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 thermal recording layer (3) laminated on a substrate (2). The thermal recording layer (3) contains a color developer, a non-phenol color former, and a non-phenol light stabilizer. The non-phenol light stabilizer contains a histamine-based light stabilizer. 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] This invention relates to a thermal recorder, and more specifically, to a thermal recorder with low safety concerns and excellent color development, lightfastness, and heat resistance. Background Technology

[0002] Thermal recorders use a chemical reaction to produce color through heating with a thermal head, thus recording an image. They are widely used not only as recording media for fax machines, automatic ticket vending machines, and scientific measuring instruments, but also as thermal recording tags and receipt paper for POS systems in retail stores.

[0003] Thermal recorders are widely used as described above. Therefore, various performance characteristics are required for thermal recorders. For example, when reading barcodes using a barcode reader, good colorfastness is required to ensure accurate reading based on the barcode reader. Additionally, thermal recorders must be resistant to yellowing (lightfastness) when exposed to strong light, including ultraviolet light, for extended periods. Furthermore, excellent heat resistance is required, ensuring that the colorfastness of the printed areas does not decrease during heating in microwave ovens or similar environments, while preventing color fading in non-printed areas.

[0004] As such a thermal recorder, for example, a thermal recorder has been proposed in which a thermal recording layer containing a colorless or light-colored electron-donating leuco dye and an electron-accepting chromogenic agent is provided on a support. The thermal recording layer contains phenolic chromogenic agents such as 4-hydroxy-4'-isopropoxydiphenyl sulfone as chromogenic agents, and also contains phenolic light stabilizers such as 2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole as ultraviolet absorbers (for example, see Patent Documents 1 to 3).

[0005] Existing technical documents

[0006] Patent documents

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

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

[0009] Patent Document 3: Japanese Patent Application Publication No. 2017-177577 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The phenolic color developers and phenolic light stabilizers used in the aforementioned patent documents 1-3, which contain phenolic hydroxyl groups (phenolic compounds), raise concerns about their safety as endocrine disruptors. Therefore, in recent years, from an environmental perspective, there has been a demand for thermal recorders that use color developers, light stabilizers, and other additives that do not have a phenolic skeleton.

[0012] This invention was made in view of such a reality, and its purpose is to provide a thermal recorder with low concerns about the safety of endocrine disruptors, etc., excellent color development and lightfastness, and excellent heat resistance.

[0013] Methods for solving problems

[0014] The inventors of this application conducted in-depth research to achieve the aforementioned objectives and discovered that by incorporating a chromogenic agent (non-phenolic chromogenic agent) without a phenolic backbone and a specific light stabilizer (non-phenolic light stabilizer) without a phenolic backbone into the thermal recording layer, a thermal recording medium with low safety concerns regarding endocrine disruptors, excellent color development and lightfastness, and excellent heat resistance can be provided. This invention is based on this insight.

[0015] That is, one aspect of the present invention provides a thermal recorder having a thermal recording layer laminated on a substrate. In the thermal recorder of the present invention, the thermal recording layer contains a chromophore, a non-phenolic chromophore, and a non-phenolic light stabilizer.

[0016] In existing thermal recording media, phenolic compounds are commonly used as chromogenic agents and light stabilizers. However, the safety of phenolic compounds as endocrine disruptors is a concern.

[0017] In contrast, in the thermal recorder according to the present invention, the color developer and light stabilizer contained in the thermal recording layer are non-phenolic compounds. Therefore, the concerns mentioned above are not generated. Furthermore, even when using non-phenolic compounds as described above, the thermal recorder of the present invention will be a thermal recorder with excellent color development, lightfastness, and heat resistance.

[0018] In the thermal recorder of the present invention, the aforementioned non-phenolic light stabilizer contains a histamine-based light stabilizer. This, in particular, improves lightfastness.

[0019] In one embodiment of the thermal recorder of the present invention, the non-phenolic chromogenic agent preferably contains a compound represented by formula (1) and / or a compound represented by formula (2).

[0020] [Chemistry 1]

[0021]

[0022] (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 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.

[0023] [Chemistry 2]

[0024]

[0025] (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.

[0026] 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).

[0027] [Chemistry 3]

[0028]

[0029] (The symbols in equation (1a) are the same as those in equation (1).)

[0030] [Chemistry 4]

[0031]

[0032] (The symbols in equation (2a) are the same as those in equation (2).)

[0033] Based on this structure, a thermal recorder with superior color development and heat resistance can be provided.

[0034] In one embodiment of the thermal recording medium of the present invention, the thermal recording layer preferably further contains a preservation enhancer.

[0035] In this case, it is preferable that the above-mentioned preservation enhancer contains a urea urethane compound as shown in formula (4).

[0036] [Chemistry 5]

[0037]

[0038] Based on this configuration, a thermal recorder with excellent printability and, in particular, resistance to plasticizers can be provided.

[0039] 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 with excellent color development and excellent heat resistance can be provided.

[0040] In another embodiment of the thermal recorder of the present invention, it is preferable that the content of the non-phenolic light stabilizer relative to the entire thermal recording layer is 1% by mass or more and 10% by mass or less. With this configuration, a thermal recorder can be provided that exhibits excellent color development and heat resistance, as well as excellent lightfastness, even with a non-phenolic light stabilizer.

[0041] Invention Effects

[0042] According to the present invention, a thermal recorder with low concerns about the safety of endocrine disruptors, etc., excellent color development and lightfastness, and excellent heat resistance can be provided. Attached Figure Description

[0043] Figure 1 This is a schematic cross-sectional view illustrating one embodiment of the thermal recording device of the present invention. Detailed Implementation

[0044] The thermal recorder of the present invention has a laminated structure in which a thermal recording layer is stacked on a substrate. In the thermal recorder of the present invention, the thermal recording layer contains a chromogenic agent, a non-phenolic chromogenic agent, and a non-phenolic light stabilizer. The non-phenolic light stabilizer contains a histamine-based light stabilizer.

[0045] Hereinafter, one embodiment of the thermal recorder of the present invention will be described in detail with reference to the accompanying drawings; however, the present invention is not limited to the following embodiments.

[0046] Figure 1This is a schematic cross-sectional view illustrating one embodiment of the thermal recording device of the present invention.

[0047] The thermal recorder 1 in this embodiment is as follows: Figure 1 As shown, it has a laminated structure in which a base coating layer 6, a thermal recording layer 3, an intermediate layer 4 and a top coating layer 5 are sequentially stacked on a sheet-like substrate 2.

[0048] In this embodiment, the substrate 2 functions as a support for the thermal recorder 1. The substrate 2 can be made of various types of paper, such as offset paper, art paper, coated paper, kraft paper, laminated paper made by laminating thermoplastic resins such as polyethylene onto these paper substrates, synthetic paper, and porous materials such as nonwoven fabric. Alternatively, transparent synthetic resin films, such as polypropylene films, polyethylene terephthalate films, polystyrene films, and polycarbonate films, can be used. It should be noted that the thickness of the substrate 2 is not particularly limited; however, by adjusting the thickness of the substrate 2 to approximately 10 μm to 100 μm, a substrate 2 with excellent coatability can be obtained. Furthermore, a substrate 2 with excellent transparency can be obtained.

[0049] In this embodiment, the base coating 6 has functions such as heat insulation and buffering to prevent the release of heat provided by the thermal head. The base coating 6 is formed, for example, by adding hollow particles as fillers to the binder.

[0050] By applying such a heat-insulating base coating 6 to the thermal recorder 1, the printing sensitivity is improved. Therefore, it is possible to suppress the increase in the applied voltage of the thermal head, resulting in the suppression of thermal head burning-off.

[0051] The average particle size of the hollow particles added as fillers to the base coating 6 is preferably 1 μm to 100 μm. Within this range, the thermal insulation of the base coating 6 is improved. Here, the average particle size refers to the weight-average particle size measured using laser diffraction. The average particle size measurement based on laser diffraction can be performed, for example, using a micrometer manufactured by Microtrac-BEL under the trade name "MT3300EX-II".

[0052] Furthermore, the hollowness of the hollow particles is preferably between 30% and 99%. Within this range, the thermal insulation of the base layer 6 is improved. Additionally, the higher the hollowness of the hollow particles, the better the thermal insulation effect. Therefore, the colorant can effectively develop color with less heat. That is, increasing the hollowness improves the printing quality of the thermal recorder 1.

[0053] Here, the hollowness of the hollow particle is calculated using the following formula.

[0054] Hollowness ratio = {(volume of voids) / (volume of hollow particles)} × 100

[0055] Furthermore, regarding the proportion of hollow particles in the base coating 6, it is preferably 40 to 90 parts by mass relative to 100 parts by mass of the base coating.

[0056] The material constituting the hollow particles is, for example, a thermoplastic resin. Examples of such thermoplastic resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl acetate resins, polyacrylate resins, polyacrylonitrile resins, and polybutadiene resins.

[0057] It should be noted that fillers other than hollow particles can also be used as fillers for the base coating 6. Examples include calcined kaolin, alumina, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomaceous earth, silica fume, magnesium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, polystyrene resin particles, urea-formaldehyde resin particles, and polyolefin resin particles. Furthermore, these fillers can be used alone or in combination of two or more.

[0058] Examples of binders contained in the base coating 6 include acrylic-styrene copolymers, styrene-butadiene copolymers, acrylic-butadiene-styrene copolymers, vinyl acetate resins, vinyl acetate-acrylic copolymers, styrene-acrylate copolymers, acrylate resins, and polyurethane resins.

