JPS5829752B2 - heat sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more specifically, a vinyl chloride resin and a zinc compound are used as coloring aids for a leuco dye that does not develop pressure-sensitive color and is sensitive to acid. This relates to the heat-sensitive recording material used.

With the recent development of information processing systems, various recording materials, which are a type of information storage medium, have been developed.

Also, heat-sensitive recording materials, which are a type of recording material, are used to copy books, printed matter, documents, and the like.

In the so-called thermography method, a recording method to obtain a hard copy from a terminal device of information equipment such as a computer, or a recording method in a facsimile with a thermal head, etc.
came into widespread use.

However, this type of recording material that has been proposed so far uses a combination of an organic metal salt and an organic spotting reagent, a substance called a leuco dye that exhibits a dye-forming reaction, and an organic acid or a phenolic substance as a thermosensitive coloring material. Since a combination of color development aids is used, there are the following drawbacks.

That is, conventional thermosensitive coloring materials are a combination of two types of substances, and it is necessary to use a binder to keep these substances separated so that they do not come into contact with each other, and to distribute them uniformly. It is not possible to reduce the thickness very much.

Furthermore, when a recording material using a conventional heat-sensitive color-forming material is pressed at room temperature, if a shock or strong pressure is carelessly applied to it, contact between the leuco dye and the color-forming auxiliary agent occurs, causing a color reaction. There is a risk of causing

For this reason, when handling the recording material in its unused state, care must be taken not to apply impact or pressure to it, which is a hassle.

As a result of various studies to solve the above-mentioned drawbacks of heat-sensitive recording materials, the present invention proposes that the resin layer itself constituting the recording material has the function of both a sheet and a heat-sensitive coloring agent. This invention was made based on the discovery that an excellent recording material free of such defects can be obtained, and that the combination of a vinyl chloride resin, an acid-sensitive leuco dye, and a zinc compound exhibits an excellent coloring function.

That is, the present invention comprises a vinyl chloride resin, an acid-sensitive leuco dye, and one or more selected from the group consisting of zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, zinc acrylate, and zinc stearate. The present invention relates to a heat-sensitive recording material whose recording layer is a film of a composition comprising a zinc compound.

Vinyl chloride resins used in the present invention include polyvinyl chloride, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene Copolymer, vinyl chloride-styrene copolymer, vinyl chloride-vinyl stearate copolymer, vinyl chloride-methyl acrylate copolymer, vinyl chloride-butyl acrylate copolymer, vinyl chloride-octyl acrylate copolymer Copolymers of vinyl chloride and other monomers, such as vinyl chloride-diptyl maleate copolymer, vinyl chloride-lauryl vinyl ether copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, chlorine Chlorinated polyethylene, chlorinated polypropylene, chlorinated vinyl polymers such as chlorinated polyvinyl chloride, chlorinated rubber,
Refers to copolymers of vinylidene chloride and other monomers, such as polyvinylidene chloride and vinylidene chloride-acrylonitrile copolymers.

In the present invention, one or more resins may be selected from among these resins as necessary, and these resins and other resins compatible with the resins may be used in combination.

In addition, in the present invention, the molecular weight of the vinyl chloride resin is preferably as small as possible and has a high degree of branching in terms of its molecular structure, and it is preferable to use one that does not impair film forming properties for film formation. is preferred.

The copolymer should preferably contain 70 moles or more of vinyl chloride or vinylidene chloride, and if the vinyl chloride resin is used in combination with another resin, the vinyl chloride resin should contain 60 mole or more of the vinylidene chloride component. It is preferable that

The acid-sensitive leuco dye used in the present invention refers to leuco dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran organic dyes that develop color by reacting with acidic substances. say.

Specific examples of the acid-sensitive leuco dyes include malachite green leucobase, malachite green leucocarbinol, malachite green leuconitrile, malachite green leucosulfonyl, crystal violet leucocarbinol, Victoria blue leucocarbinol, aniline blue leuco Leuco forms of triphenylmethane pigments such as carbinol, methyl violet leucocarbinol, rose aniline leucocarbinol, phthalide compounds of triphenylmethane pigments such as malachite green lactone, crystal violet lactone, and methyl violet lactone, rhodamine B2 lactone , leuco forms of fluoran dyes such as Rhodamine B-lactam and basic violet 10-lactone, and leuco forms of phenothiazine dyes such as leucomethylene blue and benzoyl leucomethylene blue.

Among these compounds, malachite green leuconitrile, malachite green lactone, crystal biolate lactone, rhodamine B2 lactone, and benzoyl leucomethylene blue are particularly preferably used in the present invention.

In the present invention, one or more of these acid-sensitive leuco dyes are selected and used depending on the desired color tone.

The amount used is not particularly limited and may be determined as appropriate depending on the density of the image produced during recording, but the amount is 0.1 to 100 parts by weight per 100 parts by weight of the vinyl chloride resin. Suitably used.

