JPH0657471B2 - Thermal recording medium - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

The present invention relates to an improvement in a heat-sensitive recording medium, and more particularly to a heat-sensitive recording medium which has excellent resistance to water, an aqueous electrolyte solution, and an organic solvent and does not cause blurring or blurring of heat-sensitive coloring characters even when contacted with these.

[Prior art]

It is already known to use hydrophobic guanidines as a component of a diazo thermal recording medium. Since free guanidines are alkaline, they form water-soluble salts when they come into contact with inorganic acids such as sulfuric acid, phosphoric acid and halogens, and organic acids such as acetic acid. The solubility of this type of salt in water is relatively high, and when it is in contact with water or an aqueous solution of an electrolyte for a long period of time or frequently, it causes bleeding of colored letters. This is a problem for the storability of thermal recordings.

[Problems to be Solved by the Invention]

An object of the present invention is to improve the above-mentioned drawbacks and prevent an increase in solubility due to a reaction with an acid without impairing the color-forming suitability of a diazo-based thermosensitive recording medium using a guanidine as a base agent, thereby preventing an increase in water solubility. It has excellent resistance to organic solvents, not limited to aqueous electrolyte solutions, does not cause blurring or blurring of heat-sensitive coloring characters, and also increases the polarity of the base agent to reduce the solubility in organic solvents, and when uncolored. Another object of the present invention is to provide a thermosensitive recording medium having increased chemical resistance when storing unissued tickets. Structure of the invention

[Means for solving problems]

The heat-sensitive recording medium of the present invention is a fixable heat-sensitive recording medium in which a recording layer containing a diazonium compound, a coupling agent and a base agent is provided on a support.
3-diphenylguanidine, 1,3-di-o-tolylguanidine, triphenylguanidine and 1,3-di-
It is characterized by using a salt of a guanidine derivative obtained from o-tolyl-2-phenylguanidine and an organic acid obtained from adipic acid, terephthalic acid and isophthalic acid. The above-mentioned salt of guanidine may be produced by a conventional method. Equivalent amounts of guanidine and acid previously weighed are dissolved or dispersed in a suitable solvent, and stirring is continued until the reaction is completed. It is safe to heat to a suitable temperature to accelerate the reaction and to use a slight excess of acid so that no free guanidines remain. The produced salt is extracted with a suitable solvent or crystallized, and separated and dried by a conventional method. The salt of guanidines obtained as described above is formed into a paint by a conventional method. In making a coating material, it is desirable to use a means such as a sand mill, a roll mill, a ball mill, and a pearl mill, and to grind it together with other additives. It is also possible to add polyethylene waxes, higher fatty acids such as stearic acid, amides such as stearic acid amide, and melting point depressants such as zinc stearate in order to improve thermal color development characteristics and storage stability. It is important to use an appropriate binder for these, and the binder is selected from synthetic and natural polymer compounds. Examples of the binder include acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate, cellulosic resins such as ethyl cellulose and cellulose acetate, rubber-based resins such as SBR, NBR and cyclized gon, polyester. , Polyvinyl formal, polyvinyl butyral, polyvinyl alcohol,
Vinyl resins such as polyvinyl acetate and polyvinyl chloride,
Examples include natural polymer compounds such as gelatin and casein. The binder may be used alone or in combination of two or more. The ratio of the guanidines to the binder is 0.2 to 5.0, preferably 0.5 to 5.0, relative to 1 part by weight of guanidine.
It is in the range of 2.0 parts by weight. A solvent is used to form the paint. The solvent varies depending on the type of salt to be used and the binder, and one or a mixture of two or more selected from water and general-purpose organic solvents is used. The coating material obtained by the above-mentioned method is applied onto a diazo heat-sensitive layer containing a diazonium salt, a coupling agent and, if necessary, an acid stabilizer according to a conventional method to form a base agent layer to form a heat-sensitive recording medium. The coating thickness of the base agent layer is generally 0.5 to 5 μm.
A suitable thickness depends on the type of salt and the type of binder used. A protective layer may be formed on the base layer in order to improve the running property of the thermal recording medium on the thermal head. The protective layer is prepared by adding wax or fluororesin powder to an appropriate synthetic resin. Its thickness is about 1-5 μ.