[0059] In addition, as binding agents, water-soluble polymers such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose and other cellulose derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylamide-acrylate copolymer, acrylamide-acrylate-methacrylic acid terpolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein can also be used.

[0060] The coating amount (dry weight) of the base coating 6 is preferably 1 g / m². 2 ~10g / m 2 .

[0061] The thickness of the base coating 6 is preferably 1μm to 20μm.

[0062] If the amount and thickness of the base coating 6 are adjusted to the range described above, the base coating 6 will properly perform its heat insulation function.

[0063] In this embodiment, the thermal recording layer 3 is a layer that forms a recorded image on the thermal recorder 1 by using a chemical reaction to generate color through heating by a thermal head or the like. In this embodiment, the thermal recording layer 3 contains a color-generating agent, a non-phenolic color developer, and a non-phenolic light stabilizer.

[0064] As a color-generating agent, the color-generating agent that generates color by heating is a component that generates color through a chemical reaction by heating a thermal head or the like, and forms a recorded image in the thermal recorder 1 of this embodiment. Commonly known leuco dyes can be used as the color-generating agent that generates color by heating. As leuco dyes, for example, 3-(N-isobutyl-N-ethyl)amino-6-methyl-7-aniline fluorane, 3-(N-isopentyl-N-ethyl)amino-6-methyl-7-o-chloroaniline fluorane, 3-(N-methyl-N-p-toluidine)-6-methyl-7-aniline fluorane, 3-(N-ethyl-N-p-toluidine)-6-methyl-7-aniline fluorane, 3-(N-ethyl-N-isopentyl)amino-6-methyl-7-aniline fluorane, 3-(N-ethoxypropyl-N-ethyl)amino-6-methyl-7-aniline fluorane, 3-(N-cyclohexyl-N-methyl)amino-6-methyl-7-aniline fluorane, 3-(N-methyl-N-n-propyl)amino-6- Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-toluidine fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-8-methylfluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-diethylamino-7-chlorofluorane, 3-dibutylamino-6-methyl-7-bromofluorane, 3-dibutylamino-7-(o-chloroanilino)fluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3-dimethylamino-5-methyl-7-methylfluorane, 3-pyrrolidinyl-6-methyl-7-anilinofluorane, crystal violet lactone, etc.

[0065] The particle size of the color-developing agent is preferably 0.1 to 1.0 μm. Since the color-developing agent reacts after melting, the reaction gradually slows down as the particle size increases, resulting in lower sensitivity. On the other hand, as the particle size decreases, the risk of color development at unexpected temperatures due to the heat generated during paint drying increases. In this embodiment, by setting the particle size of the color-developing agent to the range described above, the sensitivity characteristics and color development temperature of the color-developing agent can be appropriately adjusted. Here, particle size refers to the 50% average particle size measured using a Microtrac laser analysis-scattering particle size analyzer.

[0066] In this embodiment, to obtain excellent color development, it is preferable to contain approximately 10-20% by mass of a color-developing agent relative to the total thermal recording layer 3. It should be noted that it is preferable to contain the color-developing agent (described later) at a ratio of 1-3 relative to the color-developing agent 1 by dry weight.

[0067] In this embodiment, the thermal recording layer 3 does not contain conventionally used phenolic color developers, but instead contains non-phenolic color developers. Non-phenolic color developers are various electron-accepting substances that react with the leuco dyes described above upon heating to produce color in the leuco dyes; they are compounds without phenolic hydroxyl groups. In other words, the thermal recording layer 3 contains non-phenolic color developers, thus avoiding the unintentional use of phenolic color developers, which are considered to have safety concerns as endocrine disruptors. In this embodiment, by containing non-phenolic color developers instead of phenolic color developers in the thermal recording layer 3, the leuco dyes can be produced efficiently. It should be noted that the thermal recording layer 3 may sometimes unavoidably contain trace amounts of phenolic compounds in the form of impurities, to a degree that does not pose safety concerns as an endocrine disruptor. In cases where the thermal recording layer 3 unavoidably contains such trace amounts of phenolic compounds, it is considered to be within the scope of this invention.

[0068] As such non-phenolic colorimetric agents, known colorimetric agents that do not have phenolic hydroxyl groups can be used without particular limitation, such as 2,2-bis[(4-methyl-3-phenoxycarbonylaminophenyl)urea]diphenyl sulfone, 4,4'-bis(p-toluylsulfonylaminocarbonylamino)diphenylmethane, 2'-(3-phenylurea)benzenesulfonylaniline, N-(p-toluenesulfonyl)-N'-(3-p-toluenesulfonyloxyphenyl)urea, etc.

[0069] Here, the aforementioned non-phenolic colorimetric agents can also be used as colorimetric agents. However, the inventors have found that, from the viewpoint of further improving the heat resistance of the thermal recorder 1, compounds represented by the following formulas (1) and (2) are suitable.

[0070] [Chemistry 6]

[0071]

[0072] (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 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.

[0073] [Chemistry 7]

[0074]

[0075] (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.

[0076] As the aforementioned "substituents", organic groups other than hydrogen atoms can be used without particular limitation, such as halogen atoms, nitro groups, amino groups, alkyl groups, alkoxy groups, aryl groups, aryloxy groups, alkyl carbonyloxy groups, alkyl carbonyl amino groups, aryl carbonyl amino groups, alkyl sulfonyl amino groups, aryl sulfonyl amino groups, monoalkyl amino groups, dialkyl amino groups, aryl amino groups, etc.

[0077] Examples of "halogen atoms" mentioned above include fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms.

[0078] Examples of "alkyl groups" mentioned above include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, 2,3-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, and other straight-chain or branched alkyl groups with 1 to 12 carbon atoms.

[0079] Examples of "alkoxy groups" mentioned above include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, tert-pentoxy, neopentoxy, 2,3-dimethylpropoxy, 1-ethylpropoxy, 1-methylbutoxy, n-hexoxy, isohexoxy, n-heptoxy, n-octoxy, etc., which are straight-chain or branched alkoxy groups with 1 to 8 carbon atoms.

[0080] Examples of "aryl" groups include aromatic hydrocarbon groups with 6 to 10 carbon atoms, such as phenyl, 1-naphthyl, and 2-naphthyl.

[0081] In the above "dialkylamino", the two alkyl groups can be the same or different.

[0082] From the viewpoint of imparting excellent color development and heat resistance to the thermal recorder 1, the compound shown in formula (1a) is preferred as the compound shown in formula (1). Specifically, examples include N,N'-bis-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-bis-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-bis-[3-(tris(toluenesulfonyloxy)phenyl]urea, N,N'-bis-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-bis-[3-(m-toluenesulfonyloxy)phenyl]urea, and N,N'-bis-[3-(benzenesulfonyloxy)phenyl]urea, as shown in formula (1b).

[0083] [Chemistry 8]

[0084]

[0085] (The symbols in equation (1a) are the same as those in equation (1).)

[0086] [Chemistry 9]

[0087]

[0088] From the viewpoint of imparting excellent color development and heat resistance to the thermal recorder 1, the compound shown in formula (2a) is preferred as the compound shown in formula (2a). Specifically, [3-(3-phenylurea)phenyl]-4-methylbenzenesulfonate shown in formula (2b) is an example.

[0089] [Chemistry 10]

[0090]

[0091] (The symbols in equation (2a) are the same as those in equation (2).)

[0092] [Chemistry 11]

[0093]

[0094] In this embodiment, the thermal recording layer 3 may contain a non-phenolic colorimetric agent alone, or it may contain two or more types.

[0095] By using at least one or both of the compounds shown in general formula (1) and general formula (2) as non-phenolic color developers in the thermal recording layer 3, the heat resistance and color development of the thermal recorder 1 can be improved.

[0096] In this embodiment, the content of the non-phenolic color developer relative to the entire thermal recording layer 3 is preferably 10% by mass or more and 50% by mass or less. From the viewpoint of preventing a lack of color development (lower optical density) caused by insufficient color developer, a composition with a non-phenolic color developer content of 10% by mass or more is preferred. Furthermore, from the viewpoint of preventing a lack of color development (lower optical density) caused by excessive color developer (i.e., insufficient dye), a composition with a non-phenolic color developer content of 50% by mass or less is preferred.

[0097] In this embodiment, as described above, phenolic colorimetric agents are not intentionally used as colorimetric agents in the thermal recording layer 3. However, sometimes impurities, such as those used as non-phenolic colorimetric agents, inevitably contain trace amounts of phenolic compounds. Examples of such impurities in the non-phenolic colorimetric agents shown in formulas (1) and / or (2) above include sulfonates (-SO2-O-), compounds obtained by hydrolyzing all or part of alkoxy, aryloxy, alkyl carbonyloxy, etc., which are substituents. Such phenolic compounds, which are impurities, can sometimes also function as colorimetric agents.

[0098] In this embodiment, the aforementioned phenolic compounds, which are inevitably present as impurities in the thermal recording layer 3, may be present in trace amounts at the ppm level (e.g., less than 100 ppm relative to the overall thermal recording layer 3) that can be detected by machine analysis. However, it is believed that if the amount is trace, there is no concern about safety such as endocrine disruptors, and they will not actually function as color developers.

