JPH0811465B2 - Thermal recording - Google Patents

Description

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material, which has excellent recording aptitude, high recording density, and a heat-sensitive recording image having excellent gradation and storability. It concerns a recording body.

"Prior Art" Conventionally, a thermosensitive recording that utilizes a color reaction between a color-forming agent and a color-forming agent that develops color by contacting the color-forming agent, by contacting both color-forming substances with heat to obtain a color-developed image. The body is well known. Since such a recording medium is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields such as thermal labels. . However, there is a problem in that fingerprint resistance and solvent resistance are poor, and, for example, when human skin fingers or a solvent comes into contact with the recording layer, the recording density is lowered, or unnecessary coloration called background fog occurs.

As a method of solving such a defect, a method of coating an aqueous emulsion of a resin having film forming ability and chemical resistance on a heat-sensitive recording layer (JP-A-54-128347),
A method of applying a water-soluble polymer compound such as polyvinyl alcohol (Shokai 56-125354) has been proposed.

On the other hand, in recent years, various printers such as video printers that provide high-quality photo-like images have been used,
As for the thermal recording material for printout, development of a recording material having more excellent recording density and gradation is required. Therefore, development of a thermal recording material using a plastic film or synthetic paper as a support is in progress,
Even in such a heat-sensitive recording material, an overcoat of a water-based resin or the like is applied on the recording layer in order to prevent fading of the recorded image.

However, when such an overcoat layer is provided on a thermal recording medium using a plastic film or synthetic paper as a support, the overcoat layer tends to adhere to the recording head or the paper feed guide especially when recording under high humidity conditions. Appears,
It became clear that it would cause a paper jam. Further, the recording density itself is not always in a satisfactory condition.

The inventors of the present invention have made earnest researches for improving such a drawback, and as a result, when an aqueous resin intermediate layer is provided on the heat-sensitive recording layer and then an overcoat layer containing a resin curable by electron beam is provided, High density, excellent gradation and storability, and a wider surface property than when using ordinary paper as a support, and thermal sensitivity that does not cause sticking to the recording head even when recording under high humidity conditions. It has been found that a recording material can be obtained.

"Problems to be Solved by the Invention" However, even when a recording material having the above-mentioned excellent characteristics is applied to a recording apparatus which provides a high-quality image rich in gradation, such as a video printer, It has become clear that with the increase in the speed, the sticking phenomenon (sticking) to the recording head occurs even when the electron beam curable resin is used as the overcoat layer. Moreover, it became clear that the sticking phenomenon occurs regardless of humidity conditions.

In view of such a current situation, the present inventors have made diligent researches on solving the above-mentioned difficulties found in a heat-sensitive recording material using a plastic film or synthetic paper as a support and having an overcoat layer of an electron beam curing resin. As a result, a specific intermediate layer is provided between the thermal recording layer and the overcoat layer,
When an electron beam curable resin having a specific glass transition point is selectively used as a resin for forming the overcoat layer, the sticking phenomenon to the recording head does not occur even at high speed recording,
The inventors have found that a recorded image with stable and high quality can be obtained, and completed the present invention.

"Means for Solving the Problems" The present invention provides a thermosensitive recording layer containing a color former and a color former that develops color when contacted with the color former on a plastic film or synthetic paper, and the thermosensitive recording layer is provided on the thermosensitive recording layer. Water-soluble resin or water-dispersible resin, and 50 to 500 pigments per 100 parts by weight of the resin.
And an overcoat layer containing an electron beam curable resin having a glass transition temperature (Tg) of 150 ° C. or higher after curing as a main component is further provided on the intermediate layer. It is a thermosensitive recording medium characterized by the above.

"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 they are brought into contact with each other to cause a color reaction. Examples thereof include a combination of a colorless or pale basic dye and an inorganic or organic acidic substance, a combination of a higher fatty acid metal salt such as ferric stearate and a phenol such as gallic acid, and the like.

However, since the specific overcoat layer of the present invention provided on the recording layer has extremely excellent recording characteristics, particularly when applied to a combination of a basic dye and an acidic substance,
Especially preferred. Various types of basic dyes that are colorless or light-colored are known, and the following are exemplified.

