Thermosensitive recording body

Abstract

An object of the present application is to provide a thermal sensitive recording material which is excellent in safety of endocrine disruptors, color development and light resistance, and is excellent in heat resistance. A thermal sensitive recording material (1) has a constitution in which a thermal sensitive recording layer (3) is layered on a base material (2). The thermal sensitive recording layer (3) contains a color developer, a non-phenol color former and a non-phenol antioxidant. The non-phenol antioxidant contains a phosphorus-based antioxidant. The non-phenol color former preferably contains a compound represented by the following formula (1) and / or a compound represented by the following formula (2). (The definition of each symbol in the following formulae (1), (2) is shown in the description.)

Description

TECHNICAL FIELD

[0001] The present application relates to a heat-sensitive recording body, and more particularly, to a heat-sensitive recording body which is low in safety concern, excellent in color development, light resistance, and heat resistance. BACKGROUND

[0002] A heat-sensitive recording body develops color by a chemical reaction by heating with a thermal head or the like, and obtains a recorded image, and is used for a wide range of uses not only as a recording medium for a facsimile, a ticket vending machine, a scientific measuring instrument, but also as a heat-sensitive recording label for a POS system of a retail store or the like, a receipt paper, and the like.

[0003] The heat-sensitive recording body is widely used as described above. Therefore, various properties are required for the heat-sensitive recording body. For example, when a bar code is read with a bar code reader, color development that makes the accuracy of reading based on the bar code reader good is required. In addition, in a case where the heat-sensitive recording body is exposed to strong light including ultraviolet rays for a long time, a property that the heat-sensitive recording body is less likely to yellow (light resistance) is required. Furthermore, excellent heat resistance that the color development of a printed portion is not reduced in heating in a microwave oven or the like, and a non-printed portion is less likely to develop color is also required.

[0004] As such a heat-sensitive recording body, for example, a heat-sensitive recording body has been proposed, which is provided with a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting color developer on a support, and contains a phenol-based color developer such as 2,4'-dihydroxydiphenyl sulfone, and further contains a phenol-based antioxidant having a phenolic hydroxyl group such as 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane as an antioxidant in the heat-sensitive recording layer (for example, refer to Patent Literature 1).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-151948 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The phenol-based color developer, the phenol-based antioxidant, and the like having a phenolic hydroxyl group used in the above-described Patent Literature 1 are a safety concern as an endocrine disruptor. Therefore, in recent years, from the viewpoint of environmental response, a heat-sensitive recording body using an additive such as a color developer, an antioxidant, and the like that does not have a phenol skeleton is required.

[0010] The present application has been achieved in view of such circumstances, and has an object to provide a thermal recording body which is low in safety concern of endocrine disruptors or the like, excellent in color development and light resistance, and also excellent in heat resistance.

[0011] Means for solving the problem

[0012] The present inventors and others have conducted intensive studies in order to achieve the above object, and as a result, have found that a thermal recording body which is low in safety concern of endocrine disruptors or the like, excellent in color development and light resistance, and also excellent in heat resistance can be provided by incorporating, in a thermal recording layer, a color developer which does not have a phenol skeleton (non-phenol color developer) and a specific antioxidant which does not have a phenol skeleton (non-phenol antioxidant). The present application is an application completed on the basis of this insight.

[0013] That is, one aspect of the present application provides a thermal recording body in which a thermal recording layer is layered on a substrate. In the thermal recording body of the present application, the above-mentioned thermal recording layer contains a color developer, a non-phenol color developer, and a non-phenol antioxidant.

[0014] In existing thermal recording bodies, a phenol compound is generally contained as a color developer and an antioxidant. However, phenol compounds are low in safety as endocrine disruptors.

[0015] In contrast, in the thermal recording body according to the present application, the color developer and the antioxidant contained in the thermal recording layer are non-phenol compounds. Therefore, the above-mentioned concern does not arise. In addition, even in the case where a non-phenol compound as described above is used, the thermal recording body of the present application becomes a thermal recording body which is excellent in color development and light resistance, and also excellent in heat resistance.

[0016] In the thermal recording body of the present application, the above-mentioned non-phenol antioxidant contains a phosphorus-based antioxidant. Thereby, light resistance can be particularly improved.

[0017] In one embodiment of the thermal recording body of the present application, it is preferable that the above-mentioned non-phenol color developer contain a compound represented by the following formula (1) and / or a compound represented by the following formula (2).

[0018] [Chemical Formula 1]

[0019]

[0020] (In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 7 , R 8 , R 9 , R 10 , and R11 Each can independently represent a hydrogen atom or a substituent. R 6 and R 12 Each R represents a substituent independently. m represents an integer from 0 to 4. When m is greater than 2, multiple R... 6 They can be the same or different. n represents an integer from 0 to 4. When n is 2 or higher, multiple R... 12 They can be the same or different.

[0021] [Chemistry 2]

[0022]

[0023] (In equation (2), R) 13 R 14 R 15 R 16 R 17 R 19 R 20 R 21 R 22 and R 23 Each can independently represent a hydrogen atom or a substituent. R 18 Indicates a substituent. o represents an integer from 0 to 4. When o is 2 or higher, multiple R... 18 They can be the same or different.

[0024] In one embodiment of the thermal recorder of the present invention, the non-phenolic colorimetric agent preferably contains a compound represented by formula (1a) and / or a compound represented by formula (2a).

[0025] [Chemistry 3]

[0026]

[0027] (The symbols in equation (1a) are the same as those in equation (1).)

[0028] [Chemistry 4]

[0029]

[0030] (The symbols in equation (2a) are the same as those in equation (2).)

[0031] Based on this structure, a thermal recorder with superior color development and heat resistance can be provided.

[0032] In another embodiment of the thermal recorder of the present invention, the content of the non-phenolic color developer relative to the entire thermal recording layer is preferably 10% by mass or more and 50% by mass or less. With this configuration, a thermal recorder exhibiting excellent color development and excellent heat resistance can be provided.

[0033] In another embodiment of the heat-sensitive recording body of the present application, the content of the above non-phenol-based antioxidant is preferably 5% by mass or more and 10% by mass or less with respect to the entirety of the above heat-sensitive recording layer. With this configuration, even a non-phenol-based antioxidant can provide a heat-sensitive recording body that is excellent in color development and heat resistance, and is also excellent in light resistance.

[0034] Effects of the Invention

[0035] According to the present application, a heat-sensitive recording body that is low in safety concerns of endocrine disruptors and the like, is excellent in color development and light resistance, and is also excellent in heat resistance can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic cross-sectional view showing one embodiment of the heat-sensitive recording body of the present application. DETAILED DESCRIPTION

[0037] The heat-sensitive recording body of the present application has a layered structure in which a heat-sensitive recording layer is layered on a substrate. In the heat-sensitive recording body of the present application, the above heat-sensitive recording layer contains a color developer, a non-phenol-based color former, and a non-phenol-based antioxidant. The above non-phenol-based antioxidant contains a phosphorus-based antioxidant.

[0038] Hereinafter, one embodiment of the heat-sensitive recording body of the present application will be described in detail based on the drawings, although the present application is not limited to the following embodiments.

[0039] Figure 1 is a schematic cross-sectional view showing one embodiment of the heat-sensitive recording body of the present application.

[0040] The heat-sensitive recording body 1 of the present embodiment has, as shown in Figure 1 Fig. 1, a layered structure in which a primer layer 6, a heat-sensitive recording layer 3, an intermediate layer 4, and a top coat layer 5 are layered in this order on a sheet-like substrate 2.

[0041] In the present embodiment, the substrate 2 functions as a support of the heat-sensitive recording body 1. As the substrate 2, for example, a paper such as offset paper, art paper, coated paper, kraft paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on a paper substrate, synthetic paper, and a porous material such as nonwoven fabric can be used. In addition, a transparent synthetic resin film such as a polypropylene film, a polyethylene terephthalate film, a polystyrene film, a polycarbonate film, and the like can be used. Note that the thickness of the substrate 2 is not particularly limited, however, in a case where the thickness of the substrate 2 is adjusted to about 10 μm to 100 μm, a substrate 2 excellent in coatability can be obtained. In addition, a substrate 2 excellent in transparency can be obtained.

[0042] In the present embodiment, the primer layer 6 has a function of preventing release of heat supplied from the thermal head, thermal insulation, cushioning, and the like. The primer layer 6 is formed, for example, by adding hollow particles as a filler to a coagulant.

