JP2772359B2 - Thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium. More specifically, U is excellent in workability and environmental protection in forming a high-grade heat-sensitive recording medium having excellent gloss and glossiness.
The present invention relates to a thermosensitive recording medium in which a cured film is formed by applying an emulsion obtained by dispersing and emulsifying a V or EB curable resin in water.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive recording medium for obtaining a recorded image by reacting a color former and a developer by heat is relatively inexpensive, and the apparatus is compact and maintenance-free, so that it is widely used in facsimile machines and word processors. Have been. Recently, it has been used for printing various labels such as POS labels and cards, and has a wide field of application.

[0003] However, these heat-sensitive recording materials have a problem in storage stability (particularly, fading of a color-developed image by a plasticizer, oil, and water), and also have disadvantages such as background fog. As a method for solving this problem, a method of providing a UV or EB curable resin on the heat-sensitive layer (Japanese Patent Publication No. 58-35478) or a method of providing a UV or EB curable resin layer on the heat-sensitive layer via an intermediate layer Thus, there has been proposed a method of obtaining a thermosensitive recording medium having excellent storage stability and recording characteristics without fogging.
(JP-A-59-26291)

[0004]

[Problems to be Solved by the Invention] Recently, problems such as safety and health, environment, pollution, etc. have been highlighted, and conventional overcoat liquids using organic solvents will be increasingly used from the viewpoint of the Fire Service Law and the Industrial Safety and Health Law. It's getting harder to do. On the other hand, the UV or EB curable resin has an advantage that it can be used without a solvent, but the coating method is limited if no solvent is used, and at present the organic solvent is used as a diluent.

In recent years, with the trend toward diversification and high performance of thermal recording systems, printers and facsimile machines have made remarkable progress. For example, when recording with a video printer of the type that prints at high speed, UV or EB Even when the curable resin is overcoated, a good recorded image is not obtained. Also, a method of using a UV or EB curable resin having a Tg point of 200 ° C. or higher (Japanese Patent Laid-Open No. 1-125277)
A method of adding a pigment of 15 microns or less (Japanese Unexamined Patent Publication No.
1), etc., all of which have problems such as adhesion of debris to the thermal head and generation of sound during printing (sticking noise). The object of obtaining a glossy heat-sensitive recording medium which is excellent in high-speed recording characteristics and gives a sense of quality has not yet been achieved.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, the present invention is (1) a heat-sensitive layer containing a color former and the developer is formed on a support, in yet heat-sensitive recording material forming the overcoat layer, dispersed and a UV-curable resin as the overcoat layer in water A thermosensitive recording material comprising a cured film formed by coating an emulsified emulsion and evaporating water. (2) The heat-sensitive recording material as described in (1) above, wherein the emulsion contains a fine powder of a pigment. (3) The heat-sensitive recording material as described in (1) above, wherein the emulsion contains a lubricant. (4) The present invention provides the heat-sensitive recording material as described in (1) above, wherein the emulsion contains a reactive silicone compound.

The heat-sensitive recording material of the present invention has high gloss and excellent high-speed recording performance, has excellent storage stability of the heat-sensitive recording material and its color-developed image, and has a UV or E
By using an emulsion of a B-curable resin, there is a feature that an organic solvent which has a bad influence on a human body and an environment is not used. In the present invention, the color former and the developer to be contained in the heat-sensitive layer are not particularly limited, and those known per se can be used, and the color former and the developer are coated on a support using a usual binder. If necessary, fillers, sensitizers and other additives can be mixed.

Examples of the coloring agent include fluoran compounds, triarylmethane compounds, spiropyran compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds and the like. Include, for example, the following compounds.

Fluoran compound: 2-anilino-3-
Methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (N-methyl-N-cyclohexylamino) -fluoran, 2-anilino-3-methyl-6
-(N-ethyl-N-isopentylamino) fluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2- (p-chloroanilino) -3-methyl-
6- diethyl Rua Minofuruoran, 2- (p-fluoroanilino) -3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6- (p-preparative Luigi Bruno ethylamino) fluoran, 2- ( p-toluidino)-
3-methyl-6-diethylaminofluoranfluoroanilino-6-diethylaminofluoran, 2- (o-fluoroanilino) -6-dibutylaminofluoran, 2
-Anilino-3-methyll-6-biperidinofluoran, 2-anilino-3-methyl-6-pyrrolidinofluoran, 2-ethoxyethylamino-3-chloro-6-diethylaminofluoran, 2-anilino- Triarylmethane compounds, such as 3-chloro-6-diethylfluoran, 2-chloro-6-diethylaminofluoran, and 2-methyl-6-diethylaminofluoran: 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (alias: crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylaminoindol-3-ylphthalide, etc.

