JP2847732B2 - Thermal recording medium and resin composition for overcoating of thermal recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermosensitive recording medium. More specifically, the present invention relates to a thermosensitive recording medium having a high gloss surface property provided on a synthetic resin substrate having an overcoat layer made of a specific composition and a thermosensitive coloring layer.

(Prior Art) A thermal recording medium represented by thermal paper is composed of a coloring agent such as a leuco compound and an acidic substance which is a coloring agent, or a coloring agent such as an organic acid metal salt and a coloring agent. A certain organic reducing agent is separately dispersed in the form of fine particles in a water or organic solvent medium containing a water-soluble binder or an organic solvent-based binder, and the two are mixed to make paper, synthetic paper, synthetic resin film, etc. Is applied on the base material. Specific examples of such a heat-sensitive recording medium are disclosed in, for example, JP-B-44-3680, JP-B-45-14039, and JP-A-48-17344. Since such a heat-sensitive recording medium is made by applying a fine particle dispersion of several μm or less on a substrate and drying the dispersion, fine particles of several μm or less are arranged on the surface and have irregularities, and have a defect that the gloss is low. doing. As a technique for obtaining a heat-sensitive recording medium having a high gloss surface property, there is a proposal in which an intermediate layer having a specific smoothness is provided on the heat-sensitive recording layer, and thereafter, an electron beam-curable resin is overcoated (Japanese Patent Laid-Open No. 59-26291, JP-A-62-279980).

(Problems to be Solved by the Invention) However, at the time of color development by heating with a thermal pen or a thermal head, the components of the thermal recording medium melt and stick (stick) to the thermal head or the thermal pen or cause scum to adhere to the colored image. Lowering the density, sharpness, distortion of the color image, inconvenient paper feeding, or wear of the thermal head or thermal pen, etc.
There is a tendency that the so-called head matching property is reduced.

In particular, thermal recording media with a high gloss surface, made of synthetic paper or synthetic resin sheet, have a smooth surface, so the contact area with the thermal head is large, frictional resistance is large, and sticking is likely to occur. Become. Also, when dust enters between the surface of the thermal recording medium and the thermal head for some reason, the surface is smooth, so that the dust is not removed, and the printout phenomenon is likely to occur continuously in the image. is there.

(Means for Solving the Problems) In view of the current situation, using a base material made of a synthetic resin, having a high-gloss surface property, having no scum adhesion and sticking, and having little wear of a thermal head or a thermal pen, As a result of diligent research aimed at obtaining a thermosensitive recording medium with excellent so-called head matching properties, a thermosensitive recording medium using an active energy ray-curable resin composition in which inorganic fine particles are dispersed as a resin composition for overcoat is However, even when it uses a substrate made of a synthetic resin, it has been found that there is no such disadvantage as described above, and the present invention has been completed.

That is, the present invention provides a thermosensitive recording medium characterized by having a thermosensitive coloring layer and an overcoat layer of a specific active energy ray-curable resin composition in which inorganic fine particles are dispersed on a substrate made of a synthetic resin, And a resin composition for overcoating a heat-sensitive recording medium, comprising a specific active energy ray-curable compound and inorganic fine particles.

In the present invention, the combination of the coloring agent and the coloring agent contained in the thermosensitive coloring layer is not limited at all, and any combination may be used as long as the two are brought into contact by heat to cause a coloring reaction. Possible examples include a combination of a colorless or pale-colored basic dye and an inorganic or organic acidic substance, and a combination of a metal salt of a higher fatty acid such as ferric stearate and an organic reducing agent such as gallic acid. From the viewpoint of sharpness, a combination of a basic dye and an acidic substance is preferred.

Examples of the colorless or light-colored basic dyes include trienylmethane, triphenylmethanephthalide, fluoran, leuco-auramine, diphenylmethane, and the like.
Representative examples thereof include phenothiazines, phenoxazines, spiropyrans, indolines, and indigos, and among them, fluorans are preferred. Examples of the inorganic or organic acidic substance that forms a color upon contact with a basic colorless dye include, for example, 4,4′-isopropylidenediphenol, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4-hydroxybenzoate, benzyl-4-hydroxybenzoate, 4 ′
-Hydroxyacetophenone, 4-tertiaryoctylcatechol, 2,2'-dihydroxydiphenyl, 2,2 '
-Methylenebis (4-chlorophenol), 4,4'-secondary butylidenebis (2-methylphenol), 4,
Representative examples include various phenolic substances such as 4'-isopropylidenebis (2,6-dimethylphenol), fatty acids such as benzoic acid, salicylic acid, acid-tartaric acid, and gallic acid, and aromatic carboxylic acids. -4-
Hydroxybenzoate, 2,2'-dihydroxydiphenyl is preferred.