[0043] By providing such a primer layer 6 having thermal insulation to the thermal recording body 1, the sensitivity of printing is improved. Therefore, an increase in the applied voltage of the thermal head can be suppressed, and as a result, thermal adhesion of the thermal head can be suppressed.

[0044] The average particle diameter of the hollow particles added to the primer layer 6 is preferably 1 μm to 100 μm. If it is in this range, the thermal insulation of the primer layer 6 is improved. Here, the average particle diameter is a weight average particle diameter measured by a laser diffraction method. The measurement of the average particle diameter based on the laser diffraction method can be performed, for example, using a product name "MT3300EX-II" manufactured by Microtrac-BEL Corporation.

[0045] In addition, the hollow rate of the hollow particles is preferably 30% to 99%. If it is in this range, the thermal insulation of the primer layer 6 is improved. In addition, the greater the hollow rate of the hollow particles, the higher the thermal insulation effect. Therefore, the color developer can be effectively color-developed with less heat. That is, if the hollow rate is increased, the printing quality of the thermal recording body 1 is improved.

[0046] Here, the hollow rate of the hollow particles is calculated by the following formula.

[0047] Hollow rate = {(volume of voids) / (volume of hollow particles)} x 100

[0048] In addition, with respect to the content ratio of the hollow particles in the primer layer 6, it is preferably 40 parts by mass to 90 parts by mass with respect to 100 parts by mass of the primer layer.

[0049] The material constituting the hollow particles is, for example, a thermoplastic resin. As such a thermoplastic resin, for example, polystyrene-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polyvinyl acetate-based resins, polyacrylate-based resins, polyacrylonitrile-based resins, polybutadiene-based resins, and the like can be given.

[0050] Note that, as the filler of the primer layer 6, a filler other than the hollow particles can also be used. For example, calcined kaolin, alumina, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomite, white carbon, magnesium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, polystyrene resin particles, urea-formaldehyde resin particles, polyolefin resin particles, and the like can be given. In addition, these fillers can be used alone or in combination of two or more.

[0051] As the binding agent contained in the undercoat layer 6, for example, an acrylic-styrene copolymer, a styrene-butadiene copolymer, an acrylic-butadiene-styrene copolymer, a vinyl acetate resin, a vinyl acetate-acrylic acid copolymer, a styrene-acrylate copolymer, an acrylate-based resin, a polyurethane-based resin, or the like can be given.

[0052] In addition, as the binding agent, a polyvinyl alcohol, a starch and a derivative thereof, a methoxycellulose, a hydroxyethylcellulose, a carboxymethylcellulose, a methylcellulose, an ethylcellulose, or the like, a sodium polyacrylate, a polyvinylpyrrolidone, an acrylamide-acrylate copolymer, an acrylamide-acrylate-methacrylate terpolymer, a styrene-maleic anhydride copolymer alkali salt, an isobutylene-maleic anhydride copolymer alkali salt, a polyacrylamide, a sodium alginate, a gelatin, casein, or the like, a water-soluble polymer can also be used.

[0053] The coating amount (dry weight) of the undercoat layer 6 is preferably 1 g / m 2 ~ 10 g / m 2 .

[0054] The thickness of the undercoat layer 6 is preferably 1 μm ~ 20 μm.

[0055] If the coating amount and the thickness of the undercoat layer 6 are adjusted to the above range, the undercoat layer 6 will properly exert the function of thermal insulation.

[0056] In the present embodiment, the heat-sensitive recording layer 3 is a layer that forms a recorded image on the heat-sensitive recording body 1 by color development using a chemical reaction by heating with a thermal head or the like. In the present embodiment, the heat-sensitive recording layer 3 contains a color developer, a non-phenol-based color former, and a non-phenol-based antioxidant.

[0057] As the color former, the color former which performs color development by heating is a component which performs color development by chemical reaction by heating of a heat-sensitive head or the like, and forms a recorded image on the heat-sensitive recording body 1 of the present embodiment. As the color former which performs color development by heating, a generally used known leuco dye can be used. As the leuco dye, for example, 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroanilinofluoran, 3-(N-methyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-anilinofluoran, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-anilinofluoran, 3-(N-methyl-N-n-propyl)amino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-p-toluidinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-8-methylfluoran, 3-diethylamino-7-(m-trifluoromethyl anilinofluoran, 3-diethylamino-7-(o-chloroanilinofluoran, 3-diethylamino-7-chlorofluoran, 3-dibutylamino-6-methyl-7-bromofluoran, 3-dibutylamino-7-(o-chloroanilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-dimethylamino-5-methyl-7-methylfluoran, 3-pyrrolidinyl-6-methyl-7-anilinofluoran, crystal violet lactone, or the like can be used alone or in combination of two or more.

[0058] The particle diameter of the color former is preferably 0.1 to 1.0 μm. Since the color former reacts after being melted, the reaction gradually slows down and the sensitivity characteristics become lower as the particle diameter becomes larger. On the other hand, as the particle diameter becomes smaller, the risk of color development at an unexpected temperature due to heat at the time of drying of the coating increases. In the present embodiment, by setting the particle diameter of the color former to the range as described above, the sensitivity characteristics and the color development temperature of the color former can be appropriately adjusted. Here, the particle diameter means the 50% average particle diameter measured using a Microtrac laser analysis-scattering particle size analyzer.

[0059] In the present embodiment, in order to obtain excellent color development properties, it is preferable to contain about 10 to 20% by mass of the color former with respect to the entire heat-sensitive recording layer 3. Note that it is preferable to contain the color developer described later at a ratio of 1 to 3 with respect to the color former 1 in terms of dry weight ratio.

[0060] In the present embodiment, the heat-sensitive recording layer 3 does not contain a conventional phenol-based color developer, but contains a non-phenol-based color developer. The non-phenol-based color developer is a variety of electron-accepting substances that react with the above-described latent dye upon heating to develop the latent dye, and is a compound that does not have a phenolic hydroxyl group. The constitution of the heat-sensitive recording layer 3 containing the non-phenol-based color developer is, in other words, that a phenol-based color developer that is a safety concern as an endocrine disruptor is not intentionally used. In the present embodiment, by containing the non-phenol-based color developer instead of the phenol-based color developer in the heat-sensitive recording layer 3, the latent dye can be efficiently developed. Note that the heat-sensitive recording layer 3 sometimes contains a trace amount of a phenol-based compound that is not a safety concern as an endocrine disruptor in the form of an impurity or the like. In the case where the heat-sensitive recording layer 3 contains such a trace amount of a phenol-based compound, it is considered to be included in the scope of the present application.

[0061] As such a non-phenol-based color developer, a publicly known color developer that does not have a phenolic hydroxyl group can be used without particular limitation, and for example, 2,2-bis[(4-methyl-3-phenoxy carbonylaminophenyl) ureido] diphenyl sulfone, 4,4'-bis(p-tolylsulfonylaminocarbonylaminodiphenyl methane, 2'-(3-phenylureido) benzene sulfonamide, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl) urea, or the like can be used.

[0062] Here, as the color developer, the above-described non-phenol-based color developer can also be used. However, the present inventors and the like have found that, from the viewpoint of further improving the heat resistance of the heat-sensitive recording body 1, it is appropriate to be a compound represented by the following formula (1) and the following formula (2).

[0063] [Chemical Formula 5]

[0064]

[0065] (In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 7 , R 8 , R 9 , R 10 , and R 11 each independently represent a hydrogen atom or a substituent. R 6 , and R 12 each independently represent a substituent. m represents an integer of 0 to 4. In the case where m is 2 or more, a plurality of R 6 may be the same or different. n represents an integer of 0 to 4. In the case where n is 2 or more, a plurality of R 12 may be the same or different.)

[0066] [Chemical Formula 6]

[0067]

[0068] (R in Formula (2) represents a hydrogen atom or a substituent. R 13 , R 14 , R 15 , R 16 , R 17 , R 19 , R 20 , R 21 , R 22 , and R 23 each independently represent a hydrogen atom or a substituent. R 18 represents a substituent. o represents an integer of 0 to 4. In the case where o is 2 or more, a plurality of R 18 may be the same or different.)

[0069] As the above "substituent", an organic group other than a hydrogen atom can be used without particular limitation, and examples thereof include a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group, an arylamino group, and the like.

[0070] As the above "halogen atom", a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom can be mentioned.