Spiropyran compound: 3-methyl-3-spiro-dinaphthopyran, 1,3,3-trimethyl-6-nitro-
8'-methoxy-spiro (indoline -2, 2'base Nzopiran) such as, diphenyl methane compounds: N- halophenyl - such as leucoauramine, thiazine compounds: downy emissions benzoyl leuco methylene blue, etc., lactam compounds: Rhodamine - Fluorene compounds such as B-anilinolactam: 3,6-bis (dimethylamino)
Fluorene spiro (9,3 ')-6'-dimethylaminophthalide, [3,6-bis (dimethylamino) fluorene spiro (9,3')-6'-pyrrolidinophthalide], [3-dimethylamino -6-diethylaminofluorenespiro (9,3 ')-6'-pyrrolidinophthalide]. These color formers are used alone or as a mixture.

Further, as a color developer, p-octylphenol, p-tert-butylphenol, 1,1-bis (p
-Hydroxyphenyl) propane, 2,2-bis- (p
-Hydroxyphenyl) cyclohexane, 4,4'-thiobisphenol, 4,4'-sulfonyldiphenol, bis- (3-allyl-4-hydroxyphenyl) sulfone, novolak-type phenolic resin, benzyl p-hydroxybenzoate, p -Ethyl hydroxybenzoate, 4
Dimethyl-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-tert-butylsalicylic acid,
In the case of 3,5-di-α-methylbenzylsalicylic acid and the like, and aromatic carboxylic acids, polyvalent metal salts thereof can be mentioned.

As the binder constituting the heat-sensitive layer, methyl cellulose, methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, silica-modified polyvinyl alcohol, styrene acrylate Alkaline salt of copolymer, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, alkali salt of styrene-maleic anhydride copolymer, iso (or diiso) butylene-maleic anhydride copolymer Water-soluble substances such as coalesced alkali salts, or polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene, styrene / butadiene /
A water-insoluble emulsion such as an acrylic acid copolymer is used.

Examples of the filler include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum oxide, barium sulfate, polystyrene resin, and urea-formalin resin. . Examples of sensitizers include waxes such as animal and vegetable waxes, polyethylene waxes, synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, acetyl compounds of aromatic amines, aromatic ether compounds, and biphenyl derivatives. And those which are solid at ordinary temperature and have a melting point of 80 ° C. or more. Other additive materials, zinc stearate, calcium stearate, lubricants such as scan Te stearic acid aluminum and the like, and other various surfactants, can be added as necessary such as defoamers.

As a method of forming a heat-sensitive layer using the above materials, first, a color former and a color developer are separately separated from each other with a binder, water or other additives as necessary, a protective colloid substance such as polyvinyl alcohol, After pulverizing and dispersing with a dispersing machine such as a ball mill, attritor, or sand mill together with a surfactant or the like (usually, a color former or a developer is 5 to 70% of the system used for dispersion, and a binder is 5 to 50%).
% And 30 to 90% of water and then pulverized and dispersed. ), To prepare a heat-sensitive layer coating solution (the ratio of the color former to the developer is usually 1: 1 to 1:10 by dry weight ratio).
It is. ), Paper, plastic sheet, coated by a bar coater so that 5 to 40 g / m ² on a support such as synthetic paper, it is possible to obtain a heat-sensitive layer by the this drying.

In the present invention, an intermediate layer may be provided between the heat-sensitive layer and the overcoat layer. In the case where the intermediate layer is provided, a hydrophilic or water-soluble material such as polyvinyl alcohol, starch, styrene / butadiene latex / acrylic resin emulsion, etc. The main component is dispersible resin, solvent-soluble resin such as polyester resin, copolymer of acrylic resin and vinyl acetate resin. If necessary, calcium carbonate, zinc oxide, talc, kaolin, clay, colloidal silica, etc. Can be provided by applying a coating solution to which a filler such as the above and various auxiliaries such as surfactants are added in a usual manner.

When an intermediate layer is formed by using these materials, for example, the hydrophilic resin, the water-dispersible resin or the solvent-soluble resin is mixed with water or, if necessary, other fillers and surfactants in a ball mill, After dispersing with a dispersing machine such as an attritor or a sand mill (the resin component is usually contained in an amount of 5 to 80% of the system to be dispersed, and then dispersed), and then on the heat-sensitive layer obtained as described above. An intermediate layer is formed by applying a coating solution with a bar coater or the like so as to have a coating liquid amount of ² to 40 g / m ² and drying the coating solution.
The emulsified / dispersed UV or EB-curable resin is applied directly on the intermediate layer thus formed and also on the heat-sensitive layer to form an overcoat layer (water is evaporated).
And curing) to obtain the thermosensitive recording medium of the present invention.

