JPS6240197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, particularly to an improvement in a heat-sensitive recording material using a normally colorless or slightly pale-colored leuco body and an acidic substance as coloring components.

In recent years, heat-sensitive recording materials, in which a heat-sensitive color-forming layer is provided on a support such as paper, plastic film, or metal-deposited paper, which can color a recorded image by causing a chemical or physical change due to heat energy, have become popular. Electronic computers have advantages such as recording can be obtained by simply heating, no complicated developing and fixing processes are required, they do not generate noise during recording, and they are relatively easy and inexpensive to manufacture. It is widely used in various information devices such as , telex, facsimile, and measuring instruments.

Many of these heat-sensitive recording materials have been put to practical use, among which are usually colorless or slightly light-colored leuco dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes. A heat-sensitive recording material containing an acidic substance, such as an organic acid or a phenolic acidic substance, which reacts with the leuco body under heat and causes the leuco body to develop color, as a coloring component in the heat-sensitive coloring layer, produces a colored image in the resulting recorded image. It is used as a particularly useful recording material because of its high density and clarity.

Furthermore, recently, utilizing the advantages of heat-sensitive recording materials using the aforementioned leuco bodies and acidic substances, for example, ticket paper for automatic ticket issuing machines such as commuter passes, bar code paper in POS systems, display of products, etc. Application to labels, etc. is also being considered, but satisfactory results have not yet been obtained.

For example, in the case of ticket paper, it is printed with a thermal line printer and then placed in a transparent vinyl or a commuter pass with a transparent vinyl window, and in the case of barcode paper and display labels, it is printed with a label printer. After printing on the heat-sensitive layer, the colored image is used by contacting the above-mentioned resin film by pasting it on top or bottom of the polyvinyl chloride wrap film used to package the product and stacking it. However, in order to improve flexibility, plasticizers such as dioctyl phthalate (DOP) and dioctyl adipate (DOA) are used in such resin films in an amount of about 5 to 40% by weight. Ticket paper with plasticizer printed on it, barcode paper,
This has caused the inconvenience that it acts on the printed part of the label etc. and causes the printed part to fade within 1 to 10 hours of contact. Furthermore, these conventional heat-sensitive recording materials have poor water resistance, so it was necessary to avoid moisture as much as possible. In cases where heat-sensitive layers are often handled, it has been impractical to simply make the heat-sensitive layer water resistant.

In order to improve these shortcomings, the present inventors have conducted various studies and have developed a color-forming component that uses a normally colorless or slightly light-colored leuco compound and an acidic substance that reacts with the leuco compound under heat to produce color. In a heat-sensitive recording material having a heat-sensitive color-forming layer, the inventors have discovered that the above-mentioned drawbacks can be solved at once by providing a water-soluble polymer coating layer containing dialdehyde starch as a main component on the heat-sensitive color-forming layer, and have accomplished the present invention. It came to this.

Therefore, an object of the present invention is to provide a heat-sensitive recording material that does not fade even when the printed portion comes into contact with a resin film containing a plasticizer, and furthermore, it is an object of the present invention to provide a heat-sensitive recording material that does not discolor even when the printed portion comes into contact with a resin film containing a plasticizer. It is an object of the present invention to provide a heat-sensitive recording material that can maintain clear records for a long period of time without decoloring the printed portion during use.

To explain in detail about the heat-sensitive recording material of the present invention, the usually colorless or slightly light-colored leuco bodies used in the present invention include leuco bodies of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes. , this includes, for example, 3,3-pis(p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)
Phthalide, 3,3-bis(p-dimethylaminophenyl)
-6-diethylaluminophthalide, 3,3-bis(p-dimethylaminophenyl)
-6-chlorophthalide, 3-(N-p-tolyl-N-ethylamino)-
6-Methyl-7-(N-phenylamino)fluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-(3-fluoromethyl)phenylaminofluoran, benzoylleucomethylene blue, 6'-chloro- 8′-methoxy-benzoindolino-pyrylospirane, 6′-bromo-8′-methoxy-benzoindolino-pyrylospiran, 2-[3,6-bis(diethylamino)-9-
(o-chloroanilino)xanthyl], benzoic acid lactam, and the like.

