JPH08192574A - Thermal recording material - Google Patents

Abstract

PURPOSE: To improve dot reproducibility,recording density, running properties or the like, in a thermal recording material wherein a thermal color forming layer, an intermediate layer and a layer based on an ultraviolet curable resin are provided on the surface of a support, by adding oleophilic synthetic smectite to the ultraviolet curable resin layer. CONSTITUTION: In a thermal recording material wherein a thermal color forming layer containing a thermal color forming component, an intermediate layer based on a water soluble polymer and/or a water dispersible polymer and an ultraviolet curable resin layer are successively provided on the surface of a support and the color former in the thermal color forming layer is instantaneously reacted by heating using a thermal head to form a recording image, oleophilic synthetic smectite is added to the resin layer as a thickener. Since oleophilic synthetic smectite has a flat shape, the surface of the thermal recording material is not roughened and high glossiness can be obtained. Synthetic smectite is prepared by intercalating org. ions such as quaternary ammonium ions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium capable of recording an image by a thermosensitive recording system. More specifically, it relates to a thermosensitive recording medium having excellent dot reproducibility, recording density and running property.

[0002]

2. Description of the Related Art A thermosensitive recording medium generally comprises a substrate and a thermosensitive coloring layer formed on the substrate. The coloring agent in the thermosensitive coloring layer is heated by a thermal head, a heating pen, laser light or the like. React instantaneously to form a recorded image (for example, Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. 45-14039, etc.).

In such a thermosensitive recording medium, a recorded image can be obtained by a relatively simple device and the maintenance is easy.
Further, since it has an advantage that it does not generate noise, it is used in a wide range of fields such as a recorder for measurement, a facsimile, a printer, a computer terminal, a label, and an automatic ticket vending machine such as a ticket.

In particular, recently, the thermal recording method has the feature that gradation can be easily expressed, the recording medium is inexpensive, the gradation can be electronically controlled, and an image having gradation is obtained by a dry process. Due to the fact that it can be obtained, it has been used in video printers instead of monochrome silver halide photographs.

As a recording medium replacing the silver salt photograph, a thermosensitive recording material having only a thermosensitive coloring layer or a thermosensitive recording material having an overcoat layer mainly composed of a water-soluble resin thereon is adopted. Although it is conceivable, the maximum recording density is only at most about 1.50, and the maximum recording density is generally 2.0 in the case of silver salt photography which requires gradation.
Since about 0 is necessary, the gradation is poor. There is a drawback that the recording medium has a so-called narrow dynamic range.

As a method of increasing the maximum recording density, there is a phenomenon that the maximum recording density is improved by increasing the surface gloss of the recording layer. As a means for embodying this, a gloss imparting layer is provided on the heat-sensitive recording layer. It is valid.

The gloss-imparting layer may be provided on the recording layer in advance before recording, or may be provided by a method such as laminating after recording. The recording system is more complicated if it is provided before recording. It is preferable because it does not become large.

Although a water-based or solvent-based coating material can be used for the gloss-imparting layer, the gloss-imparting layer is destroyed by heat even if sticking occurs, the degree of gloss is expressed, or sticking does not occur, and the recording density is reduced. There is a drawback that it does not improve. Use of an ultraviolet curable resin can eliminate such a defect.

Providing an ultraviolet-curable resin layer on a heat-sensitive color-developing layer is known, for example, as disclosed in JP-A-54-3549. However, if the UV curable resin layer is too thick, the heat from the thermal head becomes difficult to transfer, and the sensitivity of the recording paper may be reduced, or curling may occur, and the UV curable resin is expensive. There is also an economic reason that it is necessary to obtain the desired performance with a low coating amount as much as possible.

[0010]

DISCLOSURE OF THE INVENTION The present invention is directed to improving dot reproducibility and recording by improving an ultraviolet-curable resin coating composition and applying an ultraviolet-curable resin layer uniformly on a thermosensitive recording material in a low coating amount. It is an object of the present invention to provide a heat-sensitive recording material excellent in density and running property.

As a method for providing the ultraviolet curable resin layer, a coating method or a printing method can be used. However, contact with a thermal head and high gloss,
In order to obtain the highest recording density, it is required to provide a layer having a highly smooth and uniform surface. For this purpose, the printing method is unavoidable because the generation of a transfer pattern is unavoidable, and the coating method is more advantageous.

The UV-curable resin coating material has a solid content of 0.5-0.5.
When applying 3 g / m ^2, there are micro gravure coater, reverse gravure coater, etc. as a coating machine for measuring and coating a small amount of paint, but even if they are used, the solid content concentration of the paint is changed with an organic solvent such as toluene. Stable metering cannot be performed unless the viscosity of the paint is reduced to an appropriate range by diluting.

In this way, when diluted with a solvent such as toluene, the viscosity of the coating material is apt to be extremely lowered (compared to a water-based coating material using water as a diluent, the viscosity is much lower). The coating material viscosity is controlled within an appropriate range. This is extremely difficult because of evaporation of the solvent during use. Further, when the viscosity is low, a phenomenon occurs in which additives such as pigments and lubricants are not evenly distributed and become unevenly distributed when the paint swims and the solvent evaporates.