The UV or EB curable resin used for the overcoat layer includes the following prepolymers and monomers. Prepolymers include epoxy (meth) acrylate, urethane (meth) acrylate, saturated polyester / styrene, polyethylene (meth) acrylate, polyether (meth) acrylate, silicon (meth) acrylate, polybutadiene (meth) acrylate, and polyene / thiol. , Polystyrylethyl (meth) acrylate, polyamide (meth)
Acrylate and the like. Examples of the monomer include vinyl monomers such as styrene, vinyl acetate, and N-vinylpyrrolidone, butyl acrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-decyl acrylate isobonyl acrylate, dicyclopentenyloxy ethyl acrylate, Monofunctional monomers such as phenoxyethyl acrylate, 1,4-butanediol diacrylate, 1,6
Hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol 400 diacrylate, tripropylene glycol diacrylate, bisphenol A diethoxy diacrylate, tetraethylene glycol diacrylate, hydroxypivalate neopentyl glycol diacrylate, Examples include polyfunctional monomers such as trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

Examples of photoinitiators usually required when using a UV-curable resin include acetophenone, benzophenone, benzoin ether, chloroacetophenone, diethoxyacetophenone, hydroxyacetophenone, α-aminoacetophenone, benzylmethylketal, Thioxanthone, α-acyl oxime ester, acyl phosphine oxide, glyoxy ester, 3-ketocoumarin, 2-ethylanthraquinone,
Camphorquinone, downy Njiru, but Michler's ketone and the like, this these photoinitiators can also be used Oite the present invention.

The emulsifying and dispersing agents usable in the present invention include polyoxyethylene alkyl ether, polyoxyethylene alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene derivative, oxyethylene Oxypropylene block copolymer.
Nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters and polyethylene glycol fatty acid esters, fatty acid salts, alkyl sulfate salts, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ethers Anionic properties such as terdisulfonate, alkyl phosphate, polyoxyethylene alkyl sulfate, naphthalene sulfonate formalin condensate, special polycarboxylic acid type polymer surfactant, polyoxyethylene alkyl phosphate, etc. There are various commercially available emulsifying and dispersing agents such as surfactants. Depending on the type of UB or EB curable resin to be emulsified and dispersed, one or several kinds may be selected. Used in combination with emulsifying and dispersing agents Rukoto can also.

The amount of the emulsifying / dispersing agent used is usually in the range of 0.5 to 30% by weight, more preferably 1 to 20% by weight, based on the total solid content of the overcoat liquid. When the amount is less than 0.5% by weight, a stable emulsion cannot be obtained. On the other hand, when the amount exceeds 30% by weight, problems such as adhesion to heads and storage stability occur.

UV or EB excellent in heat resistance as described above
UV or EB after applying the emulsion of the curable resin through the intermediate layer or directly on the heat sensitive layer and evaporating the moisture
When cured, a thermosensitive recording medium with high gloss can be obtained without coloring the thermosensitive layer. However, in order to further enhance the effect of preventing sticking to the head and preventing sticking during high-speed printing, UV Or, prior to emulsifying and dispersing the EB-curable resin, an inorganic pigment such as calcium carbonate, magnesium carbonate, magnesium oxide, aluminum oxide, silicon dioxide, talc, clay, kaolin, or colloidal silica, or an inorganic pigment thereof is preliminarily incorporated into the resin. Lubricants and radical-reactive silicones such as pigments obtained by surface-treating with organic acids, organic pigments such as styrene microballs and polyethylene powder, zinc stearate, stearic amide, aspartate derivatives, alkyl phosphate ester compounds, and polyethylene wax Macromer, terminal hydroxyl It was added reactive silicone compound such as a polyester modified siloxane, a ball mill, a roll mill, allowed to disperse by a sand mill, which can also be obtained overcoating solution by emulsification and dispersion.

