JPH06278370A - Thermal recording label - Google Patents

Abstract

PURPOSE:To prevent a recording image from being erased by an oily matter and to enhance a heat response and an image shelf stability by a method wherein in a thermal recording label, in which thermal recording cohesive particles essentially composed of a dye precursor, a color developer shown by a formula, and a sensitizer and made to cohere with each other by a dispersing agent are incorporated in a thermal recording layer, and a release sheet is bonded to a rear surf ace of a substrate. CONSTITUTION:A color developer is composed of one or more kinds of salicylic acid derivatives shown by a formula or metallic salts thereof. Thermal recording cohesive particles essentially composed of three components, i.e., a dye precursor, the color developer, and a sensitizer, and made to cohere with each other by a cationic dispersing agent are incorporated in a thermal recording layer. A release sheet is bonded to a rear surface of a substrate through an adhesive layer. In the formula, X and Y represent hydrogen atom or halogen atom, and R represents alkyl group or aryl group. In this manner, the cationic dispersing agent forms a pseudo coating on the surfaces of the cohesive particles so as to isolate the particles from an oily matter, such as a plasticizer, from the external. In this manner, the release sheet can be bonded to the surface of the substrate opposite to the thermal recording layer-coated surface through the adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording label excellent in heat response and image storability, and particularly to heat-sensitive recording in which disappearance of a recorded image due to an oily substance in an adhesive layer is prevented. It is about a label for use.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally has a heat-sensitive recording layer containing a colorless or light-colored dye precursor and a color developer which reacts upon heating to develop the color of the dye precursor. When provided with a heating head, a heating pen, a laser beam, etc., a dye precursor and a developer react instantaneously to obtain a recorded image. JP-B-43-4160
It is disclosed in Japanese Patent Publication No. 45-14039. Such heat-sensitive recording materials have the advantages that recording can be obtained with a relatively simple device, that they are easy to maintain, and that they do not generate noise.Measurement recorders, facsimiles, printers, computer terminals, labels, etc. It is used in a wide range of fields such as ticket vending machines.

[0003] In particular, as the label, a product label for displaying the type, price, quality, capacity, etc. of the product, a mailing product, a label for displaying an address attached to courier, etc. are widely used. As the recording method, a type ribbon method, an imprint method and the like have been used, but there are problems of maintenance such as noise, ink and ribbon replenishment. On the other hand, the heat-sensitive recording method obtains a color image by an instantaneous chemical reaction due to heat, and the apparatus is small, the recording speed is high, the noise,
There are few environmental pollution and maintenance problems, and there are advantages such as low cost, and its application as a label is progressing.

Various publications have heretofore been disclosed regarding thermal recording labels. For example, the actual exploitation sho 62-26
No. 216 can be cited. 62-26
No. 216, a release paper is attached to the back surface of a support through a pressure-sensitive adhesive layer (adhesive layer in the present invention), and a thermosensitive coloring layer (thermosensitive recording layer in the present invention), a water-soluble layer on the surface of the support. Disclosed is a heat-sensitive recording release label provided with a barrier layer (protective layer) made of a hydrophilic polymer. This publication prevents the disappearance phenomenon of recorded images when organic resin films are stacked for a long period of time. This is because the plasticizer contained in the organic film affects the recorded image and is intended to be prevented by the barrier layer. However, with regard to the prevention of the disappearance of the recorded image, it is intended to prevent the penetration of the plasticizer from the barrier layer, that is, the protective layer that protects the thermosensitive coloring layer, and the disappearance of the recorded image from the pressure-sensitive adhesive layer is mentioned. Not not.

The release label for heat-sensitive recording is one in which the release paper that has been attached is peeled off and the pressure-sensitive adhesive layer is attached to the other part to be attached, and it is attached by an adhesive action. In this case, the adhesive of the pressure-sensitive adhesive layer is one that can exert an adhesive effect at room temperature, and the adhesive generally contains an oily substance, for example, a low-molecular organic solvent. . The oily substance of the pressure-sensitive adhesive layer penetrates into the support, affects the recorded image of the thermosensitive coloring layer, and causes the recorded image to disappear.

As described above, in the conventionally known peeling label for heat-sensitive recording, the means for preventing the disappearance of the recorded image due to an external factor is provided, but the disappearance of the recorded image due to the internal factor of the integrated label. The preventive measures were not resolved.

