Thermosensitive recording body

Abstract

The present application aims to provide a thermal recording material which is low in safety concerns of endocrine disruptors, excellent in color development and light resistance, and excellent in heat resistance. The thermal recording material (1) has a configuration in which a thermal recording layer (3) is layered on a substrate (2). The thermal recording layer (3) contains a color developer, a non-phenol color former, and a non-phenol ultraviolet absorber. The non-phenol ultraviolet absorber contains an oxanilide ultraviolet absorber. 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 definitions of the symbols in the following formulae (1) and (2) are as described in the specification).

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 security 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] A heat-sensitive recording body is widely used as described above. Therefore, various properties are required for a 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 a 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 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 in which a heat-sensitive recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting color developer is provided on a support, and the heat-sensitive recording layer contains a phenol-based color developer such as 4-hydroxy-4'-isopropoxydiphenylsulfone as a color developer, and further contains a phenol-based ultraviolet absorber having a phenolic hydroxyl group such as 2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole as an ultraviolet absorber is proposed (for example, refer to Patent Documents 1 to 3).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-066897

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-134818

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-177577 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The compounds (phenolic compounds) having a phenolic hydroxyl group, such as the phenolic developers and the ultraviolet absorbers used in the above-described Patent Documents 1 to 3, are of concern for safety as endocrine disruptors. Therefore, in recent years, from the viewpoint of environmental response, there is a demand for a thermal recording body using an additive such as a developer and an ultraviolet absorber that does not have a phenol skeleton.

[0012] The present application is an application completed in view of such a fact, and aims to provide a thermal recording body that is low in concern for safety of endocrine disruptors and the like, excellent in color development and light resistance, and also excellent in heat resistance.

[0013] Means for solving the problem

[0014] The present inventors and the like have conducted intensive studies in order to achieve the above-described object, and as a result, have found that a thermal recording body that is low in concern for safety of endocrine disruptors and 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 developer that does not have a phenol skeleton (non-phenolic developer) and a specific ultraviolet absorber that does not have a phenol skeleton (non-phenolic ultraviolet absorber). The present application is an application completed on the basis of this insight.

[0015] 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-described thermal recording layer contains a developer, a non-phenolic developer, and a non-phenolic ultraviolet absorber.

[0016] In conventional thermal recording bodies, a phenolic compound is generally contained as a developer and an ultraviolet absorber. However, phenolic compounds are of concern for safety as endocrine disruptors.

[0017] In contrast, according to the thermal recording body of the present application, the developer and the ultraviolet absorber contained in the thermal recording layer are non-phenolic compounds. Therefore, the above-described concern does not arise. In addition, even in the case where a non-phenolic compound as described above is used, the thermal recording body of the present application becomes a thermal recording body that is excellent in color development and light resistance, and also excellent in heat resistance.

[0018] In the thermal recording body of the present application, the above-described non-phenolic ultraviolet absorber contains an oxanilide-based ultraviolet absorber. Thereby, light resistance can be particularly improved.

[0019] In one embodiment of the thermal recording body of the present application, it is preferable that the above-described non-phenolic developer contain a compound represented by the following formula (1) and / or a compound represented by the following formula (2).

[0020] [Chemical Formula 1]

[0021]

[0022] (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.

[0023] [Chemical Formula 2]

[0024]

[0025] (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 the same or different.

[0026] In one embodiment of the heat-sensitive recording body of the present application, it is preferable that the above-described non-phenol-based color developer contains a compound represented by the following formula (1a) and / or a compound represented by the following formula (2a).

[0027] [Chemical Formula 3]

[0028]

[0029] (in formula (1a), each symbol is the same as in formula (1)).

[0030] [Chemical Formula 4]

[0031]

[0032] (in formula (2a), each symbol is the same as in formula (2)).

[0033] According to the configuration, a thermal sensitive recording body having more excellent color development and heat resistance can be provided.

[0034] In another embodiment of the thermal sensitive recording body of the present application, the content of the non-phenol based color developer is preferably 10% by mass or more and 50% by mass or less with respect to the entire thermal sensitive recording layer. With this configuration, a thermal sensitive recording body having excellent color development and also excellent heat resistance and light resistance can be provided even with a non-phenol based ultraviolet absorber.

[0035] In another embodiment of the thermal sensitive recording body of the present application, the content of the non-phenol based ultraviolet absorber is preferably 5% by mass or more and 15% by mass or less with respect to the entire thermal sensitive recording layer. With this configuration, a thermal sensitive recording body having excellent color development and also excellent heat resistance and light resistance can be provided even with a non-phenol based ultraviolet absorber.

[0036] Effects of the Invention

[0037] According to the present application, a thermal sensitive recording body having low safety concerns for endocrine disruptors and the like, excellent color development and light resistance, and excellent heat resistance can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic cross-sectional view showing one embodiment of the thermal sensitive recording body of the present application. DETAILED DESCRIPTION

[0039] The thermal sensitive recording body of the present application has a layered structure in which a thermal sensitive recording layer is layered on a substrate. In the thermal sensitive recording body of the present application, the thermal sensitive recording layer contains a color developer, a non-phenol based color developer, and a non-phenol based ultraviolet absorber. The non-phenol based ultraviolet absorber contains an oxanilide based ultraviolet absorber.

[0040] Hereinafter, one embodiment of the thermal sensitive recording body of the present application will be described in detail based on the drawings, however the present application is not limited to each of the following embodiments.