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-ylphthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-) Yl) -6-dimethylaminophthalide, 3,3
-Bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3
Triarylmethane dyes such as -p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N- Diphenylmethane dyes such as halophenyl-leuco auramine and N-2,4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, 3-methyl-spiro-dinaphthopyran, 3 Spiro dyes such as -ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran , Rhodamine-B-anilinolacta , Rotamin (p- nitroanilino) lactam, Rhodamine (o- chloroanilino)
Lactam dyes such as lactam, 3-dimethylamino-7
-Methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3 -Diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-
N-methylaminofluorane, 3-diethylamino-7
-N-methylaminofluoran, 3-diethylamino-
7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3
-Diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-dieraminofluorane, 3- (N-ethyl-p-toluidino) -6methyl-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-amyl) amino-6-methyl-7-phenyl Aminofluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane,
3-pepyridino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-dibutylamino-
Fluorane dyes such as 7- (o-chlorophenylamino) fluorane and 3-pyrrolidino-6-methyl-7- (p-butylphenylamino) fluorane.

Various inorganic or organic acidic substances that are colored by contact with a basic colorless dye are also known, for example, activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acid substances such as aluminum silicate, Four
-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'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis (4-chlorophenol), hydroquinone, 4,4'-
Cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenolic compounds such as phenolic polymers, 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-tert -Butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (Α, α-Dimethylbenzyl) salicylic acid, 3,5-di-α-me Aromatic carboxylic acids such as benzylbenzyl salicylic acid, and organic acidic substances such as salts of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel Etc. are illustrated.

In the heat-sensitive recording material of the present invention, the use ratio of the color former and the color former in the recording layer is appropriately selected according to the type of the color former and the color former used, and is not particularly limited, however, for example, When the basic colorless dye and the acidic substance are used, generally 1 to 50 parts by weight, preferably 1 to 10 parts by weight of the acidic substance is used per 1 part by weight of the basic inorganic dye.

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

In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer are used as adhesives. Salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc. are 10 to 40% by weight of the total solid content, preferably 15 to
Used around 30% by weight.

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

In addition, 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, fine anhydrous silica, and active as required. It is also possible to add an inorganic pigment such as clay and a sensitizer such as stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, mackerel oleic acid amide, and coconut fatty acid amide.

In the thermosensitive recording medium of the present invention, a plastic film, a synthetic paper, a plastic film or a synthetic paper laminated with a coated paper or a high-quality paper via an adhesive, or a plastic laminated on a paper is used as a support. Examples of the plastic film include polyethylene, polyester, polyvinyl chloride, polystyrene and nylon films. As synthetic paper, for example, synthetic paper manufactured by the film method or fiber method is used. In the film method, synthetic resin, filler and additives are melt-kneaded and then extruded to form a film. Method, surface coating method in which a pigment coating layer is provided,
There are surface treatment methods and the like, and the fiber method synthetic paper includes synthetic pulse paper, spunbond paper and the like. Among these supports, the plastic film and the film method synthetic paper are more preferably used because they give particularly excellent recording characteristics.

The coating method of the recording layer is not particularly limited and can be formed according to a conventionally well-known and conventional technique, for example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating, etc. Is formed by a method of coating and drying. When a plastic film is used as the support, the coating efficiency can be increased by subjecting the surface to treatments such as corona discharge and electron beam irradiation. The coating amount of the coating liquid is also not particularly limited, but it is usually in the range of ² to 12 g / m ² , preferably 3 to 10 g / m ^{2 in} 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 or water-soluble resin used in the intermediate layer include the following substances. It