As for the thermal recording material including the thermal recording label, a thermal recording material excellent in thermal response has been desired with the development of a printing machine capable of high speed recording. Along with the speeding up of the printing machine, the current flowing through the thermal head is repeated for a short time of less than a few milliseconds, and the thermal energy generated thereby is transferred to the heat-sensitive recording material to carry out an image forming reaction. As described above, in order to carry out the image forming reaction by the thermal energy transferred in a short time, it is necessary to use a heat-sensitive recording material having excellent thermal responsiveness. In order to improve the thermal response, it is necessary to improve the compatibility between the dye precursor and the developer. Sensitizers are used as mediators of this compatibility. The sensitizer has a function of dissolving or incorporating a dye precursor and a developer in the vicinity when the sensitizer is melted by the transferred thermal energy to accelerate the color development reaction.

In recent years, a method has been adopted in which the thermal responsiveness of a thermal recording material is improved by developing this sensitizer. Examples of the sensitizer include, for example, JP-A-58-870.
No. 94 discloses a naphthol derivative as disclosed in JP-A-57-64.
In 592, a naphthoic acid derivative is disclosed in JP-A-58-1.
No. 12788 discloses a benzoic acid ester derivative, JP-A-60-122193 discloses parabenzyl biphenyl, JP-A-60-56588 discloses diphenoxyethanes, and JP-A-61-2242884 discloses sulfides. Etc., and various sensitizers have been conventionally disclosed.

However, regarding the thermal responsiveness of the heat-sensitive recording material, the demand is high, and a satisfactory heat-sensitive recording material has not been obtained yet.

Further, regarding the image storability, for example, as disclosed in the above-mentioned Japanese Utility Model Laid-Open No. 62-26216, a barrier layer, that is, a protective layer for protecting the heat-sensitive recording layer prevents the disappearance of the recorded image. However, there is no essential solution by the coloring component.

[0011]

As described above, in the conventional heat-sensitive recording label, the disappearance of the recorded image due to the oily substance in the adhesive layer is prevented, and the heat-sensitive recording having excellent thermal response and image storability is obtained. It is intended to provide a label for use.

[0012]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have prevented the loss of a recorded image due to an oily substance in an adhesive layer, and have excellent heat responsiveness and image storability. It provides a recording label. That is, the heat-sensitive recording label provided by the present invention usually supports a colorless or light-colored dye precursor, a heat-sensitive recording layer containing a sensitizer and a developer that reacts when heated to develop the dye precursor. In the heat-sensitive recording label provided on the body surface, the developer comprises at least one of salicylic acid derivatives represented by Chemical Formula 2 (general formula 1) or a metal salt thereof. A thermosensitive recording agglomerate containing the colorant and the sensitizer as essential components, and aggregating particles by a cationic dispersant in the thermosensitive recording layer. An adhesive layer is formed on the back surface of the support. It is characterized in that a release sheet is attached via the interposition.

[0013]

[Chemical 2] (In the formula, X ₁ and X ₂ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a halogen atom, and R represents an alkyl group, an alkenyl group, an aralkyl group or an aryl group.)

Further, the aggregative particles for heat-sensitive recording used in the present invention are characterized by having an average particle size of 2 to 30 μm.

In the heat-sensitive recording label of the present invention, it is a feature of the present invention to prevent the disappearance of the recorded image due to the oily substance in the adhesive layer.

The adhesive layer component is a polymer resin, a tackifier,
It is composed of a composition containing a fluid substance (softening agent) as a main component, and it is necessary to contain an oily substance at room temperature, such as a plasticizer, which is a fluid substance, in order to exhibit tackiness. Between the release sheet adhered to the opposite surface of the support through the adhesive layer, the oily substance which is a component of the adhesive layer penetrates into the support when left for a long time or at a temperature of room temperature or higher. Then, the heat-sensitive recording layer is reached. As a result, when recording is performed using the heat-sensitive recording label before recording, recording becomes impossible, and after recording, the recorded image of the heat-sensitive recording label disappears. As a method of preventing this, it is necessary to provide an intermediate layer of a pigment or the like between the support and the heat-sensitive recording layer or between the support and the adhesive layer, which has been conventionally relied upon.

In the heat-sensitive recording label of the present invention, it is not necessary to provide the above intermediate layer. That is, it is characterized in that the aggregate particles for heat-sensitive recording of the present invention are used as a heat-sensitive recording layer composition. The agglomerated particles for heat-sensitive recording of the present invention are three components of a dye precursor, a specific developer having excellent image storability, and a sensitizer, and the cationic particles are dispersed on the surface of the agglomerated particles. A pseudo film is formed by the liquid, which can block oily substances such as plasticizers from the outside. For this reason, a release sheet can be attached to the opposite surface of the support coated with the thermosensitive recording layer via an adhesive layer.