The uneven distribution not only causes an extreme decrease in the glossiness of the UV-curable resin layer, but also causes a non-uniform contact with the thermal head, which is a major defect that impairs the dot reproducibility of an image.

In order to solve these problems, the solid content of the paint is reduced with a solvent. At the same time, it is effective to increase the viscosity of the paint to ensure proper fluidity and coating suitability. Was considered. However, organic alkyl-substituted acid amides, vegetable oil derivatives, hydrogenated castor oil derivatives, waxes, etc., which are used as thickeners for general solvent-based paints in printing inks and paints, etc. If added to the coating layer, problems peculiar to the thermosensitive recording medium, such as sticking of dust to the Therma's head and sticking, will occur, so these cannot be used.

[0016]

Means for Solving the Problems As a result of studying various methods, the inventors of the present invention have achieved the object by using a lipophilic synthetic smectite as a thickening agent without causing a problem peculiar to a thermosensitive recording medium. I found that I can do it.

That is, a thermosensitive coloring layer containing a thermosensitive coloring component is provided on the surface of a support, an intermediate layer containing a water-soluble polymer and / or a water-dispersible polymer as a main component is provided thereon, and ultraviolet rays are further provided thereon. In providing the curable resin layer, the above-mentioned problems can be solved by incorporating the lipophilic synthetic smectite in the ultraviolet curable resin layer.

The UV-curable resin layer used in the present invention is described in detail in previously published books such as "Taiseisha: Light / Radiation Curing Technology", academic journals, etc. The UV-curable resin composition containing the monomer, the prepolymer, or the polymers and the photopolymerization initiator as essential components is polymerized by irradiating with ultraviolet rays.

The monomer and prepolymer or polymer are compatible with each other and copolymerizable. As the prepolymer, unsaturated polyester, epoxy, acrylic, various polyesters and the like can be used, and the monomer includes various ethylene derivatives.

The UV curable resin layer is 0.1 to 10 g / m ²
The amount is preferably 0.5 to 6 g / m ² , more preferably 0.5 to 3 g / m ² .

The lipophilic synthetic smectite not only has the excellent property of exhibiting a thickening effect in a small amount, but also has high heat resistance as it is an inorganic mineral, and sticking to the thermal head is higher than that of an organic compound-based thickener. It does not cause problems such as dust and adhesion of dust, but rather serves to improve these performances.

Further, since the lipophilic synthetic smectite has a flat shape, even if it is added to the UV-curable resin layer, it can maintain a high glossiness without roughening the surface and has a high transparency, so that the recording density can be improved. It does not decrease.

The lipophilic synthetic smectite used in the present invention is obtained by intercalating organic ions such as quaternary ammonium between the layers by utilizing the ion exchange ability of smectite. The details are 1992 Tohoku Industrial Technology Test. It is described in the proceedings of the 25th anniversary commemorative lectures, pages 11 to 24, JP-A-5-163014, and the like.

The heat-sensitive color-forming component used in the heat-sensitive color-forming layer is not particularly limited, and is, for example, a reaction between a leuco dye and an electron-accepting substance represented by a phenolic substance, or a reaction between an imino compound and an isocyanate compound. , A long-chain fatty acid iron salt and a polyphenol are reacted with each other.

In addition to these, the chemicals which have been used in the conventionally known heat-sensitive recording materials are used. For example, as water-soluble binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein can be used. , Water-soluble binders such as polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene A latex-based water-soluble binder such as a copolymer is used.

Further, it is necessary to provide an intermediate layer containing a water-soluble polymer and / or a water-dispersible polymer as a main component between the thermosensitive coloring layer and the ultraviolet curable resin layer. This is because the organic solvent is used for diluting the ultraviolet curable resin coating material, and thus the thermosensitive coloring layer develops color without the intermediate layer. The water-soluble binder described above can be used to form the intermediate layer, and various crosslinking agents can be used to increase the water resistance of the film.

Further, the following chemicals are added to the thermosensitive coloring layer and / or the intermediate layer and / or the ultraviolet curable resin layer according to the purpose. As the pigment, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide,
Urea-formalin resin or the like is 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, polyethylene oxide, stearamide and caster wax. Also,
Various oxalate esters such as metaterphenyl, parabenzylbisphenyl, esters of hydroxynaphthoic acid, stearic acid amide, tribenzylamine, naphthalene derivative, dibenzyl terephthalate, dibenzyl oxalate, bis (paramethylbenzyl oxalate), etc. Etc. can be used. Further, a dispersant such as sodium dioctyl sulfosuccinate, a surfactant, a fluorescent dye and the like are used as desired.

Paper is mainly used as the substrate in the heat-sensitive recording material of the present invention, but various non-woven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets combining these are optionally used. If desired, an undercoat layer may be provided between the substrate and the thermosensitive coloring layer.