In the thermosensitive recording medium of the present invention, the use ratio of the color former and the color former in the color developing layer is appropriately selected according to the type of the color former and the color former to be used. 1 to 50 parts by weight, preferably 1 to 10 parts by weight, of acidic substance are used per part.

To prepare a coating solution containing these substances, generally, water is used as a dispersion medium, and a color former and a color former are dispersed together or separately by a stirrer such as a pole mill, an attritor, a sand grinder, or a pulverizer. Liquid.

In such a coating solution, as a binder, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, polyacrylic acid, casein, gelatin, starch, polyvinylpyrrolidone,
Water-soluble binders such as polyacrylamide and derivatives thereof. In addition, water-dispersible binders such as styrene-butadiene copolymer, polyvinyl acetate and polyacrylate can be used in combination with these water-soluble binders. These binders are used in an amount of 10 to 40% by weight, preferably 15 to 30% by weight of the total solids.

Furthermore, in the coating liquid, dispersant, ultraviolet absorber, defoamer,
Fluorescent dyes, colorants, inorganic pigments, sensitizers and the like can also be added.

In the heat-sensitive recording medium of the present invention, the method of forming the recording layer and the like are not particularly limited, and can be formed according to conventionally known and commonly used techniques, for example, air knife coating, variver blade coating, and pure blade coating. It is formed by a method of applying and drying a coating liquid by short dwell coating or the like. Although there is no particular limitation on the coating amount of the coating liquid, usually dry weight 2~12g / m ^2, preferably in the range of about 3 to 10 g / m ^2.

As the substrate used in the present invention, a paper or a film containing a synthetic resin as a main component, for example, a synthetic paper or a synthetic resin film is used in order to enhance the gradation of an image. Synthetic paper has a synthetic resin film with paper-like appearance and physical properties,
Examples include synthetic fibers made by wet or dry papermaking. Among them, synthetic paper in which a synthetic resin film is given the appearance and physical properties like paper is particularly preferable. As a method of manufacturing such a synthetic paper, there is a method of coating a surface of a synthetic resin film with a white pigment, or a method of adding a filler or a foaming agent to the synthetic resin film to make the synthetic resin film opaque. It can be used as a substrate of the present invention.

Examples of the synthetic resin film used as the substrate in the present invention include conventionally known synthetic resin films, for example, polyester films, polyolefin films, cellulosic films, polyamide films and the like.

In the heat-sensitive recording medium of the present invention, an overcoat agent obtained by curing with an active energy ray is provided on the surface of the heat-sensitive coloring layer thus obtained, but an intermediate layer may be provided therebetween. The coating material used for the intermediate layer may be any as long as it does not affect the heat-sensitive coloring layer, but a coating material mainly containing an aqueous resin is generally used.

Examples of the water-soluble resin used in the intermediate layer include completely saponified or partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, a reaction product of polyvinyl alcohol with a polyvalent carboxylic acid, an esterification product of these reaction products, and a carboxy-modified product. Polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, epoxy-modified polyvinyl alcohol; poly (meth) acrylamide, aldehyde-modified poly (meth) acrylamide, polystyrene- Maleic anhydride copolymers or 2-hydroxyethyl (meth) acrylates and acrolein to such an extent that water solubility is not impaired. Polymers obtained by copolymerizing N-vinylpyrrolidone, (meth) acrylonitrile, vinyl acetate, vinyl chloride, etc .; cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose; casein; arabic gum; oxidized starch, etherified starch, Water-soluble polymers such as aldehyde starch, esterified starch and the like, and emulsions such as styrene-butadiene copolymer emulsion, vinyl acetate-vinyl chloride-ethylene copolymer emulsion and methacrylate-butadiene copolymer emulsion Is raised.

Among these water-soluble resins, various modified polyvinyl alcohols, cellulose derivatives and casein are preferred, and acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol and epoxy-modified polyvinyl alcohol are more preferred.

The amount of the aqueous resin used is not particularly limited, but the content of the total solid component in the coating solution is usually 10 to 95% by weight, preferably 15 to 90% by weight.

Further, a pigment can be added to the intermediate layer in order to increase the smoothness. Specific examples of pigments include calcium carbonate,
Inorganic pigments such as aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler ,
Organic powders such as raw starch granules are exemplified. In addition, the amount of use is generally 5 to 500 parts per 100 parts by weight of the resin component.
It is preferable that the compounding is carried out in an amount of about part by weight, preferably about 80 to 350 parts by weight.