Next, the zinc compound used in the present invention refers to one or more compounds selected from the group consisting of zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, zinc acrylate, and zinc stearate. has the effect of promoting the dehydrochlorination effect on vinyl chloride resins when heated, and also reacts with hydrogen chloride to form zinc chloride, which quickly causes color development when it comes into contact with acid-sensitive leuco dyes. It has the following.

In the present invention, since the zinc compound forms the same layer as the acid-sensitive leuco dye, zinc compounds other than those mentioned above, such as zinc chloride, zinc sulfate, zinc propiolate, zinc crotonate, and zinc nanthenate, are It cannot be used because it directly develops color upon contact with sensitive leuco dyes.

In addition, in the present invention, one or more of the above-mentioned large-scale zinc compounds are selected and used depending on the desired color tone and concentration, and the amount used may be determined as appropriate.
0.1 to 2 per 100 parts by weight of the vinyl chloride resin
An amount of 0.00 parts by weight is preferably used.

As described above, in the present invention, a composition consisting of a vinyl chloride resin, an acid-sensitive leuco dye, and a zinc compound is used, but the leuco dye in the composition is unused at room temperature, that is, when unused. Eliminates the fear of color development,
In order to improve the storage stability of the recording material, the composition may contain an electron-donating substance that does not develop color upon reaction with an acid.

Examples of electron-donating substances that develop color upon reaction with the above acids include quaternary ammonium compounds such as alkyltrimethylammonium chloride, pyridinium compounds such as alkylpyridinium chloride, primary amines such as dodecylamine, 2 like dodecylamine
Examples include heterocyclic compounds such as amines, alkyl oxazolines, and polyhydric alcohol compounds such as glycerin and polyethylene glycol, but these electron-donating substances preferably have a boiling point of 150° C. or higher.

Further, it is preferable to use the electron-donating substance in an amount of 50 parts by weight or less based on 100 parts by weight of the vinyl chloride resin.

Next, the fine powder filler that does not participate in the color reaction used in the present invention is a fine powder filler that does not have proton donating or electron donating properties, or is so weak that it does not participate in the color reaction of the leuco dye. This filler is used to adjust the color development sensitivity, impart naturalness to the appearance of the recording material, impart whiteness to the recording material, impart coating suitability when coating the composition, and apply to the thermal head of the resin constituting the recording layer. It is used for the purpose of preventing the adhesion of paper and the adhesion of gases, etc., and its purpose of use is completely different from that of the solid acid used as a coloring aid for the organic dye leuco dye conventionally used in thermal recording paper. It is.

The amount of the fine powder filler used is preferably 50 to 300 parts by weight per 100 parts by weight of the vinyl chloride resin.

Examples of the fine powder filler include calcium oxide, magnesium oxide, sodium carbonate, potassium carbonate, strontium carbonate, titanium oxide, barium sulfate,
Examples include fine powders of lithopone, basic magnesium carbonate, basic lead carbonate, basic lead sulfate, basic lead silicate, calcium carbonate, white carbon, silica, kaolin clay, tank, and the like.

In addition, those having acidity may be used after surface treatment with a basic substance.

However, in the present invention, the composition is made into a film to serve as a recording layer; however, the film may be provided with an appropriate thickness and strength and used as a recording material by itself, or The film may be provided on a suitable substrate.

As the substrate, a film capable of supporting a recording layer obtained by coating and drying the above-mentioned composition is used, and for example, cellulose paper, a plastic film such as a polyethylene film, a polypropylene film, etc. can be suitably used.

Next, in order to create a film or provide the composition in a layer on a substrate, for example, the above composition is uniformly dissolved in the presence of a vinyl chloride resin solvent, and then cast or coated on the substrate. , casting and drying to remove the solvent may be adopted.

As the solvent used in this case, for example, a solvent capable of dissolving the vinyl chloride resin, such as cyclohexanone, tetrahydrone, dichloroethane, tetrachloroethane, chlorobenzene, and dimethylformamide, is used.

It is also possible to disperse the above-mentioned composition in the form of ultrafine particles in a poor solvent of vinyl chloride resin and perform casting, or to apply it onto a substrate, cast it, and dry it.

The heat-sensitive recording material of the present invention is a sheet having the above-described structure and has heat-sensitive coloring properties, and is fed to a commonly used heat-sensitive copying apparatus to perform copying.

In other words, the heat supplied by touching and scanning the surface of the recording material with a thermal pen causes the vinyl chloride resin that makes up the composition to thermally damage the terminal double bonds and branch points that exist within its molecules. Dehydrochlorination or generation of radicals occurs from unstable parts, and the generated hydrogen chloride reacts with zinc compounds coexisting in the composition to produce zinc chloride.

