JP2837475B2 - Thermal recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermosensitive recording medium, and more particularly to a thermosensitive recording medium excellent in printing enemy and preservability of printing.

"Prior art" Conventionally, a thermosensitive recording in which a color-forming image is obtained by contacting both color-forming substances by heat using a color-forming reaction between a color-forming agent and a color-forming agent that forms a color in contact with the color-forming agent. The body is well known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and its maintenance is relatively easy. Therefore, it is used not only as a recording medium for facsimile and various computers but also in a wide field such as a thermosensitive label. I have. However, there are difficulties in fingerprint resistance and solvent resistance. For example, when human sebum or a solvent comes into contact with the recording layer, there is a defect that the recording density is lowered or unnecessary color formation called background fog is caused.

As a method of solving such a defect, a method of applying an aqueous emulsion of a resin having a film forming ability and chemical resistance on a heat-sensitive recording layer (Japanese Patent Laid-Open No. 54-128347).
A method of applying a water-soluble polymer compound such as polyvinyl alcohol (Japanese Utility Model Application Laid-Open No. 56-125354) has been proposed. However, at present, new improvements are accompanied by improvements and satisfactory results have not always been obtained.

For example, when applying an aqueous resin coating on the heat-sensitive recording layer, it is necessary to limit the drying temperature in order to avoid coloring of the recording layer due to high-temperature drying, and inevitably the curing of the resin layer becomes insufficient, and during recording, A phenomenon such as adhesion between the recording head and the resin layer occurs. For this reason, a method has been proposed in which a resin component curable by an electron beam is applied onto the heat-sensitive recording layer, and the resin component is cured by an electron beam. The resin layer that cures in the above step may cause the heat-sensitive recording layer to develop color immediately after coating, or may have a bad effect such as fading of the recorded image.

The inventors of the present invention have conducted intensive studies on the solution of such a defect, and as a result, provided an aqueous resin intermediate layer on the heat-sensitive recording layer, and thereafter provided an overcoat layer containing a resin cured by an electron beam. It was found that a heat-sensitive recording material having remarkably improved print storability without fogging of the layer, having a wide range of surface characteristics, and excellent recording characteristics was obtained, and was previously filed as Japanese Patent Application Laid-Open No. 62-279980. .

On the other hand, in recent years, the use of heat-sensitive recording materials as product labels has been increasing, and particularly excellent print storability and printing enemy are required. However, even in a heat-sensitive recording medium in which an aqueous resin intermediate layer is provided on the heat-sensitive recording layer, and then an overcoat layer containing a resin cured by an electron beam is provided, the printing enemy is not necessarily in a satisfactory state. For example, due to the large barrier property of the overcoat layer, drying may be slow with an oxidized polymerization ink, or the adhesion may be poor with a UV curable ink.

In addition, if an appropriate amount of pigment is added to the overcoat layer in order to improve the above-described printing enemy, problems such as deterioration of print preservability occur.

"Problems to be Solved by the Invention" In view of the present situation, the present inventors have made intensive studies on the improvement of the above-mentioned problems particularly occurring in a thermosensitive recording medium having an overcoat layer of an electron beam-curable resin, The layer containing the pigment and the electron beam-curable resin is irradiated with an electron beam onto the layer containing the beam-curable resin as the main component, and the cured overcoat layer is irradiated with the electron beam. It has been found that by providing such a recording medium, it is possible to obtain a thermosensitive recording medium having extremely excellent printing enemy and excellent storage stability of printing, thereby completing the present invention.

"Means for Solving the Problems" The present invention provides a heat-sensitive recording layer containing a color former and a color former that is colored upon contact with the color former on a support, and a water-soluble recording layer is provided on the heat-sensitive recording layer. An intermediate layer containing a resin or a water-dispersible resin, and an intermediate layer hardened by irradiating an electron beam to a layer containing an electron beam-curable resin as a main component thereon, and further on the intermediate layer A thermosensitive recording medium, characterized in that a layer containing a pigment and an electron beam-curable resin is provided with an overcoat layer cured by irradiating an electron beam.

