.1]
An example is one in which maleic anhydride is added to a cooligomer, and one in which on average 0.1 to 2 maleic anhydride are added to one cooligomer molecule.

[0026] The above-mentioned cooligomer and its acid-modified product are preferably amorphous cooligomers, and have a number average molecular weight of 200 to 200.
4,000 and is oil-like at room temperature. There are no particular limitations on the content of the cooligomer of ethylene and α-olefin and/or its acid-modified product, but based on 100 parts by weight of the ionizing radiation curable resin,
The amount is preferably about 0.01 parts by weight to 15 parts by weight. If the content is too small, it is difficult to expect the desired effect of the present invention, and if the content is too large, there is a risk that the recording stability of the resulting recording medium may be deteriorated. More preferably, it is adjusted within a range of about 0.05 to 10 parts by weight.

[0027]

[R represents CnH2n+1] x, y, p, and n each represent an integer of 1 or more. ]

[0028] n is preferably about 1 to 6. x,y
are each preferably about 1 to 10. p is preferably about 1 to 60. The resin components of the overcoat layer include the above-mentioned prepolymers and monomers, as well as ethylene and α-
In addition to cooligomers with olefins and/or acid-modified products thereof, calcium carbonate, barium carbonate,
Inorganic pigments such as zinc carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, and colloidal silica, and these inorganic pigments are surface-treated with organic acids. Organic pigments such as treated pigments, styrene microballs, nylon powder, polyethylene powder, urea/formalin resin powder, cellulose acetate powder, polymethyl methacrylate powder, fluororesin powder, epoxy resin powder, benzoguanamine resin powder, raw starch granules, etc. Additives such as electron beam curable resins, antifoaming agents, leveling agents, lubricants, surfactants, plasticizers, and ultraviolet absorbers may also be added as appropriate.

By adjusting the types and blending ratios of various additives, it is possible to form heat-sensitive recording materials having a wide range of surface properties from matte to highly glossy. Further, examples of non-electron beam curable resins include acrylic resins, silicone resins, alkyd resins, fluororesins, butyral resins, and the like. The overcoat layer 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. Viscosity can also be adjusted by heating. Further, although the amount of coating is not necessarily limited, if it is less than 0.1 g/m2, the desired effect of the present invention cannot be expected, and if the amount of coating exceeds 20 g/m2, the recording sensitivity of the resulting recording medium may decrease. Therefore, it is desirable to adjust the amount within a range of 0.1 to 20 g/m2, more preferably 1 to 10 g/m2.

The overcoat layer formed on the intermediate layer is cured by irradiation with ionizing radiation. Examples of ionizing radiation include electron beams, ultraviolet rays, alpha rays, beta rays, gamma rays, Therefore, electron beams and ultraviolet rays are preferably used because they are easy to handle. When using an electron beam, the amount of electron beam irradiated is preferably about 0.1 to 15 Mrad, more preferably about 0.5 to 10 Mrad. Incidentally, if it is less than 0.1 Mrad, the resin component cannot be sufficiently cured, and excessive electron beam irradiation exceeding 15 Mrad may cause color development or discoloration of the heat-sensitive recording material, and furthermore, if the support is made of paper. In this case, there is a risk that the strength of the paper will decrease. As the electron beam irradiation method, for example, a scanning method, curtain beam method, broad beam method, etc. can be adopted, and the acceleration voltage during irradiation is 100 ~
Approximately 300KV is appropriate.

On the other hand, when using ultraviolet rays, it is necessary to incorporate a sensitizer into the coating composition, and the amount is 0.2 to 10% by weight, preferably 0.5 to 10% by weight based on the resin component. It is added in an amount of about 5% by weight. In addition, as a light source for ultraviolet irradiation, 1 to 50 ultraviolet lamps, xenon lamps, tungsten lamps, etc. are used, and the power output is 40 to 200 W.
Ultraviolet rays having an intensity of about /cm are preferably irradiated.