[0071] As the above "alkyl group", a straight-chain or branched-chain alkyl group having 1 to 12 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a 2,3-dimethylpropyl group, a 1-ethylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, an n-hexyl group, an isohexyl group, a 2-hexyl group, a 3-hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, and the like.

[0072] As the above "alkoxy group", a straight-chain or branched-chain alkoxy group having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentoxy group, an isopentoxy group, a t-pentoxy group, a neopentoxy group, a 2,3-dimethylpropoxy group, a 1-ethylpropoxy group, a 1-methylbutoxy group, an n-hexyloxy group, an isohexyloxy group, an n-heptyloxy group, an n-octyloxy group, and the like.

[0073] As the above "aryl group", an aromatic hydrocarbon group having 6 to 10 carbons, such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and the like.

[0074] In the above "dialkylamino group", the 2 alkyl groups can be the same or different.

[0075] As the compound represented by formula (1), from the viewpoint of being able to impart excellent color development and heat resistance to the heat-sensitive recording body 1, a compound represented by the following formula (1a) is preferable. Specifically, N,N'-di- [3- (p-toluenesulfonyloxy) phenyl] urea, N,N'-di- [3- (p-xylene sulfonyloxy) phenyl] urea, N,N'-di- [3- (mesitylene sulfonyloxy) phenyl] urea, N,N'-di- [3- (o-toluenesulfonyloxy) phenyl] urea, N,N'-di- [3- (m-toluenesulfonyloxy) phenyl] urea, N,N'-di- [3- (benzenesulfonyloxy) phenyl] urea, and the like represented by the following formula (1b) can be mentioned.

[0076] [Chemical Formula 7]

[0077]

[0078] (The symbols in formula (1a) are the same as in formula (1).)

[0079] [Chemical Formula 8]

[0080]

[0081] As the compound represented by formula (2), from the viewpoint of being able to impart excellent color development and heat resistance to the heat-sensitive recording body 1, a compound represented by the following formula (2a) is preferable. Specifically, [3- (3-phenylureido) phenyl] -4-methylbenzenesulfonate represented by the following formula (2b) can be mentioned.

[0082] [Chemical Formula 9]

[0083]

[0084] (The symbols in formula (2a) are the same as in formula (2).)

[0085] [Chemical Formula 10]

[0086]

[0087] In the present embodiment, the heat-sensitive recording layer 3 can contain a non-phenolic color developer alone, or can contain two or more.

[0088] By using at least one or both of the compound represented by the above general formula (1) and the compound represented by the above general formula (2) as a non-phenolic color developer in the heat-sensitive recording layer 3, it is possible to improve the heat resistance and color development of the heat-sensitive recording body 1.

[0089] In the present embodiment, the content of the non-phenol-based color developer with respect to the entirety of the heat-sensitive recording layer 3 is preferably 10% by mass or more and 50% by mass or less. From the viewpoint of being able to prevent a lack of color development (a decrease in optical density) due to an insufficient amount of color developer, it is preferable that the content of the non-phenol-based color developer be 10% by mass or more. In addition, from the viewpoint of being able to prevent a lack of color development (a decrease in optical density) due to an excessive amount of color developer (i.e., an insufficient amount of dye), it is preferable that the content of the non-phenol-based color developer be 50% by mass or less.

[0090] In the present embodiment, as described above, a phenol-based color developer is not intentionally used as a color developer in the heat-sensitive recording layer 3, but a trace amount of a phenol-based compound is sometimes unavoidably contained as an impurity or the like of the non-phenol-based color developer. As such an impurity, for example, in the non-phenol-based color developer represented by the above formulae (1) and / or (2), a compound obtained by all or a part of a sulfonate (-SO2-O-), an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, or the like contained as a substituent being hydrolyzed can be mentioned. Such a phenol-based compound contained as an impurity is sometimes able to function as a color developer.

[0091] In the present embodiment, the above-described phenol-based compound that is unavoidably contained as an impurity in the heat-sensitive recording layer 3 can be contained in a trace amount (e.g., to the extent of 100 ppm or less with respect to the entirety of the heat-sensitive recording layer 3) that can be detected by machine analysis, for example, but it is considered that if the amount is this small, there are no safety concerns as an endocrine disruptor or the like, and in practice, the compound does not function as a color developer.

[0092] In the present embodiment, the heat-sensitive recording layer 3 does not contain a conventional phenol-based antioxidant, but contains a non-phenol-based antioxidant. A non-phenol-based antioxidant is a substance that prevents oxidation by capturing or decomposing hydroperoxide, and is a compound that does not have a phenolic hydroxyl group. The configuration in which the heat-sensitive recording layer 3 contains a non-phenol-based antioxidant means, in other words, that a phenol-based compound that is a safety concern as an endocrine disruptor is not intentionally used. In the present embodiment, by containing a non-phenol-based antioxidant instead of a phenol-based antioxidant in the heat-sensitive recording layer 3, the light resistance and heat resistance of the heat-sensitive recording body 1 can be improved. Note that in the case where the heat-sensitive recording layer 3 of the present embodiment contains a phenol-based antioxidant that is not a safety concern as an endocrine disruptor and does not have an impact on color development, light resistance, and heat resistance to the extent that it does not have an impact, it is considered to be included in the scope of the present application as well.

[0093] As such non-phenol-based antioxidant, a publicly known antioxidant having no phenolic hydroxyl group can be used without particular limitation. For example, phosphorus-based antioxidant, aromatic amine-based antioxidant, sulfur-based antioxidant, adipic acid, vitamin C can be cited. Moreover, the present inventors et al. have found that, from the viewpoint of further improving the light resistance and heat resistance of the heat-sensitive recording body 1, it is suitable to be a phosphorus-based antioxidant.

[0094] The phosphorus-based antioxidant is a compound having a trivalent phosphorus atom in the molecule, which is oxidized to a pentavalent phosphorus by reacting with hydroperoxide, decomposes the hydroperoxide, thereby exhibiting an antioxidant function.

[0095] The phosphorus-based antioxidant can be used without particular limitation a compound having a trivalent phosphorus atom in the molecule, for example, a phosphite compound represented by the following formula (3a), a phosphite compound represented by the following formula (3b) can be cited.

[0096] [Chem. 11]

[0097]

[0098] (In formula (3a), R 24 , R 25 and R 26 each independently represent a substituted or unsubstituted hydrocarbon group. R 24 and R 25 may be bonded through a linking group.)

[0099] [Chem. 12]

[0100]

[0101] (In formula (3b), R 27 and R 28 each independently represent a substituted or unsubstituted hydrocarbon group.)

[0102] In the above formula (3a), as R 24 , R 25 and R 26Examples of substituted or unsubstituted hydrocarbon groups include alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, etc.), cycloalkyl groups (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclododecyl, etc.), aryl groups (e.g., phenyl, tolyl, xylyl, naphthyl, 2,6-di-tert-butyl-4-methyl-1-phenyl, 2,4-di-tert-butyl-1-phenyl, etc.), cycloalkyl-alkyl groups (e.g., cyclohexylmethyl, methylcyclohexyl, etc.), aralkyl groups (e.g., benzyl, phenethyl, etc.), haloalkyl groups in which one or more hydrogen atoms in the hydrocarbon group are replaced by halogen atoms (e.g., chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, etc. haloalkyl groups), and groups in which one or more hydrogen atoms bonded to the carbon atoms of these groups are replaced by functional groups such as hydroxyl, carboxyl, nitro, substituted or unsubstituted amino, mercapto, etc.

[0103] As a bonding R 24 and R 25 The linking groups can be, specifically, single bonds, alkylene groups (such as methylene, ethylene, trimethylene, etc., which have 1 to 6 carbon atoms), -O-, -CO-, and groups formed by linking multiple of these groups.

[0104] Among them, as R 24 R 25 and R 26 Preferably, each is independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, more preferably substituted or unsubstituted alkyl (e.g., 2-ethylhexyl, stearyl, etc.), aryl (e.g., phenyl, etc.), or alkyl-substituted aryl (e.g., 2,6-di-tert-butyl-4-methyl-1-phenyl, 2,4-di-tert-butyl-1-phenyl, etc.) with 8 to 20 carbon atoms (constituting the alkyl group).