"Function" In the present invention, the combination of the color former and the color former contained in the heat-sensitive recording layer is not particularly limited, and any combination may be used as long as the two are brought into contact by heat to cause a color reaction. It is possible. Examples thereof include a combination of a colorless or light-colored basic dye and an inorganic or organic acidic substance, and a combination of a metal salt of a higher fatty acid such as ferric stearate and a phenol such as gallic acid.

However, it is particularly preferable to use a combination of a basic dye and an acidic substance, since an excellent recording characteristic can be obtained. Various types of colorless or light-colored basic dyes 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-bis (9-ethylcarbazol-3-yl) -6
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
Triallylmethane dyes such as 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, Diphenylmethane dyes such as N-halophenyl-leuco auramine and N-2,4,5-trichlorophenyl leuco auramine; thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue; 3-methyl-spiro-dinaphthopyran , 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-
Spiro dyes such as benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, Lactam dyes such as rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-
Methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-
7-N-methylaminofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-N-methyl-N-benzylaminofluoran,
3-diethylamino-7-N-chloroethyl-N-methylaminofluoran, 3-N-butylamino-6-methyl-7-phenylaminofluoran, 3-N-pentylamino-6-methyl-7-phenylamino Fluoran,
3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-ethyl-
(p-Toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-7
-Phenylaminofluoran, 3-diethylamino-7
-(2-carbomethoxy-phenylamino) fluoran, 3- (N-ethyl-N-iso-amylamino) -6
-Methyl-7-phenylaminofluoran, 3- (N-
Cyclohexyl-N-methylamino) -6-methyl-7
-Phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluoran , 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6
Fluoran dyes such as -methyl-7-p-butylphenylaminofluoran and the like.

In addition, various types of inorganic or organic acidic substances that are colored upon contact with a basic colorless dye are also known, for example, activated clay, acidic clay, attapulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate,
4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 2,2′-methylenebis (4 -Methyl-6-tert-isobutylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-isopropylidene Dendiphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone,
4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid 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-te
rt-butylsalicylic acid, 3-benzylsalicylic acid, 3-
(Α-methylbenzyl) salicylic acid, 3-chloro-5-
(Α-methylbenzyl) salicylic acid, 3,5-di-tert-
Aromatic carboxylic acids such as butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and phenolic compounds thereof; And organic acid substances such as salts with polyvalent metals such as magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and 4-hydroxy-4'-isopropoxydiphenylsulfone.

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 depending on the type of the color former and the color former used, and is not particularly limited. For example, when a basic colorless dye and an acidic substance are used, generally 1 to 50 parts by weight, preferably about 1 to 10 parts by weight of the acidic substance is 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 color former and a color former are separately or separately mixed with a ball mill, an attritor, a vertical or horizontal sand mill, or other agitator / pulverizer. Dispersed and prepared as a coating solution.

In such a coating solution, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer as an adhesive Salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc., is 10 to 40% by weight of the total solid, preferably 15 to 40% by weight.
About 30% by weight is used.

Further, various assistants can be added to the coating liquid, for example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginates, metal salts of fatty acids, and the like. Examples include benzophenone-based and triazole-based ultraviolet absorbers, other antifoaming agents, fluorescent dyes, coloring dyes, and the like.

If necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay And inorganic acid pigments such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, mala oleic acid amide, coconut fatty acid amide, 1,2-diphenoxyethane, 1,2- Screw (3
-Methylphenoquinone) ethane, 1,2-bis (4-methylphenoxine) ethane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, 1-phenoxy-2
-(4-methoxyphenoxy) ethane, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1,4
Ethers such as -bis (2-vinyloxyethoxy) benzene, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl lalephthalate, dibenzyl oxalate, bis (p-chlorobenzyl) oxalate, p-benzyloxybenzoate Esters such as benzyl acid, aromatic compounds such as p-benzylbiphenyl and m-terphenyl, and various known heat-soluble sensitizers can also be added.

The method for applying the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known technique. For example, a coating solution is applied by bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating, or the like. Is formed by a method of applying and drying. In the case where a plastic film is used as the support, the coating efficiency can be increased by applying a treatment such as corona discharge or electron beam irradiation to the surface. Although there is no particular limitation on the coating amount of the coating liquid, 2~12g / m ² at normal dry weight, preferably in the range of about 3 / 10g / m ^2.

