Thermal recording materials

Abstract

This invention provides a thermal recording material that improves color density compared to conventional materials, and also exhibits good water resistance and light resistance, even when using an N-substituted amino acid derivative, which is biodegradable and environmentally friendly, as the color developer. [Solution] By including N-(m-tolylaminocarbonyl)-phenylalanine as the first color developer and at least one of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as the second color developer, the water resistance and light resistance of the printed area are improved.

Description

Technical Field

[0001] The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material containing at least one of N-(m-tolylaminocarbonyl)-phenylalanine as a first developer, 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea, which improves the water resistance and light resistance of the printed portion.

Background Art

[0002] Generally, heat-sensitive recording materials that obtain color development recording by applying thermal energy (Joule heat) such as a thermal head or a thermal pen to a colorless or light-colored basic dye and an organic developer at room temperature have already been widely put into practical use.

[0003] The performances required for heat-sensitive recording materials include sufficient color density of the printed portion and good print running performance. Depending on the developer, there is a case where the color development ability is present but the print running performance is not good, and depending on the developer used, a sticking phenomenon due to fusion of the thermal head and the heat-sensitive recording layer may be observed. In this phenomenon, a large number of white streaks occur in the printed portion, and the portion becomes white, resulting in a decrease in the apparent color density. This phenomenon is particularly prominent at low printing energy when the coloring component begins to melt, and furthermore, it also causes a load (damage) on the thermal head due to the melt and the cause of head clogging.

[0004] Some phenolic compounds as developers are suspected of being endocrine disruptors, and their use tends to be suppressed. For example, bisphenol A (2,2-bis(4-hydroxyphenyl)propane) was widely used as a raw material for polyester and as a developer for thermal paper, etc. However, in the former law on the examination and regulation of chemicals such as manufacturing, it was designated as a second and third monitored chemical substance, and in the latter law, it was designated as a priority assessment chemical substance. Furthermore, due to the suspicion of being an endocrine disruptor, its use has already been voluntarily restricted in Europe, the United States, Canada, Japan, etc. Furthermore, due to concerns about chromosomal abnormalities and other issues, bisphenol S (4,4'-dihydroxydiphenylsulfone) was registered as a designated chemical substance and regulated as a second-class monitored chemical substance under the previous Act on Examination and Regulation of Manufacture, etc. of Chemical Substances. In addition, in Europe, due to concerns about reproductive toxicity and endocrine disruption to humans and the environment, it was registered as a substance of very high concern in January 2023. Moreover, restrictions on the use of similar phenolic colorants are beginning to be implemented in various countries.

[0005] Therefore, from the standpoint of biological safety, Patent Documents 1 and 2 report the use of N-substituted amino acid derivatives in thermal recording materials, based on the idea of ​​using amino acids, which are also food products, as color developers in thermal recording materials.

[0006] Furthermore, Patent Document 3 proposes a thermal recording material that, in addition to the N-substituted amino acid derivatives, uses Np-toluenesulfonyl N'-3-(p-toluenesulfonyloxy)phenylurea, thereby providing high storage stability of the printed area without reducing the color intensity, whiteness, or heat resistance of the thermal recording material.

[0007] Patent Document 4 proposes a thermal recording material that, in addition to the N-substituted amino acid derivative, uses an N,N'-diarylurea derivative as a preservative stabilizer, thereby providing high preservation stability of the printed area without reducing the color density, whiteness, or heat resistance of the thermal recording material. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6726048 [Patent Document 2] Patent No. 6965002 [Patent Document 3] Patent No. 6856409 [Patent Document 4] Patent No. 6865656 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, when N-substituted amino acid derivatives (Patent Documents 1 and 2) were used alone as color developers, the color intensity could not be said to be high. Furthermore, even when Np-toluenesulfonyl N'-3-(p-toluenesulfonyloxy)phenylurea (Patent Document 3) or N,N'-diarylurea derivatives (Patent Document 4) were used in combination, there were problems with water resistance and light resistance.

