JPH068068B2 - Thermal recording material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material capable of obtaining a high color density with significantly improved heat-sensitive color developing sensitivity.

<Prior Art> Generally, a heat-sensitive recording material for recording an image by heating and coloring using a thermal head, a hot pen, etc. is widely used as a recording paper for a computer output, a facsimile, a recorder, a ticket, a card, etc. Is also used.

This heat-sensitive recording material generally comprises a single-layer or multi-layered heat-sensitive color forming layer containing a binder or a leuco dye heat-sensitive color forming substance as a main component on a support such as paper or plastic film.

It is important for the heat-sensitive recording material to effectively utilize the minute heat obtained from the heat-sensitive head to obtain a high color development (printing) density. Conventionally, therefore, improvement or selection of a binder, a thermosensitive color-developing substance or an additive for the thermosensitive color developing layer has been performed.

However, the selection of the material for the leuco dye color forming layer is limited, and it has been extremely difficult to obtain particularly high sensitivity for heat-sensitive color forming.

<Problems to be Solved by the Invention> The present invention aims to obtain a heat-sensitive recording material in which the print density of the conventional leuco dye color-forming layer is improved, and minute heat given from the heat-sensitive head is released into the support. The present invention has been completed through repeated studies paying attention to the fact that keeping it in the heat-sensitive layer leads to an improvement in print density.

<Means for Solving Problems> The present invention relates to a heat-sensitive recording material having a leuco dye color-forming layer on a support, and contains bubbles due to photolysis of a photodegradable compound between the support and the leuco dye-coloring layer. The present invention relates to a heat-sensitive recording material characterized by being provided with the above intermediate layer and a method for producing the same.

The intermediate layer in the present invention is provided to prevent heat from escaping from the heat-sensitive layer, and is devised so that the thermal conductivity of the layer is as low as possible. That is, by incorporating air bubbles obtained by photodecomposing a photodecomposable compound into the intermediate layer, the thermal conductivity of the entire intermediate layer is lowered, diffusion of heat from the thermal head is prevented, and minute heat is generated. The present invention is intended to be efficiently concentrated and applied to the thermosensitive coloring layer. The present invention is composed of the following materials.

As the photodecomposable compound, a diazo compound and an azide compound which are rapidly photodecomposed by ultraviolet rays can be mentioned. As the diazo compound, those conventionally used in the field of diazo copying materials can be applied as they are. That is, specific examples thereof include 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenzene, and 4-diazo-1-diethylaminobenzene.
-Diazo-1-dipropylaminobenzene, 4-diazo-1-methylbenzylaminobenzene, 4-diazo-1
-Dibenzylaminobenzene, 4-diazo-1-ethylhydroxyethylaminobenzene, 4-diazo-1-diethylamino-3-methoxybenzene, 4-diazo-1
-Dimethylami-2-methylbenzene, 4-diazo-1
-Benzoylamino-2,5-diethoxybenzene, 4
-Diazo-1-morpholinobenzene, 4-diazo-1-
Morpholino-2,5-dimethoxybenzene, 4-diazo-1-morpholino-2,5-diethoxybenzene, 4-
Diazo-1-morpholino-2,5-dibutoxybenzene, 4-diazo-1-morpholino-2,5-diisopropoxybenzene, 4-diazo-1-anilinobenzene,
4-diazo-1-dimethylamino-3-carboxybenzene, 4-diazo-1-toluylmercapto-2,5-
Mention may be made of diethoxybenzene, 4-diazo-1-dimethylamino-2- (4'-chlorophenoxy) -5-chlorobenzene and the like.

The above diazo compound can be stabilized by forming a double salt of its chloride with a metal halide such as zinc chloride, cadmium chloride or tin chloride. Further, with the diazo compound, tetrafluoroboric acid, hexafluorophosphoric acid,
It may be stabilized by forming a complex salt with a fluoride acid such as fluorosulfuric acid or an organic boron salt such as sodium tetraboron.

On the other hand, an aromatic azide compound is particularly effective as the azide compound. That is, specific examples thereof include the following.

In addition to the above, the following compounds can be used in the present invention.

4,4'-diazido-diphenyl sulfone, 4,4'-diazidobenzosulfone, 4,4'-diazidostilbene, 4,4 '
-Diazidodibenzalacetone, 2,6-di- (4-azidobenzal) -4-methylcyclohexane, 4,4'-diazidodiphenyl sulfide, 1,2- (4,4'-diazidophenyl) ethane , 4,4'-diazidodiphenyl ether, 4,4'-diazido-diphenylmethane, 4,4'-diazidostilbene-2,2'-disulfonic acid sodium salt, azidobenzoic acid, azidobenzenesulfonic acid, etc. Can be raised. Since these azide compounds can be optically sensitized, a sensitizer may be added as necessary to improve practical photosensitivity.