Furthermore, a water-proofing agent such as glyoxal, methylol melamine, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride, boric acid, ammonium chloride, etc. is added to the coating solution for forming the intermediate layer as necessary. If necessary, lubricants such as zinc stearate, calcium stearate, stearic acid amide, polyethylene wax, carnauba wax, paraffin wax, ester wax, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate Surfactants such as esters and sodium salts, alginates, and fatty acid metal salts, and various assistants such as benzophenone-based and triazole-based ultraviolet absorbers, defoamers, fluorescent dyes, and coloring dyes can also be appropriately added.

The coating liquid for forming the intermediate layer is generally adjusted 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 applied on the heat-sensitive recording layer by various known coating apparatuses. After the application, it can be dried by irradiating ultraviolet rays or electron beams.

When a curing agent is used in combination, the curing agent can be applied not only in the coating liquid for forming the intermediate layer but also separately from the coating liquid for forming the intermediate layer. There is an advantage that there is no need to worry about life and a strong curing agent can be selected.

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

In the thermosensitive recording medium of the present invention, an overcoat layer obtained by curing with an active energy ray is provided on the surface of the thermosensitive coloring layer having or not having one or two or more intermediate layers thus formed. , This coating layer comes in direct contact with a thermal head or thermal pen, is put under high pressure, and high temperature is applied, so that it has abrasion resistance, toughness,
Heat resistance is required. The heat-sensitive recording medium overcoating resin composition used for obtaining such coating film performance contains inorganic fine particles of an active energy ray effect type compound,
The active energy ray-curable compound contains an active energy ray-curable prepolymer (A) and an active energy ray-curable reaction diluent (B) as essential components.
If necessary, a compound (composition) containing a compound (C) having no active energy ray-curable unsaturated bond can be used. The active energy ray-curable prepolymer (A) referred to here has the general formula (I) because of its excellent heat resistance and abrasion resistance. [In the formula, n is an integer of 1 to 4, and X is at least 3 or more in the general formula: (Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a single bond, an alkylene group having 1 to 8 carbon atoms or 1 carbon atom.
Represents a polyoxyalkylene group having from 8 to 8 alkylene groups. ), The remainder being 1 carbon atom
To 8 alkyl groups, hydroxyl groups, amino groups, formula: OR ³ _m H
(Wherein R ³ represents an alkylene group having 1 to 8 carbon atoms, and m is a positive integer) or a group represented by the formula: OR
³ _m OH (wherein R ³ and m are as defined above). Is essential, and it is particularly preferable to use the compound of the formula (I) in combination with a radical polymerizable compound having a triazine ring, an isocyanurate ring or a cyanurate ring skeleton.

Specific examples of the compound represented by the general formula (I) include dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripentaerythritol pentaacrylate, tripentaerythritol hexaacrylate, and tripenterythritol heptaacrylate. And the like.

Further, as a radical polymerizable unsaturated compound having a triazine ring, an isocyanurate ring or a cyanurate ring skeleton, for example, triallyl cyanurate, triallyl isocyanurate, 1,3,5-triacryloylhexahydro-S-triazine, Tris (2-hydroxyethyl)
Ε-caprolactone per 1 mol of di (meth) acrylate of isocyanuric acid, tri (meth) acrylate of tris (2-hydroxyethyl) isocyanuric acid, and 1 mol of tris (2-hydroxyethyl) isocyanurate
(Meth) of alcohol obtained by ring-opening addition of 0.5-3 mol
Acrylic acid ester, polybasic acid (anhydride), polyhydric alcohol containing 10 mol% or more of tris (hydroxyalkyl) isocyanurate and polyester poly (meth) acrylate obtained by esterifying (meth) acrylic acid, Epoxy (meth) acrylate obtained by reacting (meth) acrylic acid with glycidyl tris (hydroxyethyl) isocyanurate, JP-A-58-87117
General formula (II) described (Where R in the formula represents a hydrogen atom or a methyl group, R 'represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and n is an integer of 1 to 20). There are radically polymerizable unsaturated compounds obtained by reacting the indicated isocyanuric acid derivative with one or more polyisocyanate compounds.