[0099] In this embodiment, the thermal recording layer 3 does not contain conventionally used phenolic ultraviolet absorbers or other phenolic light stabilizers, but instead contains non-phenolic light stabilizers. Non-phenolic light stabilizers are substances (light stabilizers) that inhibit light degradation such as property reduction and discoloration caused by exposure to sunlight or other light; they are compounds without phenolic hydroxyl groups. The inclusion of non-phenolic light stabilizers in the thermal recording layer 3, in other words, means that phenolic compounds, which are considered endocrine disruptors, are not intentionally used. In this embodiment, by including non-phenolic light stabilizers in the thermal recording layer 3 instead of phenolic light stabilizers, the lightfastness and heat resistance of the thermal recorder 1 can be improved. It should be noted that if the thermal recording layer 3 in this embodiment contains phenolic light stabilizers that do not raise safety concerns as endocrine disruptors and do not affect color development, lightfastness, or heat resistance, it is considered to be included within the scope of this invention.

[0100] As such a non-phenolic light stabilizer, known light stabilizers without phenolic hydroxyl groups can be used without particular limitation. Examples include histamine-based light stabilizers, oxalate aniline-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. Furthermore, the inventors of this application have found that, from the viewpoint of further improving the lightfastness and heat resistance of the thermal recorder 1, a histamine-based light stabilizer (HALS) is suitable.

[0101] Histamine-based light stabilizers are compounds that have one or more 2,2,6,6-tetraalkylpiperidine skeletons (e.g., 2,2,6,6-tetramethylpiperidine skeletons) in their molecules. It can be assumed that the nitric oxide radicals generated by the oxidation of the nitrogen atom of piperidine capture free radicals, thereby exhibiting a stabilizing function.

[0102] As histamine-based light stabilizers, compounds having one or more 2,2,6,6-tetraalkylpiperidine skeletons (e.g., 2,2,6,6-tetramethylpiperidine skeletons) in the molecule can be used without particular limitation, for example, compounds having groups shown in the following formula (3).

[0103] [Chemistry 12]

[0104]

[0105] (In equation (3), R) a The groups in general formula (3) represent hydrogen atoms, hydroxyl groups, alkyl groups with 1 to 30 carbon atoms, alkoxy groups with 1 to 30 carbon atoms, hydroxyalkyl groups with 1 to 30 carbon atoms, hydroxyalkoxy groups with 1 to 30 carbon atoms, alkenyl groups with 2 to 30 carbon atoms, or oxygen radicals. These alkyl, alkoxy, hydroxyalkyl, hydroxyalkoxy, and alkenyl groups can be interrupted once or multiple times by oxygen atoms or carbonyl groups. Furthermore, the groups in general formula (3) are in general formula (3) (Partial bonding.)

[0106] In histamine-based light stabilizers, there may be one or more groups of the general formula (3).

[0107] R as general formula (3) aAlkyl groups with 1 to 30 carbon atoms can be used, including straight-chain alkyl groups and branched alkyl groups. Examples of straight-chain alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, nonadecanyl, triadecyl, etc. Examples of branched alkyl groups include groups obtained by substituting one or more of the above straight-chain alkyl groups with alkyl groups with 1 to 9 carbon atoms.

[0108] R as general formula (3) a Alkoxy groups with 1 to 30 carbon atoms can be used, and examples of alkoxy groups corresponding to the alkyl groups mentioned above can be given.

[0109] R as general formula (3) a Hydroxyalkyl groups with 1 to 30 carbon atoms can be used, and examples of hydroxyalkyl groups corresponding to the alkyl groups mentioned above can be given.

[0110] R as general formula (3) a Alkenyl groups with 2 to 30 carbon atoms can be used, such as vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, heptadecenyl, octadecenyl, nonadecanenyl, eicosene, dodecenyl, dodecanenyl, tridecenyl, tetradecenyl, pentadecenyl, heptadecenyl, octadecenyl, nonadecanenyl, triadecenyl, and also include alkadienyl and alktrienyl.

[0111] As the group represented by general formula (3), R is preferred from the aspects of thermal stability, colorfastness, and heat-resistant colorfastness. a It is a group consisting of hydrogen atoms or an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 30 carbon atoms, even more preferably an alkyl group having 1 to 4 carbon atoms, and most preferably a methyl group.

[0112] As a histamine-based light stabilizer, specifically, as R of general formula (3) aExamples of histamine-based light stabilizers that are hydrogen atom acceptors include 2,2,6,6-tetramethyl-4-piperidinyl stearate, 2,2,6,6-tetramethyl-4-piperidinyl benzoate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, tetra(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate, bis(2,2,6,6-tetramethyl-4-piperidinyl)·bis(tetranyl)-1,2,3,4-butanetetracarboxylate, and poly[{ 6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidinyl)imino}, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidinylamino)hexane / dibromoethane condensate, 1,6-bis(2,2,6,6-tetramethyl-4-dibromoethane)hexane / dibromoethane condensate, 1,6-Bis(2,2,6,6-tetramethyl-4-piperidinylamino)hexane / 2,4-dichloro-6-morpholino-triazine condensate, 1,5,8,12-tetra[2,4-bis(N-butyl-N-(2,2,6,6-tetramethyl-4-piperidinyl)amino)-triazine-6-yl]-1,5,8,12-tetraazadodecane, 1,6,11-tris[2,4-bis(N-butyl-N-(2,2,6,6-tetramethyl-4-piperidinyl)amino)-triazine-6-yl]-1,5,8,12-tetraazadodecane, 1,6,11-tris[2,4-bis(N- Butyl-N-(2,2,6,6-tetramethyl-4-piperidinyl)amino)-triazine-6-ylamino]undecane, 3,9-bis[1,1-dimethyl-2-{tris(2,2,6,6-tetramethyl-4-piperidinyloxycarbonyl)butylcarbonyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, 2,2,6,6-tetramethyl-4-piperidinylhexadecanoate, 2,2,6,6-tetramethyl-4-piperidinyloctadecanoate, etc., are used as R of general formula (3). aExamples of histamine-based light stabilizers for methyl groups include 1,2,2,6,6-pentamethyl-4-piperidinyl stearate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, tetra(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)·bis(tetranyl)-1,2,3,4-butanetetracarboxylate, and bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-butyl. 2-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate, 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate, 1,2,3,4-butanecarboxylic acid / 2,2-bis(hydroxymethyl)-1,3-propanediol / 3-hydroxy-2,2-dimethylpropanal / 1,2,2,6,6-pentamethyl-4-piperidinyl ester condensate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)=sebate / methyl=1,2,2,6,6-pentamethyl-4-piperidinyl=sebate mixture Compounds, 1,5,8,12-tetra[2,4-bis(N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidinyl)amino)-triazin-6-yl]-1,5,8,12-tetraazadodecane, 1,6,11-tris[2,4-bis(N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidinyl)amino)-triazin-6-ylamino]undecane, 3,9-bis[1,1-dimethyl-2-{tris(1,2,2,6,6-pentamethyl-4-piperidinyloxycarbonyl] The reaction products of β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaziro[5.5]undecane, 1,2,2,6,6-pentamethyl-4-piperidinylhexadecanoate, 1,2,2,6,6-pentamethyl-4-piperidinyloctadecanoate, 1,2,3,4-butanetetracarboxylic acid tetramethyl ester, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaziro[5.5]undecane-3,9-diethanol, etc., are used as R of general formula (3). a Histamine-based light stabilizers with alkoxy groups having 1 to 30 carbon atoms include bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate and bis(1-undecyloxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate. Among these, the R group represented by general formula (3) is preferred from the perspectives of thermal stability, colorfastness, and heat-resistant colorfastness. a Histamine-based light stabilizers that are hydrogen atoms or methyl groups, more preferably R a The light stabilizer is a methyl-based histamine-based light stabilizer. In this embodiment, the thermal recording layer 3 may contain only one type of histamine-based light stabilizer, or it may contain two or more types.

[0113] In this embodiment, the content of the non-phenolic light stabilizer relative to the overall thermal recording layer 3 is not particularly limited; however, it is preferably 1% by mass or more and 10% by mass or less, more preferably 5% by mass or more and 10% by mass or less. From the viewpoint of imparting excellent lightfastness to the thermal recorder 1 of this embodiment, a configuration in which the content of the non-phenolic light stabilizer is 1% by mass or more, more preferably 5% by mass or more, is suitable. From the viewpoint of imparting excellent color development to the thermal recorder 1 of this embodiment, a configuration in which the content of the non-phenolic light stabilizer is 10% by mass or less is suitable.

[0114] In this embodiment, the content of non-phenolic light stabilizer relative to the total amount of light stabilizer contained in the thermal recording layer 3 is not particularly limited. However, from the viewpoint of improving light and heat resistance while reducing concerns about the safety of endocrine disruptors, etc., it is preferred to be 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0115] In this embodiment, the content of histamine-based light stabilizer relative to the total amount of light stabilizer contained in the thermal recording layer 3 is not particularly limited. However, from the viewpoint of improving light and heat resistance while reducing concerns about the safety of endocrine disruptors, etc., it is preferable to be 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0116] In addition, the thermal recording layer 3 may contain additives such as binders, sensitizers, lubricants, fillers, preservation enhancers, and pigments as needed.

[0117] Examples of binders contained in the thermal recording layer 3 include 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 acetate copolymer, polyurethane, polystyrene, polyvinylpyrrolidone, acrylate, acrylonitrile, methyl vinyl ether, etc. These binders can be used alone or in combination of two or more.