The heat-sensitive recording label of the present invention will be specifically described below.

Specific examples of the salicylic acid derivative represented by the above general formula 1 or the metal salt thereof of the present invention include the followings, but the present invention is not limited thereto. 3-n-butyloxysalicylic acid, 3-
n-pentyloxysalicylic acid, 3-n-hexyloxysalicylic acid, 3-cyclohexyloxysalicylic acid,
3-n-octyloxysalicylic acid, 3-n-decyloxysalicylic acid, 3-n-dodecyloxysalicylic acid,
3-n-tetradecyloxysalicylic acid, 3-n-hexadecyloxysalicylic acid, 3-n-octadecyloxysalicylic acid, 4-n-butyloxysalicylic acid, 4-
n-pentyloxysalicylic acid, 4-n-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid,
4-n-octyloxysalicylic acid, 4-n-decyloxysalicylic acid, 4-n-dodecyloxysalicylic acid,
4-n-tetradecyloxysalicylic acid, 4-n-hexadecyloxysalicylic acid, 4-n-octadecyloxysalicylic acid, 5-n-butyloxysalicylic acid, 5-
n-pentyloxysalicylic acid, 5-n-hexyloxysalicylic acid, 5-cyclohexyloxysalicylic acid,
5-n-octyloxysalicylic acid, 5-n-decyloxysalicylic acid, 5-n-dodecyloxysalicylic acid,
5-n-tetradecyloxysalicylic acid, 5-n-hexadecyloxysalicylic acid, 5-n-octadecyloxysalicylic acid,

6-n-butyloxysalicylic acid, 6-n
-Pentyloxysalicylic acid, 6-n-hexyloxysalicylic acid, 6-cyclohexyloxysalicylic acid, 6
-N-octyloxysalicylic acid, 6-n-decyloxysalicylic acid, 6-n-dodecyloxysalicylic acid, 6
-N-tetradecyloxysalicylic acid, 6-n-hexadecyloxysalicylic acid, 6-n-octadecyloxysalicylic acid, 5-n-hexanoylsalicylic acid, 5-n
-Octanoylsalicylic acid, 3-n-hexanoyloxysalicylic acid, 3-n-octanoyloxysalicylic acid, 3-n-decanoyloxysalicylic acid, 4-n-hexanoyloxysalicylic acid, 4-n-octanoyloxysalicylic acid, 4-n-decanoyloxysalicylic acid, 5-n-hexanoyloxysalicylic acid, 5-n-
Octanoyloxysalicylic acid, 5-n-decanoyloxysalicylic acid, 6-n-hexanoyloxysalicylic acid, 6-n-octanoyloxysalicylic acid, 6-n-
Decanoyloxysalicylic acid, 5-n-octanesulfonylsalicylic acid, 3-n-hexylaminosalicylic acid,
3-n-octylaminosalicylic acid, 3-n-decylaminosalicylic acid, 3-n-octadecylaminosalicylic acid, 4-n-hexylaminosalicylic acid, 4-n-octylaminosalicylic acid, 4-n-decylaminosalicylic acid, 4- n-dodecylaminosalicylic acid, 3-n-octanoylaminosalicylic acid, 3-n-decanoylaminosalicylic acid, 4-n-octanoylaminosalicylic acid,
3-n-decanoylaminosalicylic acid and the like.

In the metal salt of the salicylic acid derivative represented by the above general formula 1 of the present invention, the metal salt contains a monovalent metal salt such as sodium, potassium and lithium, but is preferably sparingly soluble in water. Or divalent water-insoluble,
It is a trivalent or tetravalent metal salt, more preferably divalent or 3
It is a valent metal salt.

Specific examples of the divalent, trivalent or tetravalent metal salt include zinc, cadmium, mercury magnesium, calcium, barium, nickel, tin, gallium, chromium, copper molybdenum, tungsten, zirconium, strontium, manganese, The salts of cobalt, titanium, aluminum and iron can be mentioned, but the salts of zinc, calcium, barium, nickel, manganese, cobalt and aluminum are preferable. In particular, zinc salt is preferable.

In the heat-sensitive recording label of the present invention, a release sheet is attached to the surface of the support opposite to the heat-sensitive recording layer coated surface via an adhesive layer. The label is obtained by laminating a non-coated surface of a support coated with a thermosensitive recording layer and an adhesive layer surface of a release sheet in which a release layer and an adhesive layer are sequentially coated on another support.