In the overcoat liquid, the above-mentioned UV or EB curable resin, emulsifying / dispersing agent and pigment,
Additives such as polymers, leveling agents, defoamers, ultraviolet absorbers, fluorescent dyes, fluorescent pigments, coloring dyes, coloring pigments, etc., as necessary, in addition to the lubricant and the silicone compound having a polymerizable unsaturated group can do. As a method of emulsifying and dispersing the components forming the overcoat layer in water, a generally known method is used. For example,
After dissolving or dispersing the emulsifying / dispersing agent in water, while slowly stirring the phase containing the UV or EB curable resin, slowly add the aqueous phase in which the emulsifying / dispersing agent is dissolved or dispersed in advance, Emulsification and dispersion (UV or EB) using a high-speed stirrer such as a homomixer or sand mill or a microfluidizer
The curable resin composition is 20 to 90% of the system used for dispersion, and the pluronic type emulsifier / dispersant is 0.5 to 10%.
%, A pigment is 0.5 to 10%, a lubricant is 0.5 to 5%, and a silicone compound having a polymerizable unsaturated group is 0.5 to 10%.
% Emulsification / dispersion is performed. ), But the method is not limited to this.

The milky white UV- or EB-curable resin thus obtained has a uniform emulsion which is stable with time, and the emulsion diluted with water as required for coating is also stable. It is. As a method of forming an overcoat layer, the obtained emulsion is coated on the heat-sensitive layer or the intermediate layer by a method known per se using a gravure coater, a screen printer, a flexo printer, or the like, and the water is evaporated. You. Although the coating amount is not particularly limited, the object of the present invention cannot be achieved if the dry weight is 0.2 g / m ² or less, and the dry weight is 20 g / m ^2.
If m ² or more, the recording sensitivity of the heat-sensitive layer may decrease. Therefore, it is usually preferable to apply the coating in a dry weight of 0.2 to 20 g / m ² , more preferably 0.5 to 10 g / m ^2. .

When the overcoat layer coated as described above is cured by an electron beam, an electron beam accelerator having an energy of 100 to 500 eV is preferable. On the other hand, when curing with ultraviolet light, an ultraviolet irradiation device having a xenon lamp, a high-pressure mercury lamp, and a metal halide lamp is used as a light source, and the light amount and the arrangement of the light source are determined as necessary. ~ 120W /
Conveyance speed of 20-60 m / m by lamp with light intensity of cm
In, it is preferable to cure by irradiating 1 to 4 times.

[0025]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. still,
In the examples, parts mean parts by weight.

Example 1 Formation of Thermosensitive Coloring Layer [A] Solution: 2- (o-fluoroanilino-6-diethylaminofur 20 parts Oran 25% PVA aqueous solution 8 {water 72} [B] Solution: bis (3- Allyl-4-hydroxyphenyl) sulfone 10 parts p-benzyldiphenyl 8 25% PVA aqueous solution 10 water 72% [C] solution: calcium carbonate 40 parts 25% PVA aqueous solution 8 water 52% Using a sand grinder, they were separately ground and dispersed so that the average particle size became 1 to 3 μm.

Next, 10 parts of [A] liquid, 55 parts of [B] liquid,
[C] 30 parts of the liquid and 5 parts of the water-containing carboxylated SB latex copolymer (solid content = 50%) were mixed to prepare a thermosensitive layer coating solution, and the dry solid content was 9 g / m ² on a high quality paper. It was coated and dried to obtain a heat-sensitive sheet. Intermediate layer formation PVA 25 parts Water 74 コ ロ イ ド Colloidal silicate 1 を Mix the above composition to prepare an intermediate layer coating solution, and place on the polyester sheet with heat-sensitive layer obtained in Coating and drying were performed to ² g / m ² to obtain a thermal paper having an intermediate layer.

Formation of Overcoat Layer An overcoat layer coating solution having the following composition is applied to the obtained thermal paper having an intermediate layer so that the dry weight becomes 2 g / m ^2, and water is evaporated. After that, the resin component is cured by irradiating the resin component twice with a UV irradiation device (GS ASE-20; manufactured by Nippon Battery Co., Ltd.) having a high pressure mercury lamp of 80 W / cm at a transport speed of 40 m / min to cure the resin component, thereby forming an overcoat layer. The thermosensitive recording medium of the present invention was obtained. Dipentaerythritol hexaacrylate 25 parts (trade name: Kayarad DPHA, manufactured by Nippon Kayaku Co., Ltd.) Trimethylolpropane triacrylate 7〃 (trade name: Kayarad TMPTA, manufactured by Nippon Kayaku Co., Ltd.) Tripropylene glycol diacrylate 8 〃 (trade name: Kayarad TPGDA, manufactured by Nippon Kayaku Co., Ltd.) Photoinitiator (Irgacure 184 manufactured by Nippon Ciba Geigy Co., Ltd.) 5〃 Pluronic F-68 (oxyethylene / oxypropylene block-produced Co., Ltd.) 5 〃 water 50〃

Example 2 The heat-sensitive recording of the present invention was carried out in the same manner as in Example 1 except that 5 parts of calcium carbonate having an average particle size of 0.2 μm was further used as a component to form an overcoat. I got a body.