In the heat-sensitive recording medium 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 conductive resin.

Fully or partially saponified polyvinyl alcohol,
An acetoacetylated polyvinyl alcohol having an acetoacetyl group introduced by reacting polyvinyl alcohol with diketene, a reaction product of polyvinyl alcohol with a polycarboxylic acid such as fumaric acid, phthalic anhydride, trimellitic anhydride, itaconic anhydride or It is obtained as an esterified product of these reactants, or a saponified product of a copolymer of vinyl acetate and an ethylenically unsaturated carboxylic acid such as maleic acid, fumaric acid, itaconic acid, crotonic acid, acrylic acid, or methacrylic acid. Carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol obtained as a saponified product of a copolymer of olefin sulfonic acid such as vinyl acetate and ethylene sulfonic acid or allyl sulfonic acid or a salt thereof, vinyl acetate and ethylene, propylene, isobutylene, α − Octene, α-dodecene, olefin-modified polyvinyl alcohol obtained by saponifying a copolymer with an olefin such as α-octadodecene, as a saponified product of a copolymer of vinyl acetate and acrylonitrile, a nitrile such as methacrylonitrile. The obtained nitrile-modified polyvinyl alcohol, saponified amide-modified polyvinyl alcohol obtained by saponifying a copolymer of amides such as vinyl acetate and acrylamide and methacrylamide, and a copolymer of vinyl acetate and N-vinylpyrrolidone The resulting pyrrolidone-modified polyvinyl alcohol, cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, and esterified Starches such as flour, styrene - butadiene copolymer emulsion, vinyl acetate - vinyl chloride - ethylene copolymer emulsion,
Methacrylate-butadiene copolymer emulsion and the like.

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 more preferred. The amount of the water-soluble resin or water-dispersible resin used is not particularly limited, but is used in an amount of about 10 to 50% by weight, preferably about 15 to 40% by weight, based on the total solid content in the coating solution.

A pigment can be added to the intermediate layer in order to increase smoothness. Specific examples of pigments include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea. Organic pigments such as formalin resin fillers and raw starch granules are exemplified.

The amount is generally in the range of 5 to 500 parts by weight, preferably about 80 to 350 parts by weight, based on 100 parts by weight of the resin component.

In addition, glyoxal, methylol melamine, potassium persulfate,
A curing agent such as ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, and ammonium chloride may be added.If necessary, zinc stearate, calcium stearate, stearic amide, polyethylene wax, carnauba wax, Lubricants such as paraffin wax and ester wax, surfactants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, sodium alginate and fatty acid metal salts, and ultraviolet absorbers such as benzophenone and triazole Various auxiliaries such as antifoaming agents, fluorescent dyes and coloring dyes can also be added as appropriate.

The coating liquid for forming the intermediate layer is generally prepared as an aqueous coating liquid, and if necessary, sufficiently mixed and dispersed with a mixer, attritor, ball mill, roll mill, etc., followed by various known coatings. It is applied on the thermosensitive recording layer by an apparatus. After the application, curing and drying may be performed by irradiating 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 for forming the intermediate layer but also separately from the coating liquid for forming the intermediate layer. There is an advantage that there is no need to worry about life and a strong curing agent can be selected.

Further, if necessary, a similar coating layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. Further, various known techniques in the field of heat-sensitive recording materials can be added as necessary, such as providing an undercoat layer on the support, applying a pressure-sensitive adhesive treatment to the back surface of the recording material, and processing the pressure-sensitive adhesive label.

The coating amount of the coating liquid forming the intermediate layer is not particularly limited, can not be obtained sufficiently the desired effect of the present invention is less than 0.1 g / m ^2, also a 20 g / m ² Exceeds this, the recording sensitivity of the thermal recording medium may be significantly reduced.
Generally 0.1 to 20 g / m ² in dry weight, preferably 0.5 to 10 g /
It is regulated by the m ² range of about.