The components of the adhesive layer coated on the release sheet are
It is composed of a composition containing a polymer resin and a tackifier as main components.

As the polymer resin for the adhesive, styrene-butadiene latex, acrylonitrile-butadiene latex, neoprene, polyisoprene, butyl rubber, chlorinated rubber, polyisobutylene, polyacrylic ester, polyvinyl acetate, polyvinyl butyral, polyvinyl are used. Examples thereof include ether and polyvinyl chloride.

In addition, it is composed of a tackifier, a fluid substance (softening agent), a filler and the like. As a tackifier,
There are quasi-polymer resins, for example, natural resins such as rosin and dammar, polymerized rosins, modified rosins such as partially hydrogenated rosins,
Glycerin ester rosin, derivatives of rosin and modified rosins such as bentaerythrite ester rosin, polymers of α-pinene, polymers of β-pinene, polyterpene-based resins such as dipentene, terpenes-phenols, α-pinene-phenol copolymers, etc. Modified terpene, olefin polymer,
Aliphatic hydrocarbon resin such as diolefin polymer, cyclopentadiene resin, aromatic petroleum resin, phenol resin such as alkylphenol and modified phenol, alkylphenol-acetylene resin, styrene resin, xylene resin, coumarone indene Resin, vinyl toluene-
Examples thereof include α-methylstyrene copolymer.

Fluid materials (softening agents) include DOP and T
Examples thereof include plasticizers such as CP, DBP and BBP, fats and oils such as animal and vegetable fats and oils, and low molecular weight polymers.

Further, a tackifier, an antiaging agent, a stabilizer, a coloring agent, a cross-linking agent, an adhesion improver and the like can be added.

The release sheet which is adhered via the adhesive layer is composed of a release layer coated on the adhesive layer coated surface of paper, film or the like. As a release agent for the release layer, an oil type,
There are dispersion type and emulsion type. For example, dimethyl silicone, phenylmethyl silicone, alkyl aralkyl modified silicone, polyether modified silicone, fluoro modified silicone, amino modified silicone,
Examples thereof include epoxy-modified silicone.

Regarding the coating of the above-mentioned adhesive layer and release layer,
Coating can be performed using a known coating machine such as a reverse roll coater, a kiss coater, a nip coater, a gravure coater, a rod coater, an air knife coater. Regarding the coating amount of the adhesive layer and the release layer, the coating amount can be appropriately changed at the time of use, and the coating amount is not limited.

The heat-sensitive recording label of the present invention comprises three components of a dye precursor, a specific developer and a sensitizer as essential components, and these are aggregated with a cationic dispersant to form heat-sensitive recording aggregated particles. Is contained in the heat-sensitive recording layer.

The agglomerated particles for heat-sensitive recording are formed by aggregating the three components with a cationic dispersant, and the periphery of the three components is covered with a pseudo coating of the cationic dispersant. When used for, it is possible to prevent the oily substance in the adhesive layer from penetrating the support and adversely affecting the thermosensitive recording layer, and the excellent thermoresponsiveness described below and the features of the thermosensitive recording label of the present invention are provided. Is.

Regarding the agglomerated particles for heat-sensitive recording of the present invention,
The mixing ratio of the three components of the dye precursor, the color developer, and the sensitizer is 50 to 500 parts by weight with respect to 100 parts by weight of the dye precursor. Preferably, it is 100 to 300 parts by weight. Here, when the amount of each of the developer and the sensitizer is less than 50 parts by weight, when the unreacted product of the dye precursor exceeds 500 parts by weight, the unreacted product of the developer remains in a large amount. It is an economy.

The aggregative particles for heat-sensitive recording of the present invention contain three components consisting of a dye precursor, a developer and a sensitizer as essential components, and have an average particle diameter of 2 to 30 μm, preferably 3 to 20 μm.
m, more preferably 5 to 10 μm, but each of the three components is previously monodispersed or codispersed (dye precursor-sensitizer or developer-sensitizer combination) to give an average particle size of 0. ．
The one having a thickness of 1 to 0.5 μm is used. Usually, it is considered that the smaller these three components are, the higher the sensitivity becomes. However, the support used for the label for heat-sensitive recording is not completely smoothed on its surface, and irregularities due to pulp fibers are observed. Under the present circumstances, the finely dispersed particles enter the uneven portion of the pulp fiber, and the advantage of miniaturization is not fully utilized. Further, even when the heat-sensitive recording layer is coated on the intermediate layer mainly using the conventional pigment, since it has not been sufficiently smoothed, finely dispersed particles enter the uneven portion of the intermediate layer surface, It is not effective enough as an intermediate layer.