Example 3 Example 1 was repeated in the same manner as in Example 1 except that 2 parts of magnesia (high-purity ultrafine magnesia 500A: manufactured by Ube Industries, Ltd.) was used in combination as a component to form an overcoat. A thermosensitive recording medium of the present invention was obtained.

Example 4 Example 1 was repeated except that 5 parts of zinc stearate were used in combination as a component to form an overcoat.
In the same manner as in the above, a thermosensitive recording medium of the present invention was obtained.

Example 5 The procedure of Example 1 was repeated, except that 3 parts of a phosphate ester surfactant (trade name: Perex RP, manufactured by Kao Corporation) was used in combination as a component to form an overcoat. In the same manner as in Example 1, a thermosensitive recording medium of the present invention was obtained.

Example 6 In Example 1, a radical-reactive silicone macromer (trade name: X) was used as a component to form an overcoat.
-24-8200, manufactured by Shin-Etsu Chemical Co., Ltd.) in the same manner as in Example 1 except that 5 parts of the heat-sensitive recording material of the present invention was obtained.

Example 7 In Example 1, phenoxy hexaethylene glycol acrylate (trade name: NK ester AMP-60) was used in place of tripropylene glycol diacrylate.
G: Shin-Nakamura Chemical Co., Ltd.) was used to obtain a thermosensitive recording medium of the present invention in the same manner as in Example 1.

Example 8 Example 1 was repeated except that caprolactone-modified hydroxypivalate neopentyl glycol diacrylate (trade name: KAYARAD HX-620, Nippon Kayaku Co., Ltd.) was used instead of tripropylene glycol diacrylate. In the same manner as in Example 1, a thermosensitive recording medium of the present invention was obtained.

Example 9 In Example 1, Pluronic F10 was used instead of Pluronic F68 among the components to form an overcoat.
Except for using Sample No. 8, a thermosensitive recording medium of the present invention was obtained in the same manner as in Example 2.

Example 10 Example 1 was repeated except that no intermediate layer was provided.
In the same manner as in the above, a thermosensitive recording medium of the present invention was obtained.

Comparative Example 1 A comparative 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 thermal recording media, characters were printed with a dot-line thermal printer having a resistance value of 239 ohms to evaluate the runnability and storability. Table 1 shows the results. It was shown to. The following evaluation criteria were adopted.

[0040]

(1) Sticking evaluation criteria A: During high-speed printing, no sound was recorded at all, and recording was performed smoothly. ；: At the time of high-speed printing, recording was performed smoothly with almost no sound. Δ: Recording failure occurred very slightly during high-speed printing. X: The thermal recording medium did not run smoothly and recording failure occurred. (2) Evaluation criteria for head residue adhesion A: No head dirt was found at the time of high-speed printing. ；: At the time of high-speed printing, there was almost no dirt on the head. Δ: After performing high-speed printing, the head was very slightly stained. X: The head was dirty after high-speed printing.

(3) Water resistance test ；: Even when the thermosensitive recording medium colored as described above was immersed in water at 20 ° C. for 24 hours, there was almost no fading of the colored portion. C: The color-developed part faded when the thermosensitive recording medium colored as described above was immersed in water at 20 ° C. for 24 hours. (4) Plasticizer resistance test ；: A plasticizer (D
Even when OP) was dropped, almost no fading was observed. ×: A plasticizer (D) was placed on the heat-sensitive recording material colored as described above.
When OP) was dropped, fading was observed.

(5) Stability test ；: Even when the obtained emulsion was allowed to stand, no layer separation occurred. Δ: Even if the obtained emulsion was allowed to stand, there was little layer separation. X: When the obtained emulsion was allowed to stand, the layers were separated.

[0044]

According to the present invention, by applying an emulsion using a UV-curable resin and evaporating water to form a cured film, the safety of the human body and the environment during production is enhanced, and high-speed printing is achieved. As a result, a heat-sensitive recording material and a high-gloss heat-sensitive recording material having good preservability of a color image were obtained.

Claims (4)

(57) [Claims] 1. A heat-sensitive layer containing a color former and the developer provided on a support, in yet heat-sensitive recording material forming the overcoat layer, dispersed and the U V hardening type resin as the overcoat layer in water A thermosensitive recording material comprising a cured film formed by coating an emulsified emulsion and evaporating water. 2. The heat-sensitive recording material according to claim 1, wherein the emulsion contains a fine powder of a pigment. 3. The thermosensitive recording medium according to claim 1, wherein the emulsion contains a lubricant. 4. The heat-sensitive recording medium according to claim 1, wherein the emulsion contains a reactive silicone compound.