The above diazo compounds and azide compounds may be used alone or in admixture of two or more. The amount of these photodecomposable compounds used is appropriately in the range of 0.1 to 80 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the total solid content in the intermediate layer.

Next, as the binder material system in which the photodegradable compound is dispersed, at least one selected from thermoplastic resins, waxes, and rubbers can be mentioned.

As the thermoplastic resin, a thermoplastic elastomer is particularly preferable. Specific examples thereof include olefin resins such as polyethylene, polypropylene, polybutylene and polybutadiene, acrylic resins such as polymethylmethacrylate and ethylene-ethyl acrylate copolymer, polystyrene, AS resin, BS resin, ABS resin and the like. Styrene resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene / vinyl acetate copolymer, vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinylidene chloride copolymer, propylene / vinyl chloride copolymer, etc. Vinyl resins, polyamide resins such as nylon 6, nylon 66, nylon 12, saturated polyester resins, polycarbonate resins, polyacetal resins, polyphenylene oxide resins, polyphenylene sulfide resins, polysulfone resins, polyurethane resins, tetra Fluoroethylene, trifluoroethylene, polyvinylidene fluoride and other fluorocarbon resins, ethyl cellulose, cellulose acetate, nitrocellulose and other fibrous resins, epoxy resins, ionomer resins, rosin derivative resins and other organic solvent-soluble resin systems, gelatin, nikawacasein , Hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, carboxymethyl hydroxyethyl cellulose, hydroxyethyl starch, gum arabic, succharose octaacetate, ammonium alginate, sodium alginate, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyvinyl amine, polyethylene oxide, polystyrene sulfonic acid , Polyacrylic acid, polyamide, isobutylene / maleic anhydride copolymerization Water-soluble resin etc., and the like can be listed the Emarujiyon system of the organic solvent-soluble resin.

Specific examples of waxes include candelilla wax,
Carnauba wax, rice wax, plant wax such as wax, animal wax such as beeswax, lanolin and whale wax, mineral wax such as Montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, petrolatum, etc. Synthetic hydrocarbons such as petroleum wax, fisher / Tropsch wax, polyethylene wax, etc., modified waxes such as montan wax derivative, paraffin wax derivative, microcrystalline wax derivative, hydrogen wax such as hydrogenated castor oil, hydrogenated castor oil derivative, etc. Examples thereof include stearic acid amide, higher alcohols and their waxes, and blends of waxes with organic / inorganic substances.

Specific examples of rubbers include natural rubber, isoprene rubber,
Styrene / butadiene rubber (SBR), butadiene rubber, acrylonitrile / butadiene rubber, butyl rubber, ethylene propylene rubber, chloroprene rubber, acrylic rubber, chlorosulfonated polyethylene rubber, hydrin rubber, urethane rubber, polysulfide rubber, silicone rubber,
Fluorocarbon rubber and these rubbers, rubbers and organic substances,
It is possible to list a compound with an inorganic substance.

These intermediate layer binders may be used alone or in combination of two or more, but are not limited thereto.

The above-mentioned binder, photodecomposable compound and, if necessary, various additives are added and dissolved or dispersed in a suitable solvent to form an intermediate layer paint. Dissolution,
Alternatively, the dispersion can be performed by a conventionally used planetary mixer, butterfly mixer, sand mill, tank mixer, attritor, three-roll mill, vibrator mill, jet mill, or the like. The intermediate layer referred to in the present invention is formed by applying the above-mentioned coating material by a solver coating method onto a support such as paper, synthetic paper, resin film, or a composite thereof, and drying. Coating is air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater,
It can be carried out using a kiss roll coater or the like. The thickness of the intermediate layer is 0.01 to 20 μm, preferably 0.1 to 10 μm.

The leuco dye coloring layer of the present invention is composed of the following materials.

That is, as leuco dyes, crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 3-diethylamino-5.
-Methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilininofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-diethylamino-7- Dibenzylaminofluorane or the like is applied.

In addition, as a color developer that reacts with the above leuco dye when it is heated, for example, bisphenol A, 4-phenylphenol, 4-t-butylphenol, 4-hydroxyacetophenone, α-naphthol, β- Naphthol, 2,
2'-hydroxydiphenyl, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol), methyl-4
-Hydroxybenzoate and the like can be applied.