In the present invention, the aggregative particles for heat-sensitive recording are prevented from entering the irregularities on the surface of the intermediate layer and are uniformly arranged on the surface of the intermediate layer, so that high sensitivity is achieved. Furthermore, the agglomerated particles for heat-sensitive recording are finely dispersed 3
Since the components are close to each other, when the heat of the thermal head is transferred to the thermal recording agglomerated particles themselves, it has an advantage that the color is developed very efficiently.

The agglomerated particles for heat-sensitive recording have an average particle size of 2 to 30.
μm, preferably 3 to 20 μm, more preferably 5 to 1
It is 0 μm. It depends on the coating thickness of the thermosensitive recording layer. When the heat-sensitive recording agglomerated particles have a particle diameter equal to or larger than the coating layer thickness, the heat-sensitive recording agglomerated particles are exposed from the coating layer, resulting in poor surface smoothness, and cause of fog or the like. Become. On the other hand, if the average particle size is less than 2 μm, the effect cannot be sufficiently exhibited.

The aggregative particles for heat-sensitive recording of the present invention are obtained by aggregating a mixture of three components previously dispersed with an anionic dispersant with a cationic surfactant or a cationic polymer. Examples of the cationic surfactant include amine salts, quaternary ammonium salts, phosphonium salts, sulfonium salts and the like. As the cationic polymer, aminoalkyl methacrylate and its acrylamide copolymer, polyvinylpyridinium halide, polydiallylammonium halide, polyaminomethylacrylamide, polyvinylimidazoline, polyacrylamide Mannich modified product, polyethyleneimine polydiallylamine, polypyridinium halide chitosan. , Cationized starch, cationized cellulose, cationized polyvinyl alcohol, ionene-based condensate, epoxyamine-based condensate, cationized polymethacrylic acid ester resin, alkylenediamine-epichlorohydrin polycondensate, and the like.

Regarding the dye precursor used in the present invention,
Specific examples are (1) triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) ) Phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 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) -5-dimethylaminophthalide 3,3-bis (2-phenylindol-3-yl) -5- Dimethylaminophthalide, 3-p-
Dimethylaminophenyl-3- (1-methylpyrrole-
2-yl) -6-dimethylaminophthalide and the like (2) diphenylmethane compound 4,4′-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-halophenylleuco auramine, 2,4,5-trichlorophenyl Leuco auramine etc.

(3) Xanthene compound Rhodamine B anilinolactam, rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3- Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3 -Diethylamino-7
-(2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6- Methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilinofluorane,
3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-
Methyl-7-anilinofluorane, 3- (N-ethyl-
N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluorane and the like.

(4) Thiazine-based compounds Benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like.

(5) Spiro compound 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

In addition to the color developer used in the present invention, conventionally known color developers can be used in combination. Specific examples include phenol derivatives, aromatic carboxylic acid derivatives or metal compounds thereof. N, N'-diaryl thiourea derivative etc. are mentioned. Of these, particularly preferred are phenol derivatives, specifically, p-phenylphenol, p-hydroxyacetophenone, 4-hydroxy-4′-methyldiphenyl sulfone, 4-hydroxy-.
4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-benzenesulfonyloxydiphenyl sulfone, 1,1-bis (p-hydroxyphenylpropane, 1,1-bis (p-hydroxyphenyl) pentane, 1,1- Bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) cyclohexane, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) butane, 2, 2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethylhexane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 1,1-bis (P-Hydroxyphenyl) -1-phenylethane, 13-di [2-
(P-Hydroxyphenyl) -2-propyl] benzene, 1,3-di [2- (3,4-dihydroxyphenyl) -2-propyl] benzene, 1,4-di [2- (p
-Hydroxyphenyl) -2-propyl] benzene,
4,4'-dihydroxydiphenyl ether, 4,4 '
-Dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfone, 3,
3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfide, methyl 2,2-bis (4-hydroxyphenyl) acetate 2,2-bis (4 -Hydroxyphenyl) butyl acetate, 4,4'-thiobis (2-t-
Butyl-5-methylphenol), bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropyloxydiphenyl sulfone,
3,4-dihydroxy-4'-methyldiphenyl sulfone, p-hydroxybenzoic acid benzyl, p-hydroxybenzoic acid chlorobenzyl, p-hydroxybenzoic acid propyl, p-hydroxybenzoic acid butyl, 4-hydroxyphthalic acid dimethyl, gallic acid Examples thereof include benzyl acid salt, stearyl gallate, salicylanilide, and 5-chlorosalicylanilide.