[0010] Therefore, the inventors have found that by using N-(m-tolylaminocarbonyl)-phenylalanine, an amino acid derivative, as the first color developer, and further including at least one of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as the second color developer, the water resistance and light resistance of the printed area are improved, leading to the completion of the present invention. [Effects of the Invention]

[0011] By including N-(m-tolylaminocarbonyl)-phenylalanine as the first color developer and at least one of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as the second color developer, a thermal recording material with improved water resistance and / or light resistance of the printed area can be obtained. [Modes for carrying out the invention]

[0012] [1] A basic dye that is colorless or pale at room temperature, A thermal recording material comprising a thermal recording layer on a support containing a color developer that can produce color when heated and comes into contact with the dye, A thermal recording material characterized by having improved water resistance and light resistance of the printed area, wherein the color developer contains N-(m-tolylaminocarbonyl)-phenylalanine as a first color developer and one or more selected from 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as a second color developer. [2] The thermal recording material according to [1], wherein the content of the first color developer and the second color developer is in a mass ratio of 10:1 to 1:5. [3] A thermal recording material [1] or [2] using one or more of 1,2-bis(m-tolyloxy)ethane, 1,2-bis(phenoxy)ethane, and diphenylsulfone as a sensitizer.

[0013] The present invention provides a thermal recording material comprising a thermal recording layer on a support containing a colorless or pale basic dye at room temperature and a developer that can develop color upon contact with the dye by heating, characterized in that the first developer contains N-(m-tolylaminocarbonyl)-phenylalanine, and the second developer contains at least one of 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea.

[0014] The thermal recording layer of the thermal recording material of the present invention is formed by preparing a coating solution by adding the basic dye, color developer, sensitizer, binder, filler, lubricant, and various other additives, and then coating this solution onto a support such as paper, plastic film, or processed paper.

[0015] The content of the first developer N-(m-tolylaminocarbonyl)-phenylalanine and the second developer 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and / or 1,3-diphenylurea is 40:1 to 1:400 by mass ratio, preferably 10:1 to 1:5, more preferably 9:1 to 1:3, and even more preferably 3:1 to 1:3.

[0016] In the thermal recording material of the present invention, examples of basic dyes that are colorless or pale at room temperature include triphenylmethane-based, fluorane-based, diphenylmethane-based, spiro-based, fluorene-based, and thiazine-based compounds, which can be selected from conventionally known leuco dyes. For example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3,3-bis(p-methylaminophenyl)-6-dimethylaminophthalide, 3-diethylamino-7-dibenzylaminobenzo[α]fluorane, 3-(1-ethyl-2-methylindole-3-yl)-3-(4-diethylamino-2-n- Hexyloxyphenyl-4-azaphthalide, 3-(1-ethyl-2-methylindole-3-yl)-3-(4-diethylamino)-2-methylphenyl-4-azaphthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)phthalide, 3-(2-methyl-1-n-octylindole-3-yl)-3-(4-diethylamino-2-ethoxyphenyl)-4-azaphthalide, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-diethyl Diamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(o,p-dimethylanilino)fluorane, 3-(N-ethyl-Np-toluidino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-diethylamino-7-(m -Trifluoromethylanilino)fluorane, 3-di(n-pentyl)amino-6-methyl-7-anilinofluorane, 3-[N-(3-ethoxypropyl)-N-ethylamino]6-methyl-7-anilinofluorane, 3-(Nn-hexyl-N-ethylamino)-7-(o-chloroanilino)fluorane, 3-(N-ethyl-N-2-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro[phthalide-3,9'-Xanthene]-2'-ylamino]phenyl}propane and 3-dibutylamino-7-(o-chloroanilino)fluorane, 3,6-dimethoxyfluorane, 3-pyrrolidino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7,8-dibenzofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-methyl-p-toluidino)-7-methylfluorane, 3-(N-methyl-N-isoamylamino)-7,8-benzofluorane, 3,3'-bis(1-n-amyl- 2-methylindole-3-yl)phthalide, 3-(N-methyl-N-isoamylamino)-7-phenoxyfluorane, 3,3'-bis(1-n-butyl-2-methylindole-3-yl)phthalide, 3,3'-bis(1-ethyl-2-methylindole-3-yl)phthalide, 3,3'-bis(p-dimethylaminophenyl)phthalide, 3-(N-ethyl-Np-tolylamino)-7-(N-phenyl-N-methylamino)fluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-benzylaminofluorane, 3-pyrrolidino-7-dibenzylaminofluorane, The present invention is not limited to these, and more than two types may be used in combination.