Fully saponified or partially saponified polyvinyl alcohol,
Acetoacetylated pyrivinyl alcohol introduced with acetoacetyl and the like by reacting polyvinyl alcohol and diketene, a reaction product of polyvinyl alcohol and a polycarboxylic acid such as fumaric acid, fumaric anhydride, trimellitic anhydride, and itaconic anhydride. Alternatively, it can be obtained as an esterified product of these reactants, or as 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 and methacrylic acid. Sulfonic acid-modified polyvinyl alcohol, vinyl acetate and ethylene, propylene, and isobutylene obtained as saponification products of carboxy-modified polyvinyl alcohol, vinyl acetate and ethylene sulfonic acid, olefin sulfonic acids such as allylsulphonic acid, and salts thereof and copolymers thereof. , Α- octene, α- dodecene, α
An olefin-modified polyvinyl alcohol obtained by saponifying a copolymer with an olefin such as actadodecene,
Nitrile-modified polyvinyl alcohol obtained as a saponification product of a copolymer of vinyl acetate with acrylonitrile, methacrylonitrile, etc. Obtained by saponifying a copolymer of vinyl acetate with amides such as acrylamide, methacrylamide, etc. Amide-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol obtained by saponifying a copolymer of vinyl acetate and N-vinylpyrrolidone, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, casein, gum arabic, and oxidized starch,
Starches such as etherified starch, 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 or water-dispersible resins, various modified polyvinyl alcohols, cellulose derivatives and casein are preferable, and acetoacetylated polyvinyl alcohol and carboxy-modified polyvinyl alcohol are more preferable.

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

In addition, a pigment is added to the intermediate layer in the range of 50 to 500 parts by weight with respect to 100 parts by weight of the water-soluble or water-dispersible resin in order to enhance smoothness. Specific examples of pigments include inorganic carbonates 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, urea / formalin resin filler, and organic pigments such as raw starch granules.

In addition, glyoxal, methylolmelamine, potassium persulfate, if necessary, in the coating liquid that forms the intermediate layer.
A hardening agent such as ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, or ammonium chloride may be added, and if necessary, zinc stearate, calcium stearate, stearamide, 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, fatty acid metal salt, and ultraviolet rays such as benzophenone and triazole Various auxiliaries such as an absorbent, an antifoaming agent, a fluorescent dye, a coloring dye and the like can be appropriately added.

The coating liquid for forming the intermediate layer is generally prepared as an aqueous coating liquid, and if necessary, a mixer, an attritor,
After being sufficiently mixed and dispersed by a mixing / stirring machine such as a ball mill or a roll mill, it is coated on the thermosensitive recording layer by various known coating devices. After application, it can be dried by irradiation with ultraviolet rays or electron beams.

When a curing agent is used in combination, the curing agent can be applied not only in the coating liquid that forms the intermediate layer, but also separately from the coating liquid that forms the intermediate layer. There is an advantage that a strong curing agent can be selected without having to worry about life.

Further, if necessary, a similar coat layer may be provided on the back surface side of the support made of a plastic film or synthetic paper to further improve the storability. Further, for example, a non-electron beam curable resin or an electron beam curable resin may be coated to prevent the occurrence of curl, a conductive treatment may be applied to improve the running property of the recording medium, or an undercoat layer may be provided on the support. , The back side of the recording material is treated with adhesive,
Various well-known techniques in the field of heat-sensitive recording material production, such as processing into an adhesive label, can be added as necessary.

The coating amount of the coating liquid forming the intermediate layer is not particularly limited, can not be obtained sufficiently the desired curing of the present invention is less than 0.1 g / m ^2, also a 20 g / m ² Kosu When because it may significantly reduce the recording sensitivity of the heat sensitive recording material, generally 0.1 to 20 g / m ² in dry weight, preferably 0.5 to 10 g / m ²
It is desirable to adjust the range.

In the heat-sensitive recording material of the present invention, an overcoat layer mainly composed of an electron beam curable resin having a glass point transfer (Tg) after curing of 150 ° C. or higher is provided on the intermediate layer thus formed. However, such resins include, for example, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol monoacetyl triacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate,
It is formed by electron beam curing a polyfunctional monomer such as tris (acryloxyethyl) isocyanurate or an oligoester acrylate represented by the following general formula.

[In the formula, A is acrylic acid, X is a polyhydric alcohol, Y is a polybasic acid, and n is an integer of 1 to 20. In the above general formula, examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, glycerin,
Examples include trimethylolpropane, pentaerythritol, bisphenol A and the like. As the polybasic acid,
For example, maleic acid, fumaric acid, itaconic acid, carbic acid, mesaconic acid, citraconic acid, dichloromaleic acid,
Examples thereof include unsaturated polybasic acids such as chloromaleic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, saturated polybasic acids such as chlorophthalic acid and hydrophthalic acid.

