JPH04125182A - Thermal recording material - Google Patents

Abstract

PURPOSE:To achieve an excellent holding property of whiteness and to enable durability of a recording layer to be steeply improved by a method wherein a specific styrene-butadiene latex and polyvinyl alcohol are jointly used as an adhesive to be compounded in a recording layer. CONSTITUTION:A styrene-butadiene latex which contains 25-40wt.% of butadiene monomer and of which gel content is 60-80% and polyvinyl alcohol are contained as adhesives in a thermal recording layer. Further, for instance, a colorless or light colored basic dye and an inorganic or organic acidic substance are combined, and an application liquid containing those substances is prepared with water as a dispersion medium by dispersing them altogether or separately with a crusher. Then, the application liquid for the thermal recording layer which was prepared by mixing is applied onto a travelling base material via a transfer roll to be dried and the thermal recording material is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that has improved water resistance without reducing the whiteness of the recording layer and has a high recording density. be.

"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 a colored image is obtained by bringing both coloring materials into contact with each other using heat. 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, but this method is still not sufficient in terms of the storage stability of prints, and furthermore, The resin layer that is cured by the heat-sensitive recording layer may cause the heat-sensitive recording layer to develop color immediately after coating, or cause the recorded image to discolor.

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 curing resin, fogging of the recording layer can be reduced. It was discovered that a heat-sensitive recording material can be obtained which has significantly improved print storage stability without any problems, has a wide range of surface properties, and has excellent recording properties, and has previously filed an application as JP-A-62-279980.

On the other hand, in recent years, various printers such as video printers that provide high-quality, photographic images have come into use.
Even thermal recording media for printouts are required to have better recording density and gradation. 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.

As a result of studying ways to improve these drawbacks, 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 applied an electron beam curing resin. They have discovered that by providing an overcoat layer containing the above, it is possible to obtain an excellent heat-sensitive recording material that has high recording density, excellent gradation properties and storage stability, and does not stick to the recording head even under high humidity conditions.
It was previously proposed as Japanese Patent Application Laid-Open No. 63-99984.

However, even with heat-sensitive recording materials in which a plastic film or synthetic paper is used as a support and a heat-sensitive recording layer, an aqueous resin intermediate layer, and an overcoat layer of an electron beam-curable resin are sequentially provided on the support, the recording layer still has water resistance. There are cases where the gender is insufficient0
For example, if a heat-sensitive recording material having such a layer structure is recorded with a video printer with moisture condensed on the recording material, the recording layer may peel off and damage the recording head due to the lack of water resistance of the heat-sensitive recording layer. It became clear.

For this reason, there is a strong demand for heat-sensitive recording materials whose recording layers have excellent water resistance and adhesive properties.

Generally, water-soluble adhesives such as polyvinyl alcohol, methyl cellulose, casein, gelatin, starch, and their derivatives are used as adhesives in the recording layer of heat-sensitive recording materials, and such heat-sensitive recording layers have extremely high water resistance. Inferior.

Traditionally, in order to improve the water resistance of water-soluble adhesives,
For example, the use of crosslinking curing agents such as formalin, glyoxal, and dialdehyde starch has been proposed, but since high temperature drying cannot be performed in the production of heat-sensitive recording materials, sufficient crosslinking reactions do not proceed, resulting in poor water resistance. Almost no improvement effect can be obtained.

It is also known to use compounds having two or more epoxy groups or two or more ethyleneimine groups in one molecule as waterproofing agents for water-soluble adhesives.
These water resistant agents generally have a desensitizing property to the color development of the heat-sensitive recording material, and have the disadvantage of lowering the color density.

Furthermore, the use of synthetic resin latex has been proposed, but it has the disadvantage that sufficient effects may not be obtained or that the whiteness of the recording layer may decrease as the water resistance is improved.

[Problems to be Solved by the Invention] In view of the current situation, the present inventors have developed an adhesive to be incorporated into a thermosensitive coloring layer in order to provide a thermosensitive recording material with improved water resistance without particularly reducing the whiteness of the recording layer. As a result of extensive research into adhesives, the inventors have found that the above object can be achieved by using a specific latex and polyvinyl alcohol together as an adhesive, leading to the completion of the present invention.