[0017] Conventional known sensitizers can be used in combination with the sensitizer of the present invention. Examples include fatty acid amides such as stearic acid amide, bis-stearic acid amide, and palmitic acid amide; p-toluenesulfonamide; stearic acid; fatty acid metal salts such as calcium, zinc, or aluminum, including behenic acid and palmitic acid; p-benzyl biphenyl; diphenyl sulfone; benzyl benzyl benzoate; 2-benzyloxynaphthalene; 1,2-bis(p-tolyloxy)ethane; 1,2-bis(m-tolyloxy)ethane; 1,2-bis(phenoxy)ethane; 1,2-bis(3-methylphenoxy)ethane; 1,3-bis(phenoxy)propane; dibenzyl oxalate; p-methylbenzyl oxalate; m-terphenyl; and 1-hydroxy-2-naphthoic acid. Particularly, 1,2-bis(m-tolyloxy)ethane, 1,2-bis(phenoxy)ethane and diphenyl sulfone are good, and by further using and containing saturated fatty acid monoamides, the sensitivity characteristics can be improved.

[0018] Furthermore, the present invention can be used in combination with conventionally known preservatives. For example, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl m-cresol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, tris(2,6-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 4,4'-thiobis(3-methylphenol), 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenylsulfone, 4,4'-dihydroxy 3,3',5,5'-tetramethyldiphenylsulfone, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane and other hindered phenol compounds, 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenylsulfone, 4-benzyloxy-4'-(2-methylglycidyloxy)diphenylsulfone, glycidyl terephthalate, bisphenol A type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin and other epoxy compounds, N,N'-di-2-naphthyl-p-phenylenediamine, sodium salt or polyvalent metal salt of 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate, bis(4-ethyleniminocarbonylaminophenyl)methane, 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenylsulfone, and diphenylsulfone crosslinked compounds represented by the following general formula (2), etc. These stabilizers contribute to the storage stability of the printed portion of the heat-sensitive recording material.

[0019] [Chemical formula] (In the formula, n represents an integer from 1 to 7.)

[0020] Furthermore, examples of auxiliary agents include dispersants such as sodium dioctyol succinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester waxes; hydrazide compounds such as dihydrazide adipate; water-resistant agents such as glyoxal, boric acid, dialdehyde starch, methylol urea, glyoxylate salts, and epoxy compounds; defoaming agents; coloring dyes; fluorescent dyes; and pigments.

[0021] Examples of binders used in the thermal recording layer of the present invention include fully saponified polyvinyl alcohol with a degree of polymerization of 200 to 1900, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, and cellulose derivatives such as ethylcellulose and acetylcellulose, polyvinyl acetate, polyacrylamide, polyacrylic acid ester, polyvinyl butyral polystyrene and their copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and chroman resins. These binders can be used individually or in combination of two or more, and can be used dissolved in a solvent, or in an emulsified or paste-like dispersion in water or other media.

[0022] Examples of pigments incorporated into the thermal recording layer include inorganic or organic pigments such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium dioxide, zinc oxide, aluminum hydroxide, polystyrene resin, urea-formaldehyde resin, styrene-methacrylic acid copolymer, styrene-butadiene copolymer, and hollow plastic pigments.