Specific examples of the sensitizer used in the present invention include N-hydroxymethylstearic acid amide, stearic acid amide, palmitic acid amide, oleic acid amide, ethylene / bisstearic acid amide, and ricinoleic acid amide. Waxes such as paraffin wax, microcrystalline wax, polyethylene wax, rice wax and carnauba wax, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis Polyether compounds such as (3-methylphenoxy) ethane, 2,2′-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, dioxalate Examples thereof include carbonic acid such as (p-fluorobenzyl) ester and oxalic acid diester derivatives. These sensitizers can be used alone or in combination of two or more.

In addition, as a pigment, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide can be used in the heat-sensitive recording layer (also applicable to the intermediate layer). , Urea-formalin resin and the like are used. In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearamide, and castor wax, and dioctyl are also used. A dispersant such as sodium sulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, a surfactant, a fluorescent dye and the like are added as necessary.

As the binder for the intermediate layer or the heat-sensitive recording layer used in the present invention, various binders that are commonly used can be used. For example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol polyacrylic acid soda, acrylic acid amide / acrylic acid ester copolymer acrylic acid amide / acrylic acid ester / methacrylic acid ternary Water-soluble binders such as copolymers, alkali salts of styrene / maleic anhydride copolymers, alkali salts of ethylene / maleic anhydride copolymers, polyvinyl acetate, polyurethane, polyacrylic acid esters, styrene / butadiene copolymers , Latex of acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer ethylene / vinyl acetate copolymer and the like.

As the support used in the present invention, paper is mainly used, but a non-woven fabric, a plastic film, a synthetic paper, a metal foil, etc., or a sheet coated with a pigment or the like, or a combination thereof. Any composite sheet can be used.

[0047]

The label for heat-sensitive recording of the present invention is usually a colorless or light-colored dye precursor, a developer containing at least one salicylic acid derivative represented by the general formula 1 or a metal salt thereof, and a sensitizer. As an essential component, the heat-sensitive recording layer contains aggregating particles for heat-sensitive recording obtained by aggregating this with a cationic dispersant, and an adhesive layer is provided on the surface of the support opposite to the heat-sensitive recording layer coating surface. A release sheet is attached via the interposition.

By using these three components monodispersed or co-dispersed and finely divided particles of each component, the oily substance in the adhesive layer does not penetrate into the support and adversely affect the thermosensitive recording layer. . Further, the heat-sensitive recording label having excellent thermal responsiveness can be obtained without the agglomerated particles for heat-sensitive recording entering into the irregularities of the pulp fiber of the support. In particular,
Since the dye precursor and the fine particles of the color developer are in close proximity to each other, the heat-sensitive recording agglomerated particles can be a heat-sensitive recording label having further excellent thermal response. Furthermore, by using the specific color developer according to the present invention, a heat-sensitive recording label having excellent image storability can be obtained. For the above reasons, the heat-sensitive recording label of the present invention has an action not found in the conventional art.

[0049]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 1.3 Dispersion of Components A mixture having the following composition was ground and dispersed by a sand mill until the average particle diameter became about 0.2 μm. Here, anion-modified polyvinyl alcohol was used as the anionic dispersant. [Liquid A] Dispersion of dye precursor 3-dibutylamino-6-methyl-7-anilinofluorane 100 parts 10% polyvinyl alcohol aqueous solution 50 parts water 100 parts [Liquid B] developer-sensitizer co-dispersion Zinc 4-n-octyloxysalicylate 150 parts 2-benzyloxynaphthalene 150 parts 10% aqueous polyvinyl alcohol solution 150 parts water 300 parts

2.3 Agglomeration of Component 3 As a cationic dispersant, a 10% aqueous solution of cationized polyvinyl alcohol was used, and the dispersions of liquid A and liquid B obtained in the above 1 were mixed at the following ratios to prepare three components. Consisting of 1
A 0 μm aggregate particle for heat-sensitive recording was prepared. Liquid A (solid content of dye precursor: 100 parts) 250 parts Liquid B (solid content of developer and sensitizer: 250 parts each) 750 parts Cationic dispersant 200 parts