"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 In a heat-sensitive recording material provided with an intermediate layer containing a resin and/or a water-dispersible resin, and further provided with an overcoat layer of an electron beam curable resin on the intermediate layer, a butadiene monomer is used as an adhesive in the heat-sensitive recording layer. This is a heat-sensitive recording material characterized by containing an SB-based latex containing 25 to 40% by weight of polymer and a gel content of 60 to 80%, and polyvinyl alcohol.

"Function" The present invention is characterized by the combination of a specific SB latex and polyvinyl alcohol as an adhesive compounded in the recording layer as described above. The present invention provides a heat-sensitive recording material that does not cause a decrease in whiteness, has excellent whiteness retention against temperature and humidity, and has a recording layer with greatly improved water resistance.

In the present invention, an SB-based latex containing 25 to 40 weight percent of monobutadiene and a gel content of 60 to 80 percent is used, but the copolymerization rate of butadiene is 25 weight percent.
If it is less than 40% by weight, the film forming properties will be poor, and if it exceeds 40% by weight, the cohesive force will be weakened and the adhesion to the support will be reduced. Furthermore, if the gel content is out of the above range, water resistance and adhesion to the support will deteriorate. Therefore, in the present invention, the above-mentioned SB-based latex is used.

Moreover, the content of the styrene monomer constituting the SB-based latex is desirably 40 to 70% by weight in consideration of the stability of the latex.

The SB latex used in the present invention has styrene and butadiene as main constituent monomers, and further contains at least one type of various unsaturated carboxylic acid monomers for the purpose of modification in the monomer composition. Specific examples of such unsaturated carboxylic acid monomers include itaconic acid, maleic acid, acrylic acid, methacrylic acid, fumaric acid, dicarboxylic acid anhydride, dicarboxylic acid monoalkyl ester, etc. is preferably contained in the monomer composition in a proportion of 0.5 to 15% by weight.

Incidentally, if the proportion of unsaturated carboxylic acid monomer is less than 0.5% by weight, the mechanical stability of the copolymer latex will decrease, and if it exceeds 15% by weight, the viscosity of the copolymer latex will decrease. It tends to get too high.

Furthermore, the above-mentioned SB-based silatex monomer composition can contain other olefin-based monomers, and specific examples of such monomers include aromatic monomers such as α-methylstyrene, vinyltoluene, dimethylstyrene, etc. Vinyl monomers, acrylate monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, 2-
Examples include methacrylate monomers such as hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and monomers containing glycidyl groups such as glycidyl acrylate and glycidyl methacrylate. These monomers can be used in an amount of 0 to 35% by weight within a range that does not impede the effects of the present invention.

However, unsaturated nitrile monomers such as acrylonitrile and methacrylaterile, and amide group-containing monomers such as acrylamide, N-methylolacrylamide and methacrylamide are not preferred because they impede the effects of the present invention.

The method for producing the copolymer latex in the present invention is not particularly limited, and examples include continuous emulsion polymerization,
- Known emulsion polymerization methods such as porosity polymerization can be employed, and additives used in general emulsion polymerization such as various known emulsifiers, chain transfer agents, polymerization initiators, electrolytes, and chelating agents can be used as appropriate. '', and the polymerization temperature may be either high or low.

In addition, the gel content depends on the type of monomer used and the ratio of monomers used.
It can be controlled by adjusting the polymerization method, additives used in emulsion polymerization, etc.

In addition, in the present invention, the amount of these additives used is kept as small as possible (
It is preferable to use SB-based latex, especially latex produced without using an emulsifier, because a thermosensitive recording material with further improved water resistance and whiteness retention can be obtained.

The amount of the copolymer used is not particularly limited, but it is desirable to adjust it to 5 to 40% by weight, more preferably 10 to 30% by weight, based on the total solid content of the coloring layer.

In the present invention, a specific SB latex as described above and polyvinyl alcohol are used together as an adhesive for the heat-sensitive recording layer. ,1
:5 to 5:1, more preferably 1:3 to 3:1. If the ratio of polyvinyl alcohol to alcohol deviates from the above range, the recorded concentration will change,
Adhesion to the support, water resistance, etc. tend to deteriorate.

Examples of the polyvinyl alcohol include partially saponified or completely saponified polyvinyl alcohol, as well as modified polyvinyl alcohols such as acetoacetyl group-modified polyvinyl alcohol and carboxyl group-modified polyvinyl alcohol.