The active energy ray-curable reactive diluent (B) essentially used together with the component (A) in the present invention is a hydrophilic monomer such as β-hydroxyethyl (meth) acrylate, β-hydroxypropyl (meth) acrylate and It is at least one reactive diluent selected from the group consisting of 2-acryloyloxyethyl phosphate.
Other active energy ray-curable reactive diluents that can be appropriately selected and used in combination therewith include, for example, (meth) acrylic acid, methyl (meth) acrylate,
Ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, decyl (meth) acrylate, stearyl (meth) acrylate, n-hexyl (meth) acrylate, methoxyethyl (meth) ) Acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate,
-Hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy polyethylene glycol (Meth) acrylate, alkylphenoxyethyl (meth) acrylate, alkylphenoxypolyalkylene glycol (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, tetrahydrofurfuryloxypolyalkylene glycol (meth) acrylate, di Cyclopentenyl (meth) acrylate, dicyclopentenyloxyalkyl (meth) acryl Over DOO, dicyclopentenyloxyethyl polyalkylene glycol (meth) acrylate, 2-
Hydroxyalkyl (meth) acryloyl phosphate, vinyl acetate, vinyl propionate, polyfluoroalkyl (meth) acrylate, ethylene glycol di (meth) acrylate, propanediol di (meth) acrylate, butanediol di (meth) acrylate,
Neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acrylate, trimethylolpropanedi (Meth) acrylate,
Trimethylolpropane tri (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acryloylmorpholine, N-methyl (meth) acrylamide, N,
N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, Nn-butoxymethyl (meth)
Acrylamide, N, N'-methylenebis (meth) acrylamide, N-methylol (meth) acrylamide, 1,
3-di (meth) acrylamidomethyl 2-imidazoline,
Glycidyl (meth) acrylate, glycerol di (meth) acrylate, glycerol mono (meth) acrylate, glycerol (meth) acrylate alkylate, glycerol (meth) acrylate alkylate,
2- (1-aziridyl) -ethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, vinylpyrrolidone, vinylcaprolactam, divinylbenzene, trivinylbenzene, and the like. Further, carbamoyloxyalkyl (meth) acrylate, Examples include caprolactone-modified (meth) acrylate. In addition,
One or more reactive diluents (essential components and optional additional components) can be added.

Particularly, the reactive diluent desirably has a hydrophilic property in order to enhance the adhesion to the intermediate layer, and thus preferably contains a hydrophilic group. As the hydrophilic group, a phosphate group, a carboxylic acid group,
Examples include an acrylamide group, a pyrrolidone group, a morpholyl group, an amino group, a hydroxyl group, an epoxy group, a caprolactam group, an isocyanate group, and a tetrahydrofurfuryl group. Specific examples include 2-hydroxyethyl (meth) acryloyl phosphate, (meth) acrylic acid, β-hydroxyethyl (meth) acrylate / phthalic anhydride (1/1) reactant, N-methyl (meth) acrylamide,
N, N-dimethylaminopropyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide,
N, N'-methylenebis (meth) acrylamide, vinylpyrrolidone, (meth) acryloylmorpholine, diethylaminoethyl (meth) acrylate, β-hydroxyethyl (meth) acrylate, β-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate , Vinylcaprolactam, β-hydroxyethyl (meth) acrylate / isophorone diisocyanate (1 /
1) Reactants, such as tetrahydrofurfuryl (meth) acrylate.

Specific examples of the active energy ray-curable compound having no unsaturated bond include alkyl (meth) acrylate polymer, epoxy resin, liquid polybutadiene, liquid polybutadiene derivative, liquid chloroprene, liquid polypentadiene, and dicyclopentadiene derivative. , Saturated polyester oligomer, polyether oligomer, liquid polyamide,
Polyisocyanate oligomer, xylene resin, ketone resin, petroleum resin, fluorine-based oligomer, silicon-based oligomer, polysulfide-based oligomer and the like can be mentioned. Particularly, an alkyl (meth) acrylate polymer is preferable, and specific examples include methyl methacrylate, sec-butyl methacrylate, cyclohexyl methacrylate,
Isobutyl methacrylate, benzyl methacrylate,
Homopolymers such as phenyl methacrylate and ethyl methacrylate; methyl methacrylate / styrene = 80/2
0 parts by weight, methyl methacrylate / ethyl acrylate = 95/5, methyl methacrylate / methyl acrylate =
90/10, methyl methacrylate / n-butyl methacrylate = 40/60, methyl methacrylate / ethyl methacrylate = 30/70, methyl methacrylate / ethyl acrylate = 70/30, methyl methacrylate / methyl acrylate / methacrylic acid = 60/35/5 Copolymers such as methyl methacrylate / lauryl methacrylate = 90/10, methyl methacrylate / methyl acrylate / 2-hydroxyethyl methacrylate = 80/15/5, methyl methacrylate / iso-butyl methacrylate / dimethylaminoethyl methacrylate = 80/15/5 These polymers can be used singly or as a mixture of two or more.

The above-mentioned active energy ray-curable prepolymer (A),
The mixing ratio of the reactive diluent (B) and the compound having no active energy ray-curable unsaturated bond (C) is usually 40 to 100% by weight of the component (A) when the total is 100% by weight. The component (B) has a range of 0 to 60% by weight and the component (C) has a range of 0 to 40% by weight. From the viewpoint of being obtained, the range of 50 to 95% by weight of the component (A), 10 to 50% by weight of the component (B) and 5 to 35 parts by weight of the component (C) is preferable.