An intermediate layer cured by irradiating an electron beam to a layer containing an electron beam-curable resin as a main component is provided on the intermediate layer thus formed. Since a recording medium having a recording density and gloss is obtained, for example, the Bekk smoothness of the surface of the intermediate layer by performing a smoothing process with a super calender or the like, for example,
When using papers as the support, adjust the time to 50 seconds or more, more preferably 300 seconds or more, and when using plastic films as the support, adjust the time to 500 seconds or more, more preferably 1000 seconds or more. Is desirable.

Examples of the electron beam curable resin forming the intermediate layer include the following prepolymers and monomers.

(A) Aliphatic, alicyclic, and araliphatic dihydric to hexavalent polyhydric alcohols and poly (meth) polyalkylene glycols
Acrylates; (b) poly (meth) acrylates of polyhydric alcohols in the form of aliphatic, alicyclic, araliphatic, aromatic divalent to hexavalent polyhydric alcohols to which alkylene oxide is added; (c) poly ( (D) polyester poly (meth) acrylate; (e) epoxy poly (meth) acrylate; (f) polyurethane poly (meth) acrylate; (g) polyamide poly (meth) acrylate; h) a polysiloxane poly (meth) acrylate; (i) a vinyl or diene-based low polymer having a (meth) acryloyloxy group at a side chain and / or a terminal; (j) the above (a) to (i) Oligoester (meth) acrylate modified product; and the like.

Examples of the monomer include: (a) a carboxyl group-containing monomer represented by an ethylenically unsaturated mono- or polycarboxylic acid and a carboxylic acid group-containing monomer such as an alkali metal salt, an ammonium salt, and an amine salt thereof. (B) an amide group-containing monomer represented by vinyl lactams such as ethylenically unsaturated (meth) acrylamide or alkyl-substituted (meth) acrylamide, N-vinylpyrrolidone; (c) aliphatic or aromatic vinyl; Sulfonic acid group-containing monomers represented by sulfonic acids, and sulfonic acid group-containing monomers thereof such as alkali metal salts, ammonium salts and amine salts; (d) hydroxyl group-containing monomers represented by ethylenically unsaturated ethers Monomer; (e) dimethylaminoethyl (meth) acrylate-
(F) a quaternary ammonium base-containing monomer; (g) an alkyl ester of an ethylenically unsaturated carboxylic acid; (h) a nitrile group such as (meth) acrylonitrile (I) styrene; (j) esters of ethylenically unsaturated alcohols such as vinyl acetate, (meth) allyl acetate and the like; (k) mono (meth) alkylene oxide addition polymer of a compound containing active hydrogen (1) 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 (N) bisacrylamide such as N, N-methylenebisacrylamide; (o) divinylben (P) a bifunctional monomer such as divinylethylene glycol, divinyl sulfone, divinyl ether, divinyl ketone, etc .; (p) an ester group-containing polyfunctional monomer represented by a polyester of a polycarboxylic acid and an unsaturated alcohol; A) a polyfunctional monomer comprising a polyester of an alkylene oxide addition polymer of a compound containing active hydrogen and (meth) acrylic acid; and (r) a polyfunctional unsaturated monomer such as trivinylbenzene.

And the like.

In the resin component, in addition to the electron beam-curable prepolymer and monomer as described above, if necessary, for example, a non-electron beam-curable resin, an antifoaming agent, a leveling agent as long as the effects of the present invention are not impaired. Additives such as a lubricant, a surfactant, a plasticizer, an ultraviolet absorber, a fluorescent dye, a coloring dye, a pigment, a fluorescent pigment, and a coloring pigment can be appropriately added.

As the non-electron beam curable resin, for example, acrylic resin,
Silicone resin, alkyd resin, fluororesin, butyral resin and the like can be mentioned.

The resin component as described above is sufficiently mixed by a suitable mixing stirrer such as a mixer and then applied on the intermediate layer by various known methods. You can also make adjustments. Further, connexion to coating fee is not necessarily limited, it can not be the desired effect expected of the present invention is less than 0.1 g / m ^2, lowering the recording sensitivity of the recording material is obtained by a coating amount as exceeding 20 g / m ² Therefore, it is desirable to adjust the amount in the range of about 0.1 to ²⁰ g / m ² , more preferably about 0.3 to 10 g / m ² .