[0023] In this invention, the types and amounts of basic dyes, color developers, sensitizers, binders, pigments, and other additives used in the thermal recording layer are appropriately determined according to the quality performance required for the thermal recording layer.

[0024] In the thermal recording layer of the present invention, the developer is preferably 0.3 to 5 parts by mass, and more preferably 0.4 to 3 parts by mass, per 1 part by mass of the basic dye in the thermal recording layer, from the viewpoint of color development density.

[0025] Furthermore, the appropriate sensitizer is 0.2 to 4 parts by mass per part of the leuco dye, and the binder is appropriate at 5 to 50% by mass of the total solids. Suitable supports include paper, recycled paper, synthetic paper, plastic film, nonwoven fabric, and metal foil. Composite sheets combining these materials can also be used.

[0026] Furthermore, an overcoat layer made of a polymer substance containing organic pigments may be provided to enhance storage stability. Additionally, an undercoat layer containing organic pigments, inorganic pigments, or hollow microparticles may be provided to prevent residue from adhering to the thermal head, improve print quality, and enhance sensitivity.

[0027] In the present invention, the basic dyes, color developers, sensitizers, and optionally preservative stabilizers used in the thermal recording layer are finely dispersed using, for example, water as the dispersion medium by a stirring mill such as a ball mill, attritor, or sand mill, so that the average particle size is 2 μm or less. The thermal recording layer coating is prepared by mixing and stirring pigments, binders, auxiliary agents, etc., into the finely dispersed dispersion as needed. The thermal recording layer coating obtained in this way has a dry coating amount of 1.5 to 12 g / m². 2 Approximately, more preferably 3-7 g / m 2 It is formed by coating it onto a support and drying it to achieve a certain degree of texture. [Examples]

[0028] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto. In the examples, "parts" and "%" represent "parts by mass" and "mass%".

[0029] A thermal recording material was prepared using the following procedure.

[0030] [Preparation of undercoat paint] An undercoat paint was prepared by mixing 100 parts of hollow plastic particles (manufactured by Dow Chemical Japan Ltd.: Lowpake SN-1055: hollowness 55%, solids content 26.5%), 100 parts of a 50% dispersion of calcined kaolin, 25 parts of styrene-butadiene latex (manufactured by Asahi Kasei Corporation: L-1571: solids content 48%), 50 parts of a 10% aqueous solution of oxidized starch, and 20 parts of water.

[0031] (Example 1) [Creation of thermal recording paint] Solution A (Preparation of dye dispersion) 3-(N,N-dibutylamino)-6-methyl-7-anilinofluorane 10 parts 20% sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation: Gosenex L-3266) aqueous solution, 5 parts Water 31.4 parts

[0032] Solution B (Preparation of the first color developer dispersion) N-(m-tolylaminocarbonyl)-phenylalanine 10 parts 20% sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation: Gosenex L-3266) aqueous solution, 5 parts Water 31.4 parts

[0033] Solution C (Preparation of sensitizer dispersion) 1,2-Bis(m-tolyloxy)ethane (KS232) 15 parts 20% sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation: Gosenex L-3266) aqueous solution 7.5 parts Water 47.1 parts

[0034] Solution D1 (Preparation of the second color developer dispersion) 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide 10 parts 20% sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation: Gosenex L-3266) aqueous solution, 5 parts Water 31.4 parts

[0035] Solution D2 (Preparation of the second color developer dispersion) 1,3-Diphenylurea 10 parts 20% sulfonic acid-modified polyvinyl alcohol (Mitsubishi Chemical Corporation: Gosenex L-3266) aqueous solution, 5 parts Water 31.4 parts

[0036] The dispersions of liquids A, B, and C were ground in a sand grinder until the average particle size was 1 μm or less, and the dispersions were mixed in the following proportions to prepare the coating solution. Solution A (dye dispersion): 46.4 parts Solution B (first color developer dispersion) 69.6 parts Solution C (sensitizer dispersion) 69.6 parts D1 solution (second color developer dispersion) 23.2 parts

[0037] Table 1 shows the content of the first and second developer components in the total volume of the coating solution prepared in this way. For example, the B solution described earlier totaled 46.4 parts, and contained 10 parts of the first developer. Since 69.6 parts (1.5 times 46.4 parts) were used, the first developer component was present in 15 parts of the total coating solution of 208.8 parts.