[0041] Figure 1 is a schematic cross-sectional view showing one embodiment of the thermal sensitive recording body of the present application.

[0042] The thermal sensitive recording body 1 of the present embodiment has a layered structure in which a bottom coat layer 6, a thermal sensitive recording layer 3, an intermediate layer 4, and a top coat layer 5 are layered in this order on a sheet-shaped substrate 2 as shown in FIG. 1. Figure 1

[0043] ​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 a gelatin paper, an art paper, a coated paper, a kraft paper, a laminated paper obtained by laminating a thermoplastic resin such as polyethylene to a paper substrate, a synthetic paper, and a porous material such as a 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, but in a case where the thickness of the substrate 2 is adjusted to about 10 μm to 100 μm, a substrate 2 having excellent coatability can be obtained. In addition, a substrate 2 having excellent transparency can be obtained.

[0044] In the present embodiment, the undercoat layer 6 has a function of preventing release of heat supplied from the thermal head, thermal insulation, cushioning, and the like. The undercoat layer 6 is formed, for example, by adding hollow particles as a filler to a coagulant.

[0045] By providing the undercoat layer 6 having thermal insulation to the heat-sensitive recording body 1, the sensitivity of printing is improved. Thus, 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.

[0046] The average particle diameter of the hollow particles added to the undercoat layer 6 is preferably 1 μm to 100 μm. If in this range, the thermal insulation of the undercoat 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.

[0047] In addition, the hollow rate of the hollow particles is preferably 30% to 99%. If in this range, the thermal insulation of the undercoat layer 6 is improved. In addition, the greater the hollow rate of the hollow particles, the higher the thermal insulation effect. Thus, the color developer can be effectively color-developed with less heat. That is, if the hollow rate is increased, the printing quality of the heat-sensitive recording body 1 is improved.

[0048] Here, the hollow rate of the hollow particles is calculated by the following formula.

[0049] Hollow rate = {(volume of voids) / (volume of hollow particles)} x 100

[0050] In addition, with respect to the content ratio of the hollow particles in the undercoat layer 6, 40 parts by mass to 90 parts by mass to 100 parts by mass of the undercoat layer is preferable.

[0051] 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.

[0052] Note that, as the filler of the base coat 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.

[0053] As the binding agent contained in the base coat layer 6, for example, acrylic-styrene copolymers, styrene-butadiene copolymers, acrylic-butadiene-styrene copolymers, vinyl acetate resins, vinyl acetate-acrylic copolymers, styrene-acrylate copolymers, acrylate-based resins, polyurethane-based resins, and the like can be given.

[0054] In addition, as the binding agent, a water-soluble polymer such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylate copolymers, acrylamide-acrylate-methacrylate terpolymers, styrene-maleic anhydride copolymer alkali salts, isobutylene-maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, casein, and the like can also be used.

[0055] The coating amount (dry weight) of the base coat layer 6 is preferably 1 g / m 2 ~ 10 g / m 2 .

[0056] The thickness of the base coat layer 6 is preferably 1 μm ~ 20 μm.

[0057] If the coating amount and the thickness of the base coat layer 6 are adjusted to the above ranges, the base coat layer 6 will properly exert the function of thermal insulation.

[0058] 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 developer, and a non-phenol-based ultraviolet absorber.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] [Chemical Formula 5]

[0066]

[0067] (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.

[0068] [Chemical Formula 6]

[0069]

[0070] (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 the same or different.)

[0071] 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.

[0072] As the above "halogen atom", a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom can be mentioned.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In the above "dialkylamino group", the 2 alkyl groups can be the same or different.

[0077] 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.

[0078] [Chemical Formula 7]

[0079]

[0080] (The symbols in formula (1a) are the same as in formula (1).)

[0081] [Chemical Formula 8]

[0082]

[0083] 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.

[0084] [Chemical Formula 9]

[0085]

[0086] (The symbols in formula (2a) are the same as in formula (2).)

[0087] [Chemical Formula 10]

[0088]

[0089] In the present embodiment, the heat-sensitive recording layer 3 can contain a non-phenolic color developer alone, or can contain two or more.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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., an amount 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 the compound does not substantially function as a color developer.

[0094] In the present embodiment, the heat-sensitive recording layer 3 does not contain a phenol-based ultraviolet absorber that has been conventionally used, but contains a non-phenol-based ultraviolet absorber. The non-phenol-based ultraviolet absorber is a substance that absorbs ultraviolet rays, 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 ultraviolet absorber 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 ultraviolet absorber instead of a phenol-based ultraviolet absorber in the heat-sensitive recording layer 3, it is possible to improve the light resistance and heat resistance of the heat-sensitive recording body 1. Note that in the case where the heat-sensitive recording layer 3 of the present embodiment contains a phenol-based ultraviolet absorber that does not raise safety concerns as an endocrine disruptor and does not have an impact on color development, light resistance, and heat resistance, it is considered that this is also included in the scope of the present application.

[0095] As such non-phenol-based ultraviolet absorbers, publicly known ultraviolet absorbers having no phenolic hydroxyl group can be used without particular limitation. For example, oxanilide-based ultraviolet absorbers can be given. Furthermore, the present inventors have found that, from the viewpoint of further improving the light resistance and heat resistance of the thermosensitive recording body 1, a compound represented by the following formula (3) is suitable.

[0096] [Chem. 11]

[0097]

[0098] (In formula (3), R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 , and R 33 each independently represent a hydrogen atom or a substituent.)