The combination of the coloring agent and the coloring agent contained in the recording layer is not particularly limited, and any combination can be used as long as the two come into contact with each other due to heat and cause a coloring reaction.

For example, 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., diazonium compounds, couplers and basic It is also possible to apply the present invention to heat-sensitive recording materials that combine substances.

However, since the excellent effects of the present invention are particularly exhibited in the case of coating compositions consisting of a combination of a basic dye and an acidic substance, it is particularly preferably applied to combinations that are drenched.

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, 33-bis(1,2-dimethylindol-3-yl)5-dimethylaminophthalide, 3.3-bis(12-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-
Triallylmethane dyes such as methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4 ,511J
Diphenylmethane dyes such as 70 lophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue, p-nitropenzoyl leucomethylene blue,
3-Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3
- Spiro dyes such as methyl-naphtho(6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (0-ri00anilino) ) Lactam dyes such as lactam, 3-dimethylamino-7-medoxyfluoran, 3-diethylaminol 6-methoxyfluoran, 3-diethylamino-
7-Medoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7
-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-p-toluidino)-7methylfluorane, 3-diethylamino-7-N
Acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamine-7-sibenzylaminofluorane, 3-diethylamine-7-N-methyl-N-benzylaminofluorane , 3-diethylamino-7-N-chloroethyl-
N-methylaminofluorane, 3-diethylamino-7
-N-diethylaminofluorane, 3-(N-ethyl P-
1-Luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(pi-luidino)fluorane, 3-diethylamino-6-methyl -7 phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 1(N-ethyl-N-isoamylamino) )-6-methyl-7phenylaminofluorane, 3-(N-cyclohexyl-N-methylamine)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenyl Aminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-
7-xylidinofluorane, 3-diethylamino 7-(
Fluoran dyes such as o-chlorophenylamino)fluoran, 3-dibutylamino-7-(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(2t
er t-butylphenol), 4. 4'-5e
c-butylidene diphenol, 4-phenylphenol, 4,4'-isopropylidene diphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4°4'-cyclohexylidene diphenol, Phenolic compounds such as benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyfucurate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenol polymer, benzoic acid, p
-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3
．． 5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-hensylsalicylic acid, 3-(α-methylhensyl)salicylic acid, 3-chloro-5-(α-methylhensyl) Aromatic carboxylic acids such as salicylic acid, 3,5-di-butylsalicylic acid, 3-phenyl-5-(α,α-dimedylhenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic acids Examples include compounds, organic acidic substances such as salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel.

In the present invention, the usage ratio of the coloring agent and coloring agent in the recording layer is appropriately selected depending on the type of coloring agent and coloring agent used, and is not particularly limited. When using a colorless dye and an acidic substance, generally 1 to 50 parts by weight, more preferably about 1 to 10 parts by weight of the acidic substance are used per 1 part by weight of the basic colorless dye.

A coating solution containing these substances is prepared by dispersing them together or separately using water as a dispersion medium and using an agitator such as an attritor or a sand mill or a pulverizer. Note that if the average particle size of the material constituting the coating liquid exceeds 2.5 microns, there is a risk of clogging the gravure roll, and in particular, if coarse particles exceeding 15 microns are contained in an amount of 2% by weight or more, the printed pixels may be damaged. Since the stabilization of the particles decreases, it is preferable to adjust the particle size appropriately.

The coating liquid contains adhesives other than SB latex and polyvinyl alcohol, such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride. Acid copolymer salt, ethylene-acrylic acid copolymer salt,
Styrene acrylic acid copolymer salt, methyl methacrylate butadiene copolymer emulsion, urea resin, melanin resin, amide resin, etc., within the range that does not impede the effects of the present invention.
It is also possible to use it appropriately.

Furthermore, various auxiliary agents can be added to the coating liquid for the heat-sensitive recording layer as necessary, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, Examples include dispersants such as alginates and fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, antifoaming agents, fluorescent dyes, and colored dyes.

In addition, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, etc. It is also possible to add inorganic pigments such as talc, kaolin, fired clay, and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, and urea-formalin resin fillers. Furthermore, a sensitizer may be added depending on the purpose.