[0105] In the above equation (3b), R is... 27 and R 28 The substituted or unsubstituted hydrocarbon groups shown can be exemplified by those associated with R. 24 R 25 and R 26 The exemplified groups are either substituted or unsubstituted hydrocarbon groups. Wherein, as R... 27 and R 28 Whether the alkyl group is the same or different, the preferred alkyl group is substituted or unsubstituted, the preferred alkyl group is substituted or unsubstituted, the preferred alkyl group is substituted or unsubstituted with a carbon number (the number of carbons constituting the alkyl group) of 8 to 20 (e.g., 2-ethylhexyl, stearyl, etc.), the preferred alkyl group is aryl (e.g., phenyl, etc.), the preferred alkyl-substituted aryl group is alkyl-substituted (e.g., 2,6-di-tert-butyl-4-methyl-1-phenyl, 2,4-di-tert-butyl-1-phenyl, etc.).

[0106] More specifically, as the phosphorus-based antioxidant, for example, 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol-diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(mono-dinonylphenyl)phosphite, tris(2-ethylhexyl)phosphite, triphenyl phosphite, tris(mono-nonylphenyl)phosphite, triisodecyl phosphite, and the like can be given.

[0107] The phosphorus-based antioxidant can be used alone or in combination with two or more. In addition, as the phosphorus-based antioxidant, for example, commercially available products with trade names of "JP-360", "JP-308E" (manufactured by JUNEN CO., LTD.), "IRGAFOS 168" (manufactured by BASF), "Sanko Epoclean" (manufactured by Sanko Co., Ltd.), "Adekastab 3010", "Adekastab PEP-36" (manufactured by ADEKA CORPORATION), "CS1680" (manufactured by SONGWON), and the like can be used.

[0108] In the present embodiment, the content of the non-phenol-based antioxidant with respect to the entirety of the heat-sensitive recording layer 3 is not particularly limited, but is preferably 5% by mass or more and 10% by mass or less. From the viewpoint of being able to impart excellent light resistance to the heat-sensitive recording body 1 of the present embodiment, it is suitable to constitute such that the content of the non-phenol-based antioxidant is 5% by mass or more. From the viewpoint of being able to impart excellent color development to the heat-sensitive recording body 1 of the present embodiment, it is suitable to constitute such that the content of the non-phenol-based antioxidant is 10% by mass or less.

[0109] In the present embodiment, the content of the non-phenol-based antioxidant with respect to the total amount of the antioxidants contained in the heat-sensitive recording layer 3 is not particularly limited, but from the viewpoint of improving light resistance and heat resistance while reducing the concern about safety of endocrine disruptors and the like, it is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 99% by mass or more.

[0110] In the present embodiment, the content of the non-phenol-based antioxidant with respect to the total amount of the antioxidants contained in the heat-sensitive recording layer 3 is not particularly limited, but from the viewpoint of improving light resistance and heat resistance while reducing the concern about safety of endocrine disruptors and the like, it is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 99% by mass or more.

[0111] In addition, the heat-sensitive recording layer 3 can appropriately contain, as needed, additives such as a fixing agent, a sensitizer, a lubricant, a filler, a storage property improving agent, a pigment, and the like.

[0112] As the binding agent contained in the heat-sensitive recording layer 3, for example, polyvinyl alcohol, modified polyvinyl alcohol, starch, casein, gelatin, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, polyacrylate, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinylpyrrolidone, acrylate, acrylonitrile, methyl vinyl ether, and the like can be given. These binding agents can be used alone or in combination of two or more.

[0113] As the sensitizer, for example, stearic acid, stearic acid amide, stearic aniline, hydroxymethyl stearic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2,6-diisopropyl naphthalene, 1,2-diphenoxyethane, 1,2-diphenoxy methyl benzene, 1,2-bis (3,4-dimethylphenyl) ethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, bis (p-chlorobenzyl) oxalate, bis (p-methylbenzyl) oxalate, dibenzyl oxalate, p-benzyl diphenyl, m-terphenyl, diphenyl sulfone, benzyl p-benzyloxybenzoate, dibenzyl p-toluene dicarboxylate, p-toluenesulfonamide, and the like which are solid at normal temperature, preferably have a melting point of about 70°C or higher, and the like can be given. These sensitizers can be used alone or in combination of two or more.

[0114] As the lubricant, for example, paraffin wax, fatty acids such as oleic acid, polyolefin waxes such as polyethylene wax, metal soaps such as zinc stearate, ester waxes such as carnauba wax, silicone oil, oils such as whale oil can be given. These lubricants can be used alone or in combination of two or more.

[0115] As the filler, for example, aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, aluminum silicate, calcium carbonate, magnesium carbonate, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, kaolin, calcined kaolin, diatomite, white carbon, zinc oxide, silicon oxide, colloidal silica, polystyrene resin particles, urea-formaldehyde resin particles, polyolefin resin particles, and the like can be given. These fillers can be used alone or in combination of two or more.

[0116] As the preservability improving agent, for example, sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, 4,4-butylidenebis(3-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, tris(2,6-di-methyl-4-tert-butyl-3-hydroxybenzyl) isocyanurate, 4-(2-methylglycylaminoxy)-4'-benzyloxydiphenylsulfone, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), diethylthiourea, zinc dibutyldithiocarbamate, 4,4'-thiobis(6-tert-butyl-m-cresol), and a urea urethane compound represented by the following formula (4), and the like can be given.

[0117] [Chem. 13]

[0118]

[0119] These preservability improving agents can be used alone or in combination of two or more. In addition, a publicly known surfactant can also be contained.

[0120] Fresh foods such as meat and fish are sold in the form of a package wrapped with a preservative film, and a label showing a price or the like is attached to the preservative film. In addition, the package is usually displayed in a stacked state, and thus there is a case where the label comes into contact with a preservative film wrapping other package. The preservative film contains a plasticizer for imparting plasticity. In a case where the stacked packages are left for a long time, the plasticizer is transferred to the label, and thus there is a case where the printing is affected. Thus, the heat-sensitive recording body preferably has excellent characteristics such that the printing does not easily disappear or the like even if the plasticizer is transferred, that is, "plasticizer resistance" is excellent.

[0121] In the present embodiment, from the viewpoint of the printing preservability, particularly plasticizer resistance, the heat-sensitive recording layer 3 preferably contains a preservability improving agent, particularly preferably a urea urethane compound represented by the above formula (4).

[0122] It is considered that, by containing the preservability improving agent, particularly the urea urethane compound represented by formula (4), in the heat-sensitive recording layer 3, the reaction efficiency of the leuco dye with the color developer is improved, the electron transfer complex is easily generated, and the reverse reaction is not easily caused, and thus the heat-sensitive recording body has excellent color development, and in addition, the color development density is not easily reduced, and the printing preservability, particularly plasticizer resistance, is excellent.

[0123] The urea urethane compound represented by formula (4) is specifically three kinds represented by the following formulas (4a) to (4c), and they can be used alone or in combination of two or more.

[0124] [Chem. 14]

[0125]

[0126] [Chemical 15]

[0127]

[0128] [Chemical 16]

[0129]

[0130] In the present embodiment, when the heat-sensitive recording layer 3 contains the storage property improving agent, the content of the storage property improving agent with respect to the entire heat-sensitive recording layer 3 is preferably 1% by mass or more and 20% by mass or less. From the viewpoint of being able to suppress a decrease in color development density due to a plasticizer or the like and being able to provide a heat-sensitive recording body that is excellent in print storage property, particularly, plasticizer resistance, the content of the above-mentioned storage property improving agent is preferably 1% by mass or more. In addition, from the viewpoint of preventing a decrease in color development (a decrease in optical density), the content of the above-mentioned storage property improving agent is preferably 20% by mass or less.

[0131] In the present embodiment, when the heat-sensitive recording layer 3 contains the storage property improving agent, the content ratio of the storage property improving agent with respect to the non-phenol-based color developer (storage property improving agent / non-phenol-based color developer) is preferably 1 / 20 to 1 / 1. From the viewpoint of being able to prevent a decrease in color development (a decrease in optical density), the above-mentioned content ratio is preferably 1 / 1 or less. In addition, from the viewpoint of being able to suppress a decrease in color development density due to a plasticizer or the like and being able to provide a heat-sensitive recording body that is excellent in print storage property, particularly, plasticizer resistance, the above-mentioned content ratio is preferably 1 / 20 or more.

[0132] In the present embodiment, when the heat-sensitive recording layer 3 contains the urea urethane compound represented by formula (4), the content of the urea urethane compound represented by formula (4) with respect to the entire heat-sensitive recording layer 3 is preferably 1% by mass or more and 20% by mass or less. From the viewpoint of being able to suppress a decrease in color development density due to a plasticizer or the like and being able to provide a heat-sensitive recording body that is excellent in print storage property, particularly, plasticizer resistance, the content of the above-mentioned urea urethane compound is preferably 1% by mass or more. In addition, from the viewpoint of preventing a decrease in color development (a decrease in optical density), the content of the above-mentioned urea urethane compound is preferably 20% by mass or less.