In the case of curing with ultraviolet light, a compound having at least one methacryloyloxy group or at least one acryloyloxy group as a polymerizable group in the components (A) and (B) may be used.
It is preferable to use one or more species.

The blending amount of the inorganic fine particles is determined by the above resin components (A) and (B)
And (C) in a total amount of 0.01 to 25 parts by weight with respect to 100 parts by weight. In particular, the effect of improving sticking is high and excellent gloss is obtained.
0.2 to 15 parts by weight is preferred.

Regarding the size of the inorganic fine particles, the average particle size is 0.1 to 5
It is required to be in the range of μm, and particularly preferably 0.1 to 3 μm from the viewpoint of obtaining excellent gloss.

The oil absorption of the inorganic fine particles needs to be in the range of 60 to 300 ml / 100 g.

Specific examples of the inorganic fine particles include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined clay, and colloidal silica. Of these, extenders are preferred, and calcium carbonate is particularly preferred.

Active energy rays include ultraviolet rays and electron beams, α rays, β
Ray, refers to ionizing radiation such as γ-rays, it is preferable to include a photopolymerization initiator and / or a photosensitizer in the resin composition for overcoating when using ultraviolet rays. When such an ionizing radiation is used, it is rapidly cured without including a photopolymerization initiator or a photosensitizer, and therefore, it is not necessary to particularly add it.

The photopolymerization initiator for radical polymerization may be, for example, benzoin, benzoin isobutyl ether, benzyl, benzophenone, or p.
-Chlorobenzophenone, carbonyl compounds such as p-methoxybenzophenone, tetramethylthiuram monosulfide, sulfur compounds such as tetramethylthiuram sulfide, azobisisobutyronitrile, azobis-2,
Examples include azo compounds such as 4-dimethylvaleronitrile, peroxide compounds such as benzoyl peroxide and ditertiary butyl peroxide, and examples of the photosensitizer include amine compounds such as aliphatic amines and aromatic amines; Ureas such as tolylthiourea, sulfur compounds such as sodium diethyldithiophosphate, s-benzylisothiuronium-p-toluenesulfonate, nitriles such as N, N-disubstituted p-aminobenzonitrile compound, and tri-n Phosphorus compounds such as -butylphosphine; and other nitrogen compounds such as N-nitrohydroxylamine derivatives.

These photopolymerization initiators and photosensitizers are as described in the above (A),
0.01 to 100 parts by weight of the total amount of the components (B) and (C)
Usually, it is used in the range of 10 to 10 parts by weight, preferably 1 to 8 parts by weight. If the amount exceeds 10 parts by weight, the storage stability deteriorates, which is not preferable.

In addition, at the time of curing, not only active energy rays but also heat may be used for curing. However, the heating must be performed to such an extent that the thermosensitive recording medium does not develop color. In the case of curing using both heat and active energy rays, a radical polymerization initiator and a curing accelerator may be added to the overcoat resin composition. Specific examples of the radical polymerization initiator include benzoyl peroxide, t-butyl perbenzoate and the like, and the above (A), (B) and (C)
Usually, 0.01 to 10 parts by weight is added to 100 parts by weight of the total of the components.

Examples of the curing accelerator include cobalt naphthenate, zinc naphthenate, dimethylaniline, dibutyltin laurate, and the like. Usually, 0.001 to 5 parts by weight based on 100 parts by weight of the components (A), (B) and (C) in total. Parts by weight, preferably
It is used in the range of 0.005 to 4 parts by weight.

When curing is performed by using both heat and ultraviolet light, it is possible to use the radical polymerization initiator together with a photopolymerization initiator and / or a photosensitizer. The total amount added is based on 100 parts by weight of the total of the components (A), (B) and (C).
0.01-10 weight is good.

In the case of curing using both active energy rays and heat, either one may be used first. That is, after curing by heat, it may be cured by active energy rays,
After the irradiation with the active energy ray, heat curing may be performed.
The active energy ray may be irradiated while heating.

The resin composition for overcoat of the present invention may further contain various additives as necessary, and may be used after being diluted with a solvent, if desired.

Examples of the additives include a thermal polymerization inhibitor, an organic silane compound, a leveling agent, a defoaming agent, a slip agent, a pinhole / crater inhibitor, a wetting improver and other coating surface improvers, a plasticizer, and a colorant. is there.