As the binder for dispersing the above leuco dye and developer, casein, gelatin, styrene-maleic anhydride resin, polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, starch, modified starch, isobutylene-maleic anhydride resin, diisobutylene. Maleic anhydride resin, polyacrylic amide, modified polyacrylic amide, etc. are applied. Further, various additives such as inorganic and organic pigments, sensitizers, antioxidants and UV enhancers may be added to the leuco dye coloring layer of the present invention, if necessary.

The leuco dye coloring layer is formed by coating and drying the coating liquid having the above composition on the intermediate layer by the same coating method as that for the intermediate layer.

Next, in order to obtain the heat-sensitive recording material of the present invention, it is necessary to irradiate the layered leuco dye coloring layer with ultraviolet rays from a high pressure mercury lamp or the like. The diazo compound or azide compound in the intermediate layer is photolyzed by the irradiation of ultraviolet rays, and the nitrogen gas generated at that time forms bubbles to create voids in the intermediate layer, which lowers the thermal conductivity of the entire intermediate layer. Will bring about. At this time, for the purpose of thermally expanding the nitrogen gas generated by photodecomposition, heat treatment may be performed at a temperature at which the leuco dye coloring layer does not develop color, if necessary.

<Examples> Next, the present invention will be described in more detail with reference to Examples.

The parts and% shown below are parts by weight and% by weight, respectively.

Example 1 Glass beads were added to a compounding composition liquid containing a photodegradable compound as described below, and the mixture was dispersed for 100 minutes with a paint shaker, and after dissolution treatment, an intermediate layer coating material was obtained. Using a wire bar, a high-quality paper support having a basis weight of 50 g / m ² was coated so that the layer thickness after drying would be 2 μm, and the temperature was 1 at 75 ° C.
It was dried for a minute to form an intermediate layer.

Next, a coating liquid having the following composition was prepared in order to provide a leuco dye color-forming layer on the intermediate layer.

Liquids A, B, and C were pulverized and dispersed by a ball mill for 1 day to prepare dispersion liquids, and then 10 parts of liquid A, 20 parts of liquid B, and liquid 2 of C
30 parts of 0 parts of a 10% aqueous polyvinyl alcohol solution were mixed, and this was applied and dried on the intermediate layer so that the dry coating amount was 5 g / m ^2, to provide a leuco dye coloring layer.

Next, a high-pressure mercury lamp of 100 mW / cm ² was irradiated on the leuco dye coloring layer for 5 seconds to prepare a heat-sensitive recording material of the present invention.

For the leuco dye coloring layer of the heat-sensitive recording material of the present invention, a line type thin film head was used, and 0.45 W (1 mJ / do
Image recording was performed with the energy of t) and the black solid portion was measured with a Macbeth densitometer, and a clear color image of 1.18 was obtained.

Example 2 A thermal recording material of the present invention was produced in the same manner as in Example 1 except that the composition of the intermediate layer was changed to the following.

The leuco dye color-developing layer of the heat-sensitive recording material of the present invention obtained as described above was subjected to image recording with an energy of 0.45 W (1 mJ / dot) using a line type thin film thermal head as in the example. The black solid portion was measured with a Macbeth densitometer, and a clear color image of 1.12 was obtained.

Comparative Example A heat-sensitive recording material for comparison was prepared in the same manner as in Example 1 except that a photodecomposable compound was not used as the intermediate layer and the leuco dye coloring layer was not irradiated with a high pressure mercury lamp. It was made.

An energy image recording of 0.45 W (1 mJ / dot) was performed on the obtained thermal recording material for comparison using a lined type thin film thermal head, and the black solid portion was measured by a Macbeth densitometer. 82 unclear colored images.

<Effects of the Invention> Since the present invention is configured as described above, the thermal conductivity of the intermediate layer itself is lowered by the bubbles due to the photolysis of the photodegradable compound present in the intermediate layer, which reduces the thermal energy from the thermal head. It was possible to efficiently act on the leuco dye coloring layer without diffusing it into the intermediate layer and the support, and it was possible to obtain good coloring characteristics.

Claims (2)

[Claims] 1. A thermosensitive recording material having a leuco dye coloring layer on a support, wherein an intermediate layer containing bubbles due to photolysis of a photodegradable compound is provided between the support and the leuco dye coloring layer. Characteristic thermal recording material. 2. An intermediate layer containing a photodegradable compound and a leuco dye coloring layer are sequentially provided on a support, and then the surface of the leuco dye coloring layer is irradiated with ultraviolet rays to expose the photodegradable compound to light. A method for producing a heat-sensitive recording material, which comprises decomposing and generating bubbles in the intermediate layer.