[0133] In the present embodiment, in the case where the urea urethane compound represented by formula (4) is contained in the heat-sensitive recording layer 3, the ratio of the urea urethane compound represented by formula (4) to the non-phenolic color developer (urea urethane compound / non-phenolic color developer) is preferably 1 / 20 to 1 / 1. From the viewpoint of being able to prevent a lack of color development (a decrease in optical density), the above ratio is preferably 1 / 1 or less. In addition, from the viewpoint of being able to suppress a decrease in color development density due to a plasticizer or the like and to provide a heat-sensitive recording material that is excellent in print durability, particularly, plasticizer resistance, the above ratio is preferably 1 / 20 or more.

[0134] In the present embodiment, the content of the urea urethane compound represented by formula (4) is not particularly limited with respect to the total amount of the print durability improving agent contained in the heat-sensitive recording layer 3, but from the viewpoint of being able to suppress a decrease in color development density due to a plasticizer or the like and to provide a heat-sensitive recording material that is excellent in print durability, particularly, plasticizer resistance, the content is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 99% by mass or more.

[0135] In the present embodiment, by providing the intermediate layer 4 on the heat-sensitive recording layer 3, a heat-sensitive recording material 1 that is excellent in water resistance, chemical resistance, plasticizer resistance, and the like can be obtained.

[0136] As the material constituting the intermediate layer 4, for example, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, casein, gelatin, glue, gum arabic, polyamide, polyacrylamide, modified polyacrylamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl acetate, polyacrylate, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, diisobutylene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, methyl vinyl-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, styrene-butadiene copolymer, maleic acid copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyurethane, polystyrene, polyvinylpyrrolidone, acrylate, acrylonitrile, methyl vinyl ether polyvinyl alcohol, and the like water-based resins can be given. Note that the "water-based resin" means a resin component that is dispersed in water or dissolved in water. These materials can be used alone or in combination of two or more.

[0137] The above resin uses a resin having a water-soluble portion, for example, a polyvinyl alcohol (PVA) resin that belongs to a resin having a hydrophilic structure unit of a hydroxyl group, or a core-shell structured resin in which a hydrophobic core particle is coated with a water-soluble shell polymer, for example, a core-shell type acrylic resin, and the like, whereby the transparency can be improved.

[0138] As the core-shell type resin, for example, a resin sold under the name of "Bariastar (manufactured by Mitsui Chemicals, Inc.) " as a core-shell type acrylic resin, or the like can be used.

[0139] The coating amount (dry weight) of the intermediate layer 4 is preferably 0.3 g / m 2 ~ 10 g / m 2 .

[0140] The top coat layer 5 is a layer that improves the thermal head adaptability of the thermal recording body 1 to the thermal head and smoothly performs the color development of the thermal recording layer 3. Specifically, it refers to performing the color development of the thermal recording layer 3 without as much as possible causing the accumulation of adherents to the thermal head, and the undesirable condition of the surface of the thermal recording body 1 being deformed by heat.

[0141] In the present embodiment, the top coat layer 5 of the thermal recording body 1 functions to reduce the abrasion of the thermal head without reducing the life of the thermal head in a state where no elastic particles or the like are added. This means the improvement of the so-called thermal head adaptability. In addition, the top coat layer 5 needs to improve the anti-sticking property to the thermal head. Here, the so-called anti-sticking property is the property of not easily causing the undesirable condition of the components of the top layer of the thermal recording body being fused and adhering to the thermal head due to the heat of the thermal head. More specifically, it is the property of not easily causing the undesirable condition of the thermal recording body being partially not printed, or the printed surface being deformed.

[0142] The top coat layer 5 of the present embodiment has evaporation holes and cracks due to the evaporation of moisture in the form of recessed depressions on the surface thereof. Thereby, the contact area of the surface of the top coat layer 5 with the thermal head is reduced.

[0143] In order to produce the depressions, particularly cracks, on the surface of the top coat layer 5 like this, a coating liquid containing hydrophobic resin particles is used as the coating liquid for forming the top coat layer 5.

[0144] That is, in the present embodiment, the top coat layer 5 uses an emulsion of hydrophobic resin particles, for example, an emulsion obtained by water-dispersing hydrophobic acrylic resin particles, as the binder.

[0145] By using the emulsion of hydrophobic resin particles as the binder of the top coat layer 5 like this, no water-soluble polymer is used.

[0146] When the coating liquid containing a water-soluble polymer is dried after being applied, it is not easy to agglomerate and form a coating film having flexibility, and thus cracks due to shrinkage do not occur in the top coat layer 5.

[0147] On the other hand, when the emulsion of hydrophobic resin particles is dried after being applied, the hydrophobic resin particles agglomerate and shrink due to evaporation between the hydrophobic resin particles, and cracks in the form of depressions occur on the surface of the top coat layer 5.

[0148] Since the cracks are formed due to shrinkage of the agglomeration of the hydrophobic resin particles, they remain in the top coat layer 5 and do not reach the intermediate layer 4.

[0149] In addition, in the present embodiment, in order to form evaporation holes due to evaporation of moisture that become recesses on the surface of the top coat layer 5, the three layers of the heat-sensitive recording layer 3, the intermediate layer 4, and the top coat layer 5 are simultaneously coated using a curtain coater.

[0150] The curtain coater ejects each coating liquid for forming the heat-sensitive recording layer 3, the intermediate layer 4, and the top coat layer 5 from a plurality of slits to be stacked, and the stacked coating liquid continuously travels. At this time, the coating is performed by free fall onto the base coat layer 6 that is formed in advance on the substrate 2.

[0151] In such simultaneous coating of the three layers using the curtain coater, the top coat layer 5 once dried generates cracks due to the beginning of agglomeration of the hydrophobic resin particles as described above, water vapor is discharged from the cracks, and the semi-dried intermediate layer 4 and the heat-sensitive recording layer 3 are dried and cured. Most of the water vapor of the intermediate layer 4 and the heat-sensitive recording layer 3 is released from the cracks, but a part of the water vapor is released by forming evaporation holes in the top coat layer 5. Therefore, cracks and evaporation holes are formed in the vicinity of the top coat layer 5.

[0152] In the present embodiment, the evaporation holes formed in the top coat layer 5 remain in the intermediate layer 4. Therefore, even if oil or the like is attached to the surface of the top coat layer 5 as the uppermost layer, it does not reach the heat-sensitive recording layer 3, and there is no case where the heat-sensitive recording layer 3 is discolored or the like.

[0153] The top coat layer 5 contains additives such as a lubricant, a crosslinking agent, a dispersant, an antifoaming agent, a water resistance agent, a filler, and the like as needed.

[0154] As the lubricant, for example, polyethylene, zinc stearate, or the like can be given. As the crosslinking agent, for example, zirconium carbonate or the like can be given.

[0155] As the filler, for example, aluminum hydroxide, aluminum oxide, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomite, white carbon, magnesium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, polystyrene resin particles, urea-formaldehyde resin particles, polyolefin resin particles, or the like can be given. These fillers can be used alone or in combination of two or more. Note that the particle diameter of the filler contained in the top coat layer 5 is preferably 1.0 μm or less.

[0156] In the present embodiment, as the coating liquid for forming the top coat layer 5, an emulsion obtained by water-dispersing a hydrophobic acrylic resin, polyethylene wax as a lubricant, and calcium carbonate as a pigment are mixed at a mass ratio of 4:3:3 at the time of drying to produce a water-dispersed suspension, and the water-dispersed suspension is used to manufacture the heat-sensitive recording body 1.

[0157] The coating amount (dry weight) of the top coat layer 5 was set to 1 g / m 2 .

[0158] According to the present embodiment, since the cracks that become recesses and the evaporation holes of moisture are formed on the surface of the top coat layer 5 that is the uppermost layer of the heat-sensitive recording body 1 as described above, the surface of the top coat layer 5 becomes uneven. Thereby, the contact area of the top coat layer 5 with the thermal head is reduced, the wear of the thermal head is alleviated to improve the adaptability of the thermal head, and the blocking resistance is improved.