In addition, examples of acidic substances that cause a coloring reaction with the leuco body and cause the leuco body to develop color include, for example, α-naphthol, β-naphthol, 4-t-butylphenol, 4-t-octylphenol, 4-t-octylphenol,
-Phenylphenol, 2,2-bis(p-hydroxyphenyl)propane (also known as bisphenol A), 2,2-bis(p-hydroxyphenyl)butane, 4.4'-cyclohexylidene diphenol, 2, 2-bis(2,5-dibromo-4-hydroxyphenyl)propane, 4,4'-isopropylidene bis(2-t-butylphenol),
Examples include 2,2'-methylenebis(4-chlorophenol), benzoic acid, salicylic acid, tartaric acid, and gallic acid.

The above-mentioned color-forming components are formed into a heat-sensitive color-forming layer coating liquid with a binder in the conventional manner, and the liquid is applied onto a suitable support such as paper, synthetic paper, plastic film, metallized paper, etc., and dried to form a heat-sensitive color-forming layer. .

Examples of the binder include the following.

polyvinyl alcohol, methoxycellulose,
Water-soluble ones such as hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc., or water-based emulsions such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. .

Note that additives such as fillers and lubricants that are commonly used in the heat-sensitive coloring layer may be used.

A coating layer containing dialdehyde starch is further formed on the above heat-sensitive coloring layer, but to form this layer, dialdehyde starch alone or
It is dispersed in water with water-soluble polymer compounds such as polyvinyl alcohol, methylcellulose, carboxymethylcellulose, starch, starch derivatives, polyvinylpyrrolidone, gelatin, isobutylene-maleic anhydride copolymer, etc. to form a coating liquid, and a heat-sensitive coloring layer is formed. Just apply it on top and let it dry.

After drying the coating layer, the dialdehyde starch
It is preferable that the amount is at least 30% by weight, and if it is less than 30% by weight, the water resistance effect will be insufficient.

The present invention will be illustrated below with examples.

Example 1 A mixture consisting of the following formulation was milled in a ball mill for 20 minutes.
Dispersion liquid [A] and dispersion liquid [B] were prepared by time-dispersing.

Dispersion liquid [A] 3-diethylamino-7-(3-fluoromethyl)phenylaminofluorane...10 parts by weight Stearic acid amide...20 parts by weight 10% polypinyl alcohol aqueous solution [manufactured by Kuraray Co., Ltd.]
PVA-205] ...20 parts by weight Water ...50 parts by weight Dispersion [B] Bisphenol A ...20 parts by weight Calcium carbonate ...20 parts by weight 10% polyvinyl alcohol aqueous solution [Kuraray Co., Ltd.]
PVA-205] ...30 parts by weight Water ...30 parts by weight Next, 10 parts by weight of dispersion liquid [A], 20 parts by weight of dispersion liquid [B], 20% polyvinyl alcohol aqueous solution [Kuraray Co., Ltd. PVA-205] 20 Parts by weight and 30 parts by weight of water were mixed and stirred to prepare a heat-sensitive coloring layer coating solution.

This coating solution was applied to a commercially available high-quality paper with a basis weight of 52 g/m ² at a coating weight of 6 g/m ² after drying, adjusted with a wire bar, and dried to form a heat-sensitive coloring layer. A heat-sensitive recording material of the present invention was prepared by coating this heat-sensitive coloring layer with a 5% dialdehyde starch aqueous solution at a coating weight of 2 g/m ² after drying.