[0118] Examples of sensitizers include stearic acid, stearamide, stearic aniline, hydroxymethylstearamide, methylene distearate, ethylene distearate, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 2,6-diisopropylnaphthalene, 1,2-diphenoxyethane, 1,2-diphenoxymethylbenzene, 1,2-bis(3,4-dimethylphenyl)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl oxalate, p-benzylbiphenyl, m-terphenyl, diphenyl sulfone, benzyl p-benzyloxybenzoate, dibenzyl terephthalate, and p-toluenesulfonamide, which are solid at room temperature and preferably have a melting point of about 70°C or higher. These sensitizers can be used alone or in combination of two or more.

[0119] Examples of lubricants include paraffin wax, fatty acid waxes such as oleic acid, polyolefin waxes such as polyethylene wax, metallic soaps such as zinc stearate, ester waxes such as carnauba wax, silicone oil, and whale oil. These lubricants can be used alone or in combination of two or more.

[0120] Examples of fillers include 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, diatomaceous earth, silica, zinc oxide, silicon dioxide, colloidal silica, polystyrene resin particles, urea-formaldehyde resin particles, and polyolefin resin particles. These fillers can be used alone or in combination of two or more.

[0121] Examples of preservation enhancers include 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-dimethyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 4-(2-methylglycyloxy)-4'-benzyloxydiphenyl sulfone, 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 urea urethane compounds as shown in formula (4) below.

[0122] [Chemistry 13]

[0123]

[0124] These preservation enhancers can be used alone or in combination of two or more. Additionally, they may contain known surfactants.

[0125] Fresh food products such as meat and fish are sold in packages wrapped in cling film, with labels displaying prices affixed to the film. Furthermore, these packages are often stacked, leading to situations where labels come into contact with the cling film wrapping other products. This cling film contains plasticizers used to impart plasticity. When these stacked packages are left for extended periods, the plasticizers can migrate to the labels, potentially affecting print quality. Therefore, thermal recorders are preferably preferred for their excellent "plasticizer resistance," meaning they do not easily cause print loss even if plasticizers migrate.

[0126] In this embodiment, from the viewpoint of print preservation, especially plasticizer resistance, the thermal recording layer 3 preferably contains a preservation enhancer, and particularly preferably contains a urea urethane compound as shown in formula (4) above.

[0127] It can be considered that by making the thermal recording layer 3 contain a preservation enhancer, especially the urea urethane compound shown in formula (4), the reaction efficiency of the leuco dye and the color developer is improved, it is easy to generate electron transfer complexes, and it is not easy to have a reverse reaction. The color development of the thermal recorder becomes excellent. In addition, the color concentration is not easy to decrease, and the printing preservation, especially the resistance to plasticizers, is excellent.

[0128] The urea ester compounds shown in formula (4) are specifically the three types shown in formulas (4a) to (4c) below, which can be used alone or in combination of two or more.

[0129] [Chemistry 14]

[0130]

[0131] [Chemistry 15]

[0132]

[0133] [Chemistry 16]

[0134]

[0135] In this embodiment, when the thermal recording layer 3 contains a retention enhancer, the content of the retention enhancer relative to the entire thermal recording layer 3 is preferably 1% by mass or more and 20% by mass or less. From the perspective of suppressing the decrease in color intensity caused by plasticizers, etc., and achieving a thermal recorder with excellent print retention, especially plasticizer resistance, a content of 1% by mass or more of the aforementioned retention enhancer is preferred. Furthermore, from the perspective of preventing a lack of color intensity (lower optical density), a content of 20% by mass or less of the aforementioned retention enhancer is preferred.

[0136] In this embodiment, when the thermal recording layer 3 contains a retention enhancer, the ratio of the retention enhancer to the non-phenolic color developer (retention enhancer / non-phenolic color developer) is preferably 1 / 20 to 1 / 1. From the perspective of preventing a lack of color development (lower optical density), a composition with a ratio of 1 / 1 or less is preferred. Furthermore, from the perspective of suppressing the decrease in color concentration caused by plasticizers, etc., and achieving a thermal recorder with excellent print retention, especially plasticizer resistance, a composition with a ratio of 1 / 20 or more is preferred.

[0137] In this embodiment, when the thermal recording layer 3 contains the urea-urethane compound shown in formula (4), the content of the urea-urethane compound shown in formula (4) relative to the entire thermal recording layer 3 is preferably 1% by mass or more and 20% by mass or less. From the perspective of suppressing the decrease in color intensity caused by plasticizers, etc., and achieving excellent printability, especially plasticizer resistance, the composition with the content of the urea-urethane compound being 1% by mass or more is preferred. Furthermore, from the perspective of preventing a lack of color intensity (lower optical density), the composition with the content of the urea-urethane compound being 20% ​​by mass or less is preferred.

[0138] In this embodiment, when the thermal recording layer 3 contains the urea-amino ester compound shown in formula (4), the content ratio of the urea-amino ester compound shown in formula (4) relative to the non-phenolic color developer (urea-amino ester compound / non-phenolic color developer) is preferably 1 / 20 to 1 / 1. From the viewpoint of preventing lack of color development (low optical density), a composition with the above-mentioned content ratio of 1 / 1 or less is preferred. In addition, from the viewpoint of suppressing the decrease in color concentration caused by plasticizers, etc., and becoming a thermal recorder with excellent printability and, in particular, excellent resistance to plasticizers, a composition with the above-mentioned content ratio of 1 / 20 or more is preferred.

[0139] In this embodiment, the content of the urea urethane compound shown in formula (4) is not particularly limited relative to the total amount of the preservation enhancer contained in the thermal recording layer 3. However, from the viewpoint of being able to suppress the decrease in color concentration caused by plasticizers, etc., and to become a thermal recorder with excellent print preservation, especially plasticizer resistance, it is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0140] In this embodiment, by providing an intermediate layer 4 on the thermal recording layer 3, a thermal recorder 1 with excellent water resistance, chemical resistance, and plasticizer resistance can be obtained.

[0141] Materials constituting the intermediate layer 4 include, for example, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, casein, gelatin, bone 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 acetate copolymer, polyurethane, polystyrene, polyvinylpyrrolidone, acrylate, acrylonitrile, methyl vinyl ether polyvinyl alcohol, and other water-based resins. It should be noted that the term "water-based resin" refers to resin components in which these compounds are dispersed in water or dissolved in water. These materials can be used alone or in combination of two or more.

[0142] The above-mentioned resins use resins with water-soluble components, such as polyvinyl alcohol (PVA) resins, which belong to the category of resins with hydroxyl groups as hydrophilic structural units, or resins with core-shell structures formed by coating hydrophobic core particles with water-soluble shell polymers, such as core-shell type acrylic resins, thereby improving transparency.

[0143] Core-shell type resins, for example, can be resins sold as core-shell type acrylic resins under the name "Bariastar (Mitsui Chemicals Co., Ltd.)".

[0144] The coating amount (dry weight) of intermediate layer 4 is preferably 0.3 g / m². 2 ~10g / m 2 .

[0145] The top coating 5 is a layer that improves the adaptability of the thermal recorder 1 to the thermal head and facilitates the color development of the thermal recording layer 3. Specifically, it refers to the process of developing the color of the thermal recording layer 3 while minimizing the accumulation of deposits on the thermal head and the deformation of the surface of the thermal recorder 1 due to heat.

[0146] In this embodiment, the top coating 5 of the thermal recorder 1 serves to reduce wear on the thermal head without shortening its lifespan, without adding elastic particles or the like. This means improved thermal head adaptability. Furthermore, the top coating 5 needs to have improved anti-adhesion properties to the thermal head. Here, anti-adhesion means preventing the undesirable situation where the outermost layer of the thermal recorder melts due to the heat of the thermal head and adheres to it. More specifically, it means preventing undesirable situations such as localized areas of non-printing or deformed printed surfaces on the thermal recorder.

[0147] In this embodiment, the top coating 5 has evaporation pores and cracks on its surface in the form of recessed depressions caused by moisture evaporation. This reduces the contact area between the surface of the top coating 5 and the thermal head.

[0148] In order to create recesses, especially cracks, on the surface of the top coating 5, a coating liquid containing hydrophobic resin particles is used as the coating liquid for forming the top coating 5.

[0149] That is, in this embodiment, the top coating 5 uses an emulsion of hydrophobic resin particles, such as an emulsion of hydrophobic acrylic resin particles dispersed in water, as a binder.

[0150] This method uses an emulsion of hydrophobic resin particles as the binder for the top coating 5, without using water-soluble polymers.

[0151] When the coating containing water-soluble polymers dries after application, it does not easily coagulate, forming a flexible coating film. Therefore, no shrinkage cracks occur in the top coating layer 5.

[0152] In contrast, when the emulsion of hydrophobic resin particles is dried after coating, the hydrophobic resin particles agglomerate and shrink due to evaporation, resulting in concave cracks on the surface of the top coating 5.

[0153] The crack was formed due to shrinkage caused by the aggregation of hydrophobic resin particles, and therefore remained in the top coating layer 5, without reaching the intermediate layer 4.

[0154] In addition, in order to form evaporation holes caused by the evaporation of moisture into the surface of the top coating layer 5, the thermal recording layer 3, the intermediate layer 4 and the top coating layer 5 are coated simultaneously using a curtain coating machine.

[0155] The curtain coating machine sprays the coating liquids used to form the thermal recording layer 3, intermediate layer 4, and top coating layer 5 from multiple slits, stacking them up so that the stacked coating liquids travel continuously. At this time, the base coating layer 6, which has been pre-formed on the substrate 2, is freely dropped to coat it.