[0159] The thickness of the top coat layer 5 is adjusted to be, for example, less than 1 μm. In the present embodiment, it is adjusted to be about 0.8 μm. Thereby, since the distance from the surface of the top coat layer 5 to the heat-sensitive recording layer 3 is short, the heat from the thermal head is efficiently conducted to the heat-sensitive recording layer 3. In addition, since the thickness is thin, it contributes to the reduction of cost.

[0160] Further, since the cracks of the surface of the top coat layer 5 develop along the thickness direction that is the inside of the top coat layer 5, they are cut off in the direction orthogonal to the thickness direction of the top coat layer 5, that is, in the lateral direction, due to the cracks. Thereby, the release of heat from the thermal head toward the lateral direction is suppressed. As a result, the heat from the thermal head is efficiently conducted to the heat-sensitive recording layer 3 that is the lower layer in the thickness direction.

[0161] In order to reduce the contact area of the top coat layer 5 with the thermal head, the evaporation holes of moisture that are substantially circular are preferably 2 μm or more in average diameter.

[0162] The average diameter of the evaporation holes is calculated by observing the surface of the top coat layer 5 using an electron microscope (SEM) and measuring the diameter of the evaporation holes per unit area, for example, per 1 mm 2 of the surface. In addition, as for the number of evaporation holes, for example, the evaporation holes of 5 μm or more in average diameter are preferably 30 or more, more preferably 40 or more, per 1 mm 2 of the surface.

[0163] In the heat-sensitive recording body 1 of the present embodiment, by adjusting the formulation of the top coat layer 5 or the like, for example, the surface of the top coat layer 5 can be made into a surface having a large number of evaporation holes and a small number of cracks. Alternatively, the surface of the top coat layer 5 can be made into a surface having only a large number of evaporation holes without cracks.

[0164] In the present embodiment, although the three layers of the heat-sensitive recording layer 3, the intermediate layer 4, and the top coat layer 5 are simultaneously coated using a curtain coater, it is not limited to the simultaneous coating, and each of the heat-sensitive recording layer 3, the intermediate layer 4, and the top coat layer 5 can be formed one by one in order.

[0165] In the present embodiment, the primer layer 6 and the intermediate layer 4 are formed on the substrate 2, but at least either one of the primer layer 6 and the intermediate layer 4 can be omitted as another embodiment of the present application.

[0166] The heat-sensitive recording body of the above embodiment is excellent in light resistance, color development, and heat resistance because of the heat-sensitive recording layer having the above configuration.

[0167] The amount of change in white color degree (%) of the heat-sensitive recording body of the present embodiment represented by the following formula is preferably -10% or more, more preferably -9% or more, further preferably -8% or more, and particularly preferably -7% or more from the viewpoint of excellent light resistance and suppression of reduction in white color degree due to light irradiation.

[0168] Amount of change in white color degree (%) = white color degree after 100 hours under illuminance of 5000 Lux - white color degree before the test

[0169] The white color degree is a value obtained in accordance with JIS P 8148.

[0170] A negative value (-) of the above amount of change in white color degree (%) indicates the amount of reduction in white color degree, and the closer to 0%, the less the reduction in white color degree and the more excellent the light resistance.

[0171] The absolute value of Δb of the heat-sensitive recording body of the present embodiment represented by the following formula is preferably 5 or less, more preferably 4 or less, and further preferably 3 or less from the viewpoint of excellent light resistance and suppression of yellowing and bluing (bluish color) due to light irradiation.

[0172] Δb = b value after 100 hours under illuminance of 5000 Lux - b value before the test

[0173] The b value indicates the chromaticity in the L * a * b * color space prescribed in JIS Z 8781-4:2013.

[0174] The b value indicates the change from blue to yellow, and the greater, the closer to yellow, and the smaller, the closer to blue. The above Δb indicates the amount of change in the b value, and a positive value indicates yellowing, and a negative value indicates bluing. Thus, the closer to 0 of the absolute value of Δb, the less the yellowing and bluing, and the more excellent the light resistance.

[0175] The above Δb indicates the degree of yellowing, and the lower value, the less the yellowing, and the more excellent the light resistance.

[0176] The dynamic sensitivity (OD value) of the printed portion at 0.16 mj / dot of the heat-sensitive recording body of the present embodiment is preferably 0.3 or more, and more preferably 0.35 or more from the viewpoint of excellent color development.

[0177] The dynamic sensitivity (OD value) of the printed portion at 0.20 mj / dot of the thermal recording body of the present embodiment is preferably 0.9 or more, more preferably 1 or more from the viewpoint of excellent color development.

[0178] The dynamic sensitivity (OD value) of the printed portion at 0.40 mj / dot of the thermal recording body of the present embodiment is preferably 1.1 or more, more preferably 1.2 or more from the viewpoint of excellent color development.

[0179] The above dynamic sensitivity (OD value) is a value measured in the examples shown later, and the higher the value, the more excellent the color development.

[0180] The OD value of the non-printed portion in the (heat resistance evaluation) of the examples shown later of the thermal recording body of the present embodiment is preferably 0.2 or less, more preferably 0.18 or less, and further preferably 0.15 or less from the viewpoint of excellent heat resistance, i.e., the ability to clearly recognize the printed portion even after heating cooking in a microwave oven or the like.

[0181] Examples

[0182] In the following examples and comparative examples, thermal recording bodies containing a non-phenolic color developer and a non-phenolic antioxidant in the thermal recording layer were produced, and the color development, light resistance, and heat resistance were evaluated. Note that the present application is not limited to these examples.

[0183] (Examples 1 to 6, Comparative Examples 1 and 2)

[0184] (Production of thermal recording body)

[0185] <Undercoat layer>

[0186] On a 70 g / m 2 offset paper (thickness: 80 μm) as a base material, an undercoat layer coating liquid obtained by mixing and stirring a composition in which hollow particles (solid content concentration: 26.5%, ROPAQUE HP-1055: Rohm & Hass Japan Co., Ltd.) 70 parts by mass, modified styrene butadiene latex (solid content concentration: 49%) 10 parts by mass, and water 20 parts by mass were mixed at a ratio of 70:10:20 was applied, and dried to form an undercoat layer having a dry coating amount of 3.0 g / m 2 and a thickness of 5 μm.

[0187] <Thermal recording layer>

[0188] A coating liquid for forming a thermal recording layer shown in Table 1 was prepared, and the prepared coating liquid for forming a thermal recording layer was applied to the above undercoat layer so that the coating amount was 4.0 g / m 2After that, drying was performed, whereby a heat-sensitive recording layer having a thickness of 3.5 μm was formed on the undercoat layer. Note that in Table 1, the numerical values of the respective compounding materials indicate weight ratios at the time of drying.

[0189] In addition, as the compounding material, 3-dibutylamino-6-methyl-7-anilinofluorane having a particle diameter of 0.6 to 0.7 μm was used as the leuco dye, [3-(3-phenylureido)phenyl]-4-methylbenzenesulfonate represented by the above formula (2b) was used as the color developer 1, and N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea represented by the above formula (1b) was used as the color developer 2. In addition, phosphorus-based tris(2,4-di-tert-butylphenyl) phosphite (manufactured by SONGWON) was used as the antioxidant 1.

[0190] In addition, 1,2-bis(3-methylphenoxy)ethane (a material that was made into a dispersion liquid having a solid content concentration of 20% by being dispersed in an aqueous PVA solution) was used as the sensitizer, a styrene acrylic copolymer emulsion was used as the coagulant, calcium carbonate (a material that was made into a dispersion liquid having a solid content concentration of 30% by being dispersed in a 5% aqueous sodium hexametaphosphate solution) was used as the pigment, and a zinc stearate emulsion was used as the lubricant.

[0191] <Undercoat layer>

[0192] An acrylic emulsion (solid content concentration 30%) liquid was applied to the above heat-sensitive recording layer, and dried, thereby forming an undercoat layer having a dried coating amount of 1.6 g / m 2 and a thickness of 1.5 μm.

[0193] <Topcoat layer>

[0194] A liquid in which an acrylic emulsion (solid content concentration 20%) was 40 parts by mass, calcium carbonate was 5 parts by mass, a polyethylene wax (solid content concentration 40%) was 15 parts by mass, and water was 40 parts by mass was mixed and stirred, and the obtained liquid was applied to the intermediate layer, and dried, thereby forming a topcoat layer having a dried coating amount of 1.0 g / m 2 and a thickness of 0.9 μm.

[0195] By the above method, the heat-sensitive recording bodies of Examples 1 to 6 and Comparative Examples 1 and 2 were produced.