Examples of the sensitizer include thioxanthone,
Benzoin, benzoin alkyl ether xanthone,
dimethylxanthone, benzophenone, anthracene,
2,2-diethoxyacetophenone, benzyl dimethyl ketal, benzyl diphenyl disulfide, anthraquinone, 1-chloroanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, N,
Examples include N'-tetraethyl-4,4'-diaminobenzophenone and 1,1-dichloroacetophenone.

The above-mentioned electron beam irradiation method has higher productivity than the ultraviolet irradiation method, and reduces odor and odor due to the addition of sensitizers.
It is most preferably used because there is no problem of coloring and it is easy to form a uniform crosslinked structure. The heat-sensitive recording material of the present invention having the overcoat layer thus obtained can be further smoothed using a super calender or the like to further improve recording density and recording density unevenness.

[0034]

[Examples] The present invention will be explained 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 ■ Preparation of liquid A 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane
10 parts methylcellulose 5% aqueous solution
5 parts water
30 parts of this composition was ground in a sand mill until the average particle size was 3 μm. ■ Preparation of B solution Benzyl 4-hydroxybenzoate 20 parts Methyl cellulose 5% aqueous solution 5
Department water
55 parts of this composition was ground in a sand 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 to a base paper of 50 g/m2 with a coating amount of 6 g/m2 after drying.
A heat-sensitive recording material was obtained by coating and drying so as to obtain the following.

■ Formation of intermediate layer A coating liquid having the following composition was applied onto the recording layer of the obtained heat-sensitive recording material so that the coating amount after drying was 4 g/m2.
The mixture was dried and smoothed using a super calender to prepare a heat-sensitive recording material having an intermediate layer having a Bekk smoothness of 500 seconds. Acetoacetylated polyvinyl alcohol (product name: Z-
200, manufactured by Nippon Gosei Kagaku Co., Ltd.) 8% aqueous solution

1000 parts calcium carbonate (product name: Softon 1800, manufactured by Bihoku Funka Co., Ltd.) 100 parts water


100 parts ■ Formation of overcoat layer Acrylate prepolymer (product name: EBX) on the intermediate layer
135, produced by Toagosei Chemical Co., Ltd.) and 100 parts of a cooligomer acid-modified product of ethylene and α-olefin (an acid-modified product with maleic anhydride, with an average of 0.25 maleic anhydride molecules per cooligomer molecule) 1 part of the liquid mixture (product name: Lucant A-5202, manufactured by Mitsui Petrochemical Co., Ltd.) was applied to a dry coating amount of 3 g/m2, and an electron curtain type electron beam irradiation device (CB: 15
0 type (manufactured by ESI) at an irradiation dose of 3 Mrad to cure the resin component and obtain a thermosensitive recording material having an overcoat layer.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of the cooligomer acid-modified product of ethylene and α-olefin was changed to 0.06 part. Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of the cooligomer acid-modified product of ethylene and α-olefin was changed to 9 parts. Example 4 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of the cooligomer acid-modified product of ethylene and α-olefin was changed to 0.01 part. Example 5 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the amount of the cooligomer acid-modified product of ethylene and α-olefin was changed to 14 parts. Example 6 In Example 1, a cooligomer of ethylene and α-olefin (trade name: Lucant HC-20, manufactured by Mitsui Petrochemicals) was used instead of the acid-modified cooligomer of ethylene and α-olefin. A thermosensitive recording material was obtained in the same manner except for that.

Comparative Example 1 In Example 1, a silicone leveling agent (
Product name: TH-130D, manufactured by Mitsubishi Rayon Co., Ltd.) 0.0
A thermosensitive recording material was obtained in the same manner except that 5 parts were used. Comparative Example 2 In Comparative Example 1, a silicone leveling agent (product name:
A thermosensitive recording material was obtained in the same manner except that the amount of TH-130D (manufactured by Mitsubishi Rayon Co., Ltd.) was changed to 0.2 parts. Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the acid-modified cooligomer of ethylene and α-olefin was not used. Comparative Example 4 A thermosensitive recording material was obtained in the same manner as in Example 1 except that no overcoat layer was provided on the intermediate layer.