Among them, the addition of an organic silane compound is preferable because it improves the adhesion to the coloring layer or the intermediate layer, and aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N- β- (N-vinylbenzylaminoethyl) -γ
Silane coupling agents having an amino group, such as aminopropyltrimethoxysilane and hexamethyldisilazane; silane coupling agents having an epoxy group, such as β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-mercapto A silane coupling agent having a mercapto group such as propyltrimethoxysilane; and a total amount of the components (A), (B) and (C) of 10%.
Usually 0.01 to 10 parts by weight, preferably 0.05 to 0 parts by weight
It is used in the range of up to 5 parts by weight.

The coating surface improvers are (A), (B), (C) and (D)
Usually 0.001 to 5 parts by weight based on 100 parts by weight of the total amount of the components,
It is preferably used in the range of 0.005 to 4 parts by weight.

The overcoat resin composition is applied after being sufficiently mixed by a suitable mixing stirrer such as a mixer.
If necessary, the clay can be adjusted by heating.

The application method is not particularly limited, for example, gravure coat, roll coat, air knife coat, kiss coat,
There are spray coating, bridging coating, dip coating, spinner coating, wheeler coating, brush coating, solid coating using a silk screen, wire bar coating, flow coating, and the like, and printing methods such as offset printing and letterpress printing may be used. Among them, gravure coat, roll coat, air knife coat, kiss coat, wire bar coat, and flow coat are preferable in that a coated surface having high gloss surface properties can be obtained.

The coating amount of the overcoat resin composition is not necessarily limited, but is usually 0.1 g to 20 g / m ² ,
Preferably it is 0.5 to 10 g / m ² .

As an atmosphere for irradiating an active energy ray such as an ultraviolet ray or an electron beam, an inert gas atmosphere such as a nitrogen gas or a carbon dioxide gas or an atmosphere having a reduced oxygen concentration is naturally preferable, but a normal air atmosphere may be used.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples, but is not limited thereto. Further, unless otherwise specified, parts and% in the examples indicate parts by weight and% by weight, respectively.

Example 1 (I) Preparation of Liquid (Coloring Agent Dispersion) 3-Diethylamino-6-methyl-7-anilinofluoran 5.0 parts Stearic acid amide 10.0 parts 10% aqueous polyvinyl alcohol solution [PV manufactured by Kuraray Co., Ltd.]
A-117] 7.5 parts Water 25.5 parts Total 47.5 parts This composition was pulverized with a paint shoer to an average particle size of 3 μm.

(II) Liquid (colorant dispersion) preparation Bisphenol A 17.5 parts Calcium carbonate 17.5 parts 10% aqueous polyvinyl alcohol solution 7.5 parts Water 50.0 parts Total 92.5 parts This composition was averaged with a paint shaker at an average particle diameter of 3 μm.
And crushed until

Preparation of recording layer (I) solution 47.5 parts (II) solution 92.5 parts 40% aqueous glyoxal solution 2.5 parts 10% aqueous polyvinyl alcohol solution 25.0 parts water 7.5 parts 175.0 parts This composition was thoroughly stirred and mixed, and a 50% aqueous solution of triethanolamine was added. Was adjusted to 8 to obtain a coating solution for a heat-sensitive recording layer.

The obtained coating liquid is dried using a Meyer bar on the surface of a synthetic paper (Yupo PG # 60 made by Oji Yuka Synthetic Paper) obtained by forming a film containing a product containing polypropylene, a filler and additives. Was applied so that the coating amount became 8 g / m ^2, and was dried and cured by a dryer at 50 ° C. to obtain a thermosensitive recording medium.

Formation of intermediate layer 10% acetoacetylated polyvinyl alcohol aqueous solution [Z-100 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] 100 parts Calcium carbonate 10 parts Water 10 parts Total 120 parts After dispersing this composition with a paint shaker, liquid to the recording layer of the thermosensitive recording media obtained in the previous section was applied as the coating amount after drying of the 4g / m ² using a Meyer bar, dried, and cured at a 50 ° C. oven, the intermediate layer Was prepared.

Formation of Overcoat Layer On the intermediate layer of the heat-sensitive recording medium having the intermediate layer, the dry coating amount of the overcoat resin composition having the composition shown in Table 1 is shown.
The coating is 4g / m ^2, an ultraviolet lamp (Ai Cure Light H03-L31 manufactured by Eye Graphics Co., Ltd., 3 lights)
The film was irradiated with ultraviolet rays at a distance of 17 cm from the lamp and a transport speed of 30 m / 1 minute from the above to cure the coating film, thereby obtaining a thermosensitive recording medium having an overcoat layer of the present invention.

Quality Performance Test Next, a quality performance test of the heat-sensitive recording medium was performed.
Table 2 shows the results. The test items and the method are as follows.