[0038] A thermal recording coating was prepared by mixing a component consisting of 25 parts aluminum hydroxide (Hydglight H-42, manufactured by Toshin Kasei Co., Ltd.), 10 parts amorphous silica (Mizukasil P-605, manufactured by Mizusawa Chemical Industry Co., Ltd.), 100 parts 10% dissolved oxidized starch, 15.3 parts zinc stearate dispersion (Hydrin Z-8-36, manufactured by Chukyo Oil & Fat Co., Ltd.), and 58 parts water.

[0039] [Creation of thermal recording material] As a support, high-quality paper (acidic paper) with a basis weight of 53g is used, and the undercoat paint has a mass per square meter of 6g / m² after drying. 2 The paint is applied and dried in such a manner that the mass per unit area of ​​the heat-sensitive paint after drying is 3.8 g / m². 2 It was applied and dried to achieve this result. This sheet was processed using a supercalender to achieve a smoothness (JIS P8155:2010) of 900-1200 s to create a thermal recording material.

[0040] [Various examinations] 1. Thermal recording test (color development test) The prepared thermal recording material was subjected to an applied energy of 0.38 mJ / dot using a thermal recording paper printing tester (Okura Electric TH-PMD). The density of the background and printed areas was measured using a Macbeth reflectance densitometer RD-914.

[0041] 2. Water resistance evaluation Test specimens were subjected to an applied energy of 0.38 mJ / dot, immersed in 20°C water for 15 hours, and then air-dried. The density of the background and printed areas was measured using a Macbeth reflectance densitometer RD-914.

[0042] 3. Lightfastness Test Test specimens subjected to an applied energy of 0.38 mJ / dot were exposed to 5000 Lux conditions for 100 hours, after which the density of the background and printed areas was measured using a Macbeth reflectance densitometer RD-914.

[0043] Table 1 shows the first developer, second developer, and sensitizer contained in the thermal recording material in this example, as well as the results of various tests. Regarding the sensitizer, the total volume of solution C described earlier was 69.6 parts, of which 15 parts were sensitizer. Since there was no increase or decrease in the amount of sensitizer used throughout all examples, only the sensitizer used is listed in the table.

[0044] (Example 2) The procedure was the same as in Example 1, except that Solution D1 was replaced with Solution D2, which is a 1,3-diphenylurea dispersion. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0045] (Example 3) The procedure was the same as in Example 1, except that 11.6 parts of Solution D1 and another 11.6 parts of Solution D2 were used. The results of various tests on the thermal recording material used in this embodiment are similarly described in Table 1. Note that in this embodiment, 2.5 parts each of the first and second color developers were used, and this is indicated in parentheses in the table.