Specific examples of sensitizers include stearamide,
Stearic acid methylene bisamide, oleic acid amide,
Fatty acid amides such as palmitic acid amide and coconut fatty acid amide, dibenzyl terephthalate, 1,2-(3-methylphenoxy)ethane, 1,2-diphenoxyethane,
4.4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1,1.3-)lis(2-methyl-
4-Hydroxy-5-tert-butylphenyl)butane, 2.2゛-methylenebis(4-methyl-5-tert)
t-butylphenol), 4,4'-butylidene bis(5
Hindered phenols such as (tert-butyl-3-methylphenol) and various known thermofusible substances can be added.

The heat-sensitive recording layer coating solution prepared in this way is transferred onto a running support with a dry weight of 1 to 10 g via a transfer roll.
/rrf and is dried to finish as a heat-sensitive recording material.

Paper, synthetic paper, film, etc. are used as the support for such a heat-sensitive recording medium, and synthetic paper, film, etc. are suitable for more clearly exhibiting the effects of the present invention.

Furthermore, the coating efficiency can be increased by subjecting the surface of the support to treatments such as corona discharge and electron beam irradiation.

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

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, fumaric anhydride, trimetic anhydride, itaconic anhydride, etc. Reactants with polycarboxylic acids or esterified products of these reactants, and reactions between 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,
Sulfonic acid-modified polyvinyl alcohol obtained as a saponified copolymer of vinyl acetate and olefin sulfonic acid or its salts such as ethylene sulfonic acid and allyl sulfonic acid, vinyl acetate and ethylene, propylene, isobutylene, α-octene, α- Olefin-modified polyvinyl alcohol obtained by saponifying a copolymer with olefins such as dodecene and α-octadodecene, and nitrile-modified polyvinyl obtained as a saponification product of a copolymer of vinyl acetate and a nitrile such as acrylonitrile and methacrylaterile. Amide-modified polyvinyl alcohol obtained by saponifying copolymers of alcohol, vinyl acetate, and amides such as acrylamide and methacrylamide, and pyrrolidone-modified polyvinyl obtained by saponifying copolymers of vinyl acetate and N-vinylpyrrolidone. Alcohol, cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose,
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. The amount of water-soluble resin or water-dispersible resin used is not particularly limited, but is preferably 10 to 50% by weight, preferably 15 to 4% by weight based on the total solid content in the coating liquid.
It is used in an amount of about 0% by weight.

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 life, raw starch granules, etc. is exemplified. The amount used is generally 5 to 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 dodecylbenzenesulfonate, 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 benzophenone type and triazole type, antifoaming agents, fluorescent dyes, and colored dyes can 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, or other mixing/stirring machine as necessary, it is processed using various known coating devices. It is applied onto the heat-sensitive recording layer and dried. 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 not only be added to the coating liquid that forms the intermediate layer, but also applied 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 0.11lrr, the desired effect of the present invention cannot be sufficiently obtained, and if it is less than 20g/ry
If it exceeds f, the recording sensitivity of the heat-sensitive recording medium may be significantly reduced.
B. It is preferably adjusted within a range of about 0.5 to log/M.

Further, if necessary, it is also possible to further increase the shelf life by providing a similar coating layer on the back side of the heat-sensitive recording material. Furthermore, we can provide an undercoat layer on the support, apply an adhesive treatment to the back of the recording material, and process it into an adhesive label.
Various known techniques in the field of heat-sensitive recording material manufacturing may be added as necessary.

An overcoat layer containing an electron beam curing resin is provided on the intermediate layer thus formed, and by increasing the smoothness of the surface of the intermediate layer, a recording medium with high recording density and gloss can be obtained. Perform smoothing treatment with a super calender etc. to check the Beck smoothness of the surface of the intermediate layer for at least 500 seconds when the support is plastic film or synthetic paper, more preferably at least 1600 seconds, and for 50 seconds when the support is paper. It is desirable to adjust the time to 300 seconds or more, more preferably 300 seconds or more.

Examples of the electron beam curing resin forming the overcoat layer include the following prepolymers and monomers.