This heat-sensitive recording material was tested for decolorization resistance against plasticizers. Discoloration resistance test was performed using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd. at 150℃ (1sec2.0Kg/m ² )
After color development, one sample was immersed in water at 20°C for 5 minutes and then dried, and the other sample was coated with polyvinyl chloride wrap film (manufactured by Shin-Etsu Polymer) without this process. The concentration change after 24 hours was tested. As a result, the sample that was not immersed in water had a concentration of 1.25 before the test, which remained unchanged at 1.25 after the test. Also, the sample immersed in water had a pre-test concentration of 1.25, but a post-test concentration of 1.23, which was sufficiently usable for practical use.

Example 2 A heat-sensitive coloring layer was formed on wood-free paper in the same manner as in Example 1, and a coating layer of the following formulation was applied on the heat-sensitive coloring layer in an amount such that the dry coating amount was ² g/m2. The heat-sensitive recording material of the present invention was prepared by adjusting the temperature.

Coating layer coating 5% dialdehyde starch aqueous solution...50 parts by weight 10% polyvinyl alcohol aqueous solution [Kuraray Co., Ltd.]
PVA-205] ...25 parts by weight Water ...25 parts by weight This heat-sensitive recording material was tested for discoloration resistance against plasticizers in the same manner as in Example 1. As a result, the samples that were not immersed in water The concentration before the test was 1.26 and the concentration after the test was 1.25, which was almost unchanged. In addition, the sample immersed in water had a pre-test concentration of 1.26 and a post-test concentration of 1.15, which was sufficiently practical.

Comparative Example 1 A comparative heat-sensitive recording material was prepared in the same manner as in Example 1 except that the coating layer was not provided, and the fading resistance against plasticizers was tested in the same manner as in Example 1. As a result, Both samples, whether immersed in water or not, had a concentration of 1.25 before the test, but were completely unreadable after the test.

Comparative Example 2 A comparative heat-sensitive recording material was prepared in the same manner as in Example 1 except that a coating layer was provided using a 5% polyvinyl alcohol aqueous solution (Kuraray PVA-205).

This heat-sensitive recording material was subjected to a discoloration resistance test against plasticizers in the same manner as in Example 1. As a result, the sample that was not immersed in water had a concentration of 1.25 after the test, which was almost unchanged, compared to 1.25 before the test. However, the sample immersed in water had a concentration of 1.25 before the test, but the concentration after the test was 0.40-0.45, which was not practical.

Comparative Example 3 A comparative heat-sensitive recording material was prepared in the same manner as in Example 1 except that a coating layer was provided using a 5% starch aqueous solution (S-Suncizer 700, manufactured by Ajinomoto Co., Inc.).

A discoloration resistance test against a plasticizer was conducted on this heat-sensitive recording material in the same manner as in Example 1. As a result, the sample that was not immersed in water had a concentration of 1.27 before the test, and a decrease of 1.05 and 0.22 after the test. However, the sample immersed in water had a pre-test concentration of 1.27 and a post-test concentration of 0.35-0.45, which was not practical.

Comparative Example 4 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that 5 parts by weight of a 10% dialdehyde starch aqueous solution was further added to the heat-sensitive coloring layer liquid of Example 1, and no coating layer was provided.

As a result of the discoloration resistance test in the same manner as in Example 1,
The sample that was not immersed in water and the sample that was immersed in water had a pre-test concentration of 1.26, but the color had faded to an unreadable level.

As can be seen from the above results, the heat-sensitive recording material of the present invention has a coating layer containing dialdehyde starch, which is resistant to decolorization and water, on the heat-sensitive coloring layer. The image density remains unchanged even under various conditions, and the colored recorded image can be maintained clearly for a long period of time.

Claims (1)

[Claims] 1. In a heat-sensitive recording material having a heat-sensitive coloring layer containing a normally colorless or slightly light-colored leuco body and an acidic substance that reacts with the leuco body under heat to develop color as a coloring component, dialdehyde starch is provided on the heat-sensitive coloring layer. A heat-sensitive recording material characterized by being provided with a water-soluble polymer coating layer containing as a main component.