The following quality tests were conducted on each of the heat-sensitive recording bodies thus obtained, and the results are shown in Table 1. (1) Initial printing color density Test each heat-sensitive recording medium using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.: Condition 12)
Images were recorded at 0° C., 2 kg/cm 2 , 10 seconds), and the maximum color density of the recorded image was measured using a Macbeth densitometer (manufactured by Macbeth Co., Ltd., model RD-100R). (2) Glossiness The glossiness of the surface of each heat-sensitive recording material was measured using a variable angle photometer (MURAKA).
MI COLOR RAB. made by gloss meter
GM-3D) at an incident angle of 60 degrees. (The higher the number, the higher the gloss.)

(3) Recording running properties Each heat-sensitive recording medium was coated with a fully automatic labeler (product name: DP82).
0, manufactured by Ishida Koki Seisakusho Co., Ltd.), and the recording runnability was evaluated using the following evaluation criteria. ◎: Can be recorded without any problems. ○: There is a slight stick sound, but it can be recorded without any problems. △: A stick sound is heard and some recording defects occur. ×: Significant overall recording failure occurred on the stick.

(4) Plasticizer resistance test A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemical Co., Ltd.) was wrapped three times around a polypropylene pipe (40 mm diameter pipe), and printed colors were printed on it using a thermal gradient tester. The heat-sensitive recording material was sandwiched so that the color-forming side of the print was facing outward, and a vinyl chloride wrap film was wrapped five times over it.The print density after 72 hours was measured using a Macbeth densitometer to determine the density maintenance rate. I calculated it. (The larger the value, the better the plasticity resistance.) (5) Oil resistance test 0.05 c of salad oil was applied to the recording layer surface of the colored heat-sensitive recording material.
c was dropped and spread uniformly on the surface, and the print density after being left for 24 hours was measured using a Macbeth densitometer to calculate the density maintenance rate. (The larger the number, the better the oil resistance.)

0
(6) UV ink adhesion UV ink (product name: UVS-SEL) is applied onto each heat-sensitive recording material.
0.075cc/N-63 grass (manufactured by Moroboshi Ink)
m2, and after curing by irradiating light from an 80W high-pressure mercury lamp 20cm away for 10 seconds,
The adhesion of the ink was evaluated by peeling off Cellotape (manufactured by Nitto Denko Corporation) using the following evaluation criteria.

◯: Completely adhered. △: Ink peels off a little. ×: Most of the ink has peeled off and there is no close contact.

[0044]

[Table 1]

[0045]

Effects of the Invention As is clear from the results in Table 1, the heat-sensitive recording material of the present invention has a high recording density, strong gloss, and excellent storage stability, as well as excellent recording runnability and printability. Met. Further, the heat-sensitive recording material of the present invention is excellent not only in the above-mentioned UV ink adhesion but also in ink transferability. Therefore, a large amount of ink is transferred to the heat-sensitive recording medium, and a good finished printing condition can be obtained.

Claims (2)

[Claims] Claim 1: A support comprising: (1) a heat-sensitive recording layer containing a color former and a color former that develops a color when in contact with the color former, and (2) an intermediate layer containing a water-soluble resin and/or a water-dispersible resin. established,
Furthermore, in a heat-sensitive recording material formed by providing an overcoat layer containing an ionizing radiation-curable resin and irradiating it with ionizing radiation,
A heat-sensitive recording material characterized in that the overcoat layer contains a cooligomer of ethylene and α-olefin and/or an acid-modified product of the cooligomer. [Claim 2] The overcoat layer contains a cooligomer of ethylene and α-olefin represented by [Chemical formula 1] and/or
The heat-sensitive recording material according to claim 1, further comprising an acid-modified product of the cooligomer. [R represents CnH2n+1] x, y, p, and n each represent an integer of 1 or more. ]