Of these, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and pentaerythritol monoacetyl triacrylate are most preferably used in the thermosensitive recording medium of the present invention.
Moreover, two or more kinds of the above-mentioned polyfunctional monomers, oligoester acrylates and the like can be used in combination, if necessary.

The coating amount of the resin which is cured by electron beam, but are not necessarily limited, can not be the desired effect expected of the present invention is less than 0.1 g / m ^2, the coating amount as exceeding 20 g / m ² Since the recording sensitivity of the obtained recording material may be significantly lowered, 0.1 to 20 g / m ² , more preferably
It is desirable to adjust within the range of 0.3 to 10 g / m ² .

In the resin component that is cured by an electron beam, in addition to the monomers and oligomers as described above, if necessary, for example, an electron beam curable resin other than the above, a non-electron beam curable resin, an inorganic pigment, a color pigment, a fluorescent pigment. Additives such as fluorescent dyes, other organic dyes, antifoaming agents, leveling agents, lubricants, surfactants, plasticizers, and ultraviolet absorbers can be appropriately added.

By adding a pigment to the overcoat layer that contains a resin that is cured by electron beams, it is possible to improve recording problems (image defects that occur in stripes in the paper feed direction) and sticking that occur depending on the printer model. By further smoothing with a super calender or the like, a thermosensitive recording medium having no image unevenness can be obtained.

In the thermal recording material of the present invention, since a plastic film or synthetic paper is used as a support, it is possible to obtain a more glossy surface as compared with the case where ordinary paper is used. A thermosensitive recording medium having a wide range of surface properties from a matte tone to a strong gloss can be formed by adjusting the type and blending ratio.

The resin component as described above is thoroughly mixed with a suitable mixing stirrer such as a mixer and then applied on the intermediate layer by various known methods. It can also be adjusted.

The resin layer formed on the intermediate layer is cured by irradiation with an electron beam, and the amount of the irradiated electron beam is preferably in the range of 0.1 to 15 Mrad, more preferably about 0.5 to 10 Mrad. Because
If it is less than 0.1 Mrad, the resin component cannot be sufficiently cured, and excessive electron beam irradiation such as 15 Mrad may cause color development 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, etc. can be adopted, and an accelerating voltage at the time of irradiation is appropriately 100 to 300 KV.

Further, by smoothing the heat-sensitive mechanism having the electron beam-curable resin layer on the intermediate layer thus obtained by using a super calender, etc. It is possible to obtain a thermosensitive recording material having excellent image quality and high recording density.

"Examples" Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Unless otherwise specified, "parts" and "%" in the examples represent parts by weight and% by weight, respectively.

Example 1 Liquid A preparation 3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-phenylaminofluorane 10 parts Methylcellulose 5% aqueous solution 5 parts Water 30 parts This composition was mixed with a sand grinder to give an average particle size of 3 μm.
It was crushed until it reached m.

Liquid B preparation Benzyl 4-hydroxybenzoate 20 parts Methylcellulose 5% aqueous solution 5 parts Water 55 parts This composition has a mean particle size of 3μ using a sand grinder.
It was crushed until it reached m.

Formation of recording layer 45 parts of solution A, 80 parts of solution B, 50 parts of 20% aqueous solution of oxidized starch, water 10
Parts were mixed and stirred to obtain a coating liquid. The obtained coating solution was applied on a synthetic paper of 80 g / m ² (trade name; YUPO, manufactured by Oji Yuka Co., Ltd.) so that the coating amount after drying was 6 g / m ² and dried to obtain a thermosensitive recording medium. .

Formation of the intermediate layer On the recording layer of the resulting thermosensitive recording medium, a coating liquid having the following composition was applied and dried so that the coating amount after drying was 4 g / m ^2, and further smoothed with a super calender. Then, a thermal recording material having an intermediate layer was prepared.

8% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 1000 parts Calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Kouka Co., Ltd.) 100 parts Water 100 parts Overcoat layer formation Penta on the intermediate layer Erythol triacrylate was applied so that the dry coating amount was 5 g / m ^2, and 3Mard was applied with an electron curtain type electron beam irradiation device (CB: 150 type, manufactured by ESI).
To cure the resin component to obtain a thermosensitive recording medium having an electron beam curable resin (Tg 250 ° C.) overcoat layer.