3. Preparation of heat-sensitive coating liquid The heat-sensitive coating liquid was prepared according to the following formulation using the aggregating particles for heat-sensitive recording having the average particle diameter of 10 μm obtained in the above 2. Aggregate particles for heat-sensitive recording (35%) 400 parts 40% zinc stearate 25 parts 10% polyvinyl alcohol aqueous solution 200 parts calcium carbonate 50 parts water 425 parts The heat-sensitive coating solution prepared in this manner is used as a base paper having a basis weight of 40 g / m ² . Coating amount (solid content) using a Mayer bar of 5 g /
It was coated so as to have a surface area of m ² , dried and then treated with a super calendar to prepare a heat-sensitive recording layer coated sheet.

4. Preparation of release sheet Using a gravure coater on a base paper having a basis weight of 40 g / m ² , a release agent made of oily dimethyl silicone was used at 1 g /
m ^{2 was} applied and a release layer was provided. Subsequently, an adhesive layer component having the following composition was applied onto the release layer so that the amount was 10 g / m ² . Chlorinated rubber 100 parts Ester gum 20 parts Dibutyl phthalate 120 parts 5. Preparation of label for heat-sensitive recording A label for heat-sensitive recording was prepared by sticking the non-coated surface of the coated sheet of the heat-sensitive recording layer prepared in 4 above and the coated surface of the adhesive layer of the release sheet prepared in 5 above so as to face each other. It was made.

Example 2 The same heat-sensitivity as that of Example 1 except that zinc 4-n-octyloxysalicylate used in Example 1 was replaced with zinc 4-n-octanoylsalicylate. Recording agglomerated particles were obtained and a thermosensitive recording label was prepared.

Example 3 A heat-sensitive material comprising 3 components in the same manner as in Example 1 except that zinc 4-n-octyloxysalicylate used in Example 1 was replaced with zinc 4-n-butyloxysalicylate. Aggregate particles for recording were obtained, and a thermal recording layer coated sheet was prepared in the same manner as in Example 1. On the other hand, as for the release sheet, a gravure coater is used on a base paper having a basis weight of 40 g / m ^{2 and} a release agent made of oily dimethyl silicone is added at 1 g /
m ^{2 is} applied, a release layer is provided, and then an adhesive layer component of 100 parts by weight of polyvinyl butyral resin and 50 parts of castor oil is applied on the release layer so as to have a concentration of 10 g / m ^2. It was made. The heat-sensitive recording layer coating sheet and release sheet produced as described above were laminated in the same manner as in Example 1,
A thermal recording label was prepared.

Example 4 A thermosensitive recording label was prepared in the same manner as in Example 3 except that the zinc 4-n-butyloxysalicylate used in Example 3 was replaced with zinc 4-n-octadecyloxysalicylate. It was made.

Comparative Example 1 2,2-bis (4-hydroxyphenyl) was used in place of the zinc 4-octyloxysalicylate used in Example 1.
A heat-sensitive recording label was produced in the same manner as in Example 1 except that propane was used.

Comparative Example 2 A heat-sensitive coating liquid was prepared as follows, using the dispersion liquid of the liquids A and B of Example 1 as it was. Liquid A 83 parts Liquid B 250 parts 40% Zinc stearate 25 parts 10% Polyvinyl alcohol aqueous solution 193 parts Calcium carbonate 50 parts Water 365 parts The coating solution thus prepared is applied to a base paper having a basis weight of 40 g / m ² and a Meyer bar. Coating amount (solid content) of 5 g / m
^It was coated so as to have a thickness of ² , dried, and then treated with a super calendar to prepare a heat-sensitive recording layer coated sheet. Subsequently, the release sheet prepared in Example 1 was used to bond the release sheet in the same manner as in Example 1 to prepare a label for heat-sensitive recording.

The thermal recording labels produced in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated as follows, and the evaluation results are shown in Table 1 below.

[Coloring property] A printing test was conducted using a facsimile tester TH-PMD manufactured by Okura Electric. A thermal head with a dot density of 8 dots / mm and a head resistance of 185Ω is used, a head voltage of 12V, a pulse width of 0.7 and 1.
Printing was performed by energizing for 0 millisecond (ms), and the color density was measured with a Macbeth RD-918 type reflection densitometer. [Image storability] After writing with a highlighter on the recorded image portion of each thermal recording label printed with a pulse width of 1.0 millisecond (ms) used in the evaluation of color development, after leaving at room temperature for 72 hours. The density of the recorded image portion was measured by a Macbeth RD-918 type reflection densitometer and shown as a ratio (%) to the color density at the time of printing. [Chemical resistance] The chemical resistance is to judge the influence of an oily substance which is a component in the adhesive layer. In this evaluation, the pulse width used in the evaluation of color development was 1.0 millisecond (m
Each thermal recording label printed in s) is 60 ° C-80% R
After maintaining for 72 hours under accelerated conditions, the density of the recorded image area was measured with a Macbeth RD-918 type reflection densitometer and shown as a ratio (%) to the color density at the time of printing.