1) Sticking: When a thermosensitive recording medium was printed with a commercially available image printer [UP-701 manufactured by Sony Corporation], the adhesion state of the sample to the thermal head was visually judged.
No sticking (good) ○, sticky (bad) ×, sticky (notably bad) XX.

2) Adhesion of scum: When printing on the thermal recording medium with the above-mentioned image printer, the state of scum adhesion to the thermal head was visually judged.

No residue attached (good) ○, residue attached (bad) ×
** 3) Misprinting: When printing on the thermal recording medium with the above-mentioned image printer, the state of missing printing continuously appearing on the image surface was visually determined.

No missing print (good) ○, missing print (bad) ×, missing print (significantly poor) XX.

4) Print density: The density printed (solid black) by the image printer was measured with a Macbeth reflection densitometer (RD-100R, manufactured by Macbeth).

5) Gloss: The gloss of the surface of the thermal recording medium before printing is measured with a digital gloss meter (GM-3D, manufactured by Murakami Color Research Laboratory).
Measured at 0 ° incidence angle.

6) Plasticity resistance: The colored heat-sensitive recording medium is sandwiched between vinyl chloride wraps (three layers) containing a plasticizer, brought into contact with the coloring surface, and the pressure is 10 g / cm ² and the ambient temperature is 40 ° C.
The degree of decoloration of the image after standing for one day and night was visually determined.

No change (good) ○, slightly erased (bad) ×,
7) Water resistance: After immersing the printed color-sensitive thermal recording medium in water for 5 minutes, rubbing the surface 5 times with gauze and visually assessing the degree of decoloration of the image did.

No change (good) ○, slight surface (bad)
×, decolorized (significantly bad) xx 8) Moisture resistance: After leaving the heat-sensitive recording medium with printed color in a constant temperature room at 40 ° C and a humidity of 95% RH for 24 hours, the degree of decolorization of the image was visually observed. Judged.

No change, (good) ○, slightly faded (bad)
×, more than half of the color was erased (significantly worse) ×× 9) Oil resistance correct: A few drops of salad oil were dropped on the heat-sensitive recording medium on which the color was printed, and after 30 minutes, the salad oil was wiped off with a gauze, and then the image was erased. The chromaticity was determined.

No change (good) ○, slightly erased (bad) ×,
Decolor more than half (notably bad) xx 1) DP5A: dipentaerythritol heptaacrylate 2) DP6A: dipentaerythritol hexaacrylate 3) Epoxy acrylate: Lipoxy SP-1509 manufactured by Showa Polymer Co., Ltd. 4) Urethane acrylate: Evecryl 220 manufactured by UCB, Belgium 5) Polyester Acrylate: Evecryl 810 manufactured by UCB, Belgium 6) HEA: hydroxyethyl acrylate 7) N-VP: N-vinylpyrrolidone 8) PA: 2-acryloyloxyethyl phosphate 9) DEAEA: diethylaminoethyl acrylate 10) AA: acrylic acid 11) 3P2A: Tripropylene glycol diacrylate 12) Acrylic polymer A: Copolymer of butyl methacrylate / methyl methacrylate = 60/40, Tg50 ° C 13) High molecular weight tertiary amine: Ubecryl P115 manufactured by UCB, Belgium 14) High molecular weight benzophenone: Belgium UC Ubecryl P36 manufactured by Company B 15) CADOX B-CH50: Peroxide manufactured by Kayaku Nury Co., Ltd. 16) Epoxysilane: γ-glycidoxypropyltrimethoxysilane 17) Aminosilane: Nβ-aminoethyl) γ-aminopropylmethyldimethoxy Silane 18) Kayaset Blue N: Dye made by Nippon Kayaku Co., Ltd. 19) Fine Seal K-40: Silica fine particles made by Tokuyama Soda Co., Ltd. Average particle size 1.5-1.8μm Oil absorption 270-300ml / 100g 20) Mizukasil P -527: Calcium carbonate fine particles manufactured by Mizusawa Chemical Industry Co., Ltd. Average particle size 1.8 μm Oil absorption 140-180 ml / 100 g 21) Callite SA: Calcium carbonate fine particles manufactured by Shiraishi Industry Co., Ltd. Average particle size 3.3 μm Oil absorption 80-100 ml / 100g 22) Mizukasil P-78D: Calcium carbonate fine particles manufactured by Mizusawa Chemical Industry Co., Ltd. Average particle size 8.0 μm Oil absorption 230ml / 100g 23) S-300: Calcium carbonate fine particles manufactured by Sumitomo Cement Co., Ltd. Average particle size 0.8 μm Oil absorption The average particle size is a value measured with a Coulter counter (aperture tube 50 μm), and the oil absorption is JI
This is the linseed oil absorption according to SK-5101.