[0099] In formula (3), the definitions of the substituents represented by R 24 to R 33 are the same as those in formula (1).

[0100] As the compound represented by formula (3), specifically, oxanilide, 2-ethoxy-2'- ethyl oxanilide, (N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)oxamide), 2-ethoxy-5-tert-butyl-2'- ethyl oxanilide, 2-ethoxy-3'-dodecyl oxanilide, and the like can be given. In the present embodiment, the thermosensitive recording layer 3 can contain a non-phenol-based ultraviolet absorber alone, or can contain two or more non-phenol-based ultraviolet absorbers.

[0101] In the present embodiment, the content of the non-phenol-based ultraviolet absorber with respect to the entirety of the thermosensitive recording layer 3 is not particularly limited, but is preferably 5% by mass or more and 15% by mass or less. From the aspect that an excellent light resistance can be imparted to the thermosensitive recording body 1 of the present embodiment, a configuration in which the content of the non-phenol-based ultraviolet absorber is 5% by mass or more is suitable. From the aspect that an excellent color development can be imparted to the thermosensitive recording body 1 of the present embodiment, a configuration in which the content of the non-phenol-based ultraviolet absorber is 15% by mass or less is suitable.

[0102] In the present embodiment, the content of the non-phenol-based ultraviolet absorber is not particularly limited relative to the total amount of the ultraviolet absorber contained in the heat-sensitive recording layer 3, but from the viewpoint of improving light resistance and heat resistance while reducing concerns 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.

[0103] In the present embodiment, the content of the oxanilide-based ultraviolet absorber is not particularly limited relative to the total amount of the ultraviolet absorber contained in the heat-sensitive recording layer 3, but from the viewpoint of improving light resistance and heat resistance while reducing concerns 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.

[0104] In addition, the heat-sensitive recording layer 3 can appropriately contain, as needed, additives such as a binding agent, a sensitizer, a lubricant, a filler, a preservability improving agent, and a pigment.

[0105] 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.

[0106] 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 biphenyl, m-terphenyl, diphenyl sulfone, benzyl p-benzyloxybenzoate, dibenzyl p-toluic acid, p-toluenesulfonyl amide, and the like that are solid at normal temperature, preferably have a melting point of about 70°C or more, and the like can be given. These sensitizers can be used alone or in combination of two or more.

[0107] As the lubricant, for example, paraffin, 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, whale oil, and the like can be given. These lubricants can be used alone or in combination of two or more.

[0108] 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.

[0109] As the storage property 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-methylglycyl-oxy)-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.

[0110] [Chemical Formula 12]

[0111]

[0112] These storage property improving agents can be used alone or in combination of two or more. In addition, a publicly known surfactant can also be contained.

[0113] Fresh food such as meat and fish is 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 another package. A plasticizer for imparting plasticity is contained in the preservative film. 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 properties such that the printing does not easily disappear or the like even if the plasticizer is transferred, that is, "plasticizer resistance" is excellent.

[0114] In the present embodiment, from the viewpoint of printing storage property, particularly plasticizer resistance, the heat-sensitive recording layer 3 preferably contains a storage property improving agent, particularly preferably a urea urethane compound represented by the above formula (4).

[0115] It is considered that by making the heat-sensitive recording layer 3 contain the storage property improving agent, particularly the urea urethane compound represented by formula (4), 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 less likely to occur, the color developability of the heat-sensitive recording body becomes excellent, and in addition, the color density is less likely to decrease, the print storage property, particularly the plasticizer resistance, is excellent.

[0116] The urea urethane compound represented by formula (4) is specifically three kinds represented by formulae (4a) to (4c) below, and they can be used alone or in a mixture of two or more kinds.

[0117] [Chem. 13]

[0118]

[0119] [Chem. 14]

[0120]

[0121] [Chem. 15]

[0122]

[0123] In the present embodiment, in the case where the heat-sensitive recording layer 3 contains the storage property improving agent, the content of the storage property improving agent with respect to the entirety of the 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 density due to a plasticizer or the like and becoming a heat-sensitive recording body excellent in print storage property, particularly plasticizer resistance, it is preferable that the content of the above storage property improving agent be 1% by mass or more. In addition, from the viewpoint of preventing a lack of color developability (a decrease in optical density), it is preferable that the content of the above storage property improving agent be 20% by mass or less.

[0124] In the present embodiment, in the case where the heat-sensitive recording layer 3 contains the storage property improving agent, the ratio of the content 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 lack of color developability (a decrease in optical density), it is preferable that the above ratio be 1 / 1 or less. In addition, from the viewpoint of being able to suppress a decrease in color density due to a plasticizer or the like and becoming a heat-sensitive recording body excellent in print storage property, particularly plasticizer resistance, it is preferable that the above ratio be 1 / 20 or more.

[0125] In the present embodiment, when the urea urethane compound represented by formula (4) is contained in the heat-sensitive recording layer 3, 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. The content of the urea urethane compound is preferably 1% by mass or more from the viewpoint of being able to suppress a decrease in color development density caused by a plasticizer or the like and of being able to provide a heat-sensitive recording material that is excellent in print storage properties, particularly, in plasticizer resistance. The content of the urea urethane compound is preferably 20% by mass or less from the viewpoint of preventing a lack of color development (a decrease in optical density).