[0030]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, “part” and “%” represent “part by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Preparation of solution A 3-di-butylamino-6-methyl-7-anilinofluorane 10 parts 20% polyvinyl alcohol (Kuraray Poval 105, manufactured by Kuraray) 10 parts water 20 parts This composition was sand milled. And pulverized until the average particle diameter becomes 0.8 μm. Liquid B Preparation 4,4′-Diisopropylidenediphenol 10 parts 20% Polyvinyl alcohol (Kuraray Poval 105, manufactured by Kuraray) 10 parts Water 20 parts This composition was ground with a sand mill until the average particle size became 1.5 μm. . Liquid C Preparation Metaterphenyl 10 parts 20% Polyvinyl alcohol (Kuraray Poval 105, manufactured by Kuraray) 10 parts Water 20 parts This composition was ground with a sand mill until the average particle size was 1.0 μm.

Formation of thermosensitive recording layer 40 parts of solution A, 80 parts of solution B, 40 parts of solution C, 20% polyvinyl alcohol (Kuraray Poval 105 manufactured by Kuraray) 60
Parts and 50 parts of water were mixed and stirred to obtain a coating liquid for heat-sensitive recording layer.
The obtained coating solution was applied onto a synthetic paper having a thickness of 80 μ (Yupo FPG80 manufactured by Oji Oil Chemical Co., Ltd.) so that the dry weight was 4 g / m ² and dried.

Formation of Intermediate Layer 20% polyvinyl alcohol (Kuraray Poval 105,
Kuraray's 400 parts, silica (P-527 Mizusawa Chemical's) 10 parts, glyoxal 10 parts, and water 200 parts were mixed and stirred to obtain an intermediate layer coating liquid. The resulting coating liquid was applied onto the thermosensitive recording layer so that the dry weight was 2 g / m ^2, and dried.

Preparation of coating liquid for UV-curable resin composition 50% of the UV-curable resin composition (N1815 manufactured by Nippon Kayaku Co., Ltd.) was added to the overcoat layer with toluene.
And added 2% of the lipophilic synthetic smectite (SPN manufactured by Coop Chemical Co., Ltd.) of the present invention to the ultraviolet curable resin composition, and 32 cps (measurement condition; B-type viscosity 60).
A coating liquid having a viscosity adjusted to 20 ° C. by rotation was obtained.

Formation of UV-Curable Resin Layer The obtained UV-curable resin composition coating solution was applied by a reverse gravure coater to a dry weight of 2 g / m ² , and then toluene was removed by evaporation in a drying step. Then, it was cured by an ultraviolet irradiation device to obtain a recording material of the present invention.

Comparative Example 1 Example 1 In the preparation of the ultraviolet-curable resin composition coating liquid, the viscosity of the ultraviolet-curable resin composition coating liquid of the present invention to which the lipophilic synthetic smectite was not added was 7 cps (measurement condition: B-type viscosity). 60 rotations, 20 ° C). A recording body of Comparative Example 1 was obtained using this coating solution in the same manner as in Example 1 for forming the ultraviolet curable resin layer.

Comparative Example 2 Example 1 In the preparation of a coating liquid for an ultraviolet curable resin composition, 3% of an organic alkyl-substituted acid amide (Dehisol manufactured by San Nopco Ltd.) was added in place of the lipophilic synthetic smectite of the present invention. , 51 cps (measurement condition; B type viscosity 6
A coating solution having a viscosity adjusted to 0 rotation and 20 ° C.) was obtained. A recording body of Comparative Example 2 was obtained by using this coating solution in the same manner as in Example 1 for forming the ultraviolet curable resin layer.

Comparative Example 3 In the coating liquid for forming the intermediate layer of Example 1, 30 parts of 30% zinc stearate dispersion liquid (D-523, Chukyo Yushi Co., Ltd.) was further added, and the dry weight was applied on the thermosensitive recording layer. Is 2
It was applied and dried so as to be g / m ² . This recording body was a recording body of Comparative Example 3 without providing an ultraviolet curable resin layer.

Evaluation Method The four types of thermal recording materials obtained as described above were printed on a commercially available image printer (UP-860 manufactured by Sony Corporation) and evaluated. Test 1 Dot reproducibility The dot reproducibility was visually evaluated. O: Good X; Poor Test 2 Recording density The maximum density of the recorded part was measured. Test 3 Transportability 100 screens were continuously printed, and the transport sound, sticking, dust adhesion, etc. were evaluated.

[0040]

[Table 1] (Note 1) The UV-curable resin layer is non-uniform due to the swimming of the paint. (Note 2) Carrier noise and sticking occurred.

[0041]

As is clear from the results of Table 1, the thermosensitive recording materials obtained in the examples of the present invention were excellent in dot reproducibility, recording density and transportability.

Claims (1)

[Claims] 1. A thermosensitive coloring layer containing a thermosensitive coloring component is provided on the surface of a support, an intermediate layer containing a water-soluble polymer and / or a water-dispersible polymer as a main component is provided thereon, and ultraviolet rays are further provided thereon. A thermosensitive recording medium provided with a layer containing a curable resin as a main component, wherein the ultraviolet curable resin layer contains a lipophilic synthetic smectite.