Prepolymers include (a) poly(meth)acrylates of aliphatic, alicyclic, and araliphatic di- to hexavalent polyhydric alcohols and polyalkylene glycols; (C) Poly(meth)acryloyloxyalkyl phosphate ester; (d) Polyester polyester (Meta)acrylay-I・
;(e) Epoxy poly(meth)acrylate;(
f) Polyurethane poly(meth)acrylate; ((
b) Polyamide poly (meth)acrylate; (5)
Polysiloxane poly (meth)acrylate; (D
A vinyl or diene low polymer having a (meth)acryloyloxy group in its side chain and/or terminal; (j) The oligoester described in (a) to (i) above (
Prepolymers such as meth)acrylate modified products;

In addition, monomers include (a) carboxyl group-containing monomers represented by ethylenically unsaturated mono- or polycarboxylic acids, and carboxylic acid group-containing monomers such as their alkali metal salts, ammonium salts, and amine salts; (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 aromatic vinyl Sulfonic acid group-containing monomers represented by sulfonic acids and their alkali metal salts, ammonium salts, amine salts, etc.: (d) Hydroxyl group-containing monomers represented by ethylenically unsaturated ethers, etc. Monomer; (e) Amino group-containing monomer such as dimethylaminoethyl (meth)acrylate-2-vinylpyridine: (f)
Quaternary ammonium base-containing monomers; ((to) alkyl esters of ethylenically unsaturated carboxylic acids; (b) nitrile group-containing monomers such as (meth)acrylonitrile; (i) styrene; (j) vinyl acetate; Esters of ethylenically unsaturated alcohols such as (meth)allyl acetate; mono(meth)acrylates of alkylene oxide addition polymers of compounds containing active hydrogen; (1)
An ester group-containing bifunctional monomer represented by a diester of a polybasic acid and an unsaturated alcohol; (b) 2 consisting of an alkylene oxide addition polymer of an active hydrogen-containing compound and a diester of (meth)acrylic acid; Functional monomer; (n) Bisacrylamide such as N,N-methylenebisacrylamide; (0) Bifunctional monomer such as divinyl ether, divinylethylene glycol, divinyl sulfone, divinyl ether, divinyl ketone; Φ) Polycarbonate Polyfunctional monomers containing ester groups represented by polyesters of acids and unsaturated alcohols; (q) Polyfunctional monomers consisting of polyesters of alkylene oxide addition polymers of active hydrogen-containing compounds and (meth)acrylic acid; (r) Polyfunctional unsaturated monomers such as trivinylhenzene.

etc.

An electron beam curable resin having a glass transition point (T g ) of 150° C. or higher after curing is particularly preferred since it is excellent in preventing the phenomenon of sticking to the head during high-speed recording.

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 lehering agents, lubricants, surfactants, plasticizers, 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, alkyd resin, fluororesin, and butyral resin.

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. If necessary, the resin components may be heated. Viscosity can also be adjusted. Further, although the amount of coating is not necessarily limited, if it is less than 0.1 g/rrf, the desired effect of the present invention cannot be expected, and if the amount of coating exceeds 20 g/rrf, the recording sensitivity of the resulting recording medium may decrease. Therefore, it is desirable to adjust it within the range of 0.1 to 20 g/rrf, more preferably 0.3 to 10 g/rrf.

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.

The amount of electron beam irradiated is desirably within a 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.

Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 ■ Preparation of Solution A 3-(N-Ethyl-N-ynylamino)-6-methyl-7-phenylaminofluorane 10 parts Dibenzyl terephthalate 20 parts Methylcellulose 5% aqueous solution 5 parts Water
65 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

■ Preparation of Solution B 4. 30 parts of 4'-isopropylidene diphenol 5% aqueous solution of methylcellulose 5 parts of water
65 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

■ Formation of recording layer 100 parts of liquid A, 100 parts of liquid B, silicon oxide pigment (product name:
Mizuriki Seal P-527, manufactured by Mizusawa Chemical Co., Ltd.) 20 copies, 1st
A coating liquid was prepared by mixing 30 parts (as solid content) of SB latex-1 having the monomer composition and gel content shown in the table, 150 parts of a 20% aqueous polyvinyl alcohol solution, and 75 parts of water.

The obtained coating liquid was applied to synthetic paper (trade name: Yubo FPG).

After transferring onto a gravure roll (manufactured by Tamago Yuka Synthetic Paper Co., Ltd.) using a gravure roll so that the coating amount after drying is 10 g/m'', smoothing with a bar installed at the rear of the gravure roll to determine the coating amount after drying. A heat-sensitive recording material was obtained by adjusting the coating amount so that the coating amount was 5 g/m''.

