JPH0471716B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in heat-sensitive recording materials, particularly heat-sensitive recording materials that use normally colorless or slightly light-colored leuco bodies and acidic substances 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, because they have the advantages of being able to record simply by heating, do not require complicated development and fixing processes, do not generate noise during recording, and are relatively easy and inexpensive to manufacture. It is widely used in various information devices such as telex and facsimiles, as well as 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 in which a heat-sensitive coloring layer contains an acidic substance, such as an organic acid or a phenolic acidic substance, as a coloring component, which reacts with the leuco body under heat to cause the leuco body to develop color, has a high color density of the resulting recorded image. It is used as a particularly useful recording material because of its high sharpness. 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 the above-mentioned ticket paper, after printing with a thermal line printer, it is placed in a commuter pass made of transparent vinyl or with a transparent vinyl window, or
In the case of barcode paper and display labels, they are printed using a label printer and pasted on top or bottom of the polyvinyl chloride wrap film used to package the product, and then stacked on top of each other.
It is used by bringing a colored image into contact with a resin film as described above. 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 5 to 40% by weight. After coming into contact with the plasticizer, it acts on the printed parts of ticket paper, barcode paper, labels, etc.
There was an inconvenience that the printed area was discolored within 10 hours. For this reason, these conventional heat-sensitive recording materials could not be used as they were. Therefore, in order to solve the problem of color fading as described above, the applicant provided a coating layer of a water-soluble polymer compound on the heat-sensitive coloring layer to prevent the plasticizer from penetrating into the layer, thereby improving the color fading resistance. A heat-sensitive recording material has already been developed and disclosed in Utility Model Application No. 55-22304. However, since this coating layer is made of a water-soluble polymer compound, various problems have arisen. For example, barcode paper and labels are pasted on top or bottom of a polyvinyl chloride wrap film after the product is wrapped in the wrap film, but in reality, these operations are done with hands that have been exposed to water or in a humid atmosphere. The coating layer peeled off in areas wet with water, and the fade resistance of the peeled areas to plasticizers deteriorated. Therefore, the present inventors conducted further research in order to improve these drawbacks, and as a result, the present inventors developed a color-forming component that contains a normally colorless or slightly light-colored leuco body and an acidic substance that reacts with the leuco body when heated to produce a color. In a heat-sensitive recording material in which a heat-sensitive coloring layer and a coating layer containing a water-soluble polymer compound as a main component are sequentially provided on a support, by further containing a hydrophobic resin or a water-resistant agent in the coating layer. The inventors have discovered that the above-mentioned drawbacks can be solved, and have completed the present invention. Therefore, an object of the present invention is 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, and furthermore, is capable of being used under high temperature and high humidity conditions. 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. That is, the present invention provides a heat-sensitive coloring layer containing as a coloring component a normally colorless or slightly light-colored leuco body and an acidic substance that reacts with the leuco body when heated to develop color, and a coating mainly composed of a water-soluble polymer compound. In a heat-sensitive recording material in which layers are sequentially provided on a support,
The coating layer further contains a water-resistant agent that imparts water resistance by crosslinking with a hydrophilic group in a hydrophobic resin or a water-soluble polymer compound, and the content of each is based on the total solid content of the coating layer. Hydrophobic resin is 10 to 50% by weight, and water resistance agent is 5 to 5% by weight based on the water-soluble polymer compound.
It is a heat-sensitive recording material characterized by having a content of 50% by weight. To explain the heat-sensitive recording material of the present invention in detail, the water-soluble polymer compounds used in the coating layer include polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, starch, gelatin, and isobutylene anhydrous. Examples include maleic acid copolymers. In addition, in the coating layer, a hydrophobic resin or a water-resistant agent is used together with the above-mentioned water-soluble polymer compound. Among these, examples of the hydrophobic resin include styrene-butadiene rubber, polyvinyl acetate, styrene-acrylic ester, There are aqueous emulsions such as acrylic acid esters, and these are preferably used as aqueous emulsions when preparing the coating solution for the coating layer.Water resistance is improved when they are contained alone in the coating layer without using a large amount or a water-soluble polymer compound. However, since these hydrophobic resins have poor heat resistance and low solubility, they inhibit head matching properties such as states king and decoloration resistance against plasticizers. It is better to include it. Furthermore, hydrophobic resin low-molecular compounds, such as low-molecular-weight polyethylene, may actually reduce the fade resistance against plasticizers. A water resistant agent is one that imparts water resistance by crosslinking with a hydrophilic group in a water-soluble polymer compound, and includes, for example, formalin, glyoxal, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde. There are resins, polyethyleneimine resins, etc., and these are preferably used in an amount of 5 to 50% by weight based on the water-soluble polymer compound. When using a waterproofing agent in the coating layer, it may be used as a crosslinking accelerator to further promote the crosslinking reaction.
Metal salts such as NH ₄ Cl, Al ₂ (SO ₄ ) ₃ , MgSO ₄ and Ca(OH) ₂ may be added. A coating layer coating solution is prepared using the above components, and the solution is applied onto the heat-sensitive coloring layer described below and dried to form the desired coating layer. Next, the thermosensitive coloring layer of the present invention will be explained.