In order to improve the adhesion between the intermediate layer and the intermediate layer, the surface of the intermediate layer may be subjected to a corona treatment as necessary.

The intermediate layer formed on the intermediate layer is cured by irradiation with an electron beam, and the amount of the irradiated electron beam is 0.1 to 15 Mra.
d, more preferably in the range of about 0.5 to 10 Mrad.
If the amount is less than 0.1 Mrad, the resin component cannot be sufficiently cured, and excessive electron beam irradiation exceeding 15 Mrad may cause coloration or discoloration of the thermosensitive recording medium.

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 acceleration voltage for irradiation is suitably about 100 to 300 KV.

An overcoat layer containing a pigment is provided on the intermediate layer thus formed. Specific examples of the pigment include calcium carbonate, barium carbonate, zinc carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, and aluminum hydroxide. , Barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, and other inorganic pigments, and pigments obtained by surface-treating these inorganic pigments with organic acids, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin Powder, cellulose acetate powder, polymethyl methacrylate powder,
Organic pigments such as fluorine resin powder, epoxy resin powder, benzoguanamine resin powder, and raw starch granules are exemplified.

In addition, about 0.1 to 500 parts by weight, preferably about 1 to 350 parts by weight, is used for 100 parts by weight of the adhesive component.

An electron beam curable resin used when forming the intermediate layer is used as the adhesive.

In the adhesive resin component, if necessary within a range that does not impair the effects of the present invention, for example, an antifoaming agent, a leveling agent,
Lubricants, surfactants, plasticizers, UV absorbers, fluorescent dyes,
Additives such as a coloring dye, a fluorescent pigment, a coloring pigment, and a photosensitizer can be appropriately added.

By adjusting the types and mixing ratios of these various additives, it is possible to form a thermosensitive recording medium having a wide range of surface properties from matte to high gloss.

The resin component and the pigment as described above are sufficiently mixed by a suitable mixing stirrer such as a mixer, and then applied onto the intermediate layer by various known methods.If necessary, the resin component is heated. The viscosity can also be adjusted. Further, connexion to the coating weight is not necessarily limited, can not be the desired effect expected of the present invention is less than 0.1 g / m ^2, lowering the recording sensitivity of the recording material is obtained by a coating amount as exceeding 20 g / m ² 0.1 to 20 g / m ² , more preferably 0.3 to 10 g / m ²
It is desirable to adjust within a range.

In addition, 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 as necessary.

When the resin component is an electron beam-curable resin, it is cured by irradiation with an electron beam, but the amount of the irradiated electron beam is 0.1 to 1
The range is preferably 5 Mrad, more preferably about 0.5 to 10 Mrad. If the amount is less than 0.1 Mrad, the resin component cannot be sufficiently cured, and excessive electron beam irradiation exceeding 15 Mrad may cause coloration or discoloration of the thermosensitive recording medium.

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 acceleration voltage for irradiation is suitably about 100 to 300 KV. In addition, by performing a smoothing process on a recording medium provided with an overcoat layer using a super calender or the like, the recording density and the recording density unevenness can be further improved.

"Examples" Examples are shown below to explain the present invention more specifically, but of course the present invention is not limited thereto. Parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.
Is shown.

Example 1 Preparation of solution A 3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-phenylaminofluoran 10 parts Methylcellulose 5% aqueous solution 5 parts Water 30 parts This composition was sand-ground with an average particle size of 3 μm.
m.

Preparation of Solution B 20 parts of benzyl 4-hydroxybenzoate 5 parts of 5% aqueous solution of methylcellulose 5 parts 55 parts of water
m.

Formation of recording layer 45 parts of solution A, 80 parts of solution B, 50 parts of 20% oxidized starch aqueous solution, water 10
Parts were mixed and stirred to obtain a coating liquid. The resulting coating solution was applied onto 50 g / m ² base paper and dried so that the coating amount after drying was 6 g / m ² , to obtain a thermosensitive recording medium.

An intermediate layer formation resulting heat-sensitive recording material of the recording layer, a coating solution consisting of the following composition coating amount after drying was dried so as to 4g / m ^2, a further smoothing a super calender Thus, an intermediate layer having a Beck smoothness of 300 seconds was formed.