[0156] In this simultaneous three-layer coating process using a curtain coating machine, once the top coating layer 5 dries, cracks appear as described above due to the agglomeration of hydrophobic resin particles. Water vapor escapes from these cracks, while the semi-dry intermediate layer 4 and the thermal recording layer 3 dry and solidify. Most of the water vapor in the intermediate layer 4 and the thermal recording layer 3 is released through the cracks; however, some water vapor is released through evaporation pores formed in the top coating layer 5. Therefore, cracks and evaporation pores are formed near the top coating layer 5.

[0157] In this embodiment, the evaporation pores formed in the top coating layer 5 remain in the intermediate layer 4. Therefore, even if oil or other substances adhere to the surface of the top coating layer 5, which is the uppermost layer, they will not reach the thermal recording layer 3, and there will be no discoloration of the thermal recording layer 3.

[0158] The top coating 5 may contain additives such as lubricants, crosslinking agents, dispersants, defoamers, water-resistant agents, and fillers, as needed.

[0159] Examples of lubricants include polyethylene and zinc stearate. Examples of crosslinking agents include zirconium carbonate.

[0160] Examples of fillers include aluminum hydroxide, alumina, aluminum silicate, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, silica gel, activated clay, talc, clay, kaolinite, diatomaceous earth, silica fume, magnesium carbonate, magnesium oxide, magnesium hydroxide, zinc oxide, polystyrene resin particles, urea-formaldehyde resin particles, and polyolefin resin particles. These fillers can be used alone or in combination of two or more. It should be noted that the particle size of the fillers contained in the top coating layer 5 is preferably 1.0 μm or less.

[0161] In this embodiment, the thermal recorder 1 is manufactured using an aqueous suspension obtained by dispersing a hydrophobic acrylic resin in water, a polyethylene wax as a lubricant, and calcium carbonate as a pigment in a mass ratio of 4:3:3 when dried, as the coating liquid for forming the top coating layer 5.

[0162] The coating amount (dry weight) of top coating 5 is set to 1 g / m². 2 .

[0163] According to this embodiment, since the top coating layer 5, which is the uppermost layer of the thermal recorder 1, has been formed with concave cracks and moisture evaporation pores as described above, the surface of the top coating layer 5 becomes uneven. As a result, the contact area between the top coating layer 5 and the thermal head is reduced, the wear of the thermal head is reduced, the adaptability of the thermal head is improved, and the anti-adhesion property is improved.

[0164] The thickness of the top coating 5 is adjusted to, for example, less than 1 μm. In this embodiment, it is adjusted to about 0.8 μm. As a result, since the distance from the surface of the top coating 5 to the thermal recording layer 3 is short, heat from the thermal head is efficiently conducted to the thermal recording layer 3. In addition, the thin thickness contributes to cost reduction.

[0165] Furthermore, since the cracks on the surface of the top coating 5 propagate along the thickness direction that forms the interior of the top coating 5, they are transversely interrupted in a direction orthogonal to the thickness direction of the top coating 5. As a result, the release of heat from the thermistor in the transverse direction is suppressed. Consequently, heat from the thermistor is efficiently conducted to the lower thermistor recording layer 3 located in the thickness direction.

[0166] To reduce the contact area between the top coating 5 and the thermal head, the evaporation holes for water that are approximately circular preferably have an average diameter of 2 μm or more.

[0167] The average diameter of the evaporation holes was measured by observing the surface of the top coating 5 using an electron microscope (SEM) and by measuring per unit area, for example, per 1 mm. 2 The diameter of the evaporation pores is used to calculate the number of evaporation pores. Additionally, regarding the number of evaporation pores, for example, evaporation pores with an average diameter of 5 μm or more are counted per 1 mm. 2 The preferred number is 30 or more, and the more preferred number is 40 or more.

[0168] In the thermal recorder 1 of this embodiment, by adjusting the fit of the top coating 5, for example, the surface of the top coating 5 can be made to have a large number of evaporation pores and a small number of cracks. Alternatively, the surface of the top coating 5 can be made to have no cracks and only a large number of evaporation pores.

[0169] In this embodiment, although the three layers of thermal recording layer 3, intermediate layer 4 and top coating layer 5 are coated simultaneously using a curtain coating machine, it is not limited to multi-layer simultaneous coating. Each thermal recording layer 3, intermediate layer 4 and top coating layer 5 can also be formed separately and sequentially.

[0170] In this embodiment, although a base coating 6 and an intermediate layer 4 are formed on the substrate 2, in another embodiment of the present invention, at least one of the base coating 6 and the intermediate layer 4 may be omitted.

[0171] The thermal recorder of the above embodiment has excellent lightfastness, color development and heat resistance because it has the thermal record layer configured as described above.

[0172] Regarding the whiteness change (%) of the thermal recorder of this embodiment, as shown by the following formula, from the viewpoint of excellent lightfastness and suppression of whiteness reduction caused by light irradiation, it is preferably -5% or more, more preferably -4.5% or more, and even more preferably -4% or more.

[0173] Whiteness change (%) = Whiteness after 100 hours under 5000 Lux illuminance - Whiteness before test

[0174] The whiteness is a value calculated according to JIS P 8148.

[0175] The negative value (-) of the whiteness change (%) indicates the amount of whiteness reduction. The closer it is to 0%, the less the whiteness reduction and the better the lightfastness.

[0176] Regarding the absolute value of Δb shown in the following formula for the thermal recorder of this embodiment, from the viewpoint of excellent lightfastness and suppression of yellowing and blue discoloration (bluish discoloration) caused by light irradiation, it is preferably 2.5 or less, more preferably 2.4 or less, even more preferably 2.3 or less, and particularly preferably 2.2 or less.

[0177] Δb = b value after 100 hours of exposure to 5000 Lux - b value before the experiment

[0178] The b-value represents L as specified in JIS Z8781-4:2013. a b The chromaticity (b value) in a color space.

[0179] The b-value represents the change from blue to yellow; a larger value indicates a closer transition to yellow, while a smaller value indicates a closer transition to blue. The Δb value represents the amount of change in the b-value; a positive value indicates yellowing, and a negative value indicates blueing. Therefore, the closer the absolute value of Δb is to 0, the less yellowing or blueing occurs, and the better the lightfastness.

[0180] Regarding the dynamic sensitivity (OD value) of the printing portion of the thermal recorder in this embodiment at 0.16 mJ / dot, from the viewpoint of excellent color rendering, it is preferably 0.1 or more, and more preferably 0.2 or more.

[0181] Regarding the dynamic sensitivity (OD value) of the printed portion of the thermal recorder in this embodiment at 0.20 mJ / dot, from the viewpoint of excellent color development, it is preferably 0.6 or more, and more preferably 0.7 or more.

[0182] Regarding the dynamic sensitivity (OD value) of the printed portion of the thermal recorder in this embodiment at 0.40 mJ / dot, from the viewpoint of excellent color rendering, it is preferably 1.2 or higher, and more preferably 1.3 or higher.

[0183] The dynamic sensitivity (OD value) mentioned above is the value measured in the examples given below. The higher the value, the better the color development.

[0184] Regarding the OD value of the non-printed portion in the (heat resistance evaluation) of the thermal recorder described later in this embodiment, from the viewpoint of excellent heat resistance and the ability to clearly identify the printed portion even after heating and cooking in a microwave oven or the like, it is preferably 0.2 or less, more preferably 0.19 or less, and even more preferably 0.18 or less.

[0185] Regarding the OD value of the printed portion in the embodiments (water resistance evaluation) of the thermal recorder described later in this embodiment, from the viewpoint of excellent water resistance and the ability to clearly identify the printed portion even under humid conditions, it is preferably 1 or more, more preferably 1.1 or more, and even more preferably 1.2 or more.

[0186] Regarding the OD value of the printed portion in the embodiment of the thermal recorder described later (plasticizer resistance evaluation), from the viewpoint that the printed portion can be clearly identified even when placed in a state of close contact with plastic wrap containing plasticizer, it is preferably 1.25 or more, more preferably 1.3 or more, and even more preferably 1.4 or more.

[0187] Example

[0188] In the following examples and comparative examples, thermal recorders containing non-phenolic color developers and non-phenolic light stabilizers in the thermal recording layer were fabricated, and their color development, lightfastness, heat resistance, water resistance, and plasticizer resistance were evaluated. It should be noted that the present invention is not limited to these examples.

[0189] (Examples 1-10, Comparative Examples 1-4)

[0190] (The fabrication of thermal recording media)

[0191] <Undercoat>

[0192] 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.

[0193] <Thermal Recording Layer>

[0194] Prepare the coating solutions for forming the thermal recording layer shown in Tables 1 and 2, and apply the prepared coating solutions for forming the thermal recording layer onto 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 Tables 1 and 2, the values ​​for each compounding material represent the weight ratio during drying.

[0195] 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, light stabilizer 1 uses the reaction product of 1,2,2,6,6-pentamethyl-4-piperidinyl octadecanoate, 1,2,3,4-butanetetracarboxylate tetramethyl ester, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol (trade name "Adekastab LA-63P", number average molecular weight: approximately 2000, manufactured by ADEKA Corporation), and light stabilizer 2 uses benzotriazole (phenolic) α-3-(3-(2H-benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl)-1-oxopropyl-ω-hydroxy poly(ethylene oxide). In addition, preservation enhancer 1 uses the urea urethane compound shown in formula (4) above (trade name "UU", manufactured by Chemipro Chemical Co., Ltd.).