[Action]

By using a salt of a specific guanidine derivative and a specific organic acid, which has low water solubility as a base agent, the reactivity with the acid contained in the electrolyte aqueous solution is eliminated or becomes extremely small. Therefore, the durability of the thermal recording medium after fixing is increased. This salt is more polar than free guanidines and has a lower solubility in organic solvents of lesser polarity, increasing the chemical resistance of raw or unissued notes during storage and further increasing solvent selectivity during coating. To do. In this way, the resistance of the thermal recording medium to withstand water, aqueous electrolyte solution and organic solvent is improved. The protective layer provided not only improves the running performance of the thermal head but also has higher printing durability.

Example 1 An ink for a primer layer having the following composition was prepared.
("Parts" are all parts by weight.) Polyester resin "Vylon 300" (Toyobo) 10 parts Methyl ethyl ketone 40 parts Toluene 50 parts Xylylene diisocyanate "Takenate D-110N" (Takeda Chemical Industries) 1 part Total 101 parts Thickness This ink was roll-coated on a milky polyester film having a thickness of 188 μm to form a primer layer having a thickness of 1 μm after drying. A diazo photosensitive solution having the following formulation was prepared. N, N-Diethylaminobenzenediazonium tetrafluoroborate 1 part Naphthol AS-PH 1.5 parts Vinyl chloride-vinyl acetate-polyvinyl alcohol copolymer resin "Vinylite" (UCC) 5 parts Methyl ethyl ketone 20 parts Toluene 20 parts Ethanol 5 parts 52.5 parts in total This diazo photosensitive solution was gravure coated on the primer layer to form a diazo photosensitive layer having a thickness of 1.5 μm after drying. A coating material for a base agent having the following formulation was prepared. Diphenylguanidine isophthalate 5 parts Polymethylmethacrylate-polyethylmethacrylate copolymer resin 5 parts Toluene 40 parts Total 50 parts This base coating material is rod-coated on the above-mentioned diazo photosensitive layer, and the film thickness after drying is 2 μm. A base agent layer was formed. A paint for the protective layer having the following composition was prepared. Polymethylmethacrylate resin “SUMIPEX B-MMO” (Sumitomo Kasei) 10 parts Toluene 90 parts Polyethylene wax “FC-113” (Adeka Argus) 1.5 parts Fluorocarbon thermal mold release agent “F-57” (MOLDWIZ) 1 0.5 parts, 103 parts in total This coating material for a protective layer was rod-coated on the base agent layer to form a protective layer having a thickness of 2 μm after drying to manufacture a thermosensitive recording medium.

Example 2 A thermosensitive recording medium was manufactured in exactly the same manner as in Example 1, except that the base agent of the coating agent for a base agent was changed to 1,3-di-o-tolylguanidine adipate.

Comparative Example 1 A thermal recording medium was produced in exactly the same manner except that the base material of the base material coating material of Example 1 was changed to 1,3-di-o-tolylguanidine.

Comparative Example 2 A coating material for a base agent having the following composition was prepared. 1,3-Di-o-tolylguanidine 5 parts Vinyltoluene-butadiene copolymer resin "Pryolite VT" (Goodyear) 5 parts Cyclohexane 40 parts Total 50 parts A coating material for a protective layer having the following composition was prepared. Polyisobutyl methacrylate resin "Paraloid B-67" (Rohm & Haas) 10 parts Cyclohexane 90 parts Polyethylene wax "FC-113" (Adeka Argus) 1.5 parts Fluorocarbon thermal mold release agent "FC-57" (MOLDWIZ) A thermosensitive recording medium was produced in exactly the same manner except that the coating material for a base agent and the coating material for a protective layer in Example 1 were changed as described above. The evaluation results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in the table. The above results show that by forming the guanidines in the form of a salt having low solubility in water, the range of usable solvents is broadened, and the resistance to water or an aqueous electrolyte solution is significantly affected. EFFECTS OF THE INVENTION By using the heat-sensitive recording medium of the present invention,
Since it has excellent resistance to water, organic solvents, and aqueous electrolyte solutions, even if it is exposed to moisture in the air, water, various beverages, and even sweat, the thermosensitive recording is not affected. Therefore, it is durable when used on a commuter pass that needs to be presented on a mobile phone for a long period of time, and does not cause blurring or blurring of colored characters.

Claims (1)

[Claims] 1. A fixable heat-sensitive recording medium comprising a support and a recording layer containing a diazonium compound, a coupling agent and a base agent, wherein the base agent is 1,3-diphenylguanidine or 1,3-di-. o-tolylguanidine, triphenylguanidine and 1,3-di-o-tolyl-
A thermosensitive recording medium comprising a salt of a guanidine derivative selected from 2-phenylguanidine and an organic acid selected from adipic acid, terephthalic acid and isophthalic acid.