Polyvinyl alcohol (trade name; PVA-117, manufactured by Kuraray)
8% aqueous solution of 1000 parts Calcium carbonate (trade name; Softon 1800, manufactured by Bihoku Powder Co., Ltd.) 100 parts Water 100 parts Formation of intermediate layer Polyester polyacrylate (trade name; FS-3116, manufactured by Mitsubishi Rayon Co., Ltd.) on the intermediate layer 100 parts dry coating amount 4
g / m ^2, and treated with an irradiation dose of 2 Mrad with an electron curtain type electron beam irradiation device (CB: 150, manufactured by ESI) to cure the resin component and form an intermediate layer.

Formation of overcoat layer 100 parts of polyester polyacrylate (trade name; FS-3116, manufactured by Mitsubishi Rayon Co., Ltd.) and an average particle diameter of 0.2 were formed on the intermediate layer.
A mixture of 30 parts of μm calcium carbonate (trade name: PP-2, manufactured by Yonesho Lime Industry Co., Ltd.) was applied so that the dry coating amount was 3 g / m ^2, and an electron curtain type electron beam irradiation device (CB: 150
(ESI), with a radiation dose of 2 Mrad to cure the resin component and obtain a thermosensitive recording medium having an overcoat layer.

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

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

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1, except that the intermediate layer and the overcoat layer were not provided.

Using each of the thus-obtained thermosensitive recording media, printing was performed with a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) under the conditions of 120 ° C., 2 kg / cm ² , and 10 seconds. R
D-100R) and the results are shown in Table 1.

Furthermore, the plasticizer resistance shown below as the storage stability of the print,
Each evaluation test of oil resistance was performed, and the color density was measured by a Macbeth densitometer, and the density retention rate was calculated. The results are shown in Table 1.

Plasticizer resistance test method The colored heat-sensitive recording material is placed on a polypropylene pipe (40
on a polyvinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) wrapped three times on a (mmφ tube), and further wrapped the vinyl chloride wrap film five times from above, and the print density after 72 hours was measured by Macbeth. The concentration retention was calculated by measuring with a densitometer. (The higher the value, the better the plasticizer resistance.) Oil resistance test method 0.05 cc of salad oil is dropped on the recording layer surface of the colored thermal recording medium, spread evenly over the surface, and printed after standing for 24 hours The concentration was measured with a Macbeth densitometer to calculate the maintenance ratio of the concentration. (The larger the numerical value, the better the oil resistance.) Further, the following evaluation tests were performed on the adhesion of the UV ink and the drying property of the oxidized polymerization ink as the printing enemy.
It is shown in the table.

UV ink adhesion UV ink (trade name; UV-SHINEUVS-S)
EL N-63 grass, manufactured by Morohoshi Ink Co., Ltd.) to print at 0.075 cc / m ^2, and emit light from an 80 W high-pressure mercury lamp 20 cm away from the lamp.
After irradiating for 0 second and curing, the adhesiveness of the ink was evaluated by peeling off a cellotape (manufactured by Nitto Denko Corporation) according to the following evaluation criteria.

：: Completely adhered ×: Ink peeled off and not completely adhered Oxidation polymerization ink drying property Oxidation polymerization ink (trade name; TK New Bright G Ind., Manufactured by Toyo Ink Co., Ltd.) on each thermal recording medium Was printed at 0.075 cc / m ^2, and the dried state after 5 hours was evaluated according to the following evaluation criteria.

：: Completely dry ×: Not completely dried with stickiness remaining "Effects" As is clear from the results in Table 1, the heat-sensitive recording material of the present invention was a heat-sensitive recording material having excellent printing enemy and print preservability.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A heat-sensitive recording layer containing a color former and a color former which forms a color upon contact with the color former is provided on a support, and a water-soluble resin or a water-dispersible resin is contained on the heat-sensitive recording layer. An intermediate layer to be provided, on which a layer containing an electron beam-curable resin as a main component is provided with an intermediate layer cured by irradiating an electron beam, and further containing a pigment and an electron beam-curable resin on the intermediate layer. A heat-sensitive recording material, characterized in that an overcoat layer cured by irradiating an electron beam to a layer to be formed is provided.