[0196] In addition, 1,2-bis(3-methylphenoxy)ethane (a substance prepared by dispersing in an aqueous PVA solution to form a dispersion with a solid content concentration of 20%) is used as the sensitizer, styrene-acrylic copolymer emulsion is used as the binder, calcium carbonate (a substance prepared by dispersing in a 5% aqueous sodium hexametaphosphate solution to form a dispersion with a solid content concentration of 30%) is used as the pigment, and zinc stearate emulsion is used as the lubricant.

[0197] <Intermediate Layer>

[0198] An acrylic emulsion (30% solids concentration) was liquid-coated onto the aforementioned thermal recording layer and allowed to dry, resulting in a coating weight of 1.6 g / m² upon drying. 2 An intermediate layer with a thickness of 1.5 μm.

[0199] Topcoat

[0200] A liquid mixture was prepared by mixing 40 parts by weight of acrylic emulsion (20% solids concentration), 5 parts by weight of calcium carbonate, 15 parts by weight of polyethylene wax (40% solids concentration), and 40 parts by weight of water. The resulting liquid was then coated onto an intermediate layer and allowed to dry, resulting in a coating weight of 1.0 g / m² upon drying. 2 A top coating with a thickness of 0.9 μm.

[0201] Using the above methods, thermal recorders of Examples 1-10 and Comparative Examples 1-4 were produced.

[0202]

[0203]

[0204] (Lightfastness evaluation)

[0205] In the lightfastness evaluation, changes in optical density (OD value of printed portion / OD value of non-printed portion), yellowing, and whiteness were measured for both the printed and non-printed portions of each thermal recorder in each embodiment and comparative example. The steps for the lightfastness evaluation are described below.

[0206] The thermal recorder was printed using a thermal paper printing test apparatus (manufactured by Oakla Engineering Co., Ltd., trade name: Pulse Simulator TH-M2 / PP), with the following settings: printing speed 50 mm / sec, applied voltage 17.0 V, thermistor resistance 870 Ω, pulse width 0.488–1.394 ms, and printing energy 0.40 mJ / dot.

[0207] Using an illuminometer to determine the distance relative to the fluorescent lamp at a level of 5000 Lux, the thermal recorder printed above was placed at that location for 100 hours.

[0208] The optical densities (OD values ​​of printed and non-printed portions) of the thermal recorder sample before the test and after the above placement were measured using a spectrophotometer (manufactured by Videojet X-rite Co., Ltd., trade name: eXact).

[0209] In addition, the whiteness (%) and hue (L, a, b) of the thermal recorder samples were measured before the test and after the aforementioned placement. Whiteness was measured using a photoelectric reflectance density meter (manufactured by Tokyo Denshoku Co., Ltd., trade name: TC-6DS / A) according to JISP 8148.

[0210] The hue (L, a, b) was determined using a colorimeter (Videojet X-rite Co., Ltd., trade name: SpectroEye).

[0211] The measurement results obtained using the above experiments are shown in Tables 3 and 4. In the measurement results in Tables 3 and 4, a high optical density (OD value) value for both the printed and non-printed areas (i.e., low light reflectance) indicates further color development (the color development is close to black), while a low value (i.e., high light reflectance) indicates insufficient color development. A higher whiteness (%) value indicates a closer approximation to white. Among the various hue indices (L, a, b), (L) represents the change from black to white, and a higher (L) value indicates a closer approximation to white. (a) represents the change from green to red, and a higher (a) value indicates a closer approximation to red. (b) represents the change from blue to yellow, and a higher (b) value indicates a closer approximation to yellow. The lightfastness of each thermal recorder was evaluated based on these color changes.

[0212] (Dynamic sensitivity evaluation)

[0213] In the dynamic sensitivity test, each thermal recorder of each embodiment and each comparative example was printed at different printing energies, and the optical density (OD value of the printed portion) at each printing energy was measured. The dynamic sensitivity of each thermal recorder of each embodiment and each comparative example was evaluated based on these measurement results. The steps of the dynamic sensitivity test are described below.

[0214] The thermal recorder was printed using a thermal paper printing test apparatus (Oakla Engineering, trade name: Pulse Simulator TH-M2 / PP) with the following settings: printing speed 50 mm / sec, applied voltage 17.0 V, thermistor resistance 870 Ω, and pulse width 0.488–1.394 ms. Printing was performed at printing energies of 0.16 mJ / dot, 0.20 mJ / dot, and 0.40 mJ / dot. The optical density (OD value) under these printing energy conditions was measured using a spectrophotometer (X-rite, trade name: eXact).

[0215] The measurement results obtained using the above-described tests are shown in Tables 3 and 4. Similar to the lightfastness test, in the measurement results of Tables 3 and 4, a high optical density (OD) value indicates further color development, while a low value indicates insufficient color development. For example, even with low printing energy, a high OD value is considered an evaluation of "good color development." Conversely, even with high printing energy, a low OD value is considered an evaluation of "poor color development." In other words, the dynamic sensitivity test is used to evaluate color development.

[0216] (Heat resistance evaluation)

[0217] In the heat resistance test, the printed and non-printed portions of each thermal recorder of each embodiment and comparative example were heated, and the optical density (OD value of the printed portion) of the printed and non-printed portions was measured. The heat resistance of each thermal recorder of each embodiment and comparative example was evaluated based on the measurement results. The procedure for the heat resistance test is described below.

[0218] The thermal recorder was printed using a thermal paper printing test apparatus (manufactured by Oakla Engineering, trade name: Pulse Simulator TH-M2 / PP), with the following settings: printing speed 50 mm / sec, applied voltage 17.0 V, thermal head resistance 870 Ω, pulse width 0.488–1.394 ms, and printing energy 0.40 mJ / dot.

[0219] A container (diameter: 12cm, capacity: 220cc) containing 100g of water was covered with a vinyl chloride plastic wrap (thickness: 10μm), and a sample (vertical: 3cm, horizontal: 4cm) with the thermal recorder printed above was attached to the plastic wrap.

[0220] Then, to allow water vapor to escape during heating, 10 perforations are made in the plastic wrap using safety pins. It should be noted that the perforations are made avoiding the sample area and are formed in a way that ensures uniform spacing between the perforations.

[0221] Then, the container was heated in a microwave oven (1500W) for 1 minute, and then the optical density (OD value of printed part / OD value of non-printed part) of the thermal recorder sample was measured using a spectrophotometer (X-rite, trade name: eXact).

[0222] The measurement results obtained using the above-described experiments are shown in Tables 3 and 4. In this evaluation of heat resistance, a smaller optical density (OD) value for the non-printed area and a larger value for the printed area indicates a smaller thermal response of the thermal recorder. That is, it represents the degree of color development of the printed or non-printed areas when heat from the vapor generated by heating the thermal recorder in a microwave oven is applied to the thermal recorder. Therefore, since the non-printed area preferably does not develop color as much as possible, a smaller optical density (OD) value can be evaluated as "good heat resistance".

[0223] On the other hand, it was confirmed that the color in the printing section had not disappeared due to the heat caused by the steam. Specifically, a high optical density (OD value) in the printing section indicates that the response to heat is not significant.

[0224] (Water resistance evaluation)

[0225] In the water resistance evaluation, the optical density (OD value of the printed and non-printed portions) of each thermal recorder of Examples 7-10 and Comparative Example 4 was measured after immersing them in water. Based on the measurement results, the water resistance of each thermal recorder of Examples 7-10 and Comparative Example 4 was evaluated. The steps for the water resistance evaluation are described below.

[0226] The thermal recorder was printed using a thermal paper printing test apparatus (manufactured by Oakla Engineering, trade name: Pulse Simulator TH-M2 / PP), with the following settings: printing speed 50 mm / sec, applied voltage 17.0 V, thermal head resistance 870 Ω, pulse width 0.488–1.394 ms, and printing energy 0.171 mJ / dot.

[0227] The printed thermal recorder sample was immersed in water at 23°C for 24 hours and then dried.

[0228] The optical density (OD value of printed and non-printed parts) of the thermal recorder sample after the above test was measured using a spectrophotometer (manufactured by Videojet X-rite Co., Ltd., trade name: eXact).

[0229] The measurement results obtained using the above-described experiments are shown in Table 4. In Table 4, a high optical density (OD value) value for the printed portion (i.e., low light reflectance) indicates further maintenance of color intensity (maintaining a black color), while a low value (i.e., high light reflectance) indicates a decrease in color intensity. In other words, it indicates the degree to which the color intensity of the printed portion decreases after immersing the thermal recorder in water. Therefore, the water resistance of the printed portion can be assessed by confirming that the colored portion does not disappear due to water immersion. Specifically, a high optical density (OD value) value for the printed portion indicates excellent water resistance. Furthermore, since the non-printed portion preferably does not exhibit color development as much as possible, a low optical density (OD value) value can be evaluated as "good water resistance."

[0230] (Evaluation of plasticizer resistance)

[0231] In the evaluation of plasticizer resistance, the optical density (OD value of the printed and non-printed portions) of each thermal recorder of Examples 7-10 and Comparative Example 4 was measured after being sealed with plastic wrap containing plasticizer. Based on the measurement results, the plasticizer resistance of each thermal recorder of Examples 7-10 and Comparative Example 4 was evaluated. The steps for evaluating plasticizer resistance will be described below.