Example 2 Surface-treated polyester film [Lumila-F60 manufactured by Toray Industries, Inc.] as a substrate on which a coating solution for a heat-sensitive recording layer is applied
And a thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that the plasticity shown in Table 1 was used as the overcoat layer, and then a quality performance test was performed in the same manner. Table 2 shows the results.

Example 3 Using the following composition as the intermediate layer, a 5% aqueous solution of epoxidized polyvinyl alcohol [DR-587, manufactured by Denki Kagaku Kogyo Co., Ltd.] 100 parts Calcium carbonate 10 parts Water 20 parts Total 130 parts As an overcoat layer, A thermal recording medium having an overcoat layer was obtained in the same manner as in Example 2 except that the composition shown in Example 1 was used, and a quality performance test was performed in the same manner as in Example 1. Table 2 shows the results.

Example 4 A 10% carboxylic acid-modified polyvinyl alcohol aqueous solution [KL-118 manufactured by Kuraray Co., Ltd.] 100 parts Calcium carbonate 10 parts Water 10 parts Total 120 parts As an overcoat layer, the following composition was used as the intermediate layer. The thermal recording medium having an overcoat layer was obtained in the same manner as in Example 9 except that the composition shown in Table 1 was used, and a quality performance test was performed in the same manner as in Example 1. Table 2 shows the results.

Comparative Examples 1 to 4 A thermosensitive recording medium having an overcoat layer was obtained in the same manner as in Example 1 except that the composition shown in Table 1 was used as the overcoat layer, and a quality performance test was performed in the same manner. Table 2 shows the results.

(Effects of the Invention) A heat-sensitive recording medium using the resin composition for overcoat of the present invention has a high gloss surface property and a good head matching property even when a base material made of a synthetic resin is used. It has the advantage of being superior.

Continuation of the front page (56) References JP-A-63-197687 (JP, A) JP-A-63-214475 (JP, A) JP-A-62-11680 (JP, A) JP-A-58-220791 (JP) JP-A-61-197277 (JP, A) JP-A-63-38319 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (4)

(57) [Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer and an overcoat layer of an active energy ray-curable resin composition in which inorganic fine particles are dispersed on a substrate made of a synthetic resin. The composition has the general formula (I) [In the formula, n is an integer of 1 to 4, and X is at least 3 or more in the general formula: (Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a single bond, an alkylene group having 1 to 8 carbon atoms or 1 carbon atom.
Represents a polyoxyalkylene group having from 8 to 8 alkylene groups. ), The remainder being 1 carbon atom
To 8 alkyl groups, hydroxyl groups, amino groups, formula: OR ³ _m H
(Wherein R ³ represents an alkylene group having 1 to 8 carbon atoms, and m is a positive integer) or a group represented by the formula: OR
Represents a group represented by ³ _m OH (wherein R ³ and m are the same as described above). And a hydrophilic monomer, β-hydroxyethyl (meth) acrylate, β
At least one reactive diluent selected from the group consisting of -hydroxypropyl (meth) acrylate and 2-acryloyloxyethyl phosphate; oil absorption of 60 to 300 ml / 100 g as the inorganic fine particles;
m of inorganic fine particles in an amount of 0.01 to
A thermosensitive recording medium comprising 5 parts by weight. 2. The heat-sensitive recording medium according to claim 1, further comprising an intermediate layer mainly composed of an aqueous resin between the heat-sensitive coloring layer and the overcoat layer. 3. A resin composition for overcoating a heat-sensitive recording medium containing an active energy ray-curable compound and inorganic fine particles, wherein the active energy ray-curable compound is represented by the general formula (I): [In the formula, n is an integer of 1 to 4, and X is at least 3 or more in the general formula: (Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a single bond, an alkylene group having 1 to 8 carbon atoms or 1 carbon atom.
Represents a polyoxyalkylene group having from 8 to 8 alkylene groups. ), The remainder being 1 carbon atom
To 8 alkyl groups, hydroxyl groups, amino groups, formula: OR ³ _m H
(Wherein R ³ represents an alkylene group having 1 to 8 carbon atoms, and m is a positive integer) or a group represented by the formula: OR
³ _m OH (wherein R ³ and m are as defined above). And a hydrophilic monomer, β-hydroxyethyl (meth) acrylate, β
At least one reactive diluent selected from the group consisting of -hydroxypropyl (meth) acrylate and 2-acryloyloxyethyl phosphate; oil absorption of 60 to 300 ml / 100 g as the inorganic fine particles;
m of inorganic fine particles in an amount of 0.01 to
A resin composition for overcoating of a thermosensitive recording medium, characterized by containing 5 parts by weight. 4. The resin composition according to claim 3, further comprising an organic silane compound (silane coupling agent).