[0126] In the present embodiment, when the urea urethane compound represented by formula (4) is contained in the heat-sensitive recording layer 3, the content 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. The content ratio is preferably 1 / 1 or less from the viewpoint of being able to prevent a lack of color development (a decrease in optical density). The content ratio is preferably 1 / 20 or more from the viewpoint of being able to suppress a decrease in color development density caused by a plasticizer or the like and of being able to provide a heat-sensitive recording material that is excellent in print storage properties, particularly, in plasticizer resistance.

[0127] In the present embodiment, the content of the urea urethane compound represented by formula (4) with respect to the total amount of the storage property improver contained in the heat-sensitive recording layer 3 is not particularly limited, but is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 99% by mass or more, from the viewpoint of being able to suppress a decrease in color development density caused by a plasticizer or the like and of being able to provide a heat-sensitive recording material that is excellent in print storage properties, particularly, in plasticizer resistance.

[0128] 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.

[0129] 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 so-called "water-based resin" means a resin component dispersed in water or dissolved in water. These materials can be used alone or in combination of two or more.

[0130] The above resin uses a resin having a water-soluble portion, for example, a polyvinyl alcohol (PVA) resin belonging to a resin having a hydroxyl group as a hydrophilic structural unit, 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.

[0131] The core-shell type resin can be, for example, a resin sold under the name of "Bariastar (manufactured by Mitsui Chemicals, Inc.)", and the like as a core-shell type acrylic resin.

[0132] The coating amount (dry weight) of the intermediate layer 4 is preferably 0.3 g / m 2 ~ 10 g / m 2 .

[0133] 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.

[0134] 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 thermal recording body's uppermost layer component being melted by the heat of the thermal head and adhering to the thermal head. More specifically, it is the property of not easily causing the undesirable condition of no printing in a local part of the thermal recording body, or the deformation of the printed surface.

[0135] The top coat layer 5 of the present embodiment has evaporation holes due to evaporation of moisture and cracks in the form of recessed depressions on its surface. Thereby, the contact area of the surface of the top coat layer 5 with the thermal head is reduced.

[0136] In order to produce 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.

[0137] That is, in the present embodiment, an emulsion of hydrophobic resin particles, for example, an emulsion obtained by water-dispersing hydrophobic acrylic resin particles, is used as the coagulant for the top coat layer 5.

[0138] Using an emulsion of hydrophobic resin particles as the coagulant for the top coat layer 5 like this, a water-soluble polymer is not used.

[0139] A coating liquid containing a water-soluble polymer is not easily coagulated when dried after coating, and forms a coating film having flexibility, so cracks due to shrinkage do not occur in the top coat layer 5.

[0140] On the other hand, an emulsion of hydrophobic resin particles is coagulated between the hydrophobic resin particles due to evaporation when dried after coating, shrinks, and produces cracks that become depressions on the surface of the top coat layer 5.

[0141] Since the cracks are formed due to shrinkage caused by coagulation of the hydrophobic resin particles, they remain in the top coat layer 5 and do not reach the intermediate layer 4.

[0142] In the present embodiment, furthermore, in order to form evaporation holes due to evaporation of moisture that become depressions on the surface of the top coat layer 5, the three layers of the thermal recording layer 3, the intermediate layer 4, and the top coat layer 5 are simultaneously coated using a curtain coater.

[0143] The curtain coater ejects each coating liquid for forming the thermal recording layer 3, the intermediate layer 4, and the top coat layer 5, respectively, from a plurality of slits to be stacked, and the stacked coating liquid continuously travels. At this time, the coating is performed by free-falling onto the primer layer 6 formed in advance on the substrate 2.

[0144] In such simultaneous coating of three layers using a curtain coater, the top coat layer 5 once dried produces cracks due to the beginning of coagulation of the hydrophobic resin particles as described above, water vapor is discharged from the cracks, and the semi-dried intermediate layer 4 and the thermal recording layer 3 are dried and cured. Most of the water vapor of the intermediate layer 4 and the thermal 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.

[0145] 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 adheres 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.

[0146] The top coat layer 5 contains, as necessary, additives such as a lubricant, a crosslinking agent, a dispersant, an antifoaming agent, a water resistance agent, and a filler.

[0147] 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.

[0148] 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.

[0149] In the present embodiment, as the coating liquid for forming the top coat layer 5, a water dispersion suspension obtained by dispersing a hydrophobic acrylic resin in water is used, and 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, and a heat-sensitive recording body 1 is manufactured.

[0150] The coating amount (dry weight) of the top coat layer 5 is set to 1 g / m 2 .

[0151] 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 as 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 heat-sensitive head is reduced, the wear of the heat-sensitive head is alleviated, the heat-sensitive head is adapted, and the anti-blocking property is improved.

[0152] 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 heat-sensitive 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.

[0153] Further, since the cracks of the surface of the top coat layer 5 develop along the thickness direction as the inside of the top coat layer 5, they are cut 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 heat-sensitive head toward the lateral direction is suppressed. As a result, the heat from the heat-sensitive head is efficiently conducted to the heat-sensitive recording layer 3 located in the lower layer in the thickness direction.

[0154] To reduce the contact area of the top coat layer 5 with the thermal head, the water evaporation holes which are substantially circular are preferably 2 μm or more in average diameter.

[0155] 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 In addition, as for the number of evaporation holes, for example, 30 or more, more preferably 40 or more, of the evaporation holes having an average diameter of 5 μm or more are preferable per 1 mm 2

[0156] In the thermal 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.