[0232] The thermal recorder was printed using a thermal paper printing test apparatus (manufactured by Oakla Engineering, trade name: Pulse Simulator TH-M2 / PP), with the following settings: printing speed 50 mm / sec, applied voltage 17.0 V, thermal head resistance 870 Ω, pulse width 0.488–1.394 ms, and printing energy 0.171 mJ / dot.

[0233] Three sheets of polyvinyl chloride (PVC) plastic wrap (DENKA POLYMER ML-400) were superimposed on the printed thermal recording sample to ensure a tight seal with both the front and back surfaces. A 300 g / cm² layer was applied. 2 The load capacity was tested and placed at 40℃ for 15 hours.

[0234] The optical density (OD value of the printed part) of the thermal recorder sample after the above test was measured using a spectrophotometer (manufactured by Videojet X-rite Co., Ltd., trade name: eXact).

[0235] The measurement results obtained using the above-described experiments are shown in Table 4. In Table 4, a high optical density (OD value) value for the printed portion (i.e., low light reflectance) indicates further maintenance of color intensity (maintaining a black color), while a low value (i.e., high light reflectance) indicates a decrease in color intensity. This represents the degree of decrease in color intensity of the printed portion due to plasticizer transfer to the thermal recorder when sealed with plastic wrap. Therefore, the plasticizer resistance of the printed portion can be evaluated by ensuring that the colored portion does not disappear due to the sealing with plastic wrap. Specifically, a high optical density (OD value) value for the printed portion indicates excellent plasticizer resistance. Furthermore, since the non-printed portion preferably exhibits as little color as possible, a low optical density (OD value) value can be evaluated as indicating "good plasticizer resistance."

[0236]

[0237]

[0238] <Verification Results>

[0239] Based on the results shown in Tables 3 and 4, the following conclusions can be confirmed.

[0240] [Examples 1-3 and Comparative Examples 1-2]

[0241] Examples 1-3 and Comparative Examples 1-2, which contain the same color developer 1, were investigated.

[0242] (1) In the lightfastness test, Examples 1-3 showed smaller changes in whiteness compared to Comparative Example 1, and the whiteness after the test was also higher. This is presumably because Examples 1-3 contained light stabilizer 1 (a non-phenolic light stabilizer). On the other hand, Comparative Example 2, which contained the same color developer 1 as Examples 1-3 but contained a different light stabilizer 2 (a phenolic light stabilizer), had a whiteness change of -3.60. This value is less than the whiteness change of Examples 1-3. Therefore, it can be considered that Examples 1-3 have poor lightfastness compared to Comparative Example 2. That is, it can also be considered that the lightfastness is excellent when the thermal recording layer contains a conventionally used phenolic light stabilizer.

[0243] However, the whiteness of Comparative Example 2 after testing was 77.4%, which was significantly smaller compared to the whiteness of Examples 1-3. Furthermore, regarding the difference in the amount of change in whiteness, the differences between Examples 1-2 and Comparative Example 2 were also very small, at 0.90 and 0.30 respectively. In particular, Example 3, which contained the same 10 parts by weight of light stabilizer as Comparative Example 2, showed a difference of 0.1, which was practically negligible. Therefore, it can be said that even with the presence of a non-phenolic light stabilizer, the whiteness change was similar to that of Comparative Example 2.

[0244] Furthermore, in Examples 1-3 and Comparative Examples 1-2, the optical density (OD value) after the test was not significantly different.

[0245] These results confirm that the thermal recorders of Examples 1-3 containing non-phenolic light stabilizers exhibit superior lightfastness compared to Comparative Example 1 which does not contain light stabilizers, and have the same level of lightfastness as Comparative Example 2 which contains phenolic light stabilizers 2.

[0246] (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 was 1.35 to 1.41, and the optical density (OD value) of Comparative Examples 1 to 2 was 1.51 to 1.55. When the printing energy was set to 0.20 mJ / dot, the optical density (OD value) of Examples 1 to 3 was 0.88 to 0.93, and the optical density (OD value) of Comparative Examples 1 to 2 was 1.15 to 1.20. When the printing energy was set to 0.16 mJ / dot, the optical density (OD value) of Examples 1 to 3 was 0.41 to 0.47, and the optical density (OD value) of Comparative Examples 1 to 2 was 0.58 to 0.62. Examples 1 to 3 showed a trend of lower optical density (OD value) compared with Comparative Example 1, which did not contain a light stabilizer. However, the reduction of about 7-34% shows that the chromaticity is good enough to be used as a thermal recorder.

[0247] These results confirm that the thermal recorders of Examples 1-3 containing non-phenolic light stabilizers have colorimetric properties that are comparable to those of Comparative Example 1 (which does not contain a light stabilizer) and Comparative Example 2 (which contains a phenolic light stabilizer).

[0248] (3) In the heat resistance test, the optical density (OD value) of the printed portion of Examples 1-3 was 1.35-1.45, and the optical density (OD value) of the printed portion of Comparative Examples 1-2 was 1.51-1.54. Compared with Comparative Example 1 (which does not contain a light stabilizer) and Comparative Example 2 (which contains a non-phenolic light stabilizer), Examples 1-3 tended to have lower optical density (OD values). However, the decrease was only about 4-11%, maintaining the color development properties that allowed for good use as a thermal recorder. On the other hand, the optical density (OD value) of the non-printed portion of Examples 1-3 was 0.11, while the optical density (OD value) of the non-printed portion of Comparative Examples 1-2 was 0.17-0.35, which was higher than that of Examples 1-3. In particular, the optical density (OD value) of the non-printed portion of Comparative Example 2 was considerably higher than that of the non-printed portion of Examples 1-3. As described above, in the heat resistance test, the part with a lower optical density (OD value) in the non-printed area can be judged to have better heat resistance. Therefore, it can be said at least that the non-printed areas of Examples 1-3 have better heat resistance than the non-printed areas of Comparative Examples 1-2.

[0249] These results confirm that the thermal recorders of Examples 1-3 containing non-phenolic light stabilizers exhibit better heat resistance than the thermal recorders of Comparative Example 1 (which does not contain any light stabilizers) and Comparative Example 2 (which contains phenolic light stabilizer 2).

[0250] [Examples 4-6 and Comparative Example 3]

[0251] Examples 4-6 and Comparative Example 3, which contain the same color developer 2, were investigated.

[0252] (4) In the lightfastness test, the whiteness changes of Examples 4-6 were smaller than those of Comparative Example 3. Furthermore, the whiteness after the test was also greater than that of Comparative Example 3. These results confirm that Examples 4-6, containing a non-phenolic light stabilizer, are more effective in suppressing the decrease in whiteness compared to Comparative Example 3, which does not contain a light stabilizer.

[0253] (5) In the dynamic sensitivity test, when the printing energy was set to 0.40 mJ / dot, the optical density (OD value) of Examples 4-6 was 1.26-1.38, and the optical density (OD value) of Comparative Example 3 was 1.41. When the printing energy was set to 0.20 mJ / dot, the optical density (OD value) of Examples 4-6 was 0.65-0.71, and the optical density (OD value) of Comparative Example 3 was 0.75. When the printing energy was set to 0.16 mJ / dot, the optical density (OD value) of Examples 4-6 was 0.21-0.25, and the optical density (OD value) of Comparative Example 3 was 0.28. Examples 4-6 showed a trend of lower optical density (OD value) compared to Comparative Example 3, which did not contain a light stabilizer. However, the decrease was only about 2-25%, indicating good color development properties suitable for use as a thermal recorder.

[0254] These results confirm that the thermal recorders of Examples 4-6, which contain non-phenolic light stabilizers, have colorimetric properties that are comparable to those of Comparative Example 3, which does not contain light stabilizers.

[0255] (6) In the heat resistance test, the optical density (OD value) of the printed portion of Examples 4-6 was 1.26-1.34, while the optical density (OD value) of the printed portion of Comparative Example 3 was 1.39. Examples 4-6 showed a trend of lower optical density (OD value) compared to Comparative Example 3, which did not contain a light stabilizer. However, the decrease was only about 4-10%, maintaining the color development properties that allowed it to be used well as a thermal recorder. On the other hand, the optical density (OD value) of the non-printed portion of Examples 4-6 was 0.16-0.18, while the optical density (OD value) of the non-printed portion of Comparative Example 3 was 0.23, which was higher than that of Examples 4-6. As described above, in the heat resistance test, the portion with a lower optical density (OD value) of the non-printed portion can be judged to have better heat resistance. Therefore, it can be said at least that the non-printed portion of Examples 4-6 has better heat resistance than the non-printed portion of Comparative Example 3.

[0256] These results confirm that the thermal recorders of Examples 4-6, which contain non-phenolic light stabilizers, exhibit better heat resistance than the thermal recorder of Comparative Example 3, which does not contain any light stabilizers.

[0257] [Examples 7-10 and Comparative Example 4]

[0258] Examples 7 to 10 and Comparative Example 4, which contain the same color developer 1 and preservation enhancer 1, were investigated.

[0259] (7) In the lightfastness test, the whiteness changes of Examples 7-10 were smaller than those of Comparative Example 4. In addition, the whiteness after the test was also greater than that of Comparative Example 4. These results confirm that Examples 7-10, which contain non-phenolic light stabilizers and preservation stabilizers, are more effective in suppressing the decrease in whiteness compared to Comparative Example 4, which contains preservation stabilizers but no light stabilizers.