[0057]

[Table 1]

From the results shown in Table 1, Examples 1 to 4 are heat-sensitive recording labels prepared by using the heat-sensitive recording aggregated particles of the present invention, and are excellent in color developability, image storability and chemical resistance. there were. On the other hand, Comparative Example 1 uses a color developer other than the present invention, has a low color developability, and is inferior in both image storability and chemical resistance. In Comparative Example 2, neither the dye nor the color developer was used as the dispersion for the heat-sensitive recording of the present invention, and the dispersion was used. Therefore, the color developability, the image storability and the chemical resistance were poor. However, the image storability and chemical resistance were better than those of the color developers other than the present invention used in Comparative Example 1.

Comparative Example 3 In the agglomeration of the three components according to Example 1, the amount of the 10% cationized polyvinyl alcohol aqueous solution used was increased to produce aggregative particles for thermal recording having an average particle diameter of 35 μm. Using the obtained heat-sensitive recording aggregated particles, a heat-sensitive recording label was produced in the same manner as in Example 1. However, on the surface of the heat-sensitive recording layer after coating, roughness due to agglomerated particles for heat-sensitive recording was observed, which was not preferable when used as a label for heat-sensitive recording. Therefore, the evaluation of the above-mentioned color developability, image storability, and chemical resistance has not proceeded.

Examples 5-7 Instead of the cationic dispersant used in Example 1, 15%
Aggregate particles for heat-sensitive recording were produced in the same manner as in Example 1 except that an aqueous solution of polyaminomethylacrylamide was used, and using this, a label for heat-sensitive recording was obtained in the same manner as in Example 1. Here, in Examples 5 to 7, the average particle diameter of the aggregating particles for thermal recording was 3 μm, 7 μm, and 20 μm, respectively.
And

The heat-sensitive recording labels produced in Examples 5 to 7 were evaluated in the same manner as above, and the evaluation results are shown in Table 2 below.

[0062]

[Table 2]

From the results shown in Table 2, in Examples 5 to 7, the average particle size of the aggregative particles for heat-sensitive recording was within the range of the present invention, and good color development results were obtained. The image storability was good in all cases using the color developer of the present invention.
Regarding the chemical resistance, the larger the average particle size of the aggregative particles for heat-sensitive recording is, the thicker the film for pseudo-coating the agglomerated particles becomes, and the better the chemical resistance is.

[0064]

The heat-sensitive recording label of the present invention comprises a heat-sensitive recording agglomerated particle comprising a dye precursor, a specific developer and a sensitizer in the heat-sensitive recording layer. A release sheet is adhered to the back surface of the body via an adhesive layer, which has excellent heat response and image storability. In particular, due to the effect of a pseudo coating of the agglomerated particles for heat-sensitive recording, the oil in the adhesive layer is The recorded image does not disappear due to the substance, and it has excellent chemical resistance. From the above, the thermal recording label of the present invention,
It has extremely high practical value.

Claims (2)

[Claims] 1. A heat-sensitive recording label provided with a heat-sensitive recording layer containing a normally colorless to light-colored dye precursor, a color developer that reacts when heated to develop the dye precursor and a sensitizer on the surface of a support. Wherein the developer is at least one of salicylic acid derivatives represented by Chemical Formula 1 (General Formula 1) or metal salts thereof.
In the heat-sensitive recording layer, agglomerated particles for heat-sensitive recording comprising at least three kinds of dye precursors, the color-developing agent and the sensitizer as essential components, and agglomerated by a cationic dispersant. And a release sheet bonded to the back surface of the support via an adhesive layer. [Chemical 1] (In the formula, X ₁ and X ₂ represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a halogen atom, and R represents an alkyl group, an alkenyl group, an aralkyl group or an aryl group.) 2. The thermal recording aggregating particles have an average particle diameter of 2 to 3.
The label for heat-sensitive recording according to claim 1, wherein the label is 0 μm.