[0157] In the present embodiment, although the three layers of the thermal recording layer 3, the intermediate layer 4, and the top coat layer 5 are simultaneously coated using a curtain coater, the present application is not limited to simultaneous coating, and each of the thermal recording layer 3, the intermediate layer 4, and the top coat layer 5 can be formed one by one in sequence.

[0158] In the present embodiment, although the primer layer 6 and the intermediate layer 4 are formed on the substrate 2, as another embodiment of the present application, at least either one of the primer layer 6 and the intermediate layer 4 can be omitted.

[0159] The thermal recording body of the above-described embodiment is excellent in light resistance, color development, and heat resistance because it has the thermal recording layer configured as described above.

[0160] The amount of change in whiteness degree (%) of the thermal recording body of the present embodiment represented by the following formula is preferably -5% or more, more preferably -4.5% or more, and further preferably -4% or more from the viewpoint of excellent light resistance and suppression of reduction in whiteness degree due to light irradiation.

[0161] Amount of change in whiteness degree (%) = whiteness degree after 100 hours under illuminance of 5000 Lux - whiteness degree before the test

[0162] The whiteness degree is a value calculated in accordance with JIS P 8148.

[0163] A negative value (-) of the above-described amount of change in whiteness degree (%) indicates the amount of reduction in whiteness degree, and the closer to 0%, the less the reduction in whiteness degree and the more excellent the light resistance.

[0164] ​The absolute value of Δb represented by the following formula for the thermal recording body of the present embodiment is preferably 2.3 or less, more preferably 2.2 or less, further preferably 2.1 or less, and particularly preferably 2 or less from the viewpoint of excellent light resistance, suppression of yellowing, and bluing (blueing) caused by light irradiation.

[0165] Δb = b value after 100 hours under illumination of 5000 Lux - b value before the test

[0166] The b value represents L * a * b * The b value represents L

[0167] The b value represents a change from blue to yellow, and the greater the value, the closer to yellow, and the smaller the value, the closer to blue. The above Δb represents the amount of change in the b value, and a positive value represents yellowing, and a negative value represents bluing. Thus, the closer the absolute value of Δb to 0, the less yellowing and bluing, and the more excellent the light resistance.

[0168] The dynamic sensitivity (OD value) of the printed portion at 0.16 mj / dot for the thermal recording body of the present embodiment is preferably 0.5 or more, and more preferably 0.6 or more from the viewpoint of excellent color development.

[0169] The dynamic sensitivity (OD value) of the printed portion at 0.20 mj / dot for the thermal recording body of the present embodiment is preferably 1 or more, and more preferably 1.1 or more from the viewpoint of excellent color development.

[0170] The dynamic sensitivity (OD value) of the printed portion at 0.40 mj / dot for the thermal recording body of the present embodiment is preferably 1.3 or more, and more preferably 1.4 or more from the viewpoint of excellent color development.

[0171] The above dynamic sensitivity (OD value) is a value measured in the examples set forth below, and the higher the value, the more excellent the color development.

[0172] The OD value of the non-printed portion in the (heat resistance evaluation) of the examples set forth below for 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.

[0173] Examples

[0174] In the following examples and comparative examples, thermal recorders containing non-phenolic color developers and non-phenolic ultraviolet absorbers in the thermal recording layer were fabricated, and their color development, lightfastness, and heat resistance were evaluated. It should be noted that the present invention is not limited to these examples.

[0175] (Examples 1-6, Comparative Examples 1-3)

[0176] (The creation of thermal recording media)

[0177] <Undercoat>

[0178] The basis weight of the substrate is 70 g / m³. 2 On offset paper (thickness: 80 μm), a base coat solution is applied, which is a mixture of 70 parts by weight of hollow particles (solid content concentration 26.5%, ROPAQUE HP-1055: Rohm & Hass Japan Co., Ltd.), 10 parts by weight of modified styrene-butadiene latex (solid content concentration 49%), and 20 parts by weight of water. The mixture is then dried to achieve a coating weight of 3.0 g / m² upon drying. 2 A base coating with a thickness of 5μm.

[0179] <Thermal Recording Layer>

[0180] Prepare the coating solution for forming the thermal recording layer shown in Table 1, and apply the prepared coating solution to the above-mentioned base layer, such that the coating amount is 4.0 g / m² based on dry weight. 2 Afterwards, drying is performed, thereby forming a 3.5 μm thick thermal recording layer on the base coating. It should be noted that in Table 1, the values ​​for each compounding material represent the weight ratio during drying.

[0181] In addition, as a coordinating material, the leuco dye uses 3-dibutylamino-6-methyl-7-aniline fluorane with a particle size of 0.6 to 0.7 μm, the color developer 1 uses [3-(3-phenylureo)phenyl]-4-methylbenzenesulfonate as shown in formula (2b) above, and the color developer 2 uses N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea as shown in formula (1b) above. In addition, the ultraviolet absorber 1 uses N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)glyoxalamide (manufactured by SONGWON) based on oxaloylaniline (and phenolic compounds), and the ultraviolet absorber 2 uses α-3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)-1-oxopropyl-ω-hydroxypoly(ethylene oxide) based on benzotriazole (phenolic compounds).

[0182] In addition, the sensitizer used 1,2-bis(3-methylphenoxy)ethane (a substance that was made into a dispersion liquid having a solid content concentration of 20% by being dispersed in a PVA aqueous solution), the coagulant used a styrene acrylic copolymer emulsion, calcium carbonate (a substance 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.