[0260] (8) In the dynamic sensitivity test, when the printing energy was set to 0.40 mJ / dot, the optical density (OD value) of Examples 7-10 was 1.63-1.67, and the optical density (OD value) of Comparative Example 4 was 1.67. When the printing energy was set to 0.20 mJ / dot, the optical density (OD value) of Examples 7-10 was 1.25-1.36, and the optical density (OD value) of Comparative Example 4 was 1.45. When the printing energy was set to 0.16 mJ / dot, the optical density (OD value) of Examples 7-10 was 0.6-0.75, and the optical density (OD value) of Comparative Example 4 was 0.82. Examples 7-10 showed a trend of lower optical density (OD value) compared to Comparative Example 4, which did not contain a light stabilizer. However, the decrease was only about 0-27%, indicating good color development properties suitable for use as a thermal recorder.

[0261] These results confirm that the thermal recorders of Examples 7-10, which contain non-phenolic light stabilizers and preservation stabilizers, have colorimetric properties that are comparable to those of Comparative Example 4, which contains preservation stabilizers but not light stabilizers.

[0262] (9) In the heat resistance test, the optical density (OD value) of the printed portion of Examples 7-10 was 1.56-1.62, while the optical density (OD value) of the printed portion of Comparative Example 4 was 1.62. Examples 7-10 showed a trend of lower optical density (OD value) compared to Comparative Example 4, which did not contain a light stabilizer. However, the decrease was only about 0-4%, maintaining the color development properties that allowed it to be used well as a thermal recorder. On the other hand, the optical density (OD value) of the non-printed portion of Examples 7-10 was 0.10, while the optical density (OD value) of the non-printed portion of Comparative Example 4 was 0.12, which was higher than that of Examples 7-10. As described above, in the heat resistance test, it can be determined that the portion with a lower optical density (OD value) of the non-printed portion has better heat resistance. Therefore, it can be said at least that the non-printed portion of Examples 7-10 has better heat resistance than the non-printed portion of Comparative Example 4.

[0263] These results confirm that the thermal recorders of Examples 7-10, which contain non-phenolic light stabilizers and preservation stabilizers, have better heat resistance than the thermal recorder of Comparative Example 4, which contains preservation stabilizers but no light stabilizers.

[0264] (10) In the water resistance test, the optical density (OD value) of the printed portion of Examples 7-10 was 1.24-1.29, and the optical density (OD value) of the printed portion of Comparative Example 4 was 1.34. Examples 7-10 showed a trend of lower optical density (OD value) compared to Comparative Example 4, which did not contain a light stabilizer. However, the decrease was only about 4-7%, maintaining the color development properties that allowed it to be used well as a thermal recorder. On the other hand, the optical density (OD value) of the non-printed portion of Examples 7-10 was 0.05-0.06, which was the same as the optical density (OD value) of 0.05 of the non-printed portion of Comparative Example 4.

[0265] These results confirm that the thermal recorders of Examples 7-10, which contain non-phenolic light stabilizers and preservation stabilizers, exhibit the same level of excellent water resistance as the thermal recorder of Comparative Example 4, which contains preservation stabilizers but not light stabilizers.

[0266] (11) In the plasticizer resistance test, the optical density (OD value) of the printed portion of Examples 7-10 was 1.44-1.56, and the optical density (OD value) of the printed portion of Comparative Example 4 was 1.20. Examples 7-10 showed higher optical density (OD values) compared to Comparative Example 4, which did not contain a light stabilizer. In particular, Example 10, which contained a large amount of preservation stabilizer, showed an optical density as high as 1.56. On the other hand, the optical density (OD value) of the non-printed portion of Examples 7-10 was 0.04-0.06, which was the same as the optical density (OD value) of 0.05 of the non-printed portion of Comparative Example 4.

[0267] These results show that the thermal recorders of Examples 7-10, which contain non-phenolic light stabilizers and storage stabilizers, have better plasticizer resistance than the thermal recorder of Comparative Example 4, which contains storage stabilizers but not light stabilizers. In particular, the plasticizer resistance is improved by including a large amount of storage stabilizers.

[0268] [in conclusion]

[0269] Based on the above test results, even thermal recorders containing non-phenolic color developers and non-phenolic light stabilizers did not exhibit inferior lightfastness, color development, heat resistance, water resistance, or plasticizer resistance compared to thermal recorders containing phenolic light stabilizers. Furthermore, it is known that the presence of non-phenolic light stabilizers in thermal recorders can maintain good heat resistance while improving lightfastness, inhibiting whiteness reduction and yellowing. Conversely, the presence of preservation enhancers can improve plasticizer resistance based on dosage.

[0270] Furthermore, non-phenolic color developers and light stabilizers are superior in terms of safety compared to phenolic color developers and light stabilizers. Therefore, using non-phenolic color developers and light stabilizers is also very effective from an environmental protection perspective.

[0271] The following are variations of the invention.

[0272] [Appendix 1]

[0273] A thermal recorder is characterized in that a thermal recording layer is laminated on a substrate, the thermal recording layer containing a chromogenic agent, a non-phenolic chromogenic agent, and a non-phenolic light stabilizer, wherein the non-phenolic light stabilizer contains a histamine-based light stabilizer.

[0274] [Appendix 2]

[0275] According to the thermal recorder described in Appendix 1, the non-phenolic colorimetric reagent contains a compound represented by formula (1) and / or a compound represented by formula (2).

[0276] [Chemistry 17]

[0277]

[0278] (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 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.

[0279] [Chemistry 18]

[0280]

[0281] (In equation (2), R) 13 R 14 R 15 R 16 R 17 R 19 R 20 R 21 R22 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.

[0282] [Appendix 3]

[0283] According to the thermal recorder described in Appendix 1 or 2, the above-mentioned non-phenolic colorimetric reagent contains the compound shown in formula (1a) and / or the compound shown in formula (2a).

[0284] [Chemistry 19]

[0285]

[0286] (The symbols in equation (1a) are the same as those in equation (1).)

[0287] [Chemistry 20]

[0288]

[0289] (The symbols in equation (2a) are the same as those in equation (2).)

[0290] [Appendix 4]

[0291] According to any one of the appendices 1 to 3, the thermal recording medium further contains a preservation enhancer.

[0292] [Appendix 5]

[0293] According to the thermal recorder described in Appendix 4, the above-mentioned preservation enhancer contains a urea urethane compound as shown in formula (4).

[0294] [Chemistry 21]

[0295]

[0296] [Appendix 6]

[0297] According to any one of the appendices 1 to 5, the content of the non-phenolic colorimetric agent, relative to the entirety of the aforementioned thermal recording layer, is 10% by mass or more and 50% by mass or less.

[0298] [Appendix 7]

[0299] According to any one of the appendices 1 to 6, the content of the non-phenolic light stabilizer relative to the entirety of the aforementioned thermal recording layer is 1% by mass or more and 10% by mass or less.

[0300] Industrial availability

[0301] As described above, the present invention is particularly useful for thermal recorders such as printed barcodes.

[0302] Explanation of reference numerals in the attached figures

[0303] 1 Thermal recorder, 2 Substrate, 3 Thermal recording layer, 4 Intermediate layer, 5 Top coating, 6 Bottom coating.

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 chromogenic agent, a non-phenolic chromogenic agent, and a non-phenolic light stabilizer. The non-phenolic light stabilizer contains a compound having a group represented by the following formula (3): In equation (3), R a The alkyl group represents an alkyl group having 1 to 4 carbon atoms, which may be interrupted once or multiple times by an oxygen atom or a carbonyl group. Furthermore, the groups in general formula (3) are in general formula (3) The bonding of the parts.

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 claim 1, wherein, The thermal recording layer further contains a preservation enhancer.

5. The thermal recorder according to claim 4, wherein, The preservation enhancer contains a urea-amino ester compound represented by the following formula (4). 。 6. The thermal recorder according to claim 2, wherein, The thermal recording layer further contains a preservation enhancer.

7. The thermal recorder according to claim 6, wherein, The preservation enhancer contains a urea-amino ester compound represented by the following formula (4). 。 8. The thermal recorder according to claim 3, wherein, The thermal recording layer further contains a preservation enhancer.

9. The thermal recorder according to claim 8, wherein, The preservation enhancer contains a urea-amino ester compound represented by the following formula (4). 。 10. The thermal recorder according to any one of claims 1 to 9, 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.

11. The thermal recorder according to any one of claims 1 to 9, wherein, The content of the non-phenolic light stabilizer relative to the entire thermal recording layer is 1% by mass or more and 10% by mass or less.

12. The thermal recorder according to claim 10, wherein, The content of the non-phenolic light stabilizer relative to the entire thermal recording layer is 1% by mass or more and 10% by mass or less.

13. The thermal recorder according to claim 5, wherein, The ratio of the urea urethane compound shown in formula (4) to the non-phenolic color developer, i.e., the ratio of urea urethane compound to non-phenolic color developer, is 1 / 20 to 5.4 / 30.

6.

14. The thermal recorder according to claim 5, wherein, The content of the urea urethane compound represented by formula (4) is 90% by mass or more relative to the total amount of the preservation enhancer contained in the thermal recording layer.

15. The thermal recorder according to claim 1, wherein, Compounds having the group shown in formula (3) contain the reaction product of 1,2,2,6,6-pentamethyl-4-piperidinyl octadecanoate, tetramethyl 1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol and / or tetra(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate.

16. The thermal recorder according to claim 2, wherein, The non-phenolic colorimetric reagent contains the compound shown in formula (2).

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