Example 2 An overcoat layer of an electron beam curing resin (Tg 250 ° C.) was prepared in the same manner as in Example 1 except that trimethylolpropane triacrylate was used instead of pentaerythritol triacrylate as the resin forming the overcoat layer. A heat-sensitive recording material having

Example 3 A thermosensitive recording medium having an overcoat layer of an electron beam curable resin (Tg 180 ° C.) was obtained in the same manner as in Example 1 except that the electron beam irradiation dose by the electron beam irradiation apparatus was 1 Mrad.

Comparative Example 1 In Example 1, except that tripropylene glycol diacrylate (trade name: M-220, manufactured by Toagosei Co., Ltd.) was used instead of pentaerythritol triacrylate as the resin forming the overcoat layer. Similarly, a thermosensitive recording medium having an electron beam curable resin (Tg 90 ° C.) overcoat layer was obtained.

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 Formation of Intermediate Layer On the recording layer obtained in Example 1, a coating liquid having the following composition was applied and dried so that the coating amount after drying was 4 g / m ² .
Further, it was smoothed with a super calender to obtain a thermosensitive recording medium having an intermediate layer.

8% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 1000 parts Calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Powder Co., Ltd.) 32 parts Water 32 parts Overcoat layer formation On the intermediate layer, A thermal recording material having an overcoat layer was obtained in the same manner as in Example 1.

Comparative Example 4 Formation of Intermediate Layer On the recording layer obtained in Example 1, a coating liquid having the following composition was coated and dried so that the coating amount after drying was 4 g / m ² .
Further, it was smoothed with a super calender to obtain a thermosensitive recording medium having an intermediate layer.

8% aqueous solution of polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray Co., Ltd.) 1000 parts Calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Kouka Co., Ltd.) 480 parts Water 480 parts Overcoat layer formation On the intermediate layer, A thermal recording material having an overcoat layer was obtained in the same manner as in Example 1.

The thus-obtained five types of thermal recording materials were printed and colored by a Sony video printer UP103, and the running characteristics (sticking characteristics) of the recording material and the color density of the obtained recorded image were measured by a Macbeth densitometer (Masbeth RD- 100R type)
The results are shown in Table 1.

Further, Table 1 also shows the color density after the plasticizer resistance evaluation test and the glossiness of the surface of the heat-sensitive recording material before printing and coloring.

[Evaluation criteria for sticking characteristics]

◎ …… It was extremely smooth without sticking to the recording head even at high speed recording.

O: The recording material was running smoothly at high speed recording.

X: The recording medium stuck to the recording head, causing a running failure.

[Plasticizer resistance evaluation test]

Wrap a vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) on a polypropylene pipe (40 mmφ pipe) in three layers,
A thermosensitive recording material, which had been subjected to color development with a video printer, was sandwiched on top of it so that the color development surface was on the outside, and a vinyl chloride wrap film was wrapped around it five times, and the print density after 72 hours was measured.

 (The larger the value, the better the plasticizer resistance.) [Glossiness] Measured with a goniophotometer at an incident angle of 60 degrees.

(The higher the number, the higher the gloss.) [Effect] As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention was excellent in recording runnability, had high recording density, and had excellent surface gloss and print storage hostility. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-26291 (JP, A) JP-A-61-284483 (JP, A) JP-A-58-177392 (JP, A) Actual development Sho-58- 26559 (JP, U)

Claims (1)

[Claims] 1. A heat-sensitive recording layer containing a color-forming agent and a color-developing agent that develops a color when contacted with the color-forming agent is provided on a plastic film or synthetic paper, and a water-soluble resin or water-dispersible resin is provided on the heat-sensitive recording layer. , And 50 to 5 parts by weight of pigment with respect to 100 parts by weight of the resin.
And an overcoat layer containing an electron beam curable resin having a glass transition point (Tg) after curing of 150 ° C. or more as a main component on the intermediate layer. A thermosensitive recording medium characterized by