[0183] <Intermediate layer>

[0184] An acrylic emulsion (solid content concentration 30%) liquid was applied to the above-mentioned heat-sensitive recording layer, and dried to form an intermediate layer having a dried coating amount of 1.6 g / m 2 and a thickness of 1.5 μm.

[0185] <Top coat layer>

[0186] A liquid in which an acrylic emulsion (solid content concentration 20%) was 40 parts by mass, calcium carbonate was 5 parts by mass, 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 to form a top coat layer having a dried coating amount of 1.0 g / m 2 and a thickness of 0.9 μm.

[0187] Using the above method, heat-sensitive recording bodies of Examples 1 to 6 and Comparative Examples 1 to 3 were produced.

[0188]

[0189] (Light resistance evaluation)

[0190] In the light resistance evaluation, the optical density (OD value of the printed part / OD value of the non-printed part), the change in yellowing (yellowing), and the change in whiteness were measured for the printed part and the non-printed part of each heat-sensitive recording body of each example and each comparative example. The steps of the light resistance evaluation are described below.

[0191] The produced heat-sensitive recording body was printed using a heat-sensitive paper printing test device (Oakla Engineering Co., Ltd., product name: Pulse Simulator TH-M2 / PP) under conditions in which the printing speed was 50 mm / sec, the applied voltage was 17.0 V, the heat-sensitive head resistance value was 870 Ω, the pulse width was 0.488 to 1.394 ms, and the printing energy was 0.40 mJ / dot.

[0192] A light meter was used to confirm the distance from the fluorescent lamp in such a way that 5000 Lux was reached, and the heat-sensitive recording body printed above was left at this position for 100 hours.

[0193] The optical densities (OD values) of the printed portions and the non-printed portions of the samples of the thermal recording bodies before the test and after the above storage were measured using a spectrophotometer (manufactured by Videojet X-rite, trade name: eXact).

[0194] In addition, the whiteness (%) and the color tone (L, a, b) of the samples of the thermal recording bodies before the test and after the above storage were measured. The whiteness was measured using a photoelectric reflection densitometer (manufactured by Tokyo Denshoku, trade name: TC-6DS / A) in accordance with JIS P 8148.

[0195] The color tone (L, a, b) was measured using a color difference meter (manufactured by Videojet X-rite, trade name: SpectroEye).

[0196] 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 densities (OD values) of the printed portions and the non-printed portions were large (i.e., the reflectance of light was small), it was indicated that the color development was further performed (the color development state was close to black), and in the case where the optical densities were small (i.e., the reflectance of light was large), it was indicated that the color development was insufficient. The larger the value of the whiteness (%) was, the closer to white it was. Among the indexes of the color tone (L, a, b), (L) indicates the change from black to white, and the larger the value of (L) was, the closer to white it was. (a) indicates the change from green to red, and the larger the value of (a) was, the closer to red it was. (b) indicates the change from blue to yellow, and the larger the value of (b) was, the closer to yellow it was. The light resistance of each thermal recording body was evaluated based on these changes in color.

[0197] (Evaluation of Dynamic Sensitivity)

[0198] In the dynamic sensitivity test, the thermal recording bodies of each of the examples and the comparative examples were printed with different printing energies, and the optical densities (OD values) at each printing energy were measured. The dynamic sensitivity of each of the thermal recording bodies of the examples and the comparative examples was evaluated based on the measurement results. Hereinafter, the steps of the dynamic sensitivity test are described.

[0199] To the produced heat-sensitive recording body, using a heat-sensitive paper printing test device (Oakla Engineering Co., Ltd., trade 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, and a pulse width of 0.488 to 1.394 ms, printing was performed under each condition of a printing energy of 0.16 mJ / dot, 0.20 mJ / dot, and 0.40 mJ / dot, and the optical density (OD value) under the printing energy condition was measured using a spectrophotometer (X-rite Co., Ltd., trade name: eXact).

[0200] 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 numerical value of the optical density (OD value) is large, it is indicated that color development was further performed, and in the case where the numerical value is small, it is indicated that color development was insufficient. For example, even though the printing energy is small, in the case where the numerical value of the optical density (OD value) is large, it is evaluated as "color development is good". On the other hand, even though the printing energy is large, in the case where the numerical value of the optical density (OD value) is small, it is evaluated as "color development is poor". That is, the dynamic sensitivity test is an evaluation of color development.

[0201] (Evaluation of Heat Resistance)

[0202] In the heat resistance test, the printed portion and the non-printed portion of each heat-sensitive recording body of each example and each comparative example were heated, and the optical density of the printed portion and the non-printed portion (OD value of the printed portion) was measured. The heat resistance of each heat-sensitive recording body of each example and each comparative example was evaluated based on the measurement results. Hereinafter, the steps of the heat resistance test are described.

[0203] To the produced heat-sensitive recording body, using a heat-sensitive paper printing test device (Oakla Engineering Co., Ltd., trade 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, and a pulse width of 0.488 to 1.394 ms, printing was performed under the condition of a printing energy of 0.40 mJ / dot.

[0204] To a container (diameter: 12 cm, content: 220 cc) in which 100 g of water was stored, a fresh-keeping film (thickness: 10 μm) made of vinyl chloride was attached as a lid, and the sample (length: 3 cm, width: 4 cm) of the heat-sensitive recording body printed in the above was attached to the fresh-keeping film.

[0205] 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.

[0206] Then, the container was heated using a microwave oven (1500 W) for 1 minute, after which the optical densities (OD values) of the printed portion and the non-printed portion of the sample of the thermosensitive recording body were measured using a spectrophotometer (manufactured by X-rite Corporation, trade name: eXact).