[0196]

[0197] (Photo resistance evaluation)

[0198] In the light resistance evaluation, the optical density (OD value of the printed part / OD value of the non-printed part), yellowing (yellowing), and change in whiteness were measured for the printed part and the non-printed part of each of the thermal sensitive recording bodies of each of the examples and each of the comparative examples. The steps of the light resistance evaluation are described below.

[0199] The thermal sensitive recording bodies produced were printed using a thermal paper printing test device (Oakla Engineering Co., Ltd., product name: Pulse Simulator TH-M2 / PP) set to a printing speed of 50 mm / sec, an applied voltage of 17.0 V, a thermal head resistance value of 870 Ω, a pulse width of 0.488 to 1.394 ms, and a printing energy of 0.40 mJ / dot.

[0200] The thermal sensitive recording bodies printed above were placed for 100 hours at a position where the distance from a fluorescent lamp was confirmed to be 5000 Lux using an illuminometer.

[0201] The optical density (OD value of the printed part / OD value of the non-printed part) of the printed part and the non-printed part of the sample of the thermal sensitive recording body before the test and after the above placement was measured using a spectrophotometer (Videojet X-rite Co., Ltd., product name: eXact).

[0202] In addition, the whiteness (%) and the hue (L, a, b) of the sample of the thermal sensitive recording body before the test and after the above placement were measured. The whiteness was measured using a photoelectric reflection densitometer (Tokyo Denshoku Co., Ltd., product name: TC-6DS / A) in accordance with JIS P 8148.

[0203] The hue (L, a, b) was measured using a color difference meter (Videojet X-rite Co., Ltd., product name: SpectroEye).

[0204] The measurement results obtained by the above test are shown in Table 2. In the measurement results in Table 2, in the case where the optical density (OD value) of the printed part and the non-printed part is large (i.e., the reflectance of light is small), it is indicated that the color development (color development state is close to black) is further performed, and in the case where the optical density (OD value) is small (i.e., the reflectance of light is large), it is indicated that the color development is insufficient. The larger the value of the whiteness (%) is, the closer to white it is. Among the indexes of the hue (L, a, b), (L) indicates the change from black to white, and the larger the value of (L) is, the closer to white it is. (a) indicates the change from green to red, and the larger the value of (a) is, the closer to red it is. (b) indicates the change from blue to yellow, and the larger the value of (b) is, the closer to yellow it is. The light resistance of each of the thermal sensitive recording bodies was evaluated based on the changes in these colors.

[0205] (dynamic sensitivity evaluation)

[0206] In the dynamic sensitivity test, each of the thermal recording bodies of each of the examples and each of the comparative examples was printed with different printing energies, and the optical density (OD value of the printed portion) under each of the printing energies was measured. The dynamic sensitivity of each of the thermal recording bodies of each of the examples and each of the comparative examples was evaluated based on the measurement results. Hereinafter, the procedure of the dynamic sensitivity test is described.

[0207] The thermal recording bodies produced were printed using a thermal paper printing test device (Oakla Engineering Co., Ltd., trade name: Pulse Simulator TH-M2 / PP) set at a printing speed of 50 mm / sec, an applied voltage of 17.0 V, a thermal head resistance value of 870 Ω, and a pulse width of 0.488 to 1.394 ms at each of the printing energies of 0.16 mJ / dot, 0.20 mJ / dot, and 0.40 mJ / dot, and the optical density (OD value) under each of the printing energy conditions was measured using a spectrophotometer (X-rite Co., Ltd., trade name: eXact).

[0208] The measurement results obtained by the above test are shown in Table 2. As with the light resistance test described above, in the measurement results of Table 2, in the case where the value of the optical density (OD value) is large, it is indicated that the color development was further performed, and in the case where the value is small, it is indicated that the color development was insufficient. For example, in the case where the value of the optical density (OD value) is large, it is evaluated as "good color developability" even though the printing energy is small. On the other hand, in the case where the value of the optical density (OD value) is small, it is evaluated as "poor color developability" even though the printing energy is large. That is, the dynamic sensitivity test is an evaluation of color developability.

[0209] (heat resistance evaluation)

[0210] In the heat resistance test, the printed portion and the non-printed portion of each of the thermal recording bodies of each of the examples and each of the comparative examples were heated, and the optical density (OD value of the printed portion) of the printed portion and the non-printed portion was measured. The heat resistance of each of the thermal recording bodies of each of the examples and each of the comparative examples was evaluated based on the measurement results. Hereinafter, the procedure of the heat resistance test is described.

[0211] The thermal recording bodies produced were printed using a thermal paper printing test device (Oakla Engineering Co., Ltd., trade name: Pulse Simulator TH-M2 / PP) set at a printing speed of 50 mm / sec, an applied voltage of 17.0 V, a thermal head resistance value of 870 Ω, and a pulse width of 0.488 to 1.394 ms at a printing energy of 0.40 mJ / dot.

[0212] A container (diameter: 12 cm, content: 220 cc) containing 100 g of water was capped with a vinyl chloride-made preservative film (thickness: 10 μm) on which the sample (length: 3 cm, width: 4 cm) of the heat-sensitive recording body printed with the above was stuck.

[0213] Then, in order to discharge water vapor at the time of heating, 10 through-holes were formed in the preservative film using a safety pin. Note that the through-holes were formed partially avoiding the sample, and were formed in a manner such that the distance between the through-holes was uniform.

[0214] Then, the container was heated for 1 minute using a microwave oven (1500 W), after which the optical densities (OD values) of the printed and non-printed portions of the sample of the heat-sensitive recording body were measured using a spectrophotometer (X-rite Co., trade name: eXact).

[0215] The measurement results obtained by the above test are shown in Table 2. In the evaluation of heat resistance, in the case where the value of the optical density (OD value) is smaller in the non-printed portion and larger in the printed portion, it means that the heat-sensitive recording body has a small reaction to heat. That is, it indicates the degree of color development of the printed or non-printed portion when heat due to vapor caused by heating the heat-sensitive recording body using a microwave oven is applied to the heat-sensitive recording body. Therefore, since the non-printed portion is preferably as little as possible to develop color, in the case where the value of the optical density (OD value) is small, it can be evaluated as "good heat resistance". On the other hand, it is confirmed that the colored portion of the printed portion does not disappear due to heat due to vapor. Specifically, in the case where the value of the optical density (OD value) of the printed portion is large, it means that the reaction to heat is not large.

[0216]

[0217] <Verification Results>

[0218] From the results shown in Table 2, the following conclusions can be confirmed.

[0219] [Examples 1 to 3 and Comparative Example 1]

[0220] Examples 1 to 3 and Comparative Example 1 containing the same color developer 1 were investigated.

[0221] (1) In the light resistance test, the white color change amount of Examples 2 to 3 was small compared with that of Comparative Example 1, and the white color after the test was also high. It was presumed that this was because the antioxidant 1 (non-phenol antioxidant) was contained in Examples 2 to 3. On the other hand, the white color change amount of Example 1, in which the amount of the antioxidant 1 was 5 mass% which was less than that of Examples 2 to 3 (7.5 mass%, 10 mass%), was -8.2, which was higher than that of Comparative Example 1, but the difference was as small as 0.70. Thus, it can be said that the change in the white color of Example 1 was the same degree as that of Comparative Example 1. In addition, the absolute value of Δb of Examples 1 to 3 was lower than that of Comparative Example 1, and furthermore, there was no difference in the optical density (OD value) of the non-printed portion after the test between Examples 1 to 3 and Comparative Example 1.

[0222] From these results, it was confirmed that the thermal sensitive recording body of Examples 1 to 3 containing the non-phenol antioxidant was excellent in light resistance compared with Comparative Example 1 not containing the antioxidant.

[0223] (2) In the dynamic sensitivity test (color development), the optical density (OD value) of Examples 1 to 3 was 1.52 to 1.55 when the printing energy was set to 0.40 mJ / dot, and the optical density (OD value) of Comparative Example 1 was 1.58. The optical density (OD value) of Examples 1 to 3 was 1.07 to 1.16 when the printing energy was set to 0.20 mJ / dot, and the optical density (OD value) of Comparative Example 1 was 1.23. The optical density (OD value) of Examples 1 to 3 was 0.57 to 0.63 when the printing energy was set to 0.16 mJ / dot, and the optical density (OD value) of Comparative Example 1 was 0.64. Examples 1 to 3 had a tendency to have a lower optical density (OD value) compared with Comparative Example 1. However, the decrease was about 2 to 13%, and the color development was shown to be good enough to be used as a thermal sensitive recording body.