Colorless or slightly light-colored leuco compounds include leuco compounds of triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes, including, for example, 3,3-bis(p-dimethylaminophenyl). )
-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophel) 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'-trifluoromethyl)phenylaminofluoran, benzoylleucomethylene blue, 6'-chloro -methoxy-benzoindolino-pyrylospirane, 6'-promo-8'-methoxy-benzoindolino-pyrylospirane, 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), 2,
Examples include 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. 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'-trifluoromethyl)phenylaminofluorane
10 parts by weight Stearic acid amide 20 parts by weight 10% polyvinyl alcohol aqueous solution [PVA-205 manufactured by Kuraray Co., Ltd.] 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 water soluble [manufactured by 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 parts by weight of 20% polyvinyl alcohol aqueous solution [PVA-205 manufactured by Kuraray Co., Ltd.], A thermosensitive coloring layer coating solution was prepared by mixing and stirring 30 parts by weight of water. This coating solution was coated on a commercially available high-quality paper weighing 52 g/m ² using a wire bar so that the coating weight after drying was 6 g/m ² and dried to form a heat-sensitive coloring layer. On this heat-sensitive color forming layer, a coating layer coating liquid having the following composition is applied and dried to form a coating layer, with the coating amount adjusted to 15 g/m ² after drying, and the heat-sensitive recording material of the present invention is prepared. I made it. Coating layer coating liquid 10% polyvinyl alcohol water-soluble [PVA-205 manufactured by Kuraray Co., Ltd.] 40 parts by weight 45% styrene-acrylic acid ester emulsion 6 parts by weight Water 54 parts by weight About this heat-sensitive recording material Discoloration resistance against plasticizers I did a test. Toyo Seiki's fading resistance test
150℃ (1sec, 2.0Kg/m ² ) using thermal gradient tester manufactured by Co., Ltd.
After color development, one sample was placed in water at 20℃ for 5 minutes.
After being immersed for a minute, the dried sample was coated with a polyvinyl chloride wrap film (manufactured by Shin-Etsu Polymer Co., Ltd.) without this procedure, and the change in concentration was tested after 24 hours. As a result, the sample that was not immersed in water had a concentration of 1.27 before the test, which remained unchanged at 1.27 after the test.
In addition, samples immersed in water also have a concentration before testing.
While the concentration was 1.27, the concentration after the test was 1.15, which was sufficiently practical. Examples 2 to 4 A heat-sensitive coloring layer was formed on wood-free paper in the same manner as in Example 1, and a coating liquid having the following formulation was applied on the heat-sensitive coloring layer to a dry coating amount of 1.5 g/m ² The heat-sensitive recording materials of the present invention of Examples 2 to 4 were prepared by adjusting the coating amount as described above. Coating layer coating liquid (Example 2) 10% polyvinyl alcohol water-soluble [PVA-205 manufactured by Kuraray Co., Ltd.] 40 parts by weight 30% methylolmelamine resin aqueous solution 10 parts by weight Water 50 parts by weight Coating layer coating liquid (Example 3) 20% phosphorylated starch water soluble 50 parts by weight 40% glyoxal aqueous solution 10 parts by weight NH ₄ Cl 1 part by weight Water 39 parts by weight Coating layer coating liquid (Example 4) 20% polyvinyl alcohol aqueous solution [PVA-205 manufactured by Kuraray Co., Ltd. ] 30 parts by weight 12% polyamide epichlorohydrin aqueous solution
15 parts by weight Water 55 parts by weight These heat-sensitive recording materials were subjected to a discoloration resistance test against a plasticizer in the same manner as in Example 1, and the results are shown in Table 1. From the table, it can be seen that the samples immersed in water showed almost the same excellent results as the samples not immersed in water, which is extremely preferable in practical terms. 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.
A test for discoloration resistance against plasticizers was conducted in the same manner as above, and the results are shown in Table 1. As is clear from Table 1, it was not practical regardless of whether it was immersed in water or not. Comparative Example 2 A comparative heat-sensitive recording material was prepared in the same manner as in Example 1, except that the coating layer was formed using the following coating layer coating liquid. This heat-sensitive recording material was subjected to a decoloring resistance test against a plasticizer in the same manner as in Example 1, and the results are shown in Table 1. As can be seen from Table 1, the samples that were not immersed in water had good discoloration resistance, but the samples that were immersed in water were not practical. Coating layer coating liquid 20% polyvinyl alcohol aqueous solution [PVA-205 manufactured by Kuraray Co., Ltd.] 50 parts by weight Water 50 parts by weight Comparative example 3 The same procedure as in Example 1 was performed except that the coating layer was formed using the following coating layer coating liquid. A heat-sensitive recording material was prepared for comparison. <Coating layer coating liquid> 40 parts by weight of 10% polyvinyl alcohol aqueous solution 45% polyethylene wax emulsion
6 parts by weight Water 54 parts by weight This heat-sensitive recording material was subjected to a discoloration resistance test against a plasticizer in the same manner as in Example 1, and the results are shown in Table 1. As can be seen from Table 1, the fading resistance was extremely inferior to that of the Examples in both tests.

【table】

[Table] As can be seen from the above results, the heat-sensitive recording material of the present invention has a color-fastening and water-resistant coating layer on the heat-sensitive coloring layer, so that the colored recorded image can be maintained clearly for a long time. was completed.

Claims (1)

[Claims] 1 Supports a thermosensitive coloring layer containing as a coloring component a usually colorless or slightly light-colored leuco body and an acidic substance that reacts with the leuco body to develop color when heated, and a coating layer mainly composed of a water-soluble polymer compound. In the heat-sensitive recording material that is sequentially provided on the body, the coating layer further contains a water-resistant agent that becomes water-resistant by crosslinking with a hydrophilic group in a hydrophobic resin or a water-soluble polymer compound, and A heat-sensitive recording material characterized in that the amount of the hydrophobic resin is 10 to 50% by weight based on the total solid content of the coating layer, and the amount of the water resistant agent is 5 to 50% by weight based on the water-soluble polymer compound.