[0207] 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 thermosensitive recording body has a small reaction to heat. That is, it indicates the degree of color development of the printed portion or the non-printed portion when heat due to steam caused by heating the thermosensitive recording body using a microwave oven is applied to the thermosensitive 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 caused by steam. 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 too large.

[0208]

[0209] <Verification Results>

[0210] From the results shown in Table 2, the following conclusions can be confirmed.

[0211] [Examples 1 to 4 and Comparative Examples 1 to 2]

[0212] Examples 1 to 4 and Comparative Examples 1 to 2 containing the same color developer 1 were studied.

[0213] (1) In the light resistance test, the amount of change in white color was small, and the white color after the test was also high in Examples 1 to 4 as compared with Comparative Example 1. This is presumed to be because the ultraviolet absorber 1 (non-phenol-based ultraviolet absorber) was contained in Examples 1 to 4. On the other hand, the amount of change in white color of Comparative Example 2 containing the same color developer 1 as Examples 1 to 4 and containing an ultraviolet absorber 2 (phenol-based ultraviolet absorber) different from Examples 1 to 4 was -3.60. This value was smaller than the amount of change in white color of Examples 1 to 3. Therefore, it can also be considered that Examples 1 to 3 were inferior in light resistance as compared with Comparative Example 2. That is, it can also be considered that the light resistance was excellent in the case where the thermosensitive recording layer contained the conventional general-purpose phenol-based ultraviolet absorber.

[0214] However, the white color degree after the test of Comparative Example 2 was 77.4%, which was significantly smaller than that of Examples 1 to 4. In addition, regarding the difference in the white color degree change amount, the difference in the white color degree change amount was also small, 0.90, 0.30, and 0.80, respectively, in Examples 1 to 3 and Comparative Example 2. Therefore, it can be said that even if the non-phenol-based ultraviolet absorber is contained, the change in the white color degree is the same as that of Comparative Example 2. Furthermore, regarding the white color degree change amount, a smaller result was obtained in Example 4 than in Comparative Example 2. This indicates that at least Example 4 is superior in light resistance to Comparative Example 2.

[0215] In addition, in Examples 1 to 4 and Comparative Examples 1 to 2, there was no large difference in the optical density (OD value) after the test.

[0216] From these results, it was confirmed that the heat-sensitive recording body of Examples 1 to 4 containing the non-phenol-based ultraviolet absorber had the same degree of light resistance as Comparative Example 2 containing the phenol-based ultraviolet absorber 2. In addition, it was confirmed that, as shown in Example 4, if the content of the non-phenol-based ultraviolet absorber is adjusted, the light resistance is superior to that of the heat-sensitive recording body containing the phenol-based ultraviolet absorber.

[0217] (2) In the dynamic sensitivity test (color development), when the printing energy was set to 0.40 mJ / dot, the optical density (OD value) of Examples 1 to 3 and Comparative Examples 1 to 2 was 1.55 or 1.56, and, in contrast thereto, that of Example 4 was 1.50, which was smaller than the others. However, when the printing energy was set to 0.16 mJ / dot and 0.20 mJ / dot, there was no large difference in the optical density (OD value) of Examples 1 to 4 and Comparative Examples 1 to 2.

[0218] From these results, it was confirmed that the heat-sensitive recording body of Examples 1 to 4 containing the non-phenol-based ultraviolet absorber had the same degree of color development as Comparative Example 2 containing the phenol-based ultraviolet absorber.

[0219] (3) In the heat resistance test, the optical density (OD value) of the printed portion of Examples 1 to 4 was 1.50 to 1.52, and the optical density (OD value) of the non-printed portion was 0.06. The optical density (OD value) of the printed portion of Comparative Example 1 was 1.50, and the optical density (OD value) of the non-printed portion was 0.06, which was the same degree as Examples 1 to 4. In contrast, the optical density (OD value) of the printed portion of Comparative Example 2 was 1.54, and the optical density (OD value) of the non-printed portion was 0.35, which was larger than that of Examples 1 to 4. In particular, the optical density (OD value) of the non-printed portion of Comparative Example 2 was considerably larger than that of Examples 1 to 4. As described above, in the heat resistance test, the side with a smaller optical density (OD value) of the non-printed portion can be judged to have good heat resistance. Therefore, at least it can be said that the non-printed portion of Examples 1 to 4 has good heat resistance compared to the non-printed portion of Comparative Example 2.

[0220] From these results, it was confirmed that the heat-sensitive recording body of Examples 1 to 4 containing the non-phenol-based ultraviolet absorber had the same degree of heat resistance as Comparative Example 1 which did not contain any ultraviolet absorber. In addition, it was confirmed that the heat-sensitive recording body of Examples 1 to 4 had significantly good heat resistance compared to the heat-sensitive recording body of Comparative Example 2 containing the phenol-based ultraviolet absorber 2.

[0221] [Examples 5 to 6 and Comparative Example 3]

[0222] Examples 5 to 6 and Comparative Example 3 containing the same color developer 2 were investigated.

[0223] (4) In the light resistance test, the change in white color degree of Examples 5 to 6 was small compared to Comparative Example 3. In addition, the white color degree after the test was also larger than that of Comparative Example 3. From these results, it was confirmed that Examples 5 to 6 containing the non-phenol-based ultraviolet absorber were effective in inhibiting the decrease in white color degree compared to Comparative Example 3 which did not contain the ultraviolet absorber.