The zinc chloride acts as a thermal decomposition catalyst on the vinyl chloride resin and further promotes the dehydrochlorination reaction.

The hydrogen chloride button and zinc chloride thus generated react immediately with the acid-sensitive leuco dye to develop a color unique to the leuco dye.

In other words, only the portion that receives heat from the thermal pen changes color and becomes visible, so it functions as a recording material.

As described above, the heat-sensitive recording material of the present invention is composed of a vinyl chloride resin, an acid-sensitive leuco dye, and a specific zinc compound, so when heated, the vinyl chloride resin and zinc The compound acts as a color development aid for leuco dyes.

Therefore, there is no need to separately include a coloring aid such as an organic acid or a phenolic substance in the composition, and the coloring effect can be caused by the vinyl chloride resin itself constituting the film.

Therefore, the types of substances constituting the composition can be reduced, each substance can be uniformly dispersed, and the layer of the composition can be made thinner, so it is preferable as a recording material.

Further, according to the present invention, there is no need to use other substances as coloring aids, and the vinyl pentachloride resin and zinc compound act as coloring aids only when heated. Even when subjected to impact or pressure, the leuco dye does not cause a color reaction.

In other words, since the recording material of the present invention does not develop pressure-sensitive coloring, there is no need to take special care not to apply shock or pressure when handling it.

Further, according to the present invention, a dehydrochlorination reaction occurs from vinyl chloride resin by heat, and the hydrogen chloride reacts with a zinc compound to form zinc chloride, and the zinc chloride is added to the vinyl chloride resin as a thermal decomposition catalyst. The hydrogen chloride and the zinc chloride act as coloring aids for the leuco dye, resulting in images with good coloring sensitivity and clear contrast.

Next, examples of the present invention will be described.

In the Examples, "parts" simply means parts by weight.

Example 1 Vinyl chloride-vinyl acetate copolymer 100 parts (degree of polymerization 500, vinyl acetate 6.5%) Benzoylleucomethylene blue 10 parts Crystal violet lactone 10 parts Zinc oxide
100 parts Tetrahydrofuran 1200 parts A mixture having the above composition was mixed and dispersed in a homomixer for 10 minutes to obtain a coating liquid for forming a recording layer.

The weight of the recording layer after drying the coating liquid on high-quality paper with a thickness of 80μ is 6ff/rr? After coating with a wire bar so as to give a heat-sensitive recording material, the tetrahydrofuran was volatilized to obtain a heat-sensitive recording material.

The resulting recording material had a slightly bluish white color and had good storage stability.

The recording material was coated with a pen pressure of 5 f/lr? using a thermal pen whose recording needle was heated to 150°C. , recording speed 100
When scanning was performed under the conditions of cm/sec, a dark blue recorded image was obtained.

The storage stability of the recorded images was good.

Example 2 Vinyl chloride-ethylene copolymer 100 parts (degree of polymerization SOO, ethylene 4%) Rhodamine B lactam 20 parts Zinc stearate 5 parts Ethylene oxide alkyl diamine 10 parts (Kao Atlas Co., Ltd., Electrostripper EA) Tetrahydrofuran
A heat-sensitive recording material was obtained using 1200 parts of a blend having the above composition in the same manner as in Example-1.

Using a thermal pen whose recording stylus is heated to 150°C, the resulting recording material is applied with a pen pressure of 5? /lr? When scanning was performed at a recording speed of 60 cm/sec, a clear dark red image was obtained.

Example 3 Polyvinyl chloride (degree of polymerization 500) 100 parts Malachite green leuconitrile 10 parts Malachite green lactone 10 parts Dodecyltrimethylammonium chloride 10 parts Zinc oxide 100
Part titanium oxide 30 parts Tetrahydrofuran 1500 parts A mixture having the above composition was mixed and dispersed in a ball mill for 20 hours to obtain a coating liquid for forming a recording layer.

The weight of the recording layer after drying the coating liquid on high-quality paper with a thickness of 80 μm is 69/rr? After coating with a roll coater so as to give a heat-sensitive recording material, tetrahydrofuran was volatilized to obtain a heat-sensitive recording material.

The obtained recording material was white and rich in naturalness.

When recording was performed on the recording material in the same manner as in Example 2, a clear green image was obtained.

Claims (1)

[Scope of Claims] 1. A vinyl chloride resin, an acid-sensitive leuco dye, and one or two selected from the group consisting of zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, zinc acrylate, and zinc stearate. A heat-sensitive recording material having, as a recording layer, a film of a composition comprising the above zinc compound. 2. The heat-sensitive recording material according to claim 1, wherein the composition contains an electron-donating substance that does not develop color by reacting with an acid. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the composition contains a fine powder filler that does not participate in the coloring reaction. 4. The heat-sensitive recording material according to claim 1, 2 or 3, wherein the recording layer is provided on the substrate.