■ Formation of intermediate layer On the recording layer of the obtained heat-sensitive recording material, a coating liquid having the following composition was applied and dried so that the coating amount after drying was 4 g/rrr, and smoothing treatment was performed using a super calender. A heat-sensitive recording material having an intermediate layer having a Bekk smoothness of 5000 seconds was prepared.

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 ■ Formation of overcoat layer Pentaerythritol triacrylate (trade name, PET-3, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to the intermediate layer so that the dry coating amount was 4 g/rrT, and an electron curtain type coating was applied. Electron beam irradiation device (CB: 150 type, manufactured by ESI)
The resin component was cured by treatment with an irradiation dose of 3 Mrad to obtain a thermosensitive recording material having an overcoat layer of electron beam cured resin.

Example 2 In forming the recording layer of Example 1, SB-based latex-
A thermosensitive recording material was obtained in the same manner as in Example I except that SB latex-2 was used instead of SB-based latex-2.

Example 3 In forming the recording layer of Example 1, SB-based latex-
A thermosensitive recording material was obtained in the same manner as in Example 1, except that SB-based latex-3 was used instead of SB-based latex-3.

Example 4 In forming the recording layer of Example 1, SB-based latex-
A thermosensitive recording film was obtained in the same manner as in Example 1, except that the amount of Example 1 used was 10 parts (solid content) and the amount of the 20% polyvinyl alcohol aqueous solution was changed to 250 parts.

Comparative Example 1 In the formation of the recording layer of Example 1, SB-based Lux ~
A thermosensitive recording material was obtained in the same manner as in Example 1 except that SB latex-4 was used instead of SB-based latex-4.

Comparative Example 2 In forming the recording layer of Example I, SB-based latex-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that SB latex-5 was used instead of SB-based latex-5.

Comparative Example 3 In forming the recording layer of Example 1, SB-based latex-
A thermosensitive recording material was obtained in the same manner as in Example 1, except that SB-based latex-6 was used instead of SB-based latex-6.

Comparative Example 4 In the formation of the recording layer of Example 1, SB-based latex-
A thermosensitive recording material was obtained in the same manner as in Example I except that SB latex-7 was used instead of SB-based latex-7.

Comparative Example 5 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.

The nine types of heat-sensitive recording materials thus obtained were printed using a heat-sensitive printer (SONY, UP-103), and the recorded density was measured using a Macbeth densitometer (manufactured by Macbeth Co., Ltd.).

RD-100R) and are shown in Table 2.

In addition, the heat-sensitive recording medium was treated for 72 hours under the conditions of 40°C, 190χR11, and the whiteness after treatment was measured using a Hunter brightness meter (using a blue filter), and the results were used as a second
Shown in the table.

Furthermore, the dew condensation printability and adhesion to the support were evaluated using the following methods, and the results are shown in Table 2.

U1 lifetime: After processing the heat-sensitive recording material at -20°C for 2 hours, it was left for 1 hour at 40°C and 90XR11 to cause dew on the recording material.
03) to evaluate the recording runnability.

O: No abnormalities in recording running △; There is some peeling of the recording layer, but no running defects ×; There is peeling of the recording layer, causing running defects. (manufactured by) was adhered to the surface of the recording medium and heated at 40°C and 190χRH for 2 hours.
After 4 hours of treatment, the recording layer was peeled off and the peeled state of the recording layer was visually determined.

○: No abnormality in the recording layer △: Some peeling of the recording layer ×: The recording layer was completely peeled off Table 2 "Effect" As is clear from Table 2, the thermal recording material of the present invention has a high whiteness. It was a highly practical recording medium with good retention and excellent water resistance.

Claims (1)

[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 and/or a water-dispersible resin is provided on the heat-sensitive recording layer. In a heat-sensitive recording material in which an intermediate layer containing a resin is provided and an overcoat layer of an electron beam curable resin is further provided on the intermediate layer, 25 to 40% of butadiene monomer is added as an adhesive in the heat-sensitive recording layer.
SB containing % by weight and having a gel content of 60-80%
A heat-sensitive recording material characterized by containing latex and polyvinyl alcohol.