[0224] (5) In the dynamic sensitivity test, the optical density (OD value) of Examples 5 and Comparative Example 3 at each printing energy was the same degree. In Example 6, the optical density (OD value) had a tendency to decrease compared to Comparative Example 3, but the decrease was about 5 to 10%, which showed that the color development was good enough to be used as a heat-sensitive recording body.

[0225] From these results, it was confirmed that even when containing the non-phenol-based ultraviolet absorber, the color development was the same degree as Comparative Example 3 which did not contain the ultraviolet absorber.

[0226] (6) In the heat resistance test, the optical density (OD value) of the printed portion and the optical density (OD value) of the non-printed portion of Examples 5 to 6 and Comparative Example 3 were the same.

[0227] From the results, it was confirmed that even if a non-phenol-based ultraviolet absorber is contained, the heat resistance is not inferior to that of Comparative Example 3 which does not contain an ultraviolet absorber.

[0228] [CONCLUSION]

[0229] From the above-mentioned results, it was confirmed that even if a non-phenol-based color developer and a non-phenol-based ultraviolet absorber are contained in the heat-sensitive recording body, there is no case where the light resistance, color development, and heat resistance are inferior to those of a heat-sensitive recording body containing a phenol-based ultraviolet absorber. Furthermore, it was found that if a non-phenol-based ultraviolet absorber is contained in the heat-sensitive recording body, it is possible to exert the effect of improving the light resistance while maintaining the heat resistance of the heat-sensitive recording body, suppressing the decrease in whiteness, and preventing yellowing.

[0230] Furthermore, the non-phenol-based color developer and the non-phenol-based ultraviolet absorber are superior in safety to the phenol-based color developer and the ultraviolet absorber. Therefore, by using the non-phenol-based color developer and the non-phenol-based ultraviolet absorber, it is also very effective from the viewpoint of environmental response.

[0231] Hereinafter, variations of the present application are described.

[0232] [NOTE 1]

[0233] A heat-sensitive recording body characterized by having a heat-sensitive recording layer in which a color developer, a non-phenol-based color developer, and a non-phenol-based ultraviolet absorber are contained, stacked on a base material, wherein the non-phenol-based ultraviolet absorber contains an oxanilide-based ultraviolet absorber.

[0234] [NOTE 2]

[0235] 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).

[0236] [Formula 16]

[0237]

[0238] (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 6may 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.

[0239] [Chemical Formula 17]

[0240]

[0241] (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 the same or different.

[0242] [Note 3]

[0243] The heat-sensitive recording material according to any one of Notes 1 to 2, wherein the non-phenol based color developer contains a compound represented by the following formula (1a) and / or a compound represented by the following formula (2a).

[0244] [Chemical Formula 18]

[0245]

[0246] (In formula (1a), each symbol is the same as in formula (1).)

[0247] [Chemical Formula 19]

[0248]

[0249] (In formula (2a), each symbol is the same as in formula (2).)

[0250] [Note 4]

[0251] The heat-sensitive recording material according to any one of Notes 1 to 3, wherein the content of the non-phenol based color developer with respect to the entire heat-sensitive recording layer is 10% by mass or more and 50% by mass or less.

[0252] [Note 5]

[0253] The heat-sensitive recording material according to any one of Notes 1 to 4, wherein the content of the non-phenol based ultraviolet absorber with respect to the entire heat-sensitive recording layer is 5% by mass or more and 15% by mass or less.

[0254] Industrial applicability

[0255] As shown in the above description, the present application is particularly useful for a heat-sensitive recording material for printing a bar code or the like.

[0256] Explanation of reference numerals

[0257] 1 heat-sensitive recording material, 2 base material, 3 heat-sensitive recording layer, 4 intermediate layer, 5 top coat layer, 6 undercoat layer.

Claims

1. A thermal recording medium, characterized in that, It has a thermal recording layer stacked on the substrate. The thermal recording layer contains a color-developing agent, a non-phenolic color-developing agent, and a non-phenolic ultraviolet absorber. The non-phenolic ultraviolet absorber contains oxaloylaniline ultraviolet absorber.

2. The thermal recorder according to claim 1, wherein, The non-phenolic colorimetric reagent contains a compound represented by formula (1) and / or a compound represented by formula (2): In equation (1), R 1 R 2 R 3 R 4 R 5 R 7 R 8 R 9 R 10 and R 11 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 2 or more, multiple R... 6 Choose either the same or different; n represents an integer from 0 to 4; when n is 2 or more, multiple R... 12 Choose either the same or different; 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 Choose either the same or different.

3. The thermal recorder according to claim 2, wherein, The non-phenolic colorimetric reagent contains a compound represented by formula (1a) and / or a compound represented by formula (2a): The symbols in equation (1a) are the same as those in equation (1); The symbols in equation (2a) are the same as those in equation (2).

4. The thermal recorder according to any one of claims 1 to 3, wherein, The content of the non-phenolic colorimetric agent relative to the entire thermal recording layer is 10% by mass or more and 50% by mass or less.

5. The thermal recorder according to any one of claims 1 to 3, wherein, The content of the non-phenolic ultraviolet absorber relative to the entire thermal recording layer is 5% by mass or more and 15% by mass or less.

6. The thermal recorder according to claim 4, wherein, The content of the non-phenolic ultraviolet absorber relative to the entire thermal recording layer is 5% by mass or more and 15% by mass or less.

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