[0224] From these results, it was confirmed that the thermal sensitive recording body of Examples 1 to 3 containing the non-phenol antioxidant had a color development which was not inferior to that of Comparative Example 1 not containing the antioxidant.

[0225] (3) In the heat resistance test, the optical density (OD value) of the printed portion of Examples 1 to 3 was 1.48 to 1.51, and the optical density (OD value) of the non-printed portion was 0.11 to 0.12. The optical density (OD value) of the printed portion of Comparative Example 1 was 1.52, and the optical density (OD value) of the non-printed portion was 0.13. In particular, in the non-printed portion, Examples 1 to 3 had a tendency to have a lower increase in the optical density (OD value) compared with Comparative Example 1.

[0226] From these results, it was confirmed that the thermal sensitive recording body of Examples 1 to 3 containing the non-phenol antioxidant was improved in heat resistance compared with Comparative Example 1 not containing any antioxidant.

[0227] [Examples 4 to 6 and Comparative Example 2]

[0228] Examples 4 to 6 and Comparative Example 2 containing the same color developer 2 were investigated.

[0229] (4) In the light resistance test, the white color degree change amount of Examples 4 to 6 was 0 to 0.6, and that of Comparative Example 2 was 0.6, and no decrease in the white color degree was observed. In addition, the white color degree after the test was also the same degree.

[0230] From these results, it was confirmed that Examples 4 to 6 containing the non-phenol-based antioxidant showed no inferior light resistance compared to Comparative Example 2 not containing the antioxidant.

[0231] (5) In the dynamic sensitivity test, the optical density (OD value) of Examples 4 to 6 was 1.15 to 1.17 when the printing energy was set to 0.40 mJ / dot, 0.91 to 0.94 when the printing energy was set to 0.20 mJ / dot, and 0.35 to 0.42 when the printing energy was set to 0.16 mJ / dot, and the optical density (OD value) of Comparative Example 2 was 1.20, 0.97, and 0.40, respectively. Examples 4 to 6 had a tendency to have a lower optical density (OD value) compared to Comparative Example 2. However, the decrease was about 13% or less, and showed a coloring property that could be used as a good thermal recording body.

[0232] From these results, it was confirmed that the thermal recording body of Examples 4 to 6 containing the non-phenol-based antioxidant had a coloring property that was not inferior to the same degree as Comparative Example 2 not containing the antioxidant.

[0233] (6) In the heat resistance test, the optical density (OD value) of the printed part and the optical density (OD value) of the non-printed part of each of Examples 4 to 6 and Comparative Example 3 were the same degree.

[0234] From this result, it was confirmed that even with the non-phenol-based antioxidant, the heat resistance was not inferior to Comparative Example 2 not containing the antioxidant.

[0235] [Conclusion]

[0236] From the above measurement results, even with the thermal recording body containing the non-phenol-based color developer and the non-phenol-based antioxidant, no case of poor light resistance, coloring property, and heat resistance compared to the thermal recording body not containing the antioxidant was confirmed. In addition, it was known that if the non-phenol-based antioxidant was contained in the thermal recording body, the effect of improving the light resistance while maintaining the heat resistance of the thermal recording body, suppressing the decrease in the white color degree, and yellowing could be exerted.

[0237] In addition, the non-phenol-based color developer and the non-phenol-based antioxidant are excellent in safety compared with the phenol-based color developer and the phenol-based antioxidant. Therefore, by using the non-phenol-based color developer and the non-phenol-based antioxidant, it is also very effective from the viewpoint of environmental response.

[0238] Hereinafter, variations of the present application are described.

[0239] 〔Note 1〕

[0240] A heat-sensitive recording body characterized by having a heat-sensitive recording layer containing a color developer, a non-phenol-based color developer, and a non-phenol-based antioxidant, which contains a phosphorus-based antioxidant, laminated on a base material.

[0241] 〔Note 2〕

[0242] The heat-sensitive recording body according to Note 1, wherein the non-phenol-based color developer contains a compound represented by the following formula (1) and / or a compound represented by the following formula (2).

[0243] [Chemical Formula 17]

[0244]

[0245] (In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 7 , R 8 , R 9 , R 10 , and R 11 each independently represent a hydrogen atom or a substituent. R 6 , and R 12 each independently represent a substituent. m represents an integer of 0 to 4. In the case where m is 2 or more, a plurality of R 6 may be the same or different. n represents an integer of 0 to 4. In the case where n is 2 or more, a plurality of R 12 may be the same or different.)

[0246] [Chemical Formula 18]

[0247]

[0248] (In formula (2), R 13 , R 14 , R 15 , R 16 , R 17 , R 19 , R 20 , R 21, R 22 , and R 23 each independently represents a hydrogen atom or a substituent. R 18 represents a substituent. o represents an integer of 0 to 4. In the case where o is 2 or more, a plurality of R 18 may be the same or different.

[0249] 〔Note 3〕

[0250] The heat-sensitive recording material according to any one of Notes 1 to 3, wherein the non-phenolic color developer contains a compound represented by the following formula (1a) and / or a compound represented by the following formula (2a).

[0251] [Chemical Formula 19]

[0252]

[0253] (the symbols in formula (1a) are the same as those in formula (1)).

[0254] [Chemical Formula 20]

[0255]

[0256] (the symbols in formula (2a) are the same as those in formula (2)).

[0257] 〔Note 4〕

[0258] The heat-sensitive recording material according to any one of Notes 1 to 3, wherein the content of the non-phenolic color developer with respect to the entire heat-sensitive recording layer is 10 mass% or more and 50 mass% or less.

[0259] 〔Note 5〕

[0260] The heat-sensitive recording material according to any one of Notes 1 to 4, wherein the content of the non-phenolic antioxidant with respect to the entire heat-sensitive recording layer is 5 mass% or more and 10 mass% or less.

[0261] Industrial Applicability

[0262] As described in the above explanation, the present application is particularly useful for a heat-sensitive recording material for printing a bar code or the like.

[0263] Explanation of Reference Numerals

[0264] 1 heat-sensitive recording material, 2 substrate, 3 heat-sensitive recording layer, 4 intermediate layer, 5 top coat layer, 6 undercoat layer.

Claims

1. A heat-sensitive recording body, characterized by, which has a heat-sensitive recording layer stacked on a base material, the heat-sensitive recording layer contains a color developer, a non-phenol color former, and a non-phenol antioxidant, the non-phenol antioxidant contains a phosphorus-based antioxidant, the non-phenol color former contains a compound represented by the following formula (1) and / or a compound represented by the following formula (2): In formula (1), R 1 , R 2 , R 3 , R 4 , R 5 , R 7 , R 8 , R 9 , R 10 , and R 11 each independently represent a hydrogen atom or a substituent; R 6 and R 12 each independently represent a substituent; m represents an integer of 0 to 4; in the case where m is 2 or more, a plurality of R 6 may be optionally the same or different; n represents an integer of 0 to 4; in the case where n is 2 or more, a plurality of R 12 may be optionally the same or different; In formula (2), R 13 , R 14 , R 15 , R 16 , R 17 , R 19 , R 20 , R 21 , R 22 , and R 23 each independently represent a hydrogen atom or a substituent; R 18 represents a substituent; o represents an integer of 0 to 4; in the case where o is 2 or more, a plurality of R 18 may be optionally the same or different.

2. The heat-sensitive recording body according to claim 1, wherein the non-phenol color former contains a compound represented by the following formula (la) and / or a compound represented by the following formula (2a): the symbols in formula (la) are the same as those in formula (1); the symbols in formula (2a) are the same as those in formula (2).

3. The heat-sensitive recording body according to claim 1 or 2, wherein the content of the non-phenol color former is 10 mass% or more and 50 mass% or less with respect to the entire heat-sensitive recording layer.

4. The heat-sensitive recording body according to claim 1 or 2, wherein the content of the non-phenol antioxidant is 5 mass% or more and 10 mass% or less with respect to the entire heat-sensitive recording layer.

5. The heat-sensitive recording body according to claim 3, wherein the content of the non-phenol antioxidant is 5 mass% or more and 10 mass% or less with respect to the entire heat-sensitive recording layer.

6. The heat-sensitive recording body according to claim 1 or 2, wherein the color developer is a leuco dye, and the phosphorus-based antioxidant is a compound having a phosphorus atom having a valence of 3 in a molecule.

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