[0046] (Example 4) The procedure was the same as in Example 1, except that 83.52 parts of Solution B and 9.28 parts of Solution D1 were used. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0047] (Example 5) The procedure was the same as in Example 1, except that 23.2 parts of Solution B and 69.6 parts of Solution D1 were used. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0048] (Example 6) The procedure was the same as in Example 1, except that 1,2-bis(m-tolyloxy)ethane (KS232) in Solution C of Example 1 was replaced with 1,2-bis(phenoxy)ethane (KS235). The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0049] (Example 7) The same procedure as in Example 1 was followed, except that 1,2-bis(m-tolyloxy)ethane (KS232) in solution C of Example 1 was replaced with diphenyl sulfone (DPS). The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0050] (Example 8) The procedure was the same as in Example 1, except that 83.52 parts of Solution B from Example 1 were used, and 9.28 parts of Solution D2 were used instead of Solution D1. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0051] (Example 9) The procedure was the same as in Example 1, except that 46.4 parts of Solution B from Example 1 were used, and 46.4 parts of Solution D2 were used instead of Solution D1. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0052] (Example 10) The procedure was the same as in Example 1, except that 46.4 parts of Solution B, 23.2 parts of Solution D1, and an additional 23.2 parts of Solution D2 were used. The results of various tests on the thermal recording material used in this embodiment are similarly described in Table 1. Note that in this embodiment, five parts each of the first and second color developers were used, and this is indicated in parentheses in the table.

[0053] (Example 11) The procedure was the same as in Example 1, except that 1,2-bis(m-tolyloxy)ethane in solution C of Example 1 was replaced with 1,2-bis(phenoxy)ethane, and solution D1 was replaced with solution D2. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0054] (Example 12) The procedure was the same as in Example 1, except that 1,2-bis(m-tolyloxy)ethane in solution C of Example 1 was replaced with diphenyl sulfone, and solution D1 was replaced with solution D2. The results of various tests on the thermal recording material used in this example are similarly described in Table 1.

[0055] [Comparative Example 1] The procedure was the same as in Example 1, except that 92.8 parts of Solution B were used and Solution D was not used. The results of various tests are similarly described in Table 1.

[0056] [Comparative Example 2] The procedure was the same as in Example 1, except that Solution B was not used and 92.8 parts of Solution D1 were used. The results of various tests are similarly described in Table 1.

[0057] [Comparative Example 3] The procedure was the same as in Example 1, except that Solution B was not used and 92.8 parts of Solution D2 were used. The results of various tests are similarly described in Table 1.

[0058] A reference example using conventional phenol-based color developers is shown below. [Reference Example 1] The procedure was the same as in Example 1, except that N-(m-tolylaminocarbonyl)-phenylalanine in Solution B of Comparative Example 1 was replaced with bisphenol A. The results of various tests are similarly described in Table 1.

[0059] [Reference Example 2] The procedure was the same as in Example 1, except that N-(m-tolylaminocarbonyl)-phenylalanine in Solution B of Comparative Example 1 was replaced with bisphenol S (4,4'-sulfonyldiphenol). The results of various tests are similarly described in Table 1.

[0060] [Table 1]

[0061] As is clear from the examples and Table 1, by using N-(m-tolylaminocarbonyl)-phenylalanine as the first developer and 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as the second developer, the water resistance and light resistance of the printed area were improved, and a good thermal recording material was obtained. [Industrial applicability]

[0062] The present invention proposes a thermal recording material that uses N-(m-tolylaminocarbonyl)-phenylalanine, which has high safety as a color developer, and improves the water resistance and light resistance of the printed area. It has extremely promising industrial potential as a replacement for conventional thermal recording materials using phenolic color developers, which have questionable safety.

Claims

1. Basic dyes that are colorless or pale at room temperature, A thermal recording material comprising a thermal recording layer on a support containing a color developer that can produce color when heated and comes into contact with the dye, A thermal recording material characterized by having improved water resistance and light resistance of the printed area, wherein the color developer contains N-(m-tolylaminocarbonyl)-phenylalanine as a first color developer and one or more selected from 5-(N-3-methylphenyl-sulfonamide)-N',N''-bis-(3-methylphenyl)-isophthalic acid diamide and 1,3-diphenylurea as a second color developer.

2. The thermal recording material according to claim 1, wherein the mass ratio of the content of the first color developer and the second color developer is 10:1 to 1:

5.

3. A thermal recording material according to claim 1 or claim 2, wherein one or more of 1,2-bis(m-tolyloxy)ethane, 1,2-bis(phenoxy)ethane, and diphenyl